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CN 11-5639/O4
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Chin. Phys. B  
  Chin. Phys. B--2009, Vol.18, No.3
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GENERAL

Multi-component Harry--Dym hierarchy and its integrable couplings as well as their Hamiltonian structures

Yang Hong-Wei, Dong Huan-He
Chin. Phys. B, 2009, 18 (3): 845-849 doi: 10.1088/1674-1056/18/3/001
Full Text: [PDF 110 KB] (Downloads:1718)
Show Abstract
This paper obtains the multi-component Harry--Dym (H--D) hierarchy and its integrable couplings by using two kinds of vector loop algebras \widetilde{G}3 and \widetilde{G}6. The Hamiltonian structures of the above system are given by the quadratic-form identity. The method can be used to produce the Hamiltonian structures of the other integrable couplings or multi-component hierarchies.

Discrete integrable system and its integrable coupling

Li Zhu
Chin. Phys. B, 2009, 18 (3): 850-855 doi: 10.1088/1674-1056/18/3/002
Full Text: [PDF 96 KB] (Downloads:863)
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This paper derives new discrete integrable system based on discrete isospectral problem. It shows that the hierarchy is completely integrable in the Liouville sense and possesses bi-Hamiltonian structure. Finally, integrable couplings of the obtained system is given by means of semi-direct sums of Lie algebras.

Conformal invariance and Hojman conserved quantities of canonical Hamilton systems

Liu Chang, Liu Shi-Xing, Mei Feng-Xiang, Guo Yong-Xin
Chin. Phys. B, 2009, 18 (3): 856-860 doi: 10.1088/1674-1056/18/3/003
Full Text: [PDF 109 KB] (Downloads:859)
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This paper discusses the conformal invariance by infinitesimal transformations of canonical Hamilton systems. The necessary and sufficient conditions of conformal invariance being Lie symmetrical simultaneously by the action of infinitesimal transformations are given. The determining equations of the conformal invariance are gained. Then the Hojman conserved quantities of conformal invariance by special infinitesimal transformations are obtained. Finally an illustrative example is given to verify the results.

A third-order asymptotic solution of nonlinear standing water waves in Lagrangian coordinates

Chen Yang-Yih, Hsu Hung-Chu
Chin. Phys. B, 2009, 18 (3): 861-871 doi: 10.1088/1674-1056/18/3/004
Full Text: [PDF 324 KB] (Downloads:668)
Show Abstract
Asymptotic solutions up to third-order which describe irrotational finite amplitude standing waves are derived in Lagrangian coordinates. The analytical Lagrangian solution that is uniformly valid for large times satisfies the irrotational condition and the pressure p=0 at the free surface, which is in contrast with the Eulerian solution existing under a residual pressure at the free surface due to Taylor's series expansion. In the third-order Lagrangian approximation, the explicit parametric equation and the Lagrangian wave frequency of water particles could be obtained. In particular, the Lagrangian mean level of a particle motion that is a function of vertical label is found as a part of the solution which is different from that in an Eulerian description. The dynamic properties of nonlinear standing waves in water of a finite depth, including particle trajectory, surface profile and wave pressure are investigated. It is also shown that the Lagrangian solution is superior to an Eulerian solution of the same order for describing the wave shape and the kinematics above the mean water level.

Spatiotemporal multiple coherence resonances and calcium waves in a coupled hepatocyte system

Wang Bao-Hua, Lu Qi-Shao, Lü Shu-Juan, Lang Xiu-Feng
Chin. Phys. B, 2009, 18 (3): 872-880 doi: 10.1088/1674-1056/18/3/005
Full Text: [PDF 703 KB] (Downloads:634)
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Spatiotemporal multiple coherence resonances for calcium activities induced by weak Gaussian white noise in coupled hepatocytes are studied. It is shown that bi-resonances in hepatocytes are induced by the interplay and competition between noise and coupling of cells, in other words, the cell in network can be excited either by noise or by its neighbour via gap junction which can transfer calcium ions between cells. Furthermore, the intercellular annular calcium waves induced by noise are observed, in which the wave length decreases with noise intensity augmenting but increases monotonically with coupling strength increasing. And for a fixed noise level, there is an optimal coupling strength that makes the coherence resonance reach maximum.

The strain relaxation of InAs/GaAs self-organized quantum dot

Liu Yu-Min, Yu Zhong-Yuan, Ren Xiao-Min
Chin. Phys. B, 2009, 18 (3): 881-887 doi: 10.1088/1674-1056/18/3/006
Full Text: [PDF 1298 KB] (Downloads:874)
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This paper presents a detailed analysis of the dependence of degree of strain relaxation of the self-organized InAs/GaAs quantum dot on the geometrical parameters. Differently shaped quantum dots arranged with different transverse periods are simulated in this analysis. It investigates the total residual strain energy that stored in the quantum dot and the substrate for all kinds of quantum dots with the same volume, as well as the dependence on both the aspect ratio and transverse period. The calculated results show that when the transverse period is larger than two times the base of the quantum dots, the influence of transverse periods can be ignored. The larger aspect ratio will lead more efficient strain relaxation. The larger angle between the faces and the substrate will lead more efficient strain relaxation. The obtained results can help to understand the shape transition mechanism during the epitaxial growth from the viewpoint of energy, because the strain relaxation is the main driving force of the quantum dot's self-organization.

The influences of dipole--dipole interaction and detuning on the sudden death of entanglement between two atoms in the Tavis--Cummings model

Chen Li, Shao Xiao-Qiang, Zhang Shou
Chin. Phys. B, 2009, 18 (3): 888-893 doi: 10.1088/1674-1056/18/3/007
Full Text: [PDF 187 KB] (Downloads:992)
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The influences of dipole--dipole interaction and detuning on the entanglement between two atoms with different initial tripartite entangled W-like states in the Tavis--Cummings model have been investigated by means of Wootters' concurrence, respectively. The results show that the entanglement between the two atoms can be enhanced via appropriately tuning the strength of dipole--dipole interaction of two atoms or the detunings between atom and cavity, and the so-called sudden death effect can be weakened simultaneously.

A scheme for implementing quantum game in cavity QED

Cao Shuai, Fang Mao-Fa, Liu Jian-Bin, Wang Xin-Wen, Zheng Xiao-Juan
Chin. Phys. B, 2009, 18 (3): 894-897 doi: 10.1088/1674-1056/18/3/008
Full Text: [PDF 116 KB] (Downloads:794)
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In this paper, we propose a scheme for implementing quantum game (QG) in cavity quantum electrodynamics(QED). In the scheme, the cavity is only virtually excited and thus the proposal is insensitive to the cavity fields states and cavity decay. So our proposal can be experimentally realized in the range of current cavity QED techniques.

Theoretical analysis of quantum game in cavity QED

Cao Shuai, Fang Mao-Fa, Liu Jian-Bin, Wang Xin-Wen, Zheng Xiao-Juan, Li Hai
Chin. Phys. B, 2009, 18 (3): 898-901 doi: 10.1088/1674-1056/18/3/009
Full Text: [PDF 119 KB] (Downloads:718)
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Recent years, several ways of implementing quantum games in different physical systems have been presented. In this paper, we perform a theoretical analysis of an experimentally feasible way to implement a two player quantum game in cavity quantum electrodynamic(QED). In the scheme, the atoms interact simultaneously with a highly detuned cavity mode with the assistance of a classical field. So the scheme is insensitive to the influence from the cavity decay and the thermal field, and it does not require the cavity to remain in the vacuum state throughout the procedure.

Wigner function of the thermo number states

Hu Li-Yun, Fan Hong-Yi
Chin. Phys. B, 2009, 18 (3): 902-909 doi: 10.1088/1674-1056/18/3/010
Full Text: [PDF 1792 KB] (Downloads:790)
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Based on thermo field dynamics (TFD) and using the thermo Wigner operator in the thermo entangled state representation we derive the Wigner function of number states at finite temperature (named thermo number states). The figure of Wigner function shows that its shape gets smoothed as the temperature rises, implying that the quantum noise becomes larger.

Scheme for realizing quantum computation and quantum information transfer with superconducting qubits coupling to a 1D transmission line resonator

Shi Zhen-Gang, Chen Xiong-Wen, Zhu Xi-Xiang, Song Ke-Hui
Chin. Phys. B, 2009, 18 (3): 910-914 doi: 10.1088/1674-1056/18/3/011
Full Text: [PDF 158 KB] (Downloads:787)
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This paper proposes a simple scheme for realizing one-qubit and two-qubit quantum gates as well as multiqubit entanglement based on dc-SQUID charge qubits through the control of their coupling to a 1D transmission line resonator (TLR). The TLR behaves effectively as a quantum data-bus mode of a harmonic oscillator, which has several practical advantages including strong coupling strength, reproducibility, immunity to 1/f noise, and suppressed spontaneous emission. In this protocol, the data-bus does not need to stay adiabatically in its ground state, which results in not only fast quantum operation, but also high-fidelity quantum information processing. Also, it elaborates the transfer process with the 1D transmission line.

