基于高光谱的民勤土壤盐分定量分析   总被引：2，自引：0，他引：2  

庞国锦  王涛  孙家欢  李森 《中国沙漠》2014,34(4):1073-1079

土壤盐渍化是重要的生态环境问题,严重影响着干旱、半干旱区的农牧业及经济发展。高光谱遥感技术能够提供地物的连续光谱信息,易于分析细微差别,在定量研究土壤盐分含量方面具有较大优势。民勤县位于甘肃省石羊河流域下游,水力资源匮乏,盐渍化问题十分严峻。本研究基于实验室光谱数据,通过建立模型定量分析土壤盐分含量。首先对原始数据进行连续统去除（cn）预处理,然后分别建立了土壤盐分含量的高光谱指数模型（NDSI）、偏最小二乘回归模型（PLS）、间隔偏最小二乘法模型（iPLS）和反向间隔偏最小二乘法模型（BiPLS）,考察各种模型对土壤盐分的预测能力。对比分析发现,使用全部波段信息建模的PLS模型优于仅使用两个波段信息的NDSI模型,而iPLS和BiPLS模型通过选择特征波段进行建模,结果均好于全谱PLS模型。其中,BiPLS模型波段选择的能力优于iPLS模型,得出的模型结果最好,预测相对偏差RPD达到2.02,决定系数R²和模拟值与预测值线性回归的斜率分别为0.76和0.92,模型可以近似地预测土壤盐分含量。结果说明特征波段选择方法能够从大量数据中提取有效信息,简化模型,并获取比NDSI模型和全谱PLS模型更优的预测结果。这些研究对于使用高光谱数据定量分析土壤盐渍化有一定的意义。  相似文献   

水平受荷桩的弹性有限元虚拟加载上限分析     

黄茂松  李森  俞剑 《岩土力学》2016,37(8):2399-2403

基于将塑性上限分析等效为弹性迭代计算的总量虚拟加载上限分析理论,在商业化有限元软件ABAQUS中实现了弹性有限元虚拟加载上限方法（弹性有限元T-EMSD）。应用弹性有限元T-EMSD法分析了不排水黏土中的二维水平受荷桩,其获得的荷载-位移曲线与弹塑性有限元分析结果一致,其极限承载力与塑性解相近。在极限位移加载量下弹性有限元T-EMSD法对应的上限机构从弹性始速度场开始随迭代逐渐演化,迭代收敛后的速度场和解析塑性破坏机构相似。与其他基于可变强度概念（MSD）的方法相比,弹性有限元T-EMSD法对水平受荷桩桩身的分析具有更高的精度。弹性有限元T-EMSD法最大的优势在于可在计算中自然地获得塑性机构,因而可被用于研究一些塑性机构难以构造的复杂问题,并对弹塑性数值方法进行验证。  相似文献   

渤南低凸起北坡坡折带特征及其沉积充填响应     

杨悠然  杨香华  朱红涛  李森  官大勇  王昕  曾智伟  雷鸣 《现代地质》2016,30(5):1072-1084

渤南低凸起北部东二下段发育多种类型的沉积体,与坡折带的结构与演化密切相关。东二下段沉积时期,渤南低凸起北部斜坡带发育一个完整的坡折带沉积旋回：坡折带演化早期,即东二下段沉积早期,渤南低凸起北部斜坡上有断裂活动,斜坡坡度较大、起伏不平,发育一些古沟谷与洼地,其内堆积了近源碎屑物,在地震剖面上可见古沟谷内充填杂乱或蠕虫状地震反射体;坡折带演化晚期,即东二下段沉积晚期,伴随着准平原化斜坡被填低补齐,演变为沉积物的搬运通道,碎屑物借道斜坡被带到洼陷内部沉积,发育一系列高角度前积地震反射体。东二下段沉积早期斜坡内部古沟谷充填的杂乱或蠕虫状的地震反射体为近源快速堆积的产物,主要分布在第一坡折带内;东二下段沉积晚期洼陷内部发育的高角度前积地震反射体为远源沉积,主要分布在第二坡折带内。渤南低凸起北部斜坡带发育典型的坡折带演化旋回,空间上不同成因地震异常体从斜坡带向洼陷内转移,共同构成一组具有成因联系的坡折带-沉积复合体。  相似文献   

