In Scrum, who verifies "Done"?

Question: I am a QA/Test manager in my organization and until today I verified the quality of the software (tests written and executed and bugs fixed). Who will verify this in Scrum? How do I know that the team wrote and executed all the right tests? On the other hand I'm afraid that if I continue to do the verification the team will not feel empowered enough. But I need some verification process that "Done" is indeed "Done". What do you suggest?
Comment: [Microsoft article about `Done` and `Undone`](http://msdn.microsoft.com/en-us/library/hh765983(v=vs.110).aspx)
Answer: One major idea in Scrum is that the team should agree on a "definition of done". Ideally, this is something like a set of objective criteria that anyone can verify by going through a checklist.
But to reduce the chance of something slipping through, it makes perfect sense to have a rule that verifying "done" most be performed by someone other than the person who implemented an item - or a designated QA guy like you (but that risks making you a bottleneck).
If in doubt, discuss is with the team and the Scrum Master and decide together.
Comment: @MichaelBorgwardt It's why I was so clear in my reply that the Product Owner is part of the *Scrum Team*. I agree that the Product Owner is not part of the Development Team but the context did not make it clear. I was hoping to clear confusion. Seems like I may have inadvertently created some :)
Comment: @MarjanVenema The Product Owner is *very much* considered a part of the Scrum Team. In fact, without the Product Owner, Scrum has little to no chance of being successful.
Comment: @Derek: I think you're having a misunderstanding based on unclear terminology. There is both a "Scrum Team" and a "Development Team", with the latter being a part of the former, as well as the Product Owner and Scrum Master.
Comment: +1 though the product owner is normally not considered part of the team - (s)he is usually drawn outside of the team's circle - yet does have (or should have) a say in the definition of done. It is the only way the product owner can (is allowed to) influence the way the team works.
Answer: I think there is an implicit assumption in the question. There is a difference between "accepted", when a Product Owner declares a backlog item or task has satisfied the Product Owner, and "done" meaning all work associated with the backlog item is complete.
However, there is regularly more to a task than that visible to the Product Owner, usually someone semi-technical at best, including (automated and manual) testing, documentation and review. The Product Owner is rarely in a position to know the technical aspects, let alone whether they are completed.
Therefore, it is ultimately up the team to determine what "done" means. The organization may have standards and different stakeholders will have their own requirements. The scrum master or relevant managers usually are responsible for collating and enforcing the list.
In your example, as the QA/Test manager, you are the one who says whether tests are complete. However, you may not be the best person to say whether the code has been reviewed, security requirements are met, the product is internationalized, documentation is complete or whatever else constitutes "done".
Answer: The only concept of "done" is whether or not a story as a whole is completed. The team should have created a definition of done that says when they feel a story is finished or not. This will typically include things such as "code has been reviewed", "nightly tests have been run", "all acceptance criteria have been met", etc. When these things have been accomplished, the team can feel confident they've done everything expected of them to finish a story.
During a sprint, if you're trying to determine if one of those items in the definition of done has been accomplished, just ask. Scrum and agile is all about open communication. If you are part of the team, ask your teammates if anyone has written the tests, or run them, or created the nightly job, etc. If you are a stakeholder, ask the scrum master.
If you sit outside the team but still must review the tests, have the team add "tests must be reviewed by user user3251930" as part of the definition of done. If that's what it takes for a story to be done, be honest about it and make it part of the process. The whole point of the "definition of done" is so that the team can know with certainty that they have done what is required to deliver quality software. If part of that is an external review, so be it.
Ultimately, it is the product owner who signs off on a particular story, so at the end of the day he or she has the final decision as to whether a story as a whole is done or not.
Comment: I need to review the tests, otherwise I wouldn't know if the correct tests were written. The definition of "Done" doesn't include the exact tests that should be written.
Comment: @user3251930: why do you need to review them? Do you not trust your team? Though, if you really do need to review them, make part of the definition of done be "tests have been reviewed by user3251930".
Comment: If the customers get something that was not completely tested it would be really really bad. Maybe in time I'll be able to trust the team, I hope so.
Answer: First Question you should ask yourself
Are you the Scrum Master?
if yes.
In scrum processes are controlled and managed by the Scrum Master.
How do you do it:
In the requirement phase you can use the user stories for each there is a test that needs to be verified.
In each Sprint The work items are pulled from the product backlog and directed by the product owner.each of them will have verification criteria as well.
Now in Scrum requirements dont change after the sprint has started .At the end of the Sprint you can analyze the verification according to the criteria for each item done.
If its done can only be found by the response of the Product owner.
Remember in Agile you "Embrace the change" even late into the development phase
Answer: The team decides. I use a checklist, for what's considered 'Done'. What's 'Done' per story, per sprint, per release.
As others have mentioned, ultimately the decision lies with the product owner.
Comment: is this only your personal opinion or you can back it up somehow?
Answer: Agree that this is something the development/test team needs to define, depending on your own practices. Some projects run so agile that they're willing to risk releasing bugs to their alpha stream; some consider any bug which gets outside the development group a process failure.
The project I'm working on requires peer review of code changes, and requires that whoever wrote the code either provide/update regression tests or explain why it isn't possible to do so. (They and their reviewer(s) also have to certify that they've checked for known bad practices. We're generally Much Happier if they can show that they ran the full test suite and have gotten a clean result (or clean modulo known open issues, at least)  The code then has to survive intensive automated unit and functional testing on multiple platforms to demonstrate that it doesn't cause any regressions against those, and it gets further checked for common antipatterns by an automated code analysis system. Only then do we accept it into the main development stream and mark the work item complete. Note that completing one work item may only be one step toward completing a larger-scale task or story.
That obviously doesn't guarantee that nobody finds a new way to fail, but it reduces the risk to an acceptable level without greatly impeding speed of development.

In Scrum, who verifies "Done"?


Did any plantation/hacienda/fazenda owner free all his slaves?

Question: The North and South American masters that kept slaves are today criticized for it. Their income of course depended on slave labor. Anywhere in the Americas, did any of them free their slaves -- not at death like Thomas Jefferson tried to do, but all at once, perhaps following a moral epiphany?
Comment: @RedGrittyBrick i removed the term to clarify that cases of (legal) slavery in Imperial Brazil or the independent U.S. would also qualify.
Answer: Yes, some did. Ironically, one of them was Roger B. Taney, US Supreme Court Chief Justice and author of infamous Dred Scott decision.
Contrary to popular believe, Robert Lee did not free his slaves - he did not own slaves. His father-in-law named Robert Lee an executioner of his will. According to this will, all his slaves should be set free in 5 years after his death.
UPDATE.
I don't know if Roger Taney freed his domestic slaves, or they worked his land. But John Dickinson, founding father and largest Delawer farmer and slaveowner, freed his slaver by 1786. His farm moved from tobacco to less labor-intensive crops.
Comment: Did Taney have a plantation with slaves as specified in the question , or were these his household or personal servants?  The question seems to be focused on slaves which were providing income for their owners.
Comment: @user2448131 I think masters that kept household or personal servants are criticized for it today as much as planters.


Just rescued a bunny... Not eating any hay or rabbit food

Question: My mom rescued a bunny that was abandoned in a house for about 9 months, and we got her a nice big cage, with plenty of chews, and lots of hay and rabbit food. Our neighbor was feeding the bunny, but she could never catch her and she ate her food them but she isn't anymore. I've had her for 3 days, and yesterday I gave her half a carrot and about 2 or 3 broccoli. I mixed her regular Timothy pellets (her regular food she isn't eating) with Timothy hay (also something she isn't eating) with some dry oats and the carrot and broccoli. She ate everything except her pellets and hay. I know she needs to say both of them, but I'm not sure how to get her to want to eat them. What should I do??
Answer: To get her to eat more hay, feed less pellets and carrots.  A better choice for fresh vegetables is romaine lettuce.
Carrots and broccoli should both be feed with moderation What to Feed Your Rabbit at rabbit.org also see Are carrots a healthy part of a rabbit diet?
Pellets should also be feed in moderation, about 1/4 cup per pounds of body weight per day (but varies greatly depending on weight issues).
As the rabbit was outside for some time, fleas may be an issue, so take a look at How do I get rid of fleas on my rabbit?


Is there any way of dealing with or reducing lens vignetting with a wide angle?

Question: So I finally got around to purchasing a Nisi 150mm filter holder and a couple of filters for my Samyang 14mm AF lens. Seems fine so far except that the holder itself causes some vignetting, with part of the actual holder itself being visible in the frame at times. There seem to be angles at which this is less of an issue. I can't imagine there's any way to get around this, though I'm wondering whether anyone might have any advice in regards to this?
Comment: Please limit each question to a single subject. The question about light leaks should be asked separately as that is unrelated to the question about vignetting.
Answer: Stopping down the aperture (using a larger f-number) will have a two-fold effect. The FOV of the lens is narrowed slightly by stopping down. For example, on your 14mm lens, going from f/4 to f/8 would narrow the physical aperture from 3.5 to 1.75mm which would in turn reduce the diameter of the FOV by 1.75mm in a lens with rectilinear projection (slight more if its a fisheye) Moreover, reducing the aperture size will sharpen the vignette, causing it to "blur over" less of the image.
Assuming you cannot stop down the lens, consider this:
Object path vignettes have no partitive effect. In other words, if your filter holder is forward of the entrance pupil, then the vignette will not act like a field stop.
In wide angle lenses the entrance pupil is almost always behind the front element's front vertex. This is as opposed to some telephoto lenses where the entrance pupil can be in front of the front element. In such a lens the effect of vignette would be partitive (cause darkening of some or all of the scene)
What does this mean? The area experiencing vignette is the only part of the image effected and that means that you can make your images and crop the vignette out in post.
Answer: Stopping down to a narrower aperture should reduce the degree of vignetting.
Answer: There so called center filters for wide angles that are dark in the center and increasingly transparent to the edges. Example: https://www.schneideroptics.com/ecommerce/CatalogSubCategoryDisplay.aspx?CID=182
They are pretty expensive, though. But old ones can often be found cheap on auction sites.
They are made especially for this kind of problem.
Comment: These center filters are designed to compensate for the light falloff towards the edges of the field of view. They cannot compensate for vignetting caused by objects in front of the lens, such as the OP's filter holder. The objects cause more-or-less _hard vignetting_, as opposed to the gradual vignetting of light falloff off-axis from the len's optical axis.


Can a Muslim cook pork?

