地铁火灾研究

对世界各国的地铁火灾进行分析,阐述了地铁火灾产生的原因和危险性,介绍了地铁设计中的通风空调系统,探讨了火灾研究的手段,并通过实例进行模拟与分析。     

某静音型电源车通风系统设计与散热分析

针对静音型电源车通风散热要求,计算了车舱内柴油发电机组的散热量和整车通风量,根据通风量的大小对电源车通风散热结构进行了设计,包括进、排风口的大小、位置以及进、排风方式,并利用计算流体力学（ Computation-al Fluid Dynamics , CFD）方法对通风散热效果进行了仿真计算,分析了车舱内流场和柴油发电机组的温度场分布。结果表明,所使用的计算和设计方法是合理的,车舱的通风散热能够满足要求。     

汽车挡风玻璃除霜性能数值模拟

利用CFD方法建立汽车除霜性能动态模型,并量化了除霜器在挡风玻璃附近的气流速度场,对挡风玻璃除霜时间及效果进行了探讨,为汽车挡风玻璃除霜效果模拟工程提供了参考。     

多轴混合动力特种车辆空气动力学特性分析与改进设计

建立某多轴混合动力特种车辆整车外流场仿真模型,采用计算流体力学方法分析整车外流场特性.根据分析结果对驾驶室进气格栅、驾驶室与货箱之间的上部连接、驾驶室下部进风口三个部位进行优化设计.在优化设计过程中,特别关注提升各车桥分布式驱动电机的散热效果,并根据局部外流场特性确定车桥处的电机风扇朝向布置.结果表明,优化后的整车风阻...     

Longer-term changes in mode choice decisions in Chennai: a comparison between cross-sectional and dynamic models

The rapid and continuing changes in travel and mobility needs in India over the last decade necessitates the development and use of dynamic models for travel demand forecasting rather than cross-sectional models. In this context, this paper investigates mode choice dynamics among workers in Chennai city, India over a period of five years (1999–2004). Dynamics in mode choice is captured at four levels: exogenous variable change, state-dependence, changes in users’ sensitivity to attributes, and unobserved error terms. The results show that the dynamic models provide a substantial improvement (of over 500 log-likelihood points and ρ² increases from 44% to 68%) over the cross-sectional model. The performance was compared using two illustrative policy scenarios with important methodological and practical implications. The results indicate that cross-sectional models tend to provide inflated estimates of potential improvement measures. Improving the Level of Service (LOS) alone will not produce the anticipated benefits to transit agencies, as it fails to overcome the persistent inertia captured in the state-dependence factors. The results and models have important applications in the context of growing motorization and congestion management in developing countries.

机车车辆与线路最佳匹配设计原理、方法及工程实践

提出了采用系统设计思想实现机车车辆与线路最佳匹配设计的理念,论述了匹配设计的基本原理与设计方法。指出:机车车辆系统和线路系统在动态性能设计上要相互适应、相互匹配。无论设计主体对象是机车车辆还是线路,都必须将对方视为主体对象的动态环境,通过机车车辆—轨道耦合动力学理论方法考虑对方的动态影响因素,进行主体对象动力性能优化设计,同时分析评估主体设计对象对另一系统的动态作用影响,再根据动态作用影响的评估结果改进主体对象结构设计参数,如此反复,直到整体系统动态性能最优为止。由此开发了机车车辆—轨道耦合动力学仿真设计技术平台。经在若干铁路重大工程线路设计中运用,取得了显著成效。     

缓解快速线路曲线入口结构性晃车问题的探讨

为减小列车由直线进入曲线时车轮对轨道产生的横向冲击力，对曲线入口的结构性晃车问题进行了分析，进而对轮轨游间及相关技术标准进行了讨论，从机车车辆和线路2个方面提出了建议。     

客运专线道岔前后轨道刚度过渡段动力学研究

客运专线有砟轨道及无砟轨道道岔区的轨道刚度约是区间线路的2~3倍,差别较大,均需要通过设置轨道刚度过渡段来减轻轮轨动力作用,改善行车的平稳性。从保证行车安全性和舒适性、降低对轨下基础动力冲击作用的角度,提出轨道刚度过渡段动力性能的评价指标以及过渡段合理长度的确定方法,既要满足钢轨挠度变化率小于0.3 mm.m-1的要求,还应满足轮轨垂向力衰减距离以及车体加速度衰减时间的要求。应用车辆-轨道耦合动力学模型与理论,进行客运专线道岔前后轨道不同刚度过渡段方案的动力学分析。结果表明:客运专线道岔前后轨道刚度过渡段可采用轨道刚度分级过渡的方法,每一级刚度取15个轨枕间距,并依据实际线路轨道刚度差的大小在3~6级中完成过渡。     

两栖空气动力艇悬挂系统设计仿真

为了提高两栖空气动力艇在冰雪路面上的通过能力,设计了一种用于两栖空气动力艇的新型独立悬挂系统。在CATIA中建立独立悬挂系统的几何模型,通过CAD/CAE软件的数据接口技术将其导入ADAMS/VIEW环境中进行典型工况条件下的动力学仿真,根据仿真结果对独立悬挂系统进行动力学分析,确定了减震器的阻尼特性以及橡胶衬套的刚度,并验证了该系统中各个构件之间的运动关系。     

Hierarchical travel demand estimation using multiple data sources: A forward and backward propagation algorithmic framework on a layered computational graph

Aiming to develop a theoretically consistent framework to estimate travel demand using multiple data sources, this paper first proposes a multi-layered Hierarchical Flow Network (HFN) representation to structurally model different levels of travel demand variables including trip generation, origin/destination matrices, path/link flows, and individual behavior parameters. Different data channels from household travel surveys, smartphone type devices, global position systems, and sensors can be mapped to different layers of the proposed network structure. We introduce Big data-driven Transportation Computational Graph (BTCG), alternatively Beijing Transportation Computational Graph, as the underlying mathematical modeling tool to perform automatic differentiation on layers of composition functions. A feedforward passing on the HFN sequentially implements 3 steps of the traditional 4-step process: trip generation, spatial distribution estimation, and path flow-based traffic assignment, respectively. BTCG can aggregate different layers of partial first-order gradients and use the back-propagation of “loss errors” to update estimated demand variables. A comparative analysis indicates that the proposed methods can effectively integrate different data sources and offer a consistent representation of demand. The proposed methodology is also evaluated under a demonstration network in a Beijing subnetwork.