8,034 reputation
1728
bio website en.wikipedia.org/wiki/…
location United States
age 70
visits member for 3 years, 6 months
seen 19 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.


Mar
14
comment A cup of water in ZERO gravity
@user3932000: No, there's really no such thing as zero gravity, unless you go far out in the universe, far away from any galaxies, etc. Aboard the ISS, there's plenty of gravity. The whole structure and everything in it is falling toward the earth. It just happens to be going so fast horizontally that as fast as it falls, the surface of the earth bends away because it's curved, so the ISS never gets any closer to the ground. They call it "micro gravity", but all that means is everything is falling together at the same time.
Mar
14
comment In a dust cloud around a star, what causes bodies to form?
OK, that's a big help. I wonder if it extends to planetary dust clouds. I mean, we see things like comets. I wonder how they are formed. Rather than, say, disintegrated?
Mar
14
comment A cup of water in ZERO gravity
@user3932000: You don't have to be in space to be in a zero-gravity environment. In fact, a less confusing term is "free fall". It can be easily done in an aircraft.
Mar
14
asked In a dust cloud around a star, what causes bodies to form?
Mar
14
comment A cup of water in ZERO gravity
It's easy to create a zero-gravity environment. Just toss the cup of water in the air. Then while it's in the air, just grab the cup away from the water. My son once asked me how things can float in space. I just demonstrated with car keys. I tossed them up and followed them with my hand. They "floated" above my hand :)
Mar
12
answered The relation between the velocity and the static head
Mar
10
comment If there are 4 dimensions, shouldn't objects appear and disappear in 3D space?
If you want to understand this stuff, I highly recommend Sam Lilley, "Discovering Relativity for yourself".
Mar
10
comment If there are 4 dimensions, shouldn't objects appear and disappear in 3D space?
1) Time is a physical dimension (actually imaginary time is). 2&3) Physical objects can only move up to 45 degrees out of parallel with the 3 space dimensions (that's the speed of light).
Mar
5
comment What is the top speed of the SR-72 aircraft? What affects would traveling at this speed have on the human body?
+ And the ISS folks step outside all the time.
Mar
3
revised Is it possible for a physical object to have a irrational length?
added 553 characters in body
Mar
2
answered Pressure-Velocity relation at a point in a flow
Mar
2
comment Why does deflating baloon spurting through the air make circular motion?
Good answer. I would only add what every teenage rocket engineer knows - a rocket has to pass the "swing test" where you tie it to a string, at its center balance point, and swing it around you in a circle. It has a center of gravity (CG), and an aerodynamic center. The CG has to be forward of the aerodynamic center, or it will want to turn around and go backwards. If that happens under power, it will act just like your balloon :)
Feb
27
comment What happens during gravitational collapse to cause the formation of a star?
My understanding of the fusion reaction is that the caloric density is actually quite low, like a compost pile. It's just that there's so much of it.
Feb
24
revised Can a thrown egg chip (or break) a car windshield?
spelling
Feb
16
comment Why does it take so long to get to the ISS?
@Dewi: The plane of any satellite's orbit is stationary, while the launch site is traveling east, so it is under the orbit twice a day, if the orbit is sufficiently inclined.
Feb
13
comment Can I tell where a leak is in a vertical water pipe based on the water pressure at the bottom?
@Skywalker answer is right. You can only get the height of the water. You can only get the height of the leak if you let the water drain down to it. So if you measure the pressure at the bottom, you need to wait until it stops falling. Actually, that will be an asymptote. It will slow down before it gets there. Actually, you might speed it up by letting some water out the bottom.
Feb
13
comment Why does NaCl (aq) conduct electricity but NaCl (s) does not?
and in solid, they are not even ionized.
Feb
13
comment Airfoils contradict the law of the lever?
@Floris answer is right. It's about energy, not force. The drag experienced by a wing is simply lost energy. A lever is a system that does not lose energy.
Feb
8
comment Application of Bernoulli's theorem
If it helps, I think the easiest way to understand Bernoulli is the simplest: to make a fluid accelerate (change speed), you need a difference in pressure. It's just $F = ma$ for fluid.
Feb
7
comment Why does the airflow in the mid-stratosphere of the northern hemisphere rotate FASTER than the earth?
@tpg2114: I appreciate what you're saying. I looked at the simulation, and the entire southern hemisphere has a broad easterly flow, and the equator is all westerly. This makes me doubt the simulation.