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2002年, 第11卷, 第11期　刊出日期：2002-11-12 上一期    下一期

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Generalized energy integral and reduction of rotational relativistic Birkhoffian system 罗绍凯 2002 (11):  1097-1100.  doi: 10.1088/1009-1963/11/11/301 摘要 ( 1149 )   PDF(197KB) ( 508 )   We study the order reduction method of the rotational relativistic Birkhoffian equations. For a rotational relativistic autonomous Birkhoffian system, if the conservative law of the Birkhoffian holds, the conservative quantity can be called the generalized energy integral. Through the generalized energy integral, the order of the system can be reduced. If the rotational relativistic Birkhoffian system has a generalized energy integral, then the Birkhoffian equations can be reduced by at least two degrees and the Birkhoffian form can be kept. An example is given to illustrate the application of the result. 相关文章 | 计量指标

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Coherent soliton structures of the (2+1)-dimensional long-wave－short-wave resonance interaction equation 黄文华, 张解放, 盛正卯 2002 (11):  1101-1105.  doi: 10.1088/1009-1963/11/11/302 摘要 ( 1198 )   PDF(303KB) ( 641 )   The variable separation approach is used to find exact solutions of the (2+1)-dimensional long-wave－short-wave resonance interaction equation. The abundance of the coherent soliton structures of this model is introduced by the entrance of an arbitrary function of the seed solutions. For some special selections of the arbitrary function, it is shown that the coherent soliton structures may be dromions, solitoffs, etc. 相关文章 | 计量指标

GENERAL

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Stochastic resonance in a financial model 毛晓明, 孙锴, 欧阳颀 2002 (11):  1106-1110.  doi: 10.1088/1009-1963/11/11/303 摘要 ( 1555 )   PDF(224KB) ( 662 )   We report on our model study of stochastic resonance in the stock market using numerical simulation and analysis. In the model, we take the interest rate as the external signal, the randomness of traders' behaviour as the noise, and the stock price as the output. With computer simulations, we find that the system demonstrates a characteristic of stochastic resonance as noise intensity varies. An analytical explanation is proposed. 相关文章 | 计量指标

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Mapping deformation method and its application to nonlinear equations 李画眉 2002 (11):  1111-1114.  doi: 10.1088/1009-1963/11/11/304 摘要 ( 1425 )   PDF(191KB) ( 549 )   An extended mapping deformation method is proposed for finding new exact travelling wave solutions of nonlinear partial differential equations (PDEs). The key idea of this method is to take full advantage of the simple algebraic mapping relation between the solutions of the PDEs and those of the cubic nonlinear Klein－Gordon equation. This is applied to solve a system of variant Boussinesq equations. As a result, many explicit and exact solutions are obtained, including solitary wave solutions, periodic wave solutions, Jacobian elliptic function solutions and other exact solutions. 相关文章 | 计量指标

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Study of the Wada fractal boundary and indeterminate crisis 洪灵, 徐健学 2002 (11):  1115-1123.  doi: 10.1088/1009-1963/11/11/305 摘要 ( 1264 )   PDF(452KB) ( 507 )   By using the generalized cell mapping digraph (GCMD) method, we study bifurcations governing the escape of periodically forced oscillators in a potential well, in which a chaotic saddle plays an extremely important role. In this paper, we find the chaotic saddle, and we demonstrate that the chaotic saddle is embedded in a strange fractal boundary which has the Wada property, that any point on the boundary of that basin is also simultaneously on the boundary of at least two other basins. The chaotic saddle in the Wada fractal boundary, by colliding with a chaotic attractor, leads to a chaotic boundary crisis with a global indeterminate outcome which presents an extreme form of indeterminacy in a dynamical system. We also investigate the origin and evolution of the chaotic saddle in the Wada fractal boundary, particularly concentrating on its discontinuous bifurcations (metamorphoses). We demonstrate that the chaotic saddle in the Wada fractal boundary is created by the collision between two chaotic saddles in different fractal boundaries. After a final escape bifurcation, there only exists the attractor at infinity; a chaotic saddle with a beautiful pattern is left behind in phase space. 相关文章 | 计量指标

