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Chin. Phys. B  
  Chin. Phys. B--2005, Vol.14, No.7
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GENERAL

Studies of the beam finding and targeting accuracy of the CAS-LIBB single-particle microbeam

Wang Xiao-Hua, Wang Xu-Fei, Hu Zhi-Wen, Chen Lian-Yun, Zhang Jun, Zhan Fu-Ru, Li Jun, Chen Bin, Xu Ming-Liang, Wu Li-Jun, Wang Shao-Hu, Yu Zeng-Liang
Chin. Phys., 2005, 14 (7): 1277-1281 doi: 10.1088/1009-1963/14/7/001
Full Text: [PDF 437 KB] (Downloads:396)
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A single-particle microbeam facility has been constructed at the Key Laboratory of Ion Beam Bioengineering (LIBB), Chinese Academy of Sciences (CAS). The system was designed to deliver a defined number of hydrogen ions produced by a Van de Graaff accelerator, in an energy range of 2.0--3.0MeV,into an area smaller than the nuclei of individual living cells grown on thin plastic films. The beam is collimated by a borosilicate glass capillary that forms the beam-line exit. An computer integrated control program is developed to recognize the cells and to target them one by one for irradiation.Experiments for finding (capturing and recognizing) the microbeam position in the microscope imaging system and measuring the overall targeting accuracy of the facility are presented in this article. When a borosilicate glass capillary with 5$\mu$m inner diameter and 980$\mu$m length is used as the microbeam collimator, the overall targeting accuracy is that 91{\%} aimed pit clusters are located within 2.4 $\mu $m radius, and 98{\%} are within 3.6 $\mu $m radius.

Chaos in Bianchi I cosmology

Chen Ju-Hua, Wang Yong-Jiu
Chin. Phys., 2005, 14 (7): 1282-1286 doi: 10.1088/1009-1963/14/7/002
Full Text: [PDF 303 KB] (Downloads:491)
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We have investigated the dynamical evolution of the Yang--Mills (YM) field in Bianchi I cosmology background. We find that the long-time evolution behaviour of the YM field is highly sensitive to initial conditions, i.e. small fluctuations of initial conditions for fixed Hamiltonian of the system may rapidly change the evolution of the field. By using the Poincar\'{e} section method, we further illustrate that the dynamical evolution of the YM field in Bianchi I cosmology background has certain typically chaotic properties.

Unified symmetry of holonomic mechanical systems

Xu Xue-Jun, Qin Mao-Chang, Mei Feng-Xiang
Chin. Phys., 2005, 14 (7): 1287-1289 doi: 10.1088/1009-1963/14/7/003
Full Text: [PDF 189 KB] (Downloads:718)
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The definition and the criterion of a unified symmetry for a holonomic mechanical system are presented based on the total time derivative along the trajectory of the system. A new conserved quantity, as well as the Noether conserved quantity and the Hojman conserved quantity, deduced from the unified symmetry, is obtained. An example is given to illustrate the application of the results.

Hyperbolic function method for solving nonlinear differential-different equations

Zhu Jia-Min
Chin. Phys., 2005, 14 (7): 1290-1295 doi: 10.1088/1009-1963/14/7/004
Full Text: [PDF 224 KB] (Downloads:707)
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An algorithm is devised to obtained exact travelling wave solutions of differential-different equations by means of hyperbolic function. For illustration, we apply the method to solve the discrete nonlinear (2+1)-dimensional Toda lattice equation and the discretized nonlinear mKdV lattice equation, and successfully constructed some explicit and exact travelling wave solutions.

New expansion algorithm of three Riccati equations and its applications in nonlinear mathematical physics equations

Zhi Hong-Yan, Zhao Xue-Qin, Zhang Hong-Qing
Chin. Phys., 2005, 14 (7): 1296-1302 doi: 10.1088/1009-1963/14/7/005
Full Text: [PDF 366 KB] (Downloads:452)
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Based on the study of tanh function method and the coupled projective Riccati equation method, we propose a new algorithm to search for explicit exact solutions of nonlinear evolution equations. We use the higher-order Schr\"{o}dinger equation and mKdV equation to illustrate this algorithm. As a result, more new solutions are obtained, which include new solitary solutions, periodic solutions, and singular solutions.Some new solutions are illustrated in figures.

