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Volume 22 Issue 12
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Original Articles
Double Wronskian Soliton Solution for Mixed AKNS System
HAO Hong-Hai, Lü Li-Li, CHEN Deng-Yuan
Chin. Phys. Lett. 2005, 22 (12): 2987-2990 .  
Abstract   PDF(pc) (190KB) ( 696 )
The Lax pair of the mixed Ablowitz--Kap--Newell--Segur (AKNS) system is obtained from compatibility condition. Hirota’s bilinear form is derived by some dependent variable transformation. Moreover, by means of the Wronskian technique, the double Wronskian form of soliton solutions are found. Specially, the two-soliton solution is presented.
Decay Rate of Energy Eigenfunctions in Classically Energetically Inaccessible Regions in more than One Dimensional Configuration Spaces
WANG Wen-Ge
Chin. Phys. Lett. 2005, 22 (12): 2991-2993 .  
Abstract   PDF(pc) (209KB) ( 462 )
An approximate formula is proposed for the decay rate of energy eigenfunctions in classically energetically inaccessible regions in more than one-dimensional configuration spaces. This is achieved by generalizing an approach proposed recently for energy eigenfunctions in the one-dimensional configuration space. The formula is tested numerically in the Pullen--Edmonds model.
Exact Solutions of the Klein--Gordon Equation with a New Anharmonic Oscillator Potential
ZHANG Min-Cang, WANG Zhen-Bang
Chin. Phys. Lett. 2005, 22 (12): 2994-2996 .  
Abstract   PDF(pc) (181KB) ( 717 )
We solve the Klein--Gordon equation with a new anharmonic oscillator potential and present the exact solutions. It is shown that under the condition of equal scalar and vector potentials, the Klein--Gordon equation could be separated into an angular equation and a radial equation. The angular solutions are the associated-Legendre polynomial and the radial solutions are expressed in terms of the confluent hypergeometric functions. Finally, the energy equation is obtained from the boundary condition satisfied by the radial wavefunctions.
Influence of Intrinsic Decoherence on Entanglement of Superconducting Charge Qubit in a Resonant Cavity
LIU Xiao-Nan, SHAO Bin, ZOU Jian
Chin. Phys. Lett. 2005, 22 (12): 2997-3000 .  
Abstract   PDF(pc) (221KB) ( 551 )
Taking the intrinsic decoherence effect into account, we investigate the entanglement dynamics of a superconducting charge qubit in a single-mode optical cavity. Concurrence, as the measure of entanglement of the coupled field-junction system, is calculated. In comparison, we also consider the entanglement of the system by using the entanglement parameter based on the ratio between mutual entropy and partial Von-Neumann entropy to investigate how the intrinsic decoherence affects the entanglement of the coupling system. Our results show that the evolution of the entanglement parameter has the behaviour similar to the concurrence and it is thus the well measure of entanglement for the mixed state in such a coupling system.
Quantum State Transfer between Two Distant Atoms by Connecting Two Cavities via Optical Fibres
OU Yong-Cheng, YUAN Chun-Hua, ZHANG Zhi-Ming,
Chin. Phys. Lett. 2005, 22 (12): 3001-3004 .  
Abstract   PDF(pc) (190KB) ( 550 )
A scheme is proposed to unconditionally implement state transfer between two distant atoms by sending the atoms across two distant cavities connected via an optical fibre, respectively. The field state, which preserves the information about the first atom, is transmitted from one cavity to the other along the fibre. A Faraday rotator integrated in the fibre can be designed to completely stop the fields reflected from the second cavity, thus after the field interacts with the second atom for a defined time, the state transfer can be accomplished with unit efficiency.
Fidelity of Quantum Teleportation for Single-Mode Squeezed State Light
ZHANG Jun-Xiang, XIE Chang-De, PENG Kun-Chi
Chin. Phys. Lett. 2005, 22 (12): 3005-3008 .  
Abstract   PDF(pc) (229KB) ( 705 )
The fidelity of quantum teleportation of a single-mode squeezed state of light is calculated based on the general theory of quantum-mechanical measurement in the Schrödinger picture. It is shown that the criterion for the nonclassical state teleportation is different from that for coherent state. F=1/2 is no longer the rigorous boundary between classical and quantum teleportation for a squeezed state of light. When the quantum entanglement of an Einstein--Podolsky--Rosen (EPR) beam used for teleportation and the parameters of the system are given, the fidelity depends on the squeezing of the input squeezed state. The higher the squeezing is, the smaller the fidelity is, and the lower the classical limitation of fidelity is. The dependence of the optimum gain for teleporting a squeezed vacuum state upon the EPR entanglement is also calculated. The results obtained provide important references for designing experimental systems of teleporting a non classical state and judging the quality of the teleported quantum state.

Constraint Dynamics and Tracking Control to Coherence of a Thermal Dissipative Qubit
AN Jun-Hong, WANG Shun-Jin, LUO Hong-Gang,
Chin. Phys. Lett. 2005, 22 (12): 3009-3012 .  
Abstract   PDF(pc) (237KB) ( 787 )
Constraint dynamics and tracking control strategy to stabilize the coherence of a decoherent system is applied to a dissipative qubit system at a finite temperature. By using a control field dependent on the dynamical state of the qubit via the constraint equations, we show that the coherence of the qubit can be preserved within a finite time duration by the feedback effect of the qubit system. It is also shown that the temperature plays a negative role to this coherence control strategy.
Integral Equations for the Spin-Weighted Spheroidal Wave unctions
TIAN Gui-Hua
Chin. Phys. Lett. 2005, 22 (12): 3013-3016 .  
Abstract   PDF(pc) (195KB) ( 633 )
We present new integral equations for the spin-weighted spheroidal wave fuctions which in turn should lead to global uniform estimates and should help in particular in the study of their dependence on the parameters. For the prolate spheroidal wavefunction with m=0, there exists the integral equation whose kernel is (sin x)/x, and the sinc function kernel (sin x)/x is of great mathematical significance. We also extend the similar sinc function kernel (sin x)/x to the case m≠0 and s≠0, which interestingly turn out as some kind of Hankel transformations.
Lorentz Invariance and Brownian Motion of Test Particles with Constant Classical Velocity in Electromagnetic Vacuum
ZHANG Jia-Lin, YU Hong-Wei
Chin. Phys. Lett. 2005, 22 (12): 3017-3020 .  
Abstract   PDF(pc) (180KB) ( 440 )
We show that the velocity and position dispersions of a test particle with a nonzero constant classical velocity undergoing Brownian motion caused by electromagnetic vacuum fluctuations in a space with plane boundaries can be obtained from those of the static case by Lorentz transformation. We explicitly derive the Lorentz transformations relating the dispersions of the two cases and then apply them to the case of the Brownian motion of a test particle with a constant classical velocity parallel to the boundary between two conducting planes. Our results show that the influence of a nonzero initial velocity is negligible for nonrelativistic test particles.
Experimental Investigation on Dual Wavelength High-Frequency Chaos Generation and Synchronization
SANG Xin-Zhu, YU Chong-Xiu, WANG Kui-Ru, CHU Pak L.
Chin. Phys. Lett. 2005, 22 (12): 3019-3031 .  
