Search found 98 matches

by Sam Weir
Thu Sep 09, 2010 3:01 pm UTC
Forum: Science
Topic: Looking at a Bright Light
Replies: 8
Views: 4953

Re: Looking at a Bright Light

Hi - I'm not sure I agree with the conclusions I see here. Yes, the defocused image of an object (like a Christmas tree light) is bokeh. But when you see "streaks," there are a few different potential culprits. One is diffraction, such as diffraction by your (pupil, I think?) or eyelashes ...
by Sam Weir
Thu Aug 19, 2010 10:04 pm UTC
Forum: Science
Topic: Real 3D displays / autostereoscopic
Replies: 3
Views: 1033

Re: Real 3D displays / autostereoscopic

Hi - Thanks for watching! Yes, I agree with you on the light field display. There have been a series of volumetric/multiview displays that provide various solutions to the problem of "how do I create imagery with occlusion?" or stated more generally, "how do I get interesting BDRFs?&q...
by Sam Weir
Wed Aug 18, 2010 1:20 am UTC
Forum: Science
Topic: Diffraction Pattern for an Array of Apertures
Replies: 6
Views: 1420

Re: Diffraction Pattern for an Array of Apertures

Hmm... I don't know if it matters how close the apertures are to each other. My initial reaction is, since we know what the diffraction pattern of a disc is http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/cirapp.html can't we just add a bunch of those up?

sw
by Sam Weir
Wed Aug 18, 2010 1:16 am UTC
Forum: Science
Topic: Real 3D displays / autostereoscopic
Replies: 3
Views: 1033

Real 3D displays / autostereoscopic

Hi fora, I thought this might be of interest - if you are into 3-D displays, especially "when can we watch 3-D with the unaided eye?", I wanted to share something that I've been working on. I've been researching autostereo 3-D since the late 1980s, and now that so many blog-commenters are ...
by Sam Weir
Mon Sep 29, 2008 1:17 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0482: "Height"
Replies: 271
Views: 74701

Re: "Height" Discussion

If you liked this, you might also like the page "Logarithmic Maps of the Universe" - it has many images of maps from a paper in the Astrophysical Journal (2005). Like Randall's comic, it is very impessive! Check it out here: http://www.astro.princeton.edu/~mjuric/universe/ For example, one...
by Sam Weir
Tue Sep 16, 2008 6:59 pm UTC
Forum: Science
Topic: Wave propagation: basic physics question - how does it know
Replies: 17
Views: 2369

Re: Wave propagation: basic physics question - how does it know

Yup.

Thanks, everyone, for correcting my hopefully momentary lapse in reason.

-sw
by Sam Weir
Sun Sep 14, 2008 3:37 pm UTC
Forum: Science
Topic: Wave propagation: basic physics question - how does it know
Replies: 17
Views: 2369

Re: Wave propagation: basic physics question - how does it know

So what I'm hearing is that all this comes down to second derivatives, for reasons only nature understands, and that's just the way it is. The "memory" of the system from instant to instant is encoded in those derivatives, yes?

sw
by Sam Weir
Sun Sep 14, 2008 2:05 pm UTC
Forum: Science
Topic: Wave propagation: basic physics question - how does it know
Replies: 17
Views: 2369

Re: Wave propagation: basic physics question - how does it know

Klotz and Jaap - Thank you. Your explanations are making intuitive sense -- I might be neurotic about it and code up a simple discrete simulation of the spring system to convince myself of it. Is it important that the particles of these systems have nonzero mass? (If they need nonzero mass, then tha...
by Sam Weir
Sun Sep 14, 2008 1:02 pm UTC
Forum: Science
Topic: Wave propagation: basic physics question - how does it know
Replies: 17
Views: 2369

Re: Wave propagation: basic physics question - how does it know

@Matterwave1: Well, those are names of forces and equations (i've taken courses on Maxwell's equations); but what is the physical process at a discrete time step?

@jaap: Thank you for the thoughtful response. I still don't quite understand. Could you go one level deeper?

Thank you,
sw
by Sam Weir
Sun Sep 14, 2008 11:40 am UTC
Forum: Science
Topic: Wave propagation: basic physics question - how does it know
Replies: 17
Views: 2369

Wave propagation: basic physics question - how does it know

Hi - I was coding up some simple wave-propagation stuff and it suddenly dawned on me that despite all my engineering and physics studies, I don't get a very simple thing: for wave motion - any wave motion - what are some mechanical principles that dictate what direction the wave is propagating in? F...
by Sam Weir
Tue Sep 09, 2008 2:47 am UTC
Forum: News & Articles
Topic: Esquire E-ink Cover on Newsstands now!
Replies: 3
Views: 1144

Re: Esquire E-ink Cover on Newsstands now!

