A. Gürhan Kök

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F many companies, inventory record inaccuracy is a major obstacle to achieving operational excellence. In this paper, we consider an inventory system in which inventory records are inaccurate. The manager makes inventory inspection and replenishment decisions at the beginning of each period. There is a cost associated with each inspection. If an inspection(More)
Assortment planning at a retailer entails both selecting the set of products to be carried and setting inventory levels for each product. We study an assortment planning model in which consumers might accept substitutes when their favorite product is unavailable. We develop an algorithmic process to help retailers compute the best assortment for each store.(More)
We consider a retailer with limited inventories of identically priced, substitutable products. Customers arrive sequentially and the firm decides which subset of products to offer to each arriving customer depending on the customer’s preferences, the inventory levels, and the remaining time in the season. We show that the optimal assortment policy is to(More)
W consider a decentralized assembly system in which a buyer purchases components from several first-tier suppliers. We examine the dynamics of suppliers’ investments in cost-reduction initiatives over the life cycle of a product under different procurement approaches. We model the suppliers’ investment decisions under cost-contingent contracts, with(More)
T paper studies the assortment planning problem with multiple merchandise categories and basket shopping consumers (i.e., consumers who desire to purchase from multiple categories). We present a duopoly model in which retailers choose prices and variety level in each category and consumers make their store choice between retail stores and a no-purchase(More)
T newsvendor model is designed to decide how much of a product to order when the product is to be sold over a short selling season with stochastic demand and there are no additional opportunities to replenish inventory. There are many practical situations that reasonably conform to those assumptions, but the traditional newsvendor model also assumes a fixed(More)
I is common for a retailer to sell products from competing manufacturers. How then should the firms manage their contract negotiations? The supply chain coordination literature focuses either on a single manufacturer selling to a single retailer or one manufacturer selling to many (possibly competing) retailers. We find that some key conclusions from those(More)
BACKGROUND Previous studies on the molecular epidemiology of hepatitis A virus (HAV) in Amsterdam, The Netherlands, show that subgenotype 1A is mainly seen among homosexual men practising anonymous oral-anal sex in saunas and darkrooms, while subgenotype 1B is usually detected among children originating from Morocco, and subgenotype 3A is mostly found among(More)
OBJECTIVES The aim of the study was to investigate the prevalence of extended-spectrum β-lactamase and carbapenemase production among Enterobacteriaceae isolated from Egyptian patients with suspected blood stream infection. METHODS Ninety-four Enterobacteriaceae blood culture isolates from Egyptian patients with suspected blood stream infection were(More)