基于GOOSE机制的城市轨道交通中压环网继电保护方案优化

针对目前城市轨道交通中压环网继电保护存在的问题,提出了基于GOOSE(面向通用对象的变电站事件)机制的中压环网的继电保护优化方案,有效地解决了传统过流保护级差配合困难的问题.该方案是以GOOSE光纤以太网为基础,以闭锁逻辑为核心的数字通信电流保护方案.将GOOSE信号进行分类,并对中压供电环网系统各种可能出现的故障进行动作行为分析.最后,通过RTDS(动态数字仿真系统)仿真试验,证明该方案在各种故障情况下,都能保证继电保护的选择性、速动性、灵敏性和可靠性.     

Scaling analysis of thermal-hydraulics for steam generator passive heat removal system

Steam generator passive heat removal system （SG-PHRS） is used as a passively safe mode to provide decay heat removal in some advanced pressurized water reactors. Due to the structure characteristics of steam generator （SG）, there are two natural circulation loops coupling in SG-PHRS in case of a safety-related event. The existing natural circulation scaling criteria could be used to simulate the natural circulation inside SG. Two-phase natural circulation loop is studied carefully, and the dominant effects of SG on behaviors of natural circulation in passive heat removal system are presented. Based on the understanding of SG-PHRS operation, system pressure transient scaling and two-phase natural circulation scaling are analyzed by establishing the relevant continuity, integral momentum and energy equations in one-dimensional area-averaged forms. With modified equations, similarity criteria for SG-PHRS are obtained for engineering application. In addition, equal height simulation and reduced height simulation are studied.     

健康体检中胸透效用的探讨

本文通过对江西大学1977～1987年的新生入学等健康体检共23682人次胸透阳性率的调查及1986～1987年的同一人群结核菌素筛选与胸透普查肺结核病检出率的对比研究,就胸透在健康体检中的效用问题进行了一些分析和探讨.使我们较清楚地认识到:正当、合理地应用X 线这一诊断方法,避免一切不必要的医用X线照射,减少它给人类带来的辐射晚期效应和某些遗传性危害,是保护人民身体健康的重要环节.