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CN 11-5639/O4
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Chin. Phys. B  
  Chin. Phys. B--2005, Vol.14, No.12
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GENERAL

Observer-based passive control for uncertain linear systems with delay in state and control input

Li Gui-Fang, Li Hui-Ying, Yang Cheng-Wu
Chin. Phys., 2005, 14 (12): 2379-2386 doi: 10.1088/1009-1963/14/12/001
Full Text: [PDF 247 KB] (Downloads:755)
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This paper deals with the robust passivity synthesis problem for a class of uncertain linear systems with time-varying delay in state and control input. The parameter uncertainties are norm-bounded and allowed to appear in all matrices of the model. The problem aims at designing an observer-based dynamic output-feedback controller that robustly stabilizes the uncertain systems and achieves the strict passivity of closed-loop systems for all admissible uncertainties. By converting the problem at hand into a class of strictly passive control problem for a parameterized system, the explicit solution is established and expressed in terms of a linear matrix inequality. A numerical example is provided to demonstrate the validity of the proposed approach.

The homotopic mapping method for sea--air oscillator model of interdecadal climate fluctuations

Mo Jia-Qi, Lin Yi-Hua, Wang Hui
Chin. Phys., 2005, 14 (12): 2387-2390 doi: 10.1088/1009-1963/14/12/002
Full Text: [PDF 200 KB] (Downloads:524)
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The El Ni\~{n}o/La Ni\~{n}a Southern Oscillation (ENSO) is an interannual phenomenon involved in the tropical Pacific ocean--atmosphere interactions. In this paper, a coupled system of sea--air oscillator model is studied. The aim is to create an asymptotic solving method of nonlinear equation for the ENSO model. And based on a class of oscillators of ENSO model, employing the method of homotopic mapping, the approximate solution of corresponding problem is studied. It is proven from the results that the homotopic method can be used for analysing the sea surface temperature anomaly in the equatorial eastern Pacific and the thermocline depth anomaly of the atmosphere--ocean oscillation for ENSO model.

Methods of analytical mechanics for solving differential equations of first order

Wu Hui-Bin, Mei Feng-Xiang
Chin. Phys., 2005, 14 (12): 2391-2394 doi: 10.1088/1009-1963/14/12/003
Full Text: [PDF 189 KB] (Downloads:886)
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A differential equation of first order can be expressed by the equation of motion of a mechanical system. In this paper, three methods of analytical mechanics, i.e. the Hamilton--Noether method, the Lagrange--Noether method and the Poisson method, are given to solve a differential equation of first order, of which the way may be called the mechanical methodology in mathematics.

Interaction between two folded solitary waves for a modified Broer--Kaup system

Wu Xiao-Fei, Zhu Jia-Min, Ma Zheng-Yi
Chin. Phys., 2005, 14 (12): 2395-2401 doi: 10.1088/1009-1963/14/12/004
Full Text: [PDF 343 KB] (Downloads:474)
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By means of a Painlev\'{e}--B\"{a}cklund transformation and a multi-linear separation-of-variable approach, abundant localized coherent excitations of a modified Broer--Kaup system are derived. There appear possible phase shifts for the interactions of the (2+1)-dimensional novel localized structures, which are discussed in this paper.

Rotation and vibration of diatomic molecule oscillator with hyperbolic potential function

Lu Jun, Qian Hui-Xian, Li Liang-Mei, Liu Feng-Ling
Chin. Phys., 2005, 14 (12): 2402-2406 doi: 10.1088/1009-1963/14/12/005
Full Text: [PDF 224 KB] (Downloads:521)
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The explicit expressions of energy eigenvalues and eigenfunctions of bound states for a three-dimensional diatomic molecule oscillator with a hyperbolic potential function are obtained approximately by means of the hypergeometric series method. Then for a one-dimensional system, the rigorous solutions of bound states are solved with a similar method. The eigenfunctions of a one-dimensional diatomic molecule oscillator, expressed in terms of the Jacobi polynomial, are employed as an orthonormal basis set, and the analytic expressions of matrix elements for position and momentum operators are given in a closed form.

