Profiles in OR/MS: Cynthia Barnhart
|
Associate Professor,
B.S. Civil Engineering, | M.S. Transportation, MIT PhD Transportation, MIT
Contact Information: |
Questions & Answers
Q. What made you decide to pursue a career in academia? In particular, what attracted you to the operations research/transportation field?
A. As far back as I can recall, I wanted to be a teacher. In grade school and high school, I was encouraged to pursue a degree in mathematics or engineering, because I enjoyed math so much. Primarily motivated by job opportunities, I decided to major in Engineering. The courses that most interested me during my undergraduate studies were transportation and operations research, and the combination of the two.
To me, operations research is fun because it involves creativity – there isn’t necessarily a single, cookie-cutter approach especially when trying to model large, complex systems like those in transportation. This is the core of my research – working on the development of models and algorithms for large-scale problems in transportation.
Currently I am working with passenger and cargo airlines to help design their service networks, to determine the best utilization and assignment of resources (like crews and aircraft) and the best routing for passengers when disruptions occur to the schedule. We employ decomposition techniques, namely column and row generation, to limit the problem size explicitly considered and to allow (near-) optimal solutions to be generated.
Q. As can be seen from your current research projects, you continue to work on a diverse set of problems for the transportation industry. Is there a past research project that you found most memorable?
A. One project that stands out is “Fleet assignment with time windows”. This was a project, funded by a major US airline, that considered simultaneously assigning aircraft types to flights and selecting flight departure times (from within a limited time window). Fleet assignment has a tremendous impact on an airline's profits, as it directly affects flight operating costs and passenger revenues. With costs, aircraft data, and schedule data known, the objective of the basic fleet assignment problem is to find the least cost assignment of aircraft types to flights, such that each flight is covered by exactly one fleet type; flow of aircraft by type is balanced at each airport; and only the available number of aircraft of each type are used.
Models that solve the basic daily fleet assignment problem have found wide acceptance among airlines, but despite their importance, these models leave room for improvement. One of the most noticeable weaknesses of current fleet assignment models is their requirement that flight departure times be fixed. In reality, the schedule used as an input to the fleet assignment model is not cast in stone; many of the scheduled times will be tweaked in the weeks leading up to the day of departure to improve such factors as gate availability and passenger connection times. By adding time windows, which define by how much time any given flight can shift, the set of feasible fleet assignment solutions grows substantially, and the optimal solution is guaranteed to be at least as good as the basic (fixed departure time) model. So then, the fleet assignment with time windows problem is the same as the basic problem, except that time windows, rather than fixed departure times, are given for each flight.
Using data from a major U.S. airline, we show that our model can solve real, large-scale problems, can be used to evaluate the effects of schedule flexibility, and can reduce fleet assignment costs significantly beyond the optimal solution obtained using current state-of-the-art fleet assignment methodologies.
Q. What is the function of the Operations Research Center at MIT? And, what is your role as co-director of this Center?
A. The Operations Research Center (ORC) is the focal point for operations research activities at MIT: it coordinates, supports, and promotes operations research activities and research on the MIT campus. The ORC administers two degree programs in operations research, namely, the Master’s and the PhD degrees.
The Operations Research Center is the oldest continuously operating interdepartmental graduate degree program at MIT. As of June 1999, there are 38 faculty affiliated with the Operations Research Center, with faculty members from all five schools at MIT. Department affiliations include Aeronautics and Astronautics, Civil & Environmental Engineering, Electrical Engineering and Computer Science, Mathematics, Mechanical Engineering, Nuclear Engineering, Ocean Engineering, the Sloan School of Management, and Urban Studies and Planning.
As co-director of the ORC (with Jim Orlin), we are responsible for overseeing the academic programs, including admissions, helping to match research opportunities with students, organizing ORC sponsored activities (such as the seminar series), building and maintaining ORC infrastructure (including computing facilities), etc.
→ To find out more visit: http://web.mit.edu/afs/athena.mit.edu/org/o/orc/www/
Q. How do the Operations Research and Transportation programs at MIT fit in with the Civil and Environmental Engineering Department for which you are a faculty member?
A. Although I am a faculty in the Civil and Environmental Engineering department at MIT, I am affiliated with (that is, I teach courses and supervise students) in two interdepartmental programs – Transportation and Operations Research. What is unique (or at least, unusual) about these programs is that they are both interdepartmental. The faculty members who teach the courses are drawn from across the Institute and the students are able to tailor their programs to meet their specific interests.
Q. What are the most valuable skills that you believe are needed to be successful in the OR/MS industry?
A. For me, someone who works extensively on applications, I believe that it is essential to understand how to “model” problems and to understand the link between model form and tractability. It is also very important to be able to listen well and distinguish the important and unimportant features of a problem and to be able to communicate with people with different educational backgrounds.
Q. What do you find most rewarding about your career in OR/MS?
A. The development, transfer, acceptance and application of our research. The graduation and hiring of our graduates.
Q. What do you predict the future has in store for the field of OR/MS and for OR/MS practitioners?
A. I think that we have a tremendous opportunity to affect more and more decision making, in a number of application areas.