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Thermal Cycling 열처리가 AISI 4330 강의 현미경조직과 기계적 성질에 미치는 효과에 대한 연구
김태일,천성순 대한금속재료학회(대한금속학회) 1981 대한금속·재료학회지 Vol.19 No.3
Thermal Cycling treatments have been applied to AISI 4330 steel for improving the strength and impact toughness. The constant and alternate cycling have been applied. Experimental results showed that a remarkable grain refinement can be obtained by thermal cycling treatments. The strength and impact value were increased by constant cycling, but the strength tended to decrease with increasing the impact value in alternate cycling. It was found that the best thermal cycling condition was the fourth cycle of constant cycling, and the grain size was reduced from about 15∼20㎛ mean grain diameter to 2∼3㎛, by this treatment. The grain refinement can be attributed to the low austenitizing temperature and short soaking time due to the rapid heating rate and the accumulation of residual stress during repeated thermal cycling. It is believed that the increase in strength is caused by the grain refinement and fine carbide precipitation, and increase in impact value is mainly due to the reduction of plate martensite which deteriorates the toughness.
Periodontal regeneration capacity of equine particulate bone in canine alveolar bone defects
김태일,정종평,허민석,박윤정,이상훈 대한치주과학회 2010 Journal of Periodontal & Implant Science Vol.40 No.5
Purpose: This study was performed to evaluate the periodontal wound healing effect of particulate equine bone mineral on canine alveolar bone defects. Methods: Twelve adult male beagle dogs were used as study subjects. The mandibular second and fourth premolars were extracted prior to the experimental surgery, and the extraction sites were allowed to heal for 8 weeks. After periodontal probing,two-walled defects were created at the mesial and distal sides of the mandibular third premolars bilaterally, and the defects were filled with equine particulate bone with collagen membrane or bovine particulate bone with collagen membrane, or collagen membrane alone. The defects without any treatment served as negative controls. After probing depth measurement, animals were sacrificed at 10, 16, and 24 post-surgery weeks for micro-computed tomographic and histomorphometric analysis. Results: The equine particulate bone-inserted group showed significantly decreased values of probing depth and first bone contact compared to the negative control and collagen membrane alone groups at weeks 10, 16, and 24 (P < 0.05). There were no significant differences in the new cementum length, newly-formed bone area, or newly-formed bone volume between equine particulate bone- and bovine particulate bone-inserted groups, both of which showed significantly increased values compared to the negative control and collagen membrane alone groups (P < 0.05). Conclusions: Equine particulate bone showed significant differences in probing depth, first bone contact, new cementum length, newly formed bone area, and bone volume fraction values when compared to the negative control and collagen membrane alone groups. There were no significant differences between equine and bovine particulate bone substitutes in these parameters;therefore, we can conclude that equine particulate bone is equivalent to bovine bone for periodontal regeneration.
김태일,Vijayakumar Mayakrishnan,배광수,정하연,박범영,임동현 경상대학교 농업생명과학연구원 2017 농업생명과학연구 Vol.51 No.6
A diverse of recommendation has been made for the structure and management of dairy cows,despite demanding research, the relationship between lactation number and various factors is yetto be established. The present study was aimed to investigate the covariance among lactationnumber, growth performance, calving interval, and milk production was considered to increase anefficiency of selection schemes and to manage more efficiently Holstein dairy cows that havebeen raised on small-scale family farms in Republic of Korea. For that purpose, the data wereobserved from 850 Holstein dairy cows, which a total of 3929 milking, since April 2016 -January 2017. We measured the body weight, height, age, calving interval, and milk productionof the each dairy cow. Also, information about the date of lactation, calving interval, and milkproduction was recorded using an automatic milking system(AMS) with identification numbers. Milk production was calculated per udder quarter in the AMS. Our study results showed theincreased average body weight(p>0.05) in 1, 2, 3, and 4th lactating dairy cows and afterwards,we noticed the tendency on the average body weight(p<0.05) per lactation progressed. There wasno significant difference noticed on height measurement of dairy cows. From the processing dataof 850 Holstein dairy cows, the lactation number 1 and 7 had a greater calving interval withsignificantly lowered milk production, and the lactation number 2, 3, 4, 5, and 6 hadsignificantly lowered the calving interval(p<0.05) with a greater milk production. From our studyresults, we evidenced that there is a significant relationship between the lactation number, growthperformance, calving interval, and milk yield, and the maximum production of milk occurring inthe 3rd and 4th lactation dairy cows. The achieved results from this study can be used by thesmall-scale farmers to encourage the structure and management of growth performance, calvinginterval, and milk yield in Holstein dairy cows in Korea.
NGO단체의 아동개발사업을 통한 중남미 아동의 사회적 자본이 정서발달에 미치는 영향: 페루, 볼리비아 기아대책사업 중심으로
김태일,송미령 고려대학교 스페인 라틴아메리카 연구소 2019 스페인라틴아메리카연구 Vol.12 No.2
The purpose of this study was to examine the effects of child development programs(CDP), the child-sponsored programs of the NGOs, on child development. The results of this study showed that the social capital of the children invested in the child development project affected the children 's emotional development. Self-esteem, ego resilience, and happiness, which are children 's emotional development, showed a positive correlation with social capital. In addition, it was shown that the investment of social capital can predict emotional development. In other words, children who are helped to form social capital through social participation of CDP are positively affected by emotional development. In addition, it can be said that children 's emotional development is affected not only by helping the child to form social capital through the CDP activities of KFHI. Based on the above results, it can be seen that the social capital input to the children has a positive effect on the family as well as the emotional development of the child, and a virtuous cycle effect that returns the child to a better social capital again. Surrounding people such as friends, relatives, neighbors, etc., have a positive effect on children. Therefore, it is necessary to continuously invest social capital centered on the network in future projects. 본 연구는 한국 NGO 단체 중 국제기아대책기구의 아동 후원 프로그램인 아동개발사업을 분석하여 아동발달에 미치는 효과를 검증하고자 하였다. 이를 실증적으로 확인한 결과, 기아대책 아동개발사업에 투자된 아동의 사회자본이 아동의 정서발달에 영향을 미치는 것으로 나타났다. 본 연구에서 정서발달의 측정 요소로 자아존중감, 자아탄력성, 행복감을 두고 살펴본 결과 세 가지 모두 사회자본과 상호 영향을 받는 정적상관관계가 있었고 이와 더불어 사회자본의 투자로 정서발달을 예측할 수 있는 것으로 나타나 기아대책 사회참여를 통해 사회자본 형성에 도움을 받는 아동의 경우 정서발달에도 긍정적인 영향을 받는 것으로 나타났다. 여기에 더하여 기아대책 사업에 참여하여 아동 사회자본 형성에 도움을 받을 경우 아동의 정서발달에도 긍정적인 영향을 받는다고 볼 수 있다. 이상의 결과를 토대로 보면, 아동에게 투입되는 사회자본은 아동의 정서발달뿐만 아니라 가족에게도 긍정적인 영향을 미쳐 다시 아동에게 더 나은 사회자본으로 되돌아오는 선순환 효과가 있음을 알 수 있었다. 사회자본인 친구, 친척, 이웃 등의 주변인이 아동에게 긍정적인 영향을 미치고 있다. 그러므로 앞으로의 추진 사업에 관계망 중심의 사회자본을 지속적으로 투자할 필요가 있다.