• 생태와환경
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• 제40권4호
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• pp.511-519
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• 2007

It is known that phytoplankton biomass or turbidity are lower in waters with submerged macrophytes than those without submerged plants at a given nutrient level. We hypothesize that presence of submerged macrophytes would lower phytoplankton biomass below levels expected by total phosphorus levels through various mechanisms and that phytoplankton biomass would decrease more as the biomass increase of the submerged macrophytes. To find submerged macrophytes effectively lowering phytoplankton growth, we conducted spatial field surveys at 21 water bodies and a temporal monitoring at Seung-un 1 Reservoir, Anmyyeondo Island. We measured chlorophyll ${\alpha}$ concentrations and total phosphorus (TP) concentrations from waters in patches of submerged macrophytes with measurements of submerged plant biomass. Majority of our sites with submerged macrophytes showed much less chlorophyll a concentrations than the predicted ones from literature. Among submerged macrophytes studied, Myriophyllum spicatum and Hydrilla verticillata showed patterns of lowering chlorophyll ${\alpha}/TP$ ratios with increase of their biomass in both spatial and temporal surveys.

• Nuclear Engineering and Technology
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• 제45권2호
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• pp.203-210
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• 2013

The objective of this conducted research is to study the iodine removal efficiency in a self-priming venturi scrubber for submerged and non-submerged operating conditions experimentally and theoretically. The alkaline solution is used as an absorbent, which is prepared by dissolving sodium hydroxide (NaOH) and sodium thiosulphate ($Na2S_2O_3$) in water to remove the gaseous iodine ($I_2$) from the gas. Iodine removal efficiency is examined at various gas flow rates and inlet concentrations of iodine for submerged and non-submerged operating conditions. In the non-submerged venturi scrubber, only the droplets take part in iodine removal efficiency. However, in a submerged venturi scrubber condition, the iodine gas is absorbed from gas to droplets inside the venturi scrubber and from bubbles to surrounding liquid at the outlet of a venturi scrubber. Experimentally, it is observed that the iodine removal efficiency is greater in the submerged venturi scrubber as compare to a non-submerged venturi scrubber condition. The highest iodine removal efficiency of $0.99{\pm}0.001$ has been achieved in a submerged self-priming venturi scrubber condition. A mathematical correlation is used to predict the theoretical iodine removal efficiency in submerged and non-submerged conditions, and it is compared against the experimental results. The Wilkinson et al. correlation is used to predict the bubble diameter theoretically whereas the Nukiyama and Tanasawa correlation is used for droplet diameter. The mass transfer coefficient for the gas phase is calculated from the Steinberger and Treybal correlation. The calculated results for a submerged venturi scrubber agree well with experimental results but underpredicts in the case of the non-submerged venturi scrubber.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.283-296
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• 2020

A numerical model is established to investigate the run-up of a solitary wave after propagating over a triangular saw-tooth-shaped submerged breakwater. A rectangular-shaped submerged breakwater is simulated for comparison. Several factors, including the submerged depth, the lagoon length and the beach slope, are selected as independent variables. The free surface motions and velocity fields of the solitary wave interacting with the submerged breakwater are discussed. The results show that the submerged depth and lagoon length play significant roles in reducing the run-up. The influence of the beach slope is not significant. At the same submerged depth, the triangular saw-tooth-shaped submerged breakwater has only a slightly better effect than the rectangular-shaped submerged breakwater on the run-up reduction. However, a calmer reflected wave profile could be obtained with the rougher surface of the saw-tooth-shaped submerged breakwater. The study conclusions are expected to be useful for the conceptual design of saw-tooth-shaped submerged breakwaters.

• 한국해양공학회지
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• 제20권6호
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• pp.82-87
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• 2006

Numerical analysis is performed on the wave transmission coefficient of various crown widths of the double-submerged breakwater and the triple-submerged breakwater, varying the distance between submerged breakwaters. The finite element method is used, and the fluid motion is considered as linearized two-dimensional potential flow. In case of the double- and triple-submerged breakwaters, as the width of submerged breakwater increases, the minimum wave transmission coefficient decreases and the wave period at which the minimum wave transmission coefficient occurs moves to a longer wave period the distance between submerged breakwaters at which the minimum wave transmission coefficient occurs becomes larger.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.28-41
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• 2009

We know the several construction methods for underwater tunnel, but properly submerged concrete box type tunnel was mostly good structure stability and mostly shot length of tunnels. Submerged box type tunnel was buildup the unit segments in dry dock or ship yard by 10 to 20meters. The submerged box was composed with segments was join each together. It was installing the gate and waterproofing the coupling the front hull of a box. The complete submerged box rise up to the surface water, tow in the submerged box by tugboat, going to the destination of tunnel construction site. Beforehand dredge up soil at the bottom of a underwater, sinking the submerged box, connection together complete submerged box in underwater. The research and development ILM tunneling method is receiving careful study. Biggest weakness in submerged concrete box type tunnel was pressure waterproofing, box to box connecting, complete submerged boxes navigation and installation, after operation the submerged tunnel and management concrete box structure. It was positive evidence in submerged concrete box type tunnel. We make a practical application of the principle "the ILM tunneling method in underwater construction methods."

