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김철웅,서정철,윤현민,장경전,송춘호,안창범,Kim, Cheol-Woong,Seo, Jung-Chul,Youn, Hyoun-Min,Jang, Kyung-Jeon,Song, Choon-Ho,Ahn, Chang-Beohm 대한침구의학회 2001 대한침구의학회지 Vol.18 No.2
Objectives ; This study was undertaken to determine whether Carthami-Flos aquacapuncture (CFA) exerts protective effect against oxidant-induced inhibition of $Na^+-K^+$-ATPase activity in cerebral synaptosomes. Methods and Results ; The enzyme activity was dependent on incubation time and enzyme protein concentrations. An oxidant t-butylhydroperoxide (tBHP) at 1 mM concentration caused a significant inhibition of $Na^+-K^+$-ATPase activity, which was prevented by addition of 0.01% CFA. tBHP inhibition and CFA protection were independent on incubation time or enzyme protein concentrations. The enzyme activity was increased by ATP in a dose dependent manner. Effects of tBHP and CFA were not affected by ATP cocentrations. tBHP (1 mM) produced a significant increase in lipid peroxidation in cerebral synaptosomes, which was prevented by 0.01% CFA. CFA decreased oxygen free radicals generated induced by the phorbol-ester in a dose-dependent manner in human neutrophil. Conclusions ; These results suggest that CFA exerts protective effect against tBHP-induced inhibition of $Na^+-K^+$-ATPase activity, which is due to by an antioxidant action resulting from a direct scavenging effect of oxygen free radicals in the cerebral synaptosomes.
원공노치 인근에 발생한 결함의 위치변화가 균열성장률(da/dN) 및 응력확대계수범위(δK)의 관계에 미치는 영향 - 단일재 알루미늄과 Al/GFRP 적층재의 피로거동 비교 -
김철웅,고영호,이건복,Kim, Cheol-Woong,Ko, Young-Ho,Lee, Gun-Bok 대한기계학회 2007 大韓機械學會論文集A Vol.31 No.3
The objective of this study is to investigate the effect of arbitrarily located defect around the circular hole in the aircraft structural material such as Al/GFRP laminates and monolithic Al alloy sheet under cyclic bending moment. The fatigue behavior of these materials may be different due to the defect location. Material flaws in the from of pre-existing defects can severely affect the fatigue crack initiation and propagation behavior. The aim of this study is to evaluate effects of relative location of defects around the circular hole in monolithic Al alloy and Al/GFRP laminates under cyclic bending moment. The fatigue behavior i.e., the stress concentration factor($K_t$), the crack initiation life($N_i$), the relationship between crack length(a) and cycles(N), the relationship between crack growth rate(da/dN) and stress intensity factor range(${\Dalta}K$) near a circular hole are considered. Especially, the defects location at ${\theta}_1=0^{\circ}\;and\;{\theta}_2=30^{\circ}$ was strongly effective in stress concentration factor($K_t$) and crack initiation life($N_i$). The test results indicated the features of different fatigue crack propagation behavior and the different growing delamination shape according to each location of defect around the circular hole in Al/GFRP laminates.
Intra-articular Correction of the Femorotibial Joint Malalignment by Computer Assisted Surgeries
Cheol-Woong Kim(김철웅),Tae-Young Kim(김태영),Min-Hyung Park(박민형),Jung-Heum Yoon(윤정흠),Kwang-Suk Jang(장광석),Joon-Ho Wang(왕준호) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
An upper tibial opening wedge osteotomy is an operation to cure a malalignment and a degenerate arthritis. To prevent the postoperative malalignment caused by the upper tibial opening wedge osteotomy, the research to define the relationship between a Hinge Axis Angle and a Posterior Slope Angle is needed. The effect of the relationship between the hinge axis angle and the gap angle on the posterior slope angle is studied. After 3-D Compute Tomography (CT) scanning image is reconstructed, the virtual surgery is performed by the reconstructed 3-D tibia model. It was proved that the relationship between the hinge axis angle and the gap angle were constant and the simple mathematical model could be derived. To verify the suggested mathematical model, it compared with the measured data from the virtual surgery. In conclusion, while the deviation between the data from the virtual surgery and ones of the mathematical model under the gap angle<10° was less than 1%.
