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A wide class of electromagnetic problems can be expressed as a system of dual integral equations. These kinds of integral equations occur in boundary value problems wherein there is one integral equation for a certain region, and another for the rest of the region. In this paper it is shown that the equation for the potential distribution due to an insulating cylinder column with a band electrode in a conducting space, representing a well logging problem, can be put into a standard form of dual integral equations, which can then be transformed into a system of linear equation by means of a Neumann series. A general method to compute the coefficients of the linear system is discussed in order to obtain some approximate formulas and the plot of the conductance as a function of the ratio a / Δ (radius/half-length of the cylinder column).

In this paper a method is proposed for solving the problem of the computation of the longitudinal coupling impedance for a particle which passes through the center of a round aperture in a perfectly conducting metallic plane (iris). It is shown that the solution of the problem can be expressed in quadrature by means of one auxiliary function that satisfies a one-dimensional Fredholm integral equation with a continuous kernel. For small values ofkR 0 (k is the wave number andR 0 is the radius of the aperture) the impedance can be expressed in the form of converging series of this parameter. An asymptotic expansion is also given for the real part of the impedance.

In this paper the problem of a relativistic charge passing on-axis through a circular hole of an infinite conducting plane is solved. Thisclassical canonical problem has been studied by several authors in the past. The method used here has the advantage of leading to an analytical solution which gives for an ultrarelativistic charge the radiation power spectrum at any frequency allowing a better understanding of the radiation process.

In this paper we propose two new analitical and numerical methods, useful for calculating the spheroidal functions. An algorithm for the evaluation of the expansion coefficient of angle functions in series of associated Legendre functions, as well as for the calculations of the eigenvalue, is developed. The coefficients of the expansion of radial functions of first and second kind in series of product of Bessel functions are explicitly calculated; a very simple expression is obtained when the differencen - m between the degree and the order is even.

An overview of DAΦNE, the Frascati Φ-Factory project is presented. The DAΦNE project has been approved and fully funded by the INFN Board of Directors in June 1990. The end of construction is scheduled for December 1995. The short-term luminosity goal is 1.3 10^(32) cm-2 sec-1, while the ultimate luminosity target is ~10^(33) cm-2 sec-1. All critical components of the project, injector, vacuum system, RF and feedback are dimensioned to cope with the target luminosity.

An overview of DAΦNE, the Φ‐factory under construction at the INFN Frascati National Laboratory and the salient project features are presented.

In this paper the hysteretic behaviour of an iron core inductor is described by means of a new model based on a sequential algorithm. This model has been applied to study a series ferroresonant circuit. The simulations obtained using the proposed model are in good agreement with experimental results, as well as with the predictions of the classical Preisach model; nevertheless the latter may be computationally more cumbersome.

This paper deals with the nonlinear dynamics of a distributed network consisting of a lossless transmission line terminated at one end with a nonlinear resistor in parallel to a linear capacitor, and at the other end with a piece-wise linear resistor. The equations describing this system are reduced to a nonlinear difference-differential equation of the neutral type with one delay. The effects of the capacitor are investigated numerically.

In this paper we propose a new method to evaluate the longitudinal coupling impedance of a charged particle passing perpendicularly through the centre of a perfectly conducting annular ring. It is shown that the solution of the problem can be expressed as a double Neumann series, whose expansion coefficients can be easily computed. Moreover we show the causality of the wake field for a particle travelling at the speed of light.

Electromagnetic shock waves are a relatively unexplored field. This paper considers their propagation in the case of a dielectric slab. At first we examine the mathematical problem relating to the physical interpretation of the uniqueness of the solution. A link between uniqueness and irreversibility is pointed out as in the case of shock waves in gasdynamics. Then we illustrate an algorithm, based on the concept of characteristics curves, which gives a very interesting performance.

