Current equations describe everything pretty well but there are some issues considering inflation, quantum gravity, black holes,... How would we be able to verify that these do not evolve over long time periods, say several centuries? How would we describe someting like this? What would be the implications?

Hubble's constant $a(t)$ appears to be changing over time. The fine stucture constant $\alpha$, like many others in QFT, is a running constant that varies, proportional to energy being used to measure it. Therefore, it could be agued that all running constants have 'evolved' over time as the Universe has expanded and cooled. Both the local and global curvature of the Universe changes over time implying that so too does the numerical value of $\pi$. All these things are however constants (well, let's say parameters since they are not really 'constant'.)   In  with astronomer Sir Fred Hoyle, Feynman said "what today, do we not consider to be part of physics, that may ultimately become part of physics?" He then goes on to say "..it's interesting that in many other sciences there's a historical question, like in geology - the question how did the Earth evolve into the present condition? In biology - how did the various species evolve to get to be the way they are? But the one field that hasn't admitted any evolutionary question - is physics."  So have the laws of physics remained form-invariant over the liftetime of the Universe? Does the recent understanding of the aforementioned not-so-constant constants somehow filter into the actual form of the equations being used? Has advances in astronomical observations, enabling us to peer back in time as far back as the CMB, given us any evidence to suggest that the laws of nature have evolved? If Feynman thinks that "It might turn out that they're not the same all the time and that there is a historical, evolutionary question." then this is surely a question worth asking.  NB/ To be clear: this is a question concerning purely physics, whether the equations therein change as the Universe ages, and whether there is any observational evidence for this. It is not intended as an oportunity for a philosophical discussion.


I have the following code in my php file:           session_start();         include "connect.php";         if (isset($_POST['email']) && isset($_POST['password'])) {             $email = htmlspecialchars(mysqli_real_escape_string($conn, $_POST['email']));             $password = htmlspecialchars(mysqli_real_escape_string($conn, $_POST['password']));           function process() {              include "connect.php";             if  (isset($_POST['email']) && isset($_POST['password'])) {                 $email = $_POST["email"];                 $password = $_POST["password"];             }              mysqli_select_db($conn, "users");             $sql = "SELECT * FROM users WHERE email='$email' AND password='$password'";             $result = mysqli_query($conn, $sql);             $count = mysqli_num_rows($result);              if ($count >= 1) {              $_SESSION['id'] = $id;             $_SESSION['email'] = $email;             $_SESSION['password'] = $password;             header('location:index.php');     } else {         echo "Email/Password is incorrect";     } }         if ($email != "" or $password != "") {             if (isset($_POST['submit'])) {                 process();             } else {                 echo "Error: " . mysql_error();             }  } }   How would I go about preventing sql injection in my login page? I searched on the internet and most sites said I must use the mysqli_real_escape_string() function, but this did not seem to change things at all when I used the sql injection in my site again. please help :)

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


I am trying to implement Junit test using Spring boot I have written some simple test when I am running the ApplicationTests.groovy as junit test it showing green color bar when the test is successful and red upon errors but it is not displaying any output I am getting empty stack trace upon successful test methods though I am using assert.  import org.junit.Test import org.junit.runner.RunWith import org.springframework.beans.factory.annotation.Autowired import org.springframework.boot.test.SpringApplicationConfiguration import org.springframework.test.context.junit4.SpringJUnit4ClassRunner import org.springframework.test.context.web.WebAppConfiguration import org.junit.Assert.*; @RunWith(SpringJUnit4ClassRunner) @SpringApplicationConfiguration(classes = Application) @WebAppConfiguration class ApplicationTests {      @Test     void testAssertions() {         assertTrue(1 == 1)         assertEquals("test", "test")          def x = "42"         assertNotNull "x must not be null", x         assertNull null          assertSame x, x     }   }

I'd like to have it yell hooray whenever an assert statement succeeds, or at the very least have it display the number of successful assert statements that were encountered.  I'm using JUnit4.  Any suggestions?


The print-screen short-cut is set to be the Print-screen button, but when I press on it, it does not work. Any clues?  Any help will greatly be appreciated  Thank you

I'm unable to use my print screen button in Ubuntu 14.04. No effect pressing print screen. Screen-shot application works if it's launched manually.  PS: Still does not work perfectly neither in 15.04


I program using Perl and need to install Unicode String. But make install tells me:      Files found in blib/arch: installing files in blib/lib into   architecture dependent library tree   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!   ERROR: Can't create   '/Library/Perl/5.16/darwin-thread-multi-2level/Unicode' mkdir   /Library/Perl/5.16/darwin-thread-multi-2level/Unicode: Permission   denied at /System/Library/Perl/5.16/ExtUtils/Install.pm line 494.      !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!   at -e line 1. make: *** [pure_site_install] Error 13   Does anyone ever encountered this problem?

Here is my situation: I know almost nothing about Perl but it is the only language available on a porting machine. I only have permissions to write in my local work area and not the Perl install location. I need to use the  Perl module from CPAN   How do I use this Parallel::ForkManager without doing a central install? Is there an environment variable that I can set so it is located?  Thanks  JD


I am from South Africa and we are currently having what our main energy supplier is calling loadshedding. Basically various municipalities have their electricity cut at relatively random times to lift the load. The news did not report any shedding for today, but as I finished making my banana loaf batter, the power went out. It will be out for anything between 1 and 6 hours. Do I leave the batter out while waiting or in the fridge? Contains baking powder, butter and eggs, so my questions are: Will putting the batter in the fridge for that amount of time effect the outcomes of the baking? We are in Africa, so atmospheric temperatures are high, about 36 Celsius today. Is it more risky to leave the batter out, in terms of food poisoning, or in the fridge in terms of outcomes of the baking?! 😂 Also: had I already put the baking in the oven, what would have been the best course of action? Take out and wait, put in fridge or leave in oven? (recipe asks for 50 minutes in the oven)

If I left food out of the refrigerator for some period of time, is it still safe? If I left it out too long, can I salvage it by cooking it more?


I am a new user of Ubuntu. What command can I use to install something using the terminal?

How can I install applications like Google Chrome on Ubuntu?  Are there any commands to install an application?    Index of answers:


I'm having more difficulty to translate a simple filter builder to my users, with the conditionals:   "and", "or" and "(" , ")"  With based in this, I created this version:     I would like to create anyone that were simpler.  But in this model, I didn't create this conditional:   Process is equal X   AND     (             Status is equal  Canceled         OR             Status is equal Working     )  Could anyone help me?

I'm interested to know how people have, or would construct an interface which simplifies constructing logical boolean conditions? (Yes, it's a database query builder) In my mind a bad interface has them typing lots of AND, NOT IN, OR keywords etc. Or else has a million combo boxes.  I'm wondering if anyone has a good example I could glean ideas from? Or some suggestions?  At the moment I'm considering a split screen with a grid for composing the query and a canvas to display a visual representation of the sets of conditions and how they overlap etc. Like a Venn Diagram. This still gives me a problem with the usability/intuitiveness of the controls on the grid.  EDIT:  I'm very interested in ideas which simplify it for less technical users. However, ideas for a version of the UI for advanced users are very helpful as well.


I have 25 different polygons as show in fig. below. These small  polygons can form a bigger polygon without overlaps.     My goal is, according the data of 25 smaller polygons, to generate the bigger polygon that only keep its outside boundary.  Now I have selected the 25 polygons and saveas another file, but the innner lines are also included.   I have tried the layer-property-symbol level method, but there is no such button in my .shp file. I have no idea why.

Given polygons - like landcover in OpenStreetMap or street areas in cadastre - how can one suppress those polygon boundaries which are shared by objects (features) of same type in QGIS (see figure below)? AFAIK there exists no such symbolization rules in QGIS 2.6 (yet). It doesn't seem useful to aggregate (union) the geometries. But preprocessing could still be an approach, like splitting the common boundaries first, then "suppressing" these when rendering. Any ideas?


Let $A = K[x,y]/\langle y^2-x^3\rangle$. Show that $A$ is isomorphic to the subring of $K[T]$ generated by $T^2$, $T^3$.   I tried to show a map from $\phi : A \to K[T]$ which sends $x \to T^2$ and $y \to T^3$ is an isomorphism. But couldn't prove it.  Can anyone help me out?    Also,     Show that fraction field of $A \cong K(T)=$ (field of rational functions in $T$) .

How to prove that the ideal $I=(x^3-y^2)$ in $k[x,y]$ is prime?    I have constructed a map from $k[x,y]$ to $k[t]$, which maps $x$ to $t^2$, and $y$ to $t^3$. Then, I want to show that the kernel is exactly $I$. But the difficulty is that how to prove the kernel is contained in $I$.  Could you help me? Thanks a lot!


Upgraded to Ubuntu 16.4 and lost half years work, is it possible to go back to Ubuntu 14?

I just installed a new version of Ubuntu and I want to roll it back to the previous version.  How can I do that? Is that even possible?


Step by step solution would be very appreciated, I know I can use l'hopital rule but can someone explain it to me? Thanks!

I am lost in trying to figure out how to evaluate the $$\lim_{x\to 0} \frac{1-\cos(4x)}{\sin^2(7x)}.$$  So far, I have tried the following:  Multiply the numerator and denominator by the numerator's conjugate $1+\cos(4x)$, which gives $\frac{\sin^2(4x)}{(\sin^2(7x))(1+\cos(4x))}$. However, I am not sure what to do after this step.   Could anyone please help point me in the right direction as to what I am supposed to do next?  All help is appreciated.


I've a laptop on which Windows 10 Home Single Language 64-bit Operating System is installed.  I've installed the web browser 'Firefox Quantum 63.0 (64-bit)' on this laptop.  Then, I installed the web browser 'Firefox Developer Edition 64.0b4 (64-bit)' on this laptop.  I downloaded the 'Firefox Developer Edition 64.0b4 (64-bit)' installer file from the web browser 'Firefox Quantum 63.0 (64-bit)' and started the installation process by clicking on the downloaded installer file.   During the installation process only a dialog box appear having the below message :     Firefox is already running, but is not responding. The old Firefox   process must be closed to open a new window.   Then I closed the web browser 'Firefox Quantum 63.0 (64-bit)' and then the installation of web browser 'Firefox Developer Edition 64.0b4 (64-bit)' got done.  Also, when I open one of the both browsers and then try to another browser the dialog box with the same message appear, I've to close the opened browser and then the other browser can be opened.  Few days ago, this was not the problem on my laptop. I was able to use both the Firefox browsers at the same time on my laptop. But, I don't know why and how this problem suddenly started.  For your reference below is the    Locations of the .exe files at which both of these browsers are installed are as below :   'Firefox Quantum 63.0 (64-bit)' : "C:\Program Files\Mozilla Firefox\firefox.exe" 'Firefox Developer Edition 64.0b4 (64-bit)' :  "C:\Program Files\Firefox Developer Edition\firefox.exe"

I am running SysInternal's  and FireFox 3.6.2. I have noticed that while I can have Internet Explorer 8 open in multiple virtual desktops, you can not do the same with Firefox. If you try you get the error message:     Firefox is already running, but is not   responding. To open a new window, you   must close the existing Firefox   process, or restart your system.   I did a little digging around to work around this and came up with creating a second profile via the Firefox profile manager (accessed by starting Firefox with the "-p" switch). This unfortunately created a new problem which is my add-ons (of which I use many) do not stay synchronized between profiles.   Is there a better approach here?


