On the Optimal Policy for the Single-product Inventory Problem with Set-up Cost and a Restricted Production Capacity

The single-product, stationary inventory problem with set-up cost is one of the classical problems in stochastic operations research. Theories have been developed to cope with finite production capacity in periodic review systems, and it has been proved that optimal policies for these cases are not of the (modified) (s, S)-type in general, but more complex. In this paper we consider a production system such that the production rate is constrained, rather than the amount as is common in periodic review models. Thus, in our case the production rate is positive and finite when the system is on and zero when off, while a cost is incurred to switching on or off. We prove that a long-run optimal stationary policy exists for this single-item continuous review inventory problem with non-zero switching cost and finite production rate, and that this optimal policy has an (s,S)-structure. We also provide an efficient numerical procedure to compute the parameters of the optimal policy.

Probability, Networks and Algorithms PNA Probability, Networks and Algorithms A tandem queue with server slow-down and blocking

CWI is a founding member of ERCIM, the European Research Consortium for Informatics and Mathematics. CWI's research has a theme-oriented structure and is grouped into four clusters. Listed below are the names of the clusters and in parentheses their acronyms

SpaceLiner Cabin Escape System Design and Simulation of Emergency Separation from its Winged Stage

The SpaceLiner is a visionary concept of a hypersonic passenger transportation system with two parallel winged stages based on rocket propulsion. This fully reusable system has been studied by the German Aerospace Center (DLR) for over a decade and has entered its project phase A in 2017. Since it is supposed to transport up to 50 passengers on suborbital trajectories, high standards for safety and reliability have to be applied to this system. Hence, an emergency capsule (SpaceLiner Capsule) accommodating the passengers is foreseen that shall safely eject from the SpaceLiner passenger stage in case of a critical emergency. This paper focuses on the separation process and investigates the baseline capsule ejection procedure such as the cabin and separation motor design. Furthermore, the status and recent developments of the SpaceLiner are presented