• Journal of Powder Materials
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• v.27 no.5
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• pp.401-405
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• 2020

Magnesium hydroxide sulfate hydrate (MHSH) whiskers were synthesized via a hydrothermal reaction by using MgO as the reactant as well as the acid solution. The effects of the H₂SO₄ amount and reaction time at the same temperature were studied. In general, MHSH whiskers were prepared using MgSO₄ in aqueous ammonia. In this work, to reduce the formation of impurities and increase the purity of MHSH, we employed a synthesis technique that did not require the addition of a basic solution. Furthermore, the pH value, which was controlled by the H₂SO₄ amount, acted as an important factor for the formation of high-purity MHSH. MgO was used as the raw material because it easily reacts in water and forms Mg⁺ and MgOH⁺ ions that bind with SO₄^2- ions to produce MHSH. Their morphologies and structures were determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM).

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.176-176
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• 2003

The effects of oxide thickness and gate length of MgO/GaN metal oxide semiconductor field effect transistors (MOSFETs) on I-V, threshold voltage and breakdown voltage characteristics were examined using a drift-diffusion model. The saturation drain current scales in an inverse logarithmic fashion with MgO thickness and is < 10$^{-3}$ A.${\mu}{\textrm}{m}$$^{-1}$ for 0.5 ${\mu}{\textrm}{m}$ gate length devices with oxide thickness > 600 $\AA$ or for all 1 ${\mu}{\textrm}{m}$ gate length MOSFETs with oxide thickness in the range of >200 $\AA$. Gate breakdown voltage is > 100 V for gate length >0.5 ${\mu}{\textrm}{m}$ and MgO thickness > 600 $\AA$. The threshold voltage scales linearly with oxide thickness and is < 2 V for oxide thickness < 800 $\AA$ and gate lengths < 0.6 ${\mu}{\textrm}{m}$. The GaN MOSFET shows excellent potential for elevated temperature, high speed applications.

• Journal of the Mineralogical Society of Korea
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• v.27 no.2
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• pp.97-105
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• 2014

Artificial precipitation ponds, consisting of three steps of oxidation pond, successive alkalinity producing system (SAPS) and swamp, were constructed for the treatment of the acid mine drainage from the Iwal coal mine. The efficacies of the passive treatment system in terms of neutralization of mine water and removal of dissolved ions were evaluated by the chemical analyses of the water samples. Mine water in the mine adits was acidic, showing the pH value of 2.28-2.42 but the value increased rapidly to 6.17-6.53 in the Oxidation pond. The purification efficiencies for the removal of Al and Fe were 100%, whereas those of $SO_4$, Mg, Ca, and Mn were relatively low of 50%, 40%, 24%, and 59%, respectively. These results indicate a need for application of additional remediation techniques in the passive treatment systems. The precipitates that formed at the bottom of the mine water channels were mainly schwertmannite ($Fe_8O_8(OH)_6SO_4$) and those in the leachate water were 2-line ferrihydrite ($Fe_2O_3{cdot}0.5H_2O$).

• The Korean Journal of Food And Nutrition
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• v.21 no.2
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• pp.148-156
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• 2008

The purpose of this study was to analyze the changes in physicochemical characteristics and NDMA formation of Orostachys japonicus A. Berger according to harvest times. The results showed moisture, carbohydrate, crude fiber and crude protein contents of <$48.5{\pm}1.4%$, $38.2{\pm}1.2%$, $l5.8{\pm}0.4%$ and $13.2{\pm}0.6%$ respectively. The total mineral content was 4,817.1 mg/100 g, where Ca was highest($2,577.0{\pm}3.2$ mg/100 g), followed by K, Mg, Na, P and Fe. The composition amino acid of O. japonicus A. Berger showed high levels of glutamic acid and aspartic acid. And among the five free sugars detected, galactose and glucose were most abundant at $32.2{\pm}0.02$ mg/100 g and $25.3{\pm}0.1O$ mg/100 g, respectively. Upon comparing O. japonicus A. Berger extracts that came from plants harvested during $August{\sim}October$, total phenolic compound($2,703.l{\pm}5.2l{\sim}2,428.0{\pm}3.52$ mg/100 g) and flavonoid($634.2{\pm}2.33{\sim}1,324.6{\pm}1.87$ mg/100 g) contents were higher in the methanol extract than in the water extract. Also, within a reaction system, nitrite scavenging ability and NDMA inhibition were most effective at pH 2.5, and increased in proportion to the extract concentration. Finally, the methanol extract of O. japonicus A Berger harvested during $August{\sim}October$ had the highest nitrite scavenging and NDMA inhibition effects.

