Table of contents

20 August 2007, Volume 16 Issue 8 Previous issue    Next issue

GENERAL

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Quantum secure direct communication with quantum encryption based on pure entangled states Li Xi-Han(李熙涵), Li Chun-Yan(李春燕), Deng Fu-Guo(邓富国), Zhou Ping(周萍), Liang Yu-Jie(梁玉洁), and Zhou Hong-Yu(周宏余) Chinese Physics, 2007, 16 (8):  2149-2153.  DOI: 10.1088/1009-1963/16/8/001 Abstract ( 2183 )   PDF (113KB) ( 1259 )   This paper presents a scheme for quantum secure direct communication with quantum encryption. The two authorized users use repeatedly a sequence of the pure entangled pairs (quantum key) shared for encrypting and decrypting the secret message carried by the travelling photons directly. For checking eavesdropping, the two parties perform the single-photon measurements on some decoy particles before each round. This scheme has the advantage that the pure entangled quantum signal source is feasible at present and any eavesdropper cannot steal the message.

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Unified symmetry of Vacco dynamical systems Li Yuan-Cheng(李元成), Jing Hong-Xing(荆宏星), Xia Li-Li(夏丽莉), Wang Jing(王静), and Hou Qi-Bao(后其宝) Chinese Physics, 2007, 16 (8):  2154-2158.  DOI: 10.1088/1009-1963/16/8/002 Abstract ( 1318 )   PDF (101KB) ( 611 )   Based on the total time derivative along the trajectory of the time, we study the unified symmetry of Vacco dynamical systems. The definition and the criterion of the unified symmetry for the system are given. Three kinds of conserved quantities, i.e. the Noether conserved quantity, the generalized Hojman conserved quantity and the Mei conserved quantity, are deduced from the unified symmetry. An example is presented to illustrate the results.

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Discrete doubly periodic and solitary wave solutions for the semi-discrete coupled mKdV equations Wu Xiao-Fei(吴晓飞), Zhu Jia-Min(朱加民), and Ma Zheng-Yi(马正义) Chinese Physics, 2007, 16 (8):  2159-2166.  DOI: 10.1088/1009-1963/16/8/003 Abstract ( 1617 )   PDF (127KB) ( 681 )   In this paper, the improved Jacobian elliptic function expansion approach is extended and applied to constructing discrete solutions of the semi-discrete coupled modified Korteweg de Vries (mKdV) equations with the aid of the symbolic computation system Maple. Some new discrete Jacobian doubly periodic solutions are obtained. When the modulus $m \rightarrow 1$, these doubly periodic solutions degenerate into the corresponding solitary wave solutions, including kink-type, bell-type and other types of excitations.

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Study on an extended Boussinesq equation Chen Chun-Li(陈春丽), Zhang Jin E(张近), and Li Yi-Shen(李翊神) Chinese Physics, 2007, 16 (8):  2167-2179.  DOI: 10.1088/1009-1963/16/8/004 Abstract ( 1499 )   PDF (161KB) ( 576 )   An extended Boussinesq equation that models weakly nonlinear and weakly dispersive waves on a uniform layer of water is studied in this paper. The results show that the equation is not Painlevé-integrable in general. Some particular exact travelling wave solutions are obtained by using a function expansion method. An approximate solitary wave solution with physical significance is obtained by using a perturbation method. We find that the extended Boussinesq equation with a depth parameter of $1/\sqrt 2$ is able to match the Laitone's (1960) second order solitary wave solution of the Euler equations.

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The acoustoelastic effect on Rayleigh waves in elastic--plastic deformed layered rocks Liu Jin-Xia(刘金霞), Cui Zhi-Wen(崔志文), and Wang Ke-Xie(王克协) Chinese Physics, 2007, 16 (8):  2180-2187.  DOI: 10.1088/1009-1963/16/8/005 Abstract ( 1368 )   PDF (265KB) ( 577 )   On the basis of the acoustoelastic theory for elastic--plastic materials, the influence of statically deformed states including both the elastic and plastic deformations induced by applied uniaxial stresses on the Rayleigh wave in layered rocks is investigated by using a transfer matrix method. The acoustoelastic effects of elastic--plastic strains in rocks caused by static deformations, are discussed in detail. The Rayleigh-type and Sezawa modes exhibit similar trends in acoustoelastic effect: the acoustoelastic effect increasing rapidly with the frequency-thickness product and the phase velocity change approaching a constant value for thick layer and high frequency limit. Elastic--plastic deformations in the Castlegate layered rock obviously modify the phase velocity of the Rayleigh wave and the cutoff points for the Sezawa modes. The investigation may be useful for seismic exploration, geotechnical engineering and ultrasonic detection.

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Entanglement-enhanced classical communication through an amplitude-damping channel Hou Li-Zhen(侯丽珍) and Fang Mao-Fa(方卯发) Chinese Physics, 2007, 16 (8):  2188-2193.  DOI: 10.1088/1009-1963/16/8/006 Abstract ( 1409 )   PDF (110KB) ( 560 )   We consider the problem of trying to send a single classical bit through an amplitude-damping channel when two transmissions through the channel are available as a resource. It is demonstrated that two entangled transmissions can enhance the receiver's capability of making a correct inference under certain conditions compared with two product-state transmissions.

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A controlled quantum teleportation scheme of an N-particle unknown state via three-particle W1 states Xiu Xiao-Ming(修晓明), Dong Li(董莉), Gao Ya-Jun(高亚军), and Chi Feng(迟锋) Chinese Physics, 2007, 16 (8):  2194-2199.  DOI: 10.1088/1009-1963/16/8/007 Abstract ( 1427 )   PDF (235KB) ( 496 )   In this paper a controlled quantum teleportation scheme of an N-particle unknown state is proposed when N groups of three-particle W1 states are utilized as quantum channels. The quantum information of N-particle unknown state is transmitted from the sender to the recipient under the control of all supervisors. It can be realized with a certain probability. After the sender makes Bell-state measurements and the supervisors perform the computational basis measurements, the recipient will introduce auxiliary particles and carry out unitary transformations depending on classical information from the sender and the supervisors. Finally, the computational basis measurement will be performed by the recipient to confirm whether the teleportation succeeds or not. The successful completion of the scheme relies on all supervisors' cooperation. In addition, the fidelity and security of the scheme are discussed.

