Active shielding design and optimization of a wireless power transfer (WPT) system for automotive

This study deals with the optimization of a shielding structure composed by multiple active coils for mitigating the magnetic field in an automotive wireless power transfer (WPT) system at 85 kHz. Each active coil is independently powered and the most suitable excitation is obtained by an optimization procedure based on the Gradient Descent algorithm. The proposed procedure is described and applied to shield the magnetic field beside an electric vehicle (EV) equipped with SAE standard coils, during wireless charging. The obtained results show that the magnetic field in the most critical area is significantly reduced (i.e., approximately halved) with a very limited influence on the electrical performances (i.e., WPT efficiency decreases by less than 1 percentage point compared to the case without active shielding)

Cognitive performance in elderly patients undergoing carotid endarterectomy or carotid artery stenting: A twelve-month follow-up study

Background: It is still a matter of debate if and to what extent carotid endarterectomy (CEA) and carotid artery stenting (CAS) impair cognitive functioning in the elderly. Methods: We conducted a nonrandomized clinical trial on subjects with asymptomatic carotid artery stenosis comparing CEA (n = 28; 24 males and 4 females; 72.6 ± 5.8 years old) with CAS (n = 29; 17 males and 12 females; 75.1 ± 5.7 years old). Cognition, mood and functional status were evaluated by a broad spectrum of tests performed on the day prior to carotid reopening as well as 3 and 12 months after. Results: No significant differences in scores on cognitive tests including the Babcock story recall test and Rey's auditory verbal learning test (memory), category naming test (verbal fluency), trail-making test parts A and B (attention and executive function) and controlled oral word association test (executive functioning) were observed 3 and 12 months after carotid reopening independent of the technique used. Only scores on the copy drawing test (visuospatial and constructional abilities) slightly but significantly (p < 0.05) worsened in the CAS group 12 months after the intervention. No significant differences between the CEA and CAS groups were detected regarding mood and functional status after 3 and 12 months. Conclusions: CEA and CAS seem to be safe procedures in elderly patients in terms of cognitive, mood and functional status in the short and long term. CAS might be preferred for the shorter hospital stay, but further studies with a larger number of old and oldest old subjects with a longer follow-up are needed to better understand the cost-effectiveness of both treatments

Microevolution of Neisseria lactamica during nasopharyngeal colonisation induced by controlled human infection.

Neisseria lactamica is a harmless coloniser of the infant respiratory tract, and has a mutually-excluding relationship with the pathogen Neisseria meningitidis. Here we report controlled human infection with genomically-defined N. lactamica and subsequent bacterial microevolution during 26 weeks of colonisation. We find that most mutations that occur during nasopharyngeal carriage are transient indels within repetitive tracts of putative phase-variable loci associated with host-microbe interactions (pgl and lgt) and iron acquisition (fetA promotor and hpuA). Recurrent polymorphisms occurred in genes associated with energy metabolism (nuoN, rssA) and the CRISPR-associated cas1. A gene encoding a large hypothetical protein was often mutated in 27% of the subjects. In volunteers who were naturally co-colonised with meningococci, recombination altered allelic identity in N. lactamica to resemble meningococcal alleles, including loci associated with metabolism, outer membrane proteins and immune response activators. Our results suggest that phase variable genes are often mutated during carriage-associated microevolution

Artificial Material Single Layer to Model the Field Penetration Through Thin Shields in Finite-Elements Analysis

A new artificial material single layer (AMSL) model is presented to solve shielding problem. The field penetration through the conductive shield is described by lossy transmission line equations. The resulting equations are used to numerically synthetize an equivalent material for the shield region having the same geometrical configuration of the original shield, but different specific constants. The AMSL method is very accurate and highly efficient since it allows to discretizing the shield region using only a single layer of finite elements avoiding the fine discretization required by the finite-element method (FEM) to model the skin effect. The most relevant aspect of the proposed procedure is that the AMSL method can be easily implemented in FEM-based commercial software tools

Wireless charging in electric vehicles. EMI/EMC risk mitigation in pacemakers by active coils

An innovative shielding configuration of active coils is proposed to mitigate the magnetic field around an electric vehicle (EV) with a wireless power transfer (WPT) system during battery charging. The active coil is designed to reduce the risk for patients with pacemakers or similar devices produced by the time varying magnetic field generated by the 85 kHz WPT coil currents. A numerical analysis of the magnetic field levels is carried out solving the magneto-quasi-static (MQS) equations by a FEM-based commercial tool. The calculated field which exceeds the limits of electromagnetic compatibility (EMC) and electromagnetic field (EMF) safety standards for human exposure is mitigated by active coils. The magnetic field levels in the environment and the induced peak-to-peak voltage in the pacing lead is predicted in presence and in absence of active shielding

A New Transmitting Coil for Powering Endoscopic Capsules Using Wireless Power Transfer

This study focuses on using wireless power transfer (WPT) technology based on magnetic resonant coupling (MRC) to supply electric power to an endoscopic capsule to be used for the direct feeding of specific functions or for battery charging. One of the main limitations of the diffusion of endoscopic capsules is the limited autonomy of the internal battery. The aim of the paper is to present an innovative system to wirelessly power capsules using inductive coupling. Here, a new transmitting coil architecture is proposed to allow the wireless charging of the capsule equipped with a monoaxial receiving coil for any possible geometric position and orientation. The new wearable transmitting coil consists of four rectangular coils with independent excitations, and it is capable of producing a magnetic field in any direction. The obtained results in terms of electrical performance of the proposed WPT system and in terms of in situ electromagnetic physical quantities are compared with the basic restrictions of electromagnetic field (EMF) safety guidelines. The results obtained are very promising, as the proposed WPT configuration can transfer at least 250 mW in a capsule that travels along the entire gastrointestinal tract

Conductive layer modeling by improved second-order artificial material single-layer method

An improved second-order artificial material single-layer (AMSL) method is proposed to predict the electromagnetic field in the presence of conductive thin layers by the finite-element method (FEM). The AMSL, method is based on the replacement of the material physical constants of a conductive shield region with those of an artificial material. The new AMSL, physical constants are analytically extracted by equating the equivalent transmission line equations governing the field propagation inside the shield with the FEM solution. This new formulation of the method is a significant improvement of the original AMSL as it is much more robust and accurate for near field solutions, and. above all, it is much more easily implementable in commercial software tools