Sustainability and Operations Research: A Trek Down Memory Lane from Transportation to Supply Chains

Given the interest my blogpost on Professor Joe Sarkis' talk on greening supply chains generated I thought that I would write this piece on sustainability and operations research from the perspective of how we got interested in the subject and where it has taken us.

Professor Sarkis also mentioned in his presentation that he, like I and my research group, have been working on sustainability for a while - actually two decades and since we are hearing that "sustainability" is some fields, including operations management, is being perceived as being relatively new, I thought it deserved some commentary.

I have always been one who loves nature and I get some of my best ideas on hikes. Clean air, clean water, fresh food, and a healthy, peaceful environment we all deserve and they are essential to our well-being  and that of future generations.

As a research topic, I became interested in sustainability while working with two doctoral students at the Isenberg School of Management: Kanwalroop "Kathy" Dhanda and Padma Ramanujam in the 1990s.

Together we wrote the Environmental Networks book, which was published in 1999, and the year after, my Sustainable Transportation Networks book was published.

Vice President Al Gore wrote me a nice letter on the publication of my Sustainable Transportation Networks book, which now hangs in my office at the Isenberg School.

Prior to the publication of these books, I had co-authored several papers, which also provided the seeds for our sustainability work. These included a 1996 paper in Operations Research, written with Sten Thore and one of my first PhD students, Jie Pan, who tragically died of an autoimmune disease shortly after having receiving tenure. With Padma, that same year, we had also published a paper in Transportation Science.

Padma's dissertation,  Transportation Network Policy Modeling for Congestion and Pollution Control: A Variational Inequality Approach, was awarded a Transportation Science & Logistics dissertation prize from INFORMS in 1999, a great honor.

Some other early papers on various sustainability of ours included: "A Multimodal Traffic Network Equilibrium Model with Emission Pollution Permits: Compliance versus Noncompliance," published in Transportation Research D in 1998 and "Marketable Pollution Permits in Oligopolistic Markets with Transaction Costs," which appeared in Operations Research in 2000. I also wrote several papers on emission paradoxes, one with another doctoral student of mine, now Professor June Dong.

Hence, we were proposing tradeable pollution permits even for transportation networks in the 1990s. Padma is now working at SAS, a fabulous analytics firm, and is based in Cary, North Carolina, whereas Kathy has had several tenured professorships at different universities and continues to work on sustainability issues.

Interestingly, the Virtual Center for Supernetworks, which I founded in 2001 and continue to serve as Director of, was initiated because of three NSF grants that I had received at that time plus two AT&T Industrial Ecology Fellowship grants, which envisioned such a center. Hence, the sustainability theme has been central to our research.

In 2005, with a doctoral student from Japan, Fuminori Toyasaki, who is now a professor at York University in Toronto, I published a paper that is highly cited: "Reverse Supply Chain Management and Electronic Waste Recycling: A Multitiered Network Equilibrium Framework for E-cycling." This paper was recognized by Transportation Research E as a most cited paper.

In 2002, I had co-authored the paper, "A Supply Chain Network Equilibrium Model," with June Dong and Ding Zhang and this paper, which introduced multiple tiers of interacting decision-makers, who compete across a tier but cooperate between tiers, generated new frameworks for work on sustainability and supply chains as well. We also conducted research on energy supply chains and I have a series of papers in this area, some of which also include carbon taxes. An example is the paper, "Modeling Generator Power Plant Portfolios and Pollution Taxes in Electric Power Supply Chain Networks: A Transportation Network Equilibrium Transformation," co-authored with Kai Wu, Zugang Liu (another former PhD student of mine who is now a tenured professor), and John Stranlund, a faculty member at UMass in Resource Economics.

Another former very successful doctoral student of mine, Trisha Anderson Woolley, now a tenured professor,  also published several papers with me on sustainability, energy, and supply chains, as well as policy interventions. 

As the news about climate change resonated and its negative impacts, we continued to explore modeling of supply chains and an example of a paper reflecting this is: "Environmental Impact Assessment of Transportation Networks with Degradable Links in an Era of Climate Change, " which was published in 2010 and written with Patrick Qiang, my co-author of the Fragile Networks book (and whose dissertation received the Charles Wootan Award from the CUTC), and the "other" Professor Nagurney - Ladimer S. The paper, "Sustainable Supply Chain Network Design: A Multicriteria Perspective," written by the two Nagurneys, which was also published in 2010, remains one of the most highly cited articles in the International Journal of Sustainable Engineering.

