• 한국식품영양과학회지
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• 제44권6호
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• pp.888-895
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• 2015

패류의 주된 가공부산물인 패각은 주성분이 불용성의 탄산 칼슘으로, 이를 천연 칼슘소재로 활용하기 위해 개조개 패각의 소성분말로부터 가용성 개선 유기산(초산) 처리 칼슘 제조의 최적조건을 구명하고자 하였다. 반응표면분석법을 이용하여 제조한 11개의 시제 초산칼슘의 pH, 용해도 및 수율로부터 구명한 최적 반응조건은 초산 2.70 M 비율에 대하여 개조개 소성분말 1.05 M이었으며, 이의 최적조건을 적용한 개조개 초산칼슘의 실측 pH, 용해도 및 수율은 각각 pH 7.04, 93.0% 및 267.5%로 예측치와 유사한 결과를 얻었다. 시제 초산칼슘의 완충능은 pH 4.88~4.92 범위였으며, 칼슘 함량과 용해도는 20.7~22.8 g/100 g과 97.2~99.6%였다. FT-IR, XRD 분석 및 FESEM을 통한 미세구조는 비정형 결정으로 calcium acetate monohydrate로 확인되었다. 개조개 패각은 칼슘소재뿐만 아니라 가용성을 높인 유기산 칼슘으로 칼슘강화용 식품소재로의 이용 가능성이 높을 것으로 판단되었다.

• 한국산림과학회지
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• 제25권1호
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• pp.73-79
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• 1975

나자식물(裸子植物) 4과(科), 12종(種)과 피자식물(被子植物) 12과(科), 18종(種), 6품종(品種), 3계통(系統)의 한국산(韓國産) 경제수종(經濟樹種) 및 관상수종(觀賞樹種)의 종자(種子), 삽목(揷木), 접수(接穗) 및 생체(生體)에 X선(線) 또는 ${\gamma}$선(線)을 급조사(急照射), 반급조사(半急照射) 또는 완조사(緩照射)를 실시하여 수종별(樹種別) 방사선감수성(放射線感受性) 및 변이(變異)의 출현(出現)을 조사(調査)하였다. 공시수종(供試樹種)의 대부분(大部分)은 높은 방사선감수성(放射線感受性)을 보였으며 침엽수(針葉樹)는 LD-50이 1.2 kR~13.2 kR 범위(範圍)로 평균(平均) 5.4 kR의 심(甚)히 높은 감수성(感受性)을 보였고, 활엽수(濶葉樹)는 LD-50이 7.0 kR-18.5 kR범위(範圍)로 평균(平均) 12.7 kR이였으며 수종간(樹種間)의 비교방사선감수성(比較放射線感受性)을 LD-50을 기준으로 분류(分類)하였다(Table 2). 출현(出現)하는 변이중(變異中)에는 반문엽(斑紋葉)이 가장 많았고, 백자(白子), 엽록소결핍(葉綠素缺乏), 기형엽(奇形葉), 기형과(奇形果)등의 출현(出現) 및 약밤나무의 대형엽(大形葉) 아조변이(芽條變異)와 측백나무의 황색엽(黃色葉) 아조변이(芽條變異)가 유기(誘起)되었다.

• 폴리머
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• 제36권1호
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• pp.22-28
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• 2012

