Investigation of Nonuniformity of the Velocity Distribution in the Shear Layer of an Underexpanded Jet by Electric Discharge Tracing of the Flow

Streamwise and radial components of velocity in the shear layer of an underexpanded jet are measured by the method of spark tracing. The nonuniform distribution of gas-dynamic parameters of the flow in this region is caused by streamwise Görtler-type vortex structures.     

Offner成像光谱仪建模及像差分析

利用光线追迹方法得到系统的数值模型,然后运用级数展开方法,建立起系统的3阶解析模型,亦即3阶像差理论.该模型给出系统像差系数和计算系统点列图的解析表达式,可适应于包含变间距凸面光栅的系统,并具有良好的扩展性.通过追迹示例Offner系统中10000条不同波长、不同高度的光线,结果表明运用解析模型可以快速而准确地生成系统...     

微型轫致辐射X射线光源扰动器设计

利用电子轨迹跟踪方法对微型轫致辐射X射线光源的一个关键部件扰动器进行了设计研究。分析了扰动器工作原理,使用CST电磁工作室设计了扰动器的磁场分布,并计算了在此磁场分布下电子的注入效果与扰动器中心位置的关系。结果表明：扰动器的幅向中心位置越靠近电子跨越中心轨道的位置,电子注入后的振幅越小,但同时所需要的磁场强度越大。最后分析了该扰动器注入的横向、纵向接受度,其具有3 mm0.23 mrad的横向接受度和0.1%的能量接受度。     

基于子网划分的电网关键节点识别

结合电网拓扑结构和潮流追踪技术,提出一种基于子网划分的电网关键节点识别方法。首先,根据发电机节点的邻域信息和功率将发电机节点划分为不同的子集,然后根据电网的系数分配矩阵将负荷节点划分到为其提供最大功率的发电机节点子集中,完成子网划分。接着采用多属性决策法对每个子网的节点进行排序,进一步改进并计算每个子网的结构系数,作为衡量子网重要性的指标。根据子网重要性,从每个子网中提取特定比例的候选关键节点,对这些候选节点依据多属性决策法重新排序,得到关键节点的最终排序。以IEEE14、IEEE57和IEEE118三种节点系统为例进行分析,得到各个系统的子网划分结果和各个标准网络的重要节点排序结果。采用本文方法、PageRank法和多属性决策法分别进行关键节点排序,并对排序靠前的关键节点进行级联故障性能实验和网络效能实验。实验表明,本文算法选择的关键节点对整个网络的传播性能影响最大,优于其他两种关键节点识别方法。     

光学系统的偏振像差研究

综合论述了偏振像差的理论,给出了具体的例子,指出偏振是影响光学系统性能的一个重要因素,要想提高光学系统的性能,必须控制光学系统的偏振像差,而且光学系统设计必须与光学薄膜的设计结合起来。     

Performance of a noise barrier within an enclosed space

The present study involved experimental, theoretical, and numerical analyses of the insertion loss provided by rigid noise barriers in an enclosed space. The existing classical diffuse-field theory may be unable to predict the actual sound pressure level distribution and barrier insertion loss for indoor applications. Although predictions made by the ray tracing method at high frequencies are reasonably satisfactory, the method is computer-intensive and time-consuming. We propose a new formula that incorporates the effects of diffraction theory and the reflection of sound between room surfaces. Our results indicate that the present formula provides more realistic and practical predictions of the barrier insertion loss than existing approaches.     

基于可视化荷载路径的结构混凝土拉-压杆模型

通过荷载路径可以直观地了解结构实现其功能的方式。本文首先根据荷载路径的定义，介绍一种基于平衡原理，将有限元方法和流线追踪算法结合，确定二维线弹性结构中荷载路径的方法。采用这种方法结合商用有限元软件Algor13和商用数据处理软件Tecplot9．0，把前者得到的结构应力计算结果及对应的有限元网格信息通过数据文件输入后者，以得到结构内连续的可视化荷载路径。最后，本文将这种方法用于确定牛腿结构中的可视化荷载路径，并在此基础上建立该结构的拉杆-压杆模型。     

Astigmatic Characteristics of Diffractive Optical Elements with Aspherical Phase Term

Analytical expression for the two principal foci of the astigmatic image generated by the diffractive optical elements with aspheric phase term were derived using the ray tracing technique. The relation is given between the principal foci and the coefficients of the aspherical phase term expanded by polynomials. Numerical examples are discussed and compared with the experimental results previously reported. The formulas given here include the equations derived by considering the propagations of an astigmatic wavefront through a hologram.     

An algorithm for computing minimal Geršgorin sets

The existing algorithms for computing the minimal Ger?gorin set are designed for small and medium size (irreducible) matrices and based on Perron root computations coupled with bisection method and sampling techniques. Here, we first discuss the drawbacks of the existing methods and present a new approach based on the modified Newton's method to find zeros of the parameter dependent left‐most eigenvalue of a Z‐matrix and a special curve tracing procedure. The advantages of the new approach are presented on several test examples that arise in practical applications. Copyright © 2015 John Wiley & Sons, Ltd.     

基于子曲面分割和迭代的自由曲面光线追迹方法

根据光学自由曲面数学描述复杂,但面形较为平滑的特点,提出一种新的基于子曲面分割和迭代的自由曲面光线追迹方法。通过离散点分割形成子曲面阵列,根据三角形内角和定理确定目标子曲面,对目标子曲面进行切平面迭代完成光线追迹。通过数值仿真,采用所提方法分别对偶次非球面、双圆锥曲面、扩展多项式面和单透镜无像散系统进行光线追迹,并与ZEMAX追迹结果进行比对。结果表明:该方法在离散点采样密度很低的情况下（降低了计算机的内存消耗和运算时间）仍然可以保证光线追迹的精确性,与ZEMAX中光线和自由曲面交点的偏差达到10-3（nm）量级,出射光线角度的偏差达到10-3（）量级。