What is another way to say "different levels of interpretation"?

Question: I am writing a five-paragraph essay about why my assigned book is a classic. One of my paragraph topics is that it offers different levels of interpretation (you can read it just for the thrills of the story, to identify themes, to interpret it for yourself, etc). But I can't say "different levels of interpretation" when I introduce it, refer to it, and conclude it. Suggestions?
Comment: Hi Gus,  per our [FAQ](http://ell.stackexchange.com/help), specifically the ["asking questions"](http://ell.stackexchange.com/help/on-topic) section, writing advice is not on topic; you should probably try http://writers.stackexchange.com instead.
Answer: One meaning of the word "read" is "interpret".  So you can write:

The <story> can be read at several levels.

Substitute the type of work (such as "book", "novel", "poem", et cetera) in for <story>.  (Or you can substitute the name of the work in for "The <story>".)  You can expand your parenthetical note (about the different levels of interpretation) to provide some or all of the content of the paragraph.
When I am stumped for a good way to say something, I often write out a first draft of what I want to say.  For example, "different levels of interpretation".  After I have finished the rest of my rough draft, I look up one or two key words (such as "level" or "interpret" or "interpretation") in a thesaurus.  In this case, "interpret" has "read" as a synonym.


Piano in all RH chords

Question: How would I play a song in all righthand chords? Would i just play all the melody notes as chords? (My instructor used to do it, he would say it leaves the LH free to do other things)
Answer: Usually this technique allows you to add musical interest by filling out the left hand with more harmonies or a counter melody.
You'll want to keep the melody in its own musical space - so either play it with the top of the right hand or the bottom of the left hand.
To keep the melody on top, build the chords with the melody notes at the top of the chord, and try to leave a space (>3rd) to the next note. You'll probably have to leave a note out of the chord to accomplish this, probably you'll want to lose the fifth, but that may vary between chords. Follow standard voice leading rules. This leaves the left hand totally free to do an independent voice like a walking bass, or you can use it to fill out the rhythm line. You can also help the melody stand out by playing it on the beat and the chords off the beat.
To put the melody in the lowest part, you'll want to probably play it in octaves with the left hand and keep any other voices >5th away. The right hand can play the same chords as the left normally would, but generally these are broken into a more virtuosic pattern.
In any case, this is best executed by someone with fairly advanced technique, but it can also be helpful for building left hand independence.

Piano in all RH chords


Could someone recommend an introductory book on epidemiology?

Question: I'm hoping to learn the basics of epidemiological methods, terminology, etc. I come from a background in statistical economics, and I'm moving into the economics of public health. I don't know if epidemiology uses separate statistical methods, but I presume it does. I know discussion questions aren't recommended, but please list any reasons you have (personal experience, ease of introduction, etc.) for texts you would recommend.
Answer: There are two books I'd highly recommend for someone starting to dabble in Epidemiology. The first is Kenneth Rothman's Epidemiology: An Introduction, which I'm affectionately going to refer to as "Baby Rothman" from hereon out for reasons that will become obvious.
Baby Rothman is an excellent "getting your feet wet" book. It's simplistic, and clearly designed for someone with no background in Epidemiology, so it starts from things that, if you have a statistical background, you might find a bit dull. But it accomplishes two key tasks:

A basic treatment of the subject from a pre-eminent methodologist and advocate for the field that doesn't make some of the sloppy slight-of-hand mistakes many introductory books do.
An introduction to the "vocabulary" of Epidemiology as a field - what we call things, how we thing about effect estimates, etc.

The second book I would buy would be Modern Epidemiology: 3rd Edition by Rothman, Greenland and Lash. This is the definitive reference book for most epidemiological methods  currently used in the field. As I said on a related CrossValidated question, ME3 is the only epidemiology book that has always come with me, regardless of what project I'm doing, and which I have routinely found invaluable.
The other benefit of the book is that it's "platform agnostic". It's not going to try to teach you a statistics package - its going to teach you the science and philosophy of Epidemiology, the actual doing of the science, rather than the toolkit. Without that kind of methodological rigor, you can be a wizard at your language of choice and still do bad science.
If I were only going to buy one book, it would be ME3.
Comment: Excellent answer. The other post you linked is also extremely helpful. I actually had Rothman's beginner introduction in the stack of books I borrowed from my uni's library already, and upon first read I quite like it. Thank you!
Answer: Here is an online book of epidemiology for the uninitiated. I used it to get a basic understanding of epidemiology.
http://www.bmj.com/about-bmj/resources-readers/publications/epidemiology-uninitiated
Comment: I don't suppose that book is available as a PDF too, correct?
Comment: @pythonscript no, but it should be simple to cut and paste into a libre office doc and export to pdf. Or if you need it in epub not sure how to do that.
Answer: I found Clinical Epidemiology by Robert and Suzanne Fletcher extremely useful  to gain some quick insight in to the broad area of epidemiology during my first year of post-doc. It covers a wide-range of topic in clinical research and epidemiology in an accessible format with several examples and extensive illustrations.
Comment: That may be a bit advanced for me, since I do not come from a pharmacy or medical background, but I'll take a look at it for good measure once I gain a stronger understand of the field.
Answer: Leon Gordis' "Epidemiology" was my textbook in undergrad and it was quite easy to follow. It's a small textbook as well so you can read through in no time.
Comment: Small textbook with a hefty price! I may look into it, though.
Comment: If you look around you can find it used or by electronic means.


Do any NetworkManager VPN plugins support IPv6?

Question: Do any of the NetworkManager VPN plugins support IPv6?  The two I've tried so far (PPTP and StrongSwan) only show an "IPv4" tab.  I would have thought at least the IPsec one would support IPv6?
Answer: IPv6 over the VPNs in NetworkManager is not currently supported in 12.04 and prior releases of Ubuntu. It is a new feature introduced in a further release of NetworkManager (0.9.6.0), so it will be available, to begin with, on the OpenConnect plugin only. Such support will be available in Quantal Quetzal (Ubuntu 12.10).
Answer: As far as I know, no plugin for Network Manager supports IPv6. Even OpenVPN does not support it straightforward.
You can drop Networkmanager and use OpenVPN directly. I have put my experiences on setting up OpenVPN+IPv4+IPv6 on Serverfault: How can I setup OpenVPN with IPv4 and IPv6 using a tap device?.
Answer: There are two ways to handle IPv6 remote access.
OpenVPN and the like do an IPv4 tunnel but don't handle IPv6 which has an entirely different stack.  If you have a /48 or /56 IPv6 allocation you can create a /64 network and use and 6to4 tunnel to connect over the VPN.
Use native IPv6 roaming.  You will want to enable IPSec for your IPv6 network if you do this.  The roaming server will need an IPv6 address where it is.  It then notifies your IPv6 router where to route its traffic.  This is designed to handle individual systems like laptops.  At a minimum, the headers should be secured with IPv6.
Comment: Right, IPsec tunneling stuff is cool, but I'm looking for user-friendly GUI solutions if they exist.
Comment: @singpolyma: I don't think they are here yet, and I hope  the never are.  Support for encrypted remote access is built into the IPv6 protocol.  I think open-source efforts would be better spent providing GUI solutions to support IPv6 native tunneling.  I have seen a posting for adding an IPv6 addresses and route to an OpenVPN tunnel. It appears OpenVPN supports tunneling IPv6 in TAP mode.


Attic Fan and LEDs

Question: My attic fan stopped working, I swapped it out for a new fan with thermostat. Still not working, I suspect that recently installed LED lighting in my kitchen may be causing this problem with the attic fan. After I moved into the house 17 years ago, the attic fan stopped working. The put in a new fan then, but the fan continued to not work. I finally tracked the problem down to CFL bulbs that had been put into by outdoor house lights. Once I replaced the CFLs with normal incandescents, the fan started working again. The only thing I've changed lately is installing those LEDs in the kitchen. I had assumed that the attic fan was on the same circuit as the outdoor lights, so the kitchen upgrade wouldn't effect it, but now I'm not sure. I'm about to call an electrician, but I'm wondering if there is something else easy that I can check to fix this problem. I'm also open to the possibility that the LEDs are NOT the issue. Thanks
Comment: What make and model was the old fan, and what make and model is the new fan? And by "not working" I take it you mean it doesn't spin at all?
Answer: Your fan is wired in series with the lights
When the person installed the fan, the wires that he needed (hot and neutral) simply were not available in the box he wanted to tap.   So he did something crazy like tap across a light switch (hot and switched-hot).
Anyway, there's a reason he did it that way: doing it the right way was too difficult.  So you should expect the solution to this to be non-trivial and may involve fishing some cables through walls.

Attic Fan and LEDs


Triplet loss - what threshold to use to detect similarity between two embeddings?

Question: I have trained my triplet loss model using FaceNet's architecture. I used 11k hands dataset. Now I want to see how well my model performed, so I feed it 2 images of the same class and get back their embeddings. I want to compare the distance between these embeddings and if that distance is not larger than some threshold I can say that the model correctly classifies these 2 images as of the same class.
How do I select the threshold value?
Is the threshold value the same as the margin hyperparameter used in triplet loss function? (alpha = 0.2)
After examining FaceNet's code and OpenFace's code, I saw that they test 400 thresholds raging from 0.0 to 4.0 ([0.00, 0.01, ..., 3.99, 4.00]) to find the one that gives the most accurate results and then treats that as the overall accuracy.
You can see it implemented in FaceNet here and in OpenFace here.
Why does it select 0.01 as the step from 0.0 to 4.0? Why not 0.001 or 0.0001?
Moreover, FaceNet uses LFW dataset. LFW dataset defines its own specific protocol for evaluation which is implemented in FaceNet and OpenFace. So isn't it fair to say, that the way FaceNet and OpenFace evaluate their model is exclusive to only LFW dataset?
In that case, how should we evaluate our model on different datasets that LFW?
Answer: you can use ROC_CURVE from SKLEARN to determine your Threshold,
here is a link tha can help
https://scikit-learn.org/stable/modules/generated/sklearn.metrics.roc_curve.html


Successive relative clauses

Question: Is the use of two or more successive relative clauses common or grammarically accepted in English?
As in "The man who is sitting in the wheelchair and who has a broken leg. Or "The man who is sitting in the wheelchair and whose leg is broken."
I know, of course, there are ways to shorten them, but I just want to know if it sounds grammatical to native speakers of English to use successive relative clauses, whether in spoken or written language.
Comment: @Rathony I know the shortened form. I wanted to know if using successive relative clauses is common or grammatical in English.
Comment: And grammatical?
Answer: Grammatically there's nothing wrong with it. An example dialog:

Person 1: Do you see that man?
  Person 2: What man?
  Person 1: The man who is sitting in the wheelchair and whose leg is broken.

