Loading...

Table of contents

    15 May 2010, Volume 19 Issue 5 Previous issue    Next issue
    GENERAL
    Approximate symmetry reduction for perturbed nonlinear Schr?dinger equation
    Xie Shui-Ying(谢水英) and Lin Ji(林机)
    Chin. Phys. B, 2010, 19 (5):  050201.  DOI: 10.1088/1674-1056/19/5/050201
    Abstract ( 1106 )   PDF (84KB) ( 623 )  
    We investigate the one-dimensional nonlinear Schr?dinger equation with a perturbation of polynomial type. The approximate symmetries and approximate symmetry reduction equations are obtained with the approximate symmetry perturbation theory.
    A new (2+1)-dimensional supersymmetric Boussinesq equation and its Lie symmetry study
    Wang You-Fa(王友法), Lou Sen-Yue(楼森岳), and Qian Xian-Min(钱贤民)
    Chin. Phys. B, 2010, 19 (5):  050202.  DOI: 10.1088/1674-1056/19/5/050202
    Abstract ( 1298 )   PDF (101KB) ( 629 )  
    According to the conjecture based on some known facts of integrable models, a new (2+1)-dimensional supersymmetric integrable bilinear system is proposed. The model is not only the extension of the known (2+1)-dimensional negative Kadomtsev--Petviashvili equation but also the extension of the known (1+1)-dimensional supersymmetric Boussinesq equation. The infinite dimensional Kac--Moody--Virasoro symmetries and the related symmetry reductions of the model are obtained. Furthermore, the traveling wave solutions including soliton solutions are explicitly presented.
    Asymptopic solution for a class of semilinear singularly perturbed fractional differential equation
    Shi Lan-Fang(石兰芳) and Mo Jia-Qi(莫嘉琪)
    Chin. Phys. B, 2010, 19 (5):  050203.  DOI: 10.1088/1674-1056/19/5/050203
    Abstract ( 1228 )   PDF (92KB) ( 605 )  
    This paper considers a class of boundary value problems for the semilinear singularly perturbed fractional differential equation. Under the suitable conditions, firstly, the outer solution of the original problem is obtained; secondly, using the stretched variable and the composing expansion method the boundary layer is constructed; finally, using the theory of differential inequalities the asymptotic behaviour of solution for the problem is studied and the uniformly valid asymptotic estimation is discussed.
    Some discussions about the variable separating method for solving nonlinear models
    Ruan Hang-Yu(阮航宇)
    Chin. Phys. B, 2010, 19 (5):  050204.  DOI: 10.1088/1674-1056/19/5/050204
    Abstract ( 958 )   PDF (6098KB) ( 492 )  
    Through analysing the exact solution of some nonlinear models, the role of the variable separating method in solving nonlinear equations is discussed. We find that rich solution structures of some special fields of these equations come from the nonzero seed solution. However, these nonzero seed solutions is likely to result in the divergent phenomena for the other field component of the same equation. The convergence and the signification of all field components should be discussed when someone solves the nonlinear equation using the variable separating method.
    Adaptive co-evolution of strategies and network leading to optimal cooperation level in spatial prisoner's dilemma game
    Chen Han-Shuang(陈含爽), Hou Zhong-Huai(侯中怀), Zhang Ji-Qian(张季谦), and Xin Hou-Wen(辛厚文)
    Chin. Phys. B, 2010, 19 (5):  050205.  DOI: 10.1088/1674-1056/19/5/050205
    Abstract ( 1051 )   PDF (543KB) ( 582 )  
    We study evolutionary prisoner's dilemma game on adaptive networks where a population of players co-evolves with their interaction networks. During the co-evolution process, interacted players with opposite strategies either rewire the link between them with probability $p$ or update their strategies with probability $1-p$ depending on their payoffs. Numerical simulation shows that the final network is either split into some disconnected communities whose players share the same strategy within each community or forms a single connected network in which all nodes are in the same strategy. Interestingly, the density of cooperators in the final state can be maximised in an intermediate range of $p$ via the competition between time scale of the network dynamics and that of the node dynamics. Finally, the mean-field analysis helps to understand the results of numerical simulation. Our results may provide some insight into understanding the emergence of cooperation in the real situation where the individuals' behaviour and their relationship adaptively co-evolve.
    Form invariance and new conserved quantity of generalised Birkhoffian system
    Mei Feng-Xiang(梅凤翔) and Wu Hui-Bin(吴惠彬)
    Chin. Phys. B, 2010, 19 (5):  050301.  DOI: 10.1088/1674-1056/19/5/050301
    Abstract ( 1106 )   PDF (78KB) ( 496 )  
    A form invariance and a conserved quantity of the generalised Birkhoffian system are studied. Firstly, a definition and a criterion of the form invariance are given. Secondly, through the form invariance, a new conserved quantity can be deduced. Finally, an example is given to illustrate the application of the result.
    Entanglement evolution in an anisotropic two-qubit Heisenberg XYZ model with Dzyaloshinskii-Moriya interaction
    Chen Tao(陈涛), Huang Yan-Xia(黄燕霞), Shan Chuan-Jia(单传家), Li Jin-Xing(李金星), Liu Ji-Bing(刘继兵), and Liu Tang-Kun(刘堂昆)
    Chin. Phys. B, 2010, 19 (5):  050302.  DOI: 10.1088/1674-1056/19/5/050302
    Abstract ( 1279 )   PDF (780KB) ( 795 )  
    This paper investigates the entanglement evolution of a two-qubit anisotropic Heisenberg XYZ chain in the presence of Dzyaloshinskii--Moriya interaction. The time evolution of the concurrence is studied for the initial pure entangled states $\cos \theta \left\vert 00\right\rangle +\sin \theta \left\vert 11\right\rangle $ and $\cos \phi \left\vert 01\right\rangle +\sin \phi \left\vert 10\right\rangle $ at zero temperature. The influences of Dzyaloshinskii--Moriya interaction $D$, anisotropic parameter $\varDelta$ and environment coupling strength $\gamma$ on entanglement evolution are analysed in detail. It is found that the effect of noisy environment obviously suppresses the entanglement evolution, and the Dzyaloshinskii--Moriya interaction $D$ acts on the time evolution of entanglement only when the initial state is $\cos \phi \left\vert 01\right\rangle +\sin \phi \left\vert 10\right\rangle $. Finally, a formula of steady state concurrence is obtained, and it is shown that the stable concurrence, which is independent of different initial states and Dzyaloshinskii--Moriya interaction $D$, depends on the anisotropic parameter $\varDelta$ and the environment coupling strength $\gamma$.
    Unifying the theory of integration within normal-, Weyl- and antinormal-ordering of operators and the s-ordered operator expansion formula of density operators Hot!
    Fan Hong-Yi(范洪义)
    Chin. Phys. B, 2010, 19 (5):  050303.  DOI: 10.1088/1674-1056/19/5/050303
    Abstract ( 1226 )   PDF (112KB) ( 600 )  
    By introducing the $s$-parameterized generalized Wigner operator into phase-space quantum mechanics we invent the technique of integration within $s$-ordered product of operators (which considers normally ordered, antinormally ordered and Weyl ordered product of operators as its special cases). The $s$-ordered operator expansion (denoted by $\circledS \cdots \circledS)$ formula of density operators is derived, which is $$\rho=\frac{2}{1-s}\int \frac{{\rm d}^2\beta}{\pi}\left \langle -\beta \right \vert \rho \left \vert \beta \right \rangle \circledS \exp \Big\{ \frac{2}{s-1}\left( s'\beta'^{2}-\beta^{\ast}a+\beta a^{\dagger}-a^{\dagger}a\right) \Big\} \circledS.$$ The $s$-parameterized quantization scheme is thus completely established.
    Quantum phase transition and entanglement in Heisenberg XX spin chain with impurity
    Chen Shi-Rong(陈士荣), Xia Yun-Jie(夏云杰), and Man Zhong-Xiao(满忠晓)
    Chin. Phys. B, 2010, 19 (5):  050304.  DOI: 10.1088/1674-1056/19/5/050304
    Abstract ( 1373 )   PDF (968KB) ( 777 )  
    In this paper, we study the quantum phase transition and the effect of impurity on the thermal entanglement between any two lattices in three-qubit Heisenberg XX chain in a uniform magnetic field. We show that the quantum phase transition always appears when impurity parameter is an arbitrary constant and unequal to zero, the external magnetic field and impurity parameters have a great effect on it. Also, there exists a relation between the quantum phase transition and the entanglement. By modulating the temperature, magnetic field and the impurity parameters, the entanglement between any two lattices can exhibit platform-like behaviour, which can be used to realize entanglement switch.
    Unconditional preparation of multipartite continuous-variable entangled states among remote parties
    Hu Xue-Yuan(胡雪元), Gu Ying(古英), Gong Qi-Huang(龚旗煌), and Guo Guang-Can(郭光灿)
    Chin. Phys. B, 2010, 19 (5):  050305.  DOI: 10.1088/1674-1056/19/5/050305
    Abstract ( 1760 )   PDF (361KB) ( 586 )  
    We demonstrate that the $n$-partite continuous-variable entanglement can be unconditionally prepared among $n$ parties that share no common past, from $n$ two-mode squeezed states. Both GHZ-like and cluster-like states can be generated for any nonzero squeezing in the entangled sources. An application of the resulting multipartite entangled state to a teleportation network is illustrated.
    Three-party quantum secret sharing of secure direct communication based on $\chi$-type entangled states
    Yang Yu-Guang(杨宇光), Cao Wei-Feng(曹卫锋), and Wen Qiao-Yan(温巧燕)
    Chin. Phys. B, 2010, 19 (5):  050306.  DOI: 10.1088/1674-1056/19/5/050306
    Abstract ( 1801 )   PDF (112KB) ( 716 )  
    Based on $\chi $-type entangled states and the two-step protocol [Deng F G, Long G L and Liu X S 2003 Phys. Rev. A 68 042317], a quantum secret sharing protocol of secure direct communication based on $\chi$-type entangled states $\vert \chi ^{00}\rangle _{3214} $ is proposed. Using some interesting entanglement properties of this state, the agent entirety can directly obtain the secret message from the message sender only if they collaborate together. The security of the scheme is also discussed.
    Unified treatment for accurate and fast evaluation of the Fermi-Dirac functions Hot!
    I. I. Guseinov and B. A. Mamedov
    Chin. Phys. B, 2010, 19 (5):  050501.  DOI: 10.1088/1674-1056/19/5/050501
    Abstract ( 1594 )   PDF (96KB) ( 692 )  
    A new analytical approach to the computation of the Fermi-Dirac (FD) functions is presented, which was suggested by previous experience with various algorithms. Using the binomial expansion theorem, these functions are expressed through the binomial coefficients and familiar incomplete Gamma functions. This simplification and the use of the memory of the computer for calculation of binomial coefficients may extend the limits to large arguments for users and result in speedier calculation, should such limits be required in practice. Some numerical results are presented for significant mapping examples and they are briefly discussed.
    Thermodynamic properties of a finite Bose gas in a harmonic trap
    Wang Jian-Hui(王建辉) and Ma Yong-Li(马永利)
    Chin. Phys. B, 2010, 19 (5):  050502.  DOI: 10.1088/1674-1056/19/5/050502
    Abstract ( 1666 )   PDF (144KB) ( 1116 )  
    We have investigated the thermodynamic behaviour of ideal Bose gases with an arbitrary number of particles confined in a harmonic potential. By taking into account the conservation of total number N of particles and using a saddle-point approximation, we derive analytically the simple explicit expression of mean occupation number in any state of the finite system. The temperature dependence of the chemical potential, specific heat, and condensate fraction for the trapped finite-size Bose system is obtained numerically. We compare our results with the usual treatment which is based on the grand canonical ensemble. It is shown that there exists a considerable difference between them at sufficiently low temperatures, specially for the relative small numbers of Bose atoms. The finite-size scaling at the transition temperature for the harmonically trapped systems is also discussed. We find that the scaled condensate fractions for various system sizes and temperatures collapse onto a single scaled form.
