6,271 reputation
1322
bio website en.wikipedia.org/wiki/…
location United States
age 69
visits member for 2 years, 7 months
seen 1 hour 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.


Dec
23
comment Increase in velocity by loss of mass?
@Nick: It depends on which way the water exits the cart, because it's behaving like a small rocket.
Dec
21
comment Maximum liquid velocity in a siphon
@User58220: Yeah, you're right. I was just trying to keep it simple.
Dec
19
comment How do charge carriers move thermal energy? (Peltier effect)
Someone can probably give a better answer than I can, but light gasses are good heat conductors because to have the same momentum as a heavy molecule they have to travel very fast. A metal object basically contains a gas of free electrons, which travel even much faster, because they are so light.
Dec
18
comment Pressure difference between 2 side of wings of aircraft
This is troublesome, because it doesn't show the air being deflected downward, and it says nothing about the air above arriving at the trailing edge well in advance of the air underneath.
Dec
18
comment Pressure difference between 2 side of wings of aircraft
I still think this is the best, most accessible, explanation.
Dec
13
comment Speed of ejection of liquid from revolving tank
@user34304: It's basic Bernoulli, and no need for "sir" :)
Dec
11
comment Number of blades in a helicopter rotor
+ Nice photos :)
Dec
11
comment Proof of conservation of information
@joshphysics: being a CS guy myself, I'm most familiar with Shannon information, and to a lesser degree Kolmogorov information. I know there are others.
Dec
11
comment Proof of conservation of information
@joshphysics: If a system has unitary evolution, then it's reversible, right? And if it's reversible then it can always get back to a prior state if the evolution is reversed. Any definition of information I know of (which may not be much) says that the only way you can get back to a prior state is if you don't forget what it was. That's putting it colloquially, I know, but when I worked on quantum algorithms, that was basic understanding.
Dec
9
comment Why are roofs blown away by wind?
+1 on the assumption you meant to say "pressure above the surface is lower", as your video illustrates.
Dec
9
comment Why are roofs blown away by wind?
@CarlWitthoft: You're right about angle of attack, but not about no-pressure-difference. OSE is also right. If you're a wing (symmetrical for argument's sake) and you're generating lift, yes you are deflecting air downward due to angle of attack, and your reward for doing this is to see a pressure difference. There's no other way for you to feel force.
Dec
2
comment How charge distribution takes place when a battery is connected to a conductor?
+ Nice, although the long wire would also have inductance and would radiate. I'm not sure how you could take that effect out of the problem. Make it a twisted pair?
Nov
30
comment The velocity of a cloud?
That reference compares cloud speed as measured from a satellite camera, versus wind speed measured at cloud base and various altitudes within clouds. A cloud is not a solid object. It is suspended droplets, and it can be vaporizing on one side and condensing on another, all as a function of altitude, temperature, and humidity. There is also considerable vertical motion. One thing I'm very skeptical of: droplets having velocity of $5 m/s$ relative to the air they are suspended in.
Nov
26
comment Does earths gravitational force vary depending on where you are on the planet?
If you are on the equator, you are lighter than you are at the poles, not because gravity is weaker, but because you are traveling eastward in a big circle around the earth at about 1600 kph. That also makes the earth itself bulge at the equator.
Nov
25
comment Gravitational Effect Versus the Speed of Light
If the sun suddenly vanished, the earth would still have gravity and the moon would still go around it. Tides would be affected somewhat - not too much. I think the main affect would be the cold - no more sunlight, no more food, no more weather - big freeze - as we drift off into the night. We'd have to quickly learn to live on geothermal / nuclear energy.
Nov
22
comment Relative motion of airplane in the wind
It's a 3-4-5 triangle. The southeast hypotenuse is 100, the south side is 60, so the east side is 80 kph. 189/80 = your answer.
Nov
19
comment What really allows airplanes to fly?
@shortstheory: Airliners are quite capable of negative-G flight (but not for long, because of oil sumps etc.) In fact they have to be strong enough to handle multiple Gs up or down. On a fixed wing aircraft the angle of attack is changed by pitching the nose up or down. The purpose of the elevator is to control the angle of attack of the main wing by pitching the entire aircraft up or down. Notice, next time you fly, how when the aircraft slows down for landing, it pitches up, because at the slower speed more angle of attack is needed.
Nov
18
comment Hydrostatic pressure?
For the same reason hydraulic hoses work, with bends in them. Pressure in fluids can go around corners. If it couldn't, any sort of tubing would be useless, from hydroelectric sluice gates, to bent straws.
Nov
18
comment Why does a helium filled ballon move forward in a car when the car is accelerating?
@wim: It's accelerating to the left. Yes, the balloon is tied to the floor. The balloon seeks the surface so as to have the least water "above" it.
Nov
14
comment Is there a lens that would invert my vision?
@lionelbrits: Google should pick up on that!