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Table of contents

    20 September 2007, Volume 16 Issue 9 Previous issue    Next issue
    GENERAL
    An integrable Hamiltonian hierarchy and associated integrable couplings system
    Chen Xiao-Hong(陈晓红), Xia Tie-Cheng(夏铁成), and Zhu Lian-Cheng(朱连成)
    Chinese Physics, 2007, 16 (9):  2493-2497.  DOI: 10.1088/1009-1963/16/9/001
    Abstract ( 1429 )   PDF (105KB) ( 614 )  
    This paper establishes a new isospectral problem. By making use of the Tu scheme, a new integrable system is obtained. It gives integrable couplings of the system obtained. Finally, the Hamiltonian form of a binary symmetric constrained flow of the system obtained is presented.
    Controlling disease spread on networks with feedback mechanism
    Wang Li(王俐), Yan Jia-Ren(颜家壬), Zhang Jian-Guo(张建国), and Liu Zi-Ran(刘自然)
    Chinese Physics, 2007, 16 (9):  2498-2502.  DOI: 10.1088/1009-1963/16/9/002
    Abstract ( 1462 )   PDF (409KB) ( 545 )  
    Many real-world networks have the ability to adapt themselves in response to the state of their nodes. This paper studies controlling disease spread on network with feedback mechanism, where the susceptible nodes are able to avoid contact with the infected ones by cutting their connections with probability when the density of infected nodes reaches a certain value in the network. Such feedback mechanism considers the networks' own adaptivity and the cost of immunization. The dynamical equations about immunization with feedback mechanism are solved and theoretical predictions are in agreement with the results of large scale simulations. It shows that when the lethality $\alpha$ increases, the prevalence decreases more greatly with the same immunization $g$. That is, with the same cost, a better controlling result can be obtained. This approach offers an effective and practical policy to control disease spread, and also may be relevant to other similar networks.
    Asymptotical solutions of coupled nonlinear Schrödinger equations with perturbations
    Cheng Xue-Ping(程雪苹), Lin Ji(林机), and Ye Li-Jun(叶丽军)
    Chinese Physics, 2007, 16 (9):  2503-2509.  DOI: 10.1088/1009-1963/16/9/003
    Abstract ( 1421 )   PDF (1018KB) ( 552 )  
    In this paper Lou's direct perturbation method is applied to the perturbed coupled nonlinear Schrödinger equations to obtain their asymptotical solutions, which include not only the zero-order solutions but also the first-order modifications. Based on the asymptotical solutions, the effects of perturbations on soliton parameters and the collision between two solitons are then discussed in brief. Furthermore, we directly simulate the perturbed coupled nonlinear Schrödinger equations by split-step Fourier method to check the validity of the direct perturbation method. It turns out that our analytical results are well supported by the numerical calculations.
    Exponential--fraction trial function method to the 5th-order mKdV equation
    Li Ya-Zhou(李亚洲), Feng Wei-Gui(冯维贵), Li Kai-Ming(李开明), and Lin Chang(林长)
    Chinese Physics, 2007, 16 (9):  2510-2513.  DOI: 10.1088/1009-1963/16/9/004
    Abstract ( 1397 )   PDF (269KB) ( 683 )  
    This paper obtains some solutions of the 5th-order mKdV equation by using the exponential--fraction trial function method, such as solitary wave solutions, shock wave solutions and the hopping wave solutions. It successfully shows that this method may be valid for solving other nonlinear partial differential equations.
    Some new exact solutions to the Burgers--Fisher equation and generalized Burgers--Fisher equation
    Jiang Lu(姜璐), Guo Yu-Cui(郭玉翠), and Xu Shu-Jiang(徐淑奖)
    Chinese Physics, 2007, 16 (9):  2514-2522.  DOI: 10.1088/1009-1963/16/9/005
    Abstract ( 1360 )   PDF (469KB) ( 1045 )  
    Some new exact solutions of the Burgers--Fisher equation and generalized Burgers--Fisher equation have been obtained by using the first integral method. These solutions include exponential function solutions, singular solitary wave solutions and some more complex solutions whose figures are given in the article. The result shows that the first integral method is one of the most effective approaches to obtain the solutions of the nonlinear partial differential equations.
    Well-posedness of the time-varying linear electro-magnetic initial-boundary value problem
    Xie Li(谢莉) and Lei Yin-Zhao(雷银照)
    Chinese Physics, 2007, 16 (9):  2523-2536.  DOI: 10.1088/1009-1963/16/9/006
    Abstract ( 1337 )   PDF (270KB) ( 415 )  
    The well-posedness of the initial-boundary value problem of the time-varying linear electromagnetic field in a multi-medium region is investigated. Function spaces are defined, with Faraday's law of electromagnetic induction and the initial-boundary conditions considered as constraints. Gauss's formula applied to a multi-medium region is used to derive the energy-estimating inequality. After converting the initial-boundary conditions into homogeneous ones and analysing the characteristics of an operator introduced according to the total current law, the existence, uniqueness and stability of the weak solution to the initial-boundary value problem of the time-varying linear electromagnetic field are proved.
    Exciton--polaritons in ternary mixed crystals
    Liu Li(刘丽), Liang Xi-Xia(梁希侠), and Bao Jin(包锦)
    Chinese Physics, 2007, 16 (9):  2537-2543.  DOI: 10.1088/1009-1963/16/9/007
    Abstract ( 1482 )   PDF (195KB) ( 487 )  
    In this paper the bulk exciton polaritons in ternary mixed crystals (TMCs) are investigated in the Born--Huang approximation. The numerical results of the polariton frequencies as functions of the wave-vector and the compositions for ternary mixed crystals Al$_x$Ga$_{1 - x}$As, Cd$_x$Zn$_{1 - x}$Se, and Al$_x$Ga$_{1 - x}$N are obtained and discussed. The new dispersion characteristics for exciton--polaritons in TMC systems are found in comparison with binary crystals. The splitting of the two branches of exciton--polariton frequencies varies nonlinearly with the composition of TMCs and has a minimum in the long-wavelength range.
    Density matrix of two interacting particles with kinetic coupling derived in bipartite entangled state representation
    Guo Qin(郭琴)
    Chinese Physics, 2007, 16 (9):  2544-2548.  DOI: 10.1088/1009-1963/16/9/008
    Abstract ( 1437 )   PDF (113KB) ( 433 )  
    A density matrix is usually obtained by solving the Bloch equation, however only a few Hamiltonians' density matrices can be analytically derived. The density matrix for two interacting particles with kinetic coupling is hard to derive by the usual method due to this coupling; this paper solves this problem by using the bipartite entangled state representation.
    Secure deterministic communication scheme based on quantum remote state preparation
    Guo Ying(郭迎), Chen Zhi-Gang(陈志刚), and Zeng Gui-Hua(曾贵华)
    Chinese Physics, 2007, 16 (9):  2549-2556.  DOI: 10.1088/1009-1963/16/9/009
    Abstract ( 1434 )   PDF (325KB) ( 622 )  
    Based on the techniques of the quantum remote state preparation via a deterministic way, this paper proposes a quantum communication scheme to distribute the secret messages in two phases, i.e., the carrier state checking phase and the message state transmitting phase. In the first phase, the secret messages are encoded by the sender using a stabilizer quantum code and then transmitted to the receiver by implementing three CNOT gates. In the second phase, the communicators check the perfectness of the entanglement of the transmitted states. The messages can be distributed to the receiver even if some of the transmitted qubits are destroyed.
