• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.979-980
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• 2004

A multi-channel mechanical test machine for HANARO was designed and fabricated based on the design criteria of the multi-channel mechanical test machine sustained at the working conditions of $<400{\square}$, 3 W/g of gamma heating rate, $5{\times}10^{20}\;n/cm^2$, neutron flux and maximum load of 200 MPa. The multi-channel mechanical test machine made of 304 stainless steel consisted of four modules. Two of them locate upper part of the machine and the others locate lower part with 90 degree rotation. Each module was evaluated by determine load-displacement curve of zirconium specimen. Thermal insulators were also made by electron spark-machining of pure aluminum which was prepared in a domestic company.

• Journal of Astronomy and Space Sciences
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• 제32권2호
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• pp.101-112
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• 2015

Magnetic reconnection is a fundamental process occurring in a wide range of astrophysical, heliospheric and laboratory plasmas. This process alters magnetic topology and triggers rapid conversion of magnetic energy into thermal heating and nonthermal particle acceleration. Efforts to understand the physics of magnetic reconnection have been made across multiple disciplines using remote observations of solar flares and in-situ measurements of geomagnetic storms and substorms as well as laboratory and numerical experiments. This review focuses on the progress achieved with solar flare observations in which most reconnection-related signatures could be resolved in both space and time. The emphasis is on various observable emission features in the low solar atmosphere which manifest the coronal magnetic reconnection because these two regions are magnetically connected to each other. The research and application perspectives of solar magnetic reconnection are briefly discussed and compared with those in other plasma environments.

• Applied Science and Convergence Technology
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• 제24권3호
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• pp.47-52
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• 2015

The correlation between admittance and dielectric spectroscopy of dielectric relaxation in lead scandium noibate, have been investigated. Lead scandium niobate, with composition $PbSc_{0.5}Nb_{0.5}O_3$, was prepared by conventional solid state synthesis. Conductance Y'(G), susceptance Y"(B) and capacitance C of lead scandium niobate as a function of frequency and temperature were measured. From the temperature-dependence of RLC circuit, insight into physical significance of the dielectric properties of lead scandium niobate is obtained. The relative strong frequency dependent of dielectric properties in lead scandium niobate is observed, and the phase transition occurred at a broad temperature region. Also, the value of critical exponent ${\gamma}$=1.6 showed on heating process. The long relaxation times part enlarged diffuse by conductivity effects with increasing temperature, and the ordering between $Sc^{3+}$ and $Nb^{5+}$ in PSN influences complex admittance and dielectric properties. Confirmed the typical characteristic of lead-type relaxor in the Raman spectra of lead scandium niobate and major ranges are between 400 and $900cm^{-1}$.

• 한국세라믹학회지
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• 제28권7호
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• pp.568-576
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• 1991

The powder characterization and sintering behavior of alkoxide-derived alumina powders prepared by esterification were investigated. The dried powders were calcined at 700$^{\circ}C$, 900$^{\circ}C$, 1080$^{\circ}C$, 1170$^{\circ}C$ for 1 h. and the resulting crystalline forms were amorphous, {{{{ gamma }} phase, {{{{ theta }}+{{{{ alpha }} phase, and {{{{ alpha }} phase, respectively. The sinterability was best in the case of being calcined at 1170$^{\circ}C$. It was most effective to disperse sintering additive in the initial stage from which acetate was formed. At 1600$^{\circ}C$ for 4 h, 98.5% of relative density was obtained when MgO and Fe2O3 were simultaneously doped, and dense sintered body whose density was near theoretical value was obtained when heating schedule was controlled.

• Preventive Nutrition and Food Science
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• 제2권1호
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• pp.23-28
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• 1997

Physicohemical properties of corn starches isolated from non-glutinous and corn grains fol-lowing γ-irradiation up to 10kGy were investigated. Blue value, water binding capacity and swelling power decreased, while alkali number ad solubility increased by γ-irradiation , which was more pronounced in glu-tinous corn starch than in non-glutinous corn starch. The optical transmittance increased with an increment of heating temperature and applied irradiation doses. No significant difference was observed in Hunter's color value between both starches isolated from non- irradiated and irradiated and irradiated corn grains. Amylograph viscosities decreased remarkably as dose levels increased. The overall effects of γ-irradiation was more distinguished in glutinous starch than in non-glutinous starch.

