Objective To study the current situation of China’s pharmacovigilance system,and to provide some suggestions for the improvement of related policies.Methods A policy modeling consistency(PMC)index model of pharmacovi...Objective To study the current situation of China’s pharmacovigilance system,and to provide some suggestions for the improvement of related policies.Methods A policy modeling consistency(PMC)index model of pharmacovigilance policy was constructed to quantitatively assess the samples of policies combining text mining.Then,the PMC surface was established to obtain the visualization results of China’s pharmacovigilance policy samples,and their shortcomings were clearly analyzed by comparison.Results and Conclusion Forty-one percent of China’s pharmacovigilance policies were rated as excellent,54%as acceptable,and the overall evaluation was acceptable.But there is still some room for improvement.On the whole,there are problems of insufficient policy synergy,lack of policy incentives and constraints,and incomplete coverage of policy functions.It is recommended that China’s pharmacovigilance policy system should be optimized by strengthening policy coordination,increasing policy incentives and constraints,and guiding multi-subjects to participate in coordination.These findings and recommendations can provide operational ideas for the system of China’s pharmacovigilance policy.展开更多
Weighting values for different habitat variables used in multi-factor habitat suitability index (HSI) modeling reflect the relative influences of different variables on distribution of fish species. Using the winter-s...Weighting values for different habitat variables used in multi-factor habitat suitability index (HSI) modeling reflect the relative influences of different variables on distribution of fish species. Using the winter-spring cohort of neon flying squid (Ommastrephes bartramii) in the Northwestern Pacific Ocean as an example, we evaluated the impact of different weighting schemes on the HSI models based on sea surface temperature, gradient of sea surface temperature and sea surface height. We compared differences in predicted fishing effort and HSI values resulting from different weighting. The weighting for different habitat variables could greatly influence HSI modeling and should be carefully done based on their relative importance in influencing the resource spatial distribution. Weighting in a multi-factor HSI model should be further studied and optimization methods should be developed to improve forecasting squid spatial distributions.展开更多
In this article, a partially linear single-index model /or longitudinal data is investigated. The generalized penalized spline least squares estimates of the unknown parameters are suggested. All parameters can be est...In this article, a partially linear single-index model /or longitudinal data is investigated. The generalized penalized spline least squares estimates of the unknown parameters are suggested. All parameters can be estimated simultaneously by the proposed method while the feature of longitudinal data is considered. The existence, strong consistency and asymptotic normality of the estimators are proved under suitable conditions. A simulation study is conducted to investigate the finite sample performance of the proposed method. Our approach can also be used to study the pure single-index model for longitudinal data.展开更多
A semi-parametric single-index model based approach was proposed for prediction of mechanical properties of hot rolled strip. Based on industrial production data, a semi-parametric single-index model was developed by ...A semi-parametric single-index model based approach was proposed for prediction of mechanical properties of hot rolled strip. Based on industrial production data, a semi-parametric single-index model was developed by choo-sing the appropriate kernel function and window width to predict the yield strength, tensile strength and elongation. When data samples are limited, compared with regression method and neural network method, the prediction results show that the semi-parametric single-index model based method is more adaptive and the prediction performance is superior to those by both regression and neural network methods.展开更多
The single-index model with monotonic link function is investigated. Firstly, it is showed that the link function h（.） can be viewed by a graphic method. That is, the plot with the fitted response y on the horizonta...The single-index model with monotonic link function is investigated. Firstly, it is showed that the link function h（.） can be viewed by a graphic method. That is, the plot with the fitted response y on the horizontal axis and the observed y on the vertical axis can be used to visualize the link function. It is pointed out that this graphic approach is also applicable even when the link function is not monotonic. Note that many existing nonparametric smoothers can also be used to assess h（.）. Therefore, the I-spline approximation of the link function via maximizing the covariance function with a penalty function is investigated in the present work. The consistency of the criterion is constructed. A small simulation is carried out to evidence the efficiency of the approach proposed in the paper.展开更多