인공추간판 슬라이딩 코어의 곡률반경 변화가 종판의 접촉압력에 미치는 영향
김철웅(Cheol-Woong Kim) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.1
척추관 협착증은 감압술과 융합술 그리고 인공추간판 치환술 등이 있으며, 2000년대 중반부터는 인공추간판 치환술이 널리 시술되고 있다. 인공추간판의 연구는 추간판의 자유도 및 추체의 굴곡-신전, 측굴전, 축회전에 대한 해석이 핵심기술이지만, 시술 후 수년이 경과하여 발생하는 피로파손이 새롭게 큰 문제점으로 대두되고 있다. 따라서 인공추간판 연구는 슬라이딩 코어의 피로특성 및 내구성 향상에 집중되어야 한다. 본 연구에서는 세계적으로 가장 많이 사용되는 인공추간판 제품(SB Charite Ⅲ)을 기초로 유한요소모델을 제작하고, 슬라이딩 코어의 곡률반경과 마찰계수의 변화가 von-Mises 응력과 접촉압력에 미치는 영향을 평가하였다. 이와 같은 결과를 바탕으로 새로운 인공추간판 모델들 (Model-Ⅰ, -Ⅱ, -Ⅲ)을 제안하고 일정수명 후 발생할 수 있는 슬라이딩 코어의 피로파손 거동에 대해 SB Charite Ⅲ의 결과와 비교·평가하였다. The treatments for spinal canal stenosis are radicular cyst removal, spine fusion, and implantation of an artificial intervertebral disc. Artificial intervertebral discs have been most widely used since the mid-2000s. The study of artificial intervertebral discs has been focused on the analysis of the axial rotation, lateral bending, the degrees of freedom of the disc, and flexion-extension of the vertebral body. The issue of fatigue failure years after the surgery has arisen as a new problem. Hence, study of artificial intervertebral discs must be focused on the fatigue failure properties and increased durability of the sliding core. A finite element model based on an in the artificial intervertebral disc (SB Charite Ⅲ) was produced, and the influence of the radius of curvature and the change in the coefficient of friction of the sliding core on the von-Mises stress and contact pressure was evaluated. Based on the results, new artificial intervertebral disc models (Models-Ⅰ, -Ⅱ, and -Ⅲ) were proposed, and the fatigue failure behavior of the sliding core after a certain period of time was compared with the results for SB Charite Ⅲ.
경량압전 복합재료 작동기의 작동변위와 총유효모멘트의 관계
김철웅(Cheol-Woong Kim),남인창(In-Chang Nam),윤광준(Kwang-Joon Yoon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The LIghtweight Piezoelectric Ceramic Composite Actuator (LIPCA) is subject to the cyclic maximum deflection due to the resonant frequencies. Unfortunately, it could make LIPCA damageable by the cyclic large deformation. If the progressive microvoid coalescence of LIPCA interlaminar took place, the decrease of the stiffness and the weakness of stress transmission and fiber bridging effect would make the fatigue characteristics worse suddenly. Therefore, it is required to study the variation of fatigue behavior and interlaminar condition in LIPCA under resonant frequencies. These studies such as the changeable fatigue phase and interlaminar behavior of LIPCA affected by the resonant frequencies should be carried out due to the strong anisotropy of carbon/epoxy layer. Hence, these studies are as follows. Firstly, propose a method that relationship between total effective moment (ME) and performance displacement. Secondly, comparative analysis of total effective moment vs. bending theory of the Bernoulli-Euler laminate beam applicable LIPCA. Finally, Residual stresses distribution of interlaminar in LIPCA using the CLT.
