Using Arduino To Control Boot Sequence of PC

Question: I want to know if it is possible to use an arduino to tell a pc which os to boot to. I know It is possible to turn on the pc by wiring it to the motherboard pins with the power switch, and I know the arduino I have (http://www.amazon.com/SainSmart-ATmega328P-Development-Compatible-Arduino/dp/B00E5WJSHK/ref=sr_1_1?ie=UTF8&qid=1436368217&sr=8-1&keywords=sainsmart+uno+r3) can act as a mouse or keyboard. Can that be done before the pc has booted however?
Comment: Injecting key events should be do-able, the question may be more if what needs to be injected and when is context- dependent.  Why not use a customizeable boot manager like grub, and modify it to talk to you over a serial port?
Comment: "can act as a mouse or keyboard" Do you know how to make it do so, or have you heard that others can do it?
Comment: There's a [hackaday](http://hackaday.com/2012/06/29/turning-an-arduino-into-a-usb-keyboard/) article on using the board's AT16u2 to emulate an HID device.
Comment: Arduino Micro, or Arduino Leonardo would be a lot easier to emulate a keyboard. Since you want the arduino to power up the PC you'd connect it to the 5v-standy (usb will power down in some PCs, so you can't usb to power it. I don't see how this would not be possible. You could use the old power button to control the arduino. Something like, one press=>Boot Windows, two presses =>Boot Linux etc.
Comment: Ignacio- I have never used an arduino for more than a motor and sensor controller, but the documentation says that It can emulate a HID device.
Comment: I see the issue with attempting to solve my issue with a keyboard now. There is no way to tell the arduino that the computer is waiting for an os selection. Grub control via serial port sounds like the only way to go.
Answer: So it might depend on how you implement it. With an Arduino Uno, your options for creating an HID device are limited to either reprogramming the 16u2 (which will require an ISP) or using a software USB implementation (like V-USB). If you go with the first method I'm pretty sure that will work as it will be a native USB connection. As for the second method, I'm not sure how well V-USB responds to having the USB host turning on while it is running. The best thing to do is just try it and see how well it works.
The bigger challenge you will run into is being able to select your PC operating system. Because this will be a one way connection, there is no way of knowing what state the computer is in and whether or not it is time to press a key yet or not. This means you will have to be timing things fairly accurately, which can be tricky unless you are careful. The internal oscillator is not very accurate (but probably still accurate enough) and interrupts used for communicating with USB can block the main loop. That is not to mention any variations the computer might have in its boot process.
A good alternative method would be to set up a bootloader on your PC that can be controlled via a serial port. GRUB2 is a popular one that does support a serial console. All you would need to do is add a level adjuster to adapt the Arduino UART to RS232, then set up the code to wait for the GRUB prompt and then send the command necessary to select which OS you wish to use.
Comment: Thanks for the information. This is very helpful and a great place to start. Grub sounds like the way to go. I have used grub in the past, but no more than using the arrow keys to select the os. The arduino's would send the power signal to the computers to boot, and then feed the bootloader the information telling it what to boot to? The serial console is via usb? How could I do this on two separate machines at the same time? Is it the same type of thing as using the serial console to monitor the arduino through the arduino++ software?
Comment: The arduino would listen to the serial port and wait for grub to be ready, usually it does this by printing a prompt (e.g. traditionally this has been "grub>" not super sure about newer versions though). If these computers have actual serial ports (i.e. 9 pin DSUB RS232) I would try and use that and connect to it via the UART port on the Arduino, using an adapter like I mentioned. Using the USB serial port might be possible, but it just depends on whether GRUB supports them.
Comment: As far as multiple computers go, you would pretty much have to go the UART route and get an Arduino that has more than one UART. For example the Due and the Mega 2560 have 4. Other Arduino-like boards like the Teensy 3.1 also offer extra UARTs.


Why are propeller driven aircraft commonly built with a higher wing aspect ratio and a straighter wing angle?

Question: Why do propeller driven aircraft (especially smaller ones like fighters) tend to have a narrower wing with a higher aspect ratio and a more perpendicular wing angle in relation to the body, whereas jet powered aircraft have a broader wing with a lower aspect ratio (a more "delta" shape) and also more angled? Does it have something to do with the operating speed and aerodynamics?
Comment: Note that a lot of smaller jet aircraft also have straight wings (examples: Yak-40, Do 328J, Learjet 25).
Answer: Speed is the reigning factor here, and aerodynamics as well of course.

Speed.
Propeller driven aeroplanes operate at lower speeds than jet engines - propellers are more efficient until compressibility effects start to appear, and it is these same compressibility effects that influence the wing shape as well. Compressibility as in: give air enough time to move out of the way and follow the wing contour. Usually, propeller aeroplanes operate in this aerodynamically docile speed regime.
Aerodynamics.
A wing creates lift by deflecting air downwards, and is most efficient if there is a large amount of air deflected a bit: the least induced drag is created. So the wingspan is the most important parameter here. Lower speed aeroplanes will stick their wings straight out, as much as possible without creating large structural issues due to wing root bending loads becoming unmanageable.
Aerodynamics at higher speed.
Once shock waves start to appear, drag rises rapidly. But only the air flowing perpendicular to span concerns us for the lift creation, and therefore we can present the wing at an angle and use the lower perpendicular speed component for lift creation. But swept wings create many more structural problems than straight wings, and also since we're going faster already the argument of more air at less deflection speed is of less relevance. We have many more problems to tackle here than only minimise induced drag.
Comment: It's not simply a matter of jet vs propellor, either.  It's fairly easy to find subsonic jets - early fighters, trainers, bizjet - with a more straight & narrow wing.  Also consider the various "swing-wing" designs...
Comment: @jamesqf: The early straight-winged jets were the result of sticking to what is known. Witness the F-84 which mutated from a straight to a swept wing when Republic got comfortable with designing swept wings.
Comment: Another factor is stability: A stubby wing has more torsional stiffness and shifts divergence speed up. So again, it is about higher speed for jets vs. propellers.
Comment: @Peter Kämpf: Then there are others, like the T-37, that stayed with straight wings over a long lifespan.  Probably because it had a relatively low top speed: https://en.wikipedia.org/wiki/Cessna_T-37_Tweet
Comment: @jamesqf: I would count the Cessna T-37 firmly within the early jets. Cessna had no experience with swept wings whatsoever at that time and the requirement did not call for them, also.
Comment: @Peter Kämpf: Why didn't the requirement call for swept wings?  Perhaps because it didn't require a high speed?  You see this in other jets, like some of the Citation business jets, or the A-10 Warthog, that fly at comparatively low speeds.
Answer: Yes it does. The reasons are many, and complicated, but I will try to briefly summarize them here in simple terms.
A jet-powered fighter has to pop through the sound barrier with minimum ill effect and be aerodynamically predictable at supersonic speeds. It also has to withstand the great stresses associated with these actions and those imposed by high-G maneuvering, without failure. All these thing argue in favor of stubby and sharply swept wings that are either trapezoidal or delta-shaped.
I invite the experts here to add to this list and to perhaps offer more technical background.


Does altitude affect wifi signals?

Question: What is the maximum height of a wifi signal in atmosphere? I am not mentioning range and also I dont want answers in milliWatt. I want to know answer in kilometers or meters.
Comment: if you are not mentioning range, then I am confused. what do you mean by "height"? vertical range?
Comment: The maximum height is infinity because the signal gets smaller but still exists but falls below the noise threshold so maybe you need to consider this and rephrase your question to be more meaningful.
Comment: Just for the record, I down-voted and close-voted, but I did not do that due to the language used but because of the constraints of the question. It's obvious that OP doesn't know what's needed to ask the question properly, that he isn't interested in learning and that at the same time he isn't providing a good scenario where wizards who are aware of the first two things I mentioned can do their magic and provide an answer in requested units.
Comment: My guesstimate: The range would be the same as horizontally since the atmosphere does not change much during that range. One thing to consider is that those "omnidirectional" stick-like antennas don't have the same gain in *every* direction (think sphere), instead they have a slightly smaller gain along their axis (think donut shaped).
Comment: And frankly three detailed answers shows that the question is not unclear ffs.
Comment: OP has made it clear he's asking for linear vertical range. Let's re-open this.
Comment: Ya I am mentioning vertical range.
Comment: @AndrejaKo `It's obvious that OP doesn't know what's needed to ask the question properly, that he isn't interested in learning` and you base that on what exactly? He understands that the question could be answered in radio power terms (Milliwatts) so it shows some understanding. The use of "mentioning" seems to be from mechanical translation.
Answer: It's difficult (almost impossible) to answer this question.
Why? Because the range (vertial or not) depends a lot on factors that you did not specify.
First you should have a look at notions such as "Link budget" Wikipedia
$$ P_{RX} = P_{TX} + G_{TX} - L_{TX} - L_{FS} - L_M + G_{RX} - L_{RX} \,$$
where:
\$P_{RX}\$ = received power (dBm)
\$P_{TX}\$ = transmitter output power (dBm)
\$G_{TX}\$ = transmitter antenna gain (dBi)
\$L_{TX}\$ = transmitter losses (coax, connectors...) (dB)
\$L_{FS}\$ = free space loss or path loss (dB)
\$L_M\$  = miscellaneous losses (fading margin, body loss, polarization mismatch, other losses...) (dB)
\$G_{RX}\$ = receiver antenna gain (dBi)
\$L_{RX}\$ = receiver losses (coax, connectors...)  (dB)
You can see that the antenna gain is part of the equation. Using the stock "omni" antenna sold with the WiFi access point will not achieve the same distance that using a very directional antenna such as a Yagi Uda or a parabolic one.
Without specifying this, it's impossible to give you a number for the range.
Then it comes to the transmitter power and receiver sensitivity. Each access point and WiFi card is different.
But, there is also another factor not related to the strength of the signal: the time delay.
The WiFi protocol (which one? this has to be defined) defines the maximum delay between a sent packet and the related acknowledge. If the distance is too big, a timeout will occur and this will not work. But without knowing the specific WiFi norm you plan to use, it's impossible to give you a number.
According to Wikipedia page about long range WiFi using modified firmware in order to increase the timeout value and dedicated antennas, ranges up to 304 km is possible without using additional amplifiers.
Answer: It varies by Wifi version, and speed/data rates:

