How to defeat a much stronger and bigger opponent?

Question: I'm going to be undertaking a karate competition and one of my fellow club members is also attending. They are much larger, stronger and powerful. Is there any way I have the slightest chance in defeating him? Either by technique or by A certain strategy throughout the fight?
Comment: You'll get better answers if you provide more info.  This full/semi/non contact?  What code/rules?  What thoughts do you have yourself about your possible advantages over him? Are you faster, more flexible, better technique, lighter on your feet, more stamina, more experienced, better conditioned etc?  Does he seem tough mentally?  What's happened in your sparring sessions?  Have you seen other people spar him - perhaps people who're smaller but more senior?
Comment: Skill is more important than size. Do not think some trick will win. Never forget what it says in the Book of Five Rings: "Do not think dishonestly. The Way is in training."
Answer: My advice whenever you're facing either someone who's more advanced or bigger is to concentrate on your basic, "high percentage" techniques and be as precise and as quick as you can. Stick to things you know well, and avoid any temptation to do something "cool" or something you've just recently learned.
In another answer, I discussed what "high percentage" techniques are:

By "high percentage", I mean things that have a high ratio of scores over attempts in actual competition sparring. As opposed to "low percentage" techniques and strategies which have a low ratio of scores over attempts.

Specifically, I said this of point sparring:

As a general rule, striking techniques which can be used in the most situations and are fast, direct, and simple to perform will be the highest percentage ones. For hand techniques: jab punch for boxing or reverse punch for karate and Taekwondo. For foot techniques: low/mid-section round kick and front kick. I would also add side kick if you're talking about Taekwondo in particular, but not for most other kicking arts (Taekwondo really likes to use that kick).

So your main focus for preparing for this tournament should be on basic techniques - the ones you learned in white belt. That would be the basic jab punch, the reverse punch, the round kick, the front kick, and the side kick. Keep your kicks to the mid-section, rather than aiming high. Work on your blocks and keeping your guard up. And stay active, always moving sideways (not backwards), to the less dominant side of your opponent (if he's right-handed, that means moving to his left side, which is your right side). Staying active keeps him from getting a lock on you as a target. And moving to his less dominant side means he'll be less precise, slower, and not as strong.
This sounds boring, but boring wins.
Another thing to do to help prepare you is to try sparring bigger opponents. You may find that the distance you need to maintain (due to his longer reach) makes it hard for you to get in and land a kick or a punch. You're going to have to find the right timing that will allow you to enter, kick or punch, and get out without being hit.
Usually the best timing in general is "half-beat" timing, as opposed to "full-beat" timing. Full-beat timing is where your opponent does something, you block, then you do something, he blocks, and it repeats. In "half-beat" timing, you begin your technique when your opponent has just started doing his. It causes him to have to stop what he's doing, figure out what you're doing, recalculate an appropriate response, and then execute it. As you might realize, that takes extra time. And it's that extra time that you'll need to be able to get in and out without getting hit. Find that timing, and you may have a chance against someone who's bigger and has a longer reach.
Here's a wonderful example of half-beat timing:
http://38.media.tumblr.com/c5ca32a8015170e8239c0e0deb705d55/tumblr_n053fohPnf1r3gb3zo1_400.gif
Hope that helps, and good luck!
Answer: Asking for a strategy upfront is not going to be beneficial, especially on the internet - we have never met this opponent so all we know is he's bigger and stronger than you (and we have no idea how big you are).
Train hard. Be confident in your knowledge and capabilities. You should start learning to read your opponents - it's an important skill to have, you won't be able to analyze them all ahead of time. Even if you do know them there is no guarantee they will behave the way you expect on competition day.
Learn to spot and react to telegraphing. Learn to move, you should have practiced it enough that it is instinctive. Visualize what you're doing as you train, so your mind and body both know what the move is for. Most of all, ensure your mind is calm when you enter the match - it might sound cliche but it's best if you're not thinking rather than thinking too much.
Answer: Can't add comments yet, but just wanted to say that Steve Weigand has the best answer here.
just wanted to add that with time you should incorporate some "dirty boxing" into your arsenal when fighting bigger opponents (5ft5 person here). There's no other way of beating somebody who has been training as long and as good as you, and weighs 10kg+ more.
Block with your elbow strikes instead of normal karate blocks.
Block their kicks with your knees, or with knee strikes.
When coming out of the close quarter engagement/clinch, don't just move out. You have to "hook" your opponents ribs with your knuckle strike or better with a thumb strike to maximize damage to a single point.
All this is meant to do is to deter your opponent from strike you.
You will start to notice some hesitation.
So if you mix what Steve Weigand advised and what i explained here. You should be scoring 1st and 2nd places in no time ;)
Good luck.
Comment: Those are some useful tips. Purists might not like it, but this is fighting and whatever helps you win is good. Or at the very least, one should take note that techniques like this exist.


EMT Conduit Strapping to a Narrow Joist

Question: I going to run 1/2" EMT conduit on the bottom of a joist. The standard straps I have are too wide to get both nails/screws in. I would prefer to run the conduit down the center of the joist. I wouldn't be able to do this with a single nail/screw strap. I was thinking of using a thick metal tape with holes every inch or so in it. I have some holding up my gas line. Do they still make it? If so, what is it called? Or could I used plastic zip lock ties instead?
Comment: Some call it plumbers tape or strap, they do make single hole straps that would look better and only take 1 screw, I know looks under the house don't matter but I have had inspections where they wanted listed straps.
Comment: The bottom of a joist is not a particularly well guarded place to run EMT, though it is fairly tough.  Could you add a couple slight bends and have it ride along the side of the joist?
Answer: Try using a minerallac strap. I really not much for perforated strapping. See image although it is legal.

Hope this helps.
Answer: It is called perforated strapping and it comes in steel or a plastic material. That would be OK to use.
Answer: I hate these but they're what you asked for.
EMT Drive Strap

(Home Depot)
Answer: What about something like this Conduit Hanger

EMT Conduit Strapping to a Narrow Joist


Assign random color to spline list

Question: I created a spline list following this guide. Now I want to assign a different color to each spline using Cycle's random node, but it doesn't work because the splines are grouped into one object.
My solution to this is to instance the spline object and loop through each instance, creating one object for each spline. This worked when I checked Deep Copy, but did not animate. I animated the start/end for each spline and need that to be carried over as well. If I do not check Deep Copy, it duplicates the same spline, stacked on top of itself.
What other way can I do this? Or can I assign random colors to splines using animation node?
Below is a screenshot of my entire node setup.

Also, in the screen shot you can see when viewed from the instance, each object has a list of 50 splines, but when viewed through the loop, there's only 1 spline. What's the reason to this?
I am using AN 2.1, python 3.7.
Answer: You should use the Object Instancer node to create a number of empty objects, this is done by disabling Copy From Source option. Then loop over both the objects and the splines and output the splines to the objects as follows:

Assign random color to spline list


How increasing the Signal to Quantization noise increases the resolution of ADC

Question: Inside ADC we have a quantizer, when the sampled signal is passed through it, the signal values get discretized. The number of discrete levels in which the signal is discretized is called the resolution of the quantizer. I read that if we oversample the input signal and then pass it through the quantizer and pass the output again through a low pass filter called decimation filter the signal to quantization noise (SQNR) of the quantizer improves resulting in better resolution of the quantizer.
How is this possible? True that the SQNR improves but how does that  affect the resolution of the Quantizer? Isn't the number of levels inside the quantizer fixed by its hardware and thus resolution of the quantizer i.e., the number of dicrete levels in which it breaks the input fixed?
Comment: The digital decimation filter is driven by high rate, low resolution data. The filter averages that data to provide higher resolution, lower rate data at its output.
Answer: There are two aspects to how this works.  First, since the signal is oversampled there is a great deal of correlation between samples that we can take advantage of via the low-pass filter.  The noise, on the other hand, has no correlation (assuming it is white noise), and thus will often destructively interfere with itself.
Your question seems to be more about how the actual bit growth happens though.  If we have, for example, a 12-bit ADC, how can the number of bits grow to, say, 16-bits?  It is actually very simple.  FIR filters (and the same basic argument applies to IIR filters as well) essentially do a lot of multiplying and adding.  When you multiply two 12-bit values you get a 24-bit value.  When you add two of those 24-bit values together you get a 25-bit value.  The non-scaled bit width of a FIR filter is:
$$
(bw_i * 2) + log_2(numTaps)
$$
where $bw_i$ is the bit width of the input and $numTaps$ is the number of taps in the filter.  As you can see, if we have 12-bit inputs and we want 16-bit outputs there is no trouble getting the 16-bits.  You usually have to scale down the filter outputs, in fact, to restrict them to the bit widths that you want.
Comment: Recently I'm trying to **simulate** an oversampled quantizer (+noise shaping). I first create an oversampled signal to simulate the continuous input, then quantize it to N bits, say N=3, now I have a digital signal with 8 distinct levels. Now comes the LPF! LPF coefficients are 64 bit floating point values (using MATLAB's native data type) so the convolution physically produces a 64 bit output. But I try to **find** the **entropy** of filter output from which I'ld deduce the equivalent bit-size (before and after decimation)... It doesn't work? It says 12 bps, the truth being 8? any helps?
Comment: The problem is, I want to actually **compute** the SNRQE at the final stage (after the decimation) but to do that I've to **re-quantize** the output of the decimator. And in doing so am I artifically introducing entropy changes? For example if I'ld re-quantize it to N-bits again then no gain happens. I've to requantize to a **higher** number of bits, but how do I find (**measure**) that value, instead of relying on the **theoretically calculated** number of saved bits? I try to use the actuall **error** in finding that, but then **sample** syncronization problem happens due to filtering?
Comment: Another problem is on the decision of  "at which resolution shall we allow the artihmetic operations of filtering", furthermore when there is noise feedback for spectral shaping, at which resolution shall I simulate those operations as well? In numerical simulation of an oversampled ADC one has to be careful about **distinguishing**  between the entropy based information caried by the digital signal at N bits and the number of phsyical bits that represent the quantized values of the sampels being involved... any helps on the strategy?
Comment: @Fat32 How much does your LPF decimate?  I am not an expert on this, but I believe that for every decimation by a factor of 2 should theoretically garner you up to a bit of resolution.  I suggest starting your own question to get help with the problem.
Comment: I'm setting it to anything from M=2 to M=256. (LPF impulse response gets extremely long for high M) The problem can be solidified like this: given an analog signal $x_a(t)$ pass it through an ADC with 4 bits and then apply DAC conversion to produce analog $y_a(t)$, now resample this $y_a(t)$ by 16 bits ADC. So your ADC is physically outputting 16 bit quantization, but the samples do not (cannot) carry such an Entropy. As their entropy was constrained to be 4 bits before. Therefore the entropic information limits should be carefully investigated for a reliable simulation of an ADC
Answer: Here is a very simple example demonstrating how we can get increased precision by taking more samples and then filtering (averaging):
Consider "truth" to be a constant 8.2, we quantize by rounding to the closest integer, and we oversample and average (filter) in an attempt to improve the precision of the result.  If there was no noise, the result of the quantization would be:
8 8 8 8 8 8 8 8 8 ...
Clearly, no matter how much we oversample, once we average we will still get 8. No improvement in precision!
Now imagine the same with some zero-mean noise added with a uniform distribution of +/-.5; now prior to sampling the signal will vary from 8.2-.5 = 7.7 to 8.2+.5 = 8.7.  Now we get 8's and 9's, with 8's occurring much more frequently
8 8 8 8 9 8 8 8 8 8 8 9 8 8 ...
The higher the oversampling rate, the more consecutive samples we can average, and the closer we can get to "truth".
This also exposed a very important criteria for allowing this to occur in sampling a DC signal specifically; you must have noise present that surpasses the smallest quantization level. When using a waveform that is changing with time, there is usually sufficient variation in where the waveform crosses a bit sampling decision boundary (as evidenced by the quantization noise that results in being white and uniformly distributed). With sufficient levels of quantization and a high sampling rate compared to the waveform's frequency content, this is a reasonable approximation.
This gives a very high level view to give you an intuitive feel for how we can add bits by oversampling, and why systems may add "dither" to help achieve better dynamic range.
Specifically for "normal" data converters with a white noise process (meaning excluding "noise-shaping" converters such as Delta-Sigma modulators) , you expect to get a 3dB improvement (1/2 bit) every time you double in sampling frequency. Data converter analog effects such as differential and integral non-linearity will limit how far you can take this improvement through oversampling.


