Does an OpenVPN client have to be the edge device?

Question: I have a backup server I would like to use off site, and connect it to the site using OpenVPN. It would be behind a NAT firewall. Would I just need to give it an address on the same subnet as the rest of my on site network, and then forward UDP 1194 to it? Or is the configuration more complex than that?
Answer: If the remote server is going to act as the OpenVPN server then it will need to receive inbound traffic from the Internet (with the default for UDP being port 1194, as you stated). If it's going to act as the client and initiate the connection to another OpenVPN server then it only needs to be able to source traffic to the server and receive responses back (which any modern stateful firewall will handle fine).


How can I use the form X + 답다?

Question: 남자답다 was translated in another answer as 'manly'.
What is the underlying construction here? Can I use any noun + 답다?
If I want to describe someone as 'like a snake', can I say '그는 뱀다워요'?
Comment: 답다 is different from 것 같다. 답다 means that someone is X and is like X(because i. e. some are man, but may not look or behave like a man). Only in this case could 답다 be used.
Comment: I seldom see nouns attached b4 답다 being not human
Answer: X-답다: be like X, be worthy of X
From my textbook: '-답다'는 명사 뒤에 붙어서 자신의 본래 특성을 잘 가지고 있음을 나타낸다
('-답다' attached to a noun indicates having a characteristic natural to oneself)
The meaning is a bit more than just "be like", which would plainly be 같다 (그는 뱀 같아요). It's usually used to say "as X as a X should be". It includes some kind of judgement, expectation, or even stereotype.
You would usually only use it to describe something or someone that in reality is that thing or tries to be that.
You couldn't say 우리 여동생은 남자다워요 because she isn't actually a man.
Considering that, 그는 뱀다워요 doesn't seem to make much sense.
Comment: I'd like to add that ~답다 refers to qualities that are *expected* of some noun, which is the reason why @topomorto you're example for 왕답다 only works for kings and not other members in his hierarchy.
Comment: So you could describe a king with 왕답다  - saying they're 'properly king-like' - but you couldn't say 왕답다 about someone who wasn't a king?
Comment: That's how I understand it, but as I'm not a native speaker, I hope somebody else can verify.
Comment: Seems to agree with Super Cool Handsome Gel Boy's comment anyway!
Comment: Also, interesting note that this form isn't restricted only to people. It can be used with places, as well! 도시답다, 회사답다, etc...
Comment: Is it right then to describe a snake as 뱀다워요?
Comment: You could do that in theory, but what kind of characteristic do snakes have that would be worth highlighting in this way? When is a snake particularly "snakey"?
Comment: Changing 뱀 with 사자(lion), you could say 자세가 늠름한게 심바는 정말 사자다워요
Answer: '뱀답다' never works in Korean.
I am not sure what you are trying to mean by '뱀답다'. Let's change it to a more clear and easy word '여우답다'. Fox is an animal known to be sly and cunning. If you want to describe a person's characteristic, you can't use '여우답다'. You have to use '여우같다'.
The difference between '같다' and '답다' is very difficult to explain, but one noticeable difference is '답다' is used when you describe a situation where the subject acts as it is expected. For example:

그가 위험한 상황에서 그녀를 구한 것은 남자다웠다.

It can be literally translated to

It was manly of him to save her from the risky situation.

But it could also be translated to

His action of saving her from the risky situation was something that
  you could expect from a man to do.

When you use '같다', it describes an attribute or action that is related with the  preceding word. For example:

그녀가 그렇게 행동한 것은 여우같았다.

can be literally translated to

The way she acted was like a fox.
Answer:
답다 1) sharing property

꽃답다 be like a flower
그는 꽃다운 나이에 죽었다. He died at an age like a flower (=young)
아름답다 be beautiful
정답다 be friendly

2) sharing affirmative property

어른답다 be like a adult : Usually, adult is responsible, polite,
and honest. So whenever he is in any state, like adult or kid, we
can say.
그녀는 교수 답다. she is like a professor : That is, she is academic.

3) sharing typical property

이 책은 책답다 This book is really book : That is, it contains a lot
of useful information, and it satisfies a lot of properties which
should be contained in a book.
이번에 우리 아들이 선생다운 선생을 만났어 At this time, my son met a academic teacher .
@ In general, 답다 is affirmative as a whole. When we use 답다, we
must consider high cover, which is outstanding than or equal to him.
So snake is inferior to human so that we can not say 뱀답다.
Hence we can use 왕답다. In my thought, as you know, king is rare so
that it seems that we do use use it frequently.
We can use 어른 같어, 왕 같어, 뱀 같어, 교수 같어.
같어=apperance vs 답다=property (Surely we check property through
appeared act : 그는 남자 다웠다. He was like a man)
For instance, someone does not give his one to others and he check
his profit. He is like a snake. That is, he has a property of snake.
Hence when we see his stealing something (property is appeared in
outside), we say that 그는 뱀같어.

How can I use the form X + 답다?


What asymmetric key exchange algorithms are known besides DH?

Question: On Wikipedia, a lot of the subjects that are said to be different key exchange methods are often just protocols that incorporate the Diffie-Hellman algorithm into them. The only other key exchange algorithm I know of besides DH is Algebraic Eraser, of which I don't know much about. Are there any others? And I don't mean key exchange schemes based on symmetric key primitives.
Comment: I think there is some super singular elliptic curve isomorphism thingy. No idea how practical it is.
Answer: Using lattices/ring-LWE, there is Lattice Cryptography for the Internet (by me), which inherits from Ring-LWE encryption, and has been implemented by Bos et al. with further improvements by Alkim et al.
The underlying mechanism is conceptually DH-like, but uses completely different mathematics.  We start with a uniformly random $a \in R_q = R/qR$, which can be chosen by one of the parties or by a trusted third party.  Here $R$ is an appropriate choice of ring, e.g., $R=\mathbb{Z}[X]/(X^n+1)$ for power-of-two $n$ (in the few hundreds, for current security estimates).
The basic protocol works as follows (oversimplifying a bit): to establish a key, the first party chooses a "short" random $e \in R$, and announces $E \approx e \cdot a \in R_q$, where the approximation hides some short random error.  Similarly, the second party chooses a short $f \in R$, and announces $F \approx a \cdot f \in R_q$.  The first party can then compute $e \cdot F \approx e \cdot a \cdot f \in R_q$, and the second party can compute $E \cdot f \approx e \cdot a \cdot f \in R_q$.  The parties then use some kind of "reconciliation" mechanism to extract a common secret key from their shared "noisy" versions of $e \cdot a \cdot f$.
The above mechanism can be proved secure against passive eavesdroppers assuming the hardness of the corresponding Ring-LWE problem (which itself can be proved quantumly as hard as worst-case problems on ideal lattices, for appropriate parameters).  Of course, in reality we need authenticated key exchange and other properties; these can be obtained using additional techniques that originated in the DH setting (see the first link for details).
Comment: I don't understand the math behind lattices. Diffie-Hellman is very simple, requiring only a few operations learned by me as early as sixth grade.
Comment: My layman's question: If an adversary is capable to tap exactly all bits that are being transferred between the communication partners, wouldn't he be able to employ the same "reconciliation" mechanism to obtain the common secret key?
Comment: No, because the eavesdropper sees only $a, E,F$.  There's no apparent way to get anything close to $e \cdot a \cdot f$ from this: e.g., $E \cdot F$ doesn't work (just expand it out). In fact, one can prove that the reconciled key is indistinguishable from uniform to the eavesdropper, under the Ring-LWE assumption.
Comment: If you know how to add and multiply polynomials, you can understand this KE protocol.
Comment: @ChrisPeikert That I do know how to do, but I'm guessing that this requires a more exotic form of them. Polynomials, for one thing, are not numbers, so there much be some sort of novel mapping between integers and polynomials in this system. What are the key sizes necessary for strength levels of 128, 192, and 256 bits?
Answer:
different key exchange methods ... Are there any others?

More key exchange methods:

Kirchhoff's-law-Johnson-(like)-noise (KLJN) secure key distribution (a) (b)
quantum key distribution (c) (d)

(These rely more on hardware than on algorithms)


What is the value of a Coursera certificate?