그래핀의 우수한 열적 특성을 이용하여 에폭시 수지의 열전도 특성을 향상시키며 전기 절연성질을 유지하는 기능화된 그래핀/에폭시 복합체를 제작하여 전기 및 열전도도를 측정하였다. 기능화된 그래핀은 Hummers법을 이용하여 산화그래핀(GO)을 얻어낸 후 aluminum isopropoxide를 졸-젤 반응을 통해 $Al(OH)_3$를 그래핀 표면에 도입하여 제작하였다(Al-GO). GO와 Al-GO의 기능화 여부 확인을 위하여 XPS, FE-SEM, FE-TEM 분석을 시행하였으며 GO 표면에 $Al(OH)_3$ 층이 생성된 것을 확인하였다. 기능화된 그래핀/에폭시 복합체는 bisphenol A(DGEBA) 계열의 에폭시에 1, 3 wt%의 GO와 Al-GO를 첨가하여 전기저항을 측정하였으며 Al-GO가 GO와 비교하여 전기 절연성질이 우수하였다. 또한 DGEBA와 bisphenol F(DGEBF) 계열의 에폭시에 1 wt%의 GO와 Al-GO를 첨가하여 열전도 특성을 비교하였으며 순수 에폭시 레진과 비교하여 Al-GO/DGEBF는 23.3%, Al-GO/DGEBA는 21.8%의 열전도도 증가를 보였다.

• 대한치과재료학회지
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• 제43권4호
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• pp.343-349
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• 2016

This experiment was carried out to examine whether the post-firing heat treatment is effective in increasing the hardness of metal-ceramic alloy of the Pd-Au-Ag-Sn system. Precipitation hardening by holding at $600^{\circ}C$ after simulated complete porcelain firing in a metal-ceramic alloy of the Pd-Au-Ag-Sn system was examined by observing the change in hardness, crystal structure, and microstructure using a hardness test, X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The hardness of the alloy increased apparently by holding the specimen at $600^{\circ}C$ for 30 min after simulated complete porcelain firing. The formation of fine grain interior precipitates during holding at $600^{\circ}C$ caused the formation of lattice strain in the grain interior, resulting in apparent hardening. The faster cooling rate (stage 0) during simulated complete porcelain firing resulted in more effective precipitation hardening during holding at $600^{\circ}C$. From the above results, an appropriate post-firing heat treatment, such as holding at $600^{\circ}C$ for 30 min after complete porcelain firing may increase the durability of metal-ceramic prostheses composed of Pd-Au-Ag-Sn alloy.

• 대한치과재료학회지
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• 제44권3호
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• pp.197-206
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• 2017

본 연구에서는 포세린 소성과정 동안 금속하부구조물의 경도가 하강하는 문제점을 개선하기 위해 모의소성 시 산화처리 단계에서 서냉(bench cooling) 대신 급랭(ice-quenching)으로 합금을 냉각시킴으로써 나머지 소성단계 동안 경화효과를 얻을 수 있을 것으로 예측하고, 이를 확인하기 위해 실험을 진행하였다. 본 연구에서는 Pd-Ag-Sn-Au계 금속-세라믹용 합금을 사용하여 실험을 진행하여 다음과 같은 결과를 얻었다. 산화처리 후 stage 0으로 냉각한 시편과 산화처리 후 급랭한 시편을 glaze까지 모의소성한 결과, 두 시편 모두 소성 첫 단계에서 경도가 상승한 후 지속적으로 경도가 하강하였으나, 산화처리 후 급랭한 시편의 최종 경도가 더 높게 나타났다. 소성 첫 단계에서 일어난 경도의 상승은 면심입방구조의 Pd-Ag-rich 기지에서 면심정방구조의 Pd3(Sn, Ga, In)상의 석출로 인해 기지와 석출물간의 계면에 생성된 격자변형에 기인하였다. 모의소성과정에 따른 경도의 하강은 석출물이 조대화됨에 따라 석출물과 기지사이의 계면의 면적이 감소되어 격자 뒤틀림이 해소된 것에 기인하였다.

