TKCAD软件系统的运行管理

TKCAD 是在微机上开发的铁道客车计算机辅助设计软件系统,该系统要求多环境支持,并具有复杂的运行流程方式.本文实现了该软件系统的运行管理体制,并提出了内存中不留任何残余碎块的汉字操作系统的动态撤离技术.     

公路工程中混凝土配制最小费用的简单计算

应用优化原理,利用Excel软件辅助设计,解决了公路工程中混凝土配制的优化问题。     

地铁联络线建设成本优化法的0-1规划模型

地铁联络线合理布局既是城市轨道交通线网规划的重要组成部分,又是提高线路通过能力的必要保证。通过对联络线的重要性以及建设成本优化法的基本思路和寻优过程进行分析,找出了该方法的不足,建立0-1规划模型,并用lingo编程实现最优化;最后得到一般情况下该问题的数学模型。     

Line haul interstation spacing for low cost feeder modes

The choice behaviour of low cost travel (LCT) modes is very sensitive to travel distance. A line haul system designed on the basis of current planning practice of locating widely spaced stations to cater auto and bus feeder modes with the primary objective of gaining travel speed is hostile to non‐motorized and low cost feeder modes. With the revival of interest in promoting the use of walk'n ride and bike'n ride modes, there is a need to develop an appropriate tool to examine the effect of their specific characteristics in establishing the number and location of stations.

A generic normative behavioural hybrid model for locating the cost minimizing number and location of stations is developed for an LCT‐fed line haul system. The model considers the system with many to many two dimensional line haul demand density function in which the density varies in both x‐ and y‐directions. The feeder mode choice behaviour is incorporated in the model by integrating probability‐access/egress distance function with the objective function. Explicit functional relationships among the parameters of these feeder modes such as modal share as a function of access/egress distance with the parameters of line haul systems are developed. Dynamic programming is used to minimize the system cost. The generic model is shown to collapse into several simplified models capable of yielding approximate solutions for several well known special cases. It has been shown that location of stations is sensitive to the through load on board as well as users’ cost that defines the choice behaviour at large. Numerical examples are presented to demonstrate the applicability of the model.     

铁路紧急输送计划模型与算法研究

铁路日常运输生产过程中,有时会产生一些特殊需求的紧急运输。针对其运量大、时限要求紧的特点,可采用基于"固定点号"的方法安排运行计划,实现流线间的有机结合。本文阐述"固定点号"的相关概念和基本方法,建立了基于"固定点号"方法的多个0-1规划模型。在车站到发能力满足一定利用率条件下,通过对运行线的选用与匹配,明确"固定点号",使到达列车车次与出发列车车次相互接续且接续时间最短。其中,"车站对点号模型"描述前后接续的三个车站组成的"车站对"的运行线运用情况,"多车站对点号模型"描述相邻的多个"车站对"的运行线运用情况,"径路点号模型"描述运输径路的运行线运用情况。提出采用分支定界法求解上述模型,在求解规模较大的径路点号模型时,可采用动态规划方法,先计算节点间的局部径路,再求解仅包含节点的简化径路。针对上述模型提供算例,并编程计算给予验证。     

Computing 4D near-optimal trajectories for dynamic air traffic flow management with column generation and branch-and-price

Abstract

The current air traffic system faces recurrent saturation problems. Numerous studies are dedicated to this issue, including the present research on a new dynamic regulation filter holding frequent trajectory optimisations in a real-time sliding horizon loop process. We consider a trajectory optimisation problem arising in this context, where a feasible four-dimensional (4D) trajectory is to be built and assigned to each regulated flight to suppress sector overloads while minimising the cost of the chosen policy. We model this problem with a mixed integer linear programme and solve it with a branch-and-price approach. The pricing sub-problem looks for feasible trajectories in a dynamic three-dimensional (3D) network and is solved with a specific algorithm based on shortest path labelling algorithms and on dynamic programming. Each algorithm is tested on real-world data corresponding to a complete traffic day in the European air traffic system; experimental results, including computing times measurement, validate the solution process.     

Two-stage stochastic bilevel programming over a transportation network

We consider a two-stage stochastic extension of the bilevel pricing model introduced by Labbé et al. (1998). In the first stage, the leader sets tariffs on a subset of arcs of a transportation network, with the aim of maximizing profits while, at the lower level, flows are assigned to cheapest paths of a multicommodity transportation network. In the second stage, the situation repeats itself under the constraint that tariffs should not differ too widely from those set at the first stage, a condition that frequently arises in practice. We analyze properties of the model, provide numerical illustrations, and open avenues for further research into this area.     

An optimal aircraft fleet management decision model under uncertainty

Decision planning for an efficient fleet management is crucial for airlines to ensure a profit while maintaining a good level of service. Fleet management involves acquisition and leasing of aircraft to meet travelers' demand. Accordingly, the methods used in modeling travelers' demand are crucial as they could affect the robustness and accuracy of the solutions. Compared with most of the existing studies that consider deterministic demand, this study proposes a new methodology to find optimal solutions for a fleet management decision model by considering stochastic demand. The proposed methodology comes in threefold. First, a five‐step modeling framework, which is incorporated with a stochastic demand index (SDI), is proposed to capture the occurrence of uncertain events that could affect the travelers' demand. Second, a probabilistic dynamic programming model is developed to optimize the fleet management model. Third, a probable phenomenon indicator is defined to capture the targeted level of service that could be achieved satisfactorily by the airlines under uncertainty. An illustrative case study is presented to evaluate the applicability of the proposed methodology. The results show that it is viable to provide optimal solutions for the aircraft fleet management model. Copyright © 2013 John Wiley & Sons, Ltd.     

A slot reallocation model for containership schedule adjustment

Ship slot capacity is the main sale resource of container shipping lines. However, shipping lines often encounter situations, such as serious ship delays, that require adjustments of shipping schedules, causing the original delivery plans of some consignments to be altered. This study proposes an integer programming model for slot reallocation planning, based on a given adjusted schedule. Decisions regarding empty container repositioning are also examined. This model aims to maximise a company’s benefits from deliveries of consignments and movements of empty containers. Available slots are subject to port rotation changes, allowable port handlings and ship capacity. A case study of a deep ocean loop demonstrates optimal slot reallocation, and empty container repositioning is used for illustrative purposes. The reallocation characteristics due to benefit items and the model’s applicability to large-scale examples are discussed.     

地下连续墙局部与整体稳定性分析

连续墙的稳定性问题在实际工程中是比较重要的工程问题.在分析了连续墙可能的破坏形式后,提出连续墙的局部与整体破坏模式.利用极限分析上限定理,构建摩尔-库伦土体中两种破坏模式的速度机动场,并求得了相应的外力功率与内部能量耗散,利用内外功率相等,将稳定性问题转化为非线性规划问题,并提出了相应的约束条件.利用优化算法,求得了局部破坏的稳定系数与整体破坏的安全系数,并分析了连续墙的稳定性随强度参数的变化规律.