Our more recent research on sustainability and supply chains has focused on numerous different applications, and these are quite fascinating. Much of the impetus has come from outside - such as our work on fashion and sustainability - but some of it has also been internal - as in the case of our blood supply chain sustainability research and driven by common interests and passion that I share with both students and collaborators. Examples of such papers are: Sustainable Fashion Supply Chain Management Under Oligopolistic Competition and Brand Differentiation, Anna Nagurney and Min Yu, International Journal of Production Economics, Special Section on Green Manufacturing and Distribution in the Fashion and Apparel Industries 135: (2012) pp 532-540 and Supply Chain Network Design of a Sustainable Blood Banking System, Anna Nagurney and Amir H. Masoumi, in Sustainable Supply Chains: Models, Methods and Public Policy Implications, T. Boone, V. Jayaraman, and R. Ganeshan, Editors, Springer, London, England (2012) pp 49-72.

In 2014, I was delighted to co-author a paper with two of my former PhD students, Toyasaki, already mentioned, and Professor Tina Wakolbinger, and her first PhD student, Thomas Nowak, who has since received his PhD: When and for Whom Would E-waste be a Treasure Trove? Insights from a Network Equilibrium Model of E-waste Flows, Tina Wakolbinger, Fuminori Toyasaki, Thomas Nowak, and Anna Nagurney, International Journal of Production Economics 154: (2014) pp 263–273.


Some of our other recent research has included my collaborator in Sweden, Professor Jonas Floden, since I had a fabulous Visiting Professorship at the University of Gothenburg over a 4 year period. Examples are the papers: Supply Chain Network Sustainability Under Competition and Frequencies of Activities from Production to Distribution, Anna Nagurney, Min Yu, and Jonas Floden, Computational Management Science 10(4): (2013) pp 397-422 and Fashion Supply Chain Network Competition with Ecolabelling, Anna Nagurney, Min Yu, and Jonas Floden, in Sustainable Fashion Supply Chain Management: From Sourcing to Retailing, T.-M. Choi and T.C.E. Cheng, Editors, Springer (2015) pp 61-84.

Another paper that I am quite proud of in which I move from transportation to supply chains to sustainable cities is, "Design of Sustainable Supply Chains for Sustainable Cities," invited paper for the Complex-City Workshop, December 5-6, 2011, Amsterdam, The Netherlands, Environment & Planning B 42(1): (2015) pp 40-57.

Our research on food supply chains, conducted with Professor Min Yu (yes, another former terrific Isenberg UMass PhD alumna in Management Science), and published in the European Journal of Operational Research, also has components of sustainability since we consider waste. The same holds for our work on pharmaceutical supply chains.

And, for those of you interested in perishable product supply chains, including food and medical nuclear ones, in which waste is a big issue, our Networks Against Time: Supply Chain Analytics for Perishable Products, is recommended.

And the research continues into its third decade!

Sustainability is Sustainable and Good for Business, Our Health, Our World

I returned a short while ago from NYC where yesterday I took part in an extraordinary conference -- The New York Times 2013 Energy for Tomorrow Conference.

The full agenda of the conference can be accessed directly here.

It was an intellectual feast that brought together mayors, an Academy Award winner, thought leaders, scientists, environmentalists, investors, policy makers, and decision-makers, corporate employees from IBM to Google, as well as a farmer/former NBA player/MacArthur Fellow -- and these were just some of the speakers. In the audience, I met a colleague from Cornell (now retired), a diplomat from the Chinese embassy in DC, a Georgia Tech professor, numerous journalists from as far as Singapore, affordable housing advocates, urban planners, students, a researcher at MIT, head of the electric vehicle taxi program for NYC, and a financier in private equity, to single out just a few.

The conference began with a stimulating breakfast session (the food was good, too) on smart vehicles, but time was too short for me to be able to ask the question that I had -- what about cybersecurity issues in this product domain? I was thrilled that even operations research was mentioned -- indeed, where would transport studies be without OR?!

Mayor Michael Bloomberg of NYC, who needs no introduction, was introduced by Arthur Sulzberger Jr., the publisher of The New York Times, and both were absolutely brilliant.

With the paralysis in Washington (Congress) regarding environmental action, mayors and cities are leading the way.  This is the first truly urban century and cities have to (and many are) taking action. We must unlock human creativity and take actions to mitigate risk. Mayor Bloomberg chairs the C40 group, which actually consists of 60 cities.

Mayor Bloomberg had 4 major points with the first one being that one must develop a plan with goals and metrics -- you have to be able to measure. He has done much to improve air quality and water quality and, along with the Sierra Club, has been instrumental in retiring many coal-fired power plants.

750,000 trees have been planted in NYC with a goal of planting 1 million and he gave credit also to Bette Midler.

He noted how sustainability provides good economic value -- being environmentally friendly improves your brand and helps in recruiting -- vibrant, smart employees want to work in places where they can breathe clean air!