The concept of range for wireless LANs is pretty basic. Range is usually thought of as a measure of distance -- the distance between two wireless stations at which they can effectively communicate. For typical Wi-Fi systems, range is the distance between a laptop client and the access point (AP) it is using.
Any discussion of wireless range also has to include data rate (not to be confused with the actual, physical throughput). In wireless systems, you can trade off data rate for range – at lower data rates, it is possible to communicate at greater distances. The 802.11 standard supports multiple data rates at the physical layer. 802.11 has an automatic rate fallback mechanism that reduces the data rate when communication degrades in order to maintain a better link between a wireless client and AP.

And by antenna type:

And as you can see in the picture above, a standard wifi antenna like you normally get, has a donut/torus shaped radiation pattern. That means if the antenna is vertical/straight up and down/perpendicular to the ground/90° to the floor, it has basically 0 radiation at a 90° angle while weaker at other angles. If you make the antenna parallel to the ground/lay it flat, it will have better vertical (compared to us) performance.
And the farther away the two nodes are (The Wifi router/access point, and the computer/laptop), the slower the wifi speed is. 802.11n improves on 802.11b/g by using a second antenna, spaced a half wavelength away. 802.11n is shown to be 250m effective range, outdoors, with no obstructions but the data rate and type of antenna used is unknown. And that's before interference. The more wifi traffic on the same channel, the slower and weaker the effective signal will be.
In the end it depends on A, the antenna used, B, the radio power, C, obstructions, D, the direction of the antenna, E, interference from other sources on the same radio bandwidth/channel, F, Speed required, so there is no single answer.
Answer: I don't know what you mean by "I am not mentioning range."  AFAIK that is the only way to answer this question.
The range of Wi-Fi depends on the protocol.  The range of 802.11n is about twice that of 802.11b and g.
The typical outdoor range for 802.11n is approximately 820 feet.  Although this is assumed to be horizontal, it should apply to a vertical distance also.
Although not explicitly stated, I am going to assume this figure of 820 feet assumes the the use of an omnidirectional dipole antenna, since it is the most common type (i.e. the "rubber duck" antenna that comes with routers).
However by using a high-gain directional antenna, ranges of several kilometers can be achieved.  The examples given are all point to point horizontally, but it again should apply vertically also.
Comment: Are you sure will horizontal and vertical range be same?
Comment: @rajasekar25 As long as the antenna is oriented correctly, to account for the vertical vs horizontal direction, going "up" rather than "sideways" should make no difference.

Does altitude affect wifi signals?


Real world analogy for a clustered index

Question: A db index is analogous to a table of contents. This helps me understand db index in an easy way. My question is are tehre any real world analogies for a clustered index?
Answer: If the Table of Contents in the front of the book is non-clustered, the page numbering itself (on the actual pages) is the clustered index. The "clustered" nature of an index indicates that the records are stored with the index nodes (or at least in the same order). So, the page-number analogy is actually very accurate in this respect, because like a real clustered index, the page numbers are located on the pages, which are bound together in page number order.
Put another way:
When you use the book's TOC (non-clustered index), you search for a term which points to a page number. You then have to perform another search to locate the actual page.
The search performed against the page number (clustered index) leads you directly to the page. No secondary searching is required.
Not incidentally, this is why you can only have one clustered index. It defines the physical order of the records.

https://stackoverflow.com/questions/1251636/what-do-clustered-and-non-clustered-index-actually-mean
http://en.wikipedia.org/wiki/Database_index#Clustered
Answer: I would describe a clustered index as "the actual order." Thus, for example, a physical dictionary has a clustered index on word, ordered in ascending order from A-Z (slight simplification).  This also explains why a clustered index is so much faster to read than a regular index.  If I feel the urge to read a book by index entry it will require me to jump all over the book, since consecutive index entries tend to point to different pages.  On the other hand, reading every word starting with "The" in a dictionary requires less jumping around; merely find "The", then read in order.
Comment: So it is like a table of contents with the difference that the actual table is sorted based on the indexed column?
Comment: I am a bit hesitatent to call it a table of contents, because one usually would use a table of contents as a sort of index.  If I wanted to read about topic X in a book, I would read through the table of contents to find out which chapter discusses X, then flip to that page.  On the other hand, if I wanted to look up "candy" in the dictionary, I would open the dictionary and flip through pages to find the word candy.  This has major implications for join performance.  Compare someone referencing a dictionary to lookup words vs giant index...the latter has an extra layer of indirection.
Comment: I should mention that one can achieve the same performance benefits of a clustered index by just creating a non-clustered index that includes every column (or at least, every column you are using).  Of course, this is similar to creating two copies of your table (each sorted in a different order).  One could in theory create two identical animal reference books, one ordered alphabetically by an animal's common name and the other ordered alphabetically by the animal's scientific name (vs having an index by common name).
Answer: The library (or bookstore if you prefer) puts books into groups (all history books here, scifi books there) because they assume that if you want one history book, you're more likely to want other history books rather than different kinds of books. Likewise, it becomes easier to sort the scifi books by author rather than all books by author.
Comment: Ummm...but that sounds more like partitioning based on category(history, sci fi) and not cluster indexing.
Comment: @kaushik - sure, the implementation differs but it's close enough for the layman (or beginner). If it helps, magazines will often be clustered by year and then by month/week. Same concept but closer to the implementation.


PNGs on a plane

Question: I am trying to make a chain link fence using planes and a .png image as the texture, I am importing the whole environment from blender however this problem keeps on appearing, the plane gets the .png file and you can see through the fence only on one side, if you turn to the other side then the plane disappears completely. However this doesn't happen in blender when I render the image. I have tried importing the .blend file to unity and using an .fbx file however it still appears that way. Any idea on how to fix this problem?
Comment: I'm not too familiar with Blender, but isn't there an option to tell your plane to render both sides?
Answer: I think you actually mean a quad. A quad consists of 2 triangles, even if blender doesnt show that. A triangle - and with that - a quad, has a normal. Consider it to be the front of the quad. Usually, we dont draw the back of a quad because we don't need to.
Rendering is roughly twice as fast when we dont draw the triangles that face the other way, and you usually dont see that we cull them, because they're normally occluded by other triangles.
In this case, it is a little more difficult. We need to duplicate the quad, and make the copy face the other way. In blender, select your quad (or plane, if you want to keep calling it that). Shift-d to duplicate the vertices. Just move it slightly away to the side that you cant see in the other program. Press w. Click flip normals. Save and export. Im not sure if this is what the problem is but it sounds like it.
Comment: There's no need to translate the vertices used in the reflected quad.  They can in fact use the exact same vertices.  This saves some memory and is slightly faster since it allows the use of the post-transform vertex cache (back face culling occurs during primitive assembly; after vertex processing), though you won't ever notice any difference for just one quad.  There is no danger of z-fighting because when back-face culling eliminates one of the quads, it prevents it from being rasterized at all; the depth buffer won't be written.
Comment: You're absolutely right. But personally, with just a couple of quads, I'll go for the ease of duplicating and flipping in blender. But I guess I'm kind of a lazy developer. But I'm actually interested in how you would do this. Could you post it as an answer?
Comment: I don't generally use blender, but in maya, I would just use the "append to polygon" tool, click one edge of the quad, then the opposite edge.  If the geometry were more complicated than a single quad, I'd do about what you suggested: duplicate the mesh; reverse the face normals on the new mesh (but not the old one), then select both meshes, combine them into a single mesh, select all the vertices, and merge the duplicate ones (shift-right-click -> merge vertices).
Comment: Note that this technique doesn't work if you need accurate vertex normals for lighting, as the normals for one side will be different than the normals for the other side, but for the vertices to be considered "the same" all their attributes must be identical, including normal direction.  But for the purposes of face culling, only the winding order and position of the vertices matters.

PNGs on a plane


How to control playback speed of iTunes U lectures in Mac OS?

Question: I try to learn swift and opened iTunes U lectures in iTunes on Mac. I wonder how can i change playback speed? It is easy on iPad, but i have no idea how to do this while playing videos in iTunes on Mac
Answer: It is currently not possible in iTunes. I highly recommend you to give feedback about this feature to Apple.
However there is a workaround:

Download VLC

VLC is a free and open source cross-platform multimedia player and
  framework that plays most multimedia files as well as DVD, Audio CD,
  VCD, and various streaming protocols.

Right click on the file in iTunes and choose "Show in Finder"
Open the file shown in Finder with VLC
In the menu "Playback" you can find the "Playback Speed" settings.
Answer: If you're trying to speed it up, press the fast-forward button (connected two right pointing arrows). It continues to play audio and video, but at 2x-60x speed.
I don't know of any native method for playing at 0.5x, 1.5x, or any other speed slower than 2x.


