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941.
We consider the Saffman-Taylor problem describing the displacement of one fluid by another having a smaller viscosity, in a porous medium or in a Hele-Shaw configuration, and the Taylor-Saffman problem of a bubble moving in a channel containing moving fluid. Each problem is known to possess a family of solutions, the former corresponding to propagating fingers and the latter to propagating bubbles, with each member characterized by its own velocity and each occupying a different fraction of the porous channel through which it propagates. To select the correct member of the family of solutions, the conventional approach has been to add surface tension σ and then take the limit σ → 0. We propose a selection criterion that does not rely on surface tension arguments. 相似文献
942.
The long-range corrections (LRCs) to the configurational energy have been taken into consideration in the Monte Carlo simulation of the vapor-liquid interface for a pure Lennard-Jones (LJ) fluid. The simulated bulk densities agree satisfactorily with those obtained from the Gibbs ensemble method, and the simulated surface tension values agree reasonably well with those reported in the literature for a larger number of molecules and a larger cut-off distance. To compare the influence of the potential forms on the simulation results, a truncated LJ potential, and a shifted and truncated LJ potential have been examined. Although the bulk densities and surface tensions calculated for different model fluids are strongly affected by the LRC, the different potentials essentially lead to similar density values and similar surface tension values when the respective calculated values are compared on the basis of a reduced temperature scale. 相似文献
943.
Romeo Rizzi 《Discrete Mathematics》2006,306(13):1390-1404
We consider graphs which contain both directed and undirected edges (partially directed graphs). We show that the problem of covering the edges of such graphs with a minimum number of edge-disjoint directed paths respecting the orientations of the directed edges is polynomially solvable. We exhibit a good characterization for this problem in the form of a min-max theorem. We introduce a more general problem including weights on possible orientations of the undirected edges. We show that this more general weighted formulation is equivalent to the weighted bipartite b-factor problem. This implies the existence of a strongly polynomial algorithm for this weighted generalization of Euler's problem to partially directed graphs (compare this with the negative results for the mixed Chinese postman problem). We also provide a compact linear programming formulation for the weighted generalization that we propose. 相似文献
944.
《Surface and interface analysis : SIA》2005,37(3):281-287
Indium oxide thin films were grown onto Si and quartz substrates by d.c. reactive sputtering of elemental indium. X‐ray diffraction and transmission electron microscopy studies confirmed the single‐phase and polycrystalline nature of the films. Secondary ion mass spectrometry investigations of In2O3/Si structures showed the formation of an inhomogeneous interface region ~20 nm thick between In2O3 and Si. The overall feature of the interface remained the same under annealing in an oxygen atmosphere, but annealing in an argon atmosphere drastically altered the nature of the interface. The observations indicate that interface formation and stability depend critically on the availability of oxygen. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
945.
The growth of ultrathin films of Si3N4 directly on Si surfaces is studied with valence band photoemission. The information from these studies about the growth mechanism and the changes of the electronic structure is enhanced by the use of various photon energies with synchrotron radiation. The silicon nitride films are grown isothermally on the Si(1 0 0) and Si(1 1 1) surfaces by reactions with atomic N. The atomic nitrogen is produced by using a remote, microwave excited nitrogen plasma. The growth under these conditions was earlier shown to be self limiting. The details in the valence band spectra are identified and resolved with numerical methods, and followed systematically during the growth. Thus the identification of Si surface states, Si-nitride interface states and bulk nitride states becomes possible. The previously obtained separation between amorphous and crystalline growth occurring around 500 °C is further supported in the present studies. 相似文献
946.
有机-无机复合质子交换膜的制备与界面特性 总被引:3,自引:0,他引:3
有机-无机复合质子交换膜的开发是燃料电池用质子交换膜的一个重要研究方向,本文综述了有机-无机复合质子交换膜的制备方法,分析了两相之间的界面特性,并对这种复合膜的研究前景进行了展望. 相似文献
947.
In this paper we develop a theory for the calculation of the surface shear viscosity of a planar liquid-vapor interface. The theory is an extension of the generalized hydrodynamics formalism, originally developed for the calculation of linear transport coefficients in isotropic bulk fluids. We develop an expression for the surface shear viscosity in terms of the actual shear viscosity profile in the interfacial region. We derive an expression for this profile in terms of the first four moments of the autocorrelation function of the transverse parallel velocity (the component of velocity parallel to k, which is the projection of k on to the interface). Finally, we calculate these moments for a planar liquid-vapor interface. 相似文献
948.
R. Nassif Y. Boughaleb A. Hekkouri J.F. Gouyet M. Kolb 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(4):453-464
We examine the behaviour of the concentration profiles of particles with repulsive interactions diffusing on a host lattice.
At low temperature, the diffusion process is strongly influenced by the presence of ordered domains. We use mean field equations
and Monte-Carlo simulations to describe the various effects which influence the kinetic behaviour. An effective diffusion
coefficient is determined analytically and is compared with the simulations. Finite gradient effects on the ordered domains
and on the diffusion are discussed. The kinetics studied is relevant for superionic conductors, for intercalation and also
for the diffusion of particles adsorbed on a substrate.
Received: 26 June 1997 / Revised: 18 September 1997 / Accepted: 10 November 1997 相似文献
949.
Ai Qun GU Mei Ju XIE Zi Li YU 《中国化学快报》2006,17(10):1373-1376
Poly(p-phenylene sulfide) (PPS) is a high performance engineering thermoplastic with high temperature resistance, good chemical resistance and mechanical properties. Since it was commercialized by Phillips Petroleum Company in 1973, it has been widely use… 相似文献
950.
芘和苯甲醛,在对甲基苯磺酸作用下,生成了B阶COPNA树脂.用红外光谱、核磁共振氢谱及碳谱对其结构进行了表征.B阶COPNA树脂经在惰性气氛中500、600和800℃的热处理后,得到不溶不熔的COPNA树脂.电子自旋共振谱(ESR)测试表明,其稳定自由基浓度最高可达2.28×1022spins/g. 相似文献