    Controlled teleportation of high-dimension quantum-states with generalized Bell-state measurement
    Zhan You-Bang(詹佑邦)
    Chinese Physics, 2007, 16 (9):  2557-2562.  DOI: 10.1088/1009-1963/16/9/010
    Abstract ( 1387 )   PDF (107KB) ( 985 )  
    In this paper a scheme for controlled teleportation of arbitrary high-dimensional unknown quantum states is proposed by using the generalized Bell-basis measurement and the generalized Hadamard transformation. As two special cases, two schemes of controlled teleportation of an unknown single-qutrit state and an unknown two-qutrit state are investigated in detail. In the first scheme, a maximally entangled three-qutrit state is used as the quantum channel, while in the second scheme, an entangled two-qutrit state and an entangled three-qutrit state are employed as the quantum channels. In these schemes, an unknown qutrit state can be teleported to either one of two receivers, but only one of them can reconstruct the qutrit state with the help of the other. Based on the case of qutrits, a scheme of controlled teleportation of an unknown qudit state is presented.
    Probabilistic teleportation of an arbitrary pure state of two atoms
    Yang Zhen-Biao(杨贞标), Wu Huai-Zhi(吴怀志), and Su Wan-Jun(苏万钧)
    Chinese Physics, 2007, 16 (9):  2563-2568.  DOI: 10.1088/1009-1963/16/9/011
    Abstract ( 1217 )   PDF (918KB) ( 514 )  
    In the context of microwave cavity QED, this paper proposes a new scheme for teleportation of an arbitrary pure state of two atoms. The scheme is very different from the previous ones which achieve the integrated state measurement, it deals in a probabilistic but simplified way. In the scheme, no additional atoms are involved and thus only two atoms are required to be detected. The scheme can also be used for the teleportation of arbitrary pure states of many atoms or two-mode cavities.
    The transfer of the quantum correlation from two-mode nonclassical state field to the supercurrents in two distant SQUID rings
    Peng Zhao-Hui(彭朝辉), Zou Jian(邹健), and Shao Bin(邵彬)
    Chinese Physics, 2007, 16 (9):  2569-2577.  DOI: 10.1088/1009-1963/16/9/012
    Abstract ( 1278 )   PDF (1122KB) ( 616 )  
    We have considered two distant mesoscopic superconducting quantum interference device (SQUID) rings A and B in the presence of two-mode nonclassical state fields and investigated the correlation of the supercurrents in the two rings using the normalized correlation function $C_{\rm AB}$. We show that when the parameter $\alpha$ is very small for the separable state with the density matrix $\hat {\rho } = (\left| {\alpha , - \alpha } \right\rangle \left\langle {\alpha , - \alpha } \right| + \left| { - \alpha ,\alpha } \right\rangle \left\langle { - \alpha ,\alpha } \right|) / 2$ and entangled coherent state (ECS) $\left| u \right\rangle = N_1 (\left| {\alpha , - \alpha } \right\rangle + \left| { - \alpha ,\alpha } \right\rangle )$ fields, the dynamic behaviours of the normalized correlation function $C_{\rm AB}$ are similar, but it is quite different for the entangled coherent state $\left| {u}' \right\rangle = N_2 (\left| {\alpha , - \alpha } \right\rangle - \left| { - \alpha ,\alpha } \right\rangle )$ field. When the parameter $\alpha $ is very large, the dynamic behaviours of $C_{\rm AB}$ are almost the same for the separable state, entangled coherent state $\left| u \right\rangle $ and $\left| {u}' \right\rangle $ fields. For the two-mode squeezed vacuum state field the maximum of $C_{\rm AB}$ increases monotonically with the squeezing parameter $r$, and as $r \to \infty $, $C_{\rm AB} \to 1$. This means that the supercurrents in the two rings A and B are quantum mechanically correlated perfectly. It is concluded that not all the quantum correlations in the two-mode nonclassical state field can be transferred to the supercurrents; and the transfer depends on the state of the two-mode nonclassical state field prepared.
    Internal Josephson-like tunnelling in two-component Bose--Einstein condensates affected by sign of the atomic interaction and external trapping potential
    Xiong Bo(熊波) and Liu Xun-Xu(刘循序)
    Chinese Physics, 2007, 16 (9):  2578-2583.  DOI: 10.1088/1009-1963/16/9/013
    Abstract ( 1326 )   PDF (737KB) ( 439 )  
    This paper studies the Josephson-like tunnelling in two-component Bose--Einstein condensates coupled with microwave field, which is in respond to various attractive and repulsive atomic interaction under the various aspect ratio of trapping potential. It is very interesting to find that the dynamic of Josephson-like tunnelling can be controlled from fast damped oscillations to nondamped oscillation, and relative number of atoms changes from asymmetric occupation to symmetric occupation correspondingly.
    Realistic teleportation of coherent states using squeezed vacuum states
    Yan Wei(闫伟) and Zhang Wei-Jun(张为俊)
    Chinese Physics, 2007, 16 (9):  2584-2586.  DOI: 10.1088/1009-1963/16/9/014
    Abstract ( 1300 )   PDF (86KB) ( 484 )  
    This paper presents a realistic scheme for the teleportation of coherent states in which a two-mode squeezed vacuum state serves as the quantum channel and the position-sum and momentum-difference of two local modes serve as the measuring observables. The average fidelity of the teleportation of coherent states is derived for finite squeezing parameters and it turns out that fidelity greater than 1/2 cannot be achieved by using a classical channel alone and the probability distribution of the measurement result is a Gaussian distribution around the unknown parameter of the input coherent state with a width given by the squeezing parameter.
    Dynamics of network motifs in genetic regulatory networks
    Li Ying(李莹), Liu Zeng-Rong(刘曾荣), and Zhang Jian-Bao(张建宝)
    Chinese Physics, 2007, 16 (9):  2587-2594.  DOI: 10.1088/1009-1963/16/9/015
    Abstract ( 1301 )   PDF (472KB) ( 505 )  
    Network motifs hold a very important status in genetic regulatory networks. This paper aims to analyse the dynamical property of the network motifs in genetic regulatory networks. The main result we obtained is that the dynamical property of a single motif is very simple with only an asymptotically stable equilibrium point, but the combination of several motifs can make more complicated dynamical properties emerge such as limit cycles. The above-mentioned result shows that network motif is a stable substructure in genetic regulatory networks while their combinations make the genetic regulatory network more complicated.
    Stochastic resonance in linear system driven by multiplicative noise and additive quadratic noise
    Ning Li-Juan(宁丽娟), Xu Wei(徐伟), and Yao Ming-Li(姚明礼)
    Chinese Physics, 2007, 16 (9):  2595-2599.  DOI: 10.1088/1009-1963/16/9/016
    Abstract ( 1304 )   PDF (225KB) ( 566 )  
    In this paper the stochastic resonance (SR) is studied in an overdamped linear system driven by multiplicative noise and additive quadratic noise. The exact expressions are obtained for the first two moments and the correlation function by using linear response and the properties of the dichotomous noise. SR phenomenon exhibits in the linear system. There are three different forms of SR: the bona fide SR, the conventional SR and SR in the broad sense. Moreover, the effect of the asymmetry of the multiplicative noise on the signal-to-noise ratio (SNR) is different from that of the additive noise and the effect of multiplicative noise and additive noise on SNR is different.
