In this paper, we discuss the approximation operators [...] apr¯NS and [...] apr¯S which are based on NS(U) and S. We not only obtain some properties of NS(U) and S, but also give examples to show some special properties. We also study sufficient and necessary conditions when they become closure operators. In addition, we give general and topological characterizations of the covering for two types of covering-based upper approximation operators being closure operators.
In this paper, we investigate a class of higher order neutral functional differential equations, and obtain some new oscillatory criteria of solutions.
By substituting the classical lattice operator min of the unit real interval with a triangular norm of Schweizer and Sklar, the usual fuzzy relational equations theory of Sanchez can be generalized to wider theory of fuzzy equations. Considering a remarkable class of triangular norms, for such type of equations defined on finite sets, we characterize the upper an lower solutions.
We also characterize the solutions posessing a minimal fuzziness measure of Yager valued with respect to...
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