What does the 'unscented' in 'unscented transform' mean?

Question: Usually I find that if I understand the etymology, I better understand the algorithm is doing/trying to convey. I've never found where the name for this transform comes from.
Comment: I knew nothing about this but I looked it up on wikipedia.  It has to do with the extended Kalman filter which linearizes a nonlinear function.  Jeffrey Uhlmann coined the term in his PhD thesis in the 1990s.  Wikipedia describes how he came up with the term,and provides a motivating example. It helps if you know something about Kalman filters as the article is largely technical..
Answer: The Wikipedia page for Unscented transform links to an interview with its creator Jeffrey Uhlmann, which includes the following explanation:

What's with the Name "Unscented"?
Initially I only referred to it as the "new filter." Needing a more specific name, people in my lab began referring to it as the "Uhlmann filter," which obviously isn't a name that I could use, so I had to come up with an official term. One evening everyone else in the lab was at the Royal Opera House, and as I was working I noticed someone's deodorant on a desk. The word "unscented" caught my eye as the perfect technical term. At first people in the lab thought it was absurd—which is okay because absurdity is my guiding principle—and that it wouldn't catch on. My claim was that people simply accept technical terms as technical terms: for example, does anyone think about why a tree is called a tree?

Sorry if this is anticlimactic!
The interview also says:

What's the appeal of the Unscented Transform?
What was most striking to people about the UT was not the accuracy so much as the ease with which it could be implemented. There was no longer a need to derive a linearized approximation which would then have to be coded up for use in the filter.

So it may be that he associated the alternative with "code smell"?
Comment: I like the comparison to the 'code smell' of the EKF. I'll definitely remember that now!
Comment: I read some of this also without following the link to the interview.  It is difficult to see whether or not this helps the OP without knowing his background.  I worked with Kalman Filters when I was working on orbit determination problems in the Aerospace industry.  I have also seen them used in time series analysis. The interview is interesting but why is it satisfactory?


Clear screen in shell

Question: How do you clear the screen in shell?
I've seen ways like:
import os
os.system('cls')

This just opens the Windows cmd, clears the screen and closes but
I want the shell window to be cleared.
I'm using version 3.3.2 of Python.
Comment: Shell = the Python shell? Prompt `>>>`
Answer: Use the shortcut Ctrl + L.
It works for all shells, e.g., Python, Bash, MySQL, MATLAB, etc.
Comment: Unfortunately does not work on Windows including the new cmd in Windows10
Comment: When using subprocess for automation this approach do not work.
Comment: Re *"works for all shells"*: What is the assumption? For Unix-like shells?
Comment: Does it really work in MATLAB?
Answer: import os

os.system('cls')  # For Windows
os.system('clear')  # For Linux/OS X

Comment: @KyleDelaney while inefficient, it works in the shell. Also many people found this useful because that's what they were looking for.
Comment: Also, `os.system('clear')` for Mac OS X terminals (confirmed to work with the default shell, `bash`, and also for `csh`).
Comment: You can also define a function to run this, like: def cls(): os.system('cls') (hit enter twice). Then you can just type cls() to clear the screen.
Comment: The question was about how to do this in the shell.
Answer: For macOS/OS X, you can use the subprocess module and call 'cls' from the shell:
import subprocess as sp
sp.call('cls', shell=True)

To prevent '0' from showing on top of the window, replace the 2nd line with:
tmp = sp.call('cls', shell=True)

For Linux, you must replace cls command with clear
tmp = sp.call('clear', shell=True)

Comment: Try this `ctrl+L`
Comment: I am using Mac OS X, and I tried this `import subprocess as sp
sp.call('clear',shell=True)` which works, except there is a `0` at the top of the terminal window.
Comment: That works on the command line. Question was how to do it in Python.
Comment: 0 is the return value of the 'cls' command call from shell.
i edited the answer to get rid of that as well, by simply storing that value in a variable.
Comment: Thanks for the solution,  I was missing shell=True.  to prevent the 0 from showing up you can also add a semicolon to the end of the statement.

``sp.call('cls', shell=True);``
Answer: Here are some options that you can use on Windows
The first option:
import os
cls = lambda: os.system('cls')

>>> cls()

The second option:
cls = lambda: print('\n' * 100)

>>> cls()

The third option if you are in the Python REPL window:
Ctrl + L
Comment: Thanks.  Ctrl + L works fine on Windows (Anaconda Shell)
Answer: The sort of thing that you are looking for is to be found in the curses module.
I.e.,
import curses  # Get the module
stdscr = curses.initscr()  # Initialise it
stdscr.clear()  # Clear the screen

Important Note
The important thing to remember is before any exit, you need to reset the terminal to a normal mode. This can be done with the following lines:
curses.nocbreak()
stdscr.keypad(0)
curses.echo()
curses.endwin()

If you don't, you will get all sort of strange behaviour.  To ensure that this is always done, I would suggest using the atexit module. Something like:
import atexit

@atexit.register
def goodbye():
    """ Reset terminal from curses mode on exit """
    curses.nocbreak()
    if stdscr:
        stdscr.keypad(0)
    curses.echo()
    curses.endwin()

It will probably do nicely.
Comment: I'm running Mac OS X 10.7.5 and iTerm 2 for my terminal. Using Python2.7, the `stdscr = curses.initscr()` works to clear the screen, and the `stdscr.clear()` does nothing. Using Python3.4, the `stdscr = curses.initscr()` does clear the screen, but takes away the terminal's ability to process newlines. When I press enter repeatedly, it gives the following: `>>> >>> >>> >>> ` and so on. I can still type commands, but they don't show up. Also, this behavior persists even when I `exit()` Python.
AVOID USE!
Comment: Can you be more specific?
Comment: @jvriesem the curses module has been in use for a long time and has been used by a lot of people - I would suggest that you see if you can replicate the behaviour in a short, (20 lines or so), example and either post it as a stack overflow question or on the developer mailing list.
Comment: Good idea -- that's a better response than my "AVOID USE!" statement.
The first two lines of this answer were the two lines that replicate the problem for me. Do you know if there's any reason the `curses` module might have compatibility issues (Windows vs. Mac vs. Linux)? I can confirm that this issue happens on two different Mac terminals, at least. The behavior persists in BASH but not CSH. Hmm.... Do you think I should contact the curses developer, the shell developer, or just ask the SO community? Thanks again!
Comment: @jvriesem - I have updated my answer to include how to reset your terminal to standard mode once you have finished, including on any exit.
Answer: In addition to being an all-around great CLI library, click also provides a platform-agnostic clear() function:
import click
click.clear()

Answer: This function works in any OS (Unix, Linux, macOS, and Windows)
Python 2 and Python 3
import platform    # For getting the operating system name
import subprocess  # For executing a shell command

def clear_screen():
    """
    Clears the terminal screen.
    """

    # The clear command, as function of the OS
    command = "cls" if platform.system().lower()=="windows" else "clear"

    # Action
    return subprocess.call(command) == 0

In Windows, the command is cls, in unix-like systems the command is clear.
platform.system() returns the platform name. For example, 'Darwin' for macOS.
subprocess.call() performs a system call. For example, subprocess.call(['ls','-l'])
Answer: An easier way to clear a screen while in the Python shell is to use Ctrl + L though it works for the shell as well as other programs.
Answer: If you are using a Linux terminal to access Python, then Ctrl + L is the best solution to clear the screen.
Answer: I am using a class that just uses one of the above methods behind the scenes... I noticed it works on Windows and Linux... I like using it though because it's easier to type clear() instead of system('clear') or os.system('clear')
pip3 install clear-screen

from clear_screen import clear

and then when you want to clear the shell:
clear()

Answer: Using Windows 10 and pyhton3.5, I have tested many codes and nothing helped me more than this:
First define a simple function. This function will print 50 newlines; (the number 50 will depend on how many lines you can see on your screen, so you can change this number)
def cls(): print ("\n" * 50)

Then just call it as many times as you want or need:
cls()

Comment: None of the ready built command ideas worked for me. creating this, my own function of course did.
Answer: Rather than importing all of curses or shelling out just to get one control character, you can simply use (on Linux/macOS):
print(chr(27) + "[2J")

(Source: Clear terminal in Python)
Answer: Module subprocess allows you to call "cls" for Shell.
import subprocess

cls = subprocess.call('cls', shell=True)

That's as simple as I can make it.
Answer: Command + K works fine in OS X to clear the screen.
Shift + Command + K to clear only the scrollback buffer.
Answer: import curses
stdscr = curses.initscr()
stdscr.clear()

Answer:
You can use the Windows or Linux OS
import os

os.system('cls')
os.system('clear')

You can use the subprocess module
import subprocess as sp

x = sp.call('cls', shell=True)

Answer: os.system('cls') works fine when I open them. It opens in cmd style.
Answer: Here's how to make your very own cls or clear command that will work without explicitly calling any function!
We'll take advantage of the fact that the python console calls repr() to display objects on screen. This is especially useful if you have your own customized python shell (with the -i option for example) and you have a pre-loading script for it. This is what you need:
import os
class ScreenCleaner:
    def __repr__(self):
        os.system('cls')  # This actually clears the screen
        return ''  # Because that's what repr() likes

cls = ScreenCleaner()

Use clear instead of cls if you're on Linux (in both the os command and the variable name)!
Now if you just write cls or clear in the console, it will clear it! Not even cls() or clear()—just the raw variable. This is because Python will call repr(cls) to print it out, which will in turn trigger our __repr__ function.
Let's test it out:
>>> df;sag
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'df' is not defined
>>> sglknas
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'sglknas' is not defined
>>> lksnldn
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'lksnldn' is not defined
>>> cls

And the screen is clear!
To clarify, the code above needs to either be imported in the console like this
from somefile import cls

Or preloaded directly with something like:
python -i my_pre_loaded_classes.py

Answer: That's the best way:
>>>import os
>>>def cls(): os.system('cls')
>>>cls()

Comment: I don't really see how your answer improves on any of the answers already given in previous years.
Comment: he wasnt talking about improving yóur answer. He stated that your answer isn't useful, because someone else has already given the same one.
Comment: Those who need it will see. I have no need for improvement bro. thanks, bro.
Answer: For the Python IDLE 3.8.1 you can restart the Shell
CTRL + F6
On the menu Click on the Shell menu.
Then click on the Restart Shell option.

