8,542 reputation
1730
bio website en.wikipedia.org/wiki/…
location United States
age 71
visits member for 3 years, 9 months
seen 4 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
26
comment Why is the damping force on a spring oscillator linearly dependent on velocity?
Cars these days have shock absorbers that are basically dashpots with viscous drag. There was a time when cars used straight friction devices to absorb the energy in up-and-down wheel motions. It just depends what type of energy-absorbing device you use.
Apr
25
comment Equilibrium of a sphere in a water tank
To put @JohnRennie's comment another way, suppose the hole is obstructed by a circular stopper, held there by the weight of water above the hole. Then assume the sphere is trying to float but is tethered to the stopper. You want to know how much bouyancy it needs to just barely lift the stopper.
Apr
25
comment Wind effect on driving a ground-based vehicle
+ for the wig :)
Apr
22
comment Production vs. Collection, and Contaminants vs. Depositions, what might be missing in cold fusion research
@user23467: If I were you, I would edit it in place, making it clean and to-the-point. I would also not beg any premise, such as "given X is impossible". Another course of action would be to delete the question, read everything you can find on the subject, and then maybe ask another question.
Apr
22
comment Production vs. Collection, and Contaminants vs. Depositions, what might be missing in cold fusion research
I think if Ron weren't burned out on this subject, he might point you to lenr-canr.org. The way I would say it is: It is correct to be skeptical of positive results. It is also correct to be skeptical of negative results. If something is not understood, it does not demand that you pick which side to "believe". At the same time, if the potential payoff is large, inquiry is certainly justified.
Apr
22
comment Robot controling pouring process from a bottle
@Slavisa: My point is, do you have a feedback loop? When I was in grad school 40 years ago, somebody programmed a robot to pour coffee in a cup by using a video camera connected to the computer. It could sense the rising liquid level and stop pouring at the right time. It's not much about physics, it's about heuristics and feedback.
Apr
22
comment Robot controling pouring process from a bottle
Is the robot working blind, or does it have any kind of sensors? My 4-year-old grandson loves pouring liquids, and he's a long way from caring about laminar inviscid flow, blah, blah...
Apr
20
comment Physics behind the flow of gas coming out of a balloon
@john1034: Float for a longer time? Do you mean it should stop ascending, or do you mean it should not burst? I'm only asking because balloons basically ascend until they burst. You could halt the ascent by letting out some of the gas.
Apr
16
comment Concerning the curvature of an airfoil (shape)
@l3win: I think you're basically right. The camber of the airfoil controls how much the flow can be diverted, and momentum flux generated, especially at low velocity and/or angle of attack, without stalling. Check here.
Apr
14
comment Photon as the carrier of the electromagnetic force
+ Very nice. It might help if you could explain some terms unusual to us ignorencia, such as "cross section", "branching ratio", and "off mass shell". Thanks.
Apr
12
comment Effective angle of attack of a wing
Maybe you're saying this and maybe you're not, but when the yaw angle is zero, the wind "sees" just the chord slope of the wing. When the yaw angle is 90 degrees, the wind sees the dihedral angle of the upwind wing (and negative on the downwind wing). In between, it's in-between.
Apr
12
comment Does a wing in a potential flow have lift?
@Christoph: You're right. Thanks for pointing that out.
Apr
11
comment Will this type of engine produce thrust?
@Akash: No need to get carried away :) The J58-P4 engine of the SR-71 generated about 16 tons of thrust, but there's no mention of "plasma".
Apr
11
comment Will this type of engine produce thrust?
@Akash: In principle, though your heater would have to pump out as much heat as a gas flame if you want to get noticeable thrust.
Apr
10
comment Make water droplets charged?
+ I think your mention of the Kelvin water dropper is right on target.
Apr
9
comment Whats the anti-torque mechanism in horizontal take-off aircraft?
@Jim: Lots of questions here about airplanes seem to arise because of not comprehending how heavy air is. In everyday experience, air seems ephemeral, but that's an illusion. It weighs about a $kg/m^3$ and even at low aircraft speeds it takes a lot of force to muscle it around. That force increases as speed squared, so it's practically as dense as water to a speedboat.
Apr
9
comment Whats the anti-torque mechanism in horizontal take-off aircraft?
It's just one of those things that pilots learn. Planes are usually designed with some built-in trim, to act as a compromise between different flight regimes, like takeoff (high power), cruise (medium power), and landing (low power). Like if you look at the rudder of a C172, you will see a little plastic tab near the bottom. That's a built-in trim tab so you need less right rudder on takeoff. As far as roll torque is concerned, the ailerons are plenty strong enough to manage it. It's not an issue.
Apr
9
comment Whats the anti-torque mechanism in horizontal take-off aircraft?
@Martin: Rotary engines on WW1 fighters were dangerous because of gyroscopic precession. i.e. hitting the rudder for left or right yaw could knock your nose up into a stall or down into the ground.
Apr
9
comment Why water in the sink follow a curved path?
@Jim: I wouldn't have paid much attention to the sink's floor and wall, but yeah, I think that's right. You always get a vortex, but its size depends on how much angular momentum is in the water. If the water is really really still, then the vortex is really thin, but it's there.
Apr
9
comment Why water in the sink follow a curved path?
@Jim: It's almost impossible for it to have absolutely zero rotation. At the very least, it's turning with the earth at about 1/4 degree per minute. If you put in a drop of ink, of course it spreads out, but does the center of the ink blob stay in exactly one place? You can make the drain swirl clockwise or counterclockwise by just slightly stirring it with a spoon before hand, or by putting in some kind of baffle so that as it flows toward the center it is nudged in one direction or the other. You can perceive that the water has no rotation, but it only needs a tiny tiny bit.