• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.226-226
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• 2013

Si is a dominant solar material, which is the second most abundant element in the earth giving a benefit in the aspect in cost with low toxicity. However, the inherent limit of Si has an indirect band gap of 1.1 eV resulting in the limited optical absorption. Therefore, a critical issue has been raised to increase the utilization of the incident light into the Si absorber. The enhancement of light absorption is a crucial to improve the performances and thus relieves the cost burden of Si photovoltaics. For the optical aspect, an efficient design of a front surface, where the incident light comes in, has been intensively investigated to improve the performance of photon absorption. Lambertian light trapping can be attained when the light active surface is ideally rough to increase the optical length by about 50 compared to a planar substrate. This suggests that an efficient design may reduce thickness of the Si absorber from the conventional 100~300 ${\mu}m$ to less than 3 ${\mu}m$. Theoretically, a hole-array structure satisfies an equivalent efficiency of c-Si with only one-twelfth mass and one-sixth thickness. Various approaches have been applied to improve the incident light utilization in a Si absorber using textured structures, periodic gratings, photonic crystals, and nanorod arrays. We have designed hole and pillar structured Si absorbers. Four-different Si absorbers have been simultaneously fabricated on an identical Si wafer with hole arrays or pillar arrays at a fixed depth of 2 ${\mu}m$. We have found that the significant enhanced solar cell performances both for the hole arrayed and pillar arrayed Si absorbers compared to that of a planar Si wafer resulting from the effective improvement in the quantum efficiencies.

• Journal of Microbiology and Biotechnology
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• 제24권6호
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• pp.771-780
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• 2014

A putative lipolytic enzyme gene, named as est9x, was obtained from a marine microbial metagenome of the South China Sea. Sequence analysis showed that Est9X shares lower than 27% sequence identities with the characterized lipolytic enzymes, but possesses a catalytic triad highly conserved in lipolytic enzymes of the ${\alpha}/{\beta}$ hydrolase superfamily. By phylogenetic tree construction, Est9X was grouped into a new lipase/esterase family. To understand Est9X protein in depth, it was recombinantly expressed, purified, and biochemically characterized. Within potential hydrolytic activities, only lipase/esterase activity was detected for Est9X, confirming its identity as a lipolytic enzyme. When using p-nitrophenol esters with varying lengths of fatty acid as substrates, Est9X exhibited the highest activity to the C2 substrate, indicating it is an esterase. The optimal activity of Est9X occurred at a temperature of $65^{\cric}C$, and Est9X was pretty stable below the optimum temperature. Distinguished from other salt-tolerant esterases, Est9X's activity was tolerant to and even promoted by as high as 4 M NaCl. Our results imply that Est9X is a unique esterase and could be a potential candidate for industrial application under extreme conditions.

• 한국분말재료학회지
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• 제24권3호
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• pp.187-194
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• 2017

Selective laser melting (SLM) can produce a layer of a metal powder and then fabricate a three-dimensional structure by a layer-by-layer method. Each layer consists of several lines of molten metal. Laser parameters and thermal properties of the materials affect the geometric characteristics of the melt pool such as its height, depth, and width. The geometrical characteristics of the melt pool are determined herein by optical microscopy and three-dimensional bulk structures are fabricated to investigate the relationship between them. Powders of the commercially available Fe-based tool steel AISI H13 and Ni-based superalloy Inconel 738LC are used to investigate the effect of material properties. Only the scan speed is controlled to change the laser parameters. The laser power and hatch space are maintained throughout the study. Laser of a higher energy density is seen to melt a wider and deeper range of powder and substrate; however, it does not correspond with the most highly densified three-dimensional structure. H13 shows the highest density at a laser scan speed of 200 mm/s whereas Inconel 738LC shows the highest density at 600 mm/s.