Are the following linear independent?  If S $=$ {$a, b, c$} $⊆ R^3$, where $(2,3,4)$ $∉$ span {$a, b, c$}.  If S $=$ {$a, b, c$} $⊆ R^3$, where $(1,2,3)$, $(1,3,2)$, $(2,1,3)$, and $(0,1,0)$ $ϵ$ span {$a, b, c$}.  If $S = (u + v, u - v, u - 2v + w) ⊆ R^n$, where $(u, v, w) ⊆ R^n$ is a linearly independent set.    My thoughts: From what I know, linear independent means there is only one solution. As for question 1, what i understood by this $(2,3,4)$ $∉$ span {$a, b, c$} is that $$(2,3,4) ≠ \lambda_{1} a + \lambda_{2} b + \lambda_{3} c $$ where $\lambda$ are real numbers. What then does this relation means? As for question 2, I was thinking along finding any form of linear combination between the four vectors and if it exists $\implies$ they are no linear independent. Am i right to say that? If so, what is the best way to find linear combinations. As for question 3, I was thinking of forming linear combinations as well, but the additional vector w makes it impossible for me to work out a solution. Please advice thanks.

I need to determine if the following set of vectors are are linearly independent or not.  1) $S=\{\mathbf u , \mathbf v , \mathbf w\}\subseteq \mathbb R^3$, it is known that $(1,2,3) \notin \text{span}\{\mathbf u , \mathbf v , \mathbf w\}$  2) $S=\{\mathbf u + \mathbf v,\mathbf u - \mathbf v , \mathbf u - 2\mathbf v +\mathbf w\}\subseteq \mathbb R^n$ where $\{\mathbf u , \mathbf v , \mathbf w\}\subseteq \mathbb R^n$ is a linearly independent set.  3) $S=\{\mathbf u , \mathbf v , \mathbf w\}\subseteq \mathbb R^3$, where it is known that $(1,2,-3),(1,-3,2),(2,-1,5),(0,0,1)$ all belong to $\text{span}\{\mathbf u , \mathbf v , \mathbf w\}$.  I honestly have no idea how to start this, all I know is that the if the vectors $\mathbf u , \mathbf v , \mathbf w$ are linearly independent, then $a\mathbf u + b\mathbf v + c\mathbf w=0$ has only the trivial solution.  Any help here will be appreciated, many thanks!


I was reading some information about the constant of electromagnetism  $\epsilon_0$ $[\frac{C^2}{N\cdot M^2}]$ and according to my understanding it is the amount how much electric field is permitted in the space (vacuum). I do not understand this idea so much and I would like for an example in real life when the $\epsilon_0$ plays role.

From Coulomb's law, we know that $\epsilon_0$ means . It's unit is $\rm C^2 N^{-1} M^{-2}$ ( coulomb squared per Newton per square meter). But what does it mean physically?  For example, 1 Pa pressure means 1 Newton force applied perpendicularly on 1 square meter area. In a similar way, can anyone please describe $\epsilon_0$?


Why would Anakin Skywalker trust Chancellor Palpatine once he knew Palpatine was a Sith Lord?  In one scene of Revenge of the Sith, Palpatine invites Anakin to chat with him and reveals a legend about a Sith Lord that could save the people he cared about from death. (That alone should have been a big honking clue that Palpatine was a Sith Lord or in cahoots with one). Later when Anakin finally figures out that Palpatine is a Sith Lord, why would he trust anything Palpatine ever said to him? The safest assumption is that Palpatine was lying and manipulative. So when Palpatine, almost beaten by Mace Windu, says "only I can save the one you love", Anakin should have replied with "What!? You expect me to believe that? You're a sociopath!"  Edit: This is different from asking why Anakin believed turning to the Dark Side of the Force would save Padmé? For Anakin to believe Palpatine could help him save Padmé, he would first have to trust Palpatine. Once you know somebody is a murderous, lying, manipulative dictator, there is no reason to believe any word he ever said.

Just as the question asks: Why did Anakin come to believe that Padmé could be saved if he embraced the Dark side of the Force? Padmé clearly didn't believe it. Why was Anakin so driven to save Padmé through the dark side?


Question: if $G$ is non-abelian group of order $pq$ where $p$ and $q$ are distinct primes such that, $p<q$ and $p$ does not divides $q-1$ then, is $G$ is unique? If yes then, how it's looks? My attempt:  yes, $G$ must be unique and, it is nothing but, $\mathbb{Z}_q⋊ \mathbb{Z}_p $ that is, semi direct product of  $\mathbb{Z}_q$ and  $\mathbb{Z}_p$. Is am I right? But I didn't know how to prove this semidirect product is unique. Please help me.

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


In Landau-Lifshitz Classical mechanics textbook, it is said that there are generally $2s-1$ integrals of motion where $s$ is the number of degrees of freedom. Why is that? I couldn't find anywhere an answer.

Landau & Lifshitz write on the first page of chapter 2 of their Mechanics book (p.13)     The number of independent integrals of motion for a closed mechanical system with $s$ degrees of freedom is $2s-1$.   Then they go on      Since the equations of motion for a closed system do not involve time explicitly, the choice of the origin of time is entirely arbitrary, and one of the arbitrary constants in the solution of the equations can always be taken as an additive constant $t_0$ in time. Eliminating $t + t_0$ from the $2s$ functions    $$q_i=q_i(t+t_0,C_1,C_2, \ldots, C_{2s-1}),\qquad \dot{q}_i=\dot{q}_i(t+t_0,C_1,C_2, \ldots, C_{2s-1}), $$   we can express the $2s-1$ arbitrary constants $C_1,C_2, \ldots, C_{2s-1}$ as functions of $q$ and $\dot{q}$ (generalized co-ordinates and velocities) and these functions will be the integrals of the motions.    Could someone elaborate?


I am having troubles solving this exercise. I've tried using Euler's Theorem but I'm not too experienced with it. It also that, until $m=8$, the only integers that satisfy this are powers of $2$. Any help?

I have a hard time formulating proofs.  For this problem, I  can see that if $n$ is equal to $8,$ this statement is true.  $(\mathbb{Z}/8\mathbb{Z})^{\times}$ includes elements:  $1,3,5,7$, and all of these are roots of $1-x^2 \pmod 8.$  And obviously $8$ divides $24.$  But how do I prove this without depending on number calculations and only using theorems?  Help Please?  I need a step by step walk through of how to do this proof and what theorems would be appropriate to use.


You briefly accelerate a charge for some time, and it will both radiate electromagnetic energy and gain kinetic energy.  The kinetic energy it gains seems to be governed by Newton's Second Law, so by putting some amount of work into the system, somehow we get that amount, plus a little bit more, of energy out?

I understand how, and why, an accelerating charge emits radiation, and loses energy in the process, as well as the  formula for the power, and its derivation.  However, in classical mechanics, when we want to find the motion of a particle, the process is (theoretically) simple - find all forces on the particle as a function of position and time, plug in Newton's second law and solve the differential equation. It seems to me as if simply because a particle is charged, this process just ceases to work.  When talking about a charged particle, it is simply not enough to find all forces and solve Newton's law - now we need to somehow take into account the energy lost by the particle to radiation. However no one seems to mention how to take that into account, as a term in an equation of motion. It seems like all we know is the total power radiated by the particle - there is no concrete, complete description of how that loss affects its motion.  Of course, in some simple cases we can easily guess how the particle will be affected: for example, for an electron circling in a uniform magnetic field, it is obvious that energy loss due to radiation will cause the electron to spiral inward. You can, at least theoretically, write the Lorentz force acting on the particle, due to the uniform field, plug it into Newton's second law, and also write the Larmor formula, take that loss into account and find a complete description of the particle's motion.   However still, when we write simply Newton's second law here, with the only force being the Lorentz force, we find a circular, not spiral, solution; we have to synthetically add in the Larmor formula to truly recover the particle's motion. Contrary to classical mechanics where Newton's law is a complete description of the motion.   Why is Newton's law no longer enough, or put another way, what term am I missing that will fix the electron's motion, add an additional "force" the will cause it to spiral inward? Is there a general expression for that force? And how does one in general write the equation of motion for a charged particle (or a system of)?   I suspect the answer has something to do with the EM field changing not instantaneously but at the speed of light, since Newton's law of gravitation clearly yields stable, closed orbits and propagates instantaneously. Perhaps I should phrase my question this way:   How does the fact that the EM field propagates at a finite speed affect the way we have to write the equations of motion  for a charged particle (as opposed to the equations of motion for a massive particle, acted upon by an instantaneous, newtonian gravitational field)?   One last note: perhaps this has something to do with Maxwell's equations being Lorentz-invariant and not Galilean? However I find this unlikely to be the case since the electron doesn't have to move in a relativistic speed in order to experience this effect. In any case, this is also why I allowed myself to use Newton's second law and not its (special) relativistic expression - would using that fix the problem?


I want to try installing Ubuntu on a 4 year old Dell laptop but it is not listed on the certified devices. Is it okay to try to install it? or not recommended if not included from the list? What are the possible consequences that I will encounter? Please give me some advise. Thank you!

I have a device on which I would like to install Ubuntu. How do I find out if Ubuntu will work on it?


Can I shrink transaction log when database in online using below command ? DBCC SHRINKFILE(transactionloglogicalfilename, TRUNCATEONLY)   FYI my database is in production server & highly critical  Thanks in advance  regards Imra

This one seems to be a common question in most forums and all over the web, it is asked here in many formats that typically sound like this:  In SQL Server -  What are some reasons the transaction log grows so large? Why is my log file so big? What are some ways to prevent this problem from occurring? What do I do when I get myself on track with the underlying cause and want to put my transaction log file to a healthy size?


