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Chin. Phys. B  
  Chin. Phys. B--2010, Vol.19, No.4
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The extended symmetry approach for studying the general Korteweg-de Vries-type equation

Li Zhi-Fang, Ruan Hang-Yu
Chin. Phys. B, 2010, 19 (4): 040201 doi: 10.1088/1674-1056/19/4/040201
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The extended symmetry approach is used to study the general Korteweg-de Vries-type (KdV-type) equation. Several variable-coefficient equations are obtained. The solutions of these resulting equations can be constructed by the solutions of original models if their solutions are well known, such as the standard constant coefficient KdV equation and the standard compound KdV--Burgers equation, and so on. Then any one of these variable-coefficient equations can be considered as an original model to obtain new variable-coefficient equations whose solutions can also be known by means of transformation relations between solutions of the resulting new variable-coefficient equations and the original equation.

Fluctuation theorem for the mutation process in in vitro evolution Hot!

Liu Qi, Tang Chao, Ouyang Qi
Chin. Phys. B, 2010, 19 (4): 040202 doi: 10.1088/1674-1056/19/4/040202
Full Text: [PDF 186 KB] (Downloads:555)
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A proposition based on the fluctuation theorem in thermodynamics is formulated to quantitatively describe molecular evolution processes in biology. Although we cannot give full proof of its generality, we demonstrate via computer simulation its applicability in an example of DNA in vitro evolution. According to this theorem, the evolution process is a series of exponentially rare fluctuations fixed by the force of natural selection.

The 2.7 K black-body radiation background reference frame

López-Carrera Benjamín, Rosales Marco Antonio, Ares de Parga Gonzalo
Chin. Phys. B, 2010, 19 (4): 040203 doi: 10.1088/1674-1056/19/4/040203
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This paper reports that the directional temperature is used to present a scheme for deducing the velocity of the reference frame where the black-body which produces the 2.7~K radiation background is at rest. The new renormalized relativistic thermodynamics lays the foundations of the method.

A new type of conserved quantity of Lie symmetry for the Lagrange system

Fang Jian-Hui
Chin. Phys. B, 2010, 19 (4): 040301 doi: 10.1088/1674-1056/19/4/040301
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This paper studies a new type of conserved quantity which is directly induced by Lie symmetry of the Lagrange system. Firstly, the criterion of Lie symmetry for the Lagrange system is given. Secondly, the conditions of existence of the new conserved quantity as well as its forms are proposed. Lastly, an example is given to illustrate the application of the result.

Conformal invariance and conserved quantities of a general holonomic system with variable mass

Xia Li-Li, Cai Jian-Le
Chin. Phys. B, 2010, 19 (4): 040302 doi: 10.1088/1674-1056/19/4/040302
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Conformal invariance and conserved quantities of a general holonomic system with variable mass are studied. The definition and the determining equation of conformal invariance for a general holonomic system with variable mass are provided. The conformal factor expression is deduced from conformal invariance and Lie symmetry. The relationship between the conformal invariance and the Lie symmetry is discussed, and the necessary and sufficient condition under which the conformal invariance would be the Lie symmetry of the system under an infinitesimal one-parameter transformation group is deduced. The conserved quantities of the system are given. An example is given to illustrate the application of the result.

Flow difference effect in the lattice hydrodynamic model

Tian Jun-Fang, Jia Bin, Li Xing-Gang, Gao Zi-You
Chin. Phys. B, 2010, 19 (4): 040303 doi: 10.1088/1674-1056/19/4/040303
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In this paper, a new lattice hydrodynamic model based on Nagatani's model [Nagatani T 1998 Physica A 261 599] is presented by introducing the flow difference effect. The stability condition for the new model is obtained by using the linear stability theory. The result shows that considering the flow difference effect leads to stabilization of the system compared with the original lattice hydrodynamic model. The jamming transitions among the freely moving phase, the coexisting phase, and the uniform congested phase are studied by nonlinear analysis. The modified KdV equation near the critical point is derived to describe the traffic jam, and kink--antikink soliton solutions related to the traffic density waves are obtained. The simulation results are consistent with the theoretical analysis for the new model.

Bilinear B?cklund transformation and explicit solutions for a nonlinear evolution equation

Wu Yong-Qi
Chin. Phys. B, 2010, 19 (4): 040304 doi: 10.1088/1674-1056/19/4/040304
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The bilinear form of two nonlinear evolution equations are derived by using Hirota derivative. The B\"{a}cklund transformation based on the Hirota bilinear method for these two equations are presented, respectively. As an application, the explicit solutions including soliton and stationary rational solutions for these two equations are obtained.

New two-fold integration transformation for the Wigner operator in phase space quantum mechanics and its relation to operator ordering

Fan Hong-Yi
Chin. Phys. B, 2010, 19 (4): 040305 doi: 10.1088/1674-1056/19/4/040305
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Using the Weyl ordering of operators expansion formula (Hong-Yi Fan, \emph{ J. Phys.} A {\bf 25} (1992) 3443) this paper finds a kind of two-fold integration transformation about the Wigner operator $\varDelta \left( q',p'\right) $ ($\mathrm{q}$-number transform) in phase space quantum mechanics, $$\iint_{-\infty}^{\infty}\frac{{\rm d}p'{\rm d}q'}{\pi }\varDelta \left( q',p'\right) \e^{-2\i\left( p-p'\right) \left( q-q'\right) }=\delta \left( p-P\right) \delta \left( q-Q\right),$$ and its inverse% $$ \iint_{-\infty}^{\infty}{\rm d}q{\rm d}p\delta \left( p-P\right) \delta \left( q-Q\right) \e^{2\i\left( p-p'\right) \left( q-q'\right) }=\varDelta \left( q',p'\right),$$ where $Q,$ $P$ are the coordinate and momentum operators, respectively. We apply it to study mutual converting formulae among $Q$--$P$ ordering, $P$--$Q$ ordering and Weyl ordering of operators. In this way, the contents of phase space quantum mechanics can be enriched. The formula of the Weyl ordering of operators expansion and the technique of integration within the Weyl ordered product of operators are used in this discussion.

Energy eigenvalues from an analytical transfer matrix method

He Ying, Zhang Fan-Ming, Yang Yan-Fang, Li Chun-Fang
Chin. Phys. B, 2010, 19 (4): 040306 doi: 10.1088/1674-1056/19/4/040306
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A detailed procedure based on an analytical transfer matrix method is presented to solve bound-state problems. The derivation is strict and complete. The energy eigenvalues for an arbitrary one-dimensional potential can be obtained by the method. The anharmonic oscillator potential and the rational potential are two important examples. Checked by numerical techniques, the results for the two potentials by the present method are proven to be exact and reliable.

The analytical transfer matrix method for quantum reflection

Xu Tian, Cao Zhuang-Qi, Fang Jing-Huai
Chin. Phys. B, 2010, 19 (4): 040307 doi: 10.1088/1674-1056/19/4/040307
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In this paper, the analytical transfer matrix method (ATMM) is applied to study the properties of quantum reflection in three systems: a sech$^{2}$ barrier, a ramp potential and an inverse harmonic oscillator. Our results agree with those obtained by Landau and Lifshitz [Landau L D and Lifshitz E M 1977 \wx{Quantum Mechanics (Non-relativistic Theory)}{} (New York: Pergamon)], which proves that ATMM is a simple and effective method for quantum reflection.

Perturbation theory of von Neumann entropy

Chen Xiao-Yu
Chin. Phys. B, 2010, 19 (4): 040308 doi: 10.1088/1674-1056/19/4/040308
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In quantum information theory, von Neumann entropy plays an important role; it is related to quantum channel capacities. Only for a few states can one obtain their entropies. In a continuous variable system, numeric evaluation of entropy is not easy due to infinite dimensions. We develop the perturbation theory for systematically calculating von Neumann entropy of a non-degenerate system as well as a degenerate system.

Remote preparation of atomic and field cluster states from a pair of tri-partite GHZ states

Ashfaq H. Khosa, Rameez-ul-Islam, Farhan Saif
Chin. Phys. B, 2010, 19 (4): 040309 doi: 10.1088/1674-1056/19/4/040309
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We propose two simple and resource-economical schemes for remote preparation of four-partite atomic as well as cavity field cluster states. In the case of atomic state generation, we utilize simultaneous resonant and dispersive interactions of the two two-level atoms at the preparation station. Atoms involved in these interactions are individually pair-wise entangled into two different tri-partite GHZ states. After interaction, the passage of the atoms through a Ramsey zone and their subsequent detection completes the protocol. However, for field state generation we first copy the quantum information in the cavities to the atoms by resonant interactions and then adapt the same method as in the case of atomic state generation. The method can be generalised to remotely generate any arbitrary graph states in a straightforward manner.

Generation of entangled coherent states through cavity-assisted interaction

Chen Xiao-Dong, Gu Yong-Jian, Liang Hong-Hui, Ni Bin-Bin, Lin Xiu-Min
Chin. Phys. B, 2010, 19 (4): 040310 doi: 10.1088/1674-1056/19/4/040310
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We propose schemes to generate an $n$-coherent-pulse GHZ state and a cluster state via the interaction between $n$ coherent pulses and a two-sided cavity. In these schemes, a strong coupling condition is not needed, which makes the protocols possibly able to be implemented based on the current experiment technology.

Some dynamical property of the Tsallis distribution from a Fokker-Planck equation

Du Jiu-Lin
Chin. Phys. B, 2010, 19 (4): 040501 doi: 10.1088/1674-1056/19/4/040501
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This paper studies the possible dynamical property of the Tsallis distribution from a Fokker--Planck equation. For the Langevin dynamical system with an {arbitrary} potential function, Markovian friction and Gaussian white noise, it shows that the current form of Tsallis distribution cannot describe any nonequilibrium dynamics of the system, and it only stands for a simple isothermal situation of the system governed by a potential field. So the form of Tsallis distribution and many existing applications using the Tsallis distribution need to be reconsidered.

