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A complete scattering matrix representation for the ideal equal-delay topology for transformers and hybrid networks is presented. It is shown that while the operation of the hybrid as a 180[degrees] power combiner, current balun, or voltage balun is essentially frequency independent, the operation as a 0[degrees] power combiner or splitter is not. Instead, the isolation between the 0[degrees] and 180[degrees] ports is finite and frequency dependent. Moreover, the reflection coefficient at the sum port is nonzero and frequency dependent. These characteristics lead to the conclusion that while the equal-delay 180[degrees] power splitter/combiner is fundamentally frequency independent, its 0[degrees] counterpart is limited to operation well below the fundamental quarter-wave frequency of the constituent transmission lines. Full three-port scattering parameter representations, which are compatible with the calibration and analysis approach given in the CISPR 16-1 specification, are given for the three fundamental transformer and balun types derivable from the equal-delay hybrid: 1 the Guanella voltage balun, 2 the Guanella current balun, and 3 the 180[degrees] power divider or terminated hybrid balun, as specified in the CISPR 16-1 specification. Index Terms--Balancing network, balun, calculable dipole, CALTS, CISPR 16-1, equal-delay balun, equal-delay transformer, Guanella balun, Guaneila transformer, site attenuation, ultra wideband, UWB.

Dust-dust interactions in complex plasmas have been studied when effects of an external magnetic field become important. It is shown that the forces from particle magnetization may result in mutual repulsion as well as attraction. It was found that magnetized grains coalesce, forming field-aligned chains. Since the 'disruptive' electrostatic forces increase with the distance from the centre of a chain, whereas the 'cohesion' magnetic forces decrease, there is an intrinsic length scale for these particle chains. A model was developed to determine the length of these structures. These finding were then applied to recent complex plasma experiments with paramagnetic particles. Index Terms--Complex plasmas, dipole moment, dust-dust interactions, particle agglomeration.

Investigating two new options for hollow superconducting cables aimed at increasing structural current density were proposed and designed in the frameworks of R&D program for the future accelerator facility at GSI is presented. The data from cable short sample test are presented.

An experiment is described, conducted at Los Alamos National Laboratory, Los Alamos, NM, which aims to measure the neutron electric dipole moment (EDM) to 4 x 10[superscript -28].

The harmonic balance technique has been used to investigate the impact of permanent dipole moments of quantized states on intersubband harmonic generation based on quantum-interference induced transparency in semiconductor quantum wells. It is concluded that the permanent moments prompt a shift of the pump photon energy at which the conversion efficiency is greatest.

The Nb3Sn strands for Fermilab's high field dipole models were investigated and results of heat treatment optimization studies are reported.

The interaction of an electromagnetic field with a two-level molecular system where the permanent dipole moments are explicitly considered was investigated. The nonzero difference between permanent dipoles was found to induce a polarization oscillating at an increasing electromagnetic field resonance frequency. Results also showed an amplification of even harmonics and absorption of odd harmonics.

A Galerkin moment method is employed to solve the problem of a dielectric-coated dipole antenna in a dissipative medium. Piecewise sinusoids are used as basis and testing functions. The dielectric coating is modeled by equivalent-volume polarization currents, which are simply related to the conduction current distribution. No additional unknowns are introduced, and the size of the moment-method matrix is the same as that for bare antennas. Exact and approximate formulas for the near electric field are derived. The computed results exhibit excellent agreement with those previously published for a symmetric, as well as an asymmetric insulated dipole. Compared to its existing competitors, the new method appears to be more general and computationally efficient. Index Terms - Antennas in matter, Galerkin technique, insulated antennas, moment method.

