Using Genetic Algorithms to Optimize Stopping Patterns for Passenger Rail Transportation

In a passenger railroad system, the stopping pattern optimization problem determines the train stopping strategy, taking into consideration multiple train classes, station types, and customer origin‐destination (OD) demand, to maximize the profit made by a rail company. The stopping pattern is traditionally decided by rule of thumb, an approach that leaves much room for improvement. In this article, we propose an integer program for this problem and provide a systematic approach to determining the optimal train stopping pattern for a rail company. Commonly used commercial optimization packages cannot solve this complex problem efficiently, especially when problems of realistic size need to be solved. Therefore, we develop two genetic algorithms, namely binary‐coded genetic algorithm (BGA) and integer‐coded genetic algorithm (IGA). In many of the past evolutionary programming studies, the chromosome was coded using the binary alphabet as BGA. The encoding and genetic operators of BGA are straightforward and relatively easy to implement. However, we show that it is difficult for the BGA to converge to feasible solutions for the stopping pattern optimization problem due to the complex solution space. Therefore, we propose an IGA with new encoding mechanism and genetic operators. Numerical results show that the proposed IGA can solve real‐world problems that are beyond the reach of commonly used optimization packages.     

A Decision–Support Tool for Airline Yield Management Using Genetic Algorithms

Airline yield management has gained widespread acceptance in recent years. Yield management is used to estimate the number of passengers belonging to each fare class in order to maximize revenue—to increase profits. Forecasts of future booking for different classes and the fare for each class are assumed fixed and known. The complexity of the problem increases as additional attributes such as the effect of continued flights on pricing, ticket cancellations, and overbooking are considered. In addition, demand varies with time. Hence, to make the problem realistic, the dynamic nature of demand has to be accounted for in the model. The focus of this article is to develop a decision–support tool to estimate the number of seats allocated to each fare class in the yield management problem. This problem is formulated as a linear integer programming model. Genetic algorithms (GAs) are used as a solution technique. The model is coded using C programming language. The decision–support tool considers the effect of time–dependent demand, ticket cancellations, and overbooking policy. The results are consistent with expectations.     

A Fuzzy Expert System for Damage Assessment Using Genetic Algorithms and Neural Networks

Abstract: An efficient knowledge-acquisition support method is required for improvement and maintenance of the knowledge base in durability evaluation of an RC bridge deck. Such a method is proposed in this paper to automatically acquire fuzzy production rules. This method makes joint use of genetic algorithms and a neural network. Using a neural network as a subsystem, the evaluation function of genetic algorithms can be provided with the weights of the neural network. Introducing a neural network into genetic algorithms, it is possible to acquire new knowledge so that the method is useful when it is difficult to acquire knowledge in the field.     

元启发式优化中参数选择的统一方法

在十几年前,元启发式优化算法引起了广泛的注意。这些算法中不同参数的调整是个耗时很长的过程,常需通过反复计算进行。故引入集中因子,评价这些算法的性能。集中因子可对参数的匹配性进行估计,并能增强算法自动调整参数的能力。分别采用遗传算法、蚁群优化算法,粒子群优化算法和大爆炸-大危机算法,对某钢支撑框架进行拓扑优化。数值结果表明,这些算法在解决优化问题时具有一些共同点。     

A Generic Approach to Estimate Freeway Traffic Time Using Vehicle ID‐Matching Technologies

New technologies have emerged to estimate the travel time on freeways by matching certain unique identifications of passing vehicles at different locations. These types of technologies share many similarities despite having different mechanisms. In this article, a generic method is presented to estimate freeway travel times using vehicle ID‐matching technologies. In particular, the new method addresses two long‐standing challenges: outlier screening and travel time estimation. Innovations include (1) using both statistical methods and traffic flow theory to screen outliers; and (2) accounting for mechanisms of various equipment measurement errors. The effectiveness of the proposed method is demonstrated using simulation and shown to be more accurate and responsive to travel time changes than methods based on the use of traditional inductive loops.     

利用数学模型预测超大直径泥水平衡盾构法隧道工后沉降

工程建设中地表沉降是由多种原因产生的,大致可分为施工中产生的沉降和施工后产生的沉降两部分。在软土地区的隧道施工中,工后沉降占有较大比例,研究预测工后沉降具有重要的工程价值。通过实测数据与几种预测模型的比较,分析了不同模型的优缺点及其应用情况。     

基于数字信号处理的驱动机构特征点测量方法

控制棒驱动机构(CRDM)的特征点位置是一个用于判定驱动机构及电源状态的重要参数。常用的特征点位置测量方法是使用数字记录仪测量各线圈电流波形,并使用人工测量的方式寻找特征点。在本文中,提出了一种基于数字信号处理的自动特征点测量方法,并使用Lab VIEW语言编制了相应的测量程序用于工程使用。试验结果表明,使用该方法可以对特征点位置进行正确的识别。     

浅议利用年负荷增长率的变化率预测用电负荷

根据对广东省某县近十年来负荷发展的跟踪研究,发现在2006-2010年期间,年用电增长平缓、增长率稳定,不同于2001-2005年期间的跳跃式增长,同时分析了现象发生的原因,并提出采用增长率法对该县2011 ～2015年期间的用电情况进行预测.     

利用支护桩水平监测位移确定桩身弯矩的方法

利用现场监测资料确定支护桩的截面弯矩对判断桩的安全状态和完善深基坑设计方法具有重要价值,但目前的确定方法不仅监测过程复杂,而且间接换算出的弯矩也可能与实际相差较大。本文将支护桩的水平监测位移看作三次样条函数,建立了一个确定桩身截面弯矩的计算方法。将该方法应用于某实际工程的结果表明,它不仅能够较为准确地确定支护桩的最大截面弯矩,而且也可以较好地反映整个桩身的弯矩分布。     

Using Entropy Weight Method to Assess Transit Satisfaction:A Focus on Older Adults

Population aging is happening in many places, such as on the Chinese mainland and in Hong Kong. Hong Kong, with the second-highest percentage of older adults in Asia, is among the world’s fastest-aging societies. Moreover, the city has very high transit patronage:transit trips constitute approximately 90%of all trips. Given the significance of transit in Hong Kong, improving transit services for older adults is of substantial importance. In light of this, based on the data of transit satisfaction (or perception) collected by a questionnaire survey in March 2015 (N=613), this study adopts the entropy weight method to determine the importance weights of an array of transit service quality attributes (e.g., seat availability and travel stability). Then, it performs an index-based importance-satisfaction (I-S) analysis using the outcome of the previous step as a basis to determine priorities for transit service improvement. The results show that in the view of older adults, three service quality attributes in need of improvement are seat availability, waiting conditions, and service frequency. Accordingly, the paper puts forward policy implications for further implementation.     

A Simple Method Using Tracer Gas to Identify the Main Airflow and Contaminant Paths within a Room

The main airflow and contaminant paths or the spatial distribution of the age of air (or contaminant) in a room are of great interest in estimating venrilation efficiency. A simple meusurement method is presented which consists of injecting one or more tracer gases at locations of interest and analysing the concentration at several other locations, carefully chosen for best accuracy. Response functions can be fitted to these measurements, which are the age of the tracers or of the air or the concentration of the tracers as a function of the location. The salient paths, such as the dead zones, are also determined from these functions. The paper presents the method, its application and validation in a well controlled test room.