中国物理B

Select

Evolving laws of human cooperative behaviour

李克平, 范红强

2010 (9): 90101-090101. doi: 10.1088/1674-1056/19/9/090101

摘要 ( 1385 )

PDF(307KB) ( 606 )

In this study, we improve Lévy walk model, and make it suitable for simulating the collective behaviours of humans. Here we show how rescuers find missing persons by collective cooperative search in a natural background. In the search process, the search strategy represents an optimal algorithm which is used to maximize the success rates for finding missing persons. We simulate the rescuer's movement pattern, and find some basic laws governing the rescuer's cooperative search. For example, the probability that each rescuer finds missing persons shows a power law distribution.

参考文献 | 相关文章 | 计量指标

Select

Meshless analysis of three-dimensional steady-state heat conduction problems

程荣军, 葛红霞

2010 (9): 90201-090201. doi: 10.1088/1674-1056/19/9/090201

摘要 ( 1564 )

PDF(140KB) ( 2026 )

Steady-state heat conduction problems arisen in connection with various physical and engineering problems where the functions satisfy a given partial differential equation and particular boundary conditions, have attracted much attention and research recently. These problems are independent of time and involve only space coordinates, as in Poisson's equation or the Laplace equation with Dirichlet, Neuman, or mixed conditions. When the problems are too complex, it is difficult to find an analytical solution, the only choice left is an approximate numerical solution. This paper deals with the numerical solution of three-dimensional steady-state heat conduction problems using the meshless reproducing kernel particle method (RKPM). A variational method is used to obtain the discrete equations. The essential boundary conditions are enforced by the penalty method. The effectiveness of RKPM for three-dimensional steady-state heat conduction problems is investigated by two numerical examples.

参考文献 | 相关文章 | 计量指标

Select

Effect of unequal injection rates and different hopping rates on asymmetric exclusion processes with junction

肖松, 蔡九菊, 刘飞, 刘明哲

2010 (9): 90202-090202. doi: 10.1088/1674-1056/19/9/090202

摘要 ( 1670 )

PDF(2721KB) ( 667 )

In this paper, the effects of unequal injection rates and different hopping rates on the asymmetric simple exclusion process (ASEP) with a 2-input 1-output junction are studied by using a simple mean-field approach and extensive computer simulations. The steady-state particle currents, the density profiles, and the phase diagrams are obtained. It is shown that with unequal injection rates and different hopping rates, the phase diagram structure is qualitatively changed. The theoretical calculations are in good agreement with Monte Carlo simulations.

参考文献 | 相关文章 | 计量指标

Select

Payoff-based accumulative effect promotes cooperation in spatial prisoner's dilemma

刘永奎, 李智, 陈小杰, 王龙

2010 (9): 90203-090203. doi: 10.1088/1674-1056/19/9/090203

摘要 ( 1567 )

PDF(2506KB) ( 1142 )

We study the effect of accumulative payoff on the evolution of cooperation in the evolutionary prisoner's dilemma on a square lattice. We introduce a decaying factor for the accumulative payoff, which characterizes the extent that the historical payoff is accumulated. It is shown that for fixed values of the temptation to defect, the density of cooperators increases with the value of the decaying factor. This indicates that the more the historical payoff is involved, the more favourable cooperators become. In the critical region where the cooperator density converges to zero, cooperators vanish according to a power-law-like behaviour. The associated exponents agree approximately with the two-dimensional directed percolation and depend weakly on the value of the decaying factor.

参考文献 | 相关文章 | 计量指标

Select

The complex variable reproducing kernel particle method for two-dimensional elastodynamics

陈丽, 程玉民

2010 (9): 90204-090204. doi: 10.1088/1674-1056/19/9/090204

摘要 ( 1537 )

PDF(237KB) ( 813 )

On the basis of the reproducing kernel particle method (RKPM), a new meshless method, which is called the complex variable reproducing kernel particle method (CVRKPM), for two-dimensional elastodynamics is presented in this paper. The advantages of the CVRKPM are that the correction function of a two-dimensional problem is formed with one-dimensional basis function when the shape function is obtained. The Galerkin weak form is employed to obtain the discretised system equations, and implicit time integration method, which is the Newmark method, is used for time history analysis. And the penalty method is employed to apply the essential boundary conditions. Then the corresponding formulae of the CVRKPM for two-dimensional elastodynamics are obtained. Three numerical examples of two-dimensional elastodynamics are presented, and the CVRKPM results are compared with the ones of the RKPM and analytical solutions. It is evident that the numerical results of the CVRKPM are in excellent agreement with the analytical solution, and that the CVRKPM has greater precision than the RKPM.

参考文献 | 相关文章 | 计量指标

Select

Symmetry reduction and exact solutions of the (3+1)-dimensional Zakharovben–Kuznetsov equation

董仲周, 陈勇, 郎艳怀

2010 (9): 90205-090205. doi: 10.1088/1674-1056/19/9/090205

摘要 ( 1505 )

PDF(951KB) ( 889 )

By means of the classical method, we investigate the (3+1)-dimensional Zakharov--Kuznetsov equation. The symmetry group of the (3+1)-dimensional Zakharov--Kuznetsov equation is studied first and the theorem of group invariant solutions is constructed. Then using the associated vector fields of the obtained symmetry, we give the one-, two-, and three-parameter optimal systems of group-invariant solutions. Based on the optimal system, we derive the reductions and some new solutions of the (3+1)-dimensional Zakharov--Kuznetsov equation.

参考文献 | 相关文章 | 计量指标

Select

Spatial pattern formation of a ratio-dependent predator–prey model

林望

2010 (9): 90206-090206. doi: 10.1088/1674-1056/19/9/090206

摘要 ( 1488 )

PDF(9707KB) ( 583 )

This paper presents a theoretical analysis of evolutionary process that involves organisms distribution and their interaction of spatially distributed population with diffusion in a Holling-III ratio-dependent predator--prey model, the sufficient conditions for diffusion-driven instability with Neumann boundary conditions are obtained. Furthermore, it presents novel numerical evidence of time evolution of patterns controlled by diffusion in the model, and finds that the model dynamics exhibits complex pattern replication, and the pattern formation depends on the choice of the initial conditions. The ideas in this paper may provide a better understanding of the pattern formation in ecosystems.

参考文献 | 相关文章 | 计量指标

Select

Energy average formula of photon gas rederived by using the generalised Hermann–Feynman theorem

范洪义, 姜年权

2010 (9): 90301-090301. doi: 10.1088/1674-1056/19/9/090301

摘要 ( 1475 )

PDF(81KB) ( 616 )

By virtue of the generalised Hermann--Feynmam theorem we re-derive the energy average formula of photon gas. This is another useful application of the theorem.

参考文献 | 相关文章 | 计量指标

Select

Weak Noether symmetry for a nonholonomic controllable mechanical system

夏丽莉, 山灵芳

2010 (9): 90302-090302. doi: 10.1088/1674-1056/19/9/090302

摘要 ( 1481 )

PDF(85KB) ( 547 )

This paper discusses the weak Noether symmetry for a nonholonomic controllable mechanical system of Chetaev type, and presents expressions of three kinds of conserved quantities obtained by using weak Noether symmetry. Finally, the application of these new results is illustrated by an example.

参考文献 | 相关文章 | 计量指标

Select

Conformal invariance and Hojman conserved quantities for holonomic systems with quasi-coordinates

罗一平, 傅景礼

2010 (9): 90303-090303. doi: 10.1088/1674-1056/19/9/090303

摘要 ( 1549 )

PDF(97KB) ( 585 )

We propose a new concept of the conformal invariance and the conserved quantities for holonomic systems with quasi-coordinates. A one-parameter infinitesimal transformation group and its infinitesimal transformation vector of generators for holonomic systems with quasi-coordinates are described in detail. The conformal factor in the determining equations of the Lie symmetry is found. The necessary and sufficient conditions of conformal invariance, which are simultaneously of Lie symmetry, are given. The conformal invariance may lead to corresponding Hojman conserved quantities when the conformal invariance satisfies some conditions. Finally, an illustration example is introduced to demonstrate the application of the result.

参考文献 | 相关文章 | 计量指标

Select

Conformal invariance and conserved quantities of Appell systems under second-class Mei symmetry

罗一平, 傅景礼

2010 (9): 90304-090304. doi: 10.1088/1674-1056/19/9/090304

摘要 ( 1495 )

PDF(96KB) ( 804 )

In this paper we introduce the new concept of the conformal invariance and the conserved quantities for Appell systems under second-class Mei symmetry. The one-parameter infinitesimal transformation group and infinitesimal transformation vector of generator are described in detail. The conformal factor in the determining equations under second-class Mei symmetry is found. The relationship between Appell system's conformal invariance and Mei symmetry are discussed. And Appell system's conformal invariance under second-class Mei symmetry may lead to corresponding Hojman conserved quantities when the conformal invariance satisfies some conditions. Lastly, an example is provided to illustrate the application of the result.

参考文献 | 相关文章 | 计量指标

Select

Fusion and fission solitons for the (2+1)-dimensional generalized Breor–Kaup system

强继业, 马松华, 方建平

2010 (9): 90305-090305. doi: 10.1088/1674-1056/19/9/090305

摘要 ( 1551 )

PDF(4181KB) ( 834 )

With a projective equation and a linear variable separation method, this paper derives new families of variable separation solutions (including solitory wave solutions, periodic wave solutions, and rational function solutions) with arbitrary functions for (2+1)-dimensional generalized Breor--Kaup (GBK) system. Based on the derived solitary wave excitation, it obtains fusion and fission solitons.

参考文献 | 相关文章 | 计量指标

Select

Chaos and chaotic control in a relative rotation nonlinear dynamical system under parametric excitation

时培明, 韩东颖, 刘彬

2010 (9): 90306-090306. doi: 10.1088/1674-1056/19/9/090306

摘要 ( 1533 )

PDF(167KB) ( 689 )

This paper studies the chaotic behaviours of a relative rotation nonlinear dynamical system under parametric excitation and its control. The dynamical equation of relative rotation nonlinear dynamical system under parametric excitation is deduced by using the dissipation Lagrange equation. The criterion of existence of chaos under parametric excitation is given by using the Melnikov theory. The chaotic behaviours are detected by numerical simulations including bifurcation diagrams, Poincaré map and maximal Lyapunov exponent. Furthermore, it implements chaotic control using non-feedback method. It obtains the parameter condition of chaotic control by the Melnikov theory. Numerical simulation results show the consistence with the theoretical analysis. The chaotic motions can be controlled to period-motions by adding an excitation term.

参考文献 | 相关文章 | 计量指标

Select

Nonlinear two-mode squeezing obtained by analysing two-mode exponential quadrature operators in entangled state representation

刘堂昆, 单传家, 刘继兵, 范洪义

2010 (9): 90307-090307. doi: 10.1088/1674-1056/19/9/090307

摘要 ( 1524 )

PDF(90KB) ( 781 )

By analysing the properties of two-mode quadratures in an entangled state representation (ESR) we derive from ESR some complicated exponential quadrature operators for nonlinear two-mode squeezing, which directly leads to wave function of the nonlinear squeezed state in ESR.

参考文献 | 相关文章 | 计量指标

Select

Continuum states of modified Morse potential

卫高峰, 陈文利

2010 (9): 90308-090308. doi: 10.1088/1674-1056/19/9/090308

摘要 ( 1468 )

PDF(99KB) ( 1467 )

Using a proper approximation scheme to the centrifugal term, we study any l-wave continuum states of the Schrõdinger equation for the modified Morse potential. The normalised analytical radial wave functions are presented, and a corresponding calculation formula of phase shifts is derived. It is shown that the energy levels of the continuum states reduce to those of the bound states at the poles of the scattering amplitude. Some numerical results are calculated to show the accuracy of our results.

参考文献 | 相关文章 | 计量指标

Select

Exact solution of entanglement of the double Jaynes–Cummings model without rotating wave approximation

任学藻, 姜道来, 丛红璐, 黎雷

2010 (9): 90309-090309. doi: 10.1088/1674-1056/19/9/090309

摘要 ( 1777 )

PDF(671KB) ( 597 )

This paper investigates the influences of atom--field coupling and dipole--dipole coupling for atoms on the entanglement between two atoms by means of concurrence. The results show that the sudden death occurs when the atom--field coupling is strong enough, and the collapse and the revival appear when the dipole--dipole interaction is strong enough.

参考文献 | 相关文章 | 计量指标

Select

Nondestructive and complete Bell-state analysis for atomic qubit systems

何勇, 姜年权

2010 (9): 90310-090310. doi: 10.1088/1674-1056/19/9/090310

摘要 ( 1580 )

PDF(151KB) ( 608 )

This paper realizes a nondestructive and complete Bell-state analysis for atomic qubit systems by a designed nondestructive and complete Bell-state analyser. In the scheme, Bell states are completely discriminated by two bits of classical informations which comes from the locality single atom detection on two auxiliary atoms, during which the Bell states are not affected. The needed devices are well within the bounds of current technology, and then the scheme is experimentally feasible.

