Network flow-based strategies for identifying rail park-and-ride facility locations

Many cities are considering introducing or expanding rail service in an effort to diversify their modal splits. Park-and-rides are integral to this strategy because they represent private auto users’ access points to the system. Proper placement of such facilities is a strategic location decision, as it can conceivably decrease vehicular traffic on congested roadways while benefiting users. This paper models the decision to locate park-and-ride facilities in a network flow-based framework. From this perspective, optimal placement occurs at locations where vehicles will encounter facilities early during their journeys to a centralized area or major activity center. Locating park-and-rides in this fashion maximizes the chances of removing users from the network. These elements are demonstrated in three hypothetical placement scenarios that make use of synthetic network and traffic flow data. Results illustrate the functionality of our approach for identifying park-and-ride candidate locations. Lastly, implications of our work are discussed in light of broader planning concerns and practical demands on rail facility location.     

Sequential facility location with distance dependent demand

Systems providing identical service to many population centers frequently face the issue of where to locate the next retail outlet, branch, store, etc. In such systems the demand for the facilities' service depends mainly on the distance between facilities and customers. It is assumed that there are already m facilities located on a network to respond to the demand at the nodes. The paper addresses the problems of finding a location on the network for the (m +1 )st facility corresponding to a given total expected demand and of determining which demand points will be served by which facility. Also the range of the total expected demand values that can be realized along each link in the m +1 facility system is determined. Examples and a discussion of the results are provided.     

Improving access to health facilities in Nouna district,Burkina Faso

The Nouna health district in Burkina Faso, has a population of approximately 275,000 people living in 281 villages, and is served by 25 health facilities, as of 2006. For many people, the time and effort required in traveling to a health facility, which may demand a journey of many kilometers over poor roads on foot, is a deterrent to seeking proper medical care. In this study we examine how access to health facilities in Nouna may be improved by considering the configuration of the road network in addition to the locations of the facilities. We model the situation as a facility location–network design problem and draw conclusions about how best to improve the physical access of the health facilities. Our model shows the extent to which access can be improved when the road network is considered along with facility locations, in contrast to facility locations considered alone.     

Evaluating spatial service and layout efficiency of municipal Wi-Fi facilities for SmartCity planning: A case study of Wuhan city,China

This paper explores an approach to evaluating spatial service and layout efficiency of municipal Wi-Fi facilities for cyber infrastructure planning in the construction of a smart city. Based on the equilibrium principle that Wi-Fi services supply should meet the spatial demand for recreation, urgency, and security, two evaluation models were built. In the first model, the spatial service efficiency of Wi-Fi facilities is measured by a mean ratio of three types of demand spaces covered by Wi-Fi service. In the other model, spatial layout efficiency of each Wi-Fi facility is calculated by a demand load indicator - the sum of the three types of demand space's ratios of served quantity to the average quantity it should carry, and then assessed by relationship with its adjacent facilities. Corresponding statistical methods and analysis processes were also designed using the function modules found in ArcGIS software. The approach was applied to Wuhan city in 2016. After overlaying influence areas of 688 Wi-Fi facilities with demand spaces of 137 access points for recreation, 1200.99 km roads for urgency, 121.54 km² regions for security, the results show that there exists a spatial disequilibrium between supply and demand of Wi-Fi service in Wuhan due to lack of comprehensive planning. Specifically, there are 67 points, 700.76 km roads, and 42.59 km² regions of demand spaces covered by Wi-Fi service, with service efficiencies of 48.91%, 58.35%, and 35.04% respectively and an overall spatial service efficiency of 47.43%. Among all the Wi-Fi facilities, there are 481 carrying saturated demand, 3 straying from the centre of demand space, and 204 redundant. The overall spatial layout efficiency of Wi-Fi facilities is 43.01%. The conclusion is that the dense and massive redundant Wi-Fi facilities should be optimized, especially in the centre areas along the confluence of Yangtze and Han rivers and new Wi-Fi facilities supplemented in other ill-equipped areas. Since many metropolitan cities experience the same problem, this novel approach will find wide application in the future and offer improved evaluation strategies for researchers and policymakers.     

