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2004年, 第13卷, 第5期　刊出日期：2004-05-06 上一期    下一期

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Bound states of the Klein－Gordon and Dirac equations for potential V0tanh2(r/d) 强稳朝 2004 (5):  571-574.  doi: 10.1088/1009-1963/13/5/001 摘要 ( 1677 )   PDF(163KB) ( 640 )   The exact bound state wavefunctions and energy equations of Klein－Gordon and Dirac equations are given with equal scalar and vector potential s(r)=v(r)=V(r)/2=V_0tanh^2(r/d). The relation between the energy equation and that of relativistic harmonic is discussed. 相关文章 | 计量指标

GENERAL

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Bound states of the Klein－Gordon equation for ring-shaped Kratzer-type potential 强稳朝 2004 (5):  575-578.  doi: 10.1088/1009-1963/13/5/002 摘要 ( 1342 )   PDF(157KB) ( 484 )   The exact normalized bound state wavefunctions and energy equations of Klein－Gordon equation with equal scalar and vector ring-shaped Kratzer-type potential have been obtained. 相关文章 | 计量指标

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Acceleration of a test particle in the gravitational field of central mass with a large number of magnetic monopoles 王永久, 曹登 2004 (5):  579-582.  doi: 10.1088/1009-1963/13/5/003 摘要 ( 1210 )   PDF(156KB) ( 657 )   In a Kerr－Newman－Kasuya field we have obtained expressions of the acceleration effect and also studied the special case (v^i=0). We find that in this field, the acceleration of a falling particle has both radial and transverse components. The acceleration effects of electric charge q and magnetic charge φ are also discussed, separately. 相关文章 | 计量指标

GENERAL

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Chaotic evolution of the coupled scalar fields system during inflation 陈菊华, 王永久 2004 (5):  583-588.  doi: 10.1088/1009-1963/13/5/004 摘要 ( 1151 )   PDF(321KB) ( 540 )   In this paper we consider two coupled scalar fields during the inflation as a dynamical system. With the Poincaré section method, we investigate the evolution of the coupled scalar fields system. We find that the evolution of the system changes from a regular motion into a chaotic motion when the energy density and the coupling constant of the system increase. 相关文章 | 计量指标

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A new conserved quantity of mechanical systems with differential constraints 吴惠彬 2004 (5):  589-591.  doi: 10.1088/1009-1963/13/5/005 摘要 ( 1157 )   PDF(137KB) ( 519 )   A new conserved quantity of non-Noether symmetry for the mechanical systems with differential constraints is studied. First, the differential equations of motion of the systems are established. Then, the determining equations and restriction equations of the non-Noether symmetry are obtained and a new conserved quantity is given. Finally, an example is given to illustrate the application of the results. 相关文章 | 计量指标

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Multi-valued solitary waves in multidimensional soliton systems 郑春龙, 陈立群, 张解放 2004 (5):  592-597.  doi: 10.1088/1009-1963/13/5/006 摘要 ( 1213 )   PDF(369KB) ( 536 )   Considering that folded phenomena are rather universal in nature and some arbitrary functions can be included in the exact excitations of many (2+1)-dimensional soliton systems, we use adequate multivalued functions to construct folded solitary structures in multi-dimensions. Based on some interesting variable separation results in the literature, a common formula with arbitrary functions has been derived for suitable physical quantities of some significant (2+1)-dimensional soliton systems like the generalized Ablowitz－Kaup－Newell－Segur (GAKNS) model, the generalized Nizhnik－Novikov－Veselov (GNNV) system and the new (2+1)-dimensional long dispersive wave (NLDW) system. Then a new special type of two-dimensional solitary wave structure, i.e. the folded solitary wave and foldon, is obtained. The novel structure exhibits interesting features not found in the single valued solitary excitations. 相关文章 | 计量指标

GENERAL

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Effect of adiabatic variation of dust charges on dust acoustic solitary waves in magnetized dusty plasmas 段文山 2004 (5):  598-601.  doi: 10.1088/1009-1963/13/5/007 摘要 ( 1305 )   PDF(160KB) ( 498 )   The effect of dust charging and the influence of its adiabatic variation on dust acoustic waves is investigated. By employing the reductive perturbation technique we derived a Zakharov－Kuznetsov (ZK) equation for small amplitude dust acoustic waves. We have analytically verified that there are only rarefactive solitary waves for this system. The instability region for one-dimensional solitary wave under transverse perturbations has also been obtained. The obliquely propagating solitary waves to the z-direction for the ZK equation are given in this paper as well. 相关文章 | 计量指标

