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Title: A mixed-method study on the effectiveness of a buffering strategy in the relationship between risks and resilience
Author: Garrido Rios, Alexander
ISNI:       0000 0004 7425 5997
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2017
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The present research pursues two main interrelated objectives: one the one hand, to derive a unified definition of the concept of supply chain resilience (SCRes) from which a quantitative holistic measure of SCRes that appraises both dynamic and inherent resilience can be developed; on the other, to evaluate the theoretical effectiveness—due to the use of simulated experimental data—of a buffering strategy founded on the use of on-hand inventory buffers or short-term manufacturing capacity to build up SCRes. In this sense, the review of the literature uncovered not only flaws in the existing approaches to measure SCRes, but also opposing standpoints on the theoretical effectiveness of using a buffering strategy to inhibit the frequency/impact of SC disruptions. From the literature it is also unclear in which cases or under what circumstances the unit of analysis for this research should adopt a buffering strategy as mentioned. The unit of analysis selected for these purposes is a real-world military food supply chain (MFSC) operating in a risky environment that provides subsistence items to a medium-size military force (< 280,000 troop members). The research methods to address the two research objectives proposed are, first, a robust model based on discrete simulation; and second, an open-ended questionnaire administered to the staff of the MFSC. The first method—simulation—provides the data required to test the nine ex-ante hypotheses, while the second method—questionnaire—complements the previous ones by increasing their usefulness and empirical validity. The simulation experiment performed consists of subjecting the MFSC under analysis to the stepwise occurrence of three categories of risk—operational risks or R1r; natural disasters and intentional attacks or R2r; and black-swan events or R3—while on-hand inventory buffers or short-term manufacturing capacity—the buffering strategy—are gradually increased following an efficient experimental design. To test the nine hypotheses of the research, it was necessary to apply an approach based on data mining techniques— mining causal association rules—and non-parametric methods—the Kruskal-Wallis rank sum and Binomial distribution tests, and the Wilcoxon rank sum test with continuity correction. In this way, based on a novel perspective related to the application of the concept of tail autotomy effect (TAE) to obtain a measure of SCRes (ReT), the evaluation of the output data of the simulation model indicates that: (1) ceteris paribus, increases in the frequency of occurrence of seven of the nine risk events considered reduce ReT in the MFSC with 99% confidence; (2) increases in on-hand inventory buffers positively moderate the relationship between the frequency of occurrence of risks and ReT, with 99% confidence, regardless of the category of risk—R1r, R2r, or R3—affecting the MFSC; (3) increases in short-term manufacturing capacity positively moderate the relationship between the frequency of occurrence of risks and ReT, with 95% confidence for the categories of risk R1r and R3, and with 99% confidence for R2r; and (4) from the open-ended questionnaire, the staff of the MFSC shows a marked preference for the use of on-hand inventory buffers over short-term manufacturing capacity to avoid the occurrence of disruptions. Despite the theoretical implications of these findings, the assumptions of the simulation model, the non-inclusion of the cost factor, and the utilization of a single MFSC may limit to a certain extent their generalization to other scenarios or unit of analysis. To ameliorate these deficiencies, the construction of the simulation model incorporates nine types of risk, the evaluation of ninety configurations of the MFSC—simulation runs, and the consideration of a lengthy horizon of analysis of up to twenty years, allowing other military-SCs or even commercial-SCs can take advantage of the implications of the results of this research. Thus, from a practical point of view, this research provides (military) logisticians with clear guidelines for making decisions on when and how to use on-hand inventory buffers or short-term manufacturing capacity to create resilience or to inhibit the occurrence of disruptions caused by categories of risk R1r, R2r, and R3. From a theoretical standpoint, this research makes an original contribution to the body of knowledge in SC management by providing a novel conceptual framework mainly applicable to MFSCs, which includes the analysis of three categories of risk; a holistic measure of SCRes (ReT) including dynamic and inherent resilience; and the analysis of the application of a buffering strategy based on on-hand inventory buffers and short-term manufacturing capacity. In doing so, the findings of the research provide sufficient criteria for resolving the controversy concerning the theoretical effectiveness of the aforementioned strategy to create resilience and/or to inhibit the occurrence of disruptions in SCs.
Supervisor: Not available Sponsor: Universidad Militar Nueva Granada ; Departamento Administrativo de Ciencia ; Tecnología e Innovación ; Colombia ; Newton Fund ; Agencia Logística de las Fuerzas Militares
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: HD28 Management. Industrial Management