Multi-Echelon Models for Repairable Items: A Review

We review multi-echelon inventory models for repairable items. Such models have been widely applied to the management of critical spare parts for military equipment for around three decades, but the application to manufacturing and service industries seems to be much less documented. We feel that the appropriate use of models in the management of spare parts for heavily utilized equipment in industry can result in significant cost savings, in particular in those settings where repair facilities are resource constrained. In our review, we provide a strategic framework for making these decisions, place the modeling problem in the broader context of inventory control, and review the prominent models in the literature under a unified setting, highlighting some key relationships. We concentrate on describing those models which we feel are most applicable for practical application, revisiting in detail the Multi-Echelon Technique for Recoverable Item Control (METRIC) model and its variations, and then discussing a variety of more general queueing models. We then discuss the components which we feel must be addressed in the models in order to apply them practically to industrial settings

AVCAL reduction analysis model

This thesis provides decision makers with a model to analyze the impact of an Aviation Consolidated Allowance List (AVCAL) reduction onboard aircraft carriers (CVs). The Department of Defense in currently down-sizing its forces by 25 percent from FY1991 to FY1995 due to the reduction in funding caused by the significant change in the threat assessment. The implications of the current down-sizing of forces are wide-ranging throughout DoD, including the possibility of reducing a CV's AVCAL from 90 to 60 days. Both analytical and simulation models (RP-FOR and RP-SIM, respectively) have been developed. The model measure the impact of reducing an AVCAL from 90 to 60 days by comparing the benefits of savings gained from a reduction of AVCAL, versus the penalties of reduced operational availability of the aircraft.http://archive.org/details/avcalreductionan00leopLieutenant, United States NavyApproved for public release; distribution is unlimited

The resilience of asset systems to the operational risk of obsolescence: using fuzzy logic to quantify risk profiles

This thesis sets out to explore possible methodologies to enable proactive obsolescence management for end users within the Built Environment. Obsolescence has shown to be a growing operational and financial risk as technology is further embedded into our buildings, seeking enhanced performance and connectivity. Obsolescence directly impacts the supportability of an asset system, manifesting into obsolescence-driven investments, which are typically managed reactively causing lifecycle costing complications. Gaps within academic literature and industry guidance have been identified herein and will be directly addressed by the research questions. The challenge of researching into obsolescence surrounds the commercial value of the required datasets, requiring a novel methodology to address the research problem. Further to this, the multi-stakeholder nature of supply chains, along with the unknown nature of obsolescence, has created a level of ambiguity within the datasets. Fuzzy Logic was adopted, above other options, to create an Obsolescence Impact Tool (OIT) that would enable the user to quantify the risk profile of obsolescence within asset systems. This model, along with an enhanced Obsolescence Assessment Tool (OAT), were both developed and tested within a two-year case study environment. Additional research questions were answered by analysing the reverse engineered original equipment manufacturers (OEM) sales catalogues. Through the combination of both the results from OIT and OAT, along with the analysis of OEM catalogues, a visualisation of the resilience of asset systems in respect to obsolescence is presented. The findings found herein provide evidence for the use of OIT and OAT for industrial application through the insights provided by data-driven models. The two models formulate a methodology that enables decision-making and proactive obsolescence management under uncertainty. The results of the OEM analysis provide explicit evidence that can immediately be used by the reader to enhance their obsolescence management plan (OMP). Evidence of the impact of sales strategies and how an end-user could utilise and reverse engineer the findings, hold potential for all Facilities Management teams. The findings culminate in a wide range of contributions that further the understanding of obsolescence within the Built Environment and importantly bridge some of the existing gaps. The Future Works chapter covers both observations made by the author and alternative methodologies that would provide further insight i.e. Type 2 Fuzzy Sets, Adaptive Learning Techniques, and Markov Chains