Mike Dunlavey

4,239 reputation

714

bio	website	en.wikipedia.org/wiki/…
	location	United States
	age	68
visits	member for	1 year, 8 months
	seen	4 hours ago
stats	profile views	417

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)

	4,239 reputation	bio	website	en.wikipedia.org/wiki/…	visits	member for	1 year, 8 months
714 badges		location	United States		seen	4 hours ago

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4h	comment	How to find outflow pressure/force of air through a pipe en.wikipedia.org/wiki/Pipe_flow
1d	revised	rate of flow out of a reservoir added 136 characters in body
1d	answered	rate of flow out of a reservoir
2d	comment	What is the state of contempoary Quantum Physics as a discipline? Easy there! No need to jump off the diving board :) (BTW, I learned early on that there's no need on stackexchange for excitement-toned language. You're among friends.) There are plenty of people on this site who know this stuff well enough that they aren't wracked with uncertainty, so you could follow them.
2d	comment	How would a change in ambient temp affect a radiator? @Gk3Biz: Think of it like an electrical resistor being fed a constant current (heat power). Then a constant voltage (temperature difference) will appear across it. If you up your fan speed, that's like reducing the resistance, giving you less voltage (temperature) difference. Generally, electric equipment like motors have a rated temperature rise above ambient, in order to shed the heat they produce.
2d	answered	How would a change in ambient temp affect a radiator?
2d	comment	How large can planets or moons appear? John Rennie's answer is right on, but keep in mind the Roche limit is due to tidal forces overcoming the satellite's own gravity. That means the closer the main planet comes to subtending 45 degrees of sky, the closer the moon (and its inhabitants, its atmosphere/ocean, and its liquid core) come to being ripped off into their own orbits.
May 19	comment	Radio antennas that are much shorter than the wavelength FWIW: en.wikipedia.org/wiki/Fractal_antenna
May 14	comment	Definition of entropy @Ben: Right. Reading too fast.
May 14	comment	Why can't supersonic planes “just fly higher” to go faster while maintaining cost? @Jim: There are variations of what's called "class Alpha" between countries, but there are no altitudes reserved for international flights. It generally refers to heights from 18kft to 60kft, above mean sea level, with standard altimeter setting. When divided by 100ft, these are called "flight levels". Airspace class
May 14	comment	Definition of entropy You point 2 is only true if all values are equally likely. For example, if there are two outcomes, and one outcome has probability 1/1024, while the other has 1023/1024, then the entropy is 10/1024 + ~0 = ~0.01 bits, not 1 bit.
May 14	comment	Definition of entropy Don't think of it as disorder. Think of it as what you don't know, and of what, on average, you will learn if you find out what the value of the variable is.
May 14	comment	Why can't supersonic planes “just fly higher” to go faster while maintaining cost? Conventional subsonic aircraft have to contend with the coffin corner.
May 14	comment	Why can't supersonic planes “just fly higher” to go faster while maintaining cost? The heat is not just skin friction. Where the air hits a forward-facing surface it has to stop, which compresses it, which makes it very hot (stagnation temperature). Even if it's very low density, it still gets very hot. That's what spacecraft re-entry is all about.
May 13	answered	Water draining from a height into the bottom of a reservoir
May 10	comment	Equal Transit Time Fallacy Brandon's right. IMHO, that av8n link is the best, most accessible, explanation I've seen. It all has to do with the fact that air cannot reverse direction at the trailing edge of the wing. This results in an overall rotary circulation, which is at the heart of the explanation of lift.
May 10	comment	Repulsion does not exist; Gravity assist slingshot as a repulsive force Thank you for trying to ask a question in English, but I had difficulty understanding it. Certainly the slingshot effect would be about the same if gravity were repulsive.
May 5	comment	Lifting house with balloons @Someone: It's better if you put some thought into it. This site is to help people learn from each other, and that doesn't work if your brain doesn't kick in.
May 4	comment	Will a helicoper which is hovering inside a closed box move with the box when we move it? It depends on the size of the box, whether it is a 1m cube or a 10km cube. The hovering helicopter will try to have zero velocity w.r.t the air mass it is in, not perfectly of course, but over time. This is easy to see if an updraft hits it. (I'm sure you know it has nothing to do with bouyancy - i.e. floation :-)
May 4	comment	Why do focal lengths affect magnification? @articlestack: Suppose you have two stars, where the angular distance between them is .01 radian. Then if you have an objective lens that focuses them to an image plane, how big is the image of the two stars? It will be .01 times the focal length, right? 10cm -> .1cm, 100cm->1cm, 1000cm -> 10cm. So then if you look at that image plane with a keplerian eyepiece (magnifying glass), you're examining a small piece of a bigger image.