How to combine an accelerometer and a gyroscope to find robot location and orientation in 2D/3D space

Question: I have data from an accelerometer that measures X,Y,Z acceleration and data from a gyroscope that measure pitch, roll and yaw. How would I combine this data to find robot location and orientation in 2D or 3D space?
Answer: Look into nonlinear filters, particularly the unscented kalman filter (ukf). Using a ukf to fuse the data from a gyroscope and accelerometer will allow you to estimate orientation. However, these two sensors alone will not be capable of estimating position. You will need some sort of sensor that measures distance or position.
For information on the ukf, look into Probabilistic Robotics.
http://www.amazon.com/Probabilistic-Robotics-Intelligent-Autonomous-Agents/dp/0262201623/ref=sr_1_1?ie=UTF8&qid=1421178247&sr=8-1&keywords=probabilistic+robotics
Response to comment-
Imagine you are trying to estimate the position of a car that is traveling down a straight road. To estimate the position of the car, you are given a picture of the car's speedometer every second. You can get an idea of how far the car has traveled using this information but you will not know for certain. If there is any bias in the speedometer, your guess of the total distance traveled will be way off. To really know the car's position, you need to be able to measure it directly.
Comment: Why can't these two sensors alone estimate position?
Answer: Unfortunately I cannot comment.
You can, but it will most likely be very inaccurate.
If you use an accelerometer output to calculate displacement by double integration, any error will be compounding. Because you have no way to offset this error, over time it will become so large that the position value is meaningless.
The other issue is if you are moving at constant velocity the accelerometer will report 0m/s/s, so double integration with respect to time will give a displacement of 0, making the robot appear stationary.
Answer: Here's a pretty good overview of what holmeski is saying, and using multiple sensors in general for different applications.
FWIW DARPA is, and has been looking into inertial sensors with enough precision to get useful positional tracking. It's called "Micro-PNT" for "position navigation and timing" and the idea is to not need a GPS.
Also, here's some more info directly from the DARPA site.
Quoting,
"The micro-PNT initiatives seek to increase the dynamic range of inertial sensors, reduce long-term drift in clocks and inertial sensors, and to develop miniature chips providing position, orientation, and time information. "
The bottom line general answer is, current inertial sensors generate too much uncertainty to be used standalone, and sensor fusion has it's own set of limitations.
Answer: Its possible.
I did the same in my graduation project. What you need is:

Controlled movement over your machine, that you can command the machine to move 1 meter forward or 50cm back etc.
You need to train your system to learn from accelerometer data according to those controlled movements.
Train on different surfaces and also calculate the time elapsed in one particular move.
After some training your machine will understand that what does it means to move 1 meter forward or backward.

Believe me, it works like magic. My project was 3D semantic analysis and map reconstruction using autonomous agents, and I have not used GPS at all. I hope this will help you and somehow will also motivate you because its possible. :-)


Can I use Bitcoin to send money from a US bank to an Indonesian bank?

Question: I now live in Indonesia and want to send money from my US bank account to an Indonesian bank. Can I use Bitcoin to do this transfer?
Comment: Bitcoin does not use banks, nor does it care about geography. You may want to rephrase your question
Comment: Hi Billy, welcome to Bitcoin.StackExchange.com. I've taken the liberty to slightly edit your question in order to make it better fit the options available to you. I hope that I still capture the essence of your question. Otherwise, please feel free to further edit and improve it.
Answer: Bitcoin is not well integrated with the legacy banking system. What you want to do would therefore go somewhat like this:

Open an account with a Bitcoin exchange (A) that takes US customers. (Assuming you are a US citizen.)
Deposit USD into the Bitcoin exchange.
Open an account with a Bitcoin exchange (B) that serves the Indonesian market.
Buy bitcoins for USD on A, transfer the bitcoins to B, sell the bitcoins for Indonesian Rupiah on B
Withdraw Indonesian Rupiah from B to your bank account in Indonesia.

As you can see this is somewhat complicated, and there are likely ways to make this transfer more easily. However, I have successfully used a similar method to transfer money to myself in the past and it was much cheaper than an international wire transfer.
Comment: Seems easier to pull local currency from an ATM and walk into the bank with it.  In Spain, I can draw Euro from my US bank with their card, then deposit into my Spanish bank at the same ATM.  (But now I'm in USA and sending money back is tough!)
Answer: One of the ways to receive Bitcoins when the legacy banking system makes it awkward is via one of the new innovative services associated with the Bitcoin ecosystem.
Localbitcoins: https://localbitcoins.com/
 - Engage with someone and work out a price. Be careful on here, it is basically peer to peer and I don't believe its regulated.
Bitcoin Debit Cards: https://coinsbank.com/
 - Basically take out a USD card, send the Bitcoins to this account and convert into USD. Then draw out at an ATM and put into your local bank account.
Hope this helps.
Answer:
take cash out of bank.
walk to bitcoin atm
deposit to bitcoin address (don't forget receipt)
get a relative in Indonesia to go to bitcoin atm (no need to wait)
withdraw (don't forget receipt)
deposit in local bank

Each use of bitcoin ATM will cost you about 5%, so cheaper if you use an exchange or p2p method. But those methods are are slower and sometimes riskier.
Edit: I just see you're in Indonesia. Can't you withdraw from there? Do you have a proxy for physical access to the USD cash?


When I click on Data Dictionary, it brings up a blank Excel spreadsheet

Question: When I click on Data Dictionary in the College Scorecard, it brings up a blank Excel spreadsheet. Where can I find the Data Dictionary information?
Comment: The Data Dictionary in the College Scorecard.  https://collegescorecard.ed.gov/data/documentation/
Answer: That file is fine:

Two things may be incorrect:

There is something wrong with your browser downloading it. Set your browser settings to ask what to do with a download (example for PDF files for all browsers), then save the file to disk, and open it in Excel.
It is an .xlsx file, not .xls. If you have an older version of Excel, you may need to install the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint File Formats to be able to open the newer file format.


What are some good philosophical resources on nonlocality?

Question: Bernard d'Espagnat offers a good treatment of nonlocality as it pertains to physics, in his 2006 On Physics and Philosophy. What I'm interested is whether nonlocality has been observed and discussed elsewhere. For example, in The Political Illusion, sociologist Jacques Ellul observes:

But to pretend that justice and truth are given their due is only a raid and a form of hypocrisy. Those who claim to do justice by condemning a man to death deserve the same accusation of hypocrisy that Jesus leveled at the Pharisees. What we find here is an ideological construct that man builds to justify his acts: these acts are useful so that society can function and survive. Bruckerberger's argument was: If we pardon murderers, our society is done for. It is useful for the survival of a group to eliminate the nonconformists, the fools, the anarchists, the maladjusted, the criminals; and it is legitimate that the group should react in this fashion through its judges, its soldiers, its political men. It is the very role of politics to make this reaction more easily possible, for it is under such conditions that no one individual or group has to bear the responsibility. (90)

Would it be valid to say that responsibility has been nonlocalized? The terms herd mentality and bandwagon effect seem close to what I'm describing; the budding field(s) of ecological psychology could also be construed as a recognition of nonlocality in society. Finally, the idea that individuals are "socially constructed" (e.g. social constructionism, George Herbert Mead) seems connected.
I want to know if there has been any focused, philosophical treatment which covers the concepts I have attempted to sketch out. N.B. I am vaguely aware of Samuel Taylor Coleridge's philosophy of "interpenetration" and "all in ᴏɴᴇ" and "ᴏɴᴇ in all", but I am not aware of it developing much.

I just started reading David Bohm's Causality and Chance in Modern Physics and came across the following, which made me think that holism may be an important, related term:

    Indeed, when this interpretation is extended to field theories,[7] not only the inter-relationships of the parts, but also their very existence is sen to flow out of the law of the whole. There is therefore nothing left of the classical scheme, in which the whole is derived from pre-existent parts related in pre-determined ways. Rather, what we have is reminiscent of the relationship of whole and parts in an organism, in which each organ grows and sustains itself in a way that depends crucially on the whole. (xi)

Does this exist only on the quantum level, or might there be more nonlocality on day-to-day scales which we generally do not see—perhaps due to a model of causation which comes from the mechanical philosophy?
Comment: Strictly on the quantum mechanical side, Michael Redhead's book Incompleteness, Nonlocality and Realism is a classic and still well worth reading. Whether nonlocality in QM has any consequences for the big wide world is highly speculative.
Answer: Quine's discovery that every observation is theory laden, led him to adopt confirmation holism. I guess you could describe this as being a form of "epistemic non locality" in the sense that no observation is independent of a theory, and presumably of other observations which were used in constructing the theory.
In particular, this quote from the SEP article on Quine, implies a "non locality" similar to the one described in the first quote of your question.

In particular, Quine claims that holism shows that most of our sentences are not justified by the relation of the individual sentence, considered in isolation, to experience. Almost always, what matters is the relation to experience of some larger chunk of theory (and, in principle, although perhaps never in practice, of the theory as a whole). This means that the correctness of a given claim is almost never settled simply by gathering empirical evidence.


Investigating rare variants in ethnically different populations (European ancestry & African ancestry)

Question: If you are investigating low-frequency and rare variants for a complex trait using exome sequencing, why would one consider using different populations (African ancestry and European ancestry) especially considering that the populations have different allele frequencies. Is the main object to see if they're could possibly be novel rare variants in each population at different allele frequencies?
Comment: Mainly you do this because these populations have segregated long time ago and developed differently. You will find rare SNPs for pigmentation in europeans that are not present in the more ancient african population (and must therefore be occured after the populations divided), examples are the so called "golden mutation" in SLC24A5 (rs)
Answer: Too long for a comment, but sort of:
Mainly you do this because these populations have segregated long time ago and developed differently, so it is more likely to identify these polymorphisms. It is also helpful to use populations for this which mixed not too much with other populations (thats why north-americans are usually not used here, as America was kind of a melting pot).
You will find rare SNPs for pigmentation in europeans that are not present in the more ancient african population (and must therefore be occured after the populations divided), examples are the so called "golden mutation" in SLC24A5 (rs1426654) or a polymorphism in IRF4 (rs12203592).


