I have wrongly transferred 0.00184426 BTC, request please help to return it back to my wallet

Question: I have wrongly transferred 0.00184426 BTC to address (TN3W4H6rK2ce4vX9YnFQHwKENnHjoxb3m9) request you to pls help me to return it back to my account.
Answer: Did you possibly convert your BTC to something called BTCTRON?  I don't know what this is (apparently some type of wrapped Bitcoin token on the TRON blockchain), but you can supposedly convert it back to BTC again with no fees.  See  https://support.poloniex.com/hc/en-us/articles/360054846854-Using-Bitcoin-on-TRON-FAQ
The  reason I think this is what happened is that the receiving address you gave looks like it's the one that you would have used to swap your BTC for BTCTRON.
Comment: Why the downvote?


Where does the coolant go?

Question: I filled up the coolant a few months ago and today I found the coolant level is near MIN. Is it normal that coolant "evaporates" over time? Or does it mean that it is leaking somewhere?
Answer: No, it's not normal. If it happens over the course of a couple of months, it probably means that there is a very tiny leak somewhere and when the coolant gets hot enough, some of it escapes as steam. Check your cap's tightness first.
Or if you're unlucky and your car recently overheated, it may have caused your head gasket to blow in such a way that coolant gets sucked into the cylinder and is expelled through the exhaust, but that usually drinks up the coolant fairly quickly.
Comment: Your mechanic should have a tester that will check for hydrocarbons in your coolant, and this indicates you have a blown head gasket.  Just don't pour any of the various brands of miracle head gasket fixer into your coolant tank unless you really don't care about ruining the car.  That stuff keeps a lot of radiator repair shops in business.

Where does the coolant go?


How to lend money to a friend in Germany with the possibility to enforce return if he doesn't pay back?

Question: I hope the title itself is clear. I want to lend money to a friend, are there any legal ways that I can make some sort of a 'contract' for the return? What is the most practical way?
Comment: Make sure the contract says what the consequences are for not returning the money by a certain date (late fines, interest, etc.). But your friend might be offended that you ask him/her/them to sign a contract, and they don't need to obey the contract either, unless you get a court to enforce it (which costs money and won't guarantee you get anything back) or you hire debt collectors (which costs money and won't guarantee you get any money back). Any option will put a rift in your relationship with your friend without you being sure you get anything back. Lend only if you're ok with no return.
Comment: @Trish or Shakespeare "Neither a borrower nor a lender be, for loan oft loses both itself and friend."
Comment: That's exactly what I thought as well. Thanks!
Comment: There's a Saying in Germany: "Bei Geld da hört die Freundschaft auf" (~At money friendship ends). The core is: Money is not a friendship service, and many friendships broke over money. If they really want to pay back, they would want to sign an IOU or similar.
Comment: You simply want a loan agreement (Darlehensvertrag) - not very different from the contracts a bank uses. There are default rules in the law, if you don't write down anything but the amount of money and the time to pay it back. Are you in Germany too?
Comment: Are there reasons why your friend cannot obtain a loan from the usual loan sources like banks or consumer credit companies?  I suspect there is and for those same reasons you should not loan money to him.  I know this is not what you asked so I'm posting it as a comment.
Answer:
Choice of jurisdiction: You're pretty much free to choose your jurisdiction. You don't have to contract under German law. The German state will intervene though if you're doing criminal stuff.
Legally, the best is of course to draft a written agreement. You're completely free in the terms (unless it becomes immoral, § 138 BGB), but a loan, § 488 BGB (Darlehensvertrag), with a 0% interest rate (if it's meant as a short-term aid) is standard.
The next level is to collateralize your loan, specifically with a pledge, §§ 1204 ff. BGB, i. e. your friend gives you a valuable item which you may (and actually have to) sell for profit if he doesn't return the loan. However, unlike contract law, in property law you are not completely free regarding the terms (numerus clausus of property law, Typenzwang des Sachenrechts). Here it becomes too difficult though for the layman, so I wouldn't recommend that unless you know what you're doing.
Ultimately, I/we think it's nice of you to consider helping out your friend, but as Nike Dattani already portrayed it can get really nasty if you intend to legally enforce such matters. Trish mentioned the saying: Friendship ends where business begins. I, too, suggest to refer your friend to a pawnshop, research (third-party) microloan opportunities, and help him without directly giving him cash, dine together and offer company (i. e. address the psychological dimension financial troubles entail).

PS: § 9 SGB Ⅰ: Germany is (to some degree) a welfare state. Maybe your friend is eligible for some kind of assistance. However, and probably typical of Germany, if you want to get money, you have to fill in forms.
Comment: @ohwilleke Darlehensvertrag or Schuldschein (the latter being most akin to the promissory note/IOU)
Comment: Also, FWIW, the written agreement (in the U.S.) would typically be called a promissory note or IOU, and the arrangement related to collateral would be called a "security agreement" in U.S. legal terminology. I don't know what the German translations of these terms would be.
Comment: FWIW, a 0% interest rate with a large enough loan for a long enough time period could have tax implications for imputed interest accompanied by a gift back of the interest that is imputed to have been paid This doesn't change any of the analysis above about whether it is possible and legal conduct this kind of transaction.


How to restore Airport settings?

Question: I've just reverted from Lion to Snow Leopard while maintaining a time machine backup of Lion.
In Lion I used to 'remember' many wireless networks, and also have configuration for connecting from my phone. How can I recover all that using Time Machine?
Answer: The stored passwords for Wi-Fi networks (as well as many other things) are stored in your keychain file.  the easiest way to get stuff out of this is if you have a MobileMe account which has the option to synchronize the keychain, so it will appear automatically just by logging in to MobileMe.
There are 2 drawbacks to this:

You need network connectivity to login, and so if you don't have an available network because you don't have the key you are out of luck,
MobileMe is deprecated, and the functionality is not subsequently available through it's replacement iCloud.

You could always boot from your Time Machine backup, open up the Keychain Access command and export the keys you want.  They will be stored as files within the backup, but are encrypted so not a lot of use. It may be possible to import the keychain if you can find it (I'm not at a Mac right now so can't check for location) and you know the administrator password for the system is came from, but I'll leave that for another user to comment on or provide an answer for.

How to restore Airport settings?


Why does the photon density decrease more than baryon density when the universe expands?

Question: I read that most photons today are from the cosmic background radiation, so the number must have stayed roughly the same since CMB was released. Also, the baryon density has been roughly constant since the first fraction of a second. But why did photons dominate early in the universe, and now they are like 0.001%?
Answer: The rate at which energy density dilutes is different. Think of the energy of particles as $E^2=m^2c^4 + p^2c^2$.
We will consider how the energy density of those particles dilutes as the universe expands. Let's write $a$ as the characteristic size of the universe. You may think of a typical volume of universe as a cube of side length $a$ (e.g. the total volume of that characteristic amount of universe is $a^3$).
For a heavy, slow moving particle (e.g. a baryon, sometimes also referred to as dust or cold matter), almost all the energy of these particles can be written as $E\approx mc^2$. (There is a little bit of kinetic energy also, but $mc^2>>pc$, so we may ignore the contribution from kinetic energy for this discussion). As the universe expands, the number density of particles dilutes $\propto a^{-3}$ which means the energy density of these particles dilutes as $\rho =\frac{E}{V}\propto a^{-3}$.
Now let's consider what would happen to a fast-moving particle (like a photon, or some other particle where the $pc>>mc^2$ (which includes the case where $m=0$)). As the universe expands, the number density of photons dilutes as $n \propto a^{-3}$. However, the photon frequency decreases with the expansion $\nu\propto a^{-1}$. Because frequency is proportional to energy, the energy of each particle dilutes with the expansion as $E\propto a^{-1}$. Therefore, the energy density of photons in the universe decreases with time as $\rho = \frac{E}{V} \propto a^{-4}$.
Answer: To add a few things to Bob's answer:
in those regions of the universe, between galaxy clusters, where matter is not dominant, but dark energy is, in those voids of space, space itself expands.
Now as the photons travel through those regions, they travel in expanding space, so their wavelength will be stretched too.
Thus, their frequencies will decrease, their energy will decrease. Now if you take the number of photons in the universe as constant, and the number of baryons as constant, and take that expanding space does not affect the energy density of baryons, you see that photons' energy density will decrease more then baryons'.
Now as the universe expands, and in this case the expansion accelerates, the voids of inter galaxy cluster space are going to dominate the universe, and after a while even inter galaxy spaces will dominate, so even galaxies will be so far apart, that matter will not have a gravitational effect there and dark energy will dominate in these regions between galaxies.
Now as dark energy will dominate more parts of the universe, photons will more likely travel in these regions, so their energy density will decrease even more as the expansion accelerates.


Pygments style not being applied in Jekyll blog

Question: http://joshhornby.co.uk/2012/11/14/test-test-test.html
As you can see from the link the code at the bottom is just yellow. No styling is being applied. I have installed pygments through the terminal and the stylesheets are all there and working. I am using jekyll so markdown files are created then turned into .html pages.
I also have it as pygments: true in the .yml file
EDIT:
Strange i had to change my markdown in the .yml file to markdown: maruku. And it seems to be working more than in was before but what ever style i add there is always a yellow highlight over the code, and the code is never styled as i thought!
Answer: Strange i had to change my markdown in the .yml file to markdown: maruku. All working now.


Can bathroom lights be on same circuit as bedroom lights?

Question: I know bathroom outlets must be on their own circuit.  Can the bathroom lights be on the same circuit as say the bedroom and hall lights?
Answer: Yes. There's nothing different about bathroom lights vs bedroom lights. In fact, I would say it's a bad idea to tie the bathroom lights to the bathroom outlet (which should be a GFCI). Otherwise you drop your hair dryer and suddenly you're in the dark!
The only thing you might need to consider is that bathrooms tend to have exhaust fans on the same circuit as the lights. These tend to draw more amps than a light, so make sure you don't overload your circuit.
Comment: @Nic you're using words inconsistent with Code.  An "outlet" describes any usage point, including hardwired ones.  a "Receptacle" is a socket you can plug appliances into.  All receptacles are outlets, not the other way round.
Comment: Good to know, just was confused by code.  It claims bathroom receptacles must not be on same circuit as other room and then I wondered if the light counted as a receptacle or if that only meant outlets.

