MRI分割的几何活动轮廓模型的半隐式AOS迭代方法     

李刚 《南京气象学院学报》2005,28(2):225-232

几何活动轮廓模型以其计算稳定等优点，被广泛用于图像分割。给出一种基于AOS(additive operator splitting)算法的快速活动轮廓模型，将AOS方法与几何活动轮廓模型相结合构造一种半隐式迭代模型，它对迭代步长没有限制，从而可以选择较大的迭代步长，提高了模型的时间效率，并使用区域信息构造系数矩阵，使模型具有全局性。对MR(magnetic resonance)图像分割的实验表明，该模型可以得到较好的分割结果，同时时间效率也有大幅提高，方便了实时应用。  相似文献   

可持续发展评估指标、方法及应用研究   总被引：31，自引：1，他引：31  

张志强  程国栋  徐中民 《冰川冻土》2002,24(4):344-360

可持续发展评估指标及方法研究是可持续发展定量评估研究的基础,是实施可持续发展管理的依据,是生态经济学与可持续发展研究的前沿领域和热点问题之一. 在概括介绍可持续发展评估的工具--指标/指数的概念和功能、国际上代表性可持续发展研究机构指标选取的原则的基础上,全面分析归纳了可持续发展指标(体系)的类型及其框架模式. 详细介绍了联合国可持续发展委员会(UNCSD)、经济合作与发展组织(OECD)、世界保护同盟(IUCN)、世界银行等国际上代表性机构的可持续发展系统性指标体系的最新研究进展,并分析了这些系统性指标体系的优缺点. 深入分析了国际上典型的社会发展类、经济发展类、生态环境类可持续发展指标(指数)的研究、开发与实际评估应用的情况. 最后,总结了当前可持续发展指标(体系)研究的特点与趋势.  相似文献   

成像光谱仪影像的几种处理方法     

舒宁 《武汉大学学报(信息科学版)》1997,(4)

针对成像光谱仪影像的专题分析，介绍了沿用常规遥感影像分析方法时的原理和新的算法，提出了影像融合方法的应用，说明了这些方法在学术思想上的归属，并简要介绍了各种方法的实验效果。  相似文献   

集对分析及其在城市地面沉降研究中的应用   总被引：5，自引：0，他引：5  

龚士良 《上海国土资源》1997,(4):43-47

集对分析是处理本确定性问题的理论,认为在一系统中不确定性与确定性互相联系、影响、制约,并在一定条件下互相转化,用联系度及其数学表达式统一描述系统的各种不确定性,由此实现系统调控的辅助决策。本文应用集对分析理论与方法剖析了上海地面沉降问题,探讨了社会需求、资源状况、地质环境三者间的制约关系,并以此提出城市地面沉降系统调控的对策与途径。  相似文献   

计算样本相似性在油气预测中的应用     

朱晓军  申宁华 《世界地质》1996,15(2):87-91

介绍了计算样本相似性方法在油气预测中的应用的基本原理和技术。提出了利用参数的显著性进行参数优化和加权的方法。该方法简单、实用，并在塔北某区的应用取得了满意结果。由此证明了该方法的有效性及在综合信息预测工作中进行参数优化和加权工作的重要性。  相似文献   

PDC钻头切削齿受力随布齿密度变化关系研究   总被引：1，自引：0，他引：1  

罗超  王镇泉 《地质与勘探》1997,33(4):60-63

采用不同布齿方式的３个ＰＤＣ切削齿同步连续切削转动的岩石为模拟井底钻头切削齿实际工作状态，用切削岩石时相同的布齿参数切削砂轮来磨损切削以模拟切削的以模拟切削齿磨状态，试验研究了不同磨损程度的切削齿受力与布齿密度的关系。  相似文献   

