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Chin. Phys. B  
  Chin. Phys. B--2010, Vol.19, No.6
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Element-free Galerkin method for a kind of KdV equation

Wang Ju-Feng, SunFeng-Xin, Cheng Rong-Jun
Chin. Phys. B, 2010, 19 (6): 060201 doi: 10.1088/1674-1056/19/6/060201
Full Text: [PDF 150 KB] (Downloads:1010)
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The present paper deals with the numerical solution of the third-order nonlinear KdV equation using the element-free Galerkin (EFG) method which is based on the moving least-squares approximation. A variational method is used to obtain discrete equations, and the essential boundary conditions are enforced by the penalty method. Compared with numerical methods based on mesh, the EFG method for KdV equations needs only scattered nodes instead of meshing the domain of the problem. It does not require any element connectivity and does not suffer much degradation in accuracy when nodal arrangements are very irregular. The effectiveness of the EFG method for the KdV equation is investigated by two numerical examples in this paper.

Painlevé property of the modified C-KdV equation and its exact solutions

Wang Hui, DongHuan-He, Wang Yun-Hu, Wang Xin-Zeng
Chin. Phys. B, 2010, 19 (6): 060202 doi: 10.1088/1674-1056/19/6/060202
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In this paper, the Painlev\'{e} properties of the modified C-KdV equation are verified by using the W-K algorithm. Then some exact soliton solutions are obtained by applying the standard truncated expansion method and the nonstandard truncated expansion method with the help of Maple software, respectively.

Effects of average degree of network on an order-disorder transition in opinion dynamics

Feng Cun-Fang, Guan Jian-Yue, Wu Zhi-Xi, Wang Ying-Hai
Chin. Phys. B, 2010, 19 (6): 060203 doi: 10.1088/1674-1056/19/6/060203
Full Text: [PDF 172 KB] (Downloads:611)
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We have investigated the influence of the average degree \langle k \rangle of network on the location of an order--disorder transition in opinion dynamics. For this purpose, a variant of majority rule (VMR) model is applied to Watts--Strogatz (WS) small-world networks and Barab\'{a}si--Albert (BA) scale-free networks which may describe some non-trivial properties of social systems. Using Monte Carlo simulations, we find that the order--disorder transition point of the VMR model is greatly affected by the average degree \langle k \rangle of the networks; a larger value of \langle k \rangle results in a more ordered state of the system. Comparing WS networks with BA networks, we find WS networks have better orderliness than BA networks when the average degree \langle k \rangle is small. With the increase of \langle k \rangle, BA networks have a more ordered state. By implementing finite-size scaling analysis, we also obtain critical exponents \beta/\nu, \gamma/\nu and 1/\nu for several values of average degree \langle k \rangle. Our results may be helpful to understand structural effects on order--disorder phase transition in the context of the majority rule model.

The symmetries of wave equations on new lattices

He Yu-Fang, Fu Jing-Li, Li Xiao-Wei
Chin. Phys. B, 2010, 19 (6): 060301 doi: 10.1088/1674-1056/19/6/060301
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This paper focuses on studying the symmetry of a practical wave equation on new lattices. It is a new step in that the new lattice equation is applied to reduce the discrete problem of motion of an elastic thin homogeneous bar. The equation of motion of the bar can be changed into a discrete wave equation. With the new lattice equation, the translational and scaling invariant, not only is the infinitesimal transformation given, but the symmetry and Lie algebras are also calculated. We also give a new form of invariant called the ratio invariant, which can reduce the process of the computing invariant with the characteristic equation.

Some exact solutions to the inhomogeneous higher-order nonlinear Schr?dinger equation by a direct method

ZhangHuan-Ping, Li Biao, Chen Yong
Chin. Phys. B, 2010, 19 (6): 060302 doi: 10.1088/1674-1056/19/6/060302
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By symbolic computation and a direct method, this paper presents some exact analytical solutions of the one-dimensional generalized inhomogeneous higher-order nonlinear Schr?dinger equation with variable coefficients, which include bright solitons, dark solitons, combined solitary wave solutions, dromions, dispersion-managed solitons, etc. The abundant structure of these solutions are shown by some interesting figures with computer simulation.

Sudden birth versus sudden death of entanglement for the extended Werner-like state in a dissipative environment

Shan Chuan-Jia, ChenTao, Liu Ji-Bing, Cheng Wei-Wen, Liu Tang-Kun, Huang Yan-Xia, Li Hong
Chin. Phys. B, 2010, 19 (6): 060303 doi: 10.1088/1674-1056/19/6/060303
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In this paper, we investigate the dynamical behaviour of entanglement in terms of concurrence in a bipartite system subjected to an external magnetic field under the action of dissipative environments in the extended Werner-like initial state. The interesting phenomenon of entanglement sudden death as well as sudden birth appears during the evolution process. We analyse in detail the effect of the purity of the initial entangled state of two qubits via Heisenberg XY interaction on the apparition time of entanglement sudden death and entanglement sudden birth. Furthermore, the conditions on the conversion of entanglement sudden death and entanglement sudden birth can be generalized when the initial entangled state is not pure. In particular, a critical purity of the initial mixed entangled state exists, above which entanglement sudden birth vanishes while entanglement sudden death appears. It is also noticed that stable entanglement, which is independent of different initial states of the qubits (pure or mixed state), occurs even in the presence of decoherence. These results arising from the combination of the extended Werner-like initial state and dissipative environments suggest an approach to control and enhance the entanglement even after purity induced sudden birth, death and revival.

Entanglement and decoherence of coupled superconductor qubits in a non-Markovian environment

Ji Ying-Hua, Hu Ju-Ju
Chin. Phys. B, 2010, 19 (6): 060304 doi: 10.1088/1674-1056/19/6/060304
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The sudden death of entanglement is investigated for the non-Markovian dynamic process of a pair of interacting flux qubits under a thermal bath. The results show that, for initially two-qubit entangled states, entanglement sudden death (ESD) always happens in the thermal reservoir, where its appearance strongly depends on the environment. In particular, ESD of the qubits occurs more easily for the non-Markovian process than for the Markovian one.

The s-parameterized Weyl-Wigner correspondence in the entangled form and its applications

Fan Hong-Yi, Hu Li-Yun, Yuan Hong-Chun
Chin. Phys. B, 2010, 19 (6): 060305 doi: 10.1088/1674-1056/19/6/060305
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Based on the theory of integration within s-ordering of operators and the bipartite entangled state representation we introduce s-parameterized Weyl--Wigner correspondence in the entangled form. Some of its applications in quantum optics theory are presented as well.

Noisy teleportation of qubit states via the Greenberger-Horne-Zeilinger state or the W state

Li Yan-Ling, FangMao-Fa, Xiao Xing, Wu Chao, Hou Li-Zhen
Chin. Phys. B, 2010, 19 (6): 060306 doi: 10.1088/1674-1056/19/6/060306
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The effects of distributing entanglement through the amplitude damping channel or the phase damping channel on the teleportation of a single-qubit state via the Greenberger--Horne--Zeilinger state and the W state are discussed. It is found that the average fidelity of teleportation depends on the type and rate of the damping in the channel. For the one-qubit affected case, the Greenberger--Horne--Zeilinger state is as robust as the W state, i.e., the same quantum information is preserved through teleportation. For the two-qubit affected case, the W state is more robust when the entanglement is distributed via the amplitude damping channel; if the entanglement is distributed via the phase damping channel, the W state is more robust when the noisy parameter is small while the Greenberger--Horne--Zeilinger state becomes more robust when it is large. For the three-qubit affected case, the Greenberger--Horne--Zeilinger state is more robust than the W state.

Fair quantum blind signatures

WangTian-Yin, Wen Qiao-Yan
Chin. Phys. B, 2010, 19 (6): 060307 doi: 10.1088/1674-1056/19/6/060307
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We present a new fair blind signature scheme based on the fundamental properties of quantum mechanics. In addition, we analyse the security of this scheme, and show that it is not possible to forge valid blind signatures. Moreover, comparisons between this scheme and public key blind signature schemes are also discussed.

Quasinormal modes of the scalar field in five-dimensional Lovelock black hole spacetime

Chen Ju-Hua, Wang Yong-Jiu
Chin. Phys. B, 2010, 19 (6): 060401 doi: 10.1088/1674-1056/19/6/060401
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In this paper, using the third-order WKB approximation, we investigate the quasinormal frequencies of the scalar field in the background of a five-dimensional Lovelock black hole. We find that the ultraviolet correction to Einstein theory in the Lovelock theory makes the scalar field decay more slowly and oscillate more quickly, and the cosmological constant makes the scalar field decay more slowly and oscillate more slowly in the Lovelock black hole background.

Traffic dynamics of an on-ramp system with a cellular automaton model

Li Xin-Gang, GaoZi-You, Jia Bin, Jiang Rui
Chin. Phys. B, 2010, 19 (6): 060501 doi: 10.1088/1674-1056/19/6/060501
Full Text: [PDF 235 KB] (Downloads:614)
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This paper uses the cellular automaton model to study the dynamics of traffic flow around an on-ramp with an acceleration lane. It adopts a parameter, which can reflect different lane-changing behaviour, to represent the diversity of driving behaviour. The refined cellular automaton model is used to describe the lower acceleration rate of a vehicle. The phase diagram and the capacity of the on-ramp system are investigated. The simulation results show that in the single cell model, the capacity of the on-ramp system will stay at the highest flow of a one lane system when the driver is moderate and careful; it will be reduced when the driver is aggressive. In the refined cellular automaton model, the capacity is always reduced even when the driver is careful. It proposes that the capacity drop of the on-ramp system is caused by aggressive lane-changing behaviour and lower acceleration rate.

Entropy-variation with resistance in a quantized RLC circuit derived by the generalized Hellmann-Feynman theorem

Fan Hong-Yi, Xu Xue-Xiang, Hu Li-Yun
Chin. Phys. B, 2010, 19 (6): 060502 doi: 10.1088/1674-1056/19/6/060502
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By virtue of the generalized Hellmann--Feynman theorem for the ensemble average, we obtain the internal energy and average energy consumed by the resistance R in a quantized resistance--inductance--capacitance (RLC) electric circuit. We also calculate the entropy-variation with R. The relation between entropy and R is also derived. By the use of figures we indeed see that the entropy increases with the increment of R.

Stochastic resonance induced by a multiplicative periodic signal in the gene transcriptional regulatory system with correlated noises

Bai Chun-Yan, Yan Yong, Mei Dong-Cheng
Chin. Phys. B, 2010, 19 (6): 060503 doi: 10.1088/1674-1056/19/6/060503
Full Text: [PDF 301 KB] (Downloads:735)
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This paper investigates the stochastic resonance (SR) induced by a multiplicative periodic signal in the gene transcriptional regulatory system with correlated noises. The expression of the signal-to-noise ratio (SNR) is derived. The results indicate that the existence of a maximum in SNR vs. the additive noise intensity α , the multiplicative noise intensity D and the cross-correlated noise intensity \lambda is the identifying characteristic of the SR phenomenon and there is a critical phenomenon in the SNR as a function of \lambda , i.e., for the case of smaller values of noise intensity (α or D), the SNR decreases as \lambda increases; however, for the case of larger values of noise intensity (α or D), the SNR increases as \lambda increases.

