• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.85-90
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• 2010

Friction welding is a common practice to join axially symmetrical parts for automobile industry applications. The shaft for automobile reverse idle gear is generally produced by forging steel, SF 45. This method is not so good because of high cost of material and production. In this study, in order to investigate the possibility of application of SM 45C to SF 45 dissimilar friction welding, the dissimilar friction welded joints were performed using 20 mm diameter solid bar in forging steel(SF 45) to carbon steel(SM 45C). The optimal friction welding parameters were selected to ensure reliable quality welds on the basis of visual examination, tensile test, micro-Virkers hardness surveys of the bond of area and optical microstructure investigations for welded joint parts. Finally, post weld heat treatment(PWHT) of the high-frequency induction hardening was performed for the friction welded specimens under the optimal welding conditions. And then, the mechanical properties were compared for as-welded and PWHT in SM 45C to SF 45.

• Korean Journal of Microbiology
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• v.46 no.1
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• pp.63-67
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• 2010

Proteases catalyze hydrolytic cleavage of a peptide bond between amino acids and occupy pivotal positions in application in physiological and commercial fields. During the screening for novel bacteria producing extracellular protease, two bacterial strains, WD12 and WD32, were isolated from rotten trees and they made clear zone on LB plates supplemented with 1% skim milk. The similarities of 16S rRNA gene sequence of either WD12 or WD32 to GenBank database showed the highest to Pseuoxanthomonas mexicana as 97.8 and 99.8%, respectively. Phylogenetic analysis showed that both isolated was located within the cluster comprising P. mexicana and P. japonesis. WD12 and WD32 were catalase- and oxidase-positive, Gram-negative rod strains. In case of WD12, it could assimilate malate, but could not assimilate D-mannose, which were different characteristics from P. mexicana. Both Pseuoxanthomonas sp. WD12 and WD32 optimally produced extracellular protease at $35-37^{\circ}C$, and maximal activity showed as 656 unit/ml and 267 unit/ml, respectively.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.2
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• pp.449-459
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• 1997

The main component of dental plaque is the mutan containing the a-1,3 bond. The following results were obtained by using a blue mutan to assess the factors affecting the mutan-digesting activity of Streptomyces exfoliatus isolated from soil. A clear zone was produced by mutanase-producing Streptomyces exfoliatus on the minimal essential agar containing blue mutan. Streptomyces exfoliatus digested more blue mutan in the minimal essential broth at pH 7.0 than at pH 5.5 or 8.5. Streptomyces exfoliatus digested more blue mutan at $37^{\circ}C$ than at $32^{\circ}C$ or $42^{\circ}C$ (P<0.05). When the concentration of $CaCl_2$ was increased in the minimal essential broth, the digestion of blue mutan was increased (P<0.05). The optimal concentration of KCl was 10mM to digest blue mutan, but a similar amount of blue mutan was digested at the range of 0.1mM to 6.4mM of $MgCl_2$. When the culture supernatant of Streptomyces exfoliatus was mixed with 2X brain heart infusion broth containing 0.5% yeast extract and 10% sucrose, less artificial plaque was formed by Streptococcus mutans on the orthodontic wire (P<0.05). These results indicated that the secretion of mutanase was identified in culture supernatant of mutan-digesting Streptomyces exfoliatus, suppressing the formation of artificial plaque by Streptococcus mutans.

• Journal of the Daesoon Academy of Sciences
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• v.47
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• pp.173-202
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• 2023

In this study, we delve into the potential for innovative cultural education techniques that utilize the timeless tales of Princess Bari and The Tale of Shim Cheong as tailored for the upcoming generations of overseas Korean learners. With a rising number of young overseas Koreans born and raised in their host countries, there emerges a pressing need to craft an educational framework that resonates with the evolving dynamics of their generation. Our endeavor revolves around proposing educational strategies that help solidify identity while carefully considering the intrinsic motivation prevalent among most overseas Koreans. Naturally, the choice of employing the classic epics Princess Bari and The Tale of Shim Cheong as educational resources was deliberate. These narratives are rich in rites of passage and offer profound insights into the transformative journey of their protagonists. Both characters are affluent women in patriarchal societies, and both embark on quests to redefine themselves through new relationships, liberating themselves from the confines of parental ties. This narrative framework provides a unique opportunity for overseas Koreans who are often adrift in the social fabric of their adopted countries. These stories inspire them to introspect and contemplate their own identities. By intertwining their personal narratives with the empowering stories of characters, students are provided a chance to reaffirm their authentic selves. Therein, a paradigm shift can occur that allows individuals to embrace the core elements that define them. Our ultimate objective was to enable students to explore their own stories and immerse themselves in the intricate narratives of classical works. This immersive experience fosters a profound sense of unity with the characters and paves the way for a comprehensive educational plan. This plan not only celebrates the hybrid nature of identity but also cultivates a deep sense of positivity within amalgamated 'subjects.' Such an approach not only fosters a stronger connection with one's heritage but also sparks a genuine curiosity about and affinity for the rich cultural tapestry of one's home country. It's not just education; it's a transformative journey that enriches the lives of overseas Koreans and nurtures a profound bond with their cultural roots.