Choose between Bluetooth Low Energy advertizing and connection for low-power small-data application

Question: I have several sensors running on coin batteries, which are supposed to send data to a central device periodically. The data size is small: the meaningful data should be a few bytes excluding the BLE packet overhead. The transmission period is long: it can be once per hour or even per several hours. I am using a Bluetooth Low Energy (BLE) module (BL600 from Laird) which has a nRF51822 SoC inside. The goal is to minimize the average power consumption since the sensors are supposed to run from battery for a long time (a year or so?). Obviously the BLE peripheral can send data either by advertizing or connection. I am not sure which is the way to go, and what factors I should consider in making the choice. Could anyone please advice?
Comment: Doesn't connection equal advertising plus transfer? Seems to inherently include the energy requirements of advertising and more.
Comment: why use bluetooth? if only small and one-directional (or two-way using addressing) packets, use a normal NRF24L01+ or similar radio transceiver on each device and communicate that way.
Answer: If you data will fit into an advertising packet payload, then that is the lowest power possible way to get that data delivered to a receiver (or receivers). To send an atomic data set via advertising, you only need to send a single packet. A connection at very least would require a send followed by a receive.
You also indicate that you could go hours between data packets. With advertising, you can send your packets spontaneously as you like- as long as the receiver gets the packet when you do send it then the transfer is good.
Advertising packets are also much simpler to create. You could save processor cycles by laying out all the static parts of the packet in memory one and then very quickly updating only the dynamic data fields before a send.
Answer: Normally, for such long intervals between data transmission (once per hour), you would not hold a connection (as the max CON interval is much smaller - I think around 20 seconds).
So the strategy might be to turn off bluetooth on the sensor by default and activate it only when there's data to transmit - this should save a lot of power.
When waking up (with data), you need to start with advertising anyway; if you don't need any acknowledge nor special security, you can just send the data a few times in the ADV packets.
If you want to ensure that the data was received, you should enter a connection.
Also if you want to encrypt the data, you should connect, receive an encryption nonce from the central device, transmit the encrypted data (using common secret and nonce), receive the acknowledge, disconnect and turn off again.


On cards with a chip, why does every chip have a different design?

Question: Even with the same card issuer (for example, I have two Discover credit cards of the same "model" for the same account), the chip always has a different outline. What's the reason for this?
Comment: This may also be interesting https://electronics.stackexchange.com/q/34074/3552
Answer: Basically, the spec doesn't care. When you insert your card into a reader, there are six pins that will make contact, three along each edge. The area in the middle isn't really used, but should be connected to the upper-right pad (ground). As long as those six pins make contact, there's plenty of room for creativity. If your phone gives you easy access to the SIM card, you can pop it out, and see what the contact pins look like. (Fun fact: SIM cards and chip-and-pin chips use the same technology.)
https://en.wikipedia.org/wiki/Smart_card has a pinout, under "A smart-card pinout" on the right. Note that there are both 8-pin and 6-pin versions. The 8-pin version has 2 extra connectors for USB interfacing, which isn't usually needed, and so can be skipped.
Comment: Yes. The spec does care but only as far as reliable connectivity with all the applicable tolerances is concerned. For example, the card doesn't fit the slot with some micrometers precision, so the contacts must be designed such that they couple under all reasonable conditions.
Comment: The spec doesn't care, but practical concerns in the real world mean that the designs are constantly under refinement. Between shimming and FUN attacks there has been a lot of recent attention on the physical design of the chip as a security measure.


My memory leak in C++ program

Question: I'm faced a new problem something with memory allocation and leak here  is my error log:
Dr. Memory version 1.4.6 build 2 built on Mar  7 2012 10:14:04
Application cmdline: ""D:\c++\Begin\Lab3-5_OOP\Debug\Lab3-5_OOP.exe""
Recorded 62 suppression(s) from default C:\Program Files (x86)\Dr. Memory/bin/suppress-default.txt

Error #1: UNINITIALIZED READ: reading register eax
# 0 _fu89___ZSt4cout               [D:\c++\Begin\Lab3-5_OOP\Debug/../Controller.cpp:156]
# 1 main                           [D:\c++\Begin\Lab3-5_OOP\Debug/../M.cpp:25]
Note: @0:00:00.924 in thread 4584
Note: instruction: test   %eax %eax

Error #2: LEAK 12 direct bytes 0x00531420-0x0053142c + 1024 indirect bytes
# 0 libstdc++-6.dll!Znwj
# 1 constr()               [D:\c++\Begin\Lab3-5_OOP\Debug/../ListStruc.cpp:24]
# 2 main                   [D:\c++\Begin\Lab3-5_OOP\Debug/../M.cpp:18]

Error #3: LEAK 12 direct bytes 0x009bec48-0x009bec54 + 1024 indirect bytes
# 0 libstdc++-6.dll!Znwj  +0x23     (0x6fcbb523 <libstdc++-6.dll+0x7b523>)
# 1 constr()               [D:\c++\Begin\Lab3-5_OOP\Debug/../ListStruc.cpp:24]
# 2 main                   [D:\c++\Begin\Lab3-5_OOP\Debug/../M.cpp:20]

DUPLICATE ERROR COUNTS:

SUPPRESSIONS USED:

ERRORS FOUND:
      0 unique,     0 total unaddressable access(es)
      1 unique,     1 total uninitialized access(es)
      0 unique,     0 total invalid heap argument(s)
      0 unique,     0 total warning(s)
      2 unique,     2 total,   2072 byte(s) of leak(s)
      0 unique,     0 total,      0 byte(s) of possible leak(s)
ERRORS IGNORED:
     78 still-reachable allocation(s)
         (re-run with "-show_reachable" for details)
Details: C:\Users\Warzaru\AppData\Roaming/Dr. Memory/DrMemory-Lab3-5_OOP.exe.10024.000/results.txt

Struct:
const int days=31;
const int exp=6;

struct Arr{
    int days;
    int exp;
    int **M;
};
typedef Arr* Array;

Constructor:
void constr(Array &loc){
    //Construct of 31*6 Matrix, were 31 nr. of days and 6 specific types:
    //0-HouseKeeping, 1-Food, 2-Transport, 3-Clothing, 4-TelNet, 5-others
    loc=new Arr;
    loc->days = days;
    loc->exp = exp;
    loc->M = new int*[loc->days];
    for(int i=0; i<loc->days;i++ ){
       loc->M[i] = new int[loc->exp];
       for (int j = 0; j < loc->exp; j++){
           loc->M[i][j] = 0;
       }
    }
}

The program  errors me only for some  function of ti for example function:
void maxDay(Array &M){
    //Output the day with highest value
    cout<<"test";
    int hD = 0;
    int s1 = 0;
    int s2 = 0;
    cout<<"test";
    for(int i = 0; i<30;i++){
        s1=0;
        for (int j=0; i<5; j++){
            s1 = s1 + M->M[i][j];
            if(s2 <= s1){
                s2 = s1;
                hD = i;
                cout<<"test";
            }
        }
    }

}

So short, I have a structure Arr ( Matrix of 31*6) were I store ints (different types of expenses) but when I use some of my functions I get Segmentation fault. I have no experience with this kind of errors, so any advices are useful.
EDIT:
void destruc(Array &loc){
    for(int i=0; i<loc->days;i++ ){
       delete[] loc->M[i];
       for (int j = 0; j < loc->exp; j++){
           delete[] loc->M[i][j];
   }
}
}

Comment: I see `new` but not `delete`.
Comment: I suggest you replace `int **M` with `std::vector< std::vector >`. Actually, there are better approaches, but this would have the least impact on your existing solution.
Comment: @BogdanMaier: If this is homework, you need to tag it as homework, otherwise you will get proper/suitable answers that you can't use because of the restrictions imposed by your homework guidelines.
Comment: the thing  is I have to use my own structure :|
Comment: ok, thank you i`ll keep in mind for the future
Answer: Follow the rule "Deallocate every block of memory that you have allocated dynamically"
Deallocate using delete the memory you have allocated using new
This may throw some light for you http://www.cplusplus.com/doc/tutorial/dynamic/
If you allocated an array using new[] then delete it using delete[]
In this case i would suggest you to write a constructor and destructor for the struct Arr instead of writing normal functions.
Comment: You are mixing `delete[]` and `delete` with `new` and `new[]`
Comment: is it  correct like this? i edited the psot and added deconstrctor.
Answer: // I hope you intended to write j<5
for (int j=0; i<5; j++){  //infinite Loop... as j is still 0

So what happens with the statement i<5 in your program is, your inner for loop becomes an indefinite loop and tries to access unallocated memory.
Answer: 1    void destruc(Array &loc) {
2        for(int i=0; i<loc->days;i++ ) {
3            delete[] loc->M[i];
4            for (int j = 0; j < loc->exp; j++) {
5                delete[] loc->M[i][j];
6            }
7        }
8    }

i see you're delete[]'ing loc->M[i] (line 3) and yet you still references it's contents at line 5.
I suggest this is a bug as you've handed the memory back to the heap and any other part of your application can now re-use it. So by the time your application gets to line 5 it may not have the contents you expect.
I'd suggest rewriting it as...
1    void destruc(Array &loc) {
2        for(int i=0; i<loc->days;i++ ) {
3            for (int j = 0; j < loc->exp; j++) {
4                delete[] loc->M[i][j];
5            }
6            delete[] loc->M[i];
7        }
8    }

Answer: The destructor in seems to be strange
void destruc(Array &loc){
    for(int i=0; i<loc->days;i++ ){
       delete[] loc->M[i]; <-------------- deleting array of pointers to array
       for (int j = 0; j < loc->exp; j++){
           delete[] loc->M[i][j]; <------- deleting pointer to array that
                                           is already deallocated
   }
}

Destructor should look the following way (in accordance to constructor):
void destruc(Array &loc){
    for(int i=0; i<loc->days;i++ ){
       delete[] loc->M[i];
    }
    delete[] M;
}

My memory leak in C++ program


How to call a function as soon as controller is called in cakephp

Question: I am creating a simple website in cakephp.
I have kept header and footer in "element" but my problem is that  menu of header is coming from database and it will not be available until I call a function.
I want as soon as controller is called function of menu should be called by own.
Answer: In your AppController add this:
function beforeFilter(){
    $this->set('menu', $this->YourModel->findById('Id of your menu data row in database'));
}