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New infinite-dimensional hidden symmetries for the stationary axisymmetric Einstein－Maxwell equations with multiple Abelian gauge fields 高亚军 2004 (5):  602-611.  doi: 10.1088/1009-1963/13/5/008 摘要 ( 972 )   PDF(218KB) ( 474 )   By proposing a so-called extended hyperbolic complex (EHC) function method, an Ernst-like (p+2)×(p+2) matrix EHC potential is introduced for the stationary axisymmetric (SAS) Einstein－Maxwell theory with p Abelian gauge fields (EM-p theory, for short), then the field equations of the SAS EM-p theory are written as a so-called Hauser－Ernst-like self-dual relation for the EHC matrix potential. Two Hauser－Ernst-type EHC linear systems are established, based on which some new parametrized symmetry transformations for the SAS EM-p theory are explicitly constructed. These hidden symmetries are found to constitute an infinite-dimensional Lie algebra, which is the semidirect product of the Kac－Moody algebra su(p+1,1)\otimes R(t,t^{-1}) and Virasoro algebra (without centre charges). All of the SAS EM-p theories for p=0,1,2,… are treated in a unified formulation, p=0 and p=1 correspond, respectively, to the vacuum gravity and the Einstein－Maxwell cases. 相关文章 | 计量指标

GENERAL

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Newtonian forms for the motion of particles and photons in dilaton spacetime 杨荣佳, 荆继良 2004 (5):  612-617.  doi: 10.1088/1009-1963/13/5/009 摘要 ( 1225 )   PDF(173KB) ( 445 )   Using Newtonian forms for equations of motion, we consider the motion of particles and photons in the dilaton spacetime. Some classical gravitational effects, such as the bending of light rays, the perihelion advance of a planet, the delay of radar echo, and the gravitational redshifts, have been investigated. The results show that the gravitational effects arising from the dilaton can be observed provided that the dilaton is large enough. 相关文章 | 计量指标

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A new type of global bifurcation in Hénon map 徐培民, 闻邦椿 2004 (5):  618-624.  doi: 10.1088/1009-1963/13/5/010 摘要 ( 967 )   PDF(321KB) ( 415 )   A simple branch of solution on a bifurcation diagram, which begins at static bifurcation and ends at boundary crisis (or interior crisis in a periodic window), is generally a period-doubling cascade. A domain of solution in parameter space, enclosed by curves of static bifurcation and that of boundary crisis (or the interior of a periodic window), is the trace of branches of solution. A P-n branch of solution refers to the one starting from a period-n (n≥1) solution, and the corresponding domain in parameter space is named the P-n domain of solution. Because of the co-existence of attractors, there may be several branches within one interval on a bifurcation diagram, and different domains of solution may overlap each other in some areas of the parameter space. A complex phenomenon, concerned both with the co-existence of attractors and the crises of chaotic attractors, was observed in the course of constructing domains of steady state solutions of the Hénon map in parameter space by numerical methods. A narrow domain of period-m solutions firstly co-exists with (lies on) a big period-n (m≥3n) domain. Then it enters the chaotic area of the big domain and becomes period-m windows. The co-existence of attractors disappears and is called the landing phenomenon. There is an interaction between the two domains in the course of landing: the chaotic area in the big domain is enlarged, and there is a crisis step near the landing area. 相关文章 | 计量指标

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Security analysis of a spatiotemporal-chaos-based cryptosystem 吕华平, 王世红, 李晓文, 唐国宁, 匡锦瑜, 叶卫平, 胡岗 2004 (5):  625-632.  doi: 10.1088/1009-1963/13/5/011 摘要 ( 1137 )   PDF(305KB) ( 551 )   An S-box modified one-way coupled map lattice is applied as a chaotic cryptograph. The security of the system is evaluated from various attacks currently used, including those based on error function analysis, statistical property analysis, and known-plaintext and chosen-ciphertext analytical computations. It is found that none of the above attacks can be better than the brute force attack of which the cost is exhaustively quantitated by the key number in the key space. Also, the system has fairly fast encryption (decryption) speed, and has extremely long period for finite-precision computer realization of chaos. It is thus argued that this chaotic cryptosystem can be a hopeful candidate for realistic service of secure communications. 相关文章 | 计量指标