Convergent robust stabilization conditions for fuzzy chaotic systems based on the edgewise subdivision approach

ZhangHua-Guang, XieXiang-Peng, Wang Xing-Yuan
Chin. Phys. B, 2010, 19 (6): 060504 doi: 10.1088/1674-1056/19/6/060504
Full Text: [PDF 151 KB] (Downloads:577)
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This paper concerns the problem of stabilizing fuzzy chaotic systems via the viewpoint of the edgewise subdivision approach. Firstly, a new edgewise subdivision algorithm is proposed to implement the simplex edgewise subdivision which divides the overall fuzzy chaotic systems into a lot of sub-systems by a kind of algebraic description. These sub-systems have the same volume and shape characteristics. Secondly, a novel kind of control scheme which switches by the transfer of different operating sub-systems is proposed to achieve convergent stabilization conditions for the underlying controlled fuzzy chaotic systems. Finally, a numerical example is given to demonstrate the validity of the proposed methods.

Adaptive synchronization of a hyperchaotic Lü system based on extended passive control

Fu Gui-Yuan, Li Zhong-Shen
Chin. Phys. B, 2010, 19 (6): 060505 doi: 10.1088/1674-1056/19/6/060505
Full Text: [PDF 122 KB] (Downloads:721)
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This paper investigates the adaptive synchronization of hyperchaotic Lü systems based on the method of extended passive control. By combining the feedback control, the extended passive control method with two output variables is developed, which can synchronize hyperchaotic Lü systems asymptotically and globally more easily without knowing the bound of state of the hyperchaotic system. Adaptive laws are introduced to estimate the unknown parameters as well. Simulation results show the effectiveness and flexibility of the proposed control scheme.

Generating one-, two-, three- and four-scroll attractors from a novel four-dimensional smooth autonomous chaotic system

Sara Dadras, Hamid Reza Momeni
Chin. Phys. B, 2010, 19 (6): 060506 doi: 10.1088/1674-1056/19/6/060506
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A new four-dimensional quadratic smooth autonomous chaotic system is presented in this paper, which can exhibit periodic orbit and chaos under the conditions on the system parameters. Importantly, the system can generate one-, two-, three- and four-scroll chaotic attractors with appropriate choices of parameters. Interestingly, all the attractors are generated only by changing a single parameter. The dynamic analysis approach in the paper involves time series, phase portraits, Poincar\'{e} maps, a bifurcation diagram, and Lyapunov exponents, to investigate some basic dynamical behaviours of the proposed four-dimensional system.

Synchronization-based approach for parameter identification in delayed chaotic network

Cai Guo-Liang, Shao Hai-Jian
Chin. Phys. B, 2010, 19 (6): 060507 doi: 10.1088/1674-1056/19/6/060507
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This paper introduces an adaptive procedure for the problem of synchronization and parameter identification for chaotic networks with time-varying delay by combining adaptive control and linear feedback. In particular, we consider that the equations \dot {x}_i (t) (for i =r+1, r+2,\ldots , n) can be expressed by the former \dot {x}_i (t) (for i = 1, 2,\ldots , r), which is not the same as the previous equation. This approach is also able to track changes in the operating parameters of chaotic networks rapidly and the speed of synchronization and parameter estimation can be adjusted. In addition, this method is quite robust against the effect of slight noise and the estimated value of a parameter fluctuates around the correct value.

Symmetrical dynamics of peak current-mode and valley current-mode controlled switching dc-dc converters with ramp compensation

Zhou Guo-Hua, Xu Jian-Ping, Bao Bo-Cheng, Jin Yan-Yan
Chin. Phys. B, 2010, 19 (6): 060508 doi: 10.1088/1674-1056/19/6/060508
Full Text: [PDF 5772 KB] (Downloads:3800)
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The discrete iterative map models of peak current-mode (PCM) and valley current-mode (VCM) controlled buck converters, boost converters, and buck--boost converters with ramp compensation are established and their dynamical behaviours are investigated by using the operation region, parameter space map, bifurcation diagram, and Lyapunov exponent spectrum. The research results indicate that ramp compensation extends the stable operation range of the PCM controlled switching dc--dc converter to D>0.5 and that of the VCM controlled switching dc--dc converter to D<0.5. Compared with PCM controlled switching dc--dc converters with ramp compensation, VCM controlled switching dc--dc converters with ramp compensation exhibit interesting symmetrical dynamics. Experimental results are given to verify the analysis results in this paper.

Phase synchronization and its transition in two coupled bursting neurons: theoretical and numerical analysis

Wang Hai-Xia, Lu Qi-Shao, Shi Xia
Chin. Phys. B, 2010, 19 (6): 060509 doi: 10.1088/1674-1056/19/6/060509
Full Text: [PDF 3644 KB] (Downloads:904)
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It is crucially important to study different synchronous regimes in coupled neurons because different regimes may correspond to different cognitive and pathological states. In this paper, phase synchronization and its transitions are discussed by means of theoretical and numerical analyses. In two coupled modified Morris--Lecar neurons with a gap junction, we show that the occurrence of phase synchronization can be investigated from the dynamics of phase equation, and the analytical synchronization condition is derived. By defining the phase of spike and burst, the transitions from burst synchronization to spike synchronization and then toward nearly complete synchronization can be identified by bifurcation diagrams, the mean frequency difference and time series of neurons. The simulation results suggest that the synchronization of bursting activity is a multi-time-scale phenomenon and the phase synchronization deduced by the phase equation is actually spike synchronization.

Determination of the exact range of the value of the parameter corresponding to chaos based on the Silnikov criterion

Li Wei-Yi, Zhang Qi-Chang, Wang Wei
Chin. Phys. B, 2010, 19 (6): 060510 doi: 10.1088/1674-1056/19/6/060510
Full Text: [PDF 162 KB] (Downloads:663)
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Based on the Silnikov criterion, this paper studies a chaotic system of cubic polynomial ordinary differential equations in three dimensions. Using the Cardano formula, it obtains the exact range of the value of the parameter corresponding to chaos by means of the centre manifold theory and the method of multiple scales combined with Floque theory. By calculating the manifold near the equilibrium point, the series expression of the homoclinic orbit is also obtained. The space trajectory and Lyapunov exponent are investigated via numerical simulation, which shows that there is a route to chaos through period-doubling bifurcation and that chaotic attractors exist in the system. The results obtained here mean that chaos occurred in the exact range given in this paper. Numerical simulations also verify the analytical results.

Chaotic behaviours and control of chaos in the p-Ge photoconductor

Feng Yu-Ling, ZhangXi-He, Yao Zhi-Hai
Chin. Phys. B, 2010, 19 (6): 060511 doi: 10.1088/1674-1056/19/6/060511
Full Text: [PDF 1750 KB] (Downloads:969)
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The chaotic behaviours in the p--Ge photoconductor system are studied by changing the photo-excitation coefficient and the routes and parameter conditions are given for chaos generation in this system. A scheme for controlling chaos in the p--Ge photoconductor is presented by adding an ac bias current. Numerical simulations show that this scheme can be effectively used to control chaotic states into stable period states for this system. Moreover, the different period states with different period numbers can be obtained by appropriately adjusting the amplitude, frequency, and initial phase of the additional ac current.

Improved delay-dependent globally asymptotic stability of delayed uncertain recurrent neural networks with Markovian jumping parameters

Ji Yan, Cui Bao-Tong
Chin. Phys. B, 2010, 19 (6): 060512 doi: 10.1088/1674-1056/19/6/060512
Full Text: [PDF 118 KB] (Downloads:649)
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In this paper, we have improved delay-dependent stability criteria for recurrent neural networks with a delay varying over a range and Markovian jumping parameters. The criteria improve over some previous ones in that they have fewer matrix variables yet less conservatism. In addition, a numerical example is provided to illustrate the applicability of the result using the linear matrix inequality toolbox in MATLAB.

Linear-control-based synchronisation of coexisting attractor networks with time delays

Song Yun-Zhong
Chin. Phys. B, 2010, 19 (6): 060513 doi: 10.1088/1674-1056/19/6/060513
Full Text: [PDF 580 KB] (Downloads:615)
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This paper introduces the concept of linear-control-based synchronization of coexisting attractor networks with time delays. Within the new framework, closed loop control for each dynamic node is realized through linear state feedback around its own arena in a decentralized way, where the feedback matrix is determined through consideration of the coordination of the node dynamics, the inner connected matrix and the outer connected matrix. Unlike previously existing results, the feedback gain matrix here is decoupled from the inner matrix; this not only guarantees the flexible choice of the gain matrix, but also leaves much space for inner matrix configuration. Synchronization of coexisting attractor networks with time delays is made possible in virtue of local interaction, which works in a distributed way between individual neighbours, and the linear feedback control for each node. Provided that the network is connected and balanced, synchronization will come true naturally, where theoretical proof is given via a Lyapunov function. For completeness, several illustrative examples are presented to further elucidate the novelty and efficacy of the proposed scheme.

Research on the chaos recognition method based on differential entropy

Zhang Shu-Qing, Zhao Yu-Chun, Jia Jian, Zhang Li-Guo, Shangguan Han-Lu
Chin. Phys. B, 2010, 19 (6): 060514 doi: 10.1088/1674-1056/19/6/060514
Full Text: [PDF 457 KB] (Downloads:630)
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Phase space reconstruction is the first step to recognizing the chaos from observed time series. On the basis of differential entropy, this paper introduces an efficient method to estimate the embedding dimension and the time delay simultaneously. The differential entropy is used to characterize the disorder degree of the reconstructed attractor. The minimum value of the differential entropy corresponds to the optimum set of the reconstructed parameters. Simulated experiments show that the original phase space can be effectively reconstructed from time series, and the accuracy of the invariants in phase space reconstruction is greatly improved. It provides a new method for the identification of chaotic signals from time series.

A complexity measure approach based on forbidden patterns and correlation degree

Wang Fu-Lai
Chin. Phys. B, 2010, 19 (6): 060515 doi: 10.1088/1674-1056/19/6/060515
Full Text: [PDF 203 KB] (Downloads:632)
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Based on forbidden patterns in symbolic dynamics, symbolic subsequences are classified and relations between forbidden patterns, correlation dimensions and complexity measures are studied. A complexity measure approach is proposed in order to separate deterministic (usually chaotic) series from random ones and measure the complexities of different dynamic systems. The complexity is related to the correlation dimensions, and the algorithm is simple and suitable for time series with noise. In the paper, the complexity measure method is used to study dynamic systems of the Logistic map and the H\'enon map with multi-parameters.

