On the Statistical Modeling and Analysis of Repairable Systems

We review basic modeling approaches for failure and maintenance data from repairable systems. In particular we consider imperfect repair models, defined in terms of virtual age processes, and the trend-renewal process which extends the nonhomogeneous Poisson process and the renewal process. In the case where several systems of the same kind are observed, we show how observed covariates and unobserved heterogeneity can be included in the models. We also consider various approaches to trend testing. Modern reliability data bases usually contain information on the type of failure, the type of maintenance and so forth in addition to the failure times themselves. Basing our work on recent literature we present a framework where the observed events are modeled as marked point processes, with marks labeling the types of events. Throughout the paper the emphasis is more on modeling than on statistical inference.Comment: Published at http://dx.doi.org/10.1214/088342306000000448 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Reengineering Production Systems: the Royal Netherlands Naval Dockyard

Reengineering production systems in an attempt to meet tight cost, quality and leadtime standards has received considerable attention in the last decade. In this paper, we discuss the reengineering process at the Royal Netherlands Naval Dockyard. The process starts with a characterisation and a careful analysis of the production system and the set of objectives to be pursued. Next, a new production management structure is defined after which supporting planning and control systems are designed and a number of organisational changes are carried through. In this way, the Dockyard may combine high technological capabilities with an excellent logistic performance

Optimal maintenance of multi-component systems: a review

In this article we give an overview of the literature on multi-component maintenance optimization. We focus on work appearing since the 1991 survey "A survey of maintenance models for multi-unit systems" by Cho and Parlar. This paper builds forth on the review article by Dekker et al. (1996), which focusses on economic dependence, and the survey of maintenance policies by Wang (2002), in which some group maintenance and some opportunistic maintenance policies are considered. Our classification scheme is primarily based on the dependence between components (stochastic, structural or economic). Next, we also classify the papers on the basis of the planning aspect (short-term vs long-term), the grouping of maintenance activities (either grouping preventive or corrective maintenance, or opportunistic grouping) and the optimization approach used (heuristic, policy classes or exact algorithms). Finally, we pay attention to the applications of the models.literature review;economic dependence;failure interaction;maintenance policies;grouping maintenance;multi-component systems;opportunistic maintenance;maintencance optimization;structural dependence

Multiple repair sequences in everyday conversations involving people with Parkinson's disease

Background Features of dysarthria associated with Parkinson's disease (PD), such as low volume, variable rate of speech and increased pauses, impact speaker intelligibility. Those affected report restricted interactional participation, although this area is under explored. Aims To examine naturally occurring instances of problems with intelligibility that resulted in multiple attempts at repair in order to consider repair initiation strategies that might restrict or enhance participation. Methods & Procedures Thirteen people with PD (PwPD) video-recorded over 10 h of informal conversation data in their home setting involving familiar conversation partners (CPs). Using a conversation analytic (CA) approach, and drawing on an existing typology of repair initiators (RIs) for everyday talk-in-interaction and their relative power to locate a turn's repairable element, the design and ordering of RIs used by CPs was addressed, alongside their local consequences. Outcomes & Results CPs tended to increase the specificity of their RIs in line with the existing typology, progressing from open class forms (e.g. ‘mm?’) to more specific forms (e.g. questions/partial repeats). Repeated open class repair initiators (OCRIs) were used where PD speakers’ self-repair attempts provided limited information. Sometimes, however, specificity was increased too soon, before enough syntactic knowledge was gleaned, which resulted in an extended repair sequence. Where one OCRI followed another, the second always took a different form: lexically or in terms of prosodic/non-verbal features. RI forms not described in the existing typology were also identified, such as ‘prompts to modify speech’ (e.g. ‘Speak louder’) and repeating/rephrasing the original first pair part (e.g. question), and their effectiveness examined. Conclusions & Implications First steps are presented towards the design of a communication intervention promoting the efficient resolution of repair to moderate social withdrawal and increase participation for this client group. Future research will need to explore the feasibility and acceptability of such a resource

Optimal maintenance strategies for systems with partial repair options and without assuming bounded costs

We study a repairable system with Markovian deterioration and partial repair options, carried out at fixed times $n=1,2,\ldots$ and look for optimal strategies under certain conditions. Two optimality criteria are considered: expected discounted cost and long-run average cost. Douer and Yechiali found conditions under which a policy in the class of generalized control limit policies is optimal. In this paper conditions are found under which an optimal policy is a control-limit policy. We explicitly explain how to derive this optimal policy; numerical examples are given, too