Based on a refinement of the notion of internal sets in Colombeau's theory, so-called strongly internal sets, we introduce the space of generalized smooth functions, a maximal extension of Colombeau generalized functions. Generalized smooth functions as morphisms between sets of generalized points form a sub-category of the category of topological spaces. In particular, they can be composed unrestrictedly. 相似文献
Strong-stability-preserving (SSP) time-discretization methods have a nonlinear stability property that makes them particularly suitable for the integration of hyperbolic conservation laws. A collection of SSP explicit 3-stage Hermite-Birkhoff methods of orders 3 to 7 with nonnegative coefficients are constructed as k-step analogues of third-order Runge-Kutta methods, incorporating a function evaluation at two off-step points. Generally, these new methods have larger effective CFL coefficients than the hybrid methods of Huang with the same step number k. They have larger maximum scaled step sizes than hybrid methods on Burgers' equations. 相似文献
The effect of ions on the structure of liquid water is still not completely understood, despite extensive experimental and theoretical studies. A combined XANES and molecular dynamics investigation on diluted Zn(2+) and Hg(2+) aqueous solutions reveals that the influence of a single ion on the bonding pattern of water molecules is strongly dependent on the nature of the ion. While the structure of water is not altered by the presence of the Zn(2+) ion, the Hg(2+) cation has a strong impact on the hydrogen-bond network of water that extends beyond the first coordination shell. 相似文献
This article reviews measurements for the canonical flow: incompressible turbulent round jets issuing into a large, ideally
infinite, quiescent domain. The available far-field data on mean velocity, momentum-flux conservation, Reynolds stresses and
triple fluctuation correlations are presented. The budget equations for turbulent kinetic energy and for the individual Reynolds
stresses are shown, including different formulations for dissipation and pressure-velocity correlations. Evidence of the persistence
of source conditions in the self-preserving far field is observed in several cases. This article analyses and compares several
data sets, obtained at different levels of detail, against analytical constraints, discusses limitations and provides insights
aided by reference to recent numerical work. It is hoped that this will prove useful in guiding future experiments and numerical
test cases, where complete details of the jet configuration are required for validation and comparison. 相似文献
Specific activity of Pt catalysts prepared by supporting Pt(-C4H7)2 or H2PtCl6 on a honeycomb carrier in benzene hydrogenation in the kinetic region has been established to remain unchanged with increasing Pt particle size from 10 to 50 Å.
The synthetic interest of the direct substitution of protonated heteroaromatic bases by nucleophilic carbon-centered radicals is furtheron developed by the following new achievements: i) utilization of the redoc system in several solvents; ii) utilization of benzoyl peroxide in alcohols; iii) carbamoylation by HCONH2 and H2O2 in the presence of catalytic amounts of Fe(II). These systems allow to obtain either substitution till now tried without success or reactions of industrial interest. Polar effects play a dominant role in determining reactivity, selectivity and synthetic applications; in particular the role of the strongly nucleophilic intermediate radicals of pyridinyl type in the rearomatization step is emphasized. 相似文献