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61.
ShuangHe Shen ShenBin Yang BingBai Li BingXiang Tan ZengYuan Li Thuy Le Toan 《中国科学D辑(英文版)》2009,52(8):1183-1194
Information on rice growing areas and rice production is critical for most rice growing countries to make state and economic
policies. However, the areas where rice crop is cultivated are often cloudy and rainy, which entails the use of radar remote
sensing data for rice monitoring. In this paper, a practical scheme to integrate multi-temporal and multi-polarization ENVISAT
ASAR data into rice crop model for regional rice yield estimation has been presented. To achieve this, rice distribution information
should be obtained first by rice mapping method to retrieve rice fields from ASAR images, and then an assimilation method
is applied to use the observed multi-temporal rice backscattering coefficients which are grouped for each rice pixel to re-initialize
ORYZA2000 to predict rice yield. The assimilation method re-initializes the model with optimal input parameters, allowing
a better temporal agreement between the rice backscattering coefficients retrieved from ASAR data and the rice backscattering
coefficients simulated by a coupled model, i.e., the combination of ORYZA2000 and a semi-empirical rice backscatter model
through LAI. The SCE-UA optimization algorithm is employed to determine the optimal set of input parameters. After the re-initialization,
rice yield for each rice pixel is calculated, and the yield map over the area of interest is produced. The scheme was validated
over Xinghua study area located in the middle of Jiangsu Province of China by using the data set of an experimental campaign
carried out during the 2006 rice season. The result shows that the obtained rice yield map generally overestimates the actual
rice production by 13% on average and with a root mean square error of approximately 1133 kg/ha on validation sites, but the
tendency of rice growth status and spatial variation of the rice yield are well predicted and highly consistent with the actual
production variation.
Supported by the ESA-NRSCC Dragon Cooperation Program (), the Project for Jiangsu Graduate in Scientific Research and Innovation (No. CX07B_048z), and the Special Program for Scientific
Research in Public Welfare Meteorological Services (No. GYHY200806008) 相似文献
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63.
Viscous Behaviour of Soft Clay and Inducing Factors 总被引:1,自引:1,他引:0
Thu Minh Le Behzad Fatahi Hadi Khabbaz 《Geotechnical and Geological Engineering》2012,30(5):1069-1083
As a result of the scarcity of land for construction, a number of projects to construct man-made islands or to expand lands over soft grounds keeps increasing. Creep behaviour of soft ground has been considered as a challenging issue for engineers and researchers for many years. A number of studies have focused on the method to predict the creep deformation of the ground under a construction site. However, there is no unified theory to clearly explain the mechanism of soil creep deformation of soils. Results of the critical review in this paper indicate that the causes of soil creep can be categorised into five main groups, namely (a) the breakdown of the inter-particle bonds, (b) sliding between the soil particles, (c) water flow from micro-pores to macro-pores (d) the deformation due to the structural viscosity and (e) the deformation due to the jumping of bonds. This paper presents these mechanisms in details with an effort to recommend an enhanced explanation for the creep compression mechanisms of clays. 相似文献
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65.
Nguyen Trung Minh L. L. Kashkarov Cu Sy Thang Doan Dinh Hung Nguyen Duc Chuy Nguyen Trung Kien Nguyen Thi Kim Thuong Nguyen Thi Thu Nguyen Van Pho 《Geochemistry International》2014,52(11):925-938
The concentration and distribution of U were measured in zircon samples separated from the streambed sediments collected at different sites along the rivers of northern Vietnam using semiconductor alpha spectrometry and alpha- and fission-track autoradiography. Based on the absolute U content and distribution, we distinguished two groups of zircon grains of different origin. Group 1 zircons have relatively low and uniform U contents ranging from 280 to 440 μg/g. Group 2 zircons are characterized by heterogeneous U distribution and U contents ranging from 490 to 2040μg/g. The determination of absolute alpha activity values and alpha spectrometric characteristics for a number of group 2 zircon grains indicated the presence of relatively short-lived alpha-emitters. These radionuclides are probably 210Po, 232U, 236Pu, 241Am, and 243Am, and all of them can originate exclusively from anthropogenic sources. A comparison of the observed alpha activity values for group 2 zircons with those of group 1 zircons and zircons separated from the suspended colloids in river water samples provided conclusive evidence for traces of anthropogenic radioactive contamination in the Lao Cai, Yen Bai, Tuyen Quang, Thac Ba, Viet Tri, and Hanoi streams flowing in the Song Hong (Red) and Song Da (Black) river basins of northern Vietnam and sourced in the southern regions of the neighboring state. 相似文献
66.
This work is part of a research study which is intended to study the degree of anthropogenic influences of the trace metal
distribution of soils from Danang-Hoian area (Vietnam). Cu, Ni, Zn and Zr show significant effects in most of the cultivated
soil categories, especially in the industrial soils. Extremely high levels of Pb (up to 742 μg/g) are observed in the industrial
soil category, which shows an enrichment factor 114 as compared to rural soils. Cd shows only a relative local enrichment
with the maximum level of 4.6 μg/g in urban soils. Sequential extraction was performed in selected samples to evaluate the
geochemical trace metals. The result indicates that Zn and Cr are mainly found in the crystal and amorphous Fe oxide bounded
forms. The contents of Cr in these fractions comprise more than 94% of total extractable Cr. In the case of Zn, 85% of total
extractable Zn is in fractions FV and FVI. Cu is mainly found in the organic fraction at an average of 39.3% of total extractable content. On the other hand, heavy
metal contents show an increasing tendency in the fine fraction (silt and clay).
Received: 4 February 1998 · Accepted: 26 November 1998 相似文献