Quantitative fire risk assessment of cotton storage and a criticality analysis of risk control strategies

Although fires can easily occur during cotton storage, research on cotton storage fire risk assessment is limited. This work focuses on cotton storage fire risk assessment and investigates the criticality of risk control strategies. Bow-tie and Bayesian network models are established to investigate the relationships among accident causes, safety barriers, and possible consequences. The results show that the first safety barrier (detection and extinguishment before fire brigade arrival) is more controllable and more effective than the second safety barrier (fire brigade). Based on the collected probability data, the probability and risk of a common accident are higher than those of a large accident and severe accident when safety barriers succeed; when the first safety barrier fails, the probabilities and risks of large and severe accidents increase by more than 2000 times. The criticality of safety measures is investigated by analysing their structural importance, probability importance, and critical importance. The critical events for fire occurrence are an open flame and sparks during storage, and the critical events for detection and extinguishment before fire brigade arrival are watchkeeper monitoring, regular patrolling, and automatic fire alarm systems. For cotton storage safety, this work and its outcomes are used to support the decision-making of fire risk prevention and control.     

催化裂化烟气能量回收机组失效模式和危害度分析

深入分析了催化裂化烟气能量回收机组操作工艺失常状态的影响因素,建立了失效模式、效应和危害度模型;运用现场企业故障调查的实际数据,采用模糊评定方法,对能量回收机组工艺失常状态进行了定量分析;建立了危险顺序数RPN接受准则,将机组的各种失效模式进行风险排序,确定了影响能量回收机组长周期运行的关键因素及失效机理,为催化裂化装置安全可靠运行提供理论指导。     

UO2芯块运输容器核临界安全分析

目的 在开展二氧化铀（UO₂）芯块运输容器设计时,应进行临界安全分析,优化容器设计,并通过得出的临界安全指数（CSI）限定可运输货包的数量,确保在任何可信的运输情景下的核临界安全。方法 文中采用蒙特卡罗软件SuperMC对符合要求的国际临界安全手册中6类49个基准实验案例进行建模计算,获得本案例的次临界上限值,再基于运输容器经受正常运输条件与运输事故条件试验的结果,计算得出正常运输条件与运输事故条件下的单货包与货包阵列的最大中子增殖系数keff值。结果 该案例的次临界限值（USL）为0.91974;UO₂芯块运输容器在正常运输条件与运输事故条件下单货包的最大keff值分别为0.286 08,无限阵列货包的最大keff值为0.798 34。结论 UO₂芯块运输容器在正常运输条件与运输事故条件下的最大keff值均小于0.919 74,临界安全指数为0,容器设计临界安全性能可确保可运输安全。     

核电厂事故后人因可靠性分析与操纵员绩效改善

核电厂人因可靠性分析（HRA）是核电厂概率安全评价（PSA）的重要组成部分，能够较好地评价和量化核电厂主控室（MCR）操纵员的行为。通过对国内某核电厂压水堆（PWR）进行HRA分析，对事故后操纵员行为进行分类和归组并对其进行量化分析，对核电厂事件进行基本人误概率和重要度排序。基于HRA分析，从管理的角度．提出对相对应的应急规程（EOP）进行改进，对于重要度较高的操纵员行为，核电厂应加强培训，改善操纵员绩效。     

Towards a conceptual model of motorcyclists’ Risk Awareness: A comparative study of riding experience effect on hazard detection and situational criticality assessment