GENERAL

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Determining the minimum embedding dimension of nonlinear time series based on prediction method 卞春华, 宁新宝 2004 (5):  633-636.  doi: 10.1088/1009-1963/13/5/012 摘要 ( 1225 )   PDF(161KB) ( 578 )   Determining the embedding dimension of nonlinear time series plays an important role in the reconstruction of nonlinear dynamics. The paper first summarizes the current methods for determining the embedding dimension. Then, inspired by the fact that the optimum modelling dimension of nonlinear autoregressive (NAR) prediction model can characterize the embedding feature of the dynamics, the paper presents a new idea that the optimum modelling dimension of the NAR model can be taken as the minimum embedding dimension. Some validation examples and results are given and the present method shows its advantage for short data series. 相关文章 | 计量指标

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Anomalous spectral behaviour of diffracted chirped Gaussian pulses in the near field 潘留占, 吕百达 2004 (5):  637-645.  doi: 10.1088/1009-1963/13/5/013 摘要 ( 1208 )   PDF(301KB) ( 519 )   By using the Fourier transform method, analytical expressions for the axial power spectrum and near-field intensity in the spacetime domain of chirped Gaussian pulses diffracted at an aperture are derived, which permit us to study changes in spectral and temporal profiles of the chirped Gaussian pulses both analytically and numerically. Detailed numerical results and physical analysis show that spectral anomalies take place in the neighbourhood of certain critical distances, and the shifting of maximum and splitting of temporal intensity profiles appear. In particular, for ultrashort chirped pulses, there exists also spectral switch. Besides the truncation parameter, the chirp parameter and pulse duration affect the behaviour of spectral switches. 相关文章 | 计量指标

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The production of slow particles in 16O－Em interactions at 4.5 A GeV/c 吴凤娟, 张东海, 李俊生, 李振宇 2004 (5):  646-656.  doi: 10.1088/1009-1963/13/5/014 摘要 ( 1168 )   PDF(374KB) ( 376 )   A sample of 1233 events is used to study the general characteristics of {}^{16}O－Em interactions at 4.5 A GeV/c. Multiplicity and angular distributions of slow particles and correlations among them are discussed. The present data are compared with the corresponding results from the interactions of other projectiles at the same energy and also the same projectile at different energies. The results indicate that black particle production is independent of the energy and mass of the projectile, but for grey particles it is dependent on the mass of projectile. 相关文章 | 计量指标

NUCLEAR PHYSICS

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Intense beam nonlinear transport in solenoid lenses 吕建钦, 李金海, 李超龙 2004 (5):  657-661.  doi: 10.1088/1009-1963/13/5/015 摘要 ( 984 )   PDF(150KB) ( 530 )   Lie algebraic methods are used in the analysis of the nonlinear transport of charged particle beams in solenoid lenses. Space charge effects are included. The particle distribution we used is a K－V type. Similar procedures can also be used for magnetic dipoles, quadrupoles, sextupoles and other optic elements. 相关文章 | 计量指标

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Energy and fine structure of 1s2np(n≤9) states for lithium-like systems from Z=11 to 20 胡木宏, 王治文 2004 (5):  662-669.  doi: 10.1088/1009-1963/13/5/016 摘要 ( 1196 )   PDF(209KB) ( 412 )   A new variation method is extended to study the atomic systems with higher nuclear charges and in more highly excited states. The non-relativistic energies of 1s^2np (n≤9) states for the lithium-like systems from Z=11 to 20 are calculated using a full-core-plus-correlation method with multi-configuration interaction wavefunctions. Relativistic and mass-polarization effects on the energy are calculated as the first-order perturbation corrections. The fine structures are determined from the expectation values of spin-orbit and spin-other-orbit interaction operators in the Pauli－Breit approximation. The quantum-electrodynamics correction is also included. Our results are compared with experimental data in the literature. 相关文章 | 计量指标