Effect of a barrier potential on soliton dynamical characteristics in condensates

Li Jin-Hui
Chin. Phys. B, 2010, 19 (4): 040502 doi: 10.1088/1674-1056/19/4/040502
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By using the multiple-scale method, this paper analytically studies the effect of a barrier potential on the dynamical characteristics of the soliton in Bose--Einstein condensates. It is shown that a stable soliton is exhibited at the top of the barrier potential and the region of the absence of the barrier potential. Meanwhile, it is found that the height of the barrier potential has an important effect on the dark soliton dynamical characteristics in the condensates. With the increase of height of the barrier potential, the amplitude of the dark soliton becomes smaller, its width is narrower, and the soliton propagates more slowly.

Stochastic resonance in a time-delayed asymmetric bistable system with mixed periodic signal

Guo Yong-Feng, Xu Wei, Wang Liang
Chin. Phys. B, 2010, 19 (4): 040503 doi: 10.1088/1674-1056/19/4/040503
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This paper studies the phenomenon of stochastic resonance in an asymmetric bistable system with time-delayed feedback and mixed periodic signal by using the theory of signal-to-noise ratio in the adiabatic limit. A general approximate Fokker--Planck equation and the expression of the signal-to-noise ratio are derived through the small time delay approximation at both fundamental harmonics and mixed harmonics. The effects of the additive noise intensity $Q$, multiplicative noise intensity $D$, static asymmetry $r$ and delay time $\tau$ on the signal-to-noise ratio are discussed. It is found that the higher mixed harmonics and the static asymmetry $r$ can restrain stochastic resonance, and the delay time $\tau $ can enhance stochastic resonance. Moreover, the longer the delay time $\tau $ is, the larger the additive noise intensity $Q$ and the multiplicative noise intensity $D$ are, when the stochastic resonance appears.

Spatial coherence resonance induced by coloured noise and parameter diversity in a neuronal network

Sun Xiao-Juan, Lu Qi-Shao
Chin. Phys. B, 2010, 19 (4): 040504 doi: 10.1088/1674-1056/19/4/040504
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Spatial coherence resonance in a two-dimensional neuronal network induced by additive Gaussian coloured noise and parameter diversity is studied. We focus on the ability of additive Gaussian coloured noise and parameter diversity to extract a particular spatial frequency (wave number) of excitatory waves in the excitable medium of this network. We show that there exists an intermediate noise level of the coloured noise and a particular value of diversity, where a characteristic spatial frequency of the system comes forth. Hereby, it is verified that spatial coherence resonance occurs in the studied model. Furthermore, we show that the optimal noise intensity for spatial coherence resonance decays exponentially with respect to the noise correlation time. Some explanations of the observed nonlinear phenomena are also presented.

A novel chaotic stream cipher and its application to palmprint template protection

Li Heng-Jian, Zhang Jia-Shu
Chin. Phys. B, 2010, 19 (4): 040505 doi: 10.1088/1674-1056/19/4/040505
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Based on a coupled nonlinear dynamic filter (NDF), a novel chaotic stream cipher is presented in this paper and employed to protect palmprint templates. The chaotic pseudorandom bit generator (PRBG) based on a coupled NDF, which is constructed in an inverse flow, can generate multiple bits at one iteration and satisfy the security requirement of cipher design. Then, the stream cipher is employed to generate cancelable competitive code palmprint biometrics for template protection. The proposed cancelable palmprint authentication system depends on two factors: the palmprint biometric and the password/token. Therefore, the system provides high-confidence and also protects the user's privacy. The experimental results of verification on the Hong Kong PolyU Palmprint Database show that the proposed approach has a large template re-issuance ability and the equal error rate can achieve 0.02%. The performance of the palmprint template protection scheme proves the good practicability and security of the proposed stream cipher.

A mathematical model of a P53 oscillation network triggered by DNA damage

Xia Jun-Feng, Jia Ya
Chin. Phys. B, 2010, 19 (4): 040506 doi: 10.1088/1674-1056/19/4/040506
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Taking the interaction between a DNA damage repair module, an ATM module, and a P53--MDM2 oscillation module into account, this paper presents a mathematical model of a P53 oscillation network triggered by a DNA damage signal in individual cells. The effects of the DNA damage signal and the delay time of P53-induced MDM2 expression on the behaviours of the P53 oscillation network are studied. In the oscillatory state of the P53--MDM2 oscillator, it is found that the pulse number of P53--P oscillation increases with the increase of the initial DNA damage signal, whereas the amplitude and the period of P53--P oscillation are fixed for different initial DNA damage signals, and the period numbers of P53--P oscillations decrease with the increase of time delay of MDM2 expression induced by P53. These theoretical predictions are consistent with previous experimental results. The combined negative feedback of P53--MDM2 with the time delay of P53-induced MDM2 expression causes oscillation behaviour in the P53 network.

Synchronization of hyperchaotic Chen systems: a class of the adaptive control approach

Wei Wei, Li Dong-Hai, Wang Jing
Chin. Phys. B, 2010, 19 (4): 040507 doi: 10.1088/1674-1056/19/4/040507
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The synchronization of hyperchaotic Chen systems is considered. An adaptive synchronization approach and a cascade adaptive synchronization approach are presented to synchronize a drive system and a response system. By utilizing an adaptive controller based on the dynamic compensation mechanism, exact knowledge of the systems is not necessarily required, and the synchronous speed is controllable by tuning the controller parameters. Sufficient conditions for the asymptotic stability of the two synchronization schemes are derived. Numerical simulation results demonstrate that the adaptive synchronization scheme with four control inputs and the cascade adaptive synchronization scheme with only one control signal are effective and feasible in chaos synchronization of hyperchaotic systems.

Delay-aided stochastic multiresonances on scale-free FitzHugh-Nagumo neuronal networks

Gan Chun-Biao, Perc Matja?, Wang Qing-Yun
Chin. Phys. B, 2010, 19 (4): 040508 doi: 10.1088/1674-1056/19/4/040508
Full Text: [PDF 3720 KB] (Downloads:895)
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The stochastic resonance in paced time-delayed scale-free FitzHugh--Nagumo (FHN) neuronal networks is investigated. We show that an intermediate intensity of additive noise is able to optimally assist the pacemaker in imposing its rhythm on the whole ensemble. Furthermore, we reveal that appropriately tuned delays can induce stochastic multiresonances, appearing at every integer multiple of the pacemaker's oscillation period. We conclude that fine-tuned delay lengths and locally acting pacemakers are vital for ensuring optimal conditions for stochastic resonance on complex neuronal networks.

A novel chaotic system with one source and two saddle-foci in Hopfield neural networks

Chen Peng-Fei, Chen Zeng-Qiang, Wu Wen-Juan
Chin. Phys. B, 2010, 19 (4): 040509 doi: 10.1088/1674-1056/19/4/040509
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This paper presents the finding of a novel chaotic system with one source and two saddle-foci in a simple three-dimensional (3D) autonomous continuous time Hopfield neural network. In particular, the system with one source and two saddle-foci has a chaotic attractor and a periodic attractor with different initial points, which has rarely been reported in 3D autonomous systems. The complex dynamical behaviours of the system are further investigated by means of a Lyapunov exponent spectrum, phase portraits and bifurcation analysis. By virtue of a result of horseshoe theory in dynamical systems, this paper presents rigorous computer-assisted verifications for the existence of a horseshoe in the system for a certain parameter.

Traffic flow of a roundabout crossing with an open boundary condition

Bai Ke-Zhao, Tan Hui-Li, Kong Ling-Jiang, Liu Mu-Ren
Chin. Phys. B, 2010, 19 (4): 040510 doi: 10.1088/1674-1056/19/4/040510
Full Text: [PDF 986 KB] (Downloads:781)
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This paper presents a cellular automaton traffic flow model with an open boundary condition to describe the traffic flow at a roundabout crossing with an inner roundabout lane and an outer roundabout lane. The simulation results show that the boundary condition, bottlenecks and the self-organization affect the traffic flow at the roundabout crossing. Because of the effect of bottlenecks, jams easily appear on the inner roundabout lane. To improve the capacity of the roundabout system, proper values of the enter probability α and the out probability $\beta $ can be chosen.

The fractal structure in the ionization dynamics of Rydberg lithium atoms in a static electric field

Deng Shan-Hong, Gao Song, Li Yong-Ping, Xu Xue-You, Lin Sheng-Lu
Chin. Phys. B, 2010, 19 (4): 040511 doi: 10.1088/1674-1056/19/4/040511
Full Text: [PDF 397 KB] (Downloads:629)
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The ionization rate of Rydberg lithium atoms in a static electric field is examined within semiclassical theory which involves scattering effects off the core. By semiclassical analysis, this ionization process can be considered as the promoted valence electrons escaping through the Stark saddle point into the ionization channels. The resulting escape spectrum of the ejected electrons demonstrates a remarkable irregular electron pulse train in time-dependence and a complicated nesting structure with respect to the initial launching angles. Based on the Poincaré} map and homoclinic tangle approach, the chaotic behaviour along with its corresponding fractal self-similar structure of the ionization spectra are analysed in detail. Our work is significant for understanding the quantum-classical correspondence.

Geometric phases and quantum phase transitions in inhomogeneous XY spin-chains: Effect of the Dzyaloshinski-Moriya interaction

Wang Lin-Cheng, Yan Jun-Yan, Yi Xue-Xi
Chin. Phys. B, 2010, 19 (4): 040512 doi: 10.1088/1674-1056/19/4/040512
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We study geometric phases of the ground states of inhomogeneous XY spin chains in transverse fields with Dzyaloshinski--Moriya (DM) interaction, and investigate the effect of the DM interaction on the quantum phase transition (QPT) of such spin chains. The results show that the DM interaction could influence the distribution of the regions of QPTs but could not produce new critical points for the spin-chain. This study extends the relation between geometric phases and QPTs.

