Trying to split the current output of an LED driver

Question: I am currently using an 8 channel LED driver wher I have set the outputs to produce 20mA of constant current. Problem is I have 11 LEDs to drive. So I have decided to connect two LEDs in paralelled to each output, and then finally on the 6th output connect a single LED. I have 100Ohm resistors in series with each of those parallel resistors, and my LEDs can handle up to 30mA of current. However I want all 11 LEDs to have the same brightness, more or less. How do I get that 11th LED that is alone to split its current in half? Can I put a resistor in parallel with that LED? if so how do I calculate the resistor value to get it as close to 50% as possible, or should I use dummy LEDs to put in parallel?
Comment: What led driver are you using? What's your source voltage?
Answer: The LED driver regulates current, so it adjusts the voltage until the current is 20mA.
If you put two LEDs in series, the LED driver will still regulate to 20mA, but the voltage required for that will be the sum of the LED forward voltages.
The downside is that you need a high enough supply voltage, and any channel that has only a single LED will need to drop the voltage in the driver. If it's a buck converter, fine, but a linear regulator will heat up quite a bit.
Answer: If you have enough voltage headroom, you should put the LEDs in series, rather than parallel.  This way each LED is getting 20mA.
Parallel LEDs, and a resistor in parallel is not a good solution.  LEDs are not resistive devices, they behave like diodes where they have a certain voltage drop that doesn't change very much with current.
When you have your LEDs in parallel, tiny differences in their forward voltage drop will cause them to share the current unevenly.  This will make their brightness not very uniform.  The 100Ω resistors will help with this, though.
Remember, when devices are in series, they have the same current through them.  When devices are parallel, the current is different through each branch.
Comment: aside from the FUD about parallel leds here, op said they have a resistor per parallel led, not a shared one, nor does it answer Ops question.
Comment: @Passerby He is using constant current drive, he can pitch the resistors and just put the LEDs in series.  Easy way to match current/brightness.


Does matter become energy at the speed of light?

Question: According to modern physics, we can't push matter to the speed of light. It would slow down (relative to its environment). But theoretically, if matter were to travel the speed of light, would it become energy?
It seems to me that $E = mc^2$ could be rearranged to prove that it would.
If so, what kind of energy would it become, and do we know what that transition would look like?
Would the transition be instant, or is there some kind of transitional state between matter and energy?
Comment: "If it could" means changing the rules, so an answer is whatever your changed rules would have.  It does make sense to look at what happens as velocity gets arbitrarily closer to c, which I explored in my Answer.
Comment: It's important to appreciate that there are (an infinity of) inertial reference frames in which CuriousWebDeveloper is moving arbitrarily close to the speed of light; in these reference frames, you have arbitrarily large kinetic energy.  But, none of this has any effect on you because *you* are always at rest with respect to yourself.  This holds for other forms of matter too.
Answer: Your question is so confused that it's hard to give a meaningful answer...

if matter were to travel the speed of light, would it become energy?

Anything that has a rest mass $m_0$ has an energy associated with that mass of $E=m_0 c^2$. If this mass is also moving with some momentum $p$, it has a kinetic energy associated with the motion. The total energy (including both kinetic- and rest-energy) of the moving mass is:
$$
E=\sqrt{m_0^2 c^4+p^2c^2}\;.
$$
Given the relativistic definition of momentum, $p=m_0 v \frac{1}{\sqrt{1-v^2/c^2}}$, where v is the velocity, the expression for energy can be re-written as:
$$
E=m_0c^2\frac{1}{\sqrt{1-v^2/c^2}};.
$$
So, clearly, no massive body or particle can travel at the speed of light, because the energy of that body or particle would be infinite...
Comment: Nice ans.but please answer well-asked questions

,Not all questions can or should be answered here. Save yourself some frustration and avoid trying to answer questions which...

*....are unclear or lacking specific details that can uniquely identify the problem.

*....solicit opinionsrather than facts.

*....have already been askedand answered many times before.

*....require too much guidance for you to answer in full, or request answers to multiple questions.

*....are not about physics as defined in the help center.http://physics.stackexchange.com/help/how-to-answer
Answer: At hyperrelativistic speeds, a massive object has the bulk of its energy in kenetic form so the invariant mass is small residue. It acts like a very low mass particle at meerly relativistic speeds, or a almost massless neutrino at any speed.
A 7Tev proton is travelling at $0.999999991c$ and its mass is only contributing on the order of one one hundredth of a percent to that total.
It acts more like a massless particle: adding more energy does not make it go (usfully or noticably) faster, but adds to its momemtum and shortens its wavelength. The fact that it has energy even when all the momentum is removed is a tiny correction, rather than the most significant thing about it.


uBlox LEA 6H and UNO no data

Question: While using NEO 6M and getting close-to-perfect accuracy, connecting the 3dr uBlox LEA 6H shows incoming characters, but gibberish data (at 38400) like it is connecting to a wrong baud rate (although it isn't, i've checked it with u-center and works when connected to Ardupilot).
So i guess it is some kind of configuration to show only certain parts of NMEA (if it is showing NMEA and not something else).
Comment: what accuracy does your ublox lea6h gps have? I want to control quadcopter and need to find 1 GPS module has the high accuracy( may be < 1m)
Answer: Your uBlox LEA 6H is most likly configured to use the UBX binary protocol and not NMEA at all. This protocol, as well as how to switch your LEA 6H between NMEA and UBX is in this document, from the uBlox website:
http://www.u-blox.com/images/downloads/Product_Docs/u-blox6_ReceiverDescriptionProtocolSpec_%28GPS.G6-SW-10018%29.pdf
You may be able to use the code from the ArduPilotMega project to communicate in UBX, they use the UBX protocol and the code is open source, but I can't guarantee its very good quality.
Comment: Using u-center, i'll try to change the output sentences. This pdf is extremely helpful!
Answer: You can configure the ublox lea6H GPS to read either through NMEA protocol or the UBX protocol. You just need to send some configuration messages. For good data rate it is better to use UBX protocol as it gives data in binary format inducing less delay.In case you need to test your device you can use my GPS code for arduino mega - customized ardupilot gps code  - UBX protocol.
https://github.com/ksskarthik/Team_Pushpak/blob/master/TP_GPS

uBlox LEA 6H and UNO no data


Numerical integration of divergent function

Question: I am having trouble with the numerical integration of a divergent function. For example,
\begin{equation}
n= \int f(x)\,dx = \displaystyle\int \dfrac{\Theta(x-\varepsilon)\,dx}{\sqrt{x-\varepsilon}}
\end{equation}
is not behaving good when calculated numerically:
\begin{equation}
n_\text{numerical} \approx f(x_j)(x_j-\varepsilon) + \sum_{k=j+1}^N f(x_k)\Delta x
\end{equation}
with
\begin{equation}
x_i = x_\text{min} + i\Delta x
\end{equation}
and $x_j$ being the smallest point larger than $\varepsilon$. Due to the divergent behavior of $f(x)$ near $\varepsilon$, the numerical result has discontinuities and jumps at every $\varepsilon=x_i$ when I sweep $\varepsilon$.
The smoothness of this integration is crucial in the convergence of my simulations. Can anybody suggest a simple trick to solve the problem? All I need is to have a continuous numerical result by continuously changing $\varepsilon$.
Answer: I suppose your function is $f(x) = g(x)/\sqrt{x-\epsilon}$ where $g$ is bounded, and you want to  integrate this on $(\epsilon, b)$.  The change of variables $x = \epsilon + t^2$ gives you
$$ \int_\epsilon^b \dfrac{g(x)}{\sqrt{x-\epsilon}}\; dx =
2 \int_0^{\sqrt{b-\epsilon}} g(\epsilon + t^2)\; dt$$
which gets rid of the singularity.  Similarly to integrate
$g(x)/\sqrt{\epsilon - x}$ on $(a,\epsilon)$, use $x = \epsilon - t^2$.
Answer: @RobertIsrael provided the way forward here.  I thought that it would be instructive to show a simple "trick" that works well in other situations.
To that end, we assume that $g(x)$ satisfies the Holder condition
$$|g(x)-g(y)|\le C|x-y|^{\alpha} \tag 1$$
with Holder exponent $\alpha \ge 1/2$.  Then we can write
$$\begin{align}
\int_{\epsilon}^{b}\frac{g(x)}{\sqrt{x-\epsilon}}dx&=\int_{\epsilon}^{b}\frac{g(x)-g(\epsilon)}{\sqrt{x-\epsilon}}dx+g(\epsilon)\int_{\epsilon}^{b}\frac{1}{\sqrt{x-\epsilon}}dx\\\\
&=\int_{\epsilon}^{b}\frac{g(x)-g(\epsilon)}{\sqrt{x-\epsilon}}dx+2g(\epsilon)\sqrt{b-\epsilon}\tag 2
\end{align}$$
The integrand $\frac{g(x)-g(\epsilon)}{\sqrt{x-\epsilon}}$ of the integral in $(2)$ will be well-behaved for numerically small $\epsilon>0$ because of the Holder condition of $(1)$ with exponent $\alpha \ge 1/2$.

NOTE:
This approach in which we "move the offending term" works well in a fairly general class of problems.  Suppose that we have an improper, convergent  Riemann integral
$$\int_a^bf(x)dx$$
for which $f$ has a non-removable singularity at $a<\xi<b$ such that $\lim_{x\to \xi}\left(f(x)-K|x-\xi|^{-\beta}\right)$, $0<\beta<1$, exists and is finite.  Then, we can write
$$\begin{align}
\int_a^bf(x)dx&=\int_a^b\,(f(x)-K|x-\xi|^{-\beta})\,dx+\int_a^b\,K|x-\xi|^{-\beta}dx\\\\
&=\int_a^b\,(f(x)-K|x-\xi|^{-\beta})\,dx+K\frac{(b-\xi)^{1-\beta}+(\xi-a)^{1-\beta}}{1-\beta}\tag 3
\end{align}$$
where the integrand $f(x)-K|x-\xi|^{-\beta}$ is well-behaved near $\xi$ and numerical integration poses no challenge.
Comment: @maziarnoei Please let me know how I can improve my answer. I just want to give you the best answer I can.


how to move ispell correction suggestion window

Question: When running ispell-buffer, as I scroll down the document, the misspelled word is highlighted at the bottom of the window, but the correction suggestion window appears at the top of the document. Is there a way to make the correction suggestion window appear at the bottom of the window it is being executed in instead?
Answer: The library ispell.el has evolved over time.  As to Emacs 28.2, see the function ispell-display-buffer ....  (You can use M-x find-function once the ispell.el library has been loaded.)  There a couple of times the parameter 'above is used when calling split-window ... that parameter can be changed to 'below ... To redefine a function, it can be copied to the .emacs / init.el file ... make sure the library ispell.el has been loaded before redefining a function inside that library.
Comment: Terrific, thanks - I was able to add the modified function to use-package under `:config` and it worked perfectly without having to manually load ispell. Thanks!


