I have a series of 20 .tif images. I want to create an .avi video from them but I want each image to be shown for 4-5 seconds. I tried ffmpeg but I cannot find a way to make them be shown for this specific time. Does anyone have an idea?

I am attempting to create a video file from a set of JPG images. I have adapted the instructions given in  but have experienced some issues.   Firstly, not all of the required packages are available, but are replaced by libav-tools, which is already installed - so I think that's not an actual problem?   My files are named image-NN.jpg (NN being an integer) and I have used the command  avconv -i "image-%d.jpg" -r 25 -c:v libx264 -crf 20  -pix_fmt yuv420p movie.mov   as per the linked question, but this just gives a No such file image-%d.jpg error. I   I tried changing it to   avconv -i "image-*.jpg" -r 25 -c:v libx264 -crf 20  -pix_fmt yuv420p movie.mov   and this produces a video file of length 0:00 that appears to only contain one frame. (I am guessing that the * has used the first match, rather than every match).    gives a slightly different way of formatting the file name, so I tried   avconv -i "image-%02d.jpg" -r 25 -c:v libx264 -crf 20  -pix_fmt yuv420p movie.mov   This produces a larger file, and makes a video that lasts for about 3 seconds (approx the length I was expecting) but it contains just the first frame.   Another answer on the first linked question suggests using ImageMagick, so I gave this a try  convert -delay 1 image-*.jpg output.mp4   But this produced an error   convert.im6: delegate failed `"ffmpeg" -v -1 -mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 300 -i "%M%%d.jpg" "%u.%m" 2> "%Z"' @ error/delegate.c/InvokeDelegate/1065.   The version of avconv is  carl@number1 ~/Scott's stop-motion/1 $ avconv -version avconv version 9.18-6:9.18-0ubuntu0.14.04.1, Copyright (c) 2000-2014 the Libav developers built on Mar 16 2015 13:19:10 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1) avconv 9.18-6:9.18-0ubuntu0.14.04.1 libavutil     52.  3. 0 / 52.  3. 0 libavcodec    54. 35. 0 / 54. 35. 0 libavformat   54. 20. 4 / 54. 20. 4 libavdevice   53.  2. 0 / 53.  2. 0 libavfilter    3.  3. 0 /  3.  3. 0 libavresample  1.  0. 1 /  1.  0. 1 libswscale     2.  1. 1 /  2.  1. 1   Where am I going wrong, and what do I need to do?     Additional: It was suggested that I list every file individually, so with a bit of Python I generated this  avconv -i image-01.jpg image-02.jpg image-03.jpg image-04.jpg image-05.jpg image-06.jpg image-07.jpg image-08.jpg image-09.jpg image-10.jpg image-11.jpg image-12.jpg image-13.jpg image-14.jpg image-15.jpg image-16.jpg image-17.jpg image-18.jpg image-19.jpg image-20.jpg image-21.jpg image-22.jpg image-23.jpg image-24.jpg image-25.jpg image-26.jpg image-27.jpg image-28.jpg image-29.jpg image-30.jpg image-31.jpg image-32.jpg image-33.jpg image-34.jpg image-35.jpg image-36.jpg image-37.jpg image-38.jpg image-39.jpg image-40.jpg image-41.jpg image-42.jpg image-43.jpg image-44.jpg image-45.jpg image-46.jpg image-47.jpg image-48.jpg image-49.jpg image-50.jpg image-51.jpg image-52.jpg image-53.jpg image-54.jpg image-55.jpg image-56.jpg image-57.jpg image-58.jpg image-59.jpg image-60.jpg image-61.jpg image-62.jpg image-63.jpg image-64.jpg image-65.jpg image-66.jpg image-67.jpg image-68.jpg image-69.jpg image-70.jpg image-71.jpg image-72.jpg image-73.jpg image-74.jpg image-75.jpg image-76.jpg image-77.jpg image-78.jpg image-79.jpg image-80.jpg image-81.jpg image-82.jpg image-83.jpg image-84.jpg image-85.jpg image-86.jpg image-87.jpg image-88.jpg  -r 25 -c:v libx264 -crf 20  -pix_fmt yuv420p movie.mov   This had the same effect as previous - only the first frame is used.  Additional:  has been suggested as a possible duplicate, but it relates to acquiring images using a webcam connected to a PC. This is not the issue I am having. I already have the photos; they were taken with an ordinary digital camera.


Let $\gcd (a, b) = d$. So, $ax + by = d$ for some $x, y$. Then $(ca)x + (cb)y = cd$. Thus, $\gcd (ca, cb) = cd = \gcd(a, b)c$.  Does it work?

I need to prove that $z\gcd(a,b)=\gcd(za,zb)$.    I tried a lot, for example, looking at set of common divisors of the two sides, but I can't conclude anything from that. Can you please give me some advice how I can handle this problem? And $a,b,z \in \mathbb{Z}$.


My textbook is asking me to find the limit of $\frac{10^n}{n!}$. Here is how they do it:  My question is: Is this the only way to prove that the limit is $0$ ?   I know the fact that factorials diverge 'faster' than exponential, so can I just state this? I mean how am I supposed to know that at $n>20$ the ratio is $<\frac{1}{2}$ ?  Or should I just say that for some $N$, there is $n>N$ s.t. the ratio of the successive terms become less than $1$ and hence the limit is $0$?

Why is     $$\lim_{n \to \infty} \frac{2^n}{n!}=0\text{ ?}$$   Can we generalize it to any exponent $x \in \Bbb R$? This is to say, is     $$\lim_{n \to \infty} \frac{x^n}{n!}=0\text{ ?}$$     This is being repurposed in an effort to cut down on duplicates, see here: Coping with  duplicate questions.  and here: .


I'm writing a paper to describe my methods that are borrowed from other's models.   I think both the past and present tense are possible.  I can use present tense as I'm explaining it now.      However, we use only programming languages and programming paradigms for selecting programming model examples. Specifically, we choose two ...    Also, I can use the past tense as I've already used and chose something before writing the paper.      However, we used only programming languages and programming paradigms for selecting programming model examples. Specifically, we chose two ...    Which is correct or better?  ADDED  I chose to use the present tense in my paper as the sentences are in an introduction to describe details later.      However, we use only programming languages and programming paradigms for selecting programming model examples. Specifically, we choose two programming languages--Lisp and Forth--and two programming paradigms--Object Oriented and Functional--as examples of successful programming models. We analyze them to understand what elements enable these languages or paradigms, passing the test of time to be used widely and solving problems in many domains.   I assume that present tense is possible as this is a CS paper, if this is a Chemistry paper that explains my or other's past experiments, I kinda feel I need to write in the past tense.

I am writing a paper in mathematics.   Stone theorems have a long history. B [B78] proved the stone theorem for the B model. C and D [CD14] not only prove a stone theorem for the cake process in random environment, but also have a nice overview of existing results.  (here B, C and D are some names, and 'stone theorem' and 'the cake process' also represent something else, but it is not important for the structure)  Question: is it ok to use a past tense in the first sentence which refers to 1978, but use a present tense in the second sentence which describes something that happened relatively recently, in 2014?


I think this set is uncountable, but I don't really know how to prove this. Maybe somehow find an injection from $\mathcal{P}( \mathbb{N} \times  \mathbb{N}) \rightarrow A$?

Is the set of partial order relations over $ \mathbb{N}$ countable? I think it's uncountable but don't know how to prove this. I would be very helpful if someone could also give some kind of a strategy for proving uncountability, in particular how to find injective or surjective functions that help proving this.


According to the statistics displayed on my suggested edits. I mean    According to what is shown above. I have 120 edit suggestions approved but in my badge progress     Its shows 82 edits.  I even just got my  Badge. My Question is how are edits counted and what is the reason for the inconsistency?

Formerly List of all badges with full descriptions.  What are badge name's requirements? Why didn't I get badge name ? Which badges can I earn multiple times?    Jump to:                    Note: Some badges are awarded based on score. The term score means the total number of upvotes minus the total number of downvotes.  Any badge with a *** next to it is one of 20 badges that count towards the  displayed on a moderator candidate in an election. The candidate score is a total of 40 points: the first 20 are awarded based on the user's rep divided by 1000 and rounded down; the second 20 represents the total number of unique badges earned of the 20 that count. Note that if the same badge is earned multiple times, it will only count once towards the candidate score.  Any badge with a "(retired)" next to it is no longer awarded, but is retained by users who previously earned them. See  for more info on what it means for a badge to be retired.       Visit the  of the  on any site to see a complete list of badges that you can filter by earned, unearned, or type.


Which one of the following sentences is correct? Both Lionel Messi and Cristiano Ronaldo were born into working-class families. Both Lionel Messi and Cristiano Ronaldo were born into a working-class family.

In a situation where say a group (or at least a plurality) of men is being addressed — for example on a sign passed by many married men — which is correct?  "Remind your wife."  or  "Remind your wives."


I am using this  microcontroller. Can someone tell me , how is the input pin of the microcontroller would be? Can someone tell me how, if a GPIO is configured as an input pin, how would it be electrically? Just want to understand how the input impedance of the microcontroller pin would be? I could see the word CMOS input or output present in the datasheet.

I am using  64-pin Microcontroller. I want to configure the IO pins in RUN Mode, Sleep mode and Reset mode. For used pins, say IO, I2C and SPI pins, output pins, please tell me what should I give for the below questions during each modes (Run, Reset and Sleep):  Whether input or Output pin? Whether internal pull-up or pull-down to be enabled? To drive High or Low?


I am trying to figure out how to use both allocations for an assignment and I am having a hard time figuring it out. More importantly, can someone explain how to use proportional allocation to me by using an example? I have data on Gas Prices, and I want to do the proportional allocation of the cities. This is what I have, the total population is 840, with each city has a 168 population within that and the sample size n is 118 for each city.    City           count  mean  sd 1 Niagara Falls    168,  97.4, 0.980 2 Port Colborne    168,  93.8, 2.19 3 St. Catharines   168,  94.0, 2.25 4 Thorold          168,  93.6, 2.84 5 Welland          168  93.0 2.77  So any advice is greatly appreciated and if need any more information just let me know.

Suppose that a city has 90,000 dwelling units, of which 35.000 are houses, 45,000 are apartments,   and 10,000 are condominiums. We want to estimate the overall proportion (p) of households   in which energy conservation is practiced, with a bound on the error of estimation equal 0.1.   The cost for obtaining an observation is \$9 for houses, \$10 for apartment, and \$16 for   condominiums. Suppose that from an earlier study, we know that 47% of house dwellers, 23%   of apartment dwellers, and 3% of condominium residents practice energy conservation.        (a) (4 marks) Using a proportional allocation, find the strata sample sizes, $n_1$, $n_2$, and $n_3$,   and the sample size n.   (b) (4 marks) Using a optimal allocation, find the strata sample sizes, $n_1$, $n_2$, and $n_3$, and   the sample size n.   (c) (4 marks) Using a Neyman allocation, find the strata sample sizes, $n_1$, $n_2$, and $n_3$, and   the sample size n.   Neyman allocation is used when the cost of obtaining an observation is the same for all strata, while proportional allocation is used when costs are unequal among strata but variances are equal in all strata. But in this question, neither cost or variance are equal, then how can I apply the formula for Neyman and proportional allocation? Just ignore the cost and variance and set them equal or is there another formula for that?


