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  • Study of a low power dissipation, miniature laser-pumped rubidium frequency standard

    Liu Guo-Bin, Zhao Feng, Gu Si-Hong
    Chin. Phys. B 2009, 18 (9): 3839-3843
    This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping 87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broadened spectral line, it records a 5× 10-11τ-1/2 (τ 3 volume and 10-12τ -1/2 short-te...

     
  • Optical properties of hexagonal boron nitride thin films deposited by radio frequency bias magnetron sputtering

    Deng Jin-Xiang, Zhang Xiao-Kang, Yao Qian, Wang Xu-Yang, Chen Guang-Hua, He De-Yan
    Chin. Phys. B 2009, 18 (9): 4013-4018
    The optical properties of hexagonal boron nitride (h-BN) thin films were studied in this paper. The films were characterized by Fourier transform infrared spectroscopy, UV--visible transmittance and reflection spectra. h-BN thin films with a wide optical band gap Eg (5.86~eV for the as-deposited fil...

     
Chin. Phys. B  
  Chin. Phys. B--2009, Vol.18, No.9
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GENERAL

Approximate direct reduction method: infinite series reductions to the perturbed mKdV equation

Jiao Xiao-Yu, Lou Sen-Yue
Chin. Phys. B, 2009, 18 (9): 3611-3615 doi: 10.1088/1674-1056/18/9/001
Full Text: [PDF 154 KB] (Downloads:848)
Show Abstract
The approximate direct reduction method is applied to the perturbed mKdV equation with weak fourth order dispersion and weak dissipation. The similarity reduction solutions of different orders conform to formal coherence, accounting for infinite series reduction solutions to the original equation and general formulas of similarity reduction equations. Painlevé II type equations, hyperbolic secant and Jacobi elliptic function solutions are obtained for zero-order similarity reduction equations. Higher order similarity reduction equations are linear variable coefficient ordinary differential equations.

The symplectic eigenfunction expansion theorem and its application to the plate bending equation

Huang Jun-Jie, Alatancang, Wang Hua
Chin. Phys. B, 2009, 18 (9): 3616-3623 doi: 10.1088/1674-1056/18/9/002
Full Text: [PDF 172 KB] (Downloads:704)
Show Abstract
This paper deals with the bending problem of rectangular plates with two opposite edges simply supported. It is proved that there exists no normed symplectic orthogonal eigenfunction system for the associated infinite-dimensional Hamiltonian operator H and that the two block operators belonging to Hamiltonian operator H possess two normed symplectic orthogonal eigenfunction systems in some space. It is demonstrated by using the properties of the block operators that the above bending problem can be solved by the symplectic eigenfunction expansion theorem, thereby obtaining analytical solutions of rectangular plates with two opposite edges simply supported and the other two edges supported in any manner.

Asymptotic solution for a perturbed mechanism of western boundary undercurrents in the Pacific

Mo Jia-Qi, Lin Wan-Tao, Lin Yi-Hua
Chin. Phys. B, 2009, 18 (9): 3624-3627 doi: 10.1088/1674-1056/18/9/003
Full Text: [PDF 136 KB] (Downloads:804)
Show Abstract
This paper consider a class of perturbed mechanism for the western boundary undercurrents in the Pacific. The model of generalized governing equations is studied. Using the perturbation method, it constructs the asymptotic solution of the model. And the accuracy of asymptotic solution is proved by the theory of differential inequalities. Thus the uniformly valid asymptotic expansions of the solution are obtained.

The homotopic mapping solution for the solitary wave for a generalized nonlinear evolution equation

Mo Jia-Qi, Lin Su-Rong
Chin. Phys. B, 2009, 18 (9): 3628-3631 doi: 10.1088/1674-1056/18/9/004
Full Text: [PDF 139 KB] (Downloads:637)
Show Abstract
This paper studies a generalized nonlinear evolution equation. Using the homotopic mapping method, it constructs a corresponding homotopic mapping transform. Selecting a suitable initial approximation and using homotopic mapping, it obtains an approximate solution with an arbitrary degree of accuracy for the solitary wave. From the approximate solution obtained by using the homotopic mapping method, it possesses a good accuracy.

Traffic of indistinguishable particles in complex networks

Meng Qing-Kuan, Zhu Jian-Yang
Chin. Phys. B, 2009, 18 (9): 3632-3638 doi: 10.1088/1674-1056/18/9/005
Full Text: [PDF 474 KB] (Downloads:596)
Show Abstract
In this paper, we apply a simple walk mechanism to the study of the traffic of many indistinguishable particles in complex networks. The network with particles stands for a particle system, and every vertex in the network stands for a quantum state with the corresponding energy determined by the vertex degree. Although the particles are indistinguishable, the quantum states can be distinguished. When the many indistinguishable particles walk randomly in the system for a long enough time and the system reaches dynamic equilibrium, we find that under different restrictive conditions the particle distributions satisfy different forms, including the Bose--Einstein distribution, the Fermi--Dirac distribution and the non-Fermi distribution (as we temporarily call it). As for the Bose--Einstein distribution, we find that only if the particle density is larger than zero, with increasing particle density, do more and more particles condense in the lowest energy level. While the particle density is very low, the particle distribution transforms from the quantum statistical form to the classically statistical form, i.e., transforms from the Bose distribution or the Fermi distribution to the Boltzmann distribution. The numerical results fit well with the analytical predictions.

Dynamical behaviour of an epidemic on complex networks with population mobility

Zhang Hai-Feng, Small Michael, Fu Xin-Chu, Wang Bing-Hong
Chin. Phys. B, 2009, 18 (9): 3639-3646 doi: 10.1088/1674-1056/18/9/006
Full Text: [PDF 244 KB] (Downloads:771)
Show Abstract
In this paper, we study the dynamical behaviour of an epidemic on complex networks with population mobility. In our model, the number of people on each node is unrestricted as the nodes of the network are considered as cities, communities, and so on. Because people can travel between different cities, we study the effect of a population's mobility on the epidemic spreading. In view of the population's mobility, we suppose that the susceptible individual can be infected by an infected individual in the same city or other connected cities. Simulations are presented to verify our analysis.

Lagrange--Noether method for solving second-order differential equations

Wu Hui-Bin, Wu Run-Heng
Chin. Phys. B, 2009, 18 (9): 3647-3650 doi: 10.1088/1674-1056/18/9/007
Full Text: [PDF 132 KB] (Downloads:627)
Show Abstract
The purpose of this paper is to provide a new method called the Lagrange--Noether method for solving second-order differential equations. The method is, firstly, to write the second-order differential equations completely or partially in the form of Lagrange equations, and secondly, to obtain the integrals of the equations by using the Noether theory of the Lagrange system. An example is given to illustrate the application of the result.

A new multi-component integrable coupling system for AKNS equation hierarchy with sixteen-potential functions

Yu Fa-Jun, Li Li
Chin. Phys. B, 2009, 18 (9): 3651-3656 doi: 10.1088/1674-1056/18/9/008
Full Text: [PDF 152 KB] (Downloads:714)
Show Abstract
It is shown in this paper that the upper triangular strip matrix of Lie algebra can be used to construct a new integrable coupling system of soliton equation hierarchy. A direct application to the Ablowitz--Kaup--Newell-- Segur(AKNS) spectral problem leads to a novel multi-component soliton equation hierarchy of an integrable coupling system with sixteen-potential functions. It is indicated that the study of integrable couplings when using the upper triangular strip matrix of Lie algebra is an efficient and straightforward method.

Abundant exact solutions for a strong dispersion-managed system equation

Li Hua-Mei, Li Yi-Shen, Lin Ji
Chin. Phys. B, 2009, 18 (9): 3657-3662 doi: 10.1088/1674-1056/18/9/009
Full Text: [PDF 2263 KB] (Downloads:692)
Show Abstract
The generalized nonlinear Schr?dinger equation (NLSE), which governs the dynamics of dispersion-managed (DM) solitons, is considered. A novel transformation is constructed such that the DM fibre system equation with optical loss (gain) is transformed to the standard NLSE under a restricted condition. Abundant new soliton and periodic wave solutions are obtained by using the transformation and the solutions of standard NLSE. Further, we discuss their main properties and the interaction scenario between two neighbouring solitons by using direct computer simulation.

