• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.2
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• pp.1-18
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• 2017

Metal fatigue is an important aging mechanism that material characteristics can be deteriorated when even a small load is applied repeatedly. An accurate fatigue evaluation is very important for component structural integrity and reliability. In the design stage of a nuclear power plant, the fatigue evaluations of the Class 1 components have to be performed. However, operating experience shows that the design evaluation can be very conservative due to conservatism in the transient severity and number of occurrence. Therefore, the fatigue monitoring system has been considered as a practical mean to ensure safe operation of the nuclear power plants. The fatigue monitoring system can quantify accumulated fatigue damage up to date for various plant conditions. The purpose of this paper is to describe the fatigue monitoring procedure and to introduce the fatigue monitoring program developed by the authors. The feasibility of the fatigue monitoring program is demonstrated by comparing with the actual operating data and finite element analysis results.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.167-172
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• 2011

Generally, the analysis of railroad wear data is most effective method for the efficient railway maintenance. The wear of railway track affects loss of rough ride, noise or vibration of train and traveling safety. Moreover as the track is worn away, this promotes destruction of structural mechanism of rail track which can bring about increasing of rail track maintenance cost drastically. For this reason, it is very important and interested research subject to design railway track structure and to analyse train movement mechanism based on systematic analysis of the reasons causing rail wear possible in real field. In this research, for the efficient maintenance, Life Cycle Performance of rail track and maintenance characteristics are computed considering some track components such as track type, contracting type, sleeper type and roadbed type. Time - Wear probabilistic distribution relationship as well as multiple regression analysis based on time, curvature and wear data are computed to predict the service life remainder of railway track and to be adapted to safety assessment.

• Journal of Korean Society on Water Environment
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• v.26 no.2
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• pp.243-251
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• 2010

Evapotranspiration and rainfall-runoff are the major components of hydrological cycle and thereby the changes of them can directly affect the wetness/dryness or runoff characteristics of basins. In this study the wetness/dryness in Geum river basin are classified by dint of cumulative probability density function of monthly moisture index and the long term changes of them are analyzed based on climatic water balance concept. The drought events in Geum river basin are selected through evaluation of monthly moisture index and the various hydrological properties of them are investigated in detail. Also the trends of time-series of climatic water balance components are examined by Seasonal Kendall test and the variability of hydrological cycle in Geum river basin during the recent decade is inquired. It is judged that the results of this study can be contributed to establishment of the counter plan against the future drought events as the fundamental information.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.1
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• pp.45-50
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• 2001

With increasing complexity of digital logic circuits, fast and accurate verification of functional behaviour becomes most critical bottleneck in meeting time-to-market requirement. This paper presents several techniques for accelerating a cycle-based logic simulation. The acceleration techniques include parallel pattern logic evaluation, circuit size reduction, and the partition of feedback loops in sequential circuits. Among all, the circuit size reduction plays a critical role in maximizing logic simulation speedup by reducing 50% of entire circuit nodes on the average. These techniques are incorporated into a levelized table-driven logic simulation system rather than a compiled-code simulation algorithm. Finally, experimental results are given to demonstrate the effectiveness of the proposed acceleration techniques. Experimental results show more than 27 times performance improvement over single pattern levelized logic simulation.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.183-183
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• 2023

Smart water cities (SWC) are urban municipalities that utilizes modern innovations in managing and preserving the urban water cycle in the city; with the purpose of securing sustainability and improving the quality of life of the urban population. Understanding the different urban water characteristics and management strategies of cities situate a baseline in the development of evaluation scheme in determining whether the city is smart and sustainable. This research herein aims to develop measurements and evaluation for SWC Key Performance Indicators (KPIs), and set up a unified global standard and certification scheme. The assessment for SWC is performed in technical, as well as governance and prospective aspects. KPI measurements under Technical Pillar assess the cities' use of technologies in providing sufficient water supply, monitoring water quality, strengthening disaster resilience, minimizing hazard vulnerability, and maintaining and protecting the urban water ecosystem. Governance and Prospective Pillar on the other hand, evaluates the social, economic and administrative systems set in place to manage the water resources, delivering water services to different levels of society. The performance assessment is composed of a variety of procedures performed in a quantitative and qualitative manner, such as computations through established equations, interviews with authorities in charge, field survey inspections, etc. The developed SWC KPI measurements are used to evaluate the urban water management practices for Busan Eco Delta city, a Semulmeori waterfront area in Gangseo district, Busan. The evaluation and scoring process was presented and established, serving as the basis for the application of the smart water city certification all over the world. The established guideline will be used to analyze future cities, providing integrated and comprehensive information on the status of their urban water cycle, gathering new techniques and proposing solutions for smarter measures.