Separating emails from a common iTunes account

Question: My wife and I share a common iTunes account. She bought a new iPad Air 2 and we used iTunes from my iPad to download her new iPad via iTunes. My e-mails come on her mail. How do I get her e-mails to come into her mail? We both use gmail.
Comment: What do you mean by "we used iTunes from my iPad to download her new iPad via iTunes"? And could you please clarify the whole issue with a few more details? The more the better, thank you!
Answer: I assume you've restored your iPad onto the new one of your wife. To change the email configuration on your wife's iPad

go to Settings -> Mail, Contacts, Calendar
delete your email account under Accounts (which will just remove it from the iPad and not actually delete it on Gmail's side)
add your wife's Gmail account


Effect size calculations in mixed ANOVA design for power analysis

Question: I need to calculate effect size for a mixed ANOVA design.  I need it because I'm using GPower3 to calculate a rough sample size for a full study.  I have pilot data.  Based on this page:
http://www.xlstat.com/en/features/statistical-power-analysis-of-variance-anova.htm
and the GPower3 software, it looks like there are 3 ways to calculate an effect size:

eta²
use variances
use group means

Is there any rational for picking one over another?  Since I have the pilot data, I guess I was just going to use the variances to calculate the effect size.  The formula I have for that is:
f (effect size) = sqrt(Variance Explained / Variance Error)
Based on the summation rule:
Total Variance = Variance Explained + Variance Error
Is this correct?
If I have unequal group sizes, could I use the pooled variance formula for the Variance Error term?
I also noticed that this effect size formula using the variances is quite similar to the F statistic:
F = Variance Explained / Variance Error
Is this correct and/or is there a relationship between them?
Thanks in advance.
Answer: I am not familiar with Gpower3 so this does not exactly address your question, but here is another approach that you may want to consider.
For power and sample size studies more complicated than simple 2 sample tests I prefer to use simulation rather than prepackaged routines.  The basic steps are:

Think through what your data will look like (structure, means, variances, distributions, ...)
Think through how you will analyse the data
Generate data based on current assumptions and analyze it
Repeate step 3 many times and compute the percentage of times that the null is rejected (this is the power)
Repeate steps 3 and 4 for different sets of assumptions

One of the advantages of this approach is that you know exactly what assumptions are being made and what the nature of the data and analysis is.  The main disadvantage is that it takes a bit more work and time than just plugging in a few numbers to a canned routine.
Comment: Hi Greg! This is a very interesting idea. I would like to try it out. Are you aware of any examples in published articles that make use of this way of power analysis?
Comment: I don't know of any specific articles.  I plan to write one (probably for the R Journal) sometime, but have not had the time yet.


Why am I suddenly getting all these review tasks?

Question: Over the past two or three weeks, I have noticed an uptick in the number of review tasks open to me (which is pretty cool- it's neat to help out more).  How are review tasks assigned?  Is it based on rep?  Am I suddenly paying more attention?  Or am I only noticing now due to recent changes to the site?
Comment: Are you referring to number of TYPES of review tasks, or of reviewable items within specific type?
Comment: As in, last month I was rarely reviewing anything at all, now I suddenly have review tasks of all types almost daily.
Answer: Review tasks are first come first serve. If you have more, it either means you are checking them more, more are generated, or fewer people are working on the queue.
Answer: We've also been under a fairly minor troll attack over the past week or two as well; nothing that can't be handled through standard procedures but it does mean that more questions/answers being flagged means more in the review queue.


What does "anime franchises" mean?

Question: I've seen many anime but faced with a word I could not find the meaning of -  anime "franchises" such as Fate/Stay Night.
What does "franchises" mean in this context?
Answer: Definition #11 of "franchise" at en.wiktionary is what you want:

The loose collection of fictional works pertaining to a particular universe, including literary, film or television series from various sources.

I would dispute the notion that this sense of "franchise" necessarily involves "an authorization granted by a government or company". This is certainly true of franchises in the legal sense (the McDonald's sense), but in common parlance today, we would refer to Fate as a franchise even if all of its component works were produced by the same corporate entity (Type-Moon, say).
I would say that a defining feature of a "franchise" in this sense is the existence of a wide variety of media constituting the franchise. For example, it would be odd to describe a standalone novel as a franchise, but if there was also an associated manga or anime or something, it would be more "franchise-esque".
Answer: Franchise

an authorization granted by a government or company to an individual or group enabling them to carry out specified commercial activities, e.g., providing a broadcasting service or acting as an agent for a company's products.

What this means in the context of anime is that someone has an original idea, usually a manga, and has given the right to make anime, merchandise, extend the idea/story as they see fit, etc. to a second person/entity.
This blog post talks extensively about what a franchise means to an anime fan:

They're an anime but also a manga, light novel, video game, trading card game, collection of toys, or any number of mediums. I wonder how many anime fans get into all the franchise branches of a particular series, or whether they're content to just watch the anime and nothing more…
Answer: The more general term for this is "media franchise" which is also famously known as "media mix" in Japan.
Quoting Wikipedia,

A media franchise is a collection of related media in which several derivative works have been produced from an original creative work, such as a film, a work of literature, a television program or a video game.

In Japanese culture and entertainment, media mix (wasei-eigo: メディアミックス, mediamikkusu) is a strategy to disperse content across multiple representations: different broadcast media, gaming technologies, cell phones, toys, amusement parks, and other methods. The term gained its circulation in late 1980s, however the origins of the strategy can be traced back to 1960s with the proliferation of anime with its interconnection of media and commodity goods. It is the Japanese equivalent of a media franchise.

To conclude and reiterate, it is when an original work (e.g. anime) has derivative works on other media (e.g. manga, game). Recent media includes manga, anime, light novel, game, music CD, TV drama, movie, web radio, figures, talent (Love Live!), trading card (Yu-Gi-Oh!), plastic model (Gundam) and others.
Example:

Tenchi Muyo!: an OVA spawning TV anime, game, radio drama, light novel, manga, etc. (considered as the pioneer of media mix in Japan)
Code Geass: a TV anime spawning manga, game, light novel, drama CD, radio, live-stage and musical performance
Guilty Crown: a TV anime spawning light novel, manga, game, web radio

Some references were taken from Japanese Wikipedia counterpart

What does "anime franchises" mean?


Nexus 5 stuck on "flying color dots lollipop" screen after Hard Factory Reset

Question: I updated my Nexus 5 to Lollipop a month back and it was working fine. Suddenly one day my device didn't boot up so I did a factory reset and I got wipe/cache error and if I switch off the power and restart I get the flying color dots page and nothing comes up after that. I went to service center and they said it's a software issue and they can't do anything about it. How can I fix this?
Comment: The initial bootup for lollipop takes around 10 to 15 minutes. How long did you wait?
Answer: There is nothing to worry. You just have to flash the images properly.
Please follow the steps mentioned in this Android Enthusiasts answer.
The initial bootup usually takes time around 10 to 15 minutes. I'm up and running 5.0.1 without any problems.

Nexus 5 stuck on “flying color dots lollipop” screen after Hard Factory Reset


God's sovereignty and man's predicament in light of evil forces

Question: Since God is sovereign and is not answerable to anyone about his doing, why should God allow the evil to continue to grow and the aftermath of man suffering the consequences while the fallen demonic or angelic beings who foment man's rebellion against God go scot-free for thousands of years?  Would God not know that we humans are pawns in the hands of two awesome spiritual forces that war against each other? At any given point of time in human history, we do not find righteous people exceeding the evil doers?  This remains a conundrum for me.  Any answer.
Comment: Welcome to Stack Exchange, we are glad you are here.  Wehn you get a chance, be sure to check out the [site tour](http://christianity.stackexchange.com/tour) and read up on  how this site is [a little different](http://meta.christianity.stackexchange.com/questions/1808/how-we-are-different-than-other-sites) than other sites around the web.
Answer: I recommend reading the book of Habakkuk, particularly the first two chapters. It deals with this same train of thought. Habakkuk, in a nutshell, asks God why there's so much wrong and injustice, so much murder, etc, and why God is seemingly not doing anything about it.
Habakkuk 1:1-4 The Message (MSG) Version
"The problem as God gave Habakkuk to see it: God, how long do I have to cry out for help before you listen? How many times do I have to yell, "Help! Murder! Police!" before you come to the rescue? Why do you force me to look at evil, stare trouble in the face day after day? Anarchy and violence break out, quarrels and fights all over the place. Law and order fall to pieces. Justice is a joke. The wicked have the righteous hamstrung and stand justice on its head."
God's reply to Habakkuk, in a nutshell, is: brace yourself, because justice coming. This was all on the eve of God using the Babylonian nation as a lightning rod against His people, Israel.
In short, God is not blind. He knows what's going on, sees all the evil, but He is longsuffering, because He doesn't want anyone to perish. He promised to deal with evil and reward righteousness and godliness, and it may seem like He's slacking on that promise, but He's not.
2 Peter 3:9 HCSB
"The Lord does not delay His promise, as some understand delay, but is patient with you, not wanting any to perish but all to come to repentance."
It's just like in the days of Noah:
1 Peter 3:20 KJV
"Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water."
Think on it from this perspective: yes, another day going by means another day evil gets to flourish, but it's also a day wherein the same evil has an opportunity to repent. As for the angels who have fallen, we must simply accept that they are reserved for judgment.
2 Peter 2:4 KJV
"For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;"
2 Peter 2:4 Young's Literal Translation
"For if God messengers who sinned did not spare, but with chains of thick gloom, having cast them down to Tartarus, did deliver them to judgment, having been reserved,"
As for our role in this massive spiritual war, don't underestimate our purpose. Yes, this is an incredible battle with some serious beings on the battlefield, but we, though being in the physical right now have been equipped to do some spiritual damage- read Ephesians 6. Remember that as a Christian, you are on a team- the winning team.
consider this incident in the book of Daniel:
Daniel 10:12-13
"Then he said to me, "Do not be afraid, Daniel, for from the first day that you set your heart on understanding this and on humbling yourself before your God, your words were heard, and I have come in response to your words. "But the prince of the kingdom of Persia was withstanding me for twenty-one days; then behold, Michael, one of the chief princes, came to help me, for I had been left there with the kings of Persia."
As for the side of good seemingly not winning over evil, Remember the divine perspective. Remember that God is eternal and sees the beginning from the end. Christians do not fight for victory- we fight from victory. We have already won, no matter what things may look like.
Highlights:
God is aware of evil
God is longsuffering, just as he was in the days of Noah, giving man a chance to repent.
God will reward the righteous and godly in due time; the fallen are reserved for judgment
We are in the physical, but we still can make a massive spiritual difference.
Christians are already victories.


