Table of contents

16 October 2003, Volume 12 Issue 10 Previous issue    Next issue

GENERAL

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Evolution property of soliton solutions for the Whitham－Broer－Kaup equation and variant Boussinesq equation Lin Ji (林机), Xu You-Sheng (许友生), Wu Feng-Min (吴锋民) Chinese Physics, 2003, 12 (10):  1049-1053.  DOI: 10.1088/1009-1963/12/10/301 Abstract ( 1068 )   PDF (326KB) ( 691 )   Using the standard Painlevé analysis approach, the (1+1)-dimensional Whitham－Broer－Kaup (WBK) and variant Boussinesq equations are solved. Some significant and exact solutions are given. We investigate the behaviour of the interactions between the multi-soliton-kink-type solution for the WBK equation and the multi-solitonic solutions and find the interactions are not elastic. The fission of solutions for the WBK equation and the fusions of those for the variant Boussinesq equation may occur after their interactions.

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Bound states of the Klein－Gordon and Dirac equations for potential $V(r)=Ar^{-2}-Br^{-1}$ Qiang Wen-Chao (强稳朝) Chinese Physics, 2003, 12 (10):  1054-1057.  DOI: 10.1088/1009-1963/12/10/302 Abstract ( 1608 )   PDF (218KB) ( 639 )   The exact normalized bound-state wavefunctions and energy equations of Klein－Gordon and Dirac equations are given with equal scalar and vector potentials $s(r)=v(r)=V(r)/2=(Ar^{-2}-Br^{-1})/2$.

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Form invariance for systems of generalized classical mechanics Zhang Yi (张毅), Mei Feng-Xiang (梅凤翔) Chinese Physics, 2003, 12 (10):  1058-1061.  DOI: 10.1088/1009-1963/12/10/303 Abstract ( 1436 )   PDF (200KB) ( 571 )   This paper presents a form invariance of canonical equations for systems of generalized classical mechanics. According to the invariance of the form of differential equations of motion under the infinitesimal transformations, this paper gives the definition and criterion of the form invariance for generalized classical mechanical systems, and establishes relations between form invariance, Noether symmetry and Lie symmetry. At the end of the paper, an example is given to illustrate the application of the results.

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Minimum signals in classical physics Deng Wen-Ji (邓文基), Xu Ji-Huan (许基桓), Liu Ping (刘平) Chinese Physics, 2003, 12 (10):  1062-1065.  DOI: 10.1088/1009-1963/12/10/304 Abstract ( 1061 )   PDF (202KB) ( 430 )   The bandwidth theorem for Fourier analysis on any time-dependent classical signal is shown using the operator approach to quantum mechanics. Following discussions about squeezed states in quantum optics, the problem of minimum signals presented by a single quantity and its squeezing is proposed. It is generally proved that all such minimum signals, squeezed or not, must be real Gaussian functions of time.

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Quantum teleportation of entangled squeezed vacuum states Cai Xin-Hua (蔡新华) Chinese Physics, 2003, 12 (10):  1066-1069.  DOI: 10.1088/1009-1963/12/10/305 Abstract ( 1241 )   PDF (192KB) ( 633 )   An optical scheme for probabilistic teleporting entangled squeezed vacuum states (SVS) is proposed. In this scheme, the teleported state is a bipartite entangled SVS, and the quantum channel is a tripartite entangled SVS. The process of the teleportation is achieved by using a 50/50 symmetric beamsplitter and photon detectors with the help of classical information.

