• Nuclear Engineering and Technology
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• 제55권3호
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• pp.958-967
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• 2023

This work studies the defect features in a dilute FeMnNi alloy by an Object Kinetic Monte Carlo (OKMC) model based on the "grey-alloy" method. The dose rate effect is studied at 573 K in a wide range of dose rates from 10^-8 to 10^-4 displacement per atom (dpa)/s and demonstrates that the density of defect clusters rises while the average size of defect clusters decreases with increasing dose rate. However, the dose-rate effect decreases with increasing irradiation dose. The model considered two realistic mechanisms for producing <100>-type self-interstitial atom (SIA) loops and gave reasonable production ratios compared with experimental results. Our simulation shows that the proportion of <100>-type SIA loops could change obviously with the dose rate, influencing hardening prediction for various dose rates irradiation. We also investigated ways to compensate for the dose rate effect. The simulation results verified that about a 100 K temperature shift at a high dose rate of 1×10^-4 dpa/s could produce similar irradiation microstructures to a lower dose rate of 1×10^-7 dpa/s irradiation, including matrix defects and deduced solute migration events. The work brings new insight into the OKMC modeling and the dose rate effect of the Fe-based alloys.

• 대한수의학회지
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• 제34권4호
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• pp.665-678
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• 1994

This study was undertaken to investigate histological changes according to the radiosensitivity in the spermatogenic cells in Korean native pheasants. During spermatogenetic period, testes wete collected from male adult Korean native pheasant and they were used as experimental and control birds. The experimental group was divided into a single-dose whole body irradiation group(400, 600, 800 and 1000 rads) and a split-dose whole body irradiation groups(400/2, 600/2, 800/2 and 1000/2 rads). A Henseky's $^{60}Co$ ${\gamma}$-radiotherapy machine was used for this experiment and the dose rate of $^{60}Co$ ${\gamma}$-ray was 104 rads/min. The experimental birds were sacrificed at 24 and 72 hrs after irradiation and the control pheasants were sacrificed at the same time. General histological changes of seminiferous epithelial cells were observed by hematoxylin-eosin stain with light microscope. The results obtained are summarized as follows ; 1. In the single-dose and the split-dose irradiation groups, the average diameter of the seminiferous tubule was decreased compared with control group. 2. Seminiferous epithelial cells were more severely damaged after 72 hrs than after 24 hrs of single-dose irradiation of 400, 600 and 800 rads but the difference of cell injury was almost not observable with the elapsed time in the group of the single-dose irradiation of 1000 rads. 3. The damage of spermatogenic cells were more severe after 24 hrs than after 72 hrs of the split-dose irradiation of 400 rads but the split-dose irradiation of 600, 800 and 1000 rads were more severe after 72 hrs than after 24 hrs.

• 인간식물환경학회지
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• 제23권2호
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• pp.171-178
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• 2020

The present study was conducted to determine the effects of electron beam irradiation on the postharvest quality of cut flowers. Cut flowers were irradiated with electron beam at 100, 200, 400, 600, 800, 1,000, and 2,000 Gy with a 10 MeV linear electron beam accelerator to evaluate their irradiation tolerance. Postharvest quality was determined by monitoring fresh weight loss, flower longevity, flower diameter, flowering rate, visual quality of flowers and leaves, and chlorophyll content. Cut flowers showed a radiation-induced damage with increasing the irradiation dose. Flower longevity and fresh weight of cut flowers decreased when the irradiation dose was increased. Flower bud opening was also inhibited in a dose-dependent manner. The effective irradiation doses for 10% reduction of postharvest quality (ED₁₀) values were 144.4, 451.6, and 841.2 Gy in the 'Medusa' lily, 'Montezuma' carnation, and 'Rosina White' eustoma, respectively. Although tolerance of cut flowers to electron beam irradiation vary according to species, cultivars, or maturity stage conditions, it is conceivable that 'Montezuma' carnation and 'Rosina White' eustoma could be tolerated and maintained overall postharvest quality up to 400 Gy, the generic irradiation dose approved by the Animal and Plant Health Inspection Service (APHIS) and the International Plant Protection Convention (IPPC) for postharvest phytosanitary treatments.

