A Comparison of Electrically Short Bare and Insulated Probes for Measuring the Local Radio Frequency Electric Field in Biological Systems

The problems associated with measuring the local electric field in a medium with spatally inhomogeneous electrical constitutive parameters like biological tissue are discussed. Simple theoretical analyses that describe the operation of electrically short bare and insulated electric field probes in a dissipative medium are presented. The conditions that must be satisfied for each of these probes to have an electric field response that is independent of the electrical constitutive parameters of the surrounding tissue are determined. The results of a systematic experimental study of both types of probes are presented. In the study the probes were immersed in a succession of liquids with dielectric properties similar to those for biological tissues at radio frequencies.     

Electric Field Probes in Material Media and Their Application in EMC

The use of the linear antenna as a probe to measure both the constitutive parameters of material media and the electric field interior to such media is reviewed. The advantages of using probes with a particular geometry (i. e., electricaUy short, resonant, bare or insulated) for specific applications are discussed. Applications in the areas of geophysics and biophysics are cited.     

Analysis of Miniature Electric Field Probes with Resistive Transmission Lines

The miniature dipole probe is a useful tool for measuring the electric field at high radio and microwave frequencies. A common design for the probe consists of an electrically short dipole antenna with a diode across its terminals; a resistive, parallel-wire transmission line transmits the detected signal from the diode to the monitoring instrumentation. The high resistance per unit length of the transmission line reduces the direct reception of the incident field by the line and also reduces the scattering of the incident field by the line. In addition, the resistive transmission line serves as a low-pass filter in the detection process. In this paper, the effect of the resistive transmission line on the operation of the miniature field probe is analyzed. Specifically, the reception of the incident signal by the transmission line is compared with that of the dipole. The scattering of the incident signal by the transmission line is studied by means of the scattering cross section, and the limitation imposed on the measurement of amplitude-modulated signals by the low-pass filtering by the resistive line is examined. The results of the theoretical analyses are presented as simple formulas which are useful in the design and optimization of the probe. The theoretical results are shown to be in good agreement with measurements.     

Experimental and Theoretical Studies on Electromagnetic Fields Induced Inside Finite Biological Bodies

The total electric field inside some simulated biological bodies induced by an electromagnetic wave has been quantified by the recently developed tensor integral equation method and measured by an insulated probe. In general, the induced electric field inside a biological body was found to be quite complicated. An excellent agreement was obtained between theory and experiment.     

蓝色电子墨水微胶囊的制备及其电场响应行为

利用脲甲醛树脂为壁材制备了以酞菁蓝BGS(β-CuPc)颗粒分散在四氯乙烯(TCE)中的悬浮液为核材料的蓝色电子墨水微胶囊。研究了不同改性剂与表面活性剂对β-CuPc颗粒的改性效果及在TCE中的分散性、TCE／水界面张力及囊内β-CuPc微颗粒在胶囊内表面的吸附的影响。结果表明，用十八胺(ODA)改性的β-CuPc颗粒在TCE中的分散性有很大程度提高，其电泳移动速度是未改性前的20倍；TCE／水间的界面张力越大越有利于微胶囊的形成；在TCE中的油溶性表面活性剂Span-80的浓度不低于0．062mmol／L时，β-CuPc颗粒在胶囊内表面吸附被阻止。在100V／mm的直流电场下．微胶囊囊内TCE中分散的β-CuPc颗粒表现出良好的可逆移动特征。     

基于Matlab的电场有限元数值计算分析

有限元法是对电磁场进行数值求解的重要方法,也是本科电磁场课程的教学内容之一.论文结合本科教材阐述了对电场进行有限元计算时的数学模型和算法原理,介绍了Matlab软件基本的矩阵处理编程方式和电场场域有限元分析的算法框图.进而联系教材中一个电器的电场电位分布计算实例,在Matlab环境下进行有限元计算编程的实现.数值解与解析解的比较结果表明Matlab应用在对电磁场进行有限元计算所具备的合理性与简易性.本文对本科教学中帮助学生理解电磁场的数值计算及其编程实现有一定的参考意义.     