基于蚁群算法的飞机加油车辆调度问题研究

飞机加油是停机坪地面保障作业的重要环节,能否对飞机按时按量的完成加油作业的关键因素在于对飞机加油车辆的合理调度,因此对飞机加油车辆调度的研究是十分有意义的。本文首先对飞机加油车辆的类型、功能、行驶过程及其注意事项做了简单的介绍,然后根据车辆调度的基本模型对飞机加油车辆调度的模型进行了比较具体的描述,文章最后用蚁群算法对某机场3个小时内飞机油罐加油车辆行驶情况进行仿真计算,希望通过对该模型的仿真优化计算,为机场加油车辆运行提供一种可行优化算法。     

A model of integrated regional logistics hub in supply chain

ABSTRACT

A regional logistics hub is a constellation of multiple logistics facilities in a region of several provinces or states. This research models an integrated regional logistics hub with consideration of time-phased demand in a multi-echelon, multi-period, and capacitated logistics network. The integrated logistics hub considers three phases based on the characteristics of China’s five-year planning policy. By applying mixed integer linear programming, the greedy heuristics approach, the particle swarm optimization algorithm, and the Hungarian method, the location of logistics facilities at different echelons of a supply chain is identified and the needs for facility expansion or closing during different time periods are determined.     

Siting a facility in continuous space to maximize coverage of a region

Siting facilities in continuous space such that continuously distributed demand within a region is optimally served is a challenging location problem. This problem is further complicated by the non-convexity of regions typically encountered in practice. In this paper a model for maximizing the service coverage of continuously distributed demand through the location of a single service facility in continuous space is proposed. To address this problem, theoretical conditions are established and associated methods are proposed for optimally siting a service facility in a region (convex or non-convex) with uniformly distributed demand. Through the use of geographic information systems (GIS), the developed approach is applied to identify facility sites that maximize regional coverage provided limitations on facility service ability.     

Location-allocation problem for intra-transportation system in a big company by using meta-heuristic algorithm

This paper presents the location-allocation problem of parking facilities in Mobarakeh Steel Company. The aim is to find the optimal location for the parking facilities and allocate travels between departments to each parking facility. To optimize the cost and facing the transportation demands of all departments, a mathematical model is designed and solved by a commercial software package. Also, the number of vehicles allocated to each parking facility is determined. A hybrid meta-heuristic algorithm combining a genetic algorithm with parallel simulated annealing is developed which can be used even in more complicated structure of the problem. The results show that this hybrid algorithm is highly efficient in solving this kind of problems.     

Highway congestion and congestion tolls

Highway congestion is ubiquitous. We model the speed-flow relationship, identifying private and social costs, and the implied congestion toll for a number of proposed formulations. Using data for a limited access highway, we estimate these speed-flow relationships and find that flow as a quadratic function of speed fits best. The unit of observation is the individual vehicle and flow is measured in terms of the vehicles which passed a point shortly before or after the reference vehicle. Maximum possible flow occurs at 30–35 mph and the congestion toll is infinite for slower speeds. Rush-hour drivers have greater speeds for a given volume of traffic and thus congestion tolls must vary by time of day.     

基于时空消耗理论的城市宏观路网供需研究

以路网广义容量的内涵和计算理论为前提,通过对现状及特征年宏观路网容量的分析,确定未来特征年机动车限制保有量。考虑多项影响因素,建立机动车保有量多元回归预测模型,对未来城市机动车保有量进行预测。在此基础上进行供需分析,从而为城市机动车发展战略提供重要的决策依据.最后以武汉市主城区为例对宏观路网供需情况进行分析并提出改善措施。     

山区公路交通流特性分析与评价

首先由观测数据确定代表车型的运行速度,采用实际路段调查得到的运行速度作为评价指标,分析山区公路的交通流运行状况,然后通过实地调查采集山区公路典型断面的交通流数据,统计交通量、交通组成以及不同车型运行速度的分布情况,并通过分析交通组成以及车速连贯性和离散性等直接影响道路交通安全的因素,对事故多发路段的交通流运行状态特征进行分析和评价。最后,选取京昆高速公路某典型路段,对该路段的交通流特性进行分析与评价,可为相关工作人员提供借鉴和帮助。     

