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2006年, 第15卷, 第3期　刊出日期：2006-03-20 上一期    下一期

GENERAL

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Lie-form invariance of nonholonomic mechanical systems 夏丽莉, 王静, 后其宝, 李元成 2006 (3):  467-469.  doi: 10.1088/1009-1963/15/3/001 摘要 ( 1662 )   PDF(195KB) ( 681 )   The Lie-form invariance of a nonholonomic mechanical system is studied. The definition and criterion of the Lie-form invariance of the nonholonomic mechanical system are given. The Hojman conserved quantity and a new type of conserved quantity are obtained from the Lie-form invariance. An example is given to illustrate the application of the results. 相关文章 | 计量指标

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Lie symmetries, perturbation to symmetries and adiabatic invariants of Poincaré equations 陈向炜, 刘翠梅, 李彦敏 2006 (3):  470-474.  doi: 10.1088/1009-1963/15/3/002 摘要 ( 1638 )   PDF(222KB) ( 748 )   Based on the invariance of differential equations under infinitesimal transformations, Lie symmetry, laws of conservations, perturbation to the symmetries and adiabatic invariants of Poincaré equations are presented.The concepts of Lie symmetry and higher order adiabatic invariants of Poincar\'{e} equations are proposed. The conditions for existence of the exact invariants and adiabatic invariants are proved, and their forms are also given. In addition, an example is presented to illustrate these results. 相关文章 | 计量指标

GENERAL

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A hyperbolic function approach to constructing exact solitary wave solutions of the Hybrid lattice and discrete mKdV lattice 扎其劳, 斯仁道尔吉 2006 (3):  475-477.  doi: 10.1088/1009-1963/15/3/003 摘要 ( 1684 )   PDF(177KB) ( 749 )   Some new exact solitary wave solutions of the Hybrid lattice and discrete mKdV lattice are obtained by using a hyperbolic function approach. This approach can also be applied to other nonlinear differential-difference equations. 相关文章 | 计量指标

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Teleportation of a two-atom entangled state using a single EPR pair in cavity QED 计新, 李克, 张寿 2006 (3):  478-481.  doi: 10.1088/1009-1963/15/3/004 摘要 ( 1684 )   PDF(190KB) ( 688 )   We propose a scheme for teleporting a two-atom entangled state in cavity quantum electrodynamics (QED). In the scheme, we choose a single Einstein--Podolsky--Rosen (EPR) pair as the quantum channel which is shared by the sender and the receiver. By using the atom--cavity-field interaction and introducing an additional atom, we can teleport the two-atom entangled state successfully with a probability of 1.0. Moreover, we show that the scheme is insensitive to cavity decay and thermal field. 相关文章 | 计量指标

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Quantum circuits for realizing deterministic and exact teleportation via two partially entangled pairs of particles 李文东, 张建立, 顾永建 2006 (3):  482-487.  doi: 10.1088/1009-1963/15/3/005 摘要 ( 1562 )   PDF(240KB) ( 563 )   Deterministic and exact teleportation can be achieved via two partially entangled pairs of particles [Gu Y J 2006 {\em Opt. Comm.} {\bf 259} 385]. The key point of the protocol is a generalized measurement described by a positive operator-valued measure, which can be realized by performing a unitary operation in the extended space and a conventional Von Neumann orthogonal measurement. By decomposing the evolution process from the initial state to the final state, we construct the quantum circuits for realizing the unitary operation with quantum Toffoli gates, and thus provide a physical means to realize the teleportation. Our method for constructing quantum circuits differs from the usual methods based on decomposition of unitary matrices, and is convenient for a large class of quantum processes involving generalized measurements. 相关文章 | 计量指标

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Entanglement diversion and quantum teleportation of entangled coherent states 蔡新华, 郭杰荣, 聂建军, 贾金平 2006 (3):  488-491.  doi: 10.1088/1009-1963/15/3/006 摘要 ( 1798 )   PDF(205KB) ( 764 )   The proposals on entanglement diversion and quantum teleportation of entangled coherent states are presented.In these proposals, the entanglement between two coherent states, $|\alpha\rangle$ and $|-\alpha\rangle$, with the same amplitude but a phase difference of $\pi$ is utilized as a quantum channel. The processes of the entanglement diversion and the teleportation are achieved by using the 50/50 symmetric beam splitters, the phase shifters and the photodetectors with the help of classical information. 相关文章 | 计量指标

