基于物理规律的气垫船气液介质仿真系统研究

针对全垫升气垫船气液介质复杂场景实时再现仿真需求,基于粒子系统原理和OSG渲染平台,考虑气垫船近场波浪高程模型、气垫船垫升系统压力及流量仿真模型以及气垫船气流场特点,提出了一种基于多模型的气垫船航行时气液介质特效仿真框架和实现方法。搭建了该技术的体系结构和实现流程,解决了不同开发环境下建立的异构模型仿真问题,并通过仿真模拟计算验证了该技术的可行性和正确性。仿真结果符合气垫船航行时的气液介质外形特征、作用范围以及气液介质产生的随机性和规律性特征,能快速逼真地实现气垫船航行时气液介质视景特效,对增强气垫船模拟训练效果具有重要的意义。     

三种减少直流断路器的船舶中压直流电网拓扑结构及性能比较

为保护整流变换器及减少短路时电网中电容放电的影响,船舶中压直流电网中存在大量断路器,造成结构复杂成本高,为此本文提出三种结构的变换器,即基于级联H桥与多端DC/DC的结构(TMPDC),基于MMC整流与逆变的多级调压结构(MVR)和基于不控整流与模块化多电平变换器(MMC)驱动负载结合的结构(UR-MMC)。本文对三种结构的组成与特点进行了分析,并在电压谐波,功耗,体积,故障特性等方面进行了比较,最后通过仿真进一步阐述了不同结构在运行波形上的差异。通过各结构的特性分析,为中压直流电网在船舶上的应用提供了参考。     

智慧出行MaaS大数据云平台体系架构和实践

介绍八维通科技有限公司已建的智慧出行数字票务服务平台的体系架构,并创新推出在交通出行大互通大覆盖需求下的智慧出行MaaS大数据云平台的构架设计。智慧出行MaaS大数据云平台采用企业运营数据中台的模式构架,以标准化采集为基础、开放架构为抓手、数据总线为主线,标准化的数据为基石、TT大脑为指挥中枢,安全可靠的支付服务为宗旨。云平台构架着重将差异化的需求进行共性化抽象,实现差异化的服务内容和不同支付方式接入时进行统一规范的运营支撑。目前,云平台构架和功能已在近20个城市上线运营和商用,验证了云平台构架的合理性和可靠性。     

悬链式单浮箱防波堤水动力特性试验研究

为研究悬链式单浮箱防波堤水动力特性的影响因素,采用二维物理模型试验方法,讨论规则波下相对吃水S/d、相对宽度B/L、锚链刚度k、锚链系泊倾角α等因素改变时浮堤模型的透射系数K_t和锚链上最大拉力F的变化规律。试验分析采用平均波高计算透射系数K_t,以前1/10最大拉力平均值作为最大拉力F。结果表明:相对宽度B/L0. 3时,相对宽度B/L是影响浮箱模型消浪性能的主要因素;相对吃水S/d0. 14时,相对吃水S/d是影响锚链上最大拉力F的主要因素。所得结果可以为悬链式单浮箱防波堤的设计和进一步研究提供参考。     

先张法折线预应力工字梁成桥动载试验研究

为了解先张法折线预应力工字梁成桥后结构的自振频率、振幅、冲击系数等动力特性实测参数,通过对其进行动载试验,将有限元计算的理论值与实测值进行了对比分析,发现自振频率、振幅、冲击系数等动力特性实测参数均小于理论值,表明桥梁整体受力性能良好,满足设计运营荷载等级的要求。     

支撑式TBM与双护盾式TBM在设计选型中的比较

如何对硬岩隧道(洞)施工中使用的TBM进行设计选型?相信这是每个工程业主和设计院都需要面对的问题.通过对硬岩隧道(洞)掘进中,支撑式和双护盾式TBM的施工方法及设备功能包括对地质的适应性以及初期支护与混凝土衬砌型式、不良地质地段处理方法、出碴运输方式、环境影响等进行比较,并结合辽宁省大伙房输水一期工程输水隧洞施工中TBM的工程实践,提出了弥补支撑式TBM开挖和衬砌不能平行作业的改进构想,提出了采用栈桥式仰拱模板台车和全环内通式模板台车的施工方法.通过改进,可实现一模养生、一模浇注、第三模移动框架梁的作业工序.     

