Effet de la diffusion de l'oxygène sur le comportement mécanique du Ti–6Al–2Sn–4Zr–2Mo–0.1Si

Les alliages de titane sont utilisés dans les composants aéronautiques tels que les structures secondaires de fixation du moteur. Augmenter l''efficacité du moteur conduit à une augmentation de la température de ces composants. Pour améliorer l'évaluation de la durée de vie de ces pièces, il est nécessaire d'obtenir une meilleure compréhension des changements en service, dans le comportement mécanique. Ceux-ci sont dus à l'enrichissement en oxygène de l'alliage pendant son oxydation. Dans ce travail, des échantillons minces en alliage Ti-6Al-2Sn-4Zr-2Mo-0.1Si ont été pré-oxydés pendant des durées contrôlées afin d'obtenir différentes épaisseurs de la couche affectée par l'oxygène. L'analyse par résonance acoustique permet d'obtenir le module de Young à différentes températures, des essais de traction et de fluage sont ensuite réalisés. En utilisant des échantillons minces, l'effet de la zone de diffusion de l'oxygène (ODZ) sur les propriétés mécaniques a été déterminé

La grotte ornée de Cussac (Dordogne)‎. Observations liminaires

Le 30 septembre 2000, au cours d’une prospection spéléologique menée sur la commune du Buisson-de-Cadouin, Marc Delluc devait découvrir dans la grotte de Cussac un remarquable ensemble de représentations pariétales gravées. L’analogie formelle des éléments de ce bestiaire et des entités féminines remarquée très tôt avec les figures de Pech-Merle permirent d’attribuer cette iconographie à une phase ancienne du Paléolithique supérieur, le Gravettien. Cependant, le caractère exceptionnel de ce site réside aussi dans la présence de nombreux vestiges osseux d’origine humaine, regroupant au moins cinq individus et dont la répartition calque en partie celle des figures pariétales. Le rapprochement chronologique de ces deux formes archéologiques est corroboré par la datation 14C d’un des prélèvements osseux qui donna 25 120 ± 120 ans.In September 23, 2000, during a speleological exploration inside the cave of Cussac, Marc Delluc discovered a remarkable entity of parietal engraved figures.The analogy of depicted animals and of female representations studied long before in Pech-Merle cave allows to date these images to the Gravettian, earlier period of the Upper Palaeolithic.Yet, the exceptional originality of this site consists in the presence of numerous human bones counting at least five individuals, with a location similar to the engravings. The radiocarbon dating of a bone fragment gives : 25 120±120 years and confirms the chronological comparing of both archealogical elements.

A Data Mining Analysis Applied to a Straightening Process Database

peer reviewedThe complexity of modern manufacturing processes in a highly competitive environment forces the manufacturers to invest massively in automation and monitoring systems. The large data flows from these new installations are sources of valuable and hidden knowledge that is so far hardly used. Data mining methods through integrated data analysis tools give a solution to this situation, allowing easy retrieval of knowledge starting from a data base. This is also a unique opportunity to learn faster about the process and to detect hidden and complex relationships between parameters involved. Within this framework we have decided to apply this data analysis method to the straightening process in shipbuilding. We refer to Caprace et al. (2007) for additional illustrations. In shipbuilding, the assembly of elements by welding involves temperature gradients within the ma- terial. These cause deformations which sometimes have to be reduced to obtain an acceptable surface flatness. The straightening process to eliminate these distortions for esthetical or functional reasons is labour intensive. Estimating the straightening impact on the production workload is interesting in the context of production simulation, cost assessment of ship hull, structure optimization, design for production, etc. To reach these objectives, the idea was to elaborate, through a data mining approach, a formula linking the straightening cost to the sections scantlings (plate thickness, dimension and inter-distance of longitudinal stiffeners, dimension and inter-distance of transversal frames) and to other section characteristics. This paper describes each stage of the methodology: data description, analysis of data quality, data exploration and finally choice of discriminatory attributes and the generation of the data-driven models.InterSHI

Assessing and adjusting for differences between HIV prevalence estimates derived from national population-based surveys and antenatal care surveillance, with applications for Spectrum 2013

Objective(s): To assess differences between HIV prevalence estimates derived from national population surveys and antenatal care (ANC) surveillance sites and to improve the calibration of ANC-derived estimates in Spectrum 2013 to more appropriately account for differences between these data. Design: Retrospective analysis of national population survey and ANC surveillance data from 25 countries with generalized epidemics in sub-Saharan Africa and 8 countries with concentrated epidemics. Methods: Adult national population survey and ANC surveillance HIV prevalence estimates were compared for all available national population survey data points for the years 1999–2012. For sub-Saharan Africa, a mixed-effects linear regression model determined whether the relationship between national population and ANC estimates was constant across surveys. A new calibration method was developed to incorporate national population survey data directly into the likelihood for HIV prevalence in countries with generalized epidemics. Results were used to develop default rules for adjusting ANC data for countries with no national population surveys. Results: ANC surveillance data typically overestimate population prevalence, although a wide variation, particularly in rural areas, is observed across countries and survey years. The new calibration method yields similar point estimates to previous approaches, but leads to an average 44% increase in the width of 95% uncertainty intervals. Conclusion: Important biases remain in ANC surveillance data for HIV prevalence. The new approach to model-fitting in Spectrum 2013 more appropriately accounts for this bias when producing national estimates in countries with generalized epidemics. In countries with concentrated epidemics, local sex ratios should be used to calibrate ANC surveillance estimates

Comparison of different impulse response measurement techniques

The impulse response of an acoustical space or transducer is one of its most important characterizations. In order to perform the measurement of their impulse responses, four of the most suitable methods are compared: MLS (maximum-length sequence), IRS (inverse repeated sequence), time-stretched pulses, and SineSweep. These methods have already been described in the literature. Nevertheless, the choice of one of them depending on the measurement conditions is critical. Therefore an extensive comparison has been realized. This comparison was done through the implementation and realization of a complete, fast, reliable, and cheap measurement system. Finally, a conclusion for the use of each method according to the principal measurement conditions is presented. It is shown that in the presence of nonwhite noise, the MLS and IRS techniques seem to be more accurate. On the contrary, in quiet environments the logarithmic SineSweep method seems to be the most appropriate

La grotte ornée de Cussac - Le Buisson-de-Cadouin (Dordogne) : premières observations

Aujoulat Norbert, Geneste Jean-Michel, Archambeau Christian, Delluc Marc, Duday Henri, Gambier Dominique. La grotte ornée de Cussac - Le Buisson-de-Cadouin (Dordogne) : premières observations. In: Bulletin de la Société préhistorique française, tome 99, n°1, 2002. pp. 129-137