• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.767-776
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• 2020

Due to the recent climate change caused by global warming, weather changes in a different pattern from the past have occurred, and the increase in seawater temperature has led to an increase in the size and intensity of typhoons. Accordingly, there is an increasing need for bitts that can be used to secure mooring safety of the ship when a sudden gust occurs. Based on 12 scenarios of a mooring safety evaluation program, this study analyzed the criteria for arranging bollard and bitt, and analyzed the sensitivity of mooring safety when using storm bitts. As a result of the evaluation, it was analyzed that the mooring factor value decreased compared to the general mooring line arrangement when the fore and stern breastline were added to the bitts for gusts. The results of this study can be used as basic data for proposing storm bitts arrangements for gusts in consideration of the characteristics of berth ships and ports. From the perspective of ship operators, storm bitts at the pier will be an effective method for securing the ship's mooring safety in case of a gust of wind.

• Journal of Environmental Science International
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• v.31 no.7
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• pp.543-553
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• 2022

The latest aerospace technology is important for the stable flight of a launch vehicle, but weather conditions on the day of launch are also one of the essential factors for successful launch campaign. If a launch vehicle is directly struck while preparing to take off from the launch pad on the day of launch or the electronic device are damaged by induced current during flight of the launch vehicle, this means launch failure and can lead to enormous national loss. Therefore, for a successful launch campaign, it is necessary to analyze the lightning detection characteristics of the Naro Space Center. In this study, the seasonal factors of the lightning that occurred over the Naro Space Center from 2003 to 2017, the influence of the polarity, and the correlation with the lightning intensity was confirmed. As a result, there was a high probability of intensive occurrence of multiple lightning strikes in summer, and a high proportion of positive (+) lightning strikes in winter. Lastly, in the distribution of the number of lightning strikes, an average of 2.0 to 2.5 negative (-) lightning strikes occurs in the coastal regions of the South and West Seas when one flash happens.

• Journal of Environmental Science International
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• v.31 no.1
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• pp.61-76
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• 2022

In this study, surface particulate matter (PM_2.5) concentrations were calculated based on empirical equations using measurements of ceilometer backscatter intensities and meteorological variables taken over 19 months. To quantify the importance of meteorological conditions on the calculations of surface PM_2.5 concentrations, eight different meteorological conditions were considered. For each meteorological condition, the optimal upper limit height for an integration of ceilometer backscatter intensity and coefficients for the empirical equations were determined using cross-validation processes with and without considering meteorological variables. The results showed that the optimal upper limit heights and coefficients depended heavily on the meteorological conditions, which, in turn, exhibited extensive impacts on the estimated surface PM_2.5 concentrations. A comparison with the measurements of surface PM_2.5 concentrations showed that the calculated surface PM_2.5 concentrations exhibited better results (i.e., higher correlation coefficient and lower root mean square error) when considering meteorological variables for all eight meteorological conditions. Furthermore, applying optimal upper limit heights for different weather conditions revealed better results compared with a constant upper limit height (e.g., 150 m) that was used in previous studies. The impacts of vertical distributions of ceilometer backscatter intensities on the calculations of surface PM_2.5 concentrations were also examined.

• Composites Research
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• v.22 no.5
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• pp.37-42
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• 2009

Thermal analysis properties and chemical structure of carbon fiber/epoxy composites under environmental exposure were examined using an accelerated aging tester which can simulate real weather conditions such as temperature, moisture and ultraviolet. The composite specimens were exposed to combined environmental factors up to 3000 hours. Thermal analysis properties and chemical structure of the composites were evaluated with various exposure times through Modulated DSC and FTIR. According to the results of Modulated DSC, the glass transition temperature increased as exposure time increased due to the formation of network structures in the composites. Also endotherm peaks of enthalpy relaxation related to physical aging that can affect the properties of the composites were observed as exposure time increased. From the results of FTIR, it was found that the location of the peaks was little affected by exposure time, but the intensity of the peaks slightly decreased as exposure time increased due to the curing reaction in the epoxy group.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.383-383
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• 2021