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Application of three-mode Einstein-Podolsky-Rosen entangled state with continuous variables to teleportation Hu Li-Yun(胡利云) and Lu Hai-Liang(陆海亮) Chinese Physics, 2007, 16 (8):  2200-2210.  DOI: 10.1088/1009-1963/16/8/008 Abstract ( 1357 )   PDF (158KB) ( 687 )   We consider how to teleport two- and three-mode Einstein--Podolsky--Rosen entangled states ($\left\vert \eta\right\rangle $ and $\left\vert p_{t},\chi_{2},\chi_{3}\right\rangle $) via a $\left\vert p_{t},\chi_{2},\chi_{3}\right\rangle $quantum channel for continuous variables. Using the complete and orthogonal representation of the entangled states, we can not only find the a complete basis set for the joint measurement but also propose the specific scheme of teleportation. Our calculation can be greatly simplified by using their Schmidt decompositions.

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A simple scheme for generating multi-atom GHZ state via cavity QED Wang Jun(王俊), Yu Long-Bao(余龙宝), and Ye Liu(叶柳) Chinese Physics, 2007, 16 (8):  2211-2214.  DOI: 10.1088/1009-1963/16/8/009 Abstract ( 1628 )   PDF (95KB) ( 621 )   This paper proposes a simple scheme for generating a three-atom GHZ state via cavity quantum electrodynamics (QED). The task can be achieved through the interaction between two EPR states, which can be prepared easily with current technology. In this scheme, the cavity field is only virtually excited during the interaction process, and no quantum information transfer between the atoms and the cavity is required. Thus it greatly prolongs the efficient decoherent time. Moreover, this scheme is also applicable for generating an N-atom GHZ state.

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An efficient quantum key distribution protocol with orthogonal product states Yang Yu-Guang(杨宇光) and Wen Qiao-Yan(温巧燕) Chinese Physics, 2007, 16 (8):  2215-2218.  DOI: 10.1088/1009-1963/16/8/010 Abstract ( 1647 )   PDF (99KB) ( 594 )   An efficient quantum key distribution (QKD) protocol with orthogonal product states in the 3 $\otimes$ 3 Hilbert space is presented. The sender, Alice, disorders the orthogonal product state sequence and sends it to Bob. After Alice has published the matching information of the particle sequence, Bob recovers the correct correspondences and makes an orthogonal measurement on the orthogonal product states to obtain the information sent by Alice. Finally, security analysis is also made.

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Cluster states prepared by using hot trapped ions Yang Rong-Can(杨榕灿), Li Hong-Cai(李洪才), Lin Xiu(林秀), and Huang Zhi-Ping(黄志平) Chinese Physics, 2007, 16 (8):  2219-2223.  DOI: 10.1088/1009-1963/16/8/011 Abstract ( 1450 )   PDF (112KB) ( 616 )   We propose a scheme for the preparation of one-dimensional and two-dimensional cluster states by using hot trapped ions. The scheme is based on the interaction between two ions and bichromatic radiation. The vibrational mode in our protocol is only virtually excited so that the system is insensitive to the thermal field. In addition, we only use two levels of ions as qubits and the successful probability may achieve 100%.

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Feasible schemes for preparing all five-photon graph states Zhang Jin(张瑾), Zhou Xiao-Qi(周晓祺), and Yang Tao(杨涛) Chinese Physics, 2007, 16 (8):  2224-2228.  DOI: 10.1088/1009-1963/16/8/012 Abstract ( 1541 )   PDF (417KB) ( 600 )   We propose feasible experimental schemes for preparing all five-photon graph states. Our schemes require only linear optical elements, photon detectors and post-selection, which are available in current experiment so that these schemes are within the reach of the current technology.

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Entanglement in an anisotropic spin-1 Heisenberg chain Zhu Yan(朱燕), Zhu Shi-Qun(朱士群), and Hao Xiang (郝翔) Chinese Physics, 2007, 16 (8):  2229-2236.  DOI: 10.1088/1009-1963/16/8/013 Abstract ( 1609 )   PDF (1394KB) ( 720 )   The entanglement in an anisotropic spin-1 Heisenberg chain with a uniform magnetic field is investigated. The ground-state entanglement will undergo two different kinds of transitions when the anisotropy $\varDelta$ and the amplitude of the magnetic field B are varied. The thermal entanglement of the nearest neighbour always declines when B increases no matter what the value of the anisotropy is. It is very interesting to note that the entanglement of the next-nearest neighbour can increase to a maximum at a certain magnetic field. Regardless of the boundary condition, the nearest-neighbour entanglement always decreases and approaches to a constant value when the size of the system is very large. The constant value of open boundary condition is much larger than that of periodic boundary condition.

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The separability of two-mode Gaussian state under amplification and symmetric damping Chen Xiao-Yu (陈小余), Jiang Li-Zhen (蒋丽珍), and Wu Liang-Neng (邬良能) Chinese Physics, 2007, 16 (8):  2237-2243.  DOI: 10.1088/1009-1963/16/8/014 Abstract ( 1507 )   PDF (442KB) ( 411 )   The performances of a two-mode Gaussian state under parametric amplification, symmetric amplitude damping and thermal noise are studied. The time-dependent complex correlation matrix of the state in evolution is given. The separability of the final two-mode Gaussian state is examined under symmetric amplification and asymmetric amplification separately.

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Generation and control of chaos in a Bose--Einstein condensate Xu Jun(徐军), Hai Wen-Hua(海文华), and Li Hui(李辉) Chinese Physics, 2007, 16 (8):  2244-2253.  DOI: 10.1088/1009-1963/16/8/015 Abstract ( 1323 )   PDF (1038KB) ( 905 )   For a Bose--Einstein condensate (BEC) confined in a double lattice consisting of two weak laser standing waves we find the Melnikov chaotic solution and chaotic region of parameter space by using the direct perturbation method. In the chaotic region, spatial evolutions of the chaotic solution and the corresponding distribution of particle number density are bounded but unpredictable between their superior and inferior limits. It is illustrated that when the relation $k_{1}\approx k_{2}$  between the two laser wave vectors is kept, the adjustment from $k_{2}<k_{1}$ to $k_{2}\ge k_{1}$ can transform the chaotic region into regular one or the other way round. This suggests a feasible scheme for generating and controlling chaos, which could lead to an experimental observation in the near future.

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Application of periodic orbit theory in chaos-based security analysis Long Min(龙敏) and Qiu Shui-Sheng(丘水生) Chinese Physics, 2007, 16 (8):  2254-2258.  DOI: 10.1088/1009-1963/16/8/016 Abstract ( 1110 )   PDF (1341KB) ( 838 )   Chaos-based encryption schemes have been studied extensively, while the security analysis methods for them are still problems to be resolved. Based on the periodic orbit theory, this paper proposes a novel security analysis method. The periodic orbits theory indicates that the fundamental frequency of the spiraling orbits is the natural frequency of associated linearized system, which is decided by the parameters of the chaotic system. Thus, it is possible to recover the plaintext of secure communication systems based on chaotic shift keying by getting the average time on the spiraling orbits. Analysis and simulation results show that the security analysis method can break chaos shift keying secure communication systems, which use the parameters as keys.