Adaptive local routing strategy on a scale-free network

Liu Feng, Zhao Han, Li Ming, Ren Feng-Yuan, Zhu Yan-Bo
Chin. Phys. B, 2010, 19 (4): 040513 doi: 10.1088/1674-1056/19/4/040513
Full Text: [PDF 205 KB] (Downloads:910)
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Due to the heterogeneity of the structure on a scale-free network, making the betweennesses of all nodes become homogeneous by reassigning the weights of nodes or edges is very difficult. In order to take advantage of the important effect of high degree nodes on the shortest path communication and preferentially deliver packets by them to increase the probability to destination, an adaptive local routing strategy on a scale-free network is proposed, in which the node adjusts the forwarding probability with the dynamical traffic load (packet queue length) and the degree distribution of neighbouring nodes. The critical queue length of a node is set to be proportional to its degree, and the node with high degree has a larger critical queue length to store and forward more packets. When the queue length of a high degree node is shorter than its critical queue length, it has a higher probability to forward packets. After higher degree nodes are saturated (whose queue lengths are longer than their critical queue lengths), more packets will be delivered by the lower degree nodes around them. The adaptive local routing strategy increases the probability of a packet finding its destination quickly, and improves the transmission capacity on the scale-free network by reducing routing hops. The simulation results show that the transmission capacity of the adaptive local routing strategy is larger than that of three previous local routing strategies.

Measurement and control for a repetitive nanosecond-pulse breakdown experiment in polymer films

Shao Tao, Zhang Cheng, Long Kai-Hua, Wang Jue, Zhang Dong-Dong, Yan Ping
Chin. Phys. B, 2010, 19 (4): 040601 doi: 10.1088/1674-1056/19/4/040601
Full Text: [PDF 544 KB] (Downloads:1217)
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In order to perform data acquisition and avoid unwanted over-current damage to the power supply, a convenient and real-time method of experimentally investigating repetitive nanosecond-pulse breakdown in polymer dielectric samples is presented. The measurement-acquisition and control system not only records breakdown voltage and current, and time-to-breakdown duration, but also provides a real-time power-off protection for the power supply. Furthermore, the number of applied pulses can be calculated by the product of the time-to-breakdown duration and repetition rate. When the measured time-to-breakdown duration error is taken into account, the repetition rate of applied nanosecond-pulses should be below 40~kHz. In addition, some experimental data on repetitive nanosecond-pulse breakdown of polymer films are presented and discussed.

Comparative analysis of phase extraction methods based on phase-stepping and shifting curve in grating interferometry

Liu Xiao-Song, Li En-Rong, Zhu Pei-Ping, Liu Yi-Jin, Zhang Kai, Wang Zhi-Li, Hong You-Li, Zhang Hui-Tao, Yuan Qing-Xi, Huang Wan-Xia, Wu Zi-Yu
Chin. Phys. B, 2010, 19 (4): 040701 doi: 10.1088/1674-1056/19/4/040701
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Two phase extraction methods which are based separately on phase-stepping and shifting curve are mainly used in phase-sensitive imaging in gating interferometry to determine the x-ray phase shift induced by an object in the beam. In this paper, the authors perform a full comparative analysis and present the main virtues and limitations of these two methods according to the theoretical analysis of the grating interferometry.

Analytical solutions to the electromagnetic field in a cylindrical shell excited by external axial current

Wu Jing, Xiao Chun-Yan
Chin. Phys. B, 2010, 19 (4): 044101 doi: 10.1088/1674-1056/19/4/044101
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The solutions to the electromagnetic field excited by a long axial current outside a conductive and magnetic cylindrical shell of finite length are studied in this paper. The more accurate analytical solutions are obtained by solving the proper boundary value problems by the separation variable method. Then the solutions are simplified according to asymptotic formulas of Bessel functions. Compared with the accurate solutions, the simplified solutions do not contain the Bessel functions and the inverse operation of the singular matrix, and can be calculated out fast by computers. The simplified solutions are more suitable for the cylindrical shell of high permeability and conductivity excited by a high frequency source. Both of the numerical results and the physical experimental results validate the simplified solutions obtained.

Application of the method of equivalent edge currents to composite scattering from the cone-cylinder above a dielectric rough sea surface

Guo Li-Xin, Wang Rui, Wu Zhen-Sen
Chin. Phys. B, 2010, 19 (4): 044102 doi: 10.1088/1674-1056/19/4/044102
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Compared with scattering from a rough surface only, composite scattering from a target above a rough surface has become so practical that it is a subject of great interest. At present, this problem has been solved by some numerical methods which will produce an enormous calculation amount. In order to overcome this shortcoming, the reciprocity theorem (RT) and the method of equivalent edge currents (MEC) are used in this paper. Due to the advantage of RT, the difficulty in computing the secondary scattered fields is reduced. Simultaneously, MEC, a high-frequency method with edge diffraction considered, is used to calculate the scattered field from the cone-cylinder target with a high accuracy and efficiency. The backscattered field and the polarization currents of the rough sea surface are evaluated by the Kirchhoff approximation (KA) method and physical optics (PO) method, respectively. The effects of the backscattering radar cross section (RCS) and the Doppler spectrum on the size of the target and the windspeed of the sea surface for different incident angles are analysed in detail.

A study of optical properties of a four-level atomic system via vacuum-induced coherence effects

Chen Jun, Liu Zheng-Dong, Zheng Jun, Pang Wei, You Su-Ping
Chin. Phys. B, 2010, 19 (4): 044201 doi: 10.1088/1674-1056/19/4/044201
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This paper studies the effects of vacuum-induced coherence (VIC) in a four-level atomic system. The effects of VIC lead to the coherent hole burnings exhibited in the system at some certain points of the Rabi frequency. This is also the reason for the enhancement of the coherent population trapping. In addition, optical bistability occurs in the evolution curves of absorption versus the phase of Rabi frequencies.

Energy level formula for two moving charged particles with Coulomb coupling derived via the entangled state representations

Meng Xiang-Guo, Wang Ji-Suo, Liang Bao-Long
Chin. Phys. B, 2010, 19 (4): 044202 doi: 10.1088/1674-1056/19/4/044202
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This paper derives energy level formula for two moving charged particles with Coulomb coupling by making full use of two mutually conjugate entangled state representations. These newly introduced entangled state representations seem to provide a direct and convenient approach for solving certain dynamical problems for two-body systems.

Generation of any superposition of coherent states along a straight line via resonant atom-cavity interaction

Zheng Shi-Biao
Chin. Phys. B, 2010, 19 (4): 044203 doi: 10.1088/1674-1056/19/4/044203
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This paper proposes a scheme for generating arbitrary superpositions of several coherent states along a straight line for a cavity mode. In the scheme, several atoms are sent through a cavity initially in a strong coherent state. The superposition of several coherent states with desired coefficients may be generated if each atom is detected in the excited state after it exits the cavity. The scheme is based on resonant atom--cavity interaction and no classical field is required during and after the atom--cavity interaction. Thus, the scheme is very simple and the interaction time is very short, which is important in view of decoherence.

Decoherence-immune generation of highly entangled states for two atoms

Zheng Shi-Biao
Chin. Phys. B, 2010, 19 (4): 044204 doi: 10.1088/1674-1056/19/4/044204
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This paper proposes a decoherence-immune scheme for generating highly entangled states for two atoms trapped in a cavity. The scheme is based on two resonant atom-cavity interactions. Conditional upon the detection of no photon, the two atoms may exchange an excitation via the first resonant interaction, which leads to entanglement. Due to the loss of the excitation, the two atoms are in a mixed entangled state. With the help of an auxiliary ground state not coupled to the cavity mode, the state related to the excitation loss is eliminated by the detection of a photon resulting from the second resonant interaction. Thus, the fidelity of entanglement is almost not affected by the decoherence.

Single output LD end-pumped passively mode-locked Nd:YVO4 laser with semiconductor saturable absorber mirror

Xia Pa-Keti, Yu Hai-Juan, Yan Ping, Gong Ma-Li
Chin. Phys. B, 2010, 19 (4): 044205 doi: 10.1088/1674-1056/19/4/044205
Full Text: [PDF 1233 KB] (Downloads:1098)
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A quarter-wave plate and the thin film polarizer (TFP) are used for the LD end-pumped passively mode-locked Nd:YVO$_{4}$ laser with semiconductor saturable absorber mirror (SESAM) to obtain a single beam output with a total power of 4.8~W. An optical--optical efficiency is achieved to be 24% for a stable CW mode-locking operation at 1064~nm, with a pulse repetition rate of 70~MHz and pulse width of 16~ps. The multipulse in the pulse sequence is eliminated for reaching a peak power as high as 4~kW.

Asymmetrical surface soliton trains

Yin Guo-Yan, Zheng Jiang-Bo, Yang Xiao-Yu, Dong Liang-Wei
Chin. Phys. B, 2010, 19 (4): 044206 doi: 10.1088/1674-1056/19/4/044206
Full Text: [PDF 2746 KB] (Downloads:820)
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We elucidate the existence, stability and propagation dynamics of multi-spot soliton packets in focusing saturable media. Such solitons are supported by an interface beside which two harmonically photonic lattices with different modulation depths are imprinted. We show that the surface model can support stable higher-order structures in the form of asymmetrical surface soliton trains, which is in sharp contrast to homogeneous media or uniform harmonic lattice modulations where stable asymmetrical multi-peaked solitons do not exist. Surface trains can be viewed as higher-order soliton states bound together by several different lowest order solitons with appropriate relative phases. Their existence as stable objects enriches the concept of compact manipulation of several different solitons as a single entity and offers additional freedom to control the shape of solitons by adjusting the modulation depths beside the interface.

