Electric Fleld Research Articles

Transient Scattering from Arbitrarily Shaped Two-Dimensional Objects Located on a Rough Surface

An electric fleld time-domain integral equation (TDIE) for arbitrarily two-dimensional bodies located on a time-evolving rough surface is presented. The explicit solution technique of the TDIE is considered, and the time responses of the current distributions and the far-zone fleld are investigated in detail, meanwhile, the method of moment associated with the inverse discrete Fourier transformation (MoM-IDFT) scheme is also introduced to depict the accuracy of the presented technique for the transient scattering by arbitrarily objects integrated with a rough surface. DOI: 10.2529/PIERS061007020935 Time-domain integral equation (TDIE) techniques possess a number of advantages when used to analyze wideband or nonlinear or time-varying electromagnetic scattering and radiation phenomena (1,2,4{6). During the past decade, many difierent TDIE approaches have been proposed to model transient scattering by conducting or dielectric bodies, but only few scheme is presented to solve problems of electromagnetic scattering by an object located on a rough surface. Actually, most of previous studies on such a complicated scattering problem have considered the scattering from a target on a single rough surface realization as a function of the aspect angle in term with Monte Carlo methods, or have considered the scattering from target over a rough surface use a four-path model based on the coherent re∞ection coe-cient of the rough surface (3). It is hard, however, to handle the time-dependence of the scattering by an object located on a realistic time-evolving rough surface (such as a sea surface) in those models. In this paper, the numerical models of transient scattering from one-dimensional (1-D) rough surface and the surface with arbitrarily two-dimensional (2-D) PEC bodies are analyzed. A novel explicit algorithm for the calculations of transient far-flelds using TDIE is presented and the numerical results are also compared with MoM-IDFT, to prove the better efiectiveness and accuracy of this technique for transient scattering from complex rough surfaces associated with the targets. n x 1 n x � kth segment () n f x

Analytical Solutions to the Applicators for Microwave Textile Drying by Means of Zigzag Method

This paper described the Zigzag method for solving microwave applicators for drying of textile materials, which is based on the solving transfer characteristics of waveguide with discontinuities. We can describe the wet textile as discontinuity by means of three quantities: the size of re∞ection coe-cient j‰j, its phase angle ' and phase angleof transmission coe-cient ?. The size of the transmission coe-cient is deflned by known relation ?? ⁄ = 1 i j‰j 2 which results from the principle of conservation of energy. We created diagram of EM waves inside this structure and reached the resulting expression, which is used for calculation of electric fleld strength in the plane of drying textile. This quantity depends on electrical characteristics of wet textile such as permittivity and loss factor. Measurements of these dielectric properties for the coburg is complicated and this method makes it possible to solve our problem with dielectric parameters. We can also describe the absorbed power in the textile in dependence on the dielectric properties.

A Fast Volume-surface Integral Equation Solver for Scattering Properties of NIMs

This paper presents a fast hybrid volume-surface integral equation approach for the computation of electromagnetic scattering from composed negative index media (NIM) such as split-ring-resonators (SRR) with wires. The volume electric fleld integral equation (EFIE) is applied to the dielectric region of this NIM, and the surface electric fleld integral equation is applied on the conducting surface. The method of moments (MoM) is used to discretize the integral equation into a matrix solution and adaptive integral method (AIM) is employed to reduce the memory requirement and CPU time for the matrix solution. The present approach is su-ciently versatile in handling scattering problems of composed NIMs, due to the combination of surface and volume electric fleld integral equations. Numerical results of calculating radar cross section (RCS) of such a NIM slab are flnally presented to demonstrate the accuracy and e-ciency of this technique. DOI: 10.2529/PIERS061003050010

Asymmetrically Shaped Pseudomorphic Modulation Doped Structure for Microwave Detection

In this paper we propose a microwave detector based on a AlGaAs/ InGaAs/GaAs structure. Its operation relies on non-uniform carrier heating of the two-dimensional electron gas in the microwave electric flelds which is a result of the asymmetric shape of the device fabricated on the base of pseudomorphic modulation doped AlGaAs/InGaAs/GaAs structure. The voltage sensitivity of the device at nitrogen temperature is 38 V/W for 10 GHz radiations and is higher compared to that of modulation doped AlGaAs/GaAs of the same conflguration.

