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Table of contents

    27 May 2005, Volume 14 Issue 6 Previous issue    Next issue
    GENERAL
    The discrete variational principle in Hamiltonian formalism and first integrals
    Zhang Hong-Bin (张宏彬), Chen Li-Qun (陈立群), Liu Rong-Wan (刘荣万)
    Chinese Physics, 2005, 14 (6):  1063-1068.  DOI: 10.1088/1009-1963/14/6/001
    Abstract ( 1244 )   PDF (237KB) ( 658 )  
    The aim of this paper is to show that first integrals of discrete equation of motion for Hamiltonian systems can be determined explicitly by investigating the invariance properties of the discrete Lagrangian in phase space. The result obtained is a discrete analog of the theorem of Noether in the Calculus of variations.
    Exact discrete soliton solutions of quintic discrete nonlinear Schrödinger equation
    Li Hua-Mei (李画眉), Wu Feng-Min (吴锋民)
    Chinese Physics, 2005, 14 (6):  1069-1074.  DOI: 10.1088/1009-1963/14/6/002
    Abstract ( 1257 )   PDF (252KB) ( 634 )  
    By using the extended hyperbolic function approach, we consider a quintic discrete nonlinear Schr?dinger (QDNLS) equation and obtained new exact localized solutions ,including discrete bright soliton solution, dark soliton solution, alternating phase bright soliton solution and alternating phase dark soliton solution ,if a special constraint is imposed on coefficients of the equation.
    Exact solutions of N-dimensional harmonic oscillator via Laplace transformation
    Chen Gang (陈刚)
    Chinese Physics, 2005, 14 (6):  1075-1076.  DOI: 10.1088/1009-1963/14/6/003
    Abstract ( 1194 )   PDF (168KB) ( 748 )  
    The N-dimensional Schr?dinger equation for the harmonic oscillator is reduced to a first-order differential equation in terms of the Laplace transformation and the exact bound state solutions are derived. It is shown that this method to solve the Schr?dinger equation may serve as a substitute for the standard functional, analytical approach also in lower dimensions.
    Stochastic resonance in an asymmetric bistable system driven by multiplicative and additive noise
    Xu Wei (徐伟), Jin Yan-Fei (靳艳飞), Li Wei (李伟), Ma Shao-Juan (马少娟)
    Chinese Physics, 2005, 14 (6):  1077-1081.  DOI: 10.1088/1009-1963/14/6/004
    Abstract ( 1279 )   PDF (256KB) ( 705 )  
    The phenomenon of stochastic resonance (SR) in a bistable system driven by multiplicative and additive white noises and a periodic rectangular signal with a constant component is studied according to the theory of signal-to-noise ratio (SNR) in the adiabatic limit. The analytic expression of the SNR is obtained for arbitrary signal amplitude without being restricted to small amplitudes. We find that the effects of the multiplicative noise intensity D and additive noise intensity $\alpha$ on SNR are different: the SNR-$\alpha$ curve shows SR for almost the whole range of static asymmetry r, but the SNR-D curve only displays SR for some values of static asymmetry r. It is more sensitive to control SR through adjusting the additive noise intensity $\alpha$ than adjusting the multiplicative noise intensity D, when the asymmetry of bistable potential r is not too large. Moreover, the static asymmetry r decreases the SNR.
    Another anticontrol method of chaos in the sense of Devaney from a Takagi–Sugeno fuzzy system via the overflow nonlinearity
    Lu Jun-Guo(卢俊国)
    Chinese Physics, 2005, 14 (6):  1082-1087.  DOI: 10.1088/1009-1963/14/6/005
    Abstract ( 251 )   PDF (243KB) ( 18 )  
    Another simple and systematic decentralized feedback anticontrol algorithm of chaos in the sense of Devaney is proposed for arbitrarily given discrete-time Takagi-Sugeno (TS) fuzzy systems. Based on a given discrete-time TS fuzzy system, the new chaotification algorithm uses the decentralized state feedback control and the overflow nonlinear function of the 2's complement arithmetic to construct a chaotic system. Based on the Shi–Chen theorem, we prove mathematically that the constructed system is indeed chaotic in the sense of Devaney. In particular, an explicit formula for the computation of chaotification parameters is also obtained. A numerical example is used to visualize and illustrate the theoretic results.
    Coherence resonance and synchronication of Hindmarsh-Rose neurons with noise
    Shi Xia (石霞), Lu Qi-Shao (陆启韶)
    Chinese Physics, 2005, 14 (6):  1088-1094.  DOI: 10.1088/1009-1963/14/6/006
    Abstract ( 1337 )   PDF (331KB) ( 685 )  
    Noise effects on coherence resonance and synchronization of Hindmarsh-Rose (HR) neu model are studied. The coherence resonance of a single HR neuron with Gaussian white ndded to membrane potential is investigated in situations before, near and after the Hopf bifuion, separately, with the external direct current as a bifurcation parameter. It is shown that ehough there is no coupling between neurons, uncoupled identical HR neurons driven by a comm noise can achieve complete synchronization when the noise intensity is higher than a critical va Furthermore, noise also enhances complete synchronization of weakly coupled neurons. It is cluded that synchronization in bursting neurons is easier to be induced than in spiking ones,oupling enhances the sensitivity of synchronization of neurons to noise stimulus.