参考文献 | 相关文章 | 计量指标

Select

Implementation of positive-operator-value measurements for single spin qubit via Heisenberg model

程留永, 邵晓强, 张寿, Yeon Kyu-Hwang

2010 (9): 90311-090311. doi: 10.1088/1674-1056/19/9/090311

摘要 ( 1435 )

PDF(118KB) ( 641 )

This paper shows that a proposal for implementing all possible two-operator positive-operator-value measurements of single spin qubit can be obtained via introducing another spin qubit as ancilla. The realization process is accomplished from the free evolution of the Heisenberg XX model by considering nearest-neighbour spin interaction. A controlled-NOT gate, which is a significant operator for this scheme is also constructed and the generalisation to multiple-operator is considered finally.

参考文献 | 相关文章 | 计量指标

Select

Applying invariant eigen-operator method to deriving normal coordinates of general classical Hamiltonian

范洪义, 陈俊华, 袁洪春

2010 (9): 90312-090312. doi: 10.1088/1674-1056/19/9/090312

摘要 ( 1362 )

PDF(100KB) ( 522 )

For classical Hamiltonian with general form

we find a new convenient way to obtain its normal coordinates, namely, let H be quantised and then employ the invariant eigen-operator (IEO) method (Fan et al. 2004 Phys. Lett. A 321 75) to derive them. The general matrix equation, which relies on M and L, for obtaining the normal coordinates of H is derived.

参考文献 | 相关文章 | 计量指标

Select

Teleportation and thermal entanglement in two-qubit Heisenberg XYZ spin chain with the Dzyaloshinski–Moriya interaction and the inhomogeneous magnetic field

高丹, 赵振双, 朱爱东, 王洪福, 邵晓强, 张寿

2010 (9): 90313-090313. doi: 10.1088/1674-1056/19/9/090313

摘要 ( 1688 )

PDF(125KB) ( 778 )

This paper studies the average fidelity of teleportation and thermal entanglement for a two-qubit Heisenberg XYZ chain in the presence of both an inhomogeneous magnetic field and a Dzyaloshinski--Moriya interaction. It shows that for a fixed D_z, the increase of b_z will broaden the critical temperature at the cost of decreasing the thermal entanglement. And it can modulate the inhomogeneous magnetic field and the Dzyaloshinski--Moriya interaction for the average fidelity of teleportation to be optimal.

参考文献 | 相关文章 | 计量指标

Select

Approximate solutions of Schrödinger equation for Eckart potential with centrifugal term

F. Tacskin, G. Koccak

2010 (9): 90314-090314. doi: 10.1088/1674-1056/19/9/090314

摘要 ( 1632 )

PDF(228KB) ( 2647 )

The approximate analytical solutions of the Schrõdinger equation for the Eckart potential are presented for the arbitrary angular momentum by using a new approximation of the centrifugal term. The energy eigenvalues and the corresponding wavefunctions are obtained for different values of screening parameter. The numerical examples are presented and the results are in good agreement with the values in the literature. Three special cases, i.e., s-wave, ξ=λ=1, and β=0, are investigated.

参考文献 | 相关文章 | 计量指标

Select

Concurrence, tangle and fully entangled fraction

李明, 费少明, 李先清

2010 (9): 90315-090315. doi: 10.1088/1674-1056/19/9/090315

摘要 ( 1953 )

PDF(189KB) ( 989 )

We show that although we cannot distil a singlet from many pairs of bound entangled states, the concurrence and the tangle of two entangled quantum states are always strictly larger than those of one of them, even both entangled quantum states are bound entangled. We present a relation between the concurrence and the fidelity of optimal teleportation. We also give new upper and lower bounds for concurrence and tangle.

参考文献 | 相关文章 | 计量指标

Select

Generation of GHZ state and cluster state with atomic ensembles via the dipole–blockade mechanism

倪彬彬, 顾永建, 陈晓东, 梁鸿辉, 林秀, 林秀敏

2010 (9): 90316-090316. doi: 10.1088/1674-1056/19/9/090316

摘要 ( 1700 )

PDF(123KB) ( 597 )

This paper proposes scalable schemes to generate the Greenberger--Horne--Zeilinger (GHZ) state and the cluster state with atomic ensembles via the dipole blockade mechanism on an atom chip, where the qubit is not carried by a single atom but an atomic ensemble. In the protocols, multiqubit entangled states are determinately prepared. Needlessness for single-photon source further decreases the complexity of the experiment. Based on the present laboratory technique, the schemes may be realized. The achieved results reveal a prospect for large-scale quantum communication and quantum computation.

参考文献 | 相关文章 | 计量指标

Select

Fast generation of cluster states in a linear ion trap

徐酉阳, 周飞, 张小龙, 冯芒

2010 (9): 90317-090317. doi: 10.1088/1674-1056/19/9/090317

摘要 ( 1534 )

PDF(230KB) ( 626 )

We propose a practical scheme to generate cluster states by simultaneously accomplishing two-qubit conditional gating on an array of equidistant ions by using transverse modes. Our operation is robust to heating and insensitive to Lamb--Dicke parameter. Meanwhile, as it is carried out in a geometric quantum computing fashion, our scheme enables the fast and high-fidelity generation of cluster states. The experimental feasibility is discussed with sophisticated ion trap techniques.

参考文献 | 相关文章 | 计量指标

Select

Protecting entanglement by detuning: in Markovian environments vs in non-Markovian environments

黄利元, 方卯发

2010 (9): 90318-090318. doi: 10.1088/1674-1056/19/9/090318

摘要 ( 1553 )

PDF(405KB) ( 723 )

The models of two qubits separately trapped in two independent Markovian or non-Markovian environments have been investigated. The distinction of the two-qubit entanglement dynamics in different environments has also been discussed in detail. The results show that, in non-Markovian environments, the possible usage time of entanglement can be extended due to its memory effect. On the other hand, we note that, compared to Markovian environments, the two-qubit entanglement could be protected better in non-Markovian environments by modulating the detuning between qubits and cavities. Finally, an intuitive physical interpretation for these results is given.

参考文献 | 相关文章 | 计量指标

Select

Thermal entanglement in two-qutrit spin-1 anisotropic Heisenberg model with inhomogeneous magnetic field

Erhan Albayrak

2010 (9): 90319-090319. doi: 10.1088/1674-1056/19/9/090319

摘要 ( 1680 )

PDF(5463KB) ( 949 )

The thermal entanglement of a two-qutrit spin-1 anisotropic Heisenberg XXZ chain in an inhomogeneous magnetic field is studied in detail. The effects of the external magnetic field (B), a parameter b which controls the inhomogeneity of B, and the bilinear interaction parameters J_{x_{=J_y≠J_z}}_{_{on the thermal variation of the negativity are studied in detail. It is found that negativity N decreases when the values of magnetic field, inhomogeneity b and temperature are increasing. In addition, N remains at higher temperatures for higher values of J_z and lower values of B and b.}}

参考文献 | 相关文章 | 计量指标

Select

Thermodynamic geometry of the Garfinkle–Horowitz–Strominger dilaton black hole

兰明建, 陈刚, 韩亦文

2010 (9): 90401-090401. doi: 10.1088/1674-1056/19/9/090401

摘要 ( 1556 )

PDF(95KB) ( 719 )

This paper studies the thermodynamic properties of the Garfinkle--Horowitz--Strominger dilaton black hole from the viewpoint of geometry. It calculates the heat capacity and the temperature of the black hole, Weinhold metric and Ruppeiner metric are also obtained respectively. It finds that they are both curved and the scalar curvature of the Weinhold geometry consists with the first-order transition point reproduced from the capacity, while the Ruppeiner one is both in accordance with the first-order and the second-order phase transition points reproduced from the capacity.

参考文献 | 相关文章 | 计量指标

Select

Radiation energy flux of Dirac field of static spherically symmetric black holes

孟庆苗, 蒋继建, 李中让, 王帅

2010 (9): 90402-090402. doi: 10.1088/1674-1056/19/9/090402

摘要 ( 1310 )

PDF(91KB) ( 664 )

By the statistical entropy of the Dirac field of the static spherically symmetric black hole, the result is obtained that the radiation energy flux of the black hole is proportional to the quartic of the temperature of its event horizon. That is, the thermal radiation of the black hole always satisfies the generalised Stenfan--Boltzmann law. The derived generalised Stenfan--Boltzmann coefficient is no longer a constant. When the cut-off distance and the thin film thickness are both fixed, it is a proportional coefficient related to the space--time metric near the event horizon and the average radial effusion velocity of the radiation particles from the thin film. Finally, the radiation energy fluxes and the radiation powers of the Schwarzschild black hole and the Reissner--Nordstrõm black hole are derived, separately.

参考文献 | 相关文章 | 计量指标

Select

New finite-gap solutions for the coupled Burgers equations engendered by the Neumann systems

陈金兵, 耿献国, 乔志军

2010 (9): 90403-090403. doi: 10.1088/1674-1056/19/9/090403

摘要 ( 1401 )

PDF(141KB) ( 572 )

On the tangent bundle TS^N-1 of the unit sphere S^N-1, this paper reduces the coupled Burgers equations to two Neumann systems by using the nonlinearization of the Lax pair, whose Liouville integrability is displayed in the scheme of the r-matrix technique. Based on the Lax matrix of the Neumann systems, the Abel--Jacobi coordinates are appropriately chosen to straighten out the restricted Neumann flows on the complex torus, from which the new finite-gap solutions expressed by Riemann theta functions for the coupled Burgers equations are given in view of the Jacobi inversion.

参考文献 | 相关文章 | 计量指标

Select

Energy and first law of thermodynamics for Born–Infeld–anti-de-Sitter black hole

魏益焕

2010 (9): 90404-090404. doi: 10.1088/1674-1056/19/9/090404

摘要 ( 1640 )

PDF(94KB) ( 755 )

We calculate the local energy and the energy density of the Reisner--Norstrõm--anti-de-Sitter black hole, study the first law of thermodynamics and show the Smarr formula for the Born--Infeld--anti-de-Sitter black hole. Applying the first law of thermodynamics to the black hole region, we analyse the three energy exchange processes between the black hole region and the outer and the inner regions.

参考文献 | 相关文章 | 计量指标

Select

Tangent response in coupled dynamical systems

闫华, 魏平, 肖先赐

2010 (9): 90501-090501. doi: 10.1088/1674-1056/19/9/090501

摘要 ( 1424 )

PDF(3354KB) ( 473 )

We construct new unidirectional coupling schemes for autonomous and nonautonomous drive systems, respectively. Each of these schemes makes the state of the response system asymptotically approach the first-order derivative of the state of the driver. From the point of view of geometry, the first-order derivative of the state of the driver can be viewed as a tangent vector of the trajectory of the driver, so the proposed schemes are named tangent response schemes. Numerical simulations of the Lorenz system and the forced Duffing oscillator verify the validity of the tangent response schemes. We further point out that the tangent response can be interpreted as a special kind of generalised synchronisation, thereby explaining why the response system can exhibit rich geometrical structures in its state space.

参考文献 | 相关文章 | 计量指标

Select

An improved impulsive control approach to robust lag synchronization between two different chaotic systems

马铁东, 浮洁, 孙跃

2010 (9): 90502-090502. doi: 10.1088/1674-1056/19/9/090502

摘要 ( 1882 )

PDF(2955KB) ( 2188 )

In this paper, a novel robust impulsive lag synchronization scheme for different chaotic systems with parametric uncertainties is proposed. Based on the theory of impulsive functional differential equations and a new differential inequality, some new and less conservative sufficient conditions are established to guarantee that the error dynamics can converge to a predetermined region. Finally, some numerical simulations for the Lorenz system and Chen system are given to demonstrate the effectiveness and feasibility of the proposed method. Compared with the existing results based on so-called dual-stage impulsive control, the derived results reduce the complexity of impulsive controller, moreover, a larger stable region can be obtained under the same parameters, which can be shown in the numerical simulations finally.

参考文献 | 相关文章 | 计量指标

Select

Synchronization between fractional-order chaotic systems and integer orders chaotic systems (fractional-order chaotic systems)

周平, 程元明, 邝菲

2010 (9): 90503-090503. doi: 10.1088/1674-1056/19/9/090503

摘要 ( 1762 )

PDF(143KB) ( 2130 )

Based on the idea of tracking control and stability theory of fractional-order systems, a controller is designed to synchronize the fractional-order chaotic system with chaotic systems of integer orders, and synchronize the different fractional-order chaotic systems. The proposed synchronization approach in this paper shows that the synchronization between fractional-order chaotic systems and chaotic systems of integer orders can be achieved, and the synchronization between different fractional-order chaotic systems can also be realized. Numerical experiments show that the present method works very well.

