• Current Photovoltaic Research
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• v.4 no.2
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• pp.31-41
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• 2016

n-type PERT (passivated emitter, rear totally diffused) bifacial solar cells with boron and phosphorus diffusion as p+ emitter and n+ BSF (back surface field) have attracted significant research interest recently. In this work, the influences of wafer thickness, bulk lifetime, emitter, BSF on the photovoltaic characteristics of solar cells are discussed. The performance of the solar cell is determined by using one-dimensional solar cell simulation software PC1D. The simulation results show that the key role of the BSF is to decrease the surface doping concentration reducing the recombination and thus, increasing the cell efficiency. A lightly phosphorus doped BSF (LD BSF) was experimentally optimized to get low surface dopant concentration for n type bifacial solar cells. Pre-oxidation combined with a multi-plateau drive-in, using limited source diffusion was carried out before pre-deposition. It could reduce the surface dopant concentration with minimal impact on the sheet resistance.

• Korean Journal of Ecology and Environment
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• v.46 no.1
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• pp.75-85
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• 2013

This study investigated the effects of organic matter decomposition on the emission of greenhouse gas under the influence of environmental factors such as change of climate condition ($CO_2$ concentration and temperature), vegetation, and N concentration in the soil of Gyeongan stream in the laboratory. The experimental results showed that organic matter decomposition and $CH_4$, $CO_2$ flux were influenced by changes of complex environmental conditions. Organic matter decomposition rate was affected by changes of climate condition with N concentration and climate condition with vegetation. Through the results of $CH_4$, $CO_2$ flux, $CH_4$ flux was affected by change of climate condition with N concentration and climate condition with vegetation and affected by the presence of vegetation and N concentration. $CO_2$ flux was affected by change of climate condition with vegetation and vegetation with N concentration. According to results of the study, change of (1) climate conditions, (2) vegetation, and (3) N concentration, each have an effect on organic decomposition rate, that also influences emission of greenhouse gas. It is known that climate change is related to an increase in greenhouse gasses in the atmosphere However, additional study will be needed whether vegetation could remove positive effect of nitrogen addition in soil since this study shows opposite results of organic matter decomposition in response to the nitrogen addition.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.1
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• pp.37-48
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• 2004

The purpose of this study was to evaluate adaptability of external carbon source using GPS-X program in pilot plant composed with 2-stage denitrification process. The result from analysis of pilot plant operation and GPS-X simulation showed that effluent concentration could be simulated similarly by modifying operation conditions, such as DO concentration, C/N ratio and other calibrated parameter. In order to satisfy the standard of the effluent water quality on T-N of 20mg/L, it required approximately 3.1 of C/N ratio and 50% of nitrogen removal efficiency when influent T-N is 36.9mg/L. To maintain the stable water quality of the receiving water, the effluent T-N concentration should be less than 10-15mg/L and the appropriate C/N ratio to remove nitrogen was 4.27-6.82. The analysis of sensitivity to kinetic coefficient and reaction constant showed that $Y_H$ and ${\mu}_{mAUT}$ were most sensitive to nitrate and ammonia nitrogen, relatively and sensitivity coefficient of their were 1.32, 1.98. It was concluded that as $Y_H$ decreased and ${\mu}_{mAUT}$ increased, the reaction rates of denitrification and nitrification increased and the removal efficiencies of $NO_3{^-}-N$ and $NH_4{^+}-N$ improved.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.2
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• pp.87-93
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• 2004

Nitrocarburizing was carried out with various $CH_4$ gas composition with 4 torr gas pressure at $570^{\circ}C$ for 3 hours and post oxidation was carried out with 100% $O_2$ gas atmosphere with 4 torr at different temperatures for various time. In the case of plasma nitrocarburizing, It is that the ratio of ${\varepsilon}-Fe_{2-3}$(N, C) and ${\gamma}^{\prime}-Fe_4$(C, N), which comprise the compound layer phase, depend on concentrations of $N_2$ gas and $CH_4$ such that when the concentration of $N_2$ and $CH_4$ increased, the ratio of ${\gamma}^{\prime}-Fe_4$(C, N) decreased, but the ratio of ${\varepsilon}-Fe_{2-3}$(N, C) increased. The thickness of compound layer consistently increased as gas concentration increased regardless of $N_2$ and $CH_4$ expect when the concentration of $CH_4$ was 3.5 volume%, it decreased insignificantly. When oxidizing for 15min in the temperature range of $460{\sim}570{^\circ}C$, the study found small amount of $Fe_3O_4$ at the temperature of $460{^\circ}C$ and also found that amounts of $Fe_2O_3$. and $Fe_3O_4$ on the surface and amount of ${\gamma}^{\prime}-Fe_4$(C, N) in the compound layer increased as the increased over $460^{\circ}C$, but the thickness of the compound layer decreased. Corrosion resistance was influenced by oxidation times and temperature.

