Caron, Marchet, and Perego (1998) evaluated and compared different
routing policies with storage assignment based on COI. The result
demonstrates that in COI-based storage systems the traversal
policy outperforms the basic return policy for the range of pick
densities and the COI-based ABC curves most frequently found in
real-world applications. Caron, Marchet, and Perego (2000) presented
an analytical approach to layout design of the picking area
in picker-to-part systems using COI-based and random storage policies.
The results show that layout preference seems to be strongly
affected by decisions concerning the adoption of a COI-based storage
policy. Additionally, Kallina and Lynn (1976) discussed some
practical conclusions gathered form experience in applying the
COI rule in warehouse layout. Hwang et al. (2003) proposed the
density-turnover index (DTI) rule with the objective of minimizing
the energy consumption of the material handler working in a picker-
to-part warehouse system. The DTI rule is based on the weight,
space requirement, demand rate of items and the effective distance
measure of storage location. Hwang et al. (2003) shows that the
DIT rule is substantially better than the COI rule from the view
point of human safety with some sacrifice of throughput.
Jarvis and McDowell (1991) developed the necessary and sufficient
conditions for optimally allocating items in a class of symmetric
warehouses. Simply assigning themost frequently pickeditems to the
nearest aisles will not necessarily minimize the average travel distance
if the aisles are not symmetrical. Frazelle and Sharp (1989)
showed that the storage assignment problemis in the class ofNP-hard
problemsforwhich theoptimal solutionis computationally infeasible
to obtain in problems of practical sizes, and thus proposed a heuristic
procedure based on the demand dependency between items.
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