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Papers by Jack Metters
In this study, a two-level supply chain with linear demand and seasonal swings is simulated under... more In this study, a two-level supply chain with linear demand and seasonal swings is simulated under varying operating situations in order to explore the relationships among bullwhip effect, lead time, forecast accuracy, seasonality, service levels and retailer's performance. Next, a series of univariate tests are undertaken to identify the relationships among the simulation outputs. Based on a structural equation model (SEM), a research framework is developed and tested to provide a rigorous analysis for the casual links among the SCM-related variables and retailer's performance. When the ratio of backorder to holding cost is lower than 8, lead time would appear as the most significant factor influencing total inventory cost. However, when this ratio is higher than 8, both bullwhip ratio and lead time appear to be equally important factors in improving retailer's performance. Finally, the forecast accuracy was found to have a positive effect on reducing total inventory cost.
International Journal of Production Research, 2009
Conventional thinking suggests bullwhip should necessarily be minimised within the supply chain. ... more Conventional thinking suggests bullwhip should necessarily be minimised within the supply chain. While this may be good practice where no constraints exist, in reality companies have shared resources and capacity limits that affect their ability to do this. Consequently, there is an influence upon their production strategy. This can introduce some bullwhip into the supply chain but, managed effectively, can actually be useful. We call this useful strategy "Minimum Reasonable Bullwhip" (MRB). The aim of this paper is to examine the relationship between production strategy and bullwhip where constraints exist. In doing so, three case studies are presented where distinct clusters of product types exist, each with different observed levels of bullwhip. By considering total supply chain costs, we explain why these clusters exist. The paper contributes to the literature by challenging the contention that bullwhip should always be minimised, given the importance that it is important to achieve performance objectives across the product range. It also identifies areas for future research to extend the MRB concept.
Age and Ageing, 2009
Objective: to examine whether usual gait speed, fast gait speed or speed while walking with a cog... more Objective: to examine whether usual gait speed, fast gait speed or speed while walking with a cognitive or neuromuscular challenge predicts evolving cognitive decline over 3 years. Design: prospective study. Setting: population-based sample of community-dwelling older persons. Participants: 660 older participants (age ≥65 years). Measurements: usual gait speed, fastest gait speed, gait speed during 'walking-while-talking', depression, comorbidities, education, smoking and demographics were assessed at baseline. Cognition was evaluated at baseline and follow-up. A decline in MMSE score by ≥3 points was considered as significant cognitive decline (SCD). Results: adjusting for confounders, only fast speed was associated with cognitive performance at 3-year follow-up. One hundred thirty-five participants had SCD over 3 years. Participants in the lowest quartile of usual speed or walking-whiletalking speed were more likely to develop SCD. Conversely, participants in the third and fourth quartiles of fast speed were more likely to develop SCD. J-test showed that the model including fast speed quartiles as a regressor was significantly more predictive of SCD than the models with usual speed or walking-while-talking speed quartiles. Conclusion: measuring fast gait speed in older persons may assist in identifying those at high risk of cognitive decline.
In this study, a two-level supply chain with linear demand and seasonal swings is simulated under... more In this study, a two-level supply chain with linear demand and seasonal swings is simulated under varying operating situations in order to explore the relationships among bullwhip effect, lead time, forecast accuracy, seasonality, service levels and retailer's performance. Next, a series of univariate tests are undertaken to identify the relationships among the simulation outputs. Based on a structural equation model (SEM), a research framework is developed and tested to provide a rigorous analysis for the casual links among the SCM-related variables and retailer's performance. When the ratio of backorder to holding cost is lower than 8, lead time would appear as the most significant factor influencing total inventory cost. However, when this ratio is higher than 8, both bullwhip ratio and lead time appear to be equally important factors in improving retailer's performance. Finally, the forecast accuracy was found to have a positive effect on reducing total inventory cost.
International Journal of Production Research, 2009
Conventional thinking suggests bullwhip should necessarily be minimised within the supply chain. ... more Conventional thinking suggests bullwhip should necessarily be minimised within the supply chain. While this may be good practice where no constraints exist, in reality companies have shared resources and capacity limits that affect their ability to do this. Consequently, there is an influence upon their production strategy. This can introduce some bullwhip into the supply chain but, managed effectively, can actually be useful. We call this useful strategy "Minimum Reasonable Bullwhip" (MRB). The aim of this paper is to examine the relationship between production strategy and bullwhip where constraints exist. In doing so, three case studies are presented where distinct clusters of product types exist, each with different observed levels of bullwhip. By considering total supply chain costs, we explain why these clusters exist. The paper contributes to the literature by challenging the contention that bullwhip should always be minimised, given the importance that it is important to achieve performance objectives across the product range. It also identifies areas for future research to extend the MRB concept.
Age and Ageing, 2009
Objective: to examine whether usual gait speed, fast gait speed or speed while walking with a cog... more Objective: to examine whether usual gait speed, fast gait speed or speed while walking with a cognitive or neuromuscular challenge predicts evolving cognitive decline over 3 years. Design: prospective study. Setting: population-based sample of community-dwelling older persons. Participants: 660 older participants (age ≥65 years). Measurements: usual gait speed, fastest gait speed, gait speed during 'walking-while-talking', depression, comorbidities, education, smoking and demographics were assessed at baseline. Cognition was evaluated at baseline and follow-up. A decline in MMSE score by ≥3 points was considered as significant cognitive decline (SCD). Results: adjusting for confounders, only fast speed was associated with cognitive performance at 3-year follow-up. One hundred thirty-five participants had SCD over 3 years. Participants in the lowest quartile of usual speed or walking-whiletalking speed were more likely to develop SCD. Conversely, participants in the third and fourth quartiles of fast speed were more likely to develop SCD. J-test showed that the model including fast speed quartiles as a regressor was significantly more predictive of SCD than the models with usual speed or walking-while-talking speed quartiles. Conclusion: measuring fast gait speed in older persons may assist in identifying those at high risk of cognitive decline.