• 마이크로전자및패키징학회지
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• 제30권1호
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• pp.1-16
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• 2023

전기차용 전력변환모듈의 성능향상 요구와 종래의 Si 전력반도체의 한계 극복을 위해 차세대 전력반도체인 wide-bandgap (WBG) 기반 전력반도체로의 전환이 가속화되고 있다. WBG 전력반도체로의 전환을 위해 전력변환모듈 패키징 소재 역시 높은 고온 내구성을 요구받고 있다. 전력변환모듈 패키징 공정 중 하나인 Ag 소결 다이접합 기술은 종래의 고온용 Pb 솔더링의 대체 기술로 주목받고 있다. 본 논문에서는 Ag 소결 다이접합 기술 관련 최신 연구동향에 대해 소개하고자 한다. 소결 다이접합 공정 조건에 따른 접합부 특성을 비교하고 Ag 소결층의 3차원 이미지 구현에 따른 다공성 Ag 소결 접합부의 물성 측정 방법론에 대해 고찰하였다. 또한 열충격 및 파워사이클 신뢰성 평가 연구동향을 분석하였다.

• Animal Bioscience
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• 제36권7호
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• pp.1059-1066
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• 2023

Objective: Present study was designed to evaluate the efficacy of Acacia nilotica bark extract as an alternative to antibiotic growth promoters in broilers. Methods: Six hundred, day-old broiler chicks were randomly divided into six groups (NC, without any supplementation; AB, NC+Zinc Bacitracin; PB, NC+Safmannan; ANBE1, NC+A. nilotica bark extract 0.1%; ANBE3, NC+A. nilotica bark extract 0.3%; ANBE5, NC+A. nilotica bark extract 0.5%), with ten replicates per group (10 chicks/replicate) and feeding trial was lasted for 35 days. Results: Results showed that weight gain (1,296.63 g) and feed conversion ratio (FCR, 1.59) of AB was better than NC, during the finisher phase. Overall FCR of AB (1.53), PB (1.54), and ANBE5 (1.54) was significantly (p<0.05) better than NC. From carcass parameters relative weight of wing and heart were highest in ANBE3 (2.5% and 1.51%, respectively). Significantly (p<0.05) highest blood glucose level was observed in NC (264.5 mg/dL) and highest albumin concentration was found in AB (1.46 mg/dL). In addition, antibody titer levels against ND and IBD were higher in ANBE5 than NC, while higher relative weight of bursa was observed in ANBE3 than NC. The villus height to crypt depth ratio in all experimental groups was better than NC. Conclusion: Acacia nilotica bark extract could be a suitable alternative to antibiotic growth promoters to support the growth in broilers.

• 자원리싸이클링
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• 제32권1호
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• pp.60-66
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• 2023

공급망 관리가 산업의 지속적 성장의 핵심 요소가 되면서 국가적 차원에서 또는 기업적 차원에서 원료가 되는 광물자원의 확보가 중요해지고 있다. 그리고 산업구조에 따라서 광종별 경제적 위상과 공급리스크가 상이하다. 본 연구에서는 광종별 경제적 위상을 살펴보고 위해, 산업별 수요구조와 비용, 비중 등을 반영하여, 광물자원별 국내 산업 경제중요도를 정량할 수 있는 지수(index)를 개발하고 산정하였다. 그 결과 Li, Al, Cu, Si, Co, Ni 등이 우리나라의 산업적 중요도가 높은 것으로 평가되었다. 또한 산업별로 1차금속제조·일반기계·조립금속은 Al, Cu, Zn, Pb 등 베이스메탈이, 정밀기기는 Sn, Ba, Ti이, 반도체는 Si, Ga이, 전자부품은 Li, Ni, Co, Si 등이 산업적 중요도가 높은 것으로 분석되었다. 이러한 결과를 바탕으로 공급망 리스크 등을 추가적으로 반영하여 핵심광물 등을 선정.관리하고 이를 확보하기 위한 전략을 마련해야 할 것이다.

