• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.335-340
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• 2001

$Ga_2O_3$(1 wt%)-doped ZnO(GZO) thin films were grown on ${\alpha}-Al_2O_3$ (0001) by rf magnetron sputtering at $510^{\circ}C$, whose crystal structure was polycrystalline. As-grown GZO thin film shows poor electrical properties and photoluminescence (PL) spectra. To improve these properties, GZO thin films were annealed at 800-$900^{\circ}C$ in $N_2$atmosphere for 3 min. After the rapid thermal annealing(RTA), deep defect-level emission disappears and near-band emission is greatly enhanced. Annealed GZO thin films show very low resisitivity of $2.6\times10^{-4}\Omega$/cm with $3.9\times10^{20}/\textrm{cm}^3$ carrier concentration and exceptionally high mobility of 60 $\textrm{cm}^2$/V.s. These improved physical properties are explained in terms of translation of doped-Ga atoms from interstitial to substitutional site.

• Food Science and Preservation
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• v.15 no.6
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• pp.852-858
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• 2008

This study investigated the rheological properties of bread dough supplemented with lotus (Nelumbo nucifera) seed powder. The rheological properties measured were dough volume, farinogram, amylogram, extensogram, pH and outernal. The lotus seed powder contained 7.74% moisture, 20.15% crude protein, 2.11% crude fat, 4.34% crude ash, and 2.78% crude fiber. The farinogram showed that with increasing concentration of lotus seed powder the absorption rate of the dough increased slightly, the development time and stability decreased, and the degree of attenuation tended to be grown along. From the amylogram it was found that the gelatinization onset temperature and the maximum viscosity of the dough tended to increase with increasing content of lotus seed powder. The extensogram showed that the degree of extension of the dough decreased with increasing content of lotus seed powder, while the degree of resistance and resistance/extensibility increased. The dough pH tended to decrease with fermentation time, but increased with increasing content of lotus seed powder. A concentration of $5{\sim}10%$ lotus seed powder appears to be suitable for the preparation of dough.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.11a
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• pp.29-29
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• 2001

열전재료는 열전현상을 가지고 있어 열전발전과 열선냉각이 가능하기 때분에 해저용, 우주용, 군사용의 특수 전원으로 이미 실용화되어있고, 반도체, 레이저 다이오드, 적외선 검출소자 등의 냉각기로 쓰여지고 있어 많은 연구자들이 이들 재료에 대한 연구에 관을 갖고 열전특성을 향상시키기 위하여 많은 연구를 진행하고 있다 이들 열전재료는 사용 온도구역에 따라 3종류로 구분하고 있으며, 실온부근의 저온 영역(20$0^{\circ}C$)이하에서는 $Bi_2Te_3$계 재료, 중온영역(20$0^{\circ}C$~50$0^{\circ}C$)에서sms (Pb,Ge) Te계 재료, 고온영역(50$0^{\circ}C$~lOoo$^{\circ}C$)에서는 Si-Ge계 Fe Si계 재료가 이용되고 있다. 본 연구에서는 실온에서 성능지수가 높은 Bi_2(Te,Se)_3$에 대한 연구를 진행하였다. Bi_2(Te,Se)_3$계 열전재료는 기존의 공법인 Zone melting법을 이용하는 경우 성능지수가 높으나, 단위정이 Rhombohedral 구조파 기저면(basal plane)에 벽개성이 있는 관계로 재료의 적지 않은 손실과 가공상의 어려움이 있다. 또한 사료전체에 걸쳐 화학적으로 균질한 고용체를 얻는 것도 어려운 문제점으보 부각되고 있디 따라서 이와같은 문제점을 보완하기 위하여 용질원자의 편석감소, 고용도의 증가, 균일 고용체 형성, 결정립의 미세화등의 장점이 있는 급속응고법을 본 연구에 응용하였다. 본 연구에서는 위에서와 같은 급속응고의 장점과 대량 가공이 능늪한 연간압출공정을 이용하여 제조된 분말을 성형화 하였다. 특히 열간압출 가공에 있어서 압축다이 각 변화는 재료의 소성유동에 매우 중요한 역하을 하게되며, 이와 갇은 소성유동은 본 재료의 열전특성에 중요한 영향을 미치는 C 면 배양에 중요한 역할을 한 것으 로 기대된다. 이에 본 연구에서는 압출다이 각도 변화에 따른 미세조직변화와 이들 조직이 강도와 열전특성에 미치는 영향을 석하고자 한다. 압출재의 미세조직은 XRD(X Ray Diffraction), SEM(Scanning Electron Microscopy)으로 분석하였으며, 열전특성인 Seebeck계수($\alpha$)와 전기비저항( $\rho$ )은 열전측정장치로, 기계적 강도는 MTS장비를 이용하여 이루어졌다. 또한 압축다이각도 변화에 따른 결정방위 해석은 모노크로미터가 장착된 X RD장비감 이용하여 분석되었다.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.34-40
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• 2000