Abstract   PDF(pc) (216KB) ( 427 )
Dual wavelength high-frequency chaos based on nonlinear effects is generated in an erbium-doped fibre ring laser, where tunable filters (TFs) are used to select the wavelength. A receiving fibre laser with an open-loop structure is constructed with identical parameters as the transmitting fibre laser. By tuning the TFs and the fibre delay line in the receiving fibre laser, chaos synchronization has been observed at anyone the two wavelengths after the chaos is transmitted over 1km. It is of far reaching importance to construct the high capacity chaos communication system.
Gravitational Faraday Rotation of the Earth and Its Possible Test
LIU Lin-Xia, SHAO Cheng-Gang, LUO Jun
Chin. Phys. Lett. 2005, 22 (12): 3021-3024 .  
Abstract   PDF(pc) (203KB) ( 508 )
It is shown that the rotation of the polarization plane of rays induced by a rotating body can be accumulated by means of a long baseline optical cavity. Theoretical analysis shows that the presently proposal experimental scheme is possible to test this gravitational Faraday rotation effect on the Earth, especially including how to effectively suppress the dominant part of the Sagnac effect due to the rotation of the Earth with a reasonable experimental configuration.
Escape from a Riddled-Like Basin
CHAO Xiao-Gang, DAI Jun, WANG Wen-Xiu, HE Da-Ren
Chin. Phys. Lett. 2005, 22 (12): 3025-3028 .  
Abstract   PDF(pc) (232KB) ( 342 )
We investigate a system described by a conservative and a dissipative map concatenation. A fat fractal forbidden net, induced by interaction between discontinuous and noninvertible properties, introduces rippled-like attraction basins of two periodic attractors. Small areas, which serve as escaping holes of a new type of crisis, are dominated by conventional strong dissipation and are bounded by the forbidden region, but only in the vicinity of each periodic point. Based on this understanding, the scaling behaviour of the averaged lifetime of the crisis is analytically and numerically determined to be <τ> ∝ (b-b0)γ, where b denotes the control parameter, b0 denotes its critical threshold, and γ simeq -1.5.
Casimir Effect at Finite Temperature in the Presence of Compactified Universal Extra Dimensions
CHENG Hong-Bo
Chin. Phys. Lett. 2005, 22 (12): 3032-3035 .  
Abstract   PDF(pc) (226KB) ( 393 )
We analyse the Casimir effect for parallel plates at finite temperature in the presence of compactified universal extra dimensions and analytically show the thermal corrections to the effect in detail. The Casimir effect for different sizes of universal extra dimensions is investigated to test the five-dimensional Kaluza--Klein theory.
Does There Exist Only One Solution of the Dyson--Schwinger Equation for the Quark Propagator in the Case of Non-Zero Current Quark Mass
ZONG Hong-Shi, , SUN Wei-Min, , PING Jia-Lun, Lü Xiao-Fu, WANG Fan,
Chin. Phys. Lett. 2005, 22 (12): 3036-3039 .  
Abstract   PDF(pc) (201KB) ( 449 )
It is shown on general ground that there exist two qualitatively distinct solutions of the Dyson--Schwinger equation for the quark propagator in the case of non-zero current quark mass. One solution corresponds to the ``Nambu--Goldstone'' phase and the other one corresponds to the ``Wigner'' phase in the chiral limit.
Dynamical Study on Fusion Barrier in the Synthesis of Superheavy Elements
FENG Zhao-Qing, , JIN Gen-Ming, ZHANG Feng-Shou, FU Fen, HUANG Xi,
Chin. Phys. Lett. 2005, 22 (12): 3040-3043 .  
Abstract   PDF(pc) (246KB) ( 395 )
Based on the improved isospin-dependent quantum molecular dynamics model, the fusion barrier in the synthesis of superheavy elements is studied dynamically. Deformation effect and nucleon transfer in neck region are also investigated systematically, which can lower the dynamical barrier since the neck formation. It is shown that the neck radius is dependent on the incident energy and collision orientation. For the static barrier, the model almost gives the same results with the proximity potential.
Effects of Isospin Equilibrium on Cold Fusion of Superheavy Nuclei
LIU Zu-Hua, BAO Jing-Dong,
Chin. Phys. Lett. 2005, 22 (12): 3044-3047 .  
Abstract   PDF(pc) (224KB) ( 405 )
The neutron flow model predicts that neutrons start to flow freely between the approaching nuclei 58Fe and 208Pb at s=3fm, a length in which the effective surfaces of these nuclei are 3fm apart. As a result of neutron flow, the N/Z value rapidly reaches an equilibrium distribution. Meanwhile the system, originally in the fusion valley, is injected into the asymmetric fission valley. The dynamic process of the composite nucleus in the asymmetric fission valley is treated with a two-parameter Smoluchowski equation. It is shown that the probability to overcome the asymmetric fission barrier and to achieve compound nucleus configuration, hence the fusion cross section is obviously suppressed due to the effect of isospin equilibrium.
Dynamical Effects on Sub-barrier Fusion of 40,48Ca+90,96Zr
ZHANG Huan-Qiao, LIU Zu-Huan, YANG Feng, LIN Cheng-Jian, RUAN Ming, WU Yue-Wei, LI Zhu-Xia, WU Xi-Zhen, ZHAO Kai, WANG Ning
Chin. Phys. Lett. 2005, 22 (12): 3048-3051 .  
Abstract   PDF(pc) (253KB) ( 393 )
We have measured the fusion cross sections for 48Ca+90,96 around the Coulomb barrier and presented them along with the experimental data of 40Ca+90,96. The experimental results are compared with the improved quantum molecular dynamics model calculations. It is shown in comparison that the dynamical effects play an important role in the sub-barrier fusion reactions.
Molecular Integral for the Double Electron-Repulsion Potential: A Closed Form Underived for Forty Years
Kazuhiro Ishida
Chin. Phys. Lett. 2005, 22 (12): 3052-3053 .  
Abstract   PDF(pc) (181KB) ( 462 )
A closed form of the title integral formula over the Gaussian-type orbitals is derived for the first time. The present closed form is analytical as the multiple hyper-geometric function of five variables.
Calculation of Positronium Formation Cross Sections in Positron--Mg Collision
CHENG Cheng, PENG Yue, ZHOU Ya-Jun
Chin. Phys. Lett. 2005, 22 (12): 3054-3506 .  
Abstract   PDF(pc) (210KB) ( 368 )
Using the optical-model, we theoretically investigate the positronium (Ps) formation in e+--Mg collision from the positronium threshold to 60.0eV. A complex equivalent local polarization potential is obtained to describe the rearrangement process, which reproduces Ps formation cross section. We report the total Ps (n=1+2) formation cross sections and compare them with the experimental measurements and other theoretical results.

Variations of the Speed of Light with Frequency and Implied Photon Mass
TU Liang-Cheng, YE Hong-Ling, LUO Jun
Chin. Phys. Lett. 2005, 22 (12): 3057-3060 .  
Abstract   PDF(pc) (229KB) ( 426 )
A general frequency-dependent dispersion relation of the speed of light in different mediums (vacuum, insulator, plasma) is deduced based on the Proca equations. Several recent astronomical observations of the pulsars are used to set the limits on the photon rest mass by this method and several upper bounds of larger than one order improvement than previous similar results are obtained. Considering the dispersion of the massive photon, the possible upper limits on the photon rest mass are also derived from the recently experimental results for testing the constancy of the speed of light in special relativity.
