From the Combat Zone to the Classroom: Decision Science in Practice and Theory
by John E. Bell, University of Tennessee, Knoxville
In 1997, I was a U.S. Air Force captain stationed at a rapid transportation squadron in Texas. Our mission was simple: store and maintain a stockpile of explosives and then be ready to ship them by air anywhere in the world on a moment's notice. Our unit constantly practiced for the next combat mission by chaining bombs to aircraft pallets and transporting them to the runway for upload. This training was often put to the test during the 1990s. During one particular event in 1997, our unit shipped thousands of pounds of bombs overseas to the Middle East to meet combat-aircraft-supply needs. For several days, we worked around the clock in 12-hour shifts to load and deliver our inventory to waiting aircraft. I clearly remember observing a C-5 cargo aircraft loaded with 2,000-pound bombs. But I also remember thinking just how inefficient and costly this shipment would be because the bulky explosive cargo's destination was almost halfway around the world. Surely there had to be a better way to strategically position and transport such critical combat inventories.
By that time in my career, I was very familiar with the complex logistics of operating in the Middle East. I had several overseas deployments, including two tours in Operation Desert Storm (Saudi Arabia) and had lived for two years in Incirlik, Turkey. My job was to manage the storage, maintenance, and transportation of a large inventory of munitions in Europe and the Middle East. To my frustration, the notion of dynamic and responsive location and allocation models was a foreign concept and further resisted by bureaucratic policy constraints and a system that lacked agility. Therefore, my desire to help build a more efficient system of transportation for the Air Force would set me on an academic path that I did not fully understand at the time.
Military Graduate School and Research
During the first seven years of my career, I accumulated additional business school credits at five universities around the country but was never in one place long enough to finish a graduate degree. This changed in 1997, when the Air Force assigned me to the Air Force Institute of Technology (AFIT) to earn a master's degree in Logistics Management. With a mix of both civilian and military faculty, AFIT provided the right venue to improve my operational skills and satisfy my academic interests. My coursework afforded a natural outlet to explore the operational problems that plagued me earlier in my career, in particular the complex problem of strategically re-positioning inventory. Linear Programming, a common tool for me now, was a revelation the first time I used it in solving real AF problems. I began to understand the mathematical complexity of the routing and location problems at the core of my interests. My research at AFIT focused on smaller problems related to aircraft maintenance and repair-part supply for older aircraft. Parts' obsolescence and diminishing manufacturing sources were a central part of my thesis research. With help from Air Force experts in Georgia, I built a model for my thesis to identify and eliminate future obsolete components in aircraft radar systems by providing replacement solutions for the parts that provided the maximum availability for the least amount of money. This solution method was transferred to other aircraft systems and helped to prevent aircraft downtime and to help analyze when a system should be replaced due to increasing repair cost. When I graduated in 1998, I had improved my problem-solving skills but had only begun to explore the larger network problems. I still believed there had to be a better way.
My next assignment was the Air Force Logistics Management Agency (AFLMA). This organization's mission was to analyze logistics for the Pentagon and other major Air Force Commands. Still a captain, I had access to comprehensive sets of data on global logistics networks and inventory. In addition, I managed and conducted research projects and presented the findings to Air Force general officers. One of my research projects was to track down the underlying causes for decreasing availability rates in the Air Force's F-16 aircraft. This led to a comprehensive study of several hundred aircrafts' maintenance records. Using the mixed-integer capabilities of Excel Solver and a Visual Basic Macro, we were able to create a decision-support tool to sort and identify the leading components needing repair in the aircraft system. In early 2000, we presented a formal report and the model to the Pentagon. At AFLMA, I also studied munitions- and explosive-maintenance operations around the Air Force. For months I interviewed senior officers and collected data on best practices before I helped write the Air Forces' senior officer guide for explosive operations. Finally, I worked with RAND colleagues on a complex allocation and location research. We worked on developing a large-scale mixed-integer-programming model, which not only identified the location of potential storage warehouses but also developed a multimodal transportation network to deliver combat-support material to various potential hot spots. The results included identification of new sites in Central Europe and Asia, as well as proving the notion that, under certain conditions, sea transportation can be faster than air transportation. This type of research left me more eager to develop a new tool to improve the Air Force's munitions-inventory network.
