飞机登机策略分析Ⅰ——离散事件模拟模型

我们建立了一种离散事件模拟登机模型,分析了不同的登机策略并提出了三种新的有效的登机策略.模型建立在模拟的基础上,因而是有效和精确的.模型以一种外在的多角度的方式判定一个登机策略的优劣.模型中有一些参量,通过调整这些参量可以改变模型以适应各种机型和不同的登机情形.通过灵敏度分析我们注意到"注意度"和"随意度"是两个重要的因素,它们是除登机总时间和平均时间外评价一个方案优劣的关键.     

飞机登机策略分析Ⅱ——利用微分几何模拟登机

利用微分几何学的知识建立了一种登机模型,模型主要研究一般关系的时空.它是一个机制模型,可以用来获得解析解.使用米制单位描述登机过程.乘客在登机时的妨碍关系产生了时空中自然的偏序,登机时间与最长的偏序链的大小一致.     

机票预定问题的多阶段决策模型

本文讨论了机票预定的一种方法 .通过建立多阶段决策模型 ,将订票时期分成若干个阶段 ,在每一个阶段航空公司对乘客要求订票作出不同的反应 ,保证了检票时准备登机的人数与飞机上的座位数目相当接近     

基于BP神经网络的航空公司机队可靠性评价模型

机队作为航空公司运输能力的关键,其安全性与可靠性直接影响到航空公司的经济效益.根据航空公司机队可靠性统计和数据采集方式以及实际应用情况,建立了航空公司机队可靠性评价指标体系.鉴于机队可靠性受多种复杂因素影响及各指标体系非线性等特点,结合人工神经网络基本原理和特性,提出了BP神经网络机队可靠性评价模型.最后应用该模型对航空公司机队可靠性进行了实例分析,得出了评价等级.结果表明,基于BP神经网络机队可靠性评价模型是可行的,该方法能够实现动态的评价,对提高航空公司机队可靠性评价技术水平具有现实的意义.     

航空公司维修不安全事件优先控制模型研究

鉴于机务维修不安全事件发生具有随机性、不确定性和复杂性等模糊灰色特性,建立了航空公司机务维修不安全事件模糊灰色关联优先控模型.以航空公司维修不安全事件为例,应用模型对航空公司维修不安全事件关联度和关联序进行了计算,得出了航空公司的维修不安全事件优先控制次序.结果表明,模型简单,易操作,能客观反映不安全事件发展趋势,为航空公司维修安全管理提供了一种更为科学的定量化依据.     

航空公司维修不安全事件优先控制模型研究北大核心

鉴于机务维修不安全事件发生具有随机性、不确定性和复杂性等模糊灰色特性,建立了航空公司机务维修不安全事件模糊灰色关联优先控模型.以航空公司维修不安全事件为例,应用模型对航空公司维修不安全事件关联度和关联序进行了计算,得出了航空公司的维修不安全事件优先控制次序.结果表明,模型简单,易操作,能客观反映不安全事件发展趋势,为航空公司维修安全管理提供了一种更为科学的定量化依据.     

基于签派可靠度的航空公司运行品质评价方法研究

签派可靠度是反映航空公司运行品质和运营效率的顶层参数,以签派可靠度为顶层指标,根据航空公司实际运行环境,结合航空公司各主要业务部门的运行数据,建立签派可靠度评估模型,形成影响签派可靠度的二级指标体系.利用区间数层次分析法和可能度法实现各二级指标的综合权重计算和分级排序.对航空公司运行品质影响较大的二级指标,依次为日利用率,延误率,报告故障率.以国内某个航空公司为例,根据底层指标得分情况,利用幂指数法,确定签派可靠度的综合得分,最终实现该航空公司运行品质评估.研究结果表明模型能够对航空公司运行品质做出综合评价,便于发现运行决策中的薄弱环节,重点解决维修可靠性问题,可以提升航空公司的运行品质.     

报童模型及ARMA预测在航空配餐问题中的应用

航班承载人数的不确定性,造成航空公司在配餐中利润的流失,现存的配餐模式存在较多的浪费.本文利用基于损失厌恶的报童模型和ARMA时间序列分析模型对深圳航空公司某航班的配餐份数进行了建模分析和预测,并通过对两种模型输出的比较,得出了长期预测与短期预测的模型应用理论.将实际的历史数据代人到模型中验证,其结果优于经验模式下的配餐盈利情况.本文所采用的研究方法和研究结果对航空公司的精益发展有建设性的意义.     

