Papers by Salvatore Alfonzetti
2017 AEIT International Annual Conference, 2017
In this paper, the optimization of the shielding of an axisymmetric levitation melting system is ... more In this paper, the optimization of the shielding of an axisymmetric levitation melting system is performed by means of the Particle Swarm Optimization algorithm. A non-standard Hybrid FEM-BEM is used to deal with the unbounded nature of the electromagnetic field problem and to reduce the computing effort required for optimization. The shape of the shield is derived by using Bèzier curves. Moreover, for each analyzed configuration, the equilibrium position of the workpiece to be melted is determined by means of a Newton-Raphson algorithm.
A aplicação das TICs na área de cuidado de saúde, conhecida como e-Health, pode facilitar o acess... more A aplicação das TICs na área de cuidado de saúde, conhecida como e-Health, pode facilitar o acesso aos serviços de cuidado de saúde e só será aceitável se permitir a troca de informação eficiente e segura entre os cuidadores de saúde e pacientes. O objetivo deste trabalho é apresentar uma abordagem para troca de mensagens em cenários realísticos.
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2017
There are several techniques for optimization of Frequency Selective Surfaces (FSS). Generally, i... more There are several techniques for optimization of Frequency Selective Surfaces (FSS). Generally, in literature, we can find a few articles about the Taguchi's method applied in electromagnetic. This method is based on orthogonal arrays (OAs) and it is a procedure that reduces the number of iterations required in an optimization process. For a FSS optimization using the crossed dipole geometry, the Taguchi's method, in combination of the equivalent circuit method, is used for the first time. Here, we applied the method for synthesis of FSS with crossed dipole geometry. The results show that the parameters, of the synthesized FSS, are extracted in an easy and successful way. A prototype was built for validation purpose.
IEEE Transactions on Magnetics, 2006
Compel-the International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2000
ABSTRACT Open-end capacitances for various coaxial lines are computed by means of a conformal map... more ABSTRACT Open-end capacitances for various coaxial lines are computed by means of a conformal mapping-finite difference procedure and by a refined finite element method. The results are compared with previous ones, and the accuracy of the computation methods is discussed.
2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), 2018
The hybrid FEM-BEM and FEM-DBCI numerical methods are proposed for the computation of transferred... more The hybrid FEM-BEM and FEM-DBCI numerical methods are proposed for the computation of transferred earth potentials from grounding grids. The method foresees the decomposition of the analysis domain in detached subdomains to be analyzed by means of FEM and linked together by means of integral equations, which involves the Green's function of the stratified soil. A great advantage of these methods is that the numerical solution directly gives the electric potential on the earth surface.
This paper describes a particular use of the hybrid FEM-DBCI, for the computation of low-frequenc... more This paper describes a particular use of the hybrid FEM-DBCI, for the computation of low-frequency electromagnetic fields in open-boundary domains. Once the unbounded free space enclosing the system has been truncated, the FEM is applied to the bounded domain thus obtained, assuming an unknown Dirichlet condition on the truncation boundary. An integral equation is used to express this boundary condition in which the integration surface is selected in the middle of the most external layer of finite elements, very close to the truncation boundary, so that the integral equation becomes quasi-singular. The method is described for the computation of electrostatic fields in 3D and of eddy currents in 2D, but it is also applicable to the solution of other kinds of electromagnetic problems. Comparisons are made with other methods, concluding that FEM-DBCI is competitive with the well-known FEM-BEM and coordinate transformations for what concerns accuracy and computing time.
IEEE Transactions on Magnetics, 2000
IEEE Transactions on Magnetics, 2000
In this paper optimization of the cross section of the coils of an axisymmetric electromagnetic a... more In this paper optimization of the cross section of the coils of an axisymmetric electromagnetic actuator is performed by means of two stochastic methods: Genetic Algorithms and Simulated Annealing. The finite element formulation of the electromagnetic problems is based on the magnetic vector potential. The hybrid FEM/DBCI (Dirichlet Boundary Condition Iteration) method is used to deal with the unbounded nature of the field problem and to reduce the computing effort of the whole optimization.
IEEE Transactions on Magnetics, 1992
An efficient analytical method for the computation of the magnetic vector potential from tetrahed... more An efficient analytical method for the computation of the magnetic vector potential from tetrahedral conductors carrying a uniform current density in iron-free media is presented. This method has been expressly conceived to be used in conjunction with finite element analyses. The presentation is given in an algorithmic form very near to a software implementation
2010 30th International Conference on Lightning Protection (ICLP), 2010
The electrical potential around the conductors of a grounding system is computed by means of the ... more The electrical potential around the conductors of a grounding system is computed by means of the hybrid FEM-DBCI method. The potential distribution on the earth surface is obtained directly as part of the solution, whereas the equivalent electrical resistance is computed in post-processing.
