Perhaps a question that is too naive to be on Physics.SE but I let the experts here decide (and downvote at will), but there seem to a certain company that claims to have created what it calls a "magnetic generator" where, if the machine is powered externally long enough (which is in seconds or minutes) allowing an electro-magnetic contraption to reach a certain RPM, it can start producing enough electricity to keep turning the contraption, without the aid of the external power while generating surplus electricity. This sounds like perpetual motion machine, yet a bit "snake oilish". The website of this company is done very professionally, they have some slick youtube vidoes -- but scamsters can and do pull impressive illusions off. Is there plausible physics behind this setup ?  Please note that I have no interest in the company or the product, but quite interested to know if there is some real physics behind it.  Here's a  that describes the product.

I know that a perpetual motion machine (a device that produces work without an energy source) would violate several physical laws, the first that comes to mind being the . I also understand that a claim that perpetual motion is possible would probably not be congruent with the scientific method, occum's razor, etc.  What I am interested in is whether there exists some logical and intuitively meaningful (to they lay person) demonstration that perpetual motion is universally impossible, based only on axioms rooted in observable physical phenomena, rather than the obvious reasons why it is merely improbable and incompatible with some of our physical laws.  Certain violations of physical laws, such as travelling faster than the speed of light, can be shown to be unlikely as they would cause paradoxes or logical impossibilities, such as a . In that instance, the axioms needed to establish a paradox (time dilation) are empirically observable, and a counter-claim would require the existence of new paradox-resolving laws that are not established, or the permission of paradoxes which is difficult to imagine.  Conversely, the idea that some invention is impossible on the basis of its violation of a physical law alone is difficult because it requires a .  So, without relying on the assertion that a physical law is omnipresent (e.g. conservation of energy), is there some impossibility or logical paradox that would arise from the existence of a machine that could produce work without indefinitely without an energy source?  Finally, I'm very aware that perpetual motion is a bit of a dirty word and will likely touch a nerve with people, so please take the time to let me know how I can make this question less offensive and avoid the inevitable down-votes.


I opened the terminal and did everything right, but accidentally exited out of the process while it was asking for the license and agreements.  Now, whenever I try to redo the process, it isn't able to get lock /var/lib/dpkg/lock open.

I get this error when trying to use apt-get:  E: Could not get lock /var/lib/dpkg/lock - open (11 Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?     How can I fix this?


Lets say there are two isolated sources of positive charges $q_1$ and $q_2$ $(q_1>q_2)$ located sufficiently far apart. If the two are connected to the two plates of a capacitor, then what is the resulting charge distribution across each capacitor plate?

I am confused as to whether/how capacitance changes when each plate has a different charge.  For example, consider a coaxial cable and put $20Q$ on the outer cable, and $-Q$ on the inner. Or how about concentric spheres, grounding either the inner or the outer?


What kinds of things should I look for when seeking to purchase a legacy domain (i.e. a domain previously owned and operated)?

I want to purchase a few expired domains, who have some backlinks, but some of those sites have PR of -1 with backlinks which are pretty bad.  But what exactly do I need to look for when looking for an expired domain (and I don't want to pay up the nose for a PR3+ domain).


What are some good books for learning/mastering duration analysis at an intermediate/advanced level? Would be interested in both modern suggestions as well as classics.

I am looking for a good book/tutorial to learn about survival analysis. I am also interested in references on doing survival analysis in R.


I am - unfortunately - one of the persons, for whom subpixel rendering is a visual burden instead of a help. So I am trying to disable it completely in Windows 8.1, but it still pops up a lot of places.  I have disabled ClearType in the Display control panel, which is respected by some applications. But Windows still use subpixel rendering in e.g. the control panel and other places.  Is there any way to disable it for all text-rendering?

I just got new PC and upgraded from XP to Windows 8 (yeah I skipped Vista and Win7) and now I have a problem with all this font rendering with smoothing-antialiasing-ClearType crapola. It is hard to read smaller fonts and to work as a web designer/css/html and etc., it's simply impossible, small fonts are totally unreadable and it hurts my eyes.  How do I make it render fonts in sharp pixels without any antialiasing/smoothing effects on Windows 8? Just like in good old XP?  I found that ClearType settings in Control Panel and disable it, but it wrecks the fonts totally and makes it even worse.  So I also Google'd a lot and found out some registry hacks and etc, it kinda fixed the problem, all fonts sharp and no antialiasing and etc. But now there's another problem. Firefox is not rendering the web fonts/Google fonts/the ones that comes in smooth/antialiasing by default.  So how do I keep antialiasing web fonts support on Firefox and how I keep sharp non-cleartype fonts on Windows 8 system/folder/tabs/windows at the same time?  This is serious, I cannot work on my projects with crazy issues like this.  There's what I am talking about (the one I need is 'GOOD'):


If a laptop is on the overhead bin and some moderate/strong turbulence occurs, it is possible that the laptop "jumps" several centimeters.  How to protect the laptop from this?

I flew a long range flight carrying my laptop, a quite heavy one, inside a neoprene briefcase in the passenger cabin. The recommendation by the aircrew was to place it in the overhead compartment or under the seat in front of me. However, during take-off and landing, the vibrations on the plane are quite strong and, as a result, it received minor damage.   Placing them in the overhead compartment might be equivalent to placing it on the floor under the seat, with the added issue of additional luggage in the compartment shifting.  I considered the alternative of holding the laptop by the handle while sitting, so it won't be any contact with the aircraft's floor. This is impracticable during cruise, but I thought it could be better during the take-off and landing segments. Another option I considered is to wrap it with completely with bubble wrap before boarding the plane.   Which is the safest way to transport a laptop during flight?


$f(x)$ is a real function continuously differentiable on $[0,1]$. $f(0) = f(1) = 0$  Prove that  $$ \left(\int_0^1 f(x)\mathrm{dx}\right)^2 \leq \frac {1} {12} \int_0^1 (f'(x))^2 \mathrm{dx} $$

Let $f\in C^{1}[0,1]$ such that $f(0)=f(1)=0$. Show that   $$\left(\int_{0}^{1}f(x)dx\right)^2\le\dfrac{1}{12}\int_{0}^{1}|f'(x)|^2dx.$$   I think we must use Cauchy-Schwarz inequality  $$\int_{0}^{1}|f'(x)|^2dx\ge \left(\int_{0}^{1}f(x)dx\right)^2$$ but this maybe is not useful to problem.  The coefficient $\dfrac{1}{12}$ is strange. How find it ?


I'm trying to determine what is the highest monitor resolution that will be supported by a computer.  System   Win XP-era Compaq Presario SR1750NX that contains  Radeon Xpress 200 integrated graphics on an AMD Athlon 64 based motherboard.    The Radeon Xpress 200 uses shared video memory (UMA).  The computer has 3 GB RAM.  (I'm not familiar with how UMA works and whether the video can access as much memory as it needs, or how much that would be.)  It is currently running Linux Mint 17.0.  I understand that AMD has a Linux version of Catalyst.  However, the Xpress 200 probably pre-dates ATI's acquisition by AMD, and the appearance of the UI looks generic, so the driver is probably FOSS, and possibly required some reverse-engineering. The only built-in video connector is VGA.  A VGA connector has no limit on resolution, but I understand the output quality at higher resolutions depends on the DAC and other factors.     Xpress 200 Info  The only thing I've seen that deals with maximum supported VGA resolution of the video chipset, itself, is the link posted by Daniel B in a comment, below.  The "for Intel architecture" version of the Xpress 200 is spec'ed to support up to 2048x1536 (apparently a common spec based on a 400MHz DAC).  Assuming the specs are the same in the "for AMD architecture" version, that would appear to be an upper limit.  It isn't clear whether other factors would limit it below that (e.g., maximum memory it can use).   Usage  I don't think this affects anything, but just in case, the intended use is a lot of screen real estate for static content (large spreadsheets, lots of browser tabs, and the like), I'm not trying to view hi-res video or do 3D rendering.    Info From The System  Some years ago, I upgraded the monitor to 1600x900, just guessing that it would be supported.  The available resolution settings under monitor preferences lists 1400x1050 as the only higher resolution, which is virtually the same total pixel count as the current monitor.  However, I don't know if this reflects system assumptions based on the current monitor or the actual system limitation (or perhaps the limit of the Linux driver).  The Linux driver does not have an explicit "list all" option.  Update   I checked with AMD and HP to see if they had any useful specs.  Answer: No. I used the xrandr command to see what it might show, which produced this (followed by available settings for the current monitor):  Screen 0: minimum 320 x 200, current 1600 x 900, maximum 4096 x 4096 VGA-0 connected 1600x900+0+0 (yada yada...)  The 4096 x 4096 maximum refers to the virtual screen size (maximum framebuffer), rather than a (useful) resolution possible from the VGA port.  Would that imply at least that the chipset limit is not further limited by memory (one variable eliminated)?   What I'm Looking For In An Answer  I'd like to get a higher resolution monitor, but don't know how to determine what the limit supported by the system would be, or what factor is the limitation.     An answer for this particular computer would be great.  If that can't be answered without available specs, somebody actually using a higher resolution monitor on a similar system would be good evidence. In a more general sense, how do I go about determining the limit for a given system?  Is it just the chipset limit (in which case, I probably have an answer, already), or can that be further limited by other factors (memory, drivers, etc.)?  If there can be further limits, can those be determined in a practical way, or does it basically come down to just locating specs?

I'm in the process of replacing two home laptops that have gotten weary with age, with rather simple/cheap desktop computers. Both laptops were unique that they were used in combination with external monitors, which was a a rather nice setup, and they (graphics cards and the external monitors) supported 1920x1280 resoution.  While browsing through ads, I noticed that it is more and more difficult to find out the maximum resolution a certain graphics card (or worse, graphics card integrated on a motherboard) supports.  Is there a place, or a way (something, anything ...) where one could go to easily find this out?


Seem's to be something weird going on in chat??  I actually have 5K. Am I missing something or is this a bug?

(and everyone else's) is slightly misleading. Underneath my main account, it shows my Physics.SE badges and my total network rep. To me, it looks as if I have 13k rep on Phy.SE (w00t!)--which I don't.  Anyone think that it should be slightly clearer which is which?


Its the wavelength of the reflected light that gives us the perception of color? But how is this possible while we know also that electrons emit the absorbed photons? so we get 1 color from the emitted and 1 color from the reflected light?

I understand that light (color) is part of the electromagnetic spectrum, and that it depends on what wavelengths are reflected/absorbed. Though what property of an individual atom gives it its color? Do electrons, neutrons, and other subatomic particles have color?  Basically: What intrinsic property causes the differences between how the varying wavelengths of light are reflected at the atomic scale? Also, how do photons factor into this?


