• Economic and Environmental Geology
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• v.28 no.5
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• pp.455-467
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• 1995

In order to investigate the dispersion patterns and speciations of Cu, Pb, Zn and Cd in soils, stream sediments and stream waters, geochemical studies of soil, stream sediment and stream water samples collected in the vicinity of the Shi-Heung Cu-Pb-Zn mine was carried out Cation exchange capacity measurement, size analysis, X-ray diffraction analysis and batch test were performed to select applicable soil for adsorption treatment The average content of Cu, Pb, Zn and Cd in soils collected from tailings and ore dressing plant is 1084 ppm, 2292 ppm, 3512 ppm and 29.2 ppm, respectively, and therefore, tailings and ore dressing plant site may be the major contamination sources in this study area. The mean content of Cu, Pb, Zn and Cd in stream sediments is extremely high up to 794 ppm, 1633 ppm, 2946 ppm and 25.2 ppm, respectively. Tailing particles and heavy metal ions are dispersed along the tributary system. Results from the sequential extraction analysis indicate; (1) most of Cu is bound to organic matters and sulphides, (2) fraction of Pb is mainly bound to Fe and Mn oxides. Most of Zn is largely bound to Fe and Mn oxides and residual fraction. Ion exchangeable fraction of Cd is relatively higher than those of Cu, Pb and Zn. Batch test on soils collected from the kaolinite and/or pyrophyllite mines and from the control areas was carried out to select an applicable soil samples for adsorption treatment The sample, S10, collected from the control area 2 (clay content 33.2%) shows the highest $K_d$ (distribution coefficient). Organic content in soils and several clay minerals shows relatively good correlation with $K_d$. It means that applicable soils for adsorption treatment of heavy metals show high organic and clay content.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.4
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• pp.330-333
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• 1998

This experiment was conducted to investigate the effect of long-term fertilization on the yield and quality of soybean. The yield of soybean was highest in the NPK+lime $1.5Mg\;ha^{-1}$ treatment. Carbohydrate content of soybean was high in the non-fertilizer treatment and crude protein content was high in the NPK+lime $1.5Mg\;ha^{-1}$ and NPK+silicate $1.5Mg\;ha^{-1}$ treatment, and crude lipid and ash content was high in the NPK+silicate $1.5Mg\;ha^{-1}$ treatment. The content of inorganic compounds were not different among treatments. Correlation between $P_2O_5$/T-N and carbohydrate, crude lipid was $-0.99^{**}$, $-0.94^{**}$ respectively. Correlation between Mn and carbohydrate was $0.95^*$, but others were not significantly different. Yield of soybean increased with lime application and protein content increased with silicate application.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.1
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• pp.74-81
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• 1995

In the proximate composition of the yams of home product, wild yam was most abundant in crude lipid and crude protein, and those content in the cultivated yams, cultivated long yam and cultivated short yam were similar. Cultivated long yam is the richest in crude ash. African yam had more crude lipid and crude protein compare to those of home product yams. Especially, the amount of crude lipid in African yam was four-fold of home product yams. In the mineral content, Ca was the richest mineral in four kinds of yam. The rest of mineral were in order of Fe, Mn and Zn. Among the home product yams, the Ca content of wild yam was higher than that of cultivated yam. The contents of Fe, Mn and Zn were also high in wild yam compared to cultivated yam. In the composition of free sugars, the sucrose content is the highest in wild yam, cultivated short yam and African yam. in order The fructose content was the most abundant in cultivated long yam and the next was sucrose. The composition of free fatty acids were in order of lactobacillic acid, palmitic acid and palmitoleic acid. Crude saponin contents of the home products were almost similar levle, but crude saponin of wild yam was more abundant than that of cultivated yam. And crude saponin of African yam was much more abundant compared that of other home product yams. there is not much difference in the kinds of saponin from the home product yams. However, the amount of each saponin from the home product yams was different. In case of African yam, 'b' saponin did not appear and 'e' saponin was higher compared with home product yams. In African yam, the bitter taste from ethyl acetate layer was the strongest, and the next was n-butanol layer. It is possible that there was a powerful UV absorption material in the bitter taste of ethyl acetate layer and also supposed that there were saponin and phenol is material.

