An approximate approach for the joint problem of level of repair analysis and spare parts stocking

For the spare parts stocking problem, generally metric type methods are used in the context of capital goods. Implicitly, a decision is assumed on which components to discard and which to repair upon failure, and where to perform repairs. In the military world, this decision is taken explicitly using the level of repair analysis (lora). Since the lora does not consider the availability of the installed base, solving the lora and spare parts stocking problems sequentially may lead to suboptimal solutions. We propose an iterative algorithm to solve the two problems. We compare its performance with that of the sequential approach and a recently proposed, so-called integrated algorithm. The latter finds optimal solutions for two-echelon, single-indenture problems. In our experiment, we use a set of such problems, and a set of multi-echelon, multi-indenture problems, for which we achieve a cost reduction of 3% on average (35% at maximum) compared with the sequential approach. Compared with the integrated algorithm, the gap is only 0.6% on average (5% at maximum), while the maximum computation time falls from 3 hours to 2.5 minutes. In a case study, we achieve a cost reduction of 10% compared with the sequential approach

Lower Bounds for Uniform Machine Scheduling Using Decision Diagrams

We propose a relaxed decision diagram (DD) formulation for obtaining lower bounds on uniform machine scheduling instances, based on separators to separate jobs on different machines. Experiments on the total tardiness for instances with tight due times show that for obtaining nontrivial bounds, it is important to partition the DD nodes on a layer based on their machine finishing time. When the number of jobs is small, DDs provide stronger bounds in less time than a time-indexed LP relaxation.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Algorithmic