My exhaust fan is going to be low draw, I imagine most modern day fans are.  However, in the master I will have exhaust fan / heater all in one which I am running a dedicated circuit for that in itself.


Finding all perfect squares of the form XXYY

Question: I have to find 4 digits number of the form XXYY that are perfect squares of any integer. I have written this code, but it gives the square root of all numbers when I have to filter only perfect integer numbers.
I want to show sqrt(z) only when it is an integer.
#include<math.h>
#include<iostream.h>
#include<conio.h>
void main()
{
 int x,y=4,z;
 clrscr();
 for(x=1;x<=9;x++)
 {
  z=11*(100*x+y);
  cout<<"\n"<<sqrt(z);

 }
 getch();
}

Comment: @Matthieu: `00` is also possible (1600, 2500, etc.).
Comment: To clarify, what you're asking is "How can I test when z is a square number? e.g. how can I test if sqrt(z) returns an integer result?"
Comment: Can you post an example?the question is not clear
Comment: For the unwary: A perfect square of four digits will have its last too digits be 44, so the `XXYY` pattern is in fact reduced to `XX44`. Thanks to Steve Jessop to have pointing it out to me :p
Comment: @dan04: sorry, I didn't expressed myself precisely enough. A square of the form XXYY is necessarily of the form XX44. There are other squares of 4 digits, but their first two digits are different from one another.
Comment: True, unless you count `0000`.
Answer: I'd probably check it like this, because my policy is to be paranoid about the accuracy of math functions:
double root = sqrt(z);
int introot = floor(root + 0.5); // round to nearby integer
if ((introot * introot) == z) {  // integer arithmetic, so precise
    cout << introot << " == sqrt(" << z << ")\n";
}

double can exactly represent all the integers we care about (for that matter, on most implementations it can exactly represent all the values of int). It also has enough precision to distinguish between sqrt(x) and sqrt(x+1) for all the integers we care about. sqrt(10000) - sqrt(9999) is 0.005, so we only need 5 decimal places of accuracy to avoid false positives, because a non-integer square root can't be any closer than that to an integer. A good sqrt implementation therefore can be accurate enough that (int)root == root on its own would do the job.
However, the standard doesn't specify the accuracy of sqrt and other math functions. In C99 this is explicitly stated in 22.214.171.124.2/5: I'm not sure whether C89 or C++ make it explicit.  So I'm reluctant to rule out that the result could be out by a ulp or so. int(root) == root would give a false negative if sqrt(7744) came out as 87.9999999999999-ish
Also, there are much larger numbers where sqrt can't be exact (around the limit of what double can represent exactly). So I think it's easier to write the extra two lines of code than to write the comment explaining why I think math functions will be exact in the case I care about :-)
Comment: +1 the obvious square root check is to check the produced square
Answer: #include <iostream>
int main(int argc, char** argv) {
    for (int i = 32; i < 100; ++i) {
        // anything less than 32 or greater than 100
        // doesn't result in a 4-digit number
        int s = i*i;
        if (s/100%11==0 && s%100%11==0) {
            std::cout << i << '\t' << s << std::endl;
        }
    }
}

http://ideone.com/1Bn77
Answer: There is absolutely no need to involve floating point math in this task at all. Here's an efficient piece of code that will do this job for you.
Since your number has to be a perfect square, it's quicker to only check perfect squares up front rather than all four digit numbers, filtering out non-squares (as you would do in the first-cut naive solution).
It's also probably safer to do it with integers rather than floating point values since you don't have to worry about all those inaccuracy issues when doing square root calculations.
#include <stdio.h>
int main (void) {
    int d1, d2, d3, d4, sq, i = 32;
    while ((sq = i * i) <= 9999) {
        d1 = sq / 1000;
        d2 = (sq % 1000) / 100;
        d3 = (sq % 100) / 10;
        d4 = (sq % 10);
        if ((d1 == d2) && (d3 == d4))
            printf ("   %d\n", i * i);
        i++;
    }
    return 0;
}

It relies on the fact that the first four-digit perfect square is 32 * 32 or 1024 (312 is 961). So it checks 322, 332, 342, and so on until you exceed the four-digit limit (that one being 1002 for a total of 69 possibilities whereas the naive solution would check about 9000 possibilities).
Then, for every possibility, it checks the digits for your final XXYY requirement, giving you the single answer:
7744

Comment: "it's quicker to only check perfect squares up front rather than all four digit numbers" - he's not checking all 4-digit numbers, though, he's only checking 9 of them. Not that speed is really a concern for such a small task as this, but I think you're comparing your code to a straw man.
Comment: @Steve: the question and the code disagrees though, as the question does state he wants them all. However I disagree that a brute force solution would be to test all four-digits number: we have a pattern, so we only have to check 90 of them (1 <= x <= 9, 0 <= y <= 9, xxyy), unless we also want x to be equal to 0, in which case there would be exactly 100 of them. @paxdiablo: could you state that you check from 32 to 99 (included) so that it is clear the loop is only executed 68 times ?
Comment: @Matthieu: the original poster has used mathematics. If the last two decimal digits of a square number are equal, then they necessarily are `44`. So the question and code do agree. Perhaps not obviously so: personally I think that trick deserves a comment :-)
Comment: @Steve: Ah, that would have been easier if it had been stated :p So it's 9 square root computations against 68 square computations. Our poster may already have the fastest answer :)
Comment: @Matthieu: (or `00`, but we can rule that out in this case. `aa00` isn't square for any digit `a`, because `aa` isn't square for any digit `a`). To be honest, with this much mathematics already applied it's barely worth writing any code at all, just check the last 9 cases on a calculator, and write the program as `int main() { std::cout << 7744 << "\n"; }` ;-)
Comment: @Steve (for the first comment) - Sorry, I wasn't saying my answer was more efficient than the OP's, just that it's more efficient than the first-thought brute-force solution. As to the search space for solutions, my code uses the knowledge that 32 is the minimal square root for a four digit number, something reasonably easy to deduce. The knowledge that all such numbers would end in 44 is somewhat less intuitive and, as you rightly state later, it's a short step from there to the knowledge that the answer is 7744 and just use your one-line `cout` solution :-)
Answer: We can notice that

1 + 3 = 2^2
1 + 3 + 5 = 3^2,
1 + 3 + 5 + 7 = 4^2,

i.e. sum(1 + 3 + ... (2N + 1)) for any N is a square. (it is pretty easy to prove)
Now we can generate all squares in [0000, 9999] and check each square if it is XXYY.
Answer: While I smell a homework question, here is a bit of guidance.
The problem with this solution is you are taking the square root, which introduces floating point arithmetic and the problems that causes in precise mathematics. You can get close by doing something like:
double epsilon = 0.00001;
if ((z % 1.0) < epsilon || (z % 1.0) + epsilon > 1) {
    // it's probably an integer
}

It might be worth your while to rewrite this algorithm to just check if the number conforms to that format by testing the squares of ever increasing numbers. The highest number you'd have to test is short of the square root of the highest perfect square you're looking for. i.e. sqrt(9988) = 99.93... so you'd only have to test at most 100 numbers anyway. The lowest number you might test is 1122 I think, so you can actually start counting from 34.
There are even better solutions that involve factoring (and the use of the modulo operator)
but I think those are enough hints for now. ;-)
Comment: any *reasonable* implementation of `sqrt` will return an integer for a 4-digit perfect square. I don't think the standard actually specifies accuracy, though, so it's not a bad idea to have a tolerance which is (a) larger than the most inaccurate you think a sqrt implementation will ever be; and also (b) not so large as to give false positives, which I think 0.00001 satisfies.
Comment: I should note that it's been a while since I used c++, so for all I know the sqrt operator might be (probably is) perfect for perfect squares.
Comment: @marcog: Sorry, you can do that in python and I'm a bit rusty in c++. My bad.
Answer: To check if sqrt(x) is an integer, compare it to its floored value:
sqrt(x) == (int) sqrt(x)

However, this is actually a bad way to compare floating point values due to precision issues. You should always factor in a small error component:
abs(sqrt(x) - ((int) sqrt(x))) < 0.0000001

Even if you make this correction though, your program will still be outputting the sqrt(z) when it sounds like what you want to do is output z. You should also loop through all y values, instead of just considering y=4 (note that y an also be 0, unlike x).
Answer: The way you are generating numbers is incorrect indeed correct (my bad) so all you need is right way to find square. : )
loop x: 1 to 9
  if(check_for_perfect_square(x*1100 + 44))
         print: x*1100 + 44

see here for how to find appropriate square Perfect square and perfect cube
Comment: Actually it is correct, he's using the cunning fact that if the last two decimal digits of a square number are equal, then they must be `44`.
Answer: I want to show the sqrt(z) only when it is integer.
double result = sqrt( 25); // Took 25 as an example. Run this in a loop varying sqrt
                           // parameter
int checkResult = result;
if ( checkResult == result )
    std::cout << "perfect Square" ;
else
    std::cout << "not perfect square" ;

Answer: You don't need to take square roots. Notice that you can easily generate all integer squares, and all numbers XXYY, in increasing order. So you just have to make a single pass through each sequence, looking for matches:
 int n = 0 ;
 int X = 1, Y = 0 ; // Set X=0 here to alow the solution 0000
 while (X < 10) {
   int nSquared = n * n ;
   int XXYY = 1100 * X + 11 * Y ;

   // Output them if they are equal
   if (nSquared == XXYY) cout << XXYY << endl ;

   // Increment the smaller of the two
   if (nSquared <= XXYY) n++ ;
   else if (Y < 9) Y++ ;
   else { Y = 0 ; X++ ; }
   }


Why do cell membranes let small non-polar molecules through but won't let small polar molecules through?

