Search results for "IQ"
showing 10 items of 21401 documents
The Calderón problem for the fractional Schrödinger equation with drift
2020
We investigate the Calder\'on problem for the fractional Schr\"odinger equation with drift, proving that the unknown drift and potential in a bounded domain can be determined simultaneously and uniquely by an infinite number of exterior measurements. In particular, in contrast to its local analogue, this nonlocal problem does \emph{not} enjoy a gauge invariance. The uniqueness result is complemented by an associated logarithmic stability estimate under suitable apriori assumptions. Also uniqueness under finitely many \emph{generic} measurements is discussed. Here the genericity is obtained through \emph{singularity theory} which might also be interesting in the context of hybrid inverse pro…
The fractional Calderón problem: Low regularity and stability
2017
The Calder\'on problem for the fractional Schr\"odinger equation was introduced in the work \cite{GSU}, which gave a global uniqueness result also in the partial data case. This article improves this result in two ways. First, we prove a quantitative uniqueness result showing that this inverse problem enjoys logarithmic stability under suitable a priori bounds. Second, we show that the results are valid for potentials in scale-invariant $L^p$ or negative order Sobolev spaces. A key point is a quantitative approximation property for solutions of fractional equations, obtained by combining a careful propagation of smallness analysis for the Caffarelli-Silvestre extension and a duality argumen…
On some partial data Calderón type problems with mixed boundary conditions
2021
In this article we consider the simultaneous recovery of bulk and boundary potentials in (degenerate) elliptic equations modelling (degenerate) conducting media with inaccessible boundaries. This connects local and nonlocal Calderón type problems. We prove two main results on these type of problems: On the one hand, we derive simultaneous bulk and boundary Runge approximation results. Building on these, we deduce uniqueness for localized bulk and boundary potentials. On the other hand, we construct a family of CGO solutions associated with the corresponding equations. These allow us to deduce uniqueness results for arbitrary bounded, not necessarily localized bulk and boundary potentials. T…
Partial Data Problems and Unique Continuation in Scalar and Vector Field Tomography
2022
AbstractWe prove that if P(D) is some constant coefficient partial differential operator and f is a scalar field such that P(D)f vanishes in a given open set, then the integrals of f over all lines intersecting that open set determine the scalar field uniquely everywhere. This is done by proving a unique continuation property of fractional Laplacians which implies uniqueness for the partial data problem. We also apply our results to partial data problems of vector fields.
Merging Features from Green's Functions and Time Dependent Density Functional Theory: A Route to the Description of Correlated Materials out of Equil…
2016
We propose a description of nonequilibrium systems via a simple protocol that combines exchange-correlation potentials from density functional theory with self-energies of many-body perturbation theory. The approach, aimed to avoid double counting of interactions, is tested against exact results in Hubbard-type systems, with respect to interaction strength, perturbation speed and inhomogeneity, and system dimensionality and size. In many regimes, we find significant improvement over adiabatic time dependent density functional theory or second Born nonequilibrium Green's function approximations. We briefly discuss the reasons for the residual discrepancies, and directions for future work.
Accélérer la recherche d'informations grâce aux dispositifs d'interaction : Système de navigation pour les documents numériques
2005
International audience; Cet article présente une démarche qui vise à doter les outils d'interaction tactiles usuels (souris informatique, pavé tactile) d'une commande de prévisualisation des objets désignés. Nous décrivons la genèse du dispositif ainsi que les bénéfices attendus en termes d'agrément d'usage et d'accélération des recherches d'information dans certains contextes (retrouver une page qui a déjà été consultée par exemple). Nous limiterons notre description dans le cadre de cet article aux apports du dispositif à la consultation de documents numériques et en particulier aux sites Internet.
Handicap et qualité de vie
2010
Pratique de l'enseignement de l'anglais dans les facultés de médecine en France métropolitaine
2007
Abstract English lessons have been compulsory in French medical schools since the 18th March 1992 bill. Objectives: The aim of this work is to describe the characteristics of this teaching programme as it exists in 2005. Methods: A questionnaire designed by experts in the teaching of medical English was sent to the 41 medical schools in Metropolitan France. The questionnaire covered five different areas (the number of hours of lessons, of students and of teachers; evaluation and marking methods; lesson contents and pedagogical methods; student and teacher profiles; the teaching of English for postgraduate students). Results: Twenty-six questionnaires have been returned and evaluated, which …
Dynamiques de développement et inégalités régionales en Chine
2009
Le rapide développement économique de la Chine a généré des inégalités socio-spatiales croissantes, qui se marquent par un décalage croissant entre provinces littorales et intérieures, et entre villes et campagnes. À partir de l’examen des données statistiques officielles chinoises, on peut clairement repérer une aggravation des déséquilibres internes de la Chine, qui sont des facteurs potentiels de déstabilisation sociale, en particulier dans le cas des paysans venus tenter leur chance dans les grandes aires urbaines littorales, ou chassés de leurs terres par l’expansion périmétropolitaine. Cela entraîne aujourd’hui une politique différenciée d’aménagement du territoire chinois visant à co…
UV filters: From sunscreens to human body and the environment
2007
Recognition of the harmful effects of ultraviolet (UV) radiation on the skin has triggered development of organic chemicals (commonly referred as UV filters) that can absorb UV radiation and attenuate the negative effects of sunlight exposure. Depending on the properties and the intended degree of protection, a wide array of combinations is being marketed as delivering protection against most kinds of UV-induced skin damage. However, some UV filters have dermatological implications, so maximum applicable concentrations have been established. To monitor to what extent commercial products comply with the mandatory limits, several analytical methods have been used for their determination in co…