• Membrane Journal
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• v.27 no.2
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• pp.154-166
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• 2017

Polymeric films for gas barrier applications such as food packaging and electronic devices have attracted great interest due to their cheap, light and easy processability among gas barrier materials. Especially in electronic devices, extremely low gas permeance is necessary for maintaining the device performance. However, current polymeric barrier films still suffer from relatively high gas permeance than other materials. Therefore, there have been strong needs to enhance the gas barrier performance of polymeric barrier films while keep their own advantages. Recently, graphene is highlighted as a 2D-layered material for gas barrier applications. However, owing to the poor workability and difficulty to produce in engineering scale, graphene oxide (GO) is on the rise. GO consists of oxygen-containing functional groups on surface with intrinsic 2D-layered structure and high aspect ratio, and it can be well-dispersed in aqueous polar solvents like water, resulting in scalable mass production. Here, we prepared GO incorporated polyimide (PI) nanocomposites. PI is widely used barrier polymer with high mechanical strength and thermal and chemical stability. We demonstrated that PI/GO nanocomposites could perform as a gas barrier. Furthermore, surfactants (Triton X-100 (TX) and Sodium deoxycholate (SDC)) are introduced to enhance the gas barrier performance by improving the degree of dispersion of GO in PI matrix. As a result, TX enhanced the gas barrier performance of PI/GO nanocomposites which is similar to predicted value. This finding will provide new insight to polymer nanocomposites for gas barrier applications.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.73-79
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• 2017

Maleic anhydride (MAH) grafted polypropylene (PP-g-MAH) copolymers were prepared by changing MAH and styrene monomer (SM) content, using a twin screw extruder at $190^{\circ}C$. The grafting degree was measured by non-aqueous back titration method. The grafting degree of PP-g-MAH-SM copolymer was higher than that of PP-g-MAH at the same MAH content. PP-g-MAH-SM/kenaf fiber (KF) composites were also prepared by using a PP-g-MAH as a matrix at $200^{\circ}C$ and the KF content was fixed at 20 wt%. Based on the degradation temperature investigated by TGA, the thermal stability of PP-g-MAH-SM/KF composites was more enhanced than that of PP-g-MAH only. Mechanical properties of the composites were also improved when MAH and SM applied together. The adhesion degree between the copolymer and KF was confirmed by both SEM pictures of the fractured surface and contact angles.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10a
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• pp.67-70
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• 2000

최근 네트워크 서비스 및 분산 컴퓨팅 환경의 급격한 발전과 더불어 인터넷 기반 지리정보 시스템과 이 기종 시스템간에 상호 운용성을 지원하는 분산 지리정보시스템의 기술이 혁신적으로 발전하게 되었다. 현재 이러한 상호 운용성과 더불어 기 구축된 시스템의 재 사용성을 극대화하기 위하여 개방형 컴포넌트 소프트웨어 기술이 발표[1]되었으며, 최근 발표되는 지리정보시스템들도 이러한 개방화와 컴포넌트화 기술을 채택하여 개발되고 있다. 이러한 개방형 컴포넌트 소프트웨어 기술은 컴퓨터 소프트웨어 산업 전반에 커다란 파급 효과를 끼치고 있다. 지리정보시스템 분야에서는 OpenGIS Consortium(OGC)을 주축으로 하여 개방형 컴포넌트 지리정보시스템을 위한 표준 구현 사양을 발표하고 있으며, 이러한 표준 사양을 수용한 제품들이 개발되고 있는 실정이다. 본 논문에서는 분산 환경에서 다양한 관계형 데이터베이스시스템을 이용하여 OGC가 제시한 OLE/COM 기반의 데이터 제공자 컴포넌트의 설계 및 구현에 중점을 두고 있다. 본 시스템의 데이터 제공자 컴포넌트는 순수한 관계형 데이터베이스시스템 기반 위에서 구성되므로, 우선 OGC에서 요구하는 GIS 관련 핵심 기능들을 제공하기 위해서 우선 관계형 데이터베이스와 ODBC를 이용하여 공간엔진을 구성하고 있다. 본 공간 엔진은 OGC 사양을 충족하기 위해서 이용되는 최소한의 기능-공간데이터 관리 기능, 공간 연산 처리, 공간 색인 기능 그리고 클라이언트와 통신하기 위한 기능-들을 포함하고 있다. 그러므로 본 논문에서는 이러한 공간 엔진의 기반 위에서 OGC OLE DB 제공자 컴포넌트의 설계 및 구현 방법에 대해서 자세히 살펴보고 실제 SQL Server 7.0 환경에서 구축된 공간 엔진 및 OLE DB 제공자 컴포넌트의 구현 예에 대하여 살펴볼 것이다. 혈액내방사선 조사량이 안전용량 범위(200rad)에 속하며 48시간 후 체내잔류량은 서양인과 큰 차이가 없었다.비출현의 소견을 보이는 악성종양 환자의 골 신티그람 53개중 44개 (83.0%)에서 척추 및 늑골에 미만성, 또는 다발성 침습이 관찰되었다. 또 골전이 부위를 두개골, 척추, 견대부, 늑골, 골반, 사지의 근위부 장골의 6개 부위로 나누어 분석할 경우 49개(92.5%)에서 3부위 이상에 전이가 발견되었고, 35개(66.0%)에서 4부위 이상에 전이가 발견되었으며, 5부위 이상, 6개 부위에 모두 전이가 발견된 것은 각각 20개 (37 7%), 11개(20.8%)이었다. 이상의 성적으로 보아 악성종양 환자의 골 신피그라피에서 신장 영상의 비출현은 종양의 광범위한 골전이를 간접적으로 시사하는 소견으로 생각된다. 여러 악성종양중 전립선암에서 신장 영상 비출현의 빈도가 가장 높았으며, 특히 위암에서 골전이 및 신장 영상 비출현의 빈도가 높음은 주목할 만한 것이라 하겠다.출한 결과 인,규소 증가와 자가영양성 미소플랑크톤(ANP)증가에 미치는 요인이 해안과 외해에서 동일하게 가장 큰 설명력을 보였다. N:P 비도 해안에서 36.4, 외해에서 32.6을 보이고 있어 인이 상당히 부족한 것으로 나타났다. 따라서 조사해역은 인이 식물플랑크톤 성장에 중요한 제한요인으로 작용하고 있다고 판단된다.의 회전. 전위력의 강도, 적용시점, 그리고 키, 체중등의 신체적 요인 등이 있으나 능숙한 기계사용과 정확한 슬관절 위치에서 검사할 때 전방 십자 인대 파열에 대한 진단에 유용한 기구이다.태라고 하였다. 본 연구에서는 이러한 근거를 바탕으로 개방형 문제의 유형을 다양한 답이 존재하는 문제, 다양한 해결 전략이 가능한 문제, 답이 없는 문제, 문제 만들기, 일반화가 가능한 문제 등으로 보고, 수학적 창의성 중

