Seminar, Tuesday 2 March at 2.50 pm in School of Mathematics (Building 54)
Lecture Theatre 5B, University of Southampton.

Anyone interested is welcome to attend.



Speaker: Professor David Ryan (University of Auckland)

Title: Some Aspects of Optimisation Methods in Aircrew Scheduling

Abstract: Besides constructing aircrew Tours of Duty or Pairings with
minimal cost, airlines also wish to construct pairings which are robust in
that flight schedule disruptions are less likely to propagate delays into
the future.  In general a minimal cost solution is likely to lack
robustness and conversely a solution with maximum robustness (however this
might be measured) is likely to be more expensive.  In this talk we will
describe the aircrew scheduling process and in particular the Pairings
Problem and review the development of optimization methods based on the
set partitioning model which produce minimal cost solutions.  A measure of
robustness for each pairing will then be developed and the concept of a
linear robustness objective will be discussed.  The two objectives of cost
and robustness will be treated in a bicriteria optimisation to generate
"efficient" pairings which do not allow a simultaneous improvement in cost
and robustness.  We show that treating the cost objective as a constraint
while maximizing robustness leads to very difficult integer programming
problems.  This situation can be overcome by treating the cost objective
as an elastic constraint and penalizing violations of the cost constraint
in the robustness objective.



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Chris N. Potts                        Tel: +44 (0)23 8059 3651
School of Mathematics                 Fax: +44 (0)23 8059 5147
University of Southampton
Southampton                        E-Mail: [log in to unmask]
SO17 1BJ
UK
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