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Quantum teleportation by entanglement swapping with trapped ions 郑小娟, 方卯发, 蔡建武, 廖湘萍 2006 (3):  492-495.  doi: 10.1088/1009-1963/15/3/007 摘要 ( 1874 )   PDF(195KB) ( 815 )   An effective teleportation scheme for an unknown ionic internal state via trapped ions is proposed without joint Bell-state measurement (BSM). In the constructed quantum channel process, we make use of entanglement swapping to avoid decrease in entanglement during the distributing of particles. Thus our scheme provides new prospects for quantum teleportation in a longer distance. The distinct advantage of our scheme is insensitive to the heating of vibrational mode. Furthermore, our scheme has no any individual optical access, and the successful probability also can reach 1. 相关文章 | 计量指标

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Gaussian wave formalism model for propagation of charged-particle beam through a first-order optical systems 陈宝信 2006 (3):  496-501.  doi: 10.1088/1009-1963/15/3/008 摘要 ( 1409 )   PDF(189KB) ( 442 )   An elliptical Gaussian wave formalism model of a charged-particle beam is proposed by analogy with an elliptical Gaussian light beam. In the paraxial approximation, the charged-particle beam can be described as a whole by a complex radius of curvature in the real space domains. Therefore, the propagation and transform of charged-particle beam passing through a first-order optical system is represented by the \textit{ABCD}-like law.As an example of the application of this model, the relation between the beam waist and the minimum beam spot at a fixed target is discussed. The result, well matches that from conventional phase space model, and proves that the Gaussian wave formalism model is highly effective and reasonable. 相关文章 | 计量指标

GENERAL

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The quantum spectra analysis of the circular billiards in wells 张延惠, 张丽琴, 徐学友, 葛美华, 林圣路, 杜孟利 2006 (3):  502-506.  doi: 10.1088/1009-1963/15/3/009 摘要 ( 1721 )   PDF(315KB) ( 750 )   We use a recently defined quantum spectral function and apply the method of closed-orbit theory to the 2D circular billiard system. The quantum spectra contain rich information of all classical orbits connecting two arbitrary points in the well. We study the correspondence between quantum spectra and classical orbits in the circular, 1/2 circular and 1/4 circular wells using the analytic and numerical methods. We find that the peak positions in the Fourier-transformed quantum spectra match accurately with the lengths of the classical orbits. These examples show evidently that semi-classical method provides a bridge between quantum and classical mechanics. 相关文章 | 计量指标

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Robust synchronization of uncertain chaotic systems 李芳, 胡爱花, 徐振源 2006 (3):  507-512.  doi: 10.1088/1009-1963/15/3/010 摘要 ( 1660 )   PDF(259KB) ( 848 )   This paper investigates robust unified (lag, anticipated, and complete) synchronization of two coupled chaotic systems. By introducing the concepts of positive definite symmetrical matrix and Riccati inequality and the theory of robust stability, several criteria on robust synchronization are established. Extensive numerical simulations are also used to confirm the results. 相关文章 | 计量指标

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Relation between the complex Ginzburg--Landau equation and reaction--diffusion system 邵昕, 任毅, 欧阳颀 2006 (3):  513-517.  doi: 10.1088/1009-1963/15/3/011 摘要 ( 1673 )   PDF(500KB) ( 674 )   The complex Ginzburg--Landau equation (CGLE) has been used to describe the travelling wave behaviour in reaction--diffusion (RD) systems. We argue that this description is valid only when the RD system is close to the Hopf bifurcation, and is not valid when a RD system is away from the onset. To test this, we study spirals and anti-spirals in the chlorite-iodide-malonic acid (CIMA) reaction and the corresponding CGLE. Numerical simulations confirm that the CGLE can only be applied to the CIMA reaction when it is very near the Hopf onset. 相关文章 | 计量指标

