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유계형,권대규,정경훈,이성철 한국산업안전학회 2003 한국안전학회지 Vol.18 No.1
This paper presented an experimental modal analysis of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D(pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the Rayleigh-Ritz method and compared with the experimental results. Good agreement was obtained between the analytical solution and experimental result. The experimental results in water showed that the mode shapes are not sensitive to the depth of submergence. The natural frequencies were shown to decrease drastically once the perforated plates come in contact with water. However, the natural frequencies decrease with the depth of submergence until a certain depth is reached, and become the asymptotic values beyond this depth of submergence. The depth of submergence did not affect the damping ratio greatly.
전기도금한 교정용 스테인레스스틸 선재의 세포독성에 관한 연구
이계형,조진형,이기헌,황현식 대한치과교정학회 2005 대한치과교정학회지 Vol.35 No.2
본 연구는 전기도금을 이용하여 교정용 스테인레스스틸 선재의 직경을 증가시킨 후 세포독성을 알아봄으로써 이의 임상적 적용 가능성을 알아보고자 시행되었다. 시판되고있는 교정용 스테인레스스틸 선재에 전기도금 방법을 이용하여 니켈을 도금한 후, 이를 도금하지 않은 교정용 스테인레스스틸 선재 그리고 티타늄 또는 구리와 비교하기 위하여 이들을 배지에 넣고 72시간 배양하였다. 이 배양액을 금속 유리량 측정을 위해 ICP-AES(inductively coupled plasma atomic emission spectrophotometer) 분석을 시행한 결과 전기도금한 선재에서 많은 양의 니켈 이온이 유리되었으며, 구리에서는 많은 양의 구리 이온이 유리되었다. Microplate에 Balb/c 3T3 mouse fibroblast를 넣고 각 선재를 배양한 배양액을 75%, 50%, 25%로희석시켜 첨가한 후 MTT (3-[4.5-dimethylthiazol-2yl]-2.5-diphenyl tetrazolium bromide)분석을 시행하여 이를 배지만을 첨가한 경우와 흡광도를 비교하였다. 티타늄은 모든 농도에서 배지만을 첨가한 경우에 비해 흡광도 차이를 보이지 않았지만전기도금한 선재(p<0.001), 스테인레스스틸선재(p<0.05), 구리(p<0.001)는 배지만을 첨가한 경우보다 통계적으로 유의한 흡광도 감소를 보였다. ISO 10993, part5에 따라 구리는 "강한 독성"을 보이는 반면 티타늄과 스테인레스스틸 선재는 "무독성", 그리고 전기도금 선재는 "중등도 독성"으로 나타났다. 이상의 결과는 전기도금을 이용하여 교정용 선재의 직경을 증가시키는 방법이 임상에 적용되기 위해서는 세포독성을 줄이기 위한 추가의 연구가 필요함을 시사하였다. The purpose of this study was to examine the cytotoxicity of orthodontic wire which had an increased diameter through electroplating, and to evaluate its possoble clinical applications. First nickel plating was carried out on the commercially available stainless steel wire using an electroplating technique. For the comparison of the electroplated wire with ready made stainless steelwire and titanium or copper, each wire was incybated for 72 hours in a medium. The release of the metal ion was measured using ICP-AES(Inductively Coupled Plasma Atomic Emission Spectrophotometer). Balb/c 3T3 mouse fibroblast was put on a microplate and placed in an incubated medium of 75%, 50%, and 20% dilation. An MTT analysis was used to compare with the medium only. The changein absorbency value of each wire group and the difference of absorbency value according to the change of dilution was measured. The results of ICP-AES analysis showed that great amount nickel ion was isolated from electrpolated orthodontic wires and great amount copper ion was isolated from copper.The results of the MTT analysis showed that there was no difference in the absorbency value of titanium at any dilution. However the electroplated wires(p<0.001), the stainless steel wires(p<0.05) and the copper(p<0.001) were statistically significantly lower than those of medium only at all dilutions. Assessment as per ISO 10993, part5, showed that electroplated wire was alloted to "moderate cytotoxic", the titanium and stainless steel wire were "non-cytotoxic". The results of this study indicate that the electroplated or thodontic wires need additional efforts to dectease cytotoxicity for their clinical applications.