The aggregation effects on the two-photon absorption properties of para-nitroaniline polymers by hydrogen-bond interactions

Sun Yuan-Hong, Li Jing, Zhao Ke, Wang Chuan-Kui
Chin. Phys. B, 2010, 19 (4): 044207 doi: 10.1088/1674-1056/19/4/044207
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This paper has theoretically designed a series of aggregate polymers on the basis of several para-nitroaniline monomers by hydrogen-bond interactions. At the level of time-dependent hybrid density functional theory, it has optimized their geometrical structures and studied their two-photon absorption (TPA) properties by using analytical response theory. The calculated results exhibit that the aggregation effects not only bring out the considerable red shift of the excited energies but also greatly enhance the TPA intensities of the aggregate polymers in comparison with the para-nitroaniline monomer. The aggregate configurations also have an important influence on the TPA abilities of the polymers; the trimer has the largest TPA cross section. The electron transitions between the molecular orbits involving the strong TPA excitations of the trimer are depicted to illuminate the relationship between the intermolecular charge transfer and the TPA property.

Incoherent interaction between one- and two-dimensional solitons in noncentrosymmetric photorefractive media

Xiao Fa-Jun, Zhang Peng, Liu Sheng, Gan Xue-Tao, Zhao Jian-Lin
Chin. Phys. B, 2010, 19 (4): 044208 doi: 10.1088/1674-1056/19/4/044208
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The incoherent interaction between solitons with different transverse dimensions in a noncentrosymmetric photorefractive crystal is studied both in theory and in experiment. An anomalous incoherent interaction between one- and two-dimensional solitons, whose attractive and repulsive effects depend on the soliton separation, is numerically demonstrated by employing an anisotropic model. By launching a one-dimensional green beam and a two-dimensional red beam into a biased SBN:60 crystal, the hybrid-dimensional soliton interaction is performed. The experimental results are in good agreement with the numerical ones.

Interactions between optical bullets with different velocities in the three-dimensional cubic-quintic complex Ginzburg-Landau equation

Zheng Lang, Tang Yi
Chin. Phys. B, 2010, 19 (4): 044209 doi: 10.1088/1674-1056/19/4/044209
Full Text: [PDF 1606 KB] (Downloads:491)
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By using the three-dimensional complex Ginzburg--Landau equation with cubic--quintic nonlinearity, this paper numerically investigates the interactions between optical bullets with different velocities in a dissipative system. The results reveal an abundance of interesting behaviours relating to the velocities of bullets: merging of the optical bullets into a single one at small velocities; periodic collisions at large velocities and disappearance of two bullets after several collisions in an intermediate region of velocity. Finally, it also reports that an extra bullet derives from the collision of optical bullets when optical bullets are at small velocities but with high energies.

Graded index broadband antireflection coating prepared by glancing angle deposition for a high-power laser system

Kong Wei-Jin, Shen Zi-Cai, Wang Shu-Hua, Shao Jian-Da, Fan Zheng-Xiu, Lu Chao-Jing
Chin. Phys. B, 2010, 19 (4): 044210 doi: 10.1088/1674-1056/19/4/044210
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This paper reports that SiO2 is selected to fabricate broadband antireflection (AR) coatings on fused silica substrate by using glancing angle deposition and physical vapour deposition. Through accurate control of the graded index of the SiO2 layer, transmittance of the graded broadband AR coating can achieve an average value of 98% across a spectral range of 300--1850~nm. Moreover, a laser-induced damage threshold measurement of the fabricated AR coating is performed by using a one-on-one protocol according to ISO11254-1, resulting in an average damage threshold of 17.2~J/cm$^{2}$.

A polarization stabilizer up to 12.6 krad/s with an additional function of stable state of polarization transformation

Zhang Xiao-Guang, Fang Guang-Qing, Zhao Xin-Yuan, Zhang Wen-Bo, Xi Li-Xia, Xiong Qian-Jin, Li Xi-Xiang, Zhang Guang-Yong
Chin. Phys. B, 2010, 19 (4): 044211 doi: 10.1088/1674-1056/19/4/044211
Full Text: [PDF 1725 KB] (Downloads:582)
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This paper reports on an experiment about a novel method of polarization stabilization. The polarization stabilizer proposed here has an additional function of polarization transformation from any state of polarization into any others. The particle swarm optimization is introduced as a control algorithm in the process of either searching or endless tracking. The tracking speed of the stabilizer is obtained up to 12.6~krad/s by using hardware we have in the laboratory, which means that we can achieve a higher speed practical polarization stabilizer if we have faster hardware.

Investigation of a silicon-based one-dimensional phononic crystal plate via the super-cell plane wave expansion method

Zhu Xue-Feng, Liu Sheng-Chun, Xu Tao, Wang Tie-Hai, Cheng Jian-Chun
Chin. Phys. B, 2010, 19 (4): 044301 doi: 10.1088/1674-1056/19/4/044301
Full Text: [PDF 658 KB] (Downloads:1044)
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The super-cell plane wave expansion method is employed to calculate band structures for the design of a silicon-based one-dimensional phononic crystal plate with large absolute forbidden bands. In this method, a low impedance medium is introduced to replace the free stress boundary, which largely reduces the computational complexity. The dependence of band gaps on structural parameters is investigated in detail. To prove the validity of the super-cell plane wave expansion, the transmitted power spectra of the Lamb wave are calculated by using a finite element method. With the detailed computation, the band-gap of a one-dimensional plate can be designed as required with appropriate structural parameters, which provides a guide to the fabrication of a Lamb wave phononic crystal.

Calculation of multicentre nuclear attraction integrals over Slater-type orbitals using unsymmetrical one-range addition theorems

Israfil I. Guseinov, N. Seckin Gorgun, Nimet Zaim
Chin. Phys. B, 2010, 19 (4): 043101 doi: 10.1088/1674-1056/19/4/043101
Full Text: [PDF 135 KB] (Downloads:670)
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Using the unsymmetrical one-range addition theorems introduced by one of the authors with the help of complete orthonormal sets of $\varPsi ^\alpha $-exponential type orbitals ($\alpha = 1,0, - 1, - 2,...)$, this paper presents the sets of series expansion relations for multicentre nuclear attraction integrals over Slater-type orbitals arising in Hartree--Fock--Roothaan equations for molecules. The final results are expressed through multicentre charge density expansion coefficients and basic integrals. The convergence of the series is tested by calculating concrete cases for arbitrary values of parameters of orbitals.

Stability of small Ni-Ti bimetallic clusters studied by density functional theory

Chen Zhen-Gang, Xie Zun, Li You-Cheng, Ma Qing-Min, Liu Ying
Chin. Phys. B, 2010, 19 (4): 043102 doi: 10.1088/1674-1056/19/4/043102
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The low-energy structures and the electronic and the magnetic properties of small Ni$_{n}$Ti$_{n}$ ($n=1$--$6$) and Ni$_{m}$Ti$_{n}$ ($1 \le n \le 4$, $1 \le m \le 4$, $n \ne m$) clusters are investigated by performing all-electron calculations based on density functional theory. Ground states and several isomers near the ground states are determined for these clusters. The results indicate that the growth of small Ni$_{m}$Ti$_{n}$ clusters prefers to form rich Ti--Ni and Ti--Ti bonds. When the percentage of titanium atoms is significantly greater than that of nickel atoms, the nickel atoms are most frequently found above the surface; in contrast, the titanium atoms prefer the bridging sites. A M\"{u}lliken spin population analysis indicates that the total spin of titanium-nickel clusters is not always zero.

Density-functional investigation of 3d,4d,5d impurity doped Au6 clusters

Zhang Meng, Feng Xiao-Juan, Zhao Li-Xia, He Li-Ming, Luo You-Hua
Chin. Phys. B, 2010, 19 (4): 043103 doi: 10.1088/1674-1056/19/4/043103
Full Text: [PDF 766 KB] (Downloads:960)
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The general features of the geometries and electronic properties for 3d, 4d, and 5d transition-metal atom doped Au$_{6}$ clusters are systematically investigated by using relativistic all-electron density functional theory in the generalized gradient approximation (GGA). A number of structural isomers are considered to search the lowest-energy structures of $M$@Au$_{6}$ clusters ($M$=3d, 4d and 5d transition-metal atoms), and the transition metal atom locating in the centre of an Au$_{6}$ ring is found to be in the ground state for all the $M$@Au$_{6 }$ clusters. All doped clusters, expect for Pd@Au$_{6}$, show large relative binding energies compared with a pure Au$_{7 }$ cluster, indicating that doping by 3d, 4d, 5d transition-metal atoms could stabilize the Au$_{6}$ ring and promote the formation of a new binary alloy cluster.

Selective excitation and suppression of coherent anti-Stokes Raman scattering by shaping femtosecond pulses

Zhang Shi-An, Zhang Hui, Wang Zu-Geng, Sun Zhen-Rong
Chin. Phys. B, 2010, 19 (4): 043201 doi: 10.1088/1674-1056/19/4/043201
Full Text: [PDF 153 KB] (Downloads:613)
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Femtosecond coherent anti-Stokes Raman scattering (CARS) suffers from poor selectivity between neighbouring Raman levels due to the large bandwidth of the femtosecond pulses. This paper provides a new method to realize the selective excitation and suppression of femtosecond CARS by manipulating both the probe and pump (or Stokes) spectra. These theoretical results indicate that the CARS signals between neighbouring Raman levels are differentiated from their indistinguishable femtosecond CARS spectra by tailoring the probe spectrum, and then their selective excitation and suppression can be realized by supplementally manipulating the pump (or Stokes) spectrum with the $\pi $ spectral phase step.