• 한국토양비료학회지
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• 제48권5호
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• pp.332-339
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• 2015

The objective of this study was to evaluate the effectiveness of different biochars on the removal of heavy metals from aqueous media. The experiment was carried out in aqueous solutions containing $200mg\;CdL^{-1}$ or $200mg\;PbL^{-1}$ using two different biochars derived from soybean stover and orange peel (20 mg Cd or $Pbg^{-1}$ biochar). After shaking for 24 hours, biochars were filtered out, and Cd and Pb in the filtrate were analyzed by flame atomic absorption spectrophotometer (FAAS). In order to provide information regarding metal binding strength on biochars, sequential extraction was performed by modified SM&T (formerly BCR). The results showed that 70~100% of initially added Cd and Pb was adsorbed on biochars and removed from aqueous solution. The removal rate of Pb (95%, 100%) was higher than that of Cd (70%, 91%). In the case of Cd, orange peel derived biochar (91%) showed higher adsorption rate than soybean stover derived biochar (70%). Cd was adsorbed on the biochar mainly in exchangeable and carbonates fraction (1st phase). In contrast, Pb was adsorbed on it mainly in the form of Fe-Mn oxides and residual fraction (2nd and 4th phase). The existence of Cd and Pb as a form of surface-precipitated complex was also observed on the surfaces of biochars detected by field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectrometer (EDAX).

• Journal of Electrochemical Science and Technology
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• 제9권4호
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• pp.282-291
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• 2018

The pristine fluorine-doped $SnO_2$ (abbreviated as FTO) inverse opal (IO) was developed using a 410 nm polystyrene bead template. The nanolayered copper tungsten oxide ($CuWO_4$) was decorated on the FTO IO film using a facile electrochemical deposition, subsequently followed by annealing at $500^{\circ}C$ for 90 min. The morphologies, crystalline structure, optical properties and photoelectrochemical characteristics of the FTO and $CuWO_4$-decorated FTO (briefly denoted as $FTO/CuWO_4$) IO film were investigated by field emission scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy and electrochemical impedance spectroscopy, showing FTO IO in the hexagonally closed-pack arrangement with a pore diameter and wall thickness of about 300 nm and 20 nm, respectively. Above this film, the $CuWO_4$ was electrodeposited by controlling the cycling number in cyclic voltammetry, suggesting that the $CuWO_4$ formed during 4 cycles (abbreviated as $CuWO_4$(4 cycles)) on FTO IO film exhibited partial distribution of $CuWO_4$ nanoparticles. Additional distribution of $CuWO_4$ nanoparticles was observed in the case of $FTO/CuWO_4$(8 cycles) IO film. The $CuWO_4$ layer exhibits triclinic structure with an indirect band gap of approximately 2.5 eV and shows the enhanced visible light absorption. The photoelectrochemical (PEC) behavior was evaluated in the 0.5 M $Na_2SO_4$ solution under solar illumination, suggesting that the $FTO/CuWO_4$(4 cycles) IO films exhibit a photocurrent density ($J_{sc}$) of $0.42mA/cm^2$ at 1.23 V vs. reversible hydrogen electrode (RHE, denoted as $V_{RHE}$), while the FTO IO and $FTO/CuWO_4$(8 cycles) IO films exhibited a $J_{sc}$ of 0.14 and $0.24mA/cm^2$ at $1.23V_{RHE}$, respectively. This difference can be explained by the increased visible light absorption by the $CuWO_4$ layer and the favorable charge separation/transfer event in the cascading band alignment between FTO and $CuWO_4$ layer, enhancing the overall PEC performance.

• 한국초전도ㆍ저온공학회논문지
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• 제21권1호
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• pp.18-24
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• 2019

