• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.21-26
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• 1997

Korea Atomic Energy Research Institute (KAERI) developed a risk monitor called Risk Monster which supports for plant operators and maintenance schedulers to monitor plant risk and to avoid high peak risk by rearranging maintenance work schedule. Risk Monster can update the plant risk continuously according to the change of system/component configuration since Risk Monster reevaluates the plant risk based on the Probabilistic Safety Assessment (PSA) results. A brief description of Risk Monster is provided. The PSA model of UCN 3, 4 nuclear power plant was converted by KAERI to Risk Monster model. Using this Risk Monster model, a feasibility study of the on-line maintenance of an Essential Service Water (ESW) pump was performed. On-line maintenance of one ESW pump has been shown to be acceptably safe, and has economic benefits. In addition, it is not a violation of technical specification to continue plant operation with an out-of-service ESW pump.

• Smart Structures and Systems
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• v.15 no.3
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• pp.609-625
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• 2015

Management of infrastructure stock is essential in sustainability of society, and its analysis and optimization are studied in the light of control system modeling in this paper. At the first part of the paper, cost of stock management is analyzed based on macroscopic statistics on infrastructure stock and economical growth. Stock management burden relative to economy is observed to become larger at low economic growth periods in developed economies. Then, control system modeling of stock management is introduced and by augmenting maintenance actions as control input, dynamic behavior of stock is simulated and compared with existing time history statistics. Assuming steady state conditions, applicability of the model to cross sectional data is also demonstrated. The proposed model is enhanced so that both preventive and corrective maintenance can be included as system inputs, i.e., feedforward and feedback control inputs. Optimal management strategy to achieve specified deteriorated stock level with minimal cost, expressed in terms of preventive and corrective maintenance actions, is derived based on estimated parameter values for corrosion of steel bridges. Relative cost effectiveness of preventive maintenance is shown when target deteriorated stock level is lower.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.426-434
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• 2020

This paper studies the impact of the maintenance time of anti-ship missile Harpoon on operational availability with real field data. The Harpoon maintenance simulation model is developed as a testbed for identifying the optimal inventory levels on operational availability. Using multiple linear regression analysis and integer programming, the optimal inventory levels of essential assemblies are suggested. Finally, the result of sensitivity analysis shows the quantitative impact of maintenance time on operational availability and inventory costs. The authors believe that this quantitative analysis can support policy decisions to decrease maintenance time of missiles.

• International Journal of Safety
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• v.5 no.2
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• pp.6-11
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• 2006

The time delay in servo control on LonWorks/IP Virtual Device Network (VDN) is highly stochastic in nature. LonWorks/IP VDN induced time delay deteriorates the performance and stability of the real-time distributed control system and hinders an effective preventive and predictive maintenance. Especially in real-time distributed servo applications on the factory floor, timely response is essential for predictive and preventive maintenance. In order to guarantee the stability and performance of the system for effective preventive and predictive maintenance, LonWorks/IP VDN induced time delay needs to be predicted and compensated for. In this paper position control simulation of DC servo motor using Zero Phase Error Tracking Controller (ZPETC) as a feedforward controller, and Internal Model Controllers (IMC) based on Smith predictor with disturbance observer as a feedback controller is performed. The validity of the proposed control scheme is demonstrated by comparing the IMC based on Smith predictor with disturbance observer.

• Architectural research
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• v.16 no.1
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• pp.17-25
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• 2014

