in this paper, we introduce intuitionistic fuzzy contraction mappingand prove a fixed point theorem in intuitionistic fuzzy metric spaces.

We introduce and analyse a finite volume method for the discretization of elliptic boundary value problems in R2. The method is based on nonuniform triangulations with piecewise linear nonconforming spaces. We prove optimal order error estimates in the L2–norm and a mesh dependent H1–norm.

In the framework of Sobolev (Bessel potential) spaces Hn(R,R or C), we consider the nonlinear Nemytskij operator sending a function x ∈ R 7→ f(x) into a composite function x ∈ R 7→ G(f(x), x). Assuming sufficient smoothness for G, we give a ”tame” bound on the Hn norm of this composite function in terms of a linear function of the Hn norm of f , with a coefficient depending on G and on the Ha n...

In the framework of Sobolev (Bessel potential) spaces Hn(R,R or C), we consider the nonlinear Nemytskij operator sending a function x ∈ R 7→ f(x) into a composite function x ∈ R 7→ G(f(x), x). Assuming sufficient smoothness for G, we give a ”tame” bound on the Hn norm of this composite function in terms of a linear function of the Hn norm of f , with a coefficient depending on G and on the Ha n...

In the category of operator spaces, that is, subspaces of the bounded linear operators B(H) on a complex Hilbert space H together with the induced matricial operator norm structure, objects are equivalent if they are completely isometric, i.e., if there is a linear isomorphism between the spaces which preserves this matricial norm structure. Since operator algebras, that is, subalgebras of B(H)...

This paper reveals the analytical structure of a fuzzy twoterm (PI/PD) controller which employs N1 (≥3) number of symmetric fuzzy sets for the input variable ‘displacement’, N2 (≥3) number of symmetric fuzzy sets for the input variable ‘velocity’ and N1+N2-1 number of symmetric fuzzy sets for the output variable ‘controller output’. The analytical structures are derived via triangular membershi...

In the framework of Sobolev (Bessel potential) spaces Hn(R,R or C), we consider the nonlinear Nemytskij operator sending a function x ∈ R 7→ f(x) into a composite function x ∈ R 7→ G(f(x), x). Assuming sufficient smoothness for G, we give a ”tame” bound on the Hn norm of this composite function in terms of a linear function of the Hn norm of f , with a coefficient depending on G and on the Ha n...