Question: If someone asks for my help to cook something that has pork, can I help this person? I'm not going to eat, just going to help cook the food.
Comment: I would suggest you gently decline this if you can. Also I have seen couple of your posts. My humble opinion is it is more important to know the virtues of righteous actions (Fadaail) and doing them than having knowledge of issues (Masaail). The more you do righteous actions, the more you will become enlightened and will gain deeper understanding of the Masaail. This is my opinion but you may disagree.
Answer: Eating pork is Haram in Islam and helping in a sin is prohibited in the holy Quran:

...وَتَعَاوَنُوا عَلَى الْبِرِّ وَالتَّقْوَىٰ ۖ وَلَا تَعَاوَنُوا
  عَلَى الْإِثْمِ وَالْعُدْوَانِ ۚ وَاتَّقُوا اللَّهَ ۖ إِنَّ اللَّهَ
  شَدِيدُ الْعِقَابِ
... And cooperate in righteousness and piety, but do not cooperate in
  sin and aggression. And fear Allah; indeed, Allah is severe in
  penalty.
http://tanzil.net/#5:2
Comment: Eating pork is a sin for muslims, ok. But it isn't a sin for christians or people from other religions.
Comment: So what's the word is it permissible or not? Please directly state that in the answer.
Comment: @BleedingFingers is not prohibited same as not permissible?
Comment: It is. But you should point out if cooking pork is helping in sin and why is it so, that way the answer will be complete, unambiguous and will definitely stand out.
Comment: @MFS it is sin for all. there is only one religion: http://tanzil.net/#3:19
Comment: -1, it isn't a sin for non muslims which I am confident is what the OP asks for.
Answer: It should be fine as long as you don't eat it and the person that is going to get it is not forbidden for them.
However, if for example you married a Christian/Jewish woman who drinks wine or eats pork, it is not allowed to buy/serve the Alcohol as stated in many hadiths:

لَعَنَ اللَّهُ الْخَمْرَ وَشَارِبَهَا وَسَاقِيَهَا وَبَائِعَهَا وَمُبْتَاعَهَا وَعَاصِرَهَا وَمُعْتَصِرَهَا وَحَامِلَهَا وَالْمَحْمُولَةَ إِلَيْهِ
Allah has cursed wine, its drinker, its server, its seller, its buyer, its presser, the one for whom it is pressed, the one who conveys it, and the one to whom it is conveyed

However, there is no hadith about those who serve pork, only forbiddance in selling it. In your case I don't see anything from the Sunnah or Qur'an that prohibits it.
Answer: No, we can't even cook it because our this act helps other to perform sin. In simple words our this act helps others to go against Islam.

Can a Muslim cook pork?


Best SEO software for comparing two pages

Question: Hi I am looking for software that can help me compare metrics of two pages on the web, targeting the same keyword. So if my page is on position 5 in Google I would want to analyse the no.1 spot holder and see what internal and external factors are putting the other page in front of mine. Thanks
Comment: http://www.opensiteexplorer.org/
Answer: Go to SEOmoz (http://www.seomoz.org/) They are the number one in seo, you can sign up for a free trial and use there tools. And use their on page analysis tool. http://pro.seomoz.org/tools/on-page-keyword-optimization/new its the best on the web. i have used enough of them for my job. It will tell you everything you need to know and more between that tool and the rest of their tools.
Answer: I'd like to be more specific and say that I use Website Auditor and SEO Spyglass for competition analysis.
Website Auditor is for on-page SEO, it shows you the structure of a site, shows you how the keyword/s are used in titles, site copy, anchor texts, etc. It also scans top 10 competitors and prompts the best way to optimize content.
If you'd like to compare 2 sites, you can start a separate project for each site, but analyze them against the same keyword/set of keywords.
Now, SEO Spyglass is an off-page tool. It lets you check backlinks for different URLs. So, again, you can create 2 projects and compare backlinks to two websites.
Answer: SEO Moz is probably what you want.
Raven Tools might be more your speed, but I don't have any experience with their toolset.
Answer: I'm sure ColibriTool would do the job :) It provides many statistics about traffic, backlinks, conversion for your sites but also for competitor's sites.
Answer: I've used Market Samurai with some great success before. I'm not 100% sure it will do what you want(and this question is like a year old) but anyone else who is looking for a good keyword tool or content generator. Hope this helps someone!
(I don't work for them or anything. Just a pretty user-friendly interface)
http://www.marketsamurai.com/


Are time series data always contain noise?

Question: I wonder if every time series data should contain noise or not. For example I am taking the price of a ticker, say Yahoo, every hour and noting the values. Does this data contains noise or not?
Comment: I'm no expert, but I'd say a ticker might contain two kinds of "noise". One might be rounding: the price might reported with less significant figures than the actual price. The other is time jitter: The price reported at a time instant may be the price at some indeterminate time in the past (say, anywhere between 0 to 10 seconds in the past).
Comment: In addition to @Mbaz 's aspect of ticker data simply not being a digital signal, because it's not sure to be sampled at discrete points in time, I'd also like to mention quantization noise here, which, for things like stock exchange rates, might be **highly** correlated and impossible to model as additive noise
Answer: Periodically taken ticker data is very likely not a set of samples of a band-limited function, thus can contain aliasing artifacts which can be considered noise.  This is possibly a much larger contribution than quantization and time jitter noise.
Absence of noise requires the existence of well defined signal being measured.  Proving that such a signal really exists is a separate and likely far more difficult problem for some types of time series.
Comment: Interesting, I had never thought of that. However, I think it only becomes a problem when you try to interpolate or extrapolate. The samples themselves are not noisy (up to quantization and time jitter errors).
Comment: Some might say that the last individual trades before any periodic price sampling times are just a lot of fat-tailed random noise (or can't be consistently differentiated from a random walk of such... especially with HFT systems perhaps using game theory to place some distribution of different bets every millisecond.)
Comment: I agree; that's why I believe you are correct to assume that the continuous ticker signal has a very large (if not infinite) bandwidth. Any naive interpolation or extrapolation based on the samples will likely be inaccurate because of this. On the other hand, Berlekamp made a lot of money applying information theory to the market; as far as I know he never explained exactly how he did it.
Answer: A huge yes. Perhaps stated in another way, due  to the stochasticity, you can never be certain in practice that there is absolutely no noise in your  data.
The timing at which you sample (almost periodic,  every hour) might subject to small uncertainties (whether you do it by hand or by an automatic request).  There is no infinite sampling precision.
Noting the values (do you note it by hand, actually?) is subject to perception and one can write figures noon accurately, forget a comma. Change $3.14$ as $31.4$ and you get a spurious peak on your time series.
Those are "copy or retrieval" noises.
As @hotpaw2 said, aliasing is a type of noise that occurs when converting a seemingly continuous data into a discrete one. It is  worth pointing out (I have heard "I sample this day every 24 hour, so I have no noise". Actually, an irregular sampling might help in the  case of a non band-limited signal.
Then you have almost the same issues with what Yahoo, considered here as a sensor, does. How long does it hold values? Sometimes free information is delivered at a slower pace than when it is paid? How does it round it? Does it smooth it over $3$ seconds? Moreover, does Yahoo always  perform these actions in the same manner? In other words, is your signal seem stationary, or time invariant?
Those are system/sensor noises.
Finally, you take a price for a specific goal. It is a quantity that can be observed, that you may use to model a certain "real word" behavior. There might  be events in the data that are "noises" for your purpose (slow trends, seasonality).
What is important is how those combined noises affect your modeling and processing.


Feature request: unflag

Question: Can we have the option to unflag a post? If an issue is resolved before a moderator gets around to handling the flag, it we be nice if we could get rid of the flag and save someone the time of looking at it.
Answer: As of 2016 this is possible for post flags but not comment flags. Simply click on "flag" on the post to bring up the flag dialog, then "Retract Flag":
Answer: Users have the possibility to flag as invalid an existing flag; it would help if, after X users have flagged the flag as invalid, the post would not appear anymore between the flagged posts, and moderators would not need to mark the flag as invalid.

Feature request: unflag


How to prove $ {a_n} = \frac{n!}{2^n}$ diverges to $+ \infty$?

Question: I would like to prove that the sequence $ {a_n} = \frac{n!}{2^n}$ diverges to $+ \infty$. As I understand it, this means that for all numbers $M$, I must find a number $N$ such that for all $n \ge N$, I get $a_n \ge M$. However, I'm not sure how to pick $N$.
Thanks.
Comment: also https://math.stackexchange.com/questions/77550/prove-that-lim-limits-n-to-infty-fracxnn-0-x-in-bbb-r
Answer: $1$. Using induction, prove that $n! > 3^n$ for $n > 6$.
$2$. Hence, $\dfrac{n!}{2^n} > \left(\dfrac32 \right)^n$ for $n>6$.
$3$. Now prove that $\left(\dfrac32 \right)^n \to \infty$ as $n \to \infty$.
$4$. Conclude that $\dfrac{n!}{2^n} \to \infty$ as $n \to \infty$.
Answer: Note that if $k\ge 4$, then $\frac{k}{2}\ge 2$. It follows that if $n \ge 4$, then
$$\frac{n!}{2^n} \ge \frac{6}{8} 2^{n-3}=\frac{6}{64}2^n.$$
The rest should be straightforward.
Answer: We will be using this result
Theorem 1: If ${a_n}$ be a sequence such that $\lim_{n\to \infty} \frac{a_{n+1}}{a_n}= a\,,$ then
1) if $|a|<1$, then $\lim_{n\to \infty}a_n =0 \,,$
2) if $ a>1$, then $\lim_{n\to \infty}|a_n| =\infty \,.$
Now, we have
$$ \lim_{n\to \infty} \frac{a_{n+1}}{a_n}= \frac{(n+1)!}{2^{n+1}}\frac{2^n}{n!}=\frac{n+1}{2}=\infty, $$
which implies, by part $(2)$ of the theorem, $a_n$ diverges.
Comment: @AntonioVargas: Thanks for the comment. It is already corrected.
Answer: You can use a lower bound on $n!$ instead of $n!$ itself. For example, when $n \ge 3$, $a_n = \frac{n!}{2^n} = \frac{2}{2^n}(3\cdot \ldots \cdot n) \ge \frac{2}{2^n}(3^{n-2}) = \frac{1}{2}\left(\frac{3}{2}\right)^{n-2}$. Since the sequence $\left(\frac{3}{2}\right)^n$ goes to $+\infty$ as $n$ goes to $+\infty$, $a_n$ must also go to $+\infty$.
If you wish to go all the way back to the definition, you only need to elaborate the last sentence. This can be done as follows.
Note that now we know that $a_n \ge \frac 12\left(\frac 32\right)^{n-2}
$ for $n \ge 3$. For any given $M > 0$, pick $N$ such that $\frac 12\left(\frac 32\right)^{N-2} = M$. (More specifically, $N = \frac{\log(2M)}{\log(3/2)}+2$.) If $N < 3$, we pick $N = 3$ instead. Then, for all $n > N$, we know $a_n \ge \frac 12\left(\frac 32\right)^n > M$.
Answer: Take
$$a_n:=\frac{2^n}{n!}\Longrightarrow \frac{a_{n+1}}{a_n}=\frac{2^{n+1}}{(n+1)!}\frac{n!}{2^n}=\frac{2}{n+1}\xrightarrow [n\to\infty]{}0$$
As $\,\{a_n\}\,$ is positive, the above (Ratio or D'alembert's Test) shows the infinite series $\,\displaystyle{\sum_{n=1}^\infty a_n}\,$ converges , so
$$a_n=\frac{2^n}{n!}\xrightarrow [n\to\infty]{}0\Longleftrightarrow \frac{n!}{2^n}\xrightarrow [n\to\infty]{}\infty$$
Note that instead $\,2\,$ we can take any positive real number and the result is the same
Answer: Look at the numbers. You've got $1!/ 2^0, 2!/2^2, 3!/2^3, 4!/2^4 ....$
Or $$\frac{1}{1}, \frac{1\cdot2}{2\cdot2}, \frac{1\cdot2\cdot3}{2\cdot2\cdot2}, \frac{1\cdot2\cdot3\cdot4}{2\cdot2\cdot2\cdot2}, \frac{1\cdot2\cdot3\cdot4\cdot5}{2\cdot2\cdot2\cdot2\cdot2}, ...$$
Or $1/1, 2/4, 6/8, 24/16, 120/32$ ....
After a while, they get bigger and bigger.
Looking at the second way of writing them, you can see that to get from one to the next, you multiply by: $2/2, 3/2, 4/2, 5/2$ .....
If all you want to prove is that the series blows up, you're done.
After a while, you get the next number by more-than-doubling.
If you keep doubling any number, It'll get as large as you like eventually. And your series gets bigger faster than that.


