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2010年, 第19卷, 第2期　刊出日期：2010-02-15 上一期    下一期

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Three types of generalized Kadomtsev－Petviashvili equations arising from baroclinic potential vorticity equation 张焕萍, 李彪, 陈勇, 黄菲 2010 (2):  20201-020201.  doi: 10.1088/1674-1056/19/2/020201 摘要 ( 2051 )   PDF(1446KB) ( 1230 )   By means of the reductive perturbation method, three types of generalized (2+1)-dimensional Kadomtsev--Petviashvili (KP) equations are derived from the baroclinic potential vorticity (BPV) equation, including the modified KP (mKP) equation, standard KP equation and cylindrical KP (cKP) equation. Then some solutions of generalized cKP and KP equations with certain conditions are given directly and a relationship between the generalized mKP equation and the mKP equation is established by the symmetry group direct method proposed by Lou et al. From the relationship and the solutions of the mKP equation, some solutions of the generalized mKP equation can be obtained. Furthermore, some approximate solutions of the baroclinic potential vorticity equation are derived from three types of generalized KP equations. 参考文献 | 相关文章 | 计量指标

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Existence and asymptotic estimates of periodic solutions of El Niño mechanism of atmospheric physics 李晓静 2010 (2):  20202-20202.  doi: 10.1088/1674-1056/19/2/020202 摘要 ( 2051 )   PDF(88KB) ( 685 )   This paper is devoted to studying the El Niño mechanism of atmospheric physics. The existence and asymptotic estimates of periodic solutions for its model are obtained by employing the technique of upper and lower solution, and using the continuation theorem of coincidence degree theory. 参考文献 | 相关文章 | 计量指标

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Cooperation influenced by the correlation degree of two-layered complex networks in evolutionary prisoner's dilemma games 关剑月, 吴枝喜, 黄子罡, 汪映海 2010 (2):  20203-020203.  doi: 10.1088/1674-1056/19/2/020203 摘要 ( 2148 )   PDF(1194KB) ( 902 )   An evolutionary prisoner's dilemma game is investigated on two-layered complex networks respectively representing interaction and learning networks in one and two dimensions. A parameter q is introduced to denote the correlation degree between the two-layered networks. Using Monte Carlo simulations we studied the effects of the correlation degree on cooperative behaviour and found that the cooperator density nontrivially changes with q for different payoff parameter values depending on the detailed strategy updating and network dimension. An explanation for the obtained results is provided. 参考文献 | 相关文章 | 计量指标

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Effects of orientation and shape of holes on the band gaps in water waves over periodically drilled bottoms 钟兰花, 吴福根, 钟会林 2010 (2):  20301-020301.  doi: 10.1088/1674-1056/19/2/020301 摘要 ( 1696 )   PDF(1038KB) ( 747 )   The complete band gaps (CBGs) of shallow water waves propagating over bottoms with periodically drilled holes are investigated numerically by the plane wave expansion method. Four different patterns are considered, containing triangular, square, hexagonal and circular cross-sectioned holes arranged into triangular lattices. Results show that the width of CBGs can be changed by adjusting the orientation of noncircular holes and the effect of hole shape on the width of the maximal CBGs is discussed. 参考文献 | 相关文章 | 计量指标

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Bohmian mechanics to high-order harmonic generation 赖炫扬, 蔡庆宇, 詹明生 2010 (2):  20302-020302.  doi: 10.1088/1674-1056/19/2/020302 摘要 ( 1713 )   PDF(269KB) ( 788 )   This paper introduces Bohmian mechanics (BM) into the intense laser-atom physics to study high-order harmonic generation. In BM, the trajectories of atomic electron in an intense laser field can be obtained with the Bohm--Newton equation. The power spectrum with the trajectory of an atomic electron is calculated, which is found to be irregular. Next, the power spectrum associated with an atom ensemble from BM is considered, where the power spectrum becomes regular and consistent with that from quantum mechanics. Finally, the reason of the generation of the irregular spectrum is discussed. 参考文献 | 相关文章 | 计量指标

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New equation for deriving pure state density operators by Weyl correspondence and Wigner operator 许业军, 范洪义, 刘秋宇 2010 (2):  20303-020303.  doi: 10.1088/1674-1056/19/2/020303 摘要 ( 2082 )   PDF(101KB) ( 688 )   By virtue of the completeness of Wigner operator and Weyl correspondence we construct a general equation for deriving pure state density operators. Several important examples are considered as the applications of this equation, which shows that our approach is effective and convenient for deducing these entangled state representations. 参考文献 | 相关文章 | 计量指标

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Resonant tunneling and quantum fluctuation in a driven triple-well system 卢伟涛, 王顺金, 张华 2010 (2):  20304-020304.  doi: 10.1088/1674-1056/19/2/020304 摘要 ( 1934 )   PDF(217KB) ( 747 )   The influence of parameters such as the strength and frequency of a periodic driving force on the tunneling dynamics is investigated in a symmetric triple-well potential. It is shown that for some special values of the parameters, tunneling could be enhanced considerably or suppressed completely. Quantum fluctuation during the tunneling is discussed as well and the numerical results are presented and analysed by virtue of Floquet formalism. 参考文献 | 相关文章 | 计量指标

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Exact solution of the one-dimensional Klein－Gordon equation with scalar and vector linear potentials in the presence of a minimallength Y Chargui, L Chetouani, ATrabelsi 2010 (2):  20305-020305.  doi: 10.1088/1674-1056/19/2/020305 摘要 ( 1882 )   PDF(91KB) ( 2355 )   Using the momentum space representation, we solve the Klein--Gordon equation in one spatial dimension for the case of mixed scalar and vector linear potentials in the context of deformed quantum mechanics characterized by a finite minimal uncertainty in position. The expressions of bound state energies and the associated wave functions are exactly obtained. 参考文献 | 相关文章 | 计量指标

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Electric flux distribution in photodetachment of heteronuclear diatomic molecular negative ion 王德华 2010 (2):  20306-020306.  doi: 10.1088/1674-1056/19/2/020306 摘要 ( 1684 )   PDF(464KB) ( 780 )   The photodetachment of a hetero-nuclear diatomic molecular negative ion is studied by using a two-centre model. An analytic formula is presented for the electron flux distribution of a heteronuclear diatomic molecular negative ion. Taking HF- as an example, we calculated the electron flux distributions of this ion for various detached electron energies. The results show that the electron flux distributions exhibit oscillatory structures, which are caused by the interference effect between the two nuclei. Besides, the laser light polarization also has a great influence on the electron flux distribution. The oscillation amplitude is the largest when the laser polarization is parallel to the z-axis; when the laser polarization is perpendicular to the z-axis, the oscillation almost vanishes. This study provides a new understanding of the photodetachment of a heteronuclear diatomic molecular negative ion. 参考文献 | 相关文章 | 计量指标

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A criterion for quantum teleportation of an arbitrary N-particle state via a 2N-particle quantum channel 刘大明, 王艳伟, 江秀梅, 郑亦庄 2010 (2):  20307-020307.  doi: 10.1088/1674-1056/19/2/020307 摘要 ( 1818 )   PDF(128KB) ( 764 )   A criterion for he tquantum teleportation of an arbitrary N-particle state via a 2N-particle quantum channel is presented by introducing a term of the ``judgment operator''. Using the criterion, not only the qualitative judgment of the possibility of successful teleportation can be made but also the quantitative calculation of the probability of successful teleportation can be explicitly given. In addition, a new genuine four-qubit entangled state is proposed, which could not belong to the category of previously known states under stochastic local operations and classical communication. 参考文献 | 相关文章 | 计量指标

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Deterministic quantum teleportation and information splitting via a peculiar W-class state 梅锋, 於亚飞, 张智明 2010 (2):  20308-020308.  doi: 10.1088/1674-1056/19/2/020308 摘要 ( 1779 )   PDF(95KB) ( 655 )   In the paper ({\em Phys. Rev.} 2006 A {\bf 74} 062320) Agrawal {\em et al}. have introduced a kind of W-class state which can be used for the quantum teleportation of single-particle state via a three-particle von Neumann measurement, and they thought that the state could not be used to teleport an unknown state by making two-particle and one-particle measurements. Here we reconsider the features of the W-class state and the quantum teleportation process via the W-class state. We show that, by introducing a unitary operation, the quantum teleportation can be achieved deterministically by making two-particle and one-particle measurements. In addition, our protocol is extended to the process of teleporting two-particle state and splitting information. 参考文献 | 相关文章 | 计量指标

GENERAL

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The entanglement of two moving atoms interacting with a single-mode field via a three-photon process 吴超, 方卯发 2010 (2):  20309-020309.  doi: 10.1088/1674-1056/19/2/020309 摘要 ( 1735 )   PDF(136KB) ( 760 )   In this paper, the entanglement of two moving atoms induced by a single-mode field via a three-photon process is investigated. It is shown that the entanglement is dependent on the category of the field, the average photon number N, the number p of half-wave lengths of the field mode and the atomic initial state. Also, the sudden death and the sudden birth of the entanglement are detected in this model and the results show that the existence of the sudden death and the sudden birth depends on the parameter and the category of the mode field. In addition, the three-photon process is a higher order nonlinear process. 参考文献 | 相关文章 | 计量指标