Recombination during expansion of ultracold plasma

Zhao Jian-Ming, Zhang Lin-Jie, Feng Zhi-Gang, Li Chang-Yong, Jia Suo-Tang
Chin. Phys. B, 2010, 19 (4): 043202 doi: 10.1088/1674-1056/19/4/043202
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Signals of ultracold plasma are observed by two-photon ionization of laser-cooled caesium atoms in a magneto-optical trap. Recombination of ions and electrons into Rydberg atoms during the expansion of ultracold plasma is investigated by using state-selective field ionization spectroscopy. The dependences of recombination on initial electron temperature (1--70~K) and initial ion density ($ \sim $10$^{10}$~cm$^{ - 3})$ are investigated. The measured dependence on initial ion density is $N^{1.547\pm 0.004}$ at a delay time of 5~$\mu $s. The recombination rate rapidly declines as initial electron temperature increases when delay time is increased. The distributions of Rydberg atoms on different values of principal quantum number $n$, i.e. $n=30$--60, at an initial electron temperature of 3.3~K are also investigated. The main experimental results are approximately explained by the three-body recombination theory.

Study on high-temperature spectra of asymptotic asymmetric-top radical SiO2

Wu Dong-Lan, Zeng Xue-Feng, Xie An-Dong, Wan Hui-Jun
Chin. Phys. B, 2010, 19 (4): 043301 doi: 10.1088/1674-1056/19/4/043301
Full Text: [PDF 219 KB] (Downloads:602)
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Total internal partition sums are calculated in the product approximation at temperatures up to 6000~K for the asymptotic asymmetric-top SiO2 molecule. The rotational partition function and the vibrational partition function are calculated with the rigid-top model and in the harmonic oscillator approximation, respectively. Our values of the total internal partition sums are consistent with the calculated value in the Gaussian program within $-0.137$% at 296~K. Using the calculated partition functions and the rotationless transition dipole moment squared as a constant, we calculate the line intensities of 001--000 band of SiO2 at normal, medium and high temperatures. Simulated spectra of the 001--000 band of the asymptotic asymmetric-top SiO2 molecule at 2000, 5000 and 6000~K are also obtained.

Far-infrared conductivity of CuS nanoparticles measured by terahertz time-domain spectroscopy

Yang Yu-Ping, Zhang Zhen-Wei, Shi Yu-Lei, Feng Shuai, Wang Wen-Zhong
Chin. Phys. B, 2010, 19 (4): 043302 doi: 10.1088/1674-1056/19/4/043302
Full Text: [PDF 494 KB] (Downloads:1522)
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This paper reports that terahertz time-domain spectroscopy is used to measure the optical properties of CuS nanoparticles in composite samples. The complex conductivity of pure CuS nanoparticles is extracted by applying the Bruggeman effective medium theory. The experimental data are consistent with the Drude--Smith model of conductivity in the range of 0.2--1.5~THz. The results demonstrate that carriers become localized with a backscattering behaviour in small-size nanostructures. In addition, the time constant for the carrier scattering is obtained and is only 64.3~{fs} due to increased electron interaction with interfaces and grain boundaries.

Nonsequential double ionization of the aligned hydrogen molecule in strong field

Li Yan, Yang Shi-Ping, Jia Xin-Yan, Chen Jing
Chin. Phys. B, 2010, 19 (4): 043303 doi: 10.1088/1674-1056/19/4/043303
Full Text: [PDF 126 KB] (Downloads:745)
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This paper studies the nonsequential double ionization (NSDI) process of diatomic molecules aligned parallel and perpendicular to an intense linearly polarized laser field by using a three-dimensional semiclassical model. With this model, it achieves insight into the ion momentum distribution under the combined influence of a two-centre Coulomb potential and an intense laser field, and this result shows the significant influence of molecular alignment on the ratio between double and single ionization rate. Careful investigations show that the NSDI process for different alignment molecules has a close relation to the laser intensity and the different bounding electron distribution has a significant influence on the final ion momentum distribution.

Stereodynamics study of reactions N(2D)+HD→NH+D and ND+H

Yue Xian-Fang, Cheng Jie, Li Hong, Zhang Yong-Qiang, Emilia L. Wu
Chin. Phys. B, 2010, 19 (4): 043401 doi: 10.1088/1674-1056/19/4/043401
Full Text: [PDF 174 KB] (Downloads:742)
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The product polarizations of the title reactions are investigated by employing the quasi-classical trajectory (QCT) method. The four generalized polarization-dependent differential cross-sections (PDDCSs) $({2\pi } / \sigma )(\d\sigma _{00} / \d\omega _t )$, $({2\pi } / \sigma )(\d\sigma _{20} / \d\omega _t )$, $({2\pi } / \sigma )(\d\sigma _{22 + } / \d\omega _t )$, and $({2\pi } / \sigma )(\d\sigma _{21 - } / \d\omega _t )$ are calculated in the centre-of-mass frame. The distribution of the angle between ${{\bm k}}$ and ${{\bm j^\prime }}$, $P(\theta _r )$, the distribution of the dihedral angle denoting ${{\bm k}}${--}$\bm k^\prime $--$\bm j^\prime $ correlation, $P(\phi _r )$, as well as the angular distribution of product rotational vectors in the form of polar plots $P(\theta _r ,\phi _r )$ are calculated. The isotope effect is also revealed and primarily attributed to the difference in mass factor between the two title reactions.

Density functional study on chirospectra of hydrogen-bonded systems X-(H2O) 3 (X = F,Cl,Br,I)

Mang Chao-Yong, Li Zhen-Gui, Wu Ke-Chen
Chin. Phys. B, 2010, 19 (4): 043601 doi: 10.1088/1674-1056/19/4/043601
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This paper calculates the molecular structures, infrared, Raman, circular dichroism spectra and optical rotatory powers of some hydrogen-bonded supramolecular systems as a cyclic water trimer, (H2O)3 and its pyramidal halide complexes, $X^-$(H2O)3 ($X$ = F, Cl, Br, I) with the gradient-corrected density functional theory method at the B3LYP/6--311++G(2d,2p) and B3LYP/Aug--cc--pVTZ levels. It finds that the complexation of halide anions with the water trimer can efficiently modulate the chirally optical behaviors. The calculated vibrational circular dichroism spectrum illuminates that the vibrational rotational strength of S(+)--(H2O)3 mostly originates from the O--H rocking modes, whereas chirality of S(--)--$X^-$(H2O)$_{3 }$ ($X$ = F, Cl, Br, I) has its important origin in the O--H stretching modes. The calculated optical rotatory power demonstrates that S(+)--(H2O)3 and S(+)--F$^-$(H2O)$_{3 }$ are positively chiral, whereas S(--)--$X^-$(H2O)$_{3 }$ ($X$ = Cl, Br, I) are negatively chiral. With the polarizable continuum model, calculated bulk solvent effect in the solvents water and carbontetrachloride and argon shows that the positive chirality of S(+)--(H2O)3 is enhanced and the negative chirality of S(--)--$X^-$(H2O)$_{3 }$ ($X$ = Cl, Br, I) and the positive chirality of S(+)--F$^-$(H2O)3 are reduced with an augmentation of the solvent dielectric constant.

A study on the effects of the transit parking time on traffic flow based on cellular automata theory

Qian Yong-Sheng, Shi Pei-Ji, Zeng Qiong, Ma Chang-Xi, Lin Fang, Sun Peng, Wang Hailong
Chin. Phys. B, 2010, 19 (4): 048201 doi: 10.1088/1674-1056/19/4/048201
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This paper mainly deals with the effects of transit stops on vehicle speeds and conversion lane numbers in a mixed traffic lane. Based on thorough research of traffic flow and cellular automata theory, it calibrates the cellular length and the running speed. Also, a cellular automata model for mixed traffic flow on a two-lane system under a periodic boundary condition is presented herewith, which also takes into consideration the harbour-shaped transit stop as well. By means of computer simulation, the article also studies the effects of bus parking time on the traffic volume, the transit speed and the fast lane speed at the same time. The results demonstrate that, with the increase of the bus parking time, the traffic volume of the transit stop and the transit speed decrease while the fast lane speed increases. This result could help calculate the transit delay correctly and make arrangements for transit routes reasonably and scientifically.

A first-principles study of the catalytic mechanism of the dehydriding reaction of LiNH2 through adding Ti catalysts

Zhang Hui, Liu Gui-Li, Qi Ke-Zhen, Zhang Guo-Ying, Xiao Ming-Zhu, Zhu Sheng-Long
Chin. Phys. B, 2010, 19 (4): 048601 doi: 10.1088/1674-1056/19/4/048601
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Experiments on a ball milled mixture with a 1:1 molar ratio of LiNH2 and LiH with a small amount (1~mol %) of Ti$nano$, TiCl3 and TiO$2nano$ have revealed a superior catalytic effect on Li--N--H hydrogen storage materials. In the x-ray diffraction profiles, no trace of Ti$nano$, TiCl3 and TiO$2nano$ was found in these doped composites, by which we deduced that Ti atoms enter LiNH2 by partial element substitution. A first-principles plane-wave pseudopotential method based on density functional theory has been used to investigate the catalytic effects of Ti catalysts on the dehydrogenating properties of LiNH$2$ system. The results show that Ti substitution can reduce the dehydrogenation reaction activation energy of LiNH2 and improve the dehydrogenating properties of LiNH2. Based on the analysis of the density of states and overlap populations for LiNH$2$ before and after Ti substitution, it was found that the stability of the system of LiNH$2$ is reduced, which originates from the increase of the valence electrons at the Fermi level ($EF)$ and the decrease of the highest occupied molecular orbital (HOMO)--lowest unoccupied molecular orbital (LUMO) gap ($\Delta EH-L)$ near $EF. The catalytic effect of Ti on the dehydrogenating kinetics of LiNH$2$ may be attributed to the reduction of average populations between N--H per unit bond length (nm$^{ - 1})$, which leads to the reduction of the chemical bond strength of N--H.