Modeling of plasma fibers with radiative processes

A fully three dimensional Particle in Cell model of the plasma flber had been developed. The code is written in FORTRAN 95, implementation CVF (Compaq Visual Fortran) under Microsoft Visual Studio user interface. Five particle solvers and two fleld solvers are included in the model. The solvers have relativistic and non{relativistic variants. The model can deal both with periodical and non{periodical boundary conditions. Plasma flber and its surroundings are generated during the initiation process. Many parameters of the flber, such as temperatures of electrons and ions, electric and magnetic flelds, perturbations in the shape of the flber and of the charged particle positions can be in∞uenced by the input dialog. The PIC program package simulates the behavior of the flber, namely the evolution of the magnetic fleld structures and turbulences. The numerical solution of the particle motion and calculation of the electric and magnetic flelds is the core of the program package. There are many additional routines and collaborating program packages for computer diagnostics, graphical output and other calculations such as radiation, collisions with neutrals, etc. The mechanism of the surface turbulences generation in the plasma flber was successfully simulated with the PIC program package. One of the latest goals of the PIC package was clariflcation of the onset of turbulence structures on the plasma flbers surfaces. It was shown that the development of these structures can be caused by initial a radial perturbation of plasma concentration and charge density. The surface structures simulated by PIC package were observed experimentally in various z{pinch apparatuses.

Structure of the plasma jet of a pulsed microwave plasma torch of nozzle type

The structure of a microwave torch plasma jet was investigated by taking pictures of the jet with a digital camera and processing them next with the aid of software for astronomical imaging and data visualization. The commonly accepted idea of the structure of such a plasma jet is that the jet consists of two regions: a core and an envelope around it. It can be assumed that the core is that region where the microwave power dissipation occurs. Its extent depends on the intensity and geometry of the electric fleld, which is concentrated close to the nozzle tip. The remaining region of the jet is fllled with recombining (afterglow) plasma, not held in position by the electric fleld, and forming an envelope around the core. The results reported here helped to clarify that picture. The plasma jet was produced in argon at atmospheric pressure by a pulsed 2.45 GHz microwave fleld applicator of nozzle type. The gas ∞ow rate was equal to 3 l/min and the maximum peak power amounted to 1000 W. Photographs taken with short exposure times showed that for a turbulent jet the core, rather than being immersed in the envelope, is surrounded by erratically wandering tongues of excited gas leaving the core region. Thus, the regular envelope does actually not exist as such, but is observed in long-exposure photographs or by the naked eye as a superposition of images of the excited gas tongues. The electron concentration in the core of the microwave torch plasma jet was estimated based on the core radius. The value obtained, 4£10 21 m i3 , has the correct order of magnitude for the discharge under consideration.

Development of the Pulsed Direct Current Iontophoresis and Its Clinical Application

The skin is a primary area of body contact with the environment and is the route by which many chemicals enter the body. The delivery of drugs into and through the skin has been an important area of research for many years. Iontophoresis can be deflned as the process of increasing the rate of penetration of ions into or through a tissue by the application of an external electric fleld across the tissue. Impedance spectroscopy was used to investigate the electrical response of skin to difierent ions, applied currents and flelds. The stratum corneum shows two important electrical features. First, it tends to become polarized as an electrical fleld is applied continuously. Second, its impedance changes with the frequency of the applied electrical fleld. To avoid the counterproductive polarization, the current should be applied in a periodic manner, which is called pulsed direct current. The pulsed direct current generating iontophoretic delivery system was developed. In the state of on, charged molecules are delivered by the iontophoretic difiusion process into the skin. A non-parenteral method for the delivery of macromolecules was developed by using a pulse direct current mode iontophoretic technique.

