• Nuclear Engineering and Technology
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• 제53권2호
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• pp.562-571
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• 2021

In this work, we propose a new mechanistic model for the treatment of helium behaviour which includes the description of helium solubility in oxide fuel. The proposed model has been implemented in SCIANTIX and validated against annealing helium release experiments performed on small doped fuel samples. The overall agreement of the new model with the experimental data is satisfactory, and given the mechanistic formulation of the proposed model, it can be continuously and easily improved by directly including additional phenomena as related experimental data become available.

• Nuclear Engineering and Technology
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• 제44권8호
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• pp.889-896
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• 2012

Recent progress in the computational fluid dynamics methods of two- and multiphase phase flows has already started opening up new exciting possibilities for using complete multidimensional models to simulate boiling systems. Combining this new theoretical and computational approach with novel experimental methods should dramatically improve both our understanding of the physics of boiling and the predictive capabilities of models at various scale levels. However, for the multidimensional modeling framework to become an effective predictive tool, it must be complemented with accurate mechanistic closure laws of local boiling mechanisms. Boiling heat transfer has been studied quite extensively before. However, it turns out that the prevailing approach to the analysis of experimental data for both pool boiling and forced-convection boiling has been associated with formulating correlations which normally included several adjustable coefficients rather than based on first principle models of the underlying physical phenomena. One reason for this has been the tendency (driven by practical applications and industrial needs) to formulate single expressions which encompass a broad range of conditions and fluids. This, in turn, makes it difficult to identify various specific factors which can be independently modeled for different situations. The objective of this paper is to present a mechanistic modeling concept for both pool boiling and forced-convection boiling. The proposed approach is based on theoretical first-principle concepts, and uses a minimal number of coefficients which require calibration against experimental data. The proposed models have been validated against experimental data for water and parametrically tested. Model predictions are shown for a broad range of conditions.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.349-355
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• 1996

In this study, the mechanistic critical heat flux (CHF) model and correlation for water are derived based on flow excursion (or Ledinegg instability) criterion and the simplified two-phase homogeneous model. The relationship between CHF for the water and the principal parameters such as mass flux heat of vaporization, heated length-to-diameter ratio, vapor-liquid density ratio and inlet subcooling is derived on the developed correlation. The developed CHF correlation predicts very well at the applicable ranges, 1 < P < 40 bar, 1, 300 < G 27, 00 kg/$m^2$s and inlet quality is less than -0.1. The overall mean ratio of predicted to experimental CHF value is 0.988 with standard deviation of 0.046.

• 보건행정학회지
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• 제10권1호
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• pp.31-56
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• 2000

A purpose of this study is to study on Rene Descartes's mind-body theory in medical aspect. Though Rene Descartes was not so much a doctor as a philosopher, he had health and medical science at heart. When he came into the world in 1596, he was in poor health. Therefore, he suffered from his bad health. Descartes's ideas absolutely colored Western thought for three hundred years, especially, his mind-body theory, mechanistic life-view, and reductionism had important effect on medical study and science of public health. As a rule, we know that his mind-body theory was applicable to mind-body dualism, and his mind-body dualism was connected with biomedical model of medicine. But by this study, his mind-body theory was not only mind-body dualism but also mind-body monoism. And he asserted mind-body interaction too. In other words, he advocated mind-body dualism in scientific aspect, but he knew mind-body monoism from his experence. He confessed this fact to Princess Elizabeth of Bohemia, he wrote mind-body interaction in $\boxDr$Discours de la methode$\boxUl$, $\boxDr$Meditationes de prima philosophia$\boxUl$, and $\boxDr$Traite des passions de 1'ame$\boxUl$ etc. However, only mind-body dualism of his mind-body theories was written in our medical text book, morever mental realm was excluded from the persuit of learning Descartes advocated a mechanistic world-view and mechanistic life-view, he regarded human body as a machine part. And a paticent corresponds to a troubled machine, a doctor deserves a repairman. But this point of view made holistic understanding of man impossible. Descartes divide the whole into basic building blocks, we named the approach Reductionism. Reductionism led to ontological concept in medical science, bacteriology established 'specific cause-specific disease-specific therapy'. We examined medical influence of Descartes's thought, we need to draw out a philosophic basis of medical science and science of public health by a close study of his records.

