My question is in reference to the derivation below from the physics site. It shows how the metric tensor raises and lowers indices. I cut it off halfway through because I didn't think the full derivation was relevant to the question, but  it is, just in case. I don't believe my question is a duplicate.     My question is, why is the map $\tau$ considered to be "natural"? Does the fact that the vector space has an inner product necessitate that the dual has one? (maybe so that there's an isomorphism?)  Edit: I'm asking if the fact that the vector space has an inner product induces the need for its dual to have an inner product to create an isomorphism.

(I'll explain what I know first and then I'll ask the questions). Given a finite dimensional vector space $V$, it is often remarked that there is no "natural" isomorphism from $V$ to $V^*$ (I guess this means a basis independent isomorphism?). I understand that one typically constructs an isomorphism $V \to V^*$ by fixing a basis for $V$, call this $B = \{v_1, v_2, \ldots, v_n\}$, and then mapping $v_i \mapsto \delta_i$ where $\delta_i$ is the linear functional given by $\delta_i(v_i) = \delta_{ij}$. Here are my questions:  (1) Why is there no natural isomorphism $V \to V^*$?  (2) If $V$ is a finite dimensional inner product space, we can map each $v \mapsto \langle v, \cdot \rangle$. Is this not "natural"? (I know we can consider sesquilinear forms, but let's keep the discussion to this inner product for simplicity).


How long do I cook a 10 lb chuck roast in my crock pot?

How can you tell when a roast is done?  How long should they roast for?


Well I'm trying to install Ubuntu 12.04.4 on an Acer 5349 laptop every time I plug in my live USB flash drive and boot to Ubuntu I get this message on a black screen saying   syslinux 4.07 edd 2013-07-25 copyright (c) 1994-2013 h. Peter anvin et al   also I'm not in Ubuntu it's when you turn on the computer and boot to live USB and it does not pass that message and I'm trying to replace windows 7 home with Ubuntu 12.04.4 my friend given his old laptop to me so any help will be great oh forgot to say his windows 7 not working it boots to recovery and crashes to a error code so that's why I'm try to put Ubuntu on.  What can I do to fox this?

I am trying to install linux on my laptop, a Toshiba Satellite C6550-S5200. I did it once but something happened so I removed it then I had to destroy all data on hard drive so now I have nothing on it. Well I got a iso file burned to a CD and to a flash drive. With the flash drive I get.   SYSLINUX 4.06 EDD 4.06-pre7 Copyright (C) 1994-2012 H. Peter Anvin et al  With the CD it will start booting it but somewhere loading it up, the dots turn all orange and stay that way and my CD drive turns quiet.  Oh and some more info the images work because I tried loading them up on another pc and it worked just fine.  I manage to get the CD to boot I just had to let me pc boot up first then insert the CD and have it boot the CD then. Once I get done installing ubuntu it works fine but I have to leave the PC on 24/7 for if I turn it off the PC will freeze 5-10 seconds after booting back up no matter how I install it.


I use \usepackage[backend=biber, style=authoryear-comp, maxcitenames=2]{biblatex} for my bibliography, which works perfectly fine. However, when an author appears multiple times biblatex also shows the name of the second author before printing the year. This even happens in cases of different year entries. How is it possible to suppress the printing of the second author and to label the citation with the year 2015a, 2015b instead?  Here is my bibfile:   @article{first,   title={Paper 1},   author={Ambigous, Alan and John Doe and others},    year={2015}, }  @article{second,   title={Paper 2},   author={Ambigous, Alan and Richard Roe and others},    year={2015}, }  @article{third,   title={Paper 3},   author={Miles, Juliane and Paul Waterman and others},    year={2000}, }  @article{fourth,   title={Paper 4},   author={Miles, Juliane and John Smith and others},    year={1999}, }

In the header of my document I set the maximal author names to 2:  \usepackage[style=authoryear-icomp, maxbibnames=9, maxcitenames=2, backend=biber]{biblatex}   Now, when I cite texts with two authors, LaTeX gives me the following:     (Author_A/ Author_B 2012: 232)   When I have three authors or more, LaTeX makes it:     (Author_A/ Author_B et al. 2012: 232)   But I want LaTeX to just name the first author if there are more than two authors ... like this:     (Author_A et al. 2012: 232)   Any tips on how to achieve this ?


systeminfo shows when the system came up after a restart, but does not show when it comes up after a shutdown and then a power on.  For instance when I run this command:  systeminfo | find "Sys"   the output shows:  System Boot Time:          8/10/2018, 8:45:22 AM   Which was when I did a restart.  I tried a solution in the previous question:  Get-WinEvent -LogName Microsoft-Windows-Diagnostics-Performance/Operational | Where { $_.Id -eq 200 }  and got these results on my laptop:   PS C:\Program Files\PowerShell\6.0.0> Get-WinEvent -LogName Microsoft-Windows-Diagnostics-Performance/Operational | Wher e { $_.Id -eq 200 }      ProviderName: Microsoft-Windows-Diagnostics-Performance  TimeCreated                     Id LevelDisplayName Message -----------                     -- ---------------- ------- 7/30/2018 1:54:18 PM           200 Critical         Windows has shutdown: ... 6/29/2018 9:08:40 AM           200 Critical         Windows has shutdown: ...   PS C:\Program Files\PowerShell\6.0.0>    I'm looking for the time I turn on the computer and the time I shut it down each day. I'd like a command line so I can collect the information into a batch file.

How can I know when my computer running Windows 7 was last restarted?   I prefer a solution that doesn't involve searching the event log, but something like wmic or maybe cmd commands.


The directory contains files with different extensions. I would like to delete all files with extensions .gz, zx, ext4 except the last 5 files. I can list all those files with   ls -l | grep '\.gz\|xz\|ext4$'   and I could just show the oldest 5 of them:  ls -l | grep '\.gz\|xz\|ext4$' | head -5   Or list the last 5 files:  ls -l | grep '\.gz\|xz\|ext4$' | tail -5   But I don't know how delete all of them except these 5 files that are listed in the above command.

I want to remove all the files from different directories, and want to keep only latest files 20 files. is this the correct command to do this?  ls -t1 /mnt/dwh/ftp/dwh_ftp_cbs/ARLOGS/ | tail -n +22 | xargs rm -f


I am getting a null pointer exception while trying to retrieve data using Firebase.  The following is a description of my error:-  The error was pointing on myRef = mfirebaseDatabase.getReference();  This is my full error:-   java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.vignanstudent/com.example.vignanstudent.v_b_d}: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.firebase.database.DatabaseReference com.google.firebase.database.FirebaseDatabase.getReference()' on a null object reference         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3335)         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3474)         at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)         at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)         at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2081)         at android.os.Handler.dispatchMessage(Handler.java:107)         at android.os.Looper.loop(Looper.java:214)         at android.app.ActivityThread.main(ActivityThread.java:7643)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:516)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.firebase.database.DatabaseReference com.google.firebase.database.FirebaseDatabase.getReference()' on a null object reference         at com.example.vignanstudent.v_b_d.onCreate(v_b_d.java:39)         at android.app.Activity.performCreate(Activity.java:7815)         at android.app.Activity.performCreate(Activity.java:7804)         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1318)         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3310)         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3474)          at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)          at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)          at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2081)          at android.os.Handler.dispatchMessage(Handler.java:107)          at android.os.Looper.loop(Looper.java:214)          at android.app.ActivityThread.main(ActivityThread.java:7643)          at java.lang.reflect.Method.invoke(Native Method)          at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:516)          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)

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


I want to convert Minutes as "Hours:Minutes:Seconds".  How can this achieved using c#.  I have tried this  driveHours = (totalHours.balanceDriveMinutes / 60).ToString("00") + " Hrs. "  + (totalHours.balanceDriveMinutes % 60 ).ToString("00") + " Min." +  (totalHours.balanceDriveMinutes /3600).ToString("00") + " Sec.";    But it doesn't seem to be correct.

What is the best way to convert seconds into (Hour:Minutes:Seconds:Milliseconds) time?  Let's say I have 80 seconds, are there any specialized classes/techniques in .NET that would allow me to convert those 80 seconds into (00h:00m:00s:00ms) format like to DateTime or something?


I'd like to create a product shot like the following images for a client:   I'm relatively new to Blender, I don't know that much about render passes. What I would like to do is render the bottle, with the reflection with a transparent background. I do'nt know if this is possible, if its not, maybe there is another way to get this result. Please keep in mind that I'm new to this program.

I'm pretty new to this and this is my first question here, any help would be greatly appreciated.  So basically what I want to achieve is a floor material as seen in this photo...    ...the reflections are very crisp but dim.  With a glossy shader I get the following results:    First picture: reflections are blurry  Second picture: roughness of the material looks right but reflection is bright red  Third picture: If tinted in any other color than white, it seems to produce the result I want. Reflection is sharp and gets tinted blue. What I need is the reflection to be tinted white.  Thanks for any help.


When I'm filming video with my Canon EF-S 10-18mm f/4.5-5.6 IS STM lens, strange dark spots appear in the video and they are only visible in video mode and they are visible ONLY when focusing process is finished. In the picture below you can see on the upper side clean image, because its still focusing and the bottom with all these spots.... Here is a sample video with the problem   Any ideas what is causing it and how to fix it ?

Recently, I've been doing a lot more photography, particularly with my 100-400mm telephoto and 16-35mm wide. I am skilled enough that I can capture the shot mostly as I want with just the camera gear, requiring minimal post processing. I'm a huge fan of ETTR now, so most of my shots are overexposed to support more shadow DR and improve the noise performance of my el-chepo 450D body.  I've noticed quite a bit lately during post processing in lightroom that my sky's or any other lighter areas of my shots tend have spots on them. They are soft and dull to one degree or another (seems to depend on the zoom factor), so probably something either on the sensor or the lens. I'm having a hard time figuring out exactly what they are, as I try to use my lens pen brush before any shoot, yet I still have them. I am having to make quite a few healing corrections post-process to get rid of them.  Is there an easy way to identify where the spots are on my lenses? Once identified, if a quick brush of the outer lens element with a lens pen (or soft camel hair brush) doesn't do the trick, does that mean the spots are on my sensor? Is it possible there is particulate inside the lens body (all of my gear is less than a year old outside of my 450D body, and its all Canon L-Series gear, so I would home that I don't already have detrimental particulates floating around inside my lenses messing up my shots. :|)  Here are a couple examples. The spots are harder to see on screen, and I first noticed them when I printed a few of my more recent shots. There are quite a few, and the shot the examples below were taken from, where the sky took up about 30% of the top edge of the photo, there were probably 10-12 different spots, some of them darker, many of them lighter. The darker ones are the ones that are very visible in prints, where as the softer ones are not as visible, but still apparent enough to ruin an expensive print.


