• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.116.1-116.1
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• 2011

Materials with a combination of high electrical conductivity and optical transparency are important components of many electronic and optoelectronic devices such as liquid crystal displays, solar cells, and light emitting diodes. In this study, to fabricate a low-resistance and high optical transparent electrode film for organic photovoltaic, the following steps were performed: the design and manufacture of an electroforming stamp mold, the fabrication of thermal roll imprinted (TRI) poly-carbonate (PC) patterned films, the manufacture of high-conductivity and low-resistance Ag paste which was filled into patterned PC film using a doctor blade process and then coated with a thin film layer of conductive polymer by a spin coating process. As a result of these imprinting processes the PC films obtained a line width of $10{\pm}0.5{\mu}m$, a channel length of $500{\pm}2{\mu}m$, and a pattern depth of $7.34{\pm}0.5{\mu}m$. After the Ag paste was used to fill part of the patterned film with conductive polymer coating, the following parameters were obtained: a sheet resistance of $9.65{\Omega}$/sq, optical transparency values were 83.69 % at a wavelength of 550 nm.

• Journal of Mechanical Science and Technology
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• 제16권10호
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• pp.1303-1313
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• 2002

Effects of the reduced frequency of upstream wake on downstream unsteady boundary layer flow were simulated by using a Wavier-Stokes code. The Wavier-Stokes code is based on an unstructured finite volume method and uses a low Reynolds number turbulence model to close the momentum equations. The geometry used in this paper is the MIT flapping foil experimental set-up and the reduced frequency of the upstream wake is varied in the range of 0.91 to 10.86 to study its effect on the unsteady boundary layer flow. Numerical solutions show that they can be divided into two categories. One is so called the low frequency solution, and behaves quite similar to a Stokes layer. Its characteristics is found to be quite similar to those due to either a temporal or spatial wave. The low frequency solutions are observed clearly when the reduced frequency is smaller than 3.26. The other one is the high frequency solution. It is observed for the reduced frequency larger than 7.24. It shows a sudden shift of the phase angle of the unsteady velocity around the edge of the boundary layer. The shift of phase angle is about 180 degree, and leads to separation of the boundary layer flow from corresponding outer flow. The high frequency solution shows the characteristics of a temporal wave whose wave length is half of the upstream frequency. This characteristics of the high frequency solution is found to be caused by the strong interaction between unsteady vortices. This strong interaction also leads to destroy of the upstream wake strips inside the viscous sublayer as well as the buffer layer.

• 한국작물학회지
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• 제44권3호
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• pp.296-301
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• 1999

The concerns on the crop damage by ultraviolet (UV) radiations is increasing owing to the decrease of their absorbing stratospheric ozone in the tropospheric. Cultivar differences on early growth of UV radiation among five Korean rice cultivars, four japonica types and one Tongil type (indica-japonica cross hybrid), were studied. Pot-seeded rice plants were grown under four different radiation conditions, i.e., visible radiation only, visible radiation with supplemented with high or low dose of UV-B (280~320 nm in wavelength) and UV-C (less than 280 nm in wavelength). The inhibitory degree on plant height, shoot and root weight and length of leaf blade and leaf sheath were determined at 40 days after seeding. UV-C showed the most severe inhibitory effect on the degree of biomass gain and leaf growth in most cultivars examined, followed by high UV-B and low UV-B. Among the cultivars used, the Kuemobyeo was the most sensitive cultivar and had not repair or showed resistance ability to continued irradiation of UV radiation. However, Janganbyeo and Jaekeon showed different responses that the elongation of leaf blades was promoted on 2nd and 3rd leaves and inhibited on 4th and 5th leaves but this inhibitory degree was reduced on 6 th and 7th leaves. Such tendency on leaf growth means that both cultivars had low sensitivity and most resistant ability to continued irradiation of UV radiation. While Tongil showed different response to enhanced UV radiation, ie., low UV-B promoted leaf growth but the inhibitory was severely increased by continued irradiation of high UV-B and UV-C, which means that Tongil had high threshold of UV radiation for response as an inhibitory light of plant growth. The results of this study indicate that the differences on sensitivity or resistant to the effects of UV radiation were existed among Korean rice cultivars.