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Controlling a time-delay system using multiple delay feedback control Qi Wei(祁伟), Zhang Yan(张岩), and Wang Ying-Hai(汪映海) Chinese Physics, 2007, 16 (8):  2259-2263.  DOI: 10.1088/1009-1963/16/8/017 Abstract ( 1317 )   PDF (1156KB) ( 1105 )   In this paper multiple delay feedback control (MDFC) with different and independent delay times is shown to be an efficient method for stabilizing fixed points in finite-dimensional dynamical systems. Whether MDFC can be applied to infinite-dimensional systems has been an open question. In this paper we find that for infinite-dimensional systems modelled by delay differential equations, MDFC works well for stabilizing (unstable) steady states in long-, moderate- and short-time delay regions, in particular for the hyperchaotic case.

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Continuous feedback control of KdV Burgers system Zhang Li-Ping(张丽萍) and Xue Ju-Kui(薛具奎) Chinese Physics, 2007, 16 (8):  2264-2271.  DOI: 10.1088/1009-1963/16/8/018 Abstract ( 1301 )   PDF (1467KB) ( 727 )   The chaos in the KdV Burgers equation describing a ferroelectric system has been successfully controlled by using a continuous feedback control. This system has two stationary points. In order to know whether the chaos is controlled or not, the instability of control equation has been analysed numerically. The numerical analysis shows that the chaos can be converted to one point by using one control signal, however, it can converted to the other point by using three control signals. The chaotic motion is converted to two desired stationary points and periodic orbits in numerical experiment separately.

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Impulsive control of chaotic systems with exogenous perturbations Liu Xing-Wen(刘兴文), Huang Qin-Zhen(黄勤珍), Gao Xin(高心), and Shao Shi-Quan(邵仕泉) Chinese Physics, 2007, 16 (8):  2272-2277.  DOI: 10.1088/1009-1963/16/8/019 Abstract ( 1378 )   PDF (330KB) ( 777 )   The impulsive control of chaotic systems, which are subjected to unbounded exogenous perturbations, is considered. By using the theory of impulsive differential equation together with the fuzzy control technique, the authors propose an impulsive robust chaos controlling criterion expressed as linear matrix inequalities (LMIs). Based on the proposed control criterion, the procedure for designing impulsive controllers of common (perturbed) chaotic systems is provided. Finally, a numerical example is given to demonstrate the obtained theoretical result.

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Analysis and implementation of a new hyperchaotic system Wang Guang-Yi(王光义),Liu Jing-Biao(刘敬彪), and Zheng Xin(郑欣) Chinese Physics, 2007, 16 (8):  2278-2284.  DOI: 10.1088/1009-1963/16/8/020 Abstract ( 1546 )   PDF (3031KB) ( 1124 )   Based on a modified Lorenz system, a relatively simple four-dimensional continuous autonomous hyperchaotic system is proposed by introducing a state feedback controller. The system consists of four coupled first-order ordinary differential equations with three nonlinear cross-product terms. Some dynamical properties of this hyperchaotic system, including equlibria, stability, Lyapunov exponent spectrum and bifurcation, are analysed in detail. Moreover, an electronic circuit diagram is designed for demonstrating the existence of the hyperchaos, and verifying computer simulation results.

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Nonchaotic random behaviour in the second order autonomous system Xu Yun(徐云), Zhang Jian-Xia(张建峡), Xu Xia(徐霞), and Zhou Hong(周红) Chinese Physics, 2007, 16 (8):  2285-2290.  DOI: 10.1088/1009-1963/16/8/021 Abstract ( 1279 )   PDF (615KB) ( 614 )   Evidence is presented for the nonchaotic random behaviour in a second-order autonomous deterministic system. This behaviour is different from chaos and strange nonchaotic attractor. The nonchaotic random behaviour is very sensitive to the initial conditions. Slight difference of the initial conditions will generate wholly different phase trajectories. This random behaviour has a transient random nature and is very similar to the coin-throwing case in the classical theory of probability. The existence of the nonchaotic random behaviour not only can be derived from the theoretical analysis, but also is proved by the results of the simulated experiments in this paper.

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Noise-induced striped trajectories of Rossler systems Huang Zhi-Hua(黄志华) and Dong Ya-Li(董亚丽) Chinese Physics, 2007, 16 (8):  2291-2295.  DOI: 10.1088/1009-1963/16/8/022 Abstract ( 1245 )   PDF (1477KB) ( 468 )   In this paper, the generation of striped trajectories in phase space by noise-injection is considered. With suitable amplitudes of noise, the steady-state system orbits appear in rectangular striped shape. The relationship between the shape (including the range and the number of stripes) and some parameters is discussed. The result shows that noise can also generate the striped shape effectively and simply, which is similar to the newly-discovered striped pattern generated by controlled Rossler systems.

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Density functional theory for molecular orientation of hard rod fluids in hard slits Cao Da-Peng(曹达鹏),Cheng Li-Sheng(程礼盛), and Wang Wen-Chuan (汪文川) Chinese Physics, 2007, 16 (8):  2296-2303.  DOI: 10.1088/1009-1963/16/8/023 Abstract ( 1392 )   PDF (631KB) ( 686 )   A density functional theory (DFT) is used to investigate molecular orientation of hard rod fluids in a hard slit. The DFT approach combines a modified fundamental measure theory (MFMT) for excluded-volume effect with the first order thermodynamics perturbation theory for chain connectivity. In the DFT approach, the intra-molecular bonding orientation function is introduced. We consider the effects of molecular length (i.e. aspect ratio of rod) and packing fraction on the orientations of hard rod fluids and flexible chains. For the flexible chains, the chain length has no significant effect while the packing fraction shows slight effect on the molecular orientation distribution. In contrast, for the hard rod fluids, the chain length determines the molecular orientation distribution, while the packing fraction has no significant effect on the molecular orientation distribution. By making a comparison between molecular orientations of the flexible chain and the hard rod fluid, we find that the molecular stiffness distinctly affects the molecular orientation. In addition, partitioning coefficient indicates that the longer rodlike molecule is more difficult to enter the confined phase, especially at low bulk packing fractions.

