• 한국재료학회지
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• 제21권12호
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• pp.660-665
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• 2011

1-D ZnO nanowires have been attractive for their peculiar properties and easy growth at relatively low temperature. The length, diameter, and density of ZnO nanowires were determined by the several synthetic parameters, such as PEI concentration, growth time, temperature, and zinc salt concentration. The ZnO nanowires were grown on the <001> oriented seed layer using the hydrothermal process with zinc nitrate and HMTA (hexamethylenetetramine) and their structure and optical properties were characterized. The morphology, length and diameter of the nanowires were strongly affected by the relative and/or absolute concentration of $Zn^{2+}$ and $OH^{-1}$ and the hydrothermal temperature. When the concentrations of the zinc nitrate HMTA were the same as 0.015 M, the length and diameter of the nanowires were $1.97{\mu}m$ and $0.07{\mu}m$, respectively, and the aspect ratio was 28.1 with the preferred orientation along the <001> direction. XRD and TEM results showed a high crystallinity of the ZnO nanowires. Optical measurement revealed that ZnO nanowires emitted intensive stimulated UV at 376 nm without showing visible emission related to oxygen defects.

• 식물조직배양학회지
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• 제24권3호
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• pp.161-165
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• 1997

옥수수의 색소합성을 조절하는 pattern allele의 하나인 R-mb유전자의 구조와 유전적 분석을 수행하였다. R-mb 유전자의 유전분석을 수행한 결과를 검토하여 볼 때 후대로 진행됨에 따라 색소 발현빈도_의 감소경향을 보이고 있었다. 또한 R-mb 유전자가 몇 개의 R subcomplex로 존재하는가를 알기 위해서는 우선 R specific probe인 pR-nj:1를 이용하여 Southern blot hybridization을 실시한 결과 약 3.9kb 및 약 7.75kb영역에서 2개의 band가 관찰되었다. R-mb 유전자를 클로닝하기 위하여 λFIXIIvector를 이용하여 library를 만들고 이로부터 mb-II, III, V, Ⅵ, Ⅶ 등 5개의 clone을 3차의 screen을 거쳐 확보하고 이중 mb-II 및 mb-Ⅵ를 중심으로 제한효소지도를 작성하였으며, 이 유전자의 구조와 기타 R locus관련 유전자들과 비교하였으며, 이러한 두 개의 R 요소가 어떻게 색소발현에 영향을 미치는가에 대에 검토하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.209-209
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• 2010

금(Au) 또는 은(Ag) 금속 나노입자의 모양, 크기, 분포 상태를 조절하여 가시광선과 적외선, 자외선 영역에서 강한 표면 플라즈몬 효과을 이용할 수 있는데, 최근 이러한 금속 나노입자의 표면플라즈몬 효과를 이용하여 태양광 소자의 성능을 향상시키는 연구가 매우 활발하게 이루어지고 있다. 그 중, 높은 효율과 낮은 제작비용 그리고 간단한 공정과정의 장점을 갖고 있어서 크게 주목 받고 있는 염료감응태양전지에서도 금(Au) 또는 은(Ag) 금속 나노입자을 이용하기 위한 많은 연구가 진행되고 있다. 그 예로, Au가 코팅된 $TiO_2$ 기반의 염료감응태양전지구조를 제작하여, 입사된 빛이 표면플라즈몬 효과를 통해, Au에서 여기된 전자들이 Au/$TiO_2$ 사에의 schottky 장벽을 통과하여 $TiO_2$의 전도대 전자들의 밀도가 증가하여, charge carrier generating rate을 높여 소자의 광변환 효율의 향상을 증명하였다. 이에 본 연구에서는, $TiO_2$보다 높은 전자 이동도(mobility)와 직선통로(direct path way)의 장점을 갖고 있는 ZnO nanorod에서의 charge carrier generating rate을 높일 수 있도록, 비교적 가격이 저렴한 Ag nanoparticle을 코팅하였다. ZnO nanorod 제작은 낮은 온도에서 간단하게 성장시킬 수 있는 hydrothermal 방법을 이용하였다. 기판위에 RF magnetron 스퍼터를 이용하여 AZO seed layer를 증착한 후, zinc nitrate $Zn(NO_3)_2{\cdot}6H_2O$과 hexamethylentetramines (HMT)으로 혼합된 용액을 사용해 ZnO nanorods를 성장시켰다. 이 후, Ag를 형성할 수 있도록 열증기증착법을 이용하여 코팅하였다. Ag의 증착시간에 따른 ZnO nanorods에서의 코팅된 구조와 형태를 관찰하기 위해 field emission scanning electron microscopy (FE-SEM)을 이용하여 측정하였으며, 결정성을 조사하기 위해 X-ray diffraction (XRD)을 이용하여 분석하였다. 또한 입사된 빛에 의해, 여기된 ZnO 전도대 전자들이 다시 재결합을 통해 방출되는 photoluminescence 양을 scanning PL 장비를 통해 측정하여 Ag가 코팅된 ZnO nanorod의 광특성을 분석하였다.