• 한국전기전자재료학회논문지
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• 제13권6호
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• pp.526-532
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• 2000

The paste on the glass or fabrication of the PDP(Plasma Display Panel) barrier rib was selectively etched using focused A $r_{+}$ laser(λ=514 nm) and Nd:YAG(λ=532, 266 nm) laser irradiation. The depth of the etched grooves increase with increasing a laser fluence and decreasing a laser beam scan speed. Using second harmonic of Nd:YAG laser(532 nm) the etching threshold laser fluence was 6.5 mJ/c $m^2$ for the sample of PDP barrier rib. The thickness of 180 ${\mu}{\textrm}{m}$ of the sample on the glass was clearly removed without any damage on the glass substrate by fluence of 19.5J/c $m^2$beam scan speed of 20${\mu}{\textrm}{m}$ /s. In order to increase the etch rate of the barrier rib material barrier rib samples heated by a resistive heater during laser irradiation. The heated sample has many defects and becomes to be fragile. This imperfection of the structure compared to the sample without heat treatment allows the effective etching by the focused laser beam. The etch rates were 65${\mu}{\textrm}{m}$/s and 270 ${\mu}{\textrm}{m}$/s at room temperature and 20$0^{\circ}C$, respectively.y.

• 한국패류학회지
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• 제31권3호
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• pp.165-170
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• 2015

어린 북방전복 (Haliotis discus hannai) 에 대한 포식자 (불가사리류 제외) 의 존재 여부를 확인하고자 경북 울진 연안 3개 해역 (양정, 죽진 및 봉평)에서 SCUBA diving을 이용하여 2014년 2월부터 12월까지 총 9회에 걸친 직접 관찰 조사를 수행하였다. 조사 결과 수심 10 m 이내 (최대 15 m)의 해역에서 상대적 암반 구성 비율이 가장 높은 죽진 해역 (60.3%)에서 어린 북방전복을 포식하고 있는 총 6개체의 갈색띠매물고둥 (Neptunea cumingii)이 발견되었다. 따라서, 본 연구결과는 갈색띠매물고둥이 어린 북방전복에 대한 포식자라는 새로운 사실을 제시하고 있다.

• 마이크로전자및패키징학회지
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• 제22권1호
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• pp.63-67
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• 2015

본 연구에서는 대면적 나노 금속 격자형 편광 필름 제작에서 증착 두께에 따른 광 특성 연구를 수행하였다. 나노 금속 격자형 편광필름은 PET(Polyethylene phthalate)기판 위에 알루미늄 선 격자 구조로 구성된다. 본 연구에서는 대면적 편광필름 제작을 위한 증착공정을 통한 금속 격자 형성을 목표로 하였으며, 금속 격자형 편광 필름 제작에 있어 최적의 투과율과 소광비를 가지는 금속 박막 형성 조건을 도출하였다. 최적화 공정에 의해 나노 금속 격자형 편광필름은 140 nm 주기, 70 nm 선폭, 70 nm의 금속층 높이를 가지는 금속 격자 구조로 제작 되었다. 분석결과 600 nm 파장에서 80% 이상의 최고 투과율 및 $10^6$ 이상의 소광비를 가지는 나노 금속 격자 편광필름의 높은 광 특성을 확인하였다.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.153-160
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• 2010

집적광학 바이오센서 구조에 적합한 비공진 반사 광도파로(ARROW: Antiresonant Reflecting Optical Waveguides)의 Si(기판)/$SiO_2$(클래딩)/$Si_3N_4$(비공진 클래딩)/$SiO_2$(코어)/air 다층박막 립 광도파로에 대한 최적화를 BPM 전산해석 방법을 이용해서 수행하였다. 전송손실을 최소화하기에 적합한 비 공진 클래딩의 두께를 유도하였으며, 소산파와 깊은 관련이 있는 손실모드에 대해서 이론적으로 검토하였다. 전산해석을 통해서 전송손실을 최소화하기 위한 립 광도파로의 깊이, 폭, 굴절률과 클래딩의 두께를 각각 2.3${\mu}m$, 5${\mu}m$, 1.488, 그리고 0.11${\mu}m$로 계산되었다. 최적화된 제원으로 비공진 반사 광도파로의 2차원, 3차원 전송특성을 확인하였다.