Plural form of tardy

Question: What is the plural form use of "tardy" such as: number of tardy arrivals to school, work, etc.? Word spell check does not have any suggested words in this instance.
Comment: In your example you are using *tardy* as an adjective. Back when I was in school, "tardies" referred to multiple events of being late for school. Ex: "You have three *tardies* this month, so you will have to go see the counselor." But it doesn't seem to be an official word.
Answer: tardy
noun

an occasion when you are late for a class, or a record that a teacher keeps of this

MacMillan
The plural is tardies.
See also Wiktionary:
tardy (plural tardies)
(US) A piece of paper given to students who are late to class.
The teacher gave her a tardy because she did not come into the classroom until after the bell.

Before turning to the dictionary I had posted the following:
As to saying that tardy is an adjective, well it is also used as a noun. Someone can have one absence and one tardy this week. Or someone could have two or more tardies.
We can indeed convert adjectives to nouns by using only the first part  of an "adjective-noun"  combination. Consider smiley face. That became smiley. Oh, my gosh  this girl likes to use smileys in her texts.
If a word is used as a noun, it's a noun.
Answer: Tardy is an adjective. There is no plural.
Your sentence ("number of tardy arrivals to school") is correct.
Comment: Well, you could use it as a noun and say "You're all a bunch of tardys!" That has a nice ring to it. :)
Comment: *Tardy* is also used as a noun, in American English.
Answer: While tardy as an adjective can't be made plural, you can use tardiness to talk about more than once instance of being late.

Your tardiness is becoming a problem. Please show up to meetings on time.

In the US, tardy is most commonly associated with grade school students. There are some instances of turning "tardy" into a noun, such as:

At Casey County Middle School in rural Liberty, Kentucky, Principal
  Terry Price says, "We had as many as 40 tardies per class period in
  the morning." Source

In this sense, I think the principal was shortening 'tardy students' to 'tardies' but it could also be 'tardy slips', or notices that a student was late to class. In contexts other than talking about students, some explanation of tardies might be necessary, because it is not standard English. I would be reluctant to talk about a group of adult coworkers as tardies - it seems a little bit disrespectful to talk about them like they are children.

Plural form of tardy


Is it possible to run inside visual studio .net published web site?

Question: Hello I need one confirmation from you guys.  I have one client who have published web site (asp.net 2.0) and site is live online. Client doesn't have solution or original source code of this web site project. My question is :  Is it possible to download this code localy and successively run it inside visual studio ?
Answer: Simple answer is Nope.
You do need the source code to build and run the web site within Visual Studio. Visual Studio purpose is to help the developer build the website or even extend a website (looks like what you want to do) and to do so it requires source code files.
What you can do is to try to set up IIS (Internet Information Services) and run a copy of the web site locally but it isn't Visual Studio as you stated in the question.
Comment: Thank you very much Leniel. I know this but I needed to ask again just to get some confirmation. I was not shore enough,thought maybe there is some solution in those days.
Comment: OK. It doesn't hurt to ask. :D
Answer: Sometimes you may find the source code files on the live server, or a backup of them.  If not you could use the dlls and some software to view the code using reflection.
Some of these also regenerate the Visual Studio projects for you - I know the paid version of .Net Reflector does.
If you do it that way, depending on what you use, some of the code may not come out exactly as it was written but it should work the same way.
Answer: You can run it in cassini, iis, or iis express but you can't step through the code if that's what you're after.
If you want to simply inspect the code I recommend IL spy. That's what I use.
http://ilspy.net/


Professional Scrum Master vs Certified ScrumMaster® (CSM)

Question: What is the different between the following project management certifications Professional Scrum Master (PSM) Certified ScrumMaster® (CSM)? Which one is better?
Comment: This is a very subjective question. If you google psm vs csm you'll find dozens of articles and discussions on the topic.
Answer: Ken Schwaber founded and chaired Scrum Alliance and left to form Scrum.org due to differences in values especially regarding certification.1 2 3
CSM (Scrum Alliance)

16 hour course, plus exam
35 question, 68% to pass, no time limit
Course content varies by instructor

PSM (Scrum.org)

Optional course, plus exam
80 questions, 85% to pass, 60 minute time limit
Standardized course content
Answer: Personally, I feel CSM is better.
CSM (Scrum Alliance) puts more weight-age on training the candidate. The training is hands-on with lot of real life situation. The stress in on making you learn through doing it. So, at the end of the training, the concepts goes into your head and you are already ready to apply Scrum in to your daily work.
The exam is fairly easy and is taken just to ensure that the candidate pays attention during the entire training.
PSM (Scrum.org) on the other hand puts more weight-age on exam. So at the end of the day if you pass the exam you are Scrum Master. Are you clear on the concepts or you are a lot confused in terms of how to apply those concepts? is left up to you.


If I rush does my salah become Qaza?

Question: Actually I have rushed through many of my salats or at least prayed faster than normal. So do I have to read these salats qaza again or do I ask forgiveness from Allah and repent and try not to do it again?
Comment: I indeed admire what you have asked. Since occasionally I ask myself what will be the result of such Salahs, and actually will they be accepted or not. / Of course apparently it would be accepted, but decrease its thawab, but I'm still looking for a nice answer too, in order to be more certain about that.
Answer: No actually. Have attention and consideration during pray is emphasized, but it's not a vital or necessary part of it.
It's better you ask God's forgiveness and try more concentration on your prays.
If you say words exactly and motions accurately, speed is not a factor!
Comment: you can have a better response by adding a hadith or ... But anyway, in my opinion: your answer deserve +1 as a right brief answer which can convey the right way to the questioner. Good luck mate.
Answer: You need to learn what prayer really means (coming nearer to Allah swt by purifying one's soul.
Please read Soul and Spirit
http://heliwave.com/Soul.and.Spirit.pdf
to understand the difference between then and in sha Allah understand the meaning of the rituals especially sending salaams to our Prophet )pbuh+f), ourselves, 3ibaad Allah al-saliheen, and all angels around us at the end of the prayer.
Remember in every prayer unit (ruk3a), we do two prostrations (sijoods) to simulate Death/Life/Death/Life as stated in Quran 2:28
كَيْفَ تَكْفُرُونَ بِٱللَّهِ وَكُنتُمْ أَمْوَٰتًۭا فَأَحْيَٰكُمْ ۖ ثُمَّ يُمِيتُكُمْ ثُمَّ يُحْيِيكُمْ ثُمَّ إِلَيْهِ تُرْجَعُونَ {٢٨}
002:028 How can you be unfaithful to Allah, [seeing that] you were lifeless and He gave you life, then He will make you die and then bring you to life, and then you will be brought back to Him?
God >
Comment: Hello and welcome to [islam.se]. Good words out there, but they fail to answer the question, i.e. *
If I rush does my salah become Qaza?*. Please go through [answer] and the [tour] page.

If I rush does my salah become Qaza?


Savings Account

Question: I have a question about a savings account I have with Wells Fargo. I have had the account my whole childhood, and am turning 18 in less than 2 weeks. I am pretty sure it is a "minor by" savings account, because I was not able to withdraw money...I could typically deposit it, but was always told the parent usually had to be present to deposit. I asked my father about taking the money out once I turn 18, and he said I could do it...so I was wondering what I would need then to be able to take the money out??? Do I need an I.D. or anything?
Comment: Have you contacted Wells Fargo to ask them?
Answer: By law, if the account was a "minor by", also called a "custodian" account, it automatically transfers to you once you reach the age of majority in your state, which I gather from your post is 18. Once you turn 18, all you should need to withdraw money is a state or federal government issued photo-ID, like a drivers license or a military ID, same as you would need for any other bank withdrawal at a teller. Or, an ATM card & PIN if you wanted to use an ATM.

Savings Account


heat spread from hot coil: diffusion, radiation?

Question: When modeling the heat spread from a hot object through a vacuum (or a gas), what is the dominant physical process for heat energy transportation? Thermal diffusion, thermal radiation, a mix of the two, or something else? What properties of the object or the gas may influence this?
Answer: Radiation always occurs, and it is proportional to $T^4$, but it works both ways between itself and the environment. If it is not much hotter, in absolute temperature, than its environment, its heat transfer rate is roughly linear in the temperature difference.
The rate of radiative transfer also depends on the character of the radiating surface.
For example, if it is shiny, it will reduce the rate of heat transfer.
Then if there's gas around, heat can also be transferred to the gas, by conduction.
Again it is roughly proportional to temperature difference.
If gravity is also present, then the gas may undergo convection, which enhances the conduction by carrying hot gas away, to be replaced by cooler gas.


What is the difference between accent and sforzando?

Question: In particular, on cello. I got the impression that both are strong (either by pressure or speed) at the beginning of the note, followed by quick release of pressure/speed. What is the difference between the two?
Comment: Not necessarily - some sfz can be interpreted as "hit it strong and stay strong"
Answer: I assume you mean the difference between ^ and >. Both signs are used as accents in generally. The correct designations are marcato (>) and martellato (^).
Usually marcato means accentuated and martellato means strong accentuated. So you see that there is only a small difference. And it is often discussed how exactly these two accents are played differently and in particular with a certain instrument (like in your case a cello).
However sforzato and/or sforzando (sf and sfz) are dynamics. They are dynamics and mean with sudden emphasis in the sense of sudden change of the volume.
So summarizing: accents like ^ and > are similar to dynamic instructions like sforzando and sforzato, but they are not the same.
Answer: A sforzando(sfz) is the loudest and strongest accent. It is not really considered a dynamic as another answer suggests.