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Bursting and spiking due to additional direct and stochastic currents in neuron models 杨卓琴, 陆启韶 2006 (3):  518-525.  doi: 10.1088/1009-1963/15/3/012 摘要 ( 1427 )   PDF(351KB) ( 567 )   Neurons at rest can exhibit diverse firing activities patterns in response to various external deterministic and random stimuli, especially additional currents. In this paper, neuronal firing patterns from bursting to spiking, induced by additional direct and stochastic currents, are explored in rest states corresponding to two values of the parameter $V_{\rm K}$ in the Chay neuron system. Three cases are considered by numerical simulation and fast/slow dynamic analysis, in which only the direct current or the stochastic current exists, or the direct and stochastic currents coexist. Meanwhile, several important bursting patterns in neuronal experiments, such as the period-1 ``circle/homoclinic" bursting and the integer multiple ``fold/homoclinic" bursting with one spike per burst, as well as the transition from integer multiple bursting to period-1 ``circle/homoclinic" bursting and that from stochastic ``Hopf/homoclinic" bursting to ``Hopf/homoclinic" bursting, are investigated in detail. 相关文章 | 计量指标

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Estimation of luminescence lifetime in frequency domain 张福俊, 徐征, 赵谡玲, 娄志东, 杨盛谊, 徐叙瑢 2006 (3):  526-530.  doi: 10.1088/1009-1963/15/3/013 摘要 ( 1643 )   PDF(266KB) ( 589 )   Absorption is the origin of luminescence. But it must be noticed that the lifetime of luminescence might reversely influence the rate of absorption. In this paper, it is reported that the luminescence intensity of copper and manganese changes with the driving frequency at constant voltage.The variation of luminescent intensity depends only on the lifetime of luminescence but not on the type of quenching or other factors. Generally the rate of absorption is dominantly determined by the material property and the lifetime of luminescence centres, the absorption of shorter lifetime centre will be larger than that of the longer lifetime centre at the same excited condition. 相关文章 | 计量指标

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Accurate calculation of the elastic scattering properties of 7Li atoms at ultralow temperatures 孙金锋, 张计才, 王杰敏 2006 (3):  531-535.  doi: 10.1088/1009-1963/15/3/014 摘要 ( 1594 )   PDF(258KB) ( 773 )   The elastic scattering properties for collisions between two ${}^7$Li atoms are investigated in the cold and ultracold regimes separately. Based on recent theoretical and experimental results, we present the improved hybrid potentials for the singlet X$^1\dsum\nolimits_{\rm g}^ + $ and triplet a$^3\dsum\nolimits_{\rm u}^ +$ ground states of the Li$_2$. Our calculated values for the scattering lengths $a$ and the effective ranges $r_\e $ are compared with previous ones, and found them to be in good agreement. The scattering lengths are $34.6a_0$ for the singlet state and $-27.6a_0$ for the triplet state. Shape resonances occur in the collisions at low energies. We also calculate the total cross sections and the energy positions of shape resonances for both X$^1\dsum\nolimits_{\rm g}^ + $ and a$^3\dsum\nolimits_{\rm u}^ +$ states. 相关文章 | 计量指标

ATOMIC AND MOLECULAR PHYSICS

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A non-Markov ratchet model of molecular motors: processive movement of single-headed kinesin KIF1A 谢平, 窦硕星, 王鹏业 2006 (3):  536-541.  doi: 10.1088/1009-1963/15/3/015 摘要 ( 1522 )   PDF(314KB) ( 522 )   A fluctuating ratchet model of non-Markov process is presented to describe the processive movement of molecular motors of single-headed kinesin KIF1A,where the fluctuation perturbation to the local potential is introduced and the detailed ATPase pathway of the motor is included. The theoretical results show good quantitative agreement with the previous experimental ones. 相关文章 | 计量指标

