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Chin. Phys. B  
  Chin. Phys. B--1999, Vol.8, No.12
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GENERAL

INTERFACE SHAPE AND CONCENTRATION DISTRIBUTION IN CRYSTALLIZATION FROM SOLUTION UNDER MICROGRAVITY

LIU YONG-CAI, CHEN WAN-CHUN, HUO CHONG-RU, GE PEI-WEN
Chin. Phys. B 1999, 8 (12): 881 ;  doi: 10.1088/1004-423X/8/12/001
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The influence of the gravity and interface kinetics on interface shape and interfacial concentration distribution was numerically investigated by using Galerkin finite element method.A boundary mapping technique was used for dealing with free boundary problem. A two-dimensional steady-state model of TGS crystal growth was developed. The results show that with the increase of the gravity level, the growth rate becomes faster, the growth face becomes more curved and interfacial concentration distribution more non-uniform. The consideration of interface kinetics will cause the decrease of growth rate as compared with the pure transport model. It seems that the interface shape does not change very much within two cases of k=5.7cm4/(mol·s) and k=∞, but its position does.

NEW B?CKLUND TRANSFORMATION AND EXACT SOLUTIONS FOR VARIABLE COEFFICIENT KdV EQUATION

YAN ZHEN-YA, ZHANG HONG-QING
Chin. Phys. B 1999, 8 (12): 889 ;  doi: 10.1088/1004-423X/8/12/002
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In this paper, with the aid of Lax pairs, a new B?cklund transformation for the variable coefficient KdV equation is found, Based on the B?cklund transformation, only if integration is needed, a series of exact solutions can be obtained. This method is important for finding more new and physical-signficant solutions.

A NEW STRATEGY OF CHAOS CONTROL AND A UNIFIED MECHANISM FOR SEVERAL KINDS OF CHAOS CONTROL METHODS

LUO XIAO-SHU, FANG JIN-QING, WANG LI-HU, KONG LING-JIANG, JIANG FENG
Chin. Phys. B 1999, 8 (12): 895 ;  doi: 10.1088/1004-423X/8/12/003
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Based on a general principle of physics that a physical system is in the most stable state if it is of the lowest energy stale, a new method for chaos control is proposed. A calculable generalized energy function in a nonlinear system is suggested for measuring control process, The Henon map and Lorenz system are taken as two typical examples to demonstrate the method. A series of stabilized periodic orbits as well aa inverse sequence of chaotic bands are obtained. At the same time, a unified mechanism of physics for several kinds of current cbaos control methods is studied using the idea proposed in this paper.
CLASSICAL AREAS OF PHENOMENOLOGY

OPTICAL BISTABILITY IN V MEDIUM BY SQUEEZED VACUUM INPUT

CHEN ZHAO-YANG, ZHANG JING-TAO, XU ZHI-ZHAN
Chin. Phys. B 1999, 8 (12): 902 ;  doi: 10.1088/1004-423X/8/12/004
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We discuss the optical bistable behavior of a system of N V-type three-level atoms pumped by a coherent input field and coupled to a squeezed vacuum field by treating the optical hist ability of such a system as an input-output problem. It is shown that bistability can be realized due to the squeezed vacuum input.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

INFLUENCE OF HIGHER ORDER TOROIDICITY ON COUPLING OF TEARING MODES

WANG CHUAN-BING, LI DING
Chin. Phys. B 1999, 8 (12): 908 ;  doi: 10.1088/1004-423X/8/12/005
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he general dispersion relation for toroidally coupled tearing mode including pressure and other O(ε2) order corrections is naturally derived based on the structure of ideal magnetohydro-dynamic solutions in the outer region. It is found that the inclusion of the O(ε2) order terms in the diagonal element of E-matrix does not change physical properties of the toroidally coupled tearlng mode and only make negligible contribution to the magnitude of growth rate.

NEUTRON TIME OF FLIGHT ENERGY SPECTROMETER FOR ICF ION TEMPERATURE DIAGNOSTIC

TANG ZHENG-YUAN, YANG JIAN-LUN, WEN SHU-HUAI, WANG GEN-XING, GUO YU-ZHI, YANG HONG-QIONG, MA CHI
Chin. Phys. B 1999, 8 (12): 913 ;  doi: 10.1088/1004-423X/8/12/006
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A current-mode neutron time-of-flight(nTOF) energy spectrometer for inertial confinement fusion(ICF) ion temperature measurements has been designed which will reduce measuring error of fusion neutron energy spectra when the neutron yield is low. The spectrometer consists of a shallow cup-shaped ST1422 fast plastic scintillator with a thicknees of 3mm and full effective volume of 104cm3, a microchannel plate photomultiplier tube(MCP-PMT), a piece of coaxial cable(SUJ-50-7) with a length of 20m, and a transient oscilloscope with a bandwidth of 7GHz. The main performances of the spectrometer and its components have been calibrated. The rise-time and FWHM of the temporal response function are 260ps and 850 ps, respectively. This spectrometer will be used to measure ion temperature in the direct-driven implosion experiments on Sheng-Guang 2 laser facility at Shanghai Institute of Optics and Fine Mechanica(SIOFM) next year.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

CONTRIBUTION FROM MOLDCULAR FIELD TO THE TEMPERATURE DEPENDENCE OF TUNNELING MAGNETORESISTANCE

WANG JUN-ZHONG, LI BO-ZANG, GAO JUN-SHAN
Chin. Phys. B 1999, 8 (12): 919 ;  doi: 10.1088/1004-423X/8/12/007
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Based on the nearly free-electron approximation, we have investigaed the temperature (T) dependence of spin-polarized tunneling in the magnetic tunnel junction with an asymmetrical barrier, with emphasis on the variation of molecular field with T in the same way as that of surface magnetization. It is found that the Slonczewski model can describe well the T depen-dence of spin-polarized tunneling, while the Julliere model only describes the T dependence of JMR qualitatively, but does accurately that of the difference of tunneling conductance between the parallel and antiparallal alignments for the magnetizations of FMs; Differing from the pre-vious finding, we find the electron spin polarization is not strictly proportional to the surface magnetization, for the former decreases with the increasing T more rapidly than the latter does.

LECTRONIC STRUCTURE STUDIES OF Bi2Sr2CaCu2-xSnxO8+δ SYSTEM

LI QI, PAN HAI-BIN, ZHU CHUAN-GANG, XU PENG-SHOU, ZHOU YING-XUE, ZHANG XIN-YI
Chin. Phys. B 1999, 8 (12): 927 ;  doi: 10.1088/1004-423X/8/12/008
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Photoemission measurements have been carried out for Bi2Sr2CaCu2-xSnxO8+δ system with conventional x-ray photoemission spectroscopy for core-level spectra and synchrotron radiation photoemission spectroscopy for valence band. With Sn doping, all core levels shift differently in binding energy, and the intensity near fermi energy becomes smaller in valence hand. From the experiment, we can deduce that the shifts of all core levels and valence hands may involve some other mechanisms, such ms electrostatic effects, in addition to binding energy referencing effects. We argue that the chemical environment plays a crucial role in the electronic structure of high-temperature superconductors.
8000 CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
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