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2001年, 第10卷, 第7期　刊出日期：2001-07-15 上一期    下一期

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SOME PROGRESS IN THE LATTICE BOLTZMANN MODEL 冯士德, Tsutahara Michihisa, 季仲贞 2001 (7):  587-593.  doi: 10.1088/1009-1963/10/7/301 摘要 ( 1015 )   PDF(260KB) ( 533 )   A lattice Boltzmann equation model has been developed by using the equilibrium distribution function of the Maxwell－Boltzmann-like form, which is third order in fluid velocity uα. The criteria of energy conservation between the macroscopic physical quantities and the microscopic particles are introduced into the model, thus the thermal hydrodynamic equations containing the effect of buoyancy force can be recovered in terms of the Taylor and Chapman－Enskog asymptotic expansion methods. The two-dimensional thermal convection phenomena in a square cavity and between two concentric cylinders have been calculated by implementing a heat flux boundary condition. Both numerical results are in good agreement with the conventional numerical results. 相关文章 | 计量指标

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DIRECT APPROACH FOR SOLITON PERTURBATIONS BASED ON THE GREEN'S FUNCTION 潘留仙, 颜家壬, 周光辉 2001 (7):  594-598.  doi: 10.1088/1009-1963/10/7/302 摘要 ( 1146 )   PDF(232KB) ( 517 )   A direct approach has been developed for soliton perturbations based on the Green's function. We first linearized the soliton equation, and then derived the Green's function corresponding to approximation equations of different orders. Finally, we obtained the effects of perturbation on a soliton, namely both the slow time dependence of the soliton parameters and the corrections up to the second-order approximation. The higher-order effects can also be obtained in the same way. 相关文章 | 计量指标

GENERAL

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ADDING ONE BIFURCATION IN A ROTOR SYSTEM WITH CLEARANCES 孙政策, 徐健学 2001 (7):  599-605.  doi: 10.1088/1009-1963/10/7/303 摘要 ( 981 )   PDF(194KB) ( 493 )   A mathematical model of a rotor system with clearances is analysed by the application of modern nonlinear dynamic theory. From the bifurcation diagrams, it is discovered that the rotor system alternates between periodic and chaotic motions at a supercritical rotational speed, and after undergoing a chaotic region the periodic number of the motion will increase by one. At the same time, the periodic number is equal correspondingly to the integral multiple of the critical rotational speed. At the subcritical rotational speed, it is discovered that the chaotic bands among successive orders of superharmonic responses return to the period one through a reversed period-doubling bifurcation, as a result of a period-doubling bifurcation. It is shown that the increase of damping may reduce the width of the chaotic bands and the amplitude of the periodic response; the increase of nonlinear degree also leads to the reduction of chaotic bandwidth, but makes the amplitude of the subharmonic response increase. So it is suggested that proper damping and correct material selection by considering the dynamic characteristics of the rotor system may reduce the proportion of faults and enhance the dynamic characteristics when designing the rotor system. The working speed should not be selected at N times its natural frequency and should not be set in the chaotic bands among the successive orders of periodic motion for the same purpose. 相关文章 | 计量指标

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SYNCHRONIZATION FOR A CLASS OF CHAOTIC SYSTEMS BASED UPON OBSERVER THEORY 刘锋, 任勇, 山秀明, 邱祖廉 2001 (7):  606-610.  doi: 10.1088/1009-1963/10/7/304 摘要 ( 1213 )   PDF(111KB) ( 425 )   A new synchronization theorem for a class of chaotic systems is presented based on nonlinear observer theory. We take the first state variable of the drive system as the driving scalar signal. Its linear feedback gain is a function of a free parameter. It is proven that global synchronization can be attained through simple linear output error feedback. This approach is illustrated by the WGY hyperchaotic system and Chua's oscillator. 相关文章 | 计量指标

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NEW MESON MASS RELATION AND LOWEST PSEUDOSCALAR GLUEBALL MASS 吴宁, 阮图南, 郑志鹏 2001 (7):  611-612.  doi: 10.1088/1009-1963/10/7/305 摘要 ( 1128 )   PDF(176KB) ( 472 )   After considering its mixing with the glueball, we give a new mass relation for the meson nonet. According to this mass relation and the predicted mass of the pseudoscalar glueball given by lattice calculations and the effective Hamiltonian, the expected mass of the mixed pseudoscalar glueball is about 1.7 GeV. This result is helpful in the experimental search for the mixed isoscalar pseudoscalar glueball. η(1760) is discussed as a possible candidate for this type of particle. 相关文章 | 计量指标