• Journal of Powder Materials
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• v.26 no.5
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• pp.405-409
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• 2019

Piezoelectric ceramic specimens with the $Pb(Mg_{1/3}Nb_{2/3})_{0.65}Ti_{0.35}O_3$ (PMN-PT) composition are prepared by the solid state reaction method known as the "columbite precursor" method. Moreover, the effects of the $Li_2O-Bi_2O_3$ additive on the microstructure, crystal structure, and piezoelectric properties of sintered PMN-PT ceramic samples are investigated. The addition of $Li_2O-Bi_2O_3$ lowers the sintering temperature from $1,200^{\circ}C$ to $950^{\circ}C$. Moreover, with the addition of >5 wt.% additive, the crystal structure changes from tetragonal to rhombohedral. Notably, the sample with 3 wt.% additive exhibits excellent piezoelectric properties ($d_{33}=596pC/N$ and Kp = 57%) and a sintered density of $7.92g/cm^3$ after sintering at $950^{\circ}C$. In addition, the sample exhibits a curie temperature of $138.6^{\circ}C$ at 1 kHz. Finally, the compatibility of the sample with a Cu electrode is examined, because the energy-dispersive X-ray spectroscopy data indicate the absence of interdiffusion between Cu and the ceramic material.

• The Journal of the Petrological Society of Korea
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• v.16 no.2 s.48
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• pp.59-72
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• 2007

Kilauea volcano located in the southern part of Hawaii island chains has been formed by continuous and sporadic eruption activities from 16 century to September of 1982. Kilauea volcano was investigated from collecting the samples of basalt to identify the geochemical characteristics of the lavas. Olivine, clinopyroxene, plagioclase, and opaque minerals with glass groundmass are observed. Clinopyroxene formed glomerophopyritic texture with plagioclase and zoning texture was observed in some of plagioclase phenocrysts. Major elements such as $K_2O$, $P_2O_5$, $TiO_2$ increased with respect to MgO. $Al_2O_3$ and CaO show the kink on Marker diagram due to the crystal fractionation of plagioclase and clinopyroxene with plagioclase respectively. Olivine has a wide range of Fo% ranging from 60 to 90, and MnO and FeO in the olivine are decreased with increasing Fo% oppositely increased $SiO_2$, MgO, and NiO. Ni in the whole rock is controlled not only by the mode of olivine but also by the Ni abondance in the olivine.

• Journal of The Korean Society of Grassland and Forage Science
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• v.5 no.3
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• pp.200-206
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• 1985

This field experiment was undertaken to assess the effects of three levels of inclination ($10^{\circ},\;20^{\circ},\;and\;30^{\circ}$) and four rates of $N-P_2O_5-K_2O$ (0-0-0-, 14-10-10, 28-25-25, and 42-40-40kg/10a) on establishment, yield and quality, and botanical compositions of mixed grass-clover sward. This second part is concerned with the soil chemical properties, concentrations and uptake of mineral nutrients, and percent recovery and efficiency of NPK. The results obtained after a two-year experiment are summarized as follows: 1. The pH, exchangeable Mg and Na, and base saturation in the surface soils were decreased by increasing the grade of inclination, whereas organic matter and available $P_2O_5$ tended to be increased. However, the changes in the Ca content and equivalent ratio of $K\sqrt{Ca+Mg}$ were not significant. The pH, exchangeable Ca and Mg, and base saturation were reduced by increasing the NPK rate, whereas available $P_2O_5$, exchangeable K, and equivalent ratio of $K\sqrt{Ca+Mg}$ tended to be increased. 2. The concentrations of mineral nutrients in grasses and weeds were not significantly affected by increasing the grade of slope in hilly pasture, whereas the concentrations of N, K, and Mg in legume were the lowest with the steep slope, which seemed to be related to the low legume yield. The Mg concentrations of all forage species were below the critical level for good forage growth and likelihood of grass tetany. 3. The increase of NPK rate resulted in the increment of N, K and Na concentrations, and the decrease of Mg and Ca in grasses. The P concentration was increased with P application, but there were no differences in that among the P rates applied. It resulted also in a slight increase of K, and a decrease of Mg in legume, but the contents of N, Ca, and Na were not affected by that. On the other hand, it has not affected the mineral contents in weeds except a somewhat increase of N. The mixed forages showed a increase of N and K contents, a decrease of Ca and Mg, and a slight change in P and Na. 4. The percent recovery of N, P and K by mixed forages were greatly decreased by increasing the grade of inclination and NPK rate. They were high in the order; K>N>P. The efficiency of mixed NPK applications was decreased by that. The efficiency of mixed NPK fertilizers absorbed was slightly decreased by the increased rate of NPK, but it was not affected by the grade of inclination.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.4
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• pp.605-610
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• 2011