Then, in the view, the menu will be accessible by calling echo $menu['yourModel']['menu'];
Answer: TLDR:
Instead of calling the function every time the entire controller (or all controllers) is loaded, it's better practice to just call the function when the element itself is loaded.  This allows you much more flexibility moving forward.  Eg, maybe the log-in screen doesn't need the menu - or maybe you eventually add an admin tool that has a different menu...etc etc.
CakePHP makes this VERY easy using requestAction() - read more here:  http://book.cakephp.org/2.0/en/views.html#passing-variables-into-an-element
Side Note: It's also ideal (MVC pattern and many other reasons) to keep ALL queries in a model, instead of calling them directly from a controller.
Example Code:
/**
 * MenusController (or any other controller you want)
 */
public function get_menu_main() {
    $this->set('menu', $this->Menu->getMenuMain());
}
public function get_menu_footer() {
    $this->set('menu', $this->Menu->getMenuFooter());
}

/**
 * Menu model
 */
public function getMenuMain() {
    return $this->findById('12345');
}
public function getMenuFooter() {
    return $this->findById('67891');
}

Then, in your element, just use a requestAction to retrieve the data you need for that specific element:
/**
* MainMenu element
*/
$menu = $this->requestAction('menus/get_menu_main/');

/**
* FooterMenu element
*/
$menu = $this->requestAction('menus/get_menu_footer/');

Side note: to be a little more proper, you can use $this->Html->url() instead of hard-coding the URLs to the actions.
Side note:  Some of this code might seem like adding extra code when you don't "need" it, but by breaking things up into their correct MVC spot, your code will be much cleaner, more flexible/upgradable...etc etc etc.  Getting into a habit of doing things like this will make your life MUCH easier when things start to get even slightly more complicated.  (And in all reality, the code above adds a few lines, but as far as complexity is concerned, I think it's easier to understand than having a query in the AppController that loads variables for an element(s).  /endrant


What's the name of this plant? And why the leaves become yellow?

Question: What's the name of this plant grown in my yard? And why the leaves become yellow?
Answer: It's either bearded iris (Iris germanica or Iris pallida) or possibly a Flag iris (Iris versicolor) and is dying back for the winter if you're in the Northern Hemisphere. If you're in the Southern Hemisphere, then the dying leaves are either a sign of an insect problem - probably the Iris Borer if those are common in your location - or over-watering.
Comment: It is worth digging up the worst looking ones and check the rhizomes for borer like caterpillars. In IL I dug some iris to move them and found most had big borers although the plants did not look bad.
Comment: @blacksmith37 - definitely. I lost two large clumps to borers and had two more severely damaged last year. Dug out something like 30 borers and found maybe a dozen pupae in the surrounding soil (always a good idea to search through the surrounding 4-6" of soil looking for the pupae).
Comment: Thanks for the answer! I'm in Northern Hemisphere and it is raining a lot these days, this may cause it over watered I think.


The effect black holes have on light

Question: We all know that light loses its energy when it is moving through expanding space and time. And sense a black hole can be summed up to a super compressed space time, shouldn't that mean that a photon gains energy when it enters a black hole because it is experiencing the opposite effect of the expansion of spacetime
Comment: Check out https://en.wikipedia.org/wiki/Firewall_(physics)
Comment: As is usual in these kinds of questions - according to who?
Answer: From the perspective of an observer far from a mass:
Light gains energy (increasing in frequency) when it goes from farther away from a mass to closer to a mass. Energy is conserved: the increase in the energy per photon is equal to the decrease in gravitational potential energy caused by bringing the mass-energy of the photon closer to the mass-energy of the mass.
If the light subsequently gets farther away from the mass, the same relation holds, so the frequency goes back down.
These are gravitational blueshift and gravitational redshift respectively.
A black hole is just a special case; all masses exhibit this phenomenon.

So far as I know, it is unknown whether gravitational redshift and the cosmological redshift caused by the expansion of spacetime are one in the same. As a non-expert, I find the explanation compelling, since the universe expanding moves mass-energy (including photons) farther apart, and this must do work on the gravitational field.
Answer: Basically yes it does lose energy and it can not get it back. For your second qwestion well, we don't know what happens in a black hole but we have general ideas of what happens in there and basically it's just contrubiting energy into the black hole BUT a black hole could just be a incredibly different thing like a worm hole so you would have to be more specific with your qwestion
Comment: im talking about what happens to a single photon when it enter a black hole does it get compressed or does it under go something else entirely

The effect black holes have on light


Discarding the output of a function that accepts an output iterator

Question: Suppose there´s a template function in C++ that does some useful work but also outputs a sequence of values via an output iterator. Now suppose that the sequence of values sometimes is interesting, but at others is not useful. Is there a ready-to-use iterator class in the STL that can be instantiated and passed to the function and will ignore any value the function tries to assign to it? To put in another way, send all data to /dev/null?
Answer: The STL does not provide such an iterator. But you could code it yourself (tested that code):
struct null_output_iterator :
    std::iterator< std::output_iterator_tag,
                   null_output_iterator > {
    /* no-op assignment */
    template<typename T>
    void operator=(T const&) { }

    null_output_iterator & operator++() {
        return *this;
    }

    null_output_iterator operator++(int) {
        return *this;
    }

    null_output_iterator & operator*() { return *this; }
};

It doesn't need any data by using itself as the result of operator*. The result of *it = x; is not used in the output iterator requirements, so we can give it a return type of void.

Edit: Let's go into how this operator* works. The Standard says in 24.1.2/1  about the requirements of an output iterator that in both these cases:
*it = t;
*it++ = t;

That the result of those expressions is not used. That's what makes this work:
null_output_iterator it;
*it; // returns a null_output_iterator& per definition of the `operator*`.
*it = some_value; // returns void per definition of the templated `operator=`.

Now we don't need to have any data that we return in operator*: We just use the iterator itself. Note that the templated operator= does not overwrite the builtin copy assignment operator. It's still provided.
Comment: Could you better explain the operator*?
Comment: It's used in combination with the templated operator=. Tricky, I'd use a nested helper class dev_null.
Also, I'd let operator++(int) return *this immediately. This version is inefficient.
Comment: msalters, the operational semantics state a new object is returned :)
Answer: Do you have Boost available? If so you could use a function_output_iterator wrapping an empty function.
It's not ideal though. Whatever iterator you use will still need to create an instance of the value_type for return in operator*, even if it then throws it away.
Answer: It isn't hard to write one.
template<typename T>
class NullOutputIterator
{
public:
    NullOutputIterator() {}
    NullOutputIterator& operator++() { return *this; }
    NullOutputIterator& operator++(int) { return *this; }
    T& operator*() { return m; }
    T* operator->() { return &m; }
private:
    T m;
};

I haven't tested this, and there's probably something important missing, but I think this is the idea.
Comment: The idea is good, but I don´t think you need:
T* operator->() { return &m }
And you should derive from stl::output_iterator

With this implementation a copy of T is executed at each assignment through the out iterator. Is there anyway to avoid that?
Answer: I based mine on std::back_insert_iterator, but without the container:
#include <iterator>

template<typename T>
class NullOutputIter
    : public std::iterator<std::output_iterator_tag,void,void,void,void>
{
public:
    NullOutputIter &operator=(const T &) { return *this; }
    NullOutputIter &operator*() { return *this; }
    NullOutputIter &operator++() { return *this; }
    NullOutputIter operator++(int) { return *this; }
};

This is similar to Johannes's answer, but without the template operator= that takes whatever. I like strong typing; I want *it = wrong_type_thing to be a compile-time error. Also this uses void for the various template parameters to std::iterator, like the output iterators in the standard library.
This is also similar to Mark's solution, but (a) it properly inherits from std::iterator and (b) it does not have the unneeded internal state variable.
Answer: Updated answer (2022)
With C++17,std::iterator is deprecated. If you want to avoid a warning, you have to declare the types in the public interface:
  ///
  /// @brief Allows to discard the output of functions that requires an output iterator
  ///
  template<typename T>
  struct null_output_iterator
  {
    using iterator_category = std::forward_iterator_tag;
    using value_type = T;
    using difference_type = T;
    using pointer = T*;
    using reference = T&;
    ///
    /// @brief No-op assignment
    ///
    void operator=(T const&) {}
    ///
    /// @brief Can be pre-incremented
    ///
    null_output_iterator & operator++()
    {
      return *this;
    }
    ///
    /// @brief Can be post-incremented
    ///
    null_output_iterator operator++(int)
    {
      return *this;
    }
    ///
    /// @brief Can be dereferenced
    ///
    null_output_iterator & operator*()
    {
      return *this;
    }
  };


Calculate the class limits from the kernel density depending on the percentage of the source dataset

Question: My goal is to make the class boundary of a kernel density dependent on a percentage of the input points.
Specifically I calculate the kernel density from 3000 points in a 50m x 50 m grid with a search radius of 16000 m in an area of about 357386 km². Now I want to divide the density result raster into two classes.  One class should contain 75% of the original points and the other class with the highest density values should contain 25% of the original points. So I want to set the threshold value for a density to a percentage of the original data.
Unfortunately, I have not yet found a way to make the class boundary dependent on the percentage of the original data points. Is this even possible?
I would be very happy about support. I work with ArcGIS 10.6.
Answer: I have a solution:
-   Multipart To Singlepart
-   Multipoint feature class to single point
-   Kernel density
-   extract multi values to points
-   Sort table of input points with density values in ascending order and read off threshold value;


