How to build credit history in the USA?

Question: What are the ways in which a new immigrant can begin building credit history in the United States of America ?
Comment: Bear in mind that you will need a Social Security Number in order to open just about any kind of financial account there. If you aren't eligible for Social Security then you should still be able to get a Taxpayer Identification Number from the IRS, which for most purposes works the same way.
Comment: @AndrewLott You don't need a SSN or ITIN to open a bank account.
Comment: @philippeleybaert - I think it's the other way around, the bank is forced to apply "backup withholding" (automatic tax deduction) if a SSN/ITIN or form showing foreign status (W8-BEN) isn't provided.  But in reality they'll mostly just refuse to do business without an SSN/ITIN.  And there's really no point in bothering with an interest bearing account at current rates.  Many major banks have interest rates of 0.1% or lower on their "savings" account, "high interest" accounts might be 0.85%.  If you have enough saved ($100k's) that make the interest worthwhile, there are better uses for it.
Comment: Related/duplicate: http://money.stackexchange.com/q/20315/3960
Comment: @RobHoare If you open a savings account (or any other interest-bearing account) you still don't need a SSN/ITIN but you will have to fill out a special form (I forgot the number of the form). The bank will then withhold a specific percentage of tax from all interest payments.
Comment: @RobHoare My point was just that it is perfectly possible to open any bank account (checking, savings or anything else) without SSN/ITIN. But there could be financial consequences if you do so (tax withholding on interest). And you are correct that some banks will simply refuse to open an account.
Answer: It is possible to build a reasonable credit history and score in about six months, but you have to be careful what you do.

Try to get a mortgage at a financial institution that has special programs for foreign nationals. You will probably need to make a large down payment (25% or more). On top of that, many banks will offer you an unsecured credit card if you get a mortgage (in that case you can skip step #2)
Get a secured credit card with a decent limit. Don't be tempted to deposit a very low amount in the secured savings account because your credit limit on the card will be too low. The higher your credit limit, the higher your credit score will be. $5000 or so would be a good start.
Lease a car with a company like Intl Autosource. They specialize in serving foreign nationals without a credit history. They also report all your payments to the credit bureaus.
Don't apply for loans, unsecured credit cards or store cards in the first 6 months, even if you get so-called "pre-approved offers" in the mail. You will be denied and that will affect your credit score. Also, if you're ever offered a "savings card" in a store and they want your social security number: politely decline.
Don't ever give your social security number unless it's absolutely necessary. For example, when you sign up for a cellular plan with AT&T, they'll ask your SSN and run a credit check. That will affect your score. Simply get a prepaid plan for the first 6 months.
In stores you will regularly be offered a discount if you sign up for a store card. Don't. They will ask your SSN and run a credit check, impacting your credit score.
Even if you plan to pay off your credit card every month, try to make a payment before the billing cycle ends because the bank will report the balance to the credit bureaus. You should keep the reported balance below 30% of the credit limit on your card.
Get an account at creditkarma.com to check on your progress. It's free. The only problem with creditkarma.com is that they only use data from TransUnion. If you want to track your credit reports and scores from the other 2 agencies (Equifax and Experian) you should get an account with them (not free!)
Pay all your bills on time. Doing that will not build credit history but it will make sure there's no negative information on your credit report.

If you do all of that, you should have a decent score after about 6 months. At that stage you may consider applying for unsecured credit cards.
Even if you are able to get one or more unsecured credit cards later on, it may not be a bad idea to hang on to it for at least six months. Although FICO sources claim that a closed account still counts to determine your credit history length, there's conflicting information on the different credit bureau websites. Even if it doesn't influence your credit history length, keeping the account open does help to keep your total available credit at a higher level, decreasing your credit utilization and so it helps your score.
Comment: The part about not canceling the secured card is a myth. Closed accounts will remain on your report for the next 10 years and are factored into the average age of accounts even if closed. Closing it will only affect your score inasmuch as it reduces your available balance, thereby increasing your *utilization* - the percentage of your available maximum balance that you carry. And if OP is following your advice to pay in full every month that will be of no concern.
Comment: @JonathanVanMatre While a closed account will remain on your credit history, one of the factors to calculate your credit score is the age of your oldest **open** account. If your secured credit card was your first account, it **will** affect your credit score if you close that account.
Comment: It would improve your answer to at least edit it to acknowledge that FICO says X, but your feeling is that it's still better to be extra cautious. We are a reference site, after all, and the references are clear. It's not a question of me being right, it's a question of providing the most accurate information we can to OP and to future questioners who come seeking information. This is an oft-repeated myth whose repetition will never cease unless reliable reference sites like this one begin providing better information. There is too much superstition in the world of credit advice.
Comment: It's unbelievable that US citizens have to live under this weird regime of semi-arbitrary credit history "problems" reporting and collection.
Comment: OK, let's make sure we are talking about the same credit score. I am talking specifically of the FICO score, which is the one actually *used* in a significant majority of lending decisions. Your PLUS score or CreditKarma score or whatever other score may be calculated differently, but your FICO score cares not whether the account is open or closed, only whether it is on your report. I [have](http://www.creditcards.com/credit-card-news/fico-credit-score-account-length-credit-history-1270.php) [citations](https://www.mint.com/blog/credit/fico-myths-08302010/), do you?
Comment: I'm talking about the FICO score. But I'll soon find out if it's a myth or not because I closed my secured credit card yesterday (which is my oldest account) and I'm curious to see if it will affect my score. I'll let you know when I find out :-)
Comment: I've cited a **former FICO employee** and the **consumer operations manager at myFICO.com**...but apparently we won't know the truth until we see what happens to *your* score. ;-)
Comment: With all due respect, I don't expect a former FICO employee to reveal all the details on how FICO scores are calculated. I've based my statement on what Experian tells me about *factors lowering your credit score*, which lists "*The age of your oldest open account is too low*". TransUnion is saying the same thing BTW.
Comment: They're not going to give the exact formula, but they are happy to educate on the general principles. [From FICO's own website](http://bankinganalyticsblog.fico.com/2011/07/more-scoring-myths-closing-credit-cards.html): "The FICO Score considers the age of both open and closed accounts. When an account is closed, it usually remains on the credit report for many years. The FICO Score will continue including that closed account in its assessment of length of credit history."
Comment: I hope you're right. But I think it's safer to not take chances, so I still feel that closing your first (secured) credit card account within 6 months is a risk not worth taking.
Comment: @JonathanVanMatre I've updated my answer.
Comment: @PhilippeLeybaert I **strongly** disagree with your mortgage advice in #1. Calculating the median US home price of $200,000+ against your minimum 25% deposit of $50,000, on a 30-year mortgage at your 3.5% rate, versus my 2.5% zero down rate, means you lose **at least** $20,000 in added interest payments and missed investment gains. Much better to spread that $50,000 across four 2-year high yield CDs in different banks and get unsecured bank issued cards or lines of credit, **then** get a better mortgage rate. With $50,000, no need to stand in line with everyone else looking for credit advice.
Comment: @H.J.Buell No way you can get a zero down mortgage at 2.5% within the first few years when you're new to the country. And what do you do in the meantime? Rent? Talk about throwing away money. Missed investment gains are a little overrated because the highest yield 2-year CD's only give you 1.25% at most (before tax). And speaking of taxes: having a mortgage can mean a substantial difference in your taxes. Bottom line: if you have some money to put down, owning is always better than renting, even at a modest premium in interest rates.
Comment: Another approach on the secured card:  A relative was recently doing this.  He had a secured card from Wells Fargo--and in less than a year it became a regular card without changing the card itself.
Answer: I moved to the USA in the middle of the 2008 credit crisis, so this issue hit me hard.  There are a multitude of things that you can do to build up a credit history.

