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571.
通信及其信息处理技术的发展与认识 总被引:1,自引:0,他引:1
马建萍 《铁路通信信号工程技术》2005,(2):28-30
文简要论述了通信技术、信息传输及其处理技术的发展过程,简要论述了模拟通信与数字通信技术的差异,并围绕数字通信的可靠性和信息编译码技术等内容进行了综述和探讨。 相似文献
572.
Claus Lassen Bjrge Timenes Laugen Petter Nss 《Transportation Research Part D: Transport and Environment》2006,11(6):459-463
This article addresses the potential for reducing international work-related air travelling through the use of information and communication technologies such as videoconferences and e-learning in knowledge companies. It looks at the potential for reducing travel related to such things as meetings and teaching. In the absence of regulations, however, we do not find potential for reducing the number of trips of this type because they do not facilitate face-to-face contacts. Therefore the conclusion is, that policy and planning have to look for other options for pursuing ‘sustainable mobility’ policies in the future. 相似文献
573.
利用信息熵等效转换原则,将模糊变量转变为随机变量,并给出了模糊结构弹塑性分析的一阶摄动有限元递归列式,推导了含不确定性材料参数的结构刚度矩阵对随机变量的偏导表达式以及对位移向量求导的近似计算式。采用增量理论结合弹塑性分析的摄动递归列式编制了有限元计算程序,并对具有模糊材料参数的板壳结构进行分析。 相似文献
574.
信息系统安全风险评估模型及其在铁路客票系统中的应用 总被引:2,自引:0,他引:2
提出一种基于模糊综合评判理论的信息系统安全风险综合评估模型与方法,实现量化信息系统安全风险的目标。通过确定信息系统的安全风险因素集、指标集以及因素的权重系数集,建立安全风险模糊综合评估矩阵,并应用于铁路客票预定与发售系统的安全风险评估。铁路客票预定与发售系统包括信息资产和物理资产,受到来自系统本身、外部环境以及人为和自然界的安全威胁。应用建立的信息系统安全风险评估模型,定量计算铁路客票预定与发售系统Web组件的安全风险值。根据计算值确定信息系统中的高风险组件,为系统管理与使用部门采取相应的防护技术和管理措施提供理论依据,增强系统安全性。 相似文献
575.
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
576.
577.
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
578.
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
579.
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
580.
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