• Journal of the Korean Chemical Society
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• v.37 no.7
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• pp.635-641
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• 1993

Electrochemical cell, $Pt|air(PO_2=5.3{\times}10^{-3}atm)|Zr_{0.85}Ca_{0.15}O_{1.85}|air(PO_2= 0.21atm)|Pt$, has been designed to characterize the solid electrolyte and the temperature dependence of the electromotive force (EMF) has been measured in a temperature range of 600∼1000${\circ}$C. Solid electrolyte shows pure ionic conduction of the oxygen anion. The Fe-FexO, Co-CoO, Ni-NiO, and Cu2O-CuO electrodes have been prepared by mixing the 1 : 1 mole ratio of each metal and metal oxide and then by heating at 800${\circ}$C for 6 hours. Electrochemical cells, Pt│M(s), $MO(s)|Zr_{0.85}Ca_{0.15}O_{1.85}|air(PO_2=0.21atm)|Pt$, have been designed and the temperature dependence of the EMF has also been measured in the same temperature range. The changes of the thermodynamic state functions for the formation of the metal oxides are calculated from the electromotive forces and their temperature dependences. The material properties of the oxide systems are also discussed with the function changes.

• Current Photovoltaic Research
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• v.7 no.4
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• pp.97-102
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• 2019

Bifacial and semitransparent hydrogenated amorphous silicon (a-Si:H) thin-film solar cells in p-i-n configuration were prepared with front and rear transparent conducting oxide (TCO) electrodes using plasma-enhanced chemical vapor deposition method. Fluorine-doped tin oxide and tin-doped indium oxide films were used as front and rear TCO contacts, respectively. Film thickness of intrinsic a-Si:H absorber layers were controlled from 150 nm to 450 nm by changing deposition time. The dependence of performance characteristics of solar cells on the front and rear illumination direction were investigated. For front illumination, gradual increase in the short-circuit current density (J_SC) from 10.59 mA/㎠ to 14.19 mA/㎠ was obtained, whereas slight decreases from 0.83 V to 0.81 V for the open-circuit voltage (V_OC) and from 68.43% to 65.75% for fill factor (FF) were observed. The average optical transmittance in the wavelength region of 380 ~ 780 nm of the solar cells decreased gradually from 22.76% to 15.67% as the absorber thickness was changed from 150 nm to 450 nm. In case of the solar cells under rear illumination condition, the J_SC increased from 10.81 to 12.64 mA/㎠ and the FF deceased from 66.63% to 61.85%, while the V_OC values were maintained at 0.80 V with increasing the absorber thickness from 150 nm to 450 nm. By optimizing the deposition parameters, a high-quality bifacial and semitransparent a-Si:H solar cell with 350 nm-thick i-a-Si:H absorber layer exhibited the conversion efficiencies of 7.69% for front illumination and 6.40% for rear illumination, and average visible optical transmittance of 17.20%.

• The Korean Journal of Mycology
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• v.21 no.3
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• pp.157-164
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• 1993

The effects of the iron ions on the light-induced mitochondrial $F_1-ATPase$ in Lentinus edodes was studied. This enzyme activity was stimulated by each of the ferric, ferrous and magnesium ion. Especially, the activity of the enzyme by 5.0 mM ferric ion increased up to 107% in comparision with control group(100%). In the presence of magnesium ion, each of ferric and ferrous ion increased the activity of the enzyme, particulary, coexistence of 0.1 mM magnesium and 5.0 mM ferric ion increased the activity up to 270% with magnesium ion dependence. The activity of the enzyme was stimulated up to 268% by 5.0 mM ferric ion in the presence of 0.1 mM magnesium and 0.1 mM ferrous ion. Therefore, the coexistence of ferrous ion did not affect the activity. From the above, we propose that light-induced mitochondrial $F_1-ATPase$ in Lentinus edodes is a $Mg^{2+}{\cdot}Fe^{3+}{\;}F_1-ATPase.$ The optimal pH and temperature for the enzyme were 7.5 and $66^{\circ}C$ respectively.

