Accurate forward modeling is of great significance for improving the accuracy and speed of inversion. For forward modeling of large sizes and fine structures, numerical accuracy and computational efficiency are not high, due to the stability conditions and the dense grid number. In this paper, the symplectic partitioned Runge-Kutta (SPRK) method, surface conformal technique, and graphics processor unit (GPU) acceleration technique are combined to establish a precise and efficient numerical model of electromagnetic wave propagation in complex geoelectric structures, with the goal of realizing a refined and efficient calculation of the electromagnetic response of an arbitrarily shaped underground target. The results show that the accuracy and efficiency of ground-penetrating radar (GPR) forward modeling are greatly improved when using our algorithm. This provides a theoretical basis for accurately interpreting GPR detection data and accurate and efficient forward modeling for the next step of inversion imaging.

Numerical simulation of three-layer layered electromagnetic waves is key problem for nondestructive testing of ground penetrating radar (GPR) pavement. In this paper, the difference iterative scheme of three-dimensional first-order symplectic partitioned Rung-Kutta is derived, which is applied to pavement detection of ground penetrating radar by using Higdon ABC boundary condition. Incident waves are considered as line sources. The accuracy and efficiency of the proposed algorithm are verified by the traditional 3D-FDTD algorithm. The results indicate that the accuracy and efficiency between the two methods are consistent. Unlike the traditional 3D-FDTD algorithm, the CPU time of the proposed method is reduced by 30%. The diseases location of the pavement structure is directly reflected by the numerical simulation result of the proposed method. This provides a three-dimensional symplectic partitioned Rung-Kutta algorithm, which can be applied to the forward simulation of GPR. It provides a threedimensional symplectic partitioned Rung-Kutta algorithm, which can be applied to the forward simulation of GPR. The accurate electromagnetic response information of the target can be obtained by the proposed method.INDEX TERMS Ground penetrating radar (GPR), symplectic partitioned runge-kutta method, pavement structure, higdon ABC.

No abstract

MPI-based parallel modified conformal finite difference time domain (P-MC-FDTD) method based on effective parameters for solving the scattering of electrically large coated targets is presented in this paper. The thin coating and free-space in a curved cell are replaced by an equivalent medium. The effective permittivity and electric conductivity for electric field samples on the cells are calculated by weighted-length of the medium and the free space. The modified conformal technique is used for magnetic field samples by dealing with stable conformal grids and unstable-prone conformal grids respectively. Combined with the parallel FDTD algorithm, the radar cross section (RCS) of 3-D electrically large coated targets can be calculated accurately.Index Terms-Effective parameter, electrically large coated targets, finite-difference time-domain (FDTD), radar cross section (RCS).

Ground penetrating radar (GPR), as a kind of fast, effective, and nondestructive tool, has been widely applied to nondestructive testing of road quality. The finite-difference time-domain method (FDTD) is the common numerical method studying the GPR wave propagation law in layered structure. However, the numerical accuracy and computational efficiency are not high because of the Courant-Friedrichs-Lewy (CFL) stability condition. In order to improve the accuracy and efficiency of FDTD simulation model, a parallel conformal FDTD algorithm based on graphics processor unit (GPU) acceleration technology and surface conformal technique was developed. The numerical simulation results showed that CUDA-implemented conformal FDTD method could greatly reduce computational time and the pseudo-waves generated by the ladder approximation. And the efficiency and accuracy of the proposed method are higher than the traditional FDTD method in simulating GPR wave propagation in two-dimensional (2D) complex underground structures.