However, to me it sounds sort of long-winded and unnecessarily verbose. Try:

Person 1: Do you see that man?
  Person 2: What man?
  Person 1: The one in the wheelchair, with a broken leg.

Note that "on the wheelchair" is possible, if the chair is tipped over and you are literally sitting on top of it, for example. A man with a broken leg would most likely sit in the wheelchair, not on it.
Answer: Yes, it is perfectly grammatical. And yes, it is perfectly common, too.
Here are just a few of the many examples from the Corpus of Contemporary American English and the British National Corpus, showcasing a variety of patterns (emphasis mine):

In a more elegiac vein, they read like an homage to the late Cy Twombly, who died this year and whose deceptively elegant scribbles, mysterious
pentimenti and cryptic, barely legible text passages are channeled here.
Houston Chronicle, 2011

I wasn't actually invited to the party in question,
but I had a friend who got me in, and whose name I will not reveal.
The fourth wall, Williams, Walter Jon., 2012

It was that young couple whose vehicle would be crushed
and whose survival would amaze a community.
Denver Post, 2012

The position is, of course, quite different if the witness knows the person concerned well enough to say: 'I was hit by a man I know well and whose name is Jack Spratt.'
The Criminal Law Review (1985–1994)

It is outrageous that the name of a man who is so completely discredited, and whose actions run so contrary to everything that America is supposed to be about, should be emblazoned in gold on the federal law enforcement building in Washington.
Bookseller, London: J Whitaker & sons, 1993.

Edit: in response to comments, here are more patterns still, with additional focus on those most similar to your example, and beginning with one that is exactly the same in every respect.

"I don't see that it's in our community's best interest to swear
allegiance to one Democratic candidate when there is another candidate who is wooing us and whose record is very credible on our issues."
Atlanta Journal Constitution, 1999

In a 1988 case, an employer confronted a worker who'd been performing poorly and whose wife had expressed concern about his drinking, only to be hit with $100,000 punitive damages when it turned out his problem was depression rather than booze.
Washington Monthly, 1997

"Trace amounts of a food allergen can cause a severe reaction, and just because you had one reaction one time doesn't mean it will be the same type the next time," said Schwartz, who is allergic to fish and shellfish and whose daughter is severely allergic to peanuts.
San Francisco Chronicle, 2010

I attend the dance training session presented by La 2e Porte gauche
(Second Door on the Left), a group influenced by Michel Reilhac's Bal Moderne and whose members presented to the public Marie Chouinard's
choreography for Orpheus and Euridice.
Art Journal, 2011

Follow the links for yourself to browse the hundreds upon hundreds of more examples.
Comment: The OP's example is not same as your examples (probably except for the last one) as the former can be shortened by omitting "who is" and changing the relative clause to a prepositional phrase (with a broken leg), while 4 of your examples can't.
Comment: @Rathony: so what you're saying is I was thorough and covered more than one base. Why oh why would anyone ever do that?! The horror.
Comment: But being serious for a moment: just what on Earth has the answer to whether something is possible have to do with how it can or cannot be changed? Mind you, that's a very common misconception round these parts. People will ask "is X grammatical", and then get the answer, "yes, because you can reword it as Y which is grammatical" or "no, because you can reword it as Z which is ungrammatical". But the question never was about Y or Z. It is about X. And my answer here is about X. Your Y and Z have nothing to do with anything here. We are talking about X.
Comment: You might have covered more than one base, but the OP is asking that specific sentence (which can be shortened) is grammatically correct and widely used instead of "The man with a broken leg sitting in the wheelchair" or "The man sitting in the wheelchair with a broken leg" . The question sounds more like asking us to compare them rather than whether two or more relative pronouns could be used successively. I think A.P also understood that way.
Comment: Wevs. I can provide hundreds of examples more, I don't care. Not that it changes anything at all. The answer to the question as stated was, is, and stays the same: a resounding yes. I cannot quite second your speculation that the question is asking something different from what it is actually asking (in this particular case, mind you; generally that happens a lot as we know), but of course if the OP has something different in mind, they can easily edit it to say just that.
Comment: You are right. There could be two possibilities. One, as you stated, he asks if it is grammatical to use two relative pronouns, which is rather a general question. Two, the OP is not sure whether he could use the example sentence even if it could be shortened, which is rather a specific question. We have two answers, yours for the former, A.P's for the latter. We could wait and see how he responds. BTW, Your fourth example is shortened and your second example can't be shortened because it has a different tense.

Successive relative clauses


Service Bus for Windows Server - Security/Permissions

Question: I've been experimenting with Service Bus for Windows Server.
First some information about my environment.
I have two Windows 7 boxes (let's call them Host and Client). They both belong to a workgroup (no domain). Each machine has two user accounts (let's call them Admin and User) and the passwords match. On Host the Admin account is disabled and User is a member of the Administrators group. Service Bus for Windows Server is installed on Host. It was installed by the User account. The service runs under the User account credentials and User is listed as the ManageUser for the ServiceBusDefaultNamespace.
I've managed to get a simple Sender and Receiver working (hacked from the Azure Service Bus examples) when I run them both on the same machine under the same account that Service Bus was installed.
Then I tried copying the Sender to Client and running it. I had some problems with certificates but I've gotten past those. If I log onto Client as User the sender works. If I log onto Client as Admin the sender gives me a (401) Unauthorized. If I enable the Admin account on Host, then the Sender works.
All of the above makes a certain amount of sense. Host is trying to authenticate the request and when it finds the corresponding Admin account disabled it denies the request but it seems to create a slight inconvenience in that it requires me to have active accounts on all machines.
After a bit more digging, it seemed like I should be able to specify the account. When creating the MessagingFactory I'm creating a TokenProvider, and the TokenProvider allows me to specify a different set of credentials.
MessagingFactorySettings mfSettings = new MessagingFactorySettings()
{
    TokenProvider = TokenProvider.CreateWindowsTokenProvider(
        new List<Uri>() { rootAddressManagement },
        new NetworkCredential( "Host\\User", "<User's Password>" ) )
};

But I still get the 401.
I guess I'm trying to figure out how to run (potentially) multiple Senders on different machines without requiring every account that a Sender might run under having an active account on the Host machine. Even in a domain-based environment it seems I'd run into this issue if the domain account under which the sender is running doesn't have privileges to access the host machine.
Answer: For workgroup machines, when specifying the network credential, don't add the host name, only the user. That should let your request be properly authenticated:
MessagingFactorySettings mfSettings = new MessagingFactorySettings()
{
    TokenProvider = TokenProvider.CreateWindowsTokenProvider(
        new List<Uri>() { rootAddressManagement },
        new NetworkCredential( "User", "<User's Password>" ) )
};

This other thread has more information on the setup, if you still run into problems.


What is the worst opening move, and why?

Question: Grouping of initial moves of a chess game are well known, though I've never seen analysis of the worst possible opening move, any thoughts? If so, please provide more than just a move, but the exact reason why such a move would be the worst assuming such a move was against a GM.
Answer: 1. f3 is almost certainly the single worst move.  It irrevocably weakens white's king position without doing anything useful.
Other moves like 1. b3 and 1. g3 prepare to develop a bishop, so they're not so bad.  1. c3 doesn't do too much for white, but it also doesn't hurt him.
1. a4 and 1. h4 both ignore the center, but they do help develop the rooks, and there are positions where 1. a4/h4 can be useful (especially when the kings have castled on opposite sides of the board.
Comment: `1. a4` can be met with `e5`, the bishop blocking development of the rook. It gives black a lead in tempo and center control with nothing gained immediately. It also stops you from controlling `b4` where knights and bishops sometimes like to go. It's true `a4` is sometimes useful whereas `f3` is rarely played and that `f3` weakens the king's safety, blocks development of the knight, and has little benefit. It's hard to say which one is worse. I'd guess `f3` just because it weakens king safety. Although engines aren't the best at openings, Stockfish gives `f3` a `-0.9` and `a4` a `-0.2`.
Answer: I agree with Andrew on 1. f3 (Barnes Opening).  No first move can be decisively wrong, but some first moves are questionable.  In Chess Opening Theory (Wikibooks):

Quite a rarely played passive starting move that gives up White's first move advantage. White's position is slightly weakened by the White King exposure to a check on the h4 - e1 diagonal. The kingside Knight's favourite developing square f3, is also not currently possible. In fact, this is arguably the worst possible first move by White.
No stats as 1. f3 occurs rarely among serious chess players.

Next on the list would probably be 1. h4 (Desprez Opening):

1. h4 is a rather useless move that does nothing to assist the important central squares. No top masters have ever used it in professional play, although some, most notably Hikaru Nakumura, play it during blitz. It could be said that White has made his position worse, as castling kingside is now less attractive.
This move is rarely seen among serious chess players.
Answer: The other moves cited, especially 1.f3, are bad, but I would rather plead the case of the ugly Grob opening, 1.g4?.
Pawns do not go back, so this double step weakening is much more committing than a one step pawn move. After, say 1...e5, White has not only lost time, he has also:

Self-destroyed the most natural shelter for his own king, reached by short castle.
created weaknesses for himself, as Pg4 can and will be targeted by Bc8 or Ph5.
got himself a disadvantage in the fight for the center.