In order to compare the aviation network of mid-south,northwest and southwest of China to reveal the structure similarity and difference for providing quantitative evidence to construct regional aviation network and i...In order to compare the aviation network of mid-south,northwest and southwest of China to reveal the structure similarity and difference for providing quantitative evidence to construct regional aviation network and improve its structure,hierarchical index model of regional aviation network was established through dividing the aviation network into layers to research its structure characters.Data matrixes were defined to record the basic state of regional aviation network.Index matrixes were constructed to describe the quantitative features of regional aviation network.On the basis of these indexes,several structure indexes of all layers of aviation network were calculated to show the structure features of aviation network,such as ratio of passenger volume within the region with across the region,share rate of passenger volume among layers,ratio of average number of airline for each airport,ratio of average passenger volume for each airline and ratio of airline rate.According to the statistical data,similar structure of share rate of passenger volume among layers and average passenger volume for each airline in their regional aviation network was found after calculating.But on the side of ratio of passenger volume within the region with across the region,ratio of average number of airlines for each airport and ratio of airline rate were different.展开更多
Varying-coefficient single-index model( VCSIM) avoids the so-called "curse of dimensionality " and is flexible enough to include several important statistical models. This paper considers statistical diagnos...Varying-coefficient single-index model( VCSIM) avoids the so-called "curse of dimensionality " and is flexible enough to include several important statistical models. This paper considers statistical diagnosis for VCSIM. First,the parametric estimation equation is established based on empirical likelihood. Then,some diagnosis statistics are defined. At last, an example is given to illustrate all the results.展开更多
In this article, we study the variable selection of partially linear single-index model(PLSIM). Based on the minimized average variance estimation, the variable selection of PLSIM is done by minimizing average varianc...In this article, we study the variable selection of partially linear single-index model(PLSIM). Based on the minimized average variance estimation, the variable selection of PLSIM is done by minimizing average variance with adaptive l1 penalty. Implementation algorithm is given. Under some regular conditions, we demonstrate the oracle properties of aLASSO procedure for PLSIM. Simulations are used to investigate the effectiveness of the proposed method for variable selection of PLSIM.展开更多
Grey heron (Ardea cimerca) is one kind of the great birds which are often seen in the northeast marsh area of P.R.China, and there are many grey herons to reproduce in Zhalong Nature Reserve from March to August annua...Grey heron (Ardea cimerca) is one kind of the great birds which are often seen in the northeast marsh area of P.R.China, and there are many grey herons to reproduce in Zhalong Nature Reserve from March to August annually. In this paper, through the inveingation of the grey herons nesting habitat and according to the water depth, vegetation type, cover density and plan heigh of the nesting place, the grey heron’s nesting habitat suitability index medes are established. The main model is s=(s1xs2xs3xs4)1/4,where s1 is the water depth suitability index, s2 is the vegetation type suitability index, s3 is the cover density index, sa is the plant height suitability index. These models provide a kind of reliable method for evaluating the habitat quality of the grey heron’s nesting.展开更多
Employing DEA model and Malmquist productivity index, this paper probes into the urban efficiencies of 24 typical resources-based cities in China and their changes from 2000 to 2008. The research finds that the overal...Employing DEA model and Malmquist productivity index, this paper probes into the urban efficiencies of 24 typical resources-based cities in China and their changes from 2000 to 2008. The research finds that the overall efficiencies of the resources-based cities are just at a general level, and only a few of them reach the optimal level. The scale efficiency is the major determining factor of the achievement of overall efficiency, the effect of which, nevertheless, is reducing. From the perspective of classification characteristics, the resources-based cities in northeastern region have been in the front rank in terms of overall efficiency, pure technical efficiency and scale efficiency. There is a certain positive correlation between urban population scale and urban efficiency. The analysis of urban efficiency changes shows that the changes in overall efficiency of resources-based cities from 2000 to 2008 had a weak improving tendency. Both the technical change index and productivity change index decreased, indicating that the urban efficiency did not improve during this period, and the tendency of technical recession and productivity decline was obvious. In terms of the classification of urban efficiency changes, the urban overall efficiency improved in each of the four regions from 2000 to 2008, among which western region witnessed the greatest increase. Cities with different resource types have improved their urban overall efficiencies except steel-based cities. The urban overall efficiency increased in resources-based cities of different scales, with greater improvement in small and medium-sized cities than in big cities.展开更多
