Electric Fleld Research Articles

Electric Field Calculation along the Surface of Composite Insulator Covered with Sand Grains Based on Finite Element Method

This paper aims to discuss the efiect of sand grains covered with composite insulator on the surface electric fleld distribution of insulator in sandstorm condition. Comsol Multiphysics software based on flnite element method, was used for the three-demensional modeling and simulation. Based on the calculation results, the efiects of size, charge quantity, polarity and position of sand grains on electric fleld distribution are discussed. The simulation results show sand grains with difierent sizes have difierent distortion to electric fleld. Electric fleld is severely afiected by charge quantity, polarity and position of sand grains. This study provides theoretical reference for the research of insulator ∞ashover mechanism under the dust environment.

レオロジー特性測定法とその装置

In this paper I will at first explain general method of rheology measurement, such as steady flow, strain dispersion,frequency dispersion, temperature dispersion. Next I will explain the LAOS method using a Fourier transform, and the two step flow measurement made possible by stress rheometer. At last I will explain measurement methods of the other principles, such as spring relaxation method, free dumping method, the tuning fork type viscometer, thin wire heating method, electric fleld tweezer method, and electromagnetic spinning sphere method.

EXPERIMENTAL RESEARCH OF THE ELECTRIC FIELD POTENTIAL OF A ROTATING MAGNETIZED SPHERE

We performed an experiment for the veriflcation of existing theoretical formulas for the electric fleld potential of a rotating magnetized sphere. Measurements of the electric fleld potential difierences across cylindrical capacitors were carried out. Experimental results are essentially in accord with the potential obtained using the special relativity transformations and contradict formula for the quadrupole fleld potential. Below, in a brief review, the theoretical formulas for the electric potential and electric fleld intensity of a rotating magnetized sphere are given, and some experimental results are discussed. It is known that a homogeneously magnetized sphere rotating around the axis parallel to the magnetic moment of the sphere is the source of the potential electric fleld (1). There exist difierent calculation methods for the electric fleld potential ' of the rotating magnetized sphere. The flrst, the simplest one, supposes that the Lorentz force induces a displacement of free or bond electric charges rotating with a magnet. The Lorentz force is produced by the rotating magnetized body's self-magnetic fleld (2). This method gives the correct value of the unipolar induction e.m.f. acting between the pole and the equator of the sphere and the quadrupole electric fleld. However, in the experiment of Wilson and Wilson (3), the Einstein's formula has been conflrmed. Based on this result we can conclude that the charge polarization of the rotating magnetic insulator is observed only in the external magnetic fleld of a coil that is at rest in the lab frame, and the self-magnetic fleld of a rotating magnetic dielectric does not produce any polarization. In the experiment in (4), we attempted to detect free charges displacement in an aluminum conductor which was mounted on a magnet rotating together with the conductor. The experiment did not detect any displacement of the free electric charges in the conductor under the Lorentz force action. The second method is based on several elements of the special relativity followed by the boundary- value electrostatic problem solving. In this method, the material Minkowski equations (1), the magnetic fleld transformation (2,6) inside the magnetic sphere and the magnetic moment transformation (5,6) are used. In this case, it is implicitly assumed that the special relativity transformations are applicable in the rotating frame of reference. Solutions obtained by this method also give the quadrupole electric fleld potential of the rotating magnetized sphere. In particular, the expression for the scalar potential of the sphere | conductor ( = 1, | permittivity of the sphere), which was obtained using the material Minkowski equations, is (1)

PERFORMANCE OF AN IMPLANTED ELECTRICALLY COUPLED LOOP ANTENNA INSIDE HUMAN BODY

Implanted antennas are widely used in hyperthermia and biomedical applications. The antenna needs to be extremely small while maintaining a permissible Speciflc Absorption Rate (SAR) and being able to cope with the detuning efiects due to the dielectric properties of human body tissues. Most of the proposed antennas for implanted applications are electric fleld antennas such as Planner Inverted-F Antennas (PIFA) and micro-strip patch antennas. By minimizing the size of an electric fleld antenna, the near zone electric fleld will increase, resulting in higher SAR. This work is devoted to design a miniaturized magnetic fleld antenna to overcome the above limitations. The proposed electrically coupled loop antenna (ECLA) has high magnetic fleld and low electric fleld in the near zone and therefore, has a small SAR and is less sensitive to detuning efiects. ECLA is designed at the Medical Implanted Communication Service (MICS) band with dimensions of (5£5£3mm 3 ). ECLA has been simulated inside one-layer human body model, three-layer spherical human head model, human head and human body. From the simulation results, ECLA inside the human body has a 5MHz{3dB bandwidth, i14dB gain, and radiation e-ciency of 0.525%. The 1g average SAR inside the human body for 10mW input power is about 1W/kg which is 7times lower than the SAR for a patch antenna of the same size with the same accepted power.