A unified approach in seeking the solitary wave solutions to sine-Gordon type equations

Xie Yuan-Xi, Tang Jia-Shi
Chin. Phys., 2005, 14 (7): 1303-1306 doi: 10.1088/1009-1963/14/7/006
Full Text: [PDF 190 KB] (Downloads:648)
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By utilizing the solutions of an auxiliary ordinary differential equation introduced in this paper, we present a simple and direct method to uniformly construct the exact solitary wave solutions for sine--Gordon type equations. As illustrative examples, the exact solitary wave solutions of some physically significant sine--Gordon type equations, including the sine--Gordon equation, double sine--Gordon equation and mKdV--sine--Gordon equation, are investigated by means of this method.

Application of new entangled state representation to a two-coupled oscillator system

Pang Qian-Jun
Chin. Phys., 2005, 14 (7): 1307-1312 doi: 10.1088/1009-1963/14/7/007
Full Text: [PDF 232 KB] (Downloads:329)
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We study the eigenstate problem of a two-coupled oscillator system. A new entangled state representation $\left\vert \gamma \right\rangle $ composed of the common eigenvectors of operators $% (x_{1}+p_{2})$ and $(p_{1}+x_{2})$ is established. Eigenvalues and eigenvectors of the Hamiltonian are obtained in $\left\vert \gamma \right\rangle $ representations. The same problem is studied in the second-quantization representation. We find that the second-quantization representation can be used to derive the normally ordered product expression of eigenvector in Fock space. In particular, we find that the ground state of the Hamiltonian is a kind of generalized two-mode squeezed state.

Probabilistic teleportation of an arbitrary two-particle state by a partial three-particle entangled GHZ state and a two-particle entangled state

Sun Li-Li, Fan Qiu-Bo, Zhang Shou
Chin. Phys., 2005, 14 (7): 1313-1316 doi: 10.1088/1009-1963/14/7/008
Full Text: [PDF 199 KB] (Downloads:504)
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We propose a scheme to teleport an arbitrary unknown two-particle state by a non-maximally three-particle entangled Greenberger--Horne--Zeilinger (GHZ) state and a non-maximally two-particle entangled state from a sender to either one of two receivers. We probabilistically teleport the arbitrary unknown two-particle state by performing two Bell-state measurements on the sender's side, introducing two appropriate unitary transformations on the receiver's side conditioned on a Hadamard operation and a projection measurement on the other possible receiver's side.

A systematic approximate method for the study of evolution problem beyond rotating wave approximation

Zhang Zheng-Jie, Wang Ke-Lin, Qin Gan
Chin. Phys., 2005, 14 (7): 1317-1322 doi: 10.1088/1009-1963/14/7/009
Full Text: [PDF 259 KB] (Downloads:318)
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By a model of a two-level particle coupled with boson field, we made it clear that an evolution problem can be solved beyond the rotating wave approximation. We have applied the coherent approximation method, which had been proved to be effective in dealing with stationary state problems of polaron, to the evolution problem of the system mentioned above. The results obtained showed that the coherent approximation method is effective to treat the evolution problem, and, in general cases, the non-rotating wave terms in Hamiltonian should not be ignored. Our results may provide a deep physical insight for further experiments to test the effects of non-rotating wave terms.

Implementing remotely a single-qubit rotation operation by three-qubit entanglement

Chen Li-Bing, Lu Hong, Liu Yu-Hua
Chin. Phys., 2005, 14 (7): 1323-1328 doi: 10.1088/1009-1963/14/7/010
Full Text: [PDF 236 KB] (Downloads:367)
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We investigate the problem of quantum remote implementation of a single-qubit rotation operation using three-qubit entangled state. Firstly,we utilize the entanglement property of maximally entangled Greenberger--Horne--Zeilinger (GHZ) state to design a theoretical scheme for implementing the operation remotely with unit fidelity and unit probability. Then, we put forward two schemes for conclusive implementing the non-local single-qubit rotation with unit fidelity by employing a partially entangled pure GHZ state as quantum channel. The features of these schemes are that a third side is included,who may participate the process of quantum remote implementation as a supervisor. Furthermore, when the quantum channel is partially entangled,the third side can rectify the state distorted by imperfect quantum channel.In addition to the GHZ class state, the $W$ class state can also be used to remotely implement the same operation probabilistically. The probability of successful implementation using the $W$ class state is always less than that using the GHZ class state.

