8,397 reputation
1730
bio website en.wikipedia.org/wiki/…
location United States
age 70
visits member for 3 years, 8 months
seen 3 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.


Apr
3
comment How does an aeroplane maintain balance during maneuvers?
@Dirt: Forget balance. Sure, everyday planes are designed to be more or less stable, but that's just to protect the dumb Sunday Drivers operating them. Fighter jets are designed to be unstable, to make them more maneuverable. (They can roll at 720 degrees per second.) Check out this site.
Apr
1
comment Spinning liquid to create a centrifuge effect
@Greasehauler: I think you have good ideas, and the only thing I might contribute is what I tell my kids and what I always told my programming students: Do small experiments. That way you can try things, and the failures will be educational and not very expensive.
Mar
28
comment What's the acceleration of pendulum when velocity is zero
$a=v^2/r$ is the radial acceleration, not the tangential acceleration.
Mar
27
comment Why a day is divided by 12/24 hours? Why the number 12?
How did you make that gif? It's cool.
Mar
27
comment How long can you survive 1 million degrees?
That's kinda what I was wondering about. Here you have individual nuclei peppering your skin at enormous velocities. Wouldn't they easily penetrate and do damage at depth?
Mar
27
comment Intuition behind Work
Yes. You multiply the force times the distance. The usual definition of work is "force times distance". Lift a 1-lb weight 1 foot off the floor, and you have done 1 ft-lb of work. Lift 100 lb 10 feet - 1000 ft-lb. Twice as much weight, twice as much work. Twice as much height, twice as much work.
Mar
23
comment Can anyone explain what a superleak is?
Amazing! Thanks for the video.
Mar
21
comment What mechanisms exist for generating lift on a static object?
If by propeller the OP means any sort of airfoil to which power is applied, it remains attached to the vehicle, and its lift vector can be directed upwards.
Mar
20
comment What mechanisms exist for generating lift on a static object?
+ It could be argued that this a propeller, but anyway I like it!
Mar
20
comment Surviving Free Fall with the Help of Mr. Bernoulli
@John: You're right, but it's not so much about gaining speed as about reducing the angle of attack.
Mar
19
comment Speed of the Moon
Your profile says you're a postdoc in physics, so this question seems a bit strange.
Mar
18
comment Explanation for different boiling points of water on different altitudes
+ It works the other way too. Underwater, at a depth of 1km, the water can get up to around 300C without boiling, as shown in this article.
Mar
16
comment effect of internal forces to a glider's descent
Yeah, you're basically right, I think, but don't think of the glider as making sudden changes in descent angle. Rather think of it as experiencing temporary changes in vertical acceleration, giving it short smooth curves down or up, such that the center of mass (man & glider) follows a straight line.
Mar
11
comment Experiment to measure initial speed of high speed tennis ball?
Nice. This is like the Charpy test I learned in undergrad materials science.
Mar
11
comment Experiment to measure initial speed of high speed tennis ball?
Fire it horizontally, and measure how far it goes before it hits the ground. You can calculate (or measure) how long it would take if simply dropped. That's how long it takes to go that distance. This only works if there's no spin involved. Add a fudge factor for air resistance.
Mar
6
comment Water, how do you make ripples
Shine a light on the water in the bowl and watch the reflection. It should just look like a simple mirror. Then drop in your pebble. The reflection will be all messed up for a little while. That's your ripples.
Mar
6
comment What is the optimal weight for a golf ball?
It isn't force that you're hitting it with. You have a collision between elastic objects, the ball and the driver, so think of it in terms of the momentum transferred from the driver to the ball.
Mar
6
comment Flow in parallel paths after pressure regulator
@wupdiwup: There's only one thing a valve sees - the pressure drop across it. The only way flow through valves B and C can reduce the flow through A is by reducing the pressure that A sees. If the pressure regulator is doing its job, that cannot happen. You have to make sure the pressure regulator can keep up the pressure even with all three valves open.
Mar
5
comment Flow in parallel paths after pressure regulator
+ As long as the pressure regulator does its job and maintains a constant pressure going into each valve, that's all the valve will see.
Mar
5
comment Understanding Quantum Physics
@EmilioPisanty: Thanks. Good edit. One of the best hours I've spent. I love his salt-of-the-earth presentation and Brooklyn accent.