Apply for a secured credit card (as @gerrit also indicates), where you provide the funds to completely cover the credit limit of the card, so a $2,000 limit would require you to pay the card company $2,000 up front.  So essentially you are providing the funds to borrow yourself.  If you pay the card off every month, you will build a credit history.  Typically after 12 months, unless you have other credit issues - the card company will convert the card to a normal credit card and return the initial investment.
If you have any bills - say utility bills - in your name, make sure you pay them on time. Delinquent bills will negatively impact your credit score (but unfortunately paying on time doesn't positively impact your score).
Stay in one residence where possible.  Lenders like to see that you do not move around a lot.
Pay for a credit report from a reputable business in your country of origin, ideally a business which also operates in the USA.
If you can buy a house and get a mortgage.  I know this sounds bizarre, but I found it easier to get a mortgage than to get a credit card - as I had a large deposit, and a house is security - a credit card is unsecured (unless you go with 1.
If you are renting, there are schemes available for you to pay for your rent via a service which reports to credit agencies.  If you are able to opt into such a service this might be an option.
Comment: #2 doesn't help to build credit history. Only when you don't pay your bills on time will it negatively affect your credit score. If you pay on time, nothing is reported to the credit bureaus
Comment: @PhilippeLeybaert - mmm, some bad advice I was given.  You are correct, so I have modified 2.
Comment: #2 still applies, but it's more "don't ever let a utility account go into collections". Basically, don't ever let anything turn over to a collection agency if you can avoid it, and if it does, try to settle it as soon as possible (they'll often cut you a deal, since they bought the debt for less than it's actually worth).
Comment: @TimPost True, but it doesn't help in building a credit history. Paying on time is not reported to the agencies
Comment: In some countries (e.g. Sweden) the only "credit record" that exists is a negative one.  So all they could tell the Canadians is that none of my bills have ever gone into collections.  That might not be sufficient.
Answer: I've recently started building a credit history in Canada, and I think it's the same.
The solution I have chosen is to take a secured credit-card.  Through my financial institution (a credit union), I have fixed 500$ on a savings account.  I need to fix these 500$ for one year, and during this year, these 500$ will be my credit limit.  During this year, I shall use my credit card, pay my credit card bills, and thus build up a credit record.  After one year of correct use, I will have a credit history and I will be able to apply for an unsecured credit card.
Answer: (very long answer) The easiest method to build credit in the United States is to have someone with good credit co-sign a loan or credit card for you. If you do not have that option, the fastest way to build credit for yourself in the United States is through secured credit. Using this method you will find that it's actually quite easy to quickly build a strong credit history.
The more money you have to work with, the faster you can build credit.
To start with, Banks and Creditors are risk averse. By limiting their exposure to risk before you apply, you significantly increase the likelihood of receiving credit from them.
In the example of a bank, you'll be placing your money into a secure deposit account, and then using that account as a security to obtain a commercial or personal loan. In this case, you can add additional securities to sweeten the deal for the bank, such as the purchase of a car, where you pay 60% to 80% of the car's value, financing the rest. Alternatively you can request a smaller amount $500 to $2,000 towards the purchase of a computer, letting them know that you're interested in building your credit.
This is the best method, but it takes work, and a bit of creativity.
The next best thing you can do is to obtain a secured credit card. Use Capital One for this (absolutely do not use any other company - Capital One is the number one poor credit provider in the United States, and historically is rated higher than any other company in this area). Their expertise increases your chances of being approved, and also will allow you to establish a relationship with a company that can later offer you lower rate unsecured cards.
Note: There are companies other than Capital One that have been mentioned here. While they are not bad companies, the long term impact to your finances will be negative. That is why I recommend Capital One. Other companies, such as First Premier, will give you cards that cost hundreds of dollars per year. If you close that card as soon as you get a better card, then you lost the credit history (it is no longer current), and you will have paid absurd fees for nothing. Worse, some of these companies will damage your credit by crediting payments late or worse when you try to cancel the cards.
Just avoid them. Go with Capital One, get a secured card, and in six months that card will be unsecured, and likely also have a reasonable rate. After a year, you can always call in and lower the rate even further. This way you can keep the card and the history you built with it, and not lose your money in the process. Capital One is also a bank, so you can open deposit accounts with them.
This is the second best method, and usually takes very little work. All you need is a bank account and internet access.
Next, you can visit gas stations - like Chevron, Exxon, Mobile, Shell, or others (some are joint - like Exxon/Mobile - so do some homework and only visit one at a time). Here, you can get store credit, for example, to purchase gas. With this card you can fill up your own car as you need, which will slowly build your credit, or you can use the 'student method' to quickly build credit.
The student method is to also fill up your friend's cars (they pay you cash on the spot, and you fill up their car - immediately depositing the money in your bank, and paying down the card each time). This is because you are only likely to receive approval of $50 for your first card, or another small amount. By using the card to buy gas, but also things like chips, sodas, or whatever other snacks you might want, you are using the card a lot (by the way, snacks are a bad investment, but you're building credit, so you need to spend money).
The more the company sees you using the card, the more likely they will be to increase your card limits. After a month, having maxxed out and paid off your card several times, you can call them, and explain that your work involves a great deal of travel, and it would be so much easier for you if they would just bump your credit limit up to $150 so you didn't have to constantly pay down the balance to benefit from your card.
This is a very good method for building credit, though it will rarely ever be huge amounts of credit. I think the highest limit I ever had was from Exxon, for about $600 (so I could pay for car repairs once, I believe was the justification I used to bump the limit that high).
Following that, visit department store chains (JC Penny, Macy's, Sears, etc.). Of them, JC Penny has taken a hard hit in recent years, and is desperate to have business. They would likely finance you for something small. To do this, try to buy a pair of shoes, and apply for their store credit at the register. Companies are always more likely to give you credit when you're purchasing something from them with that credit.
This should be your last option. You will need to visit these stores in person, and the credit you receive can only be used outside of the stores. You'll need to use that credit to build credit - which often means purchasing overpriced items.
Keep in mind that you need to use credit in order to benefit from it. This is because your credit report will show your total credit limit, how much you have spent, and how much you could still spend.
If you show up as always at your limit, it indicates to creditors that you're struggling. On the other hand, if you have a lot of credit, but never use it, then creditors will not know if they can trust you. Because of this, when I'm counseling people to build credit, I encourage them to max out a credit card, make the minimum payment for that month that will not cause interest and balance fees to cause them to go over the limit, and then pay the balance off in full the next month. Overall They pay very little interest this way, but show a history of carrying credit. After a few months of this, you'll show a credit history that creditors will just love.
Alternatively, you could just max and may off the cards each month, avoiding the fees - but creditors do not like this as much.
Two other methods - one of which has been mentioned here already, are mortgages and businesses.
In the case of a mortgage, this is the worst advice you could possibly follow. You will be starting off with bad credit, and therefore hit with a very high mortgage rate. That means you will end up paying enormous amounts of interest (mortgage loans front load the interest, so you will only be paying interest for the first few years).
Much better you simply get a car loan, as it's a smaller amount to pay (so less interest overall), and it's a traditional loan, which means you'll be paying down the loan value with every payment.
In the case of a business, you can occasionally 'buy' good business credit through smart investment. I say smart, because you need to be smart about who you are investing in. For example, you could invest in an established business, on condition that you received a business credit card naming you. In this case you would be the authorized user of the card, thought the business would bear ultimate responsibility for paying the credit. You would benefit from being associated with a card that was used for business expenses and such, but tied to your name as the authorized user.
Finally, as I mentioned earlier, the longevity of credit is essential. If you leave America, you can still take your credit cards with you - just tell the company that you're moving with work, or whatever. As long as you pay the balances, you'll keep good credit, and be eligible for increases as well.
Good luck, and welcome to America. :)
Disclaimer: Any advice provided in this forum is just that - advice. It is free, and carries no guarantee or warranty of service. Use it at your own risk, and after applying your own best judgment.
In the event you would like more in depth and legally binding advice, please PM me for details on my company. Note that this is not in any way a solicitation, rather, there is only so much information I can take the time to provide at no cost. I have done my best to provide a thorough, unbiased, and honest description of services and methods. Those requiring more complex structures, such as that of business investment, require much more work. Additionally, they require my lawyer, meaning they're a service can't provide without billing for it.
Comment: Hi Philippe - given the context of the initial question, my statement on mortgages is very accurate. In your example, you put down 25% on a mortgage at a 3.5% rate - which, as you know, is only 'pretty good'. You lost money in that deal, because someone with established good credit would have saved at least $12,000 over 30 years on a $75,000 mortgage at 2.5%. That's 12% of your total home value - with which you could build a garage or buy a new car or motorcycle. I would be very surprised if the average reader here was comfortable throwing away 12% of their money on interest.
Comment: Your statement on mortgages is misleading. One week after I arrived in the U.S. (no credit history) I bought a house and got a mortgage with a pretty good interest rate (3.5%). The only condition was that I had to put down 25%, which is not that unreasonable. And if you do end up with a higher interest rate, you can always refinance after a year or so.
Comment: @PhilippeLeybaert - I also want to clarify that I mean no offense at all to you. You obviously have a degree of liquidity (cash money, for the layman reader), and financial expertise that most readers looking for advice on this forum don't have. position allowed you to buy credit - at the cost of $12,000 in additional mortgage interest, and at least $9,000 in the additional 1% interest would have earned over 30 years in any other investment other than home ownership. Few people reading this forum are able to invest $25,000 in credit, while losing more than $20,000 in fees and lost interest.
Answer: If you have an American Express card from another country, you can "transfer" it to the US.
In addition to giving you an (unsecured) credit card in the US with a real credit limit that you can use to then start building your credit, American Express will report the date the account was opened as being when you first became a cardholder elsewhere in the world (presuming you have maintained continuous membership).
This means that you can end up with a credit history that pre-dates your moving to the US.
(In practice, they don't actually "transfer" the card, they just open a new card in the US. You can keep the foreign card or cancel it at your discretion)
Comment: There's a similar thing with Citibank, which includes both normal bank accounts and a credit card. Not sure if it includes "back-dating" the account opening date like Amex, but when some friends used it they found it worked very well for kick-starting their US score. Details are country-specific, but for [UK customers moving to the USA it's here](https://www.citibank.co.uk/personal/moving-uk.do)
Comment: Also, I know for sure they will not do this for an AmEx card that was issued for business purposes (by an organization to an employee) as that would qualify as a corporate card.
Comment: Out of curiosity, this does NOT work for Amex in Brazil. Amex closed their operations in Brazil some years ago, and their brand is still being offered by a brazilian bank (Bradesco), but it has no relationship to US Amex. They told me that my number is not an Amex number, and that they couldn't use my credit history in Brazil.
What worked fine for me was applying to CreditStacks. Another option is Advancial. They both provide unsecured cards for immigrants without credit history.
Answer: As @gerrit says, get a secured credit card. As soon as you can, get a regular credit card - you can use websites like creditkarma.com and creditsesame.com to get an idea of what credit cards you can use. Make that that you use the card regularly, and pay it off regularly.
There's a bit of a paradox - when you apply for an account, you take a hit to your credit score, but you need more accounts to have a good credit score. So apply carefully.
Answer: If you are moving to the Eastern USA from Canada, do yourself a favour and bank with TD Canada Trust in Canada before you leave the great white North.  They are the parent of TD Bank North America and have branches all down the eastern seaboard and into the Carolinas and Florida, where Canadian snowbirds congregate.
TD Bank in the USA can and will use your Canadian credit report - I know this personally.  They are the only bank with this ability.  Others cannot because the laws are so very different between our countries, but TD North America will OK you based on the OK of TD Canada.
If this isn't possible for you, remember that you cannot get credit (easily) if you do not have an identity with the credit bureaus, and you can't get an identity with them if you don't have credit.  It's a vicious circle.  No, the bureaus won't just open a file for you if you phone (tried that too!).
One method to create this identity is to apply every month for a credit card - remember, if you haven't an identity with the bureau you won't be impacting your credit score.  Apply online with Capital One and also in stores such as Macy's and JC Penny.  These stores all sell their client names to other credit providers.  So once you are refused by Macy's because you have a "thin file" (not enough accounts with satisfactory performance for the bureau to approve you), your name will be sold and next month you will have offers from Capital One in the mail.  When you first apply on-line with Capital One you will be refused, but once you receive an invitation from them in the mail with a special code, they will approve you for a small limit.
The only other provider I have found who will use the Canadian credit report is Verizon wireless - I got a cell phone from them by providing copies of my Canadian passport and taking it into a store location where the staff will fax it to their credit department.  Verizon does report to the credit bureau, so it's another way to establish yourself.
Answer: Start before you make the move. Do research if there are professional organizations in your country who offer credit cards, and become a member. When I moved to the US in 1997, I became a member of the IEEE at home and applied for a member credit card. It was no problem getting one. Having the card was invaluable for building credit history and being able to purchase a home after less than a year.

