Water heater overflow outside drain pipe

Question: My water heater's overflow outside drain pipe has been running hot water out of it non-stop.  I turned the inflow water valve to the water heater off and the water stopped running.  But what is causing this water to flow out like that?
Answer: Since your question says hot water, not steam escaping from overflow, my first thought would be to check for a faulty high pressure relief valve.  This is the cylinder with the little lift switch usually mounted atop the tank with the drain line attached.
Answer: How old is the water tank?
It could be rusted through the internal piping and water is finding a way out.
In our experience it doesn't matter the water quality. I live in the city where the water is softer and my parents are in the suburbs where its harder. If its going to rust, the water will find a way through.
Check the temperature also; if its to hot, expansion could be causing the water to get through somewhere; which would probably tell me its time to replace it anyways.
In the last days of ours, water was trickling out of the top where it feeds the house at the connection between the heater and the copper pipe.
In our case the tank was in excess of 10+ years and in my experience, they don't last much longer than 7 (your average GE tank from home depot or lowes)
It might be time to replace it.
If you do buy a new one, keep the paper work and we also mark the month / year we replaced it on the tank now. My father replaced his after just 3 years, called GE and they sent him a new, top of the line one because he could produce the receipt and paper work and it was within the normal operating period for the tank.


What is the advantage of krausening?

Question: Krausening seems to be a fair bit of work to the homebrewer with very little return. So, what advantages does krausening bring, other than not having to add any additional sugar to the beer for carbonation?
Answer: I assume by krausening you mean priming with gyle.  I've tried it and found no advantages to it whatsoever.  It's a pain to calculate the right amount and depending on the fermentability of the wort you can get varying carb levels.  I've tried priming with a number of things and always come back to sugar (corn or table) as the most reliable and neutral method.
The term krausening is more often used to describe adding actively fermenting wort to beer.  This can be an effective way to reduce diacetyl in a batch.
Comment: Well, I have always used the term "krausen" (perhaps erroneously) to mean prime with gyle. But yes, as far as I can see there is no merit in the procedure other than to allowing you to say that your batch has no added refined sugar.
Comment: I think the difference is that krausening uses actively fermenting wort while priming with gyle uses wort that is not fermenting.  So I guess technically you could krausen to carbonate, but that's not what people usually mean by it.
Answer: Krausen refers to either the yeasty foam in the fermenter or a method of priming beer with the wort from the batch that is being primed. gyle is another term for unfermented wort. priming with Krausen allows the beer to adhere to the rheinheitsgebot.
one would assume that Krausen would impart no foreign or undesirable flavors to the beer because it uses it's own maltose to carbonate and condition the final product whereas table sugar or corn syrup are slightly different sugar molecules that produce (albeit slightly) their own flavors.

What is the advantage of krausening?


How do I fix a condensate drain line that froze in my split electric system with heat pump?

Question: I have a split electric system with a heat pump.  It looks like my condensate drain line is frozen.  I switched to supplemental heat which does not use the heat pump.  Is this enough for now?  Our hard freeze will be over in 2 days and we will be back to temps in the 50s
Answer: Your inside coil should have two outlets to drain condensate, one running outside and the other with a float switch to shut down the unit if the outside drains clogs. You can unscrew that float unit and put a bucket there to drain the condensate until the line thaws.
You should also figure out how to correct your condensate line so that it can not freeze. In climates where freezing of the condensate line is possible, you have to run it so that you maintain an air lock on the line (with a p-trap), but also do not expose the water creating the air lock to freezing temperatures. like this:

Notice that, starting at the a/c unit, the condensate line has in this order:

an air gap, which is basically just a t-joint with a short piece of vertical pipe, left uncapped and open to the airspace shared by the air handler or the conditioned space. It should be a couple inches taller than the condensate collection pan, otherwise the condensate will flow out of this tube and never trigger your shutdown float switch, if you have one. The air gap prevents the p-trap from being sucked or blown dry by the air handler.
a p-trap to prevent your conditioned air from being blown out the condensate line, or from sucking in fumes from outside. It also keeps critters out.
a continuous down-sloped condensate line.

All of this needs to be laid out so that everything from the air handler through where the condensate line starts its downward slope will not freeze. Since the line is sloped down, it will drain, even in cold weather. It's also important to minimize the amount of line exposed to freezing weather in order to prevent the water from freezing in cold section of the line.
Also, in emergency heat mode, you may not be able to generate enough heat to keep the house comfortable. It used to be that the emergency heat coils had to be large enough to heat the house by themselves. Since heat pumps have been on the market for quite a while and their reliability and availability has improved, that is no longer the case.
Comment: Thanks for your detailed reply.  We had our thaw yesterday and tomorrow I will get an hvac tech here and give him your instructions.  m mondor


One hand and then the other

Question: I'm a beginner at piano. When practising is it best to learn how to play each hand separately at first and then put them together, or to practice the whole thing? Or does it not matter?
Answer: When you are first learning something, you need to be able to concentrate on just that single thing.  This isn't something that is isolated to learning a piece of music.  If you isolate just the single hand, you'll be able to learn it faster, without the distraction of the other hand.
Once you can play each hand by itself, start out at a slow tempo putting both hands together.  Improve your speed as you are able.
Answer: If you are a complete beginner, you should be focusing on playing only one handed pieces until the note reading and playing ability is reasonable. After that, it depends on the nature of the piece. For example, a study which focuses on right hand dexterity and simple left hand accompaniment could possibly be played all together right at the start. A slow piece with a low degree of technical difficulty but higher expression and feeling can certainly be played hands together at the start.
On the other hand, a piece with the hands playing two complex parts such as a fugue should be practised extensively hands separately, and then combined at a slow speed as mentioned above.
A simple rule of thumb is that if you are struggling to play the piece in terms of technicality (hitting the notes) then you should probably not play together straight away.

One hand and then the other


Which tense should I use when writing a post about a journey?

Question: What tense could I use when I write about a journey? Suppose if I write about a train journey and describe the countryside, would using a present tense create a deeper impact to the reader? I could make it appear as if I had been writing during the travel though the reality is I could have written it later. I would want the reader to feel the depiction and I was wondering if tense matters here.
Comment: why do we answer a question in present tense when asked in present tense ?
Answer: I think you mix things up here. Present tense does not build immediacy, immediacy should be there if you use present tense. At least I expect it when present tense is used.
As Kate mentions the sense of immediacy is independent of the used tense. But if you use present tense, your writing should better have this sense. Just using present tense will not add it.
Though the tense does matter in combination with your viewpoint. You have to be consistent to avoid puzzling the reader.
As an example let me use a thriller playing in a train (for your journey ;). There is a murder committed in the compartment next to the person watching the scenery.
Using third person view (omniscient or not is only a matter of detail here) you can use present tense and write:

Sybil watches the mountains of Montana. In the compartment next to her a man slaughters a woman.

No problem with that (besides missing suspension).
First person, present tense:

I watch the mountain ranges of Montana while the guy in the next compartment is slashing his girl-friend.

Why do you know that? How could the first person narrator know what happens in the other compartment, or that it is his girl-friend and not his stepmother (or maybe both with one kill)?
For an opening scene of a book you can use this, if you answer these questions during the book. Otherwise it is an inconsistency in your perspective.
But now we try that with past tense:

He ripped apart her chest, while I was watching the snow on the shiny peaks of Montana. When I found the blood beneath the door one hour later, he had already left the train.

Using past tense this trick is possible, because it's plausible that the narrator knows more afterwards than he did when the crime happened. If it is good style or not, I leave open for discussion (well, I like it).
When you stay consistent, it does not matter if you use present tense or not. A deeper impact is not created by tense.
Answer: I know lots of people say that present tense creates immediacy, but as a reader I've never noticed any difference.
But if you want to give a better impression that the story is being written or told as it happens, present tense will help with that. That's not quite the same thing as the reader's sense immediacy. It's related, but not quite the same.
A few caveats for present tense:
If you want the piece to read as if it were written during the journey, you'll want to make sure you would have had a reason to write it during the journey. You may not need to express that reason directly in the text, but if you're writing in present tense, the reason to start writing can't come from events later in the text.
Also, you won't be able to foreshadow overtly. If you want to foreshadow, you'll have to do it subtly, perhaps via dramatic irony (describing things and events whose significance the reader understands, but the writer does not).
Answer: Choose the tense that suits the story you want to tell.
Like you say, if you want to create the impression that the description of the journey is from a diary, then present tense could work. However, even here you could write as past tense because perhaps you wrote in your diary at the end of the day looking back over the day's activities.
Or perhaps the story you're trying to tell is from the point of view of a changed, wiser person looking back at lessons learned from a particular journey, and you want to contrast between that younger self and the later, older one.
None of these options is any better or worse than the other as long as you tell the story well, and you're consistent. The possibilities are endless, but they all depend on the story you're trying to tell, and that's what you should use to dictate the tense.
Also, trust your instincts: if you feel more comfortable with first person, present tense as a writer, then do that. If you prefer past tense, third-person, do that. The only time I would suggest present tense would perhaps be with action novels, but even there, a story well told is a story well told.
Answer: In which tense do you feel most comfortable writing?
I think that a good writer can give a sense of immediacy and impact regardless of the tense chosen.  This seems like one of those questions that we use to keep us from getting down to the hard work of actually writing - like 'what font should I use' or 'what's the best word processor'.  It doesn't really matter.  Chose one, and get going!
Comment: Actually i did write during the journey(in present tense), however later when i wanted to post it, i was wondering about the tense.


What is the best bo staff for an 8-year-old for competitions?

Question: What would be the best bo staff for an 8-year-old child to use in competitions. The bamboo toothpick is much too heavy for him. Would anyone recommend the fiberglass bo staff?
Answer: Century Martial Arts advertises their smallest bamboo toothpick starting at 12 oz. That would be the 50" (4' 2") variety. The lightest fiberglass I could find in a non-exhaustive search was still 1 lb. 5 oz.
If that's too heavy, the student should train so it is not too heavy. Lifting weights with proper form and properly trained supervision can be a safe and efficient way to increase overall strength -- a standard recommendation for children beginning reasonable weighted exercises is to start with no weight (just the bar) and perform the exercise to learn good form, then increase just 1 or 2 pounds at a time.
Comment: We're just going to have to disagree on that. Cheers.


Is there any automated online service for making white board animation?