PARAMETRIC INSTABILITY OF SURFACE ELECTRON CYCLOTRON TM-MODES

Excitation of waves at harmonics of electron cyclotron frequency due to utilization of an external alternating electric fleld is under the consideration. It is proved that they are eigen modes of plasma-dielectric-metal structures in both long (as compared with electron Larmor radius) wavelength range and short wavelength range if an external steady magnetic fleld is oriented perpendicularly to the plasma interface. It is assumed that uniform external electric fleld operates at the frequency, which belongs to the range of electron cyclotron frequencies. The problem is solved theoretically using kinetic Vlasov-Boltzmann equation for description of the plasma particles motion and Maxwell equations for description of TM-polarized fleld of these modes. Non-linear boundary condition for tangential magnetic fleld of these TM-modes is formulated using conception of non-linear surface electric current. Inflnite set of equations for harmonics of their tangential electric fleld is derived due to this condition. This set is solved using approach of the wave packet consisting of the basic harmonic and two nearest satellite harmonics. Simple analytical expression for growth rate of surface electron cyclotron TM- modes' parametric instability is obtained and analyzed numerically.

OPTIMIZING THE BOWTIE NANO-ANTENNA FOR ENHANCED PURCELL FACTOR AND ELECTRIC FIELD

With the development of nano-optic technology, the optical nano-antenna has been widely used in the flelds of novel light sources, high-sensitive biological sensors, nanometer lithography, and nano-optical imaging. The relationship between the structural parameters of the antenna and the Purcell factor is very important for engineering applications. The electric near fleld proflle of the antenna was calculated and analyzed by using the flnite-difierence time-domain (FDTD) method, and the in∞uence of the structural parameters on the Purcell factor and the electric fleld was thoroughly investigated. A careful comparison of bowtie antenna radiation characteristics with difierent structural parameters was carried out. The results show that the thickness, the length and the curvature radius have great efiects on the Purcell factor and the optical antenna's electric near fleld. These flndings are promising for improving the performance of the optical bowtie nano-antenna.

MULTICARRIER MULTIPACTOR ANALYSIS BASED ON BRANCHING LEVY WALK HYPOTHESIS

In this paper, we propose a stochastic approach for the analytical analysis of the multicarrier multipactor discharge occurring in high-power vacuum microwave devices, in which electric flelds are not homogeneously distributed. We indicate that the statistical behavior of large amount of secondary electrons in the process of a multipactor discharge can be well described by the probabilistic random walk and Levy walk theory. Based on the derived probability density of the lateral difiusion of secondary electrons in homogeneous flelds, the multicarrier multipaction in inhomogeneous flelds can be analytically computed with signiflcantly enhanced e-ciency. As a demonstration, the accumulation of secondary electrons of a multicarrier multipaction in a rectangular waveguide supporting TE10 mode is given. The theoretical results comply well with the results achieved by the time-consuming particle simulation, the slope difierence of which is less than 0.8%, while only costs one-order less computational time. To the best of our knowledge, this is the flrst time that the probability density of the lateral difiusion of secondary electrons during a multipaction is theoretically derived. This density depicts the physical picture of the statistical movement of secondary electrons during the process of a multicarrier multipactor, which can be widely used in the areas of high-power electronics and electromagnetism.

STUDY OF EM WAVE ABSORPTION AND SHIELDING CHARACTERISTICS FOR A BONSAI TREE FOR GSM-900 BAND

Electromagnetic (EM) wave absorption characteristics for a Bonsai tree are investigated at GSM-900 band. Finite Difierence in Time Domain (FDTD) method is hybridized with Friis transmission equation to carry out all the required EM simulations. The tree has been modelled using CT scan based 3D dataset considering difierent electrical parameters. Maximum local electric (E) fleld, magnetic (H) fleld, Speciflc Absorption Rate (SAR) and Shielding Efiectiveness (SE) have been calculated for the tree placing at distance of 5m away from a radiating Base Station Antenna (BSA) with 20W input power. The maximum local E fleld, H fleld, 1-g SAR and SE obtained by the simulation are found to be 70.1V/m, 0.09A/m, 0.135W/kg and 13.18dB, respectively. Plants are found to be good natural electromagnetic radiation shield.