How to build credit history in the USA?


Is it OK to nail 1/2" plywood straight to the pocket-door box?

Question: The guy I hired to frame for a new pocket-door, mounted the pocket-door box on the top (to a second-story joist) and on the bottom (toe-nailed to the floor). When I asked him to install some studs on both sides of the door, he said I don't need them because I can nail my wall material (1/2" plywood) right into the horizontal planks of the pocket-door box. I have a feeling that would be wrong, or at least not up to Code. What do you think? Any advice is very much appreciated. I am new to this, just learning the terms. But it really didn't seem safe..
Answer: The 'boxes' made for pocket doors are designed to act as the framing for your wall material (typically sheetrock). You topically can't frame out the pocket door pocket with full studs as that'd make the wall too thick.


What questions are on-topic for JL&U?

Question: I want to ask a question on Japanese Language and Usage about X. Is it on topic?
Comment: ahh thanks... was wondering how to do that
Comment: This is a work in progress to try to deal with http://meta.japanese.stackexchange.com/questions/694/faq-does-not-describe-what-is-in-or-out-of-scope
Comment: possible duplicate of [What questions are not allowed on Japanese Language and Usage?](http://meta.japanese.stackexchange.com/questions/796/what-questions-are-not-allowed-on-japanese-language-and-usage)
Comment: Yeah... sorry for sorta stealing all of this, but I liked the format of your "what are some good attributes of questions?" meta post, and thought it would work better for this type of FAQ entry. I don't really see a reason to 'close' this question, as there's nothing bad about it... but perhaps detag 'faq-proposed'?
Comment: In current form, this question is entirely superceded by [What questions are not allowed on Japanese Language and Usage?](http://meta.japanese.stackexchange.com/questions/796) and [How should I format my questions on JLU?](http://meta.japanese.stackexchange.com/questions/806), both of which are faqs.
Comment: @jkerian you need to do `[meta-tag:faq]`, like this [meta-tag:faq].
Comment: @jkerian It'd probably be best to close this as a duplicate of (both) of those then.  You'd need one person to vote for each topic for them to show up in the final list.
Answer: Disclaimer: opinions differ somewhat about what questions should or shouldn't be allowed. Also, this answer is a work in progress - I may have missed a few meta posts or examples of closed questions.
Some questions are regarded as off-topic for Japanese Language and Usage, but are permitted on meta: Allow limited resource questions in meta? . This happens especially with questions on input-methods how to type Japanese. An example of such a question is How can I learn to type on a JIS keyboard?
Questions that are pure translation requests where no effort has been made may be closed: What is a ダンディー?
Questions that are purely about Japanese culture are off-topic: https://japanese.stackexchange.com/questions/2511/is-it-a-rumor-that-eating-really-loudly-is-considered-polite
Questions that might summon Cthulhu are off-topic: https://japanese.stackexchange.com/questions/374/regex-match-sentences-except-sentences-contained-in-「」
For further information, browse the questions on meta tagged scope, allowed-questions and target-audience, or browse the closed questions on JL&U by doing a search for closed:1.
Comment: The acceptability of 'resources' question is anything but settled. Considering 1) such questions were specifically excluded by the proposal itself. 2) they are *by definition* ill-fitted for SE's format (no one specific answer) 3) while on that page Rob states he thinks they should be allowed, he himself puts restrictions that make it very unclear what questions would and wouldn't be OK in his view.
So far, I fail to see enough to overcome the previously established consensus.
Comment: **UPDATE:** [Have at it...](http://meta.japanese.stackexchange.com/questions/726/scope-amendment-should-questions-about-resources-be-allowed-on-jlu)
Comment: @Dave My answer also stated that "some" (rather than "all") [tag:learning] questions are off-topic. Do you disagree with that paragraph?
Comment: if you ask me (or the initial proposal): YUP, they are even more off-topic/unanswerable. But most of what you'd call "learning" questions can just as well be seen as "resources" question (and a bad fit for SE for the same reasons). A non-resource, learning question (*not specifically tied to an item of language*) would have to be something like "What is your method to study [X]" and is a horrible question for JLU.
Answer: This question has been superseded by What questions are not allowed on Japanese Language SE? and How should I format my questions on Japanese Language SE? , which are both tagged as faq.

What questions are on-topic for JL&U?


Configuring an SSD

Question: I just bought an Intel X25-M SSD for my netbook, running XP. I noticed some increase in speed, not so dramatic though. Is there any configuration I'm supposed to except putting my OS on it?
Comment: You didn't say which OS you put on it.
Answer: To achieve highest speed possible, you should align the partitions to the read/write page size of the SSD, preferrably to the erase block size. Usually the page size is 4096 bytes (4 kilobytes) on most SSDs. Windows Vista does align partitions to 2048kB, but XP starts the partitions at 63kB and that causes each write of default NTFS block (of 4096kB or 2048kB) to require a read from 2 pages on the SSD. Writes might require erasure of 2 blocks of 512kB instead of just one. By aligning partitions people have managed to gain 10-300% speed improvements on SSDs depending on the OS and SSD.
The easiest way to do this is to plug the SSD to a Vista machine, remove all partitions and create them with Vista and then install XP on it. This makes the partitions to be aligned to 2048kB which is better than 63kB which XP defaults to.
The correct way to do this is to first delete all partitions from the SSD and then boot with Vista install CD and partition the disk with diskpart.exe.
First boot with Vista CD, and select Repair Your Computer on the screen that has Install Now -button. Click next as you shouldn't need any special drivers and then select Command Prompt.
Type 'diskpart' and then 'list disk' to display your harddisks. Use 'select disk ' to select the SSD. 'list partition' should show no partitions as you've deleted them in advance. Then just create a partition with 'create partition primary align=4' (or you can use 512 to align the partitions to the erase block size). Then write 'active' to make this just created partition bootable. Finally 'exit' and you're done. Now you can boot with XP install CD and reinstall the OS and enjoy faster speeds.
Remember also to check under device management->IDE ATA/ATAPI controllers->primary IDE channel has DMA enabled.
Answer: there is actually a whole rake of tweaks, e.g. using a RAM disk, Flashfire (disk cache buffered into RAM), partition alignment, certain NTFS performance hacks, etc., that can be applied to boost the performance of SSD-based systems.
over at eeeuser.com is very informative thread regarding the matter. it is focused on netbooks with SSDs of the slower MLC variant but a great many of these tips apply to any SSD.
Answer: All about alignement on SSDs :)
To check alignement in case of a doubt:
http://www.techpowerup.com/articles/other/157
and realign manually if necessary:
http://forum.notebookreview.com/hardware-components-aftermarket-upgrades...
By default creating partitions in 7 or Vista, contrary to XP, will align the partition correctly.
More info in this interesting white paper:
http://www.paragon-software.com/landing-pages/WhitePapers/paragon_alignment_tool.html
Answer: talking about partition alignment, the user that posted the most text is correct in concept but terribly wrong on numbers. XP default formant offsets the partition at 63 sectors and not 63Kb. 63 sectors with 512 bytes in each one equals 31.5Kb, thus when you run AS SSD it will show alignment as 31Kb-BAD.
now recommended partition offset for SSDs is 2048 sectors, or 1024Kb. The easiest method is to run Partition Assistant Pro and it will realign the partition. Problem is only that the free version does not do alignment, only the Pro does, and it's paid.
I run XP on both my laptops with Samsung 830 256GB drives
Answer: Where have you noticed improvements? You should notice faster boot/shutdown, applications should launch faster in general, and the computer should be much more responsive immediately after booting. For transferring large files, for example, you may not notice any difference, compared to a mechanical hard disk. But you should get the benefits without additional configuration.
Also, how much free space do you have on the SSD (and what is its capacity)? SSDs can get slower with less free space.
Comment: I'm taking 11 GB out of the nominal 80 GB. I can't say really where I noticed improvements, but moving around in my IDE is still sluggish, also hibernating is still slow.
Comment: The time to hibernate/wake-up is probably dictated mainly by how much memory you have. An SSD probably wouldn't improve this much more than a hard disk. In fact, the only criticism (other than cost) of the X25-M is that its sequential write speed is relatively low - this could slow hibernating, compared to other SSDs and even hard drives.
Answer: You shouldn't need to make any significant configuration changes. You don't even need to defragment SSDs as random reads are almost as quick as sequential.
Installing an SSD should significantly reduce any slowness caused by the computer reading the drive. However tasks that are slow due to a lack of CPU power or memory may not see significant improvements. Netbooks have a relatively slow CPU to give them their long battery life, and not much installed memory, so you shouldn't expect them to perform as well as a laptop or desktop.
If you want to try and work out where the performance bottleneck is I'd suggest running the performance monitor (Start->Run, type in "perfmon").
Maybe you should just look for a less demanding IDE.

Configuring an SSD


Sort all Gmail contacts by contact frequency

Question: Is it possible to sort all Gmail contacts by contact frequency, either directly from Gmail or using a external tool/service? How?
Answer: Not in GMail. The only free consumer service with a similar function is Gist. It allows you to sort contacts by "Importance" (overall frequency & depth of conversations) and by communications sent/received to/from a contact. However, it scans only the last 30 days of communication history for new accounts. Everything else is expensive enterprise customer relationship management software.
Answer: You can also have a try at xobni.
It had this functionality on Outlook, I do think it will work for Gmail too. And it adds a lot of funny (or useful) features.


What is "dual-boxing"?