    Exact analytical solutions to the mean-field model depicting microcavity containing semiconductor quantum wells
    Song Pei-Jun(宋佩君), Lü Xin-You (吕新友), Liu Ji-Bing(刘继兵), and Hao Xiang-Ying(郝向英)
    Chin. Phys. B, 2010, 19 (5):  050503.  DOI: 10.1088/1674-1056/19/5/050503
    Abstract ( 1549 )   PDF (610KB) ( 595 )  
    By using a two-mode mean-field approximation, we study the dynamics of the microcavities containing semiconductor quantum wells. The exact analytical solutions are obtained in this study. Based on these solutions, we show that the emission from the microcavity manifests periodic oscillation behaviour and the oscillation can be suppressed under a certain condition.
    Stochastic resonance in an asymmetric bistable system driven by coloured noises
    Yang Jian-Hua(杨建华) and Liu Xian-Bin(刘先斌)
    Chin. Phys. B, 2010, 19 (5):  050504.  DOI: 10.1088/1674-1056/19/5/050504
    Abstract ( 1747 )   PDF (180KB) ( 845 )  
    The phenomenon of stochastic resonance is investigated in an asymmetric bistable system with coloured noises. The approximate Fokker--Planck equation is derived based on the Novikov theorem and the Fox approach. By applying the two-state theory, the expression of the signal-to-noise ratio is obtained in the adiabatic limit. The effects of the noise parameters on signal-to-ratio are discussed. It is found that the stochastic resonance phenomena appear in most cases and disappear in some special cases.
    An efficient method of distinguishing chaos from noise
    Wei Heng-Dong(魏恒东), Li Li-Ping(李立萍), and Guo Jian-Xiu(郭建秀)
    Chin. Phys. B, 2010, 19 (5):  050505.  DOI: 10.1088/1674-1056/19/5/050505
    Abstract ( 1607 )   PDF (287KB) ( 844 )  
    It is an important problem in chaos theory whether an observed irregular signal is deterministic chaotic or stochastic. We propose an efficient method for distinguishing deterministic chaotic from stochastic time series for short scalar time series. We first investigate, with the increase of the embedding dimension, the changing trend of the distance between two points which stay close in phase space. And then, we obtain the differences between Gaussian white noise and deterministic chaotic time series underlying this method. Finally, numerical experiments are presented to testify the validity and robustness of the method. Simulation results indicate that our method can distinguish deterministic chaotic from stochastic time series effectively even when the data are short and contaminated.
    Fault tolerant synchronization of chaotic systems based on T-S fuzzy model with fuzzy sampled-data controller
    Ma Da-Zhong(马大中), Zhang Hua-Guang(张化光), Wang Zhan-Shan(王占山), and Feng Jian(冯健)
    Chin. Phys. B, 2010, 19 (5):  050506.  DOI: 10.1088/1674-1056/19/5/050506
    Abstract ( 1548 )   PDF (211KB) ( 959 )  
    In this paper the fault tolerant synchronization of two chaotic systems based on fuzzy model and sample data is investigated. The problem of fault tolerant synchronization is formulated to study the global asymptotical stability of the error system with the fuzzy sampled-data controller which contains a state feedback controller and a fault compensator. The synchronization can be achieved no matter whether the fault occurs or not. To investigate the stability of the error system and facilitate the design of the fuzzy sampled-data controller, a Takagi--Sugeno (T--S) fuzzy model is employed to represent the chaotic system dynamics. To acquire the good performance and produce less conservative analysis result, a new parameter-dependent Lyapunov--Krasovksii functional and a relaxed stabilization technique are considered. The stability conditions based on linear matrix inequality are obtained to achieve the fault tolerant synchronization of the chaotic systems. Finally, a numerical simulation is shown to verify the results.
    A new approach to stability analysis of neural networks with time-varying delay via novel Lyapunov--Krasovskii functional
    S. M. Lee, O. M. Kwon, and Ju H. Park
    Chin. Phys. B, 2010, 19 (5):  050507.  DOI: 10.1088/1674-1056/19/5/050507
    Abstract ( 1648 )   PDF (103KB) ( 863 )  
    In this paper, new delay-dependent stability criteria for asymptotic stability of neural networks with time-varying delays are derived. The stability conditions are represented in terms of linear matrix inequalities (LMIs) by constructing new Lyapunov--Krasovskii functional. The proposed functional has an augmented quadratic form with states as well as the nonlinear function to consider the sector and the slope constraints. The less conservativeness of the proposed stability criteria can be guaranteed by using convex properties of the nonlinear function which satisfies the sector and slope bound. Numerical examples are presented to show the effectiveness of the proposed method.
    Embedding adaptive arithmetic coder in chaos-based cryptography
    Li Heng-Jian(李恒建) and Zhang Jia-Shu(张家树)
    Chin. Phys. B, 2010, 19 (5):  050508.  DOI: 10.1088/1674-1056/19/5/050508
    Abstract ( 1606 )   PDF (147KB) ( 894 )  
    In this study an adaptive arithmetic coder is embedded in the Baptista-type chaotic cryptosystem for implementing secure data compression. To build the multiple lookup tables of secure data compression, the phase space of chaos map with a uniform distribution in the search mode is divided non-uniformly according to the dynamic probability estimation of plaintext symbols. As a result, more probable symbols are selected according to the local statistical characters of plaintext and the required number of iterations is small since the more probable symbols have a higher chance to be visited by the chaotic search trajectory. By exploiting non-uniformity in the probabilities under which a number of iteration to be coded takes on its possible values, the compression capability is achieved by adaptive arithmetic code. Therefore, the system offers both compression and security. Compared with original arithmetic coding, simulation results on Calgary Corpus files show that the proposed scheme suffers from a reduction in compression performance less than 12\% and is not susceptible to previously carried out attacks on arithmetic coding algorithms.
    Dynamical analysis and experimental verification of valley current controlled buck converter
    Zhou Guo-Hua(周国华), Bao Bo-Cheng(包伯成), Xu Jian-Ping(许建平), and Jin Yan-Yan(金艳艳)
    Chin. Phys. B, 2010, 19 (5):  050509.  DOI: 10.1088/1674-1056/19/5/050509
    Abstract ( 1574 )   PDF (2551KB) ( 1252 )  
    The dynamical behaviours of valley current controlled buck converter are studied by establishing its corresponding discrete iterative map model in this paper. Time-domain waveforms and phase portraits of valley current controlled buck converter are obtained by Runge--Kutta algorithm through a piecewise smooth switching model. The research results indicate that the valley current controlled buck converter exhibits rich nonlinear phenomena, and it has routes to chaos through period-doubling bifurcation and border-collision bifurcation in a wide parameter range. Interesting inverse nonlinear behaviours compared with peak current controlled buck converter are observed in the valley current controlled buck converter. Analysis and simulation results are verified by experimental results.
    Filtering noisy chaotic signal via sparse representation based on random frame dictionary
    Xie Zong-Bo(谢宗伯) and Feng Jiu-Chao(冯久超)
    Chin. Phys. B, 2010, 19 (5):  050510.  DOI: 10.1088/1674-1056/19/5/050510
    Abstract ( 1646 )   PDF (136KB) ( 649 )  
    The denoising problem of impure chaotic signals is addressed in this paper. A method based on sparse representation is proposed, in which the random frame dictionary is generated by a chaotic random search algorithm. The numerical simulation shows the proposed algorithm outperforms those recently reported alternative denoising methods.
    Random-phase-induced chaos in power systems
    Qin Ying-Hua(覃英华), Luo Xiao-Shu(罗晓曙), and Wei Du-Qu(韦笃取)
    Chin. Phys. B, 2010, 19 (5):  050511.  DOI: 10.1088/1674-1056/19/5/050511
    Abstract ( 1560 )   PDF (383KB) ( 660 )  
    This paper studies how random phase (namely, noise-perturbed phase) effects the dynamical behaviours of a simple model of power system which operates in a stable regime far away from chaotic behaviour in the absence of noise. It finds that when the phase perturbation is weak, chaos is absent in power systems. With the increase of disturbed intensity $\sigma$, power systems become unstable and fall into chaos as $\sigma$ further increases. These phenomena imply that random phase can induce and enhance chaos in power systems. Furthermore, the possible mechanism behind the action of random phase is addressed.
    Control and synchronization of second Julia sets
    Zhang Yong-Ping(张永平), Sun Wei-Hua(孙伟华), and Liu Chang-An(刘长安)
    Chin. Phys. B, 2010, 19 (5):  050512.  DOI: 10.1088/1674-1056/19/5/050512
    Abstract ( 1331 )   PDF (894KB) ( 1054 )  
    A visualization of Julia sets of the complex Henon map system with two complex variables is introduced in this paper. With this method, the optimal control function method is introduced to this system and the control and synchronization of its Julia sets are achieved. Control and synchronization of generalized Julia sets are also achieved with this optimal control method. The simulations illustrate the efficacy of this method.
    Doppler instability of antispiral waves in discrete oscillatory reaction-diffusion media
    Qian Yu(钱郁), Huang Xiao-Dong(黄晓东), Liao Xu-Hong(廖旭红), and Hu Gang(胡岗)
    Chin. Phys. B, 2010, 19 (5):  050513.  DOI: 10.1088/1674-1056/19/5/050513
    Abstract ( 1474 )   PDF (4834KB) ( 665 )  
    This paper investigates antispiral wave breakup phenomena in coupled two-dimensional FitzHugh--Nagumo cells with self-sustained oscillation via Hopf bifurcation. When the coupling strength of the active variable decreases to a critical value, wave breakup phenomenon first occurs in the antispiral core region where waves collide with each other and spontaneously break into spatiotemporal turbulence. Measurements reveal for the first time that this breakup phenomenon is due to the mechanism of antispiral Doppler instability.
    Distributed predictive control of spiral wave in cardiac excitable media
    Gan Zheng-Ning(甘正宁) and Cheng Xin-Ming(成新明)
    Chin. Phys. B, 2010, 19 (5):  050514.  DOI: 10.1088/1674-1056/19/5/050514
    Abstract ( 1223 )   PDF (986KB) ( 523 )  
    In this paper, we propose the distributed predictive control strategies of spiral wave in cardiac excitable media. The modified FitzHugh--Nagumo model was used to express the cardiac excitable media approximately. Based on the control-Lyapunov theory, we obtained the distributed control equation, which consists of a positive control-Lyapunov function and a positive cost function. Using the equation, we investigate two kinds of robust control strategies: the time-dependent distributed control strategy and the space-time dependent distributed control strategy. The feasibility of the strategies was demonstrated via an illustrative example, in which the spiral wave was prevented to occur, and the possibility for inducing ventricular fibrillation was eliminated. The strategies are helpful in designing various cardiac devices. Since the second strategy is more efficient and robust than the first one, and the response time in the second strategy is far less than that in the first one, the former is suitable for the quick-response control systems. In addition, our spatiotemporal control strategies, especially the second strategy, can be applied to other cardiac models, even to other reaction-diffusion systems.
    Reflection and refraction of waves in oscillatory media
    Gu Guo-Feng(顾国锋), LÜ Yao-Ping(吕耀平), and Tang Guo-Ning(唐国宁)
    Chin. Phys. B, 2010, 19 (5):  050515.  DOI: 10.1088/1674-1056/19/5/050515
    Abstract ( 1269 )   PDF (1084KB) ( 643 )  
    This paper uses the two-dimensional Brusselator model to study reflection and refraction of chemical waves. It presents some boundary conditions of chemical waves, with which occurence of observed phenomena at interface as refraction and reflection of chemical waves can be interpreted. Moreover, the angle of reflection may be calculated by using the boundary conditions. It finds that reflection and refraction of chemical waves can occur simultaneously even if plane wave goes from a medium with higher speed to a medium with lower speed, provided the incident angle is larger than the critical angle.
    Intermittencies in complex Ginzburg-Landau equation by varying system size
    Li Hai-Hong(李海红), Xiao Jing-Hua(肖井华), Hu Gang(胡岗), and Hu Bambi(胡斑比)
    Chin. Phys. B, 2010, 19 (5):  050516.  DOI: 10.1088/1674-1056/19/5/050516
    Abstract ( 1298 )   PDF (3849KB) ( 798 )  
    Dynamical behaviour of the one-dimensional complex Ginzburg--Landau equation (CGLE) with finite system size $L$ is investigated, based on numerical simulations. By varying the system size and keeping other system parameters in the defect turbulence region (defect turbulence in large $L$ limit), a number of intermittencies new for the CGLE system are observed in the processes of pattern formations and transitions while the system dynamics varies from a homogeneous periodic oscillation to strong defect turbulence.
