Piergiorgio Alotto | Università degli Studi di Padova (original) (raw)

Papers by Piergiorgio Alotto

Research paper thumbnail of Linear systems of equations arising in the (almost) FEM solution of low-frequency electromagnetic problems

Numerical Mathematics and Advanced Applications, 2003

ABSTRACT This paper discusses the linear algebra implications of the solution of Maxwell’s equati... more ABSTRACT This paper discusses the linear algebra implications of the solution of Maxwell’s equations including materials, topology, space discretization, coupling, duality and graph theoretical techniques. In addition some commercial and research codes are described.

Research paper thumbnail of Electromagnetic Device Optimization with Stochastic Methods

Stochastic Optimization - Seeing the Optimal for the Uncertain, 2011

Research paper thumbnail of A field‐based finite element method for magnetostatics derived from an error minimization approach

International Journal for Numerical Methods in Engineering, 2000

ABSTRACT Cited By (since 1996): 5, Export Date: 19 July 2012, Source: Scopus, CODEN: IJNMB, doi: ... more ABSTRACT Cited By (since 1996): 5, Export Date: 19 July 2012, Source: Scopus, CODEN: IJNMB, doi: 10.1002/1097-0207(20001010)49:4<573::AID-NME964>3.0.CO;2-N, Language of Original Document: English, Correspondence Address: Alotto, P.; Universita di Genova, Genova, Italy

Research paper thumbnail of A FIT Formulation of Bianisotropic Materials Over Polyhedral Grids

IEEE Transactions on Magnetics, 2000

ABSTRACT Modeling bianisotropic constitutive equations, i.e., magnetoelectric coupling, in electr... more ABSTRACT Modeling bianisotropic constitutive equations, i.e., magnetoelectric coupling, in electromagnetics simulation is increasingly important, in particular in metamaterials applications. This paper introduces for the first time such constitutive relationships in the framework of finite integration technique and, furthermore, does so by allowing full generality in the discretization through arbitrary polyhedral grids. The resulting formulation is consistent, stable, and preserves the thermodynamic properties of the bianisotropic constitutive equations because of the energetic approach used to construct the interpolating functions.

Research paper thumbnail of Tree-Cotree implicit condensation in magnetostatics

IEEE Transactions on Magnetics, 2000

ABSTRACT A tree-cotree decomposition of the graph associated with a finite-element mesh allows th... more ABSTRACT A tree-cotree decomposition of the graph associated with a finite-element mesh allows the implementation of a method which is equivalent to a mixed one but which gives rise to a symmetric positive definite linear system with a reduced number of unknowns. We will refer to this method as TCIC (Tree-Cotree Implicit Condensation). A possible preconditioning scheme for the resulting linear system is presented and the effect of the choice of particular tree-cotree decompositions is discussed from the point of view of numerical performance

Research paper thumbnail of Matrix Properties of a Vector Potential Cell Method for Magnetostatics

IEEE Transactions on Magnetics, 2004

In this paper, a proof of the symmetry of the system matrix arising in a class of vector potentia... more In this paper, a proof of the symmetry of the system matrix arising in a class of vector potential cell methods with nonsymmetric material matrices is presented. Some remarks on how to construct other schemes with symmetric system matrices are also presented. The explicit expression of the matrix entries derived in order to prove the symmetry is also used to show that this matrix is identical to the one arising in the standard edge finite-element method. Finally, some remarks on discrete regularizations of these formulations are given.