DUAL-BAND CIRCULAR POLARIZER AND LINEAR POLARIZATION TRANSFORMER BASED ON TWISTED SPLIT-RING STRUCTURE ASYMMETRIC CHIRAL METAMATERIAL

In this paper, a bi-layer twisted split-ring structure asymmetric chiral metamaterial was proposed, which could achieve circularly polarized (giant circular dichroism efiect) wave with dual bands and linear polarization transformation (giant optical activity) with asymmetric transmission wave emissions simultaneously from linearly polarized incident wave at microwave frequencies. Experiment and simulation calculations are in good agreement, indicating that the dual-band circular polarizer features high conversion e-ciency around 5.32GHz and 6.6GHz in addition to large polarization extinction ratio of more than 16dB, while cross linear polarization transformation with asymmetric transmission is observed around 10.52GHz. The transformation behavior for both circular and linear polarizations could be further illustrated by simulated surface current and electric fleld distributions. The proposed asymmetric chiral metamaterial structure could be useful in designing novel EM or optical devices, as well as polarization control devices.

AN INTEGRAL EQUATION FORMULATION FOR TM SCATTERING BY A CONDUCTING CYLINDER COATED WITH AN INHOMOGENEOUS DIELECTRIC/MAGNETIC MATERIAL

A volume-surface integral equation (VSIE) formulation is developed for determining the electromagnetic TM scattering by a two-dimensional conducting cylinder coated with an inhomogeneous dielectric/magnetic material. The electric fleld integral equations (EFIEs) are utilized to derive the VSIE. The surface EFIE is applied to the conducting surface, while the volume EFIE is applied to the coating region. By employing the surface and equivalence principles, the problem is reduced into a set of coupled integral equations in terms of equivalent electric and magnetic currents radiating into unbounded space. The moment method is used to solve the integral equations. Numerical results for the bistatic radar cross section for difierent structures are presented. The well-known exact series-solution for a conducting circular cylinder coated with multilayers of homogeneous materials is used along with the available published data to validate the results. The in∞uence of using coatings with double-positive (DPS) and/or double-negative (DNG) materials on the radar cross section is investigated.

MIXED FINITE ELEMENT METHOD FOR 2D VECTOR MAXWELL'S EIGENVALUE PROBLEM IN ANISOTROPIC MEDIA

It is well known that the conventional edge element method in solving vector Maxwell's eigenvalue problem will lead to the presence of nonphysical zero eigenvalues. This paper uses the mixed flnite element method to suppress the presence of these nonphysical zero eigenvalues for 2D vector Maxwell's eigenvalue problem in anisotropic media. We introduce a Lagrangian multiplier to deal with the constraint of divergence-free condition. Our method is based on employing the flrst-order edge element basis functions to expand the electric fleld and linear nodal element basis functions to expand the Lagrangian multiplier. Our numerical experiments show that this method can successfully remove all nonphysical zero and nonzero eigenvalues. We verify that when the cavity has a connected perfect electric boundary, then there is no physical zero eigenvalue. Otherwise, the number of physical zero eigenvalues is one less than the number of disconnected perfect electric boundaries.

LARGE-SIGNAL FIELD ANALYSIS OF A LINEAR BEAM TRAVELING WAVE AMPLIFIER FOR A SHEATH-HELIX MODEL OF THE SLOW-WAVE STRUCTURE SUPPORTED BY DIELECTRIC RODS. PART 1: THEORY