The scattering states of the generalized Hulthén potential with an improved new approximate scheme to the centrifugal term

Wei Gao-Feng, Chen Wen-Li, Wang Hong-Ying, Li Yuan-Yuan
Chin. Phys. B, 2009, 18 (9): 3663-3669 doi: 10.1088/1674-1056/18/9/010
Full Text: [PDF 214 KB] (Downloads:651)
Show Abstract
This paper finds the approximate analytical scattering state solutions of the arbitrary l-wave Schr?dinger equation for the generalized Hulthén potential by taking an improved new approximate scheme for the centrifugal term. The normalized analytical radial wave functions of the l-wave Schr?dinger equation for the generalized Hulthén potential are presented and the corresponding calculation formula of phase shifts is derived. Some useful figures are plotted to show the improved accuracy of the obtained results and two special cases for the standard Hulthén potential and Woods--Saxon potential are also studied briefly.

Non-commutative Fock-- Darwin system and its magnetism properties

Yu Xiao-Min, Li Kang
Chin. Phys. B, 2009, 18 (9): 3670-3676 doi: 10.1088/1674-1056/18/9/011
Full Text: [PDF 277 KB] (Downloads:590)
Show Abstract
The Fock--Darwin system is studied in noncommutative quantum mechanics. We not only obtain its energy eigenvalues and eigenstates in noncommutative phase space, but also give an electron orbit description as well as the general expressions of the magnetization and the susceptibility in a noncommutative situation. Further, we discuss two particular cases of temperature and present some interesting results different from those obtained from usual quantum mechanics such as the susceptibility dependent on a magnetic field at high temperatures, the occurrence of the magnetization in a zero magnetic field and zero temperature limit, and so on.

Tunable thermal entanglement in an effective spin-star system using coupled microcavities

Yang Wan-Li, Wei Hua, Feng Mang, An Jun-Hong
Chin. Phys. B, 2009, 18 (9): 3677-3686 doi: 10.1088/1674-1056/18/9/012
Full Text: [PDF 1712 KB] (Downloads:680)
Show Abstract
We theoretically explore the possibility of realizing controllable thermal entanglement of effective spins in a four-qubit anisotropic Heisenberg XXZ coupling spin-star system constructed by coupled microcavities. We analyse the dependence of thermal entanglement in this system on temperature, inhomogeneity of the magnetic field, and anisotropy, which can be readily tuned via the external laser fields. The peculiar characteristic and the full controllability of the thermal entanglement are demonstrated to be useful for quantum information processing.

Enhancement of next-nearest-neighbouring entanglement in quantum Ising spin chain

Shan Chuan-Jia, Liu Ji-Bing, Cheng Wei-Wen, Liu Tang-Kun, Huang Yan-Xia, Li Hong
Chin. Phys. B, 2009, 18 (9): 3687-3692 doi: 10.1088/1674-1056/18/9/013
Full Text: [PDF 188 KB] (Downloads:627)
Show Abstract
Using the method of the Jordan--Wigner transformation for solving different spin--spin correlation functions, we have investigated the generation of next-nearest-neighbouring entanglement in a one-dimensional quantum Ising spin chain with the Gaussian distribution impurities of exchange couplings and external magnetic fields taken into account. The maximal value of entanglement between the next-nearest-neighbouring qubits in the transverse Ising model was analysed in detail by varying the effectively controlled parameters such as interchange coupling, magnetic field and the system impurity. For such systems, where both exchange couplings and external magnetic field disorder appear, we show that it is possible to achieve next-nearest-neighbouring entanglement better than the previously discussed pure Ising spin chain case. We also show that the Gaussian distribution impurity can induce next-nearest-neighbouring entanglement, which can be used as a means to characterize quantum phase transition.

Initial-boundary value problems for a class of nonlinear thermoelastic plate equations

Zhang Jian-Wen, Rong Xiao-Liang, Wu Run-Heng
Chin. Phys. B, 2009, 18 (9): 3693-3701 doi: 10.1088/1674-1056/18/9/014
Full Text: [PDF 171 KB] (Downloads:563)
Show Abstract
This paper studies initial-boundary value problems for a class of nonlinear thermoelastic plate equations. Under some certain initial data and boundary conditions, it obtains an existence and uniqueness theorem of global weak solutions of the nonlinear thermoelstic plate equations, by means of the Galerkin method. Moreover, it also proves the existence of strong and classical solutions.

Economical phase-covariant cloning with multiclones

Zhang Wen-Hai, Ye Liu
Chin. Phys. B, 2009, 18 (9): 3702-3705 doi: 10.1088/1674-1056/18/9/015
Full Text: [PDF 135 KB] (Downloads:603)
Show Abstract
This paper presents a very simple method to derive the explicit transformations of the optimal economical 1 to M phase-covariant cloning. The fidelity of clones reaches the theoretic bound [D'Ariano G M and Macchiavello C 2003 Phys. Rev. A 67 042306]. The derived transformations cover the previous contributions [Delgado Y, Lamata L et al, 2007 Phys. Rev. Lett.98 150502] in which M must be odd.

Generation of a χ-type four-atom entangled state

Shen Hong-Wu, Wang Hong-Fu, Ji Xin, Zhang Shou
Chin. Phys. B, 2009, 18 (9): 3706-3709 doi: 10.1088/1674-1056/18/9/016
Full Text: [PDF 179 KB] (Downloads:745)
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This paper proposes a scheme to generate a new χ-type four-atom entangled state for the first time by using linear optics elements, four one-sided cavities (one three-level atom) and a conventional photon detector. The linear optical elements and conventional photon detector are simple and accessible in experiments, which makes the scheme more feasible with current technology. In addition, the state |χ003214 with probability 1 can be generated as long as there is no photon loss.

Faithful quantum entanglement sharing based on linear optics with additional qubits

Li Xi-Han, Duan Xiao-Jiao, Sheng Yu-Bo, Zhou Hong-Yu, Deng Fu-Guo
Chin. Phys. B, 2009, 18 (9): 3710-3713 doi: 10.1088/1674-1056/18/9/017
Full Text: [PDF 155 KB] (Downloads:653)
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This paper presents a scheme for faithfully distributing a pure entanglement between two parties over an arbitrary collective-noise channel with linear optics. The transmission is assisted by an additional qubit against collective noise. The receiver can take advantage of the time discrimination and the measurement results of the assistant qubit to reconstruct a pure entanglement with the sender. Although the scheme succeeds probabilistically, the resource used to get a pure entanglement state is finite, and so is easier to establish entanglement in practice than quantum entanglement purification.

Radon transforms of the Wigner operator on hyperplanes

Chen Jun-Hua, Fan Hong-Yi
Chin. Phys. B, 2009, 18 (9): 3714-3718 doi: 10.1088/1674-1056/18/9/018
Full Text: [PDF 168 KB] (Downloads:638)
Show Abstract
The generalization of tomographic maps to hyperplanes is considered. We find that the Radon transform of the Wigner operator in multi-dimensional phase space leads to a normally ordered operator in binomial distribution---a mixed-state density operator. Reconstruction of the Wigner operator is also feasible. The normally ordered form and the Weyl ordered form of the Wigner operator are used in our derivation. The operator quantum tomography theory is expressed in terms of some operator identities, with the merit of revealing the essence of the theory in a simple and concise way.

Relativity stability of quantum gas in a weak magnetic field

Men Fu-Dian, Liu Hui, Fan Zhao-Lan, Zhu Hou-Yu
Chin. Phys. B, 2009, 18 (9): 3719-3723 doi: 10.1088/1674-1056/18/9/019
Full Text: [PDF 147 KB] (Downloads:618)
Show Abstract
Based on the analytical expression of relativistic free energy for a weakly interacting Fermi gas in a weak magnetic field, by using the method of quantum statistics, the stability conditions of the system at both high and low temperatures are given, and the effects of magnetic field and interparticle interactions on the stability of the system are analysed. It is shown that at high temperatures, the stability conditions of the system are completely the same, no matter whether it is the ultrarelativistic case or nonrelativistic case. At extremely low temperatures, the mechanical stability conditions of the system show a similar rule through a comparison between the ultrarelativistic case and nonrelativistic case. At the same time, thermal stability of a relativistic Bose gas in a weak magnetic field is discussed, and the influence of the effect of relativity on the thermal stability of the system is investigated.

A viscous continuum traffic flow model with consideration of the coupling effect for two-lane freeways

Sun Di-Hua, Peng Guang-Han
Chin. Phys. B, 2009, 18 (9): 3724-3735 doi: 10.1088/1674-1056/18/9/020
Full Text: [PDF 1212 KB] (Downloads:780)
Show Abstract
In this paper, the viscous continuum traffic flow model for a single lane is extended to the traffic flow for two-lane freeways. The proposed model is a higher-order continuum model considering the coupling and lane changing effects of the vehicles on two adjacent lanes. It results from integrating the Taylor series expansion of the viscous continuum traffic flow model proposed by Ge (2006 Physica A 371 667) into the multi-lane model presented by Daganzo (1997 Transpn. Res. B 31 83). Our proposed model may be used to describe non-anisotropic behaviour because of lane changing in multi-lane traffic. A linear stability analysis is given and the neutral stability condition is obtained. Also, issues related to lane changing, shock waves and rarefaction waves, local clustering and phase transition are investigated through a simulation experiment. The simulation results show that the proposed model is capable of explaining some particular traffic phenomena commonly observable in real world traffic flow.