Nonlinear Optical Response of Conjugated Polymer to Electric Field

The organic π-conjugated polymers are of major interest materials for the use in electro-optical and nonlinear optical devices. In this work, for a selected polyacetylene chain, the optical absorption spectra in UV/Vis regime as well as the linear polarizabilitiy and nonlinear hyperpolarizability are calculated by using quantum chemical ab initio and semiempirical methods. The relationship of its optical property to electric field is obtained. Some physical mechanism of electric field effect on molecular optical property is discussed by means of electron distribution and intramolecular charge transfer.     

Imaging Electric Properties of Biological Tissues by RF Field Mapping in MRI

The electric properties (EPs) of biological tissue, i.e., the electric conductivity and permittivity, can provide important information in the diagnosis of various diseases. The EPs also play an important role in specific absorption rate calculation, a major concern in high-field MRI, as well as in nonmedical areas such as wireless telecommunications. The high-field MRI system is accompanied by significant wave propagation effects, and the RF radiation is dependent on the EPs of biological tissue. On the basis of the measurement of the active transverse magnetic component of the applied RF field (known as ${rm B}_{1}$-mapping technique), we propose a dual-excitation algorithm, which uses two sets of measured ${rm B}_{1}$ data to noninvasively reconstruct the EPs of biological tissues. The finite-element method was utilized in 3-D modeling and ${rm B}_{1}$ field calculation. A series of computer simulations were conducted to evaluate the feasibility and performance of the proposed method on a 3-D head model within a TEM coil and a birdcage coil. Using a TEM coil, when noise free, the reconstructed EP distribution of tissues in the brain has relative errors of 12%–28% and correlated coefficients of greater than 0.91. Compared with other ${rm B}_{1}$-mapping-based reconstruction algorithms, our approach provides superior performance without the need for iterative computations. The present simulation results suggest that good reconstruction of EPs from B1 mapping can be achieved.      

渐进圆锥D-dot电场传感器频响分析

基于等效电路建立渐进圆锥D-dot电场传感器的传递函数模型,使用CST仿真分析了端接负载阻值、地平面半径和有效面积对传感器频域响应的影响。给出展宽传感器工作频带时端接负载阻值、地平面半径和有效面积的约束条件,为渐进圆锥D-dot电场传感器的优化设计提供参考。     

ELF Electric Field Coupling to Dielectric Spheroidal Models of Biological Objects

The extremely low frequency (ELF) electric field coupling to dielectric spheroidal models of biological objects is studied. Simple expressions are obtained to determine the internal electric field strength induced inside two nonspherical spheroids; a prolate dielectric spheroid and an oblate dielectric spheroid. Certain numerical results are graphically presented for various geometric shapes of the spheroid. The results show that, unlike the symmetric dielectric sphere, the relative position of the spheroid with respect to the orientation of the impressed electric field is an extremely important parameter which considerably affects the electric field coupling.     

大带宽集成光学电场传感器的频率响应特性分析

采用马赫-曾德尔光波导干涉仪与锥形天线阵列,研制了基于铌酸锂（LiNbO3）结构、可用于电力电场测量的大带宽电场传感器,并通过实验对传感器性能进行了测试。结果表明,该传感器在10kHz～18GHz的大带宽范围内,频响特性波动小于±10dB,最小可测电场强度达到0.4V/m,可测量场强达103V/m的纳秒脉冲电场。     

Simulation of the High-Frequency Response of a Heterogeneous Ground through the Finite Difference Technique

To simulate the propagation of an electromagnetic plane wave in an inhomogeneous ground, the finite difference approach can be used. One of the main problems in using this method is imposing the boundary conditions near the ground surface, especially at high frequency. Indeed, for the E polarization, the upper top of the numerical grid must be sufficiently far away from the air-ground interface in order to neglect the field due to the heterogeneities and the discretization of the atmosphere is necessary. For magneto-telluric modeling, improved boundary conditions have already been proposed. This paper deals with a new condition, valid everywhere in air and which can be applied for E and H polarization. Thus even at high frequency, as for radar applications, only one line is added to the grid discretizing the ground.     