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A NONLINEAR ANALYTICAL AND NUMERICAL STUDY FOR AN OPEN SYSTEM WITH COHERENT OFF-RESONANCE FIELDS 樊锡君, 李萍, 田淑芬, 张郡亮, 刘呈普 2001 (7):  613-620.  doi: 10.1088/1009-1963/10/7/306 摘要 ( 1424 )   PDF(193KB) ( 394 )   An exact nonlinear analytical solution of an open V-type inversionless lasing system with two incoherent pump fields, off-resonant driving and probe fields is given. Through qualitative and quantitative comparison of the gain, dispersion and population differences of the linear and nonlinear cases, some conclusions concerning the Rabi frequencies of the driving and the probe fields are drawn and discussed in detail. 相关文章 | 计量指标

CLASSICAL AREAS OF PHENOMENOLOGY

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DESIGN OF A 532nm Nd:YVO4/KTP SINGLE-FREQUENCY LASER 徐春林, 沈乃澂, 臧二军, 孙义民, 鲁海宁, 赵昆, 张学斌 2001 (7):  621-625.  doi: 10.1088/1009-1963/10/7/307 摘要 ( 1445 )   PDF(306KB) ( 1077 )   A model of the laser-diode pumped solid-state laser is developed to deduce the minimum average radii of the pump beam in the solid medium, since the smaller the cavity waist, the higher the laser output power is expected to be. With an appropriate coupling system consisting of the collimating lens, prism pair and focusing lens, a diode-pumped single-frequency Nd:YVO4/KTP intracavity frequency-doubling cw laser has been demonstrated through the precise temperature control of the Nd:YVO4 crystal, the KTP crystal and the diode laser. The 532nm single-frequency output power of 40.4mW (in fact 55mW if the reflection loss of the triangular prism is taken into account) is obtained for an incident power of 515mW. It is derived theoretically and is verified in experiment that the frequency drift of the free-running laser can be reduced by increasing the cavity length. 相关文章 | 计量指标

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NONLINEAR PULSE PROPAGATION IN TWIN-CORE FIBRES WITH BIREFRINGENCE 李宏, 黄德修 2001 (7):  626-630.  doi: 10.1088/1009-1963/10/7/308 摘要 ( 1007 )   PDF(211KB) ( 420 )   An equation describing the nonlinear pulse propagation in twin-core fibres with birefringence is derived. Particularly, the properties of the nonlinear coupling equation are analysed, and modulational instability is discussed in detail. 相关文章 | 计量指标

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FABRICATION AND APPLICATION OF NEAR-FIELD OPTICAL FIBRE PROBE 孙家林, 徐建华, 田广彦, 郭继华, 赵钧, 谢爱芳, 张泽渤 2001 (7):  631-635.  doi: 10.1088/1009-1963/10/7/309 摘要 ( 1204 )   PDF(851KB) ( 442 )   In this paper, the fabrication of a large cone angle near-field optical fibre probe, using the two-step chemical etching method and bent probe, is introduced, and the controlling parameters of the coated Cr－Al film at the probe tip are presented. The scanning electron microscopy images display that the tip diameter of the uncoated large cone angle fibre probe obtained is less than 50nm, the cone angle over 90°, and the diameter of light aperture at the coated probe tip is less than 100nm. The measured results of the optical transmission efficiency for various probe tips show that the uncoated straight optical fibre probe, film-coated straight probe and film-coated bent probe are 3×10-1, 2×10-3, and 1×10-4 times that of the flat fibre probe, respectively. In addition, the force images and near-field optical images of a standard sample are acquired using a large cone angle and film-coated bent probe. 相关文章 | 计量指标

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TO ENHANCE THE INTENSITY OF SONOLUMINESCENCE 钱祖文 2001 (7):  636-638.  doi: 10.1088/1009-1963/10/7/310 摘要 ( 1009 )   PDF(179KB) ( 535 )   The transient resonance of a sonoluminescence bubble has been analysed. When the bubble performs its transient resonance at the nth order harmonics of the standing waves in the liquid, the light intensity strongly depends on the amplitude of the driving pressure (proportional to its 2n power, with n=fr/f, where fr is Minnaert's linear resonant frequency of the bubble and f is the frequency of driving sound). The kinetic energy of a vibrating bubble becomes maximum approximately when it is in its equilibrium size. For example, when the ambient temperature of a bubble decreases from 34℃ to 4℃, a huge increase of the light intensity emitted by it can be explained. A suggestion was made that, within the limits permitted by the phase diagrams, as high an increase in driving pressure as possible could enhance the light intensity of sonoluminescence up to four orders of magnitude. 相关文章 | 计量指标

