ON A CYLINDRICAL ANTENNA IN A HOMOGENEOUS ANISOTROPIC MEDIUM

1966 ◽  
Vol 44 (6) ◽  
pp. 1239-1266 ◽  
Author(s):  
K. Aoki
Keyword(s):  
Anisotropic Medium ◽  
Fourier Transforms ◽  
Resonance Phenomenon ◽  
Dielectric Tensor ◽  
Input Admittance ◽  
Circulating Current ◽  
Cylindrical Antenna ◽  
Antenna Length ◽  
Current Flows ◽  
Homogeneous Anisotropic Medium

The admittance problem of an antenna imbedded in a homogeneous anisotropic medium in which the dielectric tensor is given by the form in eq. (1) is formulated by the theory of Fourier transforms, and analyzed with the aid of the Wiener–Hopf technique. The current distribution and the input admittance of an infinite and finite antenna are evaluated approximately under the following assumptions: (1) the medium is loss free, (2) (radius of the antenna/wavelength) [Formula: see text], (3) the nondiagonal elements of the dielectric tensor are very small compared with its diagonal elements and ωp < ω < ωe (ωp, ω, and ωe are the plasma, signal, and cyclotron frequencies), (4) (antenna length/wavelength) is not small. Our present results have forms similar to the well-known solutions in an isotropic medium, except for two distinctions. The first is that a circulating current flows on the antenna, although its magnitude is very small. The second is an additional resonance phenomenon due to the interaction of two traveling current waves with slightly different propagation constants.

The Field in a Narrow Circumferential Slot in a Coaxial Waveguide

1973 ◽  
Vol 51 (9) ◽  
pp. 946-955 ◽  
Author(s):  
R. A. Hurd
Keyword(s):  
Electric Field ◽  
Outer Wall ◽  
Coaxial Waveguide ◽  
Input Admittance ◽  
Quantity Of Interest ◽  
Cylindrical Antenna

The first three terms in the expansion of the electric field in a narrow circumferential gap in the outer wall of a coaxial waveguide have been determined. Also found is the input admittance of an infinite, coaxially fed cylindrical antenna, a quantity of interest in the theory of sleeve antennas.

The wave front in a homogeneous anisotropic medium

1980 ◽  
Vol 70 (6) ◽  
pp. 2097-2101
Author(s):  
M. J. Yedlin
Keyword(s):  
Dispersion Relation ◽  
Wave Front ◽  
Group Velocity ◽  
Anisotropic Medium ◽  
Slowness Surface ◽  
Constant Frequency ◽  
Common Notion ◽  
The Common ◽  
Intuitive Method ◽  
Homogeneous Anisotropic Medium

abstract A simple geometric construction is derived for the shape of the wave front in a homogeneous anisotropic medium. It is shown to be equivalent to the intuitive method of constructing a wave front using Huygen's principle. Although this construction has been referred to and tersely described in the literature (Musgrave, 1970; Kraut, 1963; Duff, 1960), it is instructive to demonstrate its relationship to the common notion of the wave front obtained via consideration of the group velocity. The wave front is shown to be the polar reciprocal of the slowness surface (the dispersion relation at constant frequency). An appreciation of the pole-polar correspondence between the two surfaces allows quick inference of some of the important features of the wave front in a homogeneous anisotropic medium.

Radiation Field of a Uniformly Moving Charge in an Anisotropic Medium

1974 ◽  
Vol 29 (5) ◽  
pp. 687-692
Author(s):  
G. P. Sastry ◽  
S. Datta Majumdar
Keyword(s):  
Radiation Field ◽  
Anisotropic Medium ◽  
Point Charge ◽  
Potential Distribution ◽  
Asymptotic Form ◽  
Dielectric Tensor ◽  
Arbitrary Direction ◽  
Hankel Functions ◽  
Anisotropic Fields ◽  
Set Up