Analysis of the differential-phase-shift-keying protocol in the quantum-key-distribution system

Jiao Rong-Zhen, Feng Chen-Xu, Ma Hai-Qiang
Chin. Phys. B, 2009, 18 (3): 915-917 doi: 10.1088/1674-1056/18/3/012
Full Text: [PDF 268 KB] (Downloads:1091)
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The analysis is based on the error rate and the secure communication rate as functions of distance for three quantum-key-distribution (QKD) protocols: the Bennett--Brassard 1984, the Bennett--Brassard--Mermin 1992, and the coherent differential-phase-shift keying (DPSK) protocols. We consider the secure communication rate of the DPSK protocol against an arbitrary individual attack, including the most commonly considered intercept-resend and photon-number splitting attacks, and concluded that the simple and efficient differential-phase-shift-keying protocol allows for more than 200 km of secure communication distance with high communication rates.

New approach for analysing master equations of generalized phase diffusion models in the entangled state representation

Xu Xing-Lei, Li Hong-Qi, Fan Hong-Yi
Chin. Phys. B, 2009, 18 (3): 918-921 doi: 10.1088/1674-1056/18/3/013
Full Text: [PDF 97 KB] (Downloads:629)
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By virtue of the well-behaved properties of the bipartite entangled states representation, this paper analyse and solves some master equations for generalized phase diffusion models, which seems concise and effective. This method can also be applied to solve other master equations.

Noise in a coupling electromagnetic detecting system for high frequency gravitational waves

Li Jin, Li Fang-Yu, Zhong Yuan-Hong
Chin. Phys. B, 2009, 18 (3): 922-926 doi: 10.1088/1674-1056/18/3/014
Full Text: [PDF 129 KB] (Downloads:683)
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This paper discusses the basic categories of noise in detecting high frequency gravitational waves in the microwave band (~0.1--10 GHz), which contain shot noise from the laser and the thermal radiation photons, thermal noise from statistical fluctuation of the thermal photons and fluctuation of the temperature, radiation press noise on the fractal membrane, the noise caused by the scattering of the Gaussian Beam (GB) in the detecting tube and noise in the microwave radiometers. The analysis shows that a reasonable signal-to-noise ratio may be achieved for a detecting device with the fixed power of GB (105 W), only when the temperature of the environment is no more than T=1 K, and the optimal length of the microwave radiometers is about 0.3 m.

Reversible Carnot cycle outside a black hole

Deng Xi-Hao, Gao Si-Jie
Chin. Phys. B, 2009, 18 (3): 927-932 doi: 10.1088/1674-1056/18/3/015
Full Text: [PDF 136 KB] (Downloads:637)
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A Carnot cycle outside a Schwarzschild black hole is investigated in detail. We propose a reversible Carnot cycle with a black hole being the cold reservoir. In our model, a Carnot engine operates between a hot reservoir with temperature T1 and a black hole with Hawking temperature TH. By naturally extending the ordinary Carnot cycle to the black hole system, we show that the thermal efficiency for a reversible process can reach the maximal efficiency 1-TH/T1. Consequently, black holes can be used to determine the thermodynamic temperature by means of the Carnot cycle. The role of the atmosphere around the black hole is discussed. We show that the thermal atmosphere provides a necessary mechanism to make the process reversible.

Generating weighted community networks based on local events

Xu Qi-Xin, Xu Xin-Jian
Chin. Phys. B, 2009, 18 (3): 933-938 doi: 10.1088/1674-1056/18/3/016
Full Text: [PDF 339 KB] (Downloads:609)
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Many realistic networks have community structures, namely, a network consists of groups of nodes within which links are dense but among which links are sparse. This paper proposes a growing network model based on local processes, the addition of new nodes intra-community and new links intra- or inter-community. Also, it utilizes the preferential attachment for building connections determined by nodes' strengths, which evolves dynamically during the growth of the system. The resulting network reflects the intrinsic community structure with generalized power-law distributions of nodes' degrees and strengths.

Controlling the motion of solitons in BEC by a weakly periodic potential

Xi Yu-Dong, Wang Deng-Long, He Zhang-Ming, Ding Jian-Wen
Chin. Phys. B, 2009, 18 (3): 939-945 doi: 10.1088/1674-1056/18/3/017
Full Text: [PDF 485 KB] (Downloads:801)
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By developing multiple-scale method combined with Wentzel--Kramer--Brillouin expansion, this paper analytically studies the modulating effect of weakly periodic potential on the dynamical properties of the Bose--Einstein condensates (BEC) trapped in harmonic magnetic traps. A black--grey soliton transition is observed in the BEC trapped in harmonic magnetic potential, due to the weakly periodic potential modulating effect. Meanwhile, it finds that with the slight increase of the weakly periodic potential strength, the velocity of the soliton decreases, while its width firstly decreases then increases, a minimum exists there. These results show that the amplitude, velocity, and width of matter solitons can be effectively managed by means of a weakly periodic potential.

Effects of time delay on stochastic resonance of a periodically driven linear system with multiplicative and periodically modulated additive white noises

Du Lu-Chun, Mei Dong-Cheng
Chin. Phys. B, 2009, 18 (3): 946-951 doi: 10.1088/1674-1056/18/3/018
Full Text: [PDF 152 KB] (Downloads:749)
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Stochastic resonance (SR) of a periodically driven time-delayed linear system with multiplicative white noise and periodically modulated additive white noise is investigated. In the condition of small delay time, an approximate analytical expression of output signal-to-noise ratio (SNR) is obtained. The analytical results indicate that (1) there exists a resonance peak in the curve for SNR versus time delay; (2) the time delay will suspend the SR dramatically for SNR versus other parameters of the system, such as noise intensity, correlation intensity, and signal frequency, once a certain value is reached, the SR phenomenon disappears.

Stochastic resonance in a single-mode laser driven by frequency modulated signal and coloured noises

Jin Guo-Xiang, Zhang Liang-Ying, Cao Li
Chin. Phys. B, 2009, 18 (3): 952-957 doi: 10.1088/1674-1056/18/3/019
Full Text: [PDF 479 KB] (Downloads:808)
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By adding frequency modulated signals to the intensity equation of gain--noise model of the single-mode laser driven by two coloured noises which are correlated, this paper uses the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity. The results show that the SNR appears typical stochastic resonance with the variation of intensity of the pump noise and quantum noise. As the amplitude of a modulated signal has effects on the SNR, it shows suppression, monotone increasing, stochastic resonance, and multiple stochastic resonance with the variation of the frequency of a carrier signal and modulated signal.

Regular nonlinear response of the driven Duffing oscillator to chaotic time series

Yuan Ye, Li Yue, Danilo P. Mandic, Yang Bao-Jun
Chin. Phys. B, 2009, 18 (3): 958-968 doi: 10.1088/1674-1056/18/3/020
Full Text: [PDF 408 KB] (Downloads:1279)
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Nonlinear response of the driven Duffing oscillator to periodic or quasi-periodic signals has been well studied. In this paper, we investigate the nonlinear response of the driven Duffing oscillator to non-periodic, more specifically, chaotic time series. Through numerical simulations, we find that the driven Duffing oscillator can also show regular nonlinear response to the chaotic time series with different degree of chaos as generated by the same chaotic series generating model, and there exists a relationship between the state of the driven Duffing oscillator and the chaoticity of the input signal of the driven Duffing oscillator. One real-world and two artificial chaotic time series are used to verify the new feature of Duffing oscillator. A potential application of the new feature of Duffing oscillator is also indicated.

An improved impulsive control approach to nonlinear systems with time-varying delays

Zhang Hua-Guang, Fu Jie, Ma Tie-Dong, Tong Shao-Cheng
Chin. Phys. B, 2009, 18 (3): 969-974 doi: 10.1088/1674-1056/18/3/021
Full Text: [PDF 193 KB] (Downloads:694)
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A scheme for the impulsive control of nonlinear systems with time-varying delays is investigated in this paper. Based on the Lyapunov-like stability theorem for impulsive functional differential equations (FDEs), some sufficient conditions are presented to guarantee the uniform asymptotic stability of impulsively controlled nonlinear systems with time-varying delays. These conditions are more effective and less conservative than those obtained. Finally, two numerical examples are provided to demonstrate the effectiveness of the proposed method.