Silica-Based 64-Channel Arrayed Waveguide Gratings with Double Functions
AN Jun-Ming, LI Jian, XIA Jun-Lei, GAO Ding-Shan, WU Yuan-Da, LI Jian-Guang, WANG Hong-Jie, HU Xiong-Wei
Chin. Phys. Lett. 2005, 22 (12): 3061-3063 .  
Abstract   PDF(pc) (221KB) ( 531 )
Silica-based 64-channel arrayed waveguide gratings (AWGs) with double functions and 0.4nm (50GHz) channel spacing have been designed and fabricated. On the same component, Gauss and flat-top output response spectra are obtained simultaneously. The test results show that when the insertion loss ranges from 3.5dB to 6.4dB, the crosstalk is better than -34dB, the 1dB bandwidth is 0.12nm, the 3dB bandwidth is 0.218nm, and the polarization-dependent loss (PDL) is less than 0.5dB for Gauss response. When the insertion loss ranges from 5.8dB to 7.8dB, the crosstalk is better than -30dB, the 1dB bandwidth is 0.24nm, the 3dB bandwidth is 0.33nm, and the PDL is less than 0.2dB for flat-top response.
Generation of Three-Dimensional Entangled States for Two Atoms Trapped in Different Cavities
ZHENG Shi-Biao
Chin. Phys. Lett. 2005, 22 (12): 3064-3066 .  
Abstract   PDF(pc) (175KB) ( 474 )
We propose a scheme for generating three-dimensional entangled states for two atoms trapped in two separate cavities. The scheme is based on the detection of photons leaking from the cavities after the atom-cavity interaction. The scheme is useful for the test of quantum nonlocality and quantum information processing.
Phase Dependence of Fluorescence Spectrum of a Two-Level Atom in a Trichromatic Field
LI Jing-Yan, HU Xiang-Ming, LI Xiao-Xia, SHI Wen-Xing, XU Qing, GUO Hong-Ju
Chin. Phys. Lett. 2005, 22 (12): 3067-3070 .  
Abstract   PDF(pc) (219KB) ( 490 )
We examine the phase-dependent effects in resonance fluorescence of a two-level atom driven by a trichromatic modulated field. It is shown that the fluorescence spectrum depends crucially on the sum of relative phases of the sideband components compared to the central component, not simply on the respective phases. The appearance or disappearance of the central peak and the selective elimination of the sideband peaks are achieved simply by varying the sum phase. Once the sum phase is fixed, the spectrum keeps its features unchanged regardless of the respective relative phases.
Output Intensity Variations of the Laser Used in a Prism Coupling System and Its Application
ZHANG Xiao-Kang, LIAO Chang-Jun, LIU Song-Hao
Chin. Phys. Lett. 2005, 22 (12): 3071-3073 .  
Abstract   PDF(pc) (188KB) ( 479 )
The output intensity variations of the laser used in a prism coupling system are observed and found to be induced by the external optical feedback, which comes from the reflection on the prism. The intensity variations are explained with laser theory. The trough in the intensity variation corresponds to the position of the prism when the output light beam propagates perpendicularly to the prism. Based on the trough a new method for rotating the prism and reading out the step numbers is proposed, by which the angle 0° in the system need not to be calibrated. It is proven by experiment that the new method would improve the accuracy of the refractive index up to ±0.00001 and thickness to ±1nm.
Low-Threshold and High-Power Oxide-Confined 850nm AlInGaAs Strained Quantum-Well Vertical-Cavity Surface-Emitting Lasers Based on Intra-Cavity Contacted Structure
CHEN Min, GUO Xia, DENG Jun, GAI Hong-Xing, DONG Li-Min, QU Hong-Wei, GUAN Bao-Lu, GAO Guo, SHEN Guang-Di
Chin. Phys. Lett. 2005, 22 (12): 3074-3076 .  
Abstract   PDF(pc) (226KB) ( 657 )
The low-threshold and high-power oxide-confined 850nm AlInGaAs strained quantum-well (QW) vertical-cavity surface-emitting lasers (VCSELs) based on the intra-cavity contacted structure are fabricated. The threshold current of 0.1mA for a 10-μm oxide-aperture device is obtained with the threshold current density of 0.127kA/cm2. For a 22-μm oxide-aperture device, the peak optical output power reaches to 14.6mW at the current injection of 25mA under the room temperature and pulsed operation with a threshold current of 2mA, which corresponds to the threshold current density of 0.526kA/cm2. The lasing wavelength is 855.4nm. The full wave at half maximum is 2.2nm. The analysis of the characteristics and the fabrication of
VCSELs are also described.

High Temperature Operation of 5.5μm Strain-Compensated Quantum Cascaded Lasers
LU Xiu-Zhen, LIU Feng-Qi, LIU Jun-Qi, JIN Peng, WANG Zhan-Guo
Chin. Phys. Lett. 2005, 22 (12): 3077-3079 .  
Abstract   PDF(pc) (217KB) ( 483 )
We develop 5.5-μm InxGa1-xAs/InyAl1-yAs strain-compensated quantum cascade lasers with InP and InGaAs cladding layers by using solid-source molecular-beam epitaxy. Pulse operation has been achieved up to 323K (50°C) for uncoated 20-μm-wide and 2-mm-long devices. These devices display an output power of 36mW with a duty cycle of 1% at room temperature. In continuous wave operation a record peak optical power of 10mW per facet has been measured at 83K.
A Partial Double-Pass S-Band Erbium-Doped Fibre Amplifier
Sulaiman Wadi Harun, Nor Kamilah Saat, Harith Ahmad
Chin. Phys. Lett. 2005, 22 (12): 3080-8082 .  
Abstract   PDF(pc) (157KB) ( 764 )
An efficient and low noise short wavelength band erbium-doped fibre amplifier (S-band EDFA) is proposed and demonstrated using double-pass configuration. This amplifier provides a gain of 1500nm signal as high as 26.9dB, which is 9.6dB higher than the two-stage single-pass amplifier. The corresponding noise figure obtained is 7.5dB, which is of the same level as in the single-pass amplifier and more than 2dB lower than the previously reported double-pass amplifier [IEICE Electron. Express 2 (2005) 182]. The gain enhancement is due to the double pass-propagation of the test signal in the second stage, which increases the effective erbium-doped fibre (EDF) length. The low noise is attributed to the optical circulator between EDFs, which prevents the backward amplified spontaneous emission from propagating into the input part of the amplifier. The proposed amplifier is expected to play an important role in the development of a practical S-band EDFA.
Second-Harmonic Generation in Optical Fibres Induced by a Cross-Phase Modulation Effect
CUI Wei-Na, HUANG Guo-Xiang
Chin. Phys. Lett. 2005, 22 (12): 3083-3086 .  
Abstract   PDF(pc) (240KB) ( 432 )
When two optical pulses copropagate inside a single-mode fibre, intensity-dependent refractive index couples the pulses through a cross-phase modulation (XPM). We show that a second-harmonic generation (SHG) on a continuous-wave background is possible in the optical fibre induced by the XPM effect. By means of a multi-scale method the nonlinearly coupled envelope equations for the SHG are derived and their explicit solutions are provided and discussed.
A Novel 3R Regeneration and Its Application on PMD Mitigation
HUO Li, YANG Yan-Fu, PAN Shi-Long, LOU Cai-Yun, GAO Yi-Zhi
Chin. Phys. Lett. 2005, 22 (12): 3087-3090 .  
