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Chin. Phys. B  
  Chin. Phys. B--1994, Vol.3, No.12
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GENERAL

RELATION BETWEEN CHOOSING “GOOD” COORDINATES AND THE BEHAVIOR OF LIGHT SIGNALS

KUANG ZHI-QUAN, LIANG CAN-BIN
Chin. Phys. B 1994, 3 (12): 881 ;  doi: 10.1088/1004-423X/3/12/001
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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.
CLASSICAL AREAS OF PHENOMENOLOGY

INFLUENCE OF DETUNING ON THE BUTTERFLY EFFECT OF LASER OSCILLATION

TAN WEI-HAN, MA GUO-BIN, ZHUANG JUN, LIU REN-HONG
Chin. Phys. B 1994, 3 (12): 884 ;  doi: 10.1088/1004-423X/3/12/002
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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.

SPIN-1 (3-LEVEL) MODEL OF NMR LASER DRIVEN BY AN EXTERNAL SIGNAL

QU ZHI-LIN, YANG GUO-JIAN, MA WEN-QI, HU GANG
Chin. Phys. B 1994, 3 (12): 891 ;  doi: 10.1088/1004-423X/3/12/003
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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.

SOLITARY WAVES IN MARANGONI-BENARD CONVECTING FLUID

HUANG GUO-XIANG
Chin. Phys. B 1994, 3 (12): 900 ;  doi: 10.1088/1004-423X/3/12/004
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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.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

“PPAS” X-RAY ABSORPTION SPECTROSCOPY IN LASER-PRODUCED ALUMINUM PLASMA

WANG LIU-SHUI, LIN ZUN-QI, ZHANG HUI-HUANG, HE XING-FA, WANG DONG-JUN, LIN KANG-CHUN, GUAN FU-YI, WANG XIAO-QIN, LIN MING-YI, WEI XIAO-CHUN, HOU QING, LI JIA-MING, SHENG JIA-TIAN, ZHANG GUO-PING
Chin. Phys. B 1994, 3 (12): 909 ;  doi: 10.1088/1004-423X/3/12/005
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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.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

IRREVERSIBILITY LINE AND THERMAL DEPINNING IN YBa2Cu3O7-δ

WEN HAI-HU, ZHAO ZHONG-XIAN
Chin. Phys. B 1994, 3 (12): 917 ;  doi: 10.1088/1004-423X/3/12/006
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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.

STRUCTURE STUDY OF MODULATION-DOPED Cd1-xMnxTe: In/CdTe STRAINED LAYER MULTIPLE QUANTUM WELLS

JIANG SHAN, SHEN XUE-CHU
Chin. Phys. B 1994, 3 (12): 925 ;  doi: 10.1088/1004-423X/3/12/007
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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.
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