A model for national freight flows,distribution centers,empty trucks and urban truck movements

Trucks travel both short distances for local deliveries and long distances for transporting goods across the country. Often their travel behavior is tour-based, they run under tight schedules and under curfew on selected roads. Despite these differences from personal travel, in practice truck models largely follow person travel methods. To overcome this shortcoming, a two-layer truck model is developed for the Chicago Metropolitan Area. Long-distance trucks are driven by commodity flows, with distribution centers, rail yards, marine ports and airports being represented explicitly. Empty trucks are accounted for as well. For the short-distance truck model, a novel parameter estimation method makes use of limited data to derive region-specific parameters. The model is fully operational and validates reasonably well against traffic counts.     

Hydrodynamic forces on a two-dimensional multihull structure in waves: application of the scattering matrix theory

The diffraction and radiation problems of a two dimensional multihull structure were investigated by application of the scattering matrix theory. The scattering matrix theory is widely used to analyze wave interaction problems in various scientific fields. The research is focused on the zeros of the wave exciting force near resonance, which occurs both in the diffraction problem and the radiation problem. At the zeros of the wave exciting force, the wave exciting force for the overall structure is zero, but each demihull undergoes wave excitation. At near-resonant frequencies, the amplitude of the traveling wave between adjacent demihulls becomes very large and the demihulls experience very large wave forces. A number of simple equations for representing the hydrodynamic properties of the multihull structure at the zeros and near-resonant frequencies are obtained. Numerical examples show that these simple equations well explain the hydrodynamic forces and the wave system in the spaces between the demihulls.     

基于三角模糊数的安全评估方法

将系统安全级别划分为5个等级,分别从4个影响因素对系统的安全性进行评估,采用专家打分的方法对系统的安全等级和影响因素进行打分。根据专家权威性的不同构造专家权重矩阵;用三角模糊数将打分结果进行模糊化处理,消除专家的个人偏好;综合可信度矩阵,评价专家打分的可信程度。以地铁供电系统为例,验证了该方法的正确性。     

城市轨道交通移动闭塞列控系统列车追踪间隔研究

目前,基于通信的移动闭塞列控系统作为轨道交通列控系统的主要发展方向,在一定程度上缩短了列车之间的追踪间隔。追踪间隔的计算是列车生成移动授权的前提。列控系统中移动授权的发布由区域控制器来完成。列控系统中由于追踪模式的不同,列车追踪间隔也会有差异,从而影响移动授权生成,影响行车效率。分析了列车移动授权生成原理,研究了列车区间追踪场景下绝对追踪模式和相对追踪模式下的列车追踪间隔,并进行了仿真。仿真分析结果表明:相对追踪模式下列车生成的移动授权更大,可以进一步缩小列车追踪间隔;绝对追踪模式存在最优追踪速度。     

高层框架动力分析刚度矩阵的弯剪层模型

多层框架结构侧向变形主要为层间剪切变形,其刚度矩阵常采用层间剪切模型;高层框架结构,由于框架梁对框架柱约束作用相对较弱,其侧向变形常包含有层间剪切和弯曲两种成分,因此刚度矩阵可采用层间弯剪模型.本文根据高层框架结构变形特点,针对高层框架结构动力分析的刚度矩阵,提出了一种比较简单实用的弯剪层模型.     

从路段流量估计OD交通量的新算法

首先给出了一种增广的用户平衡配流问题的优化模型及求解算法,然后提出了一个从 路段流量估计OD交通量的双层规划棋型及求解算法.由于新方法再生迭代无需计算和存贮路 径流量,只需用到路段流量,因此可以适用于大型城市交通网的OD需求估计向题.     

Real-time traffic estimation using data expansion

This paper presents a method for estimating missing real-time traffic volumes on a road network using both historical and real-time traffic data. The method was developed to address urban transportation networks where a non-negligible subset of the network links do not have real-time link volumes, and where that data is needed to populate other real-time traffic analytics. Computation is split between an offline calibration and a real-time estimation phase. The offline phase determines link-to-link splitting probabilities for traffic flow propagation that are subsequently used in real-time estimation. The real-time procedure uses current traffic data and is efficient enough to scale to full city-wide deployments. Simulation results on a medium-sized test network demonstrate the accuracy of the method and its robustness to missing data and variability in the data that is available. For traffic demands with a coefficient of variation as high as 40%, and a real-time feed in which as much as 60% of links lack data, we find the percentage root mean square error of link volume estimates ranges from 3.9% to 18.6%. We observe that the use of real-time data can reduce this error by as much as 20%.     

线性回归模型的一个新的随机约束岭估计

研究带随机先验信息的线性回归模型，提出一种新的随机约束岭估计，得到新的估计在均方误差矩阵意义下优于混合估计、普通岭估计、随机混合估计（Yalian，2008）和另一随机混合估计（富月，2003）的充要条件。理论结果与数值实验都表明：新的估计在均方误差矩阵意义下的性能是优良的。     

索赔风险的模糊综合与辨识模型的应用

对工程各涉及方来讲,索赔风险的发现与识别既是索赔管理的首要任务,也是一个难点问题。运用索赔风险的模糊综合与辨识模型分析索赔风险,可以迅速而准确地解决这一难题。     

SiC颗粒增强铝基复合材料细观损伤的温度效应

SiC颗粒增强铝基复合材料的宏观力学行为与其微观损伤机理密切相关，随温度的升高，材料力学性能明显下降，SiCD／A356复合材料表现出不同的细观损伤机理．文中对真空双搅拌方法制备的质量分数为20％的SiC颗粒增强铝基复合材料在室温和高温下的细观损伤机制进行了研究，在试样断口上，通过扫描电镜观察到了不同的裂纹萌生和扩展机制，根据不同温度下表现出的不同失效方法，归纳出了复合材料细观损伤的温度效应曲线．研究表明，在室温下复合材料的裂纹萌生以基体撕裂和颗粒断裂为主，高温下其裂纹萌生机制以颗粒脱离和基体撕裂为主．