• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.731-739
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• 2014

Aluminum and boron co-doped zinc-oxide(AZOB) powders as transparent conducting oxide(TCO) were prepared by spray pyrolysis at $900^{\circ}C$. The micron-sized AZOB particles were prepared by spray pyrolysis from aqueous precursor solutions for aluminium, boron, and zinc. The micron-sized AZOB particle after the spray pyrloysis underwent post-heat treatment at $700^{\circ}C$ for 2 hours and it was changed fully to nano-sized AZOB particle by ball milling for 24 hours. The size of primary AZOB particle by Debye-Scherrer Equation and surface resistance of AZOB pellet were measured.

• Journal of Sensor Science and Technology
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• v.14 no.4
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• pp.258-264
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• 2005

Li+-ion conducting ($Li_{3}PO_{4}$) thin films with thickness of $0.3{\mu}m$, $0.65{\mu}$, $1.2{\mu}$ were deposited on $Al_{2}O_{3}$ substrate at room temperature by thermal evaporation. They were sintered at $700^{\circ}C$ and $800^{\circ}C$ for 2 hours, respectively. Reference electrode and sensing electrode were printed on Au-electrode by silk printing method. The EMF and the ${\Delta}EMF$/dec were increased with increasing the electrolyte thickness and sintering temperature. The sample sintered at $800^{\circ}C$ was shown a good response and recovery characteristics more than those sintered at $700^{\circ}C$. The Nernst's slop of 75 mV per decade was obtained at operating temperature of $500^{\circ}C$.

• Economic and Environmental Geology
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• v.42 no.3
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• pp.217-234
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• 2009

This study characterized groundwater quality and the influence of agrochemicals in a part of Ilgwang-Myeon agricultural area in Gijang-Gun, Busan Metropolitan City, using factor analyses. From the 1st, 2nd, and 3rd analyses of groundwater samples, the mean concentrations of $Ca^{2+}$, $Na^+$, $Mg^{2+}$, $K^+$, $Zn^{2+}$, $Cu^{2+}$, $Fe^{2+}$, $Al^{3+}$, $NO_3\;^-$, $Cl^-$, $SO_4\;^{2-}$, $F^-$, and $SiO_2$ were higher in the 2nd analysis than the other analyses. Pesticide carbofuran and herbicide alachlor were detected at the wells more than a half of all the wells in the 2nd analysis but not in the 4th analysis. This fact may be explained by that a higher precipitation induced higher infiltration rate of contaminants into groundwater during the 2nd survey. According to R- and Q-mode factor analyses, and chemical composition, inorganic constituents excepting $SiO_2$, $HC0_3\;^-$-, and $F^-$ may be influenced by anthropogenic sources (manures, synthetic fertilizers, and domestic wastes), seawater as well as water-mineral interaction. A typical indicator of groundwater contamination, nitrate, exceeds around 4-5 times over the Korean standard for drinking water. Additionally, the influence of seawater diminishes from the seaside to inland.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.1
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• pp.1-7
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• 2016

With a collimated $CO_2$ laser beam, the bidirectional current switching was realized in a two-terminal electronic device based on a highly resistive vanadium dioxide($VO_2$) thin film. A $VO_2$ thin film was grown on a $Al_2O_3$ substrate by a pulsed laser deposition method. For the fabrication of a two-terminal electronic device, the $VO_2$ thin film was etched by an ion beam-assisted milling method, and the $VO_2$ device, of which $VO_2$ patch width and electrode separation were 50 and $100{\mu}m$, respectively, was fabricated through a photolithographic method. A bias voltage range for stable bidirectional current switching was found by using the current-voltage property of the device measured in a current-controlled mode. The transient responses of bidirectionally switched currents were analyzed when the laser was modulated at a variety of pulse widths and repetition rates. A switching contrast was measured as ~3333, and rising and falling times were measured as ~39 and ~21ms, respectively.