Research paper thumbnail of An adaptive mixed formulation for 3D magnetostatics

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2000

ABSTRACT Cited By (since 1996): 1, Export Date: 19 July 2012, Source: Scopus, CODEN: CODUD, Langu... more ABSTRACT Cited By (since 1996): 1, Export Date: 19 July 2012, Source: Scopus, CODEN: CODUD, Language of Original Document: English, Correspondence Address: Alotto, P.; Univ of Genoa, Genoa, Italy, References: Alotto, P., Delfino, F., Molfino, P., Nervi, M., Penigia, I., A mixed face-edge finite element formulation for 3D magnetostatic problems (1998) IEEE Trans. on Magnetics, 34 (5), pp. 2445-2448;

Research paper thumbnail of Particle swarm optimization combined with normative knowledge applied to Loney's solenoid design

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2009

Purpose -The purpose of this paper is to show, on a widely used benchmark problem, that normative... more Purpose -The purpose of this paper is to show, on a widely used benchmark problem, that normative knowledge concepts can be incorporated into particle swarm optimization (PSO) algorithms in order to improve their search ability. Design/methodology/approach -Normative knowledge concepts are used within the framework of PSO algorithms in order to influence the cognitive and social components of the particle behaviour. Findings -It is shown that the proposed algorithm can significantly improve the performance of PSO on the selected benchmark problem, in terms of both best and average solutions. Research limitations/implications -Although the chosen benchmark is considered to be representative of typical electromagnetic problems, different test cases may give less satisfactory results. Practical implications -The proposed approach appears to be an efficient general purpose stochastic optimizer for electromagnetic design problems. Originality/value -This paper introduces the use of normative knowledge concepts to control the cognitive and social components of PSO algorithms.

Research paper thumbnail of Electromagnetic optimization based on an improved diversity-guided differential evolution approach and adaptive mutation factor

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2009

Purpose -The purpose of this paper is to show, on a widely used benchmark problem, that adaptive ... more Purpose -The purpose of this paper is to show, on a widely used benchmark problem, that adaptive mutation factors and attractive/repulsive phases guided by population diversity can improve the search ability of differential evolution (DE) algorithms. Design/methodology/approach -An adaptive mutation factor and attractive/repulsive phases guided by population diversity are used within the framework of DE algorithms. Findings -The paper shows that the combined use of adaptive mutation factors and population diversity in order to guide the attractive/repulsive behavior of DE algorithms can provide high-quality solutions with small standard deviation on the selected benchmark problem. Research limitations/implications -Although the chosen benchmark is considered to be representative of typical electromagnetic problems, different test cases may give less satisfactory results. Practical implications -The proposed approach appears to be an efficient general purpose stochastic optimizer for electromagnetic design problems. Originality/value -This paper introduces the use of population diversity in order to guide the attractive/repulsive behavior of DE algorithms.

Research paper thumbnail of Mixed finite element methods and tree-cotree implicit condensation

Calcolo, 1999

Mixed methods are widely used for the finite element analysis of differential problems. From a co... more Mixed methods are widely used for the finite element analysis of differential problems. From a computational point of view, however, the increase in the number of variables from that of the original problem and the properties of the resulting matrices often make a direct implementation of these formulations inadvisable. In this paper, the mixed formulation of Dirichlet's problem for the Laplace operator, discretised using lowest degree Raviart-Thomas elements will be considered as an example. A tree-cotree decomposition of the graph associated with the mesh allows the implementation of an equivalent method, which significantly reduces the number of degrees of freedom and gives rise to a symmetric positive definite linear system. We will refer to this novel method as tcic (Tree-Cotree Implicit Condensation). Numerical results will be presented, and the possibility of extending the proposed method to other cases will be discussed.

Research paper thumbnail of Tecniche DI Ottimizzazione Robusta Per La Progettazione DI Dispositivi Elettromagnetici

Research paper thumbnail of Selected Papers from the 10th International IGTE Symposium on Numerical Field Computation

Research paper thumbnail of A theta-method for eddy currents in time-domain with a discrete geometric approach

In this paper, a time-domain formulation for two-dimensional (2-D) eddy-current problems based on... more In this paper, a time-domain formulation for two-dimensional (2-D) eddy-current problems based on a discrete geometric approach is presented. The method bears very strong similarities with a mass-lumped -type finite-element method (FEM) formulation. Analogies and differences are highlighted, and a numerical experiment is reported.

