水下连续激光成像的图像退化模型

水下环境中的介质和悬浮颗粒产生了光散射现象,导致水下激光图像存在严重的图像退化问题,大大降低了目标图像的信噪比。本文通过对水下连续激光成像光路图的分析,推导由于前向散射和后向散射而产生的图像退化模型。     

户外非光源场景图像雾天数字仿真

在航空航天、天文观测、军事等众多领域，计算机视觉系统获得了广泛应用。为了保证视觉系统能全天候正常地工作，必须对于这些系统抗天候变化能力进行检验．以便尽量使系统能够适用于各类天气状况，提高系统的鲁棒性和可靠性。然而检验系统抗天候变化能力需要产生各种复杂天气下户外场景的图像作为测试图像，以减少大量外场试验所带来的成本问题。针对雾天环境提出了一种基于图像的、利用雾天景物成像物理模型的方法生成雾天非光源场景图像.实验结果表明，所提出的方法对雾天非光源场景成像情况实现了较为真实地数字仿真。     

复势散射(英文)

在量子物理学中,散射问题是十分重要的,在其它领域中(如天体物理学、化学、粒子物理、激光物理等)也有着非常重要的作用。然而,在一般教科书中只讨论了粒子被实势散射的情况。该文采用分波法研究了粒子被中心复势场散射的问题,求得了总散射截面。     

银包覆表面修饰提高LiFePO4的电化学性能

LiFePO4是一种用于锂离子二次电池的潜在正极材料．LiFePO4微粒通过简单的共沉淀方法合成,为了增加其电子导电率,在水中用硝酸银溶液对LiFePO4进行包覆．粒子表面高分散的银提高了电子导电率和容量．不同电流密度下银包覆LiFePO4的电化学性能和其他高导电率的LiFePO4是相似的．银包覆是一种保持容量的有效方法,甚至在高的电流密度下也是如此．     

北京同步辐射装置小角散射站实验数据归一化

北京同步辐射装置小角散射实验站的电离室配置保证了实现实验数据对厚度归一化的要求.根据该配置给出了实验数据对厚度和强度归一化的分析方法.     

Analysis of stimulated Brillouin scattering in multi-mode fiber by numerical solution

Stimulated Brillouin scattering in optical fibers is described by a theoretical model and numerical analysis. The results showed that, for an optical fiber pumped by a laser beam with ns-order-pulse width and kW-order peak-power, SBS reflectivity tends to saturate when the fiber length exceeds a limit, named “effective fiber length”. Using small core-diameter and long enough fiber, the SBS reflectivity level could be raised but is limited by optical damage of the entrance surface of the fiber. Therefore, just a small dynamic range can be obtained. Project supported by the Bundesminesterium für Bildung und Forschung (BMBF), the key Foundation of Education Ministry of China and National Natural Science Foundation of China (NSFC No. 69578017).     

Waves scattering induced by an interface crack in a coated material

INTRODUCTION Cracks are likely to occur on the interfaces of coated materials widely applied in engineering. It is important to detect the interface cracks by non-destructive means. Detecting the scattered waves induced by interfacial cracks by using ultrasonic technique can be considered as one of the most fea- sible methods. This paper focuses on the theoretical basis for the study of wave scattering induced by interfacial cracks. In the last two decades, there has been a large number o…     

水下声散射一致性时域有限差分法的并行算法

In this work, we treat scattering objects, water, surface and bottom in a truly unified manner in a parallel finite-difference time-domain (FDTD) scheme, which is suitable for distributed parallel computing in a message passing interface(MPI) programming environment. The algorithm is implemented on a cluster-based high performance computer system.Parallel computation is performed with different division methods in 2D and 3D situations. Based on analysis of main factorsaffecting the speedup rate and parallel efficiency, data communication is reduced by selecting a suitable scheme of task division.A desirable scheme is recommended, giving a higher speedup rate and better efficiency. The results indicate that the unifiedparallel FDTD algorithm provides a solution to the numerical computation of acoustic scattering.