Hark Hwang

Retailer's pricing and lot sizing policy for exponentially deteriorating products under the condition of permissible delay in payments

This article deals with the problem of determining the retailers optimal price and lot size simultaneously when the supplier permits delay in payments for an order of a product whose demand rate is represented by a constant price elasticity function. It is assumed that inventory is depleted not only by customers demand but also by deterioration. Investigation of the properties of an optimal solution allows us to develop an algorithm whose validity is illustrated using an example problem.

An optimal ordering and recovery policy for reusable items

This paper deals with a joint EOQ and EPQ model in which the stationary demand can be satisfied by recycled products and newly purchased products. The model assumes that a fixed proportion of the used products are collected from customers and later recovered for reuse. The recovered products are regarded as perfectly new ones. We obtain (i) the economic order quantity for newly procured products and (ii) the optimal inventory level of recoverable items to start the recovery process, simultaneously. According to the relationship between parameters, we propose some numerical models to analyze the system. Then a solution procedure to find the optimal control parameters is presented, and finally some numerical examples are given to illustrate the model.

Optimal pricing and ordering policies for retailers under order-size-dependent delay in payments

This paper deals with the problem of determining the retailers optimal price and order size simultaneously under the condition of order-size-dependent delay in payments. It is assumed that the length of the credit period is a function of the retailers order size, and also the demand rate is a function of the selling price. We formulate two types of mathematical models from which algorithms are derived based on properties of an optimal solution. A numerical example is presented to illustrate the algorithms developed.

An optimal credit policy to increase supplier's profits with price-dependent demand functions

Abstract This paper deals with the problem of determining an optimal length of credit period from the perspective of supplier. We assume that a retailer jointly determines the unit retail price and order size to maximize profit when he/she purchases a product for which the supplier offers a trade credit. Two widely used demand functions are adopted for the study in which demands are decreasing functions of the retail price. A procedure is presented which shows how to achieve an optimal length of credit period for suppliers. The effects of credit period on the behaviour of retailers are also investigated using an example.

Joint price and lot size determination under conditions of permissible delay in payments and quantity discounts for freight cost

Abstract This paper deals with the problem of determining the retailers optimal price and lot size simultaneously under conditions of permissible delay in payments. It is assumed that the ordering cost consists of a fixed set-up cost and a freight cost, where the freight cost has a quantity discount offered due to the economies of scale. The constant price elasticity demand function is adopted, which is a decreasing function of retail price. Investigation of the properties of an optimal solution allows us to develop an algorithm whose validity is illustrated through an example problem.

Sequencing delivery and receiving operations for yard cranes in port container terminals

Abstract In port container terminals, the amount of delay time of outside trucks in the receiving and delivery operations is one of the important measures for the evaluation of the level of customer service. A dynamic programming model is suggested for a static sequencing problem in which all the arrivals of trucks are known in advance. For dynamic situations where new trucks arrive continuously, a learning-based method for deriving decision rules is suggested. Also, several heuristic rules are suggested. A simulation study is performed to compare the performances of the suggested approaches.

Travel-time models considering the operating characteristics of the storage and retrieval machine

SUMMARY Existing travel-time models of automated storage/retrieval systems (AS/RS) assume the average uniform velocity, ignoring the operating characteristics of storage/retrieval (S/R) machine such as the acceleration/deceleration rate and the maximum velocity. Consequently, the optimal design and schedule based on the existing models is far from optimal from the practical point of view. This paper presents continuous analytical models of travel time which integrate the operating characteristics of S/R machine. Using a randomized assignment policy, travel times are determined for both single and dual command cycles. The models developed are examined through discrete evaluation procedures.

An incremental discount pricing schedule with multiple customers and single price break

Abstract This paper analyzes how a supplier can formulate the terms of a quantity discount pricing schedule. Assuming a single incremental discount system, a model is developed from which an algorithm is derived for an optimal discount schedule. The cases are investigated in which both the discount rate and the break point are unknown and either one is prescribed. A numerical example is presented to illustrate the algorithm developed.

A generalized ordering and recovery policy for reusable items

This paper deals with a joint EOQ and EPQ model in which a stationary demand is satisfied by recovered products as well as newly purchased products. It is assumed that a fixed proportion of the used products are collected from customers and later recovered for reuse. We generalize the (P, R) policy in the literature by treating the sequence of orders for newly purchasing products and setups for recovery process within a cycle as a decision variable. Through example problems we illustrate the validity of the model and solution procedure developed.

An evaluation of routing policies for order-picking operations in low-level picker-to-part system

This paper evaluates the performance of three routing policies in the order-picking process, i.e. return, traversal, and midpoint policy. It is assumed that items are assigned to storage locations on the basis of the cube-per-order index (COI) rule in a low-level picker-to-part warehousing system. First, for the three policies, analytical models are developed for the total expected travel distance of the order picker considering the number of the stocking aisles is even or odd. Then the developed models are compared with simulation results to show the validity. Finally, the performance of the three policies is examined by varying the parameter value of the COI-based ABC curve, number of picks in the pick list, and ratio of the length to the width of the warehouse.