A rigorous fleld-theoretic method of analyzing the large-signal behavior of a linear beam traveling wave tube amplifler (TWTA) with slow-wave structure modeled to be a dielectric-loaded sheath helix is presented. The key step in the analysis is a representation of the fleld components as nonlinear functionals of the electron arrival time through a Green's function sequence for the slow-wave circuit. Substitution of this functional representation for the axial electric fleld component into the electron ballistic equation casts the latter into a flxed point format for a nonlinear operator in an appropriate function space. The flxed point, and therefore the solution for the electron-arrival time and hence the solution for the electromagnetic fleld components, can be obtained by standard successive approximation techniques. The calculations of the gain, the e-ciency and the other amplifler parameters, comparison of the results of the present theory with experimental results etc., on the basis of such a successive approximation solution for the fleld components, will be presented in the second part of this paper. Ever since the invention by Rudolf Kompfner in 1943, the linear beam traveling wave tubes making use of an helix for the slow-wave structure (popularly known as helix TWTs), with their wide bandwidths and large power outputs, continue to be unsurpassed as broadband ampliflers of microwave power except possibly by gyro-TWTs. The phenomenal growth of the satellite communication industry and the proliferation of radar applications have fueled an unprecedented demand for TWTs meeting stringent design speciflcations. In high power applications, the traveling wave tube amplifler (TWTA) will invariably be operated on the verge of saturation, and hence an analytical study of its large-signal behavior will be of immense interest. The analysis of TWT as an amplifler has been carried out by Pierce and Kompfner (1{3). This theory was developed some six and half decades ago, and it was based on a coupled-wave analysis utilizing the vacuum modes of the helix and the positive and the negative energy space | charge waves of the beam. An improved theory based on an eigen-vector analysis of Maxwell's equations for the helix has been developed by Reydbeck (4). Chu and Jackson (5) and Collin (6) considered the fleld approach for a small-signal analysis of the helix-TWTA. The linearized 'solution' (6) for the axial electric fleld was obtained as a linear combination of three space charge waves, a growing wave and a decaying wave, both having phase speeds slightly smaller than the beam speed and a constant-amplitude wave with a phase speed greater than the beam speed. However, the input boundary conditions (that the total a.c. beam current density and the r.f. perturbation in the electron speed vanish at the input plane) could exactly be satisfled for a flnite beam only by the trivial solution as the (complex) phase-shift constants associated with the three waves were not equal. Moreover, in the nonlinear regime this approach is completely intractable without the introduction of multitudinous limiting assumptions (7). Freund etal. (8,9) presented a linear fleld analysis for a TWTA using radial admittances at the boundaries. The analyses

A SLIM HORIZONTALLY POLARIZED OMNIDIRECTIONAL ANTENNA BASED ON TURNSTILE SLOT DIPOLE

A novel horizontally polarized (HP) antenna with omnidirectional pattern is presented in this paper. The proposed antenna applies the concept of rotating electric fleld method to conventional slot dipoles. Two CPW-fed slot dipoles are placed in a perpendicularly conjugate form. By properly arranging the magnitude and phase of input signals, the omnidirectional pattern can be synthesized at broadside. A prototype is developed at the 2.6GHz band, which ofiers a horizontally polarized omnidirectional radiation pattern with gain of 2.5{3.4dBi, and the measured antenna e-ciency is greater than 73% through the operating band (2.4{2.8GHz). Furthermore, a 20-dB polarization purity is achieved in this design. The overall volume of the proposed antenna is 22 £ 22 £ 90mm 3 (0.19‚0£0:19‚0£0:78‚0). Distinct from the other proposed HP antennas provided with planar geometry, this antenna is slim in shape, and it can be readily integrated with vertical dipoles to form a polarization diversity system in current wireless router and AP applications.

A DUAL-BAND HIGH GAIN ANTENNA BASED ON SPLIT RING RESONATORS AND CORRUGATED PLATE

In this paper, a dual-band high-gain antenna based on the split ring resonators (SRRs) and corrugated plate is presented. By combining the SRRs and corrugated plate, the presented antenna resonating at difierent frequencies with high performance is easily achieved based on the superposition of the electric flelds radiated by the SRRs and the grooves. Both the simulated and measured results show that the gain is improved by 6dB at 12.7GHz and 6.5dB at 14.2GHz respectively compared with the conventional ∞at antenna without grooves. Moreover, half-power beam width (HPBW) of E-plane is reduced by more than 100 degrees at 12.7GHz and 14.2GHz.

SCATTERING BY A TILTED STRIP BURIED IN A LOSSY HALF-SPACE AT OBLIQUE INCIDENCE

The analysis of the scattering by a tilted perfectly conducting strip buried in a lossy half- space at oblique incidence is formulated as an electric fleld integral equation (EFIE) in the spectral domain and discretized by means of Galerkin's method with Chebyshev polynomials basis functions weighted with the edge behaviour of the surface current density on the strip. In this way, a convergence of exponential type is achieved. Moreover, a new analytical technique is introduced to rapidly evaluate the slowly converging integrals of the scattering matrix coe-cients consisting of algebraic manipulations and a suitable integration procedure in the complex plane.

