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In this paper, we consider multi-echelon, multi-indenture supply systems for repairable service parts with finite repair capacity. We show that the commonly used assumption of infinite capacity may seriously affect system performance and stock allocation decisions if the repair shop utilisation is relatively high. Both for the case of item-dedicated and shared repair shops, we modify the well-known VARI-METRIC method to allocate service part stocks in the network. The repair shops are modelled by (single or multi-class) multi-server queuing systems. We validate our procedure by comparison to results from discrete event simulation. This comparison shows that the accuracy of the technique presented in this article is on average more than five times as close to simulated values as the classical VARI-METRIC technique. r

Coronavirus 2019 (COVID-19) has disclosed the deficiencies and limitations of the existing manufacturing and supply chain systems used for medical devices and supplies. It enforces the necessity to accelerate the shift towards decentralized digital manufacturing and supply chain networks. This paper proposes a blockchain-based solution for decentralized digital manufacturing of medical devices and their supply. We develop Ethereum smart contracts to govern and track transactions in a decentralized, transparent, traceable, auditable, trustworthy, and secure manner. This allows overcoming certain issues hindering the transition towards decentralized digital manufacturing and supply, including trusted traceability, attestations, certifications, and secured intellectual property (IP) rights. We incorporate the decentralized storage of the InterPlanetary file system (IPFS) into the Ethereum blockchain to store and fetch Internet of things (IoT)based devices records and additional manufacturing and supply details. We present the system architecture and algorithms along with their full implementation and testing details. Furthermore, we present cost and security analyses to show that the proposed solution is cost-efficient and resilient against well-known vulnerabilities and security attacks. We make our smart contracts code publicly available on GitHub.

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