Table of Content

16 March 2005, Volume 12 Issue 12 Previous Issue    Next Issue

GENERAL

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The periodic wave solutions for two systems of nonlinear wave equations Wang Ming-Liang, Wang Yue-Ming, Zhang Jin-Liang 2003, 12 (12):  1341-1348.  doi: 10.1088/1009-1963/12/12/001 Abstract ( 0 )   PDF (233KB) ([an error occurred while processing this directive])   The periodic wave solutions for the Zakharov system of nonlinear wave equations and a long－short-wave interaction system are obtained by using the F-expansion method, which can be regarded as an overall generalization of Jacobi elliptic function expansion proposed recently. In the limit cases, the solitary wave solutions for the systems are also obtained.

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Perturbation to symmetries and adiabatic invariants of a type of nonholonomic singular system Chen Xiang-Wei, Li Yan-Min 2003, 12 (12):  1349-1353.  doi: 10.1088/1009-1963/12/12/002 Abstract ( 0 )   PDF (211KB) ([an error occurred while processing this directive])   Based on the theory of symmetries and conserved quantities, the perturbation to the symmetries and adiabatic invariants of a type of nonholonomic singular system are discussed. Firstly, the concept of higher order adiabatic invariants of the system is proposed. Secondly, the conditions for existence of the exact invariants and adiabatic invariants are proved, and their forms are given. Thirdly, we study the inverse problems of the perturbation to symmetries of the system. An example is presented to illustrate these results.

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Probabilistic teleportation of an arbitrary three-particle state via a partial entangled four-particle state and a partial entangled pair Dai Hong-Yi, Li Cheng-Zu, Chen Ping-Xing 2003, 12 (12):  1354-1359.  doi: 10.1088/1009-1963/12/12/003 Abstract ( 0 )   PDF (209KB) ([an error occurred while processing this directive])   We present a scheme to probabilistically teleport an arbitrary and unknown three-particle state via a two-particle non-maximally entangled state and a four-particle non-maximally entangled state as the quantum channel. With the help of Bell-state measurements, an arbitrary three-particle state can be perfectly teleported if a receiver introduces a collective unitary transformation. All kinds of unitary transformations are given in greater detail. This scheme can be generalized to the teleportation of an arbitrary and unknown multiparticle state.

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Double-wave description of mesoscopic resistance-inductance-capacitance coupled circuit with power source Zhang Shou, Zhu Ai-Dong, Jin Zhe, Li Zhe-Kui, Pan Shu-Mei, Zhao Yong-Fang, Jing Xiao-Gong, Qian Zheng-Nan, Su Wen-Hui 2003, 12 (12):  1360-1365.  doi: 10.1088/1009-1963/12/12/004 Abstract ( 0 )   PDF (251KB) ([an error occurred while processing this directive])   Quantum fluctuations in the mesoscopic capacitance-inductance-resistance coupled circuit with a power source are investigated using canonical transformation and a double wavefunction. We confirm that the fluctuations are not influenced by the power source. As a new method, the double wavefunction describes a single system of the coupled circuit, whereas the single wavefunction describes a quantum ensemble.

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Global vector-field reconstruction of nonlinear dynamical systems from a time series with SVD method and validation with Lyapunov exponents Liu Wei-Dong, K. F. Ren, S. Meunier-Guttin-Cluzel, G. Gouesbet 2003, 12 (12):  1366-1373.  doi: 10.1088/1009-1963/12/12/005 Abstract ( 0 )   PDF (297KB) ([an error occurred while processing this directive])   A method for the global vector-field reconstruction of nonlinear dynamical systems from a time series is studied in this paper. It employs a complete set of polynomials and singular value decomposition (SVD) to estimate a standard function which is central to the algorithm. Lyapunov exponents and dimension, calculated from the differential equations of a standard system, are used for the validation of the reconstruction. The algorithm is proven to be practical by applying it to a R?ssler system.

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

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Topological susceptibility from overlap fermion Ying He-Ping, Zhang Jian-Bo 2003, 12 (12):  1374-1377.  doi: 10.1088/1009-1963/12/12/006 Abstract ( 0 )   PDF (209KB) ([an error occurred while processing this directive])   We numerically calculate the topological charge of the gauge configurations on a finite lattice by the fermionic method with overlap fermions. By using the lattice index theorem, we identify the index of the massless overlap fermion operator to the topological charge of the background gauge configuration. The resulting topological susceptibility χ is in good agreement with the anticipation made by Witten and Veneziano.