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Detecting and describing the modular structures of weighted networks Li Ke-Ping(李克平) and Gao Zi-You(高自友) Chinese Physics, 2007, 16 (8):  2304-2309.  DOI: 10.1088/1009-1963/16/8/024 Abstract ( 1384 )   PDF (567KB) ( 603 )   In the functional properties of complex networks, modules play a central role. In this paper, we propose a new method to detect and describe the modular structures of weighted networks. In order to test the proposed method, as an example, we use our method to analyse the structural properties of the Chinese railway network. Here, the stations are regarded as the nodes and the track sections are regarded as the links. Rigorous analysis of the existing data shows that using the proposed algorithm, the nodes of network can be classified naturally. Moreover, there are several core nodes in each module. Remarkably, we introduce the correlation function $G_{rs}$, and use it to distinguish the different modules in weighted networks.

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Electronic structure and defect states of transition films from amorphous to microcrystalline silicon studied by surface photovoltage spectroscopy Yu Wei(于威), Wang Chun-Sheng(王春生), Lu Wan-Bing(路万兵), He Jie(何杰), Han Xiao-Xia(韩晓霞), and Fu Guang-Sheng(傅广生) Chinese Physics, 2007, 16 (8):  2310-2314.  DOI: 10.1088/1009-1963/16/8/025 Abstract ( 1360 )   PDF (621KB) ( 560 )   In this paper, surface photovoltage spectroscopy (SPS) is used to determine the electronic structure of the hydrogenated transition Si films. All samples are prepared by using helicon wave plasma-enhanced chemical vapour deposition technique, the films exhibit a transition from the amorphous phase to the microcrystalline phase with increasing temperature. The film deposited at lower substrate temperature has the amorphous-like electronic structure with two types of dominant defect states corresponding to the occupied Si dangling bond states (D0/D- and the empty Si dangling states (D+). At higher substrate temperature, the crystallinity of the deposited films increases, while their band gap energy decreases. Meanwhile, two types of additional defect states is incorporate into the films as compared with the amorphous counterpart, which is attributed to the interface defect states between the microcrystalline Si grains and the amorphous matrix. The relative SPS intensity of these two kinds of defect states in samples deposited above 300℃ increases first and decreases afterwards, which may be interpreted as a result of the competition between hydrogen release and crystalline grain size increment with increasing substrate temperature.

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The non-destructive threshold of the graphite surface by STM in the ultra-fast pulse mode Xu Chun-Kai(徐春凯), Wei Zheng(魏征), Chen Xiang-Jun(陈向军), and Xu Ke-Zun(徐克尊) Chinese Physics, 2007, 16 (8):  2315-2318.  DOI: 10.1088/1009-1963/16/8/026 Abstract ( 1323 )   PDF (705KB) ( 469 )   In this paper single ultra-fast voltage pulses are introduced to the Pt/Ir tip of a scanning tunnelling microscope (STM), and the non-destructive threshold of the graphite surface is studied systematically in a wide range of pulse durations (from 10$^{4}$ to 8 ns). Considering the waveform distortion of the pulses at the tunnelling region, this paper gives the corrected threshold curve of pulse amplitude depending on pulse duration. A new explanation of threshold power has been suggested and fits the experimental results well.

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Influence of tube voltage and current on in-line phase contrast imaging using a microfocus x-ray source Li Chen(李晨), Li Zheng(李政), Yu Ai-Min(禹爱民), and Li Cheng-Quan(黎成权) Chinese Physics, 2007, 16 (8):  2319-2324.  DOI: 10.1088/1009-1963/16/8/027 Abstract ( 1410 )   PDF (708KB) ( 585 )   In-line x-ray phase contrast imaging has attracted much attention due to two major advantages: its effectiveness in imaging weakly absorbing materials, and the simplicity of its facilities. In this paper a comprehensive theory based on Wigner distribution developed by Wu and Liu [Med. Phys. 31 2378-2384 (2004)] is reviewed. The influence of x-ray source and detector on the image is discussed. Experiments using a microfocus x-ray source and a CCD detector are conducted, which show the role of two key factors on imaging: the tube voltage and tube current. High tube current and moderate tube voltage are suggested for imaging.

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

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The solutions of the strongly nonlocal spatial solitons with several types of nonlocal response functions Ouyang Shi-Gen(欧阳世根), Guo Qi(郭旗), Lan Sheng(兰胜), and Wu Li-Jun(吴立军) Chinese Physics, 2007, 16 (8):  2325-2330.  DOI: 10.1088/1009-1963/16/8/028 Abstract ( 1396 )   PDF (1665KB) ( 571 )   The fundamental and second order strongly nonlocal solitons of the nonlocal nonlinear Schrödinger equation for several types of nonlocal responses are calculated by Ritz's variational method. For a specific type of nonlocal response, the solutions of the strongly nonlocal solitons with the same beam width but different degrees of nonlocality are identical except for an amplitude factor. For a nonlocal case where the nonlocal response function decays in direct proportion to the $m$th power of the distance near the source point, the power and the phase constant of the strongly nonlocal soliton are in inverse proportion to the $(m+2)$th power of its beam width.

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Conservation laws of the generalized nonlocal nonlinear Schrödinger equation Ouyang Shi-Gen(欧阳世根), Guo Qi (郭旗), Wu Li-Jun (吴立军), and Lan Sheng (兰胜) Chinese Physics, 2007, 16 (8):  2331-2337.  DOI: 10.1088/1009-1963/16/8/029 Abstract ( 1382 )   PDF (116KB) ( 560 )   The derivations of several conservation laws of the generalized nonlocal nonlinear Schrödinger equation are presented. These invariants are the number of particles, the momentum, the angular momentum and the Hamiltonian in the quantum mechanical analogy. The Lagrangian is also presented.

NUCLEAR PHYSICS

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Optimal reactions for synthesis of nuclides of element 108 Liu Zu-Hua (刘祖华) and Zhou Hong-Yu(周宏余) Chinese Physics, 2007, 16 (8):  2338-2342.  DOI: 10.1088/1009-1963/16/8/030 Abstract ( 1258 )   PDF (451KB) ( 503 )   The cross sections for the production of nuclides of element 108 via hot fusion evaporation reactions are studied using a two-parameter Smoluchowski equation. The optimal reactions for the synthesis of new nuclides of element 108 with mass numbers from 266 to 271 are suggested. The macroscopic-microscopic approach predicts a strong deformed shell closure at $Z \approx 108$ and $N=162$. The synthesis of more nuclides of element 108 is meaningful to the confirmation of the existence of this deformed shell closure.

