New user having trouble with simple software installation

I downloaded the latest Ubuntu software and installed from flash drive. I enabled update and within software & updates enabled clicked 4 boxes allowing third party software I then downloaded binance application for unix from their website, as it was no where to be found in Ubuntu Software application.  It downloaded as a .rpm package. I would simply like to know how to install this software.  I read I need to install alien and convert from .RPM to Deb format.  Is there another simpler way? The software is in the 'downloads' folder.  When I run the terminal within the same folder and type 'sudo apt install binance' or binance-x86_64-linux.rpm it simply says unable to locate said package. I installed alien and when i try to convert the file it simply says not found I have also ran the synaptics package manager and that too can not find the package even if i rename it and place it on the desktop. Any help would be much appreciated, as I've already spent several hours to no avail.


complex polynomial satisfying inequality

Each of the polynomial of the form $p(z)=a_0+\dots+a_{n-1}z^{n-1}+z^n$ satisfies the inequality $\sup\left\{\,|p(z)|\,\big\vert\,|z|\le 1\,\right\}\ge 1$   Is this statement true or false that we have to find. well MMP says that sup will be attained at $|z|=1$ so when $|z|=1$ we have $|p(z)|=|a_0+a_1\dots+ a_{n-1}+1|\le |a_0|+\dots+|a_{n-1}|+|1|$ I can not conclude more.plz help.


Partial orders and equivalence relations

Let $S = \{ u,v,w \} $  List all equivalence relations on S. How many of these are also partial orders?  Well I found five total equivalences classes but right now I'm confused as to which are partial orders. The confusion is because I'm thinking in transitive terms. For example, one equivalence relation I found is:  $$\{ (u,u),(v,v),(w,w),(u,v),(v,u) \}$$  Anti symmetric means that $(u,v) \land (v,u) \rightarrow u=v$ but $u$ and $v$ are two different variables and so they're not the same. So this means that they're antisymmetric? I don't know why I'm stuck here.


Is it possible to open directories as administrator?

I want to have a root privileges on some directories. How can I do this?


How to find python installation directory on Ubuntu

I have just migrated from Windows environment. I have installed Python 3.2 in a separate directory. How can I get the python installation path in Ubuntu shell?  Is there any way I can let the shell know/choose at runtime which python version is to be used for further code execution?  Are there any environment variables and search path kind of things in Ubuntu Linux as well?


How to upgrade from 18.04.3 to the last 19.10

I use Ubuntu Studio 18.04.3, with the backports PPA to get LTS.  I want to upgrade this system to the last version 19.10.  But... The automatic upgrading system just offers me to go to the 19.04 version.  How can I specifically get the last one (19.10) version?


What are the practical limitations of Asymmetric encryption vs Symmetric encryption?

I hear it commonly said that the advantages of Symmetric encryption are speed and no limit to the amount of data that can be symmetrically encrypted.  I also hear it commonly said that the advantages of Asymmetric encryption are security.  But theoretically, if I want to symmetrically encrypt a 1TB file, my algorithm is just going to break the 1TB file into smaller chunks, encrypt them, and spit out the cipher text.  Why couldn't I do the same with Asymmetric encryption?  AKA,  what are the practical limitations of using Asymmetric encryption for bulk encryption?


Why does my macbook give a slight tingling sensation when it is charging and what could i,we or Apple do about it?

I have been facing this problem since the time of purchase.  I think the shocks go away once it's fully charged.  I experience shocks regardless of whether  I sit directly on the tiled floor at my home, or on a chair with my feet on the ground, or with my shoes on at my workplace. I use the official two pin charger that came with the box. I reside in India.  I have gone through the following posts          Please help me. Many of my friends are also facing the same problem.   This question also asks what could be done by apple about it? and as to why apple is seemingly ignorant of its widespread prevalence?


How to calculate likelihood of linear regression

This is a pretty basic question, but one I am having a hard time finding an answer to. How do you calculate the likelihood of a simple linear model? Like, say, $$y=\beta_0+\beta_1x+e$$ I am working on model selection via AIC and would like to have a better sense of how it works.   edit: So I think I figured it out. When calculating the likelihood of a linear regression you are actually calculating the likelihood of the residuals. In the case that the residuals have a normal distribution the least-squares and maximum-likelihood parameter estimates are mathematically equivalent, but if you have a different distribution of residuals this will not be the case. Is this correct?


A difficult integration that contains $e^{tx} x^{\alpha - 1}(1-x)^{\beta -1}$ .

How can I integrate this integral:  $$\int^{1}_{0} e^{tx} x^{\alpha - 1}(1-x)^{\beta -1}dx.$$ Could anyone give me a hint ?


As $$\frac{dy}{dx}= \lim_{∆x \to 0}\frac{∆y}{∆x}$$ then why $$\frac{dy}{dx}$$ is not a ratio ?


When I try to install anything through console this error occurs:  E: Malformed Entry 53 in list file /etc/apt/sources.list (component) E: The list of sources could not be read E: Malformed entry 53 in list file /etc/apt/sources.list (component) E: The list of sources could not be read


How to find $\sum_{r\ge 0} \binom{n}{r}\binom{n-r}{r} 2^{n-2r}$?

Problem was to find $$\sum_{r\ge 0} \binom{n}{r}\binom{n-r}{r} 2^{n-2r}.$$ My partial progress i tried to motivate such that upper term in binomial terms gets constant rather than variable , so i thought of changing it to form $\binom{n}{n-r}\binom{n-r}{n-2r}$. Now it's of the form $\binom{n}{m}\binom{m}{k}$. We know it is equivalent to $\binom{n}{k}\binom{n-k}{m-k}$. Doing this we get $\binom{n}{2r}\binom{2r}{r}2^{n-2r}$. Now what I need to do as next step as such still nothing the upper or lower terms r any constant values(sum to ) , all are variables still. Now by one answer by Robpratt i got by snake oil , is there any other way to solve this problem ?


If $r,s,t$ are prime numbers and $p,q$ positive integers s.t. $\text{lcm}(p,q)$ is $r^2s^4t^2$, then the number of ordered pairs $(p,q)$ is?

If $r,s,t$ are prime numbers and $p,q$ are the positive integers such that LCM of $p,q$ is $r^2s^4t^2$, then the number of ordered pairs $(p,q)$ is?  My attempt to the solution:  Let $r^a s^b t^c$ be the LCM where $a=2,b=4,c=2$  Then the cases that arise are  I case   1) $p$ has $r^as^bt^c$ then there are a total of $(2+1)(4+1)(2+1)$ options  II case   1) $p$ has $r^as^b$ or $s^bt^c$,$r^at^c$ then there are total of $(2+1)(4+1)(2+1)(3)$ options.  The answers comes out to be $45*4$ but the answer is $45*5$. Which case am I missing?


How can I get Gnome3 to remember my session?

I am running Gnome3, but I had the same problem with Unity, on Ubuntu 12.04.  I have a fairly elaborate setup I enjoy using day-to-day. A LibreOffice spreadsheet with everyone's extension numbers; a window with reference data I use regularly; two mulit-tabbed Konsole/Terminal windows with several remote systems sessions, firefox with a set of open tabs, and so on. But whenever I log out, when I return, I must set up everything from scratch. I remember the good 'ol days, when I rebooted, I'd re-log in, and all my windows came back up in the same places as they were when I logged out, and my Konsole/Term would come up with the same remote logins as before.... I'd have to re -setup  some of my programs, but that's better than having to move every win into place, and resize them, etc.  How do I get this functionality back?


Let $T : V \longrightarrow W$ and $U : W \longrightarrow Z$ be linear maps. How do I prove that $(U\circ T)^{*} = T^{*}\circ U^{*}$? I'm used to seeing $V^{*}$ not $(U\circ T)^{*}$. Any help is appreciated.  $^{*}$ denotes the dual map (transpose).


Merging/Dissolving polygons by Common Attribute Field in QGIS?

I have joined corresponding Local Enterprise Partnerships table data into a polygon shapefile containing UK Local Authorities.      How do I Dissolve or Merge the the Local Authorities polygons by LEP_NAME as shown in the screenshot?   Ideally, I would like to retain the Local Authority attributes with the resultant merged polygons. I have zero scripting knowledge so am looking for a tool based solution. Any help or pointers much appreciated.    Additional Note: When attempting to use the dissolve tool the LEP_NAME field is not available as shown above. The LEP attribute data was created in Excel, saved as CSV format and joined to the Local Authority polygon shapefile. There are duplicate IDENTIFI0 fields as shown in the other screenshot - could this be the root of the issue?


Does dividing a box full of gas at equilibrium change its entropy?

Imagine you have a box full of a gas. It is at thermodynamic equilibrium.  The entropy of the gas in the box is proportional to the logarithm of the number of available microstates.  The number of microstates is proportional to the number of oscillators (abstractly speaking) times the number of available states per oscillator.  Let's limit ourselves to the translational case. In the ideal particle-in-box model, we know that the possible momenta of the particles is quantized, due to the boundary conditions imposed by the sides of the box.   If we were to put a divider in the middle of the box, half of the possible momentum states would now be disallowed. Previously, wavefunctions corresponding to each particle were allowed to have an antinode in the middle of the box ("odd solutions") but now can only have wavefunctions with a node in the middle of the box ("even solution"). There are now fewer translational microstates, so entropy should be reduced.  However, as far as I know, putting a divider in a box does not change the entropy.  A possible solution here is that perfectly rigid dividers and boxes don't exist; a particle can impart momentum into the divider, which can then be imparted to particles on the other side, etc., which would increase the effective number of microstates. However, we should still expect some reduction in available microstates, and this cannot be a complete explanation because we know that if we have two different gasses separated by a divider, by removing the divider we increase total entropy. This, and the fact that increasing volume increases entropy, is nicely explained by the fact that there are more available momentum states in a larger box. However, I cannot reconcile this with the "divider inserted into an equilibrium gas" example I gave above.  Edit: The proposed solution does not address the question in terms of additional momentum state density. I wouldn't even say it actually answers the question at all. "because the thin membrane doesn't materially change the system and carries a tiny entropy by itself. " is not an explanation, just a tautological re-statement of the question.


