Search found 225 matches

by agelessdrifter
Sat Mar 04, 2017 11:51 pm UTC
Forum: Mathematics
Topic: What happens if you de-discretize time in the blue eyes riddle?
Replies: 9
Views: 4185

What happens if you de-discretize time in the blue eyes riddle?

I assume most of the regulars are familiar with the blue eyes problem already, but if not, it's the first result on google for "blue eyes riddle," and it's an xkcd url. I'll talk about the solution below, so don't read past here if you want to solve it yourself. In the problem, the people ...
by agelessdrifter
Mon Mar 03, 2014 9:35 pm UTC
Forum: Language/Linguistics
Topic: Comparison between Korean and Japanese subject/topic markers
Replies: 1
Views: 2844

Comparison between Korean and Japanese subject/topic markers

I apologize if this has been discussed elsewhere. I did a search on the forum and, indeed, on the web in general for a discussion of this specific topic but have only found more generic comparisons of Japanese and Korean which have not addressed it. So my question is this: How hazardous is it for so...
by agelessdrifter
Mon Jan 13, 2014 7:40 pm UTC
Forum: Mathematics
Topic: necessary conditions for planarity of polygonal regions
Replies: 1
Views: 1057

necessary conditions for planarity of polygonal regions

The two figures in the image were (I believe) the first counterexamples showing that you can't hear the shape of a drum. I'm curious whether anyone with better spacial reasoning than mine can tell what conditions must be met by the parameters in the image in order that neither region overlaps itself...
by agelessdrifter
Tue Aug 13, 2013 1:26 am UTC
Forum: Language/Linguistics
Topic: Disappearing consonants in Rosetta Stone French
Replies: 4
Views: 3498

Re: Disappearing consonants in Rosetta Stone French

Ah, yes that makes intuitive sense now that you mention it. Thanks for the helpful response.
by agelessdrifter
Mon Aug 12, 2013 11:31 pm UTC
Forum: Language/Linguistics
Topic: Disappearing consonants in Rosetta Stone French
Replies: 4
Views: 3498

Disappearing consonants in Rosetta Stone French

Hi. Sorry if this post should've been made in the french practice thread or something. I did a search before posting, so I hope this hasn't been discussed already. I've just recently started using Rosetta Stone to learn French, and I've noticed that there are lots of cases where the sometimes-silent...
by agelessdrifter
Mon Jun 24, 2013 7:16 pm UTC
Forum: Mathematics
Topic: Optimisation of F(x,y,z) in a non-standard basis
Replies: 4
Views: 1078

Re: Optimisation of F(x,y,z) in a non-standard basis

I don't see anything wrong with your idea (as long as the proposition is actually true), but I think you're making things too hard on yourself. You don't need an orthogonal coordinate system; you just need coordinates that are parallel to the plane x+y+z=D. For instance, I don't see why you cou...
by agelessdrifter
Sun Jun 23, 2013 1:04 am UTC
Forum: Mathematics
Topic: Optimisation of F(x,y,z) in a non-standard basis
Replies: 4
Views: 1078

Re: Optimisation of F(x,y,z) in a non-standard basis

Well I didn't say what F was because I don't want someone else to prove it and then tell me the answer, or to give me any hints at all, really. I just want to know whether my approach makes sense, since I've only ever used this whole change of coordinate business for simplifying PDEs, and those in o...
by agelessdrifter
Sat Jun 22, 2013 7:54 pm UTC
Forum: Mathematics
Topic: Optimisation of F(x,y,z) in a non-standard basis
Replies: 4
Views: 1078

Optimisation of F(x,y,z) in a non-standard basis

So as part of a larger problem I'm working on, I'm trying to prove that, if x 0 +y 0 +z 0 =D, and F(x 0 ,y 0 ,z 0 )=L then a,b,c satisfy a+b+c=D and F(a,b,c)=L, if and only if {a,b,c}={x 0 ,y 0 ,z 0 } (ie, (a,b,c) is some permutation of (x 0 ,y 0 ,z 0 )). So my thinking is that, if this is true, the...
by agelessdrifter
Wed Jun 19, 2013 2:00 am UTC
Forum: Science
Topic: Conservation of information
Replies: 13
Views: 5124

Re: Conservation of information

Ah, that makes sense, then. Thanks, all.
by agelessdrifter
Tue Jun 18, 2013 11:37 pm UTC
Forum: Science
Topic: Conservation of information
Replies: 13
Views: 5124

