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가공열처리 및 2단시효처리에 의한 8090알루미늄 합금의 석출거동
이학용,김석원,우기도 ( Hag Yong Lee,Sug Won Kim,Kee Do Woo ) 한국열처리공학회 1994 熱處理工學會誌 Vol.7 No.4
The effects of thermomechanical and duplex aging treatment on precipitation behavior were investigated for the 8090 aluminium alloy by tensile test, hardness test, plane-strain fracture toughness test and electron microscope. Both pre-aging stretch and duplex aging with pre-aging stretch were effective to homogenize the distribution of S` phase in this alloys. The tatter makes more homogeneous distribution of S` phase than that of the former, but the sizes of S` phase in both specimens are almost same. The size and distribution of δ` phase were not changed by thermomechanical or duplex aging treatment. The strength was increased by thermomechanical treatment, but the elongation was decreased. Duplex aging treatment couldn`t change the strength and elongation. Pre-aging stretch and duplex aging with pre-aging stretch have same effect on the strength and elongation. The increase of strength by thermomechanical treatment in 8090 alumunium alloy was caused by homogeneously precipitated S` phase.
새로운 형태의 IMT-2000 기지국용 이중편파 다이버시티 능동형 배열안테나
이학용,강기조,이병제,이종철,김종헌,김남영 한국전자파학회 2002 한국전자파학회논문지 Vol.13 No.4
본 논문은 IMT-2000 기지국에 적용할 이중편파 다이버시티 능동형 배열 안테나의 새로운 형태를 제안하고, 설계 및 개발하였다. 먼저 배열 안테나를 구성하게 될 단일 안테나 소자는 마이크로 스트립 패치 안테나로서 $\pm$ 45$^{\circ}$의 편파를 갖는 패치를 설계하여 IMT-2000의 송신부와 수신부를 커버할 수 있는 대역폭 (1,885~2,200 MHz)을 갖추고, 이중편파간에 16 ㏈ 이하의 격리도를 확보하며 이득은 7 ㏈i 이상으로 확보를 하였다. 최종적으로 2$\times$8 이중편파 능동형 배열 안테나에서는 저 전력증폭기의 분산 장착 기술을 위해 균일한 특성을 갖는 전력증폭기를 각 패치의 후면에 분산하여 1,200 W 이상의 EIRP와 20 ㏈ 이상의 편파간 격리도를 확보할 수가 있었다. In this work, a new type of the active array antenna for IMT-2000 base stations by using dual-polarization diversity is proposed and developed. As an element of array antenna, a single micorstrip patch antenna of ${\pm}$ 45$^{\circ}$slanted is designed by obtaining the bandwidth of 1,885 ㎒ to 22,000 ㎒. The polarization isolation between two linearly polarized waves is less than 16 ㏈. The gain of element antenna is more than 7 ㏈i. finally, 2${\times}$8 dual-polarization active array antenna is developed with ElRP of 1,200 W and polarization isolation of 20 ㏈ by placing a low power amplifier at each antenna element.
李鶴鏞 三陟大學校 1995 論文集 Vol.28 No.2
Considering the moments and the horizontal deflections, the closely aprpoximated and simple equation are developed to estimate the optimum height of the stiffening beam of coupled shear walls by the numerical tests. The optimum positions are found by using these equation and the dimensionless bending stiffness. The value of the moment and the deflection are computed with each defferent value fo position of beam. The optimum position may be found as the values the moment and the deflection are reduced to minimum. The equation optimum are formulated as results of curve fitting.
Optimal Shape Design of the Film-Coupled Nanoparticle using the Phase Field Design Method
이학용,성홍경,유정훈 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.4
Localized surface plasmon resonance (LSPR) occurs when an electromagnetic (EM) wave hits a metal nanoparticle. The interaction between a gold (Au) nanoparticle and a thin metal film produces a strong EM wave called as LSPR at the small gap between the nanoparticle and the film. The field strength of the LSPR increases dramatically as the distance between the Au nanoparticle and the film decreases. In this study, we focus on the field enhancement at the small gap by obtaining the appropriate shape of the Au nanoparticle. Since the shape or the size of a nanoparticle to enhance the LSPR is hard to be determined theoretically, the structural optimization method based on the phase field method is employed to design the shape of the nanoparticle. To obtain reliable results taking the small gap of 2 nm into account, we proposed a new filtering scheme based on a smoothed Heaviside function and applied it to nanoparticle design.
Control of surface properties of poly(L-lactide) by mixing of lotus leaf powder
이학용,이원기,김영우,이봉,박찬영 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Biocompatible polymer composite film were prepared by casting method of the mixed solution of poly(L-lactide) and fine lotus leaf powder in chloroform. The obtained composite film showed transparent and hydrophobic properties. The surface properties of the polymer films were analyzed by scanning electron microscopy and atomic force microscopy (AFM), and contact angle measurement. The functional groups and hydrophobicity of the film were analyzed by Fourier transfer infrared spectroscopy. The biodegradability of the hydrophobic composite film to enzyme was checked by AFM which leads a morphological change. By mixing the right hydrophobic lotus leaf powder to poly(L-lactide), the biodegradation rate of poly(L-lactide) could be controlled for further commercial applications.