I have a my_module.routing.yml file and because of I have multi entity in my module its too big and not pretty.  Is there any way to split it for each entity and include them in one file like , I use below code but it's not work in drupal 8.  acme_demo_user:   resource: "@acmeDemoBundle/Resources/config/routing/user_routing.yml"   I also use absolute path for yml file but it's not work.

I have more than 50 menus which I need to create custom. as per the module structure, we need to create routing.yml in root folder. but I want to do something like this below:     myModule       -  products(folder)               - routing.yml               - src(folder)                 - productController         -  brands(folder)               - routing.yml               - src(folder)                 - brandsController.php           - myModule.info.yml       - myModule.module   is it way to do achive something like this.  I just want to make code seperation and avoid to add all routes in routing.yml


I have a cross-sectional real estate dataset with information on roughly 100000 properties, including rental price, square meter size, number of bedrooms etc. In addition, the dataset contains information about the region for each property. The total number of regions in the dataset is 400.  I would like to play around with different machine learning methods in the caret package to predict rental prices using the relevant features in the dataset. I obviously need to incorporate regional information to capture region-specific price effects.      Update: To be more formal, I have the following two model specifications in mind:  $y_i=\beta_0+\beta_1x_{i,1}+\beta_2x_{i,2}+\beta_3D_{i,1}+\beta_4D_{i,2} + \epsilon_i$  where $y_i$ refers to the rental price of property $i$, $x_{i,1}$ denotes square meter size, $x_{i,2}$ denotes the number of rooms, $D_1$ is a matrix of dummy variables capturing different characteristics like balcony, kitchen, cellar and so on, and $D_2$ is a matrix containing the 399 regional dummies.  Alternatively, the model could be specified as follows:  $y_i=\beta_0+\beta_1x_{i,1}+\beta_2x_{i,2}+\beta_3D_{i,1}+\gamma d_{j} + \epsilon_i$  where $d$ is a vector containing the median or average square meter price in each region $j$. I guess inclusion of interaction effects could also make sense (see comment below by seanv507), but I am not sure about them right now.  The obvious advantage of the last equation is that I only need one variable in my model to proxy for a regional effect. However, I also do not see too much of a problem for the first equation given the relatively large number of observations in the dataset.   I have two questions:   Which of the two specifications would be preferable or are there better alternative ways to deal with this issue? Which machine learning methods could be promising for this type of model?

What techniques are available for collapsing (or pooling) many categories to a few, for the purpose of using them as an input (predictor) in a statistical model?    Consider a variable like  (discipline chosen by an undergraduate student). It is unordered and categorical, but it can potentially have dozens of distinct levels. Let's say I want to use major as a predictor in a regression model.  Using these levels as-is for modeling leads to all sorts of issues because there are just so many. A lot of statistical precision would be thrown away to use them, and the results are hard to interpret. We're rarely interested in specific majors -- we're much more likely to be interested in broad categories (subgroups) of majors. But it isn't always clear how to divide up the levels into such higher-level categories, or even how many higher-level categories to use.  For typical data I would be happy to use factor analysis, matrix factorization, or a discrete latent modeling technique. But majors are mutually exclusive categories, so I'm hesitant to exploit their covariance for anything.  Furthermore I don't care about the major categories on their own. I care about producing higher-level categories that are coherent with respect to my regression outcome. In the binary outcome case, that suggests to me something like linear discriminant analysis (LDA) to generate higher-level categories that maximize discriminative performance. But LDA is a limited technique and that feels like dirty data dredging to me. Moreover any continuous solution will be hard to interpret.  Meanwhile something based on covariances, like multiple correspondence analysis (MCA), seems suspect to me in this case because of the inherent dependence among mutually exclusive dummy variables -- they're better suited for studying multiple categorical variables, rather than multiple categories of the same variable.  edit: to be clear, this is about collapsing categories (not selecting them), and the categories are predictors or independent variables. In hindsight, this problem seems like an appropriate time to "regularize 'em all and let God sort 'em out". Glad to see this question is interesting to so many people!


Pardon me if this is a duplicate. Say I have two objects that are heading towards each other (one going to the right and the other heading left). Both have a constant mass (let's say 2kg and 4kg respectively) and velocity (5m/s and 3m/s) before the collision. Using this information alone, is there any way to know if the collision will be elastic or inelastic. Do I need more information on the objects such as the shape or materials?

I'm a programmer and a game developer, not a mathematician or a physicist. So please go easy on the math :)  I know two things:   How to find the new velocities of two objects after an . How to find the velocity of the new object formed by two objects in an .   However what I need to know is: given the mass, the velocity, and the 'angle' the two objects are going two be when they collide - how can I know if I need to compute an elastic or an inelastic collision?  I need this for the 2D game I'm developing, that tries to simulate relatively-realistic physics. Thanks for your help


I have two HDD's unplugged for two years. It's from my old pc. I have some important files in there but I'm wondering about this problem.  Will the HDD's turn on and I'll be able to access all my files or there a possibility of these HDD's goes bad because I let them off for a long time?  People, the old question is from 2009... Now, the HDD's are different. I need a new question, a new debate from the experience from users since 2009.

If I were to archive data on a hard drive, unplug it, and set it on a (not dusty, temperature-controlled) shelf somewhere, would that drive deteriorate much?  How does the data retention of an unplugged hard drive compare to tapes?


I have a table that is needed to be split since it does not fit one page. I can not manage to divide it, is there any way to accomplish this?  \documentclass{article} \documentclass[a4paper,onesided,12pt]{report} \usepackage{array,longtable} \renewcommand*{\arraystretch}{1.5}  \begin{document} \begin{center} \begin{table} [H] \caption {Tarık's theme categories and their definition } \begin{tabular}{|m{3cm}|m{4cm}|m{7cm}| } \hline \multicolumn{1}{|c|}{Theme}  &\multicolumn{1}{|c|}{Explanation} & \multicolumn{1}{|c|}{Example} \\ \hline  Interpretation of graph & Determining the characterization of the graph based on information given in the explanation part  & T: I will get a parabolic shape when zooming out the graph since it intersects two points on x-axis. \\ \hline  Interpretation of function &     Emphasizing quadratics functions and where it can be observed in daily life & T: Where can I find a quadratic function in real life? Physics come to my mind.  I remember that velocity and time have a quadratic relationship. For example, I remember $\dfrac{1}{2}at^2$. \smallskip \\ \hline  Make sense of model representation & Searching for meaning of modeling with mathematics &   T: What am I supposed to do here if I am required to write a model? \\ \hline  Searching for variable &    Looking for different possible variable options for given graph &   T: What about location-time graph? \newline R: What do you mean? \newline T: Well.. I can state one of my variable as time and look for change of location in graph. \\ \hline  Writing equation &  Writing equations that can represent the given graph    & R: If this is a graph looking downward, then its equation may be $-x^2+3$ \\ \hline   Drawing a model &   Demonstrating his model by a simple drawing &  \medbreak \includegraphics[scale=0.9]{T_model1.png} \\ \hline   Alignment of model-graph &  Checking whether written model matches with the given graphical representation & T:I summarized what I have done here. I modelled this graph as motion of ball thrown upward from a point 3 m above the ground with an initial velocity. In addition, this graph shows the change depending on the time. It will go upward and come down.  There are two moments that are same as the ground level and those are two points that intersect x-axis on the given graph. The y values would be zero there. \\ \hline  \end{tabular} \end{table} \end{document}

I have a table such that;  \documentclass{article} \documentclass[a4paper,onesided,12pt]{report} \usepackage{array,longtable} \renewcommand*{\arraystretch}{1.5}  \begin{document}     \begin{center} \begin{table}[H] \caption{Çınar's emergent codes and corresponding themes} \begin{tabular}{|m{9cm}|m{5cm}| } \hline\multicolumn{1}{|c|}{RELEVANT CODES} & \multicolumn{1}{|c|}{THEME} \\  \hline Graph representation (false assumption) & \\  Graph completion & \multirow{1}{*}{Interpretation of    } \\  Determining slope & \multirow{1}{*}{graph} \\ Determining values for horizontal and vertical axes & \\ \hline Writing problem situation & \multirow{1}{*}{Making sense of model}  \\  Solve conflicts on variable- graph interaction by a model& \multirow{1}{*}{representation} \\  Writing reasonable real world situation & \\  \hline IV $\rightarrow$ time, DV $\rightarrow$ velocity & \\ IV $\rightarrow$ time, DV $\rightarrow$ location & \\  IV $\rightarrow$ undetermined, DV $\rightarrow$ location & \multirow{3}{*}{Searching for} \\ IV $\rightarrow$ decide to change IV except "time"& \multirow{2}{*}{variable} \\ IV $\rightarrow$ temperature, DV $\rightarrow$ temperature & \\ IV $\rightarrow$ time, DV $\rightarrow$ location & \\ IV $\rightarrow$ time, DV $\rightarrow$ subjects completed during summer school & \\ \hline IV $\rightarrow$ location, DV $\rightarrow$ time and looking their interaction & \multirow{3}{*}{Alignment of } \\  Manipulation of graph properties to fit graph to determined variables & \multirow{2}{*}{variable-graph }   \\  Finding conflict when matching variables on graph & \\ \hline  Converting graph to table & \multirow{1}{*}{Converting graph} \multirow{1}{*}{to table} \\ \hline \end{tabular} \end{table} \end{center}       \end{document}   I need to divide them into two parts since the table contains several rows and they did not fit in one page.


I have a class A that inherits from a class B and implements IEqualityComparer<A>. This means class A provides its own implementation of both Equals and GetHashCode methods. So far so good. The problem is that I don't understand why the code behaves in the following way:  debugger will only reach A's Equals implementation breakpoint if A's GetHashCode implementation returns  this.GetHashCode() instead of obj.GetHashCode(), with "obj" being the parameter that GetHashCode's signature defines(a variable of type A, in my case).  Intuitively, I thought that I should return the hashcode of the object I received, but doing so makes the compiler ignore the instance's Equals implementation.  Why does this happen?  Code demonstration:  public class A : B, IEqualityComparer<A> {     public bool Equals(A x, A y)     {         //my implementation...     }      public int GetHashCode(A obj)     {         //return obj.GetHashCode(); -> this makes my Equals implementation above be ignored! Why?         return this.GetHashCode(); -> my Equals implementation is used     } }

Given the following class  public class Foo {     public int FooId { get; set; }     public string FooName { get; set; }      public override bool Equals(object obj)     {         Foo fooItem = obj as Foo;          if (fooItem == null)          {            return false;         }          return fooItem.FooId == this.FooId;     }      public override int GetHashCode()     {         // Which is preferred?          return base.GetHashCode();          //return this.FooId.GetHashCode();     } }   I have overridden the Equals method because Foo represent a row for the Foos table.  Which is the preferred method for overriding the GetHashCode?  Why is it important to override GetHashCode?