    Quasispecies distribution of Eigen model
    Chen Jia(陈佳), Li Sheng(李晟), and Ma Hong-Ru(马红孺)
    Chinese Physics, 2007, 16 (9):  2600-2607.  DOI: 10.1088/1009-1963/16/9/017
    Abstract ( 1105 )   PDF (704KB) ( 515 )  
    We have studied sharp peak landscapes of the Eigen model from a new perspective about how the quasispecies are distributed in the sequence space. To analyse the distribution more carefully, we bring in two tools. One tool is the variance of Hamming distance of the sequences at a given generation. It not only offers us a different avenue for accurately locating the error threshold and illustrates how the configuration of the distribution varies with copying fidelity $q$ in the sequence space, but also divides the copying fidelity into three distinct regimes. The other tool is the similarity network of a certain Hamming distance $d_{0}$, by which we can gain a visual and in-depth result about how the sequences are distributed. We find that there are several local similarity optima around the centre (global similarity optimum) in the distribution of the sequences reproduced near the threshold. Furthermore, it is interesting that the distribution of clustering coefficient $C(k)$ follows lognormal distribution and the curve of clustering coefficient $C$ of the network versus $d_{0}$ appears to be linear near the threshold.
    Generalized synchronization of two different chaotic systems
    Li Guo-Hui(李国辉)
    Chinese Physics, 2007, 16 (9):  2608-2611.  DOI: 10.1088/1009-1963/16/9/018
    Abstract ( 1559 )   PDF (105KB) ( 686 )  
    In this paper, generalized synchronization of two different chaotic dynamical systems is investigated. An active control is adopted to construct a response system which synchronizes with a given drive system for a function relation. Based on rigorous analysis, the error system is asymptotically stable at the equilibrium. Numerical simulations illustrate the effectiveness of the proposed theory.
    Projective synchronization in coupled fractional order chaotic Rossler system and its control
    Shao Shi-Quan(邵仕泉), Gao Xin(高心), and Liu Xing-Wen(刘兴文)
    Chinese Physics, 2007, 16 (9):  2612-2615.  DOI: 10.1088/1009-1963/16/9/019
    Abstract ( 1419 )   PDF (312KB) ( 806 )  
    This paper proposes a method to achieve projective synchronization of the fractional order chaotic Rossler system. First, construct the fractional order Rossler system's corresponding approximate integer order system, then a control method based on a partially linear decomposition and negative feedback of state errors is utilized on the new integer order system. Mathematic analyses prove the feasibility and the numerical simulations show the effectiveness of the proposed method.
    Generation of on--off intermittency based on Rössler chaotic system
    Zhou Qian(周茜), Chen Zeng-Qiang(陈增强), and Yuan Zhu-Zhi(袁著祉)
    Chinese Physics, 2007, 16 (9):  2616-2626.  DOI: 10.1088/1009-1963/16/9/020
    Abstract ( 1385 )   PDF (4794KB) ( 554 )  
    In this paper, one-state on--off intermittency and two-state on--off intermittency are generated in two five-dimensional continuum systems respectively. In each system, a two-dimensional subsystem is driven by the R?ssler chaotic system. The parameter conditions under which the on--off intermittency occurs are discussed in detail. The statistical property of the intermittency is investigated. It is shown that the distribution of the laminar phase duration time follows a power law with an exponent of $-3/2$, which is a signature of on--off intermittency. Moreover, the phenomenon of intermingled basins is observed when attractors in the two symmetric invariant subspaces are stable. We provide an effective way to generate on--off intermittency based on a chaotic system, which is important for application and theoretical study.
    Adaptive tracking control for a class of uncertain chaotic systems
    Chen Feng-Xiang(陈凤祥),Wang Wei(王伟), and Zhang Wei-Dong(张卫东)
    Chinese Physics, 2007, 16 (9):  2627-2630.  DOI: 10.1088/1009-1963/16/9/021
    Abstract ( 1343 )   PDF (184KB) ( 529 )  
    The paper is concerned with adaptive tracking problem for a class of chaotic system with time-varying uncertainty, but bounded by norm polynomial. Based on adaptive technique, it proposes a novel controller to asymptotically track the arbitrary desired bounded trajectory. Simulation on the Rossler chaotic system is performed and the result verifies the effectiveness of the proposed method.
    Chaotic phenomena in Josephson circuits coupled quantum cellular neural networks
    Wang Sen(王森), Cai Li(蔡理), Li Qin(李芹), and Wu Gang(吴刚)
    Chinese Physics, 2007, 16 (9):  2631-2634.  DOI: 10.1088/1009-1963/16/9/022
    Abstract ( 1509 )   PDF (592KB) ( 620 )  
    In this paper the nonlinear dynamical behaviour of a quantum cellular neural network (QCNN) by coupling Josephson circuits was investigated and it was shown that the QCNN using only two of them can cause the onset of chaotic oscillation. The theoretical analysis and simulation for the two Josephson-circuits-coupled QCNN have been done by using the amplitude and phase as state variables. The complex chaotic behaviours can be observed and then proved by calculating Lyapunov exponents. The study provides valuable information about QCNNs for future application in high-parallel signal processing and novel chaotic generators.
    Canards in a rheodynamic model of cardiac pressure pulsations
    Xie Feng (谢峰) and Chen Xian-Feng (陈贤峰)
    Chinese Physics, 2007, 16 (9):  2635-2639.  DOI: 10.1088/1009-1963/16/9/023
    Abstract ( 1326 )   PDF (217KB) ( 402 )  
    This paper reports on the canard phenomenon occurring in a rheodynamic model of cardiac pressure pulsations. By singular perturbation techniques the corresponding parameter value at which canards exist is obtained. The physiological significance of canards in this model is given.
    Controlling spiral wave with target wave in oscillatory systems
    Liu Fu-Cheng(刘富成), Wang Xiao-Fei(王晓菲), Li Xue-Chen(李雪辰), and Dong Li-Fang(董丽芳)
    Chinese Physics, 2007, 16 (9):  2640-2643.  DOI: 10.1088/1009-1963/16/9/024
    Abstract ( 1599 )   PDF (809KB) ( 555 )  
    Spiral waves have been controlled by generating target waves with a localized inhomogeneity in the oscillatory medium. The competition between the spiral waves and target waves is discussed. The effect of the localized inhomogeneity size has also been studied.
    Bifurcation phenomena of photodetached electron flux in parallel external fields
    Gao Song(高嵩), Li Hong-Yun(李洪云), Yang Guang-Can(杨光参), and Lin Sheng-Lu(林圣路)
    Chinese Physics, 2007, 16 (9):  2644-2649.  DOI: 10.1088/1009-1963/16/9/025
    Abstract ( 1259 )   PDF (770KB) ( 460 )  
    A semiclassical method based on the closed-orbit theory is applied to analysing the dynamics of photodetached electron of H$^- $ in the parallel electric and magnetic fields. By simply varying the magnetic field we reveal spatial bifurcations of electron orbits at a fixed emission energy, which is referred to as the fold caustic in classical motion. The quantum manifestations of these singularities display a series of intermittent divergences in electronic flux distributions. We introduce semiclassical uniform approximation to repair the electron wavefunctions locally in a mixed phase space and obtain reasonable results. The approximation provides a better treatment of the problem.
