矩形顶管隧道群施工对后背土体扰动规律的初步研究

为更准确地计算矩形顶管隧道施工所需顶推力,揭示小间距顶管隧道群施工中后背土体在顶推力多次叠加作用扰动后的变化情况。首先,基于现有顶管顶推力相关计算公式推导出适用于矩形顶管的顶推力计算公式。然后,整理分析某顶管隧道群工程施工中后背土体水平位移、土压力实测数据,论证矩形顶管顶推力计算公式的正确性与合理性,得到后背土体受顶推力作用产生的水平位移是以隧道中心处为最大值的弓形分布、土体在顶推力二次作用下会产生更为显著的变化且存在残余应力现象等结论。最后,采用统计方法对顶推压力与后背土体水平位移、土压力之间的数据进行处理,取得后背土在顶推压力作用下产生水平位移与土压力的经验公式。     

Developing an enhanced weight-based topological map-matching algorithm for intelligent transport systems

Map-matching (MM) algorithms integrate positioning data from a Global Positioning System (or a number of other positioning sensors) with a spatial road map with the aim of identifying the road segment on which a user (or a vehicle) is travelling and the location on that segment. Amongst the family of MM algorithms consisting of geometric, topological, probabilistic and advanced, topological MM (tMM) algorithms are relatively simple, easy and quick, enabling them to be implemented in real-time. Therefore, a tMM algorithm is used in many navigation devices manufactured by industry. However, existing tMM algorithms have a number of limitations which affect their performance relative to advanced MM algorithms. This paper demonstrates that it is possible by addressing these issues to significantly improve the performance of a tMM algorithm. This paper describes the development of an enhanced weight-based tMM algorithm in which the weights are determined from real-world field data using an optimisation technique. Two new weights for turn-restriction at junctions and link connectivity are introduced to improve the performance of matching, especially at junctions. A new procedure is developed for the initial map-matching process. Two consistency checks are introduced to minimise mismatches. The enhanced map-matching algorithm was tested using field data from dense urban areas and suburban areas. The algorithm identified 96.8% and 95.93% of the links correctly for positioning data collected in urban areas of central London and Washington, DC, respectively. In case of suburban area, in the west of London, the algorithm succeeded with 96.71% correct link identification with a horizontal accuracy of 9.81 m (2σ). This is superior to most existing topological MM algorithms and has the potential to support the navigation modules of many Intelligent Transport System (ITS) services.     

Multi‐objective highway alignment optimization using a genetic algorithm

The available highway alignment optimization algorithms use the total cost as the objective function. This is a single objective optimization process. In this process, travel‐time, vehicle operation accident earthwork land acquisition and pavement construction costs are the basic components of the total cost. This single objective highway alignment optimization process has limited capability in handling the cost components separately. Moreover, this process cannot yield a set of alternative solutions from a single run. This paper presents a multi‐objective approach to overcome these shortcomings. Some of the cost components of highway alignments are conflicting in nature. Minimizing some of them will yield a straighter alignment; whereas, minimizing others would make the alignment circuitous. Therefore, the goal of the multiobjective optimization approach is to handle the trade‐off amongst the highway alignment design objectives and present a set of near optimal solutions. The highway alignment objectives, i.e., cost functions, are not continuous in nature. Hence, a special genetic algorithm based multi‐objective optimization algorithm is suggested The proposed methodology is demonstrated via a case study at the end.     

The Alternative Motor Fuels Act, alternative-fuel vehicles, and greenhouse gas emissions

The corporate average fuel economy (CAFE) standard is the major policy tool to improve the fleet average miles per gallon of automobile manufacturers in the US. The Alternative Motor Fuels Act (AMFA) provides special treatment in calculating the fuel economy of alternative-fuel vehicles to give manufacturers CAFE incentives to produce more alternative-fuel vehicles. AMFA has as its goals an increase in the production of alternative-fuel vehicles and a decrease in gasoline consumption and greenhouse gas emissions. This paper examines theoretically the effects of the program set up under AMFA. It finds that, under some conditions, this program may actually increase the production of fuel-inefficient gasoline vehicles, gasoline consumption and greenhouse gas emissions.     