Generation of maximally entangled states in a two-component Bose-Einstein condensate

Wei Wei
Chin. Phys., 2005, 14 (12): 2407-2410 doi: 10.1088/1009-1963/14/12/006
Full Text: [PDF 201 KB] (Downloads:463)
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We study analytically the generation of maximally entangled states (MESs) formed by a two-component Bose--Einstein condensate (BEC) trapped in an adiabatically driven single potential well. Under the condition of the linear interaction controlled by a driven field being much stronger than the effective nonlinear interaction between the components, MESs, as some particular cases of superpositions of spin coherent states (SSCS), may emerge periodically along with not only time evolution but also the equidifferent change of the linear coupling strength at a particular time.

Quantum tunnelling radiation of Einstein--Maxwell--Dilaton--Axion black hole

Yang Shu-Zheng, Jiang Qing-Quan, Li Hui-Ling
Chin. Phys., 2005, 14 (12): 2411-2414 doi: 10.1088/1009-1963/14/12/007
Full Text: [PDF 214 KB] (Downloads:748)
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By taking the energy conservation and angular momentum conservation into account, the characteristics of the quantum-tunnelling radiation of Einstein--Maxwell--Dilaton--Axion black hole are studied and the result shows that the tunnelling rate of such a black hole is relevant to Bekenstein--Hawking entropy and that the obtained radiation spectrum is not pure thermal.

The energy of Einstein--Maxwell dilation--axion black hole in the teleparallel geometry

Xu Shan-Xian, Jing Ji-Liang
Chin. Phys., 2005, 14 (12): 2415-2420 doi: 10.1088/1009-1963/14/12/008
Full Text: [PDF 247 KB] (Downloads:379)
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The energy of the stationary axisymmetric Einstein--Maxwell dilation--axion (EMDA) black hole is studied in the context of the Hamiltonian formulation of the teleparallel equivalence of general relativity (TEGR).The energy expression for the finite and arbitrary space-like two spheres is exactly computed by means of the integral form of the constraint equations of the formalism naturally without any restriction on the metric parameters. We also show that our results give the same values obtained by other methods for some special cases.

Generalized reduced-order synchronization of chaotic system based on fast slide mode

Gao Tie-Gang, Chen Zeng-Qiang, Yuan Zhu-Zhi
Chin. Phys., 2005, 14 (12): 2421-2427 doi: 10.1088/1009-1963/14/12/009
Full Text: [PDF 346 KB] (Downloads:428)
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A new kind of generalized reduced-order synchronization of different chaotic systems is proposed in this paper. It is shown that dynamical evolution of third-order oscillator can be synchronized with the canonical projection of a fourth-order chaotic system generated through nonsingular states transformation from a cell neural net chaotic system. In this sense, it is said that generalized synchronization is achieved in reduced-order. The synchronization discussed here expands the scope of reduced-order synchronization studied in relevant literatures. In this way, we can achieve generalized reduced-order synchronization between many famous chaotic systems such as the second-order D\"{u}ffing system and the third-order Lorenz system by designing a fast slide mode controller. Simulation results are provided to verify the operation of the designed synchronization.

Detecting dynamical complexity changes in time series using the base-scale entropy

Li Jin, Ning Xin-Bao, Wu Wei, Ma Xiao-Fei
Chin. Phys., 2005, 14 (12): 2428-2432 doi: 10.1088/1009-1963/14/12/010
Full Text: [PDF 265 KB] (Downloads:440)
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Timely detection of dynamical complexity changes in natural and man-made systems has deep scientific and practical meanings. We introduce a complexity measure for time series: the base-scale entropy. The definition directly applies to arbitrary real-word data. We illustrate our method on a practical speech signal and in a theoretical chaotic system. The results show that the simple and easily calculated measure of base-scale entropy can be effectively used to detect qualitative and quantitative dynamical changes.

