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2.5-D modeling of cross-hole electromagnetic measurement by nite element method

Petroleum Science 2008年第2期5卷 126-134页

作者： Shen Jinsong Sun Wenbo Department of Geophysics School of Resources and Information Technology China University of Petroleum Beijing 102249 China CNPC Key Lab of Geophysical Exploration China University of Petroleum Beijing 102249 China

A finite element method is developed for simulating frequency domain electromagnetic responses due to a dipole source in the 2-D conductive structures. Computing costs are considerably minimized by reducing the full three-dimensional problem to a series of two-dimensional problems. This is accomplished by transforming the problem into y-wave number （Ky） domain using Fourier transform and the y-axis is parallel to the structural strike. In the Ky domain, two coupled partial differential equations for magnetic field Hy and electric field Ey are derived. For a specific value of Ky, the coupled equations are solved by the finite element method with isoparametric elements in the x-z plane. Application of the inverse Fourier transform to the Ky, domain provides the electric and magnetic fields in real space. The equations derived can be applied to general complex two-dimensional structures containing either electric or magnetic dipole source in any direction. In the modeling of the electromagnetic measurement, we adopted a pseudo-delta function to distribute the dipole source current and circumvent the problem of singularity at the source point. Moreover, the suggested method used isoparametric finite elements to accommodate the complex subsurface formation. For the large scale linear system derived from the discretization of the Maxwell＇s equations, several iterative solvers were used and compared to select the optimal one. A quantitative test of accuracy was presented which compared the finite element results with analytic solutions for a dipole source in homogeneous space for different ranges and different wave numbers Ky. to validate the addressed the effects of the distribution range τ of the homogeneous medium. code and check its effectiveness. In addition, we pseudo-delta function on the numerical results in

关键词： 2.5-D electromagnetic modeling frequency domain isoparametric finite element pseudo-delta function

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Precision of meshfree methods and application to forward modeling of two-dimensional electromagnetic sources

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Applied Geophysics 2015年第4期12卷 503-515,627页

作者：李俊杰严家斌皇祥宇浙江省水利水电勘测设计院浙江杭州310002 中南大学地球科学与信息物理学院有色资源与地质灾害探查湖南省重点实验室湖南长沙410083

Meshfree method offers high accuracy and computational capability and constructs the shape function without relying on predefined elements. We comparatively analyze the global weak form meshfree methods, such as element-free Galerkin method （EFGM）, the point interpolation method （PIM）, and the radial point interpolation method （RPIM）. Taking two dimensional Poisson equation as an example, we discuss the support-domain dimensionless size, the field nodes, and background element settings with respect to their effect on calculation accuracy of the meshfree method. RPIM and EFGM are applied to controlled- source two-dimensional electromagnetic modeling with fixed shape parameters. The accuracy of boundary conditions imposed directly and by a penalty function are discussed in the case of forward modeling of two-dimensional magnetotellurics in a homogeneous medium model. The coupling algorithm of EFG-PIM and EFG-RPIM are generated by integrating the PIM or RPIM and EFGM. The results of the numerical modeling suggest the following. First, the proposed meshfree method and corresponding coupled methods are well-suited for electromagnetic numerical modeling. The accuracy of the algorithm is the highest when the support-domain dimensionless size is 1.0 and the distribution of field nodes is consistent with the nodes of background elements. Second, the accuracy of PIM and RPIM are lower than that of EFGM for the Poisson equation but higher than EFGM for the homogeneous medium MT response. Third, RPIM overcomes the matrix inversion problem of PIM and has a wider selection of support-domain dimensionless sizes as compared to RPIM.

关键词： Element-free Galerkin method point-interpolation method radial pointinterpolation method Poisson equation controlled-source electromagnetic modeling coupled meshfree method

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Computer Analysis of electromagnetic Transients in Grounding Systems Considering Variation of Soil Parameters with Frequency

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Journal of electromagnetic Analysis and Applications 2012年第12期4卷 475-480页

作者： Marco A.O.Schroeder Marcio M.Afonso Tarcisio A.S.Oliveira Sandro C.Assis Department of Electrical Engineering Federal University of Sao Joao del-ReiLaboratory of Applied ElectromagnetismSao Joao del-ReiBrazil Department of Electrical Engineering Federal Center of Technological Education of Minas GeraisBelo HorizonteBrazil Energetic Company of Minas Gerais Belo HorizonteBrazil

This paper presents a mathematical model to calculate transients in grounding systems. The derived equations arise from direct application of basic electromagnetic equations in frequency domain, whose solution is obtained by the application of the Moment Methods. A formulation based on experimental measurements is applied to quantify the soil parameters for each frequency. The unified approach is applied in the calculation of the grounding impedance of horizontal electrodes. Results show that the inclusion of frequency dependence of the soil parameters leads to a reduction of the values of grounding impedance, in comparison with results for soils with parameters independent of frequency.

关键词： Grounding Electrodes Grounding Impedance Transient Response Frequency Response electromagnetic modeling

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How the Macroscopic Electric Field Shape Spatio-temporal Response of Neurons by Electroconvulsive Therapy

How the Macroscopic Electric Field Shape Spatio-temporal Res...

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第三十九届中国控制会议

作者： Lin Lin Jiang Wang Guosheng Yi School of Electrical Automation and Information Engineering Tianjin University

This study explored the effect of macroscopic electric fields induced by electroconvulsive therapy（ECT） on voltage-gated ion channels of neurons. Based on the data provided by the multi-scale models, the mathematical models of the influence of the macroscopic electric field on the neuronal cell membrane potential are established. This paper introduces a computational ECT model in which biophysics of stimulation and neurophysiology are combined. The macroscopic field model is combined with the mesoscopic nerve morphology to provide the accurate vector of field for the microscopic nerve fiber bundle. Under the influence of external stimuli of ECT, the spatio-temporal response of cell membrane potentials is calculated with microsecond time resolution. The presented model gives insight in the activity propagation through the brain and can therefore explain the observed clinical responses to ECT and their inter-and/or intra-subject variability. We aspire to advance towards an accurate, flexible and personalized ECT model that helps to understand stimulation in the connected brain and to target more accurate and deeper brain regions.

关键词： Biophysics electromagnetic modeling Electric potential Finite element analysis Spatiotemporal phenomena

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FEM-based modeling of microsphereenhanced interferometry

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Light(Advanced Manufacturing) 2022年第4期3卷 73-85页

作者： Tobias Pahl Lucie Hüser Sebastian Hagemeier Peter Lehmann Measurement Technology Group Faculty of Electrical Engineering and Computer ScienceUniversity of KasselWilhelmshöher Allee 7134121 KasselGermany

To improve the lateral resolution in microscopic imaging,microspheres are placed close to the object’s surface in order to support the imaging process by optical near-field *** microsphere-assisted measurements are part of various recent studies,no generally accepted explanation for the effect of microspheres *** nanojets,enhancement of the numerical aperture,whispering-gallery modes and evanescent waves are usually named reasons in context with microspheres,though none of these effects is proven to be decisive for the resolution *** present a simulation model of the complete microscopic imaging process of microsphere-enhanced interference microscopy including a rigorous treatment of the light scattering process at the surface of the *** model consideres objective lenses of high numerical aperture providing 3D conical illumination and *** enhanced resolution and magnification by the microsphere is analyzed with respect to the numerical aperture of the objective ***,we give a criterion for the achievable resolution and demonstrate that a local enhancement of the numerical aperture is the most likely reason for the resolution enhancement.

关键词： electromagnetic modeling Microsphere-assisted microscopy Interference microscopy Coherence scanning interferometry Simulation Finite element method

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