A new car-following model with consideration of the traffic interruption probability

Tang Tie-Qiao, Huang Hai-Jun, Wong S. C., Jiang Rui
Chin. Phys. B, 2009, 18 (3): 975-983 doi: 10.1088/1674-1056/18/3/022
Full Text: [PDF 865 KB] (Downloads:1097)
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In this paper, we present a new car-following model by taking into account the effects of the traffic interruption probability on the car-following behaviour of the following vehicle. The stability condition of the model is obtained by using the linear stability theory. The modified Korteweg--de Vries (KdV) equation is constructed and solved, and three types of traffic flows in the headway sensitivity space---stable, metastable, and unstable---are classified. Both the analytical and simulation results show that the traffic interruption probability indeed has an influence on driving behaviour, and the consideration of traffic interruption probability in the car-following model could stabilize traffic flow.

Performance characteristics of an energy selective electron refrigerator with double resonances

Wang Xiao-Min, He Ji-Zhou, Tang Wei
Chin. Phys. B, 2009, 18 (3): 984-991 doi: 10.1088/1674-1056/18/3/023
Full Text: [PDF 831 KB] (Downloads:597)
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This paper establishes the energy selective electron (ESE) engine with double resonances as a refrigerator in one dimensional (1D) system. It consists of two infinitely large electron reservoirs with different temperatures and chemical potentials, and they are perfectly thermally insulated from each other and interaction only via a double `idealized energy filter' whose widths are all finite. Taking advantage of the density of state and Fermi distribution in the 1D system, the heat flux into each reservoir may then be calculated. Moreover, the coefficient of performance may be derived from the expressions for the heat flux into the hot and cold reservoirs. The performance characteristic curves are plotted by numerical analysis. The influences of the resonances widths, the energy position of resonance and the space of two resonances on performance of the ESE refrigerator are discussed. The results obtained here have theoretical significance for the understanding of thermodynamic performance of the micro--nano devices.

Tolerance of edge cascades with coupled map lattices methods

Cui Di, Gao Zi-You, Zheng Jian-Feng
Chin. Phys. B, 2009, 18 (3): 992-996 doi: 10.1088/1674-1056/18/3/024
Full Text: [PDF 279 KB] (Downloads:654)
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This paper studies the cascading failure on random networks and scale-free networks by introducing the tolerance parameter of edge based on the coupled map lattices methods. The whole work focuses on investigating some indices including the number of failed edges, dynamic edge tolerance capacity and the perturbation of edge. In general, it assumes that the perturbation is attributed to the normal distribution in adopted simulations. By investigating the effectiveness of edge tolerance in scale-free and random networks, it finds that the larger tolerance parameter λ can more efficiently delay the cascading failure process for scale-free networks than random networks. These results indicate that the cascading failure process can be effectively controlled by increasing the tolerance parameter λ. Moreover, the simulations also show that, larger variance of perturbation can easily trigger the cascading failures than the smaller one. This study may be useful for evaluating efficiency of whole traffic systems, and for alleviating cascading failure in such systems.

Fabrication of grating-like polystyrene latex monolayer structure as three-dimensional calibration standards for scanning probe microscope

Zhu Guo-Dong, Zeng Zhi-Gang, Guo Zhang, Du Qiang-Guo, Yan Xue-Jian
Chin. Phys. B, 2009, 18 (3): 997-1001 doi: 10.1088/1674-1056/18/3/025
Full Text: [PDF 1221 KB] (Downloads:423)
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This paper illuminates the preparation of grating-like polystyrene latex monolayer structure, which can minimize the effects of the size deviation of spheres and the defect transfer on the accuracy as calibration samples for microscopes. The latex films are grown on freshly cleaved mica substrates by vertical deposition method. The concentration dependence of the structure and the topography of latex films is characterized by optical microscope, ultraviolet--visible transmission spectrum and scanning probe microscope. The origination of such a grating-like structure is also discussed.
NUCLEAR PHYSICS

Judd--Oflet analysis of spectrum and laser performance of Ho:YAP crystal end-pumped by 1.91-μm Tm:YLF laser

Yao Bao-Quan, Zheng Liang-Liang, Yang Xiao-Tao, Wang Tian-Heng, Duan Xiao-Ming, Zhao Guang-Jun, Dong Qin
Chin. Phys. B, 2009, 18 (3): 1009-1013 doi: 10.1088/1674-1056/18/3/027
Full Text: [PDF 458 KB] (Downloads:989)
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The Ho:YAP crystal is grown by the Czochralski technique. The room-temperature polarized absorption spectra of Ho:YAP crystal was measured on a c-cut sample with 1 at% holmium. According to the obtained Judd--Ofelt intensity parameters Ω2=1.42× 1020 cm2, Ω4=2.92× 1020 cm2, and Ω 6=1.71× 1020 cm2, this paper calculated the fluorescence lifetime to be 6 ms for 5I75I8 transition, and the integrated emission cross section to be 2.24× 10-18 cm2. It investigates the room-temperature Ho:YAP laser end-pumped by a 1.91-μm Tm:YLF laser. The maximum output power was 4.1 W when the incident 1.91-μm pump power was 14.4 W. The slope efficiency is 40.8%, corresponding to an optical-to-optical conversion efficiency of 28.4%. The Ho:YAP output wavelength was centred at 2118 nm with full width at half maximum of about 0.8 nm.
CLASSICAL AREAS OF PHENOMENOLOGY

The design of metamaterial cloaks embedded in anisotropic medium

Ma Hua, Qu Shao-Bo, Xu Zhuo, Zhang Jie-Qiu, Wang Jia-Fu
Chin. Phys. B, 2009, 18 (3): 1025-1028 doi: 10.1088/1674-1056/18/3/030
Full Text: [PDF 694 KB] (Downloads:756)
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By using coordinate transformation method, this paper obtains an useful equation of designing meta-material cloaks embedded in anisotropic medium. This equation is the generalization of what was introduced early by Pendry et al (2006 \textit{Science} {312 1780) and can be more widely used. As an example of its applications, this paper deduces the material parameter equation for cylinder cloaks embedded in anisotropic medium, and then offers the numerical simulation. The results show that such a cylinder cloak has perfect cloaking performance and therefore verifies the method proposed in this paper.

Surface plasmon resonance transmission filters at 1053nm based on metallic grating with narrow slit

Ma Jian-Yong, Xu Cheng, Liu Shi-Jie, Zhang Da-Wei, Jin Yun-Xia, Fan Zheng-Xiu, Shao Jian-Da
Chin. Phys. B, 2009, 18 (3): 1029-1032 doi: 10.1088/1674-1056/18/3/031
Full Text: [PDF 468 KB] (Downloads:590)
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Metallic gratings with narrow slits can lead to special optical properties such as strongly enhancing the transmission and considerably strengthening the polarized effect. A narrow-band filter suitable for application in optical communication is designed by sandwiching a metallic grating between two identical dielectric films. The maximum transmission can reach 96% after optimizing the parameters of films and grating at a central wavelength of 1053 nm. It is the first time, to our knowledge, that such high transmission has been reported since the discovery of the extraordinarily high transmission through periodic holes or slits; moreover, the extremely polarized effect is also found in P mode of this symmetric grating.

Propagation of Gauss--Bessel beams in turbulent atmosphere

Chen Bao-Suan, Pu Ji-Xiong
Chin. Phys. B, 2009, 18 (3): 1033-1039 doi: 10.1088/1674-1056/18/3/032
Full Text: [PDF 2018 KB] (Downloads:794)
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This paper studies the propagation properties of Gauss--Bessel beams in a turbulent atmosphere. Based on the extended Huygens--Fresnel principle, it derives the intensity distribution expression for such beams propagating in a turbulent atmosphere. Then the influence of turbulence and source beam parameters on the beam propagation is studied in great detail. It finds that the intensity distribution of Gauss--Bessel beams will change into Gaussian profile in a turbulent atmosphere, and that stronger turbulence and smaller topological charges will lead to a faster changing.

Light scattering by a spherical particle with multiple densely packed inclusions

Sun Xian-Ming, Wang Hai-Hua, Liu Wan-Qiang, Shen Jin
Chin. Phys. B, 2009, 18 (3): 1040-1044 doi: 10.1088/1674-1056/18/3/033
Full Text: [PDF 129 KB] (Downloads:802)
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This paper calculates light scattering by a spherical water particle containing densely packed inclusions at a visible wavelength 0.55 \mum by a combination of ray-tracing and Monte Carlo techniques. While the individual reflection and refraction events at the outer boundary of a sphere particle are considered by a ray-tracing program, the Monte Carlo routine simulates internal scattering processes. The main advantage of this method is that the shape of the particle can be arbitrary, and multiple scattering can be considered in the internal scattering processes. A dense-medium light-scattering theory based on the introduction of the static structure factor is used to calculate the phase function and asymmetry parameters for densely packed inclusions. Numerical results of the single scattering characteristics for a sphere containing multiple densely packed inclusions are given.

