A fortran implementation of univariate fourier series density estimation

A set of Fortran-77 subroutines is described which compute a nonparametric density estimator expressed as a Fourier series. In addition, a subroutine is given for the estimation of a cumulative distribution. Performance measures are given based on samples from a Weibull distribution. Due to small size and modest space demands, these subroutines are easily implemented on most small computers.     

电极法测定海水中的氟离子

:本文探讨了用离子选择性电极 (ISE)测定海水中 F-含量的可能性 ,利用国产电极建立了直接测定海水中 F-的简单方法 ,精密度达± 2 %。     

信息共享环境的数据与技术模块研究

信息共享环境与国家安全和国际安全密切相关,近几年才受到国内外政府与学者的广泛关注和高度重视.数据模块与技术模块是构建信息共享环境的核心.数据模块探讨了功能标准、模块构架、数据描述的抽象模型、数据环境的抽象模型和数据共享的抽象模型等.技术模块探讨了模块架构、服务接入与输出模型、服务平台与基础设施模型、框架模型、以及服务界面与集成模型等.     

国际科学英语和中国科技英语学科地位研究

科技英语是第二次世界大战结束后,随着英语在科技领域内地位的不断提高而出现的,“文革”后传入我国。但大学生是学通用英语还是科技英语,在20世纪80年代的大学英语界引发了激烈的争论。由于决策者倾向前者并制定了基于通用英语的教学大纲和大学英语四、六级考试,科技英语教学就此停止了发展。三十年后,随着我国科学技术的迅速发展以及英语成为国际学术交流的通用语,一个严峻的事实出现了：一个大学生如无法阅读国际期刊就不可能了解本学科最新研究情况,就不能成为一个真正合格的大学生（更不要说一流大学生）。国际科学英语能力是指具有在这些国际期刊上汲取信息（阅读）和交流信息（写作）的外语能力。在新一轮世界一流大学和一流学科建设中,科技英语将成为整个外语教学,乃至整个专门用途英语中最具有实践价值和实践意义的学科,在此背景下,我们必须重新评估科技英语的地位。     

Variable kernel density estimation

This paper considers the problem of selecting optimal bandwidths for variable (sample‐point adaptive) kernel density estimation. A data‐driven variable bandwidth selector is proposed, based on the idea of approximating the log‐bandwidth function by a cubic spline. This cubic spline is optimized with respect to a cross‐validation criterion. The proposed method can be interpreted as a selector for either integrated squared error (ISE) or mean integrated squared error (MISE) optimal bandwidths. This leads to reflection upon some of the differences between ISE and MISE as error criteria for variable kernel estimation. Results from simulation studies indicate that the proposed method outperforms a fixed kernel estimator (in terms of ISE) when the target density has a combination of sharp modes and regions of smooth undulation. Moreover, some detailed data analyses suggest that the gains in ISE may understate the improvements in visual appeal obtained using the proposed variable kernel estimator. These numerical studies also show that the proposed estimator outperforms existing variable kernel density estimators implemented using piecewise constant bandwidth functions.     

Asymptotic normality of a weighted integrated squared error of kernel regression estimates with data-dependent bandwidth

Let (X, Y) be a bivariate random vector and let be the regression function of Y on X that has to be estimated from a sample of i.i.d. random vectors (X₁, Y₁),…,(X_n, Y_n) having the same distribution as (X, Y). In the present paper it is shown that the normalized integrated squared error of a kernel estimator with data-driven bandwidth is asymptotically normally distributed.