大断面海底隧道初期支护变异对二次衬砌安全性的影响

运用大型有限元通用软件ANSYS和钢拱架与混凝土间的粘结滑移退化模型,分析了海底隧道典型初期支护裂缝及钢拱架锈蚀对二次衬砌安全性的影响规律.相对于未开裂前,拱顶开裂造成二次衬砌边墙安全系数最大降幅达5.0%,拱腰开裂造成未开裂侧二次衬砌边墙安全系数最大降幅达15.6%;初期支护承受全部围岩荷载时,钢拱架锈蚀对二次衬砌拱顶安全系数的影响最大,80%锈蚀率时拱顶安全系数降幅为10.0%左右.     

大断面黄土隧道变形规律及预留变形量研究

文章统计分析了大断面黄土隧道初期支护变形量,研究了大断面黄土隧道变形规律及预留变形量合理取值范围.大断面黄土隧道变形规律表现为:隧道拱顶、拱脚下沉差异小,隧道开挖后拱部将产生一定程度的整体下沉;隧道拱顶下沉量均大于水平收敛;初期支护封闭后,隧道周边位移基本上不再发展;当隧道埋深小于40m时,隧道变形量较大且规律不明显;当隧道埋深大于40 m时,隧道变形量分布相对集中.经过对现场量测数据的统计分析可知:在Ⅳ级围岩条件下,大断面黄土隧道预留变形量可取10～15 cm;在Ⅴ级围岩条件下,大断面黄土隧道预留变形量可取25～28 cm.     

Analyzing urban bus service reliability at the stop, route, and network levels

Improving the reliability of bus service has the potential to increase the attractiveness of public transit to current and prospective riders. An understanding of service reliability is necessary to develop strategies that help transit agencies provide better services. However, few studies have been conducted analyzing bus reliability in the metropolis of China. This paper presents an in-depth analysis of service reliability based on bus operational characteristics in Beijing. Three performance parameters, punctuality index based on routes (PIR), deviation index based on stops (DIS), and evenness index based on stops (EIS), are proposed for the evaluation of bus service reliability. Reliability involves routes, stops, punctuality, deviation, and evenness. The relationship among the three parameters is discussed using a numerical example. Subsequently, through a sampling survey of bus lines in Beijing, service reliability at the stop, route, and network levels are estimated. The effects of route length, headway, the distance from the stop to the origin terminal, and the use of exclusive bus lanes are also analyzed. The results indicate low service reliability for buses in Beijing and a high correlation between service reliability and route length, headway, distance from the stop to the origin terminal, and the provision of exclusive bus lanes.     

Vulnerability analysis for large-scale and congested road networks with demand uncertainty

To assess the vulnerability of congested road networks, the commonly used full network scan approach is to evaluate all possible scenarios of link closure using a form of traffic assignment. This approach can be computationally burdensome and may not be viable for identifying the most critical links in large-scale networks. In this study, an “impact area” vulnerability analysis approach is proposed to evaluate the consequences of a link closure within its impact area instead of the whole network. The proposed approach can significantly reduce the search space for determining the most critical links in large-scale networks. In addition, a new vulnerability index is introduced to examine properly the consequences of a link closure. The effects of demand uncertainty and heterogeneous travellers’ risk-taking behaviour are explicitly considered. Numerical results for two different road networks show that in practice the proposed approach is more efficient than traditional full scan approach for identifying the same set of critical links. Numerical results also demonstrate that both stochastic demand and travellers’ risk-taking behaviour have significant impacts on network vulnerability analysis, especially under high network congestion and large demand variations. Ignoring their impacts can underestimate the consequences of link closures and misidentify the most critical links.