• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.1-6
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• 1996

A single phase Ba2(Ti8,472Zr0.528)O20 was prepared by the oxalate method from aqueous solution of BaCl2 TiCl4 and ZrOCl2. The structure ananlysis has been carried out by Rietveld analysis method at room temperature. Powder X-ray data of Ba2(Ti8,472Zr0.528)O20 was indexed with the triclinic lattice(a=7.4587 $\AA$ b=14.0672 $\AA$, c=13.3327 $\AA$, $\alpha$=89.87, $\beta$=79.45 ${\gamma}$=84.46) The R (Residual) values of structure refinement were in a range between 10.00 and 8.00 This analysis proved that the added Zr occupied Ti sites in th structure of Ba2Ti9O20. Ba2(Ti8,472Zr0.528)O20 has excellent dielectric properties(dielectric constant K=40.49 at 5.42 GHz Q=4621) so that it can be used as good microwave dielectric materials.

• Transactions of Materials Processing
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• v.31 no.5
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• pp.253-260
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• 2022

In this study, the microstructural characteristics of a high-speed-extruded Mg-5Bi-3Al (BA53) alloy and its tensile, compressive, and high-cycle fatigue properties are investigated. The BA53 alloy is successfully extruded at a die-exit speed of 16.6 m/min without any hot cracking using a large-scale extruder for mass production. The homogenized BA53 billet has a large grain size of ~900 ㎛ and it contains fine and coarse Mg₃Bi₂ particles. The extruded BA53 alloy has a fully recrystallized microstructure with an average grain size of 33.8 ㎛ owing to the occurrence of complete dynamic recrystallization during high-speed extrusion. In addition, the extruded BA53 alloy contains numerous fine lath-type Mg₃Bi₂ particles, which are formed through static precipitation during air cooling after exiting the extrusion die. The extruded BA53 alloy has a high tensile yield strength of 175.1 MPa and ultimate tensile strength of 244.4 MPa, which are mainly attributed to the relative fine grain size and numerous fine particles. The compressive yield strength (93.4 MPa) of the extruded BA53 alloy is lower than its tensile yield strength, resulting in a tension-compression yield asymmetry of 0.53. High-cycle fatigue test results reveal that the extruded BA53 alloy has a fatigue strength of 110 MPa and fatigue cracks initiate at the surface of fatigue test specimens, indicating that the Mg₃Bi₂ particles do not act as fatigue crack initiation sites. Furthermore, the extruded BA53 alloy exhibits a higher fatigue ratio of 0.45 than other commercial extruded Mg-Al-Zn-based alloys.

• Korean Journal of Materials Research
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• v.4 no.8
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• pp.870-876
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• 1994

In order to investigate the growth behavior of $Y_{2}Ba_{1}Cu_{1}O_{5}$(211) particles in $Y_{1}Ba_{2}Cu_{3}O_{7-\delta}$(123), 123 samples were quenched in air after heat treatment on polycrystal and single crystal MgO substrates at $1100^{\circ}C$ for various periods. 211 grains grew with the increase in holding time. The growth of 211 grains was faster on the polycrystal MgO substrate than on the single crystal MgO substrate. In the samples with the compositions of 211+xCuO($0.2\le X \le 0.8$), the growth rate of 211 grains increased with the increase in CuO content. In the sample with x=0.6 the largest 211 grains were observed. 211 grains in the $Y_{2}Ba_{1}Cu_{1.8}Sn_{0.1}O_{5+\delta}$ samples were distributed very finely and homogeneously. The retarding effect of $SnO_2$ addition on the growth of 211 grain appeared more pronounced in a CuO melt than in a $BaCuO_{2}$+ CuO melt.

