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실리콘 폴리우레아 도료 마찰저항 저감성능의 실험적 연구
이인원(Inwon Lee),권상훈(Sang Hoon Kwon),장호윤(Ho Yun Jang),전호환(Ho Hwan Chun) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
A novel Silicone-Polyurea paint has been newly developed and introduced for the antifouling marine paint. This paint is featured with such advantages as the shock-proofness and the scratch-proofness. In addition, the roughness of the resulting paint film is found to be much less than the conventional SPCAF paints. Ultra fast drying ability enables the formation of very thick paint film, e. g., 500㎛. The Silicone-Polyurea resin exhibits similar material behavior as that of silicone rubber in terms of hardness and elongation. This material is regarded as a potent candidate to substantiate the compliant coating for the skin friction reduction. This study aims at the assessment of the drag reducing efficiency of the silicone-polyurea paint.
점탄성 소재를 이용한 난류경계층의 마찰저항 저감의 실험적연구
이인원(Inwon Lee),전호환(Ho Hwan Chun),이호상(Ho Sang Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
A specially designed flat plate was mounted vertically over the axial line in the wind tunnel of the Aerospace Department of the Pusan National University. The measurements were performed in velocity range from 15 to 60 ㎧. Strain balances were mounted in the trailing part of the plate to measure the skin friction drag over removable insertions of 0.55×0.25m2 size. A set of the insertions was designed and manufactured: 3 ㎜ thick polished metal surface and three compliant surfaces. The compliant surfaces were manufactured of a silicone rubber Silastic® S2. To modify the viscoelastic properties of the rubber, its composition was varied. The velocity profiles measured at all four surfaces under study are self-similar. The strong compliant coating achieved 5% drag reduction within a velocity range 20~40 ㎧ while standard and weak coatings increased drag reduction.
유연벽면 점탄성 소재 배합비와 저항저감 효과의 상관관계
이인원(Inwon Lee),안남현(Nam Hyun An) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.6
A specially designed flat plate was mounted vertically over the axial line in the wind tunnel of the Pusan National University. Strain balances were mounted in the trailing part of the plate to measure the skin friction drag over removable insertions of 0.55´0.25㎡ size. A set of the insertions was designed and manufactured: 3 ㎜ thick polished metal surface and three compliant surfaces. The compliant surfaces were manufactured of a silicone rubber Silastic<SUP>®</SUP> S2 (Dow Corning company). To modify the viscoelastic properties of the rubber, its composition was varied: 90% rubber + 10% catalyst (standard), 92.5% + 7.5% (weak), 85% + 15% (strong). Modulus of elasticity and the loss factor were measured accurately for these materials in the frequency range from 40 ㎐ to 3 ㎑. The aging of the materials (variation of their properties) for the period of one year was documented as well. Along with the drag measurement using the strain balance, velocity and pressure were measured for different coating. The strong compliant coating achieved 5% drag reduction within a velocity range 20~40 m/s while standard and weak coatings increased drag reduction.
이인원(Inwon Lee),안남현(Nam Hyun An) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.5
A novel technique to measuret of viscoelastic properties of polymers is proposed to investigate complex Poisson’s ratio as a function of frequency. The forced vibration responses for the samples under the normal and the shear deformation are to be measured with varying load masses. The measured data were used to obtain the viscoelastic properties of the material based on an accurate 2D numerical deformation model of the sample. The 2D model enabled us to exclude data correction by the empirical form factor used in 1D model. Comprehensive measurements of viscoelastic properties of two slightly varied silicone RTV rubber (Silastic<SUP>®</SUP> S2) compositions were performed. Standard composition (90% PDMS polymer + 10% catalyst) and modified composition (92.5% polymer + 7.5% catalyst) were tested in temperature range from 30℃ to 70℃. Shear modulus, modulus of elasticity, loss factor, and both the real and the imaginary parts of the Poisson’s ratio were determined for frequencies from 50 to 400Hz in the linear deformation regime (at relative deformations 10<SUP>-4</SUP> ~10<SUP>-3</SUP>).
압력변동 및 속도장 조건부 평균에 의한 후향계단 유동의 응집구조
이인원(Inwon Lee),성형진(Hyung-Jin Sung),이인섭(In-Seop Lee) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.9
Time-dependent characteristics of wall pressure fluctuations in separated and reattaching flows over a backward-facing step were investigated by means of continuous wavelet transform. Emphasis was placed on the combination of time-localized analyses of wavelet transform and multi-point measurements of pressure fluctuations. Synchronized wavelet maps revealed the evolutionary behavior of pressure fluctuations and gave further insight into the modulated nature of large-scale vortical structures. It was found that there exist two modes of shed vortices: one is the global oscillation and the other is the vortex convection. The two alternating modes are synchronized with the flapping frequency component of pressure fluctuations. Toward the investigation of the direct relationship between the flow field and the relevant spatial mode of the pressure field, a new kind of wavenumber filtering of pressure distribution, termed as a spatial box filter (SBF), is introduced and examined.
민주시민교육의 연구동향 분석 : 네트워크 분석을 통해 파악한 경향과 특징을 중심으로
이인원(InWon Lee),원준희(JunHee Won),이영미(Youngmi Lee) 한국국정관리학회 2021 현대사회와 행정 Vol.31 No.2
민주주의 운영의 실효성을 제고하기 위한 수단으로써의 민주시민교육에 대한 관심은 지난 수십년 간 지속적으로 증대했으며, 최근에는 거시적으로는 제도화 및 법제화에 대한 논의가 미시적으 로는 교수법 및 학습법에 대한 심도있는 논의가 진행되었다. 이 연구는 최근 20년(2001-2020)간 민주시민교육을 주제로 학술지에 게재된 학술논문들을 대상으로 내용분석과 네트워크 분석을 시행함으로써 해당 분야의 연구 경향과 그 핵심개념 간의 구조적 관계를 파악하고자 하였다. 이를 위해 총 381편의 학술논문을 대상으로 연도별 논문 수, 연구형태, 연구주제 및 빈도 및네트워크 구조 등을 분석하였다. 분석결과, 공동연구보다는 단독연구의 비중이 높았으며, 학문분 야로는 교육학의 비중이 높은 것으로 나타났다. 또한, 키워드 분석의 결과 ‘시민사회’, ‘시민교 육’, ‘시민참여’라는 키워드의 출현빈도가 가장 높은 것으로 나타났으며, 네트워크 중심성 분석의 결과 ‘민주사회’와 ‘학교교육’ 등이 다양한 개념들을 통합하는 중요한 개념들인 것으로 나타났다.; Democratic civic education, as important vehicles for promoting efficacy of democracy, has drawn a great deal of interest from both scholars and practitioners for a couple of decades in Korea. In recent years, discussions and researches on institutionalization and legalization at the macro level, and in-depth discussions on teaching and learning methods at the micro level have been conducted. This study analyzes trends and characteristics of researches on civic education in Korea from 2001-2020 by using social network analysis. Statistics and social network analysis results show that the proportion of single-authored research is much higher than that of co-authored research, compared to the result of other social science field. In addition, the keywords such as ‘civil society’, ‘civic education’, ‘citizen participation’ are frequently utilized as key concepts, Network analysis also demonstrates that ‘civil society’ and ‘civic education’ are important integrating concepts among several keywords in this research field.