Monday  23 Sep 2013           4 comments

Curious sparkly image noise in Google Street View. The mechanism in the doggie sculpture that used to wag its tail has stopped working.

Sunday  22 Sep 2013           comment?

Cold morning here today. Not cold by winter standards, just by contrast to the summer I was digging.

I'm partial to summer for the long days, the warm nights.

Summer feels like the key season for the desert, the time when the land is in its element. Just my feeling—I make no claim this is objective.

Equinox today at 1:44 PM PDT (20:44 Zulu).

Wednesday  18 Sep 2013           1 comment

I helped a friend put a new pump in his well this evening.

The pump doesn't really look like that. The bend is an artifact of taking the pic in panorama mode. Yes, I am easily amused.

Tuesday  17 Sep 2013           comment?

Two dudes who met while waiting in line to buy beer in Russia Saturday night got to arguing about Immanuel Kant, leading to a fistfight and then to one of them taking out a pistol and shooting the other in the head (not fatally; it was a weak pistol).

News reports (English, Russian, German) do not say which of Kant's ideas they argued over, but we can speculate. Maybe it was

Reading novels weakens the memory.

Monday  16 Sep 2013           5 comments

Apart from all their other virtues, bicycles create interesting questions of physics. They're interesting in how their answers are not what you might expect. I'll take up one question here and leave others for subsequent blog postings.

Today's question: What force keeps a bicycle rim off the ground?

The rim bears the weight of the rider (as applied through the spokes). The tire (where by tire I really mean tire and inner tube) applies an upward force to the rim that opposes the weight of the rider, but how?

The seemingly obvious answer is by air pressure, as when you lie on an air mattress. Air pressure supports your weight over the area where your body contacts the mattress.

But it's a different story where a bicycle tire meets the rim. The pressurized inner tube contacts the rim symmetrically and uniformly all around its circumference, thus the net upward force of air pressure on the rim is zero.

Bike tires rely on air pressure, but pressure itself is not the force keeping the rim off the ground. The question remains: what upward force on the rim opposes the rider's weight?

Don't be thrown by any potential complications arising from there being two pieces (tire and inner tube), as the same question needs to be answered for tubeless tires as used on cars.

Friday  13 Sep 2013           1 comment

Ray Dolby died yesterday, and news reports have recounted his work in video, audio, and film technology. His name became a household word in the 1970s with the widespread use of Dolby noise reduction in tape recorders, often credited with making cassettes suitable for making high-quality recordings of music.

Dolby NR uses companding, which improves signal-to-noise ratios both audibly and measurably. Less often mentioned—both then and now— is that companding is a tradeoff. It can have effects on the sound beyond just reducing noise.

It is a matter of taste as to whether the improvement in signal-to-noise outweighs the artifacts of companding. Circa 1980, Dolby NR was ubiquitous and popular—yet among my friends, those who had recorded and listened to the most tape (both laymen and professionals) preferred not to use noise reduction.

I have a 19-year-old 4WD vehicle that I haven't bothered to upgrade the audio system in. I still play cassette mix tapes in it, some of them over 30 years old. None were recorded with Dolby on.

None if this is to impugn Dolby the man. He did a lot of good work.

Friday  06 Sep 2013           1 comment

This week:

"Representatives of the American intelligence agencies—and I hope they won’t be angry—but they could have been more professional, and the diplomats as well. After they found out that he [Snowden] was flying to us, and that he was flying as a transit passenger, there was pressure from all sides—from the Americans, from the Europeans—instead of just letting him go to a country where they could operate easily."

— Vladimir Putin, in an interview.

The tone reminds me of a line from Alfred Hitchcock's Topaz (1969):

"We would have done it better."

— Soviet defector Boris Kusenov, sneering at clumsy American tradecraft used in extricating him to the West.

Wednesday  04 Sep 2013           comment?

Current (top) and voltage (bottom) waveforms for the motor in my table saw. Yes, I am easily amused.

Monday  02 Sep 2013           1 comment

Wikipedia, on the 1986 Chernobyl disaster:

All remaining dosimeters had limits of 0.001 R/s (0.3 µA/kg) and therefore read "off scale". Thus, the reactor crew could ascertain only that the radiation levels were somewhere above 0.001 R/s (3.6 R/h, or 0.3 µA/kg), while the true levels were much higher in some areas.

Because of the inaccurate low readings, the reactor crew chief Alexander Akimov assumed that the reactor was intact. The evidence of pieces of graphite and reactor fuel lying around the building was ignored, and the readings of another dosimeter brought in by 04:30 were dismissed under the assumption that the new dosimeter must have been defective.

BBC News on Fukushima radiation levels:

The Tokyo Electric Power Company (Tepco) had originally said the radiation emitted by the leaking water was around 100 millisieverts an hour.

However, the company said the equipment used to make that recording could only read measurements of up to 100 millisieverts.

The new recording, using a more sensitive device, showed a level of 1,800 millisieverts an hour.

Unit conversion: 100 millisieverts per hour is 10 R/h.