Let $(V,\langle \cdot , \cdot\rangle)$ inner product space on $\mathbb{C}$ and let $T:V \rightarrow V$ prof or disproof. if $\forall v \in V$ $\langle T(v),v\rangle$  $ = 0$ than $T=0$.  I had found very easily counterexample for the case $F= \mathbb{R}$ by defending symmetric matrix that defines the inner product and the same matrix don't work on the complex filed than I thinking that it may be true.  the example for $F= \mathbb {R}$ :  $T(x,y) = (y,y) $ and $A = \begin{pmatrix} 1 & -1 \\ -1 & 1 \end{pmatrix}$  $\langle u,v \rangle = u^T A v$

How do I prove this statement: Let $V$ be an unitary vector space over $\Bbb C$, $(,)$ be an inner product on $V$ and $\Bbb A$ operator $V\rightarrow V$. Then $(\Bbb Av,v)=0$ if and only if $\Bbb A=0$.  I know that on $\Bbb R$ this does not apply, since we are searching for an operator that assigns to my vector a vector that is orthogonal and so every orthogonal projection on a subspace of $\Bbb R$ can be this operator. But how is this possible on $\Bbb C$? Thank you.


I've tried to make a Villager trade Some stuff for a villager spawn egg, but I end up getting a blank spawn egg... I'm playing on 1.10, and I don't know if it's a bug or something they've changed. I should also mention that I use a generator, Link . Here is the code I used:  The trade I mentioned is at the bottom  /summon Villager ~1 ~ ~ {     Profession: 2,     CustomName: "Frank",     CustomNameVisible: 1,     Career: 1,     CareerLevel: 42,     CanPickUpLoot: 0,     PersistenceRequired: 1,     Invulnerable: 1,     Attributes: [         {             Name: "generic.maxHealth",             Base: 99999         }     ],     Offers: {         Recipes: [             {                  buy: {                      id: "rotten_flesh",                      Count: 1                  },                  buyB: {                      id: "coal",                      Count: 1                  },                  maxUses: 9999999,                  sell: {                      id: "leather",                      Count: 1                  },                  rewardExp: false             },             {                 buy: {                     id: "gunpowder",                     Count: 2                 },                 buyB: {                     id: "coal",                     Count: 2                 },                 maxUses: 9999999,                 sell: {                     id: "golden_apple",                     Count: 1                 },                 rewardExp: false             },             {                 buy: {                     id: "gunpowder",                     Count: 2                 },                 buyB: {                     id: "coal",                     Count: 3,                     Damage: 1                 },                 maxUses: 9999999,                 sell: {                     id: "golden_apple",                     Count: 1                 },                 rewardExp: false             },             {                 buy: {                     id: "rotten_flesh",                     Count: 1                 },                 buyB: {                     id: "coal",                     Count: 1,                     Damage: 1                 },                 maxUses: 9999999,                 sell: {                     id: "golden_apple",                     Count: 1                 },                 rewardExp: false             },             {                 buy: {                     id: "rotten_flesh",                     Count: 64                 },                 buyB: {                     id: "bone",                     Count: 32                 },                 maxUses: 9999999,                 sell: {                     id: "spawn_egg {EntityTag:{id:Villager}}",                     Count: 1,                 },                 rewardExp: false             }         ]     } }   How do I make a villager trade a spawn egg?

I am trying to make a Custom Trade on a villager. I need to make him buy 8 gold nuggets and sell a Cow Spawn Egg.  basically you pay 8 nuggets for a Cow Spawner.  The ID of the Cow Spawn Egg is 92 but I don't know where to put it in the command /summon Villager ~ ~2 ~ {Invulnerable:1,CustomName:Spawner_Vendor,Profession:2,Career:1,Offers:{Recipes:[{buy:{id:gold_nugget,Count:8},sell:{id:spawn_egg,Count:1}}]}}


i built a code in Frame class and call another class frame named search which contains bottun. and i try to add this button action :             s=new Search();            s.button_1.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent arg) {              String a =s.text_1.getText();             JOptionPane.showMessageDialog(new JFrame() ,a);...   I try to run this but it says   Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException..

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?


My great grandmother immigrated to the US from Romania around 1900.  She identified her nationality as German in all the census she answered.    I am assuming she came from Sibiu but I don't know for sure.  Her name was Kathrine (or Catherine) Davit.    I don't know where to start looking for her family.

I have just married my husband, who is Romanian, and I want to add his family to my family tree.  However, we do not know where to start because we cannot find a website that helps.   His father is from Sibiu, Gușterița and it is his fathers side we are looking for.  If anyone can help please give me an idea as to where to start our search?


I am travelling to Europe on August 5th. Itinerary is: Arrival in Barcelona, 3 days there, 3 days in Paris, 4 in Amsterdam and 4 in Belgium and then back. I am from India and have never travelled outside of India. I applied for schengen at Netherlands and got a reject. The reason is:     "The Purpose and circumstance of the intended stay are insufficiently demonstrated.  Sufficient justification for the purpose and   circumstances of the intended stay was not provided."   I provided the following documents:   Accommodation for all four countries, To and from flight confirmed tickets Leave letter from employer Bank account statements and sufficient account balance Insurance  Internal travel tickets(train) Cover letter stating that I am visiting for tourism    I am unable to understand what is missing in the documents and why the visa was rejected.   Which of the below options is my best bet to get the visa:   Apply again to Netherlands with a more detailed cover letter(do not know what else I can change), but Netherlands takes more time to process and I am short of time. Change my itinerary and spend 6-7 days in France instead and apply to the French embassy (which is faster, usually)   Please let me know if there are any suggestions/inputs.

Schengen refusal formulae can be difficult to understand sometimes.    When an applicant receives a refusal with "Justification for the purpose and conditions of the intended stay was not provided", what does it mean?


Where can I find Free software to convert windows 7 to 32 bits ?  Thanks  Paulus

Possible Duplicate:          Tired of the unstable Win 7 64bit I got when I purchased my laptop (it was impossible to find a powerful laptop with Win 7 32 bits).  Can I legally downgrade from Win 7 64 bits to Win 7 32 bits? The key/activation will work?    Details: Everybody comments about the stability of Win 64.  Well, I made a mistake. Is not that Win 64 is unstable (it never crashed). It just works very poor. It feels choppy. Compiling a large program (on an old AMD desktop PC) takes 1.5 seconds on Win 32. The same program compiles on Win 64 in 4-5 seconds in this new and "powerful" laptop. All programs are less responsive.


I just installed MinGW and Eclipse and tried to program a very simple Demo, I jst used the Project for Building an executable and added two files for a Class. It acturally generates two objects, text.o(the function with main) and the MyClass.o. But I get the Error, there seems something wrong with the linking I guess:  12:23:24 **** Incremental Build of configuration Debug for project test **** Info: Internal Builder is used for build  g++ -O0 -g3 -Wall -c -fmessage-length=0 -o "src\MyClass.o" "..\src\MyClass.cpp"   g++ -O0 -g3 -Wall -c -fmessage-length=0 -o "src\test.o" "..\src\test.cpp"   g++ -o test.exe "src\test.o" "src\MyClass.o"   src\MyClass.o:MyClass.cpp:(.rdata$.refptr._ZN7myClass13myInternalVarE[.refptr._ZN7myClass13myInternalVarE]+0x0): undefined reference to `myClass::myInternalVar'  collect2.exe: error: ld returned 1 exit status  MyClass Headerfile:  #ifndef MYCLASS_HPP_ #define MYCLASS_HPP_  class myClass{  private:    static int myInternalVar;  protected:  public:    myClass();    myClass(int initVal);    ~myClass();    void set(int value);    int get();  };  #endif /* MYCLASS_HPP_ */   MyClass Sourcefile:  #include "MyClass.hpp"     myClass::myClass()   {    }    myClass::myClass(int initVal)   {    }    myClass::~myClass()   {    }    void myClass::set(int value)   {     myClass::myInternalVar = value;   }    int myClass::get()   {     return myClass::myInternalVar;   }   Test Source:  using namespace std; #include <iostream> #include "MyClass.hpp"   int main() {     myClass* myClass_object = new myClass( 33 );   int i = 0;   cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!!    i = myClass_object->get();    cout << "Value is: " << i << endl;      return 0; }   I tried to find a solution; I don't think it's the Code that's wrong, but the setting within eclipse. Can anyone help, I just started programming with MinGW and eclipse and it's frustrating that such an easy example fails.  Thank you very much,  Sebastian

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


I am trying to get the mean and standard deviation for the following sample means with the given sample frequencies for each mean. So in a histogram, the x-axis will show the mean range and sample frequency in the y-axis. The sample size for all samples is n=5. I see the answer is the sample mean = 49.831 and sd= 11.43. However, I am not sure what should the formula be to calculate it as I do not have the information on population standard deviation.  Range for mean  Sample frequencies 0-10             0 10-20            5 20-30            315 30-40            1606 40-50            3105 50-60            2935 60-70            1500 70-80            324 80-90            21 90-100           0

I have a dataset of sample observations, stored as counts within range bins. e.g.:  min/max  count 40/44    1 45/49    2 50/54    3 55/59    4 70/74    1   Now, finding an estimate of the average from this is pretty straight forward.  Simply use the mean (or median) of each range bin as the observation and the count as a weight and find the weighted average:  $$\bar{x}^* = \frac{1}{\sum_{i=1}^N w_i} \sum_{i=1}^N w_ix_i$$  For my test case, this gives me 53.82.  My question now is, what's the correct method of finding the standard deviation (or variance)?  Through my searching, I've found several answers, but I'm unsure which, if any, is actually appropriate for my dataset.  I was able to find the following formula both  and .  $$s^{2*} = \frac{ \sum_{i=1}^N w_i (x_i - \bar{x}^*)^2 }{ \frac{(M-1)}{M} \sum_{i=1}^N w_i }$$  Which gives a standard deviation of 8.35 for my test case.  However, the Wikipedia article on  gives both the formula:  $$s^{2*} = \frac{ \sum_{i=1}^N w_i}{(\sum_{i=1}^N w_i)^2 - \sum_{i=1}^N w_i^2} \sum_{i=1}^N w_i(x_i-\bar{x}^*)^2$$  and  $$s^{2*} = \frac{1}{(\sum_{i=1}^N w_i) - 1} \sum_{i=1}^N w_i(x_i-\bar{x}^*)^2$$  Which give standard deviations of 8.66 and 7.83, respectively, for my test case.  Update  Thanks to @whuber who suggested looking into Sheppard's Corrections, and your helpful comments related to them.  Unfortunately, I'm having a difficult time understanding the resources I can find about it (and I can't find any good examples).  To recap though, I understand that the following is a biased estimate of variance:  $$s^{2*} = \frac{1}{\sum_{i=1}^N w_i} \sum_{i=1}^N w_i(x_i-\bar{x}^*)^2$$  I also understand that most standard corrections for the bias are for direct random samples of a normal distribution.  Therefore, I see two potential issues for me:   These are binned random samples (which, I'm pretty sure, is where Sheppard's Corrections come in.)  It's unknown whether or not the data is for a normal distribution (thus I'm assuming not, which, I'm pretty sure, invalidates Sheppard's Corrections.)   So, my updated question is; What's the appropriate method for handling the bias imposed by the "simple" weighted standard deviation/variance formula on a non-normal distribution? Most specifically with regards to binned data.  Note: I'm using the following terms:     $s^{2*}$ is the weighted variance   $N$ is the number of observations.  (i.e. the number of bins) $M$ is the number of nonzero weights.  (i.e. the number of bins with counts) $w_i$ are the weights  (i.e. the counts) $x_i$ are the observations.  (i.e. the bin means) $\bar{x}^*$ is the weighted mean.


