Aire-sur-l’Adour – Crypte de Sainte-Quitterie

Le but de l’opération entreprise à l’église Sainte-Quitterie du Mas est de déterminer la chronologie des parties les plus anciennes de la crypte. Pour cela, une campagne de prélèvement a été organisée en novembre 2016 afin d’échantillonner des éléments datables par des méthodes physiques, mortiers, et d’observer in situ leurs différents faciès et leur extension. Une méthode de datation directe de l’édification de maçonneries par luminescence optiquement stimulée (OSL) selon la technique dite ..

Benchmark of different CFL conditions for IMPES

The IMplicit Pressure Explicit Saturation (IMPES) method is a prevalent way to simulate multiphase flows in porous media. The numerical stability of this sequential method implies limitations on the time step, which may depend on the flow regime studied. In this note, three stability criteria related to the IMPES method, that differ in their construction on the observed variables, are compared on homogeneous and heterogeneous configurations for different two-phase flow regimes (viscous/capillary/gravitational). This highlights that there is no single optimal criterion always ensuring stability and efficiency. For capillary dominated flows, the Todd’s condition is the most efficient one, while the standard Coat condition should be preferred for viscous flows. When gravity effects are present, Coat’s condition must be restricted, but remains more efficient than the Todd’s condition

A comparison of various methods for the numerical evaluation of porous media permeability tensor from pore-scale geometry

In this work, several boundary value problems used to numerically evaluate the absolute permeability tensors of porous media using core-scale images are compared and discussed. The various configurations differ by the type of boundary conditions used to compute the flow at the micro-scale. The issue is the ability of the method to capture anisotropy correctly and to avoid possible percolation artifacts. This study is carried on two-dimensional synthetic, isotropic or anisotropic, porous media, that are chosen to illustrate the various difficulties mentioned above. A new method is proposed which consists in embedding the porous medium in question in a homogenized one. Using an iterative optimization procedure on the surrounding permeability, the method determines the absolute permeability tensor of the original medium. The equivalent permeability tensor that minimizes the effect on the surrounding porous medium is, unlike that of classical methods, de facto symmetrical due to the use of periodic boundary conditions and exhibits significantly lower permeabilities. The way in which non-diagonal terms of the permeability tensor are obtainedwith the various methods are thoroughly discussed

Périgueux – Saint-Jean-Baptiste de la Cité

L’opération est intégrée dans un programme de recherche interdisciplinaire intitulé MoDAq (Mortar Dating in Aquitaine, porteur P. Guilbert, Iramat-CRP2A en collaboration avec Ausonius et le SRA Aquitaine) validé et cofinancé par le conseil régional d’Aquitaine en juillet 2015 pour une durée de trois années. Notre travail sur le site de la chapelle Saint-Jean-Baptiste de la Cité à Périgueux, fouillé en 2008 par Hervé Gaillard (BSR 2008, p. 40-44), a consisté à mettre en œuvre une nouvelle méth..

The potential of optically stimulated luminescence for medieval building; A case study at Termez, Uzbekistan

Luminescence techniques thermoluminescence (TL) and optically stimulated luminescence (OSL) are generally used to assess the chronology of the last firing of ceramics. In the field of building archaeology, fired bricks can be dated by these techniques. Nevertheless, these luminescence ages are not exactly related to the construction of the building itself, but to the production of the building materials. In some cases, re-use is possible and this raises problems with the interpretation of the dating results. This led us to employ optically stimulated luminescence in a less conventional way. Before bricks were sealed in masonry by mortar, they would have been exposed to day light, and, as a result, the optical traps of the crystals on the material surface should have been bleached (zeroed by light). Dating the end of the bleaching period is possible by OSL using blue light for stimulation and by IRSL (infrared stimulated luminescence) using IR stimulation. Thus the OSL or IRSL age for these crystals is directly related to the construction of the architectural structure. Experiments were carried out to determine the suitability of this approach and to solve practical problems of sampling. The results show that the bleaching light penetrates between 0.5 to 1 mm into the bricks, according to their transparency. This depth is sufficient to collect enough quartz and feldspar inclusions that have been affected by light in the past, and thus date the construction of the masonry directly. Attempts at surface dating of bricks collected at the medieval citadel of Termez, Uzbekistan, already dated by TL, were the starting point of this research

Main Determinants of Profit Sharing Policy in the French Life Insurance Industry

We use a brand new data-set built from French supervisory reports to investigate the drivers of the participation rates served on euro-denominated life-insurance contracts over the period 1999-2013. Our analysis confirms practitioners’ insight on the alignment with the 10-years French government bond, yet we show that on aggregate, insurers serve less than this target. Our data indicate that financial margins are more strictly targeted than participation. We find evidence that lapses are fairly uncorrelated with participation, suggesting other levers to pilot surrenders. If higher asset returns can imply better yield for policyholders, riskier portfolios do not translate into better participatio