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121.
Changes in the elastic and viscoelastic (creep) characteristics of polymer concrete and its structural components (polyester resin, unfilled or filled with diabase flour) during a long-term exposure to water at 20°C were studied. Modeling the structural changes in polymer concrete with time showed an increase in the relative volume content of pores filled with water and a decrease in that of unfilled pores. Based on the free-volume concept and the data on swelling due to moistening and shrinkage due to physical aging of the binder, a rather accurate estimate of the time-moisture reduction function for polymer concrete was obtained. The function was found to be nonmonotonic: the interval of increase was followed by an interval of decrease. 相似文献
122.
Simion Breaz 《Czechoslovak Mathematical Journal》2003,53(2):479-489
We present general properties for almost-flat modules and we prove that a self-small right module is almost flat as a left module over its endomorphism ring if and only if the class of g-static modules is closed under the kernels. 相似文献
123.
形式三角矩阵环的可分性和稳定度 总被引:1,自引:0,他引:1
In this paper we study the formal triangular matrix ring T =and give some necessary and sufficient conditions for T to be (strongly) separative, m-fold stable and unit 1-stable. Moreover, a condition for finitely generated projec-tive T-modules to have n in the stable range is given under the assumption that A and B are exchange rings. 相似文献
124.
Let R be a commutative ring without nil-factor. In this paper, we discuss the problem of quasi-valuation ring presented in the reference “Wang Shianghaw, On quasi-valuation ring, Northeast People‘s Univ. Natur. Sci. J., (1)(1957), 27-40”,when the quotient field of R is an algebraic number field or an algebraic function field, and we obtain a characterization of quasi-valuation rings. 相似文献
125.
设G是有限群,|G|-1∈R.本文证明了与强G-分次环R,R#k[G]*,非分次R-模和Re-模有关的两个Maschke-型定理. 相似文献
126.
127.
I. Jánossy 《Pramana》2003,61(2):435-445
It is suggested that liquid crystal—polymer interfaces are coupled systems, in which the components mutually influence the
orientational state of each other. The photo-orientation process at liquid crystal-polymer interfaces provides a striking
example of such a coupling. Experiments show that the anisotropic structure generated by polarised light at a polymer surface
is strongly affected by the phase of the liquid crystal covering the polymer. Photo-orientation is significantly more efficient
when the liquid crystal is in the isotropic phase than when it exhibits orientational order. The observations are interpreted
by assuming that in the smectic and nematic phases the liquid crystal stabilises to a large extent polymer chain-segments
aligned parallel to the director, while it blocks the photo-induced formation of chain-segments in the perpendicular direction.
Other situations, in which the coupling between the liquid crystal and the polymer can be important, are also discussed briefly. 相似文献
128.
The interactions between surfaces modified with grafted polymers is studied theoretically. The aim of this work is to find polymer surface modifications that will result in localized attractive interactions between the surfaces. The practical motivation of the work is to find means to control the distance between bilayers and solid supports in supported membranes. Two theoretical approaches are used, the analytical treatment of Alexander and a molecular theory. It is found that grafting each end of the polymer to each surface results in an interaction with a well defined minimum. The location of the minima is found to be very close to the thickness of the polymer layer when the chains are grafted to only one of the surfaces. The predictions of the analytical theory are in excellent agreement with the molecular approach in this case. It is found that increasing the surface coverage increases the strength of the interaction. However, increasing the polymer chain length at fixed surface coverage results in a decrease of the free energy cost associated with separating the surfaces from their optimal distance. For the cases in which grafting to both surfaces is not possible, the molecular theory is used to study the effect of functionalizing segments of the chain to achieve an attractive well. It is found that by functionalizing the free end-groups of the polymers with segments attracted to the membrane, the range of the attractive interaction is significantly larger than the thickness of the unperturbed layer. Functionlizing the middle segments of the chains results in a shorter range attraction but of the same strength as in the end-functionalized layers. The optimal polymer modification is found to be such that the functionlized groups are attracted to the bare surface but are not attracted to the grafting surface. The relevance of the results to the design of experimental surface modifiers is discussed. 相似文献
129.
Oelschlaeger C Buhler E Waton G Candau SJ 《The European physical journal. E, Soft matter》2003,11(1):7-20
The mixed micellization between the cationic gemini surfactant [ C12H25( CH3)2N+( C2H4) N+( CH3)2 C12H25•2Br-] and the cationic cetyltrimethylammonium bromide (CTAB) in 150 mM KBr solutions has been investigated. The variation of the
cmc of the mixtures, measured by surface tension experiments, with composition revealed synergism in micelle formation. T-Jump
and light scattering experiments performed in the vicinity of the crossover volume fraction showed the existence of two micellar
populations, possibly linear and toroidal micelles. Rheological and dynamic light scattering experiments allowed to fully
characterize the linear viscoelasticity of the mixtures. These measurements revealed synergistic gains in viscoelastic properties
with a maximum of the stress-relaxation time around the equimolar composition. These effects are ascribed to a progressive
intermicellar crosslinking resulting from a continuous increase of the end-cap energy with the 12-2-12 content in the mixture.
Received: 18 November 2002 / Accepted: 8 April 2003 / Published online: 27 May 2003
RID="a"
ID="a"e-mail: candau@fresnel.u-strasbg.fr 相似文献
130.
Cyanobacteria and myxobacteria use slime secretion for gliding motility over surfaces. The slime is produced by the nozzle-like pores located on the bacteria surface. To understand the mechanism of gliding motion and its relation to slime polymerization, we have performed molecular dynamics simulations of a molecular nozzle with growing inside polymer chains. These simulations show that the compression of polymer chains inside the nozzle is a driving force for propulsion. There is a linear relationship between the average nozzle velocity and the chain polymerization rate with a proportionality coefficient dependent on the geometric characteristics of the nozzle such as its length and friction coefficient. This minimal model of the molecular engine was used to explain the gliding motion of bacteria over surfaces. 相似文献