• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.307-312
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• 2023

In this study, a catalytic oxidation-heat recovery system was designed that can remove unreacted with a concentration of about 1% to 6% in the exhaust gas of hydrogen fuel cells and recover heat to ensure safety in the hydrogen economy. The safety system was devised by filling hydrogen oxidation catalysts at room temperature that can remove unreacted hydrogen without any energy source, and an exhaust-heat recovery device was integrated to efficiently recover the heat released from the oxidation reaction. Through CFD analysis, variations in pressure and fluid within the system were shown depending on the filling conditions of the hydrogen oxidation system. In addition, it was found that waste heat could be recovered by optimizing the temperature of the exhaust gas, flow rate, and pressure conditions within the heat recovery system and securing hot water above 40 ℃ by utilizing the exhaust gas oxidation heat source above 300 ℃. Through this study, it was possible to confirm the potential of utilizing hydrogen processes, which are applied in small to medium-sized systems such as hydrogen fuel cells, as a safety system by evaluating them at a pilot scale. Additionally, it could be a safety guideline for responding to unexpected hydrogen safety accidents through further pilot-scale studies.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.123-133
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• 2023

Commercial hydrogen fuel cell vehicles are charged by compressing gaseous hydrogen to high pressure and storing it in a storage tank in the vehicle. This process causes the temperature of the gas to rise, to ensure the safety to storage tanks, the temperature is limited. Therefore, a heat transfer model is needed to explain this temperature rise. The heat transfer model includes the convective heat transfer phenomenon, and accurate estimation is required. In this study, the convective heat transfer coefficient in the hydrogen fueling process was calculated and compared using various correlation equations considering physical phenomena. The hydrogen fueling process was classified into the fueling line from the dispenser to the tank inlet and the storage tank in the vehicle, and the convective heat transfer coefficients were estimated according to process parameters such as mass flow rate, diameter, temperature and pressure. As a result, in the case of the inside of the filling line, the convective heat transfer coefficient was about 1000 times larger than that of the inside of the storage tank, and in the case of the outside of the filling line, the convective heat transfer coefficient was about 3 times larger than that of the outside of the storage tank. Finally, as a result of a comprehensive analysis of convective heat transfer coefficients in each process, it was found that outside the storage tank was lowest in the entire hydrogen fueling process, thus dominated the heat transfer phenomenon.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.3
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• pp.266-275
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• 2008

Purpose: This research was intended to evaluate the sedative effect of the music by measuring the anxiety-level, the pain-level, the blood pressure, and the pulse rate in patients who were going through extraction of the mandibular impacted 3rd molar. Materials and methods: Patients were selected among those who visited St. Vincent's Hospital in Suwon for the surgical extraction of 3rd molar from April to May, 2007 and were divided into two groups : the first, experimental group consisting of 32 people was going through extraction with the music and the second, control group also consisting of 32 people was going through extraction without the music. The anxiety-level was measured by filling out Spielberger's State-Trait Anxiety questionnaire. The pain-level was measured by VAS (Visual analog Scale). The blood-pressure and the pulse rate were recorded at waiting period, preparation and anesthesia period, 5 minutes after anesthesia, beginning of extraction and every five minutes after extraction to the end of surgery. Results: The anxiety-level was significantly lower in the experimental group than in the control group during the extraction procedure (p<0.01). The pain-level was significantly lower in the experimental group than in the control group (p<0.05). The mean systolic blood pressure was significantly lower in the experimental group than in the control group at the beginnig of extraction and 10 minutes after extraction (p<0.01, p<0.05 each). The mean diastolic blood pressure was significantly lower in the experimental group than the control group at 10 minutes after extraction (p<0.01). The mean of pulse rate was significantly lower at the beginning of extraction (p<0.05). Conclusion: The music therapy could offer not only the psychological stability but also the physiological stability during the surgical extraction of impacted 3rd molar.