Regression Developing Countries: GDP-Growth or GDP

Question: For my master thesis I basically want to find out, why developing countries are stagnating. Next to theoretical aspects I also want to make a regression.
I want to regress GDP or GDP growth as dependent variable on many independent variables, such as tenure of head of state, life expectancy, working hours restriction, adult literacy and population growth and some (other) institutional variables over five years. My question is: Does it make more sense to regress GDP-Growth (in %) on the independent variables or should I use the real GDP-Value (e.g. in $)?
Comment: "For my master thesis I basically want to find out, why developing countries are stagnating."  that is a rather ambitious goal!
Comment: @kjetilbhalvorsen that's what grad theses are supposed to do: hail Mary moonshots!
Answer: You are interested in why countries are "stagnating"; stagnation is about a lack of growth, so, GDP growth seems logical.
A couple notes:
1. You will need data on countries that are growing at different rates.
2. If you are using data from different years for the same countries (e.g Ghana in 2011, Ghana in 2012, Ghana in 2013...) then a regular regression is probably inappropriate, Your errors are unlikely to be independent.
Comment: Yes, but I use the data for many countries over many years (at least 5), so its a paneldata. Would this solve the problem of the dependent error term?
Comment: No, it would not.  You  cannot use standard regression for this.  Some ideas are multilevel models or genearalized estimating equations.
Answer: The excellent textbook by Barro and Sala-i-Martin (Economic Growth, MIT press, 2004), can help you to choose your model.
However, as Peter Flom said, be careful with cross-section regression, it can be misleading; you might need to apply a panel data methodology (see the paper by Islam, 1995, on The Quarterly Journal of Economics 110(4), 1127-1170). Again, see Barro and Sala-i-Martin (2004) for almost all references you might need.
It might be useful for you also to check at some classical (but old!) papers on growth economics such as Sala-i-Martin (1994, European Economic Review 38(3-4), 739-747) , Islam (1995, see above) and Baumol (1986, The American Economic Review 76(5), 1072-1085) among many, many others.
Comment: Please include full citations for articles and textbooks. While the link works today, it may not work tomorrow. The goal of SE sites is to build a durable repository of knowledge for future visitors.
Comment: That's right. I've revised the citations.
Comment: This is a step in the right direction, but an author's last name and a year are not full citations. Searching for "Islam 1995" won't help anyone locate the document. Please include the author's full name, the article or chapter title, the full journal or book title, the volume and issue number and the year. Complete information about how to cite an academic source can be found in a style manual such as this. https://owl.english.purdue.edu/owl/resource/747/08/
Answer: Basically, there's no ambiguity here: you must use the differences in the regression. There could be some discussion whether it's a simple difference or a log difference, but the latter is more common in the literature. If you had a cross-section, then this wouldn't matter. For a short period of time it probably doesn't matter that much either, but you're probably going to include countries with high growth in your sample, so the rate of change would be more appropriate.
GDP is not stationary even when you suspect or observe that it's stagnant, i.e. not growing over a sample period.
I think most researchers would take it that GDP is an exponential random walk process: $\Delta \ln GDP_t=g_t \Delta t+\varepsilon_t$. However, you can google to find that some would argue that it's an exponential trend process such as $GDP_t=GDP_0 e^{g_t\Delta t}+\varepsilon_t$. In the former case you see that the growth rate is stochastic, while in the latter it's deterministic and the error simply adds up. Both are nonstationary, hence, the growth rate must be used in any case.
Comment: Difference in differences refers to something else, though: http://en.m.wikipedia.org/wiki/Difference_in_differences
Comment: @ChristophHanck, you are right. I thought OP wants to see how GDP growth rate starts declining in some countries, or something like that.
Comment: I already have the growth rates, should I even take the first difference of the growth rates itself or would that only be for the gdp value?
Comment: If you take the difference in growth rates you'll deal with difference-in-differences study as they call it in econometrics. I'm not a macroeconomist, but doubt that they have theories of unstable growth rates. In other words I don't think they say whether growth rates themselves should be growing or declining. Hence, I think you should simply use the growth rates themselves. Your hypothesis would be whether they are *too low* or negative.
Answer: A very important question is availability of data. Example, you can get the data from wto.org.
A very realistic answer to your question is that you should build your model in both ways and compare the accuracy prediction parameters e.g. $R^2$ , adjusted $R^2$, and residual graphs. Then start validating your hypotheses for which form of GDP you should take.
My hypotheses on this is that it is just equivalent to the transformation of the GDP variable.


What does this phrase mean?

Question:
You must not lament in conversation with your savior over the trifles of an average boy.

what does it mean?
Answer: To lament means; mourn aloud, wail, express sorrow, grieve for; bewail, bemoan,
 regret
Trifle in this context means; matter or object of small value or of little importance
In the sentence

You must not lament in conversation with your savior over the trifles
  of an average boy.

your pen-pal's admonishment might be interpreted in two ways.

1. The pen pal is saying not to waste your savior's time over petty, insignificant details. The aches and pains of a romantic relationship with an ordinary boy are unimportant and trivial compared to the magnitude of events, concerns and innumerable requests he has to deal with on a day to day basis. The message implied is that if you are to "pray" or beseech his guidance then do so for things which are more important. Your pen pal does not say what these things are or may be.
2. The meaning is similar to the one posted by @Ace Frahm, that your grievances over the problems of a boy may be experiencing, an average boy at that, is of little importance to your saviour. The word, "average", in this context I would read very negatively. In other words this  person, according to your pen pal, is  mediocre and ordinary and his problems are of little value and consequence.

Finally, it is worth pointing out that in both cases it has been your pen pal who has classified these problems as being trivial and insignificant. Whether she or he is correct in making these rather arrogant claims is a separate issue but one you might do well to reflect on.
Answer: Without knowing any of the context about who the "savior" is, or what the trifles are, or who the boy is [you|someone you know|your pen pal], or whether he is mutually understood as average or not,
this sentence seems to mean that:
you should not complain or express sorrow to [your savior|allah|god|jesus|superman] about this boy's problems.
Possibly because the boy is average & thus unimportant, or because the boy's problem's are no different than any other person's problems, or maybe your pen pal thinks you have more important things to talk about to [your savior|krishna|budha|jesus|aquaman].  Or maybe that you shouldn't let this boy's problems become your problems.
In any case, it sounds like bad advice to me, as gods aren't real, so you'd be wasting time better spent taking real action.  And even if they were, we should still have some concern for our fellow man.

What does this phrase mean?


How did Fleur escape during the second task of the Triwizard Tournament?

Question: On the second task of the Triwizard Tournament the champions had to dive into the great lake. Fleur Delacour didn't manage to get to her sister because she was attacked by Grindylows. But how did she escape out of the lake or who rescued her? Why would Grindylows let her go? I think they would rather kill her even if they don't eat men.
And there weren't any teachers or mermen to help her.
Comment: The task wasn't lethal. The mermen were there to supervise the challenge, not murder the competitors.
Comment: She wasn't attacked by mermen but from Grindylows.
Comment: Possible dupe: https://scifi.stackexchange.com/questions/146125/was-harrys-concern-about-fleurs-sister-gabrielle-misplaced?rq=1
Comment: I assume that there were teachers standing by in case any champion was in trouble, like in the Third Task, except that the champions were not told about them (testing their courage, bravery, blah blah). The Ministry had made sure that the Tournament wasn't fatal (whoops, Cedric).
Comment: @Righter - It wasn't the tournament that was fatal to Cedric.
Answer: She presumably escaped on her own
First of all, there is no mention of anyone else's involvement. Fleur simply describes being attacked and nothing more. After the judges converse with the Merpeople and explain what happened they do not say anything about someone needing to rescue her. In fact she received 25 points, a full half of the total, which implies some level of success. Had she not even been able to escape on her own and had to be rescued you might expect her to have gotten even fewer points, if any at all.
Second of all, Grindylows are not particularly dangerous or hard to escape from. Recall that they are taught to third years in Hogwarts, hardly an advanced level. Moreover, Lupin describes how easy it is to deal with them:

"Water demon," said Lupin, surveying the grindylow thoughtfully. "We shouldn't have much difficulty with him, not after the kappas. The trick is to break his grip. You notice the abnormally long fingers? Strong, but very brittle."

This is also echoed in Fantastic Beasts and Where to Find Them:

The grindylow has very long fingers, which, though they exert a powerful grip, are easy to break.

More importantly, the Ministry of Magic classification for Grindylow is only two stars, which is defined as "harmless/may be domesticated".
In light of this, it would hardly be surprising that a witch who is of age and has nearly completed her magical education would have been able to escape without too much difficulty.
Comment: But why didn't she continue to search for her sister after her escape?
Comment: @Milgo If I had to guess I would say that getting past the grindylows is harder than escaping from them. Also, she was probably already weakened at that point, and probably past the time limit.


How to tie the first note of the second volta in MuseScore?

Question: How to tie the (first) note of the second volta to the previous note in MuseScore?
Answer: I think this is not directly supported. See some discussion here: http://musescore.org/en/node/15720#comment-63654
Some workarounds:
- add the previous measure also into the volta
- use a slur to "fake" a tie
Comment: thanks for the link. I'll check out using a slur and the suggestions given over there.
Comment: Apparently there is no good solution. I didn't figure how to slur them. So the most readable would be to add the previous bar to the first and second voltas. However, in my case I'd even have to add the previous two bars, which makes 4 bars all in all. I think I just leave it until a ms version comes out which supports this.
Answer: As of 9 Aug 2022, this remains unsupported directly, but there are several workarounds described to accommodate various scenarios: How to create ties leading into a 2nd ending
The workarounds given are:

Use special characters (basically, position two ties by hand)
Avoid leading ties (rewrite the voltas to include the "problem" measure)
Use invisible grace notes
Use invisible ties (from the last note of volta 1 to the first note of volta 2)
Use invisible voice and ties (similar to #4, but using a second voice)

The image below was created by applying a "laissez vibrer" articulation mark (see the blue box) to the first note of the second volta, then shifting it left by hand.
Comment: I think the invisible grace note provides the best playback given that the ending note of the 1st volta does not match the starting note of the 2nd volta, which matches the first time I had to use a workaround (that wasn't avoiding the leading tie in the first place; avoiding that tie doesn't quite work when the measure before the voltas is 16th note-filled).


how to manipulate arm robot?

