A novel cross-docking EOQ-based model to optimize a multi-item multi-supplier multi-retailer inventory management system

Nowadays, the retail industry accounts for a large share of the world’s economy. Cross-docking is one of the most effective and smart inventory management systems used by retail companies to respond to demands efficiently. In this study, the aim is to develop a novel cross-docking EOQ-based model for a retail company. By considering a two-stage inventory procurement process, a new multi-item, multi-supplier, multi-retailer EOQ model is developed to minimize the total inventory costs. In the first stage, the required items are received from suppliers and are held in a central warehouse. In the second stage, these items are delivered to several retail stores. The total inventory costs include four main parts, i.e., holding costs at the central warehouse, holding costs at the retail stores, fixed ordering costs from the suppliers, and fixed ordering costs from the central warehouse. The optimal inventory policy is obtained by analyzing extrema, and a numerical example is used to confirm the efficiency of the proposed model. Based on the obtained results, it is evident that the proposed model produces the optimal policy for the cross-docking system. Furthermore, the model enables managers to analyze the effects of key factors on the costs of the system. Based on the obtained results, the annual demand of each retailer, the ordering cost by the central warehouse, the ordering cost at each retail store, and the holding cost at each retail store have a direct impact on the optimal cost. Furthermore, it is not possible to describe the effects of the holding cost at the central warehouse on the optimal cost of the system generally

AN EPQ PRODUCTION-INVENTORY MODEL WITH VARIABLE HOLDING COST

Instantaneous order replenishment and constant holding cost are two fundamental assumptions of the economic order quantity (EOQ) model. This paper presents modifications to both of these basic assumptions. First, non-instantaneous order replenishment is assumed, i.e. a finite production rate of the economic production quantity (EPQ) model is considered. Second, the holding cost per unit per time period is assumed to vary according to the length of the storage duration. Two types of holding cost variability with longer storage times are considered: retroactive increase and incremental increase. For both cases, models are formulated, solutions algorithms are developed, and examples are solved

Maximum-Profit Inventory Model with Stock-Dependent Demand, Time-Dependent Holding Cost, and All-Units Quantity Discounts

A new production-planning model with a unique set of realistic features is considered. First, the demand rate is a function of the current inventory level. Second, a new order is gradually produced according to a finite production rate. Third, the unit holding cost per time period is a function of both the unit purchase cost and the storage time duration. Fourth, the unit purchase cost is a function of the production lot size. Fifth, the starting/ending inventory for each cycle is a decision variable to be optimized. Finally, the objective of the model is to maximize the total profit per unit time. The purchase cost per unit decreases with larger lot size according to all-units quantity discount. On the other hand, the holding cost per unit increases with longer storage duration, either retroactively or incrementally. Mathematical models are formulated to represent this production planning system, and optimum solution procedures are developed

Production-inventory system with finite production rate, stock-dependent demand, and variable holding cost

In general, traditional production-inventory systems are based on a number of simplifying – but somewhat unrealistic – assumptions, including constant demand rate, constant holding cost, and instantaneous order replenishment. These assumptions have been individually challenged in numerous variations of production-inventory models. Finite production rate models, such as economic production quantity (EPQ) systems consider gradual order replenishment. Stock-dependent demand models assume the demand rate to be an elastic function of the inventory level. Variable holding cost models assume the holding cost per unit per time period to be a function of the time spent in storage. In this paper, the three simplifying assumptions are simultaneously relaxed in a new production-inventory system with a finite production rate, stock-level dependent demand rate, and variable holding cost. Mathematical models and optimum solution procedures, including nonlinear programming, are presented for two functional forms of holding cost variability. The main contribution of this paper is the formulation and solution of a new production-inventory model that more closely represents real-world situations. The realistic assumptions and efficient solution algorithms should make the model practical and useful for industrial applications

COMPRESSED WORKWEEK SCHEDULING WITH CONSECUTIVITY, FREQUENCY AND STRETCH CONSTRAINTS

ABSTRACT In this paper we consider a three-day workweek scheduling problem with three realistic daysoff scheduling constraints: (1) at least two off days per week must be consecutive, (2), employees must get a given proportion of weekends off, and (3) the number of consecutive workdays in any work stretch cannot exceed four. An integer programming model is formulated and efficiently solved by an algorithm that involves three stages: (1) determining the minimum workforce size by primal-dual relations, (2) adding a workforce-size constraint to the integer programming model to expedite its solution, and (3) constructing fair and feasible multiple-week rotation schedules