Does Bank Of America Credit Card Report to All Credit Agencies?

Question: I was added on my fathers Bank of America visa credit card about a year ago. Recently getting my credit reports I saw that only one had the card listed (Transunion). The other two (Equifax and Experion) don't have it listed. Does Bank of America report to all three companies? How can I fix this?
Answer: In your case, maybe there's something in the way BofA reports when you're not the primary account holder (i.e., someone adds you as an authorized user) so that it isn't going to show on your credit report.
Sometimes it can take awhile for accounts to appear on your credit report (up to several months), depending on how and how often the creditors report to the bureaus.
Not every creditor reports to all of the credit agencies, for varying reasons.  It seems odd that BofA wouldn't be reporting to at least both TransUnion and Equifax, so this is worth a phone call.
Sometimes when this happens its because the information the creditor is reporting is incorrect and doesn't match up to someone's credit file, so the bureaus don't list it.  A social security number, date of birth, or name doesn't match (or perhaps some other detail), so it gets sidelined and never reported.
In any event, this is worth a quick call to BofA customer service to ask, and maybe they can either fix it if there's a problem or you can simply sign up for your own BofA account and have it reported.
I hope this helps.
Good luck!
Comment: Calling the phone line the woman replied that authorized user accounts should not normally show up on credit reports and do not affect my credit score. This seems strange to me. Is this correct?
Comment: It could very well be true, and it's more of a policy issue for the bank.  The account is based off of the primary account holder's credit score and history, and authorized users are exactly that -- authorized to use the account.  But authorized users don't pay the bill and the bank doesn't hold them accountable for it, which is the danger anyone risks by putting someone on as an authorized user.  That person could max out the card and leave them paying the costs.  Now, if someone else was a *co-signer* on an account, then it would show on both your credit and theirs, so that's different.
Comment: Okay thanks. So I guess I should just let it be then and take the extra info on my Transunion report. Still strange it shows up on one and not on another.
Comment: I understand your point, but it really isn't all that strange or unusual.  There are *many* creditors out there who report to just one or two bureaus, because it costs money and time to do it (meaning they have to format the data to meet each bureau's requirements for uploading bulk data), plus they have to comply with each bureau's requirements for dispute-handling.  They often find it simpler to pick one bureau, since most of the time when your credit is run, a prospective creditor will pull combined reports from all bureaus anyway, so they know about all of your accounts regardless.
Comment: Okay makes sense. Guess my view of society is just to idealized haha. Thanks for all your help!
Comment: You're certainly welcome.  Glad to help!
Comment: As an update that account now suddenly is showing up on Equifax...strange...who knows if it was that call or just a strange coincidence, but I'm definitely not complaining


Why is the Earth's moon so big?

Question: It could just be me, but it seems like our Moon is WAY bigger than it should be for a planet of our size. If you look at satellite-to-planet mass ratios for the largest moons of Jupiter, Saturn, Uranus, Neptune and then the Earth, the values are on the order of $\mathbf{10^{-5}}$ for Jupiter, $\mathbf{10^{-4}}$ for Saturn, $\mathbf{10^{-5}}$ for Uranus, $\mathbf{10^{-4}}$ for Neptune, but a whopping $\mathbf{10^{-2}}$ for the Earth-Moon system. What gives? Why is the relative size of our Moon two orders of magnitude larger than the average for the solar system?
Comment: That's because technically the Earth-Moon system is a(lmost) a binary planet. The formation mechanism for the Moon is very different from that of the small moons of the large gas planets. The best current hypothesis for the formation is an impact of a Mars sized object into early Earth, while the smaller moons of the gas planets are formed either by condensation of material from the proto-planetary cloud or they are captured by the gas-giants at a later stage.
Comment: related (possible dup?): http://physics.stackexchange.com/questions/68476/what-if-the-moon-was-100x-more-massive-binary-planets
Comment: Is there something about this in the essay "The tragedy of the Moon" by Isaac Asimov?  As far as I can remember, it's only about the *consequences* of a large moon, not about the causes.
Comment: @Kyle Definitely related, but I am inquiring about the asymmetry found in our solar system with respect to satellite size, not hypothesizing the effect of a permutation to our current arrangement.
Comment: The mass ratio for the Pluto-Charon system is even $10^{-1} $.
Answer: Most moons are captured bits of rock left over from the formation of the planet as it swept its bit of orbit clear.
Our moon is (probably) the result of a very big bit of rock hitting the early Earth and splitting it into two. The smaller bit ended up as the moon.
This also explains the relatively high density of the Earth (it got left with all the heavy core parts) and the low density of the moon (it got all the light surface rocks)
Comment: Was the earth the thing that was split apart, or was the planet that hit the earth the thing that split apart? i.e. is the Moon mostly Earth materials, mostly OtherPlanet materials, or a decent mix of both?
Answer: The simplest answer is that the Earth is even MORE massive.
Don't let Earth's lack of stature relative to the Jovian systems fool you. The gas giants are truly massive but are not nor do they have physical land and water at their surface.
This may seem laughable on its face as what could be more massive than a gaseous body in a liquid state?
Nay, veerily...these are not rockets nor the Sun spewing forth tremendous physical energy but are objects "wildly at war with themselves" with truly spectacular countervailing winds and even an "evil eye" beckoning us towards further investigation.
The Earth by spectactural contrast is shockingly calm...travelling at plus 70,000 mph plus rotating on its axis at a leisurely 1000 plus give or take.
Neptune's Moon is the only the one relative to size and mass that I think even comes close...and amazingly Neptune's Moon rotates in the exact opposite direction of Neptune...seeminly belittling the idea of Neptune as a Planet of Importance in so doing.
Earth on the other has this very tempting "delicate air" covering its massive surface...perhaps something that makes the Moon very angry as while she can move entire Oceans it is left to the Sun to "make weather" thus belittling this very placid and nonchalant body slowly being pushed away while still being forced to face no matter her strength, power and wisdom.
Comment: Gas Giants may have solid cores which are bigger than the entire Earth or at the very least has more mass than all of Earth combined. Jupiter probably has a core that is 7 times bigger than Earth by mass.

Why is the Earth's moon so big?


Correspondence theory of truth and analyticity

Question: The correspondence theory of truth states that truth is essentially correspondence to a fact or state of affairs. How does this theory handle analytic truths - that is, 'true by definition' type statements that merely involve unfolding concepts? For example, what fact corresponds to the true sentence "a bachelor is an unmarried man"? Imagine a world where everyone dies except a married couple. Then there are no bachelors - but is still (presumably) true that a bachelor is an unmarried man. Then how can it be the case that this statement is true because of correspondence to reality?
Comment: @Logikal It sounds like you're saying that the correspondence theory of truth isn't even meant to touch upon analytic truths. But how could a good theory of truth just not even address a sizeable chunk of the kinds of statements we take to be true?
Comment: The solution would probably be to advert to a distinction between general and particular facts, and have analytic truths be true propositions that correspond to at least a subset of the general facts, with general states of affairs able to obtain even if particular instances of them do not. Having said that, I appreciate that it is not the most persuasive-sounding account of how this might work.
Comment: Another option would be to convert categorical definition sentences into conditionals, such as, "If anything is a bachelor, it is an unmarried man."
Comment: The term analytical means that it is not sense verifiable to know. We know something analytic because it is impossible to be something else. Correspondence theory is basically dependent upon us using the so called five senses. That is if my sense tell me there is an orange on the top left corner of my desk then that object is a fruit as well. Without my senses I would have no idea if something was placed or sitting on the top left corner of my desk. So you are comparing apples to oranges here. Nothing about your senses let's you know bachelors must be men --that is a language convention.
Comment: @logikal, I don't think the correspondence theory of truth is limited to empirical truth. Some versions of the correspondence theory of truth even have truthmakers as abstract objects, so the allow for abstract objects, and presumably for truths about those abstract objects.
Answer: It's the same as asking: Were jews real in Nazi Germany if they were sure to die? They were real obviously because they were born. Dying means being born first.
It would have been different if bachelors couldn't exist in the first place. Then there could have been a word for it ( bachelor) but it wouldn't correspond to reality.
Comment: How does this answer the question? How does the counterfactual "it would be different if bachelors couldn't exist in the first place" help the correspondence theory of truth make sense of how and why we, in actuality, think the statement "a bachelor is an unmarried man" is true?
Comment: @Abel If the bachelor doesnt exist in the first place there is no correspondence with it. Yet. If it cant exist at all (when they all die) then they still have to be born. But then they are not married yet. The statement "a bachelor is an unmarried man" is true by definition. Even if they are not seen in the real world (because of dying) they still can exist as non married man by changing the definition.


How do I attach a drywall corner bead to a wood door jamb?

Question: I am installing a door into a wall and I do not want to have casing on the door. I want to install corner bead directly to the door jamb to create a "hidden door". It seems that typical corner bead is too small.
Comment: Is this a door opening or is it an actual door jamb installed with a physical door mounted in the jamb?
Answer: It seems to me that there are two possibilities here. If the opening in the wall is just a pass through without an actual door itself then you would band the opening with drywall material and then put normal metal corner edging around the outside corners of the drywall.

On the other hand if there is a door jamb in use with an actual door then the width of the jamb wants to be equal to the stud width and then the drywall is installed out over the edge of the door jamb and finished off with an end cap type metal edging.
Comment: Thank you very much! J bead is something that I didn't think about.