• 한국세라믹학회지
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• 제33권1호
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• pp.92-100
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• 1996

Amorphous alumina(AA) the precursor of ${\gamma}$-alumina for catalyst support was made in the newly designed ball filled heating column. Some properties of AA as precursor were investigated. In observation of microstruc-ture and pore structure of AA and its derivatives scanning electronic microscope(SEM) and transmission electronic microscope(TEM) were used. It was found that the width of one particle in AA was 45~60$\AA$ and the average distance among the particles ranged 9~12 $\AA$ which suggested a micropore structure. When AA was reacted with water the shape of the surface was found to be altered and acicular bioehmite was formed inside AA which contributed inproved formability. Pore distribution was evaluated for the three samples of AA ground and granulated lump and La2O3 coated alumina. Acid sites were quantitatively determined by ammonia TPD method and the effect of impurity of Na on acid sites was discussed. Water adsorption capacity was evaluated in terms of a desiccant.

• 한국재료학회지
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• 제22권4호
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• pp.195-201
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• 2012

$Ce^{3+}$-doped yttrium aluminum gallium garnet (YAGG:$Ce^{3+}$), which is a green-emitting phosphor, was synthesized by solid state reaction using ${\alpha}$-phase or ${\gamma}$-phase of nano-sized $Al_2O_3$ as the Al source. The processing conditions and the chemical composition of phosphor for the maximum emission intensity were optimized on the basis of emission intensity under vacuum UV excitation. The optimum heating temperature for phosphor preparation was $1550^{\circ}C$. Photoluminescence properties of the synthesized phosphor were investigated in detail. From the excitation and emission spectra, it was confirmed that the YAGG:$Ce^{3+}$ phosphors effectively absorb the vacuum UV of 120-200 nm and emit green light positioned around 530 nm. The crystalline phase of the alumina nanoparticles affected the particle size and the luminescence property of the synthesized phosphors. Nano-sized ${\gamma}-Al_2O_3$ was more effective for the achievement of higher emission intensity than was nano-sized ${\alpha}-Al_2O_3$. This discrepancy is considered to be because the diffusion of $Al^{3+}$ into $Y_2O_3$ lattice is dependent on the crystalline phase of $Al_2O_3$, which affects the phase transformation of YAGG:$Ce^{3+}$ phosphors. The optimum chemical composition, having the maximum emission intensity, was $(Y_{2.98}Ce_{0.02})(Al_{2.8}Ga_{1.8})O_{11.4}$ prepared with ${\gamma}-Al_2O_3$. On the other hand, the decay time of the YAGG:$Ce^{3+}$ phosphors, irrespective of the crystalline phase of the nano-sized alumina source, was below 1 ms due to the allowed $5d{\rightarrow}4f$ transition of the $Ce^{3+}$ activator.

• Journal of Dairy Science and Biotechnology
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• 제23권2호
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• pp.93-98
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• 2005

본 연구는 항원성을 저감한 우유 및 유제품 개발을 위한 기초자료 도출을 위해 열처리와 감마선 조사 처리 시 우유의 화학적, 미생물학적 및 면역적 변화를 비교하였다. 열처리와 감마선 조사 처리 시 열처리 온도와 조사량이 높을수록 유리지방산 함량이 증가하는 경향을 나타내었으며 UHT 처리시와 5 kGy 조사시 유리지방산 함량은 유사하였다. $10^3$ CFU/mL 수준의 원유를 저온, 고온, 초고온으로 열처리시와 1${sim}$10 kGy로 감마선 조사처리 시 모두 일반세균과 대장균 군이 검출되지 않았으나, 일주일 지난 후에도 UHT 처리유와 5kGy 이상 조사 처리유에서 일반세균과 대장균 군이 검출되지 않았다. 원유를 열처리시 arginine, asparate, iso-leucine, leucine, lysine, methionine이 감소된 반면 조사처리에 의해 aspartate, histidine, iso-leucine, leucine, lysine이 감소되어 열처리와 조사처리가 단백질의 일차구조에도 영향을 미칠 수 있는 것(p<0.05)으로 나타났다. 또한, 우유의 항원성은 감마선 조사처리시 5kGy 이상에서 유의적(p<0.05)으로 감소하였다. 이상의 결과로 볼 때 5 kGy 정도의 감마선 조사처리로 UHT 처리시와 유사한 화학적, 미생물학적 효과와 우유의 항원성 감소효과를 기대할 수 있다.