In many applications a heterogeneous population consists of several subpopulations. When each subpopulation can be adequately modeled by a heteroscedastic single-index model, the whole population is characterized by a...In many applications a heterogeneous population consists of several subpopulations. When each subpopulation can be adequately modeled by a heteroscedastic single-index model, the whole population is characterized by a finite mixture of heteroscedastic single-index models. In this article, we propose an estimation algorithm for fitting this model, and discuss the implementation in detail. Simulation studies are used to demonstrate the performance of the algorithm, and a real example is used to illustrate the application of the model.展开更多
In this work,we construct and study a family of robust nonparametric estimators for a regression function based on kernel methods.The data are functional,independent and identically distributed,and are linked to a sin...In this work,we construct and study a family of robust nonparametric estimators for a regression function based on kernel methods.The data are functional,independent and identically distributed,and are linked to a single-index model.Under general conditions,we establish the pointwise and uniform almost complete convergence,as well as the asymptotic normality of the estimator.We explicitly derive the asymptotic variance and,as a result,provide confidence bands for the theoretical parameter.A simulation study is conducted to illustrate the proposed methodology.展开更多
Tests for nonparametric parts on partially linear single index models are considered in this paper. Based on the estimates obtained by the local linear method, the generalized likelihood ratio tests for the models are...Tests for nonparametric parts on partially linear single index models are considered in this paper. Based on the estimates obtained by the local linear method, the generalized likelihood ratio tests for the models are established. Under the null hypotheses the normalized tests follow asymptotically the χ2-distribution with the scale constants and the degrees of freedom being independent of the nuisance parameters, which is called the Wilks phenomenon. A simulated example is used to evaluate the performances of the testing procedures empirically.展开更多
This paper considers the problem of change point in single index models.In order to obtain asymptotically valid confidence intervals for the estimation of the change point,the convergence rate and asymptotic distribut...This paper considers the problem of change point in single index models.In order to obtain asymptotically valid confidence intervals for the estimation of the change point,the convergence rate and asymptotic distribution of the change point estimate is studied.Some simulation results are presented which show that the numerical performance of our estimator is satisfactory.展开更多
Single index models are widely used in medicine, econometrics and some other fields. In this paper, we consider the inference of a change point problem in single index models. Based on density-weighted average derivat...Single index models are widely used in medicine, econometrics and some other fields. In this paper, we consider the inference of a change point problem in single index models. Based on density-weighted average derivative estimation (ADE) method, we propose a statistic to test whether a change point exists or not. The null distribution of the test statistic is obtained using a permutation technique. The permuted statistic is rigorously shown to have the same distribution in the limiting sense under both null and alternative hypotheses. After the null hypothesis of no change point is rejected, an ADE-based estimate of the change point is proposed under assumption that the change point is unique. A simulation study confirms the theoretical results.展开更多
As an alternative to absolute error methods, such as the least square and least absolute deviation estimations, a product relative error estimation is proposed for a multiplicative single index regression model. Regre...As an alternative to absolute error methods, such as the least square and least absolute deviation estimations, a product relative error estimation is proposed for a multiplicative single index regression model. Regression coefficients in the model are estimated via a two-stage procedure and their statistical properties such as consistency and normality are studied. Numerical studies including simulation and a body fat example show that the proposed method performs well.展开更多
Marine big data are characterized by a large amount and complex structures,which bring great challenges to data management and retrieval.Based on the GeoSOT Grid Code and the composite index structure of the MongoDB d...Marine big data are characterized by a large amount and complex structures,which bring great challenges to data management and retrieval.Based on the GeoSOT Grid Code and the composite index structure of the MongoDB database,this paper proposes a spatio-temporal grid index model(STGI)for efficient optimized query of marine big data.A spatio-temporal secondary index is created on the spatial code and time code columns to build a composite index in the MongoDB database used for the storage of massive marine data.Multiple comparative experiments demonstrate that the retrieval efficiency adopting the STGI approach is increased by more than two to three times compared with other index models.Through theoretical analysis and experimental verification,the conclusion could be achieved that the STGI model is quite suitable for retrieving large-scale spatial data with low time frequency,such as marine big data.展开更多
