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1.
For ap-variate normal mean with known variances, the model proposed by Zellner (1986,J. Amer. Statist. Assoc.,81, 446–451) is discussed in a slightly different framework. A generalized Bayes estimate is derived from a three-stage Bayes point of view under the asymmetric loss function, and the admissibility of such estimators is proved.  相似文献
2.
Weighted Composition Operators on Bergman and Dirichlet Spaces   总被引:3,自引:0,他引:3  
Let H() denote a functional Hilbert space of analytic functions on a domain . Let w : C and : be such that w f is in H() for every f in H(). The operator wC given by f w f is called a weighted composition operator on H(). In this paper we characterize such operators and those for which (wC )* is a composition operator. Compact weighted composition operators on some functional Hilbert spaces are also characterized. We give sufficient conditions for the compactness of such operators on weighted Dirichlet spaces.  相似文献
3.
The flow simulation of a low-specific-speed high-speed centrifugal pump   总被引:2,自引:0,他引:2  
In this paper a general three-dimensional simulation of turbulent fluid flow is presented to predict velocity and pressure fields for a centrifugal pump. A commercial CFD code was used to solve the governing equations of the flow field. In order to study the most suitable turbulence model, three known turbulence models of standard kε, RNG and RSM were applied. The complex flow configuration required us to use around 5,800,000 cells, and 12 computational nodes (processors) for parallel computing. Simulation results in the form of characteristic curves were compared with available experimental data, and an acceptable agreement was obtained. Additionally, effect of number of blades on the efficiency of pump was studied. The number of blades was changed from 5 to 7. The results show that the impeller with 7 blades has the highest head coefficient. Finally, it was observed also that the position of blades with respect to the tongue of volute has great effect on the start of the separation. Thus, to analyze the effect of blade number on the characteristics of the pump, the position of blade and tongue should be similar to each other. Investigations of this kind may help to reduce the required experimental work for the development and design of such devices.  相似文献
4.
Hypercyclicity on the Algebra of Hilbert-Schmidt Operators   总被引:1,自引:0,他引:1  
We prove that the Hypercyclicity Criterion for any operator T on a Hilbert space is equivalent to the hypercyclicity of the left multiplication operator induced by T on the algebra of Hilbert-Schmidt operators.  相似文献
5.
On the supercyclicity and hypercyclicity of the operator algebra   总被引:1,自引:0,他引:1  
Let B(X) be the operator algebra for a separable infinite dimensional Hilbert space H, endowed with the strong operator topology or *-strong topology. We give sufficient conditions for a continuous linear mapping L : B(X) →B(X) to be supercyclic or ,-supercyclic. In particular our condition implies the existence of an infinite dimensional subspace of supercyclic vectors for a mapping T on H. Hypercyclicity of the operator algebra with strong operator topology was studied' by Chan and here we obtain an analogous result in the case of *-strong operator topology.  相似文献
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