The Vehicle Routing Problem: The Case of the Hong Kong Postal Service

Abstract

With the growth in population and development of business activities in Hong Kong, the range and level of services provided by Hongkong Post have multiplied. However, the schedule of its postal vehicles, including mail collection and delivery, is still constructed manually on a daily basis, based on the experience of staff and transportation reviews. In this paper, the problem of scheduling a set of n collection points (District Post Offices) from a depot (General Post Office) in Hong Kong Island is addressed. The objectives pursued are the maximization of resource utilization and minimization of operation costs. In other words, the variable cost is expected to be reduced. To achieve these goals, an integer linear programming (IP) model of the vehicle routing problem (VRP) is developed in an effort to obtain optimal solutions. As the model involves computational complexity, a commercial software package CPLEX is used to solve the problems efficiently. The results show that the proposed model can produce optimal vehicle routes and schedules.     

Evaluating the operational performance of airside and landside at Chinese airports with novel inputs

ABSTRACT

This paper evaluates the operational performance of airside and landside at Chinese airports with two novel inputs. Furthermore, the airport landside operation is decomposed into passenger-terminal operations and cargo-warehouse operations. One novel input is the capability of the runway system which is introduced into airside performance evaluation. The other novel input is cargo warehousing which is introduced into landside performance evaluation. To address multiple optimal solutions when estimating Returns to Scale in Data Envelopment Analysis, we adopted the Zhu and Shen method. This empirical study shows that neither the number of runways nor total runway length is a genuine index of runway system capability in the evaluation of airside performance. Only four airports achieved full efficiency in all eight measures while eight airports did not achieve any full efficiency. In addition, one airport did not perform well in the benchmark analysis.     

青岛清江路站隧道施工开挖方法的数值模拟与分析

依托于青岛地铁清江路站的实际工程,利用ABAQUS有限元分析软件,针对所选地铁站的地质及结构特点,建立浅埋暗挖大跨地铁车站动态开挖的力学模型,数值分析表明模拟隧道施工开挖与支护过程应符合现场实际工况、应反映现场预留的毛洞长度。对今后用ABAQUS有限元软件模拟隧道动态开挖时准确反映施工力学行为具有指导和借鉴意义。     

基于可靠性理论的桥梁承载能力评估公式

利用收集到的WIM(Weight in Motion)卡车荷载数据,开展了建立基于可靠性理论的现有桥梁评估公式研究.通过选取国内8种常见桥梁形式计算出了目前现行桥梁设计规范的隐含可靠指标.结合我国现行桥梁设计规范与公路工程可靠度设计标准,建立了基于可靠性理论的现有桥梁承载力评估公式,结果可为我国已建桥梁评估、新桥设计规范的制定和修改提供一定的参考和对照.     

整车自然曝晒与用户实际使用之间的当量研究

为了成功预测汽车内饰产品在不同区域的耐老化性能,需要了解汽车内饰典型环境下的自然曝晒与用户实际使用的当量系数,通过了解影响汽车内饰的主要环境因素:光辐射强度和温度,并利用TNR方法确定当量系数。     

杭州某高边坡危岩体影响范围分析

以杭州市“龙山石壁”风貌保护治理工程高边坡为实例,对危岩体的影响范围进行了比较系统的分析研究.通过现场滚石试验,对危岩体影响范围进行了划定,运用Rocfall软件对落石运动轨迹进行了分析,评估其崩落后的滚动距离、危岩体坠落以后可能的弹跳高度,最终得出危岩体的影响范围.     

电动助力转向系统助力特性研究

概述了电动助力转向系统(EPS)的结构和工作原理,并介绍了电动助力转向系统助力特性的设计方法。在分析了电动助力转向系统各组成部分数学模型的基础上,构建了基于Simulink与carsim的电动助力转向系统仿真模型,仿真结果表明:所设计的助力特性较好地协调了转向轻便性和路感之间的矛盾。     

90后高职生思想认识特点及对策研究

90后高职生在理想信念、人生价值、学习认知三方面的思想认识上有其鲜明时代特点。把握这些特点,分析原因,探讨对策,是丰富高职教育理论的有效途径,也是加强和改进高职院校思想政治教育的关键。同时,也是培养全面发展的高等职业技术应用人才的有力理论保障。     

乌江大桥病害成因分析及加固设计

针对斜拉-悬吊协作体系桥出现的加劲梁平面线形畸变、主梁箱室内顶板开裂渗水等病害,进行加固技术研究。在多年实践积累的大跨径柔性悬吊结构体系桥梁加固经验的基础上,提出在保持桥梁恒载不变的情况下,尽量增大结构刚度。从而提高桥梁整体结构的动力特性。     

高速公路安全事故时间关联聚类分析

随着高速公路迅猛发展,交通事故的数量、死伤人数也呈不断上升趋势,交通安全不容忽视。针对我国某高速公路2004－2010年的事故数据,利用聚类分析方法,就公路安全数据中影响安全的时间因素进行了量化聚类分析。针对月、星期、时段对高速公路安全事故指数进行聚类,并考虑路况线形因素的影响,挖掘交通事故时间分布规律,找到高发事故期,为今后的风险分析和预警模型提供科学依据。结果表明,交通事故在季节、星期和时段上分布规律显著,说明时间因素是影响交通安全的重要因素之一。