    A complementary least-mean-square algorithm of adaptive filtering for SQUID based magnetocardiography
    Li Zhuo (李倬), Chen Geng-Hua (陈赓华), Zhang Li-Hua (张利华), Yang Qian-Sheng (杨乾声), Feng Ji (冯稷)
    Chinese Physics, 2005, 14 (6):  1095-1100.  DOI: 10.1088/1009-1963/14/6/007
    Abstract ( 1205 )   PDF (317KB) ( 564 )  
    We present a complementary least-mean-square algorithm of adaptive filtering for SQUID based magnetocardiography, in which both rapid convergence and fine tracking are realized by switching the weight parameters back and forth between two filters according to the least mean square principle.
    ATOMIC AND MOLECULAR PHYSICS
    Hybrid CIS-DFT method to study electric field effects on electronic excited states of ethylene
    Ma Mei-Zhong (马美仲), Zhu Zheng-He (朱正和), Chen Xiao-Jun (陈晓军), Xu Guo-Liang (徐国亮), Zhang Yong-Bin (张永彬), Mao Hua-Ping (毛化平), Shen Xiao-Hong (谌晓洪)
    Chinese Physics, 2005, 14 (6):  1101-1107.  DOI: 10.1088/1009-1963/14/6/008
    Abstract ( 1139 )   PDF (446KB) ( 657 )  
    The present work is devoted to the study of the effects of external dipole electric field on the molecular structure of ethylene using a hybrid method which combines the single-excitation configuration interactions (CIS) with density functional theory(DFT), i.e. CIS-DFT(B3LYP). It is found that the effects of electric dipole field on the molecular geometry (D2h, D2d and C2v), dipole moment, transition dipole moment, polarizability and, particularly, excitation energy of ethylene are rather remarkable. The advantages of hybrid CIS-DFT method are that it can determine the symmetry of molecule and the correct order of excitation as well as the Molecular Orbital(MO) electron configuration, thereby the electronic excitation states of ethylene are easily derived out, and most of them are in agreement with those obtained in experiments or references. It may be the first time the effects of external electric field on ethylene molecule have been considered. Compared with other ab initio methods, the CIS-DFT method is relatively accurate and low in computation cost. We expect that it can be used to study other closed-shell molecules.
    Energy-crossings and their effects on the spectra of the neon-like ions
    Dong Chen-Zhong (董晨钟), Xie Lu-You (颉录有), Wan Jian-Jie (万建杰), Jiang Jun (蒋军)
    Chinese Physics, 2005, 14 (6):  1108-1113.  DOI: 10.1088/1009-1963/14/6/009
    Abstract ( 1209 )   PDF (267KB) ( 498 )  
    Excitation energies, transition wavelengths and probabilities of the 2p6, 2p5 3l, 2s 2p6 3l (l = 0; 1; 2) states along the Ne-like isoelectronic sequence from Z =21-92 have been calculated by using the Multi-configuration Dirac-Fock package GRASP92 and a newly developing radiative transition program REOS99. In the calculations, the correlation and relaxation effects are included systematically.Based on the calculations, all possible energy crossings among the level groups with the same parity and total angle momentum have been presented. It is found that there are strong conˉguration interactions in some particular Z regions with energy-crossings, and which can cause a dramatic change of the related transition probabilities.
    Asymmetry of the photoionization rate of H atoms by a sequence of one-cycle laser pulses
    Bai Li-Hua (白丽华), Zhang Jing-Tao (张敬涛), Xu Zhi-Zhan (徐至展)
    Chinese Physics, 2005, 14 (6):  1114-1119.  DOI: 10.1088/1009-1963/14/6/010
    Abstract ( 1071 )   PDF (273KB) ( 464 )  
    Using an unperturbated scattering theory, the characteristics of H atom photoionization are studied respectively by a linearly and by a circularly polarized one-cycle laser pulse sequence. The asymmetries for photoelectrons in two directions opposite to each other are investigated. It is found that the asymmetry degree varies with the carrier-envelope (CE) phase, laser intensity, as well as the kinetic energy of photoelectrons. For the linear polarization, the maximal ionization rate varies with the CE phase, and the asymmetry degree varies with the CE phase in a sine-like pattern. For the circular polarizaion, the maximal ionization rate keeps constant for various CE phases, but the variation of asymmetry degree is still in a sine-like variation pattern.