• The Korean Journal of Pesticide Science
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• v.7 no.1
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• pp.58-65
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• 2003

Various physicochemical parameters for the active ingredients of 245 herbicides were calculated to develope a diagnosis and estimation system for utility as herbicide. The range of physico-chemical parameters for each inhibitors of photo system II (H1), acetolactate synthase (ALS) (H2) and herbicides were confirmed. The distribution ranges of 85% dependence for each physicochemical parameters were Obs.logP :$-0.90\sim4.50$, dipol moment: $1.80\sim12.22$ (debye), molecular refractivity: $53.0\sim104.0(cm^3/mol)$, polarizability: $19.0\sim37.0(\AA^3)$, HOMO energy: $-9.98\sim-7.34$ (eV), LUMO energy:$-2.76\sim0.40$ (eV), Van der Waals molecular volumes: $558.0\sim995.0(cm^3)$, molecular weight: $202.0\sim430.0$ (amu) and surface areas (Grids): $194.0\sim356.0(\AA^2)$, hydration energy: $-10.16\sim114.7$ Kcal/mol, respectively. It is suggested that MR and polarizability constants will be able to distinguish between herbicides and medicinal drugs. Results revealed that various compounds based on the range of physicochemical parameters of herbicides could be diagnosed and estimated.

• Polymer(Korea)
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• v.24 no.1
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• pp.97-104
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• 2000

PAN-based activated carbon fibers/phenolic resin matrix composites (ACFCs) were manufactured via molding process with oxidized carbon fabrics (plain-type) and phenolic resin (resole-type) compounded by 70 : 30 wt%. The green body (as molded) was submitted to carbonization (at 100$0^{\circ}C$) in an inert environment and activation (at 700, 800, 900 and 100$0^{\circ}C$) in a $CO_2$ environment. In this work, the influence of activation temperatures was investigated in surface properties, such as pH, acid- and base-values by titration method, and in adsorption properties, i.e., specific surface area and pore structures by BET-method of the composites. Also, the pressure drops of the specimens were calibrated by ASTM. As a result, the activation temperature influenced the surface property of ACFCs. When the activation temperature was higher than 90$0^{\circ}C$, the surface was gradually developed in basic nature. And, the evolutions of specific surface area, total pore volume and pore size distribution of ACFCs could be easily confirmed the dependence on the activation temperature. Among them, well-developed pore structure from adsorption characteristics was changed of the ACFCs activated at 90$0^{\circ}C$. Also, the pressure drop was slightly decreased with increasing the temperature due to increasing the burn-off with heat treatment temperature of ACFCs.

• Korean Journal of Food Science and Technology
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• v.21 no.4
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• pp.480-485
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• 1989

Changes of color intensity and components during browning reaction of water extracts from white tail ginseng were investigated. Temperature dependence was described by the Arrhenius relationship with an activation energy of 16kcal/mole. Temperature sensitivities$(Q_{10}\;value)$ for water extracts of ginseng was 1.90 between $70^{\circ}C\;and\;80^{\circ}C$, 1.57 between $80^{\circ}C\;and\;90^{\circ}C$ and 1.46 between $90^{\circ}C\;and\;100^{\circ}C$. pH value of the solution treated at $90^{\circ}C\;and\;100^{\circ}C$ slightly increased with an increase in reaction time. Among ginseng saponins ginsenoside-Re was most unstable against heat-treatment, white diol group saponins were more stable against heat-treatment. Hydrogen donating activity (reducing activity for ${\alpha},\;{\alpha}'-diphenyl-{\beta}-picrylhydrazyl$) and 3,5-dinitrosalicylic acid(DNS) positive substances of browning reaction products increased in proportion to the length of browning reaction time and temperature, whereas folin positive substances decreased by heat-denaturation of ginseng protein at initial reaction time and then increased thereafter.

• Korean Journal of Food Science and Technology
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• v.35 no.1
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• pp.67-71
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• 2003

Alginates were irradiated in an aqueous solution with $Co^{60}$ gamma rays in the dose ranges from 0 to 100 kGy, and investigated the relationship between the intrinsic viscosity $([{\eta}])$ and the molecular weight $(M_w)$ of alginates. The molecular weight of alginate was measured by gel permeation chromatography and the ranges from 1,894 to 135,174 Da were obtained. The molecular weight of alginate decreased markedly with increasing the degree of ${\gamma}-ray$ dose rate. The intrinsic viscosity of alginate solution after ${\gamma}-irradiation$ showed the ranges from 9.83 (g/g) to 602.69 (g/g), depending upon the ${\gamma}-irradiation$ dose. The molecular weight of alginate dependence of the intrinsic viscosity of the alginate solution would be expressed by Mark-Houwink equation. With a linearization of molecular weight and the intrinsic viscosity of the alginate solution, Mark-Houwink equation could be expressed with constant variables and the real data fitted to the equation of $[{\eta}]=2.2{\times}10^{-6}\;{M_w}^{1.656}\;(R^2=0.998)$.