This research is to restructure the public assessment of housing management in a standardized fashion, and a self-administered questionnaire survey was employed for data collection and analysis. In doing so, all the assessment tools nationwide were identified and assembled to extract the items included in the survey form. The survey form was mailed out to local officers in charge of housing management and professional housing managers in the nation, and the responses were statistically analyzed in order to structure the standard assessment tool of housing management. This research classified 3 main areas (General Maintenance, Operation and Community Living) in evaluating the housing management performance, and identified 35 essential items and 52 optional items. The 35 essential items were drawn from the 16 categories of the 3 areas (11 items of 5 categories for General Maintenance, 7 items of 4 categories for Operation, and 17 items of 7 categories for Community Living), and the rest 52 optional items were from the 16 categories of the 3 areas (24 items of 7 categories for General Maintenance, 26 items of 7 categories for Operation, and 2 items of 2 categories for Community Living). While all the items in the research are quantifiable, it's suggested that qualitative measurements be complementarily utilized in the assessment not only to explore the best practices of housing management but also to refine and modify the standardized tool in response to various environmental changes. As the public assessment of housing management is context-sensitive and critically related to local housing profile, the continuous implementation of the assessment will facilitate shifting the housing paradigm from production and consumption to management and reproduction.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.520-528
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• 2018

This paper studies the optimal inventory levels of Korea Assault Amphibious Vehicle(KAAV)'s assemblies in order to assure the required operational availability. The simulation model is built and implemented for the impact of the inventory levels on operational availability. Using regression analysis and integer programming, the optimal inventory levels of essential assemblies are suggested and analyzed. Finally, sensitivity analysis is conducted with recycling maintenance delay time.

• Biomedical Science Letters
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• v.12 no.3
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• pp.185-190
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• 2006

Lysyl oxidase (LOX) catalyzes the lysine-derived cross-links of fibrillar collagens and elastin in the extracellular matrix. Recent molecular cloning has revealed existence of a LOX family consisting of LOX and four lysyl oxidase-like proteins (LOXL, LOXL2, LOXL3 and LOXL4). Pathological conditions associated with impaired LOX activity in several heritable and acquired disorders lead to severe structural and functional abnormalities of cardiovascular tissues, such as occlusion of coronary arteries and aneurysms, suggesting an essential role for the LOX family proteins in the maintenance of the cardiovascular system. However, the specific roles of the lysyl oxidase-like proteins in normal and pathological conditions of the cardiovascular tissues have not been established yet. Here, I report that LOXL3, a novel member of the LOX family, is predominantly expressed in the aorta, with an amine oxidase activity toward collagen and elastin, suggesting an essential role of LOXL3 in the development and maintenance of the aorta.

• Journal of the military operations research society of Korea
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• v.34 no.3
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• pp.41-51
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• 2008

Advanced high-tech weapons have enormous affect on combat strength in modern warfare. However, lack of maintenance can cause decrease in equipment operating rate as well as decrease in expectation on demonstrative effect of combat strength during wartime. Therefore it is essential for combat readiness that the optimum requirement of equipment maintenance cost are forecasted and included in the budget. In this paper, the trend of equipment maintenance cost about K-111 1/4t military vehicle is first analyzed by evaluating the performance data of field operation. Secondly, based on above analyzed results, the forecasting model of equipment maintenance cost is designed. Finally, by applying this forecasting model, suggestion and estimation method of equipment maintenance cost have presented for the foreseeable future.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.631-636
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• 1996

This paper presents a Reliability Centered Maintenance (RCM) framework for implementation on safety system of nuclear power plant (NPP). RCM is a systematic methodology to optimize the surveillance and maintenance tasks for critical components which provides efficiently and effectively reliability of system and safety of plant. Maintenance of the safety systems is essential for its safe and reliable operation. Reliability Centered Maintenance at NPP is the program which assure that plant system remains within original design criteria and that is not adversely affected during the plant life time. Aim of this paper is to provide the RCM framework to implement it on safety systems. RCM framework is described in four major steps.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.114-116
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• 2005

This paper presents a maintenance application for power transformer. High quality maintenance and accurate diagnosis are essential for all transformers, especially for older ones. The developed application provides maintenance guides for dry type transformer and oil-filled transformer to prevent any malfunctions and to lengthen the lifetime of transformers. Based on windows application, TTS (text to speech) and 3D graphics technologies have been used to enhance the user friendly interface. Developed application is helpful for both expert and novice operators at substation.