On May 08, Dr. Xiaolan Xie who worked in Ecole Nationale Supérieure des Mines de Saint Etienne France gave a seminar entitled "Dynamic surgery scheduling of multiple operating rooms” at room 512 in Founder Group, Peking University. Prof.Jie Song hosted this event.

In this talk, Dr. Xiaolan xie focused on daily surgery scheduling in a multi-OR setting where OR stands for Operating Rooms with random surgery durations.Dr.Xie first addressed the dynamic assignment of a given set of surgeries with planned surgeon arrival times also called appointment times. Surgeries are assigned dynamically to ORs at surgery completion events. The goal was to minimize the total expected cost incurred by surgeon waiting, OR idling, and OR overtime. He first formulated the problem as a multi-stage stochastic programming model. An efficient algorithm was then proposed by combining a two-stage stochastic programming approximation and some look-ahead strategies. A perfect information-based lower bound of the optimal expected cost was given to evaluate the optimality gap of the dynamic assignment strategy. Numerical results showed that the dynamic scheduling and optimization with the proposed approach significantly improved the performance of static scheduling and First Come First Serve (FCFS) strategy.
Dr. Xiaolan Xie then addressed the optimization of surgeon appointment times for a sequence of surgeries. Surgeries was assigned to ORs dynamically on a FCFS basis. It materially differed from past literature in the sense that dynamic assignments are proactively anticipated in the determination of appointment times. A discrete-event framework was proposed to model the execution of the surgery schedule and to evaluate the sample path gradient of a total cost incurred by surgeon waiting, OR idling and OR overtime. The sample path cost function was shown to be unimodal, Lipchitz continuous and differentiable w.p.1 and the expected cost function continuously differentiable. A stochastic approximation algorithm based on unbiased gradient estimators was proposed and extensive numerical experiments suggest that it converged to a global optimum. A series of numerical experiments were performed to show the significant benefits of Multi-OR and properties of the optimal solution with respect to various system parameters such as cost structure and numbers of surgeries and ORs.
