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2004年, 第13卷, 第1期　刊出日期：2004-01-22 上一期    下一期

GENERAL

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Backlünd transformation and multiple soliton solutions for the (3+1)-dimensional Nizhnik－Novikov－Veselov equation 白成林 2004 (1):  1-4.  doi: 10.1088/1009-1963/13/1/001 摘要 ( 1292 )   PDF(139KB) ( 607 )   We develop an approach to construct multiple soliton solutions of the (3+1)-dimensional nonlinear evolution equation. We take the (3+1)-dimensional Nizhnik－Novikov－Veselov (NNV) equation as an example. Using the extended homogeneous balance method, one can find a Backlünd transformation to decompose the (3+1)-dimensional NNV into a set of partial differential equations. Starting from these partial differential equations, some multiple soliton solutions for the (3+1)-dimensional NNV equation are obtained by introducing a class of formal solutions. 相关文章 | 计量指标

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Extended Jacobi elliptic function method and its applications to (2+1)﹣dimensional dispersive long-wave equation 陈勇, 李彪, 张鸿庆 2004 (1):  5-10.  doi: 10.1088/1009-1963/13/1/002 摘要 ( 1406 )   PDF(173KB) ( 527 )   An extended Jacobi elliptic function method is proposed for constructing the exact double periodic solutions of nonlinear partial differential equations (PDEs) in a unified way. It is shown that these solutions exactly degenerate to the many types of soliton solutions in a limited condition. The Wu－Zhang equation (which describes the (2+1)﹣dimensional dispersive long wave) is investigated by this means and more formal double periodic solutions are obtained. 相关文章 | 计量指标

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The experiment on the saturation polarization of Rb vapour 黄湘友, 游佩林, 杜为民 2004 (1):  11-13.  doi: 10.1088/1009-1963/13/1/003 摘要 ( 1435 )   PDF(158KB) ( 449 )   A cylindrical capacitor containing rubidium vapour is made. The capacitance of it at different voltages is measured under a certain Rb vapour pressure. The experimental C－V curve shows that the saturation polarization of Rb vapour is easily observed. The experiment further supports the idea that the Rb atom has a large permanent electric dipole moment. 相关文章 | 计量指标

GENERAL

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Implementation of non-local multiple qubits controlled-not operation via partially entangled channels 陈立冰, 路洪 2004 (1):  14-18.  doi: 10.1088/1009-1963/13/1/004 摘要 ( 1241 )   PDF(162KB) ( 406 )   We propose two different schemes for probabilistic implementing a non-local multiple qubits controlled-not operation via partially entangled quantum channels. The overall physical resources required for accomplishing these schemes are different, and the successful implementation probabilities are also different. 相关文章 | 计量指标

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Research on high-T-c SQUID based non-destructive evaluation 王会武, 孔祥燕, 任育峰, 于洪伟, 丁红胜, 赵士平, 陈赓华, 周岳亮, 张利华, 何豫生, 杨乾声 2004 (1):  19-23.  doi: 10.1088/1009-1963/13/1/005 摘要 ( 1256 )   PDF(1447KB) ( 426 )   A non-destructive evaluation system based on high-T_c dc-SQUID (superconducting quantum interference device) incorporating a gradient field excitation has been built. By using this system a 1mm-diameter hole at a depth of 2mm inside an aluminium plate at room temperature can be easily detected and imaged in an unshielded environment. The relation between the spatial resolution, or the smallest detectable flaw size, and experimental parameters is briefly analysed in terms of a simple metal ring model. The result shows that the spatial resolution depends strongly on the sensor-sample separation as well as on some other parameters, such as signal-to-noise ratio of excitation, excitation frequency and material conductivity. 相关文章 | 计量指标

