• Journal of Radiation Protection and Research
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• 제29권4호
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• pp.251-256
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• 2004

Phoswich 검출기를 제작하기 위하여 무기 섬광체인 CsI(Tl), $CdWO_4(CWO),\;Bi_4Ge_3O_{12}(BGO)$와 $Gd_2SiO_5:Ce(GSO)$의 특성을 연구하였다. CsI(Tl), CWO, BGO 및 GSO 섬광체의 radioluminescence 중심파장은 550 nm, 475 nm, 490 nm 및 440 nm이였고, neutral filter를 사용하여 측정한 CsI(Tl), CWO, BGO 및 GSO 섬광체의 절대광량은 각각 54890 phonon/MeV, 17762 phonon/MeV, 8322 phonon/MeV 및 8932 phonon/MeV이였으며, single photon method로 측정한 형광감쇠시간은 각각 $1.3{\mu}s,\;8.17{\mu}s$, 213 ns 및 37 ns이였다. 플라스틱 섬광체와 CsI(Tl) 섬광체를 사용하여 phoswich 검출기를 제작하였고 PSD(pulse shape discriminator) 방법으로 ${\beta}$ 입자와 ${\gamma}$ 선을 구별하며 각각의 방사선에 대한 파고 스펙트럼을 측정하였다.

• 콘크리트학회지
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• 제7권4호
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• pp.169-179
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• 1995

본 논문은 고강도 콘크리트($f'_c=700kg/cm^2$)를 사용한 보_기둥 접합부의 소성힌지 확산을 위하여 중간철근을 수직으로 앵커한 수직앵커형 중간철근으로 보 단부를 보강함으로써 보_기둥 접합부에 발생하는 소성힌지를 보 내측으로 1.0d 만큼 확산시키고자 하는 것이다. 실험의 주 변수로는 중간철근의 유물 및 앵커여부로 설정하여 중간철근의 보강형태에 따른 부재의 역학적 거동을 규명하도록 하였다. 실험결과로부터 보 단부의 1.0d부분을 수직앵커형 중간철근으로 보강하면 소성힌지를 1.0d 부분으로 확산할 수 있었으며, 에너지 분산능력도 ACI318-89에 따라 설계한 관례적인 실험체에 비하여 약 1.6배정도 향상되었다.

• Korean Chemical Engineering Research
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• 제40권6호
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• pp.752-756
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• 2002

PDP(Plasma Display Panel)용 녹색 형광체인 $Zn_2SiO_4:Mn$ 형광체의 제조에 있어 콜로이드 분무 열분해법을 도입하고, $Zn_2SiO_4$ wellimite 결정의 $Si^{4+}$ 자리를 치환하는 $Gd^{3+}/Li^+$ 부활성제를 첨가하여 형광체의 발광특성을 향상시키고자 하였다. 14 nm 크기의 fumed silica 입자를 규소 전구체로 도입한 콜로이드 분무열분해법에 의해서 제조되어진 $Zn_2SiO_4:Mn$ 입자는 응집이 없는 구형의 형상, 작은 입자 크기 및 좁은 입도 분포를 가졌다. $Gd^{3+}/Li^+$ 함량은 $Zn_2SiO_4:Mn$ 형광체 입자의 발광특성에 영향을 끼쳤으며, 적정한 함량의 $Gd^{3+}/Li^+$ 부활성제를 첨가함으로써 진공 자외선하에서 형광체의 발광휘도를 향상시키고, 잔광시간을 크게 줄일 수 있었다. 분무 열분해법에 의한 $Gd^{3+}/Li^+$이 코도핑된 $Zn_2SiO_4:Mn$ 형광체 입자의 제조에 있어서 후열처리 온도는 형광체의 발광특성을 결정짓는 주요한 인자이다. 0.1 mol%의 $Gd^{3+}/Li^+$ 부활제를 포함하고 $1,145^{\circ}C$ 온도에서 소결된 $Zn_2SiO_4:Mn$ 형광체 입자는 상업용 형광체에 비해 5% 높은 발광 휘도과 5.7 ms의 잔광시간을 가졌다.

