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91.
92.
Myron van Damme 《Transport in Porous Media》2018,125(3):589-608
During infiltration of water in soil, menisci form at the interface of water, grains, and air in the pores, inducing suction due to surface tension. Due to the random distribution of interconnected pores of different sizes, characteristic of porous media, differences in suction and friction inside pores give a diffusing infiltration front. The process of infiltration is often simulated by solving Richards’ equation in which the water flux is calculated with Darcy’s law. Underlying Darcy’s law is the assumption that the gradients in flow potential and the flow resistance due to viscous forces are independent from each other. This paper shows that these parameters are dependent and negatively correlated. A new method for calculating flows in unsaturated porous media has been developed to evaluate the impact of the covariance on infiltration predictions. The results show that the impact is significant and leads to a reduction in infiltration rate and mean friction experienced during infiltration. The method thereby provides a physical explanation for the subdiffusion observed during water infiltration in soil and is consequently expected to provide more insights into the processes of infiltration. 相似文献
93.
94.
Mark C. Curran Myron B. Allen 《Numerical Methods for Partial Differential Equations》1992,8(4):341-355
Advection-dominated flows occur widely in the transport of groundwater contaminants, the movements of fluids in enhanced oil recovery projects, and many other contexts. In numerical models of such flows, adaptive local grid refinement is a conceptually attractive approach for resolving the sharp fronts or layers that tend to characterize the solutions. However, this approach can be difficult to implement in practice. A domain decomposition method developed by Bramble, Ewing, Pasciak, and Schatz, known as the BEPS method, overcomes many of the difficulties. We demonstrate the applicability of BEPS ideas to finite element collocation on trial spaces of piecewise Hermite cubics. The resulting scheme allows one to refine selected parts of a spatial grid without destroying algebraic efficiencies associated with the original coarse grid. We apply the method to steady-state problems with boundary and interior layers and a time-dependent advection-diffusion problem. 相似文献
95.
DeLyle Eastwood Martha Schulz Hendrick Myron H. Miller 《Spectrochimica Acta Part B: Atomic Spectroscopy》1982,37(4):293-302
Sodium-induced emission enhancement of transition metal resonance lines are measured in a d.c. plasma (DCP) for wavelengths from 210 to 395 nm. Systematic differences in enhancement are observed within individual spectra (Fe I, Ni I, Sc II), and the enhancement and the excitation potential of a line are found to be linearly related. Electron density and apparent temperature data lead to an interpretation of thiis energy dependence within the context of a recombining plasma in partial thermodynamic equilibrium. 相似文献
96.
The density of states for the NiCu alloys system has been calculated as a function of concentration by the supercell method. This method takes into account inter-site interactions in contrast with current effective medium or single site theories. We show that the method is practical for the study of disordered systems. Comparison is made with previous work as well as with photoemission data. 相似文献
97.
The authors obtain results on the asymptotic behavior of the non-oscillatory solutions of a first order nonlinear neutral delay differential equation. A theorem giving sufficient conditions for all bounded solutions to be oscillatory is also proved. 相似文献
98.
Myron Anton 《Journal of Geometry》1977,10(1-2):164-178
It is well known that a projective plane nay be coordinatized by picking four arbitrary, ordered points such that no three of them are collinear. This gives rise to an algebraic structure called the planar ternary ring T with respect to the base points A,B,C,D. The existence of certain collineations in the plane will be reflected by algebraic properties in T, and conversely. In this paper the interrelationships between certain algebraic properties in T, and the linearity of those ternary rings which are obtained from T and various permutations of A,B,C,D are considered. Many well known types of algebraic structures, such as quasifields and alternative division rings will occur if the ternary rings generated by suitable permutations of A,B,C,D are linear.This research is included in the author's doctoral dissertation submitted to Temple University. The author would like to express his appreciation to Professor R. Artzy for his assistance in completing this work. 相似文献
99.
The de Haas-van Alphen technique forms a sensitive probe of the electronic structure of dilute alloys because of its dependence on the seattering rate in the forward direction. We report the results of a first principle model calculation of the scattering rate of dilute impurities in molybdenum which focuses on the anisotropy of the host wave function on the Fermi surface. This simplified model treats the impurity potential as an atomic potential screened by a Thomas-Fermi function. Substitutional impurities in bcc molybdenum have been studied using the Greens function (KKR) wave functions. The band structure calculated via the KKR method was fitted to a Fourier series representation in order to accurately determine a sufficiently large number of states on the Fermi surface. The KKR wavefunctions were used to calculate scattering rates for the substitutional impurity since the impurity potential can be best described in an angular momentum representation which is inherent to the Greens function method. Our detailed results, to be presented, suggest additional experiment to be done. 相似文献
100.
Myron Bander 《Physics Reports》1981,75(4):205-286
It is conjectured that a non-Abelian gauge theory based on the color SU(3) group will confine quarks. Various techniques that have been applied to this question are reviewed. These include approximate methods based on strong coupling expansions of Hamiltonian and Euclidian lattice theories, instanton improvements on perturbation theory, and solutions of truncated Dyson-Schwinger equations for the gauge field propagator. Formal results based on electric-magnetic duality arguments and on the study of loop field theories are presented. Deconfinement at high temperatures, the inclusion of light quarks, and a possible reconciliation with a hypothetical discovery of free quarks are discussed. 相似文献