Estimates of fracture density and uncertainties from well data

International audienceThis paper aims at building a method to estimate the probability law governing the 3D fracture density of a fractured rock conditioned to the number of traces observed on a borehole image when the spatial distribution of fracture centers is assumed to follow a Poisson process. A closed-form expression of this law, allowing to calculate its mean value as well as a confidence interval, is derived in both cases of a lineic well (scanline) and a cylindrical well. The latter is better adapted to the situation of fracture size of the same order of magnitude as the well radius, which enables the presence of partial traces. In particular, the method takes into account the bias in the density estimate due to the fact that a fracture may cut the well along two distinct traces according to the considered fracture size. Monte Carlo simulations finally show a good agreement with the theoretical results of mean density and confidence interval

An Optimization method for the Configuration of Inter Array Cables for Floating Offshore Wind Farm.

International audienceIFP Energies nouvelles (IFPEN) is involved for many years in various projects for the development of floating offshore wind turbines. The commercial deployment of such technologies is planned for 2020. The present paper proposes a methodology for the numerical optimization of the inter array cable configuration. To illustrate the potential of such an optimization, results are presented for a case study with a specific floating foundation concept [1]. The optimization study performed aims to define the least expensive configuration satisfying mechanical constraints under extreme environmental conditions. The parameters to be optimized are the total length, the armoring, the stiffener geometry and the buoyancy modules. The insulated electrical conductors and overall sheath are not concerned by this optimization. The simulations are carried out using DeepLines TM , a Finite Element software dedicated to simulate offshore floating structures in their marine environment. The optimization problem is solved using an IFPEN in-house tool, which integrates a state of the art derivative-free trust region optimization method extended to nonlinear constrained problems. The latter functionality is essential for this type of optimization problem where nonlinear constraints are introduced such as maximum tension, no compression, maximum curvature and elongation, and the aero-hydrodynamic simulation solver does not provide any gradient information. The optimization tool is able to find various local feasible extrema thanks to a multi-start approach, which leads to several solutions of the cable configuration. The sensitivity to the choice of the initial point is demonstrated, illustrating the complexity of the feasible domain and the resulting difficulty in finding the global optimum configuration

Chance Constraint Optimization of a Complex System: Application to the Fatigue Design of a Floating Offshore Wind Turbine Mooring System

In this paper, we seek to minimize the cost of the anchoring system of a floating offshore wind turbine under reliability constraints. Taking into account the uncertainties on the model, on the resistance threshold and on the environmental conditions implies constraints expressed as probabilities depending on random vectors and a piecewise stationary Gaussian process. The main difficulty of the studied problem is to compute these probabilities since reliability methods require many calls to the simulator of the system. We propose in this paper a two-step methodology allowing to solve the optimization problem with a reasonable number of calls to the simulator. First, we exploit the properties of the problem to reformulate the constraints into easier to compute ones. Then we propose a new approach based on adaptive kriging well suited to the reformulated problem: AK-ECO

Un modèle éléments finis avec contact et frottement en petits glissements pour la tension et la flexion d'un câble spiralé monotoron

National audienceEn considérant que les glissements au sein d’un câble restent petits, même lors de flexion avec des rayons de courbure d’une dizaine de mètres, nous proposons un nouveau modèle formulant le contact et le frottement entre des poutres, sans réactualisation de l’appariement de contact défini à l’état initial. Cette particularité offre un gain de 25 en temps de calcul et en robustesse par rapport aux modèles proposés dans la littérature. La distribution des tensions au sein du câble reste comparable à celle déterminée par des modèles poutre-poutre formulés en grand glissement

Anti-IL17 treatment ameliorates Down syndrome phenotypes in mice

Down syndrome (DS) is characterized by structural and functional anomalies that are present prenatally and that lead to intellectual disabilities. Later in life, the cognitive abilities of DS individuals progressively deteriorate due to the development of Alzheimer's disease (AD)-associated neuropathology (i.e., ?-amyloid (A?) plaques, neurofibrillary tangles (NFTs), neurodegeneration, synaptic pathology, neuroinflammation and increased oxidative stress). Increasing evidence has shown that among these pathological processes, neuroinflammation plays a predominant role in AD etiopathology. In AD mouse models, increased neuroinflammation appears earlier than A? plaques and NFTs, and in DS and AD models, neuroinflammation exacerbates the levels of soluble and insoluble A? species, favoring neurodegeneration. The Ts65Dn (TS) mouse, the most commonly used murine model of DS, recapitulates many alterations present in both DS and AD individuals, including enhanced neuroinflammation. In this study, we observed an altered neuroinflammatory milieu in the hippocampus of the TS mouse model. Pro-inflammatory mediators that were elevated in the hippocampus of this model included pro-inflammatory cytokine IL17A, which has a fundamental role in mediating brain damage in neuroinflammatory processes. Here, we analyzed the ability of an anti-IL17A antibody to reduce the neuropathological alterations that are present in TS mice during early neurodevelopmental stages (i.e., hippocampal neurogenesis and hypocellularity) or that are aggravated in later-life stages (i.e., cognitive abilities, cholinergic neuronal loss and increased cellular senescence, APP expression, A? peptide expression and neuroinflammation). Administration of anti-IL17 for 5?months, starting at the age of 7?months, partially improved the cognitive abilities of the TS mice, reduced the expression of several pro-inflammatory cytokines and the density of activated microglia and normalized the APP and A?1-42 levels in the hippocampi of the TS mice. These results suggest that IL17-mediated neuroinflammation is involved in several AD phenotypes in TS mice and provide a new therapeutic target to reduce these pathological characteristics.This study was supported by the Jerome Lejeune Foundation, Fundación Tatiana Pérez de Guzmán el Bueno, the Spanish Ministry of Economy and Competitiveness (PSI-2016-76194-R, SAF2014-55088-R, SAF2016-75195-R, AEI/FEDER, EU) and Luchamos por la Vida Foundatio

