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2004年, 第13卷, 第2期　刊出日期：2004-02-06 上一期    下一期

GENERAL

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A hierarchy of lattice soliton equations and its Darboux transformation 丁海勇, 徐西祥, 赵向东 2004 (2):  125-131.  doi: 10.1088/1009-1963/13/2/001 摘要 ( 1193 )   PDF(165KB) ( 448 )   A new discrete spectral problem is introduced and the corresponding hierarchy of the lattice soliton equations are derived by means of the trace identity. We find a new Darboux transformation of the lattice soliton equation, through which the explicit solutions are shown. 相关文章 | 计量指标

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A subalgebra of loop algebra ?2 and its applications 张玉峰, 谭汉华, 郭福奎 2004 (2):  132-138.  doi: 10.1088/1009-1963/13/2/002 摘要 ( 1335 )   PDF(162KB) ( 446 )   A subalgebra of loop algebra ?_2 and its expanding loop algebra \overline{G} are constructed. It follows that both resulting integrable Hamiltonian hierarchies are obtained. As a reduction case of the first hierarchy, a generalized nonlinear coupled Schr?dinger equation, the standard heat-conduction and a formalism of the well known Ablowitz, Kaup, Newell and Segur hierarchy are given, respectively. As a reduction case of the second hierarchy, the nonlinear Schr?dinger and modified Korteweg de Vries hierarchy and a new integrable system are presented. Especially, a coupled generalized Burgers equation is generated. 相关文章 | 计量指标

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New explicit exact solutions to a nonlinear dispersive－dissipative equation 那仁满都拉, 王克协 2004 (2):  139-143.  doi: 10.1088/1009-1963/13/2/003 摘要 ( 1368 )   PDF(154KB) ( 531 )   Using the first-integral method, we obtain a series of new explicit exact solutions such as exponential function solutions, triangular function solutions, singular solitary wave solution and kink solitary wave solution of a nonlinear dispersive－dissipative equation, which describes weak nonlinear ion-acoustic waves in plasma consisting of cold ions and warm electrons. 相关文章 | 计量指标

GENERAL

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The supersymmetric WKB approximation for Hartmann potential 陈刚 2004 (2):  144-146.  doi: 10.1088/1009-1963/13/2/004 摘要 ( 1164 )   PDF(139KB) ( 497 )   Using the method of supersymmetric WKB approximation, the energy spectrum of some noncentral separable potentials can be exactly obtained in r and θ dimensions. We take the Hartmann potential as an important example for its validation, and the result is consistent with that obtained by using the supersymmetric quantum mechanics and shape invariance. 相关文章 | 计量指标

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Probabilistic remote state preparation by W states 刘金明, 王育竹 2004 (2):  147-152.  doi: 10.1088/1009-1963/13/2/005 摘要 ( 1168 )   PDF(159KB) ( 633 )   In this paper we consider a scheme for probabilistic remote state preparation of a general qubit by using W states. The scheme consists of the sender, Alice, and two remote receivers Bob and Carol. Alice performs a projective measurement on her qubit in the basis spanned by the state she wants to prepare and its orthocomplement. This allows either Bob or Carol to reconstruct the state with finite success probability. It is shown that for some special ensembles of qubits, the remote state preparation scheme requires only two classical bits, unlike the case in the scheme of quantum teleportation where three classical bits are needed. 相关文章 | 计量指标

GENERAL

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The symmetries in the Maxwell－Chern－Simons theory coupled to matter fields 江金环, 刘赟, 李子平 2004 (2):  153-158.  doi: 10.1088/1009-1963/13/2/006 摘要 ( 1207 )   PDF(173KB) ( 575 )   The Maxwell－Chern－Simons gauge theory coupled to a complex scalar field is quantized in the Becchi－Rouet－Stora－Tyutin path integral formalism. Based on the symmetries of a constrained canonical (Hamiltonian) system, we obtain the quantal conserved angular momentum of the system under the global symmetry transformation. It is shown that fractional spin also appears at the quantum level. The canonical Ward identities for this system are derived under local gauge transformation. 相关文章 | 计量指标

