8,192 reputation
1728
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.


Jan
14
comment What causes an aircraft to roll when rudder is applied
@Rory: But when you put in n degrees of rudder, the plane quickly equilibrates to a certain yaw angle wrt the airflow, at which point both wingtips are at equal speed, though one is forward of the other. Then wing sweep and dihedral produce roll moment, in ways depending on specific aircraft design.
Jan
12
comment What causes an aircraft to roll when rudder is applied
I'll grant you it's a bigger and really interesting subject. Every time these issues come up I learn something new. Cheers.
Jan
12
revised How does the position of lift affect the stability of the lifted object?
added 323 characters in body
Jan
12
revised How does the position of lift affect the stability of the lifted object?
added 120 characters in body
Jan
12
comment What causes an aircraft to roll when rudder is applied
Hey @Larian, I guess we're going to disagree here :) My understanding is any rudder displacement, regardless of bank, is going to produce a roll moment in an aircraft with dihedral. I was taught, and it was definitely handy for hands-off flying, that I could hold course with just my feet, in a 172 (that seems to have no sweep).
Jan
12
answered How does the position of lift affect the stability of the lifted object?
Jan
12
comment What causes an aircraft to roll when rudder is applied
In fact, Wikipedia says fighters have exactly that, so they trade off dihedral effect in favor of maneuverability.
Jan
12
comment What causes an aircraft to roll when rudder is applied
The small Cessnas I know have dihedral, but not any sweep, that I'm aware of. Diagram C is really confusing. I'm sure the sweep of the forward wing increases roll moment just because it sticks out further, but it says the trailing wing has more AOA and the leading wing has less. How can that be (assuming there is upward dihedral angle)? My sense of geometry says the opposite. If the dihedral angle were negative (anhedral) then I could see it. Maybe that's how your fighters are made.
Jan
11
comment Simple elastic collision
On top of all these good answers, remember that momentum is a vector, not a scalar quantity. So change in momentum is also a vector.
Jan
11
revised Why does it take so long to get to the ISS?
added 200 characters in body
Jan
11
awarded  Custodian
Jan
11
reviewed Reject Why does it take so long to get to the ISS?
Jan
9
revised How come vibrations?
edited body
Jan
9
answered How come vibrations?
Jan
8
comment How to calculate uncertainties of a natural exponential function?
Just report your results as graphs on semi-log paper, with T on the log axis. Then you've just got two straight lines for your fit, one low, and one high.
Jan
8
comment How to calculate uncertainties of a natural exponential function?
1. Because it doesn't affect the gradient. 2. What do you mean "do with"?
Jan
8
comment Estimating drag due to wind - ribbon-shaped sail
Good question. I can imagine there could be technical solutions along the lines of how oscillations are addressed in airfoils and tall buildings.
Jan
7
revised Relationship between height and velocity in conservation of mechnical energy
added 1 characters in body
Jan
7
revised Relationship between height and velocity in conservation of mechnical energy
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Jan
7
answered Relationship between height and velocity in conservation of mechnical energy