Search results for "Geometry"
showing 10 items of 4487 documents
Surface plasmon routing along right angle bent metal strips
2005
International audience; An efficient routing of surface plasmon polaritons (SPP) is of fundamental importance in the development of SPP-based photonics. This paper reports that microgratings acting as Bragg mirrors can guide SPP along metal stripes waveguides featuring 90 degrees bents. The measurement of the mirrors efficiency, performed by means of photon scanning tunneling microscopy, shows that bent losses as low as 1.9 dB can be achieved. Finally, we demonstrate operating SPP beamsplitters obtained by an appropriate design of the Bragg mirrors constituting elements. (c) 2005 American Institute of Physics.
Orientation of Polar Molecules by Laser Induced Adiabatic Passage
2002
International audience; We show that two overlapping linearly polarized laser pulses of frequencies ω and its second harmonic 2ω can strongly orient linear polar molecules, by adiabatic passage along dressed states. The resulting robust orientation can be interpreted as a laser-induced localization in the effective double well potential created by the fields, which induces a preliminary molecular alignment. The direction of the orientation can be selected by the relative phase of the fields.
Fractal geometry and urban patterns – from exploring morphology to applications in planning
2014
International audience; Fractal geometry turned out to be a powerful approach in many domains for describing complex structures which have multiscale properties. In particular, fractal analysis allows making evident scaling properties and hence underlying structural order principles which cannot be discovered by other measuring approaches like densities which refer to one unique scale. We present here how this approach helps to analyze the distribution of build-up surface in urban patterns and how it can be used to link these morphologiocal properties to specific contexts of urbanization. Indeed, contemporary urban patterns have usually an irregular shape reminding rather deposits on surfac…
Fractal geometry for modeling and measuring urban patterns
2012
International audience
The role of virtual work in Levi-Civita's parallel transport
2015
International audience; According to current history of science, Levi-Civita introduced parallel transport solely to give a geometrical interpretation to the covariant derivative of absolute differential calculus. Levi-Civita, however, searched a simple computation of the curvature of a Riemannian manifold, basing on notions of the Italian school of mathematical physics of his time: holonomic constraints, virtual displacements and work, which so have a remarkable, if not dominant, role in the origin of parallel transport.
Building scenarios for a LUTI model : articulation of spaced based models and an agent based model
2013
International audience
Noise Analysis and Comparison of Phase-and Frequency-Detecting Readout Systems: Application to SAW Delay Line Magnetic Field Sensor
2019
International audience; Transmission surface acoustic wave (SAW) sensors are widely used in various fields of application. In order to improve the limit of detection (LOD) of such sensor systems, it is essential to understand and quantify the relevant noise sources. Only then, strategies for noise reduction can be developed. In this paper, low noise readout systems for the application with SAW sensors in an open-loop and a closed-loop configuration are presented and experimentally investigated with regard to their phase noise on the example of a SAW delay line magnetic field sensor. Besides a comprehensive analysis of the phaseand frequency modulated signals, respectively, previously derive…
Extension des méthodes de géométrie algorithmique aux structures fractales
2013
Defining shapes by iteration allows us to generate new structures with specific properties (roughness,lacunarity), which cannot be achieved with classic modelling.For developing an iterative modeller to design fractals described by a BCIFS, we developed a set oftools and algorithms that permits one to evaluate, to characterize and to analyse different geometricproperties (localisation, convex hull, volume, fractal dimension) of fractals. We identified properties ofstandard CAD operations (intersection, union, offset, . . . ) allowing us to approximate them for fractalsand also to optimize these approximation algorithms.In some cases, it is possible to construct a CIFS with generalised HUTCH…
A critical size for emergence of nonbulk electronic and geometric structures in dodecanethiolate-protected Au clusters.
2014
We report on how the transition from the bulk structure to the cluster-specific structure occurs in n-dodecanethiolate-protected gold clusters, Au(n)(SC12)m. To elucidate this transition, we isolated a series of Au(n)(SC12)m in the n range from 38 to ∼520, containing five newly identified or newly isolated clusters, Au104(SC12)45, Au(∼226)(SC12)(∼76), Au(∼253)(SC12)(∼90), Au(∼356)(SC12)(∼112), and Au(∼520)(SC12)(∼130), using reverse-phase high-performance liquid chromatography. Low-temperature optical absorption spectroscopy, powder X-ray diffractometry, and density functional theory (DFT) calculations revealed that the Au cores of Au144(SC12)60 and smaller clusters have molecular-like elec…
Geometric Inverse Problems
2023
This up-to-date treatment of recent developments in geometric inverse problems introduces graduate students and researchers to an exciting area of research. With an emphasis on the two-dimensional case, topics covered include geodesic X-ray transforms, boundary rigidity, tensor tomography, attenuated X-ray transforms and the Calderón problem. The presentation is self-contained and begins with the Radon transform and radial sound speeds as motivating examples. The required geometric background is developed in detail in the context of simple manifolds with boundary. An in-depth analysis of various geodesic X-ray transforms is carried out together with related uniqueness, stability, reconstruc…