Find the number b such that the line $y=b$ divides the region bounded by the curves $y = x^2$ and $y = 4$ into two regions with equal area.

Find the number $b$ such that the line $y = b$ divides the region bounded by the curves $y = x^2$  and $y = 4$ into two regions with equal area.  I could find the area of this region but i have no clue how to split it parallel to the $x$ axis perfectly... this is too abstract for me...  I found the whole area and got $\dfrac{32}{3}$... I tried plugging that back into the definite integral but that definitely wasn't right...


I am a new user to the Stack Exchange network.   I am making a proposal to add to the FAQ a Question:   This will be especially useful to the new users (FAQ is supposed to help new users, I guess).   Please explain the following:    How to effectively search for an answer/question? (Please add the discussion )  Will asking a specific question about a system whose answer is in another question which deals with the general aspect of the system be considered a duplicate and closed? (Meaning question is not exactly a duplicate, but answer can be found by extensive reading of answers from other related questions) Please add the question to the FAQ:  and    This is not a duplicate of the question 'how to avoid asking duplicate questions' because this deals with adding that question to faq.

I always search to find whether my question is a duplicate or not before asking the question on Stack Overflow. But often I cannot find anything (maybe this is a language problem) and I ask my question. Then someone finds a duplicate question of my question and votes to close mine. So how can I avoid asking a duplicate question?


So, you opened this question. If you click on the title of it (e.g. the question header), it basically reloads the page.  Does this serve any purpose? Every browser has a reload-function (F5), why is the title of a question clickable, if it doesn't lead anywhere other than to where you are at the moment?

It is possible to click on this question title above ↑, which would cause the page to refresh.  I'm wondering why the question title is a link to itself and the same page?  Why isn't it just written as solid text?  SEO perhaps?


The problem that I am having, is that when I try and render my scene, everything turns out completely black. I press render, then it takes about 1 minute 30 seconds before it actually starts rendering, then it quickly renders a black screen. I have looked through many other posts about this, but none of the solutions are working for me. I'm a beginner, so I'm sure I am just missing something obvious, but help would be appreciated. Thank you.

This is meant to solve this problem once and for all. What is every reason an object isn't showing up in a render or viewport in when using the cycles render engine?


PPS. I have added a related question now -  which addresses the point raised here.  PS. The reason not to close can found at the end  Some years ago I proposed a new StackExchange for non-Ubuntu desktop environments because   Ask Ubuntu did not like questions on Debian There are whole areas of Linux which are not Ubuntu specific Unix SE tends to be focused more on lower level, glue level aspects of Linux and the command line and it doesn't go into desktop issues as much.  utilities  bash 14758 grub 6639 swap 5937 init 5076 mysql 3618 init.d 2845 crontab 2626 systemd 2090 docker 1873 zsh 1460 system v 1451 python 1333 upstart 877 rc.d 922 puppet 502   desktops  debian 9389 arch 7574 ubuntu 7510 mint 6290 fedora 3009 gnome 1552 kde 986 kde4 322 kde5 186    You can see from the tags how much Unix/Linux is focused more on the underlying glue and utilities rather than issues relating to the desktop environment. Combining the two areas is like trying to serve Windows server administrators and Windows end users from the same forum. I don't think any SE developers and administrators would ever do that  In Linux server administrator issues are quite different from desktop user related issues, but as most Linux desktop users have to be their own administrators, there is an overlap but only the minimum desktop users need to do to fix the desktop issues and get back to work.  To be honest each of the Linux desktop derivatives need their own SE and admins can probably tag them and move them if they are miscategorized or are in the wrong forum.  I brought this up some years ago and it was shot down immediately on the grounds that Unix and Linux SE is a good substitute. You only have to look at r/unix and r/linux on reddit to see how conceptually differently they are viewed.  Whatever the case may or may not be for different Stack Exchanges for the desktop environments the desktop environments and the OS proper should have different exchanges. Linux itself is the operating system, the kernel more accurately and the derived OSs and desktop environments are quite different.  UPDATE For those who believe I should make a new proposal this is question explains the reason why. .  If there is a means of getting past a proposal which will allow other interested users to chime in before it is immediately turned down  or there is some other faq, question or Q&A on how this point can be discussed I'd like to be directed to it

I have an idea or subject that should have a Q&A, and want to propose a new site. How can I do this?  Related:


I am on a project where much of the queries are performed by including multiple tables in the FROM clause.  I know this is legal, but I have always used explicit JOINs instead.  For example, two tables (using SQL Server DDL)  CREATE TABLE Manufacturers(     ManufacturerID INT IDENTITY(1,1) PRIMARY KEY NOT NULL,     Name varchar(100))  CREATE TABLE Cars (     ModelID INT IDENTITY(1,1) PRIMARY KEY NOT NULL,     ManufacturerID INT CONSTRAINT FOREIGN KEY FK_Manufacturer REFERENCES Manufacturers(ManufacturerID),     ModelName VARCHAR(100))   If I want to find the models for GM, I could do either:  SELECT ModelName FROM Cars c, Manufacturers m WHERE c.ManufacturerID=m.ManufacturerID AND m.Name='General Motors'  or  SELECT ModelName FROM Cars c INNER JOIN Manufacturers m ON c.ManufacturerID=m.ManufacturerID WHERE m.Name='General Motors'  My question is this: does one form perform better than the other?  Aside from how the tables are defined in Oracle vs SQL Server, does one form of join work better than the other in Oracle or SQL Server?  What if you include more tables, say 3 or 4?  Does that change the performance characteristics, assuming the queries are constructed to return an equivalent record set?

Is there any efficiency difference in an explicit vs implicit inner join? For example:  SELECT * FROM table a INNER JOIN table b ON a.id = b.id;   vs.  SELECT a.*, b.* FROM table a, table b WHERE a.id = b.id;


I've imported some polygons (ways) from OpenStreetMap and now want to calculate the centroids of them.  For this purpose I wrote following code:      final List<Point2D.Double> points = getPoints();     final Point2D.Double actualCentroid = calculateCentroidOurWay(points);      LOGGER.debug("Centroid, x: " + actualCentroid.x);     LOGGER.debug("Centroid, y: " + actualCentroid.y);  private Point.Double calculateCentroidOurWay(final List<Point2D.Double> aPoints) {     final Building objectUnderTest = new Building();      objectUnderTest.setPolygon(new Polygon(aPoints));      return objectUnderTest.calculateCentroid(); }  @Override public Point2D.Double calculateCentroid() {     double x = 0.;     double y = 0.;     double area = 0.;      for (int i = 0; i < polygon.getPoints().size() - 1; i++) {         final Point2D.Double point = polygon.getPoints().get(i);         final Point2D.Double pointN = polygon.getPoints().get(i + 1);          final double temp = point.getX() * pointN.getY() - pointN.getX() * point                 .getY();         x += (point.getX() + pointN.getX()) * temp;          y += (point.getY() + pointN.getY()) * temp;          area += temp;     }      area /= 2.;      x *= 1 / 6. * area;     y *= 1 / 6. * area;      return new Point2D.Double(x, y); }   private List<Point.Double> getPoints() {     final List<Point.Double> points = new LinkedList<>();      points.add(new Point.Double(132.1764353, 43.3539477));     points.add(new Point.Double(132.1771393, 43.3539409));     points.add(new Point.Double(132.177145, 43.3542587));     points.add(new Point.Double(132.1768224, 43.3542618));     points.add(new Point.Double(132.1768183, 43.3540332));     points.add(new Point.Double(132.1766516, 43.3540348));     points.add(new Point.Double(132.1766564, 43.3542949));     points.add(new Point.Double(132.176566, 43.3542957));     points.add(new Point.Double(132.1765705, 43.3545391));     points.add(new Point.Double(132.1769718, 43.3545353));     points.add(new Point.Double(132.1769691, 43.3543859));     points.add(new Point.Double(132.177131, 43.3543843));     points.add(new Point.Double(132.1771321, 43.3544446));     points.add(new Point.Double(132.177341, 43.3544426));     points.add(new Point.Double(132.1773296, 43.3538152));     points.add(new Point.Double(132.176433, 43.3538238));     points.add(new Point.Double(132.1764353, 43.3539477));     return points; }   The result of the calculation is  Centroid, x: 1.8787362164666136E-11 Centroid, y: 6.162273026564668E-12   which is obviously wrong (it's not a latitude/longitude pair).  When I use Java Topology Suite, it returns same results.  private Coordinate calculateJtsCentroid(final List<Point2D.Double> aPoints) {     final CentroidPoint centroidPoint = new CentroidPoint();      for (final Point.Double curPoint : aPoints) {         centroidPoint.add(new Coordinate(curPoint.x, curPoint.y));     }      return centroidPoint.getCentroid(); }   How should I change my code in order to get the centroid of the polygon as a point identified by latitude and longitude?

I'd like a general way to calculate centroids for polygons on a sphere.  So far, the best online reference appears to be:      by Jeff Jenness.   The method described there suggests decomposing the polygon into multiple spherical triangles, and computing the average of spherical triangle centroids, weighted by the spherical triangle area.  I know that there are several ways to define a spherical polygon centroid, but I'm looking for something analogous to the following definitions for points and polylines:   Points: arithmetic mean of the Cartesian vectors representing the points. Polylines: weighted mean of Cartesian vectors representing midpoints of each line segment, weighted by the (spherical) length of each segment.   It seems a reasonable continuation to have polygon centroids defined as the weighted mean of the triangular decomposition, weighted by area.  My question is whether the method in the above reference will work regardless of the triangle decomposition used. In particular, it mentions decomposing into triangles relative to an arbitrary point, even external to the polygon, such that some triangles will have negative areas that contribute a negative weight.  Related:


Which sentence is correct?  In graphic design, I consider the use of color. Similarly in photography, I also consider...  In graphic design, I consider the use of color. Similarly, in photography, I also consider...  I know that there's usually a comma after "similarly" but the sentence in the second sentence sounds too long and has too many pauses. I prefer the first option because it flows better, but is it grammatically correct? If not, is there a way to write that sentence in a way that flows better?

If I have a sentence that starts with additionally, finally, consequently, etc. do I always have to put a comma after it? Or is there a different rule?


