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Vincent Knop André Nicolle Olivier Colin 《Proceedings of the Combustion Institute》2013,34(1):667-675
The present study extends the Nitrogen Oxide Relaxation Approach (NORA [Vervisch et al., Combust. Flame 158 (2011) 1480–1490]) for NOx modelling in engines by introducing alternative chemical routes to the thermal pathway as well as a speciation of nitrogen oxides into nitrogen monoxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O). Perturbations of equilibrium state are considered to identify nitrogen oxide reactivity in various mixture and thermodynamic conditions. A common Intrinsic Low-Dimensional Manifold (ILDM) is identified for NO and NO2, while nitrous oxides appear to stay in near-equilibrium state for any in-cylinder conditions. The relaxations back towards the equilibrium state after the perturbations are analysed to extract the characteristic times of relaxation, an image of the species reactivity. Tabulation of equilibrium mass fractions and characteristic relaxation times as a function of mixture and thermodynamic conditions allows nitrogen oxide modelling to be performed for internal combustion engines at very low computational cost through idealised ILDMs that are independent of the combustion ones. Results show the accuracy of the modelling approach for nitrogen oxide emissions of a Diesel engine at part and full load. 相似文献
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Zahia Houiene Mounia Merabet-Khelassi Nassima Bouzemi Olivier Riant Louisa Aribi-Zouioueche 《Tetrahedron: Asymmetry》2013,24(5-6):290-296
Herein we report results of the chemoenzymatic deracemization of a range of secondary benzylic acetates 1a–9a via a sequence of hydrolysis with CAL-B lipase in non-conventional media, combined with esterification of the recovered alcohol according to the Mitsunobu protocol following an enzymatic kinetic resolution (KR). The KR of racemic acetates 1a–9a via an enzymatic hydrolysis, with CAL-B lipase and Na2CO3, in non-aqueous media was optimized and gave high selectivities (E ? 200) at good conversions (C >49%) for all of the substrates studied. This method competes well with the traditional one performed in a phosphate buffer solution. The deracemization using Mitsunobu inversion gave the (S)-acetates in moderate to excellent enantiomeric excess 75% < ee < 99%, in acceptable isolated yields 70% < yield < 89%, and with some variations according to the acetate structure. 相似文献
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One‐Step Double Covalent Functionalization of Reduced Graphene Oxide with Xanthates and Peroxides
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Florence Pennetreau Prof. Olivier Riant Prof. Sophie Hermans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15009-15012
Radical functionalization of reduced graphene oxide has been achieved by reaction with a xanthate in the presence of peroxide as a radical initiator. X‐ray photoelectron spectroscopy, bulk elemental analyses, and thermogravimetric analyses showed that the xanthate grafting is covalent and efficient. The synthesis and use of seven xanthates and three peroxides showed that the highest grafting yield is obtained when xanthate and peroxide are introduced in stoichiometric amounts. It also revealed that the peroxide used as radical initiator is grafted at the graphenic surface during the functionalization. The method presented in this contribution therefore allows bifunctionalized reduced graphene oxide samples to be easily obtained in one single step. This method leads to undamaged graphene sheets with higher dispersibility than the pristine sample. 相似文献
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Terence Bayen Olivier Cots Pedro Gajardo 《Journal of Optimization Theory and Applications》2018,178(2):627-659
Our aim in this work is to synthesize optimal feeding strategies that maximize, over a time period, the biogas production in a continuously filled bioreactor controlled by its dilution rate. Such an anaerobic process is described by a four-dimensional dynamical system. Instead of modeling the optimization of the biogas production as a Lagrange-type optimal control problem, we propose a slightly different optimal control approach in this paper: We study the minimal time control problem to reach a target point, which is chosen in such a way that it maximizes the biogas production at steady state. Thanks to the Pontryagin maximum principle and the geometric control theory, we provide an optimal feedback control for the minimal time control problem, when the initial conditions are taken within the invariant and attractive manifold of the system. The optimal synthesis exhibits turnpike and anti-turnpike singular arcs and a cut locus. 相似文献