Molar volume, thermal expansivity and isothermal compressibility of trans-decahydronaphthalene up to 200MPa and 446K

Zhu Hu-Gang, Liu Zhi-Hua, Tian Yi-Ling, Xue Yuan, Yin Liang
Chin. Phys., 2005, 14 (12): 2433-2439 doi: 10.1088/1009-1963/14/12/011
Full Text: [PDF 264 KB] (Downloads:381)
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The molar volume isotherms of {trans}-decahydronaphthalene (C_{10}H_{18}) between 293 and 446 K and at pressures from 10 to 200 MPa have been determined. A modified Tait equation of state is used to fit each experimental molar volume isotherm with a maximum average deviation of 0.029%. The thermal expansivity (cubic expansion coefficient) \alpha and isothermal compressibility \kappa were determined by fitting the slopes of the isobaric curves and isotherms, respectively. The coefficients in the equation V_m=C_1+C_2 T+C_3 T^2 - C_4 p - C_5 pT have been fitted with an average deviation of 1.03%.

Experimental study on helium optical electron polarimetry

Ding Hai-Bing, Pang Wen-Ning, Liu Yi-Bao, Shang Ren-Cheng
Chin. Phys., 2005, 14 (12): 2440-2443 doi: 10.1088/1009-1963/14/12/012
Full Text: [PDF 220 KB] (Downloads:438)
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Optical electron polarimetry is suitable for calibration of a spin-polarized electron source, especially for measurement of polarization of spin-polarized electron beam. In this paper, a new optical electron polarimeter is described, which is based on the circularly polarized He radiation induced by the bombarding of He atoms with spin-polarized electrons. The theoretical basis of the optical electron polarimetry and the structure of the optical electron polarimeter are discussed. The measurement of polarization of spin-polarized electrons produced from a new GaAs (100) spin-polarized electron source is carried out. The result of polarization of 30.8% for our spin-polarized electron source is obtained using the He optical electron polarimeter.
NUCLEAR PHYSICS

Investigation on the deformation of Ne and Mg isotope chains within relativistic mean-field model

Chen Jin-Gen, Cai Xiang-Zhou, Wang Ting-Tai, Ma Yu-Gang, Ren Zhong-Zhou, Fang De-Qing, Zhong Chen, Wei Yi-Bin, Guo Wei, Zhou Xing-Fei, Wang Kun, Ma Guo-Liang, Tian Wen-Dong, Chen Jin-Hui, Yan Ting-Zhi, Zuo Jia-Xu, Ma Chun-Wang, Shen Wen-Qing
Chin. Phys., 2005, 14 (12): 2444-2450 doi: 10.1088/1009-1963/14/12/013
Full Text: [PDF 308 KB] (Downloads:509)
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Ne and Mg isotope chains are investigated based on constrained calculations in the framework of a deformed relativistic mean-field (RMF) model with the NL075 parameter set. The calculated quadrupole deformation and binding energy are compared with other theoretical results as well as the available experimental data. It shows that the calculated deformations of Ne and Mg with the NL075 are more accurate than those obtained with the NL-SH. It is predicted that ^{19,29,32}Ne and ^{20,31}Mg maybe have a triaxial deformation and ^{25-28}Ne and ^{27-30}Mg exhibit a shape coexistence probably. The closure effect of neutron number N=8 for ^{20}Mg is predicted to be very weak.

Fragmentation in 16O-emulsion interactions at 3.7 A GeV

Zhang Dong-Hai, Li Zhen-Yu, Li Hui-Ling, Li Jun-Sheng
Chin. Phys., 2005, 14 (12): 2451-2457 doi: 10.1088/1009-1963/14/12/014
Full Text: [PDF 244 KB] (Downloads:486)
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The topology of 16O fragmentation at 3.7 A GeV in reactions with emulsion nuclei is presented. The multiplicity distributions of projectile fragments,charged secondaries and their dependences on the projectile residues are discussed.

