• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.147-147
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• 2010

태양전지의 효율 향상을 위해 웨이퍼 표면에 반사방지막 코팅을 위한 패시베이션 물질들에 대한 연구가 활발히 진행 되고 있다. 이 과정에서 널리 사용하는 ARC 물질로 SiNx 박막이 있다. SiNx 박막은 PECVD 법으로 저온에서 실리콘 기판 위에 증착 가능한 장점이 있다. 플라즈마 분위기 가스로 아르곤 또는 질소 사용하며 SiNx 박막의 광학적, 전기적인 특성은 화학적 조성비에 의해 결정되며 증착온도 가변에 박막의 특성이 변화하며 이를 이용하여 태양전지의 효율을 향상 시킬 수 있다. 본 연구에서는 SiNx 박막을 형성하는데 질소 가스 분위기에서 PECVD를 이용하여 증착하고 그 특성을 분석하였다. 박막은 0.8 Torr의 압력에서 $150^{\circ}C\;{\sim}\;450^{\circ}C$의 기판온도로 증착되었으며 이때의 RF power은 100W ~ 300W로 가변 되었다. 증착된 박막은 1.94 에서 2.23의 폭넓은 굴절률 값을 가지고 있었다. $SiH^4/NH_3$ 가스 비의 증가에 따라 박막 두께와 굴절률이 감소함을 확인할 수 있었다.증착된 SiNx 박막의 소수반송자 수명 측정 결과 굴절률 2.23인 박막의 경우 약 87 us의 수명을 나타냈으며, 굴절률이 1.94로 줄어듦에 따라 소수 반송자 수명 역시 79 us로 감소하였다. SiNx 박막은 n-rich 보다 Si-rich 인 경우 effective 반송자 수명을 증가시켜 표면 재결합 속도를 줄이는데 유용함을 확인하였다. 또한 증착온도가 증가할수록, RF power가 증가 할수록 소수 반송자 수명 역시 증가하였다. 반사도의 경우 $SiH_4$의 비율이 증가할수록 반사도가 감소함을 확인 하였으며, 증착온도 증가에 따라, RF power 증가에 따라 반사도가 감소하였다. 결과적으로 $450^{\circ}C$의 기판온도와 300W의 RF power에서 증착된 SiNx 박막의 경우 가장 우수한 전기적, 광학적 특성을 보여주었다.

• Journal of Surface Science and Engineering
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• v.51 no.4
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• pp.249-255
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• 2018

High temperature and low temperature gaseous nitriding was performed in order to study of the surface hardening and wear properties of the nitrided AISI 410 Martensitic stainless steels. High temperature gaseous nitiridng (HTGN) was carried out using partial pressure $N_2$ gas at $1,100^{\circ}C$ for 10 hour, and Low temperature gaseous nitiridng (LTGN) was conducted in a gas mixture of NH3 and N2 at $470^{\circ}C$ for 10 hour. The nitrided samples were characterized by microhardness measurements, optical microscopy and scanning electron microscopy. The phases were identified by X-ray diffraction and nitrogen concentration was analyzed by GD-OES. The HTGN specimen had a surface hardness of about $700HV_{0.1}$, $350{\mu}m$ of case depth. A ${\sim}50{\mu}m$ thick, $1,250HV_{0.1}$ hard nitrided case formed at the surface of the AISI 410 steel by LTGN, composed nitrogen supersaturated expanded martensite and ${\varepsilon}-Fe_{24}N_{10}$ iron nitrides. Additionally, the results of the wear tests, carried out LTGN specimen was low friction coefficient and high worn mass loss of ball. The increase in wear resistance can be mainly attributed to the increase in hardness and to the lattice distortion caused by higher nitrogen concentration.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.62-68
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• 1994

Water-based magnetic fluids containing synthesized ultrafine magnetite were successfully prepared with $C_{18}$ fatty acid such as oleic acid, linoleic acid and stearic acid. Oleic acid was needed the amount of $3.0{\times}10^{-2}$ mol per 20 g magnetite to stabilize the magnetite $d\;=\;113\;\AA$ particles. From pH 8.0 to pH 11.0, stable aqueous-based fluids could be obtained. The aggregated powder after drying the water-based magnetic fluid was also successfully re-dispersed in dilute $NH_{4}OH$ solution and in kerosene. The pH levels of the magnetic fluid using oleic acid system could be predicted by the pH values obtained by calculation of therrrodynamic data.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.8
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• pp.1153-1160
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• 2019