Size transition of spiral waves using the pulse array method

Xie Ling-Ling, Gao Ji-Hua
Chin. Phys. B, 2010, 19 (6): 060516 doi: 10.1088/1674-1056/19/6/060516
Full Text: [PDF 1558 KB] (Downloads:515)
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The domain size of spiral waves is an important issue in studies of two-dimensional (2D) spatiotemporal patterns. In this work, we use the 2D complex Ginzburg--Landau equation (CGLE) as our model and find that an initially big spiral can successfully transfer to several small spirals by applying a pulse array method. The impacts of several important factors, such as array density, controlling intensity and pulsing time, are investigated. This control approach may be useful for the control of 2D spatiotemporal patterns and has potential applications in the control of some realistic systems, such as meteorological and cardiac systems.

Low-temperature heat capacities and standard molar enthalpy of formation of pyridine-2,6-dicarboxylic acid

Yang Wei-Wei, Di You-Ying, Kong Yu-Xia, Tan Zhi-Cheng
Chin. Phys. B, 2010, 19 (6): 060517 doi: 10.1088/1674-1056/19/6/060517
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This paper reports that the low-temperature heat capacities of pyridine-2,6-dicarboxylic acid were measured by a precision automatic calorimeter over a temperature range from 78~K to 380~K. A polynomial equation of heat capacities as a function of temperature was fitted by the least-squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15~K were calculated and tabulated at intervals of 5~K. The constant-volume energy of combustion of the compound was determined by means of a precision rotating-bomb combustion calorimeter. The standard molar enthalpy of combustion of the compound was derived from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound was calculated from a combination of the datum of the standard molar enthalpy of combustion of the compound with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.

A novel anti-shock silicon etching apparatus for solving diaphragm release problems

Shi Sha-Li, ChenDa-Peng, Ou Yi, Jing Yu-Peng, Xu Qiu-Xia, Ye Tian-Chun
Chin. Phys. B, 2010, 19 (6): 060701 doi: 10.1088/1674-1056/19/6/060701
Full Text: [PDF 2046 KB] (Downloads:749)
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This paper presents a novel anti-shock bulk silicon etching apparatus for solving a universal problem which occurs when releasing the diaphragm (e.g.\ SiNx), that the diaphragm tends to be probably cracked by the impact of heating-induced bubbles, the swirling of heating-induced etchant, dithering of the hand and imbalanced etchant pressure during the wafer being taken out. Through finite element methods, the causes of the diaphragm cracking are analysed. The impact of heating-induced bubbles could be the main factor which results in the failure stress of the SiNx diaphragm and the rupture of it. In order to reduce the four potential effects on the cracking of the released diaphragm, an anti-shock bulk silicon etching apparatus is proposed for using during the last etching process of the diaphragm release. That is, the silicon wafer is first put into the regular constant temperature etching apparatus or ultrasonic plus, and when the residual bulk silicon to be etched reaches near the interface of the silicon and SiNx diaphragm, within a distance of 50--80~\mu m (the exact value is determined by the thickness, surface area and intensity of the released diaphragm), the wafer is taken out carefully and put into the said anti-shock silicon etching apparatus. The wafer's position is at the geometrical centre, also the centre of gravity of the etching vessel. An etchant outlet is built at the bottom. The wafer is etched continuously, and at the same time the etchant flows out of the vessel. Optionally, two symmetrically placed low-power heating resistors are put in the anti-shock silicon etching apparatus to quicken the etching process. The heating resistors' power should be low enough to avoid the swirling of the heating-induced etchant and the impact of the heating-induced bubbles on the released diaphragm. According to the experimental results, the released SiNx diaphragm thus treated is unbroken, which proves the practicality of the said anti-shock bulk silicon etching apparatus.

A novel polarization interferometer for measuring upper atmospheric winds

Mu Ting-Kui, Zhang Chun-Min
Chin. Phys. B, 2010, 19 (6): 060702 doi: 10.1088/1674-1056/19/6/060702
Full Text: [PDF 969 KB] (Downloads:826)
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A static polarization interferometer for measuring upper atmospheric winds is presented, based on two Savart plates with their optical axes perpendicular to each other. The principle and characteristics of the interferometer are described. The interferometer with a wide field of view can offer a stable benchmark optical path difference over a specified spectral region of 0.55--0.63~\mu m because there are no quarter wave plates. Since the instrument employs a straight line common-path configuration but without moving parts and slits, it is very compact, simple, inherently robust and has high throughput. The paper is limited to a theoretical analysis.

Entropy description of a cooperation-competition system

Xu Xiu-Lian, Fu Chun-Hua, Liu Chun-Ping, He Da-Ren
Chin. Phys. B, 2010, 19 (6): 060501 doi: 10.1088/1674-1056/19/6/060501R
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Understanding the cooperation--competition dynamics is a long-standing challenge in studying complex systems. Inspired by the idea of Shannon entropy, we define competition information entropy and propose an entropy evolution model. The analytic results of the model of the relation between competition gain distribution parameters and entropy, as well as the relation between entropy and time are compared with empirical results obtained in 14 real world systems. They are found to be in good agreement with each other.

The g-factors and magnetic rotation in 82Rb

Yuan Da-Qing, Zheng Yong-Nan, Zuo Yi, Fan Ping, Zhou Dong-Mei, Wu Xiao-Guang, Zhu Li-Hua, Li Guang-Sheng, XuGuo-Ji, Fan Qi-Wen, Zhang Xi-Zhen, Zhu Sheng-Yun
Chin. Phys. B, 2010, 19 (6): 062701 doi: 10.1088/1674-1056/19/6/062701
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The g-factors of the intra-band states 12, 13, 14, 15 in a magnetic-rotational band built on the 11 state in 82Rb are measured for the first time by using a transient magnetic field-ion implantation perturbed angular distribution (TMF-IMPAD) method. The magnetic-rotational band in 82Rb is populated by the ^{60}Ni(^{27}Al,4pn)^{ 82}Rb reaction, and the time-integral Larmor precessions are measured after recoil implantation into a polarized Fe foil. The calculation of g-factors is also carried out in terms of a semi-classical model of independent particle angular momentum coupling on the basis of the four-quasiparticle configuration \pi ( {g_{9 / 2} } )^2 \otimes \pi (p_{3 / 2} ,f_{5 / 2} ) \otimes \nu ≤ft( {g_{9 / 2} } \right). The measured and calculated g-factors are in good agreement with each other. The g-factors and deduced shear angles decrease with the increase of spin along the band. This clearly illustrates the shear effect of a step-by-step alignment of the valence protons and neutrons in magnetic rotation. The semi-classical calculation also shows that the alignment of the valence neutron angular momentum is faster than that of the valence protons, which results in a decrease of g-factors with increasing spin. The present results provide solid evidence of the shear mechanism of magnetic rotation.

Monte Carlo simulation for bremsstrahlung and photoneutron yields in high-energy x-ray radiography

Xu Hai-Bo, Peng Xian-Ke, Chen Chao-Bin
Chin. Phys. B, 2010, 19 (6): 062901 doi: 10.1088/1674-1056/19/6/062901
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This paper reports on the results of calculations using a Monte Carlo code (MCNP5) to study the properties of photons, electrons and photoneutrons obtained in the converted target and their transportations in x-ray radiography. A comparison between measurements and calculations for bremsstrahlung and photoneutrons is presented. The radiographic rule and the effect of the collimator on the image are studied with the experimental model. The results provide exact parameters for the optimal design of radiographic layout and shielding systems.

Characteristics of terahertz coherent transition radiation generated from picosecond ultrashort electron bunches Hot!

Liu Wen-Xin, Tang Chuan-Xiang, Huang Wen-Hui
Chin. Phys. B, 2010, 19 (6): 062902 doi: 10.1088/1674-1056/19/6/062902
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This paper presents a method of generating terahertz (THz) coherent transition radiation (CTR) from picosecond ultrashort electron bunches including single and train bunches, which are produced by a photocathode radio frequency gun. The radiation characteristics of THz CTR including formation factor and energy spectrum are analysed in detail. With the help of a 2-dimensional particle-in-cell simulation, the radiation characteristics including power, energy and magnetic field are analysed. The results show that the radiation frequency can be adjusted by tuning the repetition frequency of the train bunch and the energy can be enhanced with the train bunches.

Multi-window invisible cloaks

WangXin-Hua, Qu Shao-Bo, Xia Song, WangBin-Ke, Xu Zhuo, Ma Hua, Wang Jia-Fu, Gu Chao, Wu Xiang, Lu Lei, Zhou Hang
Chin. Phys. B, 2010, 19 (6): 064101 doi: 10.1088/1674-1056/19/6/064101
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This paper reports that a general method of designing invisible cloaks is using variant constitutive material parameters to realize the space transformation. A hollow region can be hidden after this transformation. It was recently shown (Ma H, Qu S B, Xu Z and Wang J F 2009 \wx{Appl. Phys. Lett.}{94} 103501) that when the original point moves to the boundary of a cloak, the cloak can be designed to be open. Based on this theory, we propose multi-window invisible cloaks which can conceal a group of objects. Full wave simulations for invisible cloaks with regular and irregular shapes verified this method.

Nonsingularity in two-dimensional cylindrical invisible cloaks

Wang Xin-Hua, Qu Shao-Bo, Xia Song, Wang Bin-Ke, Xu Zhuo, Ma Hua, Wang Jia-Fu, Gu Chao, Wu Xiang, Lu Lei, Zhou Hang
Chin. Phys. B, 2010, 19 (6): 064102 doi: 10.1088/1674-1056/19/6/064102
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The method of designing electromagnetic invisible cloaks is usually based on the form-invariance of Maxwell's equations in coordinate transformation. The exterior boundary of a cylindrical invisible cloak is unchanged and the interior boundary is extended from that of a point to that of a cylindrical region in coordination transformation. This transformation process makes perfect cloaks, but it causes singularity in the constitutive material parameters of cloaks. This singularity makes the cloaks impossible to realize in practice. In order to remove this singularity, this paper sets a small cylindrical region replacing a point in the space transformation. The cylindrical region is so small that it does not affect the invisibility effects, but it can remove the singularity for material parameters. Full wave simulations based on the finite element method were used to verify the designed cloaks.

