Admission and pricing optimization of on-street parking with delivery bays

We analyze a parking lot, modeled as a loss queue, with passenger and delivery vehicles. The arrival process of delivery vehicles is exogenous, while that of passenger vehicles is a function of the parking price rate and accessibility. The aim of the parking operator is to maximize the revenue generated from passenger vehicles while providing a sufficient service level for delivery vehicles, in terms of their probability to find an available parking spot. Two levels of control are exercised: pricing and admission. From a Markov decision process approach, we prove that the optimal policy is a state-dependent reservation threshold policy that randomizes in at most one state. When some parking spots should be reserved for delivery vehicles, the price rate is selected to saturate the service level constraint, whereas when it is optimal not to restrict the parking lot accessibility, the price can also be selected as the unique local maximum of the revenue or to incentivize all potential passenger vehicles to arrive. Pricing should be used as a primary tool to control the flow of passenger vehicles. In complement, admission control is exercised with a limited use of reservation only when the service level guarantee for delivery vehicles is high.     

城市机动车停车收费绩效评价理论及策略研究

运用Delphi法和AHP法以及优化理论,构建了城市机动车停车收费绩效综合评价指标体系,依据7±2心理极限概念建立了机动车停车数学模型,选用基于"差动"原理的赋权法——Gl法计算各指标的权重,应用模糊综合评价法对其绩效进行综合评价.采用平均加权法对评价因素的各项指标进行量化处理,从而得到机动车停车收费绩效的综合评价结果.对宁波市机动车停车收费绩效进行了实际验证,比较真实地反映了其绩效状况,为宁波市静态交通的进一步发展和整改提供了理论依据.最后,有针对性地提出协调衔接停车规划与停车设施建设、合理调整停车收费结构、制定严格的停车违章处罚政策等城市机动车停车发展策略.     

Optimising passing bay locations and vehicle schedules in underground mines

In many underground mines, haulage vehicles carry ore from underground loading stations to the surface. Vehicles travel in narrow tunnels with occasional passing bays that allow descending empty vehicles to pull off the main path and wait for ascending laden vehicles to pass. The number of passing bays and their locations influence the delays to descending vehicles, and hence the haulage productivity of the mine. We formulate and solve a mixed integer programming (MIP) model to determine the optimal locations of passing bays to maximise haulage productivity for given numbers of vehicles and passing bays. The MIP also generates the corresponding vehicle schedule. Previous studies have only examined the placement of equally spaced bays. The results obtained from the MIP show that this is not always optimal. Furthermore, we observe that the best locations of passing bays are those that allow interleaving of vehicles without delays at bays.     

Ambulance location and relocation models in a crisis

This article deals with the relocation of ambulance vehicles from their origin location (i.e., position before a crisis occurs) to a crisis area and to undercovered areas (i.e., no ambulance vehicle is available for a potential emergency in a given region). Support for a crisis area can lead to insufficient coverage of other emergency patients in other regions, so decision makers need assistance with useful relocation information, including the relocation of vehicles to the crisis area and to undercovered areas. As optimization criteria, this study considers two objectives: undercoverage (i.e., unsupported demand) and the total time needed to get to the crisis area with all vehicles. A proposed model aims to minimize the time required for the vehicle relocation process and avoid relocation mistakes (e.g., sending a vehicle to support the crisis area when it would be better to leave it at its current location). Devising the relocation plan consists of three phases. First, a location model allocates all available vehicles to potential vehicle locations (positioning vehicles before the crisis occurs). Second, the same location model allocates the remaining vehicles in the case of a crisis (all vehicles not needed to manage the crisis). Third, the relocation model (phase three) moves vehicles from their position before the crisis occurs (phase one) to their position during the crisis (phase two).     

有限条法分析板在移动车载作用下的动响应

提出了一个模拟移动车辆和矩形板相互作用的板-车条.用板-车条模拟直接与车辆相接触的板条部分;用传统的板有限条模拟未直接受车辆作用的板条部分.分析中,每辆车理想化为一个具有上、下部质量块,由弹簧和阻尼器连接的单足动力系统.计算示例表明,用该方法分析得到的结果与已有结果很吻合.     

A metaheuristic for the min–max windy rural postman problem with K vehicles

In this paper we deal with the min–max version of the windy rural postman problem with K vehicles. For this problem, in which the objective is to minimize the length of the longest tour in order to find a set of balanced tours for the vehicles, we present here a metaheuristic that produces very good feasible solutions in reasonable computing times. It is based on the combination of a multi-start procedure with an Iterated Local Search. Extensive computational results on a large set of instances with up to 50 vertices, 184 edges and 5 vehicles are presented. The results are very good, the average gaps with respect to a known lower bound are less than 0.40% for instances with 2 or 3 vehicles and up to 1.60% when 4 or 5 vehicles are considered.     

