Chin. Phys. B
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CN 11-5639/O4
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Chin. Phys. B  
  Chin. Phys. B--2003, Vol.12, No.4
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GENERAL

Stability for the equilibrium state manifold of relativistic Birkhoffian systems

Fu Jing-Li, Chen Li-Qun, Luo Yi, Luo Shao-Kai
Chin. Phys., 2003, 12 (4): 351-356 doi: 10.1088/1009-1963/12/4/001
Full Text: [PDF 237 KB] (Downloads:386)
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In this paper, the stability of equilibrium state manifold for relativistic Birkhoffian systems is studied. The equilibrium state equations, the disturbance equations and their first approximation are presented. The criteria of stability for the equilibrium state manifold are obtained. The relationship between the stability of the equilibrium-state manifold of relativistic Birkhoffian systems and that of classical Birkhoffian systems is discussed. An example is given to illustrate the results.

A set of the Lie symmetrical conservation laws for the rotational relativistic Birkhoffian system

Luo Shao-Kai, Cai Jian-Le
Chin. Phys., 2003, 12 (4): 357-360 doi: 10.1088/1009-1963/12/4/002
Full Text: [PDF 206 KB] (Downloads:419)
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For a rotational relativistic Birkhoffian system, a set of the Lie symmetries and conservation laws is given under infinitesimal transformations. On the basis of the invariance of rotational relativistic Birkhoffian equations under infinitesimal transformations, Lie symmetrical transformations of the system are constructed, which only depend on the Birkhoffian variables. The determining equations of Lie symmetries are given, and a new type of non-noether conserved quantities are directly obtained from Lie symmetries of the system. An example is given to illustrate the application of the results.

Explicit and exact travelling plane wave solutions of the (2+1)-dimensional Boussinesq equation

Huang Wen-Hua, Jin Mei-Zhen
Chin. Phys., 2003, 12 (4): 361-364 doi: 10.1088/1009-1963/12/4/003
Full Text: [PDF 195 KB] (Downloads:431)
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The deformation mapping method is applied to solve a system of (2+1)-dimensional Boussinesq equations. Many types of explicit and exact travelling plane wave solutions, which contain solitary wave solutions,periodic wave solutions,Jacobian elliptic function solutions and others exact solutions, are obtained by a simple algebraic transformation relation between the (2+1)-dimensional Boussinesq equation and the cubic nonlinear Klein-Gordon equation.

Sodium atom in strong magnetic fields: a pseudospectral approach

Zou Yuan-Chuan, Zhang Zhan-Jun, Qiao Hao-Xue
Chin. Phys., 2003, 12 (4): 365-370 doi: 10.1088/1009-1963/12/4/004
Full Text: [PDF 248 KB] (Downloads:314)
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Energies and wavefunctions of low-lying states and Rydberg states for the sodium atom in uniform magnetic fields varying from 0 to 10^5T are calculated using a pseudospectral approach with a model potential in spherical coordinates. The energies are comparable with experimental results as well as those obtained by other calculations. The spectra of oscillator strength are worked out. The evolution of them with the magnetic field is shown.

Quantization of the space-time with topological defect

Gao Chang-Jun, Shen You-Gen
Chin. Phys., 2003, 12 (4): 371-376 doi: 10.1088/1009-1963/12/4/005
Full Text: [PDF 232 KB] (Downloads:317)
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We present the classical solution of Lagrange equations for the black hole with a global monopole or with a cosmic string. Then we obtain the wavefunction of the space-time by solving the Wheeler-De Witt equation. De Broglie-Bohm interpretation applied to the wavefunction gives the quantum solution of the space-time. In the end, the quantum effect on Hawking radiation is studied.

Stochastic resonance in parabolic-bistable potential system with an additive colour noise

Liang Gui-Yun
Chin. Phys., 2003, 12 (4): 377-380 doi: 10.1088/1009-1963/12/4/006
Full Text: [PDF 347 KB] (Downloads:407)
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We propose a new model (parabolic bistable system) with a colour noise source. In the presence of periodic input signal, we investigate the output signal to-noise ratio and the power spectral density of output signal, in which the self-correlation time may be an arbitrary value with no restriction. We find that the curves of signal-to-noise ratio versus the noise intensity D exhibits a bell-shape behaviour. The peak height increases with the increasing value of amplitude A_0 of the input signal. However, the position of peak does not shift. Moreover, the signal-to-noise ratio is insensitive to the modulation frequency Ω, which completely differs from result of Ref.[6]. The power spectral density also has similar behaviour.

