Yusin Lee

A heuristic for retrieving containers from a yard

This paper presents a three-phase heuristic to solve for an optimized working plan for a crane to retrieve all the containers from a given yard according to a given order. The optimization goal is to minimize the number of container movements, as well as the cranes working time. After generating an initial feasible movement sequence, the second phase reduces the length of the sequence by repeatedly formulating and generating a binary integer program. With another mixed integer program, phase three reduces the cranes working time by adjusting the movement sequence through iterations. Numerical testing results show that the heuristic is able to solve instances with more than 700 containers, which is within the range of real-world applications. Moreover, the number of movements approaches the lower bound in most cases, and the resulting movement sequence is efficient.

A model for calculating optimal vertical alignments of interchanges

In this paper we propose a model to calculate an optimal vertical alignment of an interchange with a given horizontal layout. The vertical profiles of all ramps in the interchange are solved simultaneously. The problem is formulated as a mixed integer program. A heuristic that can solve the problem very efficiently is also proposed. The model and heuristic were tested by applying the technique to a real life example, a full system interchange with 4 legs and 8 ramps. Comparison of the computational results with the real layout, which was designed by a major consulting firm, indicates that the model produces designs close to those of human experts.

Influence of gluing-solution layout on gluing-solution distribution in a realistic railway ballast

AbstractIn this article, the influence of gluing-solution layout on the gluing-solution distribution at the final stage of solidification process in a realistic railway ballast is investigated. A unified Cauchy stress model, with an asymptotic time-dependent viscosity, is proposed to account for the coupled antithixotropic and shear-thickening features of gluing solutions. Realistic railway ballast is accomplished by using the vertex-identification technique, in which regulations for gravel composition in ballast practice are followed. A network and matrix layouts of gluing solution are applied. Flow characteristics and time-dependent solidification of the gluing solution in the multiconnected conducts spanned by the gravels are simulated by using a finite-element code. Although more concrete lateral and vertical gluing adhesions among the gravels can be accomplished by spreading gluing solution in the network arrangement, the gluing-solution distribution obtained by pouring gluing solution in the matrix ...

Trainworld: A powerful tool for railway timetabling

Planning for the operation of a railway system is a very complicated task. At the center stage of this planning work is timetabling. In this work we present TrainWorld, a powerful, sophisticated software system that, among other capabilities, is able to solve for high-quality timetables for real-sized, complicated railways. Testing with Taiwan Railways Administration (TRA) data demonstrates the ability of TrainWorld in solving for real-world timetables. The TRA system has 224 stations, approximately three-quarters of the 1085Km railway are double-tracked, and the rest are single-tracked. The system offers close to 1000 daily services in its 18-hour operation hours. Some busy stations carry more than 280 services a day, resulting in an eight-minute average headway between trains. TrainWorld is able to solve a timetable for such a system in approximately 70 hours, and the result is close to the real timetable.Copyright

RDSP: A Railway Decision Support Platform for Integrating and Bridging Existed Legacy Systems

Railway system operation is a very complicated task and must be supported by the coordination of several systems including engineering, transportation, locomotive maintenance and management, ticket system and passengers service, etc. Ideally, a modern railway enterprise information system should be an integrated, consisted, and site-opened database to support railway system operation. However, multiple isolated applications instead of one integrated enterprise information system are often formed due to historical factors such as independent departments, budgetary constraint and application requirements diversification. Take Taiwan Railways Administration (TRA) as an example, four major departments have their own support systems and databases that store critical planning and operational data. Those systems are isolated and can hardly communicate with each other. As a result, most cross-systems information analyses or data reference for decision making are done manually, which significantly affect the organizational efficiency of TRA.To address the aforementioned issues, a railway decision support platform (RDSP) for integrating the legacy systems (databases) is proposed in this paper. RDSP is designed to be a railway enterprise information system that supports the critical functions of data warehouse and decision support. Furthermore, RDSP is built by integrating the existing legacy systems rather than by building it from scratch. A data bridging system (HDBS) including four modules are design and implemented, input module for connecting the external data sources, output module for exporting integrated report or dumping data by predefined criteria for other systems, configuration module with a web-based user interface for setting up the periodic operations of data input or output tasks, and DB connection module for connecting external databases. Various types of railway system data are designed in RDSP schema and collected, including facilities, timetable, train services records, tickets, centralized traffic control (CTC) system records, and automatic train protection (ATP) system records.RDSP provides a system framework to integrate many isolated island-style databases that currently exist in TRA, and can form a cross-enterprise database that serves as the primary and only data platform. To demonstrate the efficacy of the RDSP, a spatiotemporal ticket-selling analysis report, a train delay cause analysis report, and a timetable planning software (TrainWorld) are designed on top of it. In the future, RDSP will play a major supportive role in infrastructure maintenance, operations, decision support, and planning.Copyright