Mean-field approach has recently been used to model coupled atom-molecular Bose-Einstein condensates (BEC) and coupled Fermi-Bose condensates near Feshbach resonance. Sweeping of magnetic field across the resonance gives a new (nonlinear) version of Landau-Zener problem. We investigate the structure of the corresponding classical phase space and calculate change in the action which corresponds to finite-rate efficiency of the sweep. We consider the case of non-zero initial action, which corresponds to some finite initial molecular fraction. * Electronic address: alx˙it@yahoo.com 2

The present study examines the entropy generation on Couette flow of a viscous fluid in parallel plates filled with deformable porous medium. The fluid is injected into the porous channel perpendicular to the lower wall with a constant velocity and is sucked out of the upper wall with same velocity .The coupled phenomenon of the fluid flow and solid deformation in the porous medium is taken in to consideration. The exact expressions for the velocity of fluid, solid displacement and temperature distribution are found analytically. The effect of pertinent parameters on the fluid velocity, solid displacement and temperature profiles are discussed in detail. In the deformable porous layer, it is noticed that the velocity of fluid, solid displacement and temperature distribution are decreases with increasing the suction/injection velocity parameter. The results obtained for the present flow characteristic reveal several interesting behaviors that warrant further study on the deformable porous media. Furthermore, the significance of drag and the volume fraction on entropy generation number and Bejan number are discussed with the help of graphs.

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We use the mean-field approximation to numerically study the dynamics of a split condensate in MachZehnder-type atom interferometers that employ Bragg diffraction. The Husimi representation is used as a direct tool for diagnosing the dynamics in phase space, thus providing information on the interference fringe contrast. We analyze how optimization of the contrast of interference signals can result by means of compensating for the nonlinear interaction and the trapping potential for three alternative experimental schemes. The phase-space overlap in Husimi distribution as well as dynamics in phase space is shown to be important in determining the interference fringe contrast.

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