A multi‐objective approach to the parcel express service delivery problem

Parcel express service in many countries assumes door‐to‐door delivery of parcels and small packages in the fastest possible way. Delivery companies usually organize hub delivery networks, as flows between hubs are characterized by the economy of scale effect. At hubs, parcels are exchanged across vans, trucks, and planes. To organize parcel delivery in a specific region, the parcel delivery company must make appropriate decisions about the total number of parcel delivery hubs, their locations, and the allocation of demand for facilities' services to facilities. These issues are modeled in this paper as a multi‐objective problem. The model developed is based on compromise programming and genetic algorithms. We also demonstrate in the paper an interactive manner in which a defined problem can be solved. The proposed model could be implemented in large‐scale networks. The paper also shows a case study of parcel delivery service in Serbia. Copyright © 2013 John Wiley & Sons, Ltd.     

Time-dependent green vehicle routing problem with stochastic vehicle speeds: An approximate dynamic programming algorithm

This paper addresses a Time Dependent Capacitated Vehicle Routing Problem with stochastic vehicle speeds and environmental concerns. The problem has been formulated as a Markovian Decision Process. As distinct from the traditional attempts on the problem, while estimating the amount of fuel consumption and emissions, the model takes time-dependency and stochasticity of the vehicle speeds into account. The Time Dependent Capacitated Vehicle Routing Problem is known to be NP-Hard for even deterministic settings. Incorporating uncertainty to the problem increases complexity, which renders classical optimization methods infeasible. Therefore, we propose an Approximate Dynamic Programming based heuristic as a decision aid tool for the problem. The proposed Markovian Decision Model and Approximate Dynamic Programming based heuristic are flexible in terms that more environmentally friendly solutions can be obtained by changing the objective function from cost minimization to emissions minimization. The added values of the proposed decision support tools have been shown through computational analyses on several instances. The computational analyses show that incorporating vehicle speed stochasticity into decision support models has potential to improve the performance of resulting routes in terms of travel duration, emissions and travel cost. In addition, the proposed heuristic provides promising results within relatively short computation times.     

Experience sampling in and around airports. Momentary subjective wellbeing,airports, and aviation noise in England

We explore the wellbeing of people in and around English airports using real-time data from a large spatial positioning experience sampling dataset (Mappiness). We analyze the association between subjective wellbeing reported in the moment and aviation, in terms of airport location, aircraft noise, and activities within airports. This is the first time that a large Experience Sample Method (ESM) of momentary wellbeing measurements has been used to quantify the associations between aviation and subjective wellbeing. Being within areas of high levels of aircraft noise is associated with lower levels of happiness and relaxation. Those surveyed in proximity to airports report significantly lower levels of relaxation. These findings have important implications to policy. Exploiting the panel nature of the ESM data provides the strongest causal claims to date of the negative association between aviation activities and subjective wellbeing. The Mappiness application also allows us to assess the association between airports and wellbeing on those inside them, and divide activities within airports between those who work there and those who are passing through for travel purposes, as well as the effects of aircraft noise beyond airports. This gives us a broader insight into the range of impacts, both positive and negative, that aviation has on peoples’ momentary wellbeing, which may be used to inform aviation noise mitigation and compensation policies in the future.     

Adding a new station and a road link to a road–rail network in the presence of modal competition

In this paper we study the problem of locating a new station on an existing rail corridor and a new junction on an existing road network, and connecting them with a new road segment under a budget constraint. We consider three objective functions and the corresponding optimization problems, which are modeled by means of mixed integer non-linear programs. For small instances, the models can be solved directly by a standard solver. For large instances, an enumerative algorithm based on a discretization of the problem is proposed. Computational experiments show that the latter approach yields high quality solutions within short computing times.     

