龙山大跨连拱隧道设计与施工

龙山连拱隧道是为适应芜湖经济的快速增长,贯通芜湖经济开发区凤鸣湖大道而修建的城市六车道双连拱隧道。龙山双连拱隧道最大埋深13 m,是目前国内建成的跨度最大、埋深最小的六车道双连拱隧道。介绍了该隧道的设计及现场施工,对今后类似工程提供一些借鉴经验。     

简易瞬态工况法测量准确度影响因素研究

论述国家颁布的在用汽油车排放标准中简易瞬态工况法(Vm as系统)的测试原理和测量系统组成,分别采用不同的底盘测功机、不同的测试模式进行试验,分析了影响Vm as测量汽车排气污染物准确度的因素。在进行大量试验的基础上,提出了为提高测量准确度和重复性,车辆在试验前应进行必要的预处理,使用电涡流测功机应该附加机械飞轮。     

An ontological model to support communications of situation-aware vehicles

In an Intelligent Transport System (ITS) environment, the communication component is of great importance to support interactions between vehicles and roadside infrastructure. Previous studies have focused on the physical capability and capacity of the communication technologies, but the equally important development of suitable and efficient semantic content for transmission received notably less attention. Ontology is one promising approach for context modelling in ubiquitous computing environments, and in the transport domain it can be used both for context modelling and semantic contents for vehicular communications. This paper explores the development of an ontological model implementing relative geo-semantic information messages to support vehicle-to-vehicle communications. The proposed ontology model contains classes, objects, their properties/relations as well as some functions and query templates to represent and update the information of dynamic vehicles, inter-vehicle interactions and behaviour. This model was developed through a scenario enabling the evaluation of traffic conflict resolution approaches, by implementing a set of decision-making processes for intelligent vehicles. Given the scope of the proposed ontology modelling, it shows how vehicular communications can be used to update each vehicle’s context model. This work can be easily extended for more complex interactions among vehicles and the infrastructure.     

Evaluation of exclusive bus lanes in a bi-modal degradable road network

In this paper, we proposed an evaluation method of exclusive bus lanes (EBLs) in a bi-modal degradable road network with car and bus transit modes. Link travel time with and without EBLs for two modes is analyzed with link stochastic degradation. Furthermore, route general travel costs are formulated with the uncertainty of link travel time for both modes and the uncertainty of waiting time at a bus stop and in-vehicle congestion costs for the bus mode. The uncertainty of bus waiting time is considered to be relevant to the degradation of the front links of the bus line. A bi-modal user equilibrium model incorporating travelers’ risk adverse behavior is proposed for evaluating EBLs. Finally, two numerical examples are used to illustrate how the road degradation level, travelers’ risk aversion level and the front link’s correlation level with the uncertainty of the bus waiting time affect the results of the user equilibrium model with and without EBLs and how the road degradation level affects the optimal EBLs setting scheme. A paradox of EBLs setting is also illustrated where adding one exclusive bus lane may decrease share of bus.     

Effects of regulation-driven green innovations on short sea shipping's environmental and economic performance

Despite its pivotal role in European trade, today’s short sea shipping (SSS) industry faces the dual challenge of lessening its environmental footprint while improving its economic performance. To reduce the pollution caused by their operations, SSS companies are required to comply with increasingly stringent environmental regulations enacted by global and regional authorities such as the European Union and the International Maritime Organization. However, the companies tend to regard those regulations as imposing an additional burden of cost that compromises their capacity to enhance their economic performance. This paper examines the impact of external institutional driver namely regulatory pressure on the adoption of green innovations in SSS and in turn, the impact of those innovations on the environmental and economic performance of SSS companies. To investigate the hypothesised relationships of those constructs, a structural equation model was developed and tested with data from a survey conducted amongst 101 short sea shipping companies headquartered in Europe. As detailed in the paper, the analysis revealed that regulatory pressure has generated green innovations that have enhanced the environmental and economic performance of European SSS companies and, as a result, led to a win–win situation for all parties involved. The paper discusses what those findings imply for SSS firm managers and policymakers who seek to improve the environmental or economic performance of Europe’s SSS industry.     

