E. Costamagna, P. Di Barba and A. Savini
The paper seeks to present a methodology using the numerical Schwarz‐Christoffel (SC) transformation in order to extract a subdomain from a simply‐connected source‐free…
Abstract
Purpose
The paper seeks to present a methodology using the numerical Schwarz‐Christoffel (SC) transformation in order to extract a subdomain from a simply‐connected source‐free two‐dimensional field domain. The aims to present an application to the design of an electrostatic micromotor.
Design/methodology/approach
The methodology can be usefully applied to reduce the size of complicated field regions with irregularly shaped boundaries. In the subdomain, finite‐element (FEM) analyses can then be performed with limited computational effort.
Findings
The synthesis of the conditions along the sub‐domain boundary, which is piecewise approximated by potential and flux lines, is carried out by performing repeated field analyses. Several comparisons among FEM and SC results are presented, to validate the proposed approach.
Originality/value
Refined techniques of conformal mapping are used in order to extract a suitable subdomain from a large field domain of an electrostatic micromotor. This allows one to focus the analysis directly on the region where the field distribution is to be investigated.
Details
Keywords
E. Costamagna, P. Di Barba and R. Palka
The purpose of this paper is to describe a twofold methodology for evaluating the force between field excitation system and bulk in a magnetic‐levitation device based on…
Abstract
Purpose
The purpose of this paper is to describe a twofold methodology for evaluating the force between field excitation system and bulk in a magnetic‐levitation device based on high‐temperature‐superconductors (HTS). The paper focuses on two‐dimensional field models for HTS bulks. As far as field analysis is concerned, the finite‐element method in two or three dimensions is used. Alternatively, the conformal mapping approach provides a flexible and accurate calculation tool, useful for the optimization of superconducting bearings.
Design/methodology/approach
Powerful mapping algorithms, developed recently for Schwarz‐Christoffel‐like transformations, have proven successful in analyzing the fields, both in the activation and in the operation condition of superconductor devices.
Findings
Assuming small displacements of the superconductor sample with respect to the excitation magnets, the force‐displacement curve was obtained for operational field cooling via Schwarz‐Christoffel maps.
Originality/value
The specific theory used is the substitution theorem for magnetic fields, along with its capability to take complex geometries into account, making it possible to model devices for real‐life applications. Using only a scalar potential, the procedure proposed for computing fields proves, in the conformally‐mapped plane, the superposition method already introduced in FEM‐based models.
Details
Keywords
E. Costamagna, P. Di Barba and A. Savini
This paper sets out to provide a numerical procedure for field analysis and shape design for a class of MEMS devices.
Abstract
Purpose
This paper sets out to provide a numerical procedure for field analysis and shape design for a class of MEMS devices.
Design/methodology/approach
The proposed numerical procedure for field analysis relies on numerical inversion of Schwarz‐Christoffel (SC) transformations for doubly‐connected regions: the geometry of a given micromotor is mapped into an annulus, where the non‐radial field excited by the transformed electrodes is computed. In turn, the shape design relies on the definition of non‐dominated solution according to the Pareto optimality conditions.
Findings
The SC approach proposed here allows the designer to evaluate both driving torque and radial force characteristics of the device with suitable accuracy within short CPU times. In turn, this allows one to perform repeated field analyses for a large number of feasible geometries and to use enumerative approaches to design optimization. By this means, a 3D objective space is investigated to identify the optimal shape of an electrostatic micromotor, subject to prescribed constraints.
Originality/value
To the best of one's knowledge, the combination of SC transformations and Pareto optimality is an unprecedented method for MEMS design. In particular, it is expected that the proposed SC tools will supply a fast and accurate computation to compare or supplement results from FEM tools, when a large number of geometries should be analysed. This could be particularly useful in the preliminary steps of a design procedure for a given class of devices.
Details
Keywords
Stefano Costa and Eugenio Costamagna
This paper aims to solve inhomogeneous dielectric problems by matching boundary conditions at the interfaces among homogeneous subdomains. The capabilities of Hilbert transform…
Abstract
Purpose
This paper aims to solve inhomogeneous dielectric problems by matching boundary conditions at the interfaces among homogeneous subdomains. The capabilities of Hilbert transform computations are deeply investigated in the case of limited numbers of samples, and a refined model is presented by means of investigating accuracies in a case study with three subdomains.
