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31.
32.
Traditional mathematical models of multiphase flow in porous media use a straightforward extension of Darcys equation. The key element of these models is the appropriate formulation of the relative permeability functions. It is well known that for one-dimensional flow of three immiscible incompressible fluids, when capillarity is neglected, most relative permeability models used today give rise to regions in the saturation space with elliptic behavior (the so-called elliptic regions). We believe that this behavior is not physical, but rather the result of an incomplete mathematical model. In this paper we identify necessary conditions that must be satisfied by the relative permeability functions, so that the system of equations describing three-phase flow is strictly hyperbolic everywhere in the saturation triangle. These conditions seem to be in good agreement with pore-scale physics and experimental data. 相似文献
33.
Proton nuclear magnetic resonance (NMR) spin-spin relaxation measurements were made on three commercial-grade polyethylenes in the melt state, free of solvent. All samples exhibit a three-component relaxation behavior, with components being assigned to amorphous low-molecular weight material (non-network fraction), amorphous entangled network fraction, and an ordered or high-segmental-density fraction, in order of decreasing relaxation times. Sample thermal history is shown to have a considerable effect on the overall relaxation behavior, and therefore on the relative amounts of each of the three components in the melt. An adequate thermal treatment of samples produces an equilibrium melt with invariant composition of the three fractions. The effects of thermal history on the relative amount of high-segment-density regions in the melt parallels its effect on the fraction of crystalline material in the solid polymer. These results are evidence for the persistence of ordered regions in polyethylene at temperatures well above the crystalline melting point of the polymer. We further comment on the nature of the two slower relaxing components and present examples of how the components manifest themselves in other polymer characterization techniques. © 1992 John Wiley & Sons, Inc. 相似文献
34.
Eva Lesanska 《Applications of Mathematics》2002,47(1):9-23
The problem is to determine the optimum size of nonsensitiveness regions for the level of statistical tests. This is closely connected with the problem of the distribution of quadratic forms. 相似文献
35.
V. G. Krotov 《Mathematical Notes》1997,62(4):439-448
In the critical case αp=n functions from the Hardy-Sobolev spacesH
α
p
(B
n
) have a limit almost everywhere on the boundary along certain regions of exponential contact with the boundary. It is proved
in the paper that the maximal operator associated with these regions is bounded as an operator fromH
α
p
(B
n
) toL
p
(ϖB
n
).
Translated fromMatematicheskie Zametki, Vol. 62, No. 4, pp. 527–539, October, 1997.
Translated by N. K. Kulman 相似文献
36.
In the CAZy database, the α-amylase family GH13 has already been divided into 45 subfamilies, with additional subfamilies still emerging. The presented in silico study was undertaken in an effort to propose a novel GH13 subfamily represented by the experimentally characterized cyclomaltodxtrinase from Flavobacterium sp. No. 92. Although most cyclomaltodextrinases have been classified in the subfamily GH13_20. This one has not been assigned any GH13 subfamily as yet. It possesses a non-specified immunoglobulin-like domain at its N-terminus mimicking a starch-binding domain (SBD) and the segment MPDLN in its fifth conserved sequence region (CSR) typical, however, for the subfamily GH13_36. The searches through sequence databases resulted in collecting a group of 108 homologs forming a convincing cluster in the evolutionary tree, well separated from all remaining GH13 subfamilies. The members of the newly proposed subfamily share a few exclusive sequence features, such as the “aromatic” end of the CSR-II consisting of two well-conserved tyrosines with either glycine, serine, or proline in the middle or a glutamic acid succeeding the catalytic proton donor in the CSR-III. Concerning the domain N of the representative cyclomaltodextrinase, docking trials with α-, β- and γ-cyclodextrins have indicated it may represent a new type of SBD. This new GH13 subfamily has been assigned the number GH13_46. 相似文献
37.
回溯《共同纲领》中所宣示的民族区域自治制度的制度要义以及这一制度的奠基历程,可以发现:社会主义,是民族区域自治制度的本质属性;巩固中华民族大家庭,是民族区域自治制度的制度依归。民族区域自治制度,强调的是广大少数民族群众当家作主、自主管理本民族内部事务的人民性;平等,作为社会主义的天然要求,是少数民族公民当家作主、行使自治权的前提;新中国在少数民族地区进行的宗教改革,实现了政教分离和社会主义政治法律体系的统一;民族区域自治制度,旨在建立亲密合作、团结互助的社会主义新型民族关系;因此,社会主义,是民族区域自治制度区别于中国古代羁縻制度的质的规定性所在;理解民族区域自治制度,必须把握好其社会主义的本质属性。民族区域自治制度,以缔造、巩固“中华民族大家庭”为制度依归,强调大家庭成员的团结统一、不可分离;在民族区域自治制度的奠基历程中,贯彻了社会主义大家庭的政治伦理,坚持深入基层、凝聚人心的群众路线,各族人民共同发展、共同建设社会主义现代化国家,在具体民族事务处理方面,则秉着商量办事、综合权衡的大家庭式处理方式。 相似文献
38.
39.
A.N. Al-Mutib 《Journal of Computational and Applied Mathematics》1984,10(1):71-79
Stability properties of numerical methods for delay differential equations are considered. Some suitable definitions for the stability of the numerical methods are included and Runge-Kutta type methods satisfying these properties are tested on a numerical example. 相似文献
40.
The ballistic propagation of phonons in diamond and Nb3Sn at 40 and at 4.2 K is examined. The nature of variation of the phonon magnification factor has been analysed both in the
wave vector as well as group velocity spaces. Using the Polar Schmidt-net with Pole at (π/2,π/2), the mappings of phonon focussing and defocussing are made. It is shown that the mapping for theFTA mode for Nb3Sn exhibits islands acting as impenetrable barriers for phonon propagation. 相似文献