The role of GPR techniques in determining ice cave properties: Peña Castil ice cave,Picos de Europa          下载免费PDF全文

Manuel Gómez Lende  Enrique Serrano  Luis Jordá Bordehore  Senén Sandoval 《地球表面变化过程与地形》2016,41(15):2177-2190

The structure and ice content of ice caves are poorly understood. Ground penetrating radar (GPR) can provide useful insights but has only rarely been applied to ice caves. This paper interprets GPR images (radargrams) in terms of internal structure, stratification, compaction, thickness and volume of the ice block in the Peña Castil ice cave (Central Massif of Picos de Europa, northern Spain), providing the endokarst geometry of the ice cave in GPR data reflections. Eight radargrams were obtained by applying a shielded ground‐coupled antenna with a nominal frequency of 400 MHz. Although the radargrams do not depict the ice–basal bedrock interface, they suggest that the ice block is at least 54 m deep and similarly thick. Some curved reflection signatures suggest a potential vertical displacement in the block of ice, and thus certain dynamics in the ice body. Other images show numerous interbedded clasts and thin sediment layers imaged as banded reflections. In this particular cave a direct visual inspection of the ice stratigraphy is a difficult task but GPR provides clear reflectivity patterns of some of its internal features, making GPR a suitable instrument for this and future studies to achieve a better and broader understanding of the internal behavior of ice caves.  相似文献   

Development of design flood hydrographs using probability density functions   总被引：1，自引：0，他引：1  

Niranjan Pramanik  Rabindra K. Panda  Drubajyoti Sen 《水文研究》2010,24(4):415-428

Probability density functions (PDFs) are used to fit the shape of hydrographs and have been popularly used for the development of synthetic unit hydrographs by many hydrologists. Nevertheless, modelling the shapes of continuous stream flow hydrographs, which are probabilistic in nature, is rare. In the present study, a novel approach was followed to model the shape of stream flow hydrographs using PDF and subsequently to develop design flood hydrographs for various return periods. Four continuous PDFs, namely, two parameter Beta, Weibull, Gamma and Lognormal, were employed to fit the shape of the hydrographs of 22 years at a site of Brahmani River in eastern India. The shapes of the observed and PDF fitted hydrographs were compared and root mean square errors, error of peak discharge (EQ_P) and error of time to peak (ET_P) were computed. The best‐fitted shape and scale parameters of all PDFs were subjected to frequency analysis and the quartiles corresponding to 20‐, 50‐, 100‐ and 200‐year were estimated. The estimated parameters of each return period were used to develop the flood hydrographs for 20‐, 50‐, 100‐ and 200‐year return periods. The peak discharges of the developed design flood hydrographs were compared with the design discharges estimated from the frequency analysis of 22 years of annual peak discharges at that site. Lognormal‐produced peak discharge was very close to the estimated design discharge in case of 20‐year flood hydrograph. On the other hand, peak discharge obtained using the Weibull PDF had close agreement with the estimated design discharge obtained from frequency analysis in case of 50‐, 100‐ and 200‐year return periods. The ranking of the PDFs based on estimation of peak of design flood hydrograph for 50‐, 100‐ and 200‐year return periods was found to have the following order: Weibull > Beta > Lognormal > Gamma. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

2008年盈江5.9级地震序列震源参数研究   总被引：6，自引：1，他引：5  

杨晶琼  杨周胜  刘丽芳  苏有锦  张森 《地震研究》2010,33(4)