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Kinetic energy release of diatomic and linear triatomic molecules in intense femtosecond laser fields 陈建新, 马日, 任海振, 李霞, 吴成印, 杨宏, 龚旗煌 2004 (1):  24-29.  doi: 10.1088/1009-1963/13/1/006 摘要 ( 1297 )   PDF(261KB) ( 484 )   The kinetic energy release of fragment ions produced by the interaction of femtosecond laser pulse radiation with diatomic and linear triatomic molecules N_2, CO, CO_2 and CS_2 is investigated. In the case of linear polarization, angles at which the kinetic energy release of ions has the maximum value are different from the alignment of molecules though the kinetic energy release of fragment atomic ions depends on the angle between the laser polarization vector and the detection axis of the time-of-flight. For the diatomic molecules, the critical internuclear distance in multielectron dissociative ionization with a circularly polarized light is larger than that with a linearly polarized light. For linear triatomic molecules, our data indicate that a concerted Coulomb explosion process is a universal phenomenon in the interaction of molecules with intense laser fields, even in the circularly polarized regime. During two C－O (or C－S) bonds breaking simultaneously, the C ion obtained larger energy in circular polarization than that in the linear polarization. Different variations of kinetic energy release between the diatomic and the linear triatomic molecules are discussed. 相关文章 | 计量指标

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The closed-orbit and the photoabsorption spectra of lithium atom in varying magnetic fields 王德华, 丁世良 2004 (1):  30-35.  doi: 10.1088/1009-1963/13/1/007 摘要 ( 1286 )   PDF(282KB) ( 411 )   Using a simple analytic formula from closed orbit theory, we have calculated the photoabsorption spectra of Li atom in different magnetic fields. Closed orbits in the corresponding classical system have also been obtained for B=5.96T. We demonstrate schematically that the closed orbits disappear gradually with the decrease of the magnitude of the magnetic field. This gives us a good method to control the closed orbits in the corresponding system by changing the magnetic field, and thus changing the peaks in the photoabaorption spectra. By comparing the photoabsorption spectra of Li atom with those of hydrogen case, we find the core-scattered effects play an important role in multi-electron Rydberg atoms. 相关文章 | 计量指标

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Dependence of electromagnetically induced transparency on temperature 肖峰, 郭瑞民, 李路明, 杨东海, 陈徐宗 2004 (1):  36-39.  doi: 10.1088/1009-1963/13/1/008 摘要 ( 1210 )   PDF(172KB) ( 532 )   We performed an experimental study on the dependence of the linewidth of electromagetically induced transparency (EIT) on the temperature of medium in a Λ-type configuration using caesium vapour. We found that the transparent window is narrowed in the EIT whose two ground levels are composed of two hyperfine levels, and broadened in the case when the two ground levels are degenerated Zeeman sublevels, as the temperature of vapour cell is increased. The explanation for the phenomena is given qualitatively. 相关文章 | 计量指标

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A unified incompressible lattice BGK model and its application to three-dimensional lid-driven cavity flow 何南忠, 王能超, 施保昌, 郭照立 2004 (1):  40-46.  doi: 10.1088/1009-1963/13/1/009 摘要 ( 1158 )   PDF(1028KB) ( 618 )   A unified lattice Bhatnagar－Gross－Krook (ILBGK) model iDdQq for the incompressible Navier－Stokes equation is presented. To test its efficiency, the lid-driven cavity flow in three-dimensional space for Reynolds number Re=3200 and span aspect ratio SAR=1, 2 and 3 is simulated in detail on a 48×48×(48×SAR) uniform lattice using the model. The test results agree well with those in previous experiments and numerical works and show the efficiency and strong numerical stability of the proposed ILBGK model. 相关文章 | 计量指标

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Lattice Boltzmann method for three-dimensional moving particles in a Newtonian fluid 方海平, Chen Shi-Yi 2004 (1):  47-53.  doi: 10.1088/1009-1963/13/1/010 摘要 ( 1387 )   PDF(263KB) ( 571 )   A lattice Boltzmann method is developed to simulate three-dimensional solid particle motions in fluids. In the present model, a uniform grid is used and the exact spatial location of the physical boundary of the suspended particles is determined using an interpolation scheme. The numerical accuracy and efficiency of the proposed lattice Boltzmann method is demonstrated by simulating the sedimentation of a single sphere in a square cylinder. Highly accurate simulation results can be achieved with few meshes, compared with the previous lattice Boltzmann methods. The present method is expected to find applications on the flow systems with moving boundaries, such as the blood flow in distensible vessels, the particle－flow interaction and the solidification of alloys. 相关文章 | 计量指标

