• Journal of applied mathematics & informatics
• /
• 제26권1_2호
• /
• pp.45-60
• /
• 2008

Here we consider the evaluation of the the dynamic component of the second order force due to wave diffraction by a circular cylinder analytically and numerically. The cylinder is fixed, vertical, surface piercing in water of finite uniform depth. The formulation of the wave-structure interaction is based on the assumption of a homogeneous, ideal, incompressible, and inviscid fluid. The nonlinearity in the wave-structure interaction problem arises from the free surface boundary conditions, namely, dynamic and kinematic free surface boundary conditions. We expand the velocity potential and free surface elevation functions in terms of a small parameter and then consider the second order diffraction problem. After deriving the pressure using Bernoulli's equation, we obtain the analytical expression for the dynamic component of the second order force on the cylinder by integrating the pressure over the wetted surface. The computation of the dynamic force component requires only the first order velocity potential. Numerical results for the dynamic force component are presented.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2001년도 학술발표회 논문집(II)
• /
• pp.1133-1138
• /
• 2001

The focus of this paper is on the numerical investigation of obliquely incident wane interactions with a system composed of full submerged and floating dual buoy/vertical-flexible-membrane breakwaters placed in parallel with spacing. The fully submerged systems allow surface and bottom clearances to enable wave transmission over and under the system. The problem is formulated based on the two-dimensional multi-domain hydro-elastic linear wave-body interaction theory. The hydrodynamic interaction of oblique incident waves with the combination of the rigid and flexible bodies was solved by the distribution of the simple sources (modified Bessel function of fille second kind) tat satisfy the Helmholz governing equation. Using this computer program, the performance of various dual systems varying buoy radiuses and drafts, membrane lengths, clearances. spacing, mooring-lines stiffness, mooring types, water depth, and wave characteristics is thoroughly examined. It is found that the fully submerged and floating dual buoy/membrane breakwaters call, if it is properly tuned to the coming waves, have good performances ill reflecting the obliquely incident waves over a tilde range of wave frequency and headings.

• Water Engineering Research
• /
• 제6권3호
• /
• pp.123-130
• /
• 2005

A good understanding of the interaction between flow, vegetation, and sediment is required for successful river restoration and sustainable flood management. The purpose of this paper is to provide a summary of available methods to determine flow resistance of natural rivers with vegetation, and discuss the influence of vegetation on erosion and sedimentation processes. Recently, significant advances have been made, but the effects of vegetation on flow and sediment dynamics are still not fully understood. Possible solutions to close the gaps in the current knowledge are suggested, with special focus directed to the determination of the interactive width between main channel and vegetated floodplains, the flow resistance of flexible vegetation with and without leaves, and the flow over submerged vegetation with low water depth.

• 지식경영연구
• /
• 제16권1호
• /
• pp.1-19
• /
• 2015

Although the interaction effects of knowledge sourcing strategies vary depending on environmental conditions such as knowledge intensity, most prior empirical research have failed to prove the effects of environmental conditions on the relationship between knowledge sourcing strategies and firm performance. In order to fill this gap, this study examines how knowledge intensity affects the relationship between knowledge sourcing strategies and firm performance. The results of this study indicate the interaction effects of knowledge sourcing strategies in high knowledge intensity environment are different from the effects in low knowledge intensity environment. This study expands knowledge management research by identifying the effects of knowledge intensity on the relationship between knowledge sourcing strategies and firm performance. Furthermore, it offers valuable practical guidelines for managers in selecting successful combinations of knowledge sourcing strategies with the consideration of knowledge intensity.

• Journal of Mechanical Science and Technology
• /
• 제19권5호
• /
• pp.1116-1122
• /
• 2005

A finite element method was used to simulate the wave propagation of laser-generated ultrasound and its interaction with surface breaking cracks in an elastic material. Thermoelastic laser line source on the material surface was approximated as a shear dipole and loaded as nodal forces in the plane-strain finite element (FE) model. The shear dipole- FE model was tested for the generation of ultrasound on the surface with no defect. The model was found to generate the Rayleigh surface wave. The model was then extended to examine the interaction of laser generated ultrasound with surface-breaking cracks of various depths. The crack-scattered waves were monitored to size the crack depth. The proposed model clearly reproduced the experimentally observed features that can be used to characterize the presence of surface-breaking cracks.

