Stock-dependent Demand Research Articles

An Inventory Model for Maximum Life Time Products under the Price and Stock Dependent Demand Rate

An Inventory Model for Maximum Life Time Products under the Price and Stock Dependent Demand Rate

A waiting time deterministic inventory model for perishable items in stock and time dependent demand

This paper presents a deterministic inventory model for perishable items when the demand has been considered to be stock and time dependent. Shortages are allowed and are partially backlogged for the model. The deterioration rate has been considered here to be constant. The objective is to determine the optimal ordering policy by finding the optimal length of the inventory interval with positive inventory and the optimal length of order cycle for minimizing the cost. The model is solved analytically and graphically by minimizing the total inventory cost. The result is illustrated with the help of numerical example of the model. Sensitivity analysis is performed to show the effect of changes in the parameters on the optimum solution. The analysis of the model shows that the solution of the model is quite stable and can be applied for optimizing the total inventory cost of perishable items in inventory for the business enterprises.

A production-inventory model with permissible delay incorporating learning effect in random planning horizon using genetic algorithm

This paper presents a production-inventory model for deteriorating items with stock-dependent demand under inflation in a random planning horizon. The supplier offers the retailer fully permissible delay in payment. It is assumed that the time horizon of the business period is random in nature and follows exponential distribution with a known mean. Here learning effect is also introduced for the production cost and setup cost. The model is formulated as profit maximization problem with respect to the retailer and solved with the help of genetic algorithm (GA) and PSO. Moreover, the convergence of two methods—GA and PSO—is studied against generation numbers and it is seen that GA converges rapidly than PSO. The optimum results from methods are compared both numerically and graphically. It is observed that the performance of GA is marginally better than PSO. We have provided some numerical examples and some sensitivity analyses to illustrate the model.

주문량 종속 신용거래 하에서 재고 종속형 제품수요를 갖는 퇴화성제품의 공급체인 재고모형

본 연구는 공급자(supplier), 중간공급자(distributor) 그리고 고객(customer)으로 구성된 2 단계 공급사슬에서 퇴화성 제품(deteriorating products)에 대한 중간공급자의 재고모형을 분석하였다. 문제 분석을 위해 공급자는 중간공급자의 수요 증대를 목적으로 중간공급자의 주문 크기에 따라 차별적으로 외상 기간을 허용하고, 최종 고객의 수요는 중간공급자의 재고 수준에 따라 선형적(linearly)으로 증가한다는 가정 하에 모형을 분석하였다. 중간공급자의 이익을 최대화하는 경제적 주문량 결정 방법을 제시하였고, 예제를 통하여 그 해법의 타당성을 보였으며, 민감도 분석을 통하여 퇴화율이 재고정책에 미치는 영향을 분석하였다.

Multi-item integrated supply chain model for deteriorating items with stock dependent demand under fuzzy random and bifuzzy environments

In this paper, we have investigated multi-item integrated production-inventory models of supplier and retailer with a constant rate of deterioration under stock dependent demand. Here we have considered supplier’s production cost as nonlinear function depending on production rate, retailers procurement cost exponentially depends on the credit period and suppliers transportation cost as a non-linear function of the amount of quantity purchased by the retailer. The models are optimized to get the value of the credit periods and total time of the supply chain cycle under the space and budget constraints. The models are also formulated under fuzzy random and bifuzzy environments. The ordering cost, procurement cost, selling price of retailer’s and holding costs, production cost, transportation cost, setup cost of the supplier’s and the total storage area and budget are taken in imprecise environments. To show the validity of the proposed models, few sensitivity analyses are also presented under the different rate of deterioration. The models are also discussed in non deteriorating items as a special case of the deteriorating items. The deterministic optimization models are formulated for minimizing the entire monetary value of the supply chain and solved using genetic algorithm (GA). A case study has been performed to illustrate those models numerically.

A Multi-Item Inventory Model for Deteriorating Items in Limited Storage Space with Stock-Dependent Demand

SYNOPTIC ABSTRACTThis article describes a multi-item inventory model, in which the available floor space or storage space is limited. The demand of items are assumed to be stock dependent and deterioration of items is assumed to be constant over time. The model is solved analytically in order to obtain the optimal solution of the problem. It is then illustrated with the help of numerical examples.

