车桥系统气动特性的节段模型风洞试验研究

侧向风作用下的车桥耦合振动分析需要考虑相互气动影响的车辆和桥梁各自的气动参数。为考虑车辆和桥梁的相互气动影响,在常规桥梁节段模型三分力测试装置的基础上研制了一种三分力分离装置———交叉滑槽系统。该系统利用环形滑槽和直线滑槽交叉点位置的变化来调整车辆和桥梁间的相对几何关系,并能实现车桥系统的同轴转动,从而方便地进行不同攻角情况下气动力的测试。利用交叉滑槽系统通过节段模型风洞试验对车桥系统的气动特性进行了多工况对比研究,讨论了车桥系统的雷诺数效应,分析了车桥间的相互气动作用,比较了车辆在桥上位置的影响。试验结果表明,基于交叉滑槽系统的节段模型风洞试验测试是可行的;车桥间的相互气动作用对车辆和桥梁的气动力有较明显的影响。     

基于滞回分配的VBR视频流量带宽管理方案

基于VBR视频流量预测提出了一种新的动态带宽分配算法———滞回算法。与Girish提出的门限算法和Youssef提出的基于GOP场景检测的带宽分配方案相比,对缓存尺寸的需求、信元丢失率等性能有明显提高。大量的仿真表明,该算法能够以较低的开销(带宽重分配次数百分比≤2%)同时兼顾了CLR和带宽利用率,而且只有在缓存队长超过迂回门限时才触发带宽重分配过程,有利于在线实现。     

涡轮增压器进气旁通再循环系统的研究

通过对增压器压气机进气旁通再循环系统不同环槽结构、环槽位置的设置,验证其对压气机性能的影响程度,从而优化压气机进气旁通再循环系统的结构参数,为拓宽增压器压气机的适用流量范围提供依据。     

考虑健康损失的路阻模型的构建

运用高斯烟羽模型计算机动车尾气排放量,然后利用支付意愿法定量分析健康损失,同时考虑延误和健康损失构建考虑健康损失的路阻模型.根据实例,分别使用Transcad和新的路阻模型计算出2个路阻,并进行交通分配.结果 显示2次交通分配的路网流量不同,表明考虑健康损失的路阻模型影响了人们的出行选择,可有效解决主干路拥挤,增加次干...     

基于稳定度指标的分布式驱动车辆转向稳定性控制研究

针对装有轮毂电机的分布式驱动车辆,设计了一种车辆稳定性控制系统,该系统包括上层附加横摆力矩决策和下层转矩分配2个层次.基于滑模控制理论设计了上层β-ω联合控制器,并用修正的五参数菱形法划分车辆相平面的稳定域,基于此设计稳定度指标进行失稳判断与控制比例分配,下层基于动态载荷理论分配附加横摆力矩,优化了控制分配效果,在MA...     

冷补沥青混合料和易性分析与评价方法

坑槽损害是沥青路面破坏的主要形式之一。冷补沥青混合料作为一种使用方便、环境适应能力强的修补材料,被广泛采用。该文对影响冷补料和易性(或工作性)的各种因素做了深入分析,并针对冷铺料和易性的各种评价方法和评价指标进行了对比和分析。     

农村公路资金渠道配置评价的相对标度法

为评判农村公路资金渠道配置的相对合理性,在分析中国农村公路建设和养护资金渠道基础上,提出资金渠道配置评价的相对标度法。利用相对标度计算各资金渠道的重要度(权重),定义一个"标准"地区,确定标志值,估计反映各渠道配置相对合理性的匹配系数并求和,给出中国农村公路建设和养护资金主要渠道的权重参考值。实例计算结果表明:该方法简单、实用,且具有很强的灵活性,可用来优化农村公路资金渠道配置。     

故障区段判断和隔离方法

本文简要介绍了配线自动化系统中故障区段判断和隔离方法的基本原理,并论述了该方法的实施步骤。微机综合保护测控装置的直接I/O功能,使得将该方法用于地铁供电系统中成为可能。     

Modeling household interactions in daily in-home and out-of-home maintenance activity participation

The activity travel patterns of individuals in a household are inter-related, and the realistic modeling of activity-travel behavior requires that these interdependencies be explicitly accommodated. This paper examines household interactions impacting weekday in-home and out-of-home maintenance activity generation in active, nuclear family, households. The in-home maintenance activity generation is modeled by examining the duration invested by the male and female household heads in household chores using a seemingly unrelated regression modeling system. The out-of-home maintenance activity generation is modeled in terms of the decision of the household to undertake shopping, allocation of the task to one or both household heads, and the duration of shopping for the person(s) allocated the responsibility. A joint mixed-logit hazard-duration model structure is developed and applied to the modeling of out-of-home maintenance activity generation. The results indicate that traditional gender roles continue to exist and, in particular, non-working women are more likely to share a large burden of the household maintenance tasks. The model for out-of-home maintenance activity generation indicates that joint activity participation in the case of shopping is motivated by resource (automobiles) constraints. Finally, women who have a higher propensity to shop are also found to be inherently more efficient shoppers.     

Schedule-based transit assignment model with vehicle capacity and seat availability

In this paper, we propose a new schedule-based equilibrium transit assignment model that differentiates the discomfort level experienced by sitting and standing passengers. The notion of seat allocation has not been considered explicitly and analytically in previous schedule-based frameworks. The model assumes that passengers use strategies when traveling from their origin to their destination. When loading a vehicle, standing on-board passengers continuing to the next station have priority to get available seats and waiting passengers are loaded on a First-Come-First-Serve (FCFS) principle. The stimulus of a standing passenger to sit increases with his/her remaining journey length and time already spent on-board. When a vehicle is full, passengers unable to board must wait for the next vehicle to arrive. The equilibrium conditions can be stated as a variational inequality involving a vector-valued function of expected strategy costs. To find a solution, we adopt the method of successive averages (MSA) that generates strategies during each iteration by solving a dynamic program. Numerical results are also reported to show the effects of our model on the travel strategies and departure time choices of passengers.