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CAM Colloquium: Ohad Perry (Northwestern University) - Service Systems in which the Service Times Depend on the Delay in Queue

Friday, September 22, 2017 at 3:30pm

Frank H. T. Rhodes Hall, 655

In most queueing models it is assumed that the primitive processes (arrival, service, abandonment, etc.) are independent. However, data shows that the service time of a customer may depend on that customer’s patience, or on her delay in queue. In this talk I will discuss the impacts that such a dependency has on key performance measures (waiting times, queue length, proportion of abandonment and throughput), and on optimal capacity decisions. In particular, I will first consider a system with a single pool of many statistically-homogeneous agents serving one class of statistically-identical customers whose service requirements and patience times are dependent random variables. Since the assumed dependence renders exact analysis intractable, we develop a deterministic (fluid) approximation which is characterized via the entire joint distribution of the service and patience times. To evaluate the impacts of the dependence, we employ bivariate dependence orders, and provide structural results which facilitate revenue optimization when a staffing cost is incurred. Time permitting; I will also discuss an alternative model, in which the service times depend on the delay in queue, and how the two different models can be related and approximated via a unified fluid model. (Joint work with Allen Wu and Achal Bassamboo, Northwestern University)

Ohad Perry is an assistant professor in the Industrial Engineering and Management Sciences (IEMS) Department at Northwestern University, which he joined in August 2011. His undergraduate degree is in Mathematics and Statistics from Haifa University, and his M.S. and PhD degrees are from the Industrial Engineering and Operations Research (IEOR) Department at Columbia University. After completing his PhD in 2010, he spent a year and a half as a post-doctoral fellow in Centrum Wiskunde & Informatica (CWI) in Amsterdam, the Netherlands, working with Bert Zwart. His research interests center around queueing theory and applied probability. More specifically, his work focuses on developing analytical techniques, involving stochastic analysis, stability theory and dynamical-systems’ control, to design and optimize service systems, such as call centers, hospitals and inventory systems.

Event Type



College of Engineering, Mathematics, Center for Applied Mathematics


engineering, math, center for applied math, cam, College of Engineering, mathematics, center for applied mathematics


Speaker Affiliation

Industrial Engineering and Management Sciences Department, Northwestern University

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