Variations in hub service in the US domestic air transportation network

This paper looks at the various types of hubs that have evolved in the air transportation network in the USA. Since deregulation of the industry at the end of the 1970s, the major air carriers have expanded their networks to become more competitive, and the number and types of hubs have grown accordingly. A connectivity analysis using a traditional matrix approach is used to derive indices which are the basis for the development of a connectivity classification scheme. In addition, the various service functions of hubs are explored.     

由单一走向多样：平原农业区生物多样性 保护的规划途径——以辽宁省黑山县为例

平原农业区的生产和土地利用方式严重影响区域的 生物多样性,利用融合多学科的景观空间规划构建有效的评价 方法和格局优化模式以实现多样化的生境保护和恢复,提升生 物多样性具有重要的作用。以辽宁省黑山县为例,首先梳理了 平原农业区对于生物多样性威胁的机制和研究的框架;其次识 别平原农业区的特殊生境类型,使用景观格局指数和InVEST 模型的生境质量评价构建多尺度生境质量评价机制;同时使用 基于图论和电路理论的Linkage Mapper软件,识别和分级 空间中的重要生态源地、潜在廊道及廊道上的关键夹点区域。 结果显示,农业景观中空间异质性和连接性影响生物多样性; 研究区有主要生境23类,整体生境质量较差,农田面积较大 是造成该问题的主要原因;识别出核心斑块33个,重要廊道 34条,通过与卫星图比照,廊道位置与线性生境重合;关键 夹点区域位于靠近农村居民点的自然生境上,故营造人类干扰 与生态平衡农村居住区是空间规划的重点;同时根据以上研究 提出了多尺度的空间规划途径,为平原农业区生境优化和生物 多样性保护提供了一定的理论参考。     

基于城市道路通行能力的重心法在配送中心选址问题中的应用

基于重心法选址模型,通过多目标法决策理论,将道路通畅稳定性系数引入模型中来修正相关道路距离参数,使得整体模型的最终计算结果更具合理性与可行性,最后通过一个具体的模型算例证明本模型修正算法的正确性。     

Scheduling-capable autonomic manager for policy-based IT change management system

Managing large IT environments is expensive and labour intensive. Maintaining and upgrading with minimal disruption and administrative support has always been a challenging task for system administrators. One challenge faced by IT administrators is arriving at schedules for applying one or more change requests to one of the system components. Most of the time, the impact analysis of the proposed changes is done by humans and is often laborious and error-prone. Although this methodology might be suitable to handle changes that are planned way ahead in time, it is completely inappropriate for changes that need to be done sooner. In addition, such manual handling does not scale well with the size of the IT infrastructure. In this article, the focus is on the problem of scheduling change requests in the presence of organisational policies governing the use of its resources. The authors propose two approaches for change management scheduling and present the implementation details of two prototypes that prove the feasibility of the proposed approaches. Their implementation is integrated with an autonomic manager which they had described in their earlier work.     

Using connectivity for measuring equity in transit provision

This study proposes the assessment of equity in transit provision by using transit connectivity as a comprehensive impedance measure. Transit connectivity considers in-vehicle time, access/egress times, waiting time, service reliability, frequency, and ‘seamless’ transfers along multi-modal paths. In addition, transit connectivity weighs the impedance components according to their relative importance to travelers. The assessment of equity was performed for the multi-modal transit system in the Greater Copenhagen Area, renowned for its transit-oriented finger-plan. The assessment method used a GIS representation of the network (i.e., service lines, timetables, metro stations, train stations, and bus stops), and transit assignment results (i.e., level-of-service times, passenger flows). The assessment method proved effective in calculating location-based and potential-accessibility measures and Gini coefficients of inequality in the Greater Copenhagen Area. Results show that the transit-oriented development contributes to spatial equity with high connectivity in densely populated zones, vertical equity with comparable connectivity in high income and low income zones, inter-generational equity with good connectivity provision for students to higher-education and job opportunities. Also, results show that the north-west ‘finger’ is less equitable with lower connectivity for low population density and lower connectivity to higher-education opportunities regardless of the high number of students.     

