Electric field meter with dipole antenna in an alternating nonuniform electric field

Translated from Izmeritel'naya Tekhnika, No. 11, pp. 55–59, November, 1992.     

Electric field meter with a dipole antenna in an elliptically polarized electric field

A model of an electric field meter with a dipole antenna is analyzed. The model takes into account the fact that the meter incorporates other elements with a conducting surface in addition to the dipole antenna, viz.: a matching device, a signal cable, and a voltmeter. Alternative forms of the measurement equation are obtained, which differ in the error associated with the currents induced by the measured electric field on the braid of the signal cable and on the casing of the voltmeter. It is shown that this error can be eliminated partially or completely by performing additional measurements with the dipole antenna in different positions.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 45–48, February, 1994.     

Evanescent plane waves and the far field: Resolution of a controversy

Abstract

We show that the evanescent part of the plane wave representation of the free-space dyadic Green function contributes to the far field only along a distinguished axis. The claim of contribution of evanescence in all directions is incorrect as it arises from a flawed procedure, but a limited version of that claim may have merit.     

Photorefractive surface waves in sillenite crystals in an alternating-sign electric field

A theoretical model is proposed for photorefractive TE surface waves in a sillenite crystal located in an alternating-sign electric field Pis’ma Zh. Tekh. Fiz. 23, 48–53 (March 26, 1997)     

Comment on the paper: Evanescent waves do contribute to the far field

Abstract

In a series of papers [1], it has been claimed that evanescent waves contribute to the far field of a radiating dipole, i.e. that the amplitude of the sum of the evanescent waves decreases as 1/r with increasing distance, r, from the dipole. In spite of the fact that three recent papers [2] have demonstrated that these claims are incorrect and that they contradict well-established results relating to the farzone behavior of the angular spectrum representation of wavefields [3], the author continues to repeat this claim, most recently in a note with the title ‘Evanescent waves do contribute to the field’. It is the purpose of this note to point out an error in the previous publications [1] which has led to this erroneous conclusion.     

Nonlinear magnetic field calculation using dipole approximation

A program for calculating static magnetic fields using an integral method for the iron contribution to the field is presented. To calculate the magnetic coefficients one essentially uses a simple dipole approximation. The developed formalism is applied to compute the magnetic field of toroidally shaped iron geometries. Using this formalism a program tractable on microcomputers was written with a discretization of the iron in up to 1600 elements. The results agree well with those obtained with the program TOSCA     

Design of an electrodynamic model of a variable electric field meter with dipole antenna

Translated from Izmeritel'naya Tekhnika, No. 6, pp. 45–48, June, 1992.     

Evanescent magnetic field effects on entropy generation at the onset of natural convection

This paper numerically investigates the effect of an externally evanescent magnetic field on total entropy generation in a fluid enclosed in a square cavity by using a control volume finite element method to solve the conservation equations at Prandtl number of 0·71. The values of relaxation time of the magnetic field are chosen, so that the Lorentz force acts only in the transient state of entropy generation in natural convection. The total entropy generation was calculated for, fixed value of irreversibility distribution ratio, different relaxation time varying from 0 to 1/5 and Grashof number varying from 10⁴ to 10⁵. The effects of the Hartman number and the magnetic field inclination angle on the evolution of total entropy generation throughout the transient regime were investigated. Results show that the application of evanescent magnetic field not only suppresses the fluctuation of the total entropy generation in the transient state, but also reduces the gap for magnetic field relaxation time less than 1/10.     

Conductance of carbon nanotubes in a transverse electric field and an arbitrary magnetic field

The electronic and transport properties of carbon nanotubes subject to the influences of a transverse electric field and an arbitrary magnetic field are studied by the tight-binding model. The external fields would modify the energy dispersions, destroy the state degeneracy, change the symmetry characteristics, alter the energy gap, modulate the electron effective mass, and create extra band-edge states. The energy gap and the electron effective mass exhibit a rich dependence on the field strength, the magnetic field direction, and the types of carbon nanotubes. A semiconductor-metal transition would be allowed for certain field strengths and magnetic field directions. The variations of energy dispersions with the external fields will also be reflected in the conductance. Special features of the conductance, such as single-shoulder, multi-shoulder, and spike structures, are predicted.     

Electric field meter with a dipole antenna in a nonuniform alternating electric field

Translated from Izmeritel'naya Tekhnika, No. 12, pp. 44–47, December, 1992.     

Specific features of electric discharge-gas flow interaction in an external magnetic field

Ensuring stable and effective mixing and burning of gaseous fuel and oxidant in a supersonic flow within a chamber of appropriate dimensions is an important task in the creation of high-rate flow combustion systems. A promising means of intensive mixing of cocurrent jets is offered by the magnetohydrodynamic (MHD) method [1], which is based on the initiation of pulsed electric discharge in the gas flow and the interaction of this discharge with an external magnetic field for the development of vorticity. Specific features of threedimensional (3D) evolution of the discharge under such conditions have been studied using quasi-3D modeling, which is, in addition to 2D modeling and physical experiments, an affective tool for investigation of the electric discharge-gas flow interaction in the applied magnetic field.     

