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| 1 | An improved EM algorithm for remote sensing classification显示文摘The use of a general EM(expectation-maximization) algorithm in multi-spectral image classification is known to cause two problems:singularity of the variance-covariance matrix and sensitivity of randomly selected initial values.The former causes computation failure;the latter produces unstable classification results.This paper proposes a modified approach to resolve these defects.First,a modification is proposed to determine reliable parameters for the EM algorithm based on a k-means algorithm with initial centers obtained from the density function of the first principal component,which avoids the selection of initial centers at random.A second modification uses the principal component transformation of the image to obtain a set of uncorrelated data.The number of principal components as the input of the EM algorithm is determined by the principal contribution rate.In this way,the modification can not only remove singularity but also weaken noise.Experimental results obtained from two sets of remote sensing images acquired by two different sensors confirm the validity of the proposed approach. | YANG HongLei PENG JunHuan XIA BaiRu ZHANG DingXuan | 2013 | Chinese Science Bulletin2013，58，9： | 5 |
| 2 | Hydrogeochemical Modeling of the Shallow Thermal Water Evolution in Yangbajing Geothermal Field, Tibet显示文摘The exploitation of thermal water and the mix of cold water changed the properties of geofluid in shallow reservoir,which altered the concentration of the chemical constitutes and continuously built new water-rock reaction. This paper deduced reservoir pressure and temperature variation tendency from 2004 to 2013,analyzed the change of some components in the shallow reservoir water,and finally obtained the evolution of the shallow geothermal water with hydrogeochemical model. The results show the reservoir pressure decreased significantly compared with the slight decline of reservoir temperature,and much cold groundwater infiltrated into the shallow reservoir,which affected the solubility of SiO2 and led to precipitation,the increased CO2 in shallow reservoir promoted the dissolution of aluminosilicate. Calcite and kaolinite precipitation zone has extended to the north in the field,which influenced the porosity of the reservoir rock. | Xiuhua Zheng Chenyang Duan Bairu Xia Yong Jiang Jian Wen | 2019 | Journal of Earth Science2019，30，4： | 3 |
| 3 | Controlling the uncertainty in reservoir stochastic simulation显示文摘Unexpected noise in reservoir stochastic simulation realization may be too high to make the realization useful, especially when there is a lack of hard data. Through discussing the uncertainties, we present two ways to control the uncertainty ratio that is brought by the algorithm of stochastic simulation. By reasonably reducing the random value of the stochastic simulation result, the unexpected values introduced by the residual that associates with random series can be controlled. Another way when the data disperse unevenly is to control the stochastic simulation order by grouping the points that need to be simulated to make those points which can be simulated by more neighborhood hard data calculated first. Both methods do not go against the core stochastic simulation algorithm. | Cui Yong Chi Bo Chen Guo Ouyang Cheng Xia Bairu | 2010 | Petroleum Science2010，7，4： | 2 |
| 4 | Using 210 Pb uns and 137 Cs to date recent sediment cores from the Badain Jaran Desert, Inner Mongolia, China显示文摘 | Siwen Liu Narentuya Bairu Xia Guoqiang Chu Mingzhong Tian | 2012 | Quaternary Geochronology2012，，： | 1 |
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