Abstract   PDF(pc) (241KB) ( 468 )
A novel 40Gbit/s reamplified-reshaping-retiming (3R) regenerator is proposed and demonstrated based on a two-ring injection mode-locked fibre laser as the clock recovery and the electro-absorption modulator of the reshaping optical decision. A numerical model describing the cross-absorption modulation effect in a bulk electroabsorption modulator is presented. By this model, the shape and the extinction ratio of the optical decision gate is improved by optimizing the parameters. The polarization mode dispersion mitigation by the 3R regenerator is experimentally demonstrated at 40Gbit/s with improved bit-error-rate (BER) performance when the differential-time-delay value is set up to 40% of bit interval.
Dispersion Analysis and Compensation of Collinear Optical Parametric Chirped Pulse Amplification Systems
WANG Cheng, LENG Yu-Xin, LIANG Xiao-Yan, ZHANG Chun-Mei, ZHAO Bao-Zhen, XU Zhi-Zhan
Chin. Phys. Lett. 2005, 22 (12): 3091-3093 .  
Abstract   PDF(pc) (180KB) ( 442 )
In an optical parametric chirped pulse amplification (OPCPA) laser system, residual phase dispersion should be compensated as much as possible to shorten the amplified pulses and improve the pulse contrast ratio. Expressions of orders of the induced phases in collinear optical parametric amplification (OPA) processes are presented at the central signal wavelength to depict a clear physics picture and to simplify the design of phase compensation. As examples, we simulate two OPCPA systems to compensate for the phases up to the partial fourth-order terms, and obtain flat phase spectra of 200-nm bandwidth at 1064nm and 90-nm at 800nm.
Reduction of Refractive Index Contrast Threshold for Photonic Band-Gap in Square Lattices
WANG Jian-Feng, HUANG Yi-Dong, ZHANG Wei, PENG Jiang-De
Chin. Phys. Lett. 2005, 22 (12): 3094-3096 .  
Abstract   PDF(pc) (189KB) ( 839 )
The threshold of refractive index contrast (RIC) to open a photonic band gap can be reduced by symmetry breaking. For the case of square lattice composed by dielectric cylinders, the absolute band gap is demonstrated by inserting small rods in the centre of the lattices, and the threshold RIC is reduced to 3.8. As for the square lattices composed by air holes in dielectric, the minimal RIC required for an absolute band gap decreases to 2.20.
High Speed 2×2 Optical Switch in Silicon-on-Insulator Based on Plasma Dispersion Effect
SUN Fei, YU Jin-Zhong, CHEN Shao-Wu
Chin. Phys. Lett. 2005, 22 (12): 3097-3099 .  
Abstract   PDF(pc) (182KB) ( 530 )
Based on free carrier plasma dispersion effect, a 2×2 optical switch is fabricated in a silicon-on insulator substrate by inductively coupled-plasma technology and ion implantation. The device has a Mach--Zehnder interferometer structure, in which two directional couplers serve as the power splitter and combiner. The switch presents an insertion loss of 3.04dB and a response time of 496ns.
Compact Arrayed-Waveguide Grating on Silicon-on-Insulator with Integrated Waveguide Turning Mirrors
LI Guang-Bo, GONG Zhao, JIA Ke-Miao, LONG Wen-Hua, YANG Jian-Yi, JIANG Xiao-Qing, WANG Yue-Lin, WANG Ming-Hua
Chin. Phys. Lett. 2005, 22 (12): 3100-3103 .  
Abstract   PDF(pc) (231KB) ( 512 )
A compact arrayed-waveguide grating (AWG) on the silicon-on-insulator material is designed and fabricated with employment of waveguide-integrated turning mirrors (WITMs). By properly setting the incident angle with the value of 45°, the effective area of the WITM AWG is only 1.15cm×1.15cm with the arrayed waveguide area of 0.6cm×0.6cm. The crosstalk of the fabricated 1×6 AWG is better than -19dB. The on-chip insertion loss is about -8.8dB and the output nonuniformity is less than 0.6dB. The polarization-dependent central wavelength shift is about 0.048nm and the polarization dependent loss is neglectable.
Liquid--Solid Interface Waves with Laser Ultrasonic and Mirage Effect
HAN Qing-Bang, WANG Hao, QIAN Meng-Lu
Chin. Phys. Lett. 2005, 22 (12): 3104-3106 .  
Abstract   PDF(pc) (185KB) ( 887 )
We experimentally investigate the transparent-liquid/solid (water/aluminum or steel) interface waves generated by laser pulses and detected by the Mirage effect. It is shown that nearly all kinds of liquid/solid interface waves in water are detected, both their measured wave velocities and characteristic of shape are in good agreement with theoretical predictions.
Ultrawide Bandgap Locally Resonant Sonic Materials
LIU Zhi-Ming, YANG Sheng-Liang, ZHAO Xun,
Chin. Phys. Lett. 2005, 22 (12): 3107-3110 .  
Abstract   PDF(pc) (211KB) ( 860 )
We prepare a class of locally resonant (LR) sonic materials. The experiments demonstrate that the resonant frequency decreases with the increasing density of the scattering unit cores or with the reducing elastic constants of the silicone rubber coating. By combining three LR layers of different resonant frequencies and choosing 10dB as the threshold of relative attenuation, we obtain an ultrawide bandgap (200--950Hz) sound material with an average transmission loss 22dB lower than that dictated by mass density law.
Distribution of Orientations in Fibre Suspension Flowing in a Turbulent Boundary Layer
LIN Jian-Zhong, SUN Ke, LIN Jiang
Chin. Phys. Lett. 2005, 22 (12): 3111-3114 .  
Abstract   PDF(pc) (215KB) ( 362 )
The equation of probability distribution function for mean fibre orientation in a turbulent boundary layer is derived, in which the correlation terms of the fluctuating velocity, fluctuating angular velocity with the fluctuating probability distribution function are related to the gradient of mean probability distribution function and the dispersion coefficients in order to make the equation be solvable. The finite-difference method is used to solve the equation numerically. The results show that the fibres tend to align with the streamline, which is in agreement qualitatively with the experimental result given by visualization. The fibre aspect-ratio has a significant effect on the orientation distribution of fibres, while the effect of the distance from the wall is negligible.
Relative Scaling Exponents and Intermittency in Compressible Turbulent Channel Flows
HU Kai-Heng, CHEN Kai
Chin. Phys. Lett. 2005, 22 (12): 3115-3118 .  
Abstract   PDF(pc) (254KB) ( 386 )
The relative scaling exponents and intermittency of three-dimensional compressible turbulent channel flow are investigated by using direct numerical simulation. One case is subsonic flow (Ma = 0.8), the other is supersonic (Ma= 1.3), and the Reynolds numbers based on the mean bulk velocity and channel half-width are 2826 and 3010, respectively. The analysis of the local slopes of sixth order velocity structure function to third order reveals that there is a well-defined scaling range for 10 < y+ < 100. It is also noted that the intermittency of longitudinal velocity increments in this region is stronger than that of the transverse ones. Comparison with the incompressible case shows that the location of the most intensive intermittency moves toward the log-law region, which is related to the displacement of streamwise vortical structures in the near-wall region.
Modelling of a Multi-Temperature Plasma Composition
B. Liani, R. Benallal, Z. Bentalha
Chin. Phys. Lett. 2005, 22 (12): 3122-3122 .  