The $Pb_{0.94}Y_{0.04}[(Zr_{0.6}Sn_{0.4})_{0.915}Ti_{0.085}]O_3$ ceramics which corresponded to the antiferroelectric-ferroelectric phase boundary composition were prepared for digital-type-piezoelectric/electrostrictive device application. Their dielectric, field-induced polarization (P) and strain (X) behaviors were studied with variations in sintering condition and excess PbO content. The orthorhombic structure of specimens was hardly affected either by excess PbO addition or sintering temperature. With increasing excess PbO content, grains tended to be smaller and rounded ones, and the optimum sintering temperature was lowered. Excess PbO addition stabilized the antiferroelectric phase of the specimen effectively, which was confirmed by P-E and X-E analyses. Also the digital-type-strain character was found to be enhanced despite of slight increase in phase transition (AFE-FE) field and electrical resistivity, and decrease in maximum strain. These results were explained in terms of possible lattice defects and domain wall motion.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.5
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• pp.16-22
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• 2002

This paper suggests the optimum processing conditions for obtaining good quality $P^{+}$-n shallow junctions formed by pre-amorphization and furnace annealing(FA) to reflow BPSG(bore phosphosilicate glass). $BF_2$ions, the p-type dopant, were implanted with the energy of 20keV and the dose of 2$\times$10$^{15}$ cm$^{-2}$ into the substrates pre-amorphized by As or Ge ions with 45keV, 3$\times$$10^{14}$ $cm^{-2}$. High temperature annealings were performed with a furnace and a rapid thermal annealer. The temperature range of RTA was 950~$1050^{\circ}C$, and the furnace annealing was employed for BPSG reflow with the temperature of $850^{\circ}C$ for 40 minutes. To characterize the formed junctions, junction depth, sheet resistance and diode leakage current were measured. Considering the preamorphization species, Ge ion exhibited better results than As ion. Samples preamorphized with Ge ion and annealed with $1000^{\circ}C$ RTA showed the most excellent characteristics. When FA was included, Ge preamorphization with $1050^{\circ}C$ RTA plus FA showed the lowest product of sheet resistance and junction depth and exhibited the lowest leakage currents.

• Korean Journal of Food Science and Technology
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• v.39 no.6
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• pp.652-657
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• 2007

This study was performed to evaluate the physicochemical and quality characteristics of bread with Enteromorpha intenstinalis added. In order to compare the physical and organoleptic properties, 1 to 4% of E. intenstinalis powder was mixed with the flour. Among the physical characteristics of the dough, the absorption ratio in the farinogram and the degree of attenuation increased with increasing amounts of E. intenstinalis powder, whereas the development time, dough stability, the degree of extension, the degree of resistance, and R/E became reduced. In the amylogram, there was no difference in the gelatinization starting temperature among the samples, but the maximum viscosity gradually increased according to increasing amounts of E. intenstinalis powder. Also, a sensory evaluation was carried out in terms of acceptability (color, flavor, moistness, tenderness, mouth feel, and overall acceptability). Taken together, the 2% treatment showed the highest evaluation values, as compared to the other treatments.

