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bio website sjbyrnes.com
location Massachusetts
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visits member for 2 years, 10 months
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Jul
13
comment Electric Field on Surface of Capacitor
The geometry is very unclear. Each plate has two surfaces, the "inside" touching the dielectric, and the "outside". Which surface are you asking about? In order to stretch the particles, they need to be connected to two things that are moving apart. Please tell us what BOTH of those two things are. Are they the two platinum plates? Or one platinum plate and something else?
Jul
10
comment Why does a semiconductor hole have a mass?
See physics.stackexchange.com/a/10858/3811 for more details about "what is a hole" than you usually find :-)
Jul
10
comment Searching the point group of symmetry
pubs.acs.org/doi/abs/10.1021/ci990322q (copied from stackoverflow.com/questions/2750387/…)
Jul
10
comment Searching the point group of symmetry
I think you'll find better answers on math.stackexchange.com instead of here.
Jul
9
comment Friction at zero temperature?
At absolute zero, there are no thermal fluctuations, so there is no noise. Phonons are created when the materials rub against each other. But at absolute zero, the materials are not rubbing against each other. They are just sitting there perfectly stationary. Therefore, no noise.
Jul
7
comment Algorithmic approach for applying Kirchhoff's Rules to circuit analysis
One approach is Modified Nodal Analysis: en.wikipedia.org/wiki/Modified_nodal_analysis Qucs has a nice pedagogical discussion of implementation: qucs.sourceforge.net/tech/node1.html
Jul
7
revised Friction at zero temperature?
added 505 characters in body
Jul
7
answered Friction at zero temperature?
Jul
7
comment Friction at zero temperature?
This is a horrible description of friction. The bumpiness of a surface does not automatically cause friction, because gravity is a conservative force. There has to be a mechanism turning large-scale motion into microscopic vibrations (i.e. heat).
Jul
4
answered PV cell for invisible spectrum only
Jul
3
comment What's the difference between Fermi Energy and Fermi Level?
Take a small-bandgap macroscopic pure semiconductor crystal with just two n-type dopant atoms and one p-type dopant atom. At room temperature the fermi level is almost exactly in the center of the bandgap--the dopant atoms are irrelevant. At absolute zero the fermi level (i.e. fermi energy) is at the n-type impurity level near the conduction band minimum, i.e. higher. You can switch the letters "n" and "p" to get a situation where fermi energy is lower.
Jun
30
answered What's the difference between Fermi Energy and Fermi Level?
Jun
30
comment What's the difference between Fermi Energy and Fermi Level?
The fermi level is NOT necessarily higher than fermi energy. It is higher if the density of states is an increasing function of energy, or lower if the density of states is a decreasing function of energy. (I might have gotten that backwards.)
Jun
27
comment Quantum experiments in the pre-industrial era
Do you even know what electron orbitals are? All aspects of chemical bonds and reactivity--not to mention light absorption--is intimately related to detailed properties of the energy, shape, and phase of electron orbitals and their superpositions. Without quantum mechanics you can say "H2O crystals are hexagonal because that's the way H2O is", and likewise with all the millions of other crystals. But an astute person will notice patterns, and investigate, and find that a few rules explain ALL the patterns ... these rules are quantum mechanics!
Jun
26
comment Quantum experiments in the pre-industrial era
If you want to correctly explain why ice crystals are hexagonal, you need to invoke the Pauli exclusion principle, quantum superpositions, delocalized electrons, electron spin, etc. etc. Are these not part of quantum mechanics??? The original question asked for "phenomena which require QM to explain them". There is no theory besides quantum mechanics that can correctly and consistently predict the shape of every crystal.
Jun
25
comment Quantum experiments in the pre-industrial era
Chemistry requires detecting atoms?? Are you serious?? You don't need to detect atoms to know that ice crystals are hexagonal or that methane flames are blue or that nitrogen gas is less flammable than oxygen. You don't even have to be human to see that grass is a different color than rock! But if you want to explain these facts in a self-consistent and detailed framework, that framework HAS to be based on quantum mechanics.
Jun
25
revised Quantum experiments in the pre-industrial era
added 45 characters in body
Jun
25
answered Quantum experiments in the pre-industrial era
Jun
20
comment Heat of vaporization of water - dependence on relative humidity?
Sorry, you're right. I put in an "update" section. Enthalpy of a gas PER MOLECULE is more-or-less independent of pressure or partial pressure.
Jun
20
revised Heat of vaporization of water - dependence on relative humidity?
update re: comment