Proposal for quantum entanglement of six photons

You Jun, Li Jia-Hua, Xie Xiao-Tao
Chin. Phys., 2005, 14 (7): 1329-1333 doi: 10.1088/1009-1963/14/7/011
Full Text: [PDF 223 KB] (Downloads:433)
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We propose a different scheme to achieve six-photon entangled states based entirely on the concept of quantum erasure. To begin with, a scheme for making use of a group of four entangled photons to generate six-photon entangled states is presented. Then, with the same technique, the preparation of the six-photon entanglement from five-particle entanglement which is then combined with Bell states is considered. Our experimental methods can be used for the investigations of measurement-based quantum computation and multi-party quantum communication. We find that the success probability is determined by the small coefficients of the entangled states.

The crisis induced by the property transition of a system

Dai Jun, Wang Wen-Xiu, Jiang Yu-Mei, He Yue, Chen Wen, He Da-Ren
Chin. Phys., 2005, 14 (7): 1334-1341 doi: 10.1088/1009-1963/14/7/012
Full Text: [PDF 617 KB] (Downloads:361)
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A simultaneous transition in the property of a system from everywhere smooth and conservative to piecewise smooth and quasi-dissipative is observed in a kicked billiard when adjusting a single controlling parameter. The transition induces a special kind of crisis, which signifies a sudden change of a typical conservative stochastic web into a transient web formed by the forward image set of the discontinuity borderline of the system function. Iterations on the transient web finally fall in an escaping hole composed of an elliptic island chain, which appears right after the threshold of the property transition. The size of the hole becomes larger as the controlling parameter increases so that the iterations escape faster. The averaged lifetime of the iterations in the transient web therefore follows a power-law with a special scaling exponent. At the same time, a fat fractal forbidden web, which appears also at the threshold,grows up and cuts off more and more parts from the original conservative stochastic web so that the remnant transient web becomes thinner and thinner. We numerically show that another power law can also describe this.

Generating chaos in the sense of Devaney via decentralized feedback control from a stable Takagi-Sugeno fuzzy system

Lu Jun-Guo
Chin. Phys., 2005, 14 (7): 1342-1346 doi: 10.1088/1009-1963/14/7/013
Full Text: [PDF 279 KB] (Downloads:327)
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The problem of making a stable Takagi--Sugeno (TS) fuzzy system chaotic in the sense of Devaney by using decentralized state feedback control is studied. The proposed decentralized feedback controller is a decentralized linear feedback controller composed of the overflow nonlinear function of the 2's complement arithmetic. The overflow nonlinearity of the 2's complement arithmetic results in a rather complex dynamics. We apply the Shi--Chen theorem to mathematically prove that the controlled system is indeed chaotic in the sense of Devaney. In particular, an explicit formula for the computation of chaotification parameters is also obtained. A numerical example is used to visualize and illustrate the theoretical results.

H tracking control of coupled spatiotemporal chaos based on fuzzy models

Dou Chun-Xia
Chin. Phys., 2005, 14 (7): 1347-1351 doi: 10.1088/1009-1963/14/7/014
Full Text: [PDF 229 KB] (Downloads:339)
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Due to the interactions among coupled spatiotemporal subsystems, it is difficult to achieve the tracking control of the coupled spatiotemporal chaos. However, every subsystem of the coupled spatiotemporal chaos can be approximated by a set of fuzzy models, of which each represents a linearized model of the subsystem corresponding to the operating point of the controlled system. Based on these fuzzy models, an $H_\infty$ fuzzy tracking control scheme is suggested, where a linear matrix inequalities (LMI) is employed to represent the feedback controller. The parameters of controller are obtained by using convex optimization techniques of LMI. The model reference tracking control of the coupled spatiotemporal chaos is achieved,and the stability of the system is also guaranteed. The tracking performance is tested by simulation as an example.

Bifurcation behaviours of peak current controlled PFC boost converter

Ren Hai-Peng, Liu Ding
Chin. Phys., 2005, 14 (7): 1352-1358 doi: 10.1088/1009-1963/14/7/015
Full Text: [PDF 364 KB] (Downloads:627)
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Bifurcation behaviours of the peak current controlled power-factor-correction (PFC) boost converter, including fast-scale instability and low-frequency bifurcation, are investigated in this paper. Conventionally, the PFC converter is analysed in continuous conduction mode (CCM). This prevents us from recognizing the overall dynamics of the converter. It has been pointed out that the discontinuous conduction mode (DCM) can occur in the PFC boost converter, especially in the light load condition. Therefore, the DCM model is employed to analyse the PFC converter to cover the possible DCM operation. By this way, the low-frequency bifurcation diagram is derived, which makes the route from period-double bifurcation to chaos clear. The bifurcation diagrams versus the load resistance and the output capacitance also indicate the stable operation boundary of the converter, which is useful for converter design.