An analytical model to conduct a person-based evaluation of transit preferential treatments on signalized arterials

The complexities of urban transportation networks where multiple modes with different characteristics and needs travel in combination with constraints on space and funding make the sustainable management of these systems a challenge. In order to improve transit service, space (e.g., dedicated bus lanes) and time (e.g., transit signal priority strategies) Transit Preferential Treatments (TPT) are deployed to improve transit operations. The objective of this paper is to develop an analytical model that allows for a person-based evaluation of alternative TPTs when considered individually and in combination. In particular, the analytical model is developed to assess person delay and person discharge flow at any intersection that is part of a signalized arterial, where auto arrivals are in platoons. The performance of TPTs is evaluated using both the analytical model and through microsimulation tests on two intersections of San Pablo Avenue in Berkeley, CA. Space TPTs such as dedicated bus lanes and queue jumper lanes are beneficial in reducing bus person delay when provided in addition to the existing lanes; however, the effectiveness of time TPTs such as green extension depends on the level of auto demand in combination with signal settings. Changes in person discharge flow are not significant for any of the treatments tested with the exception of the bus lane substitution with and without green extension, which led to a significant decrease in person discharge flow. Increased bus frequency increases the effectiveness of transit signal priority in reducing total and bus person delay. The analytical model results produce ranking outcomes that are comparable with the microsimulation ones and therefore, the model may be used for a quantitative evaluation of TPTs without the need for data intensive and time consuming calibration efforts required for microsimulation models. The developed model can be used to guide infrastructure and investment decisions on where such TPTs should be implemented and under what conditions space TPTs should be combined with time TPTs to improve person mobility.     

带整流负载同步发电机阻尼绕组研究

阻尼绕组对发动机短路电流值大小起着决定性的影响,本文就阻尼绕组对同步发电机整流系统直流侧短路时的最大短路电流及对基本波形的影响分析别进行了分析计算和试验验证,得出了无限尼绕组同步发电机整流系统直流侧短路电流值较有阻尼绕组同步发电机有明显下降;阻尼绕组具有改善同步发电机整流系统交直流测电压波形的作用,去掉阻尼绕组使得交流电压波形谐波含量增大,波形畸变加剧;ｑ绕组对改善电压波形效果明显,可以弥补减弱阻     

爆破振动下小净距隧道围岩的力学行为分析

文章运用数值分析计算软件,对小净距隧道中既有隧道受邻近隧道爆破震动影响的动力响应特性进行分析,得出了爆破地震波作用下,隧道周边围岩应力、位移和振动速度的分布规律,为小净距隧道的设计与安全施工提供科学依据。     

软弱围岩隧道短台阶法开挖数值模拟与监测分析

文章依托炎汝高速公路花子坳隧道施工实例,利用有限元模型对隧道Ⅴ级围岩深埋段短台阶法动态开挖过程的应力及位移变化情况进行了数值模拟分析。实测结果表明：短台阶法施工效果良好,围岩压力及拱顶下沉、周边收敛变形均在可控范围内。     

借用公交专用道左转的主预信号控制方案优化

设置有路中式公交专用道的交叉口进口道存在因公交与其他车辆两股平行车流在路口同时左转、直行和右转而形成的多路交织现象,传统信号控制方案已无法消除这类交叉口相位放行造成的交织冲突问题。为解决该问题,设计了一种借用公交专用道左转的新型交叉口,规定了各流向车辆的运行规则,同时设计了主信号与预信号相位方案及相互协调配时关系。具体来说,根据公交直行车辆和其他左转、直行车辆的到达-驶离图式,分别建立各流向不同情况下车辆的延误与停车次数计算方法,以交叉口车均延误与车均停车次数加权的当量费用最小为目标,建立交叉口信号配时优化模型。为验证该优化控制策略的有效性,结合算例对传统控制方案和优化控制方案进行比较,并分析等待区长度对车辆排队演化过程的影响,确定优化方案适用场景。结果表明：相对于传统方案,优化方案增加了交叉口的通行能力,使得车均当量费用下降比例达到了32.3%;参数灵敏度分析显示,主信号等待区长度宜设置为80 m。所提出的控制策略通过借用公交专用道左转,提高了交叉口的利用效率,最大限度地降低了对公交优先策略实施的影响,能够完全消除设置有路中式公交专用道交叉口相位放行中的交通交织冲突现象,以保证交叉口行车安全。