• 생명과학회지
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• 제9권3호
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• pp.268-275
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• 1999

고저화된 Rp.palustris균을 이용한 양식장 폐수주으이 질산염 제거를 위하여 Rp.palustris균의 고정화를 위한 담체를 조사하였는데, 탈질능력과 내구성을 실험한 결과 agar,k-carrageenan,그리고 PVA 3종의 담체주우 3% agar가 가장 적합한 담체이었다.Agar bead 내부로의 기질 이동 및 sheer stress를 고려해볼 때 최적 bead 크기는 직경 4mm 였고,접종되는 세포의 양은 25mg dry $cells/cm^2$gel 이었다. 탄소원으로 ethanol이 가장 적합하였고,최적 C:N ratio는 1.5이며,온도와 pH는 각각$31^{\circ}C$,PH 6 이었다. 이러한 조건에서의 최대 탈질율은 인공합성폐수의 경우 $345{\MU}{\ell};N_2/Cm^3 gel{\cdot}hr;이었으며,;modifed MYC 배지의; 경우는; 450{\MU}{\ell}};N_2/Cm^3 gel{\cdot}hr $이었다.

• 한국미생물·생명공학회지
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• 제32권2호
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• pp.154-157
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• 2004

고정화된 Aspenillus niger 세포가 우유공장폐수에서 발효로 구연산을 생산하는데 이용되었다. 구연산 생산균주로서 A. niger ATCC 9142가 3일간 전배양되었으며, 약 2.5∼3.5 mm Ca-alginate beads 로 포획되었다. 최적의 pH와 온도는 각각 3.0과 $30^{\circ}C$였다. 발효에 대한 최적 희석률은 $0.025h^{－1}$ 인 것으로 계산되었다. 구연산의 최대 생산량은 최적화된 발효조건과 함께 4.5 g/$\ell$에서 얻어졌다. 고정화된 Aspergillus niger ATCC 9142에 의해 생산된 구연산의 수율은 70.3%였다. Shake-flask배양실험에 비해 연속식 배양실험 결과가 고정화 세포에 의해 20%증가되었다. 따라서 우유공장폐수는 구연산 발효기질로서의 이용가치가 있다고 볼 수가 있겠다.

• 한국식품영양과학회지
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• 제30권5호
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• pp.964-968
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• 2001

향균력이 있는 한약제들 중에서 추출수율과 항균력이 우수한 항금을 대상으로 식중독균에 대한 천연항균제의 적용 가능성을 검토하였다. 황금추출물의 항균작용을 알아보기 위하여 공시균주 Bacillus cereus, Listeria monocytogenes, Escherichia coli, and Vivro parahaemolyticus에 대하여 disk method에 의한 항균력 검사에서 생육어제로 인한 clear zone 이 선명하게 관찰되어 황금추출물의 항균력을 알 수 있었고, 황금추출물의 열 및 PH 안정성을 검토한 결과 다양한 범위의 온도 및 pH에 대해서 매우 안정하다는것을 확인하였으며, 공시균주들에 대한 유효저해농도를 측정한 결과 황금추출물의 농도 500 ppm 이상에서 생육이 억제되었다. 주사형전자현미경(SEM) 상에서는 처리구에서 공시균주들의 세포형태 변화를 볼수 있었고, 투과형전자현미경(TEM)상에서는 처리구에 있어서 공시균주들의 세포막 파괴로 인하여 세포내용물이 용출된 것을 볼 수 있었다. 황금추출물 처리로 인한 세포막 손상정도를 확인하기 위하여 균체내 효소인 $\beta$-gal-actosidase 활성을 정량한 결과 chlorogorm 보다 세포막을 더 손상시키는 것을 확인되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.388-388
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• 2016

