• 한국유체기계학회 논문집
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• 제12권4호
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• pp.7-13
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of inverse of heat transfer rate and friction loss. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• 한국전산유체공학회지
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• 제14권2호
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• pp.1-8
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane taken tolerance into consideration by using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of heat transfer rate and inverse of pressure drop. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.948-950
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• 2005

This paper compared the test data with the loss when a conductor is exposed to the magnetic fieldof reactors after generating external magnetic field in specimen by means of an air core reactor model and the calculation of loss came from a tying the combination of FEM and integral method. It was applied to the loss measurement of transformers due to leakage flux.

• Nuclear Engineering and Technology
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• 제49권6호
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• pp.1135-1142
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• 2017

The applicability of the algebraic collapsing acceleration (ACA) technique to the method of characteristics (MOC) in cases with scattering anisotropy and/or linear sources was investigated. Previously, the ACA was proven successful in cases with isotropic scattering and uniform (step) sources. A presentation is first made of the MOC implementation, available in the DRAGON5 code. Two categories of schemes are available for integrating the propagation equations: (1) the first category is based on exact integration and leads to the classical step characteristics (SC) and linear discontinuous characteristics (LDC) schemes and (2) the second category leads to diamond differencing schemes of various orders in space. The acceleration of these MOC schemes using a combination of the generalized minimal residual [GMRES(m)] method preconditioned with the ACA technique was focused on. Numerical results are provided for a two-dimensional (2D) eight-symmetry pressurized water reactor (PWR) assembly mockup in the context of the DRAGON5 code.

• Korean Membrane Journal
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• 제3권1호
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• pp.1-8
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• 2001

A lab-scale submerged membrane bio-reactor (MBR) with intermittent aeration was carried out for investigating the behavior of soluble microbial products (SMP). The SMP concentration of mixed liquor at Run 1 accumulated immediately at the end of running and biodegradable SMP converted into non-biodegradable SMP, but it did not occurred at the Run 2 and 3. The SMP formation coefficient (k) at the anoxic phase was a little higher than oxic phase, and the lowest k was investigated at Run 3. The combination of biological denitrification with the MBR Process was advantageous in the prevention of membrane bio-fouling.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.372-379
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• 2018

The improvement of $NO_x$ reduction by $Ag/{\gamma}-Al_2O_3$ with a hydrocarbon ($n-C_7H_6$) in the early state was investigated in a packed-bed dielectric barrier discharge plasma reactor. The results revealed that the combination of plasma with the catalyst enhanced $NO_x$ reduction efficiency at low operating temperatures, depending on the temperature and specific input energy. To sum up, the poor performance of the catalytic $NO_x$ reduction at low temperatures in the early stage before reaching thermochemical steady state can be greatly compensated for by using the atmospheric-pressure plasma generated in the catalyst bed.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.613-624
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• 2013

Multi-dimensional two-phase phenomena occur in many industrial applications, particularly in a nuclear reactor during steady operation or a transient period. Appropriate modeling of complicated behavior induced by a multi-dimensional flow is important for the reactor safety analysis results. SPACE, a safety analysis code for thermal hydraulic systems which is currently being developed, was designed to have the capacity of multi-dimensional two-phase thermo-dynamic phenomena induced in the various phases of a nuclear system. To validate the performance of SPACE, a two-dimensional two-phase flow test was performed with slab geometry of the test section having a scale of $1.43m{\times}1.43m{\times}0.11m$. The test section has three inlet and three outlet nozzles on the bottom and top gap walls, respectively, and two outlet nozzles installed directly on the surface of the slab. Various kinds of two-dimensional air/water flows were simulated by selecting combinations of the inlet and outlet nozzles. In this study, two-dimensional two-phase void fraction profiles were quantified by measuring the local gap impedance at 225 points. The flow conditions cover various flow regimes by controlling the flow rate at the inlet boundary. For each selected inlet and outlet nozzle combination, the water flow rate ranged from 2 to 20 kg/s, and the air flow rate ranged from 2.0 to 20 g/s, which corresponds to 0.4 to 4 m/s and 0.2 to 2.3 m/s of the superficial liquid and gas velocities based on the inlet port area, respectively.

