Why is my chocolate fudge not that dark?

Question: A UK chain's chocolate fudge is very dark. When I do chocolate fudge it comes out more looking the colour of milk chocolate. Is this because they use whipping cream or for some other reason?
Comment: What are you using to make the fudge chocolate flavoured?
Comment: Cocoa or Dark Chocolate - I've even tried the super dark stuff like 95% content!
Answer: It's possible that you need to add more chocolate, or use a different type of chocolate.  Dutch process cocoa has a much darker color than natural cocoa, for example.
It's also possible that the color is being lightened by microscopic air bubbles.  This can happen if you use a fluffy ingredient (such as marshmallow cream) or if you mix a lot of air into the fudge.  Although, I imagine it would take a lot of air to make a big difference.
If all else fails, try dipping pieces of fudge in dark chocolate.  I know that's cheating, but who's going to argue with chocolate covered fudge?  Sounds good to me!
Answer: Probably it's the cocoa/chocolate used - there are some brands/breeds that are a lot darker than others and this shows in the final product.
I have made the exact chocolate or marble cake with cocoa powder (same processing type) from different manufacturers and the results were optically quite different. This won't necessarily influence the taste, though, at least if the "visual expectation" of darker is more chocolate-y can be ignored.
Answer: Are you using soft brown sugar?
My fudge is very dark just using 20 grams cocoa powder and dark brown sugar recipe.
The best fudge I have ever made is from Chitty-Chitty Bang-Bang, by Ian Flemming. It is available online.  That recipe will offer you two values: one for white sugar one brown sugar.  Use the Brown sugar for darker fudge.


Undo a Deletion on an activity

Question: I deleted an activity and would like to re-add it. Please help!
I can't seem to find a search bar that would help me find the right steps to correct.
Answer: I don't think you will find a process to undelete a deleted activity via the UI. If you have access to the database then you could try finding the relevant entry from the log_civicrm_activity and log_civicrm_activity_contact to reconstruct your missing item.

Undo a Deletion on an activity


Web user authentication methods

Question: Is there any method besides using a DB with username and password for authenticating a user?
Answer: Depending on how users access the site, you might be able to authenticate simply by their IP address.
There is also HTTP authentication, both basic and digest.
But if you need to differentiate between multiple users then these need to be stored somewhere, and regardless of the method used, this is a "database".
Answer: Oh boy are there! OAuth (Facebook, Google, Twitter), SAML, LDAP, PAM, HTTP Basic, HTTP Client Certificate, IP restriction, 2-Factor authentication, RSA token, biometrics.
Comment: I like the rundown. Very impressive! I would like to have seen a couple of paragraphs that would categorize these by advantage and when and how to chose one or a set of options. Not a lot, just a bit more to be helpful and give a direction to run in. Clearly, you know what you are doing! The user does not- at least not to the degree you do. Here is an opportunity to add a bit of value. Thanks in advance!
Comment: BTW- I want to say I like your answers. I wrote my comment to be constructive and not critical. Please keep it up!
Answer: You could try using some eternal authentication like OAuth http://oauth.net/ or Facebook Login https://developers.facebook.com/docs/facebook-login/login-flow-for-web/v2.1
I believe OAuth still requires SQL usage though.

Web user authentication methods


What package is right for my computer?

Question: I am running on Ubuntu 11.10 32 bit, and I am wondering what packages of software I should download; namely, RPM, DEB, or TAR GZ. I have encountered having to choose from this list while trying to download avast! internet security and Adobe Flash Player.
Answer: Ubuntu (like Debian, on which Ubuntu is based) uses .deb packages. HOWEVER, I don't recommend downloading packages and installing them outside of the Software Center if you can help it. Ubuntu Linux is different from Windows or Mac in that regard. You can use the Ubuntu Software Center to search for and install packages, or command line tools like apt-cache and apt-get if you're feeling geeky.
For example, to get the Adobe Flash Player, simply install it via the Ubuntu Software Center. You could additionally install Ubuntu Restricted Extras, which will install other common proprietary media formats like MP3 as well.
As for Avast, it doesn't seem to be in the repositories, but perhaps you could find a suitable alternative such as ClamAV. Also, remember Anti-Virus protection isn't generally needed on a Linux system in the same way it is needed on a Windows system. I run Clam on Linux file and email servers simply to keep viruses from getting passed on to Windows machines that may connect.
Hope some of this helps you.
Answer: Ubuntu 11.10 and other Debian based distributions work best with DEB files. Usually TAR.GZ files contain the source code of the program, so you would have to compile the program yourself. RPM files are mainly used in Fedora/Red Hat based distributions.
Though it is possible to convert RPM packages to DEB ones.
Note, make sure you download the correct architecture package for your system. i386 usually means 32-bit OS, x86_64 usually means a 64-bit OS.
Answer: DEB file will be the best for you. It's binary version and very easy to install (By Just double click). It will automatically resolve dependency if have any. If you fail to find deb file then you should download tar.gz which is source-code version (not compiled). General way to compile and install tar.gz version is following
1. Extract the tar.gz file
2. Open terminal the and : cd your_file_directory/Extracted_directory
3. ./configure
4. make
5. sudo make install

The process differ from source to source. Most of the source follow this way. To make sure the process  read the READ-ME file provided by the developer(in extracted directory)
First, try to find your packages in software center which is default installed with ubuntu.
Comment: Never ever use `sudo make`. Root privileges is only needed to *install*, **not** build.
Comment: Also, installing apps via source is generally a bad idea in Ubuntu: you may miss menu entries, icons, and many other desktop and system integration. For standalone, command-line only software this may be OK, but if a .DEB is not available, an unexperienced user should think twice about going the tar.gz route
Comment: If you do find a package that is only available in a tarball (name.tar.gz), it's a good idea to install it using checkinstall.  It will keep a record of the install and allow you to easily uninstall it later.  See: http://asic-linux.com.mx/~izto/checkinstall/  . It should be available in your package manager.
Answer: First always check Ubuntu Software Center. Flash is available for Ubuntu. If you really really need to newest version you need a deb. Only need to remember that there are 32 and 64 architecture versions.
Regarding avast: if you want it to scan for virri and you only use Ubuntu... forget about it. At the moment the only thing you can use it for is for scanning incomming and outgoing traffic to and from Windows machines inside your network.
Avast is not in the repositories so if you really believe you need this download.
Comment: +1 for promoting the "First always check Ubuntu Software Center" policy. It is a best-practice no-brainer until you are more familiar with Ubuntu/Linux in general
Answer: The other answers here are largely right. You should look in the package manager first, and failing that, use a .deb file. .deb is the default package type for Debian-based systems like Ubuntu, and it'll install all the files in the right place, and you shouldn't have any problems (unless the package is out of date). Note that .deb files built for different Debian-based distros are slightly different, but will usually work. The only problem you may face is if certain required libraries aren't available, or are called different things. If that happens, your best bet is to ask here or on other ubuntu forums about how to deal with that specific problem.
If .deb files aren't available, you can use .rpm files on a debian-based system. The most reliable way is to use the alien package, which is available in the package manager. This basically converts the .rpm file to a .deb, making sure to use all the correct file paths, and then (optionally) installs it. You can simply run:
sudo alien --install /path/to/package.rpm

If you're feeling adventurous, you can compile from source using a .tar.gz. This method is quite often prone to annoying failures, such as missing libraries, but will generally work if you're persistent and are using up-to-date sources. If you plan to go down this route though, you may as well learn how to use git or what ever other version control system the software you want uses (assuming it's open source), so that you can get the most up-to-date version, with any bug-fixes (although this opens you up to newly-introduced bugs as well).
Answer: i think linux don't need to have antivirus, because when you want to install software, your OS inform you and want to get admin password from you, linux just need backup!
you can convert .rpm onto .deb, but not recommended
and you can convert .run onto .deb ...
by this action you can download any thing you want
Comment: Don't just say "you can convert...", say **how** to do it. At least mention the tools needed so the user can google for it.
Comment: Also, converting from .run and .rpm to .deb is a little too advanced for a user that is asking about Flash and Avast. And suggesting that you "can download anything you want" is a *very* bad practice in Ubuntu. It can encourage newcomers to run any flawed script he finds out there and end up messing his system way beyond his skills to fix it.

What package is right for my computer?


Numerically solving a system of nonlinear ODEs with boundary conditions

Question: I have a system of 6 second-order nonlinear ODEs involving 5 different functions of a variable $t$. Every function has a boundary condition at $0$. I've never taken a differential equations class and know very little about them, but unfortunately they just popped up in my research and now I really need to solve this system. I think it's impossible or very difficult to solve analytically and a numerical approximation would be good enough for me. I was hoping to do it in Matlab because I'm very familiar with Matlab. If Matlab already has a function for this that would be amazing but I couldn't find anything. My supervisor suggested the shooting method but upon looking this up (and Runge-Kutta methods in general), it appears to be only for one equation and not a system. Am I missing something? If not, can anybody recommend an algorithm and somewhere I can read about it for problem? Speed and ease-of-programming is more important than accuracy (although within 5%ish of the true solution would be nice) because I have to solve the system many times for different-valued constants. I can list the equations if that would help. Thank you!
Comment: See [MATLAB ode45](http://www.mathworks.com.au/help/matlab/ref/ode45.html) and other ode** functions as a place to begin with. These handle systems of equations as simply as single ODEs.
Comment: @Daryl I had seen that, but I didn't know you could turn a system of equations into a single equation. How exactly does that work? Also, reading this article it seems like they need all the equations to be of the form "Y' = ...", but my equations are all implicit. One last thing - isn't this an exact solver? I actually tried putting it through dsolve, but that made Matlab take two hours then crash without a solution.
Answer: Since you have not given the set of differential equations, this answer cannot respond exactly. However, as indicated in the comments, the system of equations is implicit. These can be written as $F(t,y,y')=0$, where $$y(t)=[y_1(t),y_2(t),\ldots,y_n(t)]^T \text{ and } y'(t)=[y'_1(t),y'_2(t),\ldots,y'_n(t)]^T.$$This system can be solved numerically in MATLAB using ode$15$i.
As an example, suppose we want to solve the implicit system of ODEs
$$
F(t,y,y')=\begin{bmatrix}\cos(y'_1)+y'_2-y_1\\t\sin(y'_2)+y'_1-y_2^2\end{bmatrix}
$$
with $y(0)=[0,0]^T$ for $0\leq t\leq T$.
ode$15$i requires consistent initial conditions for both $y$ and $y'$. Given that we do not have initial conditions, they can be approximated using the decic command.
This can be done in MATLAB as follows.
T = 5;
y0 = [0;0];
fun = @(t,y,yp) [cos(yp(1))+yp(2)-y(1);t*sin(yp(2))+yp(1)-y(2)^2];

