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Soorok RYU,Juan M. LOPEZ,Younghae DO 한국산업응용수학회 2012 한국산업응용수학회 학술대회 논문집 Vol.7 No.2
The numerical simulations of the motion of the ideal particles are considered in a relatively tall cylinders driven by the rotating endwall. These flows at a tall cylinder aspect ratio is greater than 3 are distinguished from the ones of the lower aspect ratio cylinder. The most recent of these studies observed using PIV data of these swirling flow as a multiple helix point of view [2]. In a tall cylinder case, the three dimensional rotating wave states found that it is different from the lower aspect ratios (see [1]). In more recent paper [3], they analyze their expeimenal data in terms of helical modes. Our main results are the numerical simulations of the dye or air bubble helix modes experimentally observed in [1]. Actually, motivation of analysis of helical modes appeared in [3] was the experimental results of the dye lines and air bubble lines.
류수록(Soorok Ryu),이상혁(Sang-Hyuk Lee) 한국지능시스템학회 2008 한국지능시스템학회논문지 Vol.18 No.2
데이터 분석을 위하여 데이터의 불확실성에 대한 측도로서 퍼지 집합에 대한 엔트로피를 소개하였고, 또한 데이터간의 유사도를 나타내는 유사측도를 구성하였다. 퍼지 소속 함수간의 유사측도는 거리측도를 이용하여 구성하였고, 제안한 유사측도를 증명을 통하여 확인하였다. 제안한 유사측도의 유용성을 확인하기 위하여 신뢰성 있는 데이터추출 예제에 적용하였다. 적용결과를 퍼지 엔트로피와 통계적 지식을 통하여 얻어진 이전의 결과와 비교하였다. For data analysis, fuzzy entropy is introduced as the measure of fuzziness, similarity measure is also constructed to represent similarity between data. Similarity measure between fuzzy membership functions is constructed through distance measure, and the proposed similarity measure are proved. Application of proposed similarity measure to the example of reliable data selection is also carried out. Application results are compared with the previous results that is obtained through fuzzy entropy and statistical knowledge.
Application of Similarity Measure for Fuzzy C-Means Clustering to Power System Management
Dong-Hyuk Park,Soorok Ryu,Park Hyun Jeong,Sang H. Lee 한국지능시스템학회 2008 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.8 No.1
A FCM with locational price and regional information between locations are proposed in this paper. Any point in a networked system has its own values indicating the physical characteristics of that networked system and regional information at the same time. The similarity measure used for FCM in this paper is defined through the system-wide characteristic values at each point. To avoid the grouping of geometrically distant locations with similar measures, the locational information are properly considered and incorporated in the proposed similarity measure. We have verified that the proposed measure has produced proper classification of a networked system, followed by an example of a networked electricity system.
Cooling of Heat Sources by Natural Convection Heat Transfer in a Vertical Annulus
Sankar, M.,Do, Younghae,Ryu, Soorok,Jang, Bongsoo Taylor Francis 2015 NUMERICAL HEAT TRANSFER PART A-APPLICATIONS - Vol.68 No.8
<P>This article reports convection heat transfer in a short and tall annular enclosure with two discrete isoflux heat sources of different lengths. The discrete heat sources are mounted at the inner wall and the outer wall is maintained at a lower temperature, whereas the top and bottom walls and the unheated portions of the inner wall are kept at adiabatic. An implicit finite-difference method is employed to solve the vorticity-stream function formulations of the governing equations. The significant influence of the discrete heaters on the flow and heat transfer is analyzed for a wide range of modified Rayleigh numbers, aspect ratio, and length ratio (epsilon) of heat sources. Our numerical results reveal that the average Nusselt number decreases with aspect ratio, whereas the magnitude of maximum temperature increases with the aspect ratio. For most of the parametric cases considered in the present study, the heat transfer rate is found to be higher at the bottom heater than at the top heater except for epsilon=0.5. The effect of heater length ratio on the heat transfer rate is noticeable for unit aspect ratio, whereas its effect is insignificant as the aspect ratio increases. Furthermore, it was found that the maximum temperature is found generally at the top heater except for the case epsilon=0.5, where the maximum temperature is found at the bottom heater.</P>
FIRST-ORDER SYSTEM LEAST-SQUARES METHOD FOR THE OPTIMAL CONTROL BY THE STOKES EQUATIONS
Sang Dong KIM,Hyung-Chun LEE,Soorok RYU,Xiang Fan PIAO 한국산업응용수학회 2007 한국산업응용수학회 학술대회 논문집 Vol.2 No.1
We consider the approximate solution of optimal control problem governed by the Stokes equations. For the constrained optimization problem, Lagrange multiplier method is used. We employ a least-squares functional developed in [3] for the two-and three-dimensional first order optimality systems, by introducing a velocity flux variable and associated curl and trace equations. With the provided H²-regularity of that system, ellipticity in an H¹ product norm is established. This yields optimal discretization error estimates for finite element spaces in a product H¹ norm. The resulting matrix becomes symmetric and positive definite. For numerical tests, we apply V-cycle multigrid methods to the total discrete algebraic system.
SPECTRAL ELEMENT METHODS FOR AN OPTIMAL CONTROL PROBLEM BY ELLIPTIC EQUATIONS
Sang Dong KIM,Philsu KIM,Soorok RYU 한국산업응용수학회 2009 한국산업응용수학회 학술대회 논문집 Vol.2009 No.5
The bounds of eigenvalues independent of both degrees of high-order elements and mesh sizes are shown for the preconditioned system by bilinear finite elements for the spectral element discretizations based on Legendre-Gauss-Lobatto points for a coupled elliptic operator derived from an optimal control problem. The GMRES methods are used to implement the preconditioned system. It is provided that the convergence factor of GMRES does not depend on the number of elements and degrees of polynomials with numerical evidences. Some numerical demonstrations on the effects of preconditioning are presented with applications to a test optimal control problem.