Clear screen in shell


Where is "Today" and "Yesterday" in Finder menu?

Question: A folder or place search place that contained everything I used "Today" and "Yesterday" is missing from my new Yosemite finder on the left.  Is it not possible to have this?  It was a quick easy way to recall specific things when working on a lot of different things.
Answer: They don't appear to be there by default, but you can add them back in pretty easily.

Open a Finder window
Type "today" into the search box.
It should offer you two options in a dropdown menu "Dates: today" and "Filenames - Name Matches: today". Pick the dates option.
The search should complete and the search bar should appear saying "This Mac" and the name of which ever folder the Finder window had opened. Choose "This Mac".
The search bar should also offer you a "Save" button. Click Save.
A Save panel should appear allowing you to specify a name and location for the saved search. There should also be a "Add To Sidebar" check box. Check the box.

Repeat for "Yesterday".


Gravity at the centre of the Earth

Question: At the centre of the Earth, if there is zero gravitational effect due to the Earth's mass, would the Sun's and the Moon's gravitational effect still be felt?  So does the liquid centre get pulled towards the the surface facing the Sun or Moon as the Earth rotates?
Comment: What do you mean by _"feeling gravitational effect"_? Right now I don't feel any gravitational effect by Earth. I only feel the floor pushing my legs upwards and the chair pushing the core of my body upwards and my neck pushing my head upwards etc. To illustrate this, if the chair and the floor (and everything below me for a  hundred meters) would magically disappear, I would be in free fall, where I couldn't distinguish up from down without looking or feeling the air moving relative to me. ...
Comment: Possible duplicate: [Does the Earth's core have tides?](http://physics.stackexchange.com/questions/119521/does-the-earths-core-have-tides). And related: [How much of an effect does the moon have on Earth's liquid mantle?](http://astronomy.stackexchange.com/questions/757/how-much-of-an-effect-does-the-moon-have-on-earths-liquid-mantle)
Comment: ... But there would be a small tidal force between my feet and my head, which is too tiny for me to feel but is still physically there and observable in theory. And the third possibility is that you mean that I can observe the effects of Earth's gravity on me when looking at a bigger picture. Which one of these do you mean by feeling?
Comment: I don't quite understand your question, it seems obvious to me yes, given superposition of forces.
Answer: The earth is in orbit around the sun, so the sun's gravitational pull isn't felt anywhere on the earth, because in effect we're continuously falling towards the sun.
Comment: Good answer, but I don't quite agree that the the Sun's gravitation isn't felt *anywhere* on the Earth because there is a *very* small tidal effect owing to the Earth's nonzero size. This is a pedantic point, though, because it doesn't really change the spirit of your good answer, which certainly tells the full story as far as which way the liquid would go in the OP's question.
Comment: @NeilU Actually, I've just noticed you're asking about the whole liquid core. This being a very substantial size, I retract my last comment, which applies for small bodies of liquid. I think you should probably read through the questions marked by Lemon and see whether they shed any light - I'm about to do the same!
Comment: What about the moon then , in the same way the tides are affected?
Comment: @NeilU The same principle as in SuzuHirose's answer applies - or at least approximately: the Earth is also freefalling towards the Moon. Tidal effects are owing to a body's nonzero extent in a gravitational field, such that the body straddles regions of different gravitational field and, as such, not all points on them can be freefalling at once. Therefore, internal stresses can thus arise.
Comment: It's a weird way to express it.  Isn't it true to say that we're continuously falling towards the sun *because* the sun's gravitational pull is felt everywhere on (and in) the earth?
Answer: As the gravity due to Earth is zero at the center, the mass at the center will continue moving along with the Earth's center around the sun, i.e., it will be in orbit. That is the effect of Sun's gravity.
As to the moon's effect, just like tides, the mass will suffer small fluctuations in position, if left totally free. In which case it will oscillate, and as soon as it deviates from the mean position, SHM motion due to Earth's effect will be added to it's motion.
Taking into account all the forces in the question, this is what I think of the final motion:
the object will revolve around the sun in an orbit (alongwith the Earth) and execute SHM with mean position varying due to the effect of the moon.
Answer: If Earth is really composed of concentric homogeneous spheroidal or ellipsoidal shells, then, the total Earth's gravitational field at its center is null. It is know in stellar dynamics as 1st and 2nd Newton's theorems. It is also valid for stars, spherical galaxies, or any other object with this type of mass distribution. 1st and 2nd Newton's theorem can be seen in Binney & Tremaine "Galactic Dynamics".
Sun gravitation affects Earth movement, of course. Earth acceleration is a = GM/r², where G= Gravitational constant, M= Sun Mass and r = distance Sun-Earth. all the objects on Earth feel the Sun gravitational field as well. Nevertheless, Earth different parts are pulled differently due to the tiny difference in distances between each one of these chunks and the Sun. These differences produce the Sun tidal force on Earth. Similar effect produce the Moon. The tidal acceleration is proportional to the Earth diameter D, an inverselly proportional to the distance Earth-Sun to the 3rd potence, D/R³.
Answer: INTRODUCTION
Gravity at the centre of Earth is zero because the Earth is symmetric to its axis.
SPECIFICATION
OK here is the important thing - you need to specify reference frames. That is, if you view it in the centre of Earth, then of course the gravitational force exerted by other celestial bodies cannot be felt. This is due to the Earth's centripetal motion around the Sun (and orbit fluctuation with the Moon) which balances the gravitational force between them.
EXPLANATION
If you view it from space, for example, all three celestial bodies mentioned above are attracted by each other due to Newton's Theory of Universal Gravitation. That is to say, if there exists an absolute reference frame, which allows the whole universe to be observed, any matter with positive mass will experience mutual gravitational pull, regardless of whether it is at the centre of mass or not.
CONCLUSION
Simply put, anything we know of already (positive mass) will certainly experience mutual gravitational force. However, it does not mean the iron-cobalt core of Earth will get pulled towards the celestial bodies because their convection motion and self-spin offset the forces of attraction.

Gravity at the centre of the Earth


Moving between sites using SAML

Question: I'm tasked with developing an SSO system, and was guided towards using the SAML spec. After some research I think understand the interaction between a Service Provider and an ID Provider and how a user's identity is confirmed. But what happens when I redirect the user to another Service Provider? How do I ascertain the user's identity there? Do I send his SAML assertion tokens along with the redirect request? Or does the second Service Provider need to contact the ID Provider all over again?
Answer: You actually don't have to do any of the work if you don't want to. I agree with the previous comment -- don't build a SAML library -- they exist in many shapes and forms.
Read this to start with:  https://wiki.shibboleth.net/confluence/display/SHIB2/UnderstandingShibboleth
SSO is out of the box with Shibboleth so you don't have to even monkey with trying to re-invent the wheel either.  If you want a full walk through of this, read the training material which will walk you through an entire install for the IdP and a Drupal SP:
https://spaces.internet2.edu/display/ShibInstallFest/Shibboleth+Workshop+Series+-+Linux+Identity+Provider+%28Centos+6.2%29
You will need to work out how you want to register the trust for your 'internal federation of IdP & SP' but that is a small piece of the puzzle in the grand scheme of things.
So your questions are:
But what happens when I redirect the user to another Service Provider?
Ans: the SP software will intercept the request and validate if the user is logged in. If not, redirection occurs.  If so, the SP configuration will be the gate for attributes being released (usually after the IdP releases the attributes to it).
How do I ascertain the user's identity there?
Ans:  see above.  Choose your identifier wisely.  Highly recommended to NOT use email as the identifier. TL;DR is email changes and it's a bad choice.
Do I send his SAML assertion tokens along with the redirect request?
Ans:  you don't care.  Let the Idp+SP software deal with it. Read the docs if you need to go deeper into what happens, but app folks don't need to be bothered with it.
Or does the second Service Provider need to contact the ID Provider all over again?
Ans:  The IdP is consulted to retrieve attribute information when the user has signed in properly.
The 'I'm tasked with developing an SSO system' likely needs some planning and scale considerations (e.g. technology, # of sites etc, user audience plus a number of other planning questions).  It would be healthy to nail those down :)
Answer: Ok, it has been a little while for me but I'll try. I have worked with both SimpleSAMLphp and Shibboleth implementations of SAML. SimpleSAMLphp being the easier of the two to setup demo IdPs and SPs.
Anyway, when your user visits another SP's domain that uses the same IdP that they have already authenticated to then you can either have your IdP re-authenticate them by the cookie on their machine or force them to enter their username/password again. You can also configure how long their login session lasts on the IdP.
The way you figure out their identity on the second SP is basically the same way that you would on the first SP. You can configure what user data will be sent to each SP individually, each SP can be sent the same user data or custom user data depending on the needs of that SP.
EDIT
RE: Do I send his SAML assertion tokens along with the redirect request? Or does the second Service Provider need to contact the ID Provider all over again?
I believe the SAML spec allows both. I remember that I could have the user visit the second SP's domain where the SP would then hit the IdP to get the assertion tokens or you can have the user visit the IdP first with a query string identifying the second SP and then redirect the user to the second SP along with the assertion tokens.
EDIT#2 By the way I would recommend NOT writing your own implementation of SAML unless you have a lot of time and other team members helping. Heck, last I checked Shibboleth didn't have a full implementation of the SAML spec, and they are the "SAML people." In addition, you may run into interoperability issues if you plan on supporting 3rd party SPs or IdPs if you have a custom written implementation.
Comment: RE: "Building my own implementation" I hear you. I get nervous building anything security wise. What I'm trying to do right now is to build a demo proof of concept sort of thing so that our architect can assess what to do next.
Comment: What if you call other services API? I would presume some mutually agreed token can be used to authenticate the API request?
Answer: I was looking at answers to this question and it still took a minute before something really obvious jumped out at me. If the user is already logged in at the idP then when you move from one service provider to the next, each will contact the idP and the idP will see the same cookie it left from the first time they logged in.
So if you are using SP initiated SSO then there is no extra work that needs to be done to move between SP sites. Below is some paraphrased sample code lifted from Component Space's .net SAML implementation for the idP site. Note that after you've logged in once, then when you move between SP's this code will recognize that you're already logged in and skip the if block that sends you to the login page:
<code>public class SAMLController : Controller
{
    const string ssoPendingSessionKey = "ssoPending";

    public ActionResult SSOService()
    {
        // Either an authn request has been received or login has just completed in response to a previous authn request.
        // The SSO pending session flag is false if an authn request is expected. Otherwise, it is true if
        // a login has just completed and control is being returned to this page.
        bool ssoPending = (bool?)Session[ssoPendingSessionKey] == true;

        if (!ssoPending || !User.Identity.IsAuthenticated)
        {
            string partnerSP = null;