[y0,yp0] = decic(fun,0,y0,[1;1],[0;0],[0;0]);%get consistent initial conditions

[tsol,ysol] = ode15i(fun,[0,T],y0,yp0); % solve the system

plot(tsol,ysol(:,1),'b',tsol,ysol(:,2),'r') % plot the solution

Edit: Solution to include equations
System
The system of DEs to be solved is as follows:
$$
\begin{align}
\theta '' &= \frac{\theta' \cos \theta}{R} + \frac{R'\sin \theta}{R} + \frac{\nu\sin\theta}{\kappa R} + \frac{\eta\cos\theta}{\kappa R} \tag{1}\\
\nu' &= \frac{\kappa}{2} \left( \theta' + \frac{\sin\theta}{R}-c_0 \right)\left( \theta'-\frac{\sin\theta}{R}-c_0\right) + \lambda\tag{2}\\
\eta' & =0\tag{3}\\
R' &= \cos \theta \tag{4}\\
z' &=- \sin \theta \tag{5}\end{align}
$$
No initial conditions are given, though it is stated that all zero initial conditions may be appropriate.
Solution
Noting $(3)$, the solution of $\eta'=0$ must be $\eta(t)=c$ for some constant $c$. Since $\eta(0)=0$, we must have $c=0$, giving $\eta(t)=0$. As such, $(3)$ is not needed, since $\eta(t)$ can be obtained analytically. I will assume, however, throughout the remainder of the solution below, that $\eta(t)$ need not be a zero constant, but simply any constant, as given by the initial conditions.
Furthermore, $(1)$ can be reduced to first order by introducing the auxiliary variable $A=\theta'$. Then $(1)$ becomes
$$
A'=\frac{A \cos \theta}{R} + \frac{R'\sin \theta}{R} + \frac{\nu\sin\theta}{\kappa R} + \frac{\eta\cos\theta}{\kappa R} \tag{6}
$$
with the additional equation
$$
\theta'=A\tag{7}.
$$
The system then required to be solved is $(2),\,(4),\,(5),\,(6)\text{ and }(7)$.
In MATLAB, an m-file for the ode function should be created similar to as follows
function F = odefun(t,y,yp,parms)
% evaluate the ode functions with the given parameters
% y and yp are ordered as [theta,nu,R,z,A]
% parms is a structure, containing eta, kappa, lambda, c0

% extract components from parms structure
eta = parms.eta;
kappa = parms.kappa;
lambda = parms.lambda;
c0 = parms.c0;

% extract components from y and yp for more clear use
theta = y(1); thetap = yp(1);
nu = y(2); nup = yp(2);
R = y(3); Rp = yp(3);
z = y(4); zp = yp(4);
A = y(5); Ap = yp(5);

% allocate memory for return variable
F = zeros(5,1);

% precompute some quantities
sint = sin(theta);
cost = cos(theta);

% evaluate equation (2)
F(1) = nup - (kappa/2*(thetap+sint/R-c0)*(thetap-sint/R-c0)+lambda); %****

% evaluate equation (4)
F(2) = Rp - cost;

% evaluate equation (5)
F(3) = zp + sint;

% evaluate equation (6)
F(4) = Ap - (A*cost + Rp*sint + (nu*sint+eta*cost)/kappa)/R; %****

% evaluate equation (7)
F(5) = thetap - A;

Note: Both equations marked by %**** $\left(\text{i.e. $(2)$ and $(6)$}\right)$ will have a divide by zero if $R(0)=0$.
From my previous smaller example, you should be able to make this function work with the ode15i(...) and decic(...) commands.
Comment: Your edit is awesome and so are you. Thank you!
Comment: Could you possibly do a second-order example? This was great but matlab doesn't like my attempt at generalizing.
Comment: I added the actual equations to my question. Any help would be very much appreciated :)
Comment: @SamuelReid With only a brief peruse, it looks like your only second order derivative is on $\theta$. This is usually overcome by introducing an auxiliary variable, say $\Theta$, such that $\Theta=\theta'$. Then $\theta''=\Theta'$, and the system is reduced to first order. I will expand my answer later today to include this, but it is too difficult on a mobile device.
Comment: @SamuelReid I also want to check your third equation. Is it actually $\eta'=0$. If so, then it can be simply removed, since $\eta=constant$.
Comment: Yeah, it is haha. I know that but I also don't know how to let it be an arbitrary constant (I have no idea what it would be) in matlab...
Comment: Also, good idea! I will try that later today.


What level of cellular radiation is harmful for humans?

Question: What level of radiation at the frequencies used by the cellular network(1-2 Ghz) is harmful for human health?
Comment: Yes, I mean it, mobile phone network, like gsm, CDMA, LTE and all...
Comment: This cellular network means mobile phone? Is it electromagnetic radiation?
Answer: Addition to the previous answer

First you need to understand how radiation causes cellular damage.
EM waves like γ-rays, X-rays and high-energy UV (in certain molecules even visible light) can knock out the electrons from the atom and create an ion and free radicals by breaking chemical bonds. This term — ionizing radiation is not used for low energy UV and visible light because these waves can only ionize a few types of molecules and are not ionizing in general. Moreover X-rays and γ-rays can dislodge even inner electrons which UV and visible light cannot (High energy γ-rays can also lead to the nuclear reaction of pair production). These ions that are formed are reactive and can attack other molecules (DNA/proteins etc) around them. DNA absorbs UV and this can cause DNA lesions such as dimerization of adjacent pyrimidines (via a cyclobutane bridge). Both reactive ions and pyrimidine dimers can cause cancer; the former is most frequent in melanomas which happen because of solar UV. Since UV cannot penetrate very deep, they affect mostly the skin (See here).
IR, with energy lower than visible light does not have sufficient energy to cause electronic transitions. But it can cause vibrational transitions such as bond stretching and bending. Microwaves have even lower energy and can only cause molecular rotation. Both IR and microwaves because of their property to make molecules move, generate heat.
Continuous usage of mobile phones can cause discomfort but only because of their heating effect. They can by no means cause cancer and even though mobile phone radiation is classified as a potential carcinogen (IARC Group 2B) perhaps because of the pressing allegations of certain factions, they do not have sufficient energy to cause DNA damage.
If you ask me if mobile phone radiation can be harmful to human health, then I would say yes, they can be potentially harmful with prolonged usage but in no way as harmful as to be causing cancer. I would say that it is as harmful as wine :P
Comment: One thing to note is that close proximity to cell tower microwave transmitters can and will give you radiation burns, due to the wider range of harmonics. The GSM band runs at 1800MHz, from which the first subharmonic sits inside a range (~915MHz) that is known to excite water molecules in the same way that an industrial microwave does.
Answer: Afaik. radio waves don't have enough energy to cause anything similar to the damage ionizing radiation (gamma rays) does.
What it can cause is probably heat damage similar to microwave ovens.

According to the United States Food and Drug Administration's Center for Devices and Radiological Health, a U.S. Federal Standard limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts of microwave radiation per square centimeter at approximately 5 cm (2 in) from the surface of the oven.[52] This is far below the exposure level currently considered to be harmful to human health.[53]

http://en.wikipedia.org/wiki/Microwave_oven
Advanced Measurements of Microwave Oven Leakage - http://www.arpansa.gov.au/pubs/emr/microwave.pdf

According to the article referenced by wikipedia a 35 W/kg SAR level (caused by a 30 mW/cm2 leakage) can raise the tissue temperature with 1.5°C, which probably does not any serious damage. I guess from this you can count the radiation intensities - you are interested in - to any frequencies.


What causes the aurora of other planets to have different colors?

Question: All I could come up with is it depends on the atmospheric composition of the planet as they will interact with the charged solar particles which might be true but is there is there a definite reason behind the different colors of aurorae on other worlds (Saturn's blue aurora for example)?
Answer: Ultimately, you are correct. However, there may also be some clarification in order: what blue aurora of Saturn are you referring to? The most well-known auroral images of Saturn like this one, are not true color images. That is, what we see in the photo isn't what you'd see with the naked eye; instead, the photo has been enhanced to emphasize something interesting, in this case the aurora. In reality, that beautiful blue you see in the picture isn't even of light that's visible with our eyes. It's UV light which would be completely invisible to us. People working with data taken by a specialized camera have to give the UV light some visible color or we wouldn't see it at all. The Saturn aurora images I am aware of all have been modified in this manner.
However, aurora themselves are the result of charged particles funneling down a planet's magnetic field and crashing into the planet's atmosphere. On Earth, the aurora occurs because of the atoms in the atmosphere getting energized by these collisions, and then emitting light when they de-energize. Here, it's the oxygen and nitrogen in the atmosphere that are responsible for aurora light (primarily greens from oxygen, but also reds at higher altitudes from oxygen and occasionally blues from nitrogen). In other planets' atmospheres dominated by different atoms and molecules, the reactions will be different, and the wavelengths of light emitted will be different as well. For example, Saturn's aurora are due to energized H2 molecules. On Jupiter, it can be the infalling particles themselves (sulfur and oxygen) that are responsible for auroral emission.
Comment: 'Different' You can look that up with 0 work. Gas giant atmospheres are dominated by $H_2$. It's the $H_2$ bands that radiate in the UV when excited by elctron precipitation. They don't radiate in the optical as the hydrogen molecule doesn't have allowed lines there.
Comment: It's unclear why there's a need for sass. The original question appeared to be primarily based off of a misconception concerning published images of aurora around other planets. If my answer is not of sufficient thoroughness, you should certainly feel free to submit you own? Regardless, you are only partially correct: while the mechanism for Saturn may be dominated by H2, that is not the case for Jupiter. My answer has been edited to reflect this.
Comment: @AtmosphericPrisonEscape Auroral colours are not (at least on Earth) caused by *allowed* lines.


On a transmission line, why are voltage and current waves reflected at a short circuit?

