基于可拓学的生态影响评价方法在铁路选线中的应用

针对铁路工程选线的特点,从生态环境影响的评价指标选取入手,用优势度指数、均匀度指数、树木生长率等18项指标反映铁路工程建设对生态环境影响的各个方面。采用可拓学理论中优度评价法建立评价模型,按照确定待评物元、确定权系数、筛除不满足必备条件方案、建立关联函数并计算合格度、合格度规范化、计算优度等步骤进行定量的分析评价。通过对各待评方案优度值的比较,进行合理方案的选取。运用该评价方法对工程实例进行的评价分析证明,该方法具有简单、直观等优点,为在考虑铁路建设的生态环境问题基础上的线路方案选择提供一种新的综合评价方法。     

基于实测动应力分析的车轴台架试验谱编制

通过长距离线路动应力测试,编制适用于车轴磁粉探伤周期优化研究的台架试验谱.首先,分析测试结果中车辆载重、线路工况、运行交路对车轴动应力的影响,并考虑车轮失圆的影响,确定不同影响因素的灵敏度;然后,进行应力谱极值推断,得到车轴外推应力谱;最后,得到台架试验谱,并开展台架疲劳试验.结果 表明:车轴最大应力截面上的最高频次应...     

Fault diagnosis of marine diesel engine intake and exhaust system based on dynamic feature fusion北大核心CSCD

[目的]船舶系统由多设备的复杂机构组成,各组件参数具有动态性和非线性的特点,所以故障诊断过程复杂。为提高诊断效率,提出一种动态特征融合方法。[方法]利用分形理论、动态理论及核主元分析(KPCA)法对系统状态数据进行重构、映射及筛选,得到主元特征数据矩阵,求得平方预测误差(SPE)及相应的控制限,构建出基于船舶柴油机进排气系统健康数据的离线监测模型,利用该模型对系统进行故障诊断分析。为验证模型的有效性,选取某船舶柴油机进排气系统的故障数据进行验证分析。[结果]结果表明,动态特征融合分析方法可有效实现对系统动态非线性状态数据的精确分析,实现对系统故障的高效分析和诊断。与KPCA及支持向量机(SVM)方法相比,所提方法具有更好的故障诊断性能。[结论]该方法可实现船舶柴油机进排气系统故障的检测和诊断,提升系统运行的可靠性和安全性。     

盾构静-动态泥浆渗滤成膜及支护效率控制方法

近年来，泥水盾构在越江跨海隧道中被广泛应用，隧道开挖面“泥浆-土水”相互平衡作用是工程安全的关键。盾构泥浆能否成膜、动态掘进泥膜是否存在、动态泥膜如何发挥支护作用等问题受到广泛关注，理清这些问题是保障开挖面稳定的基础。对此，基于多相流理论提出了泥浆“渗滤-成膜-生长”瞬态力学模型，探明了泥浆的流体特性和地层的水力传导性质的时空变化规律，揭示了盾构停机静态成膜和掘进动态成膜机制，并通过静、动态成膜2个实例计算验证了理论方法的适用性。研究结果表明：盾构静态停机状态下通常为全断面泥膜，泥浆以面力形式进行支护，盾构掘进时表现为动态局部泥膜，泥浆压力可较长距离前向传递，以渗透力的形式发挥作用；盾构掘进时开挖面泥膜分布为多辐扇形的局部泥膜，可分为泥膜渐变区和无泥膜区，无泥膜区域靠近先行刀臂，随着刀盘转速的增加，泥膜的厚度和泥膜面积逐渐减小；实际工程中，可以从泥浆材料和掘进参数两方面提升泥浆的支护作用，一方面根据地层-泥浆粒径比和泥浆黏度双控指标进行泥浆配置，另一方面宜降低盾构刀盘转速，同时适当增加掘进速度，充分发挥局部泥膜的支护作用，提高泥浆的支护效率和开挖面的稳定性。研究成果对泥水盾构施工安全有一定的指导意义。     

浮码头与旁靠船舶的运动响应特性研究

本文基于三维势流理论，采用数值分析方法研究了浮码头与散货船旁靠系泊的运动特性。考虑缆绳和护舷的非线性特性，探求了波浪周期对浮体运动、系缆力的影响规律。研究结果表明：考虑间隙内水体运动影响，旁靠散货船在横浪条件下的纵摇和纵荡运动有所增大。浮码头在计算工况下，缆绳受力较大，在某些工况条件下超出了国际系缆力标准的要求，旁靠散货船的缆绳在计算工况下均未超标，满足要求。研究结果为浮码头系泊系统的设计及工程运营提供理论参考。     

基于未确知测度理论的隧道施工瓦斯灾害风险评价

选取煤层厚度、煤层瓦斯含量、回风流平均瓦斯浓度、相对瓦斯涌出量、岩石类型、连通封闭性、深度值、隧道跨度、隧道长度、通风风速和涌水量等11项瓦斯灾害指标作为隧道施工瓦斯灾害风险评价指标体系,并建立各指标的等级标准。将序关系分析法(G1)和反熵权法(AEW)运用拉格朗日乘子法确定组合权重,构建各指标的单指标测度函数,并计算出各指标的综合测度评价向量。为了优化未确知测度置信度识别准则,引进集对分析(SPA)关联系数确定各隧道的瓦斯灾害风险等级。并对24个瓦斯隧道进行瓦斯灾害评价,并和FDA法评价结果和现场实测结果进行对比,精度达到91.7%,基本符合实际情况,表明了该评价方法合理有效,可为隧道施工瓦斯灾害评价提供理论参考。     