Control of soliton characteristics of the condensate by an arbitrary x-dependent external potential

Yang Ru-Shu, Yao Chun-Mei, Chen Ri-Xin
Chin. Phys. B, 2009, 18 (9): 3736-3741 doi: 10.1088/1674-1056/18/9/021
Full Text: [PDF 1605 KB] (Downloads:599)
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This paper presents a family of soliton solutions of the one-dimensional nonlinear Schr?dinger equation which describes the dynamics of the dark solitons in Bose--Einstein condensates with an arbitrary x-dependent external potential. The obtained results show that the external potential has an important effect on the dark soliton dynamical characteristics of the condensates. The amplitude, width, and velocity of the output soliton are relative to the source position of the external potential. The smaller the amplitude of the soliton is, the narrower its width is, and the slower the soliton propagates. The collision of two dark solitons is nearly elastic.

Global impulsive exponential synchronization of stochastic perturbed chaotic delayed neural networks

Zhang Hua-Guang, Ma Tie-Dong, Fu Jie, Tong Shao-Cheng
Chin. Phys. B, 2009, 18 (9): 3742-3750 doi: 10.1088/1674-1056/18/9/022
Full Text: [PDF 403 KB] (Downloads:870)
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In this paper, the global impulsive exponential synchronization problem of a class of chaotic delayed neural networks (DNNs) with stochastic perturbation is studied. Based on the Lyapunov stability theory, stochastic analysis approach and an efficient impulsive delay differential inequality, some new exponential synchronization criteria expressed in the form of the linear matrix inequality (LMI) are derived. The designed impulsive controller not only can globally exponentially stabilize the error dynamics in mean square, but also can control the exponential synchronization rate. Furthermore, to estimate the stable region of the synchronization error dynamics, a novel optimization control algorithm is proposed, which can deal with the minimum problem with two nonlinear terms coexisting in LMIs effectively. Simulation results finally demonstrate the effectiveness of the proposed method.

Robust lag synchronization between two different chaotic systems via dual-stage impulsive control

Zhang Hua-Guang, Ma Tie-Dong, Fu Jie, Tong Shao-Cheng
Chin. Phys. B, 2009, 18 (9): 3751-3757 doi: 10.1088/1674-1056/18/9/023
Full Text: [PDF 422 KB] (Downloads:814)
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In this paper, an improved impulsive lag synchronization scheme for different chaotic systems with parametric uncertainties is proposed. Based on the new definition of synchronization with error bound and a novel impulsive control scheme (the so-called dual-stage impulsive control), some new and less conservative sufficient conditions are established to guarantee that the error dynamics can converge to a predetermined level, which is more reasonable and rigorous than the existing results. In particular, some simpler and more convenient conditions are derived by taking the same impulsive distances and control gains. Finally, some numerical simulations for the Lorenz system and the Chen system are given to demonstrate the effectiveness and feasibility of the proposed method.

Impulsive control for Takagi--Sugeno fuzzy model with time-delay and its application to chaotic system

Peng Shi-Guo, Yu Si-Min
Chin. Phys. B, 2009, 18 (9): 3758-3765 doi: 10.1088/1674-1056/18/9/024
Full Text: [PDF 853 KB] (Downloads:921)
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A control approach where the fuzzy logic methodology is combined with impulsive control is developed for controlling some time-delay chaotic systems in this paper. We first introduce impulses into each subsystem with delay of the Takagi--Sugeno (TS) fuzzy IF--THEN rules and then present a unified TS impulsive fuzzy model with delay for chaos control. Based on the new model, a simple and unified set of conditions for controlling chaotic systems is derived by the Lyapunov--Razumikhin method, and a design procedure for estimating bounds on control matrices is also given. Several numerical examples are presented to illustrate the effectiveness of this method.

Synchronization and parameter identification of one class of realistic chaotic circuit

Wang Chun-Ni, Ma Jun, Chu Run-Tong, Li Shi-Rong
Chin. Phys. B, 2009, 18 (9): 3766-3771 doi: 10.1088/1674-1056/18/9/025
Full Text: [PDF 208 KB] (Downloads:836)
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In this paper, the synchronization and the parameter identification of the chaotic Pikovsky--Rabinovich (PR) circuits are investigated. The linear error of the second corresponding variables is used to change the driven chaotic PR circuit, and the complete synchronization of the two identical chaotic PR circuits is realized with feedback intensity k increasing to a certain threshold. The Lyapunov exponents of the chaotic PR circuits are calculated by using different feedback intensities and our results are confirmed. The case where the two chaotic PR circuits are not identical is also investigated. A general positive Lyapunov function V, which consists of all the errors of the corresponding variables and parameters and changeable gain coefficient, is constructed by using the Lyapunov stability theory to study the parameter identification and complete synchronization of two non-identical chaotic circuits. The controllers and the parameter observers could be obtained analytically only by simplifying the criterion dV/dt<0 (differential coefficient of Lyapunov function V with respect to time is negative). It is confirmed that the two non-identical chaotic PR circuits could still reach complete synchronization and all the unknown parameters in the drive system are estimated exactly within a short transient period.

Bifurcation and stability of an improved time-delayed fluid flow model in internet congestion control

Liu Yu-Liang, Zhu Jie, Luo Xiao-Shu
Chin. Phys. B, 2009, 18 (9): 3772-3776 doi: 10.1088/1674-1056/18/9/026
Full Text: [PDF 197 KB] (Downloads:612)
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Based on the fluid flow time-delayed model proposed by Misra et al in internet congestion control, one modified time-delayed model is presented, where the influence of the communication delay on the router queue length is investigated in detail. The main advantage of the new model is that its stability domain is larger even without an extra controller. By linear stability analysis and numerical simulation, the effectiveness and feasibility of the novel model in internet congestion control are verified.

Collective coordination of multi-agent systems guided by multiple leaders

Hu Jiang-Ping, Yuan Hai-Wen
Chin. Phys. B, 2009, 18 (9): 3777-3782 doi: 10.1088/1674-1056/18/9/027
Full Text: [PDF 365 KB] (Downloads:975)
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A neighbour-based coordination scheme is proposed for a multi-agent system with multiple leaders. Under assumptions of the connectivity of the interconnection topology and a simple first-order dynamics model for each mobile agent, the results show that all the agents will flock to the polytope region formed by the leaders.

A self-organizing shortest path finding strategy on complex networks

Shen Yi, Pei Wen-Jiang, Wang Kai, Wang Shao-Ping
Chin. Phys. B, 2009, 18 (9): 3783-3789 doi: 10.1088/1674-1056/18/9/028
Full Text: [PDF 514 KB] (Downloads:1120)
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The shortcomings of traditional methods to find the shortest path are revealed, and a strategy of finding the self-organizing shortest path based on thermal flux diffusion on complex networks is presented. In our method, the shortest paths between the source node and the other nodes are found to be self-organized by comparing node temperatures. The computation complexity of the method scales linearly with the number of edges on underlying networks. The effects of the method on several networks, including a regular network proposed by Ravasz and Barabási which is called the RB network, a real network, a random network proposed by Ravasz and Barabási which is called the ER network and a scale-free network, are also demonstrated. Analytic and simulation results show that the method has a higher accuracy and lower computational complexity than the conventional methods.

Geometrical description of denormalized thermodynamic manifold

Wu Li-Ping, Sun Hua-Fei, Cao Li-Mei
Chin. Phys. B, 2009, 18 (9): 3790-3794 doi: 10.1088/1674-1056/18/9/029
Full Text: [PDF 156 KB] (Downloads:665)
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In view of differential geometry, the state space of thermodynamic parameters is investigated. Here the geometrical structures of the denormalized thermodynamic manifold are considered. The relation of their geometrical metrics is obtained. Moreover an example is used to illustrate our conclusions.