三种类型汽车的能耗和使用成本的建模研究

本文对电动,传统,混合动力三种类型汽车的能耗和使用成本问题进行了建模、求解及分析．首先定义了电动汽车的能量利用率ηE。根据能量守恒将所有电量转换成汽油消耗量,而传统车型则直接反映到汽油的消耗上,混合动力汽车则综合电动汽车和传统汽车的能耗模型,从而统一能耗水平评价标准．这样,我们就得到了三种不同类型车的能耗模型再进行模型求解以此来分析比较三种类型车哪一种节能效果好．对电动汽车来说,使用成本主要包括驾驶维护成本、报废处理成本,而对传统汽车来说,使用成本主要包括驾驶维护成本、报废处理成本、环境成本和其他成本,混合动力汽车则结合二者使用成本．因此,根据不同车型使用成本类型建立相应的数学模型,按照建立的公式,可以得到电动汽车的使用成本LCC1、传统汽车的使用成本LCC2和混合动力汽车的使用成本LCC3,从而进行模型求解．     

基于能量增强的运动车辆车标的“四阶段法”定位技术研究

基于视频图像的运动车辆识别系统主要是由汽车牌照识别和汽车类型识别两大核心技术构成,它在智能交通领域中有着广泛的应用,同时也是计算机视觉、图像处理和模式识别等交叉学科研究的热门课题,运动车辆车标定位是车辆类型识别的核心技术之一,提出了基于能量增强的运动车辆车标定位的"四阶段法"的概念,介绍了运动车辆车标定位的方法和关键技术,对不同天气状况下不同类型的运动车辆进行了车标定位实验,实验结果表明该方法具有较强的科学依据和实用价值.     

The static bike relocation problem with multiple vehicles and visits

This paper introduces the static bike relocation problem with multiple vehicles and visits, the objective of which is to rebalance at minimum cost the stations of a bike sharing system using a fleet of vehicles. The vehicles have identical capacities and service time limits, and are allowed to visit the stations multiple times. We present an integer programming formulation, implemented under a branch-and-cut scheme, in addition to an iterated local search metaheuristic that employs efficient move evaluation procedures. Results of computational experiments on instances ranging from 10 to 200 vertices are provided and analyzed. We also examine the impact of the vehicle capacity and of the number of visits and vehicles on the performance of the proposed algorithms.     

On measuring average speed in a circulating system

The paper considers measuring speeds of vehicles which move in a circular track. By using the Schwarz inequality, it is shown that the average speed of the vehicles is over-estimated when the vehicles are observed at a fixed point in the track. It is also illustrated that the relative error is the square of an important statistical quantity, the coefficient of variation of the distribution of vehicle speeds. The results are interesting and the techniques used are elementary mathematics and statistics.     

Efficient Heuristics for the Heterogeneous Fleet Multitrip VRP with Application to a Large-Scale Real Case

The basic Vehicle Routing Problem (VRP) consists of computing a set of trips of minimum total cost, to deliver fixed amounts of goods to customers with a fleet of identical vehicles. Few papers address the case with several types of vehicles (heterogeneous fleet). Most of them assume an unlimited number of vehicles of each type, to dimension the fleet from a strategic point of view. This paper tackles the more realistic tactical or operational case, with a fixed number of vehicles of each type, and the optional possibility for each vehicle to perform several trips. It describes several heuristics, including a very efficient one that progressively merges small starting trips, while ensuring that they can be performed by the fleet. This heuristic seeks to minimize the number of required vehicles as a secondary objective. It outperforms classical VRP heuristics, can easily handle various constraints, and gives very good initial solutions for a tabu search method. The real case of a French manufacturer of furniture with 775 destination stores is presented.     

基于系统动力学的新能源汽车“绿色悖论”效应研究

面对日益严峻的环境问题, 为减少机动车排放污染气体, 我国各地政府纷纷出台相应鼓励发展新能源汽车的政策。新能源汽车主要是采用电作为推动力, 能够有效降低空气污染程度。本文运用系统动力学方法建立模型, 从系统的角度出发, 采用VENSIM软件进行仿真模拟, 探究产生“绿色悖论”的原因。动态仿真结果显示, 政策对新能源汽车的影响实施阶段有显著效果, 但是随着时间的推移, 政策的边际效用会逐渐降低; 新能源汽车总量的上升直接吞噬甚至超出了其节约的资源, 而且带来了停车位紧张、道路拥挤度上升的不良后果。     

成品油配送多车舱车辆指派及路径优化问题研究

针对成品油配送中多车型、多车舱的车辆优化调度难题,综合考虑多车型车辆指派、多车舱车辆装载及路径安排等决策,以派车成本与油耗成本之和的总成本最小为目标,建立了多车型多车舱的车辆优化调度模型。为降低模型求解的复杂性,本文提出一种基于C-W节约算法的“需求拆分→合并装载”的车辆装载策略,并综合利用Relocate和Exchange算子进行并行邻域搜索改进,获得优化的成品油配送方案。最后,通过算例验证了本文提出的模型与算法用于求解大规模成品油配送问题的有效性。并通过数据实验揭示了以下规律:1)多车舱车辆相对于单车舱车辆在运营成本上具有优越性;2)大型车辆适合远距离配送,小型车辆适合近距离配送;3)多车型车辆混合配送相对于单车型车辆配送在运营成本上具有优越性。这些规律可为成品油配送公司的车辆配置提供决策参考。     

