On Oscillation For Several Classes Nonlinear Second-order Differential Equations

The dissertation is divided into four sections according to the content.In Chapter 1, we introduce the main problems of this dissertation.In Chapter 2, we study the oscillation of the second-order nonlinear differ-ential equation By employing a generalized Riccati transformation and integral average method, we obtain several new oscillation criteria which extend and improve the main results of Zhao and Meng.In Chapter 3, we study the oscillation of the second-order nonlinear damped differential equation By using a generalized Riccati transformation and integral average method, we get several new oscillation criteria which extend and improve the results of Ro-govdleuko.In Chapter 4, we study the oscillation of second order nonlinear differential equations with perturbation We establish several new oscillation theorems for equation (4.1.1) by using gen-eralized Riccati transformation, integral average method and a function family Y.Interesting examples are also provided to illustrate our results in the last three chapters, respectively.