• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.43 no.1
• /
• pp.70-78
• /
• 2020

Under the situation which customer orders are cancelled unless all products in the order are delivered all at once, this paper concentrates on the purchase dependent demands and explores the systematic approach to implant the purchase dependence into the multi-product inventory model. First, by acknowledging that it is a challenging task to formulate a suitable inventory model for the purchase dependence, we derive the optimal solution condition using an EOQ model and extend the optimal solution condition to periodic review models. Then, through the comparison simulation of four inventory policies regarding several degrees of purchase dependence, we demonstrate that the inventory models which consider the purchase dependence generate less total cost than the inventory models which ignore the purchase dependence. In general, the inventory models which consider the purchase dependence reduce the loss of sales by maintaining more inventories, which results in reducing the total cost. Consequently, the simulation result supports the effectiveness of this paper's approach. In addition, this paper uses the individual order period and joint order period obtained from the EOQ model for the multi-product inventory model. Through the in-depth analysis of comparing the two models, we observe that the model of using the joint order period produces less total cost when the degree of purchase dependence is high, but the model of using the individual order period produces less total cost when the degree of purchase dependence is low.

• Journal of Broadcast Engineering
• /
• v.19 no.2
• /
• pp.268-271
• /
• 2014

Conventional forward error correction (FEC) code rate decision schemes using analytical source coding distortion model and channel-induced distortion model are usually complex, and require the typical process of model parameter training which involves potentially high computational complexity and implementation cost. To avoid the complex modeling procedure, we propose a simple but accurate joint source-channel distortion model to estimate channel loss threshold set for optimal FEC code rate decision.

• Journal of Communications and Networks
• /
• v.7 no.4
• /
• pp.401-407
• /
• 2005

Simulations are currently an essential tool to develop and test wireless sensor networks (WSNs) protocols and to analyze future WSNs applications performance. Researchers often simulate their proposals rather than deploying high-cost test-beds or develop complex mathematical analysis. However, simulation results rely on physical layer assumptions, which are not usually accurate enough to capture the real behavior of a WSN. Such an issue can lead to mistaken or questionable results. Besides, most of the envisioned applications for WSNs consider the nodes to be at the ground level. However, there is a lack of radio propagation characterization and validation by measurements with nodes at ground level for actual sensor hardware. In this paper, we propose to use a low-computational cost, two slope, log-normal path­loss near ground outdoor channel model at 868 MHz in WSN simulations. The model is validated by extensive real hardware measurements obtained in different scenarios. In addition, accurate model parameters are provided. This model is compared with the well-known one slope path-loss model. We demonstrate that the two slope log-normal model provides more accurate WSN simulations at almost the same computational cost as the single slope one. It is also shown that the radio propagation characterization heavily depends on the adjusted model parameters for a target deployment scenario: The model parameters have a considerable impact on the average number of neighbors and on the network connectivity.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2000.11a
• /
• pp.302-305
• /
• 2000

최근에 ITU-R에서 30～3,000MHz 주파수 범위에서 사용할 수 있는 포괄적인 전계 강도 커브를 제시하고 있다. ITU-R Question 중의 하나인 의제 210/3에서 요구하는 내용은 '30MHz～3GHz 대역의 육상이동과 지상방송 업무를 위한 전파전파 예측절차'이다. 이러한 의제를 WP SG3에서 연구하여 부속서 3K/TEMP/4에 정리하였다. 본 논문에서는 위 부속서 3K/TEMP/4에 나와있는 전송손실 예측 그래프의 적용범위와 적용환경을 알아보기 위해 일반적인 실험적 경로손실 예측식인 Okumura-Hata 모델 그리고 Cost231-Hata 모델과 비교 분석하였다.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.24 no.3
• /
• pp.109-114
• /
• 1996