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Ionization for Hf- and W-L-shell by electron impact 杨代伦, 罗小兵, 傅玉川, 何福庆, 龙先灌, 彭秀峰, 罗正明 2004 (5):  670-676.  doi: 10.1088/1009-1963/13/5/017 摘要 ( 1232 )   PDF(240KB) ( 480 )   Electron-induced Hf-, W-L-shell partial, total production cross sections, mean ionization cross sections and Hf-L_3-shell ionization cross sections (at two energies) have been measured as functions of electron energies (from near threshold to 36keV). The influence of electrons reflected from the backing of the thin targets on measured results was corrected using a model to relate to the electron transport process. The mean paths of electron multi-scattered in the target itself (including forward and backward scattering) were calculated by means of Monte Carlo program (EGS4) and they were used to correct measured results. A comparison with both theoretical predictions was given. 相关文章 | 计量指标

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Geometry and electronic properties of Cu2(n≤9) 王红艳, 李朝阳, 唐永建, 朱正和 2004 (5):  677-681.  doi: 10.1088/1009-1963/13/5/018 摘要 ( 1460 )   PDF(220KB) ( 505 )   The equilibrium geometries and the atomization energies of Cu_n(n≤9) clusters have been calculated using the B3LYP/LANL2DZ method. It is shown that the clusters do not copy the bulk structures and undergo significant geometrical changes with size and the atomization energy per atom increases monotonically with size. By analysing the energy level distribution, the Fermi level, HOMO－LUMO gaps, the electron affinities and the ionization potentials are calculated and the results are in reasonable agreement with experiment. These electronic properties are found to be strongly structure dependent, which can be used to determine which of the low-lying structures is observed experimentally. 相关文章 | 计量指标

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On the properties of electromagnetic waves propagating inside moving dielectric media 贺奇才, 徐生辉, 李平阳, 魏冬季, 凌养浩, 陈弟虎 2004 (5):  682-685.  doi: 10.1088/1009-1963/13/5/019 摘要 ( 1128 )   PDF(146KB) ( 446 )   The properties of electromagnetic waves propagating inside isotropic or uniaxial dielectric media moving in an arbitrary direction are analysed. The scalar products of electromagnetic field vectors inside these moving media are investigated in the kEB system from Maxwell's equations and Lorentz-covariant constitutive relations. Several important equations are derived. They are useful in discussing problems such as the energy density and radiation pressure, which are of interest in theoretical studies and many application subjects. 相关文章 | 计量指标

CLASSICAL AREAS OF PHENOMENOLOGY

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Transparency induced by two-photon interference in a beam splitter 汪凯戈, 杨国健 2004 (5):  686-691.  doi: 10.1088/1009-1963/13/5/020 摘要 ( 1125 )   PDF(185KB) ( 439 )   We propose a special two-photon state which is completely transparent in a 50/50 beam splitter. This effect is caused by the destructive two-photon interference and shows the signature of photon entanglement. We find that the symmetry of the two-photon spectrum plays the key role for the properties of two-photon interference. 相关文章 | 计量指标

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Amplification mechanism and effects of spontaneously generated coherence on the probe gain in a four-level system 徐卫华, 吴金辉, 高锦岳 2004 (5):  692-699.  doi: 10.1088/1009-1963/13/5/021 摘要 ( 1088 )   PDF(261KB) ( 607 )   We investigate the amplification mechanism in a four-level system by both the density-matrix and quantum-jump approaches. We show that the asymmetry between three-photon stimulated emission and one-photon absorption process is responsible for the inversionless amplification of the probe field. We also investigate the effects of spontaneously generated coherence (SGC) on the probe gain, and find that due to the SGC, the probe gain can be greatly enhanced and can be modulated by changing the relative phase between the applied fields. 相关文章 | 计量指标

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Optical phase conjugation by resonant degenerate four-wave mixing in liquid phase medium 樊荣伟, 陈德应, 房涛, 鞠有伦, 王骐, 马祖光 2004 (5):  700-703.  doi: 10.1088/1009-1963/13/5/022 摘要 ( 1017 )   PDF(4547KB) ( 489 )   In this paper, frequency-doubled Nd:YAG laser's phase conjugation has been investigated experimentally using resonant degenerate four-wave mixing (DFWM). The iodine solution was used as resonant medium. In this way, the energy of the DFWM phase conjugation beam arrived at 43μJ/pulse while the total pump beam's energy reached 8mJ/pulse. The relation between the pulse energy of the DFWM phase conjugation beam and that of the pump beam was investigated. We also measured the optical field distributions of pump beam and DFWM phase conjugation beam, from which it can be noticed that the DFWM phase conjugation can improve the laser beam quality. At the same time, we observed the influence of the pump beam's disturbance on the DFWM signal. 相关文章 | 计量指标