How do I find out what Amazon has stored?

Question: I would like to control/recover/delete files on Amazon.
How is this done?
Answer: Easy, assuming you're using your own AWS account.  Login here: http://aws.amazon.com/ec2/ then click the "Sign in to the AWS Management Console" at the very top.  Select the appropriate bucket and bam - there's your stuff.
Alternatively, if you didn't create an Amazon Web Services account, you're probably using the AWS account of the developer of whatever app you're using to store stuff there.  In which case, you'll need to ask them.
Sorry, the question is a bit vague, so I gave two answers.  If I misunderstood, could you try rephrasing the question with a little more detail?


Visible seam on the mesh

Question: I have started to model a torso. I was happy with it, until I discovered the seam in the mid of the mesh. I have not used the mirror modifier at all, what else could it be?
Comment: Not enough information. Could you add a screenshot in edit mode, and one of the modifier stack?
Comment: I edited the OP
Answer: It seems that half of the normals in your model are inverted (the normals of some faces are facing inward and some outward). This might be causing display problems.
Go to Edit Mode, select all faces and use CTRL + N to recalculate normals.
If recalculating the normals doesn't help, display face normals as lines, select only the faces with normals facing inward, and flip normals on those faces.
Comment: Happy I could help :)
Comment: You shold accept Karolinas answere. :)
Answer: It looks like your main issue is that you have some geometry hidden in the middle. Then the subdivision modifier is taking those hidden faces into account and making the crease.
I would recommend trying the "Select Non Manifold" tool, found from the 3D view header Select > Non Manifold, or the very covenant keyboard shortcut CtrlAltShiftM. Then set it to only select the Boundaries in the operator properties part of the tool shelf.

But do not just delete what it selects, it will select the bottom and top loops of your mesh, you want to keep those.
If that does not help, try looking in wireframe shading, Z to toggle between solid and wireframe, for any gemotery that is not part of the outside mesh.
You also have half of the mesh's normals reversed (the dark part). Just select everything and press CtrlN to fix that.
More info here: How to make all faces flip to the right/consistent direction?

Visible seam on the mesh


A problem on geometric random variable

Question: Let $X_i, i \geq 1,$ be independent uniform (0, 1) random variables, and define $N$ by $$N=\min\{n:X_n < X_{n-1}\}$$. I need to prove that $$P\{N \geq k \mid X_0=x\} = \frac{(1-x)^{k-1}}{(k-1)!}$$. I understand that $N$ is a geometric random variable. I am stuck when finding the quantities like $P(X_i \geq X_{i-1} \mid X_{j} \geq X_{j-1}, \forall j\lt i)$.
Answer: $\mathrm{P}\{N\ge k\mid X_0=x\}$ is the probability that at least the first $k$ entries are in non-decreasing order when the first entry is $x$. I think there is a simpler approach.
Since the entries are uniformly distributed in $[0,1]$, the probability of two entries being equal is $0$. So we will assume that none are equal.
Given that $x_0=x$, the probability that the next $k-1$ entries are at least $x$ is $(1-x)^{k-1}$. In only one of the $(k-1)!$ permutations of those $k-1$ elements are they in non-decreasing order. Thus,
$$
\mathrm{P}\{N\ge k\mid X_0=x\}=\frac{(1-x)^{k-1}}{(k-1)!}
$$
Answer: Here is another approach to the question (although I think that robjohn's answer is the best). Conditionning with respect to $X_1$, we have that
$$
\begin{align}
P(N \geq k \mid X_0 = x) &= \int_0^1 P(N \geq k \mid X_0=x,X_1=y)\,dy \\
& = \int_x^1P(N \geq k \mid X_1 = y)\,dy\\
& = \int_x^1P(N \geq k-1\mid X_0=y)\,dy
\end{align}
$$
for all integer $k \geq 1$. The result then follows by induction.

A problem on geometric random variable


What defines an Almana?

Question: I was learning with a Rabbi today and we came across the following question. An Almana, widow, is not allowed to be married to a Kohen Gadol (see Mishna Yevamos 9:2). However, what defines a widow? Meaning, if the woman was married, had biah with her husband, and then her husband dies, it's clear that because she is no longer a virgin, she can't marry the Kohen Gadol.  But suppose the man dies without having biah with his wife: Do we say that this woman cannot marry a Kohen Gadol because she is an Almana(in the simple sense that she was married then her husband die), or is it necessary that she have had biah with her husband before he died that would label her an Almana and ultimately, unable to marry the Kohen Gadol?
Comment: Related: http://judaism.stackexchange.com/q/3741/
Answer: The mishna in Y'vamos (6:4) indicates that a widow is forbidden to a Kohein Gadol whether she was a widow only from erusin (when intimacy was still forbidden) or whether she was a widow even from nisu'in:

כוהן גדול לא יישא את האלמנה--בין אלמנה מן האירוסין בין אלמנה מן הנשואין.

This is quoted as halacha by the Rambam (Hil. Isurei Bi'ah 17:11):

אלמנה בין מן האירוסין בין מן הנישואין אסורה.

Both types of widow are biblically forbidden to a Kohein Gadol. A widow from either erusin or nisu'in is forbidden to a Kohein Gadol due to a negative prohibition (Vayikra 21:14, אַלְמָנָה... לֹא יִקָּח), and a widow from nisu'in is additionally forbidden due to a positive commandment (Vayikra 21:13, וְהוּא אִשָּׁה בִבְתוּלֶיהָ יִקָּח; Sanhedrin 18b-19a; Rashi ibid. 18b, s.v. ka pasik v'tani; Sefer HaChinuch §273, or §294 in some versions).
The gemara indicates that the definition of almana (widow) for this purpose should obviously include an almana from erusin (Y'vamos 59a; Rashi ad loc., s.v. p'shita). However, since the prime example of an almana in the Pentateuch is Tamar (B'reishis 38:11), who was a widow from nisu'in, the mishna had to clarify that the term almana indeed includes even widows from erusin.
The gemara comments that, notwithstanding the example of Tamar, the parameters of the almana status vis-à-vis a Kohein Gadol are derived from the parameters of the g'rusha (divorcee) status vis-à-vis a Kohein; just as "g'rusha" is defined to include divorcees from erusin or nisu'in, so is "almana" defined to include widows from erusin or nisu'in (Y'vamos 59a; see Rashi ad loc. s.v. dumya d'grusha).
Answer: From a drush perspective, the gemara in  Kesuvos 10b expounds upon the meaning of the word "almanah":

מאי אלמנה אמר רב חנא בגדתאה אלמנה על שם מנה
Why [is a widow called an] almanah? Rav Ḥana of Baghdad said: [A widow is called an] almanah after the maneh

Namely, "almanah" is an acronym for "al shem  maneh"- ie the value of a widow's Kesuvah is worth a "maneh" (one hundred dinars).
Comment: had i known you knew i would have tagged you your own answer,,,
Comment: @user15464

What defines an Almana?


website blocked by netgear firewall

Question: I have a Netgear DGN10000 supplied by Virgin Media in the UK. It is running the latest firmware (V2.1.00.25_VG). For some reason it appears to be blocking all URLs which contain "microsoft.com" but........only in chrome. In IE, it works fine.
I've attached the router config as well.
Any ideas why it could be blocked?
Update: The error message only occurs on my computer's Chrome. On all other computers in the network microsoft.com works fine. I don't have any extensions installed.
Answer: In my case, it was a cookie. Cleared Chrome's cookies and microsoft.com started working.

website blocked by netgear firewall


What, if anything, does "RAW" stand for?

