• Journal of Applied Reliability
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• 제16권3호
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• pp.192-201
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• 2016

Purpose: In this paper, we propose the output model of the optimal inventory requirements of the Maintenance Float (M/F). Weapon systems were modernized and increased costs. Thus, the complexity increases with. Alternatives to achieve the goal of availability of weapon systems and to reduce life-cycle cost are required. Especially, securing spare parts is more effective than adding the amount of equipment or maintenance facilities to achieve the goal of availability and reduce life cycle costs. However, securing spare parts and repair costs are directly related, so exact requirements are needed. Methods: Three kinds of methods (Calculation method of applying the Poisson distribution, Calculation method of considering the number of CSP, and Calculation method of applying M&S program) that this paper proposed compare the influence of the availability and the amount of spare parts. Result: We calculate the cost of M/F when the operational availability is over than 80% and compare that result. The biggest cost was calculated from the Poisson distribution method. We found that requirements and unit price is the key factor that gives a significant effect. Conclusion: These three kinds of methods can be used as a basis for Maintenance Float calculation. Among them, the calculation method based on CSP is optimal replacement equipment requirements calculation method.

• International Journal of Concrete Structures and Materials
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• 제8권2호
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• pp.173-182
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• 2014

An experimental investigation was carried out to evaluate the mechanical properties of concrete mixtures in which coarse aggregate was partially (30, 50 or 70 %) replaced with pre-washed municipal solid waste incineration (MSWI) bottom ash. Results indicated that bottom ash reduced the compressive strength, elastic modulus, and levels of heavy metals in leachate when used as a replacement for gravel, and that the maximum amount of MSWI bottom ash in concrete should not exceed 50 %. To analyze the effect mechanism of bottom ash in concrete, the degree of hydration and the following pozzolanic reaction characterized by the pozzolanic activity index, and the porosity distribution in cement mortar. The study indicates that improved properties of concrete are not solely later strength gain and reduced levels of heavy metals in leachate but also the progression of pozzolanic reactions, where a dense structure contains a higher proportion of fine pores that are related to durability.

• The Journal of Korean Academy of Prosthodontics
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• 제43권3호
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• pp.331-337
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• 2005

For a missing teeth, orthodontic treatment may be a better choice of treatment in comparison to a conventional prosthetic replacement such as FPD, resin bonded prosthesis in view of aesthetics, periodontal health and function. Occasionally after an orthodontic treatment, an insufficient space may occur. The mini-implant could be an alternative in situations of narrow ridge dimension, where conventional root form implant could be compromised. The aim of this clinical report is to describe how a space that could not be restored with a traditional root form endosteal implant was managed and to present a technique to achieve optimal anterior esthetics in single implant restoration.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2001년도 추계학술발표대회
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• pp.598-601
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• 2001

Citrobacter sp. Y19 was studied for $H_2$ production from glucose in batch culture. Important conditions studied include phosphate concentration, temperature, glucose concentration, and gas-phase replacement. Optimal $H_2$ production was observed at 140 - 180 mM of phosphate and $36^{\circ}C$. When glucose concentration increased from 0.1 to 5% (w/v), $H_2$ production increased up to 2% and remained constant thereafter. Intermittent purging of the reaction bottle with Ar gas stimulated the $H_2$ production by alleviating the inhibition by $H_2$. The maximum productivity was observed to be 113.2 ml $H_2$/h-1.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2001년도 추계학술발표대회
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• pp.594-597
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• 2001

RhodopseudolllOllas palustris P4 was studied for $H_2$ production from glucose in batch culture. Important conditions studied include phosphate concentration, initial pH, temperature, glucose concentration, and gas-phase replacement. Optimal $H_2$ production was observed at 60 - 300 mM of phosphate and 7.8 - 8.6 of initial pH. The effect of culture temperature was negligible When glucose concentration increased from 0.1 to 5% (w/v), $H_2$ production increased up to 2% and remained constant thereafter. Intermittent purging of the reaction botlle with Ar gas stimulated the Hl production by alleviating the inhibition by $H_2$. The maximum productivity was 111.1 ml $H_2$/h-1.

• Proceedings of the KIEE Conference
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• 대한전기학회 2008년도 추계학술대회 논문집 전기설비전문위원
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• pp.92-94
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• 2008

폴리머 애자는 경량, 미려함, 소형, 비 분해 폭발 특성과 같은 다양한 장점 때문에 세라믹 애자를 대체하여 사용이 증가되고 있다. 그러나 폴리머 재료는 동일 목적의 세라믹 애자에 비하면 열화가 빠르고 성능이 저하되는 문제점이 있다. 최근 폴리머 애자의 사용기간이 10년 이상 경과하면서 이들에 대한 교체시기에 관한 관심이 증가하고 있으나 사용기간이 짧아 교체 시기론 예측하기 불가능한 실정이다. 이에 따라 본 논문에서는 국내에서 사용중인 폴리머애자 신품과 경년품의 복합가속열화시험을 실시하고 자연열화 시료와 비교하여 장기 열화특성을 평가하고 최적 교체방법을 제안하였다.

• Journal of Korean Institute of Industrial Engineers
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• 제17권1호
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• pp.1-8
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• 1991

For situations where there are several markets for a product with different profit/cost structures, an economic variables sampling plan is developed for determining the market to ship the lots to. It is assumed that the quality characteristic X is normally distributed with known variability and unknown mean having a normal prior distribution. Profit models are constructed which involve four profit/cost components ; profit from a conforming item, inspection cost, replacement cost, and cost from an accepted nonconforming item. Methods of finding optimal sampling plan are presented and a numerical example is given.

• Management Science and Financial Engineering
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• 제5권2호
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• pp.43-53
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• 1999

In many situations, the system failures depend on the operating environmental conditions that vary on time, usually with periodical manners. We use nonhomogeneous Poisson processes whose rate functions exhibit cyclic behavior as well as a long-term evolutionary trend to model the stochastic process of the failures when the rate of occurrence of the failures varies periodically, for example from day to day or between seasons. In this study, we compare optimal policies under the nonho-mogeneous process with/without a cyclic component in the failure rate function. The analytical re-sults for various situations are presented along with numerical examples using simulated data.

• Journal of the Korean Operations Research and Management Science Society
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• 제34권3호
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• pp.155-163
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• 2009

We develop a probability model to evaluate information security investment portfolios. We assume that organizations install portfolios of information security countermeasures to mitigate the damage such as loss of the transaction being processed, damage of hardware and data, etc. A queueing model and Its expected value analysis are used to derive the lost cost of transactions being processed, the replacement cost of hardwares, and the recovery cost of data. The net present value for each portfolio is derived and organizations can select the optimal information security investment portfolio by comparing portfolios.

• Journal of Korean Institute of Industrial Engineers
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• 제30권3호
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• pp.250-260
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• 2004

This study considers a linear connected-(r,s)-out-of-(m,n):F lattice system whose components are ordered like the elements of a linear (m,n )-matrix. We assume that all components are in the state 1 (operating) or 0 (failed) and identical and s-independent. The system fails whenever at least one connected (r,s)-submatrix of failed components occurs. The purpose of this paper is to present an optimization scheme that aims at minimizing the expected cost per unit time. To find the optimal threshold of maintenance intervention, we use a genetic algorithm for the cost optimization procedure. The expected cost per unit time is obtained by Monte Carlo simulation. The sensitivity analysis to the different cost parameters has also been made.