NUCLEAR PHYSICS

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Numerical simulation of the early-time high altitude electromagnetic pulse Meng Cui, Chen Yu-Sheng, Liu Shun-Kun, Xie Qin-Chuan, Chen Xiang-Yue, Gong Jian-Cheng 2003, 12 (12):  1378-1382.  doi: 10.1088/1009-1963/12/12/007 Abstract ( 0 )   PDF (262KB) ([an error occurred while processing this directive])   In this paper, the finite difference method is used to develop the Fortran software MCHII. The physical process in which the electromagnetic signal is generated by the interaction of nuclear-explosion-induced Compton currents with the geomagnetic field is numerically simulated. The electromagnetic pulse waveforms below the burst point are investigated. The effects of the height of burst, yield and the time-dependence of γ-rays are calculated by using the MCHII code. The results agree well with those obtained by using the code CHAP.

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Calculation of the heat deposition and temperature distribution of the target bombarded by high-energy protons using Monte Carlo simulation and finite element method Yin Wen, Zhang Guo-Feng, Du Jian-Hong, Liang Jiu-Qing 2003, 12 (12):  1383-1385.  doi: 10.1088/1009-1963/12/12/008 Abstract ( 0 )   PDF (186KB) ([an error occurred while processing this directive])   The Monte Carlo simulation and the finite element methods have been used to calculate the heat deposition and temperature distribution in tungsten plate target when the target is bombarded by high-energy protons from the accelerator with nuclear power of 100 kW. The results show that the heat deposition in the target, reflector and shield will be 48 kW, 15 kW and 11 kW, respectively, and the highest temperature in the target plates will be lower than 100℃ when the surfaces of plates are cooled by water.

ATOMIC AND MOLECULAR PHYSICS

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Femtosecond laser-induced long-lasting phosphorescence in Pr3+-doped ZnO-B2O3-SiO2 glass Jiang Xiong-Wei, Qiu Jian-Rong, Zeng Hui-Dan, Zhu Cong-Shan 2003, 12 (12):  1386-1389.  doi: 10.1088/1009-1963/12/12/009 Abstract ( 0 )   PDF (196KB) ([an error occurred while processing this directive])   This paper studies the phenomenon of long-lasting phosphorescence induced by a femtosecond laser in Pr^{3+}-doped ZnO-B_2O_3-SiO_2 glass. With the glass irradiated by a focused femtosecond laser for a short time, the emission of strong reddish long-lasting phosphorescence from the irradiated part of the glass can be observed. The emission peaks are located at 495 and 603 nm in wavelength, showing that the long-lasting phosphorescence originates from the emission of Pr^{3+}. The intensity of the phosphorescence decreases in inverse proportion to time after the removal of the laser. By analysing the absorption and electron spin resonance spectra of the glass, we find that colour-centres are induced in the glass matrix after the irradiation of the femtosecond laser. A possible mechanism has been provided to account for the generation of long-lasting phosphorescence.

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Near threshold photodetachment cross section of negative atomic oxygen ions Wu Jian-Hua, Yuan Jian-Min, Vo Ky Lan 2003, 12 (12):  1390-1394.  doi: 10.1088/1009-1963/12/12/010 Abstract ( 0 )   PDF (224KB) ([an error occurred while processing this directive])   A 40-target state close-coupling calculation for the photodetachment cross section of negative atomic oxygen near threshold is carried out with core－valence electron correlation by using the R-matrix method. It was shown that after considering the excitations of two electrons from the 2s shell, the electron affinity of O^- (2s^22p^5{}^2P°) agrees with the experimental result much better than that just considering the excitations of electrons only from the 2p shell as well as only one electron from the 2s shell. Total cross section as well as the main contribution of the ionization channels to the partial cross section are illustrated to show the structure near threshold clearly.