    Effects of the number of on-rampson the ring traffic flow
    Tang Tie-Qiao(唐铁桥), Huang Hai-Jun(黄海军), and Shang Hua-Yan(尚华艳)
    Chin. Phys. B, 2010, 19 (5):  050517.  DOI: 10.1088/1674-1056/19/5/050517
    Abstract ( 1325 )   PDF (978KB) ( 807 )  
    Since ramp is an important composition of traffic system and there often exist multi ramps in a traffic system, the number of ramps can have great effects on main road traffic and produce some complex phenomena. In this paper, we employ the model presented by Tang et al. [2009 Communications in Theoretical Physics  51 (1) 71] to further study the effects of the number of on-ramps on the stability of traffic flow on a ring road. The numerical results show that this model can reproduce some complex traffic phenomena resulting from multi on-ramps on the ring road and the effects of the number of on-ramps on traffic flow, but the phenomena and the effects are both related to the initial density of the main road.
    Kinetic Ising model in a time-dependent oscillating external magnetic field: effective-field theory
    Bayram Deviren, Osman Canko, and Mustafa Keskin
    Chin. Phys. B, 2010, 19 (5):  050518.  DOI: 10.1088/1674-1056/19/5/050518
    Abstract ( 1105 )   PDF (1485KB) ( 906 )  
    Recently, Shi et al. [2008  Phys. Lett. A 372 5922] have studied the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field and presented the dynamic phase diagrams by using an effective-field theory (EFT) and a mean-field theory (MFT). The MFT results are in conflict with those of earlier work of Tomé and de Oliveira, [1990 Phys. Rev. A 41 4251]. We calculate the dynamic phase diagrams and find that our results are similar to those of earlier work of Tomé and de Oliveira; hence the dynamic phase diagrams calculated by Shi et al. are incomplete within both theories, except the low values of frequencies for the MFT calculation. We also investigate the influence of external field frequency ($\omega$) and static external field amplitude ($h_{0})$ for both MFT and EFT calculations. We find that the behaviour of the system strongly depends on values of $\omega$ and $h_{0}$.
    Shot noise in electron transport through a double quantum dot: a master equation approach
    Ou-Yang Shi-Hua(欧阳仕华), Lam Chi-Hang(林志恒), and You Jian-Qiang(游建强)
    Chin. Phys. B, 2010, 19 (5):  050519.  DOI: 10.1088/1674-1056/19/5/050519
    Abstract ( 1298 )   PDF (572KB) ( 956 )  
    We study shot noise in tunneling current through a double quantum dot connected to two electric leads. We derive two master equations in the occupation-state basis and the eigenstate basis to describe the electron dynamics. The approach based on the occupation-state basis, despite being widely used in many previous studies, is valid only when the interdot coupling strength is much smaller than the energy difference between the two dots. In contrast, the calculations using the eigenstate basis are valid for an arbitrary interdot coupling. Using realistic model parameters, we demonstrate that the predicted currents and shot-noise properties from the two approaches are significantly different when the interdot coupling is not small. Furthermore, properties of the shot noise predicted using the eigenstate basis successfully reproduce qualitative features found in a recent experiment.
    Consensus problems in multi-agent systems with double integrator model
    Gao Li-Xin(高利新), Yan Hui-Juan(闫慧娟), and Jin Dan(金丹)
    Chin. Phys. B, 2010, 19 (5):  050520.  DOI: 10.1088/1674-1056/19/5/050520
    Abstract ( 1326 )   PDF (387KB) ( 782 )  
    In this paper, we consider multi-agent consensus problems in a decentralised fashion. The interconnection topology graph among the agents is switching and undirected. The agent dynamics is expressed in the form of a double integrator model. Two different cases are considered in this study. One is the leader-following case and the other is leaderless case. Based on graph theory and common Lyapunov function method, some sufficient conditions are obtained for the consensus stability of the considered systems with the neighbour-based feedback laws in both leader-following case and leaderless case respectively. Finally, two numerical examples are given to illustrate the obtained results.
    Theory of higher harmonics imaging in tapping-mode atomic force microscopy
    Li Yuan(李渊), Qian Jian-Qiang(钱建强), and Li Ying-Zi(李英姿)
    Chin. Phys. B, 2010, 19 (5):  050701.  DOI: 10.1088/1674-1056/19/5/050701
    Abstract ( 1234 )   PDF (154KB) ( 586 )  
    The periodic impact force induced by tip-sample contact in tapping mode atomic force microscope (AFM) gives rise to non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full characteristics of tip-sample interaction. A complete theoretical model describing the dynamical behaviour of tip--sample system was developed in this paper. An analytic formula was introduced to describe the relationship between time-varying tip--sample impact force and tip motion. The theoretical analysis and numerical results both show that the time-varying tip--sample impact force can be reconstructed by recording tip motion. This allows for the reconstruction of the characteristics of the tip--sample force, like contact time and maximum contact force. It can also explain the ability of AFM higher harmonics imaging in mapping stiffness and surface energy variations.
    ATOMIC AND MOLECULAR PHYSICS
    Electric-dipole allowed (E1) and forbidden (E2, M1 and M2) transition probabilities of 4f for N+
    Shen Xiao-Zhi(申晓志), Yuan Ping(袁萍), and Liu Juan(刘娟)
    Chin. Phys. B, 2010, 19 (5):  053101.  DOI: 10.1088/1674-1056/19/5/053101
    Abstract ( 1561 )   PDF (94KB) ( 834 )  
    By applying systematically enlarged multi-configuration Dirac--Fock wavefunction, the transitions for electric-dipole allowed (E1) and forbidden (E2, M1 and M2) lines are studied among 4f pair coupling and low-lying configurations for singly ionized nitrogen. Most important effects of relativity, electron correlation, the rearrangement of electron density, Breit interaction, and quantum electrodynamic effects are included in the computation. Then, allowed (E1) and forbidden (E2, M1 and M2) transition probabilities of 4f for N$^{+}$ are obtained and compared with experimental results. Good agreement with available experimental results is found and most of data of 4f are presented for the first time.
    Study on spectroscopic parameters and molecular constants of HCl(X1+) molecule by using multireference configuration interaction approach
    Zhang Xiao-Niu(张小妞), Shi De-Heng(施德恒), Zhang Jin-Ping(张金平), Zhu Zun-Lüe(朱遵略), and Sun Jin-Feng(孙金锋)
    Chin. Phys. B, 2010, 19 (5):  053401.  DOI: 10.1088/1674-1056/19/5/053401
    Abstract ( 1418 )   PDF (223KB) ( 1273 )  
    Equilibrium internuclear separations, harmonic frequencies and potential energy curves (PECs) of HCl($X^{1}\Sigma ^{ + })$ molecule are investigated by using the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with a series of correlation-consistent basis sets in the valence range. The PECs are all fitted to the Murrell--Sorbie function, and they are used to accurately derive the spectroscopic parameters ($D_{\rm e}$, $D_{0}$, $\omega_{\rm e}\chi_{\rm e}$, $\alpha_{\rm e}$ and $B_{\rm e})$. Compared with the available measurements, the PEC obtained at the basis set, aug-cc-pV5Z, is selected to investigate the vibrational manifolds. The constants $D_{0}$, $D_{\rm e}$, $R_{\rm e}$, $\omega_{\rm e}$, $\omega_{\rm e}\chi_{\rm e}$, $\alpha_{\rm e}$ and $B_{\rm e}$ at this basis set are 4.4006 eV, 4.5845 eV, 0.12757 nm, 2993.33 cm$^{ - 1}$, 52.6273 cm$^{ - 1}$, 0.2981 cm$^{ - 1}$ and 10.5841 cm$^{ - 1}$, respectively, which almost perfectly conform to the available experimental results. With the potential determined at the MRCI/aug-cc-pV5Z level of theory, by numerically solving the radial Schr?dinger equation of nuclear motion in the adiabatic approximation, a total of 21 vibrational levels are predicted. Complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are reproduced, which are in excellent agreement with the available Rydberg--Klein--Rees data. Most of these theoretical vibrational manifolds are reported for the first time to the best of our knowledge.
    Four-level model of ion-ion laser-induced collisional energy transfer and numerical calculations for Ca+-Sr+ system
    Chen De-Ying(陈德应), Zhang Hong-Ying(张洪英), and Fan Rong-Wei(樊荣伟)
    Chin. Phys. B, 2010, 19 (5):  053402.  DOI: 10.1088/1674-1056/19/5/053402
    Abstract ( 1074 )   PDF (167KB) ( 744 )  
    The four-level model of laser-induced collisional energy transfer (LICET) for ion--ion collision system is established based on the time-dependent Schr?dinger equation for the electron dynamics, through which the equations of motion of the probability amplitudes and cross section of the collision system are obtained. Numerical calculations are performed for the Ca$^+$--Sr$^+$ system, with the results showing that the peak of the LICET spectrum appears at a resonant frequency of the transfer laser. The magnitude of the obtained collision cross section is in the order of $10^{-16}$ cm$^2$, and is comparable to that obtained in atomic systems, which indicates the validity of the established four-level model.
    CLASSICAL AREAS OF PHENOMENOLOGY
    Investigation on global positioning system signal scattering and propagation over the rough sea surface
    Yang Chao(杨超), Guo Li-Xin(郭立新), and Wu Zhen-Sen(吴振森)
    Chin. Phys. B, 2010, 19 (5):  054101.  DOI: 10.1088/1674-1056/19/5/054101
    Abstract ( 1203 )   PDF (347KB) ( 810 )  
    This paper is devoted to the study of polarization properties, scattering properties and propagation properties of global positioning system (GPS) scattering signal over the rough sea surface. To investigate the polarization and the scattering properties, the scattering field and the bistatic scattering coefficient of modified Kirchhoff approximation with using the tapered incident wave is derived in detail. In modeling the propagation properties of the GPS scattering signal in the evaporation duct, the initial field of parabolic equation traditionally computed by the antenna pattern with using fast Fourier transform (FFT) is replaced by the GPS scattering field. And the propagation properties of GPS scattering signal in the evaporation duct with different evaporation duct heights and elevation angles of GPS are discussed by the improved discrete mixed Fourier transform with taking into account the sea surface roughness.
    Electromagnetic backscattering from freak waves in (1+1)-dimensional deep-water
    Xie Tao(谢涛), Shen Tao(沈涛), William Perrie, Chen Wei(陈伟), and Kuang Hai-Lan(旷海兰)
    Chin. Phys. B, 2010, 19 (5):  054102.  DOI: 10.1088/1674-1056/19/5/054102
    Abstract ( 1261 )   PDF (941KB) ( 784 )  
    To study the electromagnetic (EM) backscatter characteristics of freak waves at moderate incidence angles, we establish an EM backscattering model for freak waves in (1+1)-dimensional deep water. The nonlinear interaction between freak waves and Bragg short waves is considered to be the basic hydrodynamic spectra modulation mechanism in the model. Numerical results suggest that the EM backscattering intensities of freak waves are less than those from the background sea surface at moderate incidence angles. The normalised radar cross sections (NRCSs) from freak waves are highly polarisation dependent, even at low incidence angles, which is different from the situation for normal sea waves; moreover, the NRCS of freak waves is more polarisation dependent than the background sea surface. NRCS discrepancies between freak waves and the background sea surface with using horizontal transmitting horizomtal (HH) polarisation are larger than those with using vertical transmitting vertical (VV) polarisation, at moderate incident angles. NRCS discrepancies between freak waves and background sea surface decreases with the increase of incidence angle, in both HH and VV polarisation radars. As an application, in the synthetic-aperture radar (SAR) imaging of freak waves, we suggest that freak waves should have extremely low backscatter NRCSs for the freak wave facet with the strongest slope. Compared with the background sea surface, the freak waves should be darker in HH polarisation echo images than in VV echo images, in SAR images. Freak waves can be more easily detected from the background sea surface in HH polarisation images than in VV polarisation images. The possibility of detection of freak waves at low incidence angles is much higher than at high incidence angles.