N-dimensional algorithms for the computation of universal matrices relative to simplez Langragian... more N-dimensional algorithms for the computation of universal matrices relative to simplez Langragian finite elements of arbitrary order are shown. Such matrices are expressed in terms of the three primitive matrices T, D and C, from wich universal matrices can be derived by simple algebraic manipulations. Formulae for the primitive matrix computation are presented in a factorized form. These algorithms are employed in ELFIN, a finite-element code developed by the authors for the computation of electromagnetic fields.
European Journal of Electrical Engineering
This paper describes two iterative procedures to solve efficiently the global algebraic systems o... more This paper describes two iterative procedures to solve efficiently the global algebraic systems of equations obtained by applying the hybrid FEM-BEM method to the solution of open-boundary electrostatic problems in the presence of floating potential conductors. In both methods, non-standard boundary elements are used. In the first procedure the conjugate gradient solver is used to solve the FEM equations, whereas the BEM equations are solved by the direct LU solver. In the second method, the GMRES solver is applied to a reduced system virtually available, in which the unknowns are the values of the normal derivatives of the electric potential on the truncation boundary. The proposed methods are also applicable to other kind of electromagnetic problems such as magnetostatic and static current density problems. RÉSUMÉ. Cet article décrit deux procédures itératives pour résoudre efficacement les systèmes globaux d'équations algébriques obtenus en appliquant la méthode FEM-BEM à la solution de problèmes électrostatiques en domaines illimités en présence de conducteurs avec potentiels flottant. Des éléments de frontière non-standard sont utilisés. Dans la première procédure, le solveur du gradient conjugué est utilisé pour résoudre les équations aux éléments finis, tandis que les équations des éléments de frontière sont résolues par le solveur direct avec la décomposition LU. Dans la seconde procédure, le solveur GMRES est appliqué à un système réduit virtuellement disponible, dans lequel les inconnues sont les valeurs nodales de la dérivée normale du potentiel électrique sur la frontière de troncature. Les deux méthodes proposées sont également applicables à d'autres types de problèmes électromagnétiques, tels que des problèmes magnétostatiques et de champ de courant statique.
COMPEL - The international journal for computation and mathematics in electrical and electronic engineering
Purpose The optimization of the cross section of an axisymmetric induction heating device is perf... more Purpose The optimization of the cross section of an axisymmetric induction heating device is performed by means of genetic algorithms (GAs). Design/methodology/approach The hybrid finite element method–Dirichlet boundary condition iteration method is used to deal with the unbounded nature of the field. The formulation of the electromagnetic problems takes into account skin and proximity effects in the source currents. Findings The convergence of GAs towards the optimum is very fast, since less than a thousand analyses have been necessary. Originality/value A special derivation of the finite element global system is presented which allows us to save computing time.
International Journal of Applied Electromagnetics and Mechanics
ABSTRACT In this paper the FEM-RBCI method is successfully applied to the analysis of the scatter... more ABSTRACT In this paper the FEM-RBCI method is successfully applied to the analysis of the scattering of time-harmonic electromagnetic waves at optical frequencies from metallic nanoparticles. Plasmons are taken into account by modelling the nanoparticles by means of appropriate complex permittivities. The method is valid whatever the shape of the nanoparticles. Numerical examples are provided to validate the method.
Energies
Grounding systems are essential parts of substations and power generation stations. The evaluatio... more Grounding systems are essential parts of substations and power generation stations. The evaluation of transferred potentials from an active grounding system to other passive ones or to any near conductors is an important aspect to be considered, because transferred potentials may cause serious and fatal events. Moreover, it is an intrinsic issue of the Smart Grid where the ground systems of the power and ICT systems could be close to each other. Therefore, the estimation of the transferred potential is necessary at grounding system design stage for people safety and electric components safeguard. Numerical methods are the best choice to perform a truthful estimation, especially when large and complex grounding systems have to be designed. However, this task is complicated by the “unbounded” nature of the electromagnetic field and by the presence of components of extremely different size in the analysis domain. In this paper, an efficient hybrid finite element method is applied for t...
IEEE Transactions on Magnetics, 2017
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Papers by Salvatore Alfonzetti