大跨度隧道施工核心岩柱宽度优化研究

依托重庆轨道交通六号线红土地暗挖车站,利用有限元软件计算不同核心岩柱宽度下,围岩应力,支护结构内力,围岩塑性应变和拱顶沉降随开挖工序的变化。大量计算数据表明,深埋大跨度隧道双侧壁导坑法施工过程中,核心岩柱的宽度存在一个最优值,建议取为隧道跨度的0.3倍,该结论对其他类似的大跨度隧道双侧壁导坑法施工中核心岩柱宽度的留设具有借鉴意义。     

浅谈高速公路排水的优化完善

通过介绍平榆高速公路修建中,排水优化完善的过程和所采用的处理方法,分析了处理路基排水问题和处理已有水利管网与路基相交叉时采用的方法,处理问题时应注意的主要事项和关键时间,浅谈了高速公路排水优化完善的方法,为高速公路的排水设计和施工提出几点建议。     

一种渐变概率选择操作的实数编码量子进化算法

为进一步提高实数编码量子进化算法在进化过程中的种群多样性以及在高维复杂函数优化上的全局收敛性,参照模拟退火算法的特点,提出了一种渐变选择概率的实数编码量子进化算法,该方法通过在进化过程中逐步提高更好解的选择概率,在进化计算初期保持种群的多样性,能较为全面地对解空间进行搜索,而在进化末期,选择概率逐渐提高到1,只接受更好的解而保证算法稳定的收敛。仿真实验结果表明,该算法能有效避免早熟和局部极值问题,具有更快的收敛速度和更高的求解精度。     

基于粒子群的城市交通信号两级模糊控制

针对城市交通流的特点,设计一种单交叉口多相位两级模糊控制器,有效地减少控制规则数,实现相序、绿信比、周期随交通状况而自适应变化,并采用粒子群算法对模糊控制器的隶属度函数进行优化。仿真结果表明,该系统能有效地提高交叉口的通行能力,减少车辆平均延误。     

三峡水库航运优化调度蓄水方案研究

文章通过研究分析水库蓄水过程对坝上下游河段演变的影响,并根据汛末长江来水过程,对三峡枢纽汛末蓄水的起蓄时间、起蓄水位及下泄流量进行了研究,提出了合理的优化调度方案。该方案可降低三峡枢纽汛末蓄水对坝上回水变动区河段淤积的不利影响．提高对坝下河段浅滩的冲刷效果,并保证三峡水库按时蓄满。     

Ground delay program planning under uncertainty in airport capacity

Abstract

This paper presents an algorithm for assigning flight departure delays under probabilistic airport capacity. The algorithm dynamically adapts to weather forecasts by revising, if necessary, departure delays. The proposed algorithm leverages state-of-the-art optimization techniques that have appeared in recent literature. As a case study, the algorithm is applied to assigning departure delays to flights scheduled to arrive at San Francisco International Airport in the presence of uncertainty in the fog clearance time. The cumulative distribution function of fog clearance time was estimated from historical data. Using daily weather forecasts to update the probabilities of fog clearance times resulted in improvement of the algorithm's performance. Experimental results also indicate that if the proposed algorithm is applied to assign ground delays to flights inbound at San Francisco International airport, overall delays could be reduced up to 25% compared to current level.     

基于正装迭代法的斜拉桥二次调索计算方法研究

索力计算是斜拉桥二次调索的关键技术环节。文章以一座采用二次调索施工的斜拉桥为例,介绍了运用结合影响矩阵的正装迭代法计算斜拉桥二次调索施工索力的方法,并通过施工过程仿真分析,验证了该方法计算结果精确,能有效控制斜拉桥施工过程的内力与线形,确保设计成桥状态得以实现。     

Optimal stop spacing and headway of congested transit system considering realistic wait times

Abstract

This paper revisits the classical transit scheduling problem and investigates the relationship between stop spacing and headway, considering realistic wait time and operable transit capacity. Headway and stop spacing are important determinants for planning a transit system, which influence the service level as well as the cost of operation. A mathematical model is developed, and the objective function is user travel time which is minimized by the optimized stop spacing and headway, subject to the constraints of operable fleet size and route capacity. Optimal stop spacing and headway solutions are obtained in a numerical example. Sensitivity analysis is conducted, and the effect of model parameters on user travel time is explored.     

Disruption Management of an Inequality-Based Multi-Fleet Airline Schedule by a Multi-Objective Genetic Algorithm

Abstract

This paper presents a novel application of a Method of Inequality-based Multi-objective Genetic Algorithm (MMGA) to generate an efficient time-effective multi-fleet aircraft routing algorithm in response to the schedule disruption of short-haul flights. It attempts to optimize objective functions involving ground turn-around times, flight connections, flight swaps, total flight delay time and a 30-minute maximum delay time of original schedules. The MMGA approach, which combines a traditional Genetic Algorithm (GA) with a multi-objective optimization method, can address multiple objectives at the same time, then explore the optimal solution. The airline schedule disruption management problem is traditionally solved by Operations Research (OR) techniques that always require a precise mathematical model. However, airline operations involve too many factors that must be considered dynamically, making a precise mathematical model difficult to define. Experimental results based on a real airline flight schedule demonstrate that the proposed method, Multi-objective Optimization Airline Disruption Management by GA, can recover the perturbation efficiently within a very short time. Our results further demonstrate that the application can yield high quality solutions quickly and, consequently, has potential to be employed as a real-time decision support tool for practical complex airline operations.     

Optimization of Fare Structure and Service Frequency for Maximum Profitability of Transit Systems

Abstract

Providing efficient public transportation has been recognized as a potential way of alleviating congestion, improving mobility, mitigating air pollution, and reducing energy consumption. Many people use public transportation systems for their daily commute, while others use different transportation modes (e.g. cars, taxis, carpools, etc.). Inexpensive fares with good transit service encourages ridership, and the resulting revenue may be used to provide better service. Optimization of transit service frequency and its associated fare structure is desirable in order to increase revenue at reasonable transit operating expenditure. The objective of the study reported here is to maximize profit subject to service capacity constraint, while elastic demand is considered. The solution methodology is developed and applied to solve the profit maximization problem in a case study based on Newark, NJ, USA. Numerical results, including optimal solutions and sensitivity analyses, are presented. It is found that an optimal temporal headway and differential fare structure that maximizes total profit for the studied subway system can be efficiently solved.