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International Linear Collider damping ring lattice design with two wiggler sections Sun Yi-Peng(孙一鹏), Gao Jie(高杰), and Guo Zhi-Yu(郭之虞) Chinese Physics, 2007, 16 (8):  2343-2348.  DOI: 10.1088/1009-1963/16/8/031 Abstract ( 1277 )   PDF (1238KB) ( 376 )   The International Linear Collider (ILC), which is based on super-conducting RF acceleration technology, requires the damping rings to provide beams with extremely small equilibrium emittance, and large acceptance to ensure good injection efficiency for high-emittance, and high-energy spread beam from the positron source. In order to reduce the cost for ILC damping rings, an alternative lattice which is different from the baseline configuration design has been designed with modified FODO arc cells, and the total quadrupole number has been reduced by half. At the same time, to decrease the total cost involved in constructing access shafts needed to supply power, cryogenics etc. for the wigglers and other systems, the number of wiggler sections is decreased from 8 to 4, and further to 2. This new lattice has been optimized to have a good dynamic aperture. This alternative ILC damping ring lattice design will reduce the cost largely as compared with the baseline design.

ATOMIC AND MOLECULAR PHYSICS

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Laser pulse design for coherent laser control of potassium atoms Zhang Xian-Zhou(张现周), Jia Guang-Rui(贾光瑞), and He Hai-Fang(何海芳) Chinese Physics, 2007, 16 (8):  2349-2355.  DOI: 10.1088/1009-1963/16/8/032 Abstract ( 1472 )   PDF (624KB) ( 470 )   In this paper, the dynamics of coherent laser control of potassium atoms is studied by using the time-dependent multilevel approach (TDMA). The calculation results of population transfer are presented with different laser fields. The results show that the population can be transferred to target state completely by a specially designed laser field.

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The molecular structure and the analytical potential energy function of S2- and S3- Liu Yu-Fang(刘玉芳), Li Jun-Yu(李俊玉), Han Xiao-Qin(韩晓琴), and Sun Jin-Feng(孙金锋) Chinese Physics, 2007, 16 (8):  2356-2360.  DOI: 10.1088/1009-1963/16/8/033 Abstract ( 1523 )   PDF (262KB) ( 502 )   In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2- and S3- have been calculated at QCISD/6-311++G(3d2f) and B3P86/6-311++G(3d2f) level. The S2- ground state is of -Pig, the S3- ground state is of -B1 and S3- has a bent (C2V) structure with an angle of 115.65°. The results are in good agreement with these reported in other literature. For S3- ion, the vibration frequencies and the force constants have also been calculated. Base on the general principles of microscopic reversibility, the dissociation limits has been deduced. The Murrell--Sorbie potential energy function for S2- has been derived according to the ab initio data through the least-squares fitting. The force constants and spectroscopic data for S2- have been calculated, then compared with other theoretical data. The analytical potential energy function of S3- have been obtained based on the many-body expansion theory. The structure and energy can correctly reappear on the potential surface.

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K-shell photoionization of boron-like carbon ions: analysis of 1s-2p resonances Wang Guo-Li(王国利) and Zhou Xiao-Xin(周效信) Chinese Physics, 2007, 16 (8):  2361-2366.  DOI: 10.1088/1009-1963/16/8/034 Abstract ( 1451 )   PDF (210KB) ( 523 )   Close-coupling calculations based on an R-matrix formalism are performed for the 1s--2p resonance photoionizations from the low-lying states of boron-like carbon ions. The resonance energies, widths and oscillator strengths of 1s-2p core excitations are determined by analysing the calculated photoionization cross sections. Our calculations are in reasonable agreement with the experimental and theoretical results presented by other authors. The present numerical values may help to analyse the astrophysical and laboratory plasmas.

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Calculation of the elastic scattering properties for cold and ultracold 39K atoms in a triplet state Hu Qiu-Bo(胡秋波), Wang Xiao-Fei(王晓飞), Sun Jin-Feng(孙金锋), and Zhu Zun-Lue(朱遵略) Chinese Physics, 2007, 16 (8):  2367-2370.  DOI: 10.1088/1009-1963/16/8/035 Abstract ( 1431 )   PDF (124KB) ( 526 )   The elastic scattering properties for collisions between cold and ultracold 39K atoms in a triplet state are investigated. Based on the recent theoretical and experimental results, the improved hybrid potential is presented for a triplet a3$\Sigma$u+ ground state of K2. Our calculated value of the s-wave scattering length a by using the Numerov method for the triplet state is 79.578a0 and found to be in good agreement with the previous ones. The numbers of bound states are supported by the molecular potential. Pronounced shape resonances appear for the l = 3 partial waves for the a3$\Sigma$u+ state. Furthermore, the s-wave scattering cross section, the total cross section and energy positions of shape resonances for the a3$\Sigma$u+ state are calculated.

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Ab initio calculation on accurate analytic potential energy functions and harmonic frequencies of c3$\Sigma$+g and B1$\Pi$u states of dimer 7Li2 Yu Ben-Hai(余本海), Shi De-Heng(施德恒), Sun Jin-Feng(孙金锋), Zhu Zun-Lue(朱遵略), Liu Yu-Fang(刘玉芳), and Yang Xiang-Dong(杨向东) Chinese Physics, 2007, 16 (8):  2371-2377.  DOI: 10.1088/1009-1963/16/8/036 Abstract ( 1373 )   PDF (213KB) ( 606 )   The comparison between single-point energy scanning (SPES) and geometry optimization (OPT) in determining the equilibrium geometries of c3$\Sigma$+g and B1$\Pi$u states of dimer 7Li2 is made at numerous basis sets by using a symmetry-adapted-cluster configuration-interaction (SAC-CI) method in the Gaussian 03 program package. In this paper the difference of the equilibrium geometries obtained by SPES and by OPT is reported. The results obtained by SPES are found to be more reasonable than those obtained by OPT in full active space at the present SAC-CI level of theory. And the conclusion is attained that the cc-PVTZ is a most suitable basis set for these states. The calculated dissociation energies and equilibrium geometries are 0.8818 eV and 0.3090 nm for c3$\Sigma$+g state, and 0.3668 eV and 0.2932 nm for B1$\Pi$ u state respectively. The potential energy curves are calculated over a wide internuclear distance range from about 2.5a0 to 37a0 and have a least-squares fit into the Murrell--Sorbie function. According to the calculated analytic potential energy functions, the harmonic frequencies (\omegae and other spectroscopic data ($\omega$e$\chi$e , Be and $\alpha$e are calculated. Comparison of the theoretical determinations at present work with the experiments and other theories clearly shows that the present work is the most complete effort and thus represents an improvement over previous theoretical results.