Question: I do not intuitively understand this. A short circuit simply means there's no impedance. If there's much less impedance than the transmission line, the waves should simply move through the short-circuit, uninhibited. The voltage and current waves being reflected back do not make sense to me.
Comment: Light hitting a mirror is a similar situation. The mirror acts very much like a short-circuit. The light is not absorbed, but reflects.
Comment: Have you seen [this related question](http://electronics.stackexchange.com/q/59208/11683)?
Comment: Traveling waves don't behave like simple circuits -- they have different rules!
Comment: @Daniel But it is just common sense to me for something to travel where there is less resistance.
Comment: @glen_geek that argument is flawed because a mirror has much more impedance than air. Moving through air is easy but moving through a mirror is not.
Answer: In a transmission line, you have an electromagnetic wave traveling along. This is a time varying electric and magnetic field. When the wave reaches a short circuit, the short circuit enforces the rule that V=0 at that location. This destroys the conditions necessary for the wave to continue traveling. Because the electric field can no longer vary with time at that location. Without this time variation, the wave cannot continue to travel.
And, as it happens, it also creates the conditions needed for the wave to reflect.
You could also consider this from a conservation of energy perspective. An electromagnetic wave has energy. It is actually a form of traveling energy. The short circuit cannot dissipate energy (when V=0, power=0). BUT, the wave cannot continue to travel, either, as previously mentioned. So, really, there is no other thing that can happen other than reflection.
You could say that when a wave in a transmission line encounters a load, any energy which is not delivered to the load MUST be reflected in order to satisfy conservation of energy. Of course, if the load is an antenna, some of the energy will be radiated into space, but that does not really change anything. The antenna is modeled as some kind of load, and the energy that is radiated into space is accounted for by a resistor in the model.
Comment: You might also find some enlightenment if you read about how time domain reflectometry works. When a source applies a voltage to a transmission line, the impedance that source feels is the characteristic impedance of the line. For example, it could be 50 Ohms. So, at the source, the current will be V/50, even if the end of the line has a short circuit. Only when the reflection comes back from the short circuit will the source "feel" the 0 Ohm load. If you observe the voltage at the source with an oscilloscope, you can calculate the round trip time of the EM wave to the short.
Comment: What is the relationship between current and EM waves?
Comment: In space, there is no current associated with an EM wave.  However, if the wave encounters an antenna, it will cause current to flow in the antenna. And in the type of transmission lines we are considering here, the kind made with two conductors separated by a dielectric, the traveling wave causes current to flow in the conductors due to the time varying electric field.
Comment: What I mean is, if you take a snapshot at any instant, you will see that the electric potential varies as you move along the transmission line. This is hypothetical, if you could freeze time. Since there is an instantaneous electric field along the transmission line, there will be current flowing along the electric field gradient.
Answer: A transmission line is sometimes modeled as a series of lumped elements.  Each tiny imcrement of line has an equally tiny inductance and capacitance associated with it.

simulate this circuit – Schematic created using CircuitLab
A narrow pulse traveling down the line--say it's passing L4 at the moment--would be stored in C4 and is now passing through L4, on its way to charging C5.  As it passes through L4, it is stored there as well.  The inductor current creates a magnetic field, which builds and then collapses, producing the voltage that charges C5.  The pulse continues down the line in this fashion.
When the short is encountered, the voltage goes nearly to zero, and the current to a high value.  The current through inductance of the short stores the energy in a magnetic field, and then as the field collapses, the current continues on around (per Lenz's law) but the voltage across the inductor has reversed.
Having attempted an explanation without ropes, equations, or Star Trek terminology, I must say that the rope analogies are very good.  And there's similar question to this one, and in an answer, a link to this film from Bell Labs showing a very interesting wave demonstrator. I encourage readers to watch it.
Answer: Let's imagine waves moving down a transmission line. A current wave, and a voltage wave. Their ratio is the line impedance, V/I. For instance, a 50v wave and a 1A wave moving down a 50ohm line. They always move together, and V=50*I at every point.
If they hit an open circuit, no current can flow there. So they generate a reverse travelling wave so the 1A reverse cancels out the 1A forward to produce zero amps at the open circuit (don't ask me 'how' this reverse wave happens, but it is observed to happen). This reverse travelling wave must have a voltage component as well, which must be 50v as well, and these add up to make 100v at the far end. The 50v 1A wave travels back along the line to the source.
If they hit a short ciruit, then no voltage can exist there. So they generate a reverse travelling wave so the 50v cancels out to produce 0v at the short circuit. The 50v 1A wave travels back along the line to the source.
You can now see that if the line suddenly changes impedance to 75ohms, we can no longer have a 50v 1A wave propagating forward by itself. It generates a small reverse wave such that when you add up the voltage and current at the junction point, the forward wave now obeys V=75*I, and the reverse wave makes up the difference.
Answer: You try to apply your basic "Kirchoff's intuition" to a much more complex phenomenon.
Waves in a circuit can be correctly described only using Maxwell's equations. Kirchhoff's laws are only an approximation of Maxwell's equations that work when the waves have a wavelength that's much bigger than the physical dimensions of the circuit, i.e. only if the highest frequency component in a signal is much smaller than c/d, where c is the speed of light and d is the dimension of the circuit.
That is, KVL and KCL hold only if the circuit is working in so-called quasi-static conditions. In these conditions you can approximate Maxwell's equations and eliminate some terms from them and treat the problem as it were an electrostatics problem. In electrostatics you can define an electrostatic potential directly related to the (static) electric field, and this gives the definition of voltage. Also current becomes easily defined in term of current density.
When those simplifying assumptions no longer hold, you can't even define voltage properly. In the context of transmission lines voltage can only be meaningfully defined between two points on the same plane perpendicular to the propagation direction. I.e. you can't measure a voltage between a point in the upper wire and another point, say, two centimeters away on the other wire (as you can easily do when KVL holds).
Bottom line: drop your "Kirchhoff's mindset" when you try to understand transmission lines and try to develop a more "Maxwellian mindset".
Anyway, this thread might give you more insight in that direction.
EDIT (to answer a comment)
Common sense is not applicable in this field (pun intended). You could get away with some, very imperfect, analogy (and for that, see the link I posted above or the other answers in this thread), but that's all. There is a reason why it took mankind millennia to understand and explain electro-magnetic phenomena (static electricity was known experimentally since ancient Greece, let alone lightnings and their consequences, for instance). If these phenomena had been easy to grasp with common-sense, it wouldn't have required sages and scientists ages to understand them.
Impedance/resistance, as an element in which current flows, is a concept tightly related to Kirchhoff's laws and lumped element circuit analysis.
In EM theory impedance has a whole different meaning: it doesn't relate voltage with current, but, more or less (...hand-waving...),  E field with H field.
Fields don't flow like currents or exists across two points like voltages. Understanding exactly how, why and when fields propagate requires tons of advanced math. Maxwell's equations is, IMO, the conceptually toughest topic in Physics that an Electrical Engineer has to grok during his/her university education (bar quantum mechanics and solid-state physics).
Comment: @Goldname Unfortunately 'common sense' only repeats to us what we have already learnt from experience. When we move into a new field, that experience is irrelevant, and common sense often leads us astray.
Comment: I understand what you mean, but I am not thinking in terms of kirchkoff. I'm thinking in terms of common sense. it simply would be easier for something to go where there's less impedance/resistance, so it should go there, am I wrong?
Comment: @Goldname see my edit.
Answer: A simple analogy
Consider a long rope tied to a 'wall'. The end of the rope is flicked  to produce a 'pulse'. The pulse travels along the rope until it meets the 'wall' or NODE. (a travelling transverse wave)
At the wall the rope is prevented from moving (i.e. a point of NO DEviation).
What happens is that an equal and opposite reaction at the 'wall' creates an anti-phase pulse travelling in the opposite direction.
The superposition of the forward and reflected pulse creates the unique solution that the deviation at the wall (or NODE) is zero.

This is a general property of waves. In a transmission line the 'wall' is a short circuit and the 'wave' is the electric field component of the electromagnetic wave.
Comment: No, the wall is analogous to am open circuit.
Comment: @Goldname the 'wall' is a node - The simple analogy only shows one type of transverse wave whereas an EM wave has two mutually combined waves - the electric field and the magnetic field.  From a voltage perspective the wave is reflected by a short circuit, from a current perspective it is reflected by an open circuit. The reflection coefficient (r) can vary between +1 and -1 (= (Zl-Zc)/(Zl+Zc)) . The interesting value is when r = 0 - then there is no reflection and the transmission line is impedance matched.
Comment: I can see that the wall is a node in this case, but I am not understanding how open circuits create a node. Also, this analogy would be parallel if the wall represented an open circuit. That would make more sense.
Comment: From a current perspective its what would stop any current flowing -   R is 'infinite' , I = V/R. From a voltage perspective its what would stop a voltage from changing - R is 'zero' - V = IR. The way I look at it for an EM wave is that the electric field component produces a changing voltage, the magnetic field component produces a changing current (see Maxwell's equations). So, for both a short circuit or an open circuit  termination you get the same effect - a total reflection. Any other value will absorb the wave energy and reduce reflection. At characteristic impedance, no reflection


Why Did Anakin Skywalker Believe that Turning to the Dark Side of the Force Would Save Padmé?

Question: Just as the question asks: Why did Anakin come to believe that Padmé could be saved if he embraced the Dark side of the Force? Padmé clearly didn't believe it. Why was Anakin so driven to save Padmé through the dark side?
Comment: Who knows? The movie doesn't provide the slightest insight in to the character's inner life. I mean, *"Oh. He's messed up and angry? Well, OK. I guess."* is about all you can say about his motivations.
Comment: @dmckee - ZOMG! Darth Vader is a Goth!
Comment: @DVK I'd hit that. . .
Comment: You should read the novelization of *Revenge of the Sith*. It really helps you to understand the conflict and the inner fears in Anakin. It's a excellent book and, in my opinion, which a better quality than the movie itself.
Comment: He believed that even if Padme did die, he could use the Dark Side to bring her back. So ultimately, he wanted a little Zombie Padme action.
Answer: When he first looked for advice from Yoda about his vision, he did not hear what he wanted to hear. From Star Wars Episode 3 Revenge of the Sith Script

YODA: Careful you must be when sensing the future, Anakin. The fear of loss is a path to the dark side.
  ANAKIN: I won't let these visions come true, Master Yoda.
  YODA: Death is a natural part of life. Rejoice for those around you who transform into the Force. Mourn them, do not. Miss them, do not. Attachment leads to jealousy. The shadow of greed, that is.
  ANAKIN: What must I do, Master Yoda?
  YODA: Train yourself to let go of everything you fear to lose.