Abstract Fourier integrals are set up for the field of a point charge moving uniformly in an arbitrary direction in a uniaxial medium anisotropic in ε only. The integrals break up into several parts two of which yield the ordinary and extraordinary cones with uniform azimuthal potential distribution. The remaining integrals neither contribute to the energy radiated nor affect the size and the shape of the cones, but merely distort the field within the cones. The integrals are evaluated exactly in the non-dispersive case and closed expressions for the potential are obtained. In the dispersive case, the radiation field is determined by using the asymptotic form of the Hankel functions occurring in the integrand. The resulting expressions exhibit the high azimuthal asymmetry characteristic of anisotropic fields. From the expressions derived for a pure dielectric the potential in a doubly anisotropic medium is obtained, without a fresh calculation, by making appropriate substitutions for the coordinates of the field point and the components of the dielectric tensor.

Note on Losses in Cable Sheaths

1928 ◽  
Vol 24 (1) ◽  
pp. 65-73 ◽  
Author(s):  
F. W. Carter
Keyword(s):  
Cross Section ◽  
Eddy Current ◽  
Distribution Systems ◽  
Power Cables ◽  
Circulating Current ◽  
Outer Sheath ◽  
The Cross ◽  
Current Flows ◽  
Made In

In a recent communication to the Society, the author referred to cable-sheath losses, and gave formulae for computing them in certain cases. These appertained to power cables in which were comprised a group of conductors, arranged symmetrically and encased in a single conducting sheath. In some distribution systems, however, the conductors for the several phases are encased in separate lead sheaths, which are either laid in proximity as separate cables, or grouped and comprehended in an outer sheath. The analysis previously given does not include such cases directly. Moreover, it is common practice either to lay the elementary cables with sheaths in contact, or to bond the sheaths together at the ends of suitable sections, in order to prevent differences of potential between them; and, when this is done, a circulating current flows in the circuit of the sheaths and bonds, sufficient to maintain equality of potential between the several sheaths. This current, to which reference was made in the former paper, is additional to the eddy current discussed therein, the integral of which over the cross section of the sheath is zero. It is for convenience here referred to as the “circulating current,” to distinguish it from the “eddy current,” although there is no such distinction between them as the names imply.

scholarly journals A Ringed Non-Uniform Network: How to Raise its Efficiency

2008 ◽  
Vol 45 (6) ◽  
pp. 20-32 ◽  
Author(s):  
J. Survilo
Keyword(s):  
Electric Power ◽  
Power Quality ◽  
Power Lines ◽  
Phase Voltage ◽  
Closed Loops ◽  
Circulating Current ◽  
Current Flows ◽  
Two Sides ◽  
Made In ◽  
Supply Reliability

A Ringed Non-Uniform Network: How to Raise its Efficiency As distinct from radial electric power lines, in closed loops the consumers are fed from two sides. This is advantageous from the viewpoint of supply reliability, power quality and its losses; however, these are the least only when a loop is uniform, which is not always met in practice. In a non-uniform loop a circulating current flows, and the losses increase proportionally to its square. To reduce losses in such a non-uniform loop, the circulating current should be eliminated. For this purpose a booster transformer can be used. The voltage of such a transformer is known to be in quadrature to the phase voltage; the present consideration has shown that such orientation of the opposing voltage gives the best results only when all loads in the loop are active, otherwise the angle of opposing voltage should be regulated. The voltage value should also be regulated depending on the load. Another technique consists in introducing a complementary reactance into the terminal branches. Such reactance should be regulated if loads are changing in time disproportionately with respect to each other. The best results are achieved when all loop node loads have the same cosφ. If the complementary reactance calculated at one end of the loop is positive, then that calculated at the second end of the loop will be negative, and vice versa. The appropriate choice can be made, in particular, involving both loop terminals.

