• 한국전기전자재료학회논문지
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• 제36권4호
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• pp.413-417
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• 2023

Gallium Oxide (Ga₂O₃) is preferred as a material for next generation power semiconductors. The Ga₂O₃ should solve the disadvantages of low thermal resistance characteristics and difficulty in forming an inversion layer through p-type ion implantation. However, Ga₂O₃ is difficult to inject p-type ions, so it is being studied in a heterojunction structure using p-type oxides, such as NiO, SnO, and Cu₂O. Research the lateral-type FET structure of NiO/Ga₂O₃ heterojunction under the Gate contact using the Sentaurus TCAD simulation. At this time, the VG-ID and VD-ID curves were identified by the thickness of the Epi-region (channel) and the doping concentration of NiO of 1×10¹⁷ to 1×10¹⁹ cm-3. The increase in Epi region thickness has a lower threshold voltage from -4.4 V to -9.3 V at I_D = 1×10^-8 mA/mm, as current does not flow only when the depletion of the PN junction extends to the Epi/Sub interface. As an increase of NiO doping concentration, increases the depletion area in Ga₂O₃ region and a high electric field distribution on PN junction, and thus the breakdown voltage increases from 512 V to 636 V at I_D =1×10^-3 A/mm.

• 한국구조물진단유지관리공학회 논문집
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• 제25권4호
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• pp.28-36
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• 2021

콘크리트 구조물의 내부의 매립된 철근은 부동태 피막으로 인해 부식으로부터 보호된다고 알려져 있다. 구조물의 경제적인 내구수명 산정을 위해 부식 발생 시기를 지연시키거나 초기 부식 시점을 평가하는 것은 매우 중요하다. 본 연구에서는 3 가지 수준의 피복두께(60 mm, 45 mm, 30 mm), 물-시멘트 비(40.0%, 50.0%, 60.0%), 염화물 농도(0.0%, 3.5%, 7.0%)를 고려한 콘크리트 시편을 대상으로 부식 모니터링을 수행하였는데, 한천(Agar) 기반 소켓 형식 센서를 활용하여 OCP를 측정하였다. OCP 측정 시 습윤 조건에서는 전위가 감소하고 건조 조건에서는 감소된 전위가 일부 회복하는 거동을 확인하였다. 모든 물-시멘트 비에서 피복두께가 30 mm의 경우 가장 낮은 OCP값이 측정되었으며, 피복두께가 30 mm에서 45 mm로 증가할 때 빠르게 OCP가 회복하였다. 이는 피복두께가 염화물 이온의 침투에 효과적인 방어기구로 작용하기 때문이다. 염화물 농도가 증가함에 따라 물-시멘트 비의 영향보다 피복두께에 대한 영향이 더 지배적인 경향을 보이는 것으로 도출되었다. 시편의 해체 후 추가적인 모니터링과 염화물량의 평가를 수행하면 제안된 부식 모니터링 기법의 신뢰성을 높일 수 있을 것으로 판단된다.

• 한국축산식품학회지
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• 제38권5호
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• pp.1080-1091
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• 2018

The eggshell, which is a complex and highly ordered structure, is very important factor for food safety and egg marketing. This study investigated the changes in eggshell structure and shell components in relationship to hen age. For this study, we examined the histological change of the endometrium of the 30-, 60-, and 72-wk-old commercial layers, and analyzed the ultrastructure and ionic composition of their eggshells. The results showed that histological deformation, fibrosis, atrophy and elimination of micro-villi in the uterus endometrium were found through microscopic observation that was associated with increasing hen age. Concentration of blood-ion components such as $Ca^{2+}$, $Na^+$, $K^+$, and $Cl^-$ ions did not change with age. Along with the results from the ultrastructure analysis of the eggshell, the palisade layer ratio and the density of mammillary knobs were significantly decreased in older hens. In addition, the type B mammillary knobs were frequently observed with increasing hen age. In the mineral element assay from the eggshell, $Ca^{2+}$, $S^{2-}$, and $Co^{2+}$ significantly decreased with increasing hen age, whereas $Na^+$, $K^+$, and $V^{2+}$ significantly increased. Therefore, the damages of endometrial tissue inhibit the processes of ion transmission and the crystallization of eggshell formation, resulting in a large and non-uniform mammillary knob formation. This means the conditions of endometrial cells affect the formation of the eggshell structure. In conclusion, hen aging causes the weakness of the eggshell and degrades the eggshell quality.