A vendor–buyer JELS model with stock-dependent demand and consigned inventory under buyer’s space constraint

In this article, we consider a single-vendor single-buyer supply chain model in which the vendor produces a single product at a constant rate and delivers to the buyer following a consignment stock policy. The customers’ demand is assumed to be dependent on the on-hand stock displayed at the buyer. An integrated vendor–buyer model is developed and solved for optimal delivery batch size and number of shipments, aiming at minimizing the average cost of the system. The model is further generalized considering the space limitation at the buyer’s end. As coordination mechanism, a contract which distributes the total cost between the vendor and the buyer in an arbitrary ratio is suggested. The proposed model is numerically illustrated and the effects of the buyer’s space constraint on the optimal number of shipments, delivery batch size and overall cost are studied. The outcome of the proposed model is also compared with that of the model under lot-for-lot policy to conclude which of the policies should be preferred to the other and under what conditions.

Supply chain model with stock dependent demand, quadratic rate of deterioration with allowable shortage

The goal of this devotion of time and attention to acquiring knowledge is to develop assist calculations and prediction for supply chain (three echelons), in which an optimal ordering decision for the manufacturer–supplier–retailer chain is developed when the supplier's lead–time is considered. This paper examines deterministic inventory model with variable deterioration and stock dependent demand, where the unsatisfied demand is partially backlogged which depends on waiting time. A solution procedure is presented to determine a stock dependent demand, variable deterioration rate, shortage period and the demand during the shortage is partially backlogged which is dependent on the waiting time such that the difference between an initial outlay and the subsequent amount earned for the supply chain is maximised. Sensitivity analyses are given to illustrate the model with the help of profit maximum principle.

Inventory model with stock dependent demand and different holding cost functions

This study develops inventory models in which demand rate is stock level dependent and three different holding cost functions: 1) constant holding cost; 2) exponential time dependent; 3) stock level dependent. Mathematical models have been developed for these three different situations to determine optimal order quantities, cycle time and optimal total inventory cost. Truncated Taylor's series expansion is used for exponential terms for finding closed form numerical solutions. The results are illustrated with the help of numerical examples. The sensitivity analysis of the optimal solution with respect to the variation of the parameters of the model is also discussed.

Fuzzy rough supply chain model under inflation and credit period with stock dependent consumption rate and partial backlogging shortages via genetic algorithm

In many inventory situations, purchasers are allowed a period to pay back for the goods bought without paying any interest. Depending on the length of that payment period, the purchaser can earn interest on the sales of the inventory. This paper develops a model to determine an optimal ordering policy for deteriorating items under inflation, stock dependent demand, permissible delay of payment, allowable shortage and unfinished demand is partially backlogged in fuzzy rough environments. The present value of total cost incurred in this inventory system is developed first, then an optimal order quantity and maximum allowable shortage are obtained by using a search procedure. The effect of inflation and time value of money was investigated under given sets of inflation and discount rates. This study shows that the optimal order quantity and maximum allowable shortage vary with the difference between inflation and time discount. Computational results provide some interesting policy implications. The genetic algorithm GA is used to make decision for above inventory model. The model is illustrated with some numerical data.

Optimal Production Planning for Manufacturing Systems with Instantaneous Stock-Dependent Demand and Imperfect Yields

We consider an EPL model like manufacturing system in presence of production imperfectness and stock-demand dependence simultaneously. During the production process, the system can evolve from in-control state into out-of-control state at any random time, after which the defective items will be generated likely causing quantity loss. Meanwhile, the market demand rate is instantaneously dependent on the timely holding inventory. The manufacturer has to determine his production run length and cycle time by taking into account possible imperfect production, stock-dependent demand, and inventory holding capacity bound. We empolder a model to capture this problem and develop computational algorithm to solve it. We further conduct numerical studies to validate our model and solving method. Sensitivity analyses are reported to show the effect of parameters on the system performance.

An Inventory Model for Perishable Items with Time Varying Stock Dependent Demand and Trade Credit under Inflation

In the classical inventory models, it is assumed that the retailer pays to the supplier as soon as he received the items and in such cases the supplier offers a cash discount or credit period (permis-sible delay) to the retailer. In this paper we presented an inventory model for perishable items with time varying stock dependent demand under inflation. It is assumed that the supplier offers a credit period to the retailer and the length of credit period is dependent on the order quantity. The purpose of our study is to minimize the present value of retailer’s total cost. Numerical examples are also given to demonstrate the presented mode.