How do I calculate the correct rotation speed for a given density altitude?

Question: The Airlines calculate the rotation speed of every takeoff based off the weight given to them from their operations people and also the density altitude conditions.  In General Aviation we don't perform such calculation but usually rely on the Pilot Operating Handbook (POH) recommended rotation speed.  However the POH rotation speed is based off of gross weight at sea-level and doesn't take into account high density altitudes. Is there a formula that can predict what the ideal rotation speed will be for a specific density altitude?
Comment: Won't the IAS be pretty much the same though?  Higher TAS, longer ground roll, but rotate at the same indicated?
Comment: @MichaelHall: I agree with you with respect to GA light acrft. For air carrier type aircraft the VR speed can change with density altitude because V1 can change with density altitude due to higher TAS/GS and runway length requirements, obstacle climb requirements, etc. VR can never be less than V1. The actual *indicated* speed that the airplane would actually be able to get off the ground (VR) won't change but it needs to change in relation to the other runway/ obstacle performance speeds that are based on (faster) TAS/GS. Other factors as well.
Comment: @MichaelHall Since acceleration goes down with altitude going up, you need to rotate at a slightly higher IAS in order to be at the same IAS when the airplane leaves the ground. The difference is minuscule, though.
Answer: The given rotation speed is most often indicated air speed[IAS]. IAS is calibrated airspeed [CAS] plus instrument errors. (Outside of the airspeed guage, which as a stand alone item is usually very accurate, errors can be caused by pitot tube and static port mounting locations and large changes in angle of attack.)
CAS is a measure of dynamic pressure not true air speed. Lift is a direct function of dynamic pressure. So the required CAS for a given amount of lift is independent of the air density. If your stall speed is 50kts CAS at sea level then it will be 50kts CAS at 20,000ft.(However true airspeed will be much higher at 20,000ft.)
Airlines use, in combination with extensive performance charts; weight, air density, and temperature for calculating the true speed and thus the required auto brake settings, engine performance settings, V1 V2 Vx and Vy, and by extension determine the required length of the runway, and obstacle clearance.(All of these are determined by mass, thrust, distance, and time rather than lift alone.) Vr CAS/IAS is primarily dependent on lift.(Weight and flap settings.)
A Small aircraft POH does include charts for determining required distance of roll and 50ft obstacle clearance based on air density and maximum gross weight; many will also include selected gross weights below maximum that you can use for interpolating.
If you wish to adjust the rotation CAS based on weight[lift] the formula is the same as is used for adjusting stall speed. If needed first convert IAS to CAS using the chart in your POH, then use CAS in the following formula.
$$
S_n = S_o * \sqrt{ \frac{W_n}{ W_o} }
$$ $\text{ Where $S_o$ is original speed, $S_n$ is new speed, $W_o$ is original weight, and $W_n$ is new weight.}$
In plain text if the mathjax formula doesn't render: Sn = So*sqrt(Wn/Wo) ; speed new, speed original, weight new, weight original
After this use the chart in your POH to convert the CAS to IAS and this is your weight adjusted rotation speed.
However, it is my opinion that reducing Vr is only useful where rolling distance is the only limiting factor, because it may actually harm the distance needed to clear a 50ft obstacle. This is because as soon as you rotate you add induced drag, so acceleration before rotation is better than acceleration after rotation. The question then is about the benefit of climbing earlier at a lower initial angle[below Vx] vs later at the ideal angle[Vx for the current density].
Keep in mind that Vx is both weight and density dependent, but it is not as simple to calculate because it involves the specific aircraft design; drag, engine performance limits, and prop selection being primary variables. Mostly Vx and Vy are roughly calculated and then finalized experimentally. But you need the right instruments to accurately record climb angles and climb rates.(GPS data is simple geometry and cannot compensate for the effect of head wind or air density.)
Vx=Vy at the absolute ceiling[not "service ceiling"] for a given weight, from there Vx decreases and Vy increases as density-altitude decreases. All of the CAS numbers will decrease with decreasing weight but again precisely how much is not simple; but you may be able to interpolate existing data, and if doing experimental test pilot stuff you could extrapolate the established data in small increments.

I just want to add that transport category aircraft use a lot of automated controls like auto-brakes, auto-throttle, and an FMS which all produce much more consistent and repeatable results than the pilot of a light aircraft could manage. As such for light aircraft the variation between each takeoff roll will be greater than the difference created by doing the extra calculations. And then you have effects of runway slope, runway surface [grooved or smooth, damp, wet, snow, dry], winds, and noise abatement which are all used in the airline's computer.
Comment: Please don't put additional info in comments - include it in your answer. Comments are not always read and can get deleted. If it's only tangentially related, break it apart from the main answer by using `---` or `` to add a horizontal rule to separate it from the main answer.


streaks in polyurethane finish on freshly stained farm table

Question: I applied too much polyurethane finish on newly stained wood farm table while applying third coat. I tried sanding with 220 grit and applying a 4th coat but there are still very visible streaks.  Should I sand and coat again or do I have to strip and stain over?
Answer: I would go to a finer grit after the 220. Yes you need to sand until it is SMOOTH. Do you have a random orbit sander? Wipe on poly (50/50 poly and thinner) is a good way to go. The coats are thinner so you need 2 or3 more. Brushing works well but with a GOOD brush or a foam brush.
Answer: I don't think you need to strip it completely. It sounds like you didn't get the last coat fully sanded off.  How long are you waiting between coats? If you are sanding between coats, you have to wait 24 hours for the previous to fully dry/cure.
Personally, I prefer the wipe on poly, which is basically poly that is thinned down by 50% or so. It's much easier to get it smooth consistently.
Answer: Everything is fine. Don't worry about the small imperfections. Wait for the polyurethane to dry completely and cure as hard as possible.
Depending on the level of gloss you want, go to an auto supply store and get a bunch of different grits from 300 and up.  Get an assortment pack and stick with 3m. Cheap sanding paper is more expensive, since they don't last anywhere as long as the premium ones.
Get a sanding block or make one.  If you have a orbit or sheet sander, even better. Start with 220 and lightly sand the surface until it is evenly hazy. You should get a powdery dust on the surface. If it is gummy, then the poly isn't cured enough. Wait a few days before sanding.
Clean off the surface with a damp rag see if there is an even surface,  If the poly is thick, you can sand again and if it not, then add another coat of poly.
Now, work your way up the grits and check the surface to see if there is an even sheen. If you like the sheen level, you can stop and buff it with wax. Continue with higher grits for a glossier finish.
If you want to prevent streaks, you should use a wipe on poly or foam brush.
Answer: Check out this article: http://homesteadfinishingproducts.com/rubbing-out-finishes/.
When I first tried to get a glossy finish on a piece of stained wood with Shellac I was getting streaks in my otherwise glossy finish because I had a hard and imperfect sanding block. My solution was to stop sanding at grit 400 or 500 (probably could have stopped at 320) and then just use really fine steel wool to finish rubbing out the finish after it had hardened for a day or so (remember to let the wood harden before rubbing it out ...). This was done as suggested in the aforementioned article.
If you have a nice cork sanding block or a random orbit sander as suggested by Lee, then you can probably just sand all the way to grit 1000 to get a really glossy finish. The steel wool will give you a more matte look, but I like it that way.
I wet sanded the shellac with soap and water, but left the finish dry for the steel wool. The article mentions that you may be able to dry sand with poly though.


Kina's Gratitude Crystals Glitch?

Question: She asks for someone to plow the fields but then I have to put away pumpkins again. I've done it 3 times now and there is still no option to go get the head mole-guy. I haven't done the harp thing there is that possibly what keeps resetting it?
Comment: Have you actually gone to the Eldin volcano?
Comment: Yes I have and he says he wants to enjoy his twilight years, but no Fi to call the robot.
Answer: The sidequest becomes available only after you complete the fire sanctuary.  Once this is done, Guld will be waiting on top of one of the rock pillars as you dive underground at the base of Eldin volcano.  If Guld is not there, then that means you haven't completed enough of the story yet.  Guld will mention something about it being too hot to find treasure when the sidequest is available.
Here is the entrance to the location by Eldin Volcano you must dive to find Guld, in case it was hard to understand what I was talking about:

UPDATE:  Also, I think you have to complete all the jobs that Pumm, the owner of the Lumpy Pumpkin, has for you.
Answer: This particular quest is only available in a later part of the game. When ready, Kina will have a "..." bubble over her head and thank you for carrying pumpkins for her before asking for your help again. If you haven't had that chat with her yet, the quest is not yet unlocked.
It only becomes available when...

 You have battled the Imprisoned a second time with Groose's help.

If you haven't passed that point in the game yet, then you just have to keep playing!
Comment: I've beaten the imprisoned 3 times now and still nothing.

Kina's Gratitude Crystals Glitch?


Conflicts using Tkinter/wxPython with Python AddIn scripting?