    Study of scattering from time-varying Gerstners sea surface using second-order small slope approximation
    Zhang Yan-Min(张彦敏), Wang Yun-Hua(王运华), and Guo Li-Xin(郭立新)
    Chin. Phys. B, 2010, 19 (5):  054103.  DOI: 10.1088/1674-1056/19/5/054103
    Abstract ( 1110 )   PDF (1802KB) ( 772 )  
    Backscattered fields from one-dimensional time-varying Gerstners sea surface are calculated utilising the second-order small slope approximation. It is well known that spectral properties of the backscattered echoes relate to the velocity of the small elementary scatterers on sea surface profiles. Therefore, modeling Doppler spectra from the ocean requires an accurate description of the sea surface motion. The profile of nonlinear Gerstners sea surface shows vertical-skewness of sea waves, it is sharper at the crest and flatter at the trough than linear waves, and its maximum slope position is closer to the crest than to the trough. Furthermore, the horizontal component of the small elementary scatterers orbit velocity on the sea surface, which yields noticeable influence on Doppler spectra, can be obtained conveniently by Gerstners sea surface model. In this study, the characteristics of Doppler spectra of backscattered fields from time-varying Gerstners sea surface are investigated and the dependences of the Doppler frequency and the Doppler bandwidth on the parameters, such as the wind speed, the radar frequency, the incident angle, etc. are discussed. It is shown that the Doppler bandwidth of microwave scattered fields from Gerstners sea surface is considerably broadened. For the case of high frequency backscattered fields, the values of the higher-order spectrum peaks are larger than those obtained by linear sea surface.
    Numerical analysis of surface plasmon nanocavities formed in thickness-modulated metal-insulator-metal waveguides
    Liu Jian-Long(刘建龙), Lin Jie(林杰), Zhao Hai-Fa(赵海发), Zhang Yan(张岩), and Liu Shu-Tian(刘树田)
    Chin. Phys. B, 2010, 19 (5):  054201.  DOI: 10.1088/1674-1056/19/5/054201
    Abstract ( 1123 )   PDF (252KB) ( 1373 )  
    The enhancement characteristics of the local field in the surface plasmon nanocavities are investigated numerically. The cavity is constructed by placing a defect structure in the thickness-modulated metal--insulator--metal waveguide Bragg gratings. The characteristic impedance based transfer matrix method is used to calculate the transmission spectra and the resonant wavelength of the cavities with various geometric parameters. The finite-difference time-domain method is used to obtain the field pattern of the resonant mode and validate the results of the transfer matrix method. The calculation and simulation results reveal the existence of resonant wavelength shift and intensity variation with structural parameters, such as the modulation period of the gratings, the length and the width of the defect structure. Both numerical analysis and theoretical interpretation on these phenomena are given in details.
    Study on guided-mode resonance characteristic of multilayer dielectric grating with broadband and wide using-angle
    Wang Jian-Peng(汪剑鹏), Jin Yun-Xia(晋云霞), Ma Jian-Yong(麻健勇), Shao Jian-Da(邵建达), and Fan Zheng-Xiu(范正修)
    Chin. Phys. B, 2010, 19 (5):  054202.  DOI: 10.1088/1674-1056/19/5/054202
    Abstract ( 1146 )   PDF (4999KB) ( 1314 )  
    Guided-mode resonance in a diffraction band of multilayer dielectric gratings may lead to a catastrophic result in laser system, especially in the ultrashort pulse laser system, so the inhibition of guided-mode resonance is very important. In this paper the characteristics of guided-mode resonance in multilayer dielectric grating are studied with the aim of better understanding the physical process of guided-mode resonance and designing a broadband multilayer dielectric grating with no guided-mode resonance. By employing waveguide theory, all guided-wave modes appearing in multilayer dielectric grating are found, and the incident conditions, separately, corresponding to each guided-wave mode are also obtained. The electric field enhancement in multilayer dielectric grating is shown obviously. Furthermore, from the detailed analyses on the guided-mode resonance conditions, it is found that the reduction of grating period would effectively avoid the appearing of guided-mode resonance. And the expressions for calculating maximum periods, which ensure that no guided-mode resonance occurs in the requiring broad angle or wavelength range, are first reported. The above results calculated by waveguide theory and Fourier mode method are compared wit each other, and they are coincident completely. Moreover, the method that relies on waveguide theory is more helpful for understanding the guided-mode resonance excited process and analyzing how each parameter affects the characteristic of guided-mode resonance. Therefore, the effects of multilayer dielectric grating parameters, such as period, fill factor, thickness of grating layer, {\it et al.}, on the guided-mode resonance characteristic are discussed in detail based on waveguide theory, and some meaningful results are obtained.
    Stokes parameters of optical singularities of random electromagnetic beams
    Li Jian-Long(李建龙) and Zhu Shi-Fu(朱世富)
    Chin. Phys. B, 2010, 19 (5):  054203.  DOI: 10.1088/1674-1056/19/5/054203
    Abstract ( 1110 )   PDF (438KB) ( 674 )  
    In this paper, the relation between spectral degree of coherence and degree of polarization of random electromagnetic beams is derived by the Stokes parameters. And the concept of polarization singularity is extended from spatially fully coherent beams to partially coherent electromagnetic beams. Theoretical analysis shows that correlation vortices are linearly polarized singularities. The results are illustrated by numerical examples.
    Phase properties of odd and even circular states
    Wang Yue-Yuan(王月媛), Liu Zheng-Jun(刘正君), Liao Qing-Hong(廖庆洪), and Liu Shu-Tian(刘树田)
    Chin. Phys. B, 2010, 19 (5):  054204.  DOI: 10.1088/1674-1056/19/5/054204
    Abstract ( 1159 )   PDF (1269KB) ( 716 )  
    Phase properties of the even and odd circular states are studied within the Hermitian phase formalism of Pegg and Barnett. Exact analytical formulas for the distribution function and the variance of the phase operator are obtained and used to examine whether or not the even and odd circular states exhibit photon-number squeezing and phase squeezing.
    Steady-state analysis of three-photon absorption spectra via density-matrix method in a three-coupled-quantum-well nanostructure
    Deng Li(邓黎)
    Chin. Phys. B, 2010, 19 (5):  054205.  DOI: 10.1088/1674-1056/19/5/054205
    Abstract ( 1299 )   PDF (1055KB) ( 904 )  
    We numerically simulate three-photon absorption spectra in a three-coupled-quantum-well nanostructure interacting with a pump field, a coherent coupling field, and a probe field. We find that the three-photon absorption spectra can be dramatically influenced due to the intensities of the coupling field and pump field changing under the three-photon resonance condition. The effect of the frequency detuning of the pump field on the three-photon absorption spectra is also discussed. The study in our case is much more practical than the study in the case of its atomic counterpart in the sense of flexible design and the wide adjustable parameters. Thus it may open up some new possibilities for technological applications in optoelectronics and solid-state quantum information science.
    Phase control of spontaneous emission from a double-band photonic crystals
    Zhang Ke(张珂), Zhu Yan-Ping(祝艳萍), Jiang Li(姜丽), and Zhang Han-Zhuang(张汉壮)
    Chin. Phys. B, 2010, 19 (5):  054206.  DOI: 10.1088/1674-1056/19/5/054206
    Abstract ( 1209 )   PDF (160KB) ( 831 )  
    Through picture of dressed states, this paper investigates the spontaneous emission spectrum from a microwave-driven three-level atom embedded in a double-band photonic crystals. The physical dynamics of the phase dependent phenomenon is analysed by comparing two models `upper level coupling' and `lower level coupling'. When the phase is changed from 0 to $\pi$, the variety of spontaneous emission spectra from either of the two models are inverse to each other, in which the relative height and width of peaks are determined by the density of states in photonic crystals.
    Linearly polarised three-colour lasing emission from an evanescent wave pumped and gain coupled fibre laser
    Pu Xiao-Yun(普小云), Jiang Nan(江楠), Han De-Yu(韩德昱), Feng Yong-Li(冯永利), and Ren Yi-Tao(任一涛)
    Chin. Phys. B, 2010, 19 (5):  054207.  DOI: 10.1088/1674-1056/19/5/054207
    Abstract ( 1132 )   PDF (2107KB) ( 728 )  
    A novel Whispering--Gallery--Mode (WGM) fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a bare optical fibre immersed in a dye solution of lower refractive index. The dye molecules around the bare fibre are excited by the evanescent waves of pump light when they propagate along the fibre in a total internal reflection. When the pump beam within the fibre is a meridian beam, the WGM lasing emission from the fibre laser is a linearly polarised transverse electric wave, while it is a mixed wave of the linearly polarised transverse electric and magnetic waves if the pump beam is a skew beam within the fibre. Because the excited molecules are located within the evanescent field of WGM, a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fibre. Once the bare fibre is inserted into three glass capillaries filled with Rhodamine 6G, 610 and 640 dye solutions, respectively, WGM laser oscillations at the wavelengths of 567--575, 605--614 and 656--666~nm occur simultaneously, and a linearly polarised three-colour lasing emission is achieved in a single optical fibre.
    Design of surface emitting distributed feedback quantum cascade laser with single-lobe far-field pattern and high outcoupling efficiency
    Guo Wan-Hong(郭万红), Liu Jun-Qi(刘俊岐), Lu Quan-Yong(陆全勇), Zhang Wei(张伟), Li Lu(李路), Wang Li-Jun(王利军), Liu Feng-Qi(刘峰奇), and Wang Zhan-Guo(王占国)
    Chin. Phys. B, 2010, 19 (5):  054208.  DOI: 10.1088/1674-1056/19/5/054208
    Abstract ( 1191 )   PDF (323KB) ( 1386 )  
    A 7.8-$\mu $m surface emitting second-order distributed feedback quantum cascade laser (DFB QCL) structure with metallized surface grating is studied. The modal property of this structure is described by utilizing coupled-mode theory where the coupling coefficients are derived from exact Floquet--Bloch solutions of infinite periodic structure. Based on this theory, the influence of waveguide structure and grating topography as well as device length on the laser performance is numerically investigated. The optimized surface emitting second-order DFB QCL structure design exhibits a high surface outcoupling efficiency of 22% and a low threshold gain of 10 cm$^{ - 1}$. Using a $\pi $ phase-shift in the centre of the grating, a high-quality single-lobe far-field radiation pattern is obtained.
    Efficient corner-pumped Nd:YAG/YAG composite slab laser
    Liu Huan(刘欢) and Gong Ma-Li(巩马理)
    Chin. Phys. B, 2010, 19 (5):  054209.  DOI: 10.1088/1674-1056/19/5/054209
    Abstract ( 1115 )   PDF (1723KB) ( 1177 )  
    A corner-pumped type is a new pumping type in the diode-pumped all-solid-state lasers, which has the advantages of high pump efficiency and favourable pump uniformity. A highly efficient corner-pumped Nd:YAG/YAG composite slab laser is demonstrated in this paper. The maximal continuous-wave output power of the 1064 nm laser is up to 18.57 W with a slope efficiency and an optical-to-optical conversion efficiency of 44.9% and 39.8%, respectively. Inserting an acousto-optic $Q$-switch in the cavity, the highest average output power of the quasi-continuous wave 1064 nm laser of 6.73 W is obtained at a repetition rate of 9.26 kHz. The experimental results show that a corner-pumped type is a kind of feasible schedules in the design of diode-pumped all-solid-state lasers with low or medium output powers.
    Femtosecond laser-induced microstructure in Foturan glass
    Sun Hai-Yi(孙海轶), Luo Fang-Fang(骆芳芳), He Fei(何飞), Liao Yang(廖洋), and Xu Jian(徐剑)
    Chin. Phys. B, 2010, 19 (5):  054210.  DOI: 10.1088/1674-1056/19/5/054210
    Abstract ( 1246 )   PDF (3037KB) ( 1355 )  
    We report on the microstructure formation in Foturan glass, induced by 1 kHz, 120 femtosecond laser irradiation. It is found that the line-shaped filamentation, not void array tends to be formed in this glass. This is different from our previous experimental results in fused silica and BK7 glasses. A possible mechanism Ag$^+$ captures the free electrons generated by laser, is proposed to explain the observed phenomena.
    The propagation of dipole solitonsin highly nonlocal medium
    Zhao Jia-Yin(赵嘉胤), Wang Qi(王奇), Shen Ming(申明), Shi Jie-Long(施解龙), Kong Qian(孔茜), and Ge Li-Juan(葛丽娟)
    Chin. Phys. B, 2010, 19 (5):  054211.  DOI: 10.1088/1674-1056/19/5/054211
    Abstract ( 1104 )   PDF (182KB) ( 949 )  
    This paper studies the propagation of dipole solitons in highly nonlocal medium by using the variational method. It finds that the dipole solitons will be stable when the input power obeys a restrict value. When the incident power does not satisfy the stable conditions, the nonlocal accessible dipole solitons will undergo linear harmonic oscillation. It shows such evolution behaviours in detail.
