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1994年, 第3卷, 第12期　刊出日期：1994-12-20 上一期    下一期

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RELATION BETWEEN CHOOSING “GOOD” COORDINATES AND THE BEHAVIOR OF LIGHT SIGNALS 邝志全, 梁灿彬 1994 (12):  881-883.  doi: 10.1088/1004-423X/3/12/001 摘要 ( 1413 )   PDF(56KB) ( 341 )   It is pointed out that the statement in Ref.[1] (Rindler, assential Relativity) claiming that "the metric coefficients are time-independent if signals tracing out the same path always take the same coordinate time" is false. A counterexample and a revised statement with its proof are given in this paper. 相关文章 | 计量指标

CLASSICAL AREAS OF PHENOMENOLOGY

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INFLUENCE OF DETUNING ON THE BUTTERFLY EFFECT OF LASER OSCILLATION 谭维翰, 马国彬, 庄军, 刘仁红 1994 (12):  884-890.  doi: 10.1088/1004-423X/3/12/002 摘要 ( 1212 )   PDF(153KB) ( 437 )   In this paper the butterfly effects of single mode laser oscillation are studied. It is shown that the detuning between laser oscillation and atomic transition frequency leads to a decrease in second threshold, which makes the demonstration of chaos theory in experiment easy. 相关文章 | 计量指标

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SPIN-1 (3-LEVEL) MODEL OF NMR LASER DRIVEN BY AN EXTERNAL SIGNAL 屈支林, 杨国健, 马文麒, 胡岗 1994 (12):  891-899.  doi: 10.1088/1004-423X/3/12/003 摘要 ( 1625 )   PDF(234KB) ( 427 )   A set of NMR laser equations is presented for a spin-1 model under the assumption that the system is homogeneously broadened and spatially independent. The steady state solutions are obtained and their instabilities are revealed. The results are compared with the spin-1/2 model. Multi-codimensional bifurcation points are found. 相关文章 | 计量指标

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SOLITARY WAVES IN MARANGONI-BENARD CONVECTING FLUID 黄国翔 1994 (12):  900-908.  doi: 10.1088/1004-423X/3/12/004 摘要 ( 1207 )   PDF(232KB) ( 395 )   In this paper the evolution of nonlinear long surface waves in a Marangoni-Bénard convecting fluid is considered. The fluid system is bounded below by an isothermic plane and above a free deformable surface, on which a heat flux is fixed. We show that the nonlinear behavior of the long surface wave is governed by the Korteweg-de Vries equation when the Rayleigh number is near its critical value. A head-on collision between two solitary waves traveling from opposite directions is also investigated by use of the Poincaré-Lighthill-Kuo method. The results show that the solitary waves emerging from the collision can preserve their original identities to the second order. The phase shifts due to the collision are calculated analytically. 相关文章 | 计量指标

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“PPAS” X-RAY ABSORPTION SPECTROSCOPY IN LASER-PRODUCED ALUMINUM PLASMA 王柳水, 林尊琪, 章辉煌, 何兴法, 王东君, 林康春, 管富义, 王笑琴, 林鸣逸, 韦小春, 候氢, 李家明, 盛家田, 张国平 1994 (12):  909-916.  doi: 10.1088/1004-423X/3/12/005 摘要 ( 1618 )   PDF(255KB) ( 442 )   We have developed and successfully demonstrated the "point projection absorption spectroscopy (hereafter abbreviated to PPAS)" technique to record keV X-ray absorption spectra in the coronal region of laser produced aluminum plasma which provides spatial information in the corona. Absorption spectrum of the Al Ⅻ 1s2-1s2p resonant line for time delays up to 250, 500 and 750 ps after the peak of the incident laser pulse have been observed. Analysis of an absorption spectrum should allow a high spatial resolution (< 25μm) history of the absorbing ion population density to be determined. The 1-D hydro-code JB19 has been used to simulate the experiment and the predictions are compared to the observations. Such comparison can be useful in validating parts of the codes used for gain prediction on recombination X-ray laser transitions. 相关文章 | 计量指标

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IRREVERSIBILITY LINE AND THERMAL DEPINNING IN YBa2Cu3O7-δ 闻海虎, 赵忠贤 1994 (12):  917-924.  doi: 10.1088/1004-423X/3/12/006 摘要 ( 1355 )   PDF(254KB) ( 359 )   By measuring magnetic torque moment in a field-sweeping process, the temperature and field dependence of the critical current density j (with a criterion of electric field) and the normalized relaxation rate Q = d lnj/d ln E of a YBa2Cu3O7-δ thin film were obtained. With a minimum current density (jmin = 10A·cm-2) the irreversibility lines at different sweeping rates were determined. It was found that these irreversibility lines cannot be fitted to either the melting line or the vortex-glass transition. All the data can be interpreted by the thermally-assisted-flux-flow model. Further investigation shows that, at irreversible tem-perature and field, Uc is much smaller than kBT, which indicates that the thermal depinning is the real origin of the irreversibility line. 相关文章 | 计量指标

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STRUCTURE STUDY OF MODULATION-DOPED Cd1-xMnxTe: In/CdTe STRAINED LAYER MULTIPLE QUANTUM WELLS 姜山, 沈学础 1994 (12):  925-931.  doi: 10.1088/1004-423X/3/12/007 摘要 ( 1125 )   PDF(213KB) ( 384 )   The photomodulated reflectivity (PR) spectroscopy of modulation-doped diluted mag-netic semiconductor Cd1-xMnxTe: In/CdTe multiple quantum wells has been measured at 20-300K. Several spectral features associated with intersubband transitions have been found. The band structure of Cd1-xMnxTe: In/CdTe has been calculated by the Hartree self-consistent method. The results show that the theory is in agreement with experiments. In addition, an abnormal transition intensity ratio of 22H (the second heavy hole subband to the second electroa subband) to 11H (the first heavy hole subband to the first electron subband) caused by electron filled effect has been reported. At low temperature, a feature associated with Fermi level is observed, which has not been reported before. 相关文章 | 计量指标