End of lease period, landlord hasn't provided way to renew lease

Question: My lease is up in about 45 days. My landlord hasn't provided any way for me to renew the lease. They do online lease signing. I've been unable to login for over a month now. They can't figure out what the problem is. I've decided I want out at the end of my lease period, but the lease says i need to give 60 days notice. Is the landlord's failure to fix the renewal signing problem sufficient for me to claim they are in breach of contract and allow me out at the end of the lease, without the full 60 says notice? According to them, the renewal was supposed to be signed by now already. But I couldn't due to their failure to fix the problem that kept me from signing in.
Answer: In general, a lease is not a permanent obligation: it has a specific term, and when the lease has expired, neither party has an obligation to continue (allowing to continue to) reside at the place. The lease may be renewed, and there may even be an automatic renewal clause in the lease. Texas Property Code Ch. 92.021(b) says that:

(b)  A person may specify in writing in an original lease that the
  person will guarantee a renewal of the lease only if the original
  lease states:
(1)  the last date, as specified by the guarantor, on which the
  renewal of the lease will renew the obligation of the guarantor;
(2)  that the guarantor is liable under a renewal of the lease that
  occurs on or before that date; and
(3)  that the guarantor is liable under a renewal of the lease only if
  the renewal:
(A)  involves the same parties as the original lease; and
(B)  does not increase the guarantor's potential financial obligation
  for rent that existed under the original lease.

If there is no automatic renewal clause, there is no 60 advance notice requirement – you're done at the end of the lease (there could be a 60 day advance notice clause in case of termination before the end of the lease -- look specifically for "60 days" in connection with automatic renewal). Assuming there is such a clause in your lease, which says the things that it is supposed to say by law (last date for renewing, recognition of liability and the same-price, same-parties condition), then there should be some wording about giving notice of non-renewal, but it may be subtle (such as "renews automatically 60 days before the end of the term, if notice is not given").
Assuming the lease has a 60 day auto-renew clause (and not 30 day), you need to give notice within 60 days. There is a convenient legalese form that you can mail by certified mail. Your situation is more complex because you have (apparently) made an attempt to give notice within the 60 day period (right?) but their website was broken. You cannot be required to use their website to give non-renewal notice, and as a general rule legal notifications should be done by certified mail. If they claim that you must use their non-functional website to override automatic renewal, that is just wrong (they cannot make it impossible for you to exercise your right to terminate), but you do have to give notice by the date specified in the lease. However, you also cannot use the fact of their website being broken as an excuse for not giving written notice by the deadline.
Answer: Most likely,Yes; you can now give the minimum notice required by your jurisdictions' law. Once a lease ends without the re-signing of a new lease, ornament addendum continuing the current one, you are no longer required to be bound by the terms of the lease, but rather are now a tenant at will. You have to give as much notice as your state, town or municipality requires you give, just as any month-to-month tenant without a lease would be required. Essentially, you will be treated as if the lease never existed and you were allowed to move in without a lease, with all state laws applying as they relate to this and any other landlord tenant matters. If you would like more information at tenancy at will, I have posted  fairly broad response on this topic in the past. Typically, if you make your rent payment monthly, that would be the amount of time by which you would be required to give notice. This does not mean you can give notice on the first of the month, as  day notice is given/received is not included in the typical 30 day notice requirement-,
Rather o'clock would start the following day. If The first of each month is the date you pay rent, this means you must give notice prior to that date i.e. the day before or sooner. It should be written notice.  If you pay rent every 60 days, however,  the law will typically look to this as the period by which you are bound to give notice, If you live in a state that observes the "periodic" rule for at will tenants. Since most people pay rent monthly, this is likely not a niche you, but I mention it since you have a rather uncommon 60 day notice requirement… In the event that you do pay rent every two months this may be the minimum available to you specifically. That said, you can give your landlord notice at any time that you intend to pay rent monthly, and then sometime before the first of the month give notice. You can easily find this information by doing just a general Google search for "notice requirements regarding at-will tenancy" in your state. In the alternative, you can list where you live and that question can be answered herein. For the sake of this answer, I am assuming that you would have included in your question the pertinent information had there been a clause in your lease stating that the lease would automatically renew if 60 days notice were not given prior to the ending of the term of the lease. However, if that is the case, few states allow for automatic renewal of residential leases, while most don't. That does not mean landlords' do not have these clauses in their lease even though they may be unenforceable in your specific jurisdiction. That is why jurisdiction is often so important when individuals ask questions. That said, it may not be an intentional violation of the statute ifthere is an auto renewal clause and that is unenforceable in your jurisdiction, but rather merely a result of people buying these types of documents in stores or online rather than paying attorney to draft a document specifically for their circumstances. Form leases are not jurisdictionally specific often times, when this occurs. Feel free to ping me if you have any questions.


Can the back tail of an airplane move the neutral point backwards?

Question: I'm currently in the process of designing a prototype aircraft and since I don't have very much experience with this I have the following question: I know that the center of gravity of an airplane should be located in front of the neutral point (aerodynamic center) so it is self stabilizing. The problem with my design is that the main wings have to be in front of the center of gravity. To counteract that, can I design the back wings in a way so that the neutral point is moved behind the CoG?
Answer: Yes you can, the tail volume needs to be such that the neutral point shifts aft of the CoG. This answer has some details - positive lift from the tailplane, but it must never stall!
More details about tailplane design in the answers to this question. The absolute safest config at a wide range of CoG is the CoG in front of the Centre of Pressure of the main wing, and a downforce from the horizontal tail.
Answer: There are three approaches to this need.  First, you could build what amounts to a tandem wing.  If you check the CoG location for a Rutan Quickie or its many derivatives, I'm pretty sure you'll find it's between the front (lower) and rear (upper) wings.  Likewise, a Flying Flea (aka Pou de Ciel) has the CoG much further aft, relative to the forward/upper wing, than could be the case with a conventional layout.
The other is to build a "lifting tail" proportioned like some of the contest models of the 1940s to 1960s (and a few, like hand-launch gliders, even to the present day).  These have very little decalage, often zero, sometimes even negative -- but by airfoil choice, the designer ensured that the forward surface always flew at a higher coefficient of lift than the rear, so that any increase in speed resulted in a nose-up moment.  These designs are characterized by CoG locations near or even slightly behind the trailing edge of the wing.
The final, and most modern approach, is active control.  A number of modern high performance aircraft (warplanes, generally) are aerodynamically unstable, to the point where a human pilot cannot maintain control if the computer management fails.  They depend on a computer stability system (generally combined with fly-by-wire) to manage the surfaces to simulate static stability, while keeping the ability to respond to control inputs at rates that would be impossible with a conventionally stable aircraft.


Custom Field Groups with File fields cannot be edited as a Tab

Question: I have a site with several custom field sets that use the "Tab" style for displaying information about a contact. Included in one field set is a "File" field that is used to store a profile image for the contact.
After upgrading to 4.7.0, attempting to view this tab for a contact with a profile image results in an error message that says the value (the filename of the image) is not an Integer. For contacts that don't have an image, the tab is shown, but the file cannot be changed. The edit popover closes when I click "Save" but the file is not updated.
I replicated this issue using the CiviCRM demo site. The steps to reproduce are:

Go to Administer > Custom Data and Screens > Custom Fields in CiviCRM
Create a new set of Custom Fields or edit an existing one to use the style "Tab" and apply to Contacts (I used "Individual")
Place as many fields as you want in the Custom Field Set, including at least one File field
Find a Contact
Open the Tab of the Custom Field Set you created
Click the "Edit ..." button to change the values
Make changes to any (or several) field and click "Save"
You will be taken back to the Contact but your changes will not appear

Update Feb. 8 -
I applied the diff from CRM-17949 and while it does allow changing other fields in a Tab, images still cannot be changed. Also, the error message on existing images still appears. I attempted to replicate this on the demo site, which is currently running CiviCRM 4.7.2, but it appears to have file system permission issues that prevent uploading files.

Update Feb. 10 -
Here is how to reproduce this issues in 4.7.2:

Follow steps 1 through 6 in the previous numbered list
Upload an file (I used an image) into the file field and click "Save"
You will be taken back to the contact but the file will not be saved
Return to the Custom Fields, and click "more" > "Settings"
Change the Display Type to Inline
Return to the contact and scroll down to the group. Click "Edit"
Choose a file for the file field, and click "Save"
The image will be shown in the group
Return to Custom Fields again, and change the Display Type back to Tab
Return to the same contact and click on the tab for your custom group
You will be shown a popover message "One of parameters (value: filename.jpg) is not of the type Integer" and the tab body will display "Sorry but we are not able to provide this at the moment."
Comment: Having the same issue with 4.7.4.
Answer: A work around is to create the record without the upload and then edit. The upload works fine after that.
4.7.13 and Drupal


Where are uploaded files stored?

Question: Very naive question here: when you upload to SharePoint, are the files stored in the file system or in SQL Server?
Answer: They are stored in the Content Database on SQL Server.  There are provisions to offload the files to the file system and third party tools to assist with it.
Answer: The files are (generally) stored in SQL server in databases called content databases together with all other content, such as list items and metadata.
Answer: Files that you upload within SharePoint to Document libraries are normally stored within SQL server.
However, if you're uploading files as part of a Feature that you are developing and installing, those files can be served from the filesystem OR from the database.

Where are uploaded files stored?


My tor hidden service stopped working

Question: I have successfully hosted my first .onion site on my Raspberry Pi by following this tutorial. For some reason I needed to stop running this site for a while. So I used this command sudo /etc/init.d/tor stop to temporarily close this site and then I used sudo /etc/init.d/tor startto start the website again. But it's not working and I'm not able to visit my .onion site again. I have tried restarting my Raspberry Pi and start again but still not working. I have also tried restarting lighttpd but still not working. I have also tried sudo /etc/init.d/tor restart but still not working.
And sudo /etc/init.d/tor status shows my hidden service is active. But I'm not able to visit it anymore.
● tor.service - Anonymizing overlay network for TCP (multi-instance-master)
   Loaded: loaded (/lib/systemd/system/tor.service; enabled; vendor preset: enabled)
   Active: active (exited) since Tue 2018-11-06 00:05:42 UTC; 14min ago
  Process: 328 ExecStart=/bin/true (code=exited, status=0/SUCCESS)
 Main PID: 328 (code=exited, status=0/SUCCESS)
      CPU: 0
   CGroup: /system.slice/tor.service

Nov 06 00:05:42 raspberrypi systemd[1]: Starting Anonymizing ove…..Nov 06 00:05:42 raspberrypi systemd[1]: Started Anonymizing over…).Hint: Some lines were ellipsized, use -l to show in full.

