农业科技成果转化为现实生产力的对策

根据目前影响我国农业技术成果迅速转化为现实生产力的因素,提出了加速农业技术成果转化的对策。     

A note on the joint distribution of correlated quadratic forms

In the present paper, the authors obtained exact and asymptotic expressions for the joint distribution of correlated quadratic forms when the underlying distribution is a multivariate normal.     

Edgeworth expansion and the bootstrap for stratified sampling without replacement from a finite population

An Edgeworth expansion for a linear combination of stratum means in stratified sampling without replacement from a finite population is derived. The expansion is applied to a bootstrap proposed for this context to show that the bootstrap captures the second-order term of the expansion.     

用算子展开法求解 Fredholm 积分方程

提供了另一种求解积分方程的方法。利用 Hilbert 空间来研究 Fredholm 积分算子,并证明了可利用一组标准正交基将 Fredholn 积分算子展开,从而使积分方程得到简化。应用这一方法给出了一般第二类 Fredholm 积分方程的严格解析解。文中还对具体积分方程进行了求解并与严格解和其它方法所得的解进行了比较,结果吻合得很好。     

认知隐喻在英语词汇习得教学中的运用

隐喻从属于认知范畴,与人类的语言、思维方式以及文化系统有着多方面、深层次的联系。本文从英语词汇教学中基本词汇的感知、词义拓展以及新词学习等方面,详细介绍了英语教学过程中认知隐喻的应用情况,试图为广大一线工作者开展英语词汇习得教学提供有益的文献参考。     

中国蔬菜出口增长的二元边际分析

基于2004—2011年中国蔬菜产品HS-6位出口数据,运用二元边际分解方法对中国蔬菜出口增长进行实证分析。研究结果显示,中国蔬菜出口增长主要来自于扩展边际的贡献,但集约边际在对主要贸易伙伴的出口中也发挥着重要作用。对集约边际进一步分解后发现,中国蔬菜出口增长主要来自于数量扩张,价格边际的贡献相对较小。蔬菜出口企业应在保持蔬菜品种多样化的同时尽量开发技术含量高、附加值较高的蔬菜新产品,以实现中国蔬菜出口增长模式的转变。     

我国大都市膨胀及其解决的路径选择

我国大都市膨胀现在越来越严重,具体表现在人口的膨胀、面积的膨胀以及公共交通的膨胀。大都市膨胀必然带来一系列负面影响,其中表现最明显的是配套制度难以跟上、公共服务提供不到位、环境污染严重三个方面。治理大都市膨胀可以从合理规划城市布局、完善公共服务提供机制、完善政府绩效考核机制三个方面来努力。     

Asymptotic Properties and Variance Estimators of the M-quantile Regression Coefficients Estimators

M-quantile regression is defined as a “quantile-like” generalization of robust regression based on influence functions. This article outlines asymptotic properties for the M-quantile regression coefficients estimators in the case of i.i.d. data with stochastic regressors, paying attention to adjustments due to the first-step scale estimation. A variance estimator of the M-quantile regression coefficients based on the sandwich approach is proposed. Empirical results show that this estimator appears to perform well under different simulated scenarios. The sandwich estimator is applied in the small area estimation context for the estimation of the mean squared error of an estimator for the small area means. The results obtained improve previous findings, especially in the case of heteroskedastic data.     

The Cornish-Fisher expansion for a class of statistics in first order autoregression

ABSTRACT

This article is concerned with the derivation and study of the Cornish-Fisher expansion for a wide class of estimators of the parameter in the first order autoregressive process. Second and third order Cornish-Fisher approximations to the quantile of the distribution of the corresponding asymptotically normal standardized statistic are stated explicitly and their accuracy is examined, both theoretically and numerically, by comparing them with the exact value of the quantile obtained by Monte Carlo simulation.