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.

Identification strategy in the presence of corrupted measurements

Abstract: – To propose and develop an identification method of material parameters from dynamics test in the presence of extensively corrupted measurements., – The method we propose, which is based on the use of the error in constitutive relation for identification problems in the framework of transient dynamics, leads to nonstandard wave propagation problems. For solving this numerical difficulty, we used the transition matrix method for short‐duration tests and the combined Riccati constant/transition matrix approach for long‐duration tests., – A numerical strategy adapted to the problem. Results obtained appears to be insensitive to perturbation of measurements up to a very high level of perturbation., – Only simple case of elastic bar have been treated so far., – Without any a priori information on the level of perturbation, this method is robust with respect to the perturbation. A coupling of two resolution methods allows to deal with problem of arbitrary duration.

Fluorinated β-Diketonate Diglyme Lanthanide Complexes as New Second-Order Nonlinear Optical Chromophores: The Role of f Electrons in the Dipolar and Octupolar Contribution to Quadratic Hyperpolarizability

Abstract: The second-order nonlinear optical (NLO) properties of [Ln(hfac)(3)(diglyme)] (hfac = hexafluoroacetylacetonate; diglyme = bis(2-methoxyethyl)ether; Ln = La, Ce, Pr, Sm, Eu, Gd, Er, Lu) complexes have been investigated by a combination of electric-field second harmonic generation (EFISH) and harmonic light scattering (HLS) techniques, providing evidence for the relevant role of f electrons in tuning the second-order NLO response dominated by the octupolar contribution. These lanthanide NLO chromophores allow a clean valuation of the influence of f electrons on the quadratic hyperpolarizability and on its dipolar and octupolar contributions. Molecular quadratic hyperpolarizability values measured by the EFISH method, beta(EFISH), initially increase rapidly with the number of f electrons, the value for the Gd complex being 11 times that of the La complex, whereas this increase is much lower for the last seven f electrons, the beta(EFISH) value of the Lu complex being only 1.2 times that of the Gd complex. The increase of beta(HLS), which is dominated by an octupolar contribution, is much lower along the Ln series. Remarkably, the good beta(HLS) values of these simple systems, well known for their luminescence properties, are reached at no cost of transparency.