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주조용 B390 알루미늄합금의 조직과 기계적 성질에 대한 각종 주조법의 영향
한요섭,이호인,김성수,김정식 ( Yo Sub Han,Ho In Lee,Sung Su Kim,Jung Sik Kim ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.3
N/A The effects of casting processes-direct and indirect squeeze casting, permanent mold casting and die casting on the microstructure and mechanical properties were studied for the hypereutectic B390 aluminium alloy. The effects of T5 and T6 heat treatment were also examined. The direct and indirect squeeze casting showed no casting defects such as porosity and shrinkage were observed in permanent mold castings and die castings. The primary silicon phase was refined and homogeneously distributed in the order of indirect squeeze casting, deicasting, direct squeeze casting and permanent mold casting. Depletion of primary silicon phase in die casting surface was disappeared in indirect squeeze casting. Tensile strength of cast and heat treated specimens were increased in the order of direct squeeze casting, permanent mold casting, indirect squeeze casting and die casting. Hardness of indirect squeeze castings was larger than that of other castings. As indirect squeeze casting of B390 aluminium alloy, the time of T6 heat treatment to achieve high strength can be reduced.
AlSi7Mg 알루미늄 합금의 초정 구형화에 대한 주조조건의 영향
한요섭 ( Yo Sub Han ),이호인 ( Ho In Lee ),이재철 ( Jae Chul Lee ) 한국주조공학회 2003 한국주조공학회지 Vol.23 No.1
N/A Semisolid forming requires alloys with non-dendritic microstructure of the thixotropy. Recently, low pouring temperture method without stirring, i.e. liquidus casting has been found out new fabrication method of the semisolid metals. Effects of melt superheat and mold conditions on the globulization of primary Al of AlSi_7Mg alloy were investigated in gravity casting process without stirring. The microstructures of primary Al as function of melt superheat and mold temperature show globular, rosette and dendritic shapes. The conditions for globular microstructure of primary Al were low melt superheat < 35 K and low mold temperature < 500 K. The thermal conditions for globular microstructure of primary Al were undercooled melt at early solidification stages and slow cooling < 0.6 K/s. It was found that the initial microstructure was maintained throughout the solidification and the globules of primary Al can be obtained by high nucleation of fine and spherical nuclei due to enhanced undercooling of melt.
고강도 황동 , 알루미늄 청동 및 인청동합금의 용탕단조 조직과 기계적 성질에 관한 연구
한요섭(Yo Sub Han),이호인(Ho In Lee) 한국주조공학회 1999 한국주조공학회지 Vol.19 No.6
The microstructures and mechanical properties of high strength yellow brass, Al bronze and Sn bronze alloys fabricated by gravity die casting and squeeze casting were investigated. A rapid cooling of casting was enhanced by pressure applied during solidification of Cu alloys, the cooling rate of casting was more great for high strength yellow brass alloy than other Cu alloys. Grain size and phases of the squeeze cast products become refined to 1/2 level compared to gravity die castings. Squeeze cast Al bronze and high strength yellow brass has about 10-20% higher yield and tensile strength and slighter decreased or nearly same elongation, compared to gravity die cast ones. Sn bronze has nearly same strength and hardness, but shows increased in elongation, compared to gravity die cast ones. (Received November 1, 1999)
유승목,한요섭,이호인,홍준표 ( Seung Mok Yoo,Yo Sub Han,Ho In Lee,Chun Pyo Hong ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.6
N/A A basic heat flow model has been developed to estimate the heat transfer coefficient at the casting/mold interface during squeeze casting. Based on the measured temperature profiles in squeeze casting of Al-4.5%Si alloy, heat transfer coefficients which vary with time were calculated by numerical method. The influences of the load and the amount of fraction solid on the heat transfer coefficient have also been studied. Using the calculated heat transfer coefficient two dimensional solidification analysis in the squeeze casting process was carried out by the finite difference method, and the results were in good agreement with the experiments. It may be concluded that heat flow analysis in the squeeze casting process with accurate heat transfer coefficient at the casting /mold interface is important for a proper design of cooling in die and finally for improving productivity and die life as well.
