摆式列车检测系统中的传感器容错研究

准确可靠地获得剩余离心加速度对于摆式列车正确倾摆和安全运行至关重要。设置多个并联的加速度传感器可以提高检测该参数的可靠性,文章计算了在给定可靠性下的最优并联单元数,针对传感器的失效过程和形式,确定传感器故障的决策逻辑和故障判断的门限参数。实例仿真表明,多模硬件冗余和相应的故障决策逻辑可以有效地容忍传感器故障,对于提高摆式列车剩余离心加速度检测的可靠性是切实可行的。     

山区高速公路长陡纵坡设计理念及案例分析

一直以来,已建成的山区高速公路长陡纵坡都存在着安全隐患。分析纵坡设计指标的形成原理,研究长陡纵坡段汽车的性能、运行安全性、道路通行能力、汽车油耗等,充分认识长陡纵坡设计中存在的安全隐患,有助于设计者在山区高速公路设计时尽量避免出现长陡纵坡。如果受条件限制,不得已布设长大纵坡时,必须采取综合治理措施,以最大限度地减少恶性事故的发生。     

简易胰岛素释放试验对评价胰岛B细胞功能的意义

目的探索简易胰岛素释放试验(insulin release test,IRT)对评价2型糖尿病患者胰岛B细胞功能的价值。方法对广东医学院附属医院2003²013年门诊以及住院的1 631例2型糖尿病患者和168例健康人(正常糖耐量组,即NGT组)口服75g无水葡萄糖粉,行简易IRT和相应时点的血糖测定,按测定结果将糖尿病患者再分为空腹胰岛素低值组(A组)、空腹胰岛素正常组(B组)、空腹胰岛素高值组(C组),将A、B、C各组的结果分别与NGT组进行比较。结果 NGT组中,血清胰岛素的峰值出现在餐后1h,峰值为空腹血清胰岛素值的5倍以上,餐后2h时血清胰岛素明显降低。A组各时点的血清胰岛素值均低于NGT组,在餐后2h时出现低峰值,各时点的血清胰岛素值与NGT组相比差异均有统计学意义(P<0.05)。B组空腹和餐后1h与NGT组无差异,峰值出现在餐后2h,餐后2h血清胰岛素值与NGT组相比差异有统计学意义(P<0.05)。C组各时点血清胰岛素值均明显高于NGT组,峰值出现在餐后2h,各时点血清胰岛素值与NGT组相比差异均有统计学意义(P<0.05)。简易IRT各点的胰岛素水平与相应的糖耐量试验(OGTT)的血糖值均呈负相关。结论简易IRT对评价糖尿病患者的胰岛细胞功能具有一定的临床指导意义。     

斜拉桥双向倾斜桥塔主动横撑设计及施工控制

为了提高双向倾斜桥塔在施工过程中的稳定性和安全性,需要合理设计横撑作为临时结构,并对其进行施工控制.以某斜塔空间扭索双索面斜拉桥方案为背景,在对全桥模型进行复核和施工阶段计算后,提出横撑设置方案;对主动横撑施工过程进行监控,并对施工误差进行分析,对拆除横撑的施工控制方法及横撑拆除时机进行研究.得出如下结论:在主动横撑设计时应主要控制中塔柱根部混凝土截面应力,以内力控制为主、变形控制为辅的原则确定主动横撑预顶力;主动横撑的预顶力值确定应该包括模型受力计算值、温度影响值以及焊接变形所产生的内力变化值;施工过程中需要提高塔柱施工、横撑焊接的质量,并合理安排横撑的拆除时机.     

