• 한국해양생명과학회지
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• 제6권2호
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• pp.117-123
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• 2021

Post-disturbance recovery pattern of subtidal soft corals-macroalgae mixed community and the role of water depth were investigated. The experiment was conducted in a subtidal rock wall of Munseom, Jeju Island, Korea for 2.5 years. Artificial disturbance was done at established treatment plots at depths of 10, 15 and 20 m and were then compared with undisturbed control plots. After disturbance, recovery of soft corals was very slow, whereas macroalgae quickly occupied the plots and reached a similar level as the control in 6 months, and this pattern was consistent at all water depths. This unbalanced speed of recovery caused higher macroalgae establishment than soft corals in treatment compared to control plots, indicating a possible phase shift in the community structure. This study provides an important implication for the necessity of monitoring the influence of disturbance at a larger scale, from a conservation perspective of soft corals in Jeju coast.

• 한국해양공학회지
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• 제23권6호
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• pp.12-16
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• 2009

In this study, the wave profiles and kinematics of highly nonlinear waves at various water depths were calculated using a 2D fully nonlinear Numerical Wave Tank (NWT). The NWT was developed based on the Boundary Element Method (BEM) with the potential theory and the mixed Eulerian-Lagrangian (MEL) time marching scheme by 4th-order Runge-Kutta time integration. The spatial variation of intermediate-depth waves along the direction of wave propagation was caused by the unintended generation of 2nd-order free waves, which were originally investigated both theoretically and experimentally by Goda (1998). These free waves were induced by the mismatch between the linear motion of wave maker and nonlinear displacement of water particles adjacent to the maker. When the 2nd-order wave maker motion was applied, the spatial modulation of the waves caused by the free waves was not observed. The respective magnitudes of the nonlinear wave components for various water depths were compared. It was found that the high-order wave components greatly increase as the water depth decreases. The wave kinematics at various locations were calculated and compared with the linear and the Stokes 2nd-order theories.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.38.2-38.2
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• 2011

A large number of offshore wind turbines with fixed foundations have been installed in water depths up to 30 meters supporting 3-5MW wind turbines. Some floating platform concepts of offshore wind turbines were designed to be suitable for deployment in water depths greater than 60 meters. However the optimal design of this system in water depth 50 meters remains unknown. In this paper, a 5-MW wind turbine located on a TLP type platform was suggested for installation in this water depth. It is moored by a taut mooring line. For controlling the wind turbine always be operated at the upwind direction, one yaw controlling was attached at the tower. To study motion characteristics of this platform, a model was built with a 1/128 scale ratio. The model test was carried out in various conditions, including waves, winds and rotating rotor effect in the Ocean Engineering Wide Tank of the University Of Ulsan (UOU). The characteristic motions of the TLP platform were captured and the effective RAOs were obtained.

• 자원환경지질
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• 제56권1호
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• pp.1-11
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• 2023

이번 연구에서는 2021년 ARA12B 탐사를 통해 동시베리아해 대륙붕의 서로 다른 수심을 갖는 2개의 정점에서 수집한 망가니즈단괴 440개[ARA12B-St52 (150 m, n = 239), ARA12B-St58i (73 m, n = 201)]에 대하여 형태학적·지화학적 분석을 수행하고, 수심에 따른 단괴의 특성 변화를 고찰하였다. 단괴의 크기는 두 정점 모두에서 3 cm 이상의 크기가 일반적이다. 그러나 단괴의 외형적 특징은 수심에 따라 크게 차이가 있다. 수심 150 m에서 획득된 단괴의 일반적인 형태는 거친 표면조직을 가지는 갈색-흑색의 판상형, 원통형 및 타원체형이다. 반면, 수심 73 m에서 회수된 단괴들은 매끄러운 표면을 가지는 노랑-갈색의 판상형 단괴가 대부분을 차지한다. 또한 단괴의 내부조직, 공극률 및 구성원소와 관련이 있는 크기와 무게 간 추세선의 기울기는 150 m의 단괴의 경우 약 1.60, 83 m 단괴는 약 0.84로 큰 차이가 있음이 확인되었다. 이는 단괴의 내부조직 및 화학조성에 차이로부터 기인한다. 단괴의 내부조직과 화학조성 분석 결과, 수심 150 m의 단괴들은 핵을 중심으로 두꺼운 Mn층과 얇은 Fe층들로 이루어진 반면, 83 m의 단괴들은 핵을 중심으로 얇은 Mn 및 Fe층이 교호하며 성장한다. 마이크로 X선 형광분석(µ-XRF)을 통해 단괴의 절개면에서 분석된 평균 화학조성은 150 m 단괴의 경우 Mn 40.6 wt%, Fe 5.2 wt%, Mn/Fe 비 7.9이며, 83 m 단괴의 경우 Mn 10.3 wt%, Fe 19.0 wt%, Mn/Fe 비 0.6이다. 타 해역 단괴들의 화학조성과 비교한 결과 수심 150 m에서 회수된 단괴의 조성은 태평양의 페루 분지의 단괴들과 유사한 반면, 83 m에서 획득된 단괴의 조성은 태평양의 쿡 섬 또는 발트해의 단괴들과 유사하다. 관찰된 단괴들의 형태학적·지화학적 특성은 두 정점에서 뚜렷한 차이를 나타내며, 이는 북극해 대륙붕의 수심에 따라 단괴의 형성 당시의 환경적 조건에 명확한 차이가 있음을 지시한다.

