鲍摩-瓦尔夫模型在物流配送中心选址中的应用

物流配送中心是物流系统的重要组成部分,选址更是配送中心规划中至关重要的环节,合理的配送中心选址可以有效降低配送中心的运营成本和建造成本.鲍摩-瓦尔夫模型不仅考虑了运输成本,而且还考虑了可变成本和固定成本,因此可按其求解方法进行求解.通过实例计算,得到较好效果.最后指出该模型存在的缺点.     

连锁零售企业车辆配送路径优化研究

研究连锁零售企业配送中心车辆配送路径的新策略，即配送中心车辆在为其连锁店送货的同时，承担各店需返回物件（如商品包装、顾客退货等）的回收工作。通过建立模型定量分析了该流程的总成本，提出相应的解法，并用实例证明了该解法的可行性[编者按]     

配送中心规模的经济分析

配送中心的建设规模遵循规模经济的客观规律,通过运用边际效益递减规律和规模经济原理,从“配送中心规模与效益水平的关系”和“配送中心规模与单位配送成本的关系”出发,分析配送中心不同规模下的成本和效益,得到配送中心规模的“成本—效益”模型,并在此基础上分析配送中心最佳建设规模及其效果评价。     

铁路客运站配套停车场泊位数量计算模型

铁路客运站配套停车场主要用于停靠接、送旅客的非营运车辆和出租车与其他社会车辆。在考虑接旅客车辆在停车场停留时间、旅客列车到达时刻、乘坐接旅客车辆人数等因素的基础上,构建接旅客车辆所需泊位数计算模型,采用系数法构建送旅客车辆和其他社会车辆所需泊位数计算模型,形成停车场泊位数量计算模型。以计算石家庄客运站停车场所需泊位数量为例,通过模型应用验证,分析模型的有效性。     

物流配送中心优化选址问题研究

基于物流配送中心成本分析,建立物流配送中心优化选址模型。配送中心优化选址模型属“0-1”混合非线性规划问题,具有NP难性质。运用遗传算法,对配送中心优化选址模型进行仿真求解。最后通过一个实例验证了该选址模型的科学性和遗传算法求解该模型的有效性。     

物流配送车辆优化调度模型研究

综合我国物流配送的特点,在车辆类型、车辆载重、客户时间窗等约束条件下,建立多配送中心、多车型的物流配送车辆优化调度模型,并综合应用启发式算法中的C-W节约法和精确算法中的动态规划法进行算例分析,验证所建模型的正确性.     

应急物资配送中心选址-路径优化研究

<正>1.引言突发事件,如自然灾害、突发公共卫生事件等,严重侵害了各国人民的生命安全和社会经济的进一步发展。在重大突发事件发生后,需要将大量的应急物资运送至需求点,用于救援活动的开展。因此,如何快速决策出配送中心的位置和配送路径,将物资及时地送达,是目前应急物流网络中的重点问题。2.模型建立2.1模型假设(1)备选配送中心容量和需求量已知。(2)车辆单位负载单位行驶距离的运输成本、车辆最大负载以及固定成本已知。(3)车辆必须由某供应点出发并回到该配送中心并且每辆车只被启用一次。     

基于DEA-Shapley值法的共享配送中心成本分配研究

<正>末端配送价格逐年降低,而客户服务水平逐年提高,快递企业考虑共享配送中心实现共同配送,以降本增效。本文围绕此模式,研究共享配送中心过程中产生的固定成本、运营成本如何分配的问题。将DEA与Shapley值法应用到可分离成本与不可分离成本中,构造符合实际的计算方法。最后,本文引入某县域内共享配送中心的案例,通过本文的分配方法计算分配结果,并对分配结果进行分析。1.引言随着快递行业的不断进步和发展,共同配送的合作模式也逐渐多样化,可以合作共享的环节很多。已有研究在配送方面的研究主要包括以下几个方面：在配送模式方面,     

基于车联网技术的特殊车辆优先通行信号协调控制方法研究

在当今社会发生紧急事件后,车辆能否及时地达到现场成为了评价社会进步的指标.因此,提出了基于车联网技术的特殊车辆优先通行信号协调控制方法研究这一课题,基于车联网庞大的数据支撑,设计特殊车辆优先通行信号优先级别,对路口的相位进行计算,并预设锁定相位的范围,根据相位条件设置最小绿灯时长.基于车联网数据计算相应的信号周期,合理...     

改进蚁群算法在物流配送路径择优规划中的应用

<正>1.基于改进蚁群算法的物流配送路径择优规划方法1.1建立目标函数物流配送路径择优规划问题，是由多个配送中心和多个客户节点组成，此次研究场景为配送中心，根据物流配送路径择优规划需求，对物流配送择优规划问题提出如下假设：假设1：用于物流配送的车辆型号相同，物流配送路程不能超出配送车辆运行的最大行驶距离；假设2：物流配送车辆均从配送中心取货，     

How fleet commonality influences low-cost airline operating performance: Empirical evidence

This paper investigates the effect of fleet commonality on operating performance of low-cost airlines. It examines the role fleet size and route length variations on this relationship. Results of an analysis of 28 airlines show that fleet commonality is positively associated with operating performance. Further, fleet size positively affects this relationship, whereas route length variations do not.     