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Coupling and stability of bright holographic soliton pairs 刘劲松, 郝中华 2004 (5):  704-711.  doi: 10.1088/1009-1963/13/5/023 摘要 ( 1166 )   PDF(346KB) ( 473 )   The coupling effect and stability property of symmetric bright holographic soliton pairs have been investigated numerically. Results show that when any one of the two solitary beams from a pair is perturbed in amplitude or width, both beams will be affected by such a perturbation via the coupling effect between the beams, thus resulting in both beams propagating in the medium without a constant shape; however, these two solitary beams are still stable against small perturbations. When both solitary beams from a pair are perturbed simultaneously in amplitude, for some given absolute values of the perturbations, the two beams are stable against these perturbations if both beams are perturbed with the same sign, whereas are unstable with the different signs. When the two beams are simultaneously perturbed in width, both beams exhibit their stability property similar to that when only one beam is perturbed no matter whether both perturbations have the same or different signs. 相关文章 | 计量指标

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Numerical simulation of LBGK model for high Reynolds number flow 周晓阳, 施保昌, 王能超 2004 (5):  712-719.  doi: 10.1088/1009-1963/13/5/024 摘要 ( 1091 )   PDF(799KB) ( 484 )   A principle of selecting relaxation parameter was proposed to observe the limit computational capability of the incompressible LBGK models developed by Guo ZL (Guo model) and He SY (He model) for high Reynolds number flow. To the two-dimensional driven cavity flow problem, the highest Reynolds numbers covered by Guo and He models are in the range 58000－52900 and 28000－29000, respectively, at 0.3 Mach number and 1/256 lattice space. The simulation results also show that the Guo model has stronger robustness due to its higher accuracy. 相关文章 | 计量指标

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Synchrotron small angle x-ray scattering study of dye-sensitized/-unsensitized TiO2 nanoparticle colloidal solution 洪新国, 都鲁超, 叶满萍, 翁羽翔 2004 (5):  720-724.  doi: 10.1088/1009-1963/13/5/025 摘要 ( 1330 )   PDF(200KB) ( 634 )   The wide-gap semiconductor TiO_2 nanoparticles with and without dye sensitization have been studied by small angle x-ray scattering using synchrotron radiation. Surface properties of the colloidal TiO_2 nanoparticles have been analysed in terms of the surface fractal dimensions (D_s), showing that D_s changes from 3.25 to 2.34 when TiO_2 nanoparticles are sensitized by ATRA (all-trans-retinoic acid), which reveals that the surface of the particles become relatively smooth after dye sensitization. The size distribution of gyration radius of TiO_2 nanoparticles in the colloids M(R_g) has been successfully determined by the Shull－Roess method. The main peak of M(R_g) for the unsensitized TiO_2 colloid is located at 2.1nm, corresponding to a spherical diameter of 5.4nm, and this value for the ATRA sensitized TiO_2 increases to 2.4nm, indicating a spherical diameter of 6.4nm. Such a size enlargement of TiO_2 nanoparticles suggests that there is a coating of ATRA on the TiO_2 surface, supporting the view that a monolayer of the dye has been attached to the surface of the TiO_2 nanoparticle. 相关文章 | 计量指标

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Deposition behaviour of single Si adatom on p(2×2) Si(100) surface 黄燕, 朱晓焱 2004 (5):  725-730.  doi: 10.1088/1009-1963/13/5/026 摘要 ( 998 )   PDF(375KB) ( 478 )   The deposition of a single Si adatom on the p(2×2) reconstructed Si(100) surface has been simulated by an empirical tight-binding method. Using the perfect and defective Si surfaces as the deposition substrates, the deposition energies are mapped out around the research areas. From the calculated energy plots, the binding sites and several possible diffusion paths are achieved. The introduced defects will make the deposition behaviour different from that on the perfect surface. 相关文章 | 计量指标

