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bio website sjbyrnes.com
location Massachusetts
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visits member for 3 years, 6 months
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Dec
10
comment Is there a relation between (non-) existence of magnetic monopoles and thermodynamics?
I don't understand what point you're trying to make. Are you trying to prove "If there are magnetic monopoles, nothing is thermodynamically reversible?" Or "If there are magnetic monopoles, then everything is thermodynamically reversible?" Or "If there are magnetic monopoles, the second law of thermodynamics is false"? Or what?
Dec
7
comment What limits the doping concentration in a semiconductor?
Well, you can write it in terms of "enthalpy of mixing" etc. But if you tell me two atoms, I cannot tell you the solubility limit (or the enthalpy of mixing or anything else useful) except by experiment or numerical simulation.
Dec
4
comment Stimulated emission direction
You should look up optical amplifier - scholarpedia.org/article/Optical_amplification en.wikipedia.org/wiki/Optical_amplifier and more specifically gain guiding rp-photonics.com/gain_guiding.html
Dec
4
comment Why does a thermoelectric generator need both p and n elements?
I don't see any reason that ohmic losses are an inevitibly large problem in the design I drew, if you make reasonable choices about geometry etc. I agree that a large voltage is more practically useful in the final output, but it's not a big deal, you can always put a step-up voltage converter at the device output.
Dec
4
comment Why does a thermoelectric generator need both p and n elements?
Copper has 400X larger thermal conductivity than BiTe. So if you compare the heat conductance of a 1-meter-long, 1mm-diameter copper wire with the heat conductance of a 10cm^2, 1mm-thick BiTe, the BiTe will conduct more heat than the copper wire ... by a factor of 2000.
Dec
4
comment Why does a thermoelectric generator need both p and n elements?
You say "heat will be conducted away from the hot junction by the wire itself, so no electricity will flow." (I assume you mean "electrical current" not "electricity".) I don't understand how you reach that conclusion. Some heat will surely flow through the wire, but not all of it, indeed probably almost none of it. A long thin copper wire has a very low thermal conductance. In the design I drew, it is entirely possible to have 99% of the heat flow through the thermoelectric material and 1% flow through the wire. Then why should heat flow through the wire make any difference at all?
Nov
10
comment How to convert RGB values to physical radiometry and/or photometry quantities and back?
A few nitpicks... All modern displays and printers use sRGB, which is gamma-corrected. So you're correct that it's not logarithmic. But it's not linear either. Also, plenty of hardware can provide more accurate colors than 255-255-255, even though not all programs take advantage. See en.wikipedia.org/wiki/Color_depth
Oct
22
comment How to distinguish between the spectrum of an atom in motion and the one of a scaled atom?
OP's description isn't correct, and this is a good proof. Upvoted! However, there is something along those lines that works. If I set hbar = c = 1, I can scale all quantities with units of eV^N by a factor of 10^N. So I would increase masses and energies and frequencies by 10X, I decrease lengths and durations by 10X, etc. That would definitely be a consistent way to scale the wavelength of every spectral line. See my answer.
Oct
22
comment How to distinguish between the spectrum of an atom in motion and the one of a scaled atom?
Can you be more specific? Don't forget, the question is "if we decrease all the masses, does it result in decreasing all the emitted photon frequencies by the same ratio?" So the energy levels are supposed to be proportional to the masses. When you say that the hyperfine structure is proportional to me/mp, are you sure you're talking about the absolute energy level differences, rather than some ratio of splittings?
Oct
12
comment Experimentally diminishing random errors for low wavelength UV observations
It's not just photon shot noise right?
Oct
9
comment What challenges needed to be overcome to create (blue) LEDs?
Oops, maybe my info is out of date. Last I heard they could only make bluish-green. :-P
Oct
2
comment Spin via Change of Phase
Are you familiar with this stuff -- en.wikipedia.org/wiki/… ? Your question is very hard to understand. Why do you say "ϕ should remain as ϕ"? What can "happen in two ways"?
Sep
11
comment Definition of mean free time in the Drude model
"Duration" is not a technical jargon term, it's just a word that means "length of time".
Jul
18
comment Total internal reflection and waveguides
Could you clarify, either (1) You want to learn how to derive the Fresnel equations, or (2) You want to know how you can calculate the angle-dependent phase shift starting from the Fresnel equations, or (3) Both.
Jul
14
comment How can molecule of a few angstroms absorb visible light of a few hundred nanometers?
If you want to understand the cross-section or linewidth of an atomic absorption line, then it is not a mistake to compare the size of the molecule to the wavelength of the photon.
Jul
14
comment How can molecule of a few angstroms absorb visible light of a few hundred nanometers?
I disagree. You can learn many interesting things by learning the classical theory of electrically-small antennas (e.g. en.wikipedia.org/wiki/Chu%E2%80%93Harrington_limit ), and applying those principles to atoms interacting with light.
Jul
14
comment How can molecule of a few angstroms absorb visible light of a few hundred nanometers?
I made an animation illustrating how an electron in a superposition state moves back and forth, just like you say in the first paragraph. See en.wikipedia.org/w/…
Jun
18
comment What could magnetic monopoles do that electrically charged particles can't?
There are two good questions here, incoherently mixed together. The first is: "What applications would a real magnetic monopole have?" The second is: "What applications do the magnetic monopole quasiparticles in spin ice have?" But these two questions are unrelated, see en.wikipedia.org/wiki/…
Jun
18
comment What could magnetic monopoles do that electrically charged particles can't?
Your first paragraph is describing the magnetic monopole analogue of a capacitor.
Jun
18
comment What could magnetic monopoles do that electrically charged particles can't?
The Particle Data Group article is about real magnetic monopoles (elementary particles); the ScienceDaily article is about magnetic monopole quasiparticles. They are unrelated, and it is misleading for you to suggest that they are the same thing. See en.wikipedia.org/wiki/…