On the fundamental diagram for freeway traffic: A novel calibration approach for single-regime models

The speed-density or flow-density relationship has been considered as the foundation of traffic flow theory. Existing single-regime models calibrated by the least square method (LSM) could not fit the empirical data consistently well both in light-traffic/free-flow conditions and congested/jam conditions. In this paper, first, we point out that the inaccuracy of single-regime models is not caused solely by their functional forms, but also by the sample selection bias. Second, we apply a weighted least square method (WLSM) that addresses the sample selection bias problem. The calibration results for six well-known single-regime models using the WLSM fit the empirical data reasonably well both in light-traffic/free-flow conditions and congested/jam conditions. Third, we conduct a theoretical investigation that reveals the deficiency associated with the LSM is because the expected value of speed (or a function of it) is nonlinear with regard to the density (or a function of it).     

Modelling users’ behaviour in inter-urban carsharing program: A stated preference approach

In this paper, the effects of a inter-urban carsharing program on users’ mode choice behaviour were investigated and modelled through specification, calibration and validation of different modelling approaches founded on the behavioural paradigm of the random utility theory. To this end, switching models conditional on the usually chosen transport mode, unconditional switching models and holding models were investigated and compared. The aim was threefold: (i) to analyse the feasibility of a inter-urban carsharing program; (ii) to investigate the main determinants of the choice behaviour; (iii) to compare different approaches (switching vs. holding; conditional vs. unconditional); (iv) to investigate different modelling solutions within the random utility framework (homoscedastic, heteroscedastic and cross-correlated closed-form solutions). The set of models was calibrated on a stated preferences survey carried out on users commuting within the metropolitan area of Salerno, in particular with regard to the home-to-work trips from/to Salerno (the capital city of the Salerno province) to/from the three main municipalities belonging to the metropolitan area of Salerno. All of the involved municipalities significantly interact each other, the average trip length is about 30 km a day and all are served by public transport. The proposed carsharing program was a one-way service, working alongside public transport, with the possibility of sharing the same car among different users, with free parking slots and free access to the existent restricted traffic areas. Results indicated that the inter-urban carsharing service may be a substitute of the car transport mode, but also it could be a complementary alternative to the transit system in those time periods in which the service is not guaranteed or efficient. Estimation results highlighted that the conditional switching approach is the most effective one, whereas travel monetary cost, access time to carsharing parking slots, gender, age, trip frequency, car availability and the type of trip (home-based) were the most significant attributes. Elasticity results showed that access time to the parking slots predominantly influences choice probability for bus and carpool users; change in carsharing travel costs mainly affects carpool users; change in travel costs of the usually chosen transport mode mainly affects car and carpool users.     

Stability of transportation networks under adaptive routing policies

Growing concerns regarding urban congestion, and the recent explosion of mobile devices able to provide real-time information to traffic users have motivated increasing reliance on real-time route guidance for the online management of traffic networks. However, while the theory of traffic equilibria is very well-known, fewer results exist on the stability of such equilibria, especially in the context of adaptive routing policy. In this work, we consider the problem of characterizing the stability properties of traffic equilibria in the context of online adaptive route choice induced by GPS-based decision making. We first extend the recent framework of “Markovian Traffic Equilibria” (MTE), in which users update their route choice at each intersection of the road network based on traffic conditions, to the case of non-equilibrium conditions, while preserving consistency with known existence and uniqueness results on MTE. We then exhibit sufficient conditions on the network topology and the latency functions for those MTEs to be stable in the sense of Lyapunov for a single destination problem. For various more restricted classes of network topologies motivated by the observed properties of travel patterns in the Singapore network, under certain assumptions we prove local exponential stability of the MTE, and derive analytical results on the sensitivity of the characteristic time of convergence to network and traffic parameters. The results proposed in this work are illustrated and validated on synthetic toy problems as well as on the Singapore road network with real demand and traffic data.     

冰雪条件下中国驾驶员跟驰行为及模型研究

分析驾驶员在冰雪条件下的驾驶行为特性，建立考虑驾驶员行为特性的跟驰模型，有助于丰富现有交通流理论.通过招募驾驶员开展实车跟驰试验，对比分析正常条件与冰雪条件下的驾驶行为差异.进而基于任务难度均衡理论构建包含人类因素参数的任务难度模块，引入改进后的智能驾驶员模型，并采用车辆轨迹数据对模型进行标定和有效性验证.研究表明：驾驶员在跟驰行驶过程中受外界刺激及自身驾驶能力影响时会对车辆行驶状态进行动态调整，试图保持期望间距，且速度与前车一致的状态；冰雪条件下驾驶员采取风险补偿行为，其车头时距波动幅度较正常条件收窄，模型引入人类因素参数可以较好地描述其差异性. 模型有效性验证表明，新模型在6个仿真场景中的表现都优于传统智能驾驶员模型，且表现出更好的鲁棒性.研究结果可为冰雪条件下的交通管理措施制定提供理论支持.