Question: I understand that RAW files contain data straight from the sensor, that they're used as input to the production process that results in a final image, and that RAW isn't really one format but a collection of device-specific and mostly proprietary formats. But the fact the files are always described as "RAW" (all uppercase) rather than "raw" gives the appearance that the name is or was some sort of acronym. If that's the case, what does or did "RAW" stand for. If it's not, how did it come to be written that way?
Comment: You can expect mostly opinion based answers. But have you consider the meaning of English word **raw**?
Answer: I suspect the answer here is that the format is written as "RAW" to match other common file format names which are acronyms such as JPEG, GIF, MOV, MPEG, etc. Nikon, Canon, Pentax, Hasselblad, Olympus, Sony, and many other manufacturers all write the format in all caps, so at this point it's a de facto standard. There is a distinction to be made between a raw image file in the "RAW" sense, i.e. image data unprocessed by the device, and a raw image file in the sense of "straight from the camera, not altered using image manipulation software", and I think writing the file format as "RAW" rather than "raw" helps to make this clear. When you write it in all caps you're indicating a specific file format, even if that format changes from one device or vendor to another.
Alan Shutko points out in his comment below that older cameras used file systems that only allowed uppercase filenames, like "IMG_0001.RAW". This is an excellent point and seems a likely reason that the format was initially written in all caps.
Comment: DOS used all-caps most of its life, and the early cameras used older versions of the FAT filesystem because of lower processing requirements.  These versions were all-caps.
Comment: Which cameras store their raw images with a .RAW extension? The ones I have come across all use their own, e.g. .CR2 .NEF
Comment: Unfortunately, Casio, Panasonic, and Leica have all used .raw as a file extension which just adds to the confusion that .RAW is a specific file format that all raw images conform to rather than just one of many ways of formatting raw data from cameras.
Answer: A RAW file is a container format which includes metadata (proprietary and standard), possibly a JPEG-compressed preview, and a digitized record of the value of each sensor photosite, possibly with some low-level noise reduction applied and with dead pixels removed. This is common across the class of file formats we call RAW. Pure, "raw" sensor data alone wouldn't really be a RAW file. (And arguably wouldn't even be digital.)
People write "RAW" to make the term stand out as a graphics file format. It isn't an acronym, and it isn't even a single format, but it does mean something slightly different from the English-language word "raw" by itself. Therefore, it's useful for it to have a convention where it's written differently.
It's probably also the case that this is influenced by a tradition of writing file names and extensions in all-caps, going way back to the dawn of personal computing with DOS, when filenames were always upper-case and limited to 8 characters of the base filename plus a three-letter extension. See for example this chart comparing "DOC file" to "doc file":

or for that matter, JPEG (an acronym for Joint Photographic Experts Group) vs. JPG (the common file extension, but not an acronym) or lower-case "jpg":

You can see that even though "JPG" isn't properly an acronym, it's still more common than "jpg".
Now, there aren't, commonly, actual .RAW files, as it instead describes a class of files each with their own actual file type and format, usually specific to a manufacturer — .CR2, .NEF, .PEF, .RAF, .ARW, and so on, as well as the semi-standard .DNG (which does stand for something: Digital Negative). But, nonetheless, all-caps RAW is dominant:

So, is it proper English? Nah; it's jargon. But it is a well-established convention understood by many people and is helpful shorthand which conveys extra meaning.
Answer: "RAW" is not an acronym and shouldn't be written in uppercase, it should be written in lowercase. Raw suggests that it's the image as captured by the image sensor in your digital camera or the film without any modification.
Comment: Personally, I write it in caps so that the fact I am discussing a **file format** stands out. Lowercasing it as simply raw allows the term to get lost within the text, and may lead to ambiguity.
Comment: I totally agree grammatically it should be "raw" or if referring to a specific format it can be a proper noun: "Raw". However I long ago gave up the fight and started using RAW for the sake of convention.
Comment: I agree to some extent, but the industry doesn't: specifying the file format as "RAW" is common practice everywhere from camera interfaces to user manuals to photography-related web sites including this one.
Answer: RAW doesn't stand for anything; it just means the unprocessed (raw) form of the data that was captured.
Comment: Uncooked data? ;)
Answer: Traditionally, the filetype ".raw" was a true raw pixel format, containing only the image buffer streamed to disk with no meta data. Photoshop and other viewers would then "guess" the height, width, bit depth, and channels by matching the file size with common aspect ratios and resolutions, otherwise user interaction was required.
Now it is commonly used as a common denominator for uncompressed or even lossless compressed sensor data before bayer interpolation from the cameras incl. a lot of meta data, and jpeg thumbnails. These are not true raw files, but most of them does have a raw file inside. I say most of them, because Canon does have versions of its "CR2" format that stores half resolution "RAW" images, and these are not raw at all.
Comment: This is important to note, because RAW generally means "one of those container formats from a camera, which is probably really a DNG, CR2, NEF, PEF, ORF, RAF, or X3F file, with _that_ extension, not actually .RAW", not true _raw files_.
Answer: There is a useful discussion of this issue on the talk page for the Wikipedia entry for raw image format. To summarize, Wikipedia editors decided on "raw" because it is not an acronym and therefore they felt there was no logical basis for its capitalization. That said, they decided to note that it is often capitalized, acronym-style, in common usage. I wouldn't call Wikipedia authoritative but I generally follow its examples unless there's a good reason not to do so, so "raw" it is.
Comment: Honestly, I don't think this counts for much. This is just the opinion of a handful of randomWikipedia editors without a lot of expertise, and seems to hinge on the idea that the term is just the plain English word "raw", which is actually factually incorrect.
Answer: Let's ask the camera makers...


Why do turbofan engines not have a contrarotating second fan?

Question: Why aren't planetary gears used to have a fan in front of the fan in a turbo fan engine. Would this not lower energy consumption etc?
Comment: Related: [Why are contra-rotating jet engines so rare?](http://aviation.stackexchange.com/q/31613/1696)
Comment: It's not simple, in the same way that contra-rotating propellers are not simple and we don't see them very often.
Comment: I mean could you not have a double fan in a turbo fan going in opposite directions by using planetary gears. why isn't this done when contra-rotating propellers have advantages that I would guess are transferable to turbo fans. this seems like a simple way of doing it? @mins
Answer: The power to drive a fan through a gearbox is not beyond current technical capability. Pratt & Whitney have developed the geared turbofan, the PW1000G that first ran in 2008 and entered commercial use in 2016, flying on 4 different aircraft, including the Airbus A320neo. This enables the fan to spin at a slower speed than the low pressure turbine, such that the turbine spins at a higher speed that is more efficient for power extraction from the relatively high velocity mass flow, while the fan spins at a lower speed that avoids the blade tips lossing efficiency or creating noise at take-off, due to near sonic flow.
The engine design involves trade-offs. The complexity and weight of a counter rotating two stage fan needs to be balanced against the achievable pressure ratio with a single stage fan, and the added benefit a two stage fan would provide. Some design work has considered counter rotating compressors for example, this thesis. or even earlier work in  1992. The gas turbine industry can be quite conservative - it costs huge amounts of money, and time, to develop a new engine design, and radical steps are much less common than evolution. Pratt took a gamble, that appears to have paid off, though they do still have some issues. However, it took them decades, and around $10 billion. Rolls Royce are considering a similar design (the UltraFan), but GE are more wary. They have chosen the use of new materials as they felt the addition of the extra component would add reliability, weight, and durability challenges that they could avoid by using material improvements instead. For example, the use of ceramic matrix composites in the hot section of the CFM56 LEAP. They claim this gives 15% fuel savings, but has taken 25 years to develop. In comparison, P&W claim the GTF is 16% more fuel efficent than current generation engines. So each manufacturer choses the route they are comfortable in, and may get to the same end point.
In general, the desire has been to increase by-pass ratio, as this lowers specific fuel consumption. However, increasing BPR results in larger diameter fans, and higher tip speeds, approaching sonic velocity if the turbine is run at the optimum rpm. Hence, the geared fan approach. Clearly, Pratt & Whitney did the trade-off analysis, and decided this was the best approach for a geared fan, balancing techncial risk, reliability, performance, in-service cost, and weight.
Comment: Also, you didn't really touch on the difference between just geared turbofan, where the fan spins at different speed from turbine, and contra-rotating fans, where there would be two fan stages rotating at opposite directions. The relative speed would be greater and so there would be greater losses in the later case—with little benefit, because a stator is almost as good and much simpler.
Comment: Well, PW1000G is still just a medium engine. Nobody tried to make a geared turbofan of the size of Trent 900 yet.
Comment: @Jan.  Your comments are fair, Jan. It is more of a general answer, than really getting to the technical crux of the question.
Answer: The power needed to drive a large fan is currently beyond of what is technically possible in gearbox engineering. The swirl losses of a single-stage fan can be somewhat recouped by inclining the struts holding the fan fairing, so a contra-rotating fan is not much of a help, but a tremendous engineering challenge.

EDIT:
Clarification: Small geared fans do exist for a few decades already (Lycoming ALF502) and the maximum size of geared fans is increasing, but the size of the biggest engines is still far out of reach of today's technical possibilities. The biggest geared fan today has ⅓ of the thrust of large turbofans.
Answer: There is a reason why one might think counter-rotating fans could reduce energy consumption: any propeller or fan causes the air to move, besides the desired axial direction, also to some degree in a circular swirl manner. This is wasted energy.
There are different ways to reduce this loss. The simplest is to increase the diameter and decrease the blade angle of attack. But increasing the diameter can't be done without limits, and low AOA requires the blade tips to move faster – possibly supersonic, which creates its own problems. For this reasons, most big turboprops have relatively small, many-blade, relatively high AOA props – although that's not optimal swirl- and bladetip-vortex wise.
The most extreme approach is counter-rotation. A second coaxial propeller can cancel out the swirl, without increasing the diameter at all. So this is in particular useful for very large turboprop planes, the Tupolev TU-95 being the prime example. This plane still had supersonic prop-tips.
In a turbofan, the swirl is actually even more of an issue, because you have small diameter, lots of blades with a high angle of attack (and also high camber). But turbofans don't actively cancel that swirl, instead they use it passively to gain extra thrust. That does in fact not require contra-rotation, but only stator vanes. What these do is, they redirect the swirling motion backwards. That still recovers much of the energy loss from swirl, while being much less complex than gearing for counter-rotation would be.


Torquing Strut Nut with Tire on Ground

Question: I will be changing my wife's shocks and struts next week on her 2012 Outback. The service manual says not to tighten strut mounting nut until the car is on the ground. Do I really leave  the nut that locks the cylinder to the mounting plate loose until the car is lowered?
Comment: The answer given applies to tightening all suspension components.
Answer: You should leave them just about snug, if not just a little loose. If you tighten them before you put it on the ground, when you do get the car on the ground, there will be tension on the parts, which means it will wear quicker. So, leave them a little loose, then tighten once on the ground ... there's no worries about safety when doing so. It's not like its going to detach from the vehicle ... the nuts/bolts are still there.
Comment: For clarity, I think a better description would be to tighten the bolts once the weight of the vehicle is all back on the wheels.  So the car could be on a lift or raised off the ground with blocks of wood under the wheels, as long as the wheels are supporting the full weight of the car.  It doesn't literally have to be back on the ground.
Comment: Should all the top nuts be a touch loose or just the ones that fasten to the car?
Comment: I agree with @HandyHowie, however, the weight needs to be as it would be on the ground ... ie: all four should be suspending the weight of the vehicle at the same time. IIRC, a Subaru has two bolts which attach the bottom of the strut to the steering knuckle. These two I'd tighten. With the ones on the top, it wouldn't hurt for all of them to be just a tad loose. Try to get them back to where they were to begin with for adjustment. Don't forget to get an alignment done.

