Browsing by Author "Kompil, Mert"

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A genetic-fuzzy system modeling of trip distribution
(Izmir Institute of Technology, 2010) Kompil, Mert; Çelik, Hüseyin Murat
Trip distribution modelling is one of the most active parts of travel demand analysis. In recent years, use of soft computing techniques has introduced effective modelling approaches to the trip distribution problem. Fuzzy Rule-Based System (FRBS) and Genetic Fuzzy Rule-Based System (GFRBS: fuzzy system improved by a knowledge base learning process with genetic algorithms) modelling of trip distribution are two of these new approaches. However, much of the potential of these techniques has not been demonstrated so far. The present study explores the potential capabilities of these approaches in an urban trip distribution problem with some new features. For this purpose, a simple FRBS and a novel GFRBS were designed to model Istanbul intra-city passenger flows. Subsequently, their accuracy, applicability, and generalizability characteristics were evaluated against the well-known gravity and neural networks based trip distribution models. The overall results show that: i) traditional doubly constrained gravity models are still simple and efficient; ii) neural networks may not show expected performance when they are forced to satisfy production-attraction constraints; iii) simply-designed FRBSs, learning from observations and expertise, are both interpretable and efficient in forecasting trip interchanges even if the data is large and noisy; and iv) use of genetic algorithms in fuzzy rule base learning considerably increases modelling performance, although it brings additional computation costs.
Modeling retail structural change of Izmir using a dynamic spatial interaction model
(Izmir Institute of Technology, 2004) Kompil, Mert; Çelik, Hüseyin Murat
Retailing, one of the most important sectors in all developed economies, has always been the prominent element of urban morphology, and evolves as the city evolves and expands. The last two decades have witnessed considerable changes in retailing throughout developed countries such as, the emergence of new store formats, the increased prevalence of retail chains, the development of out-of-town and edge-of-town retail parks accompanying with the changing conditions of globalized world. Since the sector has undergone major changes in scale, organization, and geography, the urban spaces have been the scene of these ongoing changes.Under the influence of global economic transformation after 80's, there have also been dramatic changes in retail industry and retail environment in Turkey. Despite the sector in Turkey is still dominated by large number of small, independent, and single location retailers, market share and spatial prevalence of large-scale retailers' have been increasing rapidly. Especially in major cities of the country, both international and domestic retail chains have been imposing a transformation and restructuring the urban retail environment. Among all the areas of retailing, food retailing stands out as having seen the most profound changes in Turkey. With respect of this, the study explores the spatial consequences of the structural change of food retailing system in Izmir. The prevalence of large-scale food retailers such as hypermarkets and supermarkets has negative effects on the survival of many small-independent retailers. The increasing competition has led to a changing retail structure with the dominance of organized retailers where the number of small-scale retailers and their total size are decreasing. As the trends continue, this will have important and unpredictable spatial influences on urban retail environment and urban geography. Obviously, there is a strong need for a study exploring changes in retail structure and its influences in urban spaces so that policy makers and planners could take into consideration and help restructuring of this transformation process better. For this purpose, the study explores if the ongoing restructuring process of retailing and its possible geographical consequences can be modeled using a dynamic spatial interaction model as a device to be able to predict the future transformations.