Question: I want to know is there any website or software available to make white board animation as following?
Answer: The video you showed is simply a stop motion video, not an animation.
So you aren't going to be able to simply send a jpg off somewhere and have it come back as a video.
There are plenty of video houses that will happily make you a video like this, but it is time consuming. Usually they video the entire process of drawing the art, then cut out frames - to ensure they keep in important key frames.
Comment: Thank you for the answer. I have seen this kind of marketing videos so many places. So I curious to know that is this make from service like goanimate.com . So I asked
Answer: VideoScribe : Open a svg > select a hand [optional]. Thats all. Your animation is ready. But you cant provide motion animation as you can do in Flash. If you want to give painting, sketching, zooming in/out, camera move or erasing effect you can do all.
PowToon : Good for animated presentations where you don't want instant sketching effect


Counting travails

Question: How many 7 digit numbers are there (no leading zero) in which the digits 6 & 9 occur together as 69 at least once. I am having difficulty in eliminating overcounting.
Answer: The string $69$ can occur starting in position $1,2,3,4,5$, or $6$. If the number has $69$ starting in position $1$, the remaining $5$ digits are completely arbitrary, so there are $10^5$ such numbers. If the $69$ starts in any of the other five possible positions, the leading digit cannot be $0$, so there are $9\cdot 10^4$ numbers for each of these five cases.
Of course some numbers, like $6906912$, have been counted more than once. What double counting is actually possible? A number can have $69$ twice if the starting positions are $\{1,3\},\{1,4\},\{1,5\},\{1,6\},\{2,4\},\{2,5\},\{2,6\},\{3,5\},\{3,6\}$, or $\{4,6\}$. Each of the first four of these possibilities includes $10^3$ numbers; each of the other six includes only $9\cdot 10^2$, since the leading digit cannot be $0$.
Finally, triple counting is possible if the three instances of $69$ start in positions $\{1,3,5\}$, $\{1,3,6\},\{1,4,6\}$, or $\{2,4,6\}$. Each of the first three of these cases includes $10$ numbers, and the last includes $9$.
Now just do the usual inclusion-exclusion calculation: we have
$$\begin{align*}
(100000&+5\cdot 90000)-(4\cdot 1000+6\cdot 900)+(3\cdot 10+9)\\
&=550000-9400+39\\
&=540,639\;.
\end{align*}$$
Comment: @Kanna: Thanks; fixed.
Answer: This is probably a good candidate for inclusion-exclusion (at least, I can't think of another way that won't be about the same amount of work, but I'm sure someone else will come around and give one).
First: how many have at least one instance of $69$? There are six locations where it can be placed (positions one through six); in one of them (position one) there are $10^5$ ways to fill the remaining places, and in the other five there are $9\times 10^4$ ways of filling the remaining spaces; so
$$10^5 + 5\times9\times 10^4.$$
But this overcounts those that have $69$ more than once; how many have at least two occurrences? There are ten ways to put at least two $69$s: four locations for the first copy; and then $4+3+2+1$ for the second depending where the first one is, for a total of $10$ places. In six of them, you have $9\times 10^3$ ways of filling the remaining slots, in four of them you have $10^4$ ways of filling the rest, so
$$6\times 9\times 10^3 + 4\times 10^4.$$
But this removes too many times the few sequences were $69$ appears three times; if you have three copies of $69$, there are four locations where you can put the remaining digit (after all three, between the first two and the third, between first and the last two, or before all three); in three of the locations you have 10 possibilities, and on one you have nine possibilities. So there are $9+10+10+10$ ways for this to occur.
So the total is
$$\Bigl( 10^5 + 45\times 10^4\Bigr) - \Bigl(54\times 10^3 + 4\times 10^4\Bigr) + \Bigl(39\Bigr).$$
Comment: @AndréNicolas: Oops; quite right; those are disjoint cases to be added. Thanks.
Answer: Imagine $7$ boxes. If $69$ is to occur atleast once together as a  pair, we have, $6$ ways of having it.
If you chose to put it into the $1$st and $2$nd box, then, the rest of the $5$ boxes have $10$ candidates for them. So, this leaves us with $10^5$ possibilities in this case.
In any other set up, we will have a first box, where there are $9$ possible candidates and the other boxes have $10$ candidates for them. So, $9 \times 10^4$ possiblities in each set up.
$$\text{Total numbers}=10^5+(5\times9\times10^4)=55\times 10^4$$
But we have over counted those that have two 69's in them. So, let's subtract them from this count.
If we had two 69's coming in, it must arise out of the following cases: For $i<j$, let's use $(i,j)$ to denote that $i^{th}$ place and $i+1^{th}$ places are filled by $6$ and $9$ respectively. And, similarly for $j$. Note that $j−1>1$.
$$\begin{array}{|c|c|}\hline (1,3); (1,4); (1,5); (1,6) & 4 \times 10^3\\ (2,4); (2,5); (2,6) & 3 \times 9 \times 10^2\\ (3,5); (3,6) & 2 \times 9 \times 10^2 \\ (4,6) & 9 \times 10^2\\ \hline \end{array}$$
So, $$\text{Total number we have to exclude}=9400$$
But, in this process, we subtracted those with three copies of $69$ in them. Again, let's use the notation of the previous kind:
$$\begin{array}{|c|c|}\hline (1,3,5); (1,3,6) ; (1,4,6) & 3 \times 10\\ (2,4,6) &  9 \\ \hline \end{array}$$
The $$\text{Total numbers you will include}= 39$$
So, the total numbers:
$$\text{Total Numbers with the property}=550000-9400+39=\boxed{540639}$$

Counting travails


Is the real Jacquet module of a Harish-Chandra module still a Harish-Chandra module?

Question: Casselman defined the real Jacquet module for a Harish-Chandra module, if we view the Jacquet module as a module corresponding to the Levi subgroup, the question is is it still a Harish-Chandra module? In particular is it still admissible?
Answer: As I understand it, the Jacquet module for $(\mathfrak g, K)$-modules is defined so as to again be a $\mathfrak g$-module, and in fact it is a Harish-Chandra module, not for $({\mathfrak g},K)$, but rather for $(\mathfrak g,N)$ (where $N$ is the unipotent radical of the parabolic with respect to which we compute the Jacquet module).  (I am probably assuming that the original $(\mathfrak g, K)$-module has an infinitesimal character here.)
I am using the definitions of this paper, in particular the discussion of section 2.  This in turn refers to Ch. 4 of Wallach's book.  So probably this latter reference will cover things in detail.
Added: I may have misunderstood the question (due in part to a confusion on my part about definitions; see the comments below), but perhaps the following remark is helpful:
If one takes the Jacquet module (say in the sense of the above referenced paper,
which is also the sense of Wallach), say for a Borel, then it is a category {\mathcal O}-like
object: it is a direct sum of weight spaces for a maximal Cartan in ${\mathfrak g},$
and any given weight appears only finitely many times.  (See e.g. Lemma 2.3 and Prop. 2.4 in the above referenced paper; no doubt this is also in Wallach in some form; actually
these results are for the geometric Jacquet functor of that paper rather than for Wallach's
Jacquet module, but I think they should apply just as well to Wallach's.
Maybe they also apply with Casselman's definition; if so, doesn't this give the desired admissibility?
Comment: Thank, Emerton. The definition in Wallach's book is different from Casselman's, in some sense it's the dual of Casselman's. In Casselman's definition, it becomes a (g,P)-module, and in particular a module for the corresponding Levi.
Comment: Sorry, I didn't know that.  Maybe ignore the above, then!


Is dry rub necessary in making bbq ribs?

Question: Normally when I make bbq ribs in the oven at home, I have to prepare the ribs approximately a day ahead. I usually cover the ribs with a dry rub mixture (made of garlic powder, paprika, sugar, salt, pepper, etc.), wrap it up in foil and let it sit in the fridge for about a day, lather it in bbq sauce and stick it in the oven. While this method produces quite delicious ribs, it does require a lot of effort and planning. My questions are:
Is a dry rub really necessary in making bbq ribs?
Is there an alternative to this dry rub?
Will the ribs taste the same if I just lather them in bbq sauce and cook then straight away?
Answer: Your ribs will have a lot less flavor if you do not use a dry rub.  However you can minimize some of the time (and only a bit of the flavor) by putting on the rub, wrapping in foil, and immediately putting them in the oven or on the grill.  The process of putting your rub together probably takes only about 5 minutes - it's the fridge time that takes a while.
Sitting in the fridge allows some of the flavors to permeate, and if you used a more permeable material could allow your ribs to air out a bit.  These are good things, but for my rib recipe I don't put the ribs in the fridge and they still taste great.  I also don't put the barbecue sauce on until about the last 20 minutes of oven time, when the foil comes off and the sauce goes on.  Until then the ribs stay in the foil.
I looked up North Carolina (which uses a sauce that isn't tomato based in the eastern part of the state), South Carolina (a mustard sauce), Texas, Memphis (which uses no sauce), Kansas City (tomato based-sauce that is rather sweet) - all of them used a dry rub even with wide variations on the sauce and for both beef and pork ribs.
Comment: Memphis is of two minds regarding sauce or not. There are excellent restaurants serving specializing in each style.
Comment: Thanks for your answer. I might try your cooking method next time. That way I can save time.
Answer: You can certainly do without the rub before hand. Keep in mind though that one of the functions of marinating in an acidic wet rub will be to break down the connective tissues. Going straight to the grill without a marinating wont be as tender. One alternative is to cook the ribs in a slow cooker full of sauce all day while you are at work. This will cut down on the planning and result in a fall-off-the-bone outcome.
Comment: the OP indicated a dry rub rather than an acidic wet rub
Comment: Thank you for your answer. For the acidic rub, do you mean like lemon juice? Or more like yoghurt to permeate/tenderize the meat?
Comment: The OP also mentioned alternatives and cooking right away without prep
Comment: good point.  The downvote wasn't mine, but I thought you might want to edit to indicate that alternatives would be 1) an acidic wet rub instead of a dry rub or 2) Skipping any rub or 3) Slow cooker.  FYI - I didn't downvote.
Comment: Usually BBq sauce containing vinegar is a common choice but lemon juice would work as well. Can't say I've had ribs with yoghurt in it, but that could make for some interesting experiments.
Answer: For traditional BBQ (low and slow), dry rub does tend to add quite a bit to the flavour.  However, you do not need to leave it on that long.  As a matter of fact, if your rub has a lot of salt in it, leaving it on that long will result in ribs that are "hammy" (almost cured like ham or pastrami).
You'll notice after 5-10 minutes of putting on rub that the salt has been sucked into the ribs along with some moisture (they'll get a clammy look).  That's long enough.
With regards to saucing, always glaze at the very end.  If you like the sauce baked in a little, put them back in for 5-10 minutes, but keep an eye on them.  If the temperature is too high, sauce with a high sugar content will burn.  My personal preference is a really thin glaze (or none at all) and sauce on the side.  Let the meat speak for itself instead of masking it with sauce, as way too many people do.
Answer: There are other ways to keep your meat from drying out while it tenderizes, but the rub is just so darn delicious.
You could probably get away with BBQ sauce only, but it would definitely not be as robust a flavor.  A marinade would get you there in the flavor department.  I had Coca-Cola marinated babybacks once, and they were outstanding.
Or you could try putting ribs in oven immediately or shortly after applying the rub.  A salty rub can begin curing your meat, which would result in a bit of a "hammy" taste to the ribs.  I'd say, before anything else, do what you normally do except change the amount of time the ribs sit with the rub on them.  This may be enough to get you past your prep time objections, and you're only changing one variable at a time.
Answer: For most smoked/BBQ/low-slow meats, a brining or marinating process with liquid is indicated, and the dry rub is applied just before the smoking/cooking process begins.  You could try vinegar, apple cider (I love that one), watered-down beer, etc.  I've made my own marinades from combinations also; vinegar and water with Worchestershire, "liquid smoke", and Tabasco works pretty well on some things, including ribs.
I've had great success with this wet marinade/dry rub approach.
Comment: Oh, and BBQ sauce is saved for serving time (there are a few "weirdos" who don't like it ...) :-)