In this paper the design criteria for antenna structures with improved radiation efficiency while operating in close vicinity to a biological scatterer were investigated. The study was performed using a simple [Lambda]/2 dipole combined with a directive or reflective element. The optimization criteria were the effective radiation efficiency, the spatial peak specific absorption rate (SAR), and the sensitivity of the input resistance to the distance from the scatterer. It could be demonstrated that the primary design criterion to improve the radiation efficiency is not directivity but the reduction of the maximum incident magnetic field strength in the exposed skin area of the user's head. For the reflectively coupled dipole, all performance parameters could be improved by several decibels compared to a standard [Lambda]/2 dipole, whereas for some other directive structures, the performance was impaired. The study was conducted with the generalized multipole technique (GMT) numerical simulation method, the results of which were validated by measurement methods. Index Terms - Design criteria, directional antennas, mobile phones, radiation efficiency, SAR.

By studying the ability of a one-dipole model to explain the magnetic field actually resulting from two dipoles, minimum requirements for a successful separation of two dipoles were explored. Two dipoles in different depths generally require a much higher signal-to-noise ratio (SNR) than two dipoles in the same depth. For the latter condition, the dipole distance as well as the angles between the moments and the line connecting the dipole locations (connecting line) were systematically varied. A perpendicular orientation of the two dipoles turned out to be the most favorable condition: the minimum distance required for a separation of two dipoles was more than four times smaller than for a configuration with both moments oriented parallel to the connecting line. Separability of parallel dipoles was moderately enhanced if both moments assumed an orientation perpendicular to the connecting line. The separability of two antiparallel dipoles is not limited by concurrence with a one-dipole model, but by the low signal amplitudes resulting from a mutual cancelation of the fields arising from the two dipoles, and by concurrence with a quadrupole model. The results are presented so that quantitative conclusions about dipole separability can be derived for arbitrary SNR's. The study does not generally disprove the common believe that magnetoencephalography has a relatively poor spatial resolution, but it qualifies this view by suggesting that under favorable conditions two sources with a distance of only 1 cm may be resolvable. Index Terms - Dipole separability, magnetoencephalogrphy, quadrupole, spatial resolution

A reexamination of satellite-derived sea surface temperature imagery reveals many examples of Brazil Current rings, both warm and cold, in dipole configurations. The dynamical significance of the dipole model is established by considering the interaction of a cold (cyclonic) eddy with a warm (anticyclonic) ring. The ring is shown to exist as a dipole for about 60 days, or two rotation periods based on its original rotation rate of approximately 12 [degrees] per day. The observed interaction of the dipole ring with a solitary (or monopole) cold eddy is complicated, but results in the two vortices coalescing. The latter point is particularly important, since coalescence between two eddies with opposing vorticities cannot occur if they are both monopoles - one of them has to be a dipole. After coalescence, the rotation of the dipole ring temporarily reverses due to the addition of cyclonic vorticity, but the original rotation of the dipole is reestablished after an adjustment phase.

Shielding of extremely low-frequency magnetic fields is limited by fields penetrating through imperfect material and leakage around the edges of shields which do not completely enclose the shielded region. The latter effect, more specifically the effect of source geometry and shield type on leakage, is the subject of this work. Particular attention is paid to elementary cylindrical dipole sources since the dominant fields of complex two-dimensional (2-D) sources can be represented as those of dipole sources. When possible, insight is gained from a simple analytic model for shielding by semi-infinite and finite width perfect electric and perfect magnetic shields. In cases for which the simple model is not valid, insight is gained from numerical results. It has been found that source orientation and shield type are critical issues and can cause differences in shielding effectiveness in excess of 20 dB.

E-plane scan results are presented for infinite arrays of microstrip-fed dipoles printed on protruding dielectric substrates. Active impedance values are calculated for dipoles with bent arms and for the array with a near-field dielectric radome cover. It is found that bending the dipole's arms produces a small improvement in the scan range, as compared to the element with the arms straight, and that a dielectric radome with a low permittivity causes a small shift in the impedance curves. The scan limitation of the array is dictated, however, by the presence of the coplanar feedlines with improvement achievable by varying the substrate's thickness and permittivity as well as the dipole/feed geometry. A dipole element with a modified coplanar feed design is introduced for wider sean coverage.

