• Bulletin of the Korean Chemical Society
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• 제32권spc8호
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• pp.2899-2905
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• 2011

We have demonstrated that TPyPA can be used as an efficient multi-functional material for OLEDs; hole transporting material (HTL), blue and white-light emitter. The device based on TPyPA as the HTL exhibited an external quantum efficiency of 1.7% and a luminance efficiency of 4.2 cd/A; these values are 40% higher than the external quantum efficiency and luminance efficiency of the NPD-based reference device. The device based on TPyPA as a blue-light emitter exhibited an external quantum efficiency of 4.2% and a luminance efficiency of 5.3 $cdA^{-1}$ with CIE coordinates at (0.16, 0.14), the device based on TPyPA as a white-light emitter exhibited an external quantum efficiency of 3.2% and a luminance efficiency of 7.7 $cdA^{-1}$ with CIE coordinates at (0.33, 0.39). Also, TPyPA-based organic solar cell (OSC) exhibited a maximum power conversion efficiency of 0.35%. TPyPA-based organic thin-film transistors (OTFTs) exhibited highly efficient field-effect mobility (${\mu}_{FET}$) of $1.7{\times}10^{-4}cm^2V^{-1}s^{-1}$, a threshold voltage ($V_{th}$) of -15.9 V, and an on/off current ratio of $8.6{\times}10^3$.

• 농촌계획
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• 제3권2호
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• pp.81-89
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• 1997

Still today, many streams are channelized and embanked in Korea. On the other hand, some urban streams are being restored to their natural shapes by landscape planners. It would be better to improve rural streams in a way that would not require restoration in later days. Then, one important question is what kind of embankments the residents prefer for what reasons. Five simulated photos showing from very natural to artificial embankments were used in surveying 90 residents of three villages. Major findings are ; 1. Residents regard safety(from flooding) is the most critical factor to be considered in selection of stream bank materials. 2. They think ideal materials are natural stones or concrete blocks as they look tidy. Concrete retaining walls or vegetated natural slopes are not regarded good. 3. The most preferred material is concrete retaining wall, and the least preferred is vegetated natural slope. They prefer concrete retaining wall which they do not think an ideal material, because it will make a safe bank. 4. Natural stone bank is most preferred for its apperance, and vegetated natural slpoe is most disliked as it may collapse and as it does not look clean.

• 한국건축시공학회지
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• 제11권6호
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• pp.557-566
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• 2011

The surfactants facilitate the formation of foam bubbles under a proper condition and provide stability of foam bubbles by decreasing the surface tension of solutions and increasing the viscosity of foam surface. However, there have been almost no practical data of foam concrete in this regard so far. This study aims to understand the effects of foaming agents such as anionic synthetic surfactant and anionic natural material surfactant on the low density foamed concrete. From the experiment, the vegetable soap of anionic natural material surfactants showed a higher foaming rate, more open pores, slightly lower compressive strength, and a higher permeability coefficient compared to the vegetable soap of anionic synthetic surfactants. It is believed that the natural material surfactants make not only the surface tension of the solution low but also the viscosity of slurry high.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 추계 학술논문 발표대회 논문집
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• pp.43-46
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• 2006

The Hwangtoh is one of the traditional construction material used in wall, plastering material, and ondol (Korean underfloor heating system) with stone and wood. It is an important greenness material and it has much advantages such as; high storage of heat, auto-purification, antibiotic ability, and emission of far infrared rays. But, it is not developed and not used in modern construction because of its low strength and properties of dry shrinkage crack. According to the recent researches and studies, it is evaluated for natural pozzolanic material like flyash or pozzolan. It's possibility on construction material is high because it's chemical and mineralogical proportion is like as Metakaolin and Kaolinite. In this point of view, this study aims to analyze the physical properties on Hwangtoh mortar through an experiment with various activation condition of Hwangtoh, which is natural pozzolanic material, for the purpose of increase the using possibility in construction material.

