• 한국환경성돌연변이발암원학회지
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• 제16권2호
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• pp.109-116
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• 1996

To study the effect of dietary $\omega 6/\omega 3$ fatty acid ratios on the preneoplastic lesions and lipid peroxidation in rat hepatocellular chemical carcinogenesis, placental glutathione S-transferase(GST-P) positive foci area and numbers, glucose 6-phosphatase(G6Pase) activity, thiobarbituric acid reactive substances (TBARS) were measured. Male Sprague-Dawley rats were fed 5 different diets-low $\omega 6/\omega 3$ ratio with fish oil (Low-F), low $\omega 6/\omega 3$ ratio with perilia oil(Low-P), moderate ratio with perilia oil(Moderate), blend of 10 different commercial fats and oils(High-BL) and high $\omega 6/\omega 3$ ratio(High)-for 8 weeks. Hepatocarcinogenesis was induced by modified Ito model. The area of GST-P positive loci was the lowest in Moderate group and in ascending order of Low-F < Low-P < High-BL < High. But statistically, only Moderate and High groups were significantly different. The number of GST-P positive foci showed the same trend as foci area. The activities of G6Pase, membrane stability marker, were increased as $\omega 6/\omega 3$ ratio decreased. Lipid peroxidation values (TBARS) were the lowest in Low-F group and it is significantly different from Moderate, High-BL and High groups. When dietary $\omega 6/\omega 3$ ratio was moderate(4.06), hepatocarcinogenesis was suppressed compared with high or low $\omega 6/\omega 3$ ratios. Blend fat, commonly consumed among Koreans, did not show any suppressive effect on carcinogenesis because of high ratio(6.7). These results suggest that dietary $\omega 6/\omega 3$ ratio influences hepatocellular chemical carcinogenesis. It is recommended that appropriate $\omega 6/\omega 3$ ratio should be around 4.0. and we recommend to use more $\omega 3$ fatty acid in food preparation to reduce the risk of hepatocarcinogenesis.

• 한국항해학회지
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• 제1권1호
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• pp.1-16
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• 1977

The aspects of Omega phase prediction are briefly reviewed, and Swanson's Model and Pierce's Model are presented. The equations for the Omega phase prediction and the most probable coefficients of the propagating equations are derived on the base of Pierce's Model by the least square method. The coefficients are calculated from the data which are the phase differences between the pairs of the Station A (Aldra, Norway), C(Haiku, Hawaii), and D(La Mour, North Dakota) observed at Busan Harbor of the South Coast of Korea in June and September, 1976. It is clearly shown that the standard deviations of the observed lane values at Busan Harbor are as followed: 1. June, 1976. Pair (A-C) : 0.1446 Pair (C-D) : 0.2598 2.September, 1976. Pair (A-D) : 0.3958 Pafr (C-D) : 0.3278 As a conclusion of the above investigation, it is shown that the Omega phase velocity can be predicted by the method, proposed in this paper, of analyzing the diurnal and seasonal variations of the Omege phase velocity except SID, PCD and AZD. If more observed data are employed, more exact Omega phase velocity is expected to be obtained.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.45-49
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• 2007

Asymmetric force and vibration caused by separation flow at high angle of attack affect the stability of supersonic missile. As a preliminary study we verified the effect of turbulence model through general 3-D slender body for the supersonic flow at high angle of attack. ${\kappa}-{\omega}$ Wilcox model, ${\kappa}-{\omega}$ Wilcox-Durbin+ model, ${\kappa}-{\omega}$ shear-stress transport model, and Spalart-Allmaras one equation model are used. Grid sensitivity test was performed with three different grid system. results show that all models are in good agreement with the experimental data.

• Wind and Structures
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• 제7권1호
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• pp.1-12
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• 2004

Numerical simulation of flow past two-dimensional hill and valley is presented. Application of three turbulence models - the standard and modified (Kato-Launder) $k-{\varepsilon}$ models and standard $k-{\omega}$ model - is discussed. The computational methodology is briefly described. The mean velocity and turbulence intensity profiles, obtained from numerical simulations of flow past the hill, are compared with the experimental data acquired in a boundary-layer wind tunnel at Colorado State University. The mean velocity, turbulence kinetic energy and Reynolds shear stress profiles from numerical simulations of flow past the valley are compared with published experimental data. Overall, the results of simulations employing the standard $k-{\varepsilon}$ model were found to be in a better agreement with the experimental data than those obtained using the modified $k-{\varepsilon}$ model and the $k-{\omega}$ model.

