Search results for " light"
showing 10 items of 1141 documents
Fenêtres sur ciel étoilé
2019
International audience; L’engouement pour la création de réserves de « protection du ciel étoilé » s’étend à un nombre croissant de pays. Impulsé par les milieux de l’astronomie professionnelle et amateur, relayé par d’autres protagonistes publics et privés impliqués dans la réussite et la valorisation de la démarche, cet élan a notamment pris corps autour d’observatoires scientifiques de montagne. Figures emblématiques de l’histoire de l’aménagement de la montagne, ces observatoires ouvrent aussi un espace d’intermédiation entre nos sociétés contemporaines, technicistes et sophistiquées, et des mécanismes célestes porteurs d’enjeux environnementaux concrets.
Getting night lighting right taking account of nocturnal urban uses for better-lit cities
2018
Translated by Oliver Waine; International audience; Innovation in contemporary urban lighting has increasingly been driven by issues of sustainability. While environmental concerns focus attention on energy savings and reducing light pollution, taking account of how people use public spaces is important too, as artificial light can then be adjusted to actual needs. Following the pioneering work of Roger Narboni and Luc Gwiazdzinski, Samuel Challéat and Dany Lapostolle make the case for dedicated nocturnal city planning.
“Narrative Thunder; or, The Double Axes of Poetic Romanticism in ‘The LightningRod Man’”
2002
International audience
“Narrative Thunder; or, The Double Axes of Poetic Romanticism in ‘The Lightning Rod Man’”
2001
International audience
Target 5G visible light positioning signal subcarrier extraction method using particle swarm optimization algorithm
2021
International audience; With the explosive growth of demand for Internet of Things (IoT) applications and the increasing dependence of users on wireless connections, indoor location based service(LBS) under 5G-Public-Private Partnership (5G-PPP) using cases have received more attention and get rapid development. Thanks to the safty, security and customization of 5G network pointed by 5G forum white paper, indoor positioning systems using unified 5G New Radio (NR) signals have become the focus of the next generation of visible light positioning (VLP) systems. In 5G New Radio(NR) frame, totally 192 subcarriers are used to carry positioning reference signal(PRS). In order to improve the positi…
Nouveaux systèmes de contrôle de la polarisation de la lumière par effets non lineaires dans les fibres optiques
2013
This thesis deals with the work the development of an all-optical device for the control of the polarization state of light. Actually, this feature of light remains so far an uncontrolled variable, which can degrade the performances of all-optical systems. Based on nonlinear interaction between two counterpropagating waves inside an optical fiber, this device called polarization attractor allows to control the polarization state of light without polarization dependent losses.In a first part, we carry out extensive studies of the polarization attractor properties leading to the control and the regeneration of the polarization state of the 10-Gb/s NRZ and RZ telecommunication signals. Then, t…
3D acquisition system for transparent objects
2010
This thesis deals with a new automated tridimensional inspection system for transparent surfaces, based on polarization analysis. We first present an extension of the ‘Shape from Polarization’ method for transparent surfaces. After being reflected, an unpolarized light wave becomes partially linearly polarized, depending on the surface normal and on the refractive index of the media it impinges on. Hence, by measuring the polarization parameters of the reflected light, the surface normals are computed. The ambiguity concerning the normal orientation is solved here with a multispectral lighting system. Finally, the description of the whole acquisition prototype is given as well as some exper…
On improving the accuracy of Visible Light Positioning system using deep autoencoder
2020
International audience; DC-biased optical Orthogonal Frequency DivisionMultiplexing (DCO-OFDM)-based visible light positioning (VLP)technology along with the Received Signal Strength(RSS) po-sitioning algorithm is widely used to achieve centimeter levelpositioning accuracy for incoming 5G era, especially indoorenvironment. However, the DCO-OFDM has the peak-to-averagepower ratio (PAPR) issue which imposes the nonlinear distortionand it will directly affect the positioning accuracy in the VLPsystem. The PAPR reduction scheme is urgently needed. There-fore, in this paper, the impact of PAPR reduction scheme onpositioning accuracy is investigated. The positioning accuracywith and without the s…
Blaming the Light, Claiming the Night. Actors, Issues and Effects of Lighting Conflicts in France since the 1980's
2014
International audience; Regarding environmental issues, conflictuality is a privileged way to reach the political arena. "Naming, Blaming, Claiming": three steps that make the controversy emerge, constitute the public issue, then bring it to the politi- cal agenda. These three stages are clearly identifiable in the history of night protection associative movements. These movements emerged in the 1970's in the United States of America, quickly disseminated enjoying a broader context of environmental thinking. Conflicts related to artificial lighting are structurally akin to conflicts of contradictory uses of a single resource: the night. For some - the technicists -, the night is the "good-s…