Finite-Difference Time-Domain(FDTD)is the most popular time-domain approach in computational electromagnetics.Due to the Courant-Friedrich-Levy(CFL)condition and the perfect match layer(PML)boundary precision,FDTD can...Finite-Difference Time-Domain(FDTD)is the most popular time-domain approach in computational electromagnetics.Due 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 soils.Firstly,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 effects.It 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 space.After that,all the models were tested by computer performance for their simulated efficiency.When 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 best.Test modeling speeds of CPML-HIE-FDTD were compared with three kinds of waveform sources,Ricker,Blackman-Harris and Gaussian.Finally,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 algorithm.For modeling multi-scale objects in farmland soils,the methods used CPML combined with the HIE-FDTD were the most efficient and accurate ways.This study can solve the problem that the traditional FDTD algorithm cannot construct non-mesh objects by utilizing the diversity characteristics of Yee cell elements.展开更多
In this paper, we present a nonorthogonal overlapping Yee method for solv- ing Maxwell＇s equations using the diagonal split-cell model. When material interface is presented, the diagonal split-cell model does not req...In this paper, we present a nonorthogonal overlapping Yee method for solv- ing Maxwell＇s equations using the diagonal split-cell model. When material interface is presented, the diagonal split-cell model does not require permittivity averaging so that better accuracy can be achieved. Our numerical results on optical force computation show that the standard FDTD method converges linearly, while the proposed method achieves quadratic convergence and better accuracy.展开更多
In this paper, a locally non-orthogonal overlapping Yee (OY) FDTD method is proposed in order to accurately calculates the optical force on dielectric and dispersive nanoparticles. It extends our previous work to geom...In this paper, a locally non-orthogonal overlapping Yee (OY) FDTD method is proposed in order to accurately calculates the optical force on dielectric and dispersive nanoparticles. It extends our previous work to geometries with sharp corners and dispersive materials. In addition to consistently achieving the smallest errors in comparison to the standard FDTD method, the OY approach is a stable non-orthogonal FDTD method that attains second-order convergence when sharp corners are present.展开更多
为了解决利用时域有限差分(finite difference timedomain,FDTD)方法实现凸体的电磁散射特性数值计算中,普遍遇到的Yee元胞建模问题,该文提出了关于凸体的一种新的Yee元胞建模方法。其主要思路是利用凸面几何学的理论判断空间任意一点...为了解决利用时域有限差分(finite difference timedomain,FDTD)方法实现凸体的电磁散射特性数值计算中,普遍遇到的Yee元胞建模问题,该文提出了关于凸体的一种新的Yee元胞建模方法。其主要思路是利用凸面几何学的理论判断空间任意一点和凸体每一个体元之间的位置关系,进而可以判断此点与整个凸体的位置关系,由此建立了凸体的Yee元胞建模方法。此种方法称为凸体的凸面几何学Yee元胞建模(convex geometry Yee cells model building of convexobject,CGYCMBCO)方法。CGYCMBCO方法给出了4个凸体的Yee元胞建模的实验结果,实验结果表明CGYCMBCO方法适用于任意凸体,能给出任意凸体的Yee元胞。展开更多
基金This work was financially supported by the State Key Research Program of China(Grant No.2016YFD0700101)the State Key Research Program of China(Grant No.2017YFD0700404)+1 种基金the Guangdong Provincial Department of Agriculture’s Specialized Program for Rural Area Rejuvenation(Grant No.2019KJ129)and the Guangdong Provincial Department of Agriculture’s Modern Agricultural Innovation Team Program for Animal Husbandry Robotics(Grant No.200-2018-XMZC-0001-107-0130).
文摘Finite-Difference Time-Domain(FDTD)is the most popular time-domain approach in computational electromagnetics.Due 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 soils.Firstly,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 effects.It 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 space.After that,all the models were tested by computer performance for their simulated efficiency.When 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 best.Test modeling speeds of CPML-HIE-FDTD were compared with three kinds of waveform sources,Ricker,Blackman-Harris and Gaussian.Finally,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 algorithm.For modeling multi-scale objects in farmland soils,the methods used CPML combined with the HIE-FDTD were the most efficient and accurate ways.This study can solve the problem that the traditional FDTD algorithm cannot construct non-mesh objects by utilizing the diversity characteristics of Yee cell elements.
基金supported by the Air Force Office of Scientific Research (AFOSR) under Grant numbers FA9550-04-1-0213 and FA9550-07-1-0010
文摘In this paper, we present a nonorthogonal overlapping Yee method for solv- ing Maxwell＇s equations using the diagonal split-cell model. When material interface is presented, the diagonal split-cell model does not require permittivity averaging so that better accuracy can be achieved. Our numerical results on optical force computation show that the standard FDTD method converges linearly, while the proposed method achieves quadratic convergence and better accuracy.
文摘In this paper, a locally non-orthogonal overlapping Yee (OY) FDTD method is proposed in order to accurately calculates the optical force on dielectric and dispersive nanoparticles. It extends our previous work to geometries with sharp corners and dispersive materials. In addition to consistently achieving the smallest errors in comparison to the standard FDTD method, the OY approach is a stable non-orthogonal FDTD method that attains second-order convergence when sharp corners are present.
文摘为了解决利用时域有限差分(finite difference timedomain,FDTD)方法实现凸体的电磁散射特性数值计算中,普遍遇到的Yee元胞建模问题,该文提出了关于凸体的一种新的Yee元胞建模方法。其主要思路是利用凸面几何学的理论判断空间任意一点和凸体每一个体元之间的位置关系,进而可以判断此点与整个凸体的位置关系,由此建立了凸体的Yee元胞建模方法。此种方法称为凸体的凸面几何学Yee元胞建模(convex geometry Yee cells model building of convexobject,CGYCMBCO)方法。CGYCMBCO方法给出了4个凸体的Yee元胞建模的实验结果,实验结果表明CGYCMBCO方法适用于任意凸体,能给出任意凸体的Yee元胞。