Ipad TableView for UISplittview

Question: I have a splittView and on the left side of my splittview I added an UITable.
<code>@interface LeftViewController : UITableViewController
</code>
I also added all the functions which are requiered for the my Tableview.
I also can see and put data into my tableview...
Now I was trying to add a background Image or set the first cell as a default cell and I notice that I have nowhere a tableview declared in my code ( except of the tableview functions)
How is that possible and how can I set now a background image or select the first cell?
I know that this is the code to select the cell, but there is no myTableView....
<code>- (void)viewDidAppear:(BOOL)animated {
    NSIndexPath *indexPath=[NSIndexPath indexPathForRow:0 inSection:0];
    [myTableView selectRowAtIndexPath:indexPath animated:YES  scrollPosition:UITableViewScrollPositionBottom];
}
</code>
Do I have to create a new tableview?
Best regards
Answer: Customizations are normally done in the viewDidLoad method. Since you are using a UITableViewController you can access the table view through the tableView property.
<code>[self.tableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionBottom];
</code>

Ipad TableView for UISplittview


java polymorphic binary search tree

Question: How can I implement a polymorphic binary search tree (that makes use of EmptyTree and NonEmptyTree) without using downcasting or class checking?
Answer: Create a common interface such as:
interface TreeNode<K, V> {
   TreeNode<K, V> find(K key)
}

Then provide classes that implement the common interface:
class EmptyTree<K, V> implements TreeNode<K, V> {
   public TreeNode<K, V> find(K key) {
      // ...
   }
}

class NonEmptyTree<K, V> implements TreeNode<K, V> {
   public TreeNode<K, V> find(K searchKey) {
      // ...
   }
}

Your implementation for the EmptyTree will always indicate a failure in searching for the item (whether by returning null or by throwing an exception), while your implementation of NonEmptyTree will either return itself (if the provided search key matches) or delegate to the left or right subtrees. Because the left or right subtree will always exist (it will either be a NonEmptyTree or an EmptyTree), the "NonEmptyTree" class can simply refer to its children via the common interface and rely on the fact that the runtime type will do the right thing (thus it is not necessary to do any casting or type checking of the children in the implementation of the algorithm).
The only place where you need to know the runtime type is when you construct the children.

java polymorphic binary search tree


Does wartime strengthen a totalitarian leader's power?

Question: I remember in Orwell's 1984 it was suggested that constant war was used to benefit the regime in charge. Is this a realistic concept? Does wartime really improve the position of a totalitarian leader / dictator politically? Why or why not and in what ways?
Comment: It's certainly possible to make a rather long list of dictators whose positions were made materially worse, in the long run, by war.  Napoleon, Mussolini, Hitler, Saddam Hussein...
Comment: @jamesqf - nope, they still all held as much power by the time they got taken out by external enemy as they ever did. Probably, more, in case of Saddam and Napoleon.
Answer: A foreign war:

Provides a reason for recruitment into the army.
Provides an outlet for frustrated young men.
Provides a reason for military control of the means of production.
Appeals to nationalism can unite the populace.
Provides a reason why shortages may be temporary (when the war is over, we will have as much as we want to eat, to wear, etc.).
In general, provides a scapegoat.

A comment notes:

It's certainly possible to make a rather long list of dictators whose positions were made materially worse, in the long run, by war. Napoleon, Mussolini, Hitler, Saddam Hussein...

That's certainly a risk of war.  You might lose.  But note that none of those examples were deposed domestically.  They were strengthened politically, even if they were eventually deposed by the very wars that united their countries domestically.
An example of a failed war by a totalitarian leader would be the Russian intervention in World War I by Tsar Nicholas II.  Rather than uniting the country, it gave an opportunity for revolutionaries to eliminate domestic forces.  Part of the problem was that it was unclear why they needed to fight.  For average Russians, the war seemed unrelated to Russian security.  They were fighting for Serbians, et. al. rather than for Russia itself.  Even so, it initially united the country, as this theory would suggest.
The problems arose over time.  As they were losing the war, it was harder and harder to justify sacrifices that might have been acceptable if they were winning.  This culminated in protests that included substantial numbers of women.  Many of the military units mutinied rather than attack women.
If Russia had been winning the war, they would have had fewer injured soldiers with more adherence to the current regime.  As things were, the military was just as vulnerable as everyone else to claims that the government didn't know what it was doing.  So when it came time to choose between shooting women and mutinying, they mutinied.
Orwell's Big Brother was more successful at convincing the populace that they were in danger.  They were fighting the war to protect the country from the evil others.
All these examples show one important lesson:  if you want to unite your country with a war, you either need to fight on your own territory (consider the United Kingdom in World War II), or you need to offer successes.  No one wants to back a loser.  Even worse, if a totalitarian leader actually loses the war, the winner will almost certainly replace the totalitarian.
Comment: Russians saw it as a war by German tzar(ina). On top of everything else.
Comment: "Orwell's Big Brother was more successful at convincing the populace that they were in danger. They were fighting the war to protect the country from the evil others." And, more important, the fightings were far away with nearly no consequences. The book even leaves it open if the war was real or merely a fake, with some irrelevant shootings somewhere in Africa. There were virtually no losses, no corpses, just propaganda and a reason for the shortages the population faced everywhere but which they had accomodated to.
Answer: Yes. There's numerous examples but look at Stalin. He was far more popular at the end of WWII than before it, despite him basically needlessly buried Germany under literally millions of Soviets' dead bodies. He's STILL bloody popular over there, seemingly above any reason.
Additionally, a war (aside from reasons Brythan's answer gives) gives an excuse to grab more power. (This isn't limited to totalitarian leaders - Lincoln's actions during Civil War have earned him accusations of dictatorship even though he started the war not as a dictator and arguably didn't end it as one. Ditto USA post-9/11 under both parties' presidents).
Putin grabbed more power (poer vertical was born at that time, as well as elevation of "siloviki" group) under the excuse of war in Chechnya and terrorism threat. Edrogan did the same "because ISIS/Syria/Kurds".
Comment: @Thern the way he waged war was with a casual disregard to Soviet casualties. The other players tended not to see their men as cannon fodder
Comment: "despite him basically needlessly buried Germany under literally millions of Soviets' dead bodies" - not sure what you mean. Hitler attacked the Soviet Union in 1941, so of course they would strike back against Germany. The US did the same with Japan.


An universal sentence encoder for a specific language?

Question: I am making a model that uses encoded articles (multiple sentences). I have found the Universal Sentence Encoder by Tensorflow, but it says it is only for English. Specifically, I am looking for an encoder for the Macedonian language. Can I use this encoder and if not is there a multilingual model that understands Macedonian?
Answer: This Universal Sentence Encoder that you link is trained specifically on English data, so it's going to work very poorly on any other language (to be clear, it's likely to produce garbage).
Unfortunately it's quite unlikely that you'll find a similar pre-trained model for Macedonian. You would have to train your own model from Macedonian data, and you need a really large amount. Btw that's the main reason why these pre-trained models are often trained on English only, since there's a lot of English text available. In case you want to try this, there is a Macedonian corpus as part of the Universal Dependencies project.
Comment: I am planning on using it for article political bias classification. I have downloaded a lot of articles (>1Gb). I am sorry if this is a stupid question but is it better to train it on those articles or the wikipedia/UDP corpus?
Comment: @Dani it's not a stupid question at all, don't worry. There are two advantages using your articles in order to obtain embeddings: 1) your data is probably larger 2) more importantly, with this option the meaning of the words is represented specifically for your data, whereas using another dataset might cause some inaccuracies. I'd suggest starting with traditional ML methods which don't require embeddings: it's simpler and faster, and later it can be used as baseline when you develop a more advanced model.


How to configure snapper for home (restore snapper config)

Question: I've configured my openSuse installation to have /home partition formatted with btrfs and added snapper config for it (with timeline, I guess).
It was a bad idea, I know, but I was inspired by the btrfs and was willing to try it out as part of backuping strategy even for home partition (snapper + snapsync + external usb drive with btrfs).
So I had to add some subvolumes (for VMs and for .cache), but even that was not enouph.
I didn't want to lose time reconfiguring the system and simply turned off snapper (possibly by deleting snapper config somehow.
Now I have a couple of snapper snapshots for home and don't know how to clean them up.
I would like to use Yast-snapper to review the existing snapshots in a user-friendly way. But I'm missing snapper configuration.
# snapper -c home create-config /home
creating btrfs subvolume .snapshots failed since it already exists.

