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A Note on the Optimality of Generalized Cross-validation Bandwidth Selection in Partially linear Models with Kernel Smoothing Estimator

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Acta Mathematicae Applicatae Sinica 2006年第2期22卷 345-352页

作者： wang-li xu Academy of Mathematics and Systems Science Graduate School of the Chinese Academy of Sciences Beijing 100080 China

The issue of selection of bandwidth in kernel smoothing method is considered within the context of partially linear models, hi this paper, we study the asymptotic behavior of the bandwidth choice based on generalized cross-validation （CCV） approach and prove that this bandwidth choice is asymptotically optimal. Numerical simulation are also conducted to investigate the empirical performance of generalized cross-valldation.

关键词： Generalized cross-validation partially linear model kernel smoothing bandwidth selection

Some Properties for the Estimators in linear Mixed Models

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Acta Mathematicae Applicatae Sinica 2013年第1期29卷 105-116页

作者： Zai-xing li Yan Cui wang-li xu College of Science China University of Mining and Technology (Beijing) School of Statistics Renmin University of China

linear mixed models （LMMs） have become an important statistical method for analyzing cluster or longitudinal data. In most cases, it is assumed that the distributions of the random effects and the errors are normal. This paper removes this restrictions and replace them by the moment conditions. We show that the least square estimators of fixed effects are consistent and asymptotically normal in general LMMs. A closed-form estimator of the covariance matrix for the random effect is constructed and its consistent is shown. Based on this, the consistent estimate for the error variance is also obtained. A simulation study and a real data analysis show that the procedure is effective.

关键词： Moment conditions LMMs Consistency Asymptotical normality

Symmetrical Independence Tests for Two Random Vectors with Arbitrary Dimensional Graphs

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Acta Mathematica Sinica,English Series 2022年第4期38卷 662-682页

作者： Jia Min liU Gao Rong li Jian Qiang ZHANG wang li xu Center for Applied Statistics Renmin University of ChinaBeijing 100872P.R.China School of Statistics Beijing Normal UniversityBeijing 100875P.R.China

Test of independence between random vectors X and Y is an essential task in statistical *** type of testing methods is based on the minimal spanning tree of variables X and *** main idea is to generate the minimal spanning tree for one random vector X,and for each edges in minimal spanning tree,the corresponding rank number can be calculated based on another random vector *** resulting test statistics are constructed by these rank ***,the existed statistics are not symmetrical tests about the random vectors X and Y such that the power performance from minimal spanning tree of X is not the same as that from minimal spanning tree of *** addition,the conclusion from minimal spanning tree of X might conflict with that from minimal spanning tree of *** order to solve these problems,we propose several symmetrical independence tests for X and *** exact distributions of test statistics are investigated when the sample size is ***,we study the asymptotic properties of the statistics.A permutation method is introduced for getting critical values of the *** with the existing methods,our proposed methods are more efficient demonstrated by numerical analysis.

关键词： Exact distribution minimal spanning tree asymptotic distribution symmetrical independence test

Testing for Random Effects in linear Mixed Models for Longitudinal Data under Moment Conditions

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Acta Mathematica Sinica,English Series 2010年第3期26卷 497-514页

作者： Zai King li li Xing ZHU Ping WU Jian Hong WU wang li xu Department of Mathematics China University of Mining & Technology Beijing 100083 P. R. China Department of Mathematics Hong Kong Baptist University Hong Kong P. R. China School of Finance and Statistics East China Normal University Shanghai 200241 P. R. China College of Statistics and Mathematics Zhejiang Gongshang University Hangzhou 310018 P. R. China School of Statistics Renmin University of China Beijing 100872 P. R. China

In this paper, we consider whether the random effect exists in linear mixed models （LMMs） when only moment conditions are assumed. Based on the estimators of parameters and their asymptotic properties, a Wald-type test is constructed. It is consistent against global alternatives and is sensitive to the local alternatives converging to the null hypothesis at parametric rates, a fastest possibly rate for goodness-of-fit testing. Moreover, a simulation study shows the performance of the test is good. The procedure also applies to a real data.