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Improving the security of secure deterministic communication scheme based on quantum remote state preparation 秦素娟, 温巧燕 2010 (2):  20310-020310.  doi: 10.1088/1674-1056/19/2/020310 摘要 ( 1844 )   PDF(79KB) ( 692 )   The security of the quantum secure deterministic communication scheme [{\it Chin. Phys.} {\bf16} (2007) 2549] is reexamined. A security loophole is pointed out. Taking advantage of this loophole, an eavesdropper can steal all the secret messages without being detected by an intercept-and-resend attack strategy. Furthermore, a possible improvement on this protocol is presented. It makes the modified protocol secure against this kind of attack. 参考文献 | 相关文章 | 计量指标

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Brane world black holes in teleparallel theory equivalent to general relativity and their Killing vectors, energy, momentum and angular momentum Gamal G.L. Nashed 2010 (2):  20401-020401.  doi: 10.1088/1674-1056/19/2/020401 摘要 ( 1604 )   PDF(163KB) ( 864 )   The energy--momentum tensor, which is coordinate-independent, is used to calculate energy, momentum and angular momentum of two different tetrad fields. Although, the two tetrad fields reproduce the same space--time their energies are different. Therefore, a regularized expression of the gravitational energy--momentum tensor of the teleparallel equivalent of general relativity (TEGR), is used to make the energies of the two tetrad fields equal. The definition of the gravitational energy--momentum is used to investigate the energy within the external event horizon. The components of angular momentum associated with these space--times are calculated. In spite of using a static space--time, we get a non-zero component of angular momentum! Therefore, we derive the Killing vectors associated with these space--times using the definition of the Lie derivative of a second rank tensor in the framework of the TEGR to make the picture more clear. 参考文献 | 相关文章 | 计量指标

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Phase synchronization on small-world networks with community structure 王晓华, 焦李成, 吴建设 2010 (2):  20501-020501.  doi: 10.1088/1674-1056/19/2/020501 摘要 ( 1930 )   PDF(329KB) ( 765 )   In this paper, we propose a simple model that can generate small-world network with community structure. The network is introduced as a tunable community organization with parameter r, which is directly measured by the ratio of inter- to intra-community connectivity, and a smaller r corresponds to a stronger community structure. The structure properties, including the degree distribution, clustering, the communication efficiency and modularity are also analysed for the network. In addition, by using the Kuramoto model, we investigated the phase synchronization on this network, and found that increasing the fuzziness of community structure will markedly enhance the network synchronizability; however, in an abnormal region (r ≤ 0.001), the network has even worse synchronizability than the case of isolated communities (r = 0). Furthermore, this network exhibits a remarkable synchronization behaviour in topological scales: the oscillators of high densely interconnected communities synchronize more easily, and more rapidly than the whole network. 参考文献 | 相关文章 | 计量指标

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Phase diffusion of a two-component Bose-Einstein condensates:exact and short-time solutions for arbitrary coherent spin state 金光日, 王波波, 吕燕伍 2010 (2):  20502-020502.  doi: 10.1088/1674-1056/19/2/020502 摘要 ( 2004 )   PDF(296KB) ( 678 )   We investigate phase diffusion of a two-component Bose--Einstein condensates prepared initially in arbitrary coherent spin state |θ0,φ0|. Analytical expression of the phase-diffusion time is presented for θ0～π/2 case. In comparison with the symmetrical case (i.e., θ0=π/2), we find that the diffusion process becomes slow due to the reduced atom number variance. 参考文献 | 相关文章 | 计量指标

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A simplified tether model for molecular motor transporting cargo 李防震, 蒋立春 2010 (2):  20503-020503.  doi: 10.1088/1674-1056/19/2/020503 摘要 ( 1790 )   PDF(257KB) ( 596 )   Molecular motors are proteins or protein complexes which function as transporting engines in biological cells. This paper models the tether between motor and its cargo as a symmetric linear potential. Different from Elston and Peskin's work for which performance of the system was discussed only in some limiting cases, this study produces analytic solutions of the problem for general cases by simplifying the transport system into two physical states, which makes it possible to discuss the dynamics of the motor--cargo system in detail. It turns out that the tether strength between motor and cargo should be greater than a threshold or the motor will fail to transport the cargo, which was not discussed by former researchers yet. Value of the threshold depends on the diffusion coefficients of cargo and motor and also on the strength of the Brownian ratchets dragging the system. The threshold approaches a finite constant when the strength of the ratchet tends to infinity. 参考文献 | 相关文章 | 计量指标

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Influences of noise correlation and time delay on stochastic resonance induced by multiplicative signal in a cancer growth system 贾正林 2010 (2):  20504-020504.  doi: 10.1088/1674-1056/19/2/020504 摘要 ( 2089 )   PDF(130KB) ( 851 )   This paper investigates the stochastic resonance (SR) phenomenon induced by the multiplicative periodic signal in a cancer growth system with the cross-correlated noises and time delay. To describe the periodic change of the birth rate due to the periodic treatment, a multiplicative periodic signal is added to the system. Under the condition of small delay time, the analytical expression of the signal-to-noise ratio R_{\rm SNR} is derived in the adiabatic limit. By numerical calculation, the effects of the cross-correlation strength \lambda and the delay time \tau on R_{\rm SNR} are respectively discussed. The existence of a peak in the curves of R_{\rm SNR} as a function of the noise intensities indicates the occurrence of the SR phenomenon. It is found that \lambda and \tau play opposite role on the SR phenomenon, i.e., the SR is suppressed by increasing \lambda whereas it is enhanced with the increase of \tau, which is different from the case where the periodic signal is additive. 参考文献 | 相关文章 | 计量指标

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Generalized projective synchronization of chaotic systems via adaptive learning control 孙云平, 李俊民, 王江安, 王辉林 2010 (2):  20505-020505.  doi: 10.1088/1674-1056/19/2/020505 摘要 ( 1971 )   PDF(223KB) ( 931 )   In this paper, a learning control approach is applied to the generalized projective synchronisation (GPS) of different chaotic systems with unknown periodically time-varying parameters. Using the Lyapunov--Krasovskii functional stability theory, a differential-difference mixed parametric learning law and an adaptive learning control law are constructed to make the states of two different chaotic systems asymptotically synchronised. The scheme is successfully applied to the generalized projective synchronisation between the Lorenz system and Chen system. Moreover, numerical simulations results are used to verify the effectiveness of the proposed scheme. 参考文献 | 相关文章 | 计量指标

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Hierarchical-control-based output synchronization of coexisting attractor networks 宋运忠, 唐贻发 2010 (2):  20506-020506.  doi: 10.1088/1674-1056/19/2/020506 摘要 ( 1800 )   PDF(547KB) ( 581 )   This paper introduces the concept of hierarchical-control-based output synchronization of coexisting attractor networks. Within the new framework, each dynamic node is made passive at first utilizing intra-control around its own arena. Then each dynamic node is viewed as one agent, and on account of that, the solution of output synchronization of coexisting attractor networks is transformed into a multi-agent consensus problem, which is made possible by virtue of local interaction between individual neighbours; this distributed working way of coordination is coined as inter-control, which is only specified by the topological structure of the network. Provided that the network is connected and balanced, the output synchronization would come true naturally via synergy between intra and inter-control actions, where the rightness is proved theoretically via convex composite Lyapunov functions. For completeness, several illustrative examples are presented to further elucidate the novelty and efficacy of the proposed scheme. 参考文献 | 相关文章 | 计量指标

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A novel one equilibrium hyper-chaotic system generated upon Lü attractor 贾红艳, 陈增强, 袁著祉 2010 (2):  20507-020507.  doi: 10.1088/1674-1056/19/2/020507 摘要 ( 1934 )   PDF(6503KB) ( 1927 )   By introducing an additional state feedback into a three-dimensional autonomous chaotic attractor Lü system, this paper presents a novel four-dimensional continuous autonomous hyper-chaotic system which has only one equilibrium. There are only 8 terms in all four equations of the new hyper-chaotic system, which may be less than any other four-dimensional continuous autonomous hyper-chaotic systems generated by three-dimensional (3D) continuous autonomous chaotic systems. The hyper-chaotic system undergoes Hopf bifurcation when parameter c varies, and becomes the 3D modified Lü system when parameter k varies. Although the hyper-chaotic system does not undergo Hopf bifurcation when parameter k varies, many dynamic behaviours such as periodic attractor, quasi periodic attractor, chaotic attractor and hyper-chaotic attractor can be observed. A circuit is also designed when parameter k varies and the results of the circuit experiment are in good agreement with those of simulation. 参考文献 | 相关文章 | 计量指标

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The feedback control of fractional order unified chaotic system 杨捷, 齐冬莲 2010 (2):  20508-020508.  doi: 10.1088/1674-1056/19/2/020508 摘要 ( 1880 )   PDF(87KB) ( 1066 )   This paper studies the stability of the fractional order unified chaotic system. On the unstable equilibrium points, the ``equivalent passivity'' method is used to design the nonlinear controller. With the definition of fractional derivatives and integrals, the Lyapunov function is constructed by which it is proved that the controlled fractional order system is stable. With Laplace transform theory, the equivalent integer order state equation from the fractional order nonlinear system is obtained, and the system output can be solved. The simulation results validate the effectiveness of the theory. 参考文献 | 相关文章 | 计量指标

