• Journal of Industrial Technology
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• v.35
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• pp.95-102
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• 2015

Two extreme wind speed prediction models, the EWM(Extreme wind speed model) in IEC61400-1 and the Gumbel method were compared in this study. The two models were used to predict extreme wind speeds of six different sites in Korea and the results were compared with long term wind data. The NCAR reanalysis data were used for inputs to two models. Various periods of input wind data were tried from 1 year to 50 years and the results were compared with the 50 year maximum wind speed of NCAR wind data. It was found that the EWM model underpredicted the extreme wind speed more than 5 % for two sites. Predictions from Gumbel method overpredicted the extreme wind speed or underpredicted it less than 5 % for all cases when the period of the input data is longer than 10 years. The period of the input wind data less than 3 years resulted in large prediction errors for Gumbel method. Predictions from the EWM model were not, however, much affected by the period of the input wind data.

• The KSFM Journal of Fluid Machinery
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• v.15 no.1
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• pp.21-26
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• 2012

In this investigation, the aerodynamic performance evaluation of a 1MW class blade has been performed with the purpose of the verification of target output and its clear understanding of flow field using CFD commercial code, ANSYS FLUENT. Before making progress of CFD analysis the HERACLES V2.0 software based on blade element momentum theory was applied for confirmation of quick and approximate performance in the preliminary stage. The blade was designed to produce the target output of a 1MW class at a rated wind speed of 12m/s, which consists of five different airfoils such as FFA W-301, DU91-W250, DU93-W-210, NACA 63418 and NACA 63415 from hub to tip. The mechanical power by CFD is approximately 1.195MW, which is converted into the electrical power of 1.075MW if the system loss is considered to be 0.877.

• Journal of Biosystems Engineering
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• v.18 no.1
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• pp.60-70
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• 1993

In this study, the environment variations and distributions in different types of greenhouses were measured and analyzed. The elements of environment analyzed were temperature, relative humidity, illumination, carbon dioxide and wind velocity. The analyzed greenhouse types were auto-multi type which has an automatic environment control system and multiple continuous arches, regular-multi type which has an temperature control system and multiple continuous arches, and single arch type which has no environment control system without manual temperature keeping method. The results of this study can be used for the greenhouse building and managements.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.5
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• pp.96-102
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• 2019

This study investigated the heat dissipation characteristics of a heat-sensitive LED. More than 80% of the power supply is converted into heat energy, which has a fatal impact on the lifetime of the LED. Therefore, the effective heat dissipation characteristics of a heatsink, such as a 30W floodlight, through forced convection were grasped and the heat transfer characteristics were tested. As a result, it was confirmed that the smaller the number of fins, the more the temperature distribution varies according to the wind velocity. In addition, the larger the number of fins, the smaller the temperature difference according to the wind velocity. Therefore, it was found through this experiment that excellent heat dissipation performance was exhibited as the heat dissipation area and wind velocity increased.

• Korean Journal of Remote Sensing
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• v.36 no.5_1
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• pp.679-692
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• 2020

We coupled a CFD model to the WRF-Chem model (WRF-CFD model) and investigated the characteristics of flows and carbon monoxide (CO) distributions in a building-congested district. We validated the simulated results against the measured wind speeds, wind directions, and CO concentrations. The WRF-Chem model simulated the winds from southwesterly to southeasterly, overestimating the measured wind speeds. The statistical validation showed that the WRF-CFD model simulated the measured wind speeds more realistically than the WRF-Chem model. The WRF-Chem model significantly underestimated the measured CO concentrations, and the WRF-CFD model improved the CO concentration prediction. Based on the statistical validation results, the WRF-CFD model improved the performance in predicting the CO concentrations by taking complicatedly distributed buildings and mobiles sources of CO into account. At 04 KST on May 22, there was a downdraft around the AQMS, and airflow with a relatively low CO concentration was advected from the upper layer. Resultantly, the CO concentration was lower at the AQMS than the surrounding area. At 15 KST on May 22, there was an updraft around the AQMS. This resulted in a slightly higher CO concentration than the surroundings. The WRF-CFD model transported CO emitted from the mobile sources to the AQMS measurement altitude, well reproducing the measured CO concentration. At 18 KST on May 22, the WRF-CFD model simulated high CO concentrations because of high CO emission, broad updraft area, and an increase in turbulent diffusion cause by wind-shear increase near the ground.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.4
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• pp.415-426
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• 2023

In this study, the horizontal and vertical structure of wind speed and wind direction were analyzed at the origin of migratory insect pests in China. Wind rose analysis was carried out using the Land-Atmosphere Modeling Package (LAMP) - WRF data, which has the spatiotemporal resolution of about 20 km and 1 hour intervals. Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) was employed for backward trajectory analysis between South Korea and Southeastern China with Global Data Assimilation System (GDAS). The research interest date is July 16, when rice planthopper and leafhopper were observed at the same time. In order to examine where a jet stream occurs in the vertical in source regions and South Korea during the period (July 8 to July 17 in 2021), three-dimensional wind information was extracted and analyzed using the east-west, north-south, and vertical component wind data of the LAM P. The vertical distribution of wind showed that the wind changed in favor of the inflow of migratory insect pests during the period. As a result of analyzing the wind rose, about 30% or more of the wind at a point close to South Korea was classified into the low-level jet stream. In addition, majority of the wind directions for the low-level jet streams (rather than high-level jet streams) at the five origin sites were heading toward South Korea and even Japan, and this was supported by the HYSPLIT-based backward trajectory analysis.