    Potential energy surfaces of ozone in the ground state
    Shao Ju-Xiang(邵菊香), Zhu Zheng-He(朱正和), Huang Duo-Hui(黄多辉) Wang Jun(王君), Cheng Xin-Lu(程新路), and Yang Xiang-Dong(杨向东)
    Chinese Physics, 2007, 16 (9):  2650-2655.  DOI: 10.1088/1009-1963/16/9/026
    Abstract ( 1412 )   PDF (324KB) ( 607 )  
    Equilibrium parameters of ozone, such as equilibrium geometry structure parameters, force constants and dissociation energy are presented by CBS-Q  ab initio calculations. The calculated equilibrium geometry structure parameters and energy are in agreement with the corresponding experimental values. The potential energy function of ozone with a C$_{\rm 2v}$ symmetry in the ground state is described by the simplified Sorbie--Murrell many-body expansion potential function according to the ozone molecule symmetry. The contour of bond stretching vibration potential of an O$_{3}$ in the ground state, with a bond angle ($\theta )$ fixed, and the contour of O$_{3}$ potential for O rotating around O$_{1}$--O ($R_{1})$, with O$_{1}$--O bond length taken as the one at equilibrium, are plotted. Moreover, the potentials are analysed.
    Tunnelling cooling by a normal--vacuum--superconductor junction
    Zhang Xin(张鑫) and Zhang Dian-Lin(张殿琳)
    Chinese Physics, 2007, 16 (9):  2656-2660.  DOI: 10.1088/1009-1963/16/9/027
    Abstract ( 1128 )   PDF (239KB) ( 467 )  
    The possibility of cooling a system from liquid helium temperature, 4.2 K, using a tunnel junction refrigerator is analysed. Calculations show that the device can be used over a wide temperature range from 4 K down to well below 1 mK with necessary cooling power. However, several serious difficulties must be overcome before the method can be used in low temperature laboratories.
    Formation and local electronic structure of Ge clusters on Si(111)-7×7 surfaces
    Ma Hai-Feng(马海峰), Xu Ming-Chun(徐明春), Yang Bing(杨冰), Shi Dong-Xia(时东霞), Guo Hai-Ming(郭海明), Pang Shi-Jin(庞世瑾), and Gao Hong-Jun(高鸿钧)
    Chinese Physics, 2007, 16 (9):  2661-2664.  DOI: 10.1088/1009-1963/16/9/028
    Abstract ( 1390 )   PDF (1118KB) ( 454 )  
    We report the formation and local electronic structure of Ge clusters on the Si(111)-7$\times $7 surface studied by using variable temperature scanning tunnelling microscopy (VT-STM) and low-temperature scanning tunnelling spectroscopy (STS). Atom-resolved STM images reveal that the Ge atoms are prone to forming clusters with 1.0 nm in diameter for coverage up to 0.12 ML. Such Ge clusters preferentially nucleate at the centre of the faulted-half unit cells, leading to the `dark sites' of Si centre adatoms from the surrounding three unfaulted-half unit cells in filled-state images. Bias-dependent STM images show the charge transfer from the neighbouring Si adatoms to Ge clusters. Low-temperature STS of the Ge clusters reveals that there is a band gap on the Ge cluster and the large voltage threshold is about 0.9 V.
    THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
    Lie symmetry algebra of one-dimensional nonconservative dynamical systems
    Liu Cui-Mei(刘翠梅), Wu Run-Heng(吴润衡), and Fu Jing-Li(傅景礼)
    Chinese Physics, 2007, 16 (9):  2665-2670.  DOI: 10.1088/1009-1963/16/9/029
    Abstract ( 1321 )   PDF (112KB) ( 490 )  
    Lie symmetry algebra of linear nonconservative dynamical systems is studied in this paper. By using 1--1 mapping, the Lie point and Lie contact symmetry algebras are obtained from two independent solutions of the one-dimensional linear equations of motion.
    NUCLEAR PHYSICS
    Effect of strong magnetic field on electron capture of iron group nuclei in crusts of neutron stars
    Liu Jing-Jing(刘晶晶), Luo Zhi-Quan(罗志全), Liu Hong-Lin(刘宏林), and Lai Xiang-Jun(赖祥军)
    Chinese Physics, 2007, 16 (9):  2671-2675.  DOI: 10.1088/1009-1963/16/9/030
    Abstract ( 1447 )   PDF (857KB) ( 1154 )  
    In this paper electron capture on iron group nuclei in crusts of neutron stars in a strong magnetic field is investigated. The results show that the magnetic fields have only a slight effect on electron capture rates in a range of 10$^{8}-10^{13}$G on surfaces of most neutron stars, whereas for some magnetars the magnetic fields range from 10$^{13}$ to 10$^{18}$ G. The electron capture rates of most iron group nuclei are greatly decreased, reduced by even four orders of magnitude due to the strong magnetic field.
    Scaling of anisotropic flows and nuclear equation of state in intermediate energy heavy ion collisions
    Yan Ting-Zhi(颜廷志), Ma Yu-Gang(马余刚), Cai Xiang-Zhou(蔡翔舟), Fang De-Qing(方德清), Guo Wei(郭威), Ma Chun-Wang(马春旺), Shen Wen-Qing(沈文庆), Tian Wen-Dong(田文栋), and Wang Kun(王鲲)
    Chinese Physics, 2007, 16 (9):  2676-2682.  DOI: 10.1088/1009-1963/16/9/031
    Abstract ( 1127 )   PDF (1090KB) ( 517 )  
    Elliptic flow ($v_2$) and hexadecupole flow ($v_4$) of light clusters have been studied in detail for 25 MeV/nucleon $^{86}$Kr + $^{124}$Sn at large impact parameters by using a quantum molecular dynamics model with different potential parameters. Four sets of parameters including soft or hard equation of state (EOS) with or without symmetry energy term are used. Both number-of-nucleon ($A$) scaling of the elliptic flow versus transverse momentum ($p_{\rm t}$) and the scaling of $v_4/A^{2}$ versus $(p_{\rm t}/A)^2$ have been demonstrated for the light clusters in all above calculation conditions. It is also found that the ratio of $v_4/{v_2}^2$ maintains a constant of 1/2 which is independent of $p_{\rm t}$ for all the light fragments. Comparisons among different combinations of the EOS and the symmetry potential term show that the above scaling behaviours are sound and independent of the details of potential, while the strengths of flows are sensitive to the EOS and the symmetry potential term.
    Evidence of intermittent fluctuation of target fragments in 84Kr--AgBr interactions at 1.7 A GeV
    Zhang Dong-Hai(张东海), Li Xue-Qin(李雪琴), Jia Hui-Ming(贾会明), He Chun-Le(何春乐), Liu Fang(刘芳), Zhao Hui-Hua(赵惠华), Li Zhen-Yu(李振宇), and Li Jun-Sheng(李俊生)
    Chinese Physics, 2007, 16 (9):  2683-2688.  DOI: 10.1088/1009-1963/16/9/032
    Abstract ( 1424 )   PDF (457KB) ( 516 )  
    Intermittency and fractal behaviour have been studied of emission spectra of target associated fragments from $^{84}$Kr--AgBr interactions at 1.7 A GeV in emission angle space and azimuthal angle space separately. The intermittent behaviour is observed in the two spaces separately. From the intermittency exponent, the anomalous fractal dimension $d_{q}$ is calculated and the variation of $d_{q}$ with the order $q$ is investigated. It is found that the anomalous dimensions are found to increase with the order of moments $q$, thereby indicating the relation of multifractality to production mechanism of target associated fragments.
