• Korean Journal of Food Science and Technology
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• v.41 no.1
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• pp.7-10
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• 2009

An analytical method for the determination of flumequine in meats was developed and validated using high-performance liquid chromatography with fluorescence detection. The samples were mixed with sodium sulfate and extracted with ethyl acetate. After clean-up, the residues were dissolved in mobile phase. The calibration curves showed high linearity ($r^2$=0.9979) within the concentration range of 0.1-1.0 mg/kg. The limit of detection and limit of quantification were validated at 0.005 and 0.017 mg/kg, respectively. The recoveries in fortified meats ranged from 90.8 to 101.1%. The method was then validated in correspondence with the CODEX guidelines for flumequine residue in meats. Herein we monitored 150 samples of meats that were purchased in Korea (Seoul, Busan, Daegu, Daejeon, and Gwangju). Among the tested samples, flumequine was detected in 1 of beef and 1 of pork at levels in the range of 0.048-0.080 mg/kg. Overall, the flumequine residues in the tested samples were within the Maximun residue limit.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.3
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• pp.317-349
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• 1993

This study investigated the effect of filler particle size and weight% on mechanical properties of dental core porcelain. In alumina, variation in particle size and weight% and in zirconia, variation in weight%, all specimens were tested three-point bending strength, transmittance, thermal expansion coefficient, porosity and shrinkage and observed with SEM and analysed with X-ray diffractometer. In order to develop shrink-free porcelain, after firing alumina only, glass wasinfiltrated. And aluminum was added to alumina with the expanding character of aluminum oxidize into alumina, and was followed by second firing of glass infiltration procedure. Then mechanical properties were observed. The results of this study were obtained as follows. 1. The bending strength of zirconia was higher than that of alumina, and $5{\mu}m$ alumina had highest strength in variation of particle size of alumina. Except for $5{\mu}m$ alumina, increased with weight%, bending strength increased up to 80% and decreased at 90%. In case of glass infiltration, bending strength was slight higher than 80% and 90% of $5{\mu}m$ alumina. 2. Transmittance increased with increase of shrinkage, decrease of porosity, and with increase of filler size and had no direct correlation with weight%. 3. Thermal expansion coefficient of alumina group was $7.42\sim8.64\times10^{-6}/^{\circ}C$ and that of zirconia group was $9.83\sim12.11\times10^{-6}/^{\circ}C$ and the latter was higher than the former. 4. In x-ray diffraction analysis, alumina group and zirconia group increased $Al_2O_3$ peak and $t-ZrO_2$ peak with increase of weight%. The second phase(cristobalite peak) was observed in zirconia 40% group. 5. Porosity of zirconia was lower than that of alumina and $5{\mu}m$ alumina group had many pores with SEM. In case of low filler content, fracture occurred in glass and high filler content, in glass and filler. In case of aluminum addition to alumina, small oxidised aluminum was observed. 6. Zirconia group had high shrinkage than alumina group, and mixed group of alumina group had high shrinkage. In case of glass infiltration, shrinkage decreased and aluminum addition to alumina group was almost shrink-free.

• Analytical Science and Technology
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• v.16 no.1
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• pp.70-77
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• 2003

The optimum conditions for the residue analysis of hydroxyanilide fungicide fenhexamid on cucumber, strawberry and grape were investigated by gas chromatography equipped with electron capture detector (GC-ECD) and the residual amount was determined by sprayed days before harvest. Each samples were extracted with acetone, filtered and concentrated to 50 mL. The concentrated extracts were transferred to dichloromethane and then thoroughly concentrated. The concentrated phase was loaded on the filtration column stuffed with silica gel and purified with acetone:hexane (5:95, 15:85, v/v) mixed solvent. The regression equation and linearity of the standard calibration curves between 0.05~2.00 ng were as follows : cucumber; Y=312.40X+10.26, $R^2=0.9996$, strawberry; Y=313.33X+5.54, $R^2=0.9998$, grape; Y=253.27X-2.23, $R^2=0.9994$. From the standard additional experiments with 0.10 mg/L and 0.40 mg/L, the average recoveries of cucumber, strawberry and grape were 94.8%, 88.1% and 93.7%, respectively and the detection limits were all the same as 0.01 mg/L. Residual amounts in crops were ranged from 0.01 to 0.58 mg/L.

