Waveform Relaxation for the Computational Homogenization of Multiscale Magnetoquasistatic Problems

This paper proposes the application of the waveform relaxation method to the homogenization of multiscale magnetoquasistatic problems. In the monolithic heterogeneous multiscale method, the nonlinear macroscale problem is solved using the Newton--Raphson scheme. The resolution of many mesoscale problems per Gauss point allows to compute the homogenized constitutive law and its derivative by finite differences. In the proposed approach, the macroscale problem and the mesoscale problems are weakly coupled and solved separately using the finite element method on time intervals for several waveform relaxation iterations. The exchange of information between both problems is still carried out using the heterogeneous multiscale method. However, the partial derivatives can now be evaluated exactly by solving only one mesoscale problem per Gauss point.Comment: submitted to JC

Multiscale Finite Element Modeling of Nonlinear Magnetoquasistatic Problems Using Magnetic Induction Conforming Formulations

In this paper we develop magnetic induction conforming multiscale formulations for magnetoquasistatic problems involving periodic materials. The formulations are derived using the periodic homogenization theory and applied within a heterogeneous multiscale approach. Therefore the fine-scale problem is replaced by a macroscale problem defined on a coarse mesh that covers the entire domain and many mesoscale problems defined on finely-meshed small areas around some points of interest of the macroscale mesh (e.g. numerical quadrature points). The exchange of information between these macro and meso problems is thoroughly explained in this paper. For the sake of validation, we consider a two-dimensional geometry of an idealized periodic soft magnetic composite.Comment: Paper accepted for publication in the SIAM MMS journa

Cryocalcites de nappe : proxys de l’extension des environnements périglaciaires et glaciaires.

National audienceLes cristallisation de calcite des sables du Bassin de paris ont été datées par les méthodes 14C et U-Th. Les datations couvrent les dernières glaciations (Thiry et al., 2013). Le positionnement de ces datations sur les courbes du d18O des carottes de glace montrent qu’elles se forment lors des périodes de refroidissement. Ce sont des cryocalcites de nappe qui se forment apparemment par réchauffement des eaux froides d’infiltration au contact des eaux plus chaudes de la nappe. Par leur large distribution et leurs signatures isotopiques elles apparaissent comme des proxys particulièrement prometteurs pour tracer et suivre l’extension des pergélisols et des permafrosts, au moins sur l’Europe du Nord-Ouest, et des cristallisations de ce type sont également connues en Amérique du Nord

Isotope signature of sand calcites in the Paris Basin: a proxy for permafrost/groundwater paleoconditions

International audienceSand calcites occurring as rhombohedral crystals and spherolitic concretions in several Tertiary sandstone formations in the Paris basin have been dated to the cooling periods of the four last glacial stages, using 14C and U-Th methods. Sand calcites constitute a novel proxy to estimate paleo-groundwater levels and the extension of permafrost conditions. The δ13C and δ18O compositions of sand calcites are a function of precipitation depth in relation with the warming of surface water during infiltration. Sand calcites appear as precious markers for Pleistocene paleo-landscape reconstructions

Radiometric dating (U/Th) of the lower marine terrace (Tyrrhenian, MIS 5.5) west of Nice (French Riviera). Morphological and neotectonic quantitative implications.

International audienceMeasurements of U/Th desequilibrium by mass spectrometry with a plasma source were used for the dating of shells collected on the lower marine terrace to the west of Nice. The dates obtained (131-132 ka) confirm that this terrace corresponds to the Tyrrhenian Age (M.I.S 5.5) and can be correlated with the level with Strombus bubonius located east of Nice. Thus, a profile of almost 70 kms can be restored with precision from altimetric measurements of the deposits and from sedimentological indicators of the sea-level. This profile passes from the tectonic foreland of Provence to the front of the Nice Alpine Range after skirting the Pliocene Var Basin. It thus crosses major structural limits. As expected, the deformation of the lower Tyrrhenian terrace, consists of a west-to-east uplift with two boundaries: 1/ the "Var Fault" located under the Pliocene Basin, and 2/ the border fault of the Nice Range. The restoration of the exact sea-level has enabled measurements to be taken of the vertical throws since the M.I.S. 5.5: although moderate, they are notable, especially the "Var Fault" which is located outside the Alpine zone. The Quaternary vertical displacement of this fault is due to the recent reactivation of an Oligocene normal system fault located under the Basin.Des mesures de déséquilibres U/Th par spectrométrie de masse à source plasma ont été utilisées à fins de datation sur des coquilles récoltées sur la basse terrasse marine à l'ouest de Nice. Les âges obtenues (131-132 ka) confirment que cette terrassse correspond au Tyrrhénien (stade isostopique 5.5) et peut être parfaitement corrélé avec le niveau à strombes situé à l'est de Nice. Ainsi un profil de près de 70 kms peut être reconstitué avec précision à partir de l'altimétrie des témoins intégrant des indicateurs sédimentologiques de niveau marin. Ce profil passe de l'avant-pays provençal au front de l'arc alpin de Nice après avoir longé le bassin pliocène du Var. Il franchit donc des limites structurales majeures. La déformation de la basse terrasse tyrrhénienne, comme attendu, est un soulèvement d'ouest en est avec deux seuils : 1/ l'" accident du Var " situé sous le bassin pliocène et 2/ l'accident bordure de l'arc de Nice, qui ont réjoué depuis le stade 5.5. Les rejets verticaux sont calibrés : quoique modérés ils sont notables, surtout pour l'" accident du Var " qui se situe en dehors du domaine alpin. Le rejet vertical quaternaire de cet accident est attribué à la réactivation récente d'anciennes failles normales situées sous le bassin

