• Journal of Radiation Protection and Research
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• 제41권3호
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• pp.222-228
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• 2016

Background: We are developing a small size dosimeter for dose estimation in particle therapies. The developed dosimeter is an optical fiber based dosimeter mounting an radiation induced luminescence material, such as an OSL or a scintillator, at a tip. These materials generally suffer from the quenching effect under high LET particle irradiation. Materials and Methods: We fabricated two types of the small size dosimeters. They used an OSL material Eu:BaFBr and a BGO scintillator. Carbon ions were irradiated into the fabricated dosimeters at Heavy Ion Medical Accelerator in Chiba (HIMAC). The small size dosimeters were set behind the water equivalent acrylic phantom. Bragg peak was observed by changing the phantom thickness. An ion chamber was also placed near the small size dosimeters as a reference. Results and Discussion: Eu:BaFBr and BGO dosimeters showed a Bragg peak at the same thickness as the ion chamber. Under high LET particle irradiation, the response of the luminescence-based small size dosimeters deteriorated compared with that of the ion chamber due to the quenching effect. We confirmed the luminescence efficiency of Eu:BaFBr and BGO decrease with the LET. The reduction coefficient of luminescence efficiency was different between the BGO and the Eu:BaFBr. The LET can be determined from the luminescence ratio between Eu:BaFBr and BGO, and the dosimeter response can be corrected. Conclusion: We evaluated the LET dependence of the luminescence efficiency of the BGO and Eu:BaFBr as the quenching effect. We propose and discuss the correction of the quenching effect using the signal intensity ratio of the both materials. Although the correction precision is not sufficient, feasibility of the proposed correction method is proved through basic experiments.

• 대한조선학회논문집
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• 제58권1호
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• pp.49-57
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• 2021

In the production power transmitting of a floating production system like a wind offshore floating, the power cable should be connected from the surface system into the subsea system. The connection between the surface and the subsea system will make the power cable get a dynamic load like current and wave forces. Based on this condition, a dynamic power cable is required to endure external physical force and vibration in the long-term condition. It needs more requirements than static power cable for mechanical fatigue properties to prevent failures during operations in marine environments where the external and internal loads work continuously. As a process to verify, the durability test of dynamic power cables under the marine operation environment condition was carried out by using domestic technology development.

• 한국물환경학회지
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• 제35권5호
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• pp.399-408
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• 2019

The average annual water quality at Yongchon Bridge, Bonggok 2 Bridge, and Gasuwon Bridge in upstream of Gapcheon in 2018 was Ib grade (good) in organic matters, including BOD and TOC compared to the local environmental standard in Daejeon. However, their monthly changes for TOC partially exceeded the standard during the busy farming season at Bonggok 2 Bridge and Gasuwon Bridge. Although the annual average TP was within the standard, the monthly change at Bonggok 2 Bridge partially exceeded the standard. For Dugyecheon, the annual average water quality in 2018 at Umyeon-dong Bridge and Wonjeong Bridge, which are downstream of the Gyeryong public sewage treatment plant, exceeded the local environmental standard in BOD. COD was exceeded, and TP was within the standard. It seemed that the causes of deteriorated water quality downstream of Dugyecheon were discharges of agricultural water from agricultural land and effluent from the Gyeryong public sewage treatment plant. Assuming the pollution load of 100% based at the