SAR distribution in human beings when using body-worn RF transmitters

This study analyzes the exposure of the human torso to electromagnetic fields caused by wireless body-mounted or handheld devices. Because of the frequency and distance ranges from 30-5800 MHz and 10 to 200 mm, respectively, both near-field and far-field effects are considered. A generic body model and simulations of anatomical models are used to evaluate the worst case tissue composition with respect to the absorption of electromagnetic energy. Both standing wave effects and enhanced coupling of reactive near-field components can lead to a specific absorption rate (SAR) increase in comparison to homogeneous tissue. In addition, the exposure and temperature increase of different inner organs is assessed. With respect to compliance testing, the observed SAR enhancement may require the introduction of a multiplication factor for the spatial peak SAR measured in the liquid-filled phantom in order to obtain a conservative exposure assessment. The observed tissue heating at the body surface under adiabatic conditions can be significant, whereas the temperature increase in the inner organs turned out to be negligible for the cases investigated.     

An EWMA signed ranks control chart with reliable run length performances

During the design phase of a control chart, the determination of its exact run length properties plays a vital role for its optimal operation. Markov chain or integral equation methods have been extensively applied in the design phase of conventional control charts. However, for distribution-free schemes, due to the discrete nature of the statistics being used (such as the sign or the Wilcoxon signed rank statistics, for instance), it is impossible to accurately compute their run length properties. In this work, a modified distribution-free phase II exponentially weighted moving average (EWMA)-type chart based on the Wilcoxon signed rank statistic is considered and its exact run length properties are discussed. A continuous transformation of the Wilcoxon signed rank statistic, combined with the classical Markov chain method, is used for the determination of the average run length in the in- and out-of control cases. Moreover, its exact performance is derived without any knowledge of the distribution of sample observations. Finally, an illustrative example is provided showing the practical implementation of our proposed chart.     

A general form of perfectly matched layers for three-dimensional problems of acoustic scattering in lossless and lossy fluid media

The concept of perfectly matched layer (PML) has been proven very effective in absorbing electromagnetic waves in lossless media. An extension of this method and a complete three-dimensional (3-D) scheme properly suited for finite-difference, time-domain (FDTD) modeling of acoustic propagation and scattering in unbounded problems are presented in this paper. This generalized PML is constructed in such a way that it performs significant absorption of traveling waves in acoustics for both lossless and lossy media. Theoretically, no reflections occur when propagating waves encounter the lossy medium-PML interface, no matter what the angle of incidence is, introducing at the same time the possibility for further wave attenuation via the stretched coordinates idea. Numerical results support the suggested PML theory as well as reveal the proper modifications, which lead to the achievement of the optimum absorbing-boundary condition.     

Analytical Modeling of Wobble in Eddy Current Tube Testing with Bobbin Coils

By utilizing the second-order vector potential formulation we solve the eddy current problem of a coil inside a conductive tube and in an offset position to it. The study focuses on the derivation of a closed-form expression for the impedance change of the coil, which is used to calculate the signal produced by wobble in eddy current testing of tubes with bobbin coils.     

Hybrid polymer-grafted multiwalled carbon nanotubes for in vitro gene delivery

Carbon nanotubes (CNTs) consist of carbon atoms arranged in sheets of graphene rolled up into cylindrical shapes. This class of nanomaterials has attracted attention because of their extraordinary properties, such as high electrical and thermal conductivity. In addition, development in CNT functionalization chemistry has led to an enhanced dispersibility in aqueous physiological media which indeed broadens the spectrum for their potential biological applications including gene delivery. The aim of this study is to determine the capability of different cationic polymer-grafted multiwalled carbon nanotubes (MWNTs) (polymer-g-MWNTs) to efficiently complex and transfer plasmid DNA (pCMV-βGal) in vitro without promoting cytotoxicity. Carboxylated MWNT is chemically conjugated to the cationic polymers polyethylenimine (PEI), polyallylamine (PAA), or a mixture of the two polymers. In order to explore the potential of these polymer-g-MWNTs as gene delivery systems, we first study their capacity to complex plasmid DNA (pDNA) using agarose gel electrophoresis. Gel migration studies confirm pDNA binding to polymer-g-MWNT with different affinities, highest for PEI-g-MWNT and PEI/PAA-g-CNT constructs. β-galactosidase expression is assessed in human lung epithelial (A549) cells, and the cytotoxicity is determined by modified LDH assay after 24 h incubation period. Additionally, PEI-g-MWNT and/or PEI/PAA-g-MWNT reveal an improvement in gene expression when compared to the naked pDNA or to the equivalent amounts of PEI polymer alone. Mechanistically, pDNA was delivered by the polymer-g-MWNT constructs via a different pathway compared to those used by polyplexes. In conclusion, polymer-g-MWNTs may be considered in the future as a versatile tool for efficient gene transfer in cancer cells in vitro, provided their toxicological profile is established.     