• Imaging Science in Dentistry
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• 제34권3호
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• pp.137-144
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• 2004

Purpose: To investigate the effects of low dose irradiation on the calcium content and calcific nodule formation of the MC3T3-El osteoblastic cell line. Materials and Methods: Cells were irradiated with a single dose of 0.2, 0.4 and 0.6 Gy at a dose rate of 5.38 Gy/min using Cs-137 irradiator. After irradiation, the calcium content and calcific nodule formation were examined on the 1st, 2nd, 3rd and 4th week. Results: We did not find any significant difference of total calcium content after irradiation of 0.2, 0.4 and 0.6 Gy when compared with the unirradiated control group. There was no significant difference of total calcium content between 0.2, 0.4 and 0.6 Gy irradiated groups. We found an increased tendency of the calcific nodule formation after irradiation of 0.2, 0.4 and 0.6 Gy when compared with the unirradiated control group without significant difference of calcific nodule formation between 0.2, 0.4 and 0.6 Gy irradiated groups. Conclusion : The results showed an increased tendency of the calcific nodule formation after low dose irradiation. However, this tendency did not increase with the increase of irradiation dose.

• 한국환경보건학회지
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• 제8권1호
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• pp.45-53
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• 1982

To determine the effect of r-irradiation on the microorganisms destruction and the changes of general constituents of Ginseng Powder, three samples were analyzed at 1st and 3rd month after r-irradiation. The results were as follows: 1. Total bacterial counts were decreased during storage as the irradiation dose increased. It seems that about 300 Krad was satisfactory to the regulation of ginseng powder. ($5.0 \times 10^4 /g$) 2. Coliform group was also decreased during storage as the irradiation dose increased. Coliform group was not detected at the irradiation dose higher than 500 Krad. 3. Total bacterial counts and coilform group were in proportion to the content of moisture in ginseng powder. 4. The contents of moisture, ash, crude protein, crude lipid and total sugar in ginseng powder during storage had nearly no changes. 5. The content of reducing sugar in ginseng powder during storage had the increasing tendencies as the irradiation dose increased. 6. The content of amino-nitrogen in ginseng powder during storage had the decreasing tendencies as the irradiation does increased.

• 한국의학물리학회지:의학물리
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• 제31권2호
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• pp.9-19
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• 2020

Purpose: This study aims to develop a multi-purpose electron beam irradiation device for preclinical research and material testing using the research electron linear accelerator installed at the Dongnam Institute of Radiological and Medical Sciences. Methods: The fabricated irradiation device comprises a dual scattering foil and collimator. The correct scattering foil thickness, in terms of the energy loss and beam profile uniformity, was determined using Monte Carlo calculations. The ion-chamber and radiochromic films were used to determine the reference dose-rate (Gy/s) and beam profiles as functions of the source to surface distance (SSD) and pulse frequency. Results: The dose-rates for the electron beams were evaluated for the range from 59.16 Gy/s to 5.22 cGy/s at SSDs of 40-120 cm, by controlling the pulse frequency. Furthermore, uniform dose distributions in the electron fields were achieved up to approximately 10 cm in diameter. An empirical formula for the systematic dose-rate calculation for the irradiation system was established using the measured data. Conclusions: A wide dose-rate range electron beam irradiation device was successfully developed in this study. The pre-clinical studies relating to FLASH radiotherapy to the conventional level were made available. Additionally, material studies were made available using a quantified irradiation system. Future studies are required to improve the energy, dose-rate, and field uniformity of the irradiation system.

• 치과방사선
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• 제18권1호
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• pp.31-45
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• 1988