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.807-813
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• 2014

The Ag-impregnated activated carbon was produced from bamboo activated carbon by soaking method of silver nitrate solution. The carbonization and activation of raw material was conducted at $900^{\circ}C$. Soaking conditions are the variation of silver nitrate solution concentration (0.002~0.1 mol/L) and soaking time (maximum 24 h). The specific surface area and pore size distribution of the prepared activated carbons were measured. Also, NO and activated carbon reaction were conducted in a thermogravimetric analyzer in order to use for de-NOx agents of used activated carbon. Carbon-NO reactions were carried out with respect to reaction temperature ($20{\sim}850^{\circ}C$) and NO gas partial pressure (0.1~1.8 kPa). As results, Ag amounts are saturated within 2h, Ag amounts increased 1.95 mg Ag/g (0.2%)~ 88.70 mg Ag/g (8.87%) with the concentration of silver nitrate solution in the range of 0.002~0.1 mol/L. The specific volume and surface area of bamboo activated carbon of impregnated with 0.2% silver were maximum, but decreased with increasing Ag amounts of activated carbon due to pore blocking. In NO reaction, the reaction rate of impregnated bamboo activated carbon was retarded as compare with that of bamboo activated carbon. Measured reaction orders of NO concentration and activation energy were 0.63[BA], 0.69l[BA(Ag)] and 80.5 kJ/mol[BA], 66.4 kJ/mol[BA(Ag)], respectively.

• Fire Science and Engineering
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• v.33 no.3
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• pp.9-20
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• 2019

This study was examined fire risk properties of wood specimen for the constructional interiors, especially focusing on the fire performance index (FPI) and the fire growth index (FGI) as heat hazard characteristics. Flame retardants were synthesized using boric acid, boronic acid and tetraethoxyorthosilicate. Heat release characteristics were measured by using a cone calorimeter (ISO 5660-1) and cypress was used. The external heat flux as fire intensity was maintained at 50 kW/㎡. The measured fire performance index (FPI) after burning was increased by 1.6 times for boric acid/silicone (BA/Si) sol, each 1.1 times for isobutylboronic acid/silicone (IBBA/Si) sol and phenylboronic acid/silicone (PBA/Si) sol compared with cypress. Fire risk by the fire performance index was increased BA/Si, IBBA/Si ≈ PBA/Si order. The fire growth index was decreased 94% for the BA/Si and 8% for the IBBA/Si sol, and was increased by 17% for the PBA/Si sol. Fire risk by the fire growth index was increased BA/Si, IBBA/Si, PBA/Si order. Overall fire risk was higher in the order of BA/Si < IBBA/Si < PBA/Si.

• Korean Journal of Food Science and Technology
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• v.45 no.6
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• pp.727-734
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• 2013

Makgeolli mashes that were brewed using five different commercial nuruks (fermentation starters) were investigated for changes in physicochemistry, microbial diversity, and biogenic amine (BA) production. Mash A brewed with the nuruk (Gaeryang-nuruk) had the highest level of alcohol concentration and the greatest number of yeast cells, whereas mash E had the greatest number of bacterial cells. Only three biogenic amines were detected in the makgeolli mashes: tyramine, putrescine, and cadaverine. Using a PCR-DGGE technique, we observed that mash E had the highest BA production, and had the greatest number of bands on the denaturing gradient gels. We also observed that the numbers of bacterial cells correlated significantly with the putrescine and the total BA content, and that the BA content correlated significantly with the color values (L, a, b). This study shows that the quality of a makgeolli can depend on the type of nuruk. Therefore, we suggest that the quality management of makgeolli should start with the stage of nuruk manufacture.

• Applied Biological Chemistry
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• v.29 no.1
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• pp.73-77
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• 1986

Aqueous solutions of 2,4-D, BA or $GA_3(10^{-6},\;10^{-5},\;and\;10^{-4}M,\;respectively)$ were sprayed onto soybean (Glycine max) plants in the flowering stage, and proteins of immature (33days after flowering) and mature (77days after flowering) seeds were analyzed by electrophoresis to elucidate the effects of the growth reguators on protein synthesis or protein accumulation in the seeds. Accumulations of some proteins were altered by 2,4-D or BA at certain concentrations, but no proteins were affected by $GA_3$. The ${\alpha}\;and\;{\alpha}'$ subunits of 7S and acidic subunit of 11S disappeared in mature seeds after treatments at the flowering stage with 2,4-D or BA. The presence of ${\alpha}\;and\;{\alpha}'$ subunits of 7S and acidic subunit of 11S in immature seeds indicated that the absence of the above polypeptides in mature seeds did not result from inhibitions in syntheses of the polypeptides by the growth regulators. Disappearance of the above proteins in mature seeds seemed to be concerned with the action of specific proteolytic enzyme (s) (metalloendopeptidase?), and 2,4-D and BA might promote gene expression or activation of the enzyme.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.804-809
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• 2011