    High energy and long pulse generation with high-birefringence photonic crystal fibre and laser-diode pumped regenerative amplifier
    Wang He-Lin(王河林), Wang Cheng(王承), Leng Yu-Xin(冷雨欣), Xu Zhi-Zhan(徐至展), and Hou Lan-Tian(候蓝田)
    Chin. Phys. B, 2010, 19 (5):  054212.  DOI: 10.1088/1674-1056/19/5/054212
    Abstract ( 1376 )   PDF (1094KB) ( 1026 )  
    We report on the generation of a high energy and long pulse for pumping optical parametric chirped-pulse amplification (OPCPA) by a high-birefringence photonic crystal fibre (HB-PCF) and a laser-diode-pumped regenerative chirped pulse amplifier. Using the femtosecond pump pulse centred at 815 nm, a 1064 nm soliton pulse is produced in the HB-PCF. After injecting it into an Nd:YAG regenerative amplifier with the glass etalons, a narrow-band amplified pulse with an energy of $\sim $4 mJ and a duration of 235 ps is achieved at a repetition rate of 10 Hz, which is suitable for being used as a pump source in the 800 nm OPCPA system.
    Separate holographic screening soliton pairs in a biased series photorefractive crystal circuit
    Cai Xin(蔡欣), Liu Jin-Song(刘劲松), and Lü Jian-Tao(吕健滔)
    Chin. Phys. B, 2010, 19 (5):  054213.  DOI: 10.1088/1674-1056/19/5/054213
    Abstract ( 1104 )   PDF (590KB) ( 673 )  
    Holographic dark (bright) screening solitons are predicted in one dimension for a series circuit consisting of two photorefractive crystals connected electronically by electrode leads in a chain with a voltage source. Each crystal can support a holographic screening soliton. The two solitons are known collectively as a separate holographic screening soliton pair with three types: bright--bright, bright--dark and dark--dark. The numerical results show that the two solitons in a soliton pair can affect each other through a light-induced current and their coupling can affect their spatial profiles under the limit in which the optical wave has a spatial extent much less than the width of the crystal.
    Ultraslow optical solitons via electromagnetically induced transparency: a density-matrix approach
    Luo Bin(骆斌), Hang Chao(杭超), Li Hui-Jun(李慧军), and Huang Guo-Xiang(黄国翔)
    Chin. Phys. B, 2010, 19 (5):  054214.  DOI: 10.1088/1674-1056/19/5/054214
    Abstract ( 1383 )   PDF (189KB) ( 980 )  
    We study the ultraslow optical solitons in a resonant three-level atomic system via electromagnetically induced transparency under a density-matrix (DM) approach. The results of linear and nonlinear optical properties are compared with those obtained by using an amplitude variable (AV) approach. It is found that the results for both approaches are the same in the linear regime if the corresponding relations between the population-coherence decay rates in the DM approach and the energy-level decay rates in the AV approach are appropriately imposed. However, in the nonlinear regime there is a small difference for the self-phase modulation coefficient of the nonlinear Schr?dinger equation that governs the time evolution of probe pulse envelope. All analytical predicts are checked by numerical simulations.
    Relationship between group velocity and symmetry of photonic crystals
    Ye Wei-Min(叶卫民), Luo Zhang(罗章), Yuan Xiao-Dong(袁晓东), and Zeng Chun(曾淳)
    Chin. Phys. B, 2010, 19 (5):  054215.  DOI: 10.1088/1674-1056/19/5/054215
    Abstract ( 1261 )   PDF (291KB) ( 734 )  
    Group velocity (GV) of eigenmode is a crucial parameter to explain the extraordinary phenomena about light propagation in photonic crystals (PhCs). To study relationships between group velocity and symmetry of PhCs, a new general expression of GV in PhCs made up of non-dispersive material is introduced. Based on this, the GVs of eigenmodes of PhCs, especially those of degenerate eigenmodes at highly symmetric points in the first Brillouin zone, are discussed. Some interesting results are obtained. For example, the summation of degenerate eigenmodes' GVs is invariant under the operations of wave vector K-group MK. In addition, some numerical results are presented to verify them.
    Physical model of acoustic forward scattering by cylindrical shell and its experimental validation
    Lei Bo(雷波), Yang Kun-De(杨坤德), and Ma Yuan-Liang(马远良)
    Chin. Phys. B, 2010, 19 (5):  054301.  DOI: 10.1088/1674-1056/19/5/054301
    Abstract ( 1161 )   PDF (4660KB) ( 1257 )  
    Research on the underwater target scattering can provide important theoretical support for target detection. The scattering model of cylindrical shell is established in this paper. It is found that the forward target strength is much stronger and varies with angles of incident wave less significantly than backward target strength. The received forward signal strength fluctuates with the target moving due to the interference between direct signal and scattering signal, which is most significant when target approaches the baseline. An experiment is carried out in an anechoic tank to validate the scattering model. The method of acquisiting forward scattering in the tank is proposed. The forward and the backward target strengths are achieved by using the pulse compression technology, and they are about 3dB less than the modeling results. The forward scattering phenomena of quiescent and moving target are measured, which are similar to modeling results with different target types.
    Finite element modeling of acoustic scattering from an encapsulated microbubble near rigid boundary
    Huang Bei(黄蓓), Zhang Yan-Li(张艳丽), Zhang Dong(章东), and Gong Xiu-Fen(龚秀芬)
    Chin. Phys. B, 2010, 19 (5):  054302.  DOI: 10.1088/1674-1056/19/5/054302
    Abstract ( 1200 )   PDF (642KB) ( 1297 )  
    This article proposes a finite element model (FEM) for predicting the acoustic scattering from an encapsulated microbubble near rigid boundary. The validity of the model is first examined by comparing the acoustic nonlinear response of a free microbubble with that obtained by the Church model. Then this model is used to investigate the effect of the rigid boundary on acoustic scattering signals from microbubble. The results indicate that the resonance frequency decreases while the oscillation amplitude increases as the microbubble approaches the rigid boundary. In addition, the fundamental component of the acoustic scattering signal is enhanced compared with that of the free microbubble.
    Analysis and improvement of sound radiation performance of spherical cap radiator
    Tang Yi-Zheng(唐义政), Wu Zhao-Jun(吴昭军), and Tang Li-Guo(汤立国)
    Chin. Phys. B, 2010, 19 (5):  054303.  DOI: 10.1088/1674-1056/19/5/054303
    Abstract ( 1229 )   PDF (317KB) ( 648 )  
    A spherical cap radiator is one of the important parts of an underwater wide-beam imaging system. The back radiation of a traditional spherical cap radiator, which is composed of a vibrating cap and a rigid baffle, is strong and its far-field directivity function may fluctuate in big amplitude in the vicinity of the polar axis. These shortcomings complicate the processing of the reflective waves received for imaging the targets. In this study, the back radiation is weakened by adding an acoustic soft material belt between the vibrating cap and the rigid baffle. And the fluctuation mentioned above is lowered remarkably by dividing the spherical cap radiator into many annuluses and a relatively smaller spherical cap, and by controlling the phase retardations of all elements appropriately. Furthermore, the numerical experiments are carried out by the finite element method (FEM) to prove the validity of the above methods.
    Anomalous energy diffusion and heat conduction in one-dimensional system
    Li Hai-Bin(李海彬) and Li Zhen(李珍)
    Chin. Phys. B, 2010, 19 (5):  054401.  DOI: 10.1088/1674-1056/19/5/054401
    Abstract ( 1198 )   PDF (184KB) ( 667 )  
    We propose a new concept, the centre of energy, to study energy diffusion and heat conduction in one-dimensional hard-point model. For diatom model, we find an anomalous energy diffusion as $\langle x^2 \rangle\sim t^\beta$ with $\beta=1.33$, which is independent of initial condition and mass rate. The present model can be viewed as the model composed by independent quasi-particles, the centre of energy. In this way, heat current can be calculated. Based on theory of dynamic billiard, the divergent exponent of heat conductivity is estimated to be $\alpha=0.33$, which is confirmed by a simple numerical calculation.
    PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
    Generation of fast protons in moderate-intensity laser-plasma interaction from rear sheath
    Tan Zhi-Xin(谭志新), Huang Yong-Sheng(黄永盛), Lan Xiao-Fei(兰小飞) , Lu Jian-Xin(路建新), Duan Xiao-Jiao(段晓礁), Wang Lei-Jian(王雷剑), Yang Da-Wei(杨大为), Guo Shi-Lun(郭士伦), and Wang Nai-Yan(王乃彦)
    Chin. Phys. B, 2010, 19 (5):  055201.  DOI: 10.1088/1674-1056/19/5/055201
    Abstract ( 1325 )   PDF (398KB) ( 807 )  
    Forward fast protons are generated by the moderate-intensity laser--foil interaction. Protons with maximum energy 190 keV are measured by using magnetic spectrometer and CR-39 solid state track detectors along the direction normal to the rear surface. The experimental results are also modeled by the particle-in-cell method, investigating the time-varying electron temperature and the rear sheath field. The temporal and spatial structure of the sheath electrical field, revealed in the simulation, suggests that these protons are accelerated by target normal sheath acceleration (TNSA) mechanism.
    CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
    Influence of reducing anneal on the ferromagnetism in single crystalline Co-doped ZnO thin films
    Lu Zhong-Lin(路忠林), Zou Wen-Qin(邹文琴), Xu Ming-Xiang (徐明祥), and Zhang Feng-Ming(张凤鸣)
    Chin. Phys. B, 2010, 19 (5):  056101.  DOI: 10.1088/1674-1056/19/5/056101
    Abstract ( 1276 )   PDF (928KB) ( 1269 )  
    This paper reports that the high-quality Co-doped ZnO single crystalline films have been grown on $a$-plane sapphire substrates by using molecular-beam epitaxy. The as-grown films show high resistivity and non-ferromagnetism at room temperature, while they become good conductive and ferromagnetic after annealing in the reducing atmosphere either in the presence or absence of Zn vapour. The x-ray absorption studies indicate that all Co ions in these samples actually substituted into the ZnO lattice without formatting any detectable secondary phase. Compared with weak ferromagnetism (0.16 $\mu _{\rm B}$/Co$^{2 + })$ in the Zn$_{0.95}$Co$_{0.05}$O single crystalline film with reducing annealing in the absence of Zn vapour, the films annealed in the reducing atmosphere with Zn vapour are found to have much stronger ferromagnetism (0.65 $\mu _{\rm B}$/Co$^{2 + })$ at room temperature. This experimental studies clearly indicate that Zn interstitials are more effective than oxygen vacancies to activate the high-temperature ferromagnetism in Co-doped ZnO films, and the corresponding ferromagnetic mechanism is discussed.
    Elastic behaviour of a wedge disclination dipole near a sharp crack emanating from a semi-elliptical blunt crack
    Song Hao-Peng(宋豪鹏), Fang Qi-Hong(方棋洪), and Liu You-Wen (刘又文)
    Chin. Phys. B, 2010, 19 (5):  056102.  DOI: 10.1088/1674-1056/19/5/056102
    Abstract ( 1323 )   PDF (547KB) ( 809 )  
    The interaction between a wedge disclination dipole and a crack emanating from a semi-elliptic hole is investigated. Utilising the complex variable method, the closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the disclination dipole center are also calculated. The influence of the morphology of the blunt crack and the position of the disclination dipole on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases when the wedge disclination dipole approaches the tip of the crack. The effects of the morphology of the blunt crack on the stress intensity factor of the crack and the image force are very significant.