Navigating Institutional Constraints in the Process of Computational Environmental Modeling

Abstract

The use of computational models has proliferated in the last few decades due to the practical benefits that they offer in terms of understanding complex systems. However, the process of developing a computational model is not only shaped by scientific and practical concerns. Modelers must also navigate the institutional structures in which the models are constructed and implemented. In the process, they must often draw upon existing or create new social relationships that can, themselves, alter the institutional structures they are attempting to navigate. In this article, I use an ethnographic approach to examine three examples in which the process of building and implementing a computational model was constrained by institutional factors and the strategies the modelers used to navigate them. The research was conducted with computational modelers at the Chesapeake Bay Program who are involved in constructing the Chesapeake Bay modeling system for nutrient management in the watershed. Modelers in this context had to: build relationships with the broader scientific community to reinforce the “believability” of the model, draw upon institutional relationships in order to work around limitations on data-sharing between organizations, and manage differing incentive structures to motivate and coordinate the research needed to complete the model     

30年来清代广东海盗研究综述

广东区位复杂,历来盛出海盗.对30年来清代广东海盗的研究作挂一漏万式综述,以期能较为清晰地反映此一阶段广东海盗研究的现状,为研究的进一步深入做一些铺垫.     

我国肝移植领域应重视临床基础研究

随着更新型的免疫抑制剂的相继问世、手术和监护等技术的全面提高,肝移植成为治疗终末期肝病常规而有效的方法.我国临床肝移植的发展的特点为:乙型肝炎相关终末期肝病是最重要的适应证、超Milan标准的进展期肝癌占肝癌肝移植病例的多数、供体来源的不确定性.鉴于此,作者提出我国肝脏移植应在有效防治乙型肝炎病毒再感染、有效控制肝癌肝移植后肿瘤复发、边缘供体使用和器官功能保护、肝移植的免疫学、合并特殊感染疾病的肝移植等方面应更注重临床基础研究.     

公交候车时间容忍阈值的分布特征及影响因素

公交候车时间容忍阈值反映的是出行者能够容忍的最长候车时间. 研究公交候车时间容忍阈值有助于我们更好地理解出行者对候车时间的感知和态度,从而采取针对性的对策提高公交吸引力和分担率,并可以为公交运营组织提供参考. 本文采用昆明市的调查数据,对候车时间容忍阈值进行了实证研究. 首先,对候车时间容忍阈值的分布特征进行了统计分析,并采用秩和检验法对不同群体的候车时间容忍阈值的分布差异进行了检验. 进一步,基于序次Logit 模型识别了候车时间容忍阈值的影响因素,发现年龄、受教育程度、年龄和受教育程度的交互项、职业、家庭年收入、公交出行频率对候车时间容忍阈值有显著影响.     

A traffic analysis zone definition: a new methodology and algorithm

This paper develops a comprehensive approach to the definition of transportation analysis zones (TAZ), and therein, presents a new methodology and algorithm for the definition of TAZ embedded in geographic information systems software, improves the base algorithm with several local algorithms, and comprehensively analyses the obtained results. The results obtained are then compared to these presently used in the transportation analysis process of the Lisbon Metropolitan Area. The proposed algorithm presents a new methodology for TAZ design based on a smoothed density surface of geocoded travel demand data. The algorithm aims to minimise the loss of information when moving from a continuous representation of the origin and destination of each trip to their discrete representations through zones, and focuses on the trade-off between the statistical precision, geographical error, and the percentage of intra-zonal trips of the resulting OD matrix. The results for the Lisbon Metropolitan Area case study suggest a significant improvement in OD matrix estimates compared to current transportation analysis practises based on administrative units.

Risk Management in Motorway PPP Projects: Empirical-based Guidelines

Abstract

This paper deals with the topic of risk management in Public Private Partnership (PPP). The analysis of the related literature reveals that risks must be analyzed and managed on a context-specific approach, and that there is a lack of a comprehensive study on the appropriate risk mitigation strategies for each risk embedded in PPP projects. Focusing on the transport sector, based on the results of a Delphi survey, the paper provides guidelines for both public and private parties in defining a list of significant risks in PPP motorway projects, and identifying for them both the effective allocation and the suitable mitigation strategies. Results of the Delphi survey have been compared with the common practices on risk management applied in eight real motorway PPP projects.