• Korean Journal of Materials Research
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• v.29 no.10
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• pp.586-591
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• 2019

This study describes the doping effect of $Yb_2O_3$ on microstructure, electrical and dielectric properties of $ZnO-V_2O_5-MnO_2-Nb_2O_5$ (ZVMN) ceramic semiconductors sintered at a temperature as low as $900^{\circ}C$. As the doping content of $Yb_2O_3$ increases, the ceramic density slightly increases from 5.50 to $5.54g/cm^3$; also, the average ZnO grain size is in the range of $5.3-5.6{\mu}m$. The switching voltage increases from 4,874 to 5,494 V/cm when the doping content of $Yb_2O_3$ is less than 0.1 mol%, whereas further doping decreases this value. The ZVMN ceramic semiconductors doped with 0.1 mol% $Yb_2O_3$ reveal an excellent nonohmic coefficient as high as 70. The donor density of ZnO gain increases in the range of $2.46-7.41{\times}10^{17}cm^{-3}$ with increasing doping content of $Yb_2O_3$ and the potential barrier height and surface state density at the grain boundaries exhibits a maximum value (1.25 eV) at 0.1 mol%. The dielectric constant (at 1 kHz) decreases from 592.7 to 501.4 until the doping content of $Yb_2O_3$ reaches 0.1 mol%, whereas further doping increases it. The value of $tan{\delta}$ increases from 0.209 to 0.268 with the doping content of $Yb_2O_3$.

• Resources Recycling
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• v.11 no.5
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• pp.21-23
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• 2002

A new process based on the co-precipitation method was developed fer removing harmful impurities during Mn-Zn ferrite production such as $SiO_2$ and P from waste pickle liquor. By this process a final result of less than 100 ppm of $SiO_2$ and less than 10 ppm of P content in the ferric oxide is easily attained. Though Ca cannot be removed by this process, water rinsing of the ferric oxide is effective fer reducing Ca content to less than 100 pm. For further purification, the origins of each impurity must be investigated and then taken away.

• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.82-87
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• 2005

The cathode material, $LiNi_{0.5}Mn_{1.5}O_4$, for high voltage applications of Li-ion batteries exhibits impurity phases due to oxygen deficiency during the high temperature heat treatment. The impurity phase reduces the electrochemical properties of the electrode since the deficiency spinel structure disturbs the lithium ion intercalation and deintercalation. In this study, Cr-substituted $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4(0{\leq}x{\leq}0.05)$ powders are synthesized by a sol-gel method in order to reduce the amount of the impurity phases in the $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4$. Thermal analysis of the cathode material shows that the $LiNi_{0.5}Mn_{1.5}O_4$ without Cr substitution looses $2\%$ of its weight due to oxygen deficiency but the amount of weight loss is diminished when Cr is substituted. XRD analysis also supports the reduction of the impurity phases in the cathode after chromium substitution, suggesting that the improvement of the electrochemical properties such as the capacity retention and electrochemical stability are attributed to the low content of impurity phases in the Cr-substituted $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4.$

• Journal of the Korean Electrochemical Society
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• v.21 no.3
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• pp.47-54
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• 2018

To maximize the areal capacity($mAh\;cm^{-2}$) of $LiNi_{0.5}Co_{0.2}Mn_{0.3}O_2$(NCM523) electrode with the same loading level of $15mg\;cm^{-2}$, three NCM523 electrodes with 4, 2, and 1 wt% poly(vinylidene fluoride)(PVdF) binder content are fabricated. Due to the delamination issue of electrode composite at the edge during punching process, the 1 wt% electrode is excluded for further evaluation. When the PVdF binder content decreases from 4 to 2 wt%, both adhesion strength and shear stress decrease from 0.4846 to $0.2627kN\;m^{-1}$ by -46% and from 3.847 to 2.013 MPa by -48%, respectively. Regardless of these substantial decline of mechanical properties, their initial electrochemical properties such as initial coulombic efficiency and voltage profile are almost the same. However, owing to high loading level, the 2 wt% electrode not only exhibits worse cycle performance than the 4 wt% electrode, but also cannot maintain its mechanical integrity only after 80 cycles. Therefore, if the binder content is reduced to increase the area capacity, the mechanical properties as well as the cycle performance must be carefully evaluated.