    Experimental observation of pump-probe spectra of caesium D2 line with a vapour cell
    Wang Yan-Hua (王彦华), Yang Hai-Jing (杨海菁), Zhang Tian-Cai (张天才), Wang Jun-Min (王军民)
    Chinese Physics, 2005, 14 (6):  1120-1124.  DOI: 10.1088/1009-1963/14/6/011
    Abstract ( 1196 )   PDF (251KB) ( 615 )  
    Pump-probe spectra of cesium (Cs) D2 line are experimentally investigated in a Cs atomic vapor cell with co-propagating orthogonal linearly-polarized pump and probe laser beams. Absorption-reduction dips duo to electromagnetically induced transparency (EIT) in multi-$\Lambda$-type Zeeman sublevels of 6 S1/2 F=3 – 6 P3/2 F’=2 hyperfine transition and absorption-enhanced peaks due to electromagnetically induced absorption (EIA) in 6 S1/2 F=4 – 6 P3/2 F’=5 hyperfine transition are demonstrated. With detuned pump beam abnormal sign-reversed signals inside the EIT dip and the EIA peak are clearly observed.
    Total cross sections for electron scattering at 10-5000eV by polyatomic molecules CF4, CF3H, C2F4, C2F6, and C2H3F3
    Sun Jin-Feng (孙金锋), Xu Bin (徐斌), Liu Yu-Fang (刘玉芳), Shi De-Heng (施德恒)
    Chinese Physics, 2005, 14 (6):  1125-1129.  DOI: 10.1088/1009-1963/14/6/012
    Abstract ( 1041 )   PDF (249KB) ( 486 )  
    The additivity rule and complex optical potential approach have been employed to obtain the total (elastic and absorption) cross sections for electron scattering by molecules (CF4, CF3H, C2F4, C2F6, and C2H3F3) over an incident energy range from 10 to 5000eV. Compared with other calculations and experimental data wherever available, excellent agreement has been obtained. Above 1000eV, there are no experimental dates for CF3H, C2F4, C2F6 and C2H3F3, so the present results can provide comparison and foretell for experimental research
    CLASSICAL AREAS OF PHENOMENOLOGY
    Fractional Fourier transform of flat-topped multi-Gaussian beams based on the Wigner distribution function
    Wu Ping (吴平), Lü Bai-Da (吕百达), Chen Tian-Lu (陈天禄)
    Chinese Physics, 2005, 14 (6):  1130-1135.  DOI: 10.1088/1009-1963/14/6/013
    Abstract ( 1091 )   PDF (280KB) ( 631 )  
    By using the Wigner distribution function (WDF), the fractional Fourier transform (FRFT) of flat-topped multi-Gaussian(FTMG) beams is studied. Analytical expressions for the intensity distribution, beam width, far-field divergence angle, M2 factor and K parameter of FTMG beams are derived. The influence of fractional order on transformation properties of FTMG beams in the FRFT plane is illustrated with numerical examples.
    Application of an approximate vectorial diffraction model to analysing diffractive micro-optical elements
    Niu Chun-Hui (牛春晖), Li Zhi-Yuan (李志远), Ye Jia-Sheng (叶佳声), Gu Bei-Yuan (顾本源)
    Chinese Physics, 2005, 14 (6):  1136-1141.  DOI: 10.1088/1009-1963/14/6/014
    Abstract ( 1124 )   PDF (261KB) ( 478 )  
    Scalar diffraction theory, although simple and efficient, is too rough for analyzing diffractive micro-optical elements. Rigorous vectorial diffraction theory requires extensive numerical efforts,and is not a convenient design tool. In this paper we employ a simple approximate vectorial diffraction model which combines the principle of the scalar diffraction theory with an approximate local field model to analyze the diffraction of optical waves by some typical two-dimensional diffractive micro-optical elements. Both the TE and TM polarization modes are considered. We have found that the approximate vectorial diffraction model can agree much better with the rigorous electromagnetic simulation results than the scalar diffraction theory for these micro-optical elements.
    Optical polarized properties related to the oxygen vacancy defect in the PbWO4 crystal
    Liu Ting-Yu (刘廷禹), Zhang Qi-Ren (张启仁), Zhuang Song-Lin (庄松林)
    Chinese Physics, 2005, 14 (6):  1142-1146.  DOI: 10.1088/1009-1963/14/6/015
    Abstract ( 984 )   PDF (250KB) ( 782 )  
    The electronic structures, dielectric functions, complex refractive index and absorption spectra for the PbWO4(PWO) crystal with and without oxygen vacancy VO2+ have been calculated using the full-potential (linearized) augmented plane-wave (FP-LAPW) + local orbitals (LO) method with the lattice structure optimized. The calculated results indicate that the optical properties of the PWO crystal show anisotropy and its optical symmetry coincides with the lattice structure geometry of the PWO crystal. The calculated absorption spectra indicate that the stoichiometric PWO crystal does not display absorption band in the visible and near-ultraviolet range. However, in this range, the absorption spectra of the PWO crystal containing VO2+ exhibit two peaks at 3.35eV (370nm) and 2.95eV (420nm), respectively. It reveals that the 350nm and 420nm absorption bands are related to the existence of VO2+ in the PWO crystal.