But later, Palpatine told him about a possible way to save her :

PALPATINE: I thought not. It's not a story the Jedi would tell you. It's a Sith legend. Darth Plagueis was a Dark Lord of the Sith, so powerful and so wise he could use the Force to influence the midi-chlorians to create life ... He had such a knowledge of the dark side that he could even keep the ones he cared about from dying.
  ANAKIN: He could actually save people from death?
  PALPATINE: The dark side of the Force is a pathway to many abilities some consider to be unnatural.

So, Anakin's dilemma was that Yoda told him he must accept Padmé's death and Palpatine told him he could avoid it by turning to the Dark Side.
Palpatine also told him that the Dark Side is not Evil as the Jedi told him and made him doubt the real intention of the Jedi order, that they where hanging on power and that their actions where not always for the greater good. In the end, Anakin turned to the Dark Side to save Padmé, but also because he had some conflict of opinion with the order. He was convinced that he was doing the right thing.
Comment: Palpatine literally said `I have the power to save the one you love.  You must choose.`  I think that sums up the reasoning pretty well.
Comment: Worth noting: Palpatine never actually *says* he could prevent death with the dark side of the force - enough wiggle words are used to give Anakin hope, without making any *real* promises.
Comment: Although this answer has all the technical details. To say the anakin thought he was doing the right thing is a stretch. It was entirely selfish. This is even reinforced when Palpatine said the dark lord could keep those close to him from dying. What about those not close? They aren't worthy?
Answer: Because Chancellor Palpatine convinced and intrigued Anakin's hopes that only the Dark side of the force had the power to cheat death with a tale of "the tragedy of Darth Plagueis The Wise".
This was further concluded in Anakin's mind after he succumbed to the dark side and Lord Sidious remarked

To cheat death is a power only one has achieved, but if we work together, I know we can discover the secret.

As a side note, in turning to the dark side Anakin actually lead to Padme's death but what Palpatine actually told Anakin was true from a certain point of view.
Comment: Keep in mind, Palpatine previously said he knew the power.  So he has been lying to Anakin all along.  Something that Anakin should have easily seen.
Answer: DavRob60's answer only addresses part of Anakin's motivation. Anakin chose the dark side to save Padmé.  The central question is why Anakin chose to save Padmé versus letting go of her.
Anakin started his Jedi training too late. He had already developed an attachment to his mother and that served as the model for his attachment to Padmé.
These were the exact fears expressed by the Jedi council when he first went before them and it is the same reason that Yoda was reluctant to train Luke. It could be argued that Luke didn't have the same level of attachment to his aunt and uncle and after their death he had none whatsoever.
Comment: Yoda also did not have much of a choice but to train Luke (or Leia I suppose).  Who else would he train?  What would he have to lose except Luke turning to the dark side too?  It's not like he had a temple full of younglings at his disposal.  I guess he realized that this was his last hand, so he went all in.
Comment: He may have also done some reflecting and realized that maybe some of the century-old Jedi dogma and stubbornness wasn't the best path forward.  After all, look where it got them.
Answer: When Anakin tried to follow the Light side by initially ignoring his prophetic dreams about his mother, the end result was that he got there too late to save her. When he started to have similar dreams about Padmé, and especially when he was unable to foresee the fate of his child, he became fully susceptible to Sidious/Palpatine's stories about Force powers that could cheat death.
Answer: He had dreams about his mother being in trouble in Attack of the Clones and because he felt his mother's agony Anakin left to find where Shmi was. He found her eventually but he was too late to save her as the Tusken raiders did too much damage.
In Return of the Sith Anakin had  similar dreams to Shmi's where Padmé was dying in childbirth, this led to Anakin thinking it would come true like his mother's. This wasn't the case at all. So he went on a mission to try and find ways to save Padmé and also help.
He met Yoda who said "To train yourself to let go of everything you fear to lose," which meant accepting Padmé's death. He was given orders to spy on Chancellor Palpatine's dealings but when he met him the first time the Chancellor basically described the Dark Side to Anakin including how it can save the ones you love - "it's a pathway to many abilities that some consider unnatural".
As Anakin believed the Chancellor he put some deep thought about what to do. As Anakin's trust in the Jedi order was at a very low ebb, because he wasn't allowed to be a Jedi Master, he eventually came to Palpantine's aid when Mace Windu was about to kill him. Anakin was stuck in two minds before deciding to stop Windu from killing Palpatine, which caused  Windu's demise instead.
Believing Palpatine, Anakin decided to turn to the Dark Side. I think Anakin never would have listened to Padmé, and Obi-Wan's arrival topped off his hatred. Anakin turned to the Dark Side because he was too attached to the ones he loved and couldn't let go of them, and he thought the Jedi never trusted him.
I feel sorry for him because he was made out to be the bad guy when really he is the victim because he was trained too late and his mind was fucked from then on. :)
And then from there Padmé tried to stop him by meeting him in Mustufar which resulted in Anakin choking Padmé as he thought Obi Wan and her were trying to kill him. I think Anakin was never going to listen to Padmé as he knew these dreams would come true (they weren't). So Anakin turned to the Dark Side because he was to attached to her.
Answer: I think in Episode 2 you can already see what was about to happen when Anakin tried to save his mother, but had to accept that it was already too late. He never accepted that fact, and besides killing the sand people, the funeral scene on Tatooine is a key scene for the Star Wars Saga with the old man (Cliegg Lars) is mourning, but accepting the death of the woman he loves.
Young Anakin, in contrast, is staring at the grave with a hardened face, where you can see that he is fighting with his feelings of guilt. The story is well thought out, and many things accumulate until the scene where Anakin finally cuts off Mace Windu's hand and intentionally turns to the teachings of Darth Sidious.
To Anakin, the light side of The Force has proven to be inferior and weak in many events, especially because most of his "career" is spent in a time of war, where being "good" most of the time turns out to be on the losing side.
Wartime trains people to use their "dark side". This is true in our society as well. From that perspective, someone like Obi Wan even seems unrealistically moral and humane, given the circumstances. The process that changes Anakin seems to me as the more logical course a person, especially a "war hero" will go in a story like this.
Granted, the final scene when he turns to Darth Sidious just after he turned him in, is all too stereotypical, but everything that leads up to it seems quite conclusive...
Answer: Darth Sidious told him Padme would die without his help and that he could only learn the secret of saving her from the Dark Side.


What is the limit to how many satellites can orbit the earth?

Question: I would like to know how many satellites are physically able to be in place, at the same time, orbiting the earth. Lets ignore which Nations need or use the most satellites (area in space above them) and assume an even distribution. My understanding is each satellite is inline with a degree on earth (longitude), but there are only 180 of these. Would you then be able to line up satellites on each degree of latitude for each degree of longitude? So 180 x 180 = 32400? Or is there more to this? Could you put a satellite either further or nearer to the earth so they would almost overlap to make room for more?
Comment: Why do you think that a satellite always takes up one degree? Have you considered that the solid angle depends on the radius of the orbit. You could have multiple satellites above each other on the same path (projected on the eath's surface)
Comment: @luksen I dont think it takes up a degree, I thought I saw somewhere that they are positioned on a degree. So I guess you could have as many satellites as you want provided you're not bothered about all the shade down here
Comment: It's not true that all satellites have integer latitude and longitude.  See [this list of satellites in geosynchronous orbit](http://en.wikipedia.org/wiki/List_of_satellites_in_geosynchronous_orbit)
Answer: This is actually quite a complex problem.
At large numbers of satellites, gravitational effects need to be considered.
A real answer would need values such as 'every satellite has the same mass and volume' etc.
Basically you can keep adding satellites until Earth becomes a black hole.
Satellites are very dense since they have lots of metal (which is a dense material)
In my opinion, a great 'answer' to this question would be a fun computer simulation.
If we just use the values given by Phil H, we fit in satellites between 2000 km and 35786 km altitudes.
$R_E$, the radius of the Earth is 6371km.
So we calculate the volume:
$V_{total}=\frac{4}{3} \pi [(d_2+R_E)^3-(d_1+R_E)^3]=\frac{4}{3}\pi (42157^3-8371^3)=9.341\times10^{14}\,\text{km}^3$
We assume that all the satellites have mass of $m_s = 800\,\text{kg}$ (note that this is a 'fantasy' problem so we don't really need to follow real world statistics) and volume $V_s=4.8 \,\text{m} \times 4.8 \,\text{m} \times 5.5 \,\text{m} = 1.267 \times 10^{-7} \, \text{km}^3$
Thus, the total mass of the orbiting satellites will be $M_{total} =  \frac{m_s}{V_s} V_{total}= 5.90 \times 10^{24}\,\text{kg}$
Now let's compare that to the mass of the Earth, $M_E=5.97\times 10^{24} \,\text{kg}$.
Notice how $M_{total} \approx M_E$, though this is just due to some values which we chose and does not arise from some values which arise from nature.
Answer: Satellites are very small, so there would have to be an enormous number to use up the 'space' available.
You mention lattitude and longitude which suggests an explanation of LEO and GEO (Low and Geostationary Earth Orbits) would help. in Geostationary orbit (e.g. TV satellites), the satellite orbits at a specific distance so that it's always in the same place in the sky, as its orbit is then 24 hours long. This special orbit runs around the equator, as any other inclination would make it move in the sky, in a figure of eight.
In a lower orbit, the satellite appears over the horizon, zips across the sky and disappears again. This is why GPS systems don't have an antenna or dish that you point at one place, as GPS uses a constellation (group) of many satellites at 20,200 km altitude.
So the available space for satellites extends from Low Earth Orbit (2,000 km up), e.g.  telecomms satellites and Hubble, out to the moon, which is our only natural satellite. Mostly they stay between LEO and GEO (35,786 km altitude).
Having said all that, the more we put up there, the more junk we end up with as pieces fall off satellites, or they collide, or they are hit by other space junk. This is increasingly a concern as early missions largely assumed everything would end up burning up in the atmosphere eventually.
The space available for satellites, then, is very large. Even in a single LEO orbit there is more 'space' than the distance around the equator. The Geostationary orbit has a limited number of spaces available by international agreement to prevent collisions or interference.
Comment: The GEO satellites are running around the equator, and so are some of the other satellites. Most non-GEO satellites, however, have a different inclination, because the geostationary bit is the main reason to put a satellite above the equator. At low orbital altitudes, the satellite is visible for a smaller area of the Earth's surface, so to reach the majority of users in the northern hemisphere (North America, Europe) they have to have a higher inclination to be any use. These satellites are then less useful for much of their orbit.
Comment: So all the satellites are running around the equator? Or just the  GEO, TV satellites?