Thermoelastic Interaction Between Singularities and Interfaces in an Anisotropic Trimaterial

2007 ◽  
Vol 74 (6) ◽  
pp. 1285-1288
Author(s):  
Seung Tae Choi
Keyword(s):  
Analytic Continuation ◽  
Anisotropic Medium ◽  
Dissimilar Materials ◽  
Infinite Body ◽  
Series Form ◽  
Alternating Technique ◽  
Thermoelastic Interaction ◽  
General Plane ◽  
Homogeneous Anisotropic Medium ◽  
Plane Deformations

The method of analytic continuation and Schwarz-Neumann’s alternating technique were applied to the thermoelastic interaction problems of singularities and interfaces in an anisotropic “trimaterial,” which denotes an infinite body composed of three dissimilar materials bonded along two parallel interfaces. It was assumed that the linear thermoelastic materials are under general plane deformations in which the plane of deformation is perpendicular to the planes of the two parallel interfaces. The author then showed that by alternately applying the method of analytic continuation across two parallel interfaces the solution for the thermoelastic singularities in an anisotropic trimaterial can be obtained in a series form from a solution for the same singularities in a homogeneous anisotropic medium.

Theory of the Electron–Phonon Interaction

1974 ◽  
Vol 52 (14) ◽  
pp. 1304-1314 ◽  
Author(s):  
R. A. Moore ◽  
J. P. Perdew ◽  
S. H. Vosko
Keyword(s):  
Potential Model ◽  
Fourier Transforms ◽  
Dielectric Tensor ◽  
Phonon Interaction ◽  
State Matrix ◽  
First Order ◽  
Electron Phonon Interaction ◽  
Consistent Field ◽  
Diffraction Model ◽  
Self Consistent Field

An exact solution to the self-consistent field screening problem is presented in terms of Bloch-state matrix elements of the bare perturbation. This solution is equivalent to one given by Sham and Ziman in terms of Fourier transforms of the bare perturbation, but unlike the latter it avoids the convergence problem in momentum space that arises in the screening of the electron–phonon interaction because of the 'deep' part of the ionic potential. The new form of the solution converts naturally into a pseudopotential formalism. At the same time it provides a framework in which to discuss and extend the two most common calculation schemes for the electron–phonon matrix element, the rigid Schrödinger potential model and the diffraction model. The inverse dielectric tensor is evaluated to first-order in the pseudopotential. Local field effects cause the Q → 0 limit of the electron–phonon interaction to deviate from its conventional value.

Carrier Shifting Algorithms for the Mitigation of Circulating Current in Diode Clamped MLI fed Induction Motor Drive

2017 ◽  
Vol 8 (2) ◽  
pp. 844 ◽  
Author(s):  
C. Santhakumar ◽  
R. Shivakumar ◽  
C. Bharatiraja ◽  
P. Sanjeevikumar
Keyword(s):  
Low Voltage ◽  
Parasitic Capacitance ◽  
Motor Drive ◽  
Induction Motor Drive ◽  
Voltage Profile ◽  
Electrical Drives ◽  
The Past ◽  
Circulating Current ◽  
Modulation Techniques ◽  
Current Flows

Reduction of circulating current is one of the major considerations in inverter fed electrical drives. Diode clamped MLI enables higher output current per phase, thereby rating of the drive gets increased effectively. Various methods of triggering in the inverter legs creates better voltage profile and leads to the enabling of circulating current in the drive system.  The induced circulating current flows through the apparatus neutral (N) and supply ground (G) is caused by the existence of parasitic capacitance. This circulating current may cause potential danger especially when parasitic capacitance poses large. In the past, different modulation techniques and conversion topologies have been introduced to minimize the flow of circulating current. However, these techniques lead to complexity, high cost, low voltage profile and efficiency due to lower modulation parameters. This paper proposes PS, POD, PD carrier shifting PWM algorithms for diode clamped MLI to tumbling the circulating current within the each phase of inverter legs. The performances of proposed algorithm, in terms of circulating current, THD, losses and efficiencies are analyzed theoreticallyand are validated via simulation and experimental results.

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