• Asian-Australasian Journal of Animal Sciences
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• v.18 no.3
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• pp.350-353
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• 2005

Effects of sucrose supplement on the pattern of VFA production and microbial protein synthesis in the rumen were examined in sheep consuming basal diet of grass silage (2.5 kg fresh wt/d) that was provided in 24 equal meals each day by an automatic feeder. Four mature wethers were allocated to four experimental treatments in a 4${\times}$4 Latin square design with periods lasting 14 days. The treatments were (1) the basal diet, (2) supplemented with 150 g sucrose and 7.0 g urea, (3) 300 g sucrose and 13 g urea, and (4) 450 g sucrose and 20 g urea given as a continuous intraruminal infusion for 24 h. All infusions were given in 2 litres of aqueous solution per day using a peristaltic pump. The effect of sucrose level on rumen mean pH was significantly linear (p<0.01). There were not significant differences in the concentration of ammonia-N, total VFA and the molar proportions of acetate, propionate and butyrate with the level of sucrose infusion. The molar proportions of isobutyric acid (p<0.05) and isovaleric acid (p<0.001) were significantly reduced when the infused amount of sucrose was increased. The flow of microbial N was linearly (p<0.001) increased with sucrose and urea level. High levels of readily fermentable carbohydrate in a ration reduced the efficiency of microbial protein synthesis in the rumen. It was demonstrated that of the individual fatty acids, only the molar proportion of isovalerate showed a significant negative correlation (R2=$0.3501^{**}$) with the amount of microbial N produced and a significant positive correlation (R2=$0.2735^{**}$) with the efficiency of microbial growth.

• Journal of the Korean Ceramic Society
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• v.42 no.9 s.280
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• pp.618-623
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• 2005

HTGR (High Temperature Gas-Cooled Reactor) is highlighted to next generation power plant for producing the clean hydrogen gas. In this study, the spherical $UO_2$ kernel via $UO_3$ gel particles was prepared by the sol-gel process. Raw material of slightly Acid Deficient Uranyl Nitrate (ADUN) solution, which has pH = 1.10 and $[NO_3]/[U]$ mole ratio = 1.93, was obtained from dissolution of $U_3O_8$ powder with conc.-$HNO_3$. The surface of these spherical $UO_3$ gel particles, which was prepared from the broth solution, consisted of 1 M-uranium, 1 M-HMTA, and urea, were covered with the fine crystallite aggregates, and these particles were so hard that crushed well. But the other $UO_3$ gel particles prepared with the broth solution, consisted of 2 M-uranium, 2 M-HMTA, and urea, have soft surface characteristics and an amorphous phase. This type of $UO_3$ gel particles is some chance of doing possibility of high density from the compaction. The amorphous $UO_3$ gel particles was converted to $U_3O_8$ and then $UO_2$ by calcination at $600^{\circ}C\;in\;4\%\;-\;H_2\;+\;N2$ atmosphere.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.630-638
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• 2009

A computational fluid dynamics(CFD) model is developed and validated with on-site experiments for a urea-based SNCR(selective non-catalytic reduction) process to reduce the nitrogen oxides($NO_x$) in a municipal incinerator. The three-dimensional turbulent reacting flow CFD model having a seven global reaction mechanism under the condition of low CO concentration and 12% excess air and droplet evaporation is used for fluid dynamics simulation of the SNCR process installed in the incinerator. In this SNCR process, urea solution and atomizing air were injected into the secondary combustor, using one front nozzle and two side nozzles. The exit temperature($980^{\circ}C$) of simulation has the same value as in situ experiment one. The $NO_x$ reduction efficiencies of 57% and 59% are obtained from the experiment and CFD simulation, respectively at NSR=1.8(normalized stoichiometric ratio) for the equal flow rate ratio from the three nozzles. It is observed in the CFD simulations with varying the flowrate ratio of the three nozzles that the injection of a two times larger front nozzle flowrate than the side nozzle flowrate produces 8% higher $NO_x$ reduction efficiency than the injection of the equal ratio flowrate in each nozzle.

