Electronic states and tunneling properties in step-barrier structures have been investigated. The results indicate that there exists quasibound states in step-barrier structure both at zero bias and under an applied bias. Size effect on negative-differential resistances is examined and the condition for obtaining larger current peak-to-valley ratios has been discussed.

A three-dimensional oscillatory Marangoni (thermocapillary) convection with Prandtl number Pr=16.0849 and Marangoni number Ma"3.30508]104 in a large aspect ratio (As=H/R) range, As=0.2-4, in a silicone oil liquid bridge with a non-deformable cylindrical surface is investigated by the anite volume method. The azimuthal wave numbers 1, 2, 3, 4, 5, 6, 10 and 16 are obtained for different aspect ratios, As. The dimensionless main frequency f*p=fMa-1/2H2/k of periodic or quasi-periodic temperature oscillations strongly depends on aspect ratio, As. f*p increases with the increment of As with approximately a bi-linear relation, and its gradient for As=0.2-1 is less than that for As>1. The periodic and quasi-periodic oscillations are found to depend on aspect ratio, As, for fixed Pr and Ma.

从理论和数值模拟两个方面分析了ESWL中的非线性的动力学焦点和实际焦点的位置，给出三种典型的动力学焦点的数值结果，说明非线性动力学焦点和实际焦点一般不是几何焦点,指出正确确定实际焦点在ESWL技术中的重要性。

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.

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.