| 几种典型近地表有限导体瞬变电磁特征响应研究 |
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| 引用本文： | 陈曙东,郭树旭,张爽,袁志文,朱俊,张海洋,方东.几种典型近地表有限导体瞬变电磁特征响应研究[J].地球物理学报,2017,60(1):403-412. |
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| 作者姓名： | 陈曙东 郭树旭 张爽 袁志文 朱俊 张海洋 方东 |
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| 作者单位： | 1. 吉林大学电子科学与工程学院, 长春 130012;2. 近地面探测技术重点实验室, 江苏无锡 214035 |
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| 基金项目： | 近地面探测技术重点实验室开放课题（TCGZ2015A004）资助. |
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| 摘 要： | 近地表有限导体的瞬变电磁响应中包含其形状、结构特征,如何建立这些特征与其响应之间的关系是近地表有限导体探测与识别的核心问题.本文建立了几种典型有限导体响应的三维感应偶极子模型,通过有限导体早期幂函数衰减的幅度与速率、晚期指数衰减的幅度与时间常数共四个模型参数表征有限导体的形状和结构特征,利用最小二乘拟合算法提取这些模型参数,揭示有限导体的形状、结构特征与模型参数之间的内在联系.理论与实验研究结果表明:具有绕球心旋转对称性的球形目标体,其三维感应偶极子响应完全相同,早期响应呈幂函数衰减,晚期呈e指数衰减,信号幅度和时间常数均能很好反映球体半径与材料特性;具有绕轴旋转对称性目标体,其三维感应偶极子响应部分相同,早期幂函数衰减的幅度与速率主要体现目标体的长度特征,晚期e指数衰减的时间常数体现了目标体的外径与壁厚特征;非轴对称性目标体,其三维感应偶极子响应均不相同,各个感应偶极子参数差异较大.本文的研究对提高瞬变电磁系统区分轴对称目标体与金属碎片能力,降低系统探测虚警率具有重要意义.
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| 关 键 词： | 近地表地球物理 未爆弹药 瞬变电磁 三维感应偶极子模型 特征响应 目标识别 |
| 收稿时间： | 2015-11-03 |
Modeling and analysis of transient electromagnetic responses of finite conductors in the near-surface |
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| CHEN Shu-Dong,GUO Shu-Xu,ZHANG Shuang,YUAN Zhi-Wen,ZHU Jun,ZHANG Hai-Yang,FANG Dong.Modeling and analysis of transient electromagnetic responses of finite conductors in the near-surface[J].Chinese Journal of Geophysics,2017,60(1):403-412. |
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| Authors: | CHEN Shu-Dong GUO Shu-Xu ZHANG Shuang YUAN Zhi-Wen ZHU Jun ZHANG Hai-Yang FANG Dong |
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| Institution: | 1. College of Electronic Science and Engineering, Jilin University, Changchun 130012, China;2. Science and Technology on Near-Surface Detection Laboratory, Jiangsu Wuxi 214035, China |
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| Abstract: | It is a key problem in near-surface conductor detection to identify real targets from the data containing numerous interferences depending on the shape and structure characters of targets reflected in the responses. According to the results of theoretical calculation and experimental verification, this study focuses on the influence of target shape and structure on its electromagnetic transient responses. Firstly, a group of induced dipoles with coincident central and orthogonal directions are established to replace finite conductors, then parametric response models are built to describe the induced responses of dipoles, and the parameters of these responses are picked up to analyze the influences of target shapes. Studies have shown that the characters of induced dipole responses are determined by the symmetry of the target shape and structure. The difference between the dipole responses is remarkable for an asymmetric target; all the dipole responses are identical for a sphere target, and dipole responses of an axial symmetry target can be divided into two types:vertical to the axis and axially. The axially symmetric target is the main object in near-surface detection. The amplitude and decay rate of early response depend on the length of the target. The longer the length is, the greater the amplitude and the slower the attenuation will be. The decay rate of the later exponential response depends on the diameter and thickness of the target. The larger the diameter and the wall thickness are, the slower the decay will be. This study is of significance to improve the distinguishing ability between axial symmetry targets and metal fragments, and reduce the false alarm ratio of the system. |
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| Keywords: | Near-surface geophysics Unexplored ordnance (UXO) Transient electromagnetic (TEM) Three-dimensional induced dipole model Characteristic response Target identification |
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