Below exception is thrown from PayUMoney Android SDK. This is captured in Crashlyst. I cant reproduce this in local but it happens in production for few customer. Please let me know your thought? Im using latest PayUMoney sdk Caused by java.lang.NullPointerException: Attempt to invoke virtual method 'com.payumoney.core.PayUmoneySdkInitializer$PaymentParam com.payumoney.core.PayUmoneySDK.getPaymentParam()' on a null object reference Caused by java.lang.NullPointerException: Attempt to invoke virtual method 'com.payumoney.core.PayUmoneySdkInitializer$PaymentParam com.payumoney.core.PayUmoneySDK.getPaymentParam()' on a null object reference at com.payumoney.sdkui.ui.fragments.PayUMoneyFragment.onCreate(SourceFile:244) at androidx.fragment.app.Fragment.performCreate(Fragment.java:2414) at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:844) at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1229) at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1295) at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManagerImpl.java:2605) at androidx.fragment.app.FragmentManagerImpl.dispatchCreate(FragmentManagerImpl.java:2559) at androidx.fragment.app.FragmentController.dispatchCreate(FragmentController.java:234) at androidx.fragment.app.FragmentActivity.onCreate(FragmentActivity.java:304) at androidx.appcompat.app.AppCompatActivity.onCreate(AppCompatActivity.java:85) at com.payumoney.sdkui.ui.activities.BaseActivity.onCreate(SourceFile:77) at com.payumoney.sdkui.ui.activities.PayUmoneyActivity.onCreate(SourceFile:61) at android.app.Activity.performCreate(Activity.java:6904) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1136) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3266) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3415) at android.app.ActivityThread.-wrap17(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1821) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:7325) at java.lang.reflect.Method.invoke(Method.java) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)


Newtons third law explanation on a push of table

I read this example of pushing a table with your hands. So the force is applied on the table to push and the table exerts the same amount of force on our hands.   My question is, if the forces are equal and opposite, how does the table move on our push? Don't they cancel out? According to newtons third law reaction force from the table is same right.


Organization and tidiness of multiple copies of layers?

Back in the days when I was in the university I had a "Organization and tidiness" problem – I was unorganized and kept my layers in different folders without distinct names and hence had multiple copies of each layer.   Ever since I  started working, I've improved a lot – I keep special folders with special subfolders. I name my layers according to  a system which lets me be a bit more neat, but as I still have to manage multiple copies of layers (As Autocad and ArcGIS have their differences when dealing with non-Latin languages, I have to keep a copy adjusted for each program), I'd like to hear from your experiences and maybe learn a few tips from you:   How do you organize your layers? How do name them? By name, date, contents, customer?   How do you organize or deal with multiple copies (more acute: how do you update several copies at once)?   Note: I'm talking from the analyst/DBA POV and not from a web-developer's/web-manager's POV (I'm talking about organizing the layers for myself and maybe two more GIS workers, not more).


How to search for specific lines in Linux?

I recently received an error telling me that there was a problem on line 52. I am trying to learn what the best method is for finding lines instead of actually counting them.  In Windows, I often used  which displayed the lines directly to the left, so users could easily scroll to the specific line they were looking for -- However I do not see this option in Linux.  Maybe a certain application is needed?    UPDATE: I currently can not open software-store and the only text editor I have is the default nano and gedit. So please restrict your answers to solutions that don't involve me installing software.  **NOTE: ** I am not looking to find a 'String' of some sort. I am looking to quickly find the line NUMBER that the string appears on.


Python Pygame Trasparency showing as black

I am trying to blit an image with transparencies on top of a Surface with the rest of the map. ( This is the second layer. ) When I blit it, it shows with the transparency as black. Is there a way to fix this. I included the code related to it. lily_tex = spritesheet.get_sprite(1, 4).convert_alpha()  This gets the image from the spritesheet.     img = pygame.Surface((self.tilesize, self.tilesize))     img.blit(self.img, (0, 0), (x, y, self.tilesize, self.tilesize))     return img.convert()  And this is what pulls it from the sprite sheet. Below is what blits it to a surface to be blitted to the screen buffer. def create_map(self):     for map_data in self.map_data:         for row in range(len(map_data)):             for column in range(len(map_data[row])):                 if map_data[row][column] == 0:                     continue                 texture = self.key.get(map_data[row][column])                 self.map_img.blit(texture, (column * self.tilesize, row * self.tilesize))  Thank you


How can I execute command on startup (rc.local alternative) on Ubuntu 16.10

I am setting up quota on my Linode server running Ubuntu 16.10, and I get the following error      Cannot stat() mounted device /dev/root: No such file or directory   So to fix this, I reached  for the fix which is done by adding   ln -s /dev/xvda /dev/root /etc/init.d/quota restart   to the /etc/rc.local. But Ubuntu 16.10 doesn't uses rc.local anymore instead uses . What is the alternative for rc.local, How can I run the above commands on startup?  Also I enabled the service using systemctl enable rc-local.service but it didn't work for me. Any lead would be appreciated.


When I ran sudo apt-get update then I found some error. The Error is like below:  W: Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release amd64 (20130424)/dists/raring/main/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W: Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release amd64 (20130424)/dists/raring/restricted/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W: Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release amd64 (20130424)/dists/raring/main/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W: Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release amd64 (20130424)/dists/raring/restricted/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs E: Some index files failed to download. They have been ignored, or old ones used instead.   Could anyone please help me why I am getting this kind error message? I've just found the Error message today on my machine


hyperrefs have a different spacing when written inside a macro

Let's say I want to make a hyperlink like this:  A link is placed \href{www.google.com}{here} to google.     Then I decide to make a macro for that:  \newcommand\Myhref[2]{ \href{#1}{#2} } A link is placed \Myhref{www.google.com}{here} to google.     The spacing is wrong for the second example.  The motivation is that I want to apply a very custom style (with underlines and colouring and font-sizes) that is too complicated for the \hypersetup global style. So I write a macro that applies the style to the hyperlink text. But the spacing is all wrong.


Installing Linux on Wyse Cx0: minimal system needed

I got my hands on a couple of wyse thin clients   I want to use them for RDP purpose. The original plan was to install Tinycore on them and to use Rdesktop to rdp to the server, but the latest rdesktop (1.7) on Tinycore does not support windows server 2008 R2 (had some issues with my pointer device not showing on screen).   Now what I am looking for is a Linux distribution that uses under 128MB of flash memory and under 512MB of RAM. The OS must be capable of running rdesktop 1.8.3.


Generate a random number in a specific range

I am making a program that will generate a random number from 1 to 10 in main and store it in specific fields but we are instructed to use Random.java. What codes shall I put in Random.java ?


Phrase to mean one is described by his name

I found in some other languages such as Chinese an interesting idiom which describes some people; for example, when you see a person is named "Smart" and he/she is really smart, one would say: "a name fits his person" as a literal translation.  I would like to see if there is some specific phrase, idiom or proverb to describe such a situation.


I have a Czech Republic student visa, can I visit someone in Germany with my student visa or student ID? Or like do I have to apply for another visa?


I have a loop going, but there is the possibility for exceptions to be raised inside the loop. This of course would stop my program all together. To prevent that I catch the exceptions and handle them. But then the rest of the iteration runs even though an exception occurred. Is there a keyword to use in my except: clause to just skip the rest of the current iteration?


Log individual users out of a period of inactivity?

There is a setting under Security & Privacy -> Advanced, to "Log out after X minutes of inactivity".  However, this is a system wide setting.  I just want to have my kids account log out after a period of inactivity, but leave my account logged in.  Is that possible?


$\sqrt{2}$ is irrational proof using well-Ordering Property

I am having a problem understanding this proof.   Suppose that $\sqrt{2}$ was rational.   Then there would exist positive integers $a,b$ such that $\sqrt{2}=\frac{a}{b}$. Consequently, the set $S=\{k\sqrt{2} : k \text{ and } k\sqrt{2}$ are positive integers $\}$ is nonempty set of positive integers. Therefore, by the well-ordering property, $S$ has a smallest element, say, $s = t \sqrt{2}$.   We have  $s \sqrt{2}-s = s\sqrt{2}-t\sqrt{2}=(s-t)\sqrt{2}$.  Because $s\sqrt{2} = 2t$ and $s$ are both integers,  $s\sqrt{2} - s = s\sqrt{2}-t\sqrt{2} = (s-t)\sqrt{2}$  must also be an integer.   Furthermore, it is positive, because $s\sqrt{2}-s = s(\sqrt{2}-1)$ and $\sqrt{2} > 1$.   It is less than $s$, because $\sqrt{2} < 2$ so that $\sqrt{2}-1 < 1$. This contradicts the choice of $s$ as the smallest positive integer in $S$. It follows that $\sqrt{2}$ is irrational.  My main problem here is how they got the set $S$. My second confusion is the algebra part $s \sqrt{2}-s$. How did they come up with this?   If someone can explain this proof to me it would be great! thank you


Do I have to make someone coauthor if he/she solves a problem in StackExchange, asked by myself, which is later used in my paper?

Suppose, in my research (mathematical) I have a critical step that I need to solve, and, due to various reasons I cannot find decent answer to that step by myself or by contacting friends or colleagues, so that I decide to post a similar but simpler problem to the relevant StackExchange (Math). Now, if someone comes up with a good answer that I can use to further my research, will it be enough to acknowledge the contribution of the author of the answer and citing that particular thread of StackExchange, or do I need to include that person as a coauthor of the paper that I might prepare based on that answer?   I emphasize here that the paper is supposed to be not all about that particular result, there are many other things, and that particular answer is useful, albeit critically, at an intermediate stage of proving some results in the paper. I personally feel that citing and acknowledging the contribution is respectful enough. However, I want to know what the standard norm is.


Let $x,y$ be positive real numbers with $1<x<y$ and $x^y = y^x$. Prove ${\bf carefully}$ that $x<e<y$.  My attempt to the solution. Notice that if $x^y = y^x$ we can write it as $\dfrac{\ln x }{x} = \dfrac{ \ln y }{y} $ because $x,y$ are both more than 1.We know that the function $f(t) = \dfrac{ \ln t }{t}$ is maximal at $t = e$. Thus, $\dfrac{ \ln y}{y} \leq \dfrac{ \ln e }{e} = \dfrac{1}{e} $ and so $$y \geq e \ln y $$ Now, if $e \geq y$, then $\ln y \leq 1$. I can't seem to see a contradiction from here. Any hint?? Next, Notice that $\dfrac{\ln x }{x} < \dfrac{1}{e}$ then clearly $\boxed{x<e}$. But, I am still stuck on showing $y>e$.


To underscore or to not to underscore, that is the question

Are there any problems with not prefixing private fields with an underscore in C# if the binary version is going to be consumed by other framework languages? For example since C# is case-sensitive you can call a field "foo" and the public property "Foo" and it works fine.  Would this have any effect on a case-insensitive language such as VB.NET, will there by any CLS-compliance (or other) problems if the names are only distinguishable by casing?


Knowing Privilege rights on a file in Linux

i wanted to know the Read / Write Access on to a file , so i did this way   ls -l Denem.sh   This command displayed   -rwxr-xr-x  1 pavan employee 672 DEC 20  2000 pavan.sh   Could anybody please tell me what -rwxr-xr-x  indicates ?? From Wikipedia.com i found that  -rwxr-xr-x  indicates     -rwxr-xr-x   for a regular file whose user class has full permissions and whose group and others classes have only the read and execute permissions.   Now my  question is Should we take the middle thing (-xr-) into considiration ??


How do the B-cells and T-cells recognize or distinguish a body cell from a foreign particle?  I suspect something to do with this causes Auto Immune Disorders.


Best way to find if an item is in a JavaScript array?