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The bending of light ray and unphysical solutions in general relativity 鲁重贤 2004 (2):  159-167.  doi: 10.1088/1009-1963/13/2/007 摘要 ( 1188 )   PDF(206KB) ( 468 )   In general relativity, according to Einstein, a gauge is related to the time dilation and the space contractions, and thus a physically realizable gauge should be unique for a given frame of reference. Since more than one metric solution for the same frame can produce the same deflection angle, this means that an invalid space－time metric can produce the correct deflection angle for a light ray. To demonstrate this with an unambiguous example, we consider a new extreme case that there is no space contraction in the radius direction while the conditions of asymptotic flatness and the requirement for gravitational red shifts are satisfied. This solution has a distinct characteristic of "space expansion" in the other directions. Nevertheless, it turns out that, in spite of requiring far more subtle calculations, the resulting deflection angle of a light ray is the same. An interesting property of this new solution is that its event horizon corresponds to an arbitrary integral constant. Thus, this calculation demonstrates beyond doubt that an unphysical solution can produce the correct first-order approximation of light bending. This makes it clear that there is a main difference between local effects such as the gravitational red shifts and the local light speeds, which are not gauge invariant, and integrated effects such as the bending of light, which can be (restricted) gauge invariant. 相关文章 | 计量指标

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Chaos synchronization based on intermittent state observer 李国辉, 周世平, 徐得名 2004 (2):  168-172.  doi: 10.1088/1009-1963/13/2/008 摘要 ( 1385 )   PDF(167KB) ( 549 )   This paper describes the method of synchronizing slave to the master trajectory using an intermittent state observer by constructing a synchronizer which drives the response system globally tracing the driving system asymptotically. It has been shown from the theory of synchronization error-analysis that a satisfactory result of chaos synchronization is expected under an appropriate intermittent period and state observer. Compared with continuous control method, the proposed intermittent method can target the desired orbit more efficiently. The application of the method is demonstrated on the hyperchaotic R?ssler systems. Numerical simulations show that the length of the synchronization interval τ_s is of crucial importance for our scheme, and the method is robust with respect to parameter mismatch. 相关文章 | 计量指标

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Memory-based quantum repeater in quantum information communication 伍祥生 2004 (2):  173-177.  doi: 10.1088/1009-1963/13/2/009 摘要 ( 1302 )   PDF(175KB) ( 649 )   This paper studies the quantum repeater in quantum information communication. We propose to introduce the photon buffer mechanism for storing photons, which uses fibre delay loops as photon memories and a programmable 1×N switcher for distributing photon delay time. Meanwhile, we also consider entanglement purification and entanglement swapping restoration at an entanglement purification or entanglement swapping failure and introduce a protection link mechanism that allows the photonic quantum repeater of a broken connection to initiate a connection restoration process. 相关文章 | 计量指标

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High order generalized permutational fractional Fourier transforms 冉启文, 袁琳, 谭立英, 马晶, 王骐 2004 (2):  178-186.  doi: 10.1088/1009-1963/13/2/010 摘要 ( 1134 )   PDF(306KB) ( 465 )   We generalize the definition of the fractional Fourier transform (FRFT) by extending the new definition proposed by Shih. The generalized FRFT, called the high order generalized permutational fractional Fourier transform (HGPFRFT), is a generalized permutational transform. It is shown to have arbitrary natural number M periodic eigenvalues not only with respect to the order of Hermite－Gaussian functions but also to the order of the transform. This HGPFRFT will be reduced to the original FRFT proposed by Namias and Liu's generalized FRFT and Shih's FRFT at the three limits with M=+∞, M=4k(k is a natural number), and M=4, respectively. Therefore the HGPFRFT introduces a comprehensive approach to Shih's FRFT and the original definition. Some important properties of HGPFRFT are discussed. Lastly the results of computer simulations and symbolic representations of the transform are provided. 相关文章 | 计量指标

CLASSICAL AREAS OF PHENOMENOLOGY

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Scheme for directly measuring the Wigner characteristic function via the driven Jaynes－Cummings model 郑仕标 2004 (2):  187-189.  doi: 10.1088/1009-1963/13/2/011 摘要 ( 1146 )   PDF(134KB) ( 562 )   A scheme is proposed for measuring the Wigner characteristic function of a cavity field. In the scheme an atom is sent through a slightly detuned cavity and driven by a strong resonant classical field. Then the population of the atom in the ground state directly yields the Wigner characteristic function of the cavity field. 相关文章 | 计量指标

