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Jusik Park,Jihye Jeong,Jonggyu Son,Gangjun Kwon J-INSTITUTE 2021 International Journal of Martial Arts Vol.6 No.3
Jusik ParkPurpose: The purpose of this study is to provide useful information on physical fitness training to improve the performance of Taekwondo demonstration majors by identifying the characteristics of physical fitness factors ac-cording to the performance level of university Taekwondo demonstration members. Method: The subjects of this study are Taekwondo demonstration members enrolled in K University located in D city. The differences in body structure, physical fitness factors, isokinetic muscle function of the knee joint, and anaerobic exercise capacity were compared and analyzed for 3 male students in the national demonstration group and 3 male students in the general demonstration group. Results: As a result of measurement of body structure, physical fitness factors, isokinetic muscle function, and anaerobic exercise capacity of the national demonstration team and general students, there was no statistically significant difference between groups. However, through the results of this study, it was confirmed that the ratio of flexor and extensor muscles needs to be improved to an ideal ratio of 55% to 65% as suggested in previous studies to prevent damage to the lower extremities of general students. In addition, the standing long jump and sargent jump, side step, eyes closed and one leg standing, and knee joint isokinetic muscle power showed a high-er tendency in the national demonstration group compared to the general students. There was no statistically significant difference between groups in the measurement results of anaerobic exercise capacity. Conclusion: Based on the results of this study, it is thought that it will be difficult to present the characteristics of the physical fitness factors according to the performance level of Taekwondo demonstration majors. However, considering the results of many previous studies and this study, it is thought that efforts to improve agility, power, and balance ability are needed to improve the performance of Taekwondo demonstration majors. It is judged that improvement of the flexion muscle/extension muscle ratio of the lower extremities is necessary to prevent addi-tional injuries.;Jihye Jeong;Jonggyu Son;Gangjun Kwon
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연소기 열차폐 Ni-Cr 도금 적용 현황과 향후 기술 적용 확대 방안
이동영(Dongyoung Lee),손은원(Eunwon Son),김진형(Jinhyung Kim),조황래(Hwangrae Cho),방정석(Jeongsuk Bang),이병호(Byongho Lee),김종규(Jonggyu Kim),유철성(Chulsung Ryu) 한국추진공학회 2021 한국추진공학회 학술대회논문집 Vol.2021 No.5
액체로켓엔진 연소실에 적용되는 ZrO₂, NiCrAlY 기반 세라믹용사코팅은 금속과의 열팽창 계수 차이로 인한 박리 발생과 장시간 연소로 인한 삭마가 발생하는 단점이 있다. 이런 단점을 개선하기 위해 해외 기술 선진국에서 적용하고 있는 금속도금 기술을 다단연소사이클 엔진 기술검증용 연소기에 적용하였으며 열차폐 Ni-Cr 도금공정 및 상향 순환식 유동셀을 적용한 전용 도금조를 개발하고 공정 최적화를 수행하였다. 이후 기술검증용 축소형 연소실에 열차폐 Ni-Cr 도금을 확대 적용하여 연소시험을 통해 성능확인 및 기술의 완성도를 높여가고 있다. 본 연구에서는 고압엔진 연소실에 안정적인 열차폐 Ni-Cr 도금기술 적용을 위해 도금공정을 개선하고, 대형엔진 연소실에 적용 가능한 도금공정 방안을 다루었다. Zirconia, ZrO₂ and NiCrAlY-based ceramic thermal spray coating applied to the combustion chamber of a liquid rocket engine has the disadvantages that delamination due to the difference of thermal expansion coefficients between the metals and ablation due to long-time combustion occur. In order to improve these disadvantages, the metal plating technology, which is being used in overseas technologically advanced countries, was applied to the thrust chamber of technology demonstration model of staged combustion cycle engine. Ni-Cr plating process and a dedicated plating tank applied upward circulation flow cell were developed and process optimization was performed. After that, the thermal barrier Ni-Cr plating was applied to the small scale combustion chamber for technology verification. The performance was confirmed by a combustion test, and technology readiness level(TRL) is being increased. This study aims to improve the plating process to apply a stable thermal barrier Ni-Cr plating technology to the combustion chamber of a high-pressure engine and to deal with the plating process method applicable to the combustion chamber of a large scale engine.
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