改进的Hough变换在机场跑道检测中的应用

提出了一种改进的Hough变换方法用于机场跑道的检测。传统Hough变换存在计算量大等缺陷,本文利用直线边缘的梯度相位信息把Hough变换中θ的取值限定在一个较小的范围内,同时减少用于计算的像素点数,大大降低了计算量。通过实验证明了本文方法切实可行。     

大气湍流对天基遥感系统地面分辨率的影响

分辨率是所有光学成像系统最重要的技术指标之一。当成像系统与待成像目标之间存在大气湍流时,后者便会在不同程度上影响图像分辨率。天基光学遥感更加关心大气湍流对目标地面分辨率的影响。从大气湍流相干长度和到达角起伏两个角度,通过详细的公式推导和数值计算,分别讨论天基光学遥感系统成像过程中湍流对图像地面分辨率的影响。结果表明,地面分辨率0.5 m以上的甚高分辨率遥感成像需要考虑大气湍流因素。     

华北定点形变的小波分析与地震活动研究

利用小波分析方法对华北地区１９９０ 年到１９９８ 年的多台定点形变观测资料进行了分析计算,并将计算结果与该地区的地震活动进行了对比分析,同时讨论了不同阶的小波分解结果的物理意义及其与地震之间的对应关系。认为小波分解本质是窗口加权滑动平均,能有效地对各种不同频率成分的形变按不同的频段分离,为识别地震形变异常提供一种新的手段。在空间分布上,地形变的变化幅度与地震活动强度相对应,即在华北西北部地震活动性较强的包头、张家口一带,台站形变的强度明显高于华北东南部地震活动性较弱的泰安、营口等地区。在时间分布上,张北ＭＬ６ ．２ 级地震前大约两年东西方向的形变振幅随时间变化明显加大。     

小波变换应用于日长变化的研究进展

随着空间测地技术的发展,日长变化的观测资料已经达到了空前高的程度,迫切需要合适的数学工具和方法从这些高精度的观测资料中提取有价值的信息.近些年,小波变换被应用于天文学和地球科学的资料分析中,它通过伸缩和平移等运算对时间信号进行多尺度的细化分析,从中提取有效的信息.本文主要介绍了小波变换应用于日长变化的研究进展,并初步探讨该领域以后的研究方向.     

不同指标下的穗港城市走廊潜在通达性及其空间格局

本文以最短时间距离以及加权平均出行时间两种指标,其中后者以未来人口数为其加权因子,在对广州至香港之间廊道状区域的陆路交通网络现状通达性数据进行计算的基础上,对其潜在通达性及其空间格局进行预测分析。由此得出,穗港走廊内部的陆路网络潜在通达性呈现出同心环状态分布的空间格局,其潜在通达性水平以环心为最优,逐渐往外层递减;两种指标换算成通达性系数进行对比,发现利用未来人口数作为加权因子之后,走廊南部在整个网络的通达性地位得到了提升,但走廊北部的通达性地位却受到了削弱;穗港走廊潜在通达性空间格局比现状更加收敛,整体通达性水平得到提升,初始通达性水平越低的地方,提升的幅度越大。     

一种研究城市化发展的新方法

以南京市1988年TM影像为信息源,组合影像4、5波段得到建筑用地指数(NDBI),采用决策树分类方法对NDBI进行修正,分类提取建筑用地;对照TM影像修改误分的地块后转化为栅格数据,生成50×50个像元大小的格网,统计每个格网单元内的建筑用地率,将该值赋给各个格网单元的几何中心点;采用距离倒数方法由点数据插值得出整个影像范围内的建筑用地区域分异情况,进而反映出不同建筑用地率的辐射影响范围。该方法可定量提取不同建筑用地率的辐射边界,有助于根据单张影像数据分析城市的扩张趋势,可在一定程度上预测城市的发展;对于需要跨江发展的城市(如南京),该方法可以辅助桥梁等过江通道的选址。     

Elastic fields in two joined transversely isotropic media of infinite extent as a result of rectangular loading

This paper presents the closed‐form solutions for the elastic fields in two bonded rocks induced by rectangular loadings. Each of the two bonded rocks behaves as a transversely isotropic linear elastic solid of semi‐infinite extent. They are completely bonded together at a horizontal surface. The rectangular loadings are body forces along either vertical or horizontal directions and are uniformly applied on a rectangular area. The rectangular area is embedded in the two bonded rocks and is parallel to the horizontal interface. The classical integral transforms are used in the solution formulation, and the elastic solutions are expressed in the forms of elementary harmonic functions for the rectangular loadings. The stresses and displacements in the rocks induced by both the horizontal and vertical body forces are also presented. The numerical results illustrate the important effect of the anisotropic bimaterial properties on the stress and displacement fields. The solutions can be easily implemented for numerical calculations and applied to problems encountered in rock mechanics and engineering. Copyright © 2011 John Wiley & Sons, Ltd.     

Perceptions and responses to climate policy risks among California farmers

This paper considers how farmers perceive and respond to climate change policy risks, and suggests that understanding these risk responses is as important as understanding responses to biophysical climate change impacts. Based on a survey of 162 farmers in California, we test three hypotheses regarding climate policy risk: (1) that perceived climate change risks will have a direct impact on farmer's responses to climate policy risks, (2) that previous climate change experiences will influence farmer's climate change perceptions and climate policy risk responses, and (3) that past experiences with environmental policies will more strongly affect a farmer's climate change beliefs, risks, and climate policy risk responses. Using a structural equation model we find support for all three hypotheses and furthermore show that farmers’ negative past policy experiences do not make them less likely to respond to climate policy risks through participation in a government incentive program. We discuss how future research and climate policies can be structured to garner greater agricultural participation. This work highlights that understanding climate policy risk responses and other social, economic and policy perspectives is a vital component of understanding climate change beliefs, risks and behaviors and should be more thoroughly considered in future work.     

Analytic element modelling for strip aquifers

The Analytic Element Method (AEM) provides a convenient tool for groundwater flow analysis in unbounded continuous domains. The AEM is based on the superposition of analytic functions, known as elements, useful at both regional and local scales. In this study, analytic elements for strip aquifers are presented. Such aquifers occur in riverine or coastal deposits and in outcrop zones of confined aquifers. Local flow field is modelled indirectly, using a reference plane related to the aquifer domain through the Schwarz‐Christoffel transform. The regional flow is obtained as a solution of the one‐dimensional flow equation. The proposed methodology was tested by modelling two hypothetical situations, which were compared to exact solutions. It is shown that regional boundaries can be reproduced exactly while local fields are adequately reproduced with analytic elements. The developed elements are applied to simulate a real flow field in northeastern Brazil showing good agreement with measured water levels. Copyright © 2011 John Wiley & Sons, Ltd.     

由计算机产生的等距离区域分界线

本文介绍一种最近由作者在美国研制的,由计算机产生等距离区域分界线的程序及其数据结构,同时给出初步的试验结果。