高速铁路下承式大跨度系杆拱桥无碴轨道桥面结构形式的对比研究

针对高速铁路下承式大跨度无碴轨道系杆拱桥,通过有限元分析,对桥面结构采用混凝土板与纵横梁半结合方案和全结合方案的动力特性、稳定性和受力性能进行综合对比研究。研究结果表明:与半结合方案相比,全结合方案桥梁刚度较大,尤其是横向刚度;桥梁动力特性和稳定性也较好;系梁承受的纵向力较小,桥面系参与系梁的第一系统作用较大,混凝土板应力水平整体较高,尤其是在端部节间;纵梁面外弯矩及其对应的面外弯曲变形都较小,横梁面内、面外弯矩及其对应的弯曲变形也都较半结合方案的小。建议半结合方案加强纵横梁交接处的局部构造,尤其是横梁与外纵梁交接处;全结合方案混凝土桥面板宜采用高配筋,特别是端部节间。     

齿轨铁路齿轨系统及轨下基础研究

齿轨铁路采用齿条与齿轮相啮合的方法,以提高线路的爬坡能力.齿轨铁路轨道由齿轨系统、钢轨、轨枕、道床等组成,适用于以旅游观光为主的大坡度山区.具有爬坡能力强、占地面积小、建设对环境破坏小等优点,已在国外得到大量使用,我国在多个旅游地也规划了齿轨铁路.系统研究齿轨系统的种类、轮轨-齿轨过渡装置、齿轨轨下结构,研究表明:在齿...     

灵宝环城斜交桥病害分析与加固技术

在分析灵宝环城大桥病害的基础上提出斜交桥上下部整体加固设计方法。该推荐方案为基本构件和节点碳纤维加固和桥面浇筑整体化钢筋混凝土层、基础砌筑片石混凝土防护。该方案不仅提高了桥梁结构的整体刚度和承载力,达到荷载等级提高的目的;而且很好地控制裂缝的发展。通过对比加固前后静载和动载数据,得出该推荐方案在旧桥加固中的优势。     

几种肝脏食品中部分有害物质含量分析

为了解动物肝脏食品的卫生质量，保障广大消费者的利益和健康，对南宁市10个主要农贸市场中销售的猪肝、牛肝、鸡肝及鸭肝共37份样品进行了黄曲霉毒素Bl及有害元素铅、汞、镉、砷的检测。结果表明：4种肝脏食品中黄曲霉毒素Bl均未检出，有害元素汞、砷的含量也符合相应的国家卫生标准，但镉与铅含量较高，其均值分别为0．149及0．703mg/kg，超出了我国的食品卫生标准，其中主要是鸭肝和猪肝受污染严重，而牛肝的卫生质量相对较好。提示目前在动物肝脏食品中存在着一定的有害元素镉、铅的污染，应引起有关管理部门的注意。     

Evaluating marginal improvements to a transport network: An application to the Santiago underground

This paper describes a simplified methodology designed for quick investment appraisal of improvements to a transport network, and discusses its limitations and advantages particularly in the context of a developing country. The approach basically considers:

- a method to define the total population (relevant origin-destination pairs) affected by the project

- the selection of a low-cost background model to represent transport demand on a network at an aggregate level

- the choice of a suitable marginal demand model (in this case a discrete mode choice model) capable of providing the required sensitivity and accuracy to model the project

- the estimation of the marginal demand due to the project during all the years of the study horizon, and

- a sensitivity analysis to assess the robustness of the decision recommended using these two models.

Finally, the paper summarises the results of applying the methodology to the case of an extension to the Santiago underground; it was found that the project has a high social rate of return (almost 20 per cent). However, from the point of view of a private evaluation, it can cover its operating costs only.     

Travel mode choice and travel satisfaction: bridging the gap between decision utility and experienced utility

Over the past decades research on travel mode choice has evolved from work that is informed by utility theory, examining the effects of objective determinants, to studies incorporating more subjective variables such as habits and attitudes. Recently, the way people perceive their travel has been analyzed with transportation-oriented scales of subjective well-being, and particularly the satisfaction with travel scale. However, studies analyzing the link between travel mode choice (i.e., decision utility) and travel satisfaction (i.e., experienced utility) are limited. In this paper we will focus on the relation between mode choice and travel satisfaction for leisure trips (with travel-related attitudes and the built environment as explanatory variables) of study participants in urban and suburban neighborhoods in the city of Ghent, Belgium. It is shown that the built environment and travel-related attitudes—both important explanatory variables of travel mode choice—and mode choice itself affect travel satisfaction. Public transit users perceive their travel most negatively, while active travel results in the highest levels of travel satisfaction. Surprisingly, suburban dwellers perceive their travel more positively than urban dwellers, for all travel modes.     

Rail-road crossing impacts: an international synthesis

Rail-road crossings generate a range of transport, economic, social and environmental impacts. While much research has focused on selected impacts such as safety, little consideration has been given to wider impacts. The aim of this research was to therefore develop a holistic understanding of the impacts of rail-road crossings (both at-grade and grade-separated) and to identify key gaps in knowledge in this field. An international synthesis of rail-road crossing impacts was developed through a detailed literature review, which revealed a total of 18 different types of impacts associated with rail-road crossings. The review found that most research to date has focused on quantifying transport and economic impacts, particularly safety and road vehicle delay, with little consideration given to social and environmental impacts. A number of research gaps have been identified which provide a clear agenda for future research. These gaps include the use of empirical evidence to support impact assessments, and the need to better understand the impacts of grade-separating rail-road crossings in terms of safety, travel time variability, land use, traffic flow, rail vehicle delay, disability access, and crime.     

新型高速艇的CFD模拟和对比分析

高速艇具有体积小、航速高、智能等优点,可以完成搜救、探测、导航和作战等多种任务,广泛应用于军民用领域。研究高速艇的阻力性能对艇体的型线设计和艇体的流体动力学性能分析都显得十分重要。设计一种新型高速艇,通过NUMECA系列软件对不同的高速艇进行数值模拟计算,以研究此类新型高速艇的水动力性能。研究表明:加装水翼或防飞溅条均可增加艇体的升力,使艇体更快地处于滑行状态,安装了防飞溅条的翼滑艇的阻力性能良好。     

关于旋压密封式制动缸组装试验标准的探讨

旋压密封式制动缸是铁路货车制动系统中的主要部件之一,旋压密封式制动缸的性能直接影响铁路的行车安全.旋压制动缸现主要类型有14、12、10、8英寸等.其主要的性能要求基本一样,即旋压密封式制动缸的气密性和活塞移动的平稳性.     

高速列车气动噪声的研究与控制

阐述了气动噪声研究的数值仿真方法和测试技术,分析了高速列车各主要部位气动噪声的形成机理,从而可以采取准确措施,进行高速列车气动噪声的有效控制.