A fast Time Domain Integral Equation(TDIE) solver is presented for analysis of transient scattering from electrically large conducting complex objects.The numerical process of Marching-On-in-Time(MOT) method based TDI...A fast Time Domain Integral Equation(TDIE) solver is presented for analysis of transient scattering from electrically large conducting complex objects.The numerical process of Marching-On-in-Time(MOT) method based TDIE encounters high computational cost and exorbitant memory requirements.A group-style accelerated method-Plane Wave Time Domain(PWTD) algorithm,which permits rapid evaluation of transient wave field generated by temporally bandlimited sources,is employed to reduce the computational cost of MOT-based TDIE solvers.An efficient compressed storage technique for sparse matrix is adopted to decrease the enormous memory requirements of MOT.The scheme of the Multi-Level PWTD(MLPWTD)-enhanced MOT with compressed storage for sparse matrix is presented for analysis of transient scattering from electrically large complex objects in this paper.The numerical simulation results demonstrate the validity and efficiency of the presented scheme.展开更多
We introduce a new transmit/receive dipole pair array to obtain a compact quasi\|monostatic antenna structure for ground penetrating radar systems. And we analyze this transmit/receive dipole ...We introduce a new transmit/receive dipole pair array to obtain a compact quasi\|monostatic antenna structure for ground penetrating radar systems. And we analyze this transmit/receive dipole pair array in time domain. The numerical results show that if the distance between the transmit antenna and receive antenna is appropriate the array configuration is adoptable.展开更多
A time domain electric al field integral equation (TDEFIE) is formulated for the problem of a thin wire antenna in the presence of conductor bodies, and this equation is solved by the me...A time domain electric al field integral equation (TDEFIE) is formulated for the problem of a thin wire antenna in the presence of conductor bodies, and this equation is solved by the method of time marching algorithm. The analysis is valid for any arbitrarily shaped, oriented and positioned wire antennas relative to arbitrarily shaped conductor bodies. Current at the excited point, input admittance and radiation pattern are given and agree with the results computed by the method in frequency domain.展开更多
Problems in unsteady aerodynamics and aeroacoustics can sometimes be formulated as integral equations,such as the boundary integral equations.Numerical discretization of integral equations in the time domain often lea...Problems in unsteady aerodynamics and aeroacoustics can sometimes be formulated as integral equations,such as the boundary integral equations.Numerical discretization of integral equations in the time domain often leads to so-called March-On-in-Time(MOT)schemes.In the literature,the temporal basis functions used in MOT schemes have been largely limited to low-order shifted Lagrange basis functions.In order to evaluate the accuracy and effectiveness of the temporal basis functions,a Fourier analysis of the temporal interpolation schemes is carried out.Based on the Fourier analysis,the spectral resolutions of various temporal basis functions are quantified.It is argued that hybrid temporal basis functions be used for interpolation of the numerical solution and its derivatives with respect to time.Stability of the proposed hybrid schemes is studied by a matrix eigenvalue method.Substantial improvement in accuracy and efficiency by using the hybrid temporal basis functions for time domain integral equations is demonstrated by numerical examples.Compared with the traditional temporal basis functions,the use of hybrid basis functions keeps numerical errors low for a larger frequency range given the same time step size.Conversely,for a given range of frequency of interest,a larger time step can be used with the hybrid temporal basis functions,resulting in an increase in computational efficiency and,at the same time,a reduction in memory requirement.展开更多
We developed an efficient analysis the current induced in the wire structure. The analysis based on the time-Domain Integral Equation, in which a thin wire approximation is used. The time-domain electric field integra...We developed an efficient analysis the current induced in the wire structure. The analysis based on the time-Domain Integral Equation, in which a thin wire approximation is used. The time-domain electric field integral equation is used with the moment method to develop a numerical procedure for treating problems of scattering by arbitrary shaped bodies. We present an efficient numerical method for calculating the electromagnetic scattering from arbitrary shaped conducting bodies in the time domain with a comprehensive treatment of a single, straight thin wire. A time domain electric field integral equation is formulated for the problem of an arbitrary shape. The solution method is based on the moment method to solve the straight thin-wire problem.展开更多
