Underground electromagnetic fields generated by the return strokesof lightning flashes

In this paper, equations are developed in the time domain to represent lightning generated electromagnetic (EM) fields at different depths below the ground surface. The equations connect underground EM fields to surface fields that can easily be measured or calculated. Numerous examples are given to illustrate how the signature of the electric and magnetic field vary as a function of depth as well as conductivity     

Analysis of radiation from a horn with a superquadric aperture

This paper presents an analysis of radiation from a horn with a superquadric aperture, modeled using a cascade of superquadric waveguides. Electromagnetic fields within each waveguide are expressed in terms of a set of orthogonal modes derived from polynomial functions based on a Cartesian coordinate system. The scattering matrix at the horn aperture is obtained by calculating the scattering matrix at each of the waveguide junctions using mode matching, and cascading them appropriately. Radiation patterns corresponding to both x- and y-polarizations of the input excitation are then obtained by integrating the aperture field. The computed numerical results are validated by comparing them with the corresponding results obtained from measurements.     

Emulsion polymerization of an epoxy‐acrylate emulsion stabilized with polyacrylate. i. influence of salt,initiator, neutralizing amine,and stirring speed

The past decade has seen the development of high‐performance epoxy‐acrylate coatings. Some of these coatings are used exclusively as can coatings. To improve chemical resistance, emulsion polymerization in the presence of the dispersed epoxy resin can be conducted. Replicated factorial designs were designed to investigate some of the factors that contribute to the performance and stability of the epoxy‐acrylate coating. The factors investigated in this study were: the type and amount of neutralizing amine, the type of initiator, the presence or absence of salt, and the stirring speed of the impeller. The measured responses for the experimental design were particle size, particle size distribution, and conversion. It has been shown in this study that the type of amine used to neutralize the polyacrylic stabilizer significantly influenced the observed responses probably by acting as chain transfer agent during polymerization. The addition of salt significantly affected the observed responses by shielding the surface charges on the particle surface that impart stability to the latex through electrostatic repulsion. Stirring speed of the impeller and the type of initiator as factors in the range investigated do not influence the kinetics or the particle size and polydispersity to any great extent either on their own or in combination with other factors. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1347–1360, 1999     

Induced voltages in a low-voltage power installation network due tolightning electromagnetic fields: an experimental study

This paper presents experimental results on the induced common-mode (CM) voltages in a residential low-voltage power installation (LVPI) networks exposed to electromagnetic fields from lightning. The objective of this investigation was to find out the severity of induced voltages in a low voltage network due to direct coupling of the lightning electromagnetic fields with the network in the absence of transient overvoltages coming through the distribution lines. Flashes at a distance of about 25 km produced many induced-voltage pulses as large as 100 V, six such pulses in a time period of 0.4 ms in a negative CG flash, and 11 such pulses in a time period of 3 ms in a CC that immediately followed the ground flash     

Shapes and amplitudes of the initial peaks of lightning-induced voltage in power lines over finitely conducting earth: Theory and comparison with experiment

It is conclusively shown that lightning-induced voltages in power lines over finitely conducting earth can only be explained by considering the interaction of the horizontal field produced by the finitely conducting ground, with the conductors. The theory predicts narrow peaks of few microseconds width in the induced voltages, for particular positions of lightning with respect to the line. Wave propagation effects are found to be of considerable importance. To the extent allowed by the bandwidth of the measuring instruments used in this study, the prediction of the theory is confirmed.     

Large area ZnO films optimized for graded band-gap Cu(InGa)Se2-based thin-film mini-modules

In this study, two deposition methods (i.e. MOCVD and sputtering methods) to prepare n-type ZnO window layers for CIGS-based thin-film solar cells are discussed. In order to make ZnO : Al transparent conductive oxide (TCO) films prepared by DC magnetron sputtering comparable to ZnO : B TCO prepared by MOCVD, a new ZnO sputtering process is proposed by introducing a multilayer structure. Using these films, CIGS thin-film solar cells with efficiencies of greater than 14% have been fabricated with an active area of 3.2 cm². This structure was adapted to fabricate CIGS thin-film mini-modules with efficiencies around 11% having aperture area of 50 cm².     

Electromagnetic wave scattering by a system of two spheroids ofarbitrary orientation

An exact solution to the problem of the scattering of a plane electromagnetic wave by two perfectly conducting arbitrarily oriented prolate spheroids is obtained by expanding the incident and scattered electric fields in terms of an appropriate set of vector spheroidal eigenfunctions. The incident wave is considered to be a monochromatic, uniform plane electromagnetic wave of arbitrary polarization and angle of incidence. To impose the boundary conditions, the field scattered by one spheroid is expressed in terms of its spheroidal coordinates, using rotational-translational addition theorems for vector spheroidal wave functions. The column matrix of the scattered field expansion coefficients is equal to the product of a square matrix which is independent of the direction and polarization of the incident wave, and the column matrix of the known incident-field expansion coefficients. The unknown scattered-field expansion coefficients are obtained by solving the associated set of simultaneous linear equations. Numerical results for the bistatic and backscattering cross sections for prolate spheroids with various axial ratios and orientations are presented     

The Tomographic Ionized-Carbon Mapping Experiment (TIME) CII Imaging Spectrometer

The Tomographic Ionized-Carbon Mapping Experiment (TIME) and TIME-Pilot are proposed imaging spectrometers to measure reionization and large scale structure at redshifts 5–9. We seek to exploit the 158  \({\upmu } \mathrm{m}\) restframe emission of [CII], which becomes measurable at 200–300  GHz at reionization redshifts. Here we describe the scientific motivation, give an overview of the proposed instrument, and highlight key technological developments underway to enable these measurements.