参考文献 | 相关文章 | 计量指标

Select

Generalised synchronisation of spatiotemporal chaos using feedback control method and phase compression

王兴元, 张娜

2010 (9): 90504-090504. doi: 10.1088/1674-1056/19/9/090504

摘要 ( 1529 )

PDF(3101KB) ( 673 )

Coupled map lattices are taken as examples to study the synchronisation of spatiotemporal chaotic systems. First, a generalised synchronisation of two coupled map lattices is realised through selecting an appropriate feedback function and appropriate range of feedback parameter. Based on this method we use the phase compression method to extend the range of the parameter. So, we integrate the feedback control method with the phase compression method to implement the generalised synchronisation and obtain an exact range of feedback parameter. This technique is simple to implement in practice. Numerical simulations show the effectiveness and the feasibility of the proposed program.

参考文献 | 相关文章 | 计量指标

Select

A universal algorithm to generate pseudo-random numbers based on uniform mapping as homeomorphism

王福来

2010 (9): 90505-090505. doi: 10.1088/1674-1056/19/9/090505

摘要 ( 1524 )

PDF(170KB) ( 1044 )

A specific uniform map is constructed as a homeomorphism mapping chaotic time series into [0,1] to obtain sequences of standard uniform distribution. With the uniform map, a chaotic orbit and a sequence orbit obtained are topologically equivalent to each other so the map can preserve the most dynamic properties of chaotic systems such as permutation entropy. Based on the uniform map, a universal algorithm to generate pseudo random numbers is proposed and the pseudo random series is tested to follow the standard 0-1 random distribution both theoretically and experimentally. The algorithm is not complex, which does not impose high requirement on computer hard ware and thus computation speed is fast. The method not only extends the parameter spaces but also avoids the drawback of small function space caused by constraints on chaotic maps used to generate pseudo random numbers. The algorithm can be applied to any chaotic system and can produce pseudo random sequence of high quality, thus can be a good universal pseudo random number generator.

参考文献 | 相关文章 | 计量指标

Select

Novel pinning control strategies for synchronisation of complex networks with nonlinear coupling dynamics

刘兆冰, 张化光, 孙秋野

2010 (9): 90506-090506. doi: 10.1088/1674-1056/19/9/090506

摘要 ( 1513 )

PDF(610KB) ( 561 )

This paper considers the global stability of controlling an uncertain complex network to a homogeneous trajectory of the uncoupled system by a local pinning control strategy. Several sufficient conditions are derived to guarantee the network synchronisation by investigating the relationship among pinning synchronisation, network topology, and coupling strength. Also, some fundamental and yet challenging problems in the pinning control of complex networks are discussed: (1) what nodes should be selected as pinned candidates? (2) How many nodes are needed to be pinned for a fixed coupling strength? Furthermore, an adaptive pinning control scheme is developed. In order to achieve synchronisation of an uncertain complex network, the adaptive tuning strategy of either the coupling strength or the control gain is utilised. As an illustrative example, a network with the Lorenz system as node self-dynamics is simulated to verify the efficacy of theoretical results.

参考文献 | 相关文章 | 计量指标

Select

Theoretical and experimental study of Chen chaotic system with notch filter feedback control

张晓明, 陈菊芳, 彭建华

2010 (9): 90507-090507. doi: 10.1088/1674-1056/19/9/090507

摘要 ( 1740 )

PDF(1816KB) ( 944 )

Since the past two decades, the time delay feedback control method has attracted more and more attention in chaos control studies because of its simplicity and efficiency compared with other chaos control schemes. Recently, it has been proposed to suppress low-dimensional chaos with the notch filter feedback control method, which can be implemented in a laser system. In this work, we have analytically determined the controllable conditions for notch filter feedback controlling of Chen chaotic system in terms of the Hopf bifurcation theory. The conditions for notch filter feedback controlled Chen chaoitc system having a stable limit cycle solution are given. Meanwhile, we also analysed the Hopf bifurcation direction, which is very important for parameter settings in notch filter feedback control applications. Finally, we apply the notch filter feedback control methods to the electronic circuit experiments and numerical simulations based on the theoretical analysis. The controlling results of notch filter feedback control method well prove the feasibility and reliability of the theoretical analysis.

参考文献 | 相关文章 | 计量指标

Select

Low dimensional chaos in the AT and GC skew profiles of DNA sequences

周茜, 陈增强

2010 (9): 90508-090508. doi: 10.1088/1674-1056/19/9/090508

摘要 ( 1729 )

PDF(369KB) ( 697 )

This paper investigates the existence of low-dimensional deterministic chaos in the AT and GC skew profiles of DNA sequences. It has taken DNA sequences from eight organisms as samples. The skew profiles are analysed using continuous wavelet transform and then nonlinear time series methods. The invariant measures of correlation dimension and the largest Lyapunov exponent are calculated. It is demonstrated that the AT and GC skew profiles of these DNA sequences all exhibit low dimensional chaotic behaviour. It suggests that chaotic properties may be ubiquitous in the DNA sequences of all organisms.

参考文献 | 相关文章 | 计量指标

Select

A new fractal algorithm to model discrete sequences

翟明岳, Heidi Kuzuma, James W. Rector

2010 (9): 90509-090509. doi: 10.1088/1674-1056/19/9/090509

摘要 ( 1295 )

PDF(1574KB) ( 1143 )

Employing the properties of the affine mappings, a very novel fractal model scheme based on the iterative function system is proposed. We obtain the vertical scaling factors by a set of the middle points in each affine transform, solving the difficulty in determining the vertical scaling factors, one of the most difficult challenges faced by the fractal interpolation. The proposed method is carried out by interpolating the known attractor and the real discrete sequences from seismic data. The results show that a great accuracy in reconstruction of the known attractor and seismic profile is found, leading to a significant improvement over other fractal interpolation schemes.

参考文献 | 相关文章 | 计量指标

Select

Hierarchy property of traffic networks

李夏苗, 曾明华, 周进, 李科赞

2010 (9): 90510-090510. doi: 10.1088/1674-1056/19/9/090510

摘要 ( 1467 )

PDF(558KB) ( 923 )

The flourishing complex network theory has aroused increasing interest in studying the properties of real-world networks. Based on the traffic network of Chang--Zhu--Tan urban agglomeration in central China, some basic network topological characteristics were computed with data collected from local traffic maps, which showed that the traffic networks were small-world networks with strong resilience against failure; more importantly, the investigations of assortativity coefficient and average nearest-neighbour degree implied the disassortativity of the traffic networks. Since traffic network hierarchy as an important basic property has been neither studied intensively nor proved quantitatively, the authors are inspired to analyse traffic network hierarchy with disassortativity and to finely characterize hierarchy in the traffic networks by using the n-degree--n-clustering coefficient relationship. Through numerical results and analyses an exciting conclusion is drawn that the traffic networks exhibit a significant hierarchy, that is, the traffic networks are proved to be hierarchically organized. The result provides important information and theoretical groundwork for optimal transport planning.

参考文献 | 相关文章 | 计量指标

Select

A super-high resolution frequency standard measuring approach based on phase coincidence characteristics between signals

李智奇, 周渭, 陈发喜, 刘晨光

2010 (9): 90601-090601. doi: 10.1088/1674-1056/19/9/090601

摘要 ( 1570 )

PDF(91KB) ( 1960 )

A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of the two compared signals. It utilizes the regular phase shift characteristics between the signals. The resolution of the measurement approach can reach 10^-13/s at 5 MHz, and the self-calibration resolution can achieve 10^-14/s in the comparison between 10 MHz and 100 MHz, or even can reach 10^-15/s in the comparison between 10 MHz and 190 MHz. This method implies significant progress in the development of the high precision frequency standard comparison technology.

参考文献 | 相关文章 | 计量指标

Select

Spectroscopic ellipsometric study of the optical properties of Ag₂O film prepared by direct-current magnetron reactive sputtering

郜小勇, 冯红亮, 马姣民, 张增院

2010 (9): 90701-090701. doi: 10.1088/1674-1056/19/9/090701

摘要 ( 1690 )

PDF(176KB) ( 2261 )

The Ag₂O film, as-deposited by direct-current magnetron reactive sputtering at a substrate temperature of 150 °C, clearly shows a preferential orientation (111), and is capable of lowering the threshold value of the thermal decomposition temperature to about 200 °C, which is helpful to its application in optical and magneto-optical storage. This paper fits its optical constants in terms of a general oscillator model by using measured ellipsometric parameters. The fitted oscillator energy 2.487 eV is close to the optical direct interband transition energy value of the Ag₂O film determined by Tauc equation; whereas, the fitted oscillator energy 4.249 eV is far from the fitted plasma oscillator energy 4.756 eV by single-oscillator energy. The photoluminescence spectrum centred at about 2.31 eV indicates a direct-energy gap photoluminescence mechanism of the Ag₂O film.

参考文献 | 相关文章 | 计量指标

Select

Wavelength dependence four-wave mixing spectroscopy in a micrometric atomic vapour

李院院, 李莉, 张彦鹏, 毕思文

2010 (9): 90702-090702. doi: 10.1088/1674-1056/19/9/090702

摘要 ( 1553 )

PDF(350KB) ( 577 )

This paper presents a theoretical study of wavelength dependence four-wave-mixing (FWM) spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke-narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour.

参考文献 | 相关文章 | 计量指标

Select

Electron impact excitation rate coefficients of N II ion

杨宁选, 董晨钟, 蒋军, 颉录有

2010 (9): 93101-093101. doi: 10.1088/1674-1056/19/9/093101

摘要 ( 1448 )

PDF(598KB) ( 911 )

This paper calculates the electron impact excitation rate coefficients from the ground term 2s²2p^{2 3}P to the excited terms of the 2s²2p², 2s2p³, 2s²2p3s, 2s²2p3p, and 2s²2p3d configurations of N II. In the calculations, multiconfiguration Dirac--Fork wave functions have been applied to describe the target-ion states and relativistic distorted-wave calculation has been performed to generate fine-structure collision strengths. The collision strengths are then averaged over a Maxwellian distribution of electron velocities in order to generate the effective collision strengths. The calculated rate coefficients are compared with available experimental and theoretical data, and some good agreements are found for the outer shell electron excitations. But for the inner shell electron excitations there are still some differences between the present calculations and available experiments.

参考文献 | 相关文章 | 计量指标

Select

The theoretical study on the potential energy curve for X ³Δ state of TiO molecule

徐国亮, 夏要争, 贾光瑞, 刘玉芳, 张现周

2010 (9): 93102-093102. doi: 10.1088/1674-1056/19/9/093102

摘要 ( 1377 )

PDF(138KB) ( 559 )

This paper applies the density functional theory method to optimise the structure for X ³Δ state of TiO molecule with the basis sets 6-31G, 6-31++G and 6-311G^**. Comparing the attained results with the experiments, it obtains the conclusion that the basis set 6-31++G is most suitable for the optimal structure calculations of X ³Δ state of TiO molecule. The whole potential energy curve for the electronic state is further scanned by using B3P86/6-31++G method for the ground state, then it uses a least square fitted to Murrell--Sorbie functions, at last it calculates the spectroscopic constants and force constants, which are in better agreement with the experimental data.

参考文献 | 相关文章 | 计量指标

Select

Investigation of inter-molecular hydrogen bonding in the binary mixture (acetone + water) by concentration dependent Raman study and ab initio calculations

欧阳顺利, 吴楠楠, 孙成林, 刘靖尧, 里佐威, 高淑琴

2010 (9): 93103-093103. doi: 10.1088/1674-1056/19/9/093103

摘要 ( 1493 )

PDF(1557KB) ( 1916 )

This paper reports that vibrational spectroscopic analysis on hydrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water complexes with changing water concentrations. The optimised geometries and wavenumbers of the neat acetone molecule and its complexes are calculated by using ab initio method at the MP2 level with 6-311+G(d,p) basis set. Changes in wavenumber position and linewidth (fullwidth at half maximum) have been explained for neat as well as binary mixtures with different mole fractions of the reference system, acetone, in terms of intermolecular hydrogen bonding. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the concentration dependent changes in the spectral features in terms of hydrogen bonding.