Why is it necessary to avoid even traces of moisture from a Grignard reagent?

Question: This fact was written in my text book. I wonder why that should be so.
Answer: Grignard reagents are highly reactive and react with any source of proton to give hydrocarbons. Even water, alcohols, amines are sufficiently acidic to convert them to corresponding hydrocarbons.
$\ce{RMgX + H2O -> RH + Mg(OH)X}$
Where, $\ce{R}$ is a hydrocarbon.
Answer: Aside from decomposing as described, Grignard formation will not initiate given a trace of water.  There is a bulky lore of getting the things started even under carefully dried conditions.  Consider an oven-dried roundbottom containing absolute ether, Mg turnings, and a small portion of the total amount of  alkyl halide.  It routinely sits there doing nothing.
Crush a turning to expose fresh surface. Add a small iodine crystal to corrode the Mg.  Heat the thing, oh yeah, then scramble for the exotherm.  Making Grignards spawns neurotic behavior like lucky lab coats, flame drying everything, always adding a drop of freshly distilled $\ce{Me3SiCl}$ (always adding a drop of old $\ce{Me3SiCl}$), saving some of the last batch to set off the next.
Comment: I have engaged in much of the neurotic behaviour described above. I now just try to use organolithiums for all instances where Grignards are proposed.
Answer: The first answer doesn't really answer the question. It merely shows, correctly, what happens to water which is introduced into a Grignard solution already prepared.
The second one hints at it. Water passifies the surface of the Mg (presumably coating it with MgO or Mg(OH)2) making it almost impossible to initiate the reaction. I have found that the techniques used in answer usually work.
Comment: The grignard reagent (magnesium halide) has then already formed. The passivation of the magnesium surface will not play a role.


Dogs in islam is haram

Question: Not all dogs are eligible for hunting, protecting crops etc. , my question is what are the purpose of these dogs if we can't have them around?
Comment: You might as well ask what the purpose is of mosquitoes if we can't use them for hunting or protecting crops; the world's full of animals which we can't use like that, why single out dogs here?
Answer: Let me clarify a few myths and make a few points:

It is NOT haraam to own a dog, though it is not hygienic to keep a dog in the house.
It is NOT haraam to touch a dog or any other animal. If the saliva of a dog touches you or any part of your clothing, then it is required of you to wash the body part touched and the item of clothing touched by the dog's mouth or snout.
It is incumbent upon all Muslims who own animals, whether for farming or work purposes or as pets, to provide adequate shelter, food, water, and, when needed, veterinary care for their animals. Arrangements must be made, if one is going to be away from home, to have one's animals taken care of as well.
It is haraam to keep a dog or any other animal on a short lead for long periods without food, water, and shelter. Dogs need exercise and are social creatures who form organized "family" structures in nature. Dog owners therefore need to spend time daily with their dogs.
It is cruel, and therefore haraam, to keep any animal in a cage so small that it cannot behave in a natural way.
Fireworks cause untold suffering to most domestic animals because of their acute sense of hearing.
It is haraam to participate in any blood "sport," like dog fighting and trophy hunting.

No animal has been cursed in any way. Animals are referred to in many instances in the Qu'ran. In Surah Kahf, mention is made of the companions of the Cave and their dog. (S18: 18-22)
We would love for Allah to bestow His mercy upon us, so let's show mercy and compassion to all His creation. This will also give non-Muslims a true reflection of Islam, aiding da'wah.
Comment: Bit OT, but can the somewhat negative view on dogs, pigs and shrimps (in the Old Testament), have something to do with the fact that these animals could scavenge on human corpses (eg. after a battle or a boatwreck)?
Answer: Slightly aside, but when you go out you are mindful of not stepping in animal filth such as dog / cat faeces or urine. A dog isn't careful. How can you be so sure when it enters your home it hasn't stepped in that or rolled around in the grass in the park in that? Further dogs don't wipe or wash after their toilet nor wear underpants. You wouldn't sit on your sofa or car seat if you didn't wipe or wash and didn't wear underpants or trousers? How can a dog then be allowed to sit on the sofa or go in your bed (yuk)? How can it then be hygienic to have a dog in the house? Same goes for a cat etc. Pet owners have overlooked these aspects completely in my humble opinion.
Comment: Welcome to Islam SE. Answers should be elaborate and focused on addressing the question. Claims should be supported by evidence. Please visit our [tour] in the [help], and refer to [answer].
Comment: Dogs can be and are  trained to poop outside the house, they are very intelligent animals. `Further dogs don't wipe or wash after their toilet nor wear underpants. `, I hope you are kidding

Dogs in islam is haram


Difference between "empezar" and "comenzar"

Question: What is the difference between empezar and comenzar? Is one more formal than the other?
Comment: DerPolygott33 I'd suggest that you accept @c.p. as an answer instead of Quintrala's since the votes and comments support that one as a more precise and documented answer. Answers from us native speakers are good as reference, but a better answer is one supported by references and research.
Comment: I uphold @DGaleano 's request. Quintrala's answer is confusing and false.
Answer: Absolutely interchangeable as Eric states in his answer. I agree. However, I'd add that empezar is a little more common than comenzar. Actually Ngrams says in written Spanish, in the last 60 years, the frequency of use has been reversed. That is:

And comenzar is slightly more formal. But I have no other sources than native speaker's gut.
Answer: An existing answer, sadly the accepted one, has stated that empezar is more widely used than comenzar for things like "a project". That just doesn't make sense
My conclusion is not that some is used more than the other. The difference is not significant enough as for being considered as a definitive answer. That's my point.
Answer: I use them interchangeably, but if I had to distinguish I'd say that comenzar is normally a group or event, and empezar is normally a third person.
That being said, ?puedo comenzar? is perfectly acceptable so they really are pretty interchangeable.
I speak Mexican Spanish as a caveat.
Answer: Spanish verbs "comenzar" and "empezar" are synonyms. There is no difference between them. Also "iniciar" means the same. Do not confuse trying to state differences where they do not exist.
Answer: I guess most of the times are interchangeable, but take care with set phrases like for example

no tengo ni para/por-dónde empezar
no empieces a hacer el tonto",
¡No empieces!

In these cases, using "comenzar" instead of "empezar" would sound sort of funny.
Answer:
Empezar, as Eric explained is related to events. Like the beginning of history or the beginning of a work project.
Comenzar is more personalized towards a subject.

Though they mean the same, we Spanish speakers tend to use each in those contexts.
Comment: The point is that, what your are writing is false: you don't say *empezar un proyecto* more often than *comenzar un proyecto* as you stated.
Comment: *Comenzar un proyecto* is absolutely valid. Why do you state the contrary on your answer?
Comment: I am basica lly stating the most used, not the valid c.p.


How do I appropriately use inline citations for multiple quoted paragraphs?