            // Receive the authn request from the service provider (SP-initiated SSO).
            SAMLIdentityProvider.ReceiveSSO(Request, out partnerSP);

            // If the user isn't logged in at the identity provider, force the user to login.
            if (!User.Identity.IsAuthenticated)
            {
                Session[ssoPendingSessionKey] = true;
                FormsAuthentication.RedirectToLoginPage();
                return new EmptyResult();
            }
        }

        Session[ssoPendingSessionKey] = null;

        // The user is logged in at the identity provider.
        // Respond to the authn request by sending a SAML response containing a SAML assertion to the SP.
        // Use the logged in user name as the user name to send to the service provider (SP).
        // Include some user attributes.
        string userName = User.Identity.Name;

        SAMLIdentityProvider.SendSSO(Response, userName, new Dictionary<string, string>());
        return new EmptyResult();
    }

    // ... other methods such as SLO
}
</code>

Moving between sites using SAML


Getting arguments from URL

Question: How do I get arguments from the URL? in other words, what is the equivalent of the arg() function of Drupal 7 and previous versions?
Comment: I'm the maintainer for the [D7 Ported Functions for D8/9](https://www.drupal.org/project/d7d8) module, which seeks to port Drupal 7 functions into drupal 8/9 to make development easier. We have an `arg()` drop-in replacement for Drupal 8/9. It's `d7d8_arg()`.
Answer: As reported in the arg() is deprecated and will be removed change record, the Drupal 8 (procedural) equivalent of arg() is the following one.
$current_path = \Drupal::service('path.current')->getPath();
$path_args = explode('/', $current_path);

As the change record makes notice, not all the times that is the correct code to use. Depending from the context, you should use code similar to the following one.

Check if a path is for an administrative page
if (\Drupal::service('router.admin_context')->isAdminRoute()) {
  // Your code.
}

Add CSS or JavaScript conditionally, basing on the page being visited
function mymodule_page_attachments(array &$attachments) {
  if (\Drupal::routeMatch()->getRouteName() == 'my.route') {
    $attachments ['#attached']['library'][] = 'my_module/my_library'; // you'll need to define in mymodule.libraries.yml
  }
}

Load the currently viewed node
$node = \Drupal::routeMatch()->getParameter('node');

Notice that in the first and last case, in Drupal 7 you should not use arg(), but respectively path_is_admin() and menu_get_object(). The typical beginner-Drupal-developer error is using arg() also in those cases.
Answer: arg() is deprecated in drupal 8, however we can get values like arg() function does in drupal 7 & 6 by mentioned
$path = \Drupal::request()->getpathInfo();
$arg  = explode('/',$path);
print_r($arg); exit();

The output would be parameters in url except basepath or (baseurl),
Array
(
   [0] =>
   [1] => node
   [2] => add
)

Getting arguments from URL


When is the next moderator election?

Question: I was wondering when new moderators are chosen and if this information could be added to the bottom of this page.
Comment: @KorvinStarmast No, I was just wondering how and when they're chosen. The times on the election website seemed fairly random.
Comment: OK, then the answer nitsua60 gave you seems to have covered it.
Answer: There is no set timetable for elections--they come when we (the community) feel new/more moderators are necessary.
For some context, here's (roughly) how the most recent election (2017) came about.

How is the community doing?
This meta surfaced a number of concerns, including some with moderation. The existing moderators had already been discussing the need for another moderator--note that "we're having a mod election ASAP" was posted as an answer to "How is the community doing?" something like two minutes after the question was posted. The other moderation-related feedback confirmed the existing belief that an election would be beneficial, and off it went.
Do we want three moderators, or four? was discussed in relation to that upcoming election, and 4, being the second number reached, was chosen. 5 was right out.
And then the election ran as you can see detailed in the /election page. Notably meta saw the 2017 Moderator Election Q&A - Questionnaire followed by voting and the 2017 Community Moderator Election Results.

If one feels that a new election is needed a meta post to that effect would be the most likely starting place.
If one feels that a regular timetable is desirable, that's a separate case to be made. (If you're considering that I'd recommend reading Should Community Moderators be "elected for life", or have terms? and many of its linked brethren before starting that conversation. This is a well-trod topic; that is not to say that it cannot be re-examined, but rather that one should clearly demonstrate familiarity with the existing consensus if they wish to be taken seriously.)
Comment: I just want to say that this answer took me down a very informative rabbit hole of meta Q&As to the detriment of my sleeping time. Totally worth it though.
Comment: Short summary of the main reason moderators are elected for life: we have to be able to do unpopular stuff. In fact, at least half the time for most things a moderator does, the only people who notice it or know about it are probably unhappy about it, because we closed their question or removed their inappropriate content or suspended them from the site or held up a policy or etc. If we had to also be populists, ensuring everyone liked and approved of us all the time (especially going into an election cycle) it would compromise our ability to moderate — in that we couldn't do so effectively.
Comment: A point off of that ^^: our experience here tracks pretty well with the rest of the Stack as regards moderator "refresh." In 6 years as a graduated site there have been seven different moderators. So the sometimes-raised (Stack-wide) concerns about moderation teams stagnating doesn't really seem to be a practical problem here.

When is the next moderator election?


Clearing display of lcd

Question: I'm using serial communication to display the the data to my 4x20 lcd display. When I filled up all the lines of course I need to clear it. I've search over the net and found something like
    Serial.write(27);       // ESC command
Serial.print("[2J");    // clear screen command
Serial.write(27);
Serial.print("[H");     // cursor to home command
But it doesn't work. I also found a solution like Serial.println(); but that solution(cheat as they called it) will only work on serial monitor. So is there any possible solution to clear the display or delete a single character from it?
Comment: Never mind the library (it is serial communication), we/you need the documentation of that display you use.
Comment: Can you provide the link of the lcd library you are using? Is it the standard arduino library?
Comment: @alexan_e I think it is the standard library. Because I did not download any thing to successfully launching the serial commands.
Comment: @WoutervanOoijen you mean the specification of the lcd like its schematic diagram right?
Comment: No, the documentation of its serial protocol. The serial displays I know consist of the display proper, and and add-on print with a micro-controller that implements the serial protocol. The firmware of that uC determines how the display reacts to serial commands. Hence you need its documentation.
Comment: @WoutervanOoijen I only have this [E-term](http://www.e-gizmo.com/KIT/images/eterm/E-term.pdf)
Comment: That document describes the hardware only, you need a description for the protocol. You could contact the maker and ask.
Comment: @WoutervanOoijen I'll leave them a message but I think it would take 5 hours or more before they reply because its 4 am here in my country.
Answer: Summary
You can probably separate the standard parallel LCD from the serial board and use the parallel display directly.
Serial display
The E-Term looks like the display section (top board) has a 16-pin parallel 4x20 character LCD on a board which is attached by a 16-pin connector and standoffs to a parallel to serial adapter (part of bottom board).

If you have no software information on the serial-adapter command-interface, it will be very difficult to use.
Better documented displays
That vendor offers other displays which have much more documentation. Including
example Arduino sketches.
You could try these and see if your display interface uses the same or a similar system of commands (using STX and ETX characters to bracket commands within displayable data).
This may end up being a frustrating dead end.
Parallel display portion
There is a good chance the top board uses a standard 16-pin parallel controller and if so, it can be detached from the other board and can be driven using the Arduino LiquidCrystal library.
This library has many functions including ...

clear the display - clear()
position the cursor - setCursor(column, row)
move cursor to top left - home()

Since there are numerous tutorials for this and huge numbers of people using it, you may find this an easier path.
It does use six GPIO pins instead of two. You probably are not (yet) short of GPIO pins on your Arduino clone.
Note that a regular Arduino's A0-A5 (or more) pins can also be used a digital IO pins.
Arduino Megas (and similar clones) have many more GPIO pins which can also be used (so long as you load the relevant "core" into the IDE and then select the right board in the IDE)
Personally, I'd expect this to be the easiest way forward.