Design, Numerical Analysis and Test of HF Absorber

The paper presents numerical analysis of the microwave absorber design. It is possible to use modifled concept of the absorber. There were used novel numerical methods (flnite element method (FEM)) for thin layers modelling with sandwich non-isotropic electromagnetic materials. Modifled absorber has appropriate properties and it is possible to use it in non- re∞ecting chamber construction. The non-re∞ecting chamber will be used for open space testing of relativistic microwave pulse generator; Pmax = 500MW, tp = 10i100ns. An experimental testing of the proposed pyramidal absorbers was done in the laboratories at University of Defence Brno, Czech Republic. DOI: 10.2529/PIERS060901094301 Figure 2: The shielded laboratory. The calorimetric sensor has disc design. The carbon with changed crystal lattice is used as one of the thin layers. Combined calorimetric sensors was designed for microwave vircator with output power Pmax = 500MW, length of pulse tp 2 ns. Usually, two types of the absorber materials (non-re∞ecting) are used. The polyurethane foam impregnated by graphite is used in high frequency range (more than 1GHz) | the foam employs heat losses in material. The ferrite absorber is used in low frequency range | the ferrite absorber employs magnetic losses. The mentioned materials are used to prevent re∞ection of the electromag- netic waves inside the laboratory. The idea is to rebuild the laboratory in Fig. 2 to the shielded non-re∞ecting chamber for measurements and experiments with power microwave pulse generators iPmax = 500MW, length of pulse tp 2 ns. 2. SHIELDING OF THE WALLS It is possible to deflne an electromagnetic shielding by help of shielding coe-cient ?. It represents the ratio of the electrical fleld Et (magnetic fleld Ht) in the given place of the chamber to the electrical fleld Ei (magnetic fleld Hi) incoming at the absorber. ? = Et

Influence of Electro-optic Effect on Wave-guide Efficiency of Optical Fiber with Cladding Made of Uniaxial Crystal Materials

In∞uence of electric fleld running along the flber on the wave-guide e-ciency of the flber with cladding made of uniaxial anisotropic and electro-optic crystal material whose optical axis is parallel to the axis of flber was investigated. The calculated results indicate that the electric fleld has a strong impact on power distribution of this kind of flber, and more optical energy was transmitted by the cladding with it increasing. These studies provide an important basis for designing new voltage sensors and studying some characteristics of electro-optic crystal.

Numerical Model of Optimization of the Lead-acid Accumulator Grids

This article deals with chemical processes during charging and discharging of the lead-acid accumulator. There is presented one shape of electrode grids in this work, but we researched more variants. We prepared numerical models based on the combined flnite element method (FEM) and flnite volume method (FVM) of those variants and computed current density distribution on the surface of electrodes. The model joins magnetic, electric and current flelds, ∞ow fleld and chemical nonlinear ion model. Results were obtained by means of the FEM/FVM as a main application in ANSYS software.

Transverse strain of silicone dielectric elastomer actuators

Some dielectric elastomers produce large electric-field-induced strains that can be used for electromechanical actuation. When an electric field E is applied on an electroactive polymer film electroded on both sides, the film is subjected to a stress T due to the electrostatic force (Maxwell stress) and this causes it to deform, producing a strain in the plane perpendicular to the applied field. We have measured the transverse strain responses of silicone (Dow Corning HS III) Maxwell stress actuator samples of different sizes over a wide displacement range and a frequency range from DC up to 100 Hz. The static and dynamic strain responses of the materials to a variety of driving electric flelds such as step fields, AC fields and DC bias fields have been measured as functions of amplitude and frequency. The effect of a mechanical tensile pre-load on the transverse strain has also been investigated. A pre-load initially causes an increase in the strain but the strain decreases when larger values of pre-load are applied. Numerical finite element simulations of the material using the commercial software package ANSYS and suitable models of hyperelasticity provide good agreement with most of our observations on the electric field and pre-load dependencies of the transverse strain.

Modeling the Response of a Seafloor Antenna in the Limits of Low Frequency and Shallow Water