    Radiation effects on MOS and bipolar devices by 8 MeV protons, 60 MeV Br ions and 1 MeV electrons
    Li Xing-Ji(李兴冀), Geng Hong-Bin(耿洪滨), Lan Mu-Jie(兰慕杰), Yang De-Zhuang(杨德庄), He Shi-Yu(何世禹), and Liu Chao-Ming(刘超铭)
    Chin. Phys. B, 2010, 19 (5):  056103.  DOI: 10.1088/1674-1056/19/5/056103
    Abstract ( 1189 )   PDF (2089KB) ( 1086 )  
    The radiation effects of the metal-oxide-semiconductor (MOS) and the bipolar devices are characterised using 8~MeV protons, 60 MeV Br ions and 1 MeV electrons. Key parameters are measured in-situ and compared for the devices. The ionising and nonionising energy losses of incident particles are calculated using the Geant4 and the stopping and range of ions in matter code. The results of the experiment and energy loss calculation for different particles show that different incident particles may give different contribution to MOS and bipolar devices. The irradiation particles, which cause larger displacement dose within the same chip depth of bipolar devices at a given total dose, would generate more severe damage to the voltage parameters of the bipolar devices. On the contrary, the irradiation particles, which cause larger ionising damage in the gate oxide, would generate more severe damage to MOS devices. In this investigation, we attempt to analyse the sensitivity to radiation damage of the different parameter of the MOS and bipolar devices by comparing the irradiation experimental data and the calculated results using Geant4 and SRIM code.
    First-principles study of electronic and optical properties in wurtzite Zn1-xCuxO
    Zhao Long(赵龙), Lu Peng-Fei(芦鹏飞), Yu Zhong-Yuan(俞重远), Liu Yu-Min(刘玉敏), Wang Dong-Lin(王东林), and Ye Han(叶寒)
    Chin. Phys. B, 2010, 19 (5):  056104.  DOI: 10.1088/1674-1056/19/5/056104
    Abstract ( 1275 )   PDF (1404KB) ( 1937 )  
    We perform a first-principles simulation to study the electronic and optical properties of wurtzite Zn$_{1 - x}$Cu$_{x}$O. The simulations are based upon the Perdew--Burke--Ernzerhof form of generalised gradient approximation within the density functional theory. Calculations are carried out in different concentrations. With increasing Cu concentration, the band gap of Zn$_{1 - x}$Cu$_{x}$O decreases due to the shift of valence band. The imaginary part of the dielectric function indicates that the optical transition between O 2p states in the highest valence band and Zn 4s states in the lowest conduction band shifts to the low energy range as the Cu concentration increases. Besides, it is shown that the insertion of Cu atom leads to redshift of the optical absorption edge. Meanwhile, the optical constants of pure ZnO and Zn$_{0.75}$Cu$_{0.25}$O, such as loss function, refractive index and reflectivity, are discussed.
    Stabilisation analysis of multiple car-following model in traffic flow
    Peng Guang-Han(彭光含)
    Chin. Phys. B, 2010, 19 (5):  056401.  DOI: 10.1088/1674-1056/19/5/056401
    Abstract ( 1237 )   PDF (1054KB) ( 1093 )  
    An improved multiple car-following model is proposed by considering the arbitrary number of preceding cars, which includes both the headway and the velocity difference of multiple preceding cars. The stability condition of the extended model is obtained by using the linear stability theory. The modified Korteweg--de Vries equation is derived to describe the traffic behaviour near the critical point by applying the nonlinear analysis. Traffic flow can be also divided into three regions: stable, metastable and unstable regions. Numerical simulation is accordance with the analytical result for the model. And numerical simulation shows that the stabilisation of traffic is increasing by considering the information of more leading cars and there is unavoidable effect on traffic flow from the multiple leading cars' information.
    Shock-induced phase transition and spalling characteristic in pure iron and FeMnNi alloy
    Chen Yong-Tao(陈永涛), Tang Xiao-Jun(唐小军), and Li Qing-Zhong(李庆忠)
    Chin. Phys. B, 2010, 19 (5):  056402.  DOI: 10.1088/1674-1056/19/5/056402
    Abstract ( 1128 )   PDF (1511KB) ( 1249 )  
    This paper provides an investigation of the phase transition and spalling characteristic induced during shock loading and unloading in the pure iron and the FeMnNi alloy. The impact for the pure iron is symmetric and with same-thickness for both the flyer and the target plate. It is found that an abnormal multiple spalling happens in the pure iron sample as the pressure exceeds the $\alpha -\varepsilon $ transition threshold of 13 GPa. In the symmetric and same-thickness impact and reverse impact experiments of the FeMnNi alloy, two abnormal tension regions occur when the pressure exceeds the $\alpha -\varepsilon $ transition threshold of 6.3 GPa, and the reverse phase transition $\varepsilon -\alpha $ begins below 4.2 GP. The experimental process is simulated successfully from the non-equilibrium mixture phase and Boettger's model. Such abnormal spalling phenomena are believed to relate to the shocked $\alpha -\varepsilon $ phase transition. The possible reasons for the abnormal multiple spalling, which occurs during the symmetric and same-thickness impact experiments of pure iron and FeMnNi alloy, are discussed.
    Solving the initial condition of the string relaxation equation of the string model for glass transition: part-I
    Zhang Jin-Lu(张晋鲁), Wang Li-Na(王丽娜), Zhou Heng-Wei(周恒为), Zhang Li-Li(张丽丽), Zhao Xing-Yu(赵兴宇), and Huang Yi-Neng(黄以能)
    Chin. Phys. B, 2010, 19 (5):  056403.  DOI: 10.1088/1674-1056/19/5/056403
    Abstract ( 1094 )   PDF (175KB) ( 781 )  
    The string model for the glass transition can quantitatively describe the universal $\alpha $-relaxation in glassformers, including the average relaxation time, the distribution function of the relaxation time, and the relaxation strength as functions of temperature. The string relaxation equation (SRE) of the model, at high enough temperatures, simplifies to the well-known single particle mean-field Debye relaxation equation, and at low enough temperatures to the well-known Rouse--Zimm relaxation equation that describes the relaxation dynamics of linear macromolecules. However, its initial condition, necessary to the further model predictions of glassy dynamics, has not been solved. In this paper, the special initial condition (SIC) of the SRE, i.e. for straight strings and the dielectric spectrum technique that is one of the most common methods to measure the glassy dynamics, was solved exactly. It should be expected that the obtained SIC would benefit the solution of the general initial condition of the SRE of the string model, i.e. for stochastically spatially configurating strings, as will be described in separate publications.
    A molecular dynamics simulation of segregation behaviours of horizontally vibrated binary granular mixture
    Xia Ji-Hong(夏继宏), You Yu-Wei(尤玉伟), Wang Pan-Pan(汪盼盼), Wang Wei-Lu(王炜路), and Liu Chang-Song(刘长松)
    Chin. Phys. B, 2010, 19 (5):  056404.  DOI: 10.1088/1674-1056/19/5/056404
    Abstract ( 1168 )   PDF (1414KB) ( 786 )  
    This paper performs the two-dimensional, soft-sphere molecular dynamics simulations to study the granular segregation in a binary granular mixture with the same size but different density in the container with the sawtooth base under horizontal vibration. The segregation phase diagram is presented in the acceleration-frequency space. When the acceleration is high enough to result in relative motions of the particles, the system can be in various states (mixed state, vertical and horizontal segregation state), which depend on both acceleration and frequency. Due to the sawtooth base there is stratified flow effect besides density effect. The density effect raises the light particles. The stratified flow drives the particles in the upper levels to the right and the particles in the lower particles to the left, those fact results in the appearance of the left segregation state. The left segregation state can be changed to the right segregation by changing the shape of the sawtooth. As the vibration frequency increases, the stratified flow effect becomes weaker and weaker, so at high vibration frequencies the vertical segregation state appears instead of the left segregation state.
    Superhydrophobic surfaces via controlling the morphology of ZnO micro/nano complex structure
    Gong Mao-Gang(公茂刚), Xu Xiao-Liang(许小亮), Yang Zhou(杨周), Liu Yan-Song(刘艳松), and Liu Ling(刘玲)
    Chin. Phys. B, 2010, 19 (5):  056701.  DOI: 10.1088/1674-1056/19/5/056701
    Abstract ( 1278 )   PDF (2459KB) ( 1418 )  
    ZnO micro/nano complex structure films, including reticulate papillary nodes, petal-like and flake-hole, have been self-assembled by a hydrothermal technique at different temperatures without metal catalysts. The wettability of the above film surfaces was modified with a simple coating of heptadecafluorodecyltrimethoxy-silane in toluene. After modifying, the surface of ZnO film grown at 50 ${^\circ}$C was converted from superhydrophilic with a water contact angle lower than 5$^{\circ}$ to superhydrophobic with a water contact angle of 165$^{\circ}$. Additionally, the surface of reticulate papillary nodes ZnO film grown at 100 ${^\circ}$C had excellent superhydrophobicity, with a water contact angle of 173$^{\circ}$ and a sliding angle lower than 2$^{\circ}$. Furthermore, the water contact angle on the surface of petal-like and flake-hole ZnO films grown at 150 ${^\circ}$C and 200 ${^\circ}$C were found to be 140$^{\circ}$ and 120$^{\circ}$, respectively. The wettability for the samples was found to depend strongly on the surface morphology which results from the growth temperature.
    CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
    First-principles calculation of magnetism of icosahedral Fe clusters
    Cheng Zhi-Da(程志达), Ling Tao(凌涛), and Zhu Jing(朱静)
    Chin. Phys. B, 2010, 19 (5):  057101.  DOI: 10.1088/1674-1056/19/5/057101
    Abstract ( 1313 )   PDF (2018KB) ( 705 )  
    Icosahedral iron clusters are synthesized and characterized in our group by using experimental methods. But the measurements of magnetic properties still face difficulties: the sizes of the clusters and the amount of product. Therefore theoretical methods are employed to study these issues. In this paper, icosahedral iron clusters containing 13, 55, 147, 309 atoms are calculated by ab initio techniques. After the structural relaxation, the magnetism of the clusters is found to be similar to that of face centred cubic (FCC) iron with stronger ferromagnetism on surface. But the central atom of each cluster is exceptional, which has a smaller magnetic moment. We also study the electronic structural properties in the clusters for the better explanation of the magnetism. It is suggested that in small clusters, the magnetic properties still depend on the local structural arrangement.
    Molecular dynamics simulation of collective behaviour of Xe in UO2
    Tian Xiao-Feng(田晓峰), Long Chong-Sheng(龙冲生), Zhu Zheng-He(朱正和), and Gao Tao(高涛)
    Chin. Phys. B, 2010, 19 (5):  057102.  DOI: 10.1088/1674-1056/19/5/057102
    Abstract ( 1459 )   PDF (3132KB) ( 995 )  
    This paper performs atomic simulations of the nucleation and growth of Xe bubble in UO$_{2}$ at 1600 K. The bubble growth was simulated up to the bubble containing 50 Xe atoms. The Xe atoms were added directly to the bubble one by one, followed by a relaxation of the system for several picoseconds. The simulations estimated the bubble pressure and radius at different Xe concentrations. The results indicate that the bubble pressure drops with the increasing Xe/U and bubble size at low Xe concentration, while the pressure will increase with the Xe/U ratio at high Xe concentration. The swelling of the system associated with the bubble growth was also obtained. Finally, the recovery of the damaged structure was investigated.
    Field emission of carbon nanotube array with normal-gate cold cathode
    Dai Jian-Feng(戴剑锋), Mu Xiao-Wen(慕晓文), Qiao Xian-Wu(乔宪武), Chen Xiao-Xing(陈小婷), and Wang Jun-Hong(王军红)
    Chin. Phys. B, 2010, 19 (5):  057201.  DOI: 10.1088/1674-1056/19/5/057201
    Abstract ( 1250 )   PDF (923KB) ( 811 )  
    A hexagon pitch carbon nanotube (CNT) array vertical to the normal gate of cold cathode field emission displayer (FED) is simulated by solving the Laplace equation. The calculated results show that the normal gate causes the electric field around the CNT tops to be concentrated and emission electron beam become a column. The field enhancement factor and the emission current intensity step up greatly compared with those of diode structure. Emission current density increases rapidly with the decrease of normal-gate aperture. The gate voltage exerts a critical influence on the emission current.
    Influence of time-periodic potentials on electronic transport in double-well structure
    Li Chun-Lei(李春雷) and Xu Yan(徐燕)
    Chin. Phys. B, 2010, 19 (5):  057202.  DOI: 10.1088/1674-1056/19/5/057202
    Abstract ( 1236 )   PDF (475KB) ( 618 )  
    Within the framework of the Floquet theorem, we have investigated single-electron photon-assisted tunneling in a double-well system using the transfer matrix technique. The transmission probability displays satellite peaks on the both sides of main resonance peaks and these satellite peaks originate from emission or absorption photons. The single-electron resonance tunneling can be control through changing applied harmonically potential positions, such as driven potential in wells, in barriers, or in whole double-well system. This advantage should be useful in the optimization of the parameters of a transmission device.
