• Journal of Advanced Research in Ocean Engineering
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• 제1권1호
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• pp.14-24
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• 2015

A three-dimensional multidirectional nonlinear numerical wave tank (NWT) based on the Navier-Stokes equations and the Finite Volume Method (FVM) is developed by using the two-phase hydrodynamic flow solver naoe-FOAM-SJTU based on the open source toolbox OpenFOAM. The free surface is capturing with the Volume Of Fluids (VOF). The directional wave including Stokes wave, solitary wave and nonlinear wave are simulated and verified. The multi-directional waves are also simulated with particular wave spectral such as JONSWAP and wave directional spreading function. The obtained numerical results show the capability of the solver to generate different type of multidirectional nonlinear waves accurately. Meanwhile, it implies that the presented NWT can easily extend to model the wave-structures interactions, which will be great help to the offshore structures design.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.305-310
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• 2005

The velocity and pressure fields of a ship's propulsion mechanism of the Weis-Fogh type, in which a airfoil moves reciprocally in a channel, are studied in this paper using the advanced vortex method. The airfoil and the channel are approximated by a finite number of source and vortex panels, and the free vortices are introduced from the body surfaces. The viscous diffusion of fluid is represented using the core-spreading model to the discrete vortices. The velocity is calculated on the basis of the generalized Biot-Savart low and the pressure field is calculated from integrating the equation given by the instantaneous velocity and vorticity fields. Two-dimensional unsteady viscose flows of this propulsion mechanism are numerically clarified, and the calculated results agree well with the experimental ones.

• Ocean and Polar Research
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• 제35권1호
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• pp.63-68
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• 2013

The European Common Barnacle Balanus perforatus Brugiere (Crustacea, Cirripedia) has been introduced into the east coast of Korea, presumably via the ballast water of ships. The species has since been spreading along both the northern and southern coast to the east, most likely due to alongshore currents. We predicted the potential range expansion of Balanus perforatus in Korean waters using Genetic Algorithm for Rule-set Prediction (GARP), an environmental niche modeling technique. The results show that much of the southern coastal waters of Korea could be colonized by the spread of the nonindigenous species, but that the west coast is unlikely to be invaded. More sampling on the west coast would enhance the predictability of the model. To our knowledge, this is the first report of its kind for predicting marine nonindigenous species in Korean waters using GARP modeling.

• International Journal of Ocean System Engineering
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• 제4권1호
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• pp.49-56
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• 2014

A three-dimensional multidirectional nonlinear numerical wave tank (NWT) based on the Navier-Stokes equations and the Finite Volume Method (FVM) is developed by using the two-phase hydrodynamic flow solver naoe-FOAM-SJTU based on the open source toolbox OpenFOAM. The free surface is capturing with the Volume Of Fluids (VOF). The directional wave including Stokes wave, solitary wave and nonlinear wave are simulated and verified. The multi-directional waves are also simulated with particular wave spectral such as JONSWAP and wave directional spreading function. The obtained numerical results show the capability of the solver to generate different type of multidirectional nonlinear waves accurately. Meanwhile, it implies that the presented NWT can easily extend to model the wave-structures interactions, which will be great help to the offshore structures design.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1597-1604
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• 2002

In this study, numerical investigation has been performed on the impingement, spreading and solidification of a coating material droplet impacting onto a solid substrate in the thermal spray process. The numerical model is validated through the comparison of the present numerical result with experimental data fer the flat substrate without surface defects. An analysis of deposition formation on the non-polished substrate with surface defects is also performed. The parametric study is conducted with various surface defect sizes and shapes to examine the effect of surface defects on the impact and solidification of the liquid droplet on the substrate.

• 대한수학회지
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• 제51권4호
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• pp.703-719
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• 2014

This paper is concerned with the traveling wave solutions of nonlocal dispersal models with nonlocal delays. The existence of traveling wave solutions is investigated by the upper and lower solutions, and the asymptotic behavior of traveling wave solutions is studied by the idea of contracting rectangles. To illustrate these results, a delayed competition model is considered by presenting the existence and nonexistence of traveling wave solutions, which completes and improves some known results. In particular, our conclusions can deal with the traveling wave solutions of evolutionary systems which admit large time delays reflecting intraspecific competition in population dynamics and leading to the failure of comparison principle in literature.

• 한국통신학회논문지
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• 제24권7A호
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• pp.939-946
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• 1999

다중 사용자 환경의 이동통신 시스템에서 채널의 사용효율을 높이기 위해 학습 신호열을 사용하지 않고 채널을 추정할 수 있는 블라인드 채널 추정기법을 제안한다. 제안한 기법은 수신신호의 2차 통계특성과 부공간 개념을 이용하여 사용자들의 확산코드를 제외한 실제 물리적인 통신 채널만을 추정함으로써 계산량을 줄일 수 있는 장점을 가지고 있다. 모든 사용자들의 채널을 추정하기 위해 다중 채널 모델을 사용하여 비동기 DS-CDMA 시스템에서의 블라인드 기법을 유도하고 모의 실험을 통해 기존 방법에 비해 매우 적은 계산량을 요구하면서 비슷한 성능을 보임을 확인할 수 있었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.2130-2138
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• 2008

The present study investigates the ventilation effects on smoke spreading characteristics in railway tunnels with the rescue stations. Experiments were carried out for n-heptane pool fires with a square length 4 cm at different fire locations, and the heat release rates (HRR) were obtained by the measurement of burning rates. In addition, using the commercial code (FLUENT), the present article presents numerical results for smoke behavior in railway tunnels with rescue station, and it uses the MVHS (Modified Volumetric Heat Source) model for estimation of combustion products resulting from the fire source determined from the HRR measurement. As a result, it is found that smoke propagation is prevented successfully by the fire doors located inside the cross-passages and especially, the smoke behavior in the accident tunnel can be controlled through the ventilation system because of substantial change in smoke flow direction in the cross-passages.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall
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• pp.45-51
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• 1999

The attenuations of peak vertical displacements are studies using a conventional least squeare regression technique for microearthquakes occurred in the Kyungsang Basin southeastern Korea. The regression model applied to bandpass-fitered ground motion data includes parameters to account for geometric spreading anelastic attenuation depending on frequency source size and station site effects. Thirty nine displacement traces obtained by integrating velocity records for six shallow local microearthquakes are used to determine attenuation characteristics in the Basin. The regression result of the peak amplitude data leads to Q(f)=59.9 {{{{ {f }^{0.955 } }} for 1.5Hz$\leq$ f $\leq$ 25 Hz. It appears that the anelastic attenuation in the Kyungsang Basin is greater than that in the Western North America Area.

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 동계학술발표회 논문집
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• pp.231-232
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• 2008

The effect of n-electrode patterns on the current distribution in active region is investigated in GaN-based blue vertical light emitting diodes (VLEDs). A 3-dimension circuit model is adopted to analyze the current flow patterns in VLEDs. We had fabricated VLEDs having different n-electrode patterns, measured their current-voltage characteristics, and compared to the numerical simulation. It turns out that the current spreading in VLEDs is strongly dependent on the n-electrode pattern. Some design guidelines for n-electrode patterns to produce uniform current injection are presented.