Distance and time brain teasers

Question: I was asked the following in an interview:

B is 50% faster than A. A starts at 9:00 and B at 10:00. They are now
  300km apart. The speed of A is 50kmph. At what time will they meet if both
  move in opposite direction?
Comment: Are they on a circular track? Or are we supposed to think of them on the surface of the Earth? Otherwise they'll never meet moving in opposite directions...
Comment: Do they start at the same point?
Answer: At 10:00 they would be $300-(50*1) = 250 km$. The relative speed of B and A then is $50+(1.5*50) = 125 kmph$. The time taken for them to meet would then be $250/125 = 2 hrs$. So they meet at $12:00$.
Answer: First substract the 50 km A walks to  get the distance between them at 10:00 is 250.
Say X is the speed of A and y is the speed of B. Then speed of $\frac{3X}{2}=b$ so their speed toward each other is $\frac{5X}{2}$=$\frac{250}{2}$ so $250t=500$ so $t=2 hours  So they will meet at 12:00
Here is the link to a similar problem that was showed in the tv series numbers: http://numb3rs.wolfram.com/504/puzzle.html
Answer: I think there is an ambiguity about when 'now' is in the question :-). There is nothing that indicates that now is before or after 10:00, for example, so one has to be careful about assuming that the position of $A$ and $B$ can be modeled by a linear (well, affine) equation.
All of the other solutions assume that 'now' is 9:00.
I believe the answer should be that they meet no earlier than 12:00.
I am assuming that we are dealing with a 'flat' surface here, with no spherical trickiness.
Suppose $A$ starts at $x=0$, and $B$ at $x=L$, where I assume $L>0$. Also, the question asks what time 'will' they meet, so we are looking for a time in the future when they meet.
Then their positions are given by:
$A(t) = 50 \max (t-9,0)$, $B(t) = L-75 \max(t-10,0)$.
Let 'now' be $t_0$. Then $t_0$ must satisfy the constraint $|A(t_0)-B(t_0)| = 300$. If $A(t_0)>B(t_0)$ they will never meet, so in order to meet we have the constraint $B(t_0)-A(t_0) = 300$. Suppose they meet at $t_1$, then we require $t_1 \geq t_0$ and $B(t_1) - A(t_1) = 0$.
If $t_0<9$, then we must have $B(t_0)-A(t_0) = L = 300$. From this we see that $A$ covers 50km by 10:00, and the remaining 250km in $\frac{250}{125} = 2$, hence they meet at $t_1 = $ 12:00.
Now suppose that $t_0 \in [9,10)$. Then $B(t_0)-A(t_0) = L-50(t_0-9) = 300$, from which we get $t_0 = \frac{L+150}{50}$. Since $t_0 \in [9,10)$, we must have $L \in 50[9,10)-150 = [300,350)$. It is clear that $t_1>10$, so then $B(t_1) - A(t_1) = L-75(t_1-10)-50(t_1-9) = 0$, from which we get $t_1 = \frac{L+1200}{125}$. Thus we have $t_1 \in [\mbox{12:00},\mbox{12:24}]$.
Now suppose $t_0 \geq 10$. Then $B(t_0)-A(t_0) = L-75(t_0-10)-50(t_0-9) = 300$, from which we get $t_0 = \frac{L+900}{125}$. (Since $t_0 \geq 10$, this implies that $L \geq 350$.) From $B(t_1) - A(t_1) = L-75(t_1-10)-50(t_1-9) = 0$, we get $t_1 = \frac{L+1200}{125}$, as above. Since $L \geq 350$, we have $t_1 \geq \mbox{12:24}$.
So, tell your interviewer that the question is ambiguous :-).
Answer: At $10:00$ they would be only $250\  km$ apart.
The speed of $A$ is $50$kph and the speed of $B$ is $75$kph. let $d_A$ and $d_B$ represent the distances they each travel after $10:00$. When they hit:
$d_A+d_B=250$
remember, $d=v\times t$. Denote $v_A$ and $v_B$ accordingly, noting that they'll both be travelling for the same amount of time. so:
$$v_At+v_Bt=250\implies t=\frac{250}{v_A+v_B}=\frac{250}{125}=2\ hrs$$ They meet at $12:00$.

Distance and time brain teasers


Will taking Vitamin D supplements harm my bodies ability to produce it itself?

Question: It is known that the human body can produce vitamin D itself when exposed to enough sunlight. But will the body downregulate this natural production of vitamin D, if I take a vitamin D supplement? And if so, will the body increase natural vitamin D production again, when I stop taking vitamin D? Or will taking vitamin D permanently harm my bodies ability to produce vitamin D itself?
Answer: The body stops producing its own vitamin D when it has enough, whether it gets enough from supplementation/diet or sun exposure/natural means or a combination.
I'm on a nutritional therapy course now, and I've never read anything that says that is necessarily a bad thing (i.e., never read anything to suggest that supplementation will permanently shut down the body's ability to produce vitamin D for itself). That said, excess supplementation can cause problems with kidney function ("Excess vitamin D can cause the body to absorb too much calcium and can lead to kidney damage" - see link below), so it's not advised that supplements become the primary source of vitamin D.
http://www.vrg.org/journal/vj2009issue2/2009_issue2_vitamin_d.php
Answer: I am not a doctor, but given that vitamin D synthesis is primarily driven by the activity and availability of specific liver enzymes, I highly doubt that it would be possible to down-regulate its manufacture in the human body through supplementation. If that were the case, then one would expect to see similar phenomena occurring with other endogenously produced substances when they are supplemented, and I've never run across a study demonstrating that this happens. Only a drug capable of inhibiting production of said liver enzymes could impact endogenous vitamin D production, and even this effect would be normally reversible upon discontinuation of the drug. Furthermore, vitamin D toxicity requires dosages that are orders of magnitude above the RDA, so if you limit yourself to reasonable quantities, I wouldn't expect any problems to crop up.


Bodyweight exercise for traps

Question: Does anybody know a good bodyweight exercise for traps and neck?
I have tried the inverted shoulder press but would appreciate
other suggestions.
Comment: Deadlifts. Just kidding. But not really.
Answer: I like to grab a pull up bar and drop one hand hang at full extension then switch to the other hand.  As you switch you trap will be engaged to lift you up to switch hands. The longer you can sustain the state between hanging on one hand and grasping it with your other the more completely you will utilize the trap.
Answer: The best bodyweight substitution for a weighted shrug is just a shrug from the inverted hang (aka inverted shrug):

This can be done on rings, straight bar, or even parallel bars:
Answer: Shrug Dips or Dip shrugs, whatever Kelso calls them are very effective.  you get in the position of doing Dips and instead of going down push yourself up, hold this position and then lower your self down. the actual movement should be no more than 6 inches. your elbows dont bend during the whole repition. Search the internet for Kelso's dip shrug and you will get more detail on how to do it.
Answer: Bridging drills from wrestling, both forward and backward, are awesome for neck strength.
Handstand "shrugs" were recommended to me as a drill for developing the traps as well as all the muscles that assist with scapular retraction. You get in a handstand (against a wall is fine) and simply relax the shoulders forward and "down" towards your hips, then squeeze them backwards and "up" towards your head, towards a proper full handstand position. The shrug dips described in Geek's answer sound similar.

