Browsing by Author "Jaber, M. Y."

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A buyer-vendor system with untimely delivery costs: Traditional coordination vs. VMI with consignment stock
(Elsevier, 2021-04) Çömez-Dolgan, Nagihan; Moussawi-Haidar, L.; Jaber, M. Y.; Management Information Systems; ÇÖMEZ DOLGAN, Nagihan
This paper investigates the impact of coordinating a two-level supply chain that consists of a single-vendor and a single-buyer in the presence of untimely delivery costs. Specifically, early and late deliveries outside an agreed-upon delivery window are penalized. We investigate the replenishment policies of the vendor and the buyer with and without coordination. We show that untimely deliveries increase the replenishment cycle of the buyer, whether it coordinates with the vendor or not. More importantly, under untimely deliveries, coordination has a noticeable impact on aligning the decisions of both players, which is shown to be much more valuable in decreasing total costs. Implementing a coordinated solution becomes beneficial when the vendor's penalty and holding costs are high, the delivery window is narrow, and the buyer's holding and ordering costs are low. Next, we compare the traditional replenishment coordination mechanism with a vendor-managed-inventory (VMI) mechanism with consignment stock (CS) under untimely deliveries. We compare two coordination mechanisms, VMI-CS and traditional, and show that VMI-CS outperforms the other when the delivery times are random, but not so when the conditions are deterministic.
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Capacitated assortment planning of a multi-location system under transshipments
(Elsevier, 2022-09) Çömez-Dolgan, Nagihan; Moussawi-Haidar, L.; Jaber, M. Y.; Cephe, E.; Management Information Systems; ÇÖMEZ DOLGAN, Nagihan
We analyze a joint assortment optimization problem for multiple locations of a firm, where each of those locations has an assortment capacity. When one location does not keep a product in its assortment, it transships the requested product from another location when needed. If this is not possible, then demand may be fulfilled by a substitutable (second choice) product from the current location or another demand location through transshipment. We show that the resulting assortment planning problem is NP-complete. We provide structural properties of the optimal assortments that would simplify and speed up the search for the optimal solution. We specifically obtain the optimal product assortment in polynomial time when no substitutions are present. When both transshipments and substitutions are considered, the products adopted by all locations form a common assortment that includes the most popular products among customers, i.e., a popular set, which may not be valid for the individual assortment of each location. We derive an upper limit on customers' substitution probability for each location, such that at optimality, the location's capacity is utilized in full when the substitution probability is below this threshold value. Moreover, we show that when all locations have the same assortment capacity, utilizing theirs to the maximum reduces costly transshipment opportunities. Extensive numerical analyses are also conducted that illustrate the sensitivity of the optimal assortments to system characteristics and the benefits of allowing transshipment and demand substitution in multi-location assortment planning.