Question: I'm writing a paper where I have a number of sentences across a few paragraphs, all from the same source. How should I use inline citations in this situation? Should I put them after each listed fact in the sentence at the end of each paragraph, or at the end of all of the paragraphs? The paragraphs are all topically related, but each one is different enough to be a sub-topic. In case it's relevant, the topic being discussed is technology, the paragraphs detail how companies using that technology.
Comment: Your original question was migrated [here](http://writers.stackexchange.com/questions/6488/when-citing-information-from-a-source-do-i-need-multiple-citations-for-multiple); check there for other answers. As this is also relevant on our site, it's welcome here as well.
Answer: From what I've seen, the only situation in which you would use a single citation following multiple sentences is if it's obvious that you're quoting that source verbatim AND the quote is uninterrupted. If you're using your own terminology OR the quote is interrupted, you should cite each sentence separately.
This becomes obvious when considering the purpose of a citation. Citations are there to answer the question, "who said this?" If you're quoting someone verbatim, and it's obvious you're doing so, then you only need a single citation, as the reader will infer that it applies to the entire preceding quote.
On the other hand, if you have multiple claims throughout a paragraph, after each claim the reader will wonder, "what's his source for this?" In most cases, you will be using multiple sources, and you will have a mixture of references. However, even if you have a single source for lots of claims, the reader will still wonder after each claim what the source is. You should tell them the source of each and every claim separately.
The exception I've seen—and that my advisor requested I use in my writing—is in the instance of a single logical thought pattern being followed throughout a paragraph or set of paragraphs. If you're describing someone else's work, it can be justifiable to state, "the following is an overview of Bob (2007)", or something to that effect. From my experience, though, that usually only happens in review articles.
Comment: Okay so it is acceptable to have the same citation listed several sentences in a row?
Comment: @DonRigatone - I would say "yes, that's fine". You can also just read through some of the articles in whatever journal you hope to publish in to see whether that's a common occurrence in that journal.
Answer: If you really have only one reference which you take one paragraph to sum up, I'd really advise eykanal's last item (the "exception"):

Tying one's shoelaces with only one hand is notoriously difficult [1]. Although it seemed like an unsurmountable issue a few years back, the recent breakthrough of Smith et al. [2] relied on a few topological considerations which have been clearly delineated by Brown [3], and are summarized in the rest of this paragraph. [Here your description, with claims from Brown, without repeating the reference number]
However, little is known about the influence of the number of fingers used [4] in the tying process. Here, we present a research on tying shoelaces with even-fingered hands.

This is better than having a lot of claims [3] with the same reference [3] written all over one paragraph [3]. However, you need to make it crystal-clear what part is covered by the reference: using the paragraph boundary (and explicitly stating this) is a good way of doing that.
Answer: While not really an answer, this is often an indication of a lack of understanding. The original question used of language like paraphrasing, another indication of a lack of understanding. You should probably show a draft to a colleague asking for specific help.


Cooking food directly on oven rack

Question: Is it common to cook food directly on the oven racks?  I often do this (with a container for drippings) and was wondering if this is common or if there is a better solution.  It has worked out fine for me, but sometimes replacing these racks can be costly.  I do not replace them often, and they are not very hard to clean, but I would like to get some ideas on if I am doing this wrong.
Comment: I have a convection oven and cook all i can on the racks, since air doesn't flow too well through solid trays.  I think I get a better finish on all sides of roasts that way.  I've never had to replace my racks I run the self-clean cycle with the rack in, and then use the dish-washer.
Comment: The only thing I cook directly on the rack is jacket/baked potatoes.  Has to be pretty clean.
Comment: Just out of curiosity, what types of food are you cooking directly on the racks? Something like roasts or something completely different? I have never cooked anything directly on the racks.
Comment: I've cooked bacon.  I've also prepared many different recipes that say to use a grill.
Comment: Why not use a tray? I've never cooked directly on the racks either.
Answer: Presumably the reason you're cooking directly on the oven rack is to let the fat drip down.  If so, do yourself a favour and get yourself a roasting rack.  It's an inexpensive piece of equipment that you place in a baking pan or on a cookie sheet; the food cooks on the rack and the pan/sheet catches all the drippings.  Way better than trying to replace an entire oven rack.
And if you really hate cleanup, you can line the pan with parchment paper or aluminum foil and just throw the rack in the dishwasher when you're done.
Comment: And if you're using the broiler part of your oven, consider using a broiler pan, made specifically for this kind of thing. The juices/fat can still drip away from the food, but it all stays contained and is very easy to clean up. It's a good bet that your oven originally came with a broiler pan, actually.
Comment: Does a broiling pan work well even when I'm not using the broiler?  I was digging through the bottom drawer in my oven and found one of these.  I am considering using it, but I was unsure if this was going to work well for everything that the oven racks are good for.  I do like the oven rack idea.  If there are significant advantages to using an oven rack over the broiler pan, I would consider purchasing one.
Comment: @Naomi: You can, although a broiling pan is almost the opposite of a roasting rack, it's got small openings in an otherwise solid pan.  It's probably worth a try, but I don't find it works quite as well for evenly crisping up food over a long roasting period, and the bottom still ends up a little soggy sometimes.  When you're broiling it's not really a big deal because you'd only be doing it for a few minutes at a time.
Comment: @Aaronut - If you're lining such a rack with foil or parchment, wouldn't that negate the spaces in the rack?  That is, hold the drippings or whatever, to the food similar to how a pan would (or, well, a sloped pan, anyway), or even as much as lining the bare oven rack with foil or parchment?.  Or am I visualizing this wrong?
Answer: I would suggest that the answer is that it isn't common. I would normally use sheet pans/trays and a rack on top of that. It's much easier to put food in and out of the oven that way.
Comment: This is what I do as well.
Answer: Before I got a pizza stone I'd put store bought pizzas straight onto the rack as it gave a better crust.
The only reason I can think of doing it is basically laziness - I'd do it with cheese on toast if the grill pan was too dirty to use.
I'd also sometimes do baked potatoes without a tray as Id cover them with tin foil.
Answer: If you want to continue to cook on the racks in this way there is no need to ever replace them. When mine get really dirty I use this oven cleaner you just put the racks in a bag with the cleaner and the next morning they look brand new. It's probably horrible for the environment but can't be worse than producing new racks just beacuse mine are dirty.
Answer: I roast directly on rack as well using the broiler, mostly poultry(thanksgiving turkey on the rack divine).  I put the bird(breast side down) as close as possible to the upper heating element(my broiler is the top of the electric oven), and i set the temp to 320 or so, then set the drip pan on the bottom rack, as far down as it will go. I check back every 30 mins or so to make sure that that there arent any areas that are burning. I flip the bird right side up at about 1 hour just to brown the skin on the breast side a bit. Once the bird is done(at your own discretion), i let it rest for 20-30.
I dont like the idea of putting a pan directly underneath an extra rack, because in my mind, the pan limits the flow of heat to what you are baking, and still creates a humid environment directly blow that that limits the development of a crispy skin.
The cleaning aspect kinda sucks, but some oven cleaner a hot rack along with some patience is all your need  Personally, i dont clean the rack every time i roast on it, unless i plan to use a pan, or have used a pan on the rack.
Answer: I would simply purchase a wire rack for cooling cookies (not coated) and place it on top of a cookie sheet.  Alternatively, place it across a glass Lasagna pan for more air flow underneath and better drip catching.
Answer: I dont know if it's common, but I use my racks to grill pork chops and steak. I don't like the grilling outside taste so this works for me!
Answer: A leg of lamb slow cooked directly on the rack is delicious and l would never cook lanb in a pan again. Line the pan underneath with foil and the clean up is easy.
Answer: I have never heard of this until 5 minutes ago when I found a recipe for it.I don't thinkit's common and I've never done this but am considering doing it with an 8 lb bone in ribeye roast because I saw a recipe for it to be placed directly on the rack. Someone said it was lazy and many of you said to use a roasting pan, but you're missing the point: airflow. When you use a pan, you restrict airflow and when you combine a pan with a rack, you're still limiting airflow.
I t sounds like a brilliant idea If you want your meat crispy or crusty all over. I don't see why you'd have to replace your oven racks, just take them out and wash them. If you put a pan underneath,that should catch the fat. I have a roasting rack but I'm going to try this for Christmas tomorrow. I suspect my dinner guests will find it odd but I'm keeping fingers crossed dinner will
Be so delicious they'll overlook the cooking method
Comment: The top voted and accepted answer had a roasting rack with more than sufficient airflow. Simply place it over a flat pan that doesn't restrict air flow.

Cooking food directly on oven rack


No GUI after reboot, no obvious errors (openSUSE 13.2, nvidia drivers)

Question: Short version: Rebooted for the first time in months, following daily updates; proprietary Nvidia drivers; no GUI (KDE); no smoking gun (so far) in logs.
Specs:

openSUSE 13.2 (64-bit), fully up to date
kernel 3.16.7-35-desktop
Nvidia GeForce 970

G04 drivers v361.28-33.1.x86_64 (latest version at download.nvidia.com/opensuse/13.2)
but latest version available by direct download from Nvidia is 361.42

Long version:
I have a desktop computer with an Nvidia GeForce 970 video card, and two monitors connected to it, one via DVI and the other one via HDMI.
I am running openSUSE 13.2, which I update almost daily. Currently at kernel 3.16.7-35-desktop, and use the proprietary Nvidia drivers, currently at 361.28-33.1.x86_64, for the sake of games. That is the latest version of the drivers available from the official repository for openSUSE 13.2, although v361.42 is available for direct download and installation the hard way.
Kernel and video drivers had been updated at least once since the last time I rebooted (or even logged out), which was at least a few months ago.
Now I have rebooted, and cannot get into the GUI - KDE.
The console output (on the DVI monitor, which is where grub2 normally runs; the HDMI monitor, which is my primary display, now doesn't get any signal at all. From the boot process is not perfectly consistent in where it stops: sometimes:
Reached target Graphical Interface

Sometimes:
Starting Command Scheduler

Sometimes:
Started SuSEfirewall2 phase 2

But it is always after I Started X Display Manager.
CTRL+ALT+F7 shows a completely blank screen.
1 through 6 are normal console terminals, and 8 shows just a flashing underscore.
I have force-reinstalled the four Nvidia driver packages (G04) to make sure that they are compiled for my current kernel.
Interestingly, some of the package names are 361.28.k3.16.6_2-33.1.x86_64, which suggests that they are meant for kernel 3.16.6-2, whereas I am running 3.16.7-35. And compiling for 3.16.6-2 fails, with files-not-found /lib/modules/3.16.6-2-desktop/modules.{order|builtin}, although otherwise that folder looks the same as the modules for 3.16.7-35-desktop and 3.16.7-32-desktop.
journalctl --full -b

Shows messages from kdm indicating a successful start - e.g.: plymouth is active on VT7, reusing for :0.
And kdeinit5: opened connection to :0.
The only messages I can find in the boot logs that might be a cause for concern are:

NVRM: Your system is not currently configured to drive a VGA console on the primary VGA device. The NVIDIA Linux graphics driver requires the use of a text0mode VGA console. Use of other console drivers including, but not limited to, vesafb, may result in corruption and stability problems, and is not supported.
Registry: Xlib: extension "XEVIE" missing on display :0
QXcbConnection: XCB error: 148 (Unknown)
/var/log/Xorg.0.log

Has only one message, right at the end of the file, that looked in any way suspicious to me:
NVIDIA(0): ACPI: failed to connect to the ACPI event daemon; the daemon may not be running or the "AcpidSocketPath" X configuration option may not be set correctly. When the ACPI daemon is available, the NVIDIA X display driver will try to use it to receive ACPI event notifications.