Bodyweight exercise for traps


Vector field and normal of the field are both gradient fields

Question: Are there any general conditions to use to find a vector field f(x,y) that is a gradient field and f(-y,x) is also a gradient field.  It seems to me like if their second partial derivatives are zero then this is true or at least I haven't find an exception to that yet.
Comment: Indeed, your question and its title ask different questions!
Comment: The normal of a vector field $(f(x,y), g(x,y))$ is $(-g(x,y), f(x,y))$, not $(f(-y,x), g(-y,x))$ as you have written.
Answer: $\vec{f}(x,y)=(f_1(x,y),f_2(x,y))$ is a gradient field iff we have $f_1 = \frac{\partial g}{\partial x}, f_2 = \frac{\partial g}{\partial y}$ for some function $g$. Similarly, $\vec{f}(-y,x)=(f_1(-y,x),f_2(-y,x))$ is a gradient field iff we have
$$f_1(-y,x) = \frac{\partial h}{\partial x}(x,y) = -\frac{\partial h}{\partial y}(-y,x), f_2(-y,x) = \frac{\partial h}{\partial y}(x,y)=\frac{\partial h}{\partial x}(-y,x)$$
 for some function $h$. The second inequalities in each case are simply applications of the rules of differentiation. This means that $f$ is such that $f(x,y)$ and $f(-y,x)$ are both gradient fields iff
$$f_1 = \frac{\partial g}{\partial x} = -\frac{\partial h}{\partial y}$$
$$f_2 = \frac{\partial g}{\partial y} = \frac{\partial h}{\partial x}$$
can be solved by two functions $g,h$. If we let $h(x,y) = g(-y,x)$, we see that
$$\frac{\partial g}{\partial x} = -\frac{\partial h}{\partial y}$$
$$\frac{\partial g}{\partial y} = \frac{\partial h}{\partial x}$$
and so if $\vec{f}(x,y)$ is a vector field then $\vec{f}(-y,x)$ must be (and vice-versa).
Answer: If I understand the question correctly this is a somewhat unfamiliar setup. Let's see what comes out of it!
We are given a vector field
$${\bf v}(x,y):=\bigl(P(x,y), Q(x,y)\bigr)$$
defined in a neighborhood of $(0,0)\in{\mathbb R}^2$. In addition we consider the second vector field
$$\bar {\bf v}(x,y):=\bigl(\bar P(x,y),\bar Q(x,y)\bigr)$$
related to ${\bf v}$ via
$$\bar {\bf v}(x,y):={\bf v}(-y,x), \quad{\rm i.e.,}\quad
\bigl(\bar P(x,y),\bar Q(x,y)\bigr):=\bigl(P(-y,x),Q(-y,x)\bigr)\ .$$
Geometrically the field $\bar{\bf v}$ is obtained from the field ${\bf v}$ by attaching at $(x,y)$ the vector ${\bf v}(-y,x)$. The point $(-y,x)$ is obtained from $(x,y)$ by a $90^\circ$ rotation, but the vector found there is not turned.  This will have an important effect!
Now we are told that both fields ${\bf v}$ and $\bar {\bf v}$ are gradient fields. Writing $f_1$ (resp. $f_2$) for the partial derivative of some function $f$  with respect to the first (resp. second) variable we therefore have
$$P_2(x,y)\equiv Q_1(x,y)\ , \qquad  \bar P_2(x,y)\equiv \bar Q_1(x,y)\ .$$
Here $\bar P_2(x,y)$ and $\bar Q_1(x,y)$ compute as follows:
$$\eqalign{
 \bar P_2(x,y)&={\partial \over\partial y}P(-y,x)=-P_1(-y,x)\ , \cr
\bar Q_1(x,y)&={\partial \over\partial x}Q(-y,x)=Q_2(-y,x)\ . \cr}$$
This shows that we have $-P_1(-y,x)=Q_2(-y,x)$ identically in $x$ and $y$, and this is the same thing as $-P_1(x,y)=Q_2(x,y)$ identically in $x$ and $y$.
We now leave the field $\bar{\bf v}$ aside and write again $f_x$, $f_y$ for the partial derivatives. Then altogether we can say that the components $P$ and $Q$ of the original field ${\bf v}$ together satisfy the Cauchy-Riemann equations (up to a sign):
$$P_y=Q_x\ ,\qquad P_x=-Q_y\ .$$
It follows that the complex function $f(x,y):=P(x,y)-i Q(x,y)$ is an analytic function of the complex variable $z=x+ iy$.


Seeking Data visualization and maintenance tool

Question: Background
Looking to leverage an existing GIS system for exploring organizational data.
Architecture
The following figure represents a high-level overview of the system's desired features:

The most basic usage would be as follows:

The user visits a web site.
The system presents a map (having regions, cities, and buildings).
The user drills-down on the map to a particular building.
The system provides a basic CRUD interface.
The user can view and modify information about personnel (e.g., their assigned teams), equipment (e.g., network appliances), applications, and the building itself (e.g., contact and phone numbers).

Ideally, all the components should be open-source (or otherwise free).
Problem
This must be a small project that needs a quick (but functional) prototype, mostly to confirm whether or not such a system would be useful in the long term.
Questions

What software components would you use to quickly develop a working prototype?
What open-source solutions already exist, if any?

Ideas
Here is what I am thinking:

PostGIS - Define the regions, cities, and sites
Google Maps - Display an interactive, clickable map
geoJSON - Protocol between PostGIS and Google Maps
Seam - CRUD interface

Custom Development
For example, this would entail:

Installation and configuration

Configure SSH for remote logins
Subversion (or git)
PostgreSQL
PostGIS
Java
Tomcat
Seam
JasperReports

Enter GIS information into PostGIS
Aggregate data sources into PostgreSQL database
Develop starting page for map interface
Develop clickable Google Maps interface
Develop summary reports
Develop CRUD interface using Seam for data maintenance
Answer: Update 2024: OpenGeo became boundless, which was acquired then killed. MapServer or GeoServer might be a good place to start.
Original post: One of our clients uses the OpenGeo suite. There is a community edition if you don't need support.


How do I test my water?

Question: Inspired by this question. How do I test my water?
Comment: $25 http://www.ternwater.com/know-your-water/
Answer: If you have city water, they usually sent out a water profile a couple of times a year. It will be an average of the whole city, but it'll give you a general idea of what you're dealing with.
You can also send your water away to a lab to get tested. I've never bothered, so you'll need to find a reputable lab.
Answer: A city water report is the first place to look, but given where your city gets it's water, the values can fluctuate pretty significantly. For example, my city gets water from a few sources; sometimes they'll mix in well water, and thus the water has higher hardness, or they might be taking surface water shortly after a fresh rain.
The question to also ask is "why" should you test your water. To answer that, a good starting point are sections 15.0 though 15.4 in Palmer's How to Brew:
http://www.howtobrew.com/section3/chapter15-1.html
Water chemistry does have a significant affect on beer flavor. Often water chemistry is the last bit of tweaking needed to make a good beer great.  Having said that, it's also an easy way to muck up a beer. Water chemistry (aside from proper filtration) should be your last concern in making beer.  Sanitation, yeast handling, temperature control, recipe formulation and brewing process should all come first.
Answer: I mentioned this over at the other question, but it bears repeating. If you have a private well, read this.. There are links to the bottom for state certified testing agencies. If you've never had your water tested, I highly recommend doing so immediately, beer brewing notwithstanding - it's potentially a serious safety issue.
If you are on city water, then it's probably safe, but I'd be tempted to test what's coming out of your individual tap just to be sure.
Answer: The best place I've found for water testing is www.wardlab.com.  Get test W-6.  It runs about $16 and gives you all the info you need for brewing.  If you tell them you're a homebrewer, they have special info available.

How do I test my water?


What is the best way to create a splash page in SP 2010 that contains just a picture and a list of languages

Question: Do I need to create a new master page? what should be included in this master page regarding that I don't what a menu, footer, logo, and nothing but my picture and a list of languages and flags. I'm using SPS 2010 (publishing site) The entire project is in vs 2010. I've already created a page layout and a page but how can I get rid of the header other surrounding controls (the best way)?
Thank you very much.
Answer: I'm answering my question. maybe it helps someone else. The best way I found is:
1- create a new minimal masterpage and hide everything that is not required the masterpage should be packaged in a Module item in visual studio with an elements file to put the master page in Master Pages catalog in sharepoint.
2- Create a new Page template and put whatever you need in this page
3- Then you need to set the page's MasterPageFile property to the minimal master page that you have created in step 1. This step is tricky but simple. You just need to create a class that inherits from Microsoft.SharePoint.Publishing.PublishingLayoutPage, override OnPreInit and call the original OnPreInit and then set the property to somthing like this: "/_catalogs/masterpage/whatever_you_named_it.master"
4- Create a feature and package and deploy it
Answer: What I usually do for these special "landing" pages (or 404 pages) is to make sure that I have sufficient ContentPlaceHolder within my main master page around all major UI component (header, footer, navigation, ...) that way I'm making them empty in the page layout that I'm using for these special pages and finally relying on the AdditionalPageHead place holder to inject some page specific css classes to would take care of unforeseen branding / removal.
Hope it helps.


What sort of things should one look for in a water-softener?

Question: Hard water (from a well) at the house, and I was wondering what to look for in terms of getting a water-softener, or things to avoid.
Answer: For the most part, softeners are pretty simple. Softening water works by exchanging positively charged ions with sodium ions.
Because softeners backwash periodically to recharge, they have a timer (and sometimes a meter) to control when this happens. One of the problems with a mechanical unit is when the power goes out, the time freezes, and just picks up where it left off when the power comes back, so it will start backwashing at strange times - most (if not all, now) electronic timers have battery backup for the time. Electronic ones have been in use for 10+ years now, and are quite reliable now. If you use a metered timer, it will regenerate during the night only after using a certain amount of water, so it wastes less brine (salt) water.
Get one that is easy to service. Although softeners only have to be rebedded about once every 10 years, it should be possible to turn a bypass valve and disconnect the softener. I've seen some old units where you actually have to cut the plumbing to disconnect them, although I'm not sure if those are still on the market anymore. You don't want one of those.
Pay attention to how it is connected: All of your hot water should be soft. Outside taps should be hard (you don't want to water your garden/grass with soft water), with perhaps the exception of a hose in your garage for washing cars. Some people leave their kitchen cold water tap hard, so as to reduce the amount of sodium they are drinking and cooking with, but this partially depends on preference and partially on the amount of hardness (and thus amount of sodium being added). Obviously this is a bigger concern if there are people on low-sodium diets in your house.

