A local bicycle helmet ‘law’ in a Swedish municipality – the effects on helmet use

The municipality of Motala in Sweden introduced a local bicycle helmet ‘law’ on May 1, 1996. This is not a legally enacted ordinance, but instead a legislated recommendation backed up by information and education. Formally, the law applies to children (aged 6–12 years), although the intention is to increase helmet use by all cyclists. The objective of the present study was to quantitatively evaluate the impact of the Motala helmet law on observed use of helmets by children and adults. Bicycle helmet use was monitored in Motala (n = 2,458/year) and in control towns (n = 17,818/year) both before and after adoption of the helmet law (1995–1998). Chi-square tests showed that helmet wearing 1995–1998 increased in Motala among all bicyclists (from 6.1% to 10.5%) and adults biking on cycle paths (from 1.8% to 7.6%). Helmet use by school children aged 6–12 increased during the first 6 months after introduction of the law (from 65.0% to 75.7%) but then progressively decreased to the pre-law level. Considering children cycling on cycle paths and for recreation in housing areas, there was a tendency towards increased helmet use during the first post-law year, but this was followed by a reduction to a lower level in 1998 than in 1995. Logistic regression analysis taking into account data from the control towns indicated that the helmet law had a positive effect on children cycling to schools during the first 6 months, and a weak delayed but more long-term positive effect on adult cyclists on cycle paths. There were no positive effects on children in housing areas and on cycle paths. The Motala helmet law probably would have had greater and more lasting effects on helmet use by bicyclists, if certain problems had been avoided during the initiation phase. Moreover, although it did have a positive influence on both school children and adults, it is not legally binding, and hence no penalties can be imposed. Presumably, compulsory legislation would have a more substantial impact on helmet wearing than a non-mandatory helmet ‘law’ such as that introduced in Motala.     

基于 Granger 检验的能源消费与经济增长区域差异性研究

本文运用1993～2012年29省市的能源消费和经济增长数据,以能源消费弹性系数的变化规律为依据,将我国的能源———经济区划分为：经济发达区、平稳发展H区、平稳发展L区和飞速发展区四大发展区域。针对四大区域,利用Granger检验法对各区域能源消费与经济增长二者之间的关系进行了研究。研究结果表明,经济发达区的能源消费与经济增长不具有长期协整关系,平稳发展H区的能源消费与经济增长具有双向因果关系,平稳发展L区和飞速发展区能源消费与经济增长具有单向因果关系。最后针对以上结论提出了相关建议。     

Evolving United States stock market volatility: The role of conventional and unconventional monetary policies

Despite the econometric advances of the last 30 years, the effects of monetary policy stance during the boom and busts of the stock market are not clearly defined. In this paper, we use a structural heterogeneous vector autoregressive (SHVAR) model with identified structural breaks to analyse the impact of both conventional and unconventional monetary policies on U.S. stock market volatility. We find that contractionary monetary policy enhances stock market volatility, but the importance of monetary policy shocks in explaining volatility evolves across different regimes and is relative to supply shocks (and shocks to volatility itself). In comparison to business cycle fluctuations, monetary policy shocks explain a greater fraction of the variance of stock market volatility at shorter horizons, as in medium to longer horizons. Our basic findings of a positive impact of monetary policy on equity market volatility (being relatively stronger during calmer stock market periods) are also corroborated by analyses conducted at the daily frequency based on an augmented heterogeneous autoregressive model of realised volatility (HAR-RV) and a multivariate k-th order nonparametric causality-in-quantiles framework. Our results have important implications both for investors and policymakers.     

基于Plant Simulation的烟草柔性分拣系统仿真与优化

针对烟草物流配送中心场地限制和分拣效率低下等问题,根据柔性分拣系统的工作原理及流程,运用Plant Simulation仿真软件建立烟草柔性分拣系统模型,设计了条烟自动分拣的虚拟托盘算法。通过仿真分析得到限制其分拣效率的瓶颈工位,利用添加缓存区和增加码垛工位的优化方法对分拣系统进行初步优化,并且从Experiment Manager模块中的单因子多水平试验方法确定了最优缓存区容量。仿真结果表明该优化方法显著提高了分拣效率,使其达到8866.08条/h,是优化前的1.39倍,且缩短了配送时间,能够很好地满足烟草物流配送中心的分拣要求。     

基于Feed4JUnit架构的单元测试技术研究与应用

软件测试技术在软件质量控制过程中一直起着非常重要的作用。JUnit是被广泛应用的Java单元测试框架,主要测试基于java语言编写的程序代码,用于编写和运行可重复的测试。Feed4JUnit是开源的基于JUnit的扩展,通过使用Feed4JUnit提供的注释,用户可以很方便地把测试数据存放在文件或其他数据源。本文分析了应用Feed4JUnit进行单元测试的方法,并通过实际开发示例实现数据与代码分离的测试。     

浙江省区域物流与经济增长的实证研究

基于浙江省1990~2012年统计数据,运用ADL模型及格兰杰因果检验对浙江省区域物流与经济增长的相互关系进行了研究。结果表明:从长期来看,浙江省GDP、全社会货物周转量及港口货物吞吐量三者之间存在着单向的因果关系。港口货物吞吐量是全社会货物周转量增加的格兰杰原因,全社会货物周转量和港口货物吞吐量平均每增长1%,分别带动浙江省GDP增长0.8672%和0.9903%。     

土石坝砾质粘土的击实曲线研究

通过室内击实试验我们可以测定土的最大干密度和最优含水率,以此成为压实度检测的依据,以便控制好填筑土体的压实质量,更好地保障工程质量达到所规定的要求。不同土体,不同的操作方法,击实试验的结果是不同的,本文章结合苗尾水电站料场的土料的特性,通过对比颗粒含量与界限含水率的不同,分析击实曲线的变化规律。     

电梯限速器检验问题的思考

限速器是电梯发生超速和断绳时起保护作用的安全控制部件重要组成部分,必须保证动作灵敏、工作可靠,因此,电梯限速器的检验就显得尤为重要。本文结合电梯检规的检验内容与要求,详细介绍了在对限速器铭牌、电气安全装置、动作速度、位置安装和安全空间的检验中应注意的问题。     

基于主成分分析方法的上市公司财务危机预警研究

本文通过配比性原则和对在2010年被ST的上市公司t-2年财务数据进行主成分分析研究,建立模型并确定综合预警值F判定模型是否具有预警性。结果显示,基于主成分分析的方法能较好地作出上市公司财务状况是否将陷入财务危机的预警警示。     

钻机配油套加工工艺技术的研究

联动系列钻机中关键零件配油套的设计要求高、生产难度大、报废率高,因此,为提高产品质量与生产效率,增强产品的市场竞争力,需深入研究钻机配油套加工工艺技术。通过不断的试验探索,研究出最适合自身产品的合理工艺。