Sharif Digital Repository

Supply chain management integrates planning and controlling of materials, information, and finances in a process which begins from suppliers and ends with customers. Optimal planning decisions made in such a distribution network usually include transportation, facilities location, and inventory. This study presents a new approach for considering customers’ differentiation in an integrated location-allocation and inventory control model using transfer recurrent neural network (RNN). In this study, a location and allocation problem is integrated with inventory control decisions considering two classes of strategic and non-strategic customers. For the first time, a novel transfer RNN is applied... 

Supply Chain (SC) coordination, quality requirements, and environmental issues are the main areas of interest within the field of inventory management. Few studies have integrated these concepts into an inventory problem despite its overwhelming necessity. In this direction, this paper deals with a vendor-buyer SC under the Vendor-Managed Inventory with Consignment Stock (VMI-CS) agreement. According to the agreement, the vendor bears the buyer's financial holding cost in return for the storage of products in the buyer's warehouse. Further, each shipment involves a random fraction of repairable items, which need to be withdrawn from the inventory system. Unlike the existing literature, when... 

The growing environmental concerns, governmental regulations, and significant cost savings are the primary motivations for companies to consider the reuse and recovery of products in their inventory system. The previous research ignored several realistic features of reusable items inventory systems, such as the presence of multiple products and operational constraints. For the first time, this paper presents a new multiproduct economic order quantity inventory model for an inventory system of reusable products. The goal of the model is to determine the optimal replenishment quantity and reuse quantity of each item so that the system's total cost is minimized. Several operational constraints... 

The economic production quantity (EPQ) is one of the most commonly used models for production planning and inventory control problems. In this paper, a multi-product single- machine EPQ inventory model with imperfect production is extended under production capacity. In this system, produced items do not have perfect quality; they either are reworked or are scrapped. Moreover, the limited warehouse space for each item and the limited total available capital lead to constraints for storage and budget, respectively. Besides, the setup cost/time for each product depends on the quantity produced. The objective function of the developed EPQ inventory model is shown to be a convex non-linear... 

Blood availability in hospitals is of high humanitarian importance, thus blood shortage is not desired at all. High wastage rate of blood in hospitals is an important issue, which becomes more important as the standards of health care services becomes higher. In order to address blood shortage and wastage issues in a hospital, this paper develops a new inventory management model as a decision making tool to help making tactical and operational level decisions for a Hospital Blood Bank (HBB) inventory management. These decisions include issuance and ordering policy and the aim of the model is to reduce blood wastage and shortage. For this purpose, a multi period, multi-product inventory... 

The production routing problem (PRP) merges the lot-sizing problem and the vehicle routing problem, two classical problems that have been the focus of comprehensive studies for over half a century. Solving the PRP is an effort to optimize decisions about the production, inventory, distribution, and routing in an integrated manner. In the literature of the recent decade, due to economic changes and regulatory issues, reverse logistics has become a focal point. Subsequently, the vehicle routing problem with simultaneous pickup and delivery (VRPSPD) has drawn more and more attention for its considerable effect on the reverse logistics problem. In addition, one of the major arguments in supply... 

The Newsboy problem has always been an important issue in inventory management. The multi-product newsboy problem with random yield and budget constraint named as the Gardener Problem is one of the novels and popular extensions of the newsboy problem. Different from the existing studies, this paper presents a multi-product gardener problem with reservation policy. Moreover, a discount rate is offered to those customers who are willing to make reservations. In addition to the demand from the original customers, extra demand is included in the model due to the motivation received by the discount rate. A solution algorithm namely the multi-product gardener problem with reservation policy... 

Economic production and on-time ordering are among the most important topics related to production and inventory control issues. An economical production needs a comprehensive and precise planning to be implemented in all production stages. To have a controlled and comprehensive planning system, economic order quantity (EOQ) or economic production quantity (EPQ) models are usually used in various production-inventory environments to minimize costs, avoid delays in orders, and achieve high performance. To meet the demands, sometimes a multiperiod production-inventory planning that involves several products requires outsourcing. In this paper, a production-procurement plan that integrates EOQ... 

In this study, a single-period two-level inventory control problem is modeled in which the demand is a random variable and shortage is assumed as lost sales. The aim is to maximize the expected profit and the service level at the end of the season, simultaneously. The setting investigated in this research is unique in the sense that both all-units and incremental discount policies are considered under a budget constraint. The developed NP-hard bi-objective optimization problem cannot be solved using an exact method within a reasonable computational time. Thus, a meta-heuristic algorithm, namely multi-objective invasive weeds optimization algorithm (MOIWO) is developed to solve the proposed... 

This study considers a two-echelon inventory system with one central warehouse and a number of non-identical retailers with Poisson demands, constant lead times, and lost sales for a single item. The warehouse works as a cross-docking terminal with no inventory and coordinates shipments to retailers. We apply the Joint order (1, T) policy in such an inventory system. In the standard (1, T) policy, the warehouse sends one unit of the item to each retailer in a fixed cycle time, which is calculated by considering each retailer separately. In the joint order (1, T) policy, the warehouse decides to replenish one unit of the item for each retailer in a cycle time which is adjusted to be an... 

