• 한국재료학회지
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• 제30권2호
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• pp.61-67
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• 2020

BiFeO₃ with perovskite structure is a well-known material that has both ferroelectric and antiferromagnetic properties called multiferroics. However, leaky electrical properties and difficulty of controlling stoichiometry due to Bi volatility and difficulty of obtaining high relative density due to high dependency on the ceramic process are issues for BiFeO₃ applications. In this work we investigated the sintering behavior of samples with different stoichiometries and sintering conditions. To understand the optimum sintering conditions, nonstoichiometric Bi_1±xFeO_3±δ ceramics and Ti-doped Bi_1.03Fe_1-4x/3Ti_xO₃ ceramics were synthesized by a conventional solid-state route. Dense single phase BiFeO₃ ceramics were successfully fabricated using a two-step sintering and quenching process. The effects of Bi volatility on microstructure were determined by Bi-excess and Ti doping. Bi-excess increased grain size, and Ti doping increased sintering temperature and decreased grain size. It should be noted that Ti-doping suppressed Bi volatility and stabilized the BiFeO₃ phase.

• Journal of Nutrition and Health
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• 제44권1호
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• pp.5-15
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• 2011

본 연구는 임신기 동안 어미쥐의 철 섭취 수준이 모체의 철 대사지표와 산화적 스트레스 및 임신의 결과에 미치는 영향을 검토하기 위해 비임신쥐를 대조군으로 하여 수행하였다. 10주령 200 g 이상 된 암컷과 수컷 흰쥐를 1 : 1로 교배시켜 임신을 확인한 후, 비임신쥐 (대조군)와 임신쥐 (실험군)에게 식이 중 철 수준이 정상수준 (AIN-93G diet 수준, 35 mg Fe/kg diet), 고수준 (정상의 10배, 350 mg Fe/kg diet) 및 과잉수준 (정상의 30배, 1,050 mg Fe/kg diet)의 3가지 실험식이를 급여하였다. 임신 19일째 되는 날, 비임신쥐와 임신 쥐를 희생시켜 분석한 결과는 다음과 같다. 체중의 증가나 식이섭취량은 철 섭취 수준의 영향을 받지 않았고, 임신의 결과로서 태아의 수, 태아체중 및 태반무게도 철 섭취 수준의 영향은 받지 않았다. 헤모글로빈, 헤마토크릿, 혈청 철 농도 등의 혈액지표들은 철 섭취 수준의 영향은 받지 않았으나 임신에 의한 감소 경향을 보였다. 임신쥐의 철 섭취 수준의 증가에 따라 간과 지라 조직의 철 함량이 유의적으로 증가하였다. 또한 임신쥐의 간에서 페리틴 단백질 수준이 철 섭취의 증가에 따라 현저히 증가하였다. 산화적 손상지표인 지질과산화물 (MDA)은 철 섭취수준의 영향을 받지 않았고, 단백질 산화물 (protein carbonyls)은 비임신쥐와 임신쥐에서 모두 철 과잉 섭취군의 경우 유의적으로 증가하였다. 항산화효소 중에서는 철 과잉섭취군에서 간의 GPx 활성이 유의적으로 감소하였다. 결론적으로, 임신기 동안 어미쥐의 철 섭취수준의 증가는 어미쥐의 혈액지표와 임신의 결과에는 유의적인 영향을 미치지 않았지만, 간 조직 내 철 함량과 페리틴 단백질 수준을 유의적으로 증가시켰으며, 간 조직에서 단백질 산화물인 protein carbonyl 농도를 증가시키고, 항산화효소 중 특히 GPx의 활성 감소를 초래하였다. 또한 간 조직에서 세포사멸을 억제하는 중요한 인자인 Bcl-2 단백질 수준이 임신쥐에서 철 섭취의 증가에 따라 유의적으로 감소하였다. 이러한 영향이 철을 정상 수준의 10배 섭취한 군에서는 약하게 나타났으나, 30배 과잉으로 철을 섭취한 군에서는 유의적으로 차이를 보였다. 이 결과는 임신시 철 과잉 섭취의 해로운 영향이 지금까지 철 대사의 측정도구로 삼아왔던 혈액지표의 변화 보다는 체내에서 일어나는 조직의 산화적 스트레스의 증가나 조직 내 철의 축적 등에 보다 더 민감하게 반영됨을 알 수 있었다. 따라서, 철 과잉 섭취가 모체 뿐만 아니라 태생 조직의 산화적 스트레스에도 영향을 줄 수 있음을 시사하였다.

• 천문학회보
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• 제38권2호
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• pp.38.2-38.2
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• 2013

Several studies have reported the presence of sodium excess objects having neutral atomic absorption lines at $5895{\AA}$ (NaD) and $8190{\AA}$ that are deeper than expected based on stellar population models that match the stellar continuum. The origin of these lines is therefore hotly debated. van Dokkum & Conroy proposed that low-mass stars (0.3M) are more prevalent in massive early-type galaxies, which may lead to a strong NaI 8190 line strength. It is necessary to test this prediction, however, against other prominent optical line indices such as NaD, Mgb, and Fe5270, which can be measured with a significantly higher signal-to-noise ratio than NaI 8190. We identified a new sample of roughly one thousand NaD excess objects (NEOs; ~8% of galaxies in the sample) based on NaD line strength in the redshift range 0.00${\alpha}$-enhanced" ([${\alpha}/Fe$] ~ 0.3), "metal-rich" ([Z/H] ~ 0.3), and, especially, "Na-enhanced" ([Na/Fe] ~ 0.3).

