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Feng D.-S.,Central South University | Feng D.-S.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Wang X.,Central South University | Wang X.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2017

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 deduced GPR time domain finite element wave equation solution formula based on CPML (Convolutional PML) boundary, discrete time derivative with Newmark-β method. Then in narrow model as an example, we conducted the select experiment of the key parameters of CPML border m, R and κ, and determine the optimal parameter combination by contrast reflection error by contrast reflection error. By comparison error of UPML and CPML wave field snapshots and reflecting of three detection points, we can conclude CPML has better absorption effect compared with UPML. Finally, the use of irregular quadrilateral mesh makes a complex GPR model subdivision. Application loading CPML boundary conditions FETD program the model was forward. Obtain a two-dimensional cross-sectional method and wide angle method forward GPR cross-sectional view. That explains irregular quadrilateral adaptable for complex models. The boundary conditions FETD on CPML can effectively reduce the boundary reflection error and can achieve positive modeling of arbitrarily complex irregular models. © 2017, Science Press. All right reserved.

Feng D.-S.,Central South University | Feng D.-S.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Feng D.-S.,Non ferrous Resources and Geologic Disasters Prospecting Emphases Laboratory of Hunan | Wang H.-H.,Central South University | And 5 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2013

Forward simulation of Ground Penetrating Radar (GPR) is conducted by the element-free Galerkin method (EFGM) which has advantages such as simple preprocessing, high precision and solution of the high-order continuous derivatives, so it only requires nodes without elements and adopts the moving least-squares (MLS) fitting field function. The wave equation that the GPR forward simulation needs to satisfy is derived starting with the Maxwell equation, and then the constructing method of the MLS shape function is presented in detail. To address the complicated processing of the imposed boundary conditions, a penalty factor is employed to process the imposed boundary condition because the EFGM cannot meet the interpolation condition. Meanwhile, to eliminate ultra-intense reflection from the truncated boundary when the EFGM is employed in the GPR forward simulation, the truncated boundary condition is used to transmit the reflected waves from the truncated boundary, so as to restrain these reflected waves. A Matlab program for GPR forward simulation based on the EFGM is compiled and used in the forward simulation for the typical GPR geoelectric model. A comparison of the resultant profile from the simulation with the FEM forward-simulation profile based on linear interpolation shows that the EFGM simulation has better continuity and smoothness, and the consistency of the simulation results indicates the correctness and effectiveness of the EFGM used for GPR forward computation.

Peng G.,Central South University | Peng G.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Shen W.,Shanghai Ocean University | Han Z.,Shanghai Ocean University | Su W.,China Agricultural University
Sensor Letters | Year: 2011

In this paper, we present an approach that uses surface parameters retrieved from remote sensing to evaluate the tobacco planting suitability. In the processing, the Suitability Evaluation Index (SEI) with the spatial resolution of 100 m was established and used to estimate the tobacco planting suitability. The results show that, the area of tobacco planting is 11312 ha, and the area of the high suitable is 3745 ha in Mile county. The percentage between the area of tobacco planting in the high suitable and the area of tobacco planting in Mile County is only 33%. The spatial distribution of tobacco planting is very unreasonable and lopsided. The utility ratio of high quality land resources is very low. The overall rotation rate of Mile County is 80%, which has still a big gap to the target of 95%. © 2011 American Scientific Publishers.

Hu D.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Hu D.,Central South University | Zhang K.-N.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Zhang K.-N.,Central South University | He J.,Hunan University of Technology
International Journal of Earth Sciences and Engineering | Year: 2015

Making interpolation into the classical Kriging spatial interpolation for space-time expansion, and establishing the displacement prediction model of tunnel surrounding rock by space-time semivariogram; analyzing the relation of parameters and transformation, giving the calculation procedure and method for spatial and temporal interpolation. On that basis, space-time unification Kriging interpolation model is applied to predict the crown settlement displacement value within a certain scope at front of tunnel face at any time during the period of tunnel construction. Analyzing and comparing the relation of actual measurement and predicted displacement to time curve taking Sunanshan Tunnel as test object. Computed results show that the model can reflect the development and variation tendency of crown settlement and displacement better, indicating that the precision of spatial and temporal unification Kriging model meets code requirements and it is effective and feasible in displacement prediction of surrounding rock of actual tunnel project. © 2015 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.

Tang J.-T.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Hu S.-G.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Hu S.-G.,Central South University | Xiao X.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Xiao X.,Central South University
Wutan Huatan Jisuan Jishu | Year: 2015

Audio magnetotelluric (AMT) sounding has become an important method for researching the Earth's electrical structure, which needs to collect the weak and vulnerable natural telluric signal. The stability of grounding resistance is an important factor that affects the accuracy of measurement. The paper has calculated the electric field and the response of the apparent resistivity and the phase under the condition of homogeneous half - space.which is based on the theory of the circuit representation of a telluric measurement. The study shows that the influence of grounding resistance changes on the electric field, the apparent resistivity and impedance phase can not be ignored, especially in the high - frequency. High ground resistance may bring errors of 50% to the electrode field and the phase error, and bring the greatest errors of 75% to the apparent resistivity.

