• 한국해양공학회지
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• 제15권4호
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• pp.28-37
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• 2001

The water quality in Yongil Bay is getting worse due to the sewage and the waste water from the surrounding industrial complex. The study aims to simulate the current system that is necessary to build ecosystem model for the optium water quality control and clarify the correlation of current system characteristics with water quality in Yongil Bay. To clarify the characteristics of coastal water movement system and verify the applicability of the 3-D model, the current system was simulated using 3-D model baroclinic model which considers tidal current and density effects. As the results of numerical experiments, it is proved the 3-D model is the most applicable on appearing the current system of the stratificated Yongil Bay difference of density. Form the results of simulation considered tidal current only, it can be clarified that the water body flows in the inner bay through the bottom layer and flows out the outer bay through the surface layer in Yongil Bay. And the fresh water from the Hyongsan river and the thermal discharge form POSCO have a little effect on the current system in Yongil Bay, but the diffusion of heat and salt has an important effect upon the formation of the density stratification of the water quality distribution is closely related with the current structure characteristics as well as the tidal residual current system in Yongil Bay.

• International Journal of Contents
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• 제10권3호
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• pp.84-89
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• 2014

The mass-spring model has been typically employed in physical-based simulators for clothes or patches. The mass-spring model frequently utilizes equal mass and the gravity factor. The model structure of masses supports a shape applicable to fishing nets. Therefore, to create a simulation model of a fishing net, we consider the mass-spring model and adopt the tidal-current and buoyancy effects in underwater environments. These additional factors lead to a more realistic visualization of fishing-net simulations. In this paper, we propose a new mass-spring model for a fishing-net and a method to simplify the calculation equations for a real-time simulation of a fishing-net model. Our 3D mass-spring model presents a mesh-structure similar to a typical mass-spring model except that each intersection point can have different masses. The motion of each mass is calculated periodically considering additional dynamics. To reduce the calculation time, we attempt to simplify the mathematical equations that include the effect of the tidal-current and buoyancy. Through this research, we expect to achieve a real-time and realistic simulation for the fishing net.

• 신재생에너지
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• 제5권2호
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• pp.3-8
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• 2009

Tidal current power system is one of ocean renewable energies that can minimize the environmental impact with many advantages compared to other energy sources. Not like others, the produced energy can be precisely predicted without weather conditions and also the operation rate is very high. To convert the current into power, the first device encountered to the incoming flow is the rotor that can transform into rotational energy. The performance of rotor can be determined by various design parameters including numbers of blade, sectional shape, diameter, and etc. The stream lines near the rotating rotor is very complex and the interference effects around the system is also difficult to predict. The paper introduces the experiment of rotor performance and also the fundamental study on the characteristics of three different rotors and flow near the rotor by CFD.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.246-252
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• 2000

The water quality in Yeongil Bay is getting worse due to the sewage and the waste water from the surrounding industrial complex The study aims to simulate the current system that is necessary to built ecosystem model for the optium water quality control and clarify the correlation of current system characteristics with water quality in Yongil Bay. To clarify the characteristics of coastal water movement system and verify the applicability of the 3-D model, the current system was simulated using 3-D baroclinic model considered tidal current and density effects. As the results of numerical experiments, it is proved the 3-D model is the most appliable on the Yongil Bay where current flows slowly and the flow direction is varied by depths. From the results of simulation considered tidal current only, It am be clearly said the water in Yongil Bay flows in through the surface layer and flows out through the bottom layer. And the fresh water from the Hyongsan river and the heated discharge from POSCO have little effect on the current structure in Yonggil Bay, but have and important effect upon the density structure by diffusion of heat and salt. And the water quality distribution is closely related with the current structure characteristics as well as the tidal residual current system.

• 대한토목학회논문집
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• 제3권2호
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• pp.97-107
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• 1983

비선형(非線型) 2차원조석(次元潮汐)모델의 경기만남부해역(京畿灣南部海域)에의 적용(適用)이 서술(敍述)되었다. 모델을 이용(利用)하여 만체계(灣體系)의 조류유동현상(潮流流動現像), 해저마찰력(海底摩擦力) 및 에너지소산(消散)에 대(對)한 초기평가(初期評價)를 할 수 있었다. 또한 모델에 의(依)한 수치실험(數値實驗)을 통(通)해 아산만접근수로(牙山灣接近水路)를 준설(浚渫)할 경우(境遇) 주태음반일주조(主太陰半日週潮)($M_2$)의 영향(影響) 및 해면(海面)에 작용(作用)하는 $10dyne/cm^2$의 균일정상풍(均一定常風)에 의(依)한 유동현상(流動現像)의 변화(變化)를 평가(評價)하였다. 초기결과(初期結果)들이 제시(提示)되었으며 토의(討議)되었다.