Possibly I could create snapper config manually (by coping and editing one for root and adding it to /etc/sysconfig/snapper, for example).
My issue is: I don't want to configure all the subvolumes for all of the existing users and don't want my home to run out of space (it's on a separate partition, so root partition is not in danger).
But I would like to use snapper to backup home partition also (I'm only using home to store user configurations - the documents/pictures/videos are stored on separate partition, symlinked from user-dir)...
TLDR:
Does it make sense to backup home (if it contains no documents)? (haven't used backups till now)
How to restore snapper config?
Which subvolumes to create for each user under home?
How to create skeleton with subvolumes for some dirs?
Comment: Did you find answer for your questions?
Comment: Unfortunately no. I've left the issues to the time where I'm not so busy to try things out.
Answer: Follow the steps on Arch Wiki or on openSUSE github.
Briefly, it's 3 steps:

create a subvolume .snapshots manually
edit SNAPPER_CONFIGS="" in the config file (/etc/default/snapper or /etc/conf.d/snapper).
create your volume config such as /etc/snapper/configs/home.

I also had to reboot / restart snapper for changes to take effect.


Is the idea of being "fused" to/into a material as a result of a teleportation accident plausible?

Question: Assuming it were possible to phase through matter/teleport, is it possible within the laws of physics/chemistry to end up stuck/fused to solid materials?  Obviously we lack the real world ability to test this out, but are the distances between molecules in materials like plastic, wood and metal great enough that the molecules of the human body could mesh within them?
Comment: In a complete tangent to the question don't forget that the phased person will need to 1. Breathe, 2. See, and 3. Have something to walk on. It always bugs me when stuff forgets these little details :(
Comment: Also consider that atmosphere isn't empty, there is a lot of air in the volume of a human body - something will need to happen with that and that might have bearing on the interaction with solids.
Answer: If we assume that teleporting or walking around "phase shifted" or whatever technobabble word is applied this week to the idea of having two items occupying the same space at the same time is "real" (I love these kinds of questions)...
And suddenly you're back in the real world where a wall also exists...
Suddenly you have a whole bunch of atoms occuping the same physical space that don't want to occupy the same physical space.
Possibility #1 Instantaeous fusion with what I'm going to guess is a kiloton capacity.  Boom.  Really big boom.  The guy walking next to you is a shadow on the pavement boom.  Boom.
Possibility #2 Chemical realignment.  there's more mass than should be there, so there will be an expansion into space (not necessarily boom, at least not yet...), but let's assume it's not catastrophic.  Suddenly the chemicals of the body are realigning with the chemicals of the wall.  I'm not sure what you'd get.  It might burp.
Possibility #3 I consider this the least likely possibility.  Rejection.  The matrix of the wall was there first and as you "phase" back into "reality" the chemistry/physics shunts all the mass someplace else.  Some of you going forward, some backward, maybe some upward.  It's another kind of explosion, but much more sticky.  Think firecracker inside a tomato sticky.
Comment: Catastrophic fusion does assume that enough molecular cores meet and that is quite unlikely as they need to be so close that the electrostatis pressure stops being a thing (remember the "pebble in a stadium"example from highschool physics).  In all conventional fusion reactors they use either pressure (the sun) or heat (Tokamak reactors) to aggitate the atoms into fusion.
You'd probably still get a bunch of radiation from the random times it does happen but a 1:1 fusion of all molecules seems a bit pessimistic.
Comment: Hehe, I really like your answer! Just one note: I fear that a fusion would be alot more powerfull... More in the megaton range
Comment: @Borgh You're likely right and I happily defer to those who understand the matter more than I ... but it's a lot less fun.  :-)  What I would like to know is what the approximate pressure of such an event would be.  It's kinda/maybe/somewhat doubling the density of atoms in the space, but if I recall correctly, that's substantially more than simply doubling the presure.
Answer: If we handwave away the fact that we've got some non-scientific teleporter, we have to start considering the physics right after the teleport occurs, which is where the known laws of physics should resume in their entirety.  All objects consist of almost entirely empty space.  There's a few nuclii here, and electrons wizzing around, but calling an object 99% empty space is a very conservative estimate.  For a specific example, a hydrogen atom is 99.9999999999996% empty space.  That's very empty.
That doesn't mean that objects can just pass through eachother, of course.  There is always a fine balance between the electrostatic forces between electrons and other forces.  The closer two objects get, the more electrostatic force there is between them.  This occurs on astronomically small distances (picometers, for instance), so we typically think of it as instantaneous.  But for these purposes we'll have to pay attention, because our teleporter will push the atoms too close.
The pattern of "your body intermixed with some steel/plastic/etc molecules" is a highly energetic one.  You are almost 100% guaranteed to have the majority of atoms be closer than their equilibrium state.  They will try to push away from each other with great ferocity.  Consider that, even if you are holding up the weight of a car, you still can't push the atoms of the soles of your feet into the pavement.  You can push the pavement away if the object is heavy enough and your feet are small enough, but you can't push your atoms into the pavement because that would create a structure which wants to push outwards too greatly.
Your teleporter just pushed the atoms through eachother.  It did the thing which the force of a car pushing down on you (or even a tank or a plane pushing down on you) could not do.  Thus you can expect that the result will be more forceful than that of a plane crashing on top of you.  That will be an outward force, trying to expand until the electrostatic forces are in balance again.  It will look and feel very much like an explosion.
Now what is assumed here is that the teleporter does nothing but mix the atoms.  If the teleporter does not want the teleportee to go splat in a glorious fashion, it may do something else.  It may adjust the layout of the atoms in the destination space to push them all away before teleporting new atoms in.  Such adaptations are beyond scope, because they are intimately tied to your particular teleporter, and that teleporter is admittedly operating beyond the rules of physics.
Comment: This was my thought too, so I looked it up. [Apparently when you start looking at matter in a quantum frame of mind it's not empty at all](https://physics.stackexchange.com/a/126513).
Comment: @AndyD273 I think that, in this case, you can achieve a meaningful result via classical thinking.  In both classical and QM thinking, the electrostatic repulsion between electrons is a key force in keeping atoms apart.  QM adds another force, the electron pressure from the Pauli exclusion principle (as stated in the linked answer), but that becomes more important later, as you reach higher densities.  Electron pressure becomes a big deal in white dwarfs, whose density is 90,000 times as dense as lead,   There, the effects of Pauli exclusion dominate.
Answer: Most of matter is empty space so in theory you could mesh the atoms together but what would happen is the atoms would then push against each other as if they were compressed which in essence they would be.
The end result would be a very messy explosion.
Answer: It's not as outside the realm of reality as you might think. Nikola Tesla gave the world not just AC, but the idea of vibration as the means to harness energy otherwise unavailable to us (sounds kinda like magic). His experiments with resonance are historic, but of note are devices he built to find the natural harmonics within objects and amplify that specific frequency.
There was a naval experiment undertaken with results that have been hidden from the general public, but there are accounts of the sailors on board telling about the experience. They described a device such as Tesla's built on a ship, and taken out to sea. When they activated the device, it found the natural resonant frequency of the ship and began to turn the normally solid aluminum metal that the ship was constructed out of into a liquid without significantly raising the temperature. The result was that the sailors on-board did exactly what OP was asking, they fell through walls and floors when normally solid metal was turned to liquid (probably more like molten glass or honey, very thick). The device was only on for a brief time before the experiment was called off, and when that happened, the sailors were trapped in the floors and walls. Pretty sure some died, which would help explain the secrecy around it.
So I would firmly say yes, if teleportation technology or magic existed and used incorrectly, the threat of merging with solid matter would be quite real.
Comment: It's definitely another version of the alleged "philadelphia experiment"", which isn't a real experiment at all and it's actually really "outside the realm of reality" (or, at least, our history so far). Despite being on SE-WB, i'd like to read answers in which the current reality and the pure speculation are cleverly linked but not mixed.
Comment: sorry, referring to "experiment undertaken with results that have been hidden from the general public" worked only for Fermat's theorem (probably by chance)
Comment: Do you have a link to the stories of these sailors?
Comment: This sounds like the [Philidelphia Experiment](https://en.wikipedia.org/wiki/Philadelphia_Experiment).  The [crew of the Eldridge think the story is amusing](https://www.de173.com/eldridge-crew-amused-philadelphia-experiment/).
Comment: Welcome to Worldbuilding, Monstra! If you have a moment please take the [tour] and visit the [help] to learn more about the site. You may also find [meta] and [The Sandbox](https://worldbuilding.meta.stackexchange.com/q/6168) (both of which require 5 rep to post on) useful. [Here](https://worldbuilding.meta.stackexchange.com/q/6388) is a meta post on the culture and style of Worldbuilding.SE, just to help you understand our scope and methods. Have fun!
Comment: Now that you mention it, I was thinking of asking a question if there might be a realistic way of weakening a metal so it would melt in some non-thermal way.  I don't know about making a metal phase-through-able, but I can't help but wonder.
Answer: My first thought was that the saying that we're "99.999% empty space" would easily solve this problem. The atoms would just push each other around a bit, and the parts that intersected the wall would get denser, create new alloys. Or possibly explode.
Apparently the empty space thing isn't exactly true.
But really what does "being out of phase" mean?
From a higher dimension of reality point of view, it could mean that the individual has moved into a higher dimension that doesn't intersect with normal baryonic matter.
It's a stretch, but there is actually a little bit to support this idea in the real world in the shape of sterile neutrinos and dark matter.
Evidence points to both of these things existing (or possibly being the same thing?), and they do interact with our reality through gravity, but not in other ways. We don't really know why dark matter can't be detected through any normal means, and so into this uncertainty comes a possibility for worldbuilding.
M-theory suggests that there are lots of other dimensions that are alongside our frame of reference, but that we can't interact with. It is a possibility that instead of being some new, unknowable particle (that would really mess with the standard model), dark matter is instead a "normal" form of matter that is just "out of phase" in a dimension of reality that we can't interact with, except for gravity.
Dark matter isn't very dense, locally being on the order of 10^-21 kg/m^3, so you wouldn't have to worry much about bumping into it.
So how does this answer the question? Well, if you could phase into a different dimension that doesn't contain walls (or air, or floors... which is a problem), then maybe when you phase back any air (or walls) would be exchanged with your mass, so if you were to phase back inside of something solid you would just replace those atoms, and be perfectly encased in the wall, but not dead/explody.
Teleporting could work in a similar way, with a you shaped chunk of space being replaced with you. If that chunk of space contained just air then no problems. If it contained a wall then whoever is manning the transporter controls is going to get annoyed about having to clean drywall dust off his pad again.