• 농업과학연구
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• 제45권4호
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• pp.601-614
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• 2018

Chitosan with a natural antimicrobial property has been introduced to protect horticultural crops from diseases as an environmentally friendly method. The purpose of this study was to investigate the effects of the pre-harvest application of chitosan on growth and quality during the late stage of fruit development and on the simulated marketing of the peach fruit (Prunus persica L.). The application of chitosan with calcium chloride ($100mg{\cdot}L^{-1}$) three times at one week intervals 4 weeks before the harvest significantly increased the fruit weight, changed the fruit shape, and reduced the fruit length/diameter ratio giving the peach fruits a round oblate shape. The calcium treatment contributed to enhancing or maintaining the storage potential by increasing the flesh firmness. However, at higher concentrations of $CaCl_2$, i.e., > $600mg{\cdot}L^{-1}$, the positive effects of the chitosan application were offset, and fruit growth was not affected by calcium alone. The application of the chitosan/calcium mixture delayed fruit softening; however, this effect was shortened when the storage temperature was $20^{\circ}C$ rather than $15^{\circ}C$. The internal quality of the fruit was profoundly affected by the concentration of calcium added to the chitosan, and delayed fruit maturation was observed at a higher concentration of calcium. The pre-harvest application of chitosan with calcium contributes to the enhancement of food safety by inhibiting the occurrence of diseases during postharvest handling. Considering the above results, chitosan has the potential to improve both the yield of peach fruits and their storability. Because chitosan can enhance the freshness and shelf-life of fresh produce, it is necessary to examine its effects on other horticultural crops.

• 분석과학
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• 제6권5호
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• pp.501-508
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• 1993

$^{241}Am-Be$(${\alpha}$, n) 중성자 선원의 중성자/감마선(n/${\gamma}$) 복합 방사선장에서 $^6Li$(n, ${\alpha}$)T 핵반응을 이용하고 두 섬광체, BC 501($C_8H_{10}$)과 Cerium의 섬광 감쇠 시간차와 동일 섬광체 내에서의 n/${\gamma}$에 대한 서로 다른 섬광감쇠 시간차를 병용하여 PSD(Pulse Shape Disciminator) 및 CFD(Constant Fraction Discriminator) 방법으로 n와 ${\gamma}$성분을 분리 측정하였으며 $^6Li$ 속중성자 분광계의 figure of merit는 1.36으로 평가되었다.

• 한국의학물리학회지:의학물리
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• 제3권1호
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• pp.9-18
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• 1992

4MeV X-선을 제조된 beta-eucryptite 에 조사시 킨 후, 300K-600K 온도 구간에서 열자극 방광을 측정하였다. 혼합되어 측정된 열자극발광 스펙트럼은 342K, 392K, 438K, 474K 과 572K 에서 열자극발광 peak가 나타난다. 527K 의 열자극방광 스펙트럼은 retrapping이 일어나는 2nd kinetic order 임을 알았다. Peak shape 법의 활성화에너지는 1.03eV이었고 이탈진 동수는 3.9$\times$$10^{8}$sec$^{-1}$이었다. 또한 initial rise법과 온도 상승률에 따른 활성화 에너지는 각각 1.19$\pm$0.03eV, 1.02$\pm$0.05eV로 나타났다. 최고의 열자극발광 세기를 갖는 온도 527K를 유지하고 측정한 isothermal decay 스펙트럼에 의한 이탈진동수는 heating rate법의 결과와 유사한 2.8$\times$$10^{8}$sec$^{-1}$이었다. 50Gy의 조사선량 범위까지는 조사선량에 따른 열자극발광 세기의 선형성이 유지되었지만, 그 이상의 영역에서는 supralinearity가 나타난 후 saturation되었다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1993년도 수공학연구발표회논문집
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• pp.175-182
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• 1993