Comment: Did you checked your torrc? If it is OK, may be your tor service uses another torrc file. For this, start tor instance with -c for giving the right torrc and check if your hidden service is available?
Answer: Did you check your hostname file to ensure the location did not change? If the service is active, it does not sound like it is failing. That's why I'm suggesting that maybe there's an issue with how you're accessing it.

My tor hidden service stopped working


Python command to create no-arch rpm's

Question: I am creating rpm's for my project which is in pure python. I am running the command

python setup.py bdist_rpm

to build the rpm. This is creating architechture specific rpm's (x86 or x86-64). What I would like is to have a no-arch rpm. Can any of python guru's help me with creating a no-arch rpm. Any help would be appriciated. Thanks in advance
Answer: You can use the --force-arch parameter, i.e.:
python setup.py bdist_rpm --force-arch noarch

Python command to create no-arch rpm's


What is the biblical basis against polygamy in the New Covenant?

Question: Assuming the Old Covenant is obsolete and fulfilled (Heb 7:18-19), what is the biblical argument against allowing the practice of polygamy?
Comment: I don't really understand what you're asking. Why do we need to assume the old covenant has been fulfilled? If the other questions don't answer your question because they don't show that it's *immoral* then why are you now asking if there's a basis *for* it?
Comment: @curiousdannii Because if it hasn't been, there is a biblical basis, and because there are various places in the NT which state that it has been fulfilled.
Answer: God's Standard Should Be Our Standard
The biblical standard regarding marriage, from Genesis to Revelation is

One groom, one bride, what e'er betide.

Or in slightly less old fashioned verbiage:

One husband, one wife, for life.

God never sanctioned polygyny in the Tanakh, nor did Jesus sanction it in the New Covenant. God's design from the beginning was stated in Genesis 2:24-25 and reiterated by Jesus in Matthew 19:3-12 and Mark 10:2-12. I teased the following statements from Genesis, Matthew, and Mark:

Marriage between one woman and one man was instituted by God.

The man and woman who marry are fully equal in the eyes of God, but they are different in significant ways. There are obvious similarities and differences, but the differences, in particular, complement each other.

Marriage involves two families, but it is the basis of a third family in its own right. In other words, there is a leaving and a cleaving and a conceiving (though not always).

God joins together two people, one man and one woman, and the two--not three or four or more--become one flesh.

Jesus sanctioned divorce when adultery violates the oneness of the marital relationship, but by the same token Jesus did not command divorce when either husband and/or wife commits adultery. In other words, he held out for the possibility of confession, forgiveness, and restoration of the relationship. Serial monogamy is not the biblical ideal, though Jesus obviously sanctioned (but did not command) remarriage after the death of one's spouse.

Jesus' emphasis on Moses in his discussion with the Pharisees who came to Jesus to test him with their question is significant. According to Jesus, "Moses permitted divorce" because of the hardness of the Israelis' hearts, neither because God had made provision for it in his original plan nor because it was legislated in the Mosaic law.

Is There Any Wiggle Room?
No.

The levirate spoken of in Deuteronomy 25:5-10 (levirate comes from the Latin word for brother-in-law) may seem like an exception to the "one husband, one wife, for life" rule, but it is not. As Constable noted in his explanation of this passage in the NET Bible "Notes":

"The Israelites were to practice levirate marriage only in cases where the brothers had lived together (v. 5) and the remaining brother was not already married. Living together meant living in the same area, not necessarily residing under the same roof.[286] When another kinsman voluntarily assumed the responsibility of the surviving brother, that brother was apparently under no obligation to marry his sister-in-law (cf. Ruth 4). [my emphasis]
"There were several reasons for this provision. These reasons were the importance of descendants in God's purposes for Israel, the welfare of the widow, and the demonstration of love for one's brother (cf. Gen. 38).[287]"

Paul's insistence that a church elder or church deacon must be "the husband of but one
wife," or as some folks interpret it, "a one-woman man," cannot be an argument from silence that it's OK for men who do not aspire to be leaders in the local church to have multiple wives. Furthermore, the decision of the polygynous man either to keep or separate from a second or third, or more wives, would be up to the husband, his wives, and the leadership of the local church, with each case judged and ruled upon based on its merits on a case by case basis (see 1 Timothy 2:1 ff.).

A Legitimate Inference Based on Every Example of Polygyny in the Bible
I feel confident in presenting this challenge to any reader of my answer to cite a Scripture passage (not the LDS Scripture, however, as I am not a Mormon) or give me an instance in the Bible in which polygyny was not characterized by familial infighting, deceit, jealousy, strife, violence, resentment, long-standing feuds, favoritism, hurt feelings, spiritual backsliding, or any one of a host of other negative aspects and consequences. There is simply not one instance.
What can we legitimately infer from the overwhelming evidence of negative consequences based on the instances of polygyny in the Bible? The only reasonable answer, at least in my opinion, is that God does not approve of it, and to flaunt God's standards regarding marriage is to court disaster. You can count on it!
Comment: @bruisedreed: Thanks for the edit. I meant to say aspire, but I typed inspire. Sometimes my fingers and my brain are not in perfect synchronization! Don
Comment: What about the multitude of Prophets? Abraham, Solomon, etc.   Prophets are role models who lead people to the upright path.
Comment: @coolbreeze: Thanks for your comment. In a sense, the prophets were not a "special case" of folks whom God gave permission to be polygynous. They, as with virtually any other biblical character who was a true believer in YHWH, would suffer the consequences I refer to in my last two paragraphs. By the way, since when do leaders and role models always "lead people to the upright path"? Spiritual leaders can make unspiritual decisions and mistakes, and they, like us followers, suffer the consequences.
Answer: The closest that any of the NT books come to even mentioning polygamy are the pastoral epistles when Paul says that a leader must be the husband of one wife.

2 Timothy 3:1-2 ESV The saying is trustworthy: If anyone aspires to the office of overseer, he desires a noble task. Therefore an overseer must be above reproach, the husband of one wife, sober-minded, self-controlled, respectable, hospitable, able to teach

Note that Paul says this is the requirement to be an overseer. He's not necessarily condemning or condoning polygamy as a general practice.
Comment: so this is like the only biblical condemnation of polygamy
Answer: The answer is no, there is no Biblical basis in the New Testament for polygyny, or plural wives. But it is important to understand that while the old law has been fulfilled, it is only obsolete in that it has been superseded by a new law. The old law is of a lesser priesthood, and the new is of a higher priesthood.

"For the priesthood being changed, there is made of necessity a change
  also of the law." (Hebrews 7:12)

The lesser–Levitical, or Aaronic Priesthood is an appendage of the greater, or Melchizedek Priesthood. We live the higher law under the administration of the Melchizedek Priesthood, but the duties of the Aaronic Priesthood are not done away with.

From an LDS perspective, it is lawful for a man to have only one wife, unless the Lord commands otherwise by revelation.

"Wherefore, my brethren, hear me, and hearken to the word of the Lord:
  For there shall not any man among you have save it be one wife; and
  concubines he shall have none; For I, the Lord God, delight in the
  chastity of women. And whoredoms are an abomination before me; thus
  saith the Lord of Hosts. Wherefore, this people shall keep my
  commandments, saith the Lord of Hosts, or cursed be the land for their
  sakes. For if I will, saith the Lord of Hosts, raise up seed unto me,
  I will command my people; otherwise they shall hearken unto these
  things." (Jacob 2:27–30).

By revelation, plural marriage was practiced in Old Testament times and in the early days of the restored Church by the direction of the prophet who held the priesthood keys (D&C 132:34–40, 45). It is no longer practiced in the Church (D&C OD—1); today, having more than one wife is incompatible with membership in The Church of Jesus Christ of Latter-day Saints.
The only time polygamy, or more specifically polygyny is allowed, is when the Lord commands it. The law of Moses is an example of when the Lord commanded it. Christ fulfilled the law of Moses, but did not make every ordinance belonging to the priesthood obsolete. There will be a time when all the ordinances of the priesthood, like sacrifice, and possibly plural marriage, will be restored:

"These sacrifices, as well as every ordinance belonging to the
  Priesthood, will, when the Temple of the Lord shall be built, and the
  sons of Levi be purified, be fully restored and attended to in all
  their powers, ramifications, and blessings. This ever did and ever
  will exist when the powers of the Melchizedek Priesthood are
  sufficiently manifest; else how can the restitution of all things
  spoken of by the Holy Prophets be brought to pass. It is not to be
  understood that the law of Moses will be established again with all
  its rites and variety of ceremonies; this has never been spoken of by
  the prophets; but those things which existed prior to Moses' day,
  namely, sacrifice, will be continued." (Teachings, pp. 172–73.)
Comment: I think that calling them virgins is the equivalent of calling them maidens, essentially stating that they are unmarried women.
Comment: Thanks for the answer! I'm glad to hear from someone who believes polygamy is ok in some cases, as I know you've probably looked into it a lot more than someone who is against it. However, the Old Covenant is specifically referred to as obsolete in many translations in Hebrews 8:13 (ESV here) - "In speaking of a new covenant, he makes the first one obsolete. And what is becoming obsolete and growing old is ready to vanish away."
Comment: LDS read from the KJV. With re-translating the Bible comes the risk of losing plain and simple doctrines. Changing a word, even if is an accurate literal change, can also change the meaning or context of the verse from how it was meant to be delivered. In this case, while πεπαλαίωκεν can be translated, "he has made obsolete" the root παλαίω can be translated as "wrestle..." I'm no expert in Greek, but I assume there is a reason why the experts that translated the KJV, ASV, ERV, and many others that don't use the word "obsolete" translated πεπαλαίωκεν as "he hath made the first old."
Comment: That is simply a matter of interpretation on the part of the translators. The translators of the KJV also said that Jesus was in the fiery furnace in Babylon with the three people whose names I can't spell, while just about every other translation says otherwise.
Comment: Like I said, changing the translation changes the interpretation.
Comment: Does [the parable of the ten virgins](https://www.biblegateway.com/passage/?search=Matthew+25:1-11&version=KJV), where Jesus portrays himself as marrying ten women, have any bearing on the topic?
Comment: No, not at all. Where do you get that interpretation from? Christ told the parable of the 10 virgins as a [metaphor](https://www.lds.org/ensign/1995/01/the-marriage-metaphor?lang=eng) to testify of his great love for and patience with us. The ten virgins were *guests* at the wedding, *not* brides.
Comment: I don't recall where I saw it. Thanks for the link. If they were guests at the wedding, why is the fact they are virgins relevant?
Comment: http://hermeneutics.stackexchange.com/questions/406/are-the-ten-virgins-told-in-jesus-parable-multiple-brides-or-just-general-wed


Backward compatibility for plugins

Question: Are plugins normally backward comatible? I would like to buy a plugin ready for Mathematica 7 and use it on Mathematica 8.
Comment: It depends on the particular plugin. Check with the plugin's author or publisher.
Answer: I would say no. I know of one counter example: Link for Excel. When Mathematica 9 came out it wasn't compatible (see the comments below this question), but it has since been updated. If you want to be sure, contact the creators of the plugin (or package) before buying.