• 한국세라믹학회지
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• 제34권11호
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• pp.1159-1164
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• 1997

Magnetite(Fe3O4) powders were synthesized through glycothermal reaction by using crystalline $\alpha$-FeOOH as precursor and ethyleanne glycol as solvent. The phase, morphology and particle size of synthesized powders were characterized by XRD and an SEM. When only ethylene glycol was used as solvent, the phase was transformed from $\alpha$-FeOOH to $\alpha$-Fe2O3 and finally Fe3O4 at 27$0^{\circ}C$ for 6hr without morphological change. But by addition of water, Fe3O4 powders were synthesized at 23$0^{\circ}C$ for 3hr through solution-recrystalization process. As the content of water addition increased, the particle shape changed from sphere to octahedron and the partcle size increased. When the excess amount of water added, residual $\alpha$-FeOOH or $\alpha$-Fe2O3 was recrystalized.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1098-1107
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• 2001

This study is to develop the pretreatment for the excess and digested sludge by elector-coagulation and dewatering. Electrocoagulation is applied to excess and digested sludge before transferring to the pistion type for dewatering. Piston type filter press as a laboratory scale plant was used to estimate the dewaterability. MMD of excess sludge was increased from initial diameter of particles ($34.16{\mu}m$) to the 87%($64.01{\mu}m$) after electrocoagulation. Al electrode is more effective than Fe electrode for the dewaterabiltity of excess sludge Electrodewatering after electrocoagulation as pretreatment makes the water content of sludge cake 50~60 wt%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.371-374
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• 2002

Bismuth lanthanum titanate thin films with excess Bi contents were prepared onto Pt/Ti/$SiO_2$/Si substrate by metalorganic decomposition (MOD) technique. The structure and morphology of the films were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. From the XRD analysis, BLT thin films show polycrystalline structure and the layered-perovskite phase was obtained over 10% excess of Bi contents. As a result of ferroelectric characteristics related to the Bi content of the BLT thin film, the remanent polarization and dielectric constant decreased with increasing over Bi content of 10 % excess. The BLT film with Bi content of 10% excess was measured to have a dielectric constant of n9 and dielectric loss of 1.85[%]. The BLT thin films showed little polarization fatigue test up to 3.5 x $10^{9}$ bipolar switching cycling.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1992-1997
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• 2003

This study is to develop the pretreatment for the excess and digested sludge by electro-coagulation and dewatering. Electrocoagulation is applied to excess and digested sludge before transferring to the piston type press for dewatering. Piston type filter press as a laboratory scale plant was used to estimate the dewaterability. MMD of excess sludge was increased from initial diameter of particles(34.16 ${\mu}m$) to the 87%(64.01 ${\mu}m$) after electrocoagulation. AI electrode is more effective than Fe electrode for the dewaterability of excess sludge. Electrodewatering after electrocoagulation as pretreatment makes the water content of sludge cake $50{\sim}60$ wt%.

• Journal of Korean Society for Atmospheric Environment
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• 제15권E호
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• pp.9-16
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• 1999

This study has been focused on NO conversion for metal-incorporated silicates(Fe-silicate, Mn-silicate, and Fe-Mn-bimetallosilicate) with a similar MFI type. Used metallosilicates were prepared by the rapid crystallization method. Their catalytic performance for the conversion of NO under excess O2(10%) condition with the addition of hydrocarbon of low concentration(1,100ppm n-C8H18) were investigated. As a result, the NO conversion on the Fe-Mn-bimetallosilicate was enhanced compared with on the Fe- or Mn-silicates. Furthermore, the performances for NO concentration on Fe-Mn-bimetallosilicate more increased with an increased in n-C8H18 concentration, a decrease in NO concentration, and an increase in O2 concentration.

• Journal of Magnetics
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• 제14권1호
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• pp.7-10
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• 2009

In this work, we studied the effects of Sn addition on the ordering temperature of FePt thin film. The coercivity of FePtSn film was about 1000 Oe greater than the coercivity of FePt film for an annealing temperature of $600^{\circ}C$. Therefore, Sn addition was effective in promoting the $L1_0$ ordering and in reducing the ordering temperature of the FePt film. From our X-ray diffraction results, we found that in the as-deposited film, the addition of Sn induced a lattice expansion in disordered FePt thin films. After the annealing process, the excess Sn diffuses out from the ordered FePt thin film because of the difference in the solid solubility of Sn between the disordered and ordered phases. The existence of precipitates of Sn from the FePt lattice was deduced by Curie temperature measurements of the FePt and FePtSn films. Therefore, the key role played by the addition of Sn to the FePt film can be explained by a reduction in the activation energy for the $L1_0$ order-disorder transformation of FePt which originates from the high internal stress in the disordered phase induced by the supersaturated Sn atoms.

• 대한화학회지
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• 제22권5호
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• pp.311-316
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• 1978

Fe(III)과 Xylenol Orange (XO 또는 $H_6A$)의 반응을 분광광도법으로 연구하였다. Fe(III)과 XO는 조성이 Fe(III) : XO = 2 : 1 및 1 : 1 인 두가지 착물을 형성함을 확인하였다. 2 : 1 착물은 XO보다 Fe(III)를 많이 포함한 산성에서 안정하고, 1 : 1 착물은 XO가 많이 포함된 약산성용액에서 안정하다. 흡수극대는 590nm(2 : 1)와 500nm(1 : 1)이고 몰흡광계수는 각각 $3.18{\pm}0.04{\times}10^4,\;1.32{\pm}0.03{\times}10^4$이다. pH값을 변화시키면서 측정한 두 착물의 안정도상수는 $log{\beta}_{21}=18.69{\pm}0.03,\;log{\beta}_{212}=42.08{\pm}0.09,\;log{\beta}_{11}=4.17{\pm}0.04,\;and\;log{\beta}_{113}=34.47{\pm}0.07$이었다.