    Comparative study of different properties of GaN films grown on(0001) sapphire using high and low temperature AlN interlayers
    Xue Jun-Shuai(薛军帅), Hao Yue(郝跃), Zhang Jin-Cheng(张进成), and Ni Jin-Yu(倪金玉)
    Chin. Phys. B, 2010, 19 (5):  057203.  DOI: 10.1088/1674-1056/19/5/057203
    Abstract ( 1268 )   PDF (187KB) ( 905 )  
    Comparative study of high and low temperature AlN interlayers and their roles in the properties of GaN epilayers prepared by means of metal organic chemical vapour deposition on (0001) plane sapphire substrates is carried out by high resolution x-ray diffraction, photoluminescence and Raman spectroscopy. It is found that the crystalline quality of GaN epilayers is improved significantly by using the high temperature AlN interlayers, which prevent the threading dislocations from extending, especially for the edge type dislocation. The analysis results based on photoluminescence and Raman measurements demonstrate that there exist more compressive stress in GaN epilayers with high temperature AlN interlayers. The band edge emission energy increases from 3.423 eV to 3.438 eV and the frequency of Raman shift of $E_{2 }$(TO) moves from 571.3 cm$^{ - 1}$ to 572.9 cm$^{ - 1}$ when the temperature of AlN interlayers increases from 700 $^{\circ}$C to 1050 $^{\circ}$C. It is believed that the temperature of AlN interlayers effectively determines the size, the density and the coalescence rate of the islands, and the high temperature AlN interlayers provide large size and low density islands for GaN epilayer growth and the threading dislocations are bent and interactive easily. Due to the threading dislocation reduction in GaN epilayers with high temperature AlN interlayers, the approaches of strain relaxation reduce drastically, and thus the compressive stress in GaN epilayers with high temperature AlN interlayers is high compared with that in GaN epilayers with low temperature AlN interlayers.
    Fabrication of a 256-bits organic memory by soft x-ray lithography
    Liu Xing-Hua(刘兴华), Lu Wen-Sheng(鲁闻生), Ji Zhuo-Yu(姬濯宇), Tu De-Yu(涂德钰),Zhu Xiao-Li(朱效立), Xie Chang-Qing(谢常青), and Liu Ming(刘明)
    Chin. Phys. B, 2010, 19 (5):  057204.  DOI: 10.1088/1674-1056/19/5/057204
    Abstract ( 1179 )   PDF (4086KB) ( 770 )  
    This paper reports a procedure of soft x-ray lithography for the fabrication of organic crossbar structure. Electron beam lithography is employed to fabricate the mask for soft x-ray lithography, with direct writing technology to lithograph positive resist, polymethyl methacrylate on the polyimide film. Then Au is electroplated on the polyimide film. Hard contact mode exposure is used in x-ray lithography to transfer the graph from the mask to the wafer. The 256-bits organic memory is achieved with the critical dimension of 250 nm.
    The effect of initial discharge conditions on the properties of microcrystalline silicon thin films and solar cells
    Chen Yong-Sheng(陈永生), Yang Shi-E(杨仕娥), Wang Jian-Hua(汪建华), Lu Jing-Xiao(卢景霄),Gao Xiao-Yong(郜小勇), and Gu Jin-Hua(谷锦华)
    Chin. Phys. B, 2010, 19 (5):  057205.  DOI: 10.1088/1674-1056/19/5/057205
    Abstract ( 1191 )   PDF (585KB) ( 546 )  
    This paper studies the effects of silane back diffusion in the initial plasma ignition stage on the properties of microcrystalline silicon ($\mu $c-Si:H) films by Raman spectroscopy and spectroscopic ellipsometry, through delaying the injection of SiH$_{4}$ gas to the reactor before plasma ignition. By comparing with standard discharge condition, delayed SiH$_{4}$ gas condition could prevent the back diffusion of SiH$_{4}$ from the reactor to the deposition region effectively, which induced the formation of a thick amorphous incubation layer in the interface between bulk film and glass substrate. Applying this method, it obtains the improvement of spectral response in the middle and long wavelength region by combining this method with solar cell fabrication. Finally, results are explained by modifying zero-order analytical model, and a good agreement is found between model and experiments concerning the optimum delayed injection time.
    Size effect of quantum conductance in carbon nanotube Y-Junctions
    Liu Hong(刘红)
    Chin. Phys. B, 2010, 19 (5):  057206.  DOI: 10.1088/1674-1056/19/5/057206
    Abstract ( 1162 )   PDF (1591KB) ( 606 )  
    This paper studies the quantum conductance properties of three-terminated carbon nanotube Y-junctions, which are built by connecting three (5,5) single-walled carbon nanotubes. The results show that the quantum conductance at the Fermi energy oscillates periodically with the junction's size, and the number of oscillating periodic layers is 3 which is the same as that in the two terminated $(10,0)/m(5,5)/(10,0)$ junctions. Moreover, this Y-junction with different size exhibits obvious different distribution of electron current in the two drain branches, called shunt valve effect of electronic current. Thus the degree of this effect can be controlled and modulated directly by constructing the three branches' sizes or the distribution of defect. The results show in detail that the difference between the two drain currents can be up to two times for some constructions with special sizes. In addition, the uniform distribution of defects in the Y-junction leads to lower quantum conductance than that of other defect configurations.
    The initial decoherence of the mesoscopic Josephson junction flux qubit
    Su Jie(苏杰), Wang Ji-Suo(王继锁), Zhang Xiao-Yan(张晓燕), and Liang Bao-Long(梁宝龙)
    Chin. Phys. B, 2010, 19 (5):  057301.  DOI: 10.1088/1674-1056/19/5/057301
    Abstract ( 1275 )   PDF (263KB) ( 519 )  
    For a mesoscopic radio frequency superconducting quantum interference device (rfSQUID), at a degeneracy point, the system reduces to a quantum two-state system which can be used as a flux qubit. When the noise environment is equivalent to a harmonic oscillators bath, by virtue of an operator-norm measure for the short time decoherence, this paper investigates the initial decoherence of the flux qubit operating in the ohmic noise environment and illustrates its property by means of the numerical evaluation.
    Comparative studies of Ge and Si p-channel metal-oxide-semiconductor field-effect-transistors with HfSiON dielectric and TaN metal gate
    Hu Ai-Bin(胡爱斌) and Xu Qiu-Xia(徐秋霞)
    Chin. Phys. B, 2010, 19 (5):  057302.  DOI: 10.1088/1674-1056/19/5/057302
    Abstract ( 1219 )   PDF (1414KB) ( 582 )  
    Ge and Si p-channel metal--oxide--semiconductor field-effect-transistors (p-MOSFETs) with hafnium silicon oxynitride (HfSiON) gate dielectric and tantalum nitride (TaN) metal gate are fabricated. Self-isolated ring-type transistor structures with two masks are employed. W/TaN metal stacks are used as gate electrode and shadow masks of source/drain implantation separately. Capacitance--voltage curve hysteresis of Ge metal--oxide--semiconductor (MOS) capacitors may be caused by charge trapping centres in GeO$_{x}$ (1 < $x$ < 2).  Effective hole mobilities of Ge and Si transistors are extracted by using a channel conductance method. The peak hole mobilities of Si and Ge transistors are 33.4 cm2/(V$\cdot$s) and 81.0 cm2/(V$\cdot$s), respectively. Ge transistor has a hole mobility 2.4 times higher than that of Si control sample. 
    Characteristics and parameter extraction for NiGe/n-type Ge Schottky diode with variable annealing temperatures
    Liu Hong-Xia(刘红侠), Wu Xiao-Feng(吴笑峰), Hu Shi-Gang(胡仕刚), and Shi Li-Chun(石立春)
    Chin. Phys. B, 2010, 19 (5):  057303.  DOI: 10.1088/1674-1056/19/5/057303
    Abstract ( 1342 )   PDF (735KB) ( 728 )  
    Current transport mechanism in Ni-germanide/n-type Ge Schottky diodes is investigated using current--voltage characterisation technique with annealing temperatures from 300 $^\circ$C to 500 $^\circ$C. Based on the current transport model, a simple method to extract parameters of the NiGe/Ge diode is presented by using the $I$--$V$ characteristics. Parameters of NiGe/n-type Ge Schottky diodes fabricated for testing in this paper are as follows: the ideality factor $n$, the series resistance $R_{\rm s}$, the zero-field barrier height $\phi _{\rm b0}$, the interface state density $D_{\rm it}$, and the interfacial layer capacitance $C_{\rm i}$. It is found that the ideality factor $n$ of the diode increases with the increase of annealing temperature. As the temperature increases, the interface defects from the sputtering damage and the penetration of metallic states into the Ge energy gap are passivated, thus improving the junction quality. However, the undesirable crystallisations of Ni-germanide are observed together with NiGe at a temperature higher than 400 $^\circ$C. Depositing a very thin ($\sim $1 nm) heavily Ge-doped $n^{+}$ Ge intermediate layer can improve the NiGe film morphology significantly.
    Effect of interface roughness on the carrier transport in germanium MOSFETs investigated by Monte Carlo method
    Du Gang(杜刚), Liu Xiao-Yan(刘晓彦), Xia Zhi-Liang(夏志良), Yang Jing-Feng(杨竞峰), and Han Ru-Qi(韩汝琦)
    Chin. Phys. B, 2010, 19 (5):  057304.  DOI: 10.1088/1674-1056/19/5/057304
    Abstract ( 1428 )   PDF (289KB) ( 651 )  
    Interface roughness strongly influences the performance of germanium metal--organic--semiconductor field effect transistors (MOSFETs). In this paper, a 2D full-band Monte Carlo simulator is used to study the impact of interface roughness scattering on electron and hole transport properties in long- and short- channel Ge MOSFETs inversion layers. The carrier effective mobility in the channel of Ge MOSFETs and the in non-equilibrium transport properties are investigated. Results show that both electron and hole mobility are strongly influenced by interface roughness scattering. The output curves for 50~nm channel-length double gate n and p Ge MOSFET show that the drive currents of n- and p-Ge MOSFETs have significant improvement compared with that of Si n- and p-MOSFETs with smooth interface between channel and gate dielectric. The $82\%$ and $96\%$ drive current enhancement are obtained for the n- and p-MOSFETs with the completely smooth interface. However, the enhancement decreases sharply with the increase of interface roughness. With the very rough interface, the drive currents of Ge MOSFETs are even less than that of Si MOSFETs. Moreover, the significant velocity overshoot also has been found in Ge MOSFETs.
    Giant magnetocaloric effect in Tb5Ge2-xSi2-xMn2x compounds Hot!
    E. Yüzüak, B. Emre, Y. Elerman, and A. Yücel
    Chin. Phys. B, 2010, 19 (5):  057501.  DOI: 10.1088/1674-1056/19/5/057501
    Abstract ( 1227 )   PDF (1252KB) ( 516 )  
    The crystal structure, magnetic and magnetocaloric characteristics of the pseduo ternary compounds of Tb$_{5}$Ge$_{2-x}$Si$_{2-x}$Mn$_{2x}$ (0 $\leq $ 2$x$ $\leq$ 0.1) were investigated by x-ray powder diffraction and magnetization measurements. The x-ray powder diffraction results show that all compounds preserve the monoclinic phase as the majority phase and all the synthesized compounds were observed to be ferromagnetic from magnetization measurements. Magnetic phase transitions were interpreted in terms of Landau theory. Maximum isothermal magnetic entropy change value (20.84 J$\cdot$kg$^{-1}$$\cdot$K$^{-1}$) was found for Tb$_{5}$Ge$_{1.95}$Si$_{1.95}$Mn$_{0.1}$ at around 123 K in the magnetic field change of 5 T.
    First-order reversal curves of magnetic recording tapes
    Yin Jin-Hua(阴津华) and Pan Li-Qing(潘礼庆)
    Chin. Phys. B, 2010, 19 (5):  057502.  DOI: 10.1088/1674-1056/19/5/057502
    Abstract ( 1387 )   PDF (2306KB) ( 542 )  
    The interaction and its variation between magnetic grains in two kinds of magnetic recording tapes are investigated by first-order reversal curves (FORC) and the $\delta M$ method. The composition and microstructure of the samples are characterised by x-ray diffraction and scanning electron microscope. The FORC diagram can provide more accurate information of the interaction and its variation, but the $\delta M$ curves cannot. The positive interaction field and the large variation of the interaction field have opposite effects on the $\delta M$ curve.
