Development of Models and Solution Methodologies for Tree-Shaped p-Hub Median and Capacitated p-Hub Median Problems

Our doctoral student Betül Kayışoğlu has successfully defended his Ph.D. dissertation, entitled "Development of Models and Solution Methodologies for Tree-Shaped p-Hub Median and Capacitated p-Hub Median Problems". The application areas of the problems ‘multiple allocation tree of hubs location problem’ and ‘multiple allocation arc capacitated hub location problem’ that we study in this dissertation range from the optimization of fiber internet backbone to the exact configuration of the physical road network of the transportation networks of the cargo companies, from the improvement of computer or wireless communication networks to the establishment of smart electricity, water or gas distribution networks in the most efficient way, from efficient airway and railway transportation systems to smart public transportation systems with different transportation modes. These problems are directly applicable to a wide range of systems that serve to achieve two Sustainable Development Goals (SDGs), namely, ‘building resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation’ and ‘making cities and human settlements inclusive, resilient and sustainable’. According to these two goals, it is utmost importance that urban and public transportation systems, gas, water and electricity distribution systems, and telecommunication network systems are smart, resilient and sustainable. Moreover, we propose a new modelling approach for these problems that allows us to use the structure of the real physical network directly in the formulation of the problems. This approach provides more flexibility in modeling several characteristics of real-life hub networks. The developed models will find more application areas because they better represent real life problems. Moreover, one main challenge arising in real-life applications is the problem size. Mostly it is not possible to solve them with the standard optimization softwares. However, we are able to solve large-size problems that arise in real life with our proposed solution methodologies. To sum up, the modelling approach and solution methodologies that we propose for our problems will help to achieve the goals of building resilient infrastructure, sustainable transportation systems, sustainable cities and human settlements.