• Environmental Engineering Research
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• v.24 no.3
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• pp.463-473
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• 2019

Nanoscale zero-valent iron (nZVI) has proved to be an effective tool in applied environmental nanotechnology, where the decreased particle diameter provides a drastic change in the properties and efficiency of nanomaterials used in water purification. However, the agglomeration and colloidal instability represent a problematic and a remarkable reduction in nZVI reactivity. In view of that, this study reports a simple and cost-effective new strategy for ultra-small (< 7.5%) distributed functionalized nZVI-EG (1-9 nm), with high colloidal stability and reduction capacity. These were obtained without inert conditions, using a simple, economical synthesis methodology employing two stabilization mechanisms based on the use of non-aqueous solvent (methanol) and ethylene glycol (EG) as a stabilizer. The information from UV-Vis absorption spectroscopy and Fourier transform infrared spectroscopy suggests iron ion coordination by interaction with methanol molecules. Subsequently, after nZVI formation, particle-surface modification occurs by the addition of the EG. Size distribution analysis shows an average diameter of 4.23 nm and the predominance (> 90%) of particles with sizes < 6.10 nm. Evaluation of the stability of functionalized nZVI by sedimentation test and a dynamic light-scattering technique, demonstrated very high colloidal stability. The ultra-small particles displayed a rapid and high nitrate removal capacity from water.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.519-524
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• 2019

Even though stainless steel foil is not a highly efficient material for film-type solar cell, it has strong passivation capability without additional process. In this study, silicone resin was employed during a-Si:H thin film solar cell fabrication for the purpose of planarization and electrical insulation. In the first stage of process, silicone resin was coat onto the stainless steel (STS) using spin coater with thickness of $2{\sim}3{\mu}m$ and followed by aluminum deposition using ion beam application. Unexpectedly buckling was formed during aluminum deposition process. After subsequent fabrication processes, solar cell performance was evaluated. In voltage-current data, slight increase of cell performance was obtained and interpreted by the increase of light scattering.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.95-102
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• 2022

Since the organic light-emitting diodes (OLEDs) have been widely investigated as next-generation displays, it has been successfully commercialized as a flexible and rollable display. However, there is still wide room and demand to improve the device characteristics such as power efficiency and lifetime. To solve this issue, there has been a wide research effort, and among them, the internal and the external light extraction techniques have been attracted in this research field by its fascinating characteristic of material independence. In this study, a micro-nano composite structured external light extraction layer was demonstrated. A reactive ion etching (RIE) process was performed on the surfaces of hexagonally packed hemisphere micro-lens array (MLA) and randomly distributed sphere diffusing films to form micro-nano composite structures. Random nanostructures of different sizes were fabricated by controlling the processing time of the O₂ / CHF₃ plasma. The fabricated device using a micro-nano composite external light extraction layer showed 1.38X improved external quantum efficiency compared to the reference device. The results prove that the external light extraction efficiency is improved by applying the micro-nano composite structure on conventional MLA fabricated through a simple process.

• Journal of the Korean Vacuum Society
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• v.7 no.s1
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• pp.57-77
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• 1998

Heteroepitaxial $Y_2O_3$ films were grown on a Si(111) substrate by ionized cluster beam deposition(ICBD) in ultra high vacuum, and its qualities such as crystllitnity, film stress, and morphological characteristics were investigated using the various measurement methods. The crystallinity was investigated by x-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED). Interface crystallinity was also examined by Rutherford backscattering spectroscopy(RBS) channeling, transmission electron microscopy(TEM). The stress of the films was measured by RBS channeling and XRD. Surface and interface morphological characteristics were investigated by atomic force microscopy (AFM) and x-ray scattering method. Comparing the interface with the surface characteristics, we can conclude that many defects at the interface region were generated by interface reaction between the yttrium metal and SiO2 layer and by ion beam characteristic such as shallow implantation, so that they influenced the film qualities. The film quality was dominantly depended on the characteristic temperature range. In the temperature range from $500^{\circ}C$ to $600^{\circ}C$, the crystallinity was mainly improved and the surface roughness was drastically decreased. On the other hand, in the temperature range from $600^{\circ}C$ to $700^{\circ}C$, the compressive stress and film density were dominantly increased, and the island size was more decreased. Also the surface morphological shape was transformed from elliptical shape to triangular. The film stress existed dominantly at the interface region due to the defects generation.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.71-78
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• 2012

