Numerical analysis of multicomponent responses of surface-hole transient electromagnetic method

We calculate the multicomponent responses of surface-hole transient electromagnetic method. The methods and models are unsuitable as geoelectric models of conductive surrounding rocks because they are based on regular local targets. We also propose a calculation and analysis scheme based on numerical simulations of the subsurface transient electromagnetic fields. In the modeling of the electromagnetic fields, the forward modeling simulations are performed by using the finite-difference time-domain method and the discrete image method, which combines the Gaver–Stehfest inverse Laplace transform with the Prony method to solve the initial electromagnetic fields. The precision in the iterative computations is ensured by using the transmission boundary conditions. For the response analysis, we customize geoelectric models consisting of near-borehole targets and conductive wall rocks and implement forward modeling simulations. The observed electric fields are converted into induced electromotive force responses using multicomponent observation devices. By comparing the transient electric fields and multicomponent responses under different conditions, we suggest that the multicomponent-induced electromotive force responses are related to the horizontal and vertical gradient variations of the transient electric field at different times. The characteristics of the response are determined by the varying the subsurface transient electromagnetic fields, i.e., diffusion, attenuation and distortion, under different conditions as well as the electromagnetic fields at the observation positions. The calculation and analysis scheme of the response consider the surrounding rocks and the anomalous field of the local targets. It therefore can account for the geological data better than conventional transient field response analysis of local targets.

Synthesis of Antennas for Field and Polarization Control

This article presents a procedure for electromagnetic field and polarization control with antennas. The concept previously introduced by the authors for spatially distributed three-dimensional electromagnetic polarization (as time varies) is discussed and extended also to include non-ideal antennas and the control of electromagnetic field distributions (at a given instant of time). These polarizations and fields are herein referred to as “3D”, although time is also inherent to them. Even that the main objective is to introduce a mathematically/numerically consistent synthesis technique for controlling the 3D electromagnetic fields and polarizations, an effort is made to present and discuss possible applications, including but not limited to torus-knotted distributions and spatial multiplexing for transmission of information in wireless digital communication systems.

Single-chip 3D electric field microsensor

This paper presents a single-chip 3D electric field microsensor, in which a sensing element is set at the center to detect the Z-axis component of an electrostatic field. Two pairs of sensing elements with the same structure are arranged in a cross-like configuration to measure the X- and Y-axis electrostatic field components. An in-plane rotary mechanism is used in the microsensor to detect the X-, Y-, and Z-axis electrostatic field components simultaneously. The proposed microsensor is compact and presents high integration. The microsensor is fabricated through a MetalMUMPS process. Experimental results show that in the range of 0-50 kV/m, the linearity errors of the microsensor are within 5.5%, and the total measure- ment errors of the three electrostatic field components are less than 14.04%.

基于双金属球三维电场探空仪的一次雷暴云内电荷结构观测研究

本文自主研制性能稳定的双金属球三维电场探空仪,并结合气象探空仪等构建了雷暴电场-气象综合探空系统,实现了雷暴云内三维电场及温度、湿度的同步测量.2019年夏季对华北平原地区雷暴开展穿云观测,并结合地面大气电场、雷达回波、变分多普勒雷达分析系统(VDRAS)反演的动力场等资料进行综合研究,首次给出该地区雷暴云内的电场和电荷结构分布特征.对2019年8月7日发生的一次中尺度对流系统电场探空发现,在雷暴减弱阶段,其弱回波区内存在5个极性交替的电荷区:4.4~5.6 km之间的上部正电荷区(0℃附近)、3.6~4.4 km之间的中部负电荷区和1.0~3.6 km之间的下部正电荷区,此外在1 km下方有一个负极性电荷区,雷暴云顶附近5.7~6.9 km之间为一个弱负极性屏蔽电荷区.其中,中部负电荷区和下部正电荷区由多个不同强度、不同厚度的电荷层构成.此外,电场探空系统在中部负电荷区高度范围内经历的上升—下沉—再次上升的往返探空数据表明,雷暴云内动力环境复杂,电荷结构分布相似但又有所差异,反映了实际雷暴云内电荷分布的时空不均匀性和复杂性.

NUMERICAL LOCALIZATION OF ELECTROMAGNETIC IMPERFECTIONS FROM A PERTURBATION FORMULA IN THREE DIMENSIONS

This work deals with the numerical localization of small electromagnetic inhomogeneities. The underlying inverse problem considers, in a three-dimensional bounded domain, the time-harmonic Maxwell equations formulated in electric field. Typically, the domain contains a finite number of unknown inhomogeneities of small volume and the inverse problem attempts to localize these inhomogeneities from a finite number of boundary measurements. Our localization approach is based on a recent framework that uses an asymptotic expansion for the perturbations in the tangential boundary trace of the curl of the electric field. We present three numerical localization procedures resulting from the combination of this asymptotic expansion with each of the following inversion algorithms： the Current Projection method, the MUltiple Signal Classification （MUSIC） algorithm, and an Inverse Fourier method. We perform a numerical study of the asymptotic expansion and compare the numerical results obtained from the three localization procedures in different settings.

Multiple plasmon couplings in 3D hybrid Au-nanoparticles-decorated Ag nanocone arrays boosting highly sensitive surface enhanced Raman scattering

Plasmon coupling is an essential strategy to realize strong local electromagnetic(EM)field which is crucial for high-performance plasmonic devices.In this work,multiple plasmon couplings are demonstrated in three-dimensional(3D)hybrid plasmonic systems composed of polydimethylsiloxane-supported ordered silver nanocone(AgNC)arrays decorated with high-density gold nanoparticles(AuNPs)which are fabricated by a template-assisted physical vapor deposition process.Strong interparticle coupling,particle-film coupling,inter-cone coupling,and particle-cone coupling are revealed by numerical simulations in such composite nanostructures,which produce intense and high-density EM hot spots,boosting highly sensitive and reproducible surface enhanced Raman scattering(SERS)detection with an enhancement factor of-1.74×10^(8).Furthermore,a linear correlation between logarithmic Raman intensity and logarithmic concentration of probe molecules is observed in a large concentration range.These results offer new ideas to develop novel plasmonic devices,and provide alternative strategy to realize flexible and high-performance SERS sensors for trace molecule detection and quantitative analysis.