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Preventive Maintenance Modeling
Published in Mangey Ram, Reliability Engineering, 2019
Sylwia Werbińska-Wojciechowska
According to Cho and Parlar [4], “multi component maintenance models are concerned with optimal maintenance policies for a system consisting of several units of machines or many pieces of equipment, which may or may not depend on each other.” In 1986, Thomas, in his work [30], presents classification of optimal maintenance strategies for multi-unit systems. He focuses on the models that are based on one of three types of dependence that occurs between system elements—economic, failure, and structural. According to the author, economic dependence implies that an opportunity for a group replacement of several components costs less than separate replacements of the individual components. Stochastic dependence, also called failure or probabilistic dependence, occurs if the condition of components influences the lifetime distribution of other components. Structural dependence means that components structurally form a part, so that maintenance of a failed component implies maintenance of working components. These definitions are adopted in this chapter.
Data learning and expert judgment in a bayesian belief network for offshore decommissioning risk assessment
Published in Stein Haugen, Anne Barros, Coen van Gulijk, Trond Kongsvik, Jan Erik Vinnem, Safety and Reliability – Safe Societies in a Changing World, 2018
M.L. Fam, X.H. He, P. Hilber, L.S. Ong, D. Konovessis, H. K. Tan
Dependency analysis between two variables is performed for all possible combinations in order to generate an initial list of dependency relationships. The analysis is based on the Pearson’s χ2 test which was elaborated in Section 2.2. With the chisquared value, and the corresponding number of degree of freedoms, the P-value can be obtained. The confidence interval then plays an important role on the significance test on the hypothesis of independence. The most commonly set confidence interval is at 95%, i.e. a P-value exceeding 0.05. For this data set (see Table 3), the confidence interval is set at 95%, and if the obtained P-value from the dependency analysis is less than 0.05, this implies a dependency between the two factors being investigated.
F
Published in Phillip A. Laplante, Dictionary of Computer Science, Engineering, and Technology, 2017
functional dependency a relationship between attributes in database systems. Given attributes A and B, a functional dependency exists between A and B, if and only if there is only one value of A for any given B. We say B is functionally dependent on A. We say A functionally determines B. A functional dependency between A and B is denoted by A → B.
A methodological approach for mapping and analysing cascading effects of flooding events
Published in International Journal of River Basin Management, 2022
Björn Arvidsson, Nicklas Guldåker, Jonas Johansson
A dependency can be described as a relationship between two infrastructures, where the state of one correlates with the state of another (Rinaldi et al. 2001). An interdependency is then technically a relationship when two infrastructures are dependent on each other, either directly or through feedback-loops (Rinaldi et al. 2001). However, it is common to use interdependency for both kinds of relationships, as will be done in this paper. Whenever interdependencies exist, and infrastructure is directly affected by an event, it can lead to indirect effects in other infrastructures. The propagation of effects between CI is often referred to as a cascading effect or a cascading failure (Rinaldi et al. 2001, Arvidsson et al. 2015, Johansson et al. 2015, Nones and Pescaroli 2016, Hilly et al. 2018). Interdependencies can thus be seen as the mechanism that allows for cascading effects.
Maintenance policies with minimal repair and replacement on failures: analysis and comparison
Published in International Journal of Production Research, 2021
Mohamed Larbi Rebaiaia, Daoud Ait-kadi
Unlike single-component systems as developed in the above presentation, as given by Models A, B, and C, the expression of the maintenance models corresponding to multi-component systems is more complex. Two categories of systems are considered in the practice, including systems with or without the dependency property. The notion of dependency means that a physical or a functional link may exist between all or a subset of the components. That signifies, if any two or more components are twinned, then if one of them breaks down both or all components must undergo the same maintenance policy, outright a simple replacement or a minimal repair action. We then speak about forced grouping maintenance strategy. Examples of functional dependency may be failure rates, reliabilities, residual lifetimes, unit costs, or minimal time for providing a preventive maintenance action that could be close in value. If no-dependency exists between components, the single-model strategy can be independently applied to each one of the components. In the case where dependencies between components are considered, two well-known maintenance strategies could be applied, they are called grouping and opportunistic techniques. These two strategies have been introduced to minimise the maintenance costs for multi-component systems instead of using any strategy for each component apart (Do Van et al. (2012); Laggoune, Chateauneuf, and Aissani (2010)).
Integrated optimisation of stope boundary and access layout for underground mining operations
Published in Mining Technology, 2019
Jie Hou, Chaoshui Xu, Peter Alan Dowd, Guoqing Li
This simple example demonstrates the importance of considering both development and stope layouts simultaneously in optimisation. Development (decline, shafts, production drives) services many production areas at the same time and therefore the development cost should be shared by these stopes. The more stopes sharing an access, the lower the access development cost will be for these stopes. This inter-dependency must be incorporated into the optimisation process in order to generate more realistic results.