Analysis of equation of state and thermodynamic functions for trans-decahydronaphthalene up to 200~MPa and 446~K

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Chin. Phys. B, 2009, 18 (9): 3795-3801 doi: 10.1088/1674-1056/18/9/030
Full Text: [PDF 222 KB] (Downloads:553)
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This paper develops a modified Tait equation of state (EOS) for trans-decahydronaphthalene with four parameters A, B, V0 and P0 being treated as linear functions of temperature. The coefficients contained in these functions are determined through fitting the experimental compression data in the literature between 293~K and 446~K and at pressures from 10 to 200~MPa. Expressions for the thermal expansivity, isothermal compressibility and thermodynamic quantities are deduced and the numerical results are analytically derived. The numerical results show that the precision of the modified Tait EOS developed in this paper is superior to the EOS in the literature.
NUCLEAR PHYSICS

α preformation and penetration probability for heavy nuclei

Zhang Gao-Long, Le Xiao-Yun
Chin. Phys. B, 2009, 18 (9): 3810-3814 doi: 10.1088/1674-1056/18/9/032
Full Text: [PDF 284 KB] (Downloads:649)
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The α preformation factor and penetration probability have been analyzed for even--even nuclei of Po, Rn, Ra using experimental released energies and α decay half-lives in the frame of the double folding model. It is shown that N=126 is a neutron magic number from α preformation and shell effects play an important role in α preformation. The closer the nucleon number is to the magic number, the more difficult α formation in the parent nucleus is. The preformation factor can supply information on the nuclear structure and the penetration probability mainly determines α decay half-life.

Calculations of radioactivity and afterheat in the components of the CSNS target station

Yu Quan-Zhi, Liang Tian-Jiao, Yin Wen, Yan Qi-Wei, Jia Xue-Jun, Wang Fang-Wei
Chin. Phys. B, 2009, 18 (9): 3815-3818 doi: 10.1088/1674-1056/18/9/033
Full Text: [PDF 755 KB] (Downloads:785)
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This paper shows the calculations of radioactivity and afterheat in the components of the China Spallation Neutron Source (CSNS) target station, with the Monte Carlo codes LAHET, MCNP4C and the multigroup code CINDER'90. These calculations provide essential data for the detailed design and maintenance of the CSNS target station.
CLASSICAL AREAS OF PHENOMENOLOGY

Monte Carlo simulation of electron beam air plasma characteristics

Deng Yong-Feng, Han Xian-Wei, Tan Chang
Chin. Phys. B, 2009, 18 (9): 3870-3876 doi: 10.1088/1674-1056/18/9/042
Full Text: [PDF 657 KB] (Downloads:958)
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A high-energy electron beam generator is used to generate a plasma in atmosphere. Based on a Monte Carlo toolkit named GEANT4, a model including complete physics processes is established to simulate the passage of the electron beam in air. Based on the model, the characteristics of the electron beam air plasma are calculated. The energy distribution of beam electrons (BEs) indicates that high-energy electrons almost reside in the centre region of the beam, but low-energy electrons always live in the fringe area. The energy deposition is calculated in two cases, i.e., with and without secondary electrons (SEs). Analysis indicates that the energy deposition of SEs accounts for a large part of the total energy deposition. The results of the energy spectrum show that the electrons in the inlet layer of the low-pressure chamber (LPC) are monoenergetic, but the energy spectrum of the electrons in the outlet layer is not pure. The SEs are largely generated at the outlet of the LPC. Moreover, both the energy distribution of BEs and the magnitude of the density of SEs are closely related to the pressure of LPC. Thus, a conclusion is drawn that a low magnitude of LPC pressure is helpful for reducing the energy loss in the LPC and also useful for greatly increasing the secondary electron density in dense air.

Terahertz radiation from interaction between an electron beam and a planar surface plasmon structure

Hu Min, Zhang Ya-Xin, Yan Yang, Zhong Ren-Bin, Liu Sheng-Gang
Chin. Phys. B, 2009, 18 (9): 3877-3882 doi: 10.1088/1674-1056/18/9/043
Full Text: [PDF 1696 KB] (Downloads:1064)
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The possibility of an electron beam exciting surface plasmons in conducting metal is discussed in this paper. A planar perfect-structure with subwavelength holes is proposed. The phenomenon that mimicking surface plasmon waves can be excited and amplified by an electron beam is proved theoretically and numerically. The mechanism of transmission through a subwavelength hole array is exploited to enhance the interaction between the electron beam and the mimicking surface plasmons.

Can two partially coherent cosh--Gaussian beams generate far fields with the same spectral degree of coherence?

Lü Su-Ye, Lü Bai-Da
Chin. Phys. B, 2009, 18 (9): 3883-3889 doi: 10.1088/1674-1056/18/9/044
Full Text: [PDF 921 KB] (Downloads:727)
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Taking partially coherent cosh--Gaussian (ChG) beams as an example of more general partially coherent beams, we have studied the spectral degree of coherence of partially coherent ChG beams in the far field. It is shown that, unlike Gaussian Schell-model (GSM) beams, in the strict sense there do not exist two partially coherent ChG beams which can generate far fields with the same spectral degree of coherence. However, under certain conditions it is possible to find two partially coherent ChG beams with the same spectral degree of coherence in the far field.

Scheme for implementing frequency up-conversion between two collective atomic modes

Lin Li-Hua
Chin. Phys. B, 2009, 18 (9): 3890-3892 doi: 10.1088/1674-1056/18/9/045
Full Text: [PDF 140 KB] (Downloads:465)
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This paper presents a scheme for realizing the frequency up-conversion between two collective atomic modes. In the scheme two atomic samples are coupled to a cavity mode. Under the large detuning condition, the two collective atomic modes are coupled via the virtual excitation of the cavity mode and the effective Hamiltonian corresponds to the frequency up-conversion. In the scheme the cavity mode is only virtually excited and thus the process is insensitive to cavity decay.

A quasi-discrete Hankel transform for nonlinear beam propagation

You Kai-Ming, Wen Shuang-Chun, Chen Lie-Zun, Wang You-Wen, Hu Yong-Hua
Chin. Phys. B, 2009, 18 (9): 3893-3899 doi: 10.1088/1674-1056/18/9/046
Full Text: [PDF 218 KB] (Downloads:1057)
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We propose and implement a quasi-discrete Hankel transform algorithm based on Dini series expansion (DQDHT) in this paper. By making use of the property that the zero-order Bessel function derivative J' 0(0)=0, the DQDHT can be used to calculate the values on the symmetry axis directly. In addition, except for the truncated treatment of the input function, no other approximation is made, thus the DQDHT satisfies the discrete Parseval theorem for energy conservation, implying that it has a high numerical accuracy. Further, we have performed several numerical tests. The test results show that the DQDHT has a very high numerical accuracy and keeps energy conservation even after thousands of times of repeating the transform either in a spatial domain or in a frequency domain. Finally, as an example, we have applied the DQDHT to the nonlinear propagation of a Gaussian beam through a Kerr medium system with cylindrical symmetry. The calculated results are found to be in excellent agreement with those based on the conventional 2D-FFT algorithm, while the simulation based on the proposed DQDHT takes much less computing time.

High-speed 2×2 silicon-based electro-optic switch with nanosecond switch time

Xu Xue-Jun, Chen Shao-Wu, Xu Hai-Hua, Sun Yang, Yu Yu-De, Yu Jin-Zhong, Wang Qi-Ming
Chin. Phys. B, 2009, 18 (9): 3900-3904 doi: 10.1088/1674-1056/18/9/047
Full Text: [PDF 1451 KB] (Downloads:931)
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A 2× 2 electro-optic switch is experimentally demonstrated using the optical structure of a Mach--Zehnder interferometer (MZI) based on a submicron rib waveguide and the electrical structure of a PIN diode on silicon-on-insulator (SOI). The switch behaviour is achieved through the plasma dispersion effect of silicon. The device has a modulation arm of 1~mm in length and cross-section of 400~nm× 340~nm. The measurement results show that the switch has a VπLπ figure of merit of 0.145~V\cdot cm and the extinction ratios of two output ports and cross talk are 40~dB, 28~dB and -28~dB, respectively. A 3~dB modulation bandwidth of 90~MHz and a switch time of 6.8~ns for the rise edge and 2.7~ns for the fall edge are also demonstrated.

Influence of applied electric field on the absorption coefficient and subband distances in asymmetrical AlN/GaN coupled double quantum wells

Cen Long-Bin, Shen Bo, Qin Zhi-Xin, Zhang Guo-Yi
Chin. Phys. B, 2009, 18 (9): 3905-3908 doi: 10.1088/1674-1056/18/9/048
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The influence of applied electric fields on the absorption coefficient and subband distances in asymmetrical AlN/GaN coupled double quantum wells (CDQWs) has been investigated by solving Schr?dinger and Poisson equations self-consistently. It is found that the absorption coefficient of the intersubband transition (ISBT) between the ground state and the third excited state (1odd-2even) can be equal to zero when the electric fields are applied in asymmetrical AlN/GaN CDQWs, which is related to applied electric fields induced symmetry recovery of these states. Meanwhile, the energy distances between 1odd-2even and 1even-2even subbands have different relationships from each other with the increase of applied electric fields due to the different polarization-induced potential drops between the left and the right wells. The results indicate that an electrical-optical modulator operated within the opto-communication wavelength range can be realized in spite of the strong polarization-induced electric fields in asymmetrical AlN/GaN CDQWs.

