A Framework for Reconsidering the Lake Wobegon Effect

The Lake Wobegon Effect (LWE) describes the potential measurement-error bias introduced into survey-based analyses of education issues. Although this effect potentially applies to any student-report variable, the systematic overreporting of academic achievements such as grade point average is often of preeminent concern. This concern can be easily circumvented if official records data are available; however, many researchers can only access student-reported data. In this article, the authors examine whether using student-survey data in place of official records data meaningfully biases regression estimates. They motivate their contribution by noting a useful statistical feature of overreporting on bounded variables such as grade point average. Specifically, the misreports will be negatively correlated with the true grade point average, yielding a form of nonclassical measurement error that actually counteracts the bias. The authors connect this observation to reliability ratios used in labor economics, which are simple ways to adjust for attenuation bias, when needed. In two applications, we find that it is unnecessary to correct for the LWE bias because it is so small.     

对于液压系统中负载锁定问题的探讨

负载锁定作为一项负载控制功能对于液压回路的设计和安全操作而言是非常重要的。特别是执行元件做垂直或倾斜运动时，如果不设计专门的负载锁定装置，常常会导致液压系统在使用过程中出现故障，例如橡胶软管、金属管和液压元件的损坏。解决的方法包括使用机械的或者液压控制的负载锁定装置。本文对采用普通单向阀、液控单向阀、液压锁、二住换向阀、三位换向阀等组成，用于实现负载锁定功能的液压回路进行了探讨，最后重点探讨了采用平衡阀和制动阀的负载锁定回路。     

浅谈Suroca排水渠项目工程施工管理

文章简述了Suroca排水渠工程在技术管理、资源管理、质量管理以及安全文明施工的一些经验,通过对排水渠工程施工管理,为安哥拉市政工程的施工提供借鉴。     

成型设备增塑剂系统电气控制可靠性探讨

文章通过介绍成型设备增塑剂系统的流程和控制方式,运用可靠性理论,完善其控制和检测,并结合设备的实际情况,提出改进的具体方法。     

Determinants of attitudinal loyalty in Nigerian telecom service sector: Does commitment play a mediating role?

This paper explores the mediating role of commitment in the relationships between service assurance, service reliability and attitudinal loyalty. A quantitative cross-sectional data generated from 138 experienced users of telecommunication services formed the final database. Attitudinal loyalty was found to be a process-based construct that starts from service assurance and proceeds to service reliability and finally to customer commitment and loyalty. The entire process explained 69 per cent of the total variance in attitudinal loyalty. The relationship between service assurance and attitudinal loyalty was insignificant. No support was found for the proposed mediating role of customer commitment in the relationship between service assurance and attitudinal loyalty. In contrast, the relationship between service assurance and attitudinal loyalty was fully mediated by service reliability. Finally, service reliability was both directly and indirectly related to attitudinal loyalty through customer commitment. To attract customers' attitudinal loyalty therefore, services companies especially those within the low-contact service category must deliver reliable services and make efforts to assure customers that their services are reliable. The implications for customer loyalty theory and future research are also discussed.     

Community safety promotion at local,regional, and national levels. Summary report from a workshop on local organizing and societal contributions with regard to the development of Safe Communities,held at the Third International Conference on Safe Communities,June 6-8, 1994, Harstad,Norway

Aim The aim of this review was to determine the extent to which the effectiveness of countermeasures for preventing alpine skiing injuries has been evaluated. Methods The methodology involved a critical review based on the available international literature and sports equipment standards, as well as consultation with experts in the field. Where possible, the review focused on controlled trials. Results Key injury countermeasures in skiing identified in this review include physical conditioning programmes, ski-bindings and their timely release, professional adjustment of ski-bindings and the use of mechanical testing devices for this, design of ski pole handles, helmets for children (and adults), ski patrollers, skier education, speed control on the slopes and safe lifting equipment. A tabular categorisation of the types of evidence for the effectiveness of injury countermeasures is presented. This demonstrates that the weight of evidence is generally based on a combination of data-based or biomechanical testing evidence and informed opinion/anecdotal evidence. There is minimal evidence based on controlled trials in the field. The most evaluated countermeasures are ski bindings and ski pole handles. Properly adjusted ski bindings have the potential for a 3.5-fold reduction in lower extremity injuries, particularly knee injuries. Ski pole handle design needs further innovation and attention. An immediate concern is the generally poorer standard of children’s equipment, ski bindings and their adjustment. Conclusion Skiing is a sport that is growing in popularity, but with a need for controlled trials of its injury prevention countermeasures. This review provides a basis for further action in injury prevention research, development and implementation.     

对于火力发电厂燃料系统安全运行的探究分析

输煤系统是火力发电厂里重要的标志性组成部分,而输煤皮带的安全运行最为直接的影响了电厂的安全指标和经济效益。本文从火力发电厂燃料运行系统安全运行方面,对其影响因素进行分析探究,并提出防范对策,让今后在有效维护和保证系统安全运行时有所参考。     

油料供应标准制定中信息真实性问题探析

提出了油料供应标准制定中信息真实性问题,建立了信号示意模型,并对模型进行了分析,得出了解决油料供应标准制定中信息真实性问题的结论,为油料供应标准的合理制定提供理论基础。     

PASS MO在110kV变电站中应用的可行性

文章对PASS（Plug and Switch Switchgear,简称PASS，是ABB公司生产的插接式开关装置）的改进型PASS MO的特点进行分析，探讨在110kV电压等级采用该设备的可行性。     

基于可靠度理论的小城镇工程结构抗灾设计体系

文章提出了小城镇工程结构抗灾设计的目的、原则,为小城镇的抗灾设计提供了切实可行的设计准则,分析并提出了小城镇工程结构抗灾性能指标体系,为小城镇工程结构抗灾可靠度的理论分析提供了分析变量,建立了在各种灾害作用下小城镇工程结构抗灾可靠度理论的分析模型,为小城镇基础设施的防灾减灾的进一步研究提供理论依据。