Reflection and Transmission of Waves in Pyroelectric Body

The reflection and transmission theory of waves in pyroelectric medium is studied in this paper. In general in an infinite homogeneous pyroelectric medium there are four bulk wave modes: quasi-longitudinal, two quasi-transversal and temperature waves. However there are five boundary conditions in the reflection and transmission problem of the pyroelectric medium. In this paper we find that the surface wave will be revealed to satisfy the boundary conditions with other four bulk waves. The surface wave has the same wave vector component with the incident bulk waves on the interface plane. The two dimensional reflection problems of waves at the interface between the semi-infinite pyroelectric medium and vacuum is researched and an numerical example is given.

Electron Tunneling in Small-Area Junctions

Electron tunneling in small-area junctions has been treated. It is found that at the appropriate set of barrier parameters and electronic characteristics of the electrodes, the quantization of the lateral wave vector component manifests itself in the differential tunneling conductance as quite noticeable singularities. The dependance of the second derivative of the tunnel current versus the bias voltage calculated for the perfectly smooth quantized electrode should contain distinct periodic dips. It is shown that for real not perfectly smooth electrodes the resonance structure caused by the commensurate states may be observed.

The collisional drift mode in a partly-ionized plasma

The structure of the drift instability is examined in several density regimes. Let λ e be the total electron mean free path, kz the wave-vector component along the magnetic field, and ν ⊥ / ν ∥ the ratio of perpendicular ion diffusion to parallel electron streaming rates. At low densities (kz ν e > 1), the drift mode is isothermal, and should be treated kinetically. In the finite heat conduction regimethe drift instability threshold is reduced at low densities (v⊥/v‖<0·1) and increased at high densities (v⊥/v‖>0·1), as compared with the isothermal threshold. Finally, in the energy transfer limit (kzλe<(m/M)½), the drift instability behaves adiabatically in a fully-ionized plasma, and isothermally in a partly-ionized plasma, for an ion-neutral to Coulomb collision frequency ratio vin/vii>2(m/M)½ at Ti = Tc = Tn.