Example
This is an old Arduino Duemilanove - it has limited GPIO pins. However it is driving a MIDI shield which has two MIDI ports, 3 pushbuttons and 2 analog potentiometers.
I had no problems finding 6 GPIO pins (plus power and gnd) to connect up a parallel LCD. 4 data (yellow). enable (yellow) RS (blue). Your Arduino-clone has far more GPIO than this and so you shouldn't have much problem.
The mini breadboard is there to make the connections easy and to provide LCD contrast control by potentiometer.
Comment: actually my clone have 4 pins for tx and rx.pins 4-11 is filled up by my keypad, pin for GND  and AREF and pins 12 and 13. It has additionnal 10 I/O pins but I don't know if it counts as an GPIO, and 6 unused analog pins. Will there be a problem if i tap the connections of my display to the pins occupied by the keypad? BTW here is the manual of my clone [gizDuino](http://www.e-gizmo.com/KIT/images/gizDuino+/gizduino+%20hardware%20manual.pdf)
Comment: @New: see updated answer. You have at least GPIO pins 18-23 free - that is enough for a parallel LCD (with offboard contrast control)
Comment: well, I did find a quick solution in one of the answers here in the thread, but I don't think that solution can delete a single character in the display. With your answer do you think I can delete a single character in my display?
Comment: @New: See LiquidCrystal link in answer. You can overwrite any character (e.g. with space) or you can rewrite a line from buffer array. However, if you have serial working, use it.
Comment: I'll still try your solution. Coz I dont think my prof will approve it without deleting a single character. I'll ask again if I encounter any problems. I hope you'll help me again. Thanks
Answer: The only relevant info I managed to find is this discussion
According to the last comment from the owner of the board

I tried to print the ascii table from 0 to 255.
  CR, LF, BS, TAB works. other non printable characters are a no go. other characters are perfect though (well the extended characters are limited).

So I wonder if a CR+LF (carriage return, line feed) sequence has an effect of pushing the printed characters out of the screen, that is
for (int i=0; i < 4; i++)
{
  Serial.print(13);  // carriage return (CR)
  Serial.print(10);  // line feed (LF)
}

or maybe
for (int i=0; i < 4; i++)
{
  Serial.write(13);  // carriage return (CR)
  Serial.write(10);  // line feed (LF)
}

If these don't work then the alternative I see is to apply the solution that is described in the start of the linked discussion and send 40 backspace commands:
for (int i=0; i < 80; i++)
{
  Serial.print(8);  // print 40 times backspace (BS)
}

or you may need
for (int i=0; i < 80; i++)
{
  Serial.write(8);  // print 40 times backspace (BS)
}

Comment: @NewInEverything Each character you send, is received and stored in the display memory (until overwritten or deleted). When you send something using the serial command it doesn't get stored anywhere in the arduino memory.
Comment: this code works `for (int i=0; i < 40; i++)
{
  Serial.write(8);  // print 40 times backspace (BS)
}`. Thanks, but I don't it's going backwards because on the serial monitor it's going forward which means I cant delete a single character.
Comment: But why did he say it works in the discussion, he had the same board. (?) He said `(1) print "backspace" 20*4 times
(2) print line 1
(3) print line 2
(4) print line 3
(5) print line 4` By the way 20*40 =80 times so I should edit my code
Comment: but this means I'm not deleting any data thrown to the microcontroller. And if I'm right it can consume all the memory of the arduino? Am i right? and what would be the effects of having its memory full?
Answer: I don't know the answer to your specific question - but here is how this usually works.
Typically most LCD boards have an "LCD Controller" that only accepts parallel communication - the most common example would be the Hitachi HD44780.  Often for a 4 line display, there will be two controllers.  For LCDs that accepts serial communication, there is also a companion microcontroller on the LCD controller board.  This micro-controller is programmed to accept serial communication and convert it into the proper parallel commands into the LCD controller.
Long story short, I don't believe there are any "standards" and what serial commands are used to clear your display or change the cursor position is dependent on how that microcontroller has been programmed to accept those commands.  You will need to see if there is a user guide that explains the details of how to issue those commands.
Comment: actually I'm using a bit similar module. [E-term](http://www.e-gizmo.com/KIT/images/eterm/E-term.pdf)
Answer: On the Newhaven serial displays I've used, the "Clear Display" command is 0x01.
On Parallax displays, the command (called "Form Feed") is 0x0C (12 decimal).
If you have a different type of display, the command may be different again.
Comment: its a bit similar to parallax, but it has an exrta pin for **tx**. Ill try the command in parallax
Comment: so I assume that this is you command `Serial.write(12);`, or `Serial.println(12);`, `Serial.print(12);`. am I right? if it is. I still can clear the lcd.

Clearing display of lcd


Dell Inspirion 15

Question: I just ordered Dell Inspirion 15 (AMD Ryzen™ 5 5500U processor and AMD Radeon GPU). I plan to use the elementary as the only OS, as I used it from 0.4 to 5.1.7 on my old i3 laptop and it worked flawlessly and I love it :)
I wonder if anybody experienced any problem with installing/running the elementary OS on Dell Inspirion 15?
Answer: While not on a Dell machine, my Lenovo IdeaPad 5 14ALC05 uses the same CPU as yours. Right off the bat, with eOS5 I had multiple issues, mainly I was unable to change the screen brightness, and in general the system seemed to perform sub-optimally.
Instead of further investigation, I decided to install the second beta of eOS6. Thanks to the newer kernel the system was much more usable, however, Suspend/Sleep, and resume from sleep did not work.
I updated to the latest kernel (version 5.13). The laptop now manages to suspend/sleep correctly, but resuming from sleep still fails. The issue is most probably with the AMD GPU driver, there is a fairly lengthy discussion at GitLab. And there is also a post on AskUbuntu that leads to a reddit thread with some more advice.
Some report success after manually applying certain patches, others have switched to different distros in the meantime. The bottom line seems to be - the fixes will be part of Kernel 5.14. So, in about 2-3 months it should be possible to have a hassle free experience, with working suspend/sleep.
Please do report back on your experience with running eOS5/6, as I am curious if it's any better on a Dell machine. For now I am on eOS6 beta 2 - sleep does not work, neither does the fingerprint scanner (but I have to confess that I did not investigate the fingerprint scanner at all). The webcam and the microphone work fine, wifi does too.

Dell Inspirion 15


General Theory of Relativity

Question: Why is General Theory of Relativity not applicable in the singularity of Black Hole?
Answer: The singularity of a Schwarzschild black hole is not part of the manifold but instead a point in time. General Relativity deals with manifolds and thus isn't applicable in the singularity.
You can find more background here:
Is a singularity a single point?

A singularity in GR is like a piece that has been cut out of the manifold. It's not a point or point-set at all.

General Theory of Relativity


What are these insects on my Arabian Jasmine plant & how can I eradicate them?

Question: I have found these white moths (very small, winged, can fly) below the leaves of my Arabian jasmine plant, and the plant has stopped flowering and is in a poor state. There are surprisingly some white scaly patches too on the leaves, though I am not sure if these are related with the white moth. They look more like fungi to me though I might be wrong. I have tried using insecticides but they don't seem to be working, and the moths and the scales keep coming back. Can anyone please help me identify the insect/fungus and suggest a remedy?
Comment: https://en.wikipedia.org/wiki/Whitefly.
Answer: As the renowned Stephie has pointed out in the comment this is Whitefly which is a very common pest.  The scales are discarded pupae cases from the larvae.
The key in pest control is to:

remove other sources of whitefly which can reinfect the plant. Are other plants infected?  Remove them and isolate this plant from healthy ones
spray with 5ml dish soap to one liter of water, or, wipe down with a cloth soaked in the solution
repeat at five to seven day intervals so you catch the eggs as they hatch
three applications or more are likely to be needed
Comment: "renowned" - tsk! I simply didn't have time for an answer (or a duplicate search). But thanks for stepping up - have an upvote! ^_^
Comment: Does wipedown really work on a jasmine? Otherwise that answer is what I would do... @Stephie you are "The Renowned Stephie" :D
Comment: @J.Musser clarified you have to wipe w soap and water.  Tedious and time consuming but effective
Comment: @kevinsky Yes, naturally. I just meant using a small sprayer seems like it would give much better coverage, as not all plants are apt for a wipedown.
Comment: @J.Musser a wipedown will crush the eggs that will otherwise be unharmed by soap and water.  It's only the pyrethrins and perhaps neem oil that have a residual activity that will control the next hatching without more attention.  Some people don't have sprayers and have lots of time.  That method is for them.
Answer: Happened to my jasmine plant recently and it stopped flowering for a couple of months. I sprayed some alcohol on the underside of the leaves for a few days straight, trim away damaged leaves and fertilized the soil. She is flowering again almost immediately after that.


What function does 了perform in this sentence 我忘问她要电话了 ?

Question: It's a change of situation, isn't it? But what has changed? Why is 了 not used after the verb?
Answer: It is a modal particle 了 (aka 了2) that expresses "already":

我忘了問他要電話 = I forgot to ask him for (his) phone number.

我忘了問他要電話了 = I have forgotten to ask him for (his) phone number.

The first "了" indicates the completion of action "忘"; the 了 at the end indicates you have (already) done such - "問他要電話". Similarly,

我問他要電話 = I ask him for (his) phone number.

我問他要電話了 = I've asked for his phone number.

Here is a good study material - https://resources.allsetlearning.com/chinese/grammar/Uses_of_%22le%22
Answer: I found an aticle from Zhihu, which might solve your problem:
https://www.zhihu.com/question/25458789/answer/94693280

What function does 了perform in this sentence 我忘问她要电话了 ？


how to use ftp in tortoise svn checkout?

Question: I want to connect svn tortoise with FTP server which i created using FileZilla.
I am trying create a local repository in my system where others can access my FTP server to commit the files using SVN Tortoise.

enter image description here
Answer: TortoiseSVN is a Subversion client, not an FTP client. You need to use Subversion server if you want to access repositories remotely. Therefore, the question itself does not make any sense.


Selenium-dot-net-2.0rc3 with Firefox 5 - How do I run selenium server as admin?