    Intermittency in 3.7 A GeV 16O-emulsion interactions
    Zhang Dong-Hai(张东海), Zhao Hui-Hua(赵惠华), Liu Fang(刘芳), He Chun-Le(何春乐), Jia Hui-Ming(贾会明), Li Xue-Qin(李雪琴), Li Zhen-Yu(李振宇), and Li Jun-Sheng(李俊生)
    Chinese Physics, 2007, 16 (9):  2689-2700.  DOI: 10.1088/1009-1963/16/9/033
    Abstract ( 1438 )   PDF (1034KB) ( 597 )  
    The intermittency effect has been studied for an interaction of 3.7 A GeV $^{16}$O with emulsion using the distributions of both the pseudorapidity intervals and the azimuthal angle intervals of the shower particles emitted in a central rapidity region. The scaled factorial moments, reduced scaled factorial moments and multifractal moments as functions of the bin size in pseudorapidity and in azimuthal angle have been calculated and have revealed the presence of an intermittent behaviour which may be due to the random cascading property of the reaction. The anomalous fractal dimension has been found to increase with the increase of rank of the moment.
    ATOMIC AND MOLECULAR PHYSICS
    Ab initio calculations on the a3+u state properties of dimer 7Li2
    Shi De-Heng(施德恒), Sun Jin-Feng(孙金锋), Zhu Zun-Lue(朱遵略), and Liu Yu-Fang(刘玉芳)
    Chinese Physics, 2007, 16 (9):  2701-2708.  DOI: 10.1088/1009-1963/16/9/034
    Abstract ( 1415 )   PDF (222KB) ( 594 )  
    The comparison between single-point energy scanning (SPES) and geometry optimization (OPT) in determining the equilibrium geometry of the $a^{3}\Sigma ^{ + }_{\rm u}$ state for $^{7}$Li$_{2}$ is made at numerous basis sets such as 6-311++G(2df), cc-PVTZ, 6-311++G(2df,p), 6-311G(3df,3pd), 6-311++G(2df,2pd), D95(3df,3pd), 6-311++G, DGDZVP, 6-311++G(3df,2pd), 6-311G(2df,2pd), D95V++, CEP-121G, 6-311++G(d,p), 6-311++G(2df,pd) and 6-311++G(3df,3pd) in full active space using a symmetry-adapted-cluster/ symmetry-adapted-cluster configuration-interaction (SAC/SAC-CI) method presented in Gaussian03 program package. The difference of the equilibrium geometries obtained by SPES and by OPT is reported. Analyses show that the results obtained by SPES are more reasonable than those obtained by OPT. We have calculated the complete potential energy curves at these sets over a wide internuclear distance range from about 3.0$a_{0}$ to 37.0$a_{0}$, and the conclusion is that the basis set cc-PVTZ is the most suitable one. With the potential obtained at cc-PVTZ, the spectroscopic data ($T_{\rm e}$, $D_{\rm e}$, $D_{0}$, $\omega _{\rm e },\omega _{\rm e}\chi _{\rm e}$, $\alpha _{\rm e}$ and $B_{\rm e})$ are computed and they are 1.006 eV, 338.71 cm$^{ - 1}$, 307.12 cm$^{ - 1}$, 64.88 cm$^{ - 1}$, 3.41 cm$^{ - 1}$, 0.0187 cm$^{ - 1}$ and 0.279 cm$^{ - 1}$, respectively, which are in good agreement with recent measurements. The total 11 vibrational states are found at $J$=0. Their corresponding vibrational levels and classical turning points are computed and compared with available RKR data, and good agreement is found. One inertial rotation constant ($B_{\upsilon })$ and six centrifugal distortion constants ($D_{\upsilon }$ $H_{\upsilon }$, $L_{\upsilon }$, $M_{\upsilon }$, $N_{\upsilon }$ and $O_{\upsilon })$ are calculated. The scattering length is calculated to be --27.138$a_{0}$, which is in good accord with the experimental data.
    CLASSICAL AREAS OF PHENOMENOLOGY
    Analytical structure of Hermite Gaussian beam in far field
    Zhou Guo-Quan(周国泉), Chen Liang(陈亮), and Chu Xiu-Xiang(储修祥)
    Chinese Physics, 2007, 16 (9):  2709-2715.  DOI: 10.1088/1009-1963/16/9/035
    Abstract ( 1537 )   PDF (1386KB) ( 652 )  
    Based on the vectorial structure of electromagnetic beam and the method of stationary phase, the analytical structure of Hermite Gaussian beam in far field is presented. The structural energy flux distributions are also investigated in the far field. The structural pictures of some Hermite Gaussian beams are depicted in the far field. As the structure of Hermite Gaussian beam is dominated by the transverse mode numbers and the initial transverse Gaussian half width, it is more complex than that of Gaussian beam. The ratios of the structural energy fluxes to the whole energy flux are independent of the transverse mode numbers and the initial transverse Gaussian half width. The present research reveals the internal vectorial structure of Hermite Gaussian beam from other viewpoint.
    Space-charge limiting currents for magnetically focused intense relativistic electron beams
    Li Jian-Qing(李建清) and Mo Yuan-Long(莫元龙)
    Chinese Physics, 2007, 16 (9):  2716-2720.  DOI: 10.1088/1009-1963/16/9/036
    Abstract ( 1136 )   PDF (149KB) ( 448 )  
    The self-consistent differential equations, which describe a laminar-flow equilibrium state in a magnetically focused intense relativistic electron beam propagating inside a conducting waveguide, are presented. The canonical angular momentum, $p_{\theta }$, defined under the conditions at the source, uniquely determines the possible solutions of these equations. By numerically solving these equations, the space-charge limited current and the externally applied magnetic field are obtained in a solid beam and a hollow beam in two cases of $p_{\theta }=0$ (magnetically shielded source) and $p_{\theta }=$ const. (immersed source) separately. It is shown that the hollow beam is more beneficial to the propagation of the intense relativistic beam through a drift tube than the solid beam.
    An exact solution to paraxial propagation of laser beams in longitudinal inhomogeneous plasmas
    Zhou Bing-Ju(周并举), Huang Zheng(黄正), Liu Ming-Wei(刘明伟) and Liu Xiao-Juan(刘小娟)
    Chinese Physics, 2007, 16 (9):  2721-2724.  DOI: 10.1088/1009-1963/16/9/037
    Abstract ( 1451 )   PDF (128KB) ( 539 )  
    An exact, general solution for laser beams propagating in longitudinally inhomogeneous plasmas is obtained in the form of the diffraction integral. The Gaussian beam and the Hermite--Gaussian beam are taken for example. In the case of an increasing plasma density along the propagation distance, natural diffraction of the Gaussian beam is retarded. This retardance has a less effect on the central part of the Hermite--Gaussian beam while a considerable rise of the power in bucket (PIB) occurs in the surrounding part of the beam.
    Orientation-enhanced nonlinear optical properties and phase-conjugate reflective system of a novel Azobenzene doped polymer film
    Xie Ru-Sheng(谢茹胜), Fan Wen-Bin(范文彬), Lu Ming(陆明), and Zhao You-Yuan(赵有源)
    Chinese Physics, 2007, 16 (9):  2725-2730.  DOI: 10.1088/1009-1963/16/9/038
    Abstract ( 1482 )   PDF (536KB) ( 723 )  
    This paper reports that the nonlinear refractive index of a novel organic optical storage film doped azo-diphenylamine polymer is measured by using the $Z$-scan technique. The nonlinear refractive index up to $3.7\times 10 ^{ - 6 }$ cm$^{2}$/W induced by thermo-optical effect is obtained. It indicates that the sample has excellent optical nonlinear properties. The physical mechanism of the great nonlinear optical effect is analysed and the optical conjugate characteristic is also discussed with degenerate four-wave-mixing. The phase conjugate wave diffracted from the formative refractive index grating in the sample is acquired and its equivalent reflectivity reaches about 22%. On this basis, the reflective wave phase-conjugated mirror system was designed, and the image aberration experienced in propagation in the storage experiment is corrected by using the system.
