A coupled discrete element - lattice Boltzmann method to investigate internal erosion in soil

International audienceIn this paper, we present a coupled Discrete Element (DE) and Lattice Boltzmann (LB) method to model fluid-solid interactions. This method is applied to study and model a two-dimensional piping erosion through a set-up inspired by the Hole Erosion Test (HET). In this work, we mainly focus on grain detachments under hydraulic loading. Simulation results show that the erosion law classically used in such experiments, can be retrieved with our model. It illustrates that such coupled systems can be investigated with the LB-DE approach developed in this work. This approach is a promising tool which is well designed to perform such investigations at the grain scal

Proceedings of SUMo and CompoNet 2011

International audienc

Sedimentary processes in the Thau Lagoon (France): From seasonal to century time scales

As a part of the MICROBENT programme, an investigation of the sedimentation framework was carried out at the water-sediment interface in the Thau Lagoon (French Mediterranean coast). Two main sites, C4 in the middle of the lagoon and C5 near oyster farms, were visited six times between December 2001 and May 2003. Interface sediments were studied using classical sedimentology parameters (radiography RX, grain size distribution) and analysis of selected radionuclides (234Th, 7Be, 210Pb, 226Ra). On a century time scale, excess 210Pb (210Pbxs) presents classical profiles with an upper mixed layer, followed by an exponential decrease of activities to undetectable levels below 20 – 30 cm. At the central site, C4, cores seem to register episodic changes in mean grain size, presenting recurrently peaks. The upper 10 cm of 210Pbxs profiles at site C5 exhibit a mixed layer associated with coarser sediments: this could be related to biological activity. Sedimentation rates derived from 210Pbxs varied from 0.15 cm y−1 at the edge of the basin, to 0.25 cm y−1 at the central site. On a seasonal time scale, 234Th and 7Be both show significant variations in activities and in penetration within the sediment. Bioturbation rates derived from both radionuclides agree well and range between 1–10 cm2 y−1 at site C4 and 1–31 cm2 y−1 at site C5. 234Th and 7Be fluxes at the water-sediment interface show too seasonal variations, more pronounced for site C5. This latter site presents especially a higher variability that is well marked with season, probably in relation with its position near oyster farms

IChem:AVersatile Toolkit for Detecting, Comparing, and Predicting Protein-Ligand Interactions

International audienceStructure-based ligand design requires an exact description of the topology of molecular entitiesu nder scrutiny.I Chem is a softwarep ackage that reflects the many contributions of our research group in this area over the last decade. It facilitates and automates many tasks (e.g.,l igand/cofactor atom typing, identification of key water molecules) usually left to the model-er's choice. It therefore permits the detection of molecular interactions between two molecules in av ery precise and flexible manner.M oreover,I Chem enables the conversion of intricate three-dimensional (3D) molecular objectsi ntos imple representations (fingerprints, graphs) that facilitate knowledge ac-quisitiona tv ery high throughput.T he toolkiti sa ni deal companion for setting up and performing many structure-based designc omputations

Assessing the vulnerability of SMEs: a qualitative analysis

International audienceThe Very Small Business (VSB) and the Small or Medium-sized Enterprise (SME), like any other socioeconomic entity, faces multiple risks (fire, loss of a major supplier, work-related accidents, failure of a partnership, industrial espionage, etc.). However, unlike their larger counterparts, they do not have at their disposal dedicated tools for global risk management and thus lack ways to ensure their sustainability. In this context, the AFNOR Group, in collaboration with the Centre for Research on Risks and Crises of MINES ParisTech, carried out a research project to address this issue

The contribution of the Life Cycle Concept to Reduced Vulnerabilities in Small Businesses

International audienceThe focus of this article lies in the deployment of a comprehensive risk management approach within an SME (Small or Medium-sized Enterprise) which calls for a description and explanation of their idiosyncrasies, in relation to their specific needs and expectations, which change over time. It describes the evolution of the business using the lifecycle concept which highlights the modifications and changes in configuration that this type of organization experiences during its development. This concept is used in order to characterize the vulnerabilities of SMEs using a model which brings together hazards, consequences and the stage of company development. This article aims to define and legitimize the use of the lifecycle concept as a basic component of a global risk management approach in an SME. It describes an operational approach to reducing vulnerability based on the level of organizational maturity

Reducing the Risks Faced by Small Businesses:The Lifecycle Concept

International audienceThe deployment of a comprehensive risk management approach within an SME (Small or Medium-sized Enterprise) requires reconsideration of enduring preconceptions. However, it also calls for a description and explanation of their idiosyncrasies, in relation to their specific needs and expectations, which change over time. It is therefore appropriate to use the lifecycle concept to study the various phases of development of SMEs. The concept highlights the modifications and changes in configuration that this type of organization experiences during its development. This article aims to define and legitimize the use of the lifecycle concept as a basic component of a global risk management approach in an SME. It describes an operational approach to reducing vulnerability based on the level of organizational maturity

Dynamic tests on a cohesive and frictional material. Influence of high pressure and high strain rate on compaction and shear.

International audienceMany of aggregate composites are made of small size particles mixed with a highly compliant rubbery polymer. When the loading leads to high pressures, the behaviour gets closer to this of cohesive, frictional, and compactable materials. When this kind of material is subjected to an impact, the loading domain is the case of high pressure (from 100 to 1000 MPa) and high strain rate (roughly 1000 s-1). An experimental study is led by using the technique of the SHPB. The specimens are small cylinders placed in a ring which creates a passive confinement by opposing to the radial displacements. The instrumentation of the ring allows to estimate the radial stress and the radial displacement. The main point is that it makes possible the follow-up of the spherical and deviatoric parts of the stress and strain tensors during the test, without restrictive hypothesis on the behaviour of the material. The results show a high sensitivity to the strain rate. The stresses evolutions show that the frictional phenomenon is sensitive even under high pressures