• 한국해안해양공학회지
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• 제16권4
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• pp.206-212
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• 2004

본 연구에서는 폭이 좁은 1열 및 다열 잠제 대한 파랑 차단 성능을 폭이 넓은 1열 및 2열 잠제의 파랑 차단 성능과 비교$.$연구하였다. 파동장은 선형포텐셜 이론으로 모형화 하였으며 유한요소법을 적용하여 수치해석 하였다. 수치해석 결과, 1열 잠제에서는 폭이 좁은 잠제가 폭이 넓은 잠제보다 파랑 차단 성능이 다소 떨어지나 어느 정도 효과적인 파랑 차단 성능을 보여주고 있으며, 폭이 좁은 잠제를 2열 또는 3열로 배치하였을 때에는 폭이 넓은 1열 또는 2열 잠제보다 훨씬 뛰어난 파랑 차단 성능을 보이고 있다.

• 한국해양공학회지
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• 제25권6호
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• pp.29-34
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• 2011

Various types of coastal structures have been constructed to prevent coastal disasters. Among these coastal structures, submerged breakwaters have been used more widely than all of the other coastal structures because of their excellent advantages in scenery effects, construction efficiency, and environmental benefits. This study investigated the potential of the horizontal plate submerged breakwater model. Usually, it is necessary for a submerged breakwater to minimize and compensate for the negative impacts on the marine environment and ecosystem caused by the marine construction. Thus, the prevention of coastal disasters was verified for this submerged breakwater model, regardless of its function as a fish reef. The purpose of this study was to investigate the hydraulic characteristics with changes in the crest width and porosity of a horizontal plate submerged breakwater and compare the results of this study with the results of other studies on permeable and impermeable submerged breakwaters.

• 한국전산유체공학회지
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• 제19권3호
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• pp.8-13
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• 2014

In this study, wave characteristics coming with oblique incident angle to permeable trapezoidal submerged breakwater on the porous seabed are calculated by using boundary element method. This numerical analysis, based on the wave pressure function, is analyzing the continuity in the analytical region including fluid and structure. From the comparison of the reflection coefficients and damping coefficient, the results of this study are in good agreement with the existing results. The peak values of reflection coefficient obtained by permeable trapezoidal submerged breakwater on the porous seabed are smaller than those of permeable trapezoidal submerged breakwater on the non-porous seabed. The velocity vector in front of permeable trapezoidal submerged breakwater on the porous seabed is smaller than that in front of permeable trapezoidal submerged breakwater on the non-porous seabed with out the energy loss.

• 한국농공학회지
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• 제23권4호
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• pp.32-40
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• 1981

A lot of submerged tunnels which cross revers and channels have been constructed in the USA, European countries and Japan. It is very important to consider anti-seismicity of the tunnels when they are located in active seismic zone. Fortunately, the submerged tunnels have never been damaged by earthquakes, however a umber off surveys and experiments to examine the anti-seismicity of the submerged tunnels have been carried out from various points of view. the dynamic characteristics of the submerged tunnels which are buried in the ground and have long total length from that of the structures above ground. 'Specificitions of Earthquake Resistant Desion of Submerged Tunnels' was established by the Japan Society of Civil Engineers in 1975. These specifications greatly promote the construction of the submerged tunnels. In this technical paper, the outline of the construction and a few methods of earthquake resistant designs for the tunnels: earthquakes observations, indoor experiments by shaking table, and numerical analysis by computer are also mentioned.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2003년도 추계학술발표회
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• pp.149-153
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• 2003

The hydrodynamic forces acting on the submerged plate are composed of diffraction and radiation forces. Thus we have carried out the extensive experiments and numerical simulations to make clear the characteristics of the diffraction and radiation forces on the submerged plate. These experimental results are compared with the numerical ones, and we discuss the effect of nonlinear on the hydrodynamic forces acting on the submerged plate. As a result, we get the conclusion that the submerged plate is useful for reducing the wave exciting forces on the structure behind the submerged plate.