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Teleportation of a multiqubit state by an entangled qudit channel Zheng Yi-Zhuang (郑亦庄), Gu Yong-Jian (顾永建), Wu Gui-Chu (吴桂初), Guo Guang-Can (郭光灿) Chinese Physics, 2003, 12 (10):  1070-1075.  DOI: 10.1088/1009-1963/12/10/306 Abstract ( 1249 )   PDF (258KB) ( 539 )   We investigate the problem of teleportation of an M-qubit state by using an entangled qudit pair as a quantum channel and show that the teleportation of a multiparticle state can correspond to the teleportation of a multi-dimensional state. We also introduce a quantum-state converter composed of beamsplitter arrays, on/off-detectors and cross-Kerr couplers and demonstrate that the state conversion from an M-qubit to an N-dimensional qudit and vice versa can be implemented with this converter, where $N=2^M$. Based on this, an experimentally feasible scheme for the teleportation of an M-qubit via an entangled N-level qudit pair channel is proposed.

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Evaluation of the applicability of a retrospective scheme based on comparison with several difference schemes Feng Guo-Lin (封国林), Dong Wen-Jie (董文杰) Chinese Physics, 2003, 12 (10):  1076-1086.  DOI: 10.1088/1009-1963/12/10/307 Abstract ( 1203 )   PDF (647KB) ( 542 )   The evaluation of the applicability of a retrospective multi-time-level scheme (RT scheme) is carried out on the basis of comparison with the common leapfrog scheme (LF scheme) and its derivatives, and modified BOTT's positive-definite schemes used in atmospheric models. Two rational flow field tests confirm that at least the BOTT scheme tested may be applied, but apparently the best results are obtained by the RT scheme. The results of wavelet analysis show that the RT scheme can better extract the useful information from the initial fields, i.e. to memorize many main initial characteristics, such as periods, thus offering a new approach to the short-term climate numerical prediction.

ATOMIC AND MOLECULAR PHYSICS

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The periodic magnetized cylinder tube for atom guidance: quantized motion analysis Li Dai-Jun (李代军), Zhou Bo (周博), Hu Zheng-Feng (胡正峰), Li Shi-Qun (李师群) Chinese Physics, 2003, 12 (10):  1087-1095.  DOI: 10.1088/1009-1963/12/10/308 Abstract ( 883 )   PDF (407KB) ( 357 )   We have analysed the transport efficiency of an atomic waveguide constructed from a periodic axially magnetized hollow tube. We took into consideration the quantized motion of the atom inside the magnetic hollow cylinder tube, which is significant for the transportation of cold atoms. We deduced the quantized motion modes of the atomic waves in the tube by the approximation of infinite potential, which is valid for cold atoms and strong magnetization. For the atomic waveguide with weak magnetization, we have calculated the tunnelling effect of the atomic wave. The adiabatic condition for the motion of cold atoms is discussed. A time orbit potential method for solving the "zero magnetic field problem" is proposed.

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Excitonic level structures of LH1 and LH2 of purple photosynthetic bacteria using an analytical approach Yang Guang-Can (杨光参), Wang Li (汪力), Yang Guo-Zhen (杨国桢) Chinese Physics, 2003, 12 (10):  1096-1104.  DOI: 10.1088/1009-1963/12/10/309 Abstract ( 1229 )   PDF (283KB) ( 426 )   The excitonic level structure of a ring-like chain of dimers is discussed analytically in order to aid the understanding of the possible spectral properties of LH1 and LH2 of purple photosynthetic bacteria. Under the approximation of dipole－dipole interaction between Bchls, the excitonic levels, bandwidths and energy gap between two Davydov subbands are expressed analytically in terms of interaction energies and configurational parameters of dipoles. Our model includes all the interactions between pigment molecules in the system. The oscillator strengths and circular dichroism (CD) for the excitonic states are also presented analytically. The simulated absorption and CD spectra of LH1 and LH2 complexes reproduce the main features of the measured results.

CLASSICAL AREAS OF PHENOMENOLOGY

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Modulated stochastic multiresonance in single-mode laser system without input periodic signal Liang Gui-Yun (梁贵云), Cao Li (曹力), Wu Da-Jin (吴大进) Chinese Physics, 2003, 12 (10):  1105-1108.  DOI: 10.1088/1009-1963/12/10/310 Abstract ( 1011 )   PDF (206KB) ( 564 )   The stochastic resonance phenomenon in a single-mode laser system driven by multiplicative and additive Gaussian white noises without external periodic force is studied. We find that there are multiple extrema (maximum) in the curve of the mean output laser intensity versus the logarithm of multiplicative noise level. This phenomenon reveals that the mean output laser intensity can be amplified at several values of the multiplicative noise intensity, whose peaks are likely modulated by a sinusoidal function.