Question: If the hydrophobic hydrocarbon chain of the phospholipid prevents the movement of polar molecules through the membrane. Why does the hydrophilic phosphate head of the phospholipid not prevent the movement of non-polar molecules?
Comment: Possible duplicate of [Why lipophilic molecules can pass phospholipid bilayer, in spite of 2 hydrophilic layers?](https://biology.stackexchange.com/questions/52371/why-lipophilic-molecules-can-pass-phospholipid-bilayer-in-spite-of-2-hydrophili)
Comment: You might be interested in [this](http://biology.stackexchange.com/questions/40395/how-do-lipid-soluble-substances-diffuse-through-the-cell-membrane/45296#45296).
Comment: See if this helps: http://biology.stackexchange.com/questions/52371/why-lipophilic-molecules-can-pass-phospholipid-bilayer-in-spite-of-2-hydrophili/52384#52384
Comment: Polar molecules needs electrochemical gradient and protein carrier. ...whereas non polar molecules needs kinetic energy and these molecule continuously bouncing to come out from the cell membrane through the channel provide by lipoprotein structure of cell membrane and concentration gradient also effective for movement of molecules all types of molecules.
Answer: The plasma membrane consists of hydrophobic and hydrophillic characteristics. Towards the outsides, they are hydrophillic, so they can create bonds with water. The insides are hydrophobic, allowing no water inside and keeping them tight together due to the polar forces.
An non-polar particle (if small), can pass through this because it does not interfere with the hydrophobic/hydrophillic (polar) nature of the plasma membrane. However, polar particles would not have the opportunity to move in, because the insides (hydrophobic) are literally afraid of water, or charges, don't allow polar substances to pass through.
So only hydrophobic (nonpolar), gases, and small particles (nonpolar) can pass through. There are exceptions of $H_2O$ passing through the membrane in small amounts because their electric charge is very minor.
Answer: First, we should understand what causes molecules to be hydrophilic or hydrophobic.
A molecule is hydrophilic if it contains atoms with different electronegativities, that is atoms that pull electrons with different strengths. The factors determining the strength of the pull are the size of the atom (including the pre-existing electron shells) and the number of protons. Make the atom too big and electrons are too far from the nucleus, make it too small and there is not enough protons to pull the electrons. An atom that has a balance between these two factors is oxygen which has the second highest electronegativity in the periodic table. Oxygen was thought to be the maker of acids, which is literally in the name. Now we know this is not the case because all you need is to be more electronegative than hydrogen so that it becomes essentially a proton that goes into solution. Anyway, the electronegative atoms in a polar molecule form hydrogen bonds with oxygen and hydrogen in water molecules because they have opposite partial charges. This includes water forming hydrogen bonds with other water molecules that gives rise to cohesion, surface tension as well as hydrophobic interactions which we shall explain in the next paragraph.
What happens with hydrophobic interactions (not bonds) is that water molecules want to pair with each other so they push the so-called hydrophobic molecules out of the way and clump them together. They are not hydrophobic in the literal sense, they essentially don't pair with water because they are not polar enough. Examples are hydrocarbons, where hydrogen and carbon have very close electronegativities.

The cell membrane is formed of phospholipids, these are molecules with polar hydrophilic phosphate heads and non-polar hydrophobic fatty acid tails. These molecules align so that the phosphate heads face water and the fatty acid tails hide inside the membrane.
Polar molecules can't pass the membrane because they are being pulled by water outside and not being pulled by the membrane which has the hydrophobic fatty acids inside. Channels essentially form hydrophilic passages for these polar molecules so they can pass according to their concentration gradients.
Non-polar molecules are essentially hated by both bodies of water, extracellular and intacellular fluids. The question then becomes: why don't they stay inside the membrane with the hydrophobic fatty acids? Well, we need to think about this in terms of forces. You essentially have two forces:

Surface tension of the water that lines both sides of the membrane and keeps the hydrophobic molecules inside.
Pressure force (or normal force) that arises as the hydrophobic molecules accumulate and push on the surfaces of the membrane.

It has to happen that eventually the hydrophobic pressure overcomes the surface tension unless you put infinite amounts of salt in the water which increases the surface tension, or you freeze the water. It then becomes clear that the molecules are more likely to have a net movement towards the body of water that initially had less of them. This is known as simple diffusion.
Answer: Outside membrane there in water and inside membrane there is lipid.
Hydrophilic molecules are more stable in water as compared to lipid so they prefer to stay in water and not go inside lipid.
Hydrophobic molecules are more stable in lipid as compared to water so they prefer to leave water and move freely into lipid.
You are saying that hydrophilic part of membrane will obstruct the movement of hydrophobic molecules but do not forget that they are already in water, which is polar, so it doesn't matter to them.
Analogy :- 'If you are on roof of your house you can very easily jump to roof of adjacent house' similarly hydrophobic molecules which are already unstable in water can move towards hydrophilic part of membrane because they are equally unstable there.


create event observer for new attribute save action of product

Question: I want to create an event observer  when admin create a new attribute or save existing attribute from admin panel. I have not found any suitable event observer.  Please can help me??
Answer: Try using eav_entity_attribute_save_before or eav_entity_attribute_save _after.
It could also work with catalog_entity_attribute_save_before or catalog_entity_attribute_save_after.
Comment: Thank for your response. I actually save data to another table when click on **Save Attribute** or **Save and Continue Edit** button in magento admin panel under categog->Attributes->Manage Attribute.


What happens when I use a battery with too much current?

Question: I am working on creating a line-bot from a book and it calls for a 6v, 1AH battery. I have these NiMh AA batteries that are rated at 2.3AH, 1.2v. Is there a way to set these up safely for the bot? What happens if I use too much current but the correct voltage?
Comment: the AH rating of the battery tells you what its capacity is.  I.e. how long it will last for a given load.  The idea is that a 100mAH battery will supply 1mA for 100 hours, a 200mAH battery will supply 1mA for 200 hours, etc.  The actual amount of power you get out of a battery is a bit more complicated, but the idea is the more AH/mAH it has, the longer it will last
Comment: You mean a 1000 mAh battery right?
Comment: Yes! Actually the book made an error there too. Supposed to be Mah
Answer: You should be able to connect in series 5 of those AAs to reach 6V. You should be fine with your 2.3 Ah batteries. The Ah rating is a measurement of the battery capacity. So your AAs can deliver 2.3 amps for 1 hour. It has nothing to do with how much current the battery actually supplies to the robot.
Answer: You would require five of the 1.2 volt Ni Mh batteries to produce 6 volts for your line-bot.  The set of 2.3 AH (or 2300 mAH) batteries would run your line-bot about 2.3 times as long as the 1 AH (or 1000 mAH) batteries.  (note that 1 AH = 1000 mAH)
As mentioned by others, the AH rating of a battery is an indication of the energy available from the battery.  Your load will only draw the current it requires, regardless of the AH rating of the battery (providing the battery voltage is correct for the load).
Answer: the 1000mah is just how much "juice" is in the battery....if you use one that is higher....you project will run longer...it will not hurt it.


CIR process characteristic function

Question: what is the characteristic function of the CIR process given by
$dv_t = \kappa (\theta - v_t)dt + \sigma \sqrt{v_t}dW_t$
Unfortunately, I could not find the answer in the literature.
I know it is in the class of affine diffusion processes, but how can we find the characteristic function?
Answer: The distribution of the variance $v_t$ is known, see here. We have $$v_t=\frac{1}{2c_t}Y,$$ where $$c_t=\frac{2\kappa}{(1-e^{-\kappa t})\sigma^2}$$ and $Y$ follows a non-central $\chi^2$ distribution with $k=\frac{4\kappa\theta}{\sigma^2}$ degrees of freedom and  non-centrality parameter $\lambda_t=2c_tv_0e^{-\kappa t}$. The characteristic function of $Y$ is known to be
$$\varphi_Y(u)=\frac{1}{(1-2iu)^{k/2}}\exp\left(\frac{iu\lambda_t}{1-2iu}\right).$$
The characteristic function of $v_t$ is thus
$$\varphi_{v_t}(u)=\varphi_{Y/2c_t}(u)=\varphi_Y\left(\frac{u}{2c_t}\right)=\frac{1}{(1-iu/c_t)^{k/2}}\exp\left(\frac{iu\lambda_t/2}{c_t-iu}\right).$$
This is the characteristic function of $v_t$, i.e. the variance in the Heston (1993) model or the short rate $r_t$ in the Cox et al. (1985) model. This is very different to the characteristic function of the (log-)stock price in the Heston (1993) model that you need for usual option pricing.
Answer: In addition to @Kevin 's splendid answer, you can make use of the affine properties you have just described. The relevant machinery is found in DPS2000, equations (2.4) thru (2.6).
We are looking for
$$ \phi(u,t) \equiv E\left(e^{iuv_t}\right)$$
where $E(\cdot)\equiv E(\cdot|\mathcal{F_0})$. For affine processes, this expectation can be solved thru a cleverly chosen set of differential equations, i.e. Feynman-Kac (see paper):
$$ \phi(u,s) = E\left(e^{\alpha_s + \beta_s v_s}\right) \mathrm{s.t.} \alpha_t=0, \beta_t=ui$$
Where the functions $\alpha(t), \beta(t)$ satisfy ordinary differential equations in case of a CIR process:
$$\frac{\partial \beta}{\partial \tau} = -\kappa\beta_\tau + \frac{1}{2}\sigma^2\beta_\tau^2$$ subject to $\beta_0 = ui$ and
$$ \frac{\partial \alpha}{\partial \tau}=\kappa\theta\beta_\tau$$
subject to $\alpha_0=0$
NB: I have flipped the time dimension from $s:0\to t$ to $\tau:t\to 0$, hence you find different signs when comparing to the paper
You can now solve the ODEs, starting with $\beta$ and plugging the result back into the ODE for $\alpha$.

CIR process characteristic function


Does all slowed light becomes circularly polarized?

