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.

Analytical static modelling and optimization of electrostatic micropumps

Abstract: Having developed a mechanical law with a simple elementary model of membrane deflection, we demonstrate the static instability of such a system under electrostatic actuation and provide an analytical solution for the membrane position. This allows us to highlight the sticking effect and the hysteresis phenomenon of the pump strike volume due to the nonlinearity of such excitation. We determine a parameter optimization procedure for the dimensions of the electrostatic actuated membrane in order to achieve maximum volume displacement.

Fatigue crack growth under non-proportional mixed-mode loading in ferritic-pearlitic steel

Abstract: Mode II fatigue crack growth tests as well as tests in sequential mode I and then mode II were performed on ferritic‐pearlitic steel. For ΔKII ranging from 7 to 43 MPa m−−√m\sqrt{m}, bifurcation occurs after 12–450 μm of coplanar growth at a decreasing speed. By contrast, hundreds of micrometres of constant speed coplanar growth were obtained under sequential mode I and then mode II loading, for ΔKII=20MPAm−−√m\sqrt{m} and ΔKI ranging from 0.25 to 1.0 ΔKII. The crack growth rate is a simple sum of the contributions of each mode for ΔKI= 0.25 ΔKII but above this value a synergetic effect is found. The mechanism of this fast‐propagation mode is discussed in the light of strain range maps ahead of the crack tip obtained by digital SEM image correlation and elastic–plastic finite element calculations. The stability of the crack path according to the maximum growth rate criterion is demonstrated.

Modeling and Control of Induction Motors

Abstract: Emmanuel Delaleau , Jean-Paul Louis , Romeo Ortega Laboratoire des signaux et systemes, CNRS – Supelec – Universite Paris-sud Plateau de Moulon, 3 rue Joliot-Curie 91 192 Gif-sur-Yvette cedex, France delaleau,ortega @lss.supelec.fr Laboratoire d’electricite, signaux et robotique Ecole normale superieure de Cachan 61, avenue du President Wilson 94 235 Cachan cedex, France jplouis@lesir.ens-cachan.fr

Photostability of 2D Organic-Inorganic Hybrid Perovskites.

Abstract: We analyze the behavior of a series of newly synthesized (R-NH3)2PbX4 perovskites and, in particular, discuss the possible reasons which cause their degradation under UV illumination. Experimental results show that the degradation process depends a lot on their molecular components: not only the inorganic part, but also the chemical structure of the organic moieties play an important role in bleaching and photo-chemical reaction processes which tend to destroy perovskites luminescent framework. In addition, we find the spatial arrangement in crystal also influences the photostability course. Following these trends, we propose a plausible mechanism for the photodegradation of the films, and also introduced options for optimized stability.

FeatherTrait: A modest extension of Featherweight Java

Abstract: In the context of statically typed, class-based languages, we investigate classes that can be extended with trait composition. A trait is a collection of methods without state; it can be viewed as an incomplete stateless class. Traits can be composed in any order, but only make sense when imported by a class that provides state variables and additional methods to disambiguate conflicting names arising between the imported traits. We introduce FeatherTrait Java (FTJ), a conservative extension of the simple lightweight class-based calculus Featherweight Java (FJ) with statically typed traits. In FTJ, classes can be built using traits as basic behavioral bricks; method conflicts between imported traits must be resolved explicitly by the user either by (i) aliasing or excluding method names in traits, or by (ii) overriding explicitly the conflicting methods in the class or in the trait itself. We present an operational semantics with a lookup algorithm, and a sound type system that guarantees that evaluating a well-typed expression never yields a message-not-understood run-time error nor gets the interpreter stuck. We give examples of the increased expressive power of the trait-based inheritance model. The resulting calculus appears to be a good starting point for a rigorous mathematical analysis of typed class-based languages featuring trait-based inheritance.