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排序方式: 共有364条查询结果,搜索用时 31 毫秒
1.
Bazarra Noelia Castejón Alberto Fernández José R. Quintanilla Ramón 《Meccanica》2021,56(12):3025-3037
Meccanica - In this work we study, from the numerical point of view, a one-dimensional thermoelastic problem where the thermal law is of type III. Quasi-static microvoids are also assumed within... 相似文献
2.
The aim of this paper is to introduce a new functional in thestudy of swelling porous elastic soils saturated by a fluid.This new functional is a useful tool; it allows us to provethe existence of solutions in the case of a compressible fluid.We also prove the stability of solutions and the exponentialdecay in the case of an incompressible fluid. We study as wellthe continuous dependence with respect to the initial time. 相似文献
3.
Katalytische Epoxidierung und 1,2‐Dihydroxylierung von Olefinen mit Bispidin‐Eisen(II)/H2O2‐Systemen
4.
R. Quintanilla 《Applied mathematics and computation》2004,150(3):661-668
This paper concerns a continuum theory of porous media saturated by multiple immiscible fluids. The case of a porous media saturated by two immiscible fluid proposes some new mathematical difficulties. We study the exponential stability of the one-dimensional problem when the nonwetting fluid is trapped in the wetting fluid and the exponential stability of the anti-plane shear deformations when the two fluids saturate the elastic media. 相似文献
5.
6.
H. A. Levine R. Quintanilla L. E. Payne 《Mathematical Methods in the Applied Sciences》1989,11(1):71-77
We consider a three-dimensional hyperelastic cylinder in Ω = D × [0, ∞]. We study the asymptotic behaviour of the deformations of the cross-sections in an equilibrium state. In this case we show that the solutions either have exponential decay or exponential growth. We give some initial conditions such that the latter case occurs. 相似文献
7.
8.
Héctor Beltrán Nahum Masó Beatriz Julian Eloisa Cordoncillo Juan B. Carda Purificación Escribano Anthony R. West 《Journal of Sol-Gel Science and Technology》2003,26(1-3):1061-1065
Lead Magnesium Niobate, Pb(Mg1/3Nb2/3)O3 (PMN), is an important relaxor ferroelectric material. A significant problem exists, however, in the preparation of this material: it is very difficult to prepare pure phase, without the presence of a pyrochlore impurity phase which degrades the dielectric properties. Depending on the processing conditions, the amount of pyrochlore phase varies.Considering the ternary diagram PbO-MgO-Nb2O5, different compositions have been prepared by a simple sol-gel method at room temperature using Pb(CH3COO)2, Mg(CH3COO)2, Nb(OC2H5)5 as precursors. After the heat treatment, the samples obtained were analyzed by XRD and EPMA with the purpose of studying the compositions formed.From the analysis of these results, it seems to be that the appearance of pyrochlore can be related to the reactivity of the MgO and/or the presence of other phases of the binary system PbO-Nb2O5. An excess of Pb and Mg is necessary for compositions to be formed near the PMN. The control of the amount of these two elements is very important because an excess of MgO would lead to rich compositions in Mg as a secondary phase. 相似文献
9.
Masár M Kaniansky D Bodor R Jöhnck M Stanislawski B 《Journal of chromatography. A》2001,916(1-2):167-174
Isotachophoretic (ITP) separation and determination of a group of 13 organic and inorganic acids, currently present in wines, on a poly(methyl methacrylate) chip provided with on-column conductivity detection was a subject of a detailed study performed in this work. Experiments with the ITP electrolyte systems proposed to the separation of anionic constituents present in wine revealed that their separation at a low pH (2.9) provides the best results in terms of the resolution. Using a 94 mm long separation channel of the chip, the acids could be resolved within 10-15 min also in instances when their concentrations corresponded to those at which they typically occur in wines. A procedure suitable to the ITP determination of organic acids responsible for some important organoleptic characteristics of wines (tartaric, lactic, malic and citric acids) was developed. Concentrations of 2-10 mg/l of these acids represented their limits of quantitation for a 0.9 microl volume sample loop on the chip. A maximum sample load on the chip, under the preferred separating conditions, was set by the resolution of malate and citrate. A complete resolution of these constituents in wine samples was reached when their molar concentration ratio was 20:1 or less. ITP analyses of a large series of model and wine samples on the chip showed that qualitative indices [RSH (relative step height) values] of the acids, based on the response of the conductivity detector, reproduced with RSD better than 2% while reproducibilities of the determination of the acids of our interest characterized RSD values better than 3.5%. 相似文献
10.
José M. Figueroa-O'Farrill Javier Mas Eduardo Ramos 《Communications in Mathematical Physics》1993,158(1):17-43
The KP hierarchy is hamiltonian relative to a one-parameter family of Poisson structures obtained from a generalized Adler map in the space of formal pseudodifferential symbols with noninteger powers. The resulting W-algebra is a one-parameter deformation of WKP admitting a central extension for generic values of the parameter, reducing naturally to W
n
for special values of the parameter, and contracting to the centrally extended W1+, W and further truncations. In the classical limit, all algebras in the one-parameter family are equivalent and isomorphic tow
KP. The reduction induced by setting the spin-one field to zero yields a one-parameter deformation of
which contracts to a new nonlinear algebra of the W-type.Address after October 1993: Queen Mary and Westfield College, UK 相似文献