Nonparaxial propagation of a super-Lorentz-Gauss SLG01 mode beam

Zhou Guo-Quan
Chin. Phys. B, 2010, 19 (6): 064201 doi: 10.1088/1674-1056/19/6/064201
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Based on the vectorial Rayleigh--Sommerfeld integral formulae, this paper derives the analytical nonparaxial propagation equation of a super-Lorentz--Gauss (SLG) SLG01 mode beam in free space. The far field expression and the scalar paraxial result are treated with special cases of the general formulae. According to the obtained analytical representation, the nonparaxial propagation properties of the SLG01 mode beam are illustrated and analysed with numerical examples. This research provides an approach to investigate the propagation of the SLG01 mode beam within the framework of the nonparaxial regime.

Investigation on the scattering effect of ceramic Nd:YAG

Li Cheng-Ming, Zong Nan, Gao Hong-Wei, Xu Zu-Yan, Liu Wen-Bin, Pan Yu-Bai, Feng Xi-Qi
Chin. Phys. B, 2010, 19 (6): 064202 doi: 10.1088/1674-1056/19/6/064202
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This paper investigates the scattering effect of domestic 0.5 at{\%} ceramic Nd:YAG. An effective method has been utilized to measure the scattering and absorption coefficients. An end-pumped continuous wave (CW) Nd:YAG ceramic laser was also demonstrated. A maximum output power of 6.7~W at 1064~nm was obtained at an 808-nm pump power of 32.9~W. Conversion efficiency and slope efficiency have been achieved. This indicates that scattering has an important effect on the optical performance of ceramic Nd:YAG.

Study of the near-field modulation property of microwaviness on a KH2PO4 crystal surface

Chen Ming-Jun, Jiang Wei, Li Ming-Quan, Chen Kuan-Neng
Chin. Phys. B, 2010, 19 (6): 064203 doi: 10.1088/1674-1056/19/6/064203
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The KH_2PO_4 crystal is a key component in optical systems of inertial confinement fusion (ICF). The microwaviness on a KH_2PO_4 crystal surface is strongly related to its damage threshold which is a key parameter for application. To study the laser induced damage mechanism caused by microwaviness, in this paper the near-field modulation properties of microwaviness to the incident wave are discussed by the Fourier modal method. Research results indicate that the microwaviness on the machined surface will distort the incident wave and thus lead to non-uniform distribution of the light intensity inside the crystal; in a common range of microwaviness amplitude, the light intensity modulation degree increases about 0.03 whenever the microwaviness amplitude increases 10~nm; 1 order diffraction efficiencies are the key factors responsible for light intensity modulation inside the crystal; the light intensity modulation is just around the microwaviness in the form of an evanescent wave, not inside the crystal when the microwaviness period is below 0.712~\mu m; light intensity modulation degree has two extreme points in microwaviness periods of 1.064~\mu m and 1.6~\mu m, remains unchanged between periods of 3~\mu m and 150~\mum, and descends above the period of 150~\mu m to 920~\mu m.

Quantum communication and entanglement between two distant atoms via vacuum fields

Zheng Shi-Biao
Chin. Phys. B, 2010, 19 (6): 064204 doi: 10.1088/1674-1056/19/6/064204
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This paper proposes an efficient scheme for quantum communication between two atoms trapped in distant cavities which are connected by an optical fibre. During the operation, all the atomic system, the cavity modes and the fibre are not excited. The quantum state is mediated by the vacuum fields. The idea can be used to realize quantum entanglement between two distant atoms via vacuum.

Nonclassicality of photon-added squeezed vacuum states

Si Kun, Ji Xiao-Hui, Jia Huan-Yu
Chin. Phys. B, 2010, 19 (6): 064205 doi: 10.1088/1674-1056/19/6/064205
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By applying the bosonic creation operator to squeezed vacuum states, this paper introduces a new kind of quantum states: photon-added squeezed vacuum states. It also presents an experimental approach to prepare these states, and investigates their quantum statistical properties by the numerical method. The results indicate that these states reveal some interesting non-classical properties, such as anti-bunching effects, squeezing effects and negativities of the relevant Wigner functions.

The breaking point between fast- and slow-light in adegenerate two-level atomic system

Li Lu-Ming, Hu Zhen-Yan, Luo Bin, Guo Hong
Chin. Phys. B, 2010, 19 (6): 064206 doi: 10.1088/1674-1056/19/6/064206
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This paper investigates the breaking point between fast- and slow-light in a degenerate two-level atomic system, where fast-light can be converted to slow-light arbitrarily on a single transition line by adjusting the strength of the pumping field. An equivalent incoherent pumping rate is introduced in this simplified theoretical model which exploits the dependence of this feature. The experimental observation is presented as evidence of the breaking point where the injected power is about 0.08~{\rm mW}.

A generalized Collins formula derived by virtue of the displacement-squeezing related squeezed coherent state representation

Xie Chuan-Mei, Fan Hong-Yi, Wan Shao-Long
Chin. Phys. B, 2010, 19 (6): 064207 doi: 10.1088/1674-1056/19/6/064207
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Based on the displacement-squeezing related squeezed coherent state representation ≤ft\vert z\right\rangle _{g} and using the technique of integration within an ordered product of operators, this paper finds a generalized Fresnel operator, whose matrix element in the coordinate representation leads to a generalized Collins formula (Huygens--Fresnel integration transformation describing optical diffraction). The generalized Fresnel operator is derived by a quantum mechanical mapping from z to sz-rz^{\ast } in the % ≤ft\vert z\right\rangle _{g} representation, while ≤ft\vert z\right\rangle _{g} in phase space is graphically denoted by an ellipse.

High power high beam quality diode-pumped 1319-nm Nd:YAG oscillator-amplifier laser system

Xie Shi-Yong, Lu Yuan-Fu, MaQing-Lei, Wang Peng-Yuan, Shen Yu, Zong Nan, Yang Feng, Bo Yong, Peng Qin-Jun, Cui Da-Fu, XuZu-Yan
Chin. Phys. B, 2010, 19 (6): 064208 doi: 10.1088/1674-1056/19/6/064208
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This paper demonstrated a high power and high beam quality diode-pumped 1319-nm Nd:YAG master oscillator-power amplifier laser system. A thermally near-unstable resonator with four-rod birefringence compensation flat--flat cavity was adopted as the master oscillator. A solid etalon was inserted in the unidirectional ring resonator to compress the laser linewidth. Under a repetition rate of 500~Hz and pulse width of 160~\mus, the master oscillator delivers an average output power of 16.8~W at 1319~nm with linear polarisation, beam quality factor M^{2} = 1.16 and linewidth of 3.2~GHz. A double-pass power amplifier with two amplifier stages was employed for higher power scaling and the output power was amplified to be 25.9~W with M^{2} = 1.43.

Spacing-adjustable and wavelength-tunable multiwavelength fibre laser with nonlinear Brillouin gain and birefringence fibre loop mirror

Zhang Zu-Xing, Wu Jian, Xu Kun, Hong Xiao-Bin, Lin Jin-Tong
Chin. Phys. B, 2010, 19 (6): 064209 doi: 10.1088/1674-1056/19/6/064209
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This paper demonstrates a room-temperature multiwavelength fibre laser with spacing-adjustability and wavelength-tunability. The nonlinear gain of self-excited stimulated Brillouin scattering can suppress mode competition induced by homogeneous broadening of Erbium-doped fibre. With the use of a birefringence fibre loop filter, the wavelength spacing can be adjusted by changing the length of the used birefringence fibre, and the lasing wavelengths can be finely tuned through modifying the filtering profile of the birefringence filter. Multiwavelength output with spectral spacing as small as 0.076~nm and a wavelength number of more than 80 has been successfully produced.

Electron trajectory evaluation in laser-plasma interaction for effective output beam

P. Zobdeh, R. Sadighi-Bonabi, H. Afarideh
Chin. Phys. B, 2010, 19 (6): 064210 doi: 10.1088/1674-1056/19/6/064210
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Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generated from other methods such as periodic plasma wave field, spheroidal cavity regime and plasma channel guided acceleration. Trajectory of electron motion is described as hyperbolic, parabolic or elliptic paths. We find that the self-generated electron bunch has a smaller energy width and more effective gain in energy spectrum. Initial condition for the ellipsoidal cavity is determined by laser-plasma parameters. The electron trajectory is influenced by its position, energy and cavity electrostatic potential.

Relative carrier-envelope phase dependence of resonant propagation of two-colour femtosecond pulses in V-type atomic medium

Tan Xia, WangZhen-Dong, Wang Lei, Fan Xi-Jun
Chin. Phys. B, 2010, 19 (6): 064211 doi: 10.1088/1674-1056/19/6/064211
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Using numerical solution of the full Maxwell--Bloch equations, which is obtained by the finite-difference time-domain method and the iterative predictor--corrector method, we investigate the modulation effect of relative carrier--envelope phase (hereinafter referred to as the relative phase) on resonant propagation of two-colour femtosecond ultrashort laser pulses in a V-type three-level atomic medium. It is found that the pulse splitting occurs for a smaller value of relative phase; when the value of relative phase increases to a certain value, only the variation of pulse shape is present and the pulse splitting does not occur any more; moreover, when the value of relative phase is smaller, the pulse group velocity is larger. The relative phase also has an obvious effect on population and spectral property. Different population transfers can be realized by adjusting the value of relative phase. Generally speaking, for the pulses with smaller areas their spectral strengths and frequency ranges decrease obviously with the value of relative phase increasing; for the pulses with larger areas, with value of the relative phase increasing, their spectral strengths decrease remarkably but the relative strengths of the higher frequency components increase significantly, while the spectral frequency range is not varied evidently.

Cross-phase modulation instability in optical fibres with exponential saturable nonlinearity and high-order dispersion

Zhong Xian-Qiong, Xiang An-Ping
Chin. Phys. B, 2010, 19 (6): 064212 doi: 10.1088/1674-1056/19/6/064212
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Utilizing the linear-stability analysis, this paper analytically investigates and calculates the condition and gain spectra of cross-phase modulation instability in optical fibres in the case of exponential saturable nonlinearity and high-order dispersion. The results show that, the modulation instability characteristics here are similar to those of conventional saturable nonlinearity and Kerr nonlinearity. That is to say, when the fourth-order dispersion has the same sign as that of the second-order one, a new gain spectral region called the second one which is far away from the zero point may appear. The existence of the exponential saturable nonlinearity will make the spectral width as well as the peak gain of every spectral region increase with the input powers before decrease. Namely, for every spectral regime, this may lead to a unique value of peak gain and spectral width for two different input powers. In comparison with the case of conventional saturable nonlinearity, however, when the other parameters are the same, the variations of the spectral width and the peak gain with the input powers will be faster in case of exponential saturable nonlinearity.

