MoM impedance integrals in conductive media

During the past decades, much research has been done towards the efficient calculation of impedance integrals in the Method of Moments. However, these results were almost always uniquely concerned with penetrable media. In this contribution, it will be shown how the integrals can be treated in highly conductive media as well. The rapid exponential decline of the Green's function, due to the losses, is the root of all additional complexities. The method as presented here takes care of these problems in a scalable way, i.e. the computation time becomes independent of the conductivity of the material. It is not meant as a replacement for techniques in penetrable media, due to some additional costs, but is - to our knowledge - the only approach that currently exists to efficiently handle conductive media. This paper presents the ideas and techniques in a fairly condensed manner. More information can be found in [1]

Accurate and efficient algorithms for boundary element methods in electromagnetic scattering: a tribute to the work of F. Olyslager

Boundary element methods (BEMs) are an increasingly popular approach to model electromagnetic scattering both by perfect conductors and dielectric objects. Several mathematical, numerical, and computational techniques pullulated from the research into BEMs, enhancing its efficiency and applicability. In designing a viable implementation of the BEM, both theoretical and practical aspects need to be taken into account. Theoretical aspects include the choice of an integral equation for the sought after current densities on the geometry's boundaries and the choice of a discretization strategy (i.e. a finite element space) for this equation. Practical aspects include efficient algorithms to execute the multiplication of the system matrix by a test vector (such as a fast multipole method) and the parallelization of this multiplication algorithm that allows the distribution of the computation and communication requirements between multiple computational nodes. In honor of our former colleague and mentor, F. Olyslager, an overview of the BEMs for large and complex EM problems developed within the Electromagnetics Group at Ghent University is presented. Recent results that ramified from F. Olyslager's scientific endeavors are included in the survey

From 3D scan to body pressure of compression garments

Human bodies come under loads in sports. For safety or other purposes, athletes wear compression garments to help avoid wrong postures or movement. We assessed anthropometrics of elite rowers, and found significant differences with the general population, indicating compression garments would behave differently for the athletes. By combining 3D scanning technique and FEM modelling software, we were able to predict compression garment performance on part of the athlete bodies . Abaqus Explicit solver was applied to simulate movement of athletes actually putting on a compression garment, and to track stress distribution during the process

Results of the SHAPE project

The overall objective of SHAPE project (Adapted Performance Sportswear) is to develop comfortable and well-fitted sportswear for athletes whose body shapes differ from the average population. Body measurements of professional cyclists and rowers were extracted from 3D scans and compared with average Belgian population. Variation of body measurements and skin-sportswear interface pressure upon rowing and cycling postures was additionally investigated. Significant differences were found between rowers and average Belgian males. Rowing and cycling postures had significant influence on most body measurements and pressure. Fit of prototypes developed based on SHAPE-body sizing charts was positively validated by male rowers. Large number of cyclists critically evaluated their present outfit including fit and comfort. Two prototypes were designed according to individual needs of Gsport cyclists and their functionality, comfort and fit were positively evaluated

The significance of Lactobacillus crispatus and L. vaginalis for vaginal health and the negative effect of recent sex: a cross-sectional descriptive study across groups of African women

Background: Women in sub-Saharan Africa are vulnerable to acquiring HIV infection and reproductive tract infections. Bacterial vaginosis (BV), a disruption of the vaginal microbiota, has been shown to be strongly associated with HIV infection. Risk factors related to potentially protective or harmful microbiota species are not known. Methods: We present cross-sectional quantitative polymerase chain reaction data of the Lactobacillus genus, five Lactobacillus species, and three BV-related bacteria (Gardnerella vaginalis, Atopobium vaginae, and Prevotella bivia) together with Escherichia coli and Candida albicans in 426 African women across different groups at risk for HIV. We selected a reference group of adult HIV-negative women at average risk for HIV acquisition and compared species variations in subgroups of adolescents, HIV-negative pregnant women, women engaging in traditional vaginal practices, sex workers and a group of HIV-positive women on combination antiretroviral therapy. We explored the associations between presence and quantity of the bacteria with BV by Nugent score, in relation to several factors of known or theoretical importance. Results: The presence of species across Kenyan, South African and Rwandan women was remarkably similar and few differences were seen between the two groups of reference women in Kenya and South Africa. The Rwandan sex workers and HIV-positive women had the highest Gardnerella vaginalis presence (p = 0.006). Pregnant women had a higher Lactobacillus genus mean log (7.01 genome equivalents (geq)/ml) compared to the reference women (6.08 geq/ml). L. vaginalis (43%) was second to L. iners (81.9%) highly present in women with a normal Nugent score. Recent sexual exposure negatively affected the presence of Lactobacillus crispatus (<0.001), L. vaginalis (p = 0.001), and Lactobacillus genus (p < 0.001). Having more than one sexual partner in the last three months was associated with an increased prevalence of Gardnerella vaginalis (p = 0.044) and L. iners (p = 0.001). Conclusions: Although the composition of species across the studied African countries was similar, the presence of protective species i.e. Lactobacillus crispatus and L. vaginalis in women with a normal Nugent score appeared lower compared to non-African studies. Furthermore, Lactobacillus species were negatively affected by sexual behavioural. Strategies to support protective Lactobacillus species are urgently needed

