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차세대소형위성2호의 X대역 합성 개구 레이더 탑재를 위한 200 W급 송·수신 모듈의 설계 및 개발
김지흥,최현태,이정수,장태성 한국항행학회 2022 韓國航行學會論文誌 Vol.26 No.6
본 논문에서는 차세대소형위성2호의 X 대역 합성 개구 레이더(SAR; synthetic aperture radar)에 탑재하기 위한 고출력 송·수신 모듈의 설계 및 개발에 관하여 논한다. 모듈은 X 대역의 대상 주파수 범위에서 100 MHz 의 대역폭을 갖는 고출력 펄스 신호를 출력하며, 수신신호에 대해 저잡음 증폭 기능을 수행한다. 제작된 모듈의 송신경로는 200 watt (53.01 dBm) 이상의 출력 신호 세기, 0.35 dB의 펄스폭 기울기, 송신 신호 출력간 0.04 dB 의 신호 세기 변화 및 1.7 ˚ 의 위상 변화를 갖고, 수신경로는 3.81 dB 의 잡음지수, 37.38 ~ 37.46 dB 의 이득을 가짐으로써, 요구되는 성능을 만족함을 확인하였다. 제작된 모듈은 차세대소형위성2호 비행모델에 장착되어 있으며, 추후 누리호에 탑재되어 발사될 예정이다.
김지흥,Kim, Ji Heung 대한화학회 1996 Bulletin of the Korean Chemical Society Vol.17 No.1
Mono-, or di-substituted chlorodicyanovinyl benzene compound was reacted with an excess amount of ethylenediamine to give corresponding imidazoline product with high reaction yield. This reaction occurs by stable imidazoline ring-forming process through nucleophilic attack of terminal amine on the enaminonitrile adduct, the reaction intermediate, toward electropositive enamine carbon, which is accompanied by the release of neutral malononitrile moiety. The similar reaction with 1,2-phenylenediamine produced stable enaminonitrile-amine adduct at lower temperature which could be cyclized intramolecularly to thermally stable benzimidazole at elevated temperature in solution or in solid state. From the difunctional compound of both reactants, poly(enaminonitrile-amine) could be prepared as a new soluble precursor polymer for well-known polybenzimidazole (PBI). The thermal cyclization reaction accompanying the release of malononitrile molecules was studied using thermalanalysis and infrared spectroscopy.
Double network hydrogel based on poly(aspartic acid) with improved mechanical properties
김지흥,이재상,전영실,김영준,왕보 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Many efforts have been made to develop highly strong & tough hydrogels with new approaches, including double-network hydrogel, nanocomposite hydrogel, nano-structured hydrogel, etc. In this study, chemically crosslinked poly(aspartic acid)(PASP) gel, prepared by cryogelation method, was immersed in several metal ion (Fe+3, Ca+2 or Zn+2) - containing aqueous solution to induce secondary ionic crosslinking between carboxylic acid and metal ion to provide highly strong and tough gels. Another approach includes fabrication of double-network hydrogels with ductile polyacrylamide (PAAM) and subsequent metal-ion treatment. The preparation of these PASP-based tough gels, swelling behavior, morphology and mechanical properties are presented.
pH-responsive self-healing hydrogel based on PolyAspartAmide containing catechol groups
김지흥,( Bo Wang ),이재상,전영실,김영준 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Responsive and self-healing materials have a wide range of potential uses, and some significant researches have been focused on hydrogel materials crosslinked by reversible coordination bonding which can provide stimuli-responsive and self-healing properties. In this work, we present hydrogels based on biocompatible 3,4-dihydroxyphenethylamine(dopamine)-conjugated polyaspartamide, which was developed as a mussel-mimic functional poly(amino acid). The pH-responsive interaction between catechol groups and metal ion (e.g. Fe+3) or boron (B) make secondary bonding to the existing gel network to strengthen the hydrogel, as well as to provide self-healing property. Incorporation of graphene oxide (GO) within the gel was also attempted to identify a tough nanocomposite hydrogel which might show a good self-healing ability.