Although AFLMA introduced me to long-term research and the challenge of managing one-to-two-year-long projects, I felt that I needed additional training to truly delve deeply into solving the complex logistics, inventory, and transportation problems the Air Force faces every day. In addition, many times the military research sponsors decided what the studies' results should be before any research began. This created frustration because I wanted to ask questions and explore the answers in an unbiased manner. I believed getting another graduate degree might allow me this freedom. Therefore, upon the advice of several colleagues who had their doctoral degrees, I started to consider a Ph.D. This interest became a reality in April 2000, when the Air Force unexpectedly offered me an opportunity to go back to school for my doctorate.
Military Academic Career
Several senior military officers warned me against pursuing my Ph.D. At the time, the Air Force had very few munitions officers. If I stayed in the operational Air Force, I would probably have more command and promotion opportunities. Despite these risks, I couldn't turn down the opportunity to improve my problem-solving skills and pursue a more research-oriented career. In addition, with the degree, I could return to AFIT and influence young officers, and I knew my future students could improve the military systems' efficiency even more. The possibilities outweighed the risks, so in 2000 I decided to pursue my doctoral degree.
The largest problem I initially encountered was finding a school to attend. This is an additional constraint for military personnel, since there is a three-year Ph.D. program mandate that few schools can support. Fortunately, Auburn University is one of the exceptions, and under Professor Pat McMullen, I was able to finish my dissertation within the allotted time. While at Auburn, conversation revealed that Dr. McMullen's expertise included metaheuristic tools that could be applied to the problems and data that I brought from the Air Force. The metaheuristic methods I studied included simulated annealing, Tabu search, genetic algorithms, and ant-colony optimization. These were an excellent fit for large and complex Air Force logistics problems that interested me. In my dissertation I coded a simulated annealing program that simultaneously selected Air Force munitions storage locations around the globe and determined stocking levels needed to respond to a variety of potential future conflicts. This problem proved quite difficult, since the problem was multi-objective in nature, and the best solutions had to both minimize total costs and maximize customer service, as measured by a coverage distance. The final product consisted of an efficient frontier of solutions to meet these two objectives, and it also identified a robust sub-set of locations that would be in the solution set regardless of the mix of future demand scenarios.
Auburn prepared me well for an academic career. I was very excited about being a professor. However, while the Auburn degree gave me expectations about academic life, AFIT is not a "civilian" university. Within a year of arriving at AFIT, I was deployed to Qatar in support of Operation Iraqi Freedom as a newly promoted major. In Qatar, I managed the supply and aircraft maintenance support for airbases located from Afghanistan to East Africa. This experience helped expand my research focus from its original Air Force orientation to the theory behind network problems. This included several experimental efforts to improve algorithms and apply them to the vehicle routing problem. The first paper from this research included the creation of a multiple colony ant colony optimization approach for the classic vehicle routing problem. This paper was published in late 2004 in Advanced Engineering Informatics and, despite not having anything to do with the Air Force, has been my most cited publication. Additionally, I actually completed the second such study during my off-duty hours while deployed in Qatar. The paper entitled "Ant Colony Optimization (ACO) for Logistics-Oriented Vehicle Routing Problems" included a look at using ACO for problems with different spatial patterns common in delivery logistics. This paper was submitted to the Vancouver WDSI conference. It was accepted, and I was able to safely arrive back in the U.S. and present the research at WDSI '05. Writing and submitting this paper from overseas taught me that good research cannot wait. Sometimes that means going to extremes to finish a research project, even if it is at midnight in a combat zone.
