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• The rotational modulation effects on heat and mass transport in Darcy porous medium is explained. • Ginzburg Landau equations were used to quantify heat and mass. • The multidomain spectral collocation method is used to solve the Lorenz equations. • The rotational modulation was found to be a destabilizing agent. • The effect the Darcy-Prandtl was found to be destabilizing agents. A theoretical investigation of the influence of time-dependent rotational modulation on the stability, heat, and mass transfer in a Darcy porous medium with a couple stress fluid is presented. A perturbation technique dependent on the infinitesimal amplitude of the disturbance parameter is used to study the consolidated effects of modulating rotation, solute gradient, and permeability on the stability of a porous medium. The Ginzburg Landau equation is obtained and used to quantify heat and mass transport as the Nusselt and Sherwood numbers respectively. The coupled nonlinear Lorenz equations are solved using a newly developed multidomain spectral collocation method. Simulations of the phase plane trajectories are used to represent and analyze limited sets of solutions. We find among other results, that the effect of increasing the modulation amplitude is to accelerate the heat and mass transport. The results from the Ginzburg Landau approach are qualitatively similar to that of the Lorenz approach although the Lorenz approach was more efficient. [ABSTRACT FROM AUTHOR]

When a type II superconductor with slab geometry is subjected to a magnetic field which is antisymmetric with respect to the middle of the slab the induced vortex matter consists of vortex–antivortex pairs or double kinks. These double kinks and their role in the generation of a considerable asymmetry in the critical current of the slab are addressed here both numerically, in the framework of time dependent Ginzburg Landau model, and semi-analytically, using the concept of surface energy barriers for flux entry and flux exit. [ABSTRACT FROM AUTHOR]

We have studied the polarization switching in ferroelectric particles by using a time dependent Ginzburg Landau model. The surface effect is described by considering the polarization enhancement towards the surface. The influence of this phenomena and related bound charges field on switching properties is extensively discussed and their implication on the local switching mechanism has been elucidated. In particular, we have demonstrated that the effect of the bound charges field strongly depends on the location inside the particle and on the moment of the switching process. [ABSTRACT FROM AUTHOR]