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A secure communication method for a high-power information signal based on chaotic masking 李建芬, 李农 2002 (11):  1124-1127.  doi: 10.1088/1009-1963/11/11/306 摘要 ( 1285 )   PDF(216KB) ( 471 )   In this paper, we present a secure communication method for a high-power information signal based on chaotic masking. In the transmitter, an adaptive controller is adopted to pick up the change of the information signal, and to inject the controller's error into the transmitting system. At the same time, the information is directly added to the chaotic signal in transmission to drive the receiving system. In the receiver, another adaptive controller is used to maintain chaotic synchronization of the transmitting and receiving systems and to recover the information signal. Since the synchronization error is independent from the information signal, the power of the information signal can be equivalent to that of the chaotic signal, and the frequency of the information signal can be set within the range of the principal frequencies of the chaotic signal. The results of theoretical analysis and numerical simulation show that the presented method not only enhances the degree of security of low-dimensional chaotic systems but also significantly improves the signal-to-noise ratio at the receiving end. 相关文章 | 计量指标

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Analysis of the stability and density waves for traffic flow 薛郁 2002 (11):  1128-1134.  doi: 10.1088/1009-1963/11/11/307 摘要 ( 1501 )   PDF(297KB) ( 997 )   In this paper, the optimal velocity model of traffic is extended to take into account the relative velocity. The stability and density waves for traffic flow are investigated analytically with the perturbation method. The stability criterion is derived by the linear stability analysis. It is shown that the triangular shock wave, soliton wave and kink wave appear respectively in our model for density waves in the three regions: stable, metastable and unstable regions. These correspond to the solutions of the Burgers equation, Korteweg－de Vries equation and modified Korteweg－de Vries equation. The analytical results are confirmed to be in good agreement with those of numerical simulation. All the results indicate that the interaction of a car with relative velocity can affect the stability of the traffic flow and raise critical density. 相关文章 | 计量指标

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A scanning superconducting quantum interference device microscope for room temperature samples 丁红胜, 张峰会, 颜晓明, 韩士吉, 董世迎, 于洪伟, 陈赓华, 何豫生 2002 (11):  1135-1139.  doi: 10.1088/1009-1963/11/11/308 摘要 ( 1256 )   PDF(400KB) ( 563 )   We have constructed a scanning low-Tc superconducting quantum interference device (SQUID) microscope, in which the SQUID is mounted on the lower end of a copper rod and cooled to liquid helium temperature. There is a 65μm thick sapphire window under the SQUID. The sample at room temperature underneath the window can be scanned to produce magnetic images. The microscope has a spatial resolution of 100－150μm and a magnetic field sensitivity of 3－60pT/$\sqrt{Hz}$ in a magnetically unshielded environment. We have used this scanning SQUID microscope to measure various room temperature samples. 相关文章 | 计量指标

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

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Heavy meson spectra for heavy quark potential in quantum chromodynamics with dilaton 陈洪, 杨兴华, 姜焕清 2002 (11):  1140-1144.  doi: 10.1088/1009-1963/11/11/309 摘要 ( 1010 )   PDF(233KB) ( 365 )   For heavy meson systems, we study the heavy quark potential, which emerges from the effective dilaton－gluon coupling inspired from the superstring theory. We put emphasis on the new confinement generating mechanism of this potential through the investigation of the spin-averaged energy levels of the heavy meson systems. By using a unified approach to the solutions of the Schr?dinger and the spinless Salpeter equations, we can examine in a realistic way the effects of using a relativistic kinetic energy. The obtained results agree favourably with other predictions, and the relativistic equation can better account for the observed energy levels. 相关文章 | 计量指标

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A method of detecting capture γ-rays in a strong pulsed radiation field 徐荣昆, 唐正元, 何锡钧 2002 (11):  1145-1148.  doi: 10.1088/1009-1963/11/11/310 摘要 ( 1097 )   PDF(224KB) ( 451 )   We present a technology for diagnosing the D－T fusion process by detecting capture γ-rays. This technology provides an alternative route to diagnosing the D－T reaction process when a great deal of heavy Z materials surrounds the D－T region. A very important aspect of this paper is to focus on the methods of shielding low-energy γ-rays whose radiation intensity is 106 times higher than that of the capture γ-rays. Another aspect is about how to distinguish signal from noise. The result of a 50/1 signal-to-noise ratio indicates that the designed double-magnetic spectrograph is very successful for diagnosing the D－T fusion reaction process. 相关文章 | 计量指标