Torquing Strut Nut with Tire on Ground


Misplaced Terminal.app

Question: How can I find Terminal.app manually?
I believe that I moved it somewhere using a command line like this:
sudo mv Terminal.app ./Desktop

It didn't show up on my desktop, and it isn't in Applications anywhere
Comment: Can't the search engine on the top of your screen help you with that? There isn't much I like with Macs, but the search engine isn't one of them. It's really well-made.
Comment: Are you sure you didn't *re*move it?
Answer: Terminal is in /Applications/Utilities/ by default.
If you actually moved it, try typing Terminal in the Spotlight menu and pressing ⌘↩ (command-return). (If ⌘↩ doesn't do anything, it's probably because of the Apple Events bug in 10.8.2.)
If even that doesn't work, try running this in AppleScript Editor:
POSIX path of (path to application "Terminal")

Answer: If that's the command you typed, terminal is now named 'Desktop' and is still in your /Applications/Utilities folder (since you would have had to be in that folder for the command to do anything at all).
Take a look in there for stray Desktops :)

Misplaced Terminal.app


What tools can I use to deploy PHP code to an EC2 instance

Question: We can bundle all files into an Amazon Machine Instance and upload it. But I'd like to see if there is a more efficient way to regularly upload source code on to test our app and constantly have the latest version up and running. Thanks!
Answer: A while ago I discovered an easy way to deploy PHP using Git's push. The one caveat is that the process assumes you're already using Git as your VCS, and that you've installed it on both your development machine and the server:
Deploy a project using Git push
Answer: I am not sure I understand your question correctly, but an Amazon Machine Instance is just like any other machine running Linux (or Windows). You can use the same tools you would use if the machine was in your network. Of course you need to do this remotely. From a windows machine you can connect to an instance using tools like Putty or WinScp - you probably know about these, if you are able to create a new image. Use these tools to configure your instance as you would have configured a machine in your local network.
Answer: it depends on what you call 'deployment'. I've seen people calling ftp-ing files over to the server 'deployment' :)
in short you want your deployment be:

automated
atomic
reversible
manage db schema

longer description is here:
http://blog.astrails.com/2008/12/17/deployment-process-requirements
Note that you can have most of it using deployment tools from the ruby land:

capistrano
vlad


How many moves ahead does Anand calculate in his mind?

Question: I always wondered about this! How many moves ahead can strong players like Anand actually 'see' during the game? How does the calculation of a supercomputer like Deep Blue differ from that of strong human players?
Comment: Apparently not enough moves after that huge blunder he made  in game 9. Ouch.
Comment: I reworded your question a bit, hopefully without altering your intended meaning.
Comment: Post google's alpha-zero, the answers to this question would likely have to be rewritten, as the approach there is quite different from anything that has been done so far.
Answer: first of all see here. here is a quote

Asked how many moves ahead he can think, Kasparov replied that it
  depended on the positions of the pieces. "Normally, I would calculate
  three to five moves," he said. "You don't need more.... But I can go
  much deeper if it is required." For example, in a position involving
  forced moves, it's possible to look ahead as many as 12 or 14 moves,
  he noted.

for a supercomputer it obviously depends on how well-written it is, there is a concept called alpha-beta, which is used to limit thinking into unnecessary moves, like the computer usually wont consider the opponents (white) c3,b5,d6,f7, combo, on the first move. however after c3, b5 it should consider d6, and have a reply ready. from a page called Creating a chess engine from scratch on chess.com:

A computer can easily evaluate a few million positions per second, a
  human probably 1-2 positions per second!! Usually speed is measured in
  MNodes/sekund which means million positions (Nodes in computer science
  jargon) per second. Fritz running on my old laptop does about 2.5
  MNodes while Deep Blue did about 200 MNodes per second. Raw power is
  not all - the evaluation function is also very important. Pretty much
  all engines use the same algorithm for searching through the search
  tree of possible moves to find the next move. This algorithm is known
  as alfa-beta search or it is some variant of this.

an important difference is that a computer has to consider things a human takes for granted, such as the concepts behind a known opening, even though a good program can remember which combos work (and rate them, then play based on  its ratings), its extremely difficult for it to recognize concepts, such as a fork independent of the result, this can be a advantage because a human may fork, and not see another better future move.
hope that helps!
Answer: This is an ill defined question, similar to: what is my girlfriend thinking about when we ... ?
But to stab at an answer, it would be completely dependent on the position. If the position has many tactical variations possible, the answer will probably be very far, 5, 6 or more moves ahead.
If the position is very closed, and positional strategy matters, the answer is probably that he is largely relying on his previous experience, understanding of positional strategy, and analysis of openings/other tournament games in guiding his moves. This usually means he has memorized the possible variations and can move with confidence knowing he is not blundering.
If the position is considered an endgame position, once again, he should be able to see very far ahead since the number of tactics and variations is greatly reduced.
This is mostly true of all chess players, the difference being that master and grand master players can perform all of these things to a greater degree than lesser players.
In terms of how this applies to the development of a Chess Engine such as (Deep) Blue: it doesn't. Computers are largely computational beasts and other than large databases of known openings/endgame position and transposition tables they don't largely rely on previous experience. They simply search for the best move as defined to be the move such that the opponent's best (following) move is weakest (this is the principle behind the min-max search algorithm which is usually used in Chess Engines.) It is a well known trick that when a human is playing a strong computer opponent they should aim to create a largely positional game with few tactics in order to increase their chances of winning. Computers make far fewer mistakes than humans in calculating tactics and, in general, have poor positional play.
Comment: +1 for the first sentence, although a more accurate simile is "how many moves in advance does my..."
Answer: Just thought to add the famous story (likely apocryphal):
During a tournament in the 1920s a newspaper reporter asked Richard Reti how many moves ahead he could read. Reti replied "I only see one move ahead: The right one."
Comment: `+1` i should find a opponent like that, lol.
Answer: Players such as Anand and Carlsen can play top-level blindfold chess.   I assume this means that the number of moves ahead such players can "see" is essentially unlimited: at the board they can presumably visualize a continuation of the game to its conclusion.   But a single very deep search down a single branch of an enormous game tree, though very important in certain situations, is not in itself enough to produce the best moves (and also may not be the best form of time management).
Comment: I only answered the first question, since an answer to the second could run to book length.  Regarding the latter, the OP might get some insight from Feng-hsiung Hsu's book "Behind Deep Blue: Building the Computer that Defeated the World Chess Champion."
Comment: +1 While the answer may sound like nitpicking, I think many non-chessplayers simply don't understand how a grandmaster can see many moves ahead, and the question often means "how many moves can a player follow a line without moving the pieces before he starts forgetting the position" and not for example "how many moves ahead are they calculating while thinking about a move for 20 minutes".
Answer: How far ahead a strong player like Anand sees depends on the position. On move 1 he doesn't see any moves ahead because he doesn't know which of several perfectly good replies his opponent will play. In the endgame there might be a forced line which is 15 or 20 moves long which he will see and so, by the way, will many weaker players.
The two significant differences between a strong human and a supercomputer are:
1) A supercomputer can calculate much, much faster than any human and so can consider many more moves (orders of magnitude more) than any human in the same time.
2) Very strong players are much better at evaluating a position than supercomputers. This means that they can quickly reject unpromising lines and so dramatically reduce the number of variations they need to consider and do this much better than the supercomputer. Effectively they can often see as far, sometimes even further than the supercomputer.
Incidentally, this superior evaluation ability separates strong grandmasters from not only supercomputers but also ordinary players like you and me, or at least me ;-).
Weaker players are often not that much different in their calculating abilities from stronger players. They just don't recognize whether the resulting position is good or bad anything like as well as the stronger players do. Their poor evaluation abilities mean that they waste time, just like the supercomputer, analyzing unpromising variations.
Comment: Good answer, but I wonder how much of their ability to evaluate is based upon analysis that they have previously done off the clock.


How does the pi know which kernel to load?

Question: In the boot partition there are two kernels, kernel.img and kernel7.img (for the pi 1 vs 2/3). How does the system know which to load?
Answer: All the boot magic is in /boot/config.txt.

kernel:
  The alternative filename on the boot partition to use when loading the kernel; the default value is kernel.img.

from official documentation
Update: to clear up some confusion and to satisfy my curiosity, I tried the following small experiment.
I DO NOT RECOMMEND YOU TRY THIS!

On my RPi3 I do not have the kernel entry in config.txt, and the system boots up fine.
I deleted kernel.img.
I renamed kernel7.img to foo.bar.
After rebooting the RPi, the system failed to load. I got the multi-colour screen of death, as expected.
I added kernel=foo.bar to my config.txt.
Rebooted the system, and it worked.

This proves two things:

The system can intelligently select the correct kernel per architecture, within some limits.
The kernel entry in config.txt works if used.
Comment: This is **NOT** used by normal images.
Comment: @Milliways What do you consider "normal" in this context? There are several sources, for example this http://raspberrypi.stackexchange.com/q/10489/53481 and several things linked from there, that agree with me.
Comment: By "normal" I mean any of the prebuilt images downloadable from the Foundation site. The post you linked is an earlier version of the link in my answer (before loader.bin was removed).
Comment: From the linked docs it seems `/boot/config.txt` is passed as an argument to the closed source GPU firmware `start.elf` which then launches the kernel specified - the confusing bit is that it seems all the boards use the pi 1 kernel image out of the box, but still contain a `kernel7.img` in `/boot` I guess that's what's necessary for one SD card image to work across all the boards.
Comment: @plasticchris: Indeed. Pi 1 doesn't use the kernel7.img at all (and vice versa, Pi 3 doesn't user kernel.img) , but they're both included (with their dependencies). I suspect that it allows for using the same card in various RPi models *automagically*.
Answer: See http://elinux.org/RPi_Software#Overview which describes the Pi boot process.
Basically bootcode.bin analyses the hardware and (presumably) decides which kernel to load. (The source is not publicly available).
It is (or was) possible to specify a different kernel, but this is NOT used by normal images.
NOTE With the new USB/Network boot options for the Pi3 the process has changed but the principle remains similar.
For those interested in reading more about the new boot options Raspberry Pi boot modes
Comment: FYI: I tried a small experiment to verify my answer. See my update.
Comment: I think we are both saying the same thing. I was just trying to clarify my answer. Maybe I failed. Sorry.
Comment: From your link, I read that completely differently. "Second stage bootloader (bootcode.bin) - This is used to retrieve the GPU firmware from the SD card, program the firmware, then start the GPU." Reading further: "User code - This can be one of any number of binaries. By default, it is the Linux kernel (usually named kernel.img), but it can also be another bootloader (e.g. U-Boot), or a bare-bones application."
Comment: @SiKing I don't understand why you are deliberately misinterpreting my answer. I said the `kernel` option "is NOT used by normal images" NOT that it couldn't be done. This is easily verified by looking at config.txt in any standard image.
Comment: @SiKing You are also **NOT** answering the actual question "How does the system know which to load" **NOT** what other methods can be used to load kernels.
Comment: these threads have been very constructive and right on point, IMO. Understanding how these devices work is difficult and general discussion on options and limitations is super helpful.