Deterministic generation of entangled coherent states for two atomic samples

Lu Dao-Ming, Zheng Shi-Biao
Chin. Phys. B, 2009, 18 (3): 1045-1048 doi: 10.1088/1674-1056/18/3/034
Full Text: [PDF 141 KB] (Downloads:600)
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This paper proposes an efficient scheme for deterministic generation of entangled coherent states for two atomic samples. In the scheme two collections of atoms are trapped in an optical cavity and driven by a classical field. Under certain conditions the two atomic samples evolve from an coherent state to an entangled coherent state. During the interaction the cavity mode is always in the vacuum state and the atoms have no probability of being populated in the excited state. Thus, the scheme is insensitive to both the cavity decay and atomic spontaneous emission.

Generation of Schr?dinger cat state of a single trapped cold ion

Zhang Miao, Jia Huan-Yu, Ji Xiao-Hui, Si Kun
Chin. Phys. B, 2009, 18 (3): 1049-1053 doi: 10.1088/1674-1056/18/3/035
Full Text: [PDF 295 KB] (Downloads:508)
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The fidelity of the generated Schr?dinger Cat state (SCS) of a single trapped ion in the Lamb--Dicke approximation is discussed. The results show that the fidelity significantly decreases with the values of Lamb--Dicke parameter η and coherent state amplitude α increasing. For η= 0.20 and α= 3, the typical values of experimental parameters, the fidelity is rather low (30%). A scheme for generating the SCS is proposed without making the Lamb--Dike approximation in laser--ion interaction, and the fidelity of the generated SCS is about 99% for the typical values of experimental Lamb--Dicke parameters.

Effects of relative phase on transient evolution in an open resonant ladder-type atomic system

Yang Yan-Ling, Liu Zhong-Bo, Wang Lei, Tong Dian-Min, Fan Xi-Jun
Chin. Phys. B, 2009, 18 (3): 1054-1060 doi: 10.1088/1674-1056/18/3/036
Full Text: [PDF 209 KB] (Downloads:544)
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In an open ladder-type resonant atomic system, variation in relative phase between probe and driving fields does not affect the transient evolution of populations, but it has remarkable effects on gain and dispersion of the probe field. No matter whether an incoherent pump is present or absent, transient and stationary gains without inversion (GWI) always can be obtained by choosing an appropriate value of the relative phase. When the incoherent pump is absent,the values of transient and stationary GWIs are much larger and the time interval required to reach the stationary value is longer than those when the incoherent pump is present. Varying the exit rate and the ratio between injection rates can obviously change the phase-dependent GWI. In addition, in the transient evolution process, the phenomenon of high dispersion (refractive index) without absorption occurs at some values of relative phase. In the corresponding closed system, the stationary GWI can be obtained by choosing an appropriate value of relative phase only when incoherent pump exists, moreover the gain is smaller than that in the open system.

New approach for deriving density operator for describing continuum photodetection process

Fan Hong-Yi, Hu Li-Yun
Chin. Phys. B, 2009, 18 (3): 1061-1064 doi: 10.1088/1674-1056/18/3/037
Full Text: [PDF 97 KB] (Downloads:508)
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By introducing the two-mode entangled state representation <η| whose one mode is a fictitious one accompanying the system mode, this paper presents a new approach for deriving density operator for describing continuum photodetection process.

Four-mode continuous-variables entangled state: generation from beam splitter, a parametric down-conversion and a polarizer

Kuang Mai-Hua, Ma Shan-Jun, Liu Dong-Mei, Wang Shu-Jing
Chin. Phys. B, 2009, 18 (3): 1065-1071 doi: 10.1088/1674-1056/18/3/038
Full Text: [PDF 133 KB] (Downloads:596)
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We introduce a new kind of four-mode continuous variable entangled state in Fock space. The completeness relation and the partly nonorthonormal property of such a state are proven. The scheme to generate this state is presented by combining a symmetrical beamsplitter, a parametric down-conversion and a polarizer. After making a single-mode quadrature amplitude measurement, the remaining three modes are kept in entanglement. And its applications are also discussed.

Optical bistability and multistability in a three-level Δ-type atomic system under the nonresonant condition

Chen Ai-Xi, Wang Zhi-Ping, Chen De-Hai, Xu Yan-Qiu
Chin. Phys. B, 2009, 18 (3): 1072-1076 doi: 10.1088/1674-1056/18/3/039
Full Text: [PDF 152 KB] (Downloads:661)
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Under a nonresonant condition, we theoretically investigate hybrid absorptive-dispersive optical bistability and multistability behaviours in a three-level Δ-type system by using a microwave field to drive a hyperfine transition between two upper excited states inside a unidirectional ring cavity. We find that the optical bistability and multistability behaviours can be controlled by adjusting the intensity of the microwave field or the intensity of the coherent coupling field. Furthermore, our studies show an interesting phenomenon of the transition from the optical bistability to the optical multistability only by changing the negative detuning of the coupling field into the positive detuning of the coupling field.

Simultaneous all-solid-state multi-wavelength lasers --- a promising pump source for generating highly coherent terahertz waves Hot!

Liu Huan, Xu De-Gang, Yao Jian-Quan
Chin. Phys. B, 2009, 18 (3): 1077-1084 doi: 10.1088/1674-1056/18/3/040
Full Text: [PDF 1109 KB] (Downloads:811)
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A diode-end-pumped Nd:YAG dual-wavelength laser operating at 1319 and 1338 nm is demonstrated. The maximum average output power of the quasi-continuous wave linearly polarized dual-wavelength laser is obtained to be 2.1 W at a repetition rate of 50 kHz with an output power instability of less than 0.38% and beam quality factor M2 of 1.45. Using the two lines, the highly coherent and narrow linewidth terahertz radiation of 3.23 THz can be generated in an organic 4-N, N-dimethylamino--methyl-stilbazolium tosylate (DAST) crystal. Meanwhile, the multi-wavelength red laser at 659.5, 664 and 669 nm is generated by frequency doubling and sum frequency processes in a lithium triborate (LBO) crystal. The average red laser output power is enhanced up to 1.625 W at a repetition rate of 15 kHz with an output power instability of better than 0.53% and beam quality factor M2 of 6.05. Using the three lines, it is possible to generate the multi-wavelength THz radiation of 3.3, 3.43 and 6.73 THz in an appropriate difference frequency crystal.

Simulation study on terahertz vibrational absorption in liquid crystal compounds

Ma Heng, Shi De-Heng, He Jun, Peng Yu-Feng
Chin. Phys. B, 2009, 18 (3): 1085-1088 doi: 10.1088/1674-1056/18/3/041
Full Text: [PDF 397 KB] (Downloads:626)
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The terahertz (THz) spectrum absorptions of nematic liquid crystal (LC) material, i.e. N-(p-methoxybenzylidene)-p-butylaniline (MBBA), and its relevant compounds are simulated in this paper by using the density functional theory (DFT) method. A strong absorptive frequency is located at 3.65 THz for the MBBA, which is in agreement with experimental data found in the literature. The result suggests that the DFT method is effective for dealing with the anisotropic nematic LC compounds.

Thermal stability test and analysis of a 20-actuator bimorph deformable mirror

Ning Yu, Zhou Hong, Yu Hao, Rao Chang-Hui, Jiang Wen-Han
Chin. Phys. B, 2009, 18 (3): 1089-1095 doi: 10.1088/1674-1056/18/3/042
Full Text: [PDF 1650 KB] (Downloads:805)
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One of the important characteristic of adaptive mirrors is the thermal stability of surface flatness. In this paper, the thermal stability from 13℃ to 25℃ of a 20-actuator bimorph deformable mirror is tested by a Shack--Hartmann wavefront sensor. Experimental results show that, the surface P--V of bimorph increases nearly linearly with ambient temperature. The ratio is 0.11μm/℃ and the major component of surface displacement is defocused, compared with which, astigmatism, coma and spherical aberration contribute very small. Besides, a finite element model is built up to analyse the influence of thickness, thermal expansion coefficient and Young's modulus of materials on thermal stability. Calculated results show that bimorph has the best thermal stability when the materials have the same thermal expansion coefficient. And when the thickness ratio of glass to PZT is 3 and Young's modulus ratio is approximately 0.4, the surface instability behaviour of the bimorph manifests itself most severely.