Statistical inference on parametric part for the partially linear single-index model (PLSIM) is considered in this paper. A profile least-squares technique for estimating the parametric part is proposed and the asympt...Statistical inference on parametric part for the partially linear single-index model (PLSIM) is considered in this paper. A profile least-squares technique for estimating the parametric part is proposed and the asymptotic normality of the profile least-squares estimator is given. Based on the estimator, a generalized likelihood ratio (GLR) test is proposed to test whether parameters on linear part for the model is under a contain linear restricted condition. Under the null model, the proposed GLR statistic follows asymptotically the χ2-distribution with the scale constant and degree of freedom independent of the nuisance parameters, known as Wilks phenomenon. Both simulated and real data examples are used to illustrate our proposed methods.展开更多
In this paper,the unknown link function,the direction parameter,and the heteroscedastic variance in single index models are estimated by the random weight method under the random censorship,respectively.The central li...In this paper,the unknown link function,the direction parameter,and the heteroscedastic variance in single index models are estimated by the random weight method under the random censorship,respectively.The central limit theory and the convergence rate of the law of the iterated logarithm for the estimator of the direction parameter are derived,respectively.The optimal convergence rates for the estimators of the link function and the heteroscedastic variance are obtained.Simulation results support the theoretical results of the paper.展开更多
In this paper, a partially linear single-index model is investigated, and three empirical log-likelihood ratio statistics for the unknown parameters in the model are suggested. It is proved that the proposed statistic...In this paper, a partially linear single-index model is investigated, and three empirical log-likelihood ratio statistics for the unknown parameters in the model are suggested. It is proved that the proposed statistics are asymptotically standard chi-square under some suitable conditions, and hence can be used to construct the confidence regions of the parameters. Our methods can also deal with the confidence region construction for the index in the pure single-index model. A simulation study indicates that, in terms of coverage probabilities and average areas of the confidence regions, the proposed methods perform better than the least-squares method.展开更多
文摘Objective To study the current situation of China’s pharmacovigilance system,and to provide some suggestions for the improvement of related policies.Methods A policy modeling consistency(PMC)index model of pharmacovigilance policy was constructed to quantitatively assess the samples of policies combining text mining.Then,the PMC surface was established to obtain the visualization results of China’s pharmacovigilance policy samples,and their shortcomings were clearly analyzed by comparison.Results and Conclusion Forty-one percent of China’s pharmacovigilance policies were rated as excellent,54%as acceptable,and the overall evaluation was acceptable.But there is still some room for improvement.On the whole,there are problems of insufficient policy synergy,lack of policy incentives and constraints,and incomplete coverage of policy functions.It is recommended that China’s pharmacovigilance policy system should be optimized by strengthening policy coordination,increasing policy incentives and constraints,and guiding multi-subjects to participate in coordination.These findings and recommendations can provide operational ideas for the system of China’s pharmacovigilance policy.
基金supported by the National 863 project (2007AA092201 2007AA092202)+4 种基金National Development and Reform Commission Project (2060403)"Shu Guang" Project (08GG14) from Shanghai Municipal Education CommissionShanghai Leading Academic Discipline Project (Project S30702)supported by the National Distantwater Fisheries Engineering Research Center, and Scientific Observing and Experimental Station of Oceanic Fishery Resources, Ministry of Agriculture, ChinaYong Chen’s involvement in the project was supported by the Shanghai Dongfang Scholar Program
文摘Weighting values for different habitat variables used in multi-factor habitat suitability index (HSI) modeling reflect the relative influences of different variables on distribution of fish species. Using the winter-spring cohort of neon flying squid (Ommastrephes bartramii) in the Northwestern Pacific Ocean as an example, we evaluated the impact of different weighting schemes on the HSI models based on sea surface temperature, gradient of sea surface temperature and sea surface height. We compared differences in predicted fishing effort and HSI values resulting from different weighting. The weighting for different habitat variables could greatly influence HSI modeling and should be carefully done based on their relative importance in influencing the resource spatial distribution. Weighting in a multi-factor HSI model should be further studied and optimization methods should be developed to improve forecasting squid spatial distributions.