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Statistical properties of a single-mode laser driven by additive and multiplicative coloured noises with a coloured cross-correlation for different correlation times Liang Gui-Yun (梁贵云), Cao Li (曹力), Zhang Li (张莉), Wu Da-Jin (吴大进) Chinese Physics, 2003, 12 (10):  1109-1119.  DOI: 10.1088/1009-1963/12/10/311 Abstract ( 1140 )   PDF (309KB) ( 467 )   We study a system for a single-mode laser driven by additive and multiplicative coloured noises with a coloured cross-correlation. The analytical expression of the stationary intensity distribution (SID) for the laser is derived in the case of three different correlation times. The influences of each stochastic parameter on the SID are discussed, the effects of the noise "colour" and the cross-correlation of noises on the mean intensity $\langle I\rangle$, the variance, $\lambda_2(0)$, and the skewness, $\lambda_3(0)$ of the single-mode laser are investigated. We find that there are colourful phase transitions for the SID above a threshold, and re-entrant transitions induced by the "colour" of the additive noises. Further research of the curves of $\langle I\rangle -\tau_i$, $\lambda_2(0)-\tau_i$, and $\lambda_3(0)-\tau_i (i=1,2,3)$  (where $\tau_i$ is the correlation time) shows that the output intensity not only increases with the additive noise correlation time $\tau_2$ and the cross-correlation time $\tau_3$, but also the quality of the output of laser beams is optimized.

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Low frequency fluctuation with two external cavity reflectors Wang Chun-Lin (王春林), Wu Jian (伍剑), Lin Jin-Tong (林金桐) Chinese Physics, 2003, 12 (10):  1120-1123.  DOI: 10.1088/1009-1963/12/10/312 Abstract ( 1214 )   PDF (206KB) ( 450 )   The dynamics of a semiconductor laser with two optical feedbacks is studied in this paper. A new set of nonlinear rate equations that can describe external cavity semiconductor lasers with any amount of two optical feedbacks is proposed. It is found that when the laser is biased above the threshold and subjected to one feedback, the other feedback can induce low-frequency fluctuations.