강수는 수자원 분석 및 지리학적 연구에 가장 핵심적으로 쓰이는 수문인자이며, 최근 기후변화와 방재 관련한 다양한 연구에서 정확한 강수자료의 중요성이 부각되고 있다. 특히, 강수는 지표에서의 유출, 침투, 증발 등 다양한 수문현상으로 이어지므로, 수문순환, 물수지 분석에 있어 강우강도 등 강수 발생 양상과 유형에 대한 정확한 자료는 필수불가결하다. 강수량은 Automatic Weather Station (AWS)을 통해 비교적 정확하게 측정되고 있으나, 이러한 계측자료는 기상학적, 지형적 영향을 크게 받으며 대표성이 좁다는 단점을 가지고 있어 유출 및 기후 등 공간적 범위를 대상으로 한 연구에 활용하기에 한계점을 가지고 있다. 이러한 한계점을 극복하기 위해 지상강우레이더를 통한 국지적 강수자료 및 인공위성 기반 전 지구적 강수 관측 자료가 활용되고 있다. 특히 인공위성을 활용한 강우 측정방법은 미계측 유역에서 수자원 측정 및 관리 계획을 세우거나 전 지구적으로 장기적 변화를 분석하는데 있어 가장 활용도가 높다. National Aeronautics and Space Administration (NASA)의 Tropical Rainfall Measuring Mission (TRMM)을 포함한 기존 강수측정 보조 위성에 더하여 2014년 Global Precipitation Measurement (GPM) 핵심 위성이 발사된 이후 다양한 기관에서 여러 인공위성을 결합한 강수 산출물들을 제공하고 있다(NASA-IMERG, JAXA-GSMAP, NOAA-CMORPH). 본 연구에서는 세 가지 위성 기반 강수 자료의 산출 알고리즘을 비교□분석하고, 강우강도에 따른 산출물들의 정확도를 평가하였다. 본 연구결과는 높은 강우강도 발생 시 나타나는 위성 강수자료의 불확실성을 개선하는 데 기여할 수 있을 것으로 판단되며, 이후 신뢰도 높은 다중 위성 융합 강수 산출물을 구현하기 위한 바탕이 될 것으로 기대된다.

• Wind and Structures
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• v.37 no.4
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• pp.315-329
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• 2023

We investigated the wind characteristics in the near-surface layer during the landfall of Typhoon Mujigae (2015) based on observations from wind towers in the coastal areas of Guandong province. Typhoon Mujigae made landfall in this region from 01:00 UTC to 10:00 UTC on October 4, 2015. In the region influenced by the eyewall of the tropical cyclone, the horizontal wind speed was characterized by a double peak, the wind direction changed by >180°, the vertical wind speed increased by three to four times, and the angle of attack increased significantly to a maximum of 7°, exceeding the recommended values in current design criteria. The vertical wind profile may not conform to a power law distribution in the near-surface layer in the region impacted by the eyewall and spiral rainband. The gust factors were relatively dispersed when the horizontal wind speed was small and tended to a smaller value and became more stable with an increase in the horizontal wind speed. The variation in the gust factors was the combined result of the height, wind direction, and circulation systems of the tropical cyclone. The turbulence intensity and the downwind turbulence energy spectrum both increased notably in the eyewall and spiral rainband and no longer satisfied the assumption of isotropy in the inertial subrange and the -5/3 law. This result was more significant in the eyewall area than in the spiral rainband. These results provide a reference for forecasting tropical cyclones, wind-resistant design, and hazard prevention in coastal areas of China to reduce the damage caused by high winds induced by tropical cyclones.

• Atmosphere
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• v.33 no.5
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• pp.531-548
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• 2023

We developed the Aviation Convective Index (ACI) for predicting deep convective area using the operational global Numerical Weather Prediction model of the Korea Meteorological Administration. Seasonally optimized ACI (ACI_SnOpt) was developed to consider seasonal variabilities on deep convections in Korea. Yearly optimized ACI (ACI_YrOpt) in Part 1 showed that seasonally averaged values of Area Under the ROC Curve (AUC) and True Skill Statistics (TSS) were decreased by 0.420% and 5.797%, respectively, due to the significant degradation in winter season. In Part 2, we developed new membership function (MF) and weight combination of input variables in the ACI algorithm, which were optimized in each season. Finally, the seasonally optimized ACI (ACI_SnOpt) showed better performance skills with the significant improvements in AUC and TSS by 0.983% and 25.641% respectively, compared with those from the ACI_YrOpt. To confirm the improvements in new algorithm, we also conducted two case studies in winter and spring with observed Convectively-Induced Turbulence (CIT) events from the aircraft data. In these cases, the ACI_SnOpt predicted a better spatial distribution and intensity of deep convection. Enhancements in the forecast fields from the ACI_YrOpt to ACI_SnOpt in the selected cases explained well the changes in overall performance skills of the probability of detection for both "yes" and "no" occurrences of deep convection during 1-yr period of the data. These results imply that the ACI forecast should be optimized seasonally to take into account the variabilities in the background conditions for deep convections in Korea.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.797-807
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• 2023

