عنوان مقاله [English]
The classical inventory models don’t consider the real-world competitiveness situations, management desire to enhance the system and also economic parameters such as inflation and time value of money. Studies show that management is desiring to invest in system components in order to improve them and gain a compitive advantage over other businesses. Also the value of system financial resources depend on the time that the use and cash flow of different time is not agreegate. due to inflation, prices become volatile and changing constantly. so not considering inflation and time value of money parameters causes obtaining non optimal ordering policy for inventory systems in reality. For this reasons, it is necessary to considering these components for an inventory system. previous researchers have did various researches on the performance of inventory systems at various perspectives. Many of these paper have did not considered consider economic parameters and also production environment. during our studies we found a gap in literature that is related to enhancing the production capacity in inventory systems in an economic structure. The present paper peresent a literature review of time value of money, inflation and investment in inventory systems and then investigates economic production quantity (EPQ) model considering inflation and time value of money in situations that there is the possibility of investment as a decision variable with the aim of increasing production capacity. The goal of model is to find economic production quantity as well as optimal quantity of investment in production capacity so that the total profit function of consistiong of system revenues and costs is optimized. The solving algorithm process is investigated by a numerical example. Sensitivity analysis is carried out by changing various parameters. Finally, we conclude that there is an ascending relationship between npw of total profit function and number of algorithm iteration, grid factor, demand rate, selling price and inflation rate of price and a descending relationship between npw of total profit function and ordering price, purchase price, rate of return and inflation rate of sale. At the end, we propose some possible research problem for future.