Question: I want to make a robot arm with a gripper that can go to any x y z coordinates near it. the robot itself will be simple just servo motors and Arduino but I don't know how to make reach the desired coordinates, any ideas?
Comment: Welcome to *Robotics* mr.Arrow, but I'm afraid that your question would require a book on Kinematics to answer fully. We try to limit the scope of questions so that they can be reasonably answered in this format. Please take a look at [ask] & [about] for more information on how stack exchange works and read up on [Kinematics](https://en.wikipedia.org/wiki/Kinematics) & [Kinematic chains](https://en.wikipedia.org/wiki/Kinematic_chain) so we can try to help you with more specific questions you may have.
Comment: it's ok Mr Mark i already got a useful answers but please don't remove it so i can comment on this answers soon.
Comment: No problem, your question is just on hold, and we look forward to future questions when you know more about what you need to know. *8')
Answer: There are multiple way to do so. It depends on how much effort you want to put in.
In any case, you'll have to do some math and define your frames.
Solution 1
As @lucab said you can calculate those set of equations.
Then compute the inverse kinematics .
This will let you find the set of angles your joints need to have in order for the end of your arm to reach the desired position.
Solution 2
Another popular approach with robotic arms is to use the Denavit-Hartenberg convention. This convention allows you to define your arm joints with another set of parameters.
Then you can use these parameters to build your arm model thanks to Peter Corke Toolbox. This toolbox allows you to do:
- forward kinematics: which mean you it will calculate for you the position of the end of the arm for a desired set of angles
- inverse kinematics: calculate the set of angles needed to get to a position.
If you need more details, feel free to ask.
Comment: now i understand F/I kinematics .... and i already have a general picture of  the robotic arm in my mind and i can draw it on a paper..is it a must to design it on a software like solid works because i don't know how to use it?.... and the desired arm will have 4 degrees of freedom what solution should i take for that as in mr lucab page it says that arms more than 3 DoF should use inverse jacobian method not D-H method ? is that true?
Comment: You don't have to design it on a software to do the kinematics or to find the parameters. You just a pen, a paper, and sometimes your brain :p.
I don't see where they say you have to use the inverse jacobian **instead of** the D-H method. The D-H method will allow you to find parameters to define your joint. And the robotic toolbox by Peter Corke, will do all the math for you and calculate the angles you need. I can send you an example if you want with python code that uses the toolbox.
If you want to implement the math yourself then you'll need more reading about kinematics :)
Comment: glad I could help :)
Answer: Determining your x, y, and z depends greatly on how many Degrees of Freedom (DoF) the robotic arm has (which in most cases is just the amount of joints or servos there are not counting the end effector)
You may want to dive into the world of forward and inverse kinematics. In a nutshell:
forward kinematics is generally used when you have your joint angles and want to find your x, y, and z.
Inverse kinematics is used when you know what your x, y, and z is but you want to find your joint angles.
Forward kinematic equations are almost always easier to solve for than inverse kinematic equations since they usually guarantee closed form solutions whereas inverse kinematics makes no such guarantee.
The more accurate your sensors are in measuring angular displacement, the more accurate your end effector will be to the x, y, and z you choose. The process will be something like this:
Select position (x, y, z) --> plug position into inv kin equ to get thetas --> command motors to thetas
Although it may seem like you have no interest in forward kinematics, its actually very helpful in solving the inverse kinematic equations.
Start with forward kinematics, obtain what your x, y, and z equations are as a function of generic thetas (x(θ1, θ2, θ3, ...), y(θ1, θ2, θ3, ...), z(θ1, θ2, θ3, ...)), and perform inverse kinematics by turning the x, y, and z equations, which are functions of thetas, to theta equations as a function of generic x, y, and z (θ1(x, y, z), θ2(x, y, z), θ3(x, y, z), ...).
Where your thetas are your joint angles with respect to your previous link axis.
If still having issues understanding forward or inverse kinematics after researching (many textbooks seem to make it more complicated than it actually is), let me know and I can derive a couple examples.
EDIT
In order to do forward kinematics, it helps to know transformation matrices. Here is a video I put together awhile ago. Not the best video, but I plan on redoing them and making a series about this type of stuff when I get the free time.
Once you understand transformation matrices, its a matter of giving your robot several coordinate systems in unique places. Could be at each joint, or could be using the denavit-hartenberg (DH) technique to reduce the amount of parameters needed to describe the relation between coordinate systems to 4 parameters.
After the coordinate systems are in place, you'll need to multiply various rotation and translation operators with one another to get from a base coordinate system to your end effector coordinate system. Or in other words, you need to find the combination of rotations and translations to get your base coordinate system overlaid on top of your end effector coordinate system.
Once the combination of Rots and Trans operators are found, multiply them all together to get your transformation matrix of your end effector with respect to your base. It'll be a 4x4 matrix; just pick off the 3x1 vector in the top right and you'll have your x, y, and z equations that will tell you your end effector position given your thetas.
Now the difficult part:
You want to derive what your thetas should be to get to a position of your choosing, not the other way around. So use those 3 equations you picked off of the transformation matrix to to help you solve for thetas given an x, y, and z.
Unfortunately determining the thetas from these equations can be somewhat tricky, and sometimes, depending on how crazy your robot configuration is, there is no solvable answer using this approach.
If you have a three or four DoF robot (not including the end effector), and not doing anything too crazy, you should be able to solve for it using some high level algebra.
In order to help you further with the inverse kinematics, you will either need to provide the forward kinematic equations, or show what configuration you plan on having the servos in; but hopefully this was enough to push you in the right direction.
Comment: hey Mr Austin, i really got confused many videos on youtube explain inverse kinematics that i should know x y z to get the angles not the opposite...as you said peter corke's book was full of details and i found it so hard if you can nominate a book that explain how can calculate the inverse kinematics equation in a simple way that will be great.
Comment: I have edited my answer to explain things better. Please re-read all of it as I have made corrections and clarifications in what I was saying earlier.
Comment: That's awesome, I'd love to see it. You should put it on YouTube.
Answer: What you need is a set of equations that gives you the joint parameters of your robot as a function of the desired end-effector position. For this, you need to compute the inverse kinematics of your robot. Depending on how complex your robotic arm is, deriving those equations might be tricky and multiple solutions (or poses) can be possible. This page explains how to use the inverse Jacobian Matrix method to derive the inverse kinematics.
Comment: i read the page and i couldn't understand why we consider the velocity can you explain it please?

how to manipulate arm robot?


Is there a "recent visited folders" in Windows Explorer?

Question: In Windows Explorer is there any way I can have a "recent visited folders" features somehow?
Answer: This function is contained in widows Explorer itself, Just right Click on the Windows Explorer icon on your taskbar to get it:
Answer: Is there any way I can have a "recent visited folders" features somehow?
xyplorer provides a "history" of recently visited folders, as well as many other features:

XYplorer is a tabbed file manager for Windows. It features a powerful file search, a versatile preview, a highly customizable interface, optional dual pane, and a large array of unique ways to efficiently automate frequently recurring tasks. It's fast and light, it's innovative, and it's portable.

Supported Operating Systems: Windows 10, Server 2014, 8.1, 8, Server 2012, 7, Server 2008, Vista, XP, Server 2003, 2000, NT, Me, 98;
  32-bit and 64-bit versions.
XYplorer is a Portable File Manager. It doesn't require any installation or changes to your system or registry. Take it with you
  and start it from a USB stick, along with your personal configuration.
  File management to go.

There is a freeware version.

Disclaimer
I am not affiliated with xyplorer in any way, I am just an end user of the software.
Answer: There is a free application, RecentFilesView, though it shows files rather than folders, and only those opened through Windows Explorer or from a standard open/save dialog-box.
*If you wish to instrument specific folders, there's also FolderChangesView, which, I believe, utilizes a standard Windows API call to set up a callback on any change to a folder (a handy feature I've used to respond to FTP file delivery).
Apparently Windows 7 and later have a folder, C:\Users*UserName\AppData\Roaming\Microsoft\Windows\Recent Items*, but I find it is unpopulated, perhaps due to options I've selected.


Expanding paths and shapes is making strange shapes in the background CS6

Question:
When expanding a path or shape I get weird "ghost shapes" in the background i can't select these and they seam to have some relation to the bounding box? how do i stop this ?
Comment: Please provide screenshot of artwork in Preview mode. Looks like you have effects applied to your shape. i.e. drop shadow. Could be a clipped image, could be many things, but question is: what do you want to achieve and why wouldn't it be the expected result of Expanding?
Comment: It would appear that perhaps you have a clipping mask with some raster images being masked. What's it look like in preview mode?
Answer: Hard to be 100% sure without seeing the actual artwork and I don't have access to CS6 any more, but...
This is usually a result of Illustrator trying to expand the fill of the shape, turning it into an image and then using the original shape as a clipping mask for that image. If this is the case then you will have a load of embedded images added to your links palette. You can use the links palette to find and remove these images by selecting them one at a time and clicking the 'go to link' button at the bottom of the palette and then hitting delete...

Alternatively, you can select all of the affected shapes and go to Object > Clipping Mask > Release. This will get all of the images out of the paths so that you can select and delete them.
In theory, you should be able to direct select these images in Outline View, but maybe that functionality wasn't quite right in CS6.


What is the impact Facebook Questions is going to have on Stack Overflow and Stack Exchange?

Question: Is there any concern about Facebook Questions copying and taking flow away from Stack Overflow and Stack Exchange?
Comment: [Just a comment](http://imgur.com/Kunwq.png), as I have "skin in the game" so to speak and can't be trusted as unbiased.  :)
Comment: @Kevin well, which one is it? The Viking or the Samurai? What if the Samurai were supported by a Transformer, and the Viking by a Ninja Turtle?
Comment: @Piskvor: `[insert coin]`
Comment: Didn't this go live a while ago? I remember a similar question a few weeks ago
Comment: @michael they pulled it for re-tooling but this second time might be the "real" one
Comment: *[pulls out crystal ball]* Should work now, but I have to hand-crank it. *[pulls out hand crank, inserts into crystal ball, starts cranking]* C'mon... *[crystal ball starts up, crank starts spinning uncontrollably]* Whoa! *[crystal ball envelopes Piskvor in a cloud of smoke and grinds to a halt]*. Chm. Looks like I'll have to pester the manufacturer again. We'll just have to wait and see for ourselves. (sorry, couldn't resist)
Answer: There are a few reasons I'm not worried:

facebook is banned in many workplaces
it's completely unfocused, which has been the downfall of many Q&A sites
They'll never turn over as much control to users as SE sites do.  Plenty of other sites allow voting, but you only have to look at Yahoo! Answers to see that's not enough

If we're really lucky, maybe they'll steal the people who post GIVE ME TEH CODEZ questions with no context and don't search at all before asking.
Comment: +1 But ... GIVE ME TEH CODEZ :)
Comment: @Hoàng Long: the point is that Facebook most probably won't bother overcoming these points. They are not in the business of really caring about the quality of questions and answers; they are in the business of binding users to their site by adding yet another kinda-fun-yet-ultimately-useless tool to their awfully huge collection of just such gimmicks.
Comment: I really wanted to answer this question, but you covered it all. +1
Comment: Well, I agree with your comment (especially 2 & 3), but I think all of your points can be overcome by FB question itself.
Comment: I would never leave SO and ask questions on facebook as there are lot of distractions on Facebook. Plus I love SO.