• Journal of the Korean Society of Combustion
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• v.15 no.2
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• pp.1-11
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• 2010

Power generation systems based on the oxy-coal combustion with carbon dioxide capture and storage (CCS) capability are being proposed and discussed lately. Although a large number of lab scale studies for oxy-coal power plant have been made, studies of pilot scale or commercial scale power plant are not enough. Only a few demonstration projects for oxy-coal power plant are publicized recently. The proposed systems are evolving and various alternatives are to be comparatively evaluated. This paper presents a proposed approach for performance evaluation of a commercial 100 MWe class power plant, which is currently being considered for 'retrofitting' for the demonstration of the concept. The system is configurated based on design and operating conditions with proper assumptions. System components to be included in the discussion are listed. Evaluation criteria in terms of performance are summarized based on the system heat and mass balance and simple performance parameters, such as the fuel to power efficiency and brief introduction of the second law analysis. Also, gas composition is identified for additional analysis to impurities in the system including the purity of oxygen and unwanted gaseous components of nitrogen, argon and oxygen in air separation unit and $CO_2$ processing unit.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.359-366
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• 2009

A new life-cycle cost (LCC) evaluation scheme for marine reinforced concrete structures is proposed. In this method, unlike the conventional life-cycle cost evaluation performed during the design process, the life-cycle cost is updated successively whenever new information of the chloride penetration is available. This updating is performed based on the Bayesian approach. For important structures, information required for this new method can be obtained without any difficulties because it is a common element of various types of monitoring systems. Using the new method, the life-cycle maintenance cost of structures can be estimated with a good precision.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.17-27
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• 2005

This paper presents an integrated optimum design and a cost effectiveness evaluation method of a viscoelastically damped structural system. The criterion selected for the optimization is the minimization of the life?cycle cost which is a function of structural sizing variables and the amount of the viscoelastic damper. A genetic algorithm is used as a numerical searching technique in order to simultaneously find the optimum parameters of the integrated system. Optimal distributions of design variables according to various seismic characteristics are investigated by applying the proposed design method to a numerical example of a 10?story building structure. The cost effectiveness of viscoelastically damped structural system is also evaluated by comparing the life-cycle cost of the structure without viscoelastic dampers. The results show that the viscoelastic damper is effective in a region of low to moderate seismicity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.199-208
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• 1997

A local strain approach was applied to an external single and double grooved C-shaped specimen in order to evaluate and predict the fatigue crack initiation life by using low cycle fatigue properties. The low cycle fatigue properties were determined from the strain-controlled fatigue tests using smooth cylindrical axial specimens. Fatigue crack initiation life was evaluated by a life prediction software, FALIPS, based on the local strain approach. The fatigue life was significantly influenced by the mean stress, and SWT parameter represented the fatigue life effectively. The predicted fatigue crack initiation life was then compared to the experimental fatigue life evaluated from the C-shaped fatigue test specimens. A good correlation was found between the experimental and predicted fatigue lives within factors of 2 and 4 for the single and double grooved C-shaped specimens respectively. Also, experimental fatigue life of the double grooved specimen was 10-12 times longer than that of the single grooved specimen.

• Journal of Soil and Groundwater Environment
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• v.27 no.5
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• pp.18-31
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• 2022

To evaluate the impact of drought on agriculture in N. Korea, SPI (standardized precipitation index) analysis was carried out by utilizing time-series precipitation data during 1996 - 2003 when severe drought occurred throughout the country. The SPI value was estimated to reach 12 in approximately 60% of the total period, indicating that agricultural productivity deteriorated rapidly due to the long-term drought. The national average drought cycle, based on SPI 12, was estimated as 32.5 months for the last 40 years. However, when examined on 20-year basis, the drought cycle was shortened by 10.6 months in last 20 years (30.3 months) as compared to previous 20 years (40.9 months). Annual crop production continued to increase mainly in rice and maize until the mid-1990s, but declined sharply thereafter due to the drought. After the drought period, the production of potatoes of which growth is more resistant to drought started to increase to the production level comparable to those of rice and soybean. It is expected that changes in the agricultural production environment in N. Korea will be inevitable due to the climate change. To this end, using the results of the drought cycle analysis, it is possible to analyze the changes in the agricultural production environment in N. Korea in the future.