Booting into Windows, everything works as expected, so I am ruling out an issue with the video card and/or HDMI monitor.
I have not yet tried uninstalling the Nvidia drivers and switching to nouveau, nor manually updating the Nvidia drivers to 361.42.
I can get into the GUI as normal by rolling the system back to an earlier snapper snapshot, but would rather figure out the current issue than potentially lose months of files.
I am willing to dist-upgrade the system to Leap 42.1, but not without good reason to think that doing so would fix the GUI issue. Interestingly, the version of the Nvidia drivers from the official repository is the same for 42.1 as it is for 13.2: 361.28.
Answer: I am now unblocked; I ended up manually installing the nvidia drivers at v361.42 (vs 361.28 in the repo).
Note that I cross-posted this question at:
https://forums.opensuse.org/showthread.php/516893-No-GUI-after-reboot-no-obvious-errors-%28openSuSE-13-2-nvidia-drivers%29
I will update this answer here with responses to my follow-up questions there (exactly what went wrong in the first place, etc.), if any are forthcoming.
Comment: Edward, I see you have not accepted your own answer, may I know why?


Plug a 5 V fan to GPIO 1 and 2

Question: Regarding to the following picture, I understand that I can plug a 5 V fan by plugging it in between pins 1 and 2.
Is this right (+ on 1 and - on 2?)?

My need: Plug a 5 V fan to run all the time the Raspberry Pi is on.
Comment: The pin numbers are all wrong in the diagram. Please post a more suitable image.
Comment: https://www.raspberrypi.org/forums/viewtopic.php?t=14153&p=158827 Topic similar to your question. Should work I think.
Comment: Your diagram is missing some information... not helpful.
Comment: It also depends on the current needed to run the fan.
Comment: Video demo: https://www.youtube.com/watch?v=jfzOjDSyjuo by someone.
Comment: Have you looked at a good GPIO chart?  On the Rpi3 you have 5V and gnd on GPIO pins 4 and 6, right next to each other.  Or, if you want it to be quieter, you have 3.3v on pin 17.
Answer: The diagram does not show pin numbers.  Neither can I find anything on the diagram labelled 1.
The diagram does appear to correctly label the ground and 5V pins.
You can power a 5V fan by connecting its power leads to a 5V pin and a ground pin.
It will be on all the time as you can't switch the 5V pins on or off.
Do not try powering the fans from a gpio.  The likely result will be one or more broken gpios and possibly a broken Pi.
Comment: Yes, it'll rotate continuously.  To control the speed you'd need to find a different solution.
Comment: OK, so if I plug my fan on a 5V and a ground. It will work in continue ?
Comment: The new raspberry pi 3 has 2 AMP power supply, you can power up small 5V fan with it. I have a case with fan for r-pi 3, works good.
Answer:
This is right? (+ on 1 and - on 2?)

No, because you say that you have a 5V fan, and yet pin 1 is 3.3V, in addition to the fact that pin 2 on your diagram (which is in fact pin 3) is an I2C pin.
You should connect a 5V fan to the correct pin 2 (which is opposite pin 1 - the red pin in your diagram - not next to it) which is 5V and pin 6 (the black pin in your diagram) which is GND.
Raspberry Pi 1 GPIO

Raspberry Pi 2 GPIO
Answer: You may begin to find that the while using a fan the entire time takes away from the normally quiet nature of the pi. As such it may begin to become annoying. I propose a different solution one that you can customize to come on at a certain time or when the temperature reaches a given point.
You can setup the fan + lead to the 5v and connect the fan - lead to drain lead of an n channel MOSFET. Then connect the gate lead of the MOSFET to a GPIO pin of your choosing. Then connect the source lead of the MOSFET to your ground pin on the pi. In addition I would suggest either soldering on a 10K Ω resistor between the gate and source leads or using a GPIO with a built in pull down resistor and setting it in the code.
From there you can write your own fan script to control it. I have made one that you can use if you're so inclined. You can change the values and the logic to better fit your needs. The script can be found here:
https://github.com/bar1792/Raspberry-Pi/blob/master/Python/Cooling%20Fan/OSMCFan.py
In this example I have used GPIO 25, as per the BCM diagram and not the actual PIN number.
With the setup purposes above you are able to use software PWM to run the fan at submaximal speeds to keep it quieter or set it to fully on to maximize cooling.
I have used a similar setup in my media center and included 2 fans one for pushing in cooler air and one to extract the warmer air from the box. With the stress testing with the command stress I was able to keep the pi under 60 degrees C in an enclosed box with heatsinks and running a hifiberry amp+. This may be overkill for your needs, but if cooling is a real issue I find this solution to work best for cooling and silence when cooling isn't an issue.
If you need help with using such a file or setting up the FET feel free to ask.

Plug a 5 V fan to GPIO 1 and 2


Back up sump pump not working

Question: I installed a backup sump pump following the instructions.   The backup pump will turn on  but does not eject any water from the pit, the water only swirls around.     The pipes aren't clogged: the main pump works great and it is new pipe on the backup.     I tried drilling a hole in the pipe above the backup and water will shoot out the hole when the pump turns on but not up and out through the main discharge pipe.    There is a check valve on the main pipe, but is working as the main pump does empty the pit.   My only guess is that the backup line hits the main line at a 45 degree angle and the water coming up doesn't have enough force to open the check valve.   Again I installed it as indicated in the instructions.   The backup is battery operated and both the pump and battery are brand new.  Anyone have any ideas?
Comment: https://screenshots.firefox.com/1EelJgtzxfic7Azh/hw.menardc.com
Comment: Your picture does not match the diagram.
Answer: Letter I in that diagram, the primary pump check valve, is your problem. It is either missing or not operating correctly. The water being discharged by the backup pump is draining out the inlet of the primary pump.
Also, the primary pump check valve needs to located below the wye fitting and above the primary pump like it is in the diagram. If it is above the wye fitting, then it won't work.
Comment: +1  Each pump needs its own check valve before the streams are combined.  Otherwise, most of the water will just flow back down through the other pump.  That's a far easier path than fighting gravity and a tall column of water above the valve.
Answer: I'm going to take a guess that your check valves are not in the right position. Both check valves should be located before (lower than) the 45 degree angle connection.Your new pump is pumping the water up to the 45 degree connection and then the water is running down the pipe to the old pump and into the pit causing the swirling that you see in the pit. Now if the check valve for the old pump is below that 45 degree connection the water will not be able to flow down the pipe and into the pit and will be forced up and out.
Answer: If this back up pump is run from a battery, Try reversing the leads. The pump may be running backwards. If this does not work, post a picture of the pump and piping so we can see the complete hook-up

Back up sump pump not working


Has a prototype been built to demonstrate the claims made by WO 2001053721 A1?

Question: The publication number of the patent in question is WO2001053721 A1. Simply put, has a thruster been built and do the claims in the patent represent reality?
Answer: Thanks for the post to Ask Patents. This is a site for asking questions about the US patent system and for seeking help in uncovering prior art on existing US applications and granted patents. It is not particularly likely that this post will be seen by the inventor.
The document you referenced is an international patent application. From google patent you can see that there is a corresponding US application US20010032522. Looking that up in the USPTO Public PAIR database, this application went abandoned in Oct. 2001 for a lack of a response to an initial rejection and never became an actual patent. For more recent applications, the whole back-and-forth of papers between the applicant and the USPTO are visible on PAIR.
The application looks like it was written by someone who studied the book "Patent it Yourself" by David Pressman.


How do I make a login page just like Joomla's backend?

Question: I want my homepage to be like Joomla's administration page, meaning there is only a login form displayed on the page. The hard part is, although it is not hard to make a homepage like this and I can set redirection after login to another page, if a logged in user close their browser tab and reopen the homepage, they will just see the login form which now only displays a "logout" button. I can put a link here for them to get to the other pages, but that is awkward and not a very good behavior. I want it to be just like Joomla's administration page, meaning if you are logged in, when you close and reopen browser tab, you will directly get to the administration panel skipping the login page. How can I do this?
Comment: You can use system Plugin event onAfterRoute and check if it's login page and redirect the user to desired URL from there
Comment: Hmm just saw this question by you - so I guess this is how you end up with your other recent question here: https://joomla.stackexchange.com/questions/23367/has-anyone-tried-setting-homepage-access-level-to-registered
Answer: There is actually no difference in the behavior between the backend and front-end site. The mechanism and the concept is the same.
There is a restricted area that requires login. If you gain access you see the content, otherwise you see a login-form. That's the whole idea behind this.
One simple way for the front-end would be to have a template that checks for if the user has the required access (logged-in or whatever), so it will display the content of the page, otherwise it will display (load) a login-form.
For example:
$user = JFactory::getUser();

if ($user->guest) {
    //
    echo "
Welcome. Login to your account or create a new one!
";
    // Login/Registration Form - Can load the login module
}
else
{
   // Your privileged stuff goes here
}


Arguments against running BizTalk on virtual servers

Question: Are there any arguments against running BizTalk on virtual servers?
Answer: BizTalk Server 2010 IS supported on a number of virtual platforms. 2009 are not supported on 2008R2 Hyper V though.
See the link here:  http://support.microsoft.com/kb/842301
In the schema they explicitly lists Hyper-V, but at the bottom they list SVVP certified platforms are supported as well. That includes VMware esx from 3.5 and up.
What I normally see is that the BizTalk servers are ritualized, and the databases are kept on physical servers, to better control the performance of those...  Probably 50% superstition to keep the db's on physical hw if you know what you are doing with virtualization, but it does make it a little easier to ensure your db's are getting all the performance they need.
The BizTalk servers ends up needing RAM and CPU, and that usually works well just being virtualized. But it all depends on if your people know what they are doing with vitualization. That is - not heavily overcommitting resources and such....
But what you REALLY want to read is this beast of a whitepaper, where Paolo Salvatori (BizTalk Ranger) and Ewan Fairweather had a LOT of fun virtualizing both SQL and BizTalk to see what happens to the performance.
http://www.microsoft.com/downloads/en/details.aspx?FamilyID=0582bc67-0bef-4a0a-99cf-4408a111c4e3
[Spoiler] ... you don't lose very much performance when virtualizing....
Answer: One that may come to mind is the "support position" if actual support is needed from Microsoft. Will they support it as a virtual session/installation?


