7,445 reputation
1628
bio website en.wikipedia.org/wiki/…
location United States
age 70
visits member for 3 years, 1 month
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.


Oct
22
comment Weightlessness by a parabolic flight
Isn't that a bit pedantic? It's common to say astronaughts in orbit are experiencing weightlessness. If I throw a ball in the air, while it's in the air, it's experiencing exactly the same weightlessness as the astronaught.
Oct
16
comment Did Felix Baumgartner produce a sonic boom during his jump?
Just a related point. Yes speed of sound is less at higher altitude. That's a problem in jet transports, because their true stall speed increases with altitude, and where the stall speed and the speed of sound come together is called the "coffin corner". That limits the altitude of subsonic aircraft unless they have low wing-loading, like the U2.
Oct
16
comment Is a flawless trick die possible?
@Mathew: There's an even better way to do it. just play god. Film it being thrown down many times, delete all but the cases where it got 3, and post it on Utube. It'll go "viral" :-)
Oct
16
comment Is a flawless trick die possible?
@Mathew: Well, as long as the die is "smart" (having a computer, battery, accelerometer, and momentum wheels inside), then it shouldn't be too hard to program it so if it is simply placed down it will look innocent and not flip :-)
Oct
16
comment Is a flawless trick die possible?
By flawless do you mean it always falls with side 3 up (say), never any other side? Then I think it would have to be active so, for example, if you placed it on the table with side 4 up, it would detect it and spin a momentum wheel or something inside it to flip itself to the 3.
Oct
14
comment Do communicating vessels work when water is moving?
Right. The level in one should equal the bottom level in the other, assuming the tube is directly under the center of the vortex. If it's off-center, I'm not sure.
Oct
12
comment What direction a flag on an object moving in the wind shows?
@Red: Sure. It depends on the relative wind. 50 South - 5 South = 45 South. 2 South - 5 South = -3 South = 3 North. If boat speed downwind = wind speed downwind, the relative wind is 0.
Oct
12
comment What direction a flag on an object moving in the wind shows?
The trailing edge of the flag points directly in the direction of the velocity vector of the relative wind. In common terminology, an air mass whose velocity vector is South is called a North Wind, because if you face North you seem to be facing its source. But don't let that confuse you.
Oct
5
comment Why the shape of rainbow is semicircular after rain why not the whole atmosphere is colorful?
Take an outdoor shower on a clear day with the sun directly above you. You will see the rainbow in a circle around you, because the droplets are all around you, and the ones that are in just the right position will reflect the color (off their opposite surface). But lean against a wall, and now there's a side of you with no droplets. Therefore - not a full circle.
Oct
5
comment Calculating car's acceleration from change in angle of hanging object?
+ @sri: Just make a right triangle by drawing a vertical line from the attachment point, and a horizontal line from the object. Measure the height h and base b of the right triangle. Then just do the proportion. Acceleration a is to gravity g as b is to h.
Sep
21
comment Are probabilities really tangible physical real numbers?
@Arnold: OK. Define $P(B|A)=P(AB)/P(A)$. It is >1 if events can merge (or run backward in time), not simply branch forward. Happens all the time in algorithms. They gain information, then lose it. If $I = -log(P)$, and $I < 0$, then $P > 1$. Not a deep idea, actually.
Sep
21
comment Are probabilities really tangible physical real numbers?
Probability falling between 0 and 1 is an artifact of the way problems are conceived. It represents something that can become known as a process moves forward in time. Example: a binary decision point in a program having two branches. If each branch has P = 1/2, then after the point is traversed, the state contains 1 bit more of information. Conversely, if the two branches join together again, 1 bit of information is lost, corresponding to a probability of 2.
Sep
19
comment 273 + degree Celsius = Kelvin. Why 273?
Sometimes I wonder why people don't go to a logarithmic scale (kind of like decibels), at least for low temperatures. Then there would be no lower limit.
Sep
14
comment Why are L4 and L5 lagrangian points stable?
+1 Great question!
Sep
3
comment Which angle causes an object to land quickest?
@Hayeder: And another way to put it is height. The one that rises the least will hit the ground first.
Sep
1
comment Water, can it break through temperature?
@Harry: No, because there's no free lunch. The energy you get from the H and O combining was transferred from the hot object into the H and O when the water hit the the object in the first place, thus cooling it off. Think of every problem in terms of energy balance.
Sep
1
comment Water, can it break through temperature?
@Harry: You have to provide some kind of ignition, but right, it gets a lot warmer :) In fact, that powers rocket engines.
Aug
30
comment Water, can it break through temperature?
+ Yes. It's important to point out, as you did, that the zirconium stole away the oxygen.
Aug
30
comment Why is there this asymmetry between the two foci of an orbital ellipse?
Well, I don't know, but the same thing happens if you take a planar cut, at an angle, through a cone. The curve you get is an ellipse, and the center of the cone is one focus of the ellipse.
Aug
29
comment What is the possibility of a railgun assisted orbital launch?
@Phill: That exponential formula only applies for rockets that have to hoist the fuel they will use further up.