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태양동기-지상반복 궤도를 활용한 군 정찰용 초소형 위성군 설계
조성민,조남석,Cho, Sungmin,Cho, Namsuk 한국군사과학기술학회 2020 한국군사과학기술학회지 Vol.23 No.2
One of the most important steps to consider in utilizing micro-satellites for surveillance or reconnaissance operations is the design of the satellite constellation. The Walker-Delta constellation which is commonly used in designing satellite constellations is not ideal for this operation in which military satellites are required to monitor specific regions continuously in a stable manner. This study aims to discuss the methodology for designing a satellite constellation that is capable of monitoring the fixed region at the fixed time each day by using the Sun synchronous Orbit. The BB(Beach Ball) constellation that we propose outperforms the Walker-Delta constellation in terms of robustness and it holds the merit of being simple in its design, thereby making future expansions more convenient. We expect the BB constellation will have a high applicability as the operational concept of military surveillance satellites is established in the near future.
GaN-on-Si 기술을 위한 탄화텅스텐 버퍼층의 성장에 관한 연구
조성민,최정훈,최성국,조영지,이석환,장지호,Cho, Sungmin,Choi, Junghoon,Choi, Sungkuk,Cho, Youngji,Lee, Seokhawn,Chang, Jiho 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.1
Tungsten carbide (WC) has been suggested as a new buffer layer for the GaN-on-Si technology. We have investigated and optimized the sputtering condition of WC layer on the Si-substrate. We confirmed the suppression of the Si melt-back phenomenon. In addition, surface energy of WC/Si layer was measured to confirm the possibility as a buffer layer for GaN growth. We found that the surface energy(${\gamma}=82.46mJ/cm^2$) of WC layer is very similar to that of sapphire substrate(${\gamma}=82.71mJ/cm^2$). We grow GaN layer on the WC buffer by using gas-source MBE, and confirm that it is available to grow a single crystalline GaN layer.
조성민(Sungmin Cho),이도경(Dokyung Lee) 한국산업경영시스템학회 2006 한국산업경영시스템학회 학술대회 Vol.2006 No.추계
In the previous studies, we only used population variance to extract process capability index. Even though process is in control, variance by sample is not the population variance of constant but the sample variance of statistic. In contrast with population variance, sample variance has distribution. The process capability index using sample variance is also statistic. In this study, we investigated the distribution characteristic for the process capability index in respect of estimation with error. Also we spread out for applying up to system process capability index component of an individual process capability index.