• Journal of Navigation and Port Research
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• v.47 no.6
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• pp.315-323
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• 2023

Marine accidents due to loss of stability of small ships have continued to increase over the past decade. In particular, since sudden winds have been pointed out as main causes of most small ship accidents, safety measures have been established to prevent them. In this regard, to prevent accidents caused by sudden winds, a systematic analysis technique is required. The aim of the present study was to develop a probabilistic approach to estimate extreme value and evaluate effects of wind on motion characteristics of ships. The present study included studies of motion analysis, extraction of extreme values, and motion characteristics. A series analysis was conducted for three conditions: wave only, wave with uniform wind speed, and wave with the NPD wind model. Hysteresis filtering and Peak-Valley filtering techniques were applied to time-domain motion analysis results for extreme value extraction. Using extracted extreme values, the goodness of fit test was performed on four distribution functions to select the optimal distribution-function that best expressed extreme values. Motion characteristics of a fishing boat were evaluated for three periodic motion conditions (Heave, Roll, and Pitch) and results were compared. Numerical analysis was performed using a commercial solver, ANSYS-AQWA.

• Journal of the Korean Geographical Society
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• v.33 no.2
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• pp.179-190
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• 1998

한반도에 내습하는 태풍의 발생빈도와 강도는 큰 편은 아니나 우리는 거의 해마다 태풍으로 인한 재해를 경험하고 있다. 특히 태풍에 의한 경제적 손실은 1960년대 이후 경제개발과 도시화로 인한 인구과밀지역에서 크게 나타나고 있다. 본 논문에서는 태풍재해의 대책을 수립하는데 필요한 기초자료를 마련하기 위한 방향을 제시하고자, 태풍재해를 유발하는 기상적 요인과 더불어 경제.사회적 조건이 재해의 규모 및 강도에 미치는 기여도가 상당히 크다는 것을 밝히고자 하였다. 한반도에 큰 피해를 남기는 태풍의 진로는 서해를 따라 북진하다가 반도부를 거쳐 동쪽으로 빠져나가는 E경로로서 한반도의 동쪽을 통과하는 진로를 취할 때 보다 더 큰 영향을 끼친다. 재해지역의 공간분포는 대체로 남해안 지역에 집중되어 있다. 태풍재해는 일반적으로 태풍중심에서부터 피해지역가지의 최단거리, 강수량, 최대풍속 등의 기상적 요긴과 피해지역의 토지이용 및 그 지역의 산업구조를 포함하는 사회.경제적 요인 그리고 재해대책수준 및 태풍예보기술 등 다양한 원인에 의해 태풍의 피해의 정도가 결정됨을 태풍재해의 공간분포와 발생요인의 분석결과 알 수 있었다. 침수로 인한 피해는 경남과 전남의 농촌지역에서 넓게 나타나고, 경제적 손실은 대규모의 도시와 공업이 발달된 경남해안지역에 집중되고 있다. 태풍재해의 규모를 저감시키기 위해서는 보다 정확하고 신속한 기상예보기술의 향상을 도모해야 함은 물론 홍수예방시설의 확충과 더불어 GIS 기법을 활용한 방재정보시스템에 기초하는 도시종합방재대책을 수립하도록 해야 할 것이다.

• Spatial Information Research
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• v.21 no.4
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• pp.1-6
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• 2013

This study presents the analysis of temporal and spatial distribution of occurrences of wind gust over Korea from 2002 to 2009. The events during typhoons are excluded and the topographical effects on the wind speed are also corrected using KBC (2005). As the results, the frequency of the occurrences is as high as 286 and the higher occurrences appear mainly along the coastal area. This study also shows that the uncertainty of the appearance of wind gust during thunderstorm is much higher than in synoptic wind by comparing wind speed records for both events. This study also found that the spatial distribution of cumulative cloud quotient is closely correlated to that of occurrences of thunderstorm wind gust, which suggests the possible utilization of the cloud quotient as weighting factors in assessing wind gust risk.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.29-29
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• 2019

급격한 도시화와 기후변화로 인한 자연적인 물순환 구조의 변화는 기존 수자원 이용 경향을 변화시키며 하천건천화 현상을 유발하고 있다. 이를 관리하기 위해 하천건천화 평가 및 예측이 가능한 영향 평가 기술이 필요하며, 국내에서는 GIS 기반의 분포형 수문 모형인 Drying Stream Assessment Tool and Water Flow Tracking (DrySAT-WFT)이 개발되어 활용되고 있다. 그러나 격자기반의 물수지 모형은 단위 cell 안의 수직적인 물의 거동은 파악하기 용이하나, 모형의 특성상 저수지, 댐, 보와 같은 수리 시설물의 방류량에 따른 하도의 흐름 추적에는 어려움이 있다. 본 연구의 목적은 DrySAT-WFT 모형에 댐?보 방류량 자료와 연계한 하도추적 알고리즘을 개발하여 모형의 유출 모의 성능을 개선하고, 1976년부터 2015년까지의 유출 모의를 통해 전국 표준유역을 대상으로 각 유역에 대한 하천건천화 원인 추적 및 평가를 수행하고자 한다. 하천건천화영향요소를 고려하기 위한 모형의 입력 자료로 산림높이, 도로망, 지하수 이용량, 토지이용, 토심, 기상 변화에 대해 1976년부터 2015년까지 구축한 시계열 전국 자료를 활용하였으며, 일별 강우량, 상대습도, 평균풍속, 평균 및 최고, 최저 기온, 일조시간의 기상자료를 구축하였다. 개선된 DrySAT-WFT 유출 모의 결과는 선행 연구와의 비교를 통해 모의 개선점을 정량적으로 제시하고자 한다.