Characterization of Hermite-Gaussian Beams by Using Hartmann-Shack Wavefront Sensor

A Hartmann-Shack wavefront sensor (HSWS) is used in characterization of Hermite-Gaussian beams that are generated from a laser-diode pumped mode generator. By measuring the intensity distribution and the phase gradient distribution of the Hermite-Gaussian beams, we determine the beam width, radius of curvature and M^2factor from the images recorded in the HSWS. The results obtained from the HSWS measurement are compared with the ones obtained from the caustic measurement.     

横观各向同性体应力波传播问题的特征分析

本文根据广义特征理论,对横观各向同性体轴对称弹性波传播问题进行了理论分析。提出了一个简化特征分析的方法,这种方法将成为应用特征线法求解各类各向异性应力波问题的一个突破口。     

Correlation between Post-LASIK Starburst Symptom and Ocular Wavefront Aberrations

Monochromatic aberrations in post laser in-situ keratomileusis （LASIK） eyes are measured. The data are categorized into reference group and starburst group according to the visual symptoms. Statistic analysis has been made to find the correlation between the ocular wavefront aberrations and the starburst symptom. The rms aberrations of the 3rd and 4th orders for the starburst group are significantly larger than those for the reference group. The starburst symptom shows a strong correlation with vertical coma, total coma, spherical aberrations. For 3-mm pupil size and 5.8-mm pupil size, the modulation transfer function （MTF） of the starburst group are lower than those of the reference group, but their visual acuities are close. MTF and PSF analyses are made for two groups, and the results are consistent with the statistical analysis, which means the difference between the two groups is mainly due to the third- and fourth-order Zernike aberrations.     

利用迁移规律分析迈克尔逊干涉仪

本文以洛埃德镜实验作为引入,消除学生受薄膜干涉的思维定势,通过类比引导学生理解在点光源下迈克尔逊干涉仪实现干涉的方法是分波阵面法,并进一步分析等倾干涉和等厚干涉。     

燃气射流起始冲击波场形态的实验研究

介绍利用激光摩尔偏折仪和压阻式压力传感器对发动机喷流起始冲击波的基本形态进行的研究． 研究结果验证了在燃气流团前存在着起始冲击波及发展初期具有非球面的特性,并提出了喷口起始冲击波波阵面发展的新结构,对前人有关起始冲击波发展结构的研究结果进行了修正．     

一种特殊平面装药爆轰波阵面的摄影与结果分析

对由导爆索构成的平面装药的爆轰波阵面进行了高速摄影,并将其摄影照片同理论作图做了对比,结果表明此理论作图的方法是正确的。     

曲率相关的爆轰波在非结构四边形网格上的数值方法

假设爆轰波阵面的法向速度是曲率的线性函数,在非结构四边形网格上采用水平集方法模拟爆轰波阵面的运动过程.水平集方程的曲率无关项采用正格式离散,曲率项采用伽辽金等参有限元方法空间离散,时间离散采用半隐格式.在笛卡儿网格和随机网格上,含曲率的水平集方程的离散格式为强一阶精度,重新初始化方程的离散格式精度为近似一阶精度.曲率收缩的不光滑界面和多个爆轰波阵面相互作用的算例说明格式可有效地模拟爆轰波与曲率相关的运动.     

RC-28全频垂直阵列系统

RC-28采用有源分频的两路扬声器系统,含有两个V形结构的直辐射低音反射加载的8 in换能器和一个波导耦合的1.4 in出口、钛合金膜片压缩、多通道后辐射驱动器。120°水平覆盖与波阵面纠正技术相结合,扬声器     

横观各向同性含液饱和多孔介质中应力波传播的特征分析

根据广义特征理论,对横观各向同性含液饱和多孔介质中应力波传播特性进行了特征分析．给出了特征曲面的微分方程以及沿次特征线的相容条件,得到了波阵面的解析表达式．详细地讨论了应力波在横观各向同性含液饱和多孔介质中传播时,其速度曲面和波阵面的形状及性质．分析结果亦表明,纯固体中应力波传播的特征方程,是含液饱和多孔介质中应力波特征方程的特例．     

Solitary Wave and Wave Front as Viewed From Curvature

The solitary wave and wave front are two important behaviors of nonlinear evolution equations. Geometrically, solitary wave and wave front are all plane curve. In this paper, they can be represented in terms of curvature c(s), which varies with arc length s. For solitary wave when s → ±∞, then its curvature c(s) approaches zero, and when s=0, the curvature c(s) reaches its maximum. For wave front, when s → ±∞, then its curvature c(s) approaches zero, and when s=0, the curvature c(s) is still zero, but c'(s) ≠ 0. That is, s=0 is a turning point. When c(s) is given, the variance at some point (x,y) in stream line with arc length s satisfies a 2-order linear variable-coefficient ordinary differential equation. From this equation, it can be determined qualitatively whether the given curvature is a solitary wave or wave front.