Objective: The objective of this study was to investigate the effect of bamboo grass (Tiliacora triandra, Diels) pellet (Bamboo-Cass) supplementation on feed intake, nutrient digestibility, rumen microbial population and methane production in Thai native beef cattle. Methods: Four Thai native beef cattle bulls ($190{\pm}2kg$) were randomly allotted to four respective dietary treatments in a $4{\times}4$ Latin square design. Treatments were the varying levels of Bamboo-Cass supplementation at 0, 50, 100, and 150 g/head/d, respectively. Rice straw was fed ad libitum and the concentrate offered at 0.5% of body weight. Results: Under this experiment, the findings revealed that acetate and butyrate production were decreased (p<0.05), propionate increased (p<0.05), whilst ruminal $NH_3-N$ concentration was decreased (p<0.05) by supplementation of Bamboo-Cass at 150 g/head/d. Moreover, rice straw intake, and microbial population were linearly increased (p<0.05), while methane production was decreased (p<0.05). Conclusion: The results from the present study indicate that supplementation of Bamboo-Cass at 150 g/head/d significantly enhanced feed intake, decreased protozoa and increased bacterial population, rumen fermentation efficiency while decreased methane production. Therefore, Bamboo-Cass as a supplement is promising as a rumen enhancer in beef cattle fed on rice straw.

• Journal of Sensor Science and Technology
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• v.30 no.4
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• pp.255-260
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• 2021

We studied electrochemical sensors using printed carbon nanotube (CNT) film on a polyethylene terephthalate (PET) substrate. Multiwalled CNT films were printed on a PET substrate to study its feasibility as hazardous and noxious substances (HNS) detection sensor. The printed CNT film (PCF) with a 50 ㎛ thickness exhibited a specific resistance of 230 ohm. To determine the optimum sensor structure, a resistance-type PCF sensor (R-type PCF sensor) and a conductive-type PCF sensor (C-type PCF sensor) were fabricated and compared using diluted NH₃ droplets with various concentrations. The response magnitude, response time, sensitivity, linearity, and limit of detection (LOD) were compared, and it was concluded that the C-type PCF sensor exhibited superior performance. By applying a C-Type PCF sensor, we confirmed the detection performance of 12 types of floating HNS and the response of the sensor with selectivity according to the degree of polarity.

• Journal of the Korean Chemical Society
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• v.65 no.4
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• pp.260-267
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• 2021

Increasing the needs for eco-friendly natural materials, much attention on natural dyes has been attracted. Curcumin, one of abundant natural dyes available in nature, is an eco-friendly molecule found in turmeric. In this study, the colorimetric sensing behavior characteristics of ammonia and hydrogen chloride gases was analyzed using curcumin ink-printed paper and cotton fabric by inkjet printing method. The fabricated paper and fabric were utilized as a colorimetric sensor that can track food spoilage. The color changes of the samples printed on the paper and cotton upon exposure to the toxic gases, the reversibility of the color changes, and the water resistance were investigated. Both samples showed reversible reactions with NH3 and HCl, and small amount of ammonia produced by food spoilage was successfully sensed with naked eyes, confirming its capability to warn food spoilage in our daily life.

• Animal Bioscience
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• v.36 no.9
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• pp.1384-1392
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• 2023

Objective: Replacing soybean meal (SBM) with cricket (Gryllus bimaculatus) meal pellets (CMP) in concentrate diets was investigated for feed efficiency, ruminal fermentation and microbial protein synthesis in Thai native beef cattle. Methods: Four male beef cattle were randomly assigned to treatments using a 4×4 Latin square design with four levels of SBM replaced by CMP at 0%, 33%, 67%, and 100% in concentrate diets. Results: Results revealed that replacement of SBM with CMP did not affect dry matter (DM) consumption, while digestibilities of crude protein, acid detergent fiber and neutral detergent fiber were significantly enhanced (p<0.05) but did not alter digestibility of DM and organic matter. Increasing levels of CMP up to 100% in concentrate diets increased ruminal ammoniacal nitrogen (NH₃-N) concentrations, blood urea nitrogen, total volatile fatty acids and propionate concentration (p<0.05), whereas production of methane and protozoal populations decreased (p<0.05). Efficiency of microbial nitrogen protein synthesis increased when SBM was replaced with CMP. Conclusion: Substitution of SBM with CMP in the feed concentrate mixture at up to 100% resulted in enhanced nutrient digestibility and rumen fermentation efficiency, with increased volatile fatty acids production, especially propionate and microbial protein synthesis, while decreasing protozoal populations and mitigating rumen methane production in Thai native beef cattle fed a rice straw-based diet.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.87-87
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• 2021