基于直觉模糊熵的机务维修不安全因素优控模型

机务维修安全是飞行安全的基础,是航空公司健康运行的重要前提.优先控制机务维修中的不安全因素,有助于提高航空公司机务维修安全管理水平.基于直觉模糊熵,建立了航空公司机务维修不安全因素优控模型,结合某航空公司机务维修不安全事例,应用模型对航空公司机务维修不安全因素的直觉模糊熵进行了计算,得到了机务维修不安全因素的优控顺序.结果表明,方法得到的分析结果准确、可操作性强,能客观反映不安全因素的优先控制顺序,为航空公司机务维修安全管理提供了新的思路.     

航空客票销售渠道的博弈研究

为研究航空公司和机票代理人之间的博弈过程,在分析航空公司和代理人在不同策略下各自的得益基础上,建立了静态博弈模型,并运用演化博弈理论对航空公司的机票直销策略选择与代理人策略选择的互动机制进行了分析.博弈分析结果显示,航空公司和代理商在以下情况时存在进化稳定策略:当代理销售成本高于直销成本时,航空公司会加大直销力度;而航空公司的直销策略比较强势时,当代理商抵制策略的概率会大大增加;航空公司缓和推进直销时,代理会也会采取缓和策略.     

A remarkable configuration: A generalization of computergenerated results by S.-C. Chou and its connection with a plane figure by A. Emch

The paper's starting point are four theorems on conics which can be found in a collection of computer proved results by C.-S. Chou from 1987. It not only contains a generalization of two of Chou's results but also a plane figure consisting of points, lines and conics. A suitable notation will reveal a striking symmetry of this figure. Moreover, it turns out that a plane figure from 1940 found by A. Emch using algebraic methods is very similar to ours, which we obtained synthetically. As an application in finite geometry we have gone some way towards regarding our figure as a real projective model of the finite projective plane of order 4.Dedicated to Dr. J. F. Rigby on the occasion of his 65th birthday     

Dynamic cruise ship revenue management

Recently, it has been recognized that revenue management of cruise ships is different from that of airlines or hotels. Among the main differences is the presence of multiple capacity constraints in cruise ships, i.e., the number of cabins in different categories and the number of lifeboat seats, versus a single constraint in airlines and hotels (i.e., number of seats or rooms). We develop a discrete-time dynamic capacity control model for a cruise ship characterized by multiple constraints on cabin and lifeboat capacities. Customers (families) arrive sequentially according to a stochastic process and request one cabin of a certain category and one or more lifeboat seats. The cruise ship revenue manager decides which requests to accept based on the remaining cabin and lifeboat capacities at the time of an arrival as well as the type of the arrival. We show that the opportunity cost of accepting a customer is not always monotone in the reservation levels or time. This non-monotone behavior implies that “conventional” booking limits or critical time periods capacity control policies are not optimal. We provide analysis and insights justifying the non-monotone behavior in our cruise ship context. In the absence of monotonicity, and with the optimal solution requiring heavy storage for “large” (industry-size) problems, we develop several heuristics and thoroughly test their performance, via simulation, against the optimal solution, well-crafted upper bounds, and a first-come first-served lower bound. Our heuristics are based on rolling-up the multi-dimensional state space into one or two dimensions and solving the resulting dynamic program (DP). This is a strength of our approach since our DP-based heuristics are easy to understand, solve and analyze. We find that single-dimensional heuristics based on decoupling the cabins and lifeboat problems perform quite well in most cases.     

席位分配问题的一种新算法

讨论了席位分配问题的已有方法与H.P.Y oung公理体系中公理4之间的关系.通过数据算例指出已有方法都不能使公理4与极差最小同时满足.据此,我们建立了在满足公理4的前提下的最小极差法.     

Solving a school bus scheduling problem with integer programming

In many rural areas in Germany pupils on the way to school are a large if not the largest group of customers in public transport. If all schools start more or less at the same time then the bus companies need a high number of vehicles to serve the customer peak in the morning rush hours. In this article, we present an integer programming model for the integrated coordination of the school starting times and the public bus services. We discuss preprocessing techniques, model reformulations, and cutting planes that can be incorporated into a branch-and-cut algorithm. Computational results show that in our test counties a much lower number of buses would be sufficient if the schools start at different times.     

