基于“三阶段法”的高速铁路短期运量预测

考虑到我国未来年度的OD分布预测中的路网构成变化、区域经济布局变动、区域经济增长速度差异等一些具有时变性和特殊性因素,采用在“四阶段法”运量预测基础上改进而成的“三阶段法”进行高速铁路短期客运量预测。首先采用组合预测模型进行趋势运量预测,然后采用多元LOGIT模型进行方式分担,最后采用弹性系数诱增模型进行诱增运量预测。以京沪高铁为例,采用“三阶段法”预测了2014年和2015年京沪高铁本线及跨线单向客流量。     

大型活动交通分布预测方法比较及应用

大型活动的举办势必会对城市交通产生影响,为更好地制定交通管理措施,需要对大型活动进行交通需求预测。四阶段法是交通需求预测的常用方法,交通分布预测是四阶段法的第二阶段。通过对交通分布预测常用三种方法的比较分析,说明三种方法的优缺点,并通过三种方法在唐山世园会举办期间交通分布预测中的应用比较,得到交通需求总量。     

自升式海上风电安装船的模型试验分析研究

主要阐述了具备自航能力的自升式海上风电安装船在船型设计阶段的模型试验和计算分析,为相似船型和类似海洋工程装备的设计研究提供了参考.     

管幕冻结法积极冻结方案模型试验研究

港珠澳大桥珠海连接线拱北隧道工程预支护体系采用管幕法与人工冻结技术相结合的全新"管幕冻结法"施工。根据工程实际情况,首次提出了在管幕钢管内部布置"圆形主力冻结管"、"异形加强冻结管"和"升温盐水限位管"三种特殊管路构成的冻结方案。为了研究该冻结方案的有效性与可控性,进行了大型物理模型试验。文章主要介绍了模型试验概况,重点分析了开挖前积极冻结阶段冻结的试验效果。试验结果表明,积极冻结阶段冻土帷幕发展显现了预期规律,冻结效果显著;管幕间形成良好的冻土帷幕,可确保良好的止水效果。     

Euro-NCAP更新对乘用车安全评价的影响

为使我国乘用车满足2013版Euro-NCAP要求,分析了2013年实施的新版Euro-NCAP评价规则,并总结了更新点,同时介绍了2014-2017年Euro-NCAP的更新规划内容及其关注点.基于评价规则的更新内容,采用对比分析的方法,将已进行过2012版E-NCAP试验的车辆作为研究对象,通过DYNA及MADYMO软件仿真分析,获得了该车在2013版E-NCAP评价规则中的表现,基于该车的评价结果,探讨新版评价规则对未来汽车安全开发的星级评价影响,为新车安全性能开发提供参考.     

汽车控制器的热设计研究

建立了某混合动力汽车控制器的热设计仿真分析模型,并通过温度测量试验验证了该模型的有效性。基于所建立的热设计模型,分析研究了控制器PCB板不同结构对其最大温升的影响程度。根据分析结果,推荐混合动力汽车控制器的PCB板应做成板厚为1.6 mm的4层板,覆铜面积和1oz的覆铜厚度应大于50%。     

基于STAR-CCM＋的汽车除霜分析

汽车空调的除霜性能直接影响到驾驶员的视野情况及驾驶安全.利用基于有限体积方法的CFD软件STAR-CCM＋对汽车空调除霜系统进行设计和优化,分别探讨了玻璃内表面第1层网格厚度及模型计算域的大小处理对计算结果的影响.稳态除霜分析时,应先确定第1层网格厚度,可建立不完整乘员舱模型计算;瞬态除霜分析时,应建立完整乘员舱模型计算.在整车开发过程中,要综合考虑除霜分析的精度和周期,采用不同的方法建立计算模型来适应不同的开发阶段,以满足其项目要求.     

Short-Term Highway Traffic State Prediction Using Structural State Space Models

This research proposes a short-term highway traffic state prediction method based on a structural state space model, with the intention to provide a robust approach for obtaining accurate forecasts of traffic state under both recurring and non-recurring conditions. True traffic state is decomposed to three components, namely, regular traffic pattern, structural deviation, and random fluctuation. Particularly, the structural deviation term reflects the change of true traffic state from regular (historical) pattern, due to unexpected capacity reduction and/or demand variations. A polynomial trend is adopted to describe the temporal evolution of structural deviations across different time intervals. We derive an analytical form of structural deviations in a single bottleneck case based on cumulative flow count diagrams. The proposed model is incorporated in a Kalman filtering-based algorithmic framework, together with an adaptive scheme for determining the variances of random errors. A set of numerical experiments was conducted on two test beds in the northern Taiwan highway network. Experimental results show that the proposed approach is particularly superior to an ordinary Kalman filtering method presented in the literature under non-recurring conditions, highlighting the advantage of combining both the polynomial trend model and historical pattern into the proposed short-term traffic state prediction approach.     

Model Test Study on’Lost’Deformation and Corresponding Control Measures in Soft Rock Tunnels with Extremely High Ground Stress北大核心CSCD

In order to study the laws of core rock deformation and’lost’rock deformation in soft rock tunnels with high ground stress, the deformations of core rocks in front of the working face and surrounding rocks are monitored by model test method, and the tunnel excavation process is simulated in detail under different high ground stress levels and working conditions with/without lining. The results show that: (1) the ground stress plays a key role in determining the installation time of soft rock tunnel support; (2) the advance deformation within 0.5D in front of the face accounts for about 2/3 of the total advance deformation; (3) the’lost’deformation behind the tunnel face has a great impact on the monitoring and measurement. With a certain high ground stress, there is a power function relationship between the’lost’deformation and the distance from the tunnel face. With the high ground stress greater than 20 MPa, it has little impact on the’lost’deformation; (4) in order to effectively control the advance deformation in soft rock tunnels with high ground stress, it is necessary to reinforce the core rock mass within 0.5D in front of the tunnel face. For the core rock mass within 0.5D~1D in front of the tunnel face, the reinforcement depends on the actual situation. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

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研究先进出行者信息系统(ATIS)环境下道路网络系统流量的随机动态变化,有利于实现ATIS在网络系统中的进一步优化配置.在出行者经验积累过程基础上,引入ATIS作用下的认知更新过程,将路网系统的路径流量明确视为随机变量,提出了一个基于认知更新的随机动态分配模型.证明了该模型产生的路径流量渐近收敛于一个平稳概率分布.在算例网络中验证了模型的可行性,模拟有ATIS和无ATIS两种情形下路径流量的随机动态变化.结果表明,两种情形路径流量均收敛于平稳概率分布.前者的平均流量近似于随机用户平衡(SUE),而后者的平均流量不是平衡流量,但其网络总费用要低于前者.