内蒙古东乌旗遥感构造和蚀变信息提取与找矿预测     

钱建平  张渊  赵小星  赵少杰  李承礼 《国土资源遥感》2013,25(3)

为了研究内蒙古东乌旗Pb-Zn-Ag多金属成矿区的找矿远景,在对Landsat7 ETM+数据进行几何纠正、大气校正和去干扰等预处理的基础上,对多波段假彩色合成图像做滤波处理以增强区域构造信息、进行线性构造解译;运用分形几何学原理和计盒维数法求取线性构造分维值,得到线性构造的统计自相似性和分形特征;采用主成分分析和阈值分割法对图像进行铁染、羟基蚀变信息提取;最后根据区内线性构造、遥感蚀变信息、岩体分布特征、区域地球化学异常和已知矿床(点)分布资料综合分析,圈定出3个级别的7个找矿预测区,再次证实了基于遥感图像的线性构造和遥感蚀变异常信息可以作为找矿预测的标志.  相似文献   

基于GIS和分形的云南省富宁县交通网络研究     

丁贤法 《东北测绘》2013,(2):63-66

应用ArcGIS数字化了云南省富宁县扫描地图,获得了该县各等级公路的矢量数据;以县城为中心,计算出该县公路网的长度-半径分数维为1.409 9,结果显示该县公路网密度分布具有显著的分形特征,从县城向周围衰减;将公路矢量数据栅格化,计算出该县的路网分形维数为1.050 5,低于路网规划的1.585;山地地形是该县路网覆盖度较低的主要成因,基于SRTM DEM数据,得出该县坡度≤6°的土地仅占6.435%,地形崎岖导致公路建设的难度与成本增加;最后应用条带剖面法(swath profile),分析了该县广昆高速公路沿线的地形特征,总体地形自云南高原向广西丘陵降低,起伏大,沿线地貌可划分为西部小起伏中山、中部小起伏低山和东部小起伏低山丘陵三段。  相似文献   

Dimensionality reduction of hyperspectral data using spectral fractal feature     

Kriti Mukherjee  Jayanta Kumar Ghosh  Ramesh Chand Mittal 《国际地球制图》2013,28(6):515-531

A new approach for dimensionality reduction of hyperspectral data has been proposed in this article. The method is based on extraction of fractal-based features from the hyperspectral data. The features have been generated using spectral fractal dimension of the spectral response curves (SRCs) after smoothing, interpolating and segmenting the curves. The new features so generated have then been used to classify hyperspectral data. Comparing the post classification accuracies with some other conventional dimensionality reduction methods, it has been found that the proposed method, with less computational complexity than the conventional methods, is able to provide classification accuracy statistically equivalent to those from conventional methods.  相似文献   

Evidence of chaos in the rainfall-runoff process     

BELLIE SIVAKUMAR  RONNY BERNDTSSON  JONAS OLSSON  KENJI JINNO 《水文科学杂志》2013,58(1):131-145

Abstract

The transformation of rainfall into runoff is one of the most important processes in hydrology. In the past few decades, a wide variety of automated or computer-based approaches have been applied to model this process. However, many such approaches have an important limitation in that they treat the rainfall-runoff process as a realization of only a few parameters of linear relationships rather than the process as a whole. What is required, therefore, is an approach that can capture not only the overall appearance but also the intricate details of the nonlinear behaviour of the process. The purpose of this study is to investigate the possibility of understanding the dynamics of the rainfall-runoff process from a new perspective, as a chaotic process. The possible existence of chaotic behaviour in the rainfall-runoff process is studied by investigating the rainfall and runoff time series: (a) separately; and (b) jointly (using the runoff coefficient). Monthly rainfall and runoff observed over a period of 131 years (January 1807-December 1937) at the Göta River basin in the south of Sweden are analysed. The correlation dimension method is employed to identify the presence of chaos. The correlation dimensions obtained for the rainfall and runoff time series are 6.4 and 5.5, respectively. The finite dimensions obtained for the rainfall and runoff time series indicate the possible existence of chaos in these processes, implying that the joint rainfall-runoff process might also exhibit chaotic behaviour. The correlation dimension of about 7.8 obtained for the runoff coefficient also indicates the possible presence of chaos and supports the above results.  相似文献   

An investigation of the presence of low-dimensional chaotic behaviour in the sediment transport phenomenon     

BELLIE SIVAKUMAR  A. W. JAYAWARDENA 《水文科学杂志》2013,58(3):405-416

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Nonlinear analysis of seasonality and stochasticity of the Indus River     

Syed Ahmad Hassan  M. Rashid Kamal Ansari 《水文科学杂志》2013,58(2):250-265

Abstract

One of the world's largest irrigation networks, based on the Indus River system in Pakistan, faces serious scarcity of water in one season and disastrous floods in another. The system is dominated both by monsoon and by snow and glacier dynamics, which confer strong seasonal and inter-annual variability. In this paper two different forecasting methods are utilized to analyse the long-term seasonal behaviour of the Indus River. The study also assesses whether the strong seasonal behaviour is dominated by the presence of low-dimensional nonlinear dynamics, or whether the periodic behaviour is simply immersed in random fluctuations. Forecasts obtained by nonlinear prediction (NLP) and the seasonal autoregressive integrated moving average (SARIMA) methods show that the performance of NLP is relatively better than the SARIMA method. This, along with the low values of the correlation dimension, is indicative of low-dimensional nonlinear behaviour of the hydrological dynamics. A relatively better performance of NLP, using an inverse technique, may also be indicative of the low-dimensional behaviour. Moreover, the embedding dimension of the best NLP forecasts is in good agreement with the estimated correlation dimension. This provides evidence that the nonlinearity inherent in the monthly river flow due to the snowmelt and the monsoon variations dominate over the high-dimensional components and might be exploited for prediction and modelling of the complex hydrological system.

