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Reliability analysis for thermal cutting method based non-explosive separation device
Junwoo Choi,Kukha Hwang,김병규 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.12
In order to increase the reliability of a separation device for a small satellite, a new non-explosive separation device is invented. This device is activated using a thermal cutting method with a Ni-Cr wire. A reliability analysis is carried out for the proposed non-explosive separation device by applying the Fault tree analysis (FTA) method. In the FTA results for the separation device, only ten single-point failure modes are found. The reliability modeling and analysis for the device are performed considering failure of the power supply, the Ni-Cr wire burns failure and unwinds, the holder separation failure, the balls separation failure, and the pin release failure. Ultimately, the reliability of the proposed device is calculated as 0.999989 with five Ni-Cr wire coils.
최준우(Junwoo Choi),이동규(Dongkyu Lee),황국하(Kukha Hwang),이민형(Minhyung Lee),김병규(Byungkyu Kim) 한국항공우주학회 2015 韓國航空宇宙學會誌 Vol.43 No.7
본 논문에서는 형상기억합금 구동기를 이용한 소형위성용 비폭발식 분리장치를 소개한다. 앞선 연구결과를 바탕으로 분리장치의 부품의 교체를 통하여 제안된 분리장치의 신뢰성을 향상시킴으로써 고사전하중(preload) 하에서도 구동이 가능하도록 하였다. 또한 충격실험을 통하여 비폭발식분리장치의 장점인 저충격 발생을 확인하였고, 발사환경 및 우주환경실험을 통하여 안정적으로 작동하는 것을 검증하였다. 결론적으로 본 연구에서는 충격실험, 진동실험 및 열진공실험 후 고사전하중에서 저충격을 발생시키며 안정적으로 작동 가능한 비폭발식 분리장치를 개발하였다. In this paper, we report a non-explosive separation device for a small satellite which utilize a shape memory alloy actuator. Based on previous research, we try to increase the reliability of the proposed device by changing some components. It enables the proposed device to activate under high preload. Also, we confirm it generates low shock which is main advantage of non-explosive separation device. Finally, vibration test which mimics launching environment and thermal vacuum test which mimics space environment are carried out respectively. After each environment test, we confirm the proposed device is successfully activated. Conclusively, we develop a non-explosive separation device which can activate with low shock under high preload after shock and environment tests(vibration and thermal vacuum tests).
전개형 광학구조체용 메커니즘 요구조건 수립 및 후보 메커니즘의 기구학적 해석
정성문(Seongmoon Jeong),최준우(Junwoo Choi),이동규(Dongkyu Lee),황국하(Kukha Hwang),김상우(Sangwoo Kim),김장호(Jangho Kim),김병규(Byungkyu Kim) 한국항공우주학회 2014 韓國航空宇宙學會誌 Vol.42 No.8
최근 인공위성 연구는 “Faster, Smaller, Better, Cheaper라는 슬로건 하에 나노급, 마이크로급 인공위성 개발, 복수위성 발사 등에 대한 연구가 활발히 진행되고 있다. 광학구조체는 인공위성에서 대부분의 비율을 차지하며, 이를 축소하기 위한 방안으로 광학구조체에 전개 메커니즘을 접목시킨 전개형 광학구조체에 대한 연구가 각광받고 있다. 본 논문에서는 기존 고정형 광학구조체의 요구조건을 바탕으로 전개형 광학구조체 전개 시 정렬 정밀도를 제안하고, 이 정밀도를 만족시킬 수 있는 전개 메커니즘 후보를 제안하였다. 또한 기구학적 해석을 수행하여, 위성의 광학성능에 영향을 미치는 미러 사이의 tilt, de-space, de-center중, 기구의 입력 오차에 의하여 발생될 수 있는 기구장치의 de-space 정밀도를 평가하였다. In these days, there have been numerous researches on nano and micro satellites under the slogan of Faster, Smaller, Better, Cheaper. Since optical structure occupies large portion of satellite volume, research on deployable optical structure gains great attention to reduce total volume of the satellite. In this paper, we establish the requirement of deployable optical structure based on specification of conventional optical structure and propose two candidate mechanisms which can satisfy the degree of deployment precision. Then, in order to evaluate the degree of deployment precision, we carry out kinematic analysis on de-space among tilt, de-space and de-center which influences optical characteristic of a satellite.
스프링 클램프와 형상기억합금 와이어를 이용한 비폭발식 분리장치
최준우,이동규,황국하,이민형,김병규,Choi, Junwoo,Lee, Dongkyu,Hwang, Kukha,Lee, Minhyung,Kim, Byungkyu 항공우주시스템공학회 2015 항공우주시스템공학회지 Vol.9 No.2
In this paper, we report a non-explosive separation device for a small satellite which utilize a shape memory alloy actuator and spring clamp. In order to increase the preload, the proposed device employs spring clamp that can generate high toque when the shape memory alloy actuator makes the cylinder key unlatch a holding ball effectively. Owing to simple design of separation device configuration, we could obtain good repeatability(up to 30 times activation). Conclusively, we could develop a non-explosive separation device which can reliably activate within 1.2 sec under high preload(up to 300kgf).
Artocarpus nigrifolius: Cytotoxic and Antibacterial Constituents
Hoi, Tran Minh,Anh, Ha Van,Huong, Nguyen Thi Thanh,Tuyen, Nguyen Van,Anh, Le Thi Tu,Tra, Nguyen Thanh,Cham, Ba Thi,Ha, Nguyen Thi Thu,Linh, Pham Thuy,Tien, Doan Duy,Kiem, Phan Van,Ban, Ninh Khac,Kukha The Korean Society for Applied Biological Chemistr 2013 Applied Biological Chemistry (Appl Biol Chem) Vol.56 No.6
Six known compounds including ${\alpha}$-amyrin 3-acetate (1), ${\beta}$-sitosterol (2), betulinic acid (3), friedelan-3-one (4), artochamin B (5), and 2-C-methyl-D-erythritol 4-O-${\alpha}$-D-glucopyranoside (6) were isolated from the stem barks and leaves of Artocarpus nigrifolius (Moraceae) for the first time. Their structures were identified by spectroscopic methods as well as comparison with literatures. Cytotoxicity and antibacterial activity of 1-6 were evaluated. Results showed that artochamin B (5) possessed the highest cytotoxicity towards MCF7, Lu, HepG2, and KB cell lines with $IC_{50}$ values of 4.59, 20.00, 3.60, and $1.18{\mu}g/mL$, respectively. It also inhibited the growth of Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus), whereas inactive on the growth of both Gram-negative bacteria and yeast.