Ergün Eraslan

A multi‐criteria approach for determination of investment regions: Turkish case

Purpose – The major aim of this research is to determine the socio‐economic level of geographical investment regions through fuzzy multi‐criteria decision‐making (MCDM) method. The results obtained from this method are analyzed and compared with the current system and the differences are interpreted.Design/methodology/approach – A user friendly MCDM method, the fuzzy TOPSIS, was selected and ten independent criteria out of 53 were used, that have been evaluated by reduction according to the correlations among them. Therefore, the rankings of the 26 geographical investment regions of Turkey were calculated based on their criteria.Findings – The examinations of the rankings have shown that only four regions had similar rankings but the rankings of the remaining 22 regions differed according to the authority rankings. Furthermore, significant differences have been observed for eight regions.Social implications – In globalization process, certain issues are of particular importance in shaping the resource all...

Development of a component-based machining centre selection model using AHP

Machining centres are widely used in manufacturing companies all over the world. Since investments in machining centres are long-term and expensive, selection of the most appropriate machining centre is an important decision for manufacturing companies. There has been considerable effort spent in developing crisp and fuzzy multi-criteria decision-making (MCDM) models that use technical specifications provided by machining-centre manufacturers such as, axis size, power, spindle speed, tolerance, repeatability, cutting-tool change time, and number of cutting tools along with other economical and commercial factors. However, the technical specifications are directly taken from machining-centre manufacturers’ catalogues without checking their correctness, adequacies, or ability to represent the areas that are used for measurement. In such a case, one cannot be sure whether the outcomes are sound or not without a detailed check of the technical specifications, which can only be performed after actual usage of the machine itself. To overcome all such problems, an analytic hierarchy process (AHP) model that evaluates the machining centre components is developed in this paper. The new component-based AHP model is then compared with two MCDM models that use only technical specification values.

Usability ranking of intercity bus passenger seats using fuzzy axiomatic design theory

Usability, considering user satisfaction along with the user performance, is one of the key factors in determining the success of a product in today’s competitive market. Designing usable intercity bus seats is important for passengers during the long hours of traveling. Comfort, aesthetic, safety, convenience to the body posture, durability, harmoniousness with the seat accessories and operability are expected usability dimensions of seats for both user and the designers. Aim of this study is to identify and rank ten alternative seats of an intercity bus manufacturing company according to these usability attributes. The products are evaluated by five subjects and assessed for each usability attributes by using linguistic variables. Then Fuzzy Axiomatic Design Theory (FADT), which is the combination of second axiom, is used as a multi attribute decision making tool to determine most usable seat design solution. Design range is defined by design engineers and system ranges for seats are obtained from linguistic assessment of five subjects for applying conformance testing in cooperative engineering.

Fuzzy multi-criteria analysis approach for the evaluation and classification of cognitive performance factors in flexible manufacturing systems

Being affected from high technology, modern manufacturing systems have become more complex which means that performance factors of both individuals and manufacturing systems have become more critical due to the overloading of cognitive and decision-making tasks. In addition to this development, the classical performance measurement systems are insufficient to measure cognitive performance and the new measurement systems are needed. But converting the abstract factors of cognition to quantitative models is very difficult and complicated. In this paper, developing quantitative models for determination of cognitive performance factors is studied using the combination of cognitive mapping technique and the analytical hierarchy process in fuzzy theory to identify these factors, express and classify them quantitatively. The pairwise comparison matrices are constructed from cognitive maps, converted to fuzzy numbers using a scale, and the subjectiveness of decision-makers is prevented. Also, more accurate weights are obtained and the monitoring levels of performance factors are suggested. An example in Flexible Manufacturing Systems is provided throughout the paper in order to explain the concepts and discussion.

