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이형 데이터 기반의 예측 모델 생성을 위한 데이터 정제 방법론
이은경 ( Eunkyung Lee ),유연택 ( Yeontaek Yoo ),이건수 ( Keonsoo Lee ) 한국정보처리학회 2019 한국정보처리학회 학술대회논문집 Vol.26 No.2
예측 모델은 어떤 상황이 주어졌을 때, 다음 상황에 대한 예측을 수행하는 시스템으로, 현재 상황을 올바르게 인지하고, 그 인지된 상황을 토대로 미래를 예측할 수 있는 지능을 갖고 있어야 한다. 이러한 예측 모델이 올바르게 동작하기 위해서는 상황을 올바르게 인지하는 기능이 우선되어야 하지만, 원시 데이터로부터 상황을 인지하기 위해서는 원시 데이터를 올바르게 해석하기 위한 데이터 정제 과정이 필요하다. 이에 본 연구에서는 다양한 형태의 원시 데이터를 예측 모델의 유효한 입력 값으로 변환시키기 위한 데이터 정제 방법을 제안한다. 본 방법은 윈시 데이터의 형태 정의, 데이터 정규화, 속성 관계 검증, 결측치 보정, 그리고 신뢰도 적용의 5단계로 구성되어 있다.
Choi, Yeontaek,Kim, Byung-Gu,Lee, Changhoon Published by the American Physical Society through 2009 Physical review. E, Statistical, nonlinear, and so Vol.80 No.1
<P>We provide an observation suggesting a strong correlation between helicity and enstrophy in fluid turbulence. Helicity statistics were obtained in a direct numerical simulation of forced isotropic turbulence. An investigation of coherent structures revealed that intermittently large local helicity was found in the core region of the coherent rotational structures, thus showing a strong correlation with local enstrophy, not dissipation. Statistics regarding the relative helicity and the correlation between velocity and vorticity conditioned on different levels of enstrophy clearly suggest that velocity and vorticity tend to be aligned in the core of the coherent structures.</P>
최연택(Yeontaek Choi),이창훈(Changhoon Lee),조상규(Sanggyu Jo) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
We develop a generalized RPA(random phase and amplitude) formalism in wave turbulence(WT). RPA theory employ the Hamiliton mechanics description, derived directly from the 3-D inviscid and incompressible Navier-Stokes equation through the Clebsch transformation. We expand randomness even to amplitudes besides phases of wave-like motions. The newly derived equation is also a wave kinetic equation(WKE). We exploit the PDF analysis to analyze the WKE and obtain some new good results. Those are based on PDF analysis from the analysis of WT spectrum, the exact solution of the Hamilton equation.
최연택(Yeontaek Choi),이창훈(Changhoon Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
We investigated the intermittent property of helicity of the isotropic turbulence. As well known, helicity is a quadratic invariant on the inviscid Navier-Stokes flows. But unfortunately it has no invariance in the viscous fluids. Furthermore, it has a intermittent fashion through its cascade in the inertial range. We looked for the sources to raise this intermittency, handling with local quantities such as local enstrophy, dissipation, and local coupling angle of velocity and vorticity. It seems to be the preferred angles to determine the direct relation between local velocity and local vorticity, and to be guessed the source of the intermittency.
최연택(Yeontaek Choi),이창훈(Changhoon Lee) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
Helicity in isotropic turbulence was well known to have intermittent fashion in their statistics. But its exact explanation about the onset of intermittency of helicity in turbulence did not give clearly yet. Most probable causes comes from the vortical motion of the fluids. Distribution of the angle between fluid velocity and vorticity have alignment tendency. This may be a clue to investigate intermittency of helicity. In this study, we aim to review and establish approaches to reveal the mechanism and the origin of intermittency of helicity in the isotropic turbulence. To do those work, we look for some quantities like helicity, enstrophy, acceleration and its flatness. And also correlations among them are sought.
이주미,콩가라다무다,Yeontaek Lee,Hyeong Ryeol Woo,서홍원,전성호,이정태 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.4
A set of novel epinastine (1) and mefenamic acid (2) hybrids (3?7) tethered via amide bond were designed and synthesized with the artistry of molecular hybridization. Then their inhibitory effect on nitric oxide (NO) production in LPS-induced RAW-264.7 macrophages and the expression levels of prostaglandin (PG) synthesis regulatory genes were evaluated in vitro. All the hybrids were found to have remarkable NO production inhibitory potential with IC50 values ranging in between 27.69?±?3.06 and 40.19?±?5.52??M without notable cytotoxicity (CC50?≥?100??M) except 6. Comparing the inhibitory effects, cytotoxicity and in vitro efficacy index (iEI), 4 (IC50 = 32.09?±?4.04??M; iEI = 6.23) and 7 (IC50 = 27.69?±?3.06??M; iEI = 6.40) were better suited than other hybrids as well as their parent compounds EH and MA. This outcome was further harmonized with the reduced microsomal prostaglandin E synthase-1 expression and unaltered housekeeping COX-1 expression by hybrids 4 and 7 treatment. Altogether, our findings signify that hybrids 4 and 7 may serve as platforms for continued investigations for the development of more efficient anti-inflammatory agents.
박용남(Yongnam Park),최연택(Yeontaek Choi),이창훈(Chanhoon Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The geometric nature of particle trajectory is investigated for understanding the Lagrangian nature of turbulence using direct numerical simulation of isotropic turbulence. Probability density functions and autocorrelations along a fluid particle trajectory associated with geometric quantities such as curvature and torsion of the Lagrangian trajectory are provided. We propose the ratio of torsion to curvature as an important parameter to identify the particle trajectory, and it is found to play a crucial role in understanding the geometric shape of particle trajectory. The relationship between Lagrangian helicity and the ratio of torsion to curvature is investigated where Lagrangian helicity is defined as a dot product of velocity and vorticity vectors at the point of a fluid particle. We also found that probability density functions of torsion and torsion normalized by curvature clearly show well-established slope in log?log plots. Lagrangian helicity is intermittently distributed and high Lagrangian helicity is always found, where high acceleration is observed. Regarding the relationship between coherent structure and acceleration, coherent structure can be understood in terms of Lagrangian helicity, curvature, and torsion.