Eddy currents induced in a finite length layered rod by a coaxial coil

We describe the calculation of eddy currents in a two-layer conducting rod of finite length excited by a coaxial circular coil carrying an alternating current. The calculation uses the truncated region eigenfunction expansion (TREE) method. By truncating the solution region to a finite length in the axial direction, we can express the magnetic vector potential as a series expansion of orthogonal eigenfunctions instead of as a Fourier integral. The restricted domain can be arbitrarily large to yield results that are as close to the infinite domain results as desired. Integral form solutions for an infinite rod are well known and relatively simple. For a finite length cylindrical conductor, however, additional boundary conditions must be satisfied at the ends. We do this by comparing series expansions term by term to match the solutions across the end of the cylinder. We derive closed-form expressions for the electromagnetic field in the presence of a finite two-layer rod. A special case of the solution is that for a conductive tube. We illustrate the end effect by calculating the coil impedance variation with respect to the axial location of the coil. The results are in very good agreement with those obtained by using a two-dimensional finite-element code.     

Analytical and numerical solution of the eddy-current problem inspherical coordinates based on the second-order vector potentialformulation

The three-dimensional (3-D) eddy-current problem, described in spherical coordinates, is studied both analytically and numerically. Since the vector field equation is not separable in the spherical coordinate system, the second-order vector potential (SOVP) formulation is used to treat the problem by reducing it to the solution of the scalar field equation. While the analytical solution is expressed in terms of known orthogonal expansions, the numerical solution utilizes the finite difference method. Examples of engineering applications are provided, concerning computation of eddy-current distribution in a conducting sphere by a filamentary excitation of arbitrary shape     

Audio-visual speaker diarization using fisher linear semi-discriminant analysis

Speaker diarization aims to automatically answer the question “who spoke when” given a speech signal. In this work, we have focused on applying the FLsD approach, a semi-supervised version of Fisher Linear Discriminant analysis, both in the audio and the video signals to form a complete multimodal speaker diarization system. Extensive experiments have proven that the FLsD method boosts the performance of the face diarization task (i.e. the task of discovering faces over time given only the visual signal). In addition, we have proven through experimentation that applying the FLsD method for discriminating between faces is also independent of the initial feature space and remains relatively unaffected as the number of faces increases. Finally, a fusion method is proposed that leads to performance improvement in comparison to the best individual modality, which is the audio signal.     

Aerodynamic and Mobility Size Distribution Measurements to Reveal Biodiesel Effects on Diesel Exhaust Aerosol

This article examines the effect of biodiesel blends on the exhaust aerosol from a Euro 3 passenger car. Five different feedstock oils (soybean, palm, sunflower, rapeseed, and used frying oil) were used to produce fuels with 10% vol. content in biodiesel (B10). Use of the B10 blends led to a systematic reduction of PM mass emissions in the range of ～9% (rapeseed) to 23% (used frying oil) on average. The combination of particle size distributions based on the aerodynamic and the mobility diameters led to the estimation of the fractal dimension (DF) for non-volatile particles. This was found to range from 2.52 for the baseline (fossil) fuel to 2.62 for the palm oil blend, suggesting that biodiesel can affect the particle morphology, even at this low blending ratio. The differences were statistically significant. The increase of the DF is translated to more compact particle structure, which in turn denotes lower specific surface area. The volatile fraction of PM lies within a range of 1–9% when fossil diesel fuel is employed. Use of palm, sunflower and rapeseed B10 blends results to PM that contain up to 28% volatile particulate mass. The higher emissions of volatile components together with the lower specific area of non-volatile particles, promotes the formation of volatile particles, especially at high speed conditions. This increases the total particle population under motorway driving by up to three times over the baseline levels.