Ubuntu 18.10 does not seem to find my MX150

Question: I currently have Ubuntu 18.10 on my Acer Swift 3 and no matter what I do I can't seem to make it recognize my MX150. If I try to install NVIDIA versions for that it says it doesn't exist, any ideas why? I am not sure what I should post but I will when I do.
Comment: Take a look in the BIOS aka UEFI to see if it's enabled.
Comment: @spacelander There is no option on the UEFI for any cards. On the advanced tab there is only "Intel VTX", "Intel VTD" and "SATA Configuration".
Answer: Have you tried installing nvidia-driver-430 driver from Graphic Drivers PPA? You can then switch between Intel graphic card or MX 150 using Nvidia X Server Settings.
These commands may be helpful:
$ sudo add-apt-repository ppa:graphics-drivers/ppa
$ sudo apt update
$ sudo apt install nvidia-driver-430 nvidia-settings nvidia-prime

You can then run NVIDIA X Server Settings to switch between Inter or Nvidia graphic cards.
PS: I use Ubuntu 18.04.3 on my Acer Swift 3 with MX 250 (the same model with yours, but with higher graphic card), and I can switch between my MX 250 or Intel graphic card.


Close window with middle mouse button in Expose

Question: How can I configure Expose to enable closing of Windows with the middle mouse button, like it is possible in Compiz/Scale Plugin on Linux?
Answer: You can use BetterTouchTool.

Add a new button in Global for Normal Mice.
Set Middle Mouse Button.
Choose Predefined Action: 'Close Window Below Cursor (Works in Mission Control)'.
Comment: I'm sorry, I've recently tried this solution and, unfortunatelly for me, what it does is simply close the window on a mouse middle click independently from being or not in the Expose's Mission Control view. In example: when I middle click on a link in Chrome, it closes the whole window instead of opening the link in a new tab. Seems that the "Works in Mission Control" label is not that true... :(


Creating Report using field installed by Application

Question: I'm trying to Report off a field that was installed by a 3rd party application but it doesn't appear in the list of fields in Reports. There are two other custom fields apart from the 3rd party application's fields that do appear, but the one that I need does not. Any ideas on how I can make it appear? I've already checked the field level security for the field and it is indeed enabled to be viewed by my user profile.
Answer: You probably need to add the fields to the custom report type. See: Why are some expected fields not visible when creating a Custom Report Type?
Comment: I've followed the steps and added it but when I actually try to create the report, I don't see the field listed.
Comment: You are sure that you saved after editing the report type field layout?
And that you created a report of the same report type that you edited?
And you tried using the search box to find the field, instead of just eye balling it?
Sorry for all the questions, just not sure what the problem could be from what you have said.
Comment: I am sure that it's being saved and I'm using the search box to look for the field. No issues about the questions, these checkpoints are more than welcome.


prove that language is not free context

Question: $F=\{\,a^ib^j\mid i=kj\text{   for some $k>0$}\,\}$
Prove that this language is not context free.
The only thing that comes to my mind is pumping lemma; Let $p$  be the  pumping length. Given $s=a^{pk}b^p =uvxyz$ for some positive $k$.
When $v$ or $y$ contains simultaneously $a$ and $b$ then $uv^2xy^2z\notin F$.  But I have a problem now. How to continue ?
Comment: Sorry, I made a mistake. I edited
Answer: Hint: Show that $v$ is a string of all $a$ and $y$ is a string of all $b$ (Why?). Then show that the ratio of number of $a$ to number of $b$ in the strings being pumped is precisely the ratio of the length of $v$ to the length of $y$. So this is the only positive $k$ you are able to capture in your language, so you cannot have all $k$ being satisfied in your language.
Comment: I posted below,
Answer: By the pumping lemma, $a^{2p+2}b^{p+1}=uvw$ with $|uv|\le p$ and $|v|>0$ such that $uv^iw\in F$ for all $i\ge 0$. Clearly $v=a^r$ or $v=b^r$ for some $0<r\le p$ as otherwise $uvvw\notin F$. If $v=b^r$, then for $i$ large enough $uv^iw=a^{2p+2}b^{p+1+ri}\notin F$. If $v=a^r$, then $uw=a^{2p+2-r}b^{p+1}\notin F$
Comment: You showed that it is irregular, but question was about context free
Answer: I try use @user2566092 hint:

Show that $v$ is a string of all $a$ and $y$ is a string of all $b$
  (Why?)

I explained in my first post that there is no possibility that $v$ or $y$ contains simultaneoulsy $a$ and $b$. So let's suppose that $v$ and $y$ contains only $a$.  Then it must be that $|y|+|v|=p$. So let's consider $k=1$ now, $w=a^pb^p\in F$. If we pump down it then $a^0b^p=b^p\notin F$. The situation when $v$ and $y$ contains only $b$ is symetric. Last case is $v$ contains only $a$ and $y$ contains only $b$, as you demand.
I don't agree to the fact that $v$ is string of all $a$ and $y$ is string of all $b$. After all, there is constraint that $|v|+|y|\le p$, but $|v|+|y| = pk+p > p $

prove that language is not free context


QGIS - How to render QgsMapCanvas on QApplication's main window

Question: I am working with C++, QT 5.11.3, Visual Studio 2015 and QGIS 3.7
I'm trying to develop QT c++ application that uses the qgis api. I want to display simple raster and vector map in my qt application.
I create QgsVectorLayer and QgsRasterLayer that added to the QgsProject instance and then QgsMapCanvas object. That is no problem so far.
But when i turn the visible property of QgsMapCanvas object, the application crash. The error message and the crash window is above.

QCoreApplication::sendEvent: "Cannot send events to objects owned by a different thread. Current thread ... Reciever (of type 'QGSMapCanvas') ...

I try to this process at different qt thread or main thread no matter what, does not help.
What can i do wrong?
Answer: Use the following code in the constructor of your main window:
this->setCentralWidget(canvas)

where canvas is the name of your map canvas. This will replace the central area of your main window with the canvas.


Error: No such device and Error: unknown file system

Question: I was installing Lubuntu on an external flash drive (not wise) and then when I go to boot back up on Ubuntu this pops up.
Comment: I assume that Ubuntu was installed on your main hard disk. If so, you accidentally built Lubuntu on your hard disk, not the flash drive.
Comment: I don't fully understand what you did; you tried to install Lubuntu onto a flash drive (I don't see a problem there), but your chosen grub device (grub stage 0 is the MBR of what your system boots) now points to a UUID of 6fa7d... that is no longer connected (ie. pointing to the /boot/grub/ on a disconnected device; your flash drive possibly?). If you have Ubuntu installed; you need to have it point to the always-connected hdd/sdd (and had Lubuntu's grub written to thumb-drive), but I won't give further advice as I'm guessing at what you did, clarification may help.
Comment: I hope this clarifies some things:    I was trying to restore an old pc by making it boot into Lubuntu which is installed on a flash drive(#1). I said that is not wise because it is extremely slow to boot and do basic task. I had a live Lubuntu flashdrive(#2) lying around and decided to put it to use by installing it to previously mentioned flashdrive(#1). I was doing this all while my ubuntu drive is plugged in. When I took out flashdrives(#1 & 2) and tried to boot back into Ubuntu I recieved the message on the picture. Hopefully this makes sense. Do you think I installed Lubuntu over my hdd?
Answer: Like @guiverc suggests, it looks like you accidentially installed the thumbdrive's bootloader onto your harddisk.
Does your PC boot Lubuntu when you reconnect flashdrive#1 (the one you installed Lubuntu to) but set your BIOS to boot from your ubuntu-harddisk?
If yes, remove your Lubuntu-Drive again and reboot to the error message. From there you can use this guide:
https://linuxhint.com/grub_rescue_ubuntu_1804/
to restore Grub into booting Ubuntu. It explains how to use the grub cli to find your original Ubuntu-installation, boot into it manually and reinstall grub.


Why does my Aprilaire 560 make clicking noises before starting?

Question: My Aprilaire 560 humidifier will do a bang click many times before it turns the blower on. I  replaced the solenoid valve with a new factory part and it still does the same thing. What next?
Answer: If the 550 is like the 560, they use the furnace's blower and don't have a built-in fan.  In a typical setup (at least for the 550), when the furnace is generating heat, the furnace supplies voltage to the humidifier, which may activate if the relative humidity is lower than the setting on your humidistat.
You should be able to feel the solenoid click when it activates.  You can test this, with the furnace producing heat, by turning the humidistat up and down.  If you get the click, but no water comes out in your 560, and you're sure your water valve is on, it might be a clogged emitter.  They have a tiny pinhole that slows down city water pressure.  Mine is in the water line between the solenoid and the Aprilaire unit.  You can buy new or some people clean them out with a pin.


Recessed lighting malfunctioning

Question: My home is 1.5 years old.  After a thunder storm, 9 of 13 recessed lights are not functioning properly.  3 are out completely.  The others continue to dim until barely lit.  They are in 4 different rooms.  None are on dimmers.  The television & a remote on my recliner were also blown; which I have replaced.  Please help
Comment: Sounds like lighting caused a power surge in your wires.  Guessing problem lights are LEDs or CFLs and same happen to them as your TV.  Will need replacement.  If thunder storms are common in your area suggest whole house power surge protector or at least surge protectors(not power bars) for electronic equipment(TVs, computers)
Comment: Have you tried replacing the bulbs in the fixtures not working?
Comment: They are hard wired & appears that the entire unit must be replaced?
Comment: I agree with crip659 the driver circuit was probably damaged with the same power surge that damaged the TV & recliner you might have insurance coverage I would check. The only way to reduce the possibility of this happening again would be to install a whole house surge protector.
Comment: ...and whole house surge protectors have become common and inexpensive, since they are required under new codes, so more get made and the volume brings the prices down.
Comment: Wondering if anything else is damaged, being a newer house would think most major appliances will have mainly electronics controlling them and damage not noticed yet.
Comment: Agree with other's comments here, the LED drivers probably all blew out.  I had a major power surge at my cabin and found that EVERY GFCI outlet was fried and half the breakers were tripped in the main panel. I don't have a whole house protector, but even though we seldom have serious lightning storms here, I'm seriously considering installing one.
Answer: They need replacing
From the sounds of things, these are LED recessed fixtures with integral drivers.  Unfortunately, that means that if a power surge kills them, its off to get them replaced, unless somebody around's up for light fixture surgery that is.  The good news is that it's not terribly hard to find replacement fixtures as recessed lights have settled on a few "de facto" standard sizes for some time now.

Recessed lighting malfunctioning


How do I install physical copy of World of Warcraft without an optical disc drive?