Design/methodology/approach
The accuracies, refined by Richardson extrapolation to zero error, are compared to finite element (FEM) and finite difference methods. The boundary matching procedures can be easily applied to the results of a previous Schwarz–Christoffel (SC) conformal mapping stage in SC + BC procedures, to cope with field singularities or with open boundary problems.
Findings
The proposed field computations are of general interest both for electrostatic and magnetostatic field analysis and optimization. They can be useful as comparison tools for FEM results or when severe field singularities can impair the accuracies of other methods.
Research limitations/implications
This static field methodology, of course, can be used to analyse transverse electro magnetic (TEM) or quasi-TEM propagation modes. It is possible that, in some case, these may make a contribution to the analysis of axis symmetrical problems.
Originality/value
The most relevant result is the possible introduction of SC + BC computations as a standard tool for solving inhomogeneous dielectric field problems.
Details
Keywords
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.
Details
Keywords
Stefano Costa, Eugenio Costamagna and Paolo Di Barba
A novel method for modelling permanent magnets is investigated based on numerical approximations with rational functions. This study aims to introduce the AAA algorithm and other…
Abstract
Purpose
A novel method for modelling permanent magnets is investigated based on numerical approximations with rational functions. This study aims to introduce the AAA algorithm and other recently developed, cutting-edge mathematical tools, which provide outstandingly fast and accurate numerical computation of potentials and vector fields.
Design/methodology/approach
First, the AAA algorithm is briefly introduced along with its main variants and other advanced mathematical tools involved in the modelling. Then, the analysis of a circular Halbach array with a one-pole pair is carried out by means of the AAA-least squares method, focusing on vector potential and flux density in the bore and validating results by means of classic finite element software. Finally, the investigation is completed by a finite difference analysis.
Findings
AAA methods for field analysis prove to be strikingly fast and accurate. Results are in excellent agreement with those provided by the finite element model, and the very good agreement with those from finite differences suggests future improvements. They are also easy programming; the MATLAB code is less than 200 lines. This indicates they can provide an effective tool for rapid analysis.
Research limitations/implications
AAA methods in magnetostatics are novel, but their extension to analogous physical problems seems straightforward. Being a meshless method, it is unlikely that local non-linearities can be considered. An aspect of particular interest, left for future research, is the capability of handling inhomogeneous domains, i.e. solving general interface problems.
Originality/value
The authors use cutting-edge mathematical tools for the modelling of complex physical objects in magnetostatics.
Details
Keywords
Introduces the fourth and final chapter of the ISEF 1999 Proceedings by stating electric and magnetic fields are influenced, in a reciprocal way, by thermal and mechanical fields…
Abstract
Introduces the fourth and final chapter of the ISEF 1999 Proceedings by stating electric and magnetic fields are influenced, in a reciprocal way, by thermal and mechanical fields. Looks at the coupling of fields in a device or a system as a prescribed effect. Points out that there are 12 contributions included ‐ covering magnetic levitation or induction heating, superconducting devices and possible effects to the human body due to electric impressed fields.
Details
Keywords
Liang Yan, Lei Zhang, Zongxia Jiao, Hongjie Hu, Chin-Yin Chen and I-Ming Chen
Force output is extremely important for electromagnetic linear machines. The purpose of this study is to explore new permanent magnet (PM) array and winding patterns to increase…
Abstract
Purpose
Force output is extremely important for electromagnetic linear machines. The purpose of this study is to explore new permanent magnet (PM) array and winding patterns to increase the magnetic flux density and thus to improve the force output of electromagnetic tubular linear machines.
Design/methodology/approach
Based on investigations on various PM patterns, a novel dual Halbach PM array is proposed in this paper to increase the radial component of flux density in three-dimensional machine space, which in turn can increase the force output of tubular linear machine significantly. The force outputs and force ripples for different winding patterns are formulated and analyzed, to select optimized structure parameters.
Findings
The proposed dual Halbach array can increase the radial component of flux density and force output of tubular linear machines effectively. It also helps to decrease the axial component of flux density and thus to reduce the deformation and vibration of machines. By using analytical force models, the influence of winding patterns and structure parameters on the machine force output and force ripples can be analyzed. As a result, one set of optimized structure parameters are selected for the design of electromagnetic tubular linear machines.
