Cihan Çetinkaya

Two-stage vehicle routing problem with arc time windows: A mixed integer programming formulation and a heuristic approach

In this paper, we introduce a new variant of the Vehicle Routing Problem (VRP), namely the Two-Stage Vehicle Routing Problem with Arc Time Windows (TS_VRP_ATWs) which generally emerges from both military and civilian transportation. The TS_VRP_ATW is defined as finding the vehicle routes in such a way that each arc of the routes is available only during a predefined time interval with the objective of overall cost minimization. We propose a Mixed Integer Programming (MIP) formulation and a heuristic approach based on Memetic Algorithm (MA) to solve the TS_VRP_ATW. The qualities of both solution approaches are measured by using the test problems in the literature. Experimental results show that the proposed MIP formulation provides the optimal solutions for the test problems with 25 and 50 nodes, and some test problems with 100 nodes. Results also show that the proposed MA is promising quality solutions in a short computation time.

A closed-loop supply chain network design for automotive industry in Turkey

Abstract Increasing worldwide environmental and social concerns are motivating manufacturers and consumers to implement recycling strategies such as product recovery, waste management or usage of recycled materials. Besides environmental and social concerns, in some countries legislations also force recycling of products such as end-of-life vehicles (ELVs). Automotive manufactures in Turkey are responsible for free take-back of ELVs from consumers to reintegrate used parts into industry according to ELVs regulation by Republic of Turkey Ministry of Environment and Urbanization. Regarding mentioned motivation, in this study a closed-loop supply chain (CLSC) is presented, based on a case study considering the ELVs treatment in Turkey. A linear programming (LP) model is developed to handle the reverse material flows with regard to reintegrate them into forward supply chains. Several CLSC scenarios are discussed to show the performance of the proposed model and its applicability in the automotive industry.

A GIS-based risk reduction approach for the hazardous materials routing problem in Gaziantep

ABSTRACT The transportation of hazardous materials assumes a fundamental importance, especially in urban areas, in order to identify possible alternative routes and to choose the route with minimum risk. Therefore, considering minimization risk rather than minimization distance to prevent a potential danger being transformed into a real event is necessary. In this article , a geographic information system (GIS)–based solution approach is developed to quantify the factors on each link in the network that contribute to a possible route. Based on the origin and destination of each shipment, the risks associated with the routes that minimize (1) the transport distance, (2) the population exposure, (3) the probability of an incident, and (4) the emergency response are evaluated. Proposed risk models are applied to fuel-oil transportation problem between resource point and 78 gasoline stations through the road network of Gaziantep city center. Results show that the proposed framework can contribute to the thought processes of policy-makers and carriers when they evaluate possible routes in order to minimize damage for transporting fuel oil.

Evaluation of ecotourism sites: a GIS-based multi-criteria decision analysis

Purpose The aim of this study is to evaluate the potential geographic locations for ecotourism activities and to select the best one among alternatives. Design/methodology/approach The proposed model consists of four sequential phases. In the first phase, different geographic criteria are determined based on existing literature, and data are gathered using GIS. On equal criteria weighing, alternative locations are determined using GIS in the second phase. In the third phase, the identified criteria are weighted using analytical hierarchy process (AHP) by various stakeholders of potential ecotourism sites. In the fourth phase, the PROMETHEE method is applied to determine the best alternative based on the weighted criteria. Findings A framework including four sequential steps is proposed. Using real data from the Black Sea region in Turkey, the authors test the applicability of the evaluation approach and compare the best alternative obtained by the proposed method for nine cities in the region. Consequently, west of Sinop, east of Artvin and south of the Black Sea region are determined as very suitable locations for ecotourism. Research limitations/implications The first limitation of the study is considered the number of included criteria. Another limitation is the use of deterministic parameters that do not cope with uncertainty. Further research can be conducted for determining the optimum locations for different types of tourism, e.g. religion tourism, hunting tourism and golf tourism, for effective tourism planning. Practical implications The proposed approach can be applied to all area that cover the considered criteria. The approach has been tested in the Black Sea region (nine cities) in Turkey. Social implications Using the proposed approach, decision-makers can determine locations where environmentally responsible travel to natural areas to enjoy and appreciate nature that promotes conservation have a low visitor impact and provide for beneficially active socioeconomic involvement of local individuals. Originality/value To the best knowledge of the authors, this is the first study which applies a GIS-based multi-criteria decision-making approach for ecotourism site selection.

The location routing problem with arc time windows for terror regions: a mixed integer formulation

Abstract In this paper, we introduce a new variant of Location Routing Problem with the name of “Location Routing Problem with Arc Time Windows” (LRP_ATW), which emerges from the need of “safe transportation” in terror zones. In this specific problem, there are “arc time windows” on the arcs (roads) for transferring the vehicles like trucks and articulated lorries which means that these roads can be used for a specific period of time during a day. Within the scope of this paper, the problem and assumptions are described, and a Mixed Integer Programming (MIP) formulation is developed to solve the problem. Bounds are also improved using valid inequalities. The quality of the formulation is measured using the test problems in the literature. Computational results show that the proposed MIP formulation gives good quality results in a short computation time.