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Controlling chaos to unstable periodic orbits and equilibrium state solutions for the coupled dynamos system 吴淑花, 郝建红, 许海波 2010 (2):  20509-020509.  doi: 10.1088/1674-1056/19/2/020509 摘要 ( 1770 )   PDF(250KB) ( 790 )   In the case where the knowledge of goal states is not known, the controllers are constructed to stabilize unstable steady states for a coupled dynamos system. A delayed feedback control technique is used to suppress chaos to unstable focuses and unstable periodic orbits. To overcome the topological limitation that the saddle-type steady state cannot be stabilized, an adaptive control based on LaSalle's invariance principle is used to control chaos to unstable equilibrium (i.e. saddle point, focus, node, etc.). The control technique does not require any computer analysis of the system dynamics, and it operates without needing to know any explicit knowledge of the desired steady-state position. 参考文献 | 相关文章 | 计量指标

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Adaptive synchronisation of fractional-order chaotic systems 张若洵, 杨世平 2010 (2):  20510-020510.  doi: 10.1088/1674-1056/19/2/020510 摘要 ( 1664 )   PDF(252KB) ( 1011 )   A new stability theory of nonlinear dynamic systems is proposed, and a novel adaptive synchronisation method is presented for fractional-order chaotic and hyperchaotic systems based on the theory described in this paper. In comparison with previous methods, not only is the present control scheme simple but also it employs only one control strength, converges very fast, and it is also suitable for a large class of fractional-order chaotic and hyperchaotic systems. Moreover, this scheme is analytical and simple to implement in practice. Numerical and circuit simulations are used to validate and demonstrate the effectiveness of the method. 参考文献 | 相关文章 | 计量指标

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The existence of generalized synchronisation of three bidirectionally coupled chaotic systems 胡爱花, 徐振源, 过榴晓 2010 (2):  20511-020511.  doi: 10.1088/1674-1056/19/2/020511 摘要 ( 1556 )   PDF(377KB) ( 564 )   The existence of two types of generalized synchronisation is studied. The model considered here includes three bidirectionally coupled chaotic systems, and two of them denote the driving systems, while the rest stands for the response system. Under certain conditions, the existence of generalised synchronisation can be turned to a problem of compression fixed point in the family of Lipschitz functions. In addition, theoretical proofs are proposed to the exponential attractive property of generalised synchronisation manifold. Numerical simulations validate the theory. 参考文献 | 相关文章 | 计量指标

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Impulsive synchronization and control of directed transport in chaotic ratchets 过榴晓, 胡满峰, 徐振源 2010 (2):  20512-020512.  doi: 10.1088/1674-1056/19/2/020512 摘要 ( 1794 )   PDF(159KB) ( 715 )   The impulsive synchronization problem of two identical chaotic ratchets is investigated in this paper. We demonstrate that the impulsive method to control directed transport is applicable when there are multiple co-existing attractors in phase space transporting particles in different directions. Numerical simulations are carried out to illustrate the effectiveness of the proposed method. 参考文献 | 相关文章 | 计量指标

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A new car-following model yielding log-normal type headways distributions 李力, 王法, 姜锐, 胡坚明, 吉岩 2010 (2):  20513-020513.  doi: 10.1088/1674-1056/19/2/020513 摘要 ( 1879 )   PDF(1177KB) ( 1168 )   Modeling time headways between vehicles has attracted increasing interest in the traffic flow research field recently, because the corresponding statistics help to reveal the intrinsic interactions governing the vehicle dynamics. However, most previous micro-simulation models cannot yield the observed log-normal distributed headways. This paper designs a new car-following model inspired by the Galton board to reproduce the observed time-headway distributions as well as the complex traffic phenomena. The consistency between the empirical data and the simulation results indicates that this new car-following model provides a reasonable description of the car-following behaviours. 参考文献 | 相关文章 | 计量指标

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Spectral properties of Ce3+ doped yttrium lanthanum oxide transparent ceramics 杨秋红, 周洪旭, 陆神洲 2010 (2):  20701-020701.  doi: 10.1088/1674-1056/19/2/020701 摘要 ( 1874 )   PDF(1328KB) ( 1144 )   Ce3+-doped yttrium lanthanum oxide (Y0.9La0.1)2O3 transparent ceramics is fabricated with nanopowders and sintered in H2 atmosphere. The spectral properties of Ce:(Y0.9La0.1)2O3 transparent ceramics are investigated. There appear two characteristic absorption peaks of Ce3+ ions at 230~nm and 400~nm, separately. It is found that Ce3+ ions can efficiently produce emission at 384~nm from (Y0.9La0.1)2O3 transparent ceramic host, while the emission is completely quenched in Re2O3 (Re=Y, Lu, La) host materials. 参考文献 | 相关文章 | 计量指标

ATOMIC AND MOLECULAR PHYSICS

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Double ionization of helium interacting with elliptically polarized laser pulse by classical ensemble simulations 于伟威, 郭静, 刘学深 2010 (2):  23201-023201.  doi: 10.1088/1674-1056/19/2/023201 摘要 ( 1787 )   PDF(380KB) ( 729 )   This paper uses the classical ensemble method to study the double ionization of a 2-dimensional (2D) model helium atom interacting with an elliptically polarized laser pulse. The classical ensemble calculation demonstrates that the ratio of double to single ionization decreases with the increasing ellipticity of the driving field. The classical scenario shows that there are hardly any e--e recollisions with the circularly polarized laser pulse. The double ionization probability is studied for linearly and circularly polarized laser pulses. The classical numerical results are consistent with the semiclassical rescattering mechanism and in agreement with the experimental results and the quantum calculations qualitatively. 参考文献 | 相关文章 | 计量指标

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How to measure the internuclear vector from photoelectron angular distributions 任向河, 张敬涛, 王懿, 徐至展, J. T.Wang, D. S.Guo 2010 (2):  23202-023202.  doi: 10.1088/1674-1056/19/2/023202 摘要 ( 1755 )   PDF(146KB) ( 682 )   This paper uses a nonperturbative scattering theory to study photoelectron angular distributions of homonuclear diatomic molecules irradiated by circularly polarized laser fields. This study shows that the nonisotropic feature of photoelectron angular distributions is not due to the polarization of the laser field but the internuclear vector of the molecules. It suggests a method to measure the molecular orientation and the internuclear distance of molecules through the measurement of photoelectron angular distributions. 参考文献 | 相关文章 | 计量指标

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Valence orbital method of calculating harmonic emission from diatomic molecule 王玉铨, 陈德应, 夏元钦, 樊荣伟, 卢发铭 2010 (2):  23203-023203.  doi: 10.1088/1674-1056/19/2/023203 摘要 ( 1706 )   PDF(515KB) ( 689 )   We present a valence orbital method of calculating high-order harmonic generation from a diatomic molecule with arbitrary orientation by using a space rotation operator. We evaluate the effects of each valence orbital on harmonic emissions from N2 and O2 molecules in detail separately. The calculation results confirm the different properties of harmonic yields from N2 and O2 molecules which are well consistent with available experimental data. We observe that due to the orientation dependence of \sigma and \pi orbitals, the bonding orbital (\sigma _{2pz} )^2 of N2 determines the maximum of harmonic emission when the molecular axis of N2 is aligned parallel to the laser vector, and the magnitude of the high harmonic signal gradually weakens with the orientation angle of molecular axis increasing. But for O2 molecule the antibonding orbitals (\pi _{2py}^\ast )^1 and (\pi _{2pz}^\ast )^1 contribute to the maximum of harmonic yield when O2 is aligned at 45^{\circ} and bonding orbitals (\pi _{2py} )^2 and (\pi _{2pz} )^2 slightly influence the orientation angle of maximum of harmonic radiation not exactly at 45^{\circ}. 参考文献 | 相关文章 | 计量指标

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Production and guidance of pulsed atomic beams on chip 颜辉, 杨国卿, 石涛, 王谨, 詹明生 2010 (2):  23204-023204.  doi: 10.1088/1674-1056/19/2/023204 摘要 ( 1821 )   PDF(1194KB) ( 624 )   We demonstrated two experimental methods of producing and guiding pulsed atomic beams on chip. One is to trap atoms first in a U-type magneto-optical trap on the chip, then transfer them to the magnetic guide field and push them simultaneously by a continuous force from the power imbalance of the magneto-optical trap laser beams hence the pulsed cold atom beams are produced and move along the magnetic guide to the destination. The other is to trap atoms directly by a H-type magneto-optical trap, then push them to make them move along the magnetic guide field, thus high rate cold atom beams can be produced and guided on the chip. 参考文献 | 相关文章 | 计量指标

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Theoretical study of the influence of intense femtosecond laser field on the evolution of the wave packet and the population of NaRb molecule 马宁, 王美山, 杨传路, 马晓光, 王德华 2010 (2):  23301-023301.  doi: 10.1088/1674-1056/19/2/023301 摘要 ( 1744 )   PDF(219KB) ( 873 )   Employing the two-state model and the time-dependent wave packet method, we have investigated the influences of the parameters of the intense femtosecond laser field on the evolution of the wave packet, as well as the population of ground and double-minimum electronic states of the NaRb molecule. For the different laser wavelengths, the evolution of the wave packet of 6{ }^1\Sigma ^ + state with time and internuclear distance is different, and the different laser intensity brings different influences on the population of the electronic states of the NaRb molecule. One can control the evolutions of wave packet and the population in each state by varying the laser parameters appropriately, which will be a benefit for the light manipulation of atomic and molecular processes. 参考文献 | 相关文章 | 计量指标

