Safety Assessment of Closed-Loop Level Crossing Control Systems by Means of STAMP(Systems-Theoretic Accident Model and Processes)

There have been a large number of accidents at level crossings of railways and this has been considered to be a significant issue to be solved for the realization of safe and stable railway transport.A conventional level crossing control system is characterized by the use of two types of electronic train detectors;one detects a train approaching to a level crossing section and the other then detects the train having left the level crossing.By contrast,closed-loop level crossing control systems in which level crossing control equipment and train-borne equipment communicate with each other have been advocated and are expected to serve as an effective solution to the abovementioned issue.This paper describes the following three types of closed-loop level crossing control systems:decentralized level crossing control system,fully-centralized comprehensive level crossing control system and fully-centralized individual level crossing control system.This paper then assesses the safety of these systems in comparison to the conventional level crossing control system.For the purpose of the assessment of their safety,a new accident analysis model called STAMP(systems theoretic accident model and processes)that is suitable for software intensive systems is used to clarify the advantage of the proposed three types of level crossing control systems in terms of safety.

基于正交试验的铝代钢冲压成形工艺参数优化

为实现车身轻量化,利用等强度理论将高强钢替换为铝合金。选用某车型背门锁安装加强件冲压成形工艺,分别以B240P （高强钢）和5052 （铝合金）为研究对象,结合数值模拟与工艺试验评估了二者在成形过程中的减薄行为。研究结果表明,采用相同拉延工艺,铝合金存在5处开裂。通过信噪比的正交试验,获得了铝合金拉延工艺影响因素的主次顺序依次是压边力、拉深筋宽度、摩擦系数、冲压速度,最优参数组合为：压边力200 k N、拉深筋宽度15 mm、摩擦系数0. 11、冲压速度1500 mm·s^（-1）。以优化后的成形工艺参数进行冲压试验,试验结果与仿真结果相一致。同时,铝代钢后,质量减轻0. 382 kg,为今后汽车轻量化设计提供参考。

冲压生产用送料转盘机构及自动控制系统设计

目的针对目前冲压生产中手工送料产生的质量问题,设计一个自动送料旋转托架。方法通过控制矩形波信号发生器输出信号的占空比和频率来控制旋转托架的间歇旋转,利用光电传感器检测旋转托架停止位置来配合冲床完成工件的自动冲压生产。结果该设计能改进现有的手动加工方式,节省人力,实现冲床生产线的自动化运行。结论该设计对同类生产线的送料自动化生产具有参考价值。

基于随机博弈机制的物联网安全收敛算法研究

为解决当前物联网安全收敛算法存在的节点覆盖区域冲突,读写性能不强,难以解决信号干涉等不足,本文提出了基于随机博弈机制的物联网安全收敛算法。首先,采取信号正交调节方式,确定信道发射过程中最佳信噪比性能,且通过随机博弈方式进一步调节节点覆盖半径,降低因节点间频率干涉而导致的覆盖区域冲突及读写性能不强等问题,改善了节点间因工作频段相似而导致频率干涉问题;随后,考虑到单纯通过调节节点覆盖半径方式存在的精确化程度不够的问题,采取调整节点发射过程中时间戳读写的措施,构建时间戳读写规避机制,通过调整物联网节点进行信道发射过程中的时间窗口,实现对发射信号的精确传送,进一步降低了信号干涉发射的概率。仿真实验表明:与当前广泛部署的节点能量感知退避算法(Node Energy Aware Backoff Algorithm,NEAB机制),时间窗口感知调整算法(Time Window Aware Adjustment Algorithm,TW2A机制)相比,本文收敛算法具有更小的网络完全收敛时间与节点读写时间,以及更少的单节点最大收敛次数,具有很强的实际部署价值。

图像视频中ENF信号的分析及应用综述

多媒体录制设备在交流电场或交流电器设备环境中录制视频、图像或音频时,会同时记录电网频率的波动.电网频率(electric network frequency,ENF)具有实时性、连续性以及同电网一致性等特点.因此从这些录制的多媒体文件中估计出的ENF信号是一种很好的时间戳,可用于信息源检测、操作取证及媒体同步等任务.尽管音频、图像和视频中ENF信号存在的形式截然不同,但检测和估计的思路是一致的,部分处理手段是通用的.目前,ENF信号在音频这一载体的研究中已经积累了一些成果,而在图像视频分析中的研究还处于起步阶段.为了更全面地了解图像和视频中ENF信号的特点、估计方法及在信息取证等方面的应用,对相关研究成果进行了梳理总结.首先通过分析图像视频捕获过程来探究ENF信号的形成机理与特点,然后对ENF信号检测和估计中存在的问题及相关方法进行了总结分析,最后介绍了图像视频ENF信号在信息取证方面的应用并指出未来可能的研究方向.

舰载高精度发控测试系统的设计

现有发控测试系统体积较大,采用光感检测法测速时需要人工粘贴条形码使光感检测器产生脉冲,以实现速度检测。人工粘贴条形码存在褶皱、歪斜、脱落等现象,使检测产生误差;同时,存在延长发射时间、降低发射效率等问题。为了提高发控测试系统的可靠性和测试精度,在不改变发射装置机械结构的情况下,采用金属感应测速法:当发射体的金属稳定鳍从金属感应器划过,即可产生脉冲信号;记录上升沿和下降沿时间差;结合可编程逻辑控制器技术,即可实现发射速度的检测。试验测试表明,该设计时间误差小于0.1 ms、测速精度远高于1%、压力测试精度高于1.5%,满足实际要求。该设计达到了缩短发控测试系统测试时间、提升测试效率、提高测试精度、减轻测试人员劳动强度的目的。

Interlocking System for CBTC (Communication Based Train Control) System

In recent years,the environment of railways and the systems such as CBTC(communication based train control)have been changing.To respond the changes and the needs of customers,a UTCS(unified train control system)has been developed to realize a system that evolves with customers.Previous type systems consist of independent components such as ATC(Automatic train control)system,electronic interlocking system,and facility monitoring system,and there are a complicated overlap of system configurations and functions and difference in concept between the systems.On the other hand,the integrated train control system consists of horizontal layers such as function layer,network layer,and terminal layer.Therefore,the system has been developed to make it simple with no unnecessary redundancy and evolving to meet the needs of customers.In this paper,we explain a method that realizes the interlocking function for CBTC system in the function layer based on the concept of“securing a train travelling path”including path blocking and routing,and evaluate the safety of the method using STAMP/STPA.

一种铁路货车电子标签数据识别方法

货车标签被读写器发射的射频能量激活后,将连续不断地、周而复始地返回标签中的数据帧给读写器。当货车运动时,电子标签返回给读写器的信号受多径效应的影响,出现衰落现象,使读写器不能正确识别标签数据,而且标签信号出现衰落的时间是随机的。利用同步特征信号,可以采集到残缺的数据,并可以用三帧残缺的数据拼接出一帧完整的标签数据。