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51.
Jean-Pierre Coudreuse 《电信纪事》1995,50(1):98-113
Fifteen years after its first tentative steps in the laboratory, ATM seems to have reached the thankless age of confrontation with the reality of operational networks while others would say the age of potential to fulfil and promises to keep. The following article does not pretend to be an in-depth technical analysis of a particular aspect or development of ATM but rather the thoughts of a witness to a number of past, present and future issues. The objective is much more to stimulate thought on ATM than to provide definitive answers to often difficult questions. 相似文献
52.
Bruno Bazin Josiane Cillard Jean-Pierre Koskas Pierre Cillard 《Journal of the American Oil Chemists' Society》1984,61(7):1212-1215
The autoxidation of arachidonic acid dispersed in aqueous media was evaluated simultaneously with and without different agents,
e.g., α-tocopherol at different concentrations, cysteine, DNA and RNA. The autoxidation rate of arachidonic acid was evaluated
by quantitative gas liquid chromatography (GLC) determination of the unoxidized acid and by spectrophotometric measurement
of conjugated dienes. α-Tocopherol exhibited a prooxidant activity at concentrations of 1.25 × 10−4 M and 1.25 × 10−5 M and a weak antioxidant activity at a concentration of 1.25 × 10−6 M. Cysteine showed antioxidant activity and greatly reduced the prooxidant activity of α-tocopherol. DNA and RNA had no effect
in either case. α-Tocopherol oxidation was followed by high pressure liquid chromatography (HPLC). The prooxidant effect was
accompanied by a rapid oxidation of α-tocopherol, except in the presence of cysteine, which prevented the oxidation of α-tocopherol. 相似文献
53.
Jean-Pierre Coudreuse 《International Journal of Communication Systems》1988,1(4):213-221
The definition of broadband ISDN recently became a major topic of research and predevelopments. Fast packet technologies are widely recognized as the basis for BISDN. Even if international consensus has appeared far more quickly than could have been expected a few years ago, a lot of issues remain open. This paper is a contribution to discussions on some important topics relating to the definition of asynchronous transfer mode. 相似文献
54.
Jean-Pierre Guiraud Radyadour Kh. Zeytounian 《International Journal of Engineering Science》1974,12(4):311-330
An asymptotic theory to the flow in an axial compressor is presented with the aim of devising a coupling process between the so-called meridian through flow and the flow around cascades. The small parameter ? is the inverse of the (supposed ? 1) number of blades per row and/or number of stages. As a matter of fact, the cascade flow is treated as a small perturbation of the through flow and has to be computed, locally, as the two dimensional unsteady flow around an array of couples of cascades alternately fixed and in motion. The array is constructed by developing on a plane the section of the compressor by a circular cylinder, and continuing by periodicity, the couple of cascades, so obtained, at each location. The coupling between through flow and cascade flow is part of the analysis. It occurs by the way that the equations of through flow are obtained through an averaging process, completed on a domain of periodicity of the array of cascades, while the through flow appears, locally, as an unperturbed flow for the linearized problem defining the cascade flow. The tridimensional nature of the complete flow is built in by the coupling itself, as is visualized by the occurence of source terms in each of the two sets of equations describing through flow and cascade flow. This paper is aimed at giving a preliminary answer to the question of how to devise an, as rational as possible, way of inscribing the familiar scheme of cascade flow within the computation of a mean through flow. The main output is that the concept of cascade flow should be revisited and reassessed as one of unsteady flow around an array of cascades. 相似文献
55.
56.
Jean-Pierre Candy Pierre Fouilloux Michel Keddam Hisasi Takenouti 《Electrochimica acta》1981,26(8):1029-1034
Impedances of a gold-powder and a Raney-gold electrode were measured over a wide frequency range, and were found to be very similar to those of cylindrical pore of finite depth. The simulation calculation for sphere-packed electrode impedance was performed. It was observed that even though each sphere-layer shows the impedance related to an occluded pore-shape, the overall impedance is similar to that of a cylindrical pore electrode. When the penetration depth approaches the pore depth, the shape of the pore wall has little influence on the impedance. Thus, impedance measurement techniques can be applied to porous electrodes of more intricate pore-texture, and evaluate the radius, depth and pore number of its equivalent cylindrical pore electrode. These values determined for a Raney-gold electrode are in very good agreement with those determined by other methods. The case of a more realistic fuel cell electrode such as Raney-nickel with a metal-electrolyte-gas system, was also tentatively examined. 相似文献
57.