This research aims to investigate the alterations in typhoon patterns attributable to climate change and to quantitatively assess the risk of damage to residential structures. The increasing prevalence of climate anomalies and severe weather events, a consequence of global warming, is causing escalating damage globally. Notably, numerous countries are facing substantial devastation due to shifts in typhoon trajectories. Despite this, there exists a gap in empirical research quantifying the impact of these changes on building integrity and the associated risk alterations driven by climate change. In addressing this gap, our study analyzes the frequency and intensity of typhoons impacting Korea, examining the evolution of these meteorological phenomena. Furthermore, we employ the Korean Typhoon Vulnerability Function for residential facilities to quantify the altered risk posed by these changing patterns. The outcomes of this study provide the private sector with essential data to formulate diverse scenarios and business strategies in response to the escalating risks of typhoon-related damage. Additionally, it equips governmental bodies with the necessary insights to develop comprehensive risk management strategies to mitigate the effects of future typhoons.

• Journal of the Korea Institute of Building Construction
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• v.24 no.3
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• pp.363-370
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• 2024

The escalating frequency and intensity of natural disasters and extreme weather events due to climate change have caused increasingly severe damage to societal infrastructure and buildings. Government agencies and private companies are actively working to evaluate these damages, but existing technologies and methodologies often fall short of meeting the practical demands for accurate assessment and prediction. This study proposes a novel approach to assess building damage resulting from natural disasters, focusing on typhoons-one of the most devastating natural hazards experienced in the country. The methodology leverages deep learning algorithms to evaluate typhoon-related damage, providing a comprehensive framework for assessment. The framework and outcomes of this research can provide foundational data for the evaluation of natural disaster-induced damage over the entire life cycle of buildings and can be applied in various other industries and research areas for assessing risk of damage.

• Journal of the Korean Society of Safety
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• v.39 no.1
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• pp.55-61
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• 2024

In response to the COVID-19 pandemic, the logistics industry in Korea has rapidly been expanding, with offline demand concentrating on online platforms owing to the development of digital infrastructure. This has increased the workload of courier drivers considerably, along with labor intensity. A delivery driver died recently from overwork due to the continuous increase in delivery volume, which raises social concerns. Delivery drivers work long hours, (over 12 hours) and are greatly affected by weather conditions, such as snow, rain, heat waves, and cold waves. In addition, they lack a fixed workplace; perform atypical work handling workpieces of various sizes, weights, and shapes; and spend a large amount of time driving as part of their work. This work involves a high level of tension and requires attention and concentration. Despite the frequency of industrial accidents in the courier industry, studies on safety and health to quantitatively analyze and systematize the work of courier workers are very scarce. Therefore, to define the work process necessary for investigating the harmful factors in delivery service and the work analysis, this study conducted interviews and on-site surveys to analyze the unit work of the delivery service by targeting delivery workers. In other words, a framework of unit work for work analysis was presented to enable research and analysis by considering the aforementioned characteristics of the courier industry. The process was broadly divided into work, transport, storage, delay, and inspection. Work was divided into loading, sorting, unloading, and door subcategories, and transportation was divided into vehicle, cart, and walking subcategories as well as 10 small processes. Moreover, 22 unit works were again drawn by conducting field surveys and interviews. The risk of unit work derived from this study was ergonomically evaluated, and the ergonomic analysis revealed that uploading and transportation were the most dangerous. The results of this study could be used as basic data for preventing industrial accidents among courier workers, whose work has increased with the logistics volume and the development of the logistics industry.