• 대한수학회보
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• 제60권2호
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• pp.349-359
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• 2023

In this paper, we study ∆-transitivity, ∆-weak mixing and ∆-mixing for semigroup actions and give several characterizations of them, which generalize related results in the literature.

• 대한수학회지
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• 제32권2호
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• pp.321-328
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• 1995

Ibragimov(1975) showed the central limit theorem and the invariance principle for $\rho$-mixing random variables satisfying $\sigma^2(n) = nh(n) \longrightarrow \infty$ and $E$\mid$\zeta_0$\mid$^{2+\delta} < \infty$ for some $\delta > 0$ where $\sigma^2(n)$ denotes the variance of the partial sum $S_n$ and h(n) is a slowly varying function.

• Nuclear Engineering and Technology
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• 제38권8호
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• pp.809-818
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• 2006

The existing experimental data related to the turbulent mixing factor in rod arrays is examined and a new definition of the turbulent mixing factor is introduced to take into account the turbulent mixing of fluids with various Prandtl numbers. The new definition of the mixing factor is based on the eddy diffusivity of energy. With this definition of the mixing factor, it was found that the geometrical parameter, ${\delta}_{ij}/D_h$ correlates the turbulent mixing data better than Sid, which has been used frequently in existing correlations. Based on the experimental data for a highly turbulent condition in square rod arrays, a correlation describing turbulent mixing dependent on the parameter ${\delta}_{ij}/D_h$ has been developed. The correlation is insensitive to the Re number and it takes into account the effect of the turbulent Prandtl number. The proposed correlation predicts a reasonable mixing even at a lower S/d ratio.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.462-472
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• 1999

De-NOx facility using Selective Catalytic Reduction method is the most widely applied one that removes NOx from flue gas emitted from combustion facility such as boiler for power generation engine incinerator etc. Reductant $NH_3\;or\;NH_4OH$ is sprayed into flue gas to convert NOx into $H_2O$ and $N_2.$ Good mixing between flue gas and $NH_3$ is the most important factor to increase reduction in catalytic layer and to reduce unreacted NH3 slip. Therefore the development of mixer device for mixing effect is one of the important part for SCR facility. Objectives of this study are to investigate the relation between flow and concentration field by observation at the wake of delta-wing type mixer. At the first stage qualitative measurement of flow field is conducted by flow visualization using laser light sheet in lab. scale wind tunnel. Also we have conducted the quantitative analysis by comparing flow field measurement using LDV with numerical simulation. On the basis of qualitative and quantitative analysis we investigate the dis-tribution of flow and concentration in flow model facility. The results of an experimental and compu-tational examination of the vortex structures shed from delta wing type vortex generator having $40^{\circ}$ angle of attack are presented, The effects of vortex structure on the gas mixing is discussed, too.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 Proceedings of 2004 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.15-23
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• 2004

The present study is aimed to achieve dynamic visualization from the in-house 3-D stereoscopic PIV to represent quantitative flow information such as time-resolved 3-D velocity distribution, vorticity, turbulent intensity or Reynolds stresses and so on. One of the application of the present study is Leading edge extension(LEX) flow appearing on modern delta wing aircraft. The other is mixing flow in stirring tank used in industry field. LEX in a highly swept shape applied to a delta wing features the modern air-fighters. The LEX vortices generated upon the upper surface of the wing at high angle of attack enhance the lift force of the delta wing by way of increased negative suction pressure over the surfaces. The present method resolves also the complicated flow patterns of two type impellers rotating in stirring vessel. Flow quantities such as three velocity vector components, vorticity and other flow information can be easily visualized via the 3D time-resolved post-processing visualization. And it makes the easy understanding of the unsteady flow characteristics of the typical industrial mixers.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• 제21권1호
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• pp.17-30
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• 1993

해양에서의 전선형성에 관해 그 발생기작을 중심으로 검토되었으며, 특히 조석혼합에 의해 발생하는 연안전선의 발생기작이 조석전선 형성에 관계되는 미세구조의 변화를 포함하는 연안의 해수 수직면에 대한 일차원 모형을 통해 이해되었다. 이로부터 조석전선의 형성을 예측하는 새로운 기준을 설정하였다. 모형으로부터 계산된 해수의 밀도 및 난류에네지의 시간에 따른 발달은 수온약층의 형성하기 위한 조건은 $\delta$가 클 때는 (${\delta}>0.5$)$R{\delta}^{-}$ constant로서 주어지지만, $\delta$가 0에 접근함에 따라 $\delta$에 점점 무관하게 됨을 보여준다. 여기서, $R=H^4Q/{K_b}^3,{\;}{\delta}=1-D_o/H$, Q는 해수면에서의 부력속, $K_b$는 해저에서의 와확산 계수, $D_o$ 아래서 수온약층의 깊이는 조석혼합이 증가함에 따라 감소하는 것이 발견되었다. 그 결과는 기존의 연구와 비교 검토되었다.

