• 대한수학회보
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• 제41권1호
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• pp.189-198
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• 2004

In this study we consider quantum dynamical semi-group with a normal faithful invariant state. A quantum dynamical semigroup $\alpha\;=\;\{{\alpha}_t\}_{t{\geq}0}$ is a class of linear normal identity-preserving mappings on a von Neumann algebra M with semigroup property and some positivity condition. We investigate the asymptotic behaviors of the semigroup such as ergodicity or mixing properties in terms of their eigenvalues under the assumption that the semigroup satisfies positivity. This extends the result of [13] which is obtained under the assumption that the semi group satisfy 2-positivity.

• 한국가구학회지
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• 제18권4호
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• pp.268-274
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• 2007

Environmentally-friendly polymer composite films were manufactured from cellulose acetate (CA) and polyethylene (PE). To investigate the optimum manufacturing conditions for the composite, various tests such as thermal analysis, surface observation, IR spectra analysis, and elongation ratio of polymer composite films were carried out. The mixing ratio of each element and manufacture condition was found to be very important for the best goods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.919-921
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• 1998

In Color AC Plasma Display Panel(PDP). Low luminous efficiency is a major problem. We measured luminous efficiency of PDP as a function of the Ar mixing ratio. Our results show that efficiency has improved by $5{\sim}10%$ at the condition of 0.5% Ar mixing ratio, compared with Ne-Xe(4%) or He-Ne-Xe(4%) (He:Ne = 7:3) gas.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.427-430
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• 2003

The Mixers is used for the Mixing which is the most important process in the Water&Sewage water treatment. To choose proper mixer required much career and knowledge, to check many elements which are purpose, time and condition of mixing. Thus, the design method of mixers is to be utilized for the structural design of the water & Sewage water treatment.

• 한국연소학회지
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• 제3권1호
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• pp.59-69
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• 1998

The results of study on the active control of naturally occurring combustion oscillations with a single dominant frequency in an atmospheric dump combustor are presented. Control was achieved by an oscillatory infection of secondary fuel at the dump plane. A high speed solenoid valve with a maximum frequency of 250Hz was used as the actuator and a sound level meter, located at the combustor exit, measured the pressure fluctuations which served as the feedback signal for the control loop. Instability characteristics were mapped over a range of mean mixing section velocities from 6.7 m/s-9.3 m/s and with three mixing conditions. Different fuel/air mixing conditions were investigated by introducing varying percentages of primary fuel at two locations, one at the entrance to the mixing section and one 6 mixing tube diameters upstream of the dump plane. Control studies were conducted at a mean velocity of 9.3 m/s, with an air temperature of $415^{\circ}C$, and from flame blowout to the stoichiometric condition.

• Nuclear Engineering and Technology
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• 제25권2호
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• pp.215-221
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• 1993

중대 사고에 이어 형성 될 수 있는 용융 핵연료와 냉각수의 혼합체는 그 후에 일어날 수 있는 증기 폭발의 초기 조건을 이루게 되며, 또한 이러한 혼합의 정도는 증기 폭발의 강도를 결정하는 주요 요인이 된다. 본 연구는 간단한 일차원 과도 상태 모형을 이용하여 용융 핵연료와 냉각수의 혼합의 한계를 결정하였으며, 용융 핵연료의 분쇄 과정을 모사 하기 위하여 동적 분쇄모형과 순간 파열 모형을 각각 적용하여 그 결과를 비교하였다. 계산 결과에서는 용융 핵연료의 온도. 압력. 수조의 깊이, 혼합 상태에서의 분쇄물 직경 그리고 용융 핵연료 입사 직경등이 혼합량에 영향을 미치는 주요한 인자들로 나타났다.

• 대한기계학회논문집B
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• 제22권3호
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• pp.326-335
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• 1998

In this study, a steady three-dimensional incompressible turbulent flow within a torque converter was numerically analyzed with the introduction of interrow mixing model. Mixing planes were introduced to exchange the flow informations between two adjacent elements of the torque converter. The mixing planes were installed among three elements of the torque converter. Therefore, in the present method, it could be possible to calculate the flow-filed within the torque converter without any assumption of circulating flow rates or any extension of boundaries toward the upstream and the downstream for each element. The numerically calculated performances of the torque converter were in good agreement with experimental results, and the complex flow patterns were be observed according to design and off-design condition. As a conclusion, it was found that the present numerical method was very effective in the steady flow analysis of torque converters.

• 대한금속재료학회지
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• 제46권6호
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• pp.382-389
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• 2008

To manufacture Al MMCs, in-situ melt mixing process is used because it is free from contamination, and it makes reinforcements homogeneously dispersed. Large eddy simulation method is used to find the optimum melt mixing condition. At the Re 3000, the most suitable mixing is occurred between Al-Ti and Al- B melts. The in-situ formed $TiB_2$ particles has the size varying from 40 nm to 130 nm, due to the increase of cooling rate, and exhibits a homogeneous dispersion. And the interface between reinforcement and matrix is clean. Both hardness and Young's modulus of this composite are improved with increasing the cooling rate.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.93-102
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• 2021

The analysis of the fluid flow characteristics in reactor pressure vessel is an important part of the hydraulic design of nuclear power plant, which is related to the structure design of reactor internals, the flow distribution at core inlet and the safety of nuclear power plant. The flow distribution and mixing characteristics in the pressurized reactor vessel for the 1000MWe advanced pressurized water reactor is analyzed by using Computational Fluid Dynamics (CFD) method in this study. The geometry model of the full-scaled reactor vessel is built, which includes the cold and hot legs, downcomer, lower plenum, core, upper plenum, top plenum, and is verified with some parameters in DCD. Under normal condition, it is found that the flow skirt, core plate holes and outlet pipe cause pressure loss. The maximum and minimum flow coefficient is 1.028 and 0.961 respectively, and the standard deviation is 0.019. Compared with other reactor type, it shows relatively uniform of the flow distribution at the core inlet. The coolant mixing coefficient is investigated with adding additional variables, showing that mass transfer of coolant occurs near the interface. The coolant mainly distributes in the 90° area of the corresponding core inlet, and mixes at the interface with the coolant from the adjacent cold leg. 0.1% of corresponding coolant is still distributed at the inlet of the outer-ring components, indicating wide range of mixing coefficient distribution.

• International Journal of Aeronautical and Space Sciences
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• 제16권2호
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• pp.254-263
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• 2015

In this study, numerical simulations are carried out to investigate the dynamic SGS model effects in a Kerosene-LOx coaxial swirl injector under high pressure conditions. The turbulent model is based on large-eddy simulation (LES) with real-fluid transport and thermodynamics. To assess the effect of the dynamic subgrid-scale (SGS) model, the dynamic SGS model is compared with that of the algebraic SGS model. In a swirl injector under supercritical pressure, the characteristics of temporal pressure fluctuation and power spectral density (PSD) present comparable discrepancies dependant on the SGS models, which affect the mixing characteristics. Mixing efficiency and the probability density (PDF) function are conducted for a statistical description of the turbulent flow fields according to the SGS models. The back-scattering of turbulent kinetic energy is estimated in terms of the film thickness of the swirl injector.