一种舰船直流区域配电系统故障定位方法

短路故障对舰船电力系统危害极大,必须对系统中出现的短路故障迅速定位并及时排除,以减少损失。针对直流区域配电这一新型配电方式,提出了一种采用故障特征集匹配来进行故障定位的方法。经仿真试验验证,该方法可以快速定位故障位置,为及时排除故障保证舰船电力系统的安全运行提供了必要的技术支持。     

圆形区域划分的k-匿名位置隐私保护方法

用户位置信息的准确度反比于用户的隐私保护安全系数k（privacy protection level）,正比于查询服务质量;为了平衡由位置信息的准确性引起的隐私保护安全与查询服务质量之间的矛盾,借助位置k-匿名模型,提出了圆形区域划分匿名方法.将整个区域划分为相切圆及相邻的4个相切圆的顶点组成的曲边菱形形成的组合区域,当用户位置区域含有的用户数量不满足隐私保护安全系数要求时,利用区域扩充公式得到合适的匿名区域.实验结果表明该方法减小了匿名区域的面积,提高了相对匿名度,从而平衡了k与QoS的矛盾;并从匿名成功率、服务质量和信息处理时间3个角度确定了基于位置k-匿名隐私保护方法的评估模型.     

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甩挂运输是一种被国家大力推广的集约、高效、低碳的先进运输组织方式.本文根据港口改善和提升集疏运组织方式和能力的需求,提出了内河港口的甩挂运输模式;针对内河港口甩挂运输组织中货运场站的选址问题制订了选址步骤;建立了选址数学模型,设计了基于遗传算法的模型求解算法;并建立了基于Arena的仿真模型对备选地址进行评价选择;最后以广东省云浮新港为背景进行案例分析,为其设计了甩挂运输组织模式,运用上面的算法和模型进行场站选址,并使用建模仿真的方法将该方案的集装箱甩挂运输模式与传统公路集装箱运输模式进行对比,检验其优越性.     

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衔接多种运输方式之间中转货流的通用型综合交通枢纽是国家综合货物运输网路体系中的重要节点,同时也是城市交通网络的重要组成部分.本文运用无缝中转的思想,从综合交通枢纽与城市交通网络之间的动态关系出发,既保证用户广义费用最低,同时使整个货物运输系统的社会效益最大,从而构建综合交通枢纽货运站布局优化模型.该模型在考虑四种运输方式基础上,加入城市货流作为第五种运输方式,增强了模型的优越性.通过应用遗传算法求解模拟算例,验证了模型的合理性及遗传算法求解该问题的优越性.研究结果表明,该模型与实际情况吻合,是城市综合交通枢纽货运站布局优化的有效方法之一.     

基于马尔科夫链的60 GHz 点对点通信移动性优化

由于60 GHz通信在空气中可能会有高达20 dB的信号衰减,因此通信的范围和质量都可能受到影响．为此,IEEE 802.11 ad标准引入了能够定向增强信号和控制信号传播方向的波束成形技术来提高通信质量．然而,设备位置移动对波束成形的影响较大,它可能会导致通信质量下降甚至中断．为保证通信通畅,文中针对IEEE 802.11ad定义的点对点场景提出了波束成形优化算法．该算法基于马尔科夫链模型预测下一时刻设备的位置,并且提前调整相应的波束方向．该算法利用动态设备的相对位置和波束转动角度信息,代替了原波束成形方法中的波束扫描等过程．在仿真实验中,通过信息交互次数验证了该算法的有效性,提高了波束成形过程的效率,并且使该过程中的能量消耗降低了60％．     

跨声速射流冲击对挡板作用特性的模拟分析

为了得到跨声速理想膨胀射流冲击对于挡板的压力、驻点位置等规律,对射流角度为45°,60°和90°,射流距离与喷口直径比H/D为4,6,8的模型进行了数值模拟．结果表明：当H/D从4增加到8时,作用力增加约10％,改变的幅度较小;当射流角度从45°增加到90°时,作用力提高大约40％,作用力大小跟射流角度关系较大．射流角度从45°增加到90°时,驻点距离射流中心由0.07～0.10 m减小到0;射流距离变化对驻点的距离影响很小,变化幅度在10％左右．