What are the major differences between Leopard (10.5) and Snow Leopard (10.6)?

Question: Leopard was released 2007 and Snow Leopard was released 2 years later in 2009. They both look pretty much the same, with a few minor GUI exceptions. They almost work the same, again with a few minor exceptions. I know that the whole Finder was re-written, but I want to know more detail about the differences between the two. What are the major difference between Leopard (10.5) and Snow Leopard (10.6)?
Comment: If you have some time, read this great review on Ars Technica: http://arstechnica.com/apple/reviews/2009/08/mac-os-x-10-6.ars That will answer your question.
Answer: I remember watching the keynote when Snow Leopard was introduced: Steve Jobs pointed out how fast Mac OS X was being improved and new features were added. Several major upgrades have been shipped, while Microsoft took years to ship Vista.
From the beginning, Snow Leopard had the focus on improving the overall system performance and optimizing already implemented features. Also, cleanup was required as PowerPC support was dropped.
Because no major end user related features have been added, it's been widely assumed that this is why the price dropped from $129 to $29.
Changes:

support for 64-bit applications (you can also boot the kernel in 64-bit mode if supported)
Grand Central Dispatch helps to get more out of your multi core processor.
OpenCL offers GPU hardware acceleration for any application.
PowerPC support was dropped.
Microsoft Exchange Support for Mail, iCal, Address Book.
QuickTime X (full screen view, http live streaming...)
Safari introduced Top Sites, Cover Flow and sandboxing for plug-ins.
Anti-malware alerts.
Finder rewritten in Cocoa.
Comment: Subjectively, I remember Snow Leopard having some rough spots in the first two releases (10.6 and 10.6.1) but even then it felt tighter, more response, and much more cohesive than Leopard did. Aesthetically, Snow Leopard also fully did away with Carbon, did it not (no more hideous metal UIs)?
Comment: @cksum Apple did not port the Carbon library to 64-bit. Therefore applications that wanted to run 64-bit had to migrate to Cocoa. iTunes for example was still Carbon as it was still 32-bit when SL was shipped. Only in Lion iTunes is finally 64-bit and using Carbon.
Comment: Yep. I remember Adobe whining about them dropping Carbon64 (saying it was totally arbitrary; okay). And iTunes has always pushed a progressive UI compared to OS X. Only now does it truly blend with the OS (Lion) :)


How to get hard edges when using subsurf modifier?

Question: I am rather new at modeling but I am working on a nicer Porsche 944 model. I have a solid looking hood but there is a part of the hood where it drops a little and with the sub surf modifier I am having issues modeling it. I have tried extruding and then re-merging half the hood as well as just putting a loop cut in and moving half the hood down. Both of these are not producing crisp edges like seen in the photograph. Any ideas?
Comment: related http://blender.stackexchange.com/questions/18465/edges-with-mean-crease-set-to-1-are-still-rounded-by-a-subsurf-modifier/18467#18467
Answer: Couple ways to do it. One is to use an Edge Split modifier, adjust the angle at which you want an edge to be sharp, or mark specific edges sharp as needed. The other is to add additional edge loops on either side of where you want the sharp edge.
For example, here's three cylinders:

In the middle is a 32-sided cylinder with the Subsurf modifier set for 3 subdivisions. On the right is the same cylinder with the Edge Split modifier turned on. On the left, is the same cylinder with additional edge loops above and below the edge that needs to be sharp.

Same cylinders, showing the vertices on the left cylinder so you can see the two extra loops. Both approaches work. The slightly beveled edge resulting from adding more loops will arguably give you a more realistic edge, since the real car likely doesn't have a perfectly sharp edge there (few things IRL do).
Answer: This is what edge Crease is for. Crease the edges with a value of 1 to ignore subsurf's smoothing and create a hard edge.


What kind of plant is this purple plant?

Question: I took a cutting from someone's houseplant and rooted it and planted it, but I don't know what kind of plant it is.  It's doing well outside but I'll move it inside when cold weather hits.  The leaves are almond shaped and I believe it had flowers when I had it in the house.  Someone said it's an Oyster plant but the pictures I looked at don't look like those.  The leaves are purple and look like they should be fuzzy but instead they are kind of thick and rubbery.  Any idea?
Answer: It looks like Tradescantia purpurea. It's not possible to tell how tall your plant actually is from your photo, but this plant only gets around 7 inches tall and tends to spread sideways, eventually trailing or sprawling. It is frost tender, and can be used as a border or container plant during the summer months. Image and information on plant care here https://www.gardenia.net/plant/Tradescantia-pallida-Purple-Heart
Comment: Oh my goodness, thank you so much.  Mystery solved.  I love this plant, almost impossible to kill it not that I have tried.  Very easy to root cuttings too.  I might give them as Christmas gifts this year, lol.  And you are right, it's about 10 iches and looks like it will grow as a vine.  I'll read all about it now and thanks for the link.
Comment: Don't forget to accept the answer if you're happy with it, otherwise it remains open...


How do the audio controls on the steering wheel communicate with the radio?

Question: Do they use some sort of wireless protocol, such as Bluetooth? I can't imagine there is enough room to have physical connections for all of the controls that would also allow for the full rotation of the steering wheel. I am specifically interested in the Sony radio in a 2010 Ford Flex, but any information would be appreciated.
Comment: You don't need much room for a wire...
Answer: It doesn't take as many wires as you think, and they just add additional circuits to the clockspring.
The clockspring was introduced with drivers side airbags to maintain a continuous electrical connection for the airbag while allowing the steering wheel to turn. The manufacture simply added a few additional circuits to accommodate steering wheel controls.

Source
In the picture above the yellow wires are for the airbag, all the others are for steering wheel controls. Some of the controls that run through the clockspring include horn, cruise, phone, and radio.
This video show the disassembly of a typical clockspring, I DO NOT recommend doing repairs to one of these as the guy in the video suggests, I only posted the link so you could see how it works on the inside.
You don't have to have a separate wire for each button you want to control, below is pictured one example of how you can use just two wires to control several switches.

Different switches give a different resistance allowing the computer to tell which switch as been pressed.
They could also use multiplexing to communicate several commands over a single wire, it works similar to the way computers communicate over a LAN. It's not used in steering wheel controls to my knowledge so I won't go into detail here of how those systems work.
Comment: I just wanted to add: if you're going to be working at all with the clockspring (aka, trying to wire up an aftermarket radio to your in-wheel controls) please be *very safe* in regards to the airbag. (Disconnect the battery and follow manufacturer instructions to remove the airbag) before you try anything.
Comment: I know of one car, the 1984 50th Anniversary 300ZX, that used RF to communicate cruise control and stereo controls to the car. However, it still used the clockspring for power.
Comment: @Nick: That sounds quite dangerous. It definitely wasn't digital in 1984, so it wasn't encrypted. An attacker should be able to fully control the cruise control remotely.
Comment: It was line of sight, IIRC, so possible. But unlikely.
Comment: Given that touching the pedals turns of the cruise control and that cruise control will not make a car move from standstill there is not that much risk of someone taking over the cruise control buttons


What keyboard commands should be used to tag a search term in a multiple tag input field?

Question: When entering multiple search terms in to a search input. Which keys should be used to make the search term a visible tag before final form submission? The industry standard is either separating each keyword with a comma or using the tab key, however the feedback that I got was it might not be intuitive to the user to use the tab key or commas.
Comment: This is one of those questions that can only be answered by your particular users - You could test in a number of ways including A-B/Multi-variant tests and surveys. ('Space' could fall over pretty quickly if you're allowing multi-word tags)
Comment: How about space?
Answer: If this is a "pillbox" style input you are referencing -

Then you could allow multiple options as long as they are not allowed characters in your tags: comma, space, return, clicking outside the tag area itself, all might be valid ways of "registering" the tag.
Answer: Enter might be abetter option. That usually helps in educating the user that multiple items are allowed
In an ideal flow, with only single item, users usually (if not always) press enter with the intent of continuing to the next step. In this case, the next step, i am guessing, is to enter multiple items instead of 1.
On the flip side, a user who wants to enter only single item, will have a non intuitive flow if he presses enter
So it might be helpful to udnerstand how many users are currently using single vs. multiple items in the field.


How to distinguish subjunctive mood and common mood

Question: Subjunctive mood usually starts with if.
It seems:
If you are happy/if you were happy (both are right)
If you were me (right) / if you are me (wrong)
If you want to learn English / if you wanted to learn English (which is right?)
Which is subjunctive mood?
Comment: None of them. The subjunctive is a clause type that uses the plain form of the verb, as in  "It is vital that I be kept informed".
Comment: "If I were you" is not subjunctive mood?
Comment: It is in out-of date grammar. Modern grammar calls the "were" in "If I were you" the irrealis mood. See here: [link](https://www.thoughtco.com/irrealis-were-grammar-1691045)
Comment: Please show you effort first, such as a grammar tutorial.
Answer: This isn't a very clear-cut topic, so the best thing to do would be to read the materials for the particular course you're following (if any).  Also, why would you need to know?
The form to which the term "subjunctive" is most commonly and least controversially applied is the use of the plain form of the verb (identical to the bare infinitive) in mandative constructions such as:

She ordered that he stop.
He demanded that it continue.
We asked that she leave.

These mandative forms are commoner in American English than British; British English prefers either to re-word ("She ordered him to stop") or to insert "should" ("He demanded that it should continue") - although the use of the mandative subjunctive may be increasing under American influence.
Subjunctives of this kind are also found in a few set-phrases ("So be it", "Be that as it may", "Long live the Queen").  Expressions such as "Whether it be red or blue" are also occasionally used (though "is" is at least as acceptable and more common).
The "irrealis" is the use of "were" instead of "was" in counterfactual statements related to the 1st and 3rd persons singular:

If I were you, I wouldn't worry.
If she were here, you would be happier.
If that were the case, I would tell you.

