Maintenance strategy based on a multicriterion classification of equipments

In an industrial plant, the level of maintenance provided to individual equipment is directly related to the availability that is expected from it. Thus, it is hoped that the most critical equipments will not fail or, at least, that any failure will be rapidly detected and corrected in the minimum time possible. Since resources are limited, it is necessary to determine how they should be distributed, so that no important equipment remains neglected while more resources are concentrated on the most critical items. Therefore, it is necessary to classify equipment in an objective way according to its importance. The method of multicriterion classification of critical equipments (MCCE)², which is described in the present work, allows systematic and detailed quantification of the criticality of all equipment, that is to say, it provides an evaluation of the importance that its correct operation has for the plant. To provide this information, the consequences for a company of any failure in the equipment concerned are analysed. Finally, a real case example of an urban wastewater treatment plant is described, in which the MCCE method is applied.     

砂堆雪崩幂律分布现象的解释

自组织临界性的提出者Per Bak认为,处于临界状态砂堆雪崩呈现幂律分布,可作为广延耗散动力系统自组织临界性存在的证据。采用真实砂堆试验和元胞自动机砂堆模拟两种方法进行研究,提出处于亚临界状态的砂堆,在向临界状态演化的过程中,砂堆在亚临界状态发生众多小规模的雪崩,越接近临界状态,系统的波动越强,大规模的雪崩也时而发生,因此在从亚临界状态向临界状态演化的过程之中,大规模雪崩的发生次数少,小规模雪崩发生的次数多,雪崩发生的规模也呈现幂律分布,并认为这种情况更具普适性。     

软件脆弱性危险程度量化评估模型研究

软件脆弱性的危险程度是对软件脆弱性被利用来攻击系统的潜在危险的度量。在分析目前已知的相关评价方法及其局限性的基础上,提出了根据脆弱性影响的严重程度和脆弱性可利用性来评佑脆弱性危险程度的分析框架,并基于模糊理论,提出了软件脆弱性危险程度评估的量化模型,建立了模糊测评因素关联隶属关系的递阶层次结构,并重点分析了基于模糊集的指标量化、基于模糊关系矩阵的指标权重的确定和软件脆弱性危险程度的综合评价方法。最后,给出了模型的应用与实现。     

基于马尔可夫模型的可信性评估研究

研究了安全关键实时系统传统的高可信保障机制,提出了一种可支持多级关键度的新可信性保障机制。使用该机制则可根据各子系统的实际可信性需求采用相应的冗余数进行容错处理。为评估该可信性保障机制,改进了传统的多模型可信性评估方法。基于马尔可夫模型,文章建立了一种统一的可信性评估模型,使用该模型则可按不同关键度子系统的实际可信性需求进行独立的评估。同时,该文使用了大量的实例进行例证。     

Monte Carlo criticality analysis under material distribution uncertainty

Analysis framework under material distribution uncertainty is not yet established for the Monte Carlo (MC) criticality calculation of continuously mixed media formed via molten core concrete interaction. To approach this issue, one group cross-sections have specifically been prepared for burned fuel, stainless steel and concrete, and the effect of spatially continuous variation of volume fractions is inspected. Trigonometric functions and randomized Weierstrass functions (RWFs) are utilized to represent the spatially continuous variation. Here, trigonometric functions enable the amount of each material to be exactly preserved, and RWF is a randomized trigonometric series that can be generated within specified upper and lower bounds. With these functions, one can assess the influence of indeterminate material distribution. MC particle transport is conducted using the delta-tracking. Numerical results indicate that the effective multiplication factor (k_eff) under RWF variation can depart significantly from the k_eff of a reference uniform medium. These numerical results also show that the deterministic modeling of spatial variation provides a bound measure for extreme results from random realizations.     

One-group steady state diffusion in a heterogeneous slab

We derive a customized solution to the diffusion equation in a heterogeneous slab with an arbitrary contiguous source. While aspects of solution have previously been reported in the literature, its full explicit form as presented here by solving a 3-term recurrence, has not. We conclude with a series of exercises demonstrating the utility of the solution.     

Business-oriented prioritization: A novel graphical technique

Traditionally, Pareto analysis has been used to select the most critical components and failure modes of a system. A clear disadvantage of this technique is that it requires preselecting a single criterion to establish priorities. More recently, a graphical log-scatter diagram technique has been proposed. It considers three key performance indicators simultaneously: reliability (MTBF), maintainability (MTTR), and unavailability (D). This technique considers only times and does not include economical effects explicitly. This article extends both techniques to explicitly consider both direct and indirect costs to prioritize from the point of view of an asset manager or from a maintenance decision-maker, as required. Due to the economic-based approach of this article, cost discounting is also considered inside financial costs such as—but not limited to—reliability-related investments. Also, the results are displayed on simple and accessible graphs which make them particularly useful for conveying results to non-technical managers. The methodology is illustrated by analyzing a shovel from the copper mine industry, and it clearly shows how the proposed technique facilitates business oriented decisions and how they should change under different market conditions.     

高储存密度乏燃料组件储架系统的结构特点与分析

高储存密度乏核燃料组件储架可以在不改变已有燃料储存水池的条件下，把储存乏核燃料组件的能力提高一倍左右。在核电站建设中推广这种先进的储架结构可以获得很大的经济效益。本文讨论这种储架的技术背景、结构特点以及设计与分析的内容与要求。     

RCS－Ⅰ反应堆堆芯模拟程序

本文介绍堆芯三维物理—热工水力耦台计算程序ＲＣＳ－Ｉ（ＲｅａｃｔｏｒＣｏｒｅＳｉｍｕｌａｔｏｒ）．其中子学模型采用先进的粗网格节块格林函数法，热工水力计算模型采用于通道分析方法．通过考虑多种反馈，该程序比较真实地描述堆芯的燃耗过程，具有临界、燃耗、中毒、跟踪和倒料等多种功能，可用于动力堆和研究堆的设计．     

传感器可靠性技术─失效模式与效应分析在传感器上的应用

通过实例介绍了可靠性技术中常用的失效分析方法一失效模式与效应分析，并阐述了失效模式、效应与危害度分析在传感器上的应用。