Using asymptotic methods to compute diffracted pressure by curved surfaces

13 pagesInternational audienceThis article presents an original and efficient method to compute acoustic pressure diffracted by curved surfaces. Our approach is perfectly suited to be integrated into ray of beam tracing softwares

Diffraction d'une onde acoustique (ou électromagnétique) par un plateau rigide (ou parfaitement conducteur)

National audienceL'objectif des travaux brièvement présentés dans ce papier était d'implémenter au sein de deux logiciels considérant la propagation en 3D d'ondes acoustiques et électromagnétiques à lancer de faisceaux (ICARE **) et tracé de rayons (CRT *) un modèle asymptotique (TUD) permettant de prendre en compte les phénomènes de double diffraction par un écran d'épaisseur donnée. Nous l'avons ensuite mis en œuvre dans différentes configurations afin d'en étudier le comportement. La dernière étape de ce travail a consisté à valider la formulation choisie en comparéléments finis de frontière (B.E.M) [JEA

Evidence of a causal and modifiable relationship between kidney function and circulating trimethylamine N-oxide

The host-microbiota co-metabolite trimethylamine N-oxide (TMAO) is linked to increased cardiovascular risk but how its circulating levels are regulated remains unclear. We applied "explainable" machine learning, univariate, multivariate and mediation analyses of fasting plasma TMAO concentration and a multitude of phenotypes in 1,741 adult Europeans of the MetaCardis study. Here we show that next to age, kidney function is the primary variable predicting circulating TMAO, with microbiota composition and diet playing minor, albeit significant, roles. Mediation analysis suggests a causal relationship between TMAO and kidney function that we corroborate in preclinical models where TMAO exposure increases kidney scarring. Consistent with our findings, patients receiving glucose-lowering drugs with reno-protective properties have significantly lower circulating TMAO when compared to propensity-score matched control individuals. Our analyses uncover a bidirectional relationship between kidney function and TMAO that can potentially be modified by reno-protective anti-diabetic drugs and suggest a clinically actionable intervention for decreasing TMAO-associated excess cardiovascular risk

Imidazole propionate is increased in diabetes and associated with dietary patterns and altered microbial ecology

Microbiota-host-diet interactions contribute to the development of metabolic diseases. Imidazole propionate is a novel microbially produced metabolite from histidine, which impairs glucose metabolism. Here, we show that subjects with prediabetes and diabetes in the MetaCardis cohort from three European countries have elevated serum imidazole propionate levels. Furthermore, imidazole propionate levels were increased in subjects with low bacterial gene richness and Bacteroides 2 enterotype, which have previously been associated with obesity. The Bacteroides 2 enterotype was also associated with increased abundance of the genes involved in imidazole propionate biosynthesis from dietary histidine. Since patients and controls did not differ in their histidine dietary intake, the elevated levels of imidazole propionate in type 2 diabetes likely reflects altered microbial metabolism of histidine, rather than histidine intake per se. Thus the microbiota may contribute to type 2 diabetes by generating imidazole propionate that can modulate host inflammation and metabolism

Caractérisation du rendu des couleurs des nouvelles sources : les diodes électroluminescentes (LED)