I cant send the date time to the database because i dont know the datatype of it. Can you guys help me? Im stuck here for like a day or two.     if(isset($_POST['Submit'])){ $stmt = $connection->prepare("INSERT INTO user_account(Last_Name, First_Name, Middle_Name, User_name, Password, Birth_date, Address, Contact_no) VALUES (?,?,?,?,?,?,?,?,?)"); $stmt->bind_param("ssssssiss",$_POST['lName'],$_POST['fName'],$_POST['mName'],$_POST['uName'],$_POST['uPassword'],$_POST['bDate'],$_POST['uAddress'],$_POST['cNumber']);   I thought it was an integer so i declared it as an integer but it was an error can you guys help me? TIA. :)

I have a datetime column in MySQL.   How can I convert it to the display as mm/dd/yy H:M (AM/PM) using PHP?


I want to use salesforce rest api with Silverlight application. But I am getting security error.  Is there any way to allow and configure ClientAccessPolicy for salesforce rest api service.

I am creating a application with Silverlight 5 in which I have to communicate with Salesforce APIs.  Currently I used Salesforce toolkit for .net (version 1.2.1) by I am gettting error after using authentication method as -     The base class or interface 'System.Object' in assembly   'System.Runtime, Version=4.0.0.0, Culture=neutral,   PublicKeyToken=b03f5f7f11d50a3a' referenced by type   'Salesforce.Common.AuthenticationClient' could not be resolved.   System.runtime dll is referenced my application.   And Latest version of toolkit is even not installing in application. There is some compatibility issue with silverlight 5.  As per github and blogs Salesforce Toolkit is compatible with Silverlight 5. I installed it using nuget package manager.  Any idea to fix this ?  Thanks,


Why is the following code possible? (Just an example I just came up with while working on other code)  public String getLogIdentifierFromFile(final File file) {     //this.file = null; //Gives compiler error as obviously expected     nullify(file);     return ""; }  public void nullify(Object object) {     object = null; }   And how can I ensure that the final from the top function actually has an effect? This time it is me making the nullify method, but it can also be anyone's code that my method needs to call.

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


Just wanted some help with this little proof.:  Let X and Y be Finite Sets. Prove that |X^Y| = |X|^|Y|

I really cannot seem to get my head around the definition of cardinal exponentiation with regards to finite sets:  $|X|^{|Y|}=|X^Y|$  How would one even begin to prove this? Isn't $X^Y$ the set of all functions with the domain $Y$ and the codomain $X$?


This question is published in multiple textbooks and already has :  Find a recurrence relation for the number of ternary strings of length $n$ that do not contain two consecutive 0s or two consecutive 1s.  This question above has a recurrence relation $f_{n}=2f_{n-1}+f_{n-2}$. But the same problem replacing or to and seems to be much more difficult:  Find a recurrence relation for the number of ternary strings of length $n$ that do not contain two consecutive 0s and two consecutive 1s.  I tried to solve it in the way below: i) starts with 2 -> $a_{n-1}$ ii) starts with 12 or 02 -> $a_{n-2}$ iii) starts with 012 or 102 -> $a_{n-3}$ and so on . So the relation :$$f_{n}=f_{n-1}+2f_{n-2}+2f_{n-3}+....+f_{0}+2$$ that is $$f_{n}=2f_{n-1}+f_{n-2}$$ I got a same relation as with the original question using or. Please help me to find out where did I go wrong?

Note: Problem from "Kenneth Rosen's DM and it's applications" and solution from "Students solution guide for use with ... applications"  Let P(n) be the number of strings not containg two containing two consecutive zeros or two consecutive ones.  I got the answer  P(n)=P(n-1)+2P(n-2)+2P(n-3)+...+2P(0) +2  but then the book says the sequence also satisfies the recurrence relation  P(n)=2P(n-1)+P(n-2). I am not able to understand this part.


I am running Windows 10 and need to be able to use Internet Explorer for some work, but I can't seem to locate it. I've already tried typing 'Internet Explorer' in Cortana search but it didn't work.  How can I open Internet Explorer on Windows 10?

Will Internet Explorer run on Windows 10?  I can't seem to find an answer to this anywhere.  I have just updated to Windows 10 and need to be able to do web development testing on Internet Explorer, but when I go to  it says "Looking for Internet Explorer? You’re in the right place, but Internet Explorer requires a Windows PC."


When I edited a post, if I inserted some text above existing text, eventually the inserted text will 'overlap' with the older text. See this screenshot:         Closing and reopening the keyboard redrawn the text box to remove the 'overlapping', but it will happen again if I add more than 1 line of text.

When typing/editing an answer, sometimes if I scroll the editor textbox, go upwards and add lines, the text will start overlapping each other. The behaviour is that when you add a newline, the text below it does not move downwards.  Minimizing soft keyboard fixes this.  This does not affect the Ask Question box in my test.    I am using Android 4.1.2


I've got a CakePHP project running in a CentOS VirtualBox. The website is served with Apache 2.2.15.  There are JS files in the document root folder. Apache seemed to serve them file.  But after i edit a JS file, Apache would serve the old file. It will modify the size of the old file to match the size of the new file and serve the modified old file:   If the new file is smaller than the old file, it would cut the old file and serve the result; If the new file is larger than the old file, it would append � symbols to the old file and serve the result.   Restarting Apache does not resolve the issue.  The only way i found to make Apache serve the current file is to move the file to another location. Then CakePHP will display a fancy 404 page. Then i move the file back, and Apache displays the file in it's current state.  But i2.2.15t will freeze the file in that state and after modifying the file again i will have to repeat the trick again.  Apache logs are clean, the access log file displays this:     172.28.128.1 - - [12/Jul/2014:07:42:13 -0400] "GET /assets/js/compiled/editable_group.js HTTP/1.1" 200 903   What is the reason of the problem and how do i resolve it?  PS I will be happy to provide any details, logs, configs, etc. Just tell me what you want to see.

Edit: this has been almost entirely rewritten as I've narrowed down the issue.  I'm using a Vagrant VM to mirror the client's environment as closely as I can. I'm using VirtualBox 4.3 (with Guest Additions 4.3) with Vagrant 1.3.5, and the server is running CentOS 5.9, Apache 2.2.3-83, PHP 5.3.3, and Drupal 7.  When the server first starts the original files in the shared directory, where my application resides, are cached. When I change the file the original file +/- the filesize delta is served, leading to the image corruption I saw before. So additions add NUL characters on the end of the original, and deletions truncate the file. When I view the file using nano the contents are correct; restarting the httpd service makes no difference. I have to restart the VM for the changes to be served correctly.  Before:   // The quick brown fox   Changes:   // The quick brown fox jumps over the lazy dog   Apache serves:   // The quick brown fox\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0   Where exactly does this error lie? With Apache 2.2 or its dependencies, or with VirtualBox and its Guest Additions?


I am writing a JsonMapper in order to map a JSON String to the fields of a C# class using , similar to JSONUtility so that I can have greater control over the mapping. I'm not inclined to write the code for mapping each class as I will have many multiple classes with varying fields.  public class JsonMapper<T> {     public string jsonString;     public T mappedObj;      public JsonMapper(string json)     {         jsonString = json;         JSONNode jn = JSON.Parse(json);          Type t = Assembly.GetExecutingAssembly().GetType(typeof(T).FullName);         mappedObj = (T) Activator.CreateInstance(t);          foreach (FieldInfo field in typeof(T).GetFields())         {             switch (field.FieldType.Name)             {                 case "Int32":                     field.SetValue(mappedObj, int.Parse(jn[field.Name]));                     Debug.Log(field + ": " + field.GetValue(mappedObj));                     break;                     ...   I've used reflection in order to map primitive data types so far, but currently I am stuck trying to map lists. I'm trying to obtain the generic, T, of the List, and recursively create another instance of my JsonMapper. Below is an example of what I am trying to achieve:  case "List`1":     Type genericType = field.FieldType.GetGenericArguments()[0];     foreach (var genericJson in jn[field.Name])     {         //This line does not work, it is pseudocode         JsonMapper<genericType> recurJM = new JsonMapper<genericType>(genericJson.ToString());     }     break;   To do so I have referenced  to invoke generic methods using reflection and  to invoke constructors. However, I can't seem to find a way to invoke a constructor with generics.   My question is: How do I achieve this particular line of code in the above code snippet?  JsonMapper<genericType> recurJM = new JsonMapper<genericType>(genericJson.ToString());

The title is kind of obscure. What I want to know is if this is possible:  string typeName = <read type name from somwhere>; Type myType = Type.GetType(typeName);  MyGenericClass<myType> myGenericClass = new MyGenericClass<myType>();   Obviously, MyGenericClass is described as:  public class MyGenericClass<T>   Right now, the compiler complains that 'The type or namespace 'myType' could not be found." There has got to be a way to do this.


Prove: $\lim _{n\to \infty }\left(\sqrt[n]{\frac{n!}{n^n}}\right)=\frac{1}{e}$   I tried to do some algebraic manipulations and squeeze it but couldn't get further.  Any help appreciated.

I'm trying to find  $$\lim_{n\to\infty}\frac{n}{\sqrt[n]{n!}} .$$   I tried couple of methods: Stolz, Squeeze, D'Alambert  Thanks!  Edit: I can't use Stirling.


In Javascript what is the difference between:  var name = function() { //stuff to do };  {name : function() { //stuff to do } };  function name() { //stuff to do };

I've recently started maintaining someone else's JavaScript code. I'm fixing bugs, adding features and also trying to tidy up the code and make it more consistent.  The previous developer used two ways of declaring functions and I can't work out if there is a reason behind it or not.  The two ways are:  var functionOne = function() {     // Some code };     function functionTwo() {     // Some code }   What are the reasons for using these two different methods and what are the pros and cons of each? Is there anything that can be done with one method that can't be done with the other?


What is wrong with this code (I get an overfull \hbox warning in the line 5)?  \documentclass[final]{scrreprt} \usepackage{graphicx} \usepackage{blindtext} \begin{document} \begin{minipage}[t]{\textwidth}% \begin{minipage}[t]{0.48\linewidth}% \blindtext \end{minipage}% \hfill% \begin{minipage}[t]{0.48\linewidth}% \blindtext \end{minipage}% \end{minipage} \end{document}

Sometimes I have two (or more) figure environments which I want to layout on one page, and put a horizontal rule in the center. To acomplish this, I put a \vfill\hrule\vfill between the two environments. However, this only works if I create a minipage spanning the whole text-region of a page.  However, if I do this I get either a hbox or a vbox overflow, depending on the document class. For article it's a hbox overflow of 15pt, for phdthesis (a cls I grabbed of the web) it's a vbox overflow also of 15pt.  This is a minimal working example:  \documentclass{article} \newlength{\minipagewidth} \newlength{\minipageheight}  \begin{document}% %results in:  Badbox, line 9: Overfull \hbox (15.0pt too wide) in paragraph at lines 9-26 \setlength{\minipagewidth}{\textwidth}% \setlength{\minipageheight}{\textheight}% \begin{minipage}[t][\minipageheight]{\minipagewidth}% Top of the page  \vfill\hrule\vfill  Bottom of the page \end{minipage} % no vbox or hbox overflow: \addtolength{\minipagewidth}{-15pt}% %\addtolength{\minipageheight}{-15pt}% \begin{minipage}[t][\minipageheight]{\minipagewidth}% Top of the page  \vfill\hrule\vfill  Bottom of the page \end{minipage}% \end{document}   The second minipage results in no such warning, but I had to subtract 15pt from the width. Where does this 15pt come from? why is \textwidth wider than the textual area's width?