If, in some kind of handicapped game, I could choose my opponent's first move in order to maximize my chances, I would rather force him to play 1.g4 than anything else.
Comment: Although engines aren't the best at opening moves, Stockfish 14 scores `1. g4` as `-1.7` and `1. f3` as `-0.9`.  It's the lowest scoring first move.
Comment: You could say that at least 1.g4 enables one development move (Bg2) instead of preventing one like 1.f3 (Nf3), but yeah. That's just a small comfort that still doesn't make the move "good".
Answer: For an objective take on this question, one might take a look at the Chessok Opening Tree:

1.f3 -0.33
1.g4 -0.29
1.Nh3 -0.22
1.b4 -0.18
1.h4 -0.18

Given that white should be able to achieve a plus of 0.11 (according to the Tree) these are the only moves that not only lose the first move advantage but more than reverse it.
Of course these computer evaluations have to be taken with a grain of salt, but they do bear out the intuition of experienced players and provide some food for thought (especially to adherents of the Sokolski …).
Comment: I don't think that the way the leaf evaluaton parameter have been historically optimized would carry much of the expressable intuition intented by experienced players, they would have to understanding globlac optimization of some function basis (I am not even talking about NNue), the global mathematical components mutual interactions or multidimensional independence have never been studied or likely on the mind of niether de developper at the time and how they would be precenting their whole algorithm in chess interpreatable ways.
Comment: The communication would (and likely has) have been on isolated chess theory concept (via their words, themselves not really meant as measurable truths, but calibrating points of raw dichotomies, meant to attract the rest of the brain, its intuition, to firt the future experience in that "bracket".
Comment: The leaf evaluation function evolution has been frozen one dimension at a time since the first shots in early AB engine types of which SF is the epitome.  With NNue, it was officially frozen even more leaving all improvements to the evolution of NNue and its docking back into the SF search and classical leaf evaluation function (that last part frozen, but still what NNue is being evolved to universally approximate given its reduces feature set at input of the full position information).

So by objective, you were right to add the grain of salt.  Developed above.
Comment: In the first comment I should insist on correcting an important typo. I meant "the way that the leaf evaluation function parameters"..  parameter should have been plural, with emphasis.  But the optimization process in fish-test, AFAIK, has always been one parameter at a time/improving version.  Hence the importance of the plural erratum.  NNue within its output corset definition of training, is using global optimisation using its basis function of NN, to mimic that output on many positions.  But, it is assuming that the target has been objective.  Looping back to that, in this last post.
Answer: The worst move is 1. resigns. It goes from equal to lost in one move, much worse than moves like 1. f3 which go from equal to slightly worse.
Comment: "1. Resigns" might mean you don't lose rating points, though, since zero moves were played on the board. So maybe that alone makes it better than some other choices, depending.
Answer: 1. h4 has been deemed the worst move by John Watson (author of the Mastering the Chess Openings series). Other people are saying 1. h3 and 1. a3. That is not true. Michael Basman is a noted unorthodox player that opens with 1. a3/h3, etc. and is rated >2400. 1. a3/h3 come out to be useful in a variety of openings, but it's certainly not what I would start with.
Comment: Not only is 1.a3 perfectly playable, but 1.a3 e5 2.c4! is a serious try for the advantage, with the additional appeal of offering familiar paths to a White player who plays the Sicilian Defence as Black. Of course after 1. a3 g6 White is struggling to prove that he's done anything useful on move 1, but he certainly need not come out of the opening _worse_.
Answer: I agree 1. f3 is quite bad, but 1. Na3 and 1. Nh3 aren't pretty either, especially as they have to move again to avoid a doubled pawn after ...d5 or ...e5.
Answer: 1.Nh3 and 1.Na3 (Ammonia attack, Sodium attack) are REALLY bad. It breaks the "move one piece one time" rule, and 1.Nh3 blocks h3, a good move to prevent back-rank mate.
Answer: The idea of the opening moves is to allow an early development of pieces. Therefore the worst moves would be the ones that allow you the least opportunity to do so. So I would say 1. a3, 1. h3, and 1. f3 would be the worst. You not only lose the race in developing your pieces quickly (the only piece you can develop after these moves is the knight), but you also give up control on the central squares.
Answer: I would say 1. Na3.  The reason is that it is the most useless move as far as building a setup around it.  Even moves mentioned like 1. h4 and 1. f3 can be useful in some contexts - 1. f3 can be useful if you play d4 and Nc3 and plan e4.  1. h4 can be useful because you discourage your opponent from fianchettoing his bishop, and you can push it again for cramping effect.  It is difficult, however, to imagine any setup where 1. Na3 is a helpful move, and furthermore after ...e5 you will have to move the knight or play b3 to avoid getting doubled a-pawns, which are probably the worst doubled pawns since the open b-file is rarely useful and they are not supporting anything or guarding any important squares.
Comment: This is sometimes called the [Sodium Opening](http://en.wikibooks.org/wiki/Chess_Opening_Theory/1._Na3): *The Durkin or Sodium (Sodium due to the algebraic notation Na3, Na being the chemical symbol for sodium) is rarely played. The move does little to enhance the White position, although some sources consider it to be better than its reputation.
Black's best response is 1...d5, although 1...e5 is sometimes seen. White may continue with 2.b3, preparing to fianchetto with 3.Bb2, or with 2.c4. Alternatively, if black plays 1...e5, white may choose 2.Nc4 to put pressure on the e5 pawn.*
Comment: Incidentally, there is actually a system against the Sicilian which involves early `Na3` (1. e4 c5 2.Na3). Iirc this is proposed by Nigel Davies in one of his opening books
Answer: I'm just trying to protect a move that's mentioned above as being perhaps one of the worst. Grandmaster Mednis years ago wrote a little opening theory book ("How to play good opening moves," Edmar Mednis, ISBN-13: 978-0679141099) in which he states that
1.g3
is one of White's perfect opening move choices, when followed by
2.Bg2.
He does mention some of White's awful first move choices, but doesn't rank their badness.
Answer: 1. g4 ... 2. f3??
This is a horrendous opening (especially in combination with the second move) because it severely undermines the ability to castle on the king's side, very aggressively throws a pawn into action where it has no defenders and isn't helping any cause in particular.
g4 allows to fianchetto the light-square bishop, as well as hide the dark square bishop behind it later, if needed, which is an odd, but somewhat redeeming quality, but as soon as it's followed by 2. f3, the light-square bishop is entombed and white have ZERO center control or active development for whole 3 tempi, allowing black to gain a MASSIVE center presence and advantage. And after 1. ...d5 followed by 2. ...h5 the g4 square now belongs to the black and sets a great entry point to a king-side attack. If white tried to take on g5, black now has a semi-open file without ever moving the rook. Thanks for that!
Such a horrible game would typically go like this: 1. g4 d5  2. f3 e5  3. Bg2 h5 - and black is 2+ points in the lead without having taken a single piece yet, according to any decent engine. White would need a major miracle and a blunder from black to have any chance to recover from that.
Example: Hou Yifan throws game
Answer: 1.f3
PROS
The only pros of the opening is some small center support.
CONS

This opening weakens the king's safety. The f pawn is an important shelter of the e1-h4 diagonal and the g1-b7 diagonal so moving it makes the kingside pawn structure destroyed.
This opening don't open any lines fo development, and it blocked the knight!
Wasted tempo.

SUGGESTION FOR PLAYING
I do not suggest it for anyone
1.h4 and 1.a4
PROS
None
CONS

Doesn't open any lines nor development.
Weakens pawn structure.
Wasted tempo.

SUGGESTION FOR PLAYING
I do not suggest it for anyone
1.h3 and 1.a3
PROS
Does not weaken anything.
CONS

Wasted tempo.
No development lines.

SUGGESTION FOR PLAYING
For white players who want to play black.
1.Na3
PROS

It can develop to c4 or c2 but that would waste some tempos.
Support c pawn, but can't the c pawn move already?

CONS

After 1...d5 and an exchange the pawn structure is lost.
Wasted tempo.

SUGGESTION FOR PLAYING
Only in blitz.
1.Nh3
PROS

It can use another tempo to go to f4.
I'm surprised at nobody mentioning it, but it protects f2!

CONS

Wasted tempo
After 1...e5 and exchange the pawn structure is lost... and the f2 protection is gone!

SUGGESTIONS FOR PLAYING
Only in blitz.
1.c3
PROS
Support d4
CONS

No development and blocks knight
Wasted tempo.

SUGGESTION FOR PLAYING
For Caro Kann players.
1.g4
PROS
Open lines for bishop development
CONS

The g pawn is undefended.
Weakens kingside.

SUGGESTION FOR PLAYING
Only in blitz.
The third most bad is 1.Na3?! and 1.Nh3?!
The second most bad is 1.h4?! and 1.a4?!
The most bad is 1.f3?!
Comment: I like a pro and con structure when a question is not yet solved or formalized so that answers from above might be a temptation of objective looking answer.  As long as the premises and meta label on the statements/arguments are explicit. We can progress.  Reason for my voting up.  Even If  I can't concur or incur based on personal expertise in chess (I am a dedicated learner though, but not from above).
Answer: I would say 1. Nh3.
1.f3 is bad however after g3 white is only down a couple of tempos and has a somewhat reasonable position.
1.Nh3 allows black the potential to to wreck white's pawn structure and even threaten a very quick mate. Yes, white can avoid that with Ng4->Nf3 but you've wasted two tempos when you could have done the same thing with 1.Nf3
White is in a struggle for equality after 1.Nh3 and is one slip away from losing the game for the next several moves. Even if white does play perfectly, he has thrown away several tempi for no reason and allowed an equal game.
Comment: Would be interested to differentiate the arguments with the other answer on the other KQ side.  What does the KQ asymmetry would change. Or is that implied already. I may not be able to read that yet.  Maybe making that explicit would make for some discussion, so we know how much debate room is still left in such questions.
Answer: Just tell you one thing, 1.f3 is bad, it does not control the center actually, it stopped the knight, and it place the king in danger. Sometimes even followed by 2.Kf2, I think this is the hammerschlag variation, further weakening the king, this is to laugh at beginners, but no one have win me with it yet.
Comment: Assumed subjectivity, which is fine, as it is clear, or explicit.  I would guess that player pair variables in experience might alter the answer.  It might already be present in all answers.  One could, as Carlsen did in one game I read about, in bullet, play uncommitting moves for long time and find something to target in the opponent development.  One can blame bullet, but within that, one can still find chess reasonable arguments about done development weakness, and yet to be developed other side.