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Basic characteristics of an atmospheric pressure rf generated plasma jet 王守国, 李海江, 叶甜春, 赵玲利 2004 (2):  190-195.  doi: 10.1088/1009-1963/13/2/012 摘要 ( 1208 )   PDF(241KB) ( 558 )   A plasma jet has been developed which operates using radio frequency (rf) power and produces a stable homogeneous discharge at atmospheric pressure. Its discharge characteristics, especially the dependence of stable discharge operating range on the feed gas, were studied, and the electric parameters such as RMS current, RMS voltage and reflected power were obtained with different gas flows. These studies indicate that there is an optimum range of operation of the plasma jet for a filling with a gas mixture of He and O_2. Two "failure" modes of the discharge are identified. One is a filamentary arc when the input power is raised above a critical level, another is that the discharge disappears gradually as the addition of O_2 approaches 3.2%. Possible explanations for the two failure modes have been given. The current and voltage waveform measurements show that there is a clear phase shift between normal and failure modes. In addition, I－V curves as a function of pure helium and for 1% addition of oxygen have been studied. 相关文章 | 计量指标

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Three-dimensional simulation on explosions of hydrogen atomic clusters irradiated by an intense femtosecond laser pulse 夏勇, 刘建胜, 倪国权, 徐至展 2004 (2):  196-200.  doi: 10.1088/1009-1963/13/2/013 摘要 ( 1217 )   PDF(185KB) ( 449 )   Using classic particle dynamics simulations, the interaction process between an intense femtosecond laser pulse and icosahedral hydrogen atomic clusters H_{13}, H_{55} and H_{147} has been studied. It is revealed that with increasing number of atoms in the cluster, the kinetic energy of ions generated in the Coulomb explosion of the ionized hydrogen clusters increases. The expansion process of the clusters after laser irradiation has also been examined, showing that the expansion scale decreases with increasing cluster size. 相关文章 | 计量指标

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Numerical study of the scaling of the maximum kinetic energy per unit length for imploding Z-pinch liner 曾正中, 邱爱慈 2004 (2):  201-204.  doi: 10.1088/1009-1963/13/2/014 摘要 ( 1333 )   PDF(164KB) ( 364 )   Numerical computation based on a zero-dimensional thin-plasma-shell model has been carried out to study the scaling of the maximum kinetic energy per unit length, the current amplitude and the compression ratio for the imploding Z-pinch liner driven by peaked current pulses. A dimensionless scaling constant of 0.9 with an error less than 10% is extracted at the optimal choice of the current and liner parameters. Deviation of the chosen experimental parameter from the optimal exerts a minor influence on the kinetic energy for wider-shaped and slower-decaying pulses, but the influence becomes significant for narrower-shaped and faster-decaying pulses. The computation is in reasonable agreement with experimental data from the Z, Saturn, Blackjack 5 and Qiangguang-I liners. 相关文章 | 计量指标

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Yield strengths and stress induced crackles in copper films: effects of substrate and passivated layer 张建民, 徐可为 2004 (2):  205-211.  doi: 10.1088/1009-1963/13/2/015 摘要 ( 1095 )   PDF(4520KB) ( 1731 )   Yield strengths in unpassivated and 530 nm TiN passivated Cu films deposited on Ti, high-speed steel and Ni substrates have been measured by x-ray diffraction (XRD) in combination with the four-point bending method. The results show that, although the texture and average grain size, investigated by XRD and transmission electron microscopy respectively, do not vary with different substrate, the yield strength of the Cu film increases obviously when a thin passivated layer is present and varies slightly with substrates. Many crackles appear in the passivated Cu film on Ti substrate but do not appear in other samples. The experimental results have been explained satisfactorily with an expression for the yield strength of thin films given previously. 相关文章 | 计量指标

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The microscopic theory for BPI and BPII of the blue phase 杨国琛, 崔英敏, 刘建军, 沈曙曼 2004 (2):  212-224.  doi: 10.1088/1009-1963/13/2/016 摘要 ( 1128 )   PDF(273KB) ( 348 )   A statistical theory of the blue phase of chiral liquid crystal is proposed. The form of the interaction potential between molecules is assumed to be the same as that used in the theory for cholesteric phase. Using the cell model of the liquid statistical theory, we deduced the distribution function of single molecule. The free energy of the system obtained has the same form as that of the Ginzberg－Landau phenomenology theory. The order-parameter tensors of BPI and BPII phases we calculated can be compared with the experimental results. 相关文章 | 计量指标