Question: I've seen it refered to in a couple of (closed) questions like this one.
One comment seemed to indicate it's a World of Warcraft term for a second character; is that correct?
What's the meaning of the term?
Comment: Two games played with the same input? Booring. [Try four.](http://www.youtube.com/watch?v=z5pz6waED0w) ( [about](http://tasvideos.org/871M.html), [author's notes](http://tasvideos.org/1566S.html) )
Answer: Dual-boxing refers to running two clients at the same time (of the same game, usually) and controlling them via a single input (usually heavily macro'd). Multi-boxing is the general term applied to more than a single client at a time.
To "properly" dual-box in World of Warcraft, you need two separate accounts. The comment likening naming a dual-boxing character pair to an alt was misinformed.
Dual-Boxing is not forbidden by World of Warcraft's Terms of Service, though those who do the practice are generally disliked by other players, due to their greater presence and combined power level, and the intrinsic PvP nature of the game.
Comment: lol... I was thinking of variants of boxing games...
Answer: Usually it indicates one person simultaneously playing two accounts at the same time. Since this requires two computers, it's called dual-boxing.
Here's some more (WoW-specific) info: http://www.wowwiki.com/Multiboxing
Comment: Multiple computers are no longer required for multiboxing. I can run 4 WoW's off my laptop if I set it to lowest graphics, and a mid to high end gaming desktop could easily run 5 to 10 instances of the game.
Answer: Dual boxing is the art of controlling multiple characters in an RPG (usually an MMORPG) simultaneously. The other answers gave some great basic definitions so I'll try and go into detail.
Multiboxing usually works by having one character as the lead, and having the others /follow the main and /assist when casting spells or using abilities. As a result, a multiboxer has unparalleled coordination for focus firing as all the characters fire simultaneously at the same target with the press of a button.
However, there are major drawbacks - a multiboxer has downright horrible mobility and can be easily circle strafed or line-of-sighted (hiding behind walls or pillars) into oblivion. They are also very susceptible to fear mechanics, which cause the characters to be separated and facing different directions, essentially making one or more of the followers sitting ducks. They are also doubly affected by latency. Think of a  multiboxer as a big, slow, gigantic cannon made out of glass.
There are two main reasons that people multibox, and I'd like to dispel some prejudices. One reason is for the challenge brought by having to tank, heal, and dps on multiple characters at the same time (usually PvE oriented). Highly skilled multiboxers have 10-boxed or even 25-boxed their own raids, taking on all roles by themselves. Look on YouTube for some of these multibox raiding videos, it's truly astounding the amount of skill, precision and planning involved.
The other main reason is for the satisfaction of blowing up people in battlegrounds (PvP), although PvP multiboxing is definitely not easy. You may be able to one-shot two or three enemies, but if the opposing faction knows any weaknesses of multiboxing the multiboxer could easily be a waste of 5 valuable player slots. For example, my 4 Draenei elemental shaman would sometimes instill fear in enemies by zapping everyone with chain lightning, and they would all hold back causing my team to win the battleground. Other times I get absolutely curb stomped when a blood elf jumps into the middle of my characters and casts AoE silence which gives enough time for the rest of their team to pick off one of my characters, and it all goes downhill from there.

What is "dual-boxing"?


Can a man marry his mother's sister-in-law?

Question: Can a man marry his mother's sister-in-law if she is divorced?
Comment: Yes he can marry her.
Answer: Yes he can, any man can get married of any adult female who doesn't share a root or a branch with him. Neither the branches nor the roots of his wife (wife's daughter, mother, grand mother, grand daughter...)
Special cases include your wife's sister, niece, and aunt, as you cannot be married to both at the same time, but it is possible after the divorce of the wife.
Answer: Under the Shari'ah, marriages between men and women standing in a certain relationship to one another are prohibited. These prohibited degrees are either of a permanent nature or a temporary. The permanently prohibited degrees of marriage are laid down in the Noble Quran:

"And marry not those women whom your fathers married, except what has
  already happened (of that nature) in the past. Lo! It was ever
  lewdness and abomination, and an evil way. Forbidden unto you are your
  mothers and your daughters, and your sisters and your father's sisters
  and your mother's sisters, and your brother's daughters and your
  sister's daughters, and your foster-mothers and your foster-sisters,
  and your mothers-in-law and your step-daughters who are under your
  mother-in-law and your step-daughters who are under your protection
  (born) of your women unto whom you have gone into -- but if you have
  not gone into them, then it is no sin for you (to marry their
  daughters) -- and the wives of your sons from your own loins, and that
  you should have two sisters together, except what has already happened
  (of that nature) in the past. Allah is ever-Forgiving, Merciful."
  [Noble Quran 4:22-24]

These conditions apply if the person affected is married. And if the person is divorced, she is not bound by the above mentioned conditions. As such, she is free to remarry


How do I add a schematic to my question?

Question: I see some questions and answers here that include schematic drawings. How do I add a schematic to my question (or answer)?
Comment: Ah! OK, that makes sense - thanks. I didn't know if the people who need this information would ever see it here. I had the idea that 'meta' was more like a "teacher's lounge" ha ha :)
Comment: I posted this Q&A because: 1) several people don't seem to know how to do this [Example](https://raspberrypi.stackexchange.com/questions/84527/problem-with-adc-mcp3008?noredirect=1#comment134736_84527), and 2) I couldn't find where it was explained in the docs for this forum. May I ask why it was moved here?
Comment: Questions about the site itself, like this one, belong on the meta site, which is a place specifically for questions like this. Any question about how to use the site, our policies or any bugs should be posted on the meta site rather than the main site. The main site is intended for questions about the Pi, so this would be off-topic there. See also: [What's meta?](https://raspberrypi.stackexchange.com/help/whats-meta)
Answer: Look up! When you are drafting or editing your question or answer, you will see a toolbar with a number of icons at the top of your Edit area. The toolbar has several icons: B for Bold, images, links, lists, etc. There is also an icon for schematics:

When you click that link (or Control-m from the keyboard), an overlay will appear in your browser. This is the online schematic generator supplied by CircuitLab.
Using the schematic generator is easy. Create your schematic by selecting components in the galley on the left side, dropping them the grid area, and connecting them with wires. Once you've completed your schematic, simply click the Save and Insert button in the upper right corner. This will embed a "link" to your schematic in your Edit area. This link will be rendered as a schematic in your Preview area, and embedded in your Question once you post it.
If you need help using the tool, CircuitLab has several resources, including an online textbook that will get you going. And don't worry too much about minor errors in your schematic as you will be able to edit your schematic: click edit below your question, then once your Edit area opens, click edit the above schematic to reopen your schematic.
This is an incredibly useful tool. If your question involves hardware or wiring, adding a schematic to your question will help others help you by adding clarity and specificity to your question.
Comment: In case anyone gets upset, it is worth observing that while you can use it here for free, CircuitLab requires a paid membership beyond that (which applies if you, e.g., want to convert to PDF via the interface).
Comment: Yes, glad you mentioned that. I suppose if one does a lot of schematics it's worth the price; I couldn't justify it for myself (plus, I'm cheap!)


Cloud providers performance dataset

Question: I need to perform some machine learning algorithms on a data set that contains cloud providers' performance. I need some of the following information :

availability,
input/output per second,
max restore time,
processing time,
latency with internal compute resource

I'm already simulating this data, but I need data of real cloud providers and for some users in long time. Few numbers that show the average of those metrics won't do. I need a detailed and large data set. Is there a chance that any company provides such data?
Answer: I believe this dataset has exactly what you're looking for!
Comment: That is a low quality answer! You don't even mention it's name. Looking further, I see it is about *ICT usage in enterprises*, so it seems not to answer the question.

Cloud providers performance dataset


Starting point for Mobile Device Security particularly in a MDM setting?

Question: I am looking for some good reference material (books, blogs, names, etc..) regarding Mobile Device Security. I am specifically interested in Corporate Mobile Device Management (MDM)  where often companies have to deal with BYO devices. Who are the topdogs on this topic?
Answer: Check out Dark Reading. They have quite a few blog entries about this sort of thing and they offer daily and weekly e-mail subscriptions (They'll also sign you up for subscriptions to some of their partner publications). Not all of it on Dark Reading is news, and a bit of it is white papers you have to log in in order to download. Overall they've had some nice exploits and solutions over the years.
Slashdot Mobile has security topics relating to new tools on the market. It's community fed so sometimes people do not post things that are available in more main stream locations.
Also pick up a subscription to the 2600 Hacker Quarterly (available on Kindle also). They have mobile hacks from time to time and give walk-thrus on how they're being done. Also they list exploits and the whys of the vulnerability.


Does using flaked salt make a difference when using it in cooking?

Question: I have a few recipes that call for flaked salt, I can only seem to buy it in bulk 1kg bags here. I want to know that if you use "salt" in a recipe does it really matter to the final taste what kind of salt you use. I do understand that for example when I use it on top of a foccaacia bread or something similar it does create a nicer texture, enhancing the taste, but this is in the final stages of cooking. When its used through the initial stages of the cooking process, like in a stew, bread dough etc does it make any difference ?
Answer: Salt (Sodium chloride) is salt. As a topping, flakes are commonly used purely for presentation purposes only. The taste is the same, but gets more intense as the salt particles get finer, so use less if the salt is in powder form
As an ingredient, use any form you are happy with, and is economical to use. Once salt is dissolved into water it will be identical to any other form of salt
For health reasons, finely powdered salt is preferable as much less is required to impart a salty taste
Comment: While this is 'mostly true', some 'specialty salts' (particularly sea salts) that will contain other 'trace elements' that will impart a slightly different flavor.
Comment: @Cos Callis While I would like to agree with you, have you ever blind tasted this? Once you have enough "containments" to make a difference, it's not salt any more!
Comment: but it is packaged and sold as "salt"
Comment: I agree that the tastes are negligible for most salt varieties but there can also be smoked salts and other aromatic variants that aren't necessarily full of "contaminants"
Comment: Harold McGee described some studies that showed people could differentiate between types of salt in solution even if they had the same sodium content: http://www.nytimes.com/2011/04/27/dining/27curious.html?_r=2&partner=rss&emc=rss&pagewanted=all&
Answer: Something else to keep in mind is the volumetric measurements that the recipe is using. If they are referring to a "teaspoon" of flaked salt to create the desired salinity, that will be a very different measurement in, say, kosher salt or table salt. I have pushed more and more towards weighted measurements of ingredients for that very reason. 5g of flaked salt is going to be just as salty as 5g of kosher salt (pound of bricks vs a pound of feathers anyone?).
So while the saltiness factor is all the same with sodium chloride, the amount you use can differ.


