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My research can be roughly categorized as Applied Operations Research (method-wise) and Manufacturing and Service Logistics/Supply Chain Management (application-wise). Under this general heading, I conduct research in all stages of manufacturing and service logistics decision-making process: Network Design - Inventory Management - Manufacturing Planning and Scheduling - Distribution.
From this perspective, the following is the summary of my research interests:
- Methodological Areas of Expertise:
- Integer Programming and Combinatorial/Discrete Optimization
- Game Theory and Multi-agent/Distributed Algorithms
- Applications:
- Supply Chain, Distribution and Transportation Logistics
- Logistics Network Design
- Inventory Management
- Manufacturing Planning and Scheduling
- Transportation Planning
- Industrial Areas:
- After-market Service and Service Parts Logistics
- Semiconductor Manufacturing
- Truckload Trucking
- E-commerce and Auctions
Three applications have had significant effect on my research:
- Service Parts Logistics: This motivates my logistics network design and inventory management research within my NSF CAREER award, NSF REU Supplement, my collaborations with IBM's Service Parts Logistics Group, Baxter Planning Systems, and Dell's Enterprise Services Group.
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Detail: My CAREER research develops solution methods to service logistics problems where repair, recycle, and stocking of parts and material take place to provide after-market service to geographically dispersed customers. Two sectors that this research touches on are manufacturing and military.
In manufacturing, high technology equipment, electronics and automotive companies, such as Caterpillar, IBM, and Ford, perceive the service area as a promising growth opportunity as profit margins from sales continue to shrink. My research makes contributions to the $21 billion after-market service industry, by achieving cost savings through better decision making in warehousing and distribution of service parts.
In military logistics, the US military services need an adequate amount of service parts to sustain their operations and overall readiness. The developed methods position the right amounts of materials in strategically chosen locations so that the overall service readiness is maximized with minimum costs.
In my service logistics research, I closely work with IBM Global Services, and Baxter Planning Systems, a service parts software developer in Austin. I am also in touch with Dell to obtain industry support for my service logistics research.
From this line of research, I already have 3 refereed conference proceedings papers, 5 conference presentations, 3 poster presentations, and 1 submitted journal paper (Management Science), another soon-to-be-submitted (Naval Research Logistics).]
- Manufacturing Planning and Scheduling: This motivated my M.S. and Ph.D. research, and now motivates my NSF/SRC Project on Disruption Management in Semiconductor Manufacturing, and my project on Semiconductor Manufacturing Scheduling with AMD.
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Detail: I am part of a NSF grant that supports my semiconductor manufacturing research. In fact, this grant is also partially supported by two industry consortiums, Semiconductor Research Consortium (SRC) and SEMATECH (Semiconductor Manufacturing Technology). I collaborate with Joe Qin (from Chemical Engineering) and John Hasenbein (from ORIE) to develop methods for plant-wide process control and disruption management in semiconductor wafer fabrication. This grant provides support for three engineering Ph.D. students for three years, and I co-advise two of them.
My research here aims to suppress the adverse effects of disruptions on the overall plant performance by developing models and methods to adequately respond to the disruptions. I collaborate with engineers and managers from semiconductor manufacturers, such as AMD, IBM, and Intel.
I am also expanding my manufacturing planning and scheduling research by interacting closely with AMD. I recently secured the initial funding of a potentially long-term project that will redesign AMD's planning and scheduling system for their new generation, fully automated plants. My contribution at AMD is poised to affect the whole sector as modernization in planning and scheduling is perceived as an essential step for further growth in this sector.
Finally, I am part of a multi-university team (working with professors from Arizona State and Arkansas), who develop models and methods to solve large scale manufacturing and logistics problems, which are characterized by their two-stage nature: Group orders and Process grouped orders. One arm of this project is again related to semiconductor manufacturing where I address issues faced by new generation plants that have to group multiple orders coming from multiple customers into containers and have to route these containers through the machines. Without direct funding, this project has already produced numerous refereed conference papers, a journal paper submission (
IIE Transactions, first revision), and potentially three more journal papers (two with a MS ORIE student). The other arm of this research effort is related to military logistics problems where planners have to pack and load multiple entities (e.g., material, equipment, personnel) into transport vehicles (ships, aircraft, etc.) and then route these vehicles through multiple destinations to achieve a mission objective in a cost-effective manner. We found that there are many problems in military logistics, especially in Air Force operations, which would be modeled within this context. We have a proposal in review with the US Air Force Office of Scientific Research.]
- Transportation Planning and Truckload Trucking: This motivated my past Mack-Blackwell Transportation Center projects and my collaborations with JB Hunt and ABF.
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Detail: I am involved in transportation research, mainly truckload trucking problems. I collaborated with companies such as J.B. Hunt Transport Services, Inc., of Lowell, AR (one of the nation's largest truckload carriers), and ABF Freight Systems, Inc., of Fort Smith, AR (one of North America's largest less-than-truckload carriers), and worked on federally funded projects through Mack-Blackwell Transportation Center (MBTC). In fact, I graduated my first Ph.D. student on transportation research and undertook 6 different MBTC projects in less than four years. I have one published paper and one accepted paper in this area.]
I conduct both descriptive and prescriptive research. I use two fields to attack the outlined problems:
- Mathematical Modeling and Optimization: Using OR, I investigate the following issues:
- Stochastic analysis, uncertainty, robustness, variability
- Large-scale problems, optimization-based decomposition techniques and heuristics
- Integration of disparate functional areas and decision islands
- System dynamics, timing of decisions, effects of planning/rolling horizon procedures
- Game Theoretic/Auction Theoretic Analysis: With this, I focus on the following issues:
- Coordination and collaboration: How do you achieve a globally optimal solution within a distributed decision structure? (multi-agent, multi-company coordination)
- When does equilibrium (stability of agents' decisions) coincide with system optimum?
- Use of historical and a priori information in repeated coordination games and auctions
- Effects of incentives, information asymmetry, dispersed information/decentralized authority
- Agent coalitions, agent designs, effects of these on communication and convergence
- Consideration of electronic marketplaces and auctions in the context of coordination/collaboration and overall system efficiency
My long term objective is to develop a unifying theoretical framework that encompasses both fields, and to connect the system-level optimization with the distributed decision structure.

NSF CAREER Award, 2002-2007, NSF.
Summer Research Award, 2004, the University of Texas at Austin.
Graduate Scholarship, 1995-1999, Department of ISE, Lehigh University.
Graduate Scholarship, 1992-1994, Bilkent University, Ankara, Turkey.
Undergraduate Scholarship, 1987-1992, Bilkent University, Ankara, Turkey.