IL-17RA Signaling Reduces Inflammation and Mortality during Trypanosoma cruzi Infection by Recruiting Suppressive IL-10-Producing Neutrophils

Members of the IL-17 cytokine family play an important role in protection against pathogens through the induction of different effector mechanisms. We determined that IL-17A, IL-17E and IL-17F are produced during the acute phase of T. cruzi infection. Using IL-17RA knockout (KO) mice, we demonstrate that IL-17RA, the common receptor subunit for many IL-17 family members, is required for host resistance during T. cruzi infection. Furthermore, infected IL-17RA KO mice that lack of response to several IL-17 cytokines showed amplified inflammatory responses with exuberant IFN-γ and TNF production that promoted hepatic damage and mortality. Absence of IL-17RA during T. cruzi infection resulted in reduced CXCL1 and CXCL2 expression in spleen and liver and limited neutrophil recruitment. T. cruzi-stimulated neutrophils secreted IL-10 and showed an IL-10-dependent suppressive phenotype in vitro inhibiting T-cell proliferation and IFN-γ production. Specific depletion of Ly-6G+ neutrophils in vivo during T. cruzi infection raised parasitemia and serum IFN-γ concentration and resulted in increased liver pathology in WT mice and overwhelming wasting disease in IL-17RA KO mice. Adoptively transferred neutrophils were unable to migrate to tissues and to restore resistant phenotype in infected IL-17RA KO mice but migrated to spleen and liver of infected WT mice and downregulated IFN-γ production and increased survival in an IL-10 dependent manner. Our results underscore the role of IL-17RA in the modulation of IFN-γ-mediated inflammatory responses during infections and uncover a previously unrecognized regulatory mechanism that involves the IL-17RA-mediated recruitment of suppressive IL-10-producing neutrophils

2D and 3D Finite Element Restorations of Geological Structures with Sliding Contact Along Faults

International audienceA fully implicit finite element method is developed for the restoration of sedimentary basins. Internal deformationis distributed with a linear hyper-elasticity constitutive law. Deformation is also accommodated by large slidingalong faults. This mechanism is represented by a frictionless bilateral contact algorithm between deformablebodies. Application are shown with 2D forward or backward models of thrust related folding with multipleintersecting discontinuities. An example demonstrates how this restoration algorithm enables to detectmisinterpretation in the structural model. One advantage of the method is to allow 3D modeling, as shown bythe restoration of a Miocene anticline in the Iranian Zagros thrust belt. The main interest of this method will be tofacilitate the coupling between restoration and forward modeling

A study on testing techniques for concrete-like materials under compressive impact loading

An analysis of specific experimental problems encountered in the testing of concrete and concrete-like materials under impact loading, using the split Hopkinson pressure bar test (SHPB) or the so-called direct impact Hopkinson bar test (DIHB), is presented in this paper. On the one hand, in data processing, it is shown that recent improvements such as wave dispersion correction and exact time shifting are indispensable to obtain accurate measurements in those tests. On the other hand, the conventional analyses of those two kinds of tests are investigated with the aid of transient numerical simulations. It is concluded that only one of the conventionally used formula offers a good estimate of stress-strain curve for concrete-like materials. It is also illustrated that the usual assumptions of DIHB analysis are not reliable for the concrete-like specimen. An inverse approach is nevertheless possible to give more accurate results

Post-buckling of an elastic plate over an inviscid and buoyant fluid

The model problem proposed to study the buckling of stratified geological layers consists of a linearly elastic plate, capable of accommodating finite rotations, resting over an inviscid and buoyant fluid. The Lyapunov–Schmidt–Koiter decomposition is applied to construct the bifurcated equilibrium solutions. The asymptotic analysis of the post-buckling reveals a decrease in the magnitude of the lateral compressive force during an overall shortening of the stratified structure. Buckling and post-buckling are not influenced by the presence of a vertical stress gradient in the elastic plate