The objectives of this study are to investigate a bromate behaviour in the processes of advanced water treatment system (AWTS: preozonation, coagulator-settler, rapid sand filter, postozonation, biological activated carbon (BAC) beds) and to investigate the effects of ozonation, pH and ammonia nitrogen on bromate (${BrO^-}_3$) formation. As a result, $BrO_3$ was not detected in the processes of the AWTS without ozonation, while it was detected in a preozonated and postozonated water. For $BrO_3$ formation during June to November, the $BrO_3$ concentration of <9.4${\mu}g/L$ was observed in postozonated water, while it was reduced to about 46% by BAC beds. When applied ozone dosage and ozone contact time for influent with $Br^-$ of <0.3mg/L were 0.5-2.0mg/L.min and 10 min., $BrO_3$ concentration increased with increasing ozone dosage. Longer contact time and lower ozone level also was needed to inhibit the formation of $BrO_3$. At ozone dosage of 1.4 mg/L.min, the formation rate of $BrO_3$ increased with increase of pH value. When $NH_4-N$ concentration increased from 0.1mg/L to 0.4mg/L, $BrO_3$ concentration decreased to about 38%. These results revealed that $BrO_3$ concentration increased with increasing Br level, ozone dosage, and pH value, while it decreased with increase of $NH_4-N$ concentration.

• Journal of Mushroom
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• v.11 no.4
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• pp.219-225
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• 2013

This study was carried out to investigated optimum mixing ratio of Korean natural Juglans mandshurica using as functional plants. Total nitrogen and carbon source of J. mandshurica was 0.21% and 46.0%, respectively and C/N ratio was 219. Total nitrogen source and pH of substrate mixed with J. mandshurica was 2.3~2.9 and 5.0, respectively. The contents of CaO, MgO and $Na_2O$ at J. mandshurica media were higher at harvest media than inoculation media. Mycelial growth was the fastest at J. mandshurica 20%, and slower by increase of J. mandshurica substrate. Yields of fruiting body show the highest to 163 g/850 mL of medium which are addition 10% of J. mandshurica sawdust, and diameter and thick of pileus were the highest, too. The L value of pileus and stipes were increased by increase of J. mandshurica substrate, but there was no significant difference in the a-value and the b-value. The contents of $P_2O_5$ and $K_2O$ of fruiting body were increased at J. mandshurica substrate, but there was no significant difference in contents of CaO, MgO and $Na_2O$. The contents of Cu of fruiting body was decreased by increase of J. mandshurica substrate, but Fe, Mn and Zn were increased.

• Journal of Environmental Science International
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• v.28 no.5
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• pp.511-520
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• 2019

This study was investigated to improve the phosphorus release and water quality by transformation of sedimentary P fraction for application of $CaO_2$. For the experiment, 0.5% (w/w) of $CaO_2$ was homogenized in the sediment and incubated with the control for 20 days. The analytical results showed that pH increased with $CaO_2$ and redox potential (ORP) was improved in the sediment of the reactor. The growth rate of chlorophyll-a was lower in the $CaO_2$ reactor and Dissolved Oxygen (DO) of overlying water maintained higher than that of the control. Total phosphorus (T-P) concentration in the overlying water increased from the initial concentration to 0.304mg/L in the control at 20 days. The reactor of $CaO_2$ was lowered by 29.3%. Ex-P, Fe-P and Ca-P in sediment P fraction were increased with the $CaO_2$. The formation of bound Fe-P and Ca-P in the sediments seemed to control the release of P by removing the Soluble Reactive Phosphorus (SRP) presented in the pore water. From the result, this indicated that the reduction of P release from the sediments seems to be effective in suppressing the eutrophication of P and improving the oxygen condition in the water quality with the application of $CaO_2$.