I need to arrange my pictures on the way shown in the attached figure. Please any help from you.

I have three images and I want to align them in the way that one image is above the other two. Here's an example:    How can I achieve this? For my other figures I use the subcaption package, but I am not able to align the pictures that way with it.    Thanks for all your replys! The answer that is working for me is the one supposed by karlkoeller:  \documentclass{article} \usepackage{graphicx} \usepackage{subcaption}  \begin{document}  \begin{figure} \centering \begin{subfigure}[b]{.45\linewidth} \includegraphics[width=\linewidth]{example-image-a} \caption{A mouse}\label{fig:mouse} \end{subfigure}  \begin{subfigure}[b]{.45\linewidth} \includegraphics[width=\linewidth]{example-image-b} \caption{A gull}\label{fig:gull} \end{subfigure} \begin{subfigure}[b]{.45\linewidth} \includegraphics[width=\linewidth]{example-image-c} \caption{A tiger}\label{fig:tiger} \end{subfigure} \caption{Picture of animals} \label{fig:animals} \end{figure}  \end{document}


I wonder if i can ask public about their ideas related to Android. This can be a consulting such an; how better i can attract users, is button or image better to be used in this layout, how i can manage this better and so on.  It is all about encouraging people commenting and giving suggestions to user who asked question.

I want to see developers' opinions on the use of a certain language feature, where is the right place to ask that question?


I am curious about wisdom, I was questioning myself if I could figure out what is wisdom, and I guess wanted to go with obvious answer and conected wisdom with knowledge, but this is not one to one ratio. In my mind people hold both wisdom and knowledge and books can only hold knowledge. So by certain logic I get to conclusion that if wisdom is written down in a book it becomes knowledge. and this is my confusion, I wonder if this is safe assumption and what does it take for knowledge from a book to become wisdom once again, as I am certain in my mind that just by reading a piece of knowledge one is not granted with wisdom.

It is clear from Big Internet Search Engine that not all knowledge is considered wisdom but, can some knowledge be foolish?     "Wisdom cannot be imparted. Wisdom that a wise man attempts to impart always sounds like foolishness to someone else ... Knowledge can be communicated, but not wisdom." -Hermann Hesse, German novelist, poet, and painter   Other fields outside of philosophy  but, what does philosophy say about knowledge being foolish?     "Wisdom is the right use of knowledge. To know is not to be wise. Many men know a great deal, and are all the greater fools for it. There is no fool so great a fool as a knowing fool. But to know how to use knowledge is to have wisdom." ~ Charles H. Spurgeon


Which is the correct form of the following structure?     A, together with B, provide an efficient means of...   or     A, together with B, provides an efficient means of...   Certainly, "A provides", and "A and B provide". My intuition tells me that the second form is correct because A is the subject and is singular.

My question arises from , where OP asks whether he should use the singular or plural verb form after "the title, as well as the tone,"  As luck would have it, when I searched Google Books for , I found...        ...and...        At the risk of having this question closed as just peeving, I feel that the first one should have been plural "err", because without the commas it seems to me both "the title" and "the tone" have more or less equal status as "joint" subjects of the verb, making it plural.  On the other hand, I feel the commas in the second example effectively demote "the tone" to "parenthetical" status (the clause is almost incidental). Since this encourages us think of "the title" as the primary subject, it should have been singular "derives".  I'm no great fan of "grammatical rules", but it seems weird to me that the only two relevant examples for this specific wording should both (in opposite ways!) contradict my inclinations.  What's going on?


This is not a production question, just something that I've been thinking about.  When speccing out CPUs I know the general rule is a faster clock speed will make a core run faster and the greater number of cores you have the more you can do in parallel.  However what makes a "newer" CPU generally faster than an older CPU other than these two things?  For example:   There is a noticeable difference between an older i5 and a newer i5 despite having the same number of cores and around the same GHz. My current dual core i5 running at 2.5 (I believe) GHz would surely blow a Pentium 4 out of the water, despite the Pentium running at > 3GHz.  I'm sure I could blow a dual core server from 2004 out of the water as well just to make things fair core-wise.  I have never done any formal benchmarking, these are just educated guesses.   What are some things to look for when speccing out CPUs?

Why, for example, would a 2.66 GHz dual-core Core i5 be faster than a 2.66 GHz Core 2 Duo, which is also dual-core?  Is this because of newer instructions that can process information in fewer clock cycles? What other architectural changes are involved?     This question comes up often and the answers are usually the same. This post is meant to provide a definitive, canonical answer for this question. Feel free to edit the answers to add additional details.


I have been talking to a chick that says she needs 4500 euro in her bank account in order to obtain a 90 day tourist visa to visit Ireland.

My girlfriend is Russian. Last night we tried to fly her to the US on a valid tourist visa. She was stopped at DME and told she would be required to have $2700 USD to get back home immediately even though she had a return ticket. She said this was an "unwritten" rule because of the nonsense i keep seeing on CNN , Anybody else know anything? She is literally trapped and scared to death.


Which one of the following is correct use? If both are correct, what difference does this change make in a conversation?   Do you know when is this being used? Do you know when this is being used?

Can a sentence like this:      "I don't know who the first man that made such and such thing in such and such place was,"    be grammatically correct if we don't put "was" at the end of the long phrase, that is, if we write:      "I don't know who was the first man that made such and such thing in such and such place"?    I can see in Google Books examples that in such cases the verb is often put after the wh-word, but I don't know if there is a grammar rule to support this. Some examples:  "We do not know who was the first man who ascended above a poor and humble people to become Egypt's first king ..."  "... we do not know what was the ultimate judgment of the various members of the community ..."  "I do not know who was the first to suggest a connection between the problem of free will and the breakdown ..."  "I do not know what was the date of this change in me, nor of the train of ideas ..."  "We do not know what was the primitive text from which Codex Bezae derived its Latin or its Greek ..."  "We do not know what was the practice in the days of the monarchy, but the story of Athaliah shows ..."


#include <stdio.h>  void reverse(int i); main() {     reverse(1); } void reverse(int i) {     if(i>5)        return     printf("%d",i);     return reverse((i,i++)); }   This function prints integer numbers 1,2,3,4,5 as output.  My doubt is that even though we specifically mention to the compiler that this function reverse accepts only 1 parameter, how does this work ? Whats the significance of double brackets(()) inside reverse function ?


Sorry if question title isn't clear. Let me explain with an example.  Search term: Blogging  Results I got from Google     › ... › Home Business › Home Business Toolbox        I want to remove 1,2,3 and 7. I am looking only the home page (full domain) as result. Is it possible?

I want to search for job sites in Alberta, Canada. One way to proceed is to do the usual Google search for them and then somehow loop through the results for the domains that seem to correspond to job sites.  Many of them will come from the principal job sites such as monster.com or indeed.ca. Fewer will come from lesser known sites that would still be of interest to job seekers. What I want to be able to do is to collect domains and subdomains.   For instance, and thinking procedurally, once I have encountered and noted monster.com I want to ignore subsequence occurrences of it. I want to continue to look for distinct, new domains and subdomains. Any thoughts?  I haven't found a way of doing this with any collection of Google operators. Is there a way? If that's not possible, what would be a good way of doing it?


Every time I add a PPA I cannot see the package I'm trying to install. I suppose I must be doing something wrong! So here's my latest effort:  In a Terminal I typed:  sudo add-apt-repository ppa:jeromerobert/misc   and that seemed to work correctly  Then I typed:  sudo apt-get update   But when I go to Synaptic or Software Center the application I want to install is not there. Could someone please tell me what I'm doing wrong?

I am wondering what sudo apt-get update does?  What does it update?


I need to find the smallest power of two that's greater or equal to a given value. So far, I have this:  int value = 3221; // 3221 is just an example, could be any number int result = 1;  while (result < value) result <<= 1;   It works fine, but feels kind of naive. Is there a better algorithm for that problem?  EDIT. There were some nice Assembler suggestions, so I'm adding those tags to the question.

I want to write a function that returns the nearest next power of 2 number. For example if my input is 789, the output should be 1024. Is there any way of achieving this without using any loops but just using some bitwise operators?


I have a function that can return one of three values: a, b, or c.   def f():     return x # a, b, or c   I need to execute different statements based on the return value of f(): A, B, or C. The best way to do this, that I know of, is:  v = f() if v == a:     # Do A elif v == b:     # Do B else:     # Do C   Without introducing this new variable v, is there a different way to evaluate the return value of f()? Something like this, maybe?  if f() == a:     # Do A elif _value_from_above == b:     # Do B else:     # Do C

I want to write a function in Python that returns different fixed values based on the value of an input index.    In other languages I would use a switch or case statement, but Python does not appear to have a switch statement.  What are the recommended Python solutions in this scenario?


I am trying to make a Spring Helloworld application, but I get the following exception:   Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'helloWorld' defined in class path resource [spring.xml]: Initialization of bean failed; nested exception is java.lang.NoClassDefFoundError: org/springframework/core/io/support/SpringFactoriesLoader at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:529) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:626) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:469) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83) at com.sdnext.dineshonjava.tutorial.SpringJavaApp.main(SpringJavaApp.java:11)   Here are my Maven dependencies :   The SpringFactoriesLoader class is obviously missing from the package, so what should I do? I tried to change the version of the spring-core dependency to  3.2.2, but I get an error in the pom.xml saying Missing artifact org.springframework:spring-core:jar:3.2.2  In my spring.xml configuration file I have declared the following bean :   <bean class="com.sdnext.dineshonjava.tutorial.HelloWorld" id="helloWorld">    <property name="message" value="Hello World!">     I also have the class HelloWorld in that package.  I am thinking that maybe there is a version conflict somewhere, but how can I figure out where is the problem?

I am getting a NoClassDefFoundError when I run my Java application.  What is typically the cause of this?


Multiple correct options:  Which of the following is/are true?  (a) There is a surjective function $f:\mathbb{N} \to \mathbb{N} \times \mathbb{N}.$  (b) There is a injective function $f:\mathbb{N} \times \mathbb{N} \times \mathbb{N} \to \mathbb{N}.$  (c) There is a bijective function $f:\mathbb{N} \times \mathbb{N} \to \mathbb{N}  \times \mathbb{N} \times \mathbb{N}.$  (d) There is a bijective function $f:\left\{ 0,1 \right\} \times\mathbb{N} \to \mathbb{N} \times \mathbb{N}.$  I think (b) is only correct since bijective requires the same cardinality.  How should I do this one.

