Browsing by Author "Luan, PG"

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Acoustic energy confinement in randomly layered structures
(2002-04-01)
Ye, Z
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Luan, PG
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電子物理學系
;
Department of Electrophysics
Radiation from acoustic sources located inside randomly layered structures is studied using the transfer matrix method. It is shown that in contrast to the periodically layered cases where the radiation can be either enhanced or inhibited depending on the frequency and the characteristics and the material composition of the structures, in the random structures the radiation is always inhibited. The degree of inhibition depends on the acoustic frequency, number of random layers, and the randomness and acoustic parameters of the structures. Both spherically and cylindrically random structures are considered. The results point to the possibility of designing sonic waveguide devices that will not suffer from the energy loss caused by radiation, thus allowing effective energy confinement or long-range energy propagation. (C) 2002 American Institute of Physics.
Drifting diffusion on a circle as continuous limit of a multiurn Ehrenfest model
(2004-02-01)
Luan, PG
;
Kao, YM
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物理研究所
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Institute of Physics
We study the continuous limit of a multibox Erhenfest urn model proposed before by the authors. The evolution of the resulting continuous system is governed by a differential equation, which describes a diffusion process on a circle with a nonzero drifting velocity. The short time behavior of this diffusion process is obtained directly by solving the equation, while the long time behavior is derived using the Poisson summation formula. They reproduce the previous results in the large M (number of boxes) limit. We also discuss the connection between this diffusion equation and the Schrodinger equation of some quantum mechanical problems.
Effect of dielectric responses on localization in one-dimensional random periodic-on-average layered systems
(2002-06-01)
Wang, CC
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Luan, PG
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電子物理學系
;
Department of Electrophysics
Dielectric response effects on wave localization in random periodic-on-average layered systems are studied. Based on Monte Carlo simulations and products of random matrices, statistics of the Lyapunov exponent are determined efficiently for very long systems. An oscillatory behavior for Lyapunov exponent is found and explained for mildly strong scattering conditions. We also show the emergence of strongly localized states in metallic layered systems with intermediate disorder for frequencies above the plasma frequency omega(p) of metals, as is not shown in dielectrics. Furthermore, the violation of universal single parameter scaling behaviors in different regimes of multiple scattering is discussed.
Semiclassical quantization for the spherically symmetric systems under an Aharonov-Bohm magnetic flux
(2002-05-01)
Kao, WF
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Luan, PG
;
Lin, DH
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物理研究所
;
Institute of Physics
The semiclassical quantization rule is derived for a system with a spherically symmetric potential V(r)similar tor(nu)(-2>1. The rule is even derived in the large principal quantum number limit n>>1. We also discuss the power parameter nu dependence of the energy spectra pattern in this paper.
The exact Green function of a relativistic Coulomb system via the transformation method
(2000-08-18)
Chuu, DS
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Luan, PG
;
Lin, DH
;
電子物理學系
;
Department of Electrophysics
The exact Green function of a relativistic Coulomb system is given by the transformation method. The earlier treatments are based on the multiple-valued transformation of Kustaanheimo and Stiefel as well as the perturbation expansions. The method presented in this paper relates the relativistic Coulomb path integral to the simple ones and may apply to a large class of problems.