I was going through different stackexchange sites. It is found that sort options are missing when the user is not logged in. I could only see the sort option 'newest' in all of them. Tried this in chrome and firefox. Even in incognito modes, the links are invisible. There was no luck with the hard refresh on all these browsers.  Also I checked in my virtual box IE(where I have not taken any of the stackoverflow site yet) to check whether it is an issue with my cache or cookies, but the issue is replicated. By editing URL, I could sort the questions, but except 'newest' other links are not there (when not logged in).  Does anyone experience this 'lack of sort options'? Can someone please explain the reason for this unusual behavior?       Here is the latest example from meta.stackexchange.com after logged out.

I think this is platform wide (all SE sites).   Logout Choose a tag, eg.  on SO Try to sort questions by something other than newest   No matter what sorting is chosen, questions are sorted by newest


Im trying to run a select statement to group records having similar IDs but also tally the values from another column for each master ID. So for example below. The result for each line will be the first instance unique ID and the 2 names shown from each record separated by semi colon. Thanks in advance.  Current set  ID                               Name              Cnt -------------------------------- ----------------- --- 0001D72BA5F664BE129B6AB5744E2BE0 Talati, Shilpa    1 0001D72BA5F664BE129B6AB5744E2BE0 Weaver, Larry     1 0007EAB7CE9A3F2F95D2D63D0BBD08A9 St-Hilaire, Edith 1 0007EAB7CE9A3F2F95D2D63D0BBD08A9 Talati, Shilpa    1   Result:  0001D72BA5F664BE129B6AB5744E2BE0 Talati, Shilpa; Weaver, Larry

How do I get:  id       Name       Value 1          A          4 1          B          8 2          C          9   to  id          Column 1          A:4, B:8 2          C:9


My right earpiece is gone. So , I would like to send the sound only to left headphone . Is it possible ??the thing is , some sound is low in one earpiece and high in other , like the base is very low in left but louder in right. But Now I have to make all equal.

Is there an easy way of forcing mono sound output - for one ear, one earphone, one speaker?


I'm new in Linux script and i face some commands and I didn't understand them.   cat <<- _EOF_ command1 command2 command3 _EOF_   Also,  less <<- _EOF command1 command2 command3 _EOF   So, can any one explain them to me ?

What's the difference between <<, <<< and < < in bash?


I have my program using the Poppins font, that Win doesn't have by default, so I installed it and and used it in my project and everything worked fine. However, on another computer that doesn't have this font installed, it replaces it with some different font (Arial or something). How do you handle this problem correctly? Is it by making you program install that font on the user's machine or is there some way to compile the font with the program? Thank you for any advice.

I want to embed fonts in my WinForms application so that I don't have to worry about them being installed on the machine. I've searched a bit on the MSDN site and found a few hints about using native Windows API calls, for instance Michael Caplan's (sp?) tutorial linked to by Scott Hanselman. Now, do I really have to go through all that trouble? Can't I just use the resource part of my app? If not I'll probably go the installing route. In that case, can I do that programmatically? By just copying the font file to the Windows\Fonts folder? I am aware of licensing issues.


I have written the following code and when I try to run it, I get the following warnings:   warning: variable 'money' is uninitialized when used here [-Wuninitialized] GetData (money, product); note: initialize the variable 'money' to silence this warning int product, money, change; warning: variable 'product' is uninitialized when used here [-Wuninitialized] GetData (money, product); note: initialize the variable 'product' to silence this warning int product, money, change; warning: variable 'change' is uninitialized when used here [-Wuninitialized] CalculateChange (money, product, change); note: initialize the variable 'change' to silence this warning int product, money, change;   I have also typed an arrow to the relevant line. I have been trying to figure out how to fix this problem for an hour now. If you could please help, it would be much appreciated.   #include <stdio.h> #include <ctype.h>  void GetData (int money, int product) {   // Asks user how much was the product and how much they paid the cashier. //   printf("\nHow much was the product?\n");   scanf("%d", &product);    if((product < 5) || (product > 95) || (product %5 != 0))    printf("\nInvalid number!\nNumber has to be a multiple of 5 and cannot be less than 5 or    more than 95.\n");    else printf("How much did you give to the cashier? \n");   scanf("%d", &money);    if (money < product)   printf("You did not give enough money to the cashier!");    return; }  void CalculateChange (int money, int product, int change) {   // Calculates the amount of change needed. //   int fifty = 0;   int twenty = 0;   int ten = 0;   int five = 0;    change = (money - product);    fifty += change / 50;   change %= 50;    twenty += change / 20;   change %= 20;    ten += change / 10;   change %= 10;    five += change / 5;   change %= 5;    return; }  void PrintResults (int fifty, int twenty, int ten, int five) {   // Prints the amount of coins needed. //   printf("\nThe number of fifty cents: %d", fifty);   printf("\nThe number of twenty cents: %d", twenty);   printf("\nThe number of ten cents: %d", ten);   printf("\nThe number of five cents: %d", five);  return; }  int main () {   int product, money, change; <------   int fifty = 0;   int twenty = 0;   int ten = 0;   int five = 0;   char response;  do {    GetData (money, product); <-------    CalculateChange (money, product, change);    PrintResults (fifty, twenty, ten, five);    printf("\nWould like to quit the program? Enter y or n\n");   scanf("%c", &response );   response = tolower (response);   printf("--------------------------------------------------------------------------");  } while (response != 'y');   printf("\nQuitting program...\n");    return (0); }

What is the difference between    a parameter passed by reference a parameter passed by value?   Could you give me some examples, please?


How to show that they are equal? All I can come up with is using symmetric polynomials to express them, or using some substitution to simplify this identity since it is symmetric and homogeneous but they are still too complicated for one to work out during the exam. So I think there should exist some better approaches to handle this identity without too much direct computation.  In addition, this identity is supposed to be true:  $$ \frac{x^7+y^7+z^7}{7}=\frac{x^2+y^2+z^2}{2}\times\frac{x^5+y^5+z^5}{5} .$$

I have a question. I tried so to solve it, but there is a problem.  that is i don't have any idea to findout how can i work with degrees 4,5,7 ...  this is the problem :  let $ x , y $ and $ z $ three real numbers such $ x+y+z = 0 $.  prove : $ \Big(\dfrac{x^7+y^7+z^7}{7}\Big)^2=\Big(\dfrac{x^5+y^5+z^5}{5}\Big)^2\cdot\Big(\dfrac{x^4+y^4+z^4}{2}\Big) $  Please think and write your solutions! ; )


How do I find an item in array which has the most occurrences?  [1, 1, 1, 2, 3].mode => 1  ['cat', 'dog', 'snake', 'dog'].mode => dog

I have a sorted array:  [   'FATAL <error title="Request timed out.">',   'FATAL <error title="Request timed out.">',   'FATAL <error title="There is insufficient system memory to run this query.">' ]   I would like to get something like this but it does not have to be a hash:  [   {:error => 'FATAL <error title="Request timed out.">', :count => 2},   {:error => 'FATAL <error title="There is insufficient system memory to run this query.">', :count => 1} ]


I'm new to Linux and I'm having a hard time with a package. I've been trying to run the ''cmake .'' and I can't because I don't have the libevdev package. ~/joycond$ cmake . -- Checking for module 'libevdev'  --   No package 'libevdev' found CMake Error at /snap/cmake/876/share/cmake-3.20/Modules/FindPkgConfig.cmake:556 (message):   A required package was not found Call Stack (most recent call first):   /snap/cmake/876/share/cmake-3.20/Modules/FindPkgConfig.cmake:778 (_pkg_check_modules_internal)   CMakeLists.txt:10 (pkg_check_modules)   -- Configuring incomplete, errors occurred! See also "/home/louis/joycond/CMakeFiles/CMakeOutput.log".  When I try to run sudo apt install libevdev, it is unable to find it. ~$ sudo apt install libevdev Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package libevdev  I saw online that what I needed was libevdev-dev, but... ~$ sudo apt install libevdev-dev Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package libevdev-dev  If anyone could help it would be greatly appreciated since I am now completely lost.

There are now errors when updating and I cannot install most software due to a corrupted  /etc/apt/sources.list   file. Is there a copy I can download to replace it?  The file would be for Ubuntu 12.04 (Final Beta) in the United States.


I have 16h overlay in Montreal and was wondering if I can leave the airport. I am an EU citizen.  Thanks in advance, Malina

I have a Las Vegas to Rome flight booked with Air Canada, which gives me an 11-hour layover in Montreal. My luggage will go directly through to Rome from Las Vegas, so I won't need to get it in Montreal.  I already have my eTA for transit through Canada. Can I leave the airport for a sightseeing tour of Montreal? Will it be okay with Customs & Immigration? I'll carry just a small carry-on backpack with me.


