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1999年, 第8卷, 第12期　刊出日期：1999-12-15 上一期    下一期

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INTERFACE SHAPE AND CONCENTRATION DISTRIBUTION IN CRYSTALLIZATION FROM SOLUTION UNDER MICROGRAVITY 刘永才, 陈万春, 霍崇儒, 葛培文 1999 (12):  881-888.  doi: 10.1088/1004-423X/8/12/001 摘要 ( 1548 )   PDF(246KB) ( 474 )   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. 相关文章 | 计量指标

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NEW B$\ddot{A}$CKLUND TRANSFORMATION AND EXACT SOLUTIONS FOR VARIABLE COEFFICIENT KdV EQUATION 闫振亚, 张鸿庆 1999 (12):  889-894.  doi: 10.1088/1004-423X/8/12/002 摘要 ( 1035 )   PDF(128KB) ( 461 )   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. 相关文章 | 计量指标

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A NEW STRATEGY OF CHAOS CONTROL AND A UNIFIED MECHANISM FOR SEVERAL KINDS OF CHAOS CONTROL METHODS 罗晓曙, 方锦清, 王力虎, 孔令江, 江峰 1999 (12):  895-901.  doi: 10.1088/1004-423X/8/12/003 摘要 ( 1188 )   PDF(233KB) ( 493 )   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. 相关文章 | 计量指标

CLASSICAL AREAS OF PHENOMENOLOGY

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OPTICAL BISTABILITY IN V MEDIUM BY SQUEEZED VACUUM INPUT 陈朝阳, 张敬涛, 徐至展 1999 (12):  902-907.  doi: 10.1088/1004-423X/8/12/004 摘要 ( 1147 )   PDF(184KB) ( 451 )   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. 相关文章 | 计量指标

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INFLUENCE OF HIGHER ORDER TOROIDICITY ON COUPLING OF TEARING MODES 王传兵, 李定 1999 (12):  908-912.  doi: 10.1088/1004-423X/8/12/005 摘要 ( 1242 )   PDF(165KB) ( 505 )   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. 相关文章 | 计量指标

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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NEUTRON TIME OF FLIGHT ENERGY SPECTROMETER FOR ICF ION TEMPERATURE DIAGNOSTIC 唐正元, 杨建伦, 温树槐, 王根兴, 郭玉芝, 杨洪琼, 马驰 1999 (12):  913-918.  doi: 10.1088/1004-423X/8/12/006 摘要 ( 1163 )   PDF(175KB) ( 483 )   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. 相关文章 | 计量指标

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CONTRIBUTION FROM MOLDCULAR FIELD TO THE TEMPERATURE DEPENDENCE OF TUNNELING MAGNETORESISTANCE 王俊忠, 李伯藏, 高俊山 1999 (12):  919-926.  doi: 10.1088/1004-423X/8/12/007 摘要 ( 1116 )   PDF(240KB) ( 353 )   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. 相关文章 | 计量指标

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LECTRONIC STRUCTURE STUDIES OF Bi2Sr2CaCu2-xSnxO8+δ SYSTEM 李旗, 潘海斌, 祝传刚, 徐彭寿, 周映雪, 张新夷 1999 (12):  927-931.  doi: 10.1088/1004-423X/8/12/008 摘要 ( 1169 )   PDF(180KB) ( 403 )   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. 相关文章 | 计量指标

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GROWTH MODEL OF TEXTURED DIAMOND (111) FILM IN CH4/O2/H2 ATMOSPHERE 武瑾, 谢仿卿, 张青哲, 刘技文, 陈有存, 林彰达 1999 (12):  932-937.  doi: 10.1088/1004-423X/8/12/009 摘要 ( 890 )   PDF(237KB) ( 425 )   Partially oriented and highly textured diamond films on Si( 111 ) substrates were achieved by hot-filament chemical vapor deposition(HFCVD). High nucleation density greater than 5×108cm-2 was realiged in 3 min by near-surface glow discharge. The os-grown films were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD) and Raman spectroscopy. It was found that by adding a small amount of oxygen to the mixture of CH4/H2, the appearance of facet(111) was well controlled, and the secondary nucleation on the facet(111) was suppressed greatly. Growth feature of homoepitaxy on diamond (111) surface was demonstrated to be in Stranski-Krastanov model by SEM. 相关文章 | 计量指标

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TOMOGRAPHY FORMULA FOR BIOCHEMICAL IMAGING OF THIN TISSUE WITH DIFFUSE-PHOTON DENSITY WAVES 董光炯, 韩汝珊, 黄畇, KAORU SAKATANI, 庄逢源 1999 (12):  938-943.  doi: 10.1088/1004-423X/8/12/010 摘要 ( 871 )   PDF(182KB) ( 314 )   Using the transport theory to describe the near infrared light propagating in tissue with finite parallel-plane geometry, and taking the zero-boundary condition, we obtain the analytical expression of average photon density and Green's function incorporating the boundary effects in the homogeneous tissure. Making use of perturbation theory we also obtain the analytical expression of scattered wave induced by the heterogeneity, and present the 2-dimensional spatial transform of scattered wave with respect to transverse coordinate. If the information of heterogeneity on depth and thickness is available, diffraction tomography formula is presented to save the time of image reconstruction; if the information is unknown, we suggest to obtain the inhomogeneous function from the one-dimensional integral equation of 2-dimensional spatial transform of scattered wave applying the direct matrix method or iterative method for image reconstruction. This approach avoids directly solving three-dimensional integral equation of scattered wave. In our proposed approach the strong points of the direct matrix method, iterative method, and diffraction tomography are fully combined. 相关文章 | 计量指标