Question: I want to design a custom dialog window where i can select various datasets of choice using scroll down option and specify some conditions and thresholds. Right now i am using python addins within arcgis 10.1 for toolbar and tools. I came across tkinter and wxpython as options for dialog box designing. Will there be a conflict between using tkinter or wxpython within addin scripting?
Comment: A wxPython example is here: [Custom wxPython GUI's: an approach for ArcGIS 10.1](http://betablogs.esri.com/beta/arcgis/2012/05/03/custom-wxpython-guis-an-approach-for-arcgis-10-1/)
Comment: @blah238 It looks like your link is broken - perhaps you have an updated one that you could add as an answer alongside mine.
Answer: I found a technique to do this described at Another GIS Blog under the title of Python Add-Ins and Tkinter:

ArcGIS for Desktop does not support any python GUIs out of the box,
  but let's say we want to have a form pop-up anyway. ...
One way to do this is to create a wx python instance at start up,
  which is create before the desktop python loop is created.  You would
  then reference the wx loop instead of the ArcGIS python loop.. but
  it's complicated...  You can also see tons of forum posts like this,
  that describe how the in process causes python to crash with GUIs:
  ArcGIS 10.1 Python AddIn Using Multiprocessing crashes ArcMap?


Was payment on Louisiana Bonds suspended during the War of 1812?

Question: Of the Louisiana Purchase cost of $15 million, $11,250,000 had to be paid to France.  This huge sum was financed mainly by Barings Bank in London and Hope & Co. in Amsterdam.  The U.S. would faithfully service these bonds for decades, helping establish Uncle Sam as a credible credit risk.  However, within eight years the U.S. was at war with Britain -- and Barings was in the capital of the enemy.  Did the U.S. continue to pay bonds held by Barings?  Did it send money to a financial institution in an enemy country?  If not, how were payments made?  If payments were not made during the war, were they caught up after the war -- and was there a provision for interest in that case?
Answer: This question was much harder to research than I expected - despite (eventual) availability of the Barings Bank Archive web site. What I was able to determine is that:

Barings Brothers forced a reduction in the Louisiana Purchase price, from 100M French Francs to 80M French Francs, because the original asked amount was greater than it was possible to finance.
Baring Brothers remained the official agent of the U.S. Government through the War of 1812, and financed it during that war.
Baring Brothers continued as dominant to its rivals in North America even after being surpassed in London itself by Rothschild's.
Baring Brothers held an overwhelming position in the financing of early U.S. railroads through most of the 19th century.
Baring explicitly requested, and received, permission from the British government to finance the issue - as the benefit of security for British North America was expected to outweigh any advantage gained by Napoleon from the Louisiana Sale.

In this case, to paraphrase Holmes from Sir Arthur Conan Doyle's Silver Blaze:

The complete absence of mention of any default or re-financing arrangement of the largest national financing in history to that date, combined with the continuance of the relationship between the Federal government and Baring Brothers, very strongly suggests that all payments continued on schedule for
the entire lifetime of the bonds.

Or more bluntly, I find it inconceivable that a default or refinancing of this debt could have completely disappeared from the historical record.

From my comment below:

I read a couple of chapters of an old treatise on the early merchant bankers researching this - and it basically confessed that no-one knows how either Barings or Rothschilds transported much of their assets across the Atlantic. Either trade secret, or still classified in the Admiralty office. Recall though that by late 1814 the New England states were on the verge of secession over the war. Smuggling British ships in and out of Boston would likely not have been difficult.
Comment: @MAGolding: I read a couple of chapters of an old treatise on the early merchant bankers researching this - and it basically confessed that no-one knows how either Barings or Rothschilds transported much of their assets across the Atlantic. Either trade secret, or still classified in the Admiralty office. Recall though that by late 1814 the New England states were on the verge of secession over the war. Smuggling British ships in and out of Boston would likely not have been difficult.
Comment: Were all the payments do via paperwork and credits?  Actual physical shipments of coins across the Atlantic ocean would have been difficult during a war between the USA and the UK.
Comment: Your last two sentences would IMO be useful within the body of the answer. Up to you.
Answer: US federal budgets, which you can find searching google books, show remittances to London & Amsterdam for interest payments on "Louisiana stock" during the war years.
Comment: Hi Nick and welcome to History SE. Citing the relevant passages from your source would improve this answer and make it more likely that people will upvote.


Setting a Box2D Bodies Center?

Question: How do I set the center of a fixture/body consisting of multiple shapes (triangles)?
Comment: Does Box2D run in Flash?  If not, why is this tagged actionscript-3?
Comment: @synth Wow; I didn't know that.  It's been a long time since I used Box2D, but it would seem that "center" is an immutable point.  Can you move the center of a circle without moving the circle itself?  It would break the circle's very definition. This is a more complicated shape, but I think the same principle applies.  Maybe you could keep an offset vector from the "real" center and perform your rotations around the offset position.
Comment: The point of this is I'm trying to set where the center of the body is as you can see in the bottom it's in the correct place where the wheels would be by giving the it vertices where the origin (0, 0) is towards the front of the car where the steering wheels would be.

However when I triangulate this shape and attach the triangles to the fixture, the center of the body is moved to it's center. Where means when I try and rotate the car it looks odd.

@Wackidev, Yes it has been ported to Flash (http://www.box2dflash.org/)
Comment: So, it's correctly finding the center, and you want to change that to *off-center*? "the center of the body is moved to its center" Isn't that expected? Can't you just define an offset from true center to where you want your center to be?
Comment: I don't understand why you chose to triangulate these shapes? They are convex and don't have to be triangulated.. just keep them as they are.
Answer: From the box2d manual:

A body has two main points of interest. The first point is the body's origin. Fixtures and joints are
  attached relative to the body's origin. The second point of interest is the center of mass. The center of
  mass is determined from mass distribution of the attached shapes or is explicitly set with b2MassData.
  Much of Box2D's internal computations use the center of mass position. For example b2Body stores the
  linear velocity for the center of mass.
  When you are building the body definition, you may not know where the center of mass is located.
  Therefore you specify the position of the body's origin. You may also specify the body's angle in radians,
  which is not affected by the position of the center of mass. If you later change the mass properties of
  the body, then the center of mass may move on the body, but the origin position does not change and
  the attached shapes and joints do not move.

<code>bodyDef.position.Set(0.0f, 2.0f);   // the body's origin position.
bodyDef.angle = 0.25f * b2_pi;      // the body's angle in radians.
</code>
So it seems you can either set the origin, or the center of mass through the MassData.

Setting a Box2D Bodies Center?


How to Identify Objects in Space

Question: Using a depth sensing camera like Kinect, I would like to retrieve the position of an predetermined object (e.g. a cup, fork etc so that I would ultimately be able to grab the object). What would be a way to achieve this?
Comment: In its current form this question is very complicated. If you could offer some additional information you may get more traction. Specifically, are we to assume that you already know how to how to identify the cup in the point cloud returned by the Kinect? Similarly, do you already know how to generate the grasp required once you know the coordinates of the object?
Comment: I've tried to narrow the scope. I would first like to learn to identify an object in space (e.g. by analyzing the point cloud from the Kinect)
Answer: If you want to recognise a predetermined object (so one that you have seen before) in a 3d scene. It seems this would work similar to the 2d case: using features. Only in this case using 3d feature extractors/descriptors. You provide your model (so the object that you have seen before), and find salient features in the model. In your new scene you also perform feature extraction and then compare the features with your model. If they match well enough, you have found your object. Have a look at the pcl tutorials on the subject.
Answer: You probably want to do this, check it out. They also have code http://personalrobotics.ri.cmu.edu/projects/moped.php
Comment: It helps to add as much content as you can _here_ so that if the content on the other end of the link changes, it is still relevant.
Comment: Unfortunately, the topic is not simple, and remains an interesting research problem. The link above summarizes everything quite well. The moped framework is also PhD thesis that you can find here http://www.ri.cmu.edu/publication_view.html?pub_id=7326 (the content on this link will not change)

How to Identify Objects in Space


How to set SD card as default storage on Android Marshmallow?

Question: I have a Lenovo K3 Note (K50a40) and I was running Android 5.0 Lollipop until last week. I had set the default storage as SD Card on lollipop in storage settings, but that option seems to have disappeared in Android 6.0 Marshmallow. It only allows users to "Adopt the SD Card as internal storage". I do not want to reformat the SD Card as internal, as that will result in encryption of the SD Card. I just want the downloaded data, and the screenshots, Instagram pics, Whatsapp media etc to go to the SD Card, as was the case in Lollipop with SD Card as the default storage.
Answer: The applications need to support this in Marshmallow, and as of yet many applications do not support the changes that are needed in their code to allow this to occur in Marshmallow with the SD card setup as external storage.
The answer is that your app developers need to include this functionality in their apps, it is not a blanket Android setting. Unless the code is included in their apps, there is nothing you can do to change it in a stock device.
Comment: Yes, it is specific to Marshmallow... 6.0 changed the way SD cards are handled.
Comment: Is this specific to Marshmallow? Because all the data that I'm mentioning, (downloads, screenshots etc) was smoothly going to the SDCard on Lollipop.
Comment: Hello, I have the same issue. Small phone storage and I'd like to move apps to SD card, but it doesn't look possible (as you say) in Marshmallow. Does that mean that I won't be able to install any more applications? Damn that sucks..
Comment: @Warrior To use your SD card as internal storage does require Marshmallow. Although, if you are rooted you could use an app like Link2SD or App2SD to move some of the apps to the SD card and regain some space.


How does any vibrating object generate sound?