Connecting through Toronto on separate tickets

Question: Come Christmas I am booked to fly SEA-YYZ-JFK on two separate tickets. (and two airlines: UA & AA)  Can I assume that I will have to go through immigration, claim baggage and customs (unless pre-cleared?), then change terminals and do the standard check-in routine?  I have a 4-hour layover to hopefully lower the odds of a missed connection.
Comment: What is your nationality ? Not everyone knows every airport codes. Its easier to read the name of the city than the airport code.
Comment: I'm a US citizen flying Seattle-Toronto-NewYork on United and American.
Answer: Yes, your assumption is correct. Depending on the time of your flight usually the customs usually is fast. However, you have to keep in mind the Christmas rush and be swift at the airport. You also have to keep in mind that you will go through preclearance when boarding a US bound flight. If you/r bags aren't pulled over for extra scrutiny you will be fine, I think.
Answer: Pearson has a very cool Connecting Guide that answers this question for you. I entered your details, and it said (bolding mine):

Arrive at Toronto Pearson. Your flight will be arriving at Terminal 1.
Confirm your gate number. Once you're in the terminal, look for your departing flight on the flight information screens  then follow the "A" connection signage.
Go to Canada Customs. Look for the A gates signs and follow them. This can be a bit of a long walk, so take advantage of the moving sidewalks.
Pick up your baggage. Follow the signs for Baggage Claim and pick up your baggage. You'll need to take it with you to recheck it.
Recheck your baggage. Drop off your baggage at the connection drop-off belt.
Take the LINK Bus to Terminal 3. Your connecting flight will be leaving from Terminal 3, and the quickest way to get there is the wheelchair accessible Terminal Link. The bus picks up guests 24/7 from the Departures level curb of Terminal 1 and travel time is approximately 6 minutes. Follow the A gates signs to the bus stop

At this point, things get confusing because it has already told you to drop off your baggage and now it wants you to pick it up again (I think connections USA-USA are rare. Take instructions from someone locally about whether your baggage goes on the connection belt or goes with you to Terminal 3 for your conversation with US customs. My guess is it stays with you, see below.)

Pick up your baggage. Follow the signs for the A gates to the connections carousel and pick up your baggage. You'll need to take it with you to recheck it.
Go to US Customs. Look for the US Customs and Border Protection signs and follow them.
Drop off your baggage. Drop off your baggage at the baggage drop-off belt.
Go through security screening
Head to your departure gate. There are various flight information screens throughout the terminal that will point you in the direction of your departing gate.

You can find interactive maps of both terminals (AA uses Terminal 3, United uses Terminal 1) on the Pearson web site. The only possible confusing part is the double customs. You will need to clear into Canada, and then preclear into the US while still in Canada.
Longest lines I have ever been in have been up to an hour for customs - this is why I got Nexus - but in Terminal 3 they have a new automated system that is much faster for arriving from the US. A more normal customs wait is 10 or 15 minutes. Security can be no wait at all or 30 minutes in busy times. Baggage dropoff might be another wait if you don't just toss it on the connecting belt. Since you're changing airlines I think you need to go talk to a human and get a new tag. That can be a 30 minute wait if you have no status with the airline you're lining up for.
If I was doing this with a 3 hour connection I would be nervous. Probably not with real justification, but I would still be nervous. With a four hour one, you're fine. If this is something you'll do regularly, get Nexus/Canpass/Global Entry. They will save you a ton of time.


Can't pick up ammo

Question: Why can't i pick up ammunition on certain parts of each stage, from chapter 2 and onwards? I've got room for more ammo, but for some reason a red line is shown across it, therefore making it unequipable
Answer: You have limited inventory spaces, ammo takes up space in your inventory like every other item - herbs, grenades, health spray, etc. Each ammo/grenade type can hold up to a maximum amount for each inventory space, afterwards it'll take another inventory space. Check your inventory (Trinagle on PS3, I assume Y on xbox 360) and see if you have any open inventory spaces. If not, you can choose to throw away some uneeded stuff, but try using your inventory before throwing stuff away (for example, combining/equipping herbs, reloading weapons, etc.).
While it may seem your current weapon's clip still has space for more ammo, you cant reload directly from an ammo drop, you need to be able to pick it up to your inventory, then reload.
Comment: saved my file! #xboxcool

Can't pick up ammo


What graphic dimensions would allow it to be printed at the same size regardless of selected scale options?

Question: For standard letter-size paper in a basic printer, the user can select to Print Actual Size (No Scale) or Fit to Page options. I estimate that a graphic 8" by 10.1875" gets close to not appearing different sizes, but its not exact. What are the dimensions needed so the printed graphic appear exactly the same no matter which scale option is selected?
Comment: This entirely depends on your printer... the manual should tell you the printable area... and that's your answer (or set "scale to fit", which in my experience normally tells you the scale... then work out the size from that).
Answer: There is no way to answer this because each printer has a different "live" area for a page.  My desktop printer might leave a 10mm border around the edge of a paper, but yours might only leave a 5mm border.  That's why "fit to page" is a setting that is controlled by each individual printer driver, because it is dependent upon the capabilities of the individual printer.
Answer: There is no such option for most printers, and most printing mechanisms out there. Just simply not going to happen.
However, that said it IS possible to do if you are sending unaltered postscript or eps to your printer as part of the stream and the printer supports postscript. While admittedly this is a far fetched corner case, not likely to work on most printers, it can work. I have once tried to do this as a exercise with some mixed results.
Its just easier to instruct the operator to do it correctly. One nifty way to make the mistake visible is to add internal crop marks. Since most printers can not do edge to edge printing, if the marks are visible then there was a mistake.


How to better and smooth cracked heels and make them soft?

Question: How to better and smooth the cracked heels and make naturally softer my skin. Please tell me in detail, my heels are cracked and sometime more pain arises. When I use lotion/moisturizing cream then I feel pain and my heels are also looking bad. How can make them smooth?
Answer:
First of all, you need to know why you feel pain when you apply lotion
  on your skin. I recommend seeing a doctor to find out what is
  happening that makes your skin painful and with cracks.

Once your doctor has given you the treatment and with your skin on a healthy state, you can try this homemade lotion I use to smooth skin and remove cracks.
Here's the recipe:

Ten crushed acetylsalicylic acid tablets
3 tbsp of body moisturizer
25mL of glycerin
25mL of 20 Volume cream hydrogen peroxide

Mix it all together to create a lotion. Apply on your feet and cover them with socks. Keep it for eight hours and rinse with water. I like to sleep during this period. This is the only product that smoothes my heels! The lotion is very watery. You're not supposed to feel discomfort while using this lotion, so if you feel pain, you should rinse immediately.


How many domains to split components across?

Question: I understand how splitting components across domains can maximize parallel downloads, and enable you to have cookie-free static content domains, but since there's a time cost for each domain lookup what is the optimum number of domains to use?
Answer: My recommendation is that for relatively simple sites, one "static content" domain should be sufficient. DNS lookups should be cached, so only affect the first contact with that server, but it should still be kept to a minimum.
You can place all of your Javascript, CSS and static images on there to reduce the overhead of cookie processing and to provide the option of offloading that work on to a different physical server. If you are running multiple popular, related sites (e.g. Stack Overflow, Server Fault etc.), then you can share a static site between them all (e.g. sstatic.net).
Of course, there may be situations where more domains are appropriate (e.g. a photo hosting site may offload the photo serving to another separate domain).
Comment: If you use any JavaScript frameworks, you can also get Google to host these for you (http://code.google.com/apis/ajaxlibs). This has the added benefit that if the user has already visited another site which grabs JS from Google, they may already have it in cache.
Answer: I can think of one edge case where the benefits of multi-host requests outweighs the DNS setup costs.
When serving map tiles from a Google Maps-style slippy map, you can see benefits from distributing your tile locations virtually across a much larger number of hosts, even if they are all pointing at the same underlying resources (images).  In these cases, you'll want to ensure that the resources have an "affinity" set to one host based on their properties (such as some combination of the MOD of row and column numbers) so that browser caching works optimally and requests are balanced across all hosts for any given view extent.
This situation is very specialized, but it basically just emphasizes that if you have a non-standard use case make sure that you test everything, and don't forget to include both raw numbers and UX / perceived performance of all of the scenarios.


How to make an NTFS partition on HDD (12.10)

Question: I currently own a netbook running Ubuntu 12.10 and i want to install windows XP on it. I have the installation file on my pendrive as my netbook doesnt have disk drive. but when I opened the setup.exe, it didnt open. So i installed WINE on my netbook,
I opened the file and setup opens, but when I try to install it it says-
" NO valid system partitions were found, setup is unable to continue"
Then I decided to make that pendrive a bootable one,, so i could install XP, so i downloaded rufus, it didnt run on my system idk why. So i did some research and found a video which showed to make my pendrive NTFS, and then use unetbootin to make it bootable.
Si i downloaded the 7zip application and then selected the XP iso for unetbootin... I waited  for like 10 mins for the process to finish. then i rebooted and booted from the pendrive,
but it had a small blue screen saying unetbootin ( something like that) and a timer below counting down from 10 for something(for automatic boot AFAI remember), and it said press tab to edit options.and after counting to 10 the whole process starts again :(
Please help me install XP on my netbook. Can anyone tell me the solution or an easy way to install XP??  I think that making an NTFS partition on my existing 120 GB HDD will work but im afraid that it will delete ubuntu. I only have this PC at the moment HELP!
P.S. please keep in mind that im a total noob
Answer: Install GPart on your Ubuntu.
Open Gpart and select your HDD and make some free space by resize/delete option.
make usb drive as bootable and boot XP from your usb drive.


How deep should drip irrigation be installed?