A wide class of electromagnetic scattering problems can be expressed as a system of dual integral equations. This kind of integral equation, occurring in boundary value problems wherein there is one equation for a certain region and another for the dual domain, is usual in diffraction problems. Considerable attention has been drawn by many researchers in the field of optics, acoustics, scattering of elastic waves, accelerator physics, and antenna theory. Wiener-Hopf techniques enable us to solve such kinds of integral equations when the two regions are contiguous and semi-infinite. Unfortunately Wiener-Hopf techniques do not apply if one of the regions is finite; this is the case for realistic scatterers, such as irises, antennas, and drift tubes in accelerators. In this article a general method for solving such dual integral equations is discussed and applied to a particular case: Hallen's equation of cylindrical antennas. This method consists of a transformation of the dual integral equations into a Fredholm integral equation of the second kind and then into a linear system of algebraic equations. Comparisons with results obtained by other methods for a wide range of frequencies show the accuracy and the robustness of the proposed one. (C) 1995 American Institute of Physics.

This paper deals with the evaluation of the longitudinal coupling impedance due to a charged particle traveling along the axis of an iris in a circular waveguide. The solution of the electromagnetic problem is given in terms of a dual series expansion, and some interesting developments of this technique are presented in this paper. [S1098-4402(99)00032-4]

In this paper the diffusion of the magnetic field in a hysteretic iron core slab is considered. The dynamics of the field is described by means of a finite dimensional nonlinear dynamic system obtained by applying the Galerkin method. Two different models have been used to describe the magnetic hysteresis: the Preisach's scalar model and a new scaler model based on a sequential algorithm. Good agreement has been found between the simulations obtained by using the two models. >

In this paper, it is shown that the problem of the electromagnetic field coupling to a line of finite length can be put into "a standard form" of dual integral equations. A general method for solving such dual integral equations is presented and discussed. It basically consists of a transformation of the first kind Fredholm equation into a linear system of algebraic equations by means of a suitable Neumann expansion of the unknown function. This procedure, carried out in the frequency domain, has allowed evaluating the current induced on the line, which has also been computed with the classical method of moment in order to have a validation of the procedure itself.

We propose a procedure to identify the lightning return stroke current characteristics, in the context of return stroke engineering models. The main effort of the up-to-date literature is to find approximate current shapes, which best fit the experimental data. The method hereafter proposed does not follow these approaches, but proposes an inverse algorithm, which allows us to accurately identify the return stroke current for simulated data.

In this study, overvoltages produced on multiconductor power lines by indirect lightning are analysed. In particular, the case of power lines with ground wires terminated on non-linear loads is studied. The power line is represented by an equivalent time–domain m- port and the effects of the lightning excitation are represented through equivalent independent sources. The time–domain circuit has been implemented in SPICE. Simulations have been carried out in order to evaluate the shielding effect of the ground wires and to analyse the effects of surge arresters. The results have been compared to those available in the literature.

Cet article presente une methodologie generate pour l’etude des structures electromagnetiques imprimees. Les structures canoniques a microbandes peuvent etre decrites au moyen d’un systeme d’equations integrates couplees, qui peut facilement etre transforme en un systeme d’equations algebriques en utilisant une serie de Neumann, c’est-a-dire une serie de fonctions de Bessel. Une analyse numerique attentive montre que des matrices effectives petites sont necessaires dans le but d’obtenir une precision raisonnable des champs ou des potentiels. Des cas statiques et dynamiques sont etudies.

In this paper the electromagnetic field produced by a lightning current analytically described by the so called double exponential model is compared with the field produced by the same current (same peak, rise and decay time) analytically described by the model proposed by Heidler. The exponential model has been widely used in literature for its simplicity and its relatively good accuracy. The Heidler model is more complex, but removes the main problem shown by the double exponential: the non-zero derivative at the beginning of the lightning pulse in contrast with the physical phenomenon. In the lightning electromagnetic pulse (LEMP) simulations both models are now used. In the paper we aim to make a comparison between the two. In particular we show that the two models are fairly equivalent in the frequency range up to 2 MHz, namely the range of interest of typical lightning phenomena. In addition, the double exponential model is shown to be conservative for higher frequencies.