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김지성 ( Jisung Kim ),김동주 ( Dongju Kim ),박영진 ( Youngjin Park ),김하집 ( Hajip Kim ),조권상 ( Kwonsang Cho ) 한국농공학회 2011 한국농공학회 학술대회초록집 Vol.2011 No.-
1994년에 설치된 새만금 전구역수리모형은 방조제 끝막이 공사를 수행하기 위해서 조석에 따른 조위ㆍ유속 실험을 수행하였다. 2006년 새만금방조제 끝막이 완료 후에는 내부개발 계획 및 시공계획 수립에 필요한 기술지원을 수행하기 위해 모형의 경계와 축척을 변경하고 노후화된 시설을 교체하여 조석모형을 재구축하였다. 또한 2010년에는 2008년 지형 측량 자료를 기초로 지형을 수정하였다. 본 모형의 대상영역은 새만금간척사업지구를 포함하고 외해쪽으로는 선유도 말단, 내륙으로는 만경대교와 동진대교 상류하천구간을 포함한다. 새만금 호내 수위는 상류하천의 유입유량과 배수갑문의 유출입량에 의해 지배적으로 변동한다. 배수갑문의 운영은 해측의 조석현상이 지배적인 인자로 작용한다. 이러한 수위 변화 현상을 재현하기 위하여 Froude의 상사법칙을 적용하였으며, 실험시설의 규모 및 수위와 유속 재현성을 고려하여 수평축척을 1/450, 수직축척을 1/70으로 결정하였다. 사방 100m 규모의 새만금수리종합시험연구동에 새만금사업지구를 중심으로 동서방향 36km, 남북방향 40km의 영역에 대해 수리모형을 제작하였다. 새만금방조제 해측의 조석에 의한 조위는 외해측 개방경계에 위치한 6개의 조석발생위어를 이용하여 각 위어 지점에서 조위를 발생하여 재현한다. 시계열 조위 자료는 10개 분조를 이용한 합성조위로 산출한다. 하천 유입량은 만경강, 동진강 등 6개 유입하천의 유량을 시간에 따라 제어할 수 있는 공급시스템을 통해 재현하였다. 배수갑문은 전동수문을 설치하여 배수갑문 조작조건에 따른 자동제어가 가능하도록 구현하였다. 모형 검ㆍ보정은 새만금방조제 주변 해역에서의 조위와 호내 수위 및 유속 측정 결과 및 Delft3d 모델 수치해석 결과를 이용하여 수행하고 있다. 본 모형은 왜곡(왜곡도 6.43)되어 있어 수직거리가 수평거리에 비해 적게 줄어들어 모형표면이 매끄러워 모형의 조도를 증가시켜 표면마찰을 크게 하여 올바른 수면경사를 유도해야한다. 요구되는 보정조도의 크기는 Chezy 계수의 형태로 표현하면 C<sub>R</sub>=[L<sub>H</sub>/L<sub>V</sub>]<sup>1/2</sup>=[6.43]<sup>1/2</sup>=2.5이고 Chezy 계수 C는 White-Colebrook 공식으로 표현, C=18ㆍlog(12h/k), 여기서, h=수심(또는 동수반경), k=바닥의 조도이다. 수심별로 추가로 설치해야 될 조도 재료는 다음 <표 1>과 같으나 실제로 배치되는 조도재료의 양은 검정실험 결과를 통해 부분조정이 필요하다. <표 1> 추가 조도재료 계산량
DED 금속 3차원 프린팅의 레이저 파워 피드백 제어에 따른 적층 물성 연구
김지언(ChiYen Kim),김지성(JiSung Kim),이호(Ho Lee),박민규(MinKyu Park),김성욱(SungWook Kim),신성선(SeongSeon Shin),황준호(JunHo Hwang),김현덕(HyunDeok Kim) 대한용접·접합학회 2020 대한용접·접합학회지 Vol.38 No.2
This study conducted a comparative analysis of laser power feedback control by measuring the melting pool size and temperature in the Directed Energy Deposition (DED) of SUS316L, to identify the effect of a conventional melting pool monitoring system on 3D metal printing performance. In the study, a CLAMIR was used on a developing 3D metal printer to control the laser beam power by measuring the size and temperature of the melting pool using an IR camera. Test parts were built from same CAD model but under different conditions, specifically, with CLAMIR on and off. The parts were investigated three ways: by 3D scanning to measure geometric errors, CT scanning to look into pore creation and distribution, and tensile tests to analyze mechanical performance.