The nonlinear propagation of acoustic waves in a viscoelastic medium containing cylindrical micropores

Feng Yu-Lin, Liu Xiao-Zhou, Liu Jie-Hui, Ma Li
Chin. Phys. B, 2009, 18 (9): 3909-3917 doi: 10.1088/1674-1056/18/9/049
Full Text: [PDF 278 KB] (Downloads:676)
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Based on an equivalent medium approach, this paper presents a model describing the nonlinear propagation of acoustic waves in a viscoelastic medium containing cylindrical micropores. The influences of pores' nonlinear oscillations on sound attenuation, sound dispersion and an equivalent acoustic nonlinearity parameter are discussed. The calculated results show that the attenuation increases with an increasing volume fraction of micropores. The peak of sound velocity and attenuation occurs at the resonant frequency of the micropores while the peak of the equivalent acoustic nonlinearity parameter occurs at the half of the resonant frequency of the micropores. Furthermore, multiple scattering has been taken into account, which leads to a modification to the effective wave number in the equivalent medium approach. We find that these linear and nonlinear acoustic parameters need to be corrected when the volume fraction of micropores is larger than 0.1%.
ATOMIC AND MOLECULAR PHYSICS

Doubly excited 2s2p 1,3P1 resonances in photoionization of helium

Wan Jian-Jie, Dong Chen-Zhong
Chin. Phys. B, 2009, 18 (9): 3819-3827 doi: 10.1088/1674-1056/18/9/034
Full Text: [PDF 307 KB] (Downloads:745)
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The multi-configuration Dirac--Fock (MCDF) method is implemented to study doubly excited 2s2p 1,3P1 resonances of the helium atom and the interference between photoionization and photoexcitation autoionization processes. In order to reproduce the total photoionization sprectra, the excited energies from the ground 1s2 \1S0 state to the doubly excited 2s2p 1,3P1 states and the relevant Auger decay rates and widths are calculated in detail. Furthermore, the interference profile determined by the so-called Fano parameters q and ρ 2 is also reproduced. Good agreement is found between the present results and other available theoretical and experimental results. This indeed shows a promising way to investigate the Fano resonances in photoionization of atoms within the MCDF scheme, although there are some discrepancies in the present calculations of the 2s2p 3P1 state.

Radiative lifetime measurements of odd-parity high-excited levels of Sn I by time-resolved laser spectroscopy

Xu Jia-Xin, Feng Yan-Yan, Sun Gui-Juan, Dai Zhen-Wen
Chin. Phys. B, 2009, 18 (9): 3828-3832 doi: 10.1088/1674-1056/18/9/035
Full Text: [PDF 271 KB] (Downloads:747)
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Natural radiative lifetimes of five higher-lying odd-parity levels 5p7s 3P1o, 5p5d 1P1o, 5p6d 3F2o, 3D1o and 3F3o in neutral tin are measured by the time-resolved laser-induced fluorescence (TR-LIF) technique and the atomic beam method. All these lifetimes are not longer than 100 ns and they are found to be shorter than the lifetimes of even-parity levels in the same energy region. The results reported in this paper provide important transition parameters for highly-excited atomic Sn, which may be useful for theoretically calculating excited heavy atoms.

Theoretical calculation of photoionization cross sections of B-like ions: N2+, O3+ and F4+

Wang Guo-Li, Zhou Xiao-Xin
Chin. Phys. B, 2009, 18 (9): 3833-3838 doi: 10.1088/1674-1056/18/9/036
Full Text: [PDF 236 KB] (Downloads:603)
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There can be found some notable discrepancies with regard to the resonance structures when R-matrix calculations from the Opacity Project and other sources are compared with recent absolute experimental measurements of Bizau et al [Astron. Astrophts. 439 387 (2005)] for B-like ions N2+, O3+ and F4+. We performed close-coupling calculations based on the R-matrix formalism for the photoionizations of ions mentioned above both for the ground states and first excited states in the near threshold regions. The present results are compared with experimental ones given by Bizau et al and earlier theoretical ones. Excellent agreement is obtained between our theoretical results and the experimental photoionization cross sections. The present calculations show a significant improvement over the previous theoretical results.

Study of a low power dissipation, miniature laser-pumped rubidium frequency standard Hot!

Liu Guo-Bin, Zhao Feng, Gu Si-Hong
Chin. Phys. B, 2009, 18 (9): 3839-3843 doi: 10.1088/1674-1056/18/9/037
Full Text: [PDF 331 KB] (Downloads:622)
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This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping 87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broadened spectral line, it records a 5× 10-11τ-1/2 (τ <500~s) frequency stability with a table-top system in a primary experiment. The study reveals that the evaluated scheme is at the level of 2.7 watts power consumption, 90~cm3 volume and 10-12τ -1/2 short-term frequency stability.

Dynamical instability and adiabatic evolution of the atom--homonuclear--trimer dark state in a condensate system

Meng Shao-Ying, Wu Wei, Liu Bin, Ye Di-Fa, Fu Li-Bin
Chin. Phys. B, 2009, 18 (9): 3844-3849 doi: 10.1088/1674-1056/18/9/038
Full Text: [PDF 397 KB] (Downloads:910)
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This paper investigates the dynamical instability and adiabatic evolution of the atom--homonuclear--trimer dark state of a condensate system in a stimulated Raman adiabatic passage aided by Feshbach resonance. It obtains analytically the regions for the appearance of dynamical instability caused by the interparticle interactions. Moreover, the adiabatic property of the dark state is also studied in terms of a newly defined adiabatic fidelity. It shows that the nonlinear collisions have a negative effect on the adiabaticity of the dark state and hence reduce the conversion efficiency.

Role of highest occupied molecular orbitals in molecular field-free alignment by a femtosecond pulse

Chen De-Ying, Wang Yu-Quan, Xia Yuan-Qin, Fan Rong-Wei, Zhang Sheng
Chin. Phys. B, 2009, 18 (9): 3850-3855 doi: 10.1088/1674-1056/18/9/039
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This paper studies the molecular rotational excitation and field-free spatial alignment in a nonresonant intense laser field numerically and analytically by using the time-dependent Schr?dinger equation. The broad rotational wave packets excited by the femtosecond pulse are defined in conjugate angle space, and their coefficients are obtained by solving a set of coupled linear equations. Both single molecule orientation angles and an ensemble of O2 and CO molecule angular distributions are calculated in detail. The numerical results show that, for single molecule highest occupied molecular orbital (HOMO) symmetry σ tends to have a molecular orientation along the laser polarization direction and the permanent dipole moment diminishes the mean of the orientation angles; for an ensemble of molecules, angular distributions provide more complex and additional information at times where there are no revivals in the single molecule plot. In particular, at the revival peak instant, with the increase of temperature of the molecular ensemble, the anisotropic angular distributions with respect to the laser polarization direction of the π g orbital gradually transform to the symmetrical distributions regarding the laser polarization vector and for two HOMO configurations angular distributions of all directions are confined within a smaller angle when the temperature of the molecular ensemble is higher.

Investigations on molecular constants of the CD(X2П) radical and elastic collisions between ground-state C and D atoms at low temperatures

Shi De-Heng, Zhang Jin-Ping, Sun Jin-Feng, Liu Yu-Fang, Zhu Zun-Lüe
Chin. Phys. B, 2009, 18 (9): 3856-3864 doi: 10.1088/1674-1056/18/9/040
Full Text: [PDF 234 KB] (Downloads:578)
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The potential energy curve of the CD(X2П ) radical is obtained using the coupled-cluster singles-doubles-approximate-triples [CCSD(T)] theory in combination with the correlation-consistent quintuple basis set augmented with diffuse functions, aug-cc-pV5Z. The potential energy curve is fitted to the Murrell--Sorbie function, which is used to determine the spectroscopic parameters. The obtained D0, De, Re, ωe, ωeχ e, αe and Be values are 3.4971~eV, 3.6261~eV, 0.11197~nm, 2097.661~cm-1, 34.6963~cm-1, 0.2083~cm-1 and 7.7962~cm-1, respectively, which conform almost perfectly to the available measurements. With the potential obtained at the UCCSD(T)/aug-cc-pV5Z level of theory, a total of 24 vibrational states have been predicted for the first time when J = 0 by solving the radial Schr?dinger equation of nuclear motion. The complete vibrational levels, the classical turning points, the inertial rotation constants and centrifugal distortion constants are reproduced from the CD(X2П) potential when J = 0, and are in excellent agreement with the available measurements. The total and the various partial-wave cross sections are calculated for the elastic collisions between the ground-state C and D atoms at energies from 1.0× 10-11 to 1.0× 10-4a.u. when the two atoms approach each other along the CD(X2П) potential energy curve. Only one shape resonance is found in the total elastic cross sections, and the resonant energy is 8.36× 10-6~a.u. The results show that the shape of the total elastic cross section is mainly dominated by the s partial wave at very low temperatures. Because of the weak shape resonances coming from higher partial waves, most of them are passed into oblivion by the strong total elastic cross sections.