In this paper we describe a novel FDFD (flnite-difierence frequency-domain) method for computing the 2-D earth response of a 3-D subsea horizontal electric dipole (HED) source. It represents scattered fleld solutions to Maxwell's equations and uses a 1-D three-layer analytical solution for the primary fleld calculations. Comparison with the 1-D industry type of program CSEM1D gave accurate flts. DOI: 10.2529/PIERS060821043723 The basis of the Sea Bed Logging (SBL) approach is the use of a mobile horizontal electric dipole (HED) source and an array of sea∞oor electric fleld receivers (3). The transmitting dipole emits a low frequency electromagnetic signal (fundamental frequency typically ranging from 0.25 to 2Hz) that difiuses outwards, and the method relies on the large resistivity contrast between hydrocarbon- saturated reservoirs and the surrounding sedimentary layers. The generated electromagnetic sound- ings can in general be divided into three main contributions: direct EM fleld, guided modes (associ- ated with high-resistivity zones like hydrocarbons) and air waves (cf. Fig. 2(a)). In case of shallow water depths (e.g., 200meters or less) the presence of strong airwaves will mask the subsurface signals. In order to develop improved data processing schemes for such cases, modeling tools are needed that can provide controlled test data. In addition, modeling is important when planning new SBL surveys and also when carrying out feasibility analysis of possible new prospects. Since electromagnetic modeling based on time-domain methods give prohibitive large computation times in case of an air layer we concentrate on frequency-domain (methods). Several EM-modeling pro- grams have been developed (1,5,7)). However, none of these codes have neither been tailored to the SBL-case nor been documented to work accurately for the case of a low frequency operating sea∞oor antenna deployed in shallow water.

Nodal Domains in Chaotic Microwave Rough Billiards with and without Ray-Splitting Properties

We study experimentally nodal domains of wave functions (electric fleld distributions) lying in the regime of Breit{Wigner ergodicity in the chaotic microwave half-circular ray-splitting rough billiard. Using the rough billiard without ray-splitting properties we also study the wave functions lying in the regime of Shnirelman ergodicity. The wave functions “N of the ray-splitting billiard were measured up to the level number N = 204. In the case of the rough billiard without ray-splitting properties, the wave functions were measured up to N = 435. We show that in the regime of Breit{Wigner ergodicity most of wave functions are delocalized in the n, l basis. In the regime of Shnirelman ergodicity wave functions are homogeneously distributed over the whole energy surface. For such wave functions, lying both in the regimes of Breit{Wigner and Shnirelman ergodicity, the dependence of the number of nodal domains @N on the level number N was found. We show that in the regimes of Breit{Wigner and Shnirelman ergodicity least squares flts of the experimental data reveal the numbers of nodal domains that in the asymptotic limit N ! 1 coincide within the error limits with the theoretical prediction @N=N ’ 0:062. Finally, we demonstrate that the signed area distribution §A can be used as a useful criterion of quantum chaos.

Temporal Evolution of Multi-Carrier Complexes in Single GaN/AlGaN Quantum Dots

Microphotoluminescence of low-density GaN/AlxGa1ixN quantum dots grown by metal-organic vapor phase epitaxy using in situ etching of AlGaN is presented. The narrow lines in the microphotoluminescence spectra due to the single quantum dots are observed. Both energy and intensity of these lines show temporal ∞uctuations. Statistical analysis based on the correlation matrix allowed us to identify objects, which are afiected by photo-induced electric fleld ∞uctuations. Relations between emission lines participating in the spectrum are discussed.

The electrostrictive effect on wave propagation in isotropic solids subjected to initial fields

THE ELECTROSTRICTIVE EFFECT ON WAVE PROPAGATION IN ISOTROPIC SOLIDSSUBJECTED TO INITIAL FIELDSO. Simionescu-PanaitDepartment of Mechanics, Bucharest University, Str. Academiei 14, 70109 Bucharest 1, Romania.IntroductionIn the last years many authors have paid attention to the dynamics of electroelastic materials,which are subjected to initial mechanical and electric flelds (see [1-4], [7-10]). The basic equationsof piezoelectric bodies for inflnitesimal deformations and flelds superposed on the initial deforma-tions and electric flelds, were given by Eringen and Maugin in their monograph [4]. An alternatederivation of the equations of this type was obtained by Baesu et al. [1]. Using the equationsderived by Baesu et al. [1], we assume that the elastic dielectric is linear and homogeneous, theinitial homogeneous deformations are inflnitesimal, and that the initial applied electric fleld is ofsmall intensity. In this case the constitutive equations, describing the incremental behaviour ofthe material, are expressed by linear relations containing coe–cients which depend on the materialconstants and on the initial applied flelds.In the papers [7-9] we have obtained the conditions when the progressive waves can propagate inpiezoelectric crystals of 6-mm type. There, we derived the wave velocities and the polarizationdirections, as closed form solutions. Also, we deflned new coupling coe–cients, and we showedwhat in°uence have the initial flelds on the shape of slowness surfaces. We analyzed there, thecharacteristics of the obtained waves, and the physical limits of the approximations made.In this paper we study the electrostrictive efiect on the progressive wave propagation in an isotropicsolid subjected to initial mechanical and electric flelds. In this case, even the piezoelectric efiect is,obviously, absent, we flnd that the initial flelds in°uence signiflcantly the

Behavior of Sooting Diffusion Flames under Electric Flelds with Ionic Winds.

