A review of multi-component maintenance models with economic dependence

In this paper we review the literature on multi-component maintenance models with economic dependence. The emphasis is on papers that appeared after 1991, but there is an overlap with Section 2 of the most recent review paper by Cho and Parlar (1991). We distinguish between stationary models, where a long-term stable situation is assumed, and dynamic models, which can take information into account that becomes available only on the short term. Within the stationary models we choose a classification scheme that is primarily based on the various options of grouping maintenance activities: grouping either corrective or preventive maintenance, or combining preventive-maintenance actions with corrective actions. As such, this classification links up with the possibilities for grouped maintenance activities that exist in practice

Dynamic influences in multi-component maintenance

Most maintenance-optimisation models assume an infinite planning horizon and suppose that the failure process is stationary. Hence, information which is not known beforehand and which beocmes available in the short term only, must be ignored. We consider in this paper a multi-component system with economically dependent components, and we compare the costs of a stationary-planning method with the costs according to an approach which can adapt this long-term plan to dynamically changing information (such as a variable use of components and the occurrence of maintenance opportunities). With numerical experiments we show that incorporating short-term information can yield considerable cost savings

Self-Employment out of Dissatisfaction: An International Study

This paper studies differences in the rate of self-employment (business ownership) in more thantwenty Western nations and Japan for the period 1974-1994, focusing in particular on theinfluences of dissatisfaction and uncertainty avoidance. We test two types of hypotheses, pertainingto the positive influence of various forms of dissatisfaction on the level of self-employment, and todifferences between the importance of various push and pull factors in low and high uncertaintyavoidance countries. The two types of hypotheses are related, as inhabitants of high-uncertaintyavoidance cultures tend to express lower levels of satisfaction with life. Using a longitudinaldataset covering 12 European countries, and controlling for important economic factors, we findthat dissatisfaction is a very important variable for explaining differences in self-employmentlevels. Dissatisfaction seems to be a factor promoting self-employment, not only at the level of theindividual, but also at the level of societies. Hofstede's Uncertainty Avoidance Index is used todistinguish between low and high-uncertainty avoidance countries, and the factors influencingselfemployment rates within these two clusters are investigated in a set of 23 countries. In the group ofhigh-uncertainty avoidance countries a strong negative relationship between GDP per capita andthe level of self-employment is found, in low-uncertainty avoidance countries the profits associatedwith being self-employed are a significant factor. These findings, which support the hypotheses,suggest that in high-uncertainty avoidance countries self-employment is often caused by a lack ofprosperity (a push factor); in low-uncertainty avoiding countries the pull factor of expected profitsis more important.

Maintenance of Light Standards, a Case-Study

This paper discusses several strategies for the maintenance of light standards, where each light standard consists of n independent and identical lamps screwed on a chandelier. The lamps are subject to stochastic failures, and must be correctively replaced if the number of failed lamps reaches a prespecified number m; a norm that is set by the local management to guarantee a minimumluminance. As lamps have an increasing failure rate, and there is a fixed cost of hoisting the chandelier, we propose various variants of the m-failure group replacement rule which have in particular an age-criterion to indicate which of the non-failed lamps must be preventively replaced at the time that the chandelier is lowered for a corrective lamp replacement; we show how the optimalthreshold age can be determined. It appears that this modification reduces the long run average maintenance cost of the Europe Combined Terminals with approximately 8.3%.