Geoscience Reference
In-Depth Information
24.6
Future Trends
The research to date on facility location problems with disruption, although
groundbreaking, is still evolving. The impetus for such work has come from
disasters such as 9/11, the Fukushima nuclear power plant destruction in Japan,
and the more recent power disruption in Michoacan, Mexico. As such problems
are often represented as a two person game (defender-attacker) or a three person
game (defender-attacker-defender), they can be quite mathematically complex and
difficult to solve. Because of this, work is needed to expand the range of problem
sizes that can be addressed by such model structures.
The work discussed here is based upon the simplest of service systems involving
the p-median and maximal covering problems. Although these problems and
extensions can be used in many system designs, lifeline systems such as electrical
generation and transmission, water supply and distribution, and communication
networks of switches and lines, all present a level of complexity that has yet to
be addressed in an efficient and comprehensive way. Systems are interconnected
in many ways. A failure (or an attack) of one system component may lead to the
failure of another. Such cascading failures have been documented in electrical and
communication systems. In addition, the failure of an electrical system component
may render a portion of a communication system inoperable. Connections between
such systems have still to be adequately modeled as well. In addition, most models
capturing disruption ignore the temporal component. Few have addressed the
possible duration of a disrupting event as well as how best to cope with it and restore
the initial operational level. This too, is an area where more research is needed.
Facilities are but one component in a production and distribution system. Recent
flooding in Thailand demonstrated that inventories for key parts, like those for
computer disk drives, could be disrupted to the extent that the retail price for
storage drives almost doubled for a short period of time. Fully addressing such
vulnerabilities requires the modeling of facility production and inventory levels
simultaneously.
There are two principal ways in which resilient design has been approached:
scenario based with robust optimization, and bilevel optimization. Work is needed
to test the efficacy of each approach. For example, can a small number of scenarios
be used to adequately define and couch possible outcomes as compared to the use
of a bilevel optimization problem involving a defender-attacker? In addition, can
simulation models be used in an efficient manner to identify system vulnerabilities?
Further, it is important to develop better models to estimate risk.
Finally, the models developed to date to handle interdiction, fortification and
reliable design are far more complex than their base-level counterparts, adding a
level of computational difficulty that is a new research area. But, one must ask
the question: can simpler models be developed which adequately address such
uncertainties?
