• 한국환경과학회지
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• 제23권6호
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• pp.1157-1163
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• 2014

The solid phase extractant (PVC-D2EHPA bead) was prepared by immobilizing di-2-ethylhexyl-phosphoric acid (D2EHPA) with polyvinyl chloride (PVC). The prepared PVC-D2EHPA beads were characterized by using fourier transform infrared spectrometer (FTIR) and scanning electron microscopy (SEM). The removal experiments of Cu(II) by PVC-D2EHPA beads conducted batchwise. The removal kinetics of Cu(II) was found to follow the pseudo-second-order model. The equilibrium data fitted well with Langmuir isotherm model and the maximum removal capacity was 2.6 mg/g at $20^{\circ}C$. The optimum pH region was in the range of 3.5 to 6. and the standard free energy (${\Delta}G^{\circ}$) was between -4.67~-4.98 kJ/mol, indicating the spontaneous nature of Cu(II) removal by PVC-D2EHPA beads.

• 한국표면공학회지
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• 제36권2호
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• pp.200-205
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• 2003

Thermoelectric p-type $Fe_{0.98}$ $Mn_{ 0.02}$$Si_2$ bulk specimens have been produced by mechanical alloying and consolidation by vacuum hot pressing. The subsequent isothermal annealing was not able to fully transform the mestastable as -milled powders into the $\beta$ $-FeSi_2$ phase, so that the obtained matrix consisted of not only thermoelectric semiconducting $\beta$-FeSi$_2$ but also some residual, untransformed metallic $\alpha$ $- Fe_2$$Si_{ 5}$ and $\varepsilon$-FeSi mixtures. Interestingly, $\beta$ - $FeSi_2$ was more easily obtained in the low density specimen when compared to the high density specimen. The oxidation at 700 and $800^{\circ}C$ in air led to the phase transformation of the above described iron - silicides and the formation of a thin silica surface layer.

• 한국재료학회지
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• 제21권4호
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• pp.236-241
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• 2011

Polysilazane and silazane-based precursor films were deposited on stacked TiN/Ti/TEOS/Si-substrate by spin-coating, then annealed at $150{\sim}400^{\circ}C$, integrated further to form the top electrode and pad, and finally characterized. The precursor solutions were composed of 20% perhydro-polysilazane ($SiH_2NH$)n, and 20% hydropolymethyl silazane ($SiHCH_3NH$)n in dibutyl ether. Annealing of the precursor films led to the compositional change of the two chemicals into silicon (di)oxides, which was confirmed by Fourier transform infrared spectroscopy (FTIR) spectra. It is thought that the different results that were obtained originated from the fact that the two precursors, despite having the same synthetic route and annealing conditions, had different chemical properties. Electrical measurement indicated that under 0.6MV/cm, a larger capacitance of $2.776{\times}10^{-11}$ F and a lower leakage current of 0.4 pA were obtained from the polysilazane-based dielectric films, as compared to $9.457{\times}10^{-12}$ F and 2.4 pA from the silazane-based film, thus producing a higher dielectric constant of 5.48 compared to 3.96. FTIR indicated that these superior electrical properties are directly correlated to the amount of Si-O bonds and the improved chemical bonding structures of the spin-on dielectric films, which were derived from a precursor without C. The chemical properties of the precursor films affected both the formation and the electrical properties of the spin-on dielectric film.

• 한국응용곤충학회지
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• 제48권2호
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• pp.197-202
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• 2009

애반딧불이의 유충상륙은 약 5.3일이 소요되었고 고치방을 만든 후 약 6.6일에 번데기로 변태하였다. 고치방의 크기는 길이 10.1 mm, 폭 4.7 mm, 벽두께 1.3 mm이었다. 번데기는 약 10.5일이 소요되었다. 성충이 되고 고치방 속에 약 6.8일 후에 출현하였다. 성충의 출현은 PM. 9시를 전후로 최대였고 PM. 10시에 감소하였다. 성충출현의 최적지온은 $23.4^{\circ}C$였다. 실내개체군(Lab-type)의 암컷 및 수컷과 야외개체군(Nat-type)의 수컷은 수명이 비슷하였고, Nat-type의 산란 수는 200${\sim}$400립 구간을 형성하였다. 단지, Nat-type의 암컷은 수명이 짧았으며, 산란 횟수와 산란 수는 적었다. 산란횟수에서 야외개체군은 2회와 실내개체군은 4회로 차이를 보이는 것은 야외개체군은 시료 채집 이전에 산란했을 가능성을 배제할 수 없다.

