Xun Wang

Central South University | CSU · School of Geoscience and Info-Physics

Complex Frequency-Shifted PML in the long time domain has good absorption effect about litter wave and prosperous lost wave, and is widely used in FDTD simulation. In this paper, the convolution makes CFS-PML apply in the finite element time domain solution numerical of simulation GPR wave equation. In TM wave as an example, in this paper we deduce...

Irregular and complicated tunnel lining defects cannot be finely depicted with the standard finite difference simulation method based on regular mesh due to its irregular geometrical characteristics and complex physical properties of various defects. To solve this problem, a new hybrid algorithm is proposed for all-refined ground penetrating radar...

The time domain full waveform inversion (FWI) of ground penetrating radar (GPR) is difficult to calculate on personal computer due to its calculation and high memory requirements. In this paper, we use the optimized conjugate gradient method based on the GPU parallel acceleration with the dimensionality lifting scheme, and the calculation of Hessia...

Complex irregular defects of tunnel linings under complicated geological conditions cannot be accurately reconstructed with the traditional full-waveform inversion (FWI) method due to their irregular geometrical characteristics and complex dielectric properties. Because of extensive inversion calculations and high memory requirements, the tradition...

Full-waveform inversion (FWI) in the time domain of ground-penetrating radar (GPR) data involves a vast number of calculations; thus, it requires a large amount of memory and is difficult to calculate on a personal computer (PC). In this paper, GPR data are analyzed with multiscale FWI using two parameters (permittivity and conductivity) based on t...

Ground penetrating radar (GPR) is a crucial method for shallow geophysical exploration method. GPR full waveform inversion (FWI) utilizes all available information including dynamics and kinematics, and theoretically achieving the highest imaging accuracy. However, a significant challenge for FWI is its low computational efficiency, which fails to...

Ground Penetrating Radar (GPR) is a non-destructive geophysical technique utilizing electromagnetic pulses to detect subsurface material properties. The analysis of regions of interest (ROIs) in GPR images often entails the identification of hyperbolic reflection regions of underground targets through accurate segmentation, a crucial preprocessing...

In audio-magnetotellurics (AMT) inversion, the resistivity model derived from data is crucial for understanding geological properties. Current AMT inversion methods like Gaussian-Newton and nonlinear conjugate gradient have limitations, including sensitivity to data errors and reliance on initial models, leading to non-uniqueness and slow convergen...

Denoising plays a fundamental role in ground penetrating radar (GPR) data processing and determines the effect of anomaly extraction, inversion imaging, and other subsequent processing. In recent years, the sparse dictionary representation method k-singular value decomposition (K-SVD) based on K-means, which can adaptively change the basis function...

Ground penetrating radar (GPR) full waveform inversion (FWI) can make full use of kinematics information and dynamics information to achieve the highest theoretical resolution, serving as a promising tool for reconstructing subsurface structures and the physical properties of the medium. However, conventional FWI is constrained by strong nonlineari...

Ground penetrating radar (GPR) migration is a crucial imaging method to obtain the spatial position, size, and shape of the underground structures. However, Kirchhoff migration, finite-difference migration, F-K migration, and reverse time migration (RTM) focus on geometric structure imaging and cannot provide realistic reflection coefficients. Leas...

Reverse time migration (RTM) is an important technology for imaging ground penetrating radar (GPR) data. To address the problem of artifacts flooding of imaging results and high memory consumption of RTM, we propose an optimized multitraces cross-correlation window (MCW) to increase the order of magnitude difference between the signals and artifact...

Ground penetrating radar (GPR) is an important shallow electromagnetic non-destructive detection technology. The full waveform inversion (FWI) of GPR data utilizes all information including dynamics and kinematics, theoretically has the highest imaging accuracy, and meets the increasingly sophisticated needs of engineering exploration imaging. Howe...

Reverse time migration (RTM) has the advantage of high-precision imaging, and it can converge the radar wave back to its actual position, making it widely used in radar exploration. However, there are artifacts, low-frequency noise and fuzzy deep imaging in RTM results. Researchers have proposed full wavefield separation imaging condition and total...

Ground penetrating radar (GPR), geophysics exploring technology, could non-destructively acquire high-precision information about the shallow subsurface [...]

Aiming at solving the clutter flooding problem in the traditional cross-correlation reverse time migration (RTM) of ground penetrating radar (GPR), we proposed an improved RTM method based on multi-traces cross-correlation window (MCW) imaging condition. The main difference between the proposed method and the traditional direct stacking is that it...

The multi-parameter full waveform inversion (FWI) that integrates velocity and density can make full use of the kinematic and dynamic information of the measured data to reconstruct the underground model. However, it faces problems of crosstalk between multiple parameters and strong nonlinearity. This research proposes a multi-constrained, multi-pa...