One-colour resonant two-photon ionization spectrum of the 1-fluoronaphthalene dimer and ab initio calculation

Liu Ye-Chao, Zhang Shu-Dong, Zhang Ming-Xia, Sun Miao, Kong Xiang-He
Chin. Phys. B, 2009, 18 (9): 3865-3869 doi: 10.1088/1674-1056/18/9/041
Full Text: [PDF 475 KB] (Downloads:656)
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The one-colour resonant two-photon ionization (R2PI) spectrum of the 1-fluoronaphthalene (1FN) dimer has been studied in the wavelength range of 304 to 322~nm by using a supersonic molecular beam and time-of-flight mass spectrometry. Compared with the original band 000 (at 313.8~nm) of the S1 ≤ftarrow S0 transition of the 1FN monomer, a red-shifted band was observed in the 1FN dimer spectrum at about 315~nm with a relatively large linewidth, nearly 2~nm. Based on the consideration of inductive effect and ab initio calculations, this red-shifted band is assigned to the first electronic excited transition of the 1FN dimer. A possible geometric structure of the 1FN dimer is also obtained with calculations that the two 1FN molecules are combined through two hydrogen bonds which are formed between the hydrogen atom of a molecule and the fluorine atom of a neighbouring molecule. A time-dependent calculation was also carried out and the results are consistent with the experimental data.
CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

Hydrothermal synthesis and dielectric properties of chrysanthemum-like ZnO particles

Yan Jun-Feng, Zhang Zhi-Yong, You Tian-Gui, Zhao Wu, Yun Jiang-Ni
Chin. Phys. B, 2009, 18 (9): 4019-4024 doi: 10.1088/1674-1056/18/9/067
Full Text: [PDF 3637 KB] (Downloads:679)
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By orthogonal design theory, technological parameters of chrysanthemum-like ZnO particles prepared in a hydrothermal process are optimized. This paper reports a set of technological parameters for growing chrysanthemum-like ZnO particles on a large scale. It investigates the morphologies and crystalline structures of the as-synthesized three-dimensional ZnO particles with a scanning electron microscope, x-ray diffractometer and transmission electron microscope, and the possible growth mechanism on the three-dimensional ZnO particles. The experimental results indicate that the values of ε', ε '' and \tan δe gradually increase in the X band with the improvement of the developmental level of chrysanthemum-like ZnO particles, implying that the electromagnetic wave absorbing property depends on the morphologies of three-dimensional ZnO particles.

Role of defects in magnetic properties of Fe-doped SnO2 films fabricated by the Sol--Gel method

Zhou Xue-Yun, Ge Shi-Hui, Han Xiu-Feng, Zuo Ya-Lu, Xiao Yu-Hua, Wen Zhen-Chao, Zhang Li, Li Ming-Jie
Chin. Phys. B, 2009, 18 (9): 4025-4029 doi: 10.1088/1674-1056/18/9/068
Full Text: [PDF 197 KB] (Downloads:805)
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This paper obtains the room temperature ferromagnetism in Sn1-xFexO2 films fabricated by the Sol--Gel method. X-ray diffraction results show that Fe doping inhibits the growth of SnO2 and Fe3+ ions occupy the Sn sites. The measurement of resistance excludes the free carrier inducing ferromagnetism. Moreover, the temperature dependence of magnetization has been better fitted by the Curie--Weiss law and bound magnetic polaron (BMP) theory. An enhancement of ferromagnetism is achieved by annealing the samples with x=7.1% in H2, and a decrease of oxygen flow rate. All these results prove that the BMP model depending on defects can explain ferromagnetism in diluted magnetic oxides.

Upconversion emission enhancement of TiO2 coated lanthanide-doped Y2O3 nanoparticles

Lü Qiang, Zhao Lian-Cheng, Guo Feng-Yun, Li Mei-Cheng
Chin. Phys. B, 2009, 18 (9): 4030-4036 doi: 10.1088/1674-1056/18/9/069
Full Text: [PDF 1700 KB] (Downloads:676)
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To investigate the upconversion emission, this paper synthesizes Tm3+ and Yb3+ codoped Y2O3 nanoparticles, and then coats them with TiO2 shells for different coating times. The spectral results of TiO2 coated nanoparticles indicate that upconversion emission intensities have respectively been enhanced 3.2, 5.4, and 2.2 times for coating times of 30, 60 and 90 min at an excitation power density of 3.21× 102 ~W.cm2, in comparison with the emission intensity of non-coated nanoparticles. Therefore it can be concluded that the intense upconversion emission of Y2O3:Tm3+, Yb3+ nanoparticles can be achieved by coating the particle surfaces with a shell of specific thickness.

Analysis of the influence of occupation rate of public transit vehicles on mixing traffic flow in a two-lane system

Qian Yong-Sheng, Shi Pei-Ji, Zeng Qiong, Ma Chang-Xi, Lin Fang, Sun Peng, Yin Xiao-Ting
Chin. Phys. B, 2009, 18 (9): 4037-4041 doi: 10.1088/1674-1056/18/9/070
Full Text: [PDF 794 KB] (Downloads:1124)
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Based on the existing classical cellular automaton model of traffic flow, a cellular automaton traffic model with different-maximum-speed vehicles mixed on a single lane is proposed, in which public transit and harbour-shaped bus stops are taken into consideration. Parameters such as length of cellular automaton, operation speed and random slow mechanism are re-demarcated. A harbour-shaped bus stop is set up and the vehicle changing lane regulation is changed. Through computer simulation, the influence of occupation rate of public transit vehicles on mixed traffic flow and traffic capacity is analysed. The results show that a public transport system can ease urban traffic congestion but creates new jams at the same time, and that the influence of occupation rate of public transit vehicles on traffic capacity is considerable. To develop urban traffic, attention should be paid to the occupation rate of public transit vehicles and traffic development in a haphazard way should be strictly avoided.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Analysis of the decay B0→χclπ0 with light-cone QCD sum rules

Wang Zhi-Gang
Chin. Phys. B, 2009, 18 (9): 3802-3809 doi: 10.1088/1674-1056/18/9/031
Full Text: [PDF 209 KB] (Downloads:485)
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In this article, we calculate the contribution from the nonfactorizable soft hadronic matrix element to the decay B0\rightarrow χclπ0 with the light-cone quantum chromo-dynamic (QCD) sum rules. The numerical results show that its contribution is rather large and should not be neglected. The total amplitudes lead to a branching fraction which is in agreement with the experimental data marginally.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

Direct measurement of the surface dynamics of supercooled liquid-glycerol by optical scanning a film

Zhang Fang, Zhang Guo-Feng, Dong Shuang-Li, Sun Jian-Hu, Chen Rui-Yun, Xiao Lian-Tuan, Jia Suo-Tang
Chin. Phys. B, 2009, 18 (9): 3918-3921 doi: 10.1088/1674-1056/18/9/050
Full Text: [PDF 1439 KB] (Downloads:540)
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The surface dynamics of supercooled liquid-glycerol is studied by scanning the thickness of the glycerol film with single photon detection. Measurements are performed at room temperature well above the glycerol's glass transition temperature. It is shown that the surface dynamics of the glycerol film is very sensitive to the temperature. The linear relationship between the thickness of the film and the viscosity predicted by the Vogel--Fulcher--Tammann--Hesse (VFTH) law is also presented experimentally.

Synthesis and characterization of highly-ordered barium-strontium titanate nanotube arrays fabricated by sol—gel method

Chen Yu, Chen Wei, Guo Feng, Li Mei-Ya, Liu Wei, Zhao Xing-Zhong
Chin. Phys. B, 2009, 18 (9): 3922-3927 doi: 10.1088/1674-1056/18/9/051
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Highly uniformed barium-strontium titanate nanotube arrays were fabricated using a porous anodic aluminum oxide template from a barium-strontium titanate sol--gel solution. Electron microscope results showed that nanotubes with uniform length and diameter were obtained. The diameters and lengths of these nanotubes were dependent on the pore diameter and the thickness of the applied anodic aluminum oxide template. High resolution transmission electron microscopy and the selected-area electron diffraction pattern investigations demonstrated the perovskite structure and the polycrystalline of the fabricated barium-strontium titanate nanotubes. The characterization of the electrical and dielectric properties had also been made. Compared to thin film material, the intrinsic leakage current density is almost the same. Besides, at 30~℃, the dielectric constant and dielectric loss of the fabricated nanotube is 80 and 0.027 at 1~MHz respectively.