• Korean Journal of Food Science and Technology
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• v.44 no.6
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• pp.699-703
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• 2012

The quality of commercial cider vinegars was compared according to their acidity levels (low, general, double strength and triple strength). The pH, reducing sugar content and brown color intensity decreased, while the total acidity increased with the increasing acidity levels, which may be resulted from difference in formulation and manufacturing procedures. The free sugars were mainly composed of fructose and glucose, which were the highest in low acidity vinegar, followed by double strength, general, and triple strength acidity vinegars. Acetic acids and malic acids were identified as the major organic acids. The citric acid concentration was the highest in triple strength vinegars. The contents of total phenolics and flavonoids were the highest in low acidity vinegars, which indicated their dependence on the apple juice content. DPPH and ABTS radical scavenging abilities were the highest in low acidity vinegars, that showed high amounts of antioxidants.

• Investigative Magnetic Resonance Imaging
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• v.5 no.1
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• pp.33-37
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• 2001

Purpose : The water exchange rate between bulk water and bound water is an important parameter in deciding the efficiency of paramagnetic contrast agents. In this study, we evaluated the water exchange rates of various Gd-chelates using oxygen-17 NMR technique. Material and Methods : The samples (Gd-DTPA, Gd-DTPA-BMA, Gd-DOTA, Gd-EOB-DTPA) were prepared by mixing 5% $^{17}O-enriched$ water (Isotech, USA). The pH of the samples was adjusted to physiological value [pH=7.0] by buffer solution. The variable temperature $^{17}O-NMR$ measurements were performed using Bruker-600 (14.1 T, 81.3 MHz) spectrometer. Bruker VT-1000 temperature control units were used to stabilize the temperature. The $^{17}O$ spin-spin relaxation times (T2) were measured using Carr-Purcell-Meiboom-Gill (CPMG)I pulse sequence with 24 echo trains. The variable temperature T2 relaxation data were then fitted into Solomon-Bloembergen equations using least square fit algorithm to estimate the water exchange times. Results : From the measured $^{17}O-NMR$ relaxation rates, the determined water exchange rates at 300K are $0.42{\;}{\mu}s$ for Gd-DTPA, $1.99{\;}{\mu}s$ for Gd-DTPA-BMA, $0.27{\;}{\mu}s$ for Gd-DOTA, and $0.11{\;}{\mu}s$ for Gd-EOB-DTPA. The Gd-DTPA-BMA showed slowest exchange whereas Gd-EOB-DTPA had fastest water exchange rate. In addition, it was found that the water exchange rates (${\tau}_m$) of all samples had exponential temperature dependence with different decay constant. Conclusion : $^{17}O-NMR$ relaxation rate measurements, when combined with variable temperature technique, provide a solid tool for studying water exchange rate, which is very important in investigating the detailed mechanism of relaxation enhancement effect of the paramagnetic contrast agents.

• Korean Journal of Soil Science and Fertilizer
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• v.22 no.4
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• pp.257-264
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• 1989

In order to study spatial variability of soil chemical properties across the land-partitioned boundary on Hwadong silt clay loam soil (Fine clayey, mixed, mesic family of Aquic Hapludalfs) in the experimental fie ld of the wheat and Barley Research Institute in Suwon, all measured data were analyzed by means of kriging, fractile diagram, smooth frequency distribution, and autocorrelation. Sampling for soil chemical property analysis was made at 225 intersections of 15x 15 grid with 10m interval from three soil depths (0-10cm, 25-35cm, 50-60cm) in the seven patitioned fields. 1. The coefficient of variance (CV) of various chemical properties varied from 5.4 to 72.7%. Soil pH was classified into the low variation group with CV smaller than 10%, while the other chemical properties belonged to the medium variation group with C.V. between 10 and 100% 2. The approximate number of soil samples for the determination of various chemical properties with error smaller than 10% were two for pH, ten for CEC, 15 for exchangeable Ca, 32 for total nitrogen content, 39 for exchangeable Mg, 40 for exchangeable K, 61 for exchangeable Na, 82 for organic matter content, 212 for available phosphate,. 3. Smooth frequency distribution and fractile diagram showed that available phosphate was in log-normal distribution while others were in normal distribution. 4. Serial correlation analysis revaled that the soil chemical properties had spatial dependence between two nearest neighbouring grid points. Autocorrelation analysis of chemcial properties measured between the serial grid points in the direction of south to north following land-partitioned boundary showed that the zone of influence showing stationarity ranged from 20 to 50m. In the direction of east to west accross land-partitioned boundary, the autocorrelogram of many chemical properies showed peaks with the periodic interval of 30m, which were similar to the partitioned land width. This reveals that the land-partitioned boundary causes soil variability.