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Entropy evolvement properties in a system of Schr?dinger cat state light field interacting with two entangled atoms 刘堂昆 2006 (3):  542-546.  doi: 10.1088/1009-1963/15/3/016 摘要 ( 1627 )   PDF(245KB) ( 780 )   The field entropy can be regarded as a measurement of the degree of entanglement between the light field and the atoms of a system which is composed of two-level atoms initially in an entangled state interacting with the Schr\"{o}dinger cat state. The influences of the strength of light field and the phase angle between the two coherent states on the field entropy are discussed by using numerical calculations. The result shows that when the strength of light field is large enough the field entropy is not zero and the degrees of entanglement between the atoms and the three different states of the light fields are equal. When the strength of the light field is small, the degree of entanglement is maximum in a system of the two entangled atoms interacting with an odd coherent state; it is intermediate for a system of the two entangled atoms interacting with the Yurke--Stoler coherent state, and it is minimum in a system of the two entangled atoms interacting with an even coherent state. 相关文章 | 计量指标

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Diode-pumped tunable laser with dual Cr:LiSAF rods 谢国强, 王韬, 朱鹤元, 钱列加 2006 (3):  547-551.  doi: 10.1088/1009-1963/15/3/017 摘要 ( 1559 )   PDF(255KB) ( 618 )   We propose and demonstrate a simple approach to lower the thermal quenching effect and improve the output power of Cr:LiSAF lasers, which is accomplished by employing two laser rods. The resonator contains two laser rods and is designed by using two ``X'' folding cavities in cascade. A tunable laser output of $\sim $ 180\,mW has been achieved with the pump of single-striped laser diodes. Compared with lasers using single gain rod, the laser with dual rods shows less severe thermal effect and increases the output by more than two times. 相关文章 | 计量指标

CLASSICAL AREAS OF PHENOMENOLOGY

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Near-field imaging of a square-lattice metallic photonic-crystal slab at the second band 冯帅, 冯志芳, 任坤, 任承, 李志远, 程丙英, 张道中 2006 (3):  552-555.  doi: 10.1088/1009-1963/15/3/018 摘要 ( 1599 )   PDF(916KB) ( 627 )   Imaging properties of a two-dimensional photonic crystal slab lens are investigated through the finite-difference time-domain method. In this paper, we consider the photonic crystal slab consisting of a square lattice of square metallic rods immersed in a dielectric background. Through the analysis of the equifrequency-surface contours and the field patterns of a point source placed in the vicinity of the photonic crystal slab, we find that a good-quality image can form at the frequencies in the second TM-polarized photonic band. Comparing the images formed at different frequencies, we can clearly see that an excellent-quality image is formed by the mechanisms of simultaneous action of the self-collimation effect and the negative-refraction effect. 相关文章 | 计量指标

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Analyses of edge plasma characteristics in HL-2A 洪文玉, 严龙文, 钱俊, 潘宇东, 王恩耀, 罗翠文, 徐征宇, 潘莉, 李强, 袁保山, 刘莉, 丁玄同 2006 (3):  556-561.  doi: 10.1088/1009-1963/15/3/019 摘要 ( 1308 )   PDF(560KB) ( 889 )   The edge plasma characteristics are studied by both a movable array of Mach/Reynolds stress/Langmuir 10-probes in the boundary region and the fixed flush probe arrays on the 4 divertor neutralization plates at the same toroidal cross-section in the HL-2A tokamak. The dependence of the Reynolds stress on poloidal flow in the edge plasma is analysed. The result indicates that the sheared poloidal flow in tokamak plasma can be induced by the radial gradient of Reynolds stress. In the divertor experiments of HL-2A, the profiles of the electron temperature, density and floating potential on divertor plates are measured by the flush probe arrays. The edge electron temperature in divertor configuration is higher than that in limiter configuration. The temperature asymmetry between outer and inner target plates is observed. The result of magnetic surface reconstructed from 18 Mirnov coils signals is presented. Both the particle recycling and the impurity flux in the bulk plasma during divertor discharges are discussed. Neutral gas pressure in divertor chamber, measured by fast ionization gauge during divertor discharge, is given. 相关文章 | 计量指标

