6,937 reputation
1424
bio website en.wikipedia.org/wiki/…
location United States
age 70
visits member for 2 years, 10 months
seen 17 hours ago

BS Mechanical Engr.
PhD CS(AI)
CS Prof (4yr)
Numerous consulting jobs.
15 yr at http://www.pharsight.com
Published book on CS & several articles
4 kids, 2 grand
Pilot(student)

P.S. The picture is a Beta-prime distribution. It shows the program speedup factors you can get if you see a problem twice in 2, 3, 4, and 5 samples.


Jul
11
comment How effective is speeding?
It's more important to minimize time spent going slow than to go fast.
Jul
9
comment Problem understanding basic sail mechanics
+1 @T.Kiley: Don't confuse yourself with the Bernoulli kerfuffle. Just consider the centerboard of the boat as if it were a skate. Consider the sail as if it were a knife blade, and the air were jello. Then satisfy yourself that no matter how fast the boat is sailing downwind, there is a sail angle that can give it forward thrust. A simple physical analogy is a wet watermellon seed squeezed between thumb and forefinger. Here's a similar question.
Jul
3
comment Do airlocks in space decompress violently as they do in movies?
For the airlock, it depends how suddenly the air is released. People consist of lots of muscle, fat, bones, etc. plus liquid plasma in fairly strong tubes, plus air in lungs. If they don't try to hold their breath, there's not much to decompress.
Jul
3
comment How should I throttle my rocket to reach highest altitude?
Here is a *very worthwhile read: *
Jul
2
revised Will a drop of liquid flow from from the wide opening to the narrow opening of a thin funnel by the effect of air pressure?
added 210 characters in body
Jul
2
revised Will a drop of liquid flow from from the wide opening to the narrow opening of a thin funnel by the effect of air pressure?
added 210 characters in body
Jul
2
revised Will a drop of liquid flow from from the wide opening to the narrow opening of a thin funnel by the effect of air pressure?
edited body
Jul
2
answered Will a drop of liquid flow from from the wide opening to the narrow opening of a thin funnel by the effect of air pressure?
Jul
2
comment Paper airplane physics
@J...: The OP had some basic misconceptions that needed to be corrected. When that is done, the equations just fall out. I was trying to correct the misconceptions.
Jun
30
comment What does a wing do that an engine can't?
There are misconceptions in some of the answers here. Lift/Drag ratio is beside the point. Angle of the engine axis is beside the point. Gliders vs. rockets are beside the point. Falling plates are beside the point. The answers that are on point are the ones that talk about momentum vs. energy of the downwash.
Jun
30
revised What does a wing do that an engine can't?
added 13 characters in body
Jun
30
revised What does a wing do that an engine can't?
added 164 characters in body
Jun
30
answered What does a wing do that an engine can't?
Jun
28
revised How can airplanes fly upside down?
added 92 characters in body
Jun
22
comment Prerequisites for Halliday Resnick Walker
Khan Academy is hard to beat. Just be sure, when you take calculus in school, that you are humble, and take the material at the rate it is taught, even if you know it already.
Jun
12
comment Why air above airplane's wing moves faster?
It is a recurring, and absolutely wrong, conception that the air has to rejoin itself at the trailing edge. In fact, wings could not work if it did, because lift requires circulation. Check this very good explanation.
Jun
4
comment Why is the application of probability in QM fundamentally different from application of probability in other areas?
@TwoBs has it right. In QM, probabilities don't add, they interfere, because their amplitudes add. And if you're concerned about independence, just break down the cross-product, and consider each possibility independently.
Jun
3
comment What's the advantage of NASA's flying saucer over traditional aerodynamic models?
Currently they go from 1) a small aeroshell to 2) a large parachute. They want something in between, a 1.5
Jun
3
comment Does gravity cause Archimedes' principle and how?
@mpv has the right answer. Flotation has nothing to do with gravity gradient. It has everything to do with pressure gradient, which is simply the weight of liquid above. The deeper you go, the more water you are holding up, so the higher the pressure. If you are a cylinder of air, then the weight above your lower surface is less than it would be if you were full of water. That difference in weight is the buoyancy force pushing you up.
Jun
2
comment Are there any substances that allow sound to travel better then air?
A lot depends on dimensions. If the medium is fully 3d over long distances, energy falls off as $1/r^2$. If it's 2d, like a temperature layer in air or water, it is $1/r$, so sound can carry a lot farther. If it's 1d, like a tin-can string, pipe, or iron rail, the sound can go very far without dissipating.