参考文献 | 相关文章 | 计量指标

Select

Extension of high-order harmonics and generation of an isolated attosecond pulse in the chirped laser field

伍杰, 翟振, 刘学深

2010 (9): 93201-093201. doi: 10.1088/1674-1056/19/9/093201

摘要 ( 1693 )

PDF(1015KB) ( 814 )

This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by optimising the chirping parameters. The time-frequency characteristics of high-order harmonics with different chirping parameters are analysed by means of wavelet transform of the dipole acceleration. It also gives out the classical three-step model pictures of electron. By superposing a properly selected range of the harmonic spectrum, it obtains an isolated 65as pulse.

参考文献 | 相关文章 | 计量指标

Select

Matter-wave interference in an axial triple-well optical dipole trap

周琦, 陆俊发, 印建平

2010 (9): 93202-093202. doi: 10.1088/1674-1056/19/9/093202

摘要 ( 1502 )

PDF(1906KB) ( 801 )

This paper proposes a scheme of axial triple-well optical dipole trap by employing a simple optical system composed of a circular cosine grating and a lens. Three optical wells separated averagely by ～37 μm were created when illuminating by a YAG laser with power 1 mW. These wells with average trapping depth ～0.5 μK and volume ～74 μm³ are suitable to trap and manipulate an atomic Bose--Einstein condensation (BEC). Due to a controllable grating implemented by a spatial light modulator, an evolution between a triple-well trap and a single-well one is achievable by adjusting the height of potential barrier between adjacent wells. Based on this novel triple-well potentials, the loading and splitting of BEC, as well as the interference between three freely expanding BECs, are also numerically stimulated within the framework of mean-field treatment. By fitting three cosine functions with three Gaussian envelopes to interference fringe, the information of relative phases among three condensates is extracted.

参考文献 | 相关文章 | 计量指标

Select

Active manipulation of the selective alignment by two laser pulses

杨增强, 郭志荣, 葛桂贤

2010 (9): 93301-093301. doi: 10.1088/1674-1056/19/9/093301

摘要 ( 1626 )

PDF(739KB) ( 739 )

This paper solves numerically the full time-dependent Schrõdinger equation based on the rigid rotor model, and proposes a novel strategy to determine the optimal time delay of the two laser pulses to manipulate the molecular selective alignment. The results illustrate that the molecular alignment generated by the first pulse can be suppressed or enhanced selectively, the relative populations of even and odd rotational states in the final rotational wave packet can be manipulated selectively by precisely inserting the peak of the second laser pulse at the time when the slope for the alignment parameter by the first laser locates a local maximum for the even rotational states and a local minimum for the odds, and vice versa. The selective alignment can be further optimised by selecting the intensity ratio of the two laser pulses on the condition that the total laser intensity and pulse duration are kept constant.

参考文献 | 相关文章 | 计量指标

Select

Rotational analysis and line intensities of the HCO

band at 296 K

刘艳红, 杜晓峰, 程新路

2010 (9): 93302-093302. doi: 10.1088/1674-1056/19/9/093302

摘要 ( 1546 )

PDF(169KB) ( 502 )

This paper computes the rotational energy levels of the HCO

transition, especially, the higher values of the rotational quantum numbers N_{K_a K_c} and K_a, with the rotational constants which are obtained via B3LYP method with 6-311G basis set, and the results show that the calculated frequencies using the computed vibration--rotation energy levels are in reasonable agreement with the data from the experiment. Meanwhile, the line intensities of HCO are first reported, the results are of significance for the studying HCO.

参考文献 | 相关文章 | 计量指标

Select

Single electron loss in the collisions of C^{3 +}and atomic hydrogen

刘会平, 欧阳晓平, 胡华四, 苏光辉

2010 (9): 93401-093401. doi: 10.1088/1674-1056/19/9/093401

摘要 ( 1375 )

PDF(111KB) ( 510 )

This paper studies the projectile electron loss cross sections of C^{3 +}colliding with atomic hydrogen in the frame work of extended over-barrier model at intermediate velocities (25 keV/u--600 keV/u). The electron loss is calculated in terms of the interaction between the screened target nucleus and the active projectile electron and of the interaction between projectile electron and target electron. Compared with the convergent close-coupling calculations, screening and anti-screening calculations, this model satisfactorily reproduces the experimentally obtained energy dependence of the electron-impact ionisation cross sections and the single electron loss cross sections over the energy range investigated here.

参考文献 | 相关文章 | 计量指标

Select

Quantum reflection as the reflection of subwaves

袁文, 殷澄, 王贤平, 曹庄琪

2010 (9): 93402-093402. doi: 10.1088/1674-1056/19/9/093402

摘要 ( 1415 )

PDF(411KB) ( 765 )

This paper studies quantum reflection with recent research on reflection coefficient. Based on the analytical transfer matrix method, a novel explanation for this phenomenon is proposed that quantum reflection is the reflection of subwaves, which originate inherently from the inhomogeneity of the fields and is always neglected in the semiclassical regime. Comparison with exact formula and the numerical calculations for different potentials has confirmed the reliability and the validity of the proposed theory.

参考文献 | 相关文章 | 计量指标

Select

Elastic scattering of electrons from water molecule

刘俊伯, 周雅君

2010 (9): 93403-093403. doi: 10.1088/1674-1056/19/9/093403

摘要 ( 1406 )

PDF(130KB) ( 735 )

This paper uses the momentum--space optical potential method to calculate the e--H₂O scattering elastic cross sections at the energy range from 6 eV to 50 eV, and the differential cross sections in the angle from 0° to 180° at 40 eV and 50 eV. The polarisation is taken into account via an emphab initio equivalent-local potential. The cross sections are compared with experimental measurements and other theoretical calculations.

参考文献 | 相关文章 | 计量指标

Select

Interface phonon–polaritons in quantum well systems of polar ternary mixed crystals

包锦, 梁希侠

2010 (9): 94101-094101. doi: 10.1088/1674-1056/19/9/094101

摘要 ( 1568 )

PDF(1167KB) ( 657 )

The interface phonon--polaritons in quantum well systems consisting of polar ternary mixed crystals are investigated. The numerical results of the interface phonon--polariton frequencies in the GaAs/Al_xGa_{1 - x}As, ZnS_xSe_{1 - x}/ZnS, and Zn_xCd_{1 - x}Se/ ZnSe quantum well systems are obtained and discussed. It is shown that there are six branches of interface phonon--polariton modes distributed in three bulk phonon--polariton forbidden bands in the systems. The electric fields of interface phonon--polaritons are also presented and show the interface locality of the modes. The effects of the 'two-mode' and 'one-mode' behaviours of the ternary mixed crystals on the interface phonon--polariton modes are shown in the dispersion curves.

参考文献 | 相关文章 | 计量指标

Select

Comparison between relay propagation and direct propagation of Gaussian—Schell-model beam in turbulent atmosphere along a slant path

储修祥, 刘泽金, 吴毅

2010 (9): 94201-094201. doi: 10.1088/1674-1056/19/9/094201

摘要 ( 1584 )

PDF(622KB) ( 634 )

The relay propagation of Gaussian--Schell-model in turbulent atmosphere along a slant path is studied in this paper. Based on the extended Huygens--Fresnel principle and a quadratic approximation, an analytical formula of average intensity for Gaussian--Schell-model beams in turbulent atmosphere along a slant path is derived, and some special cases are discussed. From the study and the comparison with the direct propagation, we can see that the relay propagation has an advantage over the direct propagation. When the altitude of the target is low, the peak intensity of relay propagation is much larger than that of direct propagation. However, because of the limitation of the relay system aperture for relay propagation and the variation of coherence length for direct propagation, the difference in peak intensity between the two propagations decreases with the increase of the target altitude.

参考文献 | 相关文章 | 计量指标

Select

Coherent beam combining of hybrid phase control in master oscillator-power amplifier configuration

王小林, 周朴, 马阎星, 马浩统, 许晓军, 刘泽金, 赵伊君

2010 (9): 94202-094202. doi: 10.1088/1674-1056/19/9/094202

摘要 ( 1379 )

PDF(791KB) ( 830 )

A novel scalable architecture for coherent beam combining with hybrid phase control involving passive phasing and active phasing in master oscillator-power amplifier configuration is presented. Wide-linewidth mutually injected passive phasing fibre laser arrays serve as master oscillators for the power amplifiers, and the active phasing using stochastic parallel gradient descent algorithm is induced. Wide-linewidth seed laser can suppress the stimulated Brillouin scattering effectively and improve the output power of the fibre laser amplifier, while hybrid phase control provides a robust way for in-phase mode coherent beam combining simultaneously. Experiment is performed by active phasing fibre laser amplifiers with passive phasing fibre ring laser array seed lasers. Power encircled in the main-lobe increases1.57 times and long-exposure fringe contrast is obtained to be 78% when the system evolves from passive phasing to hybrid phasing.

参考文献 | 相关文章 | 计量指标

Select

Sudden death and revival of entanglement of two qubits coupled collectively to a thermal reservoir

廖湘萍, 方见树, 方卯发

2010 (9): 94203-094203. doi: 10.1088/1674-1056/19/9/094203

摘要 ( 1029 )

PDF(555KB) ( 547 )

In this paper, we investigate the entanglement of two qubits coupled collectively to a common thermal environment and find that the the collective decay can lead to a revival of the entanglement that has already been destroyed. We also show that the ability of the system to revival entanglement relies on the mean photon number of the thermal environment and the degree of entanglement of the initial state.

参考文献 | 相关文章 | 计量指标

Select

Concurrence evolution of two qubits coupled with one-mode cavity separately

刘伟慈, 王发强, 梁瑞生

2010 (9): 94204-094204. doi: 10.1088/1674-1056/19/9/094204

摘要 ( 1712 )

PDF(3311KB) ( 641 )

The concurrence evolution of two qubits coupled with one-mode cavity separately is investigated exactly without adopting the rotating-wave approximation. The results show that for the resonant case, the concurrence evolution behaviour of the system is similar to that of the Markovian case when the coupling strength is weak, while the concurrence vanishes in a finite time and might revive fractional initial entanglement before it permanently vanishes when the coupling strength is strong. And for the detuning case, the entanglement could periodically recover after complete disentanglement. These results are quite different from those of system subjected to Jaynes--Cummings model.

参考文献 | 相关文章 | 计量指标

Select

Robust generation of qutrit entanglement via adiabatic passage of dark states

杨贞标, 吴怀志, 郑仕标

2010 (9): 94205-094205. doi: 10.1088/1674-1056/19/9/094205

摘要 ( 2383 )

PDF(203KB) ( 923 )

We propose a scheme for the deterministic generation of qutrit entanglement for two atoms trapped in an optical cavity. Taking advantage of the adiabatic passage, the operation is immune to atomic spontaneous emission as the atomic excited states are never populated; under certain conditions, the probability that the cavity is excited is negligible. We also study the influences of the dissipation due to the atomic spontaneous emission and cavity decay.

参考文献 | 相关文章 | 计量指标

Select

Entanglement transfer via the Raman atom–cavity-field interaction

梁麦林, 袁兵

2010 (9): 94206-094206. doi: 10.1088/1674-1056/19/9/094206

摘要 ( 1425 )

PDF(135KB) ( 615 )

For the Raman interaction between an atom and a two-mode cavity field prepared in the state |01> or |10>, the atom and the field can be disentangled periodically. Such a property of Raman atom--field interaction allows the full entanglement transfer among many atoms and bimodal cavities. In the calculations, each atom is assumed to interact with its own cavity at a different time and so non-identical atoms can be treated conveniently. Entanglement sudden death is discussed too. Though atom--field interaction greatly changes the values of the concurrence for two atoms, configuration of the concurrence is almost not affected. When there is entanglement sudden death, atoms and cavities can still be entangled with one another. However, full entanglement transfer cannot be achieved for such systems with Raman atom--field interaction.

参考文献 | 相关文章 | 计量指标

Select

Generation of a four-particle entangled state via cross-Kerr nonlinearity

赵丽芳, 赖柏辉, 梅锋, 於亚飞, 冯勋立, 张智明

2010 (9): 94207-094207. doi: 10.1088/1674-1056/19/9/094207

摘要 ( 1553 )

PDF(105KB) ( 746 )

We propose a scheme for generating a genuine four-particle polarisation entangled state |χ⁰⁰$\rangle$ that has many interesting entanglement properties and potential applications in quantum information processing. In our scheme, we use the weak cross-Kerr nonlinear interaction between field-modes and the non-demolition measurement method based on highly efficient homodyne detection, which is feasible under the current experiment conditions.

