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서동찬,전익성,배석영,조재영 한국고분자학회 2020 Macromolecular Research Vol.28 No.12
To enhance impact strength of polyketone (PK) without loss of stiffness, PK was blended with polycarbonate (PC) via melt mixing. Three types of polyamides (PAs) with varying structures, - polyamide 6 (PA6), polyamide 612 (PA612), polyamide 12 (PA12) - were employed as polymeric compatibilizers. To elucidate the effect of the structure of PAs on the compatibilization, morphology, mechanical properties, and fracture behavior of the blends were investigated. The addition of PA6 and PA612 reduced the size of dispersed particles by encapsulating the PC phase, while PA12 was found not to affect the morphology of the PK/PC blend. The change in particle size, glass transition temperature (T g), and elongation at break exhibited that PA6 was the most effective compatibilizer for the PK/PC blends of this study. These results were interpreted with the change in interfacial tension between PK and PA due to the difference in polarity of the PAs. It was found that the impact strength was not highest in the blend with the smallest particle size. The observation of sub-surface damage zone also indicated that effective toughening by intensive crazing in polymer blends requires dispersed particles of optimum size.
Study of Hafnium Silicate Treated with NO Gas Annealing
서동찬,조만호,정권범,고대홍 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2
The physical and the electrical properties of nitrided hafnium-silicate films treated with NO gas annealing were investigated using high-resolution transmission electron microscopy, X-ray photo electron spectroscopy, near-edge X-ray absorption fine structure and capacitance-voltage measurements. We confirmed that nitrogen incorporation during the NO gas annealing treatment enhanced the thermal stability of Hf silicate. The suppression of phase separation was observed in hafnium silicate films with high nitrogen contents. Moreover, small hysteresis changes were observed in the C-V curves. The negative shift of the threshold voltage was caused by the incorporation of nitrogen in the hafnium silicate films.
탄소성 변형을 고려한 타이로드 고정 회전체의 동역학 해석
서동찬,김경희,이도훈,이보라,서준호 한국트라이볼로지학회 2024 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.40 No.1
This study conducts numerical modeling and eigen-analysis of a rod-fastened rotor, which is mainly used in aircraft gas turbine engines in which multiple disks are in contact through curvic coupling. Nayak's theory is adopted to calculate surface parameters measured from the tooth profile of the curvic coupling gear. Surface parameters are important design parameters for predicting the stiffness between contact surfaces. Based on the calculated surface parameters, elastoplastic contact analysis is performed according to the interference between two surfaces based on the Greenwood–Williamson model. The equivalent bending stiffness is predicted based on the shape and elastoplastic contact stiffness of the curvic coupling. An equation of motion of the rod-fastened rotor, including the bending stiffness of the curvic coupling, is developed. Methods for applying the bending stiffness of a curvic coupling to the equation of motion and for modeling the equation of motion of a rotor that includes both inner and outer rotors are introduced. Rotordynamic analysis is performed through one-dimensional finite element analysis, and each element is modeled based on Timoshenko beam theory. Changes in bending stiffness and the resultant critical speed change in accordance with the rod fastening force are predicted, and the corresponding mode shapes are analyzed. Keywords: Curvic coupling(곡률 커플링), Dual rotor(복 축), Rotordynamics(회전체 동역학), Contact mechanics( 접촉 역학), Elastoplastic deformation(탄소성 변형) Nomenclature An : Normal contact area of rough surface (m2) (거친 표면 수직 접촉 면적) †Corresponding author: Junho Suh Tel: +82-51-510-1475 E-mail: junhosuh@pusan.ac.kr http://orcid.org/0000-0001-5516-9637 ⓒ
서동찬 한국재정학회 2017 한국재정학회 학술대회 논문집 Vol.2017 No.-
본 연구에서는 1990-2015년의 OECD 34개 국가 데이터를 이용해 법인세율의 변동이 임금에 미치는 영향을 실증분석하였다. 개방경제에서는 법인세의 귀착이 자본이동의 경로를 통해서도 나타날수 있으므로 동태적효과를 고려하기 위해 법인세율의 시차변수를 설명변수로 포함하였고 법인세 율과 자본이동성의 상호작용항을 모형에 도입하여 국가의 자본이동성에 따른 귀착의 효과를 파악 하고자 하였다. 연립GMM모형을 통해 추정할 경우 법인세율의 인하는 임금수준에 미약한 상승효 과를 미치는 것으로 나타나는데 구체적으로는 법인세율의 1%포인트 인상이 연간임금을 약 16달러 정도 감소시키며 자본이동성을 나타나는 FDI/GDP의 값이 클수록 귀착의 효과도 미세하게 커진다. 하지만 모형에 포함된 시차에 따라, 추정방법에 따라 분석의 결론이 강건하지 못하다고 볼수 있으며 법인세율 변화의 순효과를 추출하기 위해 고려해야할 여러가지 변수들에 대한 추가적인 검토가 필요하다고 볼 수 있다.