Evolution of the European network and implications for self-connection

Self-connection has become an appealing alternative for passengers in the European air transportation market, along with the remarkable growth of the low-cost carriers (LCCs) network over the last decade. As the development of self-connectivity is not directly designed in airports and airlines' growth strategies, this study aims to deeply understand the evolution of self-connectivity options in the intra-European market over time. By implementing a quickest travel time approach, we analyse the number of quickest connections and the share of indirect quickest paths that remained un-managed in years 2006 and 2016. Results document that, overall, travelling in Europe has become faster (−5.7 min of weighted average), while European airports' coverage, that is, airport pairs that can be directly or indirectly connected, decreased from 65% to 53%. The strong increase in LCCs' seat capacity (74%) did not translate into a similar growth of indirect connections options. Due to LCCs' offer redistribution and traditional carriers' partial retreatment from the European market to concentrate on intercontinental destinations, 1-transfer managed or un-managed options available to passengers in Europe dropped by 9.5%, and the share of 1-transfer quickest paths achievable by self-connecting flights increased by only 3pp, from 66% in 2006 to 69% in 2016.     

An airline connection builder using maximum connection lag with greedy parameter selection

This paper introduces a methodology for designing an airline connection builder (CB) and adjusting its parameter settings. The objective of the proposed CB is to construct relevant connections that attract passenger demand while avoiding operationally infeasible and commercially irrelevant connections. Using worldwide MIDT booking data, we examined the sensitivity of CB results to the setting of the standard CB parameters maximum connection time and geographical detour. We demonstrated that CB performance can be increased by replacing these two parameters with connection lag, a measure that combines the impact of connection time with geographical detour on the total travel time of a given connection. We also found that the willingness of a passenger to book slower connections and the relationship between the number of passenger bookings and generated connections strongly depends on the O&D distance. Better results can thus be obtained by greedily determining the distance-specific CB parameter settings. The greedy adjustment of parameter settings reduces the number of unattractive connections generated, while keeping the number of covered passenger bookings high.     

Transit-oriented development,integration of land use and transport,and pedestrian accessibility: Combining node-place model with pedestrian shed ratio to evaluate and classify station areas in Lisbon

Transit-oriented development is being actively promoted as an urban design model for areas around transit stations. In addition, planning for accessibility is being promoted, which requires integrating land use with transportation planning, and to match the transportation features with the intensity and diversity of land use of the station areas. Nevertheless, and despite the evident similarities between the two approaches, an integrated evaluation tool of a station area in terms of its transportation, land use, and urban design features is missing. In this paper, we bring into the literature on integration of land use and transport a key feature of the transit-oriented development literature: the urban design features of the station areas, in particular their pedestrian friendliness. By complementing the node-place model with an evaluation of the pedestrian connectivity of station areas of Lisbon, we combine these two perspectives in order to evaluate and classify station areas in three different aspects: land use, transportation, and walkability conditions. Our results show that a balanced node-place is not necessarily a transit-oriented development, and vice versa, and so a complementary analysis of both is useful to identify and classify a station area. Therefore, we suggest a typology of station areas based on the three components, which might be used as a planning tool for the development of the station areas into balanced transit-oriented development areas.     

Algebraic connectivity maximization of an air transportation network: The flight routes’ addition/deletion problem

A common metric to measure the robustness of a network is its algebraic connectivity. This paper introduces the flight routes addition/deletion problem and compares three different methods to analyze and optimize the algebraic connectivity of the air transportation network. The Modified Greedy Perturbation algorithm (MGP) provides a local optimum in an efficient iterative manner. The Weighted Tabu Search (WTS) is developed for the flight routes addition/deletion problem to offer a better optimal solution with longer computation time. The relaxed semidefinite programming (SDP) is used to set a performance upper bound and then three rounding techniques are applied to obtain feasible solutions. The simulation results show the trade-off among the Modified Greedy Perturbation, Weighted Tabu Search and relaxed SDP, with which we can decide the appropriate algorithm to adopt for maximizing the algebraic connectivity of the air transportation networks of different sizes. Finally a real air transportation network of Virgin America is investigated.     

信息时代员工“缺席与逃离”：工作连通的负面效应研究

基于主体能动性理论,通过229份有效问卷调查分析,探讨工作连通对工作退缩行为的影响及作用机制。研究发现：工作连通与工作退缩行为、工作连通与角色超载均正相关;角色超载工作连通和工作退缩之间起中介作用;辱虐型领导调节了工作连通和工作退缩行为之间的关系,当辱虐型领导越强,工作连通与工作退缩的正向关系越强。