• Journal of Adhesion and Interface
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• v.7 no.1
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• pp.16-22
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• 2006

In this work, the effect of cure temperature and time on the thermal stability and the exothermic cure reaction peak of a waterborne resol-type phenol-formaldehyde resin, which may be used for preparing phenolic sheet molding compounds (SMC), has been investigated using a thermogravimetric analyzer and a differential scanning calorimeter. The weight loss of waterborne phenol-formaldehyde resin was mainly occurred at three temperature stages: near $200^{\circ}C,\;400^{\circ}C$, and $500^{\circ}C$. The carbon yield at $750^{\circ}C$ for the cured resin was about 62%~65%. Their thermal stability increased with increasing cure temperature and time. Upon cure, the exothermic reaction was taken placed in the range of $120^{\circ}C{\sim}190^{\circ}C$ and the maximum peak was found in between $165^{\circ}C$ and $170^{\circ}C$. The shape and the maximum of the exothermic curves depended on the given cure temperature and time. To remove $H_2O$ and volatile components, the uncured resin needed a heat-treatment at $100^{\circ}C$ for 60 min at least prior to cure or molding. Curing at $130^{\circ}C$ for 120 min made the exothermic peak of waterborne phenol-formaldehyde resin completely disappeared. And, post-curing at $180^{\circ}C$ for 60 min further improved the thermal stability of the cured resin.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.143-147
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• 2012

Photocatalytic properties of $TiO_2$ nanopowders has been received much attention due to their high potentials for environmental applications such as remediation of polluted environments. The $TiO_2$ nanopowders doped with metal or non-metal elements have been synthesized by variety methods such as flame method, chemical vapor synthesis, sol-gel, ion implantation, which affect a doping behavior in different ways resulting in different surface characteristics, leading to different photocatalytic activity. In addition to an effect of synthesis methods, the photocatalytic activity of $TiO_2$ nanopowders can be improved by subsequent heat-treatments. In this study, to obtain a highly efficient photocatalyst, we synthesized $TiO_2$ nanopowders doped with tungsten by the chemical vapor synthesis method (CVS) and determined their physical properties and photocatalytic activity, together with subsequent post-treatment in the range of $300^{\circ}C$ to $700^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.256-263
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• 2010

A Crofer 22 APU mesh coated with a conductive ceramic material was developed as an alternative cathode current collector to Ag-based materials for solid oxide fuel cells. $(La_{0.80}Sr_{0.20})_{0.98}MnO_3$ (LSM) layer was deposited onto the Crofer mesh using a spray-coating technique, in an attempt to mitigate the degradation of electrical properties due to surface oxidation at high temperatures. The oxidation experiments at $800^{\circ}C$ in air indicated that the areaspecific resistance (ASR) of the LSM-coated Crofer mesh was strongly dependent on the wire diameter and the contact morphology between mesh and cell. In addition, the post-heat-treatment in $H_2/N_2$ resulted in a reduced thickness of Cr-containing oxide scales at the interface between Crofer mesh and LSM layer, leading to a decreased ASR.

• Journal of the Korean Chemical Society
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• v.48 no.4
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• pp.371-378
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• 2004

The $SrGa_2S_4:Eu^{2+}$ green emitting phosphor has been studied as a luminous device for CRT (Cathode Ray Tube) or FED (Field Emission Display) and EL (Electroluminescence). This phosphor, also, is under noticed for LED (Lighting Emitting Diode) phosphor, which makes use of excitation characteristics of long wavelength region. The $SrGa_2S_4:Eu^{2+}$ phosphor was prepared generally conventional synthesis method using flux. However, this method needs high heat-treated temperature, long reaction time, complex process and harmful $H_2S$or $CS_2$ gas. In this works, therefore, we have synthesized $SrGa_2S_4:Eu^{2+}$ using SrS, $Ga_2S_3$, and EuS as starting materials, and the mixture gas of 5% H2/95% N2 was used to avoid the $H_2S$or $CS_2$. We investigated the luminescence characteristic of $SrGa_2S_4:Eu^{2+}$ phosphor prepared in various synthesis conditions, performed post-treatment and sieving process for application to LED.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.854-862
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• 2016

As the demand for a clean energy to replace fossil fuel being depleted increases, hydrogen energy is considered as a promising candidate for future energy source. Water electrolysis which produces hydrogen has high energy efficiency and stability but still has a large overpotential for oxygen evolution reaction (OER). In this study, $Co_3O_4$ catalysts with different morphology were prepared by spray pyrolysis from solutions which contain Co precursor and various organic additives (urea, sucrose, and citric acid), followed by post heat treatment. For the catalysts synthesized, X-ray diffraction (XRD) measurements were performed to identify their crystal structure. Morphology and surface shape of the catalysts were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Surface area and pore volume were examined by nitrogen adsortpion & desorption tests and X-ray photoelectron spectroscopy (XPS) was conducted to confirm nitrogen doping. Linear sweep voltammetry (LSV) was carried out to investigate OER activity of $Co_3O_4$ catalysts. As a result, bare-$Co_3O_4$ which has high surface area and small particle size determined by spray pyrolysis showed high activity toward OER.

