A network level connectivity robustness measure for connected vehicle environments

This study introduces a new CONnectivity ROBustness model (CONROB) to assess vehicle-to-vehicle communication in connected vehicle (CV) environments. CONROB is based on Newton’s universal law of gravitation and accounts for multiple factors affecting the connectivity in CV environments such as market penetration, wireless transmission range, spatial distribution of vehicles relative to each other, the spatial propagation of the wireless signal, and traffic density. The proposed methodology for the connectivity robustness calculation in CONROB accounts for the Link Expiration Time (LET) and the Route Expiration Time (RET) that are reflected in the stability of links between each two adjacent vehicles and the expiration time of communication routes between vehicles. Using a 117 sq-km (45-square mile) network in Washington County, located west of Portland city, Oregon, a microscopic simulation model (VISSIM) was built to verify CONROB model. A total of 45 scenarios were simulated for different traffic densities generated from five different traffic demand levels, three levels of market penetration (5%, 15%, and 25%), and three transmission range values [76 (250), 152 (500), and 305 (1000) m (ft)]. The simulation results show that the overall robustness increases as the market penetration increases, given the same transmission range, and relative traffic density. Similarly, the overall connectivity robustness increases as the relative traffic density increases for the same market penetration. More so, the connectivity robustness becomes more sensitive to the relative traffic density at higher values of transmission range and market penetration. Multiple regression analysis was conducted to show the significant effect of relative traffic density, transmission range, and market penetration on the robustness measure. The results of the study provide an evidence of the ability of the model to capture the effect of the different factors on the connectivity between vehicles, which provides a viable tool for assessing CV environments.     

Analysis of a cooperative variable speed limit system using microscopic traffic simulation

Variable speed limit systems where variable message signs are used to show speed limits adjusted to the prevailing road or traffic conditions are installed on motorways in many countries. The objectives of variable speed limit system installations are often to decrease the number of accidents and to increase traffic efficiency. Currently, there is an interest in exploring the potential of cooperative intelligent transport systems including communication between vehicles and/or vehicles and the infrastructure. In this paper, we study the potential benefits of introducing infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits in variable speed limit systems. We do this by proposing a cooperative variable speed limit system as an extension of an existing variable speed limit system. In the proposed system, communication between the infrastructure and the vehicles is used to transmit variable speed limits to upstream vehicles before the variable message signs become visible to the drivers. The system is evaluated by the means of microscopic traffic simulation. Traffic efficiency and environmental effects are considered in the analysis. The results of the study show benefits of the infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits for variable speed limit systems in the form of lower acceleration rates and thereby harmonized traffic flow and reduced exhaust emissions.     

美国气垫登陆艇的技术发展及分析

基于美国气垫登陆艇(LCAC)的研制实情及其最近的延寿计划(SLEP)和其未来替代者——舰岸连接器(SSC)的发展趋势,对LCAC的快速性等总体性能进行计算和分析,并追踪LCAC有关新技术在芬兰T-2000艇与韩国LSF-II艇上的应用情况。     

土工格栅加筋填挖交界路基离心模型试验研究

通过土工离心模型试验,对填挖交界路基处不同的土工格栅加筋方案对于不均匀沉降的处治效果进行研究。通过测量填挖交界路基表面测点的沉降量和位移变化,分析土工格栅铺设的层数对填挖交界路基不均匀沉降和路基整体稳定性的改善作用,因此根据对比试验获得最佳的处治方案。试验研究结果表明:铺设两层土工格栅对填挖交界路基不均匀沉降的效果要优于只铺设一层的,而铺设一层土工格栅对填挖交界路基不均匀沉降的效果要好于不铺设土工格栅的。     

开放型公共物业管理模式与收费探讨

转换养护观念,提出市政公共设施是一个"开放型公共物业管理"理念、特点、与一般小区物业管理的区别,参照小区物业管理收费模式,提出"公共物业管理"收费形式,有关经验可供相关专业人员参考。     

重粉质砂壤土中长距离大口径顶管施工

某引水枢纽工程,采用顶管法施工,总长约3.0km,共分为3段,其中4号井至3号井为1300m超长距离顶管区间段。顶管上部和切削断面均为重粉质砂壤土,采用大刀盘泥水平衡顶管掘进机施工。在顶管顶进至约80m时,开始出现大范围地面沉降,顶管顶力剧增,顶管姿态变化大,设备连续故障等现象。经认真分析原因并制订针对性施工技术措施,最终确保了重粉质砂壤土复杂地质下该超长距离顶管区间段得以贯通。该文对该超长距离顶管区间段顶管施工进行了认真分析和总结。其结论与建议可供今后类似超长距离顶管工程借鉴。     

气液增压技术在工程领域中的应用

通过对液压站,气液增压系统的分析,详细的介绍了二者之间的优缺点。经过对单向阀一钢球压装机床方案的讨论,压装力的计算,证明了气液增压技术在机床上应用的可行性,从根本上解决了液压站占地面积大,噪音大等缺点。为气液增压系统在工程领域中大量使用提供了依据。     

穿越输油管道腐蚀评价模型

随着运行时间的增加,穿越输油管道必然受到不同程度的腐蚀,如果不及时维修或更换,可发生泄漏或爆裂。为了确定管道的腐蚀情况,提出了一种模糊评判法。根据引起穿越输油管道腐蚀失效的各个因素,建立穿越输油管道腐蚀评价体系,对穿越输油管道进行腐蚀因素的模糊综合评判,通过实例分析,验证了该评价方法的实用性。     

军械电磁辐射危害试验方法

舰船、飞机等平台中存在着电磁辐射对军械的危害问题,甚至会危及到人员的安全,需要对其进行正确试验评估.讨论了平台上电磁辐射对军械危害的试验方法,详细阐述了试验原理、测试系统、实施等关键内容.     

浩吉铁路对国家能源集团煤炭运输影响的探讨

浩吉铁路目前已全线建成运营,成为我国北煤南运最便捷的通道和国内规模最大的运煤专线。华中地区是国家能源集团煤炭外运的一个重要集散地,而浩吉铁路的建成运营对国家能源集团的煤炭外运既是挑战又是机遇。在定量分析浩吉铁路与现有北煤南运通道运费的基础上,对浩吉铁路运输时效性和可靠性进行定性分析。研究表明,浩吉铁路较现有的北煤南运通道具有一定的优势。国家能源集团运煤通道应与浩吉铁路实现互联互通,做好下游煤炭集散,而浩吉铁路利用国家能源集团上游煤源和下游煤炭市场,两者将实现双赢。