Modeling of graded index waveguide fabricated by ion exchange on Er3+ doped glass

Shao Gong-Wang, Jin Guo-Liang
Chin. Phys. B, 2009, 18 (3): 1096-1104 doi: 10.1088/1674-1056/18/3/043
Full Text: [PDF 2187 KB] (Downloads:708)
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A general numerical tool, based on thermal diffusion equation and full-vectorial eigen-mode equation, has been presented for the systematic analysis of graded index channel waveguide fabricated by ion exchange on Er3+ doped glass. Finite difference method with full-vectorial formulation (FV-FDM) is applied to solving the full-vectorial modes of graded index channel waveguide for the first time. The coupled difference equations based on magnetic fields in FV-FDM are derived from the Taylor series expansion and accurate formulation of boundary conditions. Hybrid nature of vectorial guided modes for both pump (980 nm) and signal light (1550 nm) are demonstrated by the simulation. Results show that the fabrication parameters of ion exchange, such as channel opening width and time ratio of second step to first step in ion exchange, have large influence on the properties of waveguide. By optimizing the fabrication parameters, maintenance of monomode for signal light and improvement of the gain dynamics can be achieved in Er3+ doped waveguide amplifier (EDWA) fabricated by ion exchange technique. This theoretical model is significant for the design and fabrication of EDWA with ion exchange technique. Furthermore, a single polarization EDWA, which operates at wavelength from 1528 nm to 1541 nm for HE polarization, is numerically designed.

Generation of 10fs Ti:sapphire laser at repetition rate of 525MHz and measurement of carrier-envelope phase frequency Hot!

Zhang Wei, Han Hai-Nian, Teng Hao, Wei Zhi-Yi
Chin. Phys. B, 2009, 18 (3): 1105-1108 doi: 10.1088/1674-1056/18/3/044
Full Text: [PDF 435 KB] (Downloads:543)
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This paper presents a Kerr-lens mode-locked Ti:sapphire laser at the repetition rate of 525 MHz, stable laser pulse as short as 10 fs with average output power of 480 mW is obtained. By injecting the pulse into photonics crystal fibre, octave-spanning spectrum covered from 500 to 1050 nm is generated, carrier-envelope phase frequency with signal-to-noise ratio of 31dB is measured, which paves the way for the generation of a compact frequency comb.

Lateral stress-induced propagation characteristics in photonic crystal fibres

Tian Hong-Da, Yu Zhong-Yuan, Han Li-Hong, Liu Yu-Min
Chin. Phys. B, 2009, 18 (3): 1109-1115 doi: 10.1088/1674-1056/18/3/045
Full Text: [PDF 365 KB] (Downloads:697)
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Using the finite element method, this paper investigates lateral stress-induced propagation characteristics in a photonic crystal fibre of hexagonal symmetry. The results of simulation show the strong stress dependence of effective index of the fundamental guided mode, phase modal birefringence and confinement loss. It also finds that the contribution of the geometrical effect that is related only to deformation of the photonic crystal fibre and the stress-related contribution to phase modal birefringence and confinement loss are entirely different. Furthermore, polarization-dependent stress sensitivity of confinement loss is proposed in this paper.

Zero dispersion wavelength and dispersion slope control of hollow-core photonic bandgap fibres

Zhang Hu, Yang Bo-Jun, Liu Yu-Min, Wang Qiu-Guo, Yu Li, Zhang Xiao-Guang
Chin. Phys. B, 2009, 18 (3): 1116-1122 doi: 10.1088/1674-1056/18/3/046
Full Text: [PDF 255 KB] (Downloads:632)
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This paper investigates the zero dispersion wavelength and dispersion slope control of hollow-core photonic bandgap fibres (PBGFs) by using a full-vector finite element method. By simulation we found that theoretically the zero dispersion wavelength can be tailored by respectively changing the rounded diameter of air holes, pitch, refractive index, normalized thickness of core rings, and hole diameter to pitch ratio. At the same time the tailoring of dispersion slope can also be realized by changing the rounded diameter of air holes or pitch or normalized thickness of core rings. To illustrate the reasonability of fibre designs, this paper also gives the variance of normalized interface field intensity which measures the scattering loss relatively versus wavelength for different designs. From the viewpoint of loss, varying the rounded diameter and the thickness of core ring could shift zero wavelength but it is difficult to get the required parameters within so tiny range in practical drawing of PBGFs, on the other hand, it is possible in practice to respectively alter the pitch and refractive index to shift zero wavelength. But varying hole diameter to pitch ratio is not worthwhile because they each induce large increase of loss and narrowness of transmission bandwidth. The zero dispersion wavelength can be engineered by respectively varying the rounded diameter of air holes, pitch, refractive index, and normalized thickness of core rings without incurring large loss penalties.

Acoustic elliptical cylindrical cloaks

Ma Hua, Qu Shao-Bo, Xu Zhuo, Wang Jia-Fu
Chin. Phys. B, 2009, 18 (3): 1123-1126 doi: 10.1088/1674-1056/18/3/047
Full Text: [PDF 401 KB] (Downloads:640)
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By making a comparison between the acoustic equations and the 2-dimensional (2D) Maxwell equations, we obtain the material parameter equations (MPE) for acoustic elliptical cylindrical cloaks. Both the theoretical results and the numerical results indicate that an elliptical cylindrical cloak can realize perfect acoustic invisibility when the spatial distributions of mass density and bulk modulus are exactly configured according to the proposed equations. The present work is the meaningful exploration of designing acoustic cloaks that are neither sphere nor circular cylinder in shape, and opens up possibilities for making complex and multiplex acoustic cloaks with simple models such as spheres, circular or elliptic cylinders.

The numerical study of shock-induced hydrodynamic instability and mixing

Wang Tao, Bai Jing-Song, Li Ping, Zhong Min
Chin. Phys. B, 2009, 18 (3): 1127-1135 doi: 10.1088/1674-1056/18/3/048
Full Text: [PDF 1447 KB] (Downloads:860)
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Based on multi-fluid volume fraction and piecewise parabolic method (PPM), a multi-viscosity-fluid hydrodynamic code MVPPM (Multi-Viscosity-Fluid Piecewise Parabolic Method) is developed and applied to the problems of shock-induced hydrodynamic interfacial instability and mixing. Simulations of gas/liquid interface instability show that the influences of initial perturbations on the fluid mixing zone (FMZ) growth are significant, especially at the late stages, while grids have only a slight effect on the FMZ width, when the interface is impulsively accelerated by a shock wave passing through it. A numerical study of the hydrodynamic interfacial instability and mixing of gaseous flows impacted by re-shocks is presented. It reveals that the numerical results are in good agreement with the experimental results and the mixing growth rate strongly depends on initial conditions. Ultimately, the jelly layer experiment relevant to the instability impacted by exploding is simulated. The shape of jelly interface, position of front face of jelly layer, crest and trough of perturbation versus time are given; their simulated results are in good agreement with experimental results.
ATOMIC AND MOLECULAR PHYSICS

Intensity-dependent asymmetric photoionization in few-cycle laser pulses

Zhang Xiao-Ming, Zhang Jing-Tao, Gong Qi-Huang, Xu Zhi-Zhan
Chin. Phys. B, 2009, 18 (3): 1014-1018 doi: 10.1088/1674-1056/18/3/028
Full Text: [PDF 449 KB] (Downloads:679)
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The asymmetric photoionization of atoms irradiated by intense, few-cycle laser pulses is studied numerically. The results show that the pulse intensity affects the asymmetric photoionization in three aspects. First, at higher intensities, the asymmetry becomes distinctive for few-cycle pulses of longer durations. Second, as the laser intensity increases, the maximal asymmetry first decreases then increases after it has reached a minimal value. Last, the value of the carrier-envelope phase corresponding to the maximal asymmetry varies with the pulse intensity. This study reveals that the increasing of pulse intensity is helpful for observing the asymmetric photoionization.

