Search results for "Criticality"
showing 10 items of 39 documents
The computational complexity of the criticality problems in a network with interval activity times
2002
Abstract The paper analyzes the criticality in a network with interval activities duration times. A natural generalization of the criticality notion (for a path, an activity and an event) for the case of network with interval activity duration times is given. The computation complexity of five problems linked to the introduced criticality notion is presented.
System dynamics models for decision making in product multiple lifecycles
2015
The main drivers for adopting product multiple lifecycles are to gain ecological and economic advantages. However, in most of the cases it is not straight forward to estimate the potential ecological and economic gain that may result from adopting product multiple lifecycles. Even though many researchers have concluded that product multiple lifecycles result in gain, there are examples which indicate that the gain is often marginal or even none in many cases. The purpose of this research is to develop system dynamics models that can assist decision makers in assessing and analysing the potential gain of product multiple lifecycles considering the dynamics of material scarcity. The foundatio…
ELECTRE TRI-based approach to the failure modes classification on the basis of risk parameters: An alternative to the risk priority number
2017
Proposing an ELECTRE TRI-based approach for the failure modes classification into predefined and ordered risk classes.Direct identification of failure modes on which performing the corrective actions with priority.Easy definition of risk classes on the basis of DMs expertise and perception of the industrial context considered.Application to dairy manufacturing processes. Failure Mode and Effects Analysis (FMEA) is an engineering technique aimed at the detection of potential failures, their causes and consequences on the system/process under investigation. When used for the failure modes prioritization, FMEA is also referred to as Failure Mode, Effects and Criticality Analysis (FMECA). In tr…
Criticality and sensitivity analysis of the components of a system
2000
Abstract In the design of complex systems there is a great interest to know the relative importance of each of their elements. In this paper, we define a new method for measuring the relative importance of each element of the system. We have to specify that this paper concerns only non-repairable systems and components. We present a way of calculating the criticality of each component for a complex system no matter what the random distribution of the life of the component is. The paper also demonstrates a simple way of calculating how the system life improves when the life of a component is improved.
A Dempster-Shafer Theory-based approach to the Failure Mode, Effects and Criticality Analysis (FMECA) under epistemic uncertainty: application to the…
2017
Abstract Failure Mode and Effects Analysis (FMEA) is a safety and reliability analysis tool widely used for the identification of system/process potential failures, their causes and consequences. When aimed at the failure modes prioritization, FMEA is named Failure Mode, Effects and Criticality Analysis (FMECA). In the latter case, failure modes are commonly prioritized by means of the Risk Priority Number (RPN) that has been widely criticized to have several shortcomings. Firstly, in the presence of multiple experts supplying different and uncertain judgments on risk parameters, RPN is not able to deal with such a kind of information. Therefore, the present paper proposes the Dempster-Shaf…
The measurement programme at the neutron time-of-flight facility n_TOF at CERN
2016
Neutron-induced reaction cross sections are important for a wide variety of research fields ranging from the study of nuclear level densities, nucleosynthesis to applications of nuclear technology like design, and criticality and safety assessment of existing and future nuclear reactors, radiation dosimetry, medical applications, nuclear waste transmutation, accelerator-driven systems and fuel cycle investigations. Simulations and calculations of nuclear technology applications largely rely on evaluated nuclear data libraries. The evaluations in these libraries are based both on experimental data and theoretical models. CERN’s neutron time-of-flight facility n TOF has produced a considerabl…
A combined multi-criteria approach to support FMECA analyses: A real-world case
2018
[EN] The paper proposes an approach that combines reliability analyses and multi-criteria decision methods to optimize maintenance activities of complex systems. A failure mode, effects, and criticality analysts (FMECA) is initially performed and the fuzzy TOPSIS (FTOPSIS) method is then applied to rank previously identified failure modes. For prioritization, failure modes are assessed against three evaluation criteria that differ from those traditionally involved in risk priority number (RPN) computation (i.e. severity, occurrence and detection). Two criteria refer to the maintenance management reflecting the operational time taken by the maintenance activity performed after the occurrence…
Has palaeontology answers for some current environmental problems?
2021
History as an irreversible process has no role from a uniformitarian point of view in geology and palaeobiology. Contingency is another trait of history and particle palaeontology has its foundation on such principles. However, new approaches in physics and the theory of systems point out the need to consider a time arrow. Moreover, chance and necessity are interwoven in synergetics and self-organization theory and there may be some possibility of prediction. The global biota has a history resulting from a process of self-organization. A rich fossil record was produced during the Phanerozoic times and this fossil record shows us how life overcame several important crisis. A clear understand…
Risk assessment of component failure modes and human errors using a new FMECA approach: application in the safety analysis of HDR brachytherapy
2014
Failure mode, effects and criticality analysis (FMECA) is a safety technique extensively used in many different industrial fields to identify and prevent potential failures. In the application of traditional FMECA, the risk priority number (RPN) is determined to rank the failure modes; however, the method has been criticised for having several weaknesses. Moreover, it is unable to adequately deal with human errors or negligence. In this paper, a new versatile fuzzy rule-based assessment model is proposed to evaluate the RPN index to rank both component failure and human error. The proposed methodology is applied to potential radiological over-exposure of patients during high-dose-rate brach…
Safety study of an LNG regasification plant using an FMECA and HAZOP integrated methodology
2015
Abstract A safety analysis was performed to determine possible accidental events in the storage system used in the liquefied natural gas regasification plant using the integrated application of failure modes, effects and criticality analysis (FMECA) and hazard and operability analysis (HAZOP) methodologies. The goal of the FMECA technique is the estimation of component failure modes and their major effects, whereas HAZOP is a structured and systematic technique that provides an identification of the hazards and the operability problems using logical sequences of cause-deviation-consequence of process parameters. The proposed FMECA and HAZOP integrated analysis (FHIA) has been designed as a …