Why can't find you open source software in the app store?

Question: Why do you need macports or homebrew to get open source software installed? Why can't you find this kind of software in the app store?
Comment: Welcome to Ask Different.  We try to focus on practical question as opposed to "why" - especially when why amounts to thousands of decisions by thousands of people. Is there a practical problem you face or is this something more for the [chat]?
Answer: You can find open source in the app store e.g. The Unarchiver source is on BitBucket
However app store only provides apps and these have to be standalone and not depend on other apps and have other restrictions, thus Unarchiver suggests you download from outside the App Store
Most things in Macports and Homebrew are command line tools or at least launched from the command line so could not be in App Store. Also historically Macports and Homebrew existed before the app store
There are also license issues to go in the App Store you have to include some Apple non open source code - for some licences e.g. GPL this can't be done - if you get all the coders to agree you can do this but if only one contributor disagrees then the app can't go in the App Store e.g. vlc


Equivalent of badblocks on Windows or DOS

Question: Is there a utility in DOS or Windows that is as thorough as badblocks on Linux?
Answer: With the Windows Subsystem for Linux, you can run badblocks directly under a Windows 10+ host.

Have a working WSL2 installation

In a console window, identify the physical path of your disk in Windows:
wmic diskdrive list brief

Copy the "DeviceID" for the appropriate drive:

Caption                         DeviceID             Model                           Partitions  Size
SMI USB DISK USB Device         \\.\PHYSICALDRIVE6   SMI USB DISK USB Device         1           124654118400

Mount the disk so it is visible to WSL2:
wsl --mount \\.\PHYSICALDRIVE6 --bare

Inside of WSL, find the newly added device with lsblk:

$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sde      8:64   0  12.8T  0 disk
└─sde1   8:65   0  12.8T  0 part

Run badblocks against the device:
badblocks /dev/sde

After badblocks completes, don't forget to unmount the disk so that it can be used again in Windows:
wsl --unmount \\.\PHYSICALDRIVE6
Comment: These instructions are valid as of Insider Build 20231 and above. The mount feature will enter general availability in September 2021, with the Windows 10 21H2 release: https://github.com/microsoft/WSL/discussions/6061
Comment: Still not available in Win10 Pro 21H2 19044.1387
Answer: The best tool I've ever encountered for testing a hard drive for bad sectors is called SpinRite:
  SpinRite 6
  http://www.grc.com/sr/spinrite.htm
It was created by Steve Gibson (who writes most of his code in Assembler), and I remember using it back in the late 1980s on XT computers (with 4.77 MHz 8086/8088 processors) to recover bad sectors from failing hard drives.
The current version also works very well (and you also get the benefit of the many years of Steve Gibson's experience in maintaining this software to ensure it works reliably with all types of hard drives).
It is far more thorough than the ScanDisk or ChkDsk programs included with DOS and Windows.
Comment: I know this is a really old answer, but it bears pointing out - Spinrite is pointless. It claims to be able to recover data (#1) and warn about failing sectors (#2).

It does #1 by repeatedly reading the bad sectors 2000x, which can make a bad drive worse. Any data recovery professional _always_ clones a bad drive to a working one instead of reading off the bad one repeatedly. And `ddrescue` for example would be a better software option here.

#2 is just reading SMART data which any free tool can do.

**tl;dr** save your $90 and spend it on a new drive. Answer above is likely spam.
Comment: Security now is just reading a list of vulnerabilities at best, I can't say the info is generally inaccurate, but I find it dull. I can read a list faster than listening to one.
However, the software he sells is snake oil based on unfounded claims of his Elite Magical Tech Skills. At best spinrite does what a free tool could do, at worst it makes your disk unrecoverable, and I would hardly call a DOS interface "nice". But eh to each their own I guess.
Comment: I thought about buying Spinrite once. But then I read more about what it does - which is to use the drive's built-in error handling capability, triggered by reading at a low level. Simply using `dd if=/dev/sdwhatever > /dev/null` has "recovered" a couple of my semi-failing disks enough for me to get data off, I suspect in the same way that Spinrite would've done. That said: Spinrite has a nice interface, and Steve Gibson I think in general makes a positive impact on the world (Security Now is also a really good podcast). So it's certainly not a *bad* thing in my opinion to buy the software.
Answer: To update these answers for anyone who finds this as of 2014:
chkdsk with either /r or /b switches is roughly equivalent to badblocks in the default read only mode
SpinRite has far better data recovery capability run at the default level 2
Run at level 4 it's equivalent to badblocks non-destructive read write mode, but with better data recovery capabilities.
However it falls over with divide overflows on modern huge drives, you'll need to wait for SpinRite 6.1 to fix this, development has started on 6.1 according to Steve Gibson on the Security Now netcast, but is suspended again while he completes another project.

Meanwhile, the nearest functional Windows based method to recreate the non destructive read/write badblocks mode for large drives requires owning storage equal to or greater than the drive being tested and would proceed thus:

Download and install a disk image program (Macrium reflect free, Acronis True Image either the commercial or drive maker's free version, or some other)
Create the WinPE recovery disk (you'll need later) and an image of the drive, with intelligent sector copy unchecked, and continue on finding bad sectors checked (both reverse of the default).
This recreates the read pass.
Use the drive maker's DOS tool to zero fill the drive
(roughly equivalent to the write phase)
Use the recovery CD to restore the image made in step 2 to restore the image you made to it's original location.
(roughly equivalent to the write data back phase)

In the above scenario, or when using badblocks a modern drive's internal logic will handle remapping any bad sectors found when they're attempted to be written to.

To recreate the badblocks destructive test you'll need a commercial UK (not US) government approved drive wiping program and you'll need to run it at the higher security level, this will write patterns repeatedly to the drive and verify each pass much as badblocks does.

So until Spinrite 6.1 or later gets released, the question becomes, "Why would you want to do that?"
Downloading pretty much any Linux live CD/DVD will give you a bootable platform to run badblocks, which is cheaper, easier, and safer for your data, for any scenario where you need more than the read only test.
If you want the read only test, just run CHKDSK with the /r switch
If you want to run CHKDSK /R on your system drive under Vista note it will ignore that you told it to run and skip the test on reboot unless you also use FSUTIL to mark the filesystem as dirty.
Comment: `CHKDSK` = Read-only, `CHKDSK /R` = "R"ecovery, which is most definitely NOT read-only. :)  Anyhow, to me, this answer is merely commenting on existing answers and is not actually providing a new/different answer.
Comment: CHKDSK /R certainly isn't read only I'll grant, but it does no write tests, in which sense you could call it an "only read" test, it only writes for error correction purposes, this has the limitation that it can't force a remap of a defective sector the way badblocks will in read write mode.
Comment: "`chkdsk` with either `/r` or `/b` switches is roughly equivalent to badblocks in the default read only mode" - Midleading statement, as was pointed out to you in comments, and as you've admitted in comments, but didn't update the post. Downvoted.
Comment: Since the first answer only addresses how to test the first part of a large drive (owing to limitations of the software) What I've added is a method to force sector remaps further into such drives as badblocks can, using DOS/Windows methods, nobody sane is going to do it that way, but it's answered...
Comment: @Beardy - I have the latest SpinRite - I guess 6.3 - Will have to check? I also have Linux bootable to run Badblocks / FS. I need to do a thorough pre-check for 2TB WD & 2 x 1TB Seagate drives. Should I use SR or BB or both.. if so in what order? I am wondering what kind of overlap in functionality they have?
Comment: Downvoted for Spinrite marketing
Answer: chkdsk with the appropriate switch
/R Locates bad sectors and recovers readable information
/b
NTFS only: Clears the list of bad clusters on the volume and rescans all allocated and free clusters for errors. /b includes the functionality of /r. Use this parameter after imaging a volume to a new hard disk drive. Works only on vista or better.
See here for a more complete switch list
Answer: scandisk (DOS) / chkdsk (Windows) perhaps?


usb hard drive/pen drive emulation via bios

Question: I am trying to read/write usb hard drives and flash drives for a DOS application.
I read EDD spec. and it mentions that function Int13(Fn = 48h) can be used to get interface path and device path  for a particular disk drive. This also includes usb interface and ata interface.
Now this function also returns a Device Parameter Table Extension (DPTE)  table that gives I/O addresses via which a software bypassing Int13h can use to read/write the device. But this table is only for ATA afaik.
I wanna read/write to usb disk/pen drives w/o using Int 13h. Is it possible?
Actually it is a disk I/O sensitive application in protected mode. So using Int13h would involve heavy penalty in terms of performance, due to mode switching. So, I am trying to avoid using Int13h.
Does bios initalizes usb drives to appear as ATA drives too. If so, then I can use DPTE to get the I/O base addresses of the command block and control block and then access the usb drives just like ATA drives. Am I right?
Thanks
Answer: This particular issue has been discussed at length among the FreeDOS community. The best guide to the whole issue is the FreeDOS technote "USB with DOS"


