GMM Estimation with persistent panel data: an application to production functions

This paper considers the estimation of Cobb-Douglas production functions using panel data covering a large sample of companies observed for a small number of time periods. GMM estimatorshave been found to produce large finite-sample biases when using the standard first-differenced estimator. These biases can be dramatically reduced by exploiting reasonable stationarity restrictions on the initial conditions process. Using data for a panel of R&Dperforming US manufacturing companies we find that the additional instruments used in our extended GMM estimator yield much more reasonable parameter estimates.     

作为公共产品的城市管理--以无锡市为个案

城市管理是城市政府的主要职能,是城市政府为城市社会提供的最主要的公共产品之一。传统理念和体制下,城市管理公共产品供给模式效率十分低下,已不能适应城市发展的形势。在现代公共管理及公共产品供给理论框架内考察城市管理,不失为一种新的视角,是探索城市政府职能转变、城市管理体制创新的有效途径,有利于改善城市政府治理能力,整体推进城市社会的全面进步。     

Automating argument construction

Over the past five years the Artificial Intelligence Center at SRI has been developing a new technology to address the problem of automated information management within real- world contexts. The result of this work is a body of techniques for automated reasoning from evidence that we call evidential reasoning. The techniques are based upon the mathematics of belief functions developed by Dempster and Shafer and have been successfully applied to a variety of problems including computer vision, multisensor integration, and intelligence analysis.

We have developed both a formal basis and a framework for implementating automated reasoning systems based upon these techniques. Both the formal and practical approach can be divided into four parts: (1) specifying a set of distinct propositional spaces, (2) specifying the interrelationships among these spaces, (3) representing bodies of evidence as belief distributions, and (4) establishing paths of the bodies for evidence to move through these spaces by means of evidential operations, eventually converging on spaces where the target questions can be answered. These steps specify a means for arguing from multiple bodies of evidence toward a particular (probabilistic) conclusion. Argument construction is the process by which such evidential analyses are constructed and is the analogue of constructing proof trees in a logical context.

This technology features the ability to reason from uncertain, incomplete, and occasionally inaccurate information based upon seven evidential operations: fusion, discounting, translation, projection, summarization, interpretation, and gisting. These operation are theoretically sound but have intuitive appeal as well.

In implementing this formal approach, we have found that evidential arguments can be represented as graphs. To support the construction, modification, and interrogation of evidential arguments, we have developed Gister. Gister provides an interactive, menu-driven, graphical interface that allows these graphical structures to be easily manipulated.

Our goal is to provide effective automated aids to domain experts for argument construction. Gister represents our first attempt at such an aid.     

成都将军的设置及其在治理川西藏区中的作用

清乾隆年间对大小金川土司的用兵结束后,为了加强对康藏及川西藏族的统治,乾隆帝特设成都将军,统辖八旗和绿营,治理川边。成都将军在维护川西藏族地区的稳定、保持川藏大道的畅通、巩固西南边疆的安全等方面均起到了积极的作用。     

被动语态在外贸函电中的应用及其语用功能

本文贸函电为例,从语用学的角度分析,被动语态有很多独特的语用功能。     

A Bayesian sequential design with binary outcome

Several researchers have proposed solutions to control type I error rate in sequential designs. The use of Bayesian sequential design becomes more common; however, these designs are subject to inflation of the type I error rate. We propose a Bayesian sequential design for binary outcome using an alpha‐spending function to control the overall type I error rate. Algorithms are presented for calculating critical values and power for the proposed designs. We also propose a new stopping rule for futility. Sensitivity analysis is implemented for assessing the effects of varying the parameters of the prior distribution and maximum total sample size on critical values. Alpha‐spending functions are compared using power and actual sample size through simulations. Further simulations show that, when total sample size is fixed, the proposed design has greater power than the traditional Bayesian sequential design, which sets equal stopping bounds at all interim analyses. We also find that the proposed design with the new stopping for futility rule results in greater power and can stop earlier with a smaller actual sample size, compared with the traditional stopping rule for futility when all other conditions are held constant. Finally, we apply the proposed method to a real data set and compare the results with traditional designs.     

非言语交际与外语教学

非言语交际作为言语交际的重要组成部分,在外语教学中,起着不可忽视的作用。恰当地使用非言语交际行为,能够创建良好的师生关系,提高学生学习兴趣。本文分析了非言语交际行为的重要性及其在外语课堂教学中的表现形式和作用。     

我国新型农民合作社的形态、功能及其发展

按照性质不同,我国的农民合作社可划分为新型农民合作社和传统农民合作社两大类型.新型农民合作社的基本功能是农户间的团结协作和互利互惠,它有利于促进农业产业化经营;抵御农业经营风险;实现农民共同富裕;推进农村民主政治建设.从我国的情况看,在发达国家农业产业化经营的三种模式--综合型模式、合同型模式和合作社型模式中,合作社型模式更适合我国的农业产业化经营.由于当前在发展新型农民合作社中存在的,诸如合作的认识不够明确、合作的环境不够优良、合作的机制不够完善的问题,这需要通过教育普及国际公认的合作经济理论和实务知识;尽快出台<农村资金合作社法>,明确各类农民合作社的主管部门;建立、健全合作社"三会"制度及议事规则.     

Use of log−log survival function in modeling time-covariate interactions in Cox regression

Plotting of log−log survival functions against time for different categories or combinations of categories of covariates is perhaps the easiest and most commonly used graphical tool for checking proportional hazards (PH) assumption. One problem in the utilization of the technique is that the covariates need to be categorical or made categorical through appropriate grouping of the continuous covariates. Subjectivity in the decision making on the basis of eye-judgment of the plots and frequent inconclusiveness arising in situations where the number of categories and/or covariates gets larger are among other limitations of this technique. This paper proposes a non-graphical (numerical) test of the PH assumption that makes use of log−log survival function. The test enables checking proportionality for categorical as well as continuous covariates and overcomes the other limitations of the graphical method. Observed power and size of the test are compared to some other tests of its kind through simulation experiments. Simulations demonstrate that the proposed test is more powerful than some of the most sensitive tests in the literature in a wide range of survival situations. An example of the test is given using the widely used gastric cancer data.     

网络语言娱乐功能实现方式及其根源研究

在网络言语交际过程中,网络语言娱乐性的表现形式、特点及其制约机制等问题一直是学界关注的话题.为从语言功能视角阐释网络语言娱乐性的实现方式及其根源等问题,运用了比较分析和例证相结合的研究方法,通过比较分析说明网络语言的内涵及其存在形式的双重性特征,介绍了语言娱乐功能的内涵和陈望道先生的“辞趣”思想,通过网络语言在形趣、音趣和意趣方面的例证分析,对“辞趣”理论实质从语言娱乐功能实现角度重新进行了梳理,指出网络语言娱乐功能具体实现的语言结构形式途径,认为网络言语交际中娱乐性的根源来自于社会物质条件和主体内在需求的合力,因为使用了网络媒介,所以才表现出独具特色的网络言语交际形式.