Before revision:  In the field of UQ, the{\em   generalized Polynomial Chaos (gPC) method is widely popular and yields excellent approximations of the map and its moment .
After revision:  In the field of UQ, the{\em of the quantity of interest, there is a developed body of research. One widely popular approach is generalized Polynomial Chaos (gPC) method is widely popular and yields excellent approximations of the map and its moment .