Based on the joint research of Dr. Ahmed Saif and Nazanin Madani (MASc graduate), two new papers were accepted for publication in Computers & Operations Research and the International Journal of Service Systems: Operations & Logistics. Both papers address the problem of robustly designing service systems (i.e., facility location-allocation with congestion) under the condition of uncertainty about the arrival rates of customers. In the first paper, the system is represented as a network of M/M/1 queues and exact mixed-integer second-order cone programming formulations are provided for the nominal, robust and distributionally-robust problems. The second paper represents the system as a network of G/G/1 queues and provides a tight piecewise-linear approximation of the nonlinear waiting time terms such that the nominal and robust problems (with both budget and ball uncertainty sets) could be reformulated as mixed-integer quadratic programs. Furthermore, a decomposition scheme based on Lagrangian relaxation is developed to solve large instances of the problems.
A. Saif and *N. Madani (2022), "Robust Design of Service Systems with Immobile Servers under Demand Uncertainty," Computers & Operations Research (Accepted).
A. Saif and *N. Madani (2022), "Robust Design of Service Systems with Immobile Servers, General Arrival and Service Patterns, and Demand Uncertainty," International Journal of Systems Science: Operations & Logistics, Available online at https://doi.org/10.1080/23302674.2022.2092660.