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Triple differential cross section in ionization of hydrogen by electron impact Zhang Cheng-Hua, Qiu Wei, Xin Jun-Li, Niu Ying-Yu, Wang Xiao-Wei, Wang Jing-Yang 2003, 12 (12):  1395-1398.  doi: 10.1088/1009-1963/12/12/011 Abstract ( 0 )   PDF (223KB) ([an error occurred while processing this directive])   A novel model is proposed to study the ionization of atomic hydrogen by fast election impact in coplanar asymmetric geometry making use of the post form of the transition matrix element for the energy shell and the two-potential formula. Based on the approximation of projectile plane waves and three-body problems, the transition matrix element is decomposed into two parts: the structure and scattering factor and the correlation factor. The contributions of these factors to triple differential cross sections are investigated using the method of asymptotic and convergent series.

CLASSICAL AREAS OF PHENOMENOLOGY

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Two-mode mazer injected with V-type three-level atoms Liang Wen-Qing, Zhang Zhi-Ming, Xie Sheng-Wu 2003, 12 (12):  1399-1413.  doi: 10.1088/1009-1963/12/12/012 Abstract ( 0 )   PDF (408KB) ([an error occurred while processing this directive])   The properties of the two-mode mazer operating on V-type three-level atoms are studied. The effect of the one-atom pumping on the two modes of the cavity field in number-state is asymmetric, that is, the atom emits a photon into one mode with some probability and absorbs a photon from the other mode with some other probability. This effect makes the steady-state photon distribution and the steady-state photon statistics asymmetric for the two modes. The diagram of the probability currents for the photon distribution, given by the analysis of the master equation, reveals that there is no detailed balance solution for the master equation. The computations show that the photon statistics of one mode or both modes can be sub-Poissonian, that the two modes can have anticorrelation or correlation, that the photon statistics increases with the increase of thermal photons, and that the resonant position and strength of the photon statistics are influenced by the ratio of the two coupling strengths of the two modes. These properties are also discussed physically.

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A simple method for boosting the beam quality of commercial DPL Zhang Guang-Yin, Jiao Zhi-Yong, Yan Cai-Fan, Ding Xin, Zhang Chao-Bo, Zhang Xiao-Hua, Gu Xue-Wen, Song Feng 2003, 12 (12):  1414-1416.  doi: 10.1088/1009-1963/12/12/013 Abstract ( 0 )   PDF (188KB) ([an error occurred while processing this directive])   A simple method for boosting the beam quality of a commercial laser diode pumped laser (DPL) is put forward. By keeping one of the mirrors unchanged and the moving the other mirror a proper distance away from the laser rod, high beam quality laser output is realized.

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Analysis of the laser performance of Tm3+, Tb3+(Ho3+):YVO4 crystals at ～1.5μm wavelength Huang Li-Lei, Fu Yan-Bin, Wu Liang-Neng 2003, 12 (12):  1417-1422.  doi: 10.1088/1009-1963/12/12/014 Abstract ( 0 )   PDF (280KB) ([an error occurred while processing this directive])   The absorption spectra of Tb,Tm:YVO_4 and Ho,Tm:YVO_4 are measured. The radiant and non-radiant transition probabilities from higher level to lower level, A_{i,j} and ω_{i,j}, and the cross-elaxation probability are calculated in virtue of Judd－Ofelt and Dexter theories. The fluorescence lifetime of Tm^{3+} in the Tb^{3+} (or Ho^{3+}) co-doped crystal is calculated. It indicates that the lifetime of initial level {}^3H_4 of the laser transition can be shorter than that of terminal level {}^3F_4 of the transition if the atomic percentage of Tb^{3+} (or Ho^{3+}) ions is bigger than about 1 at%: namely, by means of the co-doping Tb^{3+} (or Ho^{3+}) ions the self-termination phenomenon of laser light can be eliminated. Inserting the optic parameters to the formula deduced here on the laser threshold power P^{(4)}_{th} and the slope efficiency η^{(4)}_s of the four-energy-level system, we obtain the relationship of threshold power P^{(4)}_{th} to the concentration of Tm^{3+} ions and discuss the effect of Tb^{3+} (or Ho^{3+}) ion concentration on the laser threshold power P^{(4)}_{th} around 1.5μm wavelength. The result shows that Tb,Tm:YVO_4 crystal is a better choice to make the laser at ～1.5μm wavelength than Ho,Tm:YVO_4 crystal. We give the appropriate composition of (1－2) at% Tb, (1－2) at% Tm:YVO_4, just for reference.