Every android device has a more or less customized kernel. Most of these are open source?!(I am not sure about the "most".) Is there a Linux or even better ubuntu distro which comes with has support for lots of android devices out of the box? Thanks? And which is nearly as easily installable as "Ubuntu  for Desktop"?

I have a cheap Chinese made tablet from Dubai called the Crony Dubai (www.cronydubai.com). It has a micro B, mini HDMI and a USB labeled as "Host" as well as a micro SD slot. It came with a micro B to USB adapter in box, and its running Ice Cream Sandwich. Is there a way to load Ubuntu on it? Also the tablet is very buggy and crashes often, would that be due to the tablet or the OS?


Consider a join A LEFT JOIN B ON A.id = B.a_id:   B.a_id is nullable -- most but not all B records point to an A record. A can, at most, only have one matching B record (business logic). Not all A records have a match in B.   Is there a way to tell MSSQL that there will never be more than one A:B match, thus allowing it to shortcut the join once a match is found for a given A record?  I would think that such an optimization could happen if B.a_id had a unique index, but that's not possible since it's nullable.  Complicating the issue: A and B are in different databases (same MSSQL instance).  If it matters, I'm using SQL Server 2008 R2.

I have a business requirement to have a FK field on TableA referencing TableB.  If there is a value in TableBID, it should be unique, but it's not mandatory, so there could be multiple records with null values.  Is it possible somehow to enforce this type of uniqueness on the DB level, using either an index or a constraint?


Im studying a book about stochastic processes and it is mentioned in the book that the equation below is true and we can obtain it by generating functions can anyone prove it. Thanks a lot. $$\sum_{m=0}^{\infty}\binom{2m}{m}p^m = (1 - 4p)^{-1/2}$$

How do you prove that $\sum\limits_{n=0}^{\infty}{2n \choose n}x^n=(1-4x)^{-1/2}$? I tried to identify the sum as a binomial series, but the $4$ and the $-1/2$ puzzle me. (This series arises in studying the first passage time of a simple random walk.)


Why do we say      Pauli exclusion principle   instead of     Pauli's exclusion principle   When we want to say that something belongs to somebody, we should use the "s" to form a genitive, i.e.  "this is Pauli's cat", not "this is Pauli cat".

Consider these two ways of coining a name: 1) Bolzano's theorem, Rolle's theorem 2) the Poincare conjecture, the Kantorovich theorem. What is the difference between these ways, why do people choose one over the other?  My guess is that the main difference is when you put 's at the end of a name, you strictly imply that the theorem/conjecture was written by this very person (Bolzano wrote Bolzano's theorem). But when it is "the [Name] theorem/conjecture," it doesn't mean that the person which name is used actually created this thing, maybe he just inspired it (Poincare might have only inspired the Poincare conjecture but did not propose it).  Sometimes there is only one way: ; you can not call it hairy ball's theorem.


Suppose $a : [0 , 1] \to \Bbb R$ is an infinitely smooth function. For $\lambda\ge1$, define $$F(\lambda) := \lambda \int_0^1 e^{\lambda t} a(t) \, dt.$$ If $\sup_{\lambda\ge1}|F(\lambda)|\lt\infty$, then $a$ is the identically zero function.  My professor said this assertion is true but I haven't been able to solve this for some time. He also implied that this problem is highly non-trival (at least for me).  Below are the some results I have derived:   Derivatives of any order of $a$ vanishes at $t = 1.$ For any $\delta\lt1$, $a(t)$ has a zero in the open interval $(\delta , 1).$  The same is true for all the derivatives of $a(t)$. This tells us that the $n^\text{th}$ derivative of $a$ has infinitely many distinct zeros for all natural $n$. If $a$ is analytic, then I can show that $a(t)\equiv 0.$ If $a(t)\ge0$ on $[0 , 1]$, then it is obvious that $a\equiv 0.$   I would appreciate any hint.  Actually $(1)$ and $(3)$ follows from $(2)$. For $(2)$, suppose that $a(1)\gt0$ (the case that $a(1)\lt0$ can be argued in the same way as the following), then there exists $\delta\lt1$ such that $a(t)$ is strictly positive on $I = [1-\delta , 1]$. Then write $F(\lambda) = \lambda\int_0^{1-\delta}e^{\lambda t}a(t)dt + \lambda\int_{1-\delta}^1e^{\lambda t}a(t)dt$. Now there exists $c\gt0$ such that $a(t)>c$ on $I$ since $I$ is compact, so that the second term is bounded below by $c (e^{\lambda}-e^{\lambda(1-\delta)})$. But the first term is only $O(e^{\lambda(1-\delta)})$, so this contradicts the fact that $F(\lambda)$ is bounded. Morever, using the same idea and integration by parts, one can see that $n^{th}$ derivative of $a$ must vanish at $1$.

Suppose $a : [0 , 1] \to \Bbb R$ is an infinitely smooth function. For $\lambda\ge1$, define $$F(\lambda) := \lambda \int_0^1 e^{\lambda t} a(t) \, dt.$$ If $\sup_{\lambda\ge1}|F(\lambda)|\lt\infty$, then $a$ is the identically zero function. Below are the some results I have derived:   Derivatives of any order of $a$ vanishes at $t = 1.$ For any $\delta\lt1$, $a(t)$ has a zero in the open interval $(\delta , 1).$  The same is true for all the derivatives of $a(t)$. This tells us that the $n^\text{th}$ derivative of $a$ has infinitely many distinct zeros for all natural $n$. If $a$ is analytic, then I can show that $a(t)\equiv 0.$ If $a(t)\ge0$ on $[0 , 1]$, then it is obvious that $a\equiv 0.$   I would appreciate any hint.  Actually $(1)$ and $(3)$ follows from $(2)$. For $(2)$, suppose that $a(1)\gt0$ (the case that $a(1)\lt0$ can be argued in the same way as the following), then there exists $\delta\lt1$ such that $a(t)$ is strictly positive on $I = [1-\delta , 1]$. Then write $F(\lambda) = \lambda\int_0^{1-\delta}e^{\lambda t}a(t)dt + \lambda\int_{1-\delta}^1e^{\lambda t}a(t)dt$. Now there exists $c\gt0$ such that $a(t)>c$ on $I$ since $I$ is compact, so that the second term is bounded below by $c (e^{\lambda}-e^{\lambda(1-\delta)})$. But the first term is only $O(e^{\lambda(1-\delta)})$, so this contradicts the fact that $F(\lambda)$ is bounded. Morever, using the same idea and integration by parts, one can see that $n^{th}$ derivative of $a$ must vanish at $1$.


Can someone please explain (with an example or two) what is meant by “a polynomial $p(x_1, ..., x_n)$”? Stillwell starts referring to them without defining them and they are beyond my elementary mathematics education. He usually adds “with integer coefficients.”

Let's consider a polynomial ring of single variable. One can define them informally by saying $P(X)=\sum_{i=1}^n a_n X^n$ while $X$ is an indeterminate variable. However, since mathematics is based on first-order logic, one can only talk about something that actually exists (as a set). So as its name says, indeterminate variable is not a sentence in $ZFC$. Nevertheless, we can formally define a polynomial ring $R[X]$ as a subset of $R^\omega$ whose support is finite. ($R$ is a commutative ring with unity) Just like a single variable, I want to know what would be the formal definition of a polynomial ring of several variables. What would be a formal definition? === I have figured out a candidate. That is,  Candidate for a "Definition of a polynomial ring $R[X_1,...,X_n]$". ($R$ is a commutative ring with unity) Let $R[X_1,...,X_n]$ be the set of all functions $f:\omega^n \rightarrow R$ whose support is finite. Define $(f+g)(a,b,c)=f(a,b,c)+g(a,b,c)$ and $(f•g)(a'',b'',c'')=\sum_{a+a'=a''} f(a,b,c)•g(a',b',c')$ (Note that in this way, $+,•$ are well defined.) Then, it can be checked that $(R[X_1,...,X_n],+,•)$ is a ring.  Is this a formal definition of a polynomial ring?


As stated in many textbooks, the Standard error of the slope in linear regression with one variable is  $\sqrt{\frac{s^2}{SSX}}$  or some rewrite, ${s^2}$ being the error variance and ${SSX}$ being the sum of the ${x}$-squares.   Can anybody help with an explicit proof?

In simple linear regression, we have $y = \beta_0 + \beta_1 x + u$, where $u \sim iid\;\mathcal N(0,\sigma^2)$. I derived the estimator:  $$ \hat{\beta_1} = \frac{\sum_i (x_i - \bar{x})(y_i - \bar{y})}{\sum_i (x_i - \bar{x})^2}\ , $$ where $\bar{x}$ and $\bar{y}$ are the sample means of $x$ and $y$.   Now I want to find the variance of $\hat\beta_1$. I derived something like the following:  $$ \text{Var}(\hat{\beta_1}) = \frac{\sigma^2(1 - \frac{1}{n})}{\sum_i (x_i - \bar{x})^2}\ . $$  The derivation is as follow:  \begin{align} &\text{Var}(\hat{\beta_1})\\ & = \text{Var} \left(\frac{\sum_i (x_i - \bar{x})(y_i - \bar{y})}{\sum_i (x_i - \bar{x})^2} \right) \\ & = \frac{1}{(\sum_i (x_i - \bar{x})^2)^2} \text{Var}\left( \sum_i (x_i - \bar{x})\left(\beta_0 + \beta_1x_i + u_i - \frac{1}{n}\sum_j(\beta_0 + \beta_1x_j + u_j) \right)\right)\\ & = \frac{1}{(\sum_i (x_i - \bar{x})^2)^2}  \text{Var}\left( \beta_1 \sum_i (x_i - \bar{x})^2 +  \sum_i(x_i - \bar{x}) \left(u_i - \sum_j \frac{u_j}{n}\right) \right)\\ & = \frac{1}{(\sum_i (x_i - \bar{x})^2)^2}\text{Var}\left( \sum_i(x_i - \bar{x})\left(u_i - \sum_j \frac{u_j}{n}\right)\right)\\ & = \frac{1}{(\sum_i (x_i - \bar{x})^2)^2}\;\times \\ &\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;E\left[\left( \sum_i(x_i - \bar{x})(u_i - \sum_j \frac{u_j}{n}) - \underbrace{E\left[\sum_i(x_i - \bar{x})(u_i - \sum_j \frac{u_j}{n})\right] }_{=0}\right)^2\right]\\ & = \frac{1}{(\sum_i (x_i - \bar{x})^2)^2}  E\left[\left( \sum_i(x_i - \bar{x})(u_i - \sum_j \frac{u_j}{n})\right)^2 \right] \\ & = \frac{1}{(\sum_i (x_i - \bar{x})^2)^2} E\left[\sum_i(x_i - \bar{x})^2(u_i - \sum_j \frac{u_j}{n})^2 \right]\;\;\;\;\text{ , since } u_i \text{ 's are iid} \\ & = \frac{1}{(\sum_i (x_i - \bar{x})^2)^2}\sum_i(x_i - \bar{x})^2E\left(u_i - \sum_j \frac{u_j}{n}\right)^2\\ & = \frac{1}{(\sum_i (x_i - \bar{x})^2)^2}\sum_i(x_i - \bar{x})^2 \left(E(u_i^2) - 2 \times E \left(u_i \times (\sum_j \frac{u_j}{n})\right) + E\left(\sum_j \frac{u_j}{n}\right)^2\right)\\ & = \frac{1}{(\sum_i (x_i - \bar{x})^2)^2}\sum_i(x_i - \bar{x})^2  \left(\sigma^2 - \frac{2}{n}\sigma^2 + \frac{\sigma^2}{n}\right)\\ & = \frac{\sigma^2}{\sum_i (x_i - \bar{x})^2}\left(1 - \frac{1}{n}\right) \end{align}  Did I do something wrong here?  I know if I do everything in matrix notation, I would get ${\rm Var}(\hat{\beta_1}) = \frac{\sigma^2}{\sum_i (x_i - \bar{x})^2}$. But I am trying to derive the answer without using the matrix notation just to make sure I understand the concepts.