Azimuthal distributions of final-state particles and fragments and transverse structure of emission source in high-energy nucleus--nucleus collisions

Liu Fu-Hu, Ma Yin-Qun, Duan Mai-Ying
Chin. Phys., 2005, 14 (12): 2458-2466 doi: 10.1088/1009-1963/14/12/015
Full Text: [PDF 294 KB] (Downloads:541)
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The azimuthal distributions of final-state particles and fragments produced in high-energy nucleus--nucleus collisions are described by a modified multisource ideal gas model which contains the expansions and movements of the emission sources. The transverse structures of the sources are given in the transverse plane by momentum components p_x and p_y,and described by parameters in the model. The results of the azimuthal distributions, calculated by the Monte Carlo method, are in good agreement with the experimental data in nucleus--nucleus collisions at high energies.
CLASSICAL AREAS OF PHENOMENOLOGY

Improvement in refractive-index change in LiNbO3:Ce:Cu by applying an external electric field

Dai Cui-Xia, Liu Li-Ren, Liu De-An, Zhou Yu, Chai Zhi-Fang, Luan Zhu
Chin. Phys., 2005, 14 (12): 2491-2495 doi: 10.1088/1009-1963/14/12/020
Full Text: [PDF 326 KB] (Downloads:413)
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By jointly solving two-centre material equations with a nonzero external electric field and coupled-wave equations, we have numerically studied the dependence of the non-volatile holographic recording in LiNbO$_{3}$:Ce:Cu crystals on the external electric field. The dominative photovoltaic effect of the non-volatile holographic recording in doubly doped LiNbO$_{3}$ crystals is directly verified. And an external electric field that is applied in the positive direction along the $c$-axis (or a large one in the negative direction of the $c$-axis) in the recording phase and another one that is applied in the negative direction of the $c$-axis in the fixing phase are both proved to benefit strong photorefractive performances. Experimental verifications are given with a small electric field applied externally.

Influence of Doppler-broadening on absorption-dispersion properties in a resonant coherent medium

Xu Wei-Hua, Gao Jin-Yue
Chin. Phys., 2005, 14 (12): 2496-2502 doi: 10.1088/1009-1963/14/12/021
Full Text: [PDF 248 KB] (Downloads:519)
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We investigate the influence of Doppler broadening on absorption-dispersion properties in a four-level atomic system that can evolve from a normal dispersion to an anomalous dispersion. Our results show that the absorption-dispersion properties become strongly dependent on the propagation directions of the applied fields if Doppler broadening is taken into account. Especially, the switchover in the sign of the dispersion is still achievable even in the presence of Doppler broadening if properly arranging the propagation directions of the applied fields, which is in contrast with the otherwise behaviours in some other configurations.

Investigation of photoelectron action in cubic AgCl emulsion doped with formate ions

Yang Shao-Peng, Zhou Xian, Fu Guang-Sheng, Li Xiao-Wei, Tian Xiao-Dong, Han Li
Chin. Phys., 2005, 14 (12): 2503-2506 doi: 10.1088/1009-1963/14/12/022
Full Text: [PDF 215 KB] (Downloads:474)
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In recent years, the formate ion (HCO$_2 ^-)$ as a kind of hole-to-electron converter has attracted much attention of photographic researchers. The formate ions can trap photo-generated holes, eliminate or reduce the electron loss caused by electron--hole recombination in latent image formation process. Through the hole-to-electron conversion, it can also release an extra electron or electron carrier, improving photosensitivity. In this paper the microwave absorption and dielectric spectrum detection technique is used to detect the time evolution behaviour of free photoelectrons generated by 35ps laser pulses in cubic AgCl emulsions doped with formate ions. The influence of different doping conditions of formate ions on the photoelectron decay kinetics of AgCl is analysed. It is found that when the HCO$_2 ^-$ content is 10$^{ - 3}$mol/mol Ag and the doping position is 90{\%} the electron decay time and lifetime reach their maxima due to the efficient trap of holes by formate ions.

Photonic band structures of two-dimensional photonic crystals with deformed lattices

Cai Xiang-Hua, Zheng Wan-Hua, Ma Xiao-Tao, Ren Gang, Xia Jian-Bai
Chin. Phys., 2005, 14 (12): 2507-2513 doi: 10.1088/1009-1963/14/12/023
Full Text: [PDF 279 KB] (Downloads:1330)
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Using the plane-wave expansion method, we have calculated and analysed the changes of photonic band structures arising from two kinds of deformed lattices, including the stretching and shrinking of lattices. The square lattice with square air holes and the triangular lattice with circular air holes are both studied. Calculated results show that the change of lattice size in some special ranges can enlarge the band gap, which depends strongly on the filling factor of air holes in photonic crystals; and besides, the asymmetric band edges will appear with the broken symmetry of lattices.