Is the finite Cartesian Product of Countable sets countable?  If possible, could you give a bijection that would work for any example?  Any help would be appreciated.


We randomly take $51$ numbers from 159 natural numbers $1,...,159$ without replacement. Let $\alpha$ be a random variable equal to the sum of the selected numbers. Find the variance of $\alpha$. Firstly I need to understand something about $\alpha$ destribution. There are totally $$C^{51}_{159} = \frac{159!}{51!108!}$$ kinds of sums. A lot of them are equal, because $$\sum_{i=1}^{51}i = 1326\leq\alpha\leq\sum_{i=109}^{159}i=6834$$ Consequenlty, I want to know how many subsets of $51$ numbers have the sum equal to $N$, where  $1362\leq N\leq6834$. I'm stuck here because I don't know how to do it.

From an urn with numbers $1,...,n$ we draw $k < n$ numbers without replacement.   Let $X_i$ be the $i$-th draw. The random variable is their sum $X=\sum_{i=1}^kX_i$.  I have already calculated the expected value of the sum, which is   $$\Bbb{E}[X]=\sum_{i=1}^k\Bbb{E}[X_i]=k\frac{n+1}{2}$$ because each $\Bbb{E}[X_i]=\frac{1}{n}\sum_{i=1}^n i=\frac{n+1}{2}$.  Now the variance of the sum would be $$Var[X]=\Bbb{E}[X^2]-\Bbb{E}[X]^2$$  I have read that the variance of a sum is the sum of variances if the random variables are independent, it does not seem to be the case here, as previous draws determine future draws.  Is there an elegant way to determine the first summand of the variance?    Edit: I am trying it the ugly way.  $\Bbb{E}[X^2]=\Bbb{E}[(\sum_{i=1}^kX_i)^2]=\Bbb{E}[\sum_{i=1}^k \sum_{j=1}^k X_iX_j]=\sum_{i=1}^k \sum_{j=1}^k \Bbb{E}[X_iX_j]$  To know $\Bbb{E}[X_iX_j]$ we would have to know $\Bbb{P}(X_iX_j=k)$, meaning we would have to know the number of ways to write a number as the product of two factors $1\leq X_i, X_j \leq n$... I am pretty sure I am off the track here, as I do not see a way to do it for a general $n$.    Am I wrong to regard the $X_i$ instead of the $X$, which are independent, as two draws of $k$ balls would be independent? Then $\Bbb{E}[X^2]=\Bbb{E}[X]\Bbb{E}[X]$


Actually, my Powershell can't resolve many commands while cmd/bash can: node, git, npm, etc... PS C:\Users\vssen> notepad notepad : The term 'notepad' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again. At line:1 char:1 + notepad + ~~~~~~~     + CategoryInfo          : ObjectNotFound: (notepad:String) [], CommandNotFoundException     + FullyQualifiedErrorId : CommandNotFoundException  But PowerShell MUST at least open notepad with "notepad" command! Note: it is opening notepad by "notepad.exe" command, but it must do it without ".exe". I think this error also make issues to me while I am working with git and node too, and I see a lot of opened issues similar to that, and there is still no answer. Example error behavior with other commands: npm: open new console; npm.exe --version: no output; git: not found; node: not found; git.exe: open and close console; node.exe: open nodejs console window; THINGS I TRIED:  clear all user and system paths, adding only for nodejs for example, or only system32 DISM sfc /scannow Installation of separated PowerShell 7 (cross platform) - SAME ISSUE! Get-Command can't find path without ".exe", can with ".exe"  PS C:\Users\vssen> $PSVersionTable  Name                           Value ----                           ----- PSVersion                      5.1.19041.906 PSEdition                      Desktop PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...} BuildVersion                   10.0.19041.906 CLRVersion                     4.0.30319.42000 WSManStackVersion              3.0 PSRemotingProtocolVersion      2.3 SerializationVersion           1.1.0.1  env variables vssen: Path: C:\Program Files\nodejs;C:\Users\vssen\AppData\Local\Programs\Python\Python39\Scripts\;C:\Users\vssen\AppData\Local\Programs\Python\Python39\;C:\Users\vssen\AppData\Local\Microsoft\WindowsApps;C:\Users\vssen\AppData\Local\Programs\Microsoft VS Code\bin;C:\Users\vssen\AppData\Roaming\nvm;C:\Program Files\PostgreSQL\13\bin; system: Path: C:\Program Files\nodejs;C:\Program Files\Git\cmd;C:\Program Files\Conan\conan;C:\Program Files\Common Files\Oracle\Java\javapath;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common;C:\Program Files\NVIDIA Corporation\NVIDIA NvDLISR;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\;%SYSTEMROOT%\System32\OpenSSH\;%NVM_HOME%;%NVM_SYMLINK%;C:\Program Files\PostgreSQL\13\bin;C:\Program Files\dotnet\;C:\MinGW\bin;C:\Program Files\CMake\bin;C:\Program Files\Docker\Docker\resources\bin;C:\ProgramData\DockerDesktop\version-bin;C:\Program Files\PowerShell\7\;C:\Program Files\Amazon\AWSCLIV2\ I've validated every path in env Path, all links are valid (and PowerShell & cmd must work with invalid links as well!) C:\Users\vssen>where where C:\Windows\System32\where.exe   C:\Users\vssen>where notepad C:\Windows\System32\notepad.exe C:\Windows\notepad.exe  Maybe someone know Microsoft developers) Help is much appreciated! i don't want to reinstall Windows please... PS: all possible related and non-related things to mention  OS Build: 19043.985 Windows Feature Experience Pack 120.2212.2020.0 (don't know what is it) I have WSL use nodejs via nvm have bash (from git installer)

Using Windows 10, I can't run certain commands from PowerShell but they all work correctly using cmd. PowerShell: node --version: node : The term 'node' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again. At line:1 char:1 + node --version + ~~~~     + CategoryInfo          : ObjectNotFound: (node:String) [], CommandNotFoundException     + FullyQualifiedErrorId : CommandNotFoundException  node.exe --version: no output. node.exe: opens a new black console (node.exe application itself). Get-Host | Select-Object Version: Version ------- 5.1.19041.906  Get-Command node: The term 'node' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again. At line:1 char:1 + Get-Command node + ~~~~~~~~~~~~~~~~ + CategoryInfo : ObjectNotFound: (node:String) [Get-Command], CommandNotFoundException + FullyQualifiedErrorId : CommandNotFoundException,Microsoft.PowerShell.Commands.GetCommandCommand Get-Command node.exe: CommandType Name Version Source ----------- ---- ------- ------ Application node.exe 14.16.1.0 C:\Program Files\nodejs\node.exe $env:Path output has nodejs & git & other paths. cmd: everything works fine with any command. I have git and nodejs in my PATH env variable. What's wrong with PowerShell, what a strange behavior is this and how to fix it?


The terminal is very fast and convenient way to quickly access directories and files (faster than find and click on the directory).   One thing that it cannot show in text-mode is "pictures".   What is a best way to view pictures (like you see images thumbnail in Nautilus) when you are working in the terminal (e.g. command nautilus or any program - but should be fast and convenient)?

When I am on the console (the tty, the virtual terminal, which you reach with Ctrl+Alt+F1-6, not a terminal emulator), what options do I have to view images, tiff, whatever that's not text?


I would like to do my master thesis on image processing. What will be best approach for study and selecting topic on this field?

If a master's degree candidate needs to select a thesis topic, but their advisor is unwilling to offer suggestions on the matter, how should one go about selecting a thesis?   How might one select an area to study? How can one evaluate if if is a suitable topic? Does the thesis need to focus on an area which is relatively unexplored by prior research?


As in the title,  Labcoat, lab-coat or lab coat?  Which is the correct version? And is there a convention I can use for other similar combinations of words.

Some compound words are written without hyphens (nonaggression, nonbeliever), some with hyphens (well-intentioned), and others with spaces (post office).  Is there a rule or good guide as to which option should be used?


A few years ago, I watched a sci-fi movie, but I forgot the title, and I only remember a few things about it:   It takes place in the future. Human things with blades on their hands come out from a giant machine in the ground. They put humans in the machine, and then the humans are transformed into those things. A man tries to save his family.   I hope this is enough information to find the movie title! Sorry for my bad English; I'm not that old and I’m from Germany. Thanks for the answers in advance!

I can't remember much about it other than something/one unleashed a machine within a giant pit, and then what I assume is either space marines, or regular military had to deal with the issue. It didn't go well obviously. The monsters had arms that were basically spikes and were very fast, and every human slain was dropped into the pit to become a monster via a conveyor belt and saw blades. However the hero overcame the machine after he was put in and won.


I've got a utility that outputs a list of files required by a game.  How can I run that utility within a C program and grab its output so I can act on it within the same program? UPDATE: Good call on the lack of information.  The utility spits out a series of strings, and this is supposed to be portable across Mac/Windows/Linux.  Please note, I'm looking for a programmatic way to execute the utility and retain its output (which goes to stdout).

I am looking for a way to get the output of a command when it is run from within a C++ program.  I have looked at using the system() function, but that will just execute a command. Here's an example of what I'm looking for:  std::string result = system("./some_command");   I need to run an arbitrary command and get its output. I've looked at , but I have not found anything that will give me what I need.


I'm making a calculator. It will be very long and hard to do the proper string analizer which parses strings by chars, so I thought, is there a way to turn string into a command line like this: double num = "12/6+23*4";

If I have a string with a valid math expression such as:  String s = "1 + 2 * 7";   Is there a built in library/function in .NET that will parse and evaluate that expression for me and return the result? In this case 15.


when should that be used in defining clauses. Is it only used to give more information about a person or something or can it also be used to give more information about a place. Is it informal or formal English?