The basic objective of time-scale transformation is to compress or expand the signal in time field while keeping the same spectral properties. This paper presents two methods to derive time-scale transformation formul...The basic objective of time-scale transformation is to compress or expand the signal in time field while keeping the same spectral properties. This paper presents two methods to derive time-scale transformation formula based on continuous wavelet transform. For an arbitrary given square-integrable function f(t),g(t) = f(t/λ) is derived by continuous wavelet transform and its inverse transform. The result shows that time-scale transformation may be obtained through the modification of the time-scale of wavelet function filter using equivalent substitution. The paper demonstrates the result by theoretic derivations and experimental simulation.展开更多
The equivalent stress fundamental solution for the elastoplastic dynamic plane strain problem is proposed to transform the virtual work in the third direction to the plane.Subsequently,based on Betti reciprocal theore...The equivalent stress fundamental solution for the elastoplastic dynamic plane strain problem is proposed to transform the virtual work in the third direction to the plane.Subsequently,based on Betti reciprocal theorem,by adopting the time dependent fundamental solutions in terms of displacement,traction and equivalent stress,the boundary integral equations for dynamic elastoplastic analysis for the plane strain problem are established.The establishment procedures for the displacement and the stress boundary integral equations,together with the stress equation at boundary points,are presented in details,while the standard discretization both in time and space under the frame of time domain boundary element method(TD-BEM)and the solution of the algebraic equations are also briefly stated.Two verification examples are presented from different viewpoints,for elastic and elastoplastic analysis,for 1-D and 2-D geometries,and for finite and infinite domains.The TD-BEM formulation for dynamic elastoplastic analysis is presented for the plane strain problem as an example,where the formulation is also applicable for the plane stress problem by properly transforming the elastic constants and adopting the corresponding fundamental solutions.展开更多
提出一种基于精细积分法与时域微分求积法相结合的传输线方程的数值求解方法。首先将传输线方程采用基于紧致有限差分法的四阶差分格式进行空间离散,得到关于时间的一阶线性常微分方程组,四阶差分格式对于空间微分有很好的近似精度。然...提出一种基于精细积分法与时域微分求积法相结合的传输线方程的数值求解方法。首先将传输线方程采用基于紧致有限差分法的四阶差分格式进行空间离散,得到关于时间的一阶线性常微分方程组,四阶差分格式对于空间微分有很好的近似精度。然后利用精细积分法与微分求积法对一阶线性常微分方程组进行数值求解。通过理论分析可知,与传统的传输线方程数值求解方法——时域有限差分法(Finite difference time domain,FDTD)相比,所提方法不涉及到状态矩阵求逆运算,保证了数值求解精度,并且其数值稳定性与计算时间、空间步长无关,可采用大步长进行数值计算,能够有效提高计算效率。最后利用仿真实例进行算法验证,结果显示,相比于时域有限差分法,所提方法能够抑制数值振荡,提高了计算精度。展开更多
文摘A fast Time Domain Integral Equation(TDIE) solver is presented for analysis of transient scattering from electrically large conducting complex objects.The numerical process of Marching-On-in-Time(MOT) method based TDIE encounters high computational cost and exorbitant memory requirements.A group-style accelerated method-Plane Wave Time Domain(PWTD) algorithm,which permits rapid evaluation of transient wave field generated by temporally bandlimited sources,is employed to reduce the computational cost of MOT-based TDIE solvers.An efficient compressed storage technique for sparse matrix is adopted to decrease the enormous memory requirements of MOT.The scheme of the Multi-Level PWTD(MLPWTD)-enhanced MOT with compressed storage for sparse matrix is presented for analysis of transient scattering from electrically large complex objects in this paper.The numerical simulation results demonstrate the validity and efficiency of the presented scheme.
文摘We introduce a new transmit/receive dipole pair array to obtain a compact quasi\|monostatic antenna structure for ground penetrating radar systems. And we analyze this transmit/receive dipole pair array in time domain. The numerical results show that if the distance between the transmit antenna and receive antenna is appropriate the array configuration is adoptable.
文摘A time domain electric al field integral equation (TDEFIE) is formulated for the problem of a thin wire antenna in the presence of conductor bodies, and this equation is solved by the method of time marching algorithm. The analysis is valid for any arbitrarily shaped, oriented and positioned wire antennas relative to arbitrarily shaped conductor bodies. Current at the excited point, input admittance and radiation pattern are given and agree with the results computed by the method in frequency domain.
基金This work was supported in part by a NASA Cooperative Agreement,NNX11AI63A.
