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Article
Publication date: 13 September 2011

P. Alotto, M. Guarnieri, F. Moro and A. Stella

The purpose of this paper is to simulate in the time domain three‐dimensional electrical, thermal, mechanical coupled contact problems arising in electric resistance…

Abstract

Purpose

The purpose of this paper is to simulate in the time domain three‐dimensional electrical, thermal, mechanical coupled contact problems arising in electric resistance welding (ERW) processes.

Design/methodology/approach

A three‐dimensional multiphysical numerical model for analyzing contact problems is proposed. Electrical and thermal field equations in bulk domains are discretized with the cell method (CM). Welding resistance at contact interfaces is described locally by synthetic statistic parameters and contacting domains are matched together by a non‐overlapping domain decomposition method. Contact pressure distribution is resolved by a finite‐element procedure. The model is validated with 3D FEM software package.

Findings

The semi‐analytical model describing the electric and thermal resistances at contact interfaces can be easily embedded in CM formulations, where problem variables are expressed directly in integral form. Compatibility conditions between contact members are enforced by a domain decomposition approach. System conditioning and computing time are improved by a solution strategy based on the Schur complement method.

Research limitations/implications

The electrical‐thermal analysis is not coupled strongly with the mechanical analysis and contact pressure distribution is assumed to be not depending on thermal stresses, which can be considerable near the contact area where localized joule heating occurs.

Practical implications

Resistance welding processes involve mechanical, electrical, and thermal non‐linear coupled effects that cannot be simulated by standard commercial software packages. The proposed numerical model can be used instead for designing and optimizing ERW processes.

Originality/value

The paper shows that numerical modeling of ERW processes requires a careful prediction of the localized joule heating occurring at the electrode‐material interface. This effect is reconstructed by the proposed approach simulating coupled electrical, thermal, and mechanical effects on different spatial scales.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 7 March 2008

Piergiorgio Alotto, Giambattista Gruosso, Federico Moro and Maurizio Repetto

To propose a novel 3D hybrid approach, based on a discrete formulation of Maxwell equations (the cell method – CM), suitable for solving eddy current problems in unbounded domains.

Abstract

Purpose

To propose a novel 3D hybrid approach, based on a discrete formulation of Maxwell equations (the cell method – CM), suitable for solving eddy current problems in unbounded domains.

Design/methodology/approach

Field equations for magnetodynamics are expressed directly in algebraic form thanks to the CM. The eddy current problem inside bulk conductors is formulated in terms of discrete modified vector potential, whereas magnetic scalar potential is used in order to model the free space. The CM is coupled to the boundary element method by using a surface boundary operator, which maps the surface magnetic fluxes to the surface magnetic scalar potentials. This leads to a unique set of linear equations to be solved in terms of discrete potentials. The eddy currents in bulk conductors are then obtained from discrete potentials.

Findings

It is shown that formulation of hybrid approaches can be simplified by expressing field equations directly in algebraic form without need of weighted residual techniques. An original strategy, based on Green's formula for the magnetic scalar potential, is proposed in order to couple conducting parts to the exterior domain.

Research limitations/implications

Conducting bodies with multiply connected parts cannot be modelled by the proposed approach, since it is based on the magnetic scalar potential. The resulting global matrix is partially dense and non‐symmetric; therefore, standard iterative solvers such as GMRES have to be used.

Practical implications

The proposed approach can be suitably used for analyzing eddy current problems involving models with high degree of complexity, large air domains and moving parts. These are typical of induction heating processes.

Originality/value

This paper proposes a new 3D hybrid approach, based on a discrete formulation of Maxwell equations. A novel coupling strategy relying on integral electromagnetic variables, i.e. magnetic fluxes and magnetic scalar potentials, is devised in order to solve uniquely for eddy currents inside conducting bodies.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 27 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 6 March 2017

Lorenzo Codecasa, Federico Moro and Piergiorgio Alotto

This paper aims to propose a fast and accurate simulation of large-scale induction heating problems by using nonlinear reduced-order models.

Abstract

Purpose

This paper aims to propose a fast and accurate simulation of large-scale induction heating problems by using nonlinear reduced-order models.

Design/methodology/approach

A projection space for model order reduction (MOR) is quickly generated from the first kernels of Volterra’s series to the problem solution. The nonlinear reduced model can be solved with time-harmonic phasor approximation, as the nonlinear quadratic structure of the full problem is preserved by the projection.

Findings

The solution of induction heating problems is still computationally expensive, even with a time-harmonic eddy current approximation. Numerical results show that the construction of the nonlinear reduced model has a computational cost which is orders of magnitude smaller than that required for the solution of the full problem.

Research limitations/implications

Only linear magnetic materials are considered in the present formulation.