• 대한인간공학회지
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• 제16권2호
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• pp.15-27
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• 1997

Brain potential is described using the mesocolumnar activity defined by averaged firings of excitatory and inhibitory neuron of neocortex. Lagrangian is constructed based on SMNI(Statistical Mechanics of Neocortical Interaction) and then Euler Lagrange equation is obtained. Excitatory neuron firing is assumed to be amplitude- modulated dominantly by the sum of two modes of frequency .omega. and 2 .omega. . Time series of this neuron firing is calculated numerically by Euler Lagrangian equation. I .omega. L related to low frequency distribution of power spectrum, I .omega. H hight frequency, and Sd(standard deviation) were introduced for the effective extraction of the dynamic property in the simulated brain potential. The relative behavior of I .omega. L, I .omega. H, and Sd was found by parameters .epsilon. and .gamma. related to nonlinearity and harmonics respectively. Experimental I .omega L, I .omega. H, and Sd were obtained from EEG of human in rest state and of canine in deep sleep state and were compared with theoretical ones.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.28-35
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• 1998

The seismic overstrength factor $\Omega$ is evaluated for 4-story reinforced concrete buildings in Korea(of which seismic intensity is low). The study model is designed according to aseismic guideline research - phase II in Korea. The effect of variation of span length and bay number, dead load is considered, especially including the variation of hardening ration after yielding. And push-over analysis is performed, in which the external and internal frame is connected by rigid-link and the $\Omega$ is calculated using the roof drift ratio at 2%. For Zone I, the mean value of $\Omega$ is ranged form 2.3 to 2.5, For Zone II, from 3.1 to 3.4. For low hardening ratio(3%) after yielding, $\Omega$ has little relations with the number of bay, like as the results of other research. But for 5% hardening ratio, $\Omega$ is increased as the number of bay is increased. Within general gravity-load bound, the variation of D.L. has variation of D. L. has no effect on $\Omega$. And, $\Omega$ is increased as the span length is increased.

• Journal of electromagnetic engineering and science
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• 제10권3호
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• pp.186-189
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• 2010

Reflection(R($\omega$)), transmission(T($\omega$)) and loss(L($\omega$)) characteristics of multi-layer metamaterials are investigated experimentally in free space with the incident EM waves perpendicular to the substrate plane. The sample is made of split-ring resonators(SRRs) and wires which are the typical model of metamaterials. The R($\omega$) and T($\omega$) of multi-layer metamaterials have been calculated from the measured S-parameters. In this paper, we got the impedance-matched result according to the curves of R($\omega$), meanwhile the T($\omega$) decreased with increasing number of layers. At last, we attained the result that the L($\omega$) gets to nearly 98% around 8 GHz, with R($\omega$)=T($\omega$)=0. The design presented in this paper achieves experimented loss near unity.

• 한국추진공학회지
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• 제17권1호
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• pp.18-25
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• 2013

초음속 축소-확대 노즐 유동을 정확하게 해석하기 위하여, 실험치와 해석값 사이의 비교를 통해 난류모델 성능평가를 수행한다. Boussinesq 가정을 적용한 RANS 방정식으로 2차원 노즐 유동을 해석하되, Spalart-Allmaras, RNG k-${\varepsilon}$, 그리고 k-${\omega}$ SST 난류모델을 평가에 사용한다. 각 모델들로 계산된 노즐 벽면의 압력구배 및 충격파 구조는 실험 데이터와 유사한 결과를 보였는데, 그 중에서도 SST 난류모델이 실험값에 가장 근접한 해석결과를 나타내었다.

• 한국추진공학회지
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• 제3권1호
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• pp.15-23
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• 1999

실린더 후부의 유동장에 대한 모사를 K-$\omega$ 모형을 이용하여 수행하였다. 2 방정식 난류 모형에 적용할 수 있는 압축성 수정항들을 이용하여 기존의 모형과 비교하였다. 극음속유동장에서는 성공적으로 예측이 가능하였던 것과는 달리 실린더 후부의 유동장에 적용하였을 경우에는 수정항이 없을 경우보다 악화되는 경향을 보이고 있다. 압축성 난류 수정항들은 이 유동장에서는 부정적인 역할을 하게 된다. 압축성 유동에 대한 난류 모형은 근본적으로 연구가 더 진행되어야 할 것으로 보인다.

• 한국수자원학회논문집
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• 제48권4호
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• pp.281-290
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• 2015

표준 k-${\varepsilon}$, RNG k-${\omega}$ 그리고 k-${\omega}$ SST 난류 모형과 VOF (volume of fluid)기법을 이용하여 사각형 광정위어를 통과하는 난류 흐름의 수면 변화와 유속분포를 수치모의 하였다. 지배방정식은 2차 정확도의 유한체적기법을 이용하여 해석하였으며, 두 개의 서로 다른 격자해상도에서 계산을 수행하여 수치해석 결과의 격자 민감도를 분석하였다. 계산 결과를 Kirkgoz et al. (2008)의 실험 결과 그리고 Moss (1972) 및 Zachoval et al. (2012) 무차원화된 실험값과 비교 분석하여 적용한 수치모형의 정확도를 평가하였다. 수치모의 결과는 사각형 개수로에 설치된 광정위어 흐름의 실험결과들을 합리적으로 예측하고 있으면 적용한 난류모형에 따라서 두 개의 주요 흐름분리 영역에서 계산 결과에 차이가 있는 것으로 나타났다. 표준 k-${\varepsilon}$ 모형은 이들 두 개의 흐름분리영역의 크기를 과소산정하고 있으며, k-${\omega}$ SST 모형은 위어 전면부에서 발생하는 흐름분리 영역을 다소 과대 산정하는 것으로 나타났다. RNG k-${\varepsilon}$ 모형은 전반적으로 양호하게 두 흐름분리 영역을 예측하는 한편, k-${\omega}$ SST 모형은 위어 상류부 모서리에서 발생하는 박리거품의 발생 형태를 가장 잘 예측하는 것으로 나타났다.