国际航运发展综合试验区先行先试政策

从分析国际航运发展综合试验区先行先试的内涵机制出发,研究其发展战略定位;从政府航运监管政策、航运税制改革以及航运高端服务培育等几个方面研究其先行先试的政策体系,并结合国际经验,具体分析了相关航运政策.     

Joint modified block replacement and production/inventory control policy for a failure-prone manufacturing cell

This paper considers a joint preventive maintenance (PM) and production/inventory control policy of an unreliable single machine, mono-product manufacturing cell with stochastic non-negligible corrective and preventive delays. The production/inventory control policy, which is based on the hedging point policy (HPP), consists in building and maintaining a safety stock of finished products in order to respond to demand and to avoid shortages during maintenance actions. Without considering the impact of preventive and corrective actions on the overall performance of the production system, most authors working in the reliability and maintainability domains confirm that the age-based preventive maintenance policy (ARP) outperforms the classical block-replacement policy (BRP). In order to reduce wastage incurred by the classical BRP, we consider a modified block replacement policy (MBRP), which consists in canceling a preventive maintenance action if the time elapsed since the last maintenance action exceeds a specified time threshold. The main objective of this paper is to determine the joint optimal policy that minimizes the overall cost, which is composed of corrective and preventive maintenance costs as well as inventory holding and backlog costs. A simulation model mimicking the dynamic and stochastic behavior of the manufacturing cell, based on more realistic considerations of the real behavior of industrial manufacturing cells, is proposed. Based on simulation results, the joint optimal MBRP/HPP parameters are obtained through a numerical approach that combines design of experiment, analysis of variance and response surface methodologies. The joint optimal MBRP/HPP policy is compared to classical joint ARP/HPP and BRP/HPP optimal policies, and the results show that the proposed MBRP/HPP outperforms the latter. Sensitivity analyses are also carried out in order to confirm the superiority of the proposed MBRP/HPP, and it is observed that for practitioners, the proposed joint MBRP/HPP offers not only cost savings, but is also easy to manage, as compared to the ARP/HPP policy.     

A new quantitative method for assessing sleepiness: The alpha attenuation test

Abstract

Sleepiness interferes with the ability of night-workers and shiftworkers to safely and effectively perform their jobs, and has been increasingly recognized as a major cause of industrial and transportation accidents. Current methods for the assessment of physiological sleepiness levels, such as the Multiple Sleep Latency Test (MSLT) have several limitations and are particularly impractical in field or occupational studies. In this study, the effectiveness of the Alpha Attenuation Test (AAT) for the quantification of sleepiness has been evaluated and compared to the MSLT during a 40-h sleep deprivation protocol. The AAT, a 12-min eye closed/open protocol, is a quantitative method based on the fact that EEG alpha (8-12 Hz) activity tends to increase with eyes open as individuals get sleepier, while it decreases with eyes closed. In this validation study, the AAT proved to be a sensitive measure of sleepiness induced by sleep deprivation, and it also correlated well with the MSLT. Relative to the MSLT, the AAT has the advantages of being objective, minimally intrusive, and more practical especially in industrial or field studies.     

高校英语专业口语教学主要问题研究

口语是英语专业基础课程之一,与听、读、写、译具有同等重要的地位。笔者结合多年英语专业口语教学实际,从教材适用性、教师口语水平、学生态度和水平测试四个方面分析了高校英语专业口语教学中存在的主要问题,说明了英语专业学生口语能力难以快速提高的症结所在,目的是引导教师和学生加强对口语课教学的反思和研究。     

Estimation of covariance matrix via the sparse Cholesky factor with lasso

In this paper, we discuss a parsimonious approach to estimation of high-dimensional covariance matrices via the modified Cholesky decomposition with lasso. Two different methods are proposed. They are the equi-angular and equi-sparse methods. We use simulation to compare the performance of the proposed methods with others available in the literature, including the sample covariance matrix, the banding method, and the L₁-penalized normal loglikelihood method. We then apply the proposed methods to a portfolio selection problem using 80 series of daily stock returns. To facilitate the use of lasso in high-dimensional time series analysis, we develop the dynamic weighted lasso (DWL) algorithm that extends the LARS-lasso algorithm. In particular, the proposed algorithm can efficiently update the lasso solution as new data become available. It can also add or remove explanatory variables. The entire solution path of the L₁-penalized normal loglikelihood method is also constructed.     

欧盟转基因食品立法规制及其对我国的借鉴意义

转基因生物技术自20世纪80年代问世以来发展迅速,国际社会在转基因农产品和食品安全的论争一直存在着以美国为代表的激进派和以欧盟为代表的保守派两大集团之间的分歧。欧盟是目前世界上对转基因食品的管理最为严格的国家集团,自20世纪90年代以来欧盟的转基因食品立法经过10多年的发展完善,逐步形成一个比较完备的法律体系。作者从美欧在转基因食品不同态度着手,系统阐述和探讨欧盟及国内的转基因食品立法及其最新发展并进行深入比较和分析,在参考和借鉴欧盟的成熟经验的基础上,结合我国现有的转基因食品立法和执法中存在的问题,提出相应的立法完善建议和应对措施。     

A test for the parametric form of the variance function in a partial linear regression model

We consider the problem of testing for a parametric form of the variance function in a partial linear regression model. A new test is derived, which can detect local alternatives converging to the null hypothesis at a rate n^-1/2$n^{-1/2}$ and is based on a stochastic process of the integrated variance function. We establish weak convergence to a Gaussian process under the null hypothesis, fixed and local alternatives. In the special case of testing for homoscedasticity the limiting process is a scaled Brownian bridge. We also compare the finite sample properties with a test based on an L²$L^2$-distance, which was recently proposed by You and Chen [2005. Testing heteroscedasticity in partially linear regression models. Statist. Probab. Lett. 73, 61–70].     

基于VAR模型的四川经济增长与投资消费关系实证研究

选取1990-2010年四川省经济数据,运用格兰杰因果检验、VAR模型和脉冲响应分析等方法对四川省经济增长与投资消费之间的关系进行了实证研究,结果表明：不论时间长短,投资水平对经济增长和消费水平的影响相对显著,而经济增长和消费水平在短期内对其他两项的影响不显著。     

我国转基因水稻产业化的现实困境及其出路

在当前的境遇下,我国转基因水稻的产业化主要面临风险—收益评估、利益冲突、知识产权和各方反对的现实困境。为了解决这些困境,必须建立我国转基因水稻产业化的综合效用评估体系和利益协调机制,加强研发我国具有完全自主知识产权的转基因水稻品系,扩大公众和社会参与转基因水稻的产业化决策,这样不仅有利于建立我国转基因水稻产业化的科学和民主的决策机制,也有利于其有效决策和规范管理,使其为人类带来更多的福祉。     

论大学英语词汇教学

英语语言学家威尔金斯对词汇的定义和最新颁布的《大学英语课程教学要求(》试行)对大学英语词汇教学的要求,都阐释了词汇在大学英语教学中的重要性。文章介绍了现阶段大学英语教学的情况,并通过调查分析,发现以大学英语四、六级考试为目的的大学英语词汇教学的弊病,提出科学的词汇教学方法,并对词汇教学与大学英语教学之间的关系进行了阐释。