    Linear entropies in the Jaynes-Cummings model with intensity-dependent coupling in a phase-damped cavity
    Zhou Qing-Chun (周青春), Zhu Shi-Ning (祝世宁)
    Chinese Physics, 2005, 14 (6):  1147-1151.  DOI: 10.1088/1009-1963/14/6/016
    Abstract ( 1091 )   PDF (298KB) ( 528 )  
    We investigate the evolution of a quantum system described by the Jaynes-Cummings model with an arbitrary form of intensity-dependent coupling by displaying the linear entropies of the atom, field and atom-field system in the large detuning approximation. The cavity field is assumed to be coupled to a reservoir with a phase-damping coupling. The effects of cavity phase damping on the entanglement and coherence loss of such a system are studied.
    Influence of atomic motion on squeezing of double-mode field in interaction with a moving V-type three-level atom
    Zhu Ai-Dong (朱爱东), Zhang Shou (张寿), Zhao Yong-Fang (赵永芳)
    Chinese Physics, 2005, 14 (6):  1152-1158.  DOI: 10.1088/1009-1963/14/6/017
    Abstract ( 992 )   PDF (931KB) ( 485 )  
    The influences of atomic motion on squeezing of the double-mode field are investigated in the interaction with a moving V-type three level atom by means of the quantum theory and the method of numerical analysis. The results show, on the one hand, when the initial photon field is in non-correlative coherent state of double-mode, only the quadrature U1 is squeezed and the squeezed degree of U1 increases with the increasing of the parameter β which denotes the atomic motion and structure of the field mode. On the other hand, when the initial field is in the vacuum squeezed state of double-mode, the quadrature U2 is squeezed principally and we can obtain a steady squeezed light by choosing an appropriate parameter β.
    Time evolution of the intensity correlation function in a single-mode laser driven by both the coloured pump noise with signal modulation and the quantum noise with cross-correlation between the real and imaginary parts
    Cheng Qing-Hua (程庆华), Cao Li (曹力), Xu Da-Hai (徐大海), Wu Da-Jin (吴大进)
    Chinese Physics, 2005, 14 (6):  1159-1167.  DOI: 10.1088/1009-1963/14/6/018
    Abstract ( 1038 )   PDF (646KB) ( 501 )  
    Using the linear approximation, we have studied the time evolution of intensity correlation function C(t) in a single-mode laser driven by both the coloured pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts. In the case of the pump noise with self-correlation time τ<<1, we find that the time evolution of C(t) varies with modulation signal frequency Ω, amplitude B and net gain a0. (i) As Ω increases, the time evolution of C(t) changes from monotonically descending to flat descending and finally to damply oscillating; (ii) as B increases, it changes from monotonically descending to maximal; (iii) as net gain a0 increases, it changes repeatedly from monotonically descending to monotonically ascending and to maximal, finally to monotonically descending again. However, in the case of τ>>1, the time evolution of C(t) only exhibits a form of damping oscillation.
    Thermal entanglement in 1D optical lattice chains with nonlinear coupling
    Zhou Ling (周玲), Yi Xue-Xi (衣学喜), Song He-Shan (宋鹤山), Guo Yan-Qing (郭彦青)
    Chinese Physics, 2005, 14 (6):  1168-1173.  DOI: 10.1088/1009-1963/14/6/019
    Abstract ( 1156 )   PDF (322KB) ( 681 )  
    The thermal entanglement of spin-1 atoms with nonlinear coupling in an optical lattice chain is investigated for two-particle and multi-particle systems. It is found that the relation between linear coupling and nonlinear coupling is the key to determine thermal entanglement, which shows in what kinds of atoms thermal entanglement exists. This result is true both for two-particle and multi-particle systems. For multi-particle systems, the thermal entanglement does not decrease greatly, and the critical temperature decreases only slightly.
    Theory of passively mode-locked lasers with self-frequency shift and saturable absorber response
    Song Li-Jun (宋丽军), Shi Xiao-Juan (师晓娟), Li Lu (李录), Li Zhong-Hao (李仲豪), Zhou Guo-Sheng (周国生)
    Chinese Physics, 2005, 14 (6):  1174-1180.  DOI: 10.1088/1009-1963/14/6/020
    Abstract ( 1062 )   PDF (292KB) ( 561 )  
    A general theoretical model for passively mode-locked lasers is presented, in which both the self-frequency shift and either a fast or a slow saturable absorber response are taken into account. An exact soliton-like solution and conditions for its existence are obtained under a definite compatible condition. The stability of the solution is analyzed by using a variational method, and a parameter region, in which the solution is linearly stable, is acquired theoretically. To verify the theoretical predictions, a typical example is given for stable pulse propagation over a long distance. The numerical results show that the soliton-like solution is stable under some perturbations within the linearly stable region and quite an arbitrary Gaussian pulse converges to the exact soliton-like solution after evolution in a distance.
