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The next two sets of nodes, i.e., those associated with tiers 3 and 4, represent the
storage facilities. These are the facilities to which the collected goods are shipped,
and then stored until needed. There are n S of such nodes in the network, and the
links connecting tiers 2 with 3, and 3 with 4 are referred to as “transportation” and
“storage” links, respectively. The reason that the nodes in tiers 3 and 4 are sharing
similar notation (e.g., S 1 , 1 and S 1 , 2 ) is that they correspond to the same geographical
locations but reflect different points in time.
As mentioned earlier, our model not only allows for the pre-planned procure-
ment and storage of relief goods, but also integrates the direct procurement of aid
items. The case of immediate procurement is reflected in the network in Fig. 15.1
with the curved links connecting the origin node to the storage facilities. This is the
case where the organization initiates procurement after the occurrence of the
disaster. The organization may benefit from avoiding storage costs. Even if the
organization decides to “store beforehand” as its dominant strategy rather than to
“procure afterward,” the latter can be expected to be available as a backup plan
especially under severe circumstances.
The next set of links, connecting tiers 4 and 5 of nodes, are of “transportation”
type, and correspond to the shipment of the product—either stored or freshly
procured—to the affected region. These links are used once the disaster strikes a
region. As seen in Fig. 15.1 , there may exist multiple links connecting every pair of
nodes in tiers 4 and 5. This is to allow for different modes of transportation: air,
ground, and/or sea, as feasible, for the shipment. Thus, nodes A 1 , A 2 ,
, A n A
represent the arrival portals of disaster aid items into the affected region—which
is represented by the dashed box in the network topology.
The next set of links represent the “processing” of the received items at the
portals of the affected region. Typically, a variety of goods are sent to the areas hit
by disasters—some of which may even be useless or inappropriate. As a result, the
unloading, unpacking, sorting, and the loading of the goods have to be done before
the ultimate distribution takes place. Processing is often done at the same location
as the arrival portals (e.g., airports, ports, etc.), and the corresponding facilities are
denoted by B 1 , B 2 ,
...
, B n B . Processing at international locations may include, in
addition, customs inspections and payments, etc.
Finally, the last set of nodes reflects the actual demand points in the affected
region, denoted by R 1 , R 2 ,
...
, R n R . These nodes can be the hospitals, community
centers, or points of distribution of the relief product to the disaster victims. The
links connecting the last two sets of nodes are “distribution” links, and are
represented by multiple links to allow for the possibility of various modes of
transportation within the affected region. This may be crucial when parts of the
infrastructure have been severely damaged by the disaster.
The supply chain network topology is denoted by [ N , L ], where N and L ,
respectively, denote the sets of nodes and links (arcs).
...
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