In this MSDN article   it discusses the Class Equalitycomparer and has an example.In this example about comparing boxes it has this class -   class BoxSameDimensions : EqualityComparer<Box> {     public override bool Equals(Box b1, Box b2)     {         if (b1.Height == b2.Height & b1.Length == b2.Length             & b1.Width == b2.Width)         {             return true;         }         else         {             return false;         }     }      public override int GetHashCode(Box bx)     {         int hCode = bx.Height ^ bx.Length ^ bx.Width;         return hCode.GetHashCode();     } }   I don't understand the line int hCode = bx.Height ^ bx.Length ^ bx.Width;  Could someone explain please? Why the xor?

In .NET, the  is used in a lot of places throughout the .NET base class libraries. Implementing it properly is especially important to find items quickly in a collection or when determining equality.  Is there a standard algorithm or best practice on how to implement GetHashCode for my custom classes so I don't degrade performance?


I am running an extensive code that I requires g77 to compile. (yes I could probably debug for gfortran but it took me months just to get it working so I really really don't want to). I have tried   but I get this error when I try to install:  Reading package lists... Done Building dependency tree        Reading state information... Done Package g77 is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'g77' has no installation candidate   I have seen on forums that people are installing the g77 for Ubuntu 8.04, but I am fairly new to Ubuntu and unclear of exactly how to do this.

I have just installed 12.04 LTS on my laptop and I'm kinda new in this. I am required to write some program in Fortran 77 and I need a Fortran 77 compiler. I have tried installing g77 as described in the Ubuntu website but was unable to do so. I have typed in the following in terminal:  sudo apt-get install g77   and get the following:  Reading package lists... Done Building dependency tree        Reading state information... Done Package g77 is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'g77' has no installation candidate   May I know what is the problem? I have tried searching g77 in the software center but apparently it is not there. Does this mean it is not available for 12.04?  I'm currently using an Asus K43S laptop with Intel Core i5-2450M processor and my Ubuntu is installed alongside Windows.


An object (such as a mug of coffee, expensive phone, laptop) is placed on an inclined plane and remains stationary due to friction. After an interval (observed as random) it will begin to move (and hence probably fall off).  Explain this in terms of classical mechanics.   (My guess is that it's due to a tiny amount of vibrational energy reducing the normal moment and hence the frictional force).

I have observed sometimes that when I keep some objects precariously balanced, for e.g. some objects in a cupboard, they seem quite stable at the time when I place them there but after a certain period, maybe even 8 - 12 hours suddenly you hear a noise and you can see that they have fallen for what seems like no apparent reason. What can be the reason for this? obviously, I am looking for a physics explanation and not a supernatural one.


Here is the MWE (sorry it's not too short)      \documentclass[border=2pt]{standalone}     \usepackage[utf8]{inputenc}      \usepackage{pgfplots} %pour Tikz et pgfplot     \usetikzlibrary{positioning}      \usetikzlibrary{calc,decorations.markings}      \tikzset{         damper/.style={              decoration={                 markings, mark connection node=dmp, mark=at position 0.4 with                      {                      \node (dmp) [inner sep=0pt,transform shape,rotate=-90,minimum                         width=15pt,minimum height=3pt,draw=none] {};                      \draw ($(dmp.north east)+(10pt,0)$) -- (dmp.south east) -- (dmp.south                         west) -- ($(dmp.north west)+(10pt,0)$);                      \draw ($(dmp.north)+(0,-5pt)$) -- ($(dmp.north)+(0,5pt)$);                     }                 },  decorate             },     }     \begin{document}     \begin{tikzpicture}[thick]         \node (start) at (0,0) {};         \coordinate (top) at (1,1) ;         \coordinate (join) at (3,0) ;         \draw (start) -| (top) -- ++ (0.05,0); % the last point to make it clean         \draw[damper] (top) -- ( top -| join) node[pos=0.5,above=0.3cm] {$c$};          \draw (top -| join) -| (join);         \draw (join) -- ( top -| join) ;      \end{tikzpicture}     \end{document}     The interesting bit is inside the tikzpicture   See,  if you use \draw (A) -- (B) -- (C) the junction in B will be clean. if you use \draw (A) -- (B) and \draw (B) -- (C) the junction will be visible, like on the right in the picture.  The problem is, I can't use the first way when only one line has the decoration to make the damper, that's why I kept it in the MWE.  So you can see I patched the problem for the corner on the left using -- ++ (0.05,0) which is more a bandaid than really fixing...  Got an idea ?

Questions:   Why are the top corners of this number line missing? Why aren't the bottom corners or any other corners of this number line missing? How do I ensure the corners are always there?     \documentclass{article}  \usepackage[left=1.5cm,right=1.5cm,top=2cm,bottom=2cm]{geometry} \usepackage{tikz}   \begin{document}  \begin{tikzpicture}[line width=0.08cm]  \draw (0,0)--(5,0); \draw (0,0.3)--(5,0.3);  \foreach \x in {0,...,5}  {  \node at (\x,-0.55) {\x};  \draw (\x,-0.3)--(\x,0.3);  }  \foreach \x in {0,...,5}  \draw (\x,0)--(\x,0.3);  \end{tikzpicture}  \end{document}   That code yields this:


I have set up a documentclass like this  \documentclass[     11pt,                  % Font size     final,     cleardoublepage = plain, % just for page numbers on cleardoublepages     parskip=half,          % Half a line skipped between paragraphs     twoside,               % Two-sided document     openright,             % Chapters start on right pages     bibliography=totoc,    % Bibliography in ToC     listof=totoc,          % LoF and LoT in ToC     footsepline=0.4pt, ]{scrreprt}[2015/09/15]    % Use current version of KOMA-Script % Author and title of document  % Header and footer \usepackage[automark,headwidth=textwithmarginpar,footwidth=text,footsepline=0.4pt, headsepline=0.4pt:textwithmarginpar]{scrlayer-scrpage}  % Custom header and footer \usepackage{lastpage} %needed for page number \pagestyle{scrheadings} %\setfootsepline{.4pt} THAT DIDNT WORK__________________________________________ \renewcommand{\headfont}{\normalfont\sffamily} \makeatletter \renewcommand{\chaptermark}[1]{\markboth{\@chapapp~\thechapter~--~#1}{}} \makeatother \rohead{\rightmark} \lehead{\leftmark}   The footsepline appears, but only on pages wich a) contains text and b) arent the first page of a new chapter. How do I change that, so that footseplines appear on every page with a footer?

I'm trying to use scrlayer-scrpage with a twosided document using the scrartcl class but somehow can't manage to format the plain pagestyle in a way that is similar to the scrheadings style. I prepared the following MWE – thanks in advance!  \documentclass[12,a4paper,twoside]{scrartcl} \usepackage[automark,headsepline,footsepline,markcase=nouppercase]{scrlayer-scrpage} \renewcommand*{\sectionmarkformat}{} \renewcommand*{\subsectionmarkformat}{} \renewcommand*{\headfont}{\normalfont} \automark[subsection]{section} \chead{\leftmark} \cfoot{\pagemark} \ihead{} \ohead{} \ifoot{} \ofoot{}  \begin{document}  \pagestyle{scrheadings}  \section{Blah.}  Blah.  \newpage  \section{Blah.}  Blah.  \newpage  \pagestyle{plain.scrheadings}   \section{Blah.}  Blah.  \newpage  \section{Blah.}  Blah.  \end{document}


Yesterday I noticed a Google notification indicator when Google Chrome updated to Version 35.0.1916.114.    How can I remove it and stop Google from changing my desktop like that?

After upgrading recently, I noticed that when running Chromium, there is a new bell icon in the system indicators area in the upper right. The menu gives the options as such:   Chromium - notifications Do not disturb Do not disturb for one hour Do not disturb for one day   Are these options only available via the system indicators menu, or can I remove this icon from my view, and access the same options somewhere else? How would I go about removing this?


public static void computePaths(Vertex source) {     source.minDistance = 0.;     PriorityQueue<Vertex> vertexQueue = new PriorityQueue<Vertex>();     vertexQueue.add(source);      while (!vertexQueue.isEmpty())     {         Vertex u = vertexQueue.poll();          ///////////////////////////////         // This is where the error is happening         ///////////////////////////////         for (Edge e : u.adjacencies)         {             Vertex v = e.target;              double weight = e.weight;             double distanceThroughU = u.minDistance + weight;              if (distanceThroughU < v.minDistance)             {                 vertexQueue.remove(v);                 v.minDistance = distanceThroughU;                  v.previous = u;                  vertexQueue.add(v);             }         }     } }   I'm getting the Runtime Error  Exception in thread "main" java.lang.NullPointerException at Dijkstra.computePaths(Solution.java:69) at Solution.main(Solution.java:141)   The program works fine with hard-coded vertices and paths, however the problem is going to be tested through file input, so I'm assuming it has to do with when I am taking in those values, but I can't find anything that would cause that error.  below is from where I take in the values  for (int i = 0; i < plans; i++)     {         vs[i] = new Vertex(scan.next());         destinations[i] = new Vertex(scan.next());         weights[i] = scan.nextInt();         scan.nextLine();     }      for (int i = 0; i < plans; i++)     {         vs[i].adjacencies = new Edge[]         { new Edge(destinations[i], weights[i]) };      }      Vertex[] vertices = new Vertex[plans];      for (int i = 0; i < plans; i++)     {         vertices[i] = vs[i];     }      // starting vertice     String start = scan.next();     // ending vertice     String end = scan.next();      Dijkstra.computePaths(vs[0]);

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


I was looking at logistic regression and softmax regression.  Based on this formula,   $P(y=j|\mathbf {x} )={\frac {e^{\mathbf {x} ^{\mathsf {T}}\mathbf {w} _{j}}}{\sum _{k=1}^{K}e^{\mathbf {x} ^{\mathsf {T}}\mathbf {w} _{k}}}}$  How does $k=2$ make it logistic regression? I cannot seem to derive this to this  $\sigma (t)={\frac {e^{t}}{e^{t}+1}}={\frac {1}{1+e^{-t}}}$

Is it correct to say that binary logistic regression is a special case of multinomial logistic regression when the outcome has 2 levels?