• 한국항공우주학회지
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• 제33권11호
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• pp.74-79
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• 2005

액체로켓용 터보펌프 인듀서의 성능향상을 위해서 전진익형 인듀서를 설계하고 유동해석하였다. 전진익형 인듀서의 경우 형상의 특징상 후진익형 인듀서에 비해서 짧은 축길이에도 상대적으로 큰 익단 현절비를 가지고 있으며, 큰 현절비에서도 불구하고 수력효율의 저하가 없었다. 또한 전진익형 인듀서의 경우 일반적인 후진익형 인듀서에 비해서 인듀서 입구에서 발생하는 역류의 크기가 작고, 또한 인듀서 블레이드 팁에서의 국부적인 저압영역이 작은 영역에서 발생하는 것이 관찰되었다. 따라서 전진익형 인듀서의 경우 인듀서 입구의 정압이 높아서 흡입성능의 향상이 있을 것으로 판단되었다. 후진익형 인듀서의 경우 허브의 블레이드가 입구 유동을 교란하여 입구 역류가 커지지만, 후진익형 인듀서의 경우 이러한 교란효과가 없기 때문에 역류가 줄어든 것으로 나타났다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.34-39
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• 2005

본 논문에서는 3차원 초음속 노즐 형상 변수에 따른 부분입사형 터빈의 유동 및 성능 특성을 알아보기 위하여 3차원 노즐 형상 변수를 노즐 모양 및 노즐 출구 단면 형상으로 설정하여 전산해석을 실시하였다. 먼저 노즐 모양에 따른 유동 및 성능 특성을 비교해 본 결과, 사각형 노즐이 원형 노즐보다 축방향 간극내에서 발생하는 전압력 손실이 적었으며, 이로 인하여 파워가 약 1.5% 증가하였다. 다음으로 사각형 노즐출구단면의 면적에 따른 유동 및 성능 특성을 비교해 본 결과, 노즐 출구 단면과 로터의 hub/tip 사이의 간극과 노즐간의 간격이 터빈 성능에 크게 영향을 줌을 확인할 수 있었다.

• 아시안잔디학회지
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• 제25권1호
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• pp.11-16
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• 2011

본 연구는 국내 해안 및 도서지역에 자생하고 있는 버뮤다그래스를 지역별로 수집하여 입지환경에 따른 형태적 변이 정도를 알아보고자 수행되었다. 이들 입지환경, 토양의 화학성과 형태적 특성을 조사하였다. 수집된 자생지에 따라 초장, 엽폭, 엽장, 잎털, 포복경 및 화수당 종자수 등에서 큰 변이를 보여 조사 형질 간에 다양한 변이를 보이는 것을 확인할 수 있었다. 광엽과 세엽 특성의 버뮤다그래스가 존재하고 있었으며, 광엽형의 버뮤다그래스의 경우 열악한 환경에서의 적응성이 매우 높아 중 저관리의 잔디면에 이용 가치가 높을 것으로 생각된다. 상기 입지 환경과 형태적 특성 조사 결과 및 수집된 유전자원들은 앞으로 유전자원으로서 보존 가치가 높으며, 유용유전자를 보존할 수 있는 체계가 마련되어야 할 것으로 판단된다.

• 대한기계학회논문집A
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• 제20권10호
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• pp.3199-3210
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• 1996

The buckling and postbuckling behaviors were sutdied analytically and experimentally for stiffened laminated composite panels under compression loading. The panels with I-, blade, -and hat-shapeed stiffeners were investigated. In the analysis, the stiffened panels were anlyzed using the nonlinear finite element method combined with an improved arc-length method. The progressive failure analysis was done by adopting the maximum stress criterion and complete unloading failure model. The effects of the fiber angles were investigated on the buckling and postbuckling behaviors. In the experiment, the web and the lower cap of each stiffener were formed by the continuous lay-up of the skin for cocuring the stiffened panels. Therefore, the separation between stiffener and skin was not found in the junction part even after postbuckling ultimate load and the stiffened panels had excellent postbuckling load carrying capacity. A shadow moire thchnique was used to monitor the out-of-plane deformations of the panels. The piezoelectric films were attached to the panels to get the failure characteristics of the panel. The analytical results on the buckling load, postbuckling ultimate load, and failure pattern showed good agreement with the experimental results.

