基于无人机的高层住宅最后“一百米”配送优化

针对城市高层住宅顾客对上门配送服务的需求，借助无人机停放平台，考虑包裹异质性以及无人机在不同配送阶段的精确能耗，构建以无人机飞行成本和能耗成本最小为目标，以无人机容量、电池组容量等为约束的高层住宅无人机上门配送模型，解决“垂直位置最后一百米配送”问题。基于此模型，设计带变邻域下降(VND)搜索的混合蚁群算法(HACO-VND)，引入4个算子进行变邻域下降搜索，为了提高算法的求解性能，提出两种局部搜索算子组合，根据顾客点数量使用不同的算子组合。实验结果表明，HACO-VND算法较CPLEX在求解精度与求解时间方面更优，特别是在大中型算例中表现出较佳性能。参数分析表明，高层住宅楼层数越多，无人机单次 飞行的能耗利用率越大，无人机容量与电池组容量共同对配送方案产生影响。为以后无人机送货上门服务方面的研究提供参考和思路。     

Towards measures of affective and eudaimonic subjective well-being in the travel domain

Studies of the connections between transportation and subjective well-being (SWB) require a clear understanding of the conceptual composition of travel-related SWB as well as psychometric instruments to measure these complex topics. Well-established psychological scales for measuring general SWB—including both hedonic (affective and cognitive) and eudaimonic aspects—are difficult to adapt or have yet to be tested in the travel domain. Existing measures of travel liking and travel satisfaction are somewhat inadequate for these purposes, especially for representing eudaimonia. Using a questionnaire survey of 680 commuters in the Portland, Oregon, region, exploratory and confirmatory factor analyses examined responses to a total of 42 items. Results suggested four-factor measurement models of both travel affect (Enjoyment, Attentiveness, Distress, and Fear) and travel eudaimonia (Health, Competence, Autonomy, and Security). Despite some limitations and opportunities for enhancements, these models show promise as ways of measuring affective and eudaimonic SWB in the travel domain for future studies and travel surveys.

     

Socioeconomic and usage characteristics of transportation network company (TNC) riders

Transportation - The widespread adoption of smartphones followed by an emergence of transportation network companies (TNC) have influenced the way individuals travel. The authors use the 2017...     

Costs of air pollutants from shipping: a meta-regression analysis

ABSTRACT

This study estimated the external cost of air pollution from shipping by means of a meta-regression analysis, which has not been made before. Three pollutants, which were included in most of the primary studies, were considered: nitrogen oxides (NO_x), sulphur dioxides (SO₂) and particulate matters with a diameter of max 2.5 micrometres (PM_2.5). All primary studies included damages of health and a majority added impacts on agriculture and estimated the cost of air pollutants by transferring cost estimates from studies on costs of air emissions from transports in Europe. Different regression models and estimators were used and robust results were found of statistically significant emission elasticities of below one, i.e. total external costs increase by less than 1% when emissions increase by 1%. There was a small variation between the pollutants, with the highest elasticity for PM_2.5 and lowest for NO_x. Calculations of the marginal external cost of the pollutants showed the same pattern, with this cost being approximately six times higher for PM_2.5 than for the other pollutants. Common to all pollutants was that the marginal external cost decreases when emission increases. Another robust result was a significant increase in the cost of studies published in journals compared with other publication outlets. These findings point out some caution when transferring constant external unit cost of air pollutant from shipping, which is much applied in the literature, and the cost functions estimated in this study could thus provide a complementary transfer mechanism.     

基于聚类站点客流公共特征的轨道交通车站精细分类

已有城市轨道交通车站分类多基于定性分析，不能满足精细化设计和运营的需要。本文提出一种基于聚类站点公共特征的站点精细分类方法。首先，将来源于AFC(Automatic Fare Collection)的进站客流量数据处理为时间序列数据，并基于K-Means++算法对各个站点的客流量进行聚类；其次，建立客流量聚类结果与土地利用特征多维参数的拟合方程，计算获得居住密集型、工作就业型以及区域中心型等5种大类站点的客流量公共特征。在此基础上，充分考虑属于同一大类站点不同站点的细分特性，使用5类客流量公共特征比重组合精细描述具体站点类型。 实例结果表明，使用本文提出的精细分类方法计算得到的每个站的客流量拟合值与真实客流值间的平均绝对百分比误差控制在14%以内，说明该分类方法具有可行性。     

盾构隧道壁后注浆中“定时浆”试验研究

我国盾构隧道广泛使用凝结时间较长的单液浆，但由于注入后不能及时凝结常常引发管片上浮、浆液流失等工程问题。针对这些问题提出“定时浆”的概念。通过在单液硬性浆中添加氯化铝溶液与水玻璃，基于浆液的胶结时间、流动度、28 d强度等指标研究了“定时浆”的配方。结果表明： 1）通过先加入氯化铝溶液再加入水玻璃的方法，可以实现浆液“定时”凝结； 2）在硬性浆中掺加0.50%~0.75%的氯化铝溶液、1.00%~1.25%的水玻璃，可以达到良好的定时效果； 3）通过简单的注浆设备改造可以形成“双液单注”的定时注浆工艺。     

《电加热道岔融雪系统设备》TB/T3539-2018解读

解读《电加热道岔融雪系统设备》与《客运专线铁路信号产品暂行技术条件汇编——电加热道岔融雪系统设备》标准的共性部分,并从编制背景、标准定位、技术要求、试验方法和检验规则等方面,分析两者之间的差异性.     

浅谈青藏线转辙设备的养护与维修

本文根据CTS2轨枕式转辙机本身的特点以及青藏铁路的管理模式，从养护、维修的角度，简要说明了CTS2轨枕式转辙机需要的养护工作量、故障处理方法、维修特点及在施工中要注意的问题。     

深基坑支护施工初探

1前言 为减少铁路运输运能损失,顶进施工法因其诸多优点被大量运用到既有线增建箱形桥的工程中.准备工作坑是其法施工中必不可少的工序,而在市区项目中因受地貌控制,箱形桥预制工作坑往往都成深基坑形式,支护自然成为施工保安全和进度的重要环节,应对经济有效地基坑支护方法进行研究.本文就杭州市望江路下穿铁路箱形桥工程的基坑支护施工方法作一粗浅探讨.