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Dive into the research topics where Kun-Jen Chung is active.

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Featured researches published by Kun-Jen Chung.


Computers & Operations Research | 1998

A theorem on the determination of economic order quantity under conditions of permissible delay in payments

Kun-Jen Chung

This article discusses the economic quantity under conditions of permissible delay in payments. First, this article shows that the total annual variable cost function is convex. Second, with convexity, a theorem is developed to determine the economic order quantity. The theorem also reveals that the economic order quantity under conditions of permissible delay in payments is generally higher than the economic order quantity given by the classical economic order quantity model. Numerical examples are given to illustrate the thorem.


Computers & Operations Research | 1998

Economic order quantity of deteriorating items under permissible delay in payments

Peter Chu; Kun-Jen Chung; Shaw-Ping Lan

Scope and purpose This paper considers the inventory model of deteriorating items under permissible delay in payments. Traditionally, it is well known that the total variable cost function based on average cost analysis is convex. So, the study of the convexity of the total variable cost function should be one of the main research topics of the inventory model. The main purpose of this paper is to investigate the properties of the convexity of the total variable cost function of the inventory model of the deteriorating items under a permissible delay in payments. The economic ordering policy of deteriorating items under a permissible delay in payments is presented in this paper. The inventory system discussed here is the same as that of Aggarwal and Jaggi [Aggarwal, S. P. and Jaggi, C. K., Journal of the Operational Research Society, 1995, 46, 658–662.]. At first, this paper shows that the total variable cost per unit time is piecewise-convex. Then, with the piecewise convexity, a solution procedure is developed to improve that described by Aggarwal and Jaggi. Numerical examples are also given to illustrate the solution procedure.


Computers & Operations Research | 2004

Lot-sizing decisions under trade credit depending on the ordering quantity

Kun-Jen Chung; Jui-Jung Liao

This paper deals with the problem of determining the economic order quantity for exponentially deteriorating items under the conditions of permissible delay in payments. The delay in payments depends on the quantity ordered, When the order quantity is less than at which the delay in payments is permitted, the payment for the product must be made immediately. Otherwise, the fixed trade credit period is permitted.Based upon the above arguments, this paper incorporates both Hwang and Shinn (Comput. Oper. Res. 24 (1997) 539) and Khouja and Mehrez (J. Manuf. Systems 15 (1996) 334) under above conditions. In addition, the objective function is modeled as a total variable cost-minimization problem. An algorithm to determine the economic order quantity is developed. Examples are solved to illustrate the results given in this paper. Finally, the results in this paper generalize some already published results.


Computers & Operations Research | 2003

An optimal production run time with imperfect production processes and allowable shortages

Kun-Jen Chung; Kuo-Lung Hou

This paper develops a model to determine an optimal run time for a deteriorating production system under allowable shortage. It is assumed that the elapsed time until the production process shift is arbitrarily distributed. We show that there exists a unique optimal production run time to minimize the total relevant cost function. Finally, bounds for the optimal production run time are provided to develop the solution procedure.


Computers & Operations Research | 2001

Optimal inventory replenishment models for deteriorating items taking account of time discounting

Kun-Jen Chung; Chuan-Neng Lin

Abstract This paper follows the discounted cash flow (DCF) approach to investigate inventory replenishment problem for deteriorating items taking account of time value of money over a fixed planning horizon. We develop models and optimal solutions with complete backlogging and without backlogging and prove that the total variable cost is convex. The results are discussed through numerical examples. Sensitivity analysis of the optimal solution with respect to the parameters of the system is carried out. Scope and purpose Traditional EOQ inventory models assume that the products have infinite shelf-life and neglect the effect of time discounting. The present paper deals with the inventory replenishment problem for deteriorating items taking account of time discounting. The main purpose of this paper is to establish replenishment models and develop optimal replenishment policies for items having characteristic of deterioration taking account of time value of money.


