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11.
The dynamics of electrooxidation of adsorbed CO on Pt(111) microfacets was examined in CO-saturated 0.1 M HClO4 aqueous solutions by in situ time resolved second harmonic generation (SHG). Analysis of the temporal dependence of the intensity of the SHG signals recorded for experiments in which the potential was stepped to values high enough for adsorbed CO oxidation to ensue, was found to be consistent with the mean field theory model, yielding rate constants somewhat higher than those reported by Lebedeva et al. (N. P. Lebedeva, M. T. M. Koper, J. M. Feliu and R. A. v. Santen, J. Electroanal. Chem., 2002, 524-525, 242-251) in sulfuric acid solutions. The smaller rates observed by these authors may be ascribed to the presence of anions, ie. in all likelihood bisulfate, which are capable of competing effectively for Pt sites thereby blocking formation of oxygenated species on the surface. Also discussed in this work are the virtues and limitations of in situ SHG for monitoring fast surface processes. 相似文献
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Herein, a method is presented that allows quantitative determination of faradaic efficiencies for dinitrogen (N2) generation during the electrochemical oxidation of hydroxylamine (NH2OH), , on a polycrystalline gold Au(poly) disk electrode in aqueous electrolytes over a wide pH range. This tactic involves the use of an impinging jet electrolyte configuration incorporating a gas porous ring connected in turn to a mass spectrometer. The actual amount of N2 generated at the Au(poly) disk was assayed using the oxidation of hydrazine (N2H4) in aqueous phosphate buffer (pH 7). This redox process yields N2 as the only product, allowing a direct correlation to be established between the changes in the partial pressures of N2 and the current flowing through the disk electrode. An analysis of the data collected revealed a strong dependence of both on pH and the applied potential. Although values of as high as 20 to 30 % were found in acid and neutral media over a narrow potential region, those in alkaline solution were far smaller in the entire potential range examined. 相似文献
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Infrared-to-visible wave-length conversion in the Yb3+−Er3+ doped phosphors system has been described by a simple three level model based on two ions mechanism. The excitation in the
range of 900–1000 nm of an IR-photon is first absorbed by Yb3+ ion as a sensitizer attributed to the resonant energy transition in Er3+ ion from 4
I
3/2 → 4
S
15/2 and 1
F
9/2 → 4
I
15/2, respectively for green and red emission. The essential energy transfer processes in this system i.e. upconversion from 4
I
11/2 and 1
I
13/2, cross-relaxation from 4
S
3/2 and 1
F
9/2 are taken into account. The limitations of the rate-equation approach are examined with a focus on the underlying dynamics
of this rare-earth system. 相似文献
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APPLICATION OF GENETIC ALGORITHM IN PARTICLE SIZE ANALYSIS BY MULTISPECTRAL EXTINCTION MEASUREMENTS 总被引:1,自引:0,他引:1
Gerard Grhan 《中国颗粒学报》2004,2(6):235-240
Both dependent and independent model algorithms are designed with genetic algorithm (GA) to retrieve aerosol size data from multispectral extinction measurements. Compared with the traditional dependent model algorithm, e.g., simplex, GA can locate the global optimized solution instead of local ones. As an independent model algonthm, when combined with B-splines, GA gives consistent results with Chahine and Phillip-Twomey-NNLS algorithms. Numerical simulations also show that GA has high stability and good resistance to relatively higher error levels. For a population size of 50 in the present paper, the feasible ranges for genetic operators Pc and pm are found to be [0.01, 0.5] and [0.01, 0.15], respectively, and the generation number Gen_Max should be larger than 250. 相似文献
15.
T. Strek P. Kedziora B. Maruszewski A.A. Pozniak K.V. Tretiakov K.W. Wojciechowski 《Journal of Non》2009,355(24-27):1387-1392
The influence of the Poisson’s ratio of a viscoelastic obstacle on the flow in a two-dimensional channel was studied by a finite element computer simulation. The arbitrary Lagrangian–Eulerian (ALE) formulation for deformed mesh was applied to handle the moving boundaries of the computational domain. An anomalous deformation of the obstacle was observed when the Poisson’s ratio was negative and close to its minimum value. It was also found that the maximum velocity of the fluid in the system decreased with the decreasing Poisson’s ratio. 相似文献
16.
LI YingQiu HU YangLi & LIU QuanSheng College of Mathematics Computing Sciences Changsha University of Science Technology Changsha China College of Mathematics Computer Sciences Hunan Normal University Changsha LMAM University of Bretgne-Sud BP Vannes France 《中国科学 数学(英文版)》2011,(7)
Let W be the limit of the normalized population size of a supercritical branching process in a varying or random environment. By an elementary method, we find sufficient conditions under which W has finite weighted moments of the form EWpl(W), where p > 1, l 0 is a concave or slowly varying function. 相似文献
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