• Nuclear Engineering and Technology
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• 제46권2호
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• pp.169-182
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• 2014

High-performance research reactors require fuel that operates at high specific power to high fission density, but at relatively low temperatures. Research reactor fuels are designed for efficient heat rejection, and are composed of assemblies of thin-plates clad in aluminum alloy. The development of low-enriched fuels to replace high-enriched fuels for these reactors requires a substantially increased uranium density in the fuel to offset the decrease in enrichment. Very few fuel phases have been identified that have the required combination of very-high uranium density and stable fuel behavior at high burnup. U-Mo alloys represent the best known tradeoff in these properties. Testing of aluminum matrix U-Mo aluminum matrix dispersion fuel revealed a pattern of breakaway swelling behavior at intermediate burnup, related to the formation of a molybdenum stabilized high aluminum intermetallic phase that forms during irradiation. In the case of monolithic fuel, this issue was addressed by eliminating, as much as possible, the interfacial area between U-Mo and aluminum. Based on scoping irradiation test data, a fuel plate system composed of solid U-10Mo fuel meat, a zirconium diffusion barrier, and Al6061 cladding was selected for development. Developmental testing of this fuel system indicates that it meets core criteria for fuel qualification, including stable and predictable swelling behavior, mechanical integrity to high burnup, and geometric stability. In addition, the fuel exhibits robust behavior during power-cooling mismatch events under irradiation at high power.

• 조명전기설비학회논문지
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• 제13권4호
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• pp.32-37
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• 1999

본 연구에서는 연소공정에서 발생하는 NOx를 제거하기 위해 연면방전과 AC Corona 방전을 중첩해서 특수설계 제작된 중첩방전 반응기의 방전분해 특성을 연구하였다. 실험은 SPCP, Corona Discharge 및 중첩방전에 대한 NOx의 분해율을 비교 측정하였다. 실험변수는 방전형태, 가스의 농도, 방전주파수, 가스의 유량 등에 대하여 측정하였다. 실험결과 중첩방전에 의한 NOx의 분해율은 SPCP방전고 Corona방전에 의한 분해율보다 10∼15[%] 증가하였고 소모전력도 10[%] 정도 작게 소모되었다. 중첩방전시 상부전극의 주파수의 영향은 주파수가 작을수록 NOx의 분해율이 높았고 하부전극의 SPCP만의 방전시에는 주파수가 높을수록 NOx의 분해율이 증가하였다. 방전형태에 대한 NOx의 최대분해율은 SPCP일 때 방전전력 18[W]에서 80[%] 이었고 AC코로나 방전일 때 방전전력 805[W]에서 10[%] 이었으나 중첩방전의 경우는 14[W]에서 90[%]로 중첩방전의 효과는 10[%]이상 증가하였다.

• 한국항행학회논문지
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• 제24권6호
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• pp.557-565
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• 2020

원자로의 출력신호를 감시하는 노외중성자속감시계통의 열화상태를 점검하기 위해서는 원자로에서 방출되는 중성자 펄스를 감지하여 처리하는 전자카드에서 주파수형태로 감지하여 전압으로 변환한 후 대수 형태의 직류전압 값을 얻는 방법을 이용한다. 실제로 원전에서 적용하는 방법으로서는 주파수 카운터와 flip-flop 조합으로 이 과정을 수행하거나, 또는 다이오드펌프와 캐패시터의 조합을 이용하는 방법을 쓰며, 아직도 이 방법이 일반적으로 쓰이고 있다. 이 방법들은 높은 주파수에서는 신뢰성이 높으나 낮은 주파수에는 오차가 크고 측정시간도 오래 걸린다는 문제점이 있다. 따라서 본 연구에서는 고출력대의 고주파수 범위뿐만 아니라 중위출력 범위 주파수대, 그리고 극히 저출력 범위에 속해 있는 취약주파수대인 0.21 Hz~2 kHz 범위의 낮은 주파수대에 이르는 광범위한 주파수를 대수직류전압으로 신뢰성 높게 변환시킬 수 있는 장치를 개발하였다. 개발된 선택회로의 신뢰성을 확인하기 위하여 원전에서 사용되는 실제의 데이터값을 적용하여 테스트하였으며, 그 결과를 분석하여 선택회로의 정당성을 입증하였다.