Chin. Phys. B
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CN 11-5639/O4
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Chin. Phys. B  
  Chin. Phys. B--1998, Vol.7, No.10
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GENERAL

ENVELOPE SOLITON UNDER DISSIPATION IN A FLUID-FILLED ELASTIC TUBE

Duan Wen-shan, Zhao Cun-yuan, Lü Ke-pu, Wang Ben-ren, Wei Rong-jue
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 721-726 doi: 10.1088/1004-423X/7/10/001
Full Text: [PDF 193 KB] (Downloads:392)
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By using the reductive perturbation method, the carrier wave modulation propagating in a weakly viscous fluid-filled elastic tube is investigated. It is shown that such a process can be described by equation Aτ+iBAξξ+iC|A|2A+DA=0 and the amplitude of envelope soliton will decrease as it propagates away.

AN INTEGRAL EXPRESSION OF EXACT SOLUTION FOR HARMONIC OSCILLATOR WITH TIME-VARYING FREQUENCY

Li Li-xiang, Guo Guang-can
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 727-731 doi: 10.1088/1004-423X/7/10/002
Full Text: [PDF 182 KB] (Downloads:399)
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Using Feynman's method of disentangling operators, an exact expression of evolution operator of harmonic oscillator with time-varying frequency is obtained. The parameters in this expression are related to the time-varying frequency directly. Some implications are further investigated, including general form of linear and quadratic invariants and evolution of Wigner function.

THE IMMISCIBLE DISPLACEMENT IN PERCOLATION CLUSTER

Tian Ju-ping, Yao Kai-lun
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 732-738 doi: 10.1088/1004-423X/7/10/003
Full Text: [PDF 231 KB] (Downloads:268)
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The percolation clusters with varying occupy probability were constructed in this paper. Viscous fingering (VF) in percolation cluster, based on the assumption that bond radii are Rayleigh distribution, is investigated by means of successive over-relaxation technique. The fractal dimension for VF in percolation cluster is calculated. The result shows that it can increase fractal dimension of VF as increase of percolation probability of reduce of viscous ratio. VF's fractal dimension of porous media in the limit viscous ratio →∞ is found to be identical with that in diffusion limited-aggregation. We have found that the topology and the geometry of the porous medium have strong effects on the displacement processes and the structure of the VF. We find that the sweep efficiency of the displacement processes mainly depends upon the length of the network system and also on the viscosity ratio. Moreover, the fractional flow of injected fluid as a function of mean saturation is obtained.
CLASSICAL AREAS OF PHENOMENOLOGY

PERFORMANCE OF VERTICAL VIBRATION ISOLATION SYSTEM WITH GRAVITATIONAL POSITIVE FEEDBACK

Zhao Peng-fei, Zhang Ping-hua, Tang Jia-xiang, Luo Jun
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 744-750 doi: 10.1088/1004-423X/7/10/005
Full Text: [PDF 222 KB] (Downloads:306)
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A new model of vertical vibration isolation system is presented in the paper. It is principally constructed by mounting an additional mass on the simplest passive vertical isolator, which can give rise to gravitational positive feedback. By theoretical analyzing and numerical calculating, we come to a conclusion that the resonant frequency is decreased in the new system, which agrees with the result of the experiment.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

SINE-GORDON MODEL WITH LOCAL SYMMETRIC POTENTIALS

Ye Fei, Xu Bo-wei
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 739-743 doi: 10.1088/1004-423X/7/10/004
Full Text: [PDF 178 KB] (Downloads:295)
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Effects of spatial inhomogeneity with symmetric potentials in one-dimensional quantum sine-Gordon model are treated by use of the variational Gaussian wave functional method. The properties of the ground state and the critical point of the system are investigated.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

STUDY OF IRON OVERLAYER ON SULPHUR PASSIVATED GaAs(100) BY SYNCHROTRON RADIATION PHOTOEMISSION

Zhu Chuan-gang, Xu Peng-shou, Xu Fa-qiang, Lu Er-dong, Pan Hai-bin, Guo Hong-zhi
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 751-756 doi: 10.1088/1004-423X/7/10/006
Full Text: [PDF 221 KB] (Downloads:302)
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We have studied the interface electronic structures and the chemical reaction of the Fe overlayer deposited on S-passivated GaAs(100). The chemical bond and electronic structure are different from Fe/GaAs, and the reaction between As and Fe is weakened by S atoms. This is beneficial to the magnetism in the interface. In the first stage of deposition, Fe clusters is form near S atoms due to the large electronegativity of S. The S atoms remain at the interface with Fe coverage. Magnetic ordering feature is found at a coverage higher than 0.6 nm. According to the large exchange splitting in valence band spectra, we suggest that Fe phase transition from bcc to fcc occurs with increasing coverage.