Backward compatibility for plugins


Phantom harmonics when using cosine windows why do they appear and how to avoid them?

Question: Given an $L$ order cosine window, it is possible to show that the width of the main lobe is given by:
$$\omega_w = \frac{2 \pi L}{(2N+1)}$$
Where $L$ is the order of the window, $N$ is the maximum harmonic in the signal and therefore $2N+1$ is the number of samples taken over a period. If we consider the relationship
$$\Omega = w T_s$$
then the width of the window in the frequency domain is given by
$$\Omega_w = \frac{2 \pi L}{(2N+1)T_s}=\frac{2 \pi L}{T_0}$$
Where $Ts$ is the sampling time and $T_0$ is the observation interval.
The last formula clearly shows that it is possible to reduce the width of the main lobe either by oversampling by an oversampling ratio of $L$ or by increasing the observation interval by a factor of $L$.
Let's assume the following:

Sampled signal is a pure sine wave with frequency $f = \frac{1}{T}$. Then $N=1$.
The signal is sampled according to the synchronous sampling condition ($(2N+1)T_s = T_0 = T$) so no leakage error occurs.
The Hanning window is used. The width of the main lobe should be $\Omega_w = \frac{4 \pi}{(2N+1)T_s}$ since $L = 2$.

Now, if we call $P(j\Omega)$ the spectrum of the sampled signal, $P(j\Omega) = W(j\Omega) \star S(j\Omega)$ where $W$ and $S$ are the Fourier transforms of the window and of the signal, respectively and $\star$ is the convolution operator.
What would $P(j\Omega)$ look like? In the book I use, it looks like this:

STATEMENT A:
In my understanding at least, only $c$ is real (only $c$ is a replica of the real spectrum of the signal) while $a$ and $b$ are a byproduct of the convolution with the window due to its main lobe's width. In general, the book says, it is possible to say that if we are using an $L$ order cosine window, $2L-2$ phantom (or fictitious if you will) components will appear.

STATEMENT B:
If we increase $T_0$ by $L$ then the width of the Hanning window becomes the same as the one of the rectangular window ($\Omega_w = \frac{2 \pi}{(2N+1)T_s}$), therefore the fictitious harmonic components should not appear. But isn't this the same as increasing the number of samples by a ratio $L$?

I would like to understand if the two above statements are correct, in particular if the origin of the fictitious harmonic components is indeed the convolution and how one can avoid these components.
The book that I mention is Digital Signal Processing for Measurement Systems by D'Antona and Ferrero.
Answer: The magnitude and number of the lobes/harmonics is beyond my knowledge but you always obtain them when you window a signal with a finite window. No matter what windows you choose.
With some windows like the cosine family ones you have an efficient way to compute the convolution in the frequency domain, but if you compute it in the time domain the result is the same.
Hope it helps a bit


Does Steam save on discs?

Question: I've been playing Skyrim via Steam Purchase, but I want to buy the whole Elder Scrolls Anthology for not only the Skyrim DLCs but for all the other games and their DLCs. Will the saves I have on the Steam version be there when I play Skyrim from the disk or will I have to start over?
Comment: Create Backup from Steam if you ever want to uninstall the game and it doesn't support Steam Cloud.
Answer: All content for Steam is saved either on your hard drive or in the Steam Cloud. Either way, your content will be available after the DLCs are bought.
If the Anthology is offered Via steam then there will be no issue.  As far as I know, Skyrim is steam only.
In the case that it isnt, you can always navigate to your savefile and copy it
Comment: Elder Scrolls Anthology comes with a Steam code that will unlock Morrowind GotY edition (all expansions), Oblivion GotY edition (all expansion/DLC), and Skyrim Legendary edition (all DLC) on your Steam account. Arena and Daggerfall are only available by installing from disc.
Comment: @JacobIngram You won't even need to put the disc in if it comes with a steam code. Just enter the code into Steam and the DLCs will start downloading for your existing install.
Comment: @KimMinseo That is not true
Comment: But will I need to do anything when I put in the Skyrim Disc with the DLCs on them or will I start over?
Comment: That is technically incorrect. Data is saved on the hard drive and, if enabled, is copied to your Steam Cloud after you close the game.
Comment: All games and game data in steam is saved in steam cloud. This is to ensure that for users who use multiple computers, they do not have any problem syncing games to each other.
Answer: Yes, you will keep your save. You just won't need the disk any more, so you can throw that away (not literally) and when it is downloaded you then just go to your games and start playing and start having fun with your game.
Answer: A general rule with all PC games -whether steam is involved or not- is that it will save to your Hard Disk (or a server if it's an always-online type)
If it's on your hard disk, there is normally a way to find your save file so you can copy it to a different location if another copy of the game would look in a different place. I have used this tactic for backing up saves as well as using the same save file on different physical PCs.
Steam has the steam cloud that supported games have their save files copied to so if you would change computers you keep your saves automatically.
In your case it's likely that if you buy the anthology through steam (or activate it on steam) it'll literally class it as Skyrim + DLC so you'll see no difference in your library or it'll overwrite your skyrim entry with the entry for the anthology. So your save files will likely not be affected in the slightest.
Answer:
You will probably need to copy your Skyrim Steam save files into the folder that your disk install of Skyrim uses to store its save files (a google search will find both of these directories easily). It may be that they both use the same directory by default (probably My Documents). If this is the case then you should only need to worry about the point below.
You should also ensure that your steam and disk version of the game are at the same version level (patches), not having these level can cause havoc with save files and can corrupt them.

Does Steam save on discs?


Would you rather Mix/Edit with decent headphones or cheap inexpensive monitors?

Question: I can't afford good monitors currently so I'm just curious.
Answer: Good headphones for sure over bad monitors.
When I worked on God of War 2, I hated the Genelec 1029's that Sony had set my room up with.  I tried to use them for over a year and just could not get used to them.  So, I gave up and designed most of God of War 2 using my Sennheiser HD600 headphones.
These days, it is the total opposite.  I am very happy with the sound of my room and my JBL LSR 6328/6312 system.  I never use headphones, unless I'm recording something.
Answer: speaker monitoring is as much about the room as it is about the speakers.  Cheap monitors can still give decent mixes in good sounding rooms, and excellent monitors will still lie to you in poorly treated rooms - especially in the low end.
headphones will lie to you with regards to relative balances and stereo fields - even good ones - because you're plugging speakers right into your ears.  Headphones also have wild swings in the midranges.  Check out the frequency plots of your prospective cans at this site:
alt text http://graphs.headphone.com/graphCompare.php?graphType=&graphID[]=4061&scale=30
My advice would be to settle on the cheap monitors, and spend a lot of sweat equity treating out your room to sound flat.  Compressed fiberglass and fabric can go a long way.  Later on you can upgrade your speakers.
Answer: Headphones for a short period of time, but you will find that your ears become much more fatigued with headphones as opposed to monitors.
Answer: Headphones are workable, if you "calibrate" yourself to how the stereo spectrum can be used (as in, how it needs to sound to sound somewhat correct and not "crooked" from a stereo speaker setup). Calibration can be simply done by listening to well-mixed material using the headphones and paying attention to the pannings and stereo image. The biggest difficulties are extreme pans, i.e. finding out how far is too far, and how all sorts of phase differences and the use of stereo expanders will be exaggerated (to the point of sounding "crooked") in speakers.
In frequency response headphones usually beat monitors in an uncalibrated (i.e. acoustically uncorrected) environment.
Answer: Watch out for the base! I've heard so many mixes done with headphones where the panning is quite good but the sub is working like non stop. I use headphones at home and the studio for the final mix.
Comment: Sennheiser DT 770 have a good respond in the lows. Of you Check These and the frequency analyzer you get solid mixdowns with headphones imo!