In traditional grammar, the first type of subjunctive is called the "present subjunctive" (because it is the same in form as the present tense, except in the 3rd person singular) and the second type is called the "past subjunctive".  Nowadays, these terms tend to be avoided because they are seen as confusing.  The "past" subjunctive has nothing to do with past time (although neither does the use of the past tense in sentences like "If he visited, she would be happy"), and the "present" subjunctive isn't always associated with the present, either.
Traditionally, some would regard the forms in "She asked that I stop", "If you were here", "If she kissed him" as subjunctive too.  In this perspective, there are a large number of forms that are ambiguous between indicative and subjunctive - this is called syncretism.
In modern grammar, the term "subjunctive" tends to be reserved for forms that are visibly and distinctively subjunctive, not syncretic ones that are assumed to be subjunctive.  (Additionally, in modern English, it is possible to replace irrealis "were" with "was", especially in colloquial use, so it would be odd to assume that a non-distinctive form were subjunctive.)
Answer:
1: If you want to learn English, ELL is the site to use.
   2: If you wanted to learn English, ELL would be the site to use.

I couldn't really argue with anyone who wanted to swap is / would be in those examples. The versions as given are certainly more likely, but it's not obvious to me that the alternatives would be "ungrammatical".
But consider a context like ringing through to room service in a hotel, where the person who answers might say...

[Hotel reception speaking...]
  3: ... what do you want?
  4: ... what did you want?

Both Present and "Past" are perfectly idiomatic there, but I've used "scare quotes" because I see no good reason to classify my example #4 as being significantly different to #2.
Maybe some people would say #2 is "Subjunctive", whereas #4 is "Past", but that doesn't seem a useful distinction to me.
I think English only really has 2 tenses (Present and "Not-Present"), and #4 is a typical example of "Not-Present" being used to "distance" the speaker from the utterance (introducing "hesitance, deference", characteristic of many formal contexts). A bit like asking Who might you be? rather than Who are you?, for example.

TL:DR: Using "Not-Present" verb forms in English doesn't necessarily have anything to do with time-based relationships. Example #2 above is just a common way of making the assertion more "politely tentative" (arguably implying more strongly than #1 that perhaps you might not want to learn English anyway).


VMware vCenter Server Questions

Question: I plan on deploying a cluster of 2 physical servers running vSphere. The VMs in this cluster will be ran in fault tolerance mode. Can the vCenter server be ran as a appliance on the vSphere cluster, or does it require its own server separate from the cluster? Thanks!
Comment: Please note that FT is still limited to VMs with a single vCPU, so you might not be able to protect any workload with it.
Answer: We run ours in the cluster. We don't have too many issues.
See: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2003790 for vecenter installation best practices
and http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=10087 for special considerations related to running vcenter in a virtual machine.
If you have the resources on the two hosts, run vcenter as a VM. If you are tight on resources... you could push vcenter to a physical.
Answer: It runs as an appliance on one of your hosts. The only time when you wouldn't do this is if you were running hundreds of hosts and vCenter requires more and more RAM to function.

VMware vCenter Server Questions


Does stating terminal degree as Master's (and not PhD) hamper my chances of getting selected in a grad school?

Question: I'm applying to a grad school in the US for fall 2016. While filling the application, I stated my initial and terminal degree preferences as Master's only (and not PhD) as I want to work in the industry post MS. Will it hurt my chances of getting selected?
Comment: Not if you're applying to a terminal master's program.
Comment: @JeffE, It was a regular MS program (and not a MS+PhD one). So that means it is indeed a terminal Master's program, right?
Comment: This could depend somewhat on the field and the particular department.  Make sure to read carefully the department's instructions about this.
Answer: It probably won't hurt your chances of getting accepted, but it will definitely hurt your chances of getting funding from the department.
Answer: Probably not.  In fact, each student admitted to a PhD program constitutes a fairly major commitment on the part of the university and department, so admissions standards are generally higher for Ph.D. applicants.
That said, if the program you are applying to doesn't "do" Masters, you won't get in.  For your own good, you should be limiting applications to programs that have thriving Master's Programs, because they'll probably be better at providing your education appropriately.
Further, my own opinion is that if you feel pressure from the department you're applying to to accept admission as a Ph.D. student when you've applied as a Master's, beware.
Answer: No. It might even help since a terminal Masters means you'll probably be paying your tuition and are less of a drag on the school's resources.


is there a blender/food processor combo still made?

Question: A long long time ago I had one--I think it was a sunbeam. one base unit worked for both the blender and the food processor. I could really use that now, but haven't had any luck finding one.
it doesn't have to be a sunbeam, just one which uses one base for two functions.
help?
Comment: Where are you? In the UK Kenwood still made a food processor with a blender to go on top when I last looked but I don't recognise the sunbeam brand so I suspect you're elsewhere
Answer: Yes, several companies are selling these blender/food processor combos. A quick search found this Oster and this Cuisinart, as well as several others.


Personal contacts with users

Question: Is it alright if I maintain a personal contact with a specific user? There is a user who I've found to be particularly meticulous in writing proofs. I am learning a couple of disciplines on my own and frequently am faced with the need to post (solution-verification), (proof-verification) questions. I have a contact with the specific user and is it alright if I send him a link each time I post something and ask him to check it out for me? I vow to aknowledge and give preference to answers by other users if they are better. What would be the site's policy on this situation?
Comment: If I was that user, I'd start ignoring you and your posts pretty soon.
Comment: Not being a social networking site, there is not an easy way to send messages to individuals. There is nothing wrong with asking someone to check your profile periodically for new posts, but I would not pester someone with constant requests about each post.
Comment: @robjohn: Thanks. No I don't think I'm pestering the said user. I only bother him once or twice a week (maybe exaggerated about the frequency in my question). He has been very encouraging and enthusiastic as a matter of fact. Just wanted a clarification on the site's policy on such contacts. That's all. Thanks again..
Comment: @127.0.9.6: Yeah I'll take care of my personal relationships on my own shall I? Just wanted the community's opinion on the site's policy.
Comment: What is a "situ"?
Comment: As the "specific user", let me just say that I don't mind in the least, so long as you don't mind it taking me a long time to reply as life gets in the way.  Indeed, I purposefully made my contact info available.  I must also stress that often, others have much better answers than me.  So while I appreciate your compliments, I don't really think I'm necessarily the best person to be asking (but, again, I don't mind in the least).  All that said, thus far, I've only had 2 users contact me - if a larger number of people were contacting me regularly, then it could be a problem.
Comment: And 3 downvotes?? Wow!! Lowest score  yet!
Comment: Until seeing the answer by Jason, I thought this question was about whether it was ok to contact the user in question, which I found to be an odd question. Given that answer it seems that the question is really about whether it is acceptable that you have a "preferred" answerer (which explains the last remark in the question, which I did not understand at first). My guess is that the downvotes are due to similar interpretations as my first one.
Answer: I suppose that at this point, I should just write an answer.
On Feb 17th, I answered a question of Ishfaaq's, shortly thereafter received a very polite email from him asking if he could email me whenever he posted a question.  I assented, and since then, he has emailed me asking for help on two other questions.  This works out to him asking me about a question a week, a pace that I am comfortable with.
Of course, if the pace were to significantly increase, or if many other users were asking for a question a week, or if I got the impression I was doing someone's homework/take home test/ etc, then my attitude would change, but as I said in a comment above, I purposely have my contact info available in my profile.
Why do I do it?  The same reason I've spent so much time on MSE - I enjoy helping people learn math.  Sure, I ask the occasional question (12 on this site so far), but I much more enjoy answering questions (316).  As Will Jagy mentions, proof verification is not my favorite kind of question, but I really appreciate the fact that Ishfaaq's questions (or, at least the ones he has emailed me about) have a lot of work shown - he is putting in more effort than many of our users, and I want to reward him.
Finally, I just want to note that this a personal post and is in no way intended to reflect or persuade the MSE community at large.  It's simply how I've chosen to deal with emails.  In general, I don't see any issue with a particular user attempting to contact another user via email, but I also don't see any issue with the other user ignoring the email completely.
Comment: Jason, what can I say? You sound like the nicest person ever… :)
Comment: Well I think an explanation from me too is due. I only thought of posting this question to make sure it was not a violation of general etiquette on MSE to have personal contacts with other users. I simply did not want to get into trouble for violating a regulation I didn't know about. And I sincerely apologise for any inconvenience caused hereby. I have only emailed you those questions which I think I've solved  but am not convinced about and will stick to that status quo in the future. Like Prism said you Sir are very generous indeed. And I'm sorry again about all this.
Comment: @Ishfaaq:  It's really not a problem at all ;-).  Prism: I think my students would disagree!
Answer: There is no rule against contacting other users outside MSE. The only exception would be if someone harasses another user in relation to MSE activity, which I would consider in some cases to be legitimate grounds for a suspension.
But not everything that is not forbidden should be done. When a person answers questions on MSE, the person can decide which questions to answer and when. Asking in, say, an email can put some pressure on a user.
Personally, I would only contact another user outside MSE in exceptional circumstances or if I know the person outside MSE. In that case, standard real world manners apply.
Comment: Or if you arrive to the same city as the user and wanna meet for beer and some George Carlin reminiscing... ;-)
Comment: It's just that proof writing is an art too. Just getting the right answer isn't always enough. A bit of coaching and criticism on the wording and presentation is something I have missed since high school. Like I said here, http://math.stackexchange.com/questions/679096/a-times-b-is-an-open-set-in-bbb-r2-implies-a-and-b-are-both-open-in, @Jason DeVito seems like someone who pays attention to that. And I am very grateful to him for offering to help. I'll tell you what. I shall keep the "calls for help" to a minimum. I only contacted him thrice (I believe) over the last month..
Comment: I don't agree that MSE mods should have any concern with activities of users off the MSE site.
Answer: I get a few legitimate requests a year from graduate students. If it is in my field I generally answer. If there are too many contacts from one person, I arrange contact with the faculty adviser; that happened recently. It turned out the adviser was alright with it, so I continue to guide; at the same time, I do not want to have much contact, and I refuse to step between student and adviser. (note that the spelling is usually advisor, like doctor. it's wrong, but it's usual. Advisory is a real word).
On the other hand, a week or two ago I got a question from someone who wanted me to rewrite an optimization problem roughly in the area of linear programming. From what I could see, I was picked because the question had the phrase "quadratic form" in it. He then sent a heavily edited pdf, where no question could any longer be discerned. Clearly some attempt to cheat, possibly a test, term project. I really disliked the whole experience.
In particular, I don't want to proofread work by others. I do that enough for published articles. I'm guessing Jason is polite, but I find it hard to imagine that he wants frequent contact for the purpose of checking your work. What does he get out of it?
EEDDIITT: have you asked him (Jason De Vito) about this?