GRAIN SIZE DEPENDENT MAGNETISM IN GRANULAR MANGANESE PEROVSKITE La0.82Sr0.18MnO3

Zhang Ning, Zhang Sheng, Xu Yin-lin, Ding Wei-ping, Zhong Wei, Du You-wei
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 757-763 doi: 10.1088/1004-423X/7/10/007
Full Text: [PDF 230 KB] (Downloads:432)
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La0.82Sr0.18MnO3 have been investigated. With grain growth, both an evident decrease of magnetization and the lattice distortions have been simultaneously observed. The phenomenon suggests a structure-coupled change of magnetism in the hole-doped manganese perovskite.

LOW-FREQUENCY INTERNAL FRICTION STUDY FOR SrBi2Ta2O9 FERROELECTRIC CERAMICS

Wang Zhi-yong, Chen Ting-guo, Zhu Wei-min, Fu Jian, Yan Hai-xue, Li Cheng-en
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 764-772 doi: 10.1088/1004-423X/7/10/008
Full Text: [PDF 253 KB] (Downloads:368)
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Low-frequency internal friction (IF) of SrBi2Ta2O9(SBT) ceramics has been measured at temperatures ranging from 293 to 623 K. Two IF peaks, with their locations around 393 K (P1) and 569 K (P2) (f≈1.58 Hz), respectively, are observed. P1 is found to be associated with a relaxation process with activation energy of 0.97 eV and pre-exponential factor of 3.58×10-14 s. Peak shape analyses reveal that P1 can be well described by a broadened Debye peak with the width parameter β from 2.70 to 2.92. The mechanism responsible for P1 is proposed to be relaxation of oxygen vacancies near domain walls(DWs). P2 is considered to arise from viscous motion of DWs since it shows characteristics of static hysteresis type. Comparisons for the IF behavior between SBT and Pb(Zr, Ti)O3(PZT) suggest that in SBT oxygen vacancies are much less localized near DWs than that in PZT. This result provides a possible explanation for the weak DW pinning due to oxygen vacancies in SBT.

UPCONVERSION FLUORESCENCE DYNAMICS OF Tm3+ IONS IN LiYF4 CRYSTAL

Chen Xue-yuan, Luo Zun-du
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 773-783 doi: 10.1088/1004-423X/7/10/009
Full Text: [PDF 260 KB] (Downloads:338)
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According to Judd-Ofelt parameter calculation and energy transfer theory, the cross-relaxation process of the Tm3+ ions is investigated. A four-level system of coupled rate equations is established to study the fluorescence dynamics of Tm3+ in LiYF4 crystal. Attentions are focused on the upconversion luminescence 1G43H6 (483.0 nm) in Tm3+:LiYF4. The relationship between the avalanche properties (critical pump rate, fluorescence intensity and buildup time) originated by resonant excited state absorption and the doped Tm3+ concentration is discussed, and some useful conclusions are drawn.

POSITRON ANNIHILATION STUDY OF THERMOELASTIC MARTENSITE STABILIZATION IN A THERMALLY CYCLED CuZnAl ALLOY--A DISCUSSION OF ORIGIN OF THERMOELASTIC MARTENSITE STABILIZATION

Wang Jing-cheng, You Fu-qiang, Shao Zi-chang, Qi Jin-lin, Tang Xue-feng
Acta Phys. Sin. (Overseas Edition), 1998, 7 (10): 784-788 doi: 10.1088/1004-423X/7/10/010
Full Text: [PDF 174 KB] (Downloads:331)
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The thermally cycled samples of Cu-23at%Zn-10at%Al have been studied by means of positron annihilation. It is shown that vacancies and their movement seem to be the leading factors resulting in thermoelastic martensite stabilization based on the fact that stabilization was no longer present and the great decrease of positron parameters after the samples in martensite were thermally cycled.
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