Question: I took up an introductory course to forensic science in Coursera, because it was actually the only forensics course I could find that was accessible, however I do wonder if it is worth anything in my CV, as a student it is obviously better than nothing, but is this something good enough to show?
How does it compare to courses completed directly through MIT open courses, or those from another famous university? And if these are assets to a CV, if I go ahead to complete enough for a degree, how does it fare in comparison to the proper degree from the corresponding institution?
Comment: What is the value to whom? Do you care about university admissions? Employers? Prospective spouses?
Comment: Related at Workplace.SE.com: [Are verifiable MOOC programs of study recognised by employers?](http://http://workplace.stackexchange.com/questions/32822/are-verifiable-mooc-programs-of-study-recognised-by-employers)
Comment: Related: [Can I include the completion of Udacity and Coursera classes I have attended in an academic CV?](http://academia.stackexchange.com/q/2336/4140)
Comment: @earthling +1 for "prospective spouses" :D
Comment: Depends also on the topic. If you take a programming course being a CS it adds exactly nothing; but if you take a course on something parallel to your field, it can show you have at least the basis to some knowledge for your research. For example, AI can be used by a scientist to better process data, but it is usually not taught outside CS degrees (in undergrads, at least).
Comment: Well, the last was not exactly what I had in mind, but the rest were all within the question
Comment: @Stephan, This is the correct link: http://workplace.stackexchange.com/questions/32822/are-verifiable-mooc-programs-of-study-recognised-by-employers
Answer: Value in an academic environment: zero. Everything you learn at Coursera you'd simply learn from a textbook in a few days if you needed it for your academic research or teaching.
Value to a non-academic employer: marginal, mainly as a signaling device (this person will sacrifice his spare time over a non-trivial amount of time to improve himself), but certainly lower than a certification in a field or skill directly related to your job.
Value to a prospective spouse (as suggested by earthling): depends. I'd certainly look favorably on someone who took a Coursera course instead of watching TV.
Value to yourself: again depends, but could be highest of all. I certainly know that those courses I took were mainly for my own pleasure and benefit.
Comment: I disagree, they have some value in academia. I listed MOOCs on a scholarship application and was told that the MOOCs wen't to my benefit, as I was awarded the scholarship. But I do agree that the real value is personal gain/knowledge, etc.
Comment: While I was in high school, I took several MOOCs on Coursera related to a field, and listed them on a scholarship application. I ended up getting the highest scholarship available at my institution. I feel that it showed my genuine interest in the field. It's cute for a high school student to brag about - but I think it's inappropriate for an academic.
Comment: If "Everything you learn at Coursera you'd simply learn from a textbook" is true, shouldn't then the value in an academic environment be "same as reading/working through a textbook" (and "value on CV" same as listing textbook in reading interest?)
Comment: Coursera certificates are the new bar-bragging stories.
Comment: @Stephan agree in almost everything, but although what you can learn in a Coursera MOOC is comparable to what you get reading a book, you do not usually get certificates for reading, and people usually rely a lot on certificates for applications.
Answer: One of the commentators mentioned that MOOCs might be seen in a negative light in some fields, such as software engineering. Especially for this particular field, I would not at all be surprised: Many of the current professionals got their hands-on training through working on projects on the internet in their youth, and such projects would obviously go well beyond a simple introductory course. As such, MOOCs provide only introductory material to the field, and this material has been available in an easy to access format on the internet for a long time, anyway (YouTube tutorial videos predate contemporary MOOCs by years, and simple websites even more so).
I should point out that for other fields, often more specialized in scope, the sort of lectures offered by MOOCs have not been available unless you went to university to study the stuff. Sure, books have existed, but there is a difference in learning from books and listening to lectures (the latter being much more passive, and therefore often more enjoyable, while perhaps not as deep or efficient).
Having said this, I strongly feel that taking MOOCs on your spare time shows that you have motivation to deepen your knowledge, be it in your own profession or just enlarging your horizons and understanding other fields. While reviewing the basics of a field that you are supposed to be an expert in could be viewed in a negative light, a basic understanding of project management and economics would probably help your application even if you were a software engineer.
I have heard some recruiters say that they appreciate an internet presence, and joining in on all the new fun would certainly show that you are technologically capable and follow what is happening in the world. In the software engineering world, one could well put their StackOverflow alias on their CVs. I am sure that some recruiters disagree, though.
Finally, to address your point about how online courses compare with real live universities. Traditional courses usually have a higher workload, and more stringent control on passing a course. MOOCs being very new, it is nigh impossible to know just how difficult it is to pass a particular course or whether you even know the stuff now that you have. Granted, a traditional university degree does not guarantee these things either, but prospective employers better understand how much one can expect one to remember from the courses taken at a real institution. I think MOOCs will play a slightly bigger role in the future than they do now, but we are not quite there yet.
Answer: MOOCs like those taught on Coursera are a matter of differing opinions.  I think they are great for the students since they provide a great free tool for helping learn content that may be difficult to learn, interpret or even access alone.  Unfortunately, they have problems with verification: students do not have to do very much to confirm their identity, and there is much speculation of plagiarism within the classes (even The Guardian wrote a small piece on that recently http://www.theguardian.com/education/2014/mar/14/students-cheating-plagiarism-online).
Have I taken classes on Coursera? Yes. Do I put this on my CV?  Yes...for internal purposes anyway, under a "continuing education" or "professional development" section to show my employer that I am continuing to improve myself and stay up-to-date where necessary.  I'm a scientist.
My husband (a software engineer) tells me that, while MOOCs or similar training is good on a personal level, it is considered a negative thing for people in his profession, and usually only added to CV to make up for a lack of real technical training or experience.  So, unfortunately, I guess the area of your work will make a difference to how others perceive your good intentions.  But, yes, Coursera is better than TV!
Answer: Actually these courses for self-paced learning. Those who are really interested in a subject and could not study in any regular university course in any subject of choice, can learn following a path offered by these online courses. It is Similar to "learning on your own". Practical course like programming in any particular programming language currently preferred by industry is good but certificates won't count as much as a regular university degree. In these practical value oriented courses will prove nothing because at the end efficiency will matter and industry will hire those people who have this efficiency and regular degree will always score high. This certificates won't get you an entry in any reputed University for going further with the study of the subject. Professionals take these courses mostly owing to the fact that a curricula offers better disciplined and structured way of learning in which testing what you learn provision within the curriculum is there. Professional, already in a field learn better in self paced learning way. These are the benefits among few others. But one other thing for these online courses associated with university can not be ignored. All over the world private university funding and "Live On your own" and "Live on your own earning" policy for the Universities are one of the causes for them to offer online courses to the people which in the past and still is for only a graded few is for earning money. People who are willing to earn a certificate which might give them an edge over others in the competitive market pay few dollars to enroll and at the end spending few hours earn a 'certificate of value'. These dollars are one of the ways for the universities to earn a fraction of cost to run universities.And not all subjects can be learned this way, suppose Genetic Engineering or Medicine can never be learned through online courses. Yes you can expand your horizon of your knowledge in any particular field of study of your choice. And that's the primary reasons of these courses, i.e MIT open course ware.
Answer: Alone, listing an MOOC on a resume has about the same value as expressing other interest in a topic.  It serves only to get you past early (automated) screening steps of a selection process.  This is valuable in that it might save a little time establishing common ground between interviewer and candidate.
But the I can see an opportunity for this to change with the integration course information with evidence of participation in online forums on a topic.    As a screener/interviewer, if I could and see the questions asked and answered in a classroom setting, that starts to add value.
The challenge however is scaling this to massive open online learning.   In many cases, the "good" questions one might asked and answered online and forums like stack exchange.   Posting duplicate questions often gets discouraged (voted down) in this sort of environment.   But if a MOOC platform could also let me see the related searches and clickstream generated by a candidate the possibilities are there that MOOC's might differentiate themselves through participation (even somewhat passive participation) in activities related to the course.   I've not yet seen this in practice, but it seems like what might be needed to increase the value of online information resources over textbooks.


What to and what not to mix with alcohol?

Question: Are there any restrictions to mix alcohol with other things?
A friend of mine mixed whisky with milk and then he turned sick. he got rashes all over his face. But when i searched a little bit it turned out it's fine to mix whisky and milk. I want to know are there any limitations for mixing or can we just add anything we want to alcohols(mostly any) for better taste.
Comment: This. For as far as i know, you can mix alcohol with anything. It might not always be more tastier and can create weird side effects in the mix, depending on the booze used(Baileys and cola is not a good combination, for example).
Comment: If you can eat and or drink it alone then you can mix with alcohol.  But it is hard to prove a negative so not going to say nothing.
Comment: Um, was it the milk?  When you say mixed with, do you mean literally 'mixed', or one whiskey, one milk.  I can't see why this would make anyone sick...  and believe me I have tried most combinations!  Quick edit: without the pictures, what do you mean by 'sick'?
Answer: The main hazards of mixing alcohol with milk are that you may denature the milk proteins and get curds.  Unpleasant, but probably not likely to provoke an allergic reaction.
Does your friend have any nut or pollen/tree allergies?  Depending on what the whiskey was casked in, there could be some residual allergens that were the actual culprit.
Answer: Mixing Alcohol is fine, though it's best to use common sense when doing so and not to go too overboard doing so. It worth checking other possibilities as well contributing to the unwellness: Did your friend eat before drinking, what was eaten? As for the rashes, that sounds like some sort of allergic rection.
By personal experience, Mixed Alcohol effects people differently with me, I can't drink Jager-Bombs or mix two Different wines. But I have many friends that can.


Decoding an encrypted HTML file using Javascript

Question: I am trying to decrypt the encrypted page source of an HTML file. I am searching for a decoding trick to decrypt a page containing Facebook interface UI. It is in the following post decrypted facebook UI page. The demo page of that post is encrypted. Is there any possible way to decrypt it?
Answer: That's not really encrypted, just encoded. The answer's actually right there in the source. You need to run all that stuff between the innermost quotes through the Javascript unescape() function. Here's a handy page for it: Online Unescape Decoder and Encoder.


Problem using TI CC2650

Question: I am asking this question directly on the TI forums as well, but decided to post here in case anyone has specific experience with this.
I am attempting to prototype with a CC2650 RGZ package 48 pin QFN processor from TI. I am trying to program it using the XDS100v3 debug probe on the SmartRF06 Evaluation board. The chip I am trying to program is a standalone, not the evaluation breakout board.
My only connections are a 3.3V power supply to VDDS, VDDS2, VDDS3, and the VDD_DCDC input. The DCDC output I have connected to the VDDR 1.8V inputs. My reset pin is tied through a pullup resistor to 3.3V. All pins listed above have capacitors to ground, as recommeded in the SmartRF documentation. When I tried just using that, I got 3.3V on the power rail and 5 mA being drawn from my power supply, as expected. So for that reason I believe my power connections are correct.
To program the board, I connected the cJTAG connections from the SmartRF06. This would be Pin 1 on the JTAG connector(VDD_Sense) to Power, Pin 4(Ground) to Ground, Pin 7(TMSC) to Pin 24 on the CC2650, and Pin 9(TCK) to Pin 25 on the CC2650. These follow chapter 7 recommendations from the programming guide. I ran CCS to program the board, and recieved the error "Power Failure on target CPU".
Following this, the CC2650 started drawing the current limit from my power supply at 30 mA. This persisted after I disconnected the JTAG pins. I think, therefore, that the chip was burnt somehow by the debugger. I do not, however, have any idea of why this happened.
On the SmartRF board, I disconnected the VDDtoEM jumper, but left the other default jumpers on. I also removed the evaluation breakout board. POWER switch was set to ON and BAT/USB was set to USB.
I have a couple days before my replacement chip comes in, but if anyone has experience with TI debuggers, specifically with designing boards using the CC2650, I would appreciate some advice on how I can program my chip.
For reference, here is the development kit I was using, which has the debugger onboard: http://www.ti.com/tool/cc2650dk
Thank you for any advice or help you can provide.
Answer: Have you got a full schematic to take a look at? I used the CC2650 Launchpad's debugger (XDS110) to program a custom board recently, and I removed all the headers however between the debugger and the EM. I would suggest doing the same on your debugger.

Problem using TI CC2650


What secret hats are there?

Question: I notice there are some hats available that aren't on the hat list. What other hats exist, and what do I have to do to unlock them?
Comment: dun dun dun!!!!!
Answer: There appear to be 6 hats in the sprite file that are not on the list:

Lump of Coal

Awarded for a Question or Answer Downvote.

