Bonifacio – Église Sainte-Marie-Madeleine

Si les explorations menées dans le reste de la caserne de Montlaur ont permis d’établir avec certitude la présence d’occupations du Néolithique ancien ainsi que du Néolithique récent (Ferreira et al. 2014), aucun niveau en place préhistorique n’a pu être mis en évidence dans les sondages réalisés aux abords de l’église Sainte-Marie-Madeleine de Bonifacio. Le « bruit de fond » demeure pourtant non négligeable, comme en atteste la présence de mobilier céramique et lithique dans les niveaux de c..

Transmission enhancement through square coaxial apertures arrays in metallic film: when leaky modes filter infrared light

We consider arrays of square coaxial apertures in a gold layer and study their diffractive behavior in the far infrared region. These structures exhibit a resonant transmission enhancement that is used to design tunable bandpass filters. We provide a study of their spectral features and show by a modal analysis that the resonance peak is due to the excitation of leaky modes of the open photonic structure. Fourier transform infrared (FTIR) spectrophotometry transmission measurements of samples deposited on Si substrate show good agreement with numerical results and demonstrate angular tolerance up to 30 degrees of the fabricated filters.Comment: 4 pages, 3 figure

Resonant metamaterial absorbers for infrared spectral filtering: quasimodal analysis, design, fabrication and characterization

We present a modal analysis of metal-insulator-metal (MIM) based metamaterials in the far infrared region. These structures can be used as resonant reflection bandcut spectral filters that are independent of the polarization and direction of incidence because of the excitation of quasimodes (modes associated with a complex frequency) leading to quasi-total absorption. We fabricated large area samples made of chromium nanorod gratings on top of Si/Cr layers deposited on silicon substrate and measurements by Fourier Transform spectrophotometry show good agreement with finite element simulations. A quasimodal expansion method is developed to obtain a reduced order model that fits very well full wave simulations and that highlights excitation conditions of the modes.Comment: 8 pages, 7 figure

Tridimensional multiphysics model for the study of photo-induced thermal effects in arbitrary nano-structures

In the present paper, we detail the implementation of a numerical scheme based on the Finite Element Method (FEM) dedicated to a tri-dimensional investigation of photo-induced thermal effects in arbitrary nano-structures. The distribution of Joule losses resulting from the scattering of an incident wave by an arbitrary object embedded in a multilayered media is used as source of a conductive thermal transient problem. It is shown that an appropriate and rigorous formulation of the FEM consists in reducing the electromagnetic scattering problem to a radiative one whose sources are localized inside the scatterer. This approach makes the calculation very tractable. Its advantage compared to other existing methods lies in its complete independence towards the geometric, optical and thermal properties of both the scatterer and the medium in which it lies. Among the wide range of domain of application of this numerical scheme, we illustrate its relevance when applied to two typical cases of laser damage of optical components in high power applications

Fixed bed gasification: characterization of a new experimental set-up

La gazéification étagée couplée à un moteur à gaz est une technologie prometteuse pour la production d'électricité décentralisée de petites et moyennes puissances. L'objectif de ces travaux était de concevoir, dimensionner et construire un nouveau réacteur expérimental pour caractériser l'étape de gazéification des procédés à lit fixe et étagé. Le Réacteur à Lit Fixe Continu(RLFC) du Cirad simule la zone de gazéification isolée du reste du procédé. Des sondes de mesure et d'échantillonnage ont été placées dans le lit, tous les 10 cm, dans le but d'analyser en continu les températures, les pressions et la concentration des gaz produits. Des bilans précis de matières et d'énergie ont été réalisés pour valider les performances du réacteur et la pertinence des expérimentations. Enfin, pour illustrer le haut potentiel de cet outil de recherche, des profils de températures et concentrations de gaz dans le lit de charbon sont présentés et discutés

Detailed identification and quantification of the condensable species released during torrefaction of lignocellulosic biomasses

Torrefaction is a mild thermal pretreatment which improves biomass properties and releases condensable species. Condensable species released during torrefaction of pine, ash wood, miscanthus and wheat straw at 250, 280 and 300 °C were investigated. A fixed-bed reactor was used for the laboratory scale experiments. A micro-GC, Karl Fischer titrator and GC-MS were used to analyse incondensable gases, water and other condensable species, respectively. The overall mass balance ranged from 96 to 103 wt.%. The quantification rate of condensable species was on average 77 wt.%. In addition to the major species usually reported in the literature – water, acetic acid, 2-propanone,1-hydroxy- – we show that large amounts of some anhydrosugars were produced. Additionally, 85 condensable species were identified. Among these species, many terpenes and terpenoids in pine were identified by adsorption on SPME fibre. Finally, the influence of temperature and of the nature of biomass on the yields of condensable species was highlighted

Investigation of kinetic compensation effect in lignocellulosic biomass torrefaction: Kinetic and thermodynamic analyses

The kinetic compensation effect between the activation energy and the pre-exponential factor has extensively existed in the thermochemical conversion processes of lignocellulosic biomass. The research on the kinetic compensation effect in lignocellulosic biomass torrefaction has been insufficient yet. The torrefaction of the pinewood sample was experimentally investigated by thermogravimetric analysis (TGA) at five isothermal temperatures of 220, 250, 265, 280 and 295 °C. The reaction order model was used to analyze the isothermal torrefaction kinetics of lignocellulosic biomass, and the results showed that many sets of activation energy and pre-exponential factor could describe the experimental data at each temperature equally well and they excellently satisfied the kinetic compensation effect relationship. The linear regression lines of the kinetic compensation effect points at different temperatures intersected at one point, whose values corresponded to the obtained optimal kinetic parameters. A kinetic-compensation-effect-based method was developed and verified to determine the kinetic parameters of isothermal biomass torrefaction. Based on the optimal kinetic parameters, the thermodynamic parameters (including Gibbs free energy, enthalpy, and entropy) of biomass torrefaction processes at various temperatures were calculated and analyzed