2,446 research outputs found
Asymptotic optimality and efficient computation of the leave-subject-out cross-validation
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
Unequal Error Protected JPEG 2000 Broadcast Scheme with Progressive Fountain Codes
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
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
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
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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