• 한국항만학회지
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• 제15권1호
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• pp.57-74
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• 2001

In the past, the predictions of beach processes and harbor sedimentation were mainly relied on the hydraulic model tests and empirical methods. In recent years, however, as computers have come into wide use, more accurate models have gradually been developed and thus replaced those conventional methods. For prediction of topographical change near the coastal area, we need informations of wave and current conditions in the numerical model which should be calculated in advance. Numerical model introduced in this study combines wave refraction-diffraction, breaking, bottom friction, lateral mixing, and critical shear stress and three sub-models for simulating waves, currents, and bottom change were briefly discussed. Simulations of beach processes and harbor sedimentation were also described at the coast neighboring Bangpo Harbor, Anmyundo, Chungnam, where the area has suffered accumulation of drifting sand in a small fishing harbor with a wide tidal range. We also made model test for the new layout of the harbor and planned south breakwater for preventing intrusion of sand. Although the model study gave reasonable description of beach processes and harbor sedimentation mechanism, it is necessary to collect lots of field observation data, including waves, tides and bottom materials, etc. for better prediction.

• Geomechanics and Engineering
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• 제32권6호
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• pp.627-637
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• 2023

Volleyball is an international sport with many fans. This sport has made significant progress in schools and clubs. Volleyball is suitable for all age groups and can be used in different environments. It has many social and physical benefits. During the game provides special physical training for the players and is considered one of the most exciting games. Another type of volleyball is beach volleyball, a beach sport and one of the Olympic sports held on the sand with the same rules as volleyball. This sport is usually played in coastal areas, especially with wide sandy beaches. Because this sport is played in open spaces, the players stay in this space for a long time and are exposed to dangerous ultraviolet radiation. It is a wavelength of light in the range of electromagnetic waves with a wavelength between 10 and 400 nm. This wavelength is shorter than visible light and more protracted than X-ray. Ultraviolet (UV) rays are naturally present in sunlight and include about 10% of all waves emitted from the sun's surface. Prolonged exposure to ultraviolet light causes acute and chronic damage to the skin and vision and even destroys the entire immune system. Different covers of the earth's surface reflect different amounts of UV rays. For example, snow cover, sand, and seawater surface reflect this radiation. Therefore, the health of volleyball players is in danger due to this harmful radiation. This work aims to introduce a type of clothing made of nanoparticles that can repel ultraviolet rays and protect beach volleyball players whose health is at risk from this radiation.

• 한국농공학회지
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• 제38권5호
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• pp.85-94
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• 1996

For the geotechnical analysis in the construction and Deign of the coastal structures, one of the most important factors is the existence of waves. The dynamic behavior and deformation of the seabed subjected to wave load must be considered. It is expected that the soil behavior in the seabed subjected to cyclic wave load is much different from that on the ground subjected to dynamic forces such as earthquake. The purposes of this study are as follows ; Firstly, to provide a testing method to generate wave loads in the laboratory and measuring oscillatory pore water pressures in the unsaturated marine silty sand specimen, Secondly, to analyze the mechanism of wave induced pore water pressures and liquefaction potentials under the conditions in the testing. It is shown that the test set-up manufactured especially for the test is good to generate oscillatory wave pressures to the specimen with sine wave type. From the results of this study, it is understood that the pore water pressure due to induced waves is not accumulated as the wave number increases but is periodically varied with wave passage on still water surface. The magnitude of pore water pressures measured tends to be diminished radically with a certain time lag under the action of both high and low waves as depth increases.

• Journal of the korean society of oceanography
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• 제32권4호
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• pp.181-190
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• 1997

A large subtidal sand ridge (Jungang Satoe) in Asan Bay, on the west coast of Korea, was studied in order to understand the morphology and sediment transport trend in a macrotidal setting, by means of analyzing sediment samples, current data, side-scan sonographs and seismic profiles. The ridge is about 15 km long and 2-5 km wide, with a relief of about 15 m. It is elongated in the flow direction of flood (SE) and ebb (NW) tidal currents, but asymmetrical in cross section. The western and southwestern side of the ridge is characterized by relatively gentle slopes averaging 0.4$^{\circ}$, whereas on the northeastern side, relatively steep slopes were mapped with 1.6$^{\circ}$ slope angles. Tidal currents associated with the ridge are very strong; maximum surface velo-cities range from neap values of 50 cm/s to spring values of 130 cm/s. The shear velocities during flood and ebb are strong enough to erode and transport sands on the ridge. Sand waves and megaripples (dunes) are the most common bedforms produced by the tidal currents, which show regional differences in shape and size on the ridge. The distribution pattern of these bedforms in-dicates that the flood tidal currents are dominant on the offshore (northwest) side of the ridge, whereas the onsho.e (southeast) side of the ridge is ebb-dominated. The sand transport path as inferred from bedform orientations is directed toward the ridge crest on the flanks, whereas on the crest, it is near-longitudinal to the ridge axis. The convergent, upslope movement of sands on the ridge flanks appears to be important in sand ridge building and maintenance. A significant ridge migration toward the northeast can be suspected on the basis of the ridge morphology, which may cause offshore hazards for navigation.

