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Article
Publication date: 1 June 2001

Federico Delfino, Andrea Manella, Paolo Molfino and Mansueto Rossi

The application of the equivalent source methods for the numerical calculation of the total magnetic force acting upon a permanent magnet is proposed. These methods are formulated…

730

Abstract

The application of the equivalent source methods for the numerical calculation of the total magnetic force acting upon a permanent magnet is proposed. These methods are formulated in terms of the external field, which allows the complete avoidance of the numerical inaccuracies affecting force computation due to the singularity of the self‐field of the magnet on its edges. It is shown, with the help of some 2D and 3D test cases, that the proposed formulae provide reliable and stable results, even when the FEM mesh is not refined. Such results have also been compared with those derived from more traditional methods, such as the surface integration of the Maxwell’s stress tensor and the virtual work method, exhibiting better precision and lower computational costs.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 20 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 September 2003

Federico Delfino, Renato Procopio, Mansueto Rossi and Mario Nervi

A general method to study the response of a system of multiconductors, lying above a perfectly conducting ground and excited by a HF electromagnetic field wave, is presented in…

346

Abstract

A general method to study the response of a system of multiconductors, lying above a perfectly conducting ground and excited by a HF electromagnetic field wave, is presented in this paper. The governing system of integro‐differential equations is solved by means of a numerical procedure based on a Fourier series transformation. It can be proved that the series in which the unknowns of the problem, namely the currents along the conductors, are developed converge to the exact solution and only few terms are needed. The obtained results have been compared with those of a widely employed scattering code, showing faster performances for a given accuracy. Therefore, the algorithm can be seen as a more accurate alternative to the classical transmission line theory (TL) for all the situations (short transmission line, interconnects, etc.) in which the line geometrical parameters and the frequencies of interest make TL a rough approximation.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 22 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 19 June 2007

P. Alotto, A. De Cian, G. Molinari and M. Rossi

To show a possible implementation of surface impedance boundary conditions (SIBCs) in a time domain formulation based on the cell method (CM).

292

Abstract

Purpose

To show a possible implementation of surface impedance boundary conditions (SIBCs) in a time domain formulation based on the cell method (CM).

Design/methodology/approach

The implementation is based on vector fitting (VF), a technique which allows a time domain representation of a rational approximation of the surface impedance to be found.

Findings

It is shown that very little computational effort is needed to find a very good VF approximation of simple SIBCs and that such approximation is easily fitted into existing CM codes.

Research limitations/implications

The extension to higher order SIBCs has not been taken into account.

Practical implications

The proposed approach avoids the use of convolution integrals, is accurate and easy to implement.

Originality/value

This paper introduces the use of VF for the approximate time domain representation of SIBCs.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 26 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

Available. Open Access. Open Access
Article
Publication date: 14 August 2023

Bodour Mubarak, Maisa Ahmed, Nahed Hussein and Marwa Ezz El-Din Ibrahim

This study aims to evaluate the caffeinated drinks, levels of vitamin D and calcium in the blood, and their relationship to bone mineral density (BMD) in osteoporotic women in…

1556

Abstract

Purpose

This study aims to evaluate the caffeinated drinks, levels of vitamin D and calcium in the blood, and their relationship to bone mineral density (BMD) in osteoporotic women in Al-Ahsa Saudi Arabia.

Design/methodology/approach

This study included 85 women over approximately 18 months with ages ranging from 40 to 70 years who were evaluated in the laboratory via blood analysis. Moreover, sociodemographic data and information on health and nutritional awareness were collected via a questionnaire. The BMD was measured by dual-energy X-ray absorptiometry (DXA) and considered osteopenia when the T value total of the lumbar spine or hip was between −1 and −2.5 and osteoporosis < −2.5. Blood levels of vitamin D and calcium were measured via blood analysis.

Findings

There were 54.1% and 45.9% of women who suffered from osteoporosis and low BMD, respectively. There was a significant difference in the number of osteoporotic, and low bone mineral mass groups in marital status (p = 0.04), but no difference was found in age and educational level. A significant difference (p = 0.01) between low bone mass and osteoporosis groups in heights. BMD was significantly and negatively correlated with vitamin D in the blood in individuals with osteoporosis (r = −0.358, P = 0.014). In addition, there was a significant negative correlation between calcium in the blood and total samples (r = −0.355, P = 0.0578). There was a negative significant relationship between calcium supplements and BMD in individuals with low BMD (rt = −0.279, P = 0.041). There was a significant association between cola intake with the occurrence of low BMD (p = 0.027), whereas tea drinking was not associated with risk in both groups.

Originality/value

The study indicated that there is a direct relationship between osteoporosis and low bone mass with different variables. This study was conducted to address the lack of research related to the levels of vitamin D and calcium in the blood and their relationship with BMD in women with low BMD and osteoporosis in Al-Ahsa province-KSA.

Details

Arab Gulf Journal of Scientific Research, vol. 42 no. 3
Type: Research Article
ISSN: 1985-9899

Keywords

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