To be or not to be valid in testing the significance of the slope in simple quantitative linear models with autocorrelated errors

In this article, the validity of procedures for testing the significance of the slope in quantitative linear models with one explanatory variable and first-order autoregressive [AR(1)] errors is analyzed in a Monte Carlo study conducted in the time domain. Two cases are considered for the regressor: fixed and trended versus random and AR(1). In addition to the classical t -test using the Ordinary Least Squares (OLS) estimator of the slope and its standard error, we consider seven t -tests with n-2\,\hbox{df} built on the Generalized Least Squares (GLS) estimator or an estimated GLS estimator, three variants of the classical t -test with different variances of the OLS estimator, two asymptotic tests built on the Maximum Likelihood (ML) estimator, the F -test for fixed effects based on the Restricted Maximum Likelihood (REML) estimator in the mixed-model approach, two t -tests with n - 2 df based on first differences (FD) and first-difference ratios (FDR), and four modified t -tests using various corrections of the number of degrees of freedom. The FDR t -test, the REML F -test and the modified t -test using Dutilleul's effective sample size are the most valid among the testing procedures that do not assume the complete knowledge of the covariance matrix of the errors. However, modified t -tests are not applicable and the FDR t -test suffers from a lack of power when the regressor is fixed and trended ( i.e. , FDR is the same as FD in this case when observations are equally spaced), whereas the REML algorithm fails to converge at small sample sizes. The classical t -test is valid when the regressor is fixed and trended and autocorrelation among errors is predominantly negative, and when the regressor is random and AR(1), like the errors, and autocorrelation is moderately negative or positive. We discuss the results graphically, in terms of the circularity condition defined in repeated measures ANOVA and of the effective sample size used in correlation analysis with autocorrelated sample data. An example with environmental data is presented.     

Global employment and decent jobs, 2010–2030: The forces of demography and automation

Globally, an estimated 734 million jobs will be required between 2010 and 2030 to accommodate recent and ongoing demographic shifts, account for plausible changes in labour force participation rates, and achieve target unemployment rates of at or below 4 per cent for adults and at or below 8 per cent for youth. The facts that most new jobs will be required in countries where “decent” jobs are less prevalent and workers in many occupations are increasingly subject to risks of automation further compound the challenge of job creation, which is already quite sizable in historical perspective. Failure to create the jobs that are needed through 2030 would put currently operative social security systems under pressure and undermine efforts to guarantee the national social protection floors enshrined in the Sustainable Development Goals (SDGs).     

论《镜花缘》中科幻小说之特色

清代长篇小说《镜花缘》的内容丰富多彩,其类属和特点也比较多样。鲁迅说它属博物小说,才艺小说;胡适称它为妇女问题小说,女权小说,等等。此外,小说还描写了一些精彩的科幻故事,包括科幻植物如人吃一颗饱一年的巨米,人吃了能蹿高的蹑空草,长效久饱干粮救荒豆末;包括科幻器物如人穿上能长时间潜水的皮衣皮裤,能连续高速开火的火绳枪—连珠枪,能载人载货飞行的飞车;包括科幻技术,如人能近地但不触地地行进,换心补肺的医术。文章从科学、文学、历史几方面对上述科幻故事进行了考察、解读、诠释、分析、评论,研究总结出：《镜花缘》也具科幻小说之属性和特点,是我国第一部也进行了科学幻想文学创作的长篇小说。     

Self-exciting threshold models for time series of counts with a finite range

In this article, an integer-valued self-exciting threshold model with a finite range based on the binomial INARCH(1) model is proposed. Important stochastic properties are derived, and approaches for parameter estimation are discussed. A real-data example about the regional spread of public drunkenness in Pittsburgh demonstrates the applicability of the new model in comparison to existing models. Feasible modifications of the model are presented, which are designed to handle special features such as zero-inflation.     

生产者货币计价决定因素的实证研究

利用12个发达国家和发展中国家的非平衡面板样本数据,对微观、宏观和其他因素对生产者货币计价(PCP)的影响进行实证研究,指出经济规模、市场份额、金融市场的发达程度、币值的对内稳定性和产品差异化程度是最主要的影响因素,而出口商的谈判能力、币值的对外稳定性等因素也对PCP的选择有一定影响。根据实证检验结果,对人民币作为贸易计价货币的条件进行评估,发现其优势在于我国的经济规模、出口商的市场份额及其谈判能力以及人民币汇率的相对稳定性; 劣势在于相对落后的金融市场、不可预期性较大的通货膨胀水平以及产品的差异化程度。     

论《埤雅》声训推源

《埤雅》以声符释义贯穿全书，偶有穿凿附会之处。书中广泛运用声训之法，力求阐释事物命名之意，对声训推源进行了有益的探索，具有一定的科学性与进步性。     

建安七体文论析

七体自枚乘《七发》首创之后,作者继踵。建安七体文皆是虚构一主一客问答的招隐型作品,但它们并不是简单的模拟之作,在思想倾向上,虽是以儒家思想为主,却也体现出当时对刑名之学的重视;在情感倾向上,作者的情感已由讽谏转向颂美,名为招隐,实为自招,并成为激励士人的劝仕之作;在艺术技巧上,注重语句的对仗工整,讲究音律的和谐,用典成分增多,体现出较强的骈化趋势。总之,建安七体文无论从内容还是形式,都受到了那个时代社会风气和政治背景的影响。     

Deriving Behavior Model Parameters from Survey Data: Self‐Protective Behavior Adoption During the 2009–2010 Influenza A(H1N1) Pandemic

In this paper, we demonstrate how public opinion surveys can be designed to collect information pertinent to computational behavior modeling, and we present the results of a public opinion and behavior survey conducted during the 2009–2010 H1N1 influenza pandemic. The results are used to parameterize the Health Belief Model of individual health‐protective decision making. Survey subjects were asked questions about their perceptions of the then‐circulating influenza and attitudes towards two personal protective behaviors: vaccination and avoidance of crowds. We empirically address two important issues in applying the Health Belief Model of behavior to computational infectious disease simulation: (1) the factors dynamically influencing the states of the Health Belief Model variables and (2) the appropriateness of the Health Belief Model in describing self‐protective behavior in the context of pandemic influenza.     

Comparison of computer programs for simple linear L 1 regression

A number of efficient computer codes are available for the simple linear L ₁ regression problem. However, a number of these codes can be made more efficient by utilizing the least squares solution. In fact, a couple of available computer programs already do so.

We report the results of a computational study comparing several openly available computer programs for solving the simple linear L ₁ regression problem with and without computing and utilizing a least squares solution.     

基于层次分析法的多媒体教学评价研究综述

从基于层次分析法的多媒体教学评价角度,对教学条件、教学课件、课堂教学效果及实验教学等领域的多媒体教学评价进行了综述研究,就目前这些研究方向存在的问题及其发展趋势进行了点评概括.