In this technical note we discuss a paper of Chung and Lin  recently published in Computers and Operations Research. They established the model for deteriorating items with constant demand, equal replenishment cycles while taking account of time discounting. In this paper, we extend their inventory lot-size model to allow for a general continuous time-varying demand (which is more general than constant, increasing and decreasing demand patterns). The purposes of this article are two-fold: (1) To inform readers that optimal solutions for a more general model exist. (2) To show that under the assumptions of the Chung and Lin , the optimal solution is independent of the form of the demand rate. We have also shown that it gives the global minimum. Finally, a numerical example and its sensitivity analysis for parameters are provided to assess the solution procedure.
International Journal of Information and Management Sciences 13(4), pp.55-67