The N00b Hat

First post by a new user!

Scrooge Hat

Participate in closing a question.

Braaaains

Post a question or answer from an account dead for 30 days before Hat Dash began

Batman's Cowl

Was intended to be for having three upvoted arkham-city questions or answers, but it was dropped due to time constraints

Master Mind

Average answer score of at least 5 and at least 5 answers.  This hat was not awarded until HatDash officially ended at 12:00am UTC January 7, 2012.

Plus, the hat that you start with:
Invisible Hat

Clicked on a link.
Comment: If you want to test, go upvote me. :P
Comment: Batman's Cowl would be having 3 upvoted Batman: Arkham City answers, based off the others.
Comment: Zombie could very well be related to the Necromancer badge.
Comment: and given that there was already one Community Wiki answer, why did you add another one? :P
Comment: @Powerlord Duh, the *hat*.  :P
Comment: @John Umm, community wiki usually doesn't count as activity.
Comment: @Powerlord Well, I guess we'll find out.
Comment: @Powerlord: I was busy making the images while you posted your answer. I didn't bother to refresh. If it bothers you that much I'll delete this and edit yours though.
Comment: [It appears that the Zombie Hat](http://chat.stackexchange.com/transcript/message/2742124#2742124) is related to a user returning to the site after an absence. Attempting to recruit a patsy to test this theory.
Answer: Here, I'll start a Community Wiki answer

Lump of Coal - Downvote a question, as seen on LessPopMoreFizz's hat rack.

What secret hats are there?


Image Wells, Core Data, and Sqlite files

Question: I've got a mac application that I've developed.
I use it to create sqlite files that are bundled with my iphone app. The mac app uses Core Data and bindings and is working fine except for one "weird" issue.
I use an NSImageView (or Image Well) to allow me to drag and drop jpg files.
This is bound through to an optional binary attribute in my model class.
For some reason when I drag and drop a 4k jpg file it onto the image well and save the sqlite file. The data saved to the binary column is over 15 times larger than it should be.
Whereas if I use an application like SQLiteManager and add the image into the row in the database. The binary data is the correct (expected size).
File 4k jpg
Actual size:                    2371.
Persisted via Core Data size:   35810.
Can anyone give me a suggestion as to why this might be happening?
Do I need to set some setting in Interface Builder or write some custom code?
Answer: Create dump from sqlite3 file and check which content use your space. I use plain sqlite3 to store image cache in Galileo and as far i know there db size ~ total images size.


Baptism of grandchildren

Question: My grandchildren were not baptized and I was worried about it. They are going on a trip.   Therefore, I took it upon myself to baptize them.   What if anything is the Catholic Church's view of this?  My children are not practicing Catholics.  When my oldest grandson was a baby, maybe about six months old, I was giving him a bath in the kitchen sink and poured water over him and stated specifically, "In the name of the Father, the Son, and the Holy Spirit"...  I did this to the other four today.  I told my son and daughter.  My daughter just chuckled and my son was upset with me.  They were raised Catholic and went to Catholic school, but neither are practicing now.
Comment: Welcome to Christianity.SE. For a quick overview, please take the [Site Tour](http://christianity.stackexchange.com/tour). For your question to work here, you will need to edit it to ask what the Catholic Church says about this particular situation: someone simply baptizing relatives or friends who are not practicing Catholics. We can't answer here whether something is right or wrong; only what a particular denomination *believes* is right or wrong. See: [What topics can I ask about here?](http://christianity.stackexchange.com/help/on-topic)
Comment: @LeeWoofenden FWIW, some denominations have codified rules about such things that take it beyond "belief" and into "practice" or "doctrine."
Comment: If you only said "In the name of the Father, the Son, and the Holy Spirit" and did not first say "I baptize you", then (as far as I know) this is not a valid baptism.  (It is, in any case, illicit, because lay folks like us are allowed to baptize only people who are in danger of death.)
Answer: Canon law states:

Canon 868
§1 For an infant to be baptised lawfully it is required:
1° that the parents, or at least one of them, or the person who lawfully holds their place, give their consent;
2° that there be a well-founded hope that the child will be brought up in the catholic religion. If such hope is truly lacking, the baptism is, in accordance with the provisions of particular law, to be deferred and the parents advised of the reason for this.
§2 An infant of catholic parents, indeed even of non-catholic parents, may in danger of death be baptised even if the parents are opposed to it.

Given that your grandchildren were not in imminent danger of death, it appears that your actions may have been in breach of canon law.
Comment: @AndrewLeach I humbly disagree on your first point because the grandmother makes no claim that she had been given temporary guardianship ('lawfully hold ...) - in fact the family was about to take a trip together.  Whether the baptism was valid is less clear, because it depends on the wording of 'baptised lawfully'.  As to informing the parish priest, the grandmother has overstepped the mark enough already, so in such step  should be taken by the parents if they so wish.  The grandmother should be advised to attend Confession as soon as possible.
Comment: I suppose that while the children are in the grandparents' care, it could be held that they are *in loco parentis* at that time and point 1 is satisfied. However, if the parents are not practising then point 2 is doubtful.
Comment: However, despite being irregular or even illicit, the baptism is likely to be **valid** as the matter, form and intention were correct, so the children's parish priest should be informed in order that it can be properly recorded.
Answer: While the church makes allowances for baptisms in case of emergency, for this baptism to be valid (or ruled otherwise) it is required to consult with a local priest or the local bishop/bishop's office.  Beyond the point that Dick Harfield makes regarding canon Law 868, wherein it is expressly the parent or legal guardian's role to baptize the children, there is this further consideration.

THE MINISTER OF BAPTISM
Can.  861 §1. The ordinary minister of baptism is a bishop, a
  presbyter, or a deacon, without prejudice to the prescript of ⇒ can.
  530, n. 1.
§2. When an ordinary minister is absent or impeded, a catechist or
  another person designated for this function by the local ordinary, or
  in a case of necessity any person with the right intention, confers
  baptism licitly. Pastors of souls, especially the pastor of a parish,
  are to be concerned that the Christian faithful are taught the correct
  way to baptize.
> Can.  862 Except in a case of necessity, no one is permitted to confer
  baptism in the territory of another without the required permission,
  not even upon his own subjects.
Can.  878 If the baptism was not administered by the pastor or in his
  presence, the minister of baptism, whoever it is, must inform the
  pastor of the parish in which it was administered of the conferral of
  the baptism, so that he records the baptism according to the norm of ⇒
  can. 877, §1.

By the way, your concern has arisen at our parish with some frequency by people with grandchildren.  One of our deacon's indulged in considerable discourse on this last year.  As he put it, the Church (in this diocese anyway) prefers to encourage the parents to return to "practicing" status from which baptism would follow logically.  Catholics Come Home is one of a number of programs focused on that very issue (and a ministry he is active in).
Comment: @MattGutting Edited per your point on pastoral advice.  No pastures were harmed in the editing of this post.

Baptism of grandchildren


Doubling a red velvet cake recipe

Question: I have made 4 times the recipe in order to make a half sheet cake. Do I lower the degrees and bake time?
Comment: Your title says double, your text says 4 times, which is it? Are you making one big cake or 4 smaller ones?
Comment: A half sheet pan is 18" by 13" (46 by 33 cm), is that the size you're making? Sheet pans are thin, with a 1" (2.5 cm) raised lip. This is jelly roll territory, it would either make a very thin cake or you can cut it make a many layered cake, which would make sense with a red velvet cake. Can you explain exactly what you're doing and post your quantities? 4X makes no sense, 2X maybe, depending upon your recipe.
Comment: I'm confused. The above comment and the answers refer to using a sheet pan. I don't see anywhere in the question where the OP says she is using a sheet pan. She says she is making a sheet cake. Sheet cake pans typically range from 2" to 4" deep.
Answer: If you're making the same thickness of cake, and it's a relatively thin cake (suggested by the fact that you're using a sheet pan), you typically do not need to change the time and temperature.  So if you've doubled the recipe and doubled the area of the pan, you don't need to make any changes.
A larger area cake will rise more as there won't be as much edge that will set before the rest has risen.
If it's a thicker cake (the batter is more than 1/2" / 1.25 cm deep before baking), you'll want to turn down the temperature and bake for a longer time.  If the batter is an inch or more deep, you may want to consider cooling strips and/or a heating core.
Answer: Here's a highly rated recipe for a Red Velvet Cake in a sheet pan by Lee Drummond.
If you're in fact using a sheet pan, compare the quantities of your ingredients to hers. I wouldn't go any bigger in a sheet pan, or it will overflow. I know from experience, that makes a big mess.
She uses:

2 1/2 cups cake flour
1teaspoon salt
1 cup buttermilk
1 teaspoon vanilla extract
1 teaspoon baking soda
2 whole eggs
1 1/2 teaspoons vinegar
1 1/2 teaspoons cocoa powder
1 1/2 fluid ounces red food coloring
1 cup shortening
1 3/4 cup granulated sugar

Make sure your ingredient quantites are in line with that.
She goes on to bake for 20 minutes at 350F (178C).

Doubling a red velvet cake recipe


Studies on Password Double Entry per registration

Question: Are there any recent usability / UX and conversion studies how double entry of passwords while registration a user account in ecommerce shops slows down conversion rate?
We try to ged rid of entering password twice. There is a "forgot password" flow anyways.
Answer: Double entry of Password is really unnecessary. To avoid mistakes, repetition during sign up is not a solution. Yes, there is "Power in repetition" but not in password confirmation. The solution is to provide the option to unmask the field associated with a strength indicator. Users make more errors when they can't see what they're typing while filling in a form. They, therefore, feel less confident.
https://www.nngroup.com/articles/stop-password-masking/
When signing up for Facebook or MailChimp, you don't need to enter your password twice
Facebook SignUp

MailChimp SignUp

And it's true that user account in e-commerce shops slows down conversion rate.  There is a famous case study by Formisimo where their newest version had only one password field for registration
Case Study
You can also check this
PDF
Answer: I don't think you need to refer to any studies/articles for this. The repetition during sign up is for avoiding mistakes during the password setup. A simple typo could lead to the user having to reset their password but
would the user actually know why the password is being shown to be wrong?
A typo, by nature, is mistake that gets overlooked. Which is why having to enter the password twice eliminates such mistakes. Also, "forgot password" is used to help the user when they "forget" the password. No one likes going through that flow, especially if they have just created their account.