Quantization of light energy directly from classical electromagnetic theory in vacuum

She Wei-Long
Chin. Phys., 2005, 14 (12): 2514-2521 doi: 10.1088/1009-1963/14/12/024
Full Text: [PDF 258 KB] (Downloads:466)
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It is currently believed that light quantum or the quantization of light energy is beyond classical physics, and the picture of wave--particle duality,which was criticized by Einstein but has attracted a number of experimental researches, is necessary for the description of light. It is shown in this paper, however, that the quantization of light energy in vacuum, which is the same as that in quantum electrodynamics, can be derived directly from the classical electromagnetic theory through the consideration of statistics based on classical physics. Therefore, the quantization of energy is an intrinsic property of light as a classical electromagnetic wave and has no need of being related to particles.

Local resonant characteristics of a layered cylinder embedded in the elastic medium

Qin Bo, Chen Jiu-Jiu, Cheng Jian-Chun
Chin. Phys., 2005, 14 (12): 2522-2528 doi: 10.1088/1009-1963/14/12/025
Full Text: [PDF 303 KB] (Downloads:663)
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Three kinds of resonant modes of a single layered circular elastic cylinder embedded in the elastic medium are analysed by considering the oscillation of the scatter's core, based on the fact that the core moves as a rigid body when the shell material is very compliant. The resonant frequencies of the single resonator acquired by our method are in good agreement with those calculated by the local interaction simulation approach (LISA) for the local resonant phononic crystal. Therefore, the local resonant characteristics of a single layered circular elastic cylinder can be used to evaluate the resonant frequencies of the phononic crystal. The effects of the geometrical and physical parameters of the shell and the core are also studied in details. This work is significant for designing the locally resonant phononic crystal based on the local resonant characteristics of the single resonator, and the resonant frequencies can be tuned by selecting the geometrical sizes and the materials.

Orientation distribution of fibres in a channel flow of fibre suspension

Lin Jian-Zhong, Li Jun, Zhang Wei-Feng
Chin. Phys., 2005, 14 (12): 2529-2538 doi: 10.1088/1009-1963/14/12/026
Full Text: [PDF 324 KB] (Downloads:372)
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The orientation and concentration distributions of fibres in laminar and turbulent channel flows are investigated numerically. The obtained results are in good agreement with the experimental data. In the laminar flow regime, more fibres orient to the flow direction as the Reynolds number increases. The shear rate of fluid around a fibre plays an important role in determining the orientation distribution of fibres, while the fibre density and the fibre aspect-ratio have marginal influence on the orientation distribution. In the turbulent regime, the orientation distribution of fibres becomes more homogeneous with the increase of Reynolds number, and the concentration profile is flatter than that in the laminar regime. The fluctuating intensity of fibre velocity in the downstream direction is larger than that in the lateral directions.
ATOMIC AND MOLECULAR PHYSICS

Investigation of outer valence orbital of CF2Cl2 by a new type of electron momentum spectrometer

Ning Chuan-Gang, Ren Xue-Guang, Deng Jing-Kang, Su Guo-Lin, Zhang Shu-Feng, Huang Feng, Li Gui-Qin
Chin. Phys., 2005, 14 (12): 2467-2473 doi: 10.1088/1009-1963/14/12/016
Full Text: [PDF 273 KB] (Downloads:438)
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Electronic states of CF$_{2}$Cl$_{2}$ (dichlorodifluoromethane, Freon 12) have been studied using a new type of electron momentum spectrometer with a very high efficiency at an impact energy of 1200 eV plus binding energy. The experimental electron momentum profiles are compared with the density functional theory (DFT) and Hartree--Fock (HF) calculations. The relationship between orbital assignments in different coordinate systems is discussed. A new method of difference analysis based on the new type of electron momentum spectrometer is used to clarify the ambiguities regarding the orbital ordering.

