• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.277-287
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• 1996

Based on the developments of the reliability-based steel structural analysis and design as well as the extending knowledgy on the probabilitic characteristics of loading and resistance the probability based design criteria have been successful Iy developed for many students. The existing design codes, which are genarally based on the structural theory and certain engineering experience, do not realistically consider the uncertainties of loads and resistance and the basic reliability concepts. It is recognized to develope the design criteria by ETCM(Expected Total cost Minimization). In this study, therefore, the proper probability based design criteria (Optimum load and resistance factor design formats ) has been developed based on the safety levels observed from calibration Iii th existing standards, which applies to the ultimate limit states of steel structural members.

• Computational Structural Engineering
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• v.9 no.1
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• pp.125-132
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• 1996

This study is to propose a practical and realistic reliability analysis by ETCM (Expected Total Cost Minimization). One of the main objectives is intended to propose the safety assessment and capacity rating of existing reinforced concrete members by evaluation index, that is RF(Rating Factor) from the results of the field test and inspection for reinforced concrete bridge. ETCM method is used for the reliability analysis of the proposed models. The proposed reliability model and method are applied to the safety assessment and system factors of reinforced concrete members.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.273-273
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• 2002

In this paper, we investigate a software release policy with software reliability growth factor during the warranty period by assuming that the software reliability growth is assumed to occur after the testing phase with probability p and the software reliability growth is not assumed to occur after the testing phase with probability 1-p. The optimal release policy to minimize the expected total software cost is discussed. Numerical examples are shown to illustrate the results of the optimal policy. And we consider a Bayesian decision theoretic approach to determine an optimal software release policy. This approach enables us to update our uncertainty when determining optimal software release time, When the failure time is Weibull distribution with uncertain parameters, a bayesian approach is established. Finally, numerical examples are presented for illustrative propose.

• Journal of the military operations research society of Korea
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• v.24 no.2
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• pp.146-161
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• 1998

This article develops model of the nonstationary state behavior of the multiechelon spare parts provisioning systems. This study is concerned with a problem of determining the near optimal requirements level of the spare parts, especially Concurrent Spare Parts(CSP). CSP is supplied with the procurement of new equipment system, and is used to sustain the equipment without resupply during the initial coverage period. We consider this situation as a multiechelon inventory model with several bases and one depot. And we assume an equipment system which consists of many types of parts would grounded if one of the parts fail. Also this multiechelon CSP problem is considering the nonstationary poisson failure process and nonstationary exponential repair process in a dynamic environment. We develop an efficient computational procedure to find the near optimal number of spare parts minimizing the total expected cost, while achieving the required system availability. Finally we present a simple example of suggested method.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.71-79
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• 2014

This paper discusses a method for the determination of frequency control reserve requirement with consideration of the interaction between ex-ante planning and real-time balancing. In proposed method, we consider the fact that the delivered energy for tertiary control reserve is determined based on required capacity for secondary control reserve and the expected amount of load errors. Uncertain load errors are derived by Brownian motion, an optimization method is suggested using a stochastic programming. In a short, we propose an interactive dependent method for determining secondary control reserve requirement based on the principle that it satisfies to minimize the total cost. As a result, this paper provides will analyze for an example model to demonstrate the capabilities of the method.

• Journal of Korean Society for Quality Management
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• v.15 no.1
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• pp.55-62
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• 1987

A stochastic model for an inventory system in which depletion of stock takes place due to random demand as well as random loss of items is studied under the assumption that the intervals between successive unit demands, as well as those between successive unit losses, are independently and identically distributed random variables having negative exponential distribution with respective parameters. We have derived the steady state probability distribution of the net inventory level assuming negative exponential delivery time under the continuous review (S-1, S) inventory policy. Also we have derived the total expected cost expression and necessary conditions to be satisfied for an optimal solution.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.4
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• pp.139-144
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• 1999

Based on the recent developments of the reliability-based structural analysis and design as well as the extending knowledge on the probabiliistic characteristics of load and resistances, the probability based design criteria have been successfully developed for many standards. Since the probabilistic characteristics depend highly on the local load and resistances, it is recognized to develop the design criterion compatible with domestic requirements. The existing optimum design methods, which are generally based on the structural theory and certain engineering experience, do not realistically consider the uncertainties of load and resistances and the basic reliability concepts. This study is directed to propose a optimum design based Expected Total Cost Minimization on P.S.C Box Girder Bridge system which could possibly replace optimum design based traditional provisions of the current code, based on the Neldel-Mead Method reliability theory.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.47
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• pp.87-99
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• 1998

This study is concerned with a problem of determining the optimal requirements level of the spare parts, especially Concurrent Spare Parts(CSP). CSP is supplied with the procurement of new equipment system, and is used to sustain the equipment without resupply during the initial coverage period. We consider this situation as a multiechelon inventory model with several bases and one depot. And we assume a equipment system which consists of many types of parts would grounded if one of the parts fail. Also this multiechelon CSP problem is considering a time-varing (dynamic) environment. We develop a computational procedure to find the optimal number of spare parts minimizing the total expected cost, while achieving the required system availability. Finally we present a simple example of suggested method.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1002-1003
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• 2006

This research mainly focuses on the development of sinter brazing technology for improving the process related to belt pulley made by sinter hardening. As the machine process of belt pulley takes up more than half of the total manufacturing hours, we propose changing the process to pulley groove brazed and bonded with pulley disc by applying sinter brazing to belt pulley. With the new process, the belt pulley is expected to reduce manufacturing cost to 70% of the original process by applying the sinter brazing technology; and the belt pulley bound by sinter brazing only loses 10% bonding strength compared with the original process.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.714-715
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• 2006

The Application of powder metallurgy (PM) aluminum structural parts is at its early growing stage, despite of some automotive applications. The market potential for PM aluminum, however, is large. Growth is expected from the market expansion of the existing applications and new applications, including the replacements of aluminum and zinc based castings and some ferrous PM automotive parts by PM aluminum. Compared to castings, PM is an efficient mass production technology. The PM aluminum is more competitive than die casting for some automotive applications. Besides weight saving leading to performance improvement, the total cost increase for aluminum PM parts is less than 15% compared to ferrous PM automotive parts. The future is promising for PM aluminum.