Study of second-order nonlinear hyperpolarisability of all-trans-β-carotene in solutions by linear spectroscopic technique

Fang Wen-Hui, MenZhi-Wei, Sun Cheng-Lin, Qu Guan-Nan, YangGuang, Li Zuo-Wei, Gao Shu-Qin, Lu Guo-Hui
Chin. Phys. B, 2010, 19 (6): 064213 doi: 10.1088/1674-1056/19/6/064213
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This paper demonstrates the second-order nonlinear hyperpolarisability \gamma of all-trans-β-carotene in different solvents by linear spectroscopic technique that is based on resonance Raman scattering and UV--VIS (Ultraviolet-visible) absorption spectroscopy. Owing to the two-level model well describing the link that exists between the resonance Raman scattering and stimulated Raman scattering, the stimulated Raman polarisability α_{\rm R} can be calculated through the two-photon resonance system. The value of \gamma of all-trans-β-carotene in carbon bisulfide solution is 6.435\times 10^{-33} esu (1~esu of resistance =8.98755\times10^{11}~\Omega) that is close to the true value, because the solution of all-trans-β-carotene in carbon bisulfide satisfies the rigid resonance Raman scattering condition. This method is expected to be worthy of applications to measure the second-order nonlinear hyperpolarisability of a conjugate organic molecule.

High precision Zernike modal gray map reconstruction for liquid crystal corrector

Liu Chao, Mu Quan-Quan, Hu Li-Fa, Cao Zhao-Liang, Xuan Li
Chin. Phys. B, 2010, 19 (6): 064214 doi: 10.1088/1674-1056/19/6/064214
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This paper proposes a new Zernike modal gray map reconstruction algorithm used in the nematic liquid crystal adaptive optics system. Firstly, the new modal algorithm is described. Secondly, a single loop correction experiment was conducted, and it showed that the modal method has a higher precision in gray map reconstruction than the widely used slope method. Finally, the contrast close-loop correction experiment was conducted to correct static aberration in the laboratory. The experimental results showed that the average peak to valley (PV) and root mean square (RMS) of the wavefront corrected by mode method were reduced from 2.501\lambda (\lambda =633~nm) and 0.610\lambda to 0.0334\lambda and 0.00845\lambda , respectively. The corrected PV and RMS were much smaller than those of 0.173\lambda and 0.048\lambda by slope method. The Strehl ratio and modulation transfer function of the system corrected by mode method were much closer to diffraction limit than with slope method. These results indicate that the mode method can take good advantage of the large number of pixels of the liquid crystal corrector to realize high correction precision.

Calculation of Rydberg energy levels for the francium atom

Huang Shi-Zhong, Chu Jin-Min
Chin. Phys. B, 2010, 19 (6): 063101 doi: 10.1088/1674-1056/19/6/063101
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Based on the weakest bound electron potential model theory, the Rydberg energy levels and quantum defects of the np^{2}P^{\rm \circ}_{1 / 2} (n=7--50) and np^{2}P^{\rm \circ}_{3 / 2} (n=7--50) spectrum series for the francium atom are calculated. The calculated results are in excellent agreement with the 48 measured levels, and 40 energy levels for highly excited states are predicted.

The KLL dielectronic recombination processes for highly charged krypton, iodine and barium ions

Yang Jian-Hui, Zhang Hong, Cheng Xin-Lu
Chin. Phys. B, 2010, 19 (6): 063201 doi: 10.1088/1674-1056/19/6/063201
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The KLL dielectronic recombination (DR) processes of ions from highly charged helium-like to oxygen-like krypton, iodine and barium ions are studied systematically in the relativistic distorted-wave approximation with configuration interaction. The KLL DR resonant energies, the corresponding resonant strengths and the theoretical spectra for each highly charged ion species are obtained. The results accord well with other available values. The behaviour of KLL resonant strengths for He-like ions with atomic number Z is analysed.

Experimental study of bound and autoionizing Rydberg states of the europium atom

Xiao Ying, DaiChang-Jian, Qin Wen-Jie
Chin. Phys. B, 2010, 19 (6): 063202 doi: 10.1088/1674-1056/19/6/063202
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An isolated-core-excitation (ICE) scheme and stepwise excitation are employed to study the highly excited states of the europium atom. The bound europium spectrum with odd parity in a region of 42400--43500~cm^{ - 1} is measured, from which spectral information on 38 transitions, such as level position and relative intensity, can be deduced. Combined with information about excitation calibration and the error estimation process, the selection rules enable us to determine the possible values of total angular momentum J for the observed states. The autoionization spectra of atomic europium, belonging to the 4f^{7}6p{nl} (l=0, 2) configurations, are systematically investigated by using the three-step laser resonance ionization spectroscopy (RIS) approach. With the ICE scheme, all the experimental spectra of the autoionizing states have nearly symmetric profiles whose peak positions and widths can be easily obtained. A comparison between our results and those from the relevant literature shows that our work not only confirms many reported states, but also discovers 14 bound states and 16 autoionizing states.

Photoluminescence properties of Y0.75-xGdxAl0.10BO3:Eu3+0.10, 0.05R3+ (R= Sc, Bi) (0.00≤x≤0.45)

Li Jie, Wang Yu-Hua, Dong Qi-Zheng, Liu Ji-Di
Chin. Phys. B, 2010, 19 (6): 063301 doi: 10.1088/1674-1056/19/6/063301
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Y_{0.75 - x}GdxAl0.10BO3:Eu^{3+}0.10, 0.05R3+ (R=Sc, Bi) (0.00 ≤ x ≤ 0.45) powder samples are prepared by solid-state reaction and their luminescence properties are investigated. With the replacement of Y3+ ions by Sc3+ (or Bi3+) and Gd3+ ions in (Y,Al)BO3:Eu, the intensities of emission at 254 and 147~nm are remarkably improved, because Sc3+ ions can absorb UV light and transfer the energy to Eu3+ ions efficiently. Moreover, Gd3+ and Bi^{3 + } ions act as an intermediate ``bridge'' between the sensitizer and the activator (Eu3+) in energy transfer to produce light in the (Y, Gd)BO3:Bi3+, Eu3+ system more effectively. After doping an appropriate concentration of Gd3+ into Y_{0.50}Gd_{0.25}Al0.10BO3:Eu3+_{0.01}, Bi^{3+}_{0.05}, the emission intensity reaches its maximum, which is nearly 110{\%} compared with the red commercial phosphor (Y,Gd)BO3:Eu and better chromaticity coordinates (0.650, 0.350) are obtained.

S-matrix study on alignment dependence of single ionization of molecular ions with different active orbitals

Li Yan, Jia Xin-Yan, Yang Shi-Ping, Li Wei-Dong, Chen Jing
Chin. Phys. B, 2010, 19 (6): 063302 doi: 10.1088/1674-1056/19/6/063302
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The orientation-dependent single ionization rate of the diatomic molecular ion H_2^+ with different active orbitals in an intense field is studied by using S-matrix theory. Our results show that the orientation-dependent single ionization probability of H_2^+ is greatly dependent on the symmetry and the electron density distribution of its initial states, and it can be used to identify the excited state of the molecular ion in the dissociation process.

Rovibrational quenching of BH in ultracold 3He collisions

Gong Ming-Yan, Hu Xiao-Long, Chen Xia, Niu Mei, Feng Er-Yin
Chin. Phys. B, 2010, 19 (6): 063401 doi: 10.1088/1674-1056/19/6/063401
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The interaction potential of a He--BH complex is investigated by the coupled-cluster single-double plus perturbative triples (CCSD (T)) method and an augmented correlation consistent polarized valence (aug-cc-pV)5Z basis set extended with a set of (3s3p2d1f1g) midbond functions. Using the five two-dimensional model potentials, the first three-dimensional interaction potential energy surface is constructed by interpolating along (r--r_{\rm e}) by using a fourth-order polynomial. The cross sections for the rovibrational relaxation of BH in cold and ultracold collisions with 3He atom are calculated based on the three-dimensional potential. The results show that the \Delta v = - 1 transition is more efficient than the \varDelta v = - 2 transition, and that the process of relaxation takes place mainly between rotational energy levels with the same vibration state and the \varDelta j = - 1 transition is the most efficient. The zero temperature quenching rate coefficient is finite as predicted by Wigner's law. The resonance is found to take place around 0.1--1~cm^{ - 1} translational energy, which gives rise to a step in the rate coefficients for temperatures around 0.1--1~K. The final rotational distributions in the state v = 0 resulting from the quenching of state (v = 1,j = 0) at three energies corresponding to the three different regimes are also given.

The influence of electric field on the photodetachment of H- near a metal surface

Huang Kai-Yun, Wang De-Hua
Chin. Phys. B, 2010, 19 (6): 063402 doi: 10.1088/1674-1056/19/6/063402
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The influence of electric field on the photodetachment of H^{ - } near a metal surface is investigated based on the closed-orbit theory. It is found that the photodetachment of H^{ - } near a metal surface is not only related to the electric field strength but also to the electric field direction. If the electric field is along the +z axis, it can strengthen the oscillation in the photodetachment cross section. However, if the electric field is along the -z axis, since the direction of electric field force is opposite to that of static-image force caused by the metal surface, the situation becomes much more complicated. When the electric field is very weak, its influence can be neglected. The photodetachment cross section is nearly the same as that when a single metal surface exists. When the electric field strength is strong enough, the electric field force is able to counteract the metallic attraction, therefore no closed orbit is formed. If the electric field continues to increase until its influence becomes dominant, the photodetachment cross section approaches the case of the photodetachment of H^{ - } in an electric field. Our results may be useful for guiding future experimental studies on the photodetachment of negative ions near surfaces.

Investigation of isotope effects of dynamic properties for H(D) +OF reactions by the quasi-classical trajectory method

Zhao Juan, Xu Yan, Meng Qing-Tian
Chin. Phys. B, 2010, 19 (6): 063403 doi: 10.1088/1674-1056/19/6/063403
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Quasi-classical trajectory (QCT) calculations are employed to study the dynamic properties for \mbox{H(D)} + \mbox{OF} reactions on the adiabatic potential energy surface (PES) of the \mbox{1}{ }^{3}\mbox{A}'' triplet state. Obvious differences between the reaction probabilities for J = 0, integral cross sections for J \ne 0, branch ratios of the product and internuclear distances as well as product rotational alignments between the title reactions are found. These differences are attributed mainly to the different reduced masses of the reactants and the different zero-point energies (ZPEs) of the transition state.

Investigation of the transfer ionization process in collisions of partially stripped ions on He

Liu Hui-Ping, Chen Xi-Meng, Ouyang Xiao-Ping, Xi Fa-Yuan, Su Guang-Hui
Chin. Phys. B, 2010, 19 (6): 063404 doi: 10.1088/1674-1056/19/6/063404
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In this paper a projectile ion-recoil ion coincidence technique is used to investigate the transfer ionization processes in collisions of 0.22--6.30~MeV C^{q + } ions and 0.25--6.35~MeV O^{q + } ions (q=1, 2, 3, 4) with the He atom separately. The cross section ratio f of transfer ionization to single electron transfer is measured, and the dependence of f on both charge state q and energy E of the projectiles is investigated. The electron-structure and the mechanisms leading to transfer ionization affect the dependence of f on q and E. Our measurements, along with other data published previously, suggest a similar dependence of f on charge state and energy of projectile for partially stripped ions over a large energy range. The maximum value of f is approximately 0.17q^{0.60}; the energy corresponding to maximum f is about 160q^{0.60}~keV/u.