Ultra-narrow bandwidth optical filters consisting of one-dimensional photonic crystals with anomalous dispersion materials

Liu Jiang-Tao, Zhou Yun-Song, Wang Fu-He, Gu Ben-Yuan
Chin. Phys., 2005, 14 (12): 2474-2477 doi: 10.1088/1009-1963/14/12/017
Full Text: [PDF 204 KB] (Downloads:510)
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We present a new type of optical filter with an ultra-narrow bandwidth and a wide field-of-view (FOV). This kind of optical filter consists of one-dimensional photonic crystal (PC) incorporating an anomalous-dispersion-material (ADM) with, for instance, an anomalous dispersion of $6$P$_{3/2}\leftarrow6$S$_{1/2}$ hyperfine structure transition of a caesium atom. The transmission spectra of optical filters are calculated by using the transfer-matrix method. The simulation results show that the designed optical filter has a bandwidth narrower than 0.33GHz and a wide FOV of $\pm30^{\circ}$ as well. The response of transmission spectrum to an external magnetic field is also investigated.

Superexcited states of carbon monoxide studied by fast-electron impact

Fan Lan-Lan, Zhong Zhi-Ping, Zhu Lin-Fan, Liu Xiao-Jing, Cheng Hua-Dong, Yuan Zhen-Sheng, Xu Ke-Zun
Chin. Phys., 2005, 14 (12): 2478-2483 doi: 10.1088/1009-1963/14/12/018
Full Text: [PDF 272 KB] (Downloads:687)
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Absolute optical oscillator strength density and double differential cross section spectra of CO below 120\,eV are determined by fast electron impact. Some peaks above the first ionization threshold stand out as the momentum transfer square $K^2$ increases. The doubly excited Rydberg states converging to $C~^2\Sigma^+$, $D~^2\Pi$, and $F~^2\Pi$ states of CO$^+$, respectively, are confirmed in our spectra. Another peak at around 32\,eV is assigned to the transition of $(3\sigma)^{-1}(2\pi)^1~^1\Pi\leftarrow~X^1\Sigma^+ $.

Nanosecond-time-resolved infrared spectroscopic study of fast relaxation kinetics of protein folding by means of laser-induced temperature-jump

Zhang Qing-Li, Wang Li, Weng Yu-Xiang, Qiu Xiang-Gang, Wang Wei-Chi, Yan Ji-Xiang
Chin. Phys., 2005, 14 (12): 2484-2490 doi: 10.1088/1009-1963/14/12/019
Full Text: [PDF 261 KB] (Downloads:519)
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Elucidating the initial kinetics of folding pathways is critical to the understanding of the protein folding mechanism. Transient infrared spectroscopy has proved a powerful tool to probe the folding kinetics. Herein we report the construction of a nanosecond laser-induced temperature-jump ($T$-jump) technique coupled to a nanosecond time-resolved transient mid-infrared (mid-IR) spectrometer system capable of investigating the protein folding kinetics with a temporal resolution of 50 ns after deconvolution of the instrumental response function. The mid-IR source is a liquid N$_{2}$ cooled CO laser covering a spectral range of 5.0$\mu$m (2000 cm$^{-1}) \sim $ 6.5$\mu$m (1540 cm$^{-1})$. The heating pulse was generated by a high pressure H$_{2}$ Raman shifter at wavelength of 1.9$\mu$m. The maximum temperature-jump could reach as high as 26$\pm $1$^{\circ}$C. The fast folding/unfolding dynamics of cytochrome $C$ was investigated by the constructed system, providing an example.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

The carbon impurity particle transport in ohmic discharges on the HT-7 tokamak

Zhou Qian, Wan Bao-Nian, Wu Zhen-Wei, Huang Juan
Chin. Phys., 2005, 14 (12): 2539-2545 doi: 10.1088/1009-1963/14/12/027
Full Text: [PDF 291 KB] (Downloads:834)
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The line-integrated optical measurement of impurity radiation profiles for the study of light impurity transport is performed in the HT-7 tokamak. The carbon impurity line emissivity is obtained by Abel inversion. The radial transport behaviours of carbon impurities at different central line averaged electron densities \overline {n_\e} are investigated in ohmic discharges. The diffusion coefficient D_{k}(r), the convection velocity W_{k}(r) and the total flux of the impurity ions \Ga _{k} decrease with the increase of \overline {n_\e} , which shows a reduction in the impurity particle transport at higher electron densities.