Research paper thumbnail of Parametric analysis and optimization of the shape of the transitions of a two-port rectangular TEM cell

International Symposium on Electromagnetic Compatibility - EMC EUROPE, 2012

ABSTRACT The design of a two-port TEM cell has been numerically investigated with respect to the ... more ABSTRACT The design of a two-port TEM cell has been numerically investigated with respect to the shape of the transitions connecting the small rectangular terminations, where connectors are fixed, and the TEM cell rectangular central part. At first, using a commercial code, the model has been developed and its validation has been done on an existing TEM cell. Then, starting from this TEM cell, a parametric analysis has been performed. The numerical results are shown and the effects of each parameter on the voltage standing wave ratio are discussed, with simple and practical diagrams useful for the design of a TEM cell. On the basis of the numerical analysis, modifications of the septum were performed on the TEM cell, and a substantial reduction of the highest values of VSWR has been obtained. Finally, a numerical optimized solution for the TEM cell with a maximum VSWR of 1.02 has been identified.

Research paper thumbnail of Optimization of IPM motors with Machaon rotor flux barriers

Digests of the 2010 14th Biennial IEEE Conference on Electromagnetic Field Computation, 2010

ABSTRACT The interior permanent magnet (IPM) motor is normally designed with two or more flux bar... more ABSTRACT The interior permanent magnet (IPM) motor is normally designed with two or more flux barriers per pole. The form of such flux barriers has a direct impact on the torque developed by the IPM motor, including both average value and ripple. The Machaon structure is formed by flux barriers of different shape, greatly reducing the torque ripple. Their shape must be optimized based on the number of poles, slots, winding arrangements, and PM volume. At this aim a stochastic optimizer is applied in order to find the best shape of the flux barriers with the twofold objective of achieving a smooth with a high average value.

Research paper thumbnail of Multi-physics model for regenerative PEM fuel cell energy storage

2013 IEEE International Conference on Industrial Technology (ICIT), 2013

ABSTRACT Electrochemical storage (ECES) systems are expected to become increasingly important and... more ABSTRACT Electrochemical storage (ECES) systems are expected to become increasingly important and widespread in the coming years, with the expansion of renewable energy sources, smart grids and electrical vehicles. Special advantages can be provided by those ECESs which can be independently sized in power and stored energy. Some of the most promising technologies of this type are redox flow batteries and fuel cells combined to electrolyzers. Both these technologies are under extensive R&D programs, aimed at improving their performance. As regards the latter, regenerative fuel cells (R-FCs) provide both charge and discharge functions in the same device. This paper presents a unified model able to describe both these operation modes of R-FCs of the PEM (polymer electrolyte membrane) type (R-PEMFC). The model takes into account the dependence of the electrical quantities and parameters on the major physical-chemical variables and can be used to address structural and operational optimizations.

Research paper thumbnail of Impedance Analysis of a Domestic Induction Appliance with Energy− Efficient Cookware

Research paper thumbnail of Computing Eddy Currents in Thin Shells of Arbitrary Topology by Mesh Analysis

Research paper thumbnail of Enhanced Identification of Hidden Conductive Objects with Deterministic and Stochastic Methods

Research paper thumbnail of Parallelization and Sparsification of a Surface-Volume Integral Code for Plasma-Antenna Interaction

The ADAMANT (Advanced coDe for Anisotropic Media and ANTennas) code has been developed with the a... more The ADAMANT (Advanced coDe for Anisotropic Media and ANTennas) code has been developed with the aim of computing either the power injected into the plasma by RF antennas in the case of thrusters for space applications, or the radiation pattern of antennas that rely on partially ionized gas to radiate electromagnetic waves. The code implements the numerical solution of coupled surface-volume integral equations by the Method of Moments, which lends itself to parallel execution. The parallelization and sparsification of the assembling phase are discussed, and results concerning the speed-up and memory use for different test cases are presented.