• Nuclear Engineering and Technology
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• 제42권6호
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• pp.620-635
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• 2010

In this paper we describe current activities on the project Multi-Scale Modeling and Analysis of convective boiling (MSMA), conducted jointly by the Paul Scherrer Institute (PSI) and the Swiss Nuclear Utilities (Swissnuclear). The long-term aim of the MSMA project is to formulate improved closure laws for Computational Fluid Dynamics (CFD) simulations for prediction of convective boiling and eventually of the Critical Heat Flux (CHF). As boiling is controlled by the competition of numerous phenomena at various length and time scales, a multi-scale approach is employed to tackle the problem at different scales. In the MSMA project, the scales on which we focus range from the CFD scale (macro-scale), bubble size scale (meso-scale), liquid micro-layer and triple interline scale (micro-scale), and molecular scale (nano-scale). The current focus of the project is on micro- and meso-scales modeling. The numerical framework comprises a highly efficient, parallel DNS solver, the PSI-BOIL code. The code has incorporated an Immersed Boundary Method (IBM) to tackle complex geometries. For simulation of meso-scales (bubbles), we use the Constrained Interpolation Profile method: Conservative Semi-Lagrangian $2^{nd}$ order (CIP-CSL2). The phase change is described either by applying conventional jump conditions at the interface, or by using the Phase Field (PF) approach. In this work, we present selected results for flows in complex geometry using the IBM, selected bubbly flow simulations using the CIP-CSL2 method and results for phase change using the PF approach. In the subsequent stage of the project, the importance of effects of nano-scale processes on the global boiling heat transfer will be evaluated. To validate the models, more experimental information will be needed in the future, so it is expected that the MSMA project will become the seed for a long-term, combined theoretical and experimental program.

• 한국해양생명과학회지
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• 제6권1호
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• pp.23-30
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• 2021

북방전복 Haliotis discus hannai 웅성생식세포의 분화과정과 정자의 형태를 미세구조적으로 기재하였다. 정자의 분화과정은 정원세포기, 정모세포기, 정세포기 및 정자기의 4단계로 구분하였다. 정원세포기에서 정모세포기로의 분화과정은 형태학적 변화가 크지 않았다. 그러나 정자변태과정 동안 염색질 응축, 핵의 형태 변화, 첨체와 중편 및 편모 형성 등의 급격한 형태학적 변화를 나타냈다. 북방전복의 정자는 두부, 중편 및 미부로 구성되며, 두부의 길이는 약 5.3 ㎛로 전자밀도가 높은 핵과 총알형의 첨체로 이루어져 있었다. 중편은 기저체와 미토콘드리아로 구성되어 있었으며, 기저체를 중심으로 5개의 미토콘드리아가 한 층으로 배열되어 있었다. 미부의 횡단면은 "9+2"의 미세소관 구조를 보였다. 이러한 형태 및 구조적 특징은 북방전복의 정자는 원시형(primitive type) 정자임을 보여주는 결과이다.

• 한국재료학회지
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• 제29권3호
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• pp.196-203
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• 2019

We report on the fabrication and characterization of an oxide photoanode with a zinc oxide (ZnO) nanorod array embedded in cuprous oxide ($Cu_2O$) thin film, namely a $ZnO/Cu_2O$ oxide p-n heterostructure photoanode, for enhanced efficiency of visible light driven photoelectrochemical (PEC) water splitting. A vertically oriented n-type ZnO nanorod array is first prepared on an indium-tin-oxide-coated glass substrate via a seed-mediated hydrothermal synthesis method and then a p-type $Cu_2O$ thin film is directly electrodeposited onto the vertically oriented ZnO nanorod array to form an oxide p-n heterostructure. The introduction of $Cu_2O$ layer produces a noticeable enhancement in the visible light absorption. From the observed PEC current density versus voltage (J-V) behavior under visible light illumination, the photoconversion efficiency of this $ZnO/Cu_2O$ p-n heterostructure photoanode is found to reach 0.39 %, which is seven times that of a pristine ZnO nanorod photoanode. In particular, a significant PEC performance is observed even at an applied bias of 0 V vs $Hg/Hg_2Cl_2$, which makes the device self-powered. The observed improvement in the PEC performance is attributed to some synergistic effect of the p-n bilayer heterostructure on the formation of a built-in potential including the light absorption and separation processes of photoinduced charge carriers, which provides a new avenue for preparing efficient photoanodes for PEC water splitting.

