• 한국해양공학회지
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• 제21권1호
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• pp.1-6
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• 2007

While a typhoon is traveling, characteristics of its wind fields are continuously changing, producing severe changes in local water level and wave conditions, especially, when a typhoon comes into shallow water. However, there have not been many studies related to local typhoon effects, especially, considering real time changes of wind direction related to the coastal topography. In the study, the characteristics of the wind field by typhoon and topographical characteristics in shallow water are considered, as well as conditions of wave climate estimation. These are performed by the SWAN (Simulating waves nearshore) model, in order to estimate the growth of wave energy due to the wind field. It can be strongly suggested that the wave energy of theof an inner bay should be estimated when the direction of the bay entrance and the wind direction of the typhoon are identical. The result of the numerical calculations is in better agreement with the observed data than the result of the conventional estimation techniques.

• 한국방재학회 논문집
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• 제11권1호
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• pp.93-99
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• 2011

본 연구에서는 단독형 및 2열형(multi-arranged (2 pieces)), 3열형(multi-arranged) 부유식방파제에서의 구조물간 거리와 흘수, 형상을 변화시키고 파의 주기와 파형경사를 변화시키며, 다양한 변수변화에 따른 영향을 분석하였다. 부유식방파제의 흘수변화는 전달계수에 직접적인 영향을 주며, 비교적 장주기에 해당하는 조파조건에선 단독형과 2열형 부유식방파제보다 3열형 구조에서 높은 방파효율을 나타내었다. 수리모형실험의 결과 검증을 위하여 수치모형과 동일한 조건하에 실험을 하고 LDV시스템을 이용하여 각 부유식방파제에서의 유동장을 측정하였으며, 수리모형실험을 통하여 그에 따른 전달계수을 분석하였다.

• 한국해안·해양공학회논문집
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• 제21권2호
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• pp.154-163
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• 2009

해안에서 입사파향은 일반적으로 실측 파랑자료로부터 생성한 파향 스펙트럼 분석을 통하여 구하지만, 파향의 실측기법은 현장 계기설치시 많은 인력과 비용이 소요되기 때문에 전 쇄파지역에 걸쳐 입사파향을 관측하기에는 어려움이 따른다. 이러한 이유로, 본 연구는 해안 디지털 비디오 자료에 나타나는 입사파의 파봉선을 이용하여 쇄파지역에서 입사파의 변화를 관측하는 기술을 제안한다. 파봉선은 이미지 상에서 선인식 기법을 이용하여 이미지 강도가 큰 픽셀들을 추적해 나감으로써 추출한다. 입사파향은 추출된 파봉선의 일차미분값, 즉, 실제 평면좌표 공간에서 파봉선의 기울기를 계산하여 구한다. 비디오 자료로부터 입사파향의 측정결과는 실측 파랑자료의 파향 스펙트럼으로부터 구한 파향 계산결과와 비교적 잘 일치한다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.43.2-43.2
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• 2009

Electron microbursts are the intense electron precipitation which durations are less than one second. We measured the energy spectra of the microbursts from 170 keV to 340 keV with solid state detectors aboard the low-altitude (680km), polar-orbiting Korean STSAT-1 (Science and Technology SATellite). The data showed that the loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast loss cone filling requires pitch angle diffusion coefficients larger than ~ 10-2rad2/sec, while ~10-5 rad2/sec was proposed by a wave particle interaction theory. We recalculated the diffusion coefficient, and reviewed of electron microburst generation mechanism with test particle simulations. This simulation successfully explained how chorus waves make pitch angle diffusion within such short period. From considering the resonance condition between wave and electrons, we also showed ~ 100 keV electrons could be easily aligned to the magnetic field, while ~ 1MeV electrons filled loss cone partially. This consideration explained why precipitating microbursts have lower e-folding energy than that of quasi-trapped electrons, and supports the theory that relativistic electron microbursts that have been observed by satellite in-situ measurement have same origin with ~100 keV electron microbursts that have been usually observed by balloon experiments.