We know from linear algebra, the least square solution of linear equation system : $$Ax=b$$ always exists. That is, the equation  $$A^TAx=A^Tb$$ always has at least one solution. Most of us explain it existence by interpreting least square problem as a matter of orthogonal projection. It's correct, I know. But can we prove this by showing that the rank of matrix $$A^TA$$ is equal to the rank of the augmented matrix:$$[A^TA,A^Tb]$$for any given vector b?   I've worked for hours but failed to show that.  Although there is a similar thread in mathematics.SX, but I personally think there is no good answer presented there. So I address this problem again.  Thanks at first!  [update]  Now I come up with a proof for this proposition:  suppose that rank $A^TA$=k, and the matrix $[A^TA,A^Tb]$ has one more column than $[A^TA]$, so rank $[A^TA,A^Tb]\ge k$. But on the other hand, we have $[A^TA,A^Tb]=A^T[A,b]$, using the rank inequality, we have $rank [A^TA,A^Tb]\le rank A^T$. Since (we can prove that) $ rank A^TA= rank A= rank A^T$ for any given matrix A. So the inequality is actually $rank [A^TA,A^Tb]\le k$. Combining the two inequalities, we have $rank [A^TA,A^Tb]=rank A^TA$. Q.E.D.

Does a least squares solution to $Ax=b$ always exist?


says that usually, we pronounce "the" as "thuh", but when it happens to be in front of a vowel sound, then we pronounce it as "thee".  Why is "the university" pronounced as "thuh" university rather than "thee university"? Isn't "u" a vowel, and shouldn't it therefore be pronounced "thee university"? The page I linked to gives as explanation that "university" is pronounced "youniversity" and this y in there is a consonant sound? But why should y be a consonat sound? For me it's more a vowel sound …

The is sometimes pronounced "tha" (/ðə/) or "thi" (/ðiː/). Which is the correct pronunciation of this word? Are both correct and used interchangeably at specific places? If the second question is correct, please provide the rule of pronouncing at different places.


I plugged Seagate 1 TB external hard disk into my computer and used Diskpart to check the detail information of disk. I can correctly select the USB drive. However, when I type detail disk in Diskpart, I receive an error message: there are no volumes. Why and how to fix this error?   Hint: Hard disk does not show up anywhere except in Device Manager.  Edit: The issue started after I plugged disk into my android phone then back into pc.It does not appear in   or in .Ony it appears in

what exactly happened:  I have a Seagate 1 TB external hard disk.It was working fine till now.The problem started when I plugged it in my android phone and then back in my pc then simply it does not showup anywhere and :  It does not appear in file explorer   It does not appear in disk management   It is not listed in Diskpart command   It only appears in Device Manager under disk drives   It does not appear in BIOS  only makes sound when plugged and unplugged.  disk spins and light is also showing.   . What I already tried:   updated usb drivers.  used new cable also.  plugged in another pc  usb mass storage is also enabled in BIOS  no issue in any usb port  Anything else i can do?


I read a lot about mysql security, and php script security and was just wondering if this would suit to prevent from intrusions. I made script config.php, and register.php witch are stored in folder that is above root folder ( example ../project/script/ and ../project/www/)  register.php looks like this:  <?php  require_once 'db_config.php'; $user=$_GET['username']; $pass=$_GET['password']; $db=$_GET['company'];  try {     $dbh = new PDO("mysql:host=$host", $username, $password);//connecting to        database     //check if database exists     $stmt = $dbh->query("SELECT COUNT(*) FROM INFORMATION_SCHEMA.SCHEMATA   WHERE SCHEMA_NAME = '$db'");     if($stmt->fetchColumn() == 1){     //some code     }else{         $dbh->exec("CREATE DATABASE `$db`;                     CREATE USER '$user'@'localhost' IDENTIFIED BY '$pass';                     GRANT SELECT, INSERT, UPDATE, DELETE, CREATE ON `$db`.* TO '$user'@'localhost';                     FLUSH PRIVILEGES;") or die(print_r($dbh->errorInfo(), true));         echo 'DB created';     }     }  catch (PDOException $e) {     die("DB ERROR: ". $e->getMessage()); } ?>   and test.php looks like this:  <?php include ('../scripts/db_connect.php'); include ('../scripts/register.php'); ?>   My question would be is this good coding practice, will it be secure from someone messing up my database, and what in general do you have to point out to have better looking code in general?? Also any materials on how code should look so other can read it and PHP SQL safety would be appreciated.

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


When I issue  ps aux | grep mtp   I get  ubuntu-+ 15934  0.1  0.0 519848  7068 ?        Sl   21:13   0:00 /usr/lib/gvfs/gvfsd-mtp --spawner :1.9 /org/gtk/gvfs/exec_spaw/20   So the PID in this case is 15934. But every new time this is run the PID is different. Is there any other way to kill a process other than by PID?

I started my Python program in the background using nohup as mentioned below -   nohup zook.py &   Now I am trying to kill this process so I did the ps command as mentioned below  root@phxdbx1145:/home/david/zook# ps ax | grep zook.py 16352 pts/6    S+     0:00 grep --color=auto zook.py   But somehow, everytime its PID getting changed, I don't know why. Whenever I do like this -   kill -9 16352   It always say, No Such Process.  And when I do px command again, I see that PID got changed automatically..  So I am not sure how do I kill this process?  Is there any way I can kill the process with the name somehow?  UPDATE:-  This is what I am getting. I did pkill -9 zook.py and then I did ps command as mentioned below and it is shwoing zook.py constantly?  root@dbx1145:/home/david/zook# pkill -9 zook.py  root@dbx1145:/home/david/zook# ps ax | grep zook.py 23870 pts/6    S+     0:00 grep --color=auto zook.py  root@dbx1145:/home/david/zook# ps ax | grep zook.py 23872 pts/6    S+     0:00 grep --color=auto zook.py  root@dbx1145:/home/david/zook# ps ax | grep zook.py 23874 pts/6    S+     0:00 grep --color=auto zook.py  root@dbx1145:/home/david/zook# ps ax | grep zook.py 23876 pts/6    S+     0:00 grep --color=auto zook.py


The determinant of matrix product follows the following property unlike it's sum. $$     \det (AB) = \det A\det B $$ Why is this true? What's the easiest proof?

Given two square matrices $A$ and $B$, how do you show that $$\det(AB) = \det(A)\det(B)$$ where $\det(\cdot)$ is the determinant of the matrix?


Can anyone tell me where I can download a clean version of Windows 10 Media Creation Tool 1909? The version that I currently downloaded is shown to include a PUA upon scanning the file via MetaDefender.  I am seeing  "BrowserModifier/Toolbar!khSzOxHe / W32.Toolbar.CrossRider.AE.czia.mg" show up as a threat after being scanned.    Thanks.

I need to repair my Windows 10 installation. Where can I get a clean ISO (with install.wim, no Install.ESD, so that I can run DISM against the WIM) of the specific Windows 10 build required for this?  In my case, I need the Anniversary update (Build 14393), Creators Update (Build 15063) or Fall Creators Update (Build 16299.15).


I'm sure this question must have been answered before...  What's the difference between Modal window and a Popup? What to use when? Is there a good article I can read?  Thanks, Roland

I've seen many terms used to describe message boxes that notify and alert users or display information such as modal, popup, popover and lightbox.  What is the difference between these components?  When and for what type of text should each of these components be used?


Have a list with numeric strings, like so:  numbers = ['1.2', '5.6', '1'];   Would like to convert first two list elements to float, and last element to int:  numbers = [1.2, 5.6, 1];   Is there any one liner/elegant way of doing?  currently I'm doing with:   numbers = [ float(x) for x in numbers ] numbers[-1] = int(numbers[-1])   or  functions = [float, float, int] results = [func(arg) for func, arg in zip(functions, numbers)]

In Python, how can I parse a numeric string like "545.2222" to its corresponding float value, 545.2222? Or parse the string "31" to an integer, 31?  I just want to know how to parse a float str to a float, and (separately) an int str to an int.


I looked it up on detexify but apparently it is not an inbuilt symbol

I've seen an equals sign with a small exclamation mark on top being used to say "equals because of data that was given in the problem", for example for a boundary condition or initial value in a differential equation.  A rough picture of what I mean:       ! f(x) = 4   How do I typeset this in LaTeX? I've tried $=^!$ (which doesn't produce the desired result) and looked through the "relations" section of the  without success.


When a power brick is humming is that a bad thing? What does it mean.  Does having it plugged into the wall directly or in a UPS or in a daisy chain of power strips make a difference

I have many different AC adapters and power supplies for a variety of devices, ranging from small 5V/1A USB chargers to laptop power adapters and desktop PSUs. However, I often hear a whining noise from  some of these power supplies. This happens most often when they are not connected to a device or otherwise in use, and stop making noise when I connect a load to it such as by plugging in a device that is not fully charged.  Why do some AC adapters and power supplies make this whining noise? Why do some not make this noise? Is there anything I can do to suppress it?


I'm having problems with the linker.  It gives me the following error:  [Linker error] undefined reference to `bool Polis :: deleteEdifice <Mine> (int) '   The prototype is declared as follows:  template <typename T> bool deleteEdifice(int);   deleteEdifice is empty, that does not do anything for now but it does not work.  The call to the prototype is:  obj->deleteEdifice<Mine>(3);   I also tried to do:  obj->template deleteEdifice<Mine>(3);   Print the following error:  `template' (as a disambiguator) is only allowed within templates   Could you tell me what am I doing wrong.

Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)


If the divergence caused by an act of free will cannot be sustained temporally, then would a material-deterministic universe self-correct? Or am I just changing the frame of reference here to account for free will?   Also, if consciousness directs free will, then is consciousness a derived property above-and-beyond matter which material-determinism can never account for?

If an entity existed such as Laplace's demon, that could know with precision the current state of the universe and - using the laws of physics - could tell you your future with certainty, would you then be able to change it?


I'm completely new into MultiThreading and I'm trying to test code in which there is thread.sleep, long story short it looks like this:  private class DemoRunnable implements Runnable {      private Thread t;      String status;      public void start() {         this.status = "RUN";         if (t == null)             t = new Thread(this);         t.start();     }      public void run() {         int i = 0;         while (i < 8) {             i = i + 1;             try {                 System.out.println("GO  " + i);                 Thread.sleep(300);             } catch (Exception e) {                 e.printStackTrace();             }         }          this.status = "FINISH";         System.out.println("inside " + this.status);     }      String getStatus() {         return this.status;     } }  class DemoTest {      @Test     void test() {          DemoRunnable demo = new DemoRunnable();         demo.start();          while (demo.getStatus() != "FINISH") {          }     } }   Of course it's only the draft - I cut it short to make it more clear, but kept the same concept. At first I tried to test it without the while loop but junit test would finish before the Thread and only one GO would be printed out. After adding the loop everything looks fine GO is printed out correctly and then the status is changed but the test goes on forever :< Like if it was not noticing the status change.   when I remove sleeping then test does notice the change in status and while loop is broken

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?