How does this time signature work

Question: I'm fairly new to grasping this concept so take it easy on me. In the following piece which I assume is 4/4 the sum of the notes simply do not add up. Lots of 32nd notes and some quarter notes equalling far more per bar than there should be. What am I missing I'm this time signature?
Comment: There's no time signature written, but this section could equally well have been notated in 2/4
Comment: Does this answer your question? [Why aren't there barlines in the piano solo parts in Beethoven's Piano Concerto No. 5?](https://music.stackexchange.com/questions/102248/why-arent-there-barlines-in-the-piano-solo-parts-in-beethovens-piano-concerto)
Comment: @PiedPiper - since it's solo violin, would it matter if it had a time signature at all - no-one else needs to keep time, and there's as much rubato as the soloist wants to put into it. Maybe with a time signature, it would restrict the soloist somewhat.
Comment: @Tim I agree that it doesn't matter. For a good  musician (and you'd need one to play this) a time signature is never a restriction.
Comment: I suggest you treat it like a cadenza, and be creative.
Answer: The smaller notes are grace notes.  They don't count for the time signature.  Traditionally there would be only one or a few per "main" note.  Here, Paganini is basically saying to play these figures ornamentally and out of time.
This is especially underlined by the fact that there is no time signature and indeed there are no bar lines.  There are no measures; there is no meter.  Play the notes freely.
Answer: Since there is no time signature, it's no good trying to guess one!
The one beat notes (crotchets, 1/4 notes), are the target notes the violinist will aim for, and play for a little longer than the flurry of other notes, which show how much of a virtuoso s/he is. Those notes are called grace notes, or ornaments, which a player like Paganini would play often, showing his prowess as a violinist. The notes themselves have little or no note timing value on their own, and are always written with smaller heads and stems to show this. Because there's no time signature, or even bar lines, there's going to be no 'pulse' running through that part of the Caprice.

How does this time signature work


Questions in other languages

Question: From what I've seen, some members of this forum do not have the most fluent grasp of the English language, which serves as this site's main mode of communication. Should we permit questions in other major languages, namely French, Spanish, and/or Yiddish and German? (The language of Hebrew is excluded from this proposal as it may warrant a different discussion.)
Comment: related http://meta.judaism.stackexchange.com/q/3437/759
Comment: I'm glad you restrict to major languages. (Even if we want posts in foreign languages, we probably don't want them in Achumawi or Mungbam or Romblomanon or Yandruwandha.) But I wonder how you decided on your list of major languages.
Comment: @msh210, re your first comment: those were languages which came to mind which are used by other members of J.SE
Comment: German is good, some people called it Yidish.
Comment: Hebrew has been brought up here http://meta.judaism.stackexchange.com/q/4148/759
Answer: No; we should not. We have built a community of experts who are fluent in English, who are capable of answering, evaluating, voting on, improving, maintaining, categorizing, moderating behavior around, etc. content in English. We have not built a community that assumes fluency in any other language of discourse. To build such a community effectively would required a significant bootstrapping effort - much more than simply beginning to allow content in other languages. Such efforts are what the Stack Exchange new site staging process is for. Allowing content in non-English languages without first doing the requisite community-building would result in portions of our content repository being systematically under-maintained and therefore of significantly lower quality.

Questions in other languages


Importance of tax to Indian goverment

Question: Currently in India there are many scams running rampant which involve illegal use of money by politicians. This is money which comes from taxes paid by the Indian people. Why should one pay such taxes to the Indian government if the politicians who use it have no accountability?
Comment: Because people with guns will come and use violence on you if you try to deny their extortion.
Answer: Let's assume that X rupees of the taxes are misused for shady purposes, and (all_taxes-X) rupees of tax money goes to good purposes.
If you want to reduce X, is not paying taxes really a good way to achieve that goal? Actually doing it on scale (for large groups of people) generally means in practice that a noticeable fraction of unpaid taxes gets spent for funding the tax-evasion schemes and bribing various officials, thus actually increasing X.
Also, generally if funding for kleptocratic regimes dries up, then they typically still serve themselves first - the historical behavior of dictatorships all around the world during severe economic crises shows that. They would fill their wallets anyways, not decreasing that X, but decreased tax income would decrease the funds that's spent on the actual neccessities of society.
I would say that the same legal mechanisms, people habits and social norms that facilitate politic scams also facilitate tax evasion, and the things that restrict politic scams also restrict tax evasion. If tax evasion is rampant, then actually the same rich magnates and politicians will gain huge amounts through tax "optimization", but it will be much harder for ordinary people to evade taxes in the same proportion.

Importance of tax to Indian goverment


Interpolate Temperature Using DEM

Question: I want to "co-interpolate" temperature with DEM. I have SRTM 90m aggregated to 1km and I want to "co-interpolate" my DEM with points with temperature data. How do I do this? I am using ArcGIS 10.
Comment: How big is your area? If it's fairly small, temperature will be likely show a significant negative correlation with elevation so a simple regression of temperature and elevation from your weather stations  will give you an equation you can use in the raster calculator.
Comment: this sounds like a something you can solve with co-kriging http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Understanding_cokriging but you will need geostatistical analyst to do it in ArcGIS
Comment: Can you define what you mean by 'co-interpolate'? This is a new term for me.
Comment: @radouxju: Yes, I think this what I want. But when I was trying to do this, and I am a newbie on this, so many things were asked. Can you help me on this?
Comment: @DevdattaTengshe: Basically, I want an interpolated temperature raster that reflects elevation as well.
Comment: Seems like the solution really is to perform Co-kriging.
Comment: I know that you are the OP who posted this question, but more context would be useful for users who come to this question in the future.
Answer: Not sure if this will suffice but; If you have 3D analyst you can interpolate your temperature raster independently then drape it over the DEM and visualize in 3D in ArcScene. This way you could analyze the heat data in relation to elevation.  Alternatively, you could generate a hillshade raster from your DEM and either overlay the hillshade model over your heat raster and make the top raster semi-transparent or to preserve colour intesity combine the hillshade and the heat raster using Image Analysis Function technique described here.
You can also use the Image Analysis function result to drape over the input DEM in ArcScene which will make the hillshade component of the Image Analysis Function layer more pronounced while still preserving the colour intensity of the heat raster.
Answer: What I think you mean is Co kriging your temperature data based on a DEM.
What you need:
-Shapefile of points with temperature data
-DEM of your study area
You need to have the geostatisical analyst tool (see customize, toolbars). Open de geostatisitcal wizard in this toolbar. You can now choose kriging/co-kriging. You need to select two datasets. So the first is you shapefile with temperature points and the second is the DEM. In the following tabs you can adjust many parameters (try optimize model, upper right corner, tab 3. or check out this video https://www.youtube.com/watch?v=EUcGDgPVcTA .
Also check out this esri page: http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Creating_a_map_using_cokriging .
Good luck!

Interpolate Temperature Using DEM


FxCop, compose list of callers from dependent assembly

Question: I'm building a couple of customs FxCop rules and one of the rules needs to enforce that a constructor is called in specific methods. For that, I need to create a list of callers, to that specific constructor, prior to performing the actual test. How is this possible? Is there some kind of handle to acquire a list of all loaded assemblies in the ApplicationDomain, where I can iterate through the classes and find the constructor Method object? Ideally the list of callers should be composed in the BeforeAnalysis method.
Answer: The Microsoft.FxCop.Sdk.CallGraph.CallersFor(Method) method may give you what you want.  However, the general approach you seem to be describing is rarely a good idea because it would typically assign the problems to the wrong target.  For example, in the scenario you describe, it would presumably be desirable to attribute the problems to the methods that should but do not contain the target contructor call.  However, if your analysis target is the constructor, the detected problems will be attributed to the constructor rather than the methods that should have called it.
Answer: I think I haven't explained the question very well, but I see your point.
I have 3 different assemblies and for certain method calls from one assembly to another, I need to ensure that a benchmark constructor invoked. The benchmark class resides in a 4th assembly. Now my problem was that only VS2010 only loads one target assembly for analysis and when I used the CallGraph to construct the a list of methods calling the constructur, it would  not find any. When Invoking FxCopCmd.exe manually I could just add the dependent assemblies manually with the /file: parameter.
My solution is to load the different assemblies manually (not relying on the loaded assembly in RuleUtilities.AnalysisAssemblies and contruct the list of callers in the BeforeAnalysis method.
<code>            RuleUtilities.GetAssembly(
            RuleUtilities.AnalysisAssemblies
            .First().Directory + "\\" + additionalAssemblyFilename)
            .Types.SelectMany(type => type.Members)
            .Where(member => member.IsPublic)
            .Where(CanBeCastedToMethod)
            .Cast<Method>()
            .SelectMany(CallGraph.CallersFor);
</code>
With this approach I can contruct a list of callers, for each of the assemblies and for the benchmark class constructor. Works perfectly i VS2010.


Why do you sometimes have to press the device rotation tile twice for it to function?

Question: I have a auto rotate quick tile  which was originally on stock Android on my Nexus 6p running Android 7.1.2 nougat. I realized that in some cases, after I press the autorotate tile to change from portrait mode to auto-rotate or vice-versa, it doesn't change and instead stays at what it was before (auto rotate or portrait) until I press the tile again. This occurrence seems to be random and at other times the tile works perfectly normally with each press. How do I make it so that this tile works with one press every time?
Comment: I have the same problem. Most of the times it's working just fine and as intended, but sometimes I have to click the tile twice.
Happened on Android 8 and still does on Android 9 on the Google Pixel (1st Gen).
The weird thing is: The click is recognized, as I can see the background animation for the button, but the state does not toggle.
Answer: When you tap that button, what is actually happening is a settings file in the phone is updated. If it isn't working on the first tap, it's either caused by lag, or an issue with the quicksetting pane itself. There isn't much you can do as far as a real solution besides a factory reset or using a custom ROM.
Comment: I understand. I installed a lot of tiles on my quicksettings so that's probably it.