Illite-smectite mixed layers (I-S) occurring authigenically in diagenetic and hydrothermal environments reacts toward more illite-rich phases as temperature and potassium ion concentration increase. For that reason, I-S is often used as geothermometry and/or geochronometry at the field of hydrocarbons or ore minerals exploration. Generally, I-S shows X-ray powder diffraction (XRD) patterns of ultra-thin lamellar structures, which consist of restricted numbers of sillicate layers (normally, 5 ~ 15 layers) stacked in parallel to a-b planes. This ultra-thinness is known to decrease I-S expandability (%S) rather than theoretically expected one (short-stacking effect). We attempt here to quantify the short stacking effect of I-S using the difference of two types of expandability: one type is a maximum expandability ($%S_{Max}$) of infinite stacks of fundamental particles (physically inseparable smallest units), and the other type is an expandability of finite particle stacks normally measured using X-ray powder diffraction (XRD) ($%S_{XRD}$). Eleven I-S samples from the Geumseongsan volcanic complex, Uiseong, Gyeongbuk, have been analyzed for measuring $%S_{XRD}$ and average coherent scattering thickness (CST) after size separation under 1 ${\mu}m$. Average fundamental particle thickness ($N_f$) and $%S_{Max}$ have been determined from $%S_{XRD}$ and CST using inter-parameter relationships of I-S layer structures. The discrepancy between $%S_{Max}$ and $%S_{XRD}$ (${\Delta}%S$) suggests that the maximum short-stacking effect happens approximately at 20 $%S_{XRD}$, of which point represents I-S layer structures consisting of ca. average 3-layered fundamental particles ($N_f{\approx}3$). As a result of inferring the $%S_{XRD}$ range of each Reichweite using the $%S_{XRD}$ vs. $N_f$ diagram of Kang et al. (2002), we can confirms that the fundamental particle thickness is a determinant factor for I-S Reichweite, and also that the short-stacking effect shifts the $%S_{XRD}$ range of each Reichweite toward smaller $%S_{XRD}$ values than those that can be theoretically prospected using junction probability.

• Journal of Microbiology and Biotechnology
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• v.21 no.8
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• pp.808-817
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• 2011

Because of its elevated cellulolytic activity, the filamentous fungus Trichoderma harzianum has a considerable potential in biomass hydrolysis applications. Trichoderma harzianum cellobiohydrolase I (ThCBHI), an exoglucanase, is an important enzyme in the process of cellulose degradation. Here, we report an easy single-step ion-exchange chromatographic method for purification of ThCBHI and its initial biophysical and biochemical characterization. The ThCBHI produced by induction with microcrystalline cellulose under submerged fermentation was purified on DEAE-Sephadex A-50 media and its identity was confirmed by mass spectrometry. The ThCBHI biochemical characterization showed that the protein has a molecular mass of 66 kDa and pI of 5.23. As confirmed by smallangle X-ray scattering (SAXS), both full-length ThCBHI and its catalytic core domain (CCD) obtained by digestion with papain are monomeric in solution. Secondary structure analysis of ThCBHI by circular dichroism revealed ${\alpha}$- helices and ${\beta}$-strands contents in the 28% and 38% range, respectively. The intrinsic fluorescence emission maximum of 337 nm was accounted for as different degrees of exposure of ThCBHI tryptophan residues to water. Moreover, ThCBHI displayed maximum activity at pH 5.0 and temperature of $50^{\circ}C$ with specific activities against Avicel and p-nitrophenyl-${\beta}$-D-cellobioside of 1.25 U/mg and 1.53 U/mg, respectively.

• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.607-617
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• 1998

Au was dosed on $TiO_2(001)$ film grown epitaxially on Mo(100) surface in about 90 ${\AA}$ thickness. The growth mode of Au, thermal behavior and stability of the Au clusters, and the binding energy shift of Au 4f with the change in the amount of Au loading were studied by Auger Electron Spectroscopy (AES), Temperature Programmed Desorption (TPD) spectroscopy, Ion Scattering Spectroscopy (ISS), and X-ray Photoelectron Spectroscopy (XPS). Au grows three dimensionally on $TiO_2(001)$ film and the average size of Au clusters prepared at low temperature is smaller than those at higher temperature and the size increases with temperature irreversibly. Au clusters on $TiO_2(001)/Mo(100)$ start evaporation at 1000 K. TPD spectra of Au show very asymmetric peaks with the same leading edges irrespective of the amount of Au loading. The temperature at the peak maximum increases with the amount of Au. The desorption energy of Au obtained from the leading edge analysis of the TPD spectra is about 50 kcal/mol. The initial sticking coefficient of Au on $TiO_2(001)$ is constant in the temperature range of 200-600 K. The binding energy of Au 4f for the Au loaded on the film less than 2.0 MLE shifts to higher energy compared with the bulk Au. The shift is +0.3 eV at 0.1 MLE Au amount.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1992.10a
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• pp.113-116
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• 1992

소음의 발생 원인은 공기역학적 측면과 구조적 측면으로 나누어지는데, 실제 로는 유동장에서 발생되는 음원과 구조물에서 발생되는 진동과의 상호 간섭 에 의해 보다 복잡한 형태로 발생된다. 음장 문제를 두가지 범주로 구분하면 첫째는 음원과 구조물과의 상호교란에 의한 산란문제(Scattering)와 둘째로 구조물의 자체 진동에 의한 음의 전파현상과 구조물내부에 회전체와 같은 음원이 존재하는 경우에 음의 전파를 관측하는 방사문제(Radiation)가 있다. 실제로 산업용 터빈이나 비행기 엔진 흡입구에서 발생되는 소음, 또는 자동 차의 배기구를 통해 발생되는 소음 그리고 엔진의 진동에 의한 구조적 소음, 기타 가전제품의 회전체(Fan & Motor)에 의한 소음은 방사(Radiation)의 문 제로서 중요 관심 과제이다 수치적 기법으로 근래에 많이 사용하는 방법으 로 BEM(경계요소법), FEM(유한요소법), FDM(유한차분법)이 있는데 본 연 구에서는 유한요소법을 이용하기로 한다. 지금까지는 주로 BEM을 통해서 Far-Field의 음향장을 해석하였지만 복잡한 형상을 갖는 구조물내부에서의 음향장 변화나 구조물 내부에 음원이 존재하는 경우 또는 구조물 자체가 갖 는 물리적 특성치 변화 즉 물체표면에서의 부분 진동문제의 음향장 해석에 있어서 가장 잘 대체해 나갈 수 있는 방법이 유한 요소법이라고 여겨진다. 본 연구에서는 2차원 또는 기하학적으로 축대칭인 3차원 Duct내부에 음원이 존재하는 경우 음원전파에 따른 Near-field와 far-field에서 음의 방향성을 예측하기 위해 먼저 기본적인 유한요소법에 의한 Robin 경계조건을 사용하 여 계산된 결과와 Infinite Element를 도입하여 계산할 결과를 비교하여, Infinite Element가 보다 효율적이며 타당한 결과를 얻음을 확인해 보기로 한다.다 복합적인 측면에서 치료에 임하여야 할 것으로 사료된다. with such configuration.trap with 2.88[eV] deep of injected space charge from the chathode in the crystaline regions. The origin of ${\alpha}$$_2$ peak was regarded as the detrapping process of ions trapped with 0.9[eV] deep originated from impurity-ion remained in the specimen during production process of the material, in the crystalline regions. The origin of ${\beta}$ peak was concluded to be due to the depolarization process of "C=0"dipole with the activation energy of 0.75[eV] in the amorphous regions. The origin of ${\gamma}$ peak was responsible to the process combined with the depolarization of "CH$_3$", chain segment, with the activation energy of carriers from the shallow trap with 0.4[eV], in he amorphous regions.의 증발산율은 우기의 기상자료를 이용하여 구한 결과 0.05 - 0.10 mm/hr 의 범위로서 이로 인한 강우손실량은 큰 의미가 없음을 알았다.재발이 나타난 3례의 환자

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.413-413
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• 2014