Scattering properties of the ultracold 133Cs2 triplet state

Sun Jin-Feng, Du Bing-Ge, Zhang Ji-Cai, Li Wei, Zhu Zun-Lue
Chin. Phys. B, 2009, 18 (3): 1019-1024 doi: 10.1088/1674-1056/18/3/029
Full Text: [PDF 318 KB] (Downloads:659)
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The elastic scattering properties of ultracold ^{133}Cs2 triplet state are investigated in detail. We construct a potential curve of the 133Cs2 triplet state, based on the latest ab initio molecular potential data and show how the scattering parameters are obtained by using three methods: the Numerov method, the semiclassical method and the variable phase method, where the scattering lengths of the 133Cs2 triplet state, i.e. 301.79a0, 300.67a0 and 310.81a0 are obtained respectively, with a0 being the Bohr radius. We also calculate the effective range and the number of bound states for the 133Cs2 triplet state. Our results are in agreement with the recent experimental data and the theoretical calculations. This confirms that the results of the scattering properties of the ultracold ^{133}Cs2 triplet state, calculated by using these three methods, are reliable.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Topological aspect of disclinations in two-dimensional crystals

Qi Wei-Kai, Zhu Tao, Chen Yong, Ren Ji-Rong
Chin. Phys. B, 2009, 18 (3): 1002-1008 doi: 10.1088/1674-1056/18/3/026
Full Text: [PDF 452 KB] (Downloads:958)
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By using topological current theory, this paper studies the inner topological structure of disclinations during the melting of two-dimensional systems. From two-dimensional elasticity theory, it finds that there are topological currents for topological defects in homogeneous equation. The evolution of disclinations is studied, and the branch conditions for generating, annihilating, crossing, splitting and merging of disclinations are given.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

Triggering and guiding of high voltage discharge by using femtosecond laser filaments with different parameters

Zhang Zhe, Lu Xin, Liang Wen-Xi, Hao Zuo-Qiang, Zhou Mu-Lin, Wang Zhao-Hua, Zhang Jie
Chin. Phys. B, 2009, 18 (3): 1136-1140 doi: 10.1088/1674-1056/18/3/049
Full Text: [PDF 378 KB] (Downloads:725)
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This paper demonstrates the triggering and guiding of the stationary high voltage (HV) discharges at 5--40 kV by using plasma filaments generated by femtosecond laser pulses in air. A significant reduction of the breakdown voltage threshold due to the pre-ionization of the air gap by laser filamentation is observed. The discharge experiments are performed by using laser pulses with different energy from 15--60 mJ. The electron density of filaments is detected by sonography method. The influence of the electron density of laser filaments on the triggering and guiding HV discharge is experimentally investigated. The results have shown that the behaviour of plasma filaments can strongly affect the efficiency of triggering and guiding HV discharge.

Anisotropic optical feedback of single frequency intra-cavity He--Ne laser

Zhou Lu-Fei, Zhang Bin, Zhang Shu-Lian, Tan Yi-Dong, Liu Wei-Xin
Chin. Phys. B, 2009, 18 (3): 1141-1146 doi: 10.1088/1674-1056/18/3/050
Full Text: [PDF 752 KB] (Downloads:634)
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This paper presents the anisotropic optical feedback of a single frequency intra-cavity He--Ne laser. A novel phenomenon was discovered that the laser output an elliptical polarized frequency instead of the initial linear polarized one. Two intensities with a phase difference were detected, both of which were modulated in the form of cosine wave and a fringe shift corresponds to a λ/2 movement of the feedback mirror. The phase difference can be continuously modulated by the wave plate in the external cavity. Frequency stabilization was used to stabilize the laser frequency so as to enlarge the measuring range and improve the measurement precision. This anisotropic optical feedback system offers a potential displacement measurement technology with the function of subdivision of λ/2 and in-time direction judgment. The three-mirror Fabry--Perot cavity model is used to present the experimental results. Given the lack of need of lasing adjustment, this full intra-cavity laser can significantly improve the simplicity and stability of the optical feedback system.

The propagation and deposition of fast muons in dense DT mixture

Li Xue-Mei, Shen Bai-Fei, Zhang Xiao-Mei, Jin Zhang-Ying, Wang Feng-Chao
Chin. Phys. B, 2009, 18 (3): 1147-1152 doi: 10.1088/1674-1056/18/3/051
Full Text: [PDF 165 KB] (Downloads:625)
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The propagation of the fast muon population mainly due to collisional effect in a dense deuterium--tritium (DT for short) mixture is investigated and analysed within the framework of the relativistic Fokker--Planck equation. Without the approximation that the muons propagate straightly in the DT mixture, the muon penetration length, the straggling length, and the mean transverse dispersion radius are calculated for different initial energies, and especially for different densities of the densely compressed DT mixture in our suggested muon-driven fast ignition (FI). Unlike laser-driven FI requiring super-high temperature, muons can catalyze DT fusion at lower temperatures and may generate an ignition sparkle before the self-heating fusion follows. Our calculation is important for the feasibility and the experimental study of muon-driven FI.

Electron temperature fluctuation in the HT-7 Tokamak plasma observed by electron cyclotron emission imaging

Xu Xiao-Yuan, Wang Jun, Yu Yi, Wen Yi-Zhi, Yu Chang-Xuan, Liu Wan-Dong, Wan Bao-Nian, Gao Xiang, N. C. Luhmann, C. W. Domier, Jian Wang, Z. G. Xia, Zuowei Shen
Chin. Phys. B, 2009, 18 (3): 1153-1160 doi: 10.1088/1674-1056/18/3/052
Full Text: [PDF 588 KB] (Downloads:752)
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The fluctuation of the electron temperature has been measured by using the electron cyclotron emission imaging in the Hefei Tokamak-7 (HT-7) plasma. The electron temperature fluctuation with a broadband spectrum shows that it propagates in the electron diamagnetic drift direction, and the mean poloidal wave-number \bar{k}θ is calculated to be about 1.58 cm-1, or \bar{k}θ ρs≈ 0.34. It indicates that the fluctuation should come from the electron drift wave turbulence. The linear global scaling of the electron temperature fluctuation with the gradient of electron temperature is consistent with the mixing length scale qualitatively. Evolution of spectrum of the fluctuation during the sawtooth oscillation phases is investigated, and the fluctuation is found to increase with the gradient of electron temperature increasing during most phases of the sawtooth oscillation. The results indicate that the electron temperature gradient is probably the driver of the fluctuation enhancement. The steady heat flux driven by electron temperature fluctuation is estimated and compared with the results from power balance estimation.

Painleve properties and exact solutions for the high-dimensional Schwartz Boussinesq equation

Ren Bo, Lin Ji
Chin. Phys. B, 2009, 18 (3): 1161-1167 doi: 10.1088/1674-1056/18/3/053
Full Text: [PDF 1223 KB] (Downloads:654)
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The usual (1+1)-dimensional Schwartz Boussinesq equation is extended to the (1+1)-dimensional space--time symmetric form and the general (n+1)-dimensional space--time symmetric form. These extensions are Painlevé integrable in the sense that they possess the Painlevé property. The single soliton solutions and the periodic travelling wave solutions for arbitrary dimensional space--time symmetric form are obtained by the Painlevé—B?acklund transformation.

Collision induced splitting of bright soliton in Bose--Einstein condensate

Wang Yue-Yue, Zhang Jie-Fang
Chin. Phys. B, 2009, 18 (3): 1168-1171 doi: 10.1088/1674-1056/18/3/054
Full Text: [PDF 546 KB] (Downloads:798)
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This paper studies the collision dynamics of bright soliton in Bose--Einstein condensate with trapezoid potential. It is found that besides the total reflection and total transmission, one bright soliton can be divided into two bright solitons with different amplitudes in a controllable manner.

Observation of poloidal current flowed to the vessel after failure of vertical position feedback control in EAST Tokamak

Qian Jin-Ping, Wan Bao-Nian, Shen Biao, L. L. Lao, Xiao Bing-Jia, Li Jian-Gang, Lin Shi-Yao, Luo Zheng-Ping
Chin. Phys. B, 2009, 18 (3): 1172-1176 doi: 10.1088/1674-1056/18/3/055
Full Text: [PDF 215 KB] (Downloads:534)
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Plasmas with vertically elongated cross-sections tend to be unstable to an axis-symmetric instability. This paper studies the magnetohydrodynamic equilibria in elongated plasmas after failure of vertical feedback control by using magnetic data for EAST device. Vertical forces on the vessel due to the induced polodial and toroidal currents are evaluated. The maximum force of the Fzpol in vertical displacement events for EAST designed parameters is given.