Research paper thumbnail of Linear systems of equations arising in the (almost) FEM solution of low-frequency electromagnetic problems

Numerical Mathematics and Advanced Applications, 2003

ABSTRACT This paper discusses the linear algebra implications of the solution of Maxwell’s equati... more ABSTRACT This paper discusses the linear algebra implications of the solution of Maxwell’s equations including materials, topology, space discretization, coupling, duality and graph theoretical techniques. In addition some commercial and research codes are described.

Research paper thumbnail of Electromagnetic Device Optimization with Stochastic Methods

Stochastic Optimization - Seeing the Optimal for the Uncertain, 2011

Research paper thumbnail of A field‐based finite element method for magnetostatics derived from an error minimization approach

International Journal for Numerical Methods in Engineering, 2000

ABSTRACT Cited By (since 1996): 5, Export Date: 19 July 2012, Source: Scopus, CODEN: IJNMB, doi: ... more ABSTRACT Cited By (since 1996): 5, Export Date: 19 July 2012, Source: Scopus, CODEN: IJNMB, doi: 10.1002/1097-0207(20001010)49:4<573::AID-NME964>3.0.CO;2-N, Language of Original Document: English, Correspondence Address: Alotto, P.; Universita di Genova, Genova, Italy

Research paper thumbnail of A FIT Formulation of Bianisotropic Materials Over Polyhedral Grids

IEEE Transactions on Magnetics, 2000

ABSTRACT Modeling bianisotropic constitutive equations, i.e., magnetoelectric coupling, in electr... more ABSTRACT Modeling bianisotropic constitutive equations, i.e., magnetoelectric coupling, in electromagnetics simulation is increasingly important, in particular in metamaterials applications. This paper introduces for the first time such constitutive relationships in the framework of finite integration technique and, furthermore, does so by allowing full generality in the discretization through arbitrary polyhedral grids. The resulting formulation is consistent, stable, and preserves the thermodynamic properties of the bianisotropic constitutive equations because of the energetic approach used to construct the interpolating functions.

Research paper thumbnail of Tree-Cotree implicit condensation in magnetostatics

IEEE Transactions on Magnetics, 2000

ABSTRACT A tree-cotree decomposition of the graph associated with a finite-element mesh allows th... more ABSTRACT A tree-cotree decomposition of the graph associated with a finite-element mesh allows the implementation of a method which is equivalent to a mixed one but which gives rise to a symmetric positive definite linear system with a reduced number of unknowns. We will refer to this method as TCIC (Tree-Cotree Implicit Condensation). A possible preconditioning scheme for the resulting linear system is presented and the effect of the choice of particular tree-cotree decompositions is discussed from the point of view of numerical performance

Research paper thumbnail of Matrix Properties of a Vector Potential Cell Method for Magnetostatics

IEEE Transactions on Magnetics, 2004

In this paper, a proof of the symmetry of the system matrix arising in a class of vector potentia... more In this paper, a proof of the symmetry of the system matrix arising in a class of vector potential cell methods with nonsymmetric material matrices is presented. Some remarks on how to construct other schemes with symmetric system matrices are also presented. The explicit expression of the matrix entries derived in order to prove the symmetry is also used to show that this matrix is identical to the one arising in the standard edge finite-element method. Finally, some remarks on discrete regularizations of these formulations are given.