• Journal of Conservation Science
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• v.38 no.3
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• pp.217-233
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• 2022

The remains found in Geumcheok-ri, Gyeongju are located in close proximity to the Ancient Tombs in Geumcheok-ri, Gyeongju (Historic Site) which were built between the late 5th and early 6th centuries, and these tombs are known to belong to the powerful rulers of that area. Using metallurgical techniques, this study was conducted on the iron objects obtained from the excavated remains in Geumcheok-ri, Gyeongju which are presumed to have a close relation to the nearby ruins that played an important role in the growth of Silla. To identify differences in manufacturing techniques based on the purpose of the iron objects, eight objects were selected after classifying them by use and the microstructure and non-metallic inclusions were investigated. The analyses results confirmed that the manufacturing process involved forging iron with a high or low carbon content to produce a particular shape, and that the carburization process was applied to iron post forging a shape to increase its strength when necessary. The mechanical properties were improved by selectively applying the steelmaking method and the heat treatment technique considering the functions of the parts, and the low temperature reduction was applied to the smelting process. Furthermore, in comparison with the iron objects excavated from the remains located in the center of Gyeongju and its outskirts, it is confirmed that there is similarity in the smelting and manufacturing techniques between these objects.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.12
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• pp.1681-1690
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• 2000

A study on energy and protein utilization, and milk production of Bali cows on grass-legume diets was carried out using 12 first lactation cows (initial BW $263.79{\pm}21.66kg$) during a period of 16 weeks starting immediately post calving. The animals were randomly allotted into 4 dietary treatment groups R1, R2, R3 and R4, receiving from the last 2 months of pregnancy onwards, graded improved rations based on a mixture of locally available grass and legume feed ad libitum. R1 contained on a DM basis 70% elephant grass (PP, Penisetum purpureum) plus 30% Gliricidia sepia leaves (GS), R2 was 30% PP plus 55% GS supplemented with 15% Hibiscus tilliactus leaves (HT, defaunating effect), R3 and R4 were 22.5% PP+41.25% GS+11.25% HT+25% concentrate, where R3 was not and R4 supplemented with zinc di-acetate. TDN, CP and zinc contents of the diets were 58.2%, 12.05% and 18.3 mg/kg respectively for R1, 65.05%, 16.9% and 25.6 mg/kg respectively for R2, 66.03%, 16.71% and 29.02 mg/kg respectively for R3 and 66.03%, 16.71% and 60.47 mg/kg respectively for R4. Milk production and body weight were monitored throughout the experimental period. In vivo body composition by the urea space technique validated by the body density method and supported by carcass data was estimated at the start and termination of the experiment. Nutrient balance and rumen performance characteristics were measured during a balance trial of 7 days during the 3rd and 4th week of the lactation period. Results indicated that quality of ration caused improvement of ruminal total VFA concentration, increments being 52 to 65% for R2, R3 and R4 above R1, with increments of acetate being less (31 to 48%) and propionate being proportionally more in comparison to total VFA increments. Similarly, ammonia concentrations increased to 5.24 to 7.07 mM, equivalent to 7.34 to 9.90 mg $NH_3-N/100ml$ rumen fluid. Results also indicated that feed quality did not affect DE and ME intakes, and heat production (HP), but increased GE, UE, energy in milk and total retained energy (RE total) in body tissues and milk. Intake-, digestible- and catabolized-protein, and retained-protein in body tissues and milk (Rprot) were all elevated increasing the quality of ration. Similar results were obtained for milk yield and components with mean values reaching 2.085 kg/d (R4) versus 0.92 kg/d (R1) for milk yield, and 170.22 g/d (R4) vs 71.69 g/d (R1), 105.74 g/d (R4) vs 45.35 g/d (R1), 101.34 g/d (R4) vs 46.36 g/d (R1) for milk-fat, -protein, and -lactose, respectively. Relatively high yields of milk production was maintained longer for R4 as compared to the other treatment groups. There were no significant effects on body mass and components due to lactation. From the relationship $RE_{total}$ (MJ/d)=12.79-0.373 ME (MJ/d); (r=0.73), it was found that $ME_{m}=0.53MJ/kgW^{0.75}.d$. Requirement of energy to support the production of milk, ranging from 0.5 to 3.0 kg/d, follows the equation: Milk Prod. ($Q_{mp}$, kg/d)=[-2.48+4.31 ME($MJ/kg^{0.75}.d$)]; (r=0.6) or $Q_{mp}$=-3.4+[0.08($ME-RE_{body\;tissue}$)]MJ/d]; (r=0.94). The requirement for protein intake for maintenance ($IP_m$) equals $6.19 g/kg^{0.75}.d$ derived from the relationship RP=-47.4+0.12 IP; (r=0.74, n=9). Equation for protein requirement for lactation is $Q_{nl}$=[($Q_{mp}$)(% protein in milk)($I_{mp}$)]/100, where $Q_{nl}$ is g protein required for lactation, $Q_{mp}$ is daily milk yield, Bali cow's milk-protein content av. 5.04%, and $I_{mp}$ is metabolic increment for milk production ($ME_{lakt}/ME_{m}=1.46$).