沉积物中重金属的归一化问题——以Al为例   总被引：21，自引：0，他引：21  

刘素美  张经 《海洋学研究》1998,16(3):48-55

沉积物的来源、粒度和矿物组成是影响重金属在动力沉积过程中的行为的最显著的因素,用某些参考元素（如Ａｌ、Ｌｉ等）归一化的目的是为了减小沉积物中重金属含量的波动,以揭示人文活动（例如污染）的影响。通过对国内一些河流沉积物中重金属的Ａｌ归一化结果的分析,认为在岩石的风化和变质过程中元素与Ａｌ的相对迁移能力的差异和各种生物过程均可使重金属的Ａｌ归一化值产生显著的变化,在某些情况下Ｍ／Ａｌ值并不一定能准确地描述人类活动对沉积物中重金属的影响。Ａｌ归一化仅能部分地校正粒度分布引起的重金属含量的变化,但不能消除矿物组成的影响。  相似文献   

改进的AVAZ方法在裂缝型储层预测中的应用研究     

舒梦珵 《CT理论与应用研究》2017,26(1):45-52

对于裂缝型油气藏,基于叠前方位角地震数据体,利用AVAZ方法进行裂缝属性预测是目前较为有效的裂缝描述手段,然而,由于地震数据通常为窄方位采集,使得不同方位角数据覆盖次数差异较大,导致各方位振幅能量分布不均,最终造成裂缝属性预测中产生趋势性误差。振幅归一化处理技术应用到现有的AVAZ方法中,该方法能够有效地降低因数据采集所造成的趋势性误差,预测结果会更为真实、可靠。在实际油田的应用中,振幅归一化技术显著改善了AVAZ方法对裂缝属性预测的准确性,取得了较好的效果。   相似文献   

高光谱图像的JM变换自适应降维     

康孝岩  张爱武  胡少兴  肖青  柴沙驼 《遥感学报》2020,24(1):67-75

在无需先验标签样本的情况下,非监督降维可以有效简化高光谱图像的特征空间,避免目标分类中的霍夫效应。本文提出JM非线性变换优化的自适应降维模型来研究面向图像目标分类的高光谱波段选择问题。该方法考虑波段的信息量和独立性等两个重要因子,针对其测度方法的差异性问题,引入JM变换函数进行规范化优化。选用线阵高光谱和面阵显微光谱等两个图像数据集,在k最邻近和随机森林分类器下,进行了多组监督分类实验,结果表明,在Kappa系数、总体分类精度和平均分类精度上,本文方法均优于3种非监督方法MABS、InfFS和LSFS。说明本文提出的JM变换的自适应降维模型能够有效降低特征维度,满足高光谱图像分类的高精度要求。  相似文献   

矿产资源区划常态化工作设想     

肖克炎  王瑞江  邢树文 《江苏地质》2015,39(3):347-351

进入21世纪,我国固体矿产勘查已由传统的政府行为逐步转变为市场经济下的矿产资源勘查工作,相应带来了成矿远景区划和资源评价工作机制的重大改变。成矿区划和资源评价工作将分为2个层次：一是国家计划,政府和地方需要进行矿产规划;另一项是矿业公司的成矿预测和靶区优选。目前,国家找矿战略行动和“十二五”地质工作规划正在实施,全国重要矿产资源潜力评价工作逐步深化并进入汇总,矿产资源区划常态化迫在眉睫,其对降低勘查风险、保障地质找矿突破有着重要的战略和现实意义。矿产资源区划常态化工作将围绕关于“两个市场、两种资源”及资源开发保护并举的国策开展,充分利用潜力评价成果完成国家整装勘查区及省级重点勘查区优选部署工作,结合重要成矿区带矿产远景调查评价,有计划地开展整装勘查区内中大比例尺矿产预测,为找矿突破战略行动的实施提供科学依据。同时跟踪国际矿产勘查态势,积极探索全球矿产资源区划工作,为我国资源勘查工作“走出去”提供技术支撑  相似文献   

基于指标规范值的灰色聚类法的地下水质评价   总被引：1，自引：0，他引：1  

邱贵江  李祚泳  汤驰  李霞 《水文》2011,(4):35-39

为了克服传统灰色聚类法用于地下水水质评价时需要设计众多白化函数的不足,提出在设定地下水各指标"参照值"和"规范变换式"基础上,将地下水指标按同级标准的规范值的接近程度进行归类。属于同一类的指标可设计相同的白化函数,从而大大简化了函数的设计工作量。指标规范化的灰色聚类方法应用于黑龙洞泉域的地下水水质评价,得出的评价结果与识别理论方法和加权优序法的评价结果基本一致,表明该方法应用于地下水质评价中具有简单实用的特点。  相似文献   

南海上层中尺度涡统一三维结构   总被引：1，自引：0，他引：1  

郑堃  林霄沛  朱亚楠 《海洋与湖沼》2018,49(3):490-496

本文基于归一化合成分析的方法,利用卫星高度计资料和CTD观测资料,在满足静力平衡和地转平衡条件的假设下研究了南海中尺度涡的三维结构,给出了南海中尺度涡归一化之后的三维结构,并与全球大洋中尺度涡统一的三维结构进行对比。结果显示,在1.5倍涡旋半径以外,南海中尺度涡水平结构的收敛速度大约为全球大洋中尺度涡水平结构收敛速度的2.5倍,前者比后者的影响范围要小约1.5倍涡旋半径。由于数据原因,我们仅合成了南海0至800m水深中尺度涡的垂直结构,从垂直结构的合成结果来看,由于受到背景层结和科氏参数的影响,南海与全球大洋各海区中尺度涡的垂直结构具有明显的不同,随着深度的增加,南海中尺度涡垂直结构的衰减速度明显更快。  相似文献   