What is the best way to find if an object is in an array?  This is the best way I know:    function include(arr, obj) {   for (var i = 0; i < arr.length; i++) {     if (arr[i] == obj) return true;   } }  console.log(include([1, 2, 3, 4], 3)); // true console.log(include([1, 2, 3, 4], 6)); // undefined


My client have installed a managed package in his salesforce org. Now he want to disable some of the trigger in this manages package. From my researcher I am able to understand that the trigger can only be disabled by the developer who have developer the manage package. Or is their any other way to disable the trigger. Just what to confirm is their any other option from our side to disable the trigger.


Why would I open a low-rate 9 month CD instead of a higher rate savings account?

One specific (popular online) bank is offering a 9 month 1.25% CD, while it's savings account is 1.90%.  There's no way I see interest rates tumbling in the next nine months, so why should I -- why should anyone -- get a 1.25% CD when savings accounts are paying 52% more interest?  (This question is not specific to this particular bank at this particular time.  It's about the general practice of buying low-rate CDs when savings accounts have a higher rate.)


What is the difference between the built in echo command and /bin/echo?

I was playing around with the type and which commands and I discovered something strange.  type either returns the path or says that a command is a Bash built in. which either returns the path or nothing for built ins such as exit or type  What is strange is that type echo says that echo is a built in as I expected.  But which echo gives /bin/echo as the path to the echo executable. This doesn't seem to happen for any other built in commands.  I am wondering what the different between the two is, which one Bash chooses to execute in scripts and on the command line, and what the story behind the two echos is.  My system is Ubuntu Desktop 12.04


How does the electric field inside a conductor become zero?

When a conductor is placed in an external electric field, I know that the free electrons arrange themselves in such a way that the field inside the conductor due to these charges cancel the external field.   If the external field was uniform, then the field due to these induced charges would have to be uniform too.   How is an arrangement of electrons ( and positive charges)  possible so that it produces an uniform field at all points inside the conductor?


How do I find this conditional expectation?

$X$ and $Y$ are independent $U(0,1)$ random variables.   I have to find $E[X|X>Y]$.   I found it out by integrating $\int_0^1 \int_y^1 x dxdy$ to get $\frac{1}{3}$ as the answer but this is wrong according to the answer key. What is the mistake that I have made?


PHP | Searching for the user and vulnerability for attacks

I am using MySQLi to prevent any further attacks to my website. I am using PHP 5.6.16, MySQL version of: 5.7.9, and using WAMP  I'm encountering the following error when searching for the user with some weird characters, like adding a ') character in the search box.     MySQL error # 1064 and SQLi vulnerability   How can I sanitize the text box input and prevent any weird or unrecognized characters to be searched?  Screenshot:    Codes:  <?php # Essential files, please don't erase it! require_once("../functions.php"); require_once("../db-const.php"); session_start(); ?>
 View Profile

 <?php if (logged_in() == false) { echo "";     redirect_to("login.php"); } else {     if (isset($_GET['username']) && $_GET['username'] != "") {         $username = $_GET['username'];     } else {         $username = $_SESSION['username'];     }      ## connect mysql server         $mysqli = new mysqli(localhost, root, "", loginsecure);         # check connection         if ($mysqli->connect_errno) {             echo "
MySQL error no {$mysqli->connect_errno} : {$mysqli->connect_error}
";             exit();         }     ## query database         # fetch data from mysql database         $sql = "SELECT * FROM users WHERE username ='".$username."' LIMIT 1";          if ($result = $mysqli->query($sql)) {             $user = $result->fetch_array();         } else {             echo "
MySQL error no {$mysqli->errno} : {$mysqli->error}
";             exit();         }          if ($result->num_rows == 1) {             # calculating online status             if (time() - $user['status'] <= (5*200)) { // 300 seconds = 5 minutes timeout                 $status = "Yes";             } else {                 $status = "No";             }              # echo the user profile data             echo "<title> View Profile of: {$user['username']} </title>";             echo " Account Searcher:
             <form action=\"?username=\" method=\"get\">             Unique ID: <input type=\"text\" name=\"username\" placeholder=\"Searching for user: {$_GET['username']}\">             <input type=\"submit\" value=\"Search\">             </form>
             ";             echo "Unique ID: {$user['id']}\n
Username: {$user['username']}\n
First Name: {$user['first_name']}\n
Last Name: {$user['last_name']}\n
Email: {$user['email']}\n
Online? $status\n
";         } else { // If user doesn't exists - trigger this event             echo " Account Searcher:
             <form action=\"\" method=\"get\">             Username: <input type=\"text\" name=\"username\" placeholder=\"User not found!\">             <input type=\"submit\" value=\"Search\">             </form>
             ";             echo "<title> User doesn't exists! | Prospekt </title>
Error: User doesn't exist! Please register first!
";         } }  // showing the login & register or logout link if (logged_in() == true) {     echo 'Log Out |  Go to Home '; } else {     echo 'Login | Register'; } ?>


In Italian, when I write a sentence about an action (e.g. eating fish, playing), I would use the infinitive, such as  mangiare pesce fa bene alla salute (which literally is "to eat fish is healthy"), or giocare aiuta ad imparare (which literally is "to play helps to learn").   I would use the gerund in giocando si impara, but that would roughly mean "When playing, you learn." and in this case the infinitive would not be correct. (Giocare si impara is not what you would say in Italian.)  Should I use the infinitive, or the gerund, in sentences similar to the following ones?   To play with fire is dangerous. To win the lottery is just a matter of luck. To escape from Alcatraz is impossible. To practice makes you perfect.   Is the infinitive always wrong, when the verb is the subject of a sentence?


How do I make this script search through all users home folders and then rm -f the files matching EXT?

How do I make this script search through all users' home folders and then rm -f the files matching EXT? Right now it's only deleting the files matching EXT in the current folder where I am executing the script.   #!/bin/bash EXT=jpg for i in *; do   if [ "${i}" != "${i%.${EXT}}" ];then     echo "I do something with the file $i"     rm -f $i   fi done


How to name the arguments in \newcommand so that when you call the macro they don't appear as {arg1}{arg2}... etc. but with the names each argument represent {caption}{label}... etc. without the use of a .cwl file.  I'm trying to implement the following \newcommand  \documentclass{article}  \usepackage{ctable} \usepackage{mwe}  \newcommand{\qfigure}[5]{\ctable[ caption= {#1},label= fig:#2,figure, pos=H,botcap, mincapwidth= #3 mm]{c} {}{\includegraphics[width=#4\textwidth]{#5}}}  \begin{document}  % \qfigure{arg1}{arg2}{arg3}{arg4}{arg5} % They would appear like this in Texstudio \qfigure{An image example}{test}{70}{0.5}{example-image-a}  \end{document}   As you can see there are five arguments where each one represents the caption, label, min width of caption (ctable parameter), width and file name respectively.  Thanks in advance for any help.


Linux Hosting: What is the purpose of setting hostname/FQDN in hosts file?

I just bought a  VPS hosting plan and was following this  to set up. In the "Setting the Hostname" section and "Update /etc/hosts " section, it says the FQDN/hostname to be set here does not need to be related with the websites I am about to host, which makes me confused.  I did my own research by reading lots of articles but am still not very sure what role the hostname/FQDN is playing in my web hosting business. Here are some basic facts I've managed to find out, feel free to correct me if anything wrong:   FQDN must be something like xxx.somedomain.com, if "xxx." is omitted then it is not a FQDN. the xxx, which I think could be loosely called a subdomain, can also be referred to as "hostname", according to . In my local machine, by adding the following line to the hosts file  63.117.14.58 www.yahoo.com whatever   every network requests for "www.yahoo.com" or "whatever" will be redirected to IP address 63.117.14.58(which is google.com's IP). It is a way to block unwanted sites in local machine.  Now the tutorial suggests adding this line to the "hosts" file in my server  12.34.56.78(//my server's IP) myhostname.anything.com myhostname   It mentions that in the above line, domain name may or may not be the domain I am about to host, but the hostname should be the one I have already set during previous steps. My questions are:  1)Based on Facts#3, I think this line redirects any requests on the server for myhostname.anything.com or myhostname to my IP address, but what does this mean? Shouldn't any request for myhostname.anything.com from a user's computer already be translated to a certain IP address(Be it or not my IP address)? Why do I have to redirect it on my server?  My understanding about how a HTTP request works is when user type in the domain name into the browser, the browser will contact the domain server, and the domain server will direct it to a DNS server based on the domain's DNS record, and then the DNS server will resolve the IP address, and then browser fetch data from that IP address. This procedure of my understanding seems having nothing to do with the "hosts" file on my server.  2) A.In regards of the FQDN, why the hostname has to be same with the hostname I set on my server and the domain name doesn't?   B.What will happen if I do set a different hostname here?   C.And what is the purpose to set or not set my domain name as the FQDN here?   D.And what will happen if I only set a FQDN but not the hostname? like this  12.34.56.78(//my server's IP) myhostname.anything.com   Lots of questions but I believe the answers to some of them are overlapped, and overall I think the big question is "What part does setting hostname/editting hosts file play in my webhosting business?"   Thank you for your time in advance.


How to improve image sharpness on Canon 700D?

I'm currently using a Canon 700D with a few EF-S lenses, I like the Canon system, the looks, feel and ergonomics but I'm not happy with the files I'm getting. Whenever I come across a photo that appeals to me from a technical point of view it happens to be shot on a full frame camera or some Sony sensor APS-C. The most important thing I miss in my files is sharpness, overall Canon crop sensor cameras lack in focus and / or sharpening ability when compared to Nikon / Sony / Fuji etc. Would you advise me to upgrade to a full frame 6D or to switch brands to Nikon D7100 / D7200 / possibly Nikon D610? I have just 4 basic lenses so the cost wouldn't be very high. I don't want to ask another question which brand is better, just some opinions on the best / the most efficient way to raise technical image quality. I know I can buy a professional lens like Sigma 18-35, but I have just one body which I'm going to upgrade soon, and I think maybe it would be more wise to buy the Sigma lens for a Nikon body to get optimal results.


Do I always need to start at the begining when switching phones?

My phone is broken so I have switched between 2 other phones, and when im logging in I always have to start at the beginning, so I never get to a high level! Can someone help me?


Modification of StackExchange network profile

A few years ago I created an account on Askubuntu. Now I would like to change my SE network profile information because I am a member of several more SE sites.  However, It seems that the only way that I could do this would be to go back and modify my profile on my original Askubuntu  account.  How would I go about changing my network profile without changing my profile on Askubuntu?


