École normale supérieure de Cachan

About: École normale supérieure de Cachan is a education organization based out in Cachan, Île-de-France, France. It is known for research contribution in the topics: Decidability & Finite element method. The organization has 2717 authors who have published 5585 publications receiving 175925 citations.

Complete finite prefixes of symbolic unfoldings of safe time petri nets

Abstract: Time Petri nets have proved their interest in modeling real-time concurrent systems. Their usual semantics is defined in term of firing sequences, which can be coded in a (symbolic and global) state graph, computable from a bounded net. An alternative is to consider a “partial order” semantics given in term of processes, which keep explicit the notions of causality and concurrency without computing arbitrary interleavings. In ordinary place/transition bounded nets, it has been shown for many years that the whole set of processes can be finitely represented by a prefix of what is called the “unfolding”. This paper defines such a prefix for safe time Petri nets. It is based on a symbolic unfolding of the net, using a notion of “partial state”.

Quantitative Analysis of Dynamic Fault Trees based on the Structure Function

Abstract: This paper presents a probabilistic model of dynamic gates which allows to perform the quantitative analysis of any Dynamic Fault Tree (DFT) from its structure function. Both these probabilistic models and the quantitative analysis which can be performed thanks to them can accommodate any failure distribution of basic events. We illustrate our approach on a DFT example from the literature.

Brittle and ductile failure of rocks: Embedded discontinuity approach for representing mode I and mode II failure mechanisms

Abstract: In this work we present a discrete beam lattice model with embedded discontinuities capable of simulating rock failure as a result of propagating cracks through rock mass. The developed model is a 2D (plane strain) micro- scale representation of rocks as a two-phase heterogeneous material. Phase I is chosen for intact rock part, while phase II stands for pre- existing micro-cracks and other defects. The proposed model relies on Timoshenko beam elements enhanced with additional kinematics to describe localized failure mechanisms. The model can properly take into account the fracture process zone with pre-existing microcracks coalescence, along with localized failure modes, mode I of tensile opening and mode II of shear sliding. Furthermore, we give the very detailed presentation for two different approaches to capturing the evolution of mode I and mode II, and their interaction and combination. The first approach is to deal with mode I and mode II separately, where mode II can be activated but compression force may still be transferred through rock mass which is not yet completely damaged. The second approach is to represent both modes I and II being activated simultaneously at a point where complete failure is reached. A novel numerical procedure for dealing with two modes failure within framework of method of incompatible modes is presented in detail and validated by a set of numerical examples.

Ruthenium(II) Complexes for Two-Photon Absorption-Based Optical Power Limiting

Abstract: Long-lived excitation: Novel bifluorene-substituted 1,10-phenanthroline-based RuII coordination complexes are presented (see picture). They fulfil several requirements for optimized optical power limiting in the visible-NIR, as they are stable, soluble and transparent at low laser fluences. The two-photon absorption of these complexes are strongly related to those of the ligand.