Probability question with Normalized Curve

Question: This is driving me crazy...
"A Machine fills a 3 pound coffee can with a measured amount of coffee. The Weight has a normal distribution with a mean of 3.1 pounds. The standard deviation is 2.0 OUNCES. What is the probability that a can picked at random will contain less than 3 pounds.
Ok so first I converted the SD to pounds (2.0 Ounces/ 16 Ounces = 0.125 Pounds)
I calculated the Z score, $$\frac{2.9 - 3.1}{0.125} = -1.6$$
I looked up the standard area table -> 0.0548
Wouldn't this be 5.48% or am I messing something up? Or this isn't probability?
Answer: Your problem is that you calculated your Z-score as $\frac{2.9-3.1}{0.125}$. If the can contains 2.9999 pounds of coffee, that's still less than 3 pounds. So the correct Z-score is given by
$$\frac{3 - 3.1}{0.125} =-0.8$$
which gives a probability of about 21%.


How can I know my brake fluid needs changing?

Question: I have a few bikes with shimano disc brakes. I know changing the fluid is something that can be done and I could probably work out how to do it but I don't know what to look out for to know its time to change the fluid. I know someone who took in their 8 month old mountain bike to the store for a service and they said the fluid needs changing. Is this too soon? Are there any changes I can notice in my brakes that will let me know its time to change the fluid?
Comment: I don't think they are duplicates. One is asking if they do need to be changed and this one is how often
Comment: Possible duplicate of [Do I need to replace hydraulic fluid in my brakes?](https://bicycles.stackexchange.com/questions/9536/do-i-need-to-replace-hydraulic-fluid-in-my-brakes)
Comment: 8 month old bike - if it had brake problems, hope they did not pay for the fix as it would be covered by warranty. If it had no brake problems, they got ripped off - find another bike shop.
Comment: @mattnz agree this question has been asked before, but your proposed dupe does not have an answer anywhere near as good as khendrickx's.
Comment: @ArgentiApparatus So do you think it would be a good idea to close the other question as a duplicate of this one?
Comment: @Qwertie good point - I agree with you.  VTLO.
Answer: The suggested interval to bleed your brakes seems to different among manufacturers.
While  SRAMs techdocs explicitly mention to replace the fluid every year, Shimanos techdocs (p20) does only recommends to replace the oil if it becomes severely discolored. For recreational use, I think you're safe bleeding once every two years but depending of the usage and storage it might be quicker.
Magura on the other hand claims their Royal Blood oil (p21) does not age. I've ridden an MTB having HS33 brakes with 10 year old oil and indeed had a firm braking experience.
Are there any changes I can notice in my brakes that will let me know its time to change the fluid?
Replacing the fluid before the regular maintenance can be required if air got in the system. Magura suggests to replacing the oil if:

the brake does not respons immediatly when the brake lever is actuated
pressure point is not clearly defined, it is spongy or does not remain constant
the brake hose has been changed

If you have multiple bikes and like to do some own maintenance, it's even worth looking into buying your own bleeding kit. Shimano has nice technical documentation and there are various videos online giving you a feeling how to bleed your specific brake type.
Small sidenote, regarding storing your bike: ideal you put the flat and upright, so there is less chance for air coming in the brake system. While transporting the bike be sure not to press the brake levers without having the wheels in your bike, as it can cause the pistons coming out too far.
Comment: @pseyfert DOT 5.1 brake fluid deliberately absorbs any water that gets in the systems to prevent it from forming vapor when the caliper gets hot.
Comment: To my knowledge the reason for these differences is whether the fluid is mineral oil based (shimano) or DOT4/DOT5.1 (sram). The latter are glycol-ether based [wikipedia](https://en.wikipedia.org/wiki/Brake_fluid). The glycol based fluids absorb water and one wants to keep the brake system free of water (brake hot → water boils → gas in the system → brake power gone). Thus DOT4/5.1 based systems are expected to require service more often than mineral oil systems .
Comment: @ArgentiApparatus thanks for the correction, does that then have anything to do with the inspection interval? (expected to be saturated after a year?)
Comment: @pseyfert the only advice I'm willing to give wrt hydraulic brakes is *do what the manufacturer recommends*. I'm sure SRAM worked out bleed interval that will keep the vast majority of riders riding in average to wet conditions safe. If you live in Arizona or the McMurdo Dry Valleys then you probably have a massive margin of safety.
Answer: It is common in the automotive industry to change the fluid when problems arises. They have the longest experience in the field and that's what I do.
Change the oil when the brake lever feels spongy or less firm.
One trick to have the firmest lever possible is to block the lever with a cable tie overnight, making sure that it is in the highest position, so that all the air can go easily toward it(bike in oblique or vertical position, it depends on your routing).
In the mtb world some people will change fluid every 6 months to 1 year, this is a good practice if you race.
Comment: It's not clear that car brakes are a good comparison: they have to stop ten times the mass from four times the speed, with a lot of potential third-party liability if things don't work properly.


Behaviour of Zeta-function under Finite Morphism

Question: Let X ---> Y  be a finite surjective morphism of smooth, projective, connected varieties over a finite field F_q.   Can one describe the zeta function Z(X, t)  in terms of the zeta-function Z(Y,t)  of Y?  Can one say anything at all about how they are related?   What if we assume the morphism is finite etale?
Comment: Brandon: I would accept one of the answers below.  Hypothetically both, except that that's not possible.
Answer: You should be looking not at just zeta functions, but at the L-functions.
Then yes, for a finite etale Galois morphism the identity should be
        Z(Y) = Z(X) * L(X, \pi_1) * L(X, \pi_2) * ...

(where the product is over summands of the regular representation of Galois group of the morphism, Z being the L-function of the trivial representation.) This is in no way restricted to finite fields — in fact the idea as well as the notation comes from theorem about Dirichlet L-functions.
The proof is that by a definition of what is L-function it can be written either for a trivial mixed sheaf on Y (LHS) or for its pushforward on X (RHS).
Comment: To make my answer simpler, I was looking for simple introduction into what L-function is from this point of view but I don't think I know any. Anyone has some reference to recommend?
Answer: I don't think you can say much of anything of consequence unless you have better control over things.  As an example, consider the kth power map A^1 -> A^1.  This is finite, and surjective and even etale if you throw out 0, and has degree k, but the zeta functions are the same.
Another way of rerephrasing Ilya's comment is that it's not just varieties at have zeta functions; all mixed sheaves have them.  The zeta function of X is the zeta function of the pushforward of the constant sheaf on X to Y.  Now it may be that you can say something useful about this sheaf (for example, if you have a cover, it is a local system, and you can think about L-functions of pi_1 representations) but in general, that sheaf could be pretty horrible.
Comment: Still, in the case you're able to establish some results about L-functions, like in the number theory, this is a pretty useful identity!
Comment: That's true.  It just tends to be the sort of thing where conservation of trouble kicks in.  Working with zeta functions of varieties over finite fields directly is easy enough that it's not clear that thinking about L-functions will tell you much new.
Answer: Let $E\to C$ be an elliptic surface (say defined over $\mathbb{Q}$. Then Mike Rosen and I proved a formula for the rank of the group of sections $C\to E$ defined over $\mathbb{Q}$ in terms of the average number of points modulo $p$ on the fibers. (The result is conditional on Tate's conjecture for the surface $E$.) Anyway, the proof is via a comparison of the zeta function of $E$ as a surface compared to the zeta functions of the fibers and the zeta function of the base curve $C$. So not a direct relation that you seem to be asking for, but it has the flavor of your question. The paper is
M. Rosen, J.H. Silverman, On the rank of an elliptic surface, Invent. Math. 133 (1998), 43-67.
There have since been some extensions to 1-dimensional families of abelian varieties and/or to higher dimensional bases, which you can find by forward referencing our article on MathSciNet.
Answer: The paper by Aubry and Perret Divisibility of zeta functions of curves in a covering, Archiv der Math. 82(3) (2004), 205-213 contributes to this question. A free version is available at link text.


