Utopisches Erzählen nachgewiesen an Hesses Glasperlenspiel

Belhalfaoui Barbara. Utopisches Erzählen nachgewiesen an Hesses Glasperlenspiel. In: Cahiers d'Études Germaniques, numéro spécial, 1980. Utopie (actes du 13e congrès de l'AGES - Aix-en-Provence 26-28 avril 1980) pp. 27-40

Structure de flammes laminaires et diagnostics optiques (étude numérique et expérimentale)

Dans ce mémoire sont analysées les sources d'erreur dans les comparaisons calcul/mesures en conbstion laminaire. On se place tout d'abord du point de vue du calcul seul et on étudie la sensibilité de la simulation aux constantes de la cinétique chimique et du transport dans un flamme de diffusion H2/air. On examine ensuite l'effet au niveau de modélisation rentenu pour le transport des espèces, dans des flammes de diffusion H2/air, CH4/air et C3H8/air. La diffusion thermique multicomposants a un impact fort sur l'étirement d'extinction de ces flammes, en particulier lorsque le combustible y est dilué. On s'intéresse ensuite à l'émission sontanée OH* et CH* de flammes de méthane (prémélange et diffusion), et on compare des signaux expérimentaux (locaux et intégrés) et des signaux synthétiques obtenus en ajoutant au modèle de chimie complexe un sous-modèle pour l'émission spontanée. Si les signaux locaux semblent mal se recouper, les signaux globaux calculés et mesurés, en revanche, sont en bon accord qualitatif. La simulation de l'absoption du rayonnement OH* à l'aide d'un modèle raie par raie, montre l'importance de ce phénomène à haute pression et explique une partie de l'écart quantitatif entre calcul et mesures. Enfin on traite des signaux expérimentaux (diffusion Rayleigh, absoption OH et LIF OH linéaire) obtenus sur des flammes à contre-courant H2/air, CH4/air et C3H8/air. Des modèles spécifiques (sections efficaces de diffusion Rayleigh ou module LASKIN décrivant la spectroscopie LIF de OH) permettent alors, à partir de calculs en chimie complexe, de reconstituer des grandeurs locales directement comparables à l'expérience. Grâce à la bonne similitude entre signaux simulés et mesurés on est en mesure de situer les limites des hypothèses de post-traitement.CHATENAY MALABRY-Ecole centrale (920192301) / SudocSudocFranceF

Efficiency of succinylated-olive stone biosorbent on the removal of cadmium ions from aqueous solutions

International audienceChemical functionalization of olive stone wastes with succinate linkers can potentially improve the performance of wastewater treatment technologies via enhanced adsorption and high affinity of the covalently attached succinate groups for heavy metals. In this study, a novel reusable adsorbent material based on agricultural waste has been synthesized by esterifying the lignocellulosic matrix of olive stones with succinic anhydride in toluene under basic conditions. Characterization of the as-prepared material by FTIR and solid-state MAS 13C NMR spectroscopies and TGA confirmed that the heterogeneous esterification has proceeded very efficiently to yield the succinylated-olive stone (S–OS). Subsequent alkaline treatment of S–OS with saturated NaHCO3 aqueous solution led to the resulting sodic material (NaS–OS), which was subjected to batch experiments in order to evaluate its cadmium-removing efficiency from aqueous solutions at realistic concentrations of cadmium found in industrial effluents. The results obtained from the sorption characteristics have revealed that NaS–OS material is highly effective in removing cadmium from aqueous solutions, with a maximum uptake capacity of 200 mg g−1 (1.78 mmol g−1). The Langmuir isotherm model was found to fit adequately the equilibrium isotherm data. Cadmium adsorption occurs rapidly and the adsorption mechanism is a chemical sorption via ionic exchange between the adsorbate and adsorbent. Thermodynamic parameters were also evaluated from the effect of temperature studies. Regenerability of NaS–OS material was ascertained by quantitative desorption of cadmium with 1 M aqueous NaCl and the reusability of the matrix after five repeated cycles led to nearly no attenuation in its performance (less than 2% in the sorption capacity), indicating that repeated use of NaS–OS is quite feasible. Compared to other low-cost adsorbents utilized for the removal of Cd(II) from water/wastewater, NaS–OS shows higher sorption capacity. These results have important implications for the design of low-cost adsorbents based on agricultural wastes

Experimental and numerical study of chemiluminescence in methane/air high-pressure flames for active control applications

International audienceChemiluminescence of excited OH*, CH*, and C-2* radicals was investigated as a tool for combustion control. A parametric study in premixed methane/air flames is presented regarding the effects of pressure (1 to 10 bar) and equivalence ratio (0.6 to 1.1). The experimental geometry corresponds to a Bunsen-type burner, with pilot flames to achieve steady combustion at very lean conditions. The burner was set in a pressurized vessel to control ambient pressure. The chemiluminescence was spatially measured using an intensified CCD camera with interference filters centered on the three radical emission bands. A monochromator and a low-resolution spectrometer were used to obtain spectrally resolved data. The three diagnostic techniques show good agreement. The experimental results show that the chemiluminescence of the radicals investigated has different dynamics for given pressure and equivalence ratio conditions. The OH* radical seems more suitable for lean flames, while CH* and C-2* have a more monotonic behavior and stronger dynamics for richer flames. A numerical simulation with complex chemistry and transport modeling based on the PREMIX code was performed for two different kinetic schemes including OH* and CH*. A comparison is presented for integrated chemiluminescence (both spectrally and spatially), as well as for local excited radical concentration trends within the range of experimental conditions. Good qualitative agreement is found with the experimental results except for rich flames, where disagreements due to kinetic schemes are observed. As a conclusion, a new strategy for flame sensing using chemiluminescence over several wavelengths is proposed

Succinate-bonded cellulose: A regenerable and powerful sorbent for cadmium-removal from spiked high-hardness groundwater

International audienceThe primary objective of this work was to evaluate a chemically modified cellulose for the sorption efficiency and selectivity to remove cadmium from spiked high-hardness groundwater. Heterogeneous esterification of cellulose with succinic anhydride in toluene under basic conditions has proceeded very efficiently to yield the succinylated cellulose (SC) with fairly high DS value, as confirmed by FTIR and solid-state MAS 13C NMR spectroscopies. Deprotonation of the free carboxylic acid group was achieved by alkaline treatment of SC with saturated NaHCO3 aqueous solution. Batch experiments were carried out on the resulting sodic material (NaSC) to examine its cadmium-removing capability in both distilled water (DW) and spiked groundwater (GW). The results obtained from the sorption characteristics (kinetics, isotherms and pH effect) have revealed that NaSC material is particularly effective in removing cadmium from both DW and GW solutions, with a maximum uptake of 185.2 and 178.6 mg g−1, respectively. These comparable sorption capacities strongly suggest that NaSC sorbent is highly selective to heavy metal over alkaline earth cations (Ca2+ and Mg2+) and therefore less susceptible to interference from background ions, naturally present in groundwater. On the other hand, cadmium sorption is shown to decrease with a decrease in pH which is indubitably inherent to the competing proton during the ion-exchange process. Furthermore, the material has proven to be efficiently regenerable by using a NaCl brine solution. Thus, the use of the sorbent sequentially to the first regeneration led to nearly no attenuation in the material's capacity for cadmium-removal. Finally, the sorption effectiveness of NaSC is compared to those of other low-cost sorbents so far reported in the literature