The development of high power LEDs in the early 2000s have generated a need for characterization of radiometric, photometric and colorimetric properties of light sources, essentially oriented towards general lighting applications. The optical radiation team from the « Institut national de métrologie » leaned over these three aspects while working on the quality of light through colour rendering related to visual perception. Studies were conducted from physical and visual measurements on samples illuminated by LED lightings mounted in a light booth. Physical measurements focused on spectral distribution from which colorimetric parameters (chromaticity coordinates, correlated colour temperature, colour rendering indexes) have been evaluated. The metrological analysis of the experimental data was performed using a numerical method of Monte Carlo. Visual measurements were obtained from a psychophysical experiment based on a pair comparisons method. It allowed to quantify LED lightings quality over colored samples. For each sample, a classification of the LED lightings, from best to worst, could be proposed. Confrontation between results issued from physical and visual measurements led to propose some ideas to quantify the colour rendering of LED lightings. Obtained results were submitted to the technical committee TC 1-69 of the international commission on illumination (CIE), whose task is to define a new recommendation for the evaluation of the colour rendering properties of light sources within the year 2010.Le développement des LED de forte puissance, au début des années 2000, a engendré un besoin de caractérisation des propriétés radiométrique, photométrique et colorimétrique de ces sources, essentiellement pour des applications d'éclairage général. L'équipe « Rayonnements optiques » de l'Institut national de métrologie a étudié ces trois aspects en travaillant sur la thématique de la qualité de la lumière par le biais du rendu des couleurs lié à la perception visuelle. Des études ont été effectuées à partir de mesures physiques et visuelles sur des échantillons colorés éclairés par des LED montées dans une cabine à lumière. Les mesures physiques ont porté sur les répartitions spectrales des éclairages à LED à partir desquelles des paramètres colorimétriques (coordonnées chromatiques, température de couleur proximale, indices de rendu des couleurs) ont pu être évalués. L'analyse métrologique de ces données expérimentales a été réalisée à l'aide d'une méthode numérique de type Monte Carlo. Les mesures visuelles ont été obtenues à partir d'une expérience psychophysique reposant sur une méthode de comparaison par paires permettant de quantifier la qualité des éclairages à LED sur plusieurs échantillons colorés. Pour chaque échantillon, un classement des éclairages à LED, du meilleur au moins bon, a pu être proposé. La confrontation des résultats issus des mesures physiques et des mesures visuelles a conduit à présenter des pistes de quantification du rendu des couleurs des LED. Les résultats obtenus ont été transmis au comité technique TC 1-69 de la Commission internationale de l'éclairage (CIE), qui a pour rôle de définir une nouvelle recommandation pour l'évaluation des propriétés de rendu des couleurs des sources lumineuses d'ici à la fin 2010

Caractérisation du rendu des couleurs des nouvelles sources (les diodes électroluminescentes)

PARIS-CNAM (751032301) / SudocSudocFranceF

MESURES OPTIQUES POUR LA CARACTERISATION D’ECLAIRAGES A LED

International audienceNEOLUX, a French company specialized in the development of LED lightings, built a photometry laboratory for the complete characterization of luminaries. During the metrological evaluation process of its equipments, the measurement accuracy of portable spectroradiometers was studied by comparison with instruments from the French national metrology institute called “Laboratoire commun de métrologie LNE-Cnam”. Huge measurement differences were observed between the portable spectroradiometers.NEOLUX, société française spécialisée dans la conception d’éclairages à LED, s’est dotée d’un laboratoire de photométrie pour la caractérisation complète de luminaires. Dans le cadre de l’évaluation métrologique de ses équipements, l’exactitude de mesure de spectroradiomètres portatifs a été étudiée par comparaison à des équipements du Laboratoire Commun de Métrologie LNE-Cnam. D’importants écarts de mesures entre les spectroradiomètres portatifs ont été observés

Visual experiment on LED lighting quality with color quality scale colored samples

International audienceA psychophysical experiment developed to evaluate light quality of Light Emitting Diodes (LEDs) is described. It is based on coloured samples used in the “Color Quality Scale” (CQS) proposed by the NIST to replace the “Colour Rendering Index” (CRI). Predictions of the CQS and results from visual measurements are compared

Analysis of Electromagnetic Waves Spatio-Temporal Variability in the Context of Exposure to Mobile Telephony Base Station

International audienceWith the increasing number of mobile phone users, new services and mobile applications, the proliferation of radio antennas has raised concerns about human exposure to electromagnetic waves. This is now a challenging topic to many stakeholders such as local authorities, mobile phone operators, citizen and consumer groups. The study of the spatial and temporal variability of the actual downlink exposure is a very important requirement to find an accurate exposure assessment. In this paper, a concept of exposure areas linked to specific variations of the electric field is introduced. Then a measurement campaign of the temporal variability of the electric field in urban environment is presented, considering different technologies and mobile operators in the previously defined exposure areas. This study allowed to determine updated daytime and nighttime exposure profiles. A second result yielded the averaging duration needed to reach a stable evaluation of the electric field exposure levels, inside each exposure area and according to each technology

Analysis of Electric field spatial variability in simulations of electromagnetic waves exposure to mobile telephony base stations

International audience—this paper focuses on the study of electric field spatial variability in the context of mobile telephony base stations exposure. Electric field is computed using a Uniform Theory of Diffraction (UTD) based simulation technique suitable for large urban areas. Two complementary approaches of spatial variability are proposed here. One based upon spatial autocorrelation and the other one on statistical laws identification to account for electric field distribution in an urban area. The first approach allows us to quantify the spatial dependency of electric field in three representative areas of exposure. The second one demonstrates that statistical laws depending of the area type and urban typology can represent the electric field behavior