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Experimental and theoretical investigations of absolute optical oscillator strengths for valence excitations of nitric oxide 朱林繁, 钟志萍, 苑震生, 张卫华, 刘小井, 江锡满, 徐克尊, 李家明 2002 (11):  1149-1156.  doi: 10.1088/1009-1963/11/11/311 摘要 ( 1131 )   PDF(284KB) ( 462 )   The absolute optical oscillator strength density spectra of nitric oxide in the energy region of 5.0－22.0 eV have been measured by a high-resolution fast-electron energy loss spectrometer. With the calculated results obtained by the multiscattering self-consistent-field method and channel characteristics, the strongly overlapped spectra in the energy region of 7.5－9.3 eV have been analysed and the corresponding partially vibrationally resolved optical oscillator strengths have been estimated from the experimental spectra. 相关文章 | 计量指标

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Generations of dark hollow beams and their applications in laser cooling of atoms and all optical-type Bose－Einstein condensation 印建平, 高伟建, 王海峰, 龙全, 王育竹 2002 (11):  1157-1169.  doi: 10.1088/1009-1963/11/11/312 摘要 ( 1739 )   PDF(524KB) ( 906 )   We report on a new experimental result to generate dark hollow beams by using a geometric optical method. We propose two new methods to produce focused and localized hollow laser beams by using π-phase plates. Using Monte-Carlo simulations, we have studied the Sisyphus cooling of alkali atoms in pyramidal hollow beam gravito-optical traps. We discuss some potential applications of the dark hollow beams in atom optics and the preparation of an all optically-cooled and optically-trapped atomic Bose－Einstein condensation (BEC). Our research shows that an ultracold atomic sample with a temperature of ～ 2μK can be obtained in the pyramidal hollow beam dipole trap and an all optical-type BEC may be realized in a far blue-detuned, hollow beam trap. 相关文章 | 计量指标

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Analysis of far-infrared laser magnetic resonance spectra of CH2Br at 447.3 and 671.1μm 刘煜炎, 黄光明, 段传喜, 石丽华, 蔡欣 2002 (11):  1170-1174.  doi: 10.1088/1009-1963/11/11/313 摘要 ( 1353 )   PDF(264KB) ( 391 )   A simple model has been developed to describe the Zeeman patterns of far-infrared laser magnetic resonance spectra of the monobromomethyl radical CH2Br observed at 447.3 and 671.1μm. A satisfactory agreement between the experimental spectra of the radical and their simulation with this simple model has been achieved. This approach can be used to gain further information about the structure and the spectrum of this interesting radical. 相关文章 | 计量指标

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Dispersive properties of tunnelling-induced transparency in an asymmetric double quantum well 苏雪梅, 卓仲畅, 王立军, 高锦岳 2002 (11):  1175-1178.  doi: 10.1088/1009-1963/11/11/314 摘要 ( 1373 )   PDF(209KB) ( 556 )   We have investigated the dispersive properties of tunnelling-induced transparency in asymmetric double quantum well structures where two excited states are coupled by resonant tunnelling through a thin barrier in a three-level system of electronic subbands. The intersubband transitions exhibit high dispersion at zero absorption, which leads to the slow light velocity in this medium as compared with that in vacuum (c=3×108). The group velocity in a specific GaAs/AlGaAs sample is calculated to be vg=c/4.30. This structure can be used to compensate for the dispersion and energy loss in fibre optical communications. 相关文章 | 计量指标