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Multiple ionization of argon accompanied by electron loss and capture of 0.22--6.35 MeV Cq+ ions Chen Lin(陈林), Chen Xi-Meng(陈熙萌), Shao Jian-Xiong(邵剑雄), Lu Yan-Xia(鲁彦霞), Ding Bao-Wei(丁宝卫), Cui Ying(崔莹), Gao Zhi-Min(高志民), Liu Yu-Wen(刘玉文), Du Juan(杜娟), Xie Jiang-Shan(谢江山), Sun Guang-Zhi(孙光智), and Liu Zhao-Yuan(刘兆远） Chinese Physics, 2007, 16 (8):  2378-2383.  DOI: 10.1088/1009-1963/16/8/037 Abstract ( 1341 )   PDF (284KB) ( 539 )   In this paper a projectile ions--recoil ions coincidence technique is employed to investigate the target ionization and projectile charge state changing processes in the collision of 0.22--6.35 MeV Cq+(q = 1-4) ions with argon atoms. The partial cross section ratios of the double, triple, quadruplicate ionization to the single ionization (or the single capture) of argon associated with single electron loss (or single electron capture) by the projectile are measured and compared with the previous experimental results. In the present experiment, it is observed that the ratios of ionization cross sections R associated with single loss and single capture depend strongly on the projectile charge state and vary significantly with different reaction channels as impact energy increases. In addition, this paper gets empirical scaling laws for the ionization cross section ratios R corresponding to the projectile single loss and finds that the ratios of the double ionization to the single ionization associated with single electron capture remain constant in the present energy range.

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Production of recoil ions Hei+ accompanied by single electron loss of 0.2--7MeV Cq+ and 0.25--5MeV Oq+ (q=1--4) ions Chen Xi-Meng(陈熙萌), Lu Yan-Xia(鲁彦霞), Ding Bao-Wei(丁宝卫), Liu Yu-Wen(刘玉文), Cui Ying(崔莹), Gao Zhi-Min(高志民), Fu Hong-Bin(付宏斌), Du Juan (杜娟), and Shao Jian-Xiong(邵剑雄) Chinese Physics, 2007, 16 (8):  2384-2388.  DOI: 10.1088/1009-1963/16/8/038 Abstract ( 1432 )   PDF (219KB) ( 453 )   Target ionization accompanied with projectile electron loss is investigated for 0.2--7 MeV Cq+(q=1-4) with He and 0.25--5 MeV Oq+(q=1-4) with He collisions. For projectile single-electron loss channel, the He double-to-single ionization ratio R is nearly independent of projectile charge state but dependent on the nuclear charge of projectile Zp. The results are analysed with atomic structure qualitatively. So far there have not existed the experimental data comparable with our results, to our knowledge. The ratio $R$ is interpreted in terms of the two-step mechanism. This analysis agrees well with similar experiments in the literature.

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Calculations on the hyperfine constants of the ground states for lithium-like system Wu Xiao-Li(吴晓丽), Yu Kai-Zhi(俞开智), Gou Bing-Cong(苟秉聪), and Zhang Meng(张孟) Chinese Physics, 2007, 16 (8):  2389-2393.  DOI: 10.1088/1009-1963/16/8/039 Abstract ( 1222 )   PDF (124KB) ( 499 )   In this paper a relativistic many-body perturbation calculation is performed to calculate the hyperfine constants of the ground states for lithium-like isoelectronic sequence. Zeroth-order hyperfine constants are calculated with Dirac--Fock wavefunctions, and the finite basis sets of the Dirac--Fock equations are constructed by B splines. With the finite basis sets, the core polarization and the correlation effect are evaluated.

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DFT study on the structure and spectra of Ga5P5 cluster Zhang Cai-Rong(张材荣), Chen Hong-Shan(陈宏善), Song Yan(宋燕), and Xu Guang-Ji(许广济) Chinese Physics, 2007, 16 (8):  2394-2399.  DOI: 10.1088/1009-1963/16/8/040 Abstract ( 1413 )   PDF (845KB) ( 670 )   In this paper, possible structures of Ga5P5 cluster were optimized by using density functional method with generalized gradient correction (B3LYP). The electronic structure of the isomers with lower energy was studied. The most stable structure obtained for Ga5P5 is a distorted pentaprism. The Ga-P bond formed in the cluster is strongly ionic. Based on NBO analysis, an average value of 0.59 electron transfers from Gallium to Phosphorus. The bond length 2.33--2.43? is around the value in bulk GaP. The HOMO-LUMO gap is about 2.2 eV. The dipole moment and polarizability are calculated, and the IR and Raman spectra are also presented.

CLASSICAL AREAS OF PHENOMENOLOGY

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Effect of spontaneously generated coherence on inversionless lasing gain in an atomic system with Doppler broadening Ma Hui(马慧), Tan Xia(谭霞), Tian Shu-Fen(田淑芬), Tong Dian-Min(仝殿民), and Fan Xi-Jun(樊锡君) Chinese Physics, 2007, 16 (8):  2400-2406.  DOI: 10.1088/1009-1963/16/8/041 Abstract ( 1520 )   PDF (186KB) ( 542 )   We have studied the effect of the spontaneously generated coherence (SGC) on gain of lasing without inversion (LWI) in a closed three-level $\Lambda $-type atomic system with Doppler broadening. It is shown that, regardless of the driving and probe fields being co- or counter-propagating, at a suitable value of the Doppler width, we can obtain a much larger LWI gain with SGC than that without SGC; and the region of the LWI gain spectrum with SGC is obviously larger than that without SGC. When the Doppler width takes a constant value, the gain does not monotonically decrease or increase with increasing strength of SGC, the largest LWI gain can be obtained by adjusting strength of SGC. Generally speaking, the co-propagating probe and driving fields is favourable to obtain a larger LWI gain.

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Atomic coherence control on the entanglement of two atoms in two-photon processes Hu Yao-Hua(胡要花), Fang Mao-Fa(方卯发), and Wu Qin(吴琴) Chinese Physics, 2007, 16 (8):  2407-2414.  DOI: 10.1088/1009-1963/16/8/042 Abstract ( 1302 )   PDF (213KB) ( 587 )   Considering two identical two-level atoms interacting with a single-mode thermal field through two-photon processes, this paper studies the atomic coherence control on the entanglement between two two-level atoms, and finds that the entanglement is greatly enhanced due to the initial atomic coherence. The results show that the entanglement can be manipulated by changing the initial parameters of the system, such as the superposition coefficients and the relative phases of the initial atomic coherent state and the mean photon number of the cavity field.