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Self-deflection of a bright soliton in a separate bright－dark spatial soliton pair based on a higher-order space charge field Liu Jin-Song (刘劲松), Hao Zhong-Hua (郝中华) Chinese Physics, 2003, 12 (10):  1124-1134.  DOI: 10.1088/1009-1963/12/10/313 Abstract ( 1037 )   PDF (331KB) ( 446 )   The self-deflection of a bright solitary beam can be controlled by a dark solitary beam via a parametric coupling effect between the bright and dark solitary beams in a separate bright－dark spatial soliton pair supported by an unbiased series photorefractive crystal circuit. The spatial shift of the bright solitary beam centre as a function of the input intensity of the dark solitary beam ($\hat{\rho}$) is investigated by taking into account the higher-order space charge field in the dynamics of the bright solitary beam via both numerical and perturbation methods under steady-state conditions. The deflection amount ($\Delta s_0$), defined as the value of the spatial shift at the output surface of the crystal, is a monotonic and nonlinear function of $\hat{\rho}$. When $\hat{\rho}$ is weak or strong enough, $\Delta s_0$ is, in fact, unchanged with $\hat{\rho}$, whereas $\Delta s_0$ increases or decreases monotonically with $\hat{\rho}$ in a middle range of $\hat{\rho}$. The corresponding variation range ($\delta s$) depends strongly on the value of the input intensity of the bright solitary beam (r). There are some peak and valley values in the curve of $\delta s$ versus r under some conditions. When $\hat{\rho}$ increases, the bright solitary beam can scan toward both the direction same as and opposite to the crystal's c-axis. Whether the direction is the same as or opposite to the c-axis depends on the parameter values and configuration of the crystal circuit, as well as the value of  $r$. Some potential applications are discussed.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Poloidal rotation of main ions in the CT-6B tokamak Feng Chun-Hua (冯春华), Li Zan-Liang (李赞良), Yang Xuan-Zong (杨宣宗), Zheng Shao-Bai (郑少白), Li Wen-Lai (李文莱), Wang Long (王龙) Chinese Physics, 2003, 12 (10):  1135-1139.  DOI: 10.1088/1009-1963/12/10/314 Abstract ( 986 )   PDF (199KB) ( 441 )   The poloidal rotation velocity of neutral hydrogen atoms is measured using the Doppler shift of the Hα spectral line emitted in the CT-6B tokamak. The poloidal rotation of hydrogen atoms is generated through the collisions and charge-exchanges with main ions (protons). Therefore, the rotation direction of main ions can be deduced from that of neutral hydrogen atoms. The experimental results show that the main ions rotate in the electron diamagnetic drift direction, the same as the impurity ions, in the plasma core. The neutral hydrogen atoms rotate also in the electron diamagnetic drift direction in the edge region of the plasma. However, the rotation direction of main ions in the edge region cannot be judged from the experimental result due to the long mean free path of hydrogen atoms in the edge region. An inward diffusion flux of hydrogen atoms toward the torus inside with a velocity of the same order of magnitude as their poloidal rotation is also observed.

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The dielectronic recombination process in laser-produced Au plasmas Jiao Rong-Zhen (焦荣珍), Cheng Xin-Lu (程新路), Yang Xiang-Dong (杨向东) Chinese Physics, 2003, 12 (10):  1140-1142.  DOI: 10.1088/1009-1963/12/10/315 Abstract ( 1188 )   PDF (171KB) ( 488 )   The calculations of the rate coefficients for dielectronic recombination (DR) along the NiI isoelectronic sequence in the ground state Au51+ through Cu-like $3d^9n1n'f$ ($n,n′=4,5,6$) inner-shell excited configurations are performed using the spin-orbit-split array (SOSA) model. Resonant and nonresonant radiative stabilizing transitions and decays to autoionizing levels followed by radiative cascades are included. Collisional transitions following electron capture are neglected. The trend of the DR rate coefficients and the ratio of dielectronic satellite lines intensities with the change of the electron temperature are discussed.

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Effects of matrices on Mie scattering in the mid-infrared region Liu Xiao-Dong (刘晓东), Li Shu-Guang (李曙光), Guo Hong-Lian (郭红莲), Zhang Dao-Zhong (张道中), Li Zhao-Lin (李兆霖), Hou Lan-Tian (侯蓝田) Chinese Physics, 2003, 12 (10):  1143-1148.  DOI: 10.1088/1009-1963/12/10/316 Abstract ( 1240 )   PDF (316KB) ( 486 )   Various Mie scattering systems, each having a transparent matrix, are studied in the mid-infrared region. Our three theoretical scattering systems correspond to a lossless scatterer, an anomalous dispersive dielectric scatterer and a metal scatterer, each in a non-air usual matrix. The refractive-index effects of the matrix on scattering and extinction efficiencies in the mid-infrared region are found to be quite different in different cases. Although the non-air usual matrix reduces scattering and extinction efficiencies in the first kind of system, it may or may not help scatter and extinguish the mid-infrared radiation in the second, and it has little effect on them in the third.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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On the interaction between dislocations and cracks in one-dimensional hexagonal quasi-crystals Liu Guan-Ting (刘官厅), Guo Rui-Ping (郭瑞平), Fan Tian-You (范天佑) Chinese Physics, 2003, 12 (10):  1149-1155.  DOI: 10.1088/1009-1963/12/10/317 Abstract ( 1161 )   PDF (235KB) ( 670 )   The solution of elasticity problems involving the interaction between dislocations and cracks plays a fundamental role in many practical and theoretical applications. Although elasticity problems involving dislocation or cracks in quasi-crystals have been investigated in many papers, the analysis is limited to a single defect. This paper investigates the interaction of defects in one-dimensional hexagonal quasi-crystals using the complex variable function method. The interaction force between two parallel dislocations is presented and the analytic solutions of elastic fields of interaction between a dislocation and a crack are obtained. A version of the well-known Peach－Koehler formula in one-dimensional hexagonal quasi-crystals is given.

