Identifying airline cost economies: An econometric analysis of the factors affecting aircraft operating costs

This paper provides the results of an econometric analysis of the influences of airline characteristics on the average operating costs per aircraft movement. The analysis combines a comprehensive selection of airline-output variables, airline-fleet variables, and airline-market variables. The results confirm the existence of economies of density, economies of load factor, economies of aircraft utilisation and economies of aircraft size. The paper does not provide evidence of economies of scale, economies of stage length or economies of fleet commonality. Furthermore, airlines that additionally operate full freighters, airlines that are members of a worldwide alliance and airlines that operate a multi-hub system face higher average operating costs per aircraft movement. Surprisingly, the regression results demonstrate that airlines that use newer aircraft have higher average operating costs per aircraft movement, suggesting that ownership costs (depreciation and leasing costs) of new aircraft outweigh the increasing maintenance costs of old aircraft. Finally, the results show that airlines that have a dominant position at their hubs or bases have higher operating costs per aircraft movement, implying that the absence of serious competitive pressure enables airlines to charge higher ticket prices and, with that, leads to a limited focus on cost savings.     

基于模块化的中国大型民用飞机国际合作博弈分析

目前大型民用飞机已经形成全球化分工协作的基本格局,很多国家在某些部件的研制生产方面已经达到了很高的水平,而中国大型民用飞机的生产技术还远远落后于一些发达国家。从博弈分析来看,中国大型民用飞机产业的发展需要在坚持自主创新的基础上进行转包生产,同时与其他国家进行合作,充分利用其他国家的先进技术,实现双赢。     

士官《飞机结构强度》教学方法探讨

在分析士官学员特点和《飞机结构强度》课程特点的基础上,从巧妙设置问题、运用对比分析、采用归纳总结、联系部队装备、结合生活常识、引用历史典故和补充前沿知识等方面探讨了《飞机结构强度》课程的教学方法,以期达到提高教学质量、改善教学效果的目的。     

基于动态事件调度仿真的高速铁路动车组运用计划计算机协同编制方法的研究

依据动车组运用的牵引动力与载客装置不可分离的原则,动车组挂运接续和列车运行线的时点是一致的,因此将这些时点作为变量,考虑动车组整备维修、动车组站段折返接续作业时间、列车运行线铺画约束、列车挂运匹配等条件,建立以动车组运用效率和列车运行计划均衡性为指标的基本模型,采用动态事件表调度方法实现可行方案编制,研究站间固定区段运用模式下,单基地多车种的动车组运用计划与成对列车运行计划协同编制问题。最后以京津客运专线实际条件模拟编制动车运用计划,以验证模型与算法的可行性。     

服务连锁零售企业的配送中心内越库车辆调度研究

合理安排入库车辆到库时间对于保证服务连锁零售企业的配送中心内货物顺利流转和降低成本至关重要。在假设只有一个入库门和一条传送带的越库环境下,将卸货和分拣的过程视为两阶段流水作业,应用约翰逊算法求解货物(工件)工时跨度最小化问题。根据某配送中心的excel订单数据,求得中心将该批货物分拣完毕需要的最短时间,并确定最佳入库车辆到库顺序,为企业越库实践提供指导。     

新产品开发过程中的任务调度与分配

新产品开发过程工程管理是企业和研究者关注的热点,其过程中的任务调度和资源优化配置,对于资源的利用率、开发成本和开发周期都有改善作用。通过回顾新产品开发过程中的任务调度、任务分配、试验任务分配等方面的研究进展,发现这方面的研究总体上还比较匮乏,特别是试验任务调度与分配研究。在此基础上分析了其主要考虑的模型要素以及常用的求解方法,为进一步研究提供参考。     

一种面向多资源约束的关键链识别方法

针对资源受限项目调度问题,提出了一种面向多资源约束的关键链识别算法。该算法首先基于优先规则的资源受限并行调度算法生成调度结果,接着依据此结果将活动的资源约束转换为活动的时序约束,形成新的时序约束活动依赖矩阵,然后以此为基础结合传统向后调度算法计算在此时序约束下活动的总时差,最后根据总时差值来确定关键活动,并组成关键链。     

流水工序调度与生产效率的关系模型分析

提出一种基于粒子群算法的流水工序调度任务优化模型。利用流水工序调度任务的特点得到流水工序时间约束条件,利用粒子群算法的原理建立流水工序调度任务优化模型,利用粒子群算法对模型进行求解。仿真实验表明,利用该算法能够得到流水工序调度问题的最优解,提高生产效率。     

Flexibility in the gig economy: managing time on three online piecework platforms

Gig economy platforms seem to provide extreme temporal flexibility to workers, giving them full control over how to spend each hour and minute of the day. What constraints do workers face when attempting to exercise this flexibility? We use 30 worker interviews and other data to compare three online piecework platforms with different histories and worker demographics: Mechanical Turk, MobileWorks, and CloudFactory. We find that structural constraints (availability of work and degree of worker dependence on the work) as well as cultural‐cognitive constraints (procrastination and presenteeism) limit worker control over scheduling in practice. The severity of these constraints varies significantly between platforms, the formally freest platform presenting the greatest structural and cultural‐cognitive constraints. We also find that workers have developed informal practices, tools, and communities to address these constraints. We conclude that focusing on outcomes rather than on worker control is a more fruitful way to assess flexible working arrangements.     

Weekly scheduling models for traveling therapists

This paper presents a series of models that can be used to find weekly schedules for therapists who provide ongoing treatment to patients throughout a geographical region. In all cases, patient-appointment times and visit days are known prior to the beginning of the planning horizon. Variations in the models include single vs. multiple home bases, homogeneous vs. heterogeneous therapists, lunch break requirements, and a nonlinear cost structure for mileage reimbursement and overtime. The single home base and homogeneous therapist cases proved to be easy to solve and so were not thoroughly investigated. This left two cases of interest: the first included only lunch breaks while the second added nonlinear overtime and mileage reimbursement costs. For the first case, 40 data sets were solved, each consisting of either 15 or 20 therapists and between roughly 300 and 540 patient visits over five days. For each instance, we were able to obtain the minimum cost of providing residential healthcare services using a commercial solver. The results showed that CPU time increases more rapidly than total cost as the total number of visits grows. For the second case, which was much more difficult, it was necessary to develop heuristics to find good solutions quickly. Results for 5- through 20-therapist instances are presented and compared to the linear programming relaxation lower bounds. In the first of two parametric analyses, the tradeoff between the number of therapists on staff and the cost of providing service was examined. In the second, a similar tradeoff was explored between cost can the number of home bases used by the therapists.