A reliable inspection of the tree trunk internal defects is often considered vital in the health condition assessment for the living tree. There has been a desire to reconstruct the internal structure quantitatively using a non-destructive testing technology. This paper intends to apply wavefield reconstruction inversion (WRI) to obtain high-precis...

Multi-parameter elastic full waveform inversion (FWI) makes full use of the dynamic and kinematic information of all seismic wavefield. Through the mutual constraint and verification of the three parameters of P-wave velocity, S-wave velocity, and density, the joint evaluation is carried out, which is helpful to understand the structural and lithol...

Ground-penetrating radar (GPR) has been regarded as a potentially efficient way of evaluating the growth status of trees and preventing deterioration associated with trunk defects. However, the majority of current GPR data inversions focused on imaging the macroscale location of defects. As the first attempt to seek a preferable quantitative invers...

Improving the accuracy and efficiency of the numerical simulation of ground penetrating radar (GPR) becomes a pressing need with the rapidly increased amount of inversion data and the growing demand for migration imaging quality. In this paper, we present a numerical spectral element time-domain (SETD) simulation procedure for GPR forward modeling...

Full waveform inversion (FWI) of common-offset ground penetrating radar (GPR) data can make up for the defects of the traditional prospecting technology such as destructive, cumbersome, and low efficiency, which also provides a robust and high-precision tool for quantitative assessment of subsurface prospecting. Nonetheless, conventional GPR-FWI is...

Magnetotellurics (MT) is an important geophysical method for resource exploration and mineral evaluation. As a direct and effective form of data interpretation, MT inversion is usually considered to be a penalty-function constraint-based optimization strategy. However, conventional MT inversion involves a large number of calculations in penalty ter...

The full-waveform inversion (FWI) of ground-penetrating radar (GPR) data yields promise for quantitatively characterizing the parameters of the Earth's shallow subsurface. However, conventional FWI is highly nonlinear and suffers from cycle skipping once the low-frequency data are missed or the initial model is poor. Furthermore, having limited pri...

Horizontally transverse isotropy (HTI) induced by vertical or subvertical, aligned fractures is common for unconventional fractured porous shale oil or gas reservoirs. Compared with the unfractured rocks, the seismic response characteristics of PP-wave azimuthal amplitudes are usually disturbed by the fractures and the in-situ stresses. Knowledge o...

The finite element time-domain (FETD) method is an appealing electromagnetic (EM) field-solving procedure for the derivation of high-resolution field distribution of complex geological models. However, the arising computational burden has become a main bottleneck restricting the efficient implementation of ground penetrating radar (GPR) simulation...

High-precision detection of the underground pipelines is an indispensable part of the development and construction of cities. At present, the inversion technology for ground-penetrating radar (GPR) data is an effective means of realizing shallow-underground-space visualization in the field of geophysical exploration. However, the traditional full-w...

Reverse time migration (RTM) is the important intermediate step for focusing the radar diffracted energy of the targets in ground penetrating radar imaging. The conventional RTM algorithm demands a large number of iterative trial experiments and depends on the experts' decision on the estimation of the velocity or relative permittivity of the subsu...

Accurate location and depth determination of underground pipes, especially the attribute recognition, are of great importance yet remake a challenging issue in municipal environments. Single-trace phase difference analysis remains a bottleneck due to its inherent and strong randomness in object identification. This paper developed a multi-trace pha...

The ground penetrating radar (GPR) data in the complex detection environment is non-stationary, non-Gaussian, and non-uniform, so the traditional noise attenuation methods are difficult to meet the requirements of denoising. Therefore, we introduced the K-singular value decomposition (K-SVD) dictionary learning into the denoising of GPR signals. It...

The high-fidelity attenuation of random ground penetrating radar (GPR) noise is important for enhancing the signal-noise ratio (SNR). In this paper, a novel network structure for convolutional denoising autoencoders (CDAEs) was proposed to effectively resolve various problems in the noise attenuation process, including overfitting, the size of the...

Ground-penetrating radar (GPR) full-waveform inversion (FWI) is an emerging near-surface high-resolution imaging technology that has been widely used in GPR 2-D imaging to better quantitatively evaluate the permittivity and conductivity of the subsurface. However, the 2-D imaging method limits the applicability and accuracy of FWI for the 3-D objec...

Full waveform inversion (FWI) of ground-penetrating radar (GPR) data is becoming a promising technique to facilitate the interpretation of surface-GPR data and the mapping of the subsurface. However, more general FWIs still require a sufficient amount of RAM memory, and it is difficult to produce an accurate and representative reconstruction result...

Full waveform inversion (FWI) is one of the most promising techniques for the quantitative characterization of the shallow subsurface of the Earth. However, the conventional FWI with the reduced approach is highly nonlinear, a challenging source of which is the cycle skipping. It would drive FWI to spurious local minima as soon as the initial model...

