• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.380-387
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• 2016

Present research target to develop the procedure of long-term fatigue analysis of the structural details near the upper rolling chock of IMO type B tank by using the time domain modal analysis technique where both the contact and friction behavior can be accurately simulated. In order to perform the time domain analysis focused on the contact and friction, the entire model of the hull and tank was condensed with DOF reduction technique, which is obtained by transforming the global finite element model into its quasi-static modal coordinate. Modal analysis using the quasi-static deformation modes is chosen as a cost effective time domain simulation method and this is based on the fact that the structural response of the tank is quasi-static. Based on the developed cost effective time domain simulation method, the long-term fatigue analysis procedure for the structural details near the rolling chock and key of independent type tank is targeted to be established. The developed fatigue assessment procedure takes into account, wave induced stress and both contact and friction induced stress without loss of accuracy.

• Safety and Health at Work
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• v.15 no.2
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• pp.213-219
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• 2024

Background: The design, implementation, and evaluation are three important stages of occupational safety and health (OSH) interventions. Historically, there has been a tendency to prioritize implementation, often neglecting detailed design and rigorous outcome evaluation. Currently, much has changed, and contemporary approaches recognize the interdependence of these stages, considering them integral to the success of any intervention. This work presents a comprehensive procedure for implementing interventions, not only to ensure short-term effectiveness but also their long-term sustainability through continuous monitoring. The focus is on a national OSH project introducing a near-miss management system (NMS) in Italy. Methods: Initial meetings were convened among project partners, complemented by interviews with diverse stakeholders, to plan implementation steps and test the NMS. Tailored questionnaires were designed for diverse stakeholder groups - initial promoters, company managers and employers, and employees - facilitating targeted implementation, and three case studies were started in Italian regions to assess the structured implementation, involving intervention promoters and collaborating companies. Results: The primary outcome is the development of practical tools, specifically three questionnaires, which are considered valuable for establishing an effective human-centered implementation strategy, meticulously designed to facilitate ongoing monitoring of processes and continual enhancement of instruments intended for NMS integration within companies. Conclusions: This work lays the foundation for successful NMS implementation in Italy and, although the outlined procedure had specific objectives, it also provides valuable insights applicable in enhancing the effectiveness and sustainability of interventions across diverse contexts. It underscores the importance of comprehensive planning, stakeholder engagement, and continuous evaluation in achieving lasting OSH interventions.

• Journal of Wetlands Research
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• v.15 no.4
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• pp.493-500
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• 2013

Comparisons of surface sediment distributions in summer 1997 and 2011 and elevations on the tidal flats in April 1998 and March 2013 had been used for understanding the long-term changes of sedimentary environments at southern Kanghwa tidal flat, west coast of Korea. The mud sediments dominated in the eastern part and sandy mud sediments dominated in the western part of the tidal flat in 1997. In 2011, the surface sediments were dominant mud and sandy mud at Sunduri and Tonggum in the eastern part, sandy mud at Tongmakri in the middle part, and sand and muddy sand at Yeochari and Changhwari tidal flats in the western part. The area of mud sediments had decreased, but that of sand-mud mixed sediments extended to eastward tidal flat for 14 years. The long-term topographic changes showed that deposition occurred at Tongmakri and Yeochari and erosion occurred at Changhwari tidal flat during 15 years. These changes should be effected the local hydrodynamic changes by several constructions near the tidal flat since the 1990s.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.696-706
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• 2023

Consequences of an anticipated Beyond Design Basis Accident (BDBA) Long-Term Station Blackout (LTSBO) event with complete loss of grid power in the VVER-1200 reactor of Rooppur Nuclear Power Plant (NPP) of Unit-1 are assessed using the RASCAL 4.3 code. This study estimated the released radionuclides, received public radiological dose, and ground surface concentration considering 3 accident scenarios of International Nuclear and Radiological Event Scale (INES) level 7 and two meteorological conditions. Atmospheric transport, dispersion, and deposition processes of released radionuclides are simulated using a straight-line trajectory Gaussian plume model for short distances and a Gaussian puff model for long distances. Total Effective Dose Equivalent (TEDE) to the public within 40 km and radionuclides contribution for three-dose pathways of inhalation, cloudshine, and groundshine owing to airborne releases are evaluated considering with and without passive safety Emergency Core Cooling System (ECCS) in dry (winter) and wet (monsoon) seasons. Source term and their release rates are varied with the functional duration of passive safety ECCS. In three accident scenarios, the TEDE of 10 mSv and above are confined to 8 km and 2 km for the wet and dry seasons, respectively in the downwind direction. The groundshine dose is the most dominating in the wet season while the inhalation dose is in the dry season. Total received doses and surface concentration in the wet season near the plant are higher than those in the dry season due to the deposition effect of rain on the radioactive substances.

