This paper proves a general existence theorem of optimal growth theory. This theorem is neither restricted to the case of a constant technology progress, nor st
<正>An SIS epidemic model with a simple vaccination is investigated in this article. The efficiency of vaccine, the disease-related death rate and population dy
<正>In this article, the authors consider the existence of a nontrivial solution for the following equation: where q(x) satisfies some conditions. Using a Min-M