参考文献 | 相关文章 | 计量指标

Select

In-situ growth of Ca/P salt on Ti surface induced by femtosecond lasers in hydroxyapatite suspension

梁春永, 王洪水, 杨阳, 杨建军, 陈贵锋, 李长义

2010 (9): 94208-094208. doi: 10.1088/1674-1056/19/9/094208

摘要 ( 1356 )

PDF(2499KB) ( 686 )

Pure Ti plate surfaces are micro-ablated by femtosecond lasers in the ambience of hydroxyapatite suspension. It is found that three-stage hierarchical surface structures are produced with various laser energies. When the laser energy is 150 μJ, a lava-like structure with a distribution of nanoholes is dispersed evenly on the laser ablated surface. While in the case of 300 μ J, the grooves-and-islands micro-patterns covered with nanoparticles are generated on the surface. Remarkably, Ca/P based substances are revealed to firmly deposit on the micro-structured surfaces. More phosphate growth is seen for the higher laser energy. Discussions suggest that the additional elements deposition could be attributed to the chemical reaction of plasma related ions in the suspension and their subsequent crystallisation on the fresh surfaces of Ti plate due to the femtosecond laser ablation.

参考文献 | 相关文章 | 计量指标

Select

Improvement of photorefractive properties in Hf:Fe:LiNbO₃ crystals with various [Li]/[Nb] ratios

孙秀冬, 石宏新, 骆素华, 孟庆鑫, 姜永远

2010 (9): 94209-094209. doi: 10.1088/1674-1056/19/9/094209

摘要 ( 1539 )

PDF(109KB) ( 737 )

Photorefractive properties of Hf:Fe:LiNbO₃ crystals with various [Li]/[Nb] ratios have been investigated at 488 nm wavelength based on the two-wave coupling experiment. High diffraction efficiency and large recording sensitivity are observed and explained. The decrease in Li vacancies is suggested to be the main contributor to the increase in the photoconductivity and subsequently to the induction of the improvement of recording sensitivity. The saturation diffraction efficiency is measured up to 80.2%, and simultaneously the recording sensitivity of 0.91 cm/J is achieved to in the Hf:Fe:LiNbO₃ crystal grown from the melt with the [Li]/[Nb] ratio of 1.20, which is significantly enhanced as compared with those of the Hf:Fe:LiNbO₃ crystal with the [Li]/[Nb] ratio of 0.94 in melt under the same experimental conditions. Experimental results definitely show that increasing the [Li]/[Nb] ratio in crystal is an effective method for Hf:Fe:LiNbO₃ crystal to improve its photorefractive properties.

参考文献 | 相关文章 | 计量指标

Select

Investigation on performance of all optical buffer with large dynamical delay time based on cascaded double loop optical buffers

王拥军, 吴重庆, 忻向军, 余贶琭, 张晓磊

2010 (9): 94210-094210. doi: 10.1088/1674-1056/19/9/094210

摘要 ( 1379 )

PDF(1093KB) ( 731 )

Optical buffers are critical for optical signal processing in future optical packet-switched networks. In this paper, a theoretical study as well as an experimental demonstration on a new optical buffer with large dynamical delay time is carried out based on cascaded double loop optical buffers (DLOBs). It is found that pulse distortion can be restrained by a negative optical control mode when the optical packet is in the loop. Noise analysis indicates that it is feasible to realise a large variable delay range by cascaded DLOBs. These conclusions are validated by the experiment system with 4-stage cascaded DLOBs. Both the theoretical simulations and the experimental results indicate that a large delay range of 1--9999 times the basic delay unit and a fine granularity of 25 ns can be achieved by the cascaded DLOBs. The performance of the cascaded DLOBs is suitable for the all optical networks.

参考文献 | 相关文章 | 计量指标

Select

High-order ghost imaging with N-colour thermal light

刘骞, 罗开红, 陈希浩, 吴令安

2010 (9): 94211-094211. doi: 10.1088/1674-1056/19/9/094211

摘要 ( 1981 )

PDF(355KB) ( 771 )

High-order ghost imaging with thermal light consisting of N different frequencies is investigated. The high-order intensity correlation and intrinsic correlation functions are derived for such N-colour light. It is found that they are similar in form to those for the monochromatic case, thus most of the conclusions we obtained previously for monochromatic Nth-order ghost imaging are still applicable. However, we find that the visibility of the N-colour ghost image depends strongly on the wavelength used to illuminate the object, and increases as this wavelength increases when the test arm is fixed. On the contrary, changes of wavelength in the reference arms do not lead to any change of the visibility.

参考文献 | 相关文章 | 计量指标

Select

Localisation and phase transition of acoustic waves in a soft medium containing air bubbles

梁彬, 邹欣晔, 程建春

2010 (9): 94301-094301. doi: 10.1088/1674-1056/19/9/094301

摘要 ( 1381 )

PDF(178KB) ( 591 )

We study via numerical experiments the localisation property of an acoustic wave in a viscoelastic soft medium containing randomly-distributed air bubbles. The behaviours of the oscillation phases of bubbles are particularly investigated in various cases for distinguishing efficiently the acoustic localisation from the effects of acoustic absorption caused by the viscosity of medium. The numerical results reveal the phenomenon of `phase transition' characterized by an unusual collective oscillation of bubbles, which is an effective criterion to unambiguously identify the acoustic localisation in the presence of viscosity. Within the localisation region, the phenomenon of phase transition persists, and a remarkable decrease in the fluctuation of the oscillation phases of bubbles is observed. The localisation phenomenon will be impaired by the enhancement of the viscosity factors, and the extent to which the acoustic wave is localised may be determined by appropriately analyzing the values of the oscillation phases or the amount of reduction of the phase fluctuation. The results are particularly significant for the practical experiments in an attempt to observe the acoustic localisation in such a medium, which is in general subjected to the interference of the great ambiguity resulting from the effect of acoustic absorption.

参考文献 | 相关文章 | 计量指标

Select

Difference-frequency ultrasound generation from microbubbles under dual-frequency excitation

马青玉, 邱媛媛, 黄蓓, 章东, 龚秀芬

2010 (9): 94302-094302. doi: 10.1088/1674-1056/19/9/094302

摘要 ( 1412 )

PDF(338KB) ( 667 )

The difference-frequency (DF) ultrasound generated by using parametric effect promises to improve detection depth owing to its low attenuation, which is beneficial for deep tissue imaging. With ultrasound contrast agents infusion, the harmonic components scattered from the microbubbles, including DF, can be generated due to the nonlinear vibration. A theoretical study on the DF generation from microbubbles under the dual-frequency excitation is proposed in formula based on the solution of the RPNNP equation. The optimisation of the DF generation is discussed associated with the applied acoustic pressure, frequency, and the microbubble size. Experiments are performed to validate the theoretical predictions by using a dual-frequency signal to excite microbubbles. Both the numerical and experimental results demonstrate that the optimised DF ultrasound can be achieved as the difference frequency is close to the resonance frequency of the microbubble and improve the contrast-to-tissue ratio in imaging.

参考文献 | 相关文章 | 计量指标

Select

Tokamak residual zonal flow level in near-separatrix region

石秉仁

2010 (9): 95201-095201. doi: 10.1088/1674-1056/19/9/095201

摘要 ( 1305 )

PDF(187KB) ( 525 )

Residual zonal flow level is calculated for tokamak plasmas in the near-separatrix region of a diverted tokamak. A recently developed method is used to construct an analytic divertor tokamak configuration. It is shown that the residual zonal flow level becomes smaller but still keeps finite near the separatrix because the neoclassical polarisation mostly due to the trapped particles goes larger in this region.

参考文献 | 相关文章 | 计量指标

Select

Discrete Alfvén eigenmodes in international thermonuclear experimental reactor operations with negative magnetic shear

王军, 胡双辉, 代清平, 姚龙宝

2010 (9): 95202-095202. doi: 10.1088/1674-1056/19/9/095202

摘要 ( 1496 )

PDF(179KB) ( 662 )

Discrete Alfvén eigenmodes in steady-state operation scenarios with negative magnetic shear in the international thermonuclear experimental reactor are investigated in this paper. These magnetohydrodynamic eigenmodes are trapped by the α -induced potential wells along the magnetic field line. Here α =-q²Rdβ/d r with q being the safety factor, β the ratio between plasma and magnetic pressures, and R the major radius, and r the minor radius. Due to negligible continuum damping via wave energy tunneling, these Alfvén eigenmodes could be readily destabilized by energetic particles.

参考文献 | 相关文章 | 计量指标

Select

Combining SAD/SIR iteration and MR iteration in partial-model extension of proteins

张涛, 武丽杰, 古元新, 郑朝德, 范海福

2010 (9): 96101-096101. doi: 10.1088/1674-1056/19/9/096101

摘要 ( 1686 )

PDF(3630KB) ( 851 )

There are two kinds of dual-space partial-model extensions which involve the direct-method program OASIS. The first kind, named SAD/SIR iteration, uses SAD/SIR information, while the second kind, named molecular replacement (MR) iteration, does not use that information. In general, the SAD/SIR iteration is more powerful since more experimental information is used. However, in most cases when protein structures are solved with the molecular replacement method, SAD/SIR information is not available. Thus the MR iteration is particularly useful for the completion of models from molecular replacement. The SAD/SIR iteration will be automatically used in OASIS for data sets containing SAD/SIR signals, while the MR iteration will be dedicated to data sets without SAD/SIR signals. The present paper shows that for data containing SAD/SIR signals, a combination of SAD/SIR iteration and MR iteration could lead to significantly better results than that obtained from the SAD/SIR iteration alone.

参考文献 | 相关文章 | 计量指标

Select

Elastic properties of spherically anisotropic piezoelectric composites

魏恩泊, 顾国庆, 潘英明

2010 (9): 96201-096201. doi: 10.1088/1674-1056/19/9/096201

摘要 ( 1457 )

PDF(181KB) ( 803 )

Effective elastic properties of spherically anisotropic piezoelectric composites, whose spherically anisotropic piezoelectric inclusions are embedded in an infinite non-piezoelectric matrix, are theoretically investigated. Analytical solutions for the elastic displacements and the electric potentials under a uniform external strain are derived exactly. Taking into account of the coupling effects of elasticity, permittivity and piezoelectricity, the formula is derived for estimating the effective elastic properties based on the average field theory in the dilute limit. An elastic response mechanism is revealed, in which the effective elastic properties increase as inclusion piezoelectric properties increase and inclusion dielectric properties decrease. Moreover, a piezoelectric response mechanism, of which the effective piezoelectric response vanishes due to the symmetry of spherically anisotropic composite, is also disclosed.

参考文献 | 相关文章 | 计量指标

Select

Influence of pressure on the solid state phase transformation of Cu–Al–Bi alloy

李工, 刘建华, 王文魁, 刘日平

2010 (9): 96202-096202. doi: 10.1088/1674-1056/19/9/096202

摘要 ( 1502 )

PDF(5116KB) ( 850 )

The solid state phase transformation of Cu--Al--Bi alloy under high pressure was investigated by x-ray diffraction, energy dispersive spectroscopy and transmission electron microscopy. Experimental results show that the initial crystalline phase in the Cu--Al--Bi alloy annealed at 750 °C under the pressures in the range of 0--6 GPa is α-Cu solid solution (named as α-Cu phase below), and high pressure has a great influence on the crystallisation process of the Cu--Al--Bi alloy. The grain size of the α-Cu phase decreases with increasing pressure as the pressure is below about 3 GPa, and then increases (P>3 GPa). The mechanism for the effects of high pressure on the crystallisation process of the alloy has been discussed.

参考文献 | 相关文章 | 计量指标

Select

Effects of high-pressure heat treatment on the solid-state phase transformation and microstructures of Cu_61.13Zn_33.94Al_4.93 alloys

王海燕, 刘建华, 彭桂荣, 王文魁

2010 (9): 96203-096203. doi: 10.1088/1674-1056/19/9/096203

摘要 ( 1558 )

PDF(6339KB) ( 813 )

The phase transformation activation energy of the Cu_61.13Zn_33.94Al_4.93 alloys, which were treated at 4 GPa and 700 °C for 15 minutes, was calculated by means of differential scanning calorimetry curves obtained at various heating and cooling rates. Then, the effects of high-pressure heat treatments on the solid-state phase transformation and the microstructures of Cu_61.13Zn_33.94Al_4.93 alloys were investigated. The results show that high-pressure heat treatments can refine the grains and can change the preferred orientation from (111) to (200) of α phase. Compared with the as-cast alloy, the sample with high-pressure heat treatment has finer grains, lower β' → β and β → β ' transformation temperature and activation energy. Furthermore, we found that high cooling rate favours the formation of fine needle-like α phase in the range of 5--20 °C/min.

参考文献 | 相关文章 | 计量指标

Select

Localized self-trapping in two-dimensional molecular lattice with interaction between Wannier–Mott excitons and phonon lattice

徐权, 田强

2010 (9): 96301-096301. doi: 10.1088/1674-1056/19/9/096301

摘要 ( 1458 )

PDF(616KB) ( 522 )

We investigate the interactions of lattice phonons with Wannier--Mott exciton, the exciton that has a large radius in two-dimensional molecular lattice, by the method of continuum limit approximation, and obtain that the self-trapping can also appear in two-dimensional molecular lattice with a harmonic and nonlinear potential. The exciton effect on molecular lattice does not distort the molecular lattice but only makes it localized and the localization can also react, again through phonon coupling, to trap the energy and prevents its dispersion.

