Paris West University Nanterre La Défense

About: Paris West University Nanterre La Défense is a education organization based out in Paris, France. It is known for research contribution in the topics: Computer science & Politics. The organization has 895 authors who have published 1430 publications receiving 21712 citations.

On the Support of a Skorohod Anticipating Stochastic Differential Equation

Abstract: This paper deals with an anticipating one-dimensional quasilinear stochastic differential equation of the Skorohod type. Some regularity properties of the solution are proved and we characterize the support of the law of the solution

Robust Low-Rank Change Detection for Multivariate SAR Image Time Series

Abstract: This article derives a new change detector for multivariate synthetic aperture radar (SAR) image time series (ITS). Classical statistical change detection methodologies based on covariance matrix analysis are usually built upon the Gaussian assumption, as well as an unstructured signal model. Both of these hypotheses may be inaccurate for high-dimension/resolution images, where the noise can be heterogeneous (non-Gaussian) and where the relevant signals usually lie in a low-dimensional subspace (low-rank structure). These two issues are tackled by proposing a new generalized likelihood ratio test based on a robust (compound Gaussian) low-rank (structured covariance matrix) model. The interest of the proposed detector is assessed on two SAR-ITS set from UAVSAR.

La persistance de l'inflation dans les modèles néo-keynésiens

Abstract: La persistance de l'inflation dans les modeles neo-keynesiens, par Mohamed Safouane Ben Aissa et Olivier Musy Nous derivons les dynamiques de l'inflation issues des differentes hypotheses d'ajustement des prix rencontrees dans la litterature neo-keynesienne. Pour chaque modele nous calculons la reponse de l'inflation et du produit suite a un choc sur le taux de croissance de la masse monetaire. Nous constatons que seules deux modelisations reproduisent correctement certains faits stylises importants concernant l'impact de ce type de choc monetaire : la premiere est la specification avec prix predetermines de Mankiw et Reis (2002) et la seconde celle a prix fixes de Gali et Gertler (1999). Aucune des autres alternatives examinees, y compris le modele a prix fixes de Fuhrer et Moore (1995), ne genere de reponse satisfaisante. Elles sont notamment toutes incapables de reproduire une persistance suffisante de l'inflation. Ceci montre que dans les modeles a prix fixes, la structure de rigidite choisie importe autant pour le degre de persistance de l'inflation que la presence ou non de valeurs retardees de l'inflation dans la dynamique.Numeros de classification du Journal of Economic Literature : E31, E52.

Non‐Local Reconfigurable Sparse Metasurface: Efficient Near‐Field and Far‐Field Wavefront Manipulations (Advanced Optical Materials 4/2021)

Abstract: and far-field wavefront manipulations Vladislav Popov1,∗ Badreddine Ratni, Shah Nawaz Burokur2,† and Fabrice Boust1,3‡ SONDRA, CentraleSupélec, Université Paris-Saclay, F-91190, Gif-sur-Yvette, France LEME, UPL, Univ Paris Nanterre, F92410 Ville d’Avray, France and DEMR, ONERA, Université Paris-Saclay, F-91123, Palaiseau, France Abstract In recent years, metasurfaces have shown extremely powerful abilities for manipulation of electromagnetic waves. However, the local electromagnetic response of conventional metasurfaces yields to an intrinsic performance limitation in terms of efficiency, minimizing their implementation in real-life applications. The efficiency of reconfigurable metasurfaces further decreases because of the high density of meta-atoms, reaching 74 meta-atoms per λ2 area, incorporating lossy tunable elements. To address these problems, we implement strong electromagnetic non-local features in a sparse metasurface composed of electronically reconfigurable meta-atoms. As a proof-of-concept demonstration, a dynamic sparse metasurface having as few as 8 meta-atoms per λ2 area is experimentally realized in the microwave domain to control wavefronts in both near-field and far-field regions for focusing and beam-forming, respectively. The proposed metasurface with its sparsity not only facilitates design and fabrication, but also opens the door to high-efficiency real-time reprogrammable functionalities in beam manipulations, wireless power transfer and imaging holography.

Experimentum crucis: Newton’s Empiricism at the Crossroads

Abstract: In this chapter I consider Newton’s use of the Baconian label experimentum crucis in his famous 1672 paper on Light and Colors. I take it to be a sort of ‘signpost’, or methodological clue, which, properly understood, can help us to assess the kind of ‘empiricist’ commitment that may be ascribed to Newton. In order to dispel persistent misunderstandings, the first part of the chapter shows how our present understanding of crucial experiments has been shaped by nineteenth-century philosophers of science, as part of a characteristically anti-Baconian methodology. It also shed light on the particularly ambiguous character of Newton’s methodological legacy. In the remaining parts of the paper, muting these retrospective overtones, I show what crucial instances, or crucial experiments, really meant for Bacon, and for his heirs, in order to elucidate Newton’s usage in the light of its actual context (chiefly, the one provided by Bacon, Descartes and Hooke). I argue that the crucial experiment in Newton’s 1672 paper is not devised to arbitrate between competing full-blown and empirically grounded theories, but rather to make the abstract structure of a new, and still unclear, phenomenon (namely: dispersion) entirely transparent. It functions as a ‘perceptual’ index rather than a judgmental criterion. Finally, I explain why the expression has been dropped in the published text of the 1704 Opticks. The ‘exhibiting’ function of the experimentum crucis is now taken over by a long and complex pattern of experiments. It is the whole complex composition of these optical experiments that is now ‘crucially’ exhibiting the abstract structure of refraction.