Saying Hallel in Shul on Pesach Night

Question: There is a minhag by some kehillas in chutz L'aretz and by almost all kehillas in Israel to say the complete version of Hallel in the shul during maariv on the first night of Pesach (and second in chutz L'aretz). Where does this minhag come from?  Why is this done in those places that do say?
Comment: Didn't the Ge'ulah begin at night according Berakhot 4B?
Comment: https://www.torahmusings.com/2019/04/hallel-in-shul-on-seder-night-is-less-more/
Answer: The source is Shulchan Oruch Orach Chayim 487 (4)

בליל ראשון של פסח גומרים את ההלל בצבור בנעימה בברכה תחלה וסוף ובן בליל
  שני של שני ימים טובים של גליות On the first night of Pesach, we
  complete the Hallel with the community with a pleasant tune and a
  blessing at the beginning and end. The same is on the second night
  outside Israel.

The Rema points out that this is not "our" custom.
mevakeshlev gives
several approaches from the Rishonim to explain this practice.

A. In Chazal's times, there were no siddurim and therefore the common
  people davened together with the chazzan or by listening to the
  chazzan's prayer. (This is why the chazzan is called a shaliach
  tzibur, the emissary of the community, since he indeed prayed on
  behalf of many individuals.) On the days that we are required to
  recite Hallel, these people listened to the chazzan's Hallel and
  responded appropriately and thereby fulfilled their mitzvah. However,
  how could they recite Hallel Seder night? They did so by reciting
  Hallel together with the chazzan in shul before coming home (see Gra,
  Orach Chayim 487).
B. A different approach contends that the community recited Hallel in
  shul the first night of Pesach in order to fulfill the mitzvah with a
  large group. Although one may recite Hallel by oneself, reciting it
  communally is a greater observance of the mitzvah.
Neither of these two approaches necessarily assumes that Hallel on
  Seder night requires a bracha. Indeed, the Chazon Ish recited Hallel
  in shul Seder night without reciting a bracha beforehand. There are
  congregations in Bnei Braq that follow this approach.
C. A third approach contends that the primary reason for reciting
  Hallel in shul is to recite a bracha beforehand. These poskim contend
  that Hallel at the Seder would require a bracha if it was not
  interrupted by the meal; to resolve this, Hallel is recited twice,
  once in shul with a bracha without interruption, and then a second
  time during the Seder. According to this opinion, Hallel Seder night
  fulfills two different purposes:
(1) We sing Hallel to Hashem as we do on all Yomim Tovim because of
  his miracles; on Seder night we sing Hallel at night because that is
  when we were redeemed.
(2) We praise Hashem while performing the mitzvos of Seder night –
  haggadah, matzah etc. Although one could fulfill both of these mitzvos
  by reciting Hallel one time during the Seder, one would miss making a
  bracha. Therefore, Hallel is recited during davening so that it can be
  introduced with a bracha, and is sung again during the Seder so that
  it surrounds the mitzvos of the night. This is the prevalent practice
  of Sefardim, Chassidim, and the most common approach followed in Eretz
  Yisroel today (see Gra, Orach Chayim 487).
Comment: Where did the Shulchan Aruch get this from? Is that the earliest source?
Comment: The tur was earlier @Yehoshua The real question is can this hallel be said before nightfall.
Comment: The problem with (C) is that the Gaonim say that a bracha isn't recited because this Hallel is said "b'toras Shira" and not b'toras kriah (nothing to do with the fact that we are mafsik in the middle.)

Saying Hallel in Shul on Pesach Night


What camera settings esp. shutter speeds to use while driving?

Question: I haven't been able to get very good pix while in a car thats driving at about 75-95 MPH -any advice what kind of settings to use?
How fast should I set the shutter speed in proportion to MPH?
Comment: I'm hoping someone else is driving :P
Comment: @Pastel - then I really hope someone else is driving. ;)
Comment: @ChinmayKanchi yeah u can b sure about that! im 2 young 2 drive
Comment: Photos of what? The other car occupants? The car in front? Trees by the roadside? A distant mountain range? I realise this is an old question, but this stuff is pretty critical to the answer
Answer: This is a bit of a tough question, as it depends on several factors. I would in fact say that there is no possible general answer to this question.
When moving at typical vehicular speeds, the shutter speed is selected to stop motion, in this case, the photographer's motion. When you're moving at these speeds, objects closer to you appear to be moving faster than further away objects. This phenomenon is known as parallax. In addition, it would depend on whether the objects are moving to your side (like the landscape), or are more or less moving towards you (like cars in front of you).
In addition, the higher your camera's resolution, the more noticeable shake and/or motion blur will be when viewing the image at full resolution. However, for a print of a given size, shake and/or motion blur should be the same regardless of sensor resolution.
It is possible to trigonometrically calculate the apparent motion of an object at a given distance and thereby select the shutter speed based on the acceptable amount of motion blur for a given photograph, but given that you're probably going to be well past the object by the time you finish calculating, there isn't a lot of point.
So in conclusion, for close or medium distance objects, I'd try to take photos with high (1/500 seconds or less) shutter speeds and keep going higher or lower till you find an acceptable setting. For far away objects, you can go pretty low, possibly all the way down to 1/50 seconds. Eventually, you'll learn to judge the shutter speed fairly accurately depending on your sense of motion; but it will require practice and deliberate experimentation to develop that judgement.
Answer: It has been 7 years since I wrote this but I think it still applies. The main point is to crank up the shutter-speed as high as possible and take lots of shots, probably in continuous drive mode, to increase the chances of getting something usable.
There is no direct correlation between shutter-speed and movement speed because it depends on relative velocity and angle-of-view. In other words you will need a faster shutter-speed to shoot at a close-by subject than at one that is far away. It also depends the direction of movement and the focal-length you are using. The longer, the lens, the higher the shutter-speed will be required to freeze motion.
Regardless, by my estimate at 60 MPH+, you should be using close to the top shutter-speed of your camera. Most DSLRs do 1/4000s and some go to 1/8000s. Smaller cameras can reach even higher shutter-speeds, up to 1/16000s for mirrorless and 1/40000s (yes fourty-thousandth) for compact cameras but chances are you cannot compensate enough with aperture and ISO sensitivity to get a well exposed image.
Comment: Is that India in the article?
Comment: No. That would be the low-lands near plantations in Ecuador.
Answer: Two things are influencing your need for shutter speed.
First, there's the increase in shake induced by the motion of the vehicle over the surface of the road. If your lens has additional features for stability in moving vehicles (more recent Nikon lenses have this), then you want to activate that.
Second, the motion of the vehicle. So, this really, really, depends on your relationship to the subject:

Far away and large like a mountain way off in the distance is unlikely to change much in appearance during the exposure, at least from the perspective of camera. You could be as low as 1/30 for that, experiment a little.
Close to you like a person at the side of the road is going to see a position change fairly quickly relative to the car. Your options there are to push up to a really fast shutter speed (say 1/800 to start, maybe 1/1200 or more) or pan your shot as your vehicle moves, keeping the subject in place. A lot will depend on your distance, the movement of the subject, and the light.

There's a lot of variance between the two relationships with the subject distance, so I don't think there's a good hard and fast rule there. I would start with these and experiment a bit. I think with that you'll start to generate a feel for what works with your camera and skills.
Answer: Honestly, the biggest thing is probably that shooting from a moving car not only means that other things are moving, but that the vehicle is shaking, probably quite a lot.  We get used to traveling in cars a lot so we tend to not notice it too much, but you are bouncing around a lot.  A stabilization rig or a lens with lateral image stabilization would do a lot for helping with the jostling a camera gets in a car.  It is worth point out that a while a typical Image Stabilizing lens may help a little, they are designed for camera shake from holding which tends to be angular (tilting the camera) more than movement up/down/left/right.
When you factor it out, at any kind of significant distance, the amount of camera shake induced by a car is going to be comparable to quite a bit of speed of movement even though it doesn't have to move all that far.
Either way, without Image Stabilization (and even with it really) the general answer is still the same.  Shoot as fast as the available light will allow.  If changes to distance are an issue, then either set to manual focus and take the picture as it moves in to focus or try to minimally close the aperture to allow for adequate focusing.  It's going to take a bit of guess and check work since the distance and speed and quality of your AF are going to alter how good of a job your camera does at holding focus on a wide open lens.
Also, make sure that you are using the feature of your camera that will follow the target being focused on if you have one (AI Focus or AI Servo on Canon bodies, don't know the name on others.)
Comment: What do you mean missed, that was my first point!
Comment: JoanneC: Oops, I must have either missed it or we were writing at the same time.  Or I have you on ignore and just assumed you'd write a comment here. :)  There we go, edited to remove the part about others not pointing it out.
Answer: just moving the camera as you "follow" the subject since you're moving at really fast speeds hopefully it isn't a state sign or something but just a scenic view this will help out with clarity as well as higher shutter speeds.
Comment: Panning along with the car movement will cause insane amounts of shake at lower shutter speeds. Not really practical, IMO.
Comment: I said higher shutter speeds not lower.
Answer: The requirements for shooting from a moving car/train/motorcycle vary depending on which direction you are shooting. If you are shooting straight forward through the windshield, or straight backwards through the rear window, then the majority of items in your viewfinder are relatively motionless relative to your camera/sensor. If you are shooting out the side windows, or even out the front or back at a large angle to the direction of travel, then things very close to you are moving at very high speeds.
When you are shooting straight ahead, the distant scenery is essentially motionless. As is the car or truck going the same direction and speed as you. Traffic going the other way will be traveling at twice your speed, and will not stay in the frame very long.
When you are shooting at right angles to your direction of travel, the far away distant scenery is essentially motionless, but items (telephone poles, bushes, parked cars) are moving past you at extremely high relative speed. No amount of panning will keep up with nearby things on the side of the road.
Obviously, with digital cameras, you can experiment as you go. I would not have high expectations that image stabilization will help a lot.
Answer: As with everything in photography, all you need is practice and patience.
In my experience, I like to shoot at 1/250 (this will normally keep a little blur while also respecting the integrity of the desired subject) with an f-stop of f/16. Another important factor is the lens; a 28mm will allow you to frame with the interior of the car such as window frames, etc... You can always crop later. Otherwise, a 50mm will probably allow you to eliminate all notions from inside the vehicle.