Long-Term Biological Effects of Very Intense 60 Hz Electric Field on Mice

This paper presents the results of long-term exposure of mice to a 240 kV/m, 60 Hz electric field. Both males and females were subjected to this very intense field for over 4500 h before they were sacrificed for tests. The progenies resulting from breeding the various couples were also exposed to the same field. Studies were made to determine the effects of the electric field on drinkdng water consumption, rate of growth, body weight, number of progenies bom and survived, blood count and blood chemistry, protein analysis, and organs histology. In each study, the results were compared with those obtained from the corresponding control group.     

Response of the Internal Electric Field in CdZnTe to Illumination at Multiple Optical Powers

Manipulation of CdZnTe (CZT) crystals using illumination is a useful tool for altering the internal electric field present under normal bias conditions. The interactions with carriers that are trapped at either terminal are visualized by the electric field distribution through polarization. In this report, we demonstrate an ability to selectively manipulate the internal electric field of CZT using multiple-wavelength light illumination at various optical powers. The internal electric field polarization can be controlled using changes in optical power. We also investigate the electric field distributions using multiple optical powers to examine the light response as a function of light penetration depth.     

集成光学M—Z调制器的行波电极电场的有限元分析

报道了一种运用MATLAB语言对集成光学M－Z调制器行波电极的电场进行有限元分析的方法,得到了令人满意的计算结果,程序的运算时间缩短到原来的1／12。     

Comment on "Experimental and Theoretical Studies on Electromagnetic Fields Induced Inside Finite Biological Bodies" (Letters)

The above paper states unequivocally: "When a probe is immersed in a finite biological body to measure the induced electric field, the output of the probe becomes Iocation dependent, especially at the edge of the body." This statement is only true for an electrically large dipole antenna with a relatively low impedance detector as a load. We have developed a set of probe design criteria for implantable electric field probes. These criteria have been applied to produce a miniature isotropic probe which is neither location dependent nor calibration dependent with respect to the dielectric properties of the surrounding media. This calibration independence is analyzed as a function of dipole insulation thickness by Smith.     

求解时域电场积分方程的偏置网格有限差分法

细线、薄板状良导体的时域散射特性可由“全切向”时域电场积分方程（TDEFIE）描述。本文采用偏置网格的有限差分方法数值求解“全切向”TDEFIE。这种网格充分利用物体的几何、物理特性,数值实现简便。利用这种方法,本文研究了电磁辐射、散射的三个经典问题,同时分析了方法本身的数值稳定性。数值结果表明,该方法求解时域电场积分方程有效。     

Estimation of Complex Permittivities of Three-Dimensional Inhomogeneous Biological Bodies

Complex permittivities are estimated for a 36-cell model which represents the chest portion of the block model of man by using moment-method formulation of the electric field integral equation. The errors in the calculated complex permittivities are lower with saline/water the surrounding medium, as compared to air, presumably on account of better matching of energy to the biological body. It has been shown that the rest of the human body has little effect on the estimation of complex permittivities because of the near-field natore of the illuminating sonrces. small number of buried cells can be handled for solving the inverse problem, but the problem becomes ill-posed and unsolvable for a larger number of buried cells.     

在外电场作用下有限抛物量子阱中类氢杂质态结合能

采用变分方法研究GaAs/AlxGa1-xAs有限抛物量子阱中类氢杂质态能量和结合能随外电场和阱宽的变化关系.在计算中考虑了电子有效带质量和介电常数随空间坐标(或合金组分)的变化因素.结果表明,外电场对类氢杂质态能量和结合能均有明显的影响,并且这些影响随着阱宽的增大而增大.电子有效带质量和介电常数随空间坐标的变化效应使得类氢杂质态基态能量减小,结合能增大,此效应随着阱宽的增大明显变小.     

On the Electric Field Lines of the Dominant Mode in Millimetric V-Groove Guide by Finite Element Method

In this paper, the electric field lines of the dominant mode in a closed V-groove guide as well as an open one are analysed by finite element method. The results show that the electric field lines are not parallel to the parallel plate region, but perpendicular to them. Since the attenuation increase with increasing frequency when the electric field lines are perpendicular to the mental walls, the V-groove is not suitable to be used in millimeter and submillimeter wavebands, and it is can't be regarded as low-loss wave guiding structures.