Dark-lines in bifurcation plots of nonlinear dynamic systems

Gao Zhi-Ying, Shen Yun-Wen, Liu Meng-Jun
Chin. Phys., 2005, 14 (7): 1359-1364 doi: 10.1088/1009-1963/14/7/016
Full Text: [PDF 339 KB] (Downloads:343)
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Based on the regressive character of chaotic motion in nonlinear dynamic systems, a numerical regression algorithm is developed, which can be used to research the dark-lines passing through chaotic regions in bifurcation plots. The dark-lines of the parabolic mapping are obtained by using the numerical regression algorithm, and compared with those that are accurately acquired through dark-line equations. Thus the validity of this algorithm is proved. Furthermore, for the Brussel oscillation system and the piecewise linear dynamic system of a gear pair, the dark-lines are researched by using the regression algorithm. By researching the dark-lines in the bifurcation plots of nonlinear dynamic systems, the periodic windows embedded in chaotic regions can be ascertained by tangential points of dark-lines, and the turning points of chaotic attractors can be also obtained by intersected points. The results show that this algorithm is helpful to analyse dynamic behaviour of systems and control chaotic motion.

Nonexistence of ultra-subharmonic periodic orbits in periodically forced differential equation

Gao Jing-Wu, Li Qing-Shi
Chin. Phys., 2005, 14 (7): 1365-1369 doi: 10.1088/1009-1963/14/7/017
Full Text: [PDF 243 KB] (Downloads:340)
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It is proved that if there exists a periodic solution for a class of non-autonomous differential dynamic systems, it can only be subharmonic, ultra-subharmonic periodic solution is impossible. Moreover, the existence of R-type ultra-subharmonic periodic solution defined for a specified planar system is also denied. As an application of the above conclusions, through investigating some typical examples, it is pointed out that the existence of ultra-subharmonic periodic orbits in a planar perturbation system cannot be determined by second-order Melnikov method. An explanation is also provided.

Cellular automata modelling of SEIRS

Liu Quan-Xing, Jin Zhen
Chin. Phys., 2005, 14 (7): 1370-1377 doi: 10.1088/1009-1963/14/7/018
Full Text: [PDF 384 KB] (Downloads:594)
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In this paper the SEIRS epidemic spread is analysed, and a two-dimensional probability cellular automata model for SEIRS is presented. Each cellular automation cell represents a part of the population that may be found in one of five states of individuals: susceptible, exposed (or latency), infected, immunized (or recovered) and death. Here studied are the effects of two cases on the epidemic spread. i.e. the effects of non-segregation and segregation on the latency and the infected of population. The conclusion is reached that the epidemic will persist in the case of non-segregation but it will decrease in the case of segregation. The proposed model can serve as a basis for the development of algorithms to simulate real epidemics based on real data. Last we find the density series of the exposed and the infected will fluctuate near a positive equilibrium point, when the constant for the immunized is less than its corresponding constant $\tau_{0}$. Our theoretical results are verified by numerical simulations.
CLASSICAL AREAS OF PHENOMENOLOGY

Entanglement dynamics of Gaussian continuous states in correlated noisy channels

Tan Hua-Tang, Xia Hong-Xing, Li Gao-Xiang
Chin. Phys., 2005, 14 (7): 1382-1386 doi: 10.1088/1009-1963/14/7/020
Full Text: [PDF 231 KB] (Downloads:476)
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The evolution of the entanglement of an initial two-mode squeezed vacuum (TMSV) in correlated noisy channels is investigated. It is shown that the correlated environment is helpful for preserving the entanglement of the initial TMSV. The entanglement period of the initial TMSV depends on the correlation property of the correlated environment.

1.34μm Nd:YVO4 high efficiency laser end-pumped by diode-laser of flat-concave cavity type

Shang Lian-Ju, Ning Ji-Ping
Chin. Phys., 2005, 14 (7): 1387-1391 doi: 10.1088/1009-1963/14/7/021
Full Text: [PDF 245 KB] (Downloads:406)
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The parameters of 1.34$\mu $m Nd:YVO$_{4}$ laser end-pumped with flat-concave cavity are theoretically analysed. The analysis in this paper may be helpful to the designing of kindred lasers. The operation of 1.34$\mu $m Nd:YVO$_{4}$ laser end-pumped by a diode-laser with flat-concave cavity is achieved. The output power of 3.51W at 1.34$\mu$m and optical to optical conversion efficiency of 39.0{\%} are obtained at the pump power of 9.0W.