The complex nature of low flow transport and tranformation of nonconservative pollutants in natural streams with pools and riffles has been investigated using a numerical solution of a proposed mathematical model that is based on a set of mass balance equations describing hydrodynamic processes (advection, dispersion, and mass exchange mechanicms in streams and in storage zones) and chemical processes (reaction or decay). In this study, a mathematical model (named "Storage-Transformation Model") has been developed to predict adequately the non-Fickian nature of mixing and transformation mechanisms for decaying substances in natural streams under low flow conditions. Comparisons between the concentration-time curves predicted usingthe proposed model and the measured stream data shows that the Storage-Transformation Model yields better agreements in the goneral shape, peak concentration and time to peak than the 1-D dispersion model. The result of this study also demonstrates the differences between transport in pool-and-riffle streams versus transport in more uniform channels. The proposed model shows significant improvement over the conventional 1-D disperision model in predicting natural mixing and stroage processes in streams through pools and riffles.

• 한국해양공학회지
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• 제34권2호
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• pp.66-76
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• 2020

A light buoy is equipped with lighting functions and navigation signs. Its shape and colors indicate the route to vessels sailing nearby in the daytime, with its lights providing this information at night. It also plays a role in notifying the presence of obstacles such as reefs and shallows. When a light buoy operates in the ocean, the visibility and angle of light from the lantern installed on the buoy changes, which may cause them to function improperly. Therefore, it is necessary for the buoy to have stable and minimal motions under given environmental conditions, mainly waves. In this study, motion analyses for a newly developed lightweight light-buoy in waves were performed to predict the motion performance and determine the effect of the developed appendages for improving the motion performance. First, free decay tests, including benchmark cases, were performed using computational fluid dynamics (CFD) to estimate the viscous damping coefficients, which could not be obtained using potential-based simulations. A comparison was made of the results from potential-based simulations with and without considering viscous damping coefficients, which were estimated using CFD. It was confirmed that the pitch and heave motions of the buoy became smaller when the developed appendages were adopted.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.283-291
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• 2024

Sodium cooled Fast Reactors (SFR) are built with several engineered safety features and hence a severe accident such as a core melt accident is hypothetical with a probability of <10^-6/ry. However, in case of such accidents, the mixture of the molten fuel and structural materials interacts with sodium. This phenomenon is known as Molten Fuel Coolant Interaction (MFCI) and results in fragmentation of the melt due to various instabilities. The fragmented particles settle as a debris bed on the core catcher at the bottom of the reactor vessel, and continue to generate decay heat. Characteristics of the debris particles play a vital role in heat transfer from the bed and need thorough investigation. The size, shape, and physical state of the debris depend on the associated fragmentation mechanism, superheating of the melt, and sodium temperature. Experiments have been conducted by releasing simulated corium, a molten mixture of alumina and iron generated by the aluminothermy process at ~2400 ℃ into liquid sodium, to study the fragmentation phenomena. After the experiment, the fragmented debris was retrieved and the particle size distribution was determined by sieve analysis. The debris was subjected to microscopic investigation for obtaining morphological characteristics. Based on the characteristics of debris, an attempt has been made to assess of fragmentation mechanism of simulated corium in sodium.

• 한국진공학회지
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• 제12권S1호
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• pp.113-115
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• 2003

We investigate transmission of light in nanoscale structures. We present spatial and temporal domain measurements of the dephasing of surface plasmon excitations in metal films with periodic nano-hole arrays. By probing coherent spatial SP propagation lengths of a few f1. $\mu$m and an ultrafast decay of the SP polarization on a 10 fs timescale, we demonstrate that the SP transmission peaks are homogeneously broadened by the SP radiative lifetime. The pronounced wavelength and hole size dependence of the dephasing rate shows that the microscopic origin of the conversion of SP into light is a Rayleigh-like scattering by the periodic hole array. We have experimentally studied the dephasing of surface plasmon excitations in metallic nano-hole arrays. By relating nanoscopic SP propagation, ultrafast light transmission and optical spectra, we demonstrate that the transmission spectra of these plasmonic bandgap structures are homogeneously broadened. The spectral line shape and dephasing time are dominated by Rayleigh scattering of SP into light and can varied over a wide range by controlling the resonance energy and/or hole radius. This opens the way towards designing SP nano-optic devices and spatially and spectrally tailoring light -matter interactions on nanometer length scales.