Search results for "efficien"
showing 10 items of 3014 documents
Recent changes in measured wind in the NE Atlantic and variability of correlation with NAO
2010
The paper deals with wind measurements, recorded since the 1950s, at twelve meteorological stations along a transect near the westernmost European border, between 64° and 44° N. Extreme wind speed tends to decrease sharply near the northern boundary (at Reykjavick), near the middle of the study area (at Shannon and Valentia) and near the southern boundary (at Brest and Cap Ferret), to increase at Thorshavn, with less significant trends at the other stations. Average wind speeds confirm the above tendencies, with an additional increasing speed at Lerwick, Kirkwall, Malin Head, Belle-Ile and Cap Ferret. To compare changes in wind activity, the data have been subdivided into three periods: unt…
Event-Based Trajectory Prediction Using Spiking Neural Networks
2021
International audience; In recent years, event-based sensors have been combined with spiking neural networks (SNNs) to create a new generation of bio-inspired artificial vision systems. These systems can process spatio-temporal data in real time, and are highly energy efficient. In this study, we used a new hybrid event-based camera in conjunction with a multi-layer spiking neural network trained with a spike-timing-dependent plasticity learning rule. We showed that neurons learn from repeated and correlated spatio-temporal patterns in an unsupervised way and become selective to motion features, such as direction and speed. This motion selectivity can then be used to predict ball trajectory…
Network architectures and energy efficiency for high performance data centers
2017
The increasing trend to migrate applications, computation and storage into more robust systems leads to the emergence of mega data centers hosting tens of thousands of servers. As a result, designing a data center network that interconnects this massive number of servers, and providing efficient and fault-tolerant routing service are becoming an urgent need and a challenge that will be addressed in this thesis. Since this is a hot research topic, many solutions are proposed like adapting new interconnection technologies and new algorithms for data centers. However, many of these solutions generally suffer from performance problems, or can be quite costly. In addition, devoted efforts have n…
Error propagation from line parameters to spectra simulations. Illustration on high temperature methane.
2010
Astrophysical investigations generally need both complete and accurate spectroscopic databases. Despite continuous efforts in experimental and theoretical spectroscopic investigations, the lack of data in some spectral regions of interest is one of the main limitation of the presently available spectroscopic databases. Unfortunately information about missing data relevant to specific experimental conditions is rarely directly accessible from spectroscopic databases (focusing naturally on available data). Such information relies essentially on theoretical investigations which are equally limited to the present state of the art of modelling. The purpose of the talk is to show how multi-resolu…
Multi-resolution error analysis of predicted absorption coefficients. Method and computer implementation. Application to the IR spectrum of methane a…
2009
A general method for the estimation of the confidence interval of molecular absorption coefficients is presented. It combines statistical numerical experiments with analytical calculations. The method uses line parameter predictions (position and intensity) with known estimated uncertainties. The propagation of errors from line parameters to absorption coefficients or cross-sections are analyzed in detail as a function of the resolution. This work is especially intended to provide expert information for applications requiring theoretical predictions for which the present state of the art of line by line high-resolution modeling is not accurate enough to meet the experimental precision. As a…
Multi-Resolution error analysis of predicted absorption coefficients. Method and computer implementation. Application to the infrared spectrum of met…
2009
A general method for the estimation of the confidence interval of molecular absorption coefficients is presented. It combines statistical numerical experiments with analytical calculations. The method uses line parameter predictions (position and intensity) with known estimated uncertainties. The propagation of errors from line parameters to absorption coefficients or cross-sections are analyzed in detail as a function of the resolution. This work is especially intended to provide expert information for applications requiring theoretical predictions for which the present state of the art of line by line high-resolution modeling is not accurate enough to meet the experimental precision. As a…
Identification of the contaminants present on the surface of lactose for pharmaceutical use and analysis of the impact of their presence on the inter…
2018
The discovery of the problem will go through training techniques at the nanoscale characterization and chemical analysis, the discovery of the industrial problem in society Armor Proteins, the validation of a pharmaceutical lactose. With the aim to increase our knowledge on powders for food or pharmaceutical use, we propose to study the effect of manufacturing processes, shaping, granulation on the reactivity of powders. The first part is devoted to the effect of purity on interactions-Lactose Lactose and Lactose-API measured / quantified by near-field techniques (AFM, SMM, MSAFM) under ambient atmosphere and under stressful conditions storage. Deriving a second portion of the preceding par…
Quasi-phase-matched third harmonic generation in optical fibers using refractive-index gratings
2011
International audience; The purpose of this work is to demonstrate the quasi-phase-matching of third harmonic generation process in optical fibers using refractive-index gratings. We compare conversion efficiency calculated with analytical coupled modes theory and numerical approach employing system of coupled generalized nonlinear Schrödinger equation. Moreover, we show that introducing the phase matching condition that takes into account the nonlinear contribution to propagation constants significantly increases the conversion efficiency by several orders of magnitude. Finally we optimize the grating constant to maximize conversion efficiency.
Experimental and theoretical study of line mixing in methane spectra. III. The Q branch of the Raman nu(1) band
2000
International audience; The shape of the nu(1) Raman Q branch of CH4 perturbed by Ar and He at room temperature has been studied. Stimulated Raman spectroscopy (SRS) experiments have been made in the 2915-2918 cm(-1) spectral region for total pressures from 0.4 to 70 atm and mixtures of approximate to 5% CH4 with He and Ar. Analysis of the spectra demonstrates that the shape of the Q branch is significantly influenced by line mixing and much narrower than what is predicted by the addition of individual line profiles. For the first time, a model is proposed for the calculation and analysis of the effects of collisions on the considered spectra. In this approach, the rotational part of the re…
Integrated low drive voltage electro-optic Bragg modulator using a, periodically poled lithium niobate
2017
Periodically poled lithium niobate (PPLN) is currently used for frequency conversions using quasi-phase-matching, thanks to its high nonlinear coefficients and mature poling process. PPLN can also be attractive for electro-optic (EO) applications. Several studies have been conducted on PPLN-based EO deflectors, and recent realizations have lower the required applied voltage under hundred volts [1]. Indeed, for practical EO applications drive voltages as low as 5 V are usually required. For this purpose, we use a recent technique to realize high-quality isolated crystalline film out of LN [2] to implement an EO Bragg deflector with a drive voltage below 10 V. In this work we present an effic…