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Interaction of solitary waves in magnetized warm dusty plasmas with dust charging effects 薛具奎 2006 (3):  562-567.  doi: 10.1088/1009-1963/15/3/020 摘要 ( 1351 )   PDF(243KB) ( 952 )   In consideration of adiabatic dust charge variation, the combined effect of the external magnetized field and the dust temperature on head-on collision of the three-dimensional dust acoustic solitary waves is investigated. By using the extended Poincar\'e--Lighthill--Kuo method, the phase shifts and the trajectories of two solitons after the collision are obtained. The effects of the magnitude and the obliqueness of the external magnetic field and the dust temperature on the solitary wave collisions are discussed in detail. 相关文章 | 计量指标

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Successive particle acceleration by use of two tightly focused ultra-short intense laser pulses 陈民, 盛政明, 张杰 2006 (3):  568-574.  doi: 10.1088/1009-1963/15/3/021 摘要 ( 1870 )   PDF(332KB) ( 711 )   We suggest a scheme of electron acceleration by use of two tightly focused ultra-short intense laser pulses at a 100TW level. Electrons obtain a preliminary acceleration with a small angular spread by the longitudinal ponderomotive force of the first pulse. They are then injected and further accelerated to hundreds of MeV by the second laser pulse. 相关文章 | 计量指标

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Surface properties of diamond-like carbon films prepared by CVD and PVD methods 刘东平, 刘艳红, 陈宝祥 2006 (3):  575-579.  doi: 10.1088/1009-1963/15/3/022 摘要 ( 1617 )   PDF(832KB) ( 1475 )   Diamond-like carbon (DLC) films have been deposited using three different techniques: (a) electron cyclotron resonance---plasma source ion implantation, (b) low-pressure dielectric barrier discharge, (c) filtered---pulsed cathodic arc discharge. The surface and mechanical properties of these films are compared using atomic force microscope-based tests. The experimental results show that hydrogenated DLC films are covered with soft surface layers enriched with hydrogen and sp$^{3}$ hybridized carbon while the soft surface layers of tetrahedral amorphous carbon (ta-C) films have graphite-like structure. The formation of soft surface layers can be associated with the surface diffusion and growth induced by the low-energy deposition process. For typical CVD methods, the atomic hydrogen in the plasmas can contribute to the formation of hydrogen and sp$^{3}$ hybridized carbon enriched surface layers. The high-energy ion implantation causes the rearrangement of atoms beneath the surface layer and leads to an increase in film density. The ta-C films can be deposited using the medium energy carbon ions in the highly-ionized plasma. 相关文章 | 计量指标

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The characteristics of confined ablation in laser propulsion 郑志远, 张杰, 郝作强, 远晓辉, 张喆, 鲁欣, 王兆华, 魏志义 2006 (3):  580-584.  doi: 10.1088/1009-1963/15/3/023 摘要 ( 1715 )   PDF(403KB) ( 852 )   Compared with direct ablation, confined ablation provides an effective way to obtain a large target momentum and a high coupling coefficient. By using a transparent glass layer to cover the target surface, the coupling coefficient is enhanced by an order of magnitude. With the increase of the gap width between the target surface and the cover layer, the coupling coefficient exponentially decreases. It is found that the coupling coefficient is also related to the thickness of the cover layer. 相关文章 | 计量指标

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Impurity behaviours of HL-2A divertor tokamak during the initial operation period 崔正英, 孙平, 潘宇东, 李伟, 王全明, 曹曾, 王明旭 2006 (3):  585-592.  doi: 10.1088/1009-1963/15/3/024 摘要 ( 1551 )   PDF(623KB) ( 698 )   The divertor configuration was successfully formed and the siliconization as a wall conditioning was first achieved on HL-2A tokamak experimentally in 2004. The divertor configuration is reconstructed by the use of the CFC code. Impurity as an important issue is investigated in the experiments with divertor configuration and wall conditioning. Impurities dramatically decrease after both the divertor configuration is formed and silicon is coated on the surface of the vacuum vessel. 相关文章 | 计量指标