    Potential fields of merging and splitting filaments in air
    Ma Yuan-Yuan(马媛媛), Lu Xin(鲁欣), Xi Ting-Ting(奚婷婷), Hao Zuo-Qiang(郝作强), Gong Qi-Huang(龚旗煌), and Zhang Jie(张杰)
    Chinese Physics, 2007, 16 (9):  2731-2736.  DOI: 10.1088/1009-1963/16/9/039
    Abstract ( 1352 )   PDF (1154KB) ( 456 )  
    Two interacting light filaments with different initial phases propagating in air are investigated numerically by using a ray tracing method. The evolution of the rays of a filament is governed by a potential field. During propagation, the two potential wells of the two filaments can merge into one or repel each other, depending on the initial phase difference between the two filaments. The study provides a simple description of the interacting filaments.
    A method of designing photonic crystal grating slow-wave circuit for Ribbon--Beam microwave travelling wave amplifiers
    Yin Hai-Rong(殷海荣), Gong Yu-Bin(宫玉彬), Wei Yan-Yu(魏彦玉), Gong Hua-Rong(巩华荣), Yue Ling-Na(岳玲娜), Lu Zhi-Gang(路志刚), Huang Min-Zhi(黄民智), and Wang Wen-Xiang(王文祥)
    Chinese Physics, 2007, 16 (9):  2737-2744.  DOI: 10.1088/1009-1963/16/9/040
    Abstract ( 1207 )   PDF (1239KB) ( 577 )  
    A method of designing a photonic crystal grating slow-wave circuit in which the cylinders of the 2D photonic crystals dot on a cross-sectional plane is established by calculating the band structures of the 2D photonic crystals, and the eigenfrequency of the equivalent waveguide grating. For calculating the band structures, the eigenvalue equations of the photonic crystals in the system of photonic crystal grating slow-wave circuit are derived in a special polarization mode. Two examples are taken to show the method. The design result is validated by the scattering parameters of the same circuit. The result indicates that there exists no photonic band gap if the metal gratings do not extend into the photonic crystals; the design of the circuit without the metal gratings extending into the photonic crystals is less flexible than that with the metal gratings extending into the photonic crystals.
    Noninvasive temperature estimation by detecting echo-strain change including thermal expansion
    Ma Yong(马勇), Zhang Dong(章东), Gong Xiu-Fen(龚秀芬), Liu Xiao-Zhou(刘晓宙), Ma Qing-Yu(马青玉), and Qiu Yuan-Yuan(邱媛媛)
    Chinese Physics, 2007, 16 (9):  2745-2751.  DOI: 10.1088/1009-1963/16/9/041
    Abstract ( 1088 )   PDF (1080KB) ( 495 )  
    This article studies the feasibility of noninvasive temperature estimation by detecting echo-strain including thermal expansion in therapeutic ultrasound treatment. This technique evaluates distributions of echo-strain and temperature inside the tissue by detecting echo signals pre- and post-heating, in combination with the temperature dependence of sound speed and thermal expansion. In the computer simulation and experimental study, echo signals pre- and post-heating are acquired and then the temperature elevation is evaluated by correlation analysis. Results demonstrate that this technique can effectively extend the measured temperature range up to 75$^{\circ}$C with an accuracy of $\pm $2$\,^{\circ}$C.
    PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
    Influence of air pressure on mechanical effect of laser plasma shock wave
    Zhang Yu-Zhu(章玉珠), Wang Guang-An(王广安), Zhu Jin-Rong(朱金荣), Shen Zhong-Hua(沈中华), Ni Xiao-Wu(倪晓武), and Lu Jian(陆建)
    Chinese Physics, 2007, 16 (9):  2752-2756.  DOI: 10.1088/1009-1963/16/9/042
    Abstract ( 1481 )   PDF (257KB) ( 620 )  
    The influence of air pressure on mechanical effect of laser plasma shock wave in a vacuum chamber produced by a Nd:YAG laser has been studied. The laser pulses with pulse width of 10ns and pulse energy of about 320mJ at 1.06$\mu $m wavelength is focused on the aluminium target mounted on a ballistic pendulum, and the air pressure in the chamber changes from $2.8\times 10^{3}$ to 1.01$\times $10$^{5 }$Pa. The experimental results show that the impulse coupling coefficient changes as the air pressure and the distance of the target from focus change. The mechanical effects of the plasma shock wave on the target are analysed at different distances from focus and the air pressure.
    A comparison among optical emission spectroscopic methods of determining electron temperature in low pressure argon plasmas
    Niu Tian-Ye(牛田野), Cao Jin-Xiang(曹金祥), Liu Lei(刘磊), Liu Jin-Ying(刘金英), Wang Yan(王艳), Wang Liang(王亮), and Lv You(吕铀)
    Chinese Physics, 2007, 16 (9):  2757-2763.  DOI: 10.1088/1009-1963/16/9/043
    Abstract ( 1428 )   PDF (567KB) ( 1043 )  
    In this article, four kinds of optical emission spectroscopic methods of determining electron temperature are used to investigate the relationship between electron temperature and pressure in the cylindrical plasmas of dc glow discharges at low pressures in laboratory by measuring the relative intensities of ArI lines at various pressures. These methods are developed respectively on the basis of the Fermi--Dirac model, corona model, and two kinds of electron collision cross section models according to the kinetic analysis. Their theoretical bases and the conditions to which they are applicable are reviewed, and their calculation results and fitting errors are compared with each other. The investigation has indicated that the electron temperatures obtained by the four methods become consistent with each other when the pressure increases in the low pressure argon plasmas.
    CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
    Formation mechanism of Ge nanocrystals embedded in SiO2 studied by fluorescence x-ray absorption fine structure
    Yan Wen-Sheng(闫文盛), Li Zhong-Rui(李忠瑞), Sun Zhi-Hu(孙治湖), Pan Zhi-Yun(潘志云), and Wei Shi-Qiang(韦世强)
    Chinese Physics, 2007, 16 (9):  2764-2768.  DOI: 10.1088/1009-1963/16/9/044
    Abstract ( 1467 )   PDF (527KB) ( 575 )  
    This paper reports that the Ge nanocrystals embedded in SiO$_{2}$ matrix are grown on Si(100) and quartz--glass substrates, and the formation mechanism is systematically studied by using fluorescence x-ray absorption fine structure (XAFS). It is found that the formation of Ge nanocrystals strongly depends on the properties of substrate materials. In the as-prepared samples with Ge molar content of 60%, Ge atoms exist in amorphous Ge (about 36%) and GeO$_{2 }$ (about 24%) phases. At the annealing temperature of 1073 K, on the quartz--glass substrate Ge nanocrystals are generated from crystallization of amorphous Ge, rather than from the direct decomposition of GeO$_{2}$ in the as-deposited sample. However, on the Si(100) substrate, the Ge nanocrystals are generated partly from crystallization of amorphous Ge, and partly from GeO$_{2}$ phases through the permutation reaction with Si substrate. Quantitative analysis reveals that about 10% of GeO$_{2}$ in the as-prepared sample are permuted with Si wafer to form Ge nanocrystals.