Normalizing shadows in multi-temporal aerial frame imagery using relative radiometric adjustments to support near-real-time change detection     

Emanuel Arnal Storey  Douglas Alan Stow  Matthew James Plummer 《地理信息系统科学与遥感》2019,56(1):22-42

This study addresses the problem of shadows in multi-temporal imagery, which is a key issue with change detection approaches based on image comparison. We apply image-to-image radiometric normalizations including histogram matching (HM), mean-variance (MV) equalization, linear regression based on pseudo-invariant features (PIF-LR), and radiometric control sets (RCS) representing high- and low-reflectance extrema, for the novel purpose of normalizing brightness of transient shadows in high spatial resolution, bi-temporal, aerial frame image sets. Efficient shadow normalization is integral to remote sensing procedures that support disaster response efforts in a near-real-time fashion, including repeat station image (RSI) capture, wireless data transfer, shadow detection (as precursor to shadow normalization), and change detection based on image differencing and visual interpretation. We apply the normalization techniques to imagery of suburban scenes containing shadowed materials of varied spectral reflectance characteristics, whereby intensity (average of red, green, and blue spectral band values) under fully illuminated conditions is known from counterpart reference images (time-1 versus time-2). We evaluate the normalization results using stratified random pixel samples within transient shadows, considering central tendency and variance of differences in intensity relative to the unnormalized images. Overall, MV equalization yielded superior results in our tests, reducing the radiometric effects of shadowing by more than 85 percent. The HM and PIF-LR approaches showed slightly lower performance than MV, while the RCS approach proved unreliable among scenes and among stratified intensity levels. We qualitatively evaluate a shadow normalization based on MV equalization, describing its utility and limitations when applied in change detection. Application of image-to-image radiometric normalization for brightening shadowed areas in multi-temporal imagery in this study proved efficient and effective to support change detection.  相似文献   

Relative Radiometric Normalisation - performance testing of selected techniques and impact analysis on vegetation and water bodies     

Abhisek Santra  Shreyashi Santra Mitra  Debashis Mitra  Ashis Sarkar 《国际地球制图》2019,34(1):98-113

In this paper, six image-based Relative Radiometric Normalization (RRN) techniques were applied to normalize the bi-temporal Landsat 5 TM data-set. RRN techniques do not require any atmospheric and ground information at the time of image acquisition. The target image for the year 2009 was normalized in such a way that it resembled the atmospheric and sensor conditions similar to those under which the reference image of the same season for the year 1990 was acquired. Among the selected methods applied, it was found that the Iteratively Reweighted Multivariate Alteration Detection (IR-MAD) method performed better, based on the error statistic. The IR-MAD technique was found to be advantageous as it identified a large set of true time-invariant pixels automatically from the change background using iterative canonical component analysis. The technique also stretches the values of Normalized Difference Vegetation Index and Normalized Difference Water Index and may help to distinguish different vegetation and water bodies better.  相似文献   

STUDY OF RELATIONSHIP BETWEEN URBANIZATION SPEED AND CHANGE IN SPATIAL DISTRIBUTION OF RAINFALL OVER SHANGHAI     

梁萍  丁一汇  何金海  汤绪 《热带气象学报(英文版)》2013,19(1):97-103

Using daily rainfall data of 11 observatory stations over Shanghai for the period 1960-2007,the spatial differences of rainfall over the Shanghai region during periods with slow and rapid urbanization respectively are investigated based on spatial standard deviation of rainfall and its relative variables.Results show that spatial differences increase with the acceleration of urbanization.Spatial distributions of annual rainfall and rainstorm frequency exhibit distinct urban ’rain-island’ features during the rapid period of urbanization(1960-1983) while it is opposite in the case of slow urbanization(1984-2007).Changes in the spatial distribution of annual rainfall trends also take place during different periods.Specifically,the variation of annual rainfall exhibits consistent trends over the Shanghai region in the slow urbanization periods.However,inconsistent spatial distribution of variations has taken place over the central districts and suburbs of Shanghai during the rapid urbanization stage.Since the speeding-up of urbanization,the annual rainfall amount over central districts of Shanghai tends to increase while that in the suburbs shows a decreasing trend.In addition,as far as different seasons are concerned,the speed of urbanization exerts insignificant influences on the spatial distribution of rainfall during winter and spring.On the contrary,the rainfall during summer and autumn(especially summer) is featured with an island effect during the rapid urbanization period.  相似文献   

从瞬变电磁场到波场的优化算法   总被引：9，自引：5，他引：4       下载免费PDF全文

李貅  薛国强  宋建平  郭文波  武军杰 《地球物理学报》2005,48(5):1185-1190

在波场的正变换中,保证瞬变电磁场的计算精度的同时,应用两步最优化算法,成功地控制和减少了积分系数个数和离散数字积分的采样点个数,解决了在波场反变换式中,由于积分系数过多而产生的欠定方程组的问题,同时改善了第一类算子方程的不适定性.在波场反变换中,将正则化算法用于逆变换过程的计算中,通过采用偏差原理和Newton迭代格式选出最优的正则化参数,使得反变换所得到的波场稳定、可靠.通过对数值计算结果与已知波场函数对比,证明了该方法的有效性和实用性.  相似文献