Ummm... we got one. Okay, three. (Now, now - not for me, for people who said "Get me one!") Not sure what to say... it is an impressive feat of not just engineering, but the whole manufacturing and delivery chain. The recent coverage on MAKE shows a decent video, as well as the innards. -sw
by Sam Weir
Tue Sep 02, 2008 12:06 pm UTC
Forum: Science
Topic: Homemade spectrometer
Replies: 2
Views: 2447

Re: Homemade spectrometer

That's neat. Should the grating be centered on the CCD, as you show it, or should it be offset as to record the +1 order? I didn't run the numbers to guesstimate how many degrees your grating will diffract.

sw
by Sam Weir
Wed Jul 23, 2008 2:02 am UTC
Forum: The Help Desk
Topic: Mathematica v6: Fixing signed/unsigned upon TIFF import
Replies: 3
Views: 1233

Re: Mathematica v6: Fixing signed/unsigned upon TIFF import

Ah, yes, good point. I'll need to work out if the dividing line is 32767 or 32768. You know, Mathematica is astonishingly powerful, but for all the self-consistency that it proclaims, I'm still finding it very hard to internalize enough syntax to get things done fast. There's no reason why, for exam...
by Sam Weir
Tue Jul 22, 2008 9:12 pm UTC
Forum: The Help Desk
Topic: Mathematica v6: Fixing signed/unsigned upon TIFF import
Replies: 3
Views: 1233

Mathematica v6: Fixing signed/unsigned upon TIFF import

Hello - I seek help with what I think could be a 1-line Mathematica v6 command, but which has me stymied. I am trying to load a roughly 400 x 1800-pixel TIF image. Each pixel is greyscale; ie it is one number, not an RGB triad. However, the TIF went through some 16-bit unsigned/signed integer mangli...
by Sam Weir
Sat Jul 19, 2008 12:53 am UTC
Forum: Hardware
Topic: 15+ engineering and design "daemons"
Replies: 10
Views: 2798

Re: 15+ engineering and design "daemons"

Nice! The blog post has been updated.

Keep 'em coming, if you care to.

-sw
by Sam Weir
Fri Jul 18, 2008 1:35 pm UTC
Forum: Computer Science
Topic: Cheaper 3-D rendering
Replies: 9
Views: 3203

Re: Cheaper 3-D rendering

@Kerberos: Thanks for having the guts to share your idea with us. I think it is a good idea, and apparently you're not alone - to my knowledge, there have been a collection of attempts by people to achieve a similar goal. One example is in the military application of flight simulation, in which you ...
by Sam Weir
Thu Jul 17, 2008 7:02 pm UTC
Forum: Hardware
Topic: 15+ engineering and design "daemons"
Replies: 10
Views: 2798

Re: 15+ engineering and design "daemons"

Ah, yeah, good points. Why would I have forgotten "document it!" and "try it out, a lot, especially the non-obvious cases."

thanks!

-sw
by Sam Weir
Wed Jul 16, 2008 6:41 pm UTC
Forum: Hardware
Topic: 15+ engineering and design "daemons"
Replies: 10
Views: 2798

15+ engineering and design "daemons"

Hi - Have you ever been served well by a few "pointers" or "background processes" you keep in your head when you're inventing, desgining, or debugging something? You know, like, "It might actually be giving you the right answer," or "use big paper," or "b...
by Sam Weir
Fri Jun 20, 2008 2:54 am UTC
Forum: Coding
Topic: Help Wanted
Replies: 36
Views: 83375

Contract Job Opp.: Computer Vision / Image Processing

Hi there, xkcd-ers: I've asked so many questions on these fora that I thought I'd try to return the favor in some small way by posting a summer job opportunity. Okay, it helps my company, too. Actuality Medical is seeking software engineers for a contract position in image processing and machine vis...
by Sam Weir
Wed Jun 04, 2008 3:26 pm UTC
Forum: Science
Topic: multimeter weirdness
Replies: 17
Views: 2410

Re: multimeter weirdness

I'm casting a vote for the "it's due to different input impedances of the meters" theory.

sw
by Sam Weir
Sat May 24, 2008 1:21 am UTC
Forum: Science
Topic: Voltage Cap Circuit?
Replies: 7
Views: 1394

Re: Voltage Cap Circuit?