Kid with Expensive Muktzeh Item in his Hand on Shabbos

Question: If I have a little child with an Ipod (which is muktzeh) in its hand can I grab the hand and shake it out of its hand into a safe place to prevent the child from breaking it?
Answer: The Kitzur Shulchan Aruch (88:13) says that moving Muktza indirectly (as you described) is only allowed if you need the object you're shaking, and not for the sake of the Muktza object.
So you shouldn't be allowed to shake the kid in order to drop the Muktza, if your intention is only to safeguard the Muktza.
However, since you are not allowed to pick up a kid who is holding Muktza (ibid 14), you could decide you want to pick up the kid and cuddle/play; as a result you now could shake the Muktza off them (onto a safe place - ibid 13) in order to pick up the kid.
Comment: [Paragraph 5](http://hebrewbooks.org/pdfpager.aspx?req=41276&st=&pgnum=283&hilite=) is more telling.
Answer: Disclaimer: I'm not a posek!  Consult your Rabbi before accepting my opinion!
But to my mind, I think you could take the ipod directly out of the child's hand and put it somewhere safe.
Reason: a k'li shem'lachto l'isur (object whose main purpose is a forbidden activity on shabbos) can be moved "michama l'tzel" (from sun to shade) in order to protect it from being damaged.  You don't even need to use a shinui - you can just pick it up and move it.
Likewise here - the ipod is in danger of being damaged; you can just pick it up and put it somewhere out of the kid's reach.
(I have deliberately left my previous answer "struck out", because while I'm embarrassed by my previous show of ignorance, I think it's a valuable lesson in consulting your sources before opening your mouth... thanks to @msh210 for questioning me!)
Turns out "michama l'tzel" is a specifically stringent case; you can't even do that with a k'li shem'lachto l'isur (one of the most lenient cases of muktzeh) (Shabbos 123b, Rashi ad loc. d"h ומחמה לצל).
There is, however, an eitzah (recommended "trick") for someone who wants to move something muktzeh in order to protect it from damage: invent some reason why you need to use the space it's in, e.g. if it's on the grass, you can decide you want to sit down in that spot specifically.  Then you can pick up the object - and once it's already in your hands, you can go and put it down wherever you want.  Even though it's a bit of trickery, it is permitted to do this for a כלי שמלאכתו לאיסור (Shulchan Aruch HaRav, 308:12).
But after all that, I'm not sure how that translates to the kid with the ipod - maybe you want to use his hand to put some candies in...?  :)
Comment: @msh210 - THANK YOU for questioning me.  I checked my sources and i was completely wrong - "Michama l'tzel" is prohibited!  Will revise my answer accordingly...
Comment: could you please consider de-jargonifying a little? Some terms, such as "muktzeh," are understandable to anyone who gets the premise of the question, but not necessarily "eitzah," "ha'arama," etc.
Comment: A citation would be great.
Comment: Is an ipod a Kli Shemelachto Le'issur (which can be used for something permissible) or Muktzah Machmas Chisaron Kis (Muktzah because it is so expensive that you wouldn't use it for anything else)? If it was Muktzah Machmas Chisaron Kis, would that changee the answer?
Comment: @Isaac - done :)


What is the OSI model and how does it apply to todays networks?

Question:
As a system administrator what should I know about the OSI model? (Rec X.200)
Briefly, what are the layers and what do they do?
How much do I need to know about in my day-to-day work?
How does this contrast with the TCP/IP model? (RFC1122)
Does the OSI model still apply on today's networks?
Answer: I don't see anything wrong with being able to differentiate layers between the two models.  On the plus side, having knowledge of the OSI model comes in handy when you're talking to people or reading documentation referencing the top 4 layers of the OSI model:

Here are some links with explanation on what each layer does:

http://www.dummies.com/how-to/content/getting-to-know-the-osi-model-for-the-ccna-exam.html
http://www.webopedia.com/quick_ref/OSI_Layers.asp
Comment: Your numbers in the right hand column are not helpful - they may lead people to confuse which "layer" people are talking about when they say "layer 2" (which IMHO always means the Data-Link layer).
Comment: What right-column numbers?  What are you talking about?  ;) Thanks for pointing that out!
Comment: Also the left hand side says tranport instead of transport, but I'm too tired to fix it at the moment =p
Answer: As techs we use the OSI model all the time as a network tech when trouble shooting a network connection. Since our networks were built on this model we use it even if we aren't really aware of it.
When troubleshooting a network problem we often go up the OSI model.

Physical - Is the network cable plugged in?
Data Link - Do you have a link light?
Network - Are you getting an IP?
Transport - Can you ping (or more more accurately as SaveTheRbtz pointed out telnet to) your default gateway?
Session - Do you have DNS server information? Can you ping 184.108.40.206 but not google.com?
& 7. Presentation & Application - Can you browse to a site?

You use the OSI even if your not aware of it. Being aware of it might help you communicate better with people/vendors about network situations. Many companies require extensive OSI knowledge for a networking certification (I know Cisco did).
Comment: ping is ICMP and so L3 (if it's not arping or tcping, those L2 and L4 respectively). Better example is `telnet`, i think.
Comment: this is a great way to pack it all into a very common scenario. thank you!
Answer: I got my first job in 1990 by reciting the OSI layer model. They were most impressed. I didn't actually understand it but boy could I recite it well.
Comment: they had networks back then eh?
Answer: You need to know the OSI model because a lot of documentation for proxies, load balancers and other such things will refer to "Layer 7" or "Layer 4", and you need to know what they are talking about.
That wiki page does a pretty good job explaining the layers.  The TCP/IP model sits on top of the OSI model.
As to whether it applies today, the answer I'd say is, "sort of".  A lot of devices these days are hybrids and work on multiple layers at the same time to route packets more efficiently.  However, if you are doing any sort of network design, knowing at least the basics and some of the key acronyms for at least layer 2,3,4 and 7 are handy.
Answer: These days, you don't need to know the whole OSI model.
You really just need to know:

Layer 2 - ethernet, wifi, ppp, etc frames
Layer 3 - IP packets
Layer 4 - TCP and UDP packets
Layer 7 - everything else

(invert to taste, if it offends you to have Layer 7 at the bottom)
See also https://www.isc.org/logoware/isc-9-layer-osi-model-cotton-t-shirt
Answer: I find my knowledge of the OSI model incredible useful in solving networking and system issues. It is a theoretical model one can use to guide investigation into a problem even though TCP/IP does not directly map to the OSI model.
Answer: You can find information about OSI model by visiting http://www.linuxconfig.net/basic-information/osi-model
Answer: As a system administrator myself, proficiency of the OSI model helped me a lot in identifying problems on my network. The link below is a simple explanation on how you could use the OSI model to troubleshoot networks.
http://www.petri.co.il/csc_how_to_use_the_osi_model_to_troubleshoot_networks.htm
Answer: I genuinely don't believe that many, if any, sysadmins need to know the OSI model in any specific way, however the IP model is staggeringly relevant and is used all the time.


How can I attach a safety gate at the bottom of the stairs?

Question: I have a wall on one side with trim molding at baseboard and opposite end is the wooden banister. What type of gate can I attach. The drywall is not holding the screws in place and we we frequently open and close the gate. I have  regalo gate that I re-purposed but it keeps falling  off the drywall. The stud is a little fruther away from where I want the gate on the wall, if I fix it to the stud in the drywall, the gate would be at an angle to the wooden banister.
Comment: Are you opposed to using a pressure mounted gate?
Answer: Could you attach a board to the wall, that spans the distance between the stud, and your ideal hinge location for the baby gate?   For an example of what I'm talking about-- as well as plans for a cool parallelogram baby gate-- see the following:  http://woodgears.ca/home/baby_gate.html  (Note I am not talking about the gate at the top of the stairs, that you see at the top of the linked page, but rather the gate at the bottom of the stairs.)
Comment: This is the specific picture I'm referring to:  http://woodgears.ca/home/gate66-b.jpg . In addition to the parallelogram awesomeness, you'll note that he uses a board on the wall to account for the inconveniently placed stud.
Comment: I've done this myself and it has worked great for 7+ years.
Answer: There are safety gates made specifically for this configuration. See, for example, this one on amazon: Regalo Top of Stair Gate, White by Regalo http://www.amazon.com/dp/B003VNKLI4/ref=cm_sw_r_udp_awd_AUjItb1Q0882Z
I'm not endorsing it or recommending this particular one ... Just pointing out that there's a product line designed to meet this need.
Answer: I would attach a piece of wood to the drywall at the place you want it, and attach the gate to the wood.
You can make it wide enough to reach over to the stud, or leave it narrow (like a 1x4 board, 36 inches tall) and just put it in the place you want to anchor the gate.
There is only one reliable way that I have found to attach anything to drywall, which is using auger-type anchors:

(source: alliedboltinc.com)
These are available at any hardware or home-improvement store.  I highly recommend the metal ones.  The plastic augers are acceptable, but the metal ones are more durable.
Any other plastic drywall anchor is a waste of time and will not hold up to much weight, flexing, or stress.
They are quite strong.  I attached an equipment rack straight to drywall (no stud connections) with 8 of these, and did chin-ups on it (weighing 200 pounds).  It did not move at all.
For a baby gate, I would use the 1x4 board held into the drywall by 6 of these augers, in a zig-zag pattern with 3 on each side.  Drill 6 pilot holes (1/8 inch drill bit) through the wood into the drywall (that way you know your holes will all line up).  Put the augers into the drywall in those holes.  Enlarge the holes in the wood so the screw slips through (you don't want the screw threads grabbing the wood; you only want them grabbing the augers), and then screw the wood to the augers.  Then attach the gate to the wood.
Alternatively, if you use a wider piece of wood to reach the stud: either make the wood wide enough to span from one stud to the next (probably 16 inches), or else use these augers on the non-stud side of the wood.


Are there plants that add acid to soil naturally?