IPFIX - consider only first n seconds of a flow

Question: Is possible to consider via IPFIX only the first n seconds of a flow (statistics)? How to set this in OpenVSwitch if possible?
Comment: Why do you want to do this?  It doesn't really make sense to me.
Comment: You can adjust the sample rate, and you can ignore anything beyond the time period you don't want., but I don't think you are going to get every packet in a flow for a given time period. That isn't how it is built.
Comment: IPFIX aggregates statistics from sampling flows, it doesn't actually send a flow.
Comment: Maybe I expressed myself badly. I want consider only the first n seconds (at the most) of a flow for the calculation of statistics. Always if possible.
Comment: Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide your own answer and accept it.
Answer: So you need to understand how a given switching device defines a flow.  There's the obvious identifying stuff - the tuple of source and destination port/address, IP protocol number, etc.  There's also clearly a beginning time and, of course, an end time.
The beginning is pretty straightforward.  It's the first point at which the identifying tuple is observed.  The ending, however, is a lot trickier.  In the case of a TCP session seeing a FIN sequence might trigger a stop time but generally the flow end-time is going to be caused by either a timeout (i.e. a UDP session where a packet hasn't been seen in n seconds) or - much more likely in practice - the flow cache filled up and space is made for new flows by triggering the purge and export of older ones.
The thing is that the flow (as we've defined it) might not actually be over.  Indeed, a long-lived flow might actually be represented by many consecutive flow records.  It's the job of the analysis tool to tie all of these individual records together into some kind of sane whole.
It's for this reason that your question doesn't really make sense.  The actual flow collector/exporter likely has no idea whether the flow cache entry it's working from represents the beginning or end of the actual flow on the wire.  One of the nasty truths about flow-based collection mechanisms is that the relatively limited size of the cache means that a suitably large variation in identifying tuples on the wire can lead to a degenerate case where a flow record only sees a few packets before being pushed out.  This is why the use of these kinds of analytics on large-scale Internet core boxes tends to be pretty limited and in the places where flow-based measurement is occurring (aggregation/edge platforms) that it's almost exclusively sampled.
So - if you want to only look at the first few seconds of a flow then set the aging time on the collection device to be very short.  This will result in lots of flow records being exported (and lots more resources consumed) but will give you data on a very short interval.  In turn, at the point of analysis you can choose to ignore all but the first record generated.  I don't see the win to such an approach, but it at least nominally fits what you're asking for.


Open Measurable Sets Containing All Rational Numbers

Question: So I am trying to figure out a proof for the following statement, but I'm not really sure how to go about it.  The statement is: "Show that for every $\epsilon>0$, there exists an open set G in $\mathbb{R}$ which contains all of the rational numbers but $m(G)<\epsilon$."  How can it be true that the open set G contains all of the rational numbers but has an arbitrarily small measure?
Comment: See [this answer](http://math.stackexchange.com/a/195319/12042) to a related earlier question.
Answer: To elaborate on other answers, let $\{r_n\}_{n \in \mathbb{N}}$ be an enumeration of all rational numbers. This is possible because $\mathbb{Q}$ is countable. For each number $r_n$, pick the open interval $(r_n - 2^{-n-1} \epsilon, r_n + 2^{-n-1} \epsilon)$. Each open interval is an open set. The union of all such intervals is also open. The measure of each interval is its length $2^{-n} \epsilon$. If $G$ is the union of these intervals, we have:
$$
m(G) \le \sum_{n=1}^{\infty} 2^{-n} \epsilon = \epsilon
$$
Where the sum above is a geometric series.
Answer: The rationals are denumerable.  Enumerate them and then choose an interval of length less than $\epsilon/2^n$ for $n\ge 1$.  Let $G$ be the union of these intervals. It has measure less than $\epsilon$ and contains all rationals.
Comment: You can do this for any countable set.
Answer: Hint:  if you order the rationals, you can put an interval around each successive one and take the union for your set.  If the intervals decrease in length quickly enough....


Cleaning a Talis together with silver Atora

Question: Can I wash my heavy wool talis together with the silver Atora,what happens if I won't remove the Atora? I will appreciate if anyone can assist me,thank you!
Comment: Are you asking whether this is permissible according to Jewish law, or are you asking if this is advisable from a laundering perspective?
Answer: I don't know where you live. In Brooklyn, Lakewood and other areas where there is a large Jewish population, the dry cleaners will take off the Atara, clean the Talis, reconnect the Atara and your Talis and Atara will look sparkling clean.
I do not think it is a good idea to put an Atara in the washing machine.
You can also contact Mefoar Judaica and they offer cleaning and shipping for an Atara.
Answer:
If you are willing to go the dry cleaning route where they remove
the atarah and reattach it, that's the best way to go but it will cost.

If you are on a low budget, check the two answers how to wash it by
hand but keep in mind that you will need to be prepared to
properly iron it as otherwise it might look like "you slept  in it"
sort of look. This is not as easy as it sounds as wool is sometimes
hard to iron because it can be easy to make creases in the wrong
places. Also, it's very big and hard to manage on a typical ironing
board.

If you want to use a washing machine, put it in a pillowcase or some
protective washable material, use a wool cycle which is usually very
gentile and uses a lot of water and little agitation (vs. a regular
cycle) and take it out of the machine after a couple of revolutions
in the spin/rinse cycle so most of the water is extracted but the
atarah is not abused. Be prepared to be near the washing machine
to be able to to this at the right time.


Different siddur?

Question: I tried to follow a service with my orthodox Portuguese siddur at a conservative congregation service and I couldn't. What is the difference between a conservative and an orthodox Sidur?
Comment: Almost any two different Siddur editions will have some differences between them.
Comment: Do not forget that Portuguese (or even Sefard) siddurim will differ from the regular Ashkenaz siddurim. I think that Conservative was invented to move toward the Ashkenaz customs and they would have been changing from that. Thus they will have both sets of differences.
Comment: [Related](https://judaism.stackexchange.com/q/35650/472) (ma'ariv only and both siddurim involved are Ashkenazi nusach).
Comment: On a different topic altogether, Rav Moshe forbid one to daven in a Conservative synagogue. (Igros Moshe, EH 2:17)
Answer: You mentioned that you prayed from an Orthodox Portuguese siddur. I am not an expert in the customs of Portugal, but I'm going to assume your siddur was in some form of Nusach Sepharad. (And possibly is a De Sola Pool siddur?)
If that is the case, then you might have difficulty following the service even within an Orthodox congregation, if the prayers there were Nusach Ashkenaz! (And many Orthodox congregations in America do indeed use Nusach Asheknaz.)
I do not have room text box (or time in general) to outline all the differences between Nusach Sepharad and Ashkenaz, but some differences include the orders of the morning blessings, textual differences throughout the prayers, etc. Additionally, there are differences between different siddurim all claiming to be of the Sepharadi nusach! Different Sephardic communities across the globe had different traditions regarding the prayers, so the Portuguese nusach might be different from the Syrian or Moroccan nusach.
As for the Conservative siddur, the Conservative nusach is entirely Ashkenazi in nature, although you can see the differences between an Orthodox siddur and Conservative siddur here.
And, if you are unfamiliar with the word "nusach", or what I mean when I say Nusach Sepharad, Ashkenaz, etc., then please see here.
Comment: Good summary. To OP, keep in mind that every shul has its own customs. This is across all denominations. Some prayers are movable even if they may be listed in a certain order in the siddur. *Anim Zemirot* - "Hymn of Glory" commonly said on Shabbat, is a typical example of something said in various positions in the prayer depending on cong. custom. Also, some prayers may be skipped. So, these factors could also add to the confusion even if you use the shul's siddur, but are unfamiliar with their customs. Just know that you needn't be shy and ask your neighbor to help you.
Comment: @DanF Thanks. It's very hard to summarize something so complicated into a clear answer.

Different siddur?


How did the British and French train their troops during the colonial eras?