Brownian dynamics simulation of the cross-talking effect among modified histones on conformations of nucleosomes

Duan Zhao-Wen, Li Wei, Xie Ping, Dou Shuo-Xing, Wang Peng-Ye
Chin. Phys. B, 2010, 19 (4): 048701 doi: 10.1088/1674-1056/19/4/048701
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Using Brownian dynamics simulation, we studied the effect of histone modifications on conformations of an array of nucleosomes in a segment of chromatin. The simulation demonstrated that the segment of chromatin shows the dynamic behaviour that its conformation can switch between a state with nearly all of the histones being wrapped by DNA and a state with nearly all of the histones being unwrapped by DNA, thus involving the ``cross-talking'' interactions among the histones. Each state can stay for a sufficiently long time. These conformational states are essential for gene expression or gene silence. The simulation also shows that these conformational states can be inherited by the daughter DNAs during DNA replication, giving a theoretical explanation of the epigenetic phenomenon.

Finite size effect of ions and dipoles close to charged interfaces

Tong Chao-Hui, Zhu Yue-Jin
Chin. Phys. B, 2010, 19 (4): 048702 doi: 10.1088/1674-1056/19/4/048702
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The modified dipolar Poisson--Boltzmann (MDPB) equation, where the electrostatics of the dipolar interactions of solvent molecules and also the finite size effects of ions and dipolar solvent molecules are explicitly taken into account on a mean-field level, is studied numerically for a two-plate system with oppositely charged surfaces. The MDPB equation is solved numerically, using the nonlinear Multigrid method, for one-dimensional finite volume meshes. For a high enough surface charge density, numerical results of the MDPB equation reveal that the effective dielectric constant decreases with the increase of the surface charge density. Furthermore, increasing the salt concentration leads to the decrease of the effective dielectric constant close to the charged surfaces. This decrease of the effective dielectric constant with the surface charge density is opposite to the trend from the dipolar Poisson--Boltzmann (DPB) equation. This seemingly inconsistent result is due to the fact that the mean-field approach breaks down in such highly charged systems where the counterions and dipoles are strongly attracted to the charged surfaces and form a quasi two-dimensional layer. In the weak-coupling regime with the electrostatic coupling parameter (the ratio of Bjerrum length to Gouy--Chapman length) $\varXi < 1$, where the MDPB equation works, the effective dielectric constant is independent of the distance from the charged surfaces and there is no accumulation of dipoles near the charged surfaces. Therefore, there are no physical and computational advantages for the MDPB equation over the modified Poisson--Boltzmann (MPB) equation where the effect of dipolar interactions of solvent dipoles is implicitly taken into account in the renormalised dielectric constant.

Periodicity-suppressing effect of periodic lossy-dielectric-loaded cylindrical waveguide

Du Chao-Hai, Liu Pu-Kun, Xue Qian-Zhong
Chin. Phys. B, 2010, 19 (4): 048703 doi: 10.1088/1674-1056/19/4/048703
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Periodic dielectric-loaded waveguide is one of the diaphragmatic waveguides. For the excellent mode-selective propagation ability, it is of value for applications in gyrotron-traveling-wave amplifiers (gyro-TWT), accelerators, and other microwave propagation systems. This paper focuses on studying the application of the strong lossy-dielectric-loaded periodic waveguide in millimeter-wave gyro-TWT. It is revealed that due to the lossy property of the dielectric, the energy in the dielectric slots is absorbed effectively and the high order Bloch harmonics induced by the periodicity of the structure are suppressed, which changes the discrete spectrum under lossless condition into a continuous one. As a result, the periodicity of the system is severely suppressed and a mode in the hollow region could be approximated by a fast wave mode in an empty waveguide. These results bring specific guidance for the applications of the lossy dielectric-loaded waveguide in gyro-TWTs and other devices.

Elastic analysis of an elliptic notch in quasicrystals of point group 10 subjected to shear loading

Li Lian-He
Chin. Phys. B, 2010, 19 (4): 046101 doi: 10.1088/1674-1056/19/4/046101
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Based on the stress potential and complex variable function method, this paper makes an elastic analysis of an elliptic notch subjected to uniform shear stress at infinity in quasicrystals with point group 10. With the aid of conformal transformation, an exact solution for the elliptic notch of the quasicrystals is obtained. The solution of the mode {\rm II} Griffith crack as a special case is constructed. The stress intensity factor and energy release rate have been also obtained as a direct result of the crack solution.

First-principles investigation of N-Ag co-doping effect on electronic properties in p-type ZnO

Zuo Chun-Ying, Wen Jing, Bai Yue-Lei
Chin. Phys. B, 2010, 19 (4): 047101 doi: 10.1088/1674-1056/19/4/047101
Full Text: [PDF 383 KB] (Downloads:1128)
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The geometric structure, band structure and density of states of pure, Ag-doped, N-doped, and N--Ag codoped wurtzite ZnO have been investigated by the first-principles ultra-soft pseudopotential method based on the density functional theory. The calculated results show that the carrier concentration is increased in the ZnO crystal codoped by N and Ag, and the codoped structure is stable and is more in favour of the formation of p-type ZnO.

The energy levels of a two-electron two-dimensional parabolic quantum dot

Li Wei-Ping, Xiao Jing-Lin, Yin Ji-Wen, Yu Yi-Fu, Wang Zi-Wu
Chin. Phys. B, 2010, 19 (4): 047102 doi: 10.1088/1674-1056/19/4/047102
Full Text: [PDF 368 KB] (Downloads:987)
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This paper studies the two-electron total energy and the energy of the electron--electron interaction by using a variational method of Pekar type on the condition of electric--LO-phonon strong coupling in a parabolic quantum dot. It considers the following three cases: 1) two electrons are in the ground state; 2) one electron is in the ground state, the other is in the first-excited state; 3) two electrons are in the first-excited state. The relations of the two-electron total energy and the energy of the electron--electron interaction on the Coulomb binding parameter, the electron-LO-phonon coupling constant and the confinement length of the quantum dot are derived in the three cases.

A dark hollow beam from a selectively liquid-filled photonic crystal fibre

Zhang Mei-Yan, Li Shu-Guang, Yao Yan-Yan, Fu Bo, Zhang Lei
Chin. Phys. B, 2010, 19 (4): 047103 doi: 10.1088/1674-1056/19/4/047103
Full Text: [PDF 3872 KB] (Downloads:682)
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This paper reports that, based on the electromagnetic scattering theory of the multipole method, a high-quality hollow beam is produced through a selectively liquid-filled photonic crystal fibre. Instead of a doughnut shape, a typical hollow beam is produced by other methods; the mode-field images of the hollow-beam photonic crystal fibre satisfy sixth-order rotation symmetry, according to the symmetry of the photonic crystal fibre (PCF) structure. A dark spot size of the liquid-filled photonic crystal fibre-generated hollow beam can be tuned by inserting liquid into the cladding region and varying the photonic crystal fibre structure parameters. The liquid-filled PCF makes a convenient and flexible tool for the guiding and trapping of atoms and the creation of all-fibre optical tweezers.

Influence of geometrical parameters on the behaviour of SiC merged PiN Schottky rectifiers with junction termination extension

Song Qing-Wen, Zhang Yu-Ming, Zhang Yi-Men, Zhang Qian, Guo Hui, Li Zhi-Yun, Wang Zhong-Xu
Chin. Phys. B, 2010, 19 (4): 047201 doi: 10.1088/1674-1056/19/4/047201
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This paper investigates the behaviours of 4H--SiC merged PiN Schottky (MPS) rectifiers with junction termination extension (JTE) by extensive numerical simulations. The simulated results show that the present model matches the experimental data very well. The influences of the JTE design parameters such as the doping concentration and length of the JTE on the breakdown characteristics are discussed in detail. Then the temperature sensitivity of the forward behaviour is studied in terms of the different designs of 4H--SiC MPS with JTE, which provides a particularly useful guideline for the optimal design of MPS rectifiers with JTE.

Magnetotransport through an Aharonov-Bohm ring with parallel double quantum dots coupled to ferromagnetic leads

Wu Shao-Quan, Hou Tao, Zhao Guo-Ping, Yu Wan-Lun
Chin. Phys. B, 2010, 19 (4): 047202 doi: 10.1088/1674-1056/19/4/047202
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Using the Keldysh nonequilibrium Green function and equation-of-motion technique, this paper studies the magnetotransport through an Aharonov--Bohm (AB) ring with parallel double quantum dots coupled to ferromagnetic leads. It calculates the transmission probability in both the equilibrium and the nonequilibrium case, analyses the conductance and the tunnel magnetoresistance for various parameters, and obtains some new results. These results show that this system is provided with an excellent spin filtering property, and that a large tunnelling magnetoresistance and a negative tunnelling magnetoresistance can arise by adjusting relative parameters; these facts indicate that this system is a possible candidate for spin valve transistors, and has important applications in spintronics.

Influence of spin-orbit coupling induced by in-plane external electric field on the intrinsic spin-Hall effect in a Rashba two-dimensional electron gas

Yan Yu-Zhen, Hu Liang-Bin
Chin. Phys. B, 2010, 19 (4): 047203 doi: 10.1088/1674-1056/19/4/047203
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We study theoretically the influence of spin--orbit coupling induced by in-plane external electric field on the intrinsic spin-Hall effect in a two-dimensional electron gas with Rashba spin--orbit coupling. We show that, after such an influence is taken into account, the static intrinsic spin-Hall effect can be stabilized in a disordered Rashba two-dimensional electron gas, and the static intrinsic spin-Hall conductivity shall exhibit some interesting characteristics as conceived in some original theoretical proposals.

Study of a 4H-SiC epitaxial n-channel MOSFET

Tang Xiao-Yan, Zhang Yu-Ming, Zhang Yi-Men
Chin. Phys. B, 2010, 19 (4): 047204 doi: 10.1088/1674-1056/19/4/047204
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Epitaxial channel metal-oxide semiconductor field-effect transistors (MOSFETs) have been proposed as one possible way to avoid the problem of low inversion layers in traditional MOSFETs. This paper presents an equation of maximum depletion width modified which is more accurate than the original equation. A 4H--SiC epitaxial n-channel MOSFET using two-dimensional simulator ISE is simulated. Optimized structure would be realized based on the simulated results for increasing channel mobility.

