일방향응고시킨 Al-CuAl2 공정복합재료의 열적안정성에 관한 연구

홍영환,홍종휘 ( Young Hwan Hong,Jong Hwi Hong ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.5

N/A The effect of thermal cycling and isothermal exposure on the high temperature microstructural stability of unidirectionally solidified Al-CuAl₂eutectic composite has been studied. A coarsening procedures of lamellar eutectic structures were initiated at growth fault region because of diffusion through low angle boundary at this region. It was considered that thermally induced residual stresses produced by thermal cycling were high enough to increase the dislocation density in Al-rich matrix phase. However, it was also considered that dislocations generated by these high thermal stresses were annihilated at high temperature by stress relaxation. Consequently, the thermal cycling up to 1440 cycles between 20 and 520℃ did not affect the microstructural stability.

일방향응고시킨 Al-CuAl2 공정복합재료의 인장성질

홍영환,홍종휘 ( Young Hwan Hong,Jong Hwi Hong ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.6

N/A The effect of interlamellar spacing on tensile behavior and fracture mode at high temperatures has been studied for unidirectionally solidified Al-CuAl₂eutectic composite. The tensile properties at room temperature in Al-CuAl₂eutectic composite improved as the interlamellar spacing decreased due to the constraint effects of closely spaced lamellae, while the opposite behavior was observed at high temperatures due to the annihilation of the constraint effects by phase boundary sliding. The Al-CuAl₂eutectic composite exhibited brittle fracture mode below the temperature at which the reinforcing phase softened but ductile fracture mode above the temperature.

오스템퍼링 열처리한 구상흑연주철의 충격인성에 미치는 Ni 과 Mo 첨가의 영향

홍영환,홍종휘 ( Young Hwan Hong,Jong Hwi Hong ) 한국주조공학회 1989 한국주조공학회지 Vol.9 No.2

N/A The microstructural characteristics of ductile cast iron austempered for various times are characterized and correlated to Charpy impact toughness. The desired matrix structure of austempered ductile cast iron consists of a two-phase mixture of carbide-free bainitic ferrite and austenite. During austempering, bainitic transformation can be described as a too-stage reaction : 1) austenite decomposition to bainitic ferrite and carbon-enriched austenite, followed by 2) decomposition of carbon-enriched sustenite to further ferrite and carbide. Therefore, excessive austempering produces a sharp drop in impact toughness and a fracture mode transition from ductile tearing to brittle quasi-cleavage fracture by a carbide formation. Delaying the embrittling reaction by addition of Ni and Mo should allow a greater latitude in austempering time. However, the onset of the embrittling reaction cannot be detected metallographically. By the way, interruption of the austempering reaction by quenching prematurely will result in a formation of martensite. This also reduces impact toughness.

ZnO와 MnO₂를 동시에 첨가한 (K_0.5Na_0.5)NbO₃ 세라믹스의 압전 특성에 대한 연구

홍영환,박영석,정광휘,조성열,이재신,Hong, Young Hwan,Park, Young-Seok,Jeong, Gwang-Hwi,Cho, Sung Youl,Lee, Jae-Shin 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.4

We investigated the sintering behavior and piezoelectric properties of lead-free $(K_{0.5}Na_{0.5})NbO_3$ ceramics co-doped with excess 0.01 mol ZnO and x mol $MnO_2$, where x was varied from 0 to 0.03. Excess $MnO_2$ addition was found to retard the grain growth and densification during sintering. However, 0.005 mol $MnO_2$ addition improved the piezoelectric properties of 0.01 mol ZnO added $(K_{0.5}Na_{0.5})NbO_3$ ceramics. The planar mode piezoelectric coupling coefficient, electromechanical quality factor, and piezoelectric constant $d_{33}$ of 0.01 mol ZnO and 0.005 mol $MnO_2$ added specimen were 0.40, 304, and 214 pC/N, respectively.