基金Supported by the National Natural Science Foundation of China (10571008)the Natural Science Foundation of Henan (092300410149)the Core Teacher Foundationof Henan (2006141)
文摘In this article, a partially linear single-index model /or longitudinal data is investigated. The generalized penalized spline least squares estimates of the unknown parameters are suggested. All parameters can be estimated simultaneously by the proposed method while the feature of longitudinal data is considered. The existence, strong consistency and asymptotic normality of the estimators are proved under suitable conditions. A simulation study is conducted to investigate the finite sample performance of the proposed method. Our approach can also be used to study the pure single-index model for longitudinal data.
基金Item Sponsored by National Key Technology Research and Development Program of China (2006BAE03A09)National Natural Science Foundation of China ( 61203219 )
文摘A semi-parametric single-index model based approach was proposed for prediction of mechanical properties of hot rolled strip. Based on industrial production data, a semi-parametric single-index model was developed by choo-sing the appropriate kernel function and window width to predict the yield strength, tensile strength and elongation. When data samples are limited, compared with regression method and neural network method, the prediction results show that the semi-parametric single-index model based method is more adaptive and the prediction performance is superior to those by both regression and neural network methods.
基金Supported by the National Natural science Foundation of China(10701035)ChenGuang Project of Shang-hai Education Development Foundation(2007CG33)a Special Fund for Young Teachers in Shanghai Universities(79001320)
文摘The single-index model with monotonic link function is investigated. Firstly, it is showed that the link function h（.） can be viewed by a graphic method. That is, the plot with the fitted response y on the horizontal axis and the observed y on the vertical axis can be used to visualize the link function. It is pointed out that this graphic approach is also applicable even when the link function is not monotonic. Note that many existing nonparametric smoothers can also be used to assess h（.）. Therefore, the I-spline approximation of the link function via maximizing the covariance function with a penalty function is investigated in the present work. The consistency of the criterion is constructed. A small simulation is carried out to evidence the efficiency of the approach proposed in the paper.
文摘In order to compare the aviation network of mid-south,northwest and southwest of China to reveal the structure similarity and difference for providing quantitative evidence to construct regional aviation network and improve its structure,hierarchical index model of regional aviation network was established through dividing the aviation network into layers to research its structure characters.Data matrixes were defined to record the basic state of regional aviation network.Index matrixes were constructed to describe the quantitative features of regional aviation network.On the basis of these indexes,several structure indexes of all layers of aviation network were calculated to show the structure features of aviation network,such as ratio of passenger volume within the region with across the region,share rate of passenger volume among layers,ratio of average number of airline for each airport,ratio of average passenger volume for each airline and ratio of airline rate.According to the statistical data,similar structure of share rate of passenger volume among layers and average passenger volume for each airline in their regional aviation network was found after calculating.But on the side of ratio of passenger volume within the region with across the region,ratio of average number of airlines for each airport and ratio of airline rate were different.
文摘Varying-coefficient single-index model( VCSIM) avoids the so-called "curse of dimensionality " and is flexible enough to include several important statistical models. This paper considers statistical diagnosis for VCSIM. First,the parametric estimation equation is established based on empirical likelihood. Then,some diagnosis statistics are defined. At last, an example is given to illustrate all the results.
文摘In this article, we study the variable selection of partially linear single-index model(PLSIM). Based on the minimized average variance estimation, the variable selection of PLSIM is done by minimizing average variance with adaptive l1 penalty. Implementation algorithm is given. Under some regular conditions, we demonstrate the oracle properties of aLASSO procedure for PLSIM. Simulations are used to investigate the effectiveness of the proposed method for variable selection of PLSIM.
