Several notions ofconvergencefor subsets of metric space appear in the literature. In this paper, we defineWijsman  -convergenceandWijsman  -convergencefor sequences of sets and establish some basic theorems. Furthermore, we introduce the concepts ofWijsman  I-Cauchysequence andWijsman  -Cauchysequence and then study their certain properties.

In this paper, we introduce and study the notion of rough -lacunary statistical convergence of double sequences in normed linear spaces. We also introduce the notion of rough -lacunary statistical limit set of a double sequence and discuss some properties of this set.

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We consider Ulisse Dini-type helicoidal hypersurfaces with timelike axis in Minkowski 4-space E 1 4 . Calculating the Gaussian and the mean curvatures of the hypersurfaces, we demonstrate some special symmetries for the curvatures when they are flat and minimal.

This paper presents the notion of ( )-asymptotically statistical equivalence, which is a natural combination of asymptoticequivalence, and -statistical equivalence for sequences of sets. We find its relations to -asymptotically statistical convergence, strong -asymptotically equivalence, and strong Cesaro -asymptotically equivalence for sequences of sets.