Laser pulse modulation instabilities in partially stripped plasma

Hu Qiang-Lin, Liu Shi-Bing, Jiang Yi-Jian
Chin. Phys., 2005, 14 (12): 2546-2551 doi: 10.1088/1009-1963/14/12/028
Full Text: [PDF 234 KB] (Downloads:418)
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The laser pulse modulation instabilities in partially stripped plasma were discussed based on the phase and group velocities of the laser pulse and the two processes that modulation instabilities excited. The excitation condition and growth rate of the modulation instability were obtained. It was found that the positive chirp and competition between normal and abnormal dispersions play important roles in the modulation instability. In the partially stripped plasma, the increased positive chirp enhances the modulation instability, and the dispersion competition reduces it.

Topology of toroidal helical fields in non-circular cross-sectional tokamaks

Zha Xue-Jun, Zhu Si-Zheng, Yu Qing-Quan, Wang Yan
Chin. Phys., 2005, 14 (12): 2552-2559 doi: 10.1088/1009-1963/14/12/029
Full Text: [PDF 342 KB] (Downloads:569)
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The ordinary differential magnetic field line equations are solved numerically; the tokamak magnetic structure is studied on Hefei Tokamak-7 Upgrade (HT-7U) when the equilibrium field with a monotonic $q$-profile is perturbed by a helical magnetic field. We find that a single mode ($m,n$) helical perturbation can cause the formation of islands on rational surfaces with $q=m/n$ and $q=(m\pm 1, \pm 2, \pm 3,\ldots) /n$ due to the toroidicity and plasma shape (i.e. elongation and triangularity), while there are many undestroyed magnetic surfaces called Kolmogorov--Arnold--Moser (KAM) barriers on irrational surfaces. The islands on the same rational surface do not have the same size. When the ratio between the perturbing magnetic field $\tilde {B}_r (r)$ and the toroidal magnetic field amplitude $B_{\phi 0} $ is large enough, the magnetic island chains on different rational surfaces will overlap and chaotic orbits appear in the overlapping area, and the magnetic field becomes stochastic. It is remarkable that the stochastic layer appears first in the plasma edge region.

A numerical simulation of the backward Raman amplifying in plasma

Wang Hong-Yu, Huang Zu-Qia
Chin. Phys., 2005, 14 (12): 2560-2564 doi: 10.1088/1009-1963/14/12/030
Full Text: [PDF 240 KB] (Downloads:495)
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This paper describe a numerical simulation method for the interaction between laser pulses and low density plasmas based on hydrodynamic approximation. We investigate Backward Raman Amplifying (BRA) experiments and their variants. The numerical results are in good agreement with experiments.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

Nanocrystallization behaviour of a ternary amorphous alloy during isothermal annealing: a Monte Carlo simulation

Jin Shi-Feng, Wang Wei-Min, Zhou Jian-Kun, Guo Hong-Xuan, Webb J. F., Bian Xiu-Fang
Chin. Phys., 2005, 14 (12): 2565-2574 doi: 10.1088/1009-1963/14/12/031
Full Text: [PDF 746 KB] (Downloads:570)
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The nanocrystallization behaviour of Zr$_{70}$Cu$_{20}$Ni$_{10}$ metallic glass during isothermal annealing is studied by employing a Monte Carlo simulation incorporating with a modified Ising model and a $Q$-state Potts model. Based on the simulated microstructure and differential scanning calorimetry curves, we find that the low crystal-amorphous interface energy of Ni plays an important role in the nanocrystallization of primary Zr$_{2}$Ni. It is found that when $T

An improvement of the Peierls equation by taking into account the lattice effects

