• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.43.2-43.2
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• 2011

Minority Carrier recombination should be suppressed for high efficiency solar cells. However, impurities in the silicon bulk region deteriorate the minority carrier lifetimes, causes conversion efficiency drop. In this study, we introduced phosphorus external gettering for silicon heterojunction solar cell substrates. Gettering was undergone at 750, 800, 850 and $900^{\circ}C$ in furnace for 30 minutes. Bulk lifetimes and calculated diffusion length were improved. We applied phosphorus gettering to silicon heterojunction solar cells. Gettered group and ungettered group were used as substrate of silicon heterojunction solar cells. After fabrication, characteristics of solar cells were analyzed. The results were observed to see the enhancement of substrate quality which directly connects with solar cell properties.

• Carbon letters
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• v.5 no.4
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• pp.191-196
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• 2004

The electrochemical removal (ECR) of water pollutants by activated carbon fiber (ACF) electrodes from wastewater was investigated over wide range of electrochemical reaction time. The ECR capacities of ACF electrodes were associated with their internal porosity and were related to physical properties and to reaction time. And, surface morphologies and elemental analysis for the ACFs after electrochemical reaction are investigated by SEM and EDX to explain the changes in adsorption properties. The FT-IR spectra of ACFs for the investigation of functional groups show that the electrochemical treatment is consequently associated with the homogeneous removal of pollutants with the increasing surface reactivity of the activated carbon fiber surfaces. The ACFs were electrochemically reacted to waste water to investigate the removal efficiency for the COD, T-N and T-P. From these removal results of pollutants using ACFs substrate, satisfactory removal performance was obtained. The outstanding removal effects of the ACFs substrate were determined by the properties of the material for adsorption and trapping of organics, and catalytic effects.

• Current Photovoltaic Research
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• v.5 no.3
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• pp.75-82
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• 2017

High efficiency thin film solar cells require an absorber layer with high absorption and low defect, a transparent conductive oxide (TCO) film with high transmittance of over 80% and a high conductivity. Furthermore, light can be captured through the glass substrate and sent to the light absorbing layer to improve the efficiency. In this paper, morphology formation on the surface of glass substrate was investigated by using HF, mainly classified as random etching and periodic etching. We discussed about the etch mechanism, etch rate and hard mask materials, and periodic light trapping structure.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.5
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• pp.695-701
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• 1999

Thermal sprayed Ni-Cr alloy coating on the carbon steel was carried out erosion-corrosion test and electrochemical corrosion test in the marine environment. THe erosion-corrosion behavior and electrochemical corrosion characteristics of substrate(SS400) and thermal sprayed Ni-Cr coating was investigated, The erosion-corrosion control efficiency of Ni-Cr coating to substrate was also estimated quantitatively.

• The Korean Journal of Mycology
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• v.30 no.2
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• pp.99-103
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• 2002

The suitable sterilization conditions in pot cultivation of varieties of Chunchunutari-2-ho and Suhannutari-1-ho Pleurotus ostreatus were investigated. The substrate formulations for the cultivation consisted of 40% poplar sawdust, 40% waste cotton and 20% beet pulp (PWB), and 40% poplar sawdust, 40% cotton seed hull and 20% beet pulp (PCB). The increase in the sterilization temperature caused decrease in the pH of the substrate. The moisture content of PWB substrate increased by 1.8%, but that of PCB substrate decreased by 4.1 % after low temperature sterilization ($12hr\;at\;60^{\circ}C$). However, a little change in the sterilization at higher temperature ($6hr\;at\;100^{\circ}C\;and\;90min\;at\;121^{\circ}C$) did not alter the moisture content of both substrate appreciably. The duration of mycelial growth was longest and its density was lowest in low temperature sterilization ($12hr\;at\;60^{\circ}C$). The high pressure sterilization ($90min\;at\;121^{\circ}C$) of PCB substrate produced high yield (236.6 g/pot) and the highest biological efficiency (96.6%) for Chunchunutari-2-ho. On the contrary the high temperatures sterilization ($6hr\;at\;100^{\circ}C$) of PCB substrate resulted in the yield of 259.1 g/pot with the biological efficiency 94.9% for Suhannutari-2-ho.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.82-91
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• 1991

Molecular beam epitaxial growth of GaAs on Si substrate and the results on its analysis are reported. Epitaxy was performed on two different types of the substrate under various grwth conditions, and was analyzed by scanning and transmission electron microscopes, X-ray diffractometer, photoluminescence and Hall measurements. GaAs epitaxial layer has better crystalline quality when it was grown on a tilt-cut substrate. The stress seems to be releaxed more easily when multi-quantum well was introduced in the buffer layer. The epilayer was doped unintentionally with Si during growth due to the diffusion of the substrate. Also observed is that the quantum efficiency of excitonic radiative recombination of the heteroepitaxy is not as good as that of the homoepitaxy in the same doping level.

