Unsteady heat transfer of a monatomic gas between two coaxial circular cylinders
We consider a kinetic-theory treatment of the cylindrical unsteady heat transfer. A model kinetic equation of the BGK (Bhatnager-Gross-Krook) type is solved using the method of moments with a two-sided distribution function. We study the relations between the different macroscopic properties of the gas as the temperature, density, and heat flux with both the radial distance r and the time t. Also we study the problem from the viewpoint of irreversible thermodynamics and estimate the entropy, entropy production, entropy flux, thermodynamic forces, kinetic coefficients, the change in internal energy, and verify Onsager′s relation for nonequilibrium thermodynamic properties of the system.
The behavior of a gas in the continuum limit in the light of kinetic theory : the case of cylindrical Couette flows with evaporation and condensation
Cylindrical Couette flows of a rarefied gas between two concentric circular cylinders consisting of the condensed phase of the gas, where evaporation or condensation occurs, are considered on the basis of kinetic theory, with interest in the behavior of the gas in the continuum limit. The limiting solution is obtained by asymptotic analysis of the Boltzmann equation. In some range of the parameters of the problem, neither evaporation nor condensation occurs. The limiting solution in this case is different from the continuum solution (the conventional Couette flow without evaporation and condensation on the cylinders) and is subject to the effect of the flow that is induced if the effect of gas rarefaction is taken into account. This paradoxical result is confirmed by investigating the behavior of the numerical solution of the kinetic equation as the Knudsen number approaches zero.
Resonant Auger decay study of C1s -> pi* core-excited OCS
The present work aims at characterizing short-lived C1s((-1)) pi*((1)) core-excited states of the OCS molecule based on the analysis of the vibrational fine structure and lineshape profiles of the high-resolution resonant Auger decay spectra recorded at the excitation energies along the C1s -> pi* resonance in the binding energy region 15-19eV. Very different behavior in terms of lineshape and resonant enhancement is observed for the (A) over tilde, (B) over tilde and (C) over tilde final states. This is explained by (1) the variation in the C-O bond lengths for the states involved in the electronic relaxation and (2) different contributions in terms of Mulliken population to the molecular orbitals determining the electronic character of the corresponding states. Since the final-state geometries are known from a number of previous experiments and ab initio calculations, the geometry of the C1s((-1)) pi*((1)) intermediate states can be predicted in analogy with e.g. the N-2, CO2 and N2O molecules. (C) 2009 Elsevier B.V. All rights reserved. (Less)