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아리랑위성 2호, 5호의 우주파편 충돌회피기동 주기 분석
김은혁(Eun-Hyouek Kim),김해동(Hae-Dong Kim),김은규(Eun-Kyou Kim),김학정(Hak-Jung Kim) 한국항공우주학회 2011 韓國航空宇宙學會誌 Vol.39 No.11
본 논문에서는 현재 운용 중인 아리랑위성 2호와 발사예정인 아리랑위성 5호의 우주파편 충돌 회피기동 주기를 분석하였다. 이때, 각 위성들의 임무궤도 특성, 충돌 회피 여유시간, 허용 충돌확률, 위치 불확실성 등의 인자들의 변화에 따라 분석을 수행하였다. 또한, 결과의 타당성을 검증하기 위해 실제 1년 동안 생성된 NORAD TLE 카탈로그(catalog) 상의 우주 물체들과 아리랑위성 2호와의 충돌 회피기동 주기를 계산하였다. 분석 결과, 두 위성 모두 연중 약 1회 충돌 회피기동이 요구됨을 확인할 수 있었으며, 계산 인자들의 변화에 따른 결과 분석을 통해 추후 발사 예정인 저궤도 위성들의 충돌 회피기동 주기 예측 정밀도를 향상시키기 위한 방안들을 제시하였다. In this paper, a collision avoidance maneuver frequency for the KOMPSAT-2 and the KOMPSAT-5 is analyzed. For the statistical prediction of the avoidance maneuver frequency, mission orbits, responsive time, accepted collision probabilities, and positional uncertainties of primary and secondary objects are considered. In addition, the collision avoidance maneuver frequency of the KOMPSAT-2 is compared to the case that NORAD catalog during one year is used to calculate that of the KOMPSAT-2. As a result, the collision avoidance maneuver frequency is one per year on average and effective factors on the statistical prediction of the avoidance maneuver frequency are investigated. Efforts to improve its prediction accuracy are also discussed.
CAT (Computer Adaptive Test)실시를 위한 IRT (Item Response Theory)분석 연구 (Ⅰ)
이창규(Chang Kyou Lee),박종성(Jong Sung Park),이은일(Eun Il Lee),이숙자(Sook Ja Lee),박은숙(Eun Sook Park),박영주(Young Joo Park) 한국의학교육학회 2001 Korean journal of medical education Vol.13 No.1
CAT를 실시하려면 IRT에 의한 출제 문제의 모수들을 계량해야만 한다. CAT에 실제 이용되는 것은 난이도이므로 이것을 중심으로 뱅킹이 되어야 한다. 빅스텝은 소문에 의한 것보다는 실질적으로 문제의 속성을 파악을 하는데 손색이 없는 것으로 나타났다. 물론 조합문제인 K형도 여러 가지 장점이 있기는 있으나 난이도와 변별도에 있어서 사려깊게 출제를 해야 하는 것은 물론이려니와 문항반응이론에 의한 문항분석을 통하여 적절한지의 여부를 꼭 계량하지 않으면 안된다. 한국의 ETS가 개발한 엔진이 출제로부터 시험, 채점, 문항분석으로 이어지는 출제된 문항의 타당성 여부를 정확하게 검색할 수 있는 능력을 확인하였다 Prior to CAT, the parameter estimation on executed items should be accomplished by IRT.and the item banking must be build up on the basis of the parameter of difficulty. A program developed by Korea ETS Inc, Bilog and Bigsteps were all found to be very powerful to understand the attributes of items. Though multiple true-false type K items have some merits, the items should be examined quantitatively if they are appropriate or not by IRT. Through the study we have finally confirmed that the new program developed by Korea ETS has its ability to check the validities of items from preparing or scoring to item analysis.
Eun-Ju Chang,Jae-Ho Chang,Yong-Suk Ryang,Tomohiro Morio,Sang-Kyou Lee 한국분자세포생물학회 2004 Molecules and cells Vol.18 No.2
Activation of NF-κB leads to the production of proinflammatory cytokines such as IL-12 and TNF-α that are involved in innate and adaptive immunity. We determined whether T. vaginalis-induced inflammatory response in macrophages associated with NF-κB. T. vaginalis adhesion led to transient NF-κB activation at 6 h but activation declined dramatically by 8 h. Supershift assays showed that the gel-shifted complexes consisted of p65 (Rel A) and p50 (NF-κB1). NF-κB activation was accompanied by IκB-α degradation, and was inhibited by blocking T. vaginalis adhesion, indicating that the early NF-κB activation by T. vaginalis depends on IκB-α degradation. Quantitative real-time RT-PCR analyses revealed that the expression of TNF-α and IL-12 mRNA in T. vaginalis-adhesive cells was rapidly suppressed in comparison with LPS stimulation. We also observed that the parasite inhibited the nuclear translocation of NF-κB at 8 h, and diminished IL-12 and TNF-α production in response to LPS. In addition, inhibition of IκB-α degradation by MG-132 resulted in apoptosis. These results demonstrate that effects of T. vaginalis on NF-κB regulation are critical for cytokine production and the survival of macrophages. We suggest that there exist inhibitory mechanisms induced by T. vaginalis to evade host immunity.
Multi-symbol Accessing Huffman Decoding Method for MPEG-2 AAC
Eun-Seo Lee,Kyoung-Cheol Lee,Kyou-Jung Son,Seong-Pil Moon,Tae-Gyu Chang 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.4
An MPEG-2 AAC Huffman decoding method based on the fixed length compacted codeword tables, where each codeword can contain multiple number of Huffman codes, was proposed. The proposed method enhances the searching efficiency by finding multiple symbols in a single search, i.e., a direct memory reading of the compacted codeword table. The memory usage is significantly saved by separately handling the Huffman codes that exceed the length of the compacted codewords. The trade-off relation between the computational complexity and the amount of memory usage was analytically derived to find the proper codeword length of the compacted codewords for the design of MPEG-2 AAC decoder. To validate the proposed algorithm, its performance was experimentally evaluated with an implemented MPEG-2 AAC decoder. The results showed that the computational complexity of the proposed method is reduced to 54% of that of the most up-to-date method.