基于高密度子网格光线追迹的三维发射层析重建算法

三维(three- dimensional,3D) 发射层析技术(emission computerized tomography,ECT) 是一种简单、高效且准确的燃 烧场3D成像与检测技术,其中权重矩阵的计算 精度决定了层析重建的精度和质量。本文研究了一种基于高密度子网格光线追迹的权重矩阵 计算方法, 将被测区域划分为密度更高的子网格,并根据相机成像模型实现光线追迹,以确定离散网格 对投影像素 的权重因子。数值模拟和燃烧火焰重建实验表明该算法具有较高的精度和计算效率。该研究 对于3D发射层析技术的实用化具有重要的理论意义。     

Optimum design of electromagnetic shielding rooms with minimum usage of absorbing materials

In this article, a novel method has been proposed to optimize the electromagnetic shielding rooms. This method is based on using minimum electromagnetic absorbing materials on the inner surface of the rooms. The positions of the absorbing materials are found optimally to produce a “best” performance for the shielding rooms. The ray‐tracing method is used to predict the shielding effectiveness (SE) of the electromagnetic shielding rooms with apertures. The performance of the proposed method is verified by a comprehensive example. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010.     

CRT and LCD monitor and process materials evaluated for environmental improvement

Decision rules have been developed and applied to the bills of materials of a color cathode‐ray tube (CRT) and a liquid‐crystal‐display (LCD) desktop monitor to determine which product and process materials will be evaluated in an environmental life‐cycle assessment. Materials of significant mass, of technological importance, and of potential environmental impact are targeted. The list of materials identified are those for which life‐cycle inventory data will be obtained for the materials extraction and materials processing life‐cycle stages of a CRT and an LCD. Additionally, materials identified will also be used to represent life‐cycle impact in terms of resource consumption, as well as surrogates for occupational health impacts.     

数字X射线图象的成象分析及校正

数字X射线图象的形成是一个X射线信息影象的形成、转换和传递的复杂过程,且通常得到的数字X射线图象的灰度值没有准确的物理意义,在实验的基础上,提出了一种基于朗伯定律的理想图象模型,用以对数字X射线图象进行灰度的校正及线性化,经过这样的处理后,图象的灰度值与吸收体厚度之间的关键近似为线性,这对于人体特征参数的定量分析（如对心脏形态、血流的分析,以及在DSA中对造影剂浓度的分析等）具有重要作用。     

工程火警监测的计算机自动处理

阐述了采用红外摄象及计算机自动处理技术,对工程火警进行监测。采用图值,面积、形状智能识别和实时行程编码技术,系统的识别可靠性大为提高。     

三维图形生成软件POV-RAY的原理及应用

本文介绍了一种国际上广泛采用的三维图形生成软件ＰＯＶ－ＲＡＹ。该软件是为学术研究和教学研制的。它是免费、公开原代码的基于光线跟踪原理软件包。本文介绍了该软件的特点,各项功能及其与其他三维图形软件的区别。着重描述了场景描述语言的各部分结构：头文件、照相机定义、光照定义、物体描述等。根据我们的使用认为ＰＯＶ－ＲＡＹ的功能齐全、使用方便。不但可以用于生成各种三维图形,还可以作为二次开发的理想平台或参考系     

Interactive Ray Tracing of Large Models Using Voxel Hierarchies

We propose an efficient approach for interactive visualization of massive models with CPU ray tracing. A voxel‐based hierarchical level‐of‐detail (LOD) framework is employed to minimize rendering time and required system memory. In a pre‐processing phase, a compressed out‐of‐core data structure is constructed, which contains the original primitives of the model and the LOD voxels, organized into a kd‐tree. During rendering, data is loaded asynchronously to ensure a smooth inspection of the model regardless of the available I/O bandwidth. With our technique, we are able to explore data sets consisting of hundreds of millions of triangles in real‐time on a desktop PC with a quad‐core CPU.     

动态3D虚拟场景并行化光线跟踪加速结构设计

为提高光线与虚拟场景几何面片求交的计算效率,提出一种基于混合模式的空间加速结构。该方法改进传统的层次包围盒,把细分层次包围盒与空间均匀网格划分相结合,实现了可并行的混合空间加速设计。此外,把帧间可重用的数据抽取至数据缓存,建立多几何群组的加速结构共享,实现了光线跟踪算法的并行优化。实验证明,该混合加速结构能有效加快光线跟踪的光线场景求交判断速度,快速实现光线跟踪并行化计算。