参考文献 | 相关文章 | 计量指标

Select

Structural, electronic and optical properties of orthorhombic distorted perovskite TbMnO₃

蔡鲁刚, 刘发民, 钟文武

2010 (9): 97101-097101. doi: 10.1088/1674-1056/19/9/097101

摘要 ( 1708 )

PDF(649KB) ( 2077 )

This paper calculates the structural parameters, electronic and optical properties of orthorhombic distorted perovskite-type TbMnO₃ by first principles using density functional theory within the generalised gradient approximation. The calculated equilibrium lattice constants are in a reasonable agreement with theoretical and experimental data. The energy band structure, density of states and partial density of states of elements are obtained. Band structures show that TbMnO₃ is an indirect band gap between the O 2p states and Mn 3d states, and the band gap is of 0.48 eV agreeing with experimental result. Furthermore, the optical properties, including the dielectric function, absorption coefficient, optical reflectivity, refractive index and energy loss spectrum are calculated and analysed, showing that the TbMnO₃ is a promising dielectric material.

参考文献 | 相关文章 | 计量指标

Select

Effect of local atomic disorder on the half-metallicity of full-Heusler Co₂FeSi alloy: a first-principles study

李冠男, 金迎九, 李在一

2010 (9): 97102-097102. doi: 10.1088/1674-1056/19/9/097102

摘要 ( 1800 )

PDF(1507KB) ( 1033 )

This paper investigates the effect of atomic disorder on the electronic structure, magnetism, and half-metallicity of full-Heusler Co₂FeSi alloy by using the full-potential linearized augmented plane wave method within the generalized gradient approximation (GGA) and GGA+U schemes. It considers three types of atomic disorders in Co₂FeSi alloy: the Co--Fe, Co--Si, and Fe--Si disorders. Total energy calculations show that of the three types of disorders, the Fe--Si disorder is more likely to occur. It finds that for the Co--Si disorder, additional states appear in the minority band-gap at the E_F and the half-metallcity is substantially destroyed, regardless of the disorder level. On the other hand, the Co--Fe and Fe--Si disorders have little effect on the half-metallicity at a low disorder level. When increasing the disorder levels, the half-metallcity is destroyed at about 9 % of the Co--Fe disorder level, while that stays at 25 % of the Fe--Si disorder level.

参考文献 | 相关文章 | 计量指标

Select

First-principles study of Ga₇As₇ ionic cluster and influence of multi-charge on its structure

杨建宋, 李宝兴

2010 (9): 97103-097103. doi: 10.1088/1674-1056/19/9/097103

摘要 ( 1509 )

PDF(3287KB) ( 665 )

This paper investigates the structures and stabilities of neutral Ga₇As₇ cluster and its ions in detail by using first-principles density functional theory. Many low energy structures of Ga₇As₇ cluster are found. It confirms that the ground state structure of neutral Ga₇As₇ cluster is a pentagonal prism with four face atoms like a basket structure, as reported by previous works. The ground state structures of positive Ga₇As₇ cluster ions are different from that of the neutral cluster. These investigations suggest that Ga atoms occupy the capping positions more easily than As atoms. Mulliken population analyses also show that Ga atoms can lose or obtain charge more easily than As atoms. It finds that the neutral Ga₇As₇ cluster can become more stable by gaining one or two additional electrons but further more electrons would cause the decrease of binding energy. The ionisation energy increases with the increase of the number of the removed electrons. These calculated results indicate that the net magnetic moment of the neutral Ga₇As₇ cluster is zero because all electrons are paired together in their respective molecular orbits. But for the ionic Ga₇As₇ cluster with odd number of electrons, the net magnetic moment is 1.0 μ_B due to an unpaired electron.

参考文献 | 相关文章 | 计量指标

Select

Structural, curvature and electronic properties of Rh adsorption on armchair single-walled carbon nanotube

杨培芳, 吴锋民, 滕波涛, 刘莎, 蒋健中

2010 (9): 97104-097104. doi: 10.1088/1674-1056/19/9/097104

摘要 ( 1575 )

PDF(4145KB) ( 1012 )

This paper systematically studies the rolling effects of the (n, n) single-wall carbon nanotubes (SWCNT) with different curvatures on Rh adsorption behaviours by using density functional theory. The outside charge densities of SWCNTs are found to be higher than those inside, and the differences decrease with the increase of the tube radius. This electronic property led to the discovery that the outside adsorption energies are higher than the inside ones, and that the differences are reduced with the increase of the tube radius. Partial density of states and charge density difference indicate that these strong interactions induce electron transfer between Rh atoms and SWCNTs.

参考文献 | 相关文章 | 计量指标

Select

Spin glass dynamics in RKKY interacting disordered magnetic system

张开成, 宋朋云

2010 (9): 97105-097105. doi: 10.1088/1674-1056/19/9/097105

摘要 ( 1597 )

PDF(148KB) ( 664 )

Using the dynamical Monte Carlo method we investigate the nonequilibrium effects in RKKY-coupling disordered spin glass. By the simulation we reproduce the well-known aging and memory phenomena and find the energy relaxation at a certain temperature happens only to the corresponding spins, which directly causes the nonequilibrium effects. Combining the master equation and the energy relaxation we analyse these phenomena and explain them from the dynamical perspective.

参考文献 | 相关文章 | 计量指标

Select

Parameter analysis for gate metal–oxide–semiconductor structures of ion-implanted 4H silicon carbide metal–semiconductor field-effect transistors

王守国, 张义门, 张玉明

2010 (9): 97106-097106. doi: 10.1088/1674-1056/19/9/097106

摘要 ( 1712 )

PDF(486KB) ( 631 )

From the theoretical analysis of the thermionic emission model of current--voltage characteristics, this paper extracts the parameters for the gate Schottky contact of two ion-implanted 4H-SiC metal--semiconductor field-effect transistors (sample A and sample B for three and four times multiple ion-implantation channel region respectively) fabricated in the experiment, including the ideality factor, the series resistance, the zero-field barrier height, the interface oxide capacitance, the interface state density distribution, the neutral level of interface states and the fixed space charge density. The methods to improve the interface of the ion-implanted Schottky contact are given at last.

参考文献 | 相关文章 | 计量指标

Select

Study of 4H-SiC junction barrier Schottky diode using field guard ring termination

陈丰平, 张玉明, 吕红亮, 张义门, 黄建华

2010 (9): 97107-097107. doi: 10.1088/1674-1056/19/9/097107

摘要 ( 1712 )

PDF(2572KB) ( 2396 )

This paper reports that the 4H-SiC Schottky barrier diode, PiN diode and junction barrier Schottky diode terminated by field guard rings are designed, fabricated and characterised. The measurements for forward and reverse characteristics have been done, and by comparison with each other, it shows that junction barrier Schottky diode has a lower reverse current density than that of the Schottky barrier diode and a higher forward drop than that of the PiN diode. High-temperature annealing is presented in this paper as well to figure out an optimised processing. The barrier height of 0.79 eV is formed with Ti in this work, the forward drop for the Schottky diode is 2.1 V, with an ideality factor of 3.2, and junction barrier Schottky diode with blocking voltage higher than 400 V was achieved by using field guard ring termination.

参考文献 | 相关文章 | 计量指标

Select

Thermal annealing induced photocarrier radiometry enhancement for ion implanted silicon wafers

刘显明, 李斌成, 黄秋萍

2010 (9): 97201-097201. doi: 10.1088/1674-1056/19/9/097201

摘要 ( 1552 )

PDF(336KB) ( 875 )

An experimental study on the photocarrier radiometry signals of As⁺ion implanted silicon wafers before and after rapid thermal annealing is performed. The dependences of photocarrier radiometry amplitude on ion implantation dose (1×10¹¹--1×10¹⁶/cm²), implantation energy (20--140 keV) and subsequent isochronical annealing temperature (500--1100 du are investigated. The results show that photocarrier radiometry signals are greatly enhanced for implanted samples annealed at high temperature, especially for those with a high implantation dose. The reduced surface recombination rate resulting from a high built-in electric field generated by annealing-activated impurities in the pn junction is believed to be responsible for the photocarrier radiometry signal enhancement. Photocarrier radiometry is contactless and can therefore be used as an effective in-line tool for the thermal annealing process monitoring of the ion-implanted wafers in semiconductor industries.

参考文献 | 相关文章 | 计量指标

Select

A new model for electromigration grain boundary noise based on free volume

何亮, 杜磊, 庄奕琪, 陈华, 陈文豪, 李伟华, 孙鹏

2010 (9): 97202-097202. doi: 10.1088/1674-1056/19/9/097202

摘要 ( 1484 )

PDF(199KB) ( 588 )

Grain boundary plays a key role in electromigration process of polycrystal interconnection. We take a free volume to represent a 'vacancy--ion complex' as a function of grain boundary specific resistivity, and develop a new characterisation model for grain boundary noise. This model reveals the internal relation between the boundary scattering section and electromigration noise. Comparing the simulation result with our experimental result, we find the source as well as the form of noise change in the electromigration process. In order to describe the noise enhancement at grain boundary quantitatively, we propose a new parameter—grain boundary noise enhancement factor, which reflects that the grain boundary noise can characterise the electromigration damage sensitively.

参考文献 | 相关文章 | 计量指标

Select

Negative differential resistance behaviour in N-doped crossed graphene nanoribbons

陈灵娜, 马松山, 欧阳方平, 伍小赞, 肖金, 徐慧

2010 (9): 97301-097301. doi: 10.1088/1674-1056/19/9/097301

摘要 ( 1659 )

PDF(1991KB) ( 1288 )

By using first-principles calculations and nonequilibrium Green's function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance (NDR) behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.

参考文献 | 相关文章 | 计量指标

Select

The physical process analysis of the capacitance–voltage characteristics of AlGaN/AlN/GaN high electron mobility transistors

王鑫华, 赵妙, 刘新宇, 蒲颜, 郑英奎, 魏珂

2010 (9): 97302-097302. doi: 10.1088/1674-1056/19/9/097302

摘要 ( 1913 )

PDF(193KB) ( 3708 )

This paper deduces the expression of the Schottky contact capacitance of AlGaN/AlN/GaN high electron mobility transistors (HEMTs), which will help to understand the electron depleting process. Some material parameters related with capacitance--voltage profiling are given in the expression. Detailed analysis of the forward-biased capacitance has been carried on. The gate capacitance of undoped AlGaN/AlN/GaN HEMT will fall under forward bias. If a rising profile is obviously observed, the donor-like impurity or trap is possibly introduced in the barrier.

参考文献 | 相关文章 | 计量指标

Select

The dispersion relations for surface plasmon in a nonlinear–metal–nonlinear dielectric structure

刘炳灿, 于丽, 逯志欣, 张恺

2010 (9): 97303-097303. doi: 10.1088/1674-1056/19/9/097303

摘要 ( 1545 )

PDF(100KB) ( 948 )

In the asymmetric and symmetric nonlinear--metal--nonlinear dielectric structures, this paper studies the analytic dispersion relation for surface plasmon in a system consisting of a thin metallic film covered on two sides media of intensity-dependent refractive indexes by applying a generalised first integral approach. Especially in the symmetric waveguide structure, two possible modes can exist: the odd mode and the even mode. The dispersion relations of the two modes are obtained. Due to the nonlinear dielectric, the squared magnitude of the electric field at the interface appears and alters the dispersion relations. Numerical results are compared to those from a certain approximate treatment.

参考文献 | 相关文章 | 计量指标

Select

Thermal activation of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height

茹国平, 俞融, 蒋玉龙, 阮刚

2010 (9): 97304-097304. doi: 10.1088/1674-1056/19/9/097304

摘要 ( 1524 )

PDF(331KB) ( 819 )

This paper investigates the thermal activation behaviour of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height by numerical simulation. The analytical Gaussian distribution model predicted that the I--V--T curves may intersect with the possibility of the negative thermal activation of current, but may be contradictory to the thermionic emission mechanism in a Schottky diode. It shows that the cause of the unphysical phenomenon is related to the incorrect calculation of current across very low barriers. It proposes that junction voltage V_j, excluding the voltage drop across series resistance from the external bias, is a crucial parameter for correct calculation of the current across very low barriers. For correctly employing the thermionic emission model, V_j needs to be smaller than the barrier height Ф. With proper scheme of series resistance connection where the condition of V_j > Ф is guaranteed, I--V--T curves of an inhomogeneous Schottky diode with a Gaussian distribution of barrier height have been simulated, which demonstrate normal thermal activation. Although the calculated results exclude the intersecting possibility of I--V--T curves with an assumption of temperature-independent series resistance, it shows that the intersecting is possible when the series resistance has a positive temperature coefficient. Finally, the comparison of our numerical and analytical results indicates that the analytical Gaussian distribution model is valid and accurate in analysing I--V--T curves only for small barrier height inhomogeneity.

