1,720,966 research outputs found
METHOD AND SYSTEM FOR MANUFACTURING EXPANDED STRUCTURE USING RESIN-INFUSION CURING AND AVALIABLE IN SPACE
No full text우주 공간에서 이용가능한 수지 침투 경화를 이용한 확장 구조물 제조 방법은, 기압차를 이용하여 접혀진 섬유 백을 팽창시키는 단계, 상기 섬유 백의 외피층과 내피층 사이에 배치된 섬유층에 수지 조성물을 확산시키는 단계 및 상기 수지 조성물을 경화하는 단계를 포함한다
우주환경적용을 위한 폴리벤즈이미다졸(PBI) 필름이 초고속 내충격에 미치는 영향에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 항공우주공학과, 2016.8
,[viii, 57 p. :]The use of lightweight polymeric composites with better physical and multifunctional capabilities in spacecraft can reduce its operating cost. However, the conventional carbon epoxy composites(CFRP) that are employed in the space environment, mostly Low Earth Orbit(LEO), have very poor shielding performance to environmental factors like Atomic Oxygen(AO), Ultraviolet radiation(UV), high vacuum, Thermal cycling and space debris impacts. Therefore, a polymer coating using Polybenzimidazole(PBI), a high performance thermoplastic polymer, is suggested in this research as a method to improve the shielding performance towards hypervelocity debris impact. The coated samples tested for resistance to AO, UV, thermal cycling and high vacuum in a LEO simulation facility revealed that the mass loss and surface erosion decreases, inferring enhanced protection than CFRP. Hypervelocity impact tests performed using a two stage light gas gun(LGG) showed that the energy absorption of the CFRP improved by PBI coating. Therefore, the PBI film coating can effectively improve the shielding performance of the composite material. The study also discusses the effectiveness of adding nanomaterials like carbon nanotubes(CNT’s) and graphene in the PBI coating towards the LEO environment shielding performance. It was observed that adding CNT’s and graphene had no considerable improvement in impact energy absorption. Regardless of this, both nanoparticles showed a very good reduction in mass loss and surface erosion towards other LEO environmental factors making them suitable as fillers in the PBI film.한국과학기술원 :항공우주공학과
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A Study on Space Radiation and Hypervelocity Impact Shielding of Low Earth Orbit Space Structures Using Ultra-High-Molecular-Weight Polyethylene
No full textMethod for Determining Fiber Volume Fraction in Carbon/Epoxy Composites Considering Oxidation of Carbon Fiber
No full text섬유체적비에 따라 복합재료의 기계적 열적 특성이 크게 달라지기 때문에, 복합재료 설계시 섬유체적비를 올바르게 측정하는 것이 매우 중요하다. 일반적으로 섬유체적비를 측정하는 여러 방법은 산화되지 않는 유리섬유나 세라믹섬유를 사용한 복합재료의 경우에는 적합하고 효율적이다. 하지만 산화현상이 있는 탄소섬유의 경우에는 산화 방법과 조건에 따라서 다른 결과를 가져오게 되며 그러므로 올바른 섬유체적비를 측정이 어렵다. 본연구에서는 Thermogravimetric analysis를 수행하여 산화되는 탄소섬유의 질량 감소량을 보정하여 탄소섬유 복합재료의 섬유체적비를 측정하였고 현미경 단면 이미지를 이용하여 그 결과를 검증하였다.N
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