This article is concerned with the initial-boundary value problem for a equation of quasi-hyperbolic type with logarithmic nonlinearity. By applying the Galerkin method and logarithmic Sobolev inequality, we prove the existence of global weak solutions for this problem. In addition, by means of the concavity analysis, we discuss the nonexistence of global solutions in the unstable set and give the lifespan estimation of solutions.

In this paper, we study the initial boundary value problem for a class of higher-order nonlinear pseudo-parabolic equations with a memory term. First, the blow-up results of the solution when the initial energy is negative or positive are obtained by using concavity analysis, and an upper bound on the blow-up time $T^{\ast }$ is given. Second, a lower bound on the blow-up time $T^{\ast }$ is obtained by applying differential inequalities when the solutions blow up.

This paper investigated the blow-up properties of solutions to the initial value problem for a fourth-order nonlinear parabolic equation with an exponential source term. By using an improved concavity method, we obtained upper and lower bound estimates for the blow-up time of the solution.