Abstract   PDF(pc) (230KB) ( 373 )
Knowledge of plasma composition is very important for various plasma applications and prediction of plasma properties. We use the Saha equation and Debye length equation to calculate the non-local thermodynamic equilibrium plasma composition. It has been shown that the model to 2T with T representing the temperature (electron temperature and heavy-particle temperature) described by Chen and Han [J. Phys. D 32(1999)1711] can be applied for a mixture of gases, where each atomic species has its own temperature, but the model to 4T is more general because it can be applicable to temperatures distant enough of the heavy particles. This can occur in a plasma composed of big- or macro-molecules. The electron temperature Te varies in the range 8000*20000K at atmospheric pressure.
An Efficient Iterative Procedure for Solution of Plasma Loaded Helical Waveguide Problems
V. Babovic, M. Kovav cevic, K. Kanjevac
Chin. Phys. Lett. 2005, 22 (12): 3123-3125 .  
Abstract   PDF(pc) (199KB) ( 393 )
The behaviour of axially-symmetric waves travelling on plasma filled screened helical coil is comprehensively studied by Anicin [J. Phys. D: Appl. Phys. bf 33 (2000) 1276], where all analytical expressions are derived in the full-wave theory, but the diagrams are computed in the quasistatic approximation. We use an iterative procedure to overcome this limitation. The iterative procedure is rapid and we have proven that often the first-order approximant is sufficient to improve defects which are known as immanent to the quasistatic approximation. The fixed point method appears as the natural choice for numerical treatment of formulae which could arise in a broad class of physical problems usually recognized as guided surface plasma waves.
Microstructure and Wear Behaviour of WC Film Prepared by Pulsed High Energy Density Plasma
LIU Yuan-Fu, HAN Jian-Min, ZHANG Gu-Ling, WANG Jiu-Li, YANG Si-Ze
Chin. Phys. Lett. 2005, 22 (12): 3126-3129 .  
Abstract   PDF(pc) (247KB) ( 605 )
A super hard and wear resistant WC film is in-situ prepared on a 0.45% C steel substrate by pulsed high energy density plasma technique at ambient temperature. The microstructure and composition of the film are analysed by x-ray diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. The hardness profile and tribological behaviour of the film are determined with nano-indenter and wear tester, respectively. The results show that the microstructure of the film was dense and uniform and mainly composed of WC and a small amount of W2C. A wide mixing interface exists between the film and the 0.45%C steel substrate. The thickness of the film is about 2μm. The hardness and Yang’s modulus of the film are very high. The film has excellent wear resistance and low friction coefficient under dry sliding wear test conditions.
Abnormal Crystallization of Silicon Thin Films Deposited by ICP-CVD
LI Jun-Shuai, YIN Min, WANG Jin-Xiao, HE De-Yan
Chin. Phys. Lett. 2005, 22 (12): 3130-3132 .  
Abstract   PDF(pc) (182KB) ( 911 )
Silicon thin films are deposited by inductively coupled plasma chemical vapour deposition (ICP-CVD) at a low temperature of 350°C using a mixture of SiH4 and H2. The structures of the films are characterized by x-ray diffraction and Raman spectra. Under the optimum experimental conditions, we observe that the crystallinity of Si films becomes more excellent and the preferred orientation changes from (111) to (220) with the decreasing dilution of SiH4 in H2. Such an abnormal crystallization is tentatively interpreted in term of the high density, low electron temperature and spatial confinement of the plasma in the process of ICP-CVD.
Self-Assembly of Gold Nanoparticles on Nanometre-Patterned Surface
ZHANG Yong-Jun, YANG Jing-Hai, LI Wei, ZHANG Yu, XU Ling, XU Jun, HUANG Xin-Fan, CHEN Kun-Ji
Chin. Phys. Lett. 2005, 22 (12): 3133-3136 .  
Abstract   PDF(pc) (220KB) ( 538 )
The self-assembly processes of gold nanoparticles on nanometre-step-patterned Si surface and polished Si surface are investigated by the convective self-assembly method. The convective self-assembly method is used to deposit the colloids dispersed in benzene onto the substrates. The SEM results show that the configurations of the gold arrays depend on the surface morphology of the substrates. On the nanometre-step-patterned Si surface, the nanoparticles self assemble into parallel lines, and the distance between the neighbouring lines is around 35nm. On the polished Si surface the nanoparticles form compact domains. In each domain the particles are close-packed in a two-dimensional hexagonal superlattice and are separated by uniform distances. The analysis shows that on the nanometre-step-patterned Si surface, the steps play critical roles in the self-assembly process of gold nanoparticles. The capillary force from the steps drives the particles to lines along the steps. Therefore, the particles tend to self-assemble into one-dimensional
line structures when the solvent evaporates. For the polished Si substrate there is a little difference that the particles form two-dimensional hexagonal superlattices without the directional confinement.
Indentation Size Effect and Microhardness Study of β-Sn Single Crystals
O. SAHIN, O. UZUN, U. KOLEMEN, B. DUZGUN, N. UCAR
Chin. Phys. Lett. 2005, 22 (12): 3137-3140 .  
Abstract   PDF(pc) (211KB) ( 632 )
The load dependence of apparent microhardness of β-Sn single crystals having different growth directions is investigated. The measurements are performed on (110) planes of these crystals in the load range from 10 to 50mN. It is found that the degree of the microhardness anisotropy decreases for higher indentation test loads. The examined materials exhibit the behaviour of indentation size effect (ISE), i.e., the apparent hardness increases with decreasing indentation load. Neither Meyer’s law nor the proportional specimen resistance (PSR) model can fully explain the nonlinear variation of microhardness with load. Instead, preference is given to modified the PSR model based on the consideration of the effect of machining-induced residually stressed surface on the hardness measurement.

Synthesis of Boron-Rich Cubic B(CxN1-x) Compounds
GUO Li-Cong, HU Wen-Tao, HE Ju-Long, YU Dong-Li, LIU Shi-Min, LI Dong-Chun, TIAN Yong-Jun
Chin. Phys. Lett. 2005, 22 (12): 3141-3143 .  
Abstract   PDF(pc) (225KB) ( 862 )
B2CN precursor is prepared by a mechanical vibration-milling process using amorphous boron, graphite and h-BN powders with mole ratio of 1:1:1. A mixture of precursor and Ca3B2N4 catalyst is treated under high pressure and high temperature. A boron rich cubic B(CxN1-x) phase is obtained after removing the catalyst by acid treatment. The average C content of the boron-rich cubic phase is about 6 at.% detected by energy-dispersive x-ray analysis spectroscopy. It is found that the highest carbon content in the cubic phase is as large as 16 at.%.
Transition for Optimal Paths in Bimodal Directed Polymers
WANG Xiao-Hong
Chin. Phys. Lett. 2005, 22 (12): 3144-3146 .  
Abstract   PDF(pc) (194KB) ( 522 )
The problem for optimal paths in bimodal directed polymers is studied. It is shown that the distribution of the thermal average position of the endpoints of the optimal paths is discontinuous below the threshold pc. The origin is that there is a finite possibility that only one endpoint takes the global minimum energy for pc. Our results suggest that the percolation threshold for directed percolation is also the critical point of the transition for the possibility that the optimal paths converge to one endpoint.
