Search results for " Geometry."

Topological Hopf algebras, quantum groups and deformation quantization

2003

After a presentation of the context and a brief reminder of deformation quantization, we indicate how the introduction of natural topological vector space topologies on Hopf algebras associated with Poisson Lie groups, Lie bialgebras and their doubles explains their dualities and provides a comprehensive framework. Relations with deformation quantization and applications to the deformation quantization of symmetric spaces are described

Observation of laser-induced field-free permanent planar alignment of molecules

2011

International audience; Permanent planar alignment of gas-phase linear molecules is achieved by a pair of delayed perpendicularly polarized short laser pulses. The experiment is performed in a supersonic jet, ensuring a relatively high number density of molecules with moderately low rotational temperature. The effect is optically probed on a femtosecond time scale by the use of a third short pulse, enabling a time-resolved birefringence detection performed successively in two perpendicular planes of the laboratory frame. The technique allows for an unambiguous estimation of the molecular planar delocalization produced within the polarization plane of the pulse pair after the turn-off of the…

An alternative space-time meshless method for solving transient heat transfer problems with high discontinuous moving sources

2016

International audience; The aim of this work is the development of a space-time diffuse approximation meshless method (DAM) to solve heat equations containing discontinuous sources. This work is devoted to transient heat transfer problems with static and moving heat sources applied on a metallic plate and whose power presents temporal discontinuities. The space-time DAM using classical weight function is convenient for continuous transient heat transfer. Nevertheless, for problems including discontinuities, some spurious oscillations for the temperature field occur. A new weight function, respecting the principle of causality, is used to eradicate the physically unexpected oscillations.

Structural characterization of 2,2-di-n-butyl-4-methyl-1,3,2-dioxastannolane isolated from supercritical CO2 conditions

2009

The title compound has been isolated as single crystals from the synthesis of propylene carbonate from racemic 1,2-propanediol and carbon dioxide using n-Bu2SnO as a catalyst precursor. The X-ray crystallographic structure analysis revealed the self-assembly of di-n-butyltin(IV) 1,2-propanediolate units, linked together through long-distance Sn-O interactions leading to a one-dimensional polymeric architecture organized in a syndiotactic arrangement. The coordination geometry around the tin atoms can be described as an unusual faced-capped trigonal bipyramidal environment.

Towards Iron(II) Complexes with Octahedral Geometry: Synthesis, Structure and Photophysical Properties

2020

The control of ligand-field splitting in iron (II) complexes is critical to slow down the metal-to-ligand charge transfer (MLCT)-excited states deactivation pathways. The gap between the metal-centered states is maximal when the coordination sphere of the complex approaches an ideal octahedral geometry. Two new iron(II) complexes (C1 and C2), prepared from pyridylNHC and pyridylquinoline type ligands, respectively, have a near-perfect octahedral coordination of the metal. The photophysics of the complexes have been further investigated by means of ultrafast spectroscopy and TD-DFT modeling. For C1, it is shown that&mdash

Espace de Minkowski-Lorentz et des sphères : un état de l'art

2016

Dans cet article, nous faisons une présentation de l'espace de Minkowski-Lorentz généralisant, à Ê 5 l'espace utilisé dans la théorie de la relativité. Cet espace de dimension 5 contient un paraboloïde de dimension 3 et isométrique à l'espace affine euclidien usuel E 3 , l'ensembles des sphères et plans orientés de E 3 regroupés sur une pseudo-sphère unité de dimension 4. Une premier avantage de cet espace est l'écriture intuitive d'une sphère qui est caractérisée par un point, un vecteur normal en ce point et une courbure. Un deuxième avantage est la manipulation de surfaces canal qui sont représentées par des courbes. Un troisième avantage concernant la simplification des calculs quadrati…

Résolution des contraintes géométriques

1994

National audience; La modélisation par contraintes définit les objets géométriques (typiquement, en 2D, les points, droites, cercles, coniques, etc) par les contraintes qu'ils doivent vérifier (distances, angles, tangences, incidences, etc. entre paires d'objets). L'exposé tente de faire le point sur les diverses méthodes proposées à ce jour pour la résolution des contraintes, en 2D ou en 3D. Les méthodes algébriques transforment les contraintes en un système d'équations, et recourent ensuite à des méthodes numériques (relaxation, Newton-Raphson) [4] ou symboliques (bases de Grobner, méthode de Wu et Ritt) [5,3]. Les méthodes géométriques décomposent le système de contraintes en problèmes g…

Analysis of geometrical features of 3D model based on the surface curvature of a set of point cloud

2021

Modélisation géométrique de formes fractales pour la CAO

2020

International audience

Propose Semantic Formalization for 3D Reconstruction of Architectural

2010

International audience; Archi3D project is a successful practice well proved by engineering practices. In this paper, we propose to reconstruct semantics for the purpose of reconstruct 3D architecture in Archi3D fundamentally. The formalization approach starts from several hypotheses on semantics which include: there is a core mechanism of semantics which is not limited to conceptual expression level; and a complete expression of semantics necessaries the ―implicitexplicit‖ transition of human side knowledge, etc. The necessity and feasibility concerning applying the proposed method and technology to the practice of Archi3D is discussed systemically by way of semantics revelations on some …