Personally, I would avoid electronic/magnetic softeners. There has been some evidence that this can help with very low levels of hardness, there is a LOT of junk out there.
I used to work summers for my dad who ran a water treatment business. We replaced one of these electronic softeners (it had wires going from each end that wrapped around the pipes) with a real softener one time, and took the electronic one back to play with. We tore it apart, and could not find any active electronics in it except for the ones that drove 5 LEDs on the front that flashed back and forth. We hooked the wires up to an oscilloscope and all it was doing was alternating between about +10 mV and -10 mV, with almost no current. I can't see how this possibly did anything -- and the home owner was replacing it with a real softener, so what does that tell you..
Answer: I've worked on software with water conditioning companies all over North America for the past 10 years, so I have a pretty good understanding of the business.
My advice is to talk to several companies in your area about what they recommend. There are tons of dealers out there who can help you. They know the water in your area and the equipment best suited to your needs. Some water requires different filter media. I wouldn't be comfortable just purchasing something on my own, and I do pretty much everything on my own.
I would stay away from plumbers- work with people who specialize in water treatment.
To name a few companies who have dealers who can work with you:

Culligan
EcoWater Systems
Kinetico
Hellenbrand
WaterCare

It looks like you're in Boston... unfortunately, I've only worked with one dealer in MA, and they weren't anywhere close to you.
Answer: There are several types of regeneration options.  Onet thing I would recommend is getting a metered softener rather than a strictly timer option.  The metered softener regenerates at a certain time of the day when enough water has passed through it to need regenerated.  You will need to have your water tested to determine the hardness and iron levels.  These numbers are used to set your meter.
One other thing that was recommended to me was to buy a mechanical metered unit and not an electronic one.  The mechanical metered units have worked for years and do not have as many things to fail in them as the electronically metered units.
I bought a softener last year and installed it myself.  I got it from the website below. They answered my questions before I ordered it and shipped it to my house for free.
http://www.ohiopurewaterco.com/shop/customer/home.php
Comment: Good point, I had forgotton about metered units. The electronic units are very reliable now though - they are basically a circuit board and a single motor to control the valve. When they first came out, mechanical ones were probably more reliable, but now, I'd bet it's the other way around.
Answer: Another consideration is the type of salt that the softener is loaded with - some units take 25kg bags, whereas others use much lighter and easier to store salt bricks.


How do you keep all those languages straight in your head

Question: I know Java, C#, C++. I have used Perl, and am picking up Python and Actionscript 3.
This is certainly a path others have trodden, so I am asking how do you keep all these languages straight in your head?
Comment: editor with syntax highlighting. keep editing until it changes color...
Comment: I don't. I use a debugger ;-)
Comment: I don't. I use Google.
Comment: Practice makes perfect. Languages generally employ the same set of computer science constructs, so it's a simple matter of remembering syntactic differences and feature offerings.
Comment: @John, give us some examples of things you tend to confuse or forget across languages (builtin method names? operator precedence? libraries? idioms?) How frequently do you switch between languages (monthly? hourly?)
Comment: Heh, I was just commenting to somebody last week that I've learned Perl four or five times now.  I use it for a small project that spans maybe 3-4 days, then don't touch it again for two or three years.
Comment: Remembering syntax is just half (or less) of the success. I feel that the real challenge is to remember things like `0 evaluates to false in PHP, but to true in Ruby`.
Comment: @retrodrone: That depends. There are whole clusters of languages that group around the same basics, but there a similar distinct groups that are based on completely different principles.
Comment: The biggest problem I have is switching between IDEs and having different shortcuts for step-into, step-over etc.
Comment: This is why people program in every language like it's C :-)
Answer: Your brain only remembers what it considers important, with heavy bias towards the recent. So, just rotate pet projects in those languages and you'll be alright. Just like spoken languages, you'll do better if you: start early and keep your use active.
Answer: I used to post a 1-sheet railroad-style syntax diagram plus quick reference for each language on the wall until my memory kicked in sufficiently.
Still have to do that for any programming languages I haven't used in many months.
Comment: Could you please post that "1-sheet railroad-style syntax diagram plus quick reference" for C++? I'd really like to see such a beast.
Comment: +1 for not being all, "Well if you're a **real** programmer, you won't have any problems." If you program in enough different languages, syntax references are a must.
Comment: Or one for Perl. That would be a sight to see.
Comment: If you need more than you can fit on one page, you probably shouldn't be using those language features yet, until you remember the language better.
Answer: Have you looked into cheat-sheets for the languages and libraries you use regularly? I have a couple on my wall here, one for VIM and one for PL/SQL. This website: http://devcheatsheet.com/ seems to have many cheatsheets.
I suggest cheat-sheets because there's only so much the brain can easily remember. A language you use on a daily basis will become very easy to remember. Syntax and later certain libraries and functions and frameworks if you use them often enough and you won't need to look anything up in any reference material. The less you use something, the harder it is to remember, though you'll usually be able to regain your former abilities with a little practice. Which is why I keep some cheat-sheets up on my wall: for the functions/features I don't use often enough to remember quickly.
Answer: The human brain is an amazing thing. If you learn each one well enough, you should be able to look at code, recognize the language, and ramp back up to speed fairly quickly. It's never been a problem for me... but it does take time to ramp back up to speed.
Answer: I have little trouble separating languages in my head, apart from a few typing automatisms (such as having to suppress the end-of-line semicolon in Python or VB).
I guess the thing that helps me the most is that whenever I learn a language (programming or human), I also try to pick up and embrace the culture and ecosystem into which it is embedded. I'm not merely switching languages, I'm switching mindsets (something along the lines of the popular 'wearing the X hat' metaphor).
Comment: @gMale: It's not only a matter of being nice to others; embracing a language's culture is also necessary to use it to its full potential. A culture grows around a language because certain ways turn out to work better than others, and those solidify in the culture; by learning these, you can benefit from others' mistakes.
Comment: +1 for following conventions for a language. It can be tempting to just code every language with the same style but that makes it look very "foreign" to "natives."  Someday, a "native" programmer will be maintaining our code.  So we must write it in a way that feels natural for them.
Answer: It helps that all the languages you mention are relatively similar (ie imperative).
If you are just learning to use these languages they are all very similar. They basically all have the same features and all you are learning is a slightly different syntax.
Now when you come to learn the usage (not just the syntax) then it becomes way harder. Learning to use Java like a Java Programmer is not that simple for a C++ programmer (the syntax is easy the usage idioms are difficult).
Now if you had listed different styles of language (declarative/functional/logical) then I would be more sympathetic. As moving between languages were the paradigm completely shifts becomes a lot harder.
But using a language is the key. If you use a language everyday then you will not have a problem. Stop using a language and it will fade (not fast at first). But the further the language is from the language you use daily the faster it will fade. The secret is to keep practicing the languages you like (stop using the ones you dislike your brain will make room for other stuff).
Answer: That's were the IDEs come for a rescue ;-)
only thing changes in all these languages is to either have a 'if-then-else' or a 'if-else'. some will have '(' and some won't.
Its as simple as that :)
All we care is the logic and the easiest readable implementation.
Answer: I don't. I confuse them all the time, so I've worked out a set of compensating behaviors and tools.

I'm working in the codebases of large projects, so I will check the code around me.
I use a syntax highlighting editor (quick, does Perl use elsif, elif, or else if? I don't remember, but the editor will keep me on track.)
I use the language idioms -- if I'm coding in C#, I use lambdas, linq and var. That makes it look less like Java than it would if I was only using objects and classes.
I use a different environment for each language: C# -> Visual Studio, Java -> Eclipse, Perl -> Vim. The different visual styles keep me on track.
Answer: One way would be to use a distinct style for each language in which you write.  By loose analogy, in speaking Spanish or French, one might try to emulate the inflection of a native speaker.
I've seen people that will maintain a distinct bracing, indentation, etc., for each language to help their brain "shift gears" properly when switching between them
Answer: Think of it like music. The languages you learn are just different instruments in an orchestra that ultimately produce the same notes. Remembering how to play the instruments takes practice, but eventually you'll be able to pick one up you haven't played in a while and like magic the notes just fall into place. Similarly, as you continue to broaden your knowledge of music (programming), picking up a new instrument and learning to play it becomes easier and easier each time.
Cheesy analogy, but at the end of the day, practice makes perfect. Spend some time with each instrument in that orchestra every now and then so that your ability to play the notes doesn't fade.
Answer: I'm mainly a PHP developer. So forgive my biased opinion.
I have recently discovered just how similar C code is to PHP (Or the other way around depending on how you feel ;) )
My suggestion would be to perhaps stick to a family of languages (if they apply to your work or projects) and as you develop your skills further then branch off and learn new things.
Answer: i'am using javascript and HTML/CSS mainly also i love c++ when i need a little helping tool with using QT and i use VB and f# sometimes
i know it's a little bit crazy but when i feel that i started to lose a language of those especially when thay have different syntax (VB and F# and c++/javascript)
so i get my brother and told him that i am gonna teach him then i just start making examples from scratch and when i find that i dont remember how exactly to do something(once i forgot how to do IF ELSE in VB)i just google it;
Answer: Lately, I've been using google codesearch a lot.  I go there and type in a regular expression that loosely describes what I'm trying to do and find dozens of examples of production code.  When I forget a language's syntax, this is the fastest way for me to get answers.
This approach becomes even more powerful if you're good with regular expressions. Note: This is a great resource to refresh regex skills.
Answer: Actually: I don't worry much about explicitely trying to build any kind of structure within my head.
This doesn't differ a lot from other scenarios in daily life. I have to remember how to drive a car, how to read a book, how to play tennis, and so on. Just trust your brain and don't think a lot on the metalevel.


Publish From MS Word to Published Site

Question: Does anyone know if it is possible to publish directly from MS word to a published site with workflow in SharePoint 2010? The articles will have images and ideally I would like to get the images from the asset library, type my content and submit the page for approval.
Comment: It seems you are mixing two things: Possible to Save something from Word to a Sharepoint Site? Yes. Run a workflow afterwards on this newly created document? Yes.
Now you say that the articles contain images - which articles? Are the word documents supposed to contain images which you got form the SHarepoint Asset library?
Answer: I believe what you are trying to do is akin to posting to blog, basically transferring your content to SharePoint for display.
In this case, no, Word cannot perform this action.  You can use an editor and get the content in with just a few more steps, but Word isn't the best choice because it's difficult to get at HTML conversion.
I would use the MS Live Writer tool, which is a free download.
http://explore.live.com/windows-live-writer
With live writer you can format your text and pictures (see below about pictures), change the view to HTML and copy out the code. Now on your publishing page, edit the content block and from the toolbar select the view HTML button (lookl like a two brackets and a pencil) and past in your HTML.
Incidentally you don't require a publishing site to do this, you can use this with any rich text box inside SharePoint as well as the Content Editor Web Part.
Pictures
If you want to include pictures, you need to upload those pics to a SharePoint library first.  You can then grab the URL for those pics as the source and use them in Live Writer as you compose, and when you past the code in, it will still work.
You could do this from word, but you would need to save your document as an HTML document, then grab the code from there, using Live Writer or similar will at least cut out that step for you.

Publish From MS Word to Published Site


Can I add Ubuntu fonts to website? What are licenses of those?