• 한국작물학회지
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• 제44권1호
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• pp.32-37
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• 1999

The experiment was conducted to investigate emergence response of lowland weeds at different soil moisture contents, burying depths and upon changes in soil moisture. Rice germination was over 50% at all burying depths under aerobic condition, but the emergence rate of the soil surface placed seeds in saturated and flooded conditions decreased by 19% and 29%, respectively, as compared with that of aerobic condition. Rice seeds at burying depth of over 3 cm did not emerge at all. The emergence rate of Echinochloa crus­galli (L.) Beauv. in aerobic condition was lower than 30%, but the emergence pattern of E. crus galli (L.) Beauv. at different soil moisture contents and seeding depths was similar to that of rice. Emergence behavior of lschaemum rugosum Salisb., Ludwigia octovalvis (Jacq.) Raven and Sphenoclea zeylanica Gaertn. which are dominant lowland weed species in the Philippines also differed depending on soil moisture conditions and burying depths. lschaemum rugosum Salisb. emerged at all burying depths under aerobic condition, whereasLudwigia octovalvis (Jacq.) Raven emerged only at 0 cm deep under saturated and aerobic condition and Sphenoclea zeylanica Gaertn. at 0 cm deep under flooding condition. Weed seeds planted at 1, 3, and 5 cm deep in continuous flooded and saturated condition did not emerge at all, but upon a change of soil moisture condition from saturated to drainage (S$\rightarrow$D) and flooded to drainage (F$\rightarrow$D), grass weeds began to germinate again and the average emergence rate in S$\rightarrow$D and F$\rightarrow$D were 26% and 5% forE. crus­galIi (L.) Beauv., 9% and 8% forI. rugosum SaIisb., respectively. Weed seeds buried in soil in the pot showed great emergence at S$\rightarrow$D but did not emerge under continuous flooded condition. The diversity index accounting for dominance degree and occurrence aspect of weed, was the lowest at F$\rightarrow$D.

• Journal of Microbiology and Biotechnology
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• 제28권4호
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• pp.630-637
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• 2018

The high rate algal ponds (HRAP) powered and mixed by a paddlewheel have been widely used for over 50 years to culture microalgae for the production of various products. Since light incidence is limited to the surface, water depth can affect microalgal growth in HRAP. To investigate the effect of water depth on microalgal growth, a mixed microalgal culture constituting three major strains of microalgae including Chlorella sp., Scenedesmus sp., and Stigeoclonium sp. (CSS), was grown at different water depths (20, 30, and 40 cm) in the HRAP, respectively. The HRAP with 20cm of water depth had about 38% higher biomass productivity per unit area ($6.16{\pm}0.33g{\cdot}m^{-2}{\cdot}d^{-1}$) and required lower nutrients and energy consumption than the other water depths. Specifically, the algal biomass of HRAP under 20cm of water depth had higher settleability through larger floc size (83.6% settleability within 5 min). These results indicate that water depth can affect the harvesting process as well as cultivation of microalgae. Therefore, we conclude that water depth is an important parameter in HRAP design for mass cultivation of microalgae.

• 한국해양공학회지
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• 제19권3호
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• pp.39-46
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• 2005

A series of forced oscillation tests on a model mooring chain was carried out to investigate dynamic tension characteristics. The model test was conducted at two different water depths to gather basic data for a 'truncated mooring test' and 'hybrid mooring test'. The truncated and hybrid mooring tests are important for overcoming the limitation of water depth that existed in previous model tests. The resultant tension RAO provides a good possibility of approximation of dynamic tension by equivalent weight adjustment for different water depths. Because the hybrid mooring test is an adequate combination of model test and simulation, an accurate simulation model for the mooring system is essential. The simulation results show good agreement with model test results.