Research paper thumbnail of An adaptive mixed formulation for 3D magnetostatics

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2000

ABSTRACT Cited By (since 1996): 1, Export Date: 19 July 2012, Source: Scopus, CODEN: CODUD, Langu... more ABSTRACT Cited By (since 1996): 1, Export Date: 19 July 2012, Source: Scopus, CODEN: CODUD, Language of Original Document: English, Correspondence Address: Alotto, P.; Univ of Genoa, Genoa, Italy, References: Alotto, P., Delfino, F., Molfino, P., Nervi, M., Penigia, I., A mixed face-edge finite element formulation for 3D magnetostatic problems (1998) IEEE Trans. on Magnetics, 34 (5), pp. 2445-2448;

Research paper thumbnail of Particle swarm optimization combined with normative knowledge applied to Loney's solenoid design

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2009

Purpose -The purpose of this paper is to show, on a widely used benchmark problem, that normative... more Purpose -The purpose of this paper is to show, on a widely used benchmark problem, that normative knowledge concepts can be incorporated into particle swarm optimization (PSO) algorithms in order to improve their search ability. Design/methodology/approach -Normative knowledge concepts are used within the framework of PSO algorithms in order to influence the cognitive and social components of the particle behaviour. Findings -It is shown that the proposed algorithm can significantly improve the performance of PSO on the selected benchmark problem, in terms of both best and average solutions. Research limitations/implications -Although the chosen benchmark is considered to be representative of typical electromagnetic problems, different test cases may give less satisfactory results. Practical implications -The proposed approach appears to be an efficient general purpose stochastic optimizer for electromagnetic design problems. Originality/value -This paper introduces the use of normative knowledge concepts to control the cognitive and social components of PSO algorithms.

Research paper thumbnail of Electromagnetic optimization based on an improved diversity-guided differential evolution approach and adaptive mutation factor

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2009

Purpose -The purpose of this paper is to show, on a widely used benchmark problem, that adaptive ... more Purpose -The purpose of this paper is to show, on a widely used benchmark problem, that adaptive mutation factors and attractive/repulsive phases guided by population diversity can improve the search ability of differential evolution (DE) algorithms. Design/methodology/approach -An adaptive mutation factor and attractive/repulsive phases guided by population diversity are used within the framework of DE algorithms. Findings -The paper shows that the combined use of adaptive mutation factors and population diversity in order to guide the attractive/repulsive behavior of DE algorithms can provide high-quality solutions with small standard deviation on the selected benchmark problem. Research limitations/implications -Although the chosen benchmark is considered to be representative of typical electromagnetic problems, different test cases may give less satisfactory results. Practical implications -The proposed approach appears to be an efficient general purpose stochastic optimizer for electromagnetic design problems. Originality/value -This paper introduces the use of population diversity in order to guide the attractive/repulsive behavior of DE algorithms.

Research paper thumbnail of Mixed finite element methods and tree-cotree implicit condensation

Calcolo, 1999

Mixed methods are widely used for the finite element analysis of differential problems. From a co... more Mixed methods are widely used for the finite element analysis of differential problems. From a computational point of view, however, the increase in the number of variables from that of the original problem and the properties of the resulting matrices often make a direct implementation of these formulations inadvisable. In this paper, the mixed formulation of Dirichlet's problem for the Laplace operator, discretised using lowest degree Raviart-Thomas elements will be considered as an example. A tree-cotree decomposition of the graph associated with the mesh allows the implementation of an equivalent method, which significantly reduces the number of degrees of freedom and gives rise to a symmetric positive definite linear system. We will refer to this novel method as tcic (Tree-Cotree Implicit Condensation). Numerical results will be presented, and the possibility of extending the proposed method to other cases will be discussed.

Research paper thumbnail of Tecniche DI Ottimizzazione Robusta Per La Progettazione DI Dispositivi Elettromagnetici

Research paper thumbnail of Selected Papers from the 10th International IGTE Symposium on Numerical Field Computation

Research paper thumbnail of A theta-method for eddy currents in time-domain with a discrete geometric approach

In this paper, a time-domain formulation for two-dimensional (2-D) eddy-current problems based on... more In this paper, a time-domain formulation for two-dimensional (2-D) eddy-current problems based on a discrete geometric approach is presented. The method bears very strong similarities with a mass-lumped -type finite-element method (FEM) formulation. Analogies and differences are highlighted, and a numerical experiment is reported.

