类氢类氦类锂镁离子双电子复合的旁观电子角动量研究

类氢类氦类锂镁离子经中间双激发态进行的双电子复合过程在研究惯性约束聚变电子温度中占有很重要的地位.用准相对论方法计算了双电子复合经不同Rydberg态跃迁通道的复合速率系数,并给出不同离化度离子的双电子复合速率系数随电子温度的变化规律.显示出离子的相关能对峰值的电子温度有很大影响,当类氢离子跃迁通道的旁观电子角动量为1时双电子复合系数最大,而类锂离子是旁观电子角动量为3时最大. 关键词： 双电子复合 镁离子 角动量     

数码相机引入科技照像实验

介绍了数码相机的系统结构和工作原理，通过与传统相机的对比分析，在科技照相实验中应该使用数码相机。     

Controlling global stochasticity of Hamiltonian systems by nonlinear perturbation

A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust against small external noise. The mechanism underlying this high control efficiency is intuitively explained. Received 15 January 2002 Published online 6 June 2002     

有界连通区域上Dirichlet空间及其算子

本文主要讨论了有界连通区域Dirichlet空间上Toeplitz算子的Fredholm性质,计算了符号在C1中的Toeplitz算子的本性谱和Fredholm指标．     

Mössbauer and X-ray diffraction characterization of Fe60Al40 coatings prepared by thermal spraying

Microstructured (atomized) and nanostructured (milled) Fe₆₀Al₄₀ powders together with their corresponding coatings synthesized by High Velocity Oxy-fuel (HVOF) or Atmospheric Plasma Spray (APS) thermal spraying techniques have been characterized by Mössbauer Spectroscopy (MS) and X-ray Diffraction (XRD). The evolution of the microstructure and the atomic ordering degree in the powders and coatings are discussed at the light of the various processing conditions. The operational correlation between the parameters of the duplex morphology of coatings and the processing parameters is discussed.     

Spectrum Simulation of Li-Like Aluminium Plasma

X-ray emission spectra for L-shell of Li-like aluminium ions are simulated by using the flexible atomic code based on the collisional radiative model. Atomic processes including radiative recombination, dielectronic recombination, collisional ionization and resonance excitation from the neighbouring ion （Al^9＋ and Al^11＋ ） charge states of the target ion （Al^10＋） are considered in the model. In addition, the contributions of different atomic processes to the x-ray spectrum are analysed. The results show that dielectronic recombination, radiative recombination, collisional ionization and resonance excitation, other than direct collisional excitation, are very important processes.     

吸积盘的X射线辐射对周围星际物质的离化研究

利用辐射流体力学程序对三倍频纳秒激光与靶物质相互作用进行了模拟研究，得到了可以产生黑体辐射谱分布的激光等离子体X射线辐射靶的最佳厚度；数值模拟研究了黑体谱分布的X射线辐射场对等离子体系统平均离化度分布的影响，它有助于深入理解天体物理中吸积盘对它周围星际物质的离化影响. 关键词： 辐射流体力学 激光等离子体 X射线辐射 吸积盘 离化     

The monomial ideal of a finite meet-semilattice

Squarefree monomial ideals arising from finite meet-semilattices and their free resolutions are studied. For the squarefree monomial ideals corresponding to poset ideals in a distributive lattice, the Alexander dual is computed.

     

Effect of Nonradiative Recombination on Carrier Dynamics in GaInNAs/GaAs Quantum Wells

The nonradiative recombination effect on carrier dynamics in GalnNAs/GaAs quantum wells is studied by timeresolved photoluminescence （TRPL） and polarization-dependent TRPL at various excitation intensities. It is found that both recombination dynamics and spin relaxation dynamics strongly depend on the excitation intensity. Under moderate excitation intensities the PL decay curves exhibit unusual non-exponential behaviour. This result is well simulated by a rate equation involving both the radiative and non-radiative recombinations via the introduction of a new parameter of the effective concentration of nonradiative recombination centres in the rate equation. In the spin dynamics study, the spin relaxation also shows strong excitation power dependence. Under the high excitation power an increase of spin polarization degree with time is observed. This new finding provides a useful hint that the spin process can be controlled by excitation power in GaInNAs systems.