• Clean Technology
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• v.24 no.3
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• pp.212-220
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• 2018

Oxy-fuel combustion is considered as a promising greenhouse gas reduction technology in power plant. In this study, the behaviors of NO and $SO_2$ were investigated under the condition that in-furnace $deNO_x$ and $deSO_x$ methods are applied in oxy-fuel circulating fluidized bed combustion condition. In addition, the generation trends of $SO_3$, $NH_3$ and $N_2O$ were observed. For the purpose, limestone and urea solution were directly injected into the circulating fluidized bed combustor. The in-furnace $deSO_x$ method using limestone could reduce the $SO_2$ concentration in exhaust gas from ~403 to ~41 ppm. At the same experimental condition, the $SO_3$ concentration in exhaust gas was also reduced from ~3.9 to ~1.4 ppm. This trend is mainly due to the reduction of $SO_2$. The $SO_2$ is the main source of the formation of $SO_3$. The negative effect of $CaCO_3$ in limestone, however, was also appeared that it promotes the NO generation. The NO concentration in exhaust gas reduced to ~26 - 34 ppm by appling selective non-catalytic reduction method using urea solution. The $NH_3$ concentration in exhaust gas was appeared up to ~1.8 ppm during injection of urea solution. At the same time, the $N_2O$ generation also increased with increase of urea solution injection. It seems that the HNCO generated from pyrolysis of urea converted into $N_2O$ in combustion atmosphere. From the results in this study, the generation of other pollutants should be checked as the in-furnace $deNO_x$ and $deSO_x$ methods are applied.

• YAKHAK HOEJI
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• v.28 no.6
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• pp.299-303
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• 1984

In order to eluciate the effect of humidity and organic solvent on the decomposition of carbamide peroxide, the kinetic study was carried out. The carbamide peroxide was prepared from urea and 30%-hydrogen peroxide. The accelerated stability analysis for carbamide peroxide crystal in various relative humidity, and for 10%-carbamide peroxide solution of organic solvents were investigated. Both humidity and temperature were important factors influencing the decomposition rate of carbamide peroxide crystal. The higher the humidity and temperature, the greater was the reaction rate. The breakdown rate of crystal was observed as an apparent zero-order, and was faster than the rate of decomposition in dilute propylene glycol, glycerine or sorbitol solutioos which were measured as an apparent first-order reaction. The more dilute to 10% the organic solvents of 10%-carbamide peroxide, the slower was breakdown rate. It is, therefore, useful in the aspects of stability and economics to substitute solvent of carbamide peroxide topical solution (USP XXI) with 10%-propylene glycol or glycerine instead of anhydrous glycerine.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.169-172
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• 2003

Manufacturing process for autonomic microcapsules was introduced and autonomic microcapsules were manufactured by varying with various manufacturing process variables. Urea-formaldehyde resin was used for the wall of microcapsules and DCPD (dicyclopentadiene) was used for the self-healing agent. The characteristics of these microcapsules was evaluated through a particle size analyaer, an optical microscope, and a TGA. The various manufacturing process variables, such as pH and agitation speed of the emulsified solution, were considered to focus in this study. According to the results, the particle size distributions were affected on the agitation speed of the emulsified solution, and the thermal stability was influenced by pH of the emulsified solution.

• Journal of Powder Materials
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• v.19 no.3
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• pp.220-225
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• 2012

YAG:Ce yellow phosphor particles were synthesized by spray pyrolysis with changing the solution properties and their luminous properties, crystal structure, and morphological changes were studied by using PL measurement, XRD, and SEM analysis. It was clear that the solution properties significantly affected the crystal phase, crystallite size, the PL intensity, and the morphology of YAG:Ce particles. At low calcination temperature, the addition of urea only to the spray solution was helpful to form a pure YAG phase without any impurity phases, as the result, the highest luminescence intensity was achieved at the calcination temperature of $900^{\circ}C$. When the calcination temperatures were larger than $1300^{\circ}C$, however, the YAG particles prepared without any additive showed the highest luminescent intensity. Regardless of the solution conditions, the emission intensity of YAG:Ce particles prepared by spray pyrolysis showed a linear relation with the crystallite size. In terms of the morphology of YAG:Ce particles, the addition of both DCCA and $NH_4OH$ to the spray solution was effective to prepare a spherical and dense structured YAG particles.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.3
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• pp.212-219
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• 2000