超深三轴搅拌桩止水帷幕关键技术在深基坑中的应用

结合上海轨道交通10号线一期工程110 kV溧阳路主变电所的施工实践,介绍了一种全新的通过以三轴搅拌桩作为止水帷幕,垂直隔断微承压水的方法,妥善解决了城市深基坑施工所面临的抽水降压对周边环境影响的问题。     

The impact of climate change and weather on transport: An overview of empirical findings

This paper presents a survey of the empirical literature on the effects of climate change and weather conditions on the transport sector. Despite mixed evidence on many issues, several patterns can be observed. On a global scale especially shifts in tourism and agricultural production due to increased temperatures may lead to shifts in passenger and freight transport. The predicted rise in sea levels and the associated increase in frequency and intensity of storm surges and flooding incidences may furthermore be some of the most worrying consequences of climate change, especially for coastal areas. Climate change related shifts in weather patterns might also cause infrastructure disruptions. Clear patterns are that precipitation affects road safety by increasing accident frequency but decreasing severity. Precipitation also increases congestion, especially during peak hours. Furthermore, an increased frequency of low water levels may considerably increase costs of inland waterway transport. Despite these insights, the net impact of climate change on generalised costs of the various transport modes are uncertain and ambiguous, with a possible exception for inland waterway transport.     

Severity of injury resulting from pedestrian–vehicle crashes: What can we learn from examining the built environment?

This paper examines the impact of personal and environmental characteristics on severity of injuries sustained in pedestrian–vehicle crashes using a generalized ordered probit model. The data covers 2000–2004 of pedestrian–vehicle crashes taken from police incident reports for Baltimore City and supplemented with local land use, urban form and transportation information specific to the individual crash locations. The results on personal and behavioral variables confirm previous findings. Women pedestrians involved in crashes tend to be injured less frequently than their male counterparts; children have an increased likelihood of sustaining injuries and older persons are more likely to be fatally injured. Pedestrians who cross against the traffic signal, are not in a crosswalk and are involved in a crash after dark are associated with greater injury risk. Of the built environment policy variables of interest, transit access and greater pedestrian connectivity, such as central city areas, are significant and negatively associated with injury severity. These results suggest that the environmental conditions should be given more scrutiny and be an important consideration when evaluating and planning for pedestrian safety.     

船用无刷发电机励磁系统改装

船舶电站系统经多年运行后,其发电机控制系统器件老化,原始资料丢失,功能不完善,虽勉强能运行发电,但远不能满足船舶正常工作的供电需求。若更新发电机或订购原制造商的配件,需投入大量资金和时间,对于营运20多年的旧船来说,投入的可能性和经济性不大,而利用现行产品和技术对其进行改造,是1个很好的修复方案。文中的改装实例可为老龄船舶发电机的修复提供参考。     

船舶减摇方式介绍及发展趋势

针对船舶的减摇问题,综述了船舶减摇的几种方法,分析了船舶主要减摇装置舭龙骨、减摇鳍、减摇水舱、减摇舵的优缺点,指出了存在的技术难题,并展望了有价值的研究方向。     

新建航道下穿高铁桥梁时加固方案的变形控制*

为评估航道开挖下穿高铁桥梁时加固方案的变形控制效果,结合京杭运河二通道下穿沪昆高铁工程实例,采用三维有限元软件模拟分析航道围护结构施工、航道开挖、航道结构浇筑、航道通航等各阶段土体和结构的位移变形,对下穿施工过程中航道维护结构及桥墩的安全状态进行量化评价。结果表明,坚实的支护系统、分层开挖结合多次降水,可以避免较大土体沉陷并控制开挖引发的坑底隆起;加固方案也对既有结构起到了良好的保护作用,保证列车在施工期安全运行。