I've the journey which is actived wherein email send activity is used. Now if I want to change the content of email then is it possible ? ?   Or is there any other best way to design the email Content?, So that if it's used in the email which is in the actived journey and if we change the email content then it'll also reflect in the jounery builder email.   Like Content builder have a Dynamic content but will that fullfil same requirement?

I've created a journey in salesforce marketing cloud to send a set of emails. This journey is currently active & running.   I want to do some changes in existing content of one of the email (for example I want to change url of CTA button).    If I go to content builder & change content of that email. Will it reflect in ongoing journey? or  I need to stop existing journey and create a new version with updated email content.   Which one will work?


I did 5 years of post-college education in the US, 1993 to 1997. Due to financial issues, I was unable to pay my credit card bill of a certain bank. The debt remains unpaid. I do plan to pay and solve the debt later this year. Could I be denied a visa for having an unpaid bill?

I did my 3 years of College in the US, 2010-2013 due to finance issues I was unable to pay my credit card bill of a certain bank, which still lie unpaid.  However I plan on visiting the US later this year; could I be denied visa for having an unpaid bill ?


consider a table which is filled with numbers from 0 to 9 and each number is repeated exactly 10 times using graph prove that there exists a row or column with more than 3 unique digits I faced this question and couldn't solve it using graph I'll be glad if you help me solve it.

I saw this question but I couldn't find the answer. Assume that we have a 10x10 table, and it's filled with 0 to 9 numbers ( 10 of each of them are in the table, 10x zero, 10x one, and ... ) By using graph, prove that we have a column or a row that we can find at least 4 different numbers in it. edit: I have found this method to create a graph from any table-matrix :  after that, I thought that it would be a good way to use coloured edges. and now the thing to prove is to have a vertex with at least four colour edges connected to it. maybe with pigeonhole, the problem can be solved but I couldn't


I am new to photography (just 3 to 4 months of experience) and I am looking to buy a new lens (either 35mm or 50mm, but mostly 35mm because I have already decided Sigma 85mm f/1.4 DG HSM Art Lens for the creamy bokeh) for general street photography.   I like my images to be as sharp as possible. I went through many websites and youtube videos and many of them mention that Nikon 1.4g is superior to Nikon 1.8g. At the same time they also mention that Nikon 1.8g is sharper. Why do they say Nikon 1.4g better when Nikon 1.8g is sharper ?

When reading lens reviews on the Internet, I often find subjective statements about the image quality that a lens produces, such as "good contrast" or "sharp". The problem is that I don't think I am capable to actually see these qualities on an image. I don't even think I could tell the difference between a cheap kit lens and a top lens, if not by "this just looks better".  So my question is: without looking at sharpness tests and MTF curves, how do you learn to judge the quality of a lens based only on sample images? What are the characteristics you look for and what constitutes good or bad in each of them?


When asked a question about Collective Nouns, I told them that it is all right to use a singular or plural verb after a Collective Noun, as in -   The class was listening to the lecture with rapt attention.    Here the class is taken as a whole.   The class were working on their projects.    Here the the individuals are taken into consideration rather than the class as a whole.  Now the question is: Do we use singular or plural verbs with the names of countries, which are proper nouns, for the same reason?   As in:    Bhutan is said to be The Last Shangrila.   Bhutan are working on promoting their GNH Philosophy.

I'd say Microsoft have a way of bending the rules and I know that McLaren have won the championship. While this sounds strange, I believe it is correct English (sorry, I'm not native).   But when it's a small company, would you still use it this way? Is a company always plural, or are small companies singular? I.e., would you say Bakery Johnson makes fine bread or Bakery Johnson make fine bread? Is it My book seller, Woody's, have moved or is it has moved?


I would like to use linux on our company laptop Asus Eee 901 - specs:  CPU Intel Atom 1.66 GHz,  RAM 1 GB DDR2 Display 8.9 inch, 1024x600 pixels  As I am not allowed to modify the OS and MBR I want to boot from SD slot and use some SDHC card (can buy something like Class 10 for better performance).  I need some user friendly distro with GUI. In first approach the laptop will serve as portable device for sorting and backup photos (to external usb HDD) and videos on holiday and occasional web access.  So I need some usable image viewer, file manager and current web browser - capable to run on the screen only 600 pixels high... And running a little bit more quickly than the Windows :-)  What would you recommend? Lubuntu?  thanks

For a given hardware configuration, how do I find out if Ubuntu will run on it? What considerations should I take into account when choosing an Ubuntu version and  such as:    with a lighter desktop than the usual Gnome and Unity  with the even lighter LXDE desktop   Obviously Ubuntu does not run on some processor architectures. So how do I go about choosing the right version and derivate. How can I find out the minmal system requirements?


Among all his other inert Horcruxes, Voldemort created two living ones: Harry and Nagini.  When Voldemort tried to kill Harry, he was unable to do so. Instead, his curse ended up killing the piece of Voldemort's own soul that Harry carried. Logically, this means that when a living creature, that's also a Horcrux, is killed, it's not the carrier, but the soul they are carrying, that ends up dead.  However, this reasoning does not seem to work for Nagini. She was holding a piece of Voldemort's soul when she was killed, but both souls were destroyed. Shouldn't Nagini, the snake, have survived, and only Voldemort's soul died?  Even if we accept that physically killing Nagini killed both souls, how is that any different than magically killing Harry? How did the killing curse "know" which of the two souls inside Harry's body should die?

I know that this question may sound like it has a very obvious answer, and many of you may just say that Harry didn't die because he was the Master of Death, as he had the possession of the three Deathly Hallows.  Couldn't, though, the "Master of Death" be purely a figure of speech, since the owner of the Hallows would be able to kill, resurrect and dodge death?   I know this is a question that is left open in the book, but couldn't Harry have lived because he carried a piece of Voldemort's soul, and Dumbledore gave Harry the choice to really die or just kill the piece of Voldemort's soul, and then Harry could live?    Is there anything in any of the books to support either theory?


I need to know whether the sentence given below correct?     Have something to eat, if you didn't have it earlier.

In regard to this , my question is similar but that answer is not clear. I want to know why we use base form of verb, e.g. 'go' to form the past tense instead of past form such as 'went'?     Question: Did you go to a bank?  (Why we use 'go' here, rather than 'went'?)   Answer: I went to a bank.   Am I confusing verb forms with tenses? Please note that I'm not a native speaker so some clarification or reference on this would be helpful.


So I recently went to the Bannered Mare in Whiterun after learning that not only can you cook with the ingredients given, but there was a cooking pot there. There I met Saadia. No matter what I do, she won't accept my Amulet of Mara, even after I finished her quest and let her live. Is she a marriable character in Skyrim?

In the vein of  - Pete Hines, Bethesda's VP of PR and Marketing, when asked if Skyrim would support gay marriage :     You can marry anyone...Not any NPC, just mean any male or female.   So obviously some NPCs are off the list.  I assume I can't marry Jarl Balgruuf, but what about Irileth?  What about the Graybeards?  What about already-married NPCs?  Is it any "important" NPC, or is it more or less than that?  Has the Skyrim Creation Kit shed any light on how to determine this?


I would like to create a gVim AppImage using packages from 14.04 (why not 16.04? Because 16.04 packages are too new as AppImages will only run on distributions newer or the same age as the distribution who's packages they're built from). Now I would like my gVim AppImage to be for the very latest version of gVim, so I need a repository for 14.04 that provides the very latest gVim. I have searched Launchpad for Vim PPAs that are maintained and have not found any (all the ones I found are out-of-date).  My questions:   I know I can build the latest gVim as a Debian package with checkinstall, but I want to use gVim from a package repository to build my gVim AppImage as it makes things a lot simpler. Where can I find a recent Debian package of gVim? Alternatively, how can I build an AppImage container from an arbitrary set of binaries (downloaded somewhere or compiled from source)?

The breakindent feature is the greatest thing ever, but it's in 7.4.338. The latest version in the Ubuntu repos is just 7.4, I think. I notice , but I can't seem to find one for Ubuntu yet. I'm hopeless with compiling things, otherwise I'd compile it myself.


How can I take this input:     71.3.162.181.in-addr.arpa   and turn it in to this:     181.162.3.71   I'm hoping sed and awk can do this, but just don't know where to start?

If we have this string (): 192.168.1.1  How can I derive the () from this string, so it will be shown like 1.1.168.192.in-addr.arpa using a shell script?


There are 6 people on the train. Prove that there are 3 people among them that know each other or don't know each other.  My first instinct is that it might have to do something with a bipartite graph, but this seems not to work at all with 3 of them knowing each other.  But I still don't have an idea how to do this.

Prove that in any group of 6 people there are always at least 3 people who either all know one-another or all are strangers to one-another.  Hint: Use the pigeonhole principle.  I don't see how this applies to the pigeonhole principle because I keep imagining a group of 4 strangers, and then 2 friends. This would be 6 total but against what the proof is asking. Maybe I don't understand the proof in question...


what's the difference between unconditional quantile and generalized quantile regression（Powell，2016）？

The conditional quantile regression estimator by Koenker and Basset (1978) for the $\tau^{th}$ quantile is defined as $$ \widehat{\beta}_{QR} = \min_{b} \sum^{n}_{i=1} \rho_\tau (y_i - X'_i b_\tau) $$ where $\rho_\tau = u_i\cdot (\tau - 1(u_i<0))$ is a re-weighting function (called "check"-function) of the residuals $u_i$.  In a paper by , the authors state that conditional quantile regression does not give interesting effects. They say that conditional results cannot be generalized to the population (in OLS we can always go from conditional to unconditional via the law of iterated expectations but this is not available for quantiles). This is because the $\tau^{th}$ unconditional quantile $y_i$ might not be the same as the $\tau^{th}$ conditional quantile $y_i |X_i$.  If I understand correctly, part of the problem is that which covariates are included in $X_i$ has an effect on the ranking variable $u_i$ because inclusion of covariates splits the error into observed and unobserved components. I just cannot quite understand why this causes problems.  Here are my questions:     What makes conditional and unconditional quantile effects different from each other? How can I interpret the coefficients of conditional quantile regressions? Are conditional quantile regressions biased?   References:     Koenker, R., & Bassett, G. (1978) "Regression Quantiles", Econometrica, Vol. 46(1), pp. 33-50.   Firpo, S. et al. (2009) "Unconditional Quantile Regressions", Econometrica, Vol. 77(3), pp. 953-973.