Optimal lot size for an item when holding cost is moved by depletion rate of inventory above a certain stock level

In this paper, a deterministic inventory model with depletion rate dependent holding cost is developed. The demand rate is a power function of the on-hand inventory behind to a certain stock level, at which the demand rate becomes a constant. Shortages are allowed and partially backlogged with the function of waiting time of next replenishment. It is also proved in this model that the optimal replenishment policy not only exists but also is unique. Furthermore, it is provided a simple solution procedure for finding the maximum total profit per unit time. Numerical examples have also been given to illustrate the model and real managerial fact in inventory holding for stock dependent demand.

Cost Analysis for a Supplier in an Inflationary Environment with Stock Dependent Demand Rate for Perishable Items

The present study is concerned with the cost modeling of an inventory system with perishable multi-items having stock dependent demand rates under an inflationary environment of the market. The concept of permissible delay is taken into account. The study provides the cost analysis of inventory system under the decision criteria of time value of money, inflation, deterioration, and stock dependent demand. Numerical illustrations are derived from the quantitative model to validate the results. The cost of inventory and optimal time are also computed by varying different system parameters. The comparison of these results is facilitated by computing the results with neurofuzzy results.

A Note on Non-linear Profit-Maximization Entropic Order Quantity (EnOQ) Model for Deteriorating Items with Stock Dependent Demand Rate

A Note on Non-linear Profit-Maximization Entropic Order Quantity (EnOQ) Model for Deteriorating Items with Stock Dependent Demand Rate

A two-level supply chain with consignment stock agreement and stock-dependent demand

This paper presents a vendor-managed inventory (VMI) with consignment stock (CS) policy applied to the integrated vendor–buyer system, where the demand at the buyer side is stock dependent. Under the VMI with CS, the vendor manufactures a product and delivers it in batches of equal sizes to the buyer: although the goods are in the warehouse of the buyer, they remain to be the property of the vendor until the buyer registers a withdrawal. The products delivered are presented to the end customers in a display area and the demand is assumed to be positively dependent on the number of items displayed. Moreover, the model proposed considers that the product display area is replenished once its inventory level hits a given minimum. The paper investigates and compares different policies that may be adopted to exploit the advantages offered by the consignment stock agreement when stock dependent demand at the buyer side is considered.

Decaying inventory model with stock-dependent demand and shortages under two-level trade credit

In the present day, competitive marketplace, offering delay payments, has become a commonly adopted method. Previous inventory models under permissible delay in payments usually assumed that the demand of the items was either constant or merely dependent on the retailing price. This paper deals with a lot-sizing model for deteriorating items with stock-dependent demand and delay in payments. In the model, shortages are allowed to occur and demand during the stockout period is partially backlogged. In this study, not only the supplier would offer fixed credit period to the retailer, but retailer also adopt the trade credit policy to his customer in order to promote the market competition. The retailer can accumulate revenue and interest after the customer pays for the amount of purchasing cost to the retailer until the end of the trade credit period offered by the supplier. That is, the retailer can accumulate revenue and earn interest during this period with rate Ie under the condition of trade credit. At the end of the trade credit period offered by the supplier, the account is settled and the retailer starts paying the capital opportunity cost for the items in stock with an annual rate Ip. The minimization of the total annual cost is taken as the objective function to study the retailer’s optimal ordering policy. Lemmas and Theorem to determine the criterion for the existence and uniqueness of the minimum solution are subsequently developed. We provide an easy and useful computational flowchart and with the help of a computer code using the software Matlab 7.0, the optimal results are determined. A numerical example is included to demonstrate the developed model and the solution procedure. To investigate the effect of changes in some main parameter values on the optimal solution, we conduct a sensitivity analysis and discuss some important managerial insights.

Fuzzy Eoq Model for Deteriorating Items with Exponential Membership Function

In this Paper a multi item EOQ model with stock dependent demand for deteriorating items is considered in fuzzy environment. Inventory costs such as holding cost and setup cost have been represented by exponential membership function and profit, deteriorating rate and total investment constraint are represented by linear membership functions. The model has been solved by fuzzy non-linear programming (FNLP) method. Results have been presented along with those of corresponding crisp model and a sensitivity analysis.

English

English

An Inflation Induced Stock-Dependent Demand Inventory Model with Permissible delay in Payment

This paper deals with an inflation induced stock dependent demand inventory model with permissible delay in payments. In real life situations, some products maintain freshness and quality for some time. This inventory model is developed for non-instantaneous deteriorating items. The purpose of this paper is to obtain the optimal policies for maximizing the total profits. Numerical examples are provided to demonstrate the developed model and also to provide the solution algorithm.