Development and evolution of flow over three-dimensional cylinder

Wang Gang, Liang Xin-Gang
Chin. Phys., 2005, 14 (7): 1392-1397 doi: 10.1088/1009-1963/14/7/022
Full Text: [PDF 531 KB] (Downloads:411)
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By solving the three-dimensional (3D) time-dependent compressible laminar Navier--Stokes equations with a finite-volume method incorporating the third-order-accuracy discretization scheme, the flow structure around a 3D cylinder is investigated and its evolution mechanism is presented in this paper. At high incidence angles, a shed vortex series forms at leeside of the 3D cylinder with its sectional flow pattern very similar to the Karman vortex street developed behind a two-dimensional cylinder. The main, the secondary and the tertiary vortex system compose a hierarchical structure over the 3D cylinder. Each tertiary vortex develops into a new main vortex after the breakaway of its former main vortex, and merges the secondary vortex on its opposite side of the symmetry plane.

A new lattice Boltzmann model for incompressible magnetohydrodynamics

Chen Xing-Wang, Shi Bao-Chang
Chin. Phys., 2005, 14 (7): 1398-1406 doi: 10.1088/1009-1963/14/7/023
Full Text: [PDF 353 KB] (Downloads:532)
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Most of the existing lattice Boltzmann magnetohydrodynamics (MHD) models can be viewed as compressible schemes to simulate incompressible MHD flows. The compressible effect might lead to some undesired errors in numerical simulations. In this paper a new incompressible lattice Boltzmann MHD model without compressible effect is presented for simulating incompressible MHD flows. Numerical simulations of the Hartmann flow are performed. We do numerous tests and make comparison with Dellar's model in detail. The numerical results are in good agreement with the analytical solutions. The scheme preserved a consistent approximation of the divergence-free condition $\nabla \cdot {{ B}}=0$ to round-off error.
ATOMIC AND MOLECULAR PHYSICS

Absolute oscillator strength densities below 100eV of N2

Sun Jian-Min, Zhong Zhi-Ping, Zhu Lin-Fan, Liu Xiao-Jing, Yuan Zhen-Sheng, Xu Ke-Zun
Chin. Phys., 2005, 14 (7): 1378-1381 doi: 10.1088/1009-1963/14/7/019
Full Text: [PDF 253 KB] (Downloads:304)
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The absolute optical oscillator strength density (OOSD) and generalized oscillator strength densities (GOSDs) below 100eV of N$_2$ are determined with an incident electron energy of 2500eV and an energy resolution of 100 meV. The absolute generalized oscillator strengths (GOSs) for two transitions to the superexcited states at 23 and 31.4eV are determined and their momentum transfer dependence behaviours are discussed.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

Optimal injection scheme for electron acceleration by a tightly focused laser beam

Chen Min, Sheng Zheng-Ming, Zhang Jie
Chin. Phys., 2005, 14 (7): 1407-1412 doi: 10.1088/1009-1963/14/7/024
Full Text: [PDF 292 KB] (Downloads:415)
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Electron dynamics and energy gain in a tightly focused laser beam in vacuum are investigated by numerical simulations. There exist two acceleration mechanisms, i.e. acceleration by the longitudinal field or by the transverse field, which corresponds to two different trajectories. The relationship between the energy gain and the injection parameters of electrons, including the injection angle and momentum, is shown. For given laser parameters, the optimum injection parameters can be obtained.

A new method of measuring the spatial distribution of depletion fraction of silane plasma by mass spectrometer

Wang Zhao-Kui, Lin Kui-Xun, Lin Xuan-Ying, Qiu Gui-Ming, Zhu Zu-Song
Chin. Phys., 2005, 14 (7): 1413-1417 doi: 10.1088/1009-1963/14/7/025
Full Text: [PDF 253 KB] (Downloads:327)
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A newly established movable sampling apparatus of mass spectrometer is used to measure the spatial distribution of depletion fraction of silane plasma.A straight-line fit method of deducing the depletion fraction of silane is proposed. Theoretical analysis and test results demonstrate that the proposed new method is universal and more accurate than the existing one.There exist a largest peak near the middle of two electrodes and two peaks near the electrodes in the spatial distribution of silane depletion fraction, which are related to the distribution of electric field and the silane plasma sheaths.

