• Nuclear Engineering and Technology
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• 제53권3호
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• pp.833-841
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• 2021

During the postulated severe accident of nuclear reactor, eutectic reaction leads to low-temperature melting of fuel cladding and early failure of core structure. In order to model eutectic melting with the moving particle semi-implicit (MPS) method, the eutectic reaction model is developed to simulate the eutectic reaction phenomenon. The coupling of mass diffusion and phase diagram is applied to calculate the eutectic reaction with the uniform temperature. A heat transfer formula is proposed based on the phase diagram to handle the heat release or absorption during the process of eutectic reaction, and it can combine with mass diffusion and phase diagram to describe the eutectic reaction with temperature variation. The heat transfer formula is verified by the one-dimensional melting simulations and the predicted interface position agrees well with the theoretical solution. In order to verify the eutectic reaction models, the eutectic reaction of uranium and iron in two semi-infinite domains is simulated, and the profile of solid thickness decrease over time follows the parabolic law. The modified MPS method is applied to calculate Transient Reactor Test Facility (TREAT) experiment, the penetration rate in the simulations are agreeable with the experiment results. In addition, a hypothetical case based on the TREAT experiment is also conducted to validate the eutectic reaction with temperature variation, the results present continuity with the simulations of TREAT experiment. Thus the improved method is proved to be capable of simulating the eutectic reaction in the severe accident.

• 대한화학회지
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• 제50권5호
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• pp.404-414
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• 2006

연구에서는 고등학교 과학 교과서에 제시된 화학반응속도 측정을 위한 실험을 수행할 때 관찰되는 현상을 이해함으로써 교과서 실험의 문제점과 그 원인을 분석하여 개선 방안을 제시하였다. 이를 위하여 화학반응속도 측정과 관련된 단원의 교과서 내용을 분석하였으며, 실험을 수행할 때 발견되는 문제점을 실험 분석을 통해 제시하였다. 교과서에 제시된 수상치환법으로 실험을 하였을 때 부피 변화가 지연되어 관찰되는 현상과 반응속도가 초기에 증가하는 현상이 관찰되었다. 이러한 문제를 해결하기 위한 개선된 실험 방법을 제안하였다. 개선된 실험에서 반응속도는 시간에 대해 일정하게 측정되었고, 그 결과를 수소이온 농도와 마그네슘 리본의 표면적의 관점에서 해석하였다.

• 대한기계학회논문집B
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• 제28권2호
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• pp.207-214
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• 2004

The burning velocities of conventional and oxygen-enriched methane flame in various equivalence ratio were determined by experiments. The validity of existing reaction mechanisms was examined in oxygen-enriched flame on the basis of the experiment results. Modified reaction mechanism is suggested, which was able to predict burning velocity of oxygen enriched flame as well as methane-air flame. Complementary study on reaction mechanisms shows the following results : Present experiment data were found to be more reliable in comparison with existing ones in a oxygen-enrichment condition. It was found that some modification in existing reaction mechanisms is necessary, since discrepancy between measurements and predictions is increasing with oxygen enrichment ratio. The sensitivity analysis was performed to discriminate the dominantly affecting reactions on the burning velocity in various oxygen enrichment and equivalence ratio. A modified GRI 3.0 reaction mechanism based on our experiment results was suggested, in which reaction rate coefficients of (R38) H+O$_2$<=>O+OH in GRI 3.0 reaction mechanisms were corrected based on sensitivity analysis results. This mechanism showed a good agreement in predicting the burning velocity and number density of NO in oxygen-enriched flame and would provide proper reaction information of oxygen-enriched flame at this stage.

• Korean Chemical Engineering Research
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• 제56권3호
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• pp.416-420
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• 2018

A comprehensive kinetic study has been conducted on dimethyl carbonate synthesis by transesterification reaction of ethylene carbonate with methanol. An alkali base metal (KOH) was used as catalyst in the synthesis of DMC, and its catalytic ability was investigated in terms of kinetics. The experiment was performed in a batch reactor at atmospheric pressure. The reaction orders, the activation energy and the rate constants were determined for both forward and backward reactions. The reaction order for forward and backward reactions was 0.87 and 2.15, and the activation energy was 12.73 and 29.28 kJ/mol, respectively. Using the general factor analysis in the design of experiments, we analyzed the main effects and interactions according to the MeOH/EC, reaction temperature and KOH concentration. DMC yield with various reaction conditions was presented for all ranges using surface and contour plot. Furthermore, the optimal conditions for DMC yield were determined using response surface method.