文摘Grey heron (Ardea cimerca) is one kind of the great birds which are often seen in the northeast marsh area of P.R.China, and there are many grey herons to reproduce in Zhalong Nature Reserve from March to August annually. In this paper, through the inveingation of the grey herons nesting habitat and according to the water depth, vegetation type, cover density and plan heigh of the nesting place, the grey heron’s nesting habitat suitability index medes are established. The main model is s=(s1xs2xs3xs4)1/4,where s1 is the water depth suitability index, s2 is the vegetation type suitability index, s3 is the cover density index, sa is the plant height suitability index. These models provide a kind of reliable method for evaluating the habitat quality of the grey heron’s nesting.
基金National Natural Science Foundation of China, No.40701044 National Key Technology R＆D Program, No.2008BAH31B01
文摘Employing DEA model and Malmquist productivity index, this paper probes into the urban efficiencies of 24 typical resources-based cities in China and their changes from 2000 to 2008. The research finds that the overall efficiencies of the resources-based cities are just at a general level, and only a few of them reach the optimal level. The scale efficiency is the major determining factor of the achievement of overall efficiency, the effect of which, nevertheless, is reducing. From the perspective of classification characteristics, the resources-based cities in northeastern region have been in the front rank in terms of overall efficiency, pure technical efficiency and scale efficiency. There is a certain positive correlation between urban population scale and urban efficiency. The analysis of urban efficiency changes shows that the changes in overall efficiency of resources-based cities from 2000 to 2008 had a weak improving tendency. Both the technical change index and productivity change index decreased, indicating that the urban efficiency did not improve during this period, and the tendency of technical recession and productivity decline was obvious. In terms of the classification of urban efficiency changes, the urban overall efficiency improved in each of the four regions from 2000 to 2008, among which western region witnessed the greatest increase. Cities with different resource types have improved their urban overall efficiencies except steel-based cities. The urban overall efficiency increased in resources-based cities of different scales, with greater improvement in small and medium-sized cities than in big cities.
文摘In many applications a heterogeneous population consists of several subpopulations. When each subpopulation can be adequately modeled by a heteroscedastic single-index model, the whole population is characterized by a finite mixture of heteroscedastic single-index models. In this article, we propose an estimation algorithm for fitting this model, and discuss the implementation in detail. Simulation studies are used to demonstrate the performance of the algorithm, and a real example is used to illustrate the application of the model.
基金supported by PRFU of Ministry of Higher Education and Scientific Research Algeria(MESRS),University of Sciences and Technology Oran Mohamed Boudiaf(USTO-MB),Code:C00L03UN310220230005.
文摘In this work,we construct and study a family of robust nonparametric estimators for a regression function based on kernel methods.The data are functional,independent and identically distributed,and are linked to a single-index model.Under general conditions,we establish the pointwise and uniform almost complete convergence,as well as the asymptotic normality of the estimator.We explicitly derive the asymptotic variance and,as a result,provide confidence bands for the theoretical parameter.A simulation study is conducted to illustrate the proposed methodology.
文摘Tests for nonparametric parts on partially linear single index models are considered in this paper. Based on the estimates obtained by the local linear method, the generalized likelihood ratio tests for the models are established. Under the null hypotheses the normalized tests follow asymptotically the χ2-distribution with the scale constants and the degrees of freedom being independent of the nuisance parameters, which is called the Wilks phenomenon. A simulated example is used to evaluate the performances of the testing procedures empirically.
基金supported by National Natural Science Foundation for Young Scientists of China(Grant Nos.11101397,11201108)the Humanities and Social Sciences Project from Ministry of Education of China(Grant No.12YJC910007)+1 种基金Anhui Provincial Natural Science Foundation(Grant No.1208085QA12)the National Statistical Research Plan Project(Grant No.2012LZ009)
文摘This paper considers the problem of change point in single index models.In order to obtain asymptotically valid confidence intervals for the estimation of the change point,the convergence rate and asymptotic distribution of the change point estimate is studied.Some simulation results are presented which show that the numerical performance of our estimator is satisfactory.