사체 아킬레스건을 이용한 경골관통터널방식의 후방십자인대 재건술
김철웅(Cheol-Woong Kim),배지훈(Ji-Hoon Bae),오동준(Dong-Joon Oh) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.4
Posterior Cruciate Ligament (PCL) plays an important role in knee extension. Rotational instability due to injured PCL can be restored by various PCL reconstruction methods. In this study, the initial lengthening affected by fixation device and location was demonstrated, and furthermore, the slippage and the relationship between lengthening ratio and slippage ratio in the calcaneus and soft tissue fixation methods was newly suggested. Eight specimens of proximal tibia and Achilles tendon grafts were harvested from four cadavers and divided into four groups in regard to the four different types of transtibial fixation techniques. The cyclic load ranged from 50 N to 250 N applied to each graft fixed to proximal tibia in 55 degrees. The initial lengthening ratio to the total elongation has been approximately constant regardless of the fixation methods. The soft tissue fixation method with an interference screw showed about 56.4% slippage ratio to the total elongation and the same method with a double cross-pin presented about 45.4% slippage ratio. The soft tissue fixation method with an interference screw demonstrated approximately 2 ㎜less total elongation and about 13% more slippage than lengthening because of poor fixation compared to the same method with a double cross-pin.
The Design and Numerical Analysis of Ultra Miniature Eddy Current Sensor
Cheol-Woong Kim(김철웅),Cheon-Woong Park(박천웅),Gwang-Je Kim(김광제),Kyung-Don Kang(강경돈) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Shielding in magnetic field is more difficult than in electric field. So, it can be said that magnetic field influences the bio-compatibility more than electric field. In order to prevent distortions in the image or magnetic field by the micro-pin after permanent transplant of an anastomotic ring during free flap or plastic reconstruction, the current density, magnetic susceptibility, and electrical conductivity of Ti-6Al-4V must be evaluated. The result of Finite Element Model (FEM) can be highly trusted when it contains finite plane as in electrical instruments. However, the evaluative analysis is rather vague for magnetic fields, thus limits 3-dimensional region segmentation. Consequently, it is more accurate to apply Biot-Savarts law if there is no dielectric substance. In this study, human tissue model was hypothesized to be a magnetic cube cell, modeled through Impedance Network, and analyzed after converting the Maxwell equation to Circuit equation. Impedance method is highly effect for finding the inner current density or induced electric field if the frequency is low. When human tissue is exposed to a time-variant magnetic field, the human body becomes non-assimilative, hence, a critical factor that could influence the magnetic field. The eddy current can be calculated by forming an electrical network from the complex conductivity of the tissue.
인공근육에 적용되는 압전복합재료 작동기의 탄소섬유 배향각과 작동변위의 관계
김철웅(Cheol-Woong Kim),이성혁(Sung-Hyuk Lee),윤광준(Kwang-Joon Yoon) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월
The aim of this research is to evaluate the relationship between the total effective moment (M<SUP>E</SUP>) and Bernoulli-Euler bending moment (M) when the ply orientations of UD CFRP in Piezoelectric Zirconate Titanate Composite Actuator (PZTCA) are changed. The obtained results as follows. Firstly, as the performance test results by the CFRP ply orientation, the performance of [0] and [90] were stable. However, while the performance of [+45] was suddenly decreased after 5 hours. Secondly, the change of M<SUP>E</SUP> by the CFRP ply orientation was evaluated. As the CFRP ply orientation was increased from [0] to [+60], the M<SUP>E</SUP> were gradually decreased. However, they became a little bit increased from [+60] to [90]. Finally, after the change of M by the CFRP ply orientation was evaluated, it was found that M<SUP>E</SUP>=2.2M was valid for just [0] and that there was a relationship between M<SUP>E</SUP> and M according to the ply orientation.