An Agent-based Framework for Identity Management The Unsuspected Relation with ISOIEC 15504 _ presentation

The generalization of open and distributed systems and the dynamics of the environment make Information Systems (IS) and, consequently, its access rights management an increasingly complex problem. Even if support for this activity appears to be well handed by current sophisticated solutions, the definition and the exploitation of an access rights management framework appropriately adapted for a company remain challenging. This statement is explained mainly by the continuous growth of the diversity of stakeholderspsila positions and by the criticality of the resources to protect. The SIM project, which stands for ldquoSecure Identity Managementrdquo, addresses this problem. The objectives of our paper are twofold. First, to make rights management align closer to business objectives by providing an innovative approach that focuses on business goals for defining access policy. The ISO/IEC 15504 process-based assessment model has been preferred for that research. Indeed, the structured framework that it offers for the description of activities allows for the establishment of meaningful links with responsibilities concepts. Secondly, to automate the deployment of policies through the company IT infrastructurepsilas components and devices by defining a multi-agent system architecture that provides autonomy and adaptability. Free and open source components have been used for the prototyping phase

Normal Stresses and Interface Displacement: Influence of Viscoelasticity on Enhanced Oil Recovery Efficiency

International audienceOne of chemical Enhanced Oil Recovery (EOR) methods consists in injecting aqueous solutions of polymers into the reservoir in order to improve mobility ratio between the injected fluid and the remaining oil. This "polymer flooding" process is usually only characterized with the low shear viscosity of the injected fluid, even if these aqueous solutions are strongly shear thinning and may show high elastic properties evidenced by normal stresses appearance. In order to study the mechanisms at the interface level, we develop simple model experimentations with the goal of quantifying the influence of viscoelastic properties on fluid displacement in a simple geometry. For this purpose, we propose and characterize a model fluid formulation, for which elastic and viscous effects can be tuned systematically. We study then the displacement of a viscous oil by a Newtonian non elastic, a viscoelastic or a purely shear thinning fluid in a two dimensional flow cell. Observing the shape of the interface between aqueous fluids and displaced oil permits to appreciate viscoelasticity effects on the displacement. Using model geometries and controlled rheology fluids, we show that viscoelastic fluids tend to better displace immiscible liquids than Newtonian fluids and that those effects are closely related to the apparitions of normal stresses independently of shear thinning property or variation of interfacial tension as soon as viscous effects govern the flow

Enhanced displacement of a liquid pushed by a viscoelastic fluid.

International audienceWe consider the displacement, in a rectangular channel, of a Newtonian oil pushed by different types of liquids (Newtonian, shear-thinning, viscoelastic) of slightly higher apparent viscosity. ln the absence of viscoelastic effects the interface between the two fluids becomes sharper at larger velocities, so that the thickness of the lateral film left behind increases with the flow rate. On the contrary, with a viscoelastic fluid, the shape of the interface is almost independent of the velocity so that the thickness of the lateral film is approximately constant. Moreover this thickness decreases when the ratio of normal to tangential stresses increases, suggesting that this effect can be attributed to normal stress differences. A heuristic theoretical approach tends to confirm this statement

Entrance and exit effects for a viscoelastic liquid displacing a simple liquid through a contraction.

International audienceWe studied the displacement of the interface between a viscoelastic fluid pushing a simple liquid through a rectangular contraction by following the front interface deformation in time. The progressive deformation of the interface until apparent stabilization is followed, which makes it possible to identify a transient and a stationary regime. For low Weissenberg number the shape of the interface is essentially similar to that between two simple liquids. For sufficiently large Weissenberg number the shape of the interface is different: it is narrower before the entrance and wider just after the exit. The characteristics of this shape are qualitatively analogous to those of the interface between the vortices and the convected regions for the flow of a single viscoelastic fluid through a contraction- expansion. This suggests that the entrance effect is due to extensional effects and the exit effect is due to normal stress effects