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661.
针对Web信息量巨大且具有动态性、不规则性,而Web信息查询和集成存在困难,解决了对HTML格式的Web文档的信息抽取,提出了一种基于DOM的Web信息抽取方法。该方法通过附加语义、样本学习生成基于DOM路径的抽取规则,利用遍历DOM树实现信息抽取。本方法可用于Web查询,也可用于信息集成系统中包装器的构造。 相似文献
662.
663.
船舶航行安全评估主要研究船舶平台安全与海洋环境相互之间的关系.海洋环境影响船舶安全航行的空间特性决定了船舶航行安全评价适合采用定量和空间分析相结合的地理信息系统(GIS:Graphic Information System)技术,相对传统的地图分析,基于GIS技术的船舶航行安全评估在方法上有质的突破. 相似文献
664.
The scheduling operations of many paratransit agencies in the United States are undertaken manually. Those customers who are eligible to travel call in their requests the day before the trip is needed. As the trip requests are received, they are entered into a list of unscheduled trips. In order to schedule these trips, the scheduler must first determine the number of drivers and shuttle buses that are available as well as the time of availability of each. The scheduler must then try to match the rides that are in “similar” areas around the “same” time to place together on the driver's schedule. As new trip requests are made, the schedulers must adjust the trips that are already scheduled to try and schedule as many trips as possible in the most efficient way. By developing a system that would improve the scheduling system operations of, in this case, DART (Delaware Administration for Regional Transit) First State Paratransit, customers can expect to receive better service that will improve their ability to travel throughout the community. Some devices that could also improve the operations of paratransit agencies are described in this paper, such as satellite‐based Global Positioning System (GPS), radio communication systems, mobile computers, radio frequency‐based data communication systems, internet web pages, automated paratransit information systems, and card‐based data storage and transfer media. However, because paratransit systems are difficult to operate cost‐efficiently, the optimum and most cost‐efficient device must be selected. The system chosen for DART First State Paratransit includes the use of a relational database management system (RDMS) and a transportation Geographic Information System (GIS). RDMS keeps track of the database information as well as the scheduled trips and the GIS is ideal for analyzing both geographic and temporal data. This system is shown to be superior to the manual system. 相似文献
665.
Both the geographic information system (GIS) and transportation modeling environments have seen continually developing analytic concepts and techniques. However, these developments have seldom resulted in the integration of GISs and transportation models. This paper explores the potential inherent in merging of these environments through a systematic investigation of the fundamental basis of integration. To do this, the traditional four step transportation modeling process is extended to include input and output steps. We then define functional components for GIS data handling — data management, manipulation, and analysis. The steps of modeling are matched against the list of GIS data handling functions within a matrix‐based framework. GIS functions that enhance a land‐use based urban transportation modeling process are then categorized. Conclusions are drawn and directions for future developments are discussed. 相似文献
666.
黄剑 《铁路通信信号工程技术》2008,5(1):5-7
本文介绍了基于交叉感应环线的列车控制系统地面发送设备的原理及安全性,对发送设备的各个功能模块进行了详细的说明。 相似文献
667.
按照"高标准、讲科学、不懈怠"的要求,本文提出了到2012年铁路信息化实现的目标和重点推进的10个方面工作以及构建铁路网络与信息安全保障体系、建立铁路信息系统运行维护机制、造就铁路信息化人才队伍的途径,旨在全面提升铁路信息化工作科学化水平,为建设和谐铁路、实现铁路现代化提供强有力的技术支撑和保障。 相似文献
668.
Lili Du Satish Ukkusuri Wilfredo F. Yushimito Del Valle Shivkumar Kalyanaraman 《Transportation Research Part C: Emerging Technologies》2009,17(6):571-585
Broadcast capacity of the entire network is one of the fundamental properties of vehicular ad hoc networks (VANETs). It measures how efficiently the information can be transmitted in the network and usually it is limited by the interference between the concurrent transmissions in the physical layer of the network. This study defines the broadcast capacity of vehicular ad hoc network as the maximum successful concurrent transmissions. In other words, we measure the maximum number of packets which can be transmitted in a VANET simultaneously, which characterizes how fast a new message such as a traffic incident can be transmitted in a VANET. Integer programming (IP) models are first developed to explore the maximum number of successful receiving nodes as well as the maximum number of transmitting nodes in a VANET. The models embed an traffic flow model in the optimization problem. Since IP model cannot be efficiently solved as the network size increases, this study develops a statistical model to predict the network capacity based on the significant parameters in the transportation and communication networks. MITSIMLab is used to generate the necessary traffic flow data. Response surface method and linear regression technologies are applied to build the statistical models. Thus, this paper brings together an array of tools to solve the broadcast capacity problem in VANETs. The proposed methodology provides an efficient approach to estimate the performance of a VANET in real-time, which will impact the efficacy of travel decision making. 相似文献
669.
未来的海上信息战 总被引:1,自引:0,他引:1
周永存 《舰载武器(含VCD光盘)》2001,(4):43-45
信息对于战争的重要性是举足轻重的,随着通信技术和计算机网络技术的发展,信息系统已成为军事目标,本文阐述了悄然兴起的信息战及有关概念,详细论述了网络中心战及有关问题,未来海上战场将采用先进的联网技术把作战部队和作战平台等联系起来,以获取信息优势,形成综合战斗力,从而赢得信息时代的战争。 相似文献
670.
周尧明 《交通部上海船舶运输科学研究所学报》2001,24(1):57-60
叙述对集装箱车辆跟踪和管理的重要性,介绍实现集装箱车辆跟踪和管理的方法,以及采用3G(GPS、GIS、GSM)高新技术开发而成的集装箱车辆跟踪和管理系统,最后展示应用实例。 相似文献