Role Of Entropy Production Research Articles

ENTROPY PRODUCTION IN COLLISIONLESS SYSTEMS. I. LARGE PHASE-SPACE OCCUPATION NUMBERS

Certain thermal non-equilibrium situations, outside of the astrophysical realm, suggest that entropy production extrema, instead of entropy extrema, are related to stationary states. In an effort to better understand the evolution of collisionless self-gravitating systems, we investigate the role of entropy production and develop expressions for the entropy production rate in two particular statistical families that describe self-gravitating systems. From these entropy production descriptions, we derive the requirements for extremizing the entropy production rate in terms of specific forms for the relaxation function in the Boltzmann equation. We discuss some implications of these relaxation functions and point to future work that will further test this novel thermodynamic viewpoint of collisionless relaxation.

Introduction to "To the Question of Energy Use of DetonationCombustion" By Ya. B. Zel'dovich

Ya. B. Zel’dovich (1914–1987) made numerous contributions [1] to the theory of detonation, beginning with his very well known and widely translated article [2] on detonation structure that first introduced the standard Zel’dovich-von Neumann-Doring (ZND) model of shock-induced combustion. Even at that early stage of detonation research, Zel’dovich was also considering the application of detonations to propulsion and power engineering. He published these ideas in another paper [3] that has been virtually unknown in the West and has apparently remained untranslated until now. We are indebted to Sergey Frolov of the N.N. Semenov Institute of Chemical Physics for first bringing this article to our attention. We believe that the focus of this paper, which is the application of detonation waves to power generation and propulsion, is very relevant to the current activity on pulse detonation engines. In particular, Zel’dovich was apparently the first researcher to consider the questions of the relative efficiency of various combustion modes, the role of entropy production in jet propulsion, and the distinction between unsteady and steady modes of detonation in power engineering and propulsion applications. Even 60 years later, we believe that his results are relevant and can be of value in modern discussions on thermodynamic cycle analysis of detonation waves for propulsion [4]. For these reasons, we have arranged for the paper to be translated and suggested that it be published by the Journal of Propulsion and Power.

Transport Properties of a Modified Lorentz Gas

We present a detailed study of the first simple mechanical system that shows fully realistic transport behavior while still being exactly solvable at the level of equilibrium statistical mechanics. The system under consideration is a Lorentz gas with fixed freely-rotating circular scatterers interacting with point particles via perfectly rough collisions. Upon imposing a temperature and/or a chemical potential gradient, a stationary state is attained for which local thermal equilibrium holds for low values of the imposed gradients. Transport in this system is normal, in the sense that the transport coefficients which characterize the flow of heat and matter are finite in the thermodynamic limit. Moreover, the two flows are non-trivially coupled, satisfying Onsager's reciprocity relations to within numerical accuracy as well as the Green–Kubo relations. We further show numerically that an applied electric field causes the same currents as the corresponding chemical potential gradient in first order of the applied field. Puzzling discrepancies in higher order effects (Joule heating) are also observed. Finally, the role of entropy production in this purely Hamiltonian system is shortly discussed.

Linear irreversible processes and spin relaxation

The standard theories of spin relaxation have not sufficiently emphasised the connection of this phenomenon to other linear irreversible processes and the role of entropy production has also not been clearly discussed. In order to contribute to this problem, we start here with the linear relation between the generalised fluxes J i and generalised forces X i and we show the verification of the bilinear relation in fluxes and forces for the dissipation function Ψ d In this connection a general expression for the diffusion-like equation is also calculated. Furthermore, the phenomenological relaxation equation is developed, which shows the proportionalityof therelaxation rate 1/ T 1 to the phenomenological coefficient L E. The quantum-statistical treatment of relaxation starts also from the entropy production principle and one obtains a quantum-statistical alternative of the phenomenological coefficient L E, which yields finally the molecular expression for the relaxation rate 1/ T 1 . This result has been used for the treatment of spin-lattice relaxation by dipole-dipole interaction and one has obtained the same relation for 1/ T 1, relaxation rate, as by other methods, using different starting points.