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1997年, 第6卷, 第5期　刊出日期：1997-05-20 上一期    下一期

GENERAL

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POSITIVE DEFINITE PROBLEM OF ENERGY DENSITY AND RADIATIVE ENERGY FLUX FOR PULSE CYLINDRICAL GRAVITATIONAL WAVE 李芳昱, 唐孟希 1997 (5):  321-333.  doi: 10.1088/1004-423X/6/5/001 摘要 ( 1283 )   PDF(239KB) ( 439 )   By using the general expressions of energy momentum pseudo-tensor of the cylin-drical gravitational waves (GW) given by Rosen and Virbhadra in Cartesian coor-dinates, the concrete forms of energy density and radiative energy flux of the pulse cylindrical GW are obtained. Their physical properties, suitable range and asymp-totic behaviour are considered. It is found that: For the region in which space radial coordinates to origin are greater than the pulse width of the pulse cylindrical GW, the energy density and radiative energy flux of the outward travelling pulse cylindrical GW propagating along at light-cone are positive definite. However, for the region in which the space radial coordinates are less than the pulse width, there is no guarantee for the positive definite property of the radiative energy flux of the outward travelling wave. Moreover, we show that the asymptotic behaviour of the energy and energy flux densities of the pulse cylindrical GW and that of the Riemann curvature tensor have good self-consistancy in space like, time like and null infinity regions. 相关文章 | 计量指标

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TRANSITION FOR FINITE GLOBALLY COUPLED OSCILLATORS DRIVEN BY ADDITIVE AND MULTIPLICATIVE NOISES 李静辉, 黄祖洽 1997 (5):  334-340.  doi: 10.1088/1004-423X/6/5/002 摘要 ( 1217 )   PDF(244KB) ( 389 )   We study an ensemble of N globally coupled oscillators driven simultaneously by additive and multiplicative noises. By numerical simulation we find that for this model there is the same transition in the dynamics of the mean field when the coupling constant is increased as the one proposed by Pikovsky et al. (Z.Phys. B95(1994),541). The effect of the multiplicative noises on the transition is that when the multiplicative noise strength D1 is small, the effect of the multiplicative noises on the transition is feeble; but with the increase of D1 the transition is strongly influenced near a special value D′1 of D1; then with the increase of D1 when the value of D1 is larger than a critical value D10, the transition disappears. By some approximation we obtain the critical value D(1)0 of D1. 相关文章 | 计量指标

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PHASE TRANSITION FOR A NOISE-DRIVEN MODEL COUPLED BY A MEAN FIELD 李静辉, 黄祖洽 1997 (5):  341-347.  doi: 10.1088/1004-423X/6/5/003 摘要 ( 1398 )   PDF(232KB) ( 404 )   We report a new model for infinite interacting noise driven subsystems which are coupled by a mean field and study its nonequilibrium phase transitions. In this model, under some circumstances the phase transition is between the state with zero mean field and the state with non zero mean field, and has a breaking of symmetry, which is similar to that reported by Van den Broeck, Parrondo, Toral, and Armcro [Phys. Rev. Lett.,73(1994),3395; Phys. Rev., E49(1994),2639], by Pikovsky, Rateitschak, and Kurths [Z.Phys.,B95(1994),541], and by other authors. We style this nonequi librium phase transition the symmetry breaking mean field. However, under other circumstances, the nonequilibrium phase transition of our model is not of the symme try breaking mean field type, which is a new phenomenon that has not been reported before. 相关文章 | 计量指标

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SUPERCONDUCTING JUNCTIONS IN THE CASE OF CORRELATED SYMMETRIC NOISES 李静辉, 黄祖洽 1997 (5):  348-355.  doi: 10.1088/1004-423X/6/5/004 摘要 ( 1472 )   PDF(241KB) ( 354 )   We study two models for Josephson junctions, i.e.,a Gaussian white noise model and a symmetric dichotomous noises model. In this study we find that the correlated symmetric noises can produce a net voltage. This phenomenon is due to the correlation between the additive and the multiplicative noises. We show some characteristic features for this phenomenon: the net voltage is always negative and has a peak value when the strength of the additive noises varies for the former model(or when the strengths of the noises vary for the latter model). The results provide a theoretical foundation for reducing the net voltage caused by the correlated symmetric noises. 相关文章 | 计量指标

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DYNAMICS OF PLANAR RELATIVISTIC DOMAIN WALLS 陶必修, 陶必有 1997 (5):  356-360.  doi: 10.1088/1004-423X/6/5/005 摘要 ( 1031 )   PDF(185KB) ( 529 )   The dynamics of planar relativistic domain walls is investigated with the help of a new method proposed by Arodz and Larsen. Two solutions are found: one is a steady state domain wall, the other is a nonstationary domain wall. They move with the same constant velocity in the laboratory frame coordinates. When the velocity approaches light velocity c, the "width" of the nonstationary wall inflates very slowly. These domain walls can disappear again soon after their creation in the early universe by moving away from our visible universe. So they would not dominate the universe completely, but keep the observed universe approximately isotropic and homogeneous. 相关文章 | 计量指标

ATOMIC AND MOLECULAR PHYSICS

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MAGNETIC FIELD EFFECT OF THE EUROPIUM a8S7/2-z6P7/2 LINES 梅刚华, 钟达, 谭永芳, 朱熙文 1997 (5):  361-371.  doi: 10.1088/1004-423X/6/5/006 摘要 ( 1223 )   PDF(412KB) ( 429 )   The magnetic field effect of a8S7/2-z6P7/2 lines of 151Eu and 153Eu in magnetic fields up to 66.7 mT has been studied by using laser atomic beam spectroscopy. The Zeeman level structures of the europium a8S7/2 and z6P7/2 states in magnetic fields were discussed. The location and intensity of the measured Zeeman transition lines were found in good agreement with the theoretical results. 相关文章 | 计量指标

CLASSICAL AREAS OF PHENOMENOLOGY

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THE REFLECTIVE PROPERTIES OF BROADBAND OPTICAL MULTILAYERS 张道中, 李兆霖, 程丙英 1997 (5):  372-381.  doi: 10.1088/1004-423X/6/5/007 摘要 ( 1166 )   PDF(262KB) ( 509 )   Binary multilayers with a certain kind of disorder may exhibit high reflection range over a very wide bandwidth. The dependencies of this bandwidth on the center wavelength, random layers sequence, refractive contrast of the coating materials, layer thickness errors and the angle of incidence have been studied numerically. Our simulations have shown that broadband reflectors can be designed for various applications. The reflective curves for staggered multilayers are also computed. The results show that the broadening effect of irregular multilayers is dominated by its degree of disorder. A broadband TiO2-SiO2 multilayer is fabricated. The measured width of the transmittance less than 1% for this multilayer covers 400 nm, from 700 to 1100 nm, which is just the tuning range of Ti: sapphire lasers. 相关文章 | 计量指标

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THE CASIMIR FORCE BETWEEN POLARIZERS 黄湖 1997 (5):  382-390.  doi: 10.1088/1004-423X/6/5/008 摘要 ( 980 )   PDF(225KB) ( 365 )   The Casimir force between two parallel lincar polarizers oriented at an arbitrary angle is calculated. We compare two approaches, one by solving the field mode function in three-dimensional space with highly anisotropic dielectric slabs, the other by calculating the interaction between dipolcs induced by vacuum fluctuations in these slabs. 相关文章 | 计量指标