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Comment: Most unlikely technology in 1981: Handheld GPS (Score 5, Interesting) 275

I always thought the most unlikely technological development in my lifetime was the handheld GPS device. It would be "most unlikely" because it required tremendous, simultaneous, and largely unforeseen advances in several different technologies, each of which was hard to predict in 1981. The list is at least:

1. Low power, low voltage, low noise L-band receivers, sensitive enough to be compatible with the weak signal coming from the internal antenna of a handheld device;
2. Stupendous amounts of digital signal processing, also at low power and low voltage;
3. Digital map databases of (substantially) every road in the world, accurate to a few meters;
4. A substantially world-wide, wideband wireless data link to get the digital map into the handheld device in the first place;
5. Low power, low voltage, high resolution, multicolor flat panel displays;
6. Gigabytes of low power, low voltage data storage memory; and
7. High energy density, high power density batteries capable of supplying the whole thing.

And, perhaps most impressive of all, the manufacturing technology to make all of the above small enough to fit in a handheld device, at a price low enough to sell by the zillions.

Of the list above, probably only #2 could have been predicted, and then only if one were willing to extrapolate the then-relatively-new Moore's Law by a very large amount. (Recall that Mead and Conway had only written their Introduction to VLSI systems the previous year; until then it was not clear that such complex chips could even be designed on human time scales, let alone built for a profit.)

The fact that a handheld GPS device is now an anachronism, since the technology is now small enough and low-power enough to be integrated into other handheld devices, like smart phones, pleases me no end.

Comment: a bunch of dead zombies (Score 2) 307

by dtmos (#46747183) Attached to: Mathematicians Use Mossberg 500 Pump-Action Shotgun To Calculate Pi

AND a bunch of dead zombies.

What's a dead zombie? Is this some kind of recursion?

(Getting old has a lot of advantages, but one of the disadvantages is that it's harder to keep track of popular memes. I mean, I never understood the whole "vampire" thing, and now we're on to zombies. What's next?)

Comment: Value (Score 5, Interesting) 44

by dtmos (#46639311) Attached to: Data Mining the Web Reveals What Makes Puzzles Hard For Humans

Somewhere I read an article by a guy who makes and sells Sudoku puzzles to newspapers. He explained that the value of providing the puzzle was near zero, since anyone with a computer could easily generate thousands of them, and anyone without a computer could get them from any number of sources. The value of his service, and the reason newspapers paid him to provide the puzzle, he said, was that he provided an accurate difficulty estimate to the puzzle. People attempting, and failing to solve, a difficult puzzle rated "easy", and people quickly solving an easy puzzle rated "difficult", were dissatisfied, and complained. People that had the experience they expected -- easy puzzles quickly solved, hard puzzles solved only with difficulty -- were much more satisfied.

The result was, newspaper editors got fewer complaints using his puzzles than they did from his competitors, so they bought from him.

He said he spent far more time tweaking his difficulty-rating algorithm than he did his software that generated the puzzles themselves -- since that was what kept him in business.

Comment: Re:Baloney (Score 1) 653

by dtmos (#46529849) Attached to: $30K Worth of Multimeters Must Be Destroyed Because They're Yellow

The fact that there are lots of yellow multimeters for sale in the US is not relevant, for that could mean either (a) they are knockoffs, and Fluke is losing the battle against the counterfeit products; or (b) Fluke has a successful side business licensing its trademark. (n.b.: Multimeters were almost uniformly black -- e.g., the Simpson 260 -- in the years before Fluke introduced its first yellow model, in the 1980s. It was very distinctive at the time.)

And you should exercise caution in what you encourage in others: The issue at hand is a trademark, not a patent, and I think you'll find, if you look up the trademark registration certificate (the controlling legal document), that it very specifically mentions the color yellow.

Comment: Baloney (Score 3, Insightful) 653

by dtmos (#46526007) Attached to: $30K Worth of Multimeters Must Be Destroyed Because They're Yellow

Any "hobbyist electronics retailer" attempting to sell a multimeter in the US knows -- or should know -- what a Fluke multimeter looks like, and any businessman or businesswoman knows -- or should know -- that there will be problems trying to sell a product that looks like the product with a dominant share of the market.

Also, you don't need "an army of consultants or attorneys to find this information." Trademarks are freely available from the USPTO web site, in searchable form. Anybody can look them up.

Finally, most business contracts between a manufacturer and a distributor will have an indemnification clause, in which the manufacturer warrants that the product has no intellectual property issues and, should a claim be made against the distributor, the costs associated with such claims will be borne by the manufacturer. If Sparkfun's contract for the Fluke knock-offs didn't have such a clause, I'm sure their standard contract will in the future.

