• 한국방사선학회논문지
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• 제16권7호
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• pp.953-960
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• 2022

양성자과학연구단의 100-MeV 양성자선형가속기의 양성자를 사용하여 천연 ¹⁶⁹Tm과 핵반응을 일으켜 ¹⁶⁷Yb 방사성동위원소를 생성하였다. 생성된 동위원소는 17.5분의 반감기를 가지며 ¹⁶⁷Tm로 붕괴한다. 이때 발생하는 감마선을 HPGe 검출시스템을 사용하여 측정하였다. 검출기의 에너지 교정 및 검출기의 효율 측정은 표준선원을 사용하여 결정하였다. 기존에 알려진 Table of Isotopes의 주요 감마선 에너지는 모두 측정되었다. 한편, 현재까지 알려진 발생되는 감마선의 강도에 대한 정보는 매우 부정확한 상황이다. 따라서 본 연구를 통하여 주요 감마선에 대한 붕괴 강도를 정확하게 측정하였다. 전체적으로 기존에 알려져 있던 결과들과 상이한 차이를 보였으며 특히 113.3 및 106.2 keV 감마선 같은 주 붕괴 감마선의 강도들이 과대평가 되었다는 사실을 알게 되었고 62.9, 116.7 및 143.56 keV의 감마선 들은 과소평가 된 감마선들임을 알게 되었다. 본 연구의 결과는 핵융합 연구, 천체 물리학 및 핵물리 분야에 있어서 중요한 정보가 될 것으로 생각된다.

• 한국입자에어로졸학회지
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• 제9권4호
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• pp.209-219
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• 2013

We have used the modified diffusion flame burner to synthesize silica coated iron oxide nanoparticles having enhanced superparamagnetic property. Silica-encapsulated iron oxide particles were directly observed using a high resolution transmission electron microscope. From the energy dispersive X-ray spectroscopy (EDS) and zeta potential measurements, the iron oxide particles were found to be completely covered by a silica coating layer. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements revealed that the iron oxide core consists of ${\gamma}-Fe_2O_3$ rather than ${\alpha}-Fe_2O_3$. Our magnetization measurements support this conclusion. Biocompatibility test of the silica-coated iron oxide nanoparticles is also conducted using the protein adsorption onto the coated particle.

• 천문학회보
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• 제41권1호
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• pp.38.1-38.1
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• 2016

Gamma ray burst, the most brightest explosion phenomena in the current universe is well suited for study of high redshift universe. We report the afterglow multi-wavelength observation and GTC spectroscopy follow up of GRB 140304A which was exploded at z=5.283. The spectrum was shown damped Lyman alpha features and a series of absorption lines S, Si, SiII*, Oi, CII, CII*, SiIV are clearly detected at common redshift. Clear optical flares are detected when X-ray flare happened and a possible gamma-ray excess also. At this conference, we report on implications for the GRB host and environments using its absorption features which place the results in context to other well studied high redshift GRBs and studies about the ejecta using its observed flaring activities.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3795-3802
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• 2022

NaI(Tl) scintillation materials are considered to be one of many materials that are used exclusively for γ-ray detection and spectroscopy. The gamma-ray spectrometer is not an easy-to-use device, and the accuracy of the numerical values must be carefully checked based on the rules of the calibration technique. Therefore, accurate information about the detection system and its effectiveness is of greater importance. The purpose of this study is to estimate, using an analytical-numerical formula (ANF), the purely geometric solid angle, geometric efficiency, and total efficiency of a cylindrical NaI(Tl) γ-ray detector with a side-through hole. This type of detector is ideal for scanning fuel rods and pipelines, as well as for performing radio-immunoassays. The study included the calculation of the complex solid angle, in combination with the use of various points like gamma sources, located axially and non-axially inside the through detector side hole, which can be applied in a hypothetical method for calibrating the facility. An extended γ-ray energy range, the detector, source dimensions, "source-to-detector" geometry inside the side-through hole, path lengths of γ-quanta photons crossing the facility, besides the photon average path length inside the detector medium itself, were studied and considered. This study is very important for an expanded future article where the radioactive point source can be replaced by a volume source located inside the side-trough hole of the detector, or by a radioactive pipeline passing through the well. The results provide a good and useful approach to a new generation of detectors that can be used for low-level radiation that needs to be measured efficiently.

• Macromolecular Research
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• 제17권8호
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• pp.603-608
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• 2009

Novel ultra-high molecular weight polyethylene (UHMWPE)/zirconia composites were previously prepared by the in situ polymerization of ethylene using a Ti-based Ziegler-Natta catalyst supported on to the surface of zirconia, as a bearing material for artificial joints. Tribological tests revealed that a uniform dispersion of zirconia in UHMWPE markedly increased the wear resistance. The effects of zirconia content on the oxidation behavior of the ${\gamma}$-ray-treated UHMWPE/zirconia composite surfaces were examined. The oxidation index that estimates the oxidation degree as the content of total carbonyl compounds was monitored using Fourier transform infrared spectroscopy-attenuated total reflectance. The changes in the surface composition due to the oxidation were confirmed by electron spectroscopy for chemical analysis. The extent of oxidation decreased with increasing zirconia content, which was attributed to the increased crystallinity as well as the decreased polymer portion of the UHMWPE/zirconia composites.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2601-2606
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• 2020