• 한국미생물·생명공학회지
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• 제51권2호
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• pp.157-166
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• 2023

Three lactic acid bacteria (LAB) producing exopolysaccharides (EPSs) were isolated from Pa (green onion)-kimchi, and identified as Weissella confusa (SKP 173), Weissella cibaria (SKP 182), and Leuconostoc citreum (SKP 281), respectively by 16S rRNA gene sequencing. The yields of EPS were 21.27, 18.53, and 15.4 g/l for EPS from SKP 173, 182, and 281, respectively when grown in MRS broth containing sucrose (5%, w/v). Total sugar contents were 64.39, 62.84, and 65.16% (w/w) for EPS from SKP 173, 182, and 281, respectively while the protein contents were 0.33, 0.31, and 0.25% (w/w), respectively. EPSs from W. confusa SKP 173 and W. cibaria SKP 182 contained glucose only but EPS from L. citreum SKP 281 contained glucose and glucitol. Viscosities of the 2% (w/w) freeze-dried EPS solution were 9.60, 8.00, and 8.20 centipoise (cP) for EPS from SKP 173, 182, and 281, respectively. Viscosities of culture grown in MRS broth with 5% sucrose (no glucose) were 92.98, 57.19, and 18.8 cP, respectively. The average molecular weights of EPSs were larger than 2 × 10⁷ Da. Fourier transform infrared spectroscopy (FT-IR) analyses of EPSs showed typical carbohydrate peaks, suggesting that the EPSs consisted of pyranose saccharides with α-(1,6) and α-(1,3) glycosidic linkages. L. citreim SKP 281 was used as the starter for yogurt fermentation, and EPS production was confirmed.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제25권2호
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• pp.381-402
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• 2011

넓이 개념은 수학의 발생 초기에 형성된 중요한 개념의 하나이며, 역사적으로 넓이를 구하는 문제들이 연구의 중요한 시발점이 된 경우도 많았다. 본 연구에서는 중등학교 수학교과서에서 다루는 삼각형의 넓이 공식을 다양한 방법으로 변형시켜, 삼각형의 몇몇 요소들(변들, 각들, 중선들, 둘레, 외접원의 반지름)로 구성된 새로운 넓이 공식을 유도하여 제시하였다. 본 연구에서 제시된 몇몇 공식들은 과학고등학교 R&E 프로그햄의 진행 과정에서 얻어졌다. 본 연구를 통해 얻어진 결과들은 고등학교 수준의 수학 영재교육에서 수학적 발명을 지향하는 교수-학습 과정에 활용될 수 있을 것으로 기대된다.

• Asian-Australasian Journal of Animal Sciences
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• 제32권8호
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• pp.1186-1194
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• 2019

Objective: The influence of broiler carcass scalding conditions on chicken breast meat quality parameters was investigated. Methods: Two hundred and seventy Cobb broiler chickens from 42 to 48 days old were slaughtered according to the standard industry practice and scalded in five temperature/time combinations-$T_1$, $54^{\circ}C/210s$; $T_2$, $55^{\circ}C/180s$; $T_3$, $56^{\circ}C/150s$; $T_4$, $57^{\circ}C/120s$; $T_5$, $58^{\circ}C/90s$. Results: Scalding temperature increase resulted in higher values of external and ventral lightness and in protein functionality reduction-determined by emulsification capacity and protein denaturation-in chicken breast fillets 24 h post-mortem. Protein secondary structures had conformational changes, with a decrease of the ${\alpha}$-helix and an increase of the ${\beta}$-sheet and ${\beta}$-turn proportions, mainly in $T_1$ and $T_5$ samples, determined by Fourier-transform infrared spectroscopy in an attenuated reflectance mode analysis. The chemical composition, pH, water holding capacity and Warner-Bratzler shear force did not differ among the treatments. In the fatty acid profile, the 18:1n-9 was lower in $T_5$, which suggested that the high scalding-temperature could have caused the lipid oxidation. The values of the polyunsaturated fatty acids (PUFA), such as 22:2, 20:4n-6, and 22:6n-3, were highest in the $T_5$, thus being related to the phospholipid cellular membrane collapse in this experimental condition and subsequent release of these PUFA. Conclusion: Intermediate scalding-parameters avoided the negative changes in the chicken meat quality.

• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1513-1520
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• 2013

Novel chitosan (CS) based membrane networks were developed by solution casting and followed by crosslinking with different crosslinkers such as glutaraldehyde, urea-formaldehyde, and thiourea-formaldehyde. The developed membrane networks were designated as CS-GA, CS-UF and CS-TF. Crosslinking reaction of CS membranes was confirmed by Fourier transform infrared spectroscopy. Membrane rigidity and compactness were studied by the differential scanning calorimetry. The surface morphology of CS membranes was characterized by scanning electron microscopy. The sorption behaviour with respect to contact time, initial pH and initial metal ion concentration were investigated. The maximum adsorption capacity of CS-GA, CS-UF and CS-TF sorbents was found to be 1.03, 1.2 and 1.18 mM/g for $Cu^{2+}$ and 1.48, 1.55 and 2.18 mM/g for $Ni^{2+}$ respectively. Swelling experiments have been performed on the membrane networks at $30^{\circ}C$. Desorption studies were performed in acid media and EDTA and it was found that the membranes are reusable for the metal ion removal for three cycles. The developed membranes could be successfully used for the separation of $Cu^{2+}$ and $Ni^{2+}$ metal ions from aqueous solutions.

• 반도체디스플레이기술학회지
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• 제9권2호
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• pp.49-54
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• 2010

We have successfully synthesized $CeO_2$ nanopowders by means of the hydrothermal method, in a low temperature range of $100-200^{\circ}C$. In order to investigate the structure and morphology of the nanopowders, scanning electron microscopy and X-ray diffraction have been employed. In addition, for exploring the optical properties, Raman spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy have been used. In the optimized condition, with the pH, velocity, and time of 4.5, 600 rpm, and 60 h, the $CeO_2$ nanopowders with a diameter ranging from 50 to 150 nm have been synthesized. The nanopowders exhibited the visible emission mainly in the blue region. With comparing the reaction time, it is revealed that the extinction of functional groups at 60 h contributed to the growth and homogenization of the $CeO_2$ powders. Since the overgrowth and agglomeration of nanopowders were found, we suggest that the cracking/growth process is more favorable mechanism than the dissolution/precipitation process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전기설비전문위원
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• pp.207-210
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• 2008

In this paper, we researched the dielectric properties and voltage dependence on slice XLPE sheet from 22[kV] and 154[kV] power cable. We studied effects for impurities and water for semiconductor shield through a dielectric properties experiment to estimate performance of insulating materials in power cable. Capacitance and $tan{\delta}$ of 22[kV], 154[kV] were 53/43[pF] and $7.4{\times}10^{-4}$, $2.1510^{-4}$. In these results, the trend was increased with the increase of temperature. The tan6 of XLPE/semiconductor layer was increased as compared with that of XLPE. Dielectric properties reliability of tan6 was small. Also, To improve mean-life and reliability of power cable in this study, we have investigated chemical properties showing by changing the content of carbon black that is semiconductive additives for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Chemical properties of specimens was measured by FT-ATR (Fourier Transform Attenuated Total Reflectance). The condition of specimens was a solid sheet. We could observe functional group (C=O, carbonyl group) of specimens through FT-ATR. From these experimental result, the concentration of functional group (C=O) was high according to increasing the content of carbon black. We could know EEA was excellent more than other specimens from above experimental results.