• Journal of Radiation Protection and Research
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• 제47권4호
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• pp.214-225
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• 2022

Background: The conventional cerium-doped Gd₂Al₂Ga₃O₁₂ (GAGG(Ce)) scintillator-based gamma-ray imager has a bulky detector, which can lead to incorrect positioning of the gammaray source if the shielding against background radiation is not appropriately designed. In addition, portability is important in complex environments such as inside nuclear power plants, yet existing gamma-ray imager based on a tungsten mask tends to be weighty and therefore difficult to handle. Motivated by the need to develop a system that is not sensitive to background radiation and is portable, we changed the material of the scintillator and the coded aperture. Materials and Methods: The existing GAGG(Ce) was replaced with Bi₄Ge₃O₁₂ (BGO), a scintillator with high gamma-ray detection efficiency but low energy resolution, and replaced the tungsten (W) used in the existing coded aperture with lead (Pb). Each BGO scintillator is pixelated with 144 elements (12 × 12), and each pixel has an area of 4 mm × 4 mm and the scintillator thickness ranges from 5 to 20 mm (5, 10, and 20 mm). A coded aperture consisting of Pb with a thickness of 20 mm was applied to the BGO scintillators of all thicknesses. Results and Discussion: Spectroscopic characterization, imaging performance, and image quality evaluation revealed the 10 mm-thick BGO scintillators enabled the portable gamma-ray imager to deliver optimal performance. Although its performance is slightly inferior to that of existing GAGG(Ce)-based gamma-ray imager, the results confirmed that the manufacturing cost and the system's overall weight can be reduced. Conclusion: Despite the spectral characteristics, imaging system performance, and image quality is slightly lower than that of GAGG(Ce), the results show that BGO scintillators are preferable for gamma-ray imaging systems in terms of cost and ease of deployment, and the proposed design is well worth applying to systems intended for use in areas that do not require high precision.

• 대한방사선기술학회지:방사선기술과학
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• 제46권6호
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• pp.519-526
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• 2023

This study was intended to evaluate the shielding rate of radiation shields manufactured using 3D printers that have recently been used in various fields by comparing them with existing shields made of lead, and to find out their applicability through experiments. A 3D printer shield made of tungsten filament 1 mm, 2 mm, 4 mm shield, RNS-TX (nanotungsten) 1.1 mm, lead 0.2 mmPb, and 1mmPb were exposed to ^99mTc, ¹⁸F, and ²⁰¹TI for 15, 30, 45 minutes, and 60 minutes after measuring cumulative dose three times. Based on this, the shielding rate of each shield was calculated based on the dose in the absence of the shield. In addition, ^99mTc, ¹⁸F, and ²⁰¹TI were located 100 cm away from the phantom in which the OSLD nano Dot device was inserted, and if there was no shield for 60 minutes, the dose of thyroid was measured using 1.0 mm of lead shield, 1.1 mm of RNS-TX shield, and 2 mm of tungsten shield made by 3D printer. The use of shields during radiation shielding emitted from open radiation sources all resulted in a reduction in dose. The radiation dose emitted from the radionuclides under the experiment was all reduced when the shield was used. This study has been confirmed that tungsten is a material that can replace lead due to its excellent performance and efficiency as shield, and that it even shows the possibility of manufacturing a customized shield using 3D printer.

• 공업화학
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• 제35권2호
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• pp.128-133
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• 2024

안티솔벤트를 이용한 결정화는 밀도 높고 균일한 페로브스카이트 필름을 얻는 효과적인 접근 방법이나, 일반적으로 사용되는 chlorobenzene (CB)과 같은 안티솔벤트는 독성을 가지며, 공기 중에서 페로브스카이트 결정화의 제어가 용이하지 않다. 본 연구에서는 공기 중 공정에 적합하며 친환경적인 안티솔벤트인 isopropyl acetate (IA)를 사용하여 페로브스카이트 태양전지를 제작하고자 하며 사이아노기, 카보닐기 및 벤젠 고리와 같은 작용기를 포함한 ethyl-4-cyanocinnamate (E4CN)을 안티솔벤트에 첨가제로 사용함으로서 성능 및 안정성을 개선하고자 한다. E4CN과 페로브스카이트 결함과의 상호작용으로 페로브스카이트 필름에 존재하는 un-coordinated Pb²⁺ 및 I₂ 결함을 제어할 수 있으며 이로 인한 재조합의 억제와 전하추출의 개선을 관찰할 수 있다. 그 결과 E4CN을 사용한 페로브스카이트 소자는 기준 소자 대비 개선된 18.89%의 최대 전력 변환 효율을 보여준다. 더불어, 기준 소자의 경우, 소자효율이 시간에 따라 급격히 감소하여 200 시간 후 효율값이 0%까지 저하되지만 E4CN이 도입된 소자의 경우, 300 시간 후 초기 광전변환효율의 60%를 유지하는 개선된 안정성을 보여준다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.336-338
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• 1991