Kim, Jisung 국제물리치료연구학회 2019 Journal of International Academy of Physical Ther Vol.10 No.1
Background: Previous researchers have investigated the mechanical and neurophysiological effects of manual mobilization, however little research has been done on muscle tone and muscle stiffness. Objective: To compare the effects of posterior-anterior (PA) mobilization with weight bearing on sling and conventional PA mobilization on the bed. Design: Randomized controlled trial (single blind) Methods: The subjects were 16 male university students and randomized to sling mobilization group (SMG, n=8) or conventional mobilization group (CMG, n=8). SMG received PA mobilization using a sling and CMG received traditional mobilization on the bed during lumbar mobilization. Results: Both left and right muscle tones of SMG increased, but left muscle tone of SMG were increased and right muscle tone was decreased after intervention. In addition, both left and right muscle stiffness of SMG were also increased, however left muscle stiffness of SMG was increased and right muscle stiffness was decreased. The muscle tone and muscle stiffness of SMG were higher than those of DMG, especially the right side was statistically significantly higher. Extension of SMG, extension and flexion of CMG were increased statistically significantly except for Flexion of SMG (p<.05). There were no significant differences between the groups in Extension and Flexion. Conclusions: This study suggests that lumbar spine PA mobilization using sling is beneficial in improving muscle tone, muscle stiffness, and trunk movement.
Jisung Kim 국제물리치료연구학회 2019 Journal of International Academy of Physical Ther Vol.10 No.1
Background: Previous researchers have investigated the mechanical and neurophysiological effects of manual mobilization, however little research has been done on muscle tone and muscle stiffness. Objective: To compare the effects of posterior-anterior (PA) mobilization with weight bearing on sling and conventional PA mobilization on the bed. Design: Randomized controlled trial (single blind) Methods: The subjects were 16 male university students and randomized to sling mobilization group (SMG, n=8) or conventional mobilization group (CMG, n=8). SMG received PA mobilization using a sling and CMG received traditional mobilization on the bed during lumbar mobilization. Results: Both left and right muscle tones of SMG increased, but left muscle tone of SMG were increased and right muscle tone was decreased after intervention. In addition, both left and right muscle stiffness of SMG were also increased, however left muscle stiffness of SMG was increased and right muscle stiffness was decreased. The muscle tone and muscle stiffness of SMG were higher than those of DMG, especially the right side was statistically significantly higher. Extension of SMG, extension and flexion of CMG were increased statistically significantly except for Flexion of SMG (p<.05). There were no significant differences between the groups in Extension and Flexion. Conclusions: This study suggests that lumbar spine PA mobilization using sling is beneficial in improving muscle tone, muscle stiffness, and trunk movement.
Jisung Yoo,Won‑Mi Choi,Byeong‑Joo Lee,Gi‑Yong Kim,Hyungjun Kim,Won‑Doo Choi,Yong‑Jun Oh,Sunghak Lee 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.10
In order to increase the exhaust-gas temperature of austenitic stainless cast steels used for turbo-charger-housings up to1050 °C, the more excellent high-temperature strength should be obtained because it works for keeping a sustainability ofthe housing shape. Three austenitic stainless cast steels were fabricated in this study by adding Nb into the Ni/Mn-replacedconventional ASTM HK40 steel, and their high-temperature strength was investigated in relation with the carbide formationand matrix strengthening. The 1-wt%-Nb-added steel showed the enhancement in high-temperature strength over thenon-Nb-added steel. This indicated that the Nb addition was effective on the strength improvement because it raised boththe fraction of thermally-stable hard MC-type carbides and the austenite-matrix hardness. However, the 1.5-wt%-Nb-addedsteel showed the lower high-temperature strength than the 1-wt%-Nb-added steel, although it contained the more MC carbides. The more MC carbides reduced the matrix hardness, enlarged the hardness difference between carbides and matrix,and deteriorated the high-temperature strength. Our results demonstrate that the strengthened matrix as well as populatedcarbides due to the Nb addition are desirable for further improving the high-temperature strength.
Jisung Yoo,Won‑Mi Choi,Seok Su Sohn,Byeong‑Joo Lee,Gi‑Yong Kim,Hyungjun Kim,Won‑Doo Choi,Yong‑Jun Oh,Sunghak Lee 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2
For maintaining high-performance turbo-charger housings at higher exhaust-gas temperatures, e.g., 1050 °C, a high-Ni(20 wt%)-containing austenitic steel (ASTM HK40 steel) has been actively modified. As a promising method, the solidsolutionhardening obtained from the V or Cu addition was utilized in this study. Five austenitic cast steels were made byadding V or Cu in the modified HK40 steel (N16 steel; 4%-Ni replacement by 4.6%-Mn), and the high-temperature propertyimprovement was explained by detailed microstructural evolutions coupled with thermodynamically calculated phase diagrams. The V- or Cu-added steels showed improvements in high-temperature properties over the N16 steel because the additionof V or Cu raised both austenite matrix hardness and volume fraction of M7C3carbide. Considering that only 3.6–4.8vol% of M7C3was present in the five austenitic cast steels, the strengths were affected more by the matrix hardness. Whenthe V or Cu content was quite high, however, the ferrite or Cu-coring is formed, thereby leading to the serious deteriorationof high-temperature properties. The V- or Cu-added steels within proper contents are applicable well to automotive turbochargerhousings requiring or emphasizing high-temperature tensile properties.