Chemical mist deposition (CMD) of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was investigated with cavitation frequency f, solvent, flow rate of nitrogen, substrate temperature $T_s$, and substrate dc bias $V_s$ as variables for efficient PEDOT:PSS/crystalline (c-)Si heterojunction solar cells (Fig. 1). The high-speed camera and differential mobility analysis characterizations revealed that average size and flux of PEDOT:PSS mist depend on f, solvent, and $V_s$. The size distribution of mist particles including EG/DI water cosolvent is also shown at three different $V_s$ of 0, 1.5, and 5 kV for a f of 3 MHz (Fig. 2). The size distribution of EG/DI water mist without PEDOT:PSS is also shown at the bottom. A peak maximum shifted from 300-350 to 20-30 nm with a narrow band width of ~150 nm for PEDOT:PSS solution, whose maximum number density increased significantly up to 8000/cc with increasing $V_s$. On the other hand, for EG/water cosolvent mist alone, the peak maximum was observed at a 72.3 nm with a number density of ~700/cc and a band width of ~160 nm and it decreased markedly with increasing $V_s$. These findings were not observed for PEDOT:PSS/EG/DI water mist. In addition, the Mie scattering image of PEDOT:PSS mist under white bias light was not observed at $V_s$ above 5 kV, because the average size of mist became smaller. These results imply that most of solvent is solvated in PEDOT:PSS molecule and/or solvent is vaporized. Thus, higher f and $V_s$ generate preferentially fine mist particle with a narrower band width. Film deposition occurred when $V_s$ was impressed on positive to a c-Si substrate at a Ts of $30-40^{\circ}C$, whereas no deposition of films occurred on negative, implying that negatively charged mist mainly provide the film deposition. The uniform deposition of PEDOT:PSS films occurred on textured c-Si(100) substrate by adjusting $T_s$ and $V_s$. The adhesion of CMD PEDOT:PSS to c-Si enhanced by $V_s$ conspicuously compared to that of spin-coated film. The CMD PEDOT:PSS/c-Si solar cell devices on textured c-Si(100) exhibited a ${\eta}$ of 11.0% with the better uniformity of the solar cell parameters. Furthermore, ${\eta}$ increased to 12.5% with a $J_{sc}$ of $35.6mA/cm^2$, a $V_{oc}$ of 0.53 V, and a FF of 0.67 with an antireflection (AR) coating layer of 20-nm-thick CMD molybdenum oxide $MoO_x$ (n= 2.1) using negatively charged mist of 0.1 wt% 12 Molybdo (VI) phosphoric acid n-Hydrate) $H_3(PMo_{12}O_40){\cdot}nH_2O$ in methanol. CMD. These findings suggest that the CMD with negatively charged mist has a great potential for the uniform deposition of organic and inorganic on textured c-Si substrate by adjusting $T_s$ and $V_s$.

• 한국전기전자재료학회논문지
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• 제29권8호
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• pp.461-465
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• 2016

n-type silicon shows the better tolerance towards metal impurities with a higher minority carrier lifetime compared to p-type silicon substrate. Due to better lifetime stability as compared to p-type during illumination made the photovoltaic community to switch toward n-type wafers for high efficiency silicon solar cells. We fabricated the front electrode of the n-type solar cell with AgAl paste. The electrodes characteristics of the AgAl paste depend on the contact junction depth that is closely related to the firing temperature. Metal contact depth with p+ emitter, with optimized depth is important as it influence the resistance. In this study, we optimize the firing condition for the effective formation of the metal depth by varying the firing condition. The firing was carried out at temperatures below $670^{\circ}C$ with low contact depth and high contact resistance. It was noted that the contact resistance was reduced with the increase of firing temperature. The contact resistance of $5.99m{\Omega}cm^2$ was shown for the optimum firing temperature of $865^{\circ}C$. Over $900^{\circ}C$, contact junction is bonded to the Si through the emitter, resulting the contact resistance to shunt. we obtained photovoltaic parameter such as fill factor of 76.68%, short-circuit current of $40.2mA/cm^2$, open-circuit voltage of 620 mV and convert efficiency of 19.11%.

• 미생물학회지
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• 제40권2호
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• pp.147-153
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• 2004