Re: Conservation of information

This...doesn't make sense. One of the main consequences of entropy is that the universe as a whole is steadily losing information. I feel like you might have been told something incorrect. Well it comes up most consistently in the discussion of Hawking's "Information Paradox," which, from...
by agelessdrifter
Tue Jun 18, 2013 11:09 pm UTC
Forum: Science
Topic: Conservation of information
Replies: 13
Views: 5124

Conservation of information

I've heard the statement that "information cannot be [created or] destroyed" on a number of occasions and in a few different contexts, but I'm curious: in precisely what sense is this true? I've read a fair bit (no pun intended) about information theory (though it has been a while), and th...
by agelessdrifter
Thu Apr 04, 2013 3:08 pm UTC
Forum: Language/Linguistics
Topic: 日本語 (Japanese Practice)
Replies: 552
Views: 196472

Re: 日本語 (Japanese Practice)

Ok no takers on that one -- fair enough.

でも、もう一つ質問があるんです:

「妻が病気時、会社を休みます。」と 「妻が病気時、会社を休みます。」と、どちらがいい文法ですか。

I think I've been told that 病気 is treated as a noun, in general, but here it seems awfully adjective-like, so I'm leaning toward な.
by agelessdrifter
Thu Feb 21, 2013 8:46 am UTC
Forum: Language/Linguistics
Topic: 日本語 (Japanese Practice)
Replies: 552
Views: 196472

Re: 日本語 (Japanese Practice)

Is it bad form in Japan to ask a question in the form "Do you know...?" or " For instance, English speakers don't really go up to one another and say "Excuse me. What time is it?" -- you'd typically say something like "Excuse me, but do you happen to know the time?"...
by agelessdrifter
Mon Feb 18, 2013 3:52 pm UTC
Forum: Language/Linguistics
Topic: 日本語 (Japanese Practice)
Replies: 552
Views: 196472

Re: 日本語 (Japanese Practice)

No, that was very helpful, thanks.
by agelessdrifter
Mon Feb 18, 2013 1:06 pm UTC
Forum: Language/Linguistics
Topic: 日本語 (Japanese Practice)
Replies: 552
Views: 196472

Re: 日本語 (Japanese Practice)

A few of unrelated questions: 1) I find myself lacking expressions to convey humility. Say for instance I got a 100 on a test and someone says "いい学生だね。” or like "頭がいい” or something, what's the appropriate response? Like if someone says "Oh, you're a good student" or "You mus...
by agelessdrifter
Tue Feb 05, 2013 10:51 am UTC
Forum: Language/Linguistics
Topic: 日本語 (Japanese Practice)
Replies: 552
Views: 196472

Re: 日本語 (Japanese Practice)

Ah, yes that's definitely it. I missed the phrase itself and apparently I misunderstood the context as well, but that makes sense looking back on it. Thanks.
by agelessdrifter
Tue Feb 05, 2013 9:24 am UTC
Forum: Language/Linguistics
Topic: 日本語 (Japanese Practice)
Replies: 552
Views: 196472

Re: 日本語 (Japanese Practice)

Hmm, sorry for the double post but it's been a while, at least. I picked up today (I think) on the fact that, apparently, there's a common greeting in Japanese that is specifically for people who have met only once before? Something like that. I jotted down おぎさしぶります because that's what it sounded li...
by agelessdrifter
Fri Jan 18, 2013 12:21 am UTC
Forum: Language/Linguistics
Topic: 日本語 (Japanese Practice)
Replies: 552
Views: 196472

Re: 日本語 (Japanese Practice)

Ah, as I thought. Thanks.
by agelessdrifter
Thu Jan 17, 2013 3:42 pm UTC
Forum: Language/Linguistics
Topic: 日本語 (Japanese Practice)
Replies: 552
Views: 196472

Re: 日本語 (Japanese Practice)

I'm sorry if this has already come up, but it's a tough question to search for. If you're starting from the polite form of a verb, how do you tell the difference between a る verb with an i-sound as the last character in its stem and a う verb? Like how would I know that 呼びます comes from 呼ぶ while 浴びます ...
by agelessdrifter
Wed Nov 07, 2012 11:22 pm UTC
Forum: Mathematics
Topic: Hermite polynomials
Replies: 1
Views: 1507

Hermite polynomials

Am I misunderstanding something? I thought F[H m (x)exp(-x 2 /2)] (the Fourier transform of the m th Hermite polynomial) was supposed to be a constant multiple of H m (x)exp(-x 2 /2), but my calculation gives me (and Wolfram verifies) that F[H m (x)exp(-x 2 /2)](w)= -iw m exp(-w 2 /2) for every m. e...
by agelessdrifter
Thu Jun 21, 2012 3:58 am UTC
Forum: Mathematics
Topic: indicator function for points in an arbitrary region
Replies: 3
Views: 1610