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Tomographic analysis of the central magnetohydrodynamic oscillations on the HT-7 tokamak 马天鹏, 阮怀林, 胡立群, 万宝年, 高翔, 甄香君, 周立武, 孙有文, 高伟, 陈忠勇, 林士耀, 孔伟 2006 (3):  593-599.  doi: 10.1088/1009-1963/15/3/025 摘要 ( 1643 )   PDF(1177KB) ( 596 )   Multi-channel soft x-ray (SX) detectors are applied to generate images of magnetohydrodynamic (MHD) oscillation on the HT-7 tokamak, and the data from SX cameras are analysed by using the Fourier--Bessel harmonic reconstruction method and the singular value decomposition. The image reconstruction of SX emissivity is obtained on the assumption of plasma rigid rotation. One of the important phenomena in the HT-7 discharge is the transition from the sawtooth oscillations to the MHD oscillations when the plasma density grows higher. The MHD structure observed in the SX tomography is featured as follows: the magnetic surface of MHD structure is made up of the crescent-shaped ``hot core'' and the circular ``cold bubble''. The structure of the magnetic surface is relatively stable. It rotates in the direction of the electron diamagnetic drift at a frequency being the oscillation frequency of the MHD oscillations. 相关文章 | 计量指标

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Effect of longitudinal applied magnetic field on the self-pinched critical current in intense electron beam diode 刘国治, 黄文华, 邵浩, 肖仁珍 2006 (3):  600-603.  doi: 10.1088/1009-1963/15/3/026 摘要 ( 1795 )   PDF(240KB) ( 450 )   The effect of applied longitudinal magnetic field on the self-pinched critical current in the intense electron beam diode is discussed. The self-pinched critical current is derived and its validity is tested by numerical simulations. The results shows that an applied longitudinal magnetic field tends to increase the self-pinched critical current. Without the effect of anode plasma, the maximal diode current approximately equals the self-pinched critical current with the longitudinal magnetic field applied; when self-pinched occurs, the diode current approaches the self-pinched critical current. 相关文章 | 计量指标

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Effect of element Re on the grain boundary cohesion of α-Fe 陈征征, 王崇愚 2006 (3):  604-609.  doi: 10.1088/1009-1963/15/3/027 摘要 ( 1533 )   PDF(471KB) ( 594 )   The effect of Re segregation on the $\alpha $-Fe $\Sigma $5 [001] (010) grain boundary (GB) is investigated by using a software called DMol and discrete variational method (DVM). Based on the Rice--Wang model, the calculated segregation energy and defect formation energy show that Re is a strong cohesive enhancer. We also calculated the interatomic energy (IE) and bond order (BO) of several atomic pairs to investigate the mechanism of the cohesive effect of Re microscopically and locally. The results show that IEs of atomic pairs formed by those atoms which cross the plane of GB are strengthened due to the segregation of Re, while the BOs of the corresponding pairs are slightly decreased. This discrepancy demonstrates that IE which contains the Hamiltonian of interaction between atoms is a good quantity to describe the bonding strength. The analysis suggests that the electronic effect between atomic pair which comes directly from Hamiltonian is the key factor. The charge density is also presented, and the result indicates that the bonding strength between the Fe atoms on the GB is enhanced due to the segregation of Re, which is consistent with the analysis of IE. 相关文章 | 计量指标

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Investigation on quenching at a high-angle Cu grain boundary on an atomic scale 张林, 王绍青, 叶恒强 2006 (3):  610-617.  doi: 10.1088/1009-1963/15/3/028 摘要 ( 1283 )   PDF(721KB) ( 539 )   We have performed molecular dynamics simulations of structural changes due to quenching the melting interface at a Cu $\Sigma $5(310)/[001] symmetrical tilt grain boundary. The simulation results suggest that the grain boundary structures due to quenching are different from those due to heating up to the same temperature. The calculated atom density profiles show that the grain boundary structures can be significantly changed as they are quenched to quite low temperatures. 相关文章 | 计量指标