IPLAN을 이용한 ULTC와 전압안정도 해석

홍영환(Young-Hwan Hong),백영식(Young-Sik Baek) 대한전기학회 2004 대한전기학회 학술대회 논문집 Vol.2004 No.11

OODB와 GUI를 이용한 전력계통 고장해석

홍영환(Hong Young Hwan),박지호(Park Ji Ho),김정년(Kim Jung Nyun),백영식(Baek Young Sik) 대한전기학회 2003 대한전기학회 학술대회 논문집 Vol.2003 No.11

업체탐방기 : 형진열처리

홍영환 ( Young Hwan Hong ) 한국열처리공학회 2003 熱處理工學會誌 Vol.16 No.1

자유주의에서의 심의민주주의

홍영환 ( Young Hwan Hong ) 한국윤리교육학회 2007 윤리교육연구 Vol.0 No.13

현대 민주주의는 자유민주주의이고, 자유주의는 민주주의가 작동하는 정치적인 기본적 틀이다. 이 틀은 개인에게 국가, 공동체, 혹은 이웃으로부터 간섭 없이 자유와 평등한 대우 및 인권을 확보해 준다. 최근 개인에 대한 관심과 개인 권리에 초점을 맞춘 자유민주주의의 실행 능력에 의문이 제기되고 있다. 본고는 현대 민주주의를 문제점을 검토하여 자유주의적 심의민주주의의 시각에서 그것을 해결할 수 있는 민주시민성을 논의해 보려 하였다. 현대 민주주의의 문제점은 유권자들의 실질적인 참여 부족에 따른 민주주의의 결손과 대표의 실패, 정치적 부정부패로 인한 정치적 소외와 무관심의 팽배와 정부에 대한 불신에 있다. 이것은 심화되는 시민들 사이의 불일치와 차이를 수렴할 수 있는 유효한 심의에 필요한 민주시민성의 부족 때문이라고 여겨진다. 자유주의의 기본원칙은 개인 우위, 도덕적 개인주의, 도덕적 자율성, 정치적 불간섭, 그리고 정치적 중립성이다. 이러한 자유주의는 좋은 삶의 문제에 관여하지 않는다. 자유민주주의는 시민의 덕성을 계발하거나 선을 추구하지 않고, 개인들이 그들의 삶에 책임지고 자기 다름대로 자신의 선을 추구할 수 있는 사회적 조건을 확립하여 사적 이해관계와 선호가 작용하는 정치적 장치와 제도에 초점을 맞추는 당사자 민주주의이다. 자유주의적 심의민주주의는 시민들 간의 대화, 의사소통, 토론, 그리고 심의를 통하여 개인들의 선호를 계속 변화시키면서 합의된 집단적 의사를 형성하려는 것이다. 이런 심의 민주주의는 시민이 직접 심의에 참여하는 참여민주주의이다. 자유주의자는 공적 이성과 심의의 역할을 강조한다. 자유주의적 심의민주주의는 상호 자제와 제한으로 공적 이성이 보증된다는 것이다. 자유주의적 심의민주주의에서의 심의에도 덕성이 필요하다. 그러한 덕성에는 대화능력, 성실성, 정직성, 개방성과 상호성, 그리고 책임성 등이 있다. 이러한 덕성은 자유주의적 심의민주주의에서 효율적인 심의에 필요한 자율적인 민주적 시민성으로 함양되어야 한다. 담화는 표현하는 것과 받아들이는 것, 말하는 것과 듣는 것, 그리고 감정이입의 태도로 함양되어야 한다. 성실성은 공정하게 일을 처리하고 감정이입의 태도로 참여하게 되어야한다. 정직성은 이해관계나 선호가 아닌 이성에 근거하여 증거에 따라 심의해야 한다. 개방성과 상호성은 자비의 마음가짐과 관용정신으로 심의에 참여하는 것이다. 요컨대 민주적 시민성은 자유주의적 심의민주주의를 공고화하여 현대 민주주의의 문제점인 참여를 강화하고 신뢰를 회복할 것이다. In modern democracy, we are faced with a number of problems: lack of political participation, political corruption, isolation, and indifference, distrust of the government. The purpose of this paper is to solve these problems by democratic citizenship in the framework of deliberative democracy. The problems of modern democracy derive from one of the principles of liberal democracy that the government should not involve in people`s life. Therefore, the government has tried not to inculcate virtue in citizens nor to cultivate goodness. Instead, it has tried to accommodate the citizen`s personal interest and preference. As a result, modern democracy has turned into adversary democracy. In the perspective of liberal democracy, comprehensive democracy is interested in justice as a stakeholder of liberty and rationalism; political democracy enables a number of agreements overlapping based on relevant pluralistic principles. However, these principles oppose does not believe in the authenticity of political order that depends on citizen`s agreement in liberal democracy. In order to secure political bond and trust, we need to establish collective power built by citizens who value mutual agreement over individual interest. Also, for effective liberalism, we need communication, integrity, honesty, openness and mutuality, and responsibility. Such democratic citizenship should be based not on simple virtue but on deliberative virtue. The citizen should have democratic citizenship so that they can work with impartiality and empathy. They are also expected to have honesty that is based on public reason not on individualistic interest and preference. Further, they will have openness and reciprocity built upon generosity and goodness. In sum, through this democratic citizenship, we will be able to fortify deliberative democracy and restore trust.

