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961.
Nanoparticles of tungsten trioxide, WO3, are used to enhance the luminescence emission intensity of terbium(III) ions embedded in a silica matrix. Optically active components have been incorporated into silica xerogel by impregnation of silica xerogel immersed firstly in WO3 sol and subsequently in a solution with Tb(III). Photoluminescence studies make it possible to describe a plausible mechanism of the Tb(III) enhanced luminescence that could be attributed to energy transfer via excited WO3 nanoparticles to Tb(III) ions in the system: Tb(III) ions–WO3 nanocrystals–SiO2. The effect related to WO3 nanoparticles of various sizes influences not only changes in the emission intensity and band shifting of WO3 nanostructures but also the same spectral parameters of the emitting Tb(III) ions. 相似文献
962.
In the paper, formulae for optimum sample allocation between domains, strata in the domains, and sampling stages are presented for stratified two-stage sampling in domains under fixed sample size of SSUs from PSUs. 相似文献
963.
964.
Andrzej Ruszczyński 《Mathematical Programming》1993,58(1-3):201-228
A new decomposition method for multistage stochastic linear programming problems is proposed. A multistage stochastic problem is represented in a tree-like form and with each node of the decision tree a certain linear or quadratic subproblem is associated. The subproblems generate proposals for their successors and some backward information for their predecessors. The subproblems can be solved in parallel and exchange information in an asynchronous way through special buffers. After a finite time the method either finds an optimal solution to the problem or discovers its inconsistency. An analytical illustrative example shows that parallelization can speed up computation over every sequential method. Computational experiments indicate that for large problems we can obtain substantial gains in efficiency with moderate numbers of processors.This work was partly supported by the International Institute for Applied Systems Analysis, Laxenburg, Austria. 相似文献
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967.
Anna Koralewska Wojciech Augustyniak Andrzej Temeriusz Marianna Kańska 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(1-2):193-197
The impact of permethylated α-, β-, γ-cyclodextrin (TMα-CD, TMβ-CD, TMγ–CD, respectively) on TPL-catalysed decomposition of L-tyrosine was investigated by means of spectrophotometric measurements. The inhibitory effects of TM-CDs on the catalytic activity of the enzyme were shown. This phenomenon is supposed to be connected with the host–guest complex formation. CDs were found to have impact on maximal velocity and on Michaelis constant of described catalysis. 相似文献
968.
Andrzej J Maciejewski 《Indagationes Mathematicae》2004,15(1):55-72
We study some generic aspects of polynomial vector fields or polynomial derivations with respect to their integration. In particular, using a well-suited presentation of Darboux polynomials at some Darboux point as power series in local Darboux coordinates, it is possible to show, by algebraic means only, that the Jouanolou derivation in four variables has no polynomial first integral for any integer value s ≥ 2 of the parameter.Using direct sums of derivations together with our previous results we show that, for all n ≥ 3 and s ≥ 2, the absence of polynomial first integrals, or even of Darboux polynomials, is generic for homogeneous polynomial vector fields of degree s in n variables. 相似文献
969.
We continue investigations of reasonable ultrafilters on uncountable cardinals defined in Shelah [8]. We introduce a general scheme of generating a filter on λ from filters on smaller sets and we investigate the combinatorics of objects obtained this way. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
970.