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931.
Silica aerogels form mutually self-similar fractal structures for a broad range of densities and preparation conditions. This allows to scale dynamical results obtained on longitudinal acoustic waves up to the onset of the phonon to fracton crossover. An effective value of the fracton dimension
is found, and various possible interpretations of that value are discussed.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday 相似文献
932.
We show that the usual ansatz used for quantizing the collective coordinates corresponding to a rotation of chiral soliton does not satisfy the equations of motion. We suggest a more general ansatz that admits the separation of rotational degrees of freedom and does not contradict the equations of motion.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985. 相似文献
933.
In this paper we prove that there exists an elliptic semiplaneS(v, k, m) withk –m 2 if and only if there exists a group divisible design GDD
k
((k –m)(k – 1);k –m; 0, 1) withm pairwise orthogonal resolutions. As an example of this theorem, we construct an elliptic semiplaneW(45, 7, 3) and show thatW is isomorphic to the elliptic semiplaneS(45, 7, 3) given by R. D. Baker. 相似文献
934.
935.
936.
937.
938.
P. D. T. A. Elliott 《Monatshefte für Mathematik》1986,102(1):3-6
The subgroup of the positive rationals, generated by a sequence of upper density , has index essentially not exceeding –1.In honor of the seventieth birthday of Professor E. HlawkaPartially supported by N.S.F. Contract No. DMS-8500949. 相似文献
939.
Observables on hypergraphs are described by event-valued measures. We first distinguish between finitely additive observables and countably additive ones. We then study the spectrum, compatibility, and functions of observables. Next a relationship between observables and certain functionals on the set of measures M(H) of a hypergraph H is established. We characterize hypergraphs for which every linear functional on M(H) is determined by an observable. We define the concept of an effect and show that observables are related to effect-valued measures. Finally, we define operational transformations from M(H) to itself and show that they can be described as a certain combination of effects.On leave from University of Berne, Institute of Mathematical Statistics, Sidlerstrasse 5, CH-3012 Berne, Switzerland. 相似文献
940.
CO conversion to hydrocarbons at various reaction temperatures and atmospheric pressure has been investigated on alumina-supported Fe, Ni and Fe–Ni catalysts. Maxima of activity and selectivity were obtained in hydrocarbon formation as a function of Fe content in the samples, which corresponds to a certain stoichiometry of metallic components. 相似文献