• 한국분말재료학회지
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• 제29권6호
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• pp.511-516
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• 2022

Electroless plating is widely utilized in engineering for the metallization of insulator substrates, including polymers, glass, and ceramics, without the need for the application of external potential. Homogeneous nucleation of metals requires the presence of Sn-Pd catalysts, which significantly reduce the activation energy of deposition. Therefore, rinsing conducted during Sn sensitization and Pd activation is a key variable for the formation of a uniform seed layer without the lack or excess of catalysts. Herein, we report the optimized rinsing process for the functionalization of Sn-Pd catalysts, which enables the uniform FeCo metallization of the glass fibers. Rinsing enables good deposition of the FeCo alloy because of the removal of excess catalysts from the glass fiber. Concurrently, excessive rinsing results in a complete removal of the Sn-Pd nucleus. Collectively, the comprehensive study of the proposed nanomaterial preparation and surface science show that the metallization of insulators is a promising technology for electronics, solar cells, catalysts, and mechanical parts.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2022년도 추계학술대회
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• pp.187-187
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• 2022

Purple-discoloration of the uppermost leaves has been observed in some soybean cultivars in recent years. The purpose of this study was to characterize the novel phenotypic changes between the uppermost and middle leaves via multiple approaches. First, quantitative trait loci mapping was conducted to detect loci associated with the novel phenotype using 85 recombinant inbred lines (RILs) of the 'Daepung' × PI 96983 population. 180K SNP data, a major quantitative trait locus (QTL) was identified at around 60 cM of chromosome 6, which accounts for 56% of total phenotypic variance. The genomic interval is about ~700kb, and a list of annotated genes includes the T-gene which is known to control pubescence and seed coat color and is presumed to encode flavonoid 35-hydroxylase (F3'H). Based on Hyperspectral imaging, the reflectance at 528-554 nm wavelength band was extremely reduced in the uppermost leaves compared to the middle (green leaves), which is presumed die to the accumulation of anthocyanins. In addition, purple-discolored leaf tissues were observed and compared to normal leaves using a transmission electronic microscope (TEM). Base on observations of the cell organelles, the purple-discolored uppermost leaves had many pigments formed in the epidermal cells unlike the normal middle leaves, and the cell wall thickness was twice as thick in the discolored leaves. The thickness of the thylakoid layer in the chloroplast the number of starch grains, the size of starch all decreased in the discolored leaves, while the number of plastoglobule and mitochondria increased.

• 한국결정성장학회지
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• 제13권1호
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• pp.5-14
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• 2003

Principles of a novel pulse growing method are described. The method realized in the crystal growing on a seed from melts under raw melt feeding provided a more reliable control of the crystallization process when producing large alkali halide crystals. The slow natural convection of the melt in the crucible at a constant melt level is intensified by rotating the crucible, while the crystal rotation favors a more symmetrical distribution of thermal stresses over the crystal cross-section. Optimum rotation parameters for the crucible and crystal have been determined. The spatial position oi the solid/liquid phase interface relatively to the melt surface, heaters and the crucible elements are considered. Basing on that consideration, a novel criterion is stated, that is, the immersion extent of the crystallization front (CF) convex toward the melt. When the crystal grows at a <> CF immersion, the raised CF may tear off from the melt partially or completely due to its weight. This results in avoid formation in the crystal. Experimental data on the radial crystal growth speed are discussed. This speed defines the formation of a gas phase layer at the crystal surface. The layer thickness il a function of time a temperature at specific values of pressure in the furnace and the free melt surface dimensions in the gap between the crystal and crucible wall. Analytical expressions have been derived for the impurity component mass transfer at the steady-state growth stage describing two independent processes, the impurity mass transfer along the <> path and its transit along the <> one. The heater (and thus the melt) temperature variation is inherent in any control system. It has been shown that when random temperature changes occur causing its lowering at a rate exceeding $0.5^{\circ}C/min$, a kind of the CF decoration by foreign impurities or by gas bubbles takes place. Short-term temperature changes at one heater or both result in local (i.e., at the front) redistribution of the preset axial growth speed.

• 마이크로전자및패키징학회지
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• 제8권1호
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• pp.33-38
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• 2001

5인치 실리콘 기판위에 수 회 코팅기술을 이용하여 두꺼운 감광막을 얻은 후, 전기도금 법으로 솔더범프를 형성하고, 비아크기의 변화에 따른 리플로 전과, 후의 솔더범프 형성에 미치는 영향을 조사하였다. 리플로 전의 범프바닥 (bump bottom) 직경은 리플로 후에도 거의 변화가 없는 반면, 솔더범프 모양은 패턴된 비아직경 크기에 크게 의존했다. 비아직경이 클수록 높은 도금효율을 보였다. 비아직경이 작을수록 리플로 후의 범프는 리플로 전의 범프높이와 비교하여 크게 낮아졌지만, aspect ratio는 크다는 것을 알았다. 고밀도와 고aspect ratio를 갖는 범프를 얻기 위하여 비아직경과 범프피치를 줄여야하지만, 과도금 (overplating), 또는 리플로를 할 때 최인접 간 범프끼리 맞닿을 수 있기 때문에 최인접 간 범프거리 확보는 중요하다. 비아높이(film두께)를 높게 하여 과도금을 하지 않고 비아높이가지만 도금하여 과도금으로 인한 최인접 범프끼리의 맞닿음을 없애는 방법과 범프배열을 zig-zag로 하는 방법을 혼용하면 과도금, 또는 리플로를 할 때 최인접 범프 간에 맞닿는 문제는 어느 정도 해결할 수 있다.