Effect of alloying Re and Ru in the edge-dislocation core of the Ni/Ni3Al interface

Wang Cong, Wang Chong-Yu
Chin. Phys. B, 2009, 18 (9): 3928-3933 doi: 10.1088/1674-1056/18/9/052
Full Text: [PDF 828 KB] (Downloads:775)
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Investigations of alloying Re and Ru in the [110](001) dislocation core of the Ni/Ni3Al interface were conducted within the framework of density functional theory. The energetic calculations show that both elements can stabilize the [110](001) dislocation core. In the dislocation core region, Re and Ru prefer to substitute for Ni on the site in the γ -phase. Re is easier to segregate into the dislocation core region as compared with Ru; it especially prefers to substitute for Ni on the γ -(Ni)1 site.

Elastic stability and electronic structure of low energy tetragonal and monoclinic PdN2 and PtN2

Zhao Wen-Jie, Wang Yuan-Xu
Chin. Phys. B, 2009, 18 (9): 3934-3939 doi: 10.1088/1674-1056/18/9/053
Full Text: [PDF 1563 KB] (Downloads:841)
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This paper studies the elastic and electronic structure properties of two new low-energy structures of PdN2 and PtN2 by first-principles calculations. It finds that tetragonal and monoclinic structures are more stable than a pyrite one. The always positive eigenvalues of the elastic constant matrix confirm that both the tetragonal and monoclinic structures are elastically stable. The origin of the low bulk modulus of the two structures is discussed. The results of the calculated density of states show that both of the two low-energy structures are metallic.

Localized self-trapping in the two-dimensional discrete molecular lattice with the interaction between Frenkel excitons and phonons

Xu Quan, Tian Qiang
Chin. Phys. B, 2009, 18 (9): 3940-3951 doi: 10.1088/1674-1056/18/9/054
Full Text: [PDF 1247 KB] (Downloads:555)
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We investigate the interactions of lattice phonons with Frenkel exciton, which has a small radius in a two-dimensional discrete molecular lattice, by the virtue of the quasi-discreteness approximation and the method of multiple-scale, and obtain that the self-trapping can also appear in the two-dimensional discrete molecular lattice with harmonic and nonlinear potential. The excitons' effect on the molecular lattice does not distort it but only causes it to localize which enables it to react again through phonon coupling to trap the energy and prevent its dispersion.

Experimental determination of interfacial energies for Ag2Al solid solution in the CuAl2--Ag2Al system

Ocak Y, Akbulut S, Ke?lio?lu K, Mara?li N, Cad1rl1 E, Kaya H
Chin. Phys. B, 2009, 18 (9): 3952-3959 doi: 10.1088/1674-1056/18/9/055
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The equilibrated grain boundary groove shapes of solid solution Ag2Al in equilibrium with an Al--Cu--Ag liquid were observed from a quenched sample with a radial heat flow apparatus. The Gibbs--Thomson coefficient, solid--liquid interfacial energy and grain boundary energy of the solid solution Ag2Al have been determined from the observed grain boundary groove shapes. The thermal conductivity of the solid phase and the thermal conductivity ratio of the liquid phase to solid phase for Ag2Al--28.3 at the %CuAl2 alloy at the melting temperature have also been measured with a radial heat flow apparatus and Bridgman type growth apparatus, separately.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Unified nonequilibrium dynamical theory for exchange bias and training effects

Zhang Kai-Cheng, Liu Bang-Gui
Chin. Phys. B, 2009, 18 (9): 3960-3965 doi: 10.1088/1674-1056/18/9/056
Full Text: [PDF 469 KB] (Downloads:591)
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We have investigated the exchange bias and training effect in the ferromagnetic/antiferromagnetic (FM/AF) heterostructures using a unified Monte Carlo dynamical approach. The magnetization of the uncompensated AF layer is still open after the first field cycling is finished. Our simulated results show obvious shift of hysteresis loops (exchange bias) and cycling dependence of exchange bias (training effect) when the temperature is below 45~K. The exchange bias field decreases with decreasing cooling rate or increasing temperature and the number of the field cycling. Essentially, these two effects can be explained on the basis of the microscopical coexistence of both reversible and irreversible moment reversals of the AF domains. Our simulations are useful to understand the real magnetization dynamics of such magnetic heterostructures.

Simulation of grain boundary effect on characteristics of ZnO thin film transistor by considering the location and orientation of grain boundary

Zhou Yu-Ming, He Yi-Gang, Lu Ai-Xia, Wan Qing
Chin. Phys. B, 2009, 18 (9): 3966-3969 doi: 10.1088/1674-1056/18/9/057
Full Text: [PDF 177 KB] (Downloads:1542)
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The grain boundaries (GBs) have a strong effect on the electric properties of ZnO thin film transistors (TFTs). A novel grain boundary model was developed to analyse the effect. The model was characterized with different angles between the orientation of the grain boundary and the channel direction. The potential barriers formed by the grain boundaries increase with the increase of the grain boundary angle, so the degradation of the transistor characteristics increases. When a grain boundary is close to the drain edge, the potential barrier height reduces, so the electric properties were improved.

Local electric field and configuration of CO molecules adsorbed on a nanostructured surface with nanocones

You Rong-Yi, Huang Xiao-Jing
Chin. Phys. B, 2009, 18 (9): 3970-3974 doi: 10.1088/1674-1056/18/9/058
Full Text: [PDF 278 KB] (Downloads:733)
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Based on the nanostructured surface model that the (platinum, Pt) nanocones grow out symmetrically from a plane substrate, the local electric field near the conical nanoparticle surface is computed and discussed. On the basis of these results, the adsorbed CO molecules are modelled as dipoles, and three kinds of interactions, i.e. interactions between dipoles and local electric field, between dipoles and dipoles, as well as between dipoles and nanostructured substrate, are taken into account. The spatial configuration of CO molecules adsorbed on the nanocone surface is then given by Monte-Carlo simulation. Our results show that the CO molecules adsorbed on the nanocone surface cause local agglomeration under the action of an external electric field, and this agglomeration becomes more compact with decreasing conical angle, which results in a stronger interaction among molecules. These results serve as a basis for explaining abnormal phenomena such as the abnormal infrared effect (AIRE), which was found when CO molecules were adsorbed on the nanostructured transition-metal surface.

Intra-acceptor hole relaxation in Be δ-doped GaAs/AlAs multiple quantum wells

Li Su-Mei, Zheng Wei-Min, Song Ying-Xin, Liu Jing, Chu Ning-Ning
Chin. Phys. B, 2009, 18 (9): 3975-3979 doi: 10.1088/1674-1056/18/9/059
Full Text: [PDF 551 KB] (Downloads:812)
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This paper studies the dynamics of intra-acceptor hole relaxation in Be δ -doped GaAs/AlAs multiple quantum wells (MQW) with doping at the centre by time-resolved pump-probe spectroscopy using a picosecond free electron laser for infrared experiments. Low temperature far-infrared absorption measurements clearly show three principal absorption lines due to transitions of the Be acceptor from the ground state to the first three odd-parity excited states respectively. The pump-probe experiments are performed at different temperatures and different pump pulse wavelengths. The hole relaxation time from 2p excited state to 1s ground state in MQW is found to be much shorter than that in bulk GaAs, and shown to be independent of temperature but strongly dependent on wavelength. The zone-folded acoustic phonon emission and slower decay of the wavefunctions of impurity states are suggested to account for the reduction of the 2p excited state lifetime in MQW. The wavelength dependence of the 2p lifetime is attributed to the diffusion of the Be atom δ -layer in quantum wells.

Determination of the relative permittivity of the AlGaN barrier layer in strained AlGaN/GaN heterostructures

Zhao Jian-Zhi, Lin Zhao-Jun, Timothy D Corrigan, Zhang Yu, Lü Yuan-Jie, Lu Wu, Wang Zhan-Guo, Chen Hong
Chin. Phys. B, 2009, 18 (9): 3980-3984 doi: 10.1088/1674-1056/18/9/060
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Using the measured capacitance--voltage curves and the photocurrent spectrum obtained from the Ni Schottky contact on a strained Al_0.3Ga_0.7N/GaN heterostructure, the value of the relative permittivity of the AlGaN barrier layer was analysed and calculated by self-consistently solving Schr?dinger's and Poisson's equations. It is shown that the calculated values of the relative permittivity are different from those formerly reported, and reverse biasing the Ni Schottky contact has an influence on the value of the relative permittivity. As the reverse bias increases from 0 V to --3~V, the value of the relative permittivity decreases from 7.184 to 7.093.