• Journal of Mushroom
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• v.15 no.4
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• pp.164-167
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• 2017

Biological efficiency (BE), the ratio of fresh mushrooms harvested per dry substrate weight, expressed as the percentage of Lentinula edodes, also known as shiitake, was determined using the 'Sanjo 701' strain stored in the Department of Mushroom at the Korea National College of Agriculture and Fisheries. The mycelia were grown in glass columns with varying levels of moisture content and varying mixing periods of 0.5, 1, 2, and 3 hours. The substrate was sterilized using a steam pressure autoclave sterilizer at normal and high pressure to avoid contamination. The results showed that mycelial growth (126 mm/15 days) was optimized at 55% moisture content. The best mycelial growth of 117 mm/15 days was obtained with 2 hours of mixing time. Normal pressure sterilization yielded better results with mycelial growth of 96 mm/15 days at $100^{\circ}C$ compared to 88 mm /15 days with sterilization at $121^{\circ}C$. Mycelial density was higher, i.e. 3(+++), with normal pressure sterilization compared to 2(++) with high pressure sterilization. Furthermore, sawdust mixed with 5% woodchips increased the substrate porosity and yielded higher mycelial growth. Thus, we demonstrated that the optimum harvest or potential increased yield of shiitake can be obtained by modulating moisture content, mixing time, and substrate porosity.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.453.1-453.1
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• 2014

Fluorine-doped tin oxide (FTO), which is commonly used in dye-sensitized solar cells (DSSCs), is a promising material of transparent conducting oxides (TCOs) because of advantages such as high chemical stability, high resistance, high optical transparency (>80% at 550nm), and low electrical resistivity (${\sim}10-4{\Omega}{\cdot}cm$). Especially, dye-sensitized solar cells (DSSCs) have been actively studied since Gratzel's research group required FTO substrate as a charge collector. When FTO substrates are used in DSSCs, photo-injected electrons may experience recombination at interface between dye-bonded semiconductor oxides ($TiO_2$) on FTO substrate and the electrolyte. To solve these problems, one is that because recombination at FTO substrate cannot be neglected, thin $TiO_2$ layer on FTO substrate as a blocking layer was introduced. The other is to control the morphology of surface on FTO substrate to reduce a loss of electrons. The structural, electrical, and optical characteristics of morphology controlled-FTO thin films as TCO materials were analyzed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Hall Effect Measurement, and UV spectrophotometer. The performance of DSSCs fabricated with morphology controlled FTO substrates was performed using Power Conversion Efficiency (PCE). We will discuss these results in detail in Conference.

• Journal of Microbiology and Biotechnology
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• v.33 no.2
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• pp.268-276
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• 2023

Alkyl butyrate with fruity flavor is known as an important additive in the food industry. We synthesized various alkyl butyrates from various fatty alcohol and butyric acid using immobilized Rhodococcus cutinase (Rcut). Esterification reaction was performed in a non-aqueous system including heptane, isooctane, hexane, and cyclohexane. As a result of performing the alkyl butyrate synthesis reaction using alcohols of various chain lengths, it was found that the preference for the alcohol substrate had the following order: C6 > C4 > C8 > C10 > C2. Through molecular docking analysis, it was found that the greater the hydrophobicity of alcohol, the higher the accessibility to the active site of the enzyme. However, since the number of torsions increased as the chain length increased, it became difficult for the hydroxyl oxygen of the alcohol to access the ^γO of serine at the enzyme active site. These molecular docking results were consistent with substrate preference results of the Rcut enzyme. The Rcut maintained the synthesis efficiency at least for 5 days in isooctane solvent. We synthesized as much as 452 mM butyl butyrate by adding 100 mM substrate daily for 5 days and performing the reaction. These results show that Rcut is an efficient enzyme for producing alkyl butyrate used in the food industry.

• Journal of Korean Society on Water Environment
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• v.23 no.1
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• pp.19-26
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• 2007

The lab-scale BNR processes fed with Municipal Wastewater Before or After Primary Clarifier (MWBPC or MWAPC) were operated to observe the behavior of particle organic matter in terms of nitrification and denitrification efficiency. As a result of the fractionation of the COD from MWBPC or MWAPC using an aerobic respirometric serum bottle reactor, the total mass of biodegradable organic matter from MWBPC is about 52% greater than the mass from MWAPC. Batch reactors were operated to observe the effect of the Particulate Organic Matter (POM) on substrate utilization for denitrification. Although the consumption of POM for denitrification was observed, the increment of the Specific Denitrification Rate (SDNR) was not great. In terms of the effect of POM on nitrification at different HRTs, activate sludge reactors were operated to determine the optimal HRT when MWBPC and MWAPC were fed relatively. All reactors showed a great organic matter removal efficiency. Reactors fed with MWAPC had obtained the nitrification efficiency above 90% when the HRT of 4 hr, at least, was maintained, while reactors fed with MWBPC had same efficiency when the HRT longer than 5 hr was kept. Three parallel $A^2/O$ systems fed with MWBPC or MWAPC relatively were operated to investigate the effects of POM on BNR processes with varying the HRT of an anoxic reactor. For all systems, the efficiency of organic matter removal and denitrification, respectively, was great and about the same. In case of denitrification efficiency, system with MWAPC had 1.5% lower than system with MWBPC at the same HRT of anoxic reactor of 2 hr, and the increasing the HRT of the anoxic reactor by 1 hr in systems fed with MWBPC resulted in a 3.5% increment. The denitrification rate was similar while the consumption of organic matter in systems fed with MWBPC was higher than system fed with MWBPC. It suggests that POM in MWBPC was not be used significantly as a substrate for denitrification in system with the HRT of 3 hr of an anoxic reactor.