Wang H.-H.,Central South University | Wang H.-H.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Dai Q.-W.,Central South University | Dai Q.-W.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | And 2 more authors.
Journal of Environmental and Engineering Geophysics | Year: 2014

We improve the resolution and accuracy of ground-penetrating radar (GPR) forward modeling by applying the mesh-less algorithm element-free method (EFM), which is widely used in the electromagnetic field for numerical simulation. EFM dispenses with the concepts of elements, needs only a mass of node information, and adopts the moving least squares (MLS) method to structure a shape function. Advantages of EFM are simple preprocessing, high accuracy, and high successively independent variable solutions. We start with the GPR wave equation, and then discuss the EFM approach and how to combine an improved Sarma absorbing boundary with EFM for GPR forward modeling. We simulate two 2-D models with typical electrical properties. The results show that EFM can calculate stable geo-electric GPR models because the improved Sarma absorbing boundary can absorb incident GPR waves near the model boundary effectively.

Tang J.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Tang J.,Central South University | Zhou C.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Zhou C.,Central South University | And 5 more authors.
Tectonophysics | Year: 2013

The Tongling ore district is one of the most important Cu-polymetal producers in the Lower Yangtze River metallogenic belt of China. To understand deep crust structure beneath the Tongling ore district more comprehensively and objectively and to explore important scientific issues, such as characteristics of lithospheric evolution, the relationship between the crustal structure and metallogenesis, it is necessary to study the variation of crust electrical structure in the study area. For this purpose, six magnetotelluric (MT) sounding profiles have been completed by SinoProbe-03 Project. Based on the imaging results of the six profiles, electrical conductivity structure of the crust has been analyzed. The result shows that the geology beneath the profiles is characterized by layering in vertical direction and block division in horizontal direction. The high-resistivity features are related to the transparent zones detected at the upper crust in reflection seismic surveys. The absence of reflectivity from the depths indicates a homogeneous zone, which could often be related to granitic intrusions. Combining the regional tectonic evolution, MT and other geophysical data, we suggest that the high-resistivity bodies crossing the Tongling uplift reveals the center of magma activity and the layering in vertical direction in the lower crust reveals a normal lower crust model and propose a small-scale underplating model which is different with both the "partial melting of a thickened or delaminated lower continental crust" model and the "oceanic ridge subduction". The underplating might be related to small-scale lithospheric or lower crust delamination controlled by deep fault during the Early Cretaceous. The result of this MT survey is important for constraining lithospheric evolution and metallogenesis in the Lower Yangtze Metallogenic Belt, such as collision of North China Craton and Yangtze Craton, underplating models, deep structure, mechanisms of NE-SW trending rift as well as graben basin, and probable metallogenesis. © 2013 Elsevier B.V.

Feng D.-S.,Central South University | Feng D.-S.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Dai Q.-W.,Central South University | Dai Q.-W.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | And 2 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2014

The 2D data processing adopted by the high-density resistivity method regards the geological structures as two degrees, which makes the results of the 2D data inversion only an approximate interpretation; the accuracy and effect can not meet the precise requirement of the inversion. Two typical models of the geological bodies were designed, and forward calculation was carried out using finite element method. The forward-modeled profiles were obtained. 1% Gaussian random error was added in the forward models and then 2D and 3D inversions using a high-density resistivity method were undertaken to realistically simulate field data and analyze the sensitivity of the 2D and 3D inversion algorithms to noise. Contrast between the 2D and 3D inversion results of least squares inversion shows that two inversion results of high-density resistivity method all can basically reflect the spatial position of an anomalous body. However, the 3D inversion can more effectively eliminate the influence of interference from Gaussian random error and better reflect the distribution of resistivity in the anomalous bodies. Overall, the 3D inversion was better than 2D inversion in terms of embodying anomalous body positions, morphology and resistivity properties. © 2014 The Nonferrous Metals Society of China.

Hu T.,Central South University | Hu T.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Li D.-Q.,Central South University | Li D.-Q.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals
Wutan Huatan Jisuan Jishu | Year: 2014

The superiority of the E-Ex mode of Wide field electromagnetic sounding method (WFEM) on near field and distinguishing ability of the structure with a thin layer with low resistance is discussed. More concerns were put on the 2D or 3D forward and inversion computation recently. While this paper set up several groups of 1D geological model containing low resistance thin layered structure, drawing the apparent resistivity curves, analyzing features of curves, and knowing the ability of distinguishing the low resistance with thin layer structure. And then compared with the one-dimensional numerical simulation results of CSAMT, the contrasted result shows the superiority of the E-E x mode of wide field electromagnetic sounding method on near field, and helps to know the aspects of wide field apparent resistivity.

Deng J.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Deng J.,Central South University | Qiu L.,Key Laboratory of Metallogenic Prediction of Nonferrous Metals | Qiu L.,Central South University | And 4 more authors.
Advanced Materials Research | Year: 2012

According to the field geological sample classification, a spectral similarity the cluster analysis algorithm (SSCA) has been put forward. This algorithm expands and improves the spectra sort encoding algorithm on the spectral sorting and similarity computation, and adds similarity clustering analysis method. Testing on 100 field geological samples using SSCA algorithm, we get the results showing that this algorithm can make further classification for field geological samples to some extent. © (2012) Trans Tech Publications, Switzerland.

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