Personal contacts with users


What is the difference between the promoter and the advisor?

Question: I am applying for a Ph.D. position at Netherlands and I see that there will be a promoter and an advisor. I have never seen such a title as "promoter". What is the difference between the two titles?
Answer: As far as I understand, in the Netherlands, only full professors may be appointed "promoter", i.e. the official advisor, the super-boss if you will. Other faculty members must apparently get authorization from the university (see comment).
So if you are going to be supervised by someone who is not full professor (e.g. associate/assistant professor), that person will be appointed as "(co)advisor", while a full professor will be acting as an official advisor/promoter and will chair the doctoral examination committee.
Answer: To add to the previous answer: an advisor is likely to be your daily supervisor, meaning that you have most contact with him/her. This person can also be a full professor. Your Promotor is a full professor (often head of department) who is likely to be too busy to meet often (though their level of commitment differs). An assistant professor is (since a couple of years) allowed to also be a promotor.
In short: the advisor is someone you'll spend more time with and should be there to help you with practical matters.


How do you remove paint and rust from outdoor chairs?

Question: I have some outdoor metal chairs that have a few rust spots and the paint is chipping in a number of places. I'm looking for the best way to clean off the rust and paint so I can repaint them.
Comment: Do you want to strip the paint completely or just clean up the chipped parts?
Comment: Whatever would be fast, easy, and cheap.
Answer: I would try a wire brush first. Either a hand model or a rotary one that would fit into your power drill may do the trick.  You can also get small toothbrush size wire brushes to get into the small spots.  Good Luck
Comment: +1 The rotary brushes get my vote, let the power tool do the work for you.  Just wear eye protection and a dust mask.
Comment: Yeah, expect the power brush will typically move too fast to get in the crevasses.  That'll be the limiting factor.
Answer: They make spray paint designed to go on "right over the rust". A wire brush to get off any loose flaking paint and rust, then spray away. Rustoleum is one brand, but basically if you go to the hardware store, find the paint area, then look around for shelves full of spray cans, you will hit the jackpot. Read the label to be sure, but if the word Rust is in the name, generally you don't need to strip the old paint and you don't need to worry about rust that isn't forming large flakes and half falling off.
Comment: That's what we did with our outdoor metal table and chairs. Used a wire brush to smooth the rust spots and then used the Rustoleum textured paint. The texture helps hide the imperfect spots where there's chipping or rust and the furniture looks brand new.  Get a "spray grip" if you use aerosol cans.  Easier to control the paint and won't fatigue your fingers.
Answer: You could use a grinder with a heavy grit sandpaper to remove the paint and the rust.  If the rust is not that deep, you might be able to use a pressure washer with a high psi nossle.  That will remove the paint and loose rust spot very well.  For the spots of rust that are too deep, you might be able to use a rustolium primer to paint on it first after the cleaning then paint it.


Rewrite Rule for Post Meta

Question: I would like to create an endpoint for a custom field. For example, I already have a custom 'competition' post type for which rewriting is working great and resolving at website.com/competitions/my-competition. Within that competition I have award categories created using Advanced Custom Fields, all of which have a unique ID.
I would like to be able to visit website.com/competitions/competition_slug/award-category/category_slug.
I've got as far as passing the unique ID of the category to the query vars and loading a custom template but am stuck on website.com/award-category/category_slug and can't figure out how to have my rewrite rule include the parent competition. Here's my code:
function aca_award_cat_rewrite_rule() {

    add_rewrite_rule( '^award-category/([^/]*)/?', 'index.php?award_category=$matches[1]', 'top' );
}

function aca_set_award_cat_query_var( $vars ) {

    array_push( $vars, 'award_category' );
    return $vars;
}

function aca_include_award_cat_template( $template ) {
    if( get_query_var('award_category') ) {
        $award_category_template = plugin_dir_path( dirname( __FILE__ ) ) . 'public/award-category-template.php';
        if( file_exists( $award_category_template ) )
            $template = $award_category_template;
    }
    return $template;
}

I realise that right now my rewrite_rule is sending the user via index.php but I can't figure out how to accommodate the awards/award_slug bit without interfering with the existing rewrite rules for the post type.
Answer: Okay! So I got this working by just changing the rewrite_rule to include the event...
function aca_award_cat_rewrite_rule() {

    add_rewrite_rule( '^awards/([^/]*)/award-category/([^/]*)/?', 'index.php?competition=$matches[1]&award_category=$matches[2]', 'top' );
}

Rewrite Rule for Post Meta


Smalltalk and IoC

Question: I see a lot of IoC frameworks for .Net and Java.  Does anyone know why there are no equivalent frameworks for Smalltalk.  This is more a philosophy question than anything else.  I'm wondering if there is something in the Smalltalk way of doing things that precludes the necessity of having an IoC framework.
Answer: MVC was invented on Smalltalk and is arguably the original Inversion of Control framework.  While somewhat more lightweight than its java counterparts, it has the basic concepts of a model holding the data, a view rendering the data in response to events propogated from a controller.
Less flippantly, Java is actually needs a lot of framework support to do a web application without excessive quantities of boilerplate code.  Smalltalk supports programming idioms such as continuations, which allow an author to pretend they are not really writing event driven code.  Seaside works like this, giving the benefits of IoC with a somewhat more flexible development paradigm.
EDIT: MVC is a framework for UI's in Smalltalk (arguably it's not really a framework as such, but the class library has built in support for it).  It has the inversion of control property in that the view and model respond to events dispatched by the controller - the don't call us, we'll call you property.  Inversion of Control is a design pattern within frameworks that's used to reduce the need for extensive boilerplate in java applications.  In some definitions of an application framework, Inversion of Control is the main property that is viewed as distinguishing a framework from a library.
Comment: Language issue:  Delegates/Closures/Callbacks/EventHandling is so easy on a smalltalk platform, as to be unremarked upon. Because it's harder to achieve IoC on other platforms, and because it requires scaffolding (framework) code to implement well, and consistently, one might expect to see a requirement for such scaffolding code in Smalltalk. There isn't any such need. Because it's easy.
Comment: Nigel:  I was aware that MVC originated with Smalltalk.  What confuses me about this is that and IoC framework like Castle contains an MVC framework (MonoRail) and an IoC framework (Windsor) which suggests that they are different?
Answer: Functions are first class citizens in smalltalk, so it is easy to have IoC without a framework.
Answer: I think that IOC or the Dependency Injection pattern solves a problem that doesn't really exist in the Smalltalk environment.  Smalltalk is an untyped dynamic language and uses message passing to communicate.  This makes for objects that are loosely coupled by nature at the language level.  Any object can send a message to another object without regard to the type as long as it can process the message.  So, as you might guess changing dependencies at any given time is relatively easy and natural. Just have to decide where, when, and how you want to change the dependency.
Comment: "solves a problem that doesn't really exist in the Smalltalk" - *yes* Besides, Smalltalk programmers are kinder to kittens: http://www.flickr.com/photos/dafydd_ll_rees/4528702680/
Answer: A few possible reasons for this.  One is that we haven't bothered to use the "IoC" qualifier, which is essentially redundant - since calling something a framework implies the inversion of control flow.
Another is that the Smalltalk language provides direct support for "IoC" flows - in the form of closures.  One result of programming with closures is that the flow of control as found in frameworks doesn't seem so starkly different as to evoke a sense of being "inverted" from a "normal" sense of flow; rather, with closures, the flow of control is flipping back and forth between these two perspectives all of the time, and everywhere.  Even within single statements.
A third reason, perhaps, is that, even without closures, the "inversion of control" being described is not uniquely associated with frameworks - the same flows are found in most forms of code that involve I/O.
Fourth, Smalltalkers probably use these sorts of flows even more than others, as we lean more heavily on the notions of objects and the messages sent between them than on the notions of structures and the calling of member functions.  In the absense of closures, these two views are equivalent, and interchangeable, but the addition of closures changes the result - the sense of control flow in use is one of the effects.
Finally, one might even think about describing the REPL style of control flow as a "simpler", but "inverted" sense of the "normal" flow, normal in the sense that it is used nearly everywhere else.
In summary, the same sorts of frameworks exist for Smalltalk.
We describe them a bit differently is all.
The difference is, at least in part, due to the presence and utilization
of closures in Smalltalk, which many other environments do not yet provide --
-- notably C++, C#, and Java.
Answer: In Java a Dependency is created when you write
something like
MyClass32 temp  = this.theThing();
Now your code DEPENDS on the class MyClass32
being around. Your code will not work
without it. Any change in that class can
make your code uncompilable, requiring a
lot of extra changes in your code, which
may require further code-changes in class
that depend on yours. Lots of extra work.
In Smalltalk you would write
  temp  :=  self theThing;
Your code will work no matter what is returned
by #getTheThing.  Your code is not dependent
on the class MyClass32 being around.  Your only
dependency is that 'temp' must understand whatever
messages you send to it.
So in a sense the purpose of Dependency Injection
Frameworks is to make a statically typed language
like Java work more like  a dy7namically typed one.
That said, there is a DESIGN PATTERN I've often
followed in Smalltalk: Create a class-method like
MyClass that  returns SOME class. It need not have
the NAME 'MyCLass'. It could be one of several
classes, returning a different class at night.
This pattern is present in the Smalltalk MVC,
where View-classes have the method #defaultControllerClass,
which is  typically redefined by subclasses.

Smalltalk and IoC


Add a "Like" button to a native comments entries tag?