Research paper thumbnail of Parametric analysis and optimization of the shape of the transitions of a two-port rectangular TEM cell

International Symposium on Electromagnetic Compatibility - EMC EUROPE, 2012

ABSTRACT The design of a two-port TEM cell has been numerically investigated with respect to the ... more ABSTRACT The design of a two-port TEM cell has been numerically investigated with respect to the shape of the transitions connecting the small rectangular terminations, where connectors are fixed, and the TEM cell rectangular central part. At first, using a commercial code, the model has been developed and its validation has been done on an existing TEM cell. Then, starting from this TEM cell, a parametric analysis has been performed. The numerical results are shown and the effects of each parameter on the voltage standing wave ratio are discussed, with simple and practical diagrams useful for the design of a TEM cell. On the basis of the numerical analysis, modifications of the septum were performed on the TEM cell, and a substantial reduction of the highest values of VSWR has been obtained. Finally, a numerical optimized solution for the TEM cell with a maximum VSWR of 1.02 has been identified.

Research paper thumbnail of Optimization of IPM motors with Machaon rotor flux barriers

Digests of the 2010 14th Biennial IEEE Conference on Electromagnetic Field Computation, 2010

ABSTRACT The interior permanent magnet (IPM) motor is normally designed with two or more flux bar... more ABSTRACT The interior permanent magnet (IPM) motor is normally designed with two or more flux barriers per pole. The form of such flux barriers has a direct impact on the torque developed by the IPM motor, including both average value and ripple. The Machaon structure is formed by flux barriers of different shape, greatly reducing the torque ripple. Their shape must be optimized based on the number of poles, slots, winding arrangements, and PM volume. At this aim a stochastic optimizer is applied in order to find the best shape of the flux barriers with the twofold objective of achieving a smooth with a high average value.

Research paper thumbnail of Multi-physics model for regenerative PEM fuel cell energy storage

2013 IEEE International Conference on Industrial Technology (ICIT), 2013

ABSTRACT Electrochemical storage (ECES) systems are expected to become increasingly important and... more ABSTRACT Electrochemical storage (ECES) systems are expected to become increasingly important and widespread in the coming years, with the expansion of renewable energy sources, smart grids and electrical vehicles. Special advantages can be provided by those ECESs which can be independently sized in power and stored energy. Some of the most promising technologies of this type are redox flow batteries and fuel cells combined to electrolyzers. Both these technologies are under extensive R&D programs, aimed at improving their performance. As regards the latter, regenerative fuel cells (R-FCs) provide both charge and discharge functions in the same device. This paper presents a unified model able to describe both these operation modes of R-FCs of the PEM (polymer electrolyte membrane) type (R-PEMFC). The model takes into account the dependence of the electrical quantities and parameters on the major physical-chemical variables and can be used to address structural and operational optimizations.

Research paper thumbnail of Impedance Analysis of a Domestic Induction Appliance with Energy− Efficient Cookware

Research paper thumbnail of Computing Eddy Currents in Thin Shells of Arbitrary Topology by Mesh Analysis

Research paper thumbnail of Enhanced Identification of Hidden Conductive Objects with Deterministic and Stochastic Methods

Research paper thumbnail of Parallelization and Sparsification of a Surface-Volume Integral Code for Plasma-Antenna Interaction

The ADAMANT (Advanced coDe for Anisotropic Media and ANTennas) code has been developed with the a... more The ADAMANT (Advanced coDe for Anisotropic Media and ANTennas) code has been developed with the aim of computing either the power injected into the plasma by RF antennas in the case of thrusters for space applications, or the radiation pattern of antennas that rely on partially ionized gas to radiate electromagnetic waves. The code implements the numerical solution of coupled surface-volume integral equations by the Method of Moments, which lends itself to parallel execution. The parallelization and sparsification of the assembling phase are discussed, and results concerning the speed-up and memory use for different test cases are presented.