Glow and pseudo-glow discharges in a surface discharge generator

Li Xue-Chen, Dong Li-Fang, Wang Long
Chin. Phys., 2005, 14 (7): 1418-1422 doi: 10.1088/1009-1963/14/7/026
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The glow discharge in flowing argon at one atmospheric pressure is realized in a surface discharge generator. The discharge current presents one peak per half-cycle of the applied voltage. The duration of the discharge pulse is more than 1$\mu $s when the frequency of the applied voltage is 60kHz. For the glow discharge in argon, the power consumption increases with the increase of voltage or the decrease of gas pressure. This relation is explained qualitatively based on the theory of the Townsend breakdown mechanism. In contrast, the discharge current in one atmospheric pressure air gives many spikes in each half-cycle, and correspondingly this kind of discharge is called pseudo-glow discharge. Every current spike oscillates with high-frequency damping. The pseudo-glow discharge in one atmospheric pressure air might result from the streamer breakdown mechanism.

Calculation of incident ion distribution in a rectangular hollow cathode in magnetic field

Fang Tong-Zhen, Zhang Long, Wang Long
Chin. Phys., 2005, 14 (7): 1423-1427 doi: 10.1088/1009-1963/14/7/027
Full Text: [PDF 1233 KB] (Downloads:462)
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Incident ion distribution inside a rectangular hollow cathode in a uniform magnetic field is studied analytically. The analysis shows that the ion distribution on one sidewall is not interfered by the other sidewall when the depth and width of the cathode are equal, and the ion distribution on the bottom surface related to the depth of the cathode and the number of ions on the bottom surface decrease monotonically from the centre to the sidewall.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

Pyrosol process for deposition of fluorine-doped tin dioxide thin films

Qu Yi, Zhang Xin, Chen Hong, Gao Jin-Yue, Zhou Da-Fan
Chin. Phys., 2005, 14 (7): 1428-1432 doi: 10.1088/1009-1963/14/7/028
Full Text: [PDF 247 KB] (Downloads:618)
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Transparent low-resistance SnO$_{2}$:F films, suitable as a low-emissivity and conducting coating, have been deposited on silica-coated soda lime glass substrates by pyrosol process. SnCl$_{4}\cdot $5H$_{2}$O and NH$_{4}$F dissolved in solvent of 50{\%} C$_{2}$H$_{5}$OH/50{\%} H$_{2}$O served as the starting solution. With the parameters such as substrate temperature of 450${^\circ}$C, distance between the nozzle and substrate of 60mm, carrier gas flow rate of 8L/min and deposition time of 5min, the optimized SnO$_{2}$:F films having a sheet resistance of about 2$\Omega$/$\Box$, were deposited repeatedly. The relationship between sheet resistances and infrared transmission spectra of SnO$_{2}$:F films is shown schematically.

High power red laser at 671nm by intracavity frequency doubling of a Nd:YVO4 laser

Yao Ai-Yun, Hou Wei, Li Hui-Qing, Bi Yong, Li Rui-Ning, Geng Ai-Cong, Kong Yu-Peng, Cui Da-Fu, Xu Zu-Yan
Chin. Phys., 2005, 14 (7): 1433-1438 doi: 10.1088/1009-1963/14/7/029
Full Text: [PDF 848 KB] (Downloads:491)
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This paper reports a high-power quasi-continuous wave (quasi-CW) source of red laser at 671nm obtained by intracavity frequency doubling of a double-end-pumped 1342nm Nd:YVO$_{4}$ laser, based on the nonlinear crystal LiB$_{3}$O$_{5}$(LBO) The average output power of 2.9W at 671nm was obtained at the incident pump power of 19.5W. The overall optical to optical efficiency is 14.9{\%}. We have analyzed the influence of the optimal pump size, the optimal focal position and the reduction of the thermal effect on high output. The combination of double-end-pumping and the quasi-CW performance greatly reduces the thermal effect.

