2,446 research outputs found

    Asymptotic optimality and efficient computation of the leave-subject-out cross-validation

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    Although the leave-subject-out cross-validation (CV) has been widely used in practice for tuning parameter selection for various nonparametric and semiparametric models of longitudinal data, its theoretical property is unknown and solving the associated optimization problem is computationally expensive, especially when there are multiple tuning parameters. In this paper, by focusing on the penalized spline method, we show that the leave-subject-out CV is optimal in the sense that it is asymptotically equivalent to the empirical squared error loss function minimization. An efficient Newton-type algorithm is developed to compute the penalty parameters that optimize the CV criterion. Simulated and real data are used to demonstrate the effectiveness of the leave-subject-out CV in selecting both the penalty parameters and the working correlation matrix.Comment: Published in at http://dx.doi.org/10.1214/12-AOS1063 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Small-Scale Enterprises Supply Chain Lean Conversion

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    Unequal Error Protected JPEG 2000 Broadcast Scheme with Progressive Fountain Codes

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    This paper proposes a novel scheme, based on progressive fountain codes, for broadcasting JPEG 2000 multimedia. In such a broadcast scheme, progressive resolution levels of images/video have been unequally protected when transmitted using the proposed progressive fountain codes. With progressive fountain codes applied in the broadcast scheme, the resolutions of images (JPEG 2000) or videos (MJPEG 2000) received by different users can be automatically adaptive to their channel qualities, i.e. the users with good channel qualities are possible to receive the high resolution images/vedio while the users with bad channel qualities may receive low resolution images/vedio. Finally, the performance of the proposed scheme is evaluated with the MJPEG 2000 broadcast prototype

    Rateless Codes with Progressive Recovery for Layered Multimedia Delivery

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    This paper proposes a novel approach, based on unequal error protection, to enhance rateless codes with progressive recovery for layered multimedia delivery. With a parallel encoding structure, the proposed Progressive Rateless codes (PRC) assign unequal redundancy to each layer in accordance with their importance. Each output symbol contains information from all layers, and thus the stream layers can be recovered progressively at the expected received ratios of output symbols. Furthermore, the dependency between layers is naturally considered. The performance of the PRC is evaluated and compared with some related UEP approaches. Results show that our PRC approach provides better recovery performance with lower overhead both theoretically and numerically

    Strong Asymptotic Properties of Kernel Smooth Density and Hazard Function Estimation for Right Censoring NA Random Variable

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    Most studies for NA random variable is under complete sampling setting, which is actually an relatively ideal condition in application. The paper relaxes this condition to the censoring incomplete sampling data and considers the topic for kernel estimation of the density function together with the hazard function based on the Kaplan-Meier estimator. The strong asymptotic properties for the two estimators are firstly established

    Analysis of the Research Trend of Global Value Chain Based on Literature Metrology and Visualization Technology

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    With the improvement of international division of labor and cooperation and the refinement of production process division, the global value chain division of labor system is becoming the latest mode of product division. In order to deeply analyze and explore the research status and development trend in the field of global value chain, based on the Web of Science core collection SCIE and SSCI database, this paper uses the literature metrology method and CiteSpace software to conduct a visual analysis of the literature in the field of global value chain. The study discovered research hotspots, research processes, development frontiers, research distribution, and citation status of global value chains. We have comprehensively grasped the literature status of global value chain research, providing scholars with new research directions, and also providing strong reference and guidance for investment decision-making of multinational corporations and trade policy formulation of countries and international organizations
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