Performability evaluation of the ERTMS/ETCS – Level 3

Level 3 of the ERTMS/ETCS improves the capacity of railways by replacing fixed-block signalling, which prevents a train to enter a block occupied by another train, with moving block signalling, which allows a train to proceed as long as it receives radio messages ensuring that the track ahead is clear of other trains. If messages are lost, a train must stop for safety reasons within a given deadline, even though the track ahead is clear, making the availability of the communication link crucial for successful operation.We combine analytic evaluation of failures due to burst noise and connection losses with numerical solution of a non-Markovian model representing also failures due to handovers between radio stations. In so doing, we show that handovers experienced by a pair of chasing trains periodically affect the availability of the radio link, making behavior of the overall communication system recurrent over the hyper-period of periodic message releases and periodic arrivals at cell borders. As a notable aspect, non-Markovian transient analysis within two hyper-periods is sufficient to derive an upper bound on the first-passage time distribution to an emergency brake, permitting to achieve a trade-off between railway throughput and stop probability. A sensitivity analysis is performed with respect to train speed and headway distance, permitting to gain insight into the consequences of system-level design choices.     

LNG-FPSO单点系泊系统特性研究

LNG-FPSO具有开采、处理、液化天然气的功能,并可储存和装卸LNG,由单点系泊系统长期系泊于作业海域。基于BV系泊分析软件ARIANE7.0.2,采用时域计算方法分析了预张力和系泊缆长度等参数对系泊缆最小安全系数和最大躺底长度的影响,结论为系泊系统的优化提供了一定的参考。     

基于 Petri 网的航母飞行甲板火灾评价方法*

航母飞行甲板上的航空保障作业极为复杂,各种危险源互相交织,极易发生火灾事故,给人员、舰载机和系统设备安全造成了很大隐患。目前,火灾风险的随机性评价方法虽比较成熟,但难以对其进行定量和动态分析。在综合当前火灾风险评价方法的基础上,针对航母飞行甲板的火灾安全特性,提出使用面向对象的 Petri网建模和仿真方法,进行飞行甲板火灾风险评价,并建立了相应的评价模型,为飞行甲板定量评价提供了重要支撑。     

Petri网及其维修建模应用研究

Petri网描述异步并发的能力和形象直观的图形表示，使之成为系统维修过程模型描述的有力工具。文章在对Petri网的基本概念、模型描述方法作简要介绍基础上，分别就不可修系统、可修系统、维修资源共享、维修优先级以及维修费用等维修过程问题，进行了Petri网模型描述。     

基于 Petri 网的终端区冲突避免方法研究*

终端区空域结构复杂,航空器飞行架次过多,是飞行事故高发区,针对该问题,提出一种基于Petri网的终端区冲突避免方法。首先分析终端区空域运行结构,利用Petri网建立终端区空域运行模型,并根据终端区空域管制规则,建立其约束模型。然后综合约束模型,利用库所不变量方法建立终端区空域控制策略。最后针对控制策略进行案例分析,结果表明,此方法能够有效解决终端区空域运行安全问题,减轻管制员负荷。     

A FUZZY REASONING PETRI NET MODEL AND ITS REASONING ALGORITHM

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SWJTU—II型计算机联锁控制系统设计和实现

铁路信号计算机联锁系统是一个有着高可靠性、故障安全性和实时性要求的安全关键系统。本单位自行设计研制了一个满足这种高可靠性、故障安全性和实时性要求的容错计算机联锁系统SWJTUII。计算机联锁系统SWJTUII,硬件结构上,采用SIEMENS公司PLC作为主要控制部件,双机热备冗余结构,能实现无扰动的故障切换;联锁软件采用Petri网模型化,面向对象方法设计,Step7STL语言实现;通过仿真软件模拟列车运行来对系统进行仿真测试并取得良好效果。该系统已开发完成并投入应用。