TIPA package causing error in xelatex: \sups already defined

I am trying to include some of my publications in my CV, which it typeset in LaTeX. I have a .bib file and I call the references using \bibverse{}. The problem is that I am unable to compile the document, and I believe this is happening because some of the articles have IPA symbols in the title. I get the following error:  Argument of \BR@@lbibitem has an extra }. [   \bibverse{article2012}]   The bib items do not have extra }'s. My initial guess was that the IPA symbols in the title were causing the problem, so I included the TIPA package, and got the following error:  LaTeX Error: Command \sups already defined. [  \lower.8ex\hbox{\super{#2}}}{#1}}}]   I am unclear on what \sups are and google searching has not been of any help. I am aware that TIPA should not be necessary when using XeLaTex. One possibility would be to not use TIPA in my .bib file, but the problem is that I use this file in many documents that are not compiled in xelatex so I prefer to keep it constant.  This is what my preamble looks like:  \documentclass[11pt]{article} \usepackage{url,fancyhdr} \usepackage{fontspec} \usepackage{xunicode} \usepackage[usenames,dvipsnames]{color} \usepackage{tipa} \usepackage{geometry} \usepackage{multicol} \usepackage[spanish, english]{babel} \usepackage{natbib} \usepackage{bibentry} \newcommand{\bibverse}[1]{\begin{verse} \bibentry{#1}. \end{verse}}  \begin{document}  \textteshlig \bibverse{publication1}  \nobibliography* \bibliographystyle{apalike} \nobibliography{publicationsCV} \end{document}   Edit: The reason I tried to compile the document using TIPA is because the .bib file includes ipa characters (i.e. \textteshlig). The reason for using the verse environment is to be able to insert full references (my publications) where need be. For example, my cv has a section for conference presentations. If I were to simply generate a bibliography I would have no control over what goes where. Here is an example of what the bib verse looks like in the .tex file.  \bibverse{publication1}   And here is an example of what it looks like in the .bib file.  @conference{publication1, Author = {My Name}, Month = {April}, Organization = {In Selected Proceedings of the a Conference.}, Place = {University of Somewhere, City, State}, Publisher = {Some publisher}, Title = {Title with IPA symbols: /\textteshlig/}, Year = {2013}}   This works fine in other documents compiled with pdflatex.


When adding a UV Sphere mesh in Blender 2.8, the creation parameters menu on the bottom left of the attached image for this UV Sphere seems to be greyed out. Any idea why this might be? Thanks.


Pay now vs Pay later on travel booking websites

I'm planning for a trip from the US to Iceland and I've noticed some hotels give the option to pay now or later. I'm specifically talking about Expedia but they all seem to be the same anyway. I've compared it to some hotels in my local town, and the prices for both options are the same. But at the Iceland hotels the pay now option is typically cheaper. In one instance I could save $50 by paying now for a 2 night stay. The pay now option is also cheaper than booking directly with the hotel.  So what are the difference besides the obvious? I did find a couple questions similar to this one, but they were only about having the same prices for both options.


How do I make my django application perform a job at a fixed time everyday?

Some tuples in my database need to be erased after a given time. I need my django app to check if the rows have expired.  While I can definitely write the function, how do I make Django run at everyday at a fixed time?  I have heard about Task Queues like Celery. Are they too much powerful for this? Is their anything simpler? May be something build-in?


Missing terms/extra commas in link-sharing prompt at bottom of unanswered questions

I recently started encountering some strange formatting in the prompt to share unanswered questions. The names of the various sharing services other than email were missing, leaving an awkward string of commas. Screencap:    Example posts: ,


How to identify the Windows version of a dead install from Linux by having access only to its filesystem?

My question doesn't have an answer there, because all of them are windows-specific and I want a linux solution.  I have a dead windows install in one of my partitions. It doesn't have any boot data any more. Practically, it is only a filesystem dump. But I have access to read any files on its filesystem.  How could I identify, which Windows version is it? In ideal case, I think there should be some configuration setting or any file which is unique to the different Windows versions. For example, on Debian-based Linux distros I could simply read /etc/debian_version.  How could I do the same on a Win?  Extension #1: Unfortunately, I have access only to a Linux box to reach its hard disk. So, solutions requiring a Windows (for example, digging in the version of ntoskrnl.exe, or checking some registry settings) aren't in my case feasible.


Automorphism on subgroup lift to the whole group

By definition, if $H$ is characteristic subgroup of $G$, then every automorphism of $G$ restricted on $H$ is an automorphism of $H$.  From these two questions   we know it's generally false that if $H$ is characteristic subgroup of $G$, given $\varphi \in \text{Aut}(H)$, then there exists $\psi\in\text{Aut}(G)$ s.t. $\psi|_H=\varphi$. Example from $A_3$ and $S_3$ shows even if such a $\psi$ exists, it may not be unique.  My question:  Suppose $H$ is subgroup of $G$, what's the sufficient condition s.t. $\forall \varphi \in \text{Aut}(H)$, $\exists\ \psi\in\text{Aut}(G)$ s.t. $\psi|_H=\varphi$?  Background:  This question comes from studying $\text{Aut}(S_n)$ and $\text{Aut}(A_n)$.  If $n\geqslant 4$ and $n \neq 6$, then $\operatorname{Aut}(A_n)\cong\operatorname{Inn }(S_n)\cong\operatorname{Aut}(S_n)\cong S_n$.  The existence and uniqueness is true for $A_n$ and $S_n$($n\geqslant 4$ and $n \neq 6$), while uniqueness is not true for $A_3$ and $S_3$.  To move this question out of the unanswered list, I put related materials in answer.


Can you fully remove Google system apps from Android including the Play Store updates?

Believe it or not, but I want to remove a few Google Apps which I have no use for and want to free up space, resources and mobile data usage by not having them on my phone at all.  These include:   Google Currents Google Play Music Google Play Movies Google Play Newsstand Google Keyboard Google+   I have ‘uninstalled’ them via the Play Store, but they still appear in my ‘Installed’ items in ‘My apps’ in the Play Store and instead of ‘UPDATE' and ‘UNINSTALL’ for any other app in my ‘Installed’ list, they stubbornly remain and only have ‘OPEN’ AND ‘UPDATE’ options.  Also going in the ‘All’ list in ‘My Apps’, all these apps are also different from other ones, where unlike other locally uninstalled apps that have their payment status (‘FREE’ or ‘PURCHASED’) and a ‘X’ at the top to remove it from your Google Account entirely, these Google Apps that I don’t want on my Android and want to be completely optional for my Android experience, only have an ‘UPDATE’ and no X up the top of their listing.  I don’t mind them remaining on the Google Account if Google insists on this, but I just want listings to ‘update’ them in my Google Play updates list to be removed, given this is Google basically forcing me to reinstall them against my will.  Is there a way to do this?  I’m on stock 4.3 Gnex.


I'm trying to draw a lady that will get printed on a t-shirt. The lady will be positioned around the heart and will be around that size, so just a lady on the center of the chest. What size should i make the file where i will draw in Photoshop. What resolution. Thanks!


Why is it still common to use too similar glyphs for "1" and "l" in monospace?

I have difficulty differentiating "l" and "1" when reading source code, i.e. monospace serif types. I am able to tell which is which when looking more closely, but regardless of my eyesight, this requires additional concentration.  From my tests, this stems from the arrow head of the "l", which in combination with a wide base looks very similar to a classic "1" (e.g. in Courier Prime).  Notably, this confusion is greatly reduced when using either no arrow head (which looks a bit strange!), or a half width base (Fira Mono), or both (Monoid).    However, looking at , it appears the problematic combination is easily prevalent.  Why is that? Should we not work more to remove this issue? Or is it just me having trouble?  I do understand that sans serif, the letters will look similar - but I'd hope that monospace serif would fix it, by using all the additional space available. In particular since some of the offending fonts were especially created for use in programming.  Edit: It should be noted that the problematic shape (the lower case L of e.g. Courier Prime) is commonly used to denote a '1' in other fonts (though often in reduced height, e.g. in FF Seria Sans). This surely contributes to my mind reading it as a '1'.


calling a method and it doesn't do it's work

I made 2 classes one is :   public class JavaApplication5 {   public static void main(String[] args) {     int y=0;     cats catobject = new cats();     catobject.ma(y);     System.out.println(y);   } }   the other is :   class cats {    public void ma(int x){     x=x+9;   } }   it's supposed to print out 9 since the method ma should have added 9 to the integer y , but instead it prints out 0. why?


Let's say I have a sentence similar to      When a scientist publishes results, she must be careful to not enter the incorrect data.   However, I am confused as to what I should use in place of the "she".  Using a "she" to refer to an arbitrary scientist, to me, seems just as weird as referring to an arbitrary scientist as "he", while "they" just seems grammatically incorrect.  I have been told that the grammatically correct, gender neutral form of the sentence would be     When a scientist publishes results, he/she must be careful to not enter the incorrect data.   But, come on, I'm not going to write "he/she" every time I have to refer to someone of unspecified gender.   How do I go about dealing with this? I understand that I could simply rephrase the sentence as      When scientists publish results, they must be careful to not enter incorrect data.   This is what I do in most cases when I am confronted with this problem.  My question is:   What should I do if I want to stay as close as possible to the original sentence structure (for instance, maintaining the singular form of scientist? What should I do in general when I am confronted with situations like this one? What options are there (e.g. converting to plural)?


I intend to start incremental backups of my Fedora 20 system, and would like to know what root directories I should include, and what directories it is useful to exclude. I know there is a lot of information on this on the 'net already, but none of it seems to answer this simple specific question. Looking at the answers already available on this site, they are useful, but so many end in etc, instead of being specific, which is not really very helpful.  I assume that I needn't or shouldn't backup directories that are created or filled in by the system as it runs, for instance certainly not /run/media/Harry/CA6C321E6C32062B which is the hard drive that I will be saving the backup on. Are there any more like this?  I will be using rsync in the system described , which I have already tested on small runs. I have looked into luckyBackup as a GUI front end, but get lost in its technicalities (please see my footnote). I will use its task manager to form the command I need for rsync, when I know what files to include and exclude.  In the event of a crash I envisage a re-installation of Fedora, then using the backup as a resource as I get going again, rather than trying to exactly reproduce the state just before the crash.  What files should I include and exclude specifically?  Footnote: In luckyBackup I do not see the way to use datestamps as in the reference I give, and I do not understand how to use the log of a dry run: why is it printed red, after some black lines at the start which I can no longer access because the log is so long?, and how do I find details of the errors to know if they matter? These are rhetorical questions, my real question is still only : what files to include and exclude, please?


Im currently doing a cemetery mapping system for my thesis using arcgis, however i dont know how to use arcgis, i dont quite get the tutorials that i watch, i just want to make a simple map that can store the information of each person and search them.   Do you know any tutorials or know how to do so yourself related to this topic?


Why are there only derivatives to the first order in the Lagrangian?

Why is the Lagrangian a function of the position and velocity (possibly also of time) and why are dependences on higher order derivatives (acceleration, jerk,...) excluded?  Is there a good reason for this or is it simply "because it works".


Money Exchange (CHF to USD) in Switzerland, Canada or in the USA?

I want to buy US dollar with swiss francs. I have the opportunity to make this change in Switzerland (Geneva), in the USA (Seattle) or in Canada (Vancouver). Where will I likely get the best change?   is a related question that does not contain a third country (Canada) in the list of choice.


