图象恢复在工业CT中的应用

对于以影象增强器为检测系统的目标旋转式工业ＣＴ，分析了其图象退化的因素，采用对一维投影数据进行图象恢复的方法来提高ＣＴ图象质量。文中给出图象恢复公式，从计算机模拟和实验图象恢复的结果可看到所用方法提高了图象清晰度。     

多级SPOT立体影像匹配

立体影像匹配是自动提取SPOT影像高程信息的关键技术。本文根据SPOT影像在几何构像关系和影像质量上的特点,提出了多级匹配的结构策略。实际像对匹配实验表明,多级匹配法具有较好的可靠性和精度水平,而且运算速度快,在快速生成DEM数据辅助遥感信息分析方面,有重要的应用价值。     

A useful tool for image enhancement

Image enhancement provides a means to facilitate information transfer without altering the image information. A plug-in for the commonly used image capture and manipulation program Photoshop is discussed as one useful tool.     

一种实用的数字图像压缩方法

提出以C Builder 6.0为开发平台,以其所提供的TJPEGImage为核心,实现真彩色图像的压缩,为工程实际的应用提供了一种非常实用的压缩手段。该方法减少了大量程序代码的编写工作。实验表明,当综合压缩比设为65时,压缩图像与原图像相比并无明显变化,由此可见,压缩效果令人满意。     

一种基于人工免疫的图像分割算法

图像二维熵分割,一直因耗时长而限制了实际应用。本文借鉴生物免疫思想,提出二维熵图像分割的人工免疫算法。在克隆选择算法中引入疫苗的免疫接种,用于优化最优分割阈值对的搜索过程。在遥感高分辨率图像上的实验显示,该算法不仅能准确搜索到最优阈值对,而且计算时间只有传统算法的1.8%。该算法也验证了人工免疫思想用于图像分割的可行性和有效性。     

基于3S技术土地利用现状数据库更新方法探讨

本文研究了基于3S技术的1:1万土地利用现状更新调查的方法,针对其中遇到的若干问题进行了探讨,认为正射影像图制作时必须注意精度问题,影像解译采用自动分类与目视解译相结合的方法可以提高效率保证解译精度;外业调绘补测应该严把质量关,以保障整个工程的精度,外业调绘结果采用直接矢量化可以减少工作量,以减少误差;重新划分图斑号可以方便外业调查和今后土地管理工作;建议数据建库时采用地形图校正可以提高数据库的精度。     

图像重建算法FBP与OSEM在工业CT应用中的对比研究

滤波反投影法(FBP)与有序子集最大期望值法(OSEM)是图像重建中最为常用的两种方法,本文研究了这两种重建方法在工业CT中的应用,就不同的探测器数目、不同的旋转投影角度取样数、不同的噪声水平,对两种方法的重建效果进行对比与分析,结果表明在某些条件下迭代法OSEM重建图像质量明显好于解析法FBP。     

Utilisation of the image analysis method for the detection of the morphological anisotropy of calcite grains in marble

This paper presents the development and utilisation of an automated image processing algorithm for detection and analysis of grains. Using optical polarising microscopy, a set of colored images are collected from an area on a thin section. A filtering operation, using rotation of a morphological alternating sequence filter (based on a structuring element), is used to remove twinning features within individual grains. Filtering is followed by the watershed segmentation technique to determine grain boundaries. The method is used for the identification of calcite grains in marble and the subsequent analysis of morphological anisotropy.     

基于对应分析的训练样本的选择

本文提出一种基于对应分析的训练样本的选择方法。它从训练样本中自动地选择有代表性的典型训练样本,使得在自动分类中充分利用所采集的样本信息,以便得到满意的分类结果。通过实验与分析证明,该方法是可行的,它明显优于人工随机选择训练样本的方式。与基于Q型因子分析的训练样本选择方法相比,可以更快地得到较少的典型样本,满意的分类精度。     

Quasi-stationary flow structure in turbidity currents

A turbidity current is a particle-laden current driven by density differences due to suspended sediment particles. Turbidity currents can transport large amounts of sediment down slopes over great distances, and play a significant role in fluvial, lake and submarine systems. To better understand the sediment transport process, the flow system of an experimentally produced turbidity current in an inclined flume was investigated using video processing. We observed that the current progresses with constant frontal velocity and maintains an unchanged global interface geometry. In addition, the spatio-temporal profiles of the inner mean and turbulence velocity obtained by ultrasound velocity profiler (UVP) showed that similar distributions were maintained, with low dissipation. The results indicate that the turbidity current progressed in a quasi-stationary state, which enabled long-distance sediment transport. To understand the mechanisms behind the quasi-stationary flow, we analyzed the forces acting on the turbidity current. We found that under particular densities of suspended particles, the gravitational force is balanced by the viscous forces along the slope direction. We conclude that this specific force balance induces the quasi-stationary flow structure, enabling the long-distance transport of a substantial amount of sediment downstream with low dissipation.