Search results for "Fuzzy set"

fuzzy approach to the robust facility layout in uncertain production environments

2001

The proposed method approaches the problem of the optimal facility layout using fuzzy theory. The optimal layout is a robust layout that minimizes the total material handling cost, when the product market demands are uncertain variables, which are defined as fuzzy numbers. Since each department has a limited production capacity, not all possible combinations, deriving from each product's market demand, are taken into account because some combination could exceed the overall department's productivity. Therefore, the optimal solution results by solving a 'constrained' fuzzy optimization problem, in which the fuzzy material handling costs corresponding to the layouts are evaluated, and a ranki…

A Fuzzy Discrete Event Simulator for Fuzzy Production Environment Analysis

1998

Abstract Discrete Event Simulation is a powerful tool to help production managers in planning manufacturing systems. The necessity to rapid react to market conditions is pushing production planners to process requirements and information affected by vagueness. Vagueness is related with event definition, therefore it is not manageable through statistical tools, but more properly by using fuzzy mathematics. Production situations where uncertainty takes body in term of vagueness are referred as Fuzzy Production Environments. Classical Discrete Event simulators are not suitable to deal with fuzzy variables, therefore they cannot be used to model Fuzzy Production Environments. This paper aims to…

A fuzzy-logic-based controller for methane production in anaerobic fixed-film reactors

2017

The main objective of this work was to develop a controller for biogas production in continuous anaerobic fixed-bed reactors, which used effluent total volatile fatty acids (VFA) concentration as control input in order to prevent process acidification at closed loop. To this aim, a fuzzy-logic-based control system was developed, tuned and validated in an anaerobic fixed-bed reactor at pilot scale that treated industrial winery wastewater. The proposed controller varied the flow rate of wastewater entering the system as a function of the gaseous outflow rate of methane and VFA concentration. Simulation results show that the proposed controller is capable to achieve great process stability ev…

Decision making in energy planning: The electre multicriteria analysis approach compared to a fuzzy-sets methodology

1998

Every planning activity generally requires to make some choices. After a preliminary analysis of the sector under examination, a forecast of trends of input-output items, the planner must define an action plan voted to arrange all the strategies and specific interventions able to fit demand and supply during the planned time. The redaction of an action plan implies a strong effort in order to synthesize either suggestions coming from the analysis phases either all the constraints linked to technical choices. In the same time, a large number of "external" variables plays a role in orienting decision making. Some of these can be handled by numerical models (economic cost-benefit analyses, mar…

FUZZY RISK ANALYSIS OF A MODERN γ-RAY INDUSTRIAL IRRADIATOR

2011

Fuzzy fault tree analyses were used to investigate accident scenarios that involve radiological exposure to operators working in industrial γ-ray irradiation facilities. The HEART method, a first generation human reliability analysis method, was used to evaluate the probability of adverse human error in these analyses. This technique was modified on the basis of fuzzy set theory to more directly take into account the uncertainties in the error-promoting factors on which the methodology is based. Moreover, with regard to some identified accident scenarios, fuzzy radiological exposure risk, expressed in terms of potential annual death, was evaluated. The calculated fuzzy risks for the examine…

TREEZZY2, a Fuzzy Logic Computer Code for Fault Tree and Event Tree Analyses

2004

In conventional approach to reliability analysis using logical trees methodologies, uncertainties in system components or basic events failure probabilities are approached by assuming probability distribution functions. However, data are often insufficient for statistical estimation, and therefore it is required to resort to approximate estimations. Moreover, complicate calculations are needed to propagate uncertainties up to the final results. In our work, in order to take account of the uncertainties in system failure probabilities, the methodology based on fuzzy sets theory is used both in fault tree and event tree analyses. This paper just presents our work in this issue, which resulted…

Varieties of Vagueness, Fuzziness and a few foundational (and ontological) questions

2011

In this paper we discuss the multifaceted nature of vagueness, the limits of (standard) set theory in dealing with the foundational aspects that a really innovating theory of vagueness should manifest, and the difficul- ties in outlining the possible features that such a type of new formalism should exhibit in order to be able to deal with such innovative aspects. We shall highlight some aspects of the role that Fuzzy Set Theory (FST) can play in this process.

FUZZINESS: the emergence of a new scientific concept

2011

Kazem Sadegh-Zadeh's lifework on philosophy of medicine

2013

Specificities and Vagaries of Medicine from the Viewpoint of Hard Sciences

2013

Among many other beautiful reflections on the ontology of medicine, in his Handbook of Analytic Philosophy of Medicine, Sadegh Zadeh promotes Fuzzy Sets Theory among the basic instruments of logic for medical understanding, highlights the importance of vagueness in the medical language and as an intrinsic property of medical epistemology, and invokes the clear advantages of a medical fuzzy taxonomy to overcome the binary concept of being healthy/ill. We briefly discuss these aspects, relating them to the peculiarity of Fuzziness as the only purely scientific notion among the foundational tools needed to define an analytic philosophy of medicine more concerned with an explicatum of the notio…