Sergey Zeltyn

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A call center is a service network in which agents provide telephone-based services. Customers that seek these services are delayed in tele-queues. This paper summarizes an analysis of a unique record of call center operations. The data comprise a complete operational history of a small banking call center, call by call, over a full year. Taking the(More)
Motivated by call center practice, we study asymptotically optimal staffing of many-server queues with abandonment. A call center is modelled as an M/M/n+G queue, which is characterized by Poisson arrivals, exponential service times, n servers and Generally distributed patience times of customers. Our asymptotic analysis is performed as the arrival rate,(More)
Our note is dedicated to the Palm/Erlang-A Queue. This is the simplest practiceworthy queueing model, that accounts for customers’ impatience while waiting. The model is gaining importance in support of the staffing of call centers, which is a central step in their Service-Engineering. We discuss computations of performance measures, both theoretical and(More)
Simulation-Based Models of Emergency Departments: Operational, Tactical and Strategic Staffing: Online Supplement S. Zeltyn, B. Carmeli, O. Greenshpan, Y. Mesika, S. Wasserkrug, P. Vortman IBM Haifa Research Lab, Israel AND Y. Marmor, A. Mandelbaum, A. Shtub, T. Lauterman Technion – Israel Institute of Technology, Haifa, Israel AND D. Schwartz, K.(More)
4 Operational measures of performance 9 4.1 Practical measures: Waiting Time . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.2 Practical measures: accounting for Abandonment . . . . . . . . . . . . . . . . . . 10 4.3 Calculations: the 4CallCenters software . . . . . . . . . . . . . . . . . . . . . . . 12 4.4 Delay probability P{W>0} . . . . . . . .(More)
Efficiency is critical to the profitability of software maintenance and support organizations. Managing such organizations effectively requires suitable measures of efficiency that are sensitive enough to detect significant changes, and accurate and timely in detecting them. Mean time to close problem reports is the most commonly used efficiency measure,(More)
Credible queueing models of human services acknowledge human characteristics. A prevalent one is the ability of humans to abandon their wait, for example while waiting to be answered by a telephone agent, waiting for a physician’s checkup at an emergency department, or waiting for the completion of an Internet transaction. Abandonments can be very costly,(More)