不可压扰动方程高精度对称紧致差分数值解法及应用

从粘性不可压扰动方程一阶改型形式出发，对其实现了高精度对称紧致差分离散，就导出的扰动线性特征值问题给出了一个高效双重迭代局部解法，以相同精度将特征值和特征函数同时得到。通过不可压平面Poiseuille流时间稳定性算例详细对比显示了算法良好的谱分辨能力和较弱的网格依赖性，并结合复矩阵广义特征值隐式单位移QZ算法获取了一个新的扰动特征值谱计算结果。

用谱方法求解N-S方程

湍流研究具有重要的理论和工程意义,谱方法能达到快速收敛、高效和边界层中高分辨率、高精度。用谱方法边界条件处理也方便,谱方法随着数值方法的改善和计算机系统的发展,它在湍流数值模拟中的作用愈加重要。 这里介绍了一平直槽道及两个同心圆柱间的三维N-S方程数值求解的谱方法,在平直槽道中在平行壁面的x及z方向上用富氏展开,在法向(y)用契比雪夫多项式展开,与平直槽道相似,在θ和z方向用富氏展开,在法向r用契比雪夫多项式展开,为解N-S方程,在时间方向用Crank-Nicholson格式,非线性项用Adam-Bashforth格式,边界和连续条件精确满足。 由平直槽道和二同心圆柱间流动的数值模拟结果表明谱方法是N-S方程数值模拟的有效方法,数值结果与理论结果相符甚好。

爆推快点火模型分析

使用简单的爆推模型估算爆推快点火过程及其结果。首先由ns级主驱动激光直接驱动，形成中心低密度高温热斑，周围为高密度低温主燃料区，两区压力平衡（等压模型）；然后用ps级超短超强激光打入，产生超热电子，其能量在低温主燃料区沉积，主燃料区发生爆炸，一部分向外飞散，一部分向内压缩中心热斑。在这个爆推模型下，热斑体积压缩比为64，中子产率将有极大的提高，相应的中子产额和能量增益得到提高。离子温度因为主燃料区质量过大，提高不大。提高超热电子能量，或者减小低温主燃料区质量，离子温度将会显著提高。不同的初始离子温度对结果

A planar waveguide Nd : YAG laser using active Q-switching of a hybrid unstable resonator

A planar waveguide laser operating in a negative branch unstable resonator is Q-switched by an acoustooptic mod latorin anew configuration, providing effective, high-speed switching. The laser using a 200-mu m Nd:YAG core, face pumped by 10 laser diode bars, has produced 100-W output in a good beam quality at 100-kHz pulse rate, and 4.5 mJ at lower frequency with 15-ns pulse duration.

沉积温度对LaF3薄膜性能的影响

abstract {LaF₃ single-layer coatings were prepared by thermal boat evaporation at the deposition temperatures of 189, 255, 277 and 321°C respectively. The crystal structures of the coatings were characterized by X-ray diffraction (XRD). A spectrophotometer was employed to measure its transmittance. Moreover, refractive index, extinction coefficient and cut-off wavelength were obtained from the measured transmittance spectral curve. The residual stress was evaluated by the Stoney's equation and optical interferometer. Laser induce damage threshold (LIDT) was performed by a tripled Nd:YAG laser system. The results show that the crystallization status becomes better with the deposition temperature increasing. Correspondingly, the grain size also gets larger. Meanwhile, the coatings become more compact and the refractive index increases. However, the absorption of coatings seriously rises and the cut-off wavelength drifts to the long wave. In addition, the residual stress also increases and the intrinsic stress plays a determinant role in the coating. The LIDT of the coating also enhances at high temperature.}