荔枝包装的风险识别与分析

目的解决在荔枝包装过程中风险源难于辨识及定量分析的难题。方法提出一种基于霍尔三维因素空间和模糊故障树的风险识别与定量分析方法。构建荔枝包装的安全事件、时空结构(工位)、事故致因等3个维度的因素集,通过矩阵之间的映射关系和计算分析得到风险基本事件集合。建立荔枝包装的故障树模型,并对风险基本事件进行专家问卷评价。采用梯形模糊数及左右模糊排序法将专家的评判语言转化为风险概率值。结果经计算得到荔枝包装事故发生概率(0.0409)及风险基本事件的概率重要度。结论提出了强化标准化建设,加大技术投入等防范风险事故发生的措施。     

基于故障树分析法的拆除爆破飞散物事故风险分析

为充分控制拆除爆破工程中爆破飞散物对周边环境的影响,建立了以故障树分析法为理论基础,以拆除爆破工艺流程为主线的爆破飞石故障树模型。以拆除爆破中各个工艺单元为基本事件,同时通过子系统设定、系统执行设定和系统独立设定,将分析过程控制的更加严谨和合乎实际。通过最小割集-概率重要度分析指出有效控制部分基本事件使其不发生可以大大提高系统安全状态;通过最小径集分析和结构重要度分析指出了技术人员特别是高级技术人员对拆除爆破飞散物事故控制至关重要的作用。     

北京市食品冷链物流配送研究

北京市食品冷链物流配送操作十分不完善,本文通过食品冷链物流配送冷藏运输、冷藏储藏、冷藏运输和冷藏储藏的冷链对接这三个环节作为整体的完全冷链和不完全冷链的模型的建立,来计算两种模式下的货物热流量的差异,为后规范北京市场低温食品的流通途径提供一个思路,它可以对北京市倡导的安全食品起到一定的指导作用。     

硝铵炸药真空干燥工艺燃爆事故致灾因素的研究

真空干燥是硝铵炸药生产过程中一道容易发生燃爆事故的重要工序。为研究硝铵炸药真空干燥过程中发生燃爆事故的原因及机理，通过事故案例分析和现场调研，确定了导致燃爆事故的各个基本事件及其逻辑关系，并由此构建以燃爆事故作为顶事件的事故树。采用布尔代数化简事故树，得到87个最小割集和9个最小径集，结果显示每个最小径集包含的基本事件都较多，说明真空干燥工艺安全性较低。通过计算各基本事件的结构重要度并排序，得到结构重要度较大的基本事件，由此推断出导致燃爆事故的主要基本事件，并有针对性地提出相应的改进措施与建议，为企业的安全生产提供参考。     

荔枝全程冷链物流碳足迹测算分析及实证研究

目的针对系统衡量双渠道流通模式下荔枝全程冷链物流的碳排放问题,构建一种计算碳足迹模型,以衡量该过程中的碳排放情况,并对其展开实证研究。方法采用碳排放系数法、投入产出法,测算批发商开设的双渠道流通模式的荔枝采后预冷、流通加工、冷藏运输、贮存、配送、销售以及终端消费者等各环节所产生的碳排放量,并借助Matlab对模型进行优化求解,在设定参数的条件下,以及考虑碳排放的情况下,分别以总成本最小和总碳排放量最小进行运算。结果通过实证可知,总成本均为407.34万元,总碳排放量均为223.14t。通过对断链情况下的荔枝双渠道流通模式碳足迹进行对比分析发现,荔枝在断链的流通模式下的总成本为453.99万元,碳排放量为225.71 t;通过对不同包装下的腐损率进行对比分析发现,在考虑碳排放情况下,腐损率从0上升到30%时,碳排放量上升了4%。结论该模型能有效衡量双渠道流通模式下荔枝全程冷链物流活动的碳足迹,为荔枝运用全程冷链物流的经济效益和环境效益最大化协同的设计和实施提供了支撑。     

基于模糊故障树的军用气象物资包装可靠性分析

应用模糊故障树分析方法对军用气象物资包装可靠性进行了系统分析,简要介绍了模糊故障树分析方法的基本理论,利用专家判断和模糊集理论相结合的方法,评估了故障树底事件发生的模糊失效概率。并以"TFS-1通风干湿表包装"为例,建立了包装系统的故障树,采用下行法求解了引起顶事件发生的最小割集,定量分析计算,得出模糊失效率为0.0705,同时计算了各底事件的重要度。模糊故障树分析方法对于提高军用气象物资包装防护能力,确保物资装备质量,具有非常重要的意义。     

基于GO—FLOW法的荔枝冷链物流安全评价

借鉴系统可靠性工程理论,采用GO-FLOW法分析技术,建立一种评价荔枝及其他鲜活农产品物流安全风险的定量分析方法。在对荔枝冷链物流系统进行分析的基础上,建立荔枝物流系统的GO-FLOW图,并分析了其信号流、操作符和运算规则;以具体荔枝物流过程为例,进行GO运算,求出各信号流的故障率和可靠性,找出影响物流安全的关键环节和提出解决方法;指出GO-FLOW法是物流安全评价的一个有效和方便的方法。     

基于事故树的深孔爆破边坡稳定性分析

为了能够对爆破后形成的露天边坡稳定性进行合理的分析评价,结合大小鱼山岛露天爆破边坡失稳的情况,采用事故树分析方法,建立了工程爆破现场露天边坡失稳事故树模型。计算出事故树的最小割集96个,最小径集3个以及基本事件的结构重要度系数,并得到基本事件结构重要度排序,找出了导致边坡失稳的主要原因是边坡监测和边坡支护。然后根据基本事件结构重要度的排序,制定合理有序的预防措施。事故树分析方法可以全面阐述露天矿边坡失稳的各种因素和逻辑关系,并通过对结构重要性分析,提出合理预防措施,为爆破露天边坡的安全管理提供参考依据。     

