6,281 reputation
1322
bio website en.wikipedia.org/wiki/…
location United States
age 69
visits member for 2 years, 7 months
seen 22 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.


Jan
24
comment How physical objects (e.g. Earth and Apple) are aware and do computation about each other?
@KeithThompson: Totally agree. In one of Feynman's paperbacks, he tells the story of his father being asked, if there's a pumpkin in a wagon, and the wagon is pulled, why does the pumpkin roll to the back? His father said, basically, everybody knows it does, but nobody knows why.
Jan
24
comment How physical objects (e.g. Earth and Apple) are aware and do computation about each other?
@Yasser: Newton couldn't answer that question, so he assumed God did it. Einstein actually made a theory of it, which helps us understand it, regardless of any deity, but it does not not require the physical objects to know that theory.
Jan
24
comment How physical objects (e.g. Earth and Apple) are aware and do computation about each other?
If you put one block on top of another, do the blocks need to know math to know they are 2 blocks tall? No. Maybe we do.
Jan
24
comment Does rotation cause gravity?
Just to be light-hearted, some children were once asked what causes wind. The answer: the trees waving their leaves.
Jan
22
comment Who popularized $E=mc^2$?
6 August, 1945, is when the world became aware.
Jan
22
comment Why is the Fraunhoffer Pattern the Fourier transform of the slit?
There's a pretty good explanation here.
Jan
22
comment Sailing against the wind. Is this a fair model?
That model is good, and you can use the same model to show how to go downwind faster than the wind, because the "sail" can always be turned to an angle such that the balls hit it, and the normal force has a forward component.
Jan
20
comment Non-determinitric flow of water stream on vertical porcelain surface
There's probably a better answer, but the water streaming down the surface has surface tension, that apparently affects it chaotically, the same way rivers meander. Flow in a straight line is unstable, because the slightest curve tends to grow on the outside.
Jan
13
comment Mirrors into Infinity
+ Nice, and you get a similar effect if you have 1) a TV camera, connected to 2) a closed-circuit TV monitor, and 3) the camera is looking at the monitor. In the 70s this was an example of electronics "freaking out".
Jan
11
comment Homopolar motor and Lorentz force
+ I'd never seen that before. What a nifty demonstration! If you have a wire cutting through magnetic field lines a current is induced. Then the reverse has to be true also, and that's what you're seeing.
Jan
11
comment How does the pressurization in a house's water supply allow adjustable flowrates from a tap?
I'm sure you're learned in your Ph.D. studies in fluid dynamics that pipe networks and wire networks are analogous, and an adjustable tap is just like a variable resistor.
Jan
9
comment What is so special about speed of light?
@called2voyage: Right. Thanks for the correction.
Jan
8
comment Pressure difference between 2 side of wings of aircraft
@shortstheory: This is my favorite explanation of all that.
Jan
6
comment Spontaneous motion in a wind tunnel
@GoodarzMehr: At low mach number (ignoring compresibility) conservation of mass says $\rho A_1V_1 = \rho A_2V_2$, so momentum/second in equals momentum/second out, so no net thrust. (Ignoring drag on the cone.) Jet engines work by increasing $V_2$ by expanding the gas.
Jan
6
comment Would Beetee's electrocution plan work and kill the tributes in the lake?
If people are in the lake, they are basically conductors, being largely made of salt water, insulated only by a little layer of wet skin.
Dec
28
comment Exactly how much lift is needed to overcome the weight of an average person?
@User58220: It accelerates at 1g.
Dec
28
comment Exactly how much lift is needed to overcome the weight of an average person?
Aircraft have a rating - wing loading - expressed in weight per unit area. A typical small plane is in the range of 10lb/square foot, which is achieved at a speed of roughly 60 mph. Lift is proportional to speed squared, so if you halve the speed, you need 4 times as much area.
Dec
26
comment Is there a travelling speed of for electric field? If yes, what is it?
In a vacuum, you're right. Inside a metal wire, it is different, as the other answers and comments are discussing.
Dec
24
comment Increase in velocity by loss of mass?
@Nick: If the hole points downward, there won't be any rocket effect. If it points in the direction of travel, I can picture the sand coming out with enough horizontal velocity to have a momentum-transfer effect (not much, but some).
Dec
24
comment Why complex functions for explaining wave particle duality?
@RajeshD: If you want to see if there is another way to approach QM theory (or philosophy if you prefer) then try it. Maybe you will find another way. Sending out a missive like this will not do it.