How to retrieve Bitcoin transfer unconfirmed for 10 days

Question: I'm very new to Bitcoin. I had Bitcoin sent to wallet on Bitcoin.com and then sent to wallet in cash app that I am familiar with. After 12 days it still says unconfirmed and pending. Is there a way to resend and pay higher fee or what can I do to have access and be able to cash in and use money? Please help!!
Answer: My first recommendation is for you to never use bitcoin.com.  This is a scammy site which attempts to trick new users into thinking that something called "bitcoin cash" or the ticker "bch" is bitcoin. Which it is not.
But luckily the bitcoin that you bought is the real bitcoin (often referred to as btc)
By now, your transaction has probably confirmed and already reached your wallet since the activity on the network has calmed down now over the weekend.
If not, it is usually possible to use something called "Replace By Fee" or "RBF", which increases the fee that you pay for your transaction so that it will get included in a block, and thus reach your faster.
If you are interested, consider to visit bitcoin.org to find out all the details about how to install your own bitcoin node and wallet in order to increase your security and not need to trust Cashapp for holding your funds.


Tension in a string for different acceleration in each end

Question: Say a regular string, with mass, is held by two persons in each end and they are in running in different acceleration in the same direction. Will there be any tension as different ends have different acceleration? Or not as they running in the same direction?
If it does then how do you calculate that?
Answer: There are two possible scenarios:

The fast accelerating person is in front.
The slowly accelerating person in in front.

In case 2 there is no tension (the rope is not taut).*
In case 1, if the rope is rigid it will break. Otherwise the different accelerations are not possible.
Alternatively, if the rope is elastic, then elastic tension (spring force) will increase since the two people will separate more and more, corresponding to elongating the rope.

* If the rope is not massless, gravity might have an influence causing some tension within the rope depending on how it is carried and how it is hanging in its non-taut state. Finding the tension distribution depends highly on the exact shape with which it is hanging but can possibly be compared to a cable hanging between pillars of a suspension bridge.
Comment: Doesn't a non-taut massful rope still have tension to hold it up against gravity?
Comment: @user253751 Sure :) That is of course true. But let's assume an ideal massless rope in this scenario, since that is not the point we are focusing at. But for a heavy rope rather than a thin string, you are right that gravity should be considered as well.
Comment: The question explicitly specifies a massful rope
Comment: @user253751 That is a very good point... I have added a note to the answer. I believe the non-taut state is not the main focus of this question so I won't elaborate further. But good catch - thank you for the note.
Answer: If the string is not taut, then there is no tension. If the string is taut, and its ends are moving at different accelerations, then in Newtonian physics its length must be changing (and this would depend only on the difference between the accelerations, so one person acceleration at 10 m/s^2 and the other at 11 m/s^2 would be the same as one person being stationary and the other accelerating at 1 m/s^2).
If the distance is decreasing, then eventually the string would become slack. If the distance is increasing, then the string is being stretched, and stretching causes tension. The acceleration would not directly cause tension, but the acceleration would cause stretching and the stretching would cause tension. How much tension there is would depend on both the string's elasticity properties and how far it has been stretched. Eventually the increase in length would be enough to break it.
In relativity, it's more compliced, but under ordinary circumstances, we can ignore the relativistic effects.
Answer: Yes there is bound to be tension in the string . Consider an extreme case where one end is accelerated at 10000 m/ sec ^2 and the other at 1m/sec^2. Its obvious that the string would break . Why ? because of the tension of course now when the magnitude of acc is not that large there is bound to be some tension
Answer: To understand this question, you need to first specify which end is having greater acceleration.
Case 1 :  Front end is having smaller acceleration
In this case, what actually happens is that the front end moves lesser distance than the back in a given time and thus the rope becomes slack and hence it is a complete "nuisance"  to talk of tension force in this case..
Case 2 : Back end is having smaller acceleration
So I think this was the scenario you actually imagined. In this case, initially the man at the front end was having more acceleration than the back end and this will stretch the rope microscopically leading to cause some tension in the rope but the tension here will be adjusted in such a manner that the back end and the front end gets the same acceleration finally but if the initial difference gets too big the rope will eventually break apart in two pieces.


How were specific hentaigana selected for writing?

Question: I've been learning how to read older documents and trying to familiarize myself with hentaigana, but as I've started this, I've began to wonder if there is any rhyme or reason to the choices writers make when they select one hentaigana over another. Is it just a matter of the current trend? Is it a matter of style, flow, and aesthetics (especially perhaps in documents written in kuzushi-ji?), or is there something else going on here. If one used 可 for "ka" once, would it be odd for the writer to use "加" later on? What are the circumstances and rules that dictate these sorts of things?
Comment: Based on [this](https://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q11265454116), which cites [this](https://www.jstage.jst.go.jp/article/johokanri/58/6/58_438/_html/-char/ja/), originally it was totally arbitrary. Then age by age, person by person there are some vague tendencies but no strict rules.
Comment: @sundowner Thanks! It looks like according to the original citation you mentioned though, that there was a bit of rhyme and reason to it (e.g.; using certain forms for particles, certain forms for the starts of words, certain forms for the ends, etc.)
Answer: So according to this article (which is also cited in this section of Wikipedia), there were several factors that affected the choice of hentaigana:

Certain words, such as けふ, preferred certain kana.
Certain kana were predominantly used at the beginning of a word. This can somewhat be compared to the Arabic alphabet where almost every character has initial, medial and final forms.
Some kana were preferred when used as a particle. We still distinguish わ/は, を/お, へ/え, so this is understandable.
When the same sound occurred consecutively, two distinct kana were employed to avoid repetition. Maybe this was aesthetically pleasing to people in the past.
Sometimes, different hentaigana actually represented different sounds. In the old days when 濁点 was optional, the ち and ぢ sounds were sometimes denoted using different hentaigana.

Note that these rules have varied significantly over time. Since Man'yōgana, there seems to have been a trend to prioritize diversity over standardization when it came to hiragana. The unification happened only after the Meiji era. Contrastively, for katakana, there seems to have been an almost 1:1 correspondence established relatively early on.


Unit tests & lengthy setup strings: Style / Best Practice

Question: I'm interested in the opinion, practices and reccommended best practices of using lengthy setup strings in unit tests.
Do you prefer to declare the tests in-line, close to your test, or externalize in a file somewhere?
Note, I'm talking about test assets which are specific to a single unit test, so not neccessarily suitable for living in a setup() method.
I see pros/cons of both -- I'm a fan of keeping things important to your test as close to the test as possible, however a few lines of string setup can quickly become nosiy in a test method.
Eg.,  I'm writing a quick parser to strip unused css declarations from files.  I wanna test that given a specific input string, the correct text is stripped out.  My test has become really noisy with all the string concatenation.
public void removesStyleFromText()
{
    StyleCleaner styleCleaner = new StyleCleaner();
    String source = ".presentInFileOne {\r\n" +
            "}\r\n" +
            "\r\n" +
            ".presentInFileTwo {\r\n" +
            "   bottom-corners-rounded : false;\r\n" +
            "}\r\n" +
            ".notUsed {\r\n" +
            "}\r\n" +
            "";

    String actual = styleCleaner.removeDeclaration(source , "notUsed");

    String expected = ".presentInFileOne {\r\n" +
    "}\r\n" +
    "\r\n" +
    ".presentInFileTwo {\r\n" +
    "   bottom-corners-rounded : false;\r\n" +
    "}\r\n";

    assertEquals(expected , actual);
}

Given this example, I could externalize the actual / expected into external files, but that also makes the test a little unclear as to what it's actually testing for.
Thoughts?
Answer: I personally prefer to keep the strings inline in cases like this. The string is important for understanding what the test is supposed to do so having to look it up externally seems counterproductive.
If you have lots of the same tests that only differ in what string goes in and what string comes the story is a little different though, you might want to look at table-based testing solutions. In .Net you have mbunit. It allows you to run the same test with different expected input/output or you could look at tools like Fitnesse that allow you to define tables of data that you want to test against.
Answer: Definitely code, it is much easier to tell right away what you are testing and much easier to refactor when you want to reuse it. I like to keep it DRY, so I usually tend to move it to builders or concrete classes (depending on what I am doing), which gets me a default config that I can tweek for the specific test.
Answer: I would externalize the strings and write some comments on what you're testing for. Comments also have the advantage of being a lot more readable than these string constructs.
Answer: Your problems will vanish if you use a programming language which supports proper string literals. For example, Python supports multiline strings:
source = """
.presentInFileOne {
}

.presentInFileTwo {
       bottom-corners-rounded : false;
}
.notUsed {
}
"""

expected = """
.presentInFileOne {
}

.presentInFileTwo {
       bottom-corners-rounded : false;
}
"""

assert removeDeclaration(source, "notUsed") == expected

Such language constructs will make your tests more readable than anything else.
Answer: There is a hack to make multi-line Strings literals work in Java. Performance is probably not something you'd want to see in production but good enough for tests.
My rule is: If the string is small (< 10 lines), I keep them inline but in a way that I can always cut everything between the "" out and just paste the new version (this means I'm converting the strings in my assertEquals() if necessary).
If the string literal is longer, more complex or when I have a good editor (with syntax highlighting, etc), I like to keep them in a test data folder with the name of the test as the filename. You can then use a utility function in your JUnit test which uses getName() to load the string and you will know without any magic which file belongs to which test.
If you have lots of those, I use the test class name (class.getSimpleName()) as the folder name to maintain my grip on them.
Answer: I would let it this way - since it is important for that test and strictly seen if you rely in your test on something "external" it is not a strict unit-test.


How to find SMD transistors library for Altium Designer?

Question: I am new in PCB design, so excuse me if this is a bad question!
I know the basic electronics and how to draw schematics in Altium. But about SMD parts, I am a little confused! How can I find SMD transistors, diodes, resistors, inductors and capacitors? Is there any specific library for them? If not, how should I find them?
Comment: Use the symbols to draw your schematic. Then create your own footprint library and make your own footprints or use the IPC-complant footprint wizard that is built into Altium to generate them based on the dimensions provided in the datasheets.
Comment: So you say the only important thing is parts footprint and the footprint have standards(1206,0805,SOT223,Sot23,etc) and when a capacitor or resistor is in 1206 package, or a transistor in sot23 pack, it is not important is it from which company or what specifics(voltage, current, power,etc) do they have?

