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Cellular Cell Bifurcation of Cylindrical Detonations

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Chinese Physics Letters 2008年第6期25卷 2125-2127页

作者：韩桂来姜宗林王春张凡 Key Laboratory of High Temperature Gas Dynamics Institute of Mechanics Chinese Academy of Sciences Beijing 100080 Defence Research and Development Canada-Suffield PO Box 4000 Stn. Main Medicine Hat AB T1A 8K6 Canada

Cellular cell pattern evolution of cylindrically-diverging detonations is numerically simulated successfully by solving two-dimensional Euler equations implemented with an improved two-step chemical kinetic model. From the simulation, three cell bifurcation modes are observed during the evolution and referred to as concave front focusing, kinked and wrinkled wave front instability, and self-merging of cellular cells. Numerical research demonstrates that the wave front expansion resulted from detonation front diverging plays a major role in the cellular cell bifurcation, which can disturb the nonlinearly self-sustained mechanism of detonations and finally lead to cell bifurcations.

关键词： supernova explosion proto-neutron star shock wave

Persistent Spin and Charge Currents in Open Conducting Ring Subjected to Rashba Spin-Orbit Coupling

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Chinese Physics Letters 2008年第5期25卷 1844-1847页

作者：张喜花熊诗杰 National Laboratory of Solid State Mierostruetures and Department of Physics Nanjing University Nanjing 210093

We investigate persistent charge and spin currents of a one-dimensional ring with Rashba spin-orbit coupling and connected asymmetrically to two external leads spanned with angle φo. Because of the asymmetry of the structure and the spin-reflection, the persistent charge and spin currents can be induced. The magnification of persistent currents can be obtained when tuning the energy of incident electron to the sharp zero and sharp resonance of transmission depending on the Aharonov-Casher （AC） phase due to the spin-orbit coupling and the angle spanned by two leads φo. The general dependence of the charge and spin persistent currents on these parameters is obtained. This suggests a possible method of controlling the magnitude and direction of persistent currents by tuning the AC phase and φo, without the electromagnetic flux though the ring.

关键词： supernova explosion proto-neutron star shock wave

Influence of Strain-Reducing Layer on Strain Distribution of Self-Organized InAs/GaAs Quantum Dot and Redshift of Photoluminescence Wavelength

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Chinese Physics Letters 2008年第5期25卷 1850-1853页

作者：刘玉敏俞重远任晓敏 School of Science Beijing University of Posts and Telecommunication Beijing 100876 ecommunications Beijing 100876

A systematic investigation about the strain distributions around the InAs/GaAs quantum dots using the finite element method is presented. A special attention is paid to influence of an Ino.2 *** strain reducing layer. The numerical results show that the horizontal- and vertical-strain components and the biaz^ial strain are reinforced in the InAs quantum dot due to the strain-reducing layer. However, the hydrostatic strain in the quantum dot is reduced. In the framework of eight-band k · p theory, we study the band edge modifications due to the presence of a strain reducing layer. The results demonstrate that the strain reducing layer yields the decreasing band gap, i.e., the redshift phenomenon is observed in experiments. Our calculated results show that degree of the redshift will increase with the increasing thickness of the strain-reducing layer. The calculated results can explain the experimental results in the literature, and further confirm that the long wavelength emission used for optical fibre communication is realizable by adjusting the dependent parameters. However, based on the calculated electronic and heavy-hole wave function distributions, we find that the intensity of photoluminescence will exhibits some variations with the increasing thickness of the strain-reducing layer.

关键词： supernova explosion proto-neutron star shock wave

Effect of Discharge Voltage on an Ion Sheath Formed at a Grid in a Multi-Dipole Discharge Plasma

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Chinese Physics Letters 2008年第3期25卷 1011-1014页

作者： M. K. Mishra A. Phukan Centre of Plasma Physics.Tepesia Kamrup-782402 Assam INDIA

It is experimentally demonstrated that a relatively strong ion-rich sheath formed at a fixed negative bias of the grid can be changed to a rather weak ion sheath （sheath potential weakly retards electrons） only by increasing the discharge voltage in the system. At sufficiently high negative grid bias, an increase of discharge voltage enhances the ion collection current at the grid. An explanation is put forward in support of this experimental observation. A slight density enhancement with a fall in plasma electron temperature is also observed with the increasing negative grid bias.

