沥青混合料嵌锁骨架实验分析

文章借鉴体积法思想和粒子干涉理论,分析了细集料的间隙率与粗集料堆积和捣实状态下间隙率的相对关系,并通过路用性能实验分析,得出骨架嵌锁结构沥青混合料优于规范推荐的沥青混合料的结论,对沥青混合料嵌锁骨架研究具有一定的借鉴意义。     

一种工作流管理系统的模型化简方法

针对大规模复杂工作流管理系统的性能分析问题,将一个基于随机Petri网的模型化简算法应用于实际的工作流管理系统,即首先将工作流管理联盟定义的工作流模型映射为随机工作流网,在随机工作流网的4种基本模型的基础上.利用PH分布对简化之后的模型进行性能分析.通过供应链系统模型的化简与实际情况的比较,验证了本方法能够对大规模复杂随机工作流网的模型进行化简,降低了计算复杂度,同时也为工作流管理系统的性能分析提供了有效的方法.     

The Signs of the Times: Imposing a Globally Signed Condition on Willingness to Pay Distributions

A feature of recent developments in choice models that enable estimation of the distribution of willingness to pay (WTP) is that the sign of the distribution can change over the range. Behaviourally this often makes little sense for attributes such as travel time on non-discretionary travel, despite a growing recognition of positive utility over some travel time ranges. This can in part be attributed to the analytical distribution that is selected (except the cumbersome lognormal), many of which are unconstrained over the full range. Although a number of analysts have imposed constraints on various distributions for random parameters that can satisfy the single-sign condition, these restrictions are, with rare exception, only satisfied for the mean and the standard deviation estimates of a random parameter. When heterogeneity around the mean and/or heteroscedasticity around the standard deviation is allowed for, however, the constraint condition is often not satisfied. Given the popularity of distributions other than the lognormal, in order to satisfy the sign condition under the most general form of parameterisation, we need to impose a global sign condition. In this paper we show how this might be achieved in the context of the valuation of travel time savings for car commuters choosing amongst an offered set of route-specific travel times and costs. We illustrate the impact of the constraint under a globally constrained Rayleigh distribution for total travel time parameterisation, contrasting the evidence with a multinomial logit model and a range of other distributional assumptions within the mixed logit framework. Discussions with Bill Greene, John Rose, Ken Train and especially Juan de Dios Ortuzar have been invaluable as have the comments of referees.     

Analyzing travel time reliability and its influential factors of emergency vehicles with generalized extreme value theory

Travel time reliability is very critical for emergency vehicle (EV) service and operation. The travel time characteristics of EVs are quite different from those of ordinary vehicles (OVs). Although EVs own highest road privilege, they may still experience unexpected delay that results in massive loss to the society. In this study, we employ the generalized extreme value (GEV) theory to measure extremely prolonged travel time and analyze the potential influential factors. First, among three GEV distributions, Weibull distributions are found to be the best distribution model according to several goodness-of-fit tests; a new reliability index is derived to measure travel time reliability. Numerical examples demonstrate the advantages of GEV-based reliability index over variance and percentile value in the applications of EV. This index will be of great practicability in the EV operation performance and reliable route choices. Second, we further investigate the potentially influential factors of EV travel time reliability. Results show that link length and left-turn traffic volume may have an adverse impact on the link reliability while more left-turn lanes may increase the travel time reliability. The influential factor study will help us understand the causes of the EV travel time delay and the differences of travel time reliability between OVs and EVs.     

就地热再生技术在国道102线上的应用

以国道102线为例,详细介绍了就地热再生的室内试验设计及现场施工过程。热再生技术的经济、社会及环保意义十分明显,对创建节能减排及环保型社会也具有十分重大的意义。     

Probe vehicle based real-time traffic monitoring on urban roadways

Travel time estimation and prediction on urban arterials is an important component of Active Traffic and Demand Management Systems (ATDMS). This paper aims in using the information of GPS probes to augment less dynamic but available information describing arterial travel times. The direction followed in this paper chooses a cooperative approach in travel time estimation using static information describing arterial geometry and signal timing, semi-dynamic information of historical travel time distributions per time of day, and utilizes GPS probe information to augment and improve the latter. First, arterial travel times are classified by identifying different travel time states, then link travel time distributions are approximated using mixtures of normal distributions. If prior travel time data is available, travel time distributions can be estimated empirically. Otherwise, travel time distribution can be estimated based on signal timing and arterial geometry. Real-time GPS travel time data is then used to identify the current traffic condition based on Bayes Theorem. Moreover, these GPS data can also be used to update the parameters of the travel time distributions using a Bayesian update. The iterative update process makes the posterior distributions more and more accurate. Finally, two comprehensive case studies using the NGSIM Peachtree Street dataset, and GPS data of Washington Avenue in Minneapolis, were conducted. The first case study estimated prior travel time distributions based on signal timing and arterial geometry under different traffic conditions. Travel time data were classified and corresponding distributions were updated. In addition, results from the Bayesian update and EM algorithm were compared. The second case study first tested the methodologies based on real GPS data and showed the importance of sample size. In addition, a methodology was proposed to distinguish new traffic conditions in the second case study.     

形位误差的两种分布律

根据形位误差的意义与检测方案,本文推论绝对正态分布和瑞利分布是形位误差的两种基本的分布律,并通过抽样检测与统计检验证实了直线度误差、平面度误差、圆度误差、线轮廓度误差、垂直度误差、对称度误差、圆跳动误差有绝对正态分布律,平行度误差、同轴度误差有绝对正态分布和瑞利分布两种分布律.     

沥青混合料动稳定度试验的分析

我国评价沥青混合料的高温抗车辙能力一般采用车辙板试验,试验指标采用动稳定度。本文主要就动稳定度试验时所采用的试验温度、车辙板厚度、荷载压力、车辙板压实度等进行试验与评价。试验结果表明,车辙板的试验条件对沥青混合料的高温抗车辙性能有很大的影响。     

连续计量系统的工作原理及其在连续式沥青搅拌设备使用上的要求

介绍了连续计量系统的工作原理及其与批量计量方式的区别，并讨论了集料表面积对混合料含量的影响，在此基础上归纳了对连续式沥青搅拌设备使用操作上的要求     

橡胶沥青混合料生产设备

介绍了一种橡胶沥青混合料拌制与输送系统，重点介绍了其主要设备“橡胶沥青混熔机”的工作原理、结构及主要参数，最后给出了油泵与输油管道的计算方法。