Marangoni convection in a half-zone model, a simplification of the floating zone model, is steady and axisymmetric for Marangoni number Ma5Mac, but the azimuthal flow after instability (Ma>Mac) breaks the axial-symmetry, and m-foldsymmetry of the flow pattern is observed. The symmetry number m (azimuthal wave number) depends strongly on the aspect ratio, As (As=height/radius), of the half-zone. Based on the results of numerical simulation, the nature of the correlation between m and As is investigated.

Resonant tunneling in step-barrier structures is investigated by using the transfer-matrix technique. The formulas for the transmission coefficient and the current density are derived when taking into account the coupling between components of the motion of an electron in directions parallel and perpendicular to the interfaces. By making a detailed comparison of resonant tunneling among single square-barrier structures, asymmetric double-barrier structures, and step-barrier structures, the tunneling properties in step-barrier structures are revealed. It is shown that the global behavior of step-barrier structures obtained resembles that of asymmetric double-barrier structures, and step-barrier structures are superior to both single- and double-barrier structures in many aspects. In comparison to asymmetric double-barrier structures, step-barrier structures have several features, such as a wider negative-differential resistance region, easier fabrication, high-speed response, and a relatively lower transmission coefficient and current peak-to-valley ratios. Moreover, higher resonant bias is required in order to obtain optimal transmission resonances in the step-barrier structure. The results shown in this work not only shed new light on the physics of resonant tunneling in electric-barrier structures but are also helpful in designing quantum devices based on step-barrier tunneling structures.

Three-dimensional (3D) unsteady mixed thermal buoyancy, Marangoni and forced convection of LiCaAlF6 (LiCAF) melts (Prandtl number PrE1.4) are investigated numerically for model set up typically for Czochralski crystal growth. With increasing crystal rotation rate, convection evolves from steady axisymmetric to three-dimensional oscillatory convection with varying spatio-temporal features. The details of the oscillatory convection structures are presented.

The spin-dependent electron resonant tunneling through magnetically modulated quantum structures has been investigated with and without an external electric field. The spin polarization is found to be strongly dependent on the magnetic configuration, the applied bias, the incident electron energy, and the incident wave vector. It is shown that an unpolarized beam of conducting electrons can be strongly polarized for an electron tunneling through magnetic-barrier structures, which is an arrangement with unidentical magnetic barriers and wells. The external electric field greatly changes the spin polarization of electrons for small electronic energies, where the electron-spin polarization exhibits considerable wave-vector-dependent features.

We present tight-binding Green's function investigations of the influence of quantum sizes and the temperature on spin tunneling transport through a tunable ZnSe/Zn1-xMnxSe multilayers under an external electric field. It is found that the degree of polarization can be significantly induced by the size of the corresponding structure. As the size of the multilayers is increasing, both the transmission spectra and the current density spectra become more complicated and the degree of spin polarization is higher. It is also found that the degree of the spin polarization is drastically reduced as the temperature is increasing.