Numerical simulation of super-short pulsed discharge in Helium with particle-in-cell Monte--Carlo collisions technique

Shi Feng, Zhang Li-Li, Wang De-Zhen
Chin. Phys. B, 2009, 18 (3): 1177-1180 doi: 10.1088/1674-1056/18/3/056
Full Text: [PDF 125 KB] (Downloads:605)
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This paper reports that a simulation of glow discharge in pure helium gas at the pressure of 1.333×103 Pa under a high-voltage nanosecond pulse is performed by using a one-dimensional particle-in-cell Monte Carlo collisions (PIC--MCC) model. Numerical modelling results show that the cathode sheath is much thicker than that of anode during the pulse discharge, and that there exists the phenomenon of field reversal at relative high pressures near the end of the pulse, which results from the cumulative positive charges due to their finite mobility during the cathode sheath expansion. Moreover, electron energy distribution function (EEDF) and ion energy distribution function (IEDF) have been also observed. In the early stage of the pulse, a large amount of electrons can be accelerated above the ionization threshold energy. However, in the second half of the pulse, as the field in bulk plasma decreases and thereafter the reverse field forms due to the excessive charges in cathode sheath, although the plasma density grows, the high energy part of EEDF decreases. It concludes that the large volume non-equilibrium plasmas can be obtained with high-voltage nanosecond pulse discharges.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

Structure and bonding properties of Y doped ∑37 grain boundary in alumina

Wang Ya-Bin, Zhang Gang, Liu Ming-Jie, Chen Xiang-Long, and Chen Jun
Chin. Phys. B, 2009, 18 (3): 1181-1187 doi: 10.1088/1674-1056/18/3/057
Full Text: [PDF 525 KB] (Downloads:734)
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The microscopic structures and the bonding properties of Y-doped and undoped (01\bar {1}8)/[04\bar {4}1]/180° (∑37) grain boundaries in alumina are investigated by using \textit{ab initio} method. The formation energy of grain boundary and the segregation energy of Y to grain boundary are acquired. Electronic structures, potential distributions, bond orders and effective charges of Y-doped and undoped ∑37 GB systems are calculated. Our results reveal that the higher strength Y--O bond than Al--O bond is ascribed to the hybridization of Y(4p, 3d) with O(2s). Meanwhile, dopant Y also causes a change in potential distribution in the grain boundary region, thereby further affecting the transport property of ceramic alumina.

A novel interconnect-optimal repeater insertion model with target delay constraint in 65nm CMOS

Zhu Zhang-Ming, Qian Li-Bo, Yang Yin-Tang
Chin. Phys. B, 2009, 18 (3): 1188-1193 doi: 10.1088/1674-1056/18/3/058
Full Text: [PDF 144 KB] (Downloads:762)
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Repeater optimization is the key for SOC (System on Chip) interconnect delay design. This paper proposes a novel optimal model for minimizing power and area overhead of repeaters while meeting the target performance of on-chip interconnect lines. It also presents Lagrangian function to find the number of repeaters and their sizes required for minimizing area and power overhead with target delay constraint. Based on the 65 nanometre CMOS technology, the computed results of the intermediate and global lines show that the proposed model can significantly reduce area and power of interconnected lines, and the better performance will be achieved with the longer line. The results compared with the reference paper demonstrate the validity of this model. It can be integrated into repeater design methodology and CAD (computer aided design) tool for interconnect planning in nanometre SOC.

First-principles study of the (001) surface of cubic PbHfO3 and BaHfO3

Ni Guang-Xin, Wang Yuan-Xu
Chin. Phys. B, 2009, 18 (3): 1194-1200 doi: 10.1088/1674-1056/18/3/059
Full Text: [PDF 297 KB] (Downloads:931)
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Using first-principles techniques, we investigate the (001) surfaces of cubic PbHfO3 (PHO) and BaHfO3 (BHO) terminated with both AO (A=Pb and Ba) and HfO2. Surface structure, partial density of states, band structure, and surface energy are obtained. The BaO surface is found to be similar to its counterpart in BHO. For the HfO2-terminated surface of cubic PHO, the largest relaxation appears on the second-layer atoms but not on the first-layer ones. The analysis of the structure relaxation parameters reveals that the rumpling of the (001) surface for PHO is stronger than that for BHO. The surface thermodynamic stability is explored, and it is found that both the PbO- and the BaO-terminated surfaces are more stable than the HfO2-terminated surfaces for PHO and BHO, respectively. The surface energy calculations show that the (001) surface of PHO is more easily constructed than that of BHO.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Spin--polarized electronic properties of NiHe0.25 under pressures

San Xiao-Jiao, Liu Zhi-Ming, Ma Yan-Ming, Cui Tian, Liu Bing-Bing, Zou Guang-Tian
Chin. Phys. B, 2009, 18 (3): 1201-1206 doi: 10.1088/1674-1056/18/3/060
Full Text: [PDF 820 KB] (Downloads:838)
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This paper studies the effects of He atom on the spin-polarized electronic properties of nickel under pressures using {\it ab initio} pseudopotential plan-wave method. Under high pressures, the compound of NiHe0.25 can exist and helium-bubble can not create in Ni. A pressure-induced ferromagnetic to paramagnetic phase transition has been predicted in NiHe0.25 at about 218 GPa. It is found that under pressures, the magnetic property of Ni atoms is more strongly affected by He atom than by H atom and that the behaviour of He atom in Ni are completely different from that of H atom, like the bonding characteristics and the electron transfer.

Structural, thermodynamic and electronic properties of zinc-blende AlN from first-principles calculations

Zhang Wei, Cheng Yan, Zhu Jun, Chen Xiang-Rong
Chin. Phys. B, 2009, 18 (3): 1207-1213 doi: 10.1088/1674-1056/18/3/061
Full Text: [PDF 185 KB] (Downloads:892)
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Structural, thermodynamic and electronic properties of zinc-blende AlN under pressure are investigated by first-principles calculations based on the plane-wave basis set. Through the analysis of enthalpy variation of AlN in the zinc-blende (ZB) and the rock-salt (RS) structures with pressure, we find the phase transition of AlN from ZB to RS structure occurs at 6.7 GPa. By using the quasi-harmonic Debye model, we obtain the heat capacity CV, Debye temperature ΘD, Grüneisen parameter γ and thermal expansion coefficient α. The electronic properties including fundamental energy gaps and hydrostatic deformation potentials are investigated and the dependence of energy gaps on pressure is analysed.

State vector evolution localized over the edges of a square tight-binding lattice

He Liang-Ming, Shi Duan-Wen
Chin. Phys. B, 2009, 18 (3): 1214-1220 doi: 10.1088/1674-1056/18/3/062
Full Text: [PDF 421 KB] (Downloads:531)
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We study the time evolution of a state vector in a square tight-binding lattice, focusing on its evolution localized over the system surfaces. In this tight-binding lattice, the energy of atomic orbital centred at surface site is different from that at the interior (bulky) site by an energy shift U. It is shown that for the state vector initially localized on a surface, there exists an exponential law (y=a\ex/b+y0) determined by the absolute value of the energy shift, |U|, which describes the transition of the state evolving on the square tight-binding lattice, from delocalized over the whole lattice to localized over the surfaces.

Electrical, dielectric and surface wetting properties of multi-walled carbon nanotubes/nylon-6 nanocomposites

Long Yun-Ze, Li Meng-Meng, Sui Wan-Mei, Kong Qing-Shan, Zhang Lei
Chin. Phys. B, 2009, 18 (3): 1221-1226 doi: 10.1088/1674-1056/18/3/063
Full Text: [PDF 696 KB] (Downloads:1069)
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This paper reports that the multi-walled carbon nanotubes (MWCNT)/nylon-6 (PA6) nanocomposites with different MWCNT loadings have been prepared by a simple melt-compounding method. The electrical, dielectric, and surface wetting properties of the CNT/PA6 composites have been studied. The temperature dependence of the conductivity of the CNT/PA6 composite with 10.0wt% CNT loading (σRT~ 104S/cm) are measured, and afterwards a charge-energy-limited tunnelling model (ln σ (T) ~T-1/2) is found. With increasing CNT weight percentage from 0.0 to 10.0 wt%, the dielectric constant of the CNT/PA6 composites enhances and the dielectric loss tangent increases two orders of magnitude. In addition, water contact angles of the CNT/PA6 composites increase and the composites with CNT loading larger than 2.0wt% even become hydrophobic. The obtained results indicate that the electrical and surface properties of the composites have been significantly enhanced by the embedded carbon nanotubes.

Frequency selective surface with better polarization-independency for arbitrary incident angle

Jia Hong-Yan, Gao Jin-Song, Feng Xiao-Guo
Chin. Phys. B, 2009, 18 (3): 1227-1230 doi: 10.1088/1674-1056/18/3/064
Full Text: [PDF 157 KB] (Downloads:685)
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This paper investigates the frequency-selective property of a planar layer consisting of period arrays both theoretically and experimentally for different polarizations at arbitrary incident angle. The novel element is designed by loading the rectangular microstrip element with L-shaped conducting patch at its two ends. Based on the spectral-domain method, the frequency response including angle effect and polarization effect of the frequency selective surface (FSS) structure are analysed and the plots of the frequency versus transmission coefficient are obtained. As a result of the numerical analysis, it is shown that if the source polarization is changed, polarization-independence of previous FSS design can be achieved only for normal incidence, which limits most FSS applications. But in our proposed structure, the better polarization-independency for arbitrary incident angle can be achieved. It is observed that the simulated result comes very close to the experimental result.