Practical implications

The proposed MOR approach is suitable for the solution of industrial problems with a computing time which is orders of magnitude smaller than that required for the full unreduced problem, solved by traditional discretization methods such as finite element method.

Originality/value

The most common technique for MOR is the proper orthogonal decomposition. It requires solving the full nonlinear problem several times. The present MOR approach can be built directly at a negligible computational cost instead. From the reduced model, magnetic and temperature fields can be accurately reconstructed in whole time and space domains.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 16 November 2010

Massimo Guarnieri and Federico Moro

The purpose of this paper is to simulate passive proton exchange membrane fuel cells (PEMFCs) for portable electronic devices by means of a non‐linear lumped circuit based…

Abstract

Purpose

The purpose of this paper is to simulate passive proton exchange membrane fuel cells (PEMFCs) for portable electronic devices by means of a non‐linear lumped circuit based on electrical, mass transfer and electro‐kinetic equations.

Design/methodology/approach

Electrical, mass transfer and electro‐kinetic equations are combined in order to derive a non‐linear lumped circuit. The dynamic circuit model is tested in realistic operating conditions.

Findings

An original equivalent circuit model for simulating the transient behavior of passive PEMFCs is proposed. The PEMFC is represented as a non‐linear equivalent circuit with controlled lumped parameters depending on pressure, temperature, hydration, and system capacity.

Research limitations/implications

Lumped parameters are synthesized assuming a one‐dimensional fuel cell model since layer thicknesses are much smaller than other dimensions. Heat generation and transfer are not modeled even though lumped parameters depend on temperature.

Practical implications

The proposed circuit model can be implemented directly in circuit simulators for designing power management units needed to interface small‐passive PEMFCs and portable electronics such as PDAs, laptops, or mobile phones.

Originality/value

The fuel cell is represented as a non‐linear controlled generator whose parameters are derived directly from multiphysics equations rather than empirical relationships. The dynamic behaviour of PEMFCs can be simulated on completely different times scales, i.e. during transients or during the discharge phase.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 2 December 2019

Cristina Oliveira, Ana Brochado, Sérgio Moro and Paulo Rita

Overall, there is a lack of research using online reviews as a proxy of customer experience when addressing the study of tourism in island destinations.

Abstract

Purpose

Overall, there is a lack of research using online reviews as a proxy of customer experience when addressing the study of tourism in island destinations.

Design/methodology/approach

The current investigation aims to fill this gap by focussing on an African small island developing states, i.e. Cape Verde. This paper reports of tourist reviews extracted from TripAdvisor from “two islands of the senses” as coined by this archipelago’s national tourism organization, specifically Santo Antão and Fogo islands. The data analysis was performed through Leximancer software to generate concepts out of words, followed by themes.

Findings

The present research focussed on experiences in island tourism to identify their main dimensions based on visitors’ narratives in online reviews. The obtained results are of potential value to the literature by contributing to a better understanding of tourist experience in the context of tourism in islands in an understudied country, Cape Verde.

Originality/value

Results are presented and object of discussion vis-à-vis scientific literature and conclusions put forward in this journal paper.

Details

Worldwide Hospitality and Tourism Themes, vol. 11 no. 6
Type: Research Article
ISSN: 1755-4217

Keywords

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Book part
Publication date: 14 August 2015

Philippe Belley, Nathalie Havet and Guy Lacroix

This paper investigates the links between statistical discrimination, mobility, tenure, and wage profiles in the early career of workers. The model assumes that female…

Abstract

This paper investigates the links between statistical discrimination, mobility, tenure, and wage profiles in the early career of workers. The model assumes that female workers’ productivity is noisier and that the noise/signal ratio tapers off more rapidly for male workers. These two assumptions yield numerous theoretical predictions pertaining to gender wage gaps. These predictions are tested using data from the 1979 cohort of the National Longitudinal Survey of Youth. As predicted, we find that men and women have the same wage at the start of their career, but that female wages grow at a slower rate thus generating a gender wage gap.

Details

Gender in the Labor Market
Type: Book
ISBN: 978-1-78560-141-5

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Article
Publication date: 13 November 2020

Natnael Terefe Arega

Unaccompanied refugee minors (URMs) are known to be subjected to several potentially traumatic life events, risking more mental health problems than other populations of…

Abstract

Purpose

Unaccompanied refugee minors (URMs) are known to be subjected to several potentially traumatic life events, risking more mental health problems than other populations of same age. Evidence concerning the mental health of Eritrean URMs in Ethiopia is scarce. This paper aims to present an estimate of probable posttraumatic stress disorder (PTSD) within this group and describes its associations with traumatic life events and participants’ characteristics.