A point in static fluid has pressure of $\rho$ * g * h, where $\rho$ is the constant density throughout the fluid body, g the gravitational accelaration, and h is the height of the fluid column above that point.  What I can't understand is how this increase in pressure is not accompanied (or caused) by matching increase in density or temperature.  In my understanding, whether it's liquid or gas, pressure basically is the aggregate effect of randomly moving particles exerting force on their surroundings, hence it is connected to the translational kinetic energy of the particles and the frequency of their contact with the surroundings. So it seems any increase in pressure should mean either (1) decrease in volume (or increase in density) or (2) increase in temperature (increased momentum of particles). Apparently this is incorrect as no article on the internet or textbooks I could find suggest this.  What am I getting wrong? How does weight of a fluid column cause pressure rise in microscopic point of view? By making particles faster? Then how come the temperature remains unaffected?

Our class is learning about hydrostatic water pressure and we have been told that we can calculate the force of the liquid on an object at any depth using "the density x 9.8 x the depth". However, as the depth increases, wouldn't the density of the liquid increase because of the weight of the liquid above it compressing it? So should't there be something in the equation to account for the varying density? To me, "density x 9.8 x depth" seems like it is saying that the density will be constant...


I always define $\mathbb{N}$ to include $0$ but some authors don't. Since the elements of $\mathbb{N}$ are used for counting, shouldn't $0\in\mathbb{N}$? $0$ is the number of cows in a classroom for example. Moreover, $0\in\mathbb{N}$ is a consequence of the Peano axioms and in fact the digit $0$ is used in writing integers ($10$,  $205$) so why on earth would anyone define $\mathbb{N}=\{1;2;3;\cdots\}$ in the twentieth and 21th century? Is he a babylonian?

Is there a consensus in the mathematical community, or some accepted authority, to determine whether zero should be classified as a natural number?  It seems as though formerly $0$ was considered in the set of natural numbers, but now it seems more common to see definitions saying that the natural numbers are precisely the positive integers.


"The fact of its being so rare a flower ought to have made it easier to trace the source of this particular specimen, but in practice it was an impossible task."    I just found this sentence reading a book and it sounds weird to me. I understand the meaning, but I've never seen or studied this structure in English before. I did some research on the Internet but I could find nothing. Could anyone  explain the grammar? Could you please provide more examples with the same structure?

The rule says that we can use a possessive adjective or an object pronoun before a gerund. Is there a rule  that says when to use each or are they interchangeable? Some say that it's wrong to use an object pronoun before a gerund.


Consider  I attempted to help on.  The root cause of the problem is unclear, but the code was messy and may have contributed to the issue.  So as a step in resolving the OP's issue, I proposed a different, cleaner way of approaching the problem that I hoped would get him closer to finding a solution.  To me, this seemed more helpful than just leaving a comment saying "there's not enough information to say with confidence what the problem is".  However, I was downvoted by someone with 12k rep and .    Is this really the case?  I'm not worried about the -2 rep, so please don't misunderstand, it's an honest question about what is better for the OP or for the site: attempts to move the OP forward as much as possible or simply terse comments stating "insufficient details".

Is answering beyond the scope of the question a valid thing? Or should we just stick to the question asked and ignore any potential bugs which might be present (of course OP is unaware of that, as of now).  To make myself more clear, please have a look at this .  There are 3 answers which talk about the issue asked and that's it. If you look at my answer, I've added an additional point about a potential bug which the OP has missed now (may find out later). So is it a good thing to point out such potential bugs or not? Should this practice be encouraged?


Let $x$ and $y$ be two non-zero $n\times 1$ vectors. What are the eigenvalues of the $n\times n$ matrix $xy^T$?  I have one more doubt in the same question  here $x$ be a $n\times 1$ matrix so how many eigenvalues it has??  I tried in many ways but I stuck from the starting point also??

Let $x$ and $y$ be two non-zero $n × 1$ vectors. If $y^T$ denotes the transpose of $y$, what are the eigenvalues of the $n × n$ matrix $xy^T$  I have only idea that given matrix has rank $1$.


I have an OpenVPN server in US and a client in Europe. When connected all traffic is routed through VPN tunnel. A problem has been detected - for some HTTPS websites connection fails. I will present 3 cases. First one - it just gets stuck:  $ curl -v 'https://serverfault.com' * Rebuilt URL to: https://serverfault.com/ *   Trying 151.101.129.69... * TCP_NODELAY set * Connected to serverfault.com (151.101.129.69) port 443 (#0) * ALPN, offering h2 * ALPN, offering http/1.1 * successfully set certificate verify locations: *   CAfile: /etc/ssl/certs/ca-certificates.crt   CApath: /etc/ssl/certs * (304) (OUT), TLS handshake, Client hello (1):   The second case - it shows an error:  $ curl -v 'https://www.catan.com/' *   Trying 217.160.0.164... * TCP_NODELAY set * Connected to www.catan.com (217.160.0.164) port 443 (#0) * ALPN, offering h2 * ALPN, offering http/1.1 * successfully set certificate verify locations: *   CAfile: /etc/ssl/certs/ca-certificates.crt   CApath: /etc/ssl/certs * (304) (OUT), TLS handshake, Client hello (1): * (304) (IN), TLS handshake, Server hello (2): * TLSv1.2 (IN), TLS handshake, Certificate (11): * TLSv1.2 (IN), TLS handshake, Server key exchange (12): * TLSv1.2 (IN), TLS handshake, Server finished (14): * TLSv1.2 (OUT), TLS handshake, Client key exchange (16): * TLSv1.2 (OUT), TLS change cipher, Client hello (1): * TLSv1.2 (OUT), TLS handshake, Finished (20): * OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to www.catan.com:443  * stopped the pause stream! * Closing connection 0 curl: (35) OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to www.catan.com:443   And the last case - all good:  $ curl -v 'https://www.duckduckgo.com/' *   Trying 79.125.105.113... * TCP_NODELAY set * Connected to www.duckduckgo.com (79.125.105.113) port 443 (#0) * ALPN, offering h2 * ALPN, offering http/1.1 * successfully set certificate verify locations: *   CAfile: /etc/ssl/certs/ca-certificates.crt   CApath: /etc/ssl/certs * (304) (OUT), TLS handshake, Client hello (1): * (304) (IN), TLS handshake, Server hello (2): * TLSv1.2 (IN), TLS handshake, Certificate (11): * TLSv1.2 (IN), TLS handshake, Server key exchange (12): * TLSv1.2 (IN), TLS handshake, Server finished (14): * TLSv1.2 (OUT), TLS handshake, Client key exchange (16): * TLSv1.2 (OUT), TLS change cipher, Client hello (1): * TLSv1.2 (OUT), TLS handshake, Finished (20): * TLSv1.2 (IN), TLS handshake, Finished (20): * SSL connection using TLSv1.2 / ECDHE-RSA-AES128-GCM-SHA256 * ALPN, server accepted to use h2 * Server certificate: *  subject: C=US; ST=Pennsylvania; L=Paoli; O=Duck Duck Go, Inc.; CN=*.duckduckgo.com *  start date: Aug  9 00:00:00 2019 GMT *  expire date: Oct 30 12:00:00 2020 GMT *  subjectAltName: host "www.duckduckgo.com" matched cert's "*.duckduckgo.com" *  issuer: C=US; O=DigiCert Inc; CN=DigiCert SHA2 Secure Server CA *  SSL certificate verify ok. * Using HTTP2, server supports multi-use * Connection state changed (HTTP/2 confirmed) * Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0 * Using Stream ID: 1 (easy handle 0x5587b19d93f0) > GET / HTTP/2 > Host: www.duckduckgo.com > User-Agent: curl/7.58.0 > Accept: */* >  * Connection state changed (MAX_CONCURRENT_STREAMS updated)! < HTTP/2 301  < server: nginx < date: Sat, 24 Aug 2019 14:12:57 GMT < content-type: text/html < content-length: 178 < location: https://duckduckgo.com/ < strict-transport-security: max-age=31536000 < expires: Sun, 23 Aug 2020 14:12:57 GMT < cache-control: max-age=31536000 <   <title>301 Moved Permanently</title>
301 Moved Permanently

nginx   * Connection #0 to host www.duckduckgo.com left intact   What could be the cause? If additional information is needed please just ask.

I have an openvpn (version 2.1_rc15 at both ends) connection setup between two gentoo boxes using shared keys. it works fine for the most part. I use mysql, http, ftp, scp over the vpn with no problems. But when I ssh from the client to the server over the vpn, weird things happen. I can login, i can execute some commands. But if i try to run an ncurses application like top, or i try to cat a file, the connection will stall and I'll have to sever the ssh session.  I can, for example, execute "echo blah; echo .; echo blah" and it will output the three lines of text over the ssh session fine. But if i execute "cat /etc/motd" the session will freeze the moment I press enter.  I compiled openvpn 2.1.1 on my mac and copied over my config directory from my gentoo client. The mac connected and ssh sessions worked fine without freezing.  I then compiled it on my older gentoo box (2.6.26 kernel) which I am retiring due to a dying hard drive, and ssh over it also works perfectly.  Why does it fail on my brand new gentoo box ? I've tried compiling three different kernels in case it was that, but other than that there should be no difference between my older and my newer gentoo boxes that I can think of.  Any suggestions on what's wrong ?


Everyone knows that there are 4 fundamental forces:   Gravity Electromagnetic Weak Strong   At school and university you're taught that no one has been able to unify these 4 fources. However, not a single person really explains what is it that can't be unified. What happens when you try to unify them? Many have tried and failed. Do you arrive at a contradiction when you join the equations? Like when you reduce left hand side and right hand side you get 1=2 or something similar? What is the general approach to unifying forces?  This is a lot of questions but I'm a very curious person. I'd love if someone with deep knowledge explained this.

It is well known that quantum mechanics and (general) relativity do not fit well. I am wondering whether it is possible to make a list of contradictions or problems between them?  E.g. relativity theory uses a space-time continuum, while quantum theory uses discrete states.  I am not merely looking for a solution or rebuttal of such opposites, more for a survey of the field out of interest.


I have come across a couple lens manufacturers that mention that when a lens is focused such that the center of the FOV is well focused, the extreme ends of the FOV will be slightly defocused.   What is the reason for this? I was of the opinion that lenses are focused for a certain distance and if the entire FOV is filled with a target at that distance, it would be equally well focused all over.  Thank you.     edit: after going through some more I came across the page where they measure resolution of lens. It seems like they focus at the center (which reduces the resolution at the sides since it is in relative defocus). And then they turn back the focus some so that it defocus the center a bit for larger gains in focus at the ends. Is this common practice?     edit: for instance, this is an excerpt from  on Edmund Optics     This also can cause issues depending on whether the system is only focused in the center of the FOV or across the entire FOV; because of the resolution varying based on location, it can be difficult to determine when the entire FOV is in best focus. Some lenses obtain very high resolution in the center of the FOV, but very low resolution in the corners when the lens and camera system is focused on the center of the image. A slight defocusing of the lens can balance the resolution across the field, although usually to the detriment of the center resolution.