• Korean Journal of Remote Sensing
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• v.38 no.3
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• pp.265-282
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• 2022

Sea surface temperature (SST) is a factor that greatly influences ocean circulation and ecosystems in the Earth system. As global warming causes changes in the SST near the Korean Peninsula, abnormal water temperature phenomena (high water temperature, low water temperature) occurs, causing continuous damage to the marine ecosystem and the fishery industry. Therefore, this study proposes a methodology to predict the SST near the Korean Peninsula and prevent damage by predicting abnormal water temperature phenomena. The study area was set near the Korean Peninsula, and ERA5 data from the European Center for Medium-Range Weather Forecasts (ECMWF) was used to utilize SST data at the same time period. As a research method, Long Short-Term Memory (LSTM) algorithm specialized for time series data prediction among deep learning models was used in consideration of the time series characteristics of SST data. The prediction model predicts the SST near the Korean Peninsula after 1- to 7-days and predicts the high water temperature or low water temperature phenomenon. To evaluate the accuracy of SST prediction, Coefficient of determination (R²), Root Mean Squared Error (RMSE), and Mean Absolute Percentage Error (MAPE) indicators were used. The summer (JAS) 1-day prediction result of the prediction model, R²=0.996, RMSE=0.119℃, MAPE=0.352% and the winter (JFM) 1-day prediction result is R²=0.999, RMSE=0.063℃, MAPE=0.646%. Using the predicted SST, the accuracy of abnormal sea surface temperature prediction was evaluated with an F1 Score (F1 Score=0.98 for high water temperature prediction in summer (2021/08/05), F1 Score=1.0 for low water temperature prediction in winter (2021/02/19)). As the prediction period increased, the prediction model showed a tendency to underestimate the SST, which also reduced the accuracy of the abnormal water temperature prediction. Therefore, it is judged that it is necessary to analyze the cause of underestimation of the predictive model in the future and study to improve the prediction accuracy.

• Journal of the Korean housing association
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• v.27 no.6
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• pp.19-29
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• 2016

As a lifeway and social change, the neighborhood build up around elementary school based on Perry's Neighbourhood Unit becomes change. Elementary School does not function as a center of residents' activity or community any longer. Activities occurred near the school move to the community streets that many facilities are distributed to, while utilization of facilities near schools becomes lower. On the bases of the current states, this study aims to draw a practical neighborhood center of residential areas by case study. The research is being mainly about low-rise residential areas in Seoul which includes one elementary school at least. In order to deduct the center of neighborhood, the survey takes two steps. At the preliminary survey, conduct the observation and do an interview to investigate awareness and actual status. Also to analyze practical center, do a main survey about land value, pedestrian volume, distribution of public transit and facility density. The research result shows that there is another activated center street not nearby elementary school in every case. This study assumes that the neighborhood center is not limited around elementary school and could variously build up by circumstances. It has significance that we present a question about the traditional theory and also could be references of the future city maintenance in the long term.

• Economic and Environmental Geology
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• v.31 no.6
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• pp.509-518
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• 1998

Fly ashes have been deposited around Youngwol power plant until electrostatic precipitator was installed in 1981. Fresh fly ash samples from electrostatic precipitator and weathered fly ash from ash disposal site were collected from Youngwol power plant, along with 65 soil samples of nearby area to look into the influence of PFA deposit on the soils in surrounding area. In chemistry, EPA does not contain high level of toxic elements and there is no notable concentration of toxic elements in soil near power plant. Total concentrations of Co, Cr, Cu, V, and Zn are 13 ppm, 89 ppm, 73 ppm, 157 ppm and 57 ppm in PFA. Concentrations of theses elements in ash-rich soils are 15 ppm, 78 ppm, 60 ppm, 133 ppm and 68 ppm, and those in ash-poor soils are 19 ppm, 70 ppm, 38 ppm, 91 ppm and 97 ppm. But these metal elements are highly concentrated in magnetic fractions of EPA (Co, 129 ppm; Cr, 217 ppm; Cu, 210 ppm; V, 197 ppm; Zn 90 ppm). Considering the process of long-term weathering of PFA, potentially toxic substances from the ash could be leached into soils and groundwater.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.287-292
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• 2005

The flowfields generated by gaseous slot injection into a supersonic flow at a Mach number of 3.75 and a Reynolds number of $2.07{\times}10^7$ are simulated numerically. Fine-scale turbulence effects are represented by a two-equation(k-w SST model) closure model which includes $y^+$ effects on the turbulence model. Grid convergence index(GCI) is also considered to provide a measure of uncertainty of the grid convergence. Comparison is made with experimental data and other turbulence model in term of surface static pressure distributions, the length of the upstream separation region, and the penetration height. Results indicate that the k-w SST model correctly predicts mean surface pressure distribution and upstream separation length. However, it is also observed that the numerical simulation over predicts the pressure spike and penetration height compared with experimental data. All these results are taken within $1\%$ error band of grid convergence.

• Journal of Astronomy and Space Sciences
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• v.28 no.1
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• pp.37-54
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• 2011

Two semi-analytic solutions for a perturbed two-body problem known as Lagrange planetary equations (LPE) were compared to a numerical integration of the equation of motion with same perturbation force. To avoid the critical conditions inherited from the configuration of LPE, non-singular orbital elements (EOE) had been introduced. In this study, two types of orbital elements, classical Keplerian orbital elements (COE) and EOE were used for the solution of the LPE. The effectiveness of EOE and the discrepancy between EOE and COE were investigated by using several near critical conditions. The near one revolution, one day, and seven days evolutions of each orbital element described in LPE with COE and EOE were analyzed by comparing it with the directly converted orbital elements from the numerically integrated state vector in Cartesian coordinate. As a result, LPE with EOE has an advantage in long term calculation over LPE with COE in case of relatively small eccentricity.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.1
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• pp.23-30
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• 2005

A numerical scheme is proposed which is applicable to the evaluation of wave field containing floating structures, and the method is utilized to estimate the effect of the floating breakwaters to be installed in Wonjeon port near Masan. The model is based on the mild-slope equation which is widely accepted for the calculation of wave modulation near shores and an additional term is introduced to consider the wave scattering associated with the thin floating structures such as floating breakwaters. The tranquility in Wonjeon port with the floating breakwater in the east side is calculated and compared with the one with a bottom-fixed breakwater. The present method is believed to provide an efficient way of quantitative measurement of the performance of floating breakwaters.