See the Wikipedia article on .  It says that  A singularity in solutions of the Einstein field equations is one of two things:  1. a situation where matter is forced to be compressed to a point (a space-like singularity)  2. a situation where certain light rays come from a region with infinite curvature (a time-like singularity)  If matter is forced to be compressed to a point, why is this called a space-like singularity?  If certain light rays come from a region with infinite curvature, why is this called a time-like singularity?

What is the definition of a timelike and spacelike ?  Trying to find, but haven't yet, what the definitions are.


I do understand how quantum entanglement works, but I don't understand how this can help us communicate. Just because you know the value of the other, there's no way to change it (as far as I know), so it would be the same, so you couldn't send a bit. I know there's something I'm missing, but I'd really like to understand this, so it would be very helpful. If you could, please break it down for me and maybe use an example, too. Thanks in advance! EDIT: So from what I'm getting from some of the comments, I realize that it's not exactly what I'd imagined, and you can't really send data through entangled particles.

Today we rely on electromagnetic field for communication. I'm a entrepreneur, I want to know why we can't transfer data with this technology to transfer data from one place to another place. It can reduce us to rely on emf. And quantum entanglement able to send data to everywhere.


I have created a key/pair using Terminal in my Mac using the ssh-keygen -t rsa command. I have tried uploading the .pub file to Marketing Cloud but it complains about a "bad header or footer". Does anyone know how I can resolve this? I have tried with and without a passphrase.

Tried to generate SSH Key and PFX files to be imported into Key Management in Marketing Cloud.  It gives errors each time.  SSH Key Generation:  openssl genrsa -des3 -out private.pem 2048 openssl rsa -in private.pem -outform PEM -pubout -out public.pem   Error when uploading private key into Key Management:      File is not encrypted. No passphrase required.   Error when uploading private key into Key Management:         Object reference not set to an instance of an object.   PFX FIle Generation:  openssl req -x509 -days 365 -newkey rsa:2048 -keyout my-key.pem -out my-cert.pem openssl pkcs12 -export -in my-cert.pem -inkey -my-key.pem -out accountmgmt.pfx   Error when uploading PFX file into Key Management:      The key file does not contain any valid public encryption keys.   I am not sure which format would it support.


I often get popular question points/awards for questions that never received any upvotes. What exactly is the rank for popularity; impressions?

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


Lately I've been trying to look for any tutorials on how to make "shadow catcher" planes in Blender Render because I need to render ground shadows on a separate layer. However it seems every tutorial I've come across uses Cycles. But can this be done in Blender Render or not?  No this isn't a duplicate of another question. Yes I have a shadow rendered against a transparent background already, but what I am trying to do is have that shadow on a separate layer. Using Blender Render and not Cycles.

In most of my models, I usually end up setting a world background using an HDRI image of some kind or another. This has always been really useful for lighting in general or as a background for my final render.  But what if I want my model to look like it is interacting or touching part of the background? For example, in the image below that I found, the modeled objects look like they're part of the scene, and even appear to cast shadows on the ground. How can I do this?


I need to download and install Google Web browser without using a browser. My only option is windows command line. What are the commands I need to input to do this?

Without using any non-standard (Windows included) utilities, is it possible to download using the Windows command line?  The preferred version is Windows XP, but it's also interesting to know for newer versions.  To further clarify my question:   It has to be using HTTP The file needs to be saved Standard clean Windows install, no extra tools   So basically, since everybody is screaming , I want simple Wget functionality, without using Wget.


I have seen buffer overflows in other programming languages, but how does it look in Java?

Does Java have buffer overflows? If yes can you give me scenarios?


Say I run an app from a terminal, but in some cases I want to close the terminal but hope the app keeps running.   Is there anyway to do so in Linux?  I just found that when calling an app via "exec APP", either would be closed if the other was closed.

sometimes I run an app in the gnome-terminal, but then I suddenly have to restart gnome or something. I guess the answer to the question is also useful then I want to disconnect from SSH where something is happenning.  Gnome's terminal tree looks like this:  gnome-terminal     bash         some-boring-process   Can I 'detach' bash from gnome-terminal (or detach some-boring-process from bash and redirect its output somewhere)? If I just kill gnome-terminal, bash will be killed to will all its subprocesses


What is the big difference between software RAID and hardware RAID at the low level?  What is really going on that sets the two apart?  As far as I know, the only difference is the RAID card can have cache and it has its own processor on-board. But are there other aspects that go in the background that can make one better then the other in certain situations?

I'm building a new server (Small Business Server 2008), but I can't get the built-in RAID controller (AMD SB700) to work and have basically given up on it ever working with Server 2008. Fine.  But my question is... is there any real difference between Hardware (such as ) and Software (Window's built in Drive Mirroring) for RAID 1?  Assuming the drives are identical models, etc., it seems that there would be a negligible difference, just based on my guessing/wishfull thinking.


public static void main(String[] args) {     double s = 0; //Position     double v = 100; //Velocity     double g = 9.81; //Gravitational Force      for(double time = 0.01; time < 100; time = time + 0.01){        double DELTA_T = 0.01;         s = s + (v * DELTA_T);         v = v - (g * DELTA_T);          if(time % 1 == 0) { //I want to print this out, but it seems to end the program with no output             System.out.println("Seconds: " + time);             System.out.println("Position: " + s);             System.out.println("Velocity: " + v);         }     } }   I want to output the calculations when (time % 1 == 0). But when I run this, it doesn't print anything out. When I remove the if statement, and leave in the print statements, it will print.   I was wondering what is wrong with my if statement and how would I go about trying to print "s", "v", and "time" every time (time % 1 == 0)

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


The following sentence appeared in an article: "I would say 94,504 bitcoins is real folding money, but you can't fold bitcoins." A colleague said that it should have been 'are' instead of 'is.' I am torn as to whether he is correct because 'bitcoins' is plural or incorrect because '94,504 bitcoins' is a singular concept that is being equated to another singular idiom.  I think he's incorrect because 'five eggs is enough' is correct and you rarely equate a plural noun with a singular noun; 'apples are orange' doesn't work.

Possible Duplicate:    I want to say:  Those sixty dollars are gone That sixty dollars is gone  The reason I ask is because I was originally typing:  Those $60 are gone  But that looks funny to me. Which is more correct?


Given the equivalence $a^2 \equiv 1 \pmod b$ (where $b$ is known) is there an efficient way to determine if an answer other than $a = 1$ exists? Is there an efficient way to find the answer(s), especially the greatest possible value of $a$? The only constraint is $1 < a < b - 1$.

I split this into $x^2\equiv 1\pmod {7}$ and $x^2\equiv 1\pmod {13}$.  For $x^2\equiv 1\pmod {7}$, i did: $$ (\pm1 )^2\equiv 1\pmod{7}$$ $$(\pm2 )^2\equiv 4\pmod{7}$$ $$(\pm3 )^2\equiv 2\pmod{7}$$ Which shows that the solutions to $x^2\equiv 1\pmod {7}$ are $\pm1$.  For $x^2\equiv 1\pmod {13}$, i did: $$ (\pm1 )^2\equiv 1\pmod{13}$$ $$(\pm2 )^2\equiv 4\pmod{13}$$ $$(\pm3 )^2\equiv 9\pmod{13}$$ $$ (\pm4 )^2\equiv 3\pmod{13}$$ $$(\pm5 )^2\equiv {-1}\pmod{13}$$ $$(\pm6 )^2\equiv 10\pmod{13}$$Which shows that the solutions to $x^2\equiv 1\pmod {13}$ are $\pm1$.  Thus, I concluded that the solutions to $x^2\equiv 1\pmod {91}$ must be $\pm1$. I thought that $\pm1$ were the only solutions, but apparently I am incorrect! How do I go about finding the other solutions to this congruence?


I am a complete NEWBIE to Linux and Ubuntu. So I need step by step help please. I am running Ubuntu 13.04 and I have no clue how to install my printer. I am sick of Windows and want to run Ubuntu only, but right now I have to dual boot with Windows so I have access to my printer. Printer is a Brother MFC-295CN, and I want to install basic way by USB-not network. I have looked at other questions about this but I don't understand how to install packages or use terminal commands. So a step by step help is what I need. Thanks in advance for any help.

I'm trying to get the drivers for my printer going, and not doing well. I tried the following:  and the sudo dpkg -i PACKAGE.deb format. It installs the printer, but then doesn't see the printer via USB. Ideas?


I tried my code in several ways (using equals(), trim()) but the following code block seems to be not working despite the fact it executes the else block only. I am working on several arrays to get the confusion matrix in cross validation.      for (int x=0; x< clsNames.length; x++)     {          System.out.println("class: "+clsNames[x].trim());          for (int y=0; y<oftarray1.length ;y++)           {             System.out.println("first validation");                                         System.out.println(clsNames[x]);                                    System.out.println(oftarray1[y]);                                        System.out.println(clsName[y]);           if (oftarray1[y]==  clsNames[x] && clsName[y]==oftarray1[y])          {             System.out.println("tp...");             truePositives++;             System.out.println("tp : "+truePositives++);                                          }           else if (oftarray1[y]==clsNames[x] && clsName[y]!=oftarray1[y])         {                                                                      System.out.println("fn...");             falseNegatives++;             System.out.println("fn : "+falseNegatives++);          }          else if (oftarray1[y]!=clsNames[x] && clsName[y]==oftarray1[y])         {                                             System.out.println("fp...");             falsePositives++;             System.out.println("fp : "+falsePositives++);           }           else           {             System.out.println("tn...");             trueNegatives++;             System.out.println("tn : "+trueNegatives++);          }       }    }

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


My question is, which of the following sentences(#1 and #2) is grammatically correct? (This is part of a song's lyrics.)     1.You and me with empty hands.   Or     2.You and I with empty hands.

I read from a book that "you and I" replaces "we" in a sentence, while "you and me" replaces "us". Examples:   The professor wants to see you and me [us].  You and I [we] will go together.    Is this correct? I was under the notion that "I" and "me" could be used interchangeably.


In R, I am fitting a model using the multinom() function from the nnet package. There is only 1 response variable and there are >2 classes. When I have a model with >3 classes, there's an error that says there are too many weights, so I'm using 3 classes: 0, 1, and 2 (categorical variables). The output from multinom() is stored in model.  Before, when I used 2 classes, summary(model)$coefficients returned a vector of numeric coefficients. When I used 3 classes, summary(model)$coefficients returned a matrix with two rows of coefficients: one for class '1' and one for class '2'. So I'm looking to learn how multinomial logistic regression works. Why do class 1 and 2 have separate sets of coefficients? Does it run logistic regression using class 0 vs 1 and for class 1 vs 2? What about class 0 vs 2? If it compares them all, where are the coefficients for all 3C2 comparisons, instead of just for 2 comparisons?

