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차세대소형위성2호 X대역 합성 개구 레이더용 송·수신 모듈의 설계 및 개발
김지흥,김동국,장일영 한국항행학회 2024 韓國航行學會論文誌 Vol.28 No.2
본 논문에서는 차세대소형위성2호의 X대역 합성 개구 레이더 (SAR; synthetic aperture radar)에 탑재하기 위한 송·수신 모듈의 설계 및 개발에 관하여 논한다. 모듈은 DDS를 통해 X 대역의 대상 주파수 범위에서 요구 대역폭을 갖는 첩(chirp) 신호를 생성하고, 송·수신 신호에 대한 주파수 변환 및 합성, 분배 그리고 주파수 합성기능을 수행한다. 제작된 모듈의 송신 경로는 최대 96.8 MHz 까지 총 28개의 대역폭을 갖는 신호를 생성하며, + 9.37 dBm 이상의 출력신호 세기를 갖는다. 수신 경로는 15.7 dB 이하의 최소 잡음지수를 가짐으로써, 요구되는 성능을 만족함을 확인하였다. 제작된 모듈은 차세대소형위성2호 비행모델 (FM; flight model)에 장착되었고, 2023년 5월 23일 누리호 3차 발사체에 탑재 및 발사되어 운용 중에 있다. This paper describes the design and development of a transmit receiver module(TRM) for mounting on X-band synthetic aperture radar(SAR) of the NEXTSat-2. The TRM generates the chirp signal with required bandwidth through the DDS in X-band and performs frequency conversion, combination for the signal to transmit and be received and frequency synthesis. Tx. path of the TRM produces signals of total 28 bandwidths up to 96.8 M Hz and has output signal level of more than + 9.37 dBm. Rx path of the TRM has minimum noise figure of 15.7 dB. it was confirmed the TRM satisfies all requirements. The TRM mounts on the NEXTSat-2 flight model(FM), be launched by KSLV-Ⅱ(Nuri) on May 23, 2023 and then is in operation.
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.
1P-208 Silver Nanoparticles embedded in polyaspartamide-based hydrogels for biomedical applications
김지흥,( Wang Bo ),( Milene Tan ),( K. M. Fromm ) 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
The increased use of medical devices combined with the emergence of new multi-drug resistant bacteria has focused the research on biomaterials-related infections. Silver has already been proven to be effective against bacterial infections even at low concentration (0.1-10 ppm). Furthermore, it has been demonstrated that nano-particulate (NP) silver could be even more efficient due to a better interaction with bacteria and a long-lasting activity compared to ionic silver. Polyaspartamides are very promising for biomedical applications owing to their water-solubility, nontoxicity, nonantigenicity, and biodegradability. In this work, DOPA-conjugated polyaspartamide was synthesized and used to prepare the crosslinked gel via catechol-boron coordinative interactions. The adsorbed silver ion onto the remaining catechol moieties within the gel matrix will be reduced in-situ by redox process to provide the silver NP-embedded hydrogel.