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Upgrading design of the 3B1A beamline for x-ray nanometre lithography of microelectronic devices at BSRF 伊福廷, 叶甜春, 彭良强, 陈大鹏, 张菊芳, 韩勇 2004 (5):  731-736.  doi: 10.1088/1009-1963/13/5/027 摘要 ( 1194 )   PDF(199KB) ( 494 )   Beijing Synchrotron Radiation Facility is a partly dedicated synchrotron radiation source operated in either parasitic or dedicated mode. The 3B1A beamline, extracted from a bending magnet, was originally designed as a soft x-ray beamline for submicro x-ray lithography with critical lateral size just below 1μm in 1988 and no change has been made since it was built. But later the required resolution of x-ray lithography has changed from sub-micrometre to the nanometre in the critical lateral size. This beamline can longer more meet the requirement for x-ray nano lithography and has to be modified to fit the purpose. To upgrade the design of the 3B1A beamline for x-ray nano lithography, a mirror is used to reflect and scan the x-ray beam for the nano lithography station, but the mirror's grazing angle is changed to 27.9mrad in the vertical direction, and the convex curve needs to be modified to fit the change; the tiny change of mirror scanning angle is firstly considered to improve the uniformity of the x-ray spot on the wafer by controlling the convex curve. 相关文章 | 计量指标

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

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Simulating the time-dependent Ginzburg－Landau equations for type-II superconductors by finite-difference method 廖红印, 周世平, 施晓蕴 2004 (5):  737-745.  doi: 10.1088/1009-1963/13/5/028 摘要 ( 1242 )   PDF(568KB) ( 567 )   This article presents numerical solutions of the periodic time-dependent Ginzburg－Landau model for the type-II superconductors by a finite-difference approximation. Both the static and dynamical properties of a single vortex are studied as the external magnetic field varies. Vortex and anti-vortex can coexist and annihilate with time in the case of no external magnetic field, while the vortex will approach a steady state in the presence of magnetic field. We also study vortex dynamical behaviours while pinning centres exist in the sample and find that the pinning site, which has a significant potential to keep the vortex from moving, may trap the vortex. 相关文章 | 计量指标

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Spin-glass state and ferromagnetic order in Cu(II)－Fe(III) cyanides 何云, 戴耀东, 黄红波, 林俊, 夏元复 2004 (5):  746-749.  doi: 10.1088/1009-1963/13/5/029 摘要 ( 1188 )   PDF(199KB) ( 537 )   The static and dynamic magnetic properties of a Prussian blue analogue, molecular magnet Cu^Ⅱ_{3}[Fe^Ⅲ(CN)_6]_2·3NH_3·6H_2O were investigated in detail. The H dependence of the linear AC susceptibility, the irreversibility in the field-cooled (FC)/zero-field-cooled (ZFC) magnetization (M_{FC}/M_{ZFC}) and the relaxation of M_{ZFC} suggest that the magnetic system can be visualized as containing a ferromagnetic cluster of spin below T_C, mixed with small spin-glass clusters formed below temperature T_g less than T_C. The observed magnetic properties are explained with a ferromagnetic-spin-glass phase model. The magnetic ordering of the sample occurs below 19.8K. 相关文章 | 计量指标

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Ultraviolet emission of ZnO film prepared by electrophoretic deposition 王志军, 王之建, 李守春, 王泽恒, 吕有明, 元金山 2004 (5):  750-753.  doi: 10.1088/1009-1963/13/5/030 摘要 ( 1165 )   PDF(482KB) ( 501 )   We deposited high quality ZnO film by electrophoretic deposition (EPD) using high quality ZnO powder prepared by solid-state pyrolytic reaction. X-ray photoelectron spectroscopy (XPS) and the infrared (IR) absorption spectrum clearly indicate that the ZnO phase powder has been prepared. Transmission electron microscope (TEM) imaging and x-ray diffraction (XRD) show that the average grain size of the powder is about 20nm. XRD and selected-area electron diffraction (SAED) reveal that the ZnO film has a polycrystalline hexagonal wurtzite structure. Only a strong ultraviolet emission peak at 390nm can be observed at room temperature. 相关文章 | 计量指标

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Nonlinear magneto-optical effects in cold atoms of 87Rb 贺凌翔, 王育竹 2004 (5):  754-758.  doi: 10.1088/1009-1963/13/5/031 摘要 ( 1117 )   PDF(208KB) ( 498 )   With laser-cooled cold {}^{87}Rb atoms as a magneto-optical medium, a weak right circularly polarized probe field and frequency modulation technique are used to detect the magnetic distribution of the quadrupole field. A two-peak dispersion-like signal other than that of the usual nonlinear magneto-optical effect mentioned in other papers is obtained. 相关文章 | 计量指标

