• Nuclear Engineering and Technology
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• v.53 no.3
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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.

• Journal of the Korean Chemical Society
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• v.50 no.5
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• pp.404-414
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• 2006

this study we analyzed and improved an experiment measuring chemical reaction rates introduced in the high school science textbooks through an understanding of the phenomena observed in carrying out the experiment. For this purpose, the contents of textbooks related to the experiment were analyzed, and the problems observed in carrying out the experiment were addressed through experimental analysis. When the experiment was carried out by the method of aquatic transposition presented in textbooks, the observed volume change of H2 gas was delayed and chemical reaction rate was increased in the early stage of reaction period. To resolve these problems, an improved method for measuring the reaction rates was suggested. In the improved experiment the reaction rate was measured to be constant on time, which was interpreted in terms of the concentration of H+ and the surface area of magnesium.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.2
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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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• v.56 no.3
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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.

• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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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.

• Journal of the Korean Chemical Society
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• v.50 no.4
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• pp.328-337
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• 2006

purpose of this study was to find out problems in experiments for electrolysis of an aqueous CuCl2 solution in high school science textbooks and to suggest an improved experiment considering students' capability of experimenting and laboratory safety in high schools. For this study, the experiments for electrolysis of an aqueous CuCl2 solution presented in 11 high school science textbooks were classified by their experimental methods. After high school chemistry teachers performed the experiments as presented in the high school science textbooks, an analysis was performed on problems of the experiments, and an improved experiment was devised. According to the results of this study, in the experiments for electrolysis of an aqueous CuCl2 solution using a U type tube and a U type tube with branch, reaction velocity of the electrolysis was slow, therefore, a side reaction was generated. In the experiment using a beaker, reaction of each electrode could not be observed separately. And in the experiment using an electrolysis instrument, it was difficult to identify property of the reaction product. In the improved experiment using a reaction vessel of ㅂshape, reaction velocity of the electrolysis was fast, reaction of each electrode could be observed separately, and the side reaction decreased. From these results, it was suggested that the improved experiment would help high school students understand scientific conception regarding electrolysis.

• The Journal of Internal Korean Medicine
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• v.26 no.1
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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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• v.48 no.2
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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.

• Korean Journal of Cognitive Science
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• v.1 no.2
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• pp.221-239
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• 1989

The purpose of this study was to explore the processing unit in Korean word.Three experiments were conducted to examine this question.Preliminary experiment and Enperiment I were executed to delineate the processing unit in singles syllable word and Experiment 2,for words two or more syllables.The major finding of the preliminary experiment showed that the effect of the consonant type was not significant but that of the letter position was.Reaction time increased as the position of letter increased.The difference in reaction time between the first and the second position was not significant.However,the difference between the second and third was.In the Experiment 1, the effect of the number of letter was significant: reaction time increased as the number of letters increased.The size of the position effect both in the preliminary experiment and Experiment 1was comparable.Result of Experiment 2 was such that regardless of the presence of the final consonant(s),the reaction time incresased linearly as the number of svllables increased from two to four. The findings of the present study suggest that:(1)processing unit in single syllable Korean words is a syllable without the final consonant(s):(2) but in words of two or more syllables,the unit is likely to be a syllable with the final consonant(s).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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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.