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Wigner function and tomogram of the Hermite polynomial state Meng Xiang-Guo(孟祥国), Wang Ji-Suo(王继锁), and Li Yan-Ling(李艳玲) Chinese Physics, 2007, 16 (8):  2415-2421.  DOI: 10.1088/1009-1963/16/8/043 Abstract ( 1352 )   PDF (540KB) ( 582 )   Using the coherent state representation of Wigner operator and the technique of integration within an ordered product (IWOP) of operators, this paper derives the Wigner function for the Hermite polynomial state (HPS). The tomogram of the HPS is calculated with the aid of newly introduced intermediate coordinate-momentum representation in quantum optics.

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The nonlinear squeezed one-photon states and their nonclassical properties Wang Ji-Suo(王继锁) and Meng Xiang-Guo(孟祥国) Chinese Physics, 2007, 16 (8):  2422-2427.  DOI: 10.1088/1009-1963/16/8/044 Abstract ( 1252 )   PDF (213KB) ( 477 )   By virtue of the technique of integration within an ordered product (IWOP) of operators and the properties of the inverses of annihilation and creation operators of f-oscillator, this paper obtains two new types of squeezed operators and f-analogues of squeezed one-photon states, which are quite different from ones constructed by Song and Fan (Phys. Lett. A 294 (2002) 66). Subsequently, some nonclassical properties of the states are investigated in detail.

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The spatial properties of atomic Raman--Nath diffraction Li Li-Ping(李利平), Zhang Li-Yan (张利彦), Song Pei-Jun(宋佩君), Xie Xiao-Tao(谢小涛), and Li Wei-Bin(李伟斌) Chinese Physics, 2007, 16 (8):  2428-2432.  DOI: 10.1088/1009-1963/16/8/045 Abstract ( 1562 )   PDF (1156KB) ( 466 )   This paper obtains the exact analytical solution of atomic Raman--Nath diffraction in the coordinate representation and discusses the influence of different initial conditions and detunings on the atomic spatial population distribution. The phase difference between the dipole matrix element and initial atomic population may influence the atomic spatial population distribution after diffraction, which has never been discussed before as far as we know. It offers a method to measure the phase by the spatial population distribution, which is interesting in the study of quantum optics.

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Theoretical research on enhancement of gain for Ni-like Ag 13.9nm x-ray laser using a new two-layer target Zhang Guo-Ping(张国平), Zhang Tan-Xin(张覃鑫), Zheng Wu-Di(郑无敌), and Qiao Xiu-Mei(乔秀梅） Chinese Physics, 2007, 16 (8):  2433-2438.  DOI: 10.1088/1009-1963/16/8/046 Abstract ( 1452 )   PDF (232KB) ( 443 )   For experiments such as on Ni-like Ag x-ray laser, driven by $1\omega$  laser, the gain region is only several~nm depth near the target surface, this paper proposes a new two-layer target, in which a thin layer (several nm depth) of silver is plated on the surface of some other materials. Furthermore, the Ni-like Ag 13.9 nm x-ray laser produced by three new kinds of two-layer target with CH, Al and Ge as foundation, was theoretically studied.

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2D hydrodynamic simulation of a line-focused plasma in Ni-like Ag x-ray laser research Zheng Wu-Di(郑无敌) and Zhang Guo-Ping(张国平) Chinese Physics, 2007, 16 (8):  2439-2443.  DOI: 10.1088/1009-1963/16/8/047 Abstract ( 1382 )   PDF (1191KB) ( 659 )   In most collisional schemes of x-ray laser (XRL) experiments, a bow-like intensity distribution of XRL is often observed, and it is generally ascribed to the two-dimensional hydrodynamic behaviour of expanding plasma. In order to better understand its essence in physics, a newly developed two-dimensional non-equilibrium radiation hydrodynamic code XRL2D is used to simulate a quasi-steady state Ni-like Ag XRL experiment on ShenGuang-II facility. The simulation results show that the bow-like distribution of Ni-like ions caused by over-ionization in the central area of plasma is responsible for the bow-like shape of the XRL intensity distribution observed.

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Lattice Boltzmann simulations of a dumbbell moving in a Poiseuille flow Yi Hou-Hui(伊厚会), Chen Yan-Yan(陈艳燕), and Li Hua-Bing(李华兵) Chinese Physics, 2007, 16 (8):  2444-2448.  DOI: 10.1088/1009-1963/16/8/048 Abstract ( 1322 )   PDF (151KB) ( 457 )   In this paper, the lattice Boltzmann method is applied to simulate a dumbbell moving in a pressure-driven flow in a planar channel with the stress-integration method for the evaluation of hydrodynamic force acting on the cylinders. The simulation results show that the dumbbell also has the important feature of the Segré--Silberberg effect like a particle in a Poiseuille flow. The dumbbell trajectories, orientations, the cylinders vertical velocities and angular velocities all reach their equilibrium values separately independent of their initial positions. It is also found that the dumbbell equilibrium positions depend on the flow Reynolds number, blockage ratio and elastic coefficient. This study is expected to be helpful to understand the dynamics of polymer solutions, polymer synthesis and reaction, etc.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Density cavities generated by plasma--field interactions in the far wake region of a space vehicle Hu Tao-Ping(胡涛平), Luo Qing(罗青), and Li Xiao-Qing(李晓卿) Chinese Physics, 2007, 16 (8):  2449-2454.  DOI: 10.1088/1009-1963/16/8/049 Abstract ( 1514 )   PDF (416KB) ( 548 )   Under the consideration of non-steady case, a set of equations is derived, which describes the non-steady nonlinear interactions between plasma and field in the far wake region of a space vehicle. Numerical calculations are also made and the numerical results show that density cavities and electromagnetic solitary waves are generated due to the modulation instability, if the envelope of high frequency modulation field is strong enough. This is of great significance to the detection of disguised space vehicles.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Dopant diffusion and surface morphology of vanadium implanted 4H-silicon carbide Wang Chao(王超), Zhang Yi-Men(张义门), Zhang Yu-Ming(张玉明), Ma Ge-Lin(马格林), Guo Hui(郭辉), and Xu Da-Qing(徐大庆) Chinese Physics, 2007, 16 (8):  2455-2461.  DOI: 10.1088/1009-1963/16/8/050 Abstract ( 1301 )   PDF (1480KB) ( 718 )   The diffusion behaviours of vanadium implanted p- and n-type 4H-SiC are investigated by using the secondary ion mass spectrometry (SIMS). Significant redistribution, especially out-diffusion of vanadium towards the sample surface is not observed after 1650℃ annealing for both p- and n-type samples. Atomic force microscopy (AFM) is applied to the characterization of surface morphology, indicating the formation of continuous long furrows running in one direction across the wafer surface after 1650℃ annealing. The surface roughness results from the evaporation and re-deposition of Si species on the surface during annealing. The chemical compositions of sample surface are investigated using x-ray photoelectron spectroscopy (XPS). The results of C 1s and Si 2p core-level spectra are presented in detail to demonstrate the evaporation of Si from the wafer and the deposition of SiO2 on the sample surface during annealing.