• Restorative Dentistry and Endodontics
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• 제16권1호
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• pp.87-105
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• 1991

The purpose of this experiment was to measure the leaking and solubility of commonly used dental restorative materials - Silux plus (CS), Hi-pol (CH), Clearfil F-II, Fissureseal (FS), Glass-Ionomer cement Fuji Type II (GI), Amalgam Cavex 68 (AM), Zinc Phosphate Cement (ZP) and gutta-percha (GP) and investigate the relation between the solubility and marginal leakage. Disc-shape specimens were fabricated with each material and dipped into deionized water, 0.01M lactic acid and 0.005M KOH solution, thus the total ionic concentrations in each solution was measured with ion chromatograph after 1, 3, and 7 days, respectively. For the solubility test, each specimen was immersed in 0.001M and 0.01M lactic acid for 24 hours, respectively and total weight loss was calculated. Also, Zn leaking through the margin of restorations was measured. The obtained results were as follows: 1. The amounts of eluted ion from the eight materials were most in 0.01M lactic acid and least in deionized water. 2. Of the eight materials, the fluoride release was greatest for glass ionomer cement (GI) in 0.01 M lactic acid after 7 days. 3. In analysis of the divalent cation, Mg was eluted most for zinc phosphate cement (ZP) and Ca for Clearfil F-II (CF) in 0.01M lactic acid after 7 days. 4. In analysis of transition metals, Cu and Zn were detected only. 5. The solubility rate of eight materials was greater in 0.01M lactic acid than in 0.001M for 24 hours, for zinc phosphate cement (ZP) the rate was greatest (5.4%) in 0.001M lactic acid, and amalgam least (0.01%). 6. The Zn concentration of restorative material with Z.P.C base was greater in 0.01M lactic acid than in 0.001M lactic acid.

• 한국동물학회지
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• 제39권3호
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• pp.307-316
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• 1996

담배나방 (Helicoverpa assulta)의 발생기간 중 존재하는 major haemolyruph protein (MHP)을 확인하였으며, 그 발생에 따른 변화상 및 물리화학적 특성을 조사하였다. MHP는 유충-용-성충의 발생단계에서 확인되었으며, 그 함량은 유충의 성장에 따라 증가하여 용기와 성충기 동안에도 높게 유지되고 용초기와 성충 초기에서 일시적인 감소를 보여, 총 혈림프 단백질의 농도 변화와 유사한 변화양상을 보였다. ammonium sulfate precipitation, gel filtration 그리고 ion exchange chromatography를 통해 정제한 MHP의 전기영동 분석 결과, 단일 구성소 단위 (69 kDa)가 hexamer를 이룬 분자량 414kDa의 glycolipoprotein (pI 5.9)인 것으로 확인되었다. MHP의 아미노산 조성에 있어서 18.27 mole % 의 tryptophan, 7.47 mole % 의 tyrosine and 6.51 mole % 의 phenylalanine이 검출되어 다른 곤충류의 저단백질들에 비해 비교적 높은 aromatic amino acid의함량을 보였다. 지방체, 장, 말피기관 단백질의 전기영동 및 이들 단백질과 anti-MHP간의 immunodiffusion test 결과 MHP는 지방체에 존재하고 있음이 확인되었다.

• 분석과학
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• 제13권6호
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• pp.699-704
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• 2000

도금폐수중의 시안이온의 전기화학적 분해 및 아연이온의 제거에 관한 연구를 백금으로 도금된 티타늄 양극과 스텐레스 음극 전극을 사용하여 수행하였다. 전기분해시간, 셀전류, 첨가제, 염화물농도등의 여러 가지 실험파라메터를 연구하여 도금폐수중의 시안화물 분해 및 수용액중의 아연이온의 효과적인 제거에 사용하였다. 셀전류와 첨가제의 종류에 따라 시안이온의 분해 및 아연이온의 제거 효율이 크게 영향을 받는 것이 발견되었다. 시안이온의 분해 및 아연이온의 제거를 위한 경제적이며 높은 효율을 나타내는 최적화된 조건은 1시간의 전기분해시간, 12A의 전류, 그리고 0.5 M NaCl 첨가제를 사용하여 확립하였다. 양극에서의 시안이온의 분해에 관한 반응메카니즘도 논의하였다.

