• 조명전기설비학회논문지
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• 제28권3호
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• pp.26-31
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• 2014

High temperature fuel cell system, such as molten carbonate fuel cells(MCFC) and solid oxide fuel cells(SOFC), are capable of operating at MW rated power output. The power output change of high temperature fuel cell imposes the thermal and mechanical stresses on the fuel cell stack. To minimize the thermal-mechanical stresses on the stack and increase the systems reliability, we should divide the power plant configuration to several banks. However, the improvement of reliability in fuel cell power plant system causes an increase of the investment cost, for example, replacement costs, labor costs, and so on. For this reason - the balance between investment and reliability improvement - many studies about the appropriate level of investment have been conducted. In this paper, we evaluate the cost for operation and installation, the benefit for electric energy and thermal energy sales, and the system reliability for several cases : these cases relate with the bank configuration.

• Smart Structures and Systems
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• 제22권2호
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• pp.151-159
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• 2018

Maintenance activities are regarded as a key part of the repairable deteriorating system because they maintain the equipment in good condition. In practice, many maintenance policies are used in engineering fields to reduce unexpected failures and slow down the deterioration of the system. However, in traditional maintenance policies, maintenance activities have often been assumed to be performed at the same time interval, which may result in higher operational costs and more system failures. Thus, this study presents two non-periodic preventive maintenance (PM) policies for repairable deteriorating systems, employing the failure rate of the system as a conditional variable. In the proposed PM models, the failure rate of the system was restored via the failure rate reduction factors after imperfect PM activities. Operational costs were also considered, which increased along with the operating time of the system and the frequency of PM activities to reflect the deterioration process of the system. A numerical example was provided to illustrate the proposed PM policy. The results showed that PM activities performed at a low failure rate threshold slowed down the degradation of the system and thus extended the system lifetime. Moreover, when the operational cost was considered in the proposed maintenance scheme, the system replacement was more cost-effective than frequent PM activities in the severely degraded system.

• Advances in concrete construction
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• 제11권4호
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• pp.285-298
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• 2021

This study focused on experimental evaluation of mechanical properties of pervious concrete mixtures with the aim of achieving higher values of strength while considering the associated costs. The effectiveness of key parameters, including cement content, water to cement ratio (W/C), aggregate to cement ratio (A/C), and sand replacement was statistically analyzed using paired-samples t-test, Taguchi method and one-way ANOVA. Taguchi analysis determined that in general, the role of W/C was more significant in increasing strength, both compressive and flexural, than cement content and A/C. It was found that increase in replacing percent of coarse aggregate with sand could undermine specimens to percolate water, though one-way ANOVA analysis determined statistically significant increases in values of strength of mixtures. Cost analysis revealed that higher strengths did not necessarily correspond to higher costs; in addition, increasing the cement content was not an appropriate scenario to optimize both strength and cost. In order to obtain the optimal values, response surface method (RSM) was carried out. RSM optimization helped to find out that W/C of 0.40, A/C of 4.0, cement content of about 330 kg/m3 and replacing about 12% of coarse aggregate with sand could result in the best values for strength and cost while maintaining adequate permeability.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.1189-1194
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• 2009

A gutter-shaped U grating is a facility that is installed at the sides of a road to provide pedestrians with a rainwater-free road. The previous studies on this facility focused mainly on the progress of the efforts that are being made to improve its performance and interception efficiency so as to prevent damages in regional areas due to the heavy rains caused by climate change. The studies on its maintenance, however, are still inadequate. Therefore, this study was conducted to analyze and compare the life cycle costs and performance evaluations of the steel and magic gratings, which are installed in apartments. The results of the study show that the replacement period and rate of gratings differ depending on where they are installed. The initial capital investment cost of a magic grating installed at a road where many vehicles pass is quite high, but in terms of its maintenance and entire-life-cycle costs, its total expenses are lower than those of a steel grating. The results of this study are expected to serve as preliminary data for the selection of an adequate grating that is suitable for particular places in the design phase of construction projects.

• 한국항만경제학회지
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• 제33권2호
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• pp.97-109
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• 2017

터미널 운영사(TOC) 입장에서 하역 크레인의 교체는 하역 성능의 향상을 통해 매출 및 이익을 증가시키기 위하여 투자 결정을 진행한다. 또한, 이러한 투자결정의 목표를 달성하기 위해서는 많은 비용과 노력이 수반되어야 한다. 하지만, 이러한 결정에 대하여 항만 이해관계자들의 적극적인 참여도 필요하나, 항만의 이해관계자들의 입장에서는 당사자들이 얻을 수 있는 기대효과가 분명할때 적극적으로 참여하게 될 것은 분명한 사실이다. 본 연구에서는 하역장비의 교체가 진행되었을 때에 항만 이해관계자들이 얻게 되는 직 간접적 비용 절감 효과를 파악하기 위하여 여수항의 벌크 터미널에서 하역장비 교체에 따른 4년간의 효과를 분석하였다. 분석 결과에 따르면, 직접적인 효과로 선박 용선료 3,649.6백만원, 항만시설이용료 1,528.8백만원, 연료비 1,383.4백만원을 포함하여 총 6,561.8백만원의 비용절감 효과가 나타났음을 알 수 있었다. 간접적인 효과로는 환경오염비용 2,134.8백만원 및 화물 재고비용 972.2백만원을 합쳐서 총 3,107.0백만원의 절감효과가 있음을 알 수 있었다. 결과적으로 TOC의 하역장비 교체는 항만의 이해관계자인 선사, 화주 및 정부 모두에게 비용적인 측면과 다른 측면에서 긍정적인 효과가 있음을 알 수 있다. 이러한 연구 결과를 활용하면, TOC가 하역장비의 교체를 추진함에 있어 이해관계자들의 적극적인 협조를 이끌어 낼 수 있는 근거로 활용이 가능할 것으로 판단된다.