基金the National Natural Science Foundation of China (Grant Nos. 10471136, 10671189)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX3-SYW-S02)
文摘Single index models are widely used in medicine, econometrics and some other fields. In this paper, we consider the inference of a change point problem in single index models. Based on density-weighted average derivative estimation (ADE) method, we propose a statistic to test whether a change point exists or not. The null distribution of the test statistic is obtained using a permutation technique. The permuted statistic is rigorously shown to have the same distribution in the limiting sense under both null and alternative hypotheses. After the null hypothesis of no change point is rejected, an ADE-based estimate of the change point is proposed under assumption that the change point is unique. A simulation study confirms the theoretical results.
基金supported by the National Natural Science Foundation of China under Grant Nos.11231010 and 11471302
文摘As an alternative to absolute error methods, such as the least square and least absolute deviation estimations, a product relative error estimation is proposed for a multiplicative single index regression model. Regression coefficients in the model are estimated via a two-stage procedure and their statistical properties such as consistency and normality are studied. Numerical studies including simulation and a body fat example show that the proposed method performs well.
基金This research was funded by the National Key Research and Development Plan(2018YFB0505300)the Guangxi Science and Technology Major Project(AA18118025)+1 种基金the Opening Foundation of Key Laboratory of Environment Change and Resources Use in Beibu Gulf,Ministry of Education(Nanning Normal University)Guangxi Key Laboratory of Earth Surface Processes and Intelligent Simulation(Nanning Normal University)(No.NNNU-KLOP-K1905).
文摘Marine big data are characterized by a large amount and complex structures,which bring great challenges to data management and retrieval.Based on the GeoSOT Grid Code and the composite index structure of the MongoDB database,this paper proposes a spatio-temporal grid index model(STGI)for efficient optimized query of marine big data.A spatio-temporal secondary index is created on the spatial code and time code columns to build a composite index in the MongoDB database used for the storage of massive marine data.Multiple comparative experiments demonstrate that the retrieval efficiency adopting the STGI approach is increased by more than two to three times compared with other index models.Through theoretical analysis and experimental verification,the conclusion could be achieved that the STGI model is quite suitable for retrieving large-scale spatial data with low time frequency,such as marine big data.
基金supported by National Natural Science Foundation of China (Grant No. 10871072)Natural Science Foundation of Shanxi Province of China (Grant No. 2007011014)PhD Program Scholarship Fund of ECNU 2009
文摘Statistical inference on parametric part for the partially linear single-index model (PLSIM) is considered in this paper. A profile least-squares technique for estimating the parametric part is proposed and the asymptotic normality of the profile least-squares estimator is given. Based on the estimator, a generalized likelihood ratio (GLR) test is proposed to test whether parameters on linear part for the model is under a contain linear restricted condition. Under the null model, the proposed GLR statistic follows asymptotically the χ2-distribution with the scale constant and degree of freedom independent of the nuisance parameters, known as Wilks phenomenon. Both simulated and real data examples are used to illustrate our proposed methods.
基金supported by National Natural Science Foundation of China(Grant Nos.10731010,10971012 and 11071015)
文摘In this paper,the unknown link function,the direction parameter,and the heteroscedastic variance in single index models are estimated by the random weight method under the random censorship,respectively.The central limit theory and the convergence rate of the law of the iterated logarithm for the estimator of the direction parameter are derived,respectively.The optimal convergence rates for the estimators of the link function and the heteroscedastic variance are obtained.Simulation results support the theoretical results of the paper.
基金supported by the Natural Science Foundation of Beijing City(Grant No.1042002)Technology Development Plan Project of Beijing Education Committee(Grant No.KM2005 10005009)+1 种基金the Special Grants of Beijing for Talents(Grant No.20041D0501515)supported by a grant from the Research Grants Council of Hong Kong,Hong Kong(Grant No.HKU7060/04P).
文摘In this paper, a partially linear single-index model is investigated, and three empirical log-likelihood ratio statistics for the unknown parameters in the model are suggested. It is proved that the proposed statistics are asymptotically standard chi-square under some suitable conditions, and hence can be used to construct the confidence regions of the parameters. Our methods can also deal with the confidence region construction for the index in the pure single-index model. A simulation study indicates that, in terms of coverage probabilities and average areas of the confidence regions, the proposed methods perform better than the least-squares method.