Question: I just downloaded Selenium-dot-net-2.0rc3 and ran my tests on Firefox5. Firefox browser window opens up and goes to directed url but eventually it fails with error -OpenQA.Selenium.NoSuchElementException: Unable to locate element:
I read similar question on stackoverflow - titled " Selenium 2.0b3 and IE9/Firefox 4 " and the solution to this was to run selenium server as administrator.
I am guessing that this might be what I need as I am running tests on Windows 7.
Can anyone tell me how do I run selenium server as administrator?
Thank you.
Answer: You need to start the command prompt as adminstrator.
Do Start, search for command prompt and then right-click and click run as administrator


Latitude and longitude of fuel pumps in the uk

Question: I am after a dataset of latitude and longitude of all fuel pumps in the United Kingdom. Is there any free (or paid) resource for that?
Answer: OpenStreetMap has a lot of data relative to gas stations, including (obviously) coordinates. You can use overpass turbo to retrieve this data. In the overpass turbo interface, zoom on your zone of interest, and run the following query:
<code>[out:json][timeout:25];
// gather results
nwr["amenity"="fuel"]({{bbox}});
// print results
out geom;
</code>
Execute the query, then you'll be able to export the data in various open source formats (geoJSON, KML, etc.) for treatment in geographic information system software.
When you run your query, make sure to zoom on a sufficiently small zone, otherwise your request may time out. Also, it may be a good idea to read the OSM documentation to make sure this is really the data you're after.
If you need to convert the data to another format (csv, excel, or whatever), then this is a question you may want to ask on https://gis.stackexchange.com/ or possibly https://stackoverflow.com/, but then you should make extremely clear what is the specific result you're looking for (what variables you need, etc.). If you're able to write some programming scripts, geoJSON is a quite straightforward format to work with, so it should be pretty easy to convert the data to a format you're looking for. Otherwise, there might be online tools to do that for you, but I didn't look for it.


Can any one explain how issuer of a token can buy back the token?

Question: Can that be done by a simple token transfer to my contract's account? And, how?
Answer: I am assuming we are talking about regular ERC20 tokens that you issued through a crowdsale and contributors bought.
If that's so, the only way for you to buy the tokens back would be for the current token holders to transfer them back to you by using the token's transfer() method.
Somehow, you would have to get in touch with someone holding a balance in your token contract and have them send the tokens in exchange of ether. You'd probably want to do it through a custom smart contract as well to protect both parties while doing the exchange.
If not, you have to trust the other person that after you send them the ether they will send you the tokens or the other way around.
The other way would be to buy them back through a public exchange platform like EtherDelta if they are being publicly traded.


How to execute shell commands in android?

Question: I am trying to execute shell command through my code for adding entry in Iptables. The following is my piece of code
private void createShellCommand(String uidValue_param, String interface_param) {
    // TODO Auto-generated method stub
    StringBuilder cmdScript=new StringBuilder();
    script.append("iptables -A OUTPUT " + interface_param + "-m owner --uid-owner " + uidValue_param + "-j REJECT");
    writeIptables(cmdScript);

}

private void writeIptables(StringBuilder scriptfile) {
    // TODO Auto-generated method stub
    String cmd=scriptfile.toString();
    if(RootTools.isRootAvailable())
    {
        Process exec;
        try {
            exec = Runtime.getRuntime().exec(new String[]{"su","-c"});
            final OutputStreamWriter out = new OutputStreamWriter(exec.getOutputStream());
            out.write(cmd);

            // Terminating the "su" session
            out.write("exit\n");
            out.flush();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            Log.e("IPtables updation failed", "Iptable write failed"+e);
        }

    }
    else
    {
        Log.e("Root Access denied", "Access Denied");
    }
}

Here there are two methods i.e, createshellCommand() for building the shell command and writeIptables() for updating the iptables. But whenever I run the program logcat is displaying the following warning
"W  19913 su request rejected (0->0 /system/bin/sh)"
But I can manually add the entry through command prompt and its adding to the iptables but by using the above code its not updating. My phone is rooted and I am using android 2.3.4 with linux kernel 2.6.29. And I am using external library "Roottools" for checking the root access.
Please help me to rectify the error.
Answer: This Works:
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    execute_reboot();

}
void execute_reboot()
{
    Process reboot;
    try {
        reboot=Runtime.getRuntime().exec("su");
          DataOutputStream os =
              new DataOutputStream(reboot.getOutputStream());
            os.writeBytes("reboot\n");
            os.flush();

              os.writeBytes("exit\n");
              os.flush();

            reboot.waitFor();

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

This Code Works fine. There are couple of small mistakes in your program. Try the one i pasted. Its working charm. All the best. I kept it as simple as possible so that it is easy to understand. You can still use arrays and other stuff to fancy your coding.
And yaa the same one also works for chmod command where you need to pass more than one argument.
For this Just replace
"os.writeBytes("reboot\n");"
with
"chmod 777 /dev/video0\n"(or any other system file).
Thanks. LEt me know if there is something tat i can do.
Answer: public static void rebootNow() {
    Log.d(TAG, "Rebooting");
    try {
        @SuppressWarnings("unused")
        Process proc = Runtime.getRuntime().exec(
                new String[] { "su", "-c", "reboot" });
    } catch (Exception ex) {
        Log.d(TAG, "Rebooting failed (Terminal Error)");
    }
}

This one is a little more compact
You can add "proc.waitFor();" after the Process proc... line to get rid of the unused warning, but rebooting your device takes a few seconds time and if you want to disable some features during the few seconds in your UI-thread, I think its better to not wait for the process to end.
Answer: Trying using the iptables command (with sudo and without), rather than just clobbering the iptables config file.


Decidability of the cardinality of a set given that the Continuum Hypothesis is independent from ZFC

Question: I'm a Total Amateur (TM), please forgive me if this question makes no sense.
The Continuum Hypothesis states that there are no sets with cardinality strictly between that of the integers and the reals. It's negation says there is some set with such a property. Both possible axioms refer to the same sets, those existing under ZFC. Isn't therefore a simple corollary of the independence of the CH that there must exist sets in ZFC with an undecidable cardinality? I don't know if this sets can be described without an infinite amount of information, but they must exist. I'm guessing this is pretty trivial, but I've wondered about it. It would be interesting if there existed a set which has a finite description but with a cardinality that cannot be decided. Is there such a set? (I'm not sure if I'm using the concept "decidable" correctly, I mean something like "proving that such and such set has ANY one cardinality is impossible in ZFC") Thanks. Last minute edit: Wait, I just thought of something: isn't "the set of all sets with a cardinality strictly between that of the integers and the reals" such a set? I mean, you can't determine it's cardinality just with ZFC, it could be empty, or not, depending on adding CH or not! But is this set well defined? And what does "well defined" even mean in the context of a set whose cardinality depends on an undecidable statement? Anyway, thanks for any clarification.
Comment: What is the "undecidable cardinality"? Every set has a its own cardinality even if we don't know what the cardinality of the given set is $\aleph_1$, $\aleph_3$ or $\aleph_{39}$.
Answer: ZFC does not precisely specify the universe of sets, just describes some of its perceived properties.
Just like when you ask "is the set of numbers complete" the answer may be different depending on what you mean by "numbers". The reals are complete but the rationals are not.
The universe of sets has never been specified so precisely as to be able to deduce either CH or not CH. Different interpretations result in a different answer.
There are some interpretations (or rather models) of ZFC in which CH holds. In other models it doesn't. But you can't have a model of both, simultaneously. It is not the case that CH and its negation could simultaneously hold, or that you have sets of "undecidable cardinality", in the same model.
An analogy with Euclid's Fifth Postulate is often used. There are geometries in which the fifth postulate holds, and other geometries in which it does not. There is no single geometry in which the fifth postulate both holds and fails (well, unless the axioms imply a contradiction, which we hope is not the case). We do not know if the world has Euclidean or hyperbolic geometry (if this question makes sense at all), and we do not know if the ZFC universe satisfies CH or not (again, if this question makes sense at all, as sets are after all not physical objects).
Answer: I think the most important concept here is knowing what independence really means. If a theory (like ZFC) proves a statement, then every model of that theory must 'think' that statement is true. If a statement is independent from a theory, then there exists a model of the theory which thinks that statement is true, and there also exists a model of the theory which thinks that statement is false.
A simple example: consider the theory of linear orders. We have a language with one relation, and the theory asserts that the one relation is transitive, reflexive, antisymmetric, and total. Note that the statement "there is a smallest element" is independent of this theory: both the natural numbers and the integers with the usual 'less than' relation are models of this theory, but the natural numbers have a smallest element, while the integers do not. Yet both models contain zero (or one..depending on how you define $\mathbb{N}$)!
When you say "there must exist sets in ZFC with an undecidable cardinality," you are missing the mark. Formulas define sets that exist in models of ZFC. Different models of ZFC can interpret such set-defining formulas differently. Your idea of a "set of all sets with a cardinality strictly between that of the integers and the reals" is a great example. You are right that in a model of ZFC that also thinks CH, this formula would represent the empty set, while in another model of ZFC that does not think CH, this formula would represent a non-empty set.
Comment: I think I basically get it... so there are an infinity of mathematical objects or structures, basically an infinity of universes of set theory that comply with the sentences of ZFC. If I also assert CH, I'm restricting myself to studying a subset of the set of universes, if I assert not-CH then I'm studying another subset of this "universe of universes". In the universes of the subset ZFC+CH I can trivially prove the set I mentioned is empty, in the subset ZFC+~CH it's not empty. Same formula (the statement), diferent "object" (the set), different "universe" (the model). Is this about right?
Comment: Yes, that is about the size of it.
Comment: It's a language thing then. Some mathematical structures are too "big", in the sense that I can never have a "concise" description of them, so to speak. Any "concise" description of such a structure is too vague, it applies to at least another one, and then even if you pick one as "the" canonical structure its new description is also too vague, so there's an infinity of vague descriptions that don't quite capture any precise particular structure. In certain structures, the statement I said can be proven to be an empty set, in others it's not. Language is just not powerful enough 'cause Godel.
Comment: No. The structures are not too big, and the descriptions can be very precise (and concise). Consider the set of all even numbers. If your universe contains the integers, this is an infinite set. If your universe only contains the prime numbers, this is the set containing two.
Answer: The set in your edit is just one example of a general phenomenon: for an arbitrary sentence $\varphi$, let $X$ be the set of all $y$ such that

EITHER $y=0$ and $\varphi$ holds,
OR $y\not=y$ and $\varphi$ fails.