Model of transit time for SiGe HBT collector junction depletion-layer

Hu Hui-Yong, Zhang He-Ming, Dai Xian-Ying, Jia Xin-Zhang, Cui Xiao-Ying, Wang Wei, Ou Jian-Feng, Wang Xi-Yuan
Chin. Phys., 2005, 14 (7): 1439-1443 doi: 10.1088/1009-1963/14/7/030
Full Text: [PDF 251 KB] (Downloads:599)
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The transit time through collector junction depletion-layer is an important parameter that influences AC gain and frequency performance. In SiGe heterojunction bipolar transistor (HBT) collector junction, the depletion-layer width is given in three cases. The models of collector depletion-layer transit time, considering the collector current densities and base extension effect, are established and simulated using MATLAB. The influence of the different collector junction bias voltage, collector concentration of As or P dopant and collector width on collector junction transit time is quantitatively studied. When the collector junction bias voltage, collector doping concentration and collector width are large, the transit time is quite long. And, from the results of simulations, the influence of the collector depletion-layer transit time on frequency performance is considerable in SiGe HBT with a thin base, so it could not be ignored.

Thermodynamic properties of ultra-small metallic particles

Cheng Nan-Pu, Zeng Su-Min, Chen Zhi-Qian
Chin. Phys., 2005, 14 (7): 1444-1448 doi: 10.1088/1009-1963/14/7/031
Full Text: [PDF 269 KB] (Downloads:366)
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The thermodynamic properties of ultra-small metallic particles within an ensemble are affected by the level distribution and the level correlation between the discrete electronic energy levels. The specific heat and spin susceptibility of ultra-small metallic particles in the canonical ensemble with an odd or even number of electrons are numerically calculated by considering the effects of the level statistics, and their behaviour at low and high temperatures is also discussed. As an example, the specific heat and spin susceptibility of nano-Al particles are calculated numerically in this paper.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Spontaneous magnetostriction of Dy2 AlFe13 Mn3 compound

Hao Yan-Ming, Zhou Yan, Zhao Miao
Chin. Phys., 2005, 14 (7): 1449-1452 doi: 10.1088/1009-1963/14/7/032
Full Text: [PDF 216 KB] (Downloads:401)
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The structural and magnetic properties of Dy$_{2}$AlFe$_{13}$Mn$_{3}$compound have been investigated by means of x-ray diffraction and magnetization measurements. The Dy$_{2}$AlFe$_{13}$Mn$_{3}$ compound has a hexagonal Th$_{2}$Ni$_{17}$-type structure. Negative thermal expansion is found in the Dy$_{2}$AlFe$_{13}$Mn$_{3}$ compound at the temperatures ranging from 245 to 344K by x-ray dilatometry. The coefficient of the average thermal expansion is $\overline \alpha =-1.1\times 10^{-4}$K$^{-1}$. The spontaneous magnetostrictive deformations in the 105--360K temperature range have been calculated by means of the differences between the experimental values of the lattice parameters and the corresponding values extrapolated from the paramagnetic range. The result shows that the spontaneous volume magnetostrictive deformation \textit{$\omega $}$_{\rm s}$ increases from 7.0$\times $10$^{-3}$ at 105K to 9.1$\times $10$^{-3}$ at 245K, and then decreases with the temperature increasing. The spontaneous linear magnetostrictive deformation $\la_{c}$ along the $c$ axis decreases as temperature increases. The spontaneous linear magnetostrictive deformation $\la_{a}$ in basal-plane increases from 0.8$\times $10$^{-3}$ at 105K to 3.4$\times $10$^{-3}$ at 270K, and then decreases with the temperature increasing further.

ESR of dislocation defects in MgF2 crystals-with more than 130 line peaks

Hou Bi-Hui, Zheng Ying-Guang, Shao Meng, Liu Feng-Yan, Fan Zhi-Da
Chin. Phys., 2005, 14 (7): 1453-1456 doi: 10.1088/1009-1963/14/7/033
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In this work, more than 130 line peaks in electron spin resonance (ESR) spectra have been discovered of the laser material MgF$_{2}$ crystal in room-temperature experiments. A sample is cut from the shoulder part of the MgF$_{2 }$ crystal, and another is from the MgF$_{2}$:Co crystal. The samples were not treated by any irradiation. The same anisotropic ESR spectra of the two samples indicate that the dopant Co$^{2+}$ introduces defects which induce the same multinuclear free radicals as in dislocations in the sample of MgF$_{2}$. These paramagnetic solid multinuclear free radicals show good stability, and their ESR spectra are found to be anisotropic. ESR signals are derived from three different types of multinuclear free radicals from a tentative simulation analysis.When the direction of the applied magnetic field is along the [100] or [010] orientation of the crystal, the magnetic field at which the ESR signals are detected ranges from 0.2294T to 0.4654T and the width of this range is 0.2362T (corresponding to an energy band of 0.233eV); the most narrow peak in the ESR spectra has a width $\Da H$ about 1.28$\times $10$^{-3}$T. This width $\Delta H$, equivalent to the energy difference of two neighbouring levels, is very small, only 1.85$\times $10$^{-7}$eV (or 1.46$\times $10$^{- 3}$cm$^{-1}$).This fact indicates that the ground state is highly degenerate, and splits into nearly quasi-continuous energy levels like an energy band in an applied magnetic field. It may be served as a new starting point of solid laser exciter frequency modulation.

