The angular dependence of the median destructive field of magnetite particles     

A. Stephenson  J. C. Shao 《Geophysical Journal International》1994,118(1):181-184

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基于有向窗的自适应SIGMA中值滤波算法   总被引：4，自引：0，他引：4  

许才军  王华  王江林  GE Linlin 《武汉大学学报(信息科学版)》2005,30(10):873-876

提出了一种能够有效消除InSAR DEM噪声的自适应中值滤波算法:基于有向窗的自适应SIGMA中值滤波。分别采用中值滤波、基于高程的自适应SIGMA中值滤波和基于有向窗的自适应SIGMA中值滤波算法,对InSAR Tandem DEM和模拟DEM进行了滤波处理。结果表明,基于有向窗的自适应SIGMA中值滤波算法不仅能够更有效地消除噪声,而且能够更好地保留图像的边界特征。  相似文献   

Sign-constrained robust least squares, subjective breakdown point and the effect of weights of observations on robustness   总被引：3，自引：1，他引：3  

Peiliang Xu 《Journal of Geodesy》2005,79(1-3):146-159

The findings of this paper are summarized as follows: (1) We propose a sign-constrained robust estimation method, which can tolerate 50% of data contamination and meanwhile achieve high, least-squares-comparable efficiency. Since the objective function is identical with least squares, the method may also be called sign-constrained robust least squares. An iterative version of the method has been implemented and shown to be capable of resisting against more than 50% of contamination. As a by-product, a robust estimate of scale parameter can also be obtained. Unlike the least median of squares method and repeated medians, which use a least possible number of data to derive the solution, the sign-constrained robust least squares method attempts to employ a maximum possible number of good data to derive the robust solution, and thus will not be affected by partial near multi-collinearity among part of the data or if some of the data are clustered together; (2) although M-estimates have been reported to have a breakdown point of 1/(t+1), we have shown that the weights of observations can readily deteriorate such results and bring the breakdown point of M-estimates of Huber’s type to zero. The same zero breakdown point of the L ₁-norm method is also derived, again due to the weights of observations; (3) by assuming a prior distribution for the signs of outliers, we have developed the concept of subjective breakdown point, which may be thought of as an extension of stochastic breakdown by Donoho and Huber but can be important in explaining real-life problems in Earth Sciences and image reconstruction; and finally, (4) We have shown that the least median of squares method can still break down with a single outlier, even if no highly concentrated good data nor highly concentrated outliers exist. An erratum to this article is available at .  相似文献   

中值滤波技术在遥感图像处理中的应用     

路鹏  刘财  刘万崧  邢立新  刘洋  王典 《吉林大学学报(地球科学版)》2005,(Z1)

利用中值滤波技术能够很好的抑制噪声和保护边缘信息这一特性,用不同的滤波窗口对遥感图像进行处理,并做出处理后图像的归一化差值图像。通过图形分析发现差值图像上的信息比原始图像细节信息更丰富,某些地质现象更清晰。  相似文献   

沙粒粒径组成的空间异质性及其与灌丛大小和土壤风蚀相关性分析   总被引：8，自引：2，他引：8  

王利兵  胡小龙  余伟莅  李钢铁  郭建英 《干旱区地理》2006,29(5):688-693

空间异质性是土壤的重要属性之一。采用地统计学的理论和方法,研究了浑善达克沙地沙粒粒径组成的空间异质性。分析结果表明,各粒径的比例具有明显的空间异质性。在于107.30 m范围内,粉沙约有59.3%的空间异质性由随机因素引起的,而由空间自相关部分引起的空间异质性占40.7%;其余的空间异质性很少由随机因素引起的,其空间自相关部分引起的空间异质性占绝大部分。相关性分析表明:灌丛的冠幅越大,越有利于细沙、极细沙和粉沙的截留;各月的风蚀值与沙粒粒径的百分含量的相关性均和各月的平均风速有关。  相似文献   

牙轮钻头直径的计算   总被引：2，自引：1，他引：2       下载免费PDF全文

樊腊生 《探矿工程》1997,(4):28-31

采用求极值来计算牙轮钻头的直径，给出了牙轮钻头直径的计算公式，并分别对有移轴及无移轴牙轮钻头直径的计算进行了分析。  相似文献   

Particle size truncation effect on the inference of effective particle diameter     

Liu Chunlei  Yao Keya 《大气科学进展》1997,14(3):350-354

The effective ice crystal particle diameter (De) of cirrus clouds can be inferred by comparing the measured radar / lidar backscattering ratio with the theoretically calculated one. The calculated ratios are based upon assump-tions of ice crystal particle density and size distribution, and it will be affected by the artificially assumed particle size ranges. This size truncation effect on the inference of effective particle diameter will be investigated theoretically by assuming the cirrus ice particle spherical and particle density of 0.9g / cm3. Results show that the truncation at large particle end has very small effect on the inference of De , but the truncation at the small particle end will have some ef-fect on the inference of De.  相似文献   

中距离物理测距边大地主题正算     

赵文光 《武汉大学学报(信息科学版)》1987,(2)

本文提出了一套以空间任意高度直线距离为边长的、高精度的中距离大地主题正算公式,省掉了投影归算过程,可以用卫星(气球)物理测距数据计算大地位置。  相似文献   

大口径金刚石取心钻头的研究及应用          下载免费PDF全文

周晓  刘晓波  杨裕恩 《探矿工程》2003,30(6):56-58

在φ615mm大口径金刚石取心钻头中，采用了金刚石钻齿这一新的技术方案，介绍了钻齿结构及镶焊技术。经在黄河古贤水利枢纽坝址勘探中应用，取得了较好效果。  相似文献   

利用井径资料预测鱼卡煤田东部勘探区七煤顶板的稳定性     

栾安辉潘语录  田贵发 《中国煤田地质》2007,19(6):73-75

在煤田测井中，井径的变化对其它测井参数是一种干扰，但利用井径的相对变化值（井径扩大系数），可有效地评估岩石的强度等级和可采煤层顶底板的稳定性。统计鱼卡煤田东部勘探区29个钻孔孔径的变化值，按岩石抗压强度划分原则，将其七煤顶板稳定性划分为5个等级，据此固定了该煤田七煤顶板稳定性分布图。  相似文献