European Journal of Operational Research | 2000

A note on EOQ models for deteriorating items under stock dependent selling rate

Kun-Jen Chung; Peter Chu; Shaw-Ping Lan

Abstract In 1995, Padmanabhan and Vrat presented inventory models for deteriorating items with stock dependent selling rate and derived the profit functions without backlogging and with complete backlogging. First, this paper develops the necessary and sufficient conditions of the existence and uniqueness of the optimal solutions of the profit per unit time functions without backlogging and with complete backlogging Second, this paper explains that it is appropriate to use the Newton–Raphson method to find the optimal solutions of the profit functions per unit time in both situations modelled.


Computers & Operations Research | 2001

Inventory systems for deteriorating items with shortages and a linear trend in demand-taking account of time value

Kun-Jen Chung; Sui-Fu Tsai

Abstract This paper derives an inventory model for deteriorating items with the demand of linear trend and shortages during the finite planning horizon considering the time value of money. A simple solution algorithm using a line search is presented to determine the optimal interval which has positive inventories. Numerical examples are given to explain the solution algorithm. Sensitivity analysis is performed to study the effect of changes in the system parameters. Scope and purpose The traditional inventory model considers the ideal case in which depletion of inventory is caused by a constant demand rate. However, in real-life situations there is inventory loss due to deterioration. In a realistic product life cycle, demand is increasing with time and eventually reaching zero. Most of the classical inventory models did not take into account the effects of inflation and time value of money. But in the past, the economic situation of most of the countries has changed to such an extent due to large scale inflation and consequent sharp decline in the purchasing power of money. So, it has not been possible to ignore the effects of inflation and time value of money any further. The purpose of this article is to present a solution procedure for the inventory problem of deteriorating items with shortages and a linear trend in demand taking account of time value.


Computers & Operations Research | 2003

An algorithm for an inventory model with inventory-level-dependent demand rate

Kun-Jen Chung

In 1990, Datta and Pal (J. Oper. Res. Soc. 41 (1990) 971) discussed an infinite time-horizon deterministic inventory model without shortages. In essence, they concentrate on the establishment of the inventory model but do not present a concrete solution procedure to solve the model. This paper deals with an alternative approach to find the optimal order quantity for Datta and Pal.


European Journal of Operational Research | 2004

The sensitivity of the inventory model with partial backorders

Peter Chu; Kun-Jen Chung

Abstract This paper uses the rigorous methods of mathematics to explore the analysis of the sensitivity of Park [Int. J. Syst. Sci. 13 (1982) 1313]. However, Park discusses the analysis of the sensitivity by numerical examples. The results obtained by this paper show that the sensitivity of Park is not always true sometimes. Therefore, the researchers may be very careful to use the conclusions of the analysis of the sensitivity made by numerical examples in general.


Computers & Operations Research | 2003

Approximations to production lot sizing with machine breakdowns

Kun-Jen Chung

Abstract In general, the study of the convexity (concavity) of the total annual cost function (the annual net profit function) should be one of the main research topics about the inventory model. This paper first shows that the long-run average cost function per unit of time for the case of exponential failures is unimodal. However, it is neither convex nor concave. Second, the better lower bound Q l ∗ and upper bound Q u ∗ can be obtained to improve some existing results. Finally, numerical examples reveal the lower bound Q l ∗ for the optimal lot size is a rather good approximation to the optimal lot size. Scope and purpose In 1992, Groenevelt, Pintelon and Seidmann focused on the effects of machine breakdowns and corrective maintenance on the economic lot sizing decisions. They indicate that the economic manufacturing quantity (EMQ) is a good approximation to the optimal lot size. The main purpose of this paper is to provide a better approximation to the optimal lot size than EMQ.

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Peter Chu

Central Police University

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Shaw-Ping Lan

National Taiwan University of Science and Technology

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Chuan-Neng Lin

National Taiwan University of Science and Technology

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Jui-Jung Liao

National Taiwan University of Science and Technology

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