• Resources Recycling
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• v.14 no.5 s.67
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• pp.13-17
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• 2005

As a basic study for recycling molten converter slag as an ordinary portland cement (OPC) by a conversion process, the reaction mechanism and the rate of the formation of $C_4AF$ which is one of the main components of OPC were investigated. The converter slag whose basicity was controlled by adding reagent grade $SiO_2$ was melted and hold for 30 minutes in MgO crucible at $1300^{\circ}C{\sim}1350^{\circ}C$. Then, the sintered CaO pellet heated at the same temperature was dipped into the molten slag and hold for $10{\sim}30$minutes. After the reaction, the crucible was cooled in air and the specimen was cut off to the horizontal direction of the crucible. The dissolution rate of $C_3A$ pellet was measured by the change of radius of the sintered $C_3A$ pellet, and the formed phase of $C_4AF$ was observed by SEM/EDX. As a result, the dissolution rate of $C_3A$ pellet into molten slag was increased from $0.75{\times}10^{-4}(cm/sec)$ at $1300^{\circ}C$ to $1.67{\times}10^{-4}(cm/sec)$ at $1350^{\circ}C$, and the mixed layer of $C_4AF$ and $C_{12}A_7$ was found between slag and $C_3A$ pellet.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2006.05a
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• pp.90-94
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• 2006

The waste solution discharged from the LCD manufacturing process contains acids like nitric, acetic and phosphoric acid and metal ions such as Al, Mo and other impurities. It is important to removal of impurities to tess than 1ppm in phosphoric acid to reuse as an etchant because the residual impurities even in sub-ppm concentration in semiconductor materials play a major role on the electronic properties. In this study, we have been clearly established that a mixed system of solvent extraction, diffusion dialysis and ion-exchange technique, which made individually the most of characteristics is developed to commercialize in an efficient system for recovering the high-purity phosphoric acid. By applying vacuum evaporation, the yield of the process are almost 99% removal of nitric acid and acetic acid was achieved. And by applying the solvent extraction method with tri-octyl phosphate(TOP) as an extractant, the removal of acetic and nitric acid from the acid mixture was achieved effectively at the ratio O/A=1/3 with four stages and the stripping of nitric acid from organic phase is attained at a ration of O/A=1 with six stages by distilled water. About 97% and 76% removal of Al and Mo were achieved by diffusion dialysis. Essentially complete less than 1ppm removal of Al, Mo by using ion exchange ion resin and purification of the phosphoric acid was obtain.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.1783-1788
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• 2009

We newly propose that we may reuse scrap powders ($Z_rO_2$+8 mol%-$Y_2O_3$) as $Y_2O_3$-stabilized zirconia (YSZ) sintered products through sintering process at 1550$^{circ}C$ for 2hrs. We also prepared the reference specimen from fresh $Z_rO_2$+30 mol%-$Y_2O_3$ powder mixture (celluar type with 1㎛-length). The reference sample showed a dense microstructure with grains of $\sim$10㎛ in diameter, while the sintered sample from scrap powder showed irregular grains of 1$\sim$30 ㎛ in diameter. Through XRD analysis, we confirmed that the reference sample has mixed phases of $Y_2O_3$(cubic), $Z_{r0.8}O_{1.9}$(cubic), and $Z_rO_2$(monoclinic), while the sintered YSZ sample from scrap powder has only tetragonal phase. Moreover, the sintered YSZ from scrap powder showed vickers hardness and apparent density more than 70 and 4.11 g/cc, which implies that it can be suitable for structural material application.

• Polymer(Korea)
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• v.37 no.6
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• pp.744-752
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• 2013

The miscibility between poly(L-lactide) (PLLA) and poly(methyl methacrylate) (PMMA) was investigated using thermal analyses for the purpose of developing birefringence-free material at oriented state. The effect of methyl acrylate (MA) units as comonomer of PMMA on the miscibility was also studied. All the blends prepared in this study show composition-dependent single $T_g$'s between those of blend components and high transparency over the visible region, indicating the miscibility at molecular level and no discernible effect of MA units on it. No phase separation was observed at elevated temperature of $280^{\circ}C$, higher than the degradation of PLLA and PMMA. The interaction energy density in PLLA/PMMA blends with 17 mol% of MA was measured to be $-0.74J/cm^3$ from the equilibrium melting temperature depression based on the Hoffman-Weeks method. The blends show zero-${\Delta}$n behavior at a specific mixing ratio and the drawing ratio of 3 due to compensation of intrinsic orientation birefringence. Birefringence dispersion of PLLA/PMMA5 blends was also measured to examine the possibility for quarter-wave plates or polarizer protective films.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3367-3378
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• 2021

