A Pseudo-Kinetic Approach for Helmholtz Equation

A lattice Boltzmann type pseudo-kinetic model for a non-homogeneous Helmholtz equation is derived in this paper. Numerical results for some model problems show the robustness and efficiency of this lattice Boltzmann type pseudo-kinetic scheme. The computation at each site is determined only by local parameters, and can be easily adapted to solve multiple scattering problems with many scatterers or wave propagation in non-homogeneous medium without increasing the computational cost.     

EXACT SOLUTIONS TO LATTICE BOUSSINESQ-TYPE EQUATIONS

In this paper several kinds of exact solutions to lattice Boussinesq-type equations are constructed by means of generalized Cauchy matrix approach, including soliton solutions and mixed solutions. The introduction of the general condition equation set yields that all solutions contain two kinds of plane-wave factors.     

Proton NMR T 1 Studies in Methylammonium TrichlorO Stannate(II) (CH 3 NH 3 SnCl 3 )

Proton spin lattice relaxation time ( T 1 ) measurements have been carried out in methylammonium trichloro stannate(II) (CH 3 NH 3 SnCl 3 ) as a function of temperature in the range 317-5 K at a Larmor frequency of 10 MHz. The temperature dependence of T 1 shows a phase transition around 220 K and four T 1 minima (294 K, 62 K, 32 K and 12 K). The results are discussed in terms of proton dynamics, namely, uncorrelated reorientation of NH 3 and CH 3 groups at high temperatures and tunnelling of NH 3 and CH 3 protons at low temperatures.     

Broad-band dielectric spectroscopy of tetragonal PLZT x /40/60

The dielectric behaviour of tetragonal PLZT x/40/60 ceramics doped with lanthanum (x?=?5,?12 and 15%) has been investigated at 100–10¹⁴?Hz. Dielectric, THz and infrared spectra were measured from 500 to 20?K. For x?≥?12 relaxor ferroelectric behaviour was observed. All three samples showed an additional relaxational mode below phonons. Analysis of the phonon modes for ferroelectric PLZT 5/40/60 is presented together with the complete dielectric behaviour.     

Lattice dynamics of cubic PbTiO3 by inelastic neutron scattering

High-temperature dispersion relations of the phonon modes in a cubic PbTiO₃ single crystal have been investigated along the [ξ 0 0] and [ξ ξ 0] directions by inelastic neutron scattering. Above T _c, the phonon dispersions are only temperature-dependent close to the Brillouin zone centre where the mode softening comes through. The measurements indicate large cubic anisotropy of the elastic tensor and relatively low anisotropy of the soft mode dispersion. The differences from an earlier inelastic neutron scattering study are discussed.     

Lattice Vibrations of Imidazole Crystals

Abstract

Polarized low-frequency Raman spectra of imidazole single crystals were measured with a He-Ne laser source. A new band at 172 cm^?1 (Bg) was observed. An assignment for the lattice vibrations of imidazole crystals is proposed on the bases of this Raman data and far-infrared spectral data of Perchard and Novak, as well as the preliminary results calculated from Harada's and Williams' potentials.