• 공업화학
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• 제30권1호
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• pp.34-38
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• 2019

탄산화 공정을 위한 Ca 추출원으로 시멘트 산업부산물을 사용하였다. ICP와 XRD 분석을 통하여 시멘트 산업부산물은 대부분 CaO와 KCl로 구성되어 있음을 확인하였다. 최적화된 추출용제의 종류 및 농도는 1.5 M of hydrochloric acid이며 최적의 고액비는 0.1 g/mL이었다. 추출 성능 실험 결과를 통해 양이온의 추출효율은 이온 결합 형태 및 용해도에 의존함으로 판단되었다. 또한 추출 공정 후, 첨가물의 종류 및 주입 순서에 따라 선택적으로 양이온이 분리될 수 있음을 확인하였다. pH를 9.5, 13으로 조절하기 위하여 NaOH를 주입하였을 때 불순물과 $Ca(OH)_2$가 침전되었으며, $C_2H_5OH$를 주입한 경우 KCl 형태로 분리된 K가 침전되었다.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2900-2904
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• 2013

We present the synthesis and characterization of DTPA-bis(histidylamide) (1a), DTPA-bis(aspartamide) (1b), and their gadolinium complexes of the type $[Gd(L)(H_2O)]$ (2a:L = 1a; 2b:L = 1b). Thermodynamic stabilities and $R_1$ relaxivities of 2a-b compare well with Omniscan$^{(R)}$, a well-known commercial, extracellular (ECF) MRI CA which adopts the DTPA-bis(amide) framework for the chelate: $R_1$ = 5.5 and 5.1 $mM^{-1}$ for 2a and 2b, respectively. Addition of the Cu(II) ion to a solution containing 2b triggers relaxivity enhancement to raise $R_1$ as high as 15.3 $mM^{-1}$, which corresponds to a 300% enhancement. Such an increase levels off at the concentration beyond two equiv. of Cu(II), suggesting the formation of a trimetallic ($Gd/Cu_2$) complex in situ. Such a relaxivity increase is almost negligible with Zn(II) and other endogenous ions such as Na(I), K(I), Mg(II), and Ca(II). In vivo MR images and the signal-to-noise ratio (SNR) obtained with an aqueous mixture of 2b and Cu(II) ion in an 1:2 ratio demonstrate the potentiality of 2 as a copper responsive MRI CA.

• Bulletin of the Korean Chemical Society
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• 제15권3호
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• pp.256-260
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• 1994

Perovskite type oxides of the $Sr_xHo_{1-x}FeO_{3-y}$ system with compositions of x=0.00, 0.25, 0.50, 0.75, and 1.00 have been prepared at 1200$^{\circ}$C in air. X-ray powder diffraction assigns the compositions with x=0.00 and 0.25 to the orthorhombic crystal system and those with x=0.50, 0.75, and 1.00 to the cubic one. The unit cell volumes of solid solutions increase with x in the system. Nonstoichiometric chemical formulas were determined by Mohr salt titration. The mole ratio of $Fe^{4+}$ ions to total iron ions and the concentration of oxygen ion vacancies increase with x. Mossbauer spectra for the compositions of x= 0.00, 0.25, and 0.50 show six lines indicating the presence of $Fe^{3+}$ ions in the octahedral site. However, the presence of $Fe^{4+}$ ions may also be detected in the spectra for the compositions with x=0.25 and x=0.50. In the compositions with x=0.75 and 1.00, single line patterns show also the mixed valence state of $Fe^{3+}$ and $Fe^{4+}$ ions. The electrical conductivity in the temperature range of -100$^{\circ}$C to 100$^{\circ}$C under atmospheric air pressure increases sharply with x but the activation energy decreases with the mole ratio of $Fe^{4+}$ ion. The conduction mechanism of the perovskite system seems to be hopping of the conduction electrons between the mixed valence iron ions.

• 한국분말재료학회지
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• 제15권2호
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• pp.125-135
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• 2008

[ $TiO_2$ ] nanotubes for photocatalytic application have been synthesized by hydrothermal method. $TiO_2$ nanotubes are formed by washing process after reaction in alkalic solution. Nanotubes with different morphology have been fabricated by changing NaOH concentration, temperature and time. $TiO_2$ nanoparticles were treated inside NaOH aqueous solution in a Teflon vessel at $110^{\circ}C$ for 20 h, after which they were washed with HCl aqueous solution and deionized water. Nanotube with the most perfect morphology was formed from 0.1 N HCl washing treatment. $TiO_2$ nanotube was also obtained when the precursor was washed with other washing solutions such as $NH_4OH$, NaCl, $K_2SO_4$, and $Na_2SO_3$. Therefore, it was suggested that $Na^+$ ion combined inside the precursor compound slowly comes out from the structure, leaving nanosheet morphology of $TiO_2$ compounds, which in turn become the nanotube in the presence of hydroxyl ion. To stabilize the sheet morphology, the different type of washing treatment solution might be considered such as amine class compounds.