• Elastomers and Composites
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• v.42 no.1
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• pp.20-31
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• 2007

Material characteristics and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the NBR compound was prepared by sulfur-cure system, and was used in predicting the lifetime of rubber gasket made by the compound. The accelerated material aging was investigated at different temperatures at 120, 140 and $160^{\circ}C$ and aging time from 3 hours to 600 hours at 5, 6, 7 vol %. of $H_2SO_4$ concentrations The rubber strips were placed in acid solution using pyrex g1ass tube. Both ends of pyrex g1ass tube were sealed to avoid evaporation of solution during heating at given time. The material test and accelerated acid-heat aging test were carried out to predict the useful life of NBR rubber gasket for a fuel cell stack. In order to investigate the effects of acid-heat aging on the properties of the NBR, tensile strength, elongation at break, hardness and crosslink-density were measured. The tensile strength decreases as the $H_2SO_4$ concentrations and temperature increase. Results were evaluated using Arrhenius equation.

• Proceedings of the Korean Fiber Society Conference
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• 2007.11a
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• pp.385-386
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• 2007

• 한국가스학회:학술대회논문집
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• 2000.09a
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• pp.192-199
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• 2000

• 한국가스학회:학술대회논문집
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• 1999.09a
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• pp.93-99
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• 1999

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.32.2-32.2
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• 2008

• Journal of Home Health Care Nursing
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• v.25 no.3
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• pp.153-163
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• 2018

Purpose: This study is know the home care nursing specialists' copying method for life-threatening emergency situation occurred while changing the tracheotomy tube in the patient's home through case-based learning. Methods: Two cases were analyzed using structured critical reflection while changing the tracheal tube. In the first case, the patient presented with dyspnea, cyanosis, and low oxygen saturation when connected to home mechanical ventilator after replacement of the tracheotomy tube. In the second case, replacement of the tracheal tube was difficult due to a narrowed airway from proliferated granulation tissue. Results: From the case-based learning. using a critical reflection instrument, home care nursing specialists indicated that it was important to explain the possibility of danger to the client and that nurses must check the operation of the ambu-bag to prepare for an emergency when replacing a tracheotomy tube. Moreover, they stated a need for two nurses during client visits when there is the possibility of an emergency. Conclusion: Case-based learning through critical reflection provides actual practice-focused knowledge that is helpful to home care nurse specialists who face emergency situations in a restricted environment. Therefore, we hope that home care nursing specialists will use this method to strengthen their professional knowledge.

• Human Ecology Research
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• v.60 no.1
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• pp.1-20
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• 2022

This paper presents a social network analysis of changes in Home Economics education content loaded on YouTube before and after the outbreak of COVID-19. From January 1, 2008 to June 30, 2021, a basic analysis was conducted of 761 Home Economics education videos loaded on YouTube, using NetMiner 4.3 to analyze important keywords and the centrality of video titles and full texts. Before COVID-19, there were 164 Home Economics education videos posted on YouTube, increasing significantly to 597 following the emergence of the pandemic. In both periods, there was more middle school content than high school content. The content in the child-family field was the most, and the main keywords were youth and family. Before COVID-19, a performance evaluation indicated that the proportion of student content was high, whereas after the outbreak of the disease, teacher content increased significantly due to the effect of distance learning. However, compared with video use, the self-expression and participation of users were lower in both periods. The centrality analysis indicated that in the title, 'family' exhibited a high degree of both centrality and eigenvector centrality over the entire period. Degree centrality of the video title was found to be high in the order of class, online, family, management, etc. after the outbreak of COVID-19, and the connection of keywords was strong overall. Eigenvector centrality indicated that career, search, life, and design were influential keywords before COVID-19, while class, youth, online, and development were influential keywords after COVID-19.

• Journal of Life Science
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• v.19 no.10
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• pp.1346-1351
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• 2009

Recent evidence has shown that many pluripotetic neural crest cells are fate-restricted and that different fate-restricted crest cells emigrate from the neural tube at different times. Jin et al. (2001) identified the expression patterns of Wnts and its antagonists at the time that neural crest cells were being specified and suggested that Wnt signaling was involved in the segregation/differentiation of neural crest cells in the trunk in vitro. In this study, we evaluated the effects of Wnt signaling in avian neural crest lineage segregation. To accomplish this, Wnt signaling was disturbed at the time of neural crest segregation and differentiation by grafting Wnt-3a expressing cells and conducting dominant negative glycogen synthase kinase (dnGSK) electroporation. Stimulation of Wnt signaling induced neural crest lineage segregation and melanoblast specification, and increased the expression levels of genes known to be involved in neural crest development such as cadherin 7 and Slug, which suggests that they are involved in Wnt-induced neural crest lineage differentiation into melanoblasts.

• Imaging Science in Dentistry
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• v.53 no.3
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• pp.217-220
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• 2023

Purpose: This pilot study was conducted to evaluate half-value layer (HVL) measurements obtained using a semiconductor dosimeter for intraoral radiography. Materials and Methods: This study included 8 aluminum plates, 4 of which were low-purity (less than 99.9%) and 4 high-purity (greater than 99.9%). Intraoral radiography was performed using an intraoral X-ray unit in accordance with the dental protocol at the authors' affiliated hospital: tube voltage, 60 kVp and 70 kVp; tube current, 7 mA; and exposure time, 0.10 s. The accuracy of HVL measurements for intraoral radiography was assessed using a semiconductor dosimeter. A simple regression analysis was performed to compare the aluminum plate thickness and HVL in relation to the tube voltage (60 kVp and 70 kVp) and aluminum purity (low and high). Results: For the low-purity aluminum plates, the HVL at 60 kVp (Y) and 70 kVp (Y) was significantly correlated with the thickness of the aluminum plate (X), with Y=1.708+0.415X (r=0.999, P<0.05) and Y=1.980+0.484X (r=0.999, P<0.05), respectively. Similarly, for the high-purity aluminum plates, the HVL at 60 kVp (Y) and 70 kVp (Y) was significantly correlated with the plate thickness(X), with Y=1.696+0.454X (r=0.999, P<0.05) and Y=1.968+0.515X (r=0.998, P<0.05), respectively. Conclusion: This pilot study examined the relationship between aluminum plate thickness and HVL measurements using a semiconductor dosimeter for intraoral radiography. Semiconductor dosimeters may prove useful in HVL measurement for purposes such as quality assurance in dental X-ray imaging.

• Transactions of the KSME C: Technology and Education
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• v.3 no.4
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• pp.241-248
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• 2015

Most of the Stirling cryocoolers used for infrared detector cooling in domestic is imported. Because the cooler has a high price, short life and poor durability, demand for the coolers continues steadily. However, the cooler is highly related to defense and space technology, technology transfer or co-development with the countries having experties in cooler design is very limited. The pulse tube cooler to be developed in this study is such that the mechanical piston in low temperature actuating part is replaced by the gas piston and linear compressor is adopted, which results in low vibration, long life and better durability. It is expected that development of the pulse tube cooler will not only improve our technology to the level of advanced countries, but also enhance the skills in designing and manufacturing of the infrared detector.