Fuzzy set theory

The purpose of the study is to develop and test an analytical model for resilience assessment of supply chain risks against the risks of system and its individual tiers. In this regard a multi-method research approach is adopted as follows: By using data envelopment analysis (DEA) and fuzzy set theory, a fuzzy network DEA model has been proposed to assess risk in overall supply chains and their individual tiers. The proposed model is tested by surveying of 130 people as selective petrochemical companies in Iran. The survey results show a substantial variation in resilience ratings between the overall petrochemical supply chains and their individual tiers. The research findings indicate that system resilience is not necessarily indicative of the resilience of its individual tiers. On the other hand, high efficiency scores in supply chain tiers have limited influence on overall resilience of supply chain. The proposed analytical model enables the assessment of supply chain flexibility at different levels for a wide range of supply chain risks in upstream, downstream and downstream process-es.

In last decades, the skillful planning of land resources has become a major issue for rural development. The development of cultivated areas becomes gradually impossible due to ever increasing population growth and urban development. Fuzzy logic is preferred to Boolean logic for land evaluation, because fuzzy techniques lead to estimate for land use suitability on a continuous scale and can therefore, be more informative than the Boolean technique. The objective of this study is to apply fuzzy set methodology in the context of a decision making process known as the Analytic Hierarchy Process (AHP) to land evaluation for irrigated wheat. The results revealed that the results obtained with fuzzy AHP method are in better agreement (R2=0.911) with the observed yield as compared to those obtained with parametric method (R2=0.804). Although, the fuzzy AHP provided more efficient and accurate results than parametric method, the choice of membership functions, width of the transition zones and weight values are determinant to achieve its realistic results in land suitability assessment.