The only important thing when you design a PCB with SMD parts is the parts footprint, and footprints are same when you use a 0805 package resistor without attention to it's company, or voltage,power,etc!
Comment: I have no idea what you just asked because of your terrible grammar and punctuation. Can you please try to clarify using plain, correct English?
Comment: There are a few you can find online, but this was actually one of the reasons I switched to Kicad. Having libraries of digikey parts on GitHub is really nice.
Answer: Probably the easiest (and fastest) way is actually building up your own library. You could use the vault too, but don't ask me how that works ;).
Go to File > New > Library > Schematic Library to build a symbol library. If you open your [library].SchLib theres a handy wizard (Tools > Symbol Wizard).
Go to File > New > Library > PCB Library to build a footprint library. The two IPC Wizards you'll find in your [library].PcbLib under Tools > IPC Compliant Footptrint ... are, at least in my daily worklife on of the killer features of Altium.


How is the root node of a decision tree determined?

Question: Almost all the examples I have found stated how the decision tree's split is based on how much purity/information can be gained (ie: via entropy and information gain) for internal node. But is the same procedure done to determine the root node as well, or is other procedure employed to determine the root node?
Comment: As ID3 and C4.5 does greedy search, all the 10000 features are tested at the root node.
Answer: It's the same procedure. The information gain rule applies regardless of the node level. There is nothing special about the root node.
Comment: Just to dive a bit deeper. Say, there are 10000 features (with Yes or No value), does the root node test the information gain on each of these 10000 features to determine which is the best root node? Or does it randomly sample a subset for efficiency at the expense of not finding the best root node?
Comment: That depends on the algorithm you use to build the tree. Most tree building algorithms will search through all of the features. The only algorithm/model that comes to mind that does not do this is called a "Random Forest", which usually samples only 1/3 of the features at each node.
Comment: @Ryan Zotti According to Ryan's answer, root node is determined by information gain rule not random? I'm confused that
The only algorithm/model that comes to mind that  this is called a "Random Forest". In other words, do you understand does not do this called a Random Forest?


Sharing Internet Connection

Question: I have a Cable Internet (Assigned IP etc) to connect to internet and I want to connect another computer to same line of cable as well. Both in Same room. Any suggestion, affordable solution please?
Answer: A common approach is to get a wifi or ethernet router.
Connect this device to the cable internet device, then connect your computer to the wifi/ethernet router.
Take a look at http://compnetworking.about.com/cs/homenetworking/a/homenetguide.htm
Comment: I'd recommend a combined ethernet/wifi router.
Comment: Ethernet Router! gotcha...gotta go to buy one. :)
Answer: I recommend buying a Linksys WRT120N, this one is less than 50US$. There are other brands that are even less expensive, but I prefer Linksys.
There is one port for the connection to the cable modem, and there are 4 ports for computers (alternatively you can connect other computers via wireless)

Sharing Internet Connection


Automorphism of elliptic curve, Vakil 19.10.E

Question: There are many other proofs of finding all the possible automorphism groups of elliptic curves, but I am interested in the $Hint$ and the corresponding proof in the following exercise from Vakil's book.
Ex 19.10.E. Suppose $(E,e)$ is an elliptic curve over an algebraically closed field $k$ of characteristic not 2. Show that the automorphism group of $(E,e)$ is isomorphic to $\mathbb{Z}/2,\mathbb{Z}/4$, or $\mathbb{Z}/6$.
Hint: reduce to the question of automorphisms of $\mathbb{P}^1$ fixing the point $\infty$ and a set of distinct three points $\{p_1,p_2,p_3\} \in \mathbb{P}^1- \{\infty\}$.
So the proof is to use the fact that when $k=\bar{k}$ and $\text{char}~k \neq 2$, the elliptic curve is a double cover of $\mathbb{P}^1$ branched over $\{\infty,p_1,p_2,p_3\}$. So my question is how to show the 1-1 bijection between the automorphisms of $(E,e)$ and the automorphisms of $\mathbb{P}^1$ that fix $\{\infty\}$ and $\{p_1,p_2,p_3\}$, and what are they?
Answer: See Harthstorne, page 321, Corollary 4.7 and page 318, Lemma 4.4.


Spotify/pandora timer

Question: Is there an app that is preferrably free that will shut off (not just mute the phone as I don't want Pandora sucking bandwitdh all night) that will shut off Pandora or spotify after a certain amount of time?
Answer: Not free, but you probably can use Taskerto do this.   I use Pocket Casts to listen to podcasts, and have a Tasker profile set up:
3 Contexts: Shake left-right; app Pocket Cast running; Not Docked Car
2 Tasks: Notify (turn LED on, title "Sleep"); Wait 12 minutes, then Pause Simulate Media Button, then Notify Cancel title "Sleep"
Net effect is that I can shake the phone left then right, and Pocket Cast will behave as if the Pause button on a headset were pushed 12 minutes later.   I used the notification LED so I could tell whether Sleep had been activated when the screen is off.
I'm guessing Pandora would observe the headphone pause function; if it does, this profile should work for you.
Comment: Sometimes I feel like a Tasker shill because about half of my answers here mention it, but it really is like a Swiss Army Knife for personalization of my phone.
Comment: I would add that Tasker's user interface is a little on the opaque side, but once you get the hang of it, you can do all sorts of things.
Answer: Yes tasker is the key but I prefer llama because its free and its awesome. Actually its location based profile app but it can be used for your condition.
There is a condition called "time between", add that condition and choose "kill application" for its action. Add your desired time and application

Spotify/pandora timer


How long are the lunar cycles in Elder Scrolls?

Question: When doing research on Khajiit and learning about their Furstocks, I started wondering if there was a predictable lunar cycle in the elder scrolls that you could put on calenders and use to predict what type baby Khajiit at a certain time will be what type. Is there one?
Comment: As per the [tour], you can accept a correct answer by clicking on the checkmark by the voting buttons.
Comment: I'm waiting to see if I get other answers.
Comment: No worries. I just always like to let new people know pre-emptively. :) We get a lot of hit-and-runs here.
Answer: First, there are of course two moons. Secondly, this fellow has figured some things out. Long story short, it's mildly inconsistent between games, but it looks like Masser has a cycle of about 24 days, and Secunda is 30 days.
The primary basis is from this post:

I've been able to learn a bit about how the Moons function in Oblivion (I'm pretty sure it's the same system in Morrowind and Skyrim, but I'd need to check it out more thoroughly).
First observation is that the Moons rise from the Northeast and set to the Southeast.
Masser has a regular cycle of 24 days, each divided into eight sections lasting three days each, corresponding to: New, Waxing Crescent, First Quarter, Waxing Gibbous, Full, Waning Gibbous, Second Quarter, and Waning Crescent. Masser always rises at dusk, reaches its highest point at midnight, and sets at dawn.
Secunda's orbit is divided into the same eight divisions corresponding to the above descriptions (New, Waxing Crescent, etc.). However, unlike Masser, Secunda reaches its highest point in the sky at eight different times, which are (sequentially): 12 AM, 8 PM, 4 PM, 12 PM, 8 AM, 4 AM.
Another difference is that the phases of Secunda either appear three days in a row (like Masser), or four days. In the end, Secunda's cycle lasts approximately 30 days, from what I can gather, while Masser's lasts 24 days. And yes, Secunda can be full at noon... I'm afraid that if I keep on trying to make sense of this, I might end up a lunatic!


How does LUKS work?

Question: I was just curious if someone had a high level overview of how a system like LUKS worked for full disk encryption, aka. how it stores keys and how those keys are verified, and if data is de-crypted by a wrapper for all standard i/o. I've seen partial explanations elsewhere but never a full high level explanation.
Comment: Did you read LUKS' user documentation? The kernel documentation? Do you want to know about LUKS from the perspective of the user, as someone that want to hack on the kernel, or for evaluating the security for a particular purpose? Is there any thing specifically about LUKS that you wanted to know? Does it have to be LUKS or are you just interested about FDE in general?
Comment: I did not read the kernel documentation. I read different user docs. I'm interested more in FDE on linux than specifically LUKS. And I'm interested in evaluating it for security purposes.
Answer: I'm going to tell you what components compose the LUKS and how to they interact at a high level (I will not tell you the format of the metadata and how it is used).
This disk encryption solution is formed of two components: cryptsetup(userspace) and dm-crypt(kernelspace, Linux Kernel module).
cryptsetup is used to format the block device and to open the block device. Upon formatting and opening of the device you send the keys into kernelspace. The dm-crypt module instantiates an encryption context where it stores the session data/encryption key (CryptoAPI is the module inside the Linux Kernel that deals with all the criptography, it has criptographic accelerators support, etc). After you actually mount that block device, when you write/read to/from it, everything goes through that context.

How does LUKS work?


What's the sight of the ultrasonic sensor according to the distance of the object?

Question: Hey I'm programming a sumobot for a first-year university Civil Engineering project. We should need the sight of the ultrasonic sensor according tot the distance of an object.
For example, the sensor can detect an object that is located 30 cm away 55° to the right of the sensor, but an object 50 cm away from the sensor can only be detected to 45° to the right of the sensor (approximately). Does anyone know the relationship (maybe a function?) between the sight and the distance? Thanks!
Answer: ETH Zurich faculty/students conducted some experiments on exactly this back in 2006.  The relevant parts of their results have been reproduced below.  For more information, visit their website: http://www.tik.ee.ethz.ch/mindstorms/sa_nxt/index.php?page=tests_us.
The chart below shows accuracy of the sensor at detecting a 14.5 cm x 9.5 cm x 6 cm block at various distances and angles from the sensor.

Distanz is Distance in CM, Winkel is Angle in degrees, and Relative Fehler is relative error.
According to the researchers:

The results show that the ultrasonic sensor should always be placed in horizontal position, other positions decrease as well the field of vision as the sighting distance of the sensor. The sensor seems to be a bit 'blind' on the left eye, which can be explained by the fact that the left eye is actually the receiver of the ultrasonic wave while the right eye is the sender.
Comment: Could you please summarise the answer (or, possibly, copy (with permit of the ETHZ people) it in its entirety) here, in case the link goes dead? Not assuming any external resources is a part of what makes a great StackExchange answer.


