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31.
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Minimum energy pathways of propane oxidative dehydrogenation to propene and propanol on supported vanadium oxide catalyst VO x /TiO2 were studied by periodic discrete Fourier transform (DFT) using a surface oxygen radical as the active site. The propene formation pathway was shown to consist of two consecutive hydrogen abstraction steps. The first step includes Cβ–H bond activation of propane followed by the formation of a surface hydroxyl group V–O t H and a propyl radical n-C3H7. This step with the activation energy E* = 0.56 eV (54.1 kJ/mol) appears to be rate-determining. The second step involves the reaction of the bridging O b oxygen atom with the methylene C–H bond of propyl radical n-C3H7 followed by the formation of a hydroxylated surface site HO t –V4+–O b H and propene. The initial steps of the C–H bond activation during propane conversion to propanol and propene by ODH on V5+–(O t O b )? active sites are identical. The obtained results demonstrate that participation of surface oxygen radicals as the active sites of propane ODH makes it possible to explain relatively low activation energies observed for this reaction on the most active catalysts. The presence of very active radical species in low concentration seems to be the key factor for obtaining high selectivity. 相似文献
33.
Vasilii Sergeevich VLADIMIROV Steklov Mathematical Institute Rnssion of Sciences Gubkina Street Moscow Russia 《中国科学A辑(英文版)》2008,(4)
We investigate the structure of solutions of boundary value problems for a non-linear pseudodifferential equation describing the dynamics(rolling)of p-adic closed strings for a scalar tachyon field. 相似文献
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Vasilii V. Kurta 《Comptes Rendus Mathematique》2005,341(2):93-96
This Note is devoted to the study of a Liouville-type comparison principle for entire weak solutions of semilinear elliptic partial differential inequalities of the form , where is a given number and L is a linear (possibly non-uniformly) elliptic partial differential operator of second order in divergent form given formally by the relation We assume that , that the coefficients , , are measurable bounded functions on such that , and that the corresponding quadratic form is non-negative. The results obtained in this work complete similar results on solutions of quasilinear elliptic partial differential inequalities announced in Kurta [C. R. Acad. Sci. Paris, Ser. I 336 (11) (2003) 897–900]. To cite this article: V.V. Kurta, C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献
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Catalin Croitoru Silvia PatachiaNicolae Cretu Attila BoerChristian Friedrich 《Applied Surface Science》2011,257(14):6220-6225
In this paper, the influence of four types of imidazolium-based ionic liquids (ILs) on the surface properties of common aspen (Populus tremula) veneers has been studied by using contact angle, electrical conductivity and Fourier transform infrared spectroscopy analysis. The measurements showed that wood wettabillity is increased by IL treatment. The electrical conductivities of treated wood were in the 0.5-1 mS/cm range, higher than the ones reported in the reference literature. It has been determined that the ILs decrease the crystallinity and improve the flexibility of the cellulose matrix. It has been determined by photographic image analysis that the surface roughness of the IL treated veneers decreases in comparison with the untreated samples. 相似文献
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Using an improved form of the Woods-Saxon nuclear model given by Gareev, Ivanova and Kalinikin, we calculated the absoluteft values for the one-quasiparticle transitions, starting from the 5/2+[413]155Eu ground state and having as final states the first three levels belonging to the rotational band with the155Gd ground state 3/2?[521] as the band head. We found satisfactory results especially for the 5/2+[413] → 3/2?[521] and 5/2+[413]→5/2?[521] transitions. The contribution of the correction matrix elements turns out to be of the order of magnitude 0.1 to logft. 相似文献
40.
The paper discusses the asymptotics of path probabilities in Markov processes close to a central one on 3D Young graph. We consider a one-parameter family of such processes and compute the parameter value in such a way that the centrality condition is satisfied with the greatest possible accuracy. We defined a normalized dimension of paths in the 3D Young graph. We study the growth and oscillations of these normalized dimensions along greedy and random trajectories of the processes using large computer experiments involving 3D Young diagrams with millions of boxes. 相似文献