• 대한조선학회논문집
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• 제43권3호
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• pp.384-391
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• 2006

RCS effects of long-crested wave surfaces to marine targets are numerically analyzed using a 4-path model and a direct analysis method, developed based on physical optics and a combined method of physical optics/geometric optics, respectively. Reflectivity of long-crested wave surfaces is described with 'Fresnel reflection coefficients' The MPM(modified Pierson-Moskowitz) ocean spectrum is adopted to simulate long-crested waves in the direct analysis method. A numerical analysis of a benchmark model assures the validity of both methods. The direct analysis method is applied to the RCS calculation of electromagnetically large marine targets, which are vertically oriented or slanted to the long crested wave surfaces randomly generated with various significant wave heights. The long-crested wave surface much highly increases the RCS of the marine target, but those effects are decreased as the significant wave height grows up. At low elevation angle, the vertical model has entirely high RCS comparing slanted model, and the RCS of vertical flat plate is the highest on the calm sea surface, while those of slanted flat plates are the lowest on the calm sea surface. The RCS of marine targets on continuously-varying sea surface is more coherent at lower elevation angles, as well.

• 한국해안해양공학회지
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• 제2권3호
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• pp.162-181
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• 1990

동수력학모형이 황해 및 동지나해의 SEASAT 고도계 해면자료를 분석하는데 이용되었다. SEASAT 운용기간중 이 해역에서 태풍이 발생한 7월 28일~8월2일, 8월18일~21일 기간이 고려되었다. 해양모형에 필요한 기상외력은 이론 및 경험적인 관련식으로부터 유도되었다. 시공적으로 큰 변화가 있는 이 해역의 해양조석을 산정하기 위해서 M$_2$, S$_2$, $K_1$ 및 $O_1$, 조석의 4개분조가 이용되었으며 지구조석의 영향도 고려되어 위성고도계자료와 통계적인 비교를 위해 시간종속적인 해면변화를 추정하여 해저마찰연구를 수행하였다. 10경우의 SEASAT 궤적으로부터 조사된 해저마찰계수는 0.0023~0.0027의 범위에 있었다.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.177-184
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• 2003

Numerical simulation on marine wind and sea surface elevation was carried out using both three-dimensional hydrostatic and non-hydrostatic models and a simple oceanic model from 0900 LST, August 13 to 0900 LST, August 15, 1995. As daytime easterly meso-scale sea-breeze from the eastern sea penetrates Kangnung city in the center part as basin and goes up along the slope of Mt. Taegullyang in the west, it confronts synoptic-scale westerly wind blowing over the top of the mountain at the mid of the eastern slope and then the resultant wind produces an upper level westerly return flow toward the East Sea. In a narrow band of weak surface wind within 10km of the coastal sea, wind stress is generally small, less than l${\times}$10E-2 Pa and it reaches 2 ${\times}$ 10E-2 Pa to the 35 km. Positive wind stress curl of 15 $\times$ 10E-5Pa $m^{-1}$ still exists in the same band and corresponds to the ascent of 70 em from the sea level. This is due to the generation of northerly wind driven current with a speed of 11 m $S^{-1}$ along the coast under the influence of south-easterly wind and makes an intrusion of warm waters from the southern sea into the northern coast, such as the East Korea Warm Current. On the other hand, even if nighttime downslope windstorm of 14m/s associated with both mountain wind and land-breeze produces the development of internal gravity waves with a hydraulic jump motion of air near the coastal inland surface, the surface wind in the coastal sea is relatively moderate south-westerly wind, resulting in moderate wind stress. Negative wind stress curl in the coast causes the subsidence of the sea surface of 15 em along the coast and south-westerly coastal surface wind drives alongshore south-easterly wind driven current, opposite to the daytime one. Then, it causes the intrusion of cold waters like the North Korea Cold Current in the northern coastal sea into the narrow band of the southern coastal sea. However, the band of positive wind stress curl at the distance of 30km away from the coast toward further offshore area can also cause the uprising of sea waters and the intrusion of warm waters from the southern sea toward the northern sea (northerly wind driven current), resulting in a counter-clockwise wind driven current. These clockwise and counter-clockwise currents much induce the formation of low clouds containing fog and drizzle in the coastal region.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1992년도 정기학술강연회 발표논문 초록집
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• pp.69-71
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• 1992

The local horizintal flux of tidal energy is characterized by the surface density $\omega$ = $\rho$ g h ζ u ($\rho$ - sea water density, g - gravitation, h - depth, ζ - tidal surface elevation, u - vertically averaged tidal current velocity vector). In general the flux vector $\omega$ comprises active and reactive components whose relation determines the local structure of a tidal wave.(omitted)

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.373-376
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• 2006

In general, a method for generating irregular wave by combination of component waves obtained from linear wave theory is widely used. In these method, however, mean water surface elevation is rising from time to time because of nonlinear effect of wave. In this study, for the rising problem of mean water surface elevation and stabilization of calculation from time to time, mass transport velocity for horizontal velocity at wave source position is considered. The rising problem of mean water surface elevation is checked by comparing calculated wave profile from numerical technique proposed in this study with target wave profile at wave source position in numerical wave tank by using CADMAS-SURF code. And, by generating irregular wave, the validity of wave overtopping rate estimated from this numerical analysis is discussed by comparing computed results with measured results in hydraulic model experiments for vertical seawall located on a sloping sea bottom. As a results, the computations are validated against the previously experimental results by hydraulic model test and numerical results of this study and a good agreement is observed. Therefore, numerical technique of this study is a powerful tool for estimating wave overtopping rate over the crest of coastal structure.