Re: indicator function for points in an arbitrary region

Before we can talk about computation, we need to know how you're defining the curve in the first place. If you can already tell when a line crosses the bounding curve, can't you just note when the random walk itself crosses the curve? Good point. The curves I'm looking at are r(t)=<x(t),y(t)> where...
by agelessdrifter
Thu Jun 21, 2012 1:12 am UTC
Forum: Mathematics
Topic: indicator function for points in an arbitrary region
Replies: 3
Views: 1610

indicator function for points in an arbitrary region

suppose I'm given a region in the x,y-plane defined by an arbitrary, non-self-intersecting closed curve, and an arbitrary point, p, in the plane. Is there a reliable systematic approach to determining whether p is in the interior of the region? I'm trying to write a program that performs random walk...
by agelessdrifter
Thu Jun 14, 2012 1:26 am UTC
Forum: Coding
Topic: Parametrizing the boundary of a region in an image
Replies: 3
Views: 1865

Re: Parametrizing the boundary of a region in an image

I want to be able to calculate curvature at a point and integrate over the boundary. It's important that the output curve pretty closely matches the actual boundary, though, and doesn't do zany stuff like loop through itself on tight curves or skip over sharp creases in the boundary.
by agelessdrifter
Wed Jun 13, 2012 12:46 am UTC
Forum: Coding
Topic: Parametrizing the boundary of a region in an image
Replies: 3
Views: 1865

Parametrizing the boundary of a region in an image

I'm looking for code (or to write a code) that can take a photo -- say a photo of gum on a sidewalk -- that's been preprocessed to find the edges of the gum in the image, and output a smooth, differentiable parametrization (piecewise if necessary) <x(t),y(t)> or <θ, r(θ)> that agrees with the absolu...
by agelessdrifter
Sat Feb 04, 2012 3:03 am UTC
Forum: Coding
Topic: Creating a gif with python?
Replies: 13
Views: 9402

Re: Creating a gif with python?

Thanks a bunch, I'll give that a whirl.

edit: Solved that problem with the screwy color, and your advice worked. Thanks a million to everyone, I am very excited to finally have this working.
by agelessdrifter
Fri Feb 03, 2012 11:49 pm UTC
Forum: Coding
Topic: Creating a gif with python?
Replies: 13
Views: 9402

Re: Creating a gif with python?

That sounds like it's definitely the problem I'm running into, but I'm not sure I understand your suggestion about how to solve it. This is the code I was using, essentially: def animate(directory, max_gen): string = "" for i in range(0, max_gen): if os.stat(directory + "/image_"...
by agelessdrifter
Fri Feb 03, 2012 8:43 pm UTC
Forum: Coding
Topic: Creating a gif with python?
Replies: 13
Views: 9402

Re: Creating a gif with python?

Update: Well I've got python drawing the frames for me, but the only thing I've been able to find to compile the gif is ImageMagick, which I absolutely cannot figure out how to use. It's not a python library as far as I can tell -- it runs right through the command line, but I'm using a windows box ...
by agelessdrifter
Wed Feb 01, 2012 9:37 pm UTC
Forum: Coding
Topic: Creating a gif with python?
Replies: 13
Views: 9402

Re: Creating a gif with python?

thoughtfully, the relative positions of the cities is pivotal to the images, unfortunately -- I need to see where/how often paths from one city to the next are crossing, and how good a job my algorithm does of fixing the crossings to shorten the tour lengths. At least, that's what I'm *interested* i...
by agelessdrifter
Tue Jan 31, 2012 10:23 pm UTC
Forum: Coding
Topic: Creating a gif with python?
Replies: 13
Views: 9402

Re: Creating a gif with python?

Thanks for the replies. Thoughtfully, that graphviz program seems like it might be ideal for what I'm trying to do, but the language is alien to me, and a quick perusal of the documentation wasn't very enlightening -- can you give me a rough idea of what it would take to get from a txt file containi...
by agelessdrifter
Tue Jan 31, 2012 8:35 pm UTC
Forum: Coding
Topic: Creating a gif with python?
Replies: 13
Views: 9402

Creating a gif with python?

