PRIORITIZATION IN SERVICE SYSTEMS WITH NONLINEAR DELAY COSTS

Prioritization is a common strategy in service systems to improve the overall system performance. In this dissertation, our main objective is to study how priority should be assigned in different systems when the cost of waiting is not linear as is typically assumed in the literature. We study three problems motivated by prioritization decisions in service systems. In the first problem, we consider a single server queueing system with two different types of customers. Each customer incurs a cost depending on its type and waiting time in the queue, and the waiting cost functions are assumed to be nonlinear in the waiting time. We identify the best static policy under different conditions. In the second problem, we consider a stylized, discrete-time model for an Intensive Care Unit (ICU) in which patients' health conditions change over time according to a Markov chain. Our objective is to allocate the ICU beds to minimize the long-run average mortality rate. In the third problem, we consider a multi-server queueing system with impatient customers. Customers are assumed to be in one of two different stages, which can change over time. A reward is obtained at each service completion depending on the stage of the customer. Our objective is to maximize the total discounted reward and the long-run average reward over infinite horizon.Doctor of Philosoph

Appreciation to referees, 2023

Saif Benjaafar, Editor-in-Chief of Service Science, thanks the referees who have generously provided expert counsel and guidance on a voluntary basis to the journal. Without them, the journal would not be able to function. The following list acknowledges those who acted as referees for papers considered during this past calendar year