이상기후 현상으로 기후변화가 사회와 경제에 미치는 영향이 뚜렷한 추세로 변화되고 있다. 현재 기후변화에 관련된 연구는 사회 시스템에서 위험관리를 위해 기온과 강수량에 따라 다양한 분야에 미치는 영향에 대한 연구를 중점으로 이뤄지고 있다. 본 연구는 여름철 폭염에 의한 기후변화가 하천수질에 미치는 영향을 평가하기 위한 것으로, 우리나라 기상청 91개의 기상관측소에서 일일온도 33℃ 이상의 이벤트를 대상으로 환경부 수질관측망 918개에 대한 14개의 하천수질인자인 DO, BOD, COD, TOC, DOC, TN, DTN, NH4-N, NO2-N, NO3-N, TP, DTP, PO4-P, Chl-a를 분석하였다. 이를 우리나라 117개 중권역별 하천수질과 폭염강도와 지속시간을 나타내는 폭염 지수를 산정하여 분석하였다. 폭염 관련 뉴스 데이터는 2013년부터 2019년까지 Python 기반 뉴스 크롤러를 이용해 폭염 취약지수(Heat Wave Vulnerability Index, HWVI)를 기준으로 분류하여 키워드를 수집하였으며 HWVI 중 '기후노출' 키워드와 관련된 기사는 총 22,514건으로 69.9%로 수집되었다. 공간적 영향 평가를 위해 Getis-Ord Gi*를 이용하여 폭염지수와 하천수질인자간 핫스팟 분석을 실시하고 폭염관련 빅데이터가 하천수질에 미치는 영향을 평가하였다. 폭염지수는 낙동강유역 하류에 대해 Chl-a, TN, TP 항목에서 높은 밀도를 보였다. 분석대상지역 내 폭염이 발생한 확률과 반경 밖에서 발생할 확률의 우도비를 분석하기 위해 SaTScan을 이용한 공간검색통계분석을 실시하였다. 분석결과 폭염지수와 DO의 공간상관성이 높은 것으로 나타났다.

• Korean Journal of Soil Science and Fertilizer
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• v.17 no.3
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• pp.265-273
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• 1984

To investigate nitrogen supplying effect of some slowrelease N-fertilizers on barley in upland soil sulfurcoated urea(SCU), ureaform and melamine (1,3,5-Triazine-2,4,6-triamine) were treated and compared to urea. In addition, thiourea as a nitrification inhibitor was also tested. Effects of variable soil condition such as moisture content, pH and temperature on nitrogen supplying ability of the fertilizers and on growth of barley were studied through incubation test and pot culture and the obtained results were summarized as follows: The releasing rate of ammonia from urea, SCU, ureaform and melamine were resulted as 27-59%, 25-39%, 9-34% and 0.7-4.3% at maximum conversion rate, respectively. Nitrification rate of the tested fertilizers was higher at pH 6.54 markedly than at pH 4.73. Addition of thourea depressed the formation of $NO_3$ during four weeks of incubation period. Mixed application of ureaform with small amount of urea contributed to nitrogen supply till latter growth stage of barely Basal application of melamine showed lowest nitrogen supplying ability and injurious response on barley growth.

• Applied Biological Chemistry
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• v.36 no.2
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• pp.105-110
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• 1993

Inulin fructotransferase from Enterobacter sp. S45 was purified with DEAE-cellulose column chromatography and fast protein liquid chromatography. The purified enzyme gave a single band on polyacrylamide gel electrophoresis. The molecular weight was estimated to be 42,800 by SDS-polyacrylamide gel electrophoresis. The optimal pH and temperature for the enzyme reaction were pH 5.5 and $55^{\circ}C$, respectively. $Mg^{2+}$ activated the enzyme activity, but $Fe^{3+}$, $Cu^{2+}$, $Hg^{2+}$ significantly inhibited. After exhaustive digestion of inulin by the enzyme, DFA III, sucrose, 1-kestose and nystose were produced. Sucrose, 1-kestose, raffinose and melezitose can't be used as substrates by the enzyme, but nystose and 1-F-fructofuranosyl nystose were hydrolysed. The Km and Vmax for inulin of the enzyme were 1.4 mM and $0.196\;{\mu}mole/min$, respectively.