From Rotman's Algebraic Topology:  For each $n \ge 1$, $\Bbb R P^n$ is obtained from $\Bbb R P^n$ by attaching an $n$-cell, moreover, there is a disjoint union $$\Bbb RP^n = e^0 \cup \dots \cup e^n$$, where $e^n$ is an $n$-cell.  Partial proof:  If $x = (x_1, \dots, x_{n+1}) \in S^{n}$, denote its equivalence class in $\Bbb RP^n$ by $[x] = [x_1, \dots, x_{n+1}]$.  Define $e = \{[x] \in \Bbb R P^n : x_{n+1} \neq 0\}$.  The complement $Y$ of $e$ in $\Bbb R P^n$ is just $\Bbb RP^{n-1}$.  Also, $e$ is an $n$-cell, for $e \cong \Bbb R^n$ via $g : [x] \mapsto (x_{n+1}^{-1}x_1, \dots, x_{n+1}^{-1}x_n)$.  Why is $g$ a homeomorphism?  I'm having a hard time finding a way to show this.  Anyone have any ideas?

To prove that: The $n$-dimensional projective space can be presented as:  $\mathbb{RP}^n=\bigcup_{i=0}^{n} A^{i}$.  (The intersection of each two $A^{i}$ is empty)، $A^{i}$ is isomorphic to $\mathbb R^{i}$ ($A^{0}$ includes only one point). The definition of $\mathbb{RP}^n$ is: $\mathbb{RP}^n= (\mathbb R^{n+1} \setminus \{0\})/ \sim$ , $\sim$ is defined as: $x \sim \lambda x$for all $\lambda\in \mathbb R^\times$ and $x\in \mathbb R^{n+1} \setminus \{0\}$. $\mathbb R^\times $ is the productive group of scalars $\ne0$ in the field $\mathbb R$. I'm just a beginner in this field so any help would be appreciated.


I am using virtual box 4.3.10 updated version and it caused my Ubuntu 14.04 to be stuck on small resolution. Can anyone help me to fix this issue? I was read on the internet you can resolve this by installing the " insert guest additional image". When I do this it gives me an error message saying you cannot mount it this image or force it to mount . If I select force nothing really happens. I have downloaded the "guest image" to the vbox in guest account. but it doesn't let me install it cause I am not the su . I am new at Linux. Please advise what steps to take. Thanks   I fixed it 2 min ago see link below

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


I already set up a geoserver instance and add some raster stores to it. I want to use them as WMS service through different aplication like QGis and Autocad but when i try to add the WMS layer in QGis 2.18.13 i get this error:  Invalid Layer: WMS provider Cannot calculate extent Raster layer Provider is not valid (provider: wms, URI: IgnoreAxisOrientation=1&IgnoreGetFeatureInfoUrl=1&IgnoreGetMapUrl=1&contextualWMSLegend=0&crs=EPSG:32634&dpiMode=7&featureCount=10&format=image/png&layers=raster_utm:layer1_utm2&styles=&url=http://localhost:8080/geoserver/ows?version%3D1.3.0%26   This does not hapen in Qgis 3.0 or in Autocad map 2017. The EPSG used for the layer is 32634.

This works:   This does not (blank image):   Notice the 1.1.1 -> 1.3.0 and SRS->CRS are the only changes.  Is this a problem with the service or is my second URL incorrect?  I've observed the same issue with other WMS services:  Works:   Does not work (blank image):   So I'm assuming it's an issue with my 1.3.0 URLs.


How could I add a trend line to this plot? Many thanks!  \begin{tikzpicture}   \begin{axis}[     date coordinates in=x,     xtick=data,     xticklabel style=         {rotate=90,anchor=near xticklabel},     xticklabel=\day. \hour:\minute,     date ZERO=2009-08-18,% <- improves precision!   ]   \addplot coordinates {     (2009-08-18 09:00,  050)     (2009-08-18 12:00,  100)     (2009-08-18 15:00,  100)     (2009-08-18 18:35,  100)     (2009-08-18 21:30,  040)     (2009-08-19,        020)     (2009-08-19 3:00,   000)     (2009-08-19 6:0,    035) };   \end{axis} \end{tikzpicture}

Considering this code, I would like to know how to find the curve-fitting function passing through the first four points (i.e. X=[0,3]) and plot this function (e.g. the red dashed line in the desired output below).  \RequirePackage{luatex85} \documentclass{standalone} \usepackage{pgfplots, pgfplotstable} \pgfplotstableread{% X Y 0 0 1 1 2 4 3 9 4 12 5 15 }\datatable  \begin{document}     \begin{tikzpicture}     \begin{axis}[xmin=0,xmax=5,ymin=0,ymax=20]     \addplot [only marks, mark = *] table {\datatable};     \end{axis}     \end{tikzpicture} \end{document}     Desired Output


I tried this:    for(var i = 0x00; i <= 0x88; i++){     i = i.toString();     if (i.length === 1) {          i = "0" + i;     }     // console.log(i.length);     console.log(i);     // console.log(decodeURIComponent("%" + i)); }   but toString() will give the decimal representation.  So the above code is broken.

How do you convert decimal values to their hexadecimal equivalent in JavaScript?


I insert a table command between two itemized items, but the table appears at the top of the page. please help me locate this at the right place it means to be. thank you. Ardalan

I have a problem when a lot of figures are in question. Some figures tend to "fly around", that is, be a paragraph below, although I placed them before that paragraph. I use code:  \begin{figure}[ht] \begin{center} \advance\leftskip-3cm \advance\rightskip-3cm \includegraphics[keepaspectratio=true,scale=0.6]{slike/visina8} \caption{} \label{visina8} \end{center}\end{figure}   to place my figures. How can I tell latex I REALLY want the figure in that specific place, no matter how much whitespace will be left?


System Info:   Model Name: Lenovo ThinkPad 11e RAM: 4G Product Page:  Graphics and Driver Info:    00:02.0 VGA compatible controller [0300]: Intel Corporation Atom Processor Z36xxx/Z37xxx Series Graphics & Display [8086:0f31] (rev 0e)  Subsystem: Lenovo Atom Processor Z36xxx/Z37xxx Series Graphics & Display [17aa:2224]  Kernel driver in use: i915  Kernel modules: i915    App versions:   Google Chrome: Version 67 in both Ubuntu version(16.04 and 18.04) Mozilla Firefox: Version 60 in both Ubuntu version(16.04 and 18.04) Thunderbird: Version 52 in both Ubuntu version(16.04 and 18.04)   What happens:   I usually browse with multiple tabs open and suddenly the mouse and keyboard freeze and and I am forced to restart with the power button.  None of the shortcuts work once the system hangs. This happens almost every time I use the system.   Worst to Best:   Google Chrome - Hangs with just 3-4 tabs of YouTube open. Thunderbird - Hangs when present with lesser number of tabs (3-4) of Mozilla Firefox. Mozilla Firefox - Hangs with 8+ tabs present with heavy video or image  presence.   Things I have tried:   Re-installation   Current solution:  Got fed-up and downgraded to 16.04.4 which has been stable so far. Have been using 14.04 previously for many years with no issues.

All operating systems freeze sometimes, and Ubuntu is no exception. What should I do to regain control when...   just one program stops responding? nothing at all responds to mouse clicks or key presses? the mouse stops moving entirely? I have an    In what order should I try various solutions before deciding to pull the power plug?  What should I do when starting up Ubuntu fails?  Is there a diagnostic procedure I can follow?


How can I set new tab pages and browser startup pages to be blank in Chrome? The default page takes a while (5 - 10 seconds) to become usable. Not really a big deal, but annoying when browsing rapidly.  A couple more points:   I tried setting the startup webpage in Chrome settings, but this only affects the page displayed on browser startup, not pages displayed on new tab. I would rather not use extensions that merely clean the UI DOM after the page is initialized. The issue here is not visual display of the new tab page, but the delay in setting it up.   Many thanks in advance!

Does Google Chrome has anything similar to about:blank page in IE and Firefox? I did not find any suitable page mentioning this? PS: I tried about:blank but it looked like Chrome is trying to load something before showing blank page...


How can I delete the extra page created when using table of contents?  The page shows the name of the table of contents and the rest is empty.

My main file generate extra page before \tableofcontents with header title "Table of contents". How can I remove this page?  I am copying the main.tex file code for your reference.   \documentclass[twoside,12pt]{Classes/aesm_edspia}  \begin{document} \addtocounter{page}{-1} \makethese  \onehalfspacing \newpage\thispagestyle{empty}\addtocounter{page}{-5}   %depth in the table of contents and section numbering \setcounter{secnumdepth}{3} \setcounter{tocdepth}{3} \frontmatter  \pagestyle{fancy} \fancyhf{} \fancyhead[LE,RO]{Acknowledgements} \fancyfoot[RO]{\thepage} \fancyfoot[LE]{\thepage} \renewcommand{\headrulewidth}{0.5pt} \renewcommand{\footrulewidth}{0pt}  \pagestyle{fancy} \fancyhf{} \fancyhead[LE,RO]{Table of Contents} \fancyfoot[RO]{\thepage} \fancyfoot[LE]{\thepage} \renewcommand{\headrulewidth}{0.5pt} \renewcommand{\footrulewidth}{0pt}  \input{Abstract/Abstract}  \tableofcontents \listoffigures \listoftables   \mainmatter \pagestyle{fancy} \fancyhf{} \fancyhead[LE,RO]{Introduction} \fancyfoot[RO]{\thepage} \fancyfoot[LE]{\thepage} \renewcommand{\headrulewidth}{0.5pt} \renewcommand{\footrulewidth}{0pt}   \end{document}


First I just tried to install a software:  sudo apt-get install xvfb  It returns:  Err http://br.archive.ubuntu.com/ubuntu/ raring-updates/main xvfb amd64 2:1.13.3-0ubuntu6.2   404  Not Found [IP: 200.236.31.4 80] Err http://security.ubuntu.com/ubuntu/ raring-security/main xvfb amd64 2:1.13.3-0ubuntu6.2   404  Not Found [IP: 91.189.91.13 80] Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/x/xorg-server/xvfb_1.13.3-0ubuntu6.2_amd64.deb  404  Not Found [IP: 91.189.91.13 80] E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?   I just ran apt-get update and it returns a lot of 404 not found repositories from this same IP.   So I tried to update my system:  sudo update-manager -d   But it returns:  Failed to load repository information, check your internet connection.   What should I do?

Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc


Is it possible to find the hash algorithm used for a password given that you have the clear-text password and its hash?   The algorithm in question hashes the string 'password' to 'da0feea11db421a7be1173895497e71f', and there is no salt used.