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Shape of the geometrically active atomic states of carbon 熊庄, BacalisN. C. 2010 (2):  23601-023601.  doi: 10.1088/1674-1056/19/2/023601 摘要 ( 1758 )   PDF(127KB) ( 564 )   We have developed a computer code for {\em ab initio} the variational configuration interaction calculation of the electronic structure of atoms via variationally optimized Lagurre type orbitals, treating the orbital effective charges as variational parameters. Excited states of the same symmetry, in order to avoid the inherent restrictions of the standard method of Hylleraas--Unheim and MacDonald, are computed variationally by minimizing the recently developed minimization functionals for excited states. By computing, at the minimum, the one-electron density and the probability distribution of the two-electron angle, and the most probable two-electron angle, we investigate the atomic states of the carbon atom. We show that, without resorting to the (admittedly unproven) concept of hybridization, as an intrinsic property of the atomic wave function, the most probable value of the two-electron angle is around the known angles of carbon bonding, i.e. either 109^\circ or 120^\circ or 180^\circ, depending on each low-lying state of the bare carbon atom. 参考文献 | 相关文章 | 计量指标

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Collision statistics of clusters: from Poisson model to Poisson mixtures Sascha Vongehr, 唐少春, 孟祥康 2010 (2):  23602-023602.  doi: 10.1088/1674-1056/19/2/023602 摘要 ( 1716 )   PDF(398KB) ( 706 )   Clusters traverse a gas and collide with gas particles. The gas particles are absorbed, and the clusters become hosts. If the clusters are size-selected, the number of guests will be Poisson distributed. We review this by showcasing four laboratory procedures that all rely on the validity of the Poisson model. The effects of a statistical distribution of the clusters' sizes in a beam of clusters are discussed. We derive the average collision rates. Additionally, we present Poisson mixture models that also involve standard deviations. We derive the collision statistics for common size distributions of hosts and also for some generalizations thereof. The models can be applied to large noble gas clusters traversing doping gas. While outlining how to fit a generalized Poisson to the statistics, we still find even these Poisson models to be often insufficient. 参考文献 | 相关文章 | 计量指标

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Numerical study of electromagnetic scattering from one-dimensional nonlinear fractal sea surface 谢涛, 何超, William Perrie, 旷海兰, 邹光辉, 陈伟 2010 (2):  24101-024101.  doi: 10.1088/1674-1056/19/2/024101 摘要 ( 1738 )   PDF(529KB) ( 889 )   In recent years, linear fractal sea surface models have been developed for the sea surface in order to establish an electromagnetic backscattering model. Unfortunately, the sea surface is always nonlinear, particularly at high sea states. We present a nonlinear fractal sea surface model and derive an electromagnetic backscattering model. Using this model, we numerically calculate the normalized radar cross section (NRCS) of a nonlinear sea surface. Comparing the averaged NRCS between linear and nonlinear fractal models, we show that the NRCS of a linear fractal sea surface underestimates the NRCS of the real sea surface, especially for sea states with high fractal dimensions, and for dominant ocean surface gravity waves that are either very short or extremely long. 参考文献 | 相关文章 | 计量指标

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Simple measurement of nonlinear refraction by using a single pulse and beam 杨俊义, 宋瑛林, 金肖, 税敏, 李常伟 2010 (2):  24201-024201.  doi: 10.1088/1674-1056/19/2/024201 摘要 ( 1628 )   PDF(128KB) ( 843 )   A very simple technique, by which both the magnitude and the sign of nonlinear refraction can be determined through using only one single pulse and beam with a phase object, is presented. Using this technique, only the transmittance of an aperture in the far field is investigated. We study the nonlinear refraction of the carbon disulfide by using the presented technique with 21~ps pulses at a wavelength of 532~nm as a test. 参考文献 | 相关文章 | 计量指标

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Effects of optical axis direction on optical path difference and lateral displacement of Savart polariscope 张淳民, 任文艺, 穆廷魁 2010 (2):  24202-024202.  doi: 10.1088/1674-1056/19/2/024202 摘要 ( 1760 )   PDF(4722KB) ( 866 )   A simple method is applied to calculating the optical path difference (OPD) of a plane parallel uniaxial plate with an arbitrary optical axis direction. Then, the theoretical expressions of the OPD and lateral displacement (LD) of Savart polariscope under non-ideal conditions are obtained exactly. The variations of OPD and LD are simulated, and some important conclusions are obtained when the optical axis directions have an identical tolerance of \pm 1^{{\circ}}. An application example is given that the tolerances of optical axis directions are gained according to the spectral resolution tolerances of the stationary polarization interference imaging spectrometer (SPIIS). Several approximate formulae are obtained for explaining some conclusions above. The work provides a theoretical guidance for the optic design, crystal processing, installation and debugging, data analysis and spectral reconstruction of the SPIIS. 参考文献 | 相关文章 | 计量指标

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Consistency of the directionality of partially coherent beams inturbulence expressed in terms of the angular spread and the far-field average intensity 陈晓文, 季小玲 2010 (2):  24203-024203.  doi: 10.1088/1674-1056/19/2/024203 摘要 ( 1742 )   PDF(146KB) ( 589 )   Under the quadratic approximation of the Rytov's phase structure function, this paper derives the general closed-form expressions for the mean-squared width and the angular spread of partially coherent beams in turbulence. It finds that under a certain condition different types of partially coherent beams may have the same directionality as a fully coherent Gaussian beam in free space and also in atmospheric turbulence if the angular spread is chosen as the characteristic parameter of beam directionality. On the other hand, it shows that generally, the directionality of partially coherent beams expressed in terms of the angular spread is not consistent with that in terms of the normalized far-field average intensity distribution in free space, but the consistency can be achieved due to turbulence. 参考文献 | 相关文章 | 计量指标

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Measurements of femtosecond temporal speckle field of a random medium 刘文军, 高仁喜, 曲士良 2010 (2):  24204-024204.  doi: 10.1088/1674-1056/19/2/024204 摘要 ( 1772 )   PDF(920KB) ( 757 )   The femtosecond temporal speckle field of a random medium is studied theoretically and experimentally. Femtosecond temporal speckle arises from the interference of multiple randomly scattered electric fields. The femtosecond temporal speckle field is measured with a cross-correlation frequency-resolved optical gating method. The spatial average of the speckle field yields a smooth transmitted profile. The speckle field is a circular complex Gaussian variable because the scattered light beams from different trajectories have no correlation with each other. The field and the intensity profiles of individual speckle spots fluctuate randomly in time. The ensemble average of the temporal intensity profiles converges, thereby yielding the photon travel time probability distribution function. 参考文献 | 相关文章 | 计量指标

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Propagation of phase-locked truncated Gaussian beam array in turbulent atmosphere 周朴, 刘泽金, 许晓军, 储修祥 2010 (2):  24205-024205.  doi: 10.1088/1674-1056/19/2/024205 摘要 ( 1913 )   PDF(1270KB) ( 1089 )   Truncation manipulation is a simple but effective way to improve the intensity distribution properties of the phase-locked Gaussian beam array at the receiving plane. In this paper, the analytical expression for the propagation of the phase-locked truncated Gaussian beam array in a turbulent atmosphere is obtained based on the extended Huygens--Fresnel principle. Power in the diffraction-limited bucket is introduced as the beam quality factor to evaluate the influence of different truncation parameters. The dependence of optimal truncation ratio on the number of beamlets, the intensity of turbulence, propagation distance and laser wavelength is calculated and discussed. It is revealed that the optimal truncation ratio is larger for the laser array that contains more lasers, and the optimal truncation ratio will shift to a larger value with an increase in propagation distance and decrease in intensity of atmosphere turbulence. The optimal truncation ratio is independent of laser wavelength. 参考文献 | 相关文章 | 计量指标

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Polarization switching in a quasi-isotropic microchip Nd:YAG laser induced by optical feedback 任成, 谈宜东, 张书练 2010 (2):  24206-024206.  doi: 10.1088/1674-1056/19/2/024206 摘要 ( 1843 )   PDF(1054KB) ( 939 )   This paper demonstrates the influence of external optical feedback on the polarization state of longitudinal modes in quasi-isotropic microchip Nd:YAG lasers. Under optical feedback, the polarization state of longitudinal modes in quasi-isotropic lasers relies strongly on the intracavity anisotropy loss and mode competition. When the intracavity anisotropy loss is small, external optical feedback can cause polarization switching and strong mode competition between two orthogonal linearly polarized eigenstates of one laser longitudinal mode, which leads to the distortion of laser intensity modulation waveform. The polarization switching is independent of the initial external cavity length. By increasing the intracavity anisotropy loss, one polarization eigenstate can be suppressed and the laser works in single-polarization state. A theoretical analysis based on the compound cavity model is presented, which is in good agreement with the experimental results. The results offer guidance to the development of laser feedback interferometers. 参考文献 | 相关文章 | 计量指标

