4,009 research outputs found
Achieving superplasticity in a Bi-Sn alloy processed by high-pressure torsion
No full textA Bi-Sn alloy was processed by high-pressure torsion (HPT) at room temperature for 10 turns to achieve a homogeneous fine microstructure. Microhardness observations showed that the refined microstructure experienced self-annealing during storage at room temperature. Following HPT processing and storage at room temperature for 35 days, a sample had excellent superplastic properties when testing at an initial tensile strain rate of 1.0 × 10-4 s-1. The enhanced superplastic flow behavior of the fine-grained Bi-Sn alloy was attributed to the homogeneously distributed Bi-Sn and Sn-Sn boundaries after HPT processing since these are preferred sites for grain boundary sliding
Smoothing estimation of rate function for recurrent event data with informative censoring
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Kernel Estimation of Rate Function for Recurrent Event Data
No full textRecurrent event data are largely characterized by the rate function but smoothing techniques for estimating the rate function have never been rigorously developed or studied in statistical literature. This paper considers the moment and least squares methods for estimating the rate function from recurrent event data. With an independent censoring assumption on the recurrent event process, we study statistical properties of the proposed estimators and propose bootstrap procedures for the bandwidth selection and for the approximation of confidence intervals in the estimation of the occurrence rate function. It is identified that the moment method without resmoothing via a smaller bandwidth will produce a curve with nicks occurring at the censoring times, whereas there is no such problem with the least squares method. Furthermore, the asymptotic variance of the least squares estimator is shown to be smaller under regularity conditions. However, in the implementation of the bootstrap procedures, the moment method is computationally more efficient than the least squares method because the former approach uses condensed bootstrap data. The performance of the proposed procedures is studied through Monte Carlo simulations and an epidemiological example on intravenous drug users. Copyright 2005 Board of the Foundation of the Scandinavian Journal of Statistics..
Synaptotagmin–Ca2+ triggers two sequential steps in regulated exocytosis in rat PC12 cells: fusion pore opening and fusion pore dilation
No full textLand-surface deformation corresponding to seasonal ground-water fluctuation, determining by SAR interferometry in the SW Taiwan.
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