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Volume 11 Issue 1
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Original Articles
Verma Module of Uq(B2)
ZHOU Shanyou
Chin. Phys. Lett. 1994, 11 (1): 1-3 .  
Abstract   PDF(pc) (134KB) ( 403 )
This paper deals with the Verma module of quantum group Uq(B2) when q is a root of 1. It estimates how many classes of Verma submodules which are not isomorphic to each other are contained in Verma module. The character of irreducible highest weight module of Uq(B2) has also been given.
Six Sets of Symmetries of the Variable Coefficient Modified Korteweg-de Vries Equation
ZHANG Jiefang
Chin. Phys. Lett. 1994, 11 (1): 4-7 .  
Abstract   PDF(pc) (138KB) ( 549 )
In this letter, the strong symmetry and its inverse are first given, and then six sets of symmetry of the variable coefficient modified Korteweg-de Vries (mKdV) equation are obtained, finally the variable coefficient mKdV hierarchy is discussed.
Hawking Effect of Vaidya Black Hole in Higher Dimensional Space-Time
LI Zhongheng, ZHAO Zheng
Chin. Phys. Lett. 1994, 11 (1): 8-11 .  
Abstract   PDF(pc) (116KB) ( 561 )
Making use of the generalized tortoise transformation, the radial part of the Klein-Gordon equation can be reduced to the standard wave equation around the event horizon in the higher dimensional Vaidya space-time. Both the location of event horizon and the radiation temperature of black hole are shown automatically.
Modified Method for Efficiency Calibration of High Energy γ Detector
YE Zongyuan, LI Yubing, DING Shengyao, BAO Zongyu, YANG Xiaoyun, RONG Chaofan, DING Xixiang, ZHENG Jinmei
Chin. Phys. Lett. 1994, 11 (1): 12-15 .  
Abstract   PDF(pc) (195KB) ( 366 )
A modified method of absolute efficiency calibration for germanium detector has been developed based on the fact that the intensities of capture γ-rays can be determined by the 1368KeV γ-rays from sodium activation when a NaCI sample is irradiated by thermal neutrons. As a verification of this method, the intensity of the 4.44MeV γ-ray from an Am-Be neutron source was determined.
Variational Versus Nonvariational Calculations for H2Br Molecular Scattering
ZHAO Meishan (Meishan ZHAO)
Chin. Phys. Lett. 1994, 11 (1): 16-19 .  
Abstract   PDF(pc) (194KB) ( 461 )
We compare modern variational and nonvariational calculations of molecular scattering and present for H2Br system the selected numerically exact state-to-state reaction probabilities obtained from quantum variational scattering calculations, on the most accurate available potential energy surface.
A Modified ‘Position Dispersion’ Method for Nonlinear Refraction Index Measurement
TIAN Jianguo, ZANG Weiping, CHEN Jian, MA Chao, ZHANG Guangyin
Chin. Phys. Lett. 1994, 11 (1): 20-23 .  
Abstract   PDF(pc) (157KB) ( 347 )
In this report, a modified ‘position dispersion’ method, in which the detecting aperture in the far-field is replaced by a circular board, is given to enhance the measurement sensitivity of nonlinear index, while keeps the simplicity. An increase of 5 times in sensitivity is obtained in our experiment, in which we employed a solution to produce the thermally induced nonlinearity.

Auto-Oscillations and Chaotic Behavior in Plasma
LÜ, Kecheng, CHANG Shuren, LIU Zhiguo
Chin. Phys. Lett. 1994, 11 (1): 24-27 .  
Abstract   PDF(pc) (228KB) ( 609 )
Auto-oscillations and chaotic behavior were investigated experimentally in a plasma system produced by discharge through mixing He-Ne gases. The glow power spectra and the differential phase-space portraits show period-doubling and Ruelle-Takens routes to chaos. Periodic windows embedded in chaos and multiple subharmonic bifurcations occurring in the windows were observed.
Observations of Ultra Low Safety Factor Experiments on SWIP-RFP Device
ZHANG Peng, FANG Shuiquan, LI Jieping, BI Dingguo, LUO Cuiwen, LI Qiang, YI Ping, XU Ying
Chin. Phys. Lett. 1994, 11 (1): 28-30 .  
Abstract   PDF(pc) (132KB) ( 377 )
Ultra low q equilibrium with qa < 0.1 isstudied on Southwestern Institute of Physics-Reversed Field Pinch (SWIP-RFP) device. The plasma current duration over 360μs is obtained. The edge safety factor qa is about 0.056. The distribution of safety factor is decreased with the minor radius increasing.
Phonon Characterization of Raman Spectra in High Tc Superconductors Y1-xGdxBa2Cu3O7-δ
ZHANG Mingsheng (ZHANG Ming-sheng), CHEN Qiang, JIN Xin*, YIN Zhen*, YAO Xixian*
Chin. Phys. Lett. 1994, 11 (1): 31-34 .  
Abstract   PDF(pc) (201KB) ( 644 )
Concentration-dependent Raman spectra of Y1-xGdxBa2Cu3O7-δ(x=0.4, 0.6, 0.8 and 1.0) show that the Raman mode from O(4) bridging shifts upward due to the increased symmetry of crystal potential. The linewidth and intensity of 508cm-1 mode are decreased and increased with increasing x, respectively which is attributed to the charge transfer from the CuO basal planes to the CuO2 planes. Two second-order Raman modes at 798 and 896cm-1 have been observed and confirmed.
Fractal-Form of Fe Aggregate Cluster
LIANG Yiping, DENG Zhaojing, LI Jian
Chin. Phys. Lett. 1994, 11 (1): 35-38 .  
Abstract   PDF(pc) (200KB) ( 470 )
The form of the bigger clusters composed of aggregate ultrafine Fe particles possesses obvious fractal character and regularity. With the increase of aggregate density, the extended, compensated and collapsed states emerge successively, and the fractal features are decreased. The ideal fractal dimension D0 of magnetic aggregate clusters is suggested between 2 and 4.

