The aim of this paper is to discuss the modelling and optimization of condition-based maintenance policies for systems is submitted to usage profile changes. The considered system undergoes a monotone deterioration (gamma process) and its is impacted by the usage conditions (covariates) via the proportional hazards model. Four different policies are proposed and the optimal maintenance paramete...

This paper studied a continuous-time model of a production maintenance system in which a manufacturing firm produces a single product selling some and stocking the remaining. The problem of adaptive control of a production-maintenance system with unknown deterioration has been presented. Using Liapunov technique, the production rate and updating rule of deterioration rate are derived as non-lin...

BACKGROUND This study aimed to identify predictors of hearing thresholds (best-ear pure-tone average at 1, 2, and 4 kHz) and hearing deterioration in order to define potential target groups for hearing screening. METHODS We analyzed data from the Maastricht Aging Study, a Dutch cohort (aged 24-81 years; N = 1,721) that was observed for 12 years. Mixed model analysis was used to calculate each...

Exacerbations of chronic obstuctive pulmonary disease (COPD) are associated with worse health status. The Inhaled Steroids in Obstructive Lung Disease in Europe (ISOLDE) study showed that treatment with fluticasone propionate (FP) reduced exacerbation frequency and the rate of deterioration in health status as compared with placebo. The present study analysed these data to test whether the effe...