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We study the problem of aerosol filtration by formulating a unified approach that incorporates the dominant mechanisms of particle capture in cylindrical pores. The theoretical approach presented here takes into account the effects of flow slip at the pore wall and predicts an enhanced efficiency in the intermediate crossover regime between Brownian diffusion and direct interception. We also suggest how the results obtained for cylindrical pores can be used to estimate the efficiency of granular ceramic filters in the region of the most penetrating particle size, where the enhanced efficiency effects are strongly amplified by the large number of pores, or more generally unit bed elements, acting in series. Copyright 2001 Academic Press. 相似文献
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We present a deep-bed aerosol filtration model that can be used to estimate the efficiency of sintered granular membrane filters in the region of the most penetrating particle size. In this region the capture of submicrometer aerosols, much smaller than the filter pore size, takes place mainly via Brownian diffusion and direct interception acting in synergy. By modeling the disordered sintered grain packing of such filters as a simple cubic lattice, and mapping the corresponding 3D connected pore volume onto a discrete cylindrical pore network, the efficiency of a granular filter can be estimated, using new analytical results for the efficiency of cylindrical pores. This model for aerosol penetration in sintered granular filters includes flow slip and the kinetics of particle capture by the pore surface. With a unique choice for two parameters, namely the structural tortuosity and effective kinetic coefficient of particle adsorption, this semiempirical model can account for the experimental efficiency of a new class of "high-efficiency particulate air" ceramic membrane filters as a function of particle size over a wide range of filter thickness and texture (pore size and porosity) and operating conditions (face velocity). 相似文献
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The reaction of azidoalcohol on triazaphosphole takes place according to pathway and not , as shown by the isolation of spirannic phosphazene . The diazadiphosphetidines , dimers of are also caracterized. 相似文献
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A. Klaebe J.F. Brazier A.Cachapuz Carrelhas B. Garrigues M.R. Marre R. Contreras 《Tetrahedron》1982,38(14):2111-2122
The polyrimetric kinetic study, of the epimerisation of optically pure spirophosphoranes derived from α-aminoalcohols or α-aminoacids, leads to mechanistic conclusions. Evidence from isotopic, solvent and concentration effects and values of the activation parameters are consistent with a regular epimerisation mechanism in these spirophosphoranes involving the intramolecular stereolability of these molecules. 相似文献
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Michel Sanchez Marie-Rose Mazieres Rainer Bartsch Robert Wolf Jean-Pierre Majoral 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):487-490
Abstract New phosphenium cations of general formula R2N-P+-X, with a variety of X group (-N=P+R2, -N=PR3, -C°N, -C=N=S, OR) are synthesized using trimethylsilyl derivatives as reagents. 相似文献
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B. Vinter J. L. Reverchon G. Marre M. Carras C. Renard X. Marcadet V. Berger 《Comptes Rendus Physique》2003,4(10):1103-1108
A study of the optimization of the detectivity of a mid infrared double heterostructure photovoltaic detector is proposed. Simple approximate analytic expressions for the dark current are compared with full numerical calculations, and give physical insight on the mechanisms dominating the dark current. The analysis is performed step by step, from a simple p–n junction to the full double heterostructure. The influence of temperature, barrier band gap energy in a double heterostructure, doping density in the active region, on diffusion and generation–recombination mechanisms is analyzed. It is shown how the performances of a double heterostructure photovoltaic detector can be improved by a controlled doping the active region. Nevertheless, its development is still limited by the difficulties occurring during device processing. For example, the use of dry etching for the processing of InAs0.91Sb0.09 p–i–n photovoltaic detectors induces a strong leakage current along the mesa edge. In this letter, we show an improvement of the R0A characteristic by several orders of magnitude at low temperature by using an Ion Beam Etching (IBE) followed by a wet chemical etching. This optimized and reliable device processing allows us to demonstrate that the detector performance is actually limited by the diffusion current of holes. Finally, we discuss the ability of an n-type barrier made of InAs/AlSb super-lattice to avoid hole diffusion and to improve the R0A characteristic of these detectors. To cite this article: B. Vinter et al., C. R. Physique 4 (2003). 相似文献
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Dr. Baptiste Giroire Dr. Alain Garcia Dr. Samuel Marre Dr. Thierry Cardinal Dr. Cyril Aymonier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(51):12965-12970
A chemistry platform for the fast continuous synthesis of III–V quantum dots is demonstrated. III-nitride QDs are prepared by using short residence times (less than 30 s) in a one-step continuous process with supercritical solvents. GaN QDs prepared via this route exhibit strong UV photoluminescence with a structuring of the emission signal at low temperature (5 K), confirming their high quality. An example of metal site substitution is given with the synthesis of InxGa1-xN solid solution. A continuous bandgap shift towards lower energies is demonstrated when increasing the indium content with strong photoluminescence signals from UV to visible. The chemistry platform proposed could be easily extrapolated to binary and ternary III phosphides or arsenides with the homologous V source. 相似文献