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11.
Grégoire Fourrié Laurent Keirsbulck Larbi Labraga Patrick Gilliéron 《Experiments in fluids》2011,50(2):385-395
A passive flow control on a generic car model was experimentally studied. This control consists of a deflector placed on the
upper edge of the model rear window. The study was carried out in a wind tunnel at Reynolds numbers based on the model height
of 3.1 × 105 and 7.7 × 105. The flow was investigated via standard and stereoscopic particle image velocimetry, Kiel pressure probes and surface flow
visualization. The aerodynamic drag was measured using an external balance and calculated using a wake survey method. Drag
reductions up to 9% were obtained depending on the deflector angle. The deflector increases the separated region on the rear
window. The results show that when this separated region is wide enough, it disrupts the development of the counter-rotating
longitudinal vortices appearing on the lateral edges of the rear window. The current study suggests that flow control on such
geometries should consider all the flow structures that contribute to the model wake flow. 相似文献
12.
Stability analysis of jointed rock slope 总被引:2,自引:0,他引:2
The stability analysis of a jointed rock slope with two sets of unfilled joints, under its own weight, is carried out directly by considering failure surfaces along some particular joints and also going through the intact rock. Simple failure mechanisms using uniform rigid rock-block motions are incorporated in the yield design kinematic approach. They yield an improvement of known results as long as the characteristics strength of the joints are weak enough. 相似文献
13.
Mohammed Larbi Labbi 《Mathematische Nachrichten》2015,288(4):402-411
The Weitzenböck curvature operators are the curvature terms of order zero that appear in the well‐known classical Weitzenböck formula. In this paper, we use the formalism of double forms to prove a simple formula for these operators and to study their geometric properties. 相似文献
14.
Naima Bouyahia Mohamed Larbi Hamlaoui Mouna Hnaien Florence Lagarde Nicole Jaffrezic-Renault 《Bioelectrochemistry (Amsterdam, Netherlands)》2011,80(2):155-161
In this work, a new biosensor was prepared through immobilization of bovine liver catalase in a photoreticulated poly (vinyl alcohol) membrane at the surface of a conductometric transducer. This biosensor was used to study the kinetics of catalase–H202 reaction and its inhibition by cyanide. Immobilized catalase exhibited a Michaelis–Menten behaviour at low H202 concentrations (< 100 mM) with apparent constant KMapp = 84 ± 3 mM and maximal initial velocity VMapp = 13.4 μS min? 1. Inhibition by cyanide was found to be non-competitive and inhibition binding constant Ki was 13.9 ± 0.3 μM. The decrease of the biosensor response by increasing cyanide concentration was linear up to 50 μM, with a cyanide detection limit of 6 μM. In parallel, electrochemical characteristics of the catalase/PVA biomembrane and its interaction with cyanide were studied by cyclic voltammetry and impedance spectroscopy. Addition of the biomembrane onto the gold electrodes induced a significant increase of the interfacial polarization resistance RP. On the contrary, cyanide binding resulted in a decrease of Rp proportional to KCN concentration in the 4 to 50 μM range. Inhibition coefficient I50 calculated by this powerful label-free and substrate-free technique (24.3 μM) was in good agreement with that determined from the substrate-dependent conductometric biosensor (24.9 μM). 相似文献
15.
Hossini I Harrad MA Ait Ali M El Firdoussi L Karim A Valerga P Puerta MC 《Molecules (Basel, Switzerland)》2011,16(7):5886-5895
Friedel-Craft acylation at 100 °C of 2,5,9,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzocycloheptene [ar-himachalene], a sesquiterpenic hydrocarbon obtained by catalytic dehydrogenation of α-, β- and γ-himachalenes, produces a mixture of two compounds: (3,5,5,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzocyclohepten-2-yl)-ethanone (2, in 69% yield), with a conserved reactant backbone, and 3, with a different skeleton, in 21% yield. The crystal structure of 3 reveals it to be 1-(8-ethyl-8-hydroperoxy-3,5,5-trimethyl-5,6,7,8-tetrahydronaphthalen-2-yl)-ethanone. In this compound O-H…O bonds form dimers. These hydrogen-bonds, in conjunction with weaker C-H…O interactions, form a more extended supramolecular arrangement in the crystal. 相似文献
16.
Harrad MA Valerga P Puerta MC Houssini I Ali MA El Firdoussi L Karim A 《Molecules (Basel, Switzerland)》2011,16(1):367-372
A recyclable catalyst, Ni(0)-CMC-Na, composed of nickel colloids dispersed in a water soluble bioorganic polymer, sodium carboxymethylcellulose (CMC-Na), was synthesized by a simple procedure from readily available reagents. The catalyst thus obtained is stable and highly active in alkene hydrogenations. 相似文献
17.
Hanane El Hajaji Nadya Lachkar Katim Alaoui Yahya Cherrah Abdellah Farah Abdesslam Ennabili Brahim El Bali Mohammed Lachkar 《Arabian Journal of Chemistry》2011,4(3):321-324
We evaluated the in vitro antioxidant property and phytochemical constituents of the crude ethyl acetate and methanol extract of the three genders of carob tree barks (spontaneous male, spontaneous female, and grafted female). The scavenging activity on DPPH (1,1-diphenyl-2-picrylhydrazyl) was determined, as well as the phenolic contents (Folin–Ciocalteu method) of both the extracts. The highest antioxidant activity and the higher amounts of total phenols were shown in methanol crude bark extract for the three genders. Variety significantly affected the phenol content and the antioxidant activity, with the spontaneous male variety globally showed a higher polyphenol concentration and antioxidant activity than the grafted female and spontaneous female. 相似文献
18.
P. Etienne T. Woignier A. Alaoui J. Phalippou 《Journal of Sol-Gel Science and Technology》1997,8(1-3):801-806
The mechanical behaviour of silica aerogels in alcoholic environment has been interpreted in terms of stress corrosion in
analogy with silica glass. The chemical susceptibility factor has been determined by the dynamical method and we also measured
the Weibull’s modulus which characterizes the strength distribution. These data show a stress corrosion effect which is significant
in alcoholic atmosphere. The results could explain a possible fracture of gels during the supercritical drying treatment as
already observed. 相似文献
19.
Thierry Woignier George W. Scherer Adil Alaoui 《Journal of Sol-Gel Science and Technology》1994,3(2):141-150
Although supercritical drying avoids the capillary stresses that tend to warp and crack xerogels, there are other sources of stress that interfere with the preparation of monolithic aerogels. In this paper, we present experimental results showing that there is a limit to the rate at which the pressure can be released from the autoclave without causing cracking, and that the maximum rate decreases as the gel size increases. Using an analysis developed in a companion paper, the stresses generated during depressurization are compared to the modulus of rupture of our aerogels. The calculations require knowledge of the pressure-dependence of the density of the vapor (ethanol, in our experiments), as well as the permeability and modulus of the gel network. Measurements of those properties were performed on a series of silica gels made under basic and neutral conditions. We find that the calculated stresses are large enough to account for the cracking of our gels at high rates of depressurization; moreover, the predicted dependence of stress on gel diameter is in agreement with experiment. 相似文献
20.
Belmesnaoui Aqzzouz Redouane Nouira Larbi Zraoula 《Proceedings of the American Mathematical Society》2006,134(4):1161-1165
Nous donnons des conditions nécessaires et suffisantes pour que tout opérateur de Dunford-Pettis positif sur un treillis de Banach, soit faiblement compact et nous déduisons quelques conséquences.