Interaction of the perfluorinated polymer Nafion-H with water studied by proton broad-line NMR at 4 K and MAS NMR at room temperature

Broad-line¹H NMR at 4 K shows that, when Nafion-H interacts with water molecules at low concentrations, the only species formed is the hydronium ion. The chemical shift of the unsolvated hydronium ion in Nafion-H with 1 H₂O/SO ₃ ^– , determined by¹H MAS NMR at room temperature, is 10.4 ppm relative to external TMS.     

Coupleur de polarisation compact à guides demi-lune

Circular polarized antennas (as C-band [4–6 GHz] spatial telecommunications antennas) are generally fed by rotationally symmetrical structures radiating the two strongly decoupled orthogonal polarizations. We designed a light, compact and highly performant device to generate circular polarized waves in a circular waveguide.     

In-vitro availability of starch in cereal products

The in-vitro availability of starch in Heudebert breads and Lu biscuits was assessed. Starch digestibility increased in the order semi-sweet biscuits, muesli, wholemeal breads, white breads, French toast, extruded crispbread. The results confirm that manufacturing conditions play a determinant role in starch availability in vitro.     

A Unified Artificial Neural Network Architecture for Active Power Filters

In this paper, an efficient and reliable neural active power filter (APF) to estimate and compensate for harmonic distortions from an AC line is proposed. The proposed filter is completely based on Adaline neural networks which are organized in different independent blocks. We introduce a neural method based on Adalines for the online extraction of the voltage components to recover a balanced and equilibrated voltage system, and three different methods for harmonic filtering. These three methods efficiently separate the fundamental harmonic from the distortion harmonics of the measured currents. According to either the Instantaneous Power Theory or to the Fourier series analysis of the currents, each of these methods are based on a specific decomposition. The original decomposition of the currents or of the powers then allows defining the architecture and the inputs of Adaline neural networks. Different learning schemes are then used to control the inverter to inject elaborated reference currents in the power system. Results obtained by simulation and their real-time validation in experiments are presented to compare the compensation methods. By their learning capabilities, artificial neural networks are able to take into account time-varying parameters, and thus appreciably improve the performance of traditional compensating methods. The effectiveness of the algorithms is demonstrated in their application to harmonics compensation in power systems     

Microstructures of binary Cr–xNi alloys (0 ≤ Ni ≤ 50 wt.%) in their as-cast state and after high temperature exposure

Metallic materials designed for use at very high temperature must be based on elements with high melting points. In this work, several binary alloys, chosen in the Cr-rich part of the Cr–Ni diagram, were elaborated by foundry and characterised by metallography in the as-cast condition and after exposure at 1200 °C. Many of the obtained alloys are composed of imbricated body-centred cubic chromium phase saturated in Ni and face-centred cubic nickel phase saturated in Cr. These structures may evolve more or less at high temperature. High values of hardness were obtained for some of these alloys, suggesting high strength at elevated temperature. The hardness evolution vs. the Cr content was well represented by a law of mixture of the volume fractions and the hardness of the separated phases. Already intrinsically resistant to oxidation at high temperature, most alloys are also not sensitive to internal nitridation, contrary to pure Cr. Such Cr–Ni alloys may be considered as possible bases for heat-resistant alloys.     

Influence of thermal and mechanical surface modifications induced by laser shock processing on the initiation of corrosion pits in 316L stainless steel

Pure mechanical and thermo-mechanical laser shock processing treatments have been carried out on an AISI 316L stainless steel. Surface properties, mostly mechanical and metallurgical modifications, were analysed at different scales: a local scale using the nano-indentation technique and AFM analysis, and a more macroscopic scale, using microhardness, optical microscopy and residual stress determinations. After a pure mechanical laser-peening treatment, a significant improvement in the pitting corrosion resistance (+0.1 V) was observed in 0.05 M NaCl. This improvement was attributed to the combined effects of compressive residual stresses and work-hardening, and, in turn, to a mechano-electrochemical phenomenon by which a modification of cathodic reactions occurs during electrochemical tests. For the surface treated by thermo-mechanical laser peening (combination of a surface ablation and shock waves), a tendency for decreasing resistance against pitting corrosion was shown, and attributed to the processing-specific surface texture (ablation craters), which made the material susceptible for the creation of occluded cells.

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Experimental and theoretical investigation of the pixel saturation effect in digital holography

This paper presents an experimental investigation and an analytical modeling of the nonlinear pixel saturation effect in digital off-axis holography. The theoretical analysis is based on a semiempirical modeling and supported by the experimental analysis. Taking into account the nonlinearity of the phenomenon, an exponential law for the high-order harmonic amplitude is proposed and validated by the experimental results. The conclusion of this analysis is that the saturation effect can be described by the use of a linear operator that involves autoconvolution of the initial object wave, even though the saturation phenomenon is nonlinear.     

Transparent plasmonic nanocontainers protect organic fluorophores against photobleaching

Numerous research efforts are investigating the possibility of using light interactions with metallic nanoparticles to improve the fluorescence properties of nearby molecules. Few investigations have considered the encapsulation of molecules in metallic nanocavities. In this paper, we present the optical properties of new hybrid nanoparticles consisting of gold nanoshells and fluorescent organic dyes in their liquid cores. Microspectroscopy on single nanoparticle demonstrates that the extinction spectra are in good agreement with Mie's theory. Finite difference time domain (FDTD) calculations reveal that excitation and emission radiations are efficiently transmitted through the thin gold nanoshells. Thus, they can be considered as transparent plasmonic nanocontainers for photoactive cores. In agreement with FDTD calculations, measurements show that fluorophores encapsulated in gold nanoshells keep their brightness, but they show fluorescence lifetimes 1 order of magnitude shorter. As a salient consequence, the photoresistance of encapsulated organic dyes is also improved by an order of magnitude. This unusual ultraviolet photoresistance results from the reduced probability of triplet-singlet conversion that eventually exposes dyes to singlet oxygen photodegradation.