I have an audio interface device and it has a power supply requirement at 9V DC 3.5A. The original power supply adapter that came with it was 9V DC 4A. Can I replace this with an adapter rated for 9V DC 5A with no risk to the interface device?


I have a very simple problem. I want to write "a" in an equation, however output is .... Please see output. Please see "a" carefully, the problem is there. How i can overcome this problem?


Is there a way to find self's dynamic public ip address using cli in Debian?

The easiest/simplest understanding of the web is   a. When you connect to your ISP, the ISP gives a dyanmic address (like a temporary telephone number) only for the duration of that connection, the next time you connect, you will again have a different dynamic IP Address.   b. You use the browser to to different sites which have static IP Address (like permanent numbers or/and permanent address of an establishment).   Now is there a way to get self's IP address instead of going to a web-service like whatismyipaddress.com.   The connection is as follows :-  ISP - Modem/Router - System    Edit - The Modem/Router is a D-Link DSL-2750U ADSL router/modem.   I did see  but that also uses an external web-service, it would be better/nicer if we could do without going to an exernal URL/IP address for the same.


Closest equivelant to TexShop on Windows or Linux?

Just finishing up my thesis which I've created in TexShop in osx. I'd like to allow others to edit my document. I've got a desktop that's got Windows and Ubuntu installed that they could do this on (they'll be latex newbies).  My main concern is that TexShop has the feature of having a master document, with sub documents able to be compiled with a special comment line (that directs the compiler back to the main document). Are there any other editors that also support this feature?  Main question: what editor do you suggest?


Confusion regarding manuscript status in IOP's article tracking system and ScholarOne Manuscript System

I had submitted a manuscript in an IOP journal a month back. In the IOP's article tracking system, the status changed from "1st reviewer agreed to report" to "Editorial Assessment" instead of "All reviewer reports received". However, in the ScholarOne Manuscript System, the status changed from "Awaiting Referee Reports" to "Awaiting Decision". What should be the interpretation of the current status of the manuscript?


I have a table that lists various attributes of an individuals personal development plan; objective, time to complete objective, comments etc. The table is editable so the user can directly add comments without having to go to an intermediate form. The problem is that the client wants to add more columns and this is messing up the visual display.   The alternatives I have are:   allowing columns to expand out on click keeping essential attributes in table, rest in 'advanced edit option form' or somesuch I don't know - have you any ideas?   One more thing to add: I think the addition of extra columns is based on user feedback ...  edit: here is what I have gone for


How can I set a breakpoint on "dependency property changed"?

Our Silverlight app contains a third-party control, which contains some ScrollBars (among other things). In order to troubleshoot a problem, I want to be able to stop in the debugger whenever the third-party control modifies the Minimum or Maximum properties of any of its scrollbars. Then I'll be able to look at the stack trace and learn more about what's going on.  If I was interested in the ScrollBars' Value property, that would all be easy -- ScrollBar has a ValueChanged event, so I could just add some throwaway code that hooks that event on the ScrollBar, set a breakpoint inside my event handler, and debug away. But there are no corresponding CLR events for MinimumChanged or MaximumChanged, so it won't be that simple.  I ran across a blog post that talks about , but unfortunately,  doesn't exist in Silverlight.  How can I get to the point where I can set a breakpoint that fires whenever the ScrollBar's Minimum and Maximum properties change?


Where can I ask about whether Atlantropa was actually feasible?

was a gigantic engineering and colonisation idea from the 1920's. It involved building humongous hydroelectric dams and lowering the water level of the Mediterranean by something like 200 meters.  I want to ask whether that plan would have been possible, remotely feasible or just crazy.  Is this question suitable for any SE site at all?  What is the best site to ask it at? I have considered Earth Science and Engineering, but I'm not familiar with either site, so I'm not sure.


Biblatex: Attach "'s" to author name in citations

I am using biblatex with biber as backend and natbib loaded. What I am trying to achieve is appending an author's name with 's, e.g. in a situation like:     [...] as outlined in Krugman's (1989) early work   I could use \citeauthor{krugman89}'s (\citeyear{krugman89}), I suppose, but I was wondering whether there is a more direct way of appending the 's directly to the author's name. \citet[]['s]{krugman89} would not work, since this adds the 's after year in parenthesis, i.e. Krugman (1989, 's).


How can I display the table caption at the left side?  Thank you,


Is there a way to catch System.AssertException?  For example, some class is known to throw assertions in certain cases and it's ok to deal with that on some upper level. But unfortunately straightforward try-catch doesn't work for assert. I expect that this code will not throw an exception but it does:  try{     System.assert(false, 'fail'); }catch(System.AssertException asEx){     System.debug('success'); }   So, is there a way to implement ability of catching asserts?


Can the Maverick hat be made a silver badge?

It seems that there are no badges similar to the criteria of the :     answer +5 a -3 question that goes to +3   This badge would promote users to answer many underrated good questions.  Would this make a good silver badge?


How to detect interactions in a random forest model?

When I fit a regression tree model in R, I can somehow look at the plotted tree to figure out the interactions of the predictors. However, when I fit a random forest model, I cannot plot a tree because there are too many of them. I can somehow find the importance order of the predictors (using varImpPlot function), but I do not know how to detect the interactions from the model. By the way, the importance plot only gives the importance order of the predictors, how can I figure out exactly how many of them should be included for further investigation. Thank you.


Saving a mesh from a frame in a cloth simulation?

So right now I'm trying to put a mesh of a small pouch on the side of one of my characters. While I could make it like I would any other mesh, it would look kind of un-natural. When playing around in blender though, I noticed if you were to use the cloth effect to drape it over a few object that are close together, it makes something much like the desired effect.  So my question is, could I take the 'animated' cloth dropping over an object, say at frame 60, and make that the default way the shape is? Of course allowing me to then rotate it upward and edit it to the character.


Your python3 install is corrupted Please fix the '/usr/bin/python3' symlink

I am trying to update from Ubuntu 18.04 to 20.04, but when I run do-release-update, I get error:  su@sudo:~$ do-release-upgrade -d  Checking for a new Ubuntu release Get:1 Upgrade tool signature [1,554 B]                                          Get:2 Upgrade tool [1,342 kB]                                                   Fetched 1,343 kB in 0s (0 B/s)                                                  authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg'  extracting 'focal.tar.gz' Reading cache  Checking package manager  Can not upgrade   Your python3 install is corrupted. Please fix the '/usr/bin/python3'  symlink.     ls -al /usr/bin | grep python3  lrwxrwxrwx  1 root root          29 Mar 27  2018 dh_python3 -> ../share/dh-python/dh_python3 lrwxrwxrwx  1 root root          23 Apr 18 07:26 pdb3.6 -> ../lib/python3.6/pdb.py lrwxrwxrwx  1 root root          23 Nov  7  2019 pdb3.7 -> ../lib/python3.7/pdb.py lrwxrwxrwx  1 root root          31 Oct 25  2018 py3versions -> ../share/python3/py3versions.py lrwxrwxrwx  1 root root          19 Jun 10 15:12 python3 -> /usr/bin/python3.6m lrwxrwxrwx  1 root root          16 Jun 10 14:36 python3.6 -> /usr/bin/python3 lrwxrwxrwx  1 root root          33 Apr 18 07:26 python3.6-config -> x86_64-linux-gnu-python3.6-config -rwxr-xr-x  1 root root     4526456 Apr 18 07:26 python3.6m lrwxrwxrwx  1 root root          34 Apr 18 07:26 python3.6m-config -> x86_64-linux-gnu-python3.6m-config -rwxr-xr-x  2 root root     4873376 Nov  7  2019 python3.7 -rwxr-xr-x  2 root root     4873376 Nov  7  2019 python3.7m lrwxrwxrwx  1 root root          16 Oct 25  2018 python3-config -> python3.6-config lrwxrwxrwx  1 root root          10 Oct 25  2018 python3m -> python3.6m lrwxrwxrwx  1 root root          17 Oct 25  2018 python3m-config -> python3.6m-config lrwxrwxrwx  1 root root          34 Apr 18 07:26 x86_64-linux-gnu-python3.6-config -> x86_64-linux-gnu-python3.6m-config -rwxr-xr-x  1 root root        3283 Apr 18 07:26 x86_64-linux-gnu-python3.6m-config lrwxrwxrwx  1 root root          33 Oct 25  2018 x86_64-linux-gnu-python3-config -> x86_64-linux-gnu-python3.6-config lrwxrwxrwx  1 root root          34 Oct 25  2018 x86_64-linux-gnu-python3m-config -> x86_64-linux-gnu-python3.6m-config   $ dpkg -l | egrep  -v '^ii|rc'  Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend +++-=============================================-===================================================-============-================================================================================= rFR python3                                       3.6.7-1~18.04                                       amd64        interactive high-level object-oriented language (default python3 version)


Ring With Unity As a Direct Sum of Non-Zero Ideals

Let $R$ be a ring with unity. Let $ (a_i),i\in I $ be a family of non-zero ideals of $R$. Suppose that $R$ is a direct sum of the family $ (a_i),i\in I $ (i.e the additive group $R$ is a direct sum of the subgroups  $ a_i,i\in I $). I wish to prove that in this case $I$ must be a finite set.   I will explain the argument which I gave until the point of my question:   Take the identity element $ 1\in R $. Since $R$ is the direct sum of the $a_i$, there exists a finite subset $I_0 \subseteq I$ and elements $e_i \in a_i \setminus 0 , i \in I_0$ such that $1 = \sum_{i \in I_0} e_i $. Then, for every $x \in R$ we have $x = x.1 = \sum_{i \in I_0} xe_i \in \sum_{i \in I_0} a_i $ since each $a_i$ is an ideal, and so $R = \sum_{i \in I_0} a_i $.  My idea now is to prove that one must have $I = I_0$, but I have a feeling that I'm missing something trivial. Can anyone help me with this final step if possible? Thank you in advance.  On a final note, I'm assuming that each $a_i$ is an ideal, but as far as I was informed, this is also true for left ideals (or  right ideals).


To show that $\langle x-a , y-b\rangle$ is a maximal ideal of $F[x,y]$ by showing that $F[x,y]/\langle x-a , y-b\rangle$ is a field

Is there any way to show that for $a,b \in F$ , the ideal $\langle x-a , y-b\rangle$ is maximal in  $ F[x,y]$ , by showing that the quotient $F[x,y]/\langle x-a , y-b\rangle$ is a field ? Is the quotient  $F[x,y]/\langle x-a , y-b\rangle$ isomorphic with $F$ ? ( Here $F$ is a field )   I can show that the map $g : F[x,y] \to F$ given by $g( p(x,y))=p(a,b)$ is a surjective ring homomorphism with $\langle x-a , y-b\rangle \subseteq \ker g$ but I cannot show that the kernel is exactly that ; PLease help, Thanks in advance


Can anyone derive the formula for the expansion $(x + \Delta x)^{n}$ that uses Big O notation?