2008年8月21日在云南省盈江县发生了MS5.9地震。利用云南区域数字地震台网记录的ML≥2.5余震波形记录,通过对S波观测记录谱进行传播路径、场地响应和仪器响应等影响的逐一消除,得到了196个ML≥2.5地震的震源谱,进而根据Brune圆盘震源模型,利用遗传算法计算了地震矩、应力降、震源半径等震源参数,结果表明,该地震序列的地震矩在1012～1016N.m间,与近震震级有很好的线性关系,与震源半径也呈线性关系;应力降与近震震级有一定的线性趋势相关性;拐角频率和地震矩之间有明显的依赖关系。  相似文献   

冀北北岔沟门地区中生代侵入岩地质年代学和地球化学特征研究   总被引：19，自引：8，他引：11  

毛德宝陈志宏  钟长汀左义成石森  胡小蝶 《岩石学报》2003,19(4):661-674

北岔沟门地区广泛分布中生代侵入岩体.本文选取了该地区有代表性的8个岩体进行地质年代学和地球化学研究,旨在建立其年代格架并探讨岩石的成因演化.主要岩石类型为闪长玢岩、花岗闪长岩、石英二长岩、二长花岗岩、钾长花岗岩等.颗粒级锆石的U-Pb同位素测年数据表明所研究的岩体主要有三期早三叠世(245～250Ma)、晚侏罗世(140～147Ma)和早白垩世(125～137Ma).地球化学数据表明岩石普遍具有较高的钾含量、准铝质,主要属高钾钙碱性系列,部分为橄榄玄粗岩系列.岩石不同程度地显示轻稀土元素富集、高场强元素(HFSE)和大离子亲石性元素(LILE)解偶等特点.进一步的岩石地球化学研究表明区内侵入岩可划分为高BaSr和低BaSr两种类型,其中高BaSr型具有高Al2O3(≥15%)、Sr(≥400×10-6) 和低Y(≤18×10-6)、Yb(≤1.9×10-6),高的Na2O/K2O(>1), Sr/Y(>20)、La/Yb(≥10)比值;较高的Mg#(38.47～57.78)、具正的或弱的铕负异常等地球化学特征,这些特征与埃达克岩具有某些相似性;而低BaSr型岩石SiO2、K2O、Y、Yb含量相对较高、Al2O3、Sr、Ba含量相对较低、具明显的铕负异常等地球化学特征.尽管两类岩石在时空上密切共生,但可能具有不同的源区和成因机制.综合研究表明本区中生代侵入岩总体形成在加厚地壳的构造背景下,与底侵作用或壳幔相互作用有关.  相似文献   

Probabilistic model for radiative transfer problems in cylindrical shell media with complete redistribution in frequency     

T. K. Leong  K. K. Sen 《Astrophysics and Space Science》1973,21(1):59-72

A probabilistic model for solving transfer problems in non-homogeneous, isotropic, and non-coherent scattering cylindrical shell media has been proposed. The source function is considered to be frequency independent. The scattering and transmission functions have been defined for the case of complete redistribution in frequency. A tractable integrodifferential equation for the scattering function has been derived.  相似文献   

Propagation of Extra Low Frequency Waves in the Magnetosphere     

Amiya K. Sen 《Geophysical Journal International》1971,23(2):161-172

  相似文献   

Spatial simulation of geologic variables     

Zekâi Sen 《Mathematical Geology》1990,22(2):175-188

Analytical formulation of a general simulation model for generation of anisotropic as well as isotropic synthetic patterns in one, two, or three dimensions is proposed. It has significance for the purpose of modeling geologic properties such as ore grades, reservoir porosity, mineral distribution, fracture spacings, aperture, orientations, etc. General procedures for such a simulation by the autoregressive process are given for model parameters estimation and synthetic pattern generation. The model works on the square net basis and generates sequential patterns first along any desired direction for unidimensional simulation and then two-dimensional patterns are constructed with reference to two orthogonal unidimensional sequences. Applications to synthetic two-dimensional pattern are shown for isotropic cases with different model parameters. The extension of the model to three-dimensional space is readily available.  相似文献