Isomorphisms of the Lorentz group and algebra

Question: I'm trying to read a few books on QFT and some seem to say the Lorentz algebra obeys $\mathfrak{so}(1,3)\otimes \mathbb{C} \cong \mathfrak{su}(2) \oplus  \mathfrak{su}(2)$ while others say $\mathfrak{so}(1,3)\otimes \mathbb{C} \cong \mathfrak{su}(2)\otimes \mathfrak{su}(2)$. However, I didn't think one could take tensor products of Lie algebras and get another Lie algebra. Does anyone know how to decompose $\mathfrak{so}(1,3)$ into combinations of $\mathfrak{su}(2)$. Also, how does this work for the corresponding Lie groups; i.e., is $SO(1,3)\otimes \mathbb{C} \cong SU(2) \oplus SU(2)$, or $SO(1,3) \cong SU(2)\otimes SU(2)$, etc. ?
Comment: I am not sure, but can you draw the Dingkin diagram for both? If they coincide they should be isomorphic. However, I admit I do not know how to draw the Dingkin diagram for the direct sum of two Lie algebras...
Answer: The (vector space) tensor product of two Lie algebras isn't naturally a Lie algebra; the obvious choice should fail to satisfy the Jacobi identity. The sources you've been reading probably mean the direct product $\mathfrak{su}(2) \times \mathfrak{su}(2)$, which is just the direct sum.
(Also, the statement is slightly incorrect. $\mathfrak{su}(2)$ should be replaced with its complexified form $\mathfrak{su}(2) \otimes \mathbb{C} \cong \mathfrak{sl}_2(\mathbb{C})$.)
Lie groups also don't have a notion of tensor product. The correct construction in the Lie group case is the direct product again, although the correct statement is complicated; there isn't obviously a notion of the complexification of a Lie group in the same way that there is a notion of the complexification of a Lie algebra.
Comment: still up at this point...T_T
Comment: So, are you saying it should be $\mathfrak{so}(1,3)\otimes \mathbb{C} \cong \mathfrak{su(2)} \oplus \mathfrak{su}(2)$ and $SO(1,3)\otimes \mathbb{C} \cong SU(2) \oplus SU(2)$?
Comment: No, I'm saying that the first thing should be $\mathfrak{so}(1, 3) \otimes \mathbb{C} \cong \mathfrak{sl}_2(\mathbb{C}) \times \mathfrak{sl}_2(\mathbb{C})$ (I don't want to call this construction the direct sum) and that the second thing is not obviously meaningful to do (and the direct product of Lie groups definitely shouldn't be called the direct sum).
Comment: Ok, thanks. But, why don't you want to call the direct product the direct sum in the algebra case? Is it because the Lie bracket is not closed under direct sums? Also, is there a combination of $SU(2)$'s that is related to $SO(1,3)$?
Comment: It's because direct sum should mean biproduct (http://en.wikipedia.org/wiki/Biproduct), and the direct product of Lie algebras is not a biproduct (biproducts include the direct sum of abelian groups and vector spaces). And no, not directly, because $\text{SU}(2)$ is compact and $\text{SO}(1, 3)$ isn't, but they are related through their Lie algebras.
Comment: Oh yeah, sure I meant $\mathfrak{su}(2)$ as the Lie algebra of $2\times 2$ complex matrices ... .Sorry for that.


How do you create this flat cartoon style in photoshop or illustrator

Question: I saw this image and have been trying to figure out a way to create the same. The shading particularly has me confused.
Answer: The irregularities and inconsistencies in the shading make me think this was hand inked then scanned in and digitized.
It's a style that was very common in the 60s and 70s before everything was done on computers. It's also what comic book artists used to do up until tablet technology became good enough to emulate pen and paper.
A lot of times graphic designers would use tracing paper and ink and use a photo for reference. This gives you the variety in line quality that you see. There are programs that you can now use to do this on a computer, but they generally involve a sensitive tablet so you can get the hand-drawn effect. Painter is one of them.
There are Illustrator and Photoshop filters out there that you can apply to a photo to get this, but they're all bunk in my opinion. I haven't seen any that can get real artwork like the example you've provided.
Answer: I think you've already chosen a picture that you want to create in this style. Open that picture in Photoshop. First, desaturate your picture. Then go to Image -> Posterize and chose level: 1. Now you see a one level shadow in your picture.
Place that picture in Illustrator, and draw the shadows as shown on your posterized picture. After that, you can make the shading stripes like the poster with the blob brush.
I think this is the only way to do it.


Do we need to consider woofer physical volume while calculating box

Question: I am trying to create a subwoofer box enclosure on https://subbox.pro/ website. The subwoofer I picked is JBL A1500Hi. As per the manual, the volume of the box should be 28.32 Liters. So should I consider adding the physical volume of the subwoofer?
Answer: As per the instructions on that site, the volume of the enclosure ignores the speaker itself. It is simply the internal dimensions of the enclosure.


borderlands 2 skill tree blue "training" requirements

Question: Borderlands 2, in the skill tree certain skills will be highlighted blue depending on the character's level. It says more points will be granted provided training is completed. What is this training the game is referring to?
Comment: Every 5 points you put in a tree unlocks another level of the tree.
Comment: Class mods provide points to certain skills, but you need a point in it before it will take effect.
Answer: Those blue highlights do not depend on character level. They come from a Class Mod you equip.
Before bonus points from class mods take effect on any particular skill in your character's skilltree, you need to invest a point in said skill.
The "training" the game refers to is investing AT LEAST one point into said skill.  Otherwise, points from class mods will not apply to that skill.


Are game modes in Garry's Mod free?

Question: Do you have to pay for the gamemodes in Garry's Mod or are they free? I've looked up and not found anything and watched videos to try and find out but I did find a Steam page that some people say its free some say that you have to pay so are they free?
Answer: All of the game modes in Garry's Mod are free. However, some servers or custom game modes may use assets from other Source games, such as Counter-Strike: Source, Team Fortress 2, or Half Life 2: Episode 2.
If you do not own these games or do not have them installed, any missing textures from those games will replaced by a pink checkerboard while missing models will display as a red ERROR.
Answer: Garry's Mod gamemodes are completely free, with an exception being those from random websites that try and sell you a hack with the gamemode.
They can be downloaded directly into your game from the Steam Workshop.
Comment: Not really. However some maps and gamemodes require another game like CS:S. if you don't you'll just see a big ERROR over things you don't have the textures for
Comment: I'm saying you have to own games to get some modes
Comment: That's what I'm saying anyway this has already mean answered

Are game modes in Garry's Mod free?


Can I still use this old (15yrs) flux and solder?

Question: I few days ago I cut and cap a copper pipe to start repairing an underground water leak in my garage. I noticed that the flux looked rather orange and when I solder a pipe the solder didn't flow very well. Yes the pipe was clean before and fluxed. I thought my soldering skills are rusty (they are) but if I applied more heat to the pipe, it didn't help. The flux and solder are about 15 years old. They've been sitting in my garage where it is not temperature controlled. I'm in S. California where it doesn't get really cold. It's been cold now and it is about 40F outside at night. The garage is closed but not insulated so it may get to the low 50s inside. In the summer it gets hot... around 90F maybe more. Is there something wrong with this old flux? or should I just buy a new kit (solder and flux)? Here is a picture of my flux and solder:
Comment: The solder isn't going to age. It's metal.  The flux might.
Comment: The pictured solder looks quite pristine, very unlike oxidized solder.
Comment: Huh. I have some ancient flux myself and it had partially crystallized into long needles. Still did what it was supposed to, though mine was meant for PCB soldering.
Comment: Yes, but why not try a sample?
Answer: Yes, generally not a problem, most of my solder and flux is old enough to vote and/or drink and it's still fine. The flux, maybe if it's less stable than most, the solder definitely not a problem

I applied more heat to the pipe, it didn't help.

It's entirely possible to overheat a solder joint, at which point you have to stop, cool down, clean everything again, reflux and start over. If you burn the flux out of the joint, you'll never get it to go without re-cleaning. There's a narrow window between "not hot enough to melt solder" and "too hot" and it's common to head for the latter place when inexperienced.
Comment: I'll pick up some flux if I go to the store just to make myself feel better but I think the last sentence of your answer applies to me. Thanks.
Comment: Exactly my experience - I overheat the first joint after a 3-5 year lapse between episodes of plumbing, then remember how to do it.
Comment: Yeah, when you don't do it very often it becomes very easy to goof, especially when you're working on existing pipes so you're in an awkward situation.
Answer: Of these two substances, solder (tin alloyed with small amounts of other metals like copper or lead if the solder is not lead-free) is chemically unable to "age".
Well, this is not absolutely true because tin is in theory able to oxidize in open air, but the process is both fairly slow (20 years are not decisive) and the metal will lose it's metallic luster and mechanical properties.
When subjected to extremely low temperatures (~ minus 40 deg. C or F) tin can convert into grayish dust that looks nowhere like tin but can still be used for soldering as it melts back into the normal, "metallic" form of tin.
On the other hand, some fluxes are pretty much able to age down into a substance unsuitable for soldering. This includes, but is not limited to, fluxes that pretend to be biodegradable, water-soluble, non-toxic or have other advanced properties.
Simple, traditional, 1-component solid fluxes like rosin/colophony or ammonium chloride are pretty much resistant to aging (at human-life timescale), while more complex, paste-like or liquid varieties may or may not be in good shape after 10 or 20 years.
Answer: Doesn't apply to the reel of solder pictured, which is labelled "lead-free", but in the EU, the ban on solder containing lead came into force in July 2006, only just over 15 years ago - so solder that's "about" 15 years old may contain lead, with potentially deleterious health and legal consequences.
Comment: Doesn't apply because marked lead free. But also not EU - OP says "California'.
Comment: @manassehkatz-Moving2Codidact though, as we Americans tend to say as a joke, everything causes cancer in California (the "joke" being that Proposition 65 warnings seem to appear on most products).
Comment: Isn't ROHS specific to commercial electronics manufacturing, so quite unrelated to plumbing solder (to which, however, other regulations re: lead in potable water pipes might apply....)?  Also, recent EU partial sales bans on lead solder (as opposed to banning the USE in newly manufactured electronics) are REACH, not ROHS related.
Comment: @rackandboneman There was a lot of discussion in the British press in 2006 about whether it would apply to church organ pipes, but I never saw any actual conclusion to that discussion.
Comment: That could actually be an interesting discussion, given there would be a possibility for perished/disintegrating solder to be blown airborne I guess... In the EU you should be able to buy it still if it is for commercial work or bought personally at a hardware store counter. No Idea (or care for) what Brexit made of it :)
Answer: Sounds lke most likely just over heated the joint. If possible, just take apart, reclean - flux & resweat the joint, Should be fine after that. Good luck with it.


