Vers un monitoring électrique des garnitures mécaniques d'étanchéité

Cet article s'intéresse à l'évolution en temps réel du contact d'une garniture mécanique d'étanchéité en fonctionnement. Afin de simuler ce contact frottant, un banc spécifique de mesures a été développé, mettant en jeux des bagues identiques au dispositif industriel et présentant des surfaces avec des finitions industrielles. Ce banc permet d'obtenir des informations sur l'état mécanique du contact en le faisant traverser par un courant électrique sonde. Deux paramètres importants ont été explorés : la lubrification et la charge. L'étude présentée montre des signatures électriques spécifiques qui font de la mesure électrique un outil adapté pour suivre en temps réel l'évolution de l'état du contact

Interlayer strain effects on the structural behavior of BiFeO3/LaFeO3 superlattices

Artificial (BiFeO3)0.5Λ/(LaFeO3)0.5Λ superlattices have been grown by pulsed laser deposition. The periodicity Λ was varied from 150 Å to 25 Å and the relative ratio between BiFeO3 (BFO) and LaFeO3 (LFO) is kept constant in each period. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy investigations indicate antiferroelectric-like structures for large periodicity (Λ ≥ 76 Å), while Pnma LaFeO3-like structures are observed for small periodicity Λ ≤ 50 Å. Room temperature magnetic measurements were obtained by vibrating sample magnetometry and suggest antiferromagnetic ordering with weak ferromagnetism. Temperature dependent x-ray diffraction studies show an important shift of paraelectric-antiferroelectric phase transition scaling with BFO thickness. Strain and size effects explain this behavior and discussion is also made on the possible role of the oxygen octahedral rotation/tilt degree of freedom

Trait‐based analysis of subpolar North Atlantic phytoplankton and plastidic ciliate communities using automated flow cytometer

Plankton are an extremely diverse and polyphyletic group, exhibiting a large range in morphological and physiological traits. Here, we apply automated optical techniques, provided by the pulse‐shape recording automated flow cytometer—CytoSense—to investigate trait variability of phytoplankton and plastidic ciliates in Arctic and Atlantic waters of the subpolar North Atlantic. We used the bio‐optical descriptors derived from the CytoSense (light scattering [forward and sideward] and fluorescence [red, yellow/green and orange from chlorophyll a, degraded pigments, and phycobiliproteins, respectively]) and translated them into functional traits to demonstrate ecological trait variability along an environmental gradient. Cell size was the master trait varying in this study, with large photosynthetic microplankton (> 20 μm in cell diameter), including diatoms as single cells and chains, as well as plastidic ciliates found in Arctic waters, while small‐sized phytoplankton groups, such as the picoeukaryotes (< 4 μm) and the cyanobacteria Synechococcus were dominant in Atlantic waters. Morphological traits, such as chain/colony formation and structural complexity (i.e., cellular processes, setae, and internal vacuoles), appear to favor buoyancy in highly illuminated and stratified Arctic waters. In Atlantic waters, small cell size and spherical cell shape, in addition to photo‐physiological traits, such as high internal pigmentation, offer chromatic adaptation for survival in the low nutrient and dynamic mixing waters of the Atlantic Ocean. The use of automated techniques that quantify ecological traits holds exciting new opportunities to unravel linkages between the structure and function of plankton communities and marine ecosystems

1 MCI – MULTILANGUAGE DISTRIBUTED CO-SIMULATION TOOL

Nowadays the design of complex systems requires the cooperation of several teams belonging to different cultures and using different languages. It is necessary to dispose of new design and verification methods to handle multilanguage approaches. This paper presents a multilanguage co-simulation tool that allows cosimulation of multilanguage specifications for complex systems

Ferroic phase transition sequence in epitaxial BiFeO3 thin films

We report a temperature-dependent high-resolution X-ray diffraction investigation of 200 nm epitaxial BiFeO3 thin films grown on (001) SrTiO3. We were successful in making epitaxial thin films thermally stable, a key requirement for this study. Our results provide evidence that BiFeO3 undergoes three high-temperature transitions: an antiferromagnetic transition at 425°C, a first-order α–β phase transition between 745°C and 780°C and a smoother transition toward the γ-phase at 860°C. Both the α–β and β–γ transitions take place 60°C lower than the bulk values whereas the antiferromagnetic transition occurs 55°C higher. This underscores the part played by strain and also emphasizes that BiFeO3 is not a conventional ferroelectric perovskite. Reciprocal space maps reveal the unusual result that the thin films remain monoclinic on crossing the α–β phase transition. Linear extrapolation of the in-plane lattice parameters to higher temperatures rules out cubic symmetry for the γ-phase

Structural and electrical properties of K3Li2Nb5O15 thin film grown by pulsed laser deposition

International audiencePotassium lithium niobate K3Li2Nb5O15 (KLN) with tetragonal tungsten bronze-type structure (TIT) thin film was successfully deposited on MgO substrate by pulsed laser ablation method. The substrate was coated by a perovskite conductive layer of La0.5Sr0.5CoO3. X-ray diffraction revealed (001) orientation with low mosaicity. The oriented film had smooth and droplets-free surface as evidenced by reflection high electron energy diffraction and atomic force microscopy. Using Pt top electrode, dielectric measurements indicated stable dielectric permittivity of about 400 up to 10(5) Hz. A dielectric relaxation was also observed. Moreover, the capacitance voltage measurements of the obtained (001)KLN film show ferroelectric behavior. Our results provide useful insights into the growth of tetragonal tungsten and other complex materials. These results will be useful for the growth and integration of epitaxial TTB thin films on perovskite and Si substrates. (C) 2017 Elsevier Ltd. All rights reserved

Oxygen-deficient GdK

The ferroelectric compound GdK2Nb5O15 (GKN) thin film with tetragonal-tungsten-bronze–type structure was grown by pulsed-laser deposition on (001)SrRuO3/La0.5Sr0.5CoO3/MgO substrate. Using X-ray diffraction analysis we demonstrate that the phase transition temperature in the GKN thin film was shifted to high temperatures due to substrate-induced stress. Impedance spectroscopy investigations show Maxwell-Wagner–type conduction at low frequencies, which leads to resistive switching. Oxygen vacancies and temperature effects were studied to highlight the stability of the resistive switching behavior in the GKN thin film