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The persistent current in an Aharonov－Bohm ring with a side-coupled quantum dot 周波, 吴绍全, 孙威立, 周晓林 2004 (2):  225-228.  doi: 10.1088/1009-1963/13/2/017 摘要 ( 1206 )   PDF(177KB) ( 554 )   We have investigated the persistent current in a mesoscopic ring with a side-coupled quantum dot. The problems are probed by using the one-impurity Anderson Hamiltonian and are treated with the slave boson mean field theory. It is shown that the persistent current in this system has the spin fluctuations, and the charge transfers between the two subsystems are suppressed in the limit of Δ/T_K^0《1. The minimum value of the persistent current for ξ_K/L=5 of the odd parity system provides an opportunity to detect the Kondo screening cloud. 相关文章 | 计量指标

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The pairing correlations in the phased t－U Hubbard model 刘自信, 刘平, 刘亚, 文生辉 2004 (2):  229-233.  doi: 10.1088/1009-1963/13/2/018 摘要 ( 1154 )   PDF(223KB) ( 494 )   In this paper we have studied the phased t－U Hubbard model. Using the constrained path Monte Carlo method, we investigated the effects of phase factor on pairing correlation functions in the ground state, and we found that the long-range correlations are dependent on the choice of phase factor, and for some special values of phase factor there exist long-range pairing correlations only in the strong coupling region. 相关文章 | 计量指标

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

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Reduced quantum fluctuation in mesoscopic Josephson junction with nonclassical radiation field at finite temperature 詹佑邦 2004 (2):  234-237.  doi: 10.1088/1009-1963/13/2/019 摘要 ( 1130 )   PDF(146KB) ( 446 )   We have investigated the reduced fluctuation properties in a mesoscopic Josephson junction with the squeezed state at a finite temperature. It is shown that the fluctuations increase with increasing temperature and the mesoscopic Josephson junction subsystem can exhibit squeezing behaviour at an appropriately low temperature. 相关文章 | 计量指标

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Fabrication of YBCO/YSZ and YBCO/MgO thick films using electrophoretic deposition with top-seeded melt growth process 朱亚彬, 周岳亮, 王淑芳, 刘震, 张芹, 陈正豪, 吕惠宾, 杨国桢 2004 (2):  238-242.  doi: 10.1088/1009-1963/13/2/020 摘要 ( 1219 )   PDF(1796KB) ( 429 )   Superconducting thick films were grown on single crystals MgO and YSZ by electrophoretic deposition with Y_2BaCuO_5(Y211) addition. YBCO thick films were then accomplished by sintering the precursor films above the peritectic temperature. Single crystals of MgO (3×3×0.5 mm^3) were used as top-seed to control crystal structure of the thick films. As shown by scanning electron microscopy, the morphologies of YBCO/YSZ and YBCO/MgO thick films are spherulitic texture and platelet type. The critical temperature is ～89 K for the YBCO/YSZ thick film; the onset transition temperature is 86.4 K and the transition width is ～3 K for YBCO/MgO thick film. The critical current densities (as determined by Bean model) are, in A/cm^2, 3870 (77 K) for YBCO/YSZ thick films and 2399 (77 K) for YBCO/MgO thick films, which are comparable to the best J_c reported of the thick films prepared by the same method. 相关文章 | 计量指标

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Nonequilibrium dynamical phase transition of 3D kinetic Ising/Heisenberg spin system 邵元智, Lai J. K. L., Shek C. H., 林光明, 蓝图 2004 (2):  243-250.  doi: 10.1088/1009-1963/13/2/021 摘要 ( 1042 )   PDF(282KB) ( 497 )   We have studied the nonequilibrium dynamic phase transitions of both three-dimensional (3D) kinetic Ising and Heisenberg spin systems in the presence of a perturbative magnetic field by Monte Carlo simulation. The feature of the phase transition is characterized by studying the distribution of the dynamical order parameter. In the case of anisotropic Ising spin system (ISS), the dynamic transition is discontinuous and continuous under low and high temperatures respectively, which indicates the existence of a tri-critical point (TCP) on the phase boundary separating low-temperature order phase and high-temperature disorder phase. The TCP shifts towards the higher temperature region with the decrease of frequency, i.e. T_{TCP}=1.33×exp(-ω/30.7). In the case of the isotropic Heisenberg spin system (HSS), however, the situation on dynamic phase transition of HSS is quite different from that of ISS in that no stable dynamical phase transition was observed in kinetic HSS after a threshold time. The evolution of magnetization in the HSS driven by a symmetrical external field after a certain duration always tends asymptotically to a disorder state no matter what an initial state the system starts with. The threshold time τ depends upon the amplitude H_{0}, reduced temperature T/T_C and the frequency ω as τ=C·ω^α·H_0^{-β}·(T/T_C)^{-γ}. 相关文章 | 计量指标