This is somewhat of a beginner's question, but how does one interpret an exp(B) result of 6.012 in a multinomial logistic regression model?  1) is it 6.012-1.0 = 5.012 = 5012% increase in risk?  or  2) 6.012/(1+6.012) = 0.857 = 85.7% increase in risk?  In case both alternatives are incorrect, can someone please mention the correct way?  Ive searched many resources on the internet and I get to these two alternatives, and I am not entirely sure which one is correct.


I want to populating my sql tables using PHP code. For words with accent like ('pépite') , they are inserted as 'pÃ©pite'. Some extra characters are inserted in my string. Here is my code:  $word = 'pépite'; $query = "Insert into [Tracker].[dbo].[Demo] values ('".$word."')"; sqlsrv_query($conn,$query); echo $word; // output : pÃ©pite   I have tried with utf8_decode as well. But this gives some abstract output.

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


Let $T$ be a linear transformation from a vector space $V$ over reals into $V$ such that $T-T^2=I.$  Show that $T$ is invertible.   I am not able to understand how is $T$ being treated like a matrix when it is infact a linear transformation.  Is it the Matrix equivalent of $T$ being talked about?

Let $T$ be a linear transformation from a vector space $V$  over reals into $V$ such that $T-T^2=I$. Show that $T$ is invertible


In C++, what guarantees are there, if any, for two types T1 and T2 so that  sizeof(T1*) == sizeof(T2*)   will always be true? It's not guaranteed, for example, that char* and int* will be the same size on all systems.

For example: sizeof(char*) returns 4.  As does int*, long long*, everything that I've tried.  Are there any exceptions to this?


i have Nikon D3300 DSLR with Nikon 18-55mm (VR2) lens  and i want to shoot astrophotos.  i wanna know if this possible with my camera or lens   and if not , what should i upgrade ? and what to ?  Thanks

I have a Canon 20D. I'd love to take some photos of the moon and stars.   How do I get started?  I've search the web and the information is sparse and cryptic.   I'd like to know what equipment is the best for a beginner and what I should try taking a photo of first... besides the moon :).


In 2011, could a Bangladeshi citizen, with a Bangladeshi passport and a valid UK visa, enter France without needing an additional French visa?

I'm a UK passport holder; my wife isn't. We don't live in UK. If she gets a UK visit visa, does this entitle her to travel to the Schengen area or do I need to get her a separate Schengen visa?


This is my proof  Suppose not. Then, $\cup A_i$ has an open partition $\{U,V\}$ $U \subseteq \cup A_i$ so we only need to show two cases:  $U \subseteq \cup A_j$ with $U \neq \cup A_j$ for some $J \subseteq E$. Then there exists some $A_k$ such that $U \neq A_k$ with $U \cap A_k \neq \emptyset$. Thus $\{ U \cap A_k,V \cap A_k \}$ is an open partition of $A_k$. By assumption, $A_k$ is connected. It's a contradiction with [$\cup A_i$ is disconnected]  $U= \cup A_t$ for some $T \subseteq E$. Since $V \neq \emptyset$, there exists some $A_k$ such that $(A_k-U) \neq \emptyset$. Let $J=T \cup \{k\}$. Then by Case 1, It's a contradiction with [$\cup A_i$ is disconnected]    Is it okay?? I'm not sure about this...

If $\{E_\alpha\}_{\alpha\in A}$ is connected in $\mathbb{R}^n$, $\bigcap\limits_{\alpha\in A}E_\alpha \neq \emptyset$, then $\bigcup\limits_{\alpha\in A}E_\alpha$ is connected.  I have zero intuition on how to do a proof of this statement. Please help.  I started it by contradiction like this: suppose that $\bigcup\limits_{\alpha\in A}E_\alpha$ is not connected. Then there exist non-empty disjoint separating sets $U$ and $V$, such that $U$ and $V$ are relatively open in $\bigcup\limits_{\alpha\in A}E_\alpha$, and $U\cup V= \bigcup\limits_{\alpha\in A}E_\alpha$. But I have no idea what to do next.


Pi is defined as circumference/diameter, but it is an irrational number. And by definition an irrational number can't be defined by a fraction. So how is it that pi is circumference/diameter and on a side note: how are important irrational numbers like e normally found?

$\pi$ can be represented as $C/D$, and $C/D$ is a fraction, and the definition of an irrational number is that it cannot be represented as a fraction.   Then why is $\pi$ an irrational number?


I need help to solve the following sum: $$\sum_{i=0}^{k-1} 4^i(i-1)$$ I'm doing some exercises about recurrence relations in algorithms and this sum came up.   The exercise stands like:  $$T(n) = \frac {1}{2}n + 4T(\frac{n}{2} + 3)$$  And the result I get was:  $$ T(n) = 4^n T(\frac{n}{2^k}+3k)+[\sum_{i=0}^{k-1}\frac{4^in}{2^{i+1}}+4^i*3*(i-1)]$$  All of this is new to me, all the examples i saw online are way more different than this excercise   Am I getting closer to an answer?   Note: No base case was given   Thanks in advance!

I want to know the general formula for $\sum_{n=0}^{m}nr^n$ for some constant r and how it is derived.  For example, when r = 2, the formula is given by: $\sum_{n=0}^{m}n2^n = 2(m2^m - 2^m +1)$ according to   Thanks!


For $f(x,y)=x^4+y^4-2x^2-2y^2+4xy$, I need to find maxima or minima. There are three critical points: $(0,0),(\sqrt2, -\sqrt2),(-\sqrt2,\sqrt2)$ So at $(\sqrt2, -\sqrt2)$, $f$ has minimum value, $-8$ and at $(-\sqrt2,\sqrt2),$ it has same minimum value, $-8$. At $(0,0)$, after inspecting, I get that it has neither maxima or minima. But when we substitute $(0,0),$ we get $0\le f \le8,$ so should not we get $(0,0)$ as a point of maxima?


I found that the 18.04.4 LTS version has longer support than the one i installed 19.10, so can i change to the former one without doing a clean installation ?

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


I am new to Ubuntu. I downloaded the latest version of Blender (2.70a) from official blender.org site as an tar.bz2 file. My Ubuntu OS is 14.04 LTS amd64 bit os, and I am sure that I have downloaded the correct version of blender. I have read that for security reasons, Ubuntu does not allow executing exe files.   Since the downloaded package contains blender as an executable/x-executable type, it is not able to execute. I do not have an internet connection in that computer too. Also the "Allow executing file as program" checkbox is checked by default. Still double clicking it does not execute the file. Can anyone say how to open this file?  P.S: Wine also checked but requires active internet connection, which I dont have.

I installed Blender from official Ubuntu repository but its version is always behind the version available from the official Blender website.  I'm aware that I can launch the program within the downloaded folder, but i want to replace the install version with a new version downloaded from the website?   It must be present in the unity launcher.  I'm also aware of the available PPA's that are available, however I just want to install Blender manually.  Thanks in advance


Here is code:     i am trying to add event to calender without using intent..here i put code.but getting some error.help me out.and got null pointer exception as given below.what to do now?   btn_create_without_intent.setOnClickListener(new View.OnClickListener() {         @Override         public void onClick(View v) {             // Construct event details             long startMillis = 0;             long endMillis = 0;             Calendar beginTime = Calendar.getInstance();             beginTime.set(2015, 9, 21, 7, 30);             startMillis = beginTime.getTimeInMillis();             Calendar endTime = Calendar.getInstance();             endTime.set(2015, 9, 21, 8, 45);             endMillis = endTime.getTimeInMillis();              // Insert Event             ContentResolver cr = getContentResolver();             ContentValues values = new ContentValues();             TimeZone timeZone = TimeZone.getDefault();             values.put(CalendarContract.Events.DTSTART, startMillis);             values.put(CalendarContract.Events.DTEND, endMillis);             values.put(CalendarContract.Events.EVENT_TIMEZONE, timeZone.getID());             values.put(CalendarContract.Events.TITLE, "Android Example");             values.put(CalendarContract.Events.DESCRIPTION, "Android Example");             values.put(CalendarContract.Events.CALENDAR_ID, 3);             Uri uri = cr.insert(CalendarContract.Events.CONTENT_URI, values);              // Retrieve ID for new event             String eventID = uri.getLastPathSegment();         }     });   And getting this error:  E/DatabaseUtils﹕ Writing exception to parcel java.lang.NullPointerException         at com.android.providers.calendar.CalendarProvider2.insertInTransaction(CalendarProvider2.java:2523)         at com.android.providers.calendar.SQLiteContentProvider.insert(SQLiteContentProvider.java:96)         at android.content.ContentProvider$Transport.insert(ContentProvider.java:192)         at android.content.ContentProviderNative.onTransact(ContentProviderNative.java:152)         at android.os.Binder.execTransact(Binder.java:338)         at dalvik.system.NativeStart.run(Native Method) java.lang.NullPointerException         at android.os.Parcel.readException(Parcel.java:1333)         at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:182)         at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:136)         at android.content.ContentProviderProxy.insert(ContentProviderNative.java:415)         at android.content.ContentResolver.insert(ContentResolver.java:730)         at mockapp.techforce.com.calendereventexample.MainActivity$1.onClick(MainActivity.java:52)         at android.view.View.performClick(View.java:3571)         at android.view.View$PerformClick.run(View.java:14247)         at android.os.Handler.handleCallback(Handler.java:605)         at android.os.Handler.dispatchMessage(Handler.java:92)         at android.os.Looper.loop(Looper.java:137)         at android.app.ActivityThread.main(ActivityThread.java:4517)         at java.lang.reflect.Method.invokeNative(Native Method)         at java.lang.reflect.Method.invoke(Method.java:511)         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)         at dalvik.system.NativeStart.main(Native Method)

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


I wrote some codes to create a directory named "E:\hkhkhkhk\...." in c++. It actually created "...." iteratively. And the parent directory "hkhkhkhk" cannot be removed.   I was wondering how the system explains "....".  The code is as below, execute it in virtual machine.  #include <windows.h> #include <iostream>  using namespace std;  int main() {     if (!CreateDirectoryA("E:\\hkhkhkhk\\....\\", NULL))         cout << GetLastError() << endl;      getchar();     return 0; }   Josh

The folder name was listed in File Explorer with just plain four dots .....  When I tried opening it, I came into some kind of endless rabbit hole loop where I opened the exact same folder again and again - I could do this endlessly. Showing the path like C:\ExamplePath\....\....\....\....\...., etc.  It was hanging my TypeScript compilation in one specific project. It took me more than a year before I found this folder and its related problems, because it was rooted deeply in nested folders. I never expected an issue like this, so I never looked for it.  I couldn't delete the folder the normal way because of the special name. In the end, I could remove it by using the command line and deleting the parent folder with rd /s /q path.  Afterward, I tried to create the folder again but was unable to do so with both File Explorer and the command line.  In my 20-plus years of using Windows I have never seen this bug before, so I can imagine that it would really be an annoying and confusing problem for amateur users.  Does anyone know how this could have happened and how to reproduce this issue?  Update  For people who are interested: this path was located deep within a TFS folder. So probably TFS uses the bypass method @grawity explained ("Various file managers, archivers, etc")  Did I stumble on a rare TFS bug?