김진수,안재영,한요섭,이호인,홍준표 ( Jin Soo Kim,Jae Young Ahn,Yo Sub Han,Ho In Lee,Chun Pyo Hong ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.3
N/A Research in heat transfer and solidification commonly involves experimentation and mathematical modeling with associated numerical analysis and computation. Inverse problems in heat transfer are part of this paradigm. During the solidification of metal casting, an interfacial heat transfer resistance exists at the boundary between the casting and the mold, and this heat transfer resistance usually varies with time. In the case of the squeeze casting the contact heat transfer resistance is decreased by pressure and ideal contact is almost accomplished. In the present work, heat transfer coefficient, which is inverse value of the heat transfer resistance, was used for convenience. A numerical technique, Non-Linear Estimation has been adopted for calculation of the casting/mold interfacial heat transfer coefficient during the squeeze casting process. In this method, the measured temperature data from experiment were used. The computational results were applied to the analysis of heat transfer and solidification.
용탕단조 Al-Cu-Si-Mg 합금의 열처리시 제2응고상의 분해거동
김유찬,김도향,한요섭,이호인 ( Yu Chan Kim,Do Hyang Kim,Yo Sub Han,Ho In Lee ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.6
N/A The dissolution behavior of secondary solidification phases in squeeze cast Al-3.9wt%Cu-1.5wt%Si-1.0wt%Mg has been studied using a combination of optical microscope, image analyzer, scanning electron microscope(SEM), energy dispersive spectrometer(EDS), X-ray diffractometer(XRD) and differential thermal analyzer (DTA). Special emphasis was placed on the investigation of the effects of the nonequilibrium heat treatment on the dissolution of the second solidification phases. Ascast microstructure consisted of primary solidification product of α-Al and secondary solidification products of Al₂Cu, Mg₂Si and Al₂CuMg. Equilibrium and non-equilibrium solution treatments were carried out at the temperatures of 495˚C, 502˚C and 515˚C for 3 to 5 hours. The amount of the dissolved secondary phases increased with increasing solution treatment temperature, for example, area fractions of Al₂Cu, Mg₂Si and Al₂CuMg were approximately 0%, 1.6% and 4.2% after solution treatment at 495˚C for 5 hours, and were approximately 0%, 0.36% and 2% after solution treatment at 515˚C for 5hours. The best combination of tensile properties was obtained when the as-cast alloy was solution treated at 515˚C for 3hours followed by aging at 180˚C for 10 hours. Detailed DTA and TEM study showed that the strengthening behavior during aging was due to enhanced precipitation of the platelet type fine θ` phase. (Received August 23, 1997)
조다정(Da-Jung Cho),한요섭(Yo-Sub Han) 한국정보과학회 2011 한국정보과학회 학술발표논문집 Vol.38 No.2A
우리는 DNA코드와 관련된 정규 언어의 부분 집합 언어를 살펴본다. 그 중에서도 DNA코드 중 회선(involution) 특성인 Θ-strict Θ-infix와 관련하여 주어진 정규 언어가 회선 성질을 만족하는지 정규회선 코드인지를 판단하는 알고리즘을 제안한다. 제안된 방법은 주어진 정규 언어에 대한 유한 인식기와 이를 회선 연관으로 설계한 유한 인식기의 상태쌍(state-pair) 그래프를 바탕으로 실행한다.
UCC 비디오 서비스에서 소셜 네트워크를 통한 사용자 신뢰도 도출
조현철(Hyunchul Cho),한요섭(Yo-Sub Han),김래현(Laehyun Kim) 한국HCI학회 2009 한국HCI학회 학술대회 Vol.2009 No.2
최근 들어 사용자들이 직접 저작하고 이를 공유하는 UCC(User Created Content)가 급격히 증가하고 있다. 이에 따라 방대한 UCC를 사용자들에게 효과적으로 제공하기 위하여, 질이 낮은 UCC를 필터링하는 알고리즘이나 UCC의 검색 또는 추천 알고리즘에 대한 연구가 많이 진행되고 있다. 본 논문에서는 사용자에게 UCC 컨텐츠를 제공할 때 컨텐츠의 품질을 추정할 수 있는 요소로 사용자 신뢰도를 제안한다. 이를 위해 먼저 UCC 컨텐츠 제공 서비스 상에서 사용자 간의 소셜활동을 기반으로 소셜 네트워크를 구축하고, 사용자 신뢰도를 계산하기 위한 소셜 활동 정보를 추출한다. 그리고 소셜 네트워크를 통해 사용자 신뢰도를 계산하며, 다양한 소셜 정보 요소를 적용할 수 있는 확장 가능한 알고리즘을 제안한다. Recently user-generated contents have been drastically increased. In this paper, we introduce the user reputation which can be used to evaluate quality of the content they created. First we have composed a social network that is based on user activity. And we have developed the algorithm to evaluate the users' reputation using this social network.