Elastic and inelastic positron-helium scattering

Cheng Yong-Jun, Zhou Ya-Jun
Chin. Phys. B, 2010, 19 (6): 063405 doi: 10.1088/1674-1056/19/6/063405
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Elastic and inelastic positron--helium scatterings have been investigated with the coupled-channel optical method (CCO). Ionization continuum and positronium formation channels are included via a complex equivalent-local optical potential. Calculations are reported of cross sections of elastic scattering, total excitation and n=2, 3, and 4 excitations of ground-state helium for incident energies from 30~eV to 400~eV. The present calculation shows that the ionization and Ps-formation channels significantly affect the cross sections of elastic and inelastic positron--helium scatterings.

Improved light extraction of GaN-based light-emitting diodes with surface-textured indium tin oxide electrodes by nickel nanoparticle mask dry-etching

He An-He, Zhang Yong, Zhu Xue-Hui, Chen Xian-Wen, Fan Guang-Han, He Miao
Chin. Phys. B, 2010, 19 (6): 068101 doi: 10.1088/1674-1056/19/6/068101
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GaN-based light-emitting diodes (LEDs) with surface-textured indium tin oxide (ITO) as a transparent current spreading layer were fabricated. The ITO surface was textured by inductively coupled plasma (ICP) etching technology using a monolayer of nickel (Ni) nanoparticles as the etching mask. The luminance intensity of ITO surface-textured GaN-based LEDs was enhanced by about 34{\%} compared to that of conventional LED without textured ITO layer. In addition, the fabricated ITO surface-textured GaN-based LEDs would present a quite good performance in electrical characteristics. The results indicate that the scattering of photons emitted in the active layer was greatly enhanced via the textured ITO surface, and the ITO surface-textured technique could have a potential application in improving photoelectric characteristics for manufacturing GaN-based LEDs of higher brightness.

Chaos game representation of functional protein sequences, and simulation and multifractal analysis of induced measures Hot!

Yu Zu-Guo, Xiao Qian-Jun, Shi Long, Yu Jun-Wu, Vo Anh
Chin. Phys. B, 2010, 19 (6): 068701 doi: 10.1088/1674-1056/19/6/068701
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Investigating the biological function of proteins is a key aspect of protein studies. Bioinformatic methods become important for studying the biological function of proteins. In this paper, we first give the chaos game representation (CGR) of randomly-linked functional protein sequences, then propose the use of the recurrent iterated function systems (RIFS) in fractal theory to simulate the measure based on their chaos game representations. This method helps to extract some features of functional protein sequences, and furthermore the biological functions of these proteins. Then multifractal analysis of the measures based on the CGRs of randomly-linked functional protein sequences are performed. We find that the CGRs have clear fractal patterns. The numerical results show that the RIFS can simulate the measure based on the CGR very well. The relative standard error and the estimated probability matrix in the RIFS do not depend on the order to link the functional protein sequences. The estimated probability matrices in the RIFS with different biological functions are evidently different. Hence the estimated probability matrices in the RIFS can be used to characterise the difference among linked functional protein sequences with different biological functions. From the values of the D_q curves, one sees that these functional protein sequences are not completely random. The D_q of all linked functional proteins studied are multifractal-like and sufficiently smooth for the C_q (analogous to specific heat) curves to be meaningful. Furthermore, the D_q curves of the measure \mu based on their CGRs for different orders to link the functional protein sequences are almost identical if q\geq 0. Finally, the C_q curves of all linked functional proteins resemble a classical phase transition at a critical point.

AC operation and runaway electron behaviour in HT-7 tokamak

Lu Hong-Wei, Hu Li-Qun, Zhou Rui-Jie, Lin Shi-Yao, Zhong Guo-Qiang, Wang Shao-Feng, Chen Kai-Yun, Xu Ping, ZhangJi-Zong, Ling Bi-Li, Mao Song-Tao, DuanYan-Min
Chin. Phys. B, 2010, 19 (6): 065201 doi: 10.1088/1674-1056/19/6/065201
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Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition and current sustainment, is described. The behaviour of runaway electrons is analysed by four HXR detectors tangentially viewing the plasma in the equatorial plane, within energy ranges 0.3--1.2~MeV and 0.3--7~MeV, separately. High energy runaway electrons (\sim MeV) are found to circulate predominantly in the opposite direction to the plasma current, while the number of low energy runaway electrons (\sim tens to hundreds of keV) circulating along the plasma current is comparable to that in the direction opposite to the plasma current. AC operation with lower hybrid current drive (LHCD) is observed to have an additional benefit of suppressing the runaway electrons if the drop of the loop voltage is large enough.

Semi-analytical modeling of tokamak density evolution

Shi Bing-Ren
Chin. Phys. B, 2010, 19 (6): 065202 doi: 10.1088/1674-1056/19/6/065202
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Tokamak plasma density evolution is generally modeled by a diffusion--convection equation in cylindrical geometry. By using a semi-analytical approach, we solve such an equation for a given diffusion coefficient and inward convection velocity as an arbitrary function of the radial position. Through variable separation, a Sturm--Liouville-type eigenvalue problem is solved, thereby constructing a complete set of orthogonal eigenfunctions. Based on the decomposition of the solution, the initial function, and the source function in these eigenfunctions, several problems of practical interest about the density evolution are analyzed. They include the density evolution, with boundary density not being zero; the density profile with internal transport barrier; the damping profile during particle source being shut-down. Results are found to be qualitatively consistent with the tokamak experiments.

Interaction of in-band and in-gap lattice soliton trains in optically induced two-dimensional photonic lattices

Liu Sheng, Zhang Peng, XiaoFa-Jun, Gan Xue-Tao, ZhaoJian-Lin
Chin. Phys. B, 2010, 19 (6): 065203 doi: 10.1088/1674-1056/19/6/065203
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We demonstrate the coherent interactions of lattice soliton trains, including in-band solitons (IBSs) and gap soliton trains (GSTs), in optically induced two-dimensional photonic lattices with self-defocusing nonlinearity. It is revealed that the \pi-staggered phase structures of the lattice soliton trains will lead to anomalous interactions. Solely by changing their initial separations, the transition between attractive and repulsive interaction forces or reversion of the energy transfer can be obtained. The `negative refraction' effect of the soliton trains on the interaction is also discussed. Moreover, two interacting IBSs can merge into one GST when attraction or energy transfer happens.

Simulation on effect of poloidal power spectrum on lower hybrid wave propagation

Qin Yong-Liang, Ding Bo-Jiang, Kuang Guang-Li, Jia Hua, Zhang Li-Zhi
Chin. Phys. B, 2010, 19 (6): 065204 doi: 10.1088/1674-1056/19/6/065204
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The coupling of lower hybrid wave to the plasma is a crucial issue for efficient current drive in tokamaks. This paper establishes a new coupling model which assumes the antenna to be a curved face and the plasma to be a cylinder. Power spectrum considering the coupling between wave-guides in both poloidal and toroidal direction is simply estimated and discussed. The effect of the poloidal wave vector on wave propagation, power deposition and driven current is also investigated with the help of lower hybrid current drive code. Results show that the poloidal wave vector affects the ray tracing, and also has effect on power deposition and driven current. The effect of the poloidal wave vector on power deposition and driven current profile depends on plasma parameters. Preliminary studies suggest that it seems possible to control the current profile by adjusting the poloidal phase difference between the waveguide in poloidal direction.

Structural evolution of silicone oil liquid exposed to Ar plasma

Yuan Yuan, Ye Chao, Huang Hong-Wei, Shi Guo-Feng, Ning Zhao-Yuan
Chin. Phys. B, 2010, 19 (6): 065205 doi: 10.1088/1674-1056/19/6/065205
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Structure properties of silicone oil serving as a liquid substrate exposed to Ar plasma are investigated in this paper. Under the action of energetic Ar ions, the surface of silicone oil liquid substrate exhibits a branch-like fractal aggregation structure, which is related to the structure evolution of silicone oil liquid from Si--O chain to Si--O network. The radicals from the dissociation of silicone oil molecule into the Ar plasma turns the plasma into a reactive environment. Therefore, the structural evolution of silicone oil liquid substrate and the reactive radicals in the plasma space become possible factors to affect the aggregation of nanoparticles and also the structures and the compositions of nanoparticles.

Direct transition of potential of water droplets to electric energy using aligned single-walled carbon nanotubes

Liu Ji, Zheng Kai-Hong, Liu Zheng, Hu Li-Jun, Sun Lian-Feng
Chin. Phys. B, 2010, 19 (6): 066101 doi: 10.1088/1674-1056/19/6/066101
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In this paper, we report that an electromotive force (EMF) can be induced in a rope of aligned single-walled carbon nanotubes (SWNTs) when water droplets fall on this rope. The magnitude of this EMF depends sensitively on the slant angle of the SWNTs. Most interestingly, both the magnitude and the direction of the induced EFM can be modulated by applying a current to the SWNTs. The concepts of electrical slip and no-slip are proposed and can be quantitatively described by ``electrical slip resistance''. This kind of generator does not need any magnet, rotor, {etc} and shows quite a different operating mechanism and design compared with a conventional large scale hydroelectric power generator.

Synthesis and properties of Au-Fe3O4 and Ag-Fe3O4 heterodimeric nanoparticles

Ding Hao, Shen Cheng-Min, Hui Chao, Xu Zhi-Chuan, Li Chen, Tian Yuan, Shi Xue-Zhao, Gao Hong-Jun
Chin. Phys. B, 2010, 19 (6): 066102 doi: 10.1088/1674-1056/19/6/066102
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Monodisperse Au--Fe3O4 heterodimeric nanoparticles (NPs) were prepared by injecting precursors into a hot reaction solution. The size of Au and Fe3O4 particles can be controlled by changing the injection temperature. UV--Vis spectra show that the surface plasma resonance band of Au--Fe3O4 heterodimeric NPs was evidently red-shifted compared with the resonance band of Au NPs of similar size. The as-prepared heterodimeric Au--Fe3O4 NPs exhibited superparamagnetic properties at room temperature. The Ag--Fe3O4 heterodimeric NPs were also prepared by this synthetic method simply using AgNO3 as precursor instead of HAuCl4. It is indicated that the reported method can be readily extended to the synthesis of other noble metal conjugated heterodimeric NPs.