• 아시안잔디학회지
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• 제20권1호
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• pp.1-10
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• 2006

본 실험은 한국잔디 신품종 '밀록'(특허출원: 10-2005-0110051)의 개발에 관한 것으로, 국내외에서 수집한 한국잔디류중 우수계통 MJ8를 선발 한 후, 인공자식을 통하여 변이를 확대하였으며, 이들 중에서 품질이 우수한 계통(MJ8S-9)을 선발한 것이다. 신품종 '밀록'은 밀도가 기존의 한국잔디류와 비교해 가장 높았고, 또한 녹색도가 높아 우수한 잔디 품질을 보이며, 녹병에 대한 저항성이 높았다. 형태적 특성으로 엽폭은 4.2rnm로 중엽형이며, 잎 각도는 52.5도로 넓어 광합성 효율이 높다. 지면으로부터 최하위 엽의 잎몸 기부까지의 길이가 1.9cm로 짧아 낮게 깎을 수 있는 특성을 갖고 있다. 또한 '밀록'은 지상 포복경의 색이 황록색이며, RAPD 분석에서 특이밴드를 갖고 있어 다른 잔디류와 식별성이 높은 영양 번식형 신품종이다.

• 식물분류학회지
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• 제43권2호
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• pp.90-93
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• 2013

경상북도 울진군 북면 두천리에서 우리나라 꼬리고사리과의 미기록 분류군인 솔잎고사리(Asplenium septentrionale (L.) Hoffm.)가 발견되었다. 이 분류군은 유럽과 북아메리카에 주로 분포하는 것으로 알려져 있으며 동아시아에서는 대만에서 분포가 기록되었다. 솔잎고사리는 꼬리고사리과의 다른 분류군에 비해서 단엽이고 끝에서 1-2(-3) 차상분지하며, 선형으로 비교적 긴(5-20 mm) 포자낭군을 갖는 점에서 뚜렷이 구분된다. 국명은 엽신의 형태가 소나무 잎과 유사하여 '솔잎고사리'으로 신칭하였다. 주요 형질에 대한 도해와, 기재, 서식지 식물사진을 제시하였다.

• 한국안전학회지
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• 제28권4호
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• pp.14-18
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• 2013

Blades of horizontal axis are nowadays made of composite materials. Generally, composite materials satisfy design provides lower weight and good stiffness, while laminate composites have often damages as like the delamination and cracks at the interface of laminates. The box spar and tail parts of a blade are composed of the CFRP/GFRP hybrid laminate composites. However, delamination and the interfacial crack often occur in the interface of CFRP/GFRP hybrid laminate composites under the mixed mode fracture condition, especially mode I and mode II. Therefore, there is a need for the evaluation of the mixed mode fracture behavior during the delamination of CFRP/GFRP hybrid laminates. This study shows the experimental results for the delamination fracture toughness in CFRP/GFRP hybrid laminate composites. Fracture toughness experiments and estimation are performed by using DMMB(Dissimilar mixed mode bending) specimen. The materials used in the test are a commercial woven type CFRP(Carbon fiber reinforced plastic) prepreg(CF3327) and UD type GFRP(Glass fiber reinforced plastic) prepreg(HD224A). A CFRP/GFRP hybrid laminate composite is composed by the 10 plies CFRP and GFRP prepreg for DMMB. A thickness of CFRP and GFRP layer is 2.5mm and 3.0mm, respectively. Also the fulcrum location which is a loading parameter is changed from 80 to 100mm on the specimen of length 120mm because it defines the ratio of mode I to mode II. In this study, the effects of the fulcrum location are evaluated in the viewpoint of energy release rate in mode I and mode II contribution. The results show that the delamination crack initiates at higher displacement and lower load according to the increase of the fulcrum location ratio. And the variation of the energy release rate for mode I and II contributions for the mode mixity are shown.