RAMASESH, RANGA VENKATESH; PHD
THE PENNSYLVANIA STATE UNIVERSITY, 1988
BUSINESS ADMINISTRATION, MANAGEMENT (0454)
In inventory management and control, when lead times are stochastic, a dual-sourcing
technique in
which the order quantity is procured by placing split-orders on two vendors
could offer savings in holding
and shortage costs, compared to the sole-sourcing technique. Although several
studies have examined
the costs and benefits associated with these two approaches in a qualitative
and empirical way,
theoretical research on this issue is scarce. Research in this area is significant
because, in the
professional literature there is a considerable debate over the relative merits
of the two techniques. In
this dissertation, we formulate mathematical models of one- and two-vendor inventory
systems under
stochastic lead times and demand and examine their optimal total cost performance
in the framework of
single- and multifactor experiments. We first analyze a simplified base-case
model assuming a uniform
probability distribution for the lead times and a constant rate of demand. For
the two-vendor system, we
assume that the lead times for both the vendors are independent and identically
distributed and that the
order quantity is equally split between the two vendors. We then progressively
relax the assumptions
and develop models of more complicated and realistic inventory systems. Besides
the uniform
distribution model, we investigate two additional models with exponentially
distributed lead times: in one
the lead times for the two vendors are identical and in the other they are different.
For each model, our
investigation covers the development of the mathematical model, formulation
of the expression for the
total expected cost as a function of the decision variables, derivation of optimal
solutions, and
experimentation over a wide range of parameter values, under both and dual-sourcing
approaches.
Finally, the experimental results are compared to evaluate the performance of
the two techniques, and to
develop guidelines for a cost-effective choice between the two.
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