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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The dispersive properties of a dielectric-rod loaded waveguide immersed in a magnetized annular plasma 李伟, 巩马理, 魏彦玉, 谢鸿全 2004 (1):  54-59.  doi: 10.1088/1009-1963/13/1/011 摘要 ( 1134 )   PDF(206KB) ( 558 )   Propagation properties of electromagnetic waves in a dielectric-rod waveguide immersed in a magnetized annular plasma are presented in this paper. The dispersion relations are derived and calculated. The results show that the dielectric-rod loading can make the structure less dispersive and the transmission frequency-band broadened. 相关文章 | 计量指标

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The KP and ZK equations for electrostatic waves with grain charge fluctuation 薛具奎, 郎和 2004 (1):  60-64.  doi: 10.1088/1009-1963/13/1/012 摘要 ( 1287 )   PDF(172KB) ( 488 )   The propagation of three-dimensional nonlinear dust-acoustic and dust-Coulomb waves in unmagnetized/magnetized dusty plasmas consisting of electrons, ions, and charged dust particles is investigated. The grain charge fluctuation effect is also incorporated through the current balance equation. By using the perturbation method, a Kadomtsev－Petviashvili equation and a Zakharov－Kuznetsov equation governing the nonlinear waves in the unmagnetized and magnetized systems are obtained respectively. It has been shown that with the combined effects of grain charge fluctuation, the transverse perturbation, and the external magnetic field would modify the wave structures. Waves in those systems are unstable to the high-order long-wave perturbations. 相关文章 | 计量指标

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Influence of ion species ratio on grid-enhanced plasma source ion implantation 王久丽, 张谷令, 刘元富, 王友年, 刘赤子, 杨思泽 2004 (1):  65-70.  doi: 10.1088/1009-1963/13/1/013 摘要 ( 1184 )   PDF(312KB) ( 535 )   Grid-enhanced plasma source ion implantation (GEPSII) is a newly proposed technique to modify the inner-surface properties of a cylindrical bore. In this paper, a two-ion fluid model describing nitrogen molecular ions N_2^+ and atomic ions N^+ is used to investigate the ion sheath dynamics between the grid electrode and the inner surface of a cylindrical bore during the GEPSII process, which is an extension of our previous calculations in which only N_2^+ was considered. Calculations are concentrated on the results of ion dose and impact energy on the target for different ion species ratios in the core plasma. The calculated results show that more atomic ions N^+ in the core plasma can raise the ion impact energy and reduce the ion dose on the target. 相关文章 | 计量指标

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Optical vibration modes and electron－phonon interaction in ternary mixed crystals of polar semiconductors 梁希侠, 班士良 2004 (1):  71-81.  doi: 10.1088/1009-1963/13/1/014 摘要 ( 1317 )   PDF(326KB) ( 594 )   Optical vibrations of the lattice and the electron－phonon interaction in polar ternary mixed crystals are studied in the framework of the continuum model of Born and Huang and the random-element-isodisplacement model. A normal-coordinate system to describe the optical vibration in ternary mixed crystals is correctly adopted to derive a new Fr?hlich-like Hamiltonian for the electron－phonon interaction including the unit-cell volume variation influence. The numerical results for the phonon modes, the electron－phonon coupling constants and the polaronic energies for several typical materials are obtained. It is verified that the nonlinearity of the electron－phonon coupling effects with the composition is essential and the unit-cell volume effects cannot be neglected for most ternary mixed crystals. 相关文章 | 计量指标

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Effect of nonstoichiometry on Raman scattering of VO2 films 袁宏韬, 冯克成, 王学进, 李超, 何琛娟, 聂玉昕 2004 (1):  82-84.  doi: 10.1088/1009-1963/13/1/015 摘要 ( 1451 )   PDF(162KB) ( 704 )   We report on Raman scattering of VO_2 films prepared by radio frequency magnetron sputtering under different conditions. Our investigations revealed that the dominated Raman peaks shift towards high frequency for both V-rich and O-rich VO_2 films, compared with the stoichiometry VO_2 films. The experimental evidence is presented and the cause for nonstoichiometry dependence of Raman spectra of VO_2 films is discussed. 相关文章 | 计量指标