Generally, the size of our recreation sites is selected through use demand at the peak day. At same time, scale economic and diseconomic are applied to a recreation site. If you are a rational decision-maker, you would like to select the size of your park at profit-maximization point. This study is the first try for modelling a Gain-Loss by the size options of a theme park. For testing the validity of a financial model to select the size of theme parks. Ever-Land, Seoul-Land, Dream-Land's operating size was analyzed. By the size options, the revenue of each park was compared with cost. The profit-maximization point and break-even point of each park were found. Ever-Land and Dream-Land's size was selected between the profit-maximization point and the break-even point. In contrast with Ever-Land and Dream-Land's, Seoul-Land's was selected upper the break-even point. To increase the utility of this model in selecting the size of a theme park, a decision-maker must keep in mind a few limits of this study. That is, 1) this model can not be applied at public parks. 2) Sometimes the others can be more important than financial revenue and cost. Finally, there is the validity of Gain-Loss Model in estimating only the financial revenues and costs through the size options.

• Journal of Korean Society for Quality Management
• /
• v.28 no.4
• /
• pp.194-203
• /
• 2000

This paper is concerned with an economic selection of both the process mean and the lower limit for a continuous production process with the quadratic loss function. It is assumed that the quality characteristic is normally distributed with a known variability. A profit model is developed which involves selling price, production cost, reprocessing cost and the cost which is incurred by imperfect quality. Methods of finding optimum values of the process mean and the lower limit are presented, and a numerical example is given.

• Communications for Statistical Applications and Methods
• /
• v.21 no.2
• /
• pp.161-168
• /
• 2014

In mixture experiments with process variables, we consider the case that some of process variables are either uncontrollable or hard to control, which are called noise variables. Given the such mixture experimental data with process variables, first we study how to search for candidate models. Good candidate models are screened by the sequential variables selection method and checking the residual plots for the validity of the model assumption. Two methods, which use numerical optimization methods proposed by Derringer and Suich (1980) and minimization of the weighted expected loss, are proposed to find a cost-effective robust optimal condition in which the performance of the mean as well as the variance of the response for each of the candidate models is well-behaved under the cost restriction of the mixture. The proposed methods are illustrated with the well known fish patties texture example described by Cornell (2002).

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.18 no.36
• /
• pp.275-285
• /
• 1995

In recent years there has been increasing interest in the issue of process centering in manufacturing process, The traditional process capability indices Cp, Cpk and Cpu are used to provide measure of process performance, but these indices do not represent the issue of process centering. A new measure of the process capability index Cpm is proposed that takes into account the proximity to the target value as well as the process variation when assessing process performance. However, Cpm only considers acceptance cost for deviation from target value within specification limits, do not includes economic consideration for rejected items. This paper proposes flexible process performance measures that considered quadratic loss function caused by quality deviation within specification limits, rejection cost associated with the disposition of rejected items, and inspection cost. In this model disposition of rejected items are considered under perfect corrective procedures and the absence of perfect corrective procedures.

• Korean Management Science Review
• /
• v.12 no.1
• /
• pp.111-124
• /
• 1995

With the increasing interest of reducing process variation, statistical process control has served the pivotal tool in most industrial quality programs. In this study, system analyses have been performed associated with a cost incorporated version of a process control, a quadratic loss-based X over bar control chart model. Specifically, two issues, the capital/research investments for improvement of a system and the precision of a parameter estimation, have been addressed and discussed. Through the analysis of experimental results, we show that process variability is seen to be one of the most important sources of loss and quality improvement efforts should be directed to reduce this variability. We further derive the results that, even if the optimal designs may be sensitive, the model appears to be robust with regard to misspecification of parameters. The approach and discussion taken in this study provide a meaningful guide for proper process control. We conclude this study with providing general comments.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.2
• /
• pp.264-269
• /
• 2009

Marginal Loss Factor(MLF) is represented as the sensitivity of transmission loss, which is computed from the change of the generation at slack bus by the change of the load at the arbitrary bus. The MLF dependent on the selection of slack bus is one of the key factors affecting nodal pricing, Genco's profits, social welfare(SW) and Nash Equilibrium in a competitive electricity market. This paper addresses the methodology of slack bus selection by using Cournot model of Cost Based Pool market. Numerical results from sample cases show that the slack bus of MLF of the highest average is beneficial from the view points of SW.