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Bi2212/Ag 선재의 초전도 특성에 대한 열처리의 영향
김상철,하동우,송규정,오상수,이남진,한일용,오재근,손호상,Kim, S.C.,Ha, D.W.,Song, K.J.,Oh, S.S.,Lee, N.J.,Han, I.Y.,Oh, J.G.,Sohn, H.S. 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
We have fabricated double stacked 385 filamentary Bi2212/Ag round wires which have different Ag ratios. The wires have been heat-treated at the maximum temperature($T_{max}$) of $882{\sim}896^{\circ}C$ for 0.5 h. Effect of heat treatment on critical current density and critical temperature on Bi2212/Ag round wires has been studied. Critical current density of the wire heat -treated at $890^{\circ}C$ showed 206,250 $A/cm^2$ at 4.2 K, 0 T and critical temperature of the wire was 83 K. Microstructure of the wires also has been studied via optical microscopy and SEM.
InP/InGaAs/InP 분포귀환형 회절격자 위에 성장된 InAs/InAlGaAs 양자점의 구조적.광학적 특성
곽호상,김진수,이진홍,홍성의,최병석,오대곤,조용훈,Kwack, H.S.,Kim, J.S.,Lee, J.H.,Hong, S.U.,Choi, B.S.,Oh, D.K.,Cho, Y.H. 한국진공학회 2006 Applied Science and Convergence Technology Vol.15 No.3
금속유기화학증착기 (metal-organic chemical vapor deposition)를 이용하여 분포귀환형 (distributed feed back) InP/InGaAs/InP 회절격자 구조를 제작하고 원자력간현미경 (atomic force microscopy)과 주사전자현미경 (scanning electron microscopy) 실험을 통해 표면 및 단면을 분석하였다. 그 위에 분자선증착기(molecular beam epitaxy)법을 이용하여 자발형성 (self-assembled) InAs/InAlGaAs 양자점 (quantum dot)을 성장하고, 광학적 특성을 온도변화 광여기 발광 (photoluminescence)으로 회절격자 구조 없이 성장한 양자점 시료와 비교 분석하였다. 회절격자의 간격 대비 폭의 비가 약 30%인 InP/InGaAs/InP 회절격자가 제작되었으며, 그 위에 성장된 양자점의 경우 상온 파장이 1605 nm에서 PL이 관찰되었다. 이는 회절격자 없이 같은 조건에서 성장된 시료의 상온 파장인 1587 nm 보다 장파장에서 발광하였으며, 회절격자의 영향으로 양자점 크기가 변하였음을 조사하였다. We fabricated the distributed feedback (DFB) InP/InGaAs/InP grating structures on InP (100) substrates by metal-organic chemical vapor deposition, and their structural properties were investigated by atomic force microscopy and scanning electron microscopy. Self-assembled InAs/InAlGaAs quantum dots (QDs) were grown on the InP/InGaAs/InP grating structures by molecular beam epitaxy, and their optical properties were compared with InAs/InAlGaAs QDs without grating structure. The duty of the grating structures was about 30%. The PL peak position of InAs/InAlGaAs QDs grown on the grating structure was 1605 nm, which was red-shifted by 18 nm from that of the InAs/InAlGaAs QDs without grating structure. This indicates that the formation of InAs/InAlGaAs QDs was affected by the existence of the DFB grating structures.
초정밀가공기용 타원 진동절삭 공구대의 설계 및 성능실험
이대희(D. H. Lee),김호상(H. S. Kim),김의중(E. J. Kim),오창진(C. J. Oh) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
This paper presents the design and test of elliptical vibration assisted cutting tool post. It is actuated by two piezoelectric actuators which are connected to the moving part through the elastic hinge with its role of imposing the preliminary pressures. These two actuators are located at right angles so that the resulting tool tip moves like a two-dimensional ellipse. Also, the tool post is activated within the region of linear actuation in order to overcome the distorted elliptical motion. For the precise measurement of the displacement of the tool tip, three-dimensional experimental apparatus was designed and the strokes of the tool post in major and minor axes were measured. The results show that the tool post can produce the variety of vibration locus from a circle with a radius of 5 ㎛ to an ellipse with a major axis, a = 10 ㎛, and a minor axis, b = 2.5 ㎛.