Question: When un-polarized light goes through a quarter wave plate the one of the wavelength is retarded by 90° phase, resulting in circularly polarized light. Does it means that all circularly polarized light are traversing less than speed of light in vacuum?
Answer: Imagine you want to describe a linearly polarized plane wave propagating in z Direction.
$$u(z,t)=\vec p e^{i(kz-\omega t)}$$,
where $\vec p$ is a polarization vector (Jones vector). Using this formalism we can describe a quater waveplate using the following matix (i stands for a retardation of 90°).
$$W=\left(\begin{array}{aa} 1 & 0\\ 0 & i \end{array}\right)$$
Let's have a look at a linearly polarized state.
$$\vec p=\frac{1}{\sqrt 2}\left(\begin{array}{c}a\\b\end{array}\right)$$
The quater wave plate now acts on this state.
$$\vec p'=M\vec p=\vec p=\frac{1}{\sqrt 2}\left(\begin{array}{c}a\\ib\end{array}\right)$$
This is a circularly polarized light. It can be rewritten in the following way.
$$\vec p'=\frac{1}{\sqrt 2}\left(\begin{array}{c}a\\0\end{array}\right)+\frac{1}{\sqrt 2}\left(\begin{array}{c}0\\b\end{array}\right)e^{i\frac{\pi}{2}}$$
$$u'(z,t)=\vec p' e^{i(kz-\omega t)}$$
So it turns out that the circularly polarized light is just a superposition of two linearly polarized states (as you mentioned already) with a phase-shift of 90°. There is no mechanism involved changing the speed of light in the vacuum whatsoever.
Hence the answer is: No, circularly polarized light propagates at the same speed in vacuum as un-polarized light, namely at the speed of light.
Comment: Frankly speaking I was intimidated by the math however thanks for clarifying my doubts on polarization.
Answer: Light of any polarization has always the same speed c in vacuum. The quarter wave 90 degrees "retardation" is only a phase shift. It has no influence on the propagation of light in vacuum. The wave velocities (phase velocity, group velocity, signal velocity) in an optical medium can be reduced depending on the refractive index and it's dispersion.


What is the difference between "temporada" and "estación"?

Question: The words temporada and estación both mean season in English. Is there any difference between these two words? How can I use them properly?
Answer: You have to use "estación" when you refer to one of the four seasons of the year: summer, fall/autumn, winter or spring.
The word "temporada" will be used to refer to some period during which an activity is performed or some business is conducted, as in temporada de esquí. The "temporada" may coincide with a certain season, and then we have temporada invernal, temporada de verano, but these will always be used when there is some implicit activity that takes place during the period in question: En la temporada de verano los hoteles trabajan a pleno (In this case, "temporada de verano" is used to describe the hotel business during the summer.)
Comment: Agregaría que son sinónimos en expresiones como *ropa/fruta de temporada/estación*.
Answer: Estación means "season" or "station", depending on context.
Estación de verano ("season of summer", literally, or "summer season").
Temporada means "time" (over a week, a period of Time), as in "Temporada de verano" (summertime).
Comment: There is already an answer which says this and with more detail. When you have more reputation you will be able to up-vote an existing answer.
Answer: The existing answer is great but I want to give you a couple other ways of thinking about this.  Estación is at the foundation, at the level of the equinox.  It's based on what happens astronomically with the earth and the sun.  Temporada means in the time of, for example: In summertime, when the cicadas sing, you get in the mood for lemonade.
The other idea I want to share is that when you take a train, you stop at stations.  Also, as you go cycling along through the seasons of the year, you also stop at stations.  December 21st -- your train stops at the Beginning of Winter Station.  Etc.
Hopefully these ways of associating the cognates and their meanings will help you remember the difference.
Comment: @walen - Oh, you went even farther.  Very good.  I was just associating *estación* with the train stations on the Earth's annual voyage around the sun.  For *temporal* I forgot to point out the connection between *temporada* and *tiempo*.


Misfiring and loss of brake power

Question: i have a 2004 VW Golf 4 which misfire and brake loss of power.
i have bunch of codes which i don't know how to go forward.
the codes are; 18321, 18034, 18020, 18014, 17839, 17924, 16725, 17580, 17952.
can anyone please show me the way forward in solving the problems
Comment: Welcome to Motor Vehicle Maintenance & Repair!
Answer: I don't have a specific solution for you, but gave you a list of things to check at the bottom of this post.  You have codes indicating issues in 3 specific areas.  Transmission, Brakes and Engine.  I apologize for this going long.
Let's start with breaking down the fault codes and look for commonalities for your MK4.  A quick internet search lead me to
http://www.bentleypublishers.com/tech/vw/vw.dtc.table.htm.  I found Volkswagen specific descriptions at autocodes.com
Not all DTCs were listed on the Bentley Publisher's site.  I backfilled from https://sites.google.com/site/1810martin/fault-codes-18000---19999
Transmission
18034
P1626
Data-Bus Powertrain Missing Message from Transm.Contr.
Possible causes

Transmission Control Module (TCM) incorrectly coded

18022
P1614
MIL Call-up Circ./Transm.Contr.Module Range/Performance

I was unable find anything concrete, but it is related to the Transmission Control Module.

Both of these could be caused by an installed tune.  One OP on a forum had this happen with a switchable tune.  In one position, P1614 would set and he had to have it reprogrammed to resolve it.
Brakes
18014
P1606
Rough Road Spec Engine Torque ABS-ECU Electrical Malfunction

I wan't able to find much on this one.  One forum post where the OP had low system voltage (10volts under load).  Charged the battery and was able to clear the code (temporarily until the battery discharged again).  Did/do you have a low battery condition?

18321
P1913
Pressure Sensor for Brake Boost (G294), Short to Ground
Possible causes:

Faulty Brake Servo Pressure Sensor
Brake Servo Pressure Sensor harness is open or shorted
Brake Servo Pressure Sensor circuit poor electrical connection

17839
P1431
Activation of brake vacuum pump, open or short to ground
Possible causes:

Faulty Brake System Vacuum Pump
Brake System Vacuum Pump harness is open or shorted
Brake System Vacuum Pump circuit poor electrical connection

Engine
17924
P1516
Intake Manifold Changeover Valve circuit Open
Possible causes:

Faulty Intake Manifold Changeover Valve
Intake Manifold Changeover Valve harness is open or shorted
Intake Manifold Changeover Valve circuit poor electrical connection

16725
P0341
Camshaft Pos.Sensor Circ Range/Performance
Possible causes:

Faulty Camshaft Position Sensor
Camshaft Position Sensor harness is open or shorted
Camshaft Position Sensor circuit poor electrical connection
Faulty starter motor
Starting system circuit Dead (Weak) battery

17580
P1172
Throttle Actuation Potentiometer Sign.2 Signal too Low
Possible causes:

Faulty Throttle Position Sensor (TPS)
Throttle Position Sensor (TPS) harness is open or shorted
Throttle Position Sensor (TPS) circuit poor electrical connection
Faulty Throttle Drive electric motor
Faulty Throttle Valve Control Module

17952
P1544
Throttle Actuation Potentiometer Signal too High
Possible causes:

Faulty Throttle Valve Control Module
Faulty Throttle Actuator
Throttle Actuator harness is open or shorted
Throttle Actuator circuit poor electrical connection

One common theme is they mostly seem to be electrical, as in possible low voltage or bad ground(s).
As it's an older car, the engine bay might be dirty.  I would first clean it up to have good visibility, then I would check:

Battery voltage while idling and all accessories turned off.  This should read above 13.6 volts, near 14.4 would be typical.  If not, the likely culprit is the alternator.
Engine to chassis ground.
Battery to engine ground.
Worn/damaged wiring harness.

Additionally, verify your Camshaft Position Sensor is reading correctly.  Incorrect readings will cause misfire and can be caused by a bad sensor.  Also, if you have skipped a tooth on a timing chain you might receive this.  This may require a scope and a backprobe to test properly.
For your transmission codes, you may have a tune that is bad.  If you applied a tune, set it back to factory and see if the error clears.  If you are factory, the TCU may need a re-flash or replace.
Answer: Charge or replace the battery and have the alternator tested for operation.  Also check all of the earth straps and connectors of the wiring loom for corrosion and water ingress.  I've seen any number of codes thrown by a modern Golf with a dead battery.  There is a chance part of your wiring loom is full of water.  Once you've sorted the voltage supply issue, the poor performance should vanish.

Misfiring and loss of brake power


USB Hierarchy Driver

Question: Is it possible to create a driver (windows/mac) for a custom usb hub such that it appears as one device in My Computer / Finder and the attached usb card readers each show up as a sub-folder within that device? Any pointers to the right direction to look at would be appreciated.
Answer: It is possible, but unholy amounts of difficult. You really don't want to do this. Really. You'll basically be reimplementing USBHub.sys from scratch, as well as breaking the standard paradigm of drives in Windows (i.e. drives appear in My Computer).
Answer: You have two routes to doing this:
1) Build your own custom USB hub device, which presents itself as a single drive, and creates its own internal folders based on the devices attached.
2) Write some seriously ninja driver code combining multiple USB card-reader devices into a single drive. This would be extremely platform dependent (Windows v. Mac), and would require what would be at least 6 months of work, give or take.
I honestly would go with the first if it's a big must. Would take a custom piece of hardware though...