    Synthesis and photoluminescence study on ZnO nano-particles
    Li Xiang(李祥), Zhai Fei-Fei(翟斐斐), Liu Ying(刘颖), Cao Mao-Sheng(曹茂盛), Wang Fu-Chi(王富耻), and Zhang Xi-Xiang(张西祥)
    Chinese Physics, 2007, 16 (9):  2769-2772.  DOI: 10.1088/1009-1963/16/9/045
    Abstract ( 1654 )   PDF (537KB) ( 751 )  
    A new technique, namely low pressure sputtering, has been developed to fabricate Zn nanoparticles, with a subsequent oxidation to synthesize ZnO nanoparticles in the ambient atmosphere at 500$^{\circ}$C. The synthesized ZnO nanoparticle has a size of 6--8 nm with a preferred orientation of $c$-axis. The produced ZnO nanoparticles have a good UV photoluminescence (PL) emission energy of 3.349 eV with a significant enhancement of donor--acceptor pair emission located at 3.305 eV which implies a number of donor and acceptor bounded excitons existing in the synthesized ZnO nano particles. The near band edge PL emission of the fabricated ZnO is dominated by the bounded excitons at 10 K.
    Experimental study on radiation effects in floating gate read-only-memories and static random access memories
    He Chao-Hui(贺朝会) and Li Yong-Hong(李永宏)
    Chinese Physics, 2007, 16 (9):  2773-2778.  DOI: 10.1088/1009-1963/16/9/046
    Abstract ( 1443 )   PDF (686KB) ( 564 )  
    Radiation effects of the floating gate read-only-memory (FG ROM) and the static random access memory (SRAM) have been evaluated using the 14 MeV neutron and 31.9MeV proton beams and Co-60 $\gamma $-rays. The neutron fluence, when the first error occurs in the FG ROMs, is at least 5 orders of magnitude higher than that in the SRAMs, and the proton fluence, 4 orders of magnitude higher. The total dose threshold for Co-60 $\gamma $-ray irradiation is about 10$^{4}$ rad (Si) for both memories. The difference and similarity are attributed to the structure of the memory cells and the mechanism of radiation effects. It is concluded that the FG ROMs are more reliable as semiconductor memories for storing data than the SRAMs, when they are used in the satellites or space crafts exposed to high energy particle radiation.
    Molecular dynamics simulation of thermodynamic properties of YAG
    Chen Jun(陈军), Chen Dong-Quan(陈栋泉), and Zhang Jing-Lin(张景琳)
    Chinese Physics, 2007, 16 (9):  2779-2785.  DOI: 10.1088/1009-1963/16/9/047
    Abstract ( 1356 )   PDF (668KB) ( 945 )  
    In this paper we study the thermodynamic properties of Y$_{3}$Al$_{5}$O$_{12}$ (YAG) by using molecular dynamic method combined with two- and three-body potentials. The dependences of melting process, elastic constant and diffusion coefficient on temperature of crystal YAG are simulated and compared with the experimental results. Our results show that anion O has the biggest self-diffusivity and cation Y has the smallest self-diffusivity in a crystal YAG. The calculated diffusion activation energies of ions O, Al and Y are 282.55, 439.46, 469.71kJ/mol, respectively. Comparing with experimental creep activation energy of YAG confirms that cation Y can restrict the diffusional creep rate of crystal YAG.
    GaN layers with different polarities prepared by radio frequency molecular beam epitaxy and characterized by Raman scattering
    Zhong Fei(钟飞), Li Xin-Hua(李新化), Qiu Kai(邱凯), Yin Zhi-Jun(尹志军), Ji Chang-Jian(姬长建), Cao Xian-Cun(曹先存), Han Qi-Feng(韩奇峰), Chen Jia-Rong(陈家荣), and Wang Yu-Qi(王玉琦)
    Chinese Physics, 2007, 16 (9):  2786-2790.  DOI: 10.1088/1009-1963/16/9/048
    Abstract ( 1354 )   PDF (1084KB) ( 982 )  
    GaN layers with different polarities have been prepared by radio-frequency molecular beam epitaxy (RF-MBE) and characterized by Raman scattering. Polarity control are realized by controlling Al/N flux ratio during high temperature AlN buffer growth. The Raman results illustrate that the N-polarity GaN films have frequency shifts at $A_{1}$(LO) mode because of their high carrier density; the forbidden $A_{1}$(TO) mode occurs for mixed-polarity GaN films due to the destroyed translation symmetry by inversion domain boundaries (IDBS); Raman spectra for Ga-polarity GaN films show that they have neither frequency shifts mode nor forbidden mode. These results indicate that Ga-polarity GaN films have a better quality, and they are in good agreement with the results obtained from the room temperature Hall mobility. The best values of Ga-polarity GaN films are 1042 cm$^{2}$/Vs with a carrier density of 1.0$\times $10$^{17}$ cm$^{ - 3}$.
    CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
    Electronic structure and optical properties of In-doped SrTiO3 by density function theory
    Zhang Zhi-Yong(张志勇), Yun Jiang-Ni(贠江妮), and Zhang Fu-Chun(张富春)
    Chinese Physics, 2007, 16 (9):  2791-2797.  DOI: 10.1088/1009-1963/16/9/049
    Abstract ( 1541 )   PDF (1112KB) ( 925 )  
    The effect of In doping on the electronic structure and optical properties of SrTiO$_{3}$ is investigated by the first-principles calculation of plane wave ultra-soft pseudo-potential based on the density function theory (DFT). The calculated results reveal that due to the hole doping, the Fermi level shifts into valence bands (VBs) for SrTi$_{1-x}$In$_{x}$O$_{3 }$ with $x=0.125$ and the system exhibits p-type degenerate semiconductor features. It is suggested according to the density of states (DOS) of SrTi$_{0.875}$In$_{0.125}$O$_{3}$ that the band structure of p-type SrTiO$_{3}$ can be described by a rigid band model. At the same time, the DOS shifts towards high energies and the optical band gap is broadened. The wide band gap, small transition probability and weak absorption due to the low partial density of states (PDOS) of impurity in the Fermi level result in the optical transparency of the film. The optical transmittance of In doped SrTiO$_{3}$ is higher than 85% in a visible region, and the transmittance improves greatly. And the cut-off wavelength shifts into a blue-light region with the increase of In doping concentration.
    Role of atomic transverse migration in growth of diamond-like carbon films
    Ma Tian-Bao(马天宝), Hu Yuan-Zhong(胡元中), and Wang Hui(王慧)
    Chinese Physics, 2007, 16 (9):  2798-2802.  DOI: 10.1088/1009-1963/16/9/050
    Abstract ( 1370 )   PDF (596KB) ( 579 )  
    The growth of diamond-like carbon (DLC) films is studied using molecular dynamics simulations. The effect of impact angle on film structure is carefully studied, which shows that the transverse migration of the incident atoms is the main channel of film relaxation. A transverse-migration-induced film relaxation model is presented to elucidate the process of film relaxation which advances the original model of subplantation. The process of DLC film growth on a rough surface is also investigated, as well as the evolution of microstructure and surface morphology of the film. A preferential-to-homogeneous growth mode and a smoothing of the film are observed, which are due to the transverse migration of the incident atoms.
