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Chitosan-collagen sponge를 이용한 토끼 슬관절 골연골 결손의 치료
임세환,정상인,장의찬,손태일 한국공업화학회 2001 한국공업화학회 연구논문 초록집 Vol.2001 No.-
관절연골의 결손에 대한 여러 종류의 재생 방법이 알려지고 있다. 그러나 지금까지 알려진 방법은 초자양 연골을 만드는 대신에 섬유연골로 재생이 되었기 때문에 좋지 못한 결과를 얻고 있다. 본 연구자들은 관절연골의 ECM(extracellulor matrix)의 하나인 GAG(glycoaminoglycan)과 비슷한 화학구조를 가진 chitosan을 이용하여 matrix를 제작하였으며, 그 matrix는 chitosan과 collagen(type I)을 blend 하여 sponge형태 하였다. 그리고 chitosan-collagen sponge의 응용 가능성을 검토하기 위해서 토끼 슬관절에 골연골 결손을 인위적으로 만들어 관절 연골의 재생을 시도하였다. chitosan-collagen sponge는 in vitro 실험에 있어서 연골 세포가 sponge내에 부착되었으므로 세포에 대한 매개체로 사용될 수 있음을 시사하고 있다. 또한 가토의 슬관절에 골 연골 결손을 만들어 chitosan-collagen sponge를 이식 후 12주간 관찰한 결과 대조군에 비하여 계속적으로 관절연골과 유사한 결과를 나타내었다. 또한 연골세포가 sponge 위로 자라 들어 와서 초자양 연골을 생성하면서 주위 관절연골 및 연골하 조직과의 유합된 결과를 보였다. sponge 주위에 면역 거부반응을 보이지 않는 것으로 보아 골 연골 결손의 치료에 응용할 수 있을 것으로 사료된다.
다꾸찌 실험계획법을 이용한 와이어 방전가공의 최적 가공조건 선정
임세환,김주현,이위로,박주승 한국공작기계학회 2002 한국공작기계학회 추계학술대회논문집 Vol.2002 No.-
The machining parameters for the wire electrical discharge machining(WEDM), including no load voltage, pulse-on time, pulse-off time, wire tension, water flow rate, offset, etc. should be chosen properly so that a better performance can be obtained. An optimum selection of machining parameters relies heavily on the operators technologies and experience. This study presents a method by means of Taguchi method to select optimal machining parameter combination for an cutting speed or surface roughness. Experimental results demonstrate that the machining models are appropriate and the derived machining parameters satisfy the real requirements in practice.
플라즈마분자선에피탁시법을 이용한 알루미늄 플럭스 변화에 따른 질화알루미늄의 성장특성
임세환,이효성,신은정,한석규,홍순구,Lim, Se Hwan,Lee, Hyosung,Shin, Eun-Jung,Han, Seok Kyu,Hong, Soon-Ku 한국재료학회 2012 한국재료학회지 Vol.22 No.10
We have grown AlN nanorods and AlN films using plasma-assisted molecular beam epitaxy by changing the Al source flux. Plasma-assisted molecular beam epitaxy of AlN was performed on c-plane $Al_2O_3$ substrates with different levels of aluminum (Al) flux but with the same nitrogen flux. Growth behavior of AlN was strongly affected by Al flux, as determined by in-situ reflection high energy electron diffraction. Prior to the growth, nitridation of the $Al_2O_3$ substrate was performed and a two-dimensionally grown AlN layer was formed by the nitridation process, in which the epitaxial relationship was determined to be [11-20]AlN//[10-10]$Al_2O_3$, and [10-10]AlN//[11-20]$Al_2O_3$. In the growth of AlN films after nitridation, vertically aligned nanorod-structured AlN was grown with a growth rate of $1.6{\mu}m/h$, in which the growth direction was <0001>, for low Al flux. However, with high Al flux, Al droplets with diameters of about $8{\mu}m$ were found, which implies an Al-rich growth environment. With moderate Al flux conditions, epitaxial AlN films were grown. Growth was maintained in two-dimensional or three-dimensional growth mode depending on the Al flux during the growth; however, final growth occurred in three-dimensional growth mode. A lowest root mean square roughness of 0.6 nm (for $2{\mu}m{\times}2{\mu}m$ area) was obtained, which indicates a very flat surface.