There is a formula that describes this expansion using big O notation, I'm very curious on how this is derived. I also understand that the order term may very depending on what $\Delta x$ approaches to in limit ?  $(x + \Delta x)^{n} = x^{n} + nx^{n-1}\Delta x + O((\Delta x)^{2})$


We are working with two brochures, which we are looking to copy content from into one new brochure. These two brochures are different page sizes, and so image and text are different sizes as well.   What we would like to do is resize the pages of either brochure and copy them into the new brochure, keeping all the text and images in the same position and in tact (except smaller or bigger).  How would we go about doing this? Any help would be much appreciated!


Searching for "stack overflow" redirects me to the [stackoverflow] tag

I searched for "stack overflow" in the search bar, but it doesn't list the results normally. Instead, it redirects me to the tag .  Why is this happening, and how can I search for posts literally containing "stack overflow"?


apt-get broken + dependencies issue + many software uninstalled

OS=ubuntu 12.04 64bit 3.2.0-29-generic  what i did?  apt-get purge libre* which i thought will remove LO 3.5 but, which was a big mistake after couple of moments, i realise that its is removing all other software so i did cltl-c which stopped the apt process i restarted my system after that i found that following software were missing apt-get,evince(pdf), cheese etc..here is full list   i managed to install APT deb file through dpkg but now i am not able to do any installation so i just removed /var/lib/dpkg/status and created new but that didnt help   apt-get -f install  Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following extra packages will be installed:   apt-utils coreutils debconf debconf-i18n dpkg libacl1 libapt-inst1.4   libapt-pkg4.12 libattr1 libbz2-1.0 libdb5.1 libgcc1 liblocale-gettext-perl   liblzma5 libselinux1 libstdc++6 libtext-charwidth-perl libtext-iconv-perl   libtext-wrapi18n-perl perl-base tar tzdata xz-utils zlib1g Suggested packages:   debconf-doc debconf-utils whiptail dialog gnome-utils   libterm-readline-gnu-perl libgtk2-perl libnet-ldap-perl libqtgui4-perl   libqtcore4-perl apt bzip2 ncompress xz-lzma The following NEW packages will be installed:   apt-utils coreutils debconf debconf-i18n dpkg libacl1 libapt-inst1.4   libapt-pkg4.12 libattr1 libbz2-1.0 libdb5.1 libgcc1 liblocale-gettext-perl   liblzma5 libselinux1 libstdc++6 libtext-charwidth-perl libtext-iconv-perl   libtext-wrapi18n-perl perl-base tar tzdata xz-utils zlib1g 0 upgraded, 24 newly installed, 0 to remove and 0 not upgraded. 2 not fully installed or removed. Need to get 0 B/9,246 kB of archives. After this operation, 29.9 MB of additional disk space will be used. Do you want to continue [Y/n]? y E: Cannot get debconf version. Is debconf installed? debconf: apt-extracttemplates failed: No such file or directory dpkg: regarding .../libgcc1_1%3a4.6.3-1ubuntu5_amd64.deb containing libgcc1, pre-dependency problem:  libgcc1 pre-depends on multiarch-support   multiarch-support is unpacked, but has never been configured. dpkg: error processing /var/cache/apt/archives/libgcc1_1%3a4.6.3-1ubuntu5_amd64.deb (--unpack):  pre-dependency problem - not installing libgcc1 No apport report written because MaxReports is reached already                                                               Errors were encountered while processing:  /var/cache/apt/archives/libgcc1_1%3a4.6.3-1ubuntu5_amd64.deb E: Internal Error, No file name for libc6 W: Could not perform immediate configuration on 'multiarch-support:amd64'. Please see man 5 apt.conf under APT::Immediate-Configure for details. (2) E: Sub-process /usr/bin/dpkg returned an error code (1) # apt-get -u dist-upgrade Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies:  libc6 : Depends: libgcc1 but it is not installed          Depends: tzdata but it is not installed E: Unmet dependencies. Try using -f.   i have tried below link    but no help...  thanks


What exactly do the colors in htop status bars mean?

By default, htop shows colored status bars for processors, memory, and swap. From left to right, the bars are colored green, blue, yellow, and red depending on some thresholds. What does it mean when the Memory bar has a small level of green and blue, and almost all the remainder is yellow? The swap bar is empty. The color settings for htop are "default".


When one looks at the sun and the moon in the sky together, why is it that the illuminated crescent of the moon does NOT "point" at the sun?  (More correctly the perpendicular bisector of the straight line joining the end points of the moon's terminator does not point at the sun. Intuitively one feels it should - as that is where the light is coming from. It is always around 20 - 30 degrees "off target".)


I am trying to write a script that will delete all comments and everything in between inside C files in my current directory. I've been using sed, and this is what I have so far:   sed -i '/ * [^()] */d' *.c  This works when the comments are on the same line as an asterisk or backslash.   However it doesn't work when there is a commented line without a slash or asterisk.   I know sed goes line by line, I just don't know how to tell it to keep deleting until it sees a */.


What is the maximum amount of toothpaste an adult can safely use when brushing his or her teeth?

What is the maximum amount of toothpaste an adult can safely use when brushing his or her teeth, and why? The person brushes his or her teeth and rinses out the mouth thoroughly after, once a day (just before bed). Edit after the question was closed as a duplicate: the duplicate question has answers that seem to clearly indicate that there any amount of toothpaste of toothpaste can be used by an adult when brushing his or her teeth, as long as the toothpaste is not swallowed but rather spat out after use.


This is a Binomial question. I am required to find P(2X>4), and given that X~B(10,0.2), how do I convert it to 2X~B(n,p)?  Have tried converting from P(2X>4) to P(X>2), but understand that it doesn't work that way.  Do i have to use integration or any formula that i should refer?


What is a good cut of meat to use in beef bourguignon

I'm looking for a nice cut of meat that would nicely fall apart when you put a fork to it. It doesn't have to follow the "authentic" recipe. I've tried various packs of "stew meat" before and it always comes out pretty rough. I'm willing to acknowledge I'm not cooking it properly or long enough. But I'm also wondering if maybe a brisket or a specific cut of meat would work better.


What's the maximum amount of RAM I can use on an specific hardware

I've an  Notebook with an  CPU. The Asus site says that the maximum RAM is 8 GB, but Intel's says my CPU supports 16 GB. What is the maximum RAM I can use on this system under Ubuntu?


¿how filter undefined elements into an array in React?

I want to be able to pull the undefined elements out of the array, so that my table can correctly display the values. Currently I have this problem, where the following table shows the data corresponding to those tables, but it seems that the arrays occupy positions with the data that cannot be displayed, and I would like to remove them from the array:  this is the code:       team.playerHasTeams.map((player) => {         playersInTeamData.push({           idTeam: team.id,           playerName: player.bookings.full_form_data.name,           lastName: player.bookings.full_form_data.lastname,           location: player.bookings.full_form_data.location,           dateBirth: player.bookings.full_form_data.birth_date,           gender: player.bookings.full_form_data.gender,           position: player.bookings.full_form_data.position         })        })       let formatedData = playersInTeamData.map((player, index) => {         if (player.idTeam === team.id) {           return {             key: index,             assingTeam: (               <Form.Item>                 <Select placeholder="Assign">                   {searchResponse.map((team, index) => (                     <Select.Option key={index} value={team.id}>                       {team.official_name}                     </Select.Option>                   ))}                 </Select>               </Form.Item>             ),             playerName: player.playerName,             lastName: player.lastName,             location: player.location,             dateBirth: player.dateBirth,             gender: player.gender,             position: player.position           }         }       })


For a formula $ \gamma = r \leftrightarrow (p_1 \vee p_2) $ there is true that: $\rho \models \gamma $ iff $\rho(r) = \max(\rho(p_1), \rho(p_2))$  Is there exists such set of formulas $\Gamma$ that $\rho \models \Gamma$ iff $\rho(r) = \max_{n \in \mathbb{N}} (\rho(p_n))$ where $\rho$ is a vaulation.  Do I understand correctly that I should prove that there exists expected set that it is true $\rho(r) = \max_{n \in \mathbb{N}} (\rho(p_n))$ for any $r$?  $\rho \models \gamma $ means that $\rho$ satisfies $\gamma$  If yes, please hint me If no, please explain what I should do.


Fork not in sync with local clone with error, and cannot pull with rebase?

I have a fork in my github account and I cloned the fork to my local computer. Now I have made some commits, and pushed it to origin. Then, I updated the readme.md file in the fork directly in GitHub, not in the local clone. I made a commit called Updated readme.md file.  Now I wanted to sync it with my local computer. So I ran git pull. This gave me the error:  Cannot pull with rebase: You have unstaged changes.  Please commit or stash them.   After the last commit I have modified 2 files on my local computer. But I no longer want the changes. So, I wanted to remove any changes made to these 2 files and to get in sync with origin.  On branch master Your branch is up-to-date with 'origin/master'.  Changes not staged for commit:   (use "git add <file>..." to update what will be committed)   (use "git checkout -- <file>..." to discard changes in working directory)          modified:   scripts/filename.js  Untracked files:   (use "git add <file>..." to include in what will be committed)          scripts/anotherfile.js  no changes added to commit (use "git add" and/or "git commit -a")


How to handle a PC death early in a session?

Sometimes you have to end a session at a very suspenseful moment.   For example the group used the whole last session to prepare for a heist or a fight and just as the action is about start you look at the clock and have to delay the endeavor.   A week later you meet up again and after a small recap you continue on. The heist or the battle begins and... one character dies. And for the sake of it let us assume that there is no way of reviving him.   Now the player sits at the table, about 30 minutes in the session with at least  4.5 hours + food break left. How should one handle this situation?


How does transmission-daemon work ? Download don't seem to start

I installed transmission-daemon in order to have a command-line torrent downloader which I could access through SSH. My problem is that I am struggling to understand how to use it.  I have run transmission-daemon -c $HOME/TorrentFiles in order to set a folder to watch for new .torrent files  I have run transmission-daemon -w $HOME/Downloads to set the destination folder of downloaded files  As soon as I add a torrent file to the TorrentFiles folder, the extension .added is added, but the download of the torrents don't seem to begin !!  How to make it work ??  Thanks in advance !!  --  EDIT : It seems like the daemon does not start automatically the download and I'm supposed to run either transmission-remote -s or click on a button from the web interface. But I can't do it for authentication reasons (on the web interface, I get a 403 Error) : I've tried to edit .config/transmission-daemon/settings.json, but it doesn't help modifying "rpc-whitelist"'s value to "127.0.0.1,192.168.*.*" nor setting "rpc-whitelist-enabled" to false.  PS : rpc-authentication-required is already false.  PS : Obviously, I have stopped the daemon before editing and started it again afterwards.


White cloudy areas on bottom of new stainless steel skillet

I just bought my first few pot and pans "Calaphon" stainless steel trip-ply  I used my new 10" skillet tonight, and cooked pork chops. I heated the pan first, added olive oil, let it heat, then added chops. After I was done, cleaned it immediately under water, and noticed white cloud looking areas on the bottom of the skillet. They won’t wash or rub off  Do I need to return these? I did buy them for the look as well.


