Reconciling Alternative Theories for the Safety of Owner–Operators

Motor carrier safety is an important concern of shippers, carriers, policy makers, consignees, insurance providers, and the motoring public. One aspect of carrier safety that has garnered substantial attention is whether carriers making greater use of owner–operators are more or less safe vis‐à‐vis carriers making greater use of employee drivers. Currently, conflicting theoretical predictions exist regarding the direction of this relationship. In this article, we offer a reconciliation of the alternative theoretical predictions by developing a coherent theory that merges sociological rational choice theory and theory regarding motor carrier safety. We subject our theory to empirical testing by fitting a series of seemingly unrelated regression models to a vector of safety measures tracked as part of the Federal Motor Carrier Safety Administration's Compliance, Safety, and Accountability program. Our results are consistent with our proposed theory of owner—operator safety and provide meaningful theoretical and managerial implications and directions for future research.     

国家标准《数值修约规则与极限数值的表示和判定》在车用汽油胶质含量测定中的应用

本文根据胶质含量测定试验方法的要求，以车用汽油中胶质含量（包括未洗胶质含量和溶剂洗胶质含量）测定为例，探讨了0．5单位数值修约、极限数值的表示和判定在胶质含量测定数据处理和结果判定中的应用。目的在于使车用汽油产品检测工作中在数据处理、报告和结果判定方面更加规范和统一。     

浅谈高压变频调速系统特点与应用

本文以对某钢铁企业2×360m2烧结机主抽风机电机高压变频调速系统调试为例,阐述了高压变频速系统的分类、特点和应用。     

Strategic Purity and Efficiency in the Motor Carrier Industry: A Multiyear Panel Investigation

Two questions facing motor carrier managers are (1) whether carriers should specialize in providing full truckload (TL) or less‐than‐truckload (LTL) services vis‐à‐vis offering mix of both and (2) whether this decision is contingent on carrier size. Yet, the literature provides little guidance because research to date has offered contradictory theoretical predictions and inconsistent empirical findings. Drawing on the theory of strategic purity and information processing theory, we explain why service specialization is likely to increase carriers' technical efficiency and why size will have a more pronounced effect on technical efficiency for carriers specializing in LTL services versus TL services. To test our theory, we assemble a panel data set from archival government sources regarding general freight motor carriers' provision of LTL and TL services. We measure carriers' technical efficiency using data envelopment analysis and test our hypotheses by fitting a series of panel data mixed‐effects models. Our results indicate that carriers are most technically efficient when they specialize in one service type. We also find that size positively affects technical efficiency but only for carriers specializing in LTL services; no returns to scale with regard to technical efficiency exist for carriers specializing in TL services.     

The effect of cell phones on international motor vehicle fatality rates: A panel-data analysis

This paper analyzes the effects of cell phone usage and economic freedom on motor vehicle death rates by estimating regression models on data for three years across 38 countries. The models incorporate a representative set of motor vehicle fatality determinants. Results indicate that cell phone use has a statistically significant nonlinear impact on highway death rates and that economic freedom does not appear to have an effect.     

对修订后的GB17930-2011《车用汽油》标准的研究

通过对GB19730---2011《车用汽油》标准的解读,解析了标准的修订内容,指出了第Ⅲ与第Ⅳ阶段汽油技术指标的主要差异;阐述了标准的颁布缩小了与先进国家在车用汽油技术指标上的差距,为规范和提高我国车用汽油的质量提供了依据;分析了标准的实施对炼油企业汽油的生产及检验带来的影响。     

GB 12497-1995与GB／T12497-2006三相异步电动机经济运行判别方法比较

三相异步电动机耗电量占全国总用电量的60％以上。我国早在1990年就发布了GB12497—1990《三相异步电动机经济运行》国家强制性标准,又分别在1995年和2006年进行了两次修订。1995版标准与2006版标准在三相异步电动机经济运行判别模型和电动机在偏离额定电压工作时对综合效率补偿方法有较大的不同。文章就上述两个问题进行了比较分析,并进行了实际测量。     

汽车发动机预装线装配平衡改进研究

为提高已经投产的汽车总装生产线的生产平衡率,研究发动机生产线生产平衡改进研究。以现有生产节拍和各个工位操作工时作为基础,运用生产线平衡的基本概念,对现有生产线进行优化。首先确定优化目标,通过工序同期化优化,减少生产岗位,从而提高部分岗位负荷,提高生产平衡率,为企业解决实际问题,节约人力、场地等资源。     

变频器调速系统在门式起重机上的应用

随着新技术和控制系统设备的发展,变频调速技术在起重机领域得到广泛应用,为可靠调速及节能提供全新的方案。文中研究了变频调速技术在门式起重机中的应用,对变频调速系统常见故障做了归纳总结,并提出了相应的解决措施,为起重机电控系统设计及改造提供了参考。     

电动汽车所用电控系统性能介绍及设计

本文简要介绍电动汽车所用电机控制器的种类、结构、工作原理、特点和设计。