• Journal of the Korean Vacuum Society
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• v.20 no.4
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• pp.271-275
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• 2011

The role and effect of Sb surfactant on structure and properties of p type gallium nitride (GaN) epilayers have been investigated. It was found that there was a increase of hole concentration with Sb surfactant, compared to typical Mg-doped p-GaN. The structural and optical quality of p-GaN epilayers were accessed by x-ray diffraction, photoluminescence and atomic force microscope measurements. The results clearly show that the increase in hole concentration with Sb surfactant can be resulted from decrease in the dislocations and nitrogen point defects.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.10
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• pp.561-567
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• 2017

This study focused on estimating the low concentration of $NH_4{^+}-N$ removal by using simultaneous reaction of the adsorption and microbial nitrification with microbe-attached zeolite media. To evaluate the adsorption effect of the zeolite media, the expanded polypropylene (EPP) media which are not able to adsorb $NH_4{^+}-N$ were used as a control media in order to compare the adsorption ability. Each media was used to experiment after aerated 8 hr for attachment of the microbes. The batch experiment shows that nitrification occurred in zeolite media better than EPP media because nitrifiers could consume the relatively enough amount of $NH_4{^+}-N$ adsorbed onto the zeolite media. Compared to the reactor with EPP media, nitrification occurred only in the reactor with zeolite media under continuous operation at the empty bed contact time (EBCT) of 25 min and 3 mg/L of $NH_4{^+}-N$ concentration. As the EBCT of the reactor with zeolite media increased from 10 to 60 min, the nitrification efficiencies increased too. $NH_4{^+}-N$ removal efficiency showed up more than 90% at EBCT 60 min. And the difference in concentration of the total nitrogen between the influent and the effluent was 0.25 mg/L at EBCT 10 min, 0.78 mg/L at EBCT 25 min, 0.59 mg/L at EBCT 40 min and 0.37 mg/L at EBCT 60 min, respectively. This difference was due to between adsorption rate and nitrification rate of $NH_4{^+}-N$, and it was considered that $NH_4{^+}-N$ was adsorbed on the zeolite media by the gap of the concentration.

• Korean Journal of Agricultural and Forest Meteorology
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• v.24 no.4
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• pp.285-294
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• 2022

In order to accurately calculate greenhouse gas emissions in the agricultural field, Korea has been developing national-specific emission factors through direct measurement of gas fluxes using the closed-chamber method. In the rice paddy, only national-specific emission factors for methane (CH₄) have been developed. It is thus necessary to develop those for nitrous oxide (N₂O) affected by the application of nitrogen fertilizer. However, since the concentration of N₂O emission from rice cultivation is very low, the QA/QC methods such as method detection and practical quantification limits are important. In this study, N₂O emission from a rice paddy was evaluated affected by the amount of nitrogen fertilizer, by taking into account both method detection and practical quantification limits for N₂O concentration. The N₂O emission from a rice paddy soils affected by the nitrogen fertilizer application was estimated in the following order. The method detection limit (MDL) of N₂O concentration was calculated at 95% confidence level based on the pooled standard deviation of concentration data sets using a standard gas with 98 nmol mol^-1 N₂O 10 times for 3 days. The practical quantification limit (PQL) of the N₂O concentration is estimated by multiplying 10 to the pooled standard deviation. For the N₂O flux data measured during the rice cultivation period in 2021, the MDL and PQL of N₂O concentration were 18 nmol mol^-1 and 87 nmol mol^-1, respectively. The measured values above the PQL were merely about 12% of the total data. The cumulative N₂O emission estimated based on the MDL and PQL was higher than the cumulative emission without nitrogen fertilizer application. This research would contribute to improving the reliability in quantification of the N₂O flux data for accurate estimates of greenhouse gas emissions and uncertainties.