Excuse me if this topic has been brought up before though I couldn't find it. It seems that there are many similar topics related to both defining and non-defining clauses but there is still one question that bothers me. I want to know about the difference between wh- pronouns (who, which, what...) vs. that in restrictive relative clause.   For example: The man that I saw at the mall looked puzzled.  The man who I saw at the mall looked puzzled.  I omitted commas intentionally, as I'm willing to talk about defining clauses only.   The Cambridge Grammar of the English Language gives quite vague description on that and I cannot think about actual examples:  "Relative clauses are so called because they are related by their form to an antecedent. They contain within their structure an anaphoric element whose interpretation is determined by the antecedent. This anaphoric element may be overt or covert. In the overt case the relative clause is marked by the presence of one of the relative words who, whom, whose, which, etc., as or within the initial constituent: clauses of this type we call wh relatives. In non-wh relatives the anaphoric element is covert, a gap; this class is then subdivided into that relatives and bare relatives depending on the presence or absence of that." Thanks in advance!   UPD: I know that it seems that in general there is no need to dig for this information but still I need this for my research.


the sequence of Fibonacci numbers is defined as follows: $x_1=1, x_2=1$, and, for $n>2, x_n=x_{n-1} + x_{n-2}$. Prove that   $$   x_n=\frac{1}{\sqrt{5}}\left[\left(\frac{1+\sqrt{5}}{2}\right )^n - \left (\frac{1-\sqrt{5}}{2}\right )^n\right ] $$ for every natural number $n$.

[question:]      Prove by induction that the i th Fibonacci number satisfies the equality $$F_i=\frac{\phi^i-\hat{\phi^i}}{\sqrt5}$$where $\phi$ is the golden ratio and $\hat{\phi}$ is its conjugate. [end]  I've had multiple attempts at this, the most fruitful being what follows, though it is incorrect, and I cannot figure out where I am going wrong:  [my answer:] What follows is an incorrect approach, after which comes the approach that I should have done  Inductive Hypothesis: $$F_i=\frac{\phi^i-\hat{\phi^i}}{\sqrt5}, i\in\mathbb{N}  $$   (I include 0) Base case: $$F_0=\frac{\phi^0-\hat{\phi^0}}{\sqrt5}=0$$  Proof: $$\begin{eqnarray*} F_{i+1}&=&\frac{\phi^{i+1}-\hat{\phi^{i+1}}}{\sqrt5}\\ &=&\frac{\phi*\phi^i-\hat{\phi}*\hat{\phi^i}}{\sqrt5}\\ &=&\frac{\frac{1+\sqrt5}{2}*\phi^i-\frac{1-\sqrt5}{2}*\hat{\phi^i}}{\sqrt5}\\ &=&\frac{\frac{\phi^i+\sqrt5\phi^i}{2}-\frac{\hat{\phi^i}-\sqrt5\hat{\phi^i}}{2}}{\sqrt5}\\ &=&\frac{\frac{\phi^i+\sqrt5\phi^i-\hat{\phi^i}+\sqrt5\hat{\phi^i}}{2}}{\sqrt5}\\ &=&\frac{\phi^i+\sqrt5\phi^i-\hat{\phi^i}+\sqrt5\hat{\phi^i}}{2*\sqrt5}\\ &=&\frac{1}{2}\left(\frac{\phi^i+\sqrt5\phi^i-\hat{\phi^i}+\sqrt5\hat{\phi^i}}{\sqrt5}\right)\\ &=&\frac{1}{2}\left(\frac{\sqrt5\phi^i}{\sqrt5} + \frac{\sqrt5\hat{\phi^i}}{\sqrt5} +\frac{\phi^i-\hat{\phi^i}}{\sqrt5}\right)\\ &=&\frac{1}{2}\left(\phi^i+\hat{\phi^i}+F_{i}\right)\text{   by inductive hypothesis}\\ &=&\frac{1}{2}\left(\sqrt5*...\right)\\ \end{eqnarray*}$$ Actually I just saw my error in that line (I eventually multiplied by $\frac{\sqrt5}{\sqrt5}$ and  substituted for $F_i$, but I see that the conjugates are added there, not subtracted).  Correct approach: $$\begin{eqnarray*} F_{i+1}&=&F_{i} + F_{i-1}\\ &=&\frac{\phi^i-\hat{\phi^i}}{\sqrt5}+\frac{\phi^{i-1}-\hat{\phi^{i-1}}}{\sqrt5}\\ &=&\frac{\left(\phi+\hat{\phi}\right)\left(\phi^i-\hat{\phi^i}\right)-\phi\hat{\phi}\left(\phi^{i-1}-\hat{\phi^{i-1}}\right)}{\sqrt5}\text{ (see answer for why this works)}\\ &=&\frac{\phi^{i+1}-\phi\hat{\phi^i}+\hat{\phi}\phi^i-\hat{\phi^{i+1}}-\phi^i\hat{\phi}+\phi\hat{\phi^i}}{\sqrt5}\\ &=&\frac{\phi^{i+1}-\hat{\phi^{i+1}}-\phi\hat{\phi^i}+\phi\hat{\phi^i}-\hat{\phi}\phi^i+\hat{\phi}\phi^i}{\sqrt5}\\ &=&\frac{\phi^{i+1}-\hat{\phi^{i+1}}}{\sqrt5}\\ \text{Q.E.D., punk problem.} \end{eqnarray*}$$  From what I searched on the web, there is no available source proving this of the Fibonacci sequence - all inductive hypothesis proofs prove the actual sequence with induction.   Bill, it's always easy to forget about the inherent properties of special numbers... I didn't even realize $\phi$ + $\hat{\phi}$ = 1 in your first hint, as well as the multiplication, until you pointed it out. Alex, I'm sure that going through the problem that way will produce the result, also, but with Bill's, it's much faster.    Thanks for the help.


I want to download a page from a website.  The page is located at an url like:   For download I use the code (downloaded from the internet):  function Download_HTM(const sURL, sLocalFileName:string): boolean; begin   Result:=True;   with TDownLoadURL.Create(nil) do   try     URL:=sURL;     Filename:=sLocalFileName;     try       ExecuteTarget(nil);     except       Result:=False     end;   finally     Free;   end; end;   my call is:   sURL := Format('%s/status?param1=%s&param2=%s&param3=%s',              [sWeb, param1, param2, param3]);  if Download_HTM(sURL, sLocalFile) then   ....   but don't work. Also I used:   sURL := Format('%s/status?param1=%s'#38'param2=%s'#38'param3=%s',              [sWeb, param1, param2, param3]);   but don't work. I can't insert the & character in the url. Any advice?  Now, instead of Download_HTM I tried the bellow function (from a stackoverflow example):  function GetURLAsString(const aURL: string): string; var   lHTTP: TIdHTTP; begin   lHTTP := TIdHTTP.Create(nil);   try     Result := lHTTP.Get(aURL);   finally lHTTP.Free;   end; end;   but I receive: Socket error 10014 - Bad address I'm sure that my address is corect because when I put it on the internet explorer I receive the corect html page.  When I show the sURL variable with the command ShowMessage(sURL) I can see the entire url but without the & character and the character p from the param3 word is underlined (the p character follow after the last & character from the URL) and the behavoir same to be like when I use & to create a shoertcut on a menu caption !

There's a web services I want to call in my application, I can use it with importing the WSDL or by just use "HTTP GET" with the URL and parameters, so I prefer the later because it's simple thing.  I know I can use indy idhttp.get, to do the job, but this is very simple thing and I don't want to add complex indy code to my application.  UPDATE: sorry if I was not clear, I meant by "not to add complex indy code", that I don't want add indy components for just this simple task, and prefer more lighter way for that.


The bash manual says     BASH_SUBSHELL  Incremented by one within each subshell or subshell environment when the shell begins executing in that environment. The   initial value is 0.      SHLVL Incremented by one each time a new instance of Bash is started. This is intended to be a count of how deeply your Bash shells   are nested.   What are the differences between the two builtin variables?  Specifically what differences are between "subshell or subshell environment" and "Bash shells"?  In the following example, why does the value of BASH_SUBSHELL not change, while the value of SHLVL changes?  $ echo $BASH_SUBSHELL 0 $ echo $SHLVL 1 $ bash $ echo $BASH_SUBSHELL 0 $ echo $SHLVL 2

There are this two names: a subshell and a child-shell.  Yes, a child process will be started by any of this:  sh -c 'echo "Hello"' ( echo "hello" ) echo "$(echo "hello") echo "hello" | cat   Are all equivalent and share the same name? Do all share the same properties?    POSIX :     A shell execution environment consists of ....   But the last paragraph of above link has this:     A subshell environment shall be created as a duplicate of the shell environment, except that signal traps that are not being ignored shall be set to the default action.    And specially:     Command substitution, commands that are grouped with parentheses, and asynchronous lists shall be executed in a subshell environment. Additionally, each command of a multi-command pipeline is in a subshell environment; ....   The sh -c 'echo "Hello"' is not included there, should that be called a subshell also?


When connecting to my remote Windows 7 desktop with RDP, once I disconnect and later go back to this computer, all the desktop icons are rearranged from the way they had been, necessitating me to place them back in a certain order. Does anyone know a way to prevent this from happening?

I sometimes remote into my desktop PC (1900x1280) from my laptop (1280x900).  When I do, Windows (Vista) on the desktop PC rearranges all my desktop icons.  I could understand this if the RDP session's desktop size was too small to fit them in, but it's not.  I have about 12 icons, which do fit on the laptop's resolution (I've tried).  Why would Windows rearrange them all like this each time?


Why these two Jordan blocks are similar: $J_k(0)^T $ and $J_k(0)$ ?

Let $n\in\mathbb{N}$ and $A\in M_n(\mathbb{F})$. Assume that the minimal polynomial of the square matrix $A$ is defined as the minimal polynomial of the linear operator $x\mapsto Ax$ for all $x\in\mathbb{F}^n$, on $\mathbb{F}^n$. Now, assume that the minimal polynomial of $A$ splits over $\mathbb{F}$. Show that $A$ and $A^T$ are similar.  Two matrices $A$ and $B$ similar if there exists an invertible matrix $S$ such that $B=SAS^{-1}$. Finding such an $S$ for $B=A^T$ will solve the problem. Since the minimal polynomial of $A$ splits over $\mathbb{F}$, let us denote it by $$m_A(t) = (t-\lambda_1)^{m_1}...(t-\lambda_k)^{m_k}$$ for some $k\in\mathbb{N}$. We know that $m_A(A)$ corresponds to the zero linear operator, i.e. $m_A(A)x=0$, $\forall x\in \mathbb{F}^n$. I quickly noticed that if matrices $P_1,P_2,...P_q$ commute, then $(P_1P_2...P_k)^T = P_1P_2...P_k$. It may be useful to replace each $P_i$ with $(A-\lambda_i)^{m_i}$? I'm not sure how to proceed from here. I'd appreciate any hints!