How can two black holes with event horizons merge within the lifetime of the universe? Basically events are happening where events stop (to the outside observer) so does an event horizon actually exist? According to gravitational wave detectors on Earth, two black holes merged within fractions of a second.

I've read a lot of conflicting answers in these forums. However, today saw the awesome announcement of gravitational waves. Two black holes merged:   Not only that, they merged FAST. In 1/5th of a second revolving around each other 250 times a second. The entire event was quicker than a heartbeat. Moreover, we observed this happening as distant outsiders. So now we can say for sure:   Objects approaching the event horizon DO NOT appear to slow down Black holes CAN merge in a finite (and quick) amount of time And all this is wrt a frame of reference far, far away   To quote the NYTimes article:  One of them was 36 times as massive as the sun, the other 29. As they approached the end, at half the speed of light, they were circling each other 250 times a second.  And then the ringing stopped as the two holes coalesced into a single black hole, a trapdoor in space with the equivalent mass of 62 suns. All in a fifth of a second, Earth time.  However, everything I've read so far has let me to believe that an outside observer should never be able to measure the collision happening in a finite time. So what exactly is happening here? I must have read at lest 5 different versions of this so far everywhere in these forums over the past several years.


Wondering whether there is a limit in the number of bibliographies one can create while using the package multibbl.  I have  been able to create 12 but the moment I try to create the 13 I seem to have issues. The error I get is    No room for a new \write.\e@ch@ck ...message {No room for a new \string #4}\fi \fi \newbibliography{workshops}    12 seems like an odd number. Is there a way around this?

In my special package combination I get the error No room for new \write. \tablecontents and Bad number (16). \tablecontents. The following MWE throws this error in pdflatex and lualatex with TeX Live 2015. As you can see, I add the own content register loi. I can delete nearly every package separately and the error directly vanishes.  Does anyone have an idea what is wrong with this package combination?  \documentclass{scrartcl} % load packages \usepackage{ifluatex} \ifluatex     \usepackage{fontspec} \fi \usepackage{adjustbox, amsmath, blindtext, datatool, fancybox, fixme, graphicx, marginnote, pgfplots} \usepackage{imakeidx} \usepackage{biblatex} \usepackage{glossaries} \usepackage{hyperref} % load package for code code highlighting \usepackage{minted}  % define Open Issue and corresponding List of Open Issues \newcommand{\openissue}[2][Unlabeled]{%     \par%     {\refstepcounter{loicounter}%     \phantomsection% comment out if hyperref is noy used     \addcontentsline{loi}{figure}{%         \protect\numberline{%             \ifcsname c@chapter\endcsname%                 \thechapter.%             \fi%             \theloicounter%         }{#1: #2}%     }%     \textbf{Open Issue -- #1:} #2}%     \par% } % define counter \makeatletter \ifcsname c@chapter\endcsname%     \newcounter{loicounter}[chapter]% \else     \newcounter{loicounter}% \fi% \newcommand*{\listopenissuesname}{List of Open Issues} \newcommand{\listofopenissues}{%     \ifcsname chapter\endcsname%         \chapter*{\listopenissuesname}%     \else%         \section*{\listopenissuesname}%     \fi%     \@starttoc{loi}% } \makeatother  \fxsetup{status = draft} \makeglossaries \makeindex  \begin{document}  % include open issues \listofopenissues % include list of corrections \listoffixmes % include indicies \tableofcontents                            % Inhaltsverzeichnis einbinden  \end{document}


Evaluate the following definite integral by letting $u= \pi/2 - x$.  The integral is  $$\int_0^{\pi/2} \frac{\sin(x)}{\cos(x)+\sin(x)}dx.$$

This problem is given on a sample test for my calculus two class. $$ \int^{\frac{\pi}{2}}_0 \frac{\sin x}{\sin x+\cos x}\,dx $$ I can find the value of this integral using other substitutions which lead to partial fractions but the prof added a hint to use the substitution $$t=\frac{\pi}{2}-x $$ so I've been trying to figure out how to do it his way but am pretty lost. Any ideas?


I am just trying to make my game character, which is a texture (ball), to jump up in the air and then return back down to the position that it started at when the screen is pressed. I was just wondering if someone could give me a code example or help me to do this with my current code which is below. I have basically just drawn the background and the ball texture and positioned the ball where I want it to start the jump. The ball texture is what I want to make jump straight up.      public class MyGdxGame extends ApplicationAdapter {     SpriteBatch batch;     Texture background;     Texture ball;      @Override     public void create () {         batch = new SpriteBatch();         background = new Texture("gamebackground.png");          ball = new Texture("ball2.png");         ball.setFilter(Texture.TextureFilter.Nearest, Texture.TextureFilter.Nearest);     }      @Override        public void render   () {          batch.begin();           float scaleFactor = 2.0f;            batch.draw(background, 0, 0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight    ());         batch.draw(ball, 80, 145, ball.getWidth() * scaleFactor, ball.getHeight() *     scaleFactor);         batch.end();     }      @Override     public void dispose () {     } }

I am just starting out in game development and I am trying to make a simple android game using GDXLib. I want to make my sprite "ball" jump straight up in the air and then return to where it originally was. How would I do this? I have looked at multiple other answers from similar questions but none seem to work with my code. This is my code so far:  @Override public void create () {     batch = new SpriteBatch();     background = new Texture("gamebackground.png");      ball = new Texture("ball2.png");     ball.setFilter(Texture.TextureFilter.Nearest, Texture.TextureFilter.Nearest);      spike1 = new Texture("spike1.png");     spike1.setFilter(Texture.TextureFilter.Nearest, Texture.TextureFilter.Nearest);     spike2 = new Texture("spike2.png");  }  @Override public void render () {      batch.begin();     float scaleFactor = 2.0f;     batch.draw(background, 0, 0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());     batch.draw(ball, 80, 145, ball.getWidth() * scaleFactor, ball.getHeight() * scaleFactor);     batch.end();  Gdx.input.setInputProcessor(new InputAdapter () {         @Override            public boolean keyDown (int keycode) {             if(keycode==Keys.UP)             {                ball.setHeight(ball.getHeight()+50);             }             return true;      }   @Override public void dispose () {  }   }


When I hear linux I always hear UNIX, Solaris and GNU and frankly I don't understand any word of this only Linux, so could some one explain to me what is each one?

What is Unix, Linux, Ubuntu?  Are they the same thing or different versions or completely different stuff?  This has always made me confused, any explanation would be great.


This is a binary model that my colleagues and I developed that regards a connection between the distance (dependent variable) and overall satisfaction with public transport (covariate). I don't know how to interpret the results shown below.

I'm quite new on this with binomial data tests, but needed to do one and now I´m not sure how to interpret the outcome. The y-variable, the response variable, is binomial and the explanatory factors are continuous. This is what I got when summarizing the outcome:  glm(formula = leaves.presence ~ Area, family = binomial, data = n)  Deviance Residuals:  Min      1Q  Median      3Q     Max   -1.213  -1.044  -1.023   1.312   1.344    Coefficients:                         Estimate Std. Error z value Pr(>|z|)  (Intercept)           -0.3877697  0.0282178 -13.742  < 2e-16 *** leaves.presence        0.0008166  0.0002472   3.303 0.000956 *** --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1  (Dispersion parameter for binomial family taken to be 1)  Null deviance: 16662  on 12237  degrees of freedom Residual deviance: 16651  on 12236  degrees of freedom (314 observations deleted due to missingness) AIC: 16655 Number of Fisher Scoring iterations: 4   There's a number of things I don't get here, what does this really say:                          Estimate Std. Error z value Pr(>|z|)  (Intercept)           -0.3877697  0.0282178 -13.742  < 2e-16 *** leaves.presence        0.0008166  0.0002472   3.303 0.000956 ***   And what does AIC and Number of Fisher Scoring iterations mean?  > fit Call:  glm(formula = Lövförekomst ~ Areal, family = binomial, data = n)  Coefficients: (Intercept)        Areal   -0.3877697    0.0008166    Degrees of Freedom: 12237 Total (i.e. Null);  12236 Residual (314 observations deleted due to missingness) Null Deviance:      16660  Residual Deviance: 16650        AIC: 16650   And here what does this mean:  Coefficients: (Intercept)        Areal   -0.3877697    0.0008166


I am planning a trip to the UK with my wife and wanted some guidance on the same. We hold Indian passports and are currently residing in Singapore.  I have an EP (Employment Pass) and my wife is on a dependent pass. Currently my wife has no source of income and hence she does not have a bank account in Singapore, my bank account does not have her name as the joint applicant.  My questions are   How do I mention in the form that I will be paying for her travel too? Also is it ok to submit my bank statements having my name for her application? For my application, I am giving an HR letter stating my position current salary and period of leave, anything similar to be submitted for her case?

I am an Indian citizen residing in the United States. My wife and I are planning to travel to the UK for a week. We plan to apply for the UK standard visitor visa from the US. I was filling out the application and I have a few questions.   Travel History - The application asks for travel history to the United States, Canada, Australia and New Zealand. Considering that we're resident aliens in the United States, should we consider all the times we've traveled back to the US from India? Travel History - Should we also list out the times we've traveled to India from the US? Cost of the trip - Hypothetically if we plan to spend a total of ~4,000 USD on this trip, should I split up the cost and write down 2,000 USD on my application and 2,000 USD on my wife's application? Income - From what I've read on the forum, my wife must say that "someone else" i.e. me - is paying for her costs and mention my GWF number in the remarks on her application. Would that be sufficient considering that I'll be sending all income documents with my application? Savings - We have joint savings accounts. Should I mention the same amount on both our applications? Posting the documents - Is the up-to-date advice to send all documents in one packet? Or would sending them in separate packets at the same time be better? My thought was to annotate my wife's packet with my GWF number if we were to send them separately. Bank statements - We get e-statements. Would printing those out be enough?