• Korean Journal of Soil Science and Fertilizer
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• v.9 no.2
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• pp.65-70
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• 1976

The effect of leaf spray ($80{\ell}$ of 100 times diluted solution per 10a) of three liquid complex fertilizers (Compresal 1 and 2. and 3P) on rice (var, Minehikari) at 10 days before and after heading and 20 days after heading in a farmer's field was investigated by yield components and flag leaf analysis. 1. Leaf spray significantly increased filled grain ratio (at 10% level) and harvest index (at 5% level) suggesting significant yeild increase in uniform field condition. 2. Phosphorus content of flag leaf was in deficient range and increased by leaf spray while iron content was decreased indicating that liquid complex fertilizer supplied phosphorus which ratards iron translocation to the upper leaves. 3. Higher manganese content in flag leaf by leaf spray (significant at 5% level) suggests that phosphorus stimulates manganese translocation to the upper leaves resulting in favorable Fe/Mn balance. 4. Nitrogen concentration in flag leaf was in the insufficient range suggesting that nitrogen in liquid complex fertilzer had to be a nitrogen supply source. 5. In flag leaf calcium concentration was increased by leaf spray but that of boron and zinc was decreased.

• Ocean and Polar Research
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• v.26 no.2
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• pp.199-205
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• 2004

$SiO_2$ and CaO are added to decrease the smelting temperature in the reduction-smelting method for manganese nodule processing. These elements are components of the manganese nodules and might be very important controlling factors in the processing due to the locally variable content. The 707 chemical data of manganese nodules acquired from 1994 to 2001 in KODOS(Korea Deep Ocean Survey) area were used for the hierarchical cluster analysis. The chemical data were classified by the morphological types, and the averages of the chemical data for each station were classified by the facies groups and the localities. All data are plotted on the $SiO_2-CaO-MnO$ phase diagram at $1773^{\circ}K$ to compare with the best compositional area in the nodule smelting. Variations and distributions of $SiO_2$ and CaO in KODOS nodules were also reviewed. The mineral phases assigned by the cluster analysis are CFA(Carbonate Fluorapatite), Fe-oxide, Al-silicate, and Mn-oxide. MnO contents are generally higher than $SiO_2$ contents in most of the morphological types except for the Is- and It-type. The Dt- and Tt-type show wider range and the E-types show high anomaly in their CaO contents. The stations which belong to facies group A and B show generally higher MnO contents than $SiO_2$ contents, however, the stations of facies group C and D show wide range in their MnO and $SiO_2$ contents. It seems to be very important to control the $SiO_2$ contents in the processing because of the wide range in the northern area. The additions of approximately 10 wt.% CaO and 10 wt.% $SiO_2$ are recommended for the northern area, whereas, the additions of approximately 10 wt.% CaO and 20 wt.% $SiO_2$ are recommended for the southern area.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1125-1131
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• 1996

Ca or Sr-doped $PrMnO_3$ were prepared for cathode material of solid oxide fuel cell. The characteristics such as the electrical conductivity and the cathodic overpotential were investigated as to doping contents. Also the reactivity with yttria stabilized zirconia of electrolyte, and the thermal expansion coefficient were studied. The prepared perovskite powder had the mean particle size of $2{\sim}5{\mu}m$, and the particle size and the surface area was out of relation to the doping content. When Ca doping amount of electrode material was 30mol%, the electrical conductivity was the highest value of $266S{\cdot}cm^{-1}$ at $1000^{\circ}C$, and also the polarization characteristics showed the best property. The reactivity between YSZ and Ca-doped $PrMnO_3$ at $1200^{\circ}C$ for 100hours was lower than that between YSZ and Sr-doped $PrMnO_3$. The thermal expansion coefficient of $Pr_{0.7}Ca_{0.3}MnO_3$ was $1.19{\times}10^{-5}K^{-1}$ in the temperature range of $300{\sim}1000^{\circ}C$, and this value was similar to that of YSZ, $1.15{\times}10^{-5}K^{-1}$.