Comment: Indeed. (Score 2) 529

by dtmos (#46504911) Attached to: The Poor Neglected Gifted Child

I'm from the same era, and can corroborate nani's experience. Even the football players in my high school -- the guys with scratches on the back of their hands, from dragging them along the ground as they walked -- could name the planets in order.

Of course, since schools were funded by a property tax on the local landowners, the same opportunities were not available to the poorer kids going to the school on the other side of town. The desire was to raise that school to the academic level of the rich school, by spending more on education in general, but what seems to have happened is that the funding was just averaged between them, leading to the poor neglected gifted child syndrome.

Comment: Re:What is "computer-directed flight control"? (Score 1) 353

they need High voltage AC to heat the plate.

Er, no. They need high voltage DC, not AC, to bias the plate, not heat it. The goal is to encourage electrons emitted from the heated cathode due to the Edison effect (thermionic emission) to travel to the plate, rather than stay in a cloud around the cathode as they would otherwise do. To do this, in typical operation the plate is biased positive with respect to the cathode. The plate only gets heated by the energy of the electrons striking it, an undesirable secondary effect.

Comment: Re:Grading by statistics (Score 1) 264

by dtmos (#46213259) Attached to: Adjusting GPAs: A Statistician's Effort To Tackle Grade Inflation

The IQR (inter-quartile range) would probably be a better measure of spread if you are going to use the median as a measure of center.

To be sure. The difficulty with IQR is that the average college sophomore has no idea what it is. I actually tried this one semester, and ended up having to teach statistics one-by-one to each student that came in complaining about his grade. It was easier, and took less of my time, to use a system that had less technical validity, but used terms with which the students were familiar, and could independently calculate.

I personally prefer that the median correspond to the center of the C range, rather than the top.

Consider it my small concession to grade inflation.

Comment: Grading by statistics (Score 1) 264

by dtmos (#46212369) Attached to: Adjusting GPAs: A Statistician's Effort To Tackle Grade Inflation

When I taught undergraduate engineering courses at a state university, I always had large classes (> 80 students), so I decided to let the law of large numbers work to my advantage. I would grade each student's work with a numerical score, and would then find the median and standard deviation of the scores for each class. The median I defined to be the threshold between "C" and "B". One standard deviation above the median became the threshold between "B" and "A", and one standard deviation below the median became the threshold between "C" and "D". Any score below two standard deviations away from the median was a failing grade.

I used the median, instead of the mean, to ensure that I never had more than half the class with an "A" or "B". After some experimentation otherwise, it seemed like one standard deviation per grade was just about right -- most students got a "B" or "C", and only the exceptional ones got an "A" or "D" (or worse).

This scheme seemed to work well, and was no more arbitrary than any other. Plus, it was deterministic, in the sense that I could tell the students on Day One how I graded. If a student got a "C", for example, it was because more than half the class did better than he did. In addition, I could justify an "A" grade to the administration, since that person performed at least one standard deviation above the median.

Comment: Radioactivity? (Score 4, Informative) 30

by dtmos (#45901035) Attached to: Cygnus ISS Launch Delayed Due To Sun's Coronal Mass Ejection

Um, no. "Radiation" was the word for which you were looking. "Radioactivity" refers to the particles which are emitted from nuclei as a result of nuclear instability.

There was a significant solar flare at 1832z (1:32 p.m. EST) on 7 January, that bathed the Earth with electromagnetic radiation (X-rays, UV, radio, etc.). This was an X1.2-class flare, meaning that its flux would have peaked at 1.2E(-4) watts/square meter at the Earth's surface, had our atmosphere not protected those of us on the ground from the worst of its effects. The effects of the flare itself (largely attenuation of HF radio signals over the Western Hemisphere during and shortly after the event) are over and done with.

Since this flare was caused by a particular sun spot group that remains active and unstable, Orbital Sciences was concerned about a repeat performance when the Antares' avionics were in the upper atmosphere, and therefore not protected from a second, possibly even more intense, flare that the sun spot may produce.

Concurrent with this flare was a coronal mass ejection (CME), which consists largely of protons blasted out of the sun's atmosphere (the corona). Since these particles are protons, not massless photons, they travel slower than the speed of light, and it takes them a while to get here; they are expected to arrive sometime early on 9 January UTC. However, predictions of CME particle velocity are difficult and prone to error; CMEs can arrive early.

Since the CME could be arriving while the Antares was in operation (the flight was scheduled for liftoff at 1832z on 8 January), and the performance of the rocket's avionics could not be guaranteed in that environment, when this risk was combined with the risk of another X-class flare I think they just decided that a scrub was the wiser choice.

"If value corrupts then absolute value corrupts absolutely."