Question: Basically I would like to use on website a "Norasi" font, that was bundled with Ubuntu, but I cannot find any license. Am I allowed to distribute that font through website? What is its license?
Answer: Short answer: Yes. Ubuntu comes bundled with "open" fonts that are free to distribute.
Long answer: There's a LOT of information about each individual font's license. Depending on what package the font is a part of and that package's license is, certain restrictions may apply, but as a general rule of thumb you can use the default fonts that come with Ubuntu.
If you'd like info on the Ubuntu fonts themselves (Ubuntu Bold, Ubuntu Italic, etc.) you can find all of that
here.
Answer: According to this font makers homepage: http://linux.thai.net/projects/thaifonts-scalable
it is free; "License: This package collects Thai scalable fonts available in free licenses."


It's a nice vista!

Question: I overheard someone use the term "vista" while describing a view. Being a non-native speaker, I would have chosen the simpler form: "It's a nice view." Could some generous soul explain when it's a vista and when it's a view? Are these interchangeable in most circumstances?
Comment: Windows Vista is a clue
Comment: @shinynewbike: Is it?
Comment: @Urbycoz: Yes, it's just a fancy name ;)
Comment: @shinynewbike: lol, you got that right! ;-)
Answer: Vista is Italian for view. (Also Spanish, but adopted from Italian: see etymonline.)
It has been adopted into the English language and retains the same (noun) meaning, except that it is generally only applied to picturesque views.
For example:

Hey, lets pull over and take in the vista.

or

You should come out onto the balcony, there is a beautiful vista of the city below.

According to Google NGram, usage in this fashion didn't really take off until after 1900

however the phrase "beautiful vista" seems to have been around for a long while
Answer: Short answer: yes, they're interchangeable in most circumstances.
Long answer: 'View' is a more generic word.  'Vista' is specifically referring to a physical view (especially one through a long, narrow passage of eg. trees), or a similarly metaphorical long view: a long-term view of the future, for example.
Either that or a dodgy operating system.
Comment: I'd say 'vista' was an expansive rather than restricted view, but it's certainly not *different* from 'view'.

It's a nice vista!


What is the best way to Organize MP3s, Photos and Videos?

Question: Do you just use a standard directory structure? Do you use tools to help rename/move files?
Answer: I use MediaMonkey to manage my files, and I am very happy with it.
As far as videos, I take advantage of the folder views and thumbnails to make my folders nice to look at:

A cool trick I only recently learned is that you can just name the image you want to show in the folder "folder.jpg" and it will be automatically used as the thumbnail. This is particularly handy.
Answer: For music, I like the convenience afforded by dedicated apps. It's fine organizing everything yourself at first, but once your collection is reasonably large, it becomes a pain. Personally, I like iTunes for music organization. Yes, it's a bit bloated, but it runs reasonably well on a decent system and the memory usage is a small price to pay for the convenience.
I'm not a serious photographer, so I currently organize the few photos I have myself. I have heard great things about the new iPhoto and also know some happy Picasa users.
Answer: Like Andy, I use iTunes to manage my music. I have set iTunes to automatically organise the mp3s into folders according to the artist and album.
Google Picasa can arrange your photos into folders according to the year, month and week taken. Sometimes it can be really good, but when you are searching for a picture manually it can be hard to find exactly what you are looking for.
Answer: I've been very happy letting the Zune software manage these for me, though I must admit I've not given it very many photos.
Answer: I use iTunes' "Keep iTunes Music folder organised" and "Copy files to iTunes Music Folder when adding to libray"
It copies any new files into <code>[iTunes Music Path]/Artist/Album/01 - Song Name.mpg</code>
On OS X, I also use iTunes for playing music, on Windows I used Foobar2000 (with iTunes for importing/retagging)
Answer: I use Tag & Rename to tag everything and manually sort them in folders separated by genre with sub-folders according to artist. It is because I like to have complete control of my tags and locations that I no longer use iTunes and switched to a Zune like 8 months ago. The Zune software will actually check folders I predefine and (really Apple it can't be that hard, although not having used it for quite some time it's entirely possible they do it now) and the whole process has the perfect level of transparency for me. Letting iTunes copy mp3's I already have seemed quite silly to me so I stopped after about a month.
But back to Tag & Rename for a minute, I'm sure there's plenty of software that duplicate's it's functionality as well or better, but it's what I'm quickest with and it does everything I need. It searches Amazon for info and grabs the album art at the same time. That's really the most functionality I need, plus it lets me rename the files to my preferred format or [track #]-[song title].mp3 among other things.
Answer: For music, an awesome but overlooked option in this space is Helium Music Manager.
Answer: For music I prefer my own directory structure, which right now is structured like: "...\O\Orbit, William\William Orbit [2009-06] My Oracle Lives Uptown\".  I get the appeal of the "just tag everything and let iTunes sort it out!" approach but it doesn't work too well if you want to get at your music from other applications (media extenders, etc.).  I do most of my organizing in MediaMonkey, but it doesn't support some of the tags I want to manage so I have to supplement it with extra tagging in iTunes itself.  Keep hoping they'll fix that someday, 'cause I really do like MediaMonkey, but I also like seeing albums show up in the right order on my iPod.
For photos, I use iMatch to manage hierarchical categories (people, places, etc.) and write the categories and other metadata back to IPTC tags in the files themselves, which are usually in a year-month-day directory hierarchy.


Performing Raster Reclassification in QGIS

Question: Is there a way to perform a reclassify of a raster image in QGIS?
In ArcGIS Desktop you can do that in Spatial analyst Tools→Reclass→Reclassify
Answer: Using GRASS and the r.reclass module, yes.  However, you actually need to use the keyword "thru".
Example:
For a raster elevation grid, to be reclassified into values based on 100m-intervals:
500 thru 599.99 = 500
600 thru 699.99 = 600
700 thru 799.99 = 700
Etc..  And you save that into a notepad text document(with no spaces between lines).  Then when opening the r.reclass module, you will simply load that rulefile into the gui and away you go.
Experience:  I just performed a reclassification on a DEM for my thesis project in Tajikistan over the weekend using this method and it worked a treat.
*Note(caveat):  You might look into modeling this process or even using GDAL to output a *.prj file alongside the output for use in Arc, as the outputs I've seen from this thus far contain no projection definition readable by Arc.  If you're sticking with QGIS, tho, then you should be good-to-go.
One more thing, as with any QGIS/GRASS/GDAL processes, ensure you have downloaded the OSGeo4W Installer which ensures you have everything up-to-date:
http://trac.osgeo.org/osgeo4w/
Answer: I was able to reclassify a raster using the raster calculator
Here the "Habitat" raster is reclassed from continuous values (0-1) to discrete values of 1,2,3
<code>("Habitat@1"  < 0.3)* 1 + (("Habitat@1" >= 0.3) AND ("Habitat@1" < 0.6)) *2  + ("Habitat@1"  >=0.6)* 3
</code>
Answer: QGIS now has two native raster reclassify algorithms
Reclassify by layer - allows you to use a vector layer to dictate your ranges
Reclassify by table - works much like ArcGIS raster reclassify spatial analyst tool.
These were added in QGIS 3.2 see the change log here.
Answer: With the Advanced Interface option of the toolbox, I use the Reclassify Grid Values from the SAGA GIS, It a really intuitive tool with options of reclassification by single value, range and using a table.
I prefer this over the r.reclass because you do not have to create additional files.
Answer: The easier way is to use GRASS (also using the QGIS/GRASS plugin) and the r.reclass module.
You will need to create a reclassification rule file, where you can use the keyword "through" or the wildcard "*" to reclassify multiple values in one rule.
Answer: I guess my post doesn´t aswer the question accurately, but it could maybe provide some help. I haven´t found a simple way to do this in QGIS, like Bryce I use GRASS modules. However, if have ArcGIS but no Spatial Analyst, there´s another great tool: GME (http://www.spatialecology.com/gme/). It´s dependent on ArcGIS and R and has a multitude of really great features, one of them beeing 'reclassify'. Here, just like in GRASS, you need to create a text file containing the class definitions. I´ve used ArcMap to visualize the raster in question in different ways first to get a better idea of what the data looks like. Then I´ve defined the new classes based on that info. Its worked like a charm for me. I don´t know if GME will run on a system without ArcGIS, I´d be curious to know.
Answer: Raster calculator is your best bet if you don't like grass interface


right benchmark for an incompletely diversified international portfolio (for a CAPM): MSCI World or MSCI ACWI IMI?

Question: I want to calculate annual excess returns on portfolios using monthly returns for a CAPM (for the assets in the portfolio as well as for the benchmark), in order to have more information on the correlations, more precise betas.
I want to use the right benchmark for all this.
Many holdings are diversified internationally,
    but not completely, esp. not into emerging markets (over 1999-2007). Is it appealing to use an MSCI all-world
    benchmark (viz. MSCI ACWI IMI GR USD converted into SEK) as people
    "should" have diversified, so all extra risk is, well, extra? Or it makes
    much more sense to compare everything to an MSCI World (
    developed markets only) benchmark?
Full disclosure: This breaks down my longer question into specifics. Please bear with me. From: annual excess returns from CAPM on monthly total returns
Answer: Did the portfolio manager have the option of investing in emerging markets?  If yes, use MSCI All-World.  If the portfolio has holdings based in countries with "developed markets" yet has has emerging markets exposure to revenue/earnings, the convention is to use MSCI World.


Divided difference coefficient of product of two functions

Question: For any function $f$ and distinct reals $x_1,\ldots,x_n$, denote by $f[x_0,\ldots,x_n]$ the coefficient of $x^n$ of the minimal polynomial interpolating $f$ at $x_0,\ldots,x_n$.

Let $f$ and $g$ be real-valued functions defined on the real line and
  let $x_0,x_1,\ldots,x_n$ be $n+1$ distinct real numbers. Derive a
  formula for the $n$-th order divided difference
  $(fg)[x_0,x_1,\ldots,x_n]$ of the product function $fg$ at
  $x_0,x_1,\ldots,x_n$ in terms of the divided differences
  $f[x_0,x_1,\ldots,x_k]$ and $g[x_k,x_{k+1},\ldots,x_n]$ of $f$ and
  $g$, for $k=0,1,\ldots,n$.