First off, I know hashes are 1 way. There are an infinite number of inputs that can result in the same hash output. Why can't we take a hash and convert it to an equivalent string that can be hashed back to the original hash output?  eg:  string: "Hello World" hashed: a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e   unhash: "rtjwwm689phrw96kvo48rm64unc8oetb5kmrjiuh7h8huhi6dde5n5"         (a real string that gives the same hash as "Hello World") hashed: a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e    ...


I re installed MikTex and Vim LaTeX suite (for an unrelated reason) and now Vim doubles my double parentheses (or braces, etc.).   Usually if I type ( and the matching ), then I get ()<++> with my cursor inside the parentheses. After the reinstall if I type ( and the matching ) I end up with two pairs of parentheses. That is, I end up with ()()<++> with my cursor inside the second pair of parentheses.  Also, if I double type the caret ^, then I get ^^^{}<++> with my cursor inside the braces instead of ^{}<++> with my cursor inside the braces.  I don't know how to troubleshoot this. Is there a fix? I'm using the same _vimrc file (I'm on Win 8 Pro 64 bit).

I just installed the vim latex-suite plugin.  Whenever I type empty brackets, parentheses, or braces, I get an extra pair of them, and I am moved to the middle of the new pair and put into insert mode.    i.e. after typing  {}   I get  {}{}   with the cursor between the second pair of empty braces.  How can I disable this?


Which is correct? Members must use their own cards, or, members must use their own card?

The usage of singular and plural has always been confusing for me.   I often see sentences like these         People are using cell phones.   People are using a cell phone.      Does the first sentence mean everyone has a phone and they are all using their own?  Does the second sentence mean they are sharing one cell phone?   If I see a group of people holding a cell phone in their hand(s), <- even this is confusing for me, should I use the first sentence then?   Another example: you see two men, and both of them are carrying a bag. Which sentence should I say/use?        They are carrying backpacks          They are carrying a backpack      Could you please make it clear for me?


I am a python newbie and I keep seeing code like:  import numpy as np rng = np.random.RandomState(4)  # generate some random data to train on get_rand = lambda *shape: np.asarray(rng.rand(*shape) > 0.5, dtype='float32')   Is * referring a pointer ? Please help me in understanding what does * do here (I know C so I guess this looks like a pointer, but it can't be).

In the following method definitions, what does the * and ** do for param2?  def foo(param1, *param2): def bar(param1, **param2):


I have a working laptop with Ubuntu 18 LTS. I bought a newer Asus VivoBookX with Windows 10, for its greater disk capacity, planning to install Ubuntu 20LTS. For various reasons, that failed, and now it's not running either Windows or Ubuntu. I hope to re-instate the Windows, and start again from there. I have downloaded a Win10 ISO onto my working machine, and have a USB with 16GB emptied and ready, but am stuck on how to create the bootable drive. Balena Etcher spotted that it was Windows, doesn't want to handle it and recommends Rufus. For some reason I can't get Rufus to open on this machine - does it not run with Ubuntu? I'm not the first to ask a version of this question, but other replies I've seen here are very out of date, with comments that things have changed. I can follow basic instructions in small steps, but have very limited technical understanding! Thanks for any help.

I'd like to create a Windows bootable USB stick, but I don't have a Windows machine with me at the moment to do so. How could I achieve the same using Ubuntu?


I am trying to benchmark my hard disk and find the throughput in Mb/s and latency in milliseconds.  This is my code:  public class OneMB implements Timer { public static void main(String a[]) throws IOException {     OneMB oneMB = new OneMB();     oneMB.process();  } public void process() throws IOException{     RandomAccessFile randomAccessFile=null;     try{                     File file=new File("oneMByte.txt");         byte[] b=new byte[1024];         randomAccessFile=new RandomAccessFile(file, "rw");         randomAccessFile.setLength(1024*1024*10);         long endLatency=0;         int i=0;         long startWrite = this.getTimer();         randomAccessFile.writeBoolean(true);         endLatency=this.getTimer();                          for (i = 0; i < 1024*10*1024-1; i++) {             randomAccessFile.writeBoolean(true); //Writes a boolean to the file as a one-byte value.         }         long endWrite = this.getTimer();         randomAccessFile.seek(0);         randomAccessFile.readFully(b);         long endRead=this.getTimer();         double timeTaken=(endRead-startWrite)/1000000000.0;         double data=10.0;         double throughput=data/timeTaken;         double latency=(endLatency-startWrite)/1000000.0;//time for the reception of 1 byte         System.out.println(timeTaken);         System.out.println(data);         System.out.println("Throughput="+throughput+" Mb/s");         System.out.println("Latency="+latency+" ms");         randomAccessFile.close();         }         catch (Exception e) {             e.printStackTrace();             randomAccessFile.close();         } }  @Override public long getTimer() {     // TODO Auto-generated method stub     return System.nanoTime(); } }   I get the output as:  56.065550577 10.0 Throughput=0.17836264688538242 Mb/s Latency=0.057668 ms   I have a reasonably fast computer:   1 TB harddisk @ 5400 rpm Intel i7 with quad core @ 2.1 GHz 8 GB DDR3 RAM   Could someone tell me if the throughput would be that low or am I using a wrong approach?

A friend has asked me to perform maintenance oh his computer. The described symptoms point to a performance issue with the hard drive. I want to objectively confirm this suspicion by measuring the performance of his 5400 RPM disk.  Which tools would you recommend for this job? Are there any (published) standard guideline numbers that I could use for the purpose of comparing my findings?


I'm currently working on a class which writes Values into CmsXmlContent and saves them as a file. I've got many variables and it's working very well but one String seems to hate me... It returns a NullPointerException everytime.  I tried to wrote it but seriously I'm checking if the String is null AND printing it out with perfect results just a line above.  So hopefully you can help me out :)  Expose:  public class Expose {     private String address, bid, build, corridorNumber, corridorPiece, county,         floor, form, houseType, mark, number, partner, price, registry,         roofAngle, size, status, title, view, width;     private List<String> features, infra, location, media, region, use,         useType;     private List<byte[]> documents, images;     private List<ExposeAbsatz> paragraphs;      // getters and setters }   ExposeAbsatz:  public class ExposeAbsatz {     private String content, headline;     private byte[] image;      // getters and setters }   My Code:  Locale de = Locale.GERMAN; CmsXmlContent xmlContent = CmsXmlContentFactory.createDocument(cms,         de, "UTF-8", CmsXmlContentDefinition.getContentDefinitionForType(cms, "expose")); if (StringUtils.isNotEmpty(thisExpose.getTitle()))     xmlContent.getValue("/titel", de).setStringValue(cms,             StringUtils.stripToEmpty(thisExpose.getTitle())); // works if (StringUtils.isNotEmpty(thisExpose.getNumber()))     xmlContent.getValue("/properties/number", de).setStringValue(                     cms, StringUtils.stripToEmpty(thisExpose.getNumber())); // works as well if (thisExpose.getParagraphs() != null) {     int i = 0;     for (ExposeAbsatz currentExposeAbsatz : thisExpose.getParagraphs()) {     String headline = StringUtils.stripToEmpty(currentExposeAbsatz.getHeadline());         if (StringUtils.isNotEmpty(headline)) {             System.out.println("headline[" + i + "] = " + headline);             // headline[0] = aasd             // absatz is minOccurs="4" maxOccurs="5"             xmlContent.getValue("/absatz[" + i + "]/ueberschrift", de)                                 .setStringValue(cms, headline); // NullPointerException             (...)         }         (...)         i++;     } }

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


In a shell script, I'm processing, some addition process will print an output. If it is a single-digit one, then it has to add zero as a prefix. Here is my current script: c_year=2020 for i in {01..11}         do               n_year=2020             echo 'Next Year:'$n_year             if [[ $i == 11 ]]             then n_month=12             echo 'Next Month:'$n_month             else              n_month=$(($i + 1))             echo 'Next Month:'$n_month             fi             echo $date" : Processing data '$c_year-$i-01 00:00:00' and '$n_year-$n_month-01 00:00:00'"         done  The i value is in doule digit, but the n_month is still printing single digit. How do I set default shell output should return as double digit? Or any alternate way to solve this?


If a constant force is being applied to a body, without any other external forces, F = ma says that that body will accelerate at a constant rate. This acceleration will continuously increase the body's velocity. According to P = Fv, since the force is constant and the velocity is continuously increasing, the power required by the force will continuously increase. I understand all the maths, but am trying to get a better intuitive understanding of this. I cannot seem to come to terms with the fact that a constant force will need to supply an increasing power. What is this power being represented by, if the force is constant? What typical inner-workings of such a force would require its power to increase, even though its ultimate "output" is the same? What actually constitutes "power" and "force" at the "force-side" of things?

For a constant force, $P=Fv$. I understand the mathematical derivation of this, but this seems to me, intuitively, to be nonsense. I feel that my discomfort with this comes from a fundamental misunderstanding of force and Newton's Second Law, so I'm not really looking for any mathematical explanation. So, to begin:  How is it that a constant force does not add energy to a system at a fixed rate? Consider a rocket burning a fuel at a constant rate. The chemical potential energy should be converted to kinetic energy at a constant rate, that is, $(1/2)mv^2$ should be increase linearly. The magnitude of the velocity of the rocket would then increase at a less than linear rate, implying a nonconstant acceleration and therefore, a nonconstant force/thrust (F=ma).  If force is indeed a "push or a pull," shouldn't that constant rate of burning of fuel yield a constant "push or pull" as well? Clearly not, so I would have to think that, somehow, a given force applied to a certain object at rest would in some way be different than that a force of the same magnitude being applied to that same object in motion. In this sense, is force merely a mathematical construct? What does it tangibly mean, in physical terms? Would a given force acting upon me "feel" differently to me (in terms of tug) as I am moving at differing velocities?  Force being defined as a "push or pull," which is how it has been taught in my high school class, seems rather "handwavy," and maybe that's the issue. It's been troubling me for a couple of weeks and my teacher hasn't really been able to help, so thanks!


after fresh new installation of 16.04.1 the ubuntu software centre is empty  ... does not show any software at all !   and also  controls are missing   howto recover ?

After plain installation of Ubuntu 16.04 LTS gnome-software doesn't work. It has opened once with GUI, but installation of Unity Tweak Tool didn't finish.  When starting again, GUI doesn't come up. When opening from terminal, a warning appears, but the application GUI doesn't open.  $ gnome-software (gnome-software:7052): Gs-WARNING: failed to open plugin /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so: /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so: cannot open shared object file: No such file or directory   Does anybody have same experience, and eventually, a solution?    According to the recommendation:  $ dpkg-query -S /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so gnome-software: /usr/lib/gs-plugins-9/libgs_plugin_xdg_app_reviews.so   Proposed reinstall of gnome-software did not help.    As workaround, use Synaptic Package manager and command line.


