检索结果-南通市图书馆

A normalized wavefield separation cross-correlation imaging condition for reverse time migration based on poynting vector

在线全文

学校读者我要写书评

暂无评论

Applied Geophysics 2014年第2期11卷 158-166,253页

作者：陈婷何兵寿中国海洋大学海底科学与探测技术教育部重点实验室山东青岛266100

Prestack reverse time migration（PSTM） is a common imaging method; however low-frequency noises reduce the structural imaging precision. Thus, the suppression of migration noises must be considered. The generation mechanism of low-frequency noises is analyzed and the up-, down-, left-, and right-going waves are separated using the poynting vector of the acoustic wave equation. The computational complexity and memory capacitance of the proposed method are far smaller than that required when using the conventional separation algorithm of 2D Fourier transform. The normalized wavefield separation crosscorrelation imaging condition is used to suppress low-frequency noises in reverse time migration and improve the imaging precision. Numerical experiments using the Marmousi model are performed and the results show that the up-, down-, left-, and right-going waves are well separated in the continuation of the wavefield using the poynting vector. We compared the imaging results with the conventional method, Laplacian filtering, and wavefield separation with the 2D Fourier transform. The comparison shows that the migration noises are well suppressed using the normalized wavefield separation cross-correlation imaging condition and higher precision imaging results are obtained.

关键词： acoustic wave equation poynting vector wavefield separation normalized crosscorrelation migration noises

Reverse-time migration and amplitude correction in the angle-domain based on poynting vector

在线全文

学校读者我要写书评

暂无评论

Applied Geophysics 2017年第4期14卷 505-516,620,621页

作者： Liu Ji-Cheng Xie Xiao-Bi Chen Bo School of Electric and Automation engineering Changshu Institute of Technology Changshu 215500 China Institute for Geophysics and Planetary Physics University of California at Santa Cruz CA 95064 USA College of Earth Science and Engineering SUN YAT-SEN University Guangzhou 510275 China.

We propose a method based on the poynting vector that combines angle-domain imaging and image amplitude correction to overcome the shortcomings of reverse-time migration that cannot handle different angles during wave propagation. First, the local image matrix （LIM） and local illumination matrix are constructed, and the wavefield propagation directions are decomposed. The angle-domain imaging conditions are established in the local imaging matrix to remove low-wavenumber artifacts. Next, the angle-domain common image gathers are extracted and the dip angle is calculated, and the amplitude-corrected factors in the dip angle domain are calculated. The partial images are corrected by factors corresponding to the different angles and then are superimposed to perform the amplitude correction of the final image. Angle-domain imaging based on the poynting vector improves the computation efficiency compared with local plane-wave decomposition. Finally, numerical simulations based on the SEG/EAGE velocity model are used to validate the proposed method.

关键词： poynting vector angle-domain imaging local image matrix illumination analysis amolitude correction

Magnetic Monopoles, the poynting vector and Lenz’s Law

在线全文

学校读者我要写书评

暂无评论

Journal of Applied Mathematics and Physics 2024年第11期12卷 3690-3696页

作者： Anwar Y. Shiekh Department of Physics Colorado Mesa University Grand Junction CO USA

The poynting vector includes time-independent contributions which, since they represent photons of zero frequency, need to be absent;this removal resolves several paradoxes that arise when they are left in place;furthermore, magnetic monopoles, if they existed, would be accompanied by a Lenz’s law that defies conservation of energy suggesting that magnetic charges might not be found in Nature.

关键词： Magnetic Monopoles poynting vector Lenz’s Law

Electromagnetic-Energy Flow in Anisotropic Metamaterials: The Proper Choice of poynting’s vector

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Modern Physics 2016年第12期7卷 1519-1539页

作者： Carlos Prieto-López Rubén G. Barrera Instituto de Física Universidad Nacional Autónoma de México México

We study the controversy about the proper determination of the electromagnetic energy-flux field in anisotropic materials, which has been revived due to the relatively recent experiments on negative refraction in metamaterials. Rather than analyzing energy-balance arguments, we use a pragmatic approach inspired by geometrical optics, and compare the predictions on angles of refraction at a flat interface of two possible choices on the energy flux: and . We carry out this comparison for a monochromatic Gaussian beam propagating in an anisotropic non-dissipative anisotropic metamaterial, in which the spatial localization of the electromagnetic field allows a more natural assignment of directions, in contrast to the usual study of plane waves. We compare our approach with the formalism of geometrical optics, which we generalize and analyze numerically the consequences of either choice.

关键词： poynting vector Eikonal Electromagnetic-Energy Flux Anisotropic Metamaterials Geometrical Optics

Reverse time migration imaging of tunnels via the finite element method using an unstructured mesh

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied Geophysics 2020年第2期17卷 267-276,316页

作者： Wang Jing Liu Jiang-Ping Cheng Fei Yang Huai-Jie Huang Yi-Fan School of Civil Engineering Shijiazhuang Tiedao UniversityShijiazhuang 050043China Key Laboratory of Roads and Railway Engineering Safety Control(Shijiazhuang Tiedao University) Ministry of EducationShijiazhuang 050043China Hebei Technology and innovation center on safe and efficient mining of metal mines Shijiazhuang Tiedao UniversityShijiazhuang 050043China Hubei Subsurface Multi-scale Imaging Key Laboratory Institute of Geophysics and GeomaticsChina University of GeosciencesWuhan 430074China College of Marine Science and Technology China University of GeosciencesWuhan 430074China Beijing Research Institute of Uranium Geology Beijing 100029China