The title says it pretty much all. I'm asking this because I find myself always using the focus point in the center, and after I focused, I rotate my camera to make the framing right. However, if lenses do create a plane in which everything is sharp, then the focus will be slightly off after rotating the body.  Doing some maths: if I focus at distance x meters, and rotate my camera for alpha radians, then the focus plane would be off for:  ∆f = x*tan(alpha/2)*tan(alpha)   So, let's plug in: x = 2 meters, alpha = 20 degrees = 0.349 radians, we get: ∆f = 0.128 meters. So this means, my optimal focus point is now almost 13 centimeters away from the original focus point.  If they are not spherical, I will experience my focus being off. So is it safe to use other focus points except for the one at the center and immediately put my framing right? This will slow down the process of taking pictures?


I search solution to pevent my machine form the attack arp poisoning.  I believe to make my device invisible for this haker If they want to ping my machine they have any reply.  I don't khnow how I can use iptable to release it.or if they are a script python to do it to desable ping of devices.  I need help please. thanks.


What is the best way to remove html tags from an html page? I just want to have the actual text, and not the html tags. I store the text in a string without including the html tags. What is the simplest way to do this? An example page is shown below:  <HTML><HEAD> <META NAME="Docdate" CONTENT="05/02/2011"> <META NAME="m_title" CONTENT="TWO SECURITY GUARDS HACKED TO DEATH DURING A FIGHT"> <META NAME="m_author" CONTENT=""> <TITLE>MALAYSIA NEWS -- GENERAL NEWS -- 05/02/2011 -- TWO SECURITY GUARDS HACKED TO DEATH DURING A FIGHT</TITLE> </HEAD><BODY BACKGROUND="#FFFFFF"> <PRE> 05/02/2011  POLICE-FIGHT  TWO SECURITY GUARDS HACKED TO DEATH DURING A FIGHT          KUALA LUMPUR, Feb 5 (Bernama) -- Two security guards were hacked to death in  a fight that broke out at Damansara Perdana construction site last night.       Both men, aged 20 and 26, were found dead at the scene with slash wounds on  their bodies in the 8.20pm incident.       Petaling Jaya OCPD ACP Arjunaidi Mohammed said the fight started following  an argument involving a security guard and several foreign workers at the site.       "One of them had an argument with several of the workers. He then called two  of his friends who are also security guards but working in other areas.       "A group of 12 to 15 foreign workers, carrying sharp weapons, then attacked  them," he told reporters at the scene today.       The other security guard managed to flee to safety, he added.       "The foreign workers had also left the area. We have picked up a security  guard in the area and two Indonesian workers to have their statements taken," he  said, adding that a manhunt was underway for the suspects.       -- BERNAMA       NMR AKT JS      </PRE> <BODY></HTML>

Is there a good way to remove HTML from a Java string? A simple regex like replaceAll("\\<.*?>", "")   will work, but things like &amp; wont be converted correctly and non-HTML between the two angle brackets will be removed (i.e. the .*? in the regex will disappear).


An employee accidental recursively changed permissions from the root directory to apache. I reran it to root, we fixed MySQL, but SSH still doesn't work. What is the correct way to restore the ownership for sshd?

I was going to change the ownership of a directory to apache:apache, but I ended up running:  chown -R apache:apache /   Bad! Very bad! I knew what was going on when it started saying:     chown: changing ownership of `/proc/2694/fd/48': Permission denied   That's when I stopped everything (Ctrl+C).    The current system I have is a server running virtualbox running CentOS 5. This problem happened inside the VM.  Currently, everything seems to be working, but I have not restarted the system yet, and to be honest, I'm afraid that if I did something will break.  I do not know chown's order, should I be concerned and assume something will break after a reboot? Is there a way to recover form this problem without having to rely on backups? I do have a daily one, but I thought there may be a simpler way out.


I'm trying to install git with   apt-get install git   it then says  E: Could not open lock fine /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?   How do I get this?

I get this error whenever I try to install programs using the terminal:  home@ubuntu:~$ apt-get install myunity E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?   Also I'm unable to install updates using the terminal.


I am trying to use regex to match a letter against strings and then using test however, it doesn't always match a letter with every string.      x = [     'Mike',     'Mary',     'Bob',     'Julie',     'Jon',     'Adam' ];   Working: (not using new RegExp)  x.map(function(a) { console.log(a, /(m)/ig.test(a)); }); VM745:2 Mike true VM745:2 Mary true VM745:2 Bob false VM745:2 Julie false VM745:2 Jon false VM745:2 Adam true    Not working: (using new RegExp)  y = new RegExp('(m)', 'ig');        x.map(function(a) { console.log(a, y.test(a)); }); VM748:2 Mike true VM748:2 Mary false VM748:2 Bob false VM748:2 Julie false VM748:2 Jon false VM748:2 Adam true

I wrote a Javascript RegExp test to detect date string format, I added an redundant "g" flag by mistake and found something interesting.  var s = "2009/03/10"; var regex=/^\d{4}[/]\d{2}[/]\d{2}$/g; alert(regex.test(s)); alert(regex.test(s)); alert(regex.test(s)); alert(regex.test(s));   I got a 'true' followed by a 'false', then another 'true', then another 'false'.  If I use a loop to execute it, I found something more interesting, I got four "true" in IE and Safari, and true,false,true,false in FF, Chrome.  for (var i=0; i<4; i++) {   var s = "2009/03/10";   var regex=/^\d{4}[/]\d{2}[/]\d{2}$/g;   alert(regex.test(s)); }   Does anybody has idea to explain why the Javascript regex behaves like that and what cause browsers return different results? ( related to variable declaration and life scope? )


I am not a native English speaker, but I consider myself to have a solid knowledge of the language, obtained through years of reading foreign literature. I am also an amateur writer, who's now starting to write short stories in English, to publish on sci-fi and horror magazines.  I am asking this question here because I am willing to use the 'lest' contraction in a sentence. The way I constructed the sentence looks right to me, but I can't feel sure if I indeed used it correctly. Several questions about the usage of 'lest' were already asked, but since I do not possess a deep understanding of the English language (self-learner here), I am still confused about if I can or can't use it.  The sentence in question is the following:     I definitely wasn't that much popular. Very few people even talked to   me, lest be my friends. But, at least, even fewer dared to bother me.   In this sentence, I tried to use 'lest' to give a sense of 'let alone be my friends'. I chose 'lest' instead because it sounded better.  Examples of similar questions are:          Again, I am not a native speaker, and a self-learner, so pardon me if the question is somewhat already answered on any of these links.  Thanks in advance!

I am not a native English speaker/writer, but I am working on a technical thesis written in English. To me, for some unknown reason, it feels natural to write the following:     However, the simplicity of the theory implies that it is not possible in reality, lest someone would surely have already done it.   Googling for the definition of lest seems to imply that this is not a correct usage.  So, can I use lest like I do, and if not, do any of you also feel there is any merit to my spontaneous feeling that it actually is ok to use it here? The first answer of  post () seems to support my case, but i am not sure.


I tried blacklisting and everything I could find on the internet used with root and Alt+Ctrl+F1 with no solution :  nvidia-installer log file '/var/log/nvidia-installer.log' creation time: Mon Jun 17 08:35:25 2013 installer version: 319.23  PATH: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin  nvidia-installer command line:     ./nvidia-installer  Using: nvidia-installer ncurses user interface -> License accepted. -> Installing NVIDIA driver version 319.23. -> Running distribution scripts    executing: '/usr/lib/nvidia/pre-install'... -> done. -> The distribution-provided pre-install script failed!      Continue installation anyway? (Answer: Yes)  ERROR: The Nouveau kernel driver is currently in use by your system.  This driver is  incompatible with the NVIDIA driver, and must be disabled before proceeding.  Please  consult the NVIDIA driver README and your Linux distribution's documentation for  details on how to correctly disable the Nouveau kernel driver.  WARNING: One or more modprobe configuration files to disable Nouveau are already  present at: /etc/modprobe.d/nvidia-installer-disable-nouveau.conf.  Please be sure  you have rebooted your system since these files were written.  If you have rebooted,  then Nouveau may be enabled for other reasons, such as being included in the system  initial ramdisk or in your X configuration file.  Please consult the NVIDIA driver  README and your Linux distribution's documentation for details on how to correctly  disable the Nouveau kernel driver.  ERROR: Installation has failed.  Please see the file '/var/log/nvidia-installer.log'  for details.  You may find suggestions on fixing installation problems in the README  available on the Linux driver download page at www.nvidia.com.

I just ordered the Nvidia GTX card. I have a dilemma, though. Should I keep using the driver which is available in "additional drivers" in Ubuntu, or should I install the driver from the Nvidia site?  So which driver is the best for me?


I have list of dynamic created elements which when clicked fires a ajax request and displays the result. The problem is it works only when it is clicked twice. The first click on element doesn't work. Whereas the second click works perfectly. I don't understand the reason behind this. I did try unbind() but it didn't help   $("#profiles_name ul a").on('click',function(event){         $.ajax({    }   });   });.   I did try $("#profiles_name ul a").unbind().on('click',function(event).. It didnt work still.   Here is my dynamically created tag

Frontend Dev

   Also to keep in note that, For example if i have two dynamically created list, When i click on list 1(first time) it doesnt work list 1( second time) works. After page refresh,  click on list 1(first time) doesn't work and click on list 2 (first time) works. i.e First click doesnt work irrespective of the dynamically created element.

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


I have a Python script that I named moduleA.py in the text editor. I ran the script by clicking the "Run Script" button. Then I expected to be able to import the module in the console with "import moduleA" but I get an error saying that the module does not exist.  How does one test functions etc. from a Python script in the text editor in the Python console?

just downloaded todays Blender 2.8 build and it seems I can no longer import a function from another Textblock. Works well on a build from April 5th (haven't updated since then).  This simple example is not working in todays build:


Hi I want to start learning multi variable calculus specifically for learning electrodynamics. What are some good text books?

What are the best textbooks to read for the mathematical background you need for modern physics, such as, string theory?  Some subjects off the top of my head that probably need covering:   Differential geometry, Manifolds, etc. Lie groups, Lie algebras and their representation theory. Algebraic topology.


