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2003年, 第12卷, 第12期　刊出日期：2003-12-16 上一期    下一期

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The periodic wave solutions for two systems of nonlinear wave equations 王明亮, 王跃明, 张金良 2003 (12):  1341-1348.  doi: 10.1088/1009-1963/12/12/001 摘要 ( 1659 )   PDF(233KB) ( 758 )   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. 相关文章 | 计量指标

GENERAL

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Perturbation to symmetries and adiabatic invariants of a type of nonholonomic singular system 陈向炜, 李彦敏 2003 (12):  1349-1353.  doi: 10.1088/1009-1963/12/12/002 摘要 ( 1165 )   PDF(211KB) ( 569 )   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. 相关文章 | 计量指标

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Probabilistic teleportation of an arbitrary three-particle state via a partial entangled four-particle state and a partial entangled pair 戴宏毅, 李承祖, 陈平行 2003 (12):  1354-1359.  doi: 10.1088/1009-1963/12/12/003 摘要 ( 1361 )   PDF(209KB) ( 517 )   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. 相关文章 | 计量指标

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Double-wave description of mesoscopic resistance-inductance-capacitance coupled circuit with power source 张寿, 朱爱东, 金哲, 李哲奎, 潘淑梅, 赵永芳, 井孝功, 千正男, 苏文辉 2003 (12):  1360-1365.  doi: 10.1088/1009-1963/12/12/004 摘要 ( 1456 )   PDF(251KB) ( 413 )   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. 相关文章 | 计量指标

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Global vector-field reconstruction of nonlinear dynamical systems from a time series with SVD method and validation with Lyapunov exponents 刘卫东, K. F. Ren, S. Meunier-Guttin-Cluzel, G. Gouesbet 2003 (12):  1366-1373.  doi: 10.1088/1009-1963/12/12/005 摘要 ( 1144 )   PDF(297KB) ( 558 )   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. 相关文章 | 计量指标

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

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Topological susceptibility from overlap fermion 应和平, 张剑波 2003 (12):  1374-1377.  doi: 10.1088/1009-1963/12/12/006 摘要 ( 1210 )   PDF(209KB) ( 377 )   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. 相关文章 | 计量指标

NUCLEAR PHYSICS

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Numerical simulation of the early-time high altitude electromagnetic pulse 孟萃, 陈雨生, 刘顺坤, 谢秦川, 陈向跃, 龚建成 2003 (12):  1378-1382.  doi: 10.1088/1009-1963/12/12/007 摘要 ( 1341 )   PDF(262KB) ( 489 )   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. 相关文章 | 计量指标

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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 殷雯, 张国锋, 杜建红, 梁九卿 2003 (12):  1383-1385.  doi: 10.1088/1009-1963/12/12/008 摘要 ( 1295 )   PDF(186KB) ( 515 )   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. 相关文章 | 计量指标

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Femtosecond laser-induced long-lasting phosphorescence in Pr3+-doped ZnO-B2O3-SiO2 glass 姜雄伟, 邱建荣, 曾惠丹, 朱从善 2003 (12):  1386-1389.  doi: 10.1088/1009-1963/12/12/009 摘要 ( 1234 )   PDF(196KB) ( 629 )   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. 相关文章 | 计量指标

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Near threshold photodetachment cross section of negative atomic oxygen ions 吴建华, 袁建民, Vo Ky Lan 2003 (12):  1390-1394.  doi: 10.1088/1009-1963/12/12/010 摘要 ( 1284 )   PDF(224KB) ( 487 )   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. 相关文章 | 计量指标

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Triple differential cross section in ionization of hydrogen by electron impact 张程华, 邱巍, 辛俊丽, 牛英煜, 王晓伟, 王京阳 2003 (12):  1395-1398.  doi: 10.1088/1009-1963/12/12/011 摘要 ( 1414 )   PDF(223KB) ( 430 )   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. 相关文章 | 计量指标

CLASSICAL AREAS OF PHENOMENOLOGY

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Two-mode mazer injected with V-type three-level atoms 梁文青, 张智明, 谢绳武 2003 (12):  1399-1413.  doi: 10.1088/1009-1963/12/12/012 摘要 ( 1201 )   PDF(408KB) ( 473 )   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. 相关文章 | 计量指标

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A simple method for boosting the beam quality of commercial DPL 张光寅, 焦志勇, 颜彩繁, 丁欣, 张潮波, 张晓华, 顾学文, 宋峰 2003 (12):  1414-1416.  doi: 10.1088/1009-1963/12/12/013 摘要 ( 1092 )   PDF(188KB) ( 365 )   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. 相关文章 | 计量指标

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Analysis of the laser performance of Tm3+, Tb3+(Ho3+):YVO4 crystals at ～1.5μm wavelength 黄莉蕾, 付晏彬, 邬良能 2003 (12):  1417-1422.  doi: 10.1088/1009-1963/12/12/014 摘要 ( 1284 )   PDF(280KB) ( 453 )   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. 相关文章 | 计量指标

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Study of the stability of polarization mode dispersion in fibre 付松年, 吴重庆, 刘海涛, 沈平, 董晖 2003 (12):  1423-1428.  doi: 10.1088/1009-1963/12/12/015 摘要 ( 1359 )   PDF(266KB) ( 492 )   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. 相关文章 | 计量指标

CLASSICAL AREAS OF PHENOMENOLOGY

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Breakdown of the chain of ring vortices in a transitional boundary layer 李存标 2003 (12):  1429-1434.  doi: 10.1088/1009-1963/12/12/016 摘要 ( 1310 )   PDF(333KB) ( 401 )   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. 相关文章 | 计量指标

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Investigation of the photoelectron decay of silver halide microcrystal 杨少鹏, 傅广生, 董国义, 李晓苇, 韩理 2003 (12):  1435-1439.  doi: 10.1088/1009-1963/12/12/017 摘要 ( 1145 )   PDF(217KB) ( 588 )   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. 相关文章 | 计量指标

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Electronic transport properties of metallic single-walled carbon nanotubes 曹觉先, 颜晓红, 肖杨, 丁建文 2003 (12):  1440-1444.  doi: 10.1088/1009-1963/12/12/018 摘要 ( 1574 )   PDF(278KB) ( 499 )   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. 相关文章 | 计量指标

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Random matrices applied to superconductivity in nano-particles 陈志谦, 程南璞, 李振亚 2003 (12):  1445-1450.  doi: 10.1088/1009-1963/12/12/019 摘要 ( 1174 )   PDF(255KB) ( 416 )   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. 相关文章 | 计量指标

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Up-conversion luminescence research of Er(0.5):ZBLAN material for volumetric display application when excited by 1520 nm laser 陈晓波, 张福初, 陈鸾 2003 (12):  1451-1458.  doi: 10.1088/1009-1963/12/12/020 摘要 ( 1258 )   PDF(269KB) ( 343 )   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. 相关文章 | 计量指标

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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 王必本, 顾长志, 窦艳, 王国菊, 李海均, 朱满康 2003 (12):  1459-1465.  doi: 10.1088/1009-1963/12/12/021 摘要 ( 928 )   PDF(270KB) ( 500 )   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. 相关文章 | 计量指标