Outlook 2016 email search box -- drop down list of recent searches

Question: I am using Outlook 2016 on a Windows 10 laptop.
My question:  Is there a way of disabling the drop down list of recent searches that automatically appears as soon as I click in the email search box?  This feature could be helpful if it actually worked, but it doesn't work most of the time, and that has become extremely annoying.  There is another way to select from a list of recent searches so I can do without this new(?) feature that doesn't work as expected.
I see someone else posted the same question a while back but the answer was to change something in the registry.  I am definitely not comfortable nor tech-savvy enough to mess with the registry.  Is there an easier option?
When I click in the search box to start a search the drop down list of recent searches immediately appears.  Then one of two things happens:

If I click on one of the items in the drop down list to select it, most of the time one of the OTHER items in the list pops into the search box and Outlook immediately performs that search instead.
When I press Enter after manually typing in new search criteria (i.e., I don't want to use any of my previous searches shown in the drop down list), most of the time it selects one of the items from the drop down list anyway, and Outlook immediately performs that search instead.

I have noticed that if I type in search criteria and then press tab so the magnifying glass gets highlighted, the drop down list disappears (YAY!!) and THEN I can press Enter and the search is done correctly, using my new search criteria.  However.....after years of using Outlook (several different versions over the years) I just can't seem to train myself to TYPE then TAB then ENTER.  I should be able to just TYPE then ENTER, and Outlook should ignore any of the items in the drop down list.
Thank you for any help you can provide!
Jayne
Answer: According to my knowledge, there is no option available to disable the recent searches feature in Outlook. You can only clear the recent searches MRU via deleting the following registry key:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Profiles\profile-name\0a0d020000000000c000000000000046
REG_BINARY: 101f0445
You can create a .reg file as per the following Microsoft KB article to delete the registry entry as a workaround. However, it has to run the .reg file frequently as the search MRU creates once you search.
enter link description here


wpf application crashes when accessed from RDP session without showing any ERROR messages

Question: I have been working on this issue from the past 7 days but could not figure out the actual reason. I have created an MSI for WPF application and installed it in windows 7 machine. IF i physically log into that machine and access the application everything works fine.
But when I access the application using Remote Desktop Session, the application crashes without showing me any error. I checked in the application logs in event viewer and found the following Errors
1. .Net RunTime Error:
Application : Myapplication.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an internal error in the .NET Runtime at IP732E1F88 (732B0000) with exit code 80131506
2. Application Error :
Description:
Faulting application name: , version: , time stamp: 0x4e11b8da
Faulting module name: KERNELBASE.dll, version: 6.1.7601.17651, time stamp: 0x4e211319
Exception code: 0xc0000005
Fault offset: 0x0000b9bc
Faulting process id: 0xd44
Faulting application start time: 0x01ce40fa0f61d32c
Faulting application path:
Faulting module path: C:\Windows\syswow64\KERNELBASE.dll
Report Id:
Could someone please help me out where I am going wrong or do i need to change any settings
Thanks
Comment: This bug report may be relevant:  https://connect.microsoft.com/VisualStudio/feedback/details/1930838/animated-wpf-effects-cause-hard-crash-over-rdp-under-certain-conditions
Answer: Did you read: WPF global exception handler so you can get more info about the exception?
Put something like this in your App.xaml.cs
<code>protected override void OnStartup(StartupEventArgs e)
{
    AppDomain.CurrentDomain.UnhandledException += CurrentDomain_UnhandledException;
    base.OnStartup(e);
}

static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
{
   MessageBox.Show(String.Format("Error: {0} ", e.ExceptionObject));
}
</code>
Comment: Sorry missed the internal error in the .NET Runtime maybe, http://stackoverflow.com/questions/4367664/application-crashes-with-internal-error-in-the-net-runtime this can help
Comment: I have added all the exceptions as mentioned in this page [link](http://code.msdn.microsoft.com/windowsdesktop/Handling-Unhandled-47492d0b#content) but could not see any exceptions. Finally I figured out it was an issue with scroll viewer styling but could not pinpoint the exact line which is causing this issue. Thanks for your  help on this.


What exactly is mass?

Question: I was looking for a definition of mass and most of the time what I got was that "it is the amount of matter". Now that is very vague. And the way we define matter is "anything that has "mass" and occupies space". so... what exactly is mass?
Can you please answer it to the level where a highschool junior/11th grader can understand?
Comment: Gravitational or inertial mass? Do you know Newton's laws and gravity law?
Comment: Does this answer your question? [What is the definition of mass?](https://physics.stackexchange.com/q/605100/)
Comment: relevant https://physics.stackexchange.com/q/8610/
Comment: An answer to a different question but it answers this question as well: https://physics.stackexchange.com/a/340890/20427
Comment: [The True Nature of Matter and Mass](https://www.youtube.com/watch?v=gSKzgpt4HBU)
Comment: Possible duplicates:  https://physics.stackexchange.com/q/524201/2451 , https://physics.stackexchange.com/q/8610/2451 and links therein.
Answer: When we ask about such a basic property as mass, it can happen that we find it hard to put into words in a succinct way, so what we do is offer a group of ideas and equations and thus show the role that mass plays in physics.
In the case of mass, there are two main roles: one to do with inertia, the other to do with gravity. Accordingly we may speak of "inertial mass" and "gravitational mass" but, interestingly, it turns out that they are the same.
In classical physics (as opposed to quantum physics), inertial mass is defined ultimately by its role in Newton's second law. This is the one which says that rate of change of momentum is equal to force. The idea is that first we find various force-providing systems, such as a rocket motor in a given state, or an electric plate with a given amount of charge (attracting some other charge), or a rubber band at a given temperature and stretched by a given amount. Next, we imagine attaching each of these force-providing systems to a variety of objects, and we measure the acceleration of each object. It is found that the ratio of force to acceleration is the same, for a given body, independent of what kind of force was provided. So we write the equation
$$
f = m a
$$
and we define inertial mass of the body as $m = f / a$.
There remains a difficulty, however, in that we need to calibrate the whole approach. We can decide when one kind of force (say from a rubber band) is equal to another (say from a rocket motor) by applying them in opposite directions to a given object and checking whether the acceleration is zero. So this enables us to compare different types of force. But we still need an overall scale to say what one unit of force is, or what physical situation creates one unit of force. If we knew that then we could deduce what one unit of mass is by finding a body whose acceleration is one metre per second-squared when one Newton of force is applied. However in practice this is done the other way around: we come up with an agreed way of saying what kind of object has unit mass, and then we can find out the size of a force using $f = m a$.
Notice that in the above there are two issues: first, what kind of property mass is, and then how we pin it down quantitatively. The kind of property is "that which sets how much acceleration a body will have when subject to a force." The quantitative definition then employs experimental ingenuity and Newton's second law.
Comment: @chepner actually, the whole theory of general relativity is based on the equivalence principle. Find an experiment that shows a difference between the two types of mass, and GR breaks into pieces.
Comment: Wouldn't it be more accurate to say that no experiment has yet detected a difference between inertial mass and gravitation mass? IIRC, there's no theory that explains why an object's resistance to change in motion should be related to the gravitational force it exerts.
Comment: This is a great start. But I think it would be appropriate to also present an equation with gravitational mass (Newton's law of gravity), and mention how mass relates to energy and how a large amount of mass is due to binding energy. No description of mass can be complete without these points (if ever).
Answer:
The mass of an object is a fundamental property of the object; a numerical measure of its inertia; a fundamental measure of the amount of matter in the object. Definitions of mass often seem circular because it is such a fundamental quantity that it is hard to define in terms of something else. All mechanical quantities can be defined in terms of mass, length, and time.

italics mine
One has to start with the everyday concept of force, momentum, energy etc as known before they were codified in Newton's laws of motion. At that time, weight  was measured for everything, and it was a given that the weight is an invariant of the object. Even now we talk of a one kilogram mass, giving the units of weight.
Newton's laws codified this in order to develop classical mechanics. The laws are axiomatic assumptions but they worked well in theoretically fitting the data at the time and predicting new situations.

Law 1. A body continues in its state of rest, or in uniform motion in a straight line, unless acted upon by a force.

Law 2. A body acted upon by a force moves in such a manner that the time rate of change of momentum equals the force.

The $F=m*a$ where $a$ is acceleration and $p$ is the momentum $mv$
The $m$ is an axiomatic assumption that it describes the object under consideration.

Law 3. If two bodies exert forces on each other, these forces are equal in magnitude and opposite in direction.

