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.     

关于大量程超声波料位计的算法修正讨论

随着现代科学技术的不断提升,煤矿、铁矿、造纸、稀土等行业的自动化水平取得飞速发展,能否稳定、准确、智能地测量料位决定着这些行业是否能够向现代化、智能化发展。测量料位的方法有很多,其中超声波料位计采用非接触方式,能够有效避免光线、粉尘、烟雾和电磁干扰的影响。研究和设计精度高、稳定性好、性价比高的超声波料位计是充满挑战性和具有现实意义的课题。考虑到超声波的传播速度受温度的影响较大,推导出带有温度补偿的速度修正计算公式,并应用在软件算法中;为了进一步提高测量精度,本文还详细分析了超声波传播的实际路径并给出了计算公式。     

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。     

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.     

车险电销客户投保体验迫切改进点的数据挖掘

本文旨在从车险电话销售客户体验调研数据中寻找到车险电话销售客户投保体验的最迫切改进点,以期用较低的成本投入有效地提高车险电话销售成功率和产能。使用SPSS MODELER数据挖掘软件,遵从CRISP—DM数据挖掘方法论,对调研数据进行数据挖掘,得到车险电话销售客户体验最迫切的改进点,并相应提出改进的政策建议。政策建议包...     

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。     

直流电机系统的建模技术研究

本文针对传统直流电机的模型建立问题，基于曲线拟合技术，提出了简洁有效的参数辨识方法。由于实际的直流电机模型正反向参数差别很大，因此本建模方法中对直流电机的正向模型和反向模型分别对待。实验结果验证了所建立的直流电机模型的优越性能。     

超声波测量的新研究

超声波测量技术在材料特性领域中占有重要地位,因为它是状态的非破坏性和对各种材料的弹性性能的评价手段。随着计算机电子技术的突飞猛进,超声波测量速度和精度上有了很大的进步,在更大的范围内得到了新的应用。本文以超声波波谱、超声波摄像和延迟线振荡器构成传感器为例进行研究,争取有新的突破。     

基于PROTEUS的单片机对步进电机运动控制仿真

针对步进电机在各领域上越来越广泛的应用,提出了用单片机AT89C51控制运行四相步进电机方法。由于实验室里进行设计,受到场地、仪器和元件等的限制,提出了用Proteus进行仿真的方法。该软件不仅具有其它EDA工具软件的仿真功能,还能仿真单片机及外围器件。它是目前最好的仿真单片机及外围器件的工具,使设计时间大为缩短,学校的资源得以非常好的利用。