变差函数参数的计算   总被引：2，自引：0，他引：2  

矫希国 《地质论评》1997,43(6):658-663

为了求出地质统计学中变差函数理论模型的参数，首先把相应模型化成线性函数的形式，多面手应用线性方程组非负解的理论计算出它的参数。  相似文献   

Fuzzy set approaches to classification of rock masses   总被引：6，自引：0，他引：6  

A. Aydin   《Engineering Geology》2004,74(3-4):227-245

Rock mass classification is analogous to multi-feature pattern recognition problem. The objective is to assign a rock mass to one of the pre-defined classes using a given set of criteria. This process involves a number of subjective uncertainties stemming from: (a) qualitative (linguistic) criteria; (b) sharp class boundaries; (c) fixed rating (or weight) scales; and (d) variable input reliability. Fuzzy set theory enables a soft approach to account for these uncertainties by allowing the expert to participate in this process in several ways. Hence, this study was designed to investigate the earlier fuzzy rock mass classification attempts and to devise improved methodologies to utilize the theory more accurately and efficiently. As in the earlier studies, the Rock Mass Rating (RMR) system was adopted as a reference conventional classification system because of its simple linear aggregation.

The proposed classification approach is based on the concept of partial fuzzy sets representing the variable importance or recognition power of each criterion in the universal domain of rock mass quality. The method enables one to evaluate rock mass quality using any set of criteria, and it is easy to implement. To reduce uncertainties due to project- and lithology-dependent variations, partial membership functions were formulated considering shallow (<200 m) tunneling in granitic rock masses. This facilitated a detailed expression of the variations in the classification power of each criterion along the corresponding universal domains. The binary relationship tables generated using these functions were processed not to derive a single class but rather to plot criterion contribution trends (stacked area graphs) and belief surface contours, which proved to be very satisfactory in difficult decision situations. Four input scenarios were selected to demonstrate the efficiency of the proposed approach in different situations and with reference to the earlier approaches.  相似文献   

基于SuperMap的图形处理技术   总被引：6，自引：0，他引：6  

蔡国林  李永树 《四川测绘》2004,27(1):11-13

本文首先阐述了SuperMap DeskPro的基本功能，然后对利用SuperMap DeskPro进行常规图形处理的技巧进行了详细介绍，具体包括地图配准、地图拼接、数据集重新整合、对象标注、文本数据集到属性字段的转换和地图格网生成。通过这些技巧的运用，可以有效提高数据的处理能力。  相似文献   

Penny-shaped fractures revisited     

V. Grechka 《Studia Geophysica et Geodaetica》2005,49(3):365-381

All methods of seismic characterization of fractured reservoirs are based on effective media theories that relate geometrical and material properties of fractures and surrounding rock to the effective stiffnesses. In exploration seismology, the first-order theory of Hudson is the most popular. It describes the effective model caused by the presence of a single set of thin, aligned vertical fractures in otherwise isotropic rock. This model is known to be transversely isotropic with a horizontal symmetry axis (HTI). Following the theory, one can invert the effective anisotropy for the crack density and type of fluid infill of fractures, the quantities of great importance for reservoir appraisal and management.Here I compute effective media numerically using the finite element method. I deliberately construct models that contain a single set of vertical, ellipsoidal, non-intersecting and non-interconnected fractures to check validity of the first-order Hudson’s theory and establish the limits of its applicability. Contrary to conventional wisdom that Hudson’s results are accurate up to crack density e ≈ 0.1, I show that they consistently overestimate the magnitudes of all effective anisotropic coefficients ε^(V), δ^(V), and γ^(V). Accuracy of theoretically derived anisotropy depends on the type of fluid infill and typically deteriorates as e grows. While the theory gives | ε^(V)|, |δ^(V)|, |γ^(V)| and close to the upper bound of the corresponding numerically obtained values for randomly distributed liquid-filled fractures, theoretical predictions of ε^(V), δ^(V) are not supported by numerical computations when the cracks are dry. This happens primarily because the first-order Hudson’s theory makes no attempt to account for fracture interaction which contributes to the final result much stronger for gas- than for liquid-filled cracks. I find that Mori-Tanaka’s theory is superior to Hudson’s for all examined crack densities and both types of fluid infill.The paper was presented at the 11th International Workshop on Seismic Anisotropy (11IWSA) held in St. John’s, Canada in 2004.  相似文献