• Korean Journal of Soil Science and Fertilizer
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• v.15 no.4
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• pp.233-240
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• 1982

This study was conducted to elucidate the translocation pattern of photosynthate labelled by $^{14}C$ in rice cultivars and the effects of nutrient composition on the translocation in rice plant during ripening, Showing coincidence between the grain filling rate and the translocation of $^{14}C$ into the grain during ripening period, the translocation patterns of cultivars tested were grouped by three; 1) the late dominance type (Akibare), 2) the early dominance type (Taebaegbyeo, Chupungbyeo), and 3) the semi-late dominance type (Milyang #23, Milyang #42, and Yushin). The negative relation ship existed between the translocation ratio of $^{14}C$ into the grain and the nitrogen content in plants, but not significant, The nutrient depletion of P, K, Ca, Mg, and Si in water medium from the panicle initiation to the heading stage resulted in the decrease of grain weight by 4 to 12 percent and the increase of translocation of $^{14}C$ into grain assimilated at heading. The effect of resupply of these nutrients after heading was recognized by the order of P>Mg>K and Ca. But the effect of Si resupply was hardly recognized in increasing grain weight. The photosynthetic rate was greatly affected by the nitrogen status and the depletion of P, K, and Ca decreased the photosynthetic rate in single leaf at heading, while the depletion of Si enhanced the rate.

• Tunnel and Underground Space
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• v.24 no.2
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• pp.176-186
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• 2014

Roughness, aperture and filling material of rock joint are widely considered to affect the hydraulic characteristics of joint. Among these factors, in this study, the joint roughness was examined with artificial joint profiles generated by Monte Carlo simulating on the original profiles suggested by Barton and Choubey(1977). Original profiles and revised profiles were combined to establish flow channel models, in which the hydraulic characteristics were analyzed numerically on the basis of minimum aperture changes and flow channel shapes. Maximum flow rate was identified at the growing point of flow area after passing through minimum aperture generated by the two profiles, and it was resulted that maximum flow rate is inversely proportional to minimum aperture. Maximum flow rate per unit area showed different values because flow channel shapes and minimum aperture locations are different in each model. In flow channel, mechanical aperture showed approximately 1.07 ~ 3.00 times larger than hydraulic aperture. In this study, mechanical and hydraulic aperture were concluded to be closely related to $A_i$ value, and their relations can be denoted by $e_m=0.519A^{0.7169_i}$ and $e_h=0.6182A^{0.239}_i$, respectively.

• The Journal of the Korean bone and joint tumor society
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• v.16 no.2
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• pp.51-54
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• 2010

Purpose: This study was aimed to evaluate the recurrence rate of a giant cell tumor (GCT) of the bone. Materials and Methods: The medical records of fifty four patients who were diagnosed with a giant cell tumor of the bone between March 1980 and December 2008 were analysed retrospectively. Among 54 patients, 27 were men, remaining 27 were women with the mean age of 33.1 years (range, 13-67 years). The mean duration of follow-up was 67.1 months. Results: Twenty-one patients (38.9%) had a local recurrence. The mean time to recurrence was 21.5 months (range, 2-59 months). The local recurrence rate of the upper extremities was higher than that of lower extremities. According to Campanacci classification, patients with a grade I diseae had lower recurrence rate than those with grade II or III disease. There was no significant differences in the recurrence rates based on cryotherapy, the filling of bone cement or bone grafts and surgical margin. Conclusion: To prevent local recurrence of GCT of bone, curettage of the tumor and elimination of the remaining cells are more important than adjuvant therapy.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.6
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• pp.759-765
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• 1997

The process of the senescence in Oryza glaberrima Steud. strains and Oryza sativa L. cultivars were examined in terms of SPAD value(chlorophyll content) and photosynthetic rate. SPAD values and photosynthetic rates of flag leaves for 10 genotypes of each species was measured at the 1, 3 and 5 weeks after heading. SPAD values and photosynthetic rates of O. glaberrima strains tended to decrease rapidly after heading. O. sativa cultivars showed slower decrease as compared to O. glaberrima strains, in particular during the period from 1 to 3 weeks after heading. Although there was no significant difference between the two species in the mean value of photosynthetic rate and SPAD value at 1 weeks after heading, O. glaberrima had lower values after 3 weeks after heading. There were significant positive correlation coefficients between the photosynthetic rate and the SPAD value at 1 and 3 weeks after heading for O. glaberrima strains, and at 1 and 5 weeks after heading for O. sativa cultivars. There were significant positive correlation between the decreasing rates of the photosynthetic rates and the decreasing rates of the SPAD values at the period from the 1 to 3 weeks after heading for both species. At the period from 3 to 5 weeks after heading, only O. glaberrima showed a significant correlation between two traits, indicating that rapid decrease in chlorophyll content would affect the photosynthesis in O. glaberrima.