He mentioned how he, with Al Gore (former VP and of the An Inconvenient Truth fame), climbed up on a rooftop and painted it white -- with white rooftops reducing energy costs by 20% -- a quick payback.

He also emphasized private-public partnerships -- closing roads to traffic -- something I have written about, spoken about, and even been interviewed on, and how we should be stealing the best ideas in terms of transport and sustainability from around the world.

What really intrigued me is when he said that China will become a leading environmentalist in the next 10 years  He, as several others yesterday, emphasized resiliency and that we must prepare for extreme events. Hurricane Sandy was noted several times during the conference.

The next panel was the Mayors panel and the panelists were engaging, and very  entertaining with one of my favorite quotes being "cars are the next cigarettes."  The theme that people will vote with their feet (want to live and work in a sustainable location) continued.

We were then treated to a conversation between Andrew Revkin and Jeremy Irons, who has garnered not only an Academy Award, but numerous other awards for his acting. His passion for the environment resonated as did his eloquence. The night before the conference, the movie Trashed, which he was the Executive Producer of, was screened, and more info on what is being done to our globe because of garbage can be found here.  He noted that he is using the actor's power to address important problems and even emphasized electronic recycling and packaging -- his knowledge impressed me. He noted that a film can inject a feeling of purpose. He also emphasized that it is about education and that industry should prove that what it is making is 100% safe. Since my research group does a lot of work on sustainable supply chains his message was near and very dear to me. Coincidentally, Revkin is a fellow Brown University grad and I heard him deliver the Daffodil Lecture at UMass a while back.

Thomas L. Friedman of The New York Times then led a panel on renewable energy with experts from the US and abroad, including the CEO of ConEd, Kevin Burke. Joe Nocera, also of The New York Times, followed with a panel on the role of technology and innovation and I was especially moved by Stephen Kennedy Smith, who spoke on agribusiness and urban food supply. I managed to talk with him later and mentioned that when I got my PhD from Brown his nephew, John F. Kennedy Jr., received his undergraduate degree. There are also other school ties which I noted.

During lunch, we ate (a very healthy spread) and discussed the urban food supply and since one of my most recent papers was on competitive food supply chains (with Min Yu), which was published in the European Journal of Operational Research, this topic was mesmerizing. Will Allen, the Renaissance man -- farmer and MacArthur Fellow, regaled us with his work in inner cities and urban farms.

I had to then take off since it was time to get ready for the Transport and Traffic panel that I was speaking at, which was moderated by Joe Nocera, and I had terrific company!

Below are several of my fellow panelists as we get ready in the "Green" room which actually had a red door.

The day concluded with breakout sessions in which we brainstormed and a closing session Dealbook: Investing in the city of tomorrow -- provocative and timely.

Prior to that we also got to hear Bill Keller of The Times in conversation with Carol Browner -- the former energy czar. She also spoke about resilience and noted the importance of physical infrastructure, nature, and communities -- simply fabulous

The conference was videostreamed and you can access the videos of the various panels on the conference website.  The Transport and Traffic panel that I was part of can be accessed directly here.
I had to bring in the Braess paradox into the conversation as well as congestion charging and transport congestion policies dating back to Roman times -- when chariots were the problem!

And I could not resist posting photos below taken of me with Professor Richard Schuler, professor emeritus of Cornell, and of  Dr. Yajun Fang of MIT taken at the reception at the end of a very exciting day. Professor Schuler is the academic father of Professor Ben Hobbs of Hopkins, an INFORMS Fellow.


New York City was as vibrant, exciting, and stunning as always and I share with you the additional photos that I took while walking as a very happy pedestrian in NYC!



And, on the way back to Massachusetts, via Amtrak on the Vermonter, as I strolled back to the dining car for a cup of tea I heard a greeting --"Hello, Anna!" and it was one of my favorite Isenberg School of Management colleagues, Professor Glenn Wong, of sports law and sports management fame.

The Science of Internet Advertising

Given the number of requests that I have received lately from firms, especially from start-up firms, to write about them in this blog, my daughter suggested that I start charging for such "services."

Since I am a researcher and educator, for the time being, I will instead note some research of ours, which has just been published. The research is on the general theme of the Science of Internet Ads, which we have been pursuing with co-authors. Our latest paper, hot off the press is, "An Integrated Approach for the Design of Optimal Web Banners," and it appears in volume 11 of the journal Netnomics (2010), pp. 69-83. My co-authors are Professors Lili Hai and Lan Zhao of the Department of Mathematics and Computer Information Science at SUNY Old Westbury.

In this paper, we target the very first step of Internet advertising -- that of banner design using the tools of statistical analysis and optimization.

