• Nuclear Engineering and Technology
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• 제53권11호
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• pp.3764-3771
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• 2021

Based on the convolutional neural network (CNN), a novel technique is investigated for lost gamma source detection in a room. The CNN is trained with the result of a GEANT4 simulation containing a gamma source inside a meshed room. The dataset for the training process is the deposited energy in the meshes of different n-step paths. The neural network is optimized with parameters such as the number of input data and path length. Based on the proposed method, the place of the gamma source can be recognized with reasonable accuracy without human intervention. The results show that only by 5 measurements of the energy deposited in a 5-step path, (5 sequential points 50 cm apart within 1600 meshes), the gamma source location can be estimated with 94% accuracy. Also, the method is tested for the room geometry containing the interior walls. The results show 90% accuracy with the energy deposition measurement in the meshes of a 5-step path.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1524-1531
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• 2020

The aim of this work is to develop a Geiger-Muller (GM) detector system for robot to look for a radioactive source in case of a nuclear emergency or in a high radiation environment. In order to find a radiation source easily, a detector system, including 3 detectors, was designed to search γ-ray radiation sources autonomously. First, based on GEANT4 simulation, radiation dose rates in 3 Geiger-Muller (GM) counters were simulated at different source-detector distances, distances between detectors and angles. Various sensitivity analyses were performed experimentally to verify the simulated designed detector system. A mono-energetic ¹³⁷Cs γ-ray source with energy 662 keV and activity of 1.11 GBq was used for the observation. The simulated results were compared with the experimental dose rate values and good agreements were obtained for various cases. Only based on the dose rates in three detectors, the radiation source with a specific source activity and angle was localized in the different location. A method was adopted with the measured dose rates and differences of distances to find the actual location of the lost γ-ray source. The corresponding angles of deviation and detection limits were calculated to determine the sensitivity and abilities of our designed detector system. The proposed system can be used to locate radiation sources in low and high radiation environments.

• 생명과학회지
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• 제18권8호
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• pp.1066-1071
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• 2008

오미자의 건조공정에 의한 휘발성 terpene류와 색의 변화를 조사하기 위하여, 건조조건을 $50^{\circ}C$와 $70^{\circ}C$의 열풍건조, $-70^{\circ}C$의 진공동결건조의 3종 건조방법으로 건조한 후 SDE 연속추출장치로 terpene류를 추출하여 GC/MS로 분석하고, 각 건조된 오미자를 마쇄한 분말의 색도를 Hunter colorimeter로 측정하였다. 생오미자의 GC/MS 분석 결과, 15종의 monoterpene류, 28종의 sesquiterpene류 및 7종의 terpene alcohol류가 확인되었으며, 또한 myrcene (56.97 ${\mu}g/g$)과 ${\gamma}-terpinene$ (58.49 ${\mu}g/g$)이 monoterpene류, ${\beta}-elemene$ (120.16 ${\mu}g/g$), ${\alpha}$-bergamotene ($103.45{\mu}g/g$), ${\gamma}$-selinene (75.97 ${\mu}g/g$), ${\beta}$-cubebene (66.69 ${\mu}g/g$), aristolene (51.25 ${\mu}g/g$) 및 ${\alpha}$-ylangene (28.06 ${\mu}g/g$) 등이 sesquiterpene류, 그리고 T-muurolol (96.45 ${\mu}g/g$)과 terpinen-4-ol (46.02 ${\mu}g/g$)이 terpene alcohol류의 주성분이었다. 건조과정의 초기에 생오미자 terpene류의 절반 이상이 감소되었으며, 이후 건조기간의 경과에 따른 추가적 감소는 아주 적었다. 또한 총 terpene류의 절반 이상을 차지하는 sesquiterpene류의 함량은 진공동결건조에서는 소량 증가하다 6일 이후 감소하는 패턴을 보였다. 그리고 terpene alcohol류는 진공동결건조한 시료에서 그 함량이 비교적 많이 남았으나, 고온인 $70^{\circ}C$에서 열풍건조한 시료에서는 가장 적게 남아 있었다. 건조방법에 따른 L값은 동결건조, $50^{\circ}C$ 열풍건조, $70^{\circ}C$ 열풍건조 순서로 높았으며, a값 및 b값도 동결건조에서 가장 높았으며 $70^{\circ}C$ 열풍건조에서 가장 낮게 나타났다.