Question: I'm curious if there are any plants that might add acid to their soil so that they might work well in a permaculture setting, you might be able to plant X, Y or Z near a blueberry bush to eliminate the need for soil upkeep.
Comment: My gut instinct says nothing that drastically acidifying exists... but I don't have references to studies on that yet...
Answer: About the only thing that will acidify soil over a period of years, and keep it so, are certain trees, mostly conifers, though it varies between species. The variation is accounted for by the presence of calcium in the leaves - the lower the calcium content, the more acid the soil will be. The link below might be of interest on this subject
http://www.telegraph.co.uk/gardening/plants/trees/10633984/Do-conifers-make-soil-more-acid.html
However, since you're not likely to be planting in a Scots pine forest which has been present for thirty years or more, this isn't much use for your purposes.
Comment: There's always a catch! LOL
Answer: Acidic soils are great for potatoes, blueberries, hydrangea...but most vegetables do better in more neutral soils.  There are no plants that actually DECREASE the pH of the soil PER SE.  Whenever organic matter decomposes some acidity is produced but nothing that would make even a temporary change in the soil to make even blueberries happy.  The best way to reduce pH for special acid-loving plants is to add elemental sulfur.  This is a slow process and needs to be checked/amended at least yearly. For my blueberries, I add lots and lots of organic matter with periodic applications of sulfur.  They are separated from the rest of my garden in their own raised bed.  I also plant my potatoes in this bed.  I own a great pH sensor...the ones you get at Home Depot or Lowes are pretty iffy.  The tests using liquids work better than the 'meter' poke in the ground type.  Soil testing truly makes a gardener successful or not...otherwise it is all wishful thinking, grins!  And that works pretty well most of the time.  Luckily...if someone comes up with a plant that actually makes it's soil more acidic and that this is measurable would be a great thing.  Especially when working with pH neutral or more alkaline soils and wanting to grow plants that love acid.  If you live in an environment with lots of rain (water produces Hydrogen ions that decrease the pH...especially in conjunction with clay soil) you should have no trouble with acid loving plants.  In a dry climate your soil pH will be dictated by minerals, such as limestone and are usually more alkaline.  Best bet is to find an easy, inexpensive way to get soil tests.  Usually going through your closest University Extension Service is best.  Permaculture should entail using what is available versus trying to change anything...planting only those plants that thrive with your soil's attributes. Once we start trying to change things like growing acid loving plants in basically alkaline soils...well, it isn't permaculture anymore.  More akin to growing plants in POTS.  Totally dependent on us for maintenance.
Answer: Well, I suppose there's spagnum moss, but that will take even longer than the pines @Bamboo mentions, and it's not so much the growing as the decay that does most of the acidifying, though a certain amount of "locking up calcium and magnesium" is mentioned in the wikipedia article.
While the classic commercial blueberry barrens are lowland bog-type environments, the good wild blueberries where I grew up were all above treeline (good sun) on granite mountains (no nasty, nasty limestone,) basically growing in cracks and hollows in the rock that they had composted by themselves for a long time with blueberry leaves and a bit of bear (& etc.) manure.
Answer: All plants roots acidify the soil by stimulating microbial life in the soil and releasing organic acids. Any organic life can result in a buildup of organic debris over time which breaks down into humic compounds (organic acids) over time in a process known as soil acidification through biological weathering[1] - forest soil is the most acidic because this occurs at the greatest rate there due to the high density of life. This is on a longer time scale than you need.
You could possibly achieve your goals using a fungal innoculation along with a one time chemical soil amendment.[2]
"Adjusting Soil pH: When planting oaks or other acid-loving plants into neutral or alkaline soils, it is often a good practice to incorporate a soil-acidifying additive (like sulfur) along with your mycorrhizal inoculum. While this will only reduce the pH temporarily (a few weeks), it will allow the mycorrhizal fungi to colonize the roots while the pH is low. Once the fungi set up residence within the root tissue, they can take refuge from the higher soil pH and work to increase acidity inside the fungal sheath. Subsequently, as soil pH in the planting hole gradually rises, the mycorrhizal fungi are already well-established and capable of controlling the pH of the roots' micro-environment."
[1]https://en.wikipedia.org/wiki/Soil_acidification#Biological_weathering
[2]https://www.lebanonturf.com/education-center/biological-plant-treatments/mycorrhizal-fungi-and-ph-of-soil-or-water
Answer: Since it's the decay we are looking for here, and pine needle offer a lot of acidity, how about a mugo shrub? Keep it low around the base of trees, maybe.


Newly Resized Luns not Showing correct LUN Size RHel 5.3

Question: My linux servers are not showing their newly resized fibre  Luns after being extended on the fly(online).the storage guys have  successfully resized the LUNS from 1Tb to 2 Tb .We are running fibre SAN ((on HP EVA kit,PSV450) not ISCSI LUNS on RHEL 5.3 Linux machines.
I have done the following below but unsuccessful, I  still cannot see the new size of 2Tb , i still see the old size of 1Tb.Please note that these LUNS are configured as raw devices for oracle and hence no LVMs are used .
Have i missed any procedure
Rescan  scsi bus
1. echo 1 > /sys/block/sda/device/rescan
   echo 1 > /sys/block/sdb/device/rescan
Update Size of your multipath device
multipathd -k"resize map orac_backup"
3.resize2fs /dev/mapper/orac_backup
(seems to fail probably a procedure not needed  in this scenario)
I alo tried this to  test multipath failover by running]
multipathd -k
del path sda
add path sda
del path sdb
add path sdb
All commands run successfuly but still old LUN size is showing, the Linux OS or kernel  still doesnt see the new Lun size.I have tried several times and  also restarted multipath service in between each  procedure numbered(listed) above, but still unsuccessful.Please help, any help would be greatly appreciated.
Kind Regards
D
Comment: See http://serverfault.com/questions/66638/how-to-extend-a-san-based-vdisk-in-red-hat-without-rebooting/97096#97096
Answer: Have you tried to flush and reload the maps after the rescan?
multipath -f orac_backup and after that multipath -r

L


How to determine if 2 rays intersect?

Question: We are given the 2D coordinates of 2 points: the first point is where the ray starts and it goes through the second point. We are given another ray in the same way. How do we determine if they have a point of intersection? I would like to know the general algorithm and its explanation, don't mind about the extreme cases (e.g. when the rays have the same starting point).
P.S. I saw a similar question on another stack exchange, but the answers did were not backed up by explanation.
Comment: You might find a previous question/answer helpful, see https://scicomp.stackexchange.com/a/18713/2107. It computes the intersection of two infinite lines. To handle the case of two semi-infinite rays, you only need to add some checks at the end (that s>0 and t>0).
Comment: All you need to do is to present these two straight lines as a set of points (x,y) depending on the parameter which is the length along the line. Then finding the intersection boils down to solving a small linear system, and from the determinant of it you can see it there is a solution.
Comment: The distance between two skew lines is $|\vec a\times\vec b|$ which is the absolute value of the cross product. If the vectors are $\vec a =(a_x,a_y),\; \vec b=(b_x,b_y)$ then the cross product is $a_yb_x - b_ya_x$ which will be zero if the lines intersect.
Answer: Not sure if it answers your question, but here's something I wrote a few years ago for a paper.
Let $\mathbf{p}_0$ and $\mathbf{p}_1$ be the end points of the first segment and let $\mathbf{q}_0$ and $\mathbf{q}_1$ be the end points of the second segment.  Then the parametric equations of the two lines are
$$
  \mathbf{p}(t_p) = (1 - t_p) \mathbf{p}_0 + t_p \mathbf{p}_1 \quad \text{and}\quad
  \mathbf{q}(t_q) = (1 - t_q) \mathbf{q}_0 + t_q \mathbf{q}_1 \,.
$$
At the point of intersection, $\mathbf{p} = \mathbf{q}$, i.e.,
$$
  (1 - t_p) \mathbf{p}_0 + t_p \mathbf{p}_1  = (1 - t_q) \mathbf{q}_0 + t_q \mathbf{q}_1 \,.
$$
Rearrangement of the equation gives
$$
\mathbf{q}_0 - \mathbf{p}_0 = \begin{bmatrix}\mathbf{p}_1 - \mathbf{p}_0 & -(\mathbf{q}_1 - \mathbf{q}_0)\end{bmatrix}
  \begin{bmatrix} t_p \\ t_q \end{bmatrix} \,.
$$
Therefore,
$$
  \begin{bmatrix} t_p \\ t_q \end{bmatrix}  =
    \begin{bmatrix}\mathbf{p}_1 - \mathbf{p}_0  & -(\mathbf{q}_1 - \mathbf{q}_0)\end{bmatrix}^{-1} (\mathbf{q}_0 - \mathbf{p}_0)
$$
Once we have solved for $t_p$ and $t_q$ we can find the point of intersection readily.  If the intersection point is outside the $\mathbf{p}$ line then $t_p \notin [0, 1]$.  Similarly, for the other segment, if the intersection point is outside the segment, then $t_q \notin [0, 1]$.
Answer: If you only need to know whether the rays intersect, you don't have to find the point of intersection.  The following may be more stable and efficient than solving the equations for the point of intersection, as it only involves subtraction and dot products, no division.
You have your first ray starting at $p_0$ and going in the direction of $p_1$ (and infinitely beyond $p_1$), and your second ray starting at $q_0$ and going in the direction of $q_1$ (and infinitely beyond $q_1$).  Think about it visually.  For a fixed $p_0$, $p_1$, and $q_0$, which values of $q_1$ result in an intersection?  The answer is that $q_1$ must lie in a wedge-shaped region of the plane.  One side of the wedge is the line between $q_0$ and $p_0$, and the other side of the wedge is parallel to the first ray.  In the diagram, $q_1$ must be in the blue region for the rays to intersect.