For $n=1$, I've found that $(fg)[x_0,x_1]=f[x_0]g[x_0,x_1]+f[x_0,x_1]g[x_1]$. But I didn't find any nice form for $n=2$. If I can guess the correct formula, I'm quite sure it can be proved by induction.
Comment: You'll want to look up the Leibniz formula. See [this](http://www.ictp.acad.ro/anta/anta1/anii2006-2010/2006-1-08-Ivan-06-06-21.pdf) as well.
Answer: the answer is $ \sum_{j=0}^{n}f[x_{0}, x_{1},..., x_{j}]g[x_{j}, x_{j+1},..., x_{n}] $


Determine where styles are used

Question: If i create my own style sheet to modify the style of a class created by microsoft, how can i determine where the style might be used? i have been noticing that changes i make are affecting objects that i did not intend to change, so i'd like to get away from trial and error and take a more systematic approach, if possible.
Thanks
Answer: Not sure if this will help but it certainly dives into the default CSS used across SharePoint.
Heather Solomon
Answer: Dean,
What you're probably seeing is a result of the complex style structure of SharePoint. Often times, instead of seeing class="theclass" you'll see something like class="firstclass secondclass thirdclass", etc. "firstclass", "secondclass" and "thirdclass" get reused on multiple elements, not just the specific element you're trying to change, so if you were to rewrite "secondclass" you may see undesired changes on other elements in the DOM.
There's a few ways around it (depending on the scope of your project). If you're doing a ground up branding, make your own styles vs. rewriting the default ones (where possible). Microsoft prefaces all of their styles with "ms-", so I will typically preface mine with .cust-" or a similar prefix to identify ones that I have created.
If you're simply tweaking some out of the box stuff, then be sure to use the full string to that element when you write your CSS. This will ensure that your markup is only applied to the elements intended. For example, body .ms-xxxx .ms-yyyy div { font-weight: bold; } would only apply to the div(s) within the ms-yyyy class, within the ms-xxxx class, within the body element.
Thirdly, get yourself a good DOM inspector (this will make your work 100x easier). Firebug is a pretty popular plugin for Firefox, though these days I find myself using Google Chrome's integrated tools. If you've got two monitors, run the developer tools on one and the browser on the other. As you move through the DOM in the developer tools, it'll highlight the contained elements on the browser window (if you're unfamiliar with the DOM, this is a godsend). You can also edit the markup live and see what it changes, making your work far more efficient than repackaging and redeploying just to see if two lines of CSS did the trick.

Determine where styles are used


Different notification sounds for sms and email?

Question: Is there a way to use different sounds for a sms text alert and an email alert? I can't find the setting. I'm on HTC Hero, Android 2.1
Answer: You can customize the Notification settings for both Gmail and Messaging in each of the apps separately.
In Gmail press menu and go to More->Settings and look at the Notification settings section.
In Messaging press menu then Settings and look at the Notification settings section.
Comment: Sorry for the lack of description, I'm using Exchange and Handcent SMS. I'll check Handcent a little deeper
Answer: It's important to understand the differences between a platform like Android and the traditional "dumb phone" platform.
With Android, very few applications are "special".  By special I mean the OS is aware of them and treats them differently.  In Android, an application actually has to manage notifications themselves, there's no way for the OS to somehow figure it out and expose a setting for it.  Notification sound customization has to be exposed by the individual application developer, not through Android itself.  When an application creates a status bar notification, by default Android will play the sound that you set in the default Notification setting.  But the application can explicitly provide a different sound to play.  The application would have to manage that themselves (it would be nice if Android allowed apps to register for custom notifications and then it could provide a central location for all of them, but I'm not aware of a facility for doing this).
If a particular application doesn't provide support, contact them and ask them to add it.  Take away a star or two from your rating in the marketplace and explain why you did so.  Many developers actually listen.
Compare that to the traditional "dumb phone" platform where everything is tightly coupled and controlled.  The OS can easily expose settings for individual "apps" because they're baked in and don't really change.
Answer: But, sadly, Skype does not allow one to customize their notification sound.
Does anyone know how to customize the notification vibration ?
Answer: I use SMS Popup to manage notifications for text messages, and leave the email notifications to be handled by the default notification settings. This allows me to set custom sounds, vibrations and LED flashes (hardware allowing) for SMS text messages that separate them from emails and other notifications.
Comment: Sorry for the lack of description, I'm using Exchange and Handcent SMS. I'll check Handcent a little deeper
Answer: In the messaging app, click menu button, Settings, scroll to the bottom and click Select ringtone.
Answer: See below how to change your email notification sound, or how to disable it. My android is 2.3.5, gmail is 2.3.6.
You open the gmail app, menu > more > settings, tap in the account; in the very bottom there's an option "Labels to notify". In my case I have "Inbox", which I'm assuming is default; when you click on it, you have a few options:

"Email notifications" - notifies in the status bar
Ringtone - this is what you're looking for, you can set any ringtone or silent
Vibrate - well, it vibrates ;)


Safari 5.0.3 crashes

Question: I just update my Mac to 10.6.6 and Safari to 5.0.3 now almost every page I load causes Safari to crash, it does well on simple pages like Google but anything with a bunch of images or flash and it loads to about 3/4 and hangs until I force quit. Are there any known issues?
Answer: I haven't heard of any specific issues with 5.0.3 and 10.6.6.
However, there are times when upgrades to Safari will break things like plugins or extensions. I recommend disabling all extensions and plugins via the Safari preferences. Then you can enable one plugin or extension at a time and visit a website that you know will crash your browser. If things work fine, repeat this process for each plugin or extension until you discover the one that is causing things to break. Once you find the culprit, you might have to wait until they issue a new version.
Having said all of this, there is a very good chance your crashes are related to Flash. Flash is a known vector for Safari crashes on Mac OS X and Apple has repeteadly stated that a majority of the crash logs they receive are Flash-related.
Even if you were not experiencing these crashes, I would still recommend getting something like Click2Flash to disable Flash on all websites--this is a great way to get rid of pesky ads. This should considerably reduce the number of crashes in Safari, assuming what Apple says is true. With Click2Flash, you can always whitelist specific websites so you can unblock their Flash content or you can unblock Flash elements on a click-by-click basis (hehce the name, Click2Flash).
Hope this helps.

Safari 5.0.3 crashes


How does one stop sushi seaweed wrapping being too chewy?

Question: When we make home-made sushi, we often find that the seaweed wrapping (or nori) is too chewy.  The seaweed we buy is from the local supermarket, and nothing fancy.

Question: How can we ensure that the seaweed is not too chewy?
Answer: In addition to what Jason says above, which is absolutely correct, nori needs to be toasted to be crispy.  Sometimes you buy it ready-toasted, but sometimes it's not toasted and you need to toast it over an open flame yourself.  How to toast nori instructions and video.
Additionally, I've found that if you live somewhere high-humidity (like San Francisco, where I live), you sometimes need to re-toast nori even if you're buying ready-toasted packets, because it becomes moist.
Comment: Humidity is definitely a big problem for Nori. Re-toasting it is the key
Answer: Don't wait too long to eat it. I'm assuming you're talking about rolls, or makimono, rather than nigiri-zushi. Anyway, assuming the nori was reasonably freshly opened and crispy when you started, that's the main risk you have: within minutes of preparing makimono, the moisture of the rice will quickly transfer to the dry laver. The faster you eat it, the less likely it is to become mushy and chewy.
In the convenience stores in Japan, onigiri, which are, like makimono, also wrapped in nori, are now usually wrapped in a special plastic pouch. If you follow the directions, you can wrap the onigiri with the nori in one motion while you peel off the plastic. This lets you enjoy the crispy texture when you're ready to eat, which is the one advantage convenience store onigiri have over bringing mom's with you. If you make the onigiri at home, you'll usually end up with moist, slightly chewy nori when you're finally ready to eat.
Answer: As everyone has said, assuming the nori is dry enough to begin with, the problem is moisture getting into the nori from the rice. But the problem might not be just moisture transferring because you let it sit too long, but rather that the rice itself is too moist. The drying step in making sushi rice is critical, and if you under-dry your rice, you'll have problems.
Especially if your rice is pretty sticky, you may want to try drying it further. From a great Serious Eats article about making the rice:

If all goes well, your sumeshi should come out slightly sweet and tart, full of distinct grains, and have a texture that holds together when compressed, but is not overly sticky.
Answer: To further the answers already given:
Nori starts becoming chewy as soon as rice is applied to it since the rice has moisture thus you want to minimize the time between rice-on-nori to maki-in-mouth.
Besides toasting the nori and consuming the maki roll as soon as possible after producing it, I would recommend one step between those two:
Mise-en-place; not only should you have all your materials/tools/ingredients at the ready, you should have each makimono filling pre-assembled BEFORE applying the rice.  For example, if you have a roll with multiple ingredients in the filling gather enough fillings for a single roll in one pile so it can all be added to the roll all at once.
Also make sure that you have a clean and dry area for assembling, cutting, and plating the maki roll.  Again, keep moisture away from the nori as much as possible.
Answer: Nori is like anything, the more you pay the better the quality. The better the quality, means its usually a bit thinner and consumes better. Cheap seaweed will be a bit thicker and once the moisture gets in it, will be chewy. Generally, the Japanese seaweed is much better than chinese made seaweed, but as its about 4 times the price, most supermarkets only stock chinese. They figure people wont know any better.... They may be right.
Also consume within a few minutes of making and the taste experience will be so much better.
Answer: I use a propane blowtorch to crisp up my sushi.  If you try this, expect to ruin a few sushi rolls before you get it right.
Answer: https://www.youtube.com/watch?v=746lrMDFkGA
it looks like they put the rice on the very end :D so It has no time to get moist, to help tham they are using special foils , the same is with onigiri wraped in crispy nori.
Comment: The video shows an apparently pre-made convenience product. I don't think that this answers the original question.


Updating 3rd Edition Shade to 3.5e

Question: I tried the other day to get my DM let me be a Shade (a template from page 314 of the Forgotten Realms Campaign Setting, a 3.0 book) for a new campaign. He looked at its abilities and said there was no way that it should be just LA +4, and I agree. I would like to know how to update this 3.0 edition template to 3.5e so it they can be used without unbalancing the game.
Answer: I wrote about this for Dragon magazine!
The shade has a 3.5 update in Dragon #322 (August 2004). It's divided into a Savage Species style progression for the article, but is otherwise functionally identical to the version in both the Forgotten Realms Campaign Setting (2001) and Races of Faerun (2003), except for the following changes:

Level adjustment is +4, concurring with Races of Faerun rather than the original FRCS (+2) or the FRCS 3.5 errata (+5).
The shade can only use its invisibility power on itself.