The mass m, given by the weight definition at the time, and modeled with $F=ma$ was adequate both to model kinematics and gravitation and to introduce the difference between gravitational mass and inertial  mass, see this question and answers.
In the study of the high velocities where Lorentz transformation and four vectors are necessary the characteristic mass for all objects is given by the invariant mass of the four vector, the same in all inertial frames.
Answer: Andrew Steane's answer is good, but I would like to add a point.
The universe is full of stuff. Some stuff is matter and some is energy. If you look carefully at the universe, you can see patterns of behavior. If you push on matter, it changes speed. That was more or less the way physics was done in the time of Aristotle. In his view, rocks roll downhill and stop because they have a lot of earth in them, and it is the nature of earth to be low and still. By contrast, the stars and planets were full of fire. It is their nature to be high and to move.
Galileo changed that. He applied math to the patterns of the universe and found that you could match the behavior of the universe with mathematical rules very well indeed. Newton extended this idea a great deal.
So physics is a mathematical model of the universe. Different from the universe itself.
Mass is a number, a physics thing. Matter is stuff, a universe thing. So you might want to ask what mass is used for instead of what it is.
Andrew has answered that. It turns out to have two main purposes. Mass helps describe exactly how matter changes speed when you push on it. And Mass helps determine exactly how strong is the force of gravity generated by an object.
There is no obvious reason why the same number serve both purposes. So people have gone looking for any difference. It has been shown that if two different numbers are needed, the difference between them is less than one part in a trillion. More precise experiments are being planned.
Are Newton's "laws" of motion laws or definitions of force and mass? has more about this idea. In particular, see this answer.
Answer: This might oversimplify, but ---
Anything not travelling at speed $c$ and which produces momentum in response to a force is mass.   Of course this defers the question, philosophically, to what momentum is.
There is also a small school of physics which claims there is no such thing as mass, just, basically, highly localized energy or probability.
Comment: "There is also a small school of physics which claims there is no such thing as mass, just, basically, highly localized energy or probability.", can you please give me a link to that school's works?
Comment: @ÁrpádSzendrei  it's pretty much limited to the writings of the lunatic fringe  (and of course the engine running the spaceship Heart Of Gold)
Comment: @CarlWitthoft Not so lunatic fringe as you might think. In quantum mechanics, some 85% of what we normally call mass is thought to be binding energy of the strong force.
Comment: @fishinear sure, but we can, and do (in the case of all binding energies) view that field energy as having been converted to mass.  Otherwise  $E = mc^2$ wouldn't be useful.
Answer: A historical approach might do it.
Suppose you have two balls made of the same material, one bigger than the other. One finds the bigger is the heavier. The weight is proportional to volume. Three of the same size ball is heaver than one ball, another proportionality property. Balls of different material of the same size can have different weights. Four balls of one material can have the same weight as ten balls of another material. There is some fundamental property that follows a rule of proportionality held in common by both materials that is not dependent on size. A heavier object has more of whatever this is than a lighter object of the same shape and size, yet that same quality follows a strict proportionality relationship with volume for the same material. Mass was an amount of some constituency of the object. This quantity was often reckoned according to a common standard. The Ancient Roman's used Carob seeds. There are more seed-weights in this collection of items than that one. So there was some universal amount associated with weights.
In the 17th century, researchers like Galileo and Newton noticed some other features of this quantity. The more massive an object, the harder it was to change its motion. It was more difficult to start it from rest and more difficult to stop it from moving. Of two objects moving at the same speed, it was easier to stop the lighter one. This gave rise to the notion of Inertia.
While Aristotle thought heavier objects fell faster the lighter objects, Galileo realized that objects did not fall at a constant speed, but accelerated under the influence of gravity, and they accelerated at the same rate whatever the material.
Not only are heavier objects more difficult to move up and down, they are more difficult to move side to side. They have more heft. Newton realized doubling an applied force on an object doubled its acceleration. Acceleration was proportional to force. He discovered that the proportionality constant was the object's mass. So he discovered Inertial Mass.
When Newton turned to Gravity, he discovered that the Force between objects was proportional to the product of their masses and inversely proportional to the square of the distance between them. One object can be considered to cause the field that works on objects of different mass, the more massive, the stronger the force. That was passive gravitational mass. There was the mass generating the gravity which was the active gravitational mass.
More thorough experiments in Chemistry led to other considerations of mass on the microscopic level. Certain conservation principles were developed.
In the 20th century Einstein discovered a mass energy equivalence. Other radical considerations led to the concept of anti-matter, where objects are identical except for having opposite charge. Mass can be observed to convert to energy and vice versa. Massless particles were discovered. How can an object exist if mass is the amount of material and it has no mass?
In his book The Structure of Scientific Revolutions, Thomas Kuhn argues that the "mass" referred to by Newton was not known to convert to energy so was radically different from the concept of "mass" as it was referred to in the latter half of the 20th century. While the same syllable was used to refer to both concepts, they weren't actually the same term, the two notions of mass were "incommensurable". Physicists take issue with this.
So mass began as a reckoning of the amount of a substance independent of its shape or size. It was closely tied to motion and gravity. Finally, it was found not to be all that different from energy. Some question whether the 17th Century term and the 21st Century term actually refer to the same thing.
Answer: I suggest you look into Kleppner's An Introduction to Mechanics. In Section 2.5, he gives an operational definition of mass without ever resorting to the concept of force (thus avoiding circularity).
The definition is as follows. Take an airtrack with a cart holding whatever object you want to measure, tie a rubber band to it, and pull on the rubber band in such a way so that the band is always elongated at a fixed length $\ell$. Then you should see a constant acceleration. The ratio of the acceleration to the acceleration of a reference object (pulled by the same band elongated also at $\ell$) gives you what we define as inertial mass.
Interestingly enough, this definition goes all the way back to James Maxwell.
Note that the cart itself has some mass so you have to amend your definition. There are two ways you can do this.

Conceptually simple but impractical: you can imagine doing this in space with no airtrack and no cart messing things up.
Conceptually messy but practical: you take into account the fact that the cart itself has some mass in your calculations, so in the definition of mass you no longer take a simple ratio of accelerations.

In any case, this should give a proof of concept that it is possible to define mass in an operational manner.
Answer: Physics isn't mathematics. Physical quantities are defined by the methods used to measure them. So, mass may be defined by what a balance measures: given two bodies, they have the same mass if they balance. Put them together, and balance an object of twice the mass. By this means you measure gravitational mass.
Once you have a tested theory, you may use that theory to extend your suite of measuring devices. So, given the well-tested assumption that inertial mass is equal to gravitational mass, you may then do something like apply a known force to an object and measure its acceleration to infer its mass. And on it goes. But in the end, the theory cannot tell you what mass is, it can only tell you how mass behaves.
Answer: Mass is the property of an object, that

resists acceleration by requiring a force (inertial mass, $m_i$)
attracts another object (gravitational mass, $m_g$)

Once you start quantifying these observations, you arrive, respectively, at

$F = m_ia$
$F = G m_{g1} m_{g2} / r^2$

It was a deep insight that these two concepts could be treated as equivalent, i.e. $m_i = m_g$.
Answer:
«I was looking for a definition of mass and most of the time what I got was that "it is the amount of matter". Now that is very vague.»

No, that is wrong.
Chemists and physicists agree the «amount of matter» is not mass $m$ (e.g., in the unit of kg), but about a counting number n (in the unit of mol).  The mole is tied to Avogadro's constant ($\approx 6.022 \times 10^{23}\,\mathrm{mol}^{-1}$), but conceptually similar to e.g., a dozen of items; it is a more practical one in chemistry when counting electrons, atoms, molecules, etc. when balancing reaction equations (keyword stoichiometry).
A testimony about amount of matter is the standard established by BPIM.  Though the concept is older, since 1971, it is one of the SI base units and may be found e.g., in the very first section of the four-page summary of IUPAC's Green Book (link to pdf (open access)) Quantities, Units and Symbols in Physical Chemistry, which was prepared jointly by chemists (by IUPAC) and physicists (by IUPAP).

Much of IUPAC's nomenclature is summarized in one of IUPAC's Color Books (by tradition, the color of the printed editions' cover is specific to the topic) the section References about Nomenclature the sibling site chemistry.se compiled; many of them accessible freely for anybody interested (open access).

What exactly is mass?


How can I reset the scale of multiple video strips to 100% (the default) at the same time?

Question: I've been editing a video in Blender and just noticed that the scale for all the video clips has been set to .444 (X and Y) when I actually want it to be 1.  I can do it manually but I'd prefer to know how to do it in one command for the future.  I tried selecting all the video strips and setting the property, but it only sets it for the "primary" selected video strip, not all of them.
Answer: I ended up figuring it out right after posting this question.  Select all the video clips by dragging a selection box across all of them, then press F3 to bring up the search bar and type 'scale', and select Image -> Clear -> Scale.
Comment: also worth noting that with all the clips selected, changing a setting whilst holding ALT should change it on all clips
Comment: wow that's a much better solution, if you post it as an answer I'll change the question to be more general and accept your answer.
Comment: well, to be fair it's probably a duplicate, but you could add that to your answer and accept it
Comment: I don't understand; what is a duplicate of what?


Is it okay to print from monochrome onto color paper?

Question: I am interested in printing some black and white photos and can't decide on the type of paper to print my photos on. I have struggled to discover comparisons between different photo papers. For example, White Wall offers many different paper types. Other labs don't offer "b&w" paper. Would I just print monochrome onto color paper? Or why not?
Answer: There would be a legitimate question if you were looking at inkjet (giclée) printing, where the choice of paper surface is largely a matter of taste and preference. In this case, though, you're looking at "lightjet" printing, which is an optical printing process (just like in the film days) except that it uses a scanning laser instead of a projected image to expose the paper (not at all like the film days). So you can think of it in exactly the same terms as you would have with colour or black-and-white film.
The colour papers don't have a black or greyscale, they only have different combinations of cyan, magenta and yellow. No matter how careful you are when exposing colour paper, it can never truly be black and white, and can only give the appearance of being black and white under one particular set of lighting circumstances. Change the light, and the print will have a colour cast (often a sickly sort of green). There is a way around that problem, but it means choosing a non-neutral tone for the print, and one that's far enough away from neutral that you won't get any unexpected colours if the lighting changes. (Something that's very obviously "sepia" will do nicely.) And there's also differential fading of the dyes in the print to keep in mind: as the print ages, it will change colour — often very differently in different tonal ranges in the print.
Printing on black-and-white paper means using a traditional silver process. The blacks in the image are black because little grains of silver scatter and absorb (well, trap) light. That effect doesn't change with changes in visible light; the only difference will be the apparent colour of the paper if the light itself has a visible colour bias. There are no dyes to fade, although the paper or coating may age, and the silver may tarnish over the years (very old prints may develop some bluish patches, or may "bronze out" somewhat, but we're talking very old unless the prints weren't processed properly.) Done properly and framed properly, a black-and-white silver print should last well over a hundred years without showing its age.
Again, this is strictly because "lightjet" prints are just standard photochemical prints done using a different sort of machine to expose the paper. If you choose to go with an inkjet-type print instead, the choice of paper isn't as much a technical consideration as it is an aesthetic one.
Comment: Thanks. I understand that what I am asking is aesthetic, and I have not been able to find much to help guide me to learn about this section of the art. I am interested in ink jet as well, can you expound on this choice as well?
Answer: It is possible to print color negatives and color slides on color photographic paper. However, It's unlikely that high quality black & white prints will result. As previously stated --- Chemical based black & white prints yield monochrome images that display appropriate contrast and neutrality. Color photo papers display an images from imbedded transparent, yellow, cyan, and magenta dye. In theory, an observer will see a monochrome black & white image when and if these three dyes overlap in equal proportion. The problem is, color papers are unlikely to display a neutral monotone. To achieve, the lab would need to test and reprint over and over again. Such an undertaking would likely be expensive. Let me add, in art there are no rules, you are free to follow your heart. Go for it!