Effect of Quenching on the Grain Boundary Relaxation in PM2000 ODS Alloy
GAO Zhan-Yong, WU Jie, HAN Fu-Sheng
Chin. Phys. Lett. 2005, 22 (12): 3147-3150 .  
Abstract   PDF(pc) (241KB) ( 741 )
Grain boundary relaxation in a Fe-based ODS alloy is studied by internal friction measurements. It is found that a grain-boundary peak appears at a lower temperature in the quenched specimens than that in the annealed specimens. The activation energy of the peak is H=2.82±0.11eV for the former while H=2.53±0.08eV for the latter. In addition, a new relaxation peak is observed at the high temperature side of the grain boundary peak in the quenched specimens with an activation energy of 4.41±0.25eV. The height of the peak increases with increasing quenching temperature. The results suggest that both the shift of the grain-boundary peak and the appearance of the new peak are due to increasing vacancies by quenching that are favourable for the motion of the grain boundaries.
Parallel Molecular Dynamics Simulations of Ejection from the Metal Cu and Al Under Shock Loading
CHEN Qi-Feng, CAO Xiao-Lin, ZHANG Ying, CAI Ling-Cang, CHEN Dong-Quan
Chin. Phys. Lett. 2005, 22 (12): 3151-3154 .  
Abstract   PDF(pc) (256KB) ( 924 )
Large-scale non-equilibrium molecular dynamics simulations are used to investigate the ejection of the metal under a shock loading. The present work focus on the dynamic process of ejection from the metal Cu and Al surface groove under shock loading, using parallel MD implementation and the Morse potential. The ejected mass coefficient and the size distribution of ejected particles (cluster for atoms) are investigated with changes of the half-angle or the depth of groove and shock strength.
Fermi Surface Topology of Na0.5CoO2 from the Hybrid Density Functional
CHEN Zhao-Ying, XIANG Hong-Jun, YANG Jin-Long
Chin. Phys. Lett. 2005, 22 (12): 3155-3158 .  
Abstract   PDF(pc) (205KB) ( 516 )
The Fermi surface topology of Na0.5CoO2 is studied using the hybrid density functional theory. We first study a single (CoO2)0.5- layer model with the percentage of the nonlocal Hartree--Fock exchange changing from 0% to 20%. The results show that only when the mixed nonlocal Hartree--Fock exchange is between 1% and 5%, the Fermi surface topology is similar to the experimental one. With 3% HF exchange in the hybrid density functional, considering the effects of Na ions in the Na0.5CoO2 system, we find that the Fermi surface is split to double holes and small gaps open near the intersections between the Brillouin zone and the Fermi surface. Our results show that both the amounts of the nonlocal Hartree--Fock exchange in the hybrid density functional and the Na ions have much influence on the Fermi surface topology.
Conductance for a Quantum Wire with Weak Rashba Spin-Orbit Coupling
LIU Gen-Hua, ZHOU Guang-Hui,
Chin. Phys. Lett. 2005, 22 (12): 3159-3162 .  
Abstract   PDF(pc) (221KB) ( 577 )
We theoretically study the low temperature electron transport properties of a weak Rashba spin-orbit coupling (SOC) semiconductor quantum wire connected nonadiabatically to two electrode leads without SOC. The wire and the leads are defined by a parabolic confining potential, and the influence of both the wire-lead connection and the Rashba SOC on the electron transport is treated analytically by means of scattering matrix within effective free-electron approximation. From analytical analysis and numerical examples, we find that the system shows some fractional quantum conductance behaviour, and for some particular wire width a pure spin polarized current exists. Our result may imply a simple method for the design of a spin filter without involving any magnetic materials or magnetic fields.

Simulation of Confined and Interface Phonons Scattering in Terahertz Quantum Cascade Laser
HE Xiao-Yong, CAO Jun-Cheng, L{U} Jing-Tao, FENG Song-Lin
Chin. Phys. Lett. 2005, 22 (12): 3163-3165 .  
Abstract   PDF(pc) (214KB) ( 461 )
We have performed the calculation of resonant-phonon transition in a terahertz quantum cascade laser. The electron wavefunctions and energy levels are obtained by solving the Schrödinger and Poisson equations self-consistently. The scattering rates of the confined, interface, and bulk phonons are calculated by using the Fermi golden rule. It has been shown that the confined phonon scattering is comparable to the interface phonon scattering and should be taken into consideration in the calculation.
Dipolar Interaction and Magnetic Ordering Ground State in Mn12 Molecular Magnet
LIU Hai-Qing, WANG Yun-Ping
Chin. Phys. Lett. 2005, 22 (12): 3166-3168 .  
Abstract   PDF(pc) (201KB) ( 441 )
Here a direct calculation of the dipolar interaction in a single crystal Mn12, with all of Mn ions summed, shows that a transition between ferromagnetic and antiferromagnetic ground states takes place where the dimension along the a(b) axis versus the dimension along the c axis reaches a certain critical value. It is shown that the ground state is dependent upon the shape of the specimen. The reason of the shape dependence of ordering is that dipolar interaction is of long-range nature and the sign of dipolar interaction is dependent on the direction.

Interlayer Coupling in Co/Ti/(Gd--Co)/Ti Artificial Layered Ferrimagnet
A. V. Svalov, A. Fernández, V. O. Vas’kovskiy, M. Tejedor, R. Lopez Anton, J. M. Barandiarán, G. V. Kurlyandskaya
Chin. Phys. Lett. 2005, 22 (12): 3169-3172 .  
Abstract   PDF(pc) (210KB) ( 613 )
The magnetic properties and the structure of [Co/Ti/Gd0.36Co0.64/Ti]4/Co multilayers are investigated by means of torque magnetometer, vibrating sample magnetometer and transverse magneto-optic Kerr effect (TMOKE) measurements and the atomic force microscopy. Due to interlayer exchange interaction, Co and Gd--Co layers form a macroscopic ferrimagnetic system. The change in the sign of the TMOKE hysteresis loops near the compensation temperature and field induced magnetic phase transitions are found. The latter can be characterized by a critical field which shows a linear variation with the temperature. The magnetic properties of these multilayers from many points of view are similar to those of bulk ferrimagnets.
Wideband Antireflection Film Fabricated by Glancing Angle Deposition
FU Xiao-Yong, WANG Su-Mei, DENG De-Gang, YI Kui, SHAO Jian-Da, FAN Zheng-Xiu
Chin. Phys. Lett. 2005, 22 (12): 3173-3175 .  
Abstract   PDF(pc) (185KB) ( 392 )
Graded-index ZrO2 films has been fabricated on K9 glass by glancing angle deposition. Because the index mismatch at the interface has been reduced, the film results in wideband high-transmission antireflection. From 400nm to 1200nm, the film reflection is lower than 0.8% and the lowest value is 0.2% at 432nm.
Experimental Investigation on Terahertz Spectra of Amphetamine Type Stimulants
SUN Jin-Hai, SHEN Jing-Ling, LIANG Lai-Shun, XU Xiao-Yu, LIU Hai-Bo, ZHANG Cun-Lin
Chin. Phys. Lett. 2005, 22 (12): 3176-3178 .  