• Ocean and Polar Research
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• 제25권1호
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• pp.41-52
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• 2003

Sediment trap samples were collected to find out characteristic behaviors of metals in the settling particles by using time-series sediment traps at 678m and 1678m water depths in the Bransfield Strait from December 27th, 1999 to December 26th, 2000. Total mass fluxes at the intermediate water depth (678m water depth) were high in the austral summer and low in the austral winter, whereas at the deep water depth (1678m water depth) they showed high values in both the summer and winter. Total mass fluxes were generally higher in the deep water depth than in the intermediate water depth, which indicates that a substantial amount of sediments are laterally transported by strong currents into the deep basin from the shallow water depths. Aluminium contents also showed large seasonal variations with high values in the winter and low values in the summer. On the contrary, organic carbon contents were high in the summer and low in the winter. Al contents were negatively correlated with organic carbon contents, which may be ascribed that detrital particles are diluted by organic matter produced by phytoplankton in the surface waters. Metals measured in this study exhibited three characteristic behaviors; 1) a positive correlation with Al-Ti, Fe, Mn, V, Co, and Ba, 2) a negative correlation with Al-Cd and Zn, 3) no relationship with Al-Sr, Cu, Cr, Ni. Terrestrial materials may act as a major source fer metals that are positively correlated with Al, and organic matter may be a major source for metals that are negatively correlated with Al. Enrichment factor (EF) of Fe, Mn, Ba, Vi Co, Sr, Cr, and Ni ranged from 0.5 to 1.5, whereas EF of Zn, Cu, and Cd showed much higher values than 1.

• 대한조선학회지
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• 제12권2호
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• pp.59-66
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• 1975

Recently, as the dimensions of energy carriers increase, especially in draft, a reliable prediction of the ship motions at finite depths of water becomes necessary. The purpose of this paper is to probe the effect of finite water depth on the hydrodynamic forces and ship motions, particularly heave and pitch, in longitudinal regular head waves, by comparing the experimental value of Freakes and Keay with the author's theoretical value obtained by applying the modified strip theory to the Mariner class ship. It is confirmed that generally the hydrodynamic coefficients in the equations of motion increase with decreasing water depth, and the wave exciting forces and moments decrease with decreasing water depth. Amplitudes of heave and pitch in longitudinal regular head waves decrease as the water depth in the range where the length of the incident wave is comparatively long. The effects of Froude Number on the hydrodynamic coefficients increase with decreasing water depth and is more noticeable in the case of heave than pitch. In heave, generally the discrepancy between the experimental value and the theoretical value is relatively small in the case of $F_n=O$, but it is very large in the case of $F_n=0.2$. It is considered that the trend stems from the ignorance of the three dimensional effect and the other effects due to shallowness of water on the hydrodynamic coefficients in the theoretical calculation. An extension of methods for calculating the two dimensional hydrodynamic forces to included the effect of forward speed should be recommended. It is required that more experimental works in finite water depths will be carried out for correlation studies between the theoretical calculation, according tp modified strip theory, and model experiments.

• Ecology and Resilient Infrastructure
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• 제8권1호
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• pp.9-21
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• 2021

본 연구에서는 금강수계 미호천의 어류 서식지적합도지수 산정을 위해 12개 조사지점에서 어류 및 유량조사를 실시하였고, 미호천을 대표할 수 있는 2개 지점을 선정하여 어종별 수심 및 유속 등 물리적서식지 정보를 구축하여 서식지적합도지수를 산정하였다. 2019년 9월부터 2020년 5월까지 총 4회 실시한 현장조사 결과에 따르면 총 8과 37종 5,754개체가 출현하였고, 어류군집의 유영특성은 정수성 어종이 22종, 중간종 7종, 유수성종 8종으로 유속이 느린 수역을 선호하는 정수성종의 출현 종수가 가장 많은 것으로 확인되었다. 서식지적합도지수는 수심과 유속 구간별 채집된 개체수와 유량조사 결과를 이용하여 WDFW 방법에 따라 산정하였다. 우점종인 피라미와 유영성 어종을 대상으로 상류의 가산교 지점과 중류의 팔결교 지점에서 각각 산정하여 결과를 비교하였다. 단일종은 수심 0.1 - 0.5 m, 유속 0.2 - 0.5 m/s의 범위에서 상류와 하류간 큰 차이를 보이지 않았고, 유영성종의 경우 수심 0.2 - 0.5 m, 유속 0.2 - 0.5 m/s의 범위로 단일종과 유사하게 산정되었다. 우점종인 피라미의 물리적 서식범위가 광범위하였고, 유영성종 간의 서식지적합도지수는 유사하게 산정된 결과를 보였다. 이와 같은 결과는 미호천의 환경생태유량 산정 및 하천복원 계획을 위한 기초자료로 활용성이 높을 것으로 판단된다.