Question: I just moved into a new home, and the flower bed drip irrigation is buried under mulch and about 2 inches of sandy loam.  This isn't a correct install is it?
Answer: There are a variety of drip irrigation configurations, some are meant to be underground while others are meant to be above ground.
An example of underground drip system could be found at: http://www.dripworks.com/category/dripworks-drip-tape
This type of drip tape could be buried anywhere from 0" - 5" of depth.
An above-ground system would be an irrigation system that you could get at most hardware stores.
The mainline of above-ground drip systems could be buried while the emitter lines and drip emitters should be above-ground.
Answer: There is no correct way. Some dripline has special emitters that can't be clogged by roots. It might be great for some plants, but would you really want to bury this and let it become a permanent part of a tree's root system?
For transport runs it's a trade-off. Ease of maintenance or modification. Root entanglement. Tool damage. Sun damage. Rodents. Etc.
I handle my yard/plant/equipment tradeoffs as follows: Rig a surface system first. Offset long tubing runs to the side by the depth I plan to bury them later, to create the needed slack. I don't bury sections with emitters or barbed inserts, just transport runs. Once it's all set up and tested I go about selectively burying the annoying runs across the yard. Depth depends on where, how long, how likely I am to modify, and whether it will entangle tree roots.
Comment: I am considering this approach, but my concern with burying afterwards is that I might damage the supply lines with my digging tool trying to dig the trench.


Four noble truths, any single being of mankind can invent, find the new truth other than that?

Question: Gautama Buddha found the traditional path of previous Buddhas and spoke about "The four noble truths". Nowadays, people cannot talk about/discuss the truth or falsehood of idea/notion/philosophical/religious entity. Did the current generation lose the ability to judge/determine/conclude the truth or falsehood of idea/notion/philosophical/religious entity? Or do we universally accept the idea that not a single living being be able to find/invent/prove that the new truth about the entities? Do we really have to remove the words truth and false from our dictionaries since we are not allowed to use in anywhere else?
Answer: If you will study in-depth, the Four Truths are a complete system in themselves.
Asking if there is a 5th truth to be invented is like saying if there is an additional step to the scientific method... i.e. such a person does not understand the scientific method in the first place.
Answer: So, your question is from outside the perspective of Buddhism, which I have to say is wonderful.
From the Buddhist perspective, the word "truth" in English has multiple meanings which don't always strictly mean the objective truth of a situation without bias. For example, the Four Noble Truths are not true in the sense of "true/false" but rather in the sense of "true to the ideal"—in their case, true to the ideal of overcoming suffering. They are "truths" in that they are statements about that ideal as the Buddha taught, rather than being "false" and diverging from it.
We should each measure the truth of these by experience, rather than by any absolute truth or falsehood. Trying to talk about them in this sense shows a degree of lacking knowledge, and it doesn't apply in that sense.
So, no, it's not that these words are removed; it's that they don't apply in the way you want to apply them. They are faithful to the ideal teachings of the Buddha, and so cannot be claimed as false, even if they are found false by the measure of any particular person's experience.
Answer: The Four Noble Truths are absolutely true & cannot be disproven as false. Therefore, it is pointless to argue they are false.
This said, Buddhism does not encourage the dogmatic attachment to spoken truth but totally exhorts the truth must be verified by each wise person prior to belief.
In summary, the Four Noble Truths state:

All suffering is (egoistic) attachment to the five aggregates.
All suffering arises when there is craving leading to new (egoistic) becoming.
This suffering will end when craving ends.
The noble eightfold path is the way of practise to end suffering.

In short, it is impossible to show there is an arising of suffering without craving, attachment, becoming, egoism, etc.
However, people may not accept the truth due to craving, such as occurred in the Piyajatika Sutta, where a man did not believe the Buddha, when the Buddha said:

"Sorrow, lamentation, pain, grief & despair are born from one who
  is dear, come springing from one who is dear"

Instead, the man believed gamblers who said:

"Happiness & joy are born from one who is dear, come springing from one who is dear".


Shimano RD-5800 and 7 speed cassette

Question: Is Shimano RD-5800 rear derailleur compatible with a 7 speed cassette?
Answer: Nope. The RD-5800 is the previous generation 105 level derailleur that works with 11 speed shifters and cassette.
You need a derailleur intended specifically for 7 speeds. The only 7 speed models Shimano makes are in the Tourney range.
Apparently, at least for 7-9 speeds, Shimano road derailleurs are compatible with 7-9 speed shifters as the combination of shifter cable pull and derailleur ratio will index the cage correctly. This does not work for 11 speed though.
Comment: Yes the shifter does the indexing, and pulls a certain amount of cable per sprocket, but the derailleur also has a *derailleur ratio* which is how much it moves the cage per cable pulled.  AFAIK there used to be compatibility across different Shimano speed drivetrains, but 11 speed broke that.
Comment: I don't think so. The derailleur is not indexed (unlike the shifter) such that new a derailleur is compatible with old (7-speed) shifters. See http://blog.artscyclery.com/science-behind-the-magic/science-behind-the-magic-drivetrain-compatibility/
Comment: 11-speed derailleur can be installed together with shifter indexed for 7 speeds, but the combination will not index correctly for 7-speed cassette. Check "derailleur ratio" under the link you posted. 10-speed road derailleur or any Shimano derailleur for 9 or less speeds will work.
Comment: @ArgentiApparatus 5800 was superseded by R7000 a week ago, so it's not really the last 105 anymore.

Shimano RD-5800 and 7 speed cassette


Mr. Beer kit expired in 1999

Question: After reading some reviews online I'm most definitely sure the malt extract is no good, I was wondering if the yeast would be any good (just curious).
Answer: 17 year old dried yeast? Which costs maybe $5 new? And is the most critical factor in the production of beer? (Brewers make wort, yeast make beer).
Replace it.
Comment: Or give it a shot and call it Necromancer's Undead Ale ;)
Comment: I agree, replace it, by friend did the same thing, don't use those ingredients, leads to undrinkable beer and disappointment.
Comment: Agreed, replace it.
Comment: Dried yeast should be quite resilient. Why not try nurishing it, and see if it is still alive? Then make an undead ale like @Jarrod Smith said ^^
Answer: That's old. Its' ingredients are toast for a drinkable beer. Yeast is dead for sure. Hops will have nothing to offer either.
But the extract you can still make use of for yeast starters, just crash and decant the beer off. But still wouldn't be as good as using fresh DME.
The hardware should be fine, just check the plastics for cracks etc.
Answer: Yeast isnt so much the worry, its the extract and grains.  Ive brewed with LME's that have sat on the shelf for a year or so and it leads to a very unpleasant cardboard taste and thats the nice way to describe it.
Comment: Actually, yeast is the first thing to replace. Stale extract will taste unpleasant, but will work. Stale hops will still somewhat bitter. Dead yeast will do nothing and lack of fermentation will let wort to rot.

Mr. Beer kit expired in 1999


How can I convert a Word (.doc or .docx) file to a PDF on an iPad?

Question: I would have thought this was one of Goodreader's many tricks, but it doesn't seem to be the case.
Answer: If you have network access you could send it to Google Docs (upload, email, whatever) and then fetch the PDF from there.
Answer: You could open it in pages and then export to .pdf.
Source: Experience and Apple Website
Answer: I went through this same hassle and it prompted me to write a tutorial on it.  A summary:

Preview the attachment in the Mail app.
Open the attachment from Mail into GoodReader.
Connect GoodReader to Google Docs.
Upload your doc from GoodReader to Google Docs.
Open up the Google Docs site in Safari.
Open your Word file in Safari in Google Docs.
Switch to the desktop version of the Google Docs site.
Download the file as a PDF.
Comment: While this may answer the question, [it is best](http://meta.stackexchange.com/q/8259) to summarize the contents of the link and provide the link for reference. Links have a tendency disappear over time, leaving a non-applicable answer for those who may stumble upon your answer in the future.
Comment: Good call, @daviesgeek -- I added a brief description of each step.
Answer: Simple, local, free solution on the device - no online cloud services required
The solution is to open the file in the App Microsoft Word available in the Apple Appstore.
Then in the MS Word iOS App, when the document is opened, goto "Print" - "in another App" and Word will convert the docx document to a pdf and open it in another app. (This seems to work even with the free readonly version of MS Word)
Comment: Simply the best way there is.
Comment: This is the answer. Print in the current version of Word on iPad allows you save as PDF so you don't have to open it in another app.
Answer: Get Notability - connect to Google Docs, it will convert on opening the file into a PDF all on your ipad, no need for a desktop.
Answer: Tried the notability way. It worked. Thanks Anthony.
The steps I followed on iPad-

Download Notability (I already had it for work reasons. It costs $2.99)
Sync Notability to Google Drive
Open Word Document from email in Notability. It auto-converted the document to Pdf.
Email the document back from Notability to Email as Pdf.

Additional steps I followed since I needed to sign and date the document-

Open the document from email in GoodReader (Already had it for work
reasons. Costs $4.99)
Sign and date the document in GoodReader and email to the recipient.
Answer: Probably the easiest way to convert a Word Document to a PDF is to use Word Online, part of the free Office Online suite from Microsoft.
Once your .doc or .docx file is open, you just select "Download as PDF" and you have your PDF file.
This solution requires no 3rd party apps and does everything within the browser for free.
Answer: If you have a .docs on a computer, upload to google drive, open it on iPad, download the file and follow the steps below on "If you are accessing a online .docs"
If you are accessing a online .docs

Open the file online on iPad
Hit share button on upper-right
Find print
After the print window pops up, pinch out (Like zoom out a map) on the preview
You will have a file now that is still named "SOMETHING.docs" but once you hit the share icon again and import it to another app, you will have a PDF file

If you are using the word app
Open the document, hit the "document with 3 dots" icon on the upper left, hit print, follow step 4 and beyond above.
Answer: IPAD - How to change a .DOCX file into a word or PDF format so you can read it as if it were in WORD. First from the email you receive it from , Open the Doc., download it into  "drive" that's the Icon that is  shaped like a triangle, (the YELLOW , GREEN , BLUE icon). called "DRIVE" that's it! It will automatically download it as a .pdf so you edit it, move it, and view it better. From "Drive" you can Down load your now .pdf file into Word, Adobe etc. and rename it.
Comment: What is 'drive'?  What application is that?  My iPad doesn't have anything named 'drive' so can you please update your answer with more info?
Comment: Uploading a screen shot of what you are doing might help immensely. Without an edit to clarify the intent here, this is unlikely to help someone else.
Answer: Easiest way that I've found if you're using the Microsoft Office App for iPad.
1) File
2) Print
3) Open in Another App
4) Import to iBooks
It will automatically save as a PDF file in iBooks. From there you can choose to print or email the PDF. You can also connect iBooks to your iCloud Drive and have it saved there as well.
Hope this helps! =]
Comment: This answer has already been given http://apple.stackexchange.com/a/245815/237


