一种SIP协议栈中呼叫过程的设计与实现

随着VoIP技术的飞速发展,SIP协议正日益受到业界的重视,越来越多地应用于3G网络。本文提出并基于C语言编程实现一种完全自主设计的SIP协议栈,包括消息编解码模块、状态机模块、传输层模块。实现用户代理客户端和用户代理服务器间的工作状态调度,进而使得两个用户代理能够进行多媒体会话。     

传输线路故障造成基站闪断的分析处理

以中国联通徐州分公司2.5G环4为例,着重分析两纤双向复用段保护环上线路故障造成的基站闪断,最后提出为减少基站闪断的概率应给光缆中断前的衰减留较大的富裕量,适当调低传输设备检测到误码的复用段倒换门限.     

An extended systematic literature review on provision of evidence for safety certification

ContextCritical systems in domains such as aviation, railway, and automotive are often subject to a formal process of safety certification. The goal of this process is to ensure that these systems will operate safely without posing undue risks to the user, the public, or the environment. Safety is typically ensured via complying with safety standards. Demonstrating compliance to these standards involves providing evidence to show that the safety criteria of the standards are met.ObjectiveIn order to cope with the complexity of large critical systems and subsequently the plethora of evidence information required for achieving compliance, safety professionals need in-depth knowledge to assist them in classifying different types of evidence, and in structuring and assessing the evidence. This paper is a step towards developing such a body of knowledge that is derived from a large-scale empirically rigorous literature review.MethodWe use a Systematic Literature Review (SLR) as the basis for our work. The SLR builds on 218 peer-reviewed studies, selected through a multi-stage process, from 4963 studies published between 1990 and 2012.ResultsWe develop a taxonomy that classifies the information and artefacts considered as evidence for safety. We review the existing techniques for safety evidence structuring and assessment, and further study the relevant challenges that have been the target of investigation in the academic literature. We analyse commonalities in the results among different application domains and discuss implications of the results for both research and practice.ConclusionThe paper is, to our knowledge, the largest existing study on the topic of safety evidence. The results are particularly relevant to practitioners seeking a better grasp on evidence requirements as well as to researchers in the area of system safety. As a major finding of the review, the results strongly suggest the need for more practitioner-oriented and industry-driven empirical studies in the area of safety certification.     

露天矿山监管中的无人机测绘技术应用研究

传统的露天矿山矿产资源监管方法手段单一,易出现遗漏。本文结合无人机测绘技术的特点及优势,提出通过借助无人机测绘技术对露天矿山进行航测,制作矿山的高精度数字正射影像、实景三维模型和数字高程模型等数据用于矿产资源监测,并建立多源监测数据管理系统对矿山进行全面监管。该方法生产的地理信息数据和信息化监管手段为矿产资源监管工作提供了有力的技术支持,可大幅提高工作的效率和精准度。最后本文以浙江南部某露天矿的监管工作为例,说明了该方法较高的应用价值。