Germashev I.V., Derbisher E.V., Derbisher V.E., Kulikova N.Yu. Convergence of Series of Fuzzy Numbers With Unimodal Membership Function

https://doi.org/10.15688/mpcm.jvolsu.2018.1.2

Ilya Vasilyevich  Germashev
Doctor of Technical Sciences,
Professor, Department of Mathematical Analysis and Function Theory,
Volgograd State University
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Prosp. Universitetsky, 100, 400062 Volgograd, Russian Federation

Evgeniya  Vyacheslavovna  Derbisher
Candidate of Technical Sciences,
Associate Professor, Department of Analytical, Physical Chemistry and Physico-Chemistry of Polymers,
Volgograd State Technical University
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Prosp. Lenina, 28, 400005 Volgograd, Russian Federation

Vyacheslav  Evgenyevich  Derbisher
Doctor of Chemical Sciences, Professor, Department of High-Molecular
and Fibrous Materials Technology,
Volgograd State Technical University
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Prosp. Lenina, 28, 400005 Volgograd, Russian Federation

Natalya Yuryevna Kulikova
Candidate of Pedagogical Sciences, Associate Professor, Department of Computer Science and Methods
of Computer Studies Teaching,
Volgograd State Social-Pedagogical University
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Prosp. Lenina, 27, 400005 Volgograd, Russian Federation

Abstract. Solving the applied problems by the methods of fuzzy mathematics frequently generates the need to conduct operations on fuzzy numbers. The calculation of such expressions requires quite complex manipulations and a serious effort. For example, addition and subtraction formulae  can  be  obtained  by  L-R  fuzzy  numbers,  but  this  approach  enables  to  calculate multiplication and division only approximately. t-norms and interval mathematics are used to implement the arithmetics of trapezoidal numbers. We present fuzzy numbers with unimodal membership functions that can be used for fuzzy analysis in such subject fields as ecology and chemical technology. Some knowledge of behavior of these series enable us to analyze such mathematical models more effectively. The associativity of addition enables to analyze number series  effectively.  The  problem  of  convergence  of  series  of  fuzzy  numbers  with  unimodal membership  function is  considered.  The formulae  for  calculating  arithmetic operations  on sequences of fuzzy numbers are obtained. We generalize the addition formula for sequences of fuzzy numbers. We investigate convergence of series of fuzzy numbers. The conditions for divergence of a series are given. It is shown that calculations with large amount of data may cause an indefinite result. The reason of this lies in the fact that a membership function of a sum of the series is identically equal to unit. This means the complete indefiniteness of the result and enables to make a conclusion about divergence of the series. The obtained results for evaluation of the arithmetic operations enable to use fuzzy analysis for investigation of complex systems in, for instance, ecology and chemical technology. The proposed approach is quite general and can be used for rather  large class of  studies using the methods of fuzzy analysis. In this case it makes sense to limit the length of sequences of fuzzy numbers on the compromise of calculation accuracy and indefiniteness of the result.

Key words: fuzzy numbers, arithmetical operations, associativity, series of fuzzy numbers, convergence  of  a  series.

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Convergence of Series of Fuzzy Numbers With Unimodal Membership Function by Germashev  I.V., Derbisher E.V., Derbisher V.E., Kulikova  N.Yu. is licensed under a Creative Commons Attribution 4.0 International License.

Citation in English: Mathematical Physics and Computer Simulation. Vol. 21 No. 1 2018, pp. 11-17

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