Search results for "Irreversible process"
showing 3 items of 3 documents
Towards a nonequilibrium thermodynamic description of incoherent nonlinear optics
2007
pa href="http://oe.osa.org/virtual_issue.cfm?vid=36"Focus Serial: Frontiers of Nonlinear Optics/a/pThis concise review is aimed at providing an introduction to the kinetic theory of partially coherent optical waves propagating in nonlinear media. The subject of incoherent nonlinear optics received a renewed interest since the first experimental demonstration of incoherent solitons in slowly responding photorefractive crystals. Several theories have been successfully developed to provide a detailed description of the novel dynamical features inherent to partially coherent nonlinear optical waves. However, such theories leave unanswered the following important question: Which is the long term…
Small-angle x-ray scattering studies of melting
1980
The course of melting of melt-crystallized polyethylene fractions and of a poly(ethylene oxide)-polystyrene-poly(ethylene oxide) triblock copolymer has been followed by small-angle x-ray scattering (SAXS). Changes in the intensity and shape of the SAXS curves indicated that both surface melting and melting over the full crystallite thickness (full-strand melting) take place. Full strand melting is the final, irreversible process. Comparison with an analytical model indicates that in the earlier stages of the irreversible, full-strand process the crystallites melt out randomly throughout the bulk. Later stages may occur by the simultaneous melting of a larger stack of crystallites.
Coherence absorption and condensation induced by thermalization of incoherent nonlinear fields
2008
We show that a conservative system of incoherent nonlinear waves exhibits, as a rule, an irreversible process of coherence transfer, in which the incoherence of the system is absorbed by the small-amplitude field, thus allowing the high-amplitude field to evolve towards a highly condensed coherent state. This process of coherence absorption results from the natural thermalization of the fields to a thermodynamic equilibrium state. The theory reveals that, contrary to a classical gas system, a wave system does not satisfy an equipartition of energy among the particles. Such a distinctive feature is the key property underlying the existence of the coherence absorption process. The coherence a…