Quasi birth and death(QBD) models of two kinds of reentrant lines are developed with two stations and four buffers for cases where all but the first buffer capacities are assumed to be finite.

• 考虑可重入生产系统除第一个外均为有限缓冲区的情形 ；建立了两种两站四缓冲区的拟生灭过程 ( QBD)型模型 .