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Design of quantum VQ iteration and quantum VQ encoding algorithm taking $O(\sqrt N )$ steps for data compression 庞朝阳, 周正威, 陈平形, 郭光灿 2006 (3):  618-623.  doi: 10.1088/1009-1963/15/3/029 摘要 ( 1855 )   PDF(537KB) ( 561 )   Vector quantization (VQ) is an important data compression method. The key of the encoding of VQ is to find the closest vector among N vectors for a feature vector. Many classical linear search algorithms take $O(N)$ steps of distance computing between two vectors. The quantum VQ iteration and corresponding quantum VQ encoding algorithm that takes $O(\sqrt N )$ steps are presented in this paper. The unitary operation of distance computing can be performed on a number of vectors simultaneously because the quantum state exists in a superposition of states. The quantum VQ iteration comprises three oracles, by contrast many quantum algorithms have only one oracle, such as Shor's factorization algorithm and Grover's algorithm. Entanglement state is generated and used, by contrast the state in Grover's algorithm is not an entanglement state. The quantum VQ iteration is a rotation over subspace, by contrast the Grover iteration is a rotation over global space. The quantum VQ iteration extends the Grover iteration to the more complex search that requires more oracles. The method of the quantum VQ iteration is universal. 相关文章 | 计量指标

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

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The influence of trapping centres on the photoelectron decay in silver halide 李晓苇, 张荣香, 刘荣鹃, 杨少鹏, 韩理, 傅广生 2006 (3):  624-630.  doi: 10.1088/1009-1963/15/3/030 摘要 ( 1473 )   PDF(306KB) ( 662 )   Photoelectron is the foundation of latent image formation, the decay process of photoelectrons is influenced by all kinds of trapping centres in silver halide. By analysing the mechanism of latent image formation it is found that electron trap, hole trap, and one kind of recombination centre where free electron and trapped hole recombine are the main trapping centres in silver halide. Different trapping centres have different influences on the photoelectron behaviour. The effects of all kinds of typical trapping centres on the decay of photoelectrons are systematically investigated by solving the photoelectron decay kinetic equations. The results are in agreement with those obtained in the microwave absorption dielectric spectrum experiment. 相关文章 | 计量指标

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Analytical analysis of surface potential for grooved-gate MOSFET 张晓菊, 龚欣, 王俊平, 郝跃 2006 (3):  631-635.  doi: 10.1088/1009-1963/15/3/031 摘要 ( 1502 )   PDF(505KB) ( 630 )   The improvement of the characteristics of grooved-gate MOSFETs compared to the planar devices is attributed to the corner effect of the surface potential along the channel. In this paper we propose an analytical model of the surface potential distribution based on the solution of two-dimensional Poisson equation in cylindrical coordinates utilizing the cylinder approximation and the structure parameters such as the concave corner $\theta _0 $. The relationship between the minimum surface potential and the structure parameters is theoretically analysed. Results confirm that the bigger the concave corner, the more obvious the corner effect. The corner effect increases the threshold voltage of the grooved-gate MOSFETs, so the better is the short channel effect (SCE) immunity. 相关文章 | 计量指标

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Numerical simulation of transconductance of AlGaN/GaN heterojunction field effect transistors at high temperatures 常远程, 张义门, 张玉明 2006 (3):  636-640.  doi: 10.1088/1009-1963/15/3/032 摘要 ( 1736 )   PDF(261KB) ( 588 )   Based on the investigation of the influence of temperatures on parameters, including polarization, electron mobility, thermal conductivity, and conduction band discontinuity at the interface between AlGaN and GaN, the temperature dependence of transconductance for AlGaN/GaN heterojunction field effect transistors (HFETs) has been obtained by using a quasi-two-dimensional approach, and the calculated results are in good agreement with the experimental data. The reduction in transconductance at high temperatures is primarily due to the decrease in electron mobility in the channel. Calculations also demonstrate that the self-heating effect becomes serious as environment temperature increases. 相关文章 | 计量指标

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Research of the behaviour of O chemisorption on the (110) surface of Rhx--Pt1－x alloy 张辉, 张国英, 王瑞丹, 钟博 2006 (3):  641-644.  doi: 10.1088/1009-1963/15/3/033 摘要 ( 1485 )   PDF(267KB) ( 508 )   An atomic group model of the disordered binary alloy Rh$_{x}$--Pt$_{1-x}$ has been constructed to investigate surface segregation. According to the model, we have calculated the electronic structure of the Rh$_{x}$--Pt$_{1 - x }$alloy surface by using the recursion method when O atoms are adsorbed on the Rh$_{x}$--Pt$_{1-x }$(110) surface under the condition of coverage 0.5. The calculation results indicate that the chemical adsorption of O changes greatly the density of states near the Fermi level, and the surface segregation exhibits a reversal behaviour. In addition, when $x<0.3$, the surface on which O is adsorbed displays the property of Pt; whereas when $x>0.3$ it displays the property of Rh. 相关文章 | 计量指标