Citation Hassan, S. A. & Ansari, M. R. K. (2010) Nonlinear analysis of seasonality and stochasticity of the Indus River. Hydrol. Sci. J. 55(2), 250–265.  相似文献   

Experimental investigation of density current patterns using dynamic fractal analysis     

Mohammad Hosseini  Mohammad Hadi Fattahi  Saeid Eslamian 《国际泥沙研究》2021,36(2):165-176

Density currents are caused by a difference in density,though low,of an entering fluid with the ambient fluid.This type of current is two-phased and found on riverbeds or in reservoirs behind dams,and is nonlinear in nature,complex,and sensitive to initial conditions.Fractal geometry is used as a powerful tool for studying complex natural phenomena.Using experimental studies and changes in inlet current conditions,the fractal and multi-fractal analyses of the interface between the density current and the ambient fluid were done.In addition,a search was made to find a possible connection between the nonlinear patterns.According to the results,with an increase in the inlet discharge and inlet density of the current the fractal dimension decreased.Further,the smaller the range of the singularity spectrum diagram was,i.e.,the more it was less than 0.34,the lower the system's tendency was to be multi-fractal,and the system sensitive to large local changes.In the interface between the density current and the ambient fluid,using the fractal dimension-based Richardson number could improve experimental data by 12.4%.Moreover,with an increase in the Richardson number,the Reynolds number of the current decreased.Further,upon considering the fractal dimension,the Reynolds number improved by 23%and a good correlation with a coefficient of determination of 0.76.  相似文献   

中国旱涝灾害的分形结构   总被引：15，自引：1，他引：15  

朱晓华  蔡运龙  王建 《地球科学进展》2003,18(4):509-514

基于分形理论在中国旱涝灾害研究方面所存在的问题,首先系统地分析了中国华北区、西北区等不同区域和松花江、长江等不同流域旱涝灾害的分形结构,其次以唐山市为例系统分析了同一地点不同等级旱涝灾害分维的时序变化及其关系,进而探讨了以分维为中介参数在旱涝灾害与其影响因素之间建立定量化经验关系的可能。研究结果表明,中国旱涝灾害具有客观的分形结构,分维是表征中国旱涝灾害发生特征的良好参数;在此基础上,系统地计算出了中国旱涝灾害的分维值、分析了唐山市不同等级旱涝灾害分维的时序变化关系,并建立了辽河、长江等流域水系空间维数与流域洪涝分维之间的定量关系式DF=3．6179DR-4．0242(式中DR为流域水系空间维数,DF为流域洪涝分维)。  相似文献   

北西地震带地震活动空间的模糊时间分维     

刘砚越 《华北地震科学》1994,12(1):28-34

选用北西地震带１９７０年至１９９０年２１年地震资料，对所发生地震的模糊时间分维结构进行了分析和研究。分别以二个月为一个单位和一年为一个单位计算了模糊时间维数Ｄｏ并绘出以二个月Ｄｏ随ｔ变化和２１年每年Ｄｏ随ｔ变化曲线。为了更好突出中强震选取了覆盖北西地震带６个面积相等小区，分别进行模糊时间分维计算，求出每年６个Ｄｏ来，再（１／６）∑Ｄｏ，计算出每年的平均Ｄｏ来并绘出每一小区二个月Ｄｏ随ｔ变化和２１年  相似文献   

Renormalization group methods in subsurface hydrology: overview and applications in hydraulic conductivity upscaling   总被引：3，自引：0，他引：3  

Dionissios T. Hristopulos   《Advances in water resources》2003,26(12):1279

The renormalization group (RG) approach is a powerful theoretical framework, more suitable for upscaling strong heterogeneity than low-order perturbation expansions. Applications of RG methods in subsurface hydrology include the calculation of (1) macroscopic transport parameters such as effective and equivalent hydraulic conductivity and dispersion coefficients, and (2) anomalous exponents characterizing the dispersion of contaminants due to long-range conductivity correlations or broad (heavy-tailed) distributions of the groundwater velocity. First, we review the main ideas of RG methods and their hydrological applications. Then, we focus on the hydraulic conductivity in saturated porous media with isotropic lognormal heterogeneity, and we present an RG calculation based on the replica method. The RG analysis gives rigorous support to the exponential conjecture for the effective hydraulic conductivity [Water Resour. Res. 19 (1) (1983) 161]. Using numerical simulations in two dimensions with a bimodal conductivity distribution, we demonstrate that the exponential expression is not suitable for all types of heterogeneity. We also introduce an RG coarse-grained conductivity and investigate its applications in estimating the conductivity of blocks or flow domains with finite size. Finally, we define the fractional effective dimension, and we show that it justifies fractal exponents in the range 1−2/dα<1 (where d is the actual medium dimension) in the geostatistical power average.  相似文献