• Journal of the Society of Disaster Information
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• v.15 no.2
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• pp.292-300
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• 2019

Purpose: To reduce the noise and vibration of reinforced concrete slab structures, the damping performance is to be performed experimentally after installing hollow core or filling it with liquid. Method: Using the hollow rate as an experimental variable, the damping ratio and stiffness of each test specimen at impact load are obtained to determine the difference between the damping ratio and stiffness of the numerical analysis. In addition, the damping effects are reviewed by comparing the difference in the damping ratio and stiffness of a test specimen filled with liquid 50% of the study. Results: Since the difference in resistance between a specimen with or without hollow core is 5%, it is judged that there is no structural problem, and the injection of liquid into the hollow core can increase the damping ratio, which can reduce noise or vibration. Conclusion: At less than 20% of hollow rate, there was little damping effect, and at 30%, damping effect was found. However, if liquid is injected into the hollow core of the specimen, damping rate is shown to increase, and the injection of liquid into the hollow part is believed to reduce noise or vibration.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.35 no.6
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• pp.411-419
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• 2009

Objective: The purpose of this study was to determine whether cyst enucleation would be done after marsupialization of large cystic lesion on the jaws or not, and if so, when it should be done. Patients & Methods: 12 patients with cystic lesion treated by marsupialization only and 10 patients with cystic lesion treated by marsupialization followed by enucleation were examined in this study. Postoperative clinical and radiographic examinations were performed at 1, 4, 7, 10, 13, 16, 19 months on 22 patients. Bone regeneration and reduction rate of the residual cystic cavities and bone density were evaluated with a analysis of digital panoramic radiographs. Also histological evaluation of the healing process was performed on 1 patient. Results: Uneventful healing and spontaneous bony filling of the residual cavities were observed in all cases. Postoperative radiographs showed that the size of the lesions was reduced for a few months, but the reduction rate of the residual cavity was minimized for 13~16 months after marsupialization. The bone density was increased 22.5 % after 19 months. Conclusion: This results suggest that the appropriate timing to perform enucleation would be 13~16 months after marsupialization. The state of healing process could be confirmed by histological examination and radiographic evaluation of bone density. Enucleation after marsupialization could be applied appropriately to reduce the periods of bone healing in large cystic lesion on the jaws.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.633-642
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• 2006

This study evaluated the surface changes such as surface average roughness(RA), surface free energy(SFE) and wear depth among groups treated with surface penetrating sealant(Fortify, Biscover), non treated polishing group before and after tooth-brushing, analyzing the influence of the sealants in filling of surface microdefects formed during the finishing and polishing procedures of composite resin. Results were as follow(p= 0.05) : 1. Ra was increased Biscover. Fortify and Polishing group. Before abrasion and in 6 months, all groups were statistically significant. In 1 month, 2 months and 3 months no statistical difference was noticed between Fortify and Biscover 2. SFE of Polishig and Biscover group. Fortify and Biscover group were statistically significant before abrasion. SFE of Polishing and Fortify group was statistically significant in 1 month. No statistical difference was noticed among groups in 2 months. SFE of Fortify and Biscover group was statistically significant in 3 months. Polishing and Fortify group, Fortify and Biscover group were statistically significant in 6 months. 3, Wear rate between Polishing and Fortify group was statistically significant in only 1 month. Wear rate between Polishing and Biscover group was statistically different in each month except for 2 month and so it was between Fortify and Biscover group. Considering film thickness of Fortify and Biscover, Fortify almost discappeared after 2 months and Biscover did after 6 months.