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박철우,박석환,현주수,손응권 ( Cheol Woo Park,Suk Whan Park,Ju Soo Hyun,Eung Kwon Shon ) 한국화학공학회 1993 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.31 No.6
Maceral of coal and reflectance of vitrinite have been determined for the domestic and the imported coals. Also the relationship between chemical and optical properties of coal has been investigated. The maceral of coal samples is composed of both two varieties of collinite and vitrodetrinite in vitrinite group and three varieties of semifusinite, fusinite and inertodetrinite in inertinite group. Micrinite, gaphinite, mottlite and impregnite have been observed in the domestic coals. The degree of coalification for domestic coal is meta-anthracite and that of the imported coal is anthacite. As the macerals in vitrinite group is increased the amount of volatile matter and carbon increased. Also the amount of volatile matter and carbon decreased with increasing macerals in the inertinite group. As the maximum reflectance of vitrinite is increased both, the anisotropy and the carbon composition increased but, the volatile matter and hydrogen decreased.
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A Study on the Effect of Powder Forging for Cup-shaped Product
박철우,김영호,Jong-OkPark 한국정밀공학회 2002 International Journal of Precision Engineering and Vol.3 No.4
The purpose of this paper is comparing the forging effect according to the shape of preforms of cup shaped powder forging product, and extending the application of powder forging technology to more complicated cup-shaped products like pistons. In order to achieve this, preforms are provided by compacting, sintering, and machining to 5 different shapes, then forged to the final shape of products. The workability for sintered aluminium powder material was examined and confirmed its slope was 0.5 as known. Density and strain loci of forged products are also evaluated and compared. On the basis of the results, the most effective shape of preform was proposed. The preform for the piston which is 50mm in diameter was prepared and hot forged successfully to the final product.
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관상동맥용 Co-Cr 합금의 열처리 조건에 따른 신뢰성 분석에 관한 연구
박철우 한국신뢰성학회 2016 한국신뢰성학회 학술대회논문집 Vol.2016 No.11
관상동맥용 스텐트(stent)란 순환계 질환 치료에 널리 사용되는 금속망 형태의 장치로써, 1964년 Dotter 등에 의해 기능성이 없는 튜브형태로 도입되었고, 시술은 Stent 박사에 의해 최초로 소개되었다. 스텐트가 가장 많이 시술되고 있는 관상동맥 질환은 혈관 속의 콜레스테롤과 다른 지방질, 그리고 혈액 내의 다른 여러 성분이 발생한 플라그가 증가하게 되면 관상동맥의 협착을 일으키게 된다. 스텐트는 일반적으로 혈관협착을 해소 할 수 있도록 탄력적으로 확장되어야 하는데, 팽창방법에 따라 탄성을 지닌 금속재료 자체의 팽창력을 이용하는 자기확장형 스텐트와 외부 힘을 이용하는 풍선확장형 스텐트로 나눌 수 있다. 본 연구에서는 스텐트 삽입술에 많이 사용되고 있는 Co-Cr 합금(Cobalt-Chromium Alloy) 스텐트의 각 열처리 온도에 따른 스텐트의 복원력, 단축성, 경도, 탄성계수, 등의 기계적 특성에 대해서 신뢰성 분석하고자 한다.
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대기경계층 내에 놓인 실린더의 자유단 형상변화가 후류유동에 미치는 영향에 관한 연구
박철우,이상준,Park, Cheol-Woo,Lee, Sang-Joon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.1
The flow structure around the free end of a finite circular cylinder (FC) embedded in an atmospheric boundary layer (ABL) over open terrain was investigated experimentally with varying the free end shape. The experiments were carried out in a closed-return type subsonic wind tunnel. A finite cylinder with an aspect ratio (L/D) of 6 was mounted vertically on a long flat plate. The Reynolds number based on the cylinder diameter is about Re=7,500. The velocity fields near the FC free end were measured using the single-frame double-exposure PIV method. As a result, for the FC with a right-angled free end, there is a peculiar vortical structure, showing counter-rotating twin vortices near the FC free end. It is caused by the interaction between the entrained irrotational fluids from both sides of FC and the downwash flow from the FC free-end.
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