I don't know very much about formal logic, and I'm trying to understand the concept of vacuously true statements. Consider the truth table below: $$\begin{array} {|c|} \hline P & Q & P\implies Q & Q\implies P & P\iff Q  \\ \hline T & T & T & T & T  \\ \hline T & F & F & \color{blue} T & F\\ \hline F & T & \color{blue}T & F & F\\ \hline F & F & \color{blue} T & \color{blue}T & T \end{array}$$.  The blue letters are definitions. To see why these definitions are the correct choices (as opposed to $F$s), suppose we changed the lower left $\color{blue} T$ to an $F$ (this would then force the lower right $\color{blue}T$ to an $F$), so $P\iff Q$ would be $F$ for $P$ and $Q$ both $F$, which isn't want we want. So I see why this makes sense to choose the lower  entries as $\color{blue}T$.  However, it isn't clear to me why $P\implies Q$ true for $P$ false and $Q$ true is the sensible choice (same for $Q\implies P$ true for $Q$ false and $P$ true). For if the $\color{blue}T$s in the middle rows were switched to $F$s, then $P\iff Q$ would still be $F$. So I don't see what the problem would be. Can someone please explain?

I am studying entailment in classical first-order logic.  The Truth Table we have been presented with for the statement $(p \Rightarrow q)\;$ (a.k.a. '$p$ implies $q$') is: $$\begin{array}{|c|c|c|} \hline p&q&p\Rightarrow q\\ \hline T&T&T\\ T&F&F\\ F&T&T\\ F&F&T\\\hline \end{array}$$  I 'get' lines 1, 2, and 3, but I do not understand line 4.      Why is the statement $(p \Rightarrow q)$ True if both p and q are False?  We have also been told that $(p \Rightarrow q)$ is logically equivalent to $(~p || q)$ (that is $\lnot p \lor q$).  Stemming from my lack of understanding of line 4 of the Truth Table, I do not understand why this equivalence is accurate.       Administrative note. You may experience being directed here even though your question was actually about line 3 of the truth table instead. In that case, see the companion question  And even if your original worry was about line 4, it might be useful to skim the other question anyway; many of the answers to either question attempt to explain both lines.


Is there a way on MacOS notebooks to prevent applications accessing the internet? Like block all and except Chrome? As I have a limited data volume on a mobile data stick. This should be just the case while on that stick, not while I am in a Wifi. It should not throttle bandwidth.

Whenever I use Homebrew or Apple Store to download a large application, it sucks all my available bandwidth and I am then unable to browse the web.  How can limit the bandwidth per-application or per-process in OS X Yosemite (command line preferred, but GUI apps accepted)?  I've played a bit with  application, which suggested I use ALF firewall, but I don't know how to set it up.


I have a command that gets the utilization status of my infra and it needs to be run every 15mins. how do I set a cronjob for that in Mac OS. I searched for cron.hourly and cron.weekly but could not locate them in my mac. can anyone help me with this?

I have a IOS stimulator created in MAC. So for our project testing i need to run the test for every 15mins. Can someone help me create a Cron job for this?  The command i enter to run IOS script is cd /Users/Downloads/uiautomation/ ./runthis.sh


Dear moderators  This question is not a duplicate, as it is about a special case, not a general question. please open this up and let the problem be solved, as this relates to so many people. you may find the view count intresting  Problem  As for  or  or even , my computer has been infected to this sh-t and my browsers open an annoying pop-up (  ) on every single click to whatever web page I am visiting and this is repeated really unlimited times, getting me more and more nervous.  It was just Google Chrome ( 47.0.2526.106 m ), but now I have it on Opera ( 34.0.2036.25 ) too, and I think it will go through the Firefox, IE, ... soon.  Environment   Windows 10 x64 Enterprise (1151) Build 10586.29   My efforts   I found  which would be useful. Used Chrome's Help > Report and issue menu to report it to the Google.  Used the  to remove any problems at the very first moment (just before my opera get infected too). Using the tool, I noticed that the exe file ( Chrome Cleanup Tool ) gets deleted automatically right after usage and so I added an audit on the file for deletion to suspect what process deletes the chrome_cleanup_tool.exe file using Security section under Windows Logs in Windows Even Viewr. The answer was:  Object:     Object Server:          Security     Object Type:            File     Object Name:            C:\Users\{my-user-name}\Downloads\chrome_cleanup_tool.exe     Handle ID:              0x2c     Resource Attributes:    S:AI  Process Information:     Process ID:             0x179c     Process Name:           C:\Windows\SysWOW64\rundll32.exe  Access Request Information:     Accesses:               DELETE     Access Mask:            0x10000   So I am almost sure that my windows has been infected with virus and there is nothing to do with Chrome, Opera, ...   My question   How can I remove the infection from my computer? Any suggestions or similar efforts would be appreciated.

What should I do if my Windows computer seems to be infected with a virus or malware?  What are the symptoms of an infection? What should I do after noticing an infection? What can I do to get rid of it? how to prevent from infection by malware?   This question comes up frequently, and the suggested solutions are usually the same. This community wiki is an attempt to serve as the definitive, most comprehensive answer possible. Feel free to add your contributions via edits.


Don't close this question as a duplicate of either  or  but yes I agree that its similar to these questions. Yes I could edit the existing questions but I have created this question to let developers track this issue differently and can manage easily.  Current app version: 0.1.81  Steps to reproduce issues:   Open app, it shows Area51 site as an advertisement. Click on advertisement, it will show 2-3 choice to open advertisement link with. If you select Chrome or browser, it opens successfully but choose SE android app.   Issues:   site name is shown as "Unknown site a..." in title. "No items to show..." text in center of the screen instead of Area51 site feed.   P.S. One reason I have already mentioned why I have created this question separately, another reason is I am not sure whether advertisement for area51 or other sites are also getting displayed.  Here are the snaps for the same issue/s.

I came across something rather interesting today. I was browsing Area 51 on Chrome when I happened to click on . To this, I was greeted with a prompt asking:    As , and fully expecting a crash, I clicked on SE. However, that didnt happen.     Now, since Area 51 Meta is working correctly as far as Q&A is concerned, I think it should be added to the All Sites list and if at all possible, made directly browsable from within the app.


I've read the books and all but what happened to Valyria? Are there any outside sources? If you think about it, the whole empire was destroyed in this apocalyptic event. The event had to be so bad that a few hundred years afterwards no one would go there. If it was a volcano it would be pretty unlikely that they'd still shun that place in my opinion. Same with an earthquake.

What exactly was, or happened in the Doom of Valyria?  I'm nearing the end of the ASOIAF books and despite countless references, I'm still not clear on what exactly the Doom of Valyria was. If I recall correctly, there have been many different mentions of what appear to be natural disasters. For example:  In A Dance with Dragons (Chapter 33), Tyrion is quoted as thinking:     An empire built on blood and fire. The Valyrians reaped the seed they   had sown.   The implication being that fire was the Doom of Valyria.  Fire is mentioned often, with clear references to the 'Fourteen Flames' which I believe to be a chain of volcanoes.  However  Many other seemingly natural disasters are described, including earthquakes and a tsunami(?).  This makes me wonder, are all these events chained? As in, related or even caused by each other? Was the Doom of Valyria a completely natural event?  Did magic play a part, in any form? I know from references in the books that magic was very prevalent in Valyria.  As stated I'm nearing the end of the books now, so any 'spoilers' which answer my question or relevant questions are very welcome.


I have a problem to install Ubuntu12.04.3 LTS in my computer.  My Computer is DELL(CPU: P4, 3GHz RAM: 1GB HDD: 20GB).  I downloaded Ubuntu12.04.3 LTS and installed this by using wubi.  Then it was installed on rootfs.img file in FAT32 file system.  But I want to install Ubuntu on EXT4 file system.

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


In the Matrix Reloaded, Bane aka Smith begins his day as a real man for the first time, cutting himself.  He does this quite often as we come to be aware of in Revolutions, and my question is why exactly did Smith do this?   Was it because he was feeling pain for the first time and overwhelmed at actually being a real human?

In the Matrix part II and the beginning of part III the crew member who was infected by Agent Smith (Bane) cuts himself.   The female crew member in part III who brought Trinity food told her the same and speculated that they might be "VDT's".  I don't fully understand this. What are VDT's and why would Agent Smith engage in self-cutting unless he has borderline personality disorder or depression or something?


Trying to find a quick calculation to check if my value is primitive rather than working out every a^n (modP) for n= 1 to p-1?

How to test if a number is a primitive root, assuming the $\text{mod}\enspace m$ where $m$ is a prime? And if not?  Is it not enough if the number is relatively prime to the modulus or prime?  I'll write down what I've done and would like to know if I'm right:  I tested if the modulus is prime with the Rabin-miller test. It was prime, so I used python program to factor $m-1$ since $\phi(m) = m - 1$. It printed out $2$ and another prime. So then I calculated $g ^ q \bmod (m-1)$ for all factors where $q$ is the factor and they were $\neq 1$. So $g$ should be a generator, right?


I want to perform 2 query when button is clicked in adapter class, first is select data from table A and insert to Table B, the other is delete row from table A.  Adapter   mdb = new MyDatabaseHelper(v.getContext());  database = mdb.getReadableDatabase();  deleteTask = new DeleteTask();  Cursor cursor = database.rawQuery("SELECT * FROM " + MyDatabaseHelper.TABLE__TASK + " WHERE ID = ? ", new String[]{id+""}, null);  if (cursor != null && cursor.getCount() > 0) {         while (cursor.moveToNext()) {               String allTask = cursor.getString(cursor.getColumnIndex("Title"));              String name = cursor.getString(cursor.getColumnIndex("Name"));              String allTime = cursor.getString(cursor.getColumnIndex("Time"));              String allDate = cursor.getString(cursor.getColumnIndex("Date"));              insertDataToCompleteTab(id, name, allTask, allTime, allDate); //insert to Completed table              deleteTask.deleteData(id); // delete the row of data from Task Table        }  }   DeleteTask    public void deleteData(int id)     {         database = mdb.getWritableDatabase();         database.delete(MyDatabaseHelper.TABLE__TASK, MyDatabaseHelper.ID1 + "=" + id,null);         database.close();     }   Error  java.lang.NullPointerException             at com.example.seng.healthyapp.DeleteTask.deleteData(DeleteTask.java:124)             at com.example.seng.healthyapp.adapter.AllAdapter$1.onClick(AllAdapter.java:139)             at android.view.View.performClick(View.java:4230)   The error pointing to the deleteTask method. But I have done initialized them, why I still getting such error ?

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?


Some BigDecimal values can be compared with a Float by eq in Rspec3, but some values can't be.  describe "compare BigDecimal with Float" do     it { expect("83.79".to_d).to eq(83.79) } # => fail     it { expect("83.75".to_d).to eq(83.75) } # => succeed end   To avoid error, I'm using expressions like eq("83.79".to_d).  Why does the first test fail while the second succeeds?