Question: We all know that vibration is the cause of sound generation. But here my question is, Internally what happens in vibrating object which creates sound? I guess, generation of sound will be some where related to atomic level since any form of object (Solid, Liquid, Gas) can create sound.
Comment: you can hear sound due to the vibration of air molecules hitting your eardrum within a certain range I guess
Answer: May I ask what you think of as sound?
If sound is the vibration of air- or in general any material agent- then sound is the sensation you get from the changes in the pressure of the air, it's what reaches your ear and then produces some signals interpreted in your brain. Sound is the vibration, not something produced by the vibration.
This vibration which is called by us sound is a mechanical wave define as a vibration in pressure or more general in particle displacement.
Hope this helps with your question.
Answer: The most common approach to model the sound radiation from a vibrating body is generaly the same as in all wave cases: continuity is the key. Let's say that a sphere is vibrating (changing it's volume periodically), then the acoustic velocity of the air particles just on the boundary with the body must be the same as the velocity of the sphere surface. It gives us boundary condition for solving the wave equations.
If your question is ment to be more focused on the vibrating body and aiming for atomic level, then phonon should be your keyword. But in that case your question is way too broad and it should be rephrased.
Answer: Take your hand and move it. By moving your air, you moving the air. This is what a vibrating object does - it moves the air. Sound is just the movement of air (or a liquid or solid).


Jmeter load test: verifying the speed of the service response

Question: I'm doing load test with Jmeter on web application. Recently I noticed that some of the service responses from the application server started taking longer time to arrive to the client (browser). While inspecting the application code I saw that those particular functions, responsible for the service request/response, do all the mathematical calculations inside the code itself, rather then querying database and do all the calculations there. My question is: will the application behave faster if data calculation is done in the database itself, or it will be faster to do all the calculation in the code (retrieving data separately from db), so I can advise to the developers about possible causes of the slowness. Thanks.
Answer: In most of the time, Reading and Writing from an external resource plus network latency has a negative effect on performance and people love to prevent it, if possible.
That is why the most common ways to increase the performance are:

To cache data (so you don't need to read the data from external resources like Database).
Process in memory, as much as possible (your case).

So I think the performance of your application should have been increased, unless the implementation is not good (e.g alot of thread blocking or poor-performance algorithm etc).
Answer: As a general principle,

if the calculations are set-based calculations, then they will definitely be faster one in the database.
if they calculations are pure mathematical then there should be no problem in them being done by the test suite, if the language is a compiled language.

It would be interesting to try and force the same calculation (if possible) in the database versus in your application.
Comment: I think the OP means the calculations are being done in the code for the application under test, not in JMeter. He was doing tests in JMeter, saw a slowdown, and looked at the application code in response.
Comment: Ah got you ... I'll tweak the answer


How can I reduce the cost of having a cell phone?

Question: In terms of cell phone plans the U.S. is the worst followed by Spain and then Canada.  Besides the obvious get rid of the phone option what other strategies can be employed to keep the costs down?
Comment: I am curious, though, how many people still consciously forgo a cell phone to save money and just not be bothered with it.  I haven't had one in over four years at least, and I find it fine.
Answer: I have a had a TON of success by negotiating. Just talk to your current carrier and let them know that you can't afford it and there are other more reasonable options out there and they will most likely be willing to help you out.
I wrote a few posts about how to negotiate with wireless carriers as well as one detailing my success.
Comment: Thanks! If anyone has a good negotiating story, I'd love to have you come over and guest post about it for me!
Answer: For customer who can get a Google Voice account:
Use one of your plan's preferred numbers and make receiving all your calls from the Google Voice number free.
I have t-mobile with their "Fav5" plan.  I put my Google Voice number as a fav, tell Google Voice to make the caller id be that number, and to transfer calls to my cell.  When people call me it comes from Google Voice and it is free.
Answer: My family has one of those "package" deals from Verizon where we get internet, cable TV, landlines, and cell phones all bundled together. If you're going to get TV and internet anyway, it's worth at least checking to see whether the package deal might be cheaper.
Answer: In our household, we pay for two mobile phones:
Our first phone is on a plan that I use heavily for data (including occasional tethering to a laptop while on the train), but I use very little voice.  So, I have a great data plan, but a minimal voice plan.  Next, even though I am gadget-oriented person, I try not to replace my phone too often.  I want to get at least 3 years out of every phone I buy, to reduce the amortized monthly cost of the phone itself.
The second mobile phone we keep primarily for emergency purposes or a very occasional call, so we bought a cheap prepaid Virgin Mobile phone, and we charge it up with $100 per year.  That amount was chosen judiciously:  As you can see on Virgin Mobile's Topping Up page, when the top-up is at least $100, the credit doesn't expire for 365 days.  So, the cost of carrying this second cell phone for the household – provided we don't use many minutes (and we don't) – is only $8.33/month + tax.  At the time we bought this phone we checked out all other carriers in Canada that had prepaid and none of them had a credit that lasted that long.
Comment: Chris, is Virgin Mobile using GSM technology yet?
Comment: No, I think they are still on Bell's CDMA network.  I wouldn't be surprised if they're planning GSM though.  Just makes sense.
Comment: Chris W. Rea - Thanks for the info. Also, looks like the [Topping Up](https://www.virginmobile.ca/myAccount/topup-now.do) href has changed.
Answer: I find that researching the various companies and taking time to choose the right plan for your calling and texting pattern is the way to go.  Sometimes people don't take the time to properly analyze their usage, instead simply choosing a plan that has an attractive monthly rate.
In our household, we text far more than we call, so we're on "unlimited" texting plans, with very small voice packages.  It's very easy to adhere to, because I chose plans well-suited to our needs.  That way, throughout the month, we don't have to pay unnecessarily close attention to our calling/texting volumes.
Answer: Switch to sprint, check out this article about it http://honestbanker.blogspot.com/2009/03/sprint-offers-best-bang-for-your-buck.html or check out cricket wireless, http://honestbanker.blogspot.com/2009/04/do-you-hate-cell-phone-contracts-try.html and also most everything plans are becoming rather affordable these days, try checking into those regardless of who your carrier is, but id look into sprint, they also offer like 15 percent discounts to almost everyone for some reason or another, like military, or many employeers, just ask them about it


What features should I look for in prescription eyewear for playing volleyball?

Question: What features should I look for in prescription eyewear for playing volleyball?  What type of store could I find it at?
Comment: @Ian great edit to rescue this question. A warm welcome to Sports SE.
Answer: The most important feature are: a wide lateral vision (so bigger curved lens than normal glasses) and an excellent grip on the head.
I can suggest deformable plastic linked to an elastic to wear perfectly (only if you feel comfortable with it).
These featuresare not so prevalent because the athletes usually wear contact lenses.
Here you can find info on sportglasses (not only for volleyball) and also a commercial link with a lot of example.
Those two example with no elastic  and elastic solutions to understand better.
Answer: There are two main things that you'll want to be looking at, the frames and the lenses.  Ale has already provided a good answer as to what to look for in frames, so I'll just add a bit on what to look for in lenses.
The lenses should be made of a shatterproof material, such as a polycarbonate.  You'll want to make sure the lenses are custom made to your prescription (duh!) and centered for your eyes.  At least in America, most optometrists that also sell glasses will do this lens fitting for you and custom cut the lenses to fit your frame and eyesight.  If you're playing mostly outside or with bright direct lighting, you may want to consider getting an anti-glare coating.
As to where to purchase them, most eyeglass specialists will have or be able to order suitable frames and install the lenses for you.
Comment: By "centered for your eyes", do you mean pupil distance?


Need a cover up for a face to make it more horror-ish

Question: Would like to create some sort of mask during post to make a persons face look more towards the horror genre and wondered what would be the best way of doing this? It would only need a 2d image to animate over but wondered how to go about it?
Comment: Have you seen the new face-mapping technology in Blackmagic Design's Davinci Resolve 14 (announced at NAB on Monday)? It might make things easy for you. The beta version is available for free on BMD's website.
Answer: Check out this video tutorial, might help: http://www.videocopilot.net/tutorials/demon_face_warp/
To summarize: You need to motion track the face and stabilize the footage with this tracking data. Good tracking points are the corners of the eyes, nose, etc (the new face tracker might help but I haven't used it much). Once your footage is stabilized you can apply whatever you want onto your actor's face. Then it is a matter of pre-composing everything and re-applying the motion to that precomposition.


Obtaining Licensing Info via API

Question: Is there a way to identify total user licenses and allocated licenses via API? We have multiple orgs and we wanted to keep track of license allocated to each org and how many of them are in use vs free by pulling that data from various orgs and showing it in a dashboard or something similar.
Answer: I've considered doing this and I don't believe there is a specific API call, the way I was going to do it was to use Selenium and screen scrape the Summary webpage.
Answer: There is an API Call available for organization submitted to Pilot Program.
Two fields are exposed for WEB SOAP query call if target org has that Pilot Program enabled.
I have created idea to make these fields Generally Available AND available through Apex Code, SOQL, Developer Console and Workbench. You may vote for it if you agree.
Another way is dirty, unreliable and fragile screen scraping. I consider creating custom package which does this job.
Also you might be interested in another related idea.
There are UsedLicenses / TotalLicenses fields from UserLicense object available only through API call and only available for organization subscribed for related Pilot Program.
=== update ===
I created recently a managed beta package which may serve as workaround for this. It screenscrapes company profile page and gets number of total license.
This package includes a User_License_Extended__c custom object which contains Total License number and Used Licenses number ( and some more fields ), these numbers are updated whenever a user is activated or deactivated or user profile is changed assuming package is properly set up with necessary data
Install link for production-like org https://login.salesforce.com/packaging/installPackage.apexp?p0=04t580000001ENa
More details and release notes https://patlatus.wordpress.com/2016/03/07/salesforce-uletas-beta-1-0-release-notes/

Obtaining Licensing Info via API


What is behind the "message redacted" in "Chiron Beta Prime" by Jonathan Coulton

Question: So there is this song, Chiron Beta Prime by Jonathan Coulton, where he tells the story of a family that is on a mining asteroid Chiron Beta Prime and working for the robots there. It is written as a letter for christmas to a relative. And there is a point where there is "message redacted" spoken over the track. Is there a "canon" text, that belongs there?
Answer: I love Jonathan Coulton and this is an interesting question. However, I think this is just regular Coulton humour.
The family is obviously forced by the robots to stay and work on the asteroid, that's what the lyrics are all about:

Merry Christmas from Chiron Beta Prime,
  Where we're working in a mine for our robot overlords.
  Did I say overlords? I meant protectors.
  Merry Christmas from Chiron Beta Prime.

