报告摘要：We study the exact limits of the global strong solutions of the Cauchy problems for nonlinear nonhomogeneous dissipative partial differential equations arising from $n$-dimensional fluid dynamics. We use surprisingly simple ideas to obtain very general results. The main ingredients and technical tools in the rigorous mathematical analysis of the corresponding linear equations are the Fourier transformation, Plancherel's identity and energy estimates. The results of the nonlinear equations follow from the results of the linear equations, under some mild assumptions on the nonlinearity. The conditions on the model equations are weaker and the results are stronger and broader than before. We hope this method can be applied to study other limit problems.