This paper reports the effects of applying methods of electric field on a sooting diffusion flame. Essentially, two types of electric fields were tested in this experiment. One is a uniform electric field formed between parallel plate electrodes. The other is a non-uniform field formed between needle and plate electrodes. In the uniform field, the flame shape was changed by positive ions moving in the fields. Soot emission was suppressed with increasing the applied voltage, because an increase of the flame surface temperature promoted the soot oxidation. In the non-uniform field, on the contrary, ionic wind was formed by corona discharge. The ionic wind blew from a needle electrode toward a plate electrode, irrespectively of the polarity of the needle. The flame was inclined toward the plate electrode by this ionic wind. As the result, the surrounding air was entrained in the flame, and the suface temperature of flame also increased with increasing applied voltage. The soot suppression efficiency of the non-uniform electric field was higher than that of the uniform one.

Theory of Enhanced Reversed Shear Mode in Tokamaks

It is shown that toroidal magnetic fleld ripple induced particle ∞ux can drive poloidal E£B speed to bifurcate over the local maximum of the nonlinear poloidal (or parallel) viscosity. Here,E is the electric fleld andB is the magnetic fleld. This mechansim, together with the turbulence suppression due to the radial gradient of the E£B and diamagnetic angular velocity, is employed to explain enhanced reversed shear mode observed in the core region of tokamaks.

On the Mesoscopic Gate

The problem of artificial neural network constuction is now widely discussed. The first step to the creation of neurocomputer is a constuction of the corresponding elements (transistor, trigger, etc.) of nanoscale [1-3]. The physical systems, where the electron phase coherence is preserved at a scale much larger than the atomic dimensions, are often referred to as mesoscopic systems. The problem of electron transmission through a mesoscopic device may be reduced, usually, to the investigation of wave propagation in a wave guide. This approach has allowed one to describe some phenomena in nanoelectronic systems [3-9]. The aim of this paper is to suggest a possible construction of a mesoscopic gate. Namely, we shall consider the process of opening of a quantum wave guide under the action of an external transversal electric fleld due to the shift of eigenvalues. This effect may be used for a construction of the nanoelectronisc device having two states: current exists — current is equal to zero in accordance with a situation whether the quantum wave guide is open or closed.

Studies of a conductivity mechanism of β-rhombohedral boron in a strong electric field

The dependence of electric conductivity of pure BETA -rhombohedral boron on temperature and electric fleld intensity is presented. Results are discussed using three models: (I) the Poole-- Frenkel model for an isolated trapping center and for a screened Coulomb center, (II) the hopping models of Mott and Shklovskii, and (In) the small polaron model. Results of electric fleld measurements may be satisfactorily interpreted in both the screened Poole-- Frenkel and the hopping model giving for the dependence of the conductivity sigma on the electric field intensity E the relations ( sigma / sigma /sub 0/)/ sup 1/2/ ln ( sigma / sigma /sub 0/) ~ E and ln ( sigma / sigma /sub 0/) ~ E/sup 1/4/, respectively ( sigma /sub 0/ is the conductivi ty in zero field). The model III alone gives an unreasonable result for the hopping length but nevertheless the essentiality of polaronic effect for BETA -boron seems sufficient from both the expenimental and the theoretical point of view. lt is supposed that the very complex crystal lattice of BETA -rhombohedral boron has a mixed conductivity of a polaron-- Mott type. The magnetoconductivity of boron in the hopping region is also discussed. (auth)

Polarization of RaE Electrons

BS>The longitudinal polarization for RaE has been measured by Mott scattering after deflection through an electric fleld. The results for the degree of longitudinal polarization of RaE electrons are P/(-v/c) = 0.69 plus or minus 0.04, 0,75 plus or minus 0.04, 0.75 plus or minus 0.04, and 0.66 plus or minus 0.06 for E = 120, 155, 209, and 290 kev. (T.B.A.)