Degradation mechanisms of current gain in NPN transistors

Li Xing-Ji, Geng Hong-Bin, Lan Mu-Jie, Yang De-Zhuang, He Shi-Yu, Liu Chao-Ming
Chin. Phys. B, 2010, 19 (6): 066103 doi: 10.1088/1674-1056/19/6/066103
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An investigation of ionization and displacement damage in silicon NPN bipolar junction transistors (BJTs) is presented. The transistors were irradiated separately with 90-keV electrons, 3-MeV protons and 40-MeV Br ions. Key parameters were measured {\em in-situ} and the change in current gain of the NPN BJTS was obtained at a fixed collector current (I_{\rm c}=1~mA). To characterise the radiation damage of NPN BJTs, the ionizing dose D_{\i} and displacement dose D_{\d} as functions of chip depth in the NPN BJTs were calculated using the SRIM and Geant4 code for protons, electrons and Br ions, respectively. Based on the discussion of the radiation damage equation for current gain, it is clear that the current gain degradation of the NPN BJTs is sensitive to both ionization and displacement damage. The degradation mechanism of the current gain is related to the ratio of D_{\rm d}/(D_{\rm d}+D_{\rm i}) in the sensitive region given by charged particles. The irradiation particles leading to lower D_{\rm d}/(D_{\rm d}+D_{\rm i}) within the same chip depth at a given total dose would mainly produce ionization damage to the NPN BJTs. On the other hand, the charged particles causing larger D_{\rm d}/(D_{\rm d}+D_{\rm i}) at a given total dose would tend to generate displacement damage to the NPN BJTs. The Messenger--Spratt equation could be used to describe the experimental data for the latter case.

Synergistic effects of neutron and gamma ray irradiation of commercial CHMOS microcontroller

Jin Xiao-Ming, Fan Ru-Yu, Chen Wei, Lin Dong-Sheng, YangShan-Chao, Bai Xiao-Yan, Liu Yan, GuoXiao-Qiang, Wang Gui-Zhen
Chin. Phys. B, 2010, 19 (6): 066104 doi: 10.1088/1674-1056/19/6/066104
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This paper presents the experimental results of a combined irradiation environment of neutron and gamma rays on 80C196KC20, which is a 16-bit high performance member of the MCS96 microcontroller family. The electrical and functional tests were made in three irradiation environments: neutron, gamma rays, combined irradiation of neutron and gamma rays. The experimental results show that the neutron irradiation can affect the total ionizing dose behaviour. Compared with the single radiation environment, the microcontroller exhibits considerably more severe degradation in neutron and gamma ray synergistic irradiation. This phenomenon may cause a significant hardness assurance problem.

The effects of cubic potentials on discrete breathers in a mixed Klein-Gordon /Fermi-Pasta-Ulam chain

ZhouQian, Lü Bin-Bin, Tian Qiang
Chin. Phys. B, 2010, 19 (6): 066301 doi: 10.1088/1674-1056/19/6/066301
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Nonlinearity has a crucial impact on the symmetry properties of dynamical systems. This paper studies a one-dimensional mixed Klein--Gordon/Fermi--Pasta--Ulam diatomic chain using the expanded rotating plane-wave approximation and numerical calculations to determine the effect of cubic potentials on the symmetry properties of discrete breathers in this system. The results will be very useful to researchers in the field of numerical calculations on discrete breathers.

Simulation of surfactant effect on growth of metal homoexpitaxial Sb-Ag/Ag(111)

Wu Li-Li, Wu Feng-Min
Chin. Phys. B, 2010, 19 (6): 066801 doi: 10.1088/1674-1056/19/6/066801
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A kinetic Monte Carlo simulation is performed in order to study the effect of Sb atoms as a surfactant on the growth of Ag on Ag(111). In our model the repulsive mechanism in which the surfactant Sb atoms repel diffusing Ag adatoms, and the exchange mechanism between Ag and Sb atoms, are considered. Our simulations show that the effects of Sb atoms for Ag/Ag(111) growth system are mainly to increase the chances for Ag atoms to overcome the Ehrlich--Schwoebel barrier both in the interlayer growth and along the edge diffusion. The influence of the coverage of Sb atoms and substrate temperature on the growth of Ag/Sb/Ag(111) is discussed.

Electric dipolar interaction assisted growth of single crystalline organic thin films Hot!

Cai Jin-Ming, Zhang Yu-Yang, Hu Hao, Bao Li-Hong, Pan Li-Da, Tang Wei, Li Guo, Du Shi-Xuan, Shen Jian, Gao Hong-Jun
Chin. Phys. B, 2010, 19 (6): 067101 doi: 10.1088/1674-1056/19/6/067101
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We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.

Two-dimensional analysis of the interface states effects on current gain for 4H-SiC bipolar junction transistor

Zhang You-Run, Zhang Bo, Li Zhao-Ji, Deng Xiao-Chuan
Chin. Phys. B, 2010, 19 (6): 067102 doi: 10.1088/1674-1056/19/6/067102
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This paper studies two-dimensional analysis of the surface state effect on current gain for a 4H--SiC bipolar junction transistor (BJT). Simulation results indicate the mechanism of current gain degradation, which is surface Fermi level pinning leading to a strong downward bending of the energy bands to form the channel of surface electron recombination current. The experimental results are well-matched with the simulation, which is modeled by exponential distributions of the interface state density replacing the single interface state trap. Furthermore, the simulation reveals that the oxide quality of the base emitter junction interface is very important for 4H--SiC BJT performance.

Theoretical investigations of the local distortion and electron paramagnetic resonance parameter for CdCl2:V2+ and CsMgX3:V2+ (X=Cl, Br) systems

Li Cheng-Gang, Kuang Xiao-Yu, Duan Mei-Ling, Zhang Cai-Xia, Chai Rui-Peng
Chin. Phys. B, 2010, 19 (6): 067103 doi: 10.1088/1674-1056/19/6/067103
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This paper systematically investigates the local distortion and electron paramagnetic resonance (EPR) parameter for CdCl2:V2= and CsMgX3:V2= (X=Cl, Br) systems on the basis of the complete energy matrix, in which not only the contributions due to the spin--orbit coupling of the central ions but also that of the ligands are considered. To describe the difference of overlapping between d-orbits and p orbit, two spin--orbit coupling coefficients are introduced. By simulating the crystal field parameter and EPR parameter, the local distortion parameters are studied and the relationships between the EPR parameter and the spin--orbit coupling coefficients as well as divergent parameter are discussed. These results show that the local structures exhibit compression distortion for CdCl2:V2= and elongation distortions for CsMgX3:V^{2 + } (X=Cl, Br), respectively. It notes that the empirical formula R \approx R_{\rm H} + (r_{\rm i} - r_{\rm h} ) / 2 is not suitable for CdCl2:V2= and CsMgX3:V2= (X=Cl, Br) systems. The contributions of ligand to spin--orbit coupling interaction cannot be neglected for strong covalent systems, especially for V2= doped in CsMgBr3:V2=.

Influence of line defects on focusing in a two-dimensional photonic-crystal flat lens

Feng Zhi-Fang
Chin. Phys. B, 2010, 19 (6): 067201 doi: 10.1088/1674-1056/19/6/067201
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We investigate in detail the influence of line defects on focusing of electromagnetic waves in a two-dimensional photonic-crystal flat lens. Through simulations, we find that a focusing can always be observed when a line defect in the lens is introduced along the light transmission direction and the width of the line defect is less than \lambda /2. However, there appear two focusings when the width of the line defect is more than \lambda /2. When the line defect is introduced along the direction perpendicular to the transmission, there is always one focusing.

Effective AC response of nonlinear spherical coated composite

Hao Yan-Hua, ChenXiao-Gang, Hou Rui, Wang Rui
Chin. Phys. B, 2010, 19 (6): 067202 doi: 10.1088/1674-1056/19/6/067202
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An effective nonlinear response of a nonlinear composite with spherical coated inclusions randomly embedded in a host medium under the action of an external AC electric field, {{\bm E}}_a = {{\bm E}}_1 \sin (\omega t) + {{\bm E}}_3 \sin (3\omega t), is investigated using a perturbation method. The local potentials of the composite at higher harmonics are given both in the region of local inclusion particles and in the local host region under the external AC electric field. All effective nonlinear responses of the composite and the relationship between the effective nonlinear responses at the fundamental frequency and third harmonics are also studied for spherical coated inclusion in a dilute limit.

Spontaneous Josephson spin current in triplet superconductor/ferromagnet/triplet superconductor junctions

Xu Mao-Jie, Dou Xiao-Ming
Chin. Phys. B, 2010, 19 (6): 067301 doi: 10.1088/1674-1056/19/6/067301
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This paper theoretically studies Josephson spin current through triplet superconductor/ferromagnet/triplet superconductor junctions. At the ferromagnet/superconductor interfaces, the ferromagnetic scattering potential gives rise to coupling between the Andreev bound states and lifts their spin degeneracy. These spin-split Andreev states carry the Josephson spin current through the junctions. The generated spin supercurrent can be controlled by the magnetization of a ferromagnetic thin layer and bias voltage across the junctions.

Piezoelectric effects and electronic structures of InAs/GaAs quantum dots grown along (111) and (011) directions

Zhao Wei, Yu Zhong-Yuan, Liu Yu-Min
Chin. Phys. B, 2010, 19 (6): 067302 doi: 10.1088/1674-1056/19/6/067302
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Piezoelectric effects and electronic structures of InAs/GaAs quantum dots grown along (111) and (011) directions are investigated in this paper. The finite element method is used. Electronic energy levels are calculated by solving the three-dimensional effective mass Schr?dinger equation including a strain modified confinement potential and piezoelectric effects. The difference in electronic structure between quantum dots grown along the (111) direction and the (011) direction are compared. The cubic and truncated pyramidal shaped quantum dots are adopted.

Role of localised surface plasmon polaritons coupling in optical transmission through double-layer metal apertures

Gong Zhi-Qiang, Liu Jian-Qiang
Chin. Phys. B, 2010, 19 (6): 067303 doi: 10.1088/1674-1056/19/6/067303
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In this paper, we investigate the optical properties of the double-layer metal films perforated with single apertures by analysing the coupling of localized surface plasmon polaritons (LSPPs). It is found that the amplitude and the wavelength of transmission peak in such a structure can be adjusted by changing the longitudinal interval D between two films and the lateral displacements d_{x} and d_{y} which are parallel and perpendicular to the polarization direction of incident light, respectively. The variation of longitudinal interval D results in the redshift of transmission peak due to the change of coupling strength of LSPPs near the single apertures. The amplitude of transmission peak decreases with the increase of d_{y} and is less than that in the case of d_{x}, which originates from the difference in coupling manner between LSPPs and the localized natures of LSPPs.