While banner advertising has become prevalent, consumers have also become more selective. Indeed, the banners' click-through rate, which is the ratio of the number of click-throughs to the number of exposures (times that the banner is shown to Internet surfers), has declined precipitously to an average of less than one-half percent.

In order to be fully effective with banners, a scientifically sound approach using real time data is needed to determine an optimal design.

Our paper demonstrates how to use a statistical predictive technique and optimization methods to exploit the richness of data collected on banner visitors' activities in order to achieve the goal of optimizing the banner designs. The optimization procedure begins with establishing a banner information repository that complies with database technology.

The above data may change for each advertising cycle. After the establishment of the information repository, the statistical predictive model is constructed based on the data. It not only identifies the significant components, but also quantifies the contribution of each component to the click-through rate of a banner. The predictive model sets click-through rate as the function of banner components. Finally, mixed integer programming is used to maximize the click-through rate as a function of the feasible set of components.

The major benefits of our method are that it allows one to systematically improve banner advertising by capturing the dynamics of browsers and to "unintrusively" personalize web advertising at the cluster-level.

In our first paper on Internet advertising, published also in Netnomics, in 2005, Zhao and I modeled optimal Internet advertising strategies for allocating an ad budget to websites as a network optimization problem, and constructed an efficient special-purpose algorithm for the determination of the optimal solution. We then explained two different paradoxes that occur in this setting.

In a paper of ours published in the European Journal of Operational Research, the network optimization modeling framework was expanded to model Internet advertising competition in which multiple firms maximize their own ad effects within their limited marketing budgets. In that paper, we introduced an elastic Internet marketing budget in order to conjoin the online and offline marketing strategies. Consequently, the multifirm competitive equilibrium problem was modeled using game theoretic constructs as a Nash equilibrium with network structure.

Professor Lan Zhao is a Center Associate of the Virtual Center for Supernetworks that I direct, and she also consults for flowers.com so our research results have immediate practical applications.

For reprints of various articles, conducted by researchers at the Virtual Center for Supernetworks please click here.

A Female Academic Who Did It in Reverse Order and a Painful Anniversary

The recent AAUW report, which I blogged about, has certainly stirred up the waters, and I thank Dana Chivvis of AOLNews for further disseminating the important news about this study on how sterotypes and bias hurt women in math and science.

Now for some background on my personal history. In a sense, I was lucky, since I chose, while I was a doctoral student in Applied Mathematics at Brown University, a female as my dissertation advisor. Her name was Dr. Stella Dafermos, and she was the ONLY female who had an appointment in either the Division of Applied Mathematics or in Engineering (let's say that she was "double-counted," something I have experienced as well). She was also a mother with two children and her husband, Dr. Constantine Dafermos, was a very well-known applied mathematician, who was a Professor at Brown. I was Stella's first doctoral student and the impact that she had on me was tremendous. She was only the second female to receive a PhD in Operations Research in the world and she died at age 49 of cancer. I wrote her obituary in the top journal "Operations Research," and she was one of only a handful honored in that way.

On April 5, 2010, we mark the 20th anniversary of the death of this great female scholar, whose numerous research contributions in transportation, networks, spatial economics, game theory, algorithms, and variational inequalities have made and continue to make a great impact. Oh, the adventures that we had with Stella during conferences in Canada, Holland, Greece, Japan, the USA, among other places.

Now I am conducting research on paradoxes and the work that Stella and I did together and published I am now using years after (and many others have, in the meantime, as well). She had an uncanny intuition and great attention to detail and exceptional creativity.

As for "doing it in reverse order," female academics do not have it easy. First, I got tenure (after 4 years, which is unusually quick). Then I became a Full Professor (8 years after my PhD) -- the first one in the history (or should I say "herstory") in the Isenberg School (and the number of letters that were solicited for my Full is probably a record but one has to make sure that a female is "good enough," I guess). Then I had a child and after a month of "sick leave," granted to me less than willingly, I was back to teaching. That major event followed with my getting my driver's license (and that is quite the story in itself) but I had felt that I could be quite objective researching transportation, networks, and logistics, w/o a driver's license. Besides, while growing up in Yonkers we almost always took public transportation and spent a great deal of time in NYC and, as an academic, most of the interesting invitations that I was receiving required air travel. Robert Moses never got his license and neither did Barbara Walters, so I always thought that I was in rather "good company."

We need female faculty in technical fields to show new generations of students what is possible. Remember, once you solve that research problem that you have been struggling with, and all the pieces of the puzzle fall beautifully in place, that feeling is close to ecstasy. Noone can take that feeling away from you but also, remember, you had better publish that result, as well.