Effects of $Nb_2O_5$ addition ranged from 0.0 to 0.75(wt%) on the microstructure and electrical porperties of PZT ceramics have been investigated. The Pb vacancy concentration increases with increasing NbO content. However, the experimental results show the resistivity increases with increasing $Nb^{5+}$ content. This behavior can be explained as a compensation effect and $Nb^{5+}$ can serve as a donar and contribute electrons to the conduction process. According to the law of mass action, this result may reduce the total charge carrier:thus the resistivity increase with NbO content in PZT.

• KSBB Journal
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• 제13권5호
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• pp.477-482
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• 1998

A biosensor with PZT piezoelectric ceramic crystal was developed for the detection of formaldehyde gas. Poled PZT piezoelectric ceramic disk was made from ZrO2, TiO2 and Nb2O5, together with the addition of PbO and polyvinyl alcohol, through various processes of mixing, calcination drying, crushing, forming, sintering, polishing, ion coating and poling. Oscillator circuit of sensor was made of operational amplifier(AD811AN). Formaldehyde dehydrogenase was immobilized onto a piezoelectic ceramic crystal, together with the cofactors, reduced glutathione and nicotinamide adenine dinucleotide. The effect of flow rate on the sensitivity was determined by varing the flow rate of carrier gas from 24.7mL/min to 111.7mL/min through detector cell. The results indicated that as the flow rate was increased, the recovery rate was increased. And a significant increase in the sensitivity was observed in enhanced flow rate of carrier gas. Frequency difference(ΔF) of immobilized PZT piezoelectic disk increased proportionally to the concentration gas and reproduced to repeated exposures of formaldehyde gas(28ppm, Δ68Hz).

• 한국세라믹학회지
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• 제31권8호
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• pp.920-926
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• 1994

Ta doped PZT thin films were prepared by a reactive sputtering method with a 3-gun magnetron co-sputter, and effects of Ta doping on physical and electrical properties of the films were studied. Within the doping range of 0 to 3.6 at%, Ta doping enhanced the crystallographic orientation of (110), but reduced that of (100). Ta doped PZT had a larger grain size of about 20 ${\mu}{\textrm}{m}$ compared with that of 5 ${\mu}{\textrm}{m}$ for un-doped PZT. Pits and holes of PZT films which used to appear with annealing at high temperature due to evaporation of PbO were much suppressed with addition of Ta. The leakage current could be reduced down to 1.27$\times$10-8 A/$\textrm{cm}^2$ and the charge storge density as large as 25.8$\mu$C/$\textrm{cm}^2$ was obtained.

• 한국표면공학회지
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• 제29권4호
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• pp.253-260
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• 1996

Regular spangle hot dip galvanized steel sheets were made in the zinc bath containing a small amount of Al and with the addition of Pb, Sb, Sb-Mg, Sb-Cu and Bi respectively whose average glosses were measured. Zero-spangle hot dip galvanized steel sheets were also made by spraying a 2% $NH_4H_2PO_4$ solution on molten coating surfaces with exactly the same chemical compositions as above used for regular spangle and whose glosses and corrosion losses were also evaluated. For manufacturing zero- spangle hot dip galvanized steel sheets with high brightness, the zinc bath with 0.02%Sb and the spraying of a 2% $NH_4H_2PO_4$ solution were proposed and for better brightness and corrosion resistance, the zinc bath with 0.02% Sb-0.50%Mg and the spraying of a 2% $NH_4H_2PO_4$ solution were also proposed.