• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.940-947
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• 2005

An immersed boundary method for simulation of density-stratified flows has been developed and applied to computation of viscous flows past three different types of obstacle under table density stratification, namely laminar flows past a vertical barrier, a cosine hill, and a sphere, respectively. Density forcing is introduced on the body surface or inside the body. Significant changes in flow characteristics are observed depending on Fr. The numerical results are in good agreement with other authors' experimental and numerical results currently available, and shed light on computation of density-stratified flows in complex geometries.

• Journal of Mechanical Science and Technology
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• v.16 no.3
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• pp.363-375
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• 2002

The effect of the electromagnetic force (or Lorentz force) on the flow behavior around a circular cylinder is investigated by computation. Two-dimensional unsteady flow computation for Re=10$^2$is carried out using a numerical method of finite difference approximation in a curvilinear body-fitted coordinate system by solving the momentum equations including the Lorentz force as a body force. The effect of spatial variations of the Lorentz forcing region and forcing direction along the cylinder circumference is investigated. The numerical results show that the Lorentz force can effectively suppress the flow separation and oscillation of the lift force of circular cylinder cross-flow, leading to reduction of drag.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.15 no.2
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• pp.143-150
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• 2011

We consider the global existence of strong solutions of the 3D incompressible Navier-Stokes equations in a thin periodic domain. We present a simple proof that a strong solution exists globally in time when the initial velocity in $H^1$ and the forcing function in $L^p$(0,${\infty}$;$L^2$), $2{\leq}p{\leq}{\infty}$ satisfy certain condition. This condition is basically similar to that by Iftimie and Raugel[7], which covers larger and larger initial data and forcing functions as the thickness of the domain ${\epsilon}$ tends to zero.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.15 no.2
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• pp.97-122
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• 2011

Fluid dynamics driven by pumping without valves (valveless pumping) shows interesting physics. Especially, the driving function to generate valveless pump mechanism is one of important factors. We consider a closed system of valveless pump which consists of flexible tube part and stiffer part. Fluid and structure (elastic tube) interaction motions are generated by the periodic compress-and-release actions on an asymmetric location of the elastic loop of tubing. In this work, we demonstrate how important the driving forcing function affects a net flow in the valveless circulatory system and investigate which parameter set of the system gives a more efficient net flow around the loop.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.55.2-55.2
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• 2017

We study the effect of driving scheme on the density-magnetic field correlation. We numerically investigate how the correlation time of driving affects the correlation between density and magnetic field. We performed MHD turbulence simulation using two different driving schemes - a finite-correlated driving and a delta-correlated driving. In the former, the forcing vectors change continuously with a correlation time comparable to the large-eddy turnover time. In the latter, the direction and amplitude of driving changes in a very short time scale.

• Journal of the Korea Computer Industry Society
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• v.7 no.1
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• pp.33-38
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• 2006

The motions of suspension bridge as well as hanging cable are governed by nonlinear partial differential equations. Nonlinearity gives rise to a large amplitude oscillation. We use finite difference methods to compute periodic solutions to the torsional partial differential equations. We use the one-noded forcing term and a slight perturbation in the forcing term.

• Journal of the Korean Mathematical Society
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• v.49 no.2
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• pp.315-324
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• 2012

We consider the global existence of strong solutions of the 3D incompressible Navier-Stokes equations in a long periodic domain. We show by a simple argument that a strong solution exists globally in time when the initial velocity in $H^1$ and the forcing function in $L^p$([0; T);$L^2$), T > 0, $2{\leq}p{\leq}+\infty$ satisfy a certain condition. This condition common appears for the global existence in thin non-periodic domains. Larger and larger initial data and forcing functions satisfy this condition as the thickness of the domain $\epsilon$ tends to zero.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.842-846
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• 2007

Zero Forcing (ZF) 검파 결과는 신호 대 잡음 환경이 양호한 경우 약 80% 이상이 Maximum Likelihood (ML) 검파 결과와 일치한다. 간단한 검증기를 통해 ZF 검파 결과가 ML 검파 결과와 일치하는지 알 수 있다면 검증 결과에 따라 복잡한 ML 검파 과정이나 별도의 검색 과정을 생략할 수 있다. 본 논문에서는 multiple input multiple output (MIMO) 시스템에서 ZF 검파 결과에 대한 검증 방식을 제안하였다. 제안된 검증 방식은 ZF 검파 결과를 이용하여 MIMO 신호를 single input multiple output (SIMO) 신호로 변환한 후 검파를 수행하면 안테나 다이버시티 이득을 얻을 수 있고 잡음 분산이 줄어드는 효과를 이용하였다. 제안된 검증기는 컴퓨터 시뮬레이션 결과 신호 대 잡음이 양호한 경우 80%이상의 정확한 true 판정 확률을 얻었으며 이때 false 판정 확률은 $10^{-4}$이하를 보였다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.7 no.1
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• pp.34-40
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• 2007

Balasubramaniam and Muralisankar (2004) proved the existence and uniqueness of fuzzy solutions for the semilinear fuzzy integrodifferential equations with nonlocal initial condition. Park et al. (2006) found the sufficient condition of this system. Recently, Kwun et al. (2006) proved the existence and uniqueness of solutions for the semilinear fuzzy integrodifferential equations with nonlocal initial conditions and forcing term with memory in $E_N$. In this paper, we study the controllability for this system by using the concept of fuzzy number whose values are normal, convex, upper semicontinuous and compactly supported interval in $E_N$.

• Journal of Korean Association for Spatial Structures
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• v.15 no.4
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• pp.73-80
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• 2015

The new rotary friction damper was developed using several two-nodal rotary frictional components with different clamping forces. Because of these components, the rotary friction damper can be activated by building movements due to lateral forces such as a wind and earthquake. In this paper, various dependency tests such as displacement amplitude, forcing frequency and long term cyclic loading were carried out to evaluate on the structural performance and the multi-slip mechanism of the new damper. Test results show that the multi-slip mechanism is verified and friction coefficients are dependent on displacement amplitute and forcing frequency except long term cyclic loading.