The dual-parameter Full Waveform Inversion (FWI) of Ground Penetrating Radar (GPR) needs a vast amount of calculation and can easily fall into a local minimum. In addition, the crosstalk noise caused by coupling the permittivity and conductivity can affect the accuracy of the inversion for conductivity. To solve these problems, this study introduce...

Accurate and efficient 3D simulation is extremely important for both grasping the features of radar wave propagation in realistic models and the high-resolution inversion. In this paper, we propose a new numerical algorithm called the low-storage five-stage fourth-order explicit Runge-Kutta interpolation scaling function method (LSERK-ISFM) and app...

The conductivity distribution of subsurface often contains segmented structure with sharp interfaces, although the magnetotelluric (MT) inversions based on Tikhonov regularization are usually stable, the smoothing interfaces tomography result from high-resistance artifacts and boundary blurring still post a great challenge for MT inversion. On the...

To address problems, such as the computationally intensive inversion requirements, low inversion efficiency, and inadequate inversion accuracy caused by multiparameter cross-talk in a synchronous inversion, a new dynamic stochastic source encoding strategy combined with minmax-concave total variation (MCTV) regularization model constraints was prop...

Ground-penetrating radar (GPR) is a highly efficient, fast and non-destructive exploration method for shallow surfaces. High-precision numerical simulation method is employed to improve the interpretation precision of detection. Second-generation wavelet finite element is introduced into the forward modeling of the GPR. As the finite element basis...

We present a new approach of unstructured grid adaptive finite element in the frequency domain (AFEFD) based on exact perfect matching layer (EPML) boundary condition for Ground penetrating radar (GPR) simulation. The discrete equations of transverse magnetic mode are derived by using the unstructured Delaunay mesh coupled with linear interpolation...

Investigation into the electromagnetic response of porous media and the porosity distribution is a key for improved porous material. However, current ground penetrating radar (GPR) simulation techniques based on the finite difference method (FDM) or even finite element method (FEM) are mainly focused on describing macro characteristics of porous pr...

One of the great challenges of unconfined seepage through a dam lies in the accurate determination of free surface that depends on the complexity of the seepage model, especially if the model is characterized with complex geometry and sharp variations in permeability distribution. This study presents a practical methodology that combines the adapti...

In this work, an interpolating wavelet is constructed by the lifting scheme of the second generation wavelet transformation, by employing the two-dimensional wavelet transform into the wave field function of radar, both the wavelet coefficients and scale coefficients that corresponding to the computational grid of different scales can be all calcul...

Based on the variational problem derived from magnetotelluric(MT) boundary value problems, the finite element method using irregular quadrilateral mesh and bilinear interpolation was used to solve MT forward problem of steep topography model. The detailed calculation of Jacobi transformation matrix was discussed and interpolation method of arbitrar...

This article introduces the principle of CPML boundary conditions, and deduces its FDTD formula for GPR forward modeling, and then compares and analyzes the absorption properties of evanescent wave in Berenger PML, UPML, CPML. The numerical experiment of key parameters κ and α in PML were performed so as to determine its range and selection princip...

Starting from the Maxwell equations, this article studied the boundary conditions of 3D MT. By using the weighted residual method, we derived the three-dimensional MT finite element equation. The three-dimensional vector finite element hexahedral meshing mode was introduced and the basis functions were selected. Then we derived the three-dimensiona...

Based on the separable wavelet theory,the scaling functions of one-dimensional Bspline wavelet on the interval(BSWI)is employed to construct the two-dimensional B-spline wavelet bases on the interval.In order to solve the GPR wave equation,these constructed wavelet bases are used as the interpolation functions,and a transformation matrix is introdu...

Ground penetrating radar (GPR) forward is one of the geophysical research directions. Through the forward of geological model, the database of radar model can be enriched and the characteristics of typical geological radar echo images can be understood, which in turn can guide the data interpretation of GPR measured profile, thereby improving the G...

Based on the separable wavelet theory, we construct the two-dimensional Daubechies wavelet bases by means of one-dimensional Daubechies scaling functions, which is used for interpolation functions of solving the GPR wave equation, thus present the discrete format of two-dimensional Daubechies wavelet finite element GPR equation. By introducing a tr...

Considering that Daubechies wavelet finite element connection coefficient is calculated by adding complex equations currently, calculation results vary with different numbers of additional equations with high difficulty, and calculation results are not precise enough, the compound trapezoid quadrature method (CTQM) was combined with filter coeffici...

Based on the boundary value problem of partial differential equation of the two-dimensional magnetotelluric (MT) forward modeling meet, the detail algorithm of finite element method deduced by the rectangular grid subdivision and cell biquadratic interpolation method were used to solve the electromagnetic problems both in TE and TM polarization mod...