Improvement of the light output and contact resistance of InGaN-based light-emitting diodes based on tantalum-doped indium tin oxide as p-type electrodes

Huang Jun-Yi, Fan Guang-Han, Zheng Shu-Wen, Niu Qiao-Li, Li Shu-Ti, Cao Jian-Xing, Su Jun, Zhang Yong
Chin. Phys. B, 2010, 19 (4): 047205 doi: 10.1088/1674-1056/19/4/047205
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This paper reports that highly transparent and low resistance tantalum-doped indium tin oxide (Ta-doped ITO) films contacted to p-type GaN have been prepared by the electron-beam evaporation technique. The Ta-doped ITO contacts become Ohmic with a specific contact resistance of $\sim 5.65\times 10^{ - 5}$~$\Omega \cdot$cm$^{2}$ and show the transmittance of $\sim $98% at a wavelength of 440~nm when annealed at 500~\du. Blue light emitting diodes (LEDs) fabricated with Ta-doped ITO p-type Ohmic contact layers give a forward-bias voltage of 3.21~V at an injection current of 20~mA. It further shows that the output power of LEDs with Ta-doped ITO contacts is enhanced 62% at 20~mA in comparison with that of LEDs with conventional Ni/Au contacts.

Electric-stress reliability and current collapse of different thickness SiNx passivated AlGaN/GaN high electron mobility transistors

Yang Ling, Hu Gui-Zhou, Hao Yue, Ma Xiao-Hua, Quan Si, Yang Li-Yuan, Jiang Shou-Gao
Chin. Phys. B, 2010, 19 (4): 047301 doi: 10.1088/1674-1056/19/4/047301
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This paper investigates the impact of electrical degradation and current collapse on different thickness SiNx passivated AlGaN/GaN high electron mobility transistors. It finds that higher thickness SiNx passivation can significantly improve the high-electric-field reliability of a device. The degradation mechanism of the SiNx passivation layer under ON-state stress has also been discussed in detail. Under the ON-state stress, the strong electric-field led to degradation of SiNx passivation located in the gate-drain region. As the thickness of SiNx passivation increases, the density of the surface state will be increased to some extent. Meanwhile, it is found that the high NH3 flow in the plasma enhanced chemical vapour deposition process could reduce the surface state and suppress the current collapse.

Electronic and optical properties of GaN/AlN quantum dots with adjacent threading dislocations

Ye Han, Lu Peng-Fei, Yu Zhong-Yuan, Yao Wen-Jie, Chen Zhi-Hui, Jia Bo-Yong, Liu Yu-Min
Chin. Phys. B, 2010, 19 (4): 047302 doi: 10.1088/1674-1056/19/4/047302
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We present a theory to simulate a coherent GaN QD with an adjacent pure edge threading dislocation by using a finite element method. The piezoelectric effects and the strain modified band edges are investigated in the framework of multi-band $\bm k\cdot \bm p$ theory to calculate the electron and the heavy hole energy levels. The linear optical absorption coefficients corresponding to the interband ground state transition are obtained via the density matrix approach and perturbation expansion method. The results indicate that the strain distribution of the threading dislocation affects the electronic structure. Moreover, the ground state transition behaviour is also influenced by the position of the adjacent threading dislocation.

Electronic transport through a periodic array of quantum-dot rings

Xue Hai-Bin, Zhang Han-Yin, Nie Yi-Hang, Li Zhi-Jian, Liang Jiu-Qing
Chin. Phys. B, 2010, 19 (4): 047303 doi: 10.1088/1674-1056/19/4/047303
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Using the tight-binding approximation and the transfer matrix method, this paper studies the electronic transport properties through a periodic array of quantum-dot (QD) rings threaded by a magnetic flux. It demonstrates that the even--odd parity of the QD number in a single ring and the number of the QD rings in the array play a crucial role in the electron transmission. For a single QD ring, the resonance and antiresonance transmission depend not only on the applied magnetic flux but also on the difference between the number of QDs on the two arms of the ring. For an array of QD rings, the transmission properties are related not only to the even--odd parity of the number $N_{0}$ of QDs in the single ring but also to the even--odd parity of the ring number $N$ in the array. When the incident electron energy is aligned with the site energy, for the array of $N$ rings with $N_{0}={\rm odd}$ the antiresonance transmission cannot occur but the resonance transmission may occur and the transmission spectrum has $N$ resonance peaks ($N-1$ resonance peaks) in a period for $N={\rm odd}$ (for $N={\rm even}$). For the array of $N$ rings with $N_{0}={\rm even}$ the transmission properties depend on the flux threading the ring and the QD number on one arm of the ring. These results may be helpful in designing QD devices.

Influence of local environment on the intensity of the localized surface plasmon polariton of Ag nanoparticles

Huang Qian, Zhang Xiao-Dan, Zhang He, Xiong Shao-Zhen, Geng Wei-Dong, Geng Xin-Hua, Zhao Ying
Chin. Phys. B, 2010, 19 (4): 047304 doi: 10.1088/1674-1056/19/4/047304
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A combined Ag nanoparticle with an insulating or conductive layer structure has been designed for molecular detection using surface enhanced Raman scattering microscopy. Optical absorption studies revealed localized surface plasmon resonance, which shows regular red shift with increasing environmental dielectric constant. With the combined structure of surface enhanced Raman scattering substrates and rhodamine 6G as a test molecule, the results in this paper show that the absorption has a linear relationship with the local electromagnetic field for insulating substrates, and the electrical property of the substrate has a non-negligible effect on the intensity of the local electromagnetic field and hence the Raman enhancement.

Simulation research on offset field-plate used as edge termination in 4H-SiC merged PiN-Schottky diodes

Chen Feng-Ping, Zhang Yu-Ming, Zhang Yi-Men, L\"u Hong-Liang, Song Qing-Wen
Chin. Phys. B, 2010, 19 (4): 047305 doi: 10.1088/1674-1056/19/4/047305
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A new structure of 4H--silicon carbide (SiC) merged PiN-Schottky (MPS) diodes with offset field-plate (FP) as edge termination is developed. To understand the influences of 4H--SiC MPS diodes with offset FP on the characteristics, simulations have been done by using ISE TCAD. Related factors of offset FP have been studied as well to optimise the reverse characteristics of 4H--SiC MPS diodes. The simulation results show that the device using offset FP can create a higher blocking voltage under reverse bias as compared with that using field guard rings. Besides, the offset FP does not cause any extra steps in the manufacture of MPS diodes.

An oxide/silicon core/shell nanowire metal-oxide semiconductor field-effect transistor

Zhang Li-Ning, He Jin, Zhou Wang, Chen Lin, Xu Yi-Wen
Chin. Phys. B, 2010, 19 (4): 047306 doi: 10.1088/1674-1056/19/4/047306
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This paper studies an oxide/silicon {c}ore/{s}hell {n}anowire {M}OSFET (OS-CSNM). Through three-dimensional device simulations, we have demonstrated that the OS-CSNM has a lower leakage current and higher $I_{\rm on}/I_{\rm off}$ ratio after introducing the oxide core into a {t}raditional {n}anowire {M}OSFET (TNM). The oxide/silicon OS-CSNM structure suppresses threshold voltage roll-off, drain induced barrier lowering and subthreshold swing degradation. Smaller intrinsic device delay is also observed in OS-CSNM in comparison with that of TNM.

Study on the drain bias effect on negative bias temperature instability degradation of an ultra-short p-channel metal-oxide-semiconductor field-effect transistor Hot!

Cao Yan-Rong, Ma Xiao-Hua, Hao Yue, Hu Shi-Gang
Chin. Phys. B, 2010, 19 (4): 047307 doi: 10.1088/1674-1056/19/4/047307
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This paper studies the effect of drain bias on ultra-short p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) degradation during negative bias temperature (NBT) stress. When a relatively large gate voltage is applied, the degradation magnitude is much more than the drain voltage which is the same as the gate voltage supplied, and the time exponent gets larger than that of the NBT instability (NBTI). With decreasing drain voltage, the degradation magnitude and the time exponent all get smaller. At some values of the drain voltage, the degradation magnitude is even smaller than that of NBTI, and when the drain voltage gets small enough, the exhibition of degradation becomes very similar to the NBTI degradation. When a relatively large drain voltage is applied, with decreasing gate voltage, the degradation magnitude gets smaller. However, the time exponent becomes larger. With the help of electric field simulation, this paper concludes that the degradation magnitude is determined by the vertical electric field of the oxide, the amount of hot holes generated by the strong channel lateral electric field at the gate/drain overlap region, and the time exponent is mainly controlled by localized damage caused by the lateral electric field of the oxide in the gate/drain overlap region where hot carriers are produced.

Capacitance characteristics of metal-oxide-semiconductor capacitors with a single layer of embedded nickel nanoparticles for the application of nonvolatile memory

Li Wei, Xu Ling, Zhao Wei-Ming, Ding Hong-Lin, Ma Zhong-Yuan, Xu Jun, Chen Kun-Ji
Chin. Phys. B, 2010, 19 (4): 047308 doi: 10.1088/1674-1056/19/4/047308
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This paper reports that metal-oxide-semiconductor (MOS) capacitors with a single layer of Ni nanoparticles were successfully fabricated by using electron-beam evaporation and rapid thermal annealing for application to nonvolatile memory. Experimental scanning electron microscopy images showed that Ni nanoparticles of about 5~nm in diameter were clearly embedded in the SiO2 layer on p-type Si (100). Capacitance--voltage measurements of the MOS capacitor show large flat-band voltage shifts of 1.8~V, which indicate the presence of charge storage in the nickel nanoparticles. In addition, the charge-retention characteristics of MOS capacitors with Ni nanoparticles were investigated by using capacitance--time measurements. The results showed that there was a decay of the capacitance embedded with Ni nanoparticles for an electron charge after 10$^{4}$~s. But only a slight decay of the capacitance originating from hole charging was observed. The present results indicate that this technique is promising for the efficient formation or insertion of metal nanoparticles inside MOS structures.