Integer matrices of constant widths

Question: This is inspired by the settings of this MO thread.
Let $ (a_{ij})$  be an $ n\times n$   matrix with entries $ 1,...,n^2$  and increasing rows and columns.   We'll call such a matrix of constant widths or, more precisely,  $ (k,n^2-1-k)$ -wide iff $ a_{in}-a_{i1}=k\ $  and $ a_{ni}-a_{1i}=n^2-1-k $  for all $ i=1,...,n$ .
Call $ k$  feasible if a $ (k,n^2-1-k)$-wide matrix exists.
Call a $ p\times q$  board filled with $ pq$  consecutive integers in order, either row by row or column by column, trivial.
Obviously the feasible values are in $F_n:=\{n-1,...,n^2-n\}$, and the two extrema of this set are trivial in the above sense. More generally, if $ p,q|n$  then we obtain a $ (qn+p-pq-1, n^2-qn+pq-p)\ $ -wide and a $ (pn+q-pq-1, n^2-pn+pq-q)\ $ -wide matrix by putting together trivial $ p\times q$  matrices. We may consider all those cases also as trivial.
Question:

(1) For given $ n$ , which values $ k$  can yield non-trivial matrices of constant widths?

Playing around, you may have at first glance the impression that if $ n$  is a prime, no non-trivial $ k$  exist. This may be true for $ n=5$ , but for $ n=7$ , we have e.g. the $ (18,30)$ -wide matrix
$$ {\left|\begin{array}{ccccccccc}\hline
1 &2&|&7&10&13&|&18&19\
3&4&|&8&11&14&|&20&21\
5&6&|&9&12&15&|&22&23\ \hline
16&17&&24&25&26&&33&34\ \hline
27&28&|&35&38&41&|&44&45\
29&30&|&36&39&42&|&46&47\
31&32&|&37&40&43&|&48&49\ \hline
\end{array}\right|}$$
composed essentially of trivial $ 3\times2$ and $ 3\times3$ matrices as shown.
Note that as the number of conditions grows only linearly with $n$, finding solutions will get easier as $n$  grows. So I'd expect only relatively few $k\in F_n$ not to be feasible. (I have not written a program to check that!)

(2) More interesting may thus be the question of finding the smallest non-trivial feasible $ k$ , and also the ones closest to $\frac{n^2-1}2$.

Such a matrix doesn't need to be 'antisymmetric' with respect to its center, meaning
$a_{ij}+a_{n+1-i,n+1-j}=n^2+1$.   But the boundary conditions seem to impose some sort of poised-ness. So the next question is:

(3) For odd $n=2m-1\ $, are there matrices of constant widths with central entry $a_{mm}\ne\frac{n^2+1}2$ ?

There may be an easy argument to show that there aren't, but I don't see it.
Edit: for the last question, the answer is yes. Take $n=21$ and start with nine trivial $ 7\times7$ blocks filled row by row. Now modify the first four lines of the central block by filling them column by column instead of row by row. This decreases the central entry of the block (and thus of the whole matrix) by $9$.
Now, such a construction won't work if $n$ is prime. So I suggest to replace question (3) by

(3') Is there a prime $n=2m-1\ $ such that there exists a matrix of constant widths with central entry $a_{mm}\ne\frac{n^2+1}2$ ?
Answer: The answer to (3') is yes. Here's a matrix of constant widths with $n=7$ and central entry $27\ne25$:
$$\pmatrix{1&2&5&6&8&11&12\cr3&4&7&9&10&13&14\cr15&16&17&18&19&20&26\cr21&22&23&27&28&29&32\cr24&25&30&31&33&34&35\cr36&37&40&41&44&46&47\cr38&39&42&43&45&48&49\cr}$$

Integer matrices of constant widths


Why does it matter if there is a duplicate?

Question: Why does it matter if the same question is asked twice? Sometimes the second question gets better answer.
Comment: On MSO: http://meta.stackexchange.com/questions/129844/why-prevent-duplicate-questions
Comment: The problem is that if there are two open questions, one with a good answer, the other with a bad answer, someone might find the bad answer and not the good one.
Answer: That's a good question, but it's been asked already here on Mi Yodeya Meta. Now, suppose this answer I'm penning is unclear to you or incomplete. Wouldn't it be better for me to write it as an answer to the older question instead, where you can read preexisting answers also, and to link you there? And wouldn't it be better for future readers to read all the answers in one place? And if my answer duplicates those answers, then isn't it a shame that I wasted my time writing it up instead of (when reading your question) being redirected to the older question where I could see that my answer already existed?
Now, sometimes the newer question is not the same as the older one, but is very closely related. Then it should not be closed as a duplicate. But where it's the same question, it's in everybody's best interests to be redirected to one question that collects all the answers.
If you're worried that the older question is insufficiently well answered, and are therefore duplicating it on purpose, see "What should I do if no one answers my question?".
Oh, and I was kidding. Your question hadn't been asked here yet. It is on MSO, though, as Isaac Moses pointed out in a comment on the question (thanks!).
Comment: And if you find a question that wasn't answered to your satisfaction, how do you get people to answer it again?
Comment: @AL, see the paragraph "If you're..." in my answer here.
Comment: I mean if you find the answers on someone else's questions aren't working for you. Are you saying to edit someone else's question to bump it?
Comment: @AL, don't edit just to bump it. Edit to improve the wording (while keeping the asker's intent), or [post a bounty](http://judaism.stackexchange.com/helpcenter/bounty).


What is a Shard?

Question: Proof of Stake brings new concepts to the Blockchain ecosystem. In the dictionary "Shard" is defined as "A broken piece or fragment, as of pottery or glass".
Answer: Shard is a concept not so much related to the Proof-Of-Stake, but rather to the scalability improvement. The idea of 'sharding' is to split the space of possible accounts (contracts are accounts too) into subspaces, for example, based on first digits of their numerical addresses.
Each shard gets its own set of validators (therefore PoS is a pre-requisite), and these validators will not normally need to validate all the shards. Messages (transactions) between the accounts within the same shard would work in the same way as they work today.
Contracts wishing to communicate across multiple shards will need to employ some special techniques, based on the concept of transaction receipts. The crucial difference between calling a contract directly and verifying the receipts is that for direct call one needs to run the code of the contract you're calling, but for verifying a receipt you only need to be sure that receipt cannot be produced by anything else than the transaction you want.
For example, if you want to accept a payment in tokens managed by a different shard, you would generate the payment ID, give it to the payer, ask the payer to pay in the remote shard (with payment ID), and 'bring you back' the receipt.
Sharding allows scaling Ethereum further, because not all nodes of the network will have to execute all of the transactions.
Here is the DEVCON1 talk given by Vitalik Buterin explaining this:
https://www.youtube.com/watch?v=-QIt3mKLIYU
Comment: In the case of transactions across shards, how would the "receipt" differ from referencing the block containing the desired transaction? While each node no longer needs to execute each and every transaction for every contract, wouldn't the blockchain still be a universal blockchain that all nodes have access to? In this case, aren't we effectively saying that  instead of requiring everyone to scrutinize every transaction, we'll trust a small representative population of nodes to verify a block independently as long as this population has enough diversity in it to prevent foul play?
Answer: In Ethereum, all miners are working on the same problem at the same time. (This is why people usually say: "Equate the Ethereum computer to a Commodore 64". It takes a lot to keep everything in sync.)
My guess is that, with sharding, you could have different segments of miners working on different problems at the same time, and they would somehow check each other to form a global consensus. (This appears hard to me, because what if you're sending ether in a contract running on one shard to a contract running on another shard? Race conditions? I'm sure people smarter than myself are working on this though.)
Answer: It seems to me that obvious solution to the scaling problem is fragmentation or specialization. You may call it Sharding, I simply call it inevitable. No different from the evolution of a biological organism if you think about it. I suppose that the question is not so much what is Sharding, but how can it be effectively implemented. In other words, the technical challenge of designing a robust protocol that does not compromise the essence of Ethereum.

What is a Shard?


How to locate an object on a known surface

Question: I am building a small robot on wheels. The robot will be moving at a small speed in a square area of known dimensions. I need to locate the robot and know its position at any given moment so I can correct its trajectory.
I can add parts to the robot, like some sort of flag or lighting object.
It's preferable not to put any border around the area, since it would limit the flexibility of the project.
Added Info

The size of the robot is about 28 x 25 x 11cm. It will go on land and
the surface will be ideally flat (but since the friction between the
surface and the wheels can vary in different places, I need to know
if the robot arrived to the destination or not, and corrections need
to be done respectively).
I can place beacons around the field or any sort of sensors, as long as I can remove them easily and transport them.
The surface will be about 1.5x1.5m, depending on the range of the sensors, or the method used for localization.
The robot can start from a determined position.