Stationary Brownian motion in a 3/4-plane: Reduction to a Riemann–Hilbert problem via Fourier transforms

The stationary reflected Brownian motion in a three-quarter plane has been rarely analyzed in the probabilistic literature, in comparison with the quarter plane analogue model. In this context, our main result is to prove that the stationary distribution can indeed be found by solving a boundary value problem of the same kind as the one encountered in the quarter plane, up to various dualities and symmetries. The main idea is to start from Fourier (and not Laplace) transforms, allowing to get a functional equation for a single function of two complex variables.     

The give-up problem for blocked regional lists with multi-winners

The current electoral law for the Italian Parliament prescribes blocked, linearly ordered lists of candidates for each party within each constituency. The peculiarity of the Italian electoral system is that a party can present the same candidate in different constituencies. There are several seats at stake in each constituency; these seats are allocated to the parties proportionally to the total number of votes they get. If the blocked list mechanism-which assigns the seats obtained by a party in a constituency to the first candidates of the corresponding ordered list-causes some candidates to win in more than one constituency, they may retain only one of the seats, giving up all the remaining ones. Thus, the problem arises for a party to find a suitable “schedule of give-ups” that produces the final set of winners for that party. In order to do this, we assume that such decision is centralized and based on some models of global (inter-regional) preferences over the set of candidates. In this paper, we introduce two classes of models to formulate the “give-up problem”, i.e., utility and ordinal models, and we show that for both of them some natural formulations of the problem can be efficiently solved by network flows techniques.     

A Suggested Mechanism for Nonlinear Wall Roughness Effects on High Reynolds Number Flow Stability

The interactions between an uneven wall and free stream unsteadiness and their resultant nonlinear influence on flow stability are considered by means of a related model problem concerning the nonlinear stability of streaming flow past a moving wavy wall. The particular streaming flows studied are plane Poiseuille flow and attached boundary-layer flow, and the theory is presented for the high Reynolds number regime in each case. That regime can permit inter alia much more analytical and physical understanding to be obtained than the finite Reynolds number regime; this may be at the expense of some loss of real application, but not necessarily so, as the present study shows. The fundamental differences found between the forced nonlinear stability properties of the two cases are influenced to a large extent by the surprising contrasts existing even in the unforced situations. For the high Reynolds number effects of nonlinearity alone are destabilizing for plane Poiseuille flow, in contrast with both the initial suggestion of earlier numerical work (our prediction is shown to be consistent with these results nevertheless) and the corresponding high Reynolds number effects in boundary-layer stability. A small amplitude of unevenness at the wall can still have a significant impact on the bifurcation of disturbances to finite-amplitude periodic solutions, however, producing a destabilizing influence on plane Poiseuille flow but a stabilizing influence on boundary-layer flow.     

Mechanically homogenized material model for a pack of sheets

In the present contribution we discuss the modeling of a large number of plane metal sheets under compressive forces. The direct approach to this contact problem is based on a finite element (FE) discretization of each sheet and a contact formulation between each adjacent sheet. The numerical problem is highly non-linear and of very large dimension. Therefore it is difficult to be solved by conventional FE-software. We propose to replace the contact model by a homogenized constitutive law, which behaves as a pack of infinitely thin sheets. A coarser discretization as for the contact model can be used. A pack of sheets under pressure normal to the sheet plane serves as a benchmark example. The model is verified and implemented for the 2D case and numerical results of the test case are shown. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Homogenization of thin structured sheet metals by using FEM

Thin structured sheet metals promise high potential concerning lightweight design in industrial applications regarding the classical mechanical engineering and vehicle construction as well as the aeronautics. Compared to flat, unstructured sheet metals the component stiffness and buckling behavior can significantly be improved by structuring especially in out of plane direction. To be able to calculate the elastic behavior of large structures from structured sheet metals a mechanical surrogate model is developed which describes effectively average material parameters based on processes of homogenization. For the surrogate properties symmetry and antisymmetry boundaries and periodic boundaries respectively are contemplated on elementary cells whose structural mechanical behavior is decisive. By using an energetic approach [3] the stiffnesses of large plate and shell structures can be determined by a cooperatively small amount of finite elements. By means of these material properties elastic behavior can easily be calculated. With it an efficient numerical design is guaranteed. This explained analysis can be applied to other periodically built up plate structures. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)