The definition of the number $e$ that's used in my textbook is  $e = \lim\limits_{x\to \infty} (1+\frac {1}{x})^x$ which relates to compound interest.   But when trying to calculate the derivative of $e^x$, I encountered another definition of $e$: $e = \lim\limits_{x\to 0} (1+x)^\frac{1}{x}$  Now, if it were $x$ approached $0$ from the positive direction, it would've made sense to me since $\frac {1}{x}$ wold approach infinity and $1+x$ would approached $1$ with the same "speed"(sorry I don't know the term here) as the first definition. But it's approaching $0$ from both sides.  My question is, why are these two equal?  EDIT  The reason my question isn't a duplicate of the suggested one is that mine isn't really about the limit $\lim\limits_{x\to \infty} (1+\frac {1}{x})^x$. It's about its alternative form. I totally understand how the former isn't equal to $1$.  Thank you so much in advance!  P.S: I graphed the function $(1+x)^\frac {1}{x}$ and can "see" the limit exists as $x$ approaches $0$ but I would like a non-visual proof.

I'm sure that this is a very basic question, but it has been bothering me for a while:  If $e=\lim\limits_{x\to \infty} (1+x^{-1})^x$, shouldn't $e=1$?  If $x$ is tending towards infinity, why wouldn't $x^{-1}$ tend to $0$ and $e=1^\infty=1$?  Thanks


I'm am stumped. I have an article that starts with \documentclass[twocolumn,aps,prd,amsmath,showpacs,floatfix,reprint,eprint]{revtex4-2} % chktex 8 \bibliographystyle{apsrev4-2}   % chktex 8 \usepackage{amsmath} \usepackage{mathtools} \usepackage{siunitx} \usepackage[nameinlink,capitalize]{cleveref} \usepackage{comment} \usepackage{textcomp} \usepackage{subcaption} \usepackage{breqn}  \usepackage[dvipsnames]{xcolor}  \date{\today} \begin{document} \title{Relativistic Langevin Equation derived from a particle-bath Lagrangian}  \author{Aleksandr \surname{Petrosyan}} \email{ap886@cantab.cam.ac.uk} \affiliation{Cavendish Laboratory University of Cambridge JJ Thomson Avenue CB3 0HE Cambridge U.K.}  This compiles fine. If I add a comma, e.g. like this: \affiliation{Cavendish Laboratory, University of Cambridge JJ Thomson Avenue CB3 0HE Cambridge U.K.}  LaTeX starts thinking that it's in math mode after the comma: the University of cambridge has all the spaces removed, and there's an error, in \maketitle. It finds one dollar, but not the other. For reference, I don't even have $ to delineate equations (like all good LaTeX-ites I use \( and \). None of the examples of the American Physical Society help, because they never contain a comma. My questions are  How do I insert a comma? even a tacky solution will do as long as it doesn't mess up the formatting. Whom do I contact to mention this bug. I'm used to GitHub issues, but I'm considerably less versed in how LaTeX development is handled.

I recently found out about the breqn package and have been using it profusely. However, I notice that my article's title section is thrown off by this package. Specifically, the affiliation part of my text appears without spacing and the compiler throws a missing $ inserted at the \maketitle line. In constructing an MWE, I see that the breqn package is causing this glitch. How do I resolve this?  \documentclass[% reprint, amsmath,amssymb, aps,floatfix ]{revtex4-2} \usepackage{breqn} \usepackage{blindtext} \begin{document} \title{Sample title} \author{Aritra Das} \affiliation{Dept. of Physics, Indian Institute of Technology, Kanpur, Uttar Pradesh 208016, India} \date{\today} \maketitle \section{Introduction} \blindtext \end{document}    Any help is appreciated, thanks.


I read about the Diffie-Hellman Algorithm in cryptography in which we choose a natural number $g\in\{0,\ldots p-1\}$ for a prime number $p$. Then two other natural numbers $a$ and $b$ are chosen. In the first step the numbers $$A=g^a\bmod p\\ B=g^b\bmod p$$ are computed. Notice that this is not a congruence, but instead the modulus of the division. (I will denote congruences with the usual '$\equiv'$)  Then  $$ K_{1}:=B^{a}\bmod p\stackrel{(*)}{=}(g^{b}\bmod p)^{a} \bmod p=(g^{b})^{a}\bmod p=g^{ba}\bmod p$$ and $${\displaystyle K_{2}:=A^{b}\bmod p=(g^{a}\bmod p)^{b}\bmod p=(g^{a})^{b}\bmod p=g^{ab}\bmod p}$$ and therefore $K_1=K_2$. We will not discuss the cryptographical meaning of this, just take it as equations as they stand. In $(*)$ it is used that for a prime $p$ we have elementary multiplication e.g. ${\displaystyle \left((3{\bmod {5}})\cdot (3{\bmod {5}})\right){\bmod {5}}=9{\bmod {5}}}$  As I know this does not hold for non prime integers.  Now here is the thing that confused me: When I use congruence notation we have  $$A\equiv g^a\ \pmod p\\B\equiv g^b\pmod p$$  It follows by elemtary properties of the congruence relation that $$A^b\equiv g^{ab}\pmod p$$  and likewise for $B^a$. We then get $K_1\equiv K_2$. This is not equivalent to the statement before where we got equality, but it does not rely on that the modulus has to be prime.  Now in cryptographical terms I don't think this would be of concern since I can choose the smallest modulus or make it unique in a similar way.   Is what I wrote mathematically correct? Is "the price to pay for equality" that we have to consider a prime modulus? Why does the Diffie-Hellman algorithm rely on choosing a prime number as modulus?

I have been trying to understand why the diffie hellman key exchange algorithm works, specifically why the two exponents can be swapped in it without the result changing.   So my specific question is why:  (g^b mod m)^a mod m  = (g^a mod m)^b mod m  I am interested in the reasoning/proof/explanation behind why it is true.    Thank you


Are these two sentences same?     With the exception of Rob and me, everyone in the class finished   the assignment before the teacher came.      With the exception of Rob and me, everyone in the class had   finished the assignment before the teacher came.   On searching, I found that "had finished" is the correct usage. Is it because it is followed by "before the teacher came"?  If I remove the "before the teacher came" from the first sentence, to make it-     With the exception of Rob and me, everyone in the class finished the   assignment.   will it be (grammatically) correct?

I noticed that my American friends tend to use the past perfect form when they use the verb mention in its past form, almost despite of the context of the sentence. I hear them say  "you had mentioned" a lot more often even in situations where the use of simple past would have been perfectly fine. Have you noticed it too and is it one of those unwritten rules, or is there a more formal explanation to it?  It seems like there was more verbs like that, but I am having a hard time remembering it now. If I do, I will edit the post and likely change the title to accommodate other verbs.


This has been bugging me for some months since our lecturer, a fields medalist, mentioned that he couldn't solve it when he was our age, yet had had two students submit solutions to it (during our introductory analysis course). It was proposed to him by another mathematician at Cambridge who taught him then, and is still there now, who had this problem on his list of "problems for enthusiasts". ( is the lecturer).   Let $z_i \in \mathbb{C}$ be a series of complex numbers with $\displaystyle \lim_{i \to \infty}{|z_i|}=0$. Show that we can choose signs $\alpha_i \in \left\{ {-1,1} \right\}$ such that $\displaystyle \sum_{i=1}^{\infty} \alpha_iz_i$ converges.  He deemed it fruitful to first try and prove the following weaker statement to get an idea of what's involved, yet I have not managed this either.  Let $z_i \in \mathbb{C}$ be a series of complex numbers with $|z_i|=1$. Show that we can choose signs $\alpha_i \in \left\{ {-1,1} \right\}$ such that $\displaystyle \sum_{i=1}^{\infty} \alpha_iz_i$ remains bounded. (In fact, it would seem that we can make $|\displaystyle \sum_{i=1}^{k} \alpha_iz_i| \leq \sqrt2 \ \ \forall k$).  Any ideas, thoughts, or solutions would be greatly appreciated.

I am trying to figure this out:  $\mathscr{S}=\big\{(a_n),(b_n),\dots \big\}$ is a finite set of real, null sequences. Does there exist a sequence $(\epsilon_n)$, where $\epsilon_k=\pm 1$ for each $k$, such that: $$\forall\;(x_n)\in\mathscr{S}:\quad \sum_n \epsilon_n x_n<\infty\;?$$  A special case of this problem was posed by one of my lecturers: does every null sequence in $\mathbb{C}$ admit a sequence $(\epsilon_n)$ of signs such that $\sum\epsilon_nz_n$ converges?   The answer is yes. We can always choose signs so that $|\epsilon_1z_1+\cdots\epsilon_nz_n|\leq \sqrt{3}$ for all $n$, with some assumptions on $|z_n|$.  The geometric nature of the proof prevents me from generalising though. Any ideas how to deal with the general case?


We'd like to know if it is possible to have a group account to answer questions specific to some technologies. The group can have many members and anyone of them can answer questions.  At the end we'd like to know how many questions are answered by individuals and their reputation points.  I don't want reputation as a group. Individuals will work for their own reputation.  The only thing I want that somehow the group of people be seen as coming from one technology background (grouped under one hashTag) and people can see them as part of a technology/organization group and a way to add/remove people from the group by an admin.  Individual profiles remain as they are.

For example, on LinkedIn when you say that you work for some company, then it's possible to have link to that company name that will list all employees with links to their profiles.  Is something similar possible on Stack Overflow/Stack Exchange? I.e. have a short cut to a page which displays account summary for all user who said they are working for IBM or Microsoft or myconsultingcompany.com?


I'm using Windows 10 Pro version 1703 build 15063.296 in Bootcamp on a Macbook Pro '15. This setup has been running fine for two years until the last big Windows 10 update. Now I'm constantly getting out of memory errors. The laptop has 16GB of RAM which is never close to full. The committed memory though is maxing out. When I check to see what program is using a high amount of committed memory in Resource Monitor, everything is pretty low, usually less than 500MB. Windows will say Firefox or Chrome is using too much memory, but I can't find any evidence of this with Task Manager, Resource Monitor or Process Explorer.   How can I find what is actually using up all the committed memory and crashing my computer?   Here are some screenshots of the process list while the commit charge is extremely high. I had to close Chrome and Slack just to free up enough memory to take a screenshot.

