Yucel Ozturkoglu

A memetic algorithm with a variable block insertion heuristic for single machine total weighted tardiness problem with sequence dependent setup times

In this paper, a memetic algorithm with a variable block insertion heuristic is presented to solve the single machine total weighted tardiness problem with sequence dependent setup times. Together with the traditional insertion neighborhood structure, the memetic algorithm is combined with a variable block insertion heuristic in which a block of jobs are removed from a sequence and then inserted into all possible positions of the partial sequence. For this purpose, we devise a variable neighborhood descent algorithm to incorporate different block insertion heuristics having different block sizes. We also employ a simulated annealing type of acceptance criterion to diversify the population. To evaluate its performance, the memetic algorithm is tested on a set of benchmark instances from the literature. The analyses of experimental results have shown highly effective performance of the memetic algorithm against the best performing algorithms from the literature. The proposed memetic algorithm was able to find 98 out 120 optimal solutions within reasonable CPU times.

Green Supply Chain Management Practices' Effect on the Performance of Turkish Business Relationships

This paper provides a first-hand understanding about the procedures taken by Turkish business firms and their logistics providers and supply chain business firms to operate in an environmentally friendly supply chain. The main point of the study is to examine the influence of both external and internal parties on green supply chain management (GSCM) practices in business firms. The result of this research is very important to promote performance of Turkish business relations in their green perspectives. In order to find the correct answers, comprehensive questionnaire forms were designed. We collected data from 2014 May to 2015 July through Turkish companies. More than 180 companies contributed in this extensive research. Then the derived data were analyzed using statistical methods. One of the important inferred results is that the third party logistics service providers influence firms to have a proactive green behavior.

A mathematical model and optimization of total production cost and quality for a deteriorating production process

Abstract Proper production planning can considerably improve a producer’s competitiveness in delivering low-cost products with high quality and short-cycle time. In a deterioration process, the quality may change during a production run, leading to early product failures. To mitigate the impact of deterioration such as process shifting, the optimal resetting cycle before the next setup must be determined, as well as the initial settings at the beginning of a production run. The aim of this study is to propose a mathematical model that consists of a new quality loss function and adds maintenance costs to the ordering and inventory holding costs commonly considered in the classical model. The model is applied to a real-world case study to demonstrate the effect of initial settings of the mean quality characteristic. The results demonstrate the superiority of the proposed approach in terms of total production cost, as compared with the economic production quantity model.

Testing the Effects of Agile and Flexible Supply Chain on the Firm Performance Through SEM

High competition, continuous, and rapid changing in consumer demands push companies finding differentiation ways to gain competitive advantage. Supply chain and logistics practices have been seen as the core strategic tools to survive for companies. In this research, the impacts of agile and flexible supply chain practices on the customer satisfaction, service quality, sales performance, and profitability are examined. As a research area, fast fashion industry was chosen. To the aim, a theoretical model was developed and tested through structural equation modeling (SEM). The results reveal that companies performing agile and flexible supply chains can reap the benefits in terms of service quality and customer satisfaction, and at the end can reap the resulting financial benefits in terms of increased sales and profits.

Variable block insertion heuristic for the quadratic assignment problem

The aim of this paper is to apply the variable block insertion heuristic (VBIH) algorithm recently proposed in the literature for solving the quadratic assignment problem (QAP). The VBIH algorithm is concerned with making block moves in a given solution. As a local search in this paper, the VNST is employed from the literature to be applied to a solution obtained after several block moves. Besides the single-solution based VBIH, we also propose a populated VBIH (PVBIH) in this paper. The proposed algorithms were evaluated on quadratic assignment problem instances arising from real life problems as well as on a number of benchmark instances from the QAPLIB. The computational results show that the proposed algorithms are very effective in solving both types of instances. All PCB instances are further improved.

City logistics: problems and recovery proposals

The city logistics is the multidisciplinary science that makes a bridge between both urban freight transportation and sustainability of the cities. It has also focused on various subject matters such as populations, facilities, traffics and logistics activities. If all this dynamic criteria consider, different logistics scheme must be prepared for each city. Cities have to be handled and analysed individually according to their own characteristics. In order to understand the current situation and problems of urban freight transport in Turkey, this paper examines the specific focus on Turkeys third largest city Izmir in terms of city logistics with the eye of logistics service providers. A qualitative approach was used and unstructured interviews with subject matter experts were conducted to gain general insight into how logistics service providers perceive the problems in city logistics in Izmir and the solutions they propose. Regarding the gap between theory and practice, this study would be valuable for future research in city logistics studies, and the results of the study would be a practical tool for decision makers in their city logistics planning process.

End Users' Perceptions of Critical Success Factors in ERP Applications

Today’s competitive world is given the critical role of enterprise resource planning (ERP) for coordinatingtheworkflowincompaniesfromdifferentindustries.Toprovidevaluableinsightsinto ERP,identifyingthecriticalfactorsarethemostimportantissueinachievingqualityandsuccess. Bothinliteratureandpractice,therearequiteafewofsuccessfactorsforERPapplications.Oneof thepurposesofthispaperistoempiricallyclassifythemostimportantcriticalfactorsreferredby scholarsinpreviousstudies.Anotherpurposeistodeterminethecriticalsuccessfactorsinthelight ofend-userperceptions.Inthisrespect,exploratoryfactoranalysiswasconductedtodeterminethe factorialstructureofthescale.Datawascollected128ERPend-usersfromdifferentdepartmentsof companiesinmanufacturingindustry.Theresultsoftheanalysisprovidedasix-dimensionalstructure forcriticalsuccessfactors(CSFs)inqualityandsuccessfulERPapplications. KEywoRdS Critical Success Factors, End-Users, ERP Applications, Manufacturing Industry