Journal Publications

    Queueing Theoretic

    • Ibrahim, R. and W. Whitt. Real-Time Delay Estimation Based on Delay History. Manufacturing and Service Operations Management, 11(3), 2009, pp 397-415. [PDF]. Supplementary material: [PDF].
    • Ibrahim, R. and W. Whitt. Real-Time Delay Estimation in Overloaded Multiserver Queues with Abandonment. Management Science, 55(10), 2009, pp.1729-1724. [PDF]. Supplementary material: [PDF].
    • Ibrahim, R. and W. Whitt. Real-Time Delay Estimation Based on Delay History in Many-Server Service Systems with Time-Varying Arrivals. Production and Operations Management, 20(5), 2011, pp. 654-667. [PDF]. Supplementary material: [PDF].
    • Ibrahim, R. and W. Whitt. Wait-Time Predictors for Customer Service Systems with Time-Varying Demand and Capacity. Operations Research, 59(5), 2011, pp. 1106-1118. [PDF].
    • Ibrahim, R., Armony, M., and A. Bassamboo. Does the Past Predict the Future? The Case of Delay Announcements in Service Systems. [PDF]. Management Science, 63(6), 2017, pp. 1762-1780. Supplementary material: [PDF].
    • Ibrahim, R. Managing Queueing Systems Where Capacity Is Random and Customers Are Impatient. Production and Operations Management, to appear. [PDF].
      (Finalist in INFORMS JFIG paper competition, 2015.)

    Data Analytic

    • Ibrahim, R. and P. L'Ecuyer. Forecasting Call Center Arrivals: Fixed-Effects, Mixed-Effects, and Bivariate Models. Manufacturing and Service Operations Management, 15(1), 2013, pp. 72-85. [PDF].
    • Ibrahim, R., L'Ecuyer, P., Shen, H., and M. Thiongane. Inter-Dependent, Heterogeneous, and Time-Varying Service-Time Distributions in Call Centers. [PDF]. The European Journal of Operational Research, 250, 2016, pp. 480-492. Supplementary material: [PDF].
    • Ibrahim, R., Kucukyazici, B., Verter, V., Gendreau, M. and M. Bolstein. Designing Individualized Treatment: An Application to Anticoagulation Therapy. [PDF]. Production and Operations Management, 25 (5), 2016, pp. 902-918. Technical appendix: [PDF]. Supplementary material: [PDF].

Invited Papers and Book Chapters

  • Ibrahim, R., Ye, H., L'Ecuyer, P. and H. Shen. Modeling and Forecasting Call Center Arrivals: A Literature Survey and a Case Study. The International Journal of Forecasting, 32(3), 2016, pp. 865-874. [PDF].
  • Ibrahim, R. Sharing Delay Information in Service Systems: A Literature Survey. Queueing Systems, 89(1-2), 2018, pp. 49-79. [PDF].
  • Ibrahim, R. On Queues with a Random Capacity: Some Theory, and an Application. To appear in Sharing Economy: Making Supply Meet Demand, M. Hu, editor.[PDF].

Refereed Proceedings

  • Ibrahim, R. and W. Whitt. Real-Time Delay Estimation in Call Centers. Proceedings of the 2008 Winter Simulation Conference, 2008, pp. 2876-2883. [PDF].
  • Ibrahim, R. and W. Whitt. Delay Predictors for Customer Service Systems with Time-Varying Parameters. Proceedings of the 2010 Winter Simulation Conference, 2010, pp. 2375-2386. [PDF].
  • Ibrahim, R., L'Ecuyer, P., N. Regnard, and H. Shen. On the Modeling and Forecasting of Call Center Arrivals. Proceedings of the 2012 Winter Simulation Conference, 2012, pp. 23-35. [PDF].

Completed Working Papers

  • Dong, J. and R. Ibrahim. Flexible Workers or Full-Time Employees? On Staffing Service Systems with a Blended Workforce. [PDF].
  • Bassamboo, A. and R. Ibrahim. A General Framework to Compare Announcement Accuracy: Static vs LES-based Announcement. [PDF]. Supplementary material: [PDF].
  • Ibrahim, R. and S. Kim. Predicting Surgery Duration: Physician Input, Statistical Models, and Combined Models. [PDF].

Doctoral Thesis

  • Real-time delay prediction in customer service systems [PDF].