• Journal of Ecology and Environment
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• v.32 no.2
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• pp.123-127
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• 2009

Weight loss and nutrient dynamics of Quercus mongolica leaf litter during decomposition were investigated from December 2005 through August 2008 in Mt. Worak National Park as a part of National Long-Term Ecological Research Program in Korea. The decay constant (k) of Q. mongolica litter was 0.26. After 33 months decomposition, remaining weight of Q. mongolica litter was 49.3$\pm$4.4%. Initial C/N and C/P ratios of Q. mongolica litter were 43.3 and 2,032, respectively. C/N ratio in decomposing litter decreased rapidly from the beginning to nine months decomposition, and then showed more or less constant. C/P ratio increased to 2,407 after three months decomposition, and then decreased steadily thereafter. N and P concentration increased significantly during decomposition. N immobilization occurred from the beginning through 18 months decomposition, and mineralization occurred afterwards in decomposing litter. P immobilized significantly from fifteen months during decomposition. K concentration decreased rapidly from the beginning to six months decomposition. However it showed an increasing pattern during later stage of decomposition. Remaining K decreased rapidly during early stage of decomposition. There was no net K immobilization. Ca concentration increased from the beginning to twelve months decomposition, and then decreased rapidly till twenty one months elapsed. However, it increased again thereafter. Ca mineralization occurred from fifteen months. Mg concentration increased during decomposition. There was no Mg immobilization during litter decomposition. After 33 months decomposition, remaining N, P, K, Ca and Mg in Q. mongolica litter were 79.2, 110.9, 36.2, 52.7 and 74.4%, respectively.

• Bulletin of the Korean Chemical Society
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• v.27 no.5
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• pp.718-724
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• 2006

The heterogeneous association behaviour of various concentration binary mixtures of mono alkyl ethers of ethylene glycol with ethyl alcohol were investigated by dielectric measurement in benzene solutions over the entire concentration range at 25 ${^{\circ}C}$. The values of static dielectric constant $\epsilon_0$ of the mixtures were measured at 1 MHz using a four terminal dielectric liquid test fixture and precision LCR meter. The high frequency limiting dielectric constant $\epsilon_\infty$ values were determined by measurement of refractive index $n_D$ ($\epsilon_\infty\;=\;n_D\;^2$). The measured values of $\epsilon_0$ and $\epsilon_\infty$ were used to evaluate the values of excess dielectric constant $\epsilon^E$, effective Kirkwood correlation factor $g^{eff}$ and corrective correlation factor $g_f$ of the binary polar mixtures to obtain qualitative and quantitative information about the H-bond complex formation. The non-linear behaviour of the observed $\epsilon_0$ values of the polar molecules and their mixtures in benzene solvent confirms the variation in the associated structures with change in polar mixture constituents concentration and also by dilution in non-polar solvents. Appearance of the maximum in $\epsilon^E$ values at different concentration of the polar mixtures suggest the formation of stable adduct complex, which depends on the molecular size of the mono alkyl ethers of ethylene glycol. Further, the observed $\epsilon^E$ < 0 also confirms the heterogeneous H-bond complex formation reduces the effective number of dipoles in these polar binary mixtures. In benzene solutions these polar molecules shows the maximum reduce in effective number of dipoles at 50 percent dilutions. But ethyl alcohol rich binary polar mixtures in benzene solvent show the maximum reduce in effective number of dipoles in benzene rich solutions.

• Journal of Environmental Health Sciences
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• v.27 no.4
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• pp.63-71
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• 2001

PM 2.5/ samples were measured at two sites, Hadan(suburban site) and Anrak (roadside site) in Busan area. PM 2.5/ sampling was performed for 24-hour intervals by the FH9.5 particulate sampler. Aerosol samples were collected on PTFE filter. A total of 60 particulate samples were collected, dad samples were measured for Particulate mass concentration, metallic elements (Cr, Mn, Ni. Cu. Se, Fe, Pb, and Zn) and waer-soluble elements (C $l^{[-10]}$ , N $O_{3}$$^{[-10]}$ ,S $O_{4}$$^{2-}$, N $H_{4}$$^{+}$, $Ca_{2}$$^{+}$, $Mg_{2}$$^{+}$ and $^{+}$.Mass concentration in Hadan ranged 24.23~57.12 $\mu\textrm{g}$/㎥ and 60.22~72.12 $\mu\textrm{g}$/㎥m Yellow Sand Events. Major cations in Hadan and Anrak site is N $H_{4}$$^{+}$and N $a^{+}$ respectively. SO42$^{[-10]}$ was the abundant specie in the PM 2.5 fraction for Hadan site an dAnrak site. Hadan site showed igher concentration in S $O_{4}$$^{2.1}$ and N $H_{4}$ $^{+}$ In Anrak site the concentration of S $O_{4}$/sip 2-/and N $a^{+}$ was higher than other ions Prominent metallic elements were Fe and Pb in two sites. Principal component analysis showed that main source of PM 2.5 aerosol particles was non-metal related source which was resulted in relating elements as Cr, Ni, and Pb at Hadan site, Anrak site also has resulted PM2.5 aerosol paricles source, which was related its element like Zn, and Ni,. The SAS package analysis also showed that long-range transport effect at Hadan area due to Yellow Sand Event by the prevailing weaterlies.ling weaterlies.