The design phase and safety assessment of Generation IV liquid metal-cooled fast reactors calls for the improvement of fuel pin performance codes, in particular the enhancement of their predictive capabilities towards uranium-plutonium mixed oxide fuels and stainless-steel cladding under irradiation in fast reactor environments. To this end, the current capabilities of fuel performance codes must be critically assessed against experimental data from available irradiation experiments. This work is devoted to the assessment of three European fuel performance codes, namely GERMINAL, MACROS and TRANSURANUS, against the irradiation of two fuel pins selected from the SUPERFACT-1 experimental campaign. The pins are characterized by a low enrichment (~ 2 wt.%) of minor actinides (neptunium and americium) in the fuel, and by plutonium content and cladding material in line with design choices envisaged for liquid metal-cooled Generation IV reactor fuels. The predictions of the codes are compared to several experimental measurements, allowing the identification of the current code capabilities in predicting fuel restructuring, cladding deformation, redistribution of actinides and volatile fission products. The integral assessment against experimental data is complemented by a code-to-code benchmark focused on the evolution of quantities of engineering interest over time. The benchmark analysis points out the differences in the code predictions of fuel central temperature, fuel-cladding gap width, cladding outer radius, pin internal pressure and fission gas release and suggests potential modelling development paths towards an improved description of the fuel pin behaviour in fast reactor irradiation conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.442-448
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• 2021

In this work, the (K_1-xAg_x)(Ta_0.8Nb_0.2)O₃ (x=0.1-0.4) ceramics were fabricated using mixed-oxide method, and their structural and electrical properties were measured. All specimens represented a pseudo cubic structure with the lattice constant of 0.3989 nm. When 0.4 mol of Ag was added, second phases induced from metallic Ag and K₂(Ta,Nb)₆O₁₆ phase were observed. Dielectric constant and dielectric loss of K(Ta_0.8Nb_0.2)O₃ specimen doped with 0.3 mol of Ag were 2,737 and 0.446, respectively. The curie temperature was about -5℃, which does not change with Ag addition. The remanent polarization began to decrease sharply around 12~15℃, and the temperature at which the remanent polarization began to decrease as the applied voltage increased shifted to the high temperature side. The electrocaloric effect (ΔT) and electrocaloric efficiency (ΔT/ΔE) of the (K_0.7Ag_0.3)(Ta_0.8Nb_0.2)O₃ ceramics were 0.01024℃ and 0.01825 KmV^-1, respectively.

• Animal Bioscience
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• v.34 no.6
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• pp.1029-1037
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• 2021

Objective: This study was conducted to investigate effects of antifungal substance and carboxylesterase-producing inoculant on fermentation indices and rumen degradation kinetics of whole crop rice (WCR) silage ensiled at different dry matter (DM) contents. Methods: Dual-purpose inoculants, Lactobacillus brevis 5M2 and Lactobacillus buchneri 6M1, confirmed both activities of antifungal and carboxylesterase in the previous study. The WCR at mature stage was chopped, and then wilted to obtain three different DM contents consisting of 35.4%, 43.6%, and 51.5%. All WCR forages were applied distilled water (CON) or mixed inoculants with 1:1 ratio at 1×105 colony forming unit/g (INO), and ensiled into 20 L mini silo (5 kg) in quadruplicates for 108 d. Results: The INO silages had lower lactate (p<0.001) and butyrate (p = 0.022) with higher acetate (p<0.001) and propionate (p<0.001) than those of CON silages. Ammonia-N (p<0.001), lactate (tendency; p = 0.068), acetate (p = 0.030), and butyrate (p<0.001) concentrations of INO silages decreased linearly with increasing DM content of WCR forage. The INO silages presented higher lactic acid bacteria (p<0.001) with lower molds (p<0.001) than those of CON silages. Yeasts (p = 0.042) and molds (p = 0.046) of WCR silages decreased linearly with increasing DM content of WCR forage. In the rumen, INO silages had higher the total degradable fraction (p<0.001), total volatile fatty acid (tendency; p = 0.097), and acetate (p = 0.007), but lower the fractional degradation rate (p = 0.011) and propionate (p<0.001) than those of CON silage. The total degradable fraction (p<0.001), total volatile fatty acid (p = 0.001), iso-butyrate (p = 0.036), and valerate (p = 0.008) decreased linearly with increasing DM content of WCR forage, while the lag phase (p<0.001) was increased linearly. Conclusion: This study concluded that application of dual-purpose inoculants on WCR silage confirmed antifungal and carboxylesterase activities by inhibiting mold and improving rumen digestibility, while increase of wilting times decreased organic acids production and rumen digestibility.