Sarah E. Marshall

On analysing warranty data from repairable items

Fitting models to failure data is an important topic in reliability. The resulting models can be useful both for manufacturers as well as for end-users. In this paper we provide details of some methods from the literature which can be used as a starting point when analysing and fitting models to failure data from repairable items. In particular we focus on obtaining analytical estimates of the intensity of a non-homogeneous Poisson process. We illustrate some of these methods on failure data from the warranty database of a major car manufacturer.

Review of Mathematical Programming Applications in Water Resource Management Under Uncertainty

Economic development, variation in weather patterns and natural disasters focus attention on the management of water resources. This paper reviews the literature on the development of mathematical programming models for water resource management under uncertainty between 2010 and 2017. A systematic search of the academic literature identified 448 journal articles on water resource management for examination. Bibliometric analysis is employed to investigate the methods that researchers are currently using to address this problem and to identify recent trends in research in the area. The research reveals that stochastic dynamic programming and multistage stochastic programming are the methods most commonly applied. Water resource allocation, climate change, water quality and agricultural irrigation are amongst the most frequently discussed topics in the literature. A more detailed examination of the literature on each of these topics is included. The findings suggest that there is a need for mathematical programming models of large-scale water systems that deal with uncertainty and multiobjectives in an effective and computationally efficient way.

Lot-sizing for a product recovery system with quality-dependent recovery channels

Abstract The importance of sustainable manufacturing has been recognised in recent years and as such, there has been a growing interest in initiatives such as product recovery and remanufacturing. In this paper, we study a product recovery system over an infinite planning horizon, with cycles consisting of multiple fixed-sized production lots followed by multiple fixed-sized recovery lots. Our model provides two channels for recovery – recovery into serviceable items and recovery into components. The inclusion of both recovery channels may allow manufacturers to increase the proportion of returns which they recover, and thus reduce the amount of waste that they generate. We derive expressions for the total cost per time unit for the model and provide formulae for the optimal lot sizes. Bounds are developed to provide upper limits on the optimal numbers of lots per cycle, given a maximum returned inventory capacity. The properties of the model are explored and demonstrated through numerical experiments, in particular we explore the situations in which the use of both recovery channels can lead to cost savings.

Lot-Sizing for a Product Recovery System with Quality-Dependent Recovery Channels

The importance of sustainable manufacturing has been recognised in recent years and as such, there has been a growing interest in initiatives such as product recovery and remanufacturing. In this paper, we study a product recovery system over an infinite planning horizon, with cycles consisting of multiple fixed-sized production lots followed by multiple fixed-sized recovery lots. Our model provides two channels for recovery - recovery into serviceable products and recovery into components. The inclusion of both recovery channels may allow manufacturers to increase the proportion of returns which they recover, and thus reduce the amount of waste that they generate. We derive expressions for the total cost per time unit for the model and provide formulae for the optimal lot sizes. A heuristic is provided to approximate the optimal numbers of production, recovery and buying lots per cycle. The properties of the model are explored and demonstrated through numerical experiments, in particular we explore the situations in which the use of both recovery channels can lead to cost savings.