We can express one side of the wedge by saying that $q_1$ must be on the same side of the $q_0$ to $p_0$ line as $p_1$ is.  If $p_0 - q_0 = (l_x, l_y)$, then we can rotate $(l_x, l_y)$ 90 degrees to get a vector perpendicular to the line:  $(-l_y, l_x)$.  Then to check that $q_1$ and $p_1$ are on the same side, we check that $(q_1 - q_0) \cdot (-l_y, l_x)$ has the same sign as $(p_1 - q_0) \cdot (-l_y, l_x)$.
We can express the other side of the wedge by looking at the line passing through $q_0$ and $q_0 + (p_1 - p_0)$.  $q_1$ and $p_1$ must be on the same side of this line.  A vector parallel to the line is $p_1 - p_0 = (m_x, m_y)$ which we rotate 90 degrees to get $(-m_y, m_x)$.  To check that $q_1$ and $p_1$ are on the same side of this line, we check that $(p_1 - q_0) \cdot (-m_y, m_x)$ has the same sign as $(q_1 - q_0) \cdot (-m_y, m_x)$.
So to sum up:  the two rays intersect if and only if $(q_1 - q_0) \cdot (-l_y, l_x)$ has the same sign as $(p_1 - q_0) \cdot (-l_y, l_x)$, and $(p_1 - q_0) \cdot (-m_y, m_x)$ has the same sign as $(q_1 - q_0) \cdot (-m_y, m_x)$.
Answer: Since any two non-parallel lines must intersect somewhere (according to Euclid)
I imagine that the OP intended a slightly different question. For example, do the rays intersect within the convex hull of the four given (really, implied) points? (the convex hull is the region enclosed by an elastic band stretched round all four points without crossing.) That is the problem solved by Biswajit Banerjee. You do need to know where the intersection is.
Comment: Rays are not lines.  It is not the case that any two non-parallel rays must intersect.  Rays have a starting point and extend to infinity in only one direction, not two.  The convex hull of $p_0, p_1, q_0, q_1$ doesn't matter; the rays may intersect either inside or outside this hull.
Comment: https://en.wikipedia.org/wiki/Ray_(geometry)#Ray A ray is not a line segment.  A ray starting at $p_0$ and continuing to $p_1$ also continues infinitely beyond $p_1$.  This is why they can intersect outside the convex hull of $p_0, p_1, q_0, q_1$.
Comment: @causative.  Ah Thank you for the explanation!

How to determine if 2 rays intersect?


What are normal, tangent and binormal vectors and how are they used?

Question: I would like to find out the following information:

What are they?
Example usage in game development (the area they are used in)

About the following vector types:

Normal
Tangent
Binormal

A simple game development centric explanation would suffice.
Comment: I figured this may be much to ask, but on the other hand it would is nice to have this information together under one question. That is also the reason I specifically asked for simple explanations.
Comment: You are asking too many questions. It's best you just read on how vectors work. From scratch. Also patch up your trigonometry along the way.
Answer: Generally speaking, a Normal vector represents the direction pointing directly "out" from a surface, meaning it is orthogonal (at 90 degree angles to) any vector which is coplanar with (in the case of a flat surface) or tangent to (in the case of a non-flat surface) the surface at a given point.
A Tangent vector is typically regarded as one vector that exists within the surface's plane (for a flat surface) or which lies tangent to a reference point on a curved surface (ie. if a flat plane were constructed with the same normal from the reference point, the tangent vector would be coplanar with that plane).
The concept of a Binormal vector is a bit more complex; in computer graphics, it generally refers to a Bitangent vector (reference here), which is effectively the "other" tangent vector for the surface, which is orthogonal to both the Normal vector and the chosen Tangent vector.
With regards to how they are computed, this varies depending on the complexity of the surface and how precise you want the normal to be (in some cases, such as with smooth shaders, it is more desirable to calculate a normal for an approximated surface, when the actual information for a surface is not present), but there are several generalized formulas given here.
In terms of where they occur, the answer is EVERYWHERE. Normal vectors are used to position cameras and objects in 3D space, to determine trajectories, reflections, and angles in physics calculations, to map skins and textures to 3D models, to determine aim trajectory offsets in AI programming, to give hints to shaders about how to light, shade, and color points on a surface relative to lights, the camera, and other objects, and so on. They are possibly one of the most useful pieces of information to have in a 3D environment, and they even come in extremely handy in 2D as well.
Tangents and binormal vectors are used to determine things like torque and angular velocity, deflections of light or physical objects, and so forth. They are generally used in combination with the normal vector to give an angular 3-dimensional frame of reference to more complicated collisions, physics calculations, light deflections, and so forth; they're the additional information needed to ensure that angular momentum is preserved along the correct system of axes.
Comment: Damn I should have added a picture :p
Comment: It might help to read [this article](http://www.thetenthplanet.de/archives/1180) on why the square-patch assumption is invalid and why everything everyone says about _tangents_ and _bitangents_ is pretty much bogus. It outlines the proper math one should use, but sadly I'm not competent enough to author a **correct** answer with it.
Comment: Bitangent and binormal vectors are equivalent. They're names attributed to the same thing and it only depends on your "mental point-of-view" as to which name to use.
Comment: I'd like to add that the tangent is not always arbitrary. E.g., imagine you are traveling along a railway track/roller coaster. The tangent would then be the direction of travel along the curve. The normal would be something perpendicular to the curve (your local "up" when sitting in the roller coaster seat). The bitangent would then be either to the left or the right based on the co-ordinate system.
Comment: You did not mention why the tangent or bitangent are important, only the normals
Comment: Thank you for the thorough explanation! Marked as answer.
Comment: Agreeing with everything stated here; I wanted to provide an introductory-level couple of statements, a quick diagram to get the simplified version across, and enough room for people to get a quick mental image of what these concepts mean.
Answer: Normal vectors are typically used for lighting calculations. It is a vector that is supposed to be perpendicular to the surface that is approximated by the vertices of a mesh. Normals are defined at each vertice position but can be calculated differently depending on how you want light to refect at that vertice or what you want to do with your light calculations in the shader.
Tangent and Binormal vectors are vectors that are perpendicular to each other and the normal vector which essentially describe the direction of the u,v texture coordinates with respect to the surface that you are trying to render. Typically they can be used alongside normal maps which allow you to create sub surface lighting detail to your model(bumpiness).
There are obviously other ways to utilize these vectors and I have just described the average use of them. For more technical information I would suggest you pick up a book on computer graphics or explore some articles on the internet. There is plenty of information out there about this.
Answer: The difference between the tangent and the binormal is less immediately clear on surfaces, but that shouldn't be too surprising - the binormal was originally defined not for surfaces but for curves, where the concept makes a lot more sense (and where it really lives as a 'normal' in that it's orthogonal to the direction of movement, thus the name).  To be more specific, given a space curve of the form p = V(t) = (Vx(t), Vy(t), Vz(t)), then the tangent - which is a vector pointing in the direction of motion - is given by Tu = dp/dt = (dVx/dt, dVz/dt, dVz/dt).  (I'm using the subscript here to distinguish 'unnormalized' since I don't have my MathJax here.)  Then the (instantaneous) speed along the curve is just s = |Tu|, the length of the tangent vector, and the 'normalized' tangent vector is simply T = Tu/s.
Then the normal vector to the curve is the derivative of the normalized tangent vector over time, Nu=dT/dt; the reason that the normalized tangent is used here is to keep the speed along the curve from skewing the normal vector - you can show that with this definition, we always have T.Nu = 0.  Note that Nu isn't necessarily a unit vector, any more than Tu is; in fact, its magnitude k = |Nu| is the (instantaneous) curvature of the curve at the given point, and the point p+Nu is the center of the so-called osculating circle (at the given point).  The normalized normal is then just N=Nu/k, and the bitangent B is the cross product B=TxN; since T and N are both unit vectors and they're orthogonal to each other, then B is also a unit vector, and (T, N, B) is an orthogonal frame.
Note that by this definition the 'binormal' to a curve is closer to what we think of as the normal to a surface (it's the normal to the 'local' plane of the curve), and the normal to a curve is closer to what we think of as the bitangent to a surface.
(This image, sadly, doesn't really do the concept justice, but it's the best I could find on the web and I can't readily build my own...)
Answer: I know this is old but i would like to add a little practical information.
As stated by others but more specifically related to graphical programming.

A Normal aka (a surface normal) is orthogonal to a flat plane our triangles surface.
(it sticks out from it)

A Tangent can be considered to be a normal that lies along or on that plane (its co-planar) typically this is chosen from a quad on a mesh, (so a side of two triangles that form a square), is typically applied to two triangles to be the tangent for two or all of the vertices of the quad depending on how precise it needs to be.

The Bi-tangent or called a bi-normal or called a co-tangent. A vector on plane may give the notion of direction however, a complete matrix is comprised of 3 unit length vectors to describe a orientation so this is that.
The BiTangent is computed via the Cross Product as it has the property of being orthonormal or perpendicular (at 90 degrees) to both the normal and the tangent.
(actually each of these are perpendicular to the others proper and so knowing any two gives the other with a cross product)

All these vectors, the normal, the tangent and the bi-tangent, are typically unit length to say they are normalized when used in graphical programming.

Care must be taken when performing a crossproduct on these vectors to ensure that the desired Winding Order is understood, be it if you are defining it or adhering to someone else's mesh or model winding order (their intent). To say Cross(A,B) is the opposite of Cross(B,A) thus the direction would opposite.
(this can lead to, if placed into a matrix, to what amounts to a transposed matrix and or improperly defined matrix in the axis of the mistake)

The bi-tangent maybe calculated typically on the gpu or stored via pre-computation in the vertices data for a mesh or model.

Practical Relation to a 4x4 matrix.
Typically as you may be aware a commonly used right handed 4x4 matrix has 3 vectors denoting the forward the up and the right. These three unit length vectors together placed in a matrix equates to a complete orientation matrix.
(For example the matrix may relate to these vectors like so, though this is not standardized as far as i know,  m.Forward = normal, m.Up = tangent, m.Right = bi-tangent).
This forms a Orientation to say it forms a Orthogonal matrix were each vector is perpendicular to the others and one vector for each dimension x y z.
When another matrix typically a rotation matrix is applied to it (the surface being triangles in the graphical case), the orientation describing the surface will be ... rotated properly.
So then traversal across a triangle on screen in the 2d case.
x = x + 1;

Might translate so that we move across our surface in 3d directly equivalently. (Though simplified you can see that the premise of the below formula even if the matrix m is rotated will hold)
x = x + m.Right;

Practical usage.
When complex rotations are applied to a surface that is for instance texture mapped if you have all three of these values you will always have it's forward its up and right no matter what orientation the surface is rotated into. The texture uv positions can be found from this or if you like its tangent and bi-tangent vectors on the surface of the triangles can be moved along from one of a triangles vertices. As easily in a 3 dimensional space as a 2d space.
With this information you can map from 3d to 2d screen space or vice versa positionally when or if you need to for a variety of possible needs.
Concrete Application.
This is most often illustrated with the graphical technique of Normal mapping or Bump mapping which makes a flat surface appear to have depth which you can look up that term for more information.
Comment: This is WAY more useful than my answer.
Answer: As for the usage tangent and binormal (bitangent) are mostly used for normal (aka bump) mapping and related techniques. The tangent, bitangent, and normal define a rotation from tangent space (aligned with surface) to object space. When you calculate lighting, they are used to rotate a normal vector (sampled from texture map, and defined in tangent space) into object space (and then either camera or world space) for final lighting calculations. The tangents are usually calculated from the vertex normals and texture coordinates using the MikkTspace algorithm.