Question: I bought a WoW Legion DVD online but just realised my PC doesn't have a DVD reader. Does this come with a game key to install online or do I have to use the disc?
Comment: @xDaizu Why does it sound silly, WOW only requires a "low latency connecting greater then 28.8k"  The important part is the low latency not the amount of data that is transferred. Actually playing the game is "Very low data usage." Many people play from a cell phone on 3G networks. https://eu.battle.net/forums/en/wow/topic/5848175614#post-8 But you certainly would not want to install that way. The point is playing wow only takes a small chunk of data compared to installing wow.
Comment: There are many reasons that DVDs are preferable to internet downloads. Obviously not for this poster, but for many the DVD is a better option. Specially in rural areas or places where ISPs charge for data transferred.
Comment: ...do people really still use these gift plastic scare-birds to install software?
Comment: @coteyr yours is a perfectly valid point and true for several edge cases, but you will admit that it sounds a bit silly when talking _precisely_ about an MMORPG :P
Comment: You've asked four low quality question in a row. I'd highly recommend taking our tour and understanding what Arqade is all about. We have a very select standard, and opinionated questions are very frowned upon. By taking our tour, you will learn how to meet those standards, and prevent the system from automatically revoking your ability to ask questions.
Answer: You can use the CD/DVD key on the official website to play the game. You don't need the CD/DVD itself in any way.
In fact, by using the CD/DVD for an MMORPG, the installation process may take you longer than simply downloading the game in the first place, because the CD/DVD likely has outdated data on it, as most online games are frequently updating themselves with new patches and expansions that you will need to end up downloading anyway.
In the current year of 2017, you can also download & play the game for free without any CD/DVD Key & without even finishing the entire download of the game, but in that case you will have limitations on what you can do, including not being able to level past a certain point, and not being able to do certain quests or visit certain areas. In the future this may change and more limitations may be lifted on free accounts.
Comment: You can actually download the game without the CD key - you just need the blizzard launcher formerly known as battle net, and there's a way to start the download even if you don't own the account.
Comment: It will probably be faster, too. Even though your common DVD 16x drive reads at 21 MB/s, I somehow found it faster and more comfortable to download it even witha a low/mid range internet connection speed(10-50Mb/s). Also, you don't have to swap discs. Also, the first update will probably be way smaller :)
Comment: As an added bonus, you can start playing the game even before it's finished downloading thanks to Blizzard's streaming installation stuff.


Extending partition on Windows Server 2016

Question: On a Windows Server 2016 machine we have multiple partitions for separate segments of a website. However, more storage space is needed for one of the partitions, so I would like to transfer some space from the default C: drive to another partition (G:). Using the built in Disk Management program on Windows, I am unable to transfer the unallocated space obtained from C: to G: because the unallocated space is not to the right of G:. How would I go about extending the partition? The company policies are restrictive on installing unknown third party programs to manage the infrastructure, and I'm not able to find a free partition manager that works on Windows Server 16 anyways. I cannot use a bootable partition manager in order to minimize downtime
Answer: Doing this naively from Windows is not possible. Whatever program you use you'll end up with downtime as moving/resizing partitions is best done while no active processes accessing the disk, keep that in mind while I suggest the below.
Because you have too many restrictions in place I suggest that you use a bootable partition manager such as https://gparted.org, I know you don't want to have a downtime, but you'll face that wall whatever you do.
Comment: Totally agree with Noor. There are a lot of similar partition managers, but partition tool always helps us in such situations. https://www.partition-tool.com/easeus-partition-manager/extend-system-partition.htm
Answer: Maybe not exactly what you asked, but perhaps a solution with only native Windows Tools (and even meets your requirement on minimal downtime):
Assuming it is a directory on G that needs more space, say G:\2small

create a partition out of the unallocated space
mount this partition to a directory on G, say G:\VeryBig
now you can move data from G:\2small to G:\VeryBig
remove G\2small, rename G:\VeryBig to G:\2small

Keep in mind that only one directory gets bigger, and not the complete disk.  But it can be achieved with the Windows Disk Manager alone (or ist commandline counterpart DiskPart), and there is no need to boot to an external tool, and, if data from G:\2small is not in use, you can use this method even without reboot - that means no downtime at all.
If you like this solution, you may consider to create 2 (or even more) partions mounting each one to a Directory on drive G:.
It may be a limitation, but it may be an advantage, too, to have a capacity limit for each directory you create this way.
Answer: Yet another workaround for Windows's inability to change partition boundaries is to use a symbolic link to a folder elsewhere.
If G: is filling up but has got a few folders like e.g. data1, data2, data3, and so on you can move G:\data3 to C:\relocated\data3 and mklink /d G:\data3 C:\relocated\data3 so it reappears as G:\data3.
Not everything works this way but most things do. If this is a shared folder you must point the symlink to a share and your clients will need to be instructed to follow the symlink: https://technet.microsoft.com/en-us/library/cc754077(v=ws.10).aspx .
Of course, this is an ugly hack but it can be a quick fill-in solution.
Comment: This is exactly how our website is structured. The root of the site is in the partition, but many subfolders lead to symbolic links. In our case, we're trying to add some files to the root and running out of space
Comment: Assuming G: isn't that big then, can't you just recreate it somewhere else. Additionally, I wouldn't recommend mounting a webroot to the root of a drive.
Comment: I'm probably going to scrap the partition system all together and use the file server resource manager to create folders with scalable folder size quotas


Post ids are incrementing by an unknown number?

Question: It's really strange, but I've noticed that as I'm writing and publishing posts, the ids aren't incrementing by one, but rather by some arbitrary amount which I think is relative to the amount of times I hit preview. It's kind of annoying to have ids like 1, 11, 29, 37, etc. Is there a way to ensure that posts only increment by one?
Answer: Every revision or auto-draft that's saved is added to the database and given its own auto-incremented ID. So in theory, you could turn off post revisions ( adding the line define('WP_POST_REVISIONS', false); to your wp-config.php), and be very careful to write your posts in exactly the order you want your IDs to follow, and you'd get sequentially ordered posts. (Maybe, that is - I've never tried, and I think there may still be an autodraft created on first visiting the post-new.php screen, so it could be that the best you can do is make sure your post IDs increment by twos.)
This seems like a sure recipe for obsessive-compulsive disorder, though. A post ID is just a database key, no more or less, and it shouldn't have any special meaning to you.
If you need or want your posts to be represented by integers in some kind of logical descriptive order, there are other ways of doing that. Here's an answer I gave to another similar question that demonstrates a way of using post meta to sequentially number posts: Display post number not post ID number
Comment: that table also stores pages, attachments, and nav menu items, you couldn't use any of those things either.
Comment: @Milo - oh yeah, that's true, too. Wasn't even thinking about all of those!
Comment: Yep, it's OCD to the extreme.
Comment: I'm creating pages via command line with wp-cli
Despite this my IDs are still incrementing unexpectedly. I have not visited the backend of my site and gone in to edit any pages so I'm not sure why auto-draft or revisions would be in play here.

OCD? No. Consistency makes for script reliability. Especially when your script is editing pages based solely on their ID#


Topological photon mass and QED in (2+1)-D

Question: My question was: how to compute topological photon mass in (2+1) QED and why it comes?
Comment: Are you asking about the mass term of the form $m \, \epsilon_{abc} \, A_a \, \partial_b A_c$ ?
Comment: @Kostas , yes, I asked about it. I believe that I have understood its appearence and have write the answer
Answer: First of all, let me say why photon obtain non-zero mass and how. It comes from one-loop correction to photon propagator, which is given by simple fermionic loop:
$$\Pi_{\mu\nu}(k)\propto \int\frac{d^3p}{(2\pi)^3}\frac{\mathrm{Tr}\left[\gamma^{\mu}(\gamma\cdot p+m)\gamma^{\nu}(\gamma\cdot(p+k)+m)\right]}{(p^2-m^2+i\epsilon)((p+k)^2-m^2+i\epsilon)}.$$
Trace plays the crucial role in this expression because in (2+1), we have
$$\mathrm{Tr}(\gamma^{\mu}\gamma^{\nu}\gamma^{\lambda})=-2i\epsilon^{\mu\nu\lambda}.$$
Therefore, we can write down polarization tensor as
$$\Pi_{\mu\nu}^{S}(k)+\Pi_{\mu\nu}^A(k).$$
One can try to use dimensional regularization to deal with this integral but I conjecture that does not work: dimensional regularization is insensitive to odd divergencies. Then, in my view, the best way to compute $\Pi_{\mu\nu}(k)$ is dispersion relation. For $\Pi^{S}_{\mu\nu}(k)$, I can quickly obtain the following expression for imaganiary part (I know answer for (3+1) and the only difference is the factor $\sqrt{k^2/4-m^2}$),
$$\mathrm{Im}\,\,\Pi^{S}\propto\frac{4m^2+k^2}{\sqrt{k^2}},$$
where I denote $\Pi^S(k)=g^{\mu\nu}\Pi_{\mu\nu}^S/2$ Then, to regularize the expression for $\Pi_{\mu\nu}^S(k)$, we use the following dispersion relation:
$$\Pi(t)\propto t^2\int_{4m^2}^{\infty}\frac{ds}{s(s-t)}\mathrm{Im}\,\,\Pi^{S}(s),\quad s=k^2,$$
but this part of polarization tensor is not interesting. The same calculations for assymetric part of vacuum polarization gives very similar answer for $\Pi^A(k)$ and the most important fact is
$$\boxed{\Pi^A(0)\propto\frac{e^2}{4\pi}\frac{m}{|m|}.}$$
Therefore, technically, photon mass appears due to assymetric contribution to vacuum polarization tensor. Physically, it comes from parity anomaly and I do not find the best words, but roughly speaking it means that mass term are invariant on $P$-transformations only in even dimensions and I have emphasized it by denotation $m/|m|$.
Furthermore, Coleman & Hill showed that higher order corrections are zero for all possible matter fields and couplings to electromagnetic field. In addition, the same effect arises in every odd dimensional QED theory.
Finally, photon obtains mass without any topological terms in initial lagrangian and one can roughly say that it is an analogue of chiral anomaly existing in even dimensions.
To be honest, I did not check all the calculations and therefore I use $\propto$ instead of $=$, but intermediate derivitions are the same.
This answer is based on the following papers:

Scharf, G., et al. "Causal approach to (2+ 1)-dimensional QED." Annals of Physics 231.1 (1994): 185-208, link
Coleman, Sidney, and Brian Hill. "No more corrections to the topological mass term in QED3." Physics Letters B 159.2-3 (1985): 184-188, link


How can I turn off the notification for the power plug connection?

