Fast parallel algorithm for three-dimensional distance-driven model in iterative computed tomography reconstruction

The projection matrix model is used to describe the physical relationship between reconstructed object and projection.Such a model has a strong influence on projection and backprojection,two vital operations in iterative computed tomographic reconstruction.The distance-driven model(DDM) is a state-of-the-art technology that simulates forward and back projections.This model has a low computational complexity and a relatively high spatial resolution;however,it includes only a few methods in a parallel operation with a matched model scheme.This study introduces a fast and parallelizable algorithm to improve the traditional DDM for computing the parallel projection and backprojection operations.Our proposed model has been implemented on a GPU(graphic processing unit) platform and has achieved satisfactory computational efficiency with no approximation.The runtime for the projection and backprojection operations with our model is approximately 4.5 s and 10.5 s per loop,respectively,with an image size of 256×256×256 and 360 projections with a size of 512×512.We compare several general algorithms that have been proposed for maximizing GPU efficiency by using the unmatched projection/backprojection models in a parallel computation.The imaging resolution is not sacrificed and remains accurate during computed tomographic reconstruction.     

结合刚体基本运动分析三刚片体系几何构造

为探寻体系几何构造分析技巧,总结了三刚片连接的所有可能形式,在简化模型分析基础上,结合刚体的基本运动特征,针对三刚片连接形式中有无穷远瞬铰出现的特殊情况进行详细分析,获取体系构造分析中的一般规律,为学习体系几何构造分析提供帮助.     

钢框架抗震耗能节点梁的极限承载力分析1）

为提高结构的抗震性能，框架结构中以翼缘削弱型节点为代表的延性耗能节点逐渐代替传统节点，为研究翼缘削弱型节点框架梁在单向比例加载时的极限载荷，对削弱梁极限状态进行了分析，判定极限状态下削弱梁塑性铰生成的位置并计算极限载荷，将计算结果和普通梁进行对比.分析结果表明：削弱梁越长承载力下降越明显，对短梁需要选择合适的削弱参数，才能避免塑性铰出现在梁端.研究结果可为削弱梁塑性设计提供依据，同时拓展结构力学极限载荷学习内容.     

基于稀疏优化的计算机断层成像图像不完全角度重建综述

计算机断层成像(computed tomography,CT)技术在医学和工业无损检测中都具有非常广泛的应用,CT重建算法是其中的核心,而不完全角度重建问题则是实际应用中重建算法研究领域的一个热点和难点问题.近年来,随着稀疏优化理论与算法的飞速发展,基于稀疏优化的重建算法已经在不完全角度重建问题中得到了较广泛的应用,且表现出了良好的精度与速度性能.本文首先对稀疏优化的基本理论结论与常用算法进行了介绍;而后对稀疏优化理论在CT图像不完全角度重建中的应用进行归纳,分类介绍了其主要研究成果及稀疏优化所发挥的作用;最后对基于稀疏优化的不完全角度重建研究进行了展望.     

东海碎屑矿物特征的研究

本文根据东海在全球构造中的位置,海底表层沉积物中碎屑矿物的组成、成因、分布特征,讨论了碎屑重矿物群、重矿物组合类型以及碎屑矿物组合分带对沉积地段古地理环境、海底矿产、沉积相及区域构造等方面的指示意义。     

STUDY ON THE CHARACTERISTICS OF DETRITAL MINERALS OF EAST CHINA SEA FLOOR

On the basis of the position of the East China Sea in global tectonics, and of the composition, origin and distribution of the detrital minerals in the sea-bottom surface sediment, this paper discusses the geological significance of the detrital heavy mineral assemblage, the assemblage type of the heavy minerals, and the assemblage zone of the detrital minerals in the study of regional structure, paleogeographic environment, submarine mineral deposit and sedimentary facies.