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Old 4th November 2012, 12:57 AM   #28881
bcarso is offline bcarso  United States
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Originally Posted by Esperado View Post
Is these Ego problems had let traces in Silicon able to explain those disparities and non linearities against which we still have to fight today ?
peut-Ítre
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Old 4th November 2012, 01:24 AM   #28882
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Originally Posted by gedlee View Post
There is precisely one boundary that allows for the developement of a spherical wavefront from a flat circular source and that is the OS. The physics of wave motion will decide what the shape has to be for this to happen, not the horn designer. One cannot simply assume that a wave will follow a given boundary, the correct boundary has to be determined not specified.
If the speed of sound is constant, how can any wavefront _not_ be spherical at a distance sufficiently large compared to the radiating surface's diameter?

The flat wavefront assumptions from the early days were glaringly wrong in hindsight. In the early 1980's my father developed a method of successive iteration to design an exponential area horn wall with spherical wavefront. It was before serious personal computers, so he divided the length down the wall into 500 segments and made 500 HP calculations. (He had retired after doing turbine blade design and was enamoured of the prospect of personal computing. Didn't live quite long enough to see the Internet explosion.)

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Chris

Last edited by Chris Hornbeck; 4th November 2012 at 01:26 AM.
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Old 4th November 2012, 01:10 AM   #28883
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Originally Posted by bcarso View Post
Shockley was a clever and complex character, quite a promoter. Anyone in here old enough to remember his four-layer diodes? I mean, besides me And then he associated himself with the genius sperm bank stuff, hilariously parodied on Saturday Night Live when Rodney Dangerfield hosted.

Bardeen was amazingly bright and insightful, apparently rather self-effacing, and is the B of the BCS theory of superconductivity. To date he remains the only double-Nobelist in the field of physics.
Shockley - Too many blows to the head. I had a prof that worked directly with Shockley in the 60's, he had a serious car accident and was never the same. Only after this did he dwell on his racist theories.
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Last edited by scott wurcer; 4th November 2012 at 01:14 AM.
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Old 4th November 2012, 01:32 AM   #28884
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Originally Posted by Alexandre View Post
I once heard from a professor that the true inventors of the transistor were Bardeen and Brattain, with Shockley entering later as the project supervisor.
I was reading about this. According to wikipedia, Bardeen and Brattain have created the point-contact transistor, while Shockley invented and patented the junction transistor.
William Shockley - Wikipedia, the free encyclopedia

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alex
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Old 4th November 2012, 11:04 AM   #28885
gpapag is offline gpapag  Greece
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I believe the vacuum is linear for EM until you get to astonishingly high energies, like the interior of collapsed stars.
Thank you DF96
I was reading something very interesting on Heaviside.
http://archive.org/download/electrom...03heavuoft.pdf
Vol. III, pages 149-152 (p. 152-154 explanation and p.154-158 derivation)

George
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Old 4th November 2012, 11:06 AM   #28886
gpapag is offline gpapag  Greece
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Originally Posted by Chris Hornbeck View Post
If the speed of sound is constant, how can any wavefront _not_ be spherical at a distance sufficiently large compared to the radiating surface's diameter?

Thanks,
Chris
Chris
Speed of sound in air is not fixed (constant). Even if we consider air as an ideal gas and as a non-dispersive medium and assume adiabatic conditions, still local temperature variations will vary sound speed.
Speed of sound - Wikipedia, the free encyclopedia

George
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Old 4th November 2012, 03:07 PM   #28887
bcarso is offline bcarso  United States
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Originally Posted by scott wurcer View Post
Shockley - Too many blows to the head. I had a prof that worked directly with Shockley in the 60's, he had a serious car accident and was never the same. Only after this did he dwell on his racist theories.
Very interesting.

Vladimir Arnold, the late great dynamical-systems theorist, late in life had a serious car accident as well and was never quite the same, according to my friend John Norris who had worked with him. Fortunately he retained his aplomb and great sense of humor, and his contributions were prodigious before his output slowed.

Head injuries often bring about funny changes. My mother, a widow, suddenly got extremely (for her children, scandalously) affable and interested in men again in her mid-eighties, after a fall and subsequent life-threatening cranial hematoma was caught barely in the nick of time. In earlier life after such traumas, many switch interests abruptly from hard science, law, etc. to gastronomics, art, music.
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Old 4th November 2012, 03:40 PM   #28888
DF96 is offline DF96  England
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Heaviside had a reputation for annoying people, especially mathematicians and electrical engineers who for opposite reasons thought his work was wrong. Mathematicians said his work lacked rigour (true) and therefore must be wrong (not true). Engineers said his results were counter-intuitive (true) and therefore must be wrong (not true). Eventually the mathematicians found a way of accommodating his ideas into proper mathematics, and the engineers found that his results actually worked in real life (later on, they learned enough maths to understand his calculations too).

However, that fact that his results were correct does not necessarily mean that the semi-mechanical reasoning he used to guide his maths is also correct. He could not conceive of a wave without a medium. We can.
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Old 4th November 2012, 03:55 PM   #28889
bcarso is offline bcarso  United States
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I love the beginning of that third volume and the story of the boy. For some reason I couldn't scan it adequately and deleted the post after noticing lines of type were cut off. I have the three volumes in storage so maybe I'll dredge them up and scan directly.

Other visionaries of the pre-relativity and quantum theory era, William Thomson (Lord Kelvin) and Peter Guthrie Tait, had some theories about "vortex atoms" that they advanced to explain many things. There is an eerie similarity between some of their topological notions and recent physical theory.

EDIT: here's a reference link to an nice paper about this: http://www.csee.umbc.edu/~lomonaco/kelvin/kelvin23.pdf

Last edited by bcarso; 4th November 2012 at 04:08 PM. Reason: found reference
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Old 4th November 2012, 04:30 PM   #28890
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Originally Posted by gpapag View Post
Speed of sound in air is not fixed (constant). Even if we consider air as an ideal gas and as a non-dispersive medium and assume adiabatic conditions, still local temperature variations will vary sound speed.
Speed of sound - Wikipedia, the free encyclopedia
Well, sure, but it's constant enough for designing horn wall contours, in any place where people would be comfortable. Incidentally, for an exponential (on center line distance from small end) area expansion wave front contour is the involute of the horn wall with a flat central disc the size of the small end and the wave front is normal to the horn wall, for true (spherical) wavefronts.

Thanks,
Chris

Last edited by Chris Hornbeck; 4th November 2012 at 04:41 PM.
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