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Numerical and experimental study on coherent beam combining of fibre amplifiers using simulated annealing algorithm 周朴, 马阎星, 王小林, 马浩统, 许晓军, 刘泽金 2010 (2):  24207-024207.  doi: 10.1088/1674-1056/19/2/024207 摘要 ( 1700 )   PDF(943KB) ( 2848 )   We present the numerical and experimental study on the coherent beam combining of fibre amplifiers by means of simulated annealing (SA) algorithm. The feasibility is validated by the Monte Carlo simulation of correcting static phase distortion using SA algorithm. The performance of SA algorithm under time-varying phase noise is numerically studied by dynamic simulation. It is revealed that the influence of phase noise on the performance of SA algorithm gets stronger with an increase in amplitude or frequency of phase noise; and the laser array that contains more lasers will be more affected from phase noise. The performance of SA algorithm for coherent beam combining is also compared with a widely used stochastic optimization algorithm, i.e., the stochastic parallel gradient descent (SPGD) algorithm. In a proof-of-concept experiment we demonstrate the coherent beam combining of two 1083~nm fibre amplifiers with a total output power of 12~W and 93% combining efficiency. The contrast of the far-field coherently combined beam profiles is calculated to be as high as 95%. 参考文献 | 相关文章 | 计量指标

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Quantization of electromagnetic field in quadratic continuous nonlinear absorptive dielectrics 李维, 刘世炳, 于承新, 杨巍 2010 (2):  24208-024208.  doi: 10.1088/1674-1056/19/2/024208 摘要 ( 1703 )   PDF(101KB) ( 652 )   This paper reports that in the quantization of electromagnetic field in the dielectrics, the wave equation with regard to the Green function is analytically solved by a direct integral method for a quadratic continuous nonlinear absorptive dielectric medium. The quantization of the electromagnetic field in such a nonlinear absorptive dielectric is carried out for which the material dielectric function is assumed as a separable variable about the frequency and the space coordinate. The vacuum field fluctuations for different spatial continuous variations of dielectric function are numerically calculated, which shows that the present result is self-consistent. 参考文献 | 相关文章 | 计量指标

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Effect of mode-mode competition on atom－atom entanglement 吴琴, 方卯发, 蔡建武 2010 (2):  24209-024209.  doi: 10.1088/1674-1056/19/2/024209 摘要 ( 1720 )   PDF(341KB) ( 579 )   A system consisting of two atoms interacting with a two-mode vacuum is considered, where each atom is resonant with the two cavity modes through two different competing transitions. The effect of mode--mode competition on the atom--atom entanglement is investigated. We find that the entanglement between the two atoms can be induced by the mode--mode competition. For the initial atomic state |\varPsi(0)\rangle, whether the atoms are initially separated or entangled, a large or even maximal entanglement between them can be obtained periodically by introducing the mode--mode competition. For the initial atomic state |\varPhi(0)\rangle, the strong mode--mode competition can prevent the two atoms entangled initially from suffering entanglement sudden death; besides, it makes them in a more stable and longer-lived entanglement than in the non-competition case. 参考文献 | 相关文章 | 计量指标

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Partial entropy change and entanglement in the mixed state for a Jaynes－Cummings model with Kerr medium 张玉青, 谭磊, 朱中华, 熊祖周, 刘利伟 2010 (2):  24210-024210.  doi: 10.1088/1674-1056/19/2/024210 摘要 ( 1956 )   PDF(2108KB) ( 1125 )   By using the algebraic dynamical approach, an atom--field bipartite system in mixed state is employed to investigate the partial entropy change and the entanglement in a cavity filled with Kerr medium. The effects of different nonlinear intensities are studied. One can find that the Kerr nonlinearity can reduce the fluctuation amplitudes of the partial entropy changes and the entanglement of the two subsystems, and also influence their periodic evolution. Meanwhile, increasing the Kerr nonlinear strength can convert the anti-correlated behaviour of the partial entropy change to the positively correlated behaviour. Furthermore, the entanglement greatly depends on the temperature. When the temperature or the nonlinear intensity increases to a certain value, the entanglement can be suppressed greatly. 参考文献 | 相关文章 | 计量指标

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Incoherently coupled soliton pairs in nonlocal nonlinear media 卢克清, 李可昊, 赵卫, 张贻齐, 张美志, 张玉虹, 程光华, 张彦鹏 2010 (2):  24211-024211.  doi: 10.1088/1674-1056/19/2/024211 摘要 ( 1738 )   PDF(815KB) ( 673 )   We show that incoherently coupled soliton pairs can exist in nonlocal Kerr-type nonlinear media. Such solitons can propagate in bright--bright, dark--dark, and gray--gray configurations. When the nonlocal nonlinearity is absent, these bright--bright and dark--dark soliton pairs are those observed previously in local Kerr-type nonlinear media. Our analysis indicates that for a self-focusing nonlinearity the intensity full width half maximum (FWHM) of the bright--bright pair components increases with the degree of nonlocality of the nonlinear response, whereas for a self-defocusing nonlinearity the intensity FWHM of the dark--dark and gray--gray pair components decreases with the increase in the degree of nonlocality of the nonlinear response. The stability of these soliton pairs has been investigated numerically and it has been found that they are stable. 参考文献 | 相关文章 | 计量指标

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Holographic property of photopolymers with different amine photoinitiators 路海, 李若平, 孙彩霞, 肖勇, 唐道广, 黄明举 2010 (2):  24212-024212.  doi: 10.1088/1674-1056/19/2/024212 摘要 ( 1849 )   PDF(683KB) ( 899 )   Holographic parameters and photobleaching kinetics of the photopolymers with five different amine photoinitiators are studied. The maximum values of diffraction efficiency, photobleaching coefficient and quantum yield follow the sequence: Triethanolamine (TEA)> Diethanolamine (DEA)> Ethanolamine (EA)> Triethylamine (TETN)> Diethylamine (DETN). The holographic capabilities of photopolymer performances are determined by the number of functional groups in the amine molecular structure. There is an optimum proportion of the photoinitiator, the photosensitizer and the monomer in the test of holographic parameters with different amine concentrations. The maximum diffraction efficiency is 59.26\%, sensitivity is 1.72\times 10^{ - 3}~cm^{2}/mJ, and the maximum refractive modulation index is 4.64\times 10^{ - 4}. 参考文献 | 相关文章 | 计量指标

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Photonic band structure of three-dimensional colloidal crystals with field-induced lattice structure transformation 张利锋, 黄吉平 2010 (2):  24213-024213.  doi: 10.1088/1674-1056/19/2/024213 摘要 ( 1737 )   PDF(718KB) ( 768 )   By utilizing the electrorheological effect, three-dimensional colloidal crystals can be produced, whose lattice structure can be changed from the body-centered-tetragonal lattice to other lattices under the application of electric fields. This paper calculates photonic band structures of such crystals with lattice structure transformation, and demonstrates the existence of complete band gaps for some intermediate lattices. Thus, it becomes possible to use the electrorheological effect to achieve photonic crystals with desired photonic gap properties resulting from tunable structures. 参考文献 | 相关文章 | 计量指标

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Near-stoichiometric Ti:LiNbO3 strip waveguide with varied substrate refractive index in waveguide layer 张德龙, 吴嫦, 潘裕斌 2010 (2):  24214-024214.  doi: 10.1088/1674-1056/19/2/024214 摘要 ( 1712 )   PDF(524KB) ( 1385 )   We report the near-stoichiometric Ti:LiNbO3 strip waveguides fabricated by vapour transport equilibration (VTE) at 1060~^{\circ}C for 12 h and co-diffusion of 4--8~\mu m wide, 115-nm thick Ti-strips. Optical studies show that these waveguides are monomode at 1.5~\mu m and have losses of 1.3 and 1.1~dB/cm for the TM and TE modes, respectively. In the waveguide width/depth direction, the mode field follows a Gauss/Hermite--Gauss profile. A secondary ion mass spectrometry study reveals that the Ti profile follows a sum of two error functions along the width direction and a complementary error function in the depth direction. Micro-Raman analysis shows that the Li-composition in the depth direction also follows a complementary error function. The mean Li/Nb ratio in the waveguide layer is about 0.98. The inhomogeneous Li-composition profile results in a varied substrate index in the guiding layer, and the refractive index profile in the guiding layer is given. 参考文献 | 相关文章 | 计量指标

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Simulation of random mixed packing of different density particles 李元元, 夏伟, 周照耀, 何克晶, 钟文镇, 吴苑标 2010 (2):  24601-024601.  doi: 10.1088/1674-1056/19/2/024601 摘要 ( 1743 )   PDF(2369KB) ( 1597 )   This paper presents the effects of density difference on the three-dimensional (3D) distribution of random mixed packing. The random mixed packing dynamics of particles of two different densities are simulated. The initial state is homogeneous, but the final packing state is inhomogeneous. The segregation phenomenon (inhomogeneous distribution) is also observed. In the final state, the top layers are composed of mostly light particles. The several layers beneath the top contain more heavy particles than light particles. At the bottom, they also contain more heavy particles than light particles. Furthermore, at both the top and the bottom, particle clustering is observed. The current study also analyses the cause of this inhomogeneity in detail. The main cause of this phenomenon is the velocity difference after collision of these two types of particles induced by the density difference. The present study reveals that even if particles were perfectly mixed, the packing process would lead to the final inhomogeneous mixture. It suggests that special treatment may be required to get the true homogeneous packing. 参考文献 | 相关文章 | 计量指标