The performance of a planar printed strip dipole hyperthermia applicator is simulated using a computer. The applicator is modeled using an exact integral equation formulation, and Galerkin's method is used to obtain the approximate current distribution on the dipole antenna. These currents are then used to compute the input impedance and heating pattern for the applicator. The computer model is used to investigate, and eliminate, the problem of 'hot-spots' in the fat layer.

Image theory, previously developed for an electric low-frequency dipole in front of a dielectric sphere, is formulated for the magnetically permeable sphere. The low-frequency image source corresponding to an electric dipole outside the sphere arises only in the case when the orientation of the dipole is perpendicular to the radial direction. Two alternative image representations are developed. One is a combination of a magnetic strip current and a bifilar magnetic line current, both flowing between the center of the sphere and the Kelvin inversion point on the axis connecting the sphere and the dipole. The other is a combination of a magnetic strip current and an electric strip current flowing in orthogonal directions between the center and the inversion point of the sphere. A simple approximation for the image source is also derived.

Exact expressions are obtained for the leading terms in the low-frequency expansions of the far field scattered by an arbitrarily shaped cylinder with finite cross section, an arbitrarily shaped cylindrical bump on a ground plane, and an arbitrarily shaped 2cylindrical dent in a ground plane. By inserting the low-frequency expansions of the incident plane wave and Green's function into exact integral equations for the surface current, integral equations are obtained for the leading terms in the low-frequency expansions of the surface current. Simple integrations of these leading terms of the current expansion yield the leading terms in the low-frequency expansions of the scattered fields. For the cylinder with finite cross section, the leading term in the low-frequency expansion of the TM scattered far field is explicitly given by an expression that is independent of the shape of the cylinder. The explicit expression for the low-frequency TE scattered far field contains three constants that depend only on the shape of the cylinder. These three constants are found from the solutions to two electrostatic problems. The explicit expressions for the low-frequency diffracted fields of a bump or dent contain one constant that depends only on the shape of the bump or dent. Remarkably, this single constant is the same for both TM and TE polarization and can be found from the solution to either an electrostatic or magnetostatic problem. The general low-frequency expressions are confirmed by comparing them to low-frequency results obtained from exact time-harmonic eigenfunction solutions.

Arrays of slots with arbitrary orientation in a conducting plane which are infinitely periodic in one dimension and finitely periodic in another dimension are considered. The perfect conducting plane extends infinitely, and is bounded on each side by dielectric slabs of finite thickness and infinite extent. Single columns of slots are represented by equivalent magnetic scattering currents, which are solved for via the moment method. The mutual coupling (admittance) between slot columns in the presence of the stratified media is found by the array scanning method (ASM), which expresses the admittance as the average of the scan admittance of an artificially constructed doubly infinite array of slots over all real scan angles. The technique avoids the use of Sommerfeld integrals, but still gives rise to singularities at scan angles corresponding to the resonant excitation of surface waves. An analytical approximation is made to remove these surface wave singularities, thus making numerical implementation of the method practical. An approximate geometrical optics technique based on the free space periodic Green's function is used to give confidence in the admittance calculations. Fast Fourier transforms (FFT's) are used to accelerate the filling of a large admittance matrix in the moment method. Although results are shown for axial-directed slots, the method is quite general and may be extended to thin slot elements of arbitrary shape and orientation.

This paper describes a method for the estimation of equivalent source position and strength based on the estimation of the electric field from depth electroencephalographic (EEG) data. The calculation method for the electric field is based on a tetrahedral geometry. The proposed approach for source parametrization is twofold. Firstly, the distribution of electrical energy by the squared norm of the electric field vector can give an estimate of the source position, without having to assume a dipole source. Secondly, the average electric field can be related to the dipole magnitude and orientation of the equivalent source. Simulation results demonstrate the potential usefulness of the method. The effects of noise and sampling, and the geometry of the measurement system (i.e., implanted electrodes) relative to the source are also investigated through simulations.

