On the operational logistic aspects of reuse.

For still more companies, it is or will become important to pay attention to the possibilities for reusing the products they produce and the items, like pallets and package materials, that they use for distributing their products or which are used by others for supplying their products to them. One important reason for the above is the growing concern for the natural environment, among others resulting in environmental laws which not only force companies to take back their products from their customers and the items used for the distribution of these products when these products or distribution items (DIs) are no longer desired by these customers, but also to take care of the environmentally friendly disposal of these products and Dis. However, due to the same reason, this disposal is becoming still more difficult and expensive (see e.g., Cairncross, 1990). Apart from being forced by law, companies feel forced to do the above because of competition and public opinion. But there are more reasons why it may be worthwhile for companies to consider reuse: there are products, components, materials and DIs that can be obtained cheaper or more quickly via reuse than via purchasing or producing anew

Substitutie van resources voor het oplossen van tijdelijke problemen

Substitutie van resources, waaronder mensen, machines, gereedschappen, materialen, toeleveranciers en transporteurs, voor het oplossen van tijdelijke problemen met standaard gebruikte resources is de inzet van alternatieve resources om alsnog tijdig aan een vraag te kunnen voldoen

Condition-based maintenance for complex systems based on current component status and Bayesian updating of component reliability

\u3cp\u3eWe propose a new condition-based maintenance policy for complex systems, based on the status (working, defective) of all components within a system, as well as the reliability block diagram of the system. By means of the survival signature, a generalization of the system signature allowing for multiple component types, we obtain a predictive distribution for the system survival time, also known as residual life distribution, based on which of the system's components currently function or not, and the current age of the functioning components.The time to failure of the components of the system is modeled by a Weibull distribution with a fixed shape parameter. The scale parameter is iteratively updated in a Bayesian fashion using the current (censored and non-censored) component lifetimes. Each component type has a separate Weibull model that may also include test data.The cost-optimal moment of replacement for the system is obtained by minimizing the expected cost rate per unit of time. The unit cost rate is recalculated when components fail or at the end of every (very short) fixed inter-evaluation interval, leading to a dynamic maintenance policy, since the ageing of components and possible failures will change the cost-optimal moment of replacement in the course of time. Via numerical experiments, some insight into the performance of the policy is given.\u3c/p\u3

Optimal core acquisition and remanufacturing policies under uncertain core quality fractions

Cores acquired by a remanufacturer are typically highly variable in quality. Even if the expected fractions of the various quality levels are known, then the exact fractions when acquiring cores are still uncertain. Our model incorporates this uncertainty in determining optimal acquisition decisions by considering multiple quality classes and a multinomial quality distribution for an acquired lot. We derive optimal acquisition and remanufacturing policies for both deterministic and uncertain demand. For deterministic demand, we derive a simple closed-form expression for the total expected cost. In a numerical experiment, we highlight the effect of uncertainty in quality fractions on the optimal number of acquired cores and show that the cost error of ignoring uncertainty can be significant. For uncertain demand, we derive optimal newsboy-type solutions for the optimal remanufacture-up-to levels and an approximate expression for the total expected cost given the number of acquired cores. In a further numerical experiment, we explore the effects of demand uncertainty on the optimal acquisition and remanufacturing decisions, and on the total expected cost.Remanufacturing Product acquisition management Quality uncertainty

Condition-based maintenance policies for systems with multiple dependent components: a review

Condition-based maintenance (CBM) has received increasing attention in the literature over the past years. The application of CBM in practice, however, is lagging behind. This is, at least in part, explained by the complexity of real-life systems as opposed to the stylized ones studied most often. To overcome this issue, research is focusing more and more on complex systems, with multiple components subject to various dependencies. Existing classifications of these dependencies in the literature are no longer sufficient. Therefore, we provide an extended classification scheme. Besides the types of dependencies identified in the past (economic, structural, and stochastic), we add resource dependence, where multiple components are connected through, e.g., shared spares, tools, or maintenance workers. Furthermore, we extend the existing notion of structural dependence by distinguishing between structural dependence from a technical point of view and structural dependence from a performance point of view (e.g., through a series or parallel setting). We review the advances made with respect to CBM. Our main focus is on the implications of dependencies on the structure of the optimal CBM policy. We link our review to practice by providing real-life examples, thereby stressing current gaps in the literature