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Article
Publication date: 7 September 2015

Daniel Klis, Stefan Burgard, Ortwin Farle and Romanus Dyczij-Edlinger

– The purpose of this paper is to determine the broadband frequency response of the impedance matrix of wireless power transfer (WPT) systems comprising litz wire coils.

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Abstract

Purpose

The purpose of this paper is to determine the broadband frequency response of the impedance matrix of wireless power transfer (WPT) systems comprising litz wire coils.

Design/methodology/approach

A finite-element (FE)-based method is proposed which treats the microstructure of litz wires by an auxiliary cell problem. In the macroscopic model, litz wires are represented by a block with a homogeneous, artificial material whose properties are derived from the cell problem. As the frequency characteristics of the material closely resemble a Debye relaxation, it is possible to convert the macroscopic model to polynomial form, which enables the application of model reduction techniques of moment-matching type.

Findings

FE-based model-order reduction using litz wire homogenization provides an efficient approach to the broadband analysis of WPT systems. The error of the reduced-order model (ROM) is comparable to that of the underlying original model and can be controlled by varying the ROM dimension.

Research limitations/implications

Since the present model does not account for displacement currents, the operating frequency of the system must lie well below its first self-resonance frequency.

Practical implications

The proposed method is well-suited for the computer-aided design of WPT systems. It outperforms traditional FE analysis in computational efficiency.

Originality/value

The presented homogenization method employs a new formulation for the cell problem which combines the benefits of several existing approaches. Its incorporation into an order-reduction method enables the fast computation of broadband frequency sweeps.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 5 May 2015

Jill Sperandio and Lavanya Devdas

The purpose of this paper is to examine the importance of lifestyle factors including geographical relocation, accommodation for dual earner careers, and availability of family or…

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Abstract

Purpose

The purpose of this paper is to examine the importance of lifestyle factors including geographical relocation, accommodation for dual earner careers, and availability of family or non-family domestic help on the career choices of women assistant superintendents and superintendents in school districts in the USA. Women’s access to the superintendency continues to make slow progress, a trend traditionally attributed to gender bias. However, working women increasingly make career choices based on perceptions of lifestyle and domestic responsibilities that may self-limit their access to positions that would further their careers.

Design/methodology/approach

The study is set in Pennsylvania, where women occupy 26 percent of superintendents’ positions. Women superintendents and assistant superintendents in 2011-2012 were surveyed regarding their perceptions of the compatibility of the requirements of the position of superintendent with their lifestyle priorities.

Findings

The responses of 109 respondents suggest that the importance they attach to lifestyle factors limit the positions to which they apply. Most respondents would not consider family relocation or long commutes to access positions that would further their career goals. Consideration of partners/spouses work and career needs was rated as of high importance in making career decisions, and the respondents managed domestic household themselves with little expectation or recourse to extended family support or paid domestic help.

Originality/value

The findings suggest that the current demands and characteristics of the superintendency are at odds with lifestyle preferences of women qualified to hold the position, further exacerbating the effects of gender bias that maintain the lack of gender balance in educational decision making at the local level in the USA.

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