    Formation of arrayed holes on metal foil and metal film by multibeam interfering femtosecond laser beams
    Zhao Quan-Zhong (赵全忠), Qiu Jian-Rong (邱建荣), Zhao Chong-Jun (赵崇军), Jiang Xiong-Wei (姜雄伟), Zhu Cong-Shan (朱从善)
    Chinese Physics, 2005, 14 (6):  1181-1184.  DOI: 10.1088/1009-1963/14/6/021
    Abstract ( 1037 )   PDF (12804KB) ( 411 )  
    We report on an optical interference method to fabricate arrayed holes on metal nickel foil and aluminum film deposited on glass substrate by means of five-beam interference of femtosecond laser pulses. Optical microscope and scanning electron microscope observations revealed that arrayed holes of micrometer-order are fabricated on both metal foil and metal film. The present technique allows one-step, large-area, micrometer processing of metal materials for potential industrial applications.
    New equation of turbulent fibre suspensions and its solution and application to the pipe flow
    Lin Jian-Zhong (林建忠), Li Jun (李俊), Zhu Li (朱力), Olson James A.
    Chinese Physics, 2005, 14 (6):  1185-1192.  DOI: 10.1088/1009-1963/14/6/022
    Abstract ( 1040 )   PDF (452KB) ( 474 )  
    The mean motion equation of turbulent fiber suspension and the equation of probability distribution function for mean fiber orientation are derived. The successive iteration for calculating the mean orientation distribution of fiber and the mean and fluctuation-correlated quantities of suspension is presented. The equations and their solutions are applied to a turbulent pipe flow of fiber suspension, and a corresponding experiment is performed. It is found that theoretical and experimental results are in good agreement. The obtained results for turbulent pipe flow of fiber suspension show that the flow rate of fiber suspension is large under the same pressure drop in comparison with the rate of Newtonian flow in the absence of fiber suspensions. Fibers play an important role in reducing the flow drag. The amount of reduction in drag augments with the increase in the concentration of the fiber mass. The relative turbulent intensity and Reynolds stress in the fiber suspensions are smaller than those in the Newtonian flow under the same condition, which illustrates that the fibers have an effect on suppressing the turbulence. The amount of suppression is directly proportional to the concentration of the fiber mass.
    PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
    Fast electron dynamics in lower hybrid current drive experiment on HT-7 tokamak
    Shi Yue-Jiang (石跃江), Wan Bao-Nian (万宝年), Chen Zhong-Yong (陈忠勇), Hu Li-Qun (胡立群), Lin Shi-Yao (林士耀), Ruan Huai-Lin (阮怀林), Qian Jin-Ping (钱金平), Zhen Xiang-Jun (甄香君), Ding Bo-Jiang (丁伯江), Kuang Guang-Li (匡光力), Li Jian-Gang (李建刚), HT-7 Team
    Chinese Physics, 2005, 14 (6):  1193-1198.  DOI: 10.1088/1009-1963/14/6/023
    Abstract ( 943 )   PDF (543KB) ( 508 )  
    Dynamic behaviour of fast electron in lower hybrid current drive (LHCD) experiment is a crucial issue in the sense of enhancing plasma performance. A new hard x-ray diagnostic system on HT-7 allows the investigation of the lower hybrid wave dynamics. The behaviour of fast electron is studied in several kinds of LHCD experiments, including long pulse discharges, high performance discharges and counter-LHCD experiments.
    CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
    First-principle study of Li ion diffusion in copper thin film
    Xiong Zhi-Hua (熊志华), Lei Min-Sheng (雷敏生)
    Chinese Physics, 2005, 14 (6):  1199-1204.  DOI: 10.1088/1009-1963/14/6/024
    Abstract ( 1181 )   PDF (253KB) ( 647 )  
    The diffusion mechanism of Li ion in a copper thin film is investigated from first-principle calculations. The energy barriers for possible spatial hopping pathways are calculated with the adiabatic trajectory method. Theoretically, we have identified that lithium can diffuse through a copper thin film by successive nearest neighbor vacancy-atom exchanges at room temperature. It is found by comparing the different mechanisms that the nearest neighbor vacancy assisted jumping is highly probable. It is also confirmed that more free diffusion may be observed by increasing the number of copper vacancies in the thin film.
    CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
    Lasing action of high quality ZnO thin film deposited by radio-frequency magnetron sputtering
    Yao Zhi-Gang (姚志刚), Zhang Xi-Qing (张希清), Shang Hong-Kai (商红凯), Teng Xiao-Ying (滕小瑛), Wang Yong-Sheng (王永生), Huang Shi-Hua (黄世华)
    Chinese Physics, 2005, 14 (6):  1205-1208.  DOI: 10.1088/1009-1963/14/6/025
    Abstract ( 1290 )   PDF (225KB) ( 628 )  
    ZnO thin films are deposited on SiO2 substrates by radio-frequency magnetron sputtering. A and B excitons are observed from the absorption spectra at room temperature. A, B and C excitons are observed from the reflectance spectra at 19 K. These results indicate that the obtained ZnO films have a good wurtzite structure. We obtain the stimulated emission resulting from electron-hole plasma. The lasing spectrum is observed, which consist of a large number of narrow peaks with an around 0.5 nm spacing in between, corresponding to a self-formed cavity length of around 31.5 μm. The self-formation of laser cavity in the ZnO thin film is closed related to its the hexagon structure.
    Zeeman effects on the coherent tunnelling conductance in normal-metal/superconductor/normal-metal double tunnel junctions
    Dong Zheng-Chao (董正超)
    Chinese Physics, 2005, 14 (6):  1209-1216.  DOI: 10.1088/1009-1963/14/6/026
    Abstract ( 1036 )   PDF (295KB) ( 511 )  
    The coherent quantum transport is investigated in normal-metal/superconductor/normal-metal(N/S/N) double tunnel junctions under a Zeeman magnetic field on the S.Taking simultaneously into account the electron-injected current from one Nelectrode and the hole-injected current from the other Nelectrode,we derive a general formulafor the differential conductance in the N/S/N system.It is shown that the conductance spectrum exhibits oscillatory behaviour with the bias voltage, and the oscillation amplitude is reduced wiht increasing temperature and Zeeman magneti field, the Zeeman energy can lead to the Zeeman splitting of conductance peaks.In the tunnel limit, a series of bound states of quasiparticles will form in the S.
    Effective nonlinear AC response to composite with spherical particles
    Chen Xiao-Gang (陈小刚), Liang Fang-Chu (梁方楚), Wei En-Bo (魏恩泊)
    Chinese Physics, 2005, 14 (6):  1217-1222.  DOI: 10.1088/1009-1963/14/6/027
    Abstract ( 1054 )   PDF (230KB) ( 564 )  
    An effective nonlinear alternative-current (AC) response to granular nonlinear-composite with spherical inclusions embedded in a host medium under the action of an external AC field is investigated by using a perturbation approach. The local potentials of composite at higher harmonics are derived both in a region of local inclusion particles and in a local host region under the action of a sinusoidal field E1sinωt +E3sin3ωt, with frequencies ω and 3ω. An effective nonlinear-response to composite and the relationship between the effective nonlinear-responses at the fundamental frequency and the third harmonics are also studied for the spherical inclusions in a dilute limit.
    Electrical resistivity of a novel oxadiazole derivative as a function of pressure and temperature using a diamond anvil cell
    Luo Ji-Feng (骆继锋), Han Yong-Hao (韩永昊), Tang Ben-Chen (唐本臣), Gao Chun-Xiao (高春晓), Li Min (李敏), Zou Guang-Tian (邹广田)
    Chinese Physics, 2005, 14 (6):  1223-1226.  DOI: 10.1088/1009-1963/14/6/028
    Abstract ( 1177 )   PDF (359KB) ( 587 )  
    The in-situ electrical resistance measurement on the microcrystal of 1,4-bis[(4-methyloxyphenyl)-1,3,4-oxadiazolyl]- 2,5-bisheptyloxyphenylene (OXD-2) has been carried out under conditions of high pressure and temperatures higher than room temperature by using the diamond anvil cell (DAC). Sample’s resistivity was calculated with a finite element analysis method. The temperature and pressure dependencies of the resistivity of OXD-2 microcrystal were measured up to 150 oC and 16 GPa. The resistivity of OXD-2 decreases with increasing temperature, indicating that OXD-2 exhibits organic-semiconductor conducting property in the region of experimental pressure. Between 90-100 ℃, the resistivity drops with the temperature, which reveals a temperature-induced phase transition. As the pressure increases, the resistivity of OXD-2 increases and reaches a maxium at about 6 GPa, and then begins to decrease at higher pressures. Combining the in-situ x-ray diffraction data with the resistivity measurement results under pressure, the anomaly resistivity drop after 6 GPa is confirmed to be from the pressure-induced amorphous phase transition of OXD-2.