Investigation of the a-Si:H films by using thermal and light-induced annealing treatment in atomic hydrogen atmosphere in H-W-ECR CVD system

Hu Yue-Hui, Zhu Xiu-Hong, Chen Guang-Hua, Rong Yan-Dong, Li Ying, Song Xue-Mei, Zhou Huai-En, Gao Zhuo, Ma Zhan-Jie, Deng Jin-Xiang
Chin. Phys., 2005, 14 (7): 1457-1464 doi: 10.1088/1009-1963/14/7/034
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To Investigate the stability of hydrogenated amorphous silicon (a-Si:H) films, the thermal and light-induced annealing treatment in an atomic hydrogen atmosphere (TLAH) is carried out by using a new hot-wire-assisted microwave electron-cyclotron-resonance chemical vapour deposition system (H-W-ECR CVD) modified from a conventional microwave electronic cyclotron resonance chemical vapor deposition system (MWECR CVD). In order to compare with the TLAH method, the experiments of thermal annealing, and thermal and light-induced annealing are also performed. Meanwhile, for the purpose of analysing the photoconductivity degradation quantitative, the photoconductivity degradation is assumed to obey the extended exponential law: 1/$\sigma _{\rm ph}$=1/$\sigma _{\rm s}$-(1/$\sigma _{\rm s}$-1/$\sigma _{0})\exp[-(t/\tau )^{\beta }$], where the extended exponential $\beta $ and the time constant $\tau $ are gained by the slope and the intercept of the line according to the linear relationship between $\ln \left( { - \ln \left( {\dfrac{\sigma _{\rm s}^{ - 1} - \sigma _{\rm ph}^{ - 1} }{\sigma _{\rm s}^{ - 1} - \sigma _0^{ - 1} }} \right)} \right)$ and ln$t$, deduced from the extended exponential law; the photoconductivity saturation value $\sigma _{\rm s}$ can be obtained by Gaussian fitting according to the relationship between photoconductivity and light-soaking time in the logarithmic coordinate system. The experimental results show that the TLAH can improve the stability, microstructure and opto-electronic properties of the annealed a-Si:H films, obviously decrease their optical band gaps, and remarkably move their photoluminescence spectrum (PL) peaks toward low energies.

Incident angle dependence of secondary electron emission from carbon induced by swift H2+

Lu Qi-Liang, Zhou Zhu-Ying, Shi Li-Qun, Zhao Guo-Qing
Chin. Phys., 2005, 14 (7): 1465-1470 doi: 10.1088/1009-1963/14/7/035
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The incident angle dependence of secondary electron emission induced by a swift H$_{2}^{+}$ ion impinging on carbon is studied using the Monte Carlo method combined with the semiempirical theory. The relationships both between the electron emission yield and the project angle and between the statistics and the projectile angle are investigated. The results show that the backward electron emission yield deviates from the inverse cosine law, due to the effect of the valence electrons of H$_{2}^{+}$. The ratio of the forward electron emission yield to the backward electron emission yield at the inclining incidence is different from that at the normal incidence. The statistical distribution of electron emission is independent of the incident angle. The value of $b$, the deviation parameter from the Poisson distribution, increases with projectile energy.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

Uncertainty relation and black hole entropy of Kerr spacetime

Hu Shuang-Qi, Zhao Ren
Chin. Phys., 2005, 14 (7): 1477-1481 doi: 10.1088/1009-1963/14/7/037
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The properties of thermal radiation are discussed by using a new equation of state density, which is motivated by the generalized uncertainty relation in the quantum gravity. There is no burst at the last stage of the emission of Kerr black hole. When the new equation of state density is utilized to investigate the entropy of a Bosonic field and Fermionic field outside the horizon of a static Kerr black hole, the divergence appearing in the brick wall model is removed, without any cutoff. The entropy proportional to the horizon area is derived from the contribution of the vicinity of the horizon.
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