What are the different beer types?

Question: I have just started brewing my own beer and though I have made a few batches (3 to be exact), I wanted to know what categorizes a brew to be a beer (like Mead/Lager, Irish Stouts).  Is it the hops/Yeast?  I just would like to know so I can look up recipes as I start to play around with recipes of my own.
Comment: Mead is not beer, it is a different beverage completely: https://en.wikipedia.org/wiki/Mead
Comment: To help with recipes: Buy "Brewing Classic Styles"; It covers the +-80 Styles (from the 2008 BJCP Style Guide) with descriptions and award winning recipes. Highly recommended. http://www.amazon.com/Brewing-Classic-Styles-Winning-Recipes/dp/0937381926
Answer: There are many different styles of beer, and it is generally accepted that beer is brewed from malted grain (in almost all cases at least some portion is barley), water, hops and yeast. The different styles get their flavors from the types of grain used, the varieties of hops, and the strain of yeast.
Note that mead is not beer -- it is brewed from honey, not malted grain.
The Beer Judge Certification Program is a non-profit organization that promotes judging at homebrew competitions. They have documented the major styles in Style Guidelines That is one place you could start to see the list of styles. The guidelines include suggestions for ingredients, but do not contain complete recipes.
Comment: For providing a link this gets an answer checkmark.  I meant Mead vs Beer, the slash must have been a vague indicator.  Mainly looking for a good distinct definition and links.  Thank you all who answered and commented.
Answer: The two main categories are ales and lagers. They are distinguished by the yeast strains that are used. Ale yeast ferments from the top of the fermenter and lager yeast the bottom, they also have many different characteristics such as flavor profiles and temperature requirements. Lager requires colder temperatures.

What are the different beer types?


What is the genesis block?

Question: What is the genesis block? In which ways is it important or different from other blocks?
Comment: possible duplicate of [How do you make a Genesis block?](http://bitcoin.stackexchange.com/questions/9773/how-do-you-make-a-genesis-block), which asks as a secondary question "What makes it different from the other blocks in the chain?"  I assume you are trying to create the "canonical question" on this subject, but it seems like we already have questions whose answers address it.
Comment: There are many questions and answers that mention the genesis block. I thought this question might serve as a good entry point for beginners. For instance the one you refer to doesn't mention that the genesis block coinbase is special.
Answer: It is important, because it is used to seed the block and chain databases before syncing can occur (you need a block to build on). It's the root of the tree of blocks, forks, and ultimately the chain tips that represent the chains your software is tracking.
It is imported differently to others, as it's coinbase transaction is not included in the UTXO set (it's unavailable to be spent)
Changing the genesis block is a way to definitively fork yourself away from the bitcoin blockchain, ie, start a new network with it's own separate history.
However, some coins do share a common genesis block (Fluttercoin IIRC, shares Litecoins for whatever reason), but the network is forked by the use of checkpoints (genesis might be the same, but block 1 is checkpointed to Fluttercoins, instead of Litecoins).
Answer: The genesis block is the first block in a blockchain.  Every blockchain based crypto currency must have a blockchain, which is the ledger for the currency.  For example, Litecoin has it's own genesis block which is completely different than the Bitcoin genesis block.
Every block in a blockchain has a parent block, except the genesis block which has no parent block.

What is the genesis block?


Choosing between two letters of recommendation

Question: I am in the process of applying to some masters programs in machine learning, and need to make a choice between two letters of recommendation. One is from an undergraduate professor who told me they were happy to help, but my only interaction with him was one class I took senior year, and I graduated seven years ago. The second is from my current manager at work, who was a former academic whom I have a good relationship with. He knows that I am applying to full time masters programs, and that if I get in I will be leaving my job, and is still willing to help. He also knows the amount of effort I put in outside of work hours to work on machine learning projects. I understand that academic letters of recommendation are preferred, but given the fact that I graduated seven years ago, and that the letter from my manager will most likely be stronger, I am looking for some advice.
Comment: Great! Tell us a little more about those letters as it might inform your question. Are they academic or are they from work experience? Are those your stronger letters and you're trying to decide for the third place spot?
Comment: At my institution an MS in ML requires 3 letters, is this not the case for the schools you're applying to?
Comment: It is for some of the schools I am applying to. I have other letters besides the two discussed here.
Answer: I don't think it matters too much if the academic letter is about a old relationship, or whether the work letter is actually from your job and not from academia. What matters is that the academic you interacted with has an excellent opinion of you - and that seems to be the case, given the many years in between! - and hopefully that the academic stuff you have been working together is related to your master. Similarly, your employer will have lots to say about your work aethics and dedication, and hopefully his academic background and/or your current job should be somehow pertinent to your masters.
Comment: not sure I would agree with this.  Letters describing interactions older than 3 or 4 years will be stale unless the applicant stood out in some significant way (v.g. won a prize or was first author on a well known paper... that kinda thinng).
Comment: ZeroTheHero, I see your point, which is 100% valid for the typical BS-to-PhD-to-postdoc-to-Asst.Prof career. However, if you switch from academia to industry, there is simply no other option available. And if I were to consider someone for a MS in machine learning, (rather than, say, a PhD in particle physics) I would love to gauge both her/his academic, and business skills.


IPA: When to Bottle

Question: My IPA was in the primary for 10 days and gravity readings where steady before racking to the secondary.  It's been in the secondary for 13 days now and emits one bubble every 75 seconds on average.  Temps have been a few degrees lower than recommended since racking.  Can I bottle this now?
Answer: If you got consistent hydrometer readings over several successive days then yes, go ahead and bottle. 3+ weeks in the fermenter sounds like more than sufficient time for your IPA.
By the way, the bubble rate is not an accurate way of measuring fermentation activity. Bubbles can be produced by changes in ambient temperature and by simply walking past your carboy/bucket!
[edit]
I should rectify this post slightly. You should also check that your FG is reasonably close to what you expected. If it is way off (i.e. 1.03 when it should be 1.01) then you may have a "stuck fermentation" which could lead to problems with explosive bottles etc.
In summary, check that you are close to your target FG, check consistency of hydrometer readings over 3 successive days, and then bottle!
See also here.
Comment: +1 for spurious bubbles. I get that when I go to check the temperature on the buckets - a little bubble or two pops out of the airlock. I used to wonder if yeast know I'm there and are just saying "hi". But of course now I know better! ;)
Comment: Even so, your constant hydrometer readings indicate that primary fermentation is essentially complete. You may still have some active yeast in suspension which will continue to give off low levels of CO2, which is what you want for bottle conditioning for example and is nothing to worry about.
Comment: I understand however the bubbles in this case are regular.
Comment: Totally separate from the yeast, if there is C02 in suspension,  when the liquid warms up, then the C02 will bubble out. If you warm up a beer after a cool primary, you will see bubbling. Likewise if you just shake up a carboy, some bubbles will start popping. It is not necessarily a sign of any CURRENT activity by the yeast, just a sign of dissolved gas popping out of a liquid. HOWEVER, if you got bubbles, then it's prob a bad idea to bottle. Just give it more time at its current temp and make sure all activity is done.
Comment: @Graham yes you are right to say this.

IPA: When to Bottle


How can I open or loosen a metal screw cap of a bottle of polyester resin?

Question: does anyone know how I can open or loosen a metal screw cap of a bottle of polyester resin which is stuck with the resin? Last time I used this resin was 3 months ago and I wiped the mouth of the bottle as usual.
I tried to put the bottle upside down and soak the cap part in hot water, and also put the bottle in the freezer for a couple of minutes but the cap doesn't move at all.
Thank you.
Answer: Punch a hole in it and either use the last of the product or pour the remainder into a new container.

Or use the longest channel locks you can find and rip that sucker off.
Comment: Thank you, yes I cut the bottle a bit and poured the resin to a glass container covered with black paper to avoid sunlight. That was the only solution this time.
Answer: If the resin has completely set, you may need to break the cap or bottle to get out the remainder. However, it may just be extremely viscous, so you could try slow, steady force with a rubber band wound around the cap to get a better grip (squeezing with pliers will just break the container).
Gently heating the top in hot water may also reduce the viscosity, allowing the rubber-band trick to turn it.
There are also rubber strap-wrenches, but they might also crack the bottle, though less likely to do so than pliers.
Comment: Thank you DrMoishe Pippik. I heated the top part of the bottle in hot water and turned with a rubber band on but it didn't work.

I ended up with cutting the bottle a bit and decanting the resin to a glass container covered with black paper to avoid sunlight.

I actually tried everything I could do - put a rubber glove around the cap and placed in between door hinges and screwed, heated up the cap, using nail colour solvent around the cap, etc. The cap just warped.

I will avoid buying the resin in the same type of bottle and I'll think about the solution for the future. Thank you :)
Comment: @coyosa Remember that you could also use a non-lubricated condom like I explained [here](http://lifehacks.stackexchange.com/a/7378/1238).
Answer: For the future, put a bit. Of Saran Wrap over the bottle top, and
then screw on the closure.  It will now be real easy to remove the cap.


Facebook not showing "add friend"

Question: Facebook wasn't showing the "add friend" button to my profile and instead showed "follow". How can I get the add friend to show? Also I want to double check that non-friends can search me, what are the settings?
Answer: Sign into Facebook. At the top, click on the picture of the lock between your name and the gear icon. Click "who can contact me?" and under "who can send me friend requests?" choose "everyone".