Some methods
I thought of triangulating the position using two ultrasonic sensors placed at the two edges of the field. Although I am not sure if the US sensors will provide a sufficient angle and range to cover the entire area. I am also concerned about the precision.
Someone pointed to me that I could use two infrared sensors placed at the two edges, and make them turn 90deg both ways and scan the area. As soon as they find something, the position of the object can be found using triangulation.
Although I still don't know if these methods work well for a moving object.
If you think that one of the methods that I described is the way to go, please give me more insight on how to implement it in my project.
Here is an illustration of the path that the robot should go along. The basic idea of the project is that the robot should sow seeds at regular intervals, for example every 10cm; this is why I need to know if the robot really covered 10cm after the seed before, and if it has to turn.
I thought of making an imaginary grid: I tell the robot the position that it has to reach, then knowing the position of the robot I can make it turn until it is pointing in the direction of the arriving point and then it covers the distance between it's position and the arriving point.

I am very new to robotics, therefore I would really appreciate a detailed answer.
Comment: I provided a general answer.  For a more specific answer you are going to need to provide a lot more details about the field, the robot, and any limitations you have on the design.  Ex: How big is the field?  Is the surface will controlled (so the wheels don't slip)?  Is it bounded?  Are there any identifications and/or beacons you can track off?  Does the robot start in a know location?  How far is it expected to travel?  Do you have an unlimited budget (some senors can be pricey)? ...
Comment: Thanks for the answer. You're right, I added more specific informations about the project. Also my budget is not very limited but also not very high (It's a project for highschool, I don't think I can fit 4 types of sensors on this robot).
Answer: Robots usually locate themselves on a field using sensors.  None of the sensors are perfect as they each have their own limitations; hence, the more sensors the better.
Here are some sensor options:

Motor Encoders on the wheels to track the distance and turns
IMU/Gyro to track acceleration and calculate speed and position
Magnetometer to correct bearings against magnetic north
GPS (usually for large outdoor distance)
Range detectors to look for walls or objects to reference off
Line detector (for lines or path markers on the floor)
Optical Surface Texture detection (like a laser mouse uses)
LIDAR imaging
Camera imaging (sometimes stereo-graphic)
Beacon detector (some fields have beacons placed on them for reference)

Generally the FTC (First Technology Challenge) robots that have good autonomous programs have at least four different sensor types that they use for positioning.
Answer: I suggest to use a color sensor and place some RGB colours in different parts as grid to let the robot know its position.


Volatility clustering and Behavioral Finance, possible explanation

Question: Currently studying about time series modelling of financial data and faced the known GARCH$(p,q)$ model for modelling volatility. We observe that big changes are followed by large changes and vice versa, as Mandelbrot said. But, in term of qualitative analysis, what are the main behavioral factors that lead to such pattern? Does volatility persistence oppose to EMH?
Comment: Volatility clustering is not inconsistent with the efficient market hypothesis that prices reflect all available information. A perfectly rational story for volatility clustering is that the arrival of big, market making moves forecasts the arrival of additional big, market moving news. For example if war breaks out in the Persian Gulf, you're more likely to see market moving news on oil supply disruptions etc....
Answer: First, the semi strong form of the EMH (prices reflect all public information) corresponds to the returns being a martingale difference; GARCH is a martingale difference, so GARCH is compliant with the EMH.
Second, you can look into the stylized fact of financial returns called "leverage effect", in short it says that returns have a negative correlation with the changes of their volatilities. A way to look at this is:

prices go down
companies become more leveraged and thus riskier
the prices fluctuate more
as prices become more volatile the investors demand higher returns
the prices go down
repeat until prices go up and the reverse happens (less volatility)

An excellent book for this subject is Fan & Yao, 2017 The Elements of Financial Econometrics.
Answer: Can you use the information from the GARCH model to time the market and make excess risk adjust returns.
If so, its against market efficiency.
You have to ask yourself,
What market? If you can correctly predict the VIX (or other volatility index) and trade on this yes.
The market, probability not!


Microphone for indoor interview

Question: I'm using a Rode ntg2 and I feel like the sound is less than ideal in a lot of situations. I record mostly indoor interviews (sometimes echoey enviroments) and I am looking for a good mic for that purpose. I realize that it is recommended to go with a hypercardioid or a supercardioid pick-up pattern. Which microphones would you suggest that can deal well with echoey environments, yet still provide a directional pick up? Budget up to 900.
Comment: Handheld, desk, boom, or lavalier?
Comment: Boom or lav works for me
Comment: The DPA 4060 is a fabulous lav mic… but pricey.
Answer: If you have an echoey room, the only solution is to get the microphone closer to the subject.  Period.  Directionality won't solve your problem.  In high-budget productions you see people wearing lav mics for a reason.
Here's a link that tells you all you need to know about sound for video production.
Comment: Thanks for the link. I recently had a shoot where I had at ME66 about a foot away from the subject, unfortunately the ceiling were low and metal (horrible reverb). Im curious about the lav however, it has a omni/figure 8 pickup pattern; wouldn't it capture more reverb, or because its so close to the source the level of the voice is alot louder so to speak so there is just a bit of reverb in the background? I've used my ntg2 with a lav before but it wasn't a good lav (rode smart lav) and wasnt impressed by the quality of the sound. I was looking at getting the Sanken COS 11D.
Comment: Which lav do you use/would you suggest?
Comment: Another solution is to put something to catch the echo, like a towel or foam.
Comment: Due to the 1/r^2 law of sound fall-off, a microphone really close to the source is going to hear much more of the source than the reverb.  Announcers at football stadiums have headsets with mics that are almost right up to the lips, for example.
Comment: The Sanken looks like a fine mic.  We use Countryman lav mics--good but haven't spent the time to try to figure out how to make them great.
Answer: I like lavalier mics.  For $900 you should easily be able to get

2 lav's
wireless for both
receivers to XLR

Alternately, cabled lav's are fine for a studio situation!
Answer: A professional film sound mixer I used to work with swore by the Oktava Mk12. It's comparatively inexpensive, well-built, and sounded beautiful. He used it on all his interiors; for exteriors he usually switched over to the Senn 416. Even in boomy environments, his raw tracks were amazingly clear.
For lavs, I've never worked with better than the tiny Countrymans for placeability and sound quality. When the lav head is the size of a grain of rice there aren't too many places you can't put it. Try that with a Sanken or a Tram!
Answer: IMHO the NTG-2 is not a great microphone, even the Sennheiser ME66/K6 sounds better. The next step up would be a Sennheiser 8060 or mkh416 or a Rode NTG-3.
That said, they won't help much with the reverb either. In high-end sound terms, a lavalier will always sound worse than a properly boomed directional mic, by its physical characteristics alone, featuring a much smaller diaphragm, at least when comparing a good and properly setup Lav with a good and properly boomed directional mic.
BUT as the others mentioned, distance to sound source is the key to deal with a room with a lot of reflections so you might get better results using a lav in those cases. I would at least record a long room tone additionally (well, always record room tones anyway) but also the directional mic to capture the rooms characteristic during the interview. Then use the reverby directional mic together with the Lavs sound in the mix. Personally I feel that ONLY using a lav as a source sounds really dull.
As for lav mics, in Europe, to my knowledge, the sanken cos11d is pretty much the standard lav, I heard good things about DPA microphones Lavs but never tried them personally.
Generally speaking it is always a good idea to give the sound recordist at least a veto-right in terms of location choice, there are rooms which simply are not suited for recording interviews plain and simple.

Microphone for indoor interview


Sleeping Music during the Three Weeks

Question: During the three weeks, may parents put on music that helps their children sleep? Perhaps there is a difference between before Rosh Chodesh Av and after Rosh Chodesh Av.
Comment: Related answer: http://judaism.stackexchange.com/a/1050
Answer: Generally, if the music is not for one's specific enjoyment, you can listen to the music. In your scenario, you are not the one listening to the music, anyway - your child is. And, s/he is not even listening for the enjoyment of the music, itself, anyway. Plus, there may even be more leniencies for a child below bar / bat Mitzvah, anyway.
In summary, I wouldn't see a problem, personally, but confirm with your Rav.
See this article for details.

Sleeping Music during the Three Weeks


What's the advantage of using PBKDF2 vs SHA256 to generate an AES encryption key from a passphrase?

Question: I'm looking at two comparable pieces of software which encrypt data on disk using a passphrase. One uses PBKDF2 to generate the encryption key from a passphrase, while the other uses two rounds of SHA256. What's the difference? Is one preferred over the other?
Comment: Related: [How to securely hash passwords?](https://security.stackexchange.com/q/211/13154)
Comment: PBKDF2 uses SHA internally ;)
Answer: The difference is that:

PBKDF2 by design is slow
SHA256 is a good hash function; it is not slow, by design

So if someone were to try a lot of different possible passphrases, say the whole dictionary, then each word with a digit appended, then each word with a different capitalisation, then two dictionary words, etc. then this process would be much slower with PBKDF2.
But if your passphrase is truly secure, that is very long, pretty random and out of reach of any systematic enumeration process, then it makes no practical difference, except that an attacker may spend more resources trying to break your passphrase (or maybe less if they decide to give up sooner).
Comment: Couldn't that still be thwarted by mirroring the DB file thousands of times and using a coordinated multi-threaded brute force attack? It seems almost as if PBKDF2 may be (counterintuitively) most secure in a monitored online environment with backend threat detection monitoring in a physically ultra secure server room.
Comment: so what is PBKDF2 advantage??
Comment: @AminM That it's **"cryptographically slow"(1) is PBKDF2's advantage.** (1) I just made up that phrase, I mean that it would require a huge breakthrough in crypto breakage of the underlying cryptographic hash function to make it a lot more efficient. (Making hardware with more op per second doesn't count.)
Answer: Password hashing algorithms such as PBKDF2, bcrypt, and scrypt are meant for use with passwords and are purposefully slow.  Cryptographic hashing algorithms are fast.  Fast is good in most situations, but not here.  Slowing down the algorithm (usually by iteration) make the attacker's job much harder.  Password hashes also add a salt value to each hash to make it unique so that an attacker can not attack multiple hashes at the same time.
Attackers will try to recover passwords by performing dictionary and brute-force attacks where they guess passwords by hashing them and comparing them to the stored password to determine if they match. With regular cryptographic hash functions (e.g. MD5, SHA256), an attacker can guess billions of passwords per second. With PBKDF2, bcrypt, or scrypt, the attacker can only make a few thousand guesses per second (or less, depending on the configuration).
This means that every password is much stronger if PBKDF2, bcrypt, or scrypt are used instead of a regular hash function.
In addition, PBKDF2, bcrypt, and scrypt all use large random "salt" values to make sure that each user's password is hashed uniquely. Attacking 100 password hashes will take 100 times longer than attacking one hash. Attacking a million will take a million times longer, etc. With SHA256, the attacker can try to crack thousands or millions of hashes at the same time with very little slow down.
You should always use a password hash or "key derivation formula" for passwords rather than an ordinary cryptographic hash. It's very hard to select passwords that are strong enough to withstand a dedicated cracking effort if they are hashed with something like SHA or MD5. With PBKDF2, bcrypt, or scrypt, passwords can be as short as 7 or 8 characters but with MD5 or SHA, they need to be at least 13-14 characters.
Comment: You underestimate the power of this fully armed and operational GPU cracking setup.  If we take [oclHashcat] on one PC with 8x AMD R9 290X at stock core clock, it's 162 billion MD5/second, 11 billion SHA-256/second, 797 million SHA-512/second, and 1.3 million WPA or WPA2/second (WPA/WPA2 is roughly equivalent to PBKDF2-HMAC-SHA-1(pass, salt, 8192 iterations, 20 output bytes)
Answer: There are good answers above, but the immediate reason is that sha256 isn't salted and two rounds is pitifully weak in the same way that 4 digit passwords are weak, computationally:

A modern GPU setup can easily compute all of the unsalted 4-digit sha256 hashes (in milliseconds)


Is it okay to leave a 3 year old alone to nap for 1 hour and 45 minutes if she isn't napping?

Question: My wife and I disagree about this. I think it's a bit selfish and neglectful to leave her alone, especially when for the first 20 minutes she just cried and screamed. After that she was pretending her doll was her baby and feeding it and burping it. This indicates she feels a little abandoned and is looking for something to love her, even just an inanimate doll. Am I reading too much into this?
Comment: Letting the child cry is not my style. But I can leave my kid playing for quite a while. It seems it makes my child entertain himself. Which helps when things need to get done in the house.
Answer: I think you are reading too much into it. Your three-your-old calmed herself down and contented herself with quiet play instead of napping. She is playing with dolls because that's what many three-year-olds do. And while she wasn't napping, she was having quiet play which is a restful alternative. The ability to entertain oneself is an important life skill!
Answer: Let me provide a few separate comments:

"Nap time" is often also called "quiet time" because sleep is not mandatory, but the point is being quiet (and calm) for a while. So it's not a problem in my view that she doesn't actually sleep in that time. Many children of that age have outgrown the noon nap anyway. But it's good to still practice a bit of "quiet time."
I would personally not let a child "cry and scream" for 20 minutes, but that is a matter of parenting style. There's an approach called "cry it out" that basically says to let the child scream for as long as it takes. Another approach would be to stop by every few minutes with a few soothing words, then leave again. It seems to me that you have different opinions on what approach to use. Consistency is important so you should discuss this and agree on a method.
To reiterate my previous sentence, it sounds like the parents don't agree on details in the parenting style. You should discuss any such disagreements as objectively as possible - try not to get emotional because that is rarely conducive to an agreement. Talk about what "your" preferred style is and "why" that is - and also how you interpret the situation in your question (abandonment) because I suspect that your wife has a completely opposite interpretation (self-development, perhaps?). Don't assume -- neither about a situation, nor about the spouse's reasoning.

"When you assume, you make an ASS of U and ME..." <-- I'm just saying that assumptions are often misleading, and discussions help!
Comment: Yes I like the idea of nap time being quiet time. +1
Answer: First of all: playing with a doll pretending to burp it mother it in any way is normal three year old behavior and is perfectly healthy.  It by no means indicates your daughter is feeling abandoned.  Hopefully knowing that can help you to relax that your child is not/has not recieved long term damage from your wife.
As long as the child is in a safe environment free of access to dangerous tools and the like, it is considered pretty healthy for a kid of your daughter's age to be required to have some alone time (while a guardian can still hear if there is trouble).  This is time for a child to decompress, learn how to self entertain and drift off to sleep if he/she is particularly tired that day.
At three, she finds hanging out with mommy more interesting than sleeping.  Since she is also at an age where she may suddenly be needing a little less sleep, but might still need the nap on some days while not on others, she may be contending with learning how to play by herself/soothe herself, etc so she is protesting loudly - another normal three-year-old behavior.
Going to a screaming child and letting it get its way is a good way to encourage the screaming and yelling to continue.  Your wife is probably trying to make the point to your daughter that her naptime is supposed to be alone time, and she needs to accept it.  Going and discussing the idea with your daughter, probably only makes the time of protestation last longer in the long run (at the age of three - I would speak differently of a child that is younger).
Having said that, there are some preventative measure you can take so things start off well instead of with screaming.  If you or your wife, aren't already, I suggest:

recognizing your daughter may be moving away from needing a nap.  Start referring to what was her nap time as quiet time and shorten it a little.  Spend a little time teaching her what this means and treating it as a huge positive step toward growing up big and healthy.  If it really is quiet time and she needs the sleep, she'll fall asleep on the days she needs it - on those days an hour and fourty five minutes is perfectly acceptable in terms of time.
most people I know go for about an hour when it comes to quiet time, a few for only a half hour. At an hour and 45 minutes, you are verging on two hours, which, for a three year old is a really long time to keep herself appropriately entertained, if she doesn't fall asleep.  The kids that are only required 30 minutes quiet time I know fall asleep less often than the kids with the longer time so, I suggest an hour.  Set aside up to two hours without other activities that might impede upon the time, so on days she does fall asleep she can be allowed to stay asleep.
Go over some ideas with your daughter for things she can do during her quiet
time that are special quiet time things she can do that she can't
often do at other times during the day.  Maybe you could get your daughter some special quiet time items - perhaps a new bed for her doll and she can put dolly down for a nap during her quiet time.
Make it expected and predictable.  Warn her at five minute intervals starting at about fifteen minutes before quiet time is going to begin.  Then, make sure she knows exactly how long quiet time will be by deciding whether you expect her to partake in this activity for an hour, or half hour etc.  Set up a clock in her room with a picture showing her what the clock looks like when she can come out of her quiet time space again.

Selfishness can also be referred to as "self care" when in balance, and requiring your daughter to have some quiet time and/or a nap (which is also healthy for your daughter) seems perfectly in balance to me - people who have a job, "at the office" get a coffee break, the ability to use the restroom without a little one staring at them or banging on the door AND a break for lunch - your wife doesn't get any of those things.  Even the best, most devoted moms need a little time to themselves - something most three year olds are extremely reluctant to give for more than about sixty seconds (and even that is if mom is lucky) without mom forcing the issue a bit.  To help your wife get her personal needs met too, you need to consider her needs just as important as yours and the needs of your daughter's.  If your daughter is dropping her naps, your wife is probably getting even less down time than she was previously getting.  Perhaps, if you aren't already, you could step in and take over on an afternoon every other week or weekend so your wife can have some girl time with friends or some down time of her own too.
Answer: In agreement with Mary Jo's answer.
Children will play with their toys, pretending to feed and burp a doll does not mean a sign of neglect or abandonment, it has been a tradition of girls for generations and plays a part of role play, conditioning and preparation for a particular role as a parent (much as lion cubs play fight and hunt each other in preparation for hunting as adult lions).
Many mother's crave sleep (as do father's) and provided the child is safe, there should be no harm in a parent napping. Given the scarcity of details it would be hard to comment on much further on the situation. As to where your child is while your wife is napping. I would nap on the couch while my son was playing beside me (if he wasn't napping), that way he was supervised, as I would not go into a deep sleep when napping like this.
So with the issue of safety and neglect out of the way, I think we need to look at the more important issue.
Disclaimer: Please I stress, it is good to come here with questions, I am making an observation of what may be a deeper cause.
This is not a good sign to be bringing a he said she said type of post into a public forum. There are many ways to cloak a question without it being a direct reference to such a source of conflict within a relationship. As internet strangers cannot adjudicate between the two of you and decide what is right or wrong here, as we do not really have the full picture. My way of thinking this indicates that the issue that needs to be addressed is the communication between you and your wife.
Parenting puts strain on both parents, it tests a relationship and totally changes the dynamics and expectations between couples. It's a huge adjustment and can remain so for some time. For some couples it is not until the children are at school that they work out some harmony and synchronization with child raising.
The real issue here is for you and your wife to be able to communicate, her needs and feelings of fatigue and how these can be addressed, without recrimination over parenting. When my son was a baby, an old friend would say to me, for a happy child make a happy mother. I think there is a lot of wisdom in this; except of course this extends to fathers and all care givers. The primary care giver, is the one who spends the most time with a child (obviously, by definition), and as such, it pays dividends to look after this person, in the overall picture of caring for a child.


Windows Clustering Issue

Question: We are setting up a SQL Server Cluster using the Windows Server 2008 R2 Failover Cluster.  We created a cluster and added the first node to it.  We then created a second server, but I believe that my system admins did a copy of the server instead of a new install.  Now the server, although having a new name, still thinks its already part of a failover cluster.  We then decided to start over from scratch with the failover cluster and distroyed the cluster.  The second server still believes its part of a current failover cluster and we see no way of removing that.  My guess is that there are some registry settings or something that didn't get reset.  Any one know how to clear this so that we can add the server to a new failover cluster?
Answer: Command Line:
c:> Cluster node  /forcecleanup
Answer: Be sure to run sysprep if you're going to copy an image of a node or else you'll end up with problems. Clusters are easily messed up by sloppy administrators.
Answer: I dont have the rep on serverfault to respond to the comment on the previous poster's command line suggestion.
1) Thanks for pointing out the Cluster command line option, I was buried in the UI so this is good to remember.
2) There is no /forcecleanup option.  Perhaps in some older version but not in the 2008 R2 instance that the OP is asking about.
Additionally I do not see how to perform any cleanup action from the command line.

Windows Clustering Issue