The robots are apparently redacting the message preventing the family to send out a "hidden" emergency message:

That's all the family news that we're allowed to talk about.
  We really hope you'll come and visit us soon.
  I mean we're literally begging you to visit us.
  And make it quick before they [MESSAGE REDACTED].

The above lyrics snippets are from the official lyrics site, and I highly doubt that there are any "hidden" lyrics behind it. After all, MESSAGE REDACTED is part of the lyrics.
Answer: It's not canon, but I've always suspected it's "blow up the moon". It rhymes, it fits the meter and it also fits the theme very well.

That's all the family news that we're allowed to talk about.
We really hope you'll come and visit us soon.
I mean we're literally begging you to visit us.
And make it quick before they blow up the moon

But, as the accepted answer points out, the words [MESSAGE REDACTED] are the actual lyrics and the idea that they failed to get the message out is funnier than anything that could be there instead.
Answer: "Before they send us to the Moon" which scans as well as rhymes. Assuming the Moon is a scrapyard where there will be no more Andersons


How to set up Drupal 7 on Apache/2 without .htaccess files ?

Question: I would like to improve Drupal 7 and overall server performance by setting apache/2 without .htaccess files. How to configure apache/2 httpd.conf to achieve this?
Answer: You should be able to take the contents of the .htaccess file, and place them in your httpd.conf.  Exactly where depends on how you have your site running in Apache.
If you are using a virtual host, you would place everything inside a <Directory> section that matches your DocumentRoot, inside your <VirtualHost> section for the site.
If you aren't using a virtual host, then everything would (probably) still go in a <Directory> section that matches your DocumentRoot, but I can't remember the last time I didn't use a virtual host, even for servers with a single website on them.
You may get better answers over on ServerFault, as this isn't totally Drupal specific.
Answer: In a directory section that refers to your Drupal installation, you can do the following:
<Directory ...>
AllowOverride None
...paste contents of Drupal .htaccess here...
</Directory>


Input field label position, in context of view and edit mode

Question: We would like to use top aligned fields for our form page, wherein the label text is in bold and the input text, normal (not sure if this is the best scenario). In edit mode, this works fine. The same page will be seen as a view only page at a later stage. We would like to retain the same consistent look for the view only page. Have you come across any good practice, hygienic way of doing this? Any critical points we missing here?
Comment: Are you saying that the form looks exactly the same whether it's in view or edit mode? Do you have any mockups or screenshots?
Comment: the view and edit do not have to be exact copy. Its just the same grouping and format may be good to retain, so that user is in a familiar context when they revisit the page in view mode. Unfortunately i couldn't post an image since it asked for some point system.
Answer: If the people who enter the data will also be viewing it read-only, it makes sense that they will have an easier time consuming the data if the layouts for both are similar.
This is assuming that the read-only data shouldn't be in a table instead.
I like to push for labels being above their form fields because they are easier to read & use.
Comment: Great research link!
Answer: bold emphasises text and shows it as being more important than other non-emphasised text.  Do you really want to show that the label is more important than the content?  When you're filling in a form which is blank, I would say that the labels are worth emphasising, but if you want the same look and feel in view and edit modes, then you should look at other options.
Consider using something like mobile forms which handle it very well.  It should be sufficient to change the background colour of a field to show that it is editable when you are in an edit view or change the border colour.
Comment: Thanks John. I agree in view mode, the labels shouldn't be bold. My query is specifically if the value is entered in second line in edit mode and in view mode if the label and value is aligned in same line will it be too much of a inconsistency, specially if the form page is long and two column.


Open Sicilian Defense

Question: Has the dragon variation of the Sicilian defense lost favor to the Najdorf variation? I rarely see a fianchettoed bishop in the Najdorf defense.
Comment: I played it in my youth (70's), from both sides. My opinion now is that it is spent from the black side, which is why you don't see it very often at top level chess. The Yugoslav Attack is ferocious if not defended against correctly. Truly, one misstep by black and he can be mated. On the other hand, if black survives he generally has a better endgame. But, I think black can do better using other variations in the Sicilian Defense.
Answer: The Dragon Variation of Sicilian is complex and difficult to defend sometimes against White's ferocious King side attack. I will recommend Dragon to those Players only who are not timid enough to sacrifice material against activity. Since in Dragon normal theory Black does a Castling with his fianchettoed Bishop & the g6 pawn is hooked to White's h5 pawn sacrifice.
Unlike Najdorf where White also attacks mostly on K-side but Black has equally good chances to attack White on the Q-side since with a6 on move 5th b5 from Black comes faster and dislodges the Knight on c3. In Dragon the attack from Black is somewhat slow compared to Najdorf.
In Najdorf there is one variation where Black does a Fianchetto also. Below is the variation:
<code>[FEN ""]

1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.f4 g6
</code>
and with any other move from White like Qf3 or Be2 Black puts his Bishop on g7 .

Open Sicilian Defense


SSRS not available in SharePoint server

Question: I have 2 SQL Servers (SQL01 has all Content DBs and SQL02 has all Service App DBs) and 2 SharePoint 2013 Servers with Enterprise edition. Just couple days ago, I installed Power Pivot in SP mode and Analysis Services on SQL Server(SQL02). I successfully configured the Power Pivot, but I don't see SSRS Services Application listed under Manage Service Application to create one.When I try to run "Install-SPRSService" on SP Servers, I get 'The term Install-SPRSService is not recognized error. What am I missing here? Please help.
Answer: Couples of things to make sure:

install SQL Server Reporting Services in SharePoint mode
the SQL Server Reporting Services Add-in for SharePoint 2013. I think this part is missing that's why your command is not recognized.

Check more here https://msdn.microsoft.com/en-us/library/ms144289.aspx#bkmk_no_ssrs_service
Comment: I have installed both. Also I have Reporting Services- Native and Analysis Services on all same instance. Is that right? And do I need to install these on both the SQL Server. Right now, I have it on only one server(SQL02).
Comment: I uninstalled Reporting Services native mode and reinstalled "Reporting Services - SharePoint" and "Reporting Services Add-in for SharePoint Products" on both SQL servers. But I am still getting the same error. The term 'Install-SPRSService' is not recognized as the name of a cmdlet,.... I am working on this issue for sometime now, but couldn't find a solution. Any help?? Thanks
Comment: Is sharepoint server are different than sql server or everything on one box?
Comment: Did u install anything related to ssrs on sharepoint server?
Comment: I made a mistake in my previous comment and I deleted it. I installed "Reporting Services - SharePoint" and "Reporting Services Add-in for SharePoint Products" on SharePoint servers and installed everything on SQL Servers. And now I could create SQL Servers Reporting Services on SharePoint.

SSRS not available in SharePoint server


How can I view the typical flight prices between two airports prior to the COVID-19 pandemic?

Question: How can I view the typical flight prices (ideally during a given date of the year) between two airports prior to the COVID-19 pandemic? Google Flights only show the future prices.
Comment: This type of information is closely guarded and not generally available without paying a lot for it.  Sorry.
Comment: @lambshaanxy thanks, too bad. Seems easy to cron some data export script and save somewhere.
Answer: Not really an answer but too long for a comment:
Even before Covid there was no such thing as "typical" prices. I've flown US east coast to China for as little as $400 and also for over $2000: Same plane, same seats. I've flown business class to LA since it was cheaper than economy (on the same flight). Even budget carriers like Ryan Air will vary the prices by factor of three or more from one day to the next depending on how full the planes are. We flew a multi city itinerary and a single small tweak at one routing reduced the price for the total thing by a factor of 5.
In order to answer the question, you would need an operational definition of "typical".
Comment: thanks, let's say typical = median. I have a very different experience on my side, round-trip, economy prices between US west coast (SFO) and China's main airports were almost always below 1kUSD, and the typical price was between 500 and 700 USD except for typical vacation dates.
Comment: Right, a single number just doesn't cut it. There's so many variables determining a ticket price that averaging them all out would require a whole lot of subjective choices. Just as a datapoint, I have tens of tickets between several European airport pairs over the past two years, and the spreads between the cheapest and the most expensive ones are typically a factor of 5 or more. And that's already after eliminating the worst confounding factors: same booking class, no luggage or extras, same day of week and time of day, booked roughly the same time in advance.
Comment: @TooTea thanks, interesting, my experience with prices for flights between Asia and SFO is drastically different: the factor is definitely less than 2. But that's ok, in that case one could simply indicate stdev/IQR in addition to the median.
Answer: The closest thing to a useful answer is here. ExpertFlyer is a subscription service that can show historical fares up to a year ago. This is not enough to go back before COVID-19 now, but it was at the time Franck Dernoncourt's question here was posted.
The historical fares don't necessarily indicate prices at which flights could actually be purchased, because (particularly on the highly discounted end) they could be fares for which the airline did not release any seats at a given time. But they are of some use as a guide.
Also it's important to note that airfares depend on two dates, the flight date and the purchase date. The effect of COVID-19 (or any other unforeseen event) on airfares would be most directly associated with the purchase date. That is, fares quoted before March 2020 for travel after March 2020 would still be "normal".