USB Hierarchy Driver


Page ordering based on custom field of sub pages

Question: I have a custom page type of events that allows sub pages and I want to sort the events pages in order of date of the sub pages.
so my structure is something like this:
Camping trips:

texas camping trip (custom field of date: 2/12/2014)
utah camping trip (custom field of date: 3/10/2014)

Fundraisers:

bake sale (custom field of date: 1/30/2014)
silent auction (custom field of date: 5/1/2014)

etc
When querying the pages I would like them to return in order of Fundraisers then Camping trips .
Answer: I'm assuming you're using a category to separate camping trips & fundraisers, this method should be close for other methods of separating the trips/fundraisers however. I am also assuming that you want to do this outside of the loop, or as a secondary loop. I haven't tested this, but something like this should do the trick.
Basically here is what were going to do:
1) Query for both the Fundraisers and the Camping Trips, ordered by date.
2) Merge the two queries together, so that the fundraisers are first, and the camping trips second.
3) Loop through each returned post, and mark up the information however you like.
Code:
    <?php //Enter your information for each variable:
     $post_type = 'enter_your_custom_post_type_slug';
     $fundraiserCatID = 'enter_your_fundaiser_category_id';
     $campingCatID = 'enter_your_camping_category_id';
     $acfDateFieldName = 'enter_your_date_acf_field_slug';

     //Setup each Query args
    $fundraiserAgrs = array('post_type' => $post_type, 'cat' => $fundraiserCatID, 'orderby' => 'meta_value', 'meta_key' => $acfDateFieldName, 'order' => 'ASC');
    $campingAgrs = array('post_type' => $post_type, 'cat' => $fundraiserCatID, 'orderby' => 'meta_value', 'meta_key' => $acfDateFieldName, 'order' => 'ASC');

    $fundraisers = get_posts($fundraiserArgs);
    $campingTrips = get_posts($campingArgs);

    $events = array_push($fundraisers, $campingTrips); //merge the two queries, with fundraisers first, then camping trips

    if($events) : foreach($events as $event): //If we have $events, loop through each event

      //Do what you will with the $event content ?>

<?php echo $event->post_title; ?>

         <?php echo $event->post_content; ?>

Date: <?php the_field($acfDateFieldName, $event->ID); ?>

    <?php endforeach; endif; //End the loop and the conditional ?>


Is Python and pygame a good way to learn SDL?

Question: If I want to move to C++ and SDL in the future, is Python and pygame a good way to learn SDL?
Answer: Python+PyGame is a really great idea for learning SDL.
I wrote a somewhat popular game that way. Python/PyGame seems much more advanced than SDL bindings to any other language, and one huge advantage compared to C++ is that don't have to compile code, and with some simple hacking can even modify a running program, and see the feedback live. It makes a huge huge difference - like using a GUI vector graphics program vs writing SVG in a text editor. Unfortunately you don't get this out of the box, because you need to adapt your program a bit to see it.
As for other advantages of PyGame, jrpg ran with very small changes on Linux, Windows, and OSX. I had to do some tweaks to fullscreen mode switching, and double buffering as there were some differences between OSes, but no recompilation was ever necessary. If you have any problems you can get good stack trace and debug your problems live, that's not really possible with C++ once you get a memory corruption or a segfault.
I don't really know how easy or how hard would it be to mix C++ and Python for your SDL games. I think it cannot be too hard, as PyGame is a pretty straightforward but very nicely made wrapper for SDL, and Python/C++ mixing is supposed to be easy enough.
Comment: The link doesn't seem to work (404).
Comment: Pretty sure the new correct link is this: https://taw.github.io/jrpg/
Answer: pygame abstracts the SDL interface quite a lot, therefore I don't think there's much of an advantage carried over.
Answer: You can learn some techniques, ways to implement game logic etc. in SDL-based enviroment but after moving to C++/SDL you will have to use SDL functions directly, helper functions/objects from pyGame will be completely useles.
Answer: Yes. If python is much more natural to you than C++, it might be a good idea to learn pygame first. You'll have to go through a translation process when migrating to using SDL and C, but it should be a more-or-less one-to-one mapping.
Answer: Of course. You can write a sdl game or tools in really less time.
You can start with this code that display the data/chimp.bmp into a 468x60 screen :
<code>import pygame, sys,os
from pygame.locals import *

pygame.init()

window = pygame.display.set_mode((468, 60))
pygame.display.set_caption('Monkey Fever')
screen = pygame.display.get_surface()

monkey_head_file_name = os.path.join("data","chimp.bmp")

monkey_surface = pygame.image.load(monkey_head_file_name)

screen.blit(monkey_surface, (0,0))
pygame.display.flip()

def input(events):
   for event in events:
      if event.type == QUIT:
         sys.exit(0)
      else:
         print event

while True:
   input(pygame.event.get())
</code>
When you are familiar with SDL objects you can easily move to C++ (if you want again :p Pygame is fast and you can make a complexe game with it).
Answer: For your purpose PySDL2 is better than pygame. It imports SDL2 API almost directly.
Answer: You could try pyglet If you are targetting at OpenGL. It's much better thought out library than what pygame is.
But then, if you want to move to C++ and SDL in future, do it now. That way you actually learn SDL. But before doing such an irresponsible thing, it'd be perhaps a good idea to check into pyglet first. Just because for designing your apps properly in C++ as well no matter how bad your libraries are.
Answer: python won't prevent you off learning design and that's pretty much the more important thing to learn IMO, I'm doing a smash bros clone with pygame and I learnt a lot in design. And yet you will learn not to write too much suboptimal code too, python have clever and beautiful hacks too.
Answer: I wouldn't consider Python (or any managed or interpreted language, for that matter) a good way to learn any complex task, because it insulates the programmer from the workings of the system too much. As a friend of mine put it, "Python loves you and wants you to be happy." And that's all well and good if you already know the fundamentals, but if you want to learn, the last thing you want is a language that does all the work for you.
You'll learn the what very quickly, but not the why, and then when something goes badly wrong, (and it will eventually, in any non-trivial project,) you'll be left with no idea what's happening or why.


How to segment test data based on clustering run on training data- UNSUPERVISED

Question: How can I segment the 'test' datasets based on k-means used in training datasets in R. For example, I run k-means clustering in R and get 7 segments from demographic and psychographic attributes of the customer in one state. Assigned the name to all the 7 segments based on the attributes present in each cluster. Now I want to segment other state data into the same 7 segments using previously run clustering on one state data? How to do this in R? Is it possible? Please do not confuse with supervised learning(Classification problem). My query is for unsupervised.
Answer: K-means produces a set of cluster centroids that approximately minimize the cost function. A cluster is defined as the set of points that share a common closest centroid. So, suppose you've trained k-means on some training set, and now want to cluster new points in a test set. Simply find the nearest centroid to each new point. Note that this applies to k-means, but not other clustering methods.
Geometrically, k-means induces a Voronoi partition on input space, with the centroids as seeds. All points within the Voronoi cell of a particular centroid are assigned to the same cluster. For example, in this image from Wikipedia, the black points would correspond to centroids, and all points in the corresponding colored regions (Voronoi cells) would be clustered together:
Comment: You would run k-means once on the training set, which returns the centroids. For each point in the test set, find the nearest centroid, which gives the cluster assignment.
Comment: Thank you for your comment. I got you. Just checking  Do you mean I have to run k-means clustering for train data again to find the centroid and then use these centroids to cluster test data? How can I pass-on these centroid as seed using R ? I am looking for:-  Eg: suppose segment 1 in train data consist of high income-high end cars-big home-graduate plus-no child.  the segment 1 in test data have the same attributes. Your help is appreciated.
Answer: This question has been asked many many times here already. Please use the search functions to save time.
For k-means only the answer is trivial: your "test" samples should be assigned using nearest-neighbor classification to the k cluster centers. I.e. each sample is mapped to the least-squared-error center. This is fairly cheap: just k sum-of-squares computations.
For the general case - other clustering algorithms - that won't just work. Instead, the obvious strategy is to train a classifier, using the cluster labels as training data.


Is there a transparent theme?

Question: I've been looking for themes which are transparent, but I didn't find any.
Is there someone who uses a transparent theme?
Answer: I found a solution, and no longer I need transparent theme.
The solution is :
;; set transparency
(set-frame-parameter (selected-frame) 'alpha '(85 85))
(add-to-list 'default-frame-alist '(alpha 85 85))

Comment: Unfortunately, this doesn't just change the background, but also makes text transparent as well.
Comment: how do you put this into emacs? for someone new to emacs is this in a file somewhere or at a command?
Comment: Can you comment on what this code does, exactly? Why are there two parameters?
Answer: You can set transparency within Emacs by setting 'alpha frame parameter,

This parameter specifies the opacity of the frame, on graphical displays that support variable opacity. It should be an integer between 0 and 100, where 0 means completely transparent and 100 means completely opaque. It can also have a nil value, which tells Emacs not to set the frame opacity (leaving it to the window manager).
To prevent the frame from disappearing completely from view, the variable frame-alpha-lower-limit defines a lower opacity limit. If the value of the frame parameter is less than the value of this variable, Emacs uses the latter. By default, frame-alpha-lower-limit is 20.
The alpha frame parameter can also be a cons cell ('active' . 'inactive'), where 'active' is the opacity of the frame when it is selected, and 'inactive' is the opacity when it is not selected.

but more general solution is to use your compositor manager.
For example with Compton you can change Emacs' (or any window) opacity with following change in Compton's config (i.e. ~/.config/compton.conf file):
opacity-rule = [ "90:class_g = 'Emacs'", # 10% of transparency
                 "90:!focused && class_g = 'Conkeror'"] # as a bonus

Solution will vary between operating systems and windowing systems ergo I'm providing this answer only FWIW.
Answer: The current answers here are a bit outdated so I'll post more current information. The other methods will result in a blurred background, but the text will be blurred as well, impacting readability. I presume this is generally not desirable.
Fortunately, as of Emacs 29, there is a method to blur only the background and leave the text opaque: using the frame parameter alpha-background instead of the more general frame parameter (mentioned in this question's other answers), alpha.
To do this, simply run (set-frame-parameter nil 'alpha-background X), where 'X' is whatever transparency percentage you desire.
Like all Emacs configuration, you must add it to your .emacs file for it to persist between sessions. The previously linked wiki page provides ELisp code for this (it's identical to the code Vivian posted 9 years ago aside from the frame parameter*):
(set-frame-parameter nil 'alpha-background 70)
(add-to-list 'default-frame-alist '(alpha-background . 70))

and it worked nicely for me.