Numerical simulation of the screw shape of an electric arc in an external axial magnetic field

The characteristics of an electric arc of a direct current, burning in a cylindrical channel in a uniform external axial field, are numerically computed within a nonstationary three-dimensional mathematical model at partial local thermodynamic equilibrium. A method for the numeric modeling of the screw shape of an arc in this field is suggested. This approach is in addition to the “network” analogue of fluctuations for the temperature of electrons, which increases weak numeric asymmetry of electron temperature distribution that occurs randomly during computation. This asymmetry can be “picked up” by an external magnetic field and continue to increase up to a certain value, which is enough to form an arc column screw structure. If there are no fluctuations in the computation algorithm of fluctuations, the arc column in an external axial magnetic field maintains cylindrical axial symmetry and the arc screw shape is not observed.     

Heat transfer mechanism in an electric arc moving through a magnetic field

A model of an electric arc moving through a magnetic field is analyzed. Numerical estimates and universal characteristics indicate that the basic mechanism of heat removal from the arc column is the transmission of energy by the gas stream flowing inside the arc.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 4, pp. 673–680, October, 1972.     

Piezoelectric components wirelessly driven by dipole antenna-like electric field generator

A new technique of transmitting electric energy wirelessly to piezoelectric components by using a dipole antenna-like electric field generator is explored. Two square size brass plate-shaped live and ground electrodes are used to form a dipole antenna-like electric field generator. When the dipole antenna-like electric field generator in electric resonance with an inductor, a maximum output power of 2.72 mW and an energy conversion efficiency of 0.0174% have been achieved wirelessly by the piezoelectric plate area of 40 mm² operating in the thickness vibration mode, placed at the center 4 mm away from the antenna plane with an optimum electrical load of 1365 Ω, resonant frequency of 782 kHz, 1 cm electrodes separation, 2500 cm² electrode area of dipole antenna-like structure, and input ac source power of 15.58 W applied to the series of dipole antenna-like structure and inductor. The theoretically calculated results have been validated by the experimental studies. It is seen that at the resonance frequency and optimum electrical load, the output power of the wirelessly driven piezoelectric component decreases with the size of piezoelectric component, distance of piezoelectric component from the electrode of antenna plane, but increases with the antenna electrode area.     

Streamlining of a cylinder with an electric arc rotating in a magnetic field

Streamlining of a circular cylinder with a localized heat source modeling an MHD actuator in which the plasma arc channel moves along the cylinder surface under the action of the Lorentz force in a radial magnetic field is studied experimentally and simulated numerically. It is shown that the presence of a moving heat release region leads to a break in the symmetry in cylinder streamlining by the external flow and the appearance of a nonzero lift force and circulation.     

High uniformity magnetic coil for search of neutron electric dipole moment

We present in this article a prototype magnetic coil that has been developed for a new search for the electric dipole moment of the neutron at the Spallation Neutron Source at Oak Ridge National Laboratory. The gradients of the magnetic field generated by the coil have been optimized to reduce known systematic effects and to yield long polarization lifetimes of the trapped particles sampling the highly uniform magnetic field. Measurements of the field uniformity of this prototype magnetic coil are also presented.     

Analysis of open-flame electric arc in transverse magnetic field

The distribution of temperature and pressure, electromagnetic fields, and the structure of flow under the effect of an external transverse magnetic field are determined using a three-dimensional magnetogasdynamic model of a steady-state curved arc. The calculation results are consistent with the experimentally observed properties of the arc, such as stabilizing effect of current strength and the magnetogasdynamic mechanism of arc extinction.     

Evanescent wave scattering and local electric field enhancement at ellipsoidal silver particles in the vicinity of a glass surface

We report on the numerical analysis of the local electric field enhancement of nanosized silver ellipsoids placed in the evanescent field near a glass surface. Across the visible spectrum the enhancement factor for silver particles varies by more than one order of magnitude because of surface-plasmon resonance. Because of the spatially inhomogeneous excitation, higher-order modes additionally contribute and modify the spectral dependence of the electric field compared with plane-wave excitation. Moving the metal particle toward the glass surface increases the field enhancement and shifts the plasmon resonance, which in addition splits between both ends of the particle. Besides the near-field properties of such a probe we also discuss to what extent these local properties can be measured in the far field.     

Effects of an electric or magnetic field on the radiolytic degradation of two biorefractory contaminants

Effects of an electric or magnetic field on the radiolytic degradation of two biorefractory contaminants, Acid Orange 7 (AO7) and nitrobenzene (NB), were evaluated in this work. A continuous DC electric current with a low density (approximately 2.8-5.6 mA cm(-2)) applied during the radiolytic degradation of AO7 and NB solutions only led to slight enhancement in their degradation rate constants, but altered significantly the degradation mechanisms. On the other hand, application of a magnetic field (0.4 T) in irradiation processes slightly enhanced the degradation kinetics without leading to any change in degradation mechanisms.