• Journal of Environmental Science International
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• v.11 no.7
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• pp.757-763
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• 2002

The objective of this study is to delineate removal efficiency of the Linear alkylbenzene sulfonates(LAS) in solution by $TiO_2$ photocatalytic oxidation as a function of the following different experimental conditions : initial concentration of LAS, $TiO_2$ concentration, UV wavelength and pH of the solution. It was increased with decreasing initial concentration of LAS and with decreasing pH of the solution. Removal efficiency increased with increasing $TiO_2$ concentration but was almost the same at $TiO_2$ concentration of 2 g/L and 3 g/L, i.e., for initial LAS concentration of 50 mg/L. It was removal efficiency was 85% at 150 min in the case of $TiO_2$ concentration of 0.5 g/L but 100% after 150 min in the case of $TiO_2$ concentration of 1 g/L, 100% after 110 min in the case of $TiO_2$ concentration of 2 g/L and 3 g/L. UV wavelength affection on the removal efficiency of LAS decreased in the order of 254, 312 and 365 nm as increasing wavelength. But the removal efficiency of LAS was nearly the same at UV wavelength of 254 nm and 312 nm.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.378.1-378.1
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• 2014

In this study, we investigated that the resistance switching characteristics of Nb-doped HfO2 films with increasing Nb doping concentration. The Nb-doped HfO2 based ReRAM devices with a TiN/Nb-doped HfO2/Pt/Ti/SiO2 were fabricated on Si substrates. The Nb-doped HfO2 films were deposited by reactive dc magnetron co-sputtering at $300^{\circ}C$ and oxygen partial ratio of 60% (Ar: 16sccm, O2: 24sccm). Microstructure of Nb-doped HfO2 films and atomic concentration were investigated by XRD, TEM, and XPS, respectively. The Nb-doped HfO2 films showed set/reset resistance switching behavior at various Nb doping concentrations. The process voltage of forming/set is decreased and whereas the initial current level is increased in doped HfO2 films. However, the switching properties of Nb-doped HfO2 were changed above the specific doping concentration of Nb. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of non-lattice oxygen and micro-structure of Nb-doped HfO2.

• Journal of Environmental Science International
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• v.8 no.3
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• pp.281-286
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• 1999

This study was conduced to examine the monthly and seasonal variation of $SO_2$, TSP, $O_3$ concentration in Dongsamdong, Pusan coastal area. And the characteristics of air pollution of this area was compared to Kwangbokdong in Pusan and Taehadong in Ullungdo. Monthly mean concentration of $SO_2$ and TSP showed lower than Kwangbokdong, $O_3$ was higher than Kwangbokdong. In case of $SO_2$, seasonal variation of Dongsamdong was remarkabler thn Kwangbokdong and the concentration difference of early morning and daytime was higher than Kwangbokdong. Taehadong showed very lower concentration as background area. In case of TSP, Dongsamdong was lower concentration and smaller diurnal change than Kwangbokdong, Taehadong showed very lower concentration as backgound area. In case of $O_3$, Dongsamdong was 10ppb higher than Kwangbokdong at daytime maximum concentration, diurnal change of concentration was higher, too. In case of frequency distribution of concentration, $SO_2$, and TSP at Dongsamdong showed higher frequency in low concentration class and $O_3$ showed in high concentration class as compared with Kwangbokdong.

• Journal of the Korean Ceramic Society
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• v.56 no.3
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• pp.302-307
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• 2019

The intrinsic oxygen-vacancy defects in ZnO have prevented the preparation of p-type ZnO with high carrier concentration. Therefore, in this work, the effect of the concentration of H₂O₂ (used as an oxygen source) on the oxygen-vacancy concentration in ZnO prepared by atomic layer deposition was investigated. The results indicated that the oxygen-vacancy concentration in the ZnO film decreased by the oxygen-rich growth conditions when using H₂O₂ as the oxygen precursor instead of a conventional oxygen source such as H₂O. The suppression of oxygen vacancies decreased the carrier concentration and increased the resistivity. Moreover, the growth orientation changed to the (002) plane, from the combined (100) and (002) planes, with the increase in H₂O₂ concentration. The passivation of oxygen-vacancy defects in ZnO can contribute to the preparation of p-type ZnO.

• Journal of Environmental Health Sciences
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• v.26 no.4
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• pp.141-147
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• 2000

Due to a rapid in automobiles since the 1980’s, the concentration of NO, and HC has also increased along with cases of VOCs. These air pollutants have created $O_3$ concentration, which cause a harmful effect to the human health. This issue has become a subject of great public interest. For this paper, to compare the concentration of $O_3$, NO, N $O_2$ between the rural and urban area in the winter, the concentrations of each have been measuredevery hour during Jan.~Feb. 2000, 1998, respectively. To calculate the Photochemical Steady State, $\Phi$= $J_{N O_2}$[N $O_2$]/ $k_1$[NO][ $O_3$], temperature and $J_{ N O_2}$ has been determined. The NO concentration in the rural are showed at below 10 ppb while the NO concentration in the urban area showed maximum value of 90~120 ppb. But the $O_3$ concentration in both areas showed less than 30 ppb. The reason is that the N $O_2$ photodissiciation rate is low due to the temperature being below 2$^{\circ}C$ and less than 60 degrees in the solar zenith angle during the winter time, which makes the $O_3$ concentration in both areas, similar in the concentration level. N $O_2$ photodissociation rate in both ares showed maximum value of 3.0mW/$\textrm{cm}^2$. Values of $\Phi$ determined from the rural area was consistently the unity, approaching 1. But values of $\Phi$ determined from the urban was roughly higher than unity, approaching above 1or 2 for clear sky-high sun(10:00~16:00).