Some prerequisites for usage of the above:

If you're on Wayland, you'll have to have the pure GTK (PGTK) package installed, claims the wiki. However, I found it worked out of the box for me using the normal Emacs package in the official Arch repository.
Again, you must have Emacs version 29 or later

*the writer of the wiki article also has favoured the use of '`nil`' over '`(selected-window)`', but a quick `C-h f set-frame-parameter` will reveal that `set-frame-parameter` defaults to the selected frame if it supplied `nil` as an argument.

Is there a transparent theme?


Is it possible to give Balance for transactions?

Question: I know that transactions require certain fees to ensure the correctness of the network, but i was wondering if it is possible to do the reverse operation. I want to give users that send transactions Balance.
Comment: I think that's technically possible, but why? This has the same ramifications as having no fees (e.g. DoS) but it also adds incentive to do that on top.
Comment: I'm not thinking of a decentralized network, I was thinking about a private network where there are already well known addresses and if they send transactions with some information, It is already assumed to be correct. On a decentralized network I guess it will require some validators to ensure that the information is correct and later on award the providers and also the validators, but its not the case
Answer: The transaction fees are charged by the ChargeTransactionPayment signed extension. I don't believe you could configure that thing to "charge" negative amounts. But I think you can just reimplement your own SignedExtension, maybe potentially based on top of that, that will reward each transactor and replace/add to your signed extras (like here).


total transfer function of a LTI System with feedback

Question: I have calculated the transfer function of such systems many times, but now i feel like I`m going around in circles.
I have drawn a few help-signals to help me solve it, but they are dependent of one another and no matter how many times I replace the values, I just finish where I started.
I must calculate the total transfer function of the system from the attached image. The coloured lines are the help-signals that I added and their description is below.
Any help is appreciated]1
Comment: The best and classical way is: Block diagram reduction technique. Start to replace local feedback loops by one block only!
Comment: Please show us what you have come up with so far. Where exactly are you getting stuck?
Comment: I tried to replace the variables with what is after the equal sign. for example A with X+H2*C in the second and fourth relationship. The thing is, there is no end to this replacing. So let's say we replace A
B would become X+H2*C-X*H1-H1*H2*C.
D would become H4*Y+X*H1+H1*H2*C
And C would become H4*Y+X*H1+H1*H2*C+X*H3+H2*H3*C-X*H1*H3-H1*H2*H3*C.
Now i have a relationship between Y,X and C and i somehow need to find Y/X.
Comment: And if get Y/X out of that relationship with C, i would have to replace C once again, getting into another loop, because C is dependent on the other signals
Comment: C=Y/H5  since Y=C*H5
Answer: My answer comes a little late, but I think it should still be interesting.
I took the block diagram from you (@Newbie010) as a basis and added some labels which are helpful for the calculation. My method gets along here without any simplification.
At this point I ask you to check if what I have done is correct. I did not find any mistake in my calculation, but a critical consideration would be appropriate.

Block diagram with new labels:

Based on this picture, the following equations can now be determined:
$$X(s)+C(s)=B(s)=A(s) \tag{1}$$
$$D(s) = B(s) - H_1A(s) \tag{2}$$
$$E(s) = H_4Y(s)+H_1A(s) \tag{3} $$
$$F(s) = E(s) + H_3D(s) \tag{4}$$
$$Y(s) = H_5F(s) \tag{5} $$
Other important and useful equations:
$$ F(s) = \frac{Y(s)}{H_5} \tag{6}$$
$$ C(s) = H_2F(s) \tag{7}$$
$$ C(s) = H_2\frac{Y(s)}{H_5} \tag{8}$$
The aim now is to have only inputs and outputs in its transfer function $H(s)$. Important here is this connection $H(s) = \frac{Y(s)}{X(s)}$
I now begin to generate $H(s)$ by starting with equation 5 and using the relations to other equations in turn. This is straight forward:
$$ \begin{align} Y(s) &= H_5F(s) \\
&= H_5\left(E(s)+H_3D(s)\right) \\
&= H_5\left(H_4Y(s)+H_1A(s)+H_3D(s)\right) \\
&= H_5\left(H_4Y(s)+H_1A(s)+H_3B(s) - H_3H_1A(s)\right) \\
&= H_5\left(H_4Y(s)+H_1\left(X(s)+C(s)\right)+H_3\left(X(s)+C(s)\right) - H_1H_3\left(X(s)+C(s)\right)\right) \\
&= H_5\left(H_4Y(s)+H_1\left(X(s)+H_2\frac{Y(s)}{H_5}\right)+H_3\left(X(s)+H_2\frac{Y(s)}{H_5}\right) - H_1H_3\left(X(s)+H_2\frac{Y(s)}{H_5}\right)\right) \\
&= H_5H_4Y(s)+H_5H_1X(s)+H_5H_1H_2\frac{Y(s)}{H_5}+H_5H_3X(s)+H_5H_3H_2\frac{Y(s)}{H_5}-H_5H_1H_3X(s)-H_5H_1H_3H_2\frac{Y(s)}{H_5} \\
&=Y(s)\left(H_5H_4+H_1H_2+H_3H_2-H_1H_3H_2\right)+X(s)\left(H_5H_1+H_5H_3-H_5H_1H_3\right)
\end{align} $$
Therefor:
$$ Y(s)(1-H_5H_4-H_1H_2-H_3H_2+H_1H_3H_2) = X(s)(H_5H_1+H_5H_3-H_5H_1H_3) $$
It follows:
$$ H(s) = \frac{Y(s)}{X(s)} = \frac{H_5H_1+H_5H_3-H_5H_1H_3}{1-H_5H_4-H_1H_2-H_3H_2+H_1H_3H_2} $$
Now I wanted to test if what I have done can be confirmed by a simulation. Therefore I converted the block diagram in Matlab. Also I realized my generated transfer function as a block in Matlab, the results were the same!
For the simulation I used the following blocks:
$$ H_1 = 5, H_2 = \frac{1}{s}, H_3 = \frac{1}{s+2} $$
$$H_4 = 7, H_5 = \frac{1}{s}$$
If I now insert these values into my TF and let the overall expression be simplified once with the use of Wolframalpha I get the following for $H(s)$:
$$\frac{5s+6}{s^2-10s-20}, s\neq 0, s \neq -2$$
In Matlab I implemented your block diagram with the corresponding values and my simplified transfer function. Judging by the simulation, the results are the same.
I hope that my answer meets the requirements and hope that I could help a little bit with this. Thanks a lot!
Answer: Not a full answer; just some assistance....
Just one simple block diagram re-arrangement gets you an improvement (as per LvW's comment to your answer): -

Notice the added red block contans \$1-H_1(s)\$ and this removes the summing node just in front of \$H_3(s)\$. I'm assuming that was an intentional negative sign on the summing block I removed hence the negative sign in the new block I added.
Sometimes you have to add stuff to simplify but other folk may choose a different starting point.
The next thing to do (in my opinion) would be to re-arrange things like this: -

Hopefully I've not screwed up anywhere but I'm sure if i have there'll be someone eager to point it out.
Can you take it from here?


How can I get transparent window borders / titlebars in GNOME Shell?

Question: There are plenty of GNOME Shell themes with transparent panels, and I might want a transparent window border / titlebar theme to go with it. The closest thing I can think of is Emerald, but that only works with Compiz AFAIK and GNOME Shell only works with Mutter.
Comment: Here is the theme you were looking for: http://gnome-look.org/content/show.php/MOD?content=166260&PHPSESSID=bac0f2155acef94771cfc8488965ea99
Comment: 11.10 or 12.04?? LOOK at this http://ubuntuforums.org/showthread.php?p=11453890
Comment: @BlueXrider That's for Unity's panel; it's definitely not what I'm looking for. I'm using 11.10 btw, but an answer that would be applicable to 12.04 as well would be nice.
Answer: Since the release of Ubuntu 12.10, gconf-editor has been officially replaced by dconf-editor. So the answer by Ringtail will not work.
To enable Window Titlebar transparency in Ubuntu 12 onwards:

Open a Terminal (Ctrl+Alt+T)
Copy and Paste the following line:
sudo apt-get install dconf-tools

Press Enter and install the package.
Once installed, run dconf-editor in the terminal.
Navigate to org/compiz/gwd
Now change the values of the following to anything between 0 and 1:
metacity-theme-active-opacity
metacity-theme-inactive-opacity

Now you've changed the transparency of the Window Titlebars.
Answer: I couldn't get the other methods to work in Ubuntu 19.04 so I resorted to editing the gtk.css file:
nano ~/.config/gtk-3.0/gtk.css

Here is the code I used:
/* add a 3-pixel border around windows */
decoration {
    border: 5px solid rgba(10, 10, 10, .3);
    background:rgba(10, 10, 10, .3);
}

/* customize the titlebar for active window */
.titlebar {
    background: rgba(10, 10, 10, .3);
    border-top:solid 1px rgba(10, 10, 10, .3);
    color:white;
}

/* customize the titlebar for background windows */
.titlebar:backdrop  {
    background: rgba(10, 10, 10, .5);
    color:white;
}

Once the file is saved, run this command to apply your changes:
setsid gnome-shell --replace

See below for the final result.
Comment: Thank you, it works with most of the apps but not with some apps such as `nautilus`, `gedit`, etc.
Comment: I dont see a gtk.css file
Answer: You can change the window border transparency using the gconf-editor. You can change the window transparency for all the window borders or for active window borders. To change the window borders transperancy you need to have the gconf-editor installed.
To install the gconf-editor open a terminal window (press Ctrl+Alt+T) and copy+paste the following line:
sudo apt-get install gconf-editor

To start the gconf-editor press Alt+F2 and type: gconf-editor.
When the configuration editor is open click on apps -> gwd and change the value of the metacity_theme_active_opacity and the metacity_theme_opacity to a value lower then 1.0. To change a value all you have to do is double click on the name and change the value in the edit key window.
metacity_theme_active_opacity: changes transperancy for active window borders
metacity_theme_opacity: changes transperancy for all window borders
source
Comment: @GediminasJeremiahGudelis I already voted it up! The poster of this question is not me but WarriorIng64
Comment: Sorry, but this doesn't work for me, even after logging out and doing a reboot. I think `gconf` is supposed to be deprecated in favor of `dconf`, anyway.
Comment: I will keep an eye out for a better way
Comment: The answer 1 works fine.
Comment: @Hanynowsky Mark as approved the answer that worked for you.
Comment: So sorry ;) My bad...


