| This dissertation is a collection of three essays on the joint optimization of inventory and logistic decisions.; In the first two essays, we study stochastic inventory models in which products sourced from a single make-to-order supplier can be shipped by two alternative freight modes differing in lead-times and costs. The cost of placing orders and using of the freight modes exhibits economies of scale. The freight mode decision of allocating ordered product units to the two freight modes is delayed until the end of manufacturing for each order, making the freight mode decision responsive in nature. The inventory model in the first essay is a continuous review model, whereas the model considered in the second essay is a periodic review inventory model with inventory holding and back order penalty costs incurred continuously in time. For these models, we derive the optimal policy for the freight mode decision rders of arbitrary size. Further, given that each order is shipped optimally using the two freight modes, we characterize the optimal policy for placing orders. For the continuous review model, we solve for the optimal reorder point and order quantity. We provide a geometrical representation of the optimal solution, enabling easier understanding of and useful insights into the solution. For the periodic review model, we show that the optimal policy for placing orders in not a simple ( s, S) policy. We provide bounds for the optimal policy that are tight and are simpler to compute. Further, we characterize the best (s, S) policy for the model and compare it with the optimal policy. For both continuous and periodic review models, we dual freight model with single fright models.; In the third essay, we analyze stochastic inventory system of a firm that faces random delays in its shipments. For this system, we model and analyze various strategies for mitigating the risk of shipment delays. These strategies differ in operational flexibility and lead-time visibility. We provide a comparison of these strategies and establish the complementarity of operational flexibility and lead-time visibility. |
