L. Plaskota, K. Ritter, and G.W. Wasilkowski
Optimal designs for weighted approximation and integration of
stochastic processes on $[0,\infty)$.
Abstract.  
We study minimal errors and optimal designs for weighted
$L_2$-approximation and weighted integration of Gaussian
stochastic processes $X$ defined on the half-line $[0,\infty)$.
Under some regularity conditions, we obtain sharp bounds
for the minimal errors for approximation and upper bounds for
the minimal errors for integration. The upper bounds are proven
constructively for approximation and non-constructively for
integration. For integration of the $r$-fold integrated Brownian
motion, the upper bound is proven constructively and we have
a matching lower bound.