Ways to Learn More/Practice Mixing for a Newbie

Question: I've heard a lot of people say "If you want to work in post-sound you should pick what role you want to do like sound editing, designing or mixing and focus on that." as much as I'd like to do all of them I want to have more experience with all the different aspects of mixing since to be enjoying doing it a lot more than the others (I'm guessing cause I'm lazy, impatient and love playing with gadgets, this also makes me a little discouraged cause these are qualities you should have to become successful in the business). Since I'm still waiting for next year to come by so I can start film school, I'd like to know where or how I can learn some common tricks and techniques and some good ways to practice using them, and that's the main problem I don't have any projects to work on. I do occasionally make music or (try to) edit sounds to picture and mix them to get them to sound as good as I can make it (which isn't much) but I guess that's what I'm gonna have to do for now.. I've read Sonsey's great answer to a question Utopia asked on mixing before, which is pretty helpful but I feel like I need a little more info on the technical side, I'm also going to check out gearslutz more often like he mentioned but other than that any other good resources you could recommend? Thanks in advance.
Answer: I think there are two things you can do, and they are both fairly simple and relatively cheap or even free depending on what you already have at your disposal.  First thing you should do is read - read everything you can get your hands on.  Be it sound focused websites like this one, designingsound.org or many others that you can find, and books are also amazing sources for information too, go to the library and grab as many of the books in this thread as you can (http://socialsounddesign.com/questions/1945/audio-postproduction-sound-design-resources-youd-recommend).  Just because it is not about mixing specifically does not mean it will not be useful, mixers have to know how everyone else works so they can use the material they are provided with by the various editors and foley crews who have been working on the project already.  Simply devour as much information as you can, while still actually absorbing it.  This is not something that will stop once you are established, even the most experienced professionals spend many hours a week just reading up on new technology, techniques and ideas.  So start the practice now because you have decades of knowledge and theory to catch up on.
Second is doing.  You mentioned you have been trying to edit sound to picture, keep doing this.  Your results will be horrible to start with, if it wasn't then the profession would not be so hard to be successful in, it is both creative and technical and requires both sides of your brain firing off synapses to get to the end.  But the more you do it the better your work will start to be.  Pick short clips, but pick vastly different clips.  Do a scifi scene, they are fun and wildly creative as the possibilities are endless, then do a scene from a simple drama, where not much is happening but the sound can build tension, then do a car chase scene- these are extremely difficult.  You will learn what works as you go and build your own internal database of what works best.
Sadly there is no quick answer, you gotta dig in and get to work.
Comment: Excellent advice there from @AzimuthAudio. Also, try and find a mentor - someone who's skills you admire and who's willing to help you. Or it may be several mentors (I've had a few over the years). This one on one is invaluable to increasing your skills.
Answer: One simple beginner mixing tip that I heard about a while back is designed to get you familiar with throwing faders. You'll need two faders, two signal generators and a meter (the finer the resolution around 0 the better, I use PhaseScope set to VU and my dorroughs, but whatever you have will work).

Setup two tracks, each with a Signal Generator set so that when the fader is at 0 your meter reads 0.
Set the first fader at 0, the second at -INF.
Pull down the first fader while bringing up the second.
Keep your output to -+1 on the meter.

Sounds easy, right? ;)
Answer: I agree with @Azimuth and will add that I seem to remember the honourable Tim P. writing a post somewhere about how us soundies are more and more expected to be Everything Wizards.  In my experience this has definitely been the case.  In the indie scene there just isn't the money for a 12 woman/man sound team.  So take every opportunity to do everything you possibly can.
For reading materials I would highly recommend these two:
Silent Listening
The Music of Sound
They're both pretty heavy-duty so don't kill yourself trying to read them all in one go.  I tried that with The Music of Sound.  Totally OD'd on Awesome!
Luckily, sort of, Silent Listening only posts once or twice a month so you'll have plenty of time to absorb before the next load of Sound Goodness.
Answer: I think its important to learn everything to some degree. When it comes to film sound I think its vital for anyone who plans to go into post production sound that they work on production sound. Sound Recording is a hard task and you learn after time what extras you need to supply to the post production team to get the best result and thus you realise what you will want from your future production team in future.
There's a lot of composers out there or sound designers who claim they can do sound design for film, and I feel this is a massive flaw. It's completely different (even if they will work hand in hand in the future) and you should pick one or the other, although I'm sure there are some of you on here who can but generally the results I've heard on some peoples showreels are poor.
So do everything you can now, but ultimately do what you enjoy most and work at it. If you are serious about film, I'd look into getting some picture editing in as well and reading/learning about that, as you'll be telling the story together.


Powering Subpanel from CSED via Feed-Through Lugs

Question: I'm wiring my house and would like some feedback on the sizing and routing of conductors between the exterior service entrance and an interior subpanel. On the outside, I have installed a combination service entry device--aka CSED or meter main--by Square D (QC816F200C) with a 200 amp service disconnect. This panel features 8 slots, which will serve a whole-house surge arrestor (SqD HEPD80), a back-up generator power inlet (Eaton EGSPIB30), the well pump, and a branch feeder to power an outbuilding. My plan is to utilize the factory-installed feed-through lugs to then power the house subpanel, located approx. 35' to a central point in the interior. The subpanel is also by Square D (QO130M200PC) and came with a factory-installed 200 amp main breaker. The line between must pass through a sealed and conditioned (but unfinished) crawl space. Can anyone help me size the conductors, and let me know if they must be run in conduit? Many thanks.
Answer: Conduit would be a good idea, even if not strictly required
The main advantage running wires in conduit gives you is that you can put fatter wires, or more wires for something this large even, in if you find that your original run was insufficient.  In fact, a 2.5" EMT provides plenty of room for 3 250kcmil aluminum XHHW-2 conductors for now, and even expansion room for 3 more of them should you, or the next bloke who wants this place, want a 400A service later on, in addition to being the obligatory equipment grounding conductor.  If EMT is too costly an option, 3" schedule 40 PVC run within the structure could work as well, although you'd then need to run a separate equipment grounding conductor.
If you do go with the cable route, I would go with a 250kcmil-250kcmil-250kcmil aluminum SE-R cable; this gives you the full 200A, but limits you to that all the same.
That's an awfully small subpanel you have there
A 30 space panel is rather on the small side; 42 or even 60 spaces would be a much better use of your money and time here, given that it's far cheaper to buy the spaces now than it is to rip out and replace a too-small panel down the road.  Also, you can use a main lug panel on the inside of the house as it's a subpanel in the same structure (so it doesn't need to provide its own disconnecting means) and is not fed by downsized tap conductors (which are protected from overcurrent by the downstream OCPD).
Comment: Out of curiosity does OP *need* a main breaker panel on the inside of the house?
Comment: @Harper -- no, he does not
Answer: Your plan of using the thru-lugs is a good one, but necessitates 200A rated wire. That'll be 250kcmil Aluminum.  In these sizes, aluminum wire is fine; heck, the lugs are aluminum.
You mentioned a lot of parts specifically but not a generator interlock, so I trust that's in there.  This is mandatory.
Spaces, spaces, spaces
I'm concerned that you're already out of spaces in the CSED.  Then you also want a 30-space panel, which seems smallish. Please -- heed ThreePhaseEel's advice.   I'd even go further and say wildly oversize your panel -- I feel comfortable when I finish with 60% of spaces unused.
At least once a week someone comes in here and says "Help, my panel is full".  And what caused that is the person buying the panel back when it was installed.  That is where you are right now.  So I am from the forum's future warning you that saving money on panel spaces is false economy.
I notice QO doesn't make 200A panels over 30A - if that's holding you back, you are allowed to use panels with higher amp ratings e.g. 225A or 250A - your 200A main breaker will protect it just fine.
The only thing I'll alter from TPE's advice is there tends to be a painful price jump from 42 to 60, so I'd go for a 42-space panel and reserve space right next to it for another 42. Seriously.
I notice that all the items you are buying are sold by Home Depot.  One problem dealing with them is their selection is quite poor and they often "force" you into sad choices.  Buy from a for-the-trade electrical supply that specializes in QO, and you'll be able to get anything you want.  Most are happy to deal with a knowledgeable public (not a problem in your case) and if you discuss your dissatisfaction with the big box stores (a feeling they share), you are likely to get favorable pricing too.
Conduit
I work 99% in metal conduit, and it is a sheer pleasure.  I cannot recommend metal conduit more highly - and TPE got the size right -- it's more than is absolutely required, but the headroom will make the pull easier for you, and that's important when you DIY.
Metal conduit immediately resolves the issue of grounding. The conduit provides a hard grounding path from the CSED metal to the subpanel metal. Done. Make sure your neutral-ground bonding screw is pulled in the subpanel, and think no more of it.
After that, in conduit the wires are just easier to work.  Multiple wires in a jacketed cable is like wrestling an alligator.  In conduit each wire can flex and slide independently.  It helps to have a minimum (or no) elbows to pull around and make all the turns conduit bodies.
I randomly web-price 250-250-250-3/0 SE-R alligator cable at about $4.40/foot and 250kcmil XHHW-2 at $1.15 - so conduit wire is $1/foot cheaper than cable.
Comment: Generally, 42 space loadcenters don't come with feed-thru lugs, unfortunately (the only >8space loadcenter I've seen with feed-thru lugs is the QO12436L200TFT, which is only a 24 space LC and a bit pricey at that.  At least it's convertible to main breaker...)  You have to get into full-on industrial panelboards to get those sort of fancy config options...*sigh*
Comment: That's sad, the panels certainly have the room.  I'm getting downright defensive of my 11" wide 30" tall CH main lug boards...
Comment: Thanks to both of you for your detailed comments and advice!
Comment: Actually one follow-up question: if I were to plumb the run to the subpanel in metal conduit, is 2.5" the minimum by code for three 250kcmil XHHW-2 conductors, or could I go with 2"? Thanks again.
Comment: @BrettS. Sure, Code permits smaller. Code minimums *presume* you are an experienced professional with the pulling tools and the grease.  They are saying "more fill than this, *even pros* can't do it!"  The reason we recommend oversizing conduit for DIY, is that most DIYers *don't* have an electrician's truck full of pulling tools, or the experience not to wreck cables etc.  Oversizing makes the pulling task much easier and more in the DIY skill range.  Also future expansion.  Pipe is cheap.


Engine noise/rattle on startup

Question: My 2010 corolla ran very very very low on oil. I would hear a rattling sound on startup. After refilling with oil the rattling has subsided but still continues on a cold start or first startup for the day. Once engine is warm there is no noise on startup.....can this be fixed.
Comment: Does the noise seem to be coming from the top of the engine, under the valve cover? If so it's probably lifters.
Answer: Depending on how low on oil its been and how hot the internal parts have become, hopefully you may have only have suffered perhaps some wear in a hydraulic valve lifter or two. And the motor is noisier until the oil fills the hydraulic lifters. The noise really needs investigating though as depending on how noisy it is and what is actually causing it would better determine if further action was needed.
We can try and take a guess to advise you here but at the end of the day if this noise is due to something more serious then just a noisy lifter etc earlier attention and repair is better than waiting for a possible internal failure to occur.
Answer: If you live in a cold environment and your car is equipped with California emissions you have a secondary air pump somewhere. It's basically a fan that pumps air into the exhaust in order to satisfy EPA emissions. They are normally mounted to a steel bracket with rubber bushings to keep them quite when they turn on. If you can locate the pump and wiggle it back and forth and you hear a metal to metal sound the rubber bushings may be spent.

