ELICITING A DIRECTED ACYCLIC GRAPH FOR A MULTIVARIATE TIME SERIES OF VEHICLE COUNTS IN A TRAFFIC NETWORK

The problem of modelling multivariate time series of vehicle counts in traffic networks is considered. It is proposed to use a model called the linear multiregression dynamic model (LMDM). The LMDM is a multivariate Bayesian dynamic model which uses any conditional independence and causal structure across the time series to break down the complex multivariate model into simpler univariate dynamic linear models. The conditional independence and causal structure in the time series can be represented by a directed acyclic graph (DAG). The DAG not only gives a useful pictorial representation of the multivariate structure, but it is also used to build the LMDM. Therefore, eliciting a DAG which gives a realistic representation of the series is a crucial part of the modelling process. A DAG is elicited for the multivariate time series of hourly vehicle counts at the junction of three major roads in the UK. A flow diagram is introduced to give a pictorial representation of the possible vehicle routes through the network. It is shown how this flow diagram, together with a map of the network, can suggest a DAG for the time series suitable for use with an LMDM.     

中国产业结构变动与就业水平的实证研究

文章运用时间序列和计量模型研究了中国产业结构与就业水平之间的发展关系.首先运用格兰杰因果检验分析了第一、二、三次产业的产值与其就业之间的因果影响关系,继而从产值与就业两个角度定量分析了第一、二、三次产业各自对总就业水平的贡献,得出结论:第一产业和第三产业是劳动力就业的决定因素,而第二产业不是就业的决定因素;从产值角度来看,第三产业对劳动力就业的贡献最大,从就业角度来看,第一产业的就业对总体就业水平的贡献最高,其次是第三产业,而第二产业的就业对总体就业水平的贡献最小.最后根据研究结论提出相应的建议措施.     

开发区类企业的企业化博弈演进分析

基于我国开发区发展瓶颈现象和一个动态博弈模型，指出开发区类企业所具有的特殊的企业形态．该类企业在开发区初创阶段，以完成政府的效用为其义务．政府在开发区发展的各个阶段，其效用函数是不同的．当政府的期望效用基本完成之后，就应当逐渐退出其行政控制．由于政府的政绩诉求和权威惯性，其行政控制的退出往往比较迟缓．通过开发区类企业与政府的利益博弈，开发区类企业逐步完成其纯企业化的过程．这种博弈引发的交易成本可能使得开发区类企业的纯企业化过程时间过长，从而导致整个过程的非效率性．     

我国房地产市场财富效应的实证分析

本文应用格兰杰因果关系检验和协整分析方法,对我国房地产市场的财富效应作了实证分析。实证结果表明,我国房地产市场不具有财富效应而仅具有替代效应。     

试析高职高专学校近年来女生人数大幅度增加的现象

近年来高职高专学校女生人数大幅度增加这是一个不争的事实,其原因有主客观方面的因素。在这种情况下,学校原有的设施、专业和课程都难以适应,必须做出较大的调整和改进。     

基于VB的计算机考试系统的设计与实现

介绍了网络环境下的基于Visual Basic计算机考试系统的基本组成和功能结构,同时,就题库的建立和管理、随机成卷系统和评分系统等研制的难点进行了分析,并针对其中的关键技术,提出相应的解决方法。     

提高"试卷分析"的科学性

考试具有评定学生成绩,检查教师教学效果的双重作用.结合教学实践,运用统计学原理,提出了进行试卷分析的有效方法,进而达到科学评价考试质量的目的.     

An affine‐invariant multivariate sign test for cluster correlated data

The author presents a multivariate location model for cluster correlated observations. He proposes an affine‐invariant multivariate sign statistic for testing the value of the location parameter. His statistic is an adaptation of that proposed by Randles (2000). The author shows, under very mild conditions, that his test statistic is asymptotically distributed as a chi‐squared random variable under the null hypothesis. In particular, the test can be used for skewed populations. In the context of a general multivariate normal model, the author obtains values of his test's Pitman asymptotic efficiency relative to another test based on the overall average. He shows that there is an improvement in the relative performance of the new test as soon as intra‐cluster correlation is present Even in the univariate case, the new test can be very competitive for Gaussian data. Furthermore, the statistic is easy to compute, even for large dimensional data. The author shows through simulations that his test performs well compared to the average‐based test. He illustrates its use with real data.     

A partial score test for difference among heterogeneous populations

In event time data analysis, comparisons between distributions are made by the logrank test. When the data appear to contain crossing hazards phenomena, nonparametric weighted logrank statistics are usually suggested to accommodate different-weighted functions to increase the power. However, the gain in power by imposing different weights has its limits since differences before and after the crossing point may balance each other out. In contrast to the weighted logrank tests, we propose a score-type statistic based on the semiparametric-, heteroscedastic-hazards regression model of Hsieh [2001. On heteroscedastic hazards regression models: theory and application. J. Roy. Statist. Soc. Ser. B 63, 63–79.], by which the nonproportionality is explicitly modeled. Our score test is based on estimating functions derived from partial likelihood under the heteroscedastic model considered herein. Simulation results show the benefit of modeling the heteroscedasticity and power of the proposed test to two classes of weighted logrank tests (including Fleming–Harrington's test and Moreau's locally most powerful test), a Renyi-type test, and the Breslow's test for acceleration. We also demonstrate the application of this test by analyzing actual data in clinical trials.     

情态动词否定之研究

Palmer认为在英语语法中 ,最难描写的莫过于情态助动词系统 (Palmer,1 979:preface)。情态动词之所以纷繁复杂、难以描写是因为它们在各种英语文体中使用频率极高 ,并且表达的意义与人的情感和意念有着密切关系。由于情态动词的意义的多样性和模糊性 ,其否定形式及范围也是复杂多变的。我们可以依据Palmer对三类情态动词(推测性、义务性、原动性 )和两种情态级别 (可能级、必定级 )的划分 ,对情态动词的否定范围及语义进行分类分级研究 ;同时 ,鉴于可能级和必定级情态动词否定之间的语义约同现象 ,对逻辑等式Not -possible =Necessary -not;Not -necessary=Possible -not在情态动词句式中的操作规律加以探讨 ,结果表明该等式为解释情态动词否定形式间的互补现象提供了逻辑依据