• 천문학회보
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• 제37권2호
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• pp.117.2-117.2
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• 2012

It is generally accepted that sudden compressions of the magnetosphere cause electromagnetic ion cyclotron (EMIC) wave growth by increasing the proton temperature anisotropy. These compression-associated EMIC waves are expected to be on higher latitudes (i.e., higher-L regions close to the magnetopause). In this study we examine Pc1 pulsations, which are believed to be generated by the EMIC instability, observed at subauroral latitude near the nominal plasmapause when the magnetosphere is suddenly compressed by solar wind dynamic pressure variations, using induction magnetometer data obtained from Athabasca, Canada (geomagnetic latitude = 61.7 N, L ~ 4.5). We identified 9 compression-associated Pc1 waves with frequencies of ~0.5-2.0 Hz. The wave activity appears in the horizontal H (positive north) and D (positive eastward) components. All of events show low coherence between H and D components. This indicates that the Pc1 pulsations in H and D oscillate with a different frequency. Thus, we cannot determine the polarization state of the waves. We will discuss the occurrence location of compression-associated Pc1 pulsations, their spectral structure, and wave properties.

• 한국수자원학회논문집
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• 제46권3호
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• pp.301-314
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• 2013

기후변화로 야기될 수 있는 태양복사에너지의 공간적인 불균형은 수자원을 포함한 전반적인 생태 시스템에서의 에너지 불균형을 초래한다. 따라서 정확한 에너지의 흐름을 이해하기 위하여 정량적인 관측을 목적으로 하는 플럭스 타워가 세계 곳곳에 설치되어 운영되고 있다. 국내의 주역에서도 플럭스 타워를 통안 관측이 실시되고 있는 데, 본 연구에서는 이 중 설마천과 청미천 유역의 플럭스 타워의 자료를 대상으로 수문기상 및 생태학적으로 중요한 역할을 하는 에너지원인 하향 단파 및 장파 복사량과 순복사량을 기존의 연구에서 제안된 물리식을 기반으로 계산하고, 산정된 순복사량과 관측 자료를 비교 검증하였다. 이를 통하여 관측이 미흡한 수문기상인자에 대해 기존의 물리적인 방법의 사용 가능성 및 관측 자료의 활용 가능성을 확인하였다.

• 한국환경과학회지
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• 제28권7호
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• pp.617-627
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• 2019

This study investigated the relationship between heat-related illnesses obtained from healthcare big data and daily maximum temperature observed in seven metropolitan cities in summer during 2013~2015. We found a statistically significant positive correlation (r = 0.4~0.6) between daily maximum temperature and number of the heat-related patients from Pearson's correlation analyses. A time lag effect was not observed. Relative Risk (RR) analysis using the Generalized Additive Model (GAM) showed that the RR of heat-related illness increased with increasing threshold temperature (maximum RR = 1.21). A comparison of the RRs of the seven cities, showed that the values were significantly different by geographical location of the city and had different variations for different threshold temperatures. The RRs for elderly people were clearly higher than those for the all-age group. Especially, a maximum value of 1.83 was calculated at the threshold temperature of $35^{\circ}C$ in Seoul. In addition, relatively higher RRs were found for inland cities (Seoul, Gwangju, Daegu, and Daejeon), which had a high frequency of heat waves. These results demonstrate the significant risk of heat-related illness associated with increasing daily maximum temperature and the difference in adaptation ability to heat wave for each city, which could help improve the heat wave advisory and warning system.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.392-399
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• 2005