Question: Like some of the social comment engines, is there an add-on to allow users to "like" a comment within an entry (and not the entry itself)?
Answer: Likee is free and on my shortlist to try out.
http://booyant.com/likee
Comment: Thanks very much -- so far I[m leaning towards Eric's Flagmaster, but I've downloaded likee as an option.
Answer: Although not using the native EE comment module, if you use Solspace's Rating module instead, you can use the review field in a Rating form as an entry comment. This can be done without using the rating field. Then, users can rate a rating/review up or down using the {exp:rating:insert_rating_vote} tag. This could be used as an equivalent of "liking" (or "disliking") a comment.
Comment: Thanks -- as you probably know already I'm a big proponent of the Rating module. I didn't know that it could be used that way. Terrific idea.
Answer: Might be not exactly what you're looking for, but you can use Bookmarks to let users bookmark comments.
Though different, the concept is still similar to likes.
Use can use {exp:bookmarks:by type='comment' data_id='{comment_id}'}{total_results}{/exp:bookmarks:by} to display total number of bookmarks for the comment and {exp:bookmarks:check} to display 'add-to-bookmarks' form
Comment: Thanks Yuri! Although I think Flag Master would be more appropriate to what I've got going, but I'm looking to use Bookmarks on another project.
Answer: If one were so inclined, you could take Low's http://mijingo.com/products/screencasts/how-to-develop-expressionengine-add-on/ which does 'likes' for an entry and modify it to do likes for a comment entry.
Comment: Shut up, Eric! Let Steven speak! ;)
Comment: Dammit Steven! We don't want people *learning* how to do this on their own :p
Comment: LOL - I've got no plans to build an add-on. I'd be happy to always budget for a commercial one to support the awesome developer community!
Answer: Take a look at Flag Master; it's built specifically to allow you do exactly that (and a whole lot more). You can setup your own "sets" of options (or just 1) and is completely AJAX compatible and made with love.
Comment: Hi Eric,

So Flag Master allows me to "flag" any content user chooses, including individual comments in the native EE comment system?

Of course, as long as the user is logged in, each "flag" will remain personal for that user?
Comment: Pretty much, yeah. The only difference is Flag Master can also work with logged out users if you like (it's configurable). Take a look at this page: http://mithra62.com/docs/detail/export-it-installation

Both the article (entry) and comments have Flag Master used on them. The entry uses multiple options to create a poll of sorts while the comments have a single "Inappropriate" button (similar to your "Like" option).
Comment: Awesome - I'll speak with the client to get this approved for purchase. Thanks Eric!


average hop yields

Question: i'm looking to plant my own hops in my yard (yes i know i'm late. researching for next year). however, i'm trying to figure out roughly how many say cascade rhizomes i would need to make this worth my effort. meaning, if i get 5-8 rhizomes, would that yield enough to make a typical homebrew? i understand the first year or so has a low yield which is ok. at this point, getting ideas and numbers together.
Answer: It will depend on the variety and your weather.  I live in the middle of prime hop growing country.  I have one Cascade plant that's about 12 years old now.  I get anywhere from 20-27 lb. of wet hops each year from it.  Enough that it's a hassle to pick, dry, and vacuum package them.
Comment: yea i figured weather/variety would be important here. just trying to get a general idea. averages. i'm in nj right on the coast. basically between 6-7 on the hardiness.
Comment: In general, the closer you are to the 45th parallel, the better your yield will be.
Answer: If growing conditions are optimal you'll get plenty of hops.  I have 3 varieties growing and my Fuggles is the most dominant.  2nd year I had close to 2 lbs dried and packaged off a single rhizome so 5-8 rhizomes will get you plenty of picking opportunities.  I've read on average you can expect a healthy rhizome will produce 1.5 to 2 lbs in a good season.
Comment: Some quick match and a direct scaling of the recipe I just brewed which called for 8 oz of hops would result in the need for 378 lbs of hops for a 120 bbl tank.  Not perfect science there but a ballpark of what a hoppier brew would need on a craft scale.
Comment: so a good year of 1.5-2lbs, i should be able to make plenty of good beer. just so i have an idea or maybe i'm just curious but a small craft beer shop making a single batch are looking at tons needed?

average hop yields


Latest Parity Guide

Question: There is no one place to get the Latest guide on parity software usage and Ethereum plateform. All guides—which are scattered on various places—are beyond understanding for a new being. Please provide authentic and comprehensive information links or resources.
Answer: Their Wiki contains a good source for all of this information.
Go down through the index and you should find what you need.

Latest Parity Guide


Medical student vs. medicine student vs. student of medicine?

Question: What is the right phrase for calling someone who is studying medicine? I've seen "medical student" a lot but I doubt about it mostly because the student him/herself is not medical! It's his/her field of study that is medical. Also I've seen that we call the school "School of medicine". What form is the true one?
Comment: *medical student, science student, law student, football player, tennis player,...* what's the problem?
Answer: Student of medicine and School of Medicine are the older traditional terms, but medical student and medical school are far more common today in spoken English (at least in the US).
Adjectives are not always references to properties that inhere in the noun; they can indicate a relationship or association.


Button Interrupt Doesn't Work

Question: I'm working on a project for my Raspberry Pi. I have stumbled upon a problem with creating interrupts through a button on my breadboard. I have bought a PiCamera and I intend to make it so that whenever I push the applied button, the PiCamera will take a picture. For now, I'm just trying to make a message show up on my console whenever I would push the button such as: "button pressed" to make sure the interrupt works. I've tried it with my code but it doesn't seem to work. I'm pretty much lost ideas on how I could possibly solve this issue. Help is very appreciated!
I have my code down here.
I have put the button in the middle of the breadboard, connecting both the top layer and the bottom layer. I've connected one side with ground and the other one with GPIO17 (GPIO for Pi2).
Also the code contains another part of my project. Namely I have recently set my components up to measure the amount of light with a light meter. The darker the area, the more LEDs will be turned on. I have three LEDs on my breadbord. This works 100%. Now I'm trying to force in an interrupt by using a button.
My Button interrupt is at the bottom of the code.
My code:
http://pastebin.com/Y0bTLE4Y
OR...
<code>#!/usr/bin/python

import spidev
import time
import os
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)

GPIO.setup(5, GPIO.OUT)
GPIO.setup(6, GPIO.OUT)
GPIO.setup(13, GPIO.OUT)

# Open SPI bus
spi = spidev.SpiDev()
spi.open(0,0)

# Function to read SPI data from MCP3008 chip
# Channel must be an integer 0-7

def ReadChannel(channel):
  adc = spi.xfer2([1,(8+channel)<<4,0])
  data = ((adc[1]&3) << 8) + adc[2]
  return data

# Function to convert data to voltage level,
# rounded to specified number of decimal places.

def ConvertVolts(data,places):
  volts = (data * 3.3) / 1023
  volts = round(volts,places)
  return volts

# Define sensor channels
light_channel = 0

# Define delay between readings
delay = 1

while True:
  # Read the light sensor data
  light_level = 1024 - ReadChannel(light_channel)
  light_volts = ConvertVolts(light_level,2)

  print "--------------------------------------------"
  print("Light: {} ({}V)".format(light_level,light_volts))

  if light_level <350:
    GPIO.output(5, GPIO.LOW)
    GPIO.output(6, GPIO.LOW)
        GPIO.output(13, GPIO.LOW)

  if light_level >=350 and light_level <= 600:
    GPIO.output(5, GPIO.HIGH)
    GPIO.output(6, GPIO.LOW)
        GPIO.output(13, GPIO.LOW)

  if light_level >600 and light_level <= 700:
    GPIO.output(5, GPIO.HIGH)
    GPIO.output(6, GPIO.HIGH)
        GPIO.output(13, GPIO.LOW)

  if light_level >700:
    GPIO.output(5, GPIO.HIGH)
    GPIO.output(6, GPIO.HIGH)
    GPIO.output(13, GPIO.HIGH)

# Wait before repeating loop
  time.sleep(delay)

GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_UP)
print("Button pressed: " + str(index))
#TakePicture()
try:
    GPIO.wait_for_edge(17, GPIO.FALLING)
except KeyboardInterrupt:
    GPIO.cleanup()       # clean up GPIO on CTRL+C exit
GPIO.cleanup()           # clean up GPIO on normal exit
</code>
Answer: The code after the while True will never be exectuted.  It would only be executed if the while loop terminates.  So the following code has no effect.
<code>GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_UP)
print("Button pressed: " + str(index))
#TakePicture()
try:
    GPIO.wait_for_edge(17, GPIO.FALLING)
except KeyboardInterrupt:
    GPIO.cleanup()       # clean up GPIO on CTRL+C exit
GPIO.cleanup()           # clean up GPIO on normal exit
</code>
Comment: Oh okay thanks! I will move that piece to a different place next time!

Button Interrupt Doesn't Work


How do I know that I don't have a lucky test set?

Question: On a reasonably sized data file, I do a random split and get the validation and test sets (80/20 let's say). I perform a (repeated) k-fold CV on the validation portion of the data and adjust all the parameters needed and finally come up with my best model. Then I try this model on the test set (20%) I never used before and find out that it performs pretty well. Now how do I know that I wasn't just lucky in my selection (though randomised) of the test portion I set aside in the first place? Is there a procedure (similar to k-fold CV we used for the validation portion) that compensates for this effect?
Answer:
Is there a procedure (similar to k-fold CV we used for the validation portion) that compensates for this effect?

As @jxd1011 already pointed out, you can do (repeated) cross validation also at that upper level of measuring generalization performance.
However, I thought it worth while to point out that search terms for this approach ("inner" cross validation for model optimization + "outer" cross validation for final estimate of generalization error) is known as nested or double cross validation.
Answer: When learning a model, the aim is to be able to generalize well to the distribution which the data came from, and using a testing set is kind of a proxy for that, because we do not have access to this distribution.
Generalizing well essentially means that you were able to learn factors that are intrinsic properties of that distribution, and so you are able to perform well on any data sampled from that distribution. How do we know what are these intrinsic properties? We do not, and must make assumptions based on the data we can observe. So when you see something that is common to all the data samples you have access to, the assumption is that this must be a parameter of the distribution.
When your model trained on the validation set performs well, it means it has learned some parameters intrinsic to that set, but when it also performs well on the test set, it must mean that whatever it learned (that led to good performance) are also present in the test set. So in the absence of more data samples from that distribution, you can assume that these common parameters are properties of the distribution.
However if you really wanted to guard against a lucky split, you could repeat this training-testing process multiple times on different random splits and see whether the values of the parameters it learns are more or less the same. If yes, then you can be certain that there was no random luck involved. But it's likely excessive. It's possible to have an unlucky test set, consisting only of outliers for example, but if the model performs well on both seen and unseen data, then it must mean that the split led to a test set that is representative of the same distribution that the validation set came from.
Comment: Thank you @Antimony for the swift and detailed reply . Cleared it up for me.
Answer: At high level, if the data is large enough, 20% of the testing data, can be representative to the population.
In addition, there are other re-sample methods available. For example, repeated cross validation will repeat the process many times and reduce the chance of getting a skewed training or testing data.
Please check this post for details.