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Experimental observation of ionization and shock fronts in foam targets driven by thermal radiation 张继彦, 杨家敏, 江少恩, 李永升, 杨国洪, 丁耀南, 黄翼翔, 胡昕 2010 (2):  25201-025201.  doi: 10.1088/1674-1056/19/2/025201 摘要 ( 1760 )   PDF(757KB) ( 1217 )   The behaviours of ionization and shock propagation in radiatively heated material is crucial for the understanding of indirect drive inertial confinement fusion as well as some astrophysics phenomena. In this work, radiation field with a peak temperature of up to 155 eV was generated in a gold cavity heated by four laser beams on the SG-II laser system and was used to irradiate a plastic foam cylinder at one end. The radiatively ablated foam cylinder was then backlighted side-on by x-ray from a laser-irradiated Ti disk. By observing the transmission decrease due to the shock compression of the foam cylinder, the trajectories of shock front were measured, and from the onset of the intense thermal emission from the side of the cylinder, the propagations of the ionization front were also observed on the same shot. The experimental measurements were compared to predictions of the radiation hydrodynamics code Multi-1D and reasonable agreements were found. 参考文献 | 相关文章 | 计量指标

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Synthesis of high-TC ferromagnetic Mn-doped ZnO nanorods by thermal evaporation 郑凯泓, 刘政, 刘基, 胡丽君, 王东伟, 陈春英, 孙连峰 2010 (2):  26101-026101.  doi: 10.1088/1674-1056/19/2/026101 摘要 ( 1711 )   PDF(2596KB) ( 1007 )   This paper reports that a large amount of Mn-doped ZnO nanorods have been synthesized through thermal evaporation. The morphologies and properties are studied with x-ray diffraction, a scanning electron microscope, transmission electron microscope and Raman spectroscope. The results indicate that the manganese atoms occupy the zinc vacancies in the wurtzite lattice of ZnO without forming secondary phases. The exact manganese content has been studied by the x-ray fluorescence spectrum. Meanwhile, the magnetic moment versus temperature result proves that the as-prepared Mn-doped ZnO nanorods show ferromagnetic properties at temperatures as high as 400~K. These studies provide a good understanding of the origin of magnetic properties in diluted magnetic semiconductors. 参考文献 | 相关文章 | 计量指标

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Controlling the electronic structure of SnO2 nanowires by Mo-doping 罗志华, 唐东升, 海阔, 余芳, 陈亚奇, 何熊武, 彭跃华, 袁华军, 羊亿 2010 (2):  26102-026102.  doi: 10.1088/1674-1056/19/2/026102 摘要 ( 1831 )   PDF(1944KB) ( 1378 )   Mo-doped SnO2 (MTO) nanowires are synthesized by an in-situ doping chemical vapour deposition method. Raman scattering spectra indicate that the lattice symmetry of MTO nanowires lowers with the increase of Mo doping, which implies that Mo ions do enter into the lattice of SnO2 nanowire. Ultraviolet-visible diffuse reflectance spectra show that the band gap of MTO nanowires decreases with the increase of Mo concentration. The photoluminescence emission of SnO2 nanowires around 580~nm at room temperature can also be controlled accurately by Mo-doping, and it is extremely sensitive to Mo ions and will disappear when the atomic ratio reaches 0.46%. 参考文献 | 相关文章 | 计量指标

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Single crystal growth and characterizations of iron arsenide superconductor BaFe2-xNixAs2 (0.0 ≤ x ≤0.12) 李正才, 陆伟, 董晓莉, 周放, 赵忠贤 2010 (2):  26103-026103.  doi: 10.1088/1674-1056/19/2/026103 摘要 ( 1816 )   PDF(1261KB) ( 1117 )   A series of big single crystals of BaFeFe2-xNixAs2 have been prepared by the FeAs self-flux method, with nominal nickel doping x = 0--0.12. The dimensions of the cleaved crystals are over 10~mm along ab plane and ～ 2~mm in maximum along the c direction. The measurements of x-ray diffraction, electrical resistance and magnetic property are carried out on the crystals. For the undoped parent compound BaFe2As2, both resistance and magnetization data display an anomaly associated with spin density wave and/or structural phase transition, with the transition temperatures at ～ 138~K. For Ni-doped BaFe2-xNixAs2 crystals, the superconducting critical temperature Tc ranges from 4.3~K for x=0.06 sample to 20~K for the optimally doped x=0.10 crystal. 参考文献 | 相关文章 | 计量指标

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Friction phenomena in a two-dimensional Frenkel-Kontorova model 林麦麦, 段文山, 陈建敏 2010 (2):  26201-026201.  doi: 10.1088/1674-1056/19/2/026201 摘要 ( 1748 )   PDF(955KB) ( 657 )   By using the molecular dynamic simulation method with a fourth-order Runge--Kutta algorithm, a two-dimensional dc- and ac-driven Frenkel--Kontorova (FK) model with a square symmetry substrate potential for a square lattice layer has been investigated in this paper. For this system, the effects of many different parameters on the average velocity and the static friction force have been studied. It is found that not only the amplitude and frequency of ac-driven force, but also the direction of the external driving force and the misfit angle between two layers have some strong influences on the static friction force. It can be concluded that the superlubricity phenomenon appears easily with a larger ac amplitude and lower ac frequency for some special direction of the external force and misfit angle. 参考文献 | 相关文章 | 计量指标

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Wide-band underwater acoustic absorption based on locally resonant unit and interpenetrating network structure 姜恒, 王育人, 张密林, 胡燕萍, 蓝鼎, 吴群力, 逯还通 2010 (2):  26202-026202.  doi: 10.1088/1674-1056/19/2/026202 摘要 ( 1541 )   PDF(2824KB) ( 1779 )   The interpenetrating network structure provides an interesting avenue to novel materials. Locally resonant phononic crystal (LRPC) exhibits excellent sound attenuation performance based on the periodical arrangement of sound wave scatters. Combining the LRPC concept and interpenetrating network glassy structure, this paper has developed a new material which can achieve a wide band underwater strong acoustic absorption. Underwater absorption coefficients of different samples were measured by the pulse tube. Measurement results show that the new material possesses excellent underwater acoustic effects in a wide frequency range.Moreover, in order to investigate impacts of locally resonant units,some defects are introduced into the sample. The experimental result and the theoretical calculation both show that locally resonant units being connected to a network structure play an important role in achieving a wide band strong acoustic absorption. 参考文献 | 相关文章 | 计量指标

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First-principles study of lattice dynamics and thermodynamics ofosmium under pressure 刘波, 顾牡, 刘小林, 黄世明, 倪晨, 李泽仁, 王荣波 2010 (2):  26301-026301.  doi: 10.1088/1674-1056/19/2/026301 摘要 ( 1655 )   PDF(243KB) ( 858 )   We have performed the first-principles linear response calculations of the lattice dynamics, thermal equation of state and thermodynamical properties of hcp Os metal by using the plane-wave pseudopotential method. The thermodynamical properties are deduced from the calculated Helmholtz free energy by taking into account the electronic contribution and lattice vibrational contribution. The phonon frequencies at Gamma point are consistent with experimental values and the dispersion curves at various pressures have been determined. The calculated volume, bulk modulus and their pressure derivatives as a function of temperature are in excellent agreement with the experimental results. The calculated specific heat indicates that the electronic contribution is important not only at very low temperatures but also at high temperatures due to the electronic thermal excitation. The calculated Debye temperature at a very low temperature is in good agreement with experimental values and drops to a constant until 100~K. 参考文献 | 相关文章 | 计量指标

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Discrete breathers in a model with Morse potentials 吕彬彬, 邓艳平, 田强 2010 (2):  26302-026302.  doi: 10.1088/1674-1056/19/2/026302 摘要 ( 1784 )   PDF(1733KB) ( 629 )   Under harmonic approximation, this paper discusses the linear dispersion relation of the one-dimensional chain. The existence and evolution of discrete breathers in a general one-dimensional chain are analysed for two particular examples of soft (Morse) and hard (quartic) on-site potentials. The existence of discrete breathers in one-dimensional and two-dimensional Morse lattices is proved by using rotating wave approximation, local anharmonic approximation and a numerical method. The localization and amplitude of discrete breathers in the two-dimensional Morse lattice with on-site harmonic potentials correlate closely to the Morse parameter a and the on-site parameter к. 参考文献 | 相关文章 | 计量指标

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Atomic diffusion in annealed Cu/SiO2/Si (100) system prepared by magnetron sputtering 曹博, 贾艳辉, 李公平, 陈熙萌 2010 (2):  26601-026601.  doi: 10.1088/1674-1056/19/2/026601 摘要 ( 1677 )   PDF(397KB) ( 2649 )   Cu thin films are deposited on p-type Si (100) substrates by magnetron sputtering at room temperature. The interface reaction and atomic diffusion of Cu/SiO2/Si (100) systems are studied by x-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). Some significant results can be obtained. The onset temperature of interdiffusion for Cu/SiO2/Si(100) is 350~℃. With the annealing temperature increasing, the interdiffusion becomes more apparent. The calculated diffusion activation energy is about 0.91 eV. For the Cu/SiO2/Si (100) systems copper silicides are not formed below an annealing temperature of 350~℃. The formation of the copper silicides phase is observed when the annealing temperature arrives at 450~℃. 参考文献 | 相关文章 | 计量指标