• Nuclear Engineering and Technology
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• 제16권4호
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• pp.195-201
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• 1984

축방향 비균일 열유량을 가지는 서브쿨드 비등영역에서 첨단적인 mechanistic 모델을 사용하여 기포계수를 정확히 계산하고저 한다. 이 모델에서는 Lahey/Ohama model에서 구한 기포계수에 의존하는 drift-flux계수를 사용하였고 또한 실제 실험치와 비교하여 질량유량에 의존하는 응축계수의 상관식을 구하여 사용하였다. 이 모델은 고 정확도를 증명하기 위해 잘 알려진 실험치들과 비교되었고 최종적으로 고리 1호기 1주기의 고온 연료집합체 기포계수를 계산하므로서 profilefit 모델과 비교되었다. 이러한 계산결과는 실험치와 잘 일치하고 있으며 profile-fit model은 서브쿨드 비등영역에서 기포 계수를 낮게 계산하고 있음이 밝혀졌다.

• Nuclear Engineering and Technology
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• 제17권2호
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• pp.116-128
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• 1985

본 논문에는 이산화 우라늄 소결체의 노내고밀화현상을 온도와 미세구조의 함수로 정화하게 예측할 수 있는 기계론적 이론 모형이 개발.기술되어있다. 이 모형은 $UO_2$ 소결체의 결정 입계내에서 공극(vacancy)이 생성 이동되고, 결정입계에서 공극이 소멸되는 현상을 고려하고 있으며, 이 과정에서 일어나는 고밀화의 크기가 핵분열율, 조사시간, $UO_2$ 소결체밀도, 기공 크기의 분포, 결정입크기 및 온도의 함수로 기술되어 있다. 본 모형의 기공 수축에 대한 결과식은 Assmann과 Stehle가 유도한 4개의 온도 영역에 대한 결과식과는 상이한 것으로서, 소결체의 모든 온도 영역에 직접 적용된다. 본 모형에 의한 노내고밀화 크기의 예측치는 실험자료와 아주 잘 일치하며, KEFDA 전산코드에 사용된 경험적 실험 연산식에 비하여 고밀화의 경향과 절대치를 보다 정확히 예측한다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.586-591
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• 1996

Through the analysis of many experimental post-dryout data, it is shown that the most probable flow regime near dryout or quench front is not annular flow but churn-turbulent flow when the mass flux is low. A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is not applicable when the vapor superficial velocity is very low, i.e., when the flow is bubbly or slug flow regime. This is explained by the change of main entrainment mechanism with the change of flow regime. Therefore, the suggested correlation is valid only in the churn-turbulent flow regime ( $j_{g}$ $^{*}$＝0.5~4.5).).

• Journal of Microbiology and Biotechnology
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• 제16권9호
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• pp.1331-1337
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• 2006

A mathematical model has been proposed for the batch culture of Agaricus blazei with mixed carbon sources of glucose and dextrin. In the proposed model, the metabolism of A. blazei was divided into three parts: cell growth, exopolysaccharides (EPS) production, and another EPS production pathway activated by dextrin hydrolysis. Each pathway was described mathematically and incorporated into the mechanistic model structure. Batch cultures were carried out with six different carbon source compositions. Although parameters were estimated by using the experimental data from the two extreme cases such as glucose only and dextrin only, the model represented well the profiles of glucose, cell mass, and EPS concentrations for all the six different carbon source mixtures, showing a good interpolation capability. Of note, the lag in EPS production could be quite precisely predicted by assuming that the glucose-to-cell mass ratio was the governing factor for EPS production.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 춘계학술발표회요약집
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• pp.309.1-309
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• 2001

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 춘계학술발표회요약집
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• pp.152-152
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• 2001