• Journal of Energy Engineering
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• v.20 no.3
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• pp.191-199
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• 2011

The char burn-out and NOx emissions from sub-bituminous coal were investigated in drop tube furnace under $O_2/N_2$ and $O_2/CO_2$ environments with different $O_2$ concentrations of 12, 21 and 31%. Results show that the char burn-out rate is faster as $O_2$ concentration increases higher and char burn-out rate under $O_2/CO_2$ decreases due to the lower oxygen diffusion into coal surface through the $CO_2$ rich boundary layer. NO concentration increases with increasing $O_2$ concentration, but declines at $O_2$ concentration of 31%. Meanwhile, NO emission indexes decreases monotonically with increasing $O_2$ concentration, which indicates that more NO reduction occurs with higher $O_2$ concentration probably due to greater HCN formation. For all conditions of $O_2$ concentration, the NO concentration under $O_2/N_2$ maintains higher than those of $O_2/CO_2$ due to presence of thermal NO.

• Journal of the Korean Ceramic Society
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• v.30 no.10
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• pp.791-796
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• 1993

The electro-magnetic properties of the Mn-Zn ferrite single crystal with small variation of Fe2O3 concentration at the high permeability composition, 53mol% Fe2O3-28.5mol% MnO-18.5mol% ZnO, have been studied for the VCR magnetic head application. With the increase of the Fe2O3 concentration, the Fe2+ concentration increased, the specific resistivity decreased, the secondary maximum permeability shifted to the lower temperature, and the initial permeability decreased. It was concluded that the small variation of $\pm$0.5mol% Fe2O3 concentration greatly affected the electro-magnetic properties of Mn-Zn ferrite single crystals. At the composition of 53mol% Fe2O3, the initial permeability was comparatively high (650 at 5MHz) and its temperature dependence was small.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1697-1701
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• 2016

The leakage conduction and critical voltage characteristic of ZnO ceramic were investigated as a function of $Sb_2O_3$ concentration. Leakage conduction in the ohmic region increased with increasing $Sb_2O_3$ concentration and was attributed to the potential barrier height. The nonlinear coefficient increased with an increasing amount of $Sb_2O_3$. It was found that increases in the apparent critical voltages were associated with the lowered donor concentration in the grain boundary of between two ZnO grains. And the decrease of donor concentration on doping with $Sb_2O_3$ additive was attributed to the lowered capacitance in the grain boundary layer.

• Journal of the Korean institute of surface engineering
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• v.57 no.2
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• pp.86-91
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• 2024

In this study, we investigated the effect of Na₂SiO₃ concentration on the Plasma Electrolytic Oxidation(PEO) film formation of Al6061 alloy. The morphology of the PEO films were examined by Optical Microscope(OM) and Scanning Electron Microscope(SEM). PEO film thickness increases as the Na₂SiO₃ concentration increases. The elemental analysis of PEO films was conducted using Dispersive X-ray Spectrometer(EDS). The cross-sectional elemental analysis result shows that the Si concentration tends to increase as the concentration of Na₂SiO₃ increases. X-Ray Diffraction(XRD) analysis was performed to confirm the degree of phase change according to Na₂SiO₃ concentration. In addition, Vickers hardness was measured to confirm the mechanical strength of the PEO film. As the concentration of Na₂SiO₃ increases, the hardness value also tends to increase.

• Journal of Powder Materials
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• v.21 no.2
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• pp.108-113
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• 2014

Flake-like $LiCoO_2$ nanopowders were fabricated using electrospinning. To investigate their formation mechanism, field-emssion scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were carried out. Among various parameters of electrospinning, we controlled the molar concentration of the precursor and the PVP polymer. When the molar concentration of lithium and cobalt was 0.45 M, the morphology of $LiCoO_2$ nanopowders was irregular and round. For 1.27 M molar concentration, the $LiCoO_2$ nanopowders formed with flake-like morphology. For the PVP polymer, the molar concentration was set to 0.011 mM, 0.026 mM, and 0.043 mM. Irregular $LiCoO_2$ nanopowders were formed at low concentration (0.011 mM), while flake-like $LiCoO_2$ were formed at high concentration (0.026 mM and 0.043 mM). Thus, optimized molar concentration of the precursor and the PVP polymer may be related to the successful formation of flake-like $LiCoO_2$ nanopowders. As a results, the synthesized $LiCoO_2$ nanopowder can be used as the electrode material of Li-ion batteries.