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Surface tension effects on the behaviour of a rising bubble driven by buoyancy force 王含, 张振宇, 杨永明, 张慧生 2010 (2):  26801-026801.  doi: 10.1088/1674-1056/19/2/026801 摘要 ( 1988 )   PDF(2035KB) ( 2653 )   In the inviscid and incompressible fluid flow regime,surface tension effects on the behaviour of an initially spherical buoyancy-driven bubble rising in an infinite and initially stationary liquid are investigated numerically by a volume of fluid (VOF) method. The ratio of the gas density to the liquid density is 0.001, which is close to the case of an air bubble rising in water. It is found by numerical experiment that there exist four critical Weber numbers We1,~We2,~We3 and We4, which distinguish five different kinds of bubble behaviours. It is also found that when 1≤We2, the bubble will finally reach a steady shape, and in this case after it rises acceleratedly for a moment, it will rise with an almost constant speed, and the lower the Weber number is, the higher the speed is. When We >We2, the bubble will not reach a steady shape, and in this case it will not rise with a constant speed. The mechanism of the above phenomena has been analysed theoretically and numerically. 参考文献 | 相关文章 | 计量指标

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Analytical results for the cluster size distribution in controlled deposition processes 柯见洪, 陈效双, 林振权 2010 (2):  26802-026802.  doi: 10.1088/1674-1056/19/2/026802 摘要 ( 1801 )   PDF(110KB) ( 557 )   This paper proposes a controlled particle deposition model for cluster growth on the substrate surface and then presents exact results for the cluster (island) size distribution. In the system, at every time step a fixed number of particles are injected into the system and immediately deposited onto the substrate surface. It investigates the cluster size distribution by employing the generalized rate equation approach. The results exhibit that the evolution behaviour of the system depends crucially on the details of the adsorption rate kernel. The cluster size distribution can take the Poisson distribution or the conventional scaling form in some cases, while it is of a quite complex form in other cases. 参考文献 | 相关文章 | 计量指标

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Scanning tunneling microscopy study of surface reconstruction induced by N adsorption on Cu (100) surface 窦卫东, 张寒洁, 鲍世宁 2010 (2):  26803-026803.  doi: 10.1088/1674-1056/19/2/026803 摘要 ( 1968 )   PDF(3127KB) ( 630 )   The reconstructed structure of Cu (100) surface induced by atomic N adsorption is studied by using scanning tunneling microscopy (STM). The 2D structure of copper boundary between neighbouring N covered islands is found to be sensitive to the growth conditions, e.g. N+ bombardment time and annealing temperature. The copper boundary experiences a transition from nano-scale stripe to nano-particle when the substrate is continuously annealed at 623~K for a longer time. A well-defined copper-stripe network can be achieved by precisely controlling the growth conditions, which highlights the possibility of producing new templates for nanofabrication. 参考文献 | 相关文章 | 计量指标

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Structural and optical properties of Al1-xInxN epilayers on GaN template grown by metalorganic chemical vapor deposition 卢国军, 朱建军, 江德生, 王玉田, 赵德刚, 刘宗顺, 张书明, 杨辉 2010 (2):  26804-026804.  doi: 10.1088/1674-1056/19/2/026804 摘要 ( 1647 )   PDF(1455KB) ( 828 )   This paper reports that Al1-xInxN epilayers were grown on GaN template by metalorganic chemical vapor deposition with an In content of 7%--20%. X-ray diffraction results indicate that all these Al1-xInxN epilayers have a relatively low density of threading dislocations. Rutherford backscattering/channeling measurements provide the exact compositional information and show that a gradual variation in composition of the Al1-xInxN epilayer happens along the growth direction. The experimental results of optical reflection clearly show the bandgap energies of Al1-xInxN epilayers. A bowing parameter of 6.5~eV is obtained from the compositional dependence of the energy gap. The cathodoluminescence peak energy of the Al1-xInxN epilayer is much lower than its bandgap, indicating a relatively large Stokes shift in the Al1-xInxN sample. 参考文献 | 相关文章 | 计量指标

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Elastic constants and anisotropy of RuB2 under pressure 罗雰, 傅敏, 姬广富, 陈向荣 2010 (2):  27101-027101.  doi: 10.1088/1674-1056/19/2/027101 摘要 ( 1595 )   PDF(119KB) ( 919 )   The structural, elastic constants and anisotropy of RuB2 under pressure are investigated by first-principles calculations based on the plane wave pseudopotential density functional theory method within the local density approximation (LDA) as well as the generalized gradient approximation (GGA) for exchange and correlation. The results accord well with the available experimental and other theoretical data. The elastic constants, elastic anisotropy, and Debye temperature \varTheta as a function of pressure are presented. It is concluded that RuB2 is brittle in nature at low pressure, whereas it becomes ductile at higher pressures. An analysis for the calculated elastic constant has been made to reveal the mechanical stability of RuB2 up to 100~GPa. 参考文献 | 相关文章 | 计量指标

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Influencing range of vacancy defects in zigzag single-walled carbon nanotubes 罗煜聘, 田力耕, 李明宪, 李丰颖 2010 (2):  27102-027102.  doi: 10.1088/1674-1056/19/2/027102 摘要 ( 1770 )   PDF(1509KB) ( 722 )   The influencing range of a vacancy defect in a zigzag single-walled nanotube is characterized with both structural deformation and variation in bandstructure. This paper proposes a microscopic explanation to relate the structural deformation to the bandstructure variation. With an increasing defect density, the nanotubes become oblate and the energy gap between the deep localized gap state and the conducting band minimum state decreases. Theoretical results shed some light on the local energy gap engineering via vacancy density for future potential applications. 参考文献 | 相关文章 | 计量指标

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Current-voltage characteristics of lead zirconate titanate/nickel bilayered hollow cylindrical magnetoelectric composites 潘德安, 张深根, 田建军, 孙俊赛, AlexA.Volinsky, 乔利杰 2010 (2):  27201-027201.  doi: 10.1088/1674-1056/19/2/027201 摘要 ( 1733 )   PDF(1814KB) ( 885 )   Current--voltage measurements obtained from lead zirconate titanate/nickel bilayered hollow cylindrical magnetoelectric composite showed that a sinusoidal current applied to the copper coil wrapped around the hollow cylinder circumference induces voltage across the lead zirconate titanate layer thickness. The current--voltage coefficient and the maximum induced voltage in lead zirconate titanate at 1~kHz and resonance (60.1~kHz) frequencies increased linearly with the number of the coil turns and the applied current. The resonance frequency corresponds to the electromechanical resonance frequency. The current--voltage coefficient can be significantly improved by optimizing the magnetoelectric structure geometry and/or increasing the number of coil turns. Hollow cylindrical lead zirconate titanate/nickel structures can be potentially used as current sensors. 参考文献 | 相关文章 | 计量指标

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Mg doping reduced full width at half maximum of the near-band-edge emission in Mg doped ZnO films 龙雪, 李祥, 蔺彭婷, 程兴旺, 刘颖, 曹传宝 2010 (2):  27202-027202.  doi: 10.1088/1674-1056/19/2/027202 摘要 ( 1976 )   PDF(391KB) ( 1169 )   Sol--gol method was employed to synthesize Mg doped ZnO films on Si substrates. The annealing temperature-dependent structure and optical property of the produced samples were studied. An interesting result observed is that increasing Mg concentration in the studied samples induces the full width at half maximum (FWHM) of their near-band-edge (NBE) emission decrease and the defect related emission of the corresponding sample suppresses drastically. The possible mechanism of the observed result is discussed. 参考文献 | 相关文章 | 计量指标

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Surface plasmon polaritons of symmetric and asymmetric metamaterial slabs 张惠芳, 曹迪, 陶峰, 杨希华, 王燕, 阎晓娜, 白丽华 2010 (2):  27301-027301.  doi: 10.1088/1674-1056/19/2/027301 摘要 ( 1707 )   PDF(342KB) ( 984 )   The p and s-polarized surface plasmon polaritons (SPPs) of symmetric and asymmetric slabs formed arbitrarily by four types of conventional materials: dielectrics, negative dielectric permittivity materials, negative magnetic permeability materials, and left-handed materials are comprehensively analysed. The existence regions, dispersion relations, and excitation of SPPs in different frequency regions are investigated in detail. For symmetric slabs, the numbers and the frequency positions of surface polariton branches are quite different. At the same time, the pairs of the p or s-polarized SPP branches occur in the same frequency range. For asymmetric slabs, the SPP branches in mid- and high-frequency ranges are greatly different. In addition, the slab thickness has a great effect on SPPs of asymmetric and symmetric slabs. The attenuated total reflection spectra for the cases of p and s polarizations in these slabs are also calculated. 参考文献 | 相关文章 | 计量指标

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Tunneling current of the Coulomb-coupled quantum dots embedded in n-n junction 阎维贤, 赵亚平, 温玉兵, 李秀平, 许丽萍, 宫建平 2010 (2):  27302-027302.  doi: 10.1088/1674-1056/19/2/027302 摘要 ( 1666 )   PDF(1016KB) ( 998 )   Taking account of the electron--electron (hole) and electron--hole interactions, the tunneling processes of the main quantum dot (QD) Coulomb-coupled with a second quantum dot embedded in n--n junction have been investigated. The eighteen resonance mechanisms involved in the tunneling processes of the system have been identified. It is found that the tunneling current depends sensitively on the electron occupation number in the second quantum dot. When the electron occupation number in the second dot is tiny, both the tunneling current peaks and the occupation number plateaus in the main QD are determined by the intra-resonance mechanism. The increase of the electron occupation number in the second dot makes the inter-resonance mechanism participate in the transport processes. The competition between the inter and intra resonance mechanisms persists until the electron occupation number in the second dot reaches around unity, leading to the consequence that the inter-resonance mechanisms completely dominate the tunneling processes. 参考文献 | 相关文章 | 计量指标