유계형,정경훈,이성철 한국산업안전학회 2002 한국안전학회지 Vol.17 No.2
In order to investigate the vibration characteristics of fluid-structure interaction problem, we modeled two identical rectangular plates coupled with fluid. A commercial computer code, ANSYS was used to perform finite element analysis and FEM solutions were compared with the experimental results to verify the finite element model. As a result, comparison of FEM and experiment showed good agreement, and the transverse vibration modes, in-phase and out-of-phase, were observed alternately in the fluid-coupled system. The effect of fluid gap size on the fluid-coupled natural frequency were investigated. It was shown that the mode numbers increased, the normalized natural frequencies monotonically increased. And it was also found that an increase of the fluid gap reduced the coupled natural frequencies for the in-phase modes but increased the coupled natural frequencies for the out-of-phase modes, and eventually converged to the results of an infinite fluid gap.
유체로 연성된 직사각평판의 거리 변화에 따른 고유진동 해석
유계형,이명규,권대규,이성철 전북대학교 공학연구원 ( 구 전북대학교 공업기술연구소 ) 2002 工學硏究 Vol.33 No.-
This study dealt with the experimental modal analysis of the perforated rectangular plate coupled with fluid. The natural frequencies of the perforated plate and solid plate in air were obtained by the analytical method based on the relation between the reference kinetic and maximum potential energy and compared with the experimental results. Good agreement between the results was found for the natural frequencies of the perforated plate in air. It was empirically found the natural frequencies of the perforated plate coupled with fluid. The transverse vibration modes, in-phase and out-of-phase, were observed alternately in the fluid-coupled system. Additionally, the effect of distance between perforated plate and solid plate on the fluid-coupled natural frequency was investigated.
부분적으로 유체가 채워진 원통형 관내의 외팔보 진동특성에 관한 실험적 연구
권대규,유계형,소순선,이성철 전북대학교 공학연구원 ( 구 전북대학교 공업기술연구소 ) 2003 工學硏究 Vol.34 No.-
This paper presents the vibration characteristics of an intelligent cantilever beam in contact with fluid using PZT actuator and PVDF film. The effect of liquid level on free vibration of composite beam in a partially liquid-filled circular cylinder is investigated. The dynamic behaviors of a flexible beam-water interaction system are examined. The coupled system is subject to an undisturbed boundary condition in the fluid domain. In the vibration analysis of wetted beam, the decoupled analyses between beam and fluid have been conventionally employed by considering firstly the composite beam vibration in air and secondly performing the correction taking account for surrounding fluid effects. That is, this investigation was to look at how natural frequencies, mode shapes, and damping are affected by liquid level variations. Using the coupled modal reanalysis method employing the governing equations and the clamped-free and free-free boundary conditions, the vibration analysis of beam in contact with fluid is performed. We also carried out the experimental verification about reliability of theoretical methods to inclusive vibration analysis of the fluid-structure system with PZT actuator and PVDF film. It was found that the coupled natural frequencies decrease with the fluid level for the identical composite beam due to added mass effect.
연료전지자동차용 초경량 복합재료 탱크의 수소 충전 특성 연구
유계형(Gye-Hyoung Yoo),김종열(Jong-Lyul Kim),이택수(Taek-Su Lee),이중희(Joong-Hee Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In this research, the hydrogen gas filling characteristics of the ultra-light composite tanks that have a plastic liner or an aluminum liner inside the composite shell are investigated in terms of gas and tank temperatures. The temperature changes in various positions in the Type 4 tank during hydrogen gas filling were monitored to understand the effects of the filling conditions. The results was also compared with the results obtained with Type 3 tank. As the filling speed is raised, more stiff temperature rise was observed and the temperature distribution over the entire region became more discrepancy.