Originality/value
The proposed dual Halbach array and winding patterns are effective ways to improve the linear machine performance. It can also be implemented into rotary machines. The analyzing and design methods could be extended into the development of other electromagnetic machines.
Details
Keywords
Xisto L. Travassos, Sérgio L. Avila and Nathan Ida
Ground Penetrating Radar is a multidisciplinary Nondestructive Evaluation technique that requires knowledge of electromagnetic wave propagation, material properties and antenna…
Abstract
Ground Penetrating Radar is a multidisciplinary Nondestructive Evaluation technique that requires knowledge of electromagnetic wave propagation, material properties and antenna theory. Under some circumstances this tool may require auxiliary algorithms to improve the interpretation of the collected data. Detection, location and definition of target’s geometrical and physical properties with a low false alarm rate are the objectives of these signal post-processing methods. Basic approaches are focused in the first two objectives while more robust and complex techniques deal with all objectives at once. This work reviews the use of Artificial Neural Networks and Machine Learning for data interpretation of Ground Penetrating Radar surveys. We show that these computational techniques have progressed GPR forward from locating and testing to imaging and diagnosis approaches.
Details
Keywords
Rodrigo Costamagna, Sandra Idrovo-Carlier, Pedro Mendi and Alfredo Rodriguez
This paper takes a closer look at the way firms combine human resources from different departments by analyzing firm-level data obtained from a series of innovation surveys…
Abstract
Purpose
This paper takes a closer look at the way firms combine human resources from different departments by analyzing firm-level data obtained from a series of innovation surveys conducted in Colombia by Departamento Administrativo Nacional de Estadística (DANE). In particular, the authors inquire into whether there are differences in innovation performance between firms that combine human resources from different departments and firms that choose not to do so.
Design/methodology/approach
The authors apply a complementarity test between firms that combine human resources from different departments and firms that choose not to do so. As performance variables, the authors consider the propensity to innovate, the number of new innovative products that the firm introduces, the proportion of sales coming from products new to the firm and sales from new products as a percentage of current innovation expenditures.
Findings
The authors find that firms with an internal research and development (R&D) department have a better innovation performance, but the authors do not find evidence of the existence of complementarity between workers in R&D and workers in other departments, and the authors find some evidence that suggests substitutability in the case of product innovations.
Practical implications
This paper provides managers with insights about how to deploy employees to improve firm innovation performance of employees.
Originality/value
This paper combines innovation literature with human resources management literature and applies a robust methodology to data not previously tested for the same purposes.
Propósito
Este artículo mira detenidamente la manera en que las empresas colombianas combinan recursos humanos de diferentes departamentos analizando datos de empresas obtenidos de una serie de encuestas sobre innovación realizada en Colombia por el DANE. En concreto, los autores se preguntan si existen diferencias en el desempeño de innovación entre las empresas que combinan recursos humanos de diferentes departamentos y aquellas que eligen no hacerlo.
Diseño/ metodología/ aproximación
Los autores aplican una prueba de complementariedad entre las empresas que combinan recursos humanos de diferentes departamentos y aquellas que eligen no hacerlo. Como variables de desempeño, los autore toman la disposición a innovar; número de nuevos productos innovadores que la empresa introduce, la proporción de venta que ingresa por productos nuevos de la empresa, y venta de nuevos productos como porcentaje de gastos actuales de innovación.
Resultados
Los autores encuentran que las empresas con un departamento de I&D tienen mejor desempeño de innovación, pero no encuentran evidencia de complementariedad entre trabajadores de I&D y trabajadores de otros departamentos. Los autores encontran alguna evidencia que sugiere sustitución en el caso de innovación de producto.
Originalidad
Este artículo combina literatura proveniente del área de innovación con literatura del área de gestión de recursos humanos y aplica una metodología robusta a datos que no han sido analizados previamente con este propósito.
Aplicaciones prácticas
Este artículo ofrece a los gerentes y directivos una mirada distinta sobre cómo desplegar colaboradores en las distintas áreas para mejorar el desempeño de innovación de las firmas.