    High density Al2O3/TaN-based metal--insulator-- metal capacitors in application to radio frequency integrated circuits
    Ding Shi-Jin(丁士进), Huang Yu-Jian(黄宇健), Huang Yue(黄玥), Pan Shao-Hui(潘少辉), Zhang Wei(张卫), and Wang Li-Kang(汪礼康)
    Chinese Physics, 2007, 16 (9):  2803-2808.  DOI: 10.1088/1009-1963/16/9/051
    Abstract ( 1238 )   PDF (767KB) ( 858 )  
    Metal--insulator--metal (MIM) capacitors with atomic-layer-deposited Al$_{2}$O$_{3}$ dielectric and reactively sputtered TaN electrodes in application to radio frequency integrated circuits have been characterized electrically. The capacitors exhibit a high density of about 6.05 fF/$\mu $m$^{2}$, a small leakage current of $4.8\times 10^{-8}$ A/cm$^{2}$ at 3 V, a high breakdown electric field of 8.61 MV/cm as well as acceptable voltage coefficients of capacitance (VCCs) of 795 ppm/V$^{2}$ and 268 ppm/V at 1 MHz. The observed properties should be attributed to high-quality Al$_{2}$O$_{3}$ film and chemically stable TaN electrodes. Further, a logarithmically linear relationship between quadratic VCC and frequency is observed due to the change of relaxation time with carrier mobility in the dielectric. The conduction mechanism in the high field ranges is dominated by the Poole--Frenkel emission, and the leakage current in the low field ranges is likely to be associated with trap-assisted tunnelling. Meanwhile, the Al$_{2}$O$_{3}$ dielectric presents charge trapping under low voltage stresses, and defect generation under high voltage stresses, and it has a hard-breakdown performance.
    Theoretical analysis of ion kinetic energies and DLC film deposition by CH4+Ar (He) dielectric barrier discharge plasmas
    Liu Yan-Hong(刘艳红), Zhang Jia-Liang(张家良), Ma Teng-Cai(马腾才), Li Jian(李建), and Liu Dong-Ping(刘东平)
    Chinese Physics, 2007, 16 (9):  2809-2813.  DOI: 10.1088/1009-1963/16/9/052
    Abstract ( 1393 )   PDF (438KB) ( 573 )  
    The kinetic energy of ions in dielectric barrier discharge plasmas are analysed theoretically using the model of binary collisions between ions and gas molecules. Langevin equation for ions in other gases, Blanc law for ions in mixed gases, and the two-temperature model for ions at higher reduced field are used to determine the ion mobility. The kinetic energies of ions in CH$_{4}$+Ar(He) dielectric barrier discharge plasma at a fixed total gas pressure and various Ar (He) concentrations are calculated. It is found that with increasing Ar (He) concentration in CH$_{4}$+Ar (He) from 20% to 83%, the CH$_{4}^{ + }$ kinetic energy increases from 69.6 (43.9) to 92.1 (128.5) eV, while the Ar$^{ + }$ (He$^{ + })$ kinetic energy decreases from 97 (145.2) to 78.8 (75.5) eV. The increase of CH$_{4}^{ + }$ kinetic energy is responsible for the increase of hardness of diamond-like carbon films deposited by CH$_{4}$+Ar (He) dielectric barrier discharge without bias voltage over substrates.
    CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
    Synthesis of hexagonal monocrystal AlN microtubes and nanowires at low temperature
    Lv Hui-Min(吕惠民), Chen Guang-De(陈光德), Yan Guo-Jun(颜国君), and Ye Hong-Gang(耶红刚)
    Chinese Physics, 2007, 16 (9):  2814-2817.  DOI: 10.1088/1009-1963/16/9/053
    Abstract ( 1175 )   PDF (646KB) ( 528 )  
    This paper reports that pure hexagonal aluminium nitride microtubes and nanowires growing along the [0001] direction have been successfully synthesized by directly reacting AlCl$_{3}$ with NaN$_{3}$ at low temperature (450℃) under condition of non-solvent system. The grey--white powder of reacting product was characterized by high-resolution transmission electron microscope (HRTEM), which shows that the powder is long straight-wire morphology with outer diameter from 40 nm to 300 nm and length up to several micrometres. The results of both electron diffraction (ED) and x-ray diffraction (XRD) indicate that the AlN microtubes have a pure hexagonal monocrystal tubular structure with the combination of the curled AlN nanobelts. Room-temperature photoluminescence spectrum of the synthesized sample showed an emission peak, which is closely related to the small size of the microtubes.
    Vertical profiles of aerodynamic size distribution for airborne particles over Yangtze River Delta
    Wang Wei(王玮), Bao Lin-Fa(鲍林发), Liu Hong-Jie(刘红杰), Yue Xin(岳欣), Chen Jian-Hua(陈建华), Li Hong(李红), Ren Li-Hong(任丽红), Tang Da-Gang(汤大钢), Shiro Hatakeyama, and Akinori Takami
    Chinese Physics, 2007, 16 (9):  2818-2824.  DOI: 10.1088/1009-1963/16/9/054
    Abstract ( 1130 )   PDF (1241KB) ( 349 )  
    Based on the aircraft observations in the summer of 2003, we have studied the aerodynamic size distributions of airborne particles at altitudes ranging from 400 m to 2800 m over the central and southern areas of Jiangsu province located in Yangtse River Delta of China. The sizes of airborne particles are measured to be in a range of 0.47--30 $\mu $m with 57 channels, and their number concentrations, surface area concentrations and mass concentrations are also measured. The results show that the concentrations of airborne particles are very low above an altitude of 2000 m and the size distributions present a specific multi-peak mode by using insufficient samples. Below 1000 m, however, the concentrations of particles increase obviously, and their size distribution is similar to that at the ground level. The study also indicates that the concentrations, size distributions and median diameters of airborne particles above and below the boundary layer are very different, displaying different pollution features. Meanwhile, the results also show that the pollution level of airborne particles has a descending tendency with altitude increasing.
    GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
    Amplitude death in steadily forced chaotic systems
    Feng Guo-Lin(封国林) and He Wen-Ping(何文平)
    Chinese Physics, 2007, 16 (9):  2825-2829.  DOI: 10.1088/1009-1963/16/9/055
    Abstract ( 1370 )   PDF (329KB) ( 628 )  
    Steady forcing can induce the amplitude death in chaotic systems, which generally exists in coupled dynamic systems. Using the Lorenz system as a typical example, this paper investigates the dynamic behaviours of the chaotic system with steady forcing numerically, and finds that amplitude death can occur as the strength of the steady forcing goes beyond a critical constant.
    Quintessence models with an oscillating equation of state and their potentials
    Zhao Wen(赵文)
    Chinese Physics, 2007, 16 (9):  2830-2836.  DOI: 10.1088/1009-1963/16/9/056
    Abstract ( 1320 )   PDF (674KB) ( 460 )  
    In this paper, we investigate the quintessence models with an oscillating equation of state (EOS) and its potentials. From the constructed potentials, which have an EOS of $\omega_{\phi}=\omega_0+\omega_1\sin z$, we find that they are all the oscillating functions of the field $\phi$, and the oscillating amplitudes decrease (or increase) with $\phi$. From the evolutive equation of the field $\phi$, we find that this is caused by the expansion of the universe. This also makes it very difficult to build a model whose EOS oscillates forever. However one can build a model with EOS oscillating for a certain period of time. Then we discuss three quintessence models, which are the combinations of the invert power law functions and the oscillating functions of the field $\phi$. We find that they all follow the oscillating EOS.
ISSN 1674-1056   CN 11-5639/O4
, Vol. 16, No. 9

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