• 자원환경지질
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• 제32권3호
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• pp.237-245
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• 1999

The Mujeong au-Ag hydrothermal vein type deposits occur within the Teriary igneous rocks of the Janggi basin. Ore minerals consist of pyrite, pyrrhotite, sphalertite, chalcopyrite, galena, cosalite, lillianite, argentite and electrum, and associated with epidotization, sericitization and pyritization. Fluid inclusion studies reveal that ore fluids were low saline with a simple NaCl-$H_{2}O$ system. Fluid inclusion data indicate that homogenization temperatures and salinities of fluid are 150 to $340^{\circ}C$ and 1.0 to 6.5wt.% NaCl equivalent, respectively. Sulfur isotope compositions of sulfied minerals ( ${\delta}^{34}S$=6.2 to 9.6$\textperthousand$) indicate that the ${\delta}^{34}S_{H2S}$ value of ore fluids was about 10.4$\textperthousand$. This ${\delta}^{34}S_{H2S}$ value is likely consistent with and hydrothermal sulfur, whereas the fluids were highly influenced by mixing with meteoric water. Measured and calculated oxygen and hydrogen isotope values (${\delta}^{18}O_{H2O}$=-2.7 to 3.4 $\textperthousand$, ${\delta}D_{H2O}$ = -83.6 to -52.7 $\textperthousand$) of ore forming fluids suggest mixing with hydrothermal and meteoric water. Equilibrium thermodynamic interpretation by mineral assemblages and chemistry indicates that sulfur fugacities (-log $fs_2$) ore forming fluids range from 9.0 to 12.6 atm stage II.

• 한국지하수토양환경학회지:지하수토양환경
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• 제10권6호
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• pp.45-55
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• 2005

한반도의 고 지열류량 지대에 속하는 포항시 흥해지역 일대에 대한 지열수 조사를 수행하였다. 그 결과 이 지역 지열수는 지열수대 연변부로서 저류암과 완전평형을 이루지 못하는 것으로 나타났다. 동위원소분석 결과 심부 지하수(평균: ${\delta}^{18}O=-10.1\%_{\circ},\;{\delta}D=-65.8\%_{\circ}$), 중간심도(평균: ${\delta}^{18}O=-8.9\%_{\circ},\;{\delta}D=-59.6\%_{\circ}$), 천부지하수(평균: ${\delta}^{18}O=-8.0\%_{\circ},\;{\delta}D=-53.6\%_{\circ}$), 지표수(평균: ${\delta}^{18}O=-7.9\%_{\circ},\;{\delta}D=-53.3\%_{\circ}$)를 보여 심부지하수는 강우에서 기원하였고, 지형적으로 고도가 높은 지역에서 함양되었으며, 해수의 영향을 받지 않았음이 밝혀졌다. 물 지질온도계를 이용한 결과 D-2, D-5, D-6, I-04부근에서 이상 고온대가 추정된다. 실리카-엔탈피 혼합모델 추정결과 저류대 온도는 410 kJ/kg으로서 $98^{\circ}C$에 해당하여 Na-K 및 K-Mg온도계에 의한 추정결과와 일치한다.

• 한국식품영양학회지
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• 제28권6호
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• pp.1011-1018
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• 2015

The effects of mixing speed (3, 6 and 10 speed) and time (2, 5 and 10 min) on the dynamic viscoelasticity of dough and the baking properties of gluten-free rice bread were investigated. The specific gravity of the dough was not affected by the mixing speed and time before and after fermentation. The elasticity (G') and viscosity (G") of the dough increased and the tan ${\delta}$ (G"/G') decreased with higher mixing speeds and longer mixing times. The specific volume of the gluten-free rice bread was affected by the mixing time in response surface methodology (RSM). The hardness of the gluten-free rice bread showed a decreasing trend as the specific volume for the gluten-free rice bread increased. The appearance of the gluten-free rice bread was symmetrical at high mixing speeds and long mixing times. Overall results indicated that the quality of gluten-free rice bread could be improved by controlling the mixing speeds and mixing times for the dough.

• 한국해양학회지:바다
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• 제5권4호
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• pp.357-362
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• 2000

황해 남부해역에서 199년 8월에 채집된 시료로부터 산소동위원소비(${\delta}^{18}$O)와 수소동위원소비(${\delta}$D)를 측정하였다. 표층시료의 경우 염분과 ${\delta}^{18}$O 그리고 염분과 ${\delta}$D는 앙의 상관관계를 보이며, ${\delta}^{18}$O와 ${\delta}$D 또한 매우 좋은 양의 상관관계를 가진다. 이들 자료는 연구지역의 해수가 장강수와 변형된 쿠로시오수의 혼합물이며 , 산소와 수소 동위원소가 연구지역에서 수괴의 성질과 행동을 연구하는데 유용한 추적자로 사용될 수 있다는 것을 의미한다. 또한 염분과 수온만으로는 구별이 어려운 수괴를 구분하고 특성을 파악하는데도 안정등위원소가 좋은 추적자로 사용될 수도 있음을 보여 주었다.