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

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Investigation of the characteristics of GIDL current in 90nm CMOS technology 陈海峰, 郝跃, 马晓华, 张进城, 李康, 曹艳荣, 张金凤, 周鹏举 2006 (3):  645-648.  doi: 10.1088/1009-1963/15/3/034 摘要 ( 1786 )   PDF(304KB) ( 1806 )   A specially designed experiment is performed for investigating gate-induced drain leakage (GIDL) current in 90nm CMOS technology using lightly-doped drain (LDD) NMOSFET. This paper shows that the drain bias $V_{\rm D}$ has a strong effect on GIDL current as compared with the gate bias $V_{\rm G}$ at the same drain--gate voltage $V_{\rm DG}$. It is found that the difference between $I_{\rm D}$ in the off-state $I_{\rm D}-V_{\rm G}$ characteristics and the corresponding one in the off-state $I_{\rm D}-V_{\rm D}$ characteristics, which is defined as $I_{\rm DIFF}$, versus $V_{\rm DG}$ shows a peak. The difference between the influences of $V_{\rm D}$ and $V_{\rm G}$ on GIDL current is shown quantitatively by $I_{\rm DIFF}$, especially in 90nm scale. The difference is due to different hole tunnellings. Furthermore, the maximum $I_{\rm DIFF }$($I_{\rm DIFF,MAX})$ varies linearly with $V_{\rm DG}$ in logarithmic coordinates and also $V_{\rm DG}$ at $I_{\rm DIFF,MAX}$ with $V_{\rm F}$ which is the characteristic voltage of $I_{\rm DIFF}$. The relations are studied and some related expressions are given. 相关文章 | 计量指标

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Terahertz field-induced modulations of intersubband absorptions in quantum wells 张拥华, 王长 2006 (3):  649-653.  doi: 10.1088/1009-1963/15/3/035 摘要 ( 1525 )   PDF(257KB) ( 772 )   Nonlinear optical properties of intersubband electrons in a 3-level quantum well under intense terahertz field are investigated by using a density matrix approach. The results show that the terahertz fields with different frequencies cause the distinct modulations of the intersubband absorptions. The terahertz-induced sideband and Autler--Towns splitting in the absorption spectrum are obtained, respectively for the terahertz-photon energy below and close to the transition energy between the ground and first excited state. 相关文章 | 计量指标

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Monte Carlo simulation of in-plane spin-polarized transport in GaAs/GaAlAs quantum well in the three-subband approximation 孔令刚, 刘晓彦, 杜刚, 王漪, 康晋锋, 韩汝琦 2006 (3):  654-658.  doi: 10.1088/1009-1963/15/3/036 摘要 ( 1387 )   PDF(280KB) ( 920 )   We develop a Monte Carlo (MC) tool incorporated with the three-subband approximation model to investigate the in-plane spin-polarized transport in GaAs/GaAlAs quantum well. Using the tool, the effects of the electron occupation of higher subbands and the intersubband scattering on the spin dephasing have been studied. Compared with the corresponding results of the simple one-subband approximation model, the spin dephasing length is reduced four times under 0.125\,kV/cm of driving electric field at 300K by the MC tool incorporated with the three-subband approximation model, indicating that the three-subband approximation model predicts significantly shorter spin dephasing length with temperature increasing. Our simulation results suggest that the effects of the electron occupation of higher subbands and the intersubband scattering on the spin-dependent transport of GaAs 2-dimensional electron gas need to be considered when the driving electric field exceeds the moderate value and the lattice temperature is above 100K. The simulation by using the MC tool incorporated with the three-subband approximation model also indicates that, under a certain driving electric field and lattice temperature, larger channel widths cause spins to be depolarized faster. Ranges of the three components of the spins are different for three different injected spin polarizations due to the anisotropy of spin--orbit interaction. 相关文章 | 计量指标