Problem statement: Demand considered in most of the classical inventory models is constant, while in most of the practical cases the demand changes with time. In this study model has been framed to study the items whose demand changes with time and deterioration rate increases with time. The effect of permissible delay is also incorporated in this study. The objective of this research is to develop an inventory model for perishable items whose perish-ability rate as well as demand increases with time Approach: Firstly, problem is framed in the form of linear differential equation model and this model had been solved using general solution techniques of linear differential equations. The solution obtained gives the inventory level at any particular time of the cycle period. With the help of this inventory level, total as well as average inventory cost has been obtained. Results:This study developed a model to determine an optimal order quantity by using calculus technique of maxima and minima. Thus it helps retailer to decide its optimal ordering quantity under the constraints of variable deterioration rate and linear pattern of demand. Conclusion: Numerical solution of the suggested model had also been proposed, the above model can be converted into constant demand model, or for items having no deterioration. This study can further be extended for items having some other demand pattern, also time value of money and inflation can be incorporated in this model to make it more realistic and present business environment suited.

This paper attempts to find out whether organizations should follow a push strategy or pull strategy and how their supply chain works. Depending upon the organization, it can be a mix of both the strategies. This study works on factors which provides best decision fit for organizations and their business. It also discusses the advantages and disadvantages both the strategies and how the life cycle of the product helps in determining which strategy to be used. The case of dealing with perishable goods has been considered. This study also proposes about the inventory levels for each strategy.

This paper presents an inventory model for perishable items with constant demand, for which holding cost increases with time, the items considered in the model are deteriorating items with a constant rate of deterioration θ. In the majority of the earlier studies the holding cost has been considered to be constant, which is not true in most of the practical situations as the insurance cost and record keeping costs or even cost of keeping the items in the cold storage increases with time. In this paper the time dependent linear holding cost has been considered, the holding cost for the items increases with time. The approximate optimal solution has been obtained. The results are illustrated with the help of numerical examples.

Problem statement:In most of the earlier inventory models, effect of inflation has been ignored, which is playing pilot role in present environment. In this article, we have proposed an economic order quantity model for deteriorating items having stock dependent demand (whose demand varies with the stock) under the effect of inflation. Approach: Firstly, problem is framed in the form of linear differential equation model and then this model has been solved with general solution technique of linear differential equations. Using the solution the expression for total cost of inventory has been obtained. Results: Using total cost equation an optimal order quantity is obtained and convexity of various costs is also studied. This model helps retailer to decide his economic order quantity for deteriorating items having stock dependent demand. The consideration of effect of inflation makes this model more relevant for present business environment. Conclusion: The convexity of various costs proves the validity of this model. The effect of inflation with two different rates is also studied in tables below considering both constant as well as stock dependent demand. The graph of these tables shows that the optimal inventory cost increases with increase in number of cycles it increases rapidly in starting but becomes stable for large number of cycles. The proposed model can be extended in several ways. For instance, we may generalize the model to allow for shortages, quantity discounts, time value of money, finite replenishment rate, permissible delay in payments and others.

All organizations whether manufacturing or service have to keep inventory for smooth running of their business processes. This study is devoted to the items like medicines, cosmetics which are having a fixed shelf life, i.e. they will be of no use after some prescribed time. This model also considers the permissible delay which means that the buyer can pay for goods after some fixed time and has to pay interest after that fixed time. The demand considered here is fixed constant demand. The lead time varies as per the availability of the product and follows normal distribution.