Genet JP 《Accounts of chemical research》2003,36(12):908-918
This Account covers the design of Ru catalysts and ligands. Two classes of chiral phosphine ligands are prepared: the electron-rich trans-2,4-substituted phosphetanes, readily available from optically pure 1,3-diol cyclic sulfates, and atropoisomeric ligands (SYNPHOS, MeO-NAPhePHOS, bearing heterotopic biaryl moieties, and a chiral water-soluble diguanidinium binaphthyl diphosphine, Digm-BINAP). Applications of these ligands to rhodium- and ruthenium-mediated hydrogenation of ketones and olefins have been reported with high enantioselectivities. The recognition abilities of Ru-SYNPHOS for a wide range of ketones is superior to those observed with BINAP, MeO-NAPhePHOS, and MeO-BIPHEP. Several biologically active compounds have been prepared through dynamic kinetic resolution. This work gives access to a number of highly active catalysts of the type [Ru(biphosphane)(H)(eta(6)-cot)]BF(4). These catalysts have demonstrated their utility in the enantioselective hydrogenation of the tetrasubstituted cyclopentenone "dehydrodione", which leads to the commercially important perfume component Paradisone (Firmenich). 相似文献
58.
Kouamé D Girault JM Remenieras JP Chemla JP Lethiecq M 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(3):267-278
For pt.I see ibid., vol.50, no.3, p.267-78 (2003). This paper presents an application of continuous wave ultrasound Doppler velocity measurements to two-phase flow in pipes. In many petroleum wells, the multiphase flow is separated into two phases: the first is a liquid phase and the second is a gas phase with small scatterers. The problem of multiphase velocity profile measurements has not been satisfactorily solved by classical approaches due to the multiphase nature of the fluid and the presence of colored noise, which introduces a significant bias in classical frequency estimators. We propose the use of resolution frequency techniques to overcome the classical limitations. Direct estimation of Doppler frequency then obtained using either time frequency maximum frequency or arguments of poles of the parametric model that identifies the Doppler part of the signal is discussed. The tests made with synthetic Doppler signals and two-phase flow have demonstrated the excellent performance of the high resolution techniques based on reassignment and parametric techniques. 相似文献
59.
Lacour D Granet G Plumey JP Mure-Ravaud A 《Journal of the Optical Society of America. A, Optics, image science, and vision》2003,20(8):1546-1552
We demonstrate theoretically a polarization-independent guided-mode resonant filter with only a one dimensional grating. A rigorous method, the modal method by Fourier expansion, is used to compute the diffracted efficiencies of the grating. Wave-vector analysis fails to correctly design a polarization-independent structure. We show that a rigorous analysis of the resonances must be employed to obtain such a device; using a pole approach, we study the effects of grating parameters on the resonances of both polarizations. 相似文献
60.
Emmanuel Defaÿ David Wolozan Jean-Pierre Blanc Emmanuelle Serret Pierre Garrec Sophie Verrun Denis Pellissier Philippe Delpech Julie Guillan Bernard Andr Laurent Ulmer Marc Aïd Pascal Ancey 《Solid-state electronics》2007,51(11-12):1624
This paper describes realization and characterization of SrTiO3 (STO) high K MIM capacitors above BiCMOS integrated circuit (IC). These capacitances are connected to IC and are used as coupling capacitors in order to realize a high pass filter. Surface capacitance achieved is 10 nF/mm2 with capacitance value of 1.2 nF. The process for STO MIM fabrication does not exceed 400 °C, which is compatible with interconnections. Typical K and dielectric losses values obtained are, respectively 110% and 2%. Yield obtained reaches 83% for capacitors. A functional high pass filter using these STO capacitors was realized in this study. It exhibits a cut-off frequency at 6.5 kHz and a constant gain at higher frequencies of −1.3 dB. 相似文献