参考文献 | 相关文章 | 计量指标

Select

Improving performances of ITO/GaP contact on AlGaInP light-emitting diodes

李春伟, 朱彦旭, 沈光地, 张勇辉, 秦园, 高伟, 蒋文静, 邹德恕

2010 (9): 97305-097305. doi: 10.1088/1674-1056/19/9/097305

摘要 ( 1690 )

PDF(1691KB) ( 2054 )

In this paper AlGaInP light emitting diodes with different types of electrodes: Au/Zn/Au-ITO Au/Ti-ITO Au/Ge/Ni-ITO and Au-ITO are fabricated. The photoelectricity properties of those LEDs are studied. The results show that the Au/Zn/Au electrode greatly improves the performance of LEDs compared with the other electrodes. Because the Au/Zn/Au electrode not only forms a good Ohmic contact with indium tin oxide (ITO), but also reduces the specific contact resistances between ITO and GaP, which are 1.273×10^-6 Ω · cm² and 1.743×10^-3 Ω ·cm² between Au/Zn/Au-ITO and ITO-GaP respectively. Furthermore, the textured Zn/Au-ITO/Zn electrode is designed to improve the performances of LEDs, reduce the forward-voltage of the LED from 1.93 to 1.88 V, and increase the luminous intensity of the LEDs from 126 to 134 mcd when driven at 20 mA.

参考文献 | 相关文章 | 计量指标

Select

The study on mechanism and model of negative bias temperature instability degradation in P-channel metal–oxide–semiconductor field-effect transistors

曹艳荣, 马晓华, 郝跃, 田文超

2010 (9): 97306-097306. doi: 10.1088/1674-1056/19/9/097306

摘要 ( 1669 )

PDF(785KB) ( 776 )

Negative Bias Temperature Instability (NBTI) has become one of the most serious reliability problems of metal--oxide--semiconductor field-effect transistors (MOSFETs). The degradation mechanism and model of NBTI are studied in this paper. From the experimental results, the exponential value 0.25--0.5 which represents the relation of NBTI degradation and stress time is obtained. Based on the experimental results and existing model, the reaction--diffusion model with H⁺related species generated is deduced, and the exponent 0.5 is obtained. The results suggest that there should be H⁺generated in the NBTI degradation. With the real time method, the degradation with an exponent 0.5 appears clearly in drain current shift during the first seconds of stress and then verifies that H⁺generated during NBTI stress.

参考文献 | 相关文章 | 计量指标

Select

Fabrication of suspended graphene devices and their electronic properties

李强, 程增光, 李忠军, 王志华, 方英

2010 (9): 97307-097307. doi: 10.1088/1674-1056/19/9/097307

摘要 ( 1867 )

PDF(1469KB) ( 1943 )

Suspended graphene devices are successfully fabricated by using a novel PMMA/MMA/PMMA tri-layer resist technique. The gap between graphene and dielectric substrate can be easily controlled by the thickness of the bottom PMMA layer, and no wet-etching with hazardous hydrofluoric acid is involved in our fabrication process. Electrical characterizations on suspended graphene devices are performed in vacuum when in-situ current annealing directly leads to a significant improvement on transport properties of graphene, i.e., the increase of carrier mobility with the reduction of width of Dirac peak. Our results make a new opportunity to study intrinsic properties of graphene.

参考文献 | 相关文章 | 计量指标

Select

High frequency behaviours and Mössbauer study of field annealed FeCuNbSiB alloy ribbons

马小明, 李志伟, 位建强, 王涛, 李发伸

2010 (9): 97401-097401. doi: 10.1088/1674-1056/19/9/097401

摘要 ( 1393 )

PDF(170KB) ( 941 )

This paper investigates the high frequency behaviours and magnetic anisotropy of rapidly solidified FINEMET (Fe_73.5Si_13.5B₉Nb₃Cu₁) alloy ribbons annealed in an applied magnetic field. It finds that the ribbons annealed with the applied magnetic field show much higher resonance frequencies and have even higher permeability at higher frequencies than the samples annealed without the magnetic field and the non-annealed ribbons. M?ssbauer spectroscopy had been employed to study the spatial distribution of the magnetic moments of five selected FINEMET alloy ribbons in different heat-treated conditions. The results show that an easy plane has been established after annealling in the magnetic field, while for the other ribbons this effect is not significant. Hence, the relationship between magnetic field annealing and high frequency property has been bridged by the bianisotropic theory.

参考文献 | 相关文章 | 计量指标

Select

Magnetic hysteresis and refrigeration capacity of Ni–Mn–Ga alloys near Martensitic transformation

傅斌, 龙毅, 段静芳, 王超伦, 常永勤, 叶荣昌, 吴光恒

2010 (9): 97501-097501. doi: 10.1088/1674-1056/19/9/097501

摘要 ( 1549 )

PDF(640KB) ( 931 )

This paper studies the magnetic hysteresis and refrigeration capacity of Ni--Mn--Ga alloys in detail during heating and cooling isothermal magnetisation processes. The Ni--Mn--Ga alloys show larger magnetic hysteresis when they transform from austenite to martensite, but smaller magnetic hysteresis when they transform from martensite to austenite. This behaviour is independent of either the pure Ni--Mn--Ga alloys or the alloys doped with other elements. Because of the existence of the magnetic hysteresis, the relation between the magnetic entropy change and refrigeration capacity is not simply linear. For practical consideration, magnetocaloric effect of Ni--Mn--Ga alloys should be investigated both on cooling and heating processes.

参考文献 | 相关文章 | 计量指标

Select

Ferromagnetism in Eu-doped ZnO films deposited by radio-frequency magnetic sputtering

谭永胜, 方泽波, 陈伟, 何丕模

2010 (9): 97502-097502. doi: 10.1088/1674-1056/19/9/097502

摘要 ( 1468 )

PDF(112KB) ( 1065 )

This paper reports that Eu-doped ZnO films were successfully deposited on silicon (100) by radio-frequency magnetic sputtering. The x-ray diffraction patterns indicate that Eu substitutes for Zn in the lattice. Ferromagnetic loops were obtained by using superconducting quantum interference device at 10 K and room temperature. No discontinuous change was found in both of the zero-field-cooled and field-cooled curves. The observed ferromagnetism in Eu-doped ZnO can be attributed to a single magnetic phase. The saturation magnetisation decreased remarkably for the Eu-doped ZnO prepared by introducing 5% of oxygen in the sputtering gas or by the post annealing in O₂, suggesting that the defects play key roles in the development of ferromagnetism in Eu-doped ZnO films.

参考文献 | 相关文章 | 计量指标

Select

Properties study of LiNbO₃ lateral field excited device working on thickness extension mode

张志甜, 张超, 王文炎, 马廷锋, 刘岩, 冯冠平

2010 (9): 97701-097701. doi: 10.1088/1674-1056/19/9/097701

摘要 ( 1563 )

PDF(1436KB) ( 1127 )

This paper investigates the properties of thickness extension mode excited by lateral electric field on LiNbO₃ by using the extended Christoffel--Bechmann method. It finds that the lateral field excitation coupling factor for a-mode (quasi-extensional mode) reaches its maximum value of 28% on X-cut LiNbO₃. The characteristics of a lateral field excitation device made of X-cut LiNbO₃ have been investigated and the lateral field excitation device is used for the design of a high frequency ultrasonic transducer. The time and frequency domain pulse/echo response of the LiNbO₃ lateral field excitation ultrasonic transducer is analysed with the modified Krimholtz--Leedom--Matthae model and tested using traditional pulse/echo method. A LiNbO₃ lateral field excitation ultrasonic transducer with the centre frequency of 33.44 MHz and the --6 dB bandwidth of 33.8% is acquired, which is in good agreement with the results of the Krimholtz--Leedom--Matthae model. Further analysis suggests that the LiNbO₃ lateral field excitation device has great potential in the design of broadband high frequency ultrasonic transducers.

参考文献 | 相关文章 | 计量指标

Select

Monte Carlo simulation on dielectric relaxation and dipole cluster state in relaxor ferroelectrics

朱琛, 刘俊明

2010 (9): 97702-097702. doi: 10.1088/1674-1056/19/9/097702

摘要 ( 1543 )

PDF(251KB) ( 1036 )

The Ginzburg--Landau theory on ferroelectrics with random field induced by dipole defects is studied by using Monte Carlo simulation, in order to investigate the dipole configuration and the dielectric relaxation of relaxor ferroelectrics. With the increase of random field, the dipole configuration evolves from the long-range ferroelectric order into the coexistence of short-range dipole-clusters and less polarized matrix. The dipole-cluster phase above the transition temperature and superparaelectric fluctuations far below this temperature are identified for the relaxor ferroelectrics. We investigate the frequency dispersion and the time-domain spectrum of the dielectric relaxation, demonstrating the Vogel--Fulcher relationship and the multi-peaked time-domain distribution of the dielectric relaxation.

参考文献 | 相关文章 | 计量指标

Select

Role of nitrogen and oxygen in emission of Si quantum dots formed by pulse laser

黄伟其, 刘家兴, 蔡成兰, 吕泉, 刘世荣, 秦朝建

2010 (9): 97801-097801. doi: 10.1088/1674-1056/19/9/097801

摘要 ( 1468 )

PDF(3129KB) ( 922 )

Silicon quantum dots fabricated by nanosecond pulsed laser in nitrogen, oxygen or air atmosphere have enhanced photoluminescence (PL) emission with the stimulated emission observed at about 700 nm. It is difficult to distinguish between the photoluminescence peaks emitted from samples prepared in different atmospheres. The reason for the appearance of similar peaks may be the similar distribution of the localised states in the gap for different samples when silicon dangling bonds of quantum dots are passivated by nitrogen or oxygen. It is revealed that both the kind and the density of passivated bonds on quantum dot surface prepared in oxygen or nitrogen have a strong influence on the enhancement of PL emission.

参考文献 | 相关文章 | 计量指标

Select

Relationship of annealing time and intrinsic defects of unintentionally doped 4H-SiC

程萍, 张玉明, 张义门, 郭辉

2010 (9): 97802-097802. doi: 10.1088/1674-1056/19/9/097802

摘要 ( 1570 )

PDF(1578KB) ( 935 )

With annealing temperature kept at 1573 K, the effects of annealing time on stability of the intrinsic defects in epitaxial unintentionally doped 4H-SiC prepared by low pressure chemical vapour deposition have been studied by electron spin resonance (ESR) and low temperature photoluminescence. This paper reports the results shown that annealing time has an important effect on the intrinsic defects in unintentionally doped 4H-SiC when annealing temperature kept at 1573 K. When the annealing time is less than 30 min, the intensity of ESR and photoluminescence is increasing with annealing time prolonged, and reaches the maximum when annealing time is 30 min. Then the intensity of ESR and photoluminescence is rapidly decreased with the longer annealing time, and much less than that of as-grown 4H-SiC when annealing time is 60 min, which should be related with the interaction among the intrinsic defects during the annealing process.

参考文献 | 相关文章 | 计量指标

Select

An interconnect width and spacing optimization model considering scattering effect

朱樟明, 万达经, 杨银堂

2010 (9): 97803-097803. doi: 10.1088/1674-1056/19/9/097803

摘要 ( 1368 )

PDF(277KB) ( 553 )

As the feature size of the CMOS integrated circuit continues to shrink, the more and more serious scattering effect has a serious impact on interconnection performance, such as delay and bandwidth. Based on the impact of the scattering effect on latency and bandwidth, this paper first presents the quality-factor model which optimises latency and bandwidth effectively with the consideration of the scattering effect. Then we obtain the analytical model of line width and spacing with application of curve-fitting method. The proposed model has been verified and compared based on the nano-scale CMOS technology. This optimisation model algorithm is simple and can be applied to the interconnection system optimal design of nano-scale integrated circuits.