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

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Quantum fluctuations of mesoscopic damped double resonance RLC circuit with mutual capacitance--inductance coupling in thermal excitation state Xu Xing-Lei(徐兴磊), Li Hong-Qi (李洪奇), and Wang Ji-Suo(王继锁) Chinese Physics, 2007, 16 (8):  2462-2470.  DOI: 10.1088/1009-1963/16/8/051 Abstract ( 1605 )   PDF (168KB) ( 745 )   Based on the scheme of damped harmonic oscillator quantization and thermo-field dynamics (TFD), the quantization of mesoscopic damped double resonance RLC circuit with mutual capacitance--inductance coupling is proposed. The quantum fluctuations of charge and current of each loop in a squeezed vacuum state are studied in the thermal excitation case. It is shown that the fluctuations not only depend on circuit inherent parameters, but also rely on excitation quantum number and squeezing parameter. Moreover, due to the finite environmental temperature and damped resistance, the fluctuations increase with the temperature rising, and decay with time.

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Effect of Te doping on superconductivity and charge-density wave in dichalcogenides 2H-NbSe2-xTex (x=0, 0.1, 0.2) Wang Hong-Tao(王洪涛), Li Lin-Jun(李林军), Ye De-Shu(叶德枢), Cheng Xin-Hong(程新红), and Xu Zhu-An(许祝安) Chinese Physics, 2007, 16 (8):  2471-2474.  DOI: 10.1088/1009-1963/16/8/052 Abstract ( 1434 )   PDF (219KB) ( 725 )   Single crystals of Te-doped dichalcogenides 2H-NbSe2-xTex(x = 0, 0.10, 0.20) were grown by vapour transport method. The effect of Te doping on the superconducting and charge-density wave (CDW) transitions has been investigated. The sharp decrease of residual resistance ratio, RRR = R(300K)/R(8K), with increasing Te content was observed, indicating that the disorder in the conducting plane is induced by Te doping. Meanwhile the superconducting transition temperature, Tc, decreases monotonically with Te content. However, the CDW transition temperature, TCDW, shown by a small jump in the temperature dependence of the resistivity near 30 K, increases slightly. The results show that the suppression of superconductivity might be caused by the enhancement of CDW ordering. The disorder has little influence on the CDW ordering.

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Si1Sb2Te3 phase change material for chalcogenide random access memory Zhang Ting(张挺), Song Zhi-Tang(宋志棠), Liu Bo(刘波), Liu Wei-Li(刘卫丽), Feng Song-Lin(封松林), and Chen Bomy(陈邦明) Chinese Physics, 2007, 16 (8):  2475-2478.  DOI: 10.1088/1009-1963/16/8/053 Abstract ( 959 )   PDF (180KB) ( 498 )   This paper investigated phase change Si1Sb2Te3 material for application of chalcogenide random access memory. Current--voltage performance was conducted to determine threshold current of phase change from amorphous phase to polycrystalline phase. The film holds a threshold current about 0.155 mA, which is smaller than the value 0.31 mA of Ge2Sb2Te5 film. Amorphous Si1Sb2Te3 changes to face-centred-cubic structure at $\sim$ 180℃ and changes to hexagonal structure at $\sim$ 270℃. Annealing temperature dependent electric resistivity of Si1Sb2Te3film was studied by four-point probe method. Data retention of the films was characterized as well.

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Dynamics analysis on neural firing patterns by symbolic approach Gao Zhi-Ying(郜志英) and Lu Qi-Shao(陆启韶) Chinese Physics, 2007, 16 (8):  2479-2485.  DOI: 10.1088/1009-1963/16/8/054 Abstract ( 1106 )   PDF (776KB) ( 396 )   Neural firing patterns are investigated by using symbolic dynamics. Bifurcation behaviour of the Hindmarsh--Rose (HR) neuronal model is simulated with the external stimuli gradually decreasing, and various firing activities with different topological structures are orderly numbered. Through constructing first-return maps of interspike intervals, all firing patterns are described and identified by symbolic expressions. On the basis of ordering rules of symbolic sequences, the corresponding relation between parameters and firing patterns is established, which will be helpful for encoding neural information. Moreover, using the operation rule of $\ast$ product, generation mechanisms and intrinsic configurations of periodic patterns can be distinguished in detail. Results show that the symbolic approach is a powerful tool to study neural firing activities. In particular, such a coarse-grained way can be generalized in neural electrophysiological experiments to extract much valuable information from complicated experimental data.

GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

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Analysis of influence of atmosphere extinction to Raman lidar monitoring CO2 concentration profile Zhao Pei-Tao(赵培涛), Zhang Yin-Chao(张寅超), Wang Lian(王莲), Zhao Yue-Feng(赵曰峰), Su Jia(苏嘉), Fang Xin(方欣), Cao Kai-Fa(曹开法), Xie Jun(谢军), and Du Xiao-Yong(杜小勇) Chinese Physics, 2007, 16 (8):  2486-2491.  DOI: 10.1088/1009-1963/16/8/055 Abstract ( 1322 )   PDF (689KB) ( 644 )   Lidar (Light detection and ranging) system monitoring of the atmosphere is a novel and powerful technique tool. The Raman lidar is well established today as a leading research tool in the study of numerous important areas in the atmospheric sciences. In this paper, the principle of Raman lidar technique measurement CO2 concentration profile is presented and the errors caused by molecular and aerosol extinction for CO2 concentration profile measurement with Raman lidar are also presented. The standard atmosphere extinction profile and `real-time' Hefei area extinction profile are used to conduct correction and the corresponding results are yielded. Simulation results with standard atmosphere mode correction indicate that the errors caused by molecule and aerosol extinction should be counted for the reason that they could reach about 8 ppm and 5 ppm respectively. The relative error caused by Hefei area extinction correction could reach about 6%. The errors caused by the two components extinction influence could produce significant changes for CO2 concentration profile and need to be counted in data processing which could improve the measurement accuracies.