brainwagon

Well, I’m suffering from a feeling of deja-vu: recent doctor visits indicate that my weight has crept back up (no surprise) and that my BP and cholesterol aren’t doing much better either. I could make excuses about the surgery I had earlier in the year or whatever, but the reality is, that I’m back to just about the level that I was back in early 2004. Back then, it took me four months or so to drop 35 pounds, which I did mostly by using Weight Watchers and trying to increase my exercise a bit. For the near future, I’ll be taking a few hints from their play book, and religiously logging all the food as well as my weight, and we’ll see how it goes. If it doesn’t work very well, or if I get frustrated, then perhaps it’ll be back to WW for me.

Youtube has apparently now got support for 3D Video. Neat! Read about it below, and expect to see a test video of mine over the next few days.

YouTube Blog: Now in 3D: Join the Experiment With Us!

Addendum: I tried embedding this 3D video two different ways, but without good results. Witness. Annoying.

A few days ago, I posted links to a couple of videos that used fractal rendering techniques. One was the Genesis effect of Star Trek 2, Wrath of Khan, the other, a 4KB demo contest entry. My intent was to show how computer graphics have evolved over the past 25 or so years. But the reason I chose the Genesis effect was that I couldn’t find an online copy of a work called Vol Libre, Loren Carpenter’s 1980 film. I bump into Loren occasionally at lunch here at Pixar and mentioned it in passing.

I don’t know if this is a coincidence, but today on facebook, he announced that he had uploaded a copy of it to Vimeo. Thanks a bunch Loren! Sit back and enjoy the vintage computer graphics from a true CG pioneer, and you’ll probably be shocked to find out how similar it is to stuff you’d see in the modern “demo scene”.

Vol Libre from Loren Carpenter on Vimeo.

As I was “StumbleUpon”-ing tonight, I was reminded of something that I was thinking about a couple of days ago, and though I’d write it down here. Let’s say we want to multiply, oh… 47 by 69. We begin by writing the two numbers:

47 69

and then proceed by halving the first number and doubling the second number repeatedly.

47 69
23 138
11 276
5 552
2 1104
1 2208

Now, we cross out all the rows where the first column is even, and add all the remaining entries in column two:

47 69
23 138
11 276
5 552
2 1104
1 2208

If we add up 69+138+176+552+2208, we get 3243, which is indeed 47 * 69. This is so-called Russian peasant multiplication. I’ve probably known about this since I was eleven or twelve, but never really gave it much thought. Later, it seemed like the obvious way to implement multiplication on computers which had shift instructions. It’s not hard to see why this works if you are familiar with binary arithmetic, but I must admit that if you weren’t familiar with binary arithmetic, it seems to me unobvious how you would figure this stuff out. Yet, the ancient Egyptians actually knew about a closely allied technique that allowed them to do multiplication and division, so it would appear that the principles of binary arithmetic are actually exceedingly old. Wikipedia has some nice information.

NASA is obviously interested in hydroponics research as an enabling technology for long duration space flights. They are also quite good at educational outreach, so it wasn’t too hard to find this set of activities for kids on hydroponics. They are quite basic, but cover a wide variety of techniques, much wider than I would have thought. Bookmarked for later.

Hydroponics activity for kids on NASA website

I’ve been doing a bit more reading about growing plants hydroponically. In doing so, I found reference to something called “Hoagland solutions”, which are nutrient solutions used for growing plants hydroponically. Since hydroponically grown plants don’t get nutrients from trace elements in the organic matter in soil, you need to be especially careful to ensure that plants get adequate nutrition, and Hoagland and Arnon well apparently one of the first to document solutions that work. In digging up references, I found this PDF of their 1950 work on the subject. It’s very interesting, if somewhat harsh in debugging myths about hydroponics. They also document a bunch of nutrient solutions that one can use to study mineral difficiencies of various types, each one lacking some essential nutrient. Anyway, it’s very interesting, so I stashed it on Google Docs, and if you chase the link below, you can see (or share) a copy of the document.

The Water-Culture Method for Growing Plants without Soil, by Hoagland and Arnon

Well, it works! Using the information in the paper I linked earlier in the day, I spent some time and managed to code up a Robot36 SSTV encoder. Above, you see the image decoded by Multiscan on my Macbook. Here’s a link to the .wav file:

A Robot36 encoded SSTV picture

The image I used above is just one of my favorites, but I didn’t take it. It came from ladybugbkt on Flickr. Please make sure that it is only used for Non-commercial uses and with the proper attribution.

Addendum: Some time ago, I noted that I was having difficulty with the Audio Shield that I built as an audio output for my Arduino. Yesterday, I finally got around to sorting out the (as it turns out) software issue, and it began to play back .wav files from an SD card. So, I took the WAV file I generated, put it on the card, and then used the Arduino to play back the file into my Macbook. You can see it decoding in the video below. The timing of the Arduino is apparently not that close, because the image has a pretty strong skew, but not beyond which Multiscan can automatically correct. I’ll perhaps figure out how to do better with this later.

Addendum²: Oddly enough, one year ago today I linked to DJ1YFK’s webpage, where he has a Martin 1 SSTV encoder. Which reminds me, i forgot to put a link to my code. It’s ugly and inefficient, and I can think of a couple of things that are probably wrong with it, but it works. Check it out here.