Archon - It sounds like you are quite comfortable with EE. I suggest you look at pg 50 of Horowitz & Hill ( The Art of Electronics, 2nd ed. ) which discusses voltage clipping, or as they call it, voltage clamps. There are very simple diode-based circuits that require no op-amp. In fact, you can ...
by Sam Weir
Fri May 23, 2008 8:12 pm UTC
Forum: Science
Topic: Sound Wave Frequencies
Replies: 27
Views: 3909

Re: Sound Wave Frequencies

@jemthealmighty: I disagree with the suggestions that the right thing to do is to simply play the beat frequency. Rather, I agree with (evilbean??)'s comment that you use a simple formula to populate a buffer with amplitude values as a function of time. Rather than use that sin + sin = coscos thing,...
by Sam Weir
Mon May 12, 2008 1:16 pm UTC
Forum: Computer Science
Topic: Evolutionary Computing Reading
Replies: 3
Views: 1982

Re: Evolutionary Computing Reading

I recommend An Introduction to Genetic Algorithms by Melanie Mitchell. It is concise and fairly easy to understand if you have a technical background.

-sw
by Sam Weir
Sun Apr 20, 2008 2:05 am UTC
Forum: Science
Topic: Brewster angle
Replies: 2
Views: 1333

Re: Brewster angle

Hi VolatileStorm, I'd be more inclined to trust a website like this: http://scienceworld.wolfram.com/physics/BrewstersAngle.html over Wikipedia. I haven't double-checked it to my optics or E&M textbooks, but I think it's a good bet. Or.... http://hyperphysics.phy-astr.gsu.edu/Hbase/phyopt/polref...
by Sam Weir
Sun Mar 30, 2008 11:49 am UTC
Forum: Science
Topic: "Quant Software" - anyone worked on stock trading software?
Replies: 5
Views: 1453

Re: "Quant Software" - anyone worked on stock trading software?

@Nebulae - Yes, certainly. Ordinarily, I am a believer in so-called "fundamental" analysis, and most of the books I read imply that numbers-only "technical" analysis is nonsense. However, I am still interested in digging through some data to see what's there. There are certain te...
by Sam Weir
Sun Mar 30, 2008 3:25 am UTC
Forum: Science
Topic: "Quant Software" - anyone worked on stock trading software?
Replies: 5
Views: 1453

Re: "Quant Software" - anyone worked on stock trading software?

Hi - Thanks for the link to FatKat, I hadn't heard of that. Too bad that it's against the aims of quant sites to actually publicize what their technology does... and I have some skepticism about Kurzweil's recent work. Yeah, I've been reading up on GAs, going through papers online, browsing books ab...
by Sam Weir
Sun Mar 30, 2008 12:01 am UTC
Forum: Science
Topic: "Quant Software" - anyone worked on stock trading software?
Replies: 5
Views: 1453

"Quant Software" - anyone worked on stock trading software?

Hi - (Math? Science? Coding? I figured this is "Science.") Just curious -- have any of you ever worked on quantitative trading, specifically, developed software to aid in the picking of stocks? Like 100,000 other people, I admit I'm intrigued by the goings-on of quants. And like 100,000 ot...
by Sam Weir
Thu Mar 27, 2008 1:12 pm UTC
Forum: Science
Topic: led table design
Replies: 3
Views: 1583

Re: led table design

That video is neat. I bet that was a lot of work to pull off. And the table's sensitivity to light (or "inverse shadow"?) reminds me of the "Light Puddle" art piece by Hayes Raffle, a student of Hiroshi Ishii @ the MIT Media Lab. Regarding your question about the second table, pe...
by Sam Weir
Thu Mar 20, 2008 5:34 pm UTC
Forum: General
Topic: Geocaching
Replies: 48
Views: 8737

Re: Geocaching

Geocaching, baby! I think it's a great way to visit beautiful or otherwise interesting locations -- even near your house -- that you might not have heard of otherwise. Before trying it, I had the misconception that it's a "treasure hunt." Sure, you're finding an object that's listed in a p...
by Sam Weir
Fri Mar 07, 2008 3:45 am UTC
Forum: Gaming
Topic: GO weiqi igo baduk
Replies: 154
Views: 62425

Go / Weiqi / Baduk - Anyone play on KGS?