I have been trying to fill my ultracombo box with data yet it takes a signifigant amount of time. However when I run the same stored procedure from withing sql server it takes relatively no time. The line of code that the program gets hung up on is:  SprocPatientsTableAdapter.Fill(Me.PatientsDataSet.sprocPatients, SelectedCustomerID)   By signifigant differnce of time I mean the difference of less than 5 seconds in sql server and more than three hours from within the program.

Why would a stored procedure that returns a table with 9 columns, 89 rows using this code take 60 seconds to execute (.NET 1.1) when it takes < 1 second to run in SQL Server Management Studio?  It's being run on the local machine so little/no network latency, fast dev machine  Dim command As SqlCommand = New SqlCommand(procName, CreateConnection()) command.CommandType = CommandType.StoredProcedure command.CommandTimeout = _commandTimeOut Try    Dim adapter As new SqlDataAdapter(command)    Dim i as Integer    For i=0 to parameters.Length-1       command.Parameters.Add(parameters(i))    Next    adapter.Fill(tableToFill)    adapter.Dispose() Finally    command.Dispose() End Try   my paramter array is typed (for this SQL it's only a single parameter)  parameters(0) = New SqlParameter("@UserID", SqlDbType.BigInt, 0, ParameterDirection.Input, True, 19, 0, "", DataRowVersion.Current, userID)   The Stored procedure is only a select statement like so:  ALTER PROC [dbo].[web_GetMyStuffFool]    (@UserID BIGINT) AS SELECT Col1, Col2, Col3, Col3, Col3, Col3, Col3, Col3, Col3 FROM [Table]


import java.util.*; public class lab3 {     public static void main(String args[])     {          Scanner input= new Scanner (System.in);          System.out.println("Enter the height (feet;");          double height;          height= input.nextDouble();          double width;          width= input.nextDouble();          double area;          final double GALLONS_PER_SQUARE_FEET=150.0;          double gallons;          gallons = area/GALLONS_PER_SQUARE_FEET;          System.out.println("The amount of paint is " + gallons + " gallons.");      }//end main }//end class      lab3.java:19: error: variable area might not have been initialized   gallons = area /GALLONS_PER_SQUARE_FEET;

Was there any reason why the designers of Java felt that local variables should not be given a default value? Seriously, if instance variables can be given a default value, then why can't we do the same for local variables?  And it also leads to problems as explained in :     Well this rule is most frustrating when trying to close a resource in a finally block. If I instantiate the resource inside a try, but try to close it within the finally, I get this error. If I move the instantiation outside the try, I get another error stating that a it must be within a try.      Very frustrating.


Below is a position from a match between O'Sullivan and Hendry. Hendry has just nudged the cue ball into the pack of reds.    Obviously O'Sullivan could just do the same thing, hitting the cue ball into the pack very softly so it just barely touches one of the reds. Then both of them could just do that forever. Is there a rule that prevents this behavior?  Note that in straight pool there are specific rules to prevent this from happening, but in snooker, no such rule seems to exist.

In straight pool there is a rule to prevent nursing, which means nudging a ball to the rail as a safety. Without this rule players could spend hours just playing one safety after another nursing balls along the rail.  In snooker, however, there is no such rule, and, in fact, a player does not even need to hit a rail, so players could safety just by nudging balls a quarter of an inch on each hit, although I do not seem to see them do this. Is there any reason why snooker players cannot nurse balls?


The title pretty much says it all: is an AR(p) process with roots inside the unit circle non-stationary?

According to Theorem 8.8 in Time Series A.W. van der Vaart an ARMA process $$\phi (L)X_t=\theta(L)\epsilon_t$$ has a  unique stationary solution $X_t=\psi(L)\epsilon_t$ with $\psi=\theta/\phi$ if $\phi$ has no roots on the complex unit circle. This would imply that the explosive process, with $\rho>1$, is a stationary process $$X_t=\rho X_{t-1}+\epsilon_t$$ with stationary solution $X_t=\sum_{i=1}^\infty \rho^{-i}\epsilon_{t+i}$.  Now indeed $\sum_{i=1}^{\infty} \rho^{-i} < \infty$ so that weak stationarity can be proved by using this representation.   However, here on stackexchange I see a lot of question/answers that suggest that the process above is not stationary (see for example , ). In particular, the accepted answer of the latter question claims that the process is non-stationary by simulating a series and showing it displays explosive trending behaviour.  I think the only way to reconcile the theorem I mention above and the plots in the accepted answer of () is the following: the explosive process is indeed stationary but non-ergodic, that is, we cannot find the statistical properties of $X_t$ such as $\mathbb{E}(X_t)=\mu$ by observing a single infinitely long sample path of the explosive process, mathematically: $$\lim_{t \to \infty}\frac{1}{t}\sum_{t=1}X_t \neq\mathbb{E}X_t$$  Is this reading correct?


Here is the code for which I am trying to understand the output.  class A     {     public:          A();         ~A(){ cout<<"Destructor Called from A"<<endl;}         A(int x):Z(x){ cout<<"Constructor Called from A"<<endl; };      private:         int Z;     };      class B:public A     {     public:          B();         ~B(){ cout<<"Destructor Called from B"<<endl;}         B(int x):A(x),Y(x){ cout<<"Constructor Called from B"<<endl; };      private:         int Y;     };      int main() {          A *a = new B(10);                 delete a;          return 0;     }   For which I get the output as   Constructor Called from A Constructor Called from B Destructor Called from A   My question is, what happened to destructor for class B? Is object slicing playing its part here?

I have a solid understanding of most OOP theory but the one thing that confuses me a lot is virtual destructors. I thought that the destructor always gets called no matter what and for every object in the chain. When are you meant to make them virtual and why?


hello I want to ask something when we create new Xcode project then I forgot to enable button Create git repository on my mac then how to enable this and how to add my code on SVN....for git is use ?

I read the Git manual, FAQ, Git - SVN crash course, etc. and they all explain this and that, but nowhere can you find a simple instruction like:  SVN repository in: svn://myserver/path/to/svn/repos  Git repository in: git://myserver/path/to/git/repos  git-do-the-magic-svn-import-with-history \ svn://myserver/path/to/svn/repos \ git://myserver/path/to/git/repos   I don't expect it to be that simple, and I don't expect it to be a single command. But I do expect it not to try to explain anything - just to say what steps to take given this example.


I'm using a maximum likelihood estimation and I'm using the optim() function in R in a similar way as follows:  optim(c(phi,phi2, lambda), objf, method = "L-BFGS-B", lower = c(-1.5, -1.5, 0), upper = c(1.5, 1.5, 1), model = model_gaussian)  where objf is the function to estimate parameters given as:   objf <- function(pars, model, estimate = TRUE) {  model$T[is.na(model$T)] <- pars[c(1,2,3)]    if (estimate) { -logLik(model) } else { model } }   (The model$T given above is for the KFAS package)  Now, I would like to obtain the standard errors (in order to calculate t-stats) for the parameters I am estimating. However, apparently since this optimisation is a constrained maximum likelihood estimation (due to the "L-BFGS-B") I cannot use the Hessian matrix to obtain standard errors since it would not be mathematically correct, so this means I can't just add hessian=TRUE to the optim line.  For example, if I were using the BFGS(which is not restricted/constrained) rather than the L-BFGS-B method, to find standard errors is pretty simple:  opt <- optim(c(phi,phi2, lambda), objf, method = "L-BFGS-B", lower = c(-1.5, -1.5, 0), upper = c(1.5, 1.5, 1), model = model_gaussian, hessian = TRUE) standarderrors <- sqrt(abs(diag(solve(-opt$hessian))))   For this reason I thought I'd ask: what's the best way to obtain standard errors for my problem? What is the appropriate method to going about doing it? Thanks in advance.

I try to reproduce with optim the results from a simple linear regression fitted with glm or even nls R functions. The parameters estimates are the same but the residual variance estimate and the standard errors of the other parameters are not the same particularly when the sample size is low. I suppose that this is due differences in the way the residual standard error is calculated between Maximum Likelihood and Least square approaches (dividing by n or by n-k+1 see bellow in the example). I understand from my readings on the web that optimization is not a simple task but I was wondering if it would be possible to reproduce in a simple way the standard error estimates from glm while using optim.   Simulate a small dataset  set.seed(1) n = 4 # very small sample size ! b0 <- 5 b1 <- 2 sigma <- 5 x <- runif(n, 1, 100) y =  b0 + b1*x + rnorm(n, 0, sigma)    Estimate with optim  negLL <- function(beta, y, x) {     b0 <- beta[1]     b1 <- beta[2]     sigma <- beta[3]     yhat <- b0 + b1*x     likelihood <- dnorm(y, yhat, sigma)     return(-sum(log(likelihood))) }  res <- optim(starting.values, negLL, y = y, x = x, hessian=TRUE) estimates <- res$par     # Parameters estimates se <- sqrt(diag(solve(res$hessian))) # Standard errors of the estimates cbind(estimates,se)       > cbind(estimates,se)       estimates         se b0     9.016513 5.70999880 b1     1.931119 0.09731153 sigma  4.717216 1.66753138   Comparison with glm and nls  > m <- glm(y ~ x) > summary(m)$coefficients             Estimate Std. Error   t value    Pr(>|t|) (Intercept) 9.016113  8.0759837  1.116411 0.380380963 x           1.931130  0.1376334 14.030973 0.005041162 > sqrt(summary(m)$dispersion) # residuals standard error [1] 6.671833 >  > summary(nls( y ~ b0 + b1*x, start=list(b0 = 5, b1= 2)))  Formula: y ~ b0 + b1 * x  Parameters:    Estimate Std. Error t value Pr(>|t|)    b0   9.0161     8.0760   1.116  0.38038    b1   1.9311     0.1376  14.031  0.00504 ** --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1  Residual standard error: 6.672 on 2 degrees of freedom   I can reproduce the different residual standard error estimates like this :   > # optim / Maximum Likelihood estimate > sqrt(sum(resid(m)^2)/n) [1] 4.717698 >  > # Least squares estimate (glm and nls estimates) > k <- 3 # number of parameters > sqrt(sum(resid(m)^2)/(n-k+1)) [1] 6.671833


How can I add all the texters that should be on the obj soldier model? When I want to add texture, my whole model stands out. Because of this, I can add only one texture. So, I threw a photo on where there are a lot of textures, how to add them?  I can’t find the answer, I’ve been suffering for several days.  /LGhYb.jpg

I created some texture maps in MindTex to use in Blender, but I can't figure out how to properly hook them up. The maps I have:  - Diffuse  - Normal  - Height   - Specular   - Gloss   - Self Illumination  - Reflection  - Ambient Occlusion   MindTex (left) vs. Blender (right)  As you can clearly see it's a pretty big difference.  is my material node setup in Blender. In the examples I don't actually use self illumination or reflection images, but including this in the answer would be helpful.