中国大豆生产效率分析

通过建立中国省别大豆生产的随机前沿生产函数模型 ,分析近年来中国各大豆主产省大豆生产的技术效率及其影响因素 ,结果表明 ,中国大豆生产存在着明显的技术低效 ,但是这种低效近年来呈现出改进的趋势 ,这可能得益于农民负担的减轻、农产品市场化程度的加深以及农村劳动力文化程度的提高。     

Minimax Rates for Estimating the Variance and its Derivatives in Non–Parametric Regression

In this paper the van Trees inequality is applied to obtain lower bounds for the quadratic risk of estimators for the variance function and its derivatives in non–parametric regression models. This approach yields a much simpler proof compared to previously applied methods for minimax rates. Furthermore, the informative properties of the van Trees inequality reveal why the optimal rates for estimating the variance are not affected by the smoothness of the signal g . A Fourier series estimator is constructed which achieves the optimal rates. Finally, a second–order correction is derived which suggests that the initial estimator of g must be undersmoothed for the estimation of the variance.     

Product-limit survival functions with correlated survival times

A simple variance estimator for product-limit survival functions is demonstrated for survival times with nested errors. Such data arise whenever survival times are observed within clusters of related observations. Greenwood's formula, which assumes independent observations, is not appropriate in this situation. A robust variance estimator is developed using Taylor series linearized values and the between-cluster variance estimator commonly used in multi-stage sample surveys. A simulation study shows that the between-cluster variance estimator is approximately unbiased and yields confidence intervals that maintain the nominal level for several patterns of correlated survival times. The simulation study also shows that Greenwood's formula underestimates the variance when the survival times are positively correlated within a cluster and yields confidence intervals that are too narrow. Extension to life table methods is also discussed.     

Testing Covariance Stationarity

In this paper, we show that the widely used stationarity tests such as the Kwiatkowski Phillips, Schmidt, and Shin (KPSS) test have power close to size in the presence of time-varying unconditional variance. We propose a new test as a complement of the existing tests. Monte Carlo experiments show that the proposed test possesses the following characteristics: (i) in the presence of unit root or a structural change in the mean, the proposed test is as powerful as the KPSS and other tests; (ii) in the presence of a changing variance, the traditional tests perform badly whereas the proposed test has high power comparing to the existing tests; (iii) the proposed test has the same size as traditional stationarity tests under the null hypothesis of stationarity. An application to daily observations of return on U.S. Dollar/Euro exchange rate reveals the existence of instability in the unconditional variance when the entire sample is considered, but stability is found in subsamples.     

不放回样本追加策略下域的估计

 本文研究了不放回追加策略，包括基本设计和域追加设计都为简单随机抽样、分层随机抽样情形下不放回样本追加时域的估计的问题。根据不同的抽样设计给出单元的一阶及二阶包含概率的具体计算公式，并构造总体总量和域总量的Horvitz—Thompson型估计，然后基于简单随机抽样的不放回追加抽样方案，给出总体单元的前两阶包含概率。及该方案在分层抽样下的推广，在有辅助信息可用时构造域总量的分层联合比估计，并给出其方差和方差估计公式，同时我们给出了模拟结果，从模拟结果可以看出，给出的方差估计是估计量方差的近似无偏估计。     

ON NON-NEGATIVE UNBIASED ESTIMATION OF QUADRATIC FORMS IN FINITE POPULATION SAMPLING

The paper investigates non-negative quadratic unbiased (NnQU) estimators of positive semi-definite quadratic forms, for use during the survey sampling of finite population values. It examines several different NnQU estimators of the variance of estimators of population total, under various sampling designs. It identifies an optimal quadratic unbiased estimator of the variance of the Horvitz-Thompson estimator of population total.     

Empirical investigation about statistical properties of abundance estimates based on line-intercept and network sampling of tracks

Line-intercept sampling (Becker, 1991) and network sampling (Becker et al., 1998) seem to be the most appropriate procedures for estimating animal abundance in a study area on the basis of tracks. The purpose of this paper is to investigate the statistical properties of these alternative procedures by constructing confidence intervals for abundance and comparing the interval performances in terms of width and coverage.     

边疆民族地区旅游国际化与产业创新路径——兼议桥头堡建设背景下西双版纳旅游产业发展战略

旅游业是边疆民族地区对外开放中的比较优势产业,对外开放持续深入为边疆民族地区旅游业转型升级提供了重要机遇。国际化战略是边疆民族地区旅游转型升级的重要路径,产业创新是旅游业国际化的重要保证。其中。旅游国际化的战略重点是出境旅游手续便利化、入境旅游产品建设、第三国客源通道建设、国际客源市场开拓、跨境旅游新通道营销等,旅游产业创新的核心是培养创新人才、塑造学习型组织、培育创新型企业。     

中国政府机构改革与“有效政府”——基于善治视角下的理性思考

中国政府机构改革已经进入一个新的历史时期。根据以往的历史经验教训,政府机构改革应以加强政府的有效性为目标,将政府机构改革与＂有效政府＂结合起来。这需要切实转变政府治理理念,以＂善治＂理论为指导,加强政府的＂善政＂能力并大力培养和推动以＂第三部门＂和公民参与为内容的公民社会发展。     

论当前我国边疆治理中的民族认同与国家认同整合

我国是一个典型的多民族国家,这种国家的多民族在边疆表现得尤为突出,使得边疆地区的民族认同与国家认同也因此变得十分复杂。伴随着当前我国边疆地区现代化进程的加剧,边疆民族认同与国家认同的矛盾与冲突在一定程度上凸显出来,因此两者之间的整合也变得越来越迫切。在现实的认同整合过程中,必须调整我国当前的民族政策取向、转变边疆治理的思路、切实保障少数民族的正当权益,并通过国族建设实现边疆民族认同与国家认同的和谐共存。