Magnetoplasmon-Polariton Modes of Finite Cantor-Type Heterostructures
LIU Nianhua, FENG Weiguo, WU Xiang,
Chin. Phys. Lett. 1994, 11 (1): 39-42 .  
Abstract   PDF(pc) (198KB) ( 380 )
By using local theory and taking into account retardation, we investigate the plasmonpolariton modes of a finite Cantor-type heterostructures which are composed of two alternating materials with their thicknesses following Cantor sequence. The effects of an external magnetic field applied parallel to the interfaces are considered. We find that the modes have fractal structure due to the special geometry of the system, and the dispersion relations of the modes are strikingly modified by the external magnetic field. Some new modes appear because of the application of the field. By plotting the profiles of the amplitudes of the electric field, we also investigate the localization properties of the modes.

Voltage Breakdown of Ag Thin Film Deposited on Fractal Surface
WANG Jinsong, YE Gaoxiang, XU Yuqing, ZHANG Qirui
Chin. Phys. Lett. 1994, 11 (1): 43-45 .  
Abstract   PDF(pc) (166KB) ( 495 )
A new type of inhomogeneous system was constructed by depositing Ag thin films on fractal surfaces. The I-V characteristics of such samples exhibit a non-linear effect in air and a voltage breakdown effect in vacuum. Based on the special structure geometry of the samples, these unusual phenomena can be explained by the random tunnelling junction model under different environment.
Mechanism of Tc Increase in Na-Doped Bi2Sr2CaCu2O8+y
YU Yang, JIN Xin, XU Xiaonong, SHEN Jiancang, YAO Xixian
Chin. Phys. Lett. 1994, 11 (1): 46-48 .  
Abstract   PDF(pc) (159KB) ( 447 )
Samples of Bi2.2Sr1.8Ca1.05Cu2.15-xNaxO8+y (x=0, 0.7) were prepared by melt-processing technique. The maximum transition temperature increased up to 100 K, and Tc0 achieved 92.5K. In order to study the mechanism of Tc increasing, samples were annealed in a flowing oxygen, atmosphere. The reversibility of Tc was observed in undoped sample, while the Tc of Na-doped sample had no significant changes. We believe that the Tc is correlated with a redistribution of holes between the BiO layers and the CuO planes. Doping sodium changes the hole density of CuO planes into an “optimium” value so as to increase Tc.
Monte Carlo Simulations of the Quantum X-Y Model by a Loop-Cluster Algorithm
JI Daren, YING Heping
Chin. Phys. Lett. 1994, 11 (1): 49-52 .  
Abstract   PDF(pc) (210KB) ( 723 )
The quantum X-Y model of interacting spins on square lattices is simulated by a loop-cluster algorithm. It is shown that the method can be used to simulate the systems efficiently at low temperatures for lattices as large as 32x32x200.
Spin Wave Resonance in Fe/Cu Compositionally Modulated Films
JIN Qingyuan, XU Yongbing, ZHAI Ya, LU Mu, BIE Qingshan, JIANG Shulin, ZHAI Hongru
Chin. Phys. Lett. 1994, 11 (1): 53-56 .  
Abstract   PDF(pc) (215KB) ( 557 )
Fe/Cu compositionally modulated films made by rf sputtering were investigated with ferromagnetic resonance. Spin wave resonances related to interlayer exchange coupling were observed and the phase change of the spin wave was shared by both the Fe and Cu sublayers. The effective spin wave dispersion coefficient was found to increase with increasing thickness of Cu sublayers.
Electrical Conductivity of the Two-Dimensional Half-Filled Hubbard Model
CHEN Feng, YING Heping, XU Tiefeng, LI Wenzhu,
Chin. Phys. Lett. 1994, 11 (1): 57-60 .  
Abstract   PDF(pc) (168KB) ( 669 )
The electrical conductivity of the one-band Hubbard model on a two-dimensional square lattice at half-filling is studied through the grand canonical quantum Monte Calro method. Our results support that there exists an insulator-to-metal transition for the half-filled Hubbard model at high temperature.
Structure and Magnetic Properties of Sputtered Bi2DyFe5O12 Films
GU Benxi, ZHANG Hongyan, ZHAI Hongru, LU Mu, MIAO Yongzhi
Chin. Phys. Lett. 1994, 11 (1): 61-64 .  
Abstract   PDF(pc) (179KB) ( 492 )
The effects of the annealing temperature and time on the structure and magnetic properties of the sputtered BiDy-iron garnet films were investigated. X-ray diffraction analysis shows that the as-sputtered films are amorphous. After annealing at about 550°C, amorphous films crystallize into the garnet phase and an unknown phase. The intensity of the unknown phase decreases with increasing annealing temperature and time and vanishes at 650°C for 30min. It is found that the unknown phase has a large influence on the half-width of the (420) x-ray diffraction peak. The as-sputtered films have a very small magnetization of about 1 emu/g at room temperature. When films are annealed above 570°C, the magnetization increases rapidly with increasing annealing temperature and time.
17 articles