Motivated by the problem of estimating the fractal dimension of a strange a
ttractor, we prove weak consistency of U-statistics for stationary ergodic
and mixing sequences when the kernel function is unbounded, extending by th
is earlier results of Aaronson, Burton, Dehling, Gilat, Hill and Weiss. We
apply the obtained results to show consistency of the Takens estimator for
the con-elation dimension.