355nm UV 레이저를 이용한 AZ5214와 SU-8 포토레지스트 어블레이션에 관한 연구
오재용,신보성,김호상,Oh, J.Y.,Shin, B.S.,Kim, H.S. 한국레이저가공학회 2007 한국레이저가공학회지 Vol.10 No.2
We have studied a laser direct writing lithography(LDWL). This is more important to apply to micro patterning using UV laser. We demonstrate the possibility of LDWL and construct the fabrication system. We use Galvano scanner to process quickly micro patterns from computer data. And laser beam is focused with $F-{\theta}$ lens. AZ5214 and SU-8 photoresist are chosen as experimental materials and a kind of well-known positive and negative photoresist respectively. Laser ablation mechanism depends on the optical properties of polymer. In this paper, therefore we investigate the phenomenon of laser ablation according to the laser fluence variation and measure the shape profile of micro patterned holes. From these experimental results, we show that LDWL is very useful to process various micro patterns directly.
광섬유 고속생산용 헬륨 주입식 유리섬유 냉각공정에 대한 열유동 해석
오일석(I.-S. Oh),김동주(D. Kim),곽호상(H.S. Kwak),김경진(K. Kim) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
In manufacturing optical fibers, the process starts with the glass fiber drawing from the heated and softened silica preform in the furnace, and the freshly drawn glass fiber is still at high temperature when it leaves the glass fiber drawing furnace. It is necessary to cool down the glass fiber to the ambient temperature before it then enters the fiber coating applicator, since the hot glass fiber is known to cause several technical difficulties in achieving high quality fiber coating. As the fiber drawing speed keeps increasing a current manufacturing of optical fibers requires a dedicated cooling unit with helium gas injection. A series of three-dimensional flow and heat transfer computations are carried out to investigate the effectiveness of fiber cooling in the fiber cooling unit. The glass fiber cooling unit is simplified into the long cylindrical enclosure at which the hot glass fiber passes through at high speed, and the helium is being supplied through several injection slots of rectangular shape along the cooling unit. This study presents and discusses the effects of helium injection rates on the glass fiber cooling rates.
오일석(I.-S. Oh),김동주(D. Kim),우마로프 알리세르(A. Umarov),곽호상(H.S. Kwak),김경진(K. Kim) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.4
A modern optical fiber manufacturing process requires the sufficient cooling of glass fibers freshly drawn from the heated and softened silica preform in the furnace, since the inadequately cooled glass fibers are known to cause improper polymer resin coating on the fiber surface and to adversely affect the product quality of optical fibers. In order to greatly enhance the fiber cooling effectiveness at increasingly high fiber drawing speed, it is necessary to use a dedicated glass fiber cooling unit with helium gas injection between glass fiber drawing and coating processes. The present numerical study features a series of three-dimensional flow and heat transfer computations on the cooling gas and the fast moving glass fiber to analyze the cooling performance of glass fiber cooling unit, in which the helium is supplied through the discretely located rectangular injection holes. The air entrainment into the cooling unit at the fiber inlet is also included in the computational model and it is found to be critical in determining the helium purity in the cooling gas and the cooling effectiveness on glass fiber. The effects of fiber drawing speed and helium injection rate on the helium purity decrease by air entrainment and the glass fiber cooling are also investigated and discussed.
355㎚ UV 레이저를 이용한 AZ5214와 SU-8 포토레지스트 어블레이션에 관한 연구
오재용(J. Y. Oh),신보성(B. S. Shin),김호상(H. S. Kim) 한국레이저가공학회 2007 한국레이저가공학회지 Vol.10 No.2
We have studied a laser direct writing lithography(LDWL). This is more important to apply to micro patterning using UV laser. We demonstrate the possibility of LDWL and construct the fabrication system. We use Galvano scanner to process quickly micro patterns from computer data. And laser beam is focused with F-θ lens. AZ5214 and SU-8 photoresist are chosen as experimental materials and a kind of well-known positive and negative photoresist respectively. Laser ablation mechanism depends on the optical properties of polymer. In this paper, therefore we investigate the phenomenon of laser ablation according to the laser fluence variation and measure the shape profile of micro patterned holes. From these experimental results, we show that LDWL is very useful to process various micro patterns directly.