Show the coefficients of power series are the same?

Question: How to show the coefficients of power series are the same for two power series that coincide on an interval. I first thought about using $x=0$ to prove $a_0=b_0$ and using $n$th derivatives to show $a_n=b_n.$ But I realized that $0$ is not necessary in the interval of coincidence. Any hints will be appreciated!
Comment: can't you do the same, but consider a power series expanded about $x_0$, and consider the function and all derivatives at $x=x_0$.
Comment: I guess the question is like this.  Suppose two power series centered at zero have radii of convergence ${}\ge 4$, and the values of the two series coincide on the interval $(3,4)$.  Show that the coefficients of the two power series agree.  A deleted answer used complex analysis for this.  Is there a more elementary way?
Comment: That is the question.
Answer: Power series are defined for other values than $0$, so as long as you do the expansion around $x_0$ in the interior of your interval (not on the boundary), it will work.
The theorems are then the same, and you can use the relation between $n$-th derivative and $n$-th coefficient to conclude, as you suggested.


Need help identifying Japanese font

Question: It's from a tamagotchi product. I've been searching absolutely everywhere, from free to paid sites, just to know the name of this font. If anyone has a clue, I would really appreciate the help!
Answer: If you search for えれがんと 書体, you should find multiple typefaces in this style. In general, highly stylized fonts like this are only available for kana and (sometimes) Roman alphabets, with a different typeface used for the kanji characters (of which there are many thousands).
It looks to me like the font you're after is called えれがんとMat-UB. In the example below, it's been paired with another font called マティス-UB.
You can try out the font here.
Comment: Thank you so much! That really helps. My sister also found this and I think it's the same one you found. :) https://cute-freefont.flop.jp/typelabo_eregant.html

Need help identifying Japanese font


What is a headman?

Question: In many suttas in the Pali canon, the term headman is used; for example Yodhajiva Sutta. What is the Buddha referring to when he calls his visitors "headman"? Thank you.
Answer:
The village headman or village chief is a local government or tribal
  post. The village headman is the person appointed to administer an
  area that is often a single village.
  https://en.wikipedia.org/wiki/Village_head

India and much of the world at the time of the Buddha had a fairly decentralized devolution of power in keeping with the capabilities of the times. Often it would be months before news from the farthest corners of the kingdom reached the King's court, so real power and responsibility rested with local authorities like the headmen.
They were more than just bureaucrats, their function was more akin to a father figure, who would educate and care for his people. It was likely that the headman would take the day off to visit and listen to the Buddha, and then return home and recount the teachings of the Buddha for his village. In all likelihood the headman was also literally the father figure, since a large family of uncles, cousins and extended relations often settled down together to form a village (clan).
Unlike modern day mayors who rotate out of office, the headman post was usually for life, and so it was a very personal relationship one had with one's village, and hence the care that head men often seem to take in quizzing the Buddha.
Megasthenes' account of India - 'Indika' is the earliest available written account of India's governance, written about 200 years after the Buddha. It refers to headmen as overseers.

The sixth class of Indians are those called over-seers. They supervise
  everything that goes on in the country and cities, and report it to
  the king, where the Indians are governed by kings, or to the
  authorities, where they are self-governing. It is not lawful to make
  any false report to them; and no Indian was ever accused of such
  falsification.
Answer: I found a book on google books explaining what a "Headman" is and how he is elected. It's not possible to quote from the book so here is a screenshot and a link to the source.
In short it says that a headman is elected by other villagers and that his asignments are administrative tasks in a village. He has other tasks too since in some litterature it's mentioned that he takes care of business when e.g. someone has stolen something in a village. Here is link to a book wherein a headman must make a decision about a wandering monk who has stolen twice.
So it sounds like a headman is the authoritative figure of a village. A boss of some sort.
Comment: This book refers to Thailand from a 100 years ago, but I guess it's pretty much the same more or less even 2400 years ago in India - except in the modern age power is often aloof and impersonal and based on qualifications. Whereas, the headmen of olde were probably blood relatives of the village, since most villages were all of a clan blood.
Comment: Thanks Sri Lanka, I have been reading up on ancient Indian history to get a sense  of the milieu that caused so many introspective wise men to pop up in India around the same time.
Comment: Interesting knowledge you have Buddho. I didn't know about the last section of your comment.

What is a headman?


Generating FFT on data recived from 20Amp(ACS712) current sensor using arduino & processing IDE

Question: Currently, for generating FFT on the data received from ACS712,i used the following method:
 first the data is sent to the Processing IDE from the sensor via arduino. the processing code converts the data into a text file, the text file is then loaded into matlab and fft is plotted.
Are there any other ways of plotting FFT? can arduino be used to directly generate FFT from the data received?
Answer: Yes, it is possible to calculate the FFT directly on the Arduino if the data rate is slow enough, if you don't need full float/double precision and if you don't need an excessive number of bins.
You have not written anything about your data rate, the required precision, or the number of bins, so it's impossible to answer if it's good enough for your needs.
Maybe you can compare your current code with the numbers on ArduinoFFT and figure out if it's good enough.
Comment: Even if the data rate or precision is high, or the required bins is large, you can still perform "snapshot" FFTs on segments of acquired data. It won't be very real-time, but better than porting into Matlab.
Comment: Thank you, I would definitely check into your suggestions and update you accordingly..


Can Ubuntu run on a Mac with PowerPC?

Question: I have an iMac with a PowerPC chip in it. Can Ubuntu run on it? I have Mac OS X 10.4.11 running on it right now. The brand is Apple.
Comment: Have you looked at this and the pages it references? https://wiki.ubuntu.com/PowerPCDownloads
Answer: You should be able to run Ubuntu on your PowerPC Mac; you just need to get the PowerPC version.
Some third-party software is not provided for PowerPC and thus won't work, and since the PPC architecture is community-supported and has a relatively small installed user base these days, you may experience a few more bugs. But I say go for it--especially since Mac OS X v10.4 Tiger is completely unsupported and no longer receives updates even for newly discovered security vulnerabilities.
See these resources for more information:

PowerPCFAQ
PowerPCDownloads
Which version of Ubuntu will work on my PowerPC?
(which is a bit more specific than this question, and also hasn't been updated in a while)

Lubuntu is particularly lightweight, so especially if this is an older PPC Mac (G3 or G3), you might consider using that. Ubuntu MATE is also lighter-weight than "vanilla" Ubuntu and has a (much reported on) PPC version.

Can Ubuntu run on a Mac with PowerPC?


Do I need to apologize for late reply to Professor's mail?

Question: For some reasosns, I needed to email our professor in the name of the whole class as class representative. When I got the reply, I had to check if everyone in the class was OK with it. This has some time, about a week. Do I need to apologize for the late reply and explain this? Or do I just reply without minding it?
Answer: A week is very reasonable for a reply by email [*]. There is no need to apologise.
It may be useful to explain that everyone in the class agrees to "the thing". Most professors would be able to deduce from that information that you have consulted them and that this took some time. This is the second reason you do not need to apologise.

[*] obviously this depends on the urgency of the matter, but in general replying within a week is considered "fast".
Comment: However, including a polite apology doesn't hurt: "I apologise for not sending this message earlier, but I had to wait for agreement from all class mates."
Comment: Apologising too much or too early usually indicates insecurity. Many professors and teachers prefer to see professional, independent students. Sincere apologies are always good, but "political" apologies are often worse than no apologies, when none are necessary. This may strongly depend on the culture. But no one expects apologies about a late reply when the reply is actually early by most people's standards.
Comment: There is a cultural aspect. In my experience, you should err towards more politeness and formality in India.
Comment: I would not generalize the expectations like so. It sounds pretty unreasonable to ask a question pertinent to the next week's class only to receive an email with the response at 8am the very same day that class takes place.
Comment: @Lodinn If the situation you describe was what happened, OP should not have left out that essential information. My reading of this question is therefore that this is not an urgent matter, and the footnote to my answer clearly states that it does not apply to urgent matters.


How big can i make the "world"/animation set?

Question: I am setting up an animation scene that needs to be a sprawling area.  I have noticed that navigation gets awkward as I get further away from the central grid, especially in "user perspective".  I am only at the point of setting up the main parts now and I would like to know now if I am doing something wrong before I get into adding the details.  Is there a limit to how large I can make the world/set?  Can I extend the outer boundaries?  Am I doing something fundamentally wrong?  Thank you!
Answer: You can technically make the scene infinitely as large as everything scales linearly. as you start getting up to a large scale you might start running into clipping issues with the camera however this can be adjusted by adjusting the end clip of the view.

However it's not recommended to scale things up more than needed as translation and scaling starts to get a little weird especially when you add cameras to the mix.


