A scalable communication middleware for real-time data collection of dangerous goods vehicle activities

Recently, real-time monitoring of Dangerous Goods Transport has drawn a lot of attention, thanks to its capability to provide a better visibility on dynamically moving vehicles, particularly through a Web Mapping application. Yet, one of the challenges to be faced designing such a system is an effective architecture for real-time collection of telemetry and event data conveyed by the vehicle on-board system, such the Global Positioning System coordinates. In this paper, we have focused on optimizing the process for managing a large quantity of data transmitted via network sockets that use the Transmission Control Protocol. Then we prove the process efficiency through performance and scalability tests. The middleware is being implemented as a part of a project that aims to monitor the Italian petrochemical company Eni’s oil trucks shipment along Europe and USA territories.     

测绘基准欠缺条件下工程测绘项目实施的关键技术

本文结合国外某水运工程测绘项目的实施,探讨了实施过程中,在测绘基础资料欠缺的情况下遇到的两大难题:平面坐标系统和高程基准的确立及实施。系统总结了项目实例中采用的技术方案、实施方案、内业处理和数据分析等技术,可为我国测绘人员在类似测绘项目的实施提供有益的参考。     

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在目前的出租车调度系统中,调度的出租车可能需要经过城市堵车区域,不能及时为乘客提供服务,本文对城市道路堵车对出租车调度的影响进行研究.根据出租车自动上传的城市道路堵车信息,建立出租车通过堵车区域的损耗方程,结合城市各道路交叉路口之间的距离,采用Dijkstra算法对最佳调度路径进行求解.实验仿真结果给出了发生堵车时,不同单位额外损耗(β)情况下对应的调度路程、路径和规避堵车区域发生的时间.最后与未考虑城市道路堵车的调度系统进行比较.比较结果表明,通过设置合理的β值,系统可根据堵车严重程度,合理规划出租车路径,规避堵车较严重区域.     

An empirical study to determine freight travel time at a major port

Abstract

This paper examines the reliability measures of freight travel time on urban arterials that provide access to an international seaport. The findings indicate that the reliability index calculated by the median of travel time, which is less sensitive to extreme values in a highly skewed distribution, is more appropriate. This paper also examines several statistical distributions of travel time to determine the best fit to the data of freight trips. The results of goodness-of-fit tests indicate that the log-logistic is the best statistical function for freight travel time during the midday off-peak period. However, the lognormal distribution represents a better fit to arterials with heavily congested traffic during peak periods. Additionally, travel time prediction models identify the relationships between travel time, speeds and other factors that affect travel time reliability. The analysis suggests that incident-induced delays and speed fluctuations primarily contributed to the unreliability of freight movement on the urban arterials.     

GPS接收机C/A码跟踪算法及环路控制策略

高动态GPS接收机指在接收信号有较大的多普勒频率偏移及其一阶、二阶导数存在时仍能正常工作的GPS接收机。针对高动态环境下伪码跟踪所遇到的问题,重点研究了与高动态载波跟踪算法相匹配的、基于载波辅助技术的归一化非相干点积功率伪码跟踪算法,以及预检积分时间可变的伪码跟踪环路控制策略。采用MATLAB建立了系统模型,仿真结果表明:采用伪码跟踪算法以及结合相应的高动态载波跟踪算法的伪码跟踪控制策略的GPS接收机能在加速度为80 g,加速度为10 g.s-1的指标下正常工作。     

浅谈GPRS/GPS在船舶调度中的应用

针对目前船舶通信调度管理落后的现状,利用GPRS/GPS无线通信解决方案能较好地解决船舶的监控、调度等管理问题.     

电子监控系统在内河运输中的应用

针对我国内河航运发展现状,就GPS(全球卫星定位系统)和GIS(地理信息系统)在内河海事电子监控应用中出现的问题以及展望进行探讨。     

提高GPS卫星数字中频信号捕获性能的方法

GPS卫星发射的信号处于以加性高斯白噪声AWGN为干扰的背景下，若载噪比CNR较差，可能会使接收机一直都处于失捕状态，满足不了某些实时性定位应用的要求。为此，对现有的一种捕获方法——FFT相关法进行数值改进，以减小错捕、漏捕概率，并在若干个捕获周期都失捕的情况下，提出了应对的捕获措施，增大重新捕获的概率，以提高系统的可靠性。     

GPS定位技术和全站仪相配合在航道测量中的应用

内河航道工程的整治和维护,迫切需要实时准确地反映航道水深变化的航道水深地形图。而GPS定位技术的应用迅速渗透到航道工程测量领域,尤其是GPS-RTK现代测绘技术的应用,大大提高了航道水深测量的周期和精度。本文结合西江航道整治工程的航道测量中GPS定位技术和全站仪相配合使用的应用实践,探讨两者的优化组合能够快速、准确和高效地完成测量任务,取得良好的经济效益和社会效益。     

无验潮法在航道测量中的应用

介绍无验潮水下地形测量方法在航道测量中的应用,分析了使用该方法的优劣性。