  Model uncertainties and simulation uncertainties occur in mathematical
modeling of multiscale complex systems, since some mechanisms or scales are not
represented (i.e., "unresolved") due to lack in our understanding of these
mechanisms or limitations in computational power. The impact of these
unresolved scales on the resolved scales needs to be parameterized or taken
into account. A stochastic scheme is devised to take the effects of unresolved
scales into account, in the context of solving nonlinear partial differential
equations. An example is presented to demonstrate this strategy.