Deploy IIS publicly when my ISP changes my IP address regularly

Question: My Internet access provider changes my IP address regularly. Will the website that I will deploy on IIS remain available for external users, even if my IP address won't always be the same?
Answer: The easiest way is to use a Dynamic DNS (DDNS) provider.  There are a number available:
https://freedns.afraid.org/
https://www.noip.com/
https://www.duckdns.org/
Comment: Nitpick: not _only_ if you use DDNS. You need _some_ way to connect the hostname to your home server, and DDNS is one specific way. Another way would be having an external proxy for your domain that proxies to your (changing) IP address. Or setting up a IPv6 tunnel, and set up DNS for the unchanging IPv6 address. I mean, DDNS is an appropriate answer, and probably best here, but it's not the _only_ way.
Answer: One method which does not rely on DDNS is implemented by (for example) ngrok, Serveo, and Pagekite.  They essentially perform port forwarding over a tunnel to allow users to hit one of their public addresses and get redirected to your private server.  It's like this:
<code>[U]========>[ngrok]<========[Users]</code>
[U] is your computer at home.  It connects to ngrok and leaves that connection up and running.  That connection is a tunnel, which allows network traffic to be passed back and forth .  Your Users, then, connect to a public address that ngrok has assigned to you.  When they do so, ngrok says "Oh!  This traffic is for U!" and it routes that traffic over your tunnel, and your PC sends back its response via the tunnel, etc. etc.  ngrok is a little bit like a reverse proxy, a little bit like a VPN, a little bit like a router.
Since the role your computer at home plays is purely as a client in this scenario, it doesn't run afoul of the various inconveniences your ISP will scatter in your path.  Worst case they might kill long-lived connections, but the client on your machine will notice and spin another connection up.
I'm surprised Serveo is the only service being flagged.  It turns out that many people who manage and secure networks frown upon you opening up your work PC to the Internet, bypassing all the expensive firewalls and IDS and DLP controls they put in place.  (I know that doesn't apply to what you do with your PC at home.  But if you're wondering who would find these programs malicious, the answer is, any corporate IT team.)
Comment: Yeah, our corporate IT recently implemented group policies to completely kill ngrok processes even though up until the latest VS release it was among MS's recommended tools for debugging and testing a number of services...
Comment: I think you need to explain a bit more. The link to ngrok and Pagekite leaves me none the wiser.  And Serveo is tagged as dicey by MalwareBytes
Answer: Talk to your ISP and get a cost for a single static IPv4 address.
Depending on their policies, you might be required to move to a "business" grade connection which will cost more but give you a better SLA, and maybe a small routed block of static IPs.
This becomes a cost/benefit proposition if you're serving a home or business website.
Aside - its worth asking about IPv6 support too.  You would like at least a /64 fixed prefix, and a /60 would give you 16 blocks of 4 billion addresses


Handling Error on transaction request

Question: When a wallet makes a POST request to my server in transaction request and suppose any error occurred (e.g. insufficient funds). How can I send this error as a response so that the wallet trying to fetching the transaction gets this error message?
Answer: I don't think Wallets react to any error messages sent as a response to it. The Wallets just sign and send the transaction. A solution to this could be that you can show the error in the UI where the user is scanning the QR.
Comment: So the post method, which is called by the wallet and where the error might occur. Is there any special way to handle this kind of error because my fe(client)is unaware of this server and post method.
Comment: Do I need to add events from server so that client is aware of any event in server
Comment: Ya the frontend and the wallet and the backend server are kind of disjoint so yes adding a event in the server and catching it in the frontend should help
Answer: Currently the specification doesn't have a way for the server to return an error message, only the HTTP status. So generally if you respond with a 4xx or 5xx then the wallet will show a generic error message. We have an alpha 1.1 version of the Solana Pay specification which proposes a fix for this, see https://github.com/solana-labs/solana-pay/blob/master/SPEC1.1.md#error-handling. This is not currently implemented by wallets though.
For your other question of making the frontend aware, you'll need to do that off-chain, since there will be nothing on-chain to listen to when there's no transaction. For example you might want to use websockets, you could pass an identifier to the API in the QR code so that it can send a message to the websocket the frontend is listening to.

Handling Error on transaction request


Is it normal that one can access MySQL as root without entering password, although password is set?

Question: I just installed MySQL (Ver 14.14 Distrib 5.7.22) on Ubuntu 18.04 and I discovered something weird:
I installed MySQL and used mysql_secure_installation to set a password for root, but as soon as I am logged in SSH with any user with sudo-rights, I can simply access MySQL without being prompted to enter a password via mysql -u root or via mysql -u root -p & simply clicking ENTER (when asked "Enter password:").
Is this normal?
I know from prior versions that I always had to enter a password when I wanted to access MySQL, even with sudo.
Comment: Great question, and I'm surprised that MariaDB allows it.
Answer: Ubuntu's MySQL packages (which are based on Debian's) use by default the auth_socket plugin. With this plugin when connecting from the local machine no password is required, but the server identifies the operating system user and matches that user. So if you are root on the system and login you become root. This avoids having to setup a MySQL root password first.
See also https://wiki.debian.org/MySql
Comment: Yep and create a MySQL user with same username as your unix username  IDENTIFIED VIA auth_socket and you can login with no password too!
Answer: You should run SHOW GRANTS FOR 'root'@'localhost';
If it shows this line in the results:
GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED VIA unix_socket WITH GRANT OPTION

and not this line:
GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED BY PASSWORD '*xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx' WITH GRANT OPTION

that means the root user is automatically authenticated by the unix socket credential. If you don't want this, you can issue a manual GRANT command (don't shoot yourself in the foot doing this) that will override the previous, eg:
GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED BY 'mysecurepassword' WITH GRANT OPTION;

Now mysql will ask a password, but can be used by any user able to access the unix socket (so by default just using mysql -u root -p without being root but of course knowing the password). You have to ponder which one is more secure.
I don't know why the mysql_secure_installation doesn't explain about this.
Answer: On Ubuntu 18.04 with MySql 5.7 this doesn't work at all.
Do the following:

use mysql
select plugin from user where user='root';

You will notice that the plugin is 'auth_socket', which is the responsible for the behavior we do not like.
To change this you have to change the plugin and set the password within the same command. This can be be done this way:

ALTER USER 'root'@'localhost' IDENTIFIED WITH MYSQL_NATIVE_PASSWORD BY 'mypass';

Just done and it works!


How do I determine the temperature at which a dissolved substance evaporates?

Question: I would like to understand the temperature at which a substance will vaporize when dissolved in a liquid. I have researched this online for hours, but haven't found a conclusive answer. Is it the boiling point of the dissolved substance? I'm attempting to find the temperature at which caffeine vaporizes when dissolved in water or other vegetable glycerin. Many thanks for your help.
Comment: Look for phase equilibria and boiling point of binary mixtures. Once you make a mixture, you cannot speak of boiling point of one component, but only of the mixture. And then of vapor/liquid equilibrium.
Answer: First, it is a good idea to clarify the meaning of the word vaporize from here:

(Physics / General Physics) to change or cause to change into vapour or into the gaseous state
to evaporate or disappear or cause to evaporate or disappear, esp suddenly
(Physics / General Physics) to destroy or be destroyed by being turned into a gas as a result of extreme heat (for example, generated
  by a nuclear explosion)

Chemists should be careful when using this word because it can be used to describe evaporation, sublimation, and boiling.  Note the third definition, which suggests that the vaporization of matter typically involves a large amount of energy.
Since the mixture you refer to in your question is in a liquid state, I am going to focus on liquid boiling.  (Note, we can say that boiling is the rapid vaporization of a liquid.)  The boiling point of a liquid is the point at which the vapor pressure of the liquid is equal to the surrounding pressure.  The boiling point of a liquid is affected by intermolecular forces such as hydrogen bonding, dispersion and dipole-dipole interactions.
When a solute is dissolved in a pure liquid (your example of caffeine dissolved in water), these intermolecular forces are altered.  The end result is an elevation of the boiling point.  This change can be predicted quite accurately using concepts typically covered in the first year of a college-level general chemistry class.
So, we know now that a mixture of caffeine and water will have a boiling point higher than pure water; however what happens as the solution continues to boil?  I ignored an important point in the previous paragraph; boiling point elevation due to addition of a solute will only occur if the solute is nonvolatile. Caffeine is such a solute.  Therefore, as you boi your mixture, the water will be turned into a gas, but the caffeine will be left behind.  The volume of solvent is decreasing; therefore the solution concentration is increasing.  Once the caffeine solubility limit is reached, it will start to crystallize.
When you are left with a mound of caffeine you can continue to heat it.  As you heat it above about $230\,^{\circ}\mathrm{C}$ it will start to sublime, or in more general terms, vaporize.
For those interested, the experimental procedure for the extraction and purification of caffeine from tea leaves is described at an undergraduate level here.
Comment: @bobthechemist, thank you. What would happen if the mixture were directly exposed to a 230 degree heat source as opposed to a gradual heating process?
Comment: @user3904 Rapid heating would still result in the water boiling first.


what are the root causes of css failure in ie9

Question: we have a complex .net 2.0 app which uses css as intended.  for some reason a subset of web pages renders as if there is nothing on the page in ie9.  if you set ie9 to "no style", everything that should be there is visible.
we are using the correct mime types on the css files.  there are no warning or error messages in the developer tools console.  these same pages render without a problem with ie7 or ie8.  because we use asp client side validation we are unable to verify how these pages look with alternate browsers.
we tried removing the css link, no difference.  if you use the developer tools and click on one of the "invisible" elements (td for the most part) tools will highlight its location on the page and a check of the css it has inherited looks reasonable.
so at this point we are stumped.  we have tried validating the html but there are too many issues for the validator to make much progress, mostly related to the pages being tagged as xhtml transitional.  that particular setting was done long before i came on board so i have no idea of whether there was any real thought into choosing it or whether it was just a .net 2 default.
any suggestions on analysis tools or approaches to solving this type of problem?
=== followup ===
not sure if its a css issue or not.
the page in question was using a frameset with the following pattern (details ommitted)
<code>frameset rows="xxx,xxx"

    frame style="left: 0px; position: absolute; top: 0px"

    frameset cols="xxx,xxx"

        frame

        frame
</code>
and thru a process of elimination we found that
"style="left: 0px; position: absolute; top: 0px"
was the cause of the problem.  after finding that the individual frames could be loaded by themselves and they would display without a problem, we started attacking the frameset an element at a time and when the style was removed it would work.
Comment: please show some real time code/fiddle/screen shot how can we test.
Comment: evidently frames are passe but the snippet above was the essence of the page.
Answer: Gladly you already gave he awnser your self

We have tried validating the html but there are too many issues for the validator to make much progress, mostly related to the pages being tagged as xhtml transitional.

It is very common for a web browser not to display a thing on a page if the page is broken. Even if you are using xhtml transitional, it is a good practice to validate the page and fix the errors.