In this paper, we present a fabrication method of functionalized gold nanostructures on flexible substrate that can be implemented for plasmonic sensing application. For biomolecular sensing, many researchers exploit unconventional lithography method like nanoimprint lithography (NIP), contact transfer lithography, soft lithography, colloidal transfer printing due to its usability and easy to functionalization. In particular, nanoimprint and contact transfer lithography need to have anti-adhesion layer for distinctive metallic properties on the flexible substrates. However, when metallic thin film was deposited on the anti-adhesion layer coated substrates, we discover much aggravation of the mold by repetitive use. Thus it would be impossible to get a high quality of metal nanostructure on the transferred substrate for developing flexible electronics based transfer printing. Here we demonstrate a method for nano-pillar mold and transfer the controllable nanoparticle array on the flexible substrates without an anti-adhesion layer. Also functionalization of gold was investigated by the different length of thiol applied for effectively localized surface plasmonic resonance sensing. First, a focused ion beam (FIB) and ICP-RIE are used to fabricate the nanoscale pillar array. Then gold metal layer is deposited onto the patterned nanostructure. The metallic 130 nm and 250 nm nanodisk pattern are transferred onto flexible polymer substrate by bi-layer functionalized contact imprinting which can be tunable surface energy interfaces. Different thiol reagents such as Thioglycolic acid (98%), 3-Mercaptopropionic acid (99%), 11-Mercaptoundecanoic acid (95%) and 16-Mercaptohexadecanoic acid (90%) are used. Overcoming the repeatedly usage of the anti-adhesion layer mold which has less uniformity and not washable interface, contact printing method using bi-layer gold array are not only expedient access to fabrication but also have distinctive properties including anti-adhesion layer free, functionalized bottom of the gold nano disk, repeatedly replicate the pattern on the flexible substrate. As a result we demonstrate the feasibility of flexible plasmonic sensing interface and anticipate that the method can be extended to variable application including the portable bio sensor via mass production of stable nanostructure array and other nanophotonic application.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.5
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• pp.772-785
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• 1998

This study was undertaken to clarify the microstructure of the different IPS Empress ingots by etching and to observe the change of leucite crystal structure according to subsequent heat treatment and the crystal distribution according to sprue types(${\phi}2.8mm$, single sprue; ${\phi}1.8mm$, double sprue) by scanning electron microscopy. IPS Empress T1, O1 ingots used for staining technique, and Dentin(A2) ingots used for layering technique were selected for this study. To observe the microstructures of these ingots before pressing, the specimens were prepared in splinters($3{\times}3{\times}3mm$) taken from the original ingots. And to estimate crystal distribution and microstructural change by sprue type and subsequent heat treatment. the specimens($3{\times}3{\times}3mm$) were heat-pressed through the two types of sprues with different diameters and numbers, and all specimens were fired according to the recommended firing schedule. The observed surface was ground with waterproof papers($#800{\sim}#1800$) on the grind polisher and was cleaned ultrasonically. All specimen were etched with 0.5% hydrofluoric acid. After etching, the surface was treated by ion sputter coating for SEM observation at an accelerating voltage of 20kV. In all specimens, the central area of ground surface was observed because there was less difference in microstructure between the peripheral area and the central area. The results were as follows ; 1. In the microstructure according to the ingot type, there was a wide difference between the staining (T1,O1) and layering(Dentin A2) ingots, but there was not a considerable difference between the T1 ingot and the O1 ingot for staining technique. 2. In all specimens, the crystal dispersion of IPS Empress ceramic using double sprue was significantly more scattered than that of IPS Empress ceramic using single sprue. The degree of scattering was strongest in the Dentin(A2) specimen and weakest in the O1 ingot. 3. In the microstructural change according to the subsequent heat treatment, all of ingots had some microcracks in the inside of the leucite crystal and the glass matrix after pressing. The inner splinters of the leucite crystal became smaller, and more microcracks occurred in the glass matrix due to increasing heat treatment times. 4. The size of leucite crystals varied from $1{\mu}m\;to\;5{\mu}m$. The mean size of mature crystals was about $5{\mu}m$. The form of the crystal was similar to a circle when it was smaller and similar to an ellipse when it was larger.