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Study of the stability of polarization mode dispersion in fibre Fu Song-Nian, Wu Chong-Qing, Liu Hai-Tao, Shum Ping, Dong Hui 2003, 12 (12):  1423-1428.  doi: 10.1088/1009-1963/12/12/015 Abstract ( 0 )   PDF (266KB) ([an error occurred while processing this directive])   Polarization mode dispersion (PMD) is the ultimate limitation to high bit-rate fibre communication system. The stability of PMD is very important to its measurement and compensation. This paper puts forward a method to measure the stability of PMD by measuring the stability of the state of polarization (SOP) and introduces the conception of time evolution vector (TEV) of SOP. We observe the fact that the regularity of the principal state of polarization changing with time is the same as other SOPs', if we neglect the dependence of TEV on wavelength. We also measure the SOP's stability of some fibres with different lengths, and obtain results of PMD changing with time.

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Breakdown of the chain of ring vortices in a transitional boundary layer Li Cun-Biao 2003, 12 (12):  1429-1434.  doi: 10.1088/1009-1963/12/12/016 Abstract ( 0 )   PDF (333KB) ([an error occurred while processing this directive])   A large number of experiments have been devoted to the study of the generation and development of the high-frequency structures, i.e. the chain of ring-like vortices and breakdown of the chain of ring-like vortices, to the investigation of their relevance to laminar-turbulent transition in a boundary layer flow; however, the origins of turbulence via the process of flow randomization are still not well understood. For this reason a detailed experiment was performed to document the important shape and configuration of the late-stage transitional structures and to investigate some of the still insufficiently understood mechanisms of flow randomization.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Investigation of the photoelectron decay of silver halide microcrystal Yang Shao-Peng, Fu Guang-Sheng, Dong Guo-Yi, Li Xiao-Wei, Han Li 2003, 12 (12):  1435-1439.  doi: 10.1088/1009-1963/12/12/017 Abstract ( 0 )   PDF (217KB) ([an error occurred while processing this directive])   The microwave absorption dielectric spectrum can be used to study the decay process of free photoelectrons and shallow-trapped electrons in semiconductor crystals. The decay curve of free photoelectrons and shallow-trapped electrons of silver halide grains is measured using this technique. The influence of iodide and K_4Fe(CN)_6 shallow electron trap dopants on the photoelectron lifetime of silver halide grains is studied. For the unsensitized cubic AgCl crystals, when the free photoelectron lifetime (FLT) reaches a maximum, the photographic efficiency is optimal. From our analysis, we conclude that FLT is the longest for the cubic AgCl crystals doped with 0.5% iodide at 80% doping position and 1×10^{-6} mol K_4Fe(CN)_6/molAg, whereas, for the highly photosensitized cubic AgBrCl crystals doped with K_4Fe(CN)_6, the photographic efficiency is optimal when the FLT reaches its minimum. The free photoelectron lifetime reaches minimum and the sensitivity of AgBrCl emulsion reaches maximum when the doping position is 30%Ag at K_4Fe(CN)_6 content of 10^{-6}mol/molAg.

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Electronic transport properties of metallic single-walled carbon nanotubes Cao Jue-Xian, Yan Xiao-Hong, Xiao Yang, Ding Jian-Wen 2003, 12 (12):  1440-1444.  doi: 10.1088/1009-1963/12/12/018 Abstract ( 0 )   PDF (278KB) ([an error occurred while processing this directive])   We have calculated the differential conductance of metallic carbon nanotubes by the scatter matrix method. It is found that the differential conductance of metallic nanotube-based devices oscillates as a function of the bias voltage between the two leads and the gate voltage. Oscillation period T is directly proportional to the reciprocal of nanotube length. In addition, we found that electronic transport properties are sensitive to variation of the length of the nanotube.