In this study, we expanded the performance of the existing EXVol code and performed empirical experiments and calculations. A high-resolution gamma spectroscopy system was constructed, and a standard point source and a standard volume source were measured with an HPGe detector with 43.1% relative efficiency. EXVol was verified by quantitative comparison of the detection efficiencies determined by measurements and calculations. To introduce the concept of the detector scanning that occurs in the actual measurement into the EXVol code, a collimator was placed between the source and detector. The detection efficiency was determined in the asymmetric arrangement of the source and detector with a collimator. A collimator made of lead with a diameter of 15 mm and a thickness of 50 mm was installed between the source and the detector to determine the detection efficiency at a specific location. The calculation result was contour plotted so that the distribution of detection efficiency could be visually confirmed. The relative deviation between the measurements and calculations for the coaxial and asymmetric structures was 10%, and that for the collimation structure was 20%. The results of this study can be applied to research using γ-ray measurements.

• Journal of Astronomy and Space Sciences
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• 제36권3호
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• pp.115-119
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• 2019

This paper is a part of the series on positron annihilation spectroscopy of two-phase diffuse gas-and-dust aggregates, such as interstellar medium and the young remnants of type II supernovae. The results obtained from prior studies were applied here to detect the relationship between the processes of the annihilation of the K-shell electrons and incident positrons, and the effects of these processes on the optical spectra of their respective atoms. Particular attention was paid to the Doppler broadening of their optical lines. The relationship between the atomic mass of the elements and the Doppler broadening, ${\Delta}{\lambda}_D$ (${\AA}$), of their emission lines as produced in these processes was established. This relationship is also illustrated for isotope sets of light elements, namely $^3_2He$, $^6_3Li$, $^7_3Be$, $^{10}_5B$ and $^{11}_5B$. A direct correlation between the ${\gamma}-line$ luminosity ( $E_{\gamma}=1.022MeV$) and ${\Delta}{\lambda}_D$ (${\AA}$) was proved virtually. Qualitative estimates of the structure of such lines depending on the positron velocity distribution function, f(E), were made. The results are presented in tabular form and can be used to set up the objectives of further studies on active galactic nuclei and young remnants of type II supernovae.

• Nuclear Engineering and Technology
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• 제32권3호
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• pp.205-213
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• 2000

A series of laboratory experiments was conducted to investigate the fixation characteristics of poly(vinylalcohol)-poly(methacrylic acid)(PVA-PMAA) mixed solution on the soluble ${\gamma}$- radionuclides. Using the potentiometric titration technique, it was found out that the PVA and PMAA in a solution form intermacromolecular complex. The mobilized portion of each radionuclide by water from sand surface treated with a fixative was measured by ${\gamma}$-ray spectroscopy. The mobilized portion of minor radionuclides such as 241Am, 154Eu, 155Eu and 144Ce were higher than those of 134Cs and 137Cs. The capability of PVA-PMAA system was better among the candidate solutions for the fixation of total ${\gamma}$-radioactivity. 134,137Cs which is composed of more than 85 % of total ${\gamma}$-radioactivity could be fixed effectively by the PVA-PMAA solution.

• 분석과학
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• 제16권5호
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• pp.426-429
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• 2003

Neutron induced prompt gamma-ray spectroscopy (NIPS) system equipped with a $^{252}Cf$ neutron source and a n-type coaxial HPGe detector was installed for the quantitative analysis of aqueous samples in KAERI, Korea. Since the thermal neutron flux for the $^{252}Cf$ neutron source is relatively low compared to that for the reactor, the use of a thermal neutron reflector in the NIPS system may lead to improved results. The enhancement by using various reflectors was carried out by comparing the Cl peak with or without a cadmium plate between sample and the $^{252}Cf$ source. The use of pyrolitic graphite as a reflector provided a good result.

• 분석과학
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• 제16권1호
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• pp.39-47
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• 2003

시료 전처리가 필요 없는 감마선 분광분석법을 이용하여 지하수 중의 라듐 ($^{226}Ra$) 분석을 위한 측정법을 확립하였다. 방사평형된 딸핵종을 이용한 라듐의 분석 시 가장 문제가 되는 대기 중 라돈 딸핵종에 의한 바탕계수는 측정함 내부로 질소가스를 흘려주므로써 해결하였고, 라듐과 그 딸핵종들 사이의 방사평형 과정에서 생성된 라돈가스의 용기 외부로의 누출은 밀폐된 알루미늄 용기를 사용함으로써 방지할 수 있었다. 또한 측정용기 내부의 공기층에 의한 방사능 변화정도를 조사하기 위하여 임의로 공기층을 만들어 측정한 결과, 물 속에 녹은 라돈의 공기층으로의 발산에 의한 방사능 변화정도는 통상적인 측정오차인 5% 범위 이내였다. 측정 시 검출기 주위로 질소가스를 흘려줌으로서 대기 중 라돈 딸핵종에 의한 간섭을 제거하였고, 검출하한값을 0.02 Bq/L로 낮출 수 있었다. 이는 최근 US Environmental Protection Agency (EPA)에 의하여 제안된 지하수 중의$^{226}Ra$ Maximum Contaminant Level (MCL)인 0.74 Bq/L보다 충분히 작은 값으로서 감마선 분광법을 이용하여 지하수 중의 라듐을 방사능 농도를 정확히 결정할 수 있다는 것을 확인하였다.