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Modeling effectiveness and identification of multi-scale objects in farmland soils with improved Yee-FDTD methods

International Journal of Agricultural and Biological Engineering 2020年第6期13卷 150-158页

作者： Yuanhong Li Zuoxi Zhao Zhi Qiu Yangfan Luo Yuchan Zhu Department of Engineering South China Agricultural UniversityGuangzhou 510642China Southern Key Laboratory of Agricultural Equipment Machinery South China Agricultural UniversityGuangzhou 510642China Department of Biological and Agricultural Engineering Texas A&M UniversityCollege StationTX77843USA

Finite-Difference Time-Domain(FDTD)is the most popular time-domain approach in computational *** to the Courant-Friedrich-Levy(CFL)condition and the perfect match layer(PML)boundary precision,FDTD cannot simulate soil medium whose surface is connected by multiple straight lines or curves(multi-scale)accurately and efficiently,which greatly limits the application of FDTD method to simulate buried objects in ***,this study proposed the absorption boundary and adopted two typical perfect matching layers(UPML and CPML)to compare their absorption effects,and then using the three forms of improved Yee-FDTD algorithm,alternating-direction implicit(ADI-FDTD),unconditionally stable(US-FDTD)and hybrid implicit explicit finite time-domain(HIE-FDTD)to divide and contrast the boundary model *** showed that the HIE-FDTD was suitable for inversion of multi-scale structure object modeling,while ADI-FDTD and US-FDTD were ideal for single-boundary objects in both uniaxial perfectly matched layer(UMPL)and convolution perfectly matched layer(CPML)finite element *** that,all the models were tested by computer performance for their simulated *** simulating single boundary objects,UPML-US-FDTD and ADI-FDTD could achieve the ideal results,and in the boundary inversion of multi-scale objects,HIE-FDTD modeling results and efficiency were the *** modeling speeds of CPML-HIE-FDTD were compared with three kinds of waveform sources,Ricker,Blackman-Harris and ***,under the computer condition in which the CPU was i5-8250,the HIE-FDTD model still had better performance than the traditional Yee-FDTD forward modeling *** modeling multi-scale objects in farmland soils,the methods used CPML combined with the HIE-FDTD were the most efficient and accurate *** study can solve the problem that the traditional FDTD algorithm cannot construct non-mesh objects by utilizing the diversity characteristics of Yee cell element

关键词： Yee-FDTD multi-scale objects modeling effectiveness Ground Penetrating Radar farmland soils

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Advances in Greenhouse Gases Emission in farmland soils

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Agricultural Science & Technology 2012年第8期13卷 1738-1743页

作者：王璐蒋跃林安徽农业大学资源与环境学院安徽合肥230036

[Objective] The aim was to overview the emission of greenhouse gases in farmland. [Method] Based on domestic and foreign references, production mechanism, discharging characters and major influential factors of CO2, CH4 and N2O in soils of farmland were overviewed. [Result] Production and discharge of CO2, CH. and N2O played an important role in circulation of carbon and nitrogen in terrestrial ecosystem and constituted a key method for carbon and nitrogen output. It is significant to conduct research on reduction of greenhouse gas and increase of absorption. [Conclusion] The research is beneficial for exploration on discharge rule and influential factors of greenhouse gases, providing theoretical references for reduction of greenhouse gases and study on climate change.

关键词： farmland soils Carbon dioxide Methane Nitrous oxide Emission flux influential factors

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A meta-analysis of heavy metals pollution in farmland and urban soils in China over the past 20 years

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Journal of Environmental Sciences 2021年第3期33卷 217-226页

作者： Xuehong Yuan Nandong Xue Zhiguang Han State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental SciencesBeijing 100012China Technical Center for Soil Agricultural and Rural Ecology and EnvironmentMinistry of Ecology and Environment of the People’s Republic ChinaBeijing 100012China

A total of 713 research papers about field monitor experiments of heavy metals in farmland and urban soils in China,published from 2000 to 2019,were obtained.A meta-analysis was conducted to evaluate the level of China's heavy metal pollution in soils,mainly focusing on eight heavy *** was found that the average concentrations of cadmium(Cd),lead(Pb),zinc(Zn),copper(Cu),mercury(Hg),chromium(Cr),nickel(Ni),and arsenic(As)in China were 0.19,30.74,85.86,25.81,0.074,67.37,27.77 and 8.89 mg/kg,*** with the background value(0.097 mg/kg),the Cd content showed a twofold(0.19 mg/kg)rise in farmland soils and a threefold(0.29 mg/kg)rise in urban *** decreasing order of the mean Igeo was Cd(1.77)>Pb(0.62)>Zn(0.60)>Cu(0.58)>Hg(0.57)>Cr(0.54)>Ni(0.47)>As(0.28).Nearly 33.54%and 44.65%of sites in farmland and urban soils were polluted with *** average concentrations of eight heavy metals were not sensitive change in recent two decades in farmland and urban *** average P_n values for urban(2.52)and farmland(2.15)soils showed that heavy metal pollution in urban soils was more serious than that in farmland,and the middle Yangtze River regions,where industrial activity dominates,were the most *** meta-analysis comprehensively evaluated the current pollution situation of soil heavy metal,and provided important basis for soil management and environment prevention in China.

关键词： Heavy metals farmland soils Urban soils Pollution assessment Meta-analysis

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