This study was carried out to investigate the effect of milling of boron (B), which is one of raw materials of $MgB_2$, on the critical current density ($J_c$) of $MgB_2$. B powder used in this study is semi-amorphous B (Pavezyum, Turkey, 97% purity, 1 micron). The size of B powder was reduced by planetary milling using $ZrO_2$ balls (a diameter of 2 mm). The B powder and balls with a ratio of 1:20 were charged in a ceramic jar and then the jar was filled with toluene. The milling time was varied from 0 to 8 h. The milled B powders were mixed with Mg powder in the composition of (Mg+2B), and the powder mixtures were uniaxially pressed at 3 tons. The powder compacts were heat-treated at $700^{\circ}C$ for 1 h in flowing argon gas. Powder X-ray diffraction and FWHM (Full width at half maximum) were used to analyze the phase formation and crystallinity of $MgB_2$. The superconducting transition temperature ($T_c$) and $J_c$ of $MgB_2$ were measured using a magnetic property measurement system (MPMS). It was found that $B_2O_3$ was formed by B milling and the subsequent drying process, and the volume fraction of $B_2O_3$ increased as milling time increased. The $T_c$ of $MgB_2$ decreased with increasing milling time, which was explained in terms of the decreased volume fraction of $MgB_2$, the line broadening of $MgB_2$ peaks and the formation of $B_2O_3$. The $J_c$ at 5 K increased with increasing milling time. The $J_c$ increase is more remarkable at the magnetic field higher than 3 T. The $J_c$ at 5 K and 4 T was the highest as $4.37{\times}10^4A/cm^2$ when milling time was 2 h. The $J_c$ at 20 K also increased with increasing milling time. However, The $J_c$ of the samples with the prolonged milling for 6 and 8 h were lower than that of the non-milled sample.

• 한국재료학회지
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• 제29권11호
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• pp.727-733
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• 2019

In this study, the glass melting properties are evaluated to examine the possibility of using refused coal ore as replacement for ceramic materials. To fabricate the glass, refused coal ore with calcium carbonate and sodium carbonate in it (which are added as supplementary materials) is put into an alumina crucible, melted at $1,200{\sim}1,500^{\circ}C$ for 1 hr, and then annealed at $600^{\circ}C$ for 2 hrs. We fabricate a black colored glass. The properties of the glass are measured by XRD (X-ray diffractometry) and TG-DTA (thermogravimetry-differential thermal analysis). Glass samples manufactured at more than $1,300^{\circ}C$ with more than 60 % of refused coal ore are found by XRD to be non-crystalline in nature. In the case of the glass sample with 40 % of refused coal ore, from the sample melted at $1,200^{\circ}C$, a sodium aluminum phosphate peak, a disodium calcium silicate peak, and an unknown peak are observed. On the other hand, in the sample melted at $1,300^{\circ}C$, only the sodium aluminum phosphate peak and unknown peak are observed. And, peak changes that affect crystallization of the glass according to melting temperature are found. Therefore, it is concluded that glass with refused coal ore has good melting conditions at more than $1,200^{\circ}C$ and so can be applied to the construction field for materials such as glass tile, foamed glass panels, etc.

• 한국방사선학회논문지
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• 제14권7호
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• pp.899-906
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• 2020

WSS 측면 검사는 척추의 질환을 진단하기 위해 매우 중요한 검사이다. 최근 대면적의 Long Length Detector가 보급되고 있어 피폭선량과 검사 시간을 효율적으로 줄일 수 있으며, 낙상 고위험군 환자 및 소아, 청소년기 환자의 검사에 매우 효율적으로 적용할 수 있다. 하지만 1회 조사로 영상을 얻기 때문에 기하학적인 척추의 해부학적 구조상 허리뼈 보다 목뼈 부근이 상대적으로 체적이 적어 목뼈 부위의 영상 품질은 진단 가치가 매우 하락한다는 단점이 있다. 이에 본 연구는 WSS 측면 검사에서 균일한 영상품질을 얻기 위해 3D 프린팅 기술과 구리 필라멘트를 이용하여 부가 필터를 제작하고 결과를 분석하고자 한다. 3D 프린팅 기술은 원하는 모양을 손쉽게 출력할 수 있는 장점이 있어 산업 분야 전반에 광범위하게 사용되고 있으며, 최근 구리 소재의 필라멘트가 개발되어 부가 필터로서의 가능성을 확인하였다. WSS 측면 검사에서 부가 필터 적용시 CNR과 SNR이 우수하게 측정되어 부가필터의 사용 가능성을 확인 하였다.