• Environmental Analysis Health and Toxicology
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• 제31권
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• pp.26.1-26.9
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• 2016

Objectives Korea's Act on the Registration and Evaluation of Chemicals (K-REACH) was enacted for the protection of human health and the environment in 2015. Considering that about 2000 new substances are introduced annually across the globe, the extent of animal testing requirement could be overwhelming unless regulators and companies work proactively to institute and enforce global best practices to replace, reduce or refine animal use. In this review, the way to reduce the animal use for K-REACH is discussed. Methods Background of the enforcement of the K-REACH and its details was reviewed along with the papers and regulatory documents regarding the limitation of animal experiments and its alternatives in order to discuss the regulatory adoption of alternative tests. Results Depending on the tonnage of the chemical used, the data required ranges from acute and other short-term studies for a single exposure route to testing via multiple exposure routes and costly, longer-term studies such as a full two-generation reproducibility toxicity. The European Registration, Evaluation, Authorization and Restriction of Chemicals regulation provides for mandatory sharing of vertebrate test data to avoid unnecessary duplication of animal use and test costs, and obligation to revise data requirements and test guidelines "as soon as possible" after relevant, validated replacement, reduction or refinement (3R) methods become available. Furthermore, the Organization for Economic Cooperation and Development actively accepts alternative animal tests and 3R to chemical toxicity tests. Conclusions Alternative tests which are more ethical and efficient than animal experiments should be widely used to assess the toxicity of chemicals for K-REACH registration. The relevant regulatory agencies will have to make efforts to actively adopt and uptake new alternative tests and 3R to K-REACH.

• 한국건설관리학회논문집
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• 제2권2호
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• pp.59-67
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• 2001

본 연구는 사례연구를 통해서 강박스교와 PSC박스교의 생애주기비용(LCC)을 분석하여 경제성을 평가하는데 목적이 있다. 본 연구에서는 유지관리비를 산출하기 위해 보수 및 교체주기에 대한 설문조사를 실시하였으며, 교량 형식별 LCC 분석 및 비교에는 현재가치 법을 이용하였다. 본 연구의 수행 결과를 요약하면 다음과 같다. (1) 사례 연구를 통해 강박스교와 PSC박스교의 LCC 분석모델을 제시하였다. (2) 설문조사를 실시하여 강박스교와 PSC박스교 부속물의 보수 및 교체주기를 산정하였다. (3) LCC 사례 연구 결과, PSC박스교가 강박스교보다 경제적인 것으로 분석 되었다.

• 상하수도학회지
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• 제29권3호
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• pp.395-406
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• 2015

This research carried out an analysis on input cost and leakage reduction effect by leakage reduction method, focusing on the project for establishing an optimal water pipe network management system in the Taebaek region, which has been executed annually since 2009. Based on the result, optimal cost-benefit analysis models for water distribution network rehabilitation project were developed using DEA(data envelopment analysis) and multiple regression analysis, which have been widely utilized for efficiency analysis in public and other projects. DEA and multiple regression analysis were carried out by applying 4 analytical methods involving different ratios and costs. The result showed that the models involving the analytical methods 2 and 4 were of low significance (which therefore were excluded), and only the models involving the analytical methods 1 and 3 were suitable. From the result it was judged that the leakage management method to be executed with the highest priority for the improvement of revenue water ratio was installation of pressure reduction valve, followed by replacement of water distribution pipe, replacement of water supply pipe, and then leakage detection and repair; and that the execution of leakage management methods in this order would be most economical. In addition, replacement of water meter was also shown to be necessary in case there were a large number of defective water meters.

• 한국강구조학회 논문집
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• 제15권4호통권65호
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• pp.341-358
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• 2003

본 논문에서는 강교의 실용적인 생애주기비용 (LCC) 최적설계를 위한 일반화된 정식화와 LCC 설계시스템 모델을 제안하였다. 강교 최적설계를 위한 LCC는 초기비용, 직접 복구 (rehabilitation) 비용과 인적 혹은 물적 손실비용의 직접비용, 도로이용자비용, 그리고 사회-경제 손실비용을 포함한 간접비용의 현재가치의 합으로 정식화하였다. 특히 본 논문에서는 교량이 속해 있는 도로의 네트워크를 고려한 도로이용자비용과 사회-경제 손실비용 산정을 위한 새로운 모델을 제안하였다. 본 연구에서 제안된 LCC 정식화 모델은 실제 강박스 거더교와 강상판형교의 LCC 최적설계 문제에 적용하였고, 다양한 경우에 대한 LCC의 효율성에 대해 비교 고찰하였다. LCC를 고려한 강교량의 최적설계는 설계시방서에 기초한 설계방법뿐만 아니라 초기비용 절감을 위한 최적설계 방법과 비교할 때 더욱 합리적이고, 경제적이며, 안전한 설계를 유도할 수 있으리라 판단된다.

• 한국신뢰성학회지:신뢰성응용연구
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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.