derniers depôts

Ajouté le 21/09/2018

In this paper, we propose a statistical methodology to test whether the texture of an image is isotropic or not. This methodology is based on the well-known quadratic variations defined as averages of square image increments. Specific to our approach, these variations are computed in different directions using grid-preserving image rotations.

Ajouté le 20/09/2018

We consider a Glauber dynamics associated with the Ising model on a large two-dimensional box with with minus boundary conditions and in the limit of a vanishing positive external magnetic field. The volume of this box increases quadratically in the inverse of the magnetic field.

Ajouté le 18/09/2018

The numerical resolution of the Compressible Two-Layer model proposed in [Demay & Hérard, CMAT 2017] is addressed in this work with the aim of simulating mixed flows and entrapped air pockets in pipes. This five-equation model provides a unified two-phase description of such flows which involve transitions between stratified regimes (air-water herein) and pressurized or dry regimes (pipe full of water or air).

Ajouté le 18/09/2018

In this paper, we focus on the analysis of image textures modeled by anisotropic fractional Brownian fields. We propose some anisotropy indices intended to characterize the anisotropy of these textures. The construction of these indices relies upon the use of multi-oriented quadratic variations. It is based on directional quantities appearing in their asymptotic expectation. We show that anisotropy indices are invariant to some image transforms, and estimable from observed data.

Ajouté le 14/09/2018

A short enantioselective catalytic synthesis of the key C15–C27 fragment of bastimolide A, a natural product showing promising antimalarial bioactivity, is disclosed. The strategic insertion of halogen atoms such as fluorine and chlorine by enantioselective organocatalytic halogenations allowed an excellent stereochemical control for the formation of complex acyclic fragments bearing up to four stereogenic centers.

Ajouté le 12/09/2018

A short enantioselective catalytic synthesis of the key C15−C27 fragment of bastimolide A, a natural product showing promising antimalarial bioactivity, is disclosed. The strategic insertion of halogen atoms such as fluorine and chlorine by enantioselective organocatalytic halogenations allowed an excellent stereochemical control for the formation of complex acyclic fragments bearing up to four stereogenic centers.

Ajouté le 11/09/2018

Background: Plant biomass conversion for green chemistry and bio-energy is a current challenge for a modern sustainable bioeconomy. The complex polyaromatic lignin polymers in raw biomass feedstocks (i.e., agriculture and forestry by-products) are major obstacles for biomass conversions. White-rot fungi are wood decayers able to degrade all polymers from lignocellulosic biomass including cellulose, hemicelluloses, and lignin.

Ajouté le 05/09/2018

This paper addresses an efficient and robust automatic adaptive local multilevel mesh refinement strategy for unilateral frictional contact problems in elastostatics. The proposed strategy couples the Local Defect Correction multigrid method LDC (Hackbusch, 1984) with the ZZ (Zienkiewicz and Zhu, 1987) a posteriori error estimator. An extension of LDC method to frictional contact problems is introduced.

Ajouté le 05/09/2018

This article studies the complexity of the word problem in groups of automorphisms of subshifts. We show in particular that for any Turing degree, there exists a subshift whose automorphism group contains a subgroup whose word problem has exactly this degree.

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