This paper develops an economic production quantity model for a multi-product multi-objective inventory control problem with fuzzy-stochastic demand and backorders. In this model, the annual demand is represented by trapezoidal fuzzy random numbers. The centroid defuzzification and the expected value methods are applied to defuzzify and make decisions in a random environment. In the case where the warehouse space is limited, the Lagrangian relaxation procedure is first employed to determine the optimal order and the maximum backorder quantities of the products such that the total inventory cost is minimized. The optimal solution obtained by the proposed approach is compared with that... 

In this research, a single-period two-echelon inventory control problem with market targeting strategies is considered. In this problem, there are several final products and raw materials with varying usage rates. The objective is to determine the order sizes of final products and raw materials before the selling period such that customers' satisfaction is reached and expected profit is maximized within an available budget. The problem is first mathematically formulated and then a modified particle swarm optimization algorithm is employed to solve the nonlinear programming problem. To validate the results obtained, a simulated annealing algorithm is provided as a benchmark. The parameters of... 

Although inventory control under discrete demand in dynamic quantities and time intervals are very common in reality, existing literature has largely ignored them. In this paper, we investigate the inventory control decisions in a two echelon supply chain consisting of one vendor and several retailers. The vendor supplies a product to several retailers, who buy discrete quantities in pre-determined time intervals. The order quantity and order cycles for each retailer can be different from others. Vendor orders the required quantity from supplier and it will be immediately received at the vendor's warehouse. In this system, shortage is not allowed for the vendor. The transportation time from... 

This article deals with a single perishable item, continuous-review, two-echelon serial inventory system consisting of a warehouse and a retailer. Customer demands at the retailer are assumed to be Poisson. All items have a fixed shelf life and start aging on their arrival at the retailer. The demand that cannot be met immediately at the retailer is lost. All transportation times are fixed. If there is any stock in the warehouse, the lead time for the retailer would be the transportation time from the warehouse. Otherwise, the retailer orders are met with a delay. In this article, using an approximate technique, we first present a heuristic for finding cost-effective base stock policy and... 

There is a growing concern, in the last decade, about the environment and social footprint of business operations. The subject of supply chain sustainability, simultaneously considering economic, environment and/or social values, has gained attention in the academia and from the industry. Particularly for deteriorating and seasonal products, such as fresh produce, the issues of timely supply and disposal of the deteriorated products are of high concerns. This research develops a new replenishment policy in a centralized sustainable supply chain for the deteriorating items. The model considers inventory and transportation costs, as well as the environmental and social impacts, with several... 

In this paper, a design of the supply chain distributer-retailer network for a seasonal multiple-product location allocation-inventory control problem in a planning horizon consisting of multiple periods is modeled. The distance between the distributers and retailers are assumed to be Euclidean and square Euclidean while retailers purchase the products from the distributers under all-unit and incremental quantity discount policies. Furthermore, the products are delivered in packets of known size of items and in case of shortage, a fraction of demand is considered backorder and a fraction lost sale. Besides, the distributers store the manufactured products in their warehouses before... 

Recently, for zero ordering cost a new ordering policy named (1, T), in which the time interval between two consecutive orders and the value of the order size are both constant, have been developed for nonperishable products. In this paper, the (1, T) policy is developed for perishable products. Using an analogy among this inventory model, a queueing model with impatient customers, and a finite dam model, the long-run average total cost function of the inventory system is derived. It is observed that the total cost rate is independent from the lead time as is for nonperishable products. Since analyzing the convexity of the model is extremely complicated, a proposition is proved to define a... 

This paper develops an economic production quantity (EPQ) inventory model for a multiproduct single-machine lot-sizing problem with nonconforming items including scrap and rework, where reworks are classified into several groups based on failure severity. In this inventory model, shortage is allowed and is backordered. The aim is to determine the optimal period length, the lot size, and the allowable shortage of each product so as the total cost, including setup, production, warehouse construction, holding, shortage, reworking, and disposal is minimized. Besides, the available total budget is scarce and that there is a lower bound on the service level of each product. While the convexity is... 

In this paper, a multiproduct multi-chance constraint stochastic inventory control problem is considered, in which the time-periods between two replenishments are assumed independent and identically distributed random variables. For the problem at hand, the decision variables are of integer-type, the service-level is a chance constraint for each product, and the space limitation is another constraint of the problem. Furthermore, shortages are allowed in the forms of fuzzy random quantities of lost sale that are backordered. The developed mathematical formulation of the problem is shown to be a fuzzy random integer-nonlinear programming model. The aim is to determine the maximum level of... 

Inventory management of deteriorating items faces major challenges by uncertain demand, uncertain lead time, perishability, and high customer service level requirements. So, this issue is extremely important in many corporations today. The periodic up-to level policy for deteriorating products under stochastic demand and stochastic lead time is not paid enough attention up to now. In this paper we propose a new approach to study inventory up-to level policy of deteriorating products under normal distributed demand and lead time by considering service level requirements. To model deterioration process, a non-linear increasing holding cost function is considered. After developing the...