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991.
The Makeham distribution has been used to describe human mortality and establish actuarial tables. The hazard function is defined by μ(t)=A+BCt, we use the least squares type estimation to estimate the parameters of Makeham distribution in this paper. Seven cases are considered, when A, B, C are known or unknown, respectively. Also, we evaluated the mean square errors of these estimators. 相似文献
992.
In this paper we consider a numerical approximation of solution of nonhomogeneous backward heat conduction problem (BHCP) in bounded region based on Tikhonov regularization method. Error estimate at t=0 for this method is provided. According to the error estimate, a selection of regularization parameter is given. Meanwhile, a numerical implementation is described and the numerical results show that our algorithm is effective. 相似文献
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994.
An extended stochastic gradient algorithm is developed to estimate the parameters of Hammerstein–Wiener ARMAX models. The basic idea is to replace the unmeasurable noise terms in the information vector of the pseudo-linear regression identification model with the corresponding noise estimates which are computed by the obtained parameter estimates. The obtained parameter estimates of the identification model include the product terms of the parameters of the original systems. Two methods of separating the parameter estimates of the original parameters from the product terms are discussed: the average method and the singular value decomposition method. To improve the identification accuracy, an extended stochastic gradient algorithm with a forgetting factor is presented. The simulation results indicate that the parameter estimation errors become small by introducing the forgetting factor. 相似文献
995.
Scalable search-based image annotation 总被引:4,自引:0,他引:4
With the popularity of digital cameras, more and more people have accumulated considerable digital images on their personal
devices. As a result, there are increasing needs to effectively search these personal images. Automatic image annotation may
serve the goal, for the annotated keywords could facilitate the search processes. Although many image annotation methods have
been proposed in recent years, their effectiveness on arbitrary personal images is constrained by their limited scalability,
i.e. limited lexicon of small-scale training set. To be scalable, we propose a search-based image annotation algorithm that
is analogous to information retrieval. First, content-based image retrieval technology is used to retrieve a set of visually
similar images from a large-scale Web image set. Second, a text-based keyword search technique is used to obtain a ranked
list of candidate annotations for each retrieved image. Third, a fusion algorithm is used to combine the ranked lists into
a final candidate annotation list. Finally, the candidate annotations are re-ranked using Random Walk with Restarts and only
the top ones are reserved as the final annotations. The application of both efficient search techniques and Web-scale image
set guarantees the scalability of the proposed algorithm. Moreover, we provide an annotation rejection scheme to point out
the images that our annotation system cannot handle well. Experimental results on U. Washington dataset show not only the
effectiveness and efficiency of the proposed algorithm but also the advantage of image retrieval using annotation results
over that using visual features. 相似文献
996.
Image preview is a convenient way to browse large or multiple images on small displays. However, current signal-level image
resampling algorithms may remove many features of interest in the preview image. In this paper, we propose perceptual image
preview which retains more perceptual features such that users can inspect features of interest by viewing the preview image
only and without zooming in. This technology has two components, structure enhancement and perceptual feature visualization.
Structure enhancement enhances the image structure while suppressing subtle details using a gradient modulation method, thus
making the succedent perceptual features more apparent. For perceptual feature visualization, features of interest detected
in the picture is visualized on the structure enhanced preview image. We demonstrate with two examples of most commonly used image quality features, image blur and noise. The effectiveness of the proposed method is validated
by experimental results. 相似文献
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为了提高交互漫游系统中动态人物与静态场景对象之间的碰撞检测性能,提出了将动态人物采用包围盒的方法,与地面、巷道等静态物体采用三角网格面的方法相结合的思想,并将其应用于OGRE和ODE环境的巷道漫游系统中。结果表明,此方法提升了碰撞检测性能,满足了虚拟现实中实时性的要求。 相似文献