关键词： consistent estimators asymptotic normality LMMs random effects

A Granularity-Aware Parallel Aggregation Method for Data Streams

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Wuhan University Journal of Natural Sciences 2006年第1期11卷 133-137页

作者： wang Yong-li xu Hong-bing xu li-zhen QIAN Jiang-bo liU xue-jun Department of Computer Science and Engineering Southeast University Nanjing 210096 Jiangsu China

This paper focuses on the parallel aggregation processing of data streams based on the shared-nothing architecture. A novel granularity-aware parallel aggregating model is proposed. It employs parallel sampling and linear regression to describe the characteristics of the data quantity in the query window in order to determine the partition granularity of tuples, and utilizes equal depth histogram to implement partitio ning. This method can avoid data skew and reduce communi cation cost. The experiment results on both synthetic data and actual data prove that the proposed method is efficient, practical and suitable for time-varying data streams processing.

关键词： data streams parallel processing linear regression aggregation data skew

SmI_2-promoted imino-Reformatsky reaction for facile synthesis of enantioenriched β-amino acid esters

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Science China Chemistry 2011年第1期54卷 61-65页

作者： wang li SHEN Chun xu Ming-Hua Shanghai Institute of Materia Medica Chinese Academy of Sciences Shanghai 201203 China

A facile and efficient method for the stereoselective synthesis of β-amino acid esters via SmI2-promoted imino-Reformatsky reaction is *** addition of tert-butyl bromoacetate to N-tert-butanesulfinyl aldimines afforded β-amino acid esters in moderate to high yields with excellent *** synthetic utilities of the tert-butyl β-amino acid esters were expanded by the preparation of β-lactams and 3-aminoindan-1-ones derivatives.

关键词： β-amino acid ester samarium diiodide N-tert-butanesulfinyl imine Reformatsky reaction β-lactam 3-aminoindan-1-one asymmetric synthesis

Prediction and Analysis on Oxidation of H13 Hot Work Steel

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Journal of Iron and Steel Research International 2006年第1期13卷 44-49页

作者： MIN Yong-an WU Xiao-chun wang Rong li lin xu Luo-ping School of Materials Science and Engineering Shanghai University Shanghai 200072 China

The understanding of oxidation behaviors on H13 steel was helpful to improve the service life and performance of hot work moulds and dies. Thermal-Calc Software was performed to calculate the oxidation phases on H13 steel along with different partial oxygen pressures in the interesting temperature range of 500-700 ℃. In this range H13 steel samples were treated respectively in different atmosphere including flowing water vapor （0.2 MPa）, normal pressure air （0.1 MPa） and low pressure air （0. 001 MPa）. The different oxidation films were detected with optical microscopy and X-ray diffraction. The microstructures and phase constitutions of the films formed in low pressure air were similar to those of the films formed in water vapor, and obviously different to those of the films formed in normal pressure air. The oxidation mechanisms of H13 steel in different atmosphere were also discussed.

关键词： oxidatiom hot work steel surface treatment die casting

Thermal Oxidation of Silicon Carbide Substrates

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Journal of Materials Science & Technology 2009年第1期25卷 115-118页

作者： Xiufang Chen liana Ning Yingmin wang Juan li Xiangang xu Xiaobo Hu Minhua Jiang State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China

Thermal oxidation was used to remove the subsurface damage of silicon carbide （SIC） surfaces. The anisotropy of oxidation and the composition of oxide layers on Si and C faces were analyzed. Regular pits were observed on the surface after the removal of the oxide layers, which were detrimental to the growth of high quality epitaxial layers. The thickness and composition of the oxide layers were characterized by Rutherford backscattering spectrometry （RBS） and X-ray photoelectron spectroscopy （XPS）, respectively. Epitaxial growth was performed in a metal organic chemical vapor deposition （MOCVD） system. The substrate surface morphology after removing the oxide layer and gallium nitride （GaN） epilayer surface were observed by atomic force microscopy （AFM）. The results showed that the GaN epilayer grown on the oxidized substrates was superior to that on the unoxidized substrates.

关键词： SiC Thermal oxidation GaN epitaxy

High laser damage threshold coatings and damage testing technology

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光学精密工程 2005年第4期13卷 500-504页

作者： MA Ping HU Jian-ping CHEN Song-lin TANG Ming wang Zhen li Wei xu Qiao Chengdu Fine Optical Engineering Research Center Chengdu 610041China

The laser-induced damage threshold(liDT) of optical coating is a limited factor for development of a high peak power laser. The automatic damage testing facility was built to determine the liDT of optics at 1 064 nm and 355 nm.. The cleanning and processing procedure of the substrate and coating technique were improved, and the damage resistance of high-reflective coating at 1 064 nm was increased.

关键词：激光涂覆技术 liDT 自动机械光学仪器激光仪器