단백질의 serine이나 threonine의 수산기에 N-acetyl-${\beta}$-D-glucosamine (O-GlcNAc)으로 변형되는 당쇄는 대부분의 진핵세포에서 광범위하게 일어나는 번역 후 수식의 일종으로 여러 세포 내 현상에 관여하고 있다. O-GlcNAc의 변형정도는 O-GlcNAc transfearse (OGT)와 O-linked N-acetyl-${\beta}$-D-glucosaminidase (O-GlcNAcase)에 의해 조절된다. O-GlcNAcase의 효소활성 조절물질을 탐색하기 위한 시험관 내 검정계를 확립하기 위해 재조합 O-GlcNAcase의 생산을 시도하였다. O-GlcNAcase 발현을 최적화하기 위한 배양조건을 검토한 결과 유도 배양온도 $30^{\circ}C$, 유도제인 L-arabinose 0.02%, 유도 배양시간 5시간 등으로 나타났다. 위의 조건에서 대장균 형질전환체를 배양하면서 한 시간 간격으로 배양액을 채취하여 세포를 파괴하고 얻은 효소용액의 활성은 배양 후 3시간에서 5시간까지는 급격히 증가하였으나 그 이후는 거의 증가하지 않았다. Western blot으로 발현된 단백질 양을 조사한 결과는 활성 그래프와 비슷한 양상을 보였다. 이렇게 생산한 O-GlcNAcase의 최적 반응조건은 pH 6.5, 반응온도 $45^{\circ}C$, 기질의 농도 2 mM, pH 6.5로 나타났다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.100-101
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• 2012

The plasma damage free and room temperature processedthin film deposition technology is essential for realization of various next generation organic microelectronic devices such as flexible AMOLED display, flexible OLED lighting, and organic photovoltaic cells because characteristics of fragile organic materials in the plasma process and low glass transition temperatures (Tg) of polymer substrate. In case of directly deposition of metal oxide thin films (including transparent conductive oxide (TCO) and amorphous oxide semiconductor (AOS)) on the organic layers, plasma damages against to the organic materials is fatal. This damage is believed to be originated mainly from high energy energetic particles during the sputtering process such as negative oxygen ions, reflected neutrals by reflection of plasma background gas at the target surface, sputtered atoms, bulk plasma ions, and secondary electrons. To solve this problem, we developed the NBAS (Neutral Beam Assisted Sputtering) process as a plasma damage free and room temperature processed sputtering technology. As a result, electro-optical properties of NBAS processed ITO thin film showed resistivity of $4.0{\times}10^{-4}{\Omega}{\cdot}m$ and high transmittance (>90% at 550 nm) with nano- crystalline structure at room temperature process. Furthermore, in the experiment result of directly deposition of TCO top anode on the inverted structure OLED cell, it is verified that NBAS TCO deposition process does not damages to the underlying organic layers. In case of deposition of transparent conductive oxide (TCO) thin film on the plastic polymer substrate, the room temperature processed sputtering coating of high quality TCO thin film is required. During the sputtering process with higher density plasma, the energetic particles contribute self supplying of activation & crystallization energy without any additional heating and post-annealing and forminga high quality TCO thin film. However, negative oxygen ions which generated from sputteringtarget surface by electron attachment are accelerated to high energy by induced cathode self-bias. Thus the high energy negative oxygen ions can lead to critical physical bombardment damages to forming oxide thin film and this effect does not recover in room temperature process without post thermal annealing. To salve the inherent limitation of plasma sputtering, we have been developed the Magnetic Field Shielded Sputtering (MFSS) process as the high quality oxide thin film deposition process at room temperature. The MFSS process is effectively eliminate or suppress the negative oxygen ions bombardment damage by the plasma limiter which composed permanent magnet array. As a result, electro-optical properties of MFSS processed ITO thin film (resistivity $3.9{\times}10^{-4}{\Omega}{\cdot}cm$, transmittance 95% at 550 nm) have approachedthose of a high temperature DC magnetron sputtering (DMS) ITO thin film were. Also, AOS (a-IGZO) TFTs fabricated by MFSS process without higher temperature post annealing showed very comparable electrical performance with those by DMS process with $400^{\circ}C$ post annealing. They are important to note that the bombardment of a negative oxygen ion which is accelerated by dc self-bias during rf sputtering could degrade the electrical performance of ITO electrodes and a-IGZO TFTs. Finally, we found that reduction of damage from the high energy negative oxygen ions bombardment drives improvement of crystalline structure in the ITO thin film and suppression of the sub-gab states in a-IGZO semiconductor thin film. For realization of organic flexible electronic devices based on plastic substrates, gas barrier coatings are required to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency flexible AMOLEDs needs an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}gm^{-2}day^{-1}$. The key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required (under ${\sim}10^{-6}gm^{-2}day^{-1}$) is the suppression of nano-sized defect sites and gas diffusion pathways among the grain boundaries. For formation of high quality single inorganic gas barrier layer, we developed high density nano-structured Al2O3 single gas barrier layer usinga NBAS process. The NBAS process can continuously change crystalline structures from an amorphous phase to a nano- crystalline phase with various grain sizes in a single inorganic thin film. As a result, the water vapor transmission rates (WVTR) of the NBAS processed $Al_2O_3$ gas barrier film have improved order of magnitude compared with that of conventional $Al_2O_3$ layers made by the RF magnetron sputteringprocess under the same sputtering conditions; the WVTR of the NBAS processed $Al_2O_3$ gas barrier film was about $5{\times}10^{-6}g/m^2/day$ by just single layer.