Engine noise/rattle on startup


A comparison of extractors in terms of tradeoffs between time, randomness and space ?

Question: Is there a good survey that compares different extractors, concentrators and superconcentrators and lays out the best methods in terms of the tradeoff between randomness, time and space ?
Comment: Hi Suresh, I don't think extractors and (super)-concentrators are comparable. Perhaps I misread the question, and you meant comparing the construction algorithms?

Parameters for (super)-concentrators that we care about are their depths and sizes, not "randomness, time, and space".

[Radhakrishnan and Ta-shma's paper][1] has a table showing all the tight results (including references) for super-concentrators.

  [1]: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.5.3637
Comment: Thanks for the clarification. I've never quite understood the differences between them.
Answer: The default reference is Ronen Shaltiel's survey.  This predates the important results of [Barak-Impagliazzo-Wigderson '04], [Barak-Kindler-Shaltiel-Sudakov-Wigderson '05], [Barak-Rao-Shaltiel-Wigderson '06] etc.  I believe Anup Rao's Ph.D. thesis is a good recent reference that describes these developments.


Windows "Computer Locked" default dialog positioning?

Question: Is it possible to edit this value so that it isn't in the middle of the screen?  I would like it off in the corner in order to avoid obscuring my wallpaper.
Answer: If you ask Microsoft, the answer will be "this is by design and cannot be changed".
However, if you feel very adventurous, then I found this on the web.
I take no responsibility and don't vouch for its correctness.
It may answer your question or destroy your boot.
a. Install Recovery Console
b. Downolad a copy of ResourceHacker
c. Find "msgina.dll" under \windows\system32 and copy it to the root (C:) folder
d. Start ResourceHacker and open msgina.dll from the root
e. Under Dialog-1900 replace the dialog with this one:

1900 DIALOGEX 0, 0, 0, 0
  STYLE WS_POPUP | WS_VISIBLE
  CAPTION ""
  LANGUAGE LANG_ENGLISH,SUBLANG_ENGLISH_US
  FONT 0, ""
  {
  }

f. Hit "Compile Script" and save it (an original of your msgina.dll was saved automatically under C:\ with the name "msgina_original.dll")
g. Restart the computer and choose Recovery Console at start up
h. Copy the new .dll into "\windows\system32" and "\windows\system32\dllcache" (hit "y" when it asks for rewriting existing file)
these are the commands:

copy c:\msgina.dll
  c:\windows\system32\
  copy c:\msgina.dll
  c:\windows\system32\dllcache

i. type "exit"
j. Now when your Windows restarted and you Lock your computer there will not be any pop-up window. To unlock just simply hit ALT+CTRL+DEL
Comment: The things people are willing to spend their time on . . .
Comment: Nice find , hope it doesn't crash xp :)
Comment: Very Interesting. Since the target machine is my work computer, I'll probably wait to test it on one of my own machines :)
Answer: Not easily as far as I know.
You can manually edit the GINA, but you may be heading down a bad path if you do that!
http://msdn.microsoft.com/en-us/magazine/cc163803.aspx
There are millions of resources on this, they all seem to be as cryptic as each other so I cannot recommend one of another.
Comment: Jebus...talk about killing a fly with an axe.


What does 「ここでこなんことをしてられない!」mean?

Question: The sentence 「ここでこなんことをしてられない!」comes from a book I'm reading. I have no idea where してられない comes from. My guess is that it's some colloquial potential form of する or something (there's a song named じっとしてられない), but I might be completely wrong. Can someone please help? Thank you in advance.
Answer: First of all, 「こなん」 should be 「こんな」 unless it is in a dialect I am unfamiliar with.

「ここでこんなことをしてられない!」

「してられない」 is the informal form of 「していられない」= "(I) can't be doing".  So, it is the negative, potential and progressive form of 「する」.
In informal speech, the 「い」 is often dropped from phrases such as 「~ている」、「~ていた」, etc.  Unless you are very new to the language, you must have encountered this phenomenon before.
The sentence, therefore, means:

"I can't be doing something like this here!"

What does 「ここでこなんことをしてられない！」mean?


Time for sunnah prayer before fard?

Question: When the sunnah mukkadah prayer before fard prayers are prayed i pray them at home and i give azan and iqama are they prayed between them or after iqama?
Comment: Iqama is -only- done before the fard prayer starts ... that should answer your question
Answer: When the time has come for that prayer, you can pray sunnah after that and before iqamah.
For example, 2 rakat sunnah before Fajr prayer -
if fajr starts at 5:30am & sun rises at 7am then

if you pray alone, then give adhan anytime between 5:30 and before 7am (e.g. 6:30am), then pray sunnah, then give iqamah and pray fard. Remeber to finish all prayers before sun rise, in this case.
if you pray at mosque (or in Jamah), you need to pray after 5:30am and before iqamah.

Time for sunnah prayer before fard?


In the Critique of Pure Reason, what is the difference between "schema" and "synthesis"?

Question: I don't understand the difference between Schema and Synthesis. I have read the First Critique and I see Kant is using the words "schema" and "synthesis" as "intermediate" between intuitions and understanding in different places.
Answer: (Disclaimer: I am aware of the fact that there still is a lot of debate going on regarding what the schemata really are and whether or to what extent the argument works. This is a very basic question, hence a very basic answer)
The answer can be found in A137-38|B176-77. I will quote first and explain later.

[P]ure concepts of the understanding, however, in comparison
  with empirical (indeed in general sensible) intuitions, are entirely un-
  homogeneous, and can never be encountered in any intuition. Now how is the subsumption of the latter under the former, thus the application of the category to appearances possible, since no one would say
  that the category, eg., causality, could also be intuited through the
  senses and is contained in the appearance? This question, so natural and
  important, is really the cause which makes a transcendental doctrine of
  the power of judgment necessary, in order, namely, to show the possibility of applying pure concepts of the understanding to appearances
  in general. In all other sciences, where the concepts through which the
  object is thought in general are not so different and heterogeneous
  from those that represent it in concreto, as it is given, it is unnecessary to
  offer a special discussion of the application of the former to the latter.
Now it is clear that there must be a third thing, which must stand in
  homogeneity with the category on the one hand and the appearance on
  the other, and makes possible the application of the former to the lat-
  ter, This mediating representation must be pure (without anything empirical) and yet intellectual on the one hand and sensible on the other.
  Such a representation is the transcendental schema.

Effectively, he makes a logical point here: If there are two things that are inhomogenious in nature (like empirical, sensual intuitions and pure concepts) and these things are thought to be synthesised into a single representation of an object (via empirical synthesis), they need something connecting between them, a copula that has aspects of both fundamentally different things and makes a coming together possible (Note: 'Copula' as technical term can mean something entirely different depending on the context. I am using it as "the form of the connection between the elements of a judgement" here). That's what schemata are, the "in-between" that allows to bring categorically different things together.
In the quote, this is the third he is speaking of. Similar remarks can be found e.g. in the Blomberg Logic, Ak. 9:207, the Hechsel Logic 9:88-89.
In other words: Synthesis is the act of bringing intuitions and pure concepts together, while schemata are the common denominator that allows for bringing them together in the first place, hence an a priori condition of synthesis.
Possible sources of confusion
A confusing aspect of this can be that both the schemata themselves and the outcomes of synthesis - i.e. synthetic representations of determinate objects - can be characterised as "intermediates" between intuition and pure concept. One difference here is that between before and after the fact (the act of synthesis), others are where in the process of empirical synthesis (apprehension, reproduction, recognition, A97-A105) they are coming into play.
Also, there is a lot of (partially misleading, partially plain wrong) literature reading Kant from Hegel that (i.e. the literature, not Hegel himself!) takes the triad "thesis-antithesis-synthesis" to be the basic form of philosophy for both Kant and Hegel. There, synthesis is often taken to be identical to the Hegelian sublation, hence the (speculatively achieved, spontaneous) "intermediate" itself and not the process of achieving it, which as we have seen is in need of a copula to be possible at all. There, synthesis and schemata are muddled. But this goes beyond the scope of the question.


Why would you climb hard bigwall projects in Yosemite in winter?

Question: One of the hardest routes on El Cap, The Dawn Wall, was done by Tommy Caldwell and Kevin Jorgeson in January 2015. What are some of the reasons to choose to climb such a hard route in winter, when the conditions are probably more adversary?
Comment: No bugs. Fewer people. What else do you want to do? The challenge of it. Etc...
Comment: related: https://outdoors.stackexchange.com/q/7586/3143
Comment: FWIW, January in the Sierra often has a couple weeks of mild sunny weather, much more like Fall in the rest of the country. Winter storms start in Nov/Dec, there's often a break in January and the storms return in February and March.
Comment: People have died on the big walls from exposure during storms in the valley. The good news is the Pacific winter storm systems of the kind that linger for days are predicted so there is plenty of warning to bail.
Answer: I just finished Caldwell's book Push. The big walls in Yosemite are essentially vertical deserts. Even in winter they're in the full sun much of the day. It would drop below freezing at night, but during the day temperatures would regularly get above 50 °F (10° C). In the summer the heat can be overwhelming. Aside from the difficulty of performing extremely gymnastic climbing in high temps, sweaty hands make tenuous holds impossible. Gymnastic chalk can only do so much to counteract that. It also turns out that the spring and fall shoulder seasons are problematic because ice forms on the wall every night and peels off during the day. After several close calls with baseball sized hunks of ice, they found it slightly less hazardous during colder periods. On the other hand when it got too cold, the rubber on climbing shoes wouldn't grip as well, and they would just take a rest day on their porta-ledge.
Comment: The rockfall potential is somewhat higher if there is a freeze thaw cycle on milder days, which works to wrench the large flakes off the wall. This is a concern on some routes with tenuous features
Answer: I was there in early January.  While the valley was below freezing, upon the first 50 feet climb in elevation after sunrise, the air temperature was very agreeable (50+ °F/10+ °C) with lots of sun.  Rejoice for there was no ice underfoot—unlike on the valley floor.
Also, everyone who had been there before were beside themselves with how uncrowded it was.  Even with the goverment shutdown, there were almost no visible effects:  the visitor station was closed and there were no park rangers around (not even manning the entrance booth).  Bus shuttles still ran, trash was removed, all the hotels and restaurants were open and well staffed.  (If there were rangers around, would they evict the few dozen tent campers in the closed campgrounds?)
My wife and I hiked to the top of Yosemite Falls.  There were perhaps 25 small groups (2-4) of "climbers" on the trail making it to the top.  3/4 of the trail was clear with the last mile or so having packed snow with trailside snow up to a half foot deep.  Sunny, gorgeous, clean and crisp air all the way.  The overlook at the top was enchanting with a thick carpet of cushy fresh snow and spectacular viewing for about 15 people while I lingered.  (I expect it is harder to see in the summer.)
Answer: No experience of Yosemite weather, and it sounds like you have your answer, and this isn't wrong, but:
people don't climb hard projects just to get their name on the problem. That it's difficult is a big part of the attraction. So long as it isn't wet... there really isn't 'bad weather' for climbing, you just have to factor it into your expectations.
Comment: As it is, only the last sentence attempts to answer the question, and offers no explanation.
Comment: Hey ANone, and welcome to the great outdoors! Thanks for your answer - I also considered this, but thought difficulty would be high enough anyways, since the route "Free Dawn" is considered by many as one of the hardest multi-pitch route to date. But you are right, this could certainly play a role as well!
Also, make sure to check out our [tour](https://outdoors.stackexchange.com/tour) if you're not yet familiar with how things work at our site!