Laser-assisted machining에서 질화규소 시편의 표면온도와 절삭특성에 관한 연구
임세환,이제훈,신동식,김종도,김주현 한국레이저가공학회 2009 한국레이저가공학회지 Vol.12 No.1
In laser-assisted machining (LAM), laser beam is used to locally increase the temperature of a workpiece and thus to enhance the machinability. In order to set the temperature of the material removal area of a workpiece at an optimal value, process parameters, such as laser power, feed rate, and rotational velocity, have to be carefully controlled. In this work, the effects of laser power and feed rate on the temperature distribution of a silicon nitride rotating at a constant velocity were experimentally investigated. Using a pyrometer, temperatures at various locations of the silicon nitride were measured both in circumferential and axial directions. The measured temperatures were fitted to a quadratic equation to approximate the temperature at the cutting location. The machining results showed that cutting force and tool wear were decreased when the temperature at the cutting location was increased.
임세환 대한영상의학회 1988 대한영상의학회지 Vol.24 No.6
Nonvisualization of gallbladder in cholescintigraphy has been established to be a major and reliable finding for acute cholecystitis. A rim of increased pericholecystic hepatic activity (PCHA or Rim sign) in conjunction with gallblader non-visualization was reported to be secondary sign of acute cholecystitis. To determine the frequency and significance of the pericholecystic hepatic activity we evaluated 217 cholescin-tigram in patients clinically suspeted of acute cholecystitis. After brief review of cholescintigraphic findings of acute cholecystitis the significance of the Rim sign is described. 1) The frequency of the Rim sign in surfically proved acute cholecystitis including gallbladder empyema and/or pericholecystic abscess (7/22) and in noncomplicated acute cholecystitis (3/45) was 31.8% , 6.6% respectively. The present study suggests that the Rim sign appear to indicate relatively high incidence of complicated acute cholecystitis and effort should be made observing the presence of the Rim sign in cholescintigraphy.
임세환,송춘삼,홍석관,강정진,김주현 한국공작기계학회 2007 한국공작기계학회 추계학술대회논문집 Vol.2007 No.-
A plane strain finite element model is developed to simulate turning with continuous chip formation using adaptive remeshing during the thermal-mechanical coupled analysis. Comparisons between the experimental and simulation results for cutting forces are performed to validate FE analysis results. Influences of machining parameters such as depth of cut, cutting speed and feed rate on cuting force and shear angle are analyzed by Taguchi method. The more depth of cut and feed rate result in the increase of cutting forces, but the rates of increase are decrease due to the larger shear angle. As the cutting speed increases, von Mises stress of workpiece near the tool tip decreases because the strength of specimen decreases at high temperature above 500℃. This thermal effect on cutting force is negligible because the affected area is very localized and the average values of von Mises stress in the shear plane are the same among the diverse cutting parameters.
제목 고밀도 태양광 연계 배전 계통에서의 OLTC 동작 횟수 저감을 위한 협조 전압 제어
임세환,김경훈 대한전기학회 2022 전기학회논문지 Vol.71 No.8
This paper proposed coordinated voltage control between Photovoltaics (PVs) and on load tap changer (OLTC) for reducing the number of operation of OLTC based on PV and load forecasting. Nowadays, PV compensates the reactive power for improving voltage problems such as voltage violation and voltage fluctuation due to the high PV penetration in distribution system. Therefore, the direction of current of system is different from the conventional direction. Due to this reason, there is a probability that the number of operation of OLTC using line drop compensator method has increased than conventional system. This problem causes the malfunction of OLTC and financial burden for system operator. Also reactive power compensation of PV increases the line loss of the system which can also increase the financial burden of system operator. To solve these problems, proposed coordinated control which is realized by optimization algorithm for line loss reduction with constraints of OLTC for reducing the number of operation of OLTC based on forecasted data is proposed