• Journal of information and communication convergence engineering
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• 제3권4호
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• pp.179-183
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• 2005

A photodiode capable of obtaining a sufficient photo/ dark current ratio at both forward bias state and reverse bias state is proposed. The photodiode includes a glass substrate, an aluminum film formed as a lower electrode over the glass substrate, an alumina film formed as an insulator barrier over the aluminum film, a hydrogenated amorphous silicon film formed as a photo conduction layer over a portion of the alumina film, and a transparent conduction film formed as an upper electrode over the hydro-generated amorphous silicon film. A good quality alumina $(Al_2O_3)$ film is formed by oxidation of aluminum film using electrolyte solution of succinic acid. Alumina is used as a potential barrier between amorphous silicon and aluminum. It controls dark-current restriction. In case of photodiodes made by changing the formation condition of alumina, we can obtain a stable dark current $(\~10^{-12}A)$ in alumina thickness below $1000{\AA}$. At the reverse bias state of the negative voltage in ITO (Indium Tin Oxide), the photo current has substantially constant value of $5{\times}10^{-9}$ A at light scan of 100 1x. On the other hand, the photo/dark current ratios become higher at smaller thicknesses of the alumina film. Therefore, the alumina film is used as a thin insulator barrier, which is distinct from the conventional concept of forming the insulator barrier layer near the transparent conduction film. Also, the structure with the insulator thin barrier layer formed near the lower electrode, opposed to the ITO film, solves the interface problem of the ITO film because it provides an improved photo current/dark current ratio.

• 한국식품과학회지
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• 제15권2호
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• pp.189-194
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• 1983

3가지 다른 조건하에서 제조된 압출보리와 생보리를 0.31 및 0.71의 수분활성과 $25^{\circ}C$ 및 $40^{\circ}C$의 온도에서 각각 4개월 저장하면서 지방질의 산화에 대한 수분활성과 온도의 영향에 대하여 연구하였다. 모든 시료로부터 검출한 지방질 중의 Conjugated diene의 함량은 저장기간의 경과와 함께 수분활성과 온도가 증가함에 따라 증가하였고, 지방산의 U/S비는 감소하는 경향이었다. 생보리는 압출보리보다 저장 중 Conjugated diene함량의 증가와 U/S비의 감소가 더 심하였으며, 설탕을 첨가하여 제조한 압출보리는 다른 압출보리보다 저장 중 산화에 대한 지방질의 안정성이 양호하였다. 모든 시료에서 추출한 지방질 중 유리 아미노기를 함유하는 지방질의 함량은 저장 중 수분활성과 온도가 증가함에 따라 감소하였다.

• 한국분말재료학회지
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• 제16권6호
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• pp.442-448
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• 2009

$ZrB_2$-based composites are candidate materials for ultra-high temperature materials (UHTMs). $ZrB_2$ has become an indispensable ingredient in UHTMs, due to its high melting temperature, relatively low density, and excellent resistance to thermal shock or oxidation. $ZrB_2$ powders are usually synthesized by solid state reactions such as carbothermal, borothermal, or combined carbothermal reaction. SiC is added to this system in order to enhance the oxidation resistance of $ZrB_2$. In this study, $ZrB_2$?based composites were successfully synthesized and densified through two different processing paths. $ZrB_2$ or $ZrB_2$ 25 vol.%SiC was fully synthesized from oxide starting materials with reducing agents after heat treatment at 1400$^{\circ}C$. Besides, $ZrB_2$?20 vol.%SiC was fully densified with $B_4C$ as a sintering additive after hot pressing at 1900$^{\circ}C$. The synthesis mechanism and the effect of sintering additives on densification of $ZrB_2$ ?SiC composites were also discussed.

