无界算子 meaning in English

unbounded operator

But all the results were established on the basis that the operator in delay term is bounded . for the condition that the operator is unbounded in delay term which is constant , liu [ 4 ] and guo [ 8 ] have made some research and got some sufficient and necessary conditions
但上述结果都是建立在时滞项所含算子为有界算子的基础上，对于时滞项含无界算子的抽象微分方程对小时滞的鲁棒稳定性，刘康生[ 4 ] ，郭发明[ 8 ]做了一些研究并获得了一些充分必要条件。