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KOÇ UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

INDUSTRIAL ENGINEERING AND OPERATONS MANAGEMENT

PhD THESIS DEFENSE BY OKTAY KARABAĞ

 

Title: Essays on Modelling and Analysis of Purchasing Process for Producer

 

Speaker: Oktay Karabağ

 

Time: 07/13/2018, 09:30

 

Place: CASE 127

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

 

Thesis Committee Members:

Prof. Dr. Barış TAN, (Koç University)

Prof. Dr. Fikri Karaesmen (Koç University)

Prof. Dr. Gürhan Kök (Koç University)

Prof. Dr. Refik Güllü (Boğaziçi University)

Asst. Prof. Dr. Justus Arne Schwarz (University of Mannheim)

 

Abstract:

This thesis consists of three essays that address various practices and phenomena in the procurement processes of the producers. In the first two essays, we examine the group purchasing and e-auction practices by considering an industrial case. Specifically, in the first essay, we study a supply chain in which a group purchasing organization works with a set of buyers and suppliers under demand and price uncertainty. For the studied supply chain setting, we develop a two-period stochastic model and analytically derive the optimal decisions for all parties in the market. The results indicate that a group purchasing organization helps buyers and suppliers to mitigate demand and price risks effectively while collecting a premium by serving as an intermediary between them. In the second essay, we empirically examine a unique dataset collected from a third-party firm offering e-auction solutions for its corporate customers. With this effort, we provide an understanding of how the product category, the 2008 global financial crisis, the auction format, the number of bidders, the group purchasing, the contract type, and the auction platform ownership affect the buyer surplus achieved in the reverse auctions. Additionally, in the third essay, we study the purchasing, production, and sales policies for a continuous-review discrete material flow production/inventory system with fluctuating and correlated purchasing and sales prices, exponentially distributed raw material and demand inter-arrival times, and processing times. We model the system as a Markov decision process and analytically prove that the optimal purchasing, production, and sales strategies are state-dependent threshold policies. Additionally, the structural properties of the switching curves are established.

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