Predicting bankruptcy in the Texas nursing facility industry

Approximately 50% of nursing facilities in Texas petitioned for bankruptcy during the 1998–2004 period. Using a logit regression model tested for robustness, we find nursing facilities that are profit-seekers, chain members, pay higher than average wage rates, accept more intensive-care residents and obtain a larger than average portion of their funding from public sources are highly vulnerable to negative changes in regulatory policy decisions on Medicare and Medicaid reimbursement. Larger facilities having higher than average occupancy rates and quality of care are less susceptible to adverse decisions. The model correctly classifies a facility as either bankrupt or solvent in about 75% of cases. We also examine the duration of bankruptcy using accelerated failure-time models. It appears that the duration of bankruptcy depends on location, out-of-state ownership, length of ownership, volume of resident days supplied, total cost and proportion of revenues from Medicaid.     

基于预知OD的城市路网交通流路径优化研究

针对城市路网交通流分布不均引起的交通拥堵问题,提出了在预约出行交通背景下基于预知OD的交通流路径优化方法。首先,分析了预约出行交通背景下预知OD的数据环境;其次,根据动态用户均衡准则,对预知的OD进行流量分配,给出预约出行车辆的路径;接着,使用预测控制的方法,结合路网上预约车辆的状态,以路网上路段的饱和度和未预约车辆的行程时间最小化为目标,从系统和用户两个角度对未预约车辆的路径进行实时的诱导,通过连续时域的滚动优化控制,优化交通流的路径;最后,对本方法的实现和应用做了思考和探索,对本研究做了总结。     

Facility location under demand uncertainty: Response to a large-scale bio-terror attack

In the event of a catastrophic bio-terror attack, major urban centers need to efficiently distribute large amounts of medicine to the population. In this paper, we consider a facility location problem to determine the points in a large city where medicine should be handed out to the population. We consider locating capacitated facilities in order to maximize coverage, taking into account a distance-dependent coverage function and demand uncertainty. We formulate a special case of the maximal covering location problem (MCLP) with a loss function, to account for the distance-sensitive demand, and chance-constraints to address the demand uncertainty. This model decides the locations to open, and the supplies and demand assigned to each location. We solve this problem with a locate-allocate heuristic. We illustrate the use of the model by solving a case study of locating facilities to address a large-scale emergency of a hypothetical anthrax attack in Los Angeles County.     

轿车总装制造过程质量控制方法研究

“质量是上海大众的生命”这是上海大众一贯秉承的造车宗旨。对于整车制造部门来说,产品过程质量的控制是质量工作中的一个重要课题。本文将以上海大众的一个整车总装车间为研究对象,全面阐述新型QRK过程质量控制方法的基本理论、具体实施。     

具有同时送货和取货特点的单车辆配送路径优化算法

在分析具有同时送货和取货特点的单车辆配送路径问题的基础上,建立OV-VRPSDP数学模型,提出一种新的求解OV-VRPSDP问题的比值法优化算法,并通过实例验证该算法的有效性和可行性。新算法首先对配送树图的顶点和边做适当处理,计算各树枝的份量,使配送车辆优先沿着份量较大的树枝前进,选择一条最优路径。实例表明,比值法能够快速解决OV-VRPSDP问题,并且具有较好的优化效果。     

比亚迪新能源汽车开发中的创新方式研究

本案例研究以比亚迪股份有限公司为对象,针对它的新能源汽车市场开发从其较短的历史发展脉络中把握其内在的创新规律,总结其富有特色的创新方式,同时从新能源汽车开发的时代背景和创新平台、创新体系等整体角度,基于主要利益相关者的关系以及新能源汽车的市场可行性,论述比亚迪新能源汽车开放式创新的含义及其特征,在比较世界主要新能源汽车的创新模式和开发方式的基础上,结合开放式创新的有关理论,指出比亚迪汽车的发展前景和面临的挑战。比亚迪的开放式创新赢得了市场,其根本原因在于对自身核心能力的充分把握和对创新的日常化理解与实践,前者使其传统的电池技术优势得以强化和扩展,并因此掌握了未来汽车产业的发展方向,避免了传统汽车制造上的品牌短板,后者则适应了自己的国情和当今的世界竞争态势,使其创新效益最大化。     