The Fontainebleau Sandstone: bleaching, silicification and calcite precipitation under periglacial conditions

It will be show that the typical Fontainebleau Sandstone facies are in fact secondary facies, developed post‐deposition, and related to surface exposure of the formation. Quartzite pans, white sands, and even the mineralogical composition are related to subsurface (groundwater) alterationsconnected to geomorphology and result from exposure during the last glacial periods.The Fontainebleau Sandstone example is extremely spectacular. Yet, such alteration features also exist in many other formations and may extent to 50‐100 m depth. One has to be attentive to recognize them. The goal of the field trip is to bring insight into what is related to primary and to secondary processes in the outcropping formation. This is of prime/particular importance for better understanding of the geology of the Fontainebleau Sandstone … and the geochemical processes that led to make up theses exceptionally pure sandstones mined to be used in all high quality and luxury glass manufactories throughout Europe. and supply guides for prospecting such sand ores.But in a general way, when such alteration happen, it is essential to recognize them before any geochemical study because interpretations, in particular isotopic interpretations may completely diverge as a primary or a secondary hypothesis is envisaged for some facies … like marine deposits vs groundwater precipitation, dry and warm vs glacial climates, sedimentary deposition vs acidic leaching, etc

Datation des calcites et des grès de Fontainebleau : une remise à plat de l'âge des silicifications des terrains tertiaires du Bassin.de Paris

National audienceLa mise en lumière du rôle des périodes froides dans les mécanismes de précipitation de la silice permet de proposer un modèle de silicification unique, homogène et cohérent pour toutes les silicifications du Bassin de Paris : grès, calcaires silicifiés et meumières. Ce modèle doit être envisagé bien au-delà du Bassin de Paris, nombre de silicifications des formations tertiaires d’Europe, d’Amérique du nord et de régions altitudinales plus méridionales ( ?) méritent d’être revisitées avec un œil neuf

Multi-scale analysis of a viscoelastic liquid jet

WOS:000403628200001International audienceA multi-scale analyzing tool is now available to investigate the temporal evolution of two phase flows such as liquid systems experiencing an atomization process. Thanks to its multi-scale and global nature, it allows identifying all dynamics simultaneously involved in the process with no restriction of the liquid system shape. In the present work this multi-scale tool is applied on 2D visualizations of free falling jets of a low-viscosity viscoelastic solution. The jets are produced from a cylindrical discharge orifice and the liquid is a very dilute polymer solution containing 5 ppm of Poly(ethylene oxide). High spatial resolution images of the free falling jets are performed as a function of the velocity and at several distances from the discharge orifice. For every operating condition, the liquid jet remains cylindrical first, then shows the development of a sinusoidal perturbation and finally adopts a beads-on-a-string pattern before breakup occurs. The multi-scale analysis is performed on a high number of images and at several spatial positions in order to return statistical and temporal information, respectively. The results of this analysis show that during the sinusoidal perturbation stage, the large-scale region follows an exponential increase as predicted by the linear stability theory and during the beads-on-a-string stage, the small-scale region follows an exponential decrease similar to an elasto-capillary regime from which the relaxation time of the polymer solution can be extracted. This work positions the multi-scale approach as a promising and complementary tool to the currently used techniques in order to probe complex liquid rheology, especially in the case of mobile viscoelastic solutions

Clarification of the Algerian grape juice and their effects on the juice quality

The aim of this study was to find a good clarification method to eliminate the substances in Algerian grape juice and study the effects of the clarification agents on juice quality. The clarified grape juice was subjected to different treatments, namely bentonite, gelatin, combination of gelatin and bentonite, then stored for 4 weeks. The effects of fining treatment by determining the critical micillary concentration of each agent used accelerated stability test on turbidity, tannin contents (ethanol index, condensed tannins, total polyphenol and anthocyanins) and microbiological quality of clarified grape juice were evaluated during storage. Fining treatment and storage had a significant (p < 0.05) effect on turbidity, tannins, total polyphenol, condensed tannins and anthocyanins. However, a better percentage elimination was noted for freshly squeezed grape juice with a combination of gelatin and bentonite corresponding to a turbidity of 6.5 NTU. The clarifiers separately gave lower removal rates than average, up to 83% of tannins present in the freshly squeezed juice has been eliminated using the bentonite. The results obtained are very satisfactory since we were able to obtain a clear juice of good microbial quality while ensuring the preservation of the organoleptic and nutritional qualities during the treatment and the storage of the juice.   Bull. Chem. Soc. Ethiop. 2020, 34(1), 1-11. DOI: https://dx.doi.org/10.4314/bcse.v34i1.