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Chemisorption of Au on Si(001) surface 危书义, 汪建广, 马丽 2004 (1):  85-89.  doi: 10.1088/1009-1963/13/1/016 摘要 ( 1443 )   PDF(194KB) ( 516 )   The chemisorption of one monolayer of Au atoms on an ideal Si(001) surface is studied by using the self-consistent tight binding linear muffin-tin orbital method. Energies of the adsorption system of a Au atom on different sites are calculated. It is found that the most stable position is A site (top site) for the adsorbed Au atoms above the Si(001) surface. It is possible for the adsorbed Au atoms to sit below the Si(001) surface at the B_1 site(bridge site), resulting in a Au－Si mixed layer. This is in agreement with the experiment results. The layer projected density of states is calculated and compared with that of the clean surface. The charge transfer is also investigated. 相关文章 | 计量指标

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Effect of preparation procedure on the magnetic and transport properties of double perovskite Sr2FeMoO6 王锦辉, 余智, 刘公强, 都有为 2004 (1):  90-94.  doi: 10.1088/1009-1963/13/1/017 摘要 ( 1245 )   PDF(210KB) ( 379 )   Ordered and disordered double perovskite Sr_2FeMoO_6 ceramics have been investigated by powder x-ray diffraction, magnetic and transport measurements, as well as M?ssbauer spectroscopy. The heavily disordered sample can be acquired by annealing the ordered samples in argon. The annealing procedure affects not only the nature of grain boundaries but also the grain itself. The evidence of M?ssbauer spectra performed at 77 and 300 K indicates that there exist small oxygen deficient clusters of SrFeO_{3-y} in the disordered sample. The paramagnetic Fe^{4+} and Fe^{3+} ions in the compound subsist down to 77 K and the ratio of Fe^{4+}/Fe^{3+} increases with decreasing temperature. 相关文章 | 计量指标

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Transmission of electron through an Aharonov－Bohm interferometer with a quantum dot in Coulomb blockade regime 孙科伟, 熊诗杰 2004 (1):  95-99.  doi: 10.1088/1009-1963/13/1/018 摘要 ( 1364 )   PDF(200KB) ( 522 )   We calculate conductance of an Aharonov－Bohm (AB) interferometer for which a single-level quantum dot in the Coulomb blockade regime is embedded in one of its arms. Using the Schr?dinger equations and taking into account the Coulomb interaction on the dot, we calculate conductance G as a function of flux φ threaded through the ring and as a function of gate voltage V applied to the dot. It is found that the AB oscillations of G(φ) depend on the particle occupation on the dot, controlled by V. If the system is closed, there is no loss of particles, G(φ) is periodic and G(φ)=G(-φ), satisfying the Onsager relation. In this case G(φ) can reach its maximum value, 2e^2/h, at the resonance. When the system is open, one has G(φ)≠G(-φ), G(φ) yields a phase shift which depends on the loss rate of electrons in this open system. 相关文章 | 计量指标

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Development of 1.3GHz high-T-c rf SQUID 刘新元, 谢飞翔, 孟树超, 戴远东, 李壮志, 马平, 杨涛, 聂瑞娟, 王福仁 2004 (1):  100-104.  doi: 10.1088/1009-1963/13/1/019 摘要 ( 1070 )   PDF(218KB) ( 502 )   A new high-T_c (HT_c) rf SQUID working at around 1.3GHz has been developed to avoid electromagnetic interference such as growing mobile communication jamming. This new system works in a frequency range from 1.23 to 1.42GHz (centred at 1.3GHz), which is not occupied by commercial communication. The sensor used in the 1.3GHz rf SQUID is made of a HT_c coplanar superconducting resonator and a large-area HT_c superconducting film concentrator. We have achieved in the 1.3GHz HT_c rf SQUID system a minimal flux noise of 2.5×10^{-5}Φ_0/\sqrt{Hz} and a magnetic field sensitivity of 38fT/\sqrt{Hz} in white noise range, respectively. The effective area of the concentrator fabricated on a 15×15mm^2 substrate is 1.35mm^2. It is shown that the 1.3GHz rf SQUID system has a high field sensitivity. Design and implementation of 1.3GHz HT_c rf SQUID offers a promising direction of rf SQUID development for higher working frequency ranges. 相关文章 | 计量指标

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Monte Carlo simulation of magnetic nanostructured thin films 关治强, Yutaka Abe, 姜冬华, 林海, Yoshitake Yamazaki, 吴晨旭 2004 (1):  105-110.  doi: 10.1088/1009-1963/13/1/020 摘要 ( 1199 )   PDF(647KB) ( 527 )   Using Monte Carlo simulation, we have compared the magnetic properties between nanostructured thin films and two-dimensional crystalline solids. The dependence of nanostructured properties on the interaction between particles that constitute the nanostructured thin films is also studied. The result shows that the parameters in the interaction potential have an important effect on the properties of nanostructured thin films at the transition temperatures. 相关文章 | 计量指标