Transitioning to Civilian Academia
One of the mysteries of the U.S. military is why some officers are sent to earn doctoral degrees and then these officers are not left in academic positions. I, along with many fellow military academics, have experienced this. After three years as a faculty member at AFIT, following my deployment in Qatar, I was reassigned to an operational unit at Warner Robins Air Logistics Center in Georgia. This made continuing my academic career a challenge since I could not retire from the military for another four years. Fortunately, I secured an adjunct position with Georgia College & State University, teaching one or two nights each week in their MBA programs. During the day, I managed aircraft electronics equipment sales to more than 30 foreign countries. With a full-time job, teaching commitments, and a family, I had little time for doing research. But my interest in research and an academic career kept me working. Commitments to co-authors motivated me to work on several manuscripts generated by Air Force research. One of these research papers was particularly important to Air Force security. It focused on the selection of locations around the country to position fighter aircraft in case they were needed to respond to another 9-11-type incident. It included the use of an optimization model, and solutions were generated using the professional version of the Frontline Solver. Although the city names had to be masked in the final report to keep it from being classified, the study was published in Omega and impacted decisions being made by the Base Realignment and Closure (BRAC) Commission, who was considering closure of some of the locations needed in our optimal solution. Publication of these and other works kept my academic career going; by the time I had served 20 years in the military, I had publications on my vita and eight years of teaching experience.
In 2009, I began to apply for assistant professor positions outside the military. I quickly realized that, although this would be my first "real" academic job, I was not a traditional assistant professor in the job market. Although to many, it looked like I had been lost in the Air Force since 2003, I convincingly argued that, with publications and teaching experience, I had maintained an academic career. Added to this was my presence at conferences. I had managed to attend either the Decision Science Institute conference, Western Decision Science Institute conference, or the Council of Supply Chain Management Professionals (CSCMP) conference each year. These conferences also helped maintain my networks, keeping me up with current research and meeting colleagues with whom I would one day work. In particular, the Western region of DSI helped me with research and welcomed me as part of the organization. That relationship and a similar one with CSCMP really helped me believe an academic career was still possible despite four years away from academia.
Overall, my application and interview process at civilian universities was very rewarding. I had been worried about being away from a university setting for several years, but my Air Force experience strengthened my application and differentiated me. In December 2009, I accepted a position with the Department of Marketing and Supply Chain Management at the University of Tennessee. My new university was interested in my ability to teach at multiple academic levels. In addition, I had at least two separate research streams already in progress with publications and current global operational experience. But what most helped me transition from the military to academia was the ability to work on a team and put the team first. In the Air Force, we always considered "service-before-self." The team-oriented culture at Tennessee made this approach a natural fit. Today I find myself working in a new team with new academic friends who are committed to a much different, but equally exciting mission.
Looking Forward to the Future
Although I have left my original military context behind, I am still impacted by my past experiences. Occasionally, I still do Air Force research and have worked recently with colleagues at AFIT to complete two inventory-consolidation studies. Additionally, my research interests in vehicle-routing problems (VRP) continue, and I am working with colleagues from other universities on two studies related to improving algorithms for the split VRP and the classic VRP with violations of the triangle inequality. However, my interest in solving problems has also led me to a whole new group of research problems. In particular, my focus has transitioned to supply-chain risks and how they impact physical supply-chain network designs. I have recently completed two papers, one for the Journal of Business Logistics and one for Supply Chain Management Review on the impact of natural resource scarcity in supply-chain networks. I believe this will be an interesting area for my future modeling research, and it should have several applications using metaheuristics models and simulations.
I grew up in a military world where lead-time variability was measured in weeks or even months, not days; where a stock-out cost might mean the loss of someone's life and where adversaries were constantly trying to disrupt our supply chains. In that world, the strategic placement of inventory buffers today might mean the ability to operate tomorrow. Some might say the military is a "just-in-case" world; investments are made in excess capacity, contingency plans, and a massive reliance on environmental scanning and intelligence gathering. However, much of what I encountered in the military applies to risk management and operations management in the business world today. We are in an increasingly complex world. Managing networks, selecting operating locations, and determining routing strategies are just as important to my "civilian" students and the networks they manage.
Retiring from the military and joining the academic community has been a rewarding transition for me. I am proud to be a Tennessee Volunteer and a member of the DSI academic community. Many others are in the military "Ph.D. pipeline" both ahead of me and behind me at institutions such as Ohio State University, Auburn University, North Texas, Michigan State, and Georgia Southern. Who knows, you might find that your next assistant professor or next co-author had a similar experience transitioning from the combat zone to the classroom.