• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.4
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• pp.202-216
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• 2015

In the narrow water channel, which has been frequently deployed in the artificial canal in the South Korea due to the lack of available land, solitary wave type ship induced waves can occur. In order to test this hypothetical view, we carried out the numerical simulation. Numerical model consists of Navier-Stokes Equations and VOF, and the verification is implemented using the data by PIANC (1987) and the analytical model derived in this study. It was shown that numerically simulated front wave height are much larger than the one by PIANC (1987), and the fluctuation of free surface near the channel bank persists much longer (around 20s). For the case of stern waves, numerically simulated wave height are somewhat smaller than the data by PIANC (1987). These results seriously deviates from the general characteristics of ship induced waves observed in the wide water channels, and leads us to conclude that ship induced waves is severely affected by the width of water channel. It was also shown that the currents from the channel banks toward a ship, and currents from the ship toward the channel banks are alternatively occurring due to reflection at the channel banks. The velocity of currents reaches its maximum at 0.90 m/s, and these values are sustained through the entire depth. which implies that severe scourings at the channel bottom can be underway.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.4
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• pp.277-286
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• 2012

In the numerical simulation of wave fields using a multi-phase flow model that considers simultaneous flows of materials with different states such as gas, liquid and solid, there is need of an accurate representation of the interface separating the fluids. We adopted an algebraic interface capturing method called tangent of hyperbola for interface-capturing(THINC) method for the capture of the free-surface in computations of multi-phase flow simulations instead of geometrical-type methods such a volume of fluid(VOF) method. The THINC method uses a hyperbolic tangent functions to represent the surface, and compute the numerical flux for the fluid fraction functions. One of the remarkable advantages of THINC method is its easy applicability to incorporate various numerical codes based on Navier-Stokes solver because it does not require the extra geometric reconstruction needed in most of VOF-type methods. Several tests were carried out in order to investigate the advection of interfaces and to verify the applicability of the THINC method to wave fields based on the one-field model for immiscible two-phase flows (TWOPM). The numerical results revealed that the THINC method is able to track the interface between air and water separating the fluids although its algorithm is fairly simple.

• Journal of Life Science
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• v.19 no.7
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• pp.899-904
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• 2009

We purified crude urushiol from natural lacquer produced in Korea, China, and Japan and then isolated several urushiol congeners known to induce allergic reactions. The 3 major kinds of urushiol congeners that were isolated and purified were RV-l (C$_{21}$H$_{34}$O$_2$, M.W. 314.462), RV-2 ((C$_{21}$H$_{32}$O$_2$, M.W. 316.240) and RV-3 ((C$_{23}$H$_{34}$O$_2$, M.W. 342.515), occupying 80% of total crude urushiol. The content of RV-l was the highest in natural lacquer from China at 70.07%, and was the lowest in that from Japan at 62.38%. However, the content of RV-2 in natural lacquer from Japan was 9.25%, 2$\sim$3 times higher than those from Korea (4.28%) and China (3.09%). As an allergy inducing character, RV-l had strong inducing power and durability in the primary stage, showing slow recovery. RV-2 had weak power in the primary stage and also showed slow recovery. Although RV-3 had comparatively weak power at the primary stage, it induced the strongest allergy contact dermatitis after 48 hr. However, it recovered to nearly the same level as control group 72 hr after sensitization time. Accordingly, we found out that RV-1 is the most influential of urushiol congeners in inducing allergic reactions, natural lacquer from China having the most inducible strength and slowest recovery compared to those from Korea and Japan.

• Korean Journal of Ecology and Environment
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• v.53 no.4
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• pp.374-379
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• 2020

The white-spotted flower chafer (Protaetia brevitarsis) larva is one of the insects widely-used for edible and medicinal purposes in Eastern Asia. As a result of increasing demand for P. brevitarsis, massrearing systems in domestic farms have become necessary. However, the mass-rearing of larvae under confined rearing conditions could provide conditions unsuitable for preventing entomopathogenic diseases. Metarhizium anisopliae is the strongest fatal entomopathogenic fungus against P. brevitarsis. For inhibition of M. anisopliae, we used a Rhus verniciflua Stokes extract that has antifungal components. We investigated the inhibitory effect of the R. verniciflua extract at 1%, 5%, and 10% concentrations. The results showed that a 1% R. verniciflua extract added to sawdust produced a significantly low P. brevitarsis mortality rate. Moreover, extract-treated groups were heavier and had a shorter larval period than those of the untreated group. Consequently, we suggest that using an R. verniciflua extract can reduce the P. brevitarsis fatality rate from entomopathogenic fungi (e.g. M. anisopliae), resulting in more effective mass-rearing systems for P. brevitarsis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.547-558
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• 2008