Then whether $X$ has cardinality 0 or 1 is completely determined by whether $\varphi$ is true or not; and of course there's nothing special about "0" or "1", here. And we can't escape this: by Godel's incompleteness theorem, for any "reasonable" set theory $T$ (for instance, ZFC+GCH) there is a $\varphi$ which is not provable or disprovable in $T$.


Basic SharePoint

Question: I want to learn SharePoint.  But I do not know how to obtain the SharePoint foundation.  I did research to find out that the SharePoint foundation comes with servers for free, but which one?  What do I buy to obtain the basic version of SharePoint?
Answer: It depends on your OS and choice. You can install SharePoint Foundation 2010  on following OS Windows Server 2008 R2, Windows Server 2008 Service Pack 2, Windows Server 2012 and on Windows 7 and SharePoint Foundation 2013 on windows Windows Server 2008 R2 SP1, Windows Server 2012, Windows Server 2012 R2.
If you have Windows OS cals(license) then you dont need extra license for the sharepoint foundation as it is covered under os. check this one: What are the licensing requirements to implement SharePoint Foundation in an extranet environment?
Answer: Here are the best link to approaching to SharePoint for newbie:
http://sharepoint-tutorial.net/
http://technet.microsoft.com/en-us/library/jj937861.aspx
http://www.goodreads.com/shelf/show/sharepoint
http://blog.pentalogic.net/2012/05/10-things-developers-should-know-about-sharepoint/
http://www.sharepointvn.net/all/
http://blog.furuknap.net/become-a-sharepoint-professional-key-questions-to-ask-part-1-discipline

Basic SharePoint


Can an administrator see screen time when I use my computer?

Question: I'm not sure if an administrator can see my screen while I use my computer, can someone provide an answer with an explanation of how they can do it? I have an administrator on my computer, but not school level security where they have things installed.
Comment: This question is missing essential context: what kind of access has the unknown administrator to your unknown system in your unknown environment? If this is a environment where monitoring software is installed (like in some companies or schools) the administrator might have sufficient access to your system which also includes seeing what's currently on your screen.
Comment: If they administer your computer, they can install what they see fit on this computer. So technically, yes. But they might be moral issue, corporate policy, or law that might prevent them from doing so.
Comment: It also doesn't even matter what kind of software may be installed if you happen to sit down at a computer that is right in front of a security camera...
Answer: An administrator can install whatever software they want on the computer. This could include screen recording software (or keyloggers, mouse movement trackers, audio recordings, camera recordings, programs that make copies of your files, software that inserts typos, and so on). There is really no limit as to what they can do regarding installing software, with or without your knowledge.
But whether or not they have actually installed such software is between you and the administrator.
Answer: Yes it is true and 99% chance that your administrator has installed some software which can have access to your screen. I remember once i used to work for a company and they used to control there users screen. They watches what they do. But again it depends on the policy of the company and entirely on the admin of the company.
Comment: "99% chance" -- this is completely overstating the likelihood. It is *possible*, but then this answer becomes no different from the earlier answer.


Eating a big meal around a weightlifting workout - before or after?

Question: When is the best time to eat a big meal when weight training - before or after the workout? Also how much time before or after is optional / beneficial?
Comment: If you type in "eating before or after exercise" in the search box you will find multiple questions and answers to give you the info you need.
Answer: before most definatedly, when you don't eat u can't lift heavy
when you eat to soon you'll probably feel bloated and not strong enough due to the increased energy it takes to process the food.
for me an hour before is the magic timing, and I also recommend eating fat meals because it gives energy for a longer time
Comment: Many articles advocate eating something before and after weightlifting. This is to maximize muscle gains and prevent the body from burning muscles for fuel. Personally, it's irrelevant when big meals are eaten as long as the body has enough energy for the exercises to be had.
Comment: very true, although I sometimes have trouble getting a appetite after a serious lifting session so that's I focus more on the time before session. Not eating after will result in minimal gains obviouly
Comment: Personally I always eat right after weight lifting, I must feed my muscle within 45mins after workout.


Run SQL Server 2016 side-by-side with older versions?

Question: Brent Ozar had a post SQL Server 2016 and the Internet: Forced Updates, Phoning Home.  "Issue #1" is 'You probably shouldn't run 2016 side-by-side with older versions.'  So, I checked the language in all the SQL Server install ULAs and they all say the same thing.  I know some shared components will be upgraded to the newest version on a server upon install of said version and feature, but this has been around for many Glenn Berry guided instance installs.  Is there something I'm missing?
Answer: At the risk of speaking directly for @BrentOzar - I don't think he's saying you can't install SQL Server 2016 alongside a prior version.  His blog post1 states:

You probably shouldn't run 2016 side-by-side with older versions because:
... You may get updates whether you want them or not.

This does not say you will get updates that will bork your box.  Essentially, any Enterprise installation of SQL Server should be carefully managed - you probably shouldn't allow automatic updates of SQL Server at all, and I'd be quite afraid of letting Windows Update install any updates automatically without some kind of pro-active management.
Test your planned deployment on a non-production box to see if the installation of SQL Server 2016 will cause problems for your environment.  Then make an informed decision about how to go about applying updates.  Decide for yourself if you can afford the risk of a side-by-side installation, versus the extra cost of running multiple SQL Server boxes.
Answer: It's important to read the reasons pertaining to this freighting revelation

this software will automatically update and replace certain files or features within those editions with files from this software.  This feature cannot be switched off.

The way I read that, the concern is the potential for one version to overwrite at a later point in time the files shared and needed by another version. This is probably a result of DLL Hell. You can see this on the Wikipage,

Sometimes, the OS itself removed or replaced DLLs with older or obsolete versions. For example, Windows 2000 would install black-and-white printer DLLs on top of color-aware DLLs, if a black-and-white printer was installed after the color printer.

In light of that, the suggestion not to run two versions side-by-side makes perfect sense.
Future Safeing the Problem
One way to avoid DLL hell, is to upgrade and install Ubuntu which doesn't have such a problem. SQL Server 2017 will run on Ubuntu. This means that SQL Server 2018 will likely also run on Ubuntu. At such time, you'll be able to run both versions concurrently. So it's nice to see the Linux work paving the way forward. For Linux, SQL Server is currently self-contained in the /opt directory, and packaged officially with dpkg (which supports multiple versions).
Comment: We have multiple servers running more than 2 versions of SQL Server and have *never* had issues with "DLL hell".  Microsoft works very hard to ensure this kind of environment is supported and works well.
Comment: As a programmer, the question ultimately boils down to having total-concern, or no-concern. I would have no-concern if the installs were sandboxed from each other did not touch shared libraries. I would be totally perturbed if there were two competing updater's managing the same files. Without revealing my opinions of Microsoft's QA, it's *far* from bulletproof and we should not be trusting it (regardless of it is trustworthy).
Comment: The SQL Server binaries themselves *are* sandboxed, and completely independent.  The components referred to in the CYA EULA are optional and not related to the Server components themselves; think SSMS, etc.


Blasphemy that flow out of mouth

Question: Please, I need help. when I did not know what blasphemy was, blasphemy would flow out of my mouth when I was angry and I would not intend to blaspheme, am I a kafir and since I realized that I did it, I kept crying to allah to forgive me. I am also 14 year old and just reached puberty.
Answer: Blasphemy is kufr if you really meant what you said or a sin if you said it in anger. You said it was the latter.
Sin is not good but repetence is always possible (even repetence from kufr is possible). You already asked Allah to forgive you. He will. He is the All-Merciful. He promised Jannah to those who believe and do good deeds. Do so, and you will be welcome.
Answer: No. Since you have cried when repenting, let's say your repentance was accepted. No one can call you kafir because you have repented.
The door of repentence is always open. Allah is the greatest forgiver.
You can try asking to forgiven to Allah again.

Blasphemy that flow out of mouth


What is the allegorical sense of "deep" in Lk. 5:4 "Launch out into the deep."?

Question: What is the allegorical sense of "deep" in Lk. 5:4: "Launch out into the deep."?
Answer: Cyril of Alexandria gives this interpretation:

They replied, that they had been labouring the whole night, and had
caught nothing: in the name, however, of Christ, they let down the
net, and immediately it was full of fish; in order that by a visible
fact... they might be fully convinced that their labour would not be
unrewarded, nor the zeal fruitless which they displayed in spreading
out the net of the Gospel teaching; for that most certainly they
should catch within it the shoals of the heathen.

The apostles, as "fishers of men," preached the good news to "the lost sheep of the house of Israel," achieving not enough success to allow Jesus to be widely recognized. In allegorical terms, they stayed close to the shore. In future times they would "fish" in deeper waters, meaning both among Jews beyond their region of origin (the Galilee) and eventually including people of other religions and nationalities. There they would indeed find great success. Luke focuses on this theme in his sequel work, the Book of Acts, where the Gospel indeed spreads with great success among the Samaritans and the Gentiles.
Answer: St. Ambrose thinks the "duc in altum" ("launch out into the deep") means to launch

in profundum disputationum

John Henry Newman transl. of St. Thomas's Catena Aurea: "into deep researches".Ni Riain transl. (p. 115): "into the deep waters of controversy".
Ni Riain transl. of Commentary of Saint Ambrose on the Gospel According to Saint Luke, ibid.:

Although the Lord commands others to let down the nets, it is only to Peter that He says: "Launch out into the deep" (Lk 5:4). By this He means, launch out into the deep waters of controversy. No depth can be compared to the sight of the profundity of the riches (cf. Rom 11:33) of the knowledge of God's Son, and the proclamation of His divine nature. Of course, the human mind cannot grasp this mystery nor can human intelligence plumb its depths. Faith alone, Faith in all its fullness, can embrace it. For even though it is not right that I should know in what manner He was born, it is also not right that I should fail to know that He was born. The "how" of His Birth I do not know, but I recognise that fact that He was generated by His Father. We were not there when the Son of God was born of the Father; but we were there when the Father proclaimed Him Son of God (cf. Lk 3:22).