Question: My Samsung Galaxy S3 with Android 4.1 plays a sound every time I connect it to the power plug. Is there a way to turn that off without affecting all other notifications?
Answer: I solved the problem by doing this:

Root the phone
Install the posed Framework and Wanam Kit. Enable the Wanam Kit module after installing it.
Open Wanam Kit and go to the "Sounds" options, then go to the bottom and check "disable low battery sound"
Reboot


How to find thevenin resistance of a capacitor in an op amp circuit?

Question: for the following circuit could someone explain how to find the thevenin resistance across the capacitor? Most answers use the 10K resistance in parallel as the thevenin resistance but I don't understand why. Why do they neglect all the other branches, resistors and op amp?

Answer: If you're doing a static (DC) analysis to find the operating point of the circuit, then the capacitor acts as an open circuit. So the dc feedback resistance is in fact 10 kOhms, the resistance of the resistor in parallel.
If you're analyzing the AC behavior of the circuit, you should consider the impedance of the capacitor
$$Z_C=\frac{1}{j\omega{}C}$$
But we don't call that the Thevenin equivalent resistance of the capacitor, we call it the impedance of the capacitor.

Why do they neglect all the other branches, resistors and op amp?

Because what you're trying to find is the resistance in the feedback path. Later you'll consider how the feedback resistor works in combination with the 20 kOhm resistor and the op-amp itself to determine the closed-loop gain of the circuit.
Comment: Sorry the aim of the question was to actually find the step response voltage across the capacitor and not to find the gain. So that being said, why do they neglect all other branches, resistors and op amps?
Comment: Probably because that's the subcircuit they're actually interested in. Without more context there's no way for me to read the mind of whoever wrote whatever you read.


Why can't you form an anhydride from an ester via nucleophilic attack?

Question: The reaction referred to is the nucleophilic acyl substitution reaction, where the nucleophile is a carboxylate ion and the electrophile is the ester. I am having a difficult time visualizing why this cannot occur.
Comment: Carboxylate is a poor nucleophile, alkoxide a much better one. If the reaction occured, the alkoxide would then go on to react with the anhydride - a very much better electrophile - so the outcome would be ester plus carboxylate again.
Comment: @YUSUFHASAN I don't see how ester conformations are relevant. Even if it made a difference to the fundamental reactivity of esters vs anhydrides as Waylander explained (and it doesn't), it's not as if you could isolate two different conformations of the ester.
Comment: It may be somewhat plausible in the E conformation of the ester, but certainly not in the Z form
Answer: The reaction you are asking about is a carboxylate plus an ester reacting to form an anhydride plus an alcohol. The reverse reaction, making an ester from an alcohol and an anhydride, is one commonly performed in teaching labs.
So the equilibrium lies on the side of the ester. The principle of micro-reversibility would suggest that this reaction can go in either direction, but you would have trouble detecting formation of the anhydride and alcohol from the carboxylate and ester because of where the equilibrium lies.


Is the milk of donkey halal?

Question: Is milk of donkey halal in Islam? Can anybody list the animals with halal milk? May Allah bless you all.
Answer: The meat and milk of a wild donkey [onager] is halaal.  This is collected both by al-Bukhari and Muslim, a hadith narrated by Abu Qatadah:

That once he was with Allah's Messenger. When he had covered some of
  the way to Mecca, he and some companions of his, who were in the state
  of lhram. remained behind the Prophet while Abu Qatada himself was not
  in the state of Ihram. Abu Qatada, seeing an onager rode his horse and
  asked his companions to hand him a whip, but they refused. He then
  asked them to hand him his spear, but they refused. Then he took it
  himself and attacked the onager and killed it. Some of the Companions
  of Allah's Messenger ate of it, but some others refused to eat. When
  they met Allah's Apostle they asked him about that. He said, **"It was
  meal given to you by Allah."

 [al-Bukhari]
There's is dispute whether the meat of a domestic donkey is forbidden, since none of the reports actually verbally quote the Prophets words.  Instead, they are words of some of the companions claiming the Prophet forbade.  Ahmed bin Hanbal said 15 companions considered it as disliked, i.e. makruh, and not outright haraam.
And I think our Shia brethren believe it's makruh.

Can anybody list the animals with halal milk?

Safest route is to stick with all animals that are allowed to be eaten.  You can find the list of legal animals easily through search engine.  It'll be a long list.
Comment: I looked back into this subject, Concerning domestic donkey I didn't find any dispute because in Al-Bukhari and Moslem from Hadith Jabir Ibn Abdlah the prophet forbid eating its meat and from that the four madhaheb want to forbid its milk because it is coming from haram source. Sahib Al Ikna which is a Hanbaly imam considered it as Unclean "najas"
Answer: Saoudian chikh say that drinking it without necessity is haram because the prophet forbid in khaybar war eating donkey because it is dirty. From that they conclude that anything that came from it is Haram.
As for other milk the rule in islam is every meal is halal as long as God (or his prophet) did not forbid it. It is hard to find list of all halal milk so I suggest that every time you have doubt you ask an inchala someone help you
Comment: Yeah you are right. I will summarize as that any food obtained from haram source is haram.

Is the milk of donkey halal?


How to use DFA/NFA to prove the language {$0^n 1^$ | x ∈ Σ*, n ≥ 1} is regular?

Question: I'm trying to prove the language L = {$0^n 1^$ | x ∈ Σ*, n ≥ 1} is regular, but don't know how to present it in a DFA/NFA.
I'm thinking to have n+1 states in a NFA, with the start state as the accepting state. The NFA reada $0$s to go from q$0$ to q$n+1$, then reading $1$s or $0$s to stay in the q$n+1$, then reading the same number of $1$s to go back to the q$0$. Is this a valid way to prove L is regular?
Comment: There is no limit to $n$: the number of states of a *finite* automaton can't grow with it. (Oops - didn't see one star.)
Comment: Showing an FA with that language might convince even me that $L$ was regular.
Answer: Your language consists of all words starting with $0$ and ending with $1$.
Answer: Your solution depends on $n$. In this case the $n$ in the formulation of the language is not a constant, but a variable ranging over the positive integers $n\ge 1$. So we need strings of the form $0^n x 1^n$ for any $n\ge 1$, and any $x\in\Sigma^*$.
In general that would not be possible with a FSA, it cannot count and compare the numbers of $0$'s and $1$'s, but this is a trick question. See the answer by Yuval.
Answer: Your language is regular and can be rewritten as $$ L = {0\Sigma^*1}
$$ (start with 0 end with 1)


Org-mode beamer - How to create a short title, author, date?

Question: Is there any easy way in adding a short title, author, date, etc. in the .org file, without messing around with the generated .tex file?
Answer: My (in progress) Org Beamer refcard could help you.
See on https://github.com/fniessen/refcard-org-beamer, in particular the section "Creating a title page".
UPDATE -- Something like the following would do it?
#+BIND: org-latex-title-command "\\title{De leerplandoelstellingen}\n\\date[mei 2014]{9 mei 2014}\n\\maketitle"

(that's a way to fiddle with the title, but directly from the Org file...)
Comment: Sorry no it doesn't help! I'm looking for **short** title, author date and not the normal (=long) version
Comment: Thanks! I accepted your answer since it is at least a solution without messing around the .tex file. However, I hoped for something cleaner, like #+SHORT_TITLE, but maybe this can be defined somehow?
Comment: You could try and ask on the Org ML. However, as it'd be Beamer (or LaTeX) specific, I don't think such a thing will ever be added. But you can try.
Answer: Yes you can define #+SHORT_TITLE but it involves editing 2 elisp files. You need to find your ox.el and ox-beamer.el files, mine are located in the ~/.emacs.d/elpa/org-20150330 directory. There are also some compiled files ox.elc and ox-beamer.elc. I recommend you create a backup of all these files before continuing.
In file ox.el go to line 118 and add the short_title line as shown below:
 114│    (:section-numbers nil "num" org-export-with-section-numbers)
 115│    (:select-tags "SELECT_TAGS" nil org-export-select-tags split)
 116│    (:time-stamp-file nil "timestamp" org-export-time-stamp-file)
 117│    (:title "TITLE" nil nil space)
 118│    (:short_title "SHORT_TITLE" nil nil space) ;; Additional line
 119│    (:with-archived-trees nil "arch" org-export-with-archived-trees)
 120│    (:with-author nil "author" org-export-with-author)
 121│    (:with-clocks nil "c" org-export-with-clocks)
 122│    (:with-creator nil "creator" org-export-with-creator)

Save the file. Remove th ox.elc file (ensure you have a backup) and byte compile the file. This can be done from within emacs using M-x byte-compile-file and entering the file name, ensure it completes without error.
Then open file ox-beamer.el and make the following changes.
 860│     ;; 7. Title
 861│     (let ((short_title (plist-get info :short_title)))
 862│       (format "\\title[%s]{%s}\n" short_title title))

Save, remove the old ox-beamer.elc and byte compile. Restart emacs and you can now use #+SHORT_TITLE: as you wish.
Your line numbers may be different but I've included the surrounding code so you should be able to find/replace easily.
Answer: I use this to achieve the same effect:
#+TITLE: Short title
#+BEAMER_HEADER: \subtitle{long title}

This requires that you make the two titles play well together, so it does not look silly.
Credit: Learnt about the BEAMER_HEADER thing from https://github.com/fniessen/refcard-org-beamer
Answer: I understand this is an old question. I got here while searching for a solution to the same problem. And I thought others in the same boat may benefit from a cleaner solution.
Including the following before/after #+TITLE: should do the job:
#+BEAMER_HEADER: \title[short title]{long title}

Note that it replaces whatever you set in the #TITLE: line. Of course, I'm not sure if this was a possibility at the time OP asked the question.


when is てます used over ています if you are supposed to be talking "polite"

Question: I understand that てる and てます are basically shortened versions of ている and ています, but if you are supposed talking "formally"/"polite" why would you use a shortened version?
Comment: You probably don't avoid the words 'don't' or 'can't' talking to bosses, teacher etc. I imagine?
Comment: Politeness and formality are not the same concept, though they may overlap. It's not strange to speak informally in a polite way.
Comment: when would you speak like this before talking informally/short form
Answer: てる and てます are very common and safe in ordinary workplaces when you are speaking Japanese. You can even combine it with honorific verbs and say something like 見てらっしゃいます. But they are generally avoided when you are writing something formally. Also, when you are giving a formal speech with a microphone in front of dozens of people, it's safer to avoid this contraction even if it's spoken.
In general, you cannot explain an expression's register using a single axis. We need to use different adjectives that are related but different, such as "honorific", "polite", "written", "formal", "stilted" and "pompous". If I have to choose a single adjective to describe てる/てます, I would choose "colloquial", which is related to but not exactly the same as "informal".