关键词： supernova explosion proto-neutron star shock wave

Large Relative Raman Shift for Molecules Adsorbed on Metallic Nano-particles

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Chinese Physics Letters 2008年第6期25卷 2140-2143页

作者：李晓云夏宇兴詹黎冷江华 Spectroscopy Laboratory Department of PhysicsShanghai Jiao Tong University Shanghai 200240

The enhancement of two order-of-magnitudes is observed in surface-enhanced Raman spectroscopy （SERS） of gases （CO, C2H2, C2H4, etc） adsorbed on nitric acid-roughened metal foil. In addition, some Raman lines of gases adsorbed on these active substrates show larger frequency shifts and linewidth broadening, compared with the Raman spectroscopy of free gases. Using the two-oscillator electromagnetic model, we explain this phenomenon. It is related to the large non-regular particles on the active substrate we prepared. It is found that the parameters of the surface-plasmon dispersion, the distance of molecules from the surface and the radius of particles play crucial roles on the relative large Raman shifts.

关键词： supernova explosion proto-neutron star shock wave

Independent Modulation of Omnidirectional Defect Modes in Single-Negative Materials Photonic Crystal with Multiple Defects

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Chinese Physics Letters 2008年第4期25卷 1313-1316页

作者：王琼闫长春张玲玲崔一平 Advanced Photonics Center School of Electronic Science and Engineering Southeast University Nanjing 210096

Single-negative materials based on photonic crystal with multiple defect layers are designed and the free modulation of defect modes is studied. The results show that the multi-defect structure can avoid the interference between the defect states. Therefore, the designed double defect modes in the zero effective-phase gap can be adjusted independently by changing the thickness of different defect layers. In addition, the two tunable defect modes have the omnidirectional characteristics. This multi-defect structure with above-mentioned two advantages has potential applications in modern optical devices such as tunable omnidirectional filters.

关键词： supernova explosion proto-neutron star shock wave

Generation of Cluster-Type Entangled Coherent States via Cross-Kerr Nonlinearity

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Chinese Physics Letters 2008年第3期25卷 839-842页

作者：王文峰孙心瑗罗小兵 Department of Physics Jinggangshan University Ji'an 343009 Institute of Physics Chinese Academy of Sciences Beijing 100080

We propose an optical scheme for the generation of the cluster-type entangled coherent states in free travelling optical fields via cross-Kerr nonlinearity. The required resources for the generation are coherent state source, beam splitters, photodetectors, and Kerr media. We also discuss the implementation of the Hadamard gate operation for coherent states and the homodyne detection.

关键词： supernova explosion proto-neutron star shock wave

Annual Variation and Global Structures of The DE3 Tide

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Chinese Physics Letters 2008年第6期25卷 2323-2326页

作者：陈泽宇吕达仁 Institute of Atmospheric Physics Chinese Academy of Sciences PO Box 9804 Beijing 100029

The SABER/TIMED temperatures taken in 2002 2006 are used to delineate the tidal signals in the middle and upper atmosphere. Then the Hough mode decomposition is applied with the DE3 tide, and the overall features of the seasonal variations and the complete global structures of the tide are observed. Investigation results show that the tide is most prominent at 110km with the maximal amplitude of 〉 9K, and exhibits significant seasonal variation with its maximum amplitude always occurring in July every year. Results from the Hough mode decomposition reveal that the tide is composed primarily of two leading propagating Hough modes, i.e., the （-3, 3） and the （-3, 4） modes, thus is equatorially trapped. Estimation of the mean amplitude of the Hough modes show that the （-3, 3） mode and （-3, 4） mode exhibit maxima at 110km and 90km, respectively. The （-3, 3） mode plays a predominant role in shaping the global latitude-height structure of the tide, e.g., the vertical scale of 〉 50 km at the equator, and the annual course. Significant influence of the （-3, 4） mode is found below 90 km, where the tide exhibits anti-symmetric structure about the equator; meanwhile the tide at northern tropical latitudes exhibits smaller vertical wavelength of about 30 km.

关键词： supernova explosion proto-neutron star shock wave

The Minimum Model for the Iron-Based Superconductors

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Chinese Physics Letters 2008年第6期25卷 2232-2234页

作者：李健王玉鹏 Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190

A single band t-U-J1-J2 model is proposed as the minimum model to describe the superconductivity of the newly discovered iron-based superconductors R（O1-xFx）FeAs and RO1-xFeAs （R=La, Ce, Sm, Pr, Nd, Gd）. With the mean-field approach, it is found that the pairing occurs in the d-wave channel. In the likely parameter region of the real materials, by lowering temperature, the system enters firstly the dxy superconducting phase with D4h-symmetry and then enters the time-reversal-symmetry-broken dxy＋idx2-y2 superconducting phase with C4h -symmetry.

关键词： supernova explosion proto-neutron star shock wave