How did the word "copacetic" come into use?

I once heard the late John Ciardi (NPR's "A Word in Your Ear") try to explain that the 1920s idiom, "copacetic" (meaning completely satisfactory), entered into the African-American vocabulary in Harlem from the days when Jews and African Americans lived there together.  He argued that copacetic has the same meaning as the Israeli idiom "kol b'seder" which literally means "all is in order."  The problem with that, said my Harlem-raised father-in-law, is that the Jews in Harlem spoke Yiddish and kol b'seder was not used in Yiddish.  The dictionary I've got is not helpful. Can someone come up with a better explanation?


For a lower voltage drop one could use Schottky diodes, but what are the disadvantages of Schottky's?

In other words, why don't we always use Schottky diodes if they are so much better? What diode properties do Schottky diodes have that makes them unfit for certain applications?


Movie identification: YA 80's movie about a legion of robots overrunning a planet

I have very tenuous memories of this movie, watched on VHS in the mid-eighties.  The hero, a young man, had to rescue a young woman (princess?) from a massive number of obsidian, or at least shiny black, robots or golems or something.  Something significant about their hearts, maybe hearts were transplanted from living creatures into the robots?  The cover depicted a bunch of the robots in a wedge advancing across a featureless plain, the lead robot holding the woman in its arms.  The hero and his friends (mutants/aliens/monsters?) are standing on a cliff ledge overlooking the robots.


$\operatorname{Ext}$ and injectives, respectively projectives

If $\operatorname{Ext}^{ 1}_{R}(A,B) = 0  $ for all $R$-Mod $A$ then $B$ is injective ?  If $\operatorname{Ext}^{ 1}_{R}(A,B) = 0  $ for all $R$-Mod $B$ then $A$ is projective ?


I will have a valid Schengen visa multiple enteries and I have  Not entered a Schengen zone. It’s a new visa. Can I travel directly  To Croatia without having to enter a Schengen zone before.   I don’t seem to find clear information in the web regarding this matter.   Thank you.


Where in Europe can I purchase a car without residency?

I am not a resident anywhere and plan to travel for the foreseeable future, mostly in Europe. My country has good visa-free access to most of Europe, so it is conceivable I could remain without any residency for quite some time.  I enjoy driving, and maintaining cars, and I would like to purchase a car somewhere in Europe.  Where, if anywhere, in Europe (or outside of Europe, but with the ability to drive the car in Europe) can I legally purchase and insure a car as a non-resident? I am open to creative solutions like setting up a company to own the car, if the capital and ongoing paperwork requirements for the company are not too onerous.    I am aware that I could save money, get places quicker, etc, by taking trains or flying. I have a passion for cars and driving. Suggesting that I not buy a car is out of scope of this question.


I'm still very new to C++ development, please keep this in mind during the scope of my questions. I have a legacy Delphi application which sends a message to my C++ window using SendMessage() with WM_COPYDATA. The application is using a record to transmit a blob of data:  TUser = record     LastName:   String[28];     FirstName:    String[28];     ID:          String[20];     DateOfBirth: String[10];     Sex:         Boolean;     Size:        Word;     Weight:      Word;   end;   In my C++ application, I have setup the following struct to read out the transmitted information:  typedef struct {     char LastName[29];     char FirstName[29];     char ID[21];     char DateOfBirth[11];     bool Sex;     unsigned short Size;     unsigned short Weight; } Legacy_TUser;   According to the Delphi documentation, a fixed String with e.g. the length of 40 will occupy 40 + 1 bytes. However, once I receive the data, I perform a size comparison of the received data and my struct setup:  Logger::Log("Size of data: %i", pcds->cbData); Logger::Log("Size of struct: %i", sizeof(Legacy_TUser));   This results in an output of:  Size of data: 95 Size of struct: 96   Which brings me to my final question. I can't seem to find any reason why the size of my struct is one byte too large. The string length seems to be correct, the data which I read in is shifted by exactly one byte. What am I missing here?


Drivers often support various parameters. For example NIC driver e1000 supports flow-control (FlowControl) or auto-negotiation (AutoNeg) parameters. Is there a way to see which parameters were passed to driver during loading? modinfo just displays all the possible parameters for driver, but I would like to see which parameters (and the value of those parameters) were passed to module. dmesg doesn't seem to provide this information as well.   One place where I did find some information was under /sys/module/, but for example in case of e1000, only the copybreak parameter was listed in /sys/module/e1000/parameters while according to modinfo the e1000 module supports more than dozen parameters.


How to georeference using Latitude and longitude in QGIS?

I'm trying to georeference a picture using Latitude and longitude. The points are these:  top-left:  (116.30950927734372,39.970805680527725)   top-right:  (116.35620117187497,39.970805680527725)   bottom-left (116.35620117187497,39.93606595478707)   bottom-right (116.30950927734372,39.93606595478707)    When I tried to calculate the area of a polygon,the result is very small(something like e-7).I realized to my horror that the QGIS had treated the Unit as meter.What should I do?  (QGIS1.8)


empheq equation flows out of column bounds

I am using the boxed equation format shown .  However, it flows out of column bounds when following the IEEE journal format as shown in image.  \documentclass{article}  \usepackage{color} \definecolor{myblue}{rgb}{.8, .8, 1}  \usepackage{amsmath} \usepackage{empheq}  \newlength\mytemplen \newsavebox\mytempbox  \makeatletter \newcommand\mybluebox{%     \@ifnextchar[%]        {\@mybluebox}%        {\@mybluebox[0pt]}}  \def\@mybluebox[#1]{%     \@ifnextchar[%]        {\@@mybluebox[#1]}%        {\@@mybluebox[#1][0pt]}}  \def\@@mybluebox[#1][#2]#3{     \sbox\mytempbox{#3}%     \mytemplen\ht\mytempbox     \advance\mytemplen #1\relax     \ht\mytempbox\mytemplen     \mytemplen\dp\mytempbox     \advance\mytemplen #2\relax     \dp\mytempbox\mytemplen     \colorbox{myblue}{\hspace{1em}\usebox{\mytempbox}\hspace{1em}}}  \makeatother  \begin{document}    \begin{empheq}[box={\mybluebox[5pt]}]{equation*} a really long equation resides here that flows out of bounds completely, please behave \end{empheq} \end{document}   I need to contain it within the column. Usually in figures, I have the option width=\columnwidth. I tried that but it does not work in this environment. I have searched online but have no solutions.  How can I contain this boxed equation within the column?


I'm trying to enumerate over an array in C, much like pythons enumerate method.  static void enumerate(char *choices[]) {     int i;     int length = sizeof(choices)/sizeof(*choices);      for (i = 0; i < length; i++)     {         printf("[%d] %s\n", i, choices[i]);     } }   How I'd expect this to work is, create an array (or list): char *test[] = {"test", "testing}; then pass that array (or list) to the function: enumerate(test); and the expected output should be:  [0] test [1] testing   However when I try this, the output I'm getting is just the first item in the array:  [0] test    What am I doing wrong to where this will not work as I'd expect it to?


Trackpad2 clicking feedback stops after 30 seconds from initial use of the day

When I open my MBP at the morning, I can feel the clicks for around 30 seconds, and then it's still functioning but without the click feedback. kind of goes to silent clicking mode. The built-in MBP trackpad works fine and I've another trackpad2 at the office that works great. Tried:  Turn it on and off. Connent with cable and without. Removed from connected devices and re-add it. Went through all the possible checkboxes on Trackpad + Accessibility settings.


Why does key generation take an input $1^k$, and how do I represent it in practice?

In my lecture, the lecturer said:      Let $K$ be the key generation algorithm. Given a security parameter represented in unary, $1^k$, $K(1^k)$ will output a keypair $(pk; sk)$, known as the public key and the private (or secret) key, respectively.    My question is: When I want to implement the cryptosystem, how should I represent this $1^k$?  When I implement the key generation procedure, do I literally require callers to pass me a string of $k$ one-bits that the procedure will never use?  And, if so, why is it there in the first place?


How can I find all the classes which implement several interfaces at once?

In a C# program, how can I find all the classes which implement a given set of interfaces?  Can an IDE such as Visual Studio 2015 help?  Can text processing tools such as grep, awk help?  Can editor such as emacs help?


Tire size switch out to wider tire , is that possible

I have a Bacchetta Sparta with 650x 23c tires, can I switch out to a wider tire ? Seems it would be more stable.


A Comma Between Each Items Except the Last One with get_the_term_list

I search here and on Google and I can't find answer to my question, just hope you will find it relevant.  I'm doing a magazine website and I need to display names of contributors as a byline. I'm taking the information from the taxonomy 'Contributor' to display their names.   <?php echo get_the_term_list( $post->ID , 'contributors', 'By ',' and '); ?>   That gives me, By contributor1 and contributor2 and contributor3 and contributor4  But I would like to have something like that instead:  By contributor1, contributor2, contributor3 and contributor4  Maybe it's not possible, let me know.  Thanks in advance,  François


What is a simple and reliable C library for working with Excel files?

Well... that's it.   I need something simple and reliable (doesn't have to have fancy features - I need to write and read text and numbers from Excel cells)  And yes, I would like a sample "Hello Cell" code...  What do you recommend?


I am using color package in latex to highlight some of my text in specific red color using RGB format. my code is something like this :   \documentclass[10pt,letterpaper]{article} \usepackage[english]{babel} \usepackage[utf8]{inputenc} \usepackage{fancyhdr} \pagestyle{fancy} \fancyhf{} \cfoot{\hspace{55mm}CV $|$ \thepage} \renewcommand{\headrulewidth}{0mm} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{graphicx} \usepackage{marvosym} \usepackage{lipsum} \usepackage{microtype} \usepackage{siunitx} \usepackage{ifsym} \usepackage[colorlinks=false, pdfborder={0 0 0}]{hyperref} \usepackage{multicol} \usepackage[width=18.00cm, height=22.00cm]{geometry} \usepackage{plain} \usepackage{csquotes} \usepackage{enumitem} \usepackage{array} \renewcommand{\labelenumi}{[\arabic{enumi}]} \usepackage{afterpage} %\usepackage{setspace} \usepackage{titlesec} \titlespacing{\section}{0mm}{1.2mm}{1.2mm} %\titleformat{\section}{\bfseries}{\thesection}{1em}{\setstretch{0.01}}  %%%%%%%%%%_____________Color Text Box Packages______________%%%%%%%%%%% \usepackage{blindtext} \usepackage{tcolorbox} \usepackage{graphicx} \definecolor{mycolor}{rgb}{0.122, 0.435, 0.698}    %%%%%%%%%%_____________Color for Text ______________%%%%%%%%%%% \usepackage[usenames, dvipsnames]{color} \usepackage{graphicx} \definecolor{myred}{RGB}{139,0,0}      %%%%%%%%%%_____________Start of main document______________%%%%%%%%%%% \begin{document} \textcolor{myred}{     \setcounter{secnumdepth}{0}\section{Education}}  \begin{tabular}{p{23mm}p{118mm}r}     Undergrad&\href{http://www.buet.ac.bd/}{Bangladesh University of Engineering and Technology}, Dhaka&[2013-Present]\\     &B.Sc. in Mechanical Engineering, CGPA-3.36/4.00\vspace{1.5mm}&[February, 2017]\\     Higher School&\href{http://www.soshgcdhaka.edu.bd/}{SOS Hermann Gmeiner College}, Dhaka&[2010-2012]\\     &Higher Secondary Certificate (HSC), CGPA-5.00/5.00\vspace{1.5mm}&\\     &\href{https://www.acps.edu.bd/}{Adamjee Cantonment Public School}, Dhaka&[2003-2010]\\     &Secondary School Certificate (SSC), CGPA-5.00/5.00&  \end{tabular}   \end{document}   But when i try to compile, it shows error message and does not compile :      Option clash for package color. \usepackage   how can i solve this problem?