Abstract   PDF(pc) (221KB) ( 692 )
The spectral absorption features of three amphetamine-type stimulants (ATS) belonging to illicit drugs have been studied with terahertz (THz) time-domain spectroscopy (THz-TDS) and the characteristic absorption spectra (fingerprint spectra) are obtained in the range from 0.2 to 2.5THz. Fingerprint spectra of illicit drugs in terahertz band are bases to detect and to inspect nondestructively illicit drugs with terahertz technique. With fingerprint spectra of illicit drugs and strong penetrability for cloths, paper bags and leathered or plastic luggage terahertz technique would be better than other techniques in illicit drugs detection and inspection. Thus, this work would contribute to the building of corresponding fingerprint spectra database of illicit drugs and provide experimental bases for using of terahertz detection apparatus in drugs nondestructive detection and inspection in the future.
Experimental and Theoretical Study of Carnosine in THz Range
YAN Hai-Tao, WANG Wei-Ning
Chin. Phys. Lett. 2005, 22 (12): 3179-3181 .  
Abstract   PDF(pc) (206KB) ( 495 )
The characteristic fingerprints of carnosine from 0.2 to 2.6THz are first measured by terahertz time-domain spectroscopy at room temperature. For the pure carnosine, the refractive index varies between 1.79 and 1.85 with the average value 1.84, while for the carnosine-polyethylene mixture, four absorption peaks centred at 1.37, 1.56, 1.85 and 2.49THz are detected. A comparison of the theoretical predictions using the density functional theory with the experimental results shows satisfactory agreement except somewhat blue shift.
Luminescence and ESR Studies of CaS:Dy Phosphor
Vijay Singh, ZHU Jun-Jie, T. K. Gundu Rao, Manoj Tiwari, PAN Hong-Cheng
Chin. Phys. Lett. 2005, 22 (12): 3182-3185 .  
Abstract   PDF(pc) (216KB) ( 523 )
CaS phosphor activated with Dy ions is prepared by the solid-state diffusion method. The phosphor is characterized by x-ray powder diffraction, thermogravimetric analysis and photoluminescence. Defect centres formed in CaS:Dy are studied using the technique of electron spin resonance. The thermoluminescence glow curve shows peaks at around 117°C and 345°C. Irradiated CaS:Dy exhibits ESR lines due to defect centres. The thermal annealing behaviour of one of the defect centres appears to correlate with the TL peaks at 117°C and 345°C. This centre is characterized by an isotropic g-value of 2.0035 and is assigned to an F+ centre.
Determination of Al Composition in Strained AlGaN Layers
ZHOU Sheng-Qiang, WU Ming-Fang, YAO Shu-De
Chin. Phys. Lett. 2005, 22 (12): 3189-3191 .  
Abstract   PDF(pc) (208KB) ( 582 )
AlxGa1-xN/GaN heterostructures are grown on c-sapphire with the Al composition x from 0.2 to 0.4 and thicknesses from 20nm to 30nm. The lattice parameters a and c are determined from 2θ/ω scan. The AlGaN layers are found to be under tensile strain by using x-ray diffraction. Vegard’s law induces a large deviation in Al composition determination by only considering the linear relationship between one lattice parameter (a or c) and Al composition. The accurate determination of Al composition is only possible with consideration of both the lattice parameters a and c, by assuming the tetragonal distortion in the AlGaN layer. Additionally, the results obtained from x-ray diffraction are verified by Rutherford backscattering.
A New Method for Preparation of Nanocrystalline Molybdenum Nitride
SHEN Long-Hai, CUI Qi-Liang, ZHANG Jian, LI Xue-Fei, ZHOU Qiang, ZOU Guang-Tian
Chin. Phys. Lett. 2005, 22 (12): 3192-3194 .  
Abstract   PDF(pc) (196KB) ( 829 )
Nanocrystalline molybdenum nitride (γ-Mo2N) with the cubic structure is prepared by the direct current arc discharge method in N2 gas, using metal Mo or W rod as a cathode. The x-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to characterize the product. It is found that the conversion of Mo to γ-Mo2N and affinity of Mo to N2 are determined by the nitrogen pressure. Moreover, we compare the effect of Mo and W rod as a cathode for preparing γ-Mo2N. The average size of γ-Mo2N particles is about 5nm. The rapid quenching mechanism can be used to explain the formation of nanocrystalline γ-Mo2N.
Spiral Waves in Media with Spatial Period-2 Structure
YANG Jun-Zhong, ZHANG Mei
Chin. Phys. Lett. 2005, 22 (12): 3195-3198 .  
Abstract   PDF(pc) (371KB) ( 554 )
The spiral waves in a system of two-dimensional coupled oscillators with spatial period-2 structure are investigated. We find a sandwiched spiral wave where any adjacent oscillators are in anti-phase. We show that the propagation rate of the sandwiched spiral wave is insensitive to the change of the coupling constant. The influences of the local kinetics on the sandwiched spiral wave are also investigated.
An Improved Blue Polymer Light-Emitting Diode by Using Sodium Hydroxide/Ca/Al Cathode
MA Liang, XIE Zhi-Yuan, LIU Jun, YANG Jun-Wei, CHENG Yan-Xiang, WANG Li-Xiang, WANG Fo-Song
Chin. Phys. Lett. 2005, 22 (12): 3196-3188 .  
Abstract   PDF(pc) (205KB) ( 538 )
The performance of blue polymer light-emitting diodes (PLEDs) based on poly(9,9-dioctylfluorene) (PFO) is improved by introducing a thin layer of sodium hydroxide (NaOH) between the calcium cathode and the PFO emissive layer. By replacing the commonly used Ca/Al cathode by a NaOH (2.5nm)/Ca (10nm)/Al cathode, the driving voltage is reduced from 8.3V to 5.4V and the light-emitting efficiency is enhanced from 0.46cd/A to 0.72cd/A for achieving a luminance of 500cdm2, respectively. Moreover, the device with NaOH/Ca/Al cathode shows a pure blue emission of (0.17, 0.12) at high brightnesses. These improvements are attributed to introduction of a thin layer of NaOH that can lower the interfacial barrier and facilitate electron injection.
Non-Gravitational Effects with Density-Matching in Evaluating the Influence of Sedimentation on Colloidal Coagulation
LIU Jie, SUN Zhi-Wei, AA Yan
Chin. Phys. Lett. 2005, 22 (12): 3199-3202 .  
Abstract   PDF(pc) (205KB) ( 530 )
The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm (diameter) polystyrene. The liquid mixtures, in the proper proportions of water (H2O), deuterium oxide (D2O) and methanol (MeOH) as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes (reduction) in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary corrections for all factors, our experiments show that the influence of the sedimentation on coagulation rates at the initial stage of the coagulation is not observable.
Molecular Dynamical Simulation of Ice Phase Transition: Ice Ih to High-Density Amorphous
DONG Shun-Le, WANG Yan
Chin. Phys. Lett. 2005, 22 (12): 3203-3205 .  
Abstract   PDF(pc) (205KB) ( 722 )
We put 5kbar and 12kbar on perfect ice Ih lattice at 77K and 180K. After 30000 simulation steps (in units of 10-15s), high-density amorphous ice is formed. Four-site simple-pair potential TIP4P is used
for molecular interactions and the rigid molecular model is employed. Phase transition processes are fitted by an exponential function, and different phase transition times τ are obtained from O-O radial distribution functions (366 and 359fs for 77K and 180K) and O-O-O angle distribution functions (126 and 116fs for 77K and 180K).
An Intracellular Calcium Oscillations Model Including Mitochondrial Calcium Cycling
SHI Xiao-Min, LIU Zeng-Rong
Chin. Phys. Lett. 2005, 22 (12): 3206-3109 .  