• 한국식품영양과학회지
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• 제31권1호
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• pp.1-6
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• 2002

강낭콩을 가열한 후 B. subtilis ATCC 51189로 발효시켜 새로운 활성 단백질의 생성여부를 확인하였다. 생강낭콩의 수용성 단백질은 열처리에 의하여 감소하였으며, 발효과정에서 단백질의 양은 변화하지 않았으나, 새로운 아미노산이 합성되었다. 생강낭콩의 수용성 단백질(raw protein, RP)은 분자량 118 kDa의 PHA(phytohemagglutinin)의 전형적인 모습을 보였으나, 열처리한 단백질(heated protein, HP)의 경우, RP의 band는 사라지고, 저분자 peptide로 변화되었으며, 발효과정에 의하여 분자량 18.0 kDa의 새로운 단백질(fermented protein, FP)이 생성된 것을 확인하였다. 또한, RP는 128 HU, HP는 4HU, FP는 32HU의 적혈구응집효과를 보였으며, 위암세포(SNU-1)에 대하여 RP 및 FP는 비교적 높은 농도($IC_{50}$/ $\mu\textrm{g}$/mL)에서 항암활성을 보였다. 그리고, RP 및 FP의 경우 1 $\mu\textrm{g}$/mL에서 림프구 증식효과를 보였고, IFN-${\gamma}$, IL-12의 분비를 촉진하였다. 그러나 HP는 항암효과, 림프구 증식효과, cytokine의 분비촉진효과를 보이지 않았다. 따라서, 강낭콩 lectin은 가열에 의하여 활성물질이 파괴되나, B. subtilis에 의한 발효과정에서 새로운 cytokine 분비촉진물질이 생성되는 것을 확인할 수 있었다.

• 한국식품영양과학회지
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• 제32권6호
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• pp.864-869
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• 2003

방사선 조사식품의 수용성 비타민에 대한 안정성을 확인하기 위하여 방사선 조사에 가장 민감하다고 알려져 있는 수용성 비타민 B$_1$과 비타민 C를 택해 닭 가슴살과 딸기와 감귤에 방사선을 조사한 후 닭 가슴살에서 비타민 B$_1$과 딸기와 감귤에서 비타민 C의 함량변화를 조사하였다. 닭가슴살 부위의 경우 감마선 조사시 온도를 냉장과 냉동 상태로 달리 하여 조사한 후 조리 방법을 가열조리와 마이크로웨이브 조리로 달리한 결과 티아민 함량의 손실은 감마선 조사선량에 따른 영향도 관찰되었지만 냉장, 냉동 등과 같은 조사시의 온도 상태도 크게 영향을 미치는 것으로 나타났다. 귤의 비타민 C 함량은 5 kGy까지는 조사에 의한 손실이 나타타지 않았고, 딸기의 비타민 C 함량은 3 kGy의 낮은 조사선량 범위 내에서는 조사선량에 의한 영향보다는 딸기의 품종에 따른 함량이 최종비타민 함량을 더 좌우하는 것으로 나타났다. 따라서 감마선 조사시 비타민의 함량의 변화에는 일정 범위의 조사선량하에서는 조사시의 온도나 식품의 조성 등이 더 큰 인자로 작용할 수 있으며, 가열에 의한 손실도 냉장보다는 냉동 처리 후 조사함에 의해 감소시킬 수 있는 가능성을 보였다.