With the advent of super cargo ship due to the explosive increase in the amount of cargo shipped via seas, some mega ports are under construction in South Korea, to accommodate the super cargo ship, and some of them already enter their final phase. To sustain the harbor tranquility, mega ports usually comprise huge vertical type breakwaters which are intrinsically vulnerable to the attack of long waves. In this rationale, we present the chamber type breakwater with a circular curtain wall - Eco-breaker 2, to alleviate the reflection of long waves and numerically investigate the hydraulic characteristics of Eco-breaker 2. As a wave driver, we use the Navier-Stokes eq., the most robust wave driver, using SPH (Smoothed Particle Hydrodynamics) and LES (Large Eddy Simulation). For the verification of numerical results, we also carried out hydraulic model test. It is shown that Eco-breaker 2 can effectively alleviate the reflection of long waves with its inherited large organized eddies encompassing the water chamber and some region off the curtain wall of varying size. It is also shown that the scope and strength of large organized eddies strongly depends on the incident wave period, and the reflection coefficient can be lowered to 0.18 by tuning the size of water chamber such that resident time at the chamber is just short of the half period of incident waves. Based on these results, we present the specification of Eco-breaker 2 to boost its use on the development of water environment friendly harbor worldwide.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.2
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• pp.149-159
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• 2016

In this study, the solitary wave-induced tsunami force acting on an onshore bridges in coastal area was numerically modelled by means of TWOPM-3D based on Navier-Stokes solver and VOF method which can track free surface effectively. The validity of numerical analysis was verified by comparing the experimental tsunami bore force acting on vertical wall and column structure. In particular, the characteristics of tsunami force with the changing tsunami intensity were surveyed through numerical experiments. The availability of 3-dimensional numerical analysis was reviewed through the comparison between the existing numerical results and design criteria for each drag force coefficient by applying Morison equation considering only drag force. As reasonable and high-precision estimation method of tsunami force, it was suggested to apply the estimation method taking drag and inertial force into consideration at the same time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.16-25
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• 2003

A parallel computing environment based on Windows operating system was constructed and a performance test was mode in comparison with Linux based systems. The Windows 2000 cluster was composed with servers and clients connected by Fast-ethernet, within which two sub-clusters may operates together or separately. Compaq Visual Fortran complier and two MPI libraries, MPICH.NT.1.2.2 and NT-MPICHNT.1.2 were installed as computing tools. Parallel computing performance tests were carried out using two-dimensional preconditioned Navier-Stokes code to examine the dependency on the number of processors, problem size and MPI libraries, those were compared with results from Linux clusters. Results shows that a cluster based on the user-friendly Windows operating system is also useful for the parallel computing and has good performance comparable to the previous Linux clusters.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.64-71
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• 2004

A computational study on the supersonic flow around the lateral jet controlled missile has been performed. For this purpose a three dimensional Navier-Stokes computer code(AADL3D) has been developed and case studies have been performed by comparing the normal force coefficient and the moment coefficient of a missile body for different jet flow conditions including jet pressure and jet Mach number. The results show different behavior of normal force and moment variation according to jet pressure variation and jet Mach number variation. From the detailed flow field analyses, it is verified that most of the normal force loss and the pitching moment generation are taken place at the low-pressure region behind the jet nozzle. Furthermore, it is shown that the pitching moment can be efficiently reduced by obtaining the lateral thrust through higher jet Mach number rather than through high jet pressure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.16-22
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• 2004

Unsteady vortex shedding behind a rectangular cylinder near a wall influences both increasing of drag and dynamic stability of heavy vehicle, bridge or building. Incompressible Averaged Navier-Stokes equation with modified ${\varepsilon}-SST$ turbulence model is adapted for investigating the flow field between the rectangular cylinder and the wall. In case the vortex shedding happens, not only the averaged maximum velocity is higher than other cases, but the position of the maximum velocity is closer to the lower surface of rectangular cylinder. On this study, it is confirmed that the vortex shedding behind a rectangular cylinder can be suppressed by the passive control method added by horizontal and vertical fences to the lower surface of rectangular cylinder.

• Journal of the Korea Computer Graphics Society
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• v.25 no.5
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• pp.21-30
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• 2019

We propose a physical simulation method based on the shallow water equation(SWE) to represent water surface effectively. In this paper, the water which can be represented has a much larger width compared to the depth does not have a large vertical direction flow. In order to calculate the water flow efficiently, we start with the shallow water equation as the governing equation, which is a simplified version of the Navier-Stokes equation. In order to numerically calculate the advection term of the SWE, we introduce a new conservtive USCIP(CUSCIP) method which improves the Constrained Interpolation Profile (CIP) method to preserve the physical quantity while increasing the numerical accuracy. The proposed method is based on Kim et. al.'s Unsplit Semi-lagrangian CIP[9], and calculates advection term with additional constraints on term that consider integral values. The experimental results show that the CUSCIP method is robust to the loss of physical quantity due to numerical dissipation, which improves wave detail and persistence.