The effects of vehicle ownership on employment

Vehicle ownership may promote work if employment opportunities and job searches are enhanced by reliable transportation. For example, vehicles may serve to reduce potential physical isolation from employment opportunities. I examine the effects of vehicle ownership and vehicle quality on employment for single mothers with no more than a high school education using National Longitudinal Survey of Youth data. I control for potential bias by jointly estimating employment and vehicle ownership in a maximum likelihood framework using state welfare eligibility asset rules as instruments. Results show that vehicle ownership increases employment. Positive effects of vehicles do not differ for urban and rural residents, but they do change with economic conditions. Further, welfare recipients are significantly more likely to exit the program and become employed if they own a vehicle.     

Mathematical analysis of emergency ambulance location

Proper ambulance location is crucial in saving lives and reducing injury. To determine efficient and effective locations, it is necessary to evaluate both the spatial and temporal distributions of demand. Because of the complex nature of the ambulance response and transport activities, the problem is subdivided into a facility location problem and a vehicle allocation problem. A set covering model is modified to solve the location problem while a simulation is used to solve the allocation problem. Combining these two models provides a powerful methodology for systematically finding a satisfactory solution to the ambulance location problem.     

Scheduling of re-entrant flow shops

We propose and develop a scheduling system for a very special type of flow shop. This flow shop processes a variety of jobs that are identical from a processing point of view. All jobs have the same routing over the facilities of the shop and require the same amount of processing time at each facility. Individual jobs, though, may differ since they may have different tasks performed upon them at a particular facility. Examples of such shops are flexible machining systems and integrated circuit fabrication processes. In a flexible machining system, all jobs may have the same routing over the facilities, but the actual tasks performed may differ; for instance, a drilling operation may vary in the placement or size of the holes. Similarly, for integrated circuit manufacturing, although all jobs may follow the same routing, the jobs will be differentiated at the photolithographic operations. The photolitho-graphic process establishes patterns upon the silicon wafers where the patterns differ according to the mask that is used.The flow shop that we consider has another important feature, namely the job routing is such that a job may return one or more times to any facility. We say that when a job returns to a facility it reenters the flow at that facility, and consequently we call the shop a re-entrant flow shop. In integrated circuit manufacturing, a particular integrated circuit will return several times to the photolithographic process in order to place several layers of patterns on the wafer. Similarly, in a flexible machining system, a job may have to return to a particular station several times for additional metal-cutting operations.These re-entrant flow shops are usually operated and scheduled as general job shops, ignoring the inherent structure of the shop flow. Viewing such shops as job shops means using myopic scheduling rules to sequence jobs at each facility and usually requires large queues of work-in-process inventory in order to maintain high facility utilization, but at the expense of long throughput times.In this paper we develop a cyclic scheduling method that takes advantage of the flow character of the process. The cycle period is the inverse of the desired production rate (jobs per day). The cyclic schedule is predicated upon the requirement that during each cycle the shop should perform all of the tasks required to complete a job, although possibly on different jobs. In other words, during a cycle period we require each facility to do each task assigned to it exactly once. With this requirement, a cyclic schedule is just the sequencing and timing on each facility of all of the tasks that that facility must perform during each cycle period. This cyclic schedule is to be repeated by each facility each cycle period. The determination of the best cyclic schedule is a very difficult combinatorial optimization problem that we cannot solve optimally for actual operations. Rather, we present a computerized heuristic procedure that seems very effective at producing good schedules. We have found that the throughput time of these schedules is much less than that achievable with myopic sequencing rules as used in a job shop. We are attempting to implement the scheduling system at an integrated circuit fabrication facility.