Robust hub network design problem

This paper presents a robust formulation for the uncapacitated single and multiple allocation hub location problem where demand is uncertain and its distribution is not fully specified. The proposed robust model is formulated as a mixed integer nonlinear program and then transformed into a mixed integer conic quadratic program. An efficient linear relaxation strategy is proposed which is found to deliver the optimal solutions for all the cases considered in this paper. Numerical experiments suggest location of more number of hubs when accounting for demand uncertainty using robust optimization compared to the deterministic setting.     

Evolution of air transport network of China 1930–2012

This paper analyzes the evolution process of the air transport network of China (ATNC) since 1930. Based on the network analysis results, the ATNC has significantly improved in connectivity based on (1) rising alpha, beta and gamma indices, (2) declining diameter and centre index and (3) decreasing average path length and increasing clustering coefficient. The network centralization index reveals a fluctuation phase before 1952, a pre-1980 centralization phase before the economic reform era, a centralization phase after the mid-1990s deregulation, and a decentralization phase between. The k-core decomposition method helps identify the evolution of core network and hierarchy of the ATNC over time. The spatial development model characterizes its structure change in six stages: (1) scattered development, (2) trunk line connection, (3) circular linkage, (4) hub formation, (5) a complex network structure, and (6) emerging multi-airport systems.     

Code-share connectivity within global airline alliances – How much potential is utilized?

This paper analyzes the code-share connectivity of carriers from the three global alliances: Star Alliance, Sky Team and oneworld. We generate 2-leg online and code-share connections to evaluate the existing connectivity. Additionally, we generate all potential interline connections between members of the same alliance that are not yet supported with existing code-shares and analyze what share of the potential connectivity remains unused. We find that code-share connections account to about one-fourth of the total number of international connections offered by alliance members. 73% of those code-share connections are with partners from the same alliance, 6% with carriers from competing alliances and the rest with other carriers, which means that airlines seek partnerships not only within their own global alliance but even with members of competing alliances. At the same time, over 25% of the total potential code-share connections between members of the same alliance remain unused. This connectivity potential is better utilized within the network of Sky Team and oneworld than within Star Alliance. American and European carriers show a higher degree of code-share partnership with their alliance partners than Asian carriers. Overall, code-share partnerships are strongly driven by strategic decisions on bilateral airline level. Many airline-pairs fully utilize their connectivity potential (almost half of the total existing code-share connections) but some cooperate only on selected routes or not at all. Over one-third of the remaining code-share connectivity potential within alliances is attributed to airline-pairs that don't partner at all.     

2-Stage stochastic programming approach for hub location problem under uncertainty: A case study of air network of Iran

In this paper 2-stage stochastic programming has been developed for formulating stochastic uncapacitated multiple allocation hub location problem. This problem is studied under three cases. The first, stochastic demand, the second, stochastic transportation cost and the third, integrated stochastic, which is compounded of first and second cases. A case of air network in Iran is used to evaluate proposed formulations and computational results obtained by GAMS are presented. The results show that considering uncertainty into formulation could cause in different solutions.     

Multi-period hub location problems in transportation

Many transport service providers operate on hub-and-spoke network structures. Major operators may have several dedicated hub facilities that are leased for a time horizon rather than being owned or constructed. For a given discrete planning horizon, service providers must decide on the location of the hub ports (i.e. terminals), the period when the lease contract starts, the period when the existing contracts must be terminated and the flow routing over the entire planning horizon so as to minimize the total operational cost. Thus, we propose a mathematical model for a Multi-period Uncapacitated Multiple Allocation Hub Location Problem with Budget Constraint. The proposed model incorporates several features of practice, particularly from maritime and land transport practices. We also propose a meta-heuristic solution algorithm that produces high-quality solutions in a reasonable amount of time. By exploiting the decomposable structure of the model, we extended a Benders decomposition approach by proposing several improvements. Extensive computational experiments confirm the efficiency of the proposed methods and also show its limitations.     

Hub network design problems with profits

This paper presents a class of hub network design problems with profit-oriented objectives, which extend several families of classical hub location problems. Potential applications arise in the design of air and ground transportation networks. These problems include decisions on the origin/destination nodes that will be served as well as the activation of different types of edges, and consider the simultaneous optimization of the collected profit, setup cost of the hub network and transportation cost. Alternative models and integer programming formulations are proposed and analyzed. Results from computational experiments show the complexity of such models and highlight their superiority for decision-making.     

Air freight hubs in the FedEx system: Analysis of fuel use

This paper provides a data based analysis of FedEx air freighter activities from selected hub locations. The basic idea is that air freighters have a set of range and payload parameters and their corresponding fuel burn depends on weight and distance. Data from 2011 to 12 (FlightAware) are used for 180,000 + flights on origin, destination and aircraft type. The particular aircraft vary widely in payload, but additional parameters may be derived from industry web sites and BTS. The research uses flight activity at hubs such as Memphis and Indianapolis (among others) and computes the aggregate distance flown on specific aircraft. The linkage between the hub and aggregate fuel use (assuming that the out bound flights are allocated to the hub) will give some quantifiable measures of the costs allocated to the hub. The paper examines particular aspects of the air freight system that are especially vulnerable to a spike in the costs of aviation fuel. These observations suggest that traffic to regional air express and air freight hubs is likely to respond in complex ways to fuel costs.     

中泰铁路通道物流枢纽遴选与布局研究

中泰铁路的修建将极大促进沿线成员国之间的贸易合作与交流,遴选与布局中泰铁路通道物流枢纽对物流的高效运输起着重要作用。阐述物流枢纽遴选与布局研究现状,提出构建中泰铁路通道物流枢纽遴选及布局模型,选取云南、泰国铁路沿线13个城市为研究对象,对中泰铁路通道物流枢纽的遴选和布局进行实证分析。研究结果表明:可以通过遴选模型确定中泰铁路经济带的物流枢纽节点,通过布局模型进一步确定中泰铁路国际物流通道的一级物流枢纽及二级物流枢纽,为中泰铁路通道物流枢纽规划布局提供研究依据。     

强势：中国枢纽经济异军突起

中国枢纽经济是改革开放以后逐渐形成规模的,是随着综合国力的不断增强、基本建设大提速而凸显的。经过改革开放30多年的突飞猛进、日积月累、快马加鞭,具有中国特色的社会主义现代化事业实现了跨越式的发展,从而使中国枢纽经济异军突起、内引外连、成长壮大,势头越来越强劲。随着改革开放的不断深化,基本建设的迅速发展,在中国,各种类型的经济枢纽都面临着更加繁重的任务,在经济建设中起到横贯东西、纵跨南北、内引外连、星火燎原的作用,必将为经济发展、社会进步作出更大的贡献。     

兰白城际铁路引入兰州站改扩建方案研究

兰白城际铁路作为兰州站与中卫-兰州高速铁路之间便捷的联络线,可以实现兰州至白银、银川等地城际运输功能,完善兰州枢纽客运布局,引入兰州站改扩建方案对兰州铁路枢纽总图格局、兰州站接发能力及工程投资等都有较大影响。根据兰州铁路枢纽既有铁路现状,结合兰州铁路枢纽总图规划进行兰州站客运量预测,分析兰州站主要作业内容、作业量和存在问题,探讨兰白城际铁路引入兰州站改扩建方案,从运输组织、实施难度和工程投资等方面比选分析,推荐采用兰白城际与兰渝线按线路别引入兰州站方案,对兰州站扩建规模、改扩建方案、咽喉区改扩建方案进行研究。