It's also interesting to note that it is darker in the "deep", so perhaps Jesus is saying that more converts will be made of the gentiles who are farther from the Light than of those (e.g., Jews) in shallow waters closer to It; "many are the children of the desolate, more than of her that hath a husband" (Is. 54:1).


Is there a WORD For: sound made by mouth to express demeaning annoyance or feigned, mocking disbelief?

Question: The sound made by pushing middle tongue against palate, tip of tongue bent downward and pushed up against upper teeth and sucking in air sharply w/ mouth open, chin drops and holds for an instant. A forceful "thch..ahch!"  Often accompanied by eyes rolling upward.  Meant to express demeaning irritation and/or feigned, mocking disbelief at such stupidity, etc.. "Oh brother, there he goes again...! Sarcastic "Do you believe he said that?
 I would be happy to borrow from another language if there isn't an English word for it.
Comment: I still don't know what this is. Is it what is usually spelled 'tsk tsk'?
Comment: This is like *hum*, *hem* and *hmm*. The word is *tutting*, the way to spell out the sound is *tsk*. It's often associated (in the contexts you describe) with *eye-rolling*.
Comment: See https://english.stackexchange.com/questions/59684/why-do-we-write-tsk-for-the-sound-of-disapproval
Comment: I think the 'pfff' sound is appropriate to the above. It is the one made by curling the lip in a sneer and puffing out the bottom lip.
Answer: Take your pick from this excellent article on annoying noises people make: annoying sounds
This one works well for what you are asking:
Alveolar, alveopalatal, or postalveolar click
"Tongue-clucking." Specifically in disapproval. Often done with a slight upward detour of the eyes. Someone else has done something one simply doesn't do, darling, and we're not the sort of person who would actually voice disapproval — how base — but, you know, tsk. In short, an impatient, self-regarding, passive-aggressive condemnation. If you do this, try just… not… doing it.

Final rising tone: "Uptalk."

Final creaky phonation: "Vocal fry." The latest "OMG this new thing these kids do is going to destroy language!"

Fortis voiceless alveopalatal fricative: "Ssssshhhhhhh!"

Velar-ingressive linguadental fricative: "Sucking your teeth." Often this is to the side, not right in the middle.

Pulmonic-ingressive breathy-voiced rising-tone neutral vowel: "Gasp."

Fortis long final consonant with epenthetic neutral vowel: "Don't-tuh do this-suh." [My personal favorite]

Pulmonic ingressive voiceless alveolar glide and mid-central vowel, with optional unreleased final bilabial stop: Inhaled "Yeah" or "Yep."

Sustained mid-central vowel and/or bilabial nasal: "Uhhh… uhmmmm… mmmmm…"

Alveolar, alveopalatal, or postalveolar click: "Tongue-clucking." Specifically in disapproval. Often done with a slight upward detour of the eyes.

Loud long low back vowel with advanced tongue root and full oral opening: "Moose-call yawns."

The author, James Harbeck deserves a huge PRIZE for his priceless article!
There are 10 of them and so well described.
CLICK ON THE VIDEO in the LINK :)
Answer: I believe you're looking for the phrase "sucking your teeth." I didn't know what that term meant until I made that sound at a friend who said, "Don't suck your teeth at me!" Interesting article about it: http://www.telegraph.co.uk/news/worldnews/europe/france/11651574/French-schools-ban-teeth-sucking.html
Answer: Tsk tsk is the right answer. Although I guess there is another sound similar to it but it is made just once (and a bit as louder). One may call it just tsk. I don't know if in the literary community it has been universally accepted as a fact.
It involves separating both the lips also besides tongue and teeth. But quickly.
The combination of the quick separation - 1. of both lips 2. teeth and tongue from upper region of mouth (palate I guess) - make one sound that depicts frustration or disapproval.
I personally find it offensive when someone makes it even for genuine reasons. I wish no one did that.
Disclaimer. I do it sometimes myself. I try not do it.
Comment: Or "tut tut", Of course once people have read "tut" they tend to pronounce it as a word!  The same is true for many such sounds, for example "Ugh!" - a sound of revulsion made with the back of the tongue, is often pronounced "Ug" when read.  Until we start using the IPA to print English, this sort  of thing is inevitable. The standard alphabet just can't cope. Note:  "tsk tsk" could be read as "tusk tusk" or similar. This is one of the banes of an author's life.


When did the expression "best bet" come into usage - as in "Your best bet is to ..."

Question: I want to know whether someone would have been likely to use the expression just before the first world war.
Can anyone help?
Comment: My guess: As soon as the words *best* and *bet* were both English words. The "expression" **simply combines the two words straightforwardly**. Nothing more. There was no need for an invention or discovery for this "expression". (And there is no patent or copyright for it.)
Answer: From the following Ngram you can see that there were no recorded uses before 1900 and then no uses of your best bet until about 1920. Unfortunately recorded usage in books is always slightly behind spoken language and Google Ngrams only records books. Nonetheless, I'd opt for no, I doubt someone before the war would have used that expression.

safest or most reliable course of action :
  surest means to a desired end :
  most advantageous approach :
  most satisfactory choice :
  the pilot's best bet was to make an emergency landing
the best bet for stabilizing the national economy
First Known Use of best bet
  1906

(Merriam-Webster)
Comment: If whoever gave me a down vote would like to comment so I can improve my answer through their constructive criticism, I would be more than happy.
Answer: At the same time as BladorthinTheGrey was looking up Ngrams I was doing the same thing, only I used a tighter set of search criteria. This shows that 'best bet' has a few mentions in American English publications from about 1908 onwards but a similar search revealed no usage in British English until 1931. It then disappears from British English publications around 1935 and only reappears about 1950 onwards.
This suggests that 'best bet' was a newish term in the US in Edwardian times and was very uncommon or completely unknown in the UK until after WW2. If your characters are young Americans you might get away with it but if they are British it's completely inappropriate.
Doing an Ngram search for 'best chance', however, shows this in use from the early 19th century in both the UK and the US. This might be a better choice but, probably, in the form of "the best chance you have" rather than "your best chance" as the latter returned no Ngram results at all.
Comment: I commend your work but want to point out one thing, the Ngrams link you quote does indeed show that there is an American usage of 'best bet' from 1908 onwards but if you look at the scale, usage peaks at around 1927 at **0.0000000350% or 3.5x10^-7%** while the [equivalent British graph](https://books.google.com/ngrams/graph?content=best+bet&year_start=1800&year_end=1930&corpus=18&smoothing=3&share=&direct_url=t1%3B%2Cbest%20bet%3B%2Cc0)  shows usage steadily rising to **0.00000160%**, 45.7 times more recorded uses. Brits would use it more than Americans. TL;DR: be careful when using Ngrams!
Comment: "There are three kinds of lies: lies, damned lies, and statistics" - Benjamin Disraeli
Comment: @BladorthinTheGrey Yes, but the British usage does not start until after WWI. The OP was asking about usage prior to that.
Comment: That is true, yes, there is very little British use before about 1920 but my point is that even at that time it was being used around 30 times more frequently in British English than in American. Your point about "*if your characters are young Americans you might get away with it but if they are British it's completely inappropriate*"; it is, in your words **completely inappropriate**.
Comment: Thank you so much for interesting and genuinely useful responses...


How to see whats beyond the video sequence editor

Question:
Is there anyway to see movie strips outside of the video sequence viewer? The image on the left side is my normal view. The picture on the right would be an extended view. Basically I have rolling pictures on the bottom and they come on and off the screen right from left. How do I see their position when they are not in the viewer. Its important for the timing of scrolling that happens for each image.
Answer: You may choose to do some of the scrolling in the 3D View first to produce an image sequence, then  later used in the Blender Video Sequence Editor, VSE.  The 3D View can show objects not in the camera.
As another example if a Blender User wanted to have fancy 3D titling that would be created in the 3D View first as an image sequence first.  Simple titling is available in the VSE.
By using planes with a texture and a camera with orthogonal settings you camera will behave more like the VSE.  The texture is the movie or image sequence that has already been created.
I tend to have two scenes.  SceneA, 3D View and Post processing No VSE.  SceneB, VSE only.
Comment: Thank you with your thoughts. I am going to play around with those ideas. But maybe the creators of blender could add that in the future. I adjusted my workflow and understand key frames to perfect the timing.


Modularizing Rails applications

Question: I'm looking for a way to modularize Rails applications. As I've seen there is no built-in way of accomplishing it. I've found different plugins/core hacks but I feel untrusted about the way they work and their maturity.
Do you have any experience on this?
So far I found this ones:

Desert: http://github.com/pivotal/desert
Rails engines: http://rails-engines.org/
Answer: Rails engines are part of the current stable rails 2.X and so aren't really "hacks" anymore. They seem like a good fit if you want to add fairly course-grained application functionality to an application - a good example might be adding a blog or CMS-style functionality to another application. Checkout the railscast on engines here: http://railscasts.com/episodes/149-rails-engines
If you're looking to modularize on the front end - more "widget" style, you might want to look at cells: http://github.com/apotonick/cells/
Comment: I was looking for a way of modularizing sub-applications into Rails applications but that Cells plugins look interesting too. Thanks
Comment: I've seen the screencast and I don't like the fact that I need to copy and mix migrations/assets into the root application directories. Is there any way to avoid it (3rd party *rake* tasks...)?