Synchronization of the time-varying parameter chaotic system and its application to secure communication

Mu Jing, Tao Chao, Du Gong-Huan
Chin. Phys., 2003, 12 (4): 381-388 doi: 10.1088/1009-1963/12/4/007
Full Text: [PDF 288 KB] (Downloads:370)
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In this paper we propose and investigate the synchronization of a new chaotic model with time-varying parameters and apply it to improve the security of chaotic communication. In this model, the chaotic system is modulated by both the message and the varying parameters. The varying parameters distort the phase space so heavily that they prevent the carrier from being broken by nonlinear dynamic forecasting method. Theory and simulation experiments with speech signal communication indicate that the receiver can gain a perfect synchronization with the transmitter, and the intruder cannot break down this communication system. We also discuss the robustness of the new communication system.
NUCLEAR PHYSICS

Low frequency effects of surface states on 4H-SiC metal-semiconductor field effect transistor

Yang Lin-An, Yu Chun-Li, Zhang Yi-Men, Zhang Yu-Ming
Chin. Phys., 2003, 12 (4): 389-393 doi: 10.1088/1009-1963/12/4/008
Full Text: [PDF 233 KB] (Downloads:423)
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The process-related surface state effect is investigated the fabrication of SiC devices, and a nonlinear model for 4H-SiC power metal-semiconductor field effect transistor (MESFET) is proposed, which takes into account the surface-related parameters. The frequency- and temperature- dependent transconductance dispersion is readily demonstrated in terms of the improved model. Simulation results show that larger dispersion and higher transition frequency occur in 4H-SiC MESFET than in GaAs MESFET. The advantage of this analytical model over the two-dimensional numerical simulation is the simplicity of calculations, therefore it is suitable for the processing improvement of SiC devices.
CLASSICAL AREAS OF PHENOMENOLOGY

Non-conservation of energy arising from atomic dipole interactions and its effects on light field and coupled atoms

Dong Chuan-Hua
Chin. Phys., 2003, 12 (4): 408-414 doi: 10.1088/1009-1963/12/4/012
Full Text: [PDF 316 KB] (Downloads:282)
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The interactions between coupled atoms and a single mode of a quantized electromagnetic field, which involve the terms originating from the dipole interactions, are discussed. In the usual Jaynes-Cummings model for coupled atoms, the terms of non-conservation of energy originating from dipole interactions are neglected, however, we take them into consideration in this paper. The effects of these terms on the evolutions of quantum statistic properties and squeezing of the field, the squeezing of atomic dipole moments and atomic population inversion are investigated. It has been shown that the coupling between atoms modulates these evolutions of fields and atoms. The terms of non-conservation of energy affect these evolutions of fields and atoms slightly. They also have effects on the squeezing of the field, the squeezing of atomic dipole and atomic population inversions. The initial states of atoms also affect these properties.

Influence of group-velocity mismatch on soliton switching in a nonlinear fibre coupler

Li Hong, Huang De-Xiu, Wang Dong-Ning
Chin. Phys., 2003, 12 (4): 415-418 doi: 10.1088/1009-1963/12/4/013
Full Text: [PDF 209 KB] (Downloads:389)
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In this work, the influence of group-velocity mismatch on soliton self-routing pulse switching in a nonlinear fibre coupler is discussed in detail by the use of both variational approach and numerical simulation. The results obtained show that the group-velocity mismatch leads to the relative displacement between the two orthogonal polarization modes, increase of the critical power, and reduction of the elimination-light ratio. For sub-ps pulse, the influence cannot be neglected.
ATOMIC AND MOLECULAR PHYSICS

Nonlinear interaction of resonator photons with parametric magnon pairs

Shi Qing-Fan, Yan Xue-Qun, Liu Xue-Guan
Chin. Phys., 2003, 12 (4): 394-398 doi: 10.1088/1009-1963/12/4/009
Full Text: [PDF 222 KB] (Downloads:268)
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We consider the process of parametric resonance of magnons in magneto-ordered crystals in a microwave resonator. The nonlinear interaction of the resonator photons with the parametric magnon pairs is analysed theoretically, and the result expressed by the deviation frequencies relative to the pump frequency further demonstrates that the dynamics of resonator modes plays an important role once the pump power exceeds the threshold of parallel pumping.

Transmission spectroscopy in a thin vapour layer and its derivative properties

Zhao Yan-Ting, Zhao Jian-Ming, Xiao Lian-Tuan, Jia Suo-Tang
Chin. Phys., 2003, 12 (4): 399-402 doi: 10.1088/1009-1963/12/4/010
Full Text: [PDF 223 KB] (Downloads:252)
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A novel method of high-resolution spectroscopy of gases is proposed. The method is based on observing the optical behaviour of thin vapour layer when the particles cross the light beam or collide with the cell walls. The atomic motion and electronic quenching on gas-solid interfaces are explored by numerical analysis. The periodicity of peak values of transmission spectra and its derivative spectra demonstrates a sub-Doppler structure corresponding to the resonant transitions.