• Economic and Environmental Geology
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• v.23 no.2
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• pp.245-259
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• 1990

Petrochemical analyses of granitic rocks including trace element, REE and oxygen isotope were carried out to understand petrogenesis of plutonic rocks from the Chungju, Wolaksan and Jecheon granite batholiths, which might be related with tungsten-base metal-fluorite mineralization in the Hwanggangri metallogenic province. Different geochemical characteristics such as major and trace elements were found between Jurassic Daebo granitic rocks (Chungju, Jecheon, Wonju, and Boeun granitic rocks) and Cretaceous Bulgugsa granitic rocks (Wolaksan, Muamsa and Sokrisan granitic rocks). Cretaceous granitoids are characterized by high $SiO_2$and $K_2O$ contents and low $TiO_2$, $Al_2O_3$, MgO and CaO contents. They also have relatively high contents of trace elements(Zn, V, Co, Cr, Sr, and Ba) in comparison with the Jurassic granitoids. (Eu)/($Eu^*$) and $(La/Lu)_{CN}$ ratios of Jurassic plutons vary from 0.78 to 1.13 and from 26.02 to 30.5, respectively, while the ratios of Cretaceous ones range from 0.22 to 0.28 and from 4.42 to 14.2, respectively. The REE patterns of the Cretaceous and Jurassic granitic rocks have quite different Eu anomalies: large negative Eu anomaly in the former, and mild or absent Eu anomaly in the latter. The large Eu negative of Cretaceous granitic rocks are interpreted as a differentiated product of fractional crystallization of granitic magma deduced by Rayleigh fractionation model(Tsusue et al., 1987). Oxygen isotopic compositions of quartz for Daebo and Bulgugsa granitic rocks range from 9.98 to 10.51‰ and from 8.26 to 9.56‰, respectively. The Daebo granitic rocks enriched in $^{18}0$ suggest that the magma be undergone different partial melting processes from the Bulgugsa ones. Of the Bulgugsa granitoids, Wolaksan and Sokrisan mass have different contents of trace elements and ${\delta}\;^{18}0$ values of the silicate minerals, which indicate that they are not from the identical source of magma. Many mineral deposits are distributed in and/or near the Wolaksan and Muamsa granitic rocks, but a few mineral deposits are found in and near the Chungju and Jecheon granite batholiths. It might be depend on geochemisty of the related igneous rocks which have low contents of Ba, Sr, Co, V, Cr, Ni, Zn and high contents of Nb and Y, and on lithology of country rocks such as cabonate and noncarbonate rocks.

• Asian Journal of Atmospheric Environment
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• v.6 no.2
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• pp.83-95
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• 2012

China has been a top producer and exporter of refined lead products in the world since the year 2000. After the phasing-out of leaded gasoline in the late 1990s, non-ferrous metallurgy and coal combustion have been identified as potential major sources of aerosol lead in China. This paper presents the single particle analytical results of ambient aerosol particles collected near a lead smelter using a scanning electron microscopy- energy dispersive x-ray spectroscopy (SEM-EDX). Aerosol particle samples were collected over a 24-hour period, starting from 8 pm on 31 May 2002, using a high volume TSP sampler. For this near source sample, 73 particles among 377 particles analyzed (accounting for 19.4%) were lead-containing particles mixed with other species (S, Cl, K, Ca, and/or C), which probably appeared to be from a nearby lead smelter. Lead-containing particles of less than $2{\mu}m$ size in the near source sample were most frequently encountered with the relative abundances of 42%. SEM-EDX analysis of individual standard particles, such as PbO, PbS, $PbSO_4$, $PbCl_2$, and $PbCO_3$, was also performed to assist in the clear identification of lead-containing aerosol particles. Lead-containing particles were frequently associated with arsenic and zinc, indicating that the smelter had emitted those species during the non-ferrous metallurgical process. The frequently encountered particles following the lead-containing particles were mineral dust particles, such as aluminosilicates (denoted as AlSi), $SiO_2$, and $CaCO_3$. Nitrate- and sulfate-containing particles were encountered frequently in $2-4{\mu}m$ size range, and existed mostly in the forms of $Ca(NO_3,SO_4)/C$, $(Mg,Ca)SO_4/C$, and $AlSi+(NO_3,SO_4)$. Particles containing metals (e.g., Fe, Cu, and As) in this near source sample had relative abundances of approximately 10%. Although the airborne particles collected near the lead smelter contained elevated levels of lead, other types of particles, such as $CaCO_3$-containing, carbonaceous, metal-containing, nitrates, sulfates, and fly-ash particles, showed the unique signatures of samples influenced by emissions from the lead smelter.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.107-112
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• 2010