参考文献 | 相关文章 | 计量指标

Select

Improvement in the calculation of anti-Stokes energy transfer and experimental justification based on Er_0.01Yb_xY_{1 - 0.01 - x}VO₄ crystal

陈晓波, 卢建, 张蕴芝, 徐小灵, 冯宝华, 王策, Gregory J. Salamo, 杨国建

2010 (9): 97804-097804. doi: 10.1088/1674-1056/19/9/097804

摘要 ( 1390 )

PDF(549KB) ( 975 )

The improvement on the calculation of anti-Stokes energy transfer rate is studied in the present work. The additional proportion coefficient between Stokes and anti-Stokes light intensities of quantum Raman scattering theory as compared with the classical Raman theory is introduced to successfully describe the anti-Stokes energy transfer. The theoretical formula for the improvement on the calculation of anti-Stokes energy transfer rate is derived for the first time in this study. The correctness of introducing coefficient exp{ΔE / kT} from well-known Raman scatter theory is demonstrated also. Moreover, the experimental lifetime measurement in Er_0.01Yb_xY_{1 - 0.01 - x}VO₄ crystal is performed to justify the validity of our important improvement in the original phonon-assisted energy transfer theory for the first time.

参考文献 | 相关文章 | 计量指标

Select

Electroluminescence of double-doped diamond thin films

章诗, 王小平, 王丽军, 朱玉传, 梅翠玉, 刘欣欣, 李怀辉, 顾应展

2010 (9): 97805-097805. doi: 10.1088/1674-1056/19/9/097805

摘要 ( 1566 )

PDF(2998KB) ( 857 )

A new electroluminescence device is fabricated by microwave plasma chemical vapour deposition system and electron beam vapour deposition system. It is comprised of highly doped silicon/diamond/boron/nitrogen-doped diamond/indium tin oxide thin films. Effects of process parameters on morphologies and structures of the thin films are detected and analysed by scanning electron microscopy, Raman spectrometer and x-ray photoelectron spectrometer. A direct-current (DC) power supply is used to drive the electroluminescence device. The blue light emission with a luminance of 1.2 cd·m^{- 2} is observed from this double-doped diamond thin film electroluminescence device at an applied voltage of 105 V.

参考文献 | 相关文章 | 计量指标

Select

Mechanism and enhancement of photoluminescence from silicon nanocrystals implanted in SiO₂ matrix

吴志永, 刘克新, 任晓堂

2010 (9): 97806-097806. doi: 10.1088/1674-1056/19/9/097806

摘要 ( 1468 )

PDF(1529KB) ( 551 )

Photoluminescence (PL) spectra of Si nanocrystals (NCs) prepared by 130 keV Si ions implantation onto SiO₂ matrix were investigated as a function of annealing temperature and implanted ion dose. PL spectra consist of two PL peaks, originated from smaller Si NCs due to quantum confinement effect (QCE) and the interface states located at the surface of larger Si NCs. The evolution of number of dangling bonds (DBs) on Si NCs was also investigated. For hydrogen-passivated samples, a monotonic increase in PL peak intensity with the dose of implanted Si ions up to 3× 10¹⁷ ions /cm² is observed. The number of DBs on individual Si NC, the interaction between DBs at the surface of neighbouring Si NCs and their effects on the efficiency of PL are discussed.

参考文献 | 相关文章 | 计量指标

Select

Amorphous Er₂O₃ films for antireflection coatings

朱燕艳, 方泽波, 刘永生

2010 (9): 97807-097807. doi: 10.1088/1674-1056/19/9/097807

摘要 ( 1671 )

PDF(641KB) ( 941 )

This paper reports that stoichiometric, amorphous, and uniform Er₂O₃ films are deposited on Si(001) substrates by a radio frequency magnetron sputtering technique. Ellipsometry measurements show that the refractive index of the Er₂O₃ films is very close to that of a single layer antireflection coating for a solar cell with an air surrounding medium during its working wavelength. For the 90-nm-thick film, the reflectance has a minimum lower than 3% at the wavelength of 600 nm and the weighted average reflectances (400--1000 nm) is 11.6%. The obtained characteristics indicate that Er₂O₃ films could be a promising candidate for antireflection coatings in solar cells.

参考文献 | 相关文章 | 计量指标

Select

Optical transmission through basic-structural-unit superlattices

张国刚, 杨湘波

2010 (9): 97808-097808. doi: 10.1088/1674-1056/19/9/097808

摘要 ( 1494 )

PDF(541KB) ( 551 )

In this paper, by the transparent-component-decimation (TCD) method we obtain three kinds of new basic-components (BCs) through simplifying and decomposing the BCs of three-component Thue--Morse (3CTM) sequence. Based on these new BCs we propose a type of basic-structural-units (BSUs) and investigate the optical transmission of the one-dimensional (1D) superlattices composed of these BSUs. It is found that if the substrates of the 1D BSU superlattices are certain, the optical transmission at the central wavelength (CW) will be determined completely by the number and the type of BSUs and has nothing to do with the marshalling sequence. In particular, if the substrates are identical, the numbers of different types of BSUs are all the same and the middle two elements of BSUs constitute a cycle, then no matter whether the system is periodic, or quasiperiodic, or aperiodic, or unordered, or even random, it will be transparent at the CW. The conclusion is confirmed by the numerical results. Similar to the even layers of neighbourhood identical elements in TCD method, such a kind of optical BSU subsystem can also be decimated from the chain in the process of transmission investigation. There would be a potential application in the designing of some interesting optical devices.

参考文献 | 相关文章 | 计量指标

Select

Role of buffer layer in electronic structures of iron phthalocyanine molecules on Au(111)

孙家涛, 潘理达, 胡昊, 杜世萱, 高鸿钧

2010 (9): 97809-097809. doi: 10.1088/1674-1056/19/9/097809

摘要 ( 1565 )

PDF(1876KB) ( 647 )

We investigate the electronic structures of one and two monolayer iron phthalocyanine (FePc) molecules on Au(111) surfaces. The first monolayer FePc is lying flat on the Au(111) substrate, and the second monolayer FePc is tilted at ～15° relative to the substrate plane along the nearest neighbour [101^-] direction with a lobe downward to the central hole of the unit cell in the first layer. The structural information obtained by first-principles calculations is in agreement with the experiment results. Furthermore, it is demonstrated that the electronic structures of FePc molecules in one-monolayer FePc/Au(111) system are perturbed significantly, while the electronic structures of FePc molecules in the second monolayer in two-monolayer FePc/Au(111) system remain almost unchanged due to the screening of the buffer layer on Au(111).

参考文献 | 相关文章 | 计量指标

Select

Structures and magnetic behaviours of TiO₂–Mn–TiO₂ multilayers

刘发民, 丁芃, 李建奇

2010 (9): 98101-098101. doi: 10.1088/1674-1056/19/9/098101

摘要 ( 1202 )

PDF(6089KB) ( 832 )

The TiO₂--Mn--TiO₂ multilayers are successfully grown on glass and silicon substrates by alternately using radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and the magnetic behaviours of these films are characterised with x-ray diffraction, transmission electron microscope (TEM), vibrating sample magnetometer, and superconducting quantum interference device (SQUID). It is shown that the multi-film consists of a mixture of anatase and rutile TiO₂ with an embedded Mn nano-film. It is found that there are two turning points from ferromagnetic phase to antiferromagnetic phase. One is at 42 K attributed to interface coupling between ferromagnetic Mn₃O₄ and antiferromagnetic Mn₂O₃, and the other is at 97 K owing to the interface coupling between ferromagnetic Mn and antiferromagnetic MnO. The samples are shown to have ferromagnetic behaviours at room temperature from hysteresis in the M--H loops, and their ferromagnetism is found to vary with the thickness of Mn nano-film. Moreover, the Mn nano-film has a critical thickness of about 18.5 nm, which makes the coercivity of the multi-film reach a maximum of about 3.965times 10^{- 2} T.

参考文献 | 相关文章 | 计量指标

Select

Reduction of the phosphorus contamination for plasma deposition of p–i–n microcrystalline silicon solar cells in a single chamber

王光红, 张晓丹, 许盛之, 郑新霞, 魏长春, 孙建, 熊绍珍, 耿新华, 赵颖

2010 (9): 98102-098102. doi: 10.1088/1674-1056/19/9/098102

摘要 ( 1438 )

PDF(184KB) ( 865 )

This paper investigates several pretreatment techniques used to reduce the phosphorus contamination between solar cells. They include hydrogen plasma pretreatment, deposition of a p-type doped layer, i-a-Si:H or μ c-Si:H covering layer between solar cells. Their effectiveness for the pretreatment is evaluated by means of phosphorus concentration in films, the dark conductivity of p-layer properties and cell performance.

参考文献 | 相关文章 | 计量指标

Select

Effect of slow-solvent-vapour treatment on performance of polymer photovoltaic devices

冯志慧, 侯延冰, 师全民, 刘小君, 滕枫

2010 (9): 98601-098601. doi: 10.1088/1674-1056/19/9/098601

摘要 ( 1481 )

PDF(1834KB) ( 905 )

In this work, enhanced poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk-heterojunction photovoltaic devices are achieved via slow-solvent-vapour treatment. The correlations between the morphology of the active layer and the photovoltaic performance of polymer-based solar cell are investigated. The active layers are characterized by atomic force microscopy and optical absorption. The results show that slow-solvent-vapour treatment can induce P3HT self-organization into an ordered structure, leading to the enhanced absorption and efficient charge transport.

参考文献 | 相关文章 | 计量指标

Select

Propagation of partially coherent beams carrying an edge dislocation through atmospheric turbulence along a slant path

李晋红, 张洪润, 吕百达

2010 (9): 99201-099201. doi: 10.1088/1674-1056/19/9/099201

摘要 ( 1453 )

PDF(1180KB) ( 745 )

This paper derives the explicit expressions for the average intensity, beam width and angular spread of Gaussian Schell-model (GSM) beams with edge dislocation propagating through atmospheric turbulence along a slant path. The propagation of GSM beams with edge dislocation through horizontal atmospheric turbulence can be treated as a special case through a slant one. The propagation properties of GSM beams with edge dislocation through slant atmospheric turbulence are studied, where the influence of edge dislocation parameters including the slope p and off-axis distance d on the spreading of GSM beams with edge dislocation in atmospheric turbulence is stressed. It shows that the spreading of the intensity profile of GSM beams with edge dislocation along a slant path is smaller than that along a horizontal path in the long-distance atmospheric propagation. The larger the slope vert pvert and the smaller the off-axis distance vert dvert are, the less the beam-width spreading and angular spread of GSM beams with edge dislocation are affected by turbulence. The GSM beams with edge dislocation is less affected by turbulence than that of GSM beams without edge dislocation. The results are illustrated numerically and their validity is interpreted physically.

参考文献 | 相关文章 | 计量指标

Select

Effect of superstrong magnetic field on electron screening at the crusts of neutron stars

刘晶晶

2010 (9): 99601-099601. doi: 10.1088/1674-1056/19/9/099601

摘要 ( 1532 )

PDF(161KB) ( 919 )

The influences of electron screening (ES) and electron energy correction (EEC) are investigated by superstrong magnetic field (SMF). We also discuss in detail the discrepant factor between our results and those of Fushiki, Gudmundsson and Pethick (FGP) in SMF. The results show that SMF has only a slight effect on ES when B < 10⁹ T on the surfaces of most neutron stars. Whereas for some magnetars, SMF influence ES greatly when B > 10⁹ T . For instance, due to SMF the ES potential may be increased about 23.6% and the EEC may be increased about 4 orders of magnitude at ρ/μ_e = 1.0×10⁶ mol/cm³ and T₉ = 1. On the other hand, the discrepant factor shows that our results are in good agreement with FGP's when B < 10⁹ T . But the difference will be increased with increasing SMF.

参考文献 | 相关文章 | 计量指标

Select

Effect of strong magnetic field on chemical potential and electron capture in magnetar

高杰, 罗志全, 刘伟伟, 李港

2010 (9): 99701-099701. doi: 10.1088/1674-1056/19/9/099701

摘要 ( 1598 )

PDF(117KB) ( 799 )

The chemical potential of electrons in a strong magnetic field is investigated. It is shown that the magnetic field has only a slight effect on electron chemical potential when B<10¹¹ T, but electron chemical potential will decrease greatly when B>10¹¹ T. The effects of a strong magnetic field on electron capture rates for ⁶⁰Fe are discussed, and the result shows that the electron capture sharply decreases because of the strong magnetic field.

参考文献 | 相关文章 | 计量指标

Select

Interference phase of mass neutrino in Reissner–Nordström–de Sitter space–time

黄河, 王永久

2010 (9): 99702-099702. doi: 10.1088/1674-1056/19/9/099702

摘要 ( 1707 )

PDF(80KB) ( 605 )

In Reissner--Nordstr?m--de Sitter space--time, we calculate the interference phase of mass neutrino along geodesic in the radial direction, and then investigate the effects of the cosmological constant La on the phase. Morever, the expression of the interference phase can be reduced to that in Reissner--Nordstr?m space--time when Λ approaches to zero.

参考文献 | 相关文章 | 计量指标

当期目录