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ELECTRON TRANSPORT BEHAVIOURS IN THE NITROGEN DIRECT CURRENT GLOW DISCHARGE 张连珠, 于威, 王久丽, 韩理, 傅广生 2001 (7):  639-644.  doi: 10.1088/1009-1963/10/7/311 摘要 ( 1052 )   PDF(147KB) ( 542 )   A Monte Carlo simulation is presented to describe the electron transport behaviours in the nitrogen direct current glow discharge. The energy and angular distributions of the electrons at different positions of the cathode dark space are calculated; their energy and density distribution features throughout the entire discharge are discussed. The influence of molecular vibrational excitation, typical for electron－molecule collisions, has been studied and the elementary process of active species generation has been illustrated. The simulated results reveal that, in the cathode dark space, the high-energy electrons are mainly forward scattering and behave as a high-energy ‘electron beam'. The sharp increase of the number of secondary electrons plays an important role in producing active species at the interface between the cathode dark space and the negative glow region. The vibrational excitation enhances the energy loss of electrons in the negative glow region. 相关文章 | 计量指标

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ON THE SATURATION BEHAVIOUR OF TWISTED NEMATIC LIQUID CRYSTAL CELLS WITH A NONZERO PRETILT ANGLE 张志东, 于慧, 李丽 2001 (7):  645-649.  doi: 10.1088/1009-1963/10/7/312 摘要 ( 1177 )   PDF(122KB) ( 481 )   Equations are obtained for the surface tilt angle and the twist angle of the director in a twisted nematic liquid crystal cell under a high magnetic field. Under a zero pretilt angle, the two equations reduce to those obtained by Sugimura et al. This fact has also been demonstrated numerically. With finite field strength and nonzero pretilt angle, no saturation transition exists. 相关文章 | 计量指标

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INFRARED EMISSION FROM Si IMPLANTED WITH HIGH Er CONCENTRATION 肖志松, 徐飞, 张通和, 程国安, 谢大韬, 顾岚岚 2001 (7):  650-654.  doi: 10.1088/1009-1963/10/7/313 摘要 ( 1245 )   PDF(390KB) ( 520 )   Erbium-doped silicon has been fabricated by ion implantation performed on a metal vapour vacuum arc ion source. After rapid thermal annealing (RTA), 1.54μm photoluminescence was observed at 77K. Rutherford backscattering spectrum indicated that Er ions are mainly distributed near the surface of the samples, and Er concentration exceeded 1021cm-3. Needle nanometre crystalline silicon (nc-Si) was formed on the substrate surface. Band edge emission spectrum at 10K verified that the minority carrier lifetime increased upon RTA. The photocarrier mediated processes enabled energy transferring from nc-Si (or c-Si) to the Er3+ ions and resulted in light emission of 1.54μm. 相关文章 | 计量指标

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EXCITON ENERGY OF THE InAs/GaAs SELF-ASSEMBLED QUANTUM DOT IN A SEMICONDUCTOR MICROCAVITY 潘留仙, 李树深, 夏建白 2001 (7):  655-657.  doi: 10.1088/1009-1963/10/7/314 摘要 ( 1208 )   PDF(107KB) ( 482 )   We report on the theoretical study of the interaction of the quantum dot (QD) exciton with the photon waveguide models in a semiconductor microcavity. The InAs/GaAs self-assembled QD exciton energies are calculated in a microcavity. The calculated results reveal that the electromagnetic field reduces the exciton energies in a semiconductor microcavity. The effect of the electromagnetic field decreases as the radius of the QD increases. Our calculated results are useful for designing and fabricating photoelectron devices. 相关文章 | 计量指标

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A FORMULA FOR CALCULATING THE ERRORS OF SUPERCONDUCTING MAGNETIZATION CURVE 郭树权, 刘梦林, 郑东宁, 赵柏儒 2001 (7):  658-661.  doi: 10.1088/1009-1963/10/7/315 摘要 ( 1141 )   PDF(121KB) ( 485 )   Because of field inhomogeneity in the magnetization measurement system, large errors may exist in the decreasing field superconducting magnetization curves, but not in the increasing field curves. The physical origin of the large errors is proposed here. A simple formula for calculating the errors is given. This formula is consistent with the experimental data. 相关文章 | 计量指标

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GAMMA-RAY LIGHT CURVE AND PHASE-RESOLVED SPECTRA FROM GEMINGA PULSAR 张力, 边霞, 梅冬成 2001 (7):  662-665.  doi: 10.1088/1009-1963/10/7/316 摘要 ( 1040 )   PDF(138KB) ( 470 )   We calculate the light curve and phase-resolved spectra of Geminga in a three-dimensional pulsar magnetosphere model. The light curve of gamma-rays is consistent with that observed if the magnetic inclination and viewing angle are ～50° and ～86° respectively. We also model the phase-resolved spectra of the Geminga pulsar. 相关文章 | 计量指标