Vehicle routing in an automated warehouse: Analysis and optimization

This study concerns the design of an operating system for vehicles in an automated warehouse. The layout of the warehouse and the number and properties of the vehicles are given. The objective is to maximize the throughput. Using a partial enumeration technique, we simulate several alternatives for the control and interplay of the vehicles within a reasonable time horizon. A subproblem is solved by network flow techniques. The algorithm is implemented as part of an automatic control system, and it has led to a satisfactory performance.     

基于STEP-FRAM的机坪保障车辆事件分析

为了克服传统事件分析方法解决单一因素、相对简易系统故障引发的事件的不足,利用STEP-FRAM模型对机场停机坪保障车辆的不安全事件进行了系统分析,结果表明:使用这种方法可以找出导致机场保障车辆不安全事件的功能共振及其影响因素,解释事件的原因和过程,从而设计出预防和控制措施,降低机坪保障车辆不安全事件再次发生的风险.     

Dynamic scheduling of recreational rental vehicles with revenue management extensions

The rental fleet scheduling problem (RFSP) arises in vehicle-rental operations that offer a wide variety of vehicle types to customers, and allow a rented vehicle to ‘migrate’ to a setdown depot other than the pickup depot.When there is a shortage of vehicles of a particular type at a depot, vehicles may be relocated to that depot, or vehicles of similar types may be substituted.The RFSP involves assigning vehicles to rentals so as to minimise the costs of these operations, and arises in both static and online contexts. The authors have adapted a well-known assignment algorithm for application in the online context. In addition, a network-flow algorithm with more comprehensive coverage of problem conditions is used to investigate the determination of rental pricing using revenue management principles. The paper concludes with an outline of the algorithms’ use in supporting the operations of a large recreational vehicle rental company.     

高超声速飞行器热防护材料与结构的研究进展

高超声速飞行器是航空航天的一个重要发展方向,在未来国防安全中起着重要作用．高超声速飞行器热防护材料与结构是高超声速飞行器设计与制造的关键技术之一,它关系到飞行器的安全．高超声速飞行器热防护材料与结构主要有金属TPS热防护系统、超高温陶瓷、C/C复合材料等．从材料制备、抗氧化、力学与物理性能表征等方面综述了热防护材料与结构的研究与应用现状,评述了其发展趋势．     

On the history of lateral vehicle dynamics

The lateral motion of vehicles on tracks and roads is characterized by the rolling contact between wheels and guideway. Railway vehicles feature passive lateral guidance while road vehicles are operated by steering. Lateral dynamics is an extremely complex problem but the fundamental behaviour can already understood by strongly simplified mechanical models. In this paper the historical development of modelling approaches for lateral dynamics is reviewed what is very helpful for benchmarking and checking more complex problems, too. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A primal-dual approximation algorithm for a two depot heterogeneous traveling salesman problem

Surveillance applications require a collection of heterogeneous vehicles to visit a set of targets. We consider a fundamental routing problem that arises in these applications involving two vehicles. Specifically, we consider a routing problem where there are two heterogeneous vehicles that start from distinct initial locations and a set of targets. The objective is to find a tour for each vehicle such that each of the targets is visited at least once by a vehicle and the sum of the distances traveled by the vehicles is minimal. We consider an important special case of this routing problem where the travel costs satisfy the triangle inequality and the following monotonicity property: the first vehicle’s cost of traveling between any two targets is at most equal to the second vehicle’s cost of traveling between the same targets. We present a primal-dual algorithm for this case that provides an approximation ratio of 2.     

应急救援物资紧缺的配送车辆路径选择研究

针对应急救援物资总量紧缺不能全部满足各点需求量的实际情形,以单个需求点最大缺货量最小为目标,建立基于单个配送中心、车辆数目有限和带时间窗的应急救援物资配送车辆路径选择模型,并讨论了三种不同缺货情形下模型的求解。对于车辆按最短路径行驶也无法在救援时间内到达导致需求点缺货的情形,删除这些需求点的需求量后,如果剩余需求点的需求量不大于物资总量且车辆足够多,可转化为车辆最短路径问题求解;对于物资紧缺无法满足所有需求且车辆足够多的情形,设计时间复杂性为O(mn²)的精确算法A^*求解,其中m和n分别为车辆数和需求点数;对于物资紧缺且车辆数目不足无法把全部物资送达需求点的情形,设计时间复杂性为O(n²)的近似算法GA^*求解,并分析了算法GA^*的近似比。最后结合云南彝良县地震灾区局部路网进行实例分析,验证模型和算法的有效性。