• Journal of the korean society of oceanography
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• 제34권3호
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• pp.133-143
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• 1999

We carried out simultaneous and long-time observations of currents across the western channel of the Korea Strait during the period of May, 1994 to September, 1996 in order to understand the spatial and temporal variability of tidal and nontidal currents in the Strait. Results show that currents in the Strait are quite variable in space and time, and they largely consist of mean current and diurnal and semidiurnal tidal currents of about equal magnitudes. The mean currents include the Tsushima Current and the Korea Strait Undercurrent at the center of the channel. The former occupies the upper two-thirds and the latter the lower one-third of the water column. The semidiurnal and diurnal currents are largely rectilinear in the direction of NE-SW and their amplitude variation across the channel appears to be small. However, the diurnal currents at some locations show rotational characteristics with significant nontidal effects. The station close to the Korean coast leads the phase and the phase difference of the semidiurnal current across the channel appears to be less than half an hour while that of the diurnal current is over five hours.

• 천문학회보
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• 제41권1호
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• pp.68.3-68.3
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• 2016

We analyze the dependence of environment of warped galaxies by using the local background density, Tidal Index and projected distance as measures of the environment. we use galaxies with redshift less than z=0.025 from the Sloan Digital Sky Survey (SDSS) DR7. We selected 345 edge-on galaxies using color images provided by the SDSS DR7 and checked it using isophotal maps. This sample contains 136 warped galaxies, 209 non-warped galaxies. Among warped galaxies, there are 18 strongly warped galaxies which have warp angles larger than 7.5o. We calculated the fractional distributions of galaxies as a function of environmental parameters. All of these parameters show little difference between warped galaxies and non-warped galaxies if we include weakly warped galaxies. However, there is a clear difference in the fractional distributions between the strongly warped galaxies and non-warped galaxies. The fraction of warped galaxies increases with decreasing distance to the nearest neighbor galaxy but It increases with increasing background density and Tidal Index. However, the relationships between warp angles and the three environmental parameters are not strong. The effect of Tidal Index is well distinguished in small, bright galaxies whereas the effects of the background density and the distance to the nearest neighbor galaxy are more pronounced in large, bright galaxies.

• 한국수자원학회논문집
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• 제31권3호
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• pp.235-242
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• 1998

본 연구의 목적은 낙동강 하류부의 감조구간에 대하여 실시간 홍수예보를 위한 수리학적 홍수추적 모형의 적용성을 검토하고 홍수시 감조구간내의 주요 홍수 예보지점에 대한 조위의 영향을 분석하는 것이다. 또한 모형의검증을 위하여 부정류 해석법에 의하여 하도구간별, 유량규모별 최적 조도계수를 추정하였으며 추정된 최적 조도계수를 적용한 부정류 해석 결과가 관측 수위수문곡선의 전반적인 형태를 매우 잘 재현하는 것으로 나타났다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.154-164
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• 2019

A rotor dynamic analysis is mandatory for stability and design optimization of submerged propellers and turbines. An accurate simulation requires a proper consideration of fluid-induced reaction forces. This paper presents a bi-directional coupling of a bond graph method solver and an unsteady vortex lattice method solver where the former is used to model the rotor dynamics of the power train and the latter is used to predict transient hydrodynamic forces. Due to solver coupling, determination of hydrodynamic coefficients is obsolete and added mass effects are considered automatically. Additionally, power grid and structural faults like grid fluctuations, eccentricity or failure could be investigated using the same model. In this research work a fast, time resolved dynamic simulation of the complete power train is conducted. As an example, the rotor dynamics of a tidal stream turbine is investigated under two inflow conditions: I - shear flow, II - shear flow + water waves.

• 한국토양비료학회지
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• 제44권1호
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• pp.29-37
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• 2011

The experiment was carried out to find the effects of transplanting time and vinyl-film mulching treatment on the growth of artemisia by randomized block design with three replications. The experiment site ($100{\times}130$ m) was temporally established in the south-eastern part of Saemangeum reclaimed tidal land (near Gwanghwal myun, Gimjae-gun, Jellabukdo). Artemisia plants had been partly suffered from salt injury, because soil salinities in some area during growing period had been measured higher than 10 dS $m^{-1}$. Growth of plant height and survival ratio of transplanted plants had been significantly correlated with soil salinity and then the regression equations between plant height (y) and soil EC (x) and between survival ratio (y) and soil EC (x) were expressed as y=-16.59ln(x)+43.852 and $y=0.6453x^2-17.566x+103.99$, respectively. It was concluded that early transplanting and vinyl mulching was more beneficial for biomass production of artemisia, because biomass was 6.41 times more in the early transplanting than in the late transplanting, and 2.63 times more in the vinyl-film mulching than in the no mulching treatment.