Ph.D. Dissertation Defense

| Last update: 2026/11/4 |

Ms. Hamideh Bahrami, a Ph.D. candidate in Industrial Engineering, will defend her dissertation entitled “Dynamic Pricing in Manufacturer–Retailer Relationships Considering the Impact of Advertising Across Product Life Cycle Stages and Substitute Products”, under the supervision of Dr. Saeed Yaghoubi, on November 15, 2026, at 9:00 AM.

Dissertation Defense Committee: Dr. Saeed Yaghoubi, Dr. Ahmad Makui, Dr. Ebrahim Teymouri, Dr. Mohsen Sheikhsajadiyeh, Dr. Ataollah Taleizadeh

Defense Details:
Date: November 15, 2026

Time: 9:00 AM
Venue: Classroom 208, Second Floor

Student ID: 99873013

Email: hamideh_bahramiind.iust.ac.ir

Abstract:

Changes in consumer demand and preferences throughout the product life cycle (PLC), coupled with the introduction of substitute products, complicate decisions regarding pricing, advertising, quality improvement, and the timing of new product introductions. This study aims to develop an integrated framework for analyzing dynamic competition and determining the optimal decisions of manufacturers and a retailer, considering PLCs, evolving consumer preferences, and the interaction structures among supply chain members. To this end, four mathematical models are developed using differential games within a leader–follower framework. The first two models examine competition between two manufacturers, a pre-existing and a new entrant, while the other two investigate intra-brand competition and determine the optimal introduction time of a second product by a single manufacturer.

The main methodological contribution of this research lies in integrating PLC dynamics, competition between substitute products, evolving consumer preferences, and strategic supply chain decisions into an analytical framework. Accordingly, a modified Beta function and the Bass diffusion model are employed to represent distinct demand patterns by distinguishing between products already familiar to the market and novel, unfamiliar products. Further contributions include analyzing both inter-manufacturer and intra-brand competition, determining the introduction time of the second product while accounting for cannibalization effects, and comparing traditional reselling and agency selling structures while incorporating the retailer's local advertising efforts. The analytical and numerical results reveal that, in competition between established products, quality improvement efforts may reach their peak before prices and demand attain their maximum levels. Furthermore, for novel and unfamiliar products, maximum profitability does not necessarily coincide with peak demand and may occur earlier. The introduction of a second product may also encourage the manufacturer to intensify quality improvement efforts for the first product, thereby partially mitigating cannibalization effects. In the product portfolio management models, introducing the second product too early may intensify cannibalization and divert demand away from the first product. In contrast, a delayed introduction may limit the profitability opportunities of the second product. The findings further emphasize the importance of concentrating advertising efforts during the early stages of new product introduction and increasing quality improvement efforts for the first product following the introduction of the second product.

Keywords: Product Life Cycle, Dynamic Competition, Dynamic Pricing, Advertising, Quality Improvement, Manufacturer–Retailer Cooperation, Substitute Products, Differential Games, Product Cannibalization.

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