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Transient saturation absorption spectroscopy excited near the band gap at high excitation carrier density in GaAs 吴松江, 王丹翎, 蒋红兵, 杨宏, 龚旗煌, 季亚林, 陆卫 2004 (1):  111-114.  doi: 10.1088/1009-1963/13/1/021 摘要 ( 1261 )   PDF(218KB) ( 425 )   Transient saturation absorption spectroscopy in GaAs thin films was investigated using femtosecond pump and supercontinuum probe technique at excitation densities higher than 1×10^{19}cm^{-3}. The Coulomb enhancement factor of the electron－hole plasma results in a spectrum hole at the pump wavelength. Two distinct transmission peaks at two sides of the pump wavelength are observed, arising from the bleaching of transitions from the heavy- and light-hole bands to the conduction band. The dynamic process of the transient saturation absorption is fitted using a bi-exponential function. The fast decay process is dominated by the carrier-phonon scattering and the slow process may be attributed to the electron－hole recombination. 相关文章 | 计量指标

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Comprehensive research about the cooperative up-conversion luminescence of the ytterbium-doped oxyfluoride vitroceramics 陈晓波, 宋增福 2004 (1):  115-124.  doi: 10.1088/1009-1963/13/1/022 摘要 ( 1336 )   PDF(313KB) ( 431 )   The cooperative up-conversion blue luminescence of Yb^{3+} ion-doped oxyfluoride vitroceramic material (Yb:FOV) and the influence of co-doped Ho^{3+} ion, when excited by a 960 nm diode-laser, are studied in this paper. A strong blue 479.1 nm up-conversion luminescence of the Yb:FOV material is discovered. It is found that the 479.1 nm luminescence results from the cooperative up-conversion of the coupled states of the Yb^{3+}－Yb^{3+} clusters formed by two adjacent Yb^{3+} ions. The measured cooperative up-conversion luminescence main peak 479.1 nm of this paper is different from the characteristic fluorescence main peak of the Tb^{3+} ion positioned at about 495－504 nm wave-range. Our result coincides with all the published correct papers, whose cooperative up-conversion luminescence main peaks of the direct Yb^{3+}－Yb^{3+} clusters are all positioned at about 476－480 nm wave-range. All of these indicate that the large cooperative up-conversion blue luminescence of the direct Yb^{3+}－Yb^{3+} clusters discovered in this paper is stable. It further proves that the cooperative up-conversion green luminescence may result from the Yb^{3+}-Tb^{3+} cooperative effect. In particular, the original work of this paper improves considerably on the traditional concept by the experimental facts that the blue 479.1 nm cooperative up-conversion luminescence strength of Yb(5):FOV is 230 times greater than that of fluoride glass Yb(3):ZBLAN. This is a great development to meet the practical requirements for blue up-conversion luminescence strength. This result indicates that the large cooperative up-conversion blue luminescence could be achieved excellently by using a suitable material, such as oxyfluoride vitroceramic, which provides a better chance to form better Yb^{3+}－Yb^{3+} clusters and has less relaxation to keep the more efficient up-conversion luminescence. It is also found that impurities seriously reduce the cooperative up-conversion luminescence intensity due to the cross-relaxation from the Yb^{3+}－Yb^{3+} clusters, which means that the cooperative up-conversion blue luminescence could be further improved by pure Yb^{3+} ion-doped materials that have as few impurities as possible to reduce the cross-relaxation. The large cooperative up-conversion blue luminescence of Yb(5):FOV also comes from its higher concentration (5 mol%) of activator Yb^{3+} ion which acts well because the cooperative up-conversion blue luminescence intensity varies linearly against the square of the concentration of Yb^{3+} ions in the range of 0.5－5 mol%. In summary, the great improvement of our work on cooperative up-conversion blue luminescence results from the comprehensive enhancement of the factors of better-coupled chance of the Yb^{3+}－Yb^{3+} clusters, less cross-relaxation, better concentration contribution of Yb^{3+} activator, non-saturation, and better up-conversion luminescence efficiency. 相关文章 | 计量指标