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[2017/4/28]M/PH/c Queue under CBS Policy with Applications in Operations of Steel Industry



M/PH/c Queue under CBS Policy with

  Applications in Operations of Steel



报告人Zhe George Zhang

Beedie School of Business

Simon Fraser University


Department of Decision Sciences

Western Washington University


主持人: 宋洁





Abstract: We analyze a queueing system with changeable number of servers to avoid either idle or over-congested situation. Specifically, if the queue length is over a threshold, the maximum number of servers are serving customers; and if the number of idle servers reach a threshold, these idle servers are turn off. We call this policy the Congestion Based Staffing (CBS) with two thresholds. Optimizing these thresholds under a certain cost structure is the focus of this paper. The hey factor of modeling a manufacturing or service system with random service requests by a queueing model is to realistically model the random service time. Although using the exponential distribution for service time of a call center is quite successful, it is not appropriate for manufacturing or service systems. We propose to use a PH distribution for modeling the service times in a manufacturing system as it is more flexible and can fit any shape of distribution in theory. Therefore, we build a M/PH/C model with CBS policy and develop the solution procedure to compute the queue length stationary distribution. Based on the stationary distribution, we investigate a real-world system based on Shanghai Baogang Steel Company. Under a reasonable cost structure, we found the optimal CBS policy to minimize the operating cost.

Joint work with Yanhe Jia and Lixin Tang



Zhe George Zhang is a professor of Management Science in the Department of Decision Sciences at Western Washington University and a professor of Operations Management in Beedie School of Business at Simon Fraser University. He is also visiting professor of Sauder School of Business at the University of British Columbia. Dr. Zhang received his BS in Computer Science and MA in Economics from Nankai University, China; his MBA from the Schulich School of Business at York University; and his PhD in Operations research from the University of Waterloo. Professor Zhang has published over 80 papers in prestigious journals such as Management Science, Operations Research, Manufacturing & Service Operations Management, Production and Operations Management, IIE Transactions, IEEE Transactions, Queueing Systems, Journal of Applied Probability.

Professor Zhang's research interests include queueing theory and applications and stochastic models for manufacturing and service systems. The main theme of his research is to bridge the gap between theory and application, obtaining unobservable and sometimes counter-intuitive but significant/practical management insights via modelling and quantitative analysis. Currently, he is particularly interested in the quantitative and economic analysis of the congestion problems in urban/mass transportation networks, health/medical care systems, and public service systems with both customer service quality and security concerns.

Co-authored with N. Tian, his research monograph entitled Vacation Queueing Models-Theory and Applications has been published in 2006 by Springer Science. This is the first book that discusses both single and multiple server queueing systems with vacations. Professor Zhang is an associate editor of INFOR and is on the editorial board of several international journals