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Deep level transient spectroscopy investigation of deep levels in CdS/CdTe thin film solar cells with Te:Cu back contact 王钊, 黎兵, 郑旭, 谢婧, 黄征, 刘才, 冯良桓, 郑家贵 2010 (2):  27303-027303.  doi: 10.1088/1674-1056/19/2/027303 摘要 ( 1653 )   PDF(156KB) ( 947 )   Deep levels in Cds/CdTe thin film solar cells have a potent influence on the electrical property of these devices. As an essential layer in the solar cell device structure, back contact is believed to induce some deep defects in the CdTe thin film. With the help of deep level transient spectroscopy (DLTS), we study the deep levels in CdS/CdTe thin film solar cells with Te:Cu back contact. One hole trap and one electron trap are observed. The hole trap H1, localized at Ev+0.128~eV, originates from the vacancy of Cd (VCd. The electron trap E1, found at Ec-0.178~eV, is considered to be correlated with the interstitial Cui= in CdTe. 参考文献 | 相关文章 | 计量指标

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Charged vortex structure in high-temperature superconductors 査国桥, 周世平 2010 (2):  27401-027401.  doi: 10.1088/1674-1056/19/2/027401 摘要 ( 1719 )   PDF(1060KB) ( 670 )   By using a model Hamiltonian with competing antiferromagnetic (AFM) spin density wave (SDW) and d-wave superconductivity orders, the effect of next-nearest-neighbour (nnn) hopping on spin and charge structures in high-temperature superconductors is investigated at finite temperatures. For an optimally doped sample, we find that the AFM order magnitude in the vortex core is firstly enhanced and then suppressed, accompanied with a ``positively → negatively → positively" charged vortex structure transition with increasing nnn hopping strength, which implies that the AFM order is unnecessarily bounded to an electron-rich vortex core. In addition, a charge ordering pattern with four negatively charged peaks localized in a small region is also found around the vortex core centre without net charge. Recent scanning-tunneling-microscopy experimental observations of the checkerboard structure are hopefully understood. 参考文献 | 相关文章 | 计量指标

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Enhancement of ferromagnetism in polycrystalline Si0.965Mn0.035:B films by boron plasma treatment 刘兴翀, 黄小平, 张凤鸣 2010 (2):  27501-027501.  doi: 10.1088/1674-1056/19/2/027501 摘要 ( 1745 )   PDF(434KB) ( 641 )   This paper reports that the polycrystalline Si0.965Mn0.035:B films have been prepared by cosputtering deposition followed by rapid thermal annealing for crystallization.The polycrystalline thin films consist of two ferromagnetic phases.The low temperature ferromagnetic phase with Curie temperature (Tc) of about 50~K is due to the Mn4Si7 phase in the films, while the high temperature one (Tc～ 250~K) is resulted from the incorporation of Mn into silicon. The films are treated by boron plasma excited with the approach of microwave plasma enhanced chemical vapor deposition for 40 minutes. After plasma treatment, it is observed that no extra magnetic phases or magnetic complexes exist in the films, while both the high temperature saturation magnetization and the hole concentration in the films increase. The obvious correlation between the magnetic properties and the electrical properties of the polycrystalline Si0.965Mn0.035:B films suggests that the hole carriers play an important role in Si:Mn diluted magnetic semiconductors. 参考文献 | 相关文章 | 计量指标

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Effect of annealing atmosphere on ferromagnetism in Mn doped ZnO films 刘兴翀, 陆智海, 张凤鸣 2010 (2):  27502-027502.  doi: 10.1088/1674-1056/19/2/027502 摘要 ( 1964 )   PDF(122KB) ( 848 )   This paper reports that Zn0.97Mn0.03O thin films have been prepared by radio-frequency sputtering technology followed by rapid thermal processing in nitrogen and oxygen ambient respectively. Magnetic property investigation indicates that the films are ferromagnetic and that the Curie temperature (Tc) is over room temperature. It is observed that the saturation magnetization of the films increases after annealing in nitrogen ambience but decreases after annealing in oxygen. Room temperature photoluminescence spectra indicate that the amount of defects in the films differs after annealing in the different ambiences. This suggests that the ferromagnetism in Zn0.97Mn0.03O films is strongly related to the defects in the films. 参考文献 | 相关文章 | 计量指标

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Magnetoelastic instability in the XXZ rings with next-nearest neighbour coupling 李鹏飞, 陈中华 2010 (2):  27503-027503.  doi: 10.1088/1674-1056/19/2/027503 摘要 ( 1766 )   PDF(124KB) ( 543 )   This paper numerically investigates the magnetoelastic instability in the S = 1/2 {XXZ} rings containing finite spins N with antiferromagnetic nearest-neighbour ({NN}) and next-nearest neighbour ({NNN}) coupling. It finds that, as the {NN} anisotropy Δ1 equals the {NNN} anisotropy \varDelta2, there exists a critical {NNN} coupling strength J2c(≈0.5), at which the systems always locate in dimerized phase for arbitrary large spring constant. As Δ1 \ne Δ2, the values of J2^{\rm c} are dependent on N and the difference of (Δ1-\varDelta2). 参考文献 | 相关文章 | 计量指标

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Doping effects of Nb5+ on red long afterglow phosphor CaTiO3:Pr3+ 蒋自强, 王育华, 龚宇 2010 (2):  27801-027801.  doi: 10.1088/1674-1056/19/2/027801 摘要 ( 1523 )   PDF(576KB) ( 1391 )   A series of Nb5+ codoped red long afterglow phosphors CaTi1-xNbxO3:Pr 0.0023+ (0 ≤ x ≤ 0.05) is prepared by a solid state reaction method. Their photoluminescence, phosphorescence and thermoluminescence are investigated. The results indicate that codoping Nb5+ can improve the photoluminescence and phosphorescence property of CaTiO3:Pr3+ significantly. When 3-mol% Nb5+ is codoped, the emission intensity of CaTiO3:Pr3+ is enhanced twice, while the afterglow time is extended from 10 min to about 40 min. Thermoluminescence results reveal that the trapping level of CaTiO3:Pr3+ is reduced from 0.82~eV to 0.62~eV by codoping Nb5+. The effect of Nb5+ doping on enhancing the photoluminescence intensity and afterglow time of CaTiO3:Pr3+ is discussed. 参考文献 | 相关文章 | 计量指标

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Cylindrical-confinement-induced phase behaviours of diblock copolymer melts 刘美娇, 李士本, 章林溪, 王向红 2010 (2):  28101-028101.  doi: 10.1088/1674-1056/19/2/028101 摘要 ( 1285 )   PDF(1801KB) ( 543 )   The phase behaviours of diblock copolymers under cylindrical confinement are studied in two-dimensional space by using the self-consistent field theory. Several phase parameters are adjusted to investigate the cylindrical-confinement-induced phase behaviours of diblock copolymers. A series of lamella-cylinder mixture phases, such as the mixture of broken-lamellae and cylinders and the mixture of square-lamellae and cylinders, are observed by varying the phase parameters, in which the behaviours of these mixture phases are discussed in the corresponding phase diagrams. Furthermore, the free energies of these mixture phases are investigated to illustrate their evolution processes. Our results are compared with the available observations from the experiments and simulations respectively, and they are in good agreement and provide an insight into the phase behaviours under cylindrical confinement. 参考文献 | 相关文章 | 计量指标

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Dielectric properties of electrospun titanium compound/polymer composite nanofibres 李蒙蒙, 龙云泽, 谭金山, 尹红星, 隋万美, 张志明 2010 (2):  28102-028102.  doi: 10.1088/1674-1056/19/2/028102 摘要 ( 1632 )   PDF(5196KB) ( 999 )   Poly(vinylpyrrolidone)/tetrabutyl titanate (PVP/ [CH3(CH2)3O]4Ti) composite nanofibres are prepared by electrospinning. After calcining parts of composite nanofibres in air at 700 ~℃, petal-like TiO2 nanostructures are obtained. The characterizations of composite nanofibres and TiO2 nanostructures are carried out by a scanning electron microscope, an x-ray diffractometer, and an infrared spectrometer. Electrospun nanofibres are pressed into pellets under different pressures in order to explore their dielectric properties. It is found that the dielectric constants decrease with frequency increasing. The dielectric constant of the composite nanofibre pellet increases whereas its dielectric loss tangent decreases due to the doped titanium ions compared with those of pure PVP nanofibre pellets. In addition, it is observed that the dielectric constant of the composite nanofibre pellet decreases with the increase of the pressure applied in pelletization. 参考文献 | 相关文章 | 计量指标

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Turbulence-induced changes in degree of polarization, degree of coherence and spectrum of partially coherent electromagnetic beams 季小玲, 蒲政才 2010 (2):  29201-029201.  doi: 10.1088/1674-1056/19/2/029201 摘要 ( 1943 )   PDF(1411KB) ( 787 )   Based on a recently formulated unified theory of coherence and polarization, a method is described to study turbulence-induced changes in the polarization, the coherence and the spectrum of partially coherent electromagnetic beams on propagation. The electromagnetic Gaussian Schell-model beam is taken as a typical example of partially coherent electromagnetic beams, and the closed-form expressions for the degree of polarization, the degree of coherence and the spectrum of electromagnetic Gaussian Schell-model beams propagating through atmospheric turbulence are derived in the quadratic approximation of Rytov's phase structure function. Some interesting results are obtained, which are illustrated by numerical examples and are explained in physics. 参考文献 | 相关文章 | 计量指标