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.65-75
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• 2017

This study proposes development of 3U CubeSat standard platform whose function and performance are verified via KAUSAT-5 development. 3U CubeSat platform specification was selected for the design of 3U Cubesat standard platform by examining existing CubeSat and state-of-art technology, and consequently a universally usable 3U CubeSat platform was designed. Standard platform was manufactured in 1.5U size and developed with a modular concept to be able to add and expand payloads and ADCS actuators for meeting the user's needs. In addition, in case of the power system, the solar panel, the battery, and the deployment mechanism are designed to be configured by the user. In the mechanical system design of a standard platform, subsystem and micro equipment functions/performance could be integrated and miniaturized on micro-sized PCBs and maximized electrical capability to accommodate multiple payloads. In the development of the 3U CubeSat, the satellite platform adopts the developed standard platform, which can reduce the cost and schedule for the whole satellite development by reducing the additional function verification.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.5
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• pp.613-621
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• 2006

This study was performed to evaluate the storage quality of milk bread added with $\beta$-glucan (10 20 and 30%), which is a functional food material produced from Agrobacterium spp. R259 KCTC 10197BP. During storage ($20^{\circ}C$, 40% relative humidity) the pH of all breads gradually increased, although there were no significant differences in pH of the $\beta$-glucan added milk bread from those of the control. During storage, the moisture content of all groups decreased, however, moisture contents in the $\beta$-glucan added breads were higher than that in the control. Hunter color values ($L^*,\;a^*\;and\;b^*\;value$) of the milk bread added upto 20% $\beta$-glucan were not significantly different, but the lightness increased during storage. Rapid increase of hardness in the milk bread during storage was observed in control, while the hardness of $\beta$-glucan added bread increased slowly. Also, the degree of retrogradation of bread decreased as $\beta$-glucan addition amount increased. Sensory evaluation showed that the score of over-all acceptability of the bread added with 20% $\beta$-glucan was the highest among treated groups until four days of storage. This study confirmed that the addition of $\beta$-glucan to milk bread maintained the moisture content and delayed hardness during storage.

• Clean Technology
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• v.28 no.1
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• pp.24-31
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• 2022

Petroleum-based plastics are used for various purposes and pose a significant threat to the earth's environment and ecosystem. Many efforts have been taken globally in different areas to find alternatives. As part of these efforts, this study manufactured alginate-based polyvinyl alcohol (PVA) blended films by casting from an aqueous solution prepared by mixing 10 wt% petroleum-based PVA with biodegradable, marine biomass-derived alginate. Glutaraldehyde was used as a cross-linking agent, and cardanol, an alkyl phenol-based bio-oil extracted from cashew nut shell, was added in the range of 0.1 to 2.0 wt% to grant antibacterial activity to the films. FTIR and TGA were performed to characterize the manufactured blended films, and the tensile strength, degree of swelling, and antibacterial activity were measured. Results obtained from the FTIR, TGA, and tensile strength test showed that alginate, the main component, was well distributed in the PVA by forming a matrix phase. The brittleness of alginate, a known weakness as a single component, and the low thermal durability of PVA were improved by cross-linking and hydrogen bonding of the functional groups between alginate and PVA. Addition of cardanol to the alginate-based PVA blend significantly improved the antibacterial activity against S. aureus and E. coli. The antibacterial performance was excellent with a death rate of 98% or higher for S. aureus and about 70% for E. coli at a contact time of 60 minutes. The optimal antibacterial activity of the alginate-PVA blended films was found with a cardanol content range between 0.1 to 0.5 wt%. These results show that cardanol-containing alginate-PVA blended films are suitable for use as various antibacterial materials, including as food packaging.