Light-induced nonlinear effects on dispersion relation of ultracold Bose gas

Hu Zheng-Feng, Du Chun-Guang, Li Shi-Qun
Chin. Phys., 2003, 12 (4): 403-407 doi: 10.1088/1009-1963/12/4/011
Full Text: [PDF 224 KB] (Downloads:327)
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We have investigated the optical properties of Λ-configuration ultracold dense Bose gas interacting with two laser pulses, which usually result in electromagnetically induced transparency. With the nonrelativistic quantum electrodynamics and taking into account the atomic dipole-dipole interaction and local field effect, we have derived the Maxwell-Bloch equations of the system. The dispersion relation of an ultracold Bose gas has been obtained and the light-induced nonlinear effects have been analysed. The light-induced nonlinear effects are different from the effects induced by two-body collision of Bose-Einstein condensation atoms which have a frequency shift of transparent window.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Inspection of the number of electrons in the ring of a quantum dot

Huang Gang-Ming, Bao Cheng-Guang
Chin. Phys., 2003, 12 (4): 419-425 doi: 10.1088/1009-1963/12/4/014
Full Text: [PDF 554 KB] (Downloads:386)
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On the electronic structures of quantum dots, there is a new viewpoint saying that, in some specific states, a few electrons might behave as valence electrons moving outside surrounding a core. To clarify the validity of this viewpoint, a numerical calculation was performed in this paper. The results are against this viewpoint.

Effect of crystalline microstructure on the photophysical performance of polymer/perylene composite films

Feng Wei, Xu You-Long, Yi Wen-Hui, Zhou Feng, Wang Xiao-Gong, Yoshino Katsumi
Chin. Phys., 2003, 12 (4): 426-432 doi: 10.1088/1009-1963/12/4/015
Full Text: [PDF 284 KB] (Downloads:397)
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To obtain high carrier mobility, better charge injection capability, and high photovoltaic device conversion efficiency, a powerful strategy is to improve the morphology of the polymer/dye composite films. Conjugated conducting polymer (CP) thin films doped with perylene derivative (PV) of various concentrations were prepared by spin-casting method, and their morphology and photovoltaic characteristics were examined. The change in morphology and molecular reorientation occurring in CP-PV composite films upon annealing at different temperatures was investigated using scanning electron microscopy, x-ray diffraction, Fourier transform infrared and UV-vis absorption. By changing the annealing temperature, PV microcrystallines of 8-10μm in size lying parallel to the substrate surface can be obtained. Annealing effect improved the photovoltaic performance of ITO/CP-PV/Al Schottky-type solar cells, which can be attributed to the formation of an electron conducting PV crystal network. Preliminary studies indicate that the morphological structure in CP-PV composite films has an important influence to their photovoltaic properties.

Composites of nanotubular polyaniline containing Fe3O4 nanoparticles

Long Yun-Ze, Chen Zhao-Jia, Liu Zhen-Xing, Zhang Zhi-Ming, Wan Mei-Xiang, Wang Nan-Lin
Chin. Phys., 2003, 12 (4): 433-437 doi: 10.1088/1009-1963/12/4/016
Full Text: [PDF 390 KB] (Downloads:429)
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Results of charge-transport and magnetic measurements of nanotubular polyaniline (PANI) composites containing Fe_3O_4 nanoparticles (~10nm) synthesized by a "template-free" method are reported. The T^{-1/2} resistivity has been observed, and dc magnetic susceptibility data are fitted to an equation χ=χ^*_P+C/T. With increasing weight ratio of Fe_3O_4, the electrical conductivity and temperature- independent susceptibility χ^*_P increase, and the Curie-type susceptibility is suppressed at low temperatures. Further discussions have been given. The PANI-H_3PO_4/Fe_3O_4 composite containing 27wt% of Fe_3O_4 nanoparticles is superparamagnetic, exhibiting very little hysteresis even at 5K.

Role of amorphous silicon domains on Er3+ emission in the Er-doped hydrogenated amorphous silicon suboxide film

Chen Chang-Yong, Chen Wei-De, Li Guo-Hua, Song Shu-Fang, Ding Kun, Xu Zhen-Jia
Chin. Phys., 2003, 12 (4): 438-442 doi: 10.1088/1009-1963/12/4/017
Full Text: [PDF 345 KB] (Downloads:355)
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An investigation on the correlation between amorphous Si (a-Si) domains and Er^{3+} emission in the Er-doped hydrogenated amorphous silicon suboxide (a-Si:O:H) film is presented. On one hand, a-Si domains provide sufficient carriers for Er^{3+} carrier-mediated excitation which has been proved to be the highest excitation path for Er^{3+} ion; on the other hand, hydrogen diffusion from a-Si domains to amorphous silicon oxide (a-SiO_x) matrix during annealing has been found and this possibly decreases the number of nonradiative centres around Er^{3+} ions. This study provides a better understanding of the role of a-Si domains on Er^{3+} emission in a-Si:O:H films.
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