Hi there -

I attempted to search for a pre-existing conversation about go, but it's a difficult search term. :-)

I am a beginner at go, ranked somewhere around 20k, and have played a bit here in the Boston area at a local go club.

Do any of you play go? Do you play on servers like KGS?

-sw
by Sam Weir
Mon Mar 03, 2008 4:30 am UTC
Forum: Computer Science
Topic: Genetic Algorithms
Replies: 19
Views: 5215

Re: Genetic Algorithms

Regarding the original request for books about genetic algorithms -- as a not-serious C programmer I was able to understand the first few chapters of this book, and then go off and code up my own simple GA. I have to admit it was a lot of fun, and a great excuse to start figuring out the Xcode IDE o...
by Sam Weir
Fri Feb 29, 2008 12:26 am UTC
Forum: Science
Topic: Optics question
Replies: 4
Views: 1855

Re: Optics question

No problem!

-sw
by Sam Weir
Thu Feb 28, 2008 6:58 pm UTC
Forum: Science
Topic: Optics question
Replies: 4
Views: 1855

Re: Optics question

Hi - I'm afraid I can't be of much help as I haven't used Jones matrices. However, I do have a popular book on optics, and it says: (Let's first see if your notes match this book's conventions.) Here is the matrix for a quarter-wave plate, fast axis vertical [ 1 0 ] [ 0 -i ] Here is quarter-wave pla...
by Sam Weir
Tue Feb 26, 2008 10:11 pm UTC
Forum: The Help Desk
Topic: Mac OS X pre-10.5 Remote Desktop - free options?
Replies: 4
Views: 2434

Re: Mac OS X pre-10.5 Remote Desktop - free options?

@b.i.o.: That is absolutely amazing! Thank you so much for recommending LogMeIn Free. Our former IT group used to use that, so I had assumed it would be very expensive. Within 15 minutes I talked my father over the phone how to install it, and it worked - my WinXP box to his iMac and we did remote d...
by Sam Weir
Mon Feb 25, 2008 3:29 am UTC
Forum: The Help Desk
Topic: Mac OS X pre-10.5 Remote Desktop - free options?
Replies: 4
Views: 2434

Mac OS X pre-10.5 Remote Desktop - free options?

Hello - (I note that there's a previous discussion here that touches upon Remote Desktop for OS X, but for a different goal.) Can anyone recommend a free method of allowing me to see and control my parents' Mac OS X 10.4 machine remotely (i.e., I'm in MA, they're in CT)? Ideally, the solution would ...
by Sam Weir
Fri Feb 15, 2008 2:34 pm UTC
Forum: Science
Topic: On Analysing Systems (System Theory)
Replies: 17
Views: 3554

Re: On Analysing Systems (System Theory)

You might enjoy Concilience: The Unity of Knowledge by Edward O. Wilson, or Emergence: The Connected Lives of Ants, Brains, Cities, and Software by Steven Johnson. I forgot what country you're in, but places like Barnes & Noble usually have them. You might get interesting ideas from them. -sw
by Sam Weir
Thu Feb 14, 2008 4:31 am UTC
Forum: Science
Topic: DIY laser
Replies: 9
Views: 2665

Re: DIY laser

Hi - You might also want to try asking your question to the nice folks at the Holography Forum phpBB. You could try driving a diode laser. I had bad luck with that in college; they are extraordinarily sensitive to electrostatic discharge & require a carefully-designed drive circuit (i.e. transis...
by Sam Weir
Wed Feb 13, 2008 2:41 pm UTC
Forum: Science
Topic: E&M Homework
Replies: 5
Views: 1239

Re: E&M Homework

@Thinker: Do you think it's weird that k isn't normal to the plane of polarization?

I guess I just learned something.

-sw
by Sam Weir
Wed Feb 13, 2008 4:15 am UTC
Forum: Science
Topic: Freaky Touch-Activated Lamp
Replies: 15
Views: 3190

Re: Freaky Touch-Activated Lamp

Oh, sorry. MOSFET = transistor = switch.

-sw
by Sam Weir
Tue Feb 12, 2008 9:00 pm UTC
Forum: Science
Topic: Freaky Touch-Activated Lamp
Replies: 15
Views: 3190

Re: Freaky Touch-Activated Lamp

Hmm. I guess this isn't the time to get into Feynman's argument regarding "the difference between knowing things and knowing the names of things." I'm not sure what "making a capacitor" means in this context, and I don't know what a neophyte would make of that phrase, either, oth...

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