坡面细沟侵蚀的冲刷试验研究

细沟侵蚀是土壤侵蚀的重要方式之一，但定量研究困难很大。本文设计并完成了一系列小规模细沟侵蚀冲刷试验，研究细沟侵蚀过程中的动力学规律。试验结果表明了一些细沟侵蚀的趋势性规律，也反映出其中存在较强的随机性。通过分析试验数据，得到了细沟宽度及过水断面湿周与流量和坡度的经验关系，并发现湿周与它们的关系更为密切。

BP神经网络在泥石流研究中的应用

以泥石流预测为例讨论了ＢＰ型神经网络在泥石流研究中的应用。首先针对泥石流情况对网络作了适当改进。结果表明，神经网络用于泥石流有广阔前景。

第十三届国际等离子体化学会议简介

第十三届国际等离子体化学会议简介＠吴承康￥中国科学院力学研究所第十三届国际等离子体化学会议简介吴承康中国科学院力学研究所，北京１０００８０１概况国际等离子体化学会议（ＩｎｔｅｒｎａｔｉｏｎａｌＳｙｍｐｏｓｉｕｍｏｎＰｌａｓｍａＣｈｅｍｉｓｔｒｙ，ＩＳＰＣ...

CWCO_2激光辐照下硅的光吸收特性

本文基于半导体材料硅(Si)中电子、空穴的费米统计分布,计算了Si对CO_2 激光的透射率随温度的变化,并用实验理论作了验证.说明在强CO_2激光辐照下,Si对CO_2激光能量有着强烈的吸收,其机理主要是自由载流子吸收.

An ultra-broadband spatially dispersed regenerative amplifier free from spatial chirp

An ultra-broadband Ti:sapphire regenerative amplifier based on spatially dispersed amplification is demonstrated experimentally. Departing from previous reports, a new design of the cavity gets the amplified pulse free from spatial chirp. Utilizing this new regenerative amplifier, chirped pulses with bandwidth (FWHM) of about 80 nm are obtained, and the bandwidth is limited only by that of the incident seed pulses.

Degenerated optical parametric chirped-pulse amplification with cesium lithium borate

A gain amplifier for degenerated optical parametric chirped-pulse amplification (OPCPA) with lithium triborate and cesium lithium borate (CLBO) crystals was demonstrated in a near-collinear configuration, The signal gain of the final energy amplifier with CLBO was similar to 6. After compression, the 123 fs pulse duration was obtained. Compared with potassium dihydrogen phosphate, it is confirmed that CLBO is more effective as a nonlinear crystal in a final power amplifier for terawatt or petawatt OPCPA systems. To our knowledge, this is the first demonstration of OPCPA with CLBO. (c) 2006 Optical Society of America.

Optimization of positions and currents of tokamak poloidal field coils using genetic algorithms

Plasma equilibrium geometry has a great influence on the confinement and magnetohydrodynamic stability in tokamaks. The poloidal field (PF) system of a tokamak should be optimized to support the prescribed plasma equilibrium geometry. In this paper, a genetic algorithm-based method is applied to solve the optimization of the positions and currents of tokamak PF coils. To achieve this goal, we first describe the free-boundary code EQT Based on the EQT code, a genetic algorithm-based method is introduced to the optimization. We apply this new method to the PF system design of the fusion-driven subcritical system and plasma equilibrium geometry optimization of the Experimental Advanced Superconducting Tokamak (EAST). The results indicate that the optimization of the plasma equilibrium geometry can be improved by using this method.

双倍密度光栅的飞秒压缩技术

飞秒激光技术是当前激光前沿领域的发展内容之一，飞秒脉冲的压缩手段更是其中重要的研究内容。在飞秒脉冲的压缩中，必须使用负的色散元件来补偿飞秒激光钛宝石晶体本身所具有的正的色散以实现压缩。现有的负色散补偿技术包括使用以下三种方式：高密度光栅对、棱镜对、啁啾镜。这三种补偿方式各有优缺点，其中，传统的高密度光栅对只能提供较大的色散量，往往用于飞秒脉冲大范围的展宽和压缩；啁啾镜提供的啁啾量较小，成本也太高；棱镜对的色散能力较小，需要较长的工作距离才能有足够的色散量，往往体积庞大，而且也太重。因此，发展一种新型的补偿

Analytic expression of the diffraction of a circular aperture

Recurring to the characteristic of Bessel function, we give the analytic expression or the Fresnel diffraction by a circular aperture, thus the diffractions on the propagation axis and along the boundary of the geometrical shadow are discussed conveniently. Since it is difficult to embody intuitively the physical meaning from this series expression of the Fresnel diffraction, after weighing the diffractions on the axis and along the boundary of the geometrical shadow, we propose a simple approximate expression of the circular diffraction, which is equivalent to the rigorous solution in the further propagation distance. It is important for the measurement of the parameter or the beam, such as the quantitative analysis of the relationship of the wave error and the divergence of the beam, In this paper, the relationship of the fluctuation of the transverse diffraction profile and the position of the axial point is discussed too. (c) 2005 Elsevier GrnbH. All rights reserved.

基于同步移相技术的1/4波片快轴方位角的实时测量

提出了一种基于同步移相技术的1/4波片快轴方位角的实时测量方法。由正交光栅、光阑、检偏器组和四象限探测器实现同步移相功能。检偏器组由4个不同方位角的检偏器组成。通过检偏器组的四束光束的光强由四象限探测器同时测量。1/4波片的快轴方位角由这四光束的光强得到。由于该方法不需旋转偏振器件，从而实现的1/4波片的快轴方位角的实时测量。

Devitrification of TeO2-doped fluoroaluminate glass

Crystallization behavior of the glass system AlF3-MgF2-CaF2-SrF2-BaF2-YF3-TeO2 (AMCSBY-TeO2) Was studied by the nonisothermal method using differential thermal analysis. The activation energy E and Avrami exponent n were determined by nonisothermal method. It is found that the value of E varies with increasing TeO2 and reaches a minimum at 10 mol fraction TeO2, while n decreases from 3.65 to 1.78 with the addition of TeO2. X-ray diffraction shows that Ba2Te3O8, MgTe2O5, and SrTeO3 phase formed when the glasses were reheated. The addition of TeO2 changes the crystallization mechanism and improves the stability of the fluoroaluminate glass.