Question: From what I saw in movies, during many battles throughout the 1700s to early 1800s involving the French or British armies, rows of troops from both sides would fire volleys of bullets into each other and many soldiers would get hit and fall, but the rest of the soldiers would hold their ground or advance without flinching, and I was wondering how were these soldiers trained to be so disciplined and why would anyone sign up for war, as they would likely die.
Comment: Most deaths were from disease, not battle.  For example, see http://necrometrics.com/wars19c.htm
Comment: There are two questions here that should be treated separately. 1) How were troops trained? and 2) why would men sign up?  If you are interested in the second, I'd remove the emotional language.  Young men sign up for war for a variety of reasons - deceitful manipulation by recruiters, patriotism, uniforms, regular pay, the chance for plunder, the chance for adventure, and the chance for something other than the prospect of ceaseless, familiar and soul numbing labor.
Answer: as all battles in the period were decided by one side giving way and giving up the fight by running or fleeing, the men were not robots and morale was a very important factor and it soldiers failing to be steady and press forward or whole ground was a regular occurrence
casualties in battle were often not particularly huge, the volleys often rapidly obscured vision, (musket gunpowder produced lot of smoke) the hit rate with muskets was ridiculously low in general, whole range of factors, such levelling not readily understood by many. these were confusing battlefields, noise and smoke.
the superior morale in the ability of the troops to remain steady under fire was a crucial factor. the principal factor in troop quality rather than the skills in shooting and fighting.
the British did not use conscription, and generally their troops were better paid. However the enlistments tended be those with few other choices. the Scots, Irish and kings German subjects were often very large parts of the British army.
"For much of the 18th century, the army was recruited in a wide variety of places, and many of its recruits were mercenaries from continental Europe, including Danes, Hessians and Hanoverians.[3] These mercenaries were hired out by other rulers on contracted terms. Other regiments were formed of volunteers such as French Huguenots. By 1709, during the War of the Spanish Succession, the British Army totalled 150,000 men, of whom 81,000 were foreign mercenaries"
https://en.wikipedia.org/wiki/Recruitment_in_the_British_Army#18th_and_19th_centuries
pre revolutionary France from what I can research did not use conscription either (for regular units in peace time) but when short or wartime unofficial impressment rather than conscription was used.
http://www.napolun.com/mirror/web2.airmail.net/napoleon/FRENCH_ARMY.htm
"The French royal army of the 17th and 18th centuries had consisted primarily of long-service regulars together with a number of regiments recruited from foreign mercenaries. Limited conscription for local militia units was widely resented and only enforced in times of emergency."
https://en.wikipedia.org/wiki/Conscription_in_France
Comment: This reminds me of a point about bayonets I should try to track down - some theories are that bayonet charges saved a lot of lives because the fear of them caused men to flee while they would otherwise be more willing to trade shots back and forth.
Answer: In typical European armies, troops were trained on a conscription basis.  The training is a mix of the general background of the soldiers and what was expected of them in a battle.  However, there were also volunteer armies and large-scale mercenaries, but mostly we're talking conscription.
In a European conscription army, men would be called or pressed into service largely at random, willingly or unwillingly, and particularly from the lower classes.  For an unpopular war or service (like a navy), conscription gangs that would grab whomever they could.  A popular war may see a lot of volunteers, though.  Those from the upper classes/nobility would usually have an out or buy a commission and be an officer.
Because it was conscription and because there was usually war already at hand, training would be short and simple.  Everyone walk together, move at the same time, fire at the same time, etc.  In 17th and 18th century war theory, a massed group was viewed as the most effective presentation of force and fire, because most battle was with edged weapons.  Muskets existed but were overrated, as mentioned in other posts.  The bayonet was seen as the ultimate "battlefield sweeper," and only a massed group can do it with the required effect.  It wasn't until the American Civil War that the bayonet charge was shown to be very risky to the charger, and in WWI it was suicidal.
Military training seeks to create a desired response in the soldier when exposed to combat.  Even today military training seems harsh and simplistic and repetitive and it is (and I've been through it in my service), it is on purpose because those actions need to become the soldier's automatic behavior when really bad stuff starts to happen around him.  In the age we're talking about, the soldier needed to stay in line and do what the officer told them.  The officer often felt free to shoot/stab soldiers who didn't do the right thing because they needed to assert their authority over the situation to overcome the battle.
It is CRITICAL in battle (then and now) that everyone does what they are supposed to do.  If someone doesn't, then things start to fall apart.  Because lives and nations are on the line, you get draconian rules to ensure everyone does what they are supposed to do.
So, if you are standing in a regimental line with bayonet attached, you were probably pressed into service, had a brief military course and are doing what everyone else is doing because the officer behind you is calling the shots and will shoot you too if you don't behave.  Also, the 17th and 18th century army is likely operating without much support so you are probably very hungry, cold and getting sick.  You'll ravage local farms as you march by for food and warmth.  In those times, when an army came through your village – even your own army – you'd probably lose your food and some possessions.
As mentioned in other posts, the kill rate in 17th and 18th century fighting wasn't as bad as Hollywood makes it to be.  Disease was a worse killer than bullets or edged weapons.  Morale and not breaking and running was a very important part of the formula, as mentioned by @pugsville.  When the shrapnel and bullet kill rate eclipsed that of edged weapons and disease, things began to change into modern warfare.
Comment: big period but mass armies only really start with the french revolutionary wars, before that armies were much smaller more professional with generally longer training periods , also foraging was not overly used but armies were generally well supplied and moved with supply train depots, well defined camps.
Comment: This is correct. The "Napoleonic Square" was and still is a devastating tactic against an inferior military society. The advantage of disciplined musketry work against socities used to simple frontal assaults was truly devastating...so colonial Armies were trained first to recconoiter a suitable place for an Army to encamp (drinking water, provisioning, bivouacing, reinforcing, maintaining lines of retreat) in order to test for suitability for colonizing and or building small towns, communities, even Cities.
Answer: Most jobs in those days, farm and factory work, was nearly as dangerous as the military.In the military, young men at least got a uniform, more or less enough to eat, and a place to sleep, which was more than many migrant farm or factory workers could count on. And a few were attracted by opportunities for travel and adventure and plunder.
Battles were bloody when fought, but fortunately few and far between. As to training, it helped that most men of the time (other than officers) were illiterate, and could be drilled relentlessly to march and shoot without thinking, and be "numb" to the death around them.
Comment: Your wording implies that illiterate men were easier to drill and would effectively fight as automatons What's your evidence for that, given that illiterate is not a synonym for unintelligent?
Comment: Three meal a day - only *les Grognards* got served three meals a day, and then only when in Paris. Typical rations was a small loaf of bread and a hunk of cheese daily - forage for everything else. A few days supply of hard-tack was issued at the beginning of a campaign  as an emergency ration, in case the bakers fell behind the army.
Comment: pre the revolutionary and napoleonic wars, forging was only used sparingly , armies moved with supply trains, depots, tents, formed camps,and much smaller armies. what happened later 1790s on was not standard before
Comment: @SteveBird: "Illiterate" meant not being able to read works of contemporary authors like Montesquieu's "Rights of Man," or Thomas Paine's "Common Sense" that encouraged people not to be automations. And if a man was illiterate but "intelligent," he probably wouldn't be in the army..Certainly, the drillmasters of their time found that their men could be trained as automatons.
Comment: @PieterGeerkens: I changed "three meals a day" to "more or less enough to eat." Would you agree with me that soldiers had a lower chance of starving to death  than itinerant farm workers or artisans, to offset their higher chances of getting killed "on the job.?"


what is difference between stock and dividend?

Question: What is the difference between stock and dividend,bonds. And how can i buy stocks and what is the place to buy them can anyone please tell me iam new to this world of finance and stock market.
Answer: From Wikipedia - Stock:

The stock (also capital stock) of a corporation constitutes the equity
  stake of its owners. It represents the residual assets of the company
  that would be due to stockholders after discharge of all senior claims
  such as secured and unsecured debt. Stockholders' equity cannot be
  withdrawn from the company in a way that is intended to be detrimental
  to the company's creditors

Wikipedia - Dividend:

A dividend is a payment made by a corporation to its shareholders,
  usually as a distribution of profits. When a corporation earns a
  profit or surplus, it can re-invest it in the business (called
  retained earnings), and pay a fraction of this reinvestment as a
  dividend to shareholders. Distribution to shareholders can be in cash
  (usually a deposit into a bank account) or, if the corporation has a
  dividend reinvestment plan, the amount can be paid by the issue of
  further shares or share repurchase.

Wikipedia - Bond:

In finance, a bond is an instrument of indebtedness of the bond issuer
  to the holders. It is a debt security, under which the issuer owes the
  holders a debt and, depending on the terms of the bond, is obliged to
  pay them interest (the coupon) and/or to repay the principal at a
  later date, termed the maturity date. Interest is usually payable
  at fixed intervals (semiannual, annual, sometimes monthly). Very often
  the bond is negotiable, i.e. the ownership of the instrument can be
  transferred in the secondary market. This means that once the transfer
  agents at the bank medallion stamp the bond, it is highly liquid on
  the second market.

Thus, stock is about ownership in the company, dividends are the payments those owners receive, which may be additional shares or cash usually, and bonds are about lending money. Stocks are usually bought through brokers on various stock exchanges generally. An exception can be made under "Employee Stock Purchase Plans" and other special cases where an employee may be given stock or options that allow the purchase of shares in the company through various plans. This would apply for Canada and the US where I have experience just as a parting note.
This is without getting into Convertible Bond that also exists:

In finance, a convertible bond or convertible note or convertible debt
  (or a convertible debenture if it has a maturity of greater than 10
  years) is a type of bond that the holder can convert into a specified
  number of shares of common stock in the issuing company or cash of
  equal value. It is a hybrid security with debt- and equity-like
  features.  It originated in the mid-19th century, and was used by
  early speculators such as Jacob Little and Daniel Drew to counter
  market cornering. Convertible bonds are most often issued by
  companies with a low credit rating and high growth potential.
Comment: Thank u so much for ur valuable information, can i know the place where we can buy the stocks and bonds.I dont know the actual place where it happens and i dont know what is the process  to hold and sell the stocks.
Answer: stocks represent ownership in a company. their price can go up or down depending on how much profit the company makes (or is expected to make).  stocks owners are sometimes paid money by the company if the company has extra cash.  these payments are called dividends.
bonds represent a debt that a company owes.  when you buy a bond, then the company owes that debt to you.  typically, the company will pay a small amount of money on a regular basis to the bond owner, then a large lump some at some point in the future. assuming the company does not file bankrupcy, and you keep the bond until it becomes worthless, then you know exactly how much money you will get from buying a bond.
because bonds have a fixed payout (assuming no bankrupcy), they tend to have lower average returns.  on the other hand, while stocks have a higher average return, some stocks never return any money.
in the usa, stocks and bonds can be purchased through a brokerage account. examples are etrade, tradeking, or robinhood.com.
before purchasing stocks or bonds, you should probably learn a great deal more about other investment concepts such as: diversification, volatility, interest rates, inflation risk, capital gains taxes, (in the usa: ira's, 401k's, the mortgage interest deduction).  at the very least, you will need to decide if you want to buy stocks inside an ira or in a regular brokerage account. you will also probably want to buy a low-expense ration etf (e.g. an index fund etf) unless you feel confident in some other choice.
Answer: Stock basically implies your ownership in the company. If you own 1% ownership in a company, the value of your stake becomes equal to 1% of the valuation of the entire company.
Dividends are basically disbursal of company's profits to its shareholders. By holding stocks of a company, you become eligible to receiving dividends proportional to your ownership in the company. Dividends though are not guaranteed, as the company may incur losses or the management may decide to use the cash for future growth instead of disbursing it to the shareholders.
For example, let's say a company called ABC Inc, is listed on NYSE and has a total of 1 million shares issued. Let's say if you purchase 100 stocks of ABC, your ownership in ABC will become
Ownership = Shares Owned/Shares Issued = 100/1000000 = 0.01%

Let's say that the share price at the time of purchase was $10 each.
Total Investment = Stock Price * Number of Stocks Purchased = $10 * 100 = $1,000
Now, let's say that the company declares a dividend of $1 per share. Then,
Dividend Yield = Dividend/Stock Price = $1/$10 = 10%
If one has to draw analogy with other banking products, one can think of stock and dividend as Fixed Deposits (analogous to stock) and the interest earned on the Fixed Deposit (analogous to dividend).


How are forward and aft CG limits calculated?