• 한국응용과학기술학회지
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• 제33권3호
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• pp.492-497
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• 2016

The intermediate product resulting from the radical degradation experiment of PCE and the atomic charge gained through Gaussian03W were compared against each other. The result was that the ratio of PCE radical degradation was almost 98% or higher after the 9 hr point in reaction time. The reaction speed constant was $0.16hr^{-1}$ and it followed the first reaction. We could see that at each location of the PCE molecule, dechlorination happened at a point where the negative atomic charge was the greatest. Moreover, the intermediate product of PCE radical degradation that was confirmed in the experiment and literature coincided exactly with the intermediate product in the atomic charge calculation. Therefore, when the atomic charge is calculated, the radical degradation pathway of the organic chlorine compound could be forecast.

• 대한화학회지
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• 제50권4호
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• pp.328-337
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• 2006

연구의 목적은 고등학교 과학 교과서에 제시된 염화구리(II) 수용액의 전기분해 실험의 문제점을 분석하여, 학생들이 실험을 용이하게 수행하게 하고 환기 장치가 없는 과학실 여건을 고려해 염소 기체 발생으로 인한 안전 문제의 발생을 줄이기 위한 개선 실험을 제시하기 위한 것이다. 연구를 위하여 고등학교 11종 과학 교과서에 제시된 염화구리(II) 수용액의 전기분해 실험을 실험 방법에 따라 분류하고, 중등학교 화학 교사들에게 과학 교과서에 제시된 실험 방법대로 실험을 수행하게 한 후 문제점을 분석하여 개선 실험을 모색하였다. 연구 결과에 의하면, U 자관과 가지달린 U 자관을 반응 용기로 사용한 염화구리(II) 수용액의 전기분해 실험에서는 반응속도가 느려서 부반응으로 부산물이 발생하는 문제점이 있었으며, 비커를 반응 용기로 사용한 실험에서는 두 전극이 분리되어 있지 않아 각 전극에서 일어나는 화학반응을 분리하여 관찰할 수 없었다. 그리고 전기분해 장치를 반응 용기로 사용한 실험에서는 반응 생성물의 성질을 확인하기 어려운 문제점이 있었다. 이러한 문제점들을 개선하기 위하여 ㅂ자 모양의 반응 용기를 사용한 결과, 전기분해 반응속도가 빨라졌고, 각 전극에서 생성되는 반응 생성물의 특성을 분리해서 관찰할 수 있었다. 또한, 염화구리(II) 수용액의 사용량과 (-)극 주변에서 일어나는 부반응으로 인한 부산물의 생성량을 줄일 수 있었다. 그러므로 ㅂ자 모양의 반응 용기를 사용하는 개선 실험을 고등학교 과학 탐구 실험에 활용한다면, 염화구리(II) 수용액의 전기분해 실험을 용이하게 수행할 수 있어, 수용액의 전기분해에 관한 과학적인 개념 형성에 도움을 줄 수 있을 것이다.

• 대한한방내과학회지
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• 제26권1호
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• pp.12-47
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• 2005

First, mice were dosed with 50mg/kg of streptozotocin(STZ) twice every 24 hours to cause high blood-sugar. Then, after three days, mice were injected with 100mg/kg of STZ again. Two different dosages of Saengjihwangeumja-gami were given to the experiment groups: SA group, 15mg/kg/day, and SB group, 90mg/kg/day, in order to determine the effects of Saengjihwangeumja-gami, which has been known to be good for DM(Diabetes Mellitus). By observing weight and blood-sugar level changes, blood tolerance, the numerical value of BUN(Blood Urea Nitrogen) and creatinine in blood, and through light-electronicmicroscopic and immunohistologic investigations of pancreas and kidneys, the following results were obtained: 1. The experiment groups showed a high suppressive effect of weight-loss. 2. The experiment groups' blood-sugar and blood tolerance showed an effective lowering of blood-sugar levels. 3. The experiment groups did not show any noticeable change in the numerical value of BUN and creatinine in blood compared with that of the control groups. 4. The experiment groups showed a higher Insulin positive reaction of pancreatic islets ${/beta}-cell$ than the control groups. 5. The experiment groups showed a higher immuno-reaction against IGF- II than the control groups. 6. Observation of apoptosis of the pancreatic islets showed that the cells of experiment groups were less injured compared with those of the control groups, and fewer apoptag-positive reaction cells were seen in experiment groups than in the control groups. 7. Uunder electron-microscopy, the insulin-containing granules in pancreatic islets ${/beta}-cells$ had increased more in the experiment groups than in the control groups. 8. Under light microscopy, the injury on the inner & outer membrane of the glomerulus and epithelial cells of capillaries and cells among vessels were fewer in the experiment groups than in the control groups. 9. More apoptag-positive reaction cells in the kidney were seen in the control groups than in the experiment groups. 10. PAS-positive reaction substances had increased more in the substrate among the vessels of a glomerulus belonging to the control group than those of the experiment group. 11. Uunder electron-microscopy, the nucleonic membrane, nucleoplasm and mitochondria of proximal and distal renal tubular were more injured in the control groups than in the experiment groups. In conclusion, strong evidence for the efficacy of Saengjihwangeumja-gami in lowering blood-sugar, and in recovery and generation of pancreatic tissues injured by DM was observed. Results suggest Saengjihwangeumja-gami is an effective treatment for DM. Further study of the principles of blood-sugar dropping effects of Saengjihwangeumja-gami are needed, as well as further study of recovery and regeneration of pancreatic tissues injured by DM.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.368-375
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• 2016