Modularizing Rails applications


Implementing wet and dirty materials

Question: How you would implement wet and dirty materials or material overlays that you can clean like in PowerWash Simulator.
Comment: Welcome to [gamedev.se]! There is a lot of things missing from your question: what have you tried so far, why did it not work? what technology are you using to make your game? we're not familiar with PowerWash simulator, you need to add one or two screenshots or a link to a video showing what you want.
Comment: Hey, thanks for your comments. So I'm not developing a specific game but I've heard CG this term in university and asked myself how this works in games like PowerWash or Splatoon. I know a lot about programming in general but never worked with 3d graphics before touched GLSL shaders for the first time in this course.
Comment: This is basically like the painting effect in Splatoon or Portal 2 in reverse: your level starts off already painted, and instead of adding paint to the surfaces, your tools clear the paint mask to show the surface underneath. So you can search for a tutorial for painting effects in your engine of choice, follow that tutorial's steps to the end, and then invert the paint mask to make it a cleaning mechanic instead. Try that, and ask here if you run into trouble with any specific step along the way.
Comment: How much do you know about shader programming? How much do you know about programming in general?
Answer: I've never implemented any of this stuff before.
But from my understanding there's two basic ways you could solve this problem.
Decals
The simplest solution would be to just to just put simple billboards with "wet" or "clean" materials on top of the surfaces. This has the real world equivalent of placing an animatable sticker on top of surfaces.  This works great for when the effects your placing are small, and self contained (they don't need to interact with other entities of the same type to achieve their desired effect). Bullet holes, in FPSs, are ideal candidates for decals. As soon the effect needs to know where it is on a surface, or know about other nearby decals, or must curve around complicated meshes, you're out of luck unless you make your decal system much more complicated and likely much less performant.

Textures and an alpha mask
What's probably happening in PowerWash, is that there are two sets of textures for every cleanable object, and then a texture mask which determines which set are visible and where. When you power wash something, you're simply coloring the alpha mask from white to black (or vice versa) which changes which set of textures (dirty or clean) are visible. From a technical POV, the hardest part of this technique would be the projection from 3D world space to 2D texture space when you have to find out where on the object's texture you're spraying.

extras
There seems to be more complicated effects happening in PowerWash  which adds to the main effect. When you spray objects, they seem to briefly become wet, drip, and then dry. There's probably another texture which represents the wetness of every object, which gets set by the powerwash but then fades back to its original dry state (texture value) overtime.
pros/cons
This method is much more powerful because you have access to all the mesh and textures of whatever object you're on (unlike with decals). But it means you have to  have duplicate sets of textures for every object which could get very expensive.
edit
DMGregory mentions that there's ways to reduce the memory cost of this approach by tiling and re-using materials
Comment: Note that these textures can often be tiling materials that are re-used across large surfaces or between different objects, cutting down the expense of the multi-texturing approach.
Comment: Thanks for your detailed answer! Let's assume we would write the shaders ourselves. Couldn't we just give the fragment shader, which does the texturing and puts the "dirty" texture over the normal texture, a value for each vertex to indicate whether it is still dirty or has already been cleaned, and then put the texture over it or not?

I mean, the calculations of the intersections are of course complex, but for a trashy game that could be sufficient, or not? :D
Comment: @hefe You could definitely add extra vertex attributes to encode a vertex-based alpha mask. That's actually a common optimization technique (texture -> vertex attrib) that's used in open world games when certain objects are really far away. But if you do this always: you're then coupling the resolution of the effect with the mesh geometry though, which is probably not desirable. This would mean a simple cube would have very very low resolution (8 vertices), while a character model would have a multiple order of magnitude higher resolution (potentially over 10k vertices).

Implementing wet and dirty materials


Can user protect his files from untrusted administrator?

Question: I am looking for means to prevent my Windows administrator from accessing my files.
My plan is to cipher my files with EFS. As far as I know administrator can access ciphered files if he has EFS recovery agent role. So I'm worried about the possibility that admin can grant himself recovery agent permissions, steal data and take permissions away. My research shows that in that case my files would have a recovery agent information entry in it's metadata and admin has no means to delete it. So at least I can detect the steel post factum. The potential opportunity to detect steel gives me enough sense of security.
Am I right? Please review my deductions.
Comment: Social/human resource problems cannot be solved through technological solutions...
Comment: Unless you're the owner / a director, you don't own the data on your computer, the company that employes you does, and it's hired this admin to manage its network, and that includes having access to the data on all the computers on the network if they need it to do their job. If you feel this person is being unprofessional, you should address it through your line manager. If you're the owner / a director level employee then you should have the employee removed from their job if you can't trust them. Playing around with encryption is no solution.
Answer: Your first problem is you have an administrator that you don't trust. This is a human resources issue, and you may need to take it up as such.
Second, you could only "protect" them by placing the files in a volume that's encrypted separate from Windows (encapsulating the data). There are methods to do this and products to do so if you google for it.
BUT
Do you own this material? Or is it company owned? Are you in effect stealing from the company?
And beyond that, this material could still be copied, and the computer could be monitored via keystroke capture and monitored remotely through screen capture/viewer programs, both of which are usually allowed in most countries because in the workplace, your employer owns the computer and the network.
You need to take this up with your employer. The sysadmin has full access to the computer, and the employer owns the resources. Whatever your issue is with the sysadmin you need to work that out without a technology solution.
Answer: Nothing would prevent the admin to install keyloggers etc., and you wouldn't even notice, so: No, your assumptions are wrong.
Answer: An "untrusted" administrator should be getting his rights revoked. There are tons of other ways to steal data if you have full rights on a server.
Comment: I would wonder why he's untrusted...is this an employee interaction issue? Political? Company problem?


What are some books on demonology to read from a Jewish perspective?

Question: I have recently developed an interest in demonology and I'm looking to study it from a Jewish perspective. Can anybody recommend books on the topic?
Comment: As always with requests for recommendations, you'll get better answers if you specify criteria of importance to you.
Comment: Classic stories of the Baal Shem Tov, e.g. this sort of thing, http://folkmasa.org/yashpeh/mb_yashp.php?mishtane=716
Answer: Belief in demons exists in Judaism but is very peripheral. Many leading Jewish thinkers thought they didn't exist while others felt they did exist but we should distance ourselves from the occult.
See here for an excellent balanced overview by R Shlomo Brody as well as further sources here, here and there.
The only book on the topic I am aware of is Ascending Jacob's Ladder: Jewish Views of Angels, Demons, and Evil Spirits by Ronald Isaacs
Answer: For this subject, I'd most definitely recommend this book:

The "Minhat Yehuda"
by Rabbi Yehuda Fetaya

Amazon Link:
https://www.amazon.com/dp/1885220677/?coliid=IWAQ4V7BU95MY&colid=3KH5ZAS39A9P7&psc=1&ref_=lv_ov_lig_dp_it

Important:
First and foremost, sorry for this long rant, but I really loved this book yet I hope it will answer your questions without petrifying you (like it kinda did to me on the first read). It's actually Rabbi Yehoshua Zitron (who gives amazing classes on Youtube) that suggested it to me.*

TL;DR:
It's seriously a read that's not for the faintest of hearts, as it deals with what I'd call the precise laws & mechanics of the "metaphysical judiciary system" (i.e. what happens between a soul's passing to the other side, and its final destination in the Gan Eden and/or next Reincarnation), which, to bear in mind, is all set with the very best intention for one's soul. It all starts from people being possessed and Rabbi Fettaya healing those poor souls hiding in people's body, the evil spirits that pursue them, and some other interesting facts about the different realms / spiritual planes, and "Surgeon Angels".

It might sound corny, but if if you're not in a happy mood, alone at night, or particularly stressed and worried, just refrain from reading it for the time being, as it can be really overwhelming.
That said, keep in mind that nowadays we're living in an era that's waaay out of touch with what it really should be, and we're all judged according (and relatively) to the "spiritual level" of our generation, and this book was written in an era where people were way more "tsniut" (modest / humble) than in our generation, specially in the impudence, promiscuity & temptation departments. Compared to the late 18th century, we're reaching the "49th level of Tumah" (impurity): in other words, we're all influenced by an opaque veil of futilities in a way or another, but the good news is G.od and his "Celestial Court" are well aware of it, which somehow weighs in our favor.
If you're not very versed in the study of Torah, I'd strongly suggest to start the book with last few chapters (after having read the intro), which deals with 'Hidushim (novel Torah teachings on the Parashiot / Torah portions of the week), general Jewish Wisdom, and some other precious advices. Keep in mind that G.od is very patient and forgiving, and that Teshuvah / Repentance is at reach to anyone who's genuinely asking for it.
Hope this helps!
Answer: Go buy an artscroll edition of Tractate Pesachim of the Talmud, and go to page 109b from the words ולא יפחתו לו…artscroll has a great intro into the different beliefs about demons that basically takes up the whole page, and the Talmud itself spends numerous pages talking about demons and superstitions


Master Slave database syncronization

Question: Hi I have just started reading about this replication concept and one thing I want to ask is that when we change something in the slave db how is it going to effect the master db? Is there a sync algo that will change it in master db as well?
and another thing is if there are multiple databases can we apply replication on them as well? like multiple databases in masters server replicated into multiple databases in slave server. Thanks
Answer: How replication happens:

DMLs on Master are written to Binary logs.
Slave connects to master from it's IO thread and reads the binary logs. Save them as Relay log.
Slave's SQL Thread execute the Relay log SQLs to apply the changes.

Now, if you need slave's changes to be reflected on master, you need your master to be replicating from your slave as well. That's known as master-master replication. You can find plenty of posts around that.
By default, all the databases are replicated. If you want to replicate only few of the objects (DB / tables) there are replication filters for that.
Answer: "...when we change something in the slave"  STOP.  Do not do that!
Or do you want "dual master", which is two servers, each acting like both Master and Slave.  But that can be a nightmare.  Duplicate keys.  AUTO_INCREMENT issues.  Etc.
Using binlog/replicate_do/ignore_* (in my.cnf) you can control what is (or is not) sent out of the Master (binlog_) and what is not (or is) ignored by the Slave (replicate_).

Master Slave database syncronization