STD 11강의 마모특성에 미치는 서브제로처리의 영향

홍영환 ( Young Hwan Hong ),송건 ( Keun Song ) 한국열처리공학회 2003 熱處理工學會誌 Vol.16 No.3

N/A Effects of cryogenic treatment and tempering temperature on the amount of retained austenite, hardness and wear properties has been investigated using alloy tool steel, STD 11. Cryogenic treatments were performed at the temperatures of -100℃, -150℃ and -196℃, and tempering were performed at 200℃ and 530℃. It was shown that lower hardness value was obtained on high temperature (530℃) tempering even after cryogenic treatment. And retained austenite was not entirely transformed to martensite after cryogenic treatment even at -196℃, which was not consistent with the belief that -80℃ was sufficient to entirely transform any austenite retained in the quenched microstructure. Austenite retained in cryogenic treated condition was completely transformed to martensite only after tempering at 530℃. As far as wear test conditions in this investigation, it was found that cryogenic treatments improved the sliding wear resistance, but improvement of wear resistance was not directly related with retained austenite contents. And it was found that predominent wear mechanisms of STD11 steel were oxidation wear and adhesive wear in sliding wear conditions.

일방향응고시킨 Ni 기 (基) 초내열 (超耐熱) 공정복합재료에 관한 연구

이주홍,홍영환,홍종휘 ( Joo Hong Lee,Young Hwan Hong,Jong Hwi Hong ) 한국주조공학회 1988 한국주조공학회지 Vol.8 No.4

N/A The effect of interlamellar spacing on microstructural stability at high temperature was studied for unidirectionally solidified ternary Ni / Ni₃ Al-Ni₃ Nb and binary Ni-Ni₃Nb eutectic composite. The interlamellar spacing of both alloy systems were varied with the growth rate according to λ²R=constant relationship. As a result of isothermal heat treatments at high temperature it was considered that coarsening of lamellar structure was due to concentration gradient between the tip with a relatively small radius of curvature and the side of the thick lamellae with a larger radius of the opposite sign. Fault density was increased as the interlamellar spacing decreased. Therefore it is also considered that the higher coarsening rate of the specimen with the smaller interlamellar spacing was due to higher fault density. And the diference of coarsening rate between Ni / Ni₃Al-Ni₃Nb and Ni-Ni₃Nb eutectic composites was not observed when the interlamellar spacing was similar in size. This means that the presence of γ` in γ/γ` -δ eutectic had no b arrier effect to diffusion through the γ matrix.