• 한국항해학회지
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• 제13권1호
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• pp.77-106
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• 1989

Two numerical models of the shoreline change and sediment transport rates, explicit and implicit, are simulated with shore structures such as breakwaters, a jetty, groins and a seawall. The applied study area is songdo Beach, Youngil bay, Korea since it has all the shore structures mentinoed above. The two models investigate the beach line changes and sedimen transport rates for the beach before design of three groins with and without an offshore breakwater. In order to estimate the shoreline changes after three groins were built, the beach response inside the three groin compartiments and the offshore barrier are also investigated. The simulation based on the initial shoreline conditions surveyed by the Hydrographic office, Koreai 1979 and 1984. The breaking wave characteristics are introduced into the models by calculation from the empirical equations and modification from the numerical and hydraulic model test results developed for waves behind an offshore breakwater. The numerical simulation describes well the tendencies of the sand transport and shoreline changes affected by wave diffraction behind a detached breakwater and by interruption of sand transport at three groins.

• 대한화학회지
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• 제5권1호
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• pp.84-87
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• 1961

A polarographic method for rapid determination of Uranium in the presence of foreign ions was proposed. The method is based on the measurement of polarogram in the sulfuric acid as supporting electrolyte. In this medium Uranyl ions give well defined reduction waves, and half-wave potentials are -0.19V vs. S.C.E. as first wave, and uncertain volt. vs. S.C.E. as second wave in $2.4 N-H_2SO_4.$ The first wave has a linear relationship between the concentration of Uranyl ion and wave height. The author also studied a method for rapid determination of Uranium in Korean monazite sand without eliminating the foreign ions. The Korean monazite sands were analyzed by this method and satisfactory result were obtained.

• 한국구조물진단유지관리공학회 논문집
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• 제4권2호
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• pp.167-174
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• 2000

Ground penetrating radar(GPR) was applied for measuring depths, sizes and intervals of rebars embedded in concrete. A concrete wall was constructed for this study and a sand pool and a concrete block were used for simulation. Result of this study shows that GPR can be used for measuring rebar depths and intervals, even though it is limitary, but that measuring sizes is almost impossible. Simulation with the sand pool was helpful for research on the versatile rebar arrays though signal was not clear as real concrete wall. A concrete block with many cylindrical holes for inserting different sized rebars could not be used for simulator due to many unknown reflective waves. Antenna orientation must be perpendicular to rebars for large reflection signal.

• 한국수산과학회지
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• 제10권3호
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• pp.179-187
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• 1977

서귀포 연안에 인공어초를 설치하여 어군의 형태와 어군의 위집에 관한 연구에서 아래와 같은 결과를 얻었다. 1. 어초설치 해역의 15.28cm/sec였고 유향은 WSW가 $20.5\%$에 대한 취송류는 최고유속이 15.28cm/sec 유향은 WSW가 $20.5\%$였다. 2. 흐름과 파에 의한 원형수하형어초의 유체저항은 약 890kg이 최대였고, 어초에 부착된 멍의 중량은 1,200kg로서 고정력이 충분하였다. 3. 파라슈트어초에 대한 최대저항은 전개용 자료가 약하여 유지되지 못하였다. 4. 제주도 근해산 중요어류 53종중 인공어초에 위집한 어종은 16종이었고 어획조성비는 참돔 $23\%, 볼라 $13\%, 보리멸 $11\%$, 우럭볼락 $7\%$, 주치 $6\%$이고 잠수관찰에서 어초의 중층부에 많은 치어가 위집된 것을 확인하였다.

• International Journal of Ocean System Engineering
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• 제1권4호
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• pp.185-191
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• 2011

This research was described the prevention of coastal topographical change and sediment diffusive concentration incoming from small estuary after construction jetties. This structure is constructed to decrease sediment deposition incoming from the upstream river due to the urbanization and industrial development and to minimize effects on the coastal ecosystem. The physical modeling and numerical modeling for waves were conducted to analyze the configuration of Imrang sand beach deformation without and with construction of jetty. The specification of the installed jetty, which is able to control sedimentation concentration was decided based on the prediction of the Imrang beach area changes by space and time. As a result, the jetties constructed in the estuary retarded the rate of sand sediment, so that the effect area of sand sedimentation was obviously decreased. In addition, the measured field data indicated that the sediment deposition inside of dikes could be controlled and the right side area of jetties could be preserved without sediment deposition.

• Geomechanics and Engineering
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• 제28권6호
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• pp.585-598
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• 2022

The monopile-friction wheel hybrid foundation is an innovative solution for offshore structures which are mainly subjected to large lateral eccentric load induced by winds, waves, and currents during their service life. This paper presents an extensive numerical analysis to investigate the lateral load and moment bearing performances of hybrid foundation, considering various potential influencing factors in sand-overlaying-clay soil deposits, with the complex lateral loads being simplified into a resultant lateral load acting at a certain height above the mudline. Finite element models are generated and validated against experimental data where very good agreements are obtained. The failure mechanisms of hybrid foundations under lateral loading are illustrated to demonstrate the effect of the friction wheel in the hybrid system. Parametric study shows that the load bearing performances of the hybrid foundation is significantly dependent of wheel diameter, pile embedment depth, internal friction angle of sand, loading eccentricity (distance from the load application point to the ground level), and the thickness of upper sandy layer. Simplified empirical formulae is proposed based on the numerical results to predict the corresponding lateral load and moment bearing capacities of the hybrid foundation for design application.