    Thermodynamics of squeezed states in mesoscopic circuits
    Ji Ying-Hua (嵇英华), Luo Hai-Mei (罗海梅), Liu Qing (刘清), Lei Min-Sheng (雷敏生)
    Chinese Physics, 2005, 14 (6):  1227-1231.  DOI: 10.1088/1009-1963/14/6/029
    Abstract ( 1181 )   PDF (222KB) ( 510 )  
    Based on information theory, we present a density matrix to discuss coherent and squeezed states for a mesoscopic LC circuit with time-dependent frequency. With the relevant operators included in the density matrix, a connection between the appearance of coherent and squeezed states is established, i.e., the quantum state evolution of system is highly relevant to the initial state. Generally speaking, due to the effect of circumstance temperature, mesoscopic LC circuit will evolve to squeezed state when it initially lies in an excited state. In particular, at a low temperature, step changes of circuit parameters will result in the squeezed minimum uncertainty state if the resonance frequency remains consistent after the change.
    Effect of electron-phonon interactions on dynamical localization of semiconductor superlattices
    Wang Zhi-Gang (王志刚), Duan Su-Qing (段素青), Zhao Xian-Geng (赵宪庚)
    Chinese Physics, 2005, 14 (6):  1232-1237.  DOI: 10.1088/1009-1963/14/6/030
    Abstract ( 999 )   PDF (271KB) ( 488 )  
    Effect of the electron-phonon interactions on the property of dynamical localization of semiconductor superlattices in a single-band model under the actions of the electric dc and acfield, respectively, are investigated. The results show that the electron-phonon interactions can destroy the dynamical localization of the electron. For the same phonon frequency, when the strength of the electron-phonon interactions becomes larger, the electron is more quickly scattered. When the phonon frequency equals to the Bloch frequency ΩB in dc field or Ωin ac field or one of them in dc-ac field, the electron initially localized at the 0th site can be rapidly scattered to the other sites, where Ω is the frequency of the ac field. The property of the dynamical localization of the electron is seriously destroyed by the photon-phonon resonant field.
    Evolution of structure and magnetic properties of nanocrystalline FeXN thin films via Ta and Al addition
    Wu Guo-Guang (伍国光), Wu Dong-Ping (吴东平), Zheng Kuo-Hai (郑阔海), Wei Fu-Lin (魏福林), Yang Zheng (杨正), Kamzin A. S.
    Chinese Physics, 2005, 14 (6):  1238-1242.  DOI: 10.1088/1009-1963/14/6/031
    Abstract ( 1141 )   PDF (998KB) ( 484 )  
    Nanocrystalline FeAlN and FeTaN films are prepared by direct growth and crystallization of their as-deposited amorphous films, respectively. Although both films show soft magnetism of nanocrys-talline, the uniaxial anisotropy is to be observed different. Measurements of microstructure reveal that Ta addition leads to higher N-solubility in these films, and results in larger lattice dilation and more compressive stress. The uniaxial anisotropy is the consequence of the anisotropic distribution of inter-stitial N atoms in anα-Fe lattice. Al is easy to react with nitrogen, therefore, the α-Fe is purer in an FeAlN films than in an FeTaN ˉlm and the stress is tensile in FeAlN film. The difference of anisotropy may be attributed to the difference between the microstructures in both films.
    Physical properties of ferroelectric superlattice A3/B3 system in electric field
    Jiang Wei (姜伟), Lo Veng-Cheong (罗永祥), Bai Bao-Dong (白保东)
    Chinese Physics, 2005, 14 (6):  1243-1245.  DOI: 10.1088/1009-1963/14/6/032
    Abstract ( 1087 )   PDF (206KB) ( 469 )  
    The transverse Ising model (TIM) in the effective-field theory based on the differential operator technique is developed to study the physical properties of a ferroelectric superlattice A3/B3 system. The effects of an external electric field on the polarization, susceptibility and pyroelectric coefficient of the ferroelectric superlattice A3/B3 system are discussed in detail. The susceptibility of the ferroelectric superlattice A3/B3 system decreases with the increasing of the electric field, implying that the polarization is weak.
    Dependence of interface motion on pressure in ferroelectrics
    Ai Shu-Tao (艾树涛)
    Chinese Physics, 2005, 14 (6):  1246-1249.  DOI: 10.1088/1009-1963/14/6/033
    Abstract ( 936 )   PDF (223KB) ( 468 )  
    The motion of the paraelectric-ferroelectric interface in KNbO3 under hydrostatic pressure is studied in the framework of the mean-field theory. The kink solution is applied to the calculations of the width and velocity of the interface at different pressures. The calculations are based on the experimental data for the Curie-Weiss constant and the parameter of the Ginzburg-Landau expression for the free energy. The response to hydrostatic pressure and tricritical point is investigated nonempirically.
