7,030 reputation
1524
bio website en.wikipedia.org/wiki/…
location United States
age 70
visits member for 2 years, 11 months
seen 2 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.


Aug
17
comment How does a car turn without any skidding?
@mcFreid: Actually, since a tire contacts the road in a patch, not a point, the side of the patch away from C does have to travel a larger distance. So it does skid a little bit that depends on how wide the tire is.
Aug
17
comment How does a car turn without any skidding?
@mcFreid: As long as we're simplifying, idealize the wheel to be zero width (a knife edge of super-hard material). It rolls forward and backward without slipping. The path on which it rolls does not have to be perfectly straight, does it? From instant to instant, it can turn a little bit without slipping, because it contacts the road at an infinitessimal point.
Aug
16
comment What would be an appropiate shape for a parachute?
@user1002327: It's the same as in any aircraft. For the given weight and wing area, there is a speed that's too slow, called the "stall speed", where the wing ceases flying and becomes a parachute. The speed that gives maximum time aloft is just above stall speed. You adjust the speed by trimming the weight more or less forward.
Aug
12
comment What differs string theory from philosophy or religion?
@Ron: I should clarify that the comment regarded a time before Christianity really got going, and the religions being talked about were whatever the various tribal peoples being conquered happened to have.
Aug
12
comment What differs string theory from philosophy or religion?
If can interject a slightly humorous aside, Gibbon, in "Decline and Fall of the Roman Empire" related that adherents of religions knew they were true, philosophers knew they were false, and magistrates knew they were useful.
Aug
12
comment What is the relationship between kinetic energy and momentum?
Look here.
Aug
8
comment Why are radians more natural than any other angle unit?
I seem to remember when it was considered to divide the circle into 400 "degrees", to make navigation a little less error-prone. As it is, pilots have to just "know" that 7 and 25 are opposite ends of a runway, and be really really careful not to mix up 13 and 31.
Aug
8
comment Why are radians more natural than any other angle unit?
Nice...........
Jul
26
comment Rotation, cats landing on their feet, and conservation of angular momentum
@Physikslover: No need to reason about it, try it. Sit on a bar stool. Hold a heavy weight in one hand, hanging at your side. Then swing it up to horizontally in front of you (call that 12 oclock). Then swing it horizontally to the 3:00 position. That will of course turn you somewhat to the left. Then drop the weight back down to your side, where it started from. Now you are just as you were when you started, except you remain oriented to the left of where you started.
Jul
26
comment Rotation, cats landing on their feet, and conservation of angular momentum
@Physikslover: Relative rotation does not require a swivel joint. Have you ever tried to swing a hula-hoop around your waist? It's the same motion. If you do that while standing on a frictionless platform, you will turn, and when you stop, you will be facing in a new direction. Alternatively, sit on the bar stool and swing your feet in a circle.
Jul
26
comment Rotation, cats landing on their feet, and conservation of angular momentum
@Physikslover: But simplify the cat down to two rotating masses, where one mass is larger than the other. One has rotated one way, one has rotated the other. When they come into alignment again, they are no longer pointing in the original direction. If you are sitting on a stool with a weight in one hand, simply swing the weight around your head a few times - same thing.
Jul
26
comment Can I study Quantum Computing or Quantum Mechanics with an Engineering background?
You can learn anything you want, whenever you want. All it takes is spending time.
Jul
19
comment What will happen if a plane trys to take off whilst on a treadmill?
@dmckee: I was agreeing with you until I got a mental image of a leg-propelled hang-glider launching off a hillside :-)
Jul
18
comment What will happen if a plane trys to take off whilst on a treadmill?
@JamieHutber: The whole reason an airplane has freely-rotating wheels is to eliminate friction between itself and the surface. Now, if you turned the plane sideways, that would be another matter.
Jul
18
comment Areas of computer science required for quantum computing
+1 I would just add some basic automata theory. (Once I investigated simulating a finite state machine in a quantum computer, and it was possible after transforming the FSM into a reversible one. That's the key. Computations have to be reversible. They cannot lose information.)
Jul
18
comment What will happen if a plane trys to take off whilst on a treadmill?
What matters to an airplane is relative wind, period. (This is not rocket science ;-)
Jul
17
comment Why is the steam from cooling towers not used?
It isn't steam. It is water vapor cooled enough to form droplets - i.e. a cloud.
Jul
17
comment The possibility of free electrical energy?
Don't put anybody on a pedestal. Try to learn what they are saying. So what if they're a "genius"? You are smarter than you might think.
Jul
16
comment Why do we still not have an exact definition for a kilogram?
@Emilio: That silicon sphere is just begging to be put on a billiard table.
Jul
16
comment Why do we still not have an exact definition for a kilogram?
+1 Nice post. I would daydream maybe someday it could be done by counting atoms, or maybe some kind of interference effect, where you could make a crystal of 1000 atoms, then make 9 more of those & put them together in precise alignment, etc., until you got a molar quantity.