Tubular $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-${\delta}$}$ membranes were prepared by extrusion. TGA results of green body membrane after extrusion showed three successive weight losses due to decomposition of organic additives and carbonate. Drying shrinkage rate of tubular $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-${\delta}$}$ membranes was no change after 68 h and higher in the membrane with large outer diameter. XRD and SEM results showed the sintered membranes were the single phase structure and dense. The stoichiometric molar ratio agreed well with composition ratio calculated by EDS results for $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-${\delta}$}$ membrane. Radial crushing strength of tubular $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-${\delta}$}$ membrane with 0.95 mm thickness was 5.7 kgf/$mm^2$ and the oxygen permeation rate of same membrane was 146.85 mL/min ($Jo_2$=2.33 mL/$min{\cdot}cm^2$) at $950^{\circ}C$. Therefore, it was known that use of vacuum pump was more effective than that of sweep gas to obtain higher oxygen permeation flux.

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.559-565
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• 2003

An analytical method the determination of benzo(a)pyrene (BaP) and its hydroxylated metabolites, 1-hydroxybenzo(a)pyrene (1-OHBaP), 3-hydroxybenzo(a)pyrene (3-OHBaP), benzo(a)pyrene-4,5-dihydrodiol (4,5-diolBaP) and benzo(a)pyrene-7,8-dihydrodiol (7,8-diolBaP), in rat urine and plasma has been developed by HPLC/FLD and GC/MS. The derivatization with alkyl iodide was employed to improve the resolution and the detection of two mono hydroxylated metabolites, 1-OHBaP and 3-OHBaP, in LC and GC. BaP and its four metabolites in spiked urine were successfully separated by gradient elution on reverse phase ODS $C_{18}$ column (4.6 mm I.D., 100 mm length, particle size 5 ㎛) using a binary mixture of MeOH/H₂O (85/15, v/v) as mobile phase after ethylation at 90 ℃ for 10 min. The extraction recoveries of BaP and its metabolites in spiked samples with liquid-liquid extraction, which was better than solid phase extraction, were in the range of 90.3- 101.6% in n-hexane for urine and 95.7-106.3% in acetone for plasma, respectively. The calibration curves has shown good linearity with the correlation coefficients (R²) varying from 0.992 to 1.000 for urine and from 0.996 to 1.000 for plasma, respectively. The detection limits of all analytes were obtained in the range of 0.01-0.1 ng/mL for urine and 0.1-0.4 ng/mL for plasma, respectively. The metabolites of BaP were excreted as mono hydroxy and dihydrodiol forms after intraperitoneal injection of 20 mg/kg of BaP to rats. The total amounts of BaP and four metabolites excreted in dosed rat urine were 3.79 ng over the 0-96 hr period from adminstration and the excretional recovery was less than 0.065% of the injection amounts of BaP. The proposed method was successfully applied to the determination of BaP and its hydroxylated metabolites in rat urine and plasma for the pharmacokinetic studies.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.819-826
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• 2002

In this paper, the performance of Au / $Ba_{0.5}Sr_{0.5}TiO_3$ (BST) / Magnesium oxide (MgO) two-layered electrically tunable band-pass Filters (BPFs) is demonstrated. The devices consist of microstrip, coplanar waveguide (CPW), and conductor-backed coplanar waveguide (CBCPW) structures. These BST thin film band-pass filters have been designed by the 2.5 D field simulator, IE3D, Zeland Inc., and fabricated by thin film process. The simulation results, using the 2-pole microstrip, CPW, and CBCPW band-pass filters, show the center frequencies of 5.89 GHz, 5.88 GHz, and 5.69 GHz, and the corresponding insertion losses are 2.67 dB, 1.14 dB, and 1.60 dB, with 3 %, 9 %, and 7 % bandwidth, respectively. The measurement results show the center frequencies of 6.4 GHz, 6.14 GHz, and 6.04 GHz, and their corresponding insertion losses are 6 dB, 4.41 dB, and 5.41 dB, respectively, without any bias voltage. With the bias voltage of 40 V, the center frequencies for the band-pass filters are measured to be 6.61 GHz, 6.31 GHz, and 6.21 GHz, and their insertion losses are observed to be 7.33 dB, 5.83 dB, and 6.83 dB, respectively. From the experiment, the tuning range for the band-pass filters are determined as about 3 % ~ 8 %.