Floating car based travel times for city logistics

City logistics routing requires time-dependent travel times for each network link. We rely on the concept of Floating Car Data (FCD) to develop and provide such travel times. Different levels of aggregation in the determination of time-dependent travel times from a database of historical FCD are presented and evaluated with regard to routing quality. Furthermore, a Data Mining approach is introduced, allowing for a substantial reduction of the volume of input data required for city logistics routing. The different approaches are investigated and evaluated by a huge amount of FCD collected for the urban area of Stuttgart, Germany. The results show that the Data Mining approach enables efficient provision of time-dependent travel times without a significant loss of routing quality for city logistics applications.     

The unmet travel needs of the older population: a review of the literature

Unmet travel needs can be defined as trips and activities that people need or would like to do more, but for a variety of reasons they are prevented from doing so. This paper provides a critical evaluation of the literature focused on unmet travel needs, with the aim of assessing the scope of existing studies on this topic and better understanding the full context of older people’s mobility. This narrative review identifies how travel needs in later life have been assessed, and the barriers that affect the ability of older people to fulfil these needs. Due to the heterogeneity of older people and differences in research approaches, the analysis of the literature is not conclusive in terms of identifying the real impact of the analysed variables and measures on unrealised mobility. Nevertheless, of the studies analysed, on average at least one-third of older people report unmet travel needs. This situation was found to worsen with age, and women were reported to be more affected than men. The pursuit of leisure, and in particular visiting friends and family, was found to be the activity most associated with unmet travel needs.     

基于相似案例推理的应急物资需求预测方法研究*

为保证突发事件应急救援的高效顺利开展,应急物资需求预测的准确性是应急救援工作的关键环节之一。针对传统应急物资需求预测方法的不足,本文通过考虑特征因素值的不精确性和各特征因素受时间变化的影响,引入了区间数的概念来描述案例的不精确属性和相应的计算方法,运用时间影响因子对特征因素影响权重系数进行调整,获得特征因素的影响权重系数,提出了目标案例关键特征因素与案例间特征因素需相符和相似的条件下,搜索出最佳相似源案例,以解决灾区应急物资需求问题的案例推理方法。最后,以实例分析了该方法的可行性和合理性。可很好地解决信息不完备条件下应急物资需求的预测,为应急决策者提供一定的理论参考依据。     

城市轨道交通站间距优化研究

通过对受站间距影响的城市轨道交通相关指标分析,学习并借鉴国内外城市轨道交通站间距优化方面的成功经验及研究方法,以实际数据作为基础,首先对客流分布和乘客出行时间这两个影响因素进行分析,通过分析认为城市轨道客流随着乘坐距离的变化存在着一个先增后减的函数变化;根据对客流分布以及乘客出行时间的分析,将乘客出行时间成本转化成经济效益指标,将票价收入标准与客流分布进行结合得到地铁票价收入的经济效益;之后结合乘客出行时间的经济效益和票价收入的经济效益按照总收益最大化建立城市轨道交通站间距优化模型,并实施优化计算,碍到理论上的最优站间距.     

停车需求分布的双层规划模型及算法

针对停车需求给定条件下的停车设施选择问题,建立了描述停车设施选择和出行路线选择行为的双层规划模型,并基于在部分增广乘子法中嵌套Frank-Wolfe算法的思路设计了求解模型的有效算法.上层模型在满足停车需求和设施停放车辆数有限条件下,力图最小化实际停车需求分布与期望分布间的差异.下层模型假设出行者路线选择行为遵循用户均衡原则.上下层模型通过设施选择概率函数实现有效关联.部分增广乘子法中嵌套Frank-Wolfe 算法求解上层模型可以有效利用上层模型的单纯形式约束特征.算例分析验证了新模型与算法的有效性.研究结论拓展了现有理论的应用场景,为相关研究提供了新的建模分析思路.     

“杀伤链”对数据链新技术的需求分析

针对信息化战争中以火力打击为目的的“杀伤链”作战样式,论述了数据链技术在其中的应用,就“杀伤链”对数据链新技术的需求进行了分析。     

Computing airfare elasticities or opening Pandora's box

Airfare elasticities are crucial for policy instruments for the stakeholders of tourism industry. Modellers attempting to estimate these elasticities face several challenges in the absence of microeconomic data on consumer preferences. The aim of this paper is to offer a critical analysis of the practice of computing airfare elasticities from tourism demand studies. It identifies and discusses potential sources of measurement errors in the data and drawbacks that investigators face and assesses their implications for the estimated parameters in the respective models. The use of price of crude oil and distance between origin and destination as proxies for transportation costs are evaluated. It is recommended that authors be more systematic in reporting their results. They need to comment on the limitations of their elasticity estimates since these have repercussions on policy recommendations made based on their results.     

大型公园和绿地周边支路断面设计方法研究

大型公园和绿地周边支路除需满足公园、绿地以及周边地块交通集散的基本服务功能外,还需满足节假日等高峰期为市民提供临时停车和应急疏散等辅助功能需求。大型公园和绿地周边支路断面的设计方法,可通过开展规划前期调研,分析交通出行特征来确定道路功能定位和需求;然后对设计年限内机动车、非机动车和行人的工作日、节假日或特殊活动日进行交通流量预测,再进行路段通行能力分析和服务水平评价,从而确定车道数和宽度规模,拟定断面各技术标准和参数;最后提出断面多方案比选,经技术、经济等综合分析后确定最终方案。     

不同承台结构形式对大跨刚构桥抗震性能的影响分析

为探究高烈度区不同承台结构形式对大跨预应力混凝土连续刚构桥梁抗震性能的影响,以某座108 m+188 m+108 m双幅双肢薄壁墩连续刚构桥为工程背景,采用时程分析方法对该桥进行三向激励,对比研究纵联横离式、纵联横联式、纵离横离式、纵离横联式共4种承台结构形式对两幅桥墩柱和桩基内力、位移动力响应的影响。结果表明：采用纵离的承台形式在纵向地震下,桩基内力需求降低了30%~70%,墩柱内力需求降低了26%~33%,且与纵联的承台形式相比,桩身拉力减少较多;采用横联的承台形式在横向地震下,桩身轴力需求降低11%,且基本不存在拉力,桩基和墩柱的内力响应虽分别增大30%和16%,但与纵向减小量的相比,增加幅度较小。因此,为提高特大桥全寿命周期的安全性和经济性,对于以地震响应为控制设计核心要素的高烈度区大跨连续刚构桥梁,建议采用纵离横联式的承台结构形式。