Wavefield extrapolation is critical in reverse time migration(RTM).The finite diff erence method is primarily used to achieve wavefi eld extrapolation in case of the RTM imaging of ***,complex tunnel models,including those for karsts and fault fracture zones,are constructed using regular grids with straight curves,which can cause numerical dispersion and reduce the imaging *** this study,wavefi eld extrapolation was conducted for tunnel RTM using the finite element method,wherein an unstructured mesh was considered to be the body-fi tted partition in a complex ***,a poynting vector calculation equation suitable for the unstructured mesh considered in the fi nite element method was established to suppress the interference owing to low-frequency *** tunnel space was considered during wavefi eld extrapolation to suppress the mirror artifacts based on the fl exibility of mesh ***,the infl uence of the survey layouts(one and two sidewalls)on the tunnel imaging results was *** RTM results obtained for a simple tunnel model with an inclined interface demonstrate that the method based on unstructured meshes can effectively suppress the low-frequency noise and mirror artifacts,obtaining clear imaging ***,the two-sidewall tunnel survey layout can be used to accurately obtain the real position of the inclined interface ahead of the tunnel *** complex tunnel numerical modeling and actual data migration results denote the eff ectiveness of the fi nite element method in which an unstructured mesh is used.

关键词： Tunnel advanced prediction fi nite element method unstructured mesh poynting vector mirror artifacts

Extraction of P-and S-wave angle-domain common-image gathers based on first-order velocity-dilatation-rotation equations

在线全文

学校读者我要写书评

暂无评论

Applied Geophysics 2020年第1期17卷 92-102,169页

作者： Li Kai-Rui He Bing-Shou Ocean University of China Qingdao 266100China Evaluation and Detection Technology Laboratory of Marine Mineral Resources Qingdao National Laboratory for Marine Science and TechnologyQingdao 266071China Key Laboratory of Submarine Geosciences and Prospecting Techniques Ministry of EducationQingdao 266100China

Accuracy of angle-domain common-image gathers(ADCIGs)is the key to multiwave AVA inversion and migration velocity analysis,and of which poynting vectors of pure P-and S-wave are the decisive factors in obtaining multi-component seismic data ADCIGs.A poynting vector can be obtained from conventional velocity-stress elastic wave equations,but it focused on the propagation direction of mixed P-and S-wave fields,and neither on the propagation direction of the P-wave nor the direction of the *** poynting vectors of pure P-or pure S-wave can be calculated from first-order velocity-dilatation-rotation *** study presents a method of extracting ADCIGs based on first order velocitydilatation-rotation elastic wave equations reverse-time migration *** method is as follows:calculating the pure P-wave poynting vector of source and receiver wavefields by multiplication of P-wave particle-velocity vector and dilatation scalar,calculating the pure S-wave poynting vector by vector multiplying S-wave particle-velocity vector and rotation vector,selecting the poynting vector at the time of maximum P-wave energy of source wavefield as the propagation direction of incident P-wave,and obtaining the reflected P-wave(or converted S-wave)propagation direction of the receiver wavefield by the poynting vector at the time of maximum P-(S-)wave energy in each grid ***,the P-wave incident angle is computed by the two propagation ***,the P-and S-wave ADGICs can obtained Numerical tests show that the proposed method can accurately compute the propagation direction and incident angle of the source and receiver wavefields,thereby achieving high-precision extraction of P-and S-wave ADGICs.

关键词： first-order velocity-dilatation-rotation equations RTM poynting vector ADCIGs

As Regards the Speed in a Medium of the Electromagnetic Radiation Field

在线全文

学校读者我要写书评

暂无评论

Journal of Modern Physics 2016年第11期7卷 1320-1330页

作者： Robert M. Yamaleev A. R. Rodríguez-Domínguez Joint Institute for Nuclear Research Dubna Russia Instituto de Física Universidad Autónoma de San Luis Potosí San Luis Potosí México

The velocity of the electromagnetic radiation in a perfect dielectric, containing no charges and no conduction currents, is explored and determined on making use of the Lorentz transformations. Besides the idealised blackbody radiation, whose vacuum propagation velocity is the universal constant c, being this value independent of the observer, there is another behaviour of electromagnetic radiation, we call inertial radiation, which is characterized by an electromagnetic inertial density , and therefore, it happens to be described by a time-like poynting four-vector field which propagates with velocity . is found to be a relativistic invariant expressible in terms of the relativistic invariants of the electromagnetic field. It is shown that there is a rest frame, where the poynting vector is equal to zero. Both phase and group velocities of the electromagnetic radiation are evaluated. The wave and eikonal equations for the dynamics of the radiation field are formulated.

关键词： Inertial Radiation Field Mass Field Density Rest State poynting vector Wave and Eikonal Equations of the Radiation Field Dynamics

An imaging condition for reverse time migration based on wavefield decomposition

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Global Geology 2015年第2期18卷 122-126页

作者： ZHAO Xu LIU Cai XU Cong College of Geo-Exploration Science and Technology Jilin University Northeast Electric Power Design Institute China Power Engineering Consulting Group

Reverse Time Migration(RTM) is a high precision imaging method of seismic wavefield at present,but low-frequency noises severely affect its imaging *** one of most important aspect of RTM is to select the proper noise suppression *** wavefield characteristics of the poynting vector are analyzed and the upgoing,downgoing,leftgoing and rightgoing waves are decomposed using the poynting vector of the acoustic wave *** normalized wavefield decomposition cross-correlation imaging condition is used to suppress low-frequency noises in RTM and improve the imaging *** experiments using the Mamousi velocity model are performed and the results demonstrate that the upgoing,downgoing,leftgoing and rightgoing waves are well decomposed using the poynting *** with the normalized cross-correlation imaging and Laplacian filtering method,the results indicate that the low-frequency noises are well suppressed by using the normalized wavefield decomposition cross-correlation imaging condition.

关键词： acoustic wave equation reverse time migration wavefield decomposition poynting vector low- frequency noises