• 한국재료학회지
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• 제22권4호
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• pp.190-194
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• 2012

The formation of high-quality polycrystalline silicon (poly-Si) on relatively low cost substrate has been an important issue in the development of thin film solar cells. Poly-Si seed layers were fabricated by an inverse aluminum-induced crystallization (I-AIC) process and the properties of the resulting layer were characterized. The I-AIC process has an advantage of being able to continue the epitaxial growth without an Al layer removing process. An amorphous Si precursor layer was deposited on Corning glass substrates by RF magnetron sputtering system with Ar plasma. Then, Al thin film was deposited by thermal evaporation. An $SiO_2$ diffusion barrier layer was formed between Si and Al layers to control the surface orientation of seed layer. The crystallinity of the poly-Si seed layer was analyzed by Raman spectroscopy and x-ray diffraction (XRD). The grain size and orientation of the poly-Si seed layer were determined by electron back scattering diffraction (EBSD) method. The prepared poly-Si seed layer showed high volume fraction of crystalline Si and <100> orientation. The diffusion barrier layer and processing temperature significantly affected the grain size and orientation of the poly Si seed layer. The shorter oxidation time and lower processing temperature led to a better orientation of the poly-Si seed layer. This study presents the formation mechanism of a poly seed layer by inverse aluminum-induced crystallization.

• 한국세라믹학회지
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• 제41권12호
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• pp.900-906
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• 2004

현재까지 개발되어 온 고체산화물 연료전지는 전해질로 사용되는 산소이온전도성 산화물의 저온에서의 낮은 전도도로 인해 그 사용영역이 제한되어 왔으며, 기판재료가 연료가스 확산층으로 사용되어야 한다는 점 때문에 저온작동을 위한 박막화 역시 명확한 한계를 가지고 있다. 이러한 문제점은 고도의 평활도를 갖는 균일한 나노기공성 기판재를 도입함으로써 해결될 수 있으며, 본 연구에서는 나노기공성 기판에 비정질 금속박막을 증착/산화하는 방안을 제시한다. 초박막형 성공정으로서, 산화 후 산소이온전도성 산화물을 구성하는 합금 타겟을 장착한 DC-magnetron sputter를 사용하여 $20{\sim}200nm$의 기공크기를 갖는 나노기공성 양극산화 알루미나 기판에 비정질 금속합금막을 형성하여 산화/열처리 과정을 거쳐 초박막 산화물 전해질의 제조공정을 실현하였다. 얻어진 박막의 가스투과특성, 입자/입계의 관찰, 상전이에 따른 결정구조/미세구조변화를 관찰하여 초박막 증착 및 전해질의 나노구조제어에 필요한 제반 기본물성데이터를 확보하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.456-456
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• 2008

In the past few years, the deposition and characterization of cadmium sulfide semiconducting thin films has received a considerable amount of interest due to their potential application in the area of electronic and opto-electronic devices fabrications. Polycrystalline CdS thin films posses good optical transmittance, wide band-gap and electrical properties makes it as one of the ideal material for their application to solar cell fabrication. Cadmium sulfate thin films were deposited by the chemical bath deposition method using tartaric acid and triethanolamine as a complexing agent. Deposition parameters such as pH, temperature, deposition time and concentration of the reactant species were optimized so as to obtain reflecting, good adherent uniform thin films on the glass substrate. Reaction mechanism of the thin film formation is also reported. The crystallographic structure and the crystallite size were studied by the X-ray diffraction pattern. The optical band-gap of deposited film is identified by measuring the transmittance in the visible region. Temperature dependence of resistivity confirmed the semiconducting behavior of the film. Scanning electron micrographs (SEM) showed the presence of grain particles of size 50 nm.