Highly sensitive room-temperature gas sensors based on hydrothermal synthesis of Cr2O3 hollow nanospheres

Li Sheng, Li Feng-Li, Zhou Shao-Min, Wang Peng, Cheng Ke, Du Zu-Liang
Chin. Phys. B, 2009, 18 (9): 3985-3989 doi: 10.1088/1674-1056/18/9/061
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This paper reports that Cr2O3 hollow nanospheres (HNs) were synthesized via a hydrothermal approach and characterized by scanning electron microscopy, x-ray powder diffraction, transmission electron microscopy (TEM), selective area electron diffraction and high resolution TEM, respectively. In addition, the room-temperature (RT) gas sensing properties of Cr2O3 HNs and conventional powders (CPs) were investigated by means of the surface photovoltage technique. The experimental data demonstrate that the RT gas sensor of the as-fabricated HNs reaches below 5~ppm whereas that of the CPs is about 40~ppm, which results from there being much more adsorbed and desorbed oxygen in HNs than in CPs at RT. The as-prepared Cr2O3 HNs could have potential applications as RT nanosensors.

Study on characteristics of a double-conductible channel organic thin-films transistor with an ultra-thin hole-blocking layer

Yuan Guang-Cai, Xu Zheng, Zhao Su-Ling, Zhang Fu-Jun, Xu Na, Tian Xue-Yan, Xu Xu-Rong
Chin. Phys. B, 2009, 18 (9): 3990-3994 doi: 10.1088/1674-1056/18/9/062
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The properties of top-contact organic thin-film transistors (TC-OTFTs) using ultra-thin 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline (BCP) as a hole-blocking interlayer have been improved significantly and a BCP interlayer was inserted into the middle of the pentacene active layer. This paper obtains a fire-new transport mode of an OTFT device with double-conductible channels. The accumulation and transfer of the hole carriers are limited by the BCP interlayer in the vertical region of the channel. A huge amount of carriers is located not only at the interface between pentacene and the gate insulator, but also at the two interfaces of pentacene/BCP interlayer and pentacene/gate insulator, respectively. The results suggest that the BCP interlayer may be useful to adjust the hole accumulation and transfer, and can increase the hole mobility and output current of OTFTs. The TC-OTFTs with a BCP interlayer at VDS=-20~V showed excellent hole mobility μFE and threshold voltage VTH of 0.58~cm2/(V\cdots) and --4.6~V, respectively.

A novel structure of a high current gain 4H-SiC BJT with a buried layer in base

Zhang You-Run, Zhang Bo, Li Zhao-Ji, Deng Xiao-Chuan, Liu Xi-Ling
Chin. Phys. B, 2009, 18 (9): 3995-3999 doi: 10.1088/1674-1056/18/9/063
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In this paper, a new structure of a 4H-SiC bipolar junction transistor (BJT) with a buried layer (BL) in the base is presented. The current gain shows an approximately 100% increase compared with that of the conventional structure. This is attributed to the creation of a built-in electric field for the minority carriers to transport in the base which is explained based on 2D device simulations. The optimized design of the buried layer region is also considered by numeric simulations.

Doping dependent metal to insulator transition in the (Bi,Pb)-2212 system: The evolution of structural and electronic properties with europium substitution

Shabna Razia, Sarun Pallian, Murikoli, Vinu Surendran, Syamaprasad Upendran
Chin. Phys. B, 2009, 18 (9): 4000-4006 doi: 10.1088/1674-1056/18/9/064
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The present work investigates the effect of europium substitution on the (Bi, Pb)-2212 system in the concentration range 0.5 ≤ x ≤ 1.0. Phase analysis and lattice parameter calculations on the powder diffraction data and the elemental analysis of EDX show that the Eu atoms are successfully substituted into the (Bi, Pb)-2212 system. Resistivity measurements (64--300~K) reveal that the system exhibits superconductivity at x ≤ 0.5 and semiconductivity at x > 0.5. With the complete suppression of superconductivity which is known to be a quasi-two dimensional phenomenon in these materials, a metal to insulator transition takes place at x=0.6 and the predominant conduction mechanism is found to be variable range hopping between localized states, resulting in macroscopic semiconducting behaviour. The results of electrical and structural properties of the doped (Bi, Pb)-2212 compounds suggest that the decrease of charge carrier concentration and the induced structural disorder are the more effective and dominant mechanisms in the origin of the metal to insulator transition and suppression of superconductivity due to Eu substitution at its Sr site.

Structural, electrical and optical characterization of InGaN layers grown by MOVPE

Y1ld1z A, ?ztürk M Kemal, Bosi M, ?z?elik S, Kasap M
Chin. Phys. B, 2009, 18 (9): 4007-4012 doi: 10.1088/1674-1056/18/9/065
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We present a study on n-type ternary InGaN layers grown by atmospheric pressure metalorganic vapour phase epitaxy (MOVPE) on GaN template/(0001) sapphire substrate. An investigation of the different growth conditions on n-type InxGa_1-xN (x=0.06-0.135) alloys was done for a series of five samples. The structural, electrical and optical properties were characterized by high resolution x-ray diffraction (HRXRD), Hall effect and photoluminescence (PL). Experimental results showed that different growth conditions, namely substrate rotation (SR) and change of total H2 flow (THF), strongly affect the properties of InGaN layers. This case can be clearly observed from the analytical results. When the SR speed decreased, the HRXRD scan peak of the samples shifted along a higher angle. Therefore, increasing the SR speed changed important structural properties of InGaN alloys such as peak broadening, values of strain, lattice parameters and defects including tilt, twist and dislocation density. From PL results it is observed that the growth conditions can be changed to control the emission wavelength and it is possible to shift the emission wavelength towards the green. Hall effect measurement has shown that the resistivity of the samples changes dramatically when THF changes.

Optical properties of hexagonal boron nitride thin films deposited by radio frequency bias magnetron sputtering Hot!

Deng Jin-Xiang, Zhang Xiao-Kang, Yao Qian, Wang Xu-Yang, Chen Guang-Hua, He De-Yan
Chin. Phys. B, 2009, 18 (9): 4013-4018 doi: 10.1088/1674-1056/18/9/066
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The optical properties of hexagonal boron nitride (h-BN) thin films were studied in this paper. The films were characterized by Fourier transform infrared spectroscopy, UV--visible transmittance and reflection spectra. h-BN thin films with a wide optical band gap Eg (5.86~eV for the as-deposited film and 5.97~eV for the annealed film) approaching h-BN single crystal were successfully prepared by radio frequency (RF) bias magnetron sputtering and post-deposition annealing at 970~K. The optical absorption behaviour of h-BN films accords with the typical optical absorption characteristics of amorphous materials when fitting is made by the Urbach tail model. The annealed film shows satisfactory structure stability. However, high temperature still has a significant effect on the optical absorption properties, refractive index n, and optical conductivity σ of h-BN thin films. The blue-shift of the optical absorption edge and the increase of Eg probably result from stress relaxation in the film under high temperatures. In addition, it is found that the refractive index clearly exhibits different trends in the visible and ultraviolet regions. Previous calculational results of optical conductivity of h-BN films are confirmed in our experimental results.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

An improvement on measure methods of the complexity theory and its applications

Wang Fu-Lai, Yang Hui-Huang
Chin. Phys. B, 2009, 18 (9): 4042-4048 doi: 10.1088/1674-1056/18/9/071
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A new method is proposed to transform the time series gained from a dynamic system to a symbolic series which extracts both overall and local information of the time series. Based on the transformation, two measures are defined to characterize the complexity of the symbolic series. The measures reflect the sensitive dependence of chaotic systems on initial conditions and the randomness of a time series, and thus can distinguish periodic or completely random series from chaotic time series even though the lengths of the time series are not long. Finally, the logistic map and the two-parameter Henón map are studied and the results are satisfactory.

Analytical solutions for the slow neutron capture process of heavy element nucleosynthesis

Wu Kai-Su
Chin. Phys. B, 2009, 18 (9): 4049-null doi: 10.1088/1674-1056/18/9/072
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In this paper, the network equation for the slow neutron capture process (s-process) of heavy element nucleosynthesis is investigated. Dividing the s-process network reaction chains into two standard forms and using the technique of matrix decomposition, a group of analytical solutions for the network equation are obtained. With the analytical solutions, a calculation for heavy element abundance of the solar system is carried out and the results are in good agreement with the astrophysical measurements.
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