The bistatic radar scattering cross section (BRSCS) of a chaff cloud is investigated in the ground-based system for arbitrarily polarized transmitters and receivers. Chaff wire orientations uniformly random in space, as well as uniform in azimuth and Gaussian in elevation, are considered and the effects on the cross section are also discussed.

The fast Fourier transform (FFT) is used in conjunction with analytical techniques to obtain an approximate expression for the Sommerfeld integral associated with a vertical electric dipole above a half-space. The resulting expression, which is an analytic function of the source and observation locations, can be used in lieu of a numerical integration of the Sommerfeld integral. It can be used in either the near zone or the far zone, and it can even be applied for observation angles close to grazing. The accuracy of the expansion directly depends on the number of terms used in the fast Fourier transform. Results obtained using the expansion are compared with those obtained both from a direct numerical integration of the Sommerfeld integral and the reflection coefficient method.

The communication presents numerical results in the form of a comparison of predictions due to a numerical algorithm using a previously published exact nonlocal Absorbing Boundary Condition (ABC) and analytical results for the field radiated by an infinitely small dipole. The numerical approximations are derived, and application to the FDTD method is straightforward. The method is compared to a related approach due to De Moerlose et al., and it is shown that the method yields better accuracy since higher order interpolation and numerical integration schemes may be used with this formulation.

A new methodology for making quantitative micromagnetic measurements of the in-plane moment canting in Fe-based amorphous alloys, via polarized Mossbauer spectroscopy, is introduced and explained. The technique is applied to the measurement of the approach to magnetic saturation of a field-annealed [Fe.sub.78][B.sub.13][Si.sub.9] ribbon. It is demonstrated that even in a field of 200 k[Am.sup.-1] the moments are not completely saturated, and are canted by on average [approximately] 3 [degrees] to the applied field.

This paper describes methods permitting the determination of the magnetic dipole moments of volume microdefects in thin films with a perpendicular anisotropy. The methods are based on the study of solitary defect interactions with a stripe domain, a flat wall in a gradient magnetic field, and with a bubble. Mathematical models of these interactions are developed and realized with computer. Magnetic moment magnitudes are determined for the attractive and repulsive defects in the garnet films. Results obtained by means of various methods agree within 30%.

The macromolecular technique of calculating the dipole moment of particles in a mixture, such as an artificial magnetodielectric (AMD) material, is quite general and also computer intensive. The conjugate gradient (CG) method has proven to be an efficient solver for equations resulting from the macro-molecule formulation. The conjugate gradient solver presented here has been applied to an electric and magnetic dipole problem with coupling of the dipole moments. The CG method is compared to other solvers for this application.

Magnetic field mitigation for overhead power lines using a passive loop conductor was studied. The aim of this study is to clarify the requirements for effective mitigation not in a specific region such as at the edge of the ROW (right of way) but everywhere around the conductors. For this purpose, the concept of current dipole moment was introduced and applied to the problem. First to determine the validity of the derived formula which estimates the induced current to the passive loop, a miniature transmission line model experiment was performed. Then, the mitigation effectiveness of the actual dimensions of several kinds of overhead transmission line arrangements were estimated by the calculation. The application of a current dipole moment was sufficient for explaining the differences in the mitigation effectiveness depending on the conductor arrangement and for clarifying the requirements for effective mitigation. Index Terms--ELF Magnetic Field, Mitigation, Passive Loop, Current Dipole Moment.

A study on the propagation of electromagnetic pulses generated by an electric dipole in a conducting medium is being criticized. The researchers usage of a delta-function excitation leads to mathematical difficulties which have not been noticed. The researchers' application of their formulas specifically to sea water also prevents them from doing the requisite evaluation of integrals containing modified Bessel functions. These flaws create questionable results. An authors' reply to these comments is also presented.