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Critical properties of XY model on two-layer Villain－ferromagnetic lattice 王漪, R. Quartu, 刘晓彦, 韩汝琦, 堀口刚 2004 (2):  251-257.  doi: 10.1088/1009-1963/13/2/022 摘要 ( 1220 )   PDF(477KB) ( 427 )   We investigate phase transitions of the XY model on a two-layer square lattice which consists of a Villain plane (J) and a ferromagnetic plane (I), using Monte Carlo simulations and a histogram method. Depending on the values of interaction parameters (I,J), the system presents three phases: namely, a Kosterlitz－Thouless (KT) phase in which the two planes are critical for I predominant over J, a chiral phase in which the two planes have a chiral order for J predominant over I and a new phase in which only the Villain plane has a chiral order and the ferromagnetic plane is paramagnetic with a small value of chirality. We clarify the nature of phase transitions by using a finite size scaling method. We find three different kinds of transitions according to the values of (I,J): the KT transition, the Ising transition and an XY-Ising transition with ν=0.849(3). It turns out that the Ising or XY-Ising transition is associated with the disappearance of the chiral order in the Villain plane. 相关文章 | 计量指标

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Optical transitions and upconversion properties of Er3+-doped chloride tellurite glasses 温磊, 李顺光, 黄国松, 胡丽丽, 姜中宏 2004 (2):  258-263.  doi: 10.1088/1009-1963/13/2/023 摘要 ( 1149 )   PDF(228KB) ( 442 )   Er^{3+}-doped lead chloride tellurite glasses were prepared using the conventional melting and quenching method. The absorption spectra were measured and the Judd－Ofelt analysis was performed. The spectroscopic parameters such as the intensity parameters, transition probabilities, radiative lifetimes, and branching ratios were obtained. Intense infrared emission and visible upconversion luminescence under 976 nm excitation were observed. For the 1.55μm emission, the full width at half maximum and the emission cross sections are more than 50 nm and 8×10^{- 20}cm^2, respectively. Three efficient visible luminescences centred at 525, 547, and 658nm are assigned to the transitions from the excited states {}^{2}H_{11/2}, {}^{4}S_{3/2}, and {}^{4}F_{9/2} to the ground state {}^{4}I_{15/2}, respectively. The upconversion mechanisms and the power-dependent intensities are also discussed and evaluated. 相关文章 | 计量指标

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A comparative study of electroluminescence from Ge/SiO2 and Si/SiO2 films 马书懿, 陈辉, 萧勇, 马自军, 孙爱民 2004 (2):  264-267.  doi: 10.1088/1009-1963/13/2/024 摘要 ( 983 )   PDF(156KB) ( 374 )   Ge/SiO_2 and Si/SiO_2 films were deposited using the two-target alternation magnetron sputtering technique. The Au/Ge/SiO_2/p-Si and Au/Si/SiO_2/p-Si structures were fabricated and their electroluminescence (EL) characteristics were comparatively studied. Both Au/Ge/SiO_2/p-Si and Au/Si/SiO_2/p-Si structures have rectifying property. All the EL spectra from the two types of the structure have peak positions around 650－660 nm. The EL mechanisms of the structures are discussed. 相关文章 | 计量指标

GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

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Bosonic and fermionic entropy of black holes with different temperatures on horizon surface 丁天然, 武月琴, 张丽春 2004 (2):  268-272.  doi: 10.1088/1009-1963/13/2/025 摘要 ( 1084 )   PDF(166KB) ( 425 )   By using the method of quantum statistics, we derive directly the partition functions of bosonic and fermionic field in the black hole space－time with different temperatures on horizon surface. The statistical entropy of the black hole is obtained by an improved brick-wall method. When we choose a proper parameter in our results, we can obtain that the entropy of the black hole is proportional to the area of horizon. In our result, there do not exist any neglected term or divergent logarithmic term as given in the original brick-wall method. We have avoided the difficulty in solving the wave equation of the scalar and Dirac field. A simple and direct way of studying entropy of the black hole is given. 相关文章 | 计量指标