I'm a very new ArcGIS user currently working on my first project regarding chemical spills on land.  The Background:  Software that I have to use is ArcMap.  Currently, I am trying to use the pour-point tool to delineate the flow path from a proposed spill/leak point of a chemical bearing pipeline.  So far I have used only the Hydrology Toolset and this is what I did in sequence...   Filling the LiDAR Data Generate Flow Direction Generate Flow Accumulation from the Flow Direction Delineate the drainage Basin and also turned it to polygon features to outline the flow accumulation passages. I created a new point shapefile and assume it as the "proposed leaking point" (Please view the hand drawn diagram below)   The problem:  Firstly I measure by estimating the distance of the "proposed leaking point" to the nearest flow accumulation line (12m). Then I run the snap-pour point tool with a little addition to the measurement (snap-distance: 15m). After it transforms the point shapefile of the "proposed leaking point" as a pour-point (as shown in blue in the diagram below) and snapped it to the nearest highest flow accumulation point... I then use the watershed tool..  However... This only delineates the whole stream (watershed) which contributes to the pour-point. This is not what I am looking for as it is not taking into account the "proposed leaking point".  The Question:  How do I get the delineation or the flow line of the chemical from the "proposed leaking point"?    ArcMap is not working so I had to draw this.  Edit: Additional Images   Image above shows the pour-point that creates a watershed of the contributing streams.   Image above shows where I would like the flow line to be if there is a leak at that point of the pipeline.

I am currently mapping Lahar flows on Montserrat Island (as many have done before!). I have the Cost Distance analysis below, the circle is the origin and the triangle the destination. With a known destination a Cost Path analysis can easily be performed, however I would like to use the Cost Distance map below to automatically find the destination point, based purely on the the direction of flow from the origin/circle.  I was thinking of using a filter to include only edge cells of the raster, and then find the one with the lowest value, is there a way to do this?  Software: Arc GIS Desktop 10.5


Is it possible for a wizard to research the magical spell within an item, thus learning how it's composed and legally copy it into his/her spellbook? After some discussion with people who have come with answers stating that it's not possible to learn spells from item which doesn't contain a written spell (like a scroll or a book /tome). I then wonder why it shouldn't be possible for the wizard to research the spell embedded into the magic item, trace the process backwards or just keep using the spell to gain an understanding of how it works and the magics that lies within.  ... For a real-world example, it's the difference between finding a recipe, and finding a cake. You can study the cake all you like, but you probably won't be able to bake one exactly like it unless you find the recipe somewhere. ... //anaximander  This guy definitely has a point, but then again, if you can taste the cake you can figure out what basic components are needed in it, especially if you were a pastry chef or something alike. Shouldn't that go for wizards as well? The reason I'm not satisfied with the given answers is because so far there hasn't been a specific rule stating that it's not possible, just hinting towards and suggesting. Now if we take the cake example and apply it to the wand, we try to backtrack the process of embedding a spell into a wand. How is that done? Is the spell written inside the wand and thus readable with some kind of divination magic maybe? Is there actually a good rule that helps my case (I want it to be possible, but if I get a solid proof that directly states it's impossible I'm accepting defeat) or is it just up to the DM to make a final decision? Summary: Can a wizard learn Magic Missile from the item Wand of Magic Missile? If yes/no, why/why not?  After having asked on the official  page, I've gotten the answer that it's not possible for a Wizard to learn a spell from a magic item the way I've described it. Here's the direct quotes from the person(s) I was in contact with.  The rules on page 114 of the Player's Handbook are pretty specific as far as to what you can use to copy down a spell. Generally, the rules do not support learning spells from magic items that perform similar roles. You are, however, more than welcome to work with your Dungeon Master on a house rule for this if you feel like it should function differently! The rules do only support written sources, as you indicated from that section. Something like a spellbook or a scroll would be able to provide the verbal incantations necessary for a spell, while an item may not necessarily do that. These are the means that are explicitly provided by the rules. Again, you are more than welcome to coordinate with your DM about a house rule!  We see that the major reason why my theory fell apart (sadly) was due to the wand not being able to provide the "verbal incantations necessary". So we can now all rest as the issue has fully resolved. The previous question can be found here:

I'm now wondering after googling for a while, what are the different sources a Wizard can learn his spells from? Is it only limited to scrolls and tomes, or can a Wizard learn spells from other magic items?  The following quotes are from the PHB, page 114 Your spellbook      You might find other spells during your adventures. You could discover a spell recorded on a scroll in an evil wizard's chest, for example, or in a dusty tome in an ancient library.      Copying a Spell into the Book   When you find a wizard spell of 1st level or higher, you can add it to your spellbook if it is of a level for which you have spell slots and if you can spare the time to decipher and copy it.      For each level of the spell, the process takes 2 hours and costs 50gp. The costs represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it. Once you have spent this time and money, you can prepare the spell just like your other spells.   The way this is worded and considering the few examples we're given, shouldn't it be possible to learn a spell from more than just written sources?  An example would be Wand of Magic Missile: would it be possible for a Wizard to learn the spell Magic Missile by studying the spell when used by the item and write down his research and thus learning how to use the spell on his own and eventually master it?


Let $(X_n)$ be a sequence of independent RVs that converges in probability to some RV $X$. Show that $X$ is constant a.e.  My attempt  So from definition of convergence I have:  $$\forall\epsilon>0 \:\:\:\mathbb{P}(|X_n-X|>\epsilon)\longrightarrow0$$  I think that there is some useful theorem that I don't know. Can anyone help? I mean just give me some tip, not necessarily full answer.

Let $X_n$ be a sequence of independent random variable which converges in probability to $X$. Prove $X$ is a constant.  Can someone give me a hint how I should go about proving this? I tried proving this by contradiction by saying $X$ taking 2 different values, but this can still still happen because $X$ is only almost surely constant.


I cannot change the color of the page number at right bottom. The setting applied to black but still be white, why?  How can I change the one to black??  ¥documentclass[dvipdfmx,11pt,notheorems]{beamer} ¥usetheme{Madrid} ¥usefonttheme{professionalfonts} ¥setbeamertemplate{frametitle}[default][left] ¥setbeamertemplate{navigation symbols}{} ¥setbeamercovered{transparent}  % Footer ¥setbeamertemplate{footline}[page number] ¥setbeamerfont{footline}{size=¥normalsize, series=¥bfseries} ¥setbeamercolor{footline}{fg = black, bg = black}   ¥usepackage{amsmath,amssymb} ¥usepackage{amsthm} ¥usepackage[T1]{fontenc}% ¥usepackage{textcomp}% ¥usepackage[utf8]{inputenc}% ¥usepackage{otf}% ¥usepackage{helvet}%  ¥begin{document}  ¥begin{frame}¥frametitle{test} ¥begin{block}{aaa} ¥begin{itemize} ¥item aaa ¥item bbb ¥end{itemize} ¥end{block}  ¥begin{exampleblock}{Example} ¥begin{equation*} ¥frac{¥pi}{2} =¥left( ¥int_{0}^{¥infty} ¥frac{¥sin x}{¥sqrt{x}} dx ¥right)^2 =¥sum_{k=0}^{¥infty} ¥frac{(2k)!}{2^{2k}(k!)^2} ¥frac{1}{2k+1} =¥prod_{k=1}^{¥infty} ¥frac{4k^2}{4k^2 - 1} ¥end{equation*} ¥end{exampleblock}  ¥begin{exampleblock}{Example} ¥begin{equation*} ¥frac{¥pi}{2} =¥left( ¥int_{0}^{¥infty} ¥frac{¥sin x}{¥sqrt{x}} dx  ¥right)^2 =¥sum_{k=0}^{¥infty} ¥frac{(2k)!}{2^{2k}(k!)^2} ¥frac{1}{2k+1} =¥prod_{k=1}^{¥infty} ¥frac{4k^2}{4k^2 - 1} ¥end{equation*} ¥end{exampleblock}  ¥begin{exampleblock}{Example} ¥begin{equation*} ¥frac{¥pi}{2} =¥left( ¥int_{0}^{¥infty} ¥frac{¥sin x}{¥sqrt{x}} dx ¥right)^2 =¥sum_{k=0}^{¥infty} ¥frac{(2k)!}{2^{2k}(k!)^2} ¥frac{1}{2k+1} =¥prod_{k=1}^{¥infty} ¥frac{4k^2}{4k^2 - 1} ¥end{equation*} ¥end{exampleblock}  ¥end{frame}   ¥end{document}

The following MWE does not print frame numbers with MacTeX 2017 (beamer v3.50, LuaTeX 1.0.4):  \documentclass{beamer} \usetheme{PaloAlto} %\beamertemplatenavigationsymbolsempty \setbeamertemplate{footline}[frame number] %\setbeamertemplate{page number in head/foot}[framenumber]  \begin{document} \begin{frame}   \frametitle{Test}   Bar \end{frame} \end{document}     But it works with TeXLive 2016 (beamer v3.41, LuaTeX 0.95.0):    Using setbeamertemplate{page number in head/foot}[framenumber] instead of \setbeamertemplate{footline}[frame number] does not help. How can I fix it?


I've come across this Topology layout a few times now and I'm wondering if its bad Topology or not. I know it's a quad, but it just feels distorted. Are there any downsides to it? If so, what should be the appropriate way to fix it.

For curved meshes I've often noticed that in my desperation to avoid tris, I tend to extrude the mesh in a way which creates these long rectangular quads:    In this case at least, the mesh is all quads, however the edge flow causes loopcutting to be awkward in some places:    I tried creating the same mesh with more even topology, however I found tris unavoidable. Maybe it was because I was starting with the long-quad mesh, but I also found myself using the knife tool for everything..    This makes loopcuts less necessary and easier to place in most cases, though the occasional tri does get in the way.  An annoying thing about the tris are the poles, though they aren't too noticeable in this particular case.    Both techniques seems to have their advantages and their disadvantages:    Which is considered "better", if any? Are there any better workflows for creating even topology with as few tris as possible? Or is there some trick I'm missing altogether?