Reliability and operations: Keys to lumpy aircraft spare parts demands

This study provides unique new insights into the reasons for lumpy aircraft spare parts demands, and identifies opportunities to improve the regularity of aircraft spares demands. The study develops its unique insights into aircraft spare parts demands by considering the typical failure probability distribution (Weibull Distribution) for aircraft spare parts. The study identifies the range of Weibull model parameters that explain typical aircraft part failure rates, and uses these parameters to perform a Monte Carlo simulation of notional aircraft components in typical aircraft fleet sizes and operations. Each notional component is repeatedly used to failure and replaced, providing a simulated spare part demand rate. The data is evaluated to uncover patterns that allow a deeper understanding of how reliability and operational input factors impact the spare part demand characteristics. The study finds that the aircraft fleet size has the greatest impact on the lumpiness of aircraft spare parts demands. The study also recommends other measures that fleet managers may take to reduce the lumpiness of their spares demands.     

Three-stage airline fleet planning model

One of the main factors affecting airline success is bringing supply and demand as closely together as possible. In order to achieve this goal, an airline needs to adopt an appropriate methodological approach for the fleet planning process. Selection of an aircraft for operating a defined route network is a key element which has a direct impact on the increase of an airline's profitability and on the reduction of an airline's costs. The objective of this paper is to develop a robust model for fleet planning that deals with both fleet size and fleet composition problems for airlines operating on short haul and medium haul routes. The three-stage model for fleet planning involves approximate fleet composition, fleet sizing and aircraft type selection based on fuzzy logic, heuristic and analytic approaches, and multi-criteria decision making, respectively. This model is exemplified with a hypothetical airline based at Belgrade Airport.     

The dynamics between freight volatility and fleet size growth in dry bulk shipping markets

This paper studies the relationship between the time-varying volatility of dry bulk freight rates and the change of the supply of fleet trading in dry bulk markets. An abundance of research has been done to understand the time-varying characteristics of freight rate volatility, yet few have discussed the determinants of freight volatility. We therefore examine freight volatility against the changes in fleet size and other shipping market variables over January 1973–October 2010. The study employs a two-step model specification. The first step is the measurement of freight rate volatility through an AR-GARCH model; the second step is the analysis of the relationship between freight rate volatility and fleet size growth through a GMM regression. We confirm similar findings in the literature that freight rate volatility is time varying. Furthermore, the results reveal that the change in fleet size positively affects freight rate volatility, while the spot rate volatility of Capesize dry bulk exhibits a stronger reaction to the change in fleet size. The results of this study contribute in a general sense to understanding the systematic risk of shipping markets.     

Truck and trailer scheduling in a real world,dynamic and heterogeneous context

We present a new variant of the Vehicle Routing Problem based on a real industrial scenario. This VRP is dynamic and heavily constrained and uses time-windows, a heterogeneous vehicle fleet and multiple types of job. A constructive solver is developed and tested using dynamic simulation of real-world data from a leading Scottish haulier. Our experiments establish the efficiency and reliability of the method for this problem. Additionally, a methodology for evaluating policy changes through simulation is presented, showing that our technique supports operations and management. We establish that fleet size can be reduced or more jobs handled by the company.     

Optimal fleet utilization and replacement

The fleet replacement problem of a profit-maximizing manager is examined using an optimal control model that captures both utilization and replacement decisions. Conditions for optimal utilization of each vessel in the fleet and optimal vessel acquisition and retirement strategies are discussed. The results indicate that the optimal replacement schedule and fleet size are influenced by utilization schedules, and vice versa. Thus, replacement and utilization strategies should be determined jointly. We develop a numerical example to illustrate the model's potential as a practical management decision tool and the procedures to solve it.     

An effective genetic algorithm for the fleet size and mix vehicle routing problems

This paper studies the fleet size and mix vehicle routing problem (FSMVRP), in which the fleet is heterogeneous and its composition to be determined. We design and implement a genetic algorithm (GA) based heuristic. On a set of twenty benchmark problems it reaches the best-known solution 14 times and finds one new best solution. It also provides a competitive performance in terms of average solution.     

Container fleet sizing and empty repositioning in liner shipping systems

This paper considers the joint container fleet sizing and empty container repositioning problem in multi-vessel, multi-port and multi-voyage shipping systems with dynamic, uncertain and imbalanced customer demands. The objective is to minimize the expected total costs including inventory-holding costs, lifting-on/lifting-off costs, transportation costs, repositioning costs, and lost-sale penalty costs. A simulation-based optimization tool is developed to optimize the container fleet size and the parameterized empty repositioning policy simultaneously. The optimization procedure is based on Genetic Algorithms and Evolutionary Strategy combined with an adjustment mechanism. Case studies are given to demonstrate the results.     

The transformation of a legacy carrier – A case study of Turkish Airlines

This study examines the metronomic rise of Turkish Airlines into a global carrier in the period following domestic deregulation and part privatisation. Using a comparative assessment of the carrier's network and its competitive strategies during the 2003–2013/2014 period it was found that Turkish Airlines now benefits from considerable network, cost, service and brand advantages over competing European and to a lesser extent Middle-Eastern airlines. Its network operation based in Istanbul Ataturk airport enjoys strong geographic and demographic advantages, which enables it to optimise the use of its large and young short-haul fleet between a significant number of domestic and international points. This study has important implications for partially or fully state owned legacy carriers as to how to gain competitive advantages in an increasingly open and liberal airline industry.     

The impact of control strategies on the management of returnable transport items

This research examines the impact of different control strategies on the management of returnable transport items (RTIs) in closed-loop supply chains. A simulation model is developed based on an empirical case and is used to explore different scenarios. The results suggest that the choice of control strategy has a significant impact on investments and operating costs, and that RTI shrinkage can be controlled either through the use of tracking systems, or choice of control strategy. Moreover, a simulation-based method for estimating the fleet size required to operate the system for the different strategies is presented.