Title

:

Modeling Stochastic Demand and Supply Systems

Speaker

:

Prof. Zhe George Zhang

Date

:

December 28th, 2007 (Friday)

Time

:

4:30 p.m. - 5:30 p.m.

Venue

:

Room 513

William M.W. Mong Engineering Building

(Engineering Building Complex Phase 2)

CUHK

Part I: Service Systems:
Motivated by Flexible Staffing of the US-Canada Border Crossings

Abstract: In the first part of this research, we study waiting line problems at the border-crossings between the U.S. and Canada. To evaluate a practical staffing policy, we develop an analytical model to compute the important performance measures. The policy is called \"congestion based staffing\" or CBS, because the number of open inspection booths is adjusted according to the queue length during each planning period. Our analysis is based on the matrix-geometric solution, the regeneration cycle, and the fluid approximations. With a certain cost structure, we provide a numerical search approach to determine the best CBS policy for border-crossing stations. Under certain conditions, we can obtain the close-form solution for the optimal policy parameters and prove the convexity of the average cost function.

Part II: Manufacturing Systems:
Apply the CBS model to Production/Inventory Systems

Abstract: In the second part of this research, we show that CBS model can be applied to study a fixed number of production facilities producing a specific type of items with random demand and production time. The inventory policy is a base-stock (s, S) type with continuous review. Some production facilities can be switched to producing other secondary products if the inventory level is high and switched back when the inventory level is slow. Under a cost structure which includes a set-up cost, a linear holding cost, and a possible linear backorder cost, an average cost function is developed. Using reasonable approximation methods, we obtain the closed form formulas for computing the optimal inventory and production policy. Excellent approximation with high accuracy has been illustrated by extensive numerical analysis. These easy-to-use formulas provide practitioners with a useful tool in determining the best inventory and production control policy under the random demand and production time environment.

Zhe George Zhang is a Professor of Operations Research in the Department of Decision Sciences (College of Business and Economics) at Western Washington University, Bellingham, Washington and a Professor of Management Science (SFU Business School) at Simon Fraser University in Vancouver, British Columbia. He holds a B.S. degree from Nankai University, an MBA from the Schulich School of Business at York University, and a Ph.D. from the University of Waterloo.

Professor Zhang\'s research interests include queueing theory and applications, stochastic dynamic programming, probability models in reliability, and supply chain management issues in manufacturing and service organizations. His publications have appeared in a variety of journals in applied probability and operations research. Co-authored with N. Tian, his research monograph entitled Vacation Queueing Models - Theory and Applications has been published in August, 2006 by Springer Science (Kluwer Academic Publisher). This is the first book that discusses both single and multiple server queueing systems with vacations. It provides a comprehansive treatment of the extention of the queueing theory. The book contains the updated research results and some practical applications of this class of models.

Host

:

Prof. Sean X. Zhou

Tel

:

(852) 2609 8336

Email

:

zhoux@se.cuhk.edu.hk

Enquiries

:

Prof. Nan Chen or Prof. Sean X. Zhou

:

Department of Systems Engineering and Engineering Management

CUHK

Website

:

http://www.se.cuhk.edu.hk/~seg5810

Email

:

seg5810@se.cuhk.edu.hk