The author studied the histopathologic changes according to a single or a split dose and the time after irradiation on the acinar cells of rat parotid gland. 99 Sprague Dawley rats, weighing about l20gm, were divided into control and 3 experimental groups. In experimental groups, GroupⅠ and Ⅱ were delivered a single dose of l5Gy, 18Gy and Group Ⅲ and Ⅳ were delivered two equal split doses of 9Gy, 10.5Gy for a 4 hours interval, respectively. The experimental groups were delivered by a cobalt-60 teletherapy unit with a dose rate of 222cGy/min, source-skin distance of 50㎝, depth of l㎝ and a field size of l2×5㎝. The animals were sacrificed at 1, 2, 3, 6, 12 hours, 1, 3, 7 days after irradiation and examined by light and electron microscopy. The results were as follows: 1. As the radiation dose increased and the acinar cells delivered a single dose exposure were more damaged, and the change of acinar cells appeared faster than those of a split dose exposure. 2. The histopathologic change of acinar cells appeared at 1 hour after irradiation. The recovery from damaged acinar cells appeared at 1 day after irradiation and there was a tendency that the recovery from damage of a split dose exposure was somewhat later than that of a single dose exposure. 3. Light microscope showed atrophic change of acinar cells and nucleus, degeneration and vesicle formation of cytoplasm, widening of intercellular space and interlobular space. 4. Electron microscope showed loss of nuclear membrane, degeneration of nucleus and nucleoli, clumping of cytoplasm, widening and degeneration of rough endoplasmic reticulum, loss of cristae of mitochondria, lysosome, autophagosome and lipid droplet. 5. Electron microscopically, the change of rough endoplasmic reticulum was the most prominent and this appeared at 1 hour after irradiation as early changes of acinar cells. The nuclear change appeared at 2 hours after irradiation and the loss of cristae of mitochondria was observed at 2 hours after irradiation in all experimental groups.

• 대한방사선기술학회지:방사선기술과학
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• 제18권1호
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• pp.97-110
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• 1995

This study was undertaken to investigate ultrastructural changes according to the radiosensitivity in the spermatogenic cells and Sertoli cell of the seminiferous tubules in Korean native pheasants. During spermatogenetic period, testes were collected from male adult Korean native pheasant and they were used as experimental and control birds. The experimental group was divided into a single-dose whole body irradiation group (400, 600, 800 and 1,000 rads) and a split-dose whole body irradiation groups(400/2, 600/2, 800/2 and 1,000/2 rads). The experimental birds were sacrificed at 24 and 72 hrs after irradiation and the control pheasants were sacrificed at the same time. Ultrastructural changes of Sertoli cells and spermatogonia were investigated by ultrathin section with electron microscope. The results obtained are summarized as follows; 1. The apoptosis was observed after 72 hrs group of the single-dose irradiation of 400 rads. 2. The cytoplasmic organelles of spermatogonia were severely damaged more than that of sertoli cell in 72 hours group of split-dose irradiation of 800 rads. 3. The cytoplasmic organelles of Sertoli cell were severely damaged except the nuclear membrane of Sertoli cells in 72 hrs group of split-dose irradiation of 1,000 rads.

• Journal of Radiation Protection and Research
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• 제21권2호
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• pp.99-105
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• 1996

림프구와 림프종에 고준위 방사선(8Gy)을 조사했을 때. 저준위 방사선을 먼저 조사한 경우 세포 생존률이 3.7배 증가하는 것이 관찰되었다 세포 생존률은 고준위 방사선 조사로 발생되는 산소 라디칼의 제거. 변성된 유전자와 단백질의 제거, 변화된 세포의 제거 등으로 증가할 수 있다. 본 연구에서는 저준위 방사선 조사로 유도되는 방사선 저항기전을 알아보기 위하여, 고준위 방사선 조사시 발생되는 산소 라디칼을 제거하는 효소들의 활성과 방사선 보호제로 알려진 glutathione의 양을 측정하였다 림프종의 경우 저준위 방사선 조사시 peroxidase의 활성이 133.3%로 증가하였다. 림프구의 경우는 superoxide dismutase, glucose-6-phoshpate dehydrogenase와 glutathione의 활성이 각각 138.5%. 122.4%. 120.8%로 증가하였으며. 이들 효소들의 활성은 저 준위방사선 조사 간격이 7 시간일 때 가장 증가되었다.

• 한국콘텐츠학회논문지
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• 제5권5호
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• pp.281-286
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• 2005

전국 16개 시도의 44개 종합병원에서 근무하는 방사선사 623명을 대상으로, 1998년부터 2002년도까지의 5년간 병원 방사선사의 피폭선량을 2003년 7월부터 8월까지 조사했다. 조사된 방사선사의 연간 평균피폭선량은 $1.73{\pm}0.10mSv$로 나타났다. 연도별로 보면 2000년이 $1.80{\pm}0.15mSv$로 가장 높고, 1998년이 $1.36{\pm}0.12mSv$로 가장 낮은 것으로 나타났다. 그러나 병원의 방사선피폭 환경에 근무하는 방사선사는 직업상 만성피폭이 될 가능성이 있으므로 이에 대한 장기적인 대안이 제시되어야 할 것으로 사료된다.