Abstract   PDF(pc) (213KB) ( 501 )
Calcium is a ubiquitous second messenger. Mitochondria contributes significantly to intracellular Ca2+ dynamics. The experiment of Kaftan et al. [J. Biol. Chem. 275(2000) 25465] demonstrated that inhibiting mitochondrial Ca2+ uptake can reduce the frequency of cytosolic Ca2+ concentration oscillations of gonadotropes. By considering the mitochondrial Ca2+ cycling we develop a three-variable model of intracellular Ca2+oscillations based on the models of Atri et al. [Biophys. J. 65 (1993) 1727] and Falcke et al. [Biophys. J. 77 (1999) 37]. The model reproduces the fact that mitochondrial Ca2+ cycling increases the frequency of cytosolic Ca2+ oscillations, which accords with Kaftan's results. Moreover the model predicts that when the mitochondria overload with Ca2+, the cytosolic Ca2+ oscillations vanish, which may trigger apoptosis.
Lattice Boltzmann Simulation of Blood Flow in Blood Vessels with the Rolling Massage
YI Hou-Hui, XU Shi-Xiong, QIAN Yue-Hong, FANG Hai-Ping
Chin. Phys. Lett. 2005, 22 (12): 3210-3213 .  
Abstract   PDF(pc) (220KB) ( 804 )
The rolling massage manipulation is a classic Chinese massage, which is expected to improve the circulation by pushing, pulling and kneading of the muscle. A model for the rolling massage manipulation is proposed and the lattice Boltzmann method is applied to study the blood flow in the blood vessels. The simulation results show that the blood flux is considerably modified by the rolling massage and the explicit value depends on the rolling frequency, the rolling depth, and the diameter of the vessel. The smaller the diameter of the blood vessel, the larger the enhancement of the blood flux by the rolling massage. The model, together with the simulation results, is expected to be helpful to understand the mechanism and further development of rolling massage techniques.
Physical Mechanism of Formation of the Bimodal Structure in the Meiyu Front System
CUI Xiao-Peng, GAO Shou-Ting, ZONG Zhi-Ping, LIU Wen-Ming, LI Xiao-Fan
Chin. Phys. Lett. 2005, 22 (12): 3218-3220 .  
Abstract   PDF(pc) (202KB) ( 492 )
The bimodal structure of the Meiyu front system is readdressed after Zhou et al.(2005). The physical mechanism of the formation of the bimodal distribution is discussed. The bimodal structure of the Meiyu front system considerably results from atmospheric moisture gradients, though atmospheric temperature gradients are also not negligible. According to the definition of equivalent potential temperature, and by scale analysis, we find that atmospheric equivalent potential temperature gradients, which could be regarded as an indicator of the Meiyu front system, could be mainly attributed to the variations of atmospheric potential temperature gradients with a scaling factor of 1 and moisture gradients multiplied by a scaling factor of an order of about 2.5×103, which means that small variations of atmospheric moisture gradients could lead to large variations of equivalent potential temperature gradients, and thus large variations of the Meiyu front system. Quantitative diagnostics with a mesoscale simulation data in the vicinity of the Meiyu front system show that moisture gradients contribute to equivalent potential temperature gradients more than potential temperature gradients.
Earth’s Magnetosphere Impinged by Interplanetary Shocks of Different Orientations
GUO Xiao-Cheng, HU You-Qiu, WANG Chi
Chin. Phys. Lett. 2005, 22 (12): 3221-3224 .  
Abstract   PDF(pc) (236KB) ( 455 )
Using a recently developed PPMLR-MHD code, we carry out a global numerical simulation of the interaction between interplanetary shocks and Earth's magnetosphere. The initial magnetosphere is in a quasi-steady state, embedded in a uniform solar wind and a spiral interplanetary magnetic field (IMF). An interplanetary (IP) shock interacts in turn with the bow shock, the magnetosheath, the magnetopause, and the magnetosphere, and changes the magnetosphere in shape and structure, and the distribution of the electric current and potential in the ionosphere as well. A preliminary comparison is made between two IP shocks of the same solar wind dynamic pressure and a vanishing IMF Bz on the downstream side, but with different propagation directions, one parallel and the other oblique to the Sun--Earth line. The numerical results show that both shocks cause a compression of the magnetosphere, an enhancement of magnetic field strength and field-aligned current in the magnetosphere, and an increase of the dawn-dusk electric potential drops across the polar ionosphere. Moreover, the magnetosphere--ionosphere system approaches a similar quasi-steady state after the interaction, for the downstream states are very close for the two shocks. However, the evolution processes of the system are remarkably different during the interaction with the two shocks of different orientations. The shock with the normal oblique to the Sun--Earth line results in a much longer evolution time for the system. This demonstrates that the shock orientation plays an important role in determining the associated geophysical effects and interpreting multisatellite observations of IP shock--magnetosphere interaction events.
New Evidence for Magnetic Reconnection in the Tail of Interplanetary Magnetic Cloud
ZHONG Ding-Kun, WEI Feng-Si, FENG Xue-Shang, YANG Fang,
Chin. Phys. Lett. 2005, 22 (12): 3225-3228 .  
Abstract   PDF(pc) (270KB) ( 504 )
We analyse the WIND data of an interplanetary magnetic cloud (MC) on 2 November 2001, and find new evidences for magnetic reconnection in the tail of this MC. In the MC tail, the largely dip and the large change of the orientation of the magnetic field occurred simultaneously, Δθ approx 45°, and ΔФ changed from 90° to 320°. Correspondingly, the number density of ions increased, and the superthermal electrons were heated and accelerated, however its number density decreased. Meanwhile, inverse jets and Hall term were observed. The pitch-angle distributions of the electrons with lower energy and higher energy showed strong turbulence and bi-direction flow, respectively. The plasma wave activity enhanced near the electron plasma frequency, fpe and 2fpe. These important physical characteristics are new evidences for magnetic reconnection existing in interplanetary space.
A Quasi-Periodic Solar Radio Fluctuation at Microwave Band
XU Fu-Ying, HUANG Guang-Li, WU Hong-Ao,
Chin. Phys. Lett. 2005, 22 (12): 3229-3232 .  
Abstract   PDF(pc) (206KB) ( 564 )
A rare but interesting solar radio fine structure, quasi-periodic fluctuations, on 25 August 1999 was observed at microwave band for the first time. They fluctuated initially at a nearly stable frequency level then at a reverse drift component up to 5.49GHz. The individual fluctuation consists of a bi-directional drift component. The features are characterized by narrow bandwidth of Δf/f≤3%, quasi-periodicity of ~ms as well as a slowly reverse and a rapidly normal drift rates on the bi-directional drift component. The associated data of the Yohkoh soft and hard x-ray telescope and Nobeyama radio heliograph at 17GHz showed that there are several bright spots (i.e. inhomogeneities) along the soft x-ray loop, and the locations of both radio and soft x-ray sources are closely consistent. Therefore, the fluctuations are most likely caused by the inhomogeneities within a flare loop. Based on the two-component atmospheric model, we suggest a three-component atmospheric model with large scale length λ and small scale lengths λ1 and λ2 to describe equilibrium atmosphere and inhomogeneity. With the beam model, the characters of fluctuations may be interpreted reasonably by the quasi-equidistant inhomogeneity along a flare loop.

68 articles