• 한국지형학회지
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• 제25권2호
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• pp.31-42
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• 2018

This study analyzes the spatial distribution of the highest level terrace which can be regarded as an initial land surface before the uplift of the Taebaek Mountains and estimates spatial characteristics of the incision and uplift rates around the Mountains. The altitude above the riverbed of the 54 highest level terraces seems to be greatly influenced by the incision of large stream and their elevation shows a high correlation with the uplift of the Mountains. The elevation of the terraces in the north and middle parts decreases westward with a rate of 5~6 m/km and meets with the sea level at area 100~120 km apart from the Mountains. Therefore, it can be suggested that the west coast of Korea might have generally experienced subsidence during the Quaternary. The elevation of the terraces suggests that area with a direction of N-S or NNW-SSE from Yeoryang-myeon, Jeongseon-gun to Taebaek-si shows the highest uplift rate around the Mountains and area with a direction of N-S connecting Girin-myeon, Inje-gun and Pyeongchang-eup, Pyeongchang-gun also indicates a high uplift rate.

• 한국패류학회지
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• 제28권3호
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• pp.277-291
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• 2012

Aquaculture is challenged by a number of constraints with future efforts towards sustainable production. Global climate change has a potential damage to the sustainability by changing environmental surroundings unfavorably. The damaging parameters identified are water temperature, sea level, surface physical energy, precipitation, solar radiation, ocean acidification, and so on. Of them, temperature, mostly temperature elevation, occupies significant concern among marine ecologists and aquaculturists. Ocean acidification particularly draws shellfish aquaculturists' attention as it alters the marine chemistry, shifting the equilibrium towards more dissolved CO2 and hydrogen ions ($H^+$) and thus influencing signaling pathways on shell formation, immune system, and other biological processes. Temperature elevation by climate change is of double-sidedness: it can be an opportunistic parameter besides being a generally known damaging parameter in aquaculture. It can provide better environments for faster and longer growth for aquaculture species. It is also somehow advantageous for alleviation of aquaculture expansion pressure in a given location by opening a gate for new species and aquaculture zone expansion northward in the northern hemisphere, otherwise unavailable due to temperature limit. But in the science of climate change, the ways of influence on aquaculture are complex and ambiguous, and hence are still hard to identify and quantify. At the same time considerable parts of our knowledge on climate change effects on aquaculture are from the estimates from data of fisheries and agriculture. The consequences may be different from what they really are, particularly in the temperature region. In reality, bivalves and tunicates hung or caged in the longline system are often exposed to temperatures higher than those they encounter in nature, locally driving the farmed shellfish into an upper tolerable temperature extreme. We review recent climate change and following environment changes which can be factors or potential factors affecting shellfish aquaculture production in the temperate region.

• 한국수산과학회지
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• 제20권6호
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• pp.477-483
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• 1987

조석방정식에 근거한 객관적 방법으로 동해내 반일주조($M_2$조)의 조석도를 자성하였다. 조석도의 작성은 라프라스 조석방정식으로부터 유도된 해면변위 방정식의 해로서 구하였으며, 이때 연안 검조소에서 관측된 해면변위의 진폭과 위상을 경계조건으로 사용하였다. 본 연구에서는 동해의 해저 지형과 조류에 따른 마찰력이 동해의 조석도 분포에 미치는 영향을 구명하였다. 또한, 동해 전역의 조석도의 견과를 기초로 하여, 한반도 동해안 외해의 국지적 영역의 반일주조에 대한 정밀조석도를 작성하였다.

• 한국군사과학기술학회지
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• 제13권5호
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• pp.725-733
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• 2010

A simulator is proposed in this paper for predicting the RF signal level after propagating over sea and land surfaces. Various sea and land types and transmit/receive antenna patterns, as well as the locus of the transmit antenna, are considered for this simulator. At first, microwave reflection characteristics of various sea surfaces have been computed, based on an empirical formula which is developed in this study for the relation between the sea surface roughness and wind speed. Then, microwave reflections from land surfaces such as forests, agricultural areas, and bare surfaces, are computed using the first-order vector radiative transfer theory. Finally, the signal paths over sea and land surfaces are found using the ray tracing technique and the digital elevation model, and the signal level received by a receiving antenna is computed by the using the reflection coefficients of sea and land surfaces and the signal paths.

• Journal of information and communication convergence engineering
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• 제6권2호
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• pp.146-149
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• 2008

Simulation and signal conditioning on the time domain surface elevation records are conducted to verify the proposed Welch's method in non-directional ocean wave spectrum analysis. These spectrum data are further conditioned to provide wave characteristic that better describe the sea states. Comparison of significant wave height and zero crossing period between the proposed method and a reference toolkit are presented.