• Korean Journal of Breeding Science
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• v.40 no.3
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• pp.324-327
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• 2008

'Onnuri' is a japonica rice cultivar developed from the cross between 'Milyang 165' and HR14732-B-67-2-3 at Honam Agricultural Research Institute (HARI), NICS, RDA, in 2005. This cultivar has a short grain shape and about 121 days growth duration from transplanting to harvesting in Korean climate condition. In reaction to biotic and abiotic stresses, it shows resistance to blast, bacterial blight pathogen from $K_1$ to $K_3$ and stripe virus, but susceptible to other major diseases and insect pests. The milled kernel of 'Onnuri' is translucent with non-glutinous endosperm. It has about 18.6% of amylose content and better palatability of cooked rice compared with 'Chucheongbyeo' cultivated in Kyunggi province. The milled rice yield of 'Onnuri' is about 5.94 MT/ha under the standard fertilizer level of the ordinary transplanting cultivation. 'Onnuri' would be adaptable to southern plain of Cheonan, middle-northern plain, and southern mid-mountainous of Korea.

• Microbiology and Biotechnology Letters
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• v.11 no.3
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• pp.233-239
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• 1983

Bacillus thuringiensis was mutagenized with UV light irradiation and nitrosoguanidine. Twenty-four tem perature-sensitive ts mutants were isolated at 42$^{\circ}C$ and classified into two groups by growth on nutrient agar at 42$^{\circ}C$. First is the lethal group, which did not grow at the nonpermissive temperature, the second is the reduced group whose growth was restricted from one-half to one-fourth, Thirteen ts mutants belong to the lethal group and eleven ts mutants belong to the reduced group. Auxotrophic mutant, A-N28 required five amino acids as growth factors, A-N65 also five amino acids, A-N92 seven, A-N115 four and A-N156 three. Bacillus thuringiensis wild type is resistant to penicillin, ampicillin, and cephalothin. The ts-Ul7l, A-N92 and A-Nl15 are sensitive to the three antibiotics. The ts -U601, -U603, -U604 and -Ul71 did not grow at the permissive temperature after temperature-shifting from 42$^{\circ}C$. Four auxotrophic mutants (A-N38, A-N65, A-N92 and A-Nl15) did not form spores in their cells.

• Journal of the Korean Geotechnical Society
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• v.40 no.3
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• pp.55-63
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• 2024

Xanthan gum biopolymer is an ecofriendly ground stabilizer that maintains stability in a wide range of temperatures and pH values. The binding effect of sandy soil particles realized by injecting xanthan gum biopolymer is dependent on the xanthan gum matrix, which is formed during the drying process; thus a study on the effects of the drying process of the xanthan gum solution on the changes in stiffness characteristics of sandy soil is required. In this study, shear wave velocity and electrical resistivity were monitored in sandy soil specimens saturated with biopolymer solutions of different gravimetric concentrations to investigate the improvement effects of biopolymer-treated sandy soils with the drying process. The experimental results reveal that both shear wave velocity and electrical resistivity increase during drying process. The results demonstrate the stiffness improvement effects of biopolymer-treated sandy soils. In addition, a higher stiffness improvement effect was monitored in the biopolymer-treated sandy soils with a higher gravimetric concentration. The results of this study may be used to estimate the stiffness improvement effects of sandy soils treated with biopolymer solutions with the drying process.

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.16-22
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• 2024

Polymer electrolyte membrane fuel cells have the advantage of low operating temperatures and fast startup and response characteristics compared to others. Simulation studies are actively researched because their cost and time benefits. In this study, the resistance of water residual in the gas diffusion layer (GDL) of the unit cell was added to the existing equation to compare the actual data with the model data. The experiments were conducted with a 25 cm² unit cell, and the samples were separated into stopping times of 0, 10, and 60 minutes following primary impedance measurement, activation, and polarization curve data acquisition. This gives 0, 10, and 60 minutes for the residual water in the GDL to evaporate. Without the rest period, the magnitude of the performance improvement was not significantly different at the same potential and flow rate, but the rest period did improve the performance of the membrane electrode assembly when measuring impedance. By changing the magnitude of the resistance reduction to an overvoltage, the voltage difference between the fuel cell model with and without residual water was compared, and the error rate in the high current density region, which is dominated by concentration losses, was reduced.