Design/methodology/approach

This cross-sectional quantitative study surveyed a random sample of 384 Eritrean URMs, aged 12–17 years, in the Shimelba refugee camp. The Stressful Life Events (SLE) questionnaire and the Reactions of Adolescents to Traumatic Stress (RATS) questionnaire were used to assess traumatic events and PTSD symptoms, respectively. Descriptive statistics, the chi-square test with the odds-ratio and stepwise regression were used to analyze data.

Findings

Large proportions of the URMs had experienced traumatic events including physical abuse (261, 68%), separation from family against will (240, 62.5%), a stressful life event in which they were in danger (198, 51.6%), and important changes in family life (196, 51%). About 38% of the URMs met the criteria for classifying probable PTSD diagnosis, suggesting that they are likely to have PTSD. The odds-ratio statistic revealed that girls and the oldest age group (15–17 years) were at a greater risk for PTSD. The total score on the SLE appeared to be the robust predictor, explaining 28% of the variance in RATS total scores.

Research limitations/implications

Self-report questionnaires used in this study yield less diagnostic information than extensive interviews. Additional information should be collected from the viewpoint of significant adults (caregivers/ teachers). Such information would be crucial in assessing the degree of impairment in daily functioning and the severity of the symptoms.

Originality/value

Awareness of the stressful experiences and the mental health status of the URMs has implications for taking preventive and curative measures to provide a broad range of intervention programs and psychosocial support.

Details

International Journal of Migration, Health and Social Care, vol. 17 no. 1
Type: Research Article
ISSN: 1747-9894

Keywords

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Book part
Publication date: 14 December 2018

Julie M. Maier and Shannon L. Jette

To examine the exercise experiences of women with obsessive-compulsive disorder (OCD) in order to highlight the complex relationship between mental illness and physical…

Abstract

Purpose

To examine the exercise experiences of women with obsessive-compulsive disorder (OCD) in order to highlight the complex relationship between mental illness and physical activity, as it intersects with other identities and social locations (e.g., gender and sexuality) as well as other mental health conditions (e.g., eating disorders and exercise addiction).

Method

Semi-structured interviews were conducted with 14 women who self-identify as having OCD. A thematic analysis was conducted to understand the role of physical activity in the participants’ lives.

Findings

The participants experience holistic benefits from being physically active. At the same time, however, their symptoms of OCD and related disorders (e.g., eating disorders) make it challenging to be physically active in meaningful and healthy ways.

Implications

Public health messages promoting exercise as a form of therapy must take into account the complex relationship between physical activity and mental illness. Additional research and programing is also needed in order to help women with mental health issues be physically active in safe and enjoyable ways.

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Book part
Publication date: 14 November 2017

Hue Chi Dao and Bruce C. Martin

We contribute to the growing literature examining how social enterprises might best accommodate their hybrid structure when pursuing dual goals of social improvement and…

Abstract

We contribute to the growing literature examining how social enterprises might best accommodate their hybrid structure when pursuing dual goals of social improvement and economic sustainability. Drawing on extant literature, the case is made for why synergy between the social and commercial business models that hybrid social enterprises employ should positively impact effectiveness in delivering organization outcomes. We then develop a method for comparing the synergy between the social and commercial business models employed within and across organizations, and test the method using a sample of seven social enterprises operating in different social fields. Results demonstrate that our method can be applied consistently across a range of social enterprise types and that variation in degree of synergy is considerable with overlap rates ranging from 9% to 77%. Using learning from this exploratory study, we develop propositions describing how and why social entrepreneurs develop business model synergy, the relationship between business model synergy and organizational performance, and suggest future research to test these propositions. Implications for theory development and practice are discussed.

Details

Hybrid Ventures
Type: Book
ISBN: 978-1-78743-078-5

Keywords

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Article
Publication date: 9 September 2013

Piergiorgio Alotto, Massimo Guarnieri, Federico Moro and Andrea Stella

The purpose of this paper is to show the main features of the redox flow battery technology, present the current state-of-the-art of both industrial and research systems…

Abstract

Purpose

The purpose of this paper is to show the main features of the redox flow battery technology, present the current state-of-the-art of both industrial and research systems and to highlight the main research challenges.

Design/methodology/approach

The study is based on an extensive survey of recent literature as well as on the authors' own experience in the modelling of RFB systems.

Findings

RFBs present unique features which make them suitable for distributed storage and thus particularly interesting in the context of smart grids. Current research aims at resolving some outstanding issues which still limit the widespread use of RFBs.

Practical implications

A more widespread use of energy storage technologies, and RFBs in particular, will allow a much higher penetration of renewable energy sources.

Originality/value

The paper presents one of the few comprehensive studies on RFBs including both technological and modelling aspects.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 32 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

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