Eclipse Plugin or else for coding footnote

Question: I love the Manning In Action Series. One of appealing area is that the code listing inside the book always has a footnote where there is a detailed explanation by a reference number. See below the example:

So I'm wondering if there is an Eclipse plugin or online blogging service that allows footnote taking in the source code?
Answer: I think the closest you'll get is the the eclipse "NotePad" plugin. It doesn't create footnotes directly, but rather just takes plaintext notes and puts them in the metadata. You'll find it at: http://eclipsenotepad.sourceforge.net/
Better, though, is to use eclipse's built-in indexing, and leave yourself
/* @TODO 1) take note of this notey note */

comments near important lines.
"But sleepynate", you may say, "that's madness! I don't have anything TODO there!"
While this is true, eclipse automatically indexes certain comment tags, like @TODO and @FIXME, and puts them in your "Tasks" window. (Window > Show View > Tasks if yours is currently hidden. You can then double-click any one of them to jump to that line. You can also arbitrarily add tasks from the Edit menu with whatever label you want, in any resource and location within your project.
Comment: Also, Eclipse has a bookmarks feature that does something similar.
Comment: Yea, I this is true. They all show up in the "annotations" section of the preferences :)

I personally like the @ annotations because you don't have to stop coding to add them.


How would I troubleshoot a faulty GE electric oven?

Question: When in bake mode the bake element will start to function by heating up, but after a brief time, there will be 2 audible clicks and it will shut off well before reaching the designated temp. It basically short cycles and will repeat without the oven ever getting warm.
Comment: the model# would be helpfull. many of these ovens have a control board with relays that turn the bake elements on. the relay contacts fail some times wiping out the board. with more info we may be able to even find part #'s
Comment: Note - the broiler works just fine. It is just the bake function.
Answer: It could be the element, to test it you would need an ohm meter. here is a link to the repair clinic with parts and additional testing videos


Encrypting/Decrypting a single file in Ubuntu 12.04 LTS

Question: I need to be able to encrypt/decrypt a single text file stored on my external HD in 12.04 LTS, preferably a GUI application, if any, or the command line otherwise. Thank you.
Answer: A simple way to encrypt a single file is with openssl:
openssl des3 < youfile.txt > yourfile.txt.des3

This will prompt you for a passphrase, which you will need to enter later when decrypting the file.
openssl des3 -d < yourfile.txt.des3 > yourfile.txt.decrypted

To make this "graphical" you could put it in a Nautilus script and make it accessible from the context menu. (See the docs of Nautilus for that.)
UPDATE
des3 is just an example. Run openssl enc -ciphers or openssl list -cipher-algorithms to see the full list of ciphers.
Comment: Why `des3`? You can do much better encryption faster with `openssl aes-128-cbc`
Comment: @BrendanLong: I guess the reason is that `aes-128-cbc` in not mentioned in `man openssl` - I wonder why. It works, though.
Comment: Note, I just tried to encrypt a file on Ubuntu with des and decrypt it on Windows, and got an error `7C230000:error:1C800064:Provider routines:ossl_cipher_unpadblock:bad decrypt:providers\implementations\ciphers\ciphercommon_block.c:124`
Answer: Lets assume that a person wants to encrypt a file called 'message.txt':
1. Encrypting a file using GPG, for personal use
I. Using a passphrase to encrypt the file (and not the private key)
I.i. The command:
gpg -c message.txt
does it; it asks for a password (and a password confirmation) and generates an encrypted 'message.txt.gpg', which is binary.
I.ii. If you want to generate an ASCII encrypted file, which is base64(i think) of that file, you can use
gpg -c --armor message.txt
This will generate an 'message.txt.asc', which is the same as the generated by the command before, but base64 coded, i.e., the encrypted file in text mode (.asc, not binary as .gpg would be).
II. Using a private key to  encrypt a file
II.i. If you want to encrypt a file using your key, instead of only a passphare, use the command gpg -e -r 'yourname' message.txt.
The argument 'yourname' should contain a part of the name that you used to create the private key. If you dont give the -r parameter, gpg will ask for it. You can type our name then (the same that you would type on command line).
II.ii. Point II.i would give you a binary file. If you want to get an ASCII file, use --armor. gpg -e -r 'yourname' --armor message.txt.
2. Decrypting the file encrypted with GPG
To decrypt, the file, use the command gpg -d --output OUTPUTFILE message.txt.gpg. This will ask for the passphrase and then decrypt the file message.txt.gpg to OUTPUTFILE, if the passphrase is correct. This passhrase is that which you used directly (point I., the -c parameter), or through your private key (point II., the -e parameter) This works for both binary (.gpg) or ascii (.asc) files. If you supress the --output FILE, it is outputted to console (stdout), then you can do this also, that is, redirect it to a file: gpg -d message.txt.gpg > OUTPUTFILE.txt Both do the same. 8 )
Answer: Try http://www.aescrypt.com/ it works great.
Answer: https://stackoverflow.com/questions/2811528/can-i-use-my-ssh-public-key-to-decrypt-a-file
Is a question on a related subject. You can use the same principles for encryption if I am not mistaken.
Answer: For (GnuPG) 1.4.16
gpg -a --output outfile.txt --encrypt infile.txt

You will next be prompted:
Enter the user ID.  End with an empty line:

where the "user ID" can be found by running
gpg --list-keys


I can't get my iPod classic 4th gen 20gb to turn on; what might be going wrong?

Question: A few months ago I bought an iPod classic 4th gen from Ebay. I did a factory reset on it (just to be safe) and it worked great. I used it a few times then set it aside for a while (while trying to find a car cable for it). The AC in my house died and it got pretty hot for 2 days while I waited for the repair guy. I tried to use it the other day and it was dead. Figuring the battery was dead, I put it on a wall charger all night and it still didn't turn on. I get absolutely nothing. I can't do any sort of reset since it won't turn on. And it won't register on my Mac Book either - like I never plugged it in. I tried Apple's help site and all they have to say is charge it and reset it, pay to have Apple fix it, or buy a new one. I have a touch and I hate it A LOT. Help, please.
Comment: You say "help please" but what is your question? What information do you hope to gain from this site?
Comment: We have a nice guide on [ask] that might help with editing. Since you haven't gotten any answers in quite a while and haven't indicated if the existing answer helps, let's close this for work before accepting any more answers. Just edit and flag for review please.
Answer: If you are good with small tools and cables you can try dis-assembling the iPod and replace the battery (which you can probably purchase for $20.)
See iFixit:
http://www.ifixit.com/Guide/Installing-iPod-4th-Generation-or-Photo-Battery/393/1
You can also take it to the Apple Store and have them try charging it with a Firewire cable (I've seen those occasionally revive a dead 4th Gen iPod.)
Unfortunately that iPod is approx. 7 years old, so it may not have been long for this world...


Can I carry 5 mobile phones to US from India?

Question: I am planning to carry 5 mobile phones with me to US from India. All the phones are new but unpacked. I have laptop too. Am planning to carry evrything in my hand luggage. Is that fine? Or will this put me into trouble?
Comment: It is not the actual number, it is the value. Can you edit the question to include that. In US $ would be best.
Comment: Are you going to sell or leave them in the United States? Then you need to declare them in your customs form.
Comment: I would also suggest being prepared to answer _why_ you have so many phones, probably from everyone/anyone who looks at or scans your luggage.
Comment: @JoErNanO … save for the fact that it has next to nothing to do with it, it's about importing phones *from* India *to* the US.
Comment: Thanks for d response guys! It's for personal use only. Should I pay duty even if it's unpacked?
Answer: I believe it's perfectly fine. Just declare them as you enter (on any form you might have to fill in and when talking to a customs officer) and they will tell you if you need to pay any tax or duty. As long as you are upfront and proactive, you will not get in trouble. Bringing any invoice or receipt you have is also a good idea.
Comment: If you're taking goods in to the country (above certain limits that vary from country to country) and they will *remain* in the country, then you are importing them and will be required to pay applicable taxes.
Comment: yeah, I guess he wants to know how much he'll owe.

Assuming these are to be left in the US of course, if they're all his personal phones maybe he won't owe but it's likely they won't believe him, or if they do, they'll thing he's a drug dealer.
Comment: Thanks for the reply guys!  It's for personal use only. Should I pay duty on it even if it's unpacked?
Comment: It is the value that makes whether you need to pay duty, not whether they are packed.


Are all real and imaginary numbers complex numbers?