Facebook not showing "add friend"


Multiple Single Post templates

Question: I have a custom post type called funerals and a page the lists all the posts part of that custom post type.  To display a single page I create a file called single-funerals.php and that all works well.  But, now I need to have another single post page that only displays a video for a funeral.  How would I set that up and link to it from the main page that lists all the posts?
Answer: As I answered here, since WordPress 4.7 Post-Type-Templates are enabled in the WordPress core.
That means that you can create multiple templates for the single post-type view. You create these templates like you would create a normal page template. But you need to add a little more code to these templates:
/*
Template Name: Funerals Video Template
Template Post Type: post, funerals
*/

So you will need to copy your single-funerals.php file, rename it, add some code like the above to the top of the file.
After this, you should see a template select box on the post and funerals edit-screen. (because I specified these 2 post-types with Template Post Type: post, funerals)
Read more about post-type-templates here.
Comment: Thanks for this. I didn't know this existed. This should the accepted answer.
Answer: You could turn the single-funerals.php code into a 'page template', then use that template when you create the page.
Read about page templates here: https://developer.wordpress.org/themes/template-files-section/page-templates/
Comment: I'm not understanding your response..
Answer: you can create Post Type Templates It's default WordPress directories file.
For More information:
https://codex.wordpress.org/Post_Type_Templates
https://developer.wordpress.org/themes/template-files-section/custom-post-type-template-files/
single-{post_type}.php create this file where your single.php file
single-{post_type}.php

Multiple Single Post templates


How to get the function help without typing?

Question: I'm already used to press C-h f and type a function name to ask for help on that function. But if the function name is already under the cursor (e.g. while visiting the .emacs configuration file), is there a way to avoid typing the whole thing again?
Comment: This is the default… just press `C-h f RET`.
Comment: I feel quite stupid, I didn't try the obvious. Anyways, I learned a couple of very nice tricks from the answers below.
Answer: From gnu.org:

If you type C-h f <RET>, it describes the function called by the
  innermost Lisp expression in the buffer around point, provided that
  function name is a valid, defined Lisp function. (That name appears as
  the default while you enter the argument.
Answer: Just hitting RET should be enough. Alternatively, try the following snippet to define a function that describes the function at point:
(defun my-describe-function-at-point ()
  (interactive)
  (describe-function (function-called-at-point)))

Answer: As Sean Alfred commented above, the default for C-h f is to already preselect the function at point as the default.
But you could also use helm-apropos which is part of the standard helm package (available from package repositories, e.g. from MELPA).
Helm apropos will preselect the function under the cursor, and I find it one of the nicest tool to locate documentation.
Answer: In addition to what others have said, if you use library help-fns+.el then the defaulting is a bit better - the cursor needs only to be near the symbol (e.g. function name) that you want to use.
(The vanilla Emacs behavior picks up only the symbol used for the function call surrounding the cursor, even if the cursor is on top of another function name that you want to investigate. Not too good for a language that passes functions around as arguments etc.)
There are also other enhancements to the Emacs help functions in help-fns+.el.
Answer: My current favorite reference defun (requires popup.el):

(require 'popup)

(defun describe-thing-in-popup ()
  (interactive)
  (let* ((thing (symbol-at-point))
         (help-xref-following t)
         (description (save-window-excursion
                        (with-temp-buffer
                          (help-mode)
                          (help-xref-interned thing)
                          (buffer-string)))))
    (popup-tip description
               :point (point)
               :around t
               :height 20
               :scroll-bar t
               :margin t)))

Use that with your key binding of choice for unobtrusive help reference for symbol-at-point.
Answer: I get Elisp documentation with lispy.
There, C-1 toggles the inline doc for current function.
Here's how it looks:

If the docstring is very large, *Help* window is used instead.
Answer: You might want to have the documentation display immediately when you type C-h f on a command (that is, without having to press <RET>), while keeping the original behaviour of being able to type the function name when you're anywhere else.
That is not so trivial to do, because function-at-point is very greedy. Telling it to display its first suggestion will result in you being unable to use C-h f's prompt almost anywhere, because it will always find a neighbour suggestion.
So here's my solution, adapted from wasamasa's answer and EmacsWiki's brilliant Describe thing at point :

(defun my-describe-function-at-point ()
  "Behaves like function-at-point, but removes the need to type <RET>
when point is over a function."
  (interactive)
  (let (sym)
    ;; sigh, function-at-point is too clever.  we want only the first half.
    (cond ((setq sym (ignore-errors
               (with-syntax-table emacs-lisp-mode-syntax-table
             (save-excursion
               (or (not (zerop (skip-syntax-backward "_w")))
                   (eq (char-syntax (char-after (point))) ?w)
                   (eq (char-syntax (char-after (point))) ?_)
                   (forward-sexp -1))
               (skip-chars-forward "`'")
               (let ((obj (read (current-buffer))))
                 (and (symbolp obj) (fboundp obj) obj))))))
       (describe-function sym))
      (t
        (call-interactively 'describe-function)))))

(define-key emacs-lisp-mode-map (kbd "C-h f") 'my-describe-function-at-point)


Is snow less likely to appear at a coastal area?

Question: Is it true that a coastal area is less likely to see snow compared with inland area nearby? If so, what are the reasons?
Comment: It depends.  The coastal side of mountains may see more snow (because more precipitation) than the inland sides, such as between Norway and Sweden.
Answer: I don't know if someone has conducted statistical research on this. It certainly depends on the situation. Here are some situations:
More snow in coast

Like @gerrit commented, elevation increases precipitation as air is forced to lift up and thus cools condensing water vapor -> rain/snow. This is true when predominant winds are from the sea.

Lake-effect snow situations

Less snow in coast

The air temperatures are affected by nearby bodies of water so situations where temperatures are freezing, but the sea isn't frozen yet will keep the coastal temperatures higher. Thus melting falling and fallen snow faster than in inland.
Comment: This is the right answer, but maybe you can add some more explanation and examples.
Comment: I like to keep it simple.
Answer: To add to Communnisty but too long for comment:
In general, open water with moderate temperatures, make them a bit cooler in summer or in tropics than otherwise would be likely, warmer in winter and in far north/south and where in the ocean currents a location is matters, but as a generality these statements are true.  So, in an area that is marginal for snow temperatures, say Seattle, they will receive less coastal snow because of the warmer temps.  Once you drop below the marginal temperature, say Mount Baker or Mount Rainier, still in the coastal moisture increase zone but higher altitude to push consistently below freezing in the winter, you have snow.   Lots and lots of it.
Answer: The warmer the air, the greater the water vapor pressure. So the heaviest snowfalls occur where and when it is as warm as possible without the snow melting --- just barely below freezing. If average temperatures are above freezing, temperatures being too high limits snow, and snow is more likely and heavier inland, away from the water whose high heat capacity moderates temperatures. If average temperatures are far below freezing, low water vapor pressure limits snow, and snow is more likely and heavier at the coast.


Removing and restoring stickers/decals

Question: I have a collection of coal minig stickers that were my father's.  They are all in good condition and I want to preserve them and keep them safe.  I took them to a local chain store hobby shop to be put into a shadow box.  The person helping me told me the stickers would be attached to the backing board with two sided tape.  However, when I picked up the finished product, the employee who actually did the project peeled the backing off the stickers and applied them directly to the mounting surface and did a terrible job in the process!  I am beside myself.  The whole point was to save them in their original condition.  Is there a safe way to remove them and restore them to their original state?
Comment: Before you do another thing, research "archival restoration" in your area. Normally these experts deal with paintings, books, and reproductions that have faded, there are professionals who may have some experience to help with this particular kind of recovery. Good luck. Courts may have legal means to recover the expenses from the original chain store.
Comment: I would make the person who lied to u replace the stickers or sue the hobby store.Those stickers were from your dad others may look the same but will never be the ones from your dad.
Irresponsible people like that literally irratate me to no end...
Answer: Using the steam from a kettle will loosen the stickers enough for you to slowly and carefully peel them off.
As soon as you get them off I would try to keep them straight so they don't dry all crinkled and twisted.
Be very careful. If you steam them for too long you may ruin the finish on them.
Answer: Unfortunately, no.
Stickers -- especially old stickers -- only stick once. This is because they are either 1) not sticky enough or 2) pull fibers from the present backing making the surface no longer sticky. Even if you were able to get the stickers to peel off, they'd be curled beyond repair.
Answer: Tools:
Get a heat gun (some auto parts stores will rent you one)
A straight edge razor
Non-stick paper (like the original backing of the sticker, craft stores will have)
Action:
Put the heat gun on the lowest setting and hold at least 6"s from the sticker. Wave the heat gun in a side to side motion until you can feel that the sticker is very warm. Using the razor, gently try to slide the blade under the edges of the sticker, lifting them from the base. Repeat until you can get your thumb and pointer fingers firmly on the edges.
Use your heat gun with one hand and start slowly lifting the sticker with the other. Hold the heat gun at a safe distance from your hand and keep waving left to right. Once sticker, is removed, place on non-stick paper.
Good Luck!!!
Answer: You could spend some time cutting around the edges with an x-acto knife. This would be time consuming, and it wouldn't restore them to their original state, but it would at least leave them able to be put somewhere else using double-sided tape or whatever.

Removing and restoring stickers/decals


How to control the speed of servo?

Question: I am using FPGA board and servo, I read that with PWM I can control where the servo will rotate. If the duty cycle in PWM is 1.5 ms it goes to the center, if it is 2 ms it goes to clockwise and if it is 1 ms it rotates to counter-clockwise. But, I couldn't find any clue on how to control the speed of the servo. Can you help me please?
Answer: Vary the voltage to the servo.
If your servo operates full power at 5V at 2.5V it will operate at half speed.
If your FPGA can output an analogue signal you could use that to drive the motor speed, otherwise you'll need to put in a DAC to get the analogue signal.
Answer: Many of the dedicated servo-controlling boards include an option to set the speed for each servo. I know for a fact that the Pololu Maestro boards do (as I've used those myself), and I'd expect that the Lynxmotion and Adafruit branded boards also have that feature. But, FPGA boards don't have it built in. You'll need to create your own function to send a signal for incremental movements at an interval.
Lowering the voltage can work, but I believe that it lowers the torque as well, so that may not be ideal for your situation.
Answer: The main application of servos is to move to a position, not at a constant speed, but in order to change the speed while maintaining the torque, you can simply slowly change the pwm duty cycle from one value to another (eg 1500 to 2000) and the servo will slowly move. If you would like to control the velocity precisely, then a motor with an encoder output would be better.

How to control the speed of servo?


How can I supply a table name at runtime using LINQ to SQL?

Question: I have to use LINQ to SQL and along with it a pure SQL classic query. And this SQL query has the Table from where my data will be generated, but I will not know this Table previously. It will be known in compile time.
So how can I make LINQ understand from what Table I want to make the query?
Answer: Good discussion here: Dynamic SQL table name