Inventory Model for an Inventory System with Time-varing Demand Rate

The standard inventory problems of multi-period have been modeled under different situations, namely we consider whether demand subjects to a continuous distribution or a discrete distribution and whether demand of each period is unchanged or not. A method to get an economic order quantity in inventory systems with discrete and unchanged demand was presented in former paper and this method has been generalized to an inventory model with a varying continuous demand. However it is not achieved because there are many cases in general situations. In this article the method as above is discussed in the case discrete demand is decreasing or increasing from period to period. A theoretical method is presented by using former results and some examples are given which suggests the concept how to handle our inventory system. An algorithm to make the decision is also presented under some conditions and examples are shown by a computer soft Mathematica in order to explain it. In general case we view the optimal policy in the inventory problem of a few periods.