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


So I'm looking to compare different combinations of features and classifiers. But I'm getting a lot of combinations that achieve 100% cross validation accuracy. I'm trying to figure out how I would compare the usefulness of each combination.  For example I can both train an SVM using Features 1, 10, 15 to get 100% accuracy. But at the same time I can train a logistic regression classifier only using Feature 7 to get 100% accuracy. Also this is a binary classification problem.


I have signed a confidentiality agreement with my university so I have hidden some of the content in the picture, I hope that is okay with the community here.  This is the output of R code with glm regression (Binomial-Logit) with both dependent/independent variables as binary(can take either 0 or 1 value).  As can be seen in my results there is this coefficient sign change while adding more regressors, and I am not sure why is that?  My independent variables are all binary and can take only binary values, but still I have ran the cor() test in R for the matrix which showed no collinearity. I have also checked VIF function in R that also shows no collinearity.   I have searched on internet and they talk about confounding variable( I don't know how to find one and I don't have access to further data from this niche industry).  Can you guys help me interpret these results ? or fix them if you think there is a problem?  Regards.

In my logistic regression the sign of coefficients of a variable (location distance of an amenity) changes based on other variables (with time -ve, with travel distance +ve) in the model. When the location distance is the only variable in the model, it has +ve sign.    Should the variable need to maintain the +ve sign no matter what other variables are added in the model? Does changing sign signify a multicollinearity issue? Some IVs are gaining significance while in a bivariate model, they didn't show significance and vice versa. Is it okay to add variables that don't have much significance (ex: travel distance has a significance of 0.33 individually, but 0.05 when added with other variables) but becomes significant in the model? thanks.


I am checking my tags and I see vote counts as in the attached image  As clearly visible php has 39 counts for 67 php answers/ question. But as I count the votes for php by search 'user:1699833 [php]' it is 46.  I want to know why it is showing 39?

I have a  on a given tag () which has a few upvotes. However, when I look at my , I have none. How can that happen?


I searched in internet and all I found was that we have to search the name of journal in "https://mjl.clarivate.com/" and if it indexed as: SCIE or SSCI or ESCI then the journal is indexed as ISI journal. but I wanted to submit my paper in "https://academic.oup.com/painmedicine" and I serached it in clarivate and it said that it is indexed as SCIE. But when I email to the editor of painmedicine journal he said that their journal is not rated or indexed as ISI. Now I am very confused that which journal is ISI?

What are the main difference between SCI and ISI Journals?  How  can you determine whether a a journal is indexed in SCI or ISI?


I bought a cheap electronics components kit(for the first time, I'm a rookie electronics hobbyist) which came with some cheap resistors with no clear written specifications.  The resistor I am looking to integrate into my simple circuit is colored blue, and it has five color bands.  I don't want to say what color band is last or first(I don't know how to determine the order of the color bands) but the two outer bands are both brown, with there being three black bands in between them, again, making a total of five color bands.   What does all this specify? Does anybody know where I can get quality resistors(that are better documented and come with written specifications) at a good deal?     And if I have this problem again, can someone please supply me with links that can instruct me on how to competently decipher resistor color coding and anatomy. Thank you.

few days ago i bought few (about 500) resistors and i noticed that they have 5 color bands instead of 4. My question is how do i count them (which color is the tollerence) and how should i put them? Do they have a good or bad orientation like + or - ? I tried to use an online calculator but i dont know the first and the last band.


Should down voters be notified about your improvements? It seems like the who down votes your post will not come back and see what you have done.   My Reasons  For many new users like me, we do not automatically understand the the right approach to ask questions. (So we deserve to be down voted for that reason). But as we read and understand feedback from other experienced users, we can improve our post. But the down votes we received from previous newbie mistakes has already impacted us.   1. We are already in the verge of question ban after our first question.      2. We risk to get question banned if we want to ask another question.  3. Down voters who don't leave feed back does not allow new users to understand what is needed to be improved. 4. It would take some time for down voted post to gain some positive votes.    //by that time, the answer you were seeking for is less valued.   As a  that has the simliar mindset.  Lastly, If your post is receiving many down votes with no reasoning, should you delete your post or continue revising and take the risk of losing asking question privileges?

Is a notification sent to someone who downvoted a question when that question has been updated?  Initially, my question got a downvote because it was lacking sufficient information/code/explanation/etc..  Now, I have updated my question & it looks good. Will a notification be sent to the downvoter that this question has been updated, so that the downvoter can review the question again & if it looks good to him/her they can remove the downvote?


For any value of $y$,  is $7|y^2 + 1?$ and $3|y^2 +1$?  as well as   $19|y^2 +1$?  If there is no such $y$, how do you prove it.  Also, I want to know about free software to check these type of divisions in online. Please let me know, if exists such softwares.

I came across this problem and I believe Lagrange's theorem is the key to its solution.  The question is:     Let $p$ be an odd prime. Prove that there is some integer $x$ such that $x^2 \equiv −1 \pmod p$ if and only if $p \equiv 1 \pmod 4$.   I appreciate any help.  Thanks.


The following is an exercise in Real Analysis and Foundations(4th ed, Steven G. Krantz, 105p).  Give an example of a function $f : \mathbb{R} \to \mathbb{R}$ so that $\mathbb{lim}_{x \to c} f(x) $ exists when $c$ is irrational but does not exist when $c$ is rational.  The solution manual for this book(by the author) suggests Thomae function. But this isn't true because although it isn't continuous at rational numbers, it does have a limit $0$ at rational numbers, as mentioned in . What can be a proper example of the question?

This is the starred example 5.1.8 in Krantz' Real Analysis and Foundations.     Give an example of a function $f: \mathbb{R} \rightarrow \mathbb{R}$ so that $\lim_{x\rightarrow c} f(x)$ exists when $c$ is irrational but does not exist when $c$ is rational.   I'm aware of the Dirichlet and Thomae functions but this seems slightly different. I'm not even sure a solution exists. Thanks for any help!


I am trying to do a diagram over a map from Colombia, I use a  and then with tikz draw over it, but I was wondering if there is a way to do a shape or a silhouette of this map with tikz, maybe there is a  package that already have the shape of some countries? Or an easy way to construct this map? Thanks.

I'm trying to draw maps similar to these in a LaTeX pdf document:      I want to auto-generate them from a list of pairs (country,color) to determine the colors.  I have found the package pst-map2dII in pst-geo, however its  is from 2004, is in French and the tutorial examples in it no longer seem to work (or I failed to understand something important in the French part).  Is this package still working somehow, and if so how do I get a basic version to work? Either an English manual or a simple tutorial example similar to the world map above, would greatly be welcomed. If not, other packages or methods to auto-generate them outside LaTeX would be equally welcome.


So I updated my Ubuntu to 20.04 and many small squares with random pixel colors often appear on my desktop background. They are not glued to my screen though; they only appear on desktop. I've attached a screenshot.  .  What can I do?  PS: This has never happened on Windows, so I guess it must be OS-related.  Workaround: Restarting Gnome with Alt+F2 and then entering r solves the problem but only until the next restart.  Update: I changed the driver to NVIDIA's driver and still no luck. Some other random pixels are now on the background. And they remained there even after I changed the driver back to X.Org X server. And one other thing, those pixels go away when I change the background, but they come back the next time Ubuntu starts. Also, changing the background and changing it back to the same one returns the pixels too. It's somehow attached to that specific photo. Plus, Ubuntu is using my Intel graphics card by default, so I don't know if NVIDIA is the problem.  Temporary solution: I changed the desktop environment to Ubuntu on Wayland (you could do that from the login screen using the little tiny settings button if you reading this are also a noob like me :D) and it's fixed for now. I saw some stuff on the Internet that it uses more power, but for now I'll stick with it until I find a solution for the default DE. Will post if I find anything.

I have recently upgraded Ubuntu 19.10 to latest LTS Ubuntu 20.04. After updating, I get serious artifacts on my screen. Every time I reboot (or log-in), my screen is fuzzy or scrambled (picture attached):     This is temporary. The fuzzy screen goes away when I change the background. But it reappears the moment I reboot or log back in.   I have Intel HD Graphics 520 (Skylake GT2).  The output of lspci -nn |grep -E 'VGA|Display' is:  00:02.0 VGA compatible controller [0300]: Intel Corporation Skylake GT2 [HD Graphics 520] [8086:1916] (rev 07)   Update:   On enabling Wayland in Ubuntu 20.04 and logging in to, these artifacts are however cured.   This is okay for now, but I am not sure about Wayland as I have not yet used it before.   Is there a way to correct the graphic issue with normal Ubuntu startup?


Is this good to keep or should i avoid them?

I think my question relates to a fundamental of 3D modeling that I haven't picked up on yet. It's very simple:  Let's say I have a flat quad. A plane on the XY plane inserted into am empty blender file is a great example. Now let's say I start moving each of the 4 vertices around on in any direction, especially the Z axis.   At this point, there would still be one face, but its extremely unlikely that the face would be planar (I just learned this word). So blender does its best to make sense of what this should look like.  The problem I'm having is that it seems like my quads are always like this, but they never look the way I want. There are edges and seams that look like they are dangling in space, and what tends to happen is that my mesh looks great when viewed from most angles, but if you look at it from just the right angle, you notice the dangling edges or sometimes even some kind of impossible geometry. And so I might try to nudge the problematic vertices around, but this often seems to either make it worse, or just hide the bad geometry until you see it from a different angle.  For me, this always seems to happen whenever I'm trying to move vertices to add roundness to something that is originally square.   There is another question on here about how to actually flatten the quads. That's great, and I might use some of the techniques mentioned there. My question is:   Why does this happen? (Can someone explain this better?) What are some tips and tricks to avoid this situation? What are some tips and tricks to mitigate this situation?   EDIT Here is an illustration:  The overall mesh as viewed from a distance looks decent (for my skill level)    But if you get closer and look from a certain angle...    Super close up:    The "edge" that is pointed to by the arrow is not actually an edge, but some kind of artifact created when blender tries to show the quad. The way the vertices are positioned, it shouldn't actually be possible to see the sliver of the face that I marked in red, since this face is supposed to be around the corner from the edges. The edges should form the silhouette on the right side of my figure.     Here is the side view. Maybe it is the angled topology that skews the face in a funny way?  But I'm not looking for help with this one particular issue, but rather a better understanding of why this happens, and ideas to prevent this in future models.