I was looking up technical information suitable for implementing some of the SSTV modes (Robot 36, given the recent satellite activity). Here’s a paper by JL Barber, N7CXI that gives you what you need to know. Robot36 is particularly fussy: uses an odd color space, Y, R-Y, and B-Y, with the difference channels sent only at half the rate of the Y (intensity) information. I have something in mind for this, and I’ll probably dummy up a Robot36 encoder soon.

BibliOdyssey is a terrific blog which posts incredible images from old books that have entered the public domain. By way of example, check out this awesome collection of images of “extinct monster”, megafauna and dinosaurs. Very nice images, such as the giant sloth on the right. If you like old illustratons, check it out, then subscribe to this blog:

BibliOdyssey: Extinct Monsters.

A couple of weeks ago during lunch, someone had mentioned that a breakthrough in the world of cryptography had occurred: that someone had succeeded in creating something called a “homomorphic encryption scheme”. The thing was, nobody at the table really understood what that was all about. I did a brief bit of reading on it, and once I got the basic idea, I realized that yes indeed, it was a pretty amazing result, and pretty surprising. But rather than try to describe it to you, I’ll toss you to this recent link on Bruce Schneier’s website for his explanation.

Schneier on Security: Homomorphic Encryption Breakthrough

Lately everyone I talk to seems to think ham radio is dying. I wonder why they think that. Anybody have any guesses?

Okay, not really, but on this day in 2002, I did start this blog. Since then, I’ve made 3,106 posts, and there have been 5,461 comments. I’ve gone through two different hosting services, as well as hosting this on my own web server. And I’ve had a great time. I’ve gone through several different phases, some where I’ve talked about science, or space, or amateur radio, or web technology, or programming checkers games, or cryptography. I hope some of it has been fun for you. It has been for me.

Here’s a very nice article about the game phenomena that was Lunar Lander:

Forty Years of Lunar Lander | Technologizer

Addendum: Here’s a screen grab of the arcade version of the game. I used to love this game.

Tonight the amateur satellite AO-51 made an evening pass that was almost directly overhead, and was sending a congratulatory message for Apollo 11, along with a slow scan TV image. I managed to record it, although not the greatest quality, using my little Yaesu VX-3R and my Arrow antenna. Here are links to the recording as well as the four tries at the SSTV image:

July 20th, 6:40PM recording of AO-51 over CM87

Here was the pass as predicted by my Python code (times are in UTC):

  01:39:06  +0.0° 165.4° ? 12.8°N 115.9°W - AOS 696.4
  01:40:00  +3.6° 165.4° ? 16.1°N 116.6°W -     695.9
  01:41:00  +8.3° 165.5° ? 19.7°N 117.4°W -     695.6
  01:42:00 +14.2° 165.4° ? 23.3°N 118.3°W -     695.6
  01:43:00 +22.4° 165.3° ? 27.0°N 119.1°W -     695.8
  01:44:00 +34.9° 165.0° ? 30.6°N 120.1°W -     696.2
  01:45:00 +55.9° 163.8° ? 34.2°N 121.0°W -     696.9
  01:46:00 +88.1°  99.1° ? 37.8°N 122.1°W -     697.8
  01:46:01 +88.2°  80.1° ? 37.8°N 122.1°W - MAX 697.8
  01:47:00 +57.1° 349.6° ? 41.4°N 123.2°W -     698.9
  01:48:00 +35.9° 348.3° ? 45.0°N 124.4°W -     700.3
  01:49:00 +23.3° 348.0° ? 48.5°N 125.7°W -     701.9
  01:50:00 +15.1° 348.0° ? 52.1°N 127.2°W -     703.7
  01:51:00  +9.1° 348.0° ? 55.7°N 129.0°W -     705.8
  01:52:00  +4.4° 348.1° ? 59.2°N 131.0°W -     708.0
  01:53:00  +0.4° 348.3° ? 62.7°N 133.4°W -     710.4
  01:53:06  +0.0° 348.3° ? 63.0°N 133.7°W - LOS 710.7

And here are the resulting SSTV images as decoded with Multiscan under Mac OS X:

Addendum: I played back the recording with some adjusted settings, and got this picture (somewhat better):

Last night’s reading reminded me that I have never really been satisfied with my understanding of how siphons work. Apparently I’m not the only one, since there was this interesting exchange on Straight Dope which pointed out some of the disconcerting issues that surround explanations of their actions. I’m still not convinced I have a good understanding of their action. For example, in the cartoon above, it implies that air pressure pushes down on the tank above, but surely it also applies to the water below in the bucket, yes? I’m guess I’m skeptical about this “air pressure” idea. Tom suggested briefly in lunch that as long as the fluid’s vapor pressure was such that the weight of the downward column was insufficient to introduce cavitation, that the siphon action would continue. That sounds more like the truth to me, since it doesn’t rely on any notion of “atmospheric pressure” pushing on things. But I’m still not 100% satisfied with my understanding.

via The Straight Dope: How does a siphon work?.

Addendum: Wikipedia has a nice article, including some helpful math.