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PP/MMT 나노복합재료의 열안정성 및 기계적 계면 특성에 관한 연구
박수진,전병렬,송시용,이종문 한국공업화학회 2004 공업화학 Vol.15 No.1
본 연구에서는 몬모릴로나이트(Na^(-)-montmorillonite, MMT)를 dodecylammonium chloide로 유기적 개질하여 폴리프로필렌(PP) 나노복합재료의 열안정성과 기계적 계면 물성에 미치는 영향을 조사하였다. 나노복합재료의 구조 및 표면 특성은 각각 XRD와 FT-IR을 통해 알아보았고, 열안정성은 TGA를 통해 알아보았으며, 주조된 시편의 기계적 계면 물성은 K_(IC)와 G_(IC)를 통해 알아보았다. 실험 결과, dodecylammonium chloide을 이용한 MMT의 유기적 개질(DA-MMT)은 약 7.3 Å의 실리케이트 층간을 증가시켰고, DA-MMT 내의 CH_(2) 기에 의해 2800~2900 ㎝^(-1)에서 새로운 피크가 나타났다. PP/DA-MMT 나노복합재료의 열안정성은 순수한 PP 수지에 비해 향상되었는데, 이는 DA-MMT 입자와 PP 사이의 분자간 상호작용에 의한 것으로 판단된다. 또한, PP/DA-MMT 나노복합재료가 높은 기계적 계면 물성을 나타냈는데, 이러한 결과는 층간이 증가된 실리케이트에 PP가 쉽게 삽입되기 때문으로 판단된다. In this work. the effect of organic modification of Na-montmorillonite (MMT) with dodecylammonium chloride on thermal stabilities and mechanical interfacial properties of PP nanocomposites was investigated. The structure and surface properties of the nanocomposites were determined by XRD and FT-IR, respectively. The thermal stabilities of the nanocomposites were studied using a TGA analysis. Also, the mechanical interfacial properties were confirmed by KIC and GIC of casting specimens. As a result, the organic modification of MMT by dodecylammonium chloride(DA-MMT) led to the increase of the silicate layers to about 7.3 A, and the new peaks at 2800∼2900 cm^(-1) hand were shown in the presence of the CH groups on the DA-MMT. The thermal stahilities of PP/DA-MMT nanocomposites were higher than that of pure PP resin, which can be attributed to the increase of intermolecular interaction between DA-MMT particles and PP matrix. Also, the PP/DA-MMT nanocomposites had higher mechanical interfacial properties than those of pristime nanocomposites. These results explained that the pp was easily inserted in the spacing of the silcate interlayers of which were increased.
이한남 ( John Rhee ),곽동민 ( Dong-min Kwak ),박세원 ( Sewon Park ),엄진희 ( Jin-hee Um ) 한국정보처리학회 2015 한국정보처리학회 학술대회논문집 Vol.22 No.1
본 연구에서는 글의 구성요소를 추측하는 가장 높은 성능을 나타내는 알고리즘을 제시한다. 실험 방법은 글의 각 문장에 대한 자질을 추출, 자질 선택, 그리고 데이터에 대해 여러 기계학습 알고리즘을 학습시킨 후 성능을 비교하여 진행하였다. 또한 이 중 가장 높은 성능을 보이는 CRF 를 기존에 연구되어 있는 성능과도 비교하였다. 마지막으로 CRF 가 구성요소를 추측하는 데 있어서 가장 높은 성능을 보이는 이유에 대해 분석하였다. 국내의 유명 어학원 및 토플 웹사이트를 통해 1969 개의 토플 에세이를 수집했으며 2 명의 전문 평가자를 통해 각 문장을 8 개의 분류로 나누었다. 이를 CRF 를 적용한 결과 87.2%의 F score 가 나왔으며 기존 연구결과, 그리고 다른 알고리즘보다 높은 성능을 보였다.
Dolan, John R,Yang, Eun Jin,Kang, Sung-Ho,Rhee, Tae Siek Springer Science and Business Media LLC 2016 The ISME journal Vol.10 No.9
<P>The latitudinal diversity gradient is a well-known biogeographic pattern. However, rarely considered is how a cline in species richness may be reflected in the characteristics of species assemblages. Fewer species may equal fewer distinct ecological types, or declines in redundancy (species functionally similar to one another) or fewer trace species, those occurring in very low concentrations. We focused on tintinnid ciliates of the microzooplankton in which the ciliate cell is housed inside a species-specific lorica or shell. The size of lorica oral aperture, the lorica oral diameter (LOD), is correlated with a preferred prey size and maximum growth rate. Consequently, species of a distinct LOD are distinct in key ecologic characteristics, whereas those of a similar LOD are functionally similar or redundant species. We sampled from East Sea/Sea of Japan to the High Arctic Sea. We determined abundance distributions of biological species and also ecological types by grouping species in LOD size-classes, sets of ecologically similar species. In lower latitudes there are more trace species, more size-classes and the dominant species are accompanied by many apparently ecologically similar species, presumably able to replace the dominant species, at least with regard to the size of prey exploited. Such redundancy appears to decline markedly with latitude in assemblages of tintinnid ciliates. Furthermore, the relatively small species pools of the northern high latitude assemblages suggest a low capacity to adapt to changing conditions.</P>
Assessment of Great Vessels for Anterior Access of L5/S1 Using Patient Positioning
Choi John,Rhee Isaac,Ruparel Sameer 대한척추외과학회 2020 Asian Spine Journal Vol.14 No.4
Study Design: This was a prospective cross-sectional study.Purpose: The aim was to describe the effect of patient positioning, from supine to lateral decubitus position, on the width of the L5/S1 anterior disk space defined by the great vessels.Overview of Literature: The application of the lateral decubitus position interbody fusion has been rapidly increasing; however, there are concerns regarding the access to the lumbosacral region due to the great vessels, which necessitates further morphometric data.Methods: A total of 20 consecutive live patients awaiting lumbar surgery were subjected to two magnetic resonance imaging scans on the same day in both supine and lateral decubitus positions at a single center to investigate the anterior L5/S1 disk space.Results: The bare anterior L5/S1 disk window was present in all patients of this study population, and the mean width was 27 mm in the supine and 22 mm in the lateral decubitus position, with a mean reduction of 5.2 mm between the positions. The oblique corridor angle was measured at a mean of 33°.Conclusions: The bare window of L5/S1 disk space was present within this population group, and it was found to be mobile and changed significantly with patient positioning. Therefore, the spine surgeon or the access surgeon must consider the increased potential vascular risk during disk access in lateral decubitus anterior lumbar interbody spinal fusion surgery.