Selecting line with specific numeric field value using inline variable for arcpy.UpdateCursor()

Question: I'm currently away in a remote field station using Arc 10.0 and having a hard time using an inline variable substitution for a numeric field value. I am trying to use UpdateCursor to select only a specific line by designating a "POSITION" field = to a numeric value that I can increment each time I go through the for loop.   When I use a number in the line, it works. However, I can't seem to get the right syntax to substitute the hard-coded number for a variable.
here's the section of code:
<code>## Attempt to update the cursor, then get value, then setvalue using an inline variable for the desired Field value
## THIS does not work
stefile = "ste1.shp"
stefield = "POSITION"
steclus = "CLUSTER"
steac = "AC"
stevalue = 100
stepos = 22
Z = arcpy.UpdateCursor(stefile, '"POSITION" = stepos')        # This needs to be changed eg; '"POSITION" = a memvar') ...and at end of loop memvar +=1
for row in Z:
    print row.getValue(steclus)
    memvar = row.getValue(steclus)
    row.setValue(steac, stevalue)
    Z.updateRow(row)
    print row.getValue(steac)
    del Z
    del row

### HERE are the error messages
# Runtime error <type 'exceptions.RuntimeError'>: ERROR 999999:
# Error executing function.
# A column was specified that does not exist.
</code>
Am I simply using the wrong syntax?
Answer: The where clause is currently evaluating stepos literally as the value stepos, not the variable value 22.
Move the stepos variable outside the where clause string, casting the numeric value to a string, like:
<code>arcpy.UpdateCursor(stefile, ' "POSITION" = ' + str(stepos))
</code>


Is the sum of two white noise processes necessarily a white noise?

Question: Let $a_t$ and $b_t$ be white noise processes. Can we say $c_t=a_t+b_t$ is necessarily a white noise process?
Comment: What's your definition of white noise?
Comment: What kind of white noise..?
Comment: Let $b_t = -a_t$. Is $b_t$ a white noise process? Is $b_t + a_t$?
Comment: Are you talking about white **Gaussian** noise or white noise?
Answer: No, you need more (at least under Hayashi's definition of white noise). For example, the sum of two independent white noise processes is white noise.
Why is $a_t$ and $b_t$ white noise insufficient for $a_t+b_t$ to be white noise?
Following Hayashi's Econometrics, a covariance stationary process $\{z_t\}$ is defined to be white noise if $\mathrm{E}[z_t] = 0$ and $\mathrm{Cov}\left(z_t, z_{t-j} \right) = 0$ for $j \neq 0$.
Let $\{a_t\}$ and $\{b_t\}$ be white noise processes. Define $c_t = a_t + b_t$. Trivially we have $\mathrm{E}[c_t] = 0$. Checking the covariance condition:
\begin{align*}
\mathrm{Cov} \left( c_t, c_{t-j} \right) &= \mathrm{Cov} \left( a_t, a_{t-j}\right) + \mathrm{Cov} \left( a_t, b_{t-j}\right) + \mathrm{Cov} \left( b_t, a_{t-j}\right) + \mathrm{Cov} \left( b_t, b_{t-j}\right)
\end{align*}
Applying that $\{a_t\}$ and $\{b_t\}$ are white noise:
\begin{align*}
\mathrm{Cov} \left( c_t, c_{t-j} \right) &=  \mathrm{Cov} \left( a_t, b_{t-j}\right) + \mathrm{Cov} \left( b_t, a_{t-j}\right)
\end{align*}
So whether $\{c_t\}$ is white noise depends on whether $\mathrm{Cov} \left( a_t, b_{t-j}\right) + \mathrm{Cov} \left( b_t, a_{t-j}\right) = 0$ for all $j\neq 0$.
Example where sum of two white noise processes is not white noise:
Let $\{a_t\}$ be white noise. Let $b_t = a_{t-1}$. Observe that process $\{b_t\}$ is also white noise. Let $c_t = a_t + b_t$, hence  $c_t = a_t + a_{t-1}$, and observe that process $\{c_t\}$ is not white noise.
Comment: I'd love to see other, non-econometric, non-economics based definitions of white noise. It's a term that's often thrown around, and I'm not sure how it's used in other fields (or even other definitions used in finance/economics).
Comment: Comment to Matthew (add a comment link doesn't work for me): according to more commonly used more rigorous definitions of white noise, even adding two independent white noise sources won't yield true white noise, because the amplitudes are no longer uniform but enveloped.
Comment: Another example: Let $d_t = -a_t$ then $a_t + b_t = 0$ for all $t$ so not white noise. @MatthewGunn I'd say that the definition in finance would be the same but I don't have a source.
Answer: Even simpler than @MatthewGunn's answer,
Consider $b_t = -a_t$. Obviously $c_t \equiv 0$ is not white noise -- it'd be hard to call it any kind of noise.
The broader point is, if we don't know anything about the joint distribution of $a_t$ and $b_t$, we won't be able to say what happens when we try and examine objects which depend on both of them. The covariance structure is essential to this end.

Addendum:
Of course, this is exactly the purpose of noise-cancelling headphones! -- to reverse the frequency of external noises and cancel them out -- so, going back to the physical definition of white noise, this sequence is literal silence. No noise at all.
Comment: Objection withdrawn.
Comment: @StigHemmer a usual requirement is that for $j = 0$, $\operatorname{Cov}(c_t,c_{t-j}) = \operatorname{Var}(c_t) = \sigma^2>0$.
Comment: @StigHemmer see edit -- it's in fact a very natural definition for 0 _not_ to be white noise (in fact it's rather the opposite, by the common definition -- we can exactly predict the value of the sequence given _any_ past value)
Comment: 0 is a perfectly fine white noise.
Answer: In electronics, white noise is defined as having a flat frequency spectrum ('white') and being random ('noise'). Noise generally can be contrasted with 'interference', one or more undesired signals being picked up from elsewhere and being added to the signal of interest, and 'distortion', undesired signals being generated from nonlinear processes acting on the signal of interest itself.
While it is possible for two different signals to have correlated parts, and therefore cancel differently at different frequencies or at different times, e.g. completely canceling over a certain band of frequencies or during a certain interval of time, but then not canceling, or even adding constructively over another band of frequencies or during a certain interval of time, the correlation between the two signals presumes a correlation, which is precluded by the presumably random aspect of 'noise', which is what was asked about.
If, indeed, the signals are 'noise' and therefore independent and random, then no such correlations should/would exist, so adding them together will also have a flat frequency spectrum and will therefore also be white.
Also, trivially, if the noises are exactly anti-correlated, then they could cancel to give zero output at all times, which also has a flat frequency spectrum, zero power at all frequencies, which could fall under a sort of degenerate definition of white noise, except that it isn't random and can be perfectly predicted.
Noise in electronics can come from several places.  For example, shot noise, arising from the random arrival of electrons in a photocurrent (coming from the random arrival times of photons), and Johnson noise, coming from the Brownian motion of electrons in a resistive element warmer than absolute zero, both produce white noise, although, always with a finite bandwidth at both ends of the spectrum in any real system measured over a finite length of time.
Answer: if both white noise sound is traveling in same direction And if their frequency is in phase matched up, then only they get added. But, one thing i am not sure about is after adding up will it remain as white noise or it will become some other type of sound having different frequency.
Comment: (However, this does appear to be an attempt to answer the question, so reviewers should consider downvoting instead of deletion.)
Comment: It seems to me you might be thinking about physical noise rather than statistically? I'm not sure that this answer adds very much - e.g. how can white noise have a single frequency to be matched up? Try looking at a spectrogram of white noise.
Comment: The sum of two white noise signals will be white noise if they are *uncorrelated* noise. I also came here from the Hot Network Questions list, not noticing which site it was on. I expect that the statistical definition of white noise is equivalent to the signal-processing definition.  About your thought that the two noises will add together occasionally -- yes, they will, but only in certain (random) locations.  In other locations, they will subtract.  It doesn't stop the result from also being white noise.
Comment: @Justin, _"The sum of two white noise signals will be white noise if they are uncorrelated noise."_ - I may be misunderstanding what you mean by "if they are uncorrelated", but under my interpretation your conclusion is wrong. If $a_t$ is white noise and $b_t = a_{t-1}$ (Matthew Gunn's example) then both $a_t$ and $b_t$ are white noise, and ${\rm cor}(a_t, b_t) = 0$ for every $t$. Yet, $c_t = a_t + b_t$ is not white noise.
Comment: @not_bonferroni - Yes, I suppose I was using incorrectly "uncorrelated" to mean "independent".
Comment: @Justin, $a_t$ and $b_t$ are also independent for every $t$.