Piergiorgio Alotto, Paolo Di Barba, Alessandro Formisano, Gabriele Maria Lozito, Raffaele Martone, Maria Evelina Mognaschi, Maurizio Repetto, Alessandro Salvini and Antonio Savini
Inverse problems in electromagnetism, namely, the recovery of sources (currents or charges) or system data from measured effects, are usually ill-posed or, in the numerical…
Abstract
Purpose
Inverse problems in electromagnetism, namely, the recovery of sources (currents or charges) or system data from measured effects, are usually ill-posed or, in the numerical formulation, ill-conditioned and require suitable regularization to provide meaningful results. To test new regularization methods, there is the need of benchmark problems, which numerical properties and solutions should be well known. Hence, this study aims to define a benchmark problem, suitable to test new regularization approaches and solves with different methods.
Design/methodology/approach
To assess reliability and performance of different solving strategies for inverse source problems, a benchmark problem of current synthesis is defined and solved by means of several regularization methods in a comparative way; subsequently, an approach in terms of an artificial neural network (ANN) is considered as a viable alternative to classical regularization schemes. The solution of the underlying forward problem is based on a finite element analysis.
Findings
The paper provides a very detailed analysis of the proposed inverse problem in terms of numerical properties of the lead field matrix. The solutions found by different regularization approaches and an ANN method are provided, showing the performance of the applied methods and the numerical issues of the benchmark problem.
Originality/value
The value of the paper is to provide the numerical characteristics and issues of the proposed benchmark problem in a comprehensive way, by means of a wide variety of regularization methods and an ANN approach.
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Paolo Di Barba and Antonio Savini
The purpose of this paper is to propose a method, reducing the order of the analysis problem, to help the solution of optimal shape design problems in electricity and magnetism.
Abstract
Purpose
The purpose of this paper is to propose a method, reducing the order of the analysis problem, to help the solution of optimal shape design problems in electricity and magnetism.
Design/methodology/approach
The proposed method, the background of which relies on the generalized Thévenin theorem, exploits a principle of field diakoptics.
Findings
After assessing the proposed method on a benchmark of inverse magnetostatics, the shape optimisation of the stress‐control ring in a power transformer is considered as the case study.
Originality/value
The proposed method makes it possible to reduce the cost of an optimisation procedure, when the direct problem is solved by means of finite‐element analysis.
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Paolo Di Barba, Maria Evelina Mognaschi, Guido Nolte, Ryszard Palka and Antonio Savini
The purpose of this paper is to develop a source reconstruction technique, applied to a case study in biomagnetism, using both evolutionary optimization and regularization…
Abstract
Purpose
The purpose of this paper is to develop a source reconstruction technique, applied to a case study in biomagnetism, using both evolutionary optimization and regularization techniques.
Design/methodology/approach
The magnetic field, produced by a current dipole in a spheroidal domain modeling the head, is calculated. Although the model is very simple, the magnetic effect of a brain source is appropriately simulated. In order to solve the source identification problem, the following approaches have been implemented: a single‐objective minimization of a residual function, based on an evolutionary algorithm, is applied first; then, the L‐curve criterion for regularization is implemented by means of an iterative search.
Findings
A variable number of unknown parameters, defining direction and magnitude of the current dipole, have been considered. As a consequence, several optimization problems are solved: a technique based on the use of the lead field matrix identifies the source with the smallest error. Eventually, an iterative procedure based on Tikhonov regularization is proposed. The algorithm is tested with and without noise affecting data. The results showed an accuracy comparable to that obtained independently with the optimization approach.
Originality/value
A model problem in inverse biomagnetism, which is both simple and significant, has been formulated and solved. The magnetic source of brain activity is reconstructed in a fast way and with small errors by means of two techniques of field inversion.
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Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community…
Abstract
Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.
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One common feature of different variants of participatory and action research is rejection of technocratic, undemocratic elements in science and inquiry, aiming to break the…
Abstract
One common feature of different variants of participatory and action research is rejection of technocratic, undemocratic elements in science and inquiry, aiming to break the dominance of traditional academic views of science. These variants open up broader participation of people, and emancipate knowledge creation for the production of actionable knowledge with transformative potentials. The purpose of this chapter is to recognize and clarify a striving for knowledge democracy in these explicit or implicit democratizing ambitions and tendencies in the sense of broadening the participation of concerned parties in research and development work on open and equal terms. This recent concept, still in the process of formulation, has been proposed as a global mobilizing and unifying thinking for distributed networks and movements for participatory oriented research. The concept and movement had an initial embedding in the First Global Assembly for Knowledge Democracy in June 2017, Cartagena, Columbia. The purpose of the chapter is to elaborate on the meaning of knowledge democracy as a vision for the participatory and action research community. Particularly I will distinguish between different orientation to knowledge democracy, and the character of the logic of a more, open, democratic and coproductive science that can be a carrier of it.
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Roberta Bertani, Flavio Ceretta, Paolo Di Barba, Fabrizio Dughiero, Michele Forzan, Rino Antonio Michelin, Paolo Sgarbossa, Elisabetta Sieni and Federico Spizzo
Magnetic fluid hyperthermia experiment requires a uniform magnetic field in order to control the heating rate of a magnetic nanoparticle fluid for laboratory tests. The automated…
Abstract
Purpose
Magnetic fluid hyperthermia experiment requires a uniform magnetic field in order to control the heating rate of a magnetic nanoparticle fluid for laboratory tests. The automated optimal design of a real-life device able to generate a uniform magnetic field suitable to heat cells in a Petri dish is presented. The paper aims to discuss these issues.
Design/methodology/approach
The inductor for tests has been designed using finite element analysis and evolutionary computing coupled to design of experiments technique in order to take into account sensitivity of solutions.
Findings
The geometry of the inductor has been designed and a laboratory prototype has been built. Results of preliminary tests, using a previously synthesized and characterized magneto fluid, are presented.
Originality/value
Design of experiment approach combined with evolutionary computing has been used to compute the solution sensitivity and approximate a 3D Pareto front. The designed inductor has been tested in an experimental set-up.