Wang Shao-Feng
Chin. Phys., 2005, 14 (12): 2575-2584 doi: 10.1088/1009-1963/14/12/032
Full Text: [PDF 287 KB] (Downloads:485)
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An improvement of the Peierls equation has been made by including the lattice effects. By using the non-trivially gluing mechanism for the simple cubic lattice, in which atoms interact with its first and second nearest neighbours through a central force, the dislocation equation has been derived rigorously for the isotropic case. In the slowly varying approximation, the Peierls equation with the improvement by including the lattice effects has been obtained explicitly. The new equation can be used to substitute for the old one in theoretical investigations of dislocations. The major change of the predicted dislocation structure is in the core region. The width of the dislocation given by using the new equation is about three times that given by the classical Peierls--Nabarro theory for the simple cubic lattice.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Vibrational analysis of L-serine using the density functional theory

Zhang Ying, Yin Wen, Zhang Peng, Xu Chang-Ye, Han Sheng-Hao, Li Ji-Chen
Chin. Phys., 2005, 14 (12): 2585-2589 doi: 10.1088/1009-1963/14/12/033
Full Text: [PDF 254 KB] (Downloads:584)
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In this paper, we present a computational study of L-serine using ab initio molecular dynamics simulation based on density functional theory (DFT) within the ultrasoft pseudopotentials and generalized-gradient approximation. Taking into account the intermolecular interactions, we can indeed simulate the features of the experimental results very well for L-serine zwitterions in its solid state. The vibrational spectrum of L-serine performed by DFT was in excellent agreement with our previous inelastic incoherent neutron scattering spectra measured at 20K for L-serine in the 10--200meV region on HET spectrometers at ISIS, Rutherford Appleton Laboratory.

Energy transfer probability in organic electrophosphorescence device with dopant

Dai Guo-Zhang, Li Hong-Jian, Pan Yan-Zhi, Dai Xiao-Yu, Xie Qiang
Chin. Phys., 2005, 14 (12): 2590-2594 doi: 10.1088/1009-1963/14/12/034
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Based on the energy transfer process from host to dopant in an organic electrophosphorescent (EP) device, the expression of energy transfer probability ($\eta )$ between the host (TPD) and guest (Ir(ppy)$_{3})$ EP systems was proposed. The results show that: ({1}) The rate of the triplet energy transfer ($K_{\rm HG}$ and $K_{\rm GH})$ increases exponentially with increasing donor-acceptor molecular distance ($R$), whereas decreases as the intermolecular distance ($R_{\rm HH})$ increases from 0.8 to 2.4 nm. Furthermore, $K_{\rm GH}$ changes more quickly than $K_{\rm HG.}$ ({2}) The energy transfer probability ($\eta )$ increases as $R$ reduces, and the $R_{\rm HH}$ changes can be safely neglected for $R<$0.9 nm. The situation changes for 0.9nm$ < R < 1.1$nm, $R_{\rm HH }$ ($<1$nm) plays an essential role when $\eta $ changes and increases with the latter. However, if $R > 1.1$nm, the transfer probability will be below zero. Here, the energy transfer principle may be less important, and the high electroluminescence (EL) quantum efficiency of phosphorescent system will be attributed to the direct electron-hole recombination in phosphorescent molecules. ({3}) The $\eta $ will increase when the Forster radius ($R_{0})$ increases or Gibb's energy decreases.

Origin of ultraviolet photovoltaic effect in Fe3O4 thin films

Zhao Kun, Feng Jia-Feng, Huang Yan-Hong, Zhao Jian-Gao, Lü Hui-Bin, Han Xiu-Feng, Zhan Wen-Shan
Chin. Phys., 2005, 14 (12): 2595-2597 doi: 10.1088/1009-1963/14/12/035
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We have investigated the transport and ultraviolet photovoltaic properties of Fe$_{3}$O$_{4}$ thin films grown on glass substrates by facing-target sputtering technique. The nonlinear dependence of current-density on voltage suggests that the transport process is most likely the tunnelling process and grain boundaries act as barriers. Furthermore, nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for Fe$_{3}$O$_{4}$ film under ultraviolet laser, since the energy gap of Fe$_{3}$O$_{4}$ is smaller than the ultraviolet photon energy. And then the built-in electric field near the grain boundaries will separate carriers, leading to the appearance of an instant photovoltage.
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