However, the shade's ability set is extremely good, and I'd think very carefully before allowing it as a PC race. It gets flat bonuses to saving throws, skills, attack, damage and AC that ease the penalty of level adjustment considerably. Fast healing lets him heal to full between combats, for free. His hiding becomes exceptional. In dungeon campaigns, you rarely encounter daylight, so the shade rarely loses his powers.
That said, if you often fight encounters in bright light so that the shade can't use his powers in every encounter, I actually consider it balanced at +4. The invisibility ability consumes a standard action so it's not as good as plain sneaking, and what you gain in defensive abilities (saving throws, AC, spell resistance and improved hiding) you lose in hit points and class abilities. The control light and darkness-reliant abilities hinder allies who can't see through magical darkness.
Answer: In General
Generally, see the other question How compatible are books for D&D 3.0 and D&D 3.5? especially the first answer, which has links to the conversion docs.
Shades
For this template in particular, it's a little complicated. The FRCS errata document adjusted the template's LA to +5. There's a newer version as an actual PC race that's LA +4 in Races of Faerun.  The D&D Wiki has a fan 3.5'ed version with various LAs noted.
Also see the Shade wikipedia article for some Dragon mags it's appeared in that might help.

Updating 3rd Edition Shade to 3.5e


Would it be possible to generate the original data from a SHA-512 checksum?

Question: So, I have a file that is XY Exabytes big. I create a SHA-512 hash from it.
Are there any theoretical chances that I can retrieve the original data just from the sha512 hash?
Also, are there any better hashes then sha512?
Answer: No, because a  hash behaves (simply put) like a lossy compression function.
Meaning: you can use a hash like a sort of checksum, which enables you to identify and compare data. Using hashes, you can see if data has been modified (which, if re-hashed, would show a different hash as a result), or if two or more data packages are the same (every data package you hash will produce the same hash if the data is the same too).
But: you can not recreate the original data that was hashed. For that, you would need a (loss-less) compression function like you might know it from ZIP files.
So, no, you can not recreate the original data from it's hash. The only thing a hash is good for is to compare it with other hashes to see if the hashed data is identical or not.
To give you a real-world perspective on hashing data and your question about "extracting" the original data from a hash: expecting someone to be able to reproduce the original data from a hash, would be like asking someone to create a nice dinner for all of us while only having a receipt available.
The only option to try to recreate data that results in a predefined hash, would be to "brute-force" it with a trail-and-error approach where you create random data sets, hash those, and hope that they produce the same hash you've got. While such a brute-force method works with small data packages, it won't work for big data-sets as you describe them since it would take too long until you "by chance" happen to produce exactly the same data-set that once existed and which produced the originalhash. Good luck with that... you can safely expect to waste a life-time trying to get that one lucky match that fits a specific, predefined hash.
While I'm at it: it might be interesting for you to know that older and mostly broken hashes (MD2 etc) are known to have certain weaknesses that result in so-called "hash collisions". Such hashes are broken because those hash collisions mean nothing else than  that two different data-sets produce the same hash, which should not happen as a hash is expected to produce a unique values for different data-sets. But that's just additional knowledge as hash collisions merely show the related hash fails it's job; they can not and will not help you recreate the data either. Why? Because a hash is something like an identification tag. It does not hold all the hashed data, and can therefore not reproduce it in any way.
Answer: Your wording is important: "retrieve the original data just from the sha512 hash" - the answer to that (strictly speaking) is no.
The best you can do is to try hashing a given number of possible byte-combinations (eg, the contents of the file) until you find an output that matches your original hash.
For a short byte-string, this attack is viable (this is why simply hashing a password and storing it in a database is not considered secure).  However, brute-forcing an exabyte of data to find a corresponding hash is way too expensive to be considered realistic.
As for your other question - it's too subjective to answer.  Suffice to say, sha512 is considered strong and you should feel confident using it.
Answer: The short answer is no.
The longer answer is that there may be an infinite number of matching plaintexts however finding one is expected to be very time consuming for a given hash.
Answer: Hash functions have several security criteria, one of which is called pre-image resistance. Pre-image resistance means that given an output hash value $h$ and hash function $H$, an input $m$ such that $h=H(m)$ cannot be computed efficiently.
SHA-512 is currently in good security standing. There are no practical pre-image attacks, which means that, no, the original data could not be calculated.
(As an aside, note that SHA-512 is 512 bits long. You cannot in general compress a string much longer than 512 bits to something less than 512 bits, so many, many messages will output the same hash. Even if SHA-512 were weak and gave information about the original message, at a minimum only partial information could be extracted since the attacker would have many potential strings mapping to $h$ and wouldn't know which was the original.)
Answer: The answer depends on what the XY Exabytes big data contains. If it contains very small amount of information, it may be possible for attacker to find the correct input by a trial. Maybe the XY exabytes of data is just some large 8K resolution video available from specific http://xxx.xx.xxx address or just full of zero bits, or ...
In case the XY Exabytes big data contains significant amount of information, then it'll be practically impossible for any attacker (with current knowledge) to be able to find the data matching the hash.

BTW, calculating SHA-512 hash of very large data takes substantial amount of time. SHA-512 hash does not allow calculating blocks in parallel, but each blocks needs to be calculated as a chain. To calculate SHA-512 hash of one exabyte takes somewhere around 100 years using a modern PC. (Expect somewhere around 300 Mbytes/second from quite good PC). Therefore, attacker equipped with modern PC is actually limited to trying calculating something based on recalculated results. Even attacker with custom hardware is likely going to have some issues with the amount of data to hash.
In fact so are you. How do you produce the hash for the large data in the first place? Expect it to take a while.
If you have data this large, the SHA-512 algorithm may be impractical for other reasons than security. The hash is very strong, but calculation will take long time. Maybe you'd like to use hash tree (using e.g. SHA-512 as hash function). Then the result will be different than using SHA-512 hash over the entire data, but the calculation can be parallelized to make the task practical again.

The SHA-512 is not compression function. But if the data exists somewhere (e.g. in the Internet or maybe hard disk of somebody else, or on a book), it is most likely easier to retrieve the data from the alternative source than recreate it from the hash, especially given that there are infinite number of other possible inputs of same size which give the same hash.


Should I focus on gaining strength or weight?

Question: I am underweight and only able to do 3 pushups at best. I am wondering what I should focus on: getting stronger or gaining weight?
Comment: If you gain muscles you'll gain weight too, isn't that great?
Comment: More detail on your height, weight, and goals would help.
Comment: What good is muscle if you look fat? Try to gain muscle weight not fat weight.
Comment: Don't put off starting because you're afraid you'll make a mistake. Having said that I have to ask if you think you're healthy - no diabetes, anemia etc. You sound a little worried. Pushups are hard - no shame there, but with obesity such a problem, perhaps you should keep a food diary for a few days. You might be pleasantly surprised to see that you are just under eating. All the best!
Answer: Focus on getting stronger.
You may also gain weight (if you're underweight), but it will just happen naturally when you lift weights and feed yourself enough to support your strength gains.
Comment: I'll see if this works. If it does, I will accept your answer. Thanks for answering.
Answer: I think this also depends on your age.  But putting that aside you should treat yourself to whatever you can get your hands on and eat the motherload out of it.  Then get yourself in the weight room, decrease the cardio to a minimum, and hit some solid weights.  Don't worry about any strict programming in training, merely focus on doing something.  After the body goes through the adaptation process you can look into certain workouts posted in t-nation or even bodybuilding.com.  Any of those will work.
As for diet add olive oil to everything, have protein shakes like no tomorrow, try to drink a half of gallon a milk a day, eat eggs like their your girlfriend.  After you get a good increase of quality protein meals in your system, have hit the weight room 3-4 times a week, diminished cardio then look into refining your structure.  It will come naturally since you learn how your body reacts to certain movements, meals, etc.  You will build an excellent rhythm after a few weeks and months and fall in love in training.  Here's a trick: Try to really focus on a heavy protein diet and training for 14 days straight.  You'll kick start a habit ritual in your system and everything else will seem easy from then on.
After training for 3-4 years on a very consistent basis you can really drill down the details that will help you get your squat over 600pds and get your bodyfat % below 9%.  Then you're on fire and will look back at your post and laugh at your 3 pushups.  Until then it's being super consistent, have a big freaking breakfast for quality energy throughout the day and punch it hard like Chewie did.
Answer: Well by gaining weight and not strength essentially means you'll be gaining fat???!! Meaning you may not be able to do those 3 press ups at all.
Focus on strength - check out my answer on a previous question:
Is this program good to achieve functional strength and fitness?
Train simple and hard, eat and rest!  Good luck
Answer: Honestly, I think whether you are over or under-weight it is never healthy to fixate on the scale.  Total body weight is like a thermometer, it only tells you if something is wrong--but it doesn't tell you what it could be.
Gaining muscle requires that you work hard, and eat a lot of food.  For some reason, there are people who's bodies tell them they had enough food very early.  Other people whether through years of ignoring the full signals or just genetically don't get that feeling as quickly tend to pack on weight.  The hormone most associated with this affect is Leptin.  If you struggle to put on weight, your body either makes too much of it, or is too sensitive to it and you stop eating before you can gain weight.  If you struggle with gaining weight, then the body either doesn't make enough Leptin, or it is too insensitive to it.
Leptin, like insulin, is sensitive to carb intake.  Also like insulin, overstuffing yourself with carbs over time will make you insensitive to that hormone.  For people already overweight, backing off carbs for a few weeks will help restore some sensitivity.  If you are underweight, you may want to pack up on carbs during this time.  The purpose is to decrease your sensitivity to leptin.
That said, make sure you have the physical activity to match the food.  Work hard to the point of depleting all the energy from you muscles, and then eat a meal with a decent amount of protein, but go for a lot of carbs.  It really doesn't matter at this point what kind.  The bulk of what you eat will go into your muscles to replenish what you need.
So if you work your diet like this:

Protein: ~1g per pound total body weight.  remains constant--easy to figure out
Carbs on rest day: keep it low.  No more 0.5g per pound total body weight.
Carbs on training days: ~1g per pound total body weight, most after training
Fat: fill in your caloric needs to move towards your weight goals

You should be able to get bigger and increase your body weight in a way that still looks good.  The same structure can be used to lose weight--but in that case you should probably take 10 days and keep the carbs at or below 30g, and on rest days keep the carbs as low as 30g.