    Spectroscopic properties and thermal stability of Er3+/Yb3+-codoped fluorophosphate glasses
    Li Tao (李涛), Zhang Qin-Yuan (张勤远), Zhao Chun (赵纯), Feng Zhou-Ming (冯洲明), Shi Dong-Mei (石冬梅), Deng Zai-De (邓再德), Jiang Zhong-Hong (姜中宏)
    Chinese Physics, 2005, 14 (6):  1250-1254.  DOI: 10.1088/1009-1963/14/6/034
    Abstract ( 1007 )   PDF (266KB) ( 500 )  
    A comprehensive study on the thermal stability and spectroscopic properties of Er3+/Yb3+-codoped Al(PO3)3-based fluorophosphate glasses have been reported for 1.5-mm fiber amplifiers in this paper. From optical absorption spectra, the Judd-Ofelt parameters of Er3+ in the glasses and then several important optical properties, i.e., the radiative transition probability, the branching ratio and the spontaneous emission probability, have been calculated by Judd-Ofelt theory. The fluorophosphate glass exhibits broadband near-infrared emission at 1.53 mm with a full width at half-maximum over 63 nm, and a large calculated stimulated-emission cross-section of 6.85×10-21 cm2.
    SiCGe/SiC heterojunction and its MEDICI simulation of optoelectronic characteristics
    Lü Zheng (吕政), Chen Zhi-Ming (陈治明), Pu Hong-Bin (蒲红斌)
    Chinese Physics, 2005, 14 (6):  1255-1258.  DOI: 10.1088/1009-1963/14/6/035
    Abstract ( 1111 )   PDF (253KB) ( 548 )  
    Optoelectronic characteristics of the SiC1-xGex /SiC heterojunction photodiode are simulated using MEDICI after the theoretical investigation of key properties for SiC1-xGex. The calculations show that SiC1-xGex /SiC with x=0.3 may have a small lattice mismatch with 3C-SiC and a good response to the visible light and near infrared light. The response spectrum of the SiC1-xGex /SiC heterojunction photodiodes, which consists of a p-type SiC1-xGex absorption layer with a doping concentration of $1\times10^{15}$cm-3, a thickness of 1.6μm and x=0.3, has a peak value of 250mA/W at 0.52μm and the peak value can even reach 102 mA/W at 0.7μm.
    GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
    A microwave emissivity model of sea surface under wave breaking
    Wei En-Bo (魏恩泊), Ge Yong (葛勇)
    Chinese Physics, 2005, 14 (6):  1259-1264.  DOI: 10.1088/1009-1963/14/6/036
    Abstract ( 1156 )   PDF (290KB) ( 455 )  
    With effective medium approximation theory of composites, a remedial model is proposed for estimating the microwave emissivity of sea surface under wave breaking driven by strong wind on the basis of an empirical model given by Pandey and Kakar. In our model, the effects of the shapes of seawater droplets and the thickness of whitecaps layer (i.e. a composite layer of air and sea water droplets) over the sea surface on the microwave emissivity are investigated by calculating the effective dielectric constant of whitecaps layer. The wind speed is included in our model, and the responses of water droplets shapes, such as sphere and ellipsoid, to the emissivity are also discussed at different microwave frequencies. The model is in good agreement with the experimental data of microwave emissivity of sea surface at microwave frequencies of 6.6, 10.7 and 37 GHz.
    Evolution characteristics of the precipitation in the Yangtze River delta based on the probability density
    Zeng Hong-Ling (曾红玲), Gao Xin-Quan (高新全), Zhang Wen (张文)
    Chinese Physics, 2005, 14 (6):  1265-1271.  DOI: 10.1088/1009-1963/14/6/037
    Abstract ( 1041 )   PDF (272KB) ( 439 )  
    The dryness/wetness (DW) grade data of the Yangtze River delta are transformed in this paper into the temporal evolution of precipitation probability (PP), and its hierarchically distributive characters are revealed. Research results show that the precipitation of the Yangtze River delta displays the interannual, interdecadal, as well as more than a century quasi-periodic changes, and the periods are all significant at a confidence level of more than 0.05. In the DW grade series of 530 years, although the frequency of the small probability events (SPEs) of drought/flood in each area of the Yangtze River delta is different, the frequency of the SPEs triggered by the climatic background state is yet the same. This research result fully narrates the significant impact of the climatic evolution as a background state upon the occurrence of SPEs, which will play an instructional role in climatic prediction theory and in raising the accuracy of climatic prediction.
    Electron capture in fp shell at presupernova stage
    Luo Zhi-Quan (罗志全), Liu Men-Quan (刘门全), Lin Li-Bin (林理彬), Peng Qiu-He (彭秋和)
    Chinese Physics, 2005, 14 (6):  1272-1275.  DOI: 10.1088/1009-1963/14/6/038
    Abstract ( 994 )   PDF (225KB) ( 431 )  
    The electron capture of neutron-rich nuclei in fp shell in massive stars at presupernova stage is discussed based on the nuclear shell model. The Gamow-Teller resonance transition strength is modified by introducing a Gaussian function. As a result, the electron capture rate in high density is evidently larger than the previous results given by some authors.
ISSN 1674-1056   CN 11-5639/O4
, Vol. 14, No. 6

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