COMPLEX RESONANCES OF A RECTANGULAR PATCH IN A MULTILAYERED MEDIUM: A NEW ACCURATE AND EFFICIENT ANALYTICAL TECHNIQUE

A new analytical technique to study the complex resonances of a rectangular patch in a multilayered medium is introduced. The problem is formulated as an electric fleld integral equation (EFIE) in the spectral domain and discretized by means of products of Chebyshev polynomials of flrst and second kind multiplied by their orthogonal weights in a Galerkin's scheme. The method is fast convergent, i.e., few expansion functions are needed to achieve accurate results, but leads to the numerical evaluation of inflnite double integrals of oscillating and slowly decaying functions. To overcome this problem, suitable half-space contributions are pulled out of the kernels of such integrals in order to obtain exponentially decaying integrands. Moreover, the slowly converging integrals of the extracted contributions are expressed as combinations of quickly converging integrals by means of algebraic manipulations and an appropriate integration procedure in the complex plane.

ABSORPTION COEFFICIENT IN A MQW INTERSUBBAND PHOTODETECTOR WITH NON-UNIFORM DOPING DENSITY & LAYER DISTRIBUTION

Selective wavelength tuning of multiple quantum well based infrared photodetector is achieved by non-uniform doping distribution as well as dimensional variation in the structure. Result is obtained from the computation of the intersubband transition energy through self-consistent solution of the Poisson's and Schrodinger equations with appropriate boundary conditions. Absorption coe-cient is estimated in presence of external electric fleld applied along the direction of conflnement. Suitable choice of structural parameters is required to tailor the peak position of absorption spectra for application in the infrared range as optical receiver.

STUDY OF WHISTLER MODE WAVE BY INJECTION OF RELATIVISTIC HOT ELECTRONS BEAM IN THE MAGNETOSPHERE OF URANUS

In present paper, the efiect of relativistic hot electron beam for fleld aligned Whistler mode waves has been studied theoretically in the presence of AC electric fleld perpendicular to magnetic fleld. Studies have been performed using perturbative approach along with the method of characteristic solutions and are valid for comparatively small ambient magnetic fleld of Uranus, of the order of nano Tesla, as observed by Voyager 2. The detailed derivation and calculations has been done for dispersion relation and growth rate for magnetosphere of Uranus. Analyses are done by changing various plasma parameters which are explained in result and discussions section of this paper. Extensive study of wave- particle interactions and numerical calculations concludes that in case of injection of a distribution of particles having a positive slope in v?, temperature anisotropy remains the main source of free energy. It is seen that other efiective parameters for the growth of whistler mode waves are AC frequency and higher number density of hot electrons. We also learn that even the minimal presence of such energetic particles having a positive slope of distribution function and increasing power of perpendicular thermal velocity can increase the growth rate signiflcantly in the magnetosphere of Uranus. The present work is basically based upon the theoretical investigation and mathematical analysis of the magnetosphere of Uranus, supported by satellite data.

GEOMETRICAL AND PHYSICAL PARAMETERS AFFECTING DISTANT ELECTRIC FIELDS RADIATED BY LIGHTNING RETURN STROKES.

In this paper detailed numerical results are presented for the estimation of the electric fleld generated by the flrst return stroke, in order to reproduce the main characteristics of fleld waveforms measured at distances beyond 50km. The efiect of parameters such as the lightning channel geometry, distance from the source, return-stroke current speed, its attenuation along the channel is discussed by comparing numerical and experimental results.

FIELD MEASUREMENTS WITHIN A LARGE RESONANT CAVITY BASED ON THE PERTURBATION THEORY

Due to the sensitivity of the fleld distribution within a resonant cavity to the presence of an object, conventional measurement techniques employing a probe sufier from a limited accuracy. Therefore we propose a new measurement technique of the electric fleld distribution that avoids the use of a probe. Based on the perturbation theory, it consists of a measure of the cavity resonant frequency variation while displacing a small perturbing object within the cavity. The choice of the perturbing object shape, dimension and material is discussed with the help of simulation and measurement results in a canonical case. The case of reverberation chamber equipped with a mode stirrer is also considered, as well as the insertion of a metallic box within the cavity. Our measurement setup is very low-cost, simple to set up and to use, and adapted to any cavity geometry.