• 한국염색가공학회:학술대회논문집
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• 한국염색가공학회 2012년도 제46차 학술발표회
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• pp.101-101
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• 2012

천연가죽에 색상을 부여하기 위한 염색공정에서 종전의 합성염료가 아닌 자연에서 추출한 천연염료를 이용하여 블루색상을 가지는 피혁 제조 공정을 확립하였다. 피혁에 적용 가능한 블루색상을 가지는 천연염료 중에 쪽 염료가 유일한 상황이다. 가죽 무게 대비 5%의 쪽염료를 가죽 제조 드럼에 투입하여 100분간 충분히 회전시킨 후에 가죽의 유연성을 부여하는 가지제를 12% 추가로 투입하여 블루 색상을 가지는 가죽을 제조하였다. 그 결과 마찰견뢰도, 일광견뢰도, K/S가 우수한 피혁 염색공정을 확립하였다.

• 한국기계가공학회지
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• 제18권12호
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• pp.28-37
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• 2019

Due to their flexible tailoring qualities, composites have become fascinating materials for structural engineers. While the research area of fiber-reinforced composite materials was previously limited to synthetic materials, natural fibers have recently become the primary research focus as the best alternative to artificial fibers. The natural fibers are eco-friendly and relatively cheaper than synthetic fibers. The main concern of current research into natural fiber-reinforced composites is the prediction and enhancement of the effective material properties. In the present work, finite element analysis is used with a numerical homogenization approach to determine the effective material properties of jute fiber-reinforced epoxy composites with various volume fractions of fiber. The finite element analysis results for the jute fiber-reinforced epoxy composite are then compared with several well-known analytical models.

• Structural Engineering and Mechanics
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• 제57권2호
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• pp.239-263
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• 2016

The paper studies the natural oscillation of the three-layered solid sphere with a middle layer made of Functionally Graded Material (FGM). It is assumed that the materials of the core and outer layer of the sphere are homogeneous and isotropic elastic. The three-dimensional exact equations and relations of linear elastodynamics are employed for the investigations. The discrete-analytical method proposed by the first author in his earlier works is applied for solution of the corresponding eigenvalue problem. It is assumed that the modulus of elasticity, Poisson's ratio and density of the middle-layer material vary continuously through the inward radial direction according to power law distribution. Numerical results on the natural frequencies related to the torsional and spheroidal oscillation modes are presented and discussed. In particular, it is established that the increase of the modulus of elasticity (mass density) in the inward radial direction causes an increase (a decrease) in the values of the natural frequencies.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.923-924
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• 2012

• Macromolecular Research
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• 제15권2호
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• pp.191-194
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• 2007

• 자원환경지질
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• 제39권5호
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• pp.615-626
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• 2006

천연자원 및 물질순환은 자원채광, 운반, 처리, 활용, 회수 및 폐기 등과 관련된 모든 인간의 활동을 포함한다. 지속가능한 물질 관리는 물질순환을 통해 경제적 매개체에 맞추어진 통합된 정책수단이며 경제적으로 효율적이고 환경적으로 효과적인 물질의 사용을 위한 것이다. 산업광물, 금속광물 및 화석연료의 물질흐름은 회수, 처리, 소비 및 최종 폐기와 관련된 환경적 압력 때문에 지금껏 환경정책의 주된 영역이었다. OECD의 물질흐름분석연구는 회원국의 경제운용에서 물질자원의 중요성에 대한 이해의 폭을 넓혀 국가별국가간 천연자원 및 물질흐름에 대한 정량적이고 분석적인 지식기반을 증진하는 것이다. 현재 EU에서는 물질흐름계정이 몇몇 회원국에서 공식통계로 활용되고 있다. 주로 물질흐름분석은 물질흐름계정으로부터 정보를 활용하여 물질사용의 효율성을 평가하는 가치화기법으로서 기존의 경제모니터링시스템에서 파악되지 않는 천연자원 등의 폐기를 인지하는데 활용된다. 물질흐름분석에서 자원사용과 효율성은 장기간의 지속가능성 및 환경정책을 위한 중요한 주제로 떠오르고 있는 것이다.