• Journal of the Korean Operations Research and Management Science Society
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• v.14 no.2
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• pp.75-86
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• 1989

Joint stocking and preventive age replacement policy is considered for non-repairable items assuming instantaneous replenishment. A recursive relationship among the optimal preventive replacement ages is obtained, which shows that the preventive replacement ages in a replenishment cycle form an increasing sequence due to the inventory carrying cost. Using this relationship, a procedure is given for determining how many units to purchase on each order and when to replace each unit after it has begun operating so as to minimize the total cost per unit time over an infinite time span. The problem can be simplified if equal preventive replacement ages are assumed, and the solution is very close to that of the original unconstrained problem.

• Management Science and Financial Engineering
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• v.15 no.2
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• pp.53-68
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• 2009

In this paper, we address a problem for minimizing the number of items inspected in a back-light-unit (BLU) inspection system, which includes a K-stage inspection system, a source inspection shop, and a re-inspection shop. In order to formulate our objective, we make a steady-state flow analysis between nodes (or shops), and derive the steady-state amount of flows between nodes and defective rates by solving a nonlinear balance equation. We provide an enumeration method for determining an optimal value of K which minimizes the number of items inspected. Our methodology could be applied and extended to similar situations with slight modification.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.2
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• pp.246-262
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• 2013

With increases in international oil prices, the proportion of fuel cost to the operational costs of a ship is currently increasing. To reduce fuel cost, a method for determining an economical route for a ship based on the acquisition of the sea state and the estimation of fuel consumption is proposed. The proposed method consists of three items. The first item is to acquire the sea state information in real time. The second item is to estimate the fuel consumption of a ship according to the sea state. The last item is to find an economical route for minimal fuel consumption based on the previous two items. To evaluate the applicability of the proposed method, it was applied to routing problems in various ocean areas. The result shows that the proposed method can yield economical ship routes that minimize fuel consumption. The results of this study can contribute to energy savings for environmentally friendly ships.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.772-777
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• 2002

In this paper, economic screening procedures with dichotomous performance variable T and continuous screening variable X are considered when the rejected items are reprocessed. Two models are considered; normal and logistic models. It is assumed that X given T is normally distributed in the normal model, and $P(T=1{\mid}X=x)$ Is given by a logistic function in the logistic model. Profit models are constructed which involve four price/cost components; selling price, cost from an accepted nonconforming item, and reprocessing and inspectioncosts. Methods of finding the optimal screening procedures are presented and numerical examples are given.

• Journal of the Korea Safety Management & Science
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• v.8 no.2
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• pp.155-167
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• 2006

본 논문은 제품공급자, 중간분배자 그리고 고객으로 구성된 2 단계 공급사슬에서 공급자가 수요 증대를 목적으로 중간분배자에게 일정기간 동안 제품대금에 대한 지불연기를 허용하는 상황을 고려하여 중간분배자의 신뢰성있는 판매가격 및 재고보충정책을 결정하는 문제를 다루었다. 문제 분석을 위하여 고려하는 제품은 시간에 따라 일정률로 퇴화한다는 가정과 함께 수송량에 따라 할인되는 수송비를 고려하여 모형을 수립하였고, 중간분배자의 수익 증대를 위한 경제적 판매가격 및 재고보충정책 결정을 위한 해법을 개발하였다.

• Journal of Korean Institute of Industrial Engineers
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• v.28 no.3
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• pp.240-246
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• 2002

In this paper, economic screening procedures with dichotomous performance variable T and continuous screening variable X are considered when the rejected items are reprocessed. Two models are considered; normal and logistic models. It is assumed that X given T is normally distributed in the normal model, and P(T=1|X=x) is given by a logistic function in the logistic model. Profit models are constructed which involve four price/cost components; selling price, cost from an accepted nonconforming item, and reprocessing and inspection costs. Methods of finding the optimal screening procedures are presented and numerical examples are given.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.187-188
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• 2017

Korean government is trying to adopt 'CM at Risk(CMR)' method to solve some problems of traditional project delivery method such as cost increase, delay, low quality. Pre-construction service(PCS) is a project management methodology of CMR and BIM is the best tool for efficient PCS execution. PCS is consisted of several main items such as Target costing, Cost trending, GMP, Design optimization, Constructability review and Productivity. The purpose of this research is to analyse contractor's PCS application case result and to find improvement items.

• Journal of Korean Institute of Industrial Engineers
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• v.40 no.2
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• pp.233-239
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• 2014

This paper presents an extended EMQ model which determines an optimal production run length in an deteriorating production process. The production process is subject to a random deterioration from an in-control state to an out-of-control state and thus producing some proportion of defective items. Defective items produced are re-processed in the rework process to convert them into non-defectives. Through the mathematical modeling, an optimal solution minimizing the average cost per unit time as well as minimum average cost are derived. Numerical experiment is carried out to examine the behavior of the proposed model depending on model parameters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1229-1234
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• 2001

There are three items, which are panhead displacement, tilting angle of pan head, required moment of main shaft, which representing kinematic performance of pantograph. Kinematic variables effective on kinematic performance are length of each components and installation angle, In this study, cost function is defined with 3 items, By this cost function, length of thrust rod was optimized. Finite element analysis was used to consider structural soundness. Finite element model was qualified by comparison between analysis result with experiment result. By qualified F.E, model various severe condition was simulated to consider structural soundness.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.147-149
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• 2015

A nuclear power plant construction project normally involves a large construction work of which the total project cost is over 5 trillion Won, Such a large-scale construction project has the risks of schedule delay and quality degradation due to increase in project cost, because designs are changed due to design errors. The reasons for design changes during installation are 1) insufficient engineering capability of the owner, 2) information discontinuance due to the multiple package method, and 3) inefficient constructability review processes. Accordingly, this study proposes, through problem analysis, a method of developing a constructability review system that utilizes constructability review processes and a data-based technology (3D modeling) that are optimized for nuclear power plant construction projects. It also presents a method of establishing a system for reviewing constructability in which constructability review processes and a Database (3D model, Schedule, Design change Items) are linked each other.