Question: I have been tasked to create a POH for my aero engineering coursework and part of this task is to create the CG envelope for the theoretical 65 passenger aircraft. I have figured out weight, moment and cg for all loading scenarios but I am wondering how to create the actual envelope using forward and aft limits, as surely not all these scenarios will be able to fly? TIA
Comment: Aft CG is primarily stability margin (say, 10%). For forward CG, you can use the ability to rotate at V_rotate as a good approximation.
Answer: You have done half of the way. Since you have computed the CG variations in all loading scenario, you know approximate limits. This limits are the ideal limit from loading and unloading point-of-view. But in real application, the design of the aircraft does not allow such broad limits.
There are many factors that limits the aircraft aft CG movement:

MLG load: The loads on MLG increases as the aircraft weight is increased or the CG is moved aft. Since in most of cases, the MLG's are designed for touch down loads at maximum landing weight, which is lower that the maximum ramp/take-off weight, the static loads at maximum ramp weight may exceed the dynamics load at touch down. So, a limitation may be imposed on aft CG location regarding this issue.
Take-off Tip-Up: At the take-off conditions, the engines are producing their maximum thrust. If the engines are located below the CG, which is the case for under-wing mounted engines, this thrust produces pitch-up moment. This pitch-up moment reduces the load on the NLG. From the other hand, as the aircraft weight decreases combined with aft cg movements, the load on the NLG will be further decreased. At light enough NLG loads, steering effectiveness is reduced, and eventually, the NLG load can become negative causing the airplane to tip up. So an aft CG limits may be imposed to maintain enough loads on the NLG.
Static Stability: Too far aft CG may cause neutral or negative stability, so a margin (normally 10% of MAC) should be provided between the CG and the aerodynamic center.
Go-Around: At go-around condition, the engines are producing the maximum thrust, and a huge pitch-up moment. Elevator deflection are required to counter this moment with pitch down moment. This moment is proportional to amount of upward acting load on the tail a the arm of this acting load. The distance between the tail and the CG is the arm. As the cg moves aft, if the tail reaches its maximum lift the aircraft can not maintain its path. So a limit may be imposed to prevent pitch-up at go-around.

By combining the above limits, and other limits that may arise from that specific configuration, an aft CG limit can be estimated.
Comment: Of these, (3) is by far the most important and should be #1. Other things _sometimes_ may be a factor that imposes further limit, but static stability always applies. Sometimes, the aft limit is imposed by things like spin recovery, but it's broadly the same category. (4) is not practically an issue: the arm change is not very significant (esp. for aircraft with underwing engines), while reduction of the aerodynamic moment due to relaxed stability is. It is the _forward_ limit (which you didn't cover) that is largely determined by _controlability_ (i.e. available elevator control).
Comment: Another is the ability to stall the aircraft (forward CG limit). Stick force during go-around could also limit the forward CG is the engines are tail mounted.
Answer: For conceptual design, the longitudinal CG limits can be evaluated with:

Static Margin: you probably want at least 10% static margin at aft CG at the early conceptual stage for at least the flaps in configuration.
Trimmability: the amount of elevators or stabilizer (if movable) required to trim both full power and power off, for all flaps. For tail mounted engines, full power may limit the forward CG; for wing mounted engines, full power may limit the aft CG.
Takeoff Rotation: ensure your aircraft can rotate at $V_R-10kt$ or $V_R-7\%$ at takeoff flap at forward CG. This assumes the landing gears are positioned to give adequate tip-over margin.

Once you are in the preliminary design, then you have lots more things to look at.


Zend Studio Debug Url with Http Headers

Question: Can I send http headers when using 'Debug URL' in Zend Studio (eclipse)? I'm debugging an application on a remote server that requires http headers for authentication, json context, etc. I'm able to debug using the Zend Debugger browser extension which I assume uses the auth cookie stored in firefox, but when I try to debug directly through Zend Studio I can't figure out a way to send headers. Am I missing something?
Answer: I would use something like XHR Poster for Chrome which would allow you to set headers.  You can initiate a debug session by appending the following get query to your URL:
?debug_host=[ZEND_STUDIO_IP_ADDRESS]&debug_port=10137&start_debug=1&original_url=[URL_OF PAGE_UNDER_TEST]&use_remote=1&debug_stop=1
substitute the IP address for the machine Zend Studio is listening on for [ZEND_STUDIO_IP_ADDRESS] and the URL you're testing for [URL_OF PAGE_UNDER_TEST].
Instead of setting the get query you could emulate the Cookies that would otherwise be set by your browser extension by inspecting what cookies are set with Developer Tools and then emulating that header in XHR Poster in addition to whatever other headers you wish to send.

Zend Studio Debug Url with Http Headers


Photo Viewer that allows me to mark photos for further review

Question: I took a lot a photos and want to pick the best one. To do that I would like a free software that runs on Windows 10 that shows me an image and allows me to mark the image for further review via a hotkey and that has another hotkey to switch to the next key.
After I went through all the pictures I want to easily browse those images that I marked.
Answer: You can use GeoSetter for this. Give the image a rating using the shortcuts 1 to 5 and once you are finished show images only with that rating.


Meaning and pronunciation of יישר כחך

Question: What is the exact meaning of the phrase "יישר כחך", and what is the gramatically-correct way to pronounce it?
Comment: See here: http://mi.yodeya.com/questions/5991/words-often-mispronounced/6019#6019
Comment: Most of the people I know say Yasher Koach, not Kochacha.
Comment: The second half of the question seems off-topic.
Answer: The expression is taken from the Talumd (Shabbat 87a and several other locations). The sage Resh Lakish expands the word "אשר" to the now ubiquitous "ישר כחך" .
You can see from the following Talmudic excerpt (Shabbat 87a) that the original use was to validate Moshe Rabeinu's action. It would seem to me that current usage is quite the same. When one performs a Mitzvah those around him will confirm that the action was proper and worthy of validation and strengthening (the action or possibly the performer.)

For it was taught, Three things did
  Moses do of his own understanding, and
  the Holy One, blessed be He, gave His
  approval: he added one day of his own
  understanding, he separated himself
  from his wife, and he broke the
  Tables. ... 'He broke the Tables': ...
  And how do we know that the Holy One,
  blessed be He, gave His approval?
  Because it is said, which thou
  brakest, and Resh Lakish interpreted
  this: All strength to thee (=יישר כחך) that thou
  brakest it.

What a great question! Shkoiyech!
Comment: How do I spell _Yasher koach_? That's the phrase used ubiquitously in my circles (Reconstructionist and Conservative). I guessed ישר כוח, since I've never heard ישר כחך.
Answer: Literally it means "He (i.e. Hashem) should straighten your energy." It means that Hashem should guide you in choosing actions that will allow your energy to flow on a straight path from its source on high down to you.
It is correctly pronounced "Yi/Ya/sher Ko/cha/cha". Its Yiddish pronunciation is "Ya/shi/koi/yach".
Comment: Most of the people pronounce it: yi/shar/ ko/cha/cha (that actually means - your energy will be accepted by hashem, and he will think it's good. Don't know if this is the right meaning, or that we are pronouncing it wrong).
Answer: Hebrew Wikipedia entry says that "ישר" is an Aramaic root meaning "חזק" and that the phrase therefore means "may your power be strengthened" or, for a pretty good English idiomatic equivalent, "more power to you".
Comment: Welcome to Mi Yodeaya Andy! Thanks for the answer! Hopefully you will choose to stick around the site.
Answer: Good Moed:
As referenced above - Rashi - in the concluding Rashi of The Torah quotes maseches "Shabbos" (87a) where HaShem says to Moshe - "יישר כוחך ששברת". Grammatically, the phrase would be pronounced as "Yishar Kochacha" - may your strength be made straight. In the Hoshanos in the Artscroll Siddur, the word is written as "Yishar" - see page 738. Also, HaShem wouldn't be referring to Himself in the third-person by saying "may He straighten your strength" - referring to Himself. That's why it doesn't make sense to pronounce it "Yiyasher Kochacha.
Also see:
https://www.kby.org/english/torat-yavneh/view.asp?id=4011
Comment: But when the phrase is not being used as being spoken BY haShem (i.e., not quoting haShem TO Moshe), but is used by us mortals as a wish/prayer/encouragement that HE will straighten the strength of the person to whom it is being said, i.e., He will empower the strength of that person to continue to do such good deeds (have an aliya to the torah), acts of kindness (do CPR on one in need, or sponsor a celebratory kiddush for the congregants), etc., it would not be Him referring to Himself!! Thus, y'yasher kochacha (or kokachaych) would be grammatically valid.
Answer: Most people (wrongly) pronounce it "yashar koach" or "shkoyach" and this is the way it is said in Yeshivish circles and in Yiddish. However it should properly be pronounced something like "yishar kochacha" based on the way it's spelled. I often tell people it's meaning is something like "more power to you" and although this isn't the most accurate translation it gets the point across. "Shkoyach" is used somewhat like "thank you".
Comment: I just wanted to say that _shkayach_ is not wrong (or proper either), but it is just the way how Yiddish renders this expression.
Comment: From a certain perspective wrong. _Shaleshudes_ is also wrong, or it is how in Yiddish you say it?
Comment: @Kazibácsi You say it in Yiddish Shuleshsudes you're right

Meaning and pronunciation of יישר כחך


Mirroring File/Print Servers

Question: In our office we are currently running a windows XP pro desktop as a file/print server.  My question is, am I able to mirror this windows Xp pro machine to another windows Xp pro machine so that in the event of hardware failure I can take down the downed machine and put up the working one and keep the office up and running?
Answer: All you can really do is assemble the various increments of protection/backup and present the options to the decision-maker to determine how much they want to spend / be protected.
This could be as simple as buying a 2nd drive and setting up RAID to guard against hard drive failure.  However, that doesn't help if the computer goes belly-up, so the next step would be to ensure that you have a secondary system onsite.  Of course, if the building burns down, it's generally catastrophic to the business to lose that data completely, so now you've also got to start producing an offsite backup.
There are scores of answers on this site on each of these topics, but what you choose will ultimately depend on your company & budget.
Answer: You could just back it up and restore it to another machine then take that second machine down, in the even of the first machine falling over you would be able to start the second machine and it would work fine. Bit of a 1980's solution but it will work.
Answer: If your WinXP file/print server does not have RAID, I would recommend upgrading that system so that it does. However, RAID is not a replacement for backing up, so for creating a cost-effective mirror I would probably recommend using Norton Ghost.
Given your configuration, I'm assuming that a more commercial buy and install solution, such as Norton's Ghost, would be a better fit for you. If that's a bad assumption on my part, then you might want to look at something like Bacula although that would require having a Linux system, as I believe that while Bacula does support Windows clients, the Bacula Director doesn't run on Windows.

Mirroring File/Print Servers