Shear modulus (or rigidity) of dam material is an important parameter which can be directly associated with the deformation of dam. Seepage or leakage of water can cause the defects or cracks of dam body. The existence of cracks and rigidity of dam body are decisive information for the estimation of dam safety. Rigidity of material is mainly determined from S-wave velocity and the defects of dam body can be detected by seismic reflection survey. Therefore, seismic reflection survey will be a desirable method which can give a solution about dam safety problem. Among various physical properties of dam body, S-wave velocity is the most important information but it is not easy to get the information. In this study, diverse measuring techniques of S-wave reflection survey were attempted to get the information about S-wave velocity of dam body. Ultimately, S-wave velocity could be estimated by the analysis of SH reflection events which can be easily observed in shot gather data obtained from SH measuring technique. Meanwhile, P-wave reflection survey was also performed at the same profile. P-beam radiation technique which can reduce the surface waves and reinforce the P-wave reflection events was applied for giving a help to analyse P-wave velocity. In the end, P-and S-wave velocity, Vs/Vp, Poisson's ratio distribution of the vertical section under the profile could be acquired.

• 한국해안·해양공학회논문집
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• 제32권4호
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• pp.230-241
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• 2020

포항신항이 단계별로 완공된 후 제기되어 온 항내정온도 불량 문제는 항만가동율 저하의 주요 원인으로 제기되어 왔으며 이의 개선을 위해 2018~2020년 포항신항 외항방파제의 외해 측에 도제(Detached breakwater)를 건설하고 있다. 본 연구에서는 도제의 효과를 검증하기 위하여 도제 설치 전후로 취득된 항내외의 파랑 관측자료를 분석하여 항내에서의 파고감소율을 비교한 결과를 제시한다. 먼저 이전 수치모델 연구를 통해 예측된 파고는 항내 4개 지점 중 3개 지점에서 관측값과 비슷하게 나타났으며 나머지 1개 지점에서의 오차는 수치모델이 부두 안쪽에 발생하는 중복파 현상을 잘 재현하지 못했기 때문으로 판단된다. 도제 건설 전후 기간의 관측값을 비교한 결과 도제 설치가 항내정온도 개선에 기여한 것으로 나타났는데, 항내 4개 관측지점 모두에서 포항신항 정온 목표파고인 0.3 m를 초과하는 파고의 출현빈도가 도제 건설 후에 크게 감소하였다. 또한 항내외 파고를 비교한 항내 파고 감소율도 모든 파향에 대해 도제 건설 후에 유의미하게 개선된 것으로 나타났다. 본 연구결과는 적절하게 설치된 연안구조물이 항내정온도 향상에 기여하는 효과를 증명한 것으로 향후 유사한 경우의 문제 해결에 유용하게 적용될 수 있음을 보여준다.

• Journal of Astronomy and Space Sciences
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• 제32권4호
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• pp.327-333
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• 2015

Previously, all-sky airglow images observed at Shigaraki ($34.9^{\circ}N$, $136.1^{\circ}E$), Japan, during 2004 and 2005 were analyzed in relation to those observed at Mt. Bohyun ($36.2^{\circ}N$, $128.9^{\circ}E$) for a comparison of their gravity wave characteristics (Kim et al. 2010). By applying the same selection criteria of waves and cloud coverages as in the case of Mt. Bohyun all-sky images, we derived apparent wavelengths, periods, phase velocities, and monthly occurrence rates of gravity waves at Shigaraki in this study. The distributions of wavelengths, periods, and speeds derived for Shigaraki were found to be roughly similar to those for Mt. Bohyun. However, the overall occurrence rates of gravity waves at Shigaraki were 36% and 34% for OI 557.7 nm and OH Meinel band airglow layers, respectively, which were significantly higher than those at Mt. Bohyun. The monthly occurrence rates did not show minima near equinox months, unlike those for Mt. Bohyun. Furthermore, the seasonal preferential directions that were clearly apparent for Mt. Bohyun were not seen in the wave propagation trends for Shigaraki. These differences between the two sites imply different origins of the gravity waves near the Korean peninsula and the Japanese islands. The gravity waves over the Japanese islands may originate from sources at various altitudes; therefore, wind filtering may not be effective in causing any seasonal preferential directions in the waves in the airglow layers. Our analysis of the Shigaraki data supports recent theoretical studies, according to which gravity waves can be generated from in situ sources, such as mesosphere wind shear or secondary wave formation, in the mesosphere.