Experimental studies of extraordinary light transmission through periodic arrays of subwavelength square and rectangular holes in metal films

Hua Yi-Lei, Fu Jin-Xin, Li Jiang-Yan, Li Zhi-Yuan, Yang Hai-Fang
Chin. Phys. B, 2010, 19 (4): 047309 doi: 10.1088/1674-1056/19/4/047309
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We fabricate a series of periodic arrays of subwavelength square and rectangular air holes on gold films, and measure the transmission spectra of these metallic nanostructures. By changing some geometrical and physical parameters, such as array period, air hole size and shape, and the incident light polarization, we verify that both global surface plasmon resonance and localized waveguide mode resonance are influential on enhancing the transmission of light through nanostructured metal films. These two resonances induce different behaviours of transmission peak shift. The transmission through the rectangular air-hole structures exhibits an obvious polarization effect dependent on the morphology. Numerical simulations are also made by a plane-wave transfer-matrix method and in good consistency with the experimental results.

Pressure effect study on the IV property of the GaAs-based resonant tunnelling structure by photoluminescence measurement

Li Qiu-Zhu, Wang Kai-Qun, Jian Ao-Qun, Liu Xin, Zhang Bin-Zhen
Chin. Phys. B, 2010, 19 (4): 047310 doi: 10.1088/1674-1056/19/4/047310
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This paper discusses the $I$--$V$ property of the GaAs-based resonant tunnelling structure (RTS) under external uniaxial pressure by photoluminescence studies. Compressive pressure parallel to the [110] direction, whose value is determined by Hooke's law, is imposed on the sample by a helix micrometer. With the increase of the applied external uniaxial compressive pressure, the blue shift and splitting of the luminescence peaks were observed, which have some influence on the $I$--$V$ curve of RTS from the point of view of the energy gap, and the splitting became more apparent with applied pressure. Full width at half maximum broadening could also be observed.

Effect of Dy substitution on magnetic properties and magnetocaloric effects of Tb6Co1.67Si3 compounds

Zhao Jin-Liang, Shen Jun, Li Yang-Xian, Hu Feng-Xia, Sun Ji-Rong, Shen Bao-Gen
Chin. Phys. B, 2010, 19 (4): 047501 doi: 10.1088/1674-1056/19/4/047501
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The magnetic and magnetocaloric properties of (Tb$_{1 - x}$Dy$_{x})_{6}$Co$_{1.67}$Si3 ($0 \le x \le 0.8$) have been experimentally investigated. The compounds exhibit a Ce$_{6}$Ni2Si3-type hexagonal structure and undergo a second-order magnetic transition. The Curie temperature decreases from $\sim 187$~K to 142~K as the content of Dy grows from 0 to 0.8. The maximal magnetic entropy change, for a field change of 0--5~T, varies between $\sim 6.2$ and $\sim 7.4$~J/kg$\cdot$K, slightly decreasing when Dy is introduced. The substitution of Dy leads to a remarkable increase in refrigeration capacity (RC). A large RC value of $\sim 626$~J/kg is achieved for $x=0.4$ under a field change of 0--5~T.

Order of magnetic transition and large magnetocaloric effect in Er3Co* Hot!

Shen Jun, Zhao Jin-Liang, Hu Feng-Xia, Wu Jian-Feng, Sun Ji-Rong, Shen Bao-Gen
Chin. Phys. B, 2010, 19 (4): 047502 doi: 10.1088/1674-1056/19/4/047502
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We have studied the magnetic and magnetocaloric properties of the Er3Co compound, which undergoes ferromagnetic ordering below the Curie temperature $T_{\rm C}=13$~K. It is found by fitting the isothermal magnetization curves that the Landau model is appropriate to describe the Er3Co compound. The giant magnetocaloric effect (MCE) without hysteresis loss around $T_{\rm C}$ is found to result from the second-order ferromagnetic-to-paramagnetic transition. The maximal value of magnetic entropy change is 24.5~J/kg$\cdot$K with a refrigerant capacity (RC) value of 476~J/kg for a field change of 0--5~T. Large reversible MEC and RC indicate the potentiality of Er3Co as a candidate magnetic refrigerant at low temperatures.

Up-conversion photoluminescence characteristics of Yb3+:Er3+:Tm3+ co-doped borosilicate glasses

Li Cheng-Ren, Xu Wei, Dong Bin, Li Shu-Feng, Ding Jian-Hua, Cheng Yu-Qi, Yin Hai-Tao
Chin. Phys. B, 2010, 19 (4): 047801 doi: 10.1088/1674-1056/19/4/047801
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Yb3+:Er3+:Tm3+co-doped borosilicate glasses are prepared. Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared, which are excited by a 978-nm laser diode, are measured, and the mechanisms of energy transfer among Yb3+, Er3+ and Tm3+ ions are discussed. The results show that there is an unexpected wavelength at 900-nm emission from Yb3+ Stark splitting levels to pump Tm3+ ions and there exists an optimum pump power. The concentration of the Tm3+ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the Yb3+:Er3+:Tm3+ co-doped borosilicate glasses.

Exciplex elimination in an organic light-emitting diode based on a fluorene derivative by inserting 4,4'-N,N'-dicarbazole-biphenyl into donor/acceptor interface

Zhang Wei, Yu Jun-Sheng, Huang Jiang, Jiang Ya-Dong, Zhang Qing, Cao Kang-Li
Chin. Phys. B, 2010, 19 (4): 047802 doi: 10.1088/1674-1056/19/4/047802
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Organic light-emitting diodes (OLEDs) composed of a novel fluorene derivative of 2,3-bis(9,9-dihexyl-9H-fluoren-2-yl)-6,7-difluoroquinoxaline (F2Py) were fabricated, and exciplex emission was observed in the device. To depress the exciplex in an OLED for pure colour light emission, 4, 4'-N,N'-dicarbazole-biphenyl (CBP) was inserted as a separator at the donor/acceptor interface. It was found that the device without the CBP layer emitted a green light peaking at 542~nm from the exciplex and a shoulder peak about 430~nm from F2Py. In contrast, the OLED with CBP layer emitted only a blue light peak at about 432~nm from F2Py. Device efficiencies were calculated by a simulative mode in an injection controlled type mechanism, and the results showed that exciplexes yield much lower quantum efficiency than excitons. The device with CBP has a higher power efficiency as no exciplex was present.

Thermoluminescence and optically stimulated luminescence disadvantages of α-Al2O3:C crystal grown by the temperature gradient technique

Yang Xin-Bo, Xu Jun, Li Hong-Jun, Bi Qun-Yu, Cheng Yan, Su Liang-Bi, Tang Qiang
Chin. Phys. B, 2010, 19 (4): 047803 doi: 10.1088/1674-1056/19/4/047803
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Recently, α-Al2O3:C crystal with highly sensitive thermoluminescence (TL) and optically stimulated luminescence (OSL) has been successfully grown by the temperature gradient technique. This paper investigates the heating rate dependence of TL sensitivity, light-induced fading of TL signals and thermal stability of OSL of α-Al2O3:C crystals. As the heating rate increases, the integral TL response decreases and the dosimetric glow peak shifts to higher temperatures in α-Al2O3:C crystals. Light-induced fading of TL increases with the irradiation dose, and TL response decreases as the exposure time increases, especially in the first 15 minutes. With the increasing intensity of the exposure light, the TL fading of α-Al2O3:C crystal increases sharply. The OSL response of as-grown α-Al2O3:C crystal is quite stable below 373 K and decreases sharply for higher temperatures.

Ray tracing/correlation approach to estimation of surface-based duct parameters from radar clutter

Zhao Xiao-Feng, Huang Si-Xun, Sheng Zheng
Chin. Phys. B, 2010, 19 (4): 049201 doi: 10.1088/1674-1056/19/4/049201
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This paper describes a technique to estimate surface-based duct parameters by using a simple ray tracing/correlation method. The approach is novel in that it incorporates the Spearman rank-order correlation scheme between the observed surface clutter and the surface ray density for a given propagation path. The simulation results and the real data results both demonstrate the ability of this method to estimate surface-based duct parameters. Compared with the results obtained by a modified genetic algorithm combined with the parabolic wave equation, the results retrieved from the ray tracing/correlation scheme show a minor reduction in accuracy but a great improvement on computation time. Therefore the ray tracing/correlation method might be used as a precursor to more sophisticated and slower techniques, such as genetic algorithm and particle filters, by narrowing the parameter search space and providing a comprehensive and more efficient estimation algorithm.

Second-harmonic generation as a DNA malignancy indicator of prostate glandular epithelial cells

Zhuang Zheng-Fei, Liu Han-Ping, Guo Zhou-Yi, Zhuo Shuang-Mu, Yu Bi-Ying, Deng Xiao-Yuan
Chin. Phys. B, 2010, 19 (4): 049501 doi: 10.1088/1674-1056/19/4/049501
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This paper first demonstrates second-harmonic generation (SHG) in the intact cell nucleus, which acts as an optical indicator of DNA malignancy in prostate glandular epithelial cells. Within a scanning region of $2.7~\mu$m$\times 2.7~\mu$m in cell nuclei, SHG signals produced from benign prostatic hyperplasia (BPH) and prostate carcinoma (PC) tissues (mouse model C57BL/6) have been investigated. Statistical analyses ($t$ test) of a total of 405 measurements (204 nuclei from BPH and 201 nuclei from PC) show that SHG signals from BPH and PC have a distinct difference ($p < 0.05)$, suggesting a potential optical method of revealing very early malignancy in prostate glandular epithelial cells based upon induced biochemical and/or biophysical modifications in DNA.
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