This research investigates risk awareness abilities among different populations of motorcyclists. Risk awareness is defined here as an extension of the Situational Awareness theory applied to critical driving situations. This study is more particularly focused on two main cognitive abilities supporting risk awareness: hazard detection, corresponding to riders’ skill to perceive critical event occurring in the road environment and to identify it as a threat, and situational criticality assessment, corresponding to a subjective assessment of the accident risk. From this theoretical framework, the aim is to compare motorcyclists’ performances in risk awareness according to their experience in motorcycling. Four populations of motorcyclists are investigated: Professional (Policemen), Experienced riders, Novices, and Beginners. Method implemented is based of a set of 25 video sequences of driving situations presenting a risk of collision. Participants’ task was firstly to stop the video film if they detect a hazard. Then, at the end of each sequence, they have also to assess the criticality of the driving situation as a whole, with a Likert scale (from 0 to 100% of criticality). Results obtained show that cognitive abilities in both (i) hazard detection and (ii) situational criticality assessment depend of the riding experience, and are learnt from two different timing. On one side, Professional and Experienced riders obtained better results than Novices and Beginners for hazard perception (i.e. shortest reaction time). In terms of situational criticality assessment, Beginners underestimate the situational risk and seem overconfident in their abilities to manage the situational risk, against Novices, Professional and Experienced riders, who have better competences in criticality assessment. From these empirical results, a conceptual model of motorcyclists’ Risk Awareness is proposed.     

一种计算混合关键任务响应时间的方法

混合关键系统中不同关键等级的任务在同一个平台运行,任务的可调度性分析更加复杂.基于目前最有效的固定优先级混合关键的调度算法AMC(adaptive mixed criticality),提出了一种任务响应时间分析算法AMC-PM(AMC partition max).该算法将任务最长执行时间(worst case execution time,简称WCET)分成低关键等级态执行时间与高关键等级态执行时间,将这两部分对应的最长响应时间加起来得到总的响应时间上界.通过仿真实验,与已有的AMC响应式分析算法进行比较,结果表明,在任务高关键下最长执行时间较小时,与AMC-rtb相比,AMC-PM能够显著地提高系统的可调度性.同时与AMC-max相比,AMC-PM能够显著降低算法的运行时间.     

基于系统观的网络突现性研究

因特网作为一个复杂适应系统，呈现了许多突现性。本文重点提出因特网中的两个突现现象：网络流量呈现自相似以及拓扑结构呈Power-law分布，并对其现象及其形成机制进行了初步探讨；同时，对网络上业务量的自组织临界性进行了简单的分析，从而提出用复杂科学理论来研究探索网络复杂性，对研究和开发下一代网络体系结构具有积极作
用和影响。     

Quantum Nonlinear Sigma Model with a Damping Term; Finite Temperature Renormalization Group Analysis

We study the behavior of the finite temperature quantum nonlinear sigma model in two dimensions in the presence of the damping of the formf (|θ _n |) = γ|ω _n |^α, whereα satisfiesα ≥ 1. The analytical calculations will be performed usingα=2 and the results will be compared with the standard results obtained for the standard quantum nonlinear sigma model. The behavior of such a system is connected with the pseudogap which appears in the normal state of the cuprate superconductors.     

Presto—A System Environment for Mission-Critical Multimedia Applications

Summarized in this report is a multiphased R and D program, presto, conducted for developing a multimedia system environment to support a variety of mission-critical applications. The concepts, software design, and system prototype developed during the first phase of the program are presented. In particular, the work on real-time scheduling, multimedia storage and retrieval, and application programming model is described. The major results of the presto Phase I program are a set of new techniques and system software for QoS- and criticality-based, adaptive multiresource management, raw-I/O-based continuous multimedia file management, and data flow-oriented programming with integrated real-time scheduling support.     

混合关键级多任务调度中低关键级任务的积极处理

当前的混合关键级多任务调度,一旦高关键级任务的执行时间需求增加,通常的做法是立即抛弃相对低关键级任务,以确保高关键级任务获得足够处理器时间。考虑到数据访问的一致性和完整性以及相应的性能损失,这种处理低关键级任务的方法过于消极;同时,任务的实际执行时间并不总是能达到最差情况下执行时间,且多处理器平台上的调度存在可观的空闲时隙。因此,完全可以也应该对低关键级任务采取更为积极的处理方法。基于同构多处理器平台,构建了两类队列,一类队列容纳回收的空闲时隙,另一类队列为任务队列,包括就绪任务队列和被抛弃的低关键级任务队列,针对这两种任务队列的特性采取不同的调度方案：就绪任务队列采用混合关键级局部调度,被抛弃的低关键级任务则对空闲时隙进行分配。仿真实验表明,此调度方法在保证高关键级任务截止时限的同时,能够使混合关键级系统的可接受任务集数目获得明显提升。