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Exciton and donor binding energies in quantum-well wires and quantum dots a fractional-dimensional space approach 李红, 孔小均 2004 (5):  759-764.  doi: 10.1088/1009-1963/13/5/032 摘要 ( 1365 )   PDF(224KB) ( 407 )   A simple method for calculating the free-exciton binding energies in the fractional-dimensional-space model for single-quantum-well structure has been extended to quantum-well wires and quantum dots, in which the real anisotropic system is modelled through an effective isotropic environment with a fractional dimension. In this scheme, the fractional-dimensional parameter is chosen via an analytical procedure and involves no ansatz. We calculated the ground-state binding energies of excitons and donors in quantum-well wires with rectangular cross sections. Our results are found to be in good agreement with previous variational calculations and available experimental measurements. We also discussed the ground-state exciton binding energy changing with different shapes of quantum-well wires. 相关文章 | 计量指标

8000 CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Dynamics of aggregation－annihilation process with cluster removals 王向红, 柯见洪, 林振权 2004 (5):  765-771.  doi: 10.1088/1009-1963/13/5/033 摘要 ( 990 )   PDF(195KB) ( 307 )   We have studied the kinetic behaviours of irreversible aggregation－annihilation models with cluster removals. In the models, an irreversible aggregation reaction occurs between any two clusters of the same species and an irreversible annihilation reaction occurs simultaneously between two different species; meanwhile, the clusters of large size are gradually removed from the system. In a mean-field limit, we obtain the general solutions of the cluster-mass distributions for the cases with an arbitrary removal probability. We found that the cluster-mass distribution of either species satisfies a generalized or modified scaling form. The results also indicate that the evolution behaviours of the systems depend strongly on the details of the reaction events. 相关文章 | 计量指标

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Dynamic scaling of migration-driven aggregate growth 柯见洪, 王向红, 林振权, 庄友谊 2004 (5):  772-777.  doi: 10.1088/1009-1963/13/5/034 摘要 ( 822 )   PDF(184KB) ( 326 )   We study the kinetic behaviour of the growth of aggregates driven by reversible migration between any two aggregates. For a simple model with the migration rate K(i;j)=K′(i;j)∝i^uj^v at which the monomers migrate from the aggregates of size i to those of size j, we find that the aggregate size distribution in the system with u+v≤3 and u<2 approaches a conventional scaling form, which reduces to the Smoluchovski form in the u=1 case. On the other hand, for the system with u<2, the average aggregate size S(t) grows exponentially in the u+v=3 case and as (tlnt)^{1/(5-2u)} in another special case of v=u-2. Moreover, this typical size S(t) grows as t^{1/(3-u-v)} in the general u-2 相关文章 | 计量指标

8000 CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Depinning dynamics of driven colloids with random pinning: a numerical study 陈江星, 冯春木, 汪友梅, 曹义刚, 焦正宽 2004 (5):  778-782.  doi: 10.1088/1009-1963/13/5/035 摘要 ( 1076 )   PDF(256KB) ( 318 )   Using Langevin simulations, we have investigated numerically the depinning dynamics of driven two-dimensional colloids subject to the randomly distributed point-like pinning centres. With increasing strength of pinning, we find a crossover from elastic to plastic depinnings, accompanied by an order to disorder transition of state and a substantial increase in the depinning force. In the elastic regime, no peaks are found in the differential curves of the velocity－force dependence (VFD) and the transverse motion is almost none. In addition, the scaling relationship between velocity and force is found to be valid above depinning. However, when one enters the plastic regime, a peak appears in the differential curves of VFD and transverse diffusion occurs above depinning. Furthermore, history dependence is found in the plastic regime. 相关文章 | 计量指标

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Spin-glass-like behaviour and positive magnetoresistance in oxygen deficient La2/3Ca1/3MnO3-δ thin films 张福昌, 陈卫然, 龚伟志, 许波, 邱祥冈, 赵柏儒 2004 (5):  783-788.  doi: 10.1088/1009-1963/13/5/036 摘要 ( 1358 )   PDF(656KB) ( 526 )   The magnetism and magnetoresistance (MR) in a series of oxygen-deficient La_{2/3}Ca_{1/3}MnO_{3-δ} (LCMO) thin films have been investigated. Compared with the films with stoichiometric oxygen concentration, the oxygen-deficient LCMO thin films show a spin-glass-like behaviour at low temperatures, and a positive MR effect above the metal－insulator transition temperature. The mechanism of such unusual phenomena is discussed. 相关文章 | 计量指标