Question:
This image makes it seem like real and imaginary numbers are all complex numbers. I thought complex numbers were numbers composed of a real and imaginary part. This got me thinking, and I think I might see it now. All real numbers can be written as $$r \times i^{4k}$$ and all imaginary numbers can be written as $$i^k \times 1$$ or $$i^k + 0$$ There are other ways to combine them in ways that does nothing to the value. So, is it these combinations that make all real and imaginary numbers into complex numbers?
Comment: A number is complex , if it can be written as $a+bi$ with real numbers $a,b$. So , yes, a complex number can be purely imaginary and also real. And every real number as well as every purely imgainary number is complex. For the real numbers we just set $b=0$ and for the purely imgainary numbers we set $a=0$ to get the desiresd representation.
Comment: So... it is more correct to say that the complex numbers contains a subset which is isomorphic to the reals... and if we refer to a number such as $1$, it could just as well have been referring to the complex number $1$, the real number $1$, the rational $1$, or whichever other that we wanted... The process of switching between them is so second nature and glossed over so heavily that many people do it without thinking and many ley persons aren't aware of it at all in the first place.
Comment: Does this answer your question? [Set Theoretic Definition of Numbers](https://math.stackexchange.com/questions/14828/set-theoretic-definition-of-numbers)
Comment: No, the number or types of different representations is irrelevant.  The base formal definition is what matters here if you want to talk about true equality.  If you want to talk about *informal* equality, then as alluded to earlier... we often say that the natural number $1$ is (*informally*) "equal" to the integer $1$.  As for the natural being written as $0.5+0.5$... I would not have allowed that... since if we were working purely in the context of naturals you have $0.5$ is not defined.  That is a rational number (*or real or higher*), not a natural number.
Comment: This is a more complicated question than you realize.  Far simpler question... "Is the *natural number* $1$ **equal** to the *integer number* $1$?"  As sets?  No, they are not equal.  The natural number $1$ is equal to $\{\emptyset\}$ if defined via Von Neumann's construction of the naturals while the integer $1$ is $\{(1,0),(2,1),(3,2),(4,3),(5,4),\dots\}$ (*where the numbers appearing are the natural numbers*).  Despite this, there is a very clear association between the natural number $1$ and the integer $1$ and we often gloss over the distinction and freely switch between them at will.
Comment: TLDR:  The reals *might as well* be considered complex numbers.
Comment: @JMoravitz I think I understand what you're saying: the natural number 1 is not the same as the integer number 1, because the integer version can just written as $1$, or $1 + 0$ or $1 \times 1$, but the natural number 1 can also be written as $0.5 + 0.5$ or $1.5 - 0.5$ and so on? They have infinitely many different ways of being written, but depending on what set they exist in, the possible ways differ.
Comment: @JMoravitz Aha I see, I'll have to read up on some set theory then to understand.
Comment: @JMoravitz I didn't see the change in your comment until now. I mixed up some of the sets, as natural numbers are all positive integers (sometimes including 0, sometimes not), and integers are all negative and positive integers (plus 0). For some reason I mixed up natural with rational however.  I think you got my misunderstanding though, as 0.5 + 0.5 is a representation of 1 if rational numbers are permissible to use.
Comment: It would make me happy to just eliminate the blob with $\mathbb I$ altogether.
Answer: Perhaps we could modify the Venn diagram to let $\mathbb I$ intersect with $\mathbb Z$  (and consequently $\mathbb R$). (Which integer can be considered imaginary? Which imaginary number can be considered an integer?)
rschwieb: It would make me happy to just eliminate the blob with  altogether. $\quad$ Yes that's true, actually; the set of prime numbers is arguably more deserving of being singled out in this Venn diagram.
And yes, I would certainly classify all real and imaginary numbers as complex; the complex plane includes both the real and imaginary axes, after all.
P.S. I'd never encountered the symbol $\mathbb I$ (which here denotes the set of imaginary numbers) prior to this, but apparently, in the days of yore, it sometimes denoted the set of integers...
Comment: @A. Kvåle edited-)
Comment: I got this Venn diagram off the internet so I can't take credit for it (only saying this since you used the word *your*).
Comment: @A.Kvåle: If you post images taken from somewhere else, you should at least give credit to the source.
Answer: The actual fact of the matter is that different definitions can lead to different answers on whether the real numbers are complex numbers. (In case you've never worried about definitions before, then…What, exactly, is a real number, anyway? A complex number?)
What is most important is that, no matter what your answer to that question is, one can always see the real numbers inside the complex numbers by associating the real numbers $a$ to the complex number $a+0i.$ The possibility of such an association, which is the same as looking at the "copy" of the usual number line given by the real axis in the complex plane, is the only issue at hand that has serious mathematician significance, not whether real numbers literally are complex numbers, or are something quite different.


Roast beef for the next day

Question: So I'm cooking roast beef for Xmas Dinner tomorrow but have to do it tonight as I have no time. Once it's reached temperature I have time to take it out and rest it until it reaches the intended temperature of Medium. But then what do I do once it's reached that temperature while resting? Do I just leave it in the foil to cool down? the fear being that it will continue to cook and go tough. Do I try and cool it as quickly as possible so I can get it into the fridge?
Answer: There's no need to take special measures. Beef doesn't overcook from being left at a given temperature, just from reaching too high a temperature in the first place. You can let it rest for the normal period (10-20 minutes would be fine) and then refrigerate it.

Roast beef for the next day


Drupal Translations

Question: I'm downloading .po files from http://localize.drupal.org/translate/downloads which is great for Drupal Core translations, but I'm wondering if it's possible to download a .po file which could update custom text/menu items/etc?
Answer: If you install the i18n module you can both export and import custom translations for your site which sit outside of any other module translation.  The module groups translations by source including the Built-in interface, Blocks, CCK, Content types, Menus and Taxonomy depending on which submodules you enable.

Drupal Translations


Are composite bosons superradiant scattering candidates?

Question: Massive bosons can experience superradiant scattering in an ergosphere. This can in principle be used as a power source. However, elementary massive bosons ($H^0,\,W^\pm,\,Z^0$) are short-lived. Are stable but composite bosons such as deuterons candidates?
Answer: The onset of superradiant instability from massive bosons is governed by the dimensionless parameter $\alpha=\mu M/ m_\text{P}^2$, where $\mu$ is the mass of boson particles, $M$ is the black hole mass and $m_\text{P}$ is the Planck mass. For the efficient energy extraction from the black hole the parameter must satisfy the condition $\alpha \lesssim 1 $.
This condition could not be satisfied with astrophysical black holes and composite bosons of the Standard Model. For example for deuteron and black hole of $1 M_\odot$ we have $\alpha \approx 1.4\times 10^{19}$. For such large values of $\alpha$, the timescales of evolution of superradiant modes would be enormous (on the order of $M  \exp( C \alpha)$ in GR units, with $C$ a constant of order 1 ) much greater than the lifetime of the Universe, and even much greater than expected lifetime of such a black hole due to Hawking radiation.
If there are very small black holes (primordial) that could provide the necessary small value of $\alpha$, then still superradiance from massive composite bosons would be impossible for a variety of reasons:

Since $\alpha < 1$ means that Compton wavelength of a particle is larger than Schwarzschild radius of the black hole, tidal forces near the horizon of the black hole would be exceeding forces (e.g. nuclear) holding the particle together.  The approximation of an effective field of the particle would not hold under those circumstances and one has to consider the quantum fields of  constituent particles.
For such small black hole there would be considerable Hawking radiation interacting with our composite bosons, making it impossible to consider them as free fields/particles interacting only gravitationally.

For overview of black hole (and other types of) superradiance I would recommend a book:

Brito, R., Cardoso, V., & Pani, P. (2015). Superradiance. Lect. Notes Phys, 906(1), 1501-06570, arXiv:1501.06570.
Comment: I see, I was referring to numbering in the book, in e-print this is eq. 5.27 and figure 28, respectively
Comment: Thank you. The timescale is exponential in $\alpha$ viz. Eq. (5.30). Where is it explained why $\alpha=0$ and $\alpha\gg 1$ respectively lead to no extraction and inefficient extraction?
Comment: The case $\alpha\ll 1$ corresponds to non-relativistic quantum Kepler problem plus small corrections, smaller  $\alpha$ leads to smaller corrections. In eq. 4.27 of the book, two terms of $\omega_I$ correspond to two effects: dampening through absorption by BH ($\sim r_+$) and amplification by superradiance. See also Fig. 4.9, for the dependence on $\alpha$ of $\omega_I$, Individual modes have a characteristic "tooth" shape, but as $\alpha$ increases different teeth/modes produce max values, and for large $\alpha$ the teeth aggregate along the curve of eq. 4.30.
Comment: I'm afraid I don't see how $L^{(0)}=\frac{\sqrt{2Mr_0\Delta}-2aM}{r_0-2M},\,\mathcal{E}^{j}=\frac{\mu_0}{2}\left(1\mp(-1)^j\sqrt{\frac{2M(1-4\mu_\text{fin}^2/\mu_0^2)}{r_0}}\right)$ address these issues, probably due to my not understanding how their notation relates to your own.


What does 400kW(e) mean?

Question: I am trying to read a document and it says a power grid is 400kW(e) what does this mean?
Answer: The symbol kW(e) or kW${}_e$ refers to the "kilowatt electrical". It is the part of the power that is actually used by the devices connected to the power station or the grid, effectively the average of $P = U\cdot I$. The "kilowatt electrical" should be contrasted with "kilowatt thermal" i.e. kW(th) which represents the power including the thermal losses. So the figure in "kilowatt electrical" is much smaller than the figure in front of "kilowatt thermal". In your case, with 30% efficiency, the grid could be powered by 1,200 kW(th).
The unit kW(e) isn't an officially correct unit of the international system of units, SI. The correct description uses the regular universal unit, kilowatt, and the fact that we talk about the "electric power" is represented on the left hand side. So your notation would say
$$ P = 400\,{\rm kW(e)} $$
but the correct recommended logic to describe the same idea is
$$ P_e = 400\,{\rm kW} $$
Comment: 1200 $\times$ 30% = 360... Which might lead to some confusion. Perhaps use 40% and 1000 for credible round numbers.
Comment: OK, what was meant was 33.3%.

What does 400kW(e) mean?


Which layout techniques do you use: HTML tables, CSS tables, absolute positioning, floating or some mixture of those?

Question: Although, I know that a lot may depend on a particular web site, what is the mainstream? =) And also, what do you think of implementing CSS table-based layouts while IE6 and 7 are in use?
Answer: I use CSS floating at the general level, tables for tabular data, and absolute positioning if necessary.
Answer: i personally use a mixture of them all.  For grid like data, I favor tables.  For advanced layering, I use absolute positioning.
Answer: For website layouts I use a mix of CSS layout techniques. Depending on whether I am building a fixed-width site or elastic-width site the CSS techniques differ somewhat.
But, when I want to create any layouts for e-mail marketing then table layouts is the only thing I work with. And now with Outlook 2010 still supporting the Word HTML Renderer I don't think I will be using any CSS layouts for e-mails anytime soon.
As for CSS table layouts, you can use conditional comments to provide a seperate CSS style sheet for IE 6 and 7. Something like this:
<code><!--[if lt IE 8]
//different style sheet goes here.
-->
</code>
I would recommend reading the following two books:

Bulletproof Web Design, Dan Cederholm
Everything you know about CSS is Wrong, Rachel Andrew & Kevin Yank

The first book will show you CSS layout techniques for both fixed and fluid designs, whereas the second one will provide information about CSS table layout, including how to deal with browsers that don't support it.
Hope this information is helpful.
Comment: Yeah, I've just read the Everything you know about CSS is Wrong book.
Answer: Floating combined with absolute positioning.
I never use tables, perhaps mostly because I got tired of them back when I had to use them because there was no alternatives.
Answer: Tables are not semantically appropriate for making a layout. The "correct" way to do things isn't anything you said in particular.
You should be using semantically-appropriate tags: header tags for titles, div tags for sections, lists for navigation/lists, etc.
Once you have this set up, style the elements in CSS, adding divs, spans, ids, and classes as appropriate. Floats, absolute positioning, etc. should be used as you see fit.
Answer: Things are dependent.
I want to put is that you should know what is needed.
One thing Div based layout renders fast than table base. There are some things that might affect your page render time in browse Like use external CSS only etc.