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The complete proof of the virial theorem in the refined TFD theory for all electrons of an atom in a solid Zhu Ru-Zeng (朱如曾), Qian Jin (钱劲), Yang Quan-Wen (杨全文), Wen Yu-Hua (文玉华) Chinese Physics, 2003, 12 (10):  1156-1158.  DOI: 10.1088/1009-1963/12/10/318 Abstract ( 873 )   PDF (177KB) ( 391 )   The complete proof of the virial theorem in refined Thomas－Fermi－Dirac theory for all electrons of an atom in a solid is given.

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Research on the ultrafast fluorescence property of thylakoid membranes of the wild-type and mutant rice Ren Zhao-Yu (任兆玉), Xu Xiao-Ming (许晓明), Wang Shui-Cai (王水才), Xin Yue-Yong (辛越勇), He Jun-Fang (贺俊芳), Hou Xun (侯洵) Chinese Physics, 2003, 12 (10):  1159-1165.  DOI: 10.1088/1009-1963/12/10/319 Abstract ( 817 )   PDF (278KB) ( 319 )   A high yielding rice variety mutant (Oryza sativa L., Zhenhui 249) with low chlorophyll b (Chl b) has been discovered in natural fields. It has a quality character controlled by a pair of recessive genes (nuclear gene). The partial loss of Chl b in content affects the efficiency of light harvest in a light harvest complex (LHC), thus producing the difference of the exciting energy transfer and the efficiency of photochemistry conversion between the mutant and wild-type rice in photosynthetic unit. The efficiency of utilizing light energy is higher in the mutant than that in the wild-type rice relatively. For further discussion of the above-mentioned difference and learning about the mechanism of the increase in the photochemical efficiency of the mutant, the pico-second resolution fluorescence spectrum measurement with delay-frame-scanning single photon counting technique is adopted. Thylakoid membranes of the mutant and the wild-type rice are excited by an Ar^+ laser with a pulse width of 120 ps, repetition rate of 4 MHz and wavelength of 514 nm. Compared with the time and spectrum property of exciting fluorescence, conclusions of those ultrafast dynamic experiments are: 1) The speeds of the exciting energy transferred in photo-system I are faster than that in photo-system II in both samples. 2) The speeds of the exciting energy transfer of mutant sample are faster than those of the wild-type. This might be one of the major reasons why the efficiency of photosynthesis is higher in mutant than that in the wild-type rice.

RAPID COMMUNICATION

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Interaction between compacton and anticompacton, peakon and antipeakon in (2+1)-dimensional spaces Han Ping (韩平), Zhang Jie-Fang (张解放), Meng Jian-Ping (孟剑平) Chinese Physics, 2003, 12 (10):  1166-1171.  DOI: 10.1088/1009-1963/12/10/320 Abstract ( 1063 )   PDF (322KB) ( 450 )   Starting from the variable separation solution obtained by using the extended homogenous balance method, a class of novel localized coherent structures such as the multi-peakon－antipeakons solution and the multi-compacton－anticompactons solution of the (2+1)-dimensional dispersive long wave equation are found by selecting appropriate functions. These new structures exhibit some novel interaction features that are different from one of the known results. Their interaction behaviour is very similar to the completely elastic collisions between two classical particles.