“…The approach is based on converting the underlying differential equations into an integral equation through integration, approximating various signals involved in the equation by truncated orthogonal series, and using the operational matrix of integration P to eliminate the integral operations. Typical examples are the Walsh functions [1], block-pulse functions [2], Legendre polynomials [3], Chebyshev polynomials [4], Fourier series [5], Haar series [6] and Hartley series [7]. The utilization of these series have the common objective of representing models efficiently and calculating intermediate parameters rapidly for the given problem.…”