Should a non-blocking code push CPU to 100%

Question: I've been thinking today about NodeJS and it attitude towards blocking, it got me thinking, if a block of code is purely non-blocking, say calculating some real long alogirthm and variables are all present in the stack etc.. should this push a single core non hyperthreaded to CPU as Windows Task Manager defines it to 100% as it aims to complete this task as quickly as possible? Say  that this is generally calculation that can take minutes.
Comment: Encouraging answers, the next time a sys admin tells me my non-blocking app is using 100% CPU I'll take it as a complement...
Comment: THE busy loops killer line in windows
::MsgWaitForMultipleObjects(0, NULL, FALSE, 1, NULL);
Answer: Yes, it should. The algorithm should run as fast as it can. It's the operating system's job to schedule time to other processes if necessary.
Answer: If your non-blocking computation intensive code doesn't use 100% of the CPU then you are wasting cycles in the idle task. It always irritates me to see the idle task using 99% of the CPU.
Answer: As long as the CPU is "given" to other processes when there are some that need it to do their calculations, I suppose it's OK : why not use the CPU if it's available and there is some work to do ?
Answer: As RAM can be paged out to disk, all applications are potentially blocking. This would happen if the algorithm uses more RAM than available on the system. As a result, it won't hit 100%.


What steps should be taken to clean a pc when moving to a new job?

Question: What steps should be taken to clean a pc when moving to a new job?  I don't want to leave behind any personal information on my work computer.
Comment: You should **NOT** have **ANY** personal info on your work PC, if you do, you're off to a bad start already. And all that data could be recovered.  At my company we physically destroy drives still from old PCs or ones that are donated.
Comment: Definitely need more detail here, this is far too vague to properly answer.
Comment: It is a vague question but I'm hoping for suggestions :)
Answer: Given the code on my work machine i think having it burned by a priest, extinguished with holy water and buried in a nuclear waste store is the only way to be sure!
Comment: I'm tempted to mark this one as the answer! :)
Answer: Give the guy a break. Sure, he shouldn't be using his work PC for personal use but that doesn't answer his question. Holy terrible attitude Batman.
Run Temp File Cleaner - it will remove temporary files from your computer. It is better than CCleaner.
Delete email you don't want to leave behind. There is a chance that it's backed up somewhere but not always (you'd be surprised!). At my company, the only email we can recover is whatever is left in the Exchange mailbox. That being said, some people have Outlook archives that are kept on the file server which is backed up nightly. However, I've yet to see a backup restored to recover a .pst file from an old employee.
Use Add/Remove programs to remove software you may have installed.
Delete files that you don't want to leave behind. If the files were stored on a company server there is a good chance that it may be backed up. But, unless there is a reason I don't think anyone will be going back to snoop on what your documents may be.
Depending on how important your job was or what kind of company you were working for will determine how far they will go to recover deleted data. If you're that worried, use DBAN to wipe the drive and give them back a computer with nothing on it (that will surely anger someone though and you may not want to burn that bridge).
Answer: At my company they have a data retention policy, all email etc is hosted on the mail server, so you can't really delete it, even if you did, there is usually a policy (at least at my corporation) that email is to be left intact, and besides they have backups if need be, which I think they require by law).
As far as personal data, you should NOT have any personal data @ work, it is NOT your PC (unless you bought it and own it and have that in writing).  Usually corporate PC's have corporate policies applied (which applications can/cannot be installed) and 3rd party apps are usually forbidden.  I know at my company they are anal about non-standard apps (most dumb users get infected apps / screensavers / garbage) that is not good for a corporate network.
I think your best approach (I am assuming here due to your lack of information) you should talk to your HR person / IT manager, see what data is retained, and what you should remove.
Like I said, at my company they do a full GHOST image of a persons machine when they leave/terminated (usually terminations result in immediate migration of individual away from PC / Servers so that no damage could be done).
UPDATE
I would use this question thread as a plan for your future job, don't put personal data on your work PC. That's a big no-no.  Depending on your future company they will monitor your usage both on the web/email/programs you use, some will say "who has time for that", machines do... They log stuff ;)
Then if need be they get a human to read the logs. Most corporations do this (I'm not saying its a good thing, just something to keep in mind at your next job.)
Answer: You may want to look at Eraser if you're worried about your personal security.  CCleaner is good for cleaning up browser and temp data that you may not want the IT dept to see.
Answer: It depends on the policies your implemented by your company.  Since it's a work PC, you shouldn't have anything personal on it.  Any business-related documents should live on a server somewhere, but if you have any local information that should be provided to your replacement/manager/hr.
Answer: Give him a brake, it may not be the type of personal info your thinking of. For all we know it could be a home email address he setup with imap at work.
Simple thing is to delete the files, securely if you feel the need to. with Eraser or similar products. Run ccleaner, or glary utls. and then wipe free disk space to make sure its not recoverable.
Portableapps.com has a lot of these apps that can run off a USB stick, if you are not allowed to install apps on the work computer.
Answer: If the company IT knows what it's doing then it should reformat your PC anyway, so a simple delete of any personal data should suffice, despite what anyone says you will have accumulated some over the time at your company - if only browsing histories. Any more and you're doing your IT department's job for them.
Also, most people aren't going to have the time or inclination to download undelete utilities and the like to investigate what what on the machine previously - I know I wouldn't.
Comment: However, the reformat will take place AFTER they archive the contents of the drive (in case they need it later, either to try to locate missing data or in case of discovery for a lawsuit).  Or, they'll simply replace the drive and archive the entire old drive.
Comment: What if there is a legal issue? Then the COMPANY would be inclined to do so, say if you had warez, or copyright material on there. Or something else questionable.
Comment: @Jakub - then you've got serious problems.
Answer: A single zeroing should be enough to ensure data is not recovered, there is a ongoing challenge for professional recovery firms, to recover data from a single zeroed hard drive, and no one has taken the challenge so far

Source: http://hostjury.com/blog/view/195/the-great-zero-challenge-remains-unaccepted


O2 sensor location for 1990 pickup 4x4 3.0L

Question: I'm trying to locate the oxygen sensor on my 1990 Toyota pickup SR5 4x4 w/3.0L. I bought the truck from a kid who had the knock sensor wire rigged into the harness plug for the o2. I fixed the knock sensor by bypassing it. Does my truck have an O2 sensor? The new o2 sensor I bought has a pig tail about 16 inches long. Bosch part number 15711. I read somewhere that only Canada made trucks have these. How do I know where it was built? Help please
Answer: The oxygen sensor is bolted to the exhaust pipe just ahead of the catalytic converter. This is under the truck below the drivers seat.
The first character of the VIN number denotes the country of origin.
J= Japan
 2= Canada
 3= Mexico
 4 & 5= USA


How should I adjust the baking temperature?

Question: I just baked a sponge cake, its sides are fluffy and fine but in the middle it's a bit stiff. When I stick a toothpick in the center it comes out clean and when I cut the cake up, it's not wet. So how should I adjust the baking temperature/time for this case? Thanks!
Comment: How long did you bake it and at what temperature?
Answer: The very first thing to do is to put an oven thermometer in your oven and find out if your thermostat is accurate. It will take a little while to do this test, because the oven will first overheat then cool then overheat, etc. After 20-30 minutes, you should get a good reading as the interior heats up and the temperatures fluctuations subside. If your reading on the thermometer is different from the t-stat setting, then you will be able to compensate.If it won't hold a steady temp, you should replace the thermostat Sometimes you can recalibrate a home oven t-stat, but it might cost more than it's worth as long as you allow for the discrepancy.
Answer: I would not fumble with temperature, as it is important for proper rising. If your cake is too stiff and dry, bake for a shorter time.
If you are getting a very large difference in doneness between sides and center, you will probably have to try to make a more even gradient, like described in this answer about doming. You should also be baking the proper recipe - you can't just pour a bundt optimized recipe into a flat pan and expect it to bake evenly.
But your description sounds a bit strange to me, because you say your middle gets baked through before the sides, which is the opposite of what usually happens. Are you sure your batter is properly mixed? Or maybe your oven has a large hot spot in the middle?
Comment: The middle feels stiff as in "a bit wet stiff", not "too dry stiff", but it's not actually wet, somehow. I've read the other answer and I think that it might settle my problem. (The best cake I can make now is Swiss roll, which is thin and made in a large pan. This fits in the theory proposed there)
Comment: This seems to be a combination of overbaking and the wrong recipe then. If you are talking about the recipe from your other question, it is very eggy, which can give a rubbery texture. If underbaked, I can imagine that "wet stiff" is a way to describe it. In choosing a recipe, go by weight. The standard ratio for sponge is 1:1:1:1 fat/flour/sugar/egg (~55 g per egg). If the recipe you choose strays far from that ratio, try another one. If you are doing chocolate cake with cocoa powder, the sum of flour and cocoa powder together should make the "1". Melted chocolate is more complicated.


Are all epoxy created equal?

Question: I'm under mounting a sink to a slab of granite and there many different brands of epoxy. Is one better for this type of job?
Comment: Just curious - are you using epoxy anchors or glue the sink directly to the slab?
Comment: epoxy anchors is the plan
Answer: Absolutely not. Epoxies are formulated for different cure times, cure temperatures, bonding to different materials, performance in various extreme environments, etc. That said, amongst the various hardware store 5 minute general purpose epoxies, I doubt there is a lot of difference between brands. I know nothing of the specifics for this application, I would expect there is a specific adhesive to use and recommended by the sink manufacturer. If not, I would check with the stone supplier for recommendations.
Comment: +1. It's best to check with the sink manufacturer and/or stone supplier, to determine what product to use.
Answer: The common 2 part epoxies from the hardware store or home center are NOT waterproof. I learned this the hard way using them on boat projects. If you are going to use epoxy, it's worth the few extra bucks for a good one, like WEST System. You will probably also want some fillers like colloidal silica or glass micro beads to control the viscosity and sag of the final mix for an application like this.
Check out polyurethane adhesives like 3M 5200. They are made for use in continuously wet environments, and are generally easier to work with than 2 part epoxies. "Goes on smoothly, won't sag, and remains workable up to four hours. Cures in 5-7 days with no shrinking." Easier application and clean up than epoxies, too.

Are all epoxy created equal?