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1.
Joaquín Cortés Eliana Valencia Gonzalo Aguila Esteban Orellana Paulo Araya 《Catalysis Letters》2008,126(1-2):63-71
An experimental study is made of the time decay of activity of the CO–NO reaction on a Pd/Al2O3 looking at the effect on reaction order and apparent activation energy. The optimum kinetics parameters fitting the steady state data at moderate pressures are determined. The time decay curves are analyzed through various catalyst deactivation models. 相似文献
2.
In this paper the design of pole placement feedback controllers for interval plants is addressed within an Interval Analysis framework. Three main topics connected by the concept of interval Diophantine equation are treated: a relatively straightforward investigation about robust coprimeness of interval polynomials, a reliable computing approach for the design of pole placement controllers in the presence of inaccuracies of interval type, and the design of robust controllers with regional pole placement specifications. After explicitly characterizing a convex subset of robust controllers, the problem of designing non-fragile controllers is formulated as a design centering problem, which is then solved by a global optimization algorithm. Numerical examples illustrate the main characteristics of the approach proposed.This paper has been partially supported by grants from Conselho Nacional de Desenvolvimento Científico e Tecnológico–Brazil. 相似文献
3.
When one wants to understand and model the drying of high water content gels, one needs to gather all thermal physical parameters and to derive a physical model based on independently measured parameters. We chose to work experimentally and theoretically on water diffusion and drying of spheres of polyacrylamide gel.
We have demonstrated the strong influence of vitreous transition on the relationship of water diffusivity with moisture content. Values of the diffusion coefficient and temperature shift factor for diffusion have been proposed.
Convective and micro-wave drying kinetics show the presence of a drying phase purely specific to radiation absorption. Finally, we have proposed a mathematical model containing independent physical parameters, which' not only predicts mass fluxes but also analyses critical physical phenomena. 相似文献
We have demonstrated the strong influence of vitreous transition on the relationship of water diffusivity with moisture content. Values of the diffusion coefficient and temperature shift factor for diffusion have been proposed.
Convective and micro-wave drying kinetics show the presence of a drying phase purely specific to radiation absorption. Finally, we have proposed a mathematical model containing independent physical parameters, which' not only predicts mass fluxes but also analyses critical physical phenomena. 相似文献
4.
Celso M. F. Lapa Cludio M. N. A. Pereira Paulo F. Frutuoso e Melo 《Reliability Engineering & System Safety》2003,81(1):103-109
In order to maximize systems average availability during a given period of time, it has recently been developed a non-periodic surveillance test optimization methodology based on genetic algorithms (GA). The fact of allowing non-periodic tests turns the solution space much more flexible and schedules can be better adjusted, providing gains in the overall system average availability, when compared to those obtained by an optimized periodic test scheme. This approach, however, turns the optimization problem more complex. Hence, the use of a powerful optimization technique, such as GA, is required.Considering that some particular features of certain systems can turn it advisable to introduce other specific constraints in the optimization problem, this work investigates the application of seasonal constraints for the set of the Emergency Diesel Generation of a typical four-loop pressurized water reactor in order to planning and optimizing its surveillance test policy. In this analysis, the growth of the blackout accident probability during summer, due to electrical power demand increases, was considered. Here, the used model penalizes surveillance test interventions when the blackout probability is higher.Results demonstrate the ability of the method in adapting the surveillance test policy to seasonal constraints. The knowledge acquired by the GA during the searching process has lead to test schedules that drastically minimize test interventions at periods of high blackout probability. It is compensated by more frequent redistributed tests through the periods of low blackout probability in order to improve on the overall average availability at the system level. 相似文献
5.
Bellovin Steven M. Benzel Terry V. Blakley Bob Denning Dorothy E. Diffie Whitfield Epstein Jeremy Verissimo Paulo 《Security & Privacy, IEEE》2008,6(1):16-23
A virtual roundtable (featuring panelists Steven Bellovin, Terry Benzel, Bob Blakely, Dorothy Denning, Whitfield Diffie, Jeremy Epstein, and Paulo Verissimo) discussing the next 15 years in computer security. 相似文献
6.
Influence of pencil lead hardness on voltammetric response of graphite reinforcement carbon electrodes 总被引:1,自引:0,他引:1
Paulo Henrique Campos Prado Tavares Paulo Jorge Sanches Barbeira 《Journal of Applied Electrochemistry》2008,38(6):827-832
This work studied the voltammetric response of graphite reinforcement electrodes made of different pencil lead hardness. The
studies showed that harder graphite leads, regardless of their manufacturer, are more appropriate as electrode material for
voltammetric purposes due to their higher peak currents, increasing sensitivity and reproducibility, with ΔEp closer to the theoretical value for a reversible system. 相似文献
7.
F. R. Perioto M. E. T. Alvarez W. A. Araujo M. R. Wolf‐Maciel R. Maciel Filho 《应用聚合物科学杂志》2008,110(6):3544-3551
A new calculation procedure for free‐volume parameters is considered in this work by using viscosity prediction methods and the Levenberg‐Marquardt calculation scheme. All parameters used in the Vrentas–Duda free‐volume theory can be estimated from pure component properties. The prediction results are compared with experimental data for some polymer/solvent systems. The diffusion coefficient calculated by Vrentas–Duda theory can be used in the modeling of membrane separation processes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
8.
9.
Newman H.S. Ebel J.L. Judy D. Maciel J. 《Microwave and Wireless Components Letters, IEEE》2008,18(2):100-102
Radio frequency microelectromechanical systems (RF MEMS) cantilever contact switches have been tested for lifetime. The mean cycles-to-failure measured on an ensemble of switches was 430 billion switch cycles. The longest lifetime exhibited without degradation of the switch was 914 billion switch cycles. The devices were switched at 20 kHz with an incident RF frequency of 10 GHz and an incident RF power of 20 dBm. Testing was performed continuously over a period of approximately 18 months. The switches were operated in a cold-switched mode. 相似文献
10.