文摘Problems in unsteady aerodynamics and aeroacoustics can sometimes be formulated as integral equations,such as the boundary integral equations.Numerical discretization of integral equations in the time domain often leads to so-called March-On-in-Time(MOT)schemes.In the literature,the temporal basis functions used in MOT schemes have been largely limited to low-order shifted Lagrange basis functions.In order to evaluate the accuracy and effectiveness of the temporal basis functions,a Fourier analysis of the temporal interpolation schemes is carried out.Based on the Fourier analysis,the spectral resolutions of various temporal basis functions are quantified.It is argued that hybrid temporal basis functions be used for interpolation of the numerical solution and its derivatives with respect to time.Stability of the proposed hybrid schemes is studied by a matrix eigenvalue method.Substantial improvement in accuracy and efficiency by using the hybrid temporal basis functions for time domain integral equations is demonstrated by numerical examples.Compared with the traditional temporal basis functions,the use of hybrid basis functions keeps numerical errors low for a larger frequency range given the same time step size.Conversely,for a given range of frequency of interest,a larger time step can be used with the hybrid temporal basis functions,resulting in an increase in computational efficiency and,at the same time,a reduction in memory requirement.
基金This paper is supported by two projects(2006),Philosophicaland Social Science Project of Guangdong Province (06E18)theEleventh Five-Year-Programming Project of Philosophical andSocial Science Development of Guangzhou(06- Z4-6).
文摘We developed an efficient analysis the current induced in the wire structure. The analysis based on the time-Domain Integral Equation, in which a thin wire approximation is used. The time-domain electric field integral equation is used with the moment method to develop a numerical procedure for treating problems of scattering by arbitrary shaped bodies. We present an efficient numerical method for calculating the electromagnetic scattering from arbitrary shaped conducting bodies in the time domain with a comprehensive treatment of a single, straight thin wire. A time domain electric field integral equation is formulated for the problem of an arbitrary shape. The solution method is based on the moment method to solve the straight thin-wire problem.
文摘The basic objective of time-scale transformation is to compress or expand the signal in time field while keeping the same spectral properties. This paper presents two methods to derive time-scale transformation formula based on continuous wavelet transform. For an arbitrary given square-integrable function f(t),g(t) = f(t/λ) is derived by continuous wavelet transform and its inverse transform. The result shows that time-scale transformation may be obtained through the modification of the time-scale of wavelet function filter using equivalent substitution. The paper demonstrates the result by theoretic derivations and experimental simulation.
基金The authors would like to acknowledge the financial support provided by Hebei Education Department(Grant QN2020135)the National Key R&D Program of China(Grants 2019YFC1511105 and 2019YFC1511104)the National Natural Science Foundation of China(Grant 51778193).
文摘The equivalent stress fundamental solution for the elastoplastic dynamic plane strain problem is proposed to transform the virtual work in the third direction to the plane.Subsequently,based on Betti reciprocal theorem,by adopting the time dependent fundamental solutions in terms of displacement,traction and equivalent stress,the boundary integral equations for dynamic elastoplastic analysis for the plane strain problem are established.The establishment procedures for the displacement and the stress boundary integral equations,together with the stress equation at boundary points,are presented in details,while the standard discretization both in time and space under the frame of time domain boundary element method(TD-BEM)and the solution of the algebraic equations are also briefly stated.Two verification examples are presented from different viewpoints,for elastic and elastoplastic analysis,for 1-D and 2-D geometries,and for finite and infinite domains.The TD-BEM formulation for dynamic elastoplastic analysis is presented for the plane strain problem as an example,where the formulation is also applicable for the plane stress problem by properly transforming the elastic constants and adopting the corresponding fundamental solutions.
文摘提出一种基于精细积分法与时域微分求积法相结合的传输线方程的数值求解方法。首先将传输线方程采用基于紧致有限差分法的四阶差分格式进行空间离散,得到关于时间的一阶线性常微分方程组,四阶差分格式对于空间微分有很好的近似精度。然后利用精细积分法与微分求积法对一阶线性常微分方程组进行数值求解。通过理论分析可知,与传统的传输线方程数值求解方法——时域有限差分法(Finite difference time domain,FDTD)相比,所提方法不涉及到状态矩阵求逆运算,保证了数值求解精度,并且其数值稳定性与计算时间、空间步长无关,可采用大步长进行数值计算,能够有效提高计算效率。最后利用仿真实例进行算法验证,结果显示,相比于时域有限差分法,所提方法能够抑制数值振荡,提高了计算精度。
