**7. Conclusion**

In this chapter, the applications of regular and homotopy perturbation methods to thermal, fluid flow and dynamic behaviors of engineering systems have been presented. Regular perturbation was used in the first example to developed approximate analytical solutions for thermal behavior of convective-radiative fin with end cooling and thermal contact resistance. In the second example, homotopy perturbation method utilized to study squeezing flow and heat transfer of Casson nanofluid between two parallel plates embedded in a porous medium under the influences of slip, Lorentz force, viscous dissipation and thermal radiation. The same method was used in the third example to analyze the dynamic behavior of piezoelectric nanobeam embedded in linear and nonlinear elastic foundations operating in a thermal-magnetic environment. It is hoped that the vivid presentation and applications of these perturbation methods in this chapter will advance better understanding of methods especially for real world applications.

*A Collection of Papers on Chaos Theory and Its Applications*
