Failure mechanisms and surface roughness statistics of fractured Fontainebleau sandstone

In an effort to investigate the link between failure mechanisms and the geometry of fractures of compacted grains materials, a detailed statistical analysis of the surfaces of fractured Fontainebleau sandstones has been achieved. The roughness of samples of different widths W is shown to be self affine with an exponent zeta=0.46 +- 0.05 over a range of length scales ranging from the grain size d up to an upper cut-off length \xi = 0.15 W. This low zeta value is in agreement with measurements on other sandstones and on sintered materials. The probability distributions P(delta z,delta h) of the variations of height over different distances delta z > d can be collapsed onto a single Gaussian distribution with a suitable normalisation and do not display multifractal features. The roughness amplitude, as characterized by the height-height correlation over fixed distances delta z, does not depend on the sample width, implying that no anomalous scaling of the type reported for other materials is present. It is suggested, in agreement with recent theoretical work, to explain these results by the occurence of brittle fracture (instead of damage failure in materials displaying a higher value of zeta = 0.8).Comment: 7 page

Modélisation et statistiques en génétique des populations

Travaux soutenus dans le cadre d'une Action Incitative Programmée de l'INRA 1996-1997 *INRA, Laboratoire de Biométrie, Jouy en Josas Diffusion du document : INRA, Laboratoire de Biométrie, Jouy en JosasNational audienc

Direct and one-pot conversion of polyguluronates and alginates into alkyl-L-guluronamide-based surfactant compositions

International audienceWe describe here an efficient one-pot process for the synthesis of 100% bio-based L-guluronic acid based surfactant compositions as emulsion stabilizers, directly from L-polyguluronate or whole alginate, a renewable polysaccharide extracted from brown seaweeds. The transformation of these polymers into long-chain alkyl-L-guluronamides associated with D-mannuronamides when the alginate was used, has been achieved through the preparation of n-butyl uronate monosaccharide intermediates involving methane sulfonic acid-promoted hydrolysis, Fisher glycosylation and esterification reactions, followed by an in situ solvent-free aminolysis reaction with fatty amines

Juin 99. Proposition de programme scientifique : diffusion d'organismes génétiquement modifiés et environnement

*INRA, Laboratoire de Biométrie, Jouy en Josas Diffusion du document : INRA, Laboratoire de Biométrie, Jouy en JosasNational audienc

Analyse rétrospective sur le devenir de variétés de colza 0 et 00 dans l'environnement

National audienc

Changements d'echelles de flux de gènes. Analyse spatio-temporelle en vue de l'aide à la décision

International audienc

Computer Science and Engineering Research Review 1976-1977

Table of Contents: Introduction / Robert L. Sproull p. 3; RIG, Rochester's Intelligent Gateway: System Overview / Eugene Ball, Richart Rashid p. 5; The CERF Computer System / Neil Wilhelm, Daved Pessell, Charles Merriam p. 12; Geometric Modelling of Mechanical Parts and Processes / Herbert Voelcker, Aristides Requicha p. 17; Automatic Data Structure Selection / Jerome Feldman, James Low, Paul Rovner p. 29; Seminar Meetings p. 34; Publications p. 37; Grant Support p. 3