• 한국환경과학회지
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• 제24권12호
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• pp.1629-1637
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• 2015

To develop various usable water from coal seam gas (CSG) water that needs to be pumped out from coal seams for methane gas production, a feasibility study was carried out, evaluating and analysing a recent report (Coal Seam Gas Water Management Policy 2012) from Queensland State Government in Australia to suggest potential CSG water treatment options for fit-for-purpose usable water production. As CSG water contains intrinsically high salinity-driven total dissolved solid (TDS), bicarbonate, aliphatic carbon, $Ca^{+2}$, $Mg^{+2}$ and so on, it was found that appropriate treatment technologies are required to reduce the hardness below 60 mg/L as $CaCO_3$ by setting the reduction rates of $Ca^{+2}$, $Mg^{+2}$ and Na+ concentrations, as well as TDS reduction. Also, Along with fiber filtration and membrane separation, an oxidation degradation process was found to be required. Along with salinity reduction, as CSG water contains organic compounds (TOC: 248 mg/L, $C_6-C_9$: <20 mg/L and $C_{10}-C_{36}$: <60 mg/L), compounds with relatively high molecular weights ($C_{10}-C_{36}$) need to be treated first. Therefore, this study suggests a combined system design with filtration (Reverse osmosis) and oxidation reduction (electrolysis) technologies, offering proper operating conditions to produce fit-for-purpose usable water from CSG water.

• BMB Reports
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• 제32권4호
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• pp.350-357
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• 1999

At concentrations of 1 mM, the protective effects of carnosine and related compounds including anserine, homocarnosine, histidine, ${\beta}$-alanine were investigated against copper-catalyzed oxidative damage to deoxyribose, ascorbic acid, human serum albumin, liposome, and erythrocytes. Carnosine and anserine reduced Cu (II) to bathocuproine-reactive Cu (I) in a time- a and a dose-dependent manner while the others did not. Carnosine reduced 86% of $100\;{\mu}M$ Cu (II) in 60 min. Carnosine, homocarnosine, anserine, and histidine inhibited copper-catalyzed deoxyribose degradation by 75, 66, 65, and 45%, respectively. In the presence of $1\;{\mu}M$ Cu (II), carnosine and related compounds inhibited ascorbic acid oxidation by 55-85% after incubation for 20 min. In the presence of 0.15 mM ascorbic acid and 0.8 mM $H_2O_2$, carnosine, anserine, homocarnosine, and histidine inhibited copper-catalyzed oxidation of human serum albumin by 41, 21, 29, and 24%, respectively, as determined by carbonyl formation. These compounds also significantly inhibited copper-catalyzed liposomal lipid peroxidation as measured by malondialehyde and lipid hydroperoxides. Carnosine, anserine, homocarnosine, and histidine inhibited hemolysis of bovine erythrocytes induced by 0.1 mM Cu (II). These results suggest that histidine-containing dipeptides may play an important role in protecting against free radical-mediated tissue damage.

• 한국재료학회지
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• 제21권2호
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• pp.120-124
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• 2011

Silicon heterojunction solar cells have been studied by many research groups. In this work, silicon heterojunction solar cells having a simple structure of Ag/ZnO:Al/n type a-Si:H/p type c-Si/Al were fabricated. Samples were fabricated to investigate the effect of transparent conductive oxide growth conditions on the interface between ZnO:Al layer and a-Si:H layer. One sample was deposited by ZnO:Al at low working pressure. The other sample was deposited by ZnO:Al at alternating high working pressure and low working pressure. Electrical properties and chemical properties were investigated by light I-V characteristics and AES method, respectively. The light I-V characteristics showed better efficiency on sample deposited by ZnO:Al by alternating high working pressure and low working pressure. Atomic concentrations and relative oxidation states of Si, O, and Zn were analyzed by AES method. For poor efficiency samples, Si was diffused into ZnO:Al layer and O was diffused at the interface of ZnO:Al and Si. Differentiated O KLL spectra, Zn LMM spectra, and Si KLL spectra were used for interface reaction and oxidation state. According to AES spectra, sample deposited by high working pressure was effective at reducing the interface reaction and the Si diffusion. Consequently, the efficiency was improved by suppressing the SiOx formation at the interface.

• 한국세라믹학회지
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• 제48권4호
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• pp.303-306
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• 2011