A Comparative Holistic Fuzzy Approach for Evaluation of the Chain Performance of Suppliers

The competition between the companies in the dynamic market conditions has made the Supply Chain Management (SCM) a more important issue. The companies which have organized their supply chain effectively have obtained more flexibility in their manufacturing processes in addition to delivery of the customer demands. In this study, two different multicriteria decision making algorithms composed of the FAHP and a holistic hybrid method using FTOPSIS were utilized for an electronic company in wholly fuzzy processes. The FAHP is used for determination of the global weights of the factors and the performances of alternative suppliers are evaluated by using both FAHP-based and FAHP-FTOPSIS hybrid methods for synthetic extent values of pairwise comparisons. The sequences of the suppliers differed for the algorithms. The performances of the proposed approaches are quite successful and flexible in a narrow interval. The managerial advantages obtained from the proposed fuzzy algorithms are also analyzed and interpreted.

Daily newspaper distribution planning with integer programming: an application in Turkey

Abstract This paper concerns the newspaper distribution problem. It addresses the transportation of newspapers from printing plant to newsagents with distribution vehicles under various particular constraints. The objective is to minimize the distance traveled by the vehicles and/or the number of vehicles. In this study, the routes for vehicles of a leading newspaper distributor company in the Turkish press sector are examined. The problem is defined as determining optimal delivery routes for a fleet of homogeneous vehicles, starting and ending at the printing plant that is required to serve a number of geographically dispersed newsagents with known demands under capacity and time constraints, while minimizing the total distribution cost. An integar linear programming model is proposed as a solution using Cplex. Computational results demonstrate that the proposed model is fast and able to find optimal solutions for problem scenarios with up to 55 newsagents within reasonable computing times. It was found that the proposed model reduced the delivery cost by 21% on average when compared to the current manual method. The results show that this model is adequate for medium-sized distribution problems.

The Efficiency of Variance Reduction in Manufacturing and Service Systems: The Comparison of the Control Variates and Stratified Sampling

There has been a great interest in the use of variance reduction techniques (VRTs) in simulation output analysis for the purpose of improving accuracy when the performance measurements of complex production and service systems are estimated. Therefore, a simulation output analysis to improve the accuracy and reliability of the output is required. The performance measurements are required to have a narrow and strong confidence interval. For a given confidence level, a smaller confidence interval is supposed to be better than the larger one. The wide of confidence interval, determined by the half length, will depend on the variance. Generally, increased replication of the simulation model appears to have been the easiest way to reduce variance but this increases the simulation costs in complex-structured and large-sized manufacturing and service systems. Thus, VRTs are used in experiments to avoid computational cost of decision-making processes for more precise results. In this study, the effect of Control Variates (CVs) and Stratified Sampling (SS) techniques in reducing variance of the performance measurements of M/M/1 and GI/G/1 queue models is investigated considering four probability distributions utilizing randomly generated parameters for arrival and service processes.

A New Approach for Wage Management System Using Fuzzy Brackets in Industry

Job evaluation is used to determine the relative importance of each job in a company in order to structure an accurate wage management system. Job evaluation can be also defined as a multicriteria decision-making problem. However, according to the diversity of managers’ assessment, the evaluation processes are often resulting in pay inequity. This outcome can be circumvented by utilizing a fuzzy job evaluation system. In this study, one of the more robust multicriteria decision-making methods, Fuzzy Analytic Hierarchy Process (FAHP), is performed in job evaluation system in order to rank predetermined 13 criteria. The fuzzy wage brackets are developed and inserted into the process which is obtained from the results of mathematical model to designate the bounds for predefined 86 jobs. Eventually an accurate payment system is proposed for a company in steel industry by using Fuzzy Regression Analysis (FRA).

The impact of automation and FMS in flight safety: results of a survey and an experimental study

The main aim in the adoption of automation technologies of airplanes is to decrease the errors due to human factors whereas some applications and empirical researches showed that automation causes new type of errors in the cockpit. When the aviation accidents due to automation have been surveyed, it is seen that the automation errors related to FMS (Flight Management System) are very high. The FMS supports pilots in different tasks like flight planning, navigation, performance management and monitoring of flight progress. In this study, the effect of automation and FMS in flight safety is researched. A survey was conducted to a group of pilots of a turboprop airplane with high level automation. Following the survey, an experimental study was performed to analyze effects of last minute changes on FMS which was highlighted as the most prominent problem in the survey. Finally, based on the results of experiment, recommendations were given so as to improve design and usability of FMS.