Rendering both cycles and internal in one

My blender project has the mountain in cycles and the water in internal, how do i render both in one scene. But when i use render, i have to change the engine to see it.


Which tool can tell me the distribution of Linux that is running when uname is generic?

I normally use uname to determine which OS is running, but I have accounts on several machines where I don't know the particular distribution that is running.  When uname returns Linux, I tried uname -a and I see only the following:   Linux host123 3.0.58-0.6.6-pae blah blah blah i686 i686 i386 GNU/Linux   My guess is this is a SUSE distribution, but is there a better way to know which distribution is installed similar to how uname normally shows AIX, Darwin, etc...?


Is it safe to eat cooked chicken that has been out for 4 hours?

When I go to school and bring my lunch I like to have chicken but I go at 7:30 and eat at 11:20. Is it still safe to eat or I should not eat it?


Find the minimum value of      $\sin^{2} \theta +\cos^{2} \theta+\sec^{2} \theta+\csc^{2} \theta+\tan^{2} \theta+\cot^{2} \theta$   $a.)\ 1 \ \ \ \ \ \ \ \ \ \ \ \ b.)\ 3 \\ c.)\ 5 \ \ \ \ \ \ \ \ \ \ \ \ d.)\ 7 $  $\sin^{2} \theta +\cos^{2} \theta+\sec^{2} \theta+\csc^{2} \theta+\tan^{2} \theta+\cot^{2} \theta \\  =\sin^{2} \theta +\dfrac{1}{\sin^{2} \theta }+\cos^{2} \theta+\dfrac{1}{\cos^{2} \theta }+\tan^{2} \theta+\dfrac{1}{\tan^{2} \theta } \\ \color{blue}{\text{By using the AM-GM inequlity}} \\ \color{blue}{x+\dfrac{1}{x} \geq 2} \\  =2+2+2=6 $  Which is not in options.  But I am not sure if I can use that $ AM-GM$ inequality in this case.  I look for a short and simple way .  I have studied maths upnto $12$th grade .


How do you click and drag lower right corner of a cell (autofill) in excel using the keyboard?

If I press CRTL+Down I move to the cell before the empty cell.    If I press CTRL+SHIFT+End I end up selecting everything between the active cell and the next empty cell.    Now if I want to auto fill the same range of cells, what is the keyboard shortcut for that? (Autofill; also known as clicking the handle in the lower right hand corner of the cell and dragging)


Is it necessary to use Antivirus software?

If I don't use any Anti-Virus is there any problem ? To keep my data safe what should I do ?


What is the concept behind "tty" in linux?

Where did the terminology "tty" come from in Linux?


surface plot — end points get connect connected (tikzpicture)


How can I use a custom graphical interface in Ubuntu 16.04?

I've made a graphical interface and I want to use it. When my Ubuntu starts, I want my own graphical interface to load instead of the default one. How can I do that?


There should be an option to make the answers 'uneditable'

.. or at least let me preview all suggestions first.  On one of the Stack Exchange sites I had a perfectly good answer, and somebody edited it so that it contained broken English and wrong answers. I don't care how much reputation the editor has, the OP should have the final say as to whether the edit is appropriate or not.   Or the OP should have the option of 'locking' his answer so that others cannot edit it, perhaps as an overall setting in their profile. I suppose it could be a matter of preference. Some people are much more diligent in their writing than others.


How do I reset Ubuntu 18.04 to factory defaults?

so I have a PC with Ubuntu 18.04 on it and I'm going to be selling it. I'm just asking how I can reset it to factory defaults, like getting rid of everything I installed and everything? Thanks in advance.


I tried to make two spheres with bounding sphere to detect collision so they stop when they collide. But it seems that im having a precision issue. They stey stuck together because of small decimal keeping it stuck. Is there a way around this? Since they are in a 3d space, adding or subtracting a little off seems impossible and expensive. How can I solve these precision issues?   oldleftright = leftright, oldupdown = updown;  if(GetAsyncKeyState(VK_RIGHT))     leftright += 0.0001; if(GetAsyncKeyState(VK_LEFT))     leftright -= 0.0001; if(GetAsyncKeyState(VK_DOWN))     updown -= 0.0001; if(GetAsyncKeyState(VK_UP))     updown += 0.0001;  collide = test.Intersect(test2); if (collide) {     leftright = oldleftright;     updown = oldupdown; } collide = false;


I have heard this phrase in "True Detective". What's the background?  (It was used by police detective, 2nd episode, the dialog in a car.)  update:  Because of the discussion, I found that scene and have listened it exactly with headphones. The exact phrase (32:46) - "She do not look like"  The meaning of the question remains. Using 3rd person + "do".


FN key seems stuck on MacBook Air. Can't use function keys as normal

When I press the function keys they act like the fn key is pressed. For example f11 usually lowers the volume, but when fn is pressed at the same time it shows the keyboard - and that's what happening now whether fn is pressed or not. This results in that I can't for example lower my volume (f11), or play music (f8).  I've tried:   Restarting my computer Changing "Use F1, F2, etc as normal function keys" (System preferences > Keyboard) on and off Spamming the fn key trying to feel if something is physically stuck making it being pressed down Booting in safe mode   TL;DR  Expected behaviour  When pressing f11 the volume should step down  Actual behaviour  The desktop is shown (windows moves aside)  Mojave: 10.14.6


Sometimes, websites and scientific papers that introduce and/or handle cryptographic algorithms also provide speed-analysis and tables comparing the individual performance of cryptographic implementations. I would like to do the same, but I'm not sure how to calculate the “cycles”.  I have this data:   processor clock frequency: 2,1 ghz   message length: 16 byte   Speed: 4,3 Mbytes/s   How can I calculate “cycles” and “cycles per byte” from that data?


What is the hypernym of Earnings and Deduction?

If Earnings means an item that adds value to any stack.  And, If Deductions means any item that subtracts value from any stack.  Then what single <word> can be an either Earning or Deduction?  As in:   You will be Earning 200 this June.  (plus 200) You will be Deducted 100 this July.  (less 100) You will be <word> +500 this August.  (plus 500) You will be <word> -400 this September.  (less 400)


why is this happening? ntfs drive.   edit: I did NOT hibernate my Windows and fast startup is off. also this is a USB disk not a HARD DRIVE


Find an equation of the plane that passes through the point $(1, 3, 1)$ and contains the line: $x = t, y = t$ and $z = -2 + t$.    My attempt:  The points are $(1,3,1), (0,0,-2)$ and if $t = 1$: $(1,,1,-1)$  $a = (1,1,-1) - (0,0,-2) = [1,1,1]$  $b = (1,1,-1) - (1,3,1) = [0,-2,-2]$  normal vector is $n = a \times b = 2j - 2k = [0,2,-2]$  Therefore the equation is found by $[0,2,-2] \cdot [x-1, y-3, z-1] = 0$  $\leftrightarrow 2y -2z = 4$  $\leftrightarrow y - z = 2$  right?


Solving a quadratic congruence $x^2-2x+4 \equiv 0 \pmod 9$ where $x\in \mathbb{Z}_9$.   My idea:  $x^2-2x+4\equiv (x-1)^2+3 \equiv 0 \pmod{9} \iff (x-1)^2=6\pmod{9}$. How can I deal with mod 9 since it's not prime...


How come $\frac{d}{dt}\left(\frac{\partial {r_i}}{\partial {q_j}}\right) = \frac{\partial {\dot r_i}}{\partial {q_j}}$ in Lagrangian mechanics?

It is written in the Goldstein's Classical Mechanics text that  $$\frac{\mathrm d}{\mathrm dt}\left(\frac{\partial {r_i}}{\partial {q_j}}\right) = \frac{\partial {\dot r_i}}{\partial {q_j}}=\sum_k \frac{\partial^2{r_i}}{\partial {q_j}\partial{q_k}}\dot q_k+\frac{\partial^2{r_i}}{\partial {q_j}\partial t},\tag{1.50b}$$ where $$\dot r_i=\frac{\mathrm d}{\mathrm dt}r_i=\sum_k\frac{\partial{}r_i}{\partial{q_k}}\dot q_k+\frac{\partial {r_i}}{\partial t}.\tag{1.46}$$ But it seems to me that there is another term in $\frac{\partial {\dot r_i}} {\partial {q_j}}$ because of product rule which is $$\sum_k \frac{\partial{r_i}}{\partial{q_k}}\frac{\partial{\dot q_k}}{\partial{q_j}},$$ which I think is equal to $$\frac{\partial{r_i}}{\partial{q_j}}\frac{\partial{\dot q_j}}{\partial{q_j}}$$ since $q_j$'s are independent among themselves.   Then how come $$\frac{\mathrm d}{\mathrm dt}\left(\frac{\partial {r_i}}{\partial {q_j}}\right) = \frac{\partial {\dot r_i}}{\partial {q_j}}~?\tag{1.50b}$$ Does $$\frac{\partial{\dot q_j}}{\partial{q_j}} = 0\ ?$$


I'd like to know if this proposition is true:   $$ \left\{ x_n \right\} | x_{n+1}>x_n \wedge \lim_{n \to \infty}x_n = \infty \Rightarrow $$ $$\sum_{n \geq 1} \left( 1 - \frac{x_n}{x_{n+1} }  \right) = \infty$$ Can anyone help me?


Simple question.   SO had turned me into a better developer by far, I like to browse questions that strike my interest and curiosity and just read through the answers. I never fail to learn something new everyday, whether it's something trivial or something much more complex.  When I receive reputation it means a lot to me, almost a self achievement of sorts. Something I can show to someone to prove my "worth". I think it works for me as a great confidence booster, also its something I can show my friends who don't understand what I do.   It almost feels like I can finally have something to back me up if need to be.  So the question is what does YOUR reputation mean to YOU? Is it simply a number, is it a score as if you're playing a game, or does it help you mentally achieve your goals and improve yourself like it does for me.