One
of Professor Nagurneys colleagues, Assistant Professor Georgia
Perakis who teaches Management Science at MITs Sloan School,
explained Nagurneys work using the very concrete example of
getting to the office: Think of when you want to get to work
and get there as fast as you can. You want to do that, and so do
many other drivers that are on the streets. Annas work tries
to analyze these systems with all their complexity. It is
in her reevaluation of the concept of network, that Prof. Nagurney
has made a great leap for her field.
We
all have understood networks as the connections between two or
more places, or in Management Science vocabulary, nodes.
In human terms, we network to find jobs, or contracts,
or an apartment. Networks are also systems, such as the telecommunications
network, or the Internet. Through her mathematical descriptions,
Professor Nagurney brought a more realistic concept of network
as a dynamic system with many, many variables. Her networks are
spatial. Her systems acknowledge competition instead of assuming
cooperation.
Back
to the transportation example: there are many drivers trying to
reach their destination and they are often, especially in urban
areas, in competition in the process. There is no communication
in a cooperative way, even though drivers have been known to make
their opinions known to other drivers using choice hand signals
and other verbal forms of communication. As this kind of competition
accelerates, however, it increases the variables that need to
be included in the equations that make up the mathematical model.
The best models are very close descriptions of reality, explains
Professor Perakis. Nagurneys work, incorporating dynamic
and spatial variables in her networks, makes her models better
represent reality.
Once Nagurney has developed a model that accurately reflects a
problem, such as moving people from point A to point B using a
particular method of transportation, she then solves the problem
with an algorithm, a step-by-step problem-solving procedure, especially
an established, recursive computational procedure for solving
a problem in a finite number of steps. So, Professor Nagurney
starts with the outcome, arriving at work in one piece, and works
backwards, using an algorithm to find a solution.. Here is one
of her algorithms derived from her traffic modeling work. It represents
how to solve the problem of getting to work in the most efficient
way. Remember, nodes are intersections at the nether ends of the
network. And when Nagurney is referring to cost, she is using
the old adage time is money.
Consider
an origin/destination pair of nodes; compute the longest used
travel path and the shortest travel path; redistribute the flow
from the longest to the shortest so that their costs are equalized;
continue doing this procedure until the traffic network equilibrium
conditions hold for that origin/destination pair and proceed to
the next, and so on, until the traffic network equilibrium conditions
are satisfied for the entire network, that is, only the minimal
cost travel paths are used for each origin/destination pairs and
no others.
This algorithm also has a reasonable behavioral underpinning,
in that travelers change their paths so as to improve their travel
cost or time and will continue to do so until they cant
do any better. So, once the algorithm is applied for
each possible route with all the variables that have been plugged
into the model, a driver will know which is the most efficient
way to get to work. This kind of modeling has practical application
potential for in-car systems that communicate with satellites.
Professor
Nagurney has extended her models to capture other kinds of networks,
including financial networks, where her models can be used by
large companies trying to optimize their investments. Using Prof.
Nagurneys models, large firms can make decisions on how
to build their portfolios.
Professor
Nagurneys vita is already 29 pages long, and it needs updating
regularly. It does not list her newest book on environmental networks,
nor does it note the Eisenhower Faculty fellowship from the Federal
Highway Administration, an appointment to Girls, Inc., and who
knows what else.
Anna Nagurney has written over 50 different algorithms to solve
her models. She would like to write a theory of networks that
encompasses all of economics and business; in fact, she would
like to write a theoretical framework comprising the world as
a massive network that could be solved by one algorithm. That
sounds big-headed, doesnt it? she asked. No more big-headed
than writing the Great American Novel.