The Cu$(In_{1-x}Ga_x)Se_2$ is the absorber material for thin film solar cell with high absorption coefficient of $1{\times}10^5cm^{-1}$. In the case of CIGS, the movable energy band gap from $CuInSe_2$ (1.00 eV) to $CuGaSe_2$ (1.68 eV) can be acquired while controlling Ga contain ratio. Generally, the co-evaporator method have used for development and fabrication of the CIGS absorption layer. However, this method should need many steps and lengthy deposition time with high temperature. For these reasons, in this paper, a new growth method of CIGS layer was attempted to hydride vapor transport (HVT) method. The CIGS mixed-source material reacted for HCl gas in the source zone was deposited on the substrate after transporting to growth zone. c-plane $Al_2O_3$ and undoped GaN were used as substrates for growth. The characteristics of grown samples were measured from SEM and EDS.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.66.1-66.1
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• 2013

We present various observational results toward a small group of Young Stellar Objects (YSOs), L1251C. Observations by Spitzer Space Telescope legacy program "From Molecular Cores to Planet Forming Disks" (c2d; Evans et al. 2003) revealed that there are three YSOs within ~15" in L1251C: IRS1 (Class I), IRS2 (Class II), and IRS3 (Class II). In order to understand the molecular environment around these YSOs, we carried out the KVN single-dish observations in $HCO^+$ J=1-0, $H^{13}CO^+$ J=1-0, $N_2H^+$ J=1-0 and HCN J=1-0. $^{12}CO$ J=1-0 was also mapped in L1251C with the TRAO 14m telescope. Integrated intensity maps of high density tracers such as $H^{13}CO^+$ J=1-0, $N_2H^+$ J=1-0 and HCN J=1-0 show similar emission distributions, whose peaks are off the positions of YSOs. A compact $HCO^+$ J=1-0 outflow and an extended $^{12}CO$ J=1-0 outflow were observed, but their outflow axes are not cosistent ($HCO^+$: NW-SE, $^{12}CO$: EW). However, the highest velocity component of the $^{12}CO$ J=1-0 outflow shows similar morphology to the $HCO^+$ J=1-0 outflow, and ~ 23 % of $^{12}CO$ outflow momentum flux is loaded onto this high velocity component. Furthermore, continuum emission has been observed at 350, 450, 850 ${\mu}m$, and 1.3mm. With the KVN single dish, the 22 GHz $H_2O$ maser emission has been also monitored toward L1251C to find variations of the systemic velocity and intensity with time.

• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.179-184
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• 2016

The interface between the surface of a cathode material and the electrolyte gives rise to surface reactions such as solid electrolyte interface (SEI) and chemical side reactions. These reactions lead to increased surface resistance and charge transfer resistance. It is consequently necessary to improve the electrochemical characteristics by suppressing these reactions. In order to suppress unnecessary surface reactions, we coated cathode material using polypropylene (PP). The PP coating layer effectively reduced the SEI film that is generated after a 4.3 V initial charging process. By mitigating the formation of the SEI film, the PP-coated Li[(Ni_0.6Co_0.1Mn_0.3)_0.36(Ni_0.80Co_0.15Al0.05)_0.64)]O₂(NCS) electrode provided enhanced transport of Li⁺ ions due to reduced SEI resistance (R_SEI) and charge transfer resistance (R_ct). The initial charge and discharge efficiency of the PP-coated NCS electrode was 96.2 % at a current density of 17 mA/g in a voltage range of 3.0 ~ 4.3 V, whereas the efficiency of the NCS electrode was only 94.7 %. The presence of the protective PP layer on the cathode improved the thermal stability by reducing the generated heat, and this was confirmed via DSC analysis by an increased exothermic peak.

• Clean Technology
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• v.18 no.2
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• pp.216-220
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• 2012

The objective of the present study was to evaluate catalytic performance of a commercial catalyst (Co/$ZrO_2-Al_2O_3$) for the decomposition of perfluorinated chemicals in a pilot scale reactor containing 30 L of catalysts. At a reaction condition of GHSV $1,800h^{-1}$, $T_{95}$ of $SF_6$ was increased from 580 to $610^{\circ}C$ with increasing of $SF_6$ concentration from 1,000 to 10,000 ppm. $T_{95}$ of $SF_6$ in catalytic decomposition was much smaller than that of thermal decomposition ($1,600^{\circ}C$). The 99% conversion of $SF_6$ was maintained for 72 hours a reaction temperature of $650^{\circ}C$. In order to maintain the $SF_6$ conversion more than 99%, it is necessary to operate at a reaction condition of GHSV less than $2,000h^{-1}$. An operating temperature of $710^{\circ}C$ was required to achieve >95% destruction of the $CF_4$, which was much higher than that of catalytic decomposition of $SF_6$.