• 한국해양공학회지
• /
• 제12권3호통권29호
• /
• pp.75-85
• /
• 1998

A finite difference model for predicting time-dependent, wave-induced nearshore current is studied. The model includes wave refraction, wave-current interaction, bottom friction and wind effect. This model iteratively solved the linear the linear set of conservation of both mass and momentum, which were time averaged (over one wave period) and depth integrated, for mean velocities and free surface displacement. Numerical simulations of nearshore current under oblique wave attack, and for wave and wind induced current on a longshore periodic beach are carried out. Longshore velocities tend to zero in some distances outside the breaker line. And the peak velocity is shifted shoreward at the breaker line. The results represent the general characteristics of the nearshore current induced by wave.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
• /
• pp.120-129
• /
• 2000

As structure-soil interaction analysis for the seismic analysis of structures requires a nonlinear analysis of a structure-soil system considering the inelastic characteristics of soil layers nonlinear analyses of the foundation-soil system with the horizontal excitation were performed considering the nonlinear soil conditions for the nonlinear seismic analysis of structures. Stiff soil profile of SD and soft soil profile of SE specified in UBC were considered for the soil layers of a foundation and Ramberg-Osgood model was assumed for the nonlinear characteristics of soil layers. Studies on the changes of dynamci stiffnesses and damping rations of surface and embedded foundations depending on foundation size soil layer depth and piles were performed to investigate the effects of the nonlinear soil layer on the horizontal and rotational dynamic stiffnesses and damping ratios of the foundation-soil system According to the study results nonlinear prperties of a soil laryer decreeased horizontal and rotational linear stiffnesses and increased damping ratios largely Effects of foundation size soil layer depth and piles were also significant suggesting the necessity of nonlinear seismic analyses of structures.

• 한국해안·해양공학회논문집
• /
• 제28권4호
• /
• pp.222-231
• /
• 2016

최근 해상풍력터빈에 대한 하부구조물로 재킷 또는 트라이포드 형태의 고정식 하부구조물이 기존의 모노파일을 대체하는 좋은 대안으로 제시되고 있다. 이러한 재킷 또는 트라이포트 하부구조물은 이미 기술성숙도가 높고 25-50 m 사이의 중수심에서 경제성 확보가 가능하다. 본 논문에서는 모노파일을 포함하여 트라이포드, 재킷 하부구조물을 채택한 고정식 해상풍력터빈에 대하여 지반물성치 및 하중의 불확실성, 그리고 세굴 깊이를 고려하여 신뢰성 해석을 수행하였다. NREL 5 MW 풍력터빈 제원을 이용한 수치해석을 통하여, 지반물성치의 불확실성을 고려한 신뢰도 지수 분석 결과 모노파일 기초를 채택한 해상풍력터빈의 신뢰도 지수가 세굴깊이가 증가함에 따라 크게 감소하는 것을 알 수 있었으며, 재킷 또는 트라이포드 기초를 채택한 경우 세굴깊이가 신뢰도 지수에 미치는 영향이 크지 않음을 알 수 있었다. 결론적으로 재킷 또는 트라이포드 기초를 채택한 해상풍력터빈의 경우 지반-말뚝 상호작용을 고려하지 않아도 구조 신뢰성 해석을 수행할 수 있으나, 모노파일을 채택한 경우, 신뢰성 해석 시 지반물성치 및 이에 포함되어 있는 불확실성의 정보가 상대적으로 중요함을 알 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권2호
• /
• pp.1019-1031
• /
• 2017

In this study, we propose a new method for simulating water responding to human motion. Motion data obtained from motion-capture devices are represented as a jointed skeleton, which interacts with the velocity field in the water simulation. To integrate the motion data into the water simulation space, it is necessary to establish a mapping relationship between two fields with different properties. However, there can be severe numerical instability if the mapping breaks down, with the realism of the human-water interaction being adversely affected. To address this problem, our method extends the joint velocity mapped to each grid point to neighboring nodes. We refine these extended velocities to enable increased robustness in the water solver. Our experimental results demonstrate that water animation can be made to respond to human motions such as walking and jumping.

• 한국레이저가공학회지
• /
• 제15권2호
• /
• pp.1-5
• /
• 2012

Gelatin is used as a model for soft biological tissues in studying laser interaction with the soft tissues. In this work, we analyze the interaction between gelatin and excimer and Ti:Sapphire femtosecond laser under various conditions, especially by varying the laser, laser fluence and pulse number. The results show that swelling of the surface and ablation depth can be controlled by adjusting the process parameters.