• 한국기계가공학회지
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• 제19권8호
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• pp.94-103
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• 2020

This study investigated the effects of ultrasonic nanocrystal surface modification (UNSM) on the deteriorated surface of AISI SUS316L additively manufactured (AM) using the powder bed fusion (PBF) technique. Specifically, the effects of UNSM conditions on surface topology, hardness, and anti-corrosion were examined. Before UNSM treatment, the stainless steel 316L powder was processed via the PBF machine to prepare a substrate. We observed surface changes due to UNSM treatments in PBF SUS316L substrates and examined the correlation between topology changes, roughness, hardness, and anti-corrosion. After UNSM treatment, the coarse as-built surface was refined, and a regular micro-profile was implemented. Compared to the non-treated PBF sample, the waviness and roughness of the surfaces after UNSM treatment decreased by up to 56.0% and 94.5%, respectively, and decreased further as the interval decreased. The hardness improved by up to 63.0% at a maximum depth of 500 ㎛ from top surface by the UNSM treatment. The results of the corrosion test showed that the corrosion resistance of the UNSM specimens was moderately improved compared to that of the untreated surface. This study confirmed that UNSM is an effective post-processing technique for additively manufactured parts.

• Composites Research
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• 제32권6호
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• pp.314-318
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• 2019

본 연구에서는 습식 코팅 방식 중 하나인 다층박막적층법의 자동화 시스템을 제작하였다. 특히, 본 연구에서 제안한 자동화 시스템은 다층박막적층법의 공정 변수(예를 들어, 증착 재료, 코팅 깊이, 코팅 및 헹굼 시간)를 제어함으로써 손으로 작업하는 것과 동일한 변수 조작이 가능하게 설계되었다. 자동화 시스템을 통해 기판을 완벽하게 용액 안으로 침액시킬 수 있으며, 이를 통해 특별한 분자간 결합(예를 들어, 정전기적 인력, 공유 및 수소 결합)을 통해 기판 위에 균일한 다층의 박막 형성이 가능하다. 두 종류 이상의 용액으로 기판이 침액될 때, 이 기판은 다른 용액으로 이동되기 전에 청소 구역에서 헹굼과 건조 과정을 거친다. 이러한 담금, 헹굼, 건조 과정은 모두 컴퓨터 프로그램에 의해 제어 가능하다. 본 연구에서는 자동화 시스템을 통해 그래핀을 기반으로 하는 다층박막 샘플을 제작하였고, 균일한 그래핀의 적층 여부를 분석하기 위해 제작된 샘플의 흡광도와 두께를 측정하였다. 기판 위에 그래핀과 고분자 층의 적층이 진행될수록 흡광도와 두께가 균일하게 증가하는 결과를 통해, 본 연구에서 제작한 자동화 시스템이 수작업을 통한 다층박막의 적층을 완벽하게 대체 가능함을 알 수 있었다.

• 환경생물
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• 제34권4호
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• pp.272-280
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• 2016

Changes in land use and increase in urban energy consumption influence urban life. This study analyzed the characteristics and patterns of urban heat and presents management schemes to generate a comfortable and sustainable urban environment. The study aimed to demonstrate the positive effects of artificial ground greening on improving the microclimate through evapotranspiration using perennial herbs. We have designed a chamber that could control constant temperature and humidity, measure temperature reductions in each plant and changes in sensible heat and latent heat. This study identified Sedum kamtschaticum as the most effective plant in controlling temperature. At $22^{\circ}C$, $3.2^{\circ}C$ temperature reduction was observed, whereas four other plants showed a $1.5^{\circ}C$ reduction. At $25^{\circ}C$, $2.0^{\circ}C$ temperature reduction was observed. On the other hand, the use of Sedum sarmentosum resulted in the lowest effect. Zoysia japonica is the most commonly used ground covering plant, although the temperature reduction of Lysimachia nummularia was more effective at high temperature conditions. Sensible heat and latent heat were calculated to evaluate the thermal performance of energy. At a temperature >$30^{\circ}C$, L. nummularia and S. sarmentosum emitted high latent heat. In this study, we analyzed the thermal performance of green roof perennial plants; in particular, we analyzed the evapotranspiration and temperature reduction of each plant. Since the substrate depth and types, plant species, and seasonal change may influence temperature reduction and latent heat of green roofs, further studies are necessary.