A sodiume-water reaction takes place when high-pressured water vapor leaks into sodium through a tiny defect on the surface of the heat transfer tube in a steam generator of the sodium-cooled fast reactor. The sodiume-water reaction brings deterioration of the mechanical strength of the heat transfer tube at the initial leakage site. As a result, it damages the crack itself, which may eventually enlarge into a larger opening. This self-enlargement is called "self-wastage phenomenon." In this study, a simulant experiment was proposed to reproduce the self-enlargement of a crack and to evaluate the mechanism of the self-wastage. The damage on the surface of the crack was simulated by making the neutralization reaction with hydrochloric acid solution and sodium hydroxide solution. A numerical investigation was carried out to validate the feasibility of the approach and to determine experimental conditions. From the computation results, it is observed that when 5M HCl is injected into 5M of NaOH with 0.05 m/s inlet velocity, the temperature at the surface near the crack increased over 319.26 K. The computational results show that the self-wastage phenomenon is capable of being reproduced by the simulant experiment.

• 인지과학
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• 제1권2호
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• pp.221-239
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• 1989

한글 낱말의 처리단의를 검증하기 위해 3개의 실험을 실시 하였다.예비 실험과 실험1은 한음절 글자, 실험 2는 2음절 이상 글자에서의 처리단위를 밝혀보고자 하였다.예비실험에서,자음유형효과는 통계적으로 유의미하지 않았으나 낱말 위치 효과는 유의미했다.Newman-Keuls 검증결과 초성조건과 중성조건간 차이는 유의미하지 않았으나 중성조건과 중성조건간의 차이는 유의미했다.실험 1에서는 낱자수가 증가함에 따라 반응시간도 증가했다.낱말 위치 효과는 예비실험과 동일했다.실험 2에서는 종성유무와는 관계없이 음절이 증가함에 따라 반응시간이 증가했다.본 연구의 시사점은 다음과 같다:(1)한 음절의 글자에서는 초성과 종성으로만 구성된 음절을 단위로 정보처리가 이루어지나 (2) 두 음절이상의 글자에서는 종성이 포함된 음절을 단위로 정보처리가 이루어진다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1160-1165
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• 2004

The purpose of this study was to calculate three dimensional angular displacements, moments and joint reaction forces of the ankle joint during the waist pulling, and to assess the ankle joint reaction forces according to different perturbation modes and different levels of perturbation magnitude. Ankle joint model was assumed 3-D ball and socket joint which is capable of three rotational movements. We used 6 cameras, force plate and waist pulling system. Two different waist pulling systems were adopted for forward sway with three magnitudes each. From motion data and ground reaction forces, we could calculate 3-D angular displacements, moments and joint reaction forces during the recovery of postural balance control. From the experiment using falling mass perturbation, joint moments were larger than those from the experiment using air cylinder pulling system with milder perturbation. However, JRF were similar nevertheless the difference in joint moment. From this finding, we could conjecture that the human body employs different strategies to protect joints by decreasing joint reaction forces, like using the joint movement of flexion or extension or compensating joint reaction force with surrounding soft tissues. Therefore, biomechanical analysis of human ankle joint presented in this study is considered useful for understanding balance control and ankle injury mechanism.