8,667 reputation
1730
bio website en.wikipedia.org/wiki/…
location United States
age 71
visits member for 3 years, 10 months
seen 13 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.


Jun
21
comment why can't you use your cellphone on an airplane?
From a pilot's perspective, what matters are the odds. If there is the slightest chance of a problem, and the stakes are high, it's probably not worth taking that chance just for some people's convenience. The accidents that happen are ones thought to be unlikely.
Jun
11
comment Calculating rotor torque out of mass center
I don't understand your use of the word "fit", as in "after fitting this engine out of mass center". Any such question can be answered by considering a propeller blade to be a rotary wing.
Jun
5
comment Static as opposed to Kinetic Friction in Rolling Motion
Since you're talking about rolling motion, it might be useful to understand how gears work.
Jun
4
comment What is the Coandă effect? How is it defined, and what causes it?
Try this terrific site. It discusses the Coandă effect and how it is different from the usual process by which wings produce lift.
Jun
1
comment How to calculate pressure exerted on the wheels of a robotic car?
What's to calculate? Just take all the components and weigh them.
May
31
comment Is the “How to break the speed of light” minute physics video wrong?
Speed of light is 3e8 m/s. Diameter of moon is a bit larger than 3e6 m, so it takes about .01 sec for light to traverse the moon. So you have two lasers A pointed at right side of moon, and B pointed at left. A fires a pulse, and .001 s later B fires a pulse. So B's pulse arrives at the moon .001 second after A's. Now if you thought it was one laser being moved, not 2, you would say "Gosh, the point moved at 10c, how can that be?"
May
30
comment Is it possible to make a light beam act like a stream of water from a spining hose?
dmckee's comment says it all. Your spinning hose is shooting pieces of water, each of which travels in a straight line. Your spinning laser is doing the same thing with pieces of light. The curvature of the stream is only a perception. The particles are each moving in a straight line, not in a curve.
May
27
comment Why is light called an 'electromagnetic wave' if it's neither electric nor magnetic?
+ Close. The electric field does not directly vibrate the water molecules. It causes impurity ions that carry charge, like sodium and chloride, to move (i.e. have electric current) in the water, just like charges move in an antenna. Since that current encounters resistance, it generates heat, that cooks the food.
May
27
comment Why is light called an 'electromagnetic wave' if it's neither electric nor magnetic?
It's like the difference between air pressure and sound. Sound is just rapidly changing air pressure.
May
23
comment Will a spinning object come to rest?
When two orbitting bodies become tidally locked, they have not stopped spinning. They have simply joined their angular momentum. The time to complete one rotation is the same as the time to complete one orbit.
May
23
comment How to find outflow pressure/force of air through a pipe
en.wikipedia.org/wiki/Pipe_flow
May
20
comment How would a change in ambient temp affect a radiator?
@Gk3Biz: Think of it like an electrical resistor being fed a constant current (heat power). Then a constant voltage (temperature difference) will appear across it. If you up your fan speed, that's like reducing the resistance, giving you less voltage (temperature) difference. Generally, electric equipment like motors have a rated temperature rise above ambient, in order to shed the heat they produce.
May
20
comment How large can planets or moons appear?
John Rennie's answer is right on, but keep in mind the Roche limit is due to tidal forces overcoming the satellite's own gravity. That means the closer the main planet comes to subtending 45 degrees of sky, the closer the moon (and its inhabitants, its atmosphere/ocean, and its liquid core) come to being ripped off into their own orbits.
May
19
comment Radio antennas that are much shorter than the wavelength
FWIW: en.wikipedia.org/wiki/Fractal_antenna
May
14
comment Definition of the entropy
@Ben: Right. Reading too fast.
May
14
comment Why can't supersonic planes “just fly higher” to go faster while maintaining cost?
@Jim: There are variations of what's called "class Alpha" between countries, but there are no altitudes reserved for international flights. It generally refers to heights from 18kft to 60kft, above mean sea level, with standard altimeter setting. When divided by 100ft, these are called "flight levels". Airspace class
May
14
comment Definition of the entropy
You point 2 is only true if all values are equally likely. For example, if there are two outcomes, and one outcome has probability 1/1024, while the other has 1023/1024, then the entropy is 10/1024 + ~0 = ~0.01 bits, not 1 bit.
May
14
comment Definition of the entropy
Don't think of it as disorder. Think of it as what you don't know, and of what, on average, you will learn if you find out what the value of the variable is.
May
14
comment Why can't supersonic planes “just fly higher” to go faster while maintaining cost?
Conventional subsonic aircraft have to contend with the coffin corner.
May
14
comment Why can't supersonic planes “just fly higher” to go faster while maintaining cost?
The heat is not just skin friction. Where the air hits a forward-facing surface it has to stop, which compresses it, which makes it very hot (stagnation temperature). Even if it's very low density, it still gets very hot. That's what spacecraft re-entry is all about.