[ $V_2O_5$ ]doped Karrooite pigments were synthesized by the solid state method to get stabilized brown pigment in oxidation and reduction atmosphere. Optimum substitution condition and limited dopant with $V_2O_5$ for Karrooite pigment was investigated. With calcination at $1250^{\circ}C{\sim}1400^{\circ}C$, compositions were designed varying $V_2O_5$ molar ratio by increasing 0.02mole to the formula $Mg_1-xTi_2-xM_{2x}O_5$(x = 0.01~0.09 mole). Synthesized pigments were analyzed by XRD, Raman spectroscopy and UV-vis. When $V_2O_5$ was doped from 0.01 to 0.05 mole, single phase of Karrooite was observed at temperature $1300^{\circ}C$ and soaking time 4h by Raman spectroscopy. However, it was found that excess $VO_2$ peak appeared with 0.07 and 0.09 mole of $V_2O_5$ doped to $MgTi_2O_5$. This result indicated that the maximum limit of solid solution is 0.05 mole $V_2O_5$. Karrooite pigments were applied as a ceramic pigment to achieve brown colors in lime magnesia glaze and lime barium graze at both of oxidation and reduction atmosphere. CIE color coordinates are $L^*$ = 40.34, $a^*$ = 9.94, $b^*$ = 21.40 in lime magnesia glaze.

• 공업화학
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• 제9권7호
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• pp.956-960
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• 1998

Cu와 Zn의 몰비가 1/2, 1/1, 2/1인 촉매를 제조하여 메탄올 수증기 개질반응의 활성을 측정하고, 가장 좋은 활성을 보이는 Cu/Zn의 몰비가 2/1인 촉매를 선정하여 $TiO_2$의 첨가량을 달리하여, 메탄올 수증기 개질반응에 대한 활성을 측정하였다. 반응의 압력은 상압, 온도는 $250^{\circ}C$, 수증기/메탄올 몰비 1.5, 접촉시간 0.1 g-cat.hr/mL-feed의 조건에서 활성을 비교한 결과, $TiO_2$의 첨가량이 3 mol%인 촉매의 경우 최대 전화율을 보였고, 전범위에서 수소로의 선택도는 매우 높았다. 촉매의 특성 분석결과 촉매의 비표면적보다는 $N_2O$흡착, 분해방법에 의한 금속구리의 비표면적의 영향이 더욱 큼을 알 수 있었고, 적정 $TiO_2$의 첨가로 금속구리의 비표면적을 높일 수 있었다. XRD, XPS분석결과 반응중에 아연의 산화상태는 달라지지 않으나, 구리는 대부분이 0가와 1가의 상태로 존재함을 확인하였다.

• 한국응용과학기술학회지
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• 제20권3호
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• pp.230-236
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• 2003

Synthesis gas is commercially produced by a steam reforming process. However, the process is highly endothermic and energy-consuming. Thus, this study was conducted to produce synthesis gas by the partial oxidation of methane to decrease the energy cost. Supported Ni catalysts were prepared by the impregnation method. To examine the activity of the catalysts, a differential fixed bed reactor was used, and the reaction was carried out at $750{\sim}850^{\circ}C$ and 1 atm. The fresh and used catalysts were characterized by XRD, XPS, TGA and AAS. The highest catalytic activity was obtained with the 13wt% Ni/MgO catalyst, with which methane conversion was 81%, and $H_2$ and CO selectivities were 94% and 93%, respectively. 13wt% Ni/MgO catalyst showed the best $MgNiO_2$ solid solution state, which can explain the highest catalytic activity of the 13wt% Ni/MgO catalyst.

• 한국대기환경학회지
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• 제27권5호
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• pp.534-544
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• 2011

The secondary aerosol forming potential of ambient air was first measured with the Potential Aerosol Mass(PAM) chamber at Gosan supersite on Jeju island from October 22 to November 5, 2010. PAM chamber is a small flowthrough photo-oxidation chamber with extremely high OH and $O_3$ levels. The OH exposure in the PAM chamber was $(2{\pm}0.4){\times}10^{11}{\sim}(6{\pm}1.2){\times}10^{11}$ molecules $cm^{-3}$ s and was similar to 2 to 5 days of aging in the atmosphere. By periodically turning on and off UV lamps in the PAM chamber, ambient aerosol and newly formed aerosol (e.g. called as PAM aerosol) was alternately measured. Aerosol number and mass concentration in the range of 10~487 nm in diameter was measured by SMPS 3034. With UV lamps on, the nucleation mode particles smaller than 50 nm in diameters were formed. Their number concentration was greater than 105 $cm^{-3}$, leading to increase in aerosol mass by 0~8 ${\mu}gm^{-3}$. The variations of PAM and ambient aerosols were greatly dependent on characteristics of air masses such as precursor concentrations and degree of aging. This preliminary results suggests that PAM chamber is useful to assess the aerosol formation potential of air mass and its impact on the air quality. The further analysis of data with gaseous and particulate measurements will be done.