An oxide filled extended trench gate super junction MOSFET structure

Wang Cai-Lin, Sun Jun
Chin. Phys. B, 2009, 18 (3): 1231-1236 doi: 10.1088/1674-1056/18/3/065
Full Text: [PDF 788 KB] (Downloads:1852)
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This paper proposes an oxide filled extended trench gate super junction (SJ) MOSFET structure to meet the need of higher frequency power switches application. Compared with the conventional trench gate SJ MOSFET, new structure has the smaller input and output capacitances, and the remarkable improvements in the breakdown voltage, on-resistance and switching speed. Furthermore, the SJ in the new structure can be realized by the existing trench etching and shallow angle implantation, which offers more freedom to SJ MOSFET device design and fabrication.

Solution-based metal induced crystallization of a-Si

Wu Chun-Ya, Li Xue-Dong, Zhao Shu-Yun, Li Juan, Meng Zhi-Guo, Xiong Shao-Zhen, Zhang Fang
Chin. Phys. B, 2009, 18 (3): 1237-1241 doi: 10.1088/1674-1056/18/3/066
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This paper investigates a simplified metal induced crystallization (MIC) of a-Si, named solution-based MIC (S-MIC). The nickel inducing source was formed on a-Si from salt solution dissolved in de-ionized water or ethanol. a-Si thin film was deposited with low pressure chemical vapour deposition or plasma enhanced chemical vapour deposition as precursor material for MIC. It finds that the content of nickel source formed on a-Si can be controlled by solution concentration and dipping time. The dependence of crystallization rate of a-Si on annealing time illustrated that the linear density of nickel source was another critical factor that affects the crystallization of a-Si, besides the diffusion of nickel disilicide. The highest electron Hall mobility of thus prepared S-MIC poly-Si is 45.6cm2/(V.s). By using this S-MIC poly-Si, thin film transistors and display scan drivers were made, and their characteristics are presented.

A novel micro accelerometer with adjustable sensitivity based on resonant tunneling diodes

Xiong Ji-Jun, Mao Hai-Yang, Zhang Wen-Dong, Wang Kai-Qun
Chin. Phys. B, 2009, 18 (3): 1242-1247 doi: 10.1088/1674-1056/18/3/067
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Resonant tunnelling diodes (RTDs) have negative differential resistance effect, and the current--voltage characteristics change as a function of external stress, which is regarded as meso-piezoresistance effect of RTDs. In this paper, a novel micro-accelerometer based on AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs RTDs is designed and fabricated to be a four-beam-mass structure, and an RTD-Wheatstone bridge measurement system is established to test the basic properties of this novel accelerometer. According to the experimental results, the sensitivity of the RTD based micro-accelerometer is adjustable within a range of 3 orders when the bias voltage of the sensor changes. The largest sensitivity of this RTD based micro-accelerometer is 560.2025 mV/g which is about 10 times larger than that of silicon based micro piezoresistive accelerometer, while the smallest one is 1.49135 mV/g.

First principle study on the elastic and thermodynamic properties of TiB2 crystal under high temperature

Wang Chun-Lei, Yu Ben-Hai, Huo Hai-Liang, Chen Dong, Sun Hai-Bin
Chin. Phys. B, 2009, 18 (3): 1248-1252 doi: 10.1088/1674-1056/18/3/068
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This paper predicts the elastic and thermodynamic characteristics of TiB2 crystal through the method of density functional theory within the generalized gradient approximation (GGA). The five independent elastic constants (Cij), the bulk modulus (B0), the dependence of bulk modulus (B0) on temperature T and pressure P and the coefficient of thermal expansion (αL) at various temperatures have been evaluated and discussed. According to calculation, the bulk modulus will increase with increasing pressure while decrease with the increasing temperature. The coefficient of thermal expansion is consistent with the famous Grüneisen's law when the temperature is not too high. The obtained results agree well with the experimental and other theoretical results.

Local structure distortion and spin Hamiltonian parameters of oxide-diluted magnetic semiconductor Mn-doped ZnO

Yang Zi-Yuan
Chin. Phys. B, 2009, 18 (3): 1253-1260 doi: 10.1088/1674-1056/18/3/069
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The local structure distortion, the spin Hamiltonian (SH) parameters, and the electric fine structure of the ground state for Mn2+(3d5) ion in ZnO crystals are systematically investigated, where spin--spin (SS), spin--other--orbit (SOO) and orbit--orbit (OO) magnetic interactions, besides the well-known spin--orbit (SO) coupling, are taken into account for the first time, by using the complete diagonalization method. The theoretical results of the second-order zero-field splitting (ZFS) parameter D, the fourth-order ZFS parameter (a-F), the Zeeman g-factors: g// and g, and the energy differences of the ground state: \delta1 and \delta2 for Mn2+ in Mn2+: ZnO are in good agreement with experimental measurements when the three O2- ions below the Mn2+ ion rotate by 1.085o away from the [111]-axis. Hence, the local structure distortion effect plays an important role in explaining the spectroscopic properties of Mn2+ ions in Mn2+: ZnO crystals. It is found for Mn2+ ions in Mn2+: ZnO crystals that although the SO mechanism is the most important one, the contributions to the SH parameters, made by other four mechanisms, i.e. SS, SOO, OO, and SO~SS~SOO~OO mechanisms, are significant and should not be omitted, especially for calculating ZFS parameter D.

Annealing effects on the microwave permittivity and permeability properties of Fe79Si16B5 microwires and their micowave absorption performances

Han Man-Gui, Ou Yu, Liang Di-Fei, Deng Long-Jiang
Chin. Phys. B, 2009, 18 (3): 1261-1265 doi: 10.1088/1674-1056/18/3/070
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This paper reports that amorphous magnetic microwires (Fe79Si16B5) have been fabricated by a melt-extraction technique and have been annealed at 600℃ and 750℃ respectively. Differential scanning calorimeter measurements show that nanocrystalline magnetic phase (α-Fe) has been formed in the amorphous matrix when it was annealed at 600℃. Hard magnetic phase (Fe2B) was formed in the microwires annealed at 750℃, which increases the magnetic coercivity. Microwave permittivity and permeability are found to be dependent on the microstructures. The permittivity fitting results show that multi Lorentzian dispersion processes exist. For microwires annealed at 750℃, their resonance peaks due to the domain wall movements and natural resonance are found higher than those of microwires annealed at 600℃. The microwave absorption performance of microwires annealed at 600℃ is found better than microwires annealed at 750℃.

Effect of growth temperature on morphology, structure and luminescence of Tb-doped BN thin films

Liu Quan-Lin, Yu Guang-Hua, Jiang Yong
Chin. Phys. B, 2009, 18 (3): 1266-1269 doi: 10.1088/1674-1056/18/3/071
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This paper investigates the effect of growth temperature on morphology, structure and photoluminescence (PL) of Tb-doped boron nitride (BN) films grown by magnetron sputtering, and the relationships of growth-temperature-structure-PL by scanning electron microscopy, transmission electron microscopy and PL. The characteristic emission lines of the Tb3+ were observed in the PL spectra at room temperature. The 473-K-grown film is mainly consisted of amorphous BN particles. With the growth temperature increasing up to 1273 K, the amount of amorphous BN decreases, while the amount of turbostratic BN increases. Correspondingly, the PL intensities from the Tb3+ ions increase with the increase of temperature in the range of 473--1273 K.

Analysis of space harmonic selectivity of period-varying folded waveguide

Xu Ao, Wang Wen-Xiang, Wei Yan-Yu, Gong Yu-Bin
Chin. Phys. B, 2009, 18 (3): 1270-1275 doi: 10.1088/1674-1056/18/3/072
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A period-varying folded waveguide is formed by varying the period of a folded waveguide. It has the advantages of the space harmonic selectivity and the wide bandwidth. However, the regularities of the variety of these period-varying folded waveguides are unavailable from the published papers. In order to solve this problem, the principle of the space harmonic selectivity of a period-varying folded waveguide is analysed, and the conditions to select the space harmonic for this slow wave system are obtained. In addition, the space harmonic selectivities for a linear period-varying folded waveguide and a hyperbolic sine-varying period folded waveguide are also analysed as examples.
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