One-dimensional continuous analytic potential solution to generic oxide-silicon-oxide system

Zhang Jian, He Jin, Zhang Li-Ning
Chin. Phys. B, 2010, 19 (6): 067304 doi: 10.1088/1674-1056/19/6/067304
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A one-dimensional continuous analytic potential solution to a generic oxide--silicon--oxide system is developed. With the analytic solution, the potential distribution in the silicon film is predicted. A physics-based relation between surface potentials is also derived and then applied to the generic oxide--silicon--oxide metal--oxide--semiconductor field-effect transistors (MOSFETs) for the calculation of surface potentials

Hydration effect on the electronic transport properties of oligomeric phenylene ethynylene molecular junctions

Li Zong-Liang, Li Huai-Zhi, Ma Yong, ZhangGuang-Ping, Wang Chuan-Kui
Chin. Phys. B, 2010, 19 (6): 067305 doi: 10.1088/1674-1056/19/6/067305
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A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecules accumulated in the vicinity as recently reported by Na {\it et al.} [\wx{Nanotechnology}{18} 424001 (2007)]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H2O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H2O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H2O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.

Phase escape of current-biased Josephson junctions

Cao Wen-Hui, Yu Hai-Feng, Tian Ye, Chen Geng-Hua, Zhao Shi-Ping
Chin. Phys. B, 2010, 19 (6): 067401 doi: 10.1088/1674-1056/19/6/067401
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Switching current distributions of an Nb/Al--AlO_x/Nb Josephson junction are measured in a temperature range from 25~mK to 800~mK. We analyse the phase escape properties by using the theory of Larkin and Ovchinnikov (LO) which takes discrete energy levels into account. Our results show that the phase escape can be well described by the LO approach for temperatures near and below the crossover from thermal activation to macroscopic quantum tunneling. These results are helpful for further study of macroscopic quantum phenomena in Josephson junctions where discrete energy levels need to be considered.

Simulation of dielectric resonator for high-Tc radio frequency superconducting quantum interference device

Gao Ji, Yang Tao, Ma Ping, Dai Yuan-Dong
Chin. Phys. B, 2010, 19 (6): 067402 doi: 10.1088/1674-1056/19/6/067402
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Nowadays, the high-critical-temperature radio frequency superconducting quantum interference device (high-T_{\rm c } rf SQUID) is usually coupled to a dielectric resonator that is a standard 10\times 10\times 1~mm3 SrTiO3 (STO) substrate with a YBa2Cu3O_{7 - \delta } (YBCO) thin-film flux focuser deposited on it. Recently, we have simulated a dielectric resonator for the high-T_{\rm c } rf SQUID by using the ANSOFT High Frequency Structure Simulator (ANSOFT HFSS). We simulate the resonant frequency and the quality factor of our dielectric resonator when it is unloaded or matches a 50-\Omega impedance. The simulation results are quite close to the practical measurements. Our study shows that ANSOFT HFSS is quite suitable for simulating the dielectric resonator used for the high-Tc rf SQUID. Therefore, we think the ANSOFT HFSS can be very helpful for investigating the characteristics of dielectric resonators for high-Tc rf SQUIDs.

Magnetic properties and magnetocaloric effect in compound PrFe12B6

Wang Fang, Shen Bao-Gen, Zhang Jian, Sun Ji-Rong, Meng Fan-Bin, Li Yang-Xian
Chin. Phys. B, 2010, 19 (6): 067501 doi: 10.1088/1674-1056/19/6/067501
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Magnetic properties and magnetocaloric effect of compound PrFe12B6 are investigated. The coexistence of hard phase PrFe12B6 and soft phase α--Fe causes interesting phenomena on the curves for the temperature dependence of magnetization. PrFe12B6 experiences a first order phase transition at the Curie temperature 200~K, accompanied by an obvious lattice contraction, which in turn results in a large magnetic entropy change. The Maxwell relation fails to give the correct information about magnetic entropy change due to the first order phase transition nature. The large magnetic entropy changes of PrFe_{12.3}B_{4.7} obtained from heat capacity method are 11.7 and 16.2~J/kg.K for magnetic field changes of 0--2~T and 0--5~T respectively.

Anomalous thermal expansion and spontaneous magnetostriction of Gd2Fe16Cr compound

Hao Yan-Ming, Tan Ming, Wang Wei, Wang Fang
Chin. Phys. B, 2010, 19 (6): 067502 doi: 10.1088/1674-1056/19/6/067502
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The structural and the magnetic properties of Gd2Fe16Cr compound are investigated by x-ray diffraction and magnetization measurements. The Gd2Fe16Cr compound has a rhombohedral Th2Zn_{17}-type structure. There exist an anisotropic strong spontaneous magnetostriction and a negative thermal expansion in the magnetic state of Gd2Fe16Cr compound. The average thermal expansion coefficient \bar {\alpha }=-7.03\times 10^{ - 6}/K in a temperature range of 294--454~K and \bar {\alpha }=-1.31\times 10^{ - 5}/K in 454--572~K are obtained. The spontaneous magnetostrictive deformation and the Curie temperature are discussed.

Synthesis, structure and antiferromagnetic behaviour of brannerite MnV2O6

Zhou Chuan-Cang, Liu Fa-Min, Ding Peng, Cai Lu-Gang, Zhong Wen-Wu, Zhang Huan
Chin. Phys. B, 2010, 19 (6): 067503 doi: 10.1088/1674-1056/19/6/067503
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Brannerite MnV2O_{6 } with plate-like shape is successfully synthesized by hydrothermal method. Its crystal structure and morphology are investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), high resolution transmission electron microscopy (HRTEM) and select area electronic diffraction (SAED). The results show that the brannerite MnV2O6 with monoclinic structure has a uniform plate-like shape with a diameter of about 5--8~\mu m and a thickness of about 500~nm. SAED patterns further confirm the structure of the brannerite MnV2O6 and the single crystalline character of the plate crystal. Magnetic properties are measured by superconducting quantum interference device (SQUID) in a temperature range of 2--300~K under a magnetic field of 1~T. The magnetic measurement results indicate that the material undergoes an antiferromagnetic transition with a N\'{e}el temperature of 17~K. Above 50~K, the inverse susceptibility is fitted well to the Curie--Weiss law with a calculated moment of 5.98~\mu_{\rm B}. Finally, the origin of antiferromagnetic behaviour in the brannerite MnV2O6 is explained by means of Anderson model.

The magnetization reversal behaviour for SmCo6.8Zr0.2 and SmCo6.8Zr0.2/α -(Fe,Co) nanocrystalline magnets at low temperature

Liu Zhuang, Chen Ren-Jie, Li Dong, Yan Ar-Ru
Chin. Phys. B, 2010, 19 (6): 067504 doi: 10.1088/1674-1056/19/6/067504
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This paper reports that the SmCo6.8Zr0.2 nanocrystalline permanent magnets and SmCo6.8Zr0.2/\al-(Fe,Co) nanocomposite permanent magnets are successfully produced by mechanical alloying and subsequently annealing at 700~{^\circ}C for 10 minutes. The x-ray diffraction results show that the phase structure of SmCo6.8Zr0.2 nanocrystalline permanent magnets is composed of SmCo_{7} phase and SmCo6.8Zr0.2/\al-(Fe,Co) nanocomposite permanent magnets is composed of SmCo_{7} and α -(Fe,Co) phases. The mechanism of magnetization reversal is mainly controlled by inhomogeneous domain wall pinning in SmCo6.8Zr0.2 and SmCo6.8Zr0.2/\al-(Fe,Co) magnets. The inter-grain exchange interaction at low temperature is investigated, which shows that the inter-grain exchange interaction of SmCo6.8Zr0.2/\al-(Fe,Co) magnets increases greatly by the decrease of the measured temperature. According to \Delta m_{\rm irr}--H/H_{\rm cj}, \Delta m_{\rm rev}--H/H_{\rm cj} and \chi_{\rm irr}--H/H_{\rm cj} curves at room temperature and 100~K, the changes of irreversible and reversible magnetization behaviours of SmCo6.8Zr0.2 and SmCo6.8Zr0.2/\al-(Fe,Co) magnets with the decreasing temperature are analysed in detail. The magnetic viscosity and the activation volume of SmCo6.8Zr0.2 and SmCo6.8Zr0.2/\al-(Fe,Co) magnets at different temperatures are also studied.

Characterization of the radiation from single-walled zig-zag carbon nanotubes at terahertz range

Wu Qun, Wang Yue, Wu Yu-Ming, Zhuang Lei-Lei, Li Le-Wei, Gui Tai-Long
Chin. Phys. B, 2010, 19 (6): 067801 doi: 10.1088/1674-1056/19/6/067801
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This paper investigates the radiation characteristics of metal single-walled zig-zag carbon nanotubes as a dipole antenna at terahertz wave range. The current distribution, input impedance and mutual impedance are calculated for various geometrical parameters of vertically-aligned carbon nanotubes. The numerical results demonstrate the properties of the antenna depending strongly on the geometrical parameters such as the radius, the lengths of carbon nantobues, and the spacing between nanotubes. It is found that the zig-zag carbon nanotubes exhibit very high input impedance and the mutual impedances for antenna array applications. These unique high impedance properties are different from the conventional metal thin wire antenna. The far-field patterns and gain of antenna array are also calculated. The maximum gain of array of 100-element array is up to 20.0~dB, which is larger than the gain of 0.598~dB of single dipole antenna at distance d = 0.5\lambda .

Z-scan analysis of high-order nonlinear refraction effect induced by using elliptic Gaussian beam

Guo Shi-Fang, Tian Qiang
Chin. Phys. B, 2010, 19 (6): 067802 doi: 10.1088/1674-1056/19/6/067802
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The irradiance of an elliptic Gaussian beam that is high enough to excite high-order nonlinear refraction effect is used to calculate the normalized on-axis transmittance function in the z-scan technique by introducing complex beam parameters which make the calculation simpler. The transmittance formula is applied to the first-, first two-, and first three-order nonlinearities. Numerical evaluation shows that the symmetry no longer holds when using an elliptic Gaussian beam instead of a circular Gaussian beam. A distortion is observed in the central part of the curve, which decreases as ellipticity increases. Moreover, the variation of the normalized peak-valley difference decreases as ellipticity decreases.

Confirmation on origin of primary electron in solid state cathodoluminescence

Huang Jin-Zhao, Li Shi-Shuai, FengXiu-Peng, Wang Pei-Ji, Zhang Zhong
Chin. Phys. B, 2010, 19 (6): 067803 doi: 10.1088/1674-1056/19/6/067803
Full Text: [PDF 106 KB] (Downloads:590)
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This paper utilizes the brightness-voltage waveform curve to investigate the primary electron in solid state cathodoluminescence. The results indicate that the primary electron is from the interface state of SiO2/MEH-PPV (Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) under the lower electric field which contributes to the 580-nm emission. With increasing the electric field, the 405-nm emission is obtained, and under this condition, the origin of the primary electron is mainly from tunneling.
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