Spotlight taking a lot of power on macOS

Question: I recently installed macOS, but I have noticed that "Spotlight.app" has had high CPU usage. It is not indexing.
Answer: The Average Energy Impact column in Activity Monitor takes past energy usage into account. For example for me it shows 23,87 for Time Machine even though it is not backing up at the moment.
Apparently Spotlight has been very active but has now finished indexing.


The onion link cannot be accessed

Question: I can't access onion links that I could access before. I tried using another computer and they still work. When I try to log in I get the error Details: 0xF0 — The requested onion service descriptor can't be found on the hashring and therefore the service is not reachable by the client.
Has anyone had this error before and been able to fix it?
Thank you
Comment: Are you sure you're trying the exact same onion address on both computers? You're trying both computers at the same time? And one computer always works and the other doesn't?
Answer: Looks like your other PC with Tor can not bootstrap properly or suffers censorship while working. Attach your logs for more detailed help - but even with the data you've provided - try pre-seeding the faulty computer via another working Internet channel, like mobile 4G: the traffic will not be the issue, wait until it will bootstrap to 100% and try reaching your onion then. If it works - you can swap back your connection and it will use the actual consensus. Also - consider using your working PC as a private bridge for a non-working one, it helps sometimes

The onion link cannot be accessed


Add horizon line and grid lines to render image

Question: Can anyone tell me how to make grid lines and a horizon line show when I render from Blender?  I am running version 2.82 and I can find no toggle for these.  I do NOT have any drop down that says "Overlays".  In the top right corner I have something that says "Options."  I am new to Blender.  I have been trying to change the background color and toggle grid lines and a horizon line on for about 5 days with no luck.  Any help would be appreciated.
Comment: Maybe show us  a capture  of your 3D view? (reduce the size of the window to give a reasonable size image, but not so far as to conceal any headers you _do_ have)
Answer: The feature you are looking for does not exist, The laziest solution would be to just create a plane and sub-divde it a few times and apply a wireframe modifier.
Answer: I dont know how to enable them for normal render like you say but there are ways to get around it. Like you can recreate them as 3d models. (edges with wireframe modifier)
Or you can render viewport it self from top left just by clicking: view and then sellect you viewport render preference.


fetch specific title in every page with nutch and solr

Question: I have solr and nutch installed and my web page structure is that in every page the title is the same; e.g. Bank Something; but in every page there is a tag with an ID of TITLE, something like:

my page specific title

I want to add another field to solr like second Title that fetch my page specific title and search words in it.(indeed now my page specific title is in content field and i want to have this in other field)
How can I do this?!
Answer: Check Nutch Plugin which should allow you to extarct an element from a web page.


Is it possible to direct mount an EXT4 disk with data on it to a XenServer guest vm?

Question: I have a few ext4 disks (3GB each) with data on them (almost full).  And I would like to mount them on a Xenserver, and have them mounted directly to an Ubuntu guest vm.  Is this possible? (and easy.  I am a newbie with Xenserver).  I am trying to convert a fileserver to a xenserver but still serve files (ie: one of the vm will be a fileserver).  Thanks in advance!
Answer: I too have looked into this. I believe it is possible although I'm more curious about the stability of it.
Some reading/instructions:http://techblog.conglomer.net/sata-direct-local-disk-access-on-xenserver/
http://knowledgelayer.softlayer.com/procedure/add-hard-drive-citrix-xenserver
Might want to look at second link first as it explains how to add the hard drive to the host first, then the first link explains how to attach to a VM.
I haven't tried this yet. Am in the process of switching my file server around to create a viable XenServer so I can practice with spare hdds. Since you are a newbie with Xenserver like myself, I suggest you do the same :)
Hope this helps you, if not points you in the right direction. Let me know how you get on anyway.
Regards
Jono
Comment: Thanks Jono! I have read link #2 before and actually have done adding drive successfully.  But link #1 is good, adding as removable drive, interesting, never will thought of that.  Agree with you also regarding stability.  I guess time will tell ;-)  Thanks again!!!


What is Panoptic Segmentation?

Question: In computer vision what is Panoptic Segmentation about? How it relates to Semantic Segmentation? and how it compares to Instance Segmentation?
Answer: Panoptic Segmentation (PS) is a computer vision (CV) task that aims at unifying both semantic and instance segmentation.

Semantic segmentation: each pixel is labeled with a category ($C$ in total), obtaining a dense prediction over an image. The output image has the same resolution of the original one, but only contains the predicted categories of each pixel. If we consider a specific category $c$ in the output image, we obtain the segmentation mask that ideally corresponds to the area that all the objects belonging to category $c$ occupy. Usually, the categories $C$ depict stuff objects: amorphous regions of same texture and/or material, like the roads and walls. Popular dataset are the PASCAL-VOC2, COCO, ADE20k, and CityScapes. Segmentation models are evaluated with a generalized IoU measure over segmentation masks. Differently from object detection, since there is no overlap among pixels there is no need to apply non-maximum suppression to reject multiple predictions. Common neural network architectures are the FCNs, U-Net, and DeepLab based ones.
Instance segmentation: is about separating different categories at the pixel level into different instances of the same class. Compared to object detection, instance segmentation provides an accurate segmentation of the object (instead of a rectangular region) that localizes it in the space. Each detected instance of the same category is assigned an ID. Mask-RCNN is a notable approach that builds on the Faster R-CNN object detection model, adding a segmentation branch in the per-region network that predicts the mask of the instance. Turns out that this method can be extended to pose estimation. Instance segmentation cares about detecting things objects, like cars, and people.

Panoptic Segmentation
Panoptic Segmentation unifies stuff and things categories with instances as well. The categories are divided into two classes: stuff (uncountable and/or amorphous objects, like the sky, walls, and road), and things (countable objects, like cars and people). Moreover, ambiguous or out-of-class pixels are assigned a special void label, also each pixel predicted as thing is assigned an instance ID. The Panoptic FPN builds on Mask R-CNN: it uses two FCNs to predict stuff and things pixels, while a mask FCN predicts the segmentation mask as well. It builds on the idea of Feature Pyramid Network (FPN) - introduced in Faster R-CNN - that rescales and merges extracted features at multiple levels (resolutions), to provide enough information for the semantic segmentation predictions.
Panoptic segmentation predictions are evaluated using a single unified metric the Panoptic Quality (PQ), that involves two steps:

Segment matching: finds the predicted segmentations that match with the ground-truth (GT). A match occurs only if the IoU between the prediction and the GT is above 0.5, having each GT at most one associated segmentation.
PQ computation: each match is split into true positives (TP), false positives (FP), and false negatives (FN) used in the following formula that is not evaluated for void pixels
$$PQ = \frac{\sum_{(p,g)\in TP}IoU(p,g)}{|TP|+\frac12|FP|+\frac12|FN|}$$

To train a panoptic segmentation model is possibile to reuse the dataset that provide both semantic and instance segmentation annotations, like: Cityscapes, ADE20k, and Mapillary Vistas.
Comment: Are you sure that this Panoptic FPN introduces the idea of "Feature Pyramid Network"? Wasn't this already present in some previous model? It's been many months since I've done anything related to computer vision but I remember these FPNs and they were not introduced, as far as I remember, with this Panoptic FPN (because I don't remember this Panoptic FPN).
Comment: @nbro You're totally right, thanks for pointing that out! FPN were first introduced in Faster R-CNN. The Panoptic FPN "reuses" that concept. I'll edit that and provide the reference to faster r-cnn, thanks again.

What is Panoptic Segmentation?


How can 「うん」 be used to mean both "yes" and "no?"

Question: I was told by my Japanese teacher that 「うん」 can be used as a casual way to say "yes" as well as "no." If this is true, how can you tell the difference, absent any additional information?
Answer: It's possible that your teacher was talking about how to respond to negative questions in Japanese. This is a good explanation for that.
In this case, though, I think your teacher was talking about うん vs ううん.
A straightforward うん with a falling intonation means yes. A lengthened ううん, often with high, then lower, then middle pitch can be used to express doubt, denial or disagreement (it may be helpful to ask your teacher to demonstrate).
As oldergod says, this is often used when answering a negative-question, but it doesn't have to be used this way. In my friend's copy of Genki I have seen something like:

A: 子供の時、元気だった?
  B: うん、元気だった / ううん、元気じゃなかった
Comment: On a side note, I really need to go through Genki myself. I've been stuck with some pretty awful textbooks in my Japanese classes so far!
Comment: I know this is old, but I've just seen "う…ん" in a book I'm reading in response to a positive question - is that yes or no?
Judging by the context it means no, but it looks halfway between うん and ううん :)
Comment: @user3379824 not something I've seen before and difficult to say without context but I guess it's conveying uncertainty?
Answer: By default, it means yes/correct.
But regardless of the question form: negative or positive, the うん confirms it. ううん denies it.
In English, I am not sure but I don't think you would say "No, I am going" after being asked "Aren't you going to school today ?". But in Japanese, ううん would be used.


Android ndk kernel module compile in windows

Question: i would like to compile android lkm. my compile environment is windows. i saw many other tips for compile in linux, but no tips for windows. how could i set android.mk files ?
<code>KERNELDIR = /lib/modules/$(shell    uname   -r)/build

obj-m   := sample.o

KDIR    :=  /lib/modules/$(shell    uname   -r)/build
PWD :=  $(shell pwd)

default:
    $(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules

clean:
    rm  -rf *.ko
    rm  -rf *.mod.*
    rm  -rf .*.cmd
    rm  -rf *.o
    rm  -rf .tmp_versions
</code>
Comment: Get Linux / Cygwin, http://stackoverflow.com/a/6561884/995891
Answer: They say you only can build Android source code under Linux http://source.android.com/source/initializing.html
If you went as far as recompiling the android source it would be better to have Linux
I wouldn't recommend using Cygwin, you can surely use Oracle VM Box but then why do you need Windows anyway
Answer: In order to compile LKM, you need:

Linux environment (necessary, I recommend you to at least have Linux
in a VirtualBox)
Android's linux kernel source code (same version
with your target ROM or else later on you will have problem with
Version Magic). In my case, I got HTC Nexus one with CyanogenMod
7.2, so my kernel is 126.96.36.199-cyanogenmod
A GCC that was used with your kernel source code. In my case, it is Sourcery Mentor's GCC

You can check my previous question here
Unable to compile LKM for Android
I provided steps and procedures to compile the LKM