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Random matrices applied to superconductivity in nano-particles Chen Zhi-Qian, Cheng Nan-Pu, Li Zhen-Ya 2003, 12 (12):  1445-1450.  doi: 10.1088/1009-1963/12/12/019 Abstract ( 0 )   PDF (255KB) ([an error occurred while processing this directive])   In this paper we introduce an approach in which the random matrices are applied to superconducting nano-particles, and obtain the effects of enhancement and attenuation simultaneously. We also explore the influence of magnetic fields on the superconductivity and the condensation energies in nano-particles. Comparisons with other models and some experimental results are given.

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Up-conversion luminescence research of Er(0.5):ZBLAN material for volumetric display application when excited by 1520 nm laser Chen Xiao-Bo, Zhang Fu-Chu, Chen Luan 2003, 12 (12):  1451-1458.  doi: 10.1088/1009-1963/12/12/020 Abstract ( 0 )   PDF (269KB) ([an error occurred while processing this directive])   The up-conversion luminescence of the ZBLAN fluoride glass Er(0.5):ZBLAN, when excited by a 1520 nm semiconductor laser, is studied in this paper. The absorption and common-fluorescence spectra are also measured in order to understand the up-conversion clearly. It is found that there are seven strong up-conversion luminescence lines (406.97^m, 410.42 nm), (521.97^m, 527.56 nm), (542.38^m, 549.27 nm), (654.27^m, 665.70 nm), 801.57^m nm, 819.46 nm, and 840.00 nm, which can be recognized as the fluorescence transitions of ({}^2G^4F^2H)_{9/2}→{}^4I_{15/2},{}^2H_{11/2}→ {}^4I_{15/2},{}^4S_{3/2}→{}^4I_{15/2},{}^4F_{9/2}→{}^4I_{15/2}, {}^4I_{9/2}→ {}^4I_{15/2}, ({}^2G^4F^2H)_{9/2}→{}^4I_{9/2}, and {}^4S_{3/2}→{}^4I_{13/2} respectively. Meanwhile, the small up-conversion fluorescence lines 379.20 nm, 453.10 nm and 490.60 nm are the transitions of {}^4G_{11/2}→{}^4I_{15/2},{}^4F_{5/2}→{}^4I_{15/2} and {}^4F_{7/2}→ {}^4I_{15/2} respectively. It is interesting that the slopes of log F－logP curves, the double-logarithmic variation of up-conversion luminescence intensity F with laser power P, are different from each other for these observed up-conversion luminescence, this being valuable for the volumetric display. Comprehensive discussions find that the {}^4G_{11/2}→{}^4I_{15/2}, (^2G^4F^2H)_{9/2}→{}^4I_{15/2}, (^2H_{11/2}→{}^4I_{15/2},{}^4S_{3/2}→{}^4I_{15/2},{}^4F_{9/2}→ {}^4I_{15/2}), and {}^4I_{9/2}→{}^4I_{15/2} up-conversion luminescences are five-photon, four-photon, three-photon, and two-photon up-conversion luminescences respectively. It is found also that the absorption from ground-state {}^4I_{15/2} level to {}^4I_{13/2} level is very large, which is beneficial to the sequential energy transfer up-conversion to occur.

CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Effects of N2 and glow discharge on growth behaviours of carbon nanotubes prepared by the hot filament chemical vapour deposition method Wang Bi-Ben, Gu Chang-Zhi, Dou Yan, Wang Guo-Ju, Li Hai-Jun, Zhu Man-Kang 2003, 12 (12):  1459-1465.  doi: 10.1088/1009-1963/12/12/021 Abstract ( 0 )   PDF (270KB) ([an error occurred while processing this directive])   Carbon nanotubes (CNTs) are prepared by the hot filament chemical vapour deposition method using CH_4 and H_2 as reaction gases, and the growth behaviours are investigated by scanning electron microscopy and transmission electron microscopy. The results indicate that the CNTs prepared in the absence of N_2 or glow discharge are bent; however, they are in an aligned state after introducing N_2 into the chamber or forming glow discharge under a negative biased voltage. The results also indicate that the CNTs are of a bamboo-like structure when N_2 is intruded as a reaction gas and the alignment degree of the CNTs grown under glow discharge is higher than that grown in N_2. This illustrates that the nitric environment and glow discharge play important roles in the growth of CNTs. Combining with the theory related to alloy thermodynamics and collisions, we have analysed the growth mechanism of the CNTs in nitric environment and glow discharge.