    Effect of F doping on capacitance-voltage characteristics of SiCOH low-k films metal-insulator-semiconductor structure
    Ye Chao(叶超) and Ning Zhao-Yuan(宁兆元)
    Chin. Phys. B, 2010, 19 (5):  057701.  DOI: 10.1088/1674-1056/19/5/057701
    Abstract ( 1125 )   PDF (209KB) ( 657 )  
    This paper investigates the capacitance--voltage ($C$--$V$) characteristics of F doping SiCOH low dielectric constant films metal--insulator--semiconductor structure. The F doping SiCOH films are deposited by decamethylcyclopentasiloxane (DMCPS) and trifluromethane (CHF$_{3})$ electron cyclotron resonance plasmas. With the CHF$_{3}$/DMCPS flow rate ratio from 0 to 0.52, the positive excursion of $C$--$V$ curves and the increase of flat-band voltage $V_{\rm FB}$ from $-6.1$ V to 32.2 V are obtained. The excursion of $C$--$V$ curves and the shift of $V_{\rm FB}$ are related to the change of defects density and type at the Si/SiCOH interface due to the decrease of Si and O concentrations, and the increase of F concentration. At the CHF$_{3}$/DMCPS flow rate ratio is 0.12, the compensation of F-bonding dangling bond to Si dangling bond leads to a small $V_{\rm FB}$ of 2.0 V.
    Negative refraction in ferromagnetic materials under external magnetic field: a theoretical analysis
    Wei Jing-Song(魏劲松) and Xiao Mu-Fei(肖暮霏)
    Chin. Phys. B, 2010, 19 (5):  057801.  DOI: 10.1088/1674-1056/19/5/057801
    Abstract ( 1024 )   PDF (1128KB) ( 562 )  
    We present a detailed theoretical analysis on the possibilities and conditions for negative permeability and negative refraction occuring in the magnetic materials with both pronounced magnetic and dielectric responses to electromagnetic waves. The results indicate that the permeability is always positive for $\delta=(2q+0.5)\pi$ ($\delta$ is the initial phase difference of magnetic components $h_{x}$ and $h_{y }$ of incident electromagnetic wave, $q$ is integer), which means that it is difficult to realize negative refraction. However, for $\delta=2q\pi$, $\delta=(2q+1)\pi$, or $\delta=(2q-0.5)\pi$, the negative permeability occurs at some range of free procession frequency, which means that the refraction can become negative under certain conditions. Further analysis reveals that for general positive permittivity there are various opportunities for realizing the negative refraction provided that some requirements are met. One concludes also that the refractive index for $\delta=2q\pi$ case is similar to $\delta=(2q+1)\pi$. The only difference between two cases of $\delta=2q\pi$ and $\delta=(2q+1)\pi$ is that the $x$-direction for $\delta=2q\pi$ corresponds to the $y$-direction for $\delta=(2q+1)\pi$, and the $y$-direction for $\delta=2q\pi$ corresponds to the $x$-direction for $\delta=(2q+1)\pi$. The results are valuable for designing and analysing the complex negative refraction of magnetic materials.
    Role of Ga vacancies in enhancing the leakage current of GaN Schottky barrier ultraviolet photodetectors
    Zhao De-Gang(赵德刚), Zhang Shuang(张爽), Liu Wen-Bao(刘文宝), Hao Xiao-Peng(郝小鹏), Jiang De-Sheng(江德生), Zhu Jian-Jun(朱建军), Liu Zong-Shun(刘宗顺), Wang Hui(王辉), Zhang Shu-Ming(张书明), Yang Hui(杨辉), and Wei Long(魏龙)
    Chin. Phys. B, 2010, 19 (5):  057802.  DOI: 10.1088/1674-1056/19/5/057802
    Abstract ( 1246 )   PDF (327KB) ( 914 )  
    The leakage current of GaN Schottky barrier ultraviolet photodetectors is investigated. It is found that the photodetectors adopting undoped GaN instead of lightly Si-doped GaN as an active layer show a much lower leakage current even when they have a higher dislocation density. It is also found that the density of Ga vacancies in undoped GaN is much lower than in Si-doped GaN. The Ga vacancies may enhance tunneling and reduce effective Schottky barrier height, leading to an increase of leakage current. It suggests that when undoped GaN is used as the active layer, it is necessary to reduce the leakage current of GaN Schottky barrier ultraviolet photodetector.
    A novel yellow emitting phosphor Dy3+, Bi3+ co-doped YVO4 potentially for white light emitting diodes
    Ci Zhi-Peng(慈志鹏), Wang Yu-Hua(王育华), and Zhang Jia-Chi(张加弛)
    Chin. Phys. B, 2010, 19 (5):  057803.  DOI: 10.1088/1674-1056/19/5/057803
    Abstract ( 1203 )   PDF (194KB) ( 1299 )  
    Novel Y$_{1 - x - y}$VO$_{4}$:$x$Dy$^{3 + }$, $y$Bi$^{3 + }$ ($0.01 \le x \le 0.05, 0 \le y \le 0.20$) phosphors for light emitting diode (LED) were successfully synthesised by solid-state reaction. The calculation results of electronic structure show that YVO$_{4}$ has a direct band gap with 3 eV at $G$. The top of the valence band is dominated by O 2p state and the bottom of the conduction band is mainly composed of O 2p and V 3d states. An efficient yellow emission under near-ultraviolet (365 nm) excitation is observed. Compared with the pure YVO$_{4}$:Dy$^{3 + }$ samples, the Dy$^{3 + }$, Bi$^{3 + }$ co-doped samples show a more intensive emission peak (at 574 nm) and a new broad emission band (450--770 nm), due to the $^{4}F_{9 / 2}-{}^{6}H_{13 / 2 }$ transition of Dy$^{3 + }$ and the emission of the VO$_{4}^{3 - }-$Bi$^{3 + }$ complex respectively. The optimum chromaticity index of Y$_{1 - x - y}$VO$_{4}$:$x$Dy$^{3 + }$, $y$Bi$^{3 + }$ ($0.01 \le x \le 0.05, 0 \le y \le 0.20$) is (0.447, 0.497), which indicates that YVO$_{4}$:Dy$^{3 + }$, Bi$^{3 + }$ has higher colour saturation than the commercial phosphor YAG: Ce$^{3 + }$. The effects of concentration of Dy$^{3 + }$, Bi$^{3 + }$, electric states and the photoluminescence properties are discussed in details.
    CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
    Rotation of hydrogen molecules during the dissociative adsorption on the Mg(0001) surface: a first-principles study
    Li Yan-Fang(李艳芳), Yang Yu(杨宇), Sun Bo(孙博), Song Hong-Zhou(宋红州), Wei Ying-Hui(卫英慧), and Zhang Ping(张平)
    Chin. Phys. B, 2010, 19 (5):  058201.  DOI: 10.1088/1674-1056/19/5/058201
    Abstract ( 950 )   PDF (1359KB) ( 123 )  
    Using first-principles calculations, we systematically study the potential energy surfaces and dissociation processes of the hydrogen molecule on the Mg(0001) surface. It is found that during the dissociative adsorption process with the minimum energy barrier, the hydrogen molecule firstly orients perpendicular, and then rotates to get parallel to the surface. It is also found that the orientation of the hydrogen molecule in the transition state is neither perpendicular nor parallel to the surface. Most importantly, we find that the rotation causes a reduction of the calculated dissociation energy barrier for the hydrogen molecule. The underlying electronic mechanism for the rotation of the hydrogen molecule is also discussed in the paper.
    Electrostatic interaction of a spherical particle in the vicinity of a circular orifice
    Lian Zeng-Ju(连增菊)
    Chin. Phys. B, 2010, 19 (5):  058202.  DOI: 10.1088/1674-1056/19/5/058202
    Abstract ( 831 )   PDF (201KB) ( 327 )  
    Electrostatic interaction of a charged spherical particle in the vicinity of an orifice plane has been investigated in this paper. The particle can creep along the axis of the orifice and is immersed in a bulk electrolyte. By solving the Poisson--Boltzmann problem, we have obtained the effective electrostatic interaction for several values of reduced orifice radius $\tilde{h}$, including the cases of $\tilde{h}>1$, $\tilde{h}=1$ and $\tilde{h}<1$. Two kinds of boundary conditions of the orifice plane are considered. One is constant potential model corresponding to a conducting plane, the other is constant charge model. In the constant potential model, there is an electrostatic attraction between the particle and the orifice plane when they get close to each other, while there is a pure electrostatic repulsion in the constant charge model. The interactions in both boundary models are sensitive to the parameters of the reduced orifice radius, the reduced particle--orifice distance, surface charge densities of the particle and orifice plane, and the reduced Debye screen constant corresponding to the salt-ion concentration and ion valence.
    A method for extracting human gait series from accelerometer signals based on the ensemble empirical mode decomposition
    Fu Mao-Jing(符懋敬), Zhuang Jian-Jun(庄建军), Hou Feng-Zhen(侯凤贞), Zhan Qing-Bo(展庆波),Shao Yi(邵毅), and Ning Xin-Bao(宁新宝)
    Chin. Phys. B, 2010, 19 (5):  058701.  DOI: 10.1088/1674-1056/19/5/058701
    Abstract ( 894 )   PDF (1137KB) ( 254 )  
    In this paper, the ensemble empirical mode decomposition (EEMD) is applied to analyse accelerometer signals collected during human normal walking. First, the self-adaptive feature of EEMD is utilised to decompose the accelerometer signals, thus sifting out several intrinsic mode functions (IMFs) at disparate scales. Then, gait series can be extracted through peak detection from the eigen IMF that best represents gait rhythmicity. Compared with the method based on the empirical mode decomposition (EMD), the EEMD-based method has following advantages: it remarkably improves the detection rate of peak values hidden in the original accelerometer signal, even when the signal is severely contaminated by the intermittent noises; this method effectively prevents the phenomenon of mode mixing found in the process of EMD. And a reasonable selection of parameters for the stop-filtering criteria can improve the calculation speed of the EEMD-based method. Meanwhile, the endpoint effect can be suppressed by using the auto regressive and moving average model to extend a short-time series in dual directions. The results suggest that EEMD is a powerful tool for extraction of gait rhythmicity and it also provides valuable clues for extracting eigen rhythm of other physiological signals.
    Periodic-cylinder vesicle with minimal energy
    Zhou Xiao-Hua(周晓华)
    Chin. Phys. B, 2010, 19 (5):  058702.  DOI: 10.1088/1674-1056/19/5/058702
    Abstract ( 1009 )   PDF (129KB) ( 420 )  
    We give some details about the periodic cylindrical solution found by Zhang and Ou-Yang in [1996 Phys. Rev. E 53 4206] for the general shape equation of vesicle. Three different kinds of periodic cylindrical surfaces and a special closed cylindrical surface are obtained. Using the elliptic functions contained in mathematic, we find that this periodic shape has the minimal total energy for one period when the period--amplitude ratio $\beta\simeq1.477$, and point out that it is a discontinuous deformation between plane and this periodic shape. Our results also are suitable for DNA and multi-walled carbon nanotubes (MWNTs).
    GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
    A two scale nonlinear fractal sea surface model in a one dimensional deep sea
    Xie Tao(谢涛),Zou Guang-Hui(邹光辉), William Perrie, Kuang Hai-Lan(旷海兰), and Chen Wei(陈伟)
    Chin. Phys. B, 2010, 19 (5):  059201.  DOI: 10.1088/1674-1056/19/5/059201
    Abstract ( 1011 )   PDF (753KB) ( 676 )  
    Using the theory of nonlinear interactions between long and short waves, a nonlinear fractal sea surface model is presented for a one dimensional deep sea. Numerical simulation results show that spectra intensity changes at different locations (in both the wave number domain and temporal-frequency domain), and the system obeys the energy conservation principle. Finally, a method to limit the fractal parameters is also presented to ensure that the model system does not become ill-posed.
ISSN 1674-1056   CN 11-5639/O4
, Vol. 19, No. 5

Previous issues

1992 - present