There is an observation to be made for Windows 10 on my laptop running with 24G memory available, and 2.5G used.  There is no 'memory pressure'.  Other questions have looked at memory consumption (which isn't the problem here).  In all the related questions here and elsewhere, I havn't been able to find an adequate explanation to the issue of this exccessive cpu utilization over the last month or two after one of the Windows 10 updates.  I can accept that there is value in this service or process, but to run continually, and to use additional cpu resources, and as a consequence, use battery power less efficiently, that is the issue I am trying to resolve.  In some article on this site, it was suggested that I turn off SuperFetch, and set a registry entry for PrefetchParameters to 0.  I did both and performed a reboot.  I reboot the machine, turn off screen saver, and start the task manager.  After a few minutes, the service labeled as 'System and compressed memory' starts taking 5% of my cpu, consistently. My base cpu utilization is maybe 1%, which keeps the fan low.  But when the 'system and compressed memory' service runs at the 5%, the fans ramp up. And just keeps running.  Sillyness.  Why does that service need to be running consistently like that with no memory pressure?  Any additional mechanisms I can try for turning it off or determining what it is actually doing?  Are there logs file entries somewhere?  Or an in-depth diagnostic tool?   -- no real answers here             - now need a link for info on how to interpret the info


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.)


I am using PDO with PHP to submit queries to my SQL server. I need to use the LIKE clause to check a username to ensure that it is allowed (eg; it does not contain any banned words), so I am using this SQL query...  SELECT * FROM `table` WHERE (`name` LIKE %?%);   I am then inserting the paramater with PDO later like this...  $statement->bindParam(1, $username)   When I try to run this, I get this error...     Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '%'dibdibs'%)' at line 1' in C:\xampp\htdocs\scripts\sql.php:57 Stack trace: #0 C:\xampp\htdocs\scripts\sql.php(57): PDOStatement->execute() #1 C:\xampp\htdocs\api\users.php(30): dibdibs\pdo->query('SELECT * FROM `...', Array) #2 {main} thrown in C:\xampp\htdocs\scripts\sql.php on line 5   The PDO code works fine for other queries, when I am using = instead of LIKE, but is is throwing the above error when I try to use the LIKE clause.  I have put my full code on , if you need to check it. I am using GET to get data, as I am using this with AJAX (which is also working fine), but the username I have tried is 'dibdibs', which works fine in other queries.

Here's my attempt at it:  $query = $database->prepare('SELECT * FROM table WHERE column LIKE "?%"');  $query->execute(array('value'));  while ($results = $query->fetch())  {     echo $results['column']; }


Given an arbitrary nonzero vector space $V$, is there a nonzero linear functional on $V$, without assuming axiom of choice? I know that by assuming existence of a basis for $V$, we can consider the dual basis for a subspace of $V^*$, which justifies the existence of nonzero linear functional, but this argument fails without axiom of choice. I guess there may not always be a nonzero linear functional, but my knowledge on axiom of choice and infinite-dimensional vector spaces is lacking. A quick search on Google fails to give an answer.  Note that I am not talking about normed spaces or continuous linear functionals, just plain vector spaces with no additional structure.

For every vector space $V$ does there exist a linear functional $f$ ( a linear map from $V$ to $F$ the underlying field ) such that for some $ \vec v \in V$ , $f(\vec v) \ne 0$ ? If it does exist , can we prove the existence without the "axiom of choice " ? Is the existence equivalent to axiom of choice ?


Since I'm not really great with using the terminal, I would like to see hidden folders on my Mac through the regular user interface. However, I cannot show my hidden folders. I tried things I found on the internet but they did not work for me. I tried  cmd+shift+dot - nothing happens  settings > Keyboard > turning on and off "Use F1, F2, etc. keys as standard function keys"  settings > Keyboard > Shortcuts > Restore Defaults  terminal.app > defaults write com.apple.finder AppleShowAllFiles ["yes"/"YES"/" "]   at the folder I want to view the hidden contents of, I pressed Alt while clicking Go. after the "Library" folder showed up in "Go," I clicked it and saw many folders in Library, but still didn't see any folders with . in front.    My main goal is to copy and paste into a .gitignore file that is stored in a specific folder on my desktop. I am having troubles doing it through the terminal so I thought this would be easier but it is apparently not. :) Question: How can I fix this issue and allow myself to see hidden folders on my Mac? I don't have a strong background in this stuff and am not trained in computer science/tech stuff. I have macOS Mojave.

On my MacBook with OS Mojave, Command Shift Period (show hidden files) stop working. How to restore it?? Thanks in advance!


Let's say I have a string..  lyrics = "Never gonna give you up Never gonna let you down Never gonna run around and desert you Never gonna make you cry Never gonna say goodbye Never gonna tell a lie and hurt you"   I only want to display 23 characters on a line:  Never gonna give you up Never gonna let you dow n Never gonna run aroun d and desert you Never  gonna make you cry Neve r gonna say goodbye Nev er gonna tell a lie and hurt you   (hopefully I didn't mess that up, let's pretend there is 24 characters on each line, I am very sleepy I can't even count)  What is the best way to go about this?

I have a list of arbitrary length, and I need to split it up into equal size chunks and operate on it. There are some obvious ways to do this, like keeping a counter and two lists, and when the second list fills up, add it to the first list and empty the second list for the next round of data, but this is potentially extremely expensive.  I was wondering if anyone had a good solution to this for lists of any length, e.g. using generators.  I was looking for something useful in itertools but I couldn't find anything obviously useful. Might've missed it, though.  Related question:


I'm trying to add validation (i.e. constraints) to a field added to a specific (node) entity.  As per documentation here  i'm trying to change the Field Definition to add a constraint through setPropertyConstraints().  I seem to be able to do so through hook_entity_bundle_field_info_alter(), but only for base fields, not for fields added with Field UI.  My code so far:  function validation_test_entity_bundle_field_info_alter(&$fields, \Drupal\Core\Entity\EntityTypeInterface $entity_type, $bundle) {   if ($entity_type->id() == 'node' && $bundle == 'article') {     // This works!     $fields['title']->setPropertyConstraints('value', array('Length' => array('max' => 3)));     // This doesn't - setPropertyConstraints() doesn't seem to exist     if (!empty($fields['field_test_field'])) {       $fields['field_test_field']->setPropertyConstraints('value', array('Length' => array('max' => 3)));     }   } }   Though hook_entity_bundle_field_info_alter somewhat implies that the $fields array would be FieldDefinition classes (or subclasses), this doesn't seem to be the case? At least the setPropertyConstraints() method is not callable.  I've been debugging for a few hours to find out how this works, but I'm probably missing something obvious. Anyone has any pointers? Am I using the wrong hook or place to try to alter it?  Thanks! Sven

I have an entity that has a field attached to it and the values that user types into the field has to be globally(website) unique(compared to other entities).  I have added validation to the entity form but what if I create this entity programmatically? How can I prevent the entity to be saved into the storage?  I've noticed there is a validate method in ContentEntityBase, though not in ConfigEntityBase. Is this the place for it? If so, I could use some examples.


I need to dynamically load the functions of java.lang.Math and when chosenbe able to use that function.   I've tried this but it didn't work.It gives me a null pointer exception.  private static Class<Math> Math;   for (PropertyDescriptor propertyDescriptor                 : Introspector.getBeanInfo(Math).getPropertyDescriptors()) {              System.out.println(propertyDescriptor.getReadMethod());         }

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?


The definition for completeness is that if a statistic $s(x)$ is complete, we have that for every measurable $g$, $$E_\theta(g(s(x))) = 0\,, \ \forall\,\theta\ \Rightarrow\  g(s) = 0 \text{ a.s.}$$  I've heard that we can think of completeness as saying that if we wanted to estimate the zero function using a complete $s(x)$, among the class of all zero-unbiased functions of the statistic, the only one is one which takes value 0 almost surely. This seems like a bizarre notion--why would we want to estimate the zero function?  I've also heard that in estimating parameters of a probability model $P_\theta$, one does not need any more than a sufficient statistic. I heard that having any more than the sufficient statistic provides no additional information. How does this connect to the definition of completeness above (Basu's, maybe?) ?  Is there some better intuition for the (seemingly) bizarre condition above?

In classical statistics, there is a definition that a statistic $T$ of a set of data $y_1, \ldots, y_n$ is defined to be complete for a parameter $\theta$ it is impossible to form an unbiased estimator of $0$ from it nontrivially. That is, the only way to have $E h(T (y )) = 0$ for all $\theta$ is to have $h$ be $0$ almost surely.   Is there a intuition behind this? Is seems like a rather mechanical way of defining this, I am aware this has been asked before, but was wondering if there was a very easy to understand intuition that would make introductory students have an easier time digesting the material.


I have a fairly simple scene - large ground plane, five uv spheres, Pro-Lighting envmap - that's consistently and almost instantaneously crashing Blender on render.  From my tests, it seems to be a result of a very high subdivision on my primary ground plane (which is approx. 2.8x7 blender units with around 54k verts), combined with a high subsurf level (for microdisplacement). It handles a Level 3 Level 4 subsurf fine; crashes almost immediately at Level 5.   I've done a number of large scenes with millions of verts on this machine before (scene + 20k object particles, with randomly between 1500 and 17k verts each) and while it takes forever and an age to build, eventually it cranks through and renders just fine. I've had a few slow almost to a complete standstill for a while, but I've never had one crash outright.  I know someone is going to quote the subsurf exponent table to me, and I acknowledge that it's almost ridiculously high, but I do legitimately see a difference in the scene at that level.   Given that it crashes almost instantly, as soon as it attempts to synchronize that mesh object, is there a mathematical limit that it's hitting before memory even comes into play (this is a 16GB system)?  Is there some internal limitation to the number of vertices a scene can trigger via rendertime subsurf?

Essentially, my problem is that i am trying to render a scene, however, blender crashes on me early during the render. I only have about 14 total objects in the scene. (It's not that complex) I tried to render a different blender file which was bigger than the one that i am having problems with, and the scene renders just fine. There is no difference in the render presets for both of these files. However, i still cannot render the other scene. It gets to preparing scene data, but then it crashes.  Thank you.


I have transformed my explanatory variables to a normal distribution as these variables include, proportions (logit transformed) and non normally distributed data (various transformations).  The dependent variable is a count, hence I am using "family = poisson".  I have read in some sources that it is uneccessary to transform the explanatory data but I don't understand the reasoning behind this.     Was transforming this data incorrect?

I am always struggling with normality testing for quantitative predictors (no factors) and transforming them to normality.    If I am running a GLMM and my predictors are really non-normal, should I  transform them as well to try to make them normally distributed?  I know that this is important for the response variable but what should be done with predictors?   P.S.: I really could not find a similar question.