Effect of biaxial stretch and domestic washing on air permeability of elastic knitted fabrics for sportswear

This paper introduces a non-automatic device to apply biaxial stretch and investigates the effect of biaxial stretch and domestic washing on air permeability of polyamide-elastane knitted fabrics for sportswear. Air permeability of the selected fabrics significantly increased upon biaxial stretch, regardless the fabric type and stretch level (5% or 10%) applied. Generally, air permeability of relaxed fabrics decreased due to slight shrinkage that occurred upon washing, but domestic washing was not found to have a statistical significant influence on air permeability of the selected fabrics. The manual device proposed applies stretch in one or two directions, it is robust and easy to handle, and fabric preparation is quite straightforward. The fabric holder used in this study is particularly suited to the head of the air permeability tester and the level of stretch applied depends on type of fabric

Low frequency stability of the mixed discretization of the MFIE

Recently, a novel discretization for the magnetic field integral equation (MFIE) was presented. This discretization involves both Rao-Wilton-Glisson (RWG) basis functions and Buffa-Christiansen (BC) basis functions and is dubbed `mixed'. The scheme conforms to the functional spaces most natural to electromagnetics and thus can be expected to yield more accurate results. In this contribution, this intuition is corroborated by an analysis of the low frequency behavior of the classical and mixed discretizations of the MFIE. It is proved that the mixed discretization of the MFIE yields accurate results at very low frequencies whereas the classical discretization breaks down, as was already discussed extensively in literature

Fit evaluation of sportswear for Belgian elite male rowers in static and dynamic rowing postures

The main objective of the SHAPE study was to assess the anthropometry of elite male rowers and develop customized size charts and sportswear with adequate fit in static and dynamic rowing postures. This paper briefly discusses the anthropometry of Belgian elite male rowers and focuses on the fit features of a related unisuit called SHAPE which is compared against a reference (SMARTFIT) with similar materials and design, whereof the garment construction is based on body charts of average Belgian males. Four elite male rowers evaluated both unisuits in garment size 52 and 58. Most of the ten fit features investigated for SHAPE unisuit were allocated average scores between 3 (adequate fit) and 4 (very good fit). In static posture, the overall fit of the SHAPE unisuit was found slightly better than of SMARTFIT unisuit (average score 3.8 and 3.1 respectively). Unlike SMARTFIT, SHAPE unisuit based on rowers body dimensions scored equally well in static and dynamic rowing postures catch and finish and will likely successfully accommodate repetitive sport movements

Recent advances in boundary element methods applied to conducting and dielectric electromagnetic scattering problems

Boundary element methods (BEMs) are an increasingly popular approach to the modeling of electromagnetic scattering both by perfect conductors and dielectric objects. Several mathematical, numerical, and computational techniques pullu-lated from the research into BEMs, enhancing its efficiency. The Fast Multipole Method (FMM) and its descendants accelerate the matrix-vector product that constitutes the BEM's computational bottleneck. In particular, dedicated FMMs have been conceived for the computation of the electromagnetic scattering at complex metallic and/or dielectric objects in free space and in layered background media. Caldero n preconditioning of the BEM's system matrix lowers the number of matrix-vector products required to reach an accurate solution, and thus the time to reach it. Parallelization distributes the remaining workload over a battery of affordable computational nodes, diminishing the wall-clock computation time. In honor of our former colleague and mentor, Prof. F. Olyslager, an overview of some dedicated BEMs for large and complex EM problems developed within the Electromagnetics Group at Ghent University is presented. Recent results that ramified from Prof. Olyslager's scientific endeavors are included in the survey