“…Despite the enormous interest, the first-passage problem is still a challenging problem in stochastic theory, and analytical solutions are limited even for one-dimensional case. Many useful methods, such as Monte Carlo (MC) simulation, finite element method (Bergman and Heinrich, 1982), generalized cell mapping method (Han et al, 2015; Sun and Hsu, 1990), and other methods (Xu et al, 2017), have been developed so far for solving the first-passage problem. However, for a multi-degree-of-freedom system, the associated backward Kolmogorov equation (BKE), which normally governs the reliability function of a random system, is often a high-dimensional partial differential equation which is usually very difficult to be solved.…”