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Lasing features of dye-doped pendant drops added with polymer particles: spectral blueshift and intensity enhancement 普小云, 张曙, 陈超华, 李荣基 2002 (11):  1179-1183.  doi: 10.1088/1009-1963/11/11/315 摘要 ( 999 )   PDF(237KB) ( 521 )   When micrometre-sized polymer particles were added into a dye-doped pendant drop that acted as a quasi-two-dimensional circular resonator, we found a blueshift of the peak wavelength of its lasing spectrum. The lasing output was also enhanced by the particles. The spectral blueshift was explained by a model of dye lasing in a circular cavity. The model includes losses of the scattering particles, medium absorption, and radiation leakage. An optimum particle density for maximum lasing output was deduced. The results are consistent with our experimental findings. 相关文章 | 计量指标

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Modulational instability of ion-acoustic waves in a warm plasma 薛具奎, 段文山, 郎和 2002 (11):  1184-1187.  doi: 10.1088/1009-1963/11/11/316 摘要 ( 1505 )   PDF(218KB) ( 1165 )   Using the standard reductive perturbation technique, a nonlinear Schr?dinger equation is derived to study the modulational instability of finite-amplitude ion-acoustic waves in a non-magnetized warm plasma. It is found that the inclusion of ion temperature in the equation modifies the nature of the ion-acoustic wave stability and the soliton structures. The effects of ion plasma temperature on the modulational stability and ion-acoustic wave properties are investigated in detail. 相关文章 | 计量指标

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Bulk sound velocity of porous materials at high pressures 耿华运, 吴强, 谭华, 蔡灵仓, 经福谦 2002 (11):  1188-1192.  doi: 10.1088/1009-1963/11/11/317 摘要 ( 1459 )   PDF(248KB) ( 837 )   A correction of Walsh's method for bulk sound velocity calculation for shocked porous materials is accomplished based on the Wu－Jing thermodynamic equation of state. The corrected bulk velocities for solid and porous samples with low porosities are in good agreement with the corresponding experimental data published previously. On the basis of this corrected equation, the influence of thermoelectrons on the bulk velocity of shocked materials is discussed in detail at pressures of 50, 70 and 200 GPa. Some interesting phenomena are revealed, which seem to be the unique features of a dynamic-pressure-loading process and could not be found in static experiments. 相关文章 | 计量指标

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The virial theorem in refined Thomas－Fermi－Dirac theory for the interior of atoms in a solid 朱如曾, 文玉华, 钱劲 2002 (11):  1193-1195.  doi: 10.1088/1009-1963/11/11/318 摘要 ( 999 )   PDF(145KB) ( 582 )   The virial theorem in refined Thomas－Fermi－Dirac theory for the interior of atoms in a solid is given and proven. 相关文章 | 计量指标

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Reversible, electrical and optical switching on silver 3-phenyl-1-ureidonitrile complex thin films 张昊旭, 时东霞, 宋延林, 刘虹雯, 侯士敏, 薛增泉, 高鸿钧 2002 (11):  1196-1199.  doi: 10.1088/1009-1963/11/11/319 摘要 ( 1155 )   PDF(238KB) ( 534 )   We report on the reversible, electrical and optical switching on silver 3-phenyl-1-ureidonitrile complex thin films. The films can switch from a high impedance state to a low impedance state with an applied electric field at the threshold of 3.5×107V/m. Furthermore, the films can be switched back to the original state by treating the samples at about 80℃. The optical recording is fulfilled using a semiconductor laser with a wavelength of 780 nm. Erasure can be accomplished by bulk heating or by the laser working with the power beneath the threshold. No loss of the organic was found in the experiments. This material may have a potential application in ultrahigh data density storage. 相关文章 | 计量指标

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

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Dynamic behaviour of a single-Cooper-pair box in a single-mode quantized field with dissipation 姚延荪, 邹健, 邵彬 2002 (11):  1200-1204.  doi: 10.1088/1009-1963/11/11/320 摘要 ( 988 )   PDF(218KB) ( 482 )   We study the quantum dynamics of a single-Cooper-pair box biased by a classical voltage and also irradiated by a single-mode quantized field. We demonstrate that under the weak damping, the collapse-revival phenomena can exist in this system. We also demonstrate that the revivals of oscillations are sensitive to the initial coherent field and the damping rate of the single-mode quantized field. 相关文章 | 计量指标