What is perpetual check?

Question: I know that there is 6 types of draws including mutual agreement, stalemate, insufficient material, 3 move repetition and the fifty move rule, but I do not know what is perpetual check.
Comment: Perpetual check is not one of the types of draws.
Comment: not a type of draw?
Comment: Perpetual check can result in threefold repetition. However, in the rules, you cannot claim draw because of perpetual check, only because of threefold repetition.
Comment: Okay then it is threefold repititon.
Comment: Even if perpetual check isn't mentioned in the rules, it is still an important concept both in strategy and tactics.
Answer: Perpetual check isn't a thing any more. But the idea is that one side demonstrates that they can keep putting the opponent's king in check, regardless of what the response is. Sooner or later it will turn into a threefold repetition or run afoul of the fifty move rule.
Answer: Well... Yes, it is still a thing, many top level games end in threefold repetition, but that is due to the perpetual check. So in a way, you can't draw a game by perpetual 'per se' but perpetual check can implicate threefold repetition occurring.
Answer: FIDE Laws of Chess do not recognize "perpetual check." They only recognize a case where the same position appears 3 times on the board. If it does, the player about to make the move that will cause it to appear for the 3rd time may claim a draw, but must do so before he makes his move. Once he makes his move, he no longer has any rights to claim a draw, because this can only be done while the player is still "on move".  Once he moves, his opponent is "on move".
The term "Threefold Repetition" is widely used, but misleading. Many players take it to mean what it seems to say, that a repetition has occurred 3 times, i.e. the position occurred once (no repetition), then again (1st repetition), then once again (2nd repetition; draw claim already available), and then one more time (3rd repetition, but 4th occurrence of the position; draw claim still available).  It's quite possible that 2 repetitions may occur, but the opponent may then vary to avoid a draw claim, in which case the 3rd repetition would not.  If this came about, the player who wanted to claim a draw missed his chance, and he won't get another.
It pays to understand the rules, not just know what people call them.

What is perpetual check?


White Walkers sparing the odd member of the Night's Watch

Question: Why do White Walkers spare members of the Night's Watch such as Will from the pilot episode and Samwell Tarly, although they don't seem like a merciful species?
Comment: See also: [Did the White Walkers spare Sam?](http://movies.stackexchange.com/q/11810/1876) on *Movies & TV SE*.
Comment: Sam's not odd! He's *uncommon*
Answer: They don't
Will's case:
In the first episode, he managed to escape. He just ran. Fast. In the books, although it is not the same character, he also escapes.
Samwell Tarly: In the scene you refer to, it did not clearly appear that there was more than one White Walker. So once Samwell

 kills him with the obsidian blade

they are safe. They run "just in case", in my opinion. Spoiler alert: I describe what happens in the books and what will probably happen in the remaining episodes:

In the books, Samwell and Vere are surrounded by Others (books equivalent to White Walkers) and they are rescued by "Coldhands", a mysterious character.

EDIT after evilsoup comment about the events at the very end of the second season:
At the very end of the second season, Sam is surrounded by a bunch of wights, and the White Walker which looks at him doesn't kill him. It does not happen this way in the books. I can't explain this part. Maybe the White Walker looked at the rock which Sam was hiding behind, and not directly at Sam.
Craster: He is safe because he is a "godful man" (these are his words) : he gives them his own baby boys to satisfy them. It appears giving them a baby boy once in a while is enough to ensure your safety.
Comment: In the books, Sam and Gilly is surrounded by *wights*, not Others. If they had been surrounded by Others, I doubt Coldhands would have been able to save them.
Comment: At the end of the second season, Sam is surrounded by an army of Wights and at least one White Walker - it looks him in the eye and sneers at him. For some reason, they didn't kill him - there was a battle soon after that, but it seems like there was more than enough time to kill Sam, and they don't.
Comment: It will be interesting to see what drives the white walkers, maybe some more context on why they like the babies will be forthcoming.
Answer: Some say that the Others are really trying to protect the world from the destruction that the fire breathing dragons will bring this world and someone said that George Martin hinted at that by saying, they are misunderstood creatures. That is why they spared some characters.

Of course that doesn't seem to stay true to the books events where they killed a lot of people. But if it is true, the white walkers would need to kill their most devoted enemy (the nights watch) to be able to help the rest of the world undistracted.
Comment: Wow... can you find a reference from GRRM for this? It would completely change my (and I suspect, _our_) understanding of the book series!
Comment: That would certainly be a very interesting development.  Their apparent bloodlust could also be explained by an instinctual drive to wipe out anyone with even a trace of Targaryen blood.
Answer: YOu forget that in the first episode of the third series, a deadman tries to kill Sam Tarly...
In the first episode, the whites let the ranger go (as enemies did) so that there would be someone to tell of whats coming..(to strike fear in their enemies)..
 I suspect the whitewalkers and dragons will battle (as have NEVER done in the histories an dlore of westeros) ..
The whites are smart and honourable..thats all...they sense that Samwell is no real threat (projects cowardess) so they leave him...
That makes them VERY interesting...more honourable than a dragon could ever be (i.e.killing little girls)..


How can one determine approximately what percentage of options trades are buyer-initiated vs. seller-initiated?

Question: How can one determine approximately what percentage of options trades are buyer-initiated vs. seller-initiated?  What measures of order flow are available specifically for options, preferably for individual contracts covering specific strikes and maturities?
Comment: @RYogi I edited the question to reflect what I believe is the OP's intent, namely disentangling buyer vs. seller initiated trades and obtaining/estimating order flow for options.  I also removed the superfluous example.
Comment: Can you be more specific? What do you mean by "% buying" and "% selling"?
Answer: For every option bought there is an equal quantity of options sold.
For example, when reporters say "stocks dropped because of heavy selling", this is strictly speaking impossible. For every stock sold someone is on the other side of the trade -- so stocks dropped because of heavy buying as well with equal intensity. What is happening is that the willingess to pay for stock (demand curve) has shifted to the left, therefore prices have dropped.
Comment: But each trade is either buyer or seller initiated, no? Open interest doesn't help in answering Beatrice's question. Instead, one needs order flow.
Comment: I disagree. Markets are clearing -- quantity sold = quantity purchased. Let's say I post a limit order to sell an option on the inside ask, and someone else posts market order to purchase an option. Both buyer and seller "initiated" the trade. This is the same fallacy as saying "money flowed into stocks" today. Money only flows into the stock market on an initial public offering -- not on trades on the secondary markets. Maybe Beatrice is asking to estimate the demand and supply curves for options, or measure the cumulative tick.
Comment: I read the question from a microstructure perspective: "Buyer/seller initiated trade" is common parlance for price taking in a certain direction, in contrast to providing liquidity with a limit order. This decision is an execution decision. Switching from cash to equity (or vice versa) is an allocation decision.
Comment: Got it. In this view, you are correct that order flow would be req'd.
Answer: Pan and Poteshman (2006) were able to obtain a "unique dataset from the Chicago Board Options Exchange (CBOE) which breaks down the daily trading volume of both call and put options into four categories according to whether a trade is initiated by a buyer or a seller, and whether the initiator opens a new option position or closes an existing option position."  I don't know where they got the data, but obviously this would answer your question.
Otherwise, you could use the Lee and Ready (1991) algorithm to infer, with some noise, whether a trade is buyer or seller initiated.  In fact, Amin and Lee (1997) did precisely this in a paper studying options trading around earnings announcements.


How do you leave a guild in Godville?

Question: Is it possible?  I want to leave the guild the game put me in and create my own.
Answer: You can only join a guild after your hero reaches level 12. If you are already in a guild and want to join another one type in "leave guild and join "Guild Name" guild" (this works best when your hero is idle outside of town; do not cancel your current quest first).

How do you leave a guild in Godville?


How can I increase the size of my mint leaves

Question: Recently I observed that the leaf size of my mint plant has started to shrink. Previously the leaf size used to be around 2-2.5cm. Presently it has shrinked down to 1-1.5cm. What might be the reason? How can I rectify this issue. I water the plants daily. It recieves 4-5 hrs of direct sunlight. I tried to provide some shade however, the leaves size is still not growing. I feed them with urea once every month.
Answer: This is the same effect we see when a clump of mint is planted in open soil - it starts to form a circle growing outwards, and as the roots get thicker in the middle of the circle the leaves get smaller but those on the outside remain big and healthy since the roots have room to expand. We can maintain larger leaves artificially by heavy feeding but even this starts to fail.
The remedy is to turn the plant out of the pot, extract some healthy roots and plant in fresh soil. In your case you might be able to dig out one half of the mass of roots in the soil and use this for fresh propagating material, leaving the other half still producing leaves. Then you have the basis for a renewable system, one young and one older planter, with each being renewed at a different time to ensure a continuous supply of leaves.
Answer: By the look of it, I think Colin is right about it being rootbound. Plants seem to get smaller leaves, sometimes, when they can't grow to their full potential.
Low phosphorus is also known to reduce leaf size.