基于事故树的深孔爆破边坡稳定性分析

为了能够对爆破后形成的露天边坡稳定性进行合理的分析评价,结合大小鱼山岛露天爆破边坡失稳的情况,采用事故树分析方法,建立了工程爆破现场露天边坡失稳事故树模型。计算出事故树的最小割集96个,最小径集3个以及基本事件的结构重要度系数,并得到基本事件结构重要度排序,找出了导致边坡失稳的主要原因是边坡监测和边坡支护。然后根据基本事件结构重要度的排序,制定合理有序的预防措施。事故树分析方法可以全面阐述露天矿边坡失稳的各种因素和逻辑关系,并通过对结构重要性分析,提出合理预防措施,为爆破露天边坡的安全管理提供参考依据。     

液氦温区大型低温制冷系统的可靠性评估

针对改进Claude循环的大型氦低温制冷系统,以制冷量不足为顶事件建立了故障树模型。利用结构法对故障树模型进行定性分析,分析得到系统的最小割集为18个。利用来自不同数据库的部件失效率对故障树模型进行定量计算,得到了不同的结果,并分析其原因。对各部件的关键重要度进行了计算,以衡量各个部件对系统发生故障的贡献程度。并通过增加系统冗余部件和提高关键部件可靠度等措施,为提高系统可靠性找到了有效的解决途径。     

A practical method for accurate quantification of large fault trees

This paper describes a practical method to accurately quantify top event probability and importance measures from incomplete minimal cut sets (MCS) of a large fault tree. The MCS-based fault tree method is extensively used in probabilistic safety assessments. Several sources of uncertainties exist in MCS-based fault tree analysis. The paper is focused on quantification of the following two sources of uncertainties: (1) the truncation neglecting low-probability cut sets and (2) the approximation in quantifying MCSs. The method proposed in this paper is based on a Monte Carlo simulation technique to estimate probability of the discarded MCSs and the sum of disjoint products (SDP) approach complemented by the correction factor approach (CFA). The method provides capability to accurately quantify the two uncertainties and estimate the top event probability and importance measures of large coherent fault trees. The proposed fault tree quantification method has been implemented in the CUTREE code package and is tested on the two example fault trees.     

A PSA-based vital area identification methodology development

This paper presents a vital area identification method based on the current probabilistic safety assessment (PSA) techniques. The vital area identification method in this paper is focused on core melt rather than radioactive material release. Furthermore, it describes a conceptual framework with which the risk from sabotage-induced events could be assessed.Location minimal cut sets (MCSs) are evaluated after developing a core melt location fault tree (LFT). LFT is a fault tree whose basic events are sabotage-induced damages on the locations within which various safety-related components are located. The core melt LFT is constructed by combining all sequence LFTs of various event trees with OR gates. Each sequence LFT is constructed by combining the initiating event LFT and the mitigating event LFTs with an AND gate. The vital area could be identified by using the location importance measures on the core melt location MCSs. An application was made to a typical 1000 MWe pressurized water reactor power plant located at the Korean seashore.The methodology suggested in the present paper is believed to be very consistent and most complete in identifying the vital areas in a nuclear power plant because it is based on the well-proven PSA technology.     

On simplification of large fault trees

This paper describes some fault tree optimization algorithms used in STUK PSA code SPSA that is capable of generating minimal cut sets for fault trees containing 12 000 gates and basic events. The complexity of a minimal cut set search is a function of multiple gates and basic events. In a fault tree containing 1000 multiple elements, these optimizations reduce the number of multiple elements often by 30 to 50%. One novel feature of the algorithm is that no boolean reduction rules are used, since the fault tree itself contains its simplification rules.     

Quantitative analysis of a fault tree with priority AND gates

A method for calculating the exact top event probability of a fault tree with priority AND gates and repeated basic events is proposed when the minimal cut sets are given. A priority AND gate is an AND gate where the input events must occur in a prescribed order for the occurrence of the output event. It is known that the top event probability of such a dynamic fault tree is obtained by converting the tree into an equivalent Markov model. However, this method is not realistic for a complex system model because the number of states which should be considered in the Markov analysis increases explosively as the number of basic events increases. To overcome the shortcomings of the Markov model, we propose an alternative method to obtain the top event probability in this paper. We assume that the basic events occur independently, exponentially distributed, and the component whose failure corresponds to the occurrence of the basic event is non-repairable. First, we obtain the probability of occurrence of the output event of a single priority AND gate by Markov analysis. Then, the top event probability is given by a cut set approach and the inclusion–exclusion formula. An efficient procedure to obtain the probabilities corresponding to logical products in the inclusion–exclusion formula is proposed. The logical product which is composed of two or more priority AND gates having at least one common basic event as their inputs is transformed into the sum of disjoint events which are equivalent to a priority AND gate in the procedure. Numerical examples show that our method works well for complex systems.     

Finding minimal cut sets in a fault tree

This paper presents a new method for identification of minimal cut sets in a fault tree. The (non-minimal) cut sets are found by a modification of the well-known MOCUS algorithm. These cut sets are stored in a virtual tree structure which requires far less core space than the MOCUS cut set matrix. The minimal cut sets are found by traversing this virtual tree a number of times. In the first cycle, all cut sets of order one are identified. In the next cycle, all cut sets of order two are identified and compared with the cut sets of order one to exclude non-minimal stes. This procedure is continued until all minimal cut sets are identified. The procedure is very fast. Compared to the standard MOCUS program the computer time is reduced by at least a factor of ten.