Geoscience Reference
In-Depth Information
models dealing with uncertainty, dynamic and multi-modal models, and competition
and collaboration.
12.4.1
Hub Network Topologies
Full interconnection between hub nodes may be prohibitive in applications where
there is a considerable setup cost associated with the hub arcs (see O'Kelly and
Miller
1994
; Klincewicz
1998
). To overcome this difficulty, several models consid-
ering incomplete hub networks have been studied. HALPs, originally introduced
in Campbell et al. (
2005a
,
b
), relax the assumption of full interconnection between
hubs and consider the location of a set of hub arcs that may (or may not) require
a particular topological structure of their induced network. Some of these models
do not even require the hub arcs to define a single connected component. Alumur
et al. (
2009
) and Calık et al. (
2009
) study the design of incomplete hub networks
with single assignments in which no network structure other than connectivity is
imposed on the backbone network. Other works study models that do not consider
a complete backbone network but rather, a particular topological structure. Kim and
Tcha (
1992
), Contreras et al. (
2009b
,
2010
) and Martins de Sá et al. (
2013
), study
the design of tree-star hub networks in which the hubs are connected by means of a
tree and the O/D nodes are assigned to exactly one hub. Labbé and Yaman (
2008
)
and Yaman (
2008
) consider the design of star-star networks in which hub nodes are
directly connected to a central node (i.e. star backbone network) and the O/D nodes
are assigned to exactly one hub node. Martins de Sá et al. (
2015
) study the problem
of designing a hub-line network in which hubs are connected by means of a line
and the aim is to minimize the total service time between pairs of nodes. Martins de
Sá et al. (
2014
) present and extension of this problem to the case in which multiple
hub-lines are to be located. Lee et al. (
1993
) and Contreras et al. (
2013
) focus on the
design of cycle-star networks in which the hubs are connected by means of a cycle.
Figure
12.2
shows some examples of different hub network structures.
Ya m a n (
2009
) studies the problem of designing a three-layer hub-and-spoke
network, where the top layer consists of a complete network connecting the central
hubs, and the second and third layers are unions of start networks connecting the
remaining hubs to central hubs and the O/D nodes to hubs, respectively. Yaman and
Elloumi (
2012
) consider the design of two-level start networks, while taking into
consideration the service quality in terms of the length of paths between pair of O/D
nodes. Adler and Smilowitz (
2007
) focus on the design of global three-layer hub
networks in which two types of hub facilities are considered, international gateways
and regional hubs. The backbone network associated with each hub-layer is assumed
to be complete.
Some papers focus on the design of more complex access networks that are
not longer determined by a single or multiple assignment pattern of O/D nodes to
hubs. Aykin (
1994
,
1995
) and Sung and Jin (
2001
) present models that explicitly
consider direct connections between non-hub nodes (i.e. they relax Assumption 1).