This study was conducted to investigate methane emission among nitrogen fertilizers in paddy soil(Jeonbug series, occurring on fluvio-alluvial plain). The application rates of rice straw was $5,000kg\;ha^{-1}$ with $110kg\;N\;ha^{-1}$ as chemical fertilizer. It was found that the methane flux tended to be lower in ammonium sulfate than in urea and latex coated urea(LCU). The seasonal variations of the methane emission flux was high during the heading stage of the rice plant. Methane concentration in the soil solution was the highest at 5cm depth, but decreased with upper and lower depth. Methane emission under rice straw application was $0.265g\;m^{-2}\;day^{-1}$ by urea application. $0.207g\;m^{-2}\;day^{-1}$ by ammonium sulfate application, $0.318g\;m^{-2}\;day^{-1}$ by latex coated urea(LCU) application while methane emission under non rice straw application was $0.192g\;m^{-2}\;day^{-1}$ by urea application, $0.165g\;m^{-2}\;day^{-1}$ by ammonium sulfate application, $0.179g\;m^{-2}\;day^{-1}$ by latex coated urea(LCU) application.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.597-608
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• 1994

A new process for the production of high purity ${\alpha}-Al_2O_3$ from ammonium aluminium sulfate solution abtained through the sulfation of low grade bauxite ore with $(NH_4)_2SO_4$, and leaching of the sulfated product was investigated. This process is consisted of solvent extraction for Fe component removal from ammonium aluminum sulfate solution and homogeneous precipitation of Al containing precipitate from the refined ammonium aluminium sulfate solution by using urea as precipitator. The optimum conditions of solvent extraction with Alamine 336 as extractant were shaking time of 4min, organic phase ratio to aqueous phase of 0.25. The types of precipitation products from this precipitation were amorphous alumina gel, pseudo-boehmite and crystalline boehmite in the lower temperature of $100^{\circ}C$, in the range from $125^{\circ}C$ to $150^{\circ}C$, and above $150^{\circ}C$, respectively. And also amorphous alumina gel hydrate in $1000^{\circ}C$ and crystalline boehmite in $1250^{\circ}C$ were tranfered to ${\alpha}-Al_2O_3$, respectively. This alumina was identified as ${\alpha}-Al_2O_3$ of purity 99.7%.

• Korean Journal of Soil Science and Fertilizer
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• v.7 no.4
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• pp.201-207
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• 1974

Some effects of nitrogen, phosphorus, potassium and respiratory inhibitor on growth of rice plant and activity of GOT, GPT and peroxidase for the rice root were investigated. Obtained results were summarized as follows: 1. Growth of rice root and plant applied with $NO_3$-N in culture solution was generally increased in the length and weight compared with that of $NH_4$-N plot. On the other hand, the GOT, GPT and peroxidase activity was more increased in the $NH_4$-N plot than in the $NO_3$-N plot. 2. Oxidative power of ${\alpha}$-naphthylamine in rice root was stronger in the $NO_3$-N plot than in the $NH_4$-N plot. 3. When rice plant was cultured in the medium which did not supplied nitrogen, phosphorus or potassium, respectively, GOT activity was more decreased than GPT activity, while peroxidase activity was increased mostly in the potassium-free plot. 4. When rice plant was cultivated in the culture solution added respiratory inhibitor, NaF, plant height was shortened in the order of nitrogen-free > $NH_4$-H > urea-N > $NO_3$-N plot, and GOT and GPT activity was also decreased in the order of nitrogen-free > $NH_4$-N > urea-N > $NO_3$-N plot.