I've been doing work on a genetic algorithm for the Traveling Salesman Problem for the last month or so. It doesn't perform very well, as of yet. I recently tried to bump up my mutation operator from a 2-opt hill climb to a 3-opt, but it murdered the run-time to the point where it's not even worth t...
by agelessdrifter
Mon Jan 16, 2012 8:00 am UTC
Forum: Coding
Topic: random.shuffle() in python
Replies: 6
Views: 5378

Re: random.shuffle() in python

Oh, wow. If that's what's going on I'm really surprised I haven't tripped over that before now, but that definitely would explain it. Thanks.
by agelessdrifter
Mon Jan 16, 2012 6:00 am UTC
Forum: Coding
Topic: random.shuffle() in python
Replies: 6
Views: 5378

random.shuffle() in python

hello, I don't think I've ever posted in Coding before, so I apologize if I err I'm working on a rudimentary GA to tackle the traveling salesman problem, and I've encountered trouble with the function random.shuffle(x). I've tried a lot of variations of the code below, all with the same results: q=[...
by agelessdrifter
Fri Dec 16, 2011 11:37 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0991: "Phantom Menace"
Replies: 110
Views: 37647

Re: 0991: "Phantom Menace"

Before the prequels came out there were a lot of really well-written books based around the original three movies. There were dozens of authors writing them all, but they were all really coherent and consistent with one-another and with the films as far as the back-stories given to the characters, a...
by agelessdrifter
Fri Dec 16, 2011 6:32 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0991: "Phantom Menace"
Replies: 110
Views: 37647

Re: 0991: "Phantom Menace"

All three prequels were objectively terrible films. redlettermedia's review of the prequels on youtube is highly worth the watch, whether you liked the movies or not. I'd link them, but I dunno what the policy is on that, since I don't have that many posts. They're easy enough to find, though.
by agelessdrifter
Sun Dec 04, 2011 9:59 pm UTC
Forum: Science
Topic: Mechanics problem involving moment of inertia
Replies: 3
Views: 3225

Re: Mechanics problem involving moment of inertia

Oh, yeah, I see what you're saying -- there's definitely an easier way to go. I have a tendency to over-complicate things. I am still curious, though -- does anything jump out at you (anyone) as being obviously wrong with my approach above, aside from it being needlessly complicated? Even if it's no...
by agelessdrifter
Sun Dec 04, 2011 7:37 pm UTC
Forum: Science
Topic: Mechanics problem involving moment of inertia
Replies: 3
Views: 3225

Mechanics problem involving moment of inertia

Starting to kinda panic about my final for this class -- I'm just going back and reworking old problems and other problems from the text to brush up on everything. The problem I'm looking at right now is about a cube in unstable equilibrium, balanced on one edge. I have to prove that the angular vel...
by agelessdrifter
Tue Nov 29, 2011 4:27 pm UTC
Forum: Science
Topic: Spring system, center of mass frame
Replies: 3
Views: 1451

Re: Spring system, center of mass frame

What I know is that R=(m 1 r 1 +m 2 r 2 )/(m 1 +m 2 ). So I believe R ' =(m 1 r 1 ' +m 2 r 2 ' )/(m 1 +m 2 ). But the kinetic energy associated with each mass and its respective velocity along the radius is (1/2)m 1 r 1 ' 2 and (1/2)m 2 r 2 ' 2 , and I can't figure out how to manipulate the expressi...
by agelessdrifter
Tue Nov 29, 2011 2:36 am UTC
Forum: Science
Topic: Spring system, center of mass frame
Replies: 3
Views: 1451

Spring system, center of mass frame

Ok, this is review for the impending final for my classical mechanics class. I've discovered that my fundamentals basically suck, and I'm studying like crazy trying to rectify that before next Monday. The problem is this: A weightless spring of length (equilibrium lenght) b connects two masses, m1 a...
by agelessdrifter
Wed Nov 23, 2011 7:23 am UTC
Forum: Mathematics
Topic: expression for the product of n rotation matrices
Replies: 16
Views: 2039

Re: expression for the product of n rotation matrices

The talk went really well, I think. Thank you all again.
by agelessdrifter
Mon Nov 21, 2011 8:13 pm UTC
Forum: Mathematics
Topic: ITT: Motivate me to care about pursuing ever larger ordinals
Replies: 19
Views: 5876

Re: ITT: Motivate me to care about pursuing ever larger ordi

Thanks, I'll check that stuff out.

Turns out I jumped the gun -- the rest of the semester will be review, and today's lecture was kind of a hand-wavy discussion of the use of inaccessible cardinals in metamathematics, which was pretty interesting.

Go to advanced search