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82.
The van der Waals equation of state for binary mixtures has been used to determine the location and shape of the Griffiths shield region (where three tricritical lines intersect). If one takes the geometric mean fora
12, the arithmetic mean forb
12, and the configurational free energy as ideal, the center of the Griffiths shield region is found only when the ratio of molecular sizes is infinite. When the Flory equation for the configurational free energy for mixtures of chain molecules is substituted for the ideal form, the results appear to be somewhat different. However, for all the cases studied, with systems which approach geometric mean behavior one finds the shield region only when the ratio of molecular size is very large and when the internal pressure of the small molecule is very much greater than that of the long-chain molecule.This paper is dedicated to our colleague Howard Reiss on the occasion of his 66th birthday. 相似文献
83.
Among other waveguide elements directional couplers are required in integrated millimeterwave circuits in image guide technique. Hereby an I-guide is used which consists of a dielectric slab between two conducting plates on which the electric field is perpendicularily. Flat coupling behaviour and better isolation can be reached by use of a dielectric coupling element and absorber materials. Thereby the frequency dependence is reduced significantly. Further the coupling can be steered by an additional premagnetized ferrite slab. In this way switched couplers can be realized. 相似文献
84.
Slawomir Rams 《Proceedings of the American Mathematical Society》2005,133(1):11-13
We give an example of a smooth surface of degree that contains pairwise disjoint lines. In particular, our example shows that the degree in Miyaoka's bound is sharp.
85.
Application of the Cross-Entropy Method to the Buffer Allocation Problem in a Simulation-Based Environment 总被引:4,自引:0,他引:4
G.?Alon D.?P.?KroeseEmail author T.?Raviv R.?Y.?Rubinstein 《Annals of Operations Research》2005,134(1):137-151
The buffer allocation problem (BAP) is a well-known difficult problem in the design of production lines. We present a stochastic algorithm for solving
the BAP, based on the cross-entropy method, a new paradigm for stochastic optimization. The algorithm involves the following iterative steps: (a) the generation of
buffer allocations according to a certain random mechanism, followed by (b) the modification of this mechanism on the basis
of cross-entropy minimization. Through various numerical experiments we demonstrate the efficiency of the proposed algorithm
and show that the method can quickly generate (near-)optimal buffer allocations for fairly large production lines. 相似文献
86.
87.
Suresh Chandra 《Pramana》1980,14(1):41-46
The effect of dielectronic recombination as an excitation process in the intensity of solar x-ray lines of calcium ions is
investigated. It is found that x-ray line intensities are enhanced by 15% to 88% with the inclusion of dielectronic recombination
as an excitation mechanism. 相似文献
88.
An adaptive-grid finite-difference method is applied to a model for non-isothermal, coupled flow and transport of brine in porous media. In the vicinity of rock salt formations the salt concentration in the fluid becomes large, giving rise to disparate scales in the salt concentrations profiles. A typical situation one encounters is that of a sharp freshwater-saltwater interface that moves in time. In such situations adaptive-grid methods are more effective than standard fixed-grid methods, since they refine the space grid locally and, hence, provide for substantial reduction in the number of grid points, memory use and CPU time. The adaptive-grid method of this paper is a static, local uniform grid refinement method. Its main feature is that it integrates on nested sequences of locally uniformly refined Cartesian space grids, which are automatically adjusted in time to follow rapid spatial transitions. Variable time steps are used to cope with rapid temporal transitions, including a fast march to possible steady-state solutions. For time stepping, the implicit, second-order BDF scheme is used. Two specific example problems are numerically illustrated. The main physical properties involved here are advection and dispersion and in case of dominant advection sharp freshwater-saltwater interfaces arise. 相似文献
89.
在对类Ne、类Na、类Mg和类Al碘离子的3d-2p跃迁波长和跃迁几率详细计算的基础上,考虑了各个谱线的加宽和谱线间的重迭效应。在局部热动平衡近似和高温条件下,模拟了各离化态离子共同存在时产生的光谱结构,给出了具有带状分布特征的伴线峰的中心波长和半最大全宽度。讨论了这种光谱在等离子体状态诊断方面的应用。 相似文献
90.
Critical comparison of emission spectroscopic determination of dissociation in hydrogen RF discharges 总被引:1,自引:0,他引:1
The degree of dissociation of molecular hydrogen in a RF parallel plate plasma reactor is analyzed by three dif erent emission spectroscopic methods. These schemes are based on the comparison of line intensities of atomic and molecular hydrogen and of argon which is admixed as a tracer gas (actinometry). The different schemes yield similar results in the parameter ranges where they are applicable. The basic assumptions, the available cross sections, and the conditions and limitations of applicability of the different schemes are compared and discussed. 相似文献