When I highlight a bit of text using \colorbox, it prevents line breaking.  How does one give tex permission to break lines?  Example:  \documentclass{article} \usepackage{color} \begin{document} Lorem ipsum dolor sit amet, consectetur adipisicing elit, \colorbox{yellow}{Stop playing with latex and start writing your article!} tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. \end{document}     I'm sure the gut reaction will be to tell me to use such-and-such other method which already permits line-breaking.  By all means!  But resist the urge to do so while not answering my question :)

In  I've found the following amazing code to highlight text on several lines.  The problem is that code dosen't work well with formulas : for example, fraction using the mode display are partially out of the highlighting frame.   Here is the code with one content showing the problem.  \documentclass{article}     \usepackage{soul}     \usepackage{tikz}     \usetikzlibrary{calc}     \usepackage{amsmath}     \usepackage{xcolor}      \makeatletter         \newcommand{\defhighlighter}[3][]{%             \tikzset{every highlighter/.style={color=#2, fill opacity=#3, #1}}%         }          \defhighlighter{yellow}{.5}          \newcommand{\highlight@DoHighlight}{             \fill[                 outer sep = -15pt, inner sep = 0pt,                  every highlighter, this highlighter              ](                 $(begin highlight)+(0,8pt)$) rectangle ($(end highlight)+(0,-3pt)$             );         }          \newcommand{\highlight@BeginHighlight}{             \coordinate (begin highlight) at (0,0) ;         }          \newcommand{\highlight@EndHighlight}{             \coordinate (end highlight) at (0,0) ;         }          \newdimen\highlight@previous         \newdimen\highlight@current          \DeclareRobustCommand*\highlight[1][]{%             \tikzset{this highlighter/.style={#1}}%             \SOUL@setup             %             \def\SOUL@preamble{%                 \begin{tikzpicture}[overlay, remember picture]                     \highlight@BeginHighlight                     \highlight@EndHighlight                 \end{tikzpicture}%             }%             %             \def\SOUL@postamble{%                 \begin{tikzpicture}[overlay, remember picture]                     \highlight@EndHighlight                     \highlight@DoHighlight                 \end{tikzpicture}%             }%             %             \def\SOUL@everyhyphen{%                 \discretionary{%                     \SOUL@setkern\SOUL@hyphkern                     \SOUL@sethyphenchar                     \tikz[overlay, remember picture] \highlight@EndHighlight ;%                 }{}{%                     \SOUL@setkern\SOUL@charkern                 }%             }%             %             \def\SOUL@everyexhyphen##1{%                 \SOUL@setkern\SOUL@hyphkern                 \hbox{##1}%                 \discretionary{%                     \tikz[overlay, remember picture] \highlight@EndHighlight ;%                 }{}{%                     \SOUL@setkern\SOUL@charkern                 }%             }%             %             \def\SOUL@everysyllable{%                 \begin{tikzpicture}[overlay, remember picture]                     \path let \p0 = (begin highlight), \p1 = (0,0) in \pgfextra                     \global\highlight@previous=\y0                     \global\highlight@current =\y1                     \endpgfextra (0,0) ;                     \ifdim\highlight@current < \highlight@previous                         \highlight@DoHighlight                         \highlight@BeginHighlight                     \fi                 \end{tikzpicture}%                 \the\SOUL@syllable                 \tikz[overlay, remember picture] \highlight@EndHighlight ;%             }%             \SOUL@         }     \makeatother   \begin{document}  Lorem ipsum \highlight{dolor sit amet, consectetur adipis-icing elit, sed do eiusmod tempor} incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation \highlight[red]{ullamco $laboris$ nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit} in voluptate velit esse cillum dolore eu fugiat nulla pariatur.  Excepteur sint occaecat \highlight[green, draw=blue]{cupidatat non proident  $\dfrac{789}{7889}$ % The frame is not good for that formula ! suntinculpaquiofficiadeseruntmollitanimidestlaborum. Loremipsumdolorsitametconsecteturadipisicingelitseddoeiusmodtemporincididuntutlabore-etdoloremagnaaliqua.} I suppose I could write some more text here.  \end{document}     Is someone could help me to fix it?


My spellchecker insists on replacing "furthest" with "farthest". I was under the impression that farthest is strictly speaking in terms of distance, whereas furthest is more abstract.   gives the following example:     The further [quantity] you walk, the farther [distance] you get.   What gives?

I know I learned the difference between the usage of farther and further in school, but I can never remember where each one should be used.  Can someone help me out here?


i have just a little problems with my DOM after append but i don't know how resolve it  i look several post but with the mouseup and mousedown i did nt find  this my function    $(function() {     var action;     $(".number-spinner button").mousedown(function () {         btn = $(this);         input = btn.closest('.number-spinner').find('input');         btn.closest('.number-spinner').find('button').prop("disabled", false);          if (btn.attr('data-dir') == 'up') {             action = setInterval(function(){                 if ( input.attr('max') == undefined || parseInt(input.val()) < parseInt(input.attr('max')) ) {                     input.val(parseInt(input.val())+1);                 }else{                     btn.prop("disabled", true);                     clearInterval(action);                 }             }, 50);         } else {             action = setInterval(function(){                 if ( input.attr('min') == undefined || parseInt(input.val()) > parseInt(input.attr('min')) ) {                     input.val(parseInt(input.val())-1);                 }else{                     btn.prop("disabled", true);                     clearInterval(action);                 }             }, 50);         }     }).mouseup(function(){         clearInterval(action);     }); });   and this is my append code      $("#dispostock"+cpt).append('
  <button class="btn btn-default btn-info" data-dir="dwn">  </button><input type="text" class="form-control text-center" value="1" min="-10" max="40"> <button class="btn btn-default btn-info" data-dir="up"> </button>
');   the class of dispostock is .dispostock  thanks in advance

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


I want to format some text in a React app, and for some reason, the whitespace is getting removed. For example, if I have I class with the render method   render() {      return (

{"average time: " + 5}

{"best    time: " + 1}

); }   then the rendered output removes the spaces I have in the second line, yielding an output that looks like   average time: 5 best time: 1   However, I want the output to look like   average time: 5 best    time: 1   How do I achieve that?   Elsewhere, I read that adding a className with display: block would fix this, but that did not help. Specifically, I tried this:  render() {      return (

{"average time: " + 5}

{"best    time: " + 1}

); }   where the css file has   .stats_entry {   display: block; }   EDIT:   Per suggestion, I tried changing the css to   .stats_entry {   white-space: pre; }   but this did not fix the issue.  EDIT:   wrapping the text with pre solved the issue:  render() {      return (

{"average time: " + 5}

{"best    time: " + 1}

); }

I have long recognized that any set of whitespace in an HTML file will only be displayed as a single space.  For instance, this:
Hello.        Hello. Hello. Hello.                       Hello.
   displays as:  Hello.        Hello. Hello. Hello.                       Hello.  This is perfectly fine, as if you need multiple spaces of pre-formatted text you can just use the
 tag.  But what is the reason?  More precisely, why is this in the specification for HTML?


I installed Ubuntu 18.04 LTS on my desktop in drive D. My desktop has Window 10 installed on Drive C.   I deleted the Ubuntu OS from my D drive uisng window 10 disc management where I delete the drive D and make a new volume D again.   But when I press the F11 key upon restart, its still showing me the options to choose the OS like Windows and Ubuntu.   Can you please help me how to get rid of this option when I press F11.   My desktop Motherboard  is of MSI Brand.   I am attaching the picture when I press the F11 keys.

I wish to remove Ubuntu and I'm not quite sure how. I know it has something to do with partitions. I have 3 partitions. 1. OS [683 GB]  2. Recovery [14 GB] 3. Ubuntu 12.04 LTS (E:)  I know it says Ubuntu but when I installed Ubuntu I think I put 14 gigabytes for it so I think its the recovery one but I'm not sure. I could have sworn I put more than 700 megabytes for it.  I have googled this and I can't seem to find an answer. Any help would be nice.


I understand the answer to this question is that it entirely depends on the data set.  However, this does not help people understand if their model is suitable or whether they should explore other variables.  So I am attempting to getting this question answered by people with experience in different fields where statistics is applied.   Assuming the model was not overfit and no other problems existed with the model, what I would like to know from someone experienced is the vastly different projects they worked on from very different industries and R^2 they obtained from their models so that people may gain a 'feel' whether they are heading in the right direction.  This question is of a highly atypical format so let me know if this is inappropriate for this website and I will remove it. Any suggestions on where to post this will also be appreciated.

I was skimming through  by Cosma Shalizi (in particular, section 2.1.1 of the ), and was reminded that you can get very low $R^2$ even when you have a completely linear model.  To paraphrase Shalizi's example: suppose you have a model $Y = aX + \epsilon$, where $a$ is known. Then $\newcommand{\Var}{\mathrm{Var}}\Var[Y] = a^2 \Var[x] + \Var[\epsilon]$ and the amount of explained variance is $a^2 \Var[X]$, so $R^2 = \frac{a^2 \Var[x]}{a^2 \Var[X] + \Var[\epsilon]}$. This goes to 0 as $\Var[X] \rightarrow 0$ and to 1 as $\Var[X] \rightarrow \infty$.  Conversely, you can get high $R^2$ even when your model is noticeably non-linear. (Anyone have a good example offhand?)  So when is $R^2$ a useful statistic, and when should it be ignored?


I have a Lenovo G510, running Windows 10 Home 32-bit, and 4 GB RAM, but on the Task manager it shows that I can use only 1.5 GB of it.  In order to speed up my computer and free ram, I've downloaded Wise Memory Optimizer, and it shows that I can use only 2.5 GB.  So, how much RAM can I really use? And if it less than 4 GB, then how can I use really 4 GB?

I recently upgraded my computer's RAM to 4 GB. My 32-bit Windows installation shows only 3574 MB of the memory. How can I make Windows use the full amount of RAM?


I was trying to make a bootable usb stick but i accidently formatted my 1TB hard disk. Is there a way to recover my files. The command that i used for formatting my disk   sudo dd if=ubuntu-gnome-15.10-desktop-amd64.iso of=/dev/sdc bs=1M

I'm an idiot, I was writing an image to a USB drive using dd when instead of typing /dev/sdb I typed /dev/sdd and wrote the 135mb image to my 750gb External Hardrive full of files. Is there ANY possibility of recovering the files or did dd completely zero out the drive? Please help, as this is one of the lowest points of my life EVER.  dd finished writing the 135mb image in 5 seconds, so I didn't have a chance to stop it. By the time I knew what happened to was too late. The command was as follows:   sudo dd if=generic.img of=/dev/sdd bs=1M   EDIT2: The External Harddrive's filesystem was FAT32(I've had the drive for awhile and FAT32 was the most Universal FS at the time). I also have a 2TB drive I just got which I was planning on moving most of the files to from the 750gb, If needed I can use it to transfer the Recovered files to.


I recently found this series and the result: $$   \sum_{k=1}^{\infty}{\frac{((k-1)!)^2}{(2k)!}} = \frac{\pi^2}{18} $$ However I'm not able to justify why. Is there a special function (zeta, beta) that I don't know and that may help? Thank you

I've been trying to prove, by arithmetical means, that  $$\sum_{k=1}^\infty \frac{((k-1)!)^2}{(2k)!} =\frac{1}{3}\sum_{k=1}^{\infty}\frac{1}{k^{2}}$$  without success.  When I say "by arithmetical means" I mean to say, go from the left to the right expression just by symbolic manipulation.  Can anyone devise a way of doing this?


Can somebody explain what's the difference between these two terms? This answer  contradicts with what I found on the internet:  CPU is essentially a microprocessor, not all microprocessors are CPUs.  vs  A microprocessor is essentially a processor that happens to be on a chip (or a small number of chips), as opposed to one made from a large number of individual components.  in the answer. As far as I understood, MPU contains in it CPU + additional stuff, specific to its purpose. GPU is a MPU, even a sound card is a MPU. CPU itself is used when we refer to the main processor of the computer. Am I right? Also, I've found this image:

What is the difference between CPU and Microprocessor?


When Rutherford proposed his model of atom, he mentioned that "Nucleus is surrounded by electrons that move around the nucleus with very high speed in circular paths called orbits. James Maxwell contradicted this with his theory of electromagnetic radiation which stated "Charged particles, when accelerated, should emit electromagnetic radiation". In Schrodinger's model of atom, the electrons move around the nucleus within a permissible zone.   The question is that even in the latter case, the electron is moving around the nucleus in undefined paths, which means that the electron is an accelerated, charged particle. How in this case electromagnetic radiation is not given out by it? It is just stating that electrons do not lose energy while moving around the nucleus. What is the actual reason for the electron not losing the energy in form of electromagnetic radiation?

I'm having trouble understanding the simple "planetary" model of the atom that I'm being taught in my basic chemistry course.   In particular,    I can't see how a negatively charged electron can stay in "orbit" around a positively charged nucleus. Even if the electron actually orbits the nucleus, wouldn't that orbit eventually decay?  I can't reconcile the rapidly moving electrons required by the planetary model with the way atoms are described as forming bonds. If electrons are zooming around in orbits, how do they suddenly "stop" to form bonds.     I understand that certain aspects of quantum mechanics  to address these problems, and that there are  of atoms. My question here is whether the planetary model itself addresses these concerns in some way (that I'm missing) and whether I'm right to be uncomfortable with it.


Which of the following is correct? If both are acceptable which is preferred?  Our product lets you manage all of your stuff in one easy place. Our product lets you manage all of your stuff in one, easy place.

You can also contact me to customize your template, or create a new unique one.   Do I need to put a comma between the new and unique adjectives in this sentence?  In my native language (if I am not mistaken) we don't put a comma if the adjectives are of a different type. Not sure about English though, and if it's the case here anyway. Any help would be appreciated!


Show that $n_0 = 32$ is the smallest value of $n$ for which the equation $5x+9y=n$ has a solution in $(\mathbb N \cup \{0\})^2$ for all $n \geq n_0$. Wouldn't $(x,y)=(1,1)$ be a valid solution for $n=14$? The example that appears before this question consider $(x,y)=(1,1)$ as a solution for $3x+5y=n$ in $(\mathbb N \cup \{0\})^2$ for $n \geq 8$.

I am asked to prove that:       For integers $n, x,y > 0$, where $x,y$ are relatively prime,        every $n \ge (x-1) (y-1)$ can be expressed as $xa + yb$, with nonnegative integers $a,b \ge0$.   How should I approach this? I have very limited knowledge in number theory.


I have a toy for my son, it's great but it flies round and round in the dark,  I was thinking of sticking an LED on it like we used to do at school - back then LED's were rubbish but they had long legs and were designed for electronics and soldering - I am 43 now - but I remember we had to calculate the resistance put in a resistor and then it wouldn't blow the LED .. we made a fuse tester back then..  since then LED's have changed markedly.. but is there still a "brand/family" of LED .. a single stand LED... that will plug straight into a 1.5v AA without blowing that comes with REALLY long wire legs so I can solder it direct to the terminals of the AA battery in series, and fit it into the battery enclosure simply by putting the battery cover on top of it? and do they still come with thin stiff wire long metal legs that can be bent, hold a shape and remain put?  OR. If I need a resister in series what is the resistor I need can someone help me calculate?  and also, they are still a diode, are they forgiving of the polarity or will they blow if placed the wrong way round?

I have a simple circuit:    The max rating (current) of the LED is 30mA.  How can I work out what the resistance of the resistor needs to be? By using ohm's law I found it to be \$3V/0.03A = 100 \Omega\$. However using software called , and trial and error I got the minimum possible resistance to be 36Ω. However, if I use a 35Ω resistor, then the LED breaks. Is the software wrong, or (more likely) am I doing something wrong?


I set up my CRM on-premise. Within CRM set up sync to Google Calendar.  A manual test run within the CRM demonstrates that sync is working. The CRM implementation guidelines state the following: For Unix/Linux systems, as a root user, edit the crontab file in /etc, and add an extra line at the end The documentation provides a sample and explanation below: */5 * * * * <username> cd </srv/www/vhosts/1crm>; </usr/bin/php> scheduler.php  where <username> is the username that the web server runs as (usually defaults to 'apache' or ‘wwwrun’), and where </srv/www/vhosts/1crm> is the path to your 1CRM directory, and where </usr/bin/php> is the path to your php executable file. I figure how to edit as root or enter crontab e -u root in Konsole of Kubuntu. I modify the above as follows: */5 * * * * www-data cd /var/www/1crm; /usr/bin/php7.4 scheduler.php  And gained no result, so what am I missing? Did I get the user wrong or should it be just PHP, or is it picking up the right scheduler.php (presumably the one in the crm directory).  How do I test a cron job, for that matter?  Right now, I am going in the crm and checking if calendar new test calendar items got sync, from google calendar to the crm calendar.

I did edit /etc/crontab using corntab -e. I have only one entry  After save contab is not created despite the message.  To be honest I have no idea what to do. I simply want to create a simple daily job. Second question. How can I change the editor for crontab -e?


Recently upgraded to High Sierra, Trackpad only searches for bluetooth trackpad,  And shows "No trackpad found".  My trackpad functions very well and it's not defective so it's not a hardware issue, I can see the relevant information of my trackpad in system information.  I want to edit settings for my 13" 2011 Macbook Pro internal trackpad/touchpad.  On Sierra I had:    Now on High Sierra I have:    System Information: (Taken from Sierra)    System Information: (Taken from High Sierra)    My Mac:

The trackpad on my Macbook Pro of 2 years has suddenly stopped working out of blue.  The trackpad doesn't move, respond to any gestures nor do any clicks work. This is really frustrating as I used gestures a lot to navigate around my laptop, and even though I use a bluetooth mouse it makes using my laptop unnecessarily laborious.  Does anyone know what may be causing the problem, and any solutions?


Generics are used to decouple logic from data type.   public class Calc<T> {    public T Add(T a, T b)    {        return (a+b);    } }   But this is throwing the below compile time error  Operator + cannot be applied on type T.  I am not understanding why so. because if it allows from main.cs  main() {      Calc<int> obj = new Calc<int>();      int c = obj.Add(10,20); }   Can somebody please explain why I am getting Build errors??

What would I do if I want to have a generic method that only accepts types that have overloaded an operator, for instance the subtraction operator. I tried using an interface as a constraint but interfaces can't have operator overloading.   What is the best way to achieve this?


For latest TensorFlow version 2.4 the Nvidia CUDA toolkit is required in version 11. However, the official Ubuntu repo does only include CUDA toolkit version 10: $ sudo apt install nvidia-cuda-toolkit Reading package lists... Done Building dependency tree Reading state information... Done nvidia-cuda-toolkit is already the newest version (10.1.243-3). 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.  I know one can install CUDA (toolkit) directly from Nvidia deb packages, but I would rather stick to the official Ubuntu repo, if possible. Is there any estimation when the latest CUDA toolkit version 11 will be released in the official Ubuntu repo?

Why are packages in the official Ubuntu repositories older than the latest (upstream) versions from Debian Sid, PPAs, the authors, etc.?


I've recently gone into developing with AngularJS. It's confusing to me the different between these two:   $scope.myScope = function () {   var x = 'do something with variable here';  $scope.anotherScope = x; };   and   function myFunction () {  var x = 'do something with variable here';  $scope.anotherScope = x; }   They both seem to be able to do the same thing (I use them a lot inside controllers). Is there a best practice for when and where to use these two?

I've recently started maintaining someone else's JavaScript code. I'm fixing bugs, adding features and also trying to tidy up the code and make it more consistent.  The previous developer used two ways of declaring functions and I can't work out if there is a reason behind it or not.  The two ways are:  var functionOne = function() {     // Some code };     function functionTwo() {     // Some code }   What are the reasons for using these two different methods and what are the pros and cons of each? Is there anything that can be done with one method that can't be done with the other?


While I write a draft, I would like to:  Have a hyperlink, say on the very right lower corner of every page's margin, with some symbol (e.g. a visible large red asterisk). Have this hyperlink to bring me back to the table of contents when I click it.  I assume this type of customization is probably more common in the beamer class. In presentations, presenter goes back and forth, say between the current slide and appendix. How would I do this in Article class? I am a newbie, so please help! Thank you in advance...!

I thought that someone must have asked this, but my searches didn't find it.  I am looking to refer back to the table of contents from places in my document. How can I do this?


I'm very new with LaTeX. My setup is as follows:  \documentclass{llncs} \usepackage{makeidx} \usepackage{listings} \usepackage{graphicx} %the above just for the case that it is relevant to the problem  \section{Introduction}  FIRST PARAGRAPH  SECOND PARAGRAPH  THIRD PARAGRAPH  Nth PARAGRAPH  \section{Next-Section}   Between each paragraph I got just one blank line. Let every paragraph be the sentence "Nth blue bird." The problem now is that the output is formatted like so:  First blue bird     Second blue bird      Third blue bird      Nth blue bird.   I.e. the second paragraph is just indented as I want it to be. But every consecutive paragraph is not only indented but also has a blank line inserted before.  Note that if I shorten the third paragraph the problem vanishes. (I did not check though if shortening of other paragraphs yields the same result).  Any idea? (Impeding deadline; Quick help is highly appreciated)

I have a problem. I have several large equations within the text. And when LaTeX does not manage to put the equation on the same page and moves it to the next one, he spreads the paragraphs of the text in the first page. How could I prevent this? I know about \pagebreak and \newpage, but I do not want to force the \newpage, as the text may move (if I add something later or so on) and the pagebreaks may not be valid. I would like to make LaTeX not to spread the paragraphs over a page automatically. Is it possible?  I tried to make an example:  \documentclass[a4paper,12pt,twoside]{book} \usepackage{amsmath} \begin{document}  LaLaLa\\\  LaLaLa\\\  LaLaLa\\\  LaLaLa\\\  \begin{eqnarray} 123&+&123 \\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ \end{eqnarray}  LaLaLa\\\  LaLaLa\\\  \begin{eqnarray} 123&+&123 \\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ \end{eqnarray}  \end{document}


I have a Python script that needs to accept the "greater than" character > as a command-line argument. python myscript.py -f "VALUE>100"  However, even if I wrap that argument in double-quotes, python is still parsing that character as a redirect operator. I checked it through the Python debugger in VS Code and it shows that the > character and succeeding characters are not included in argv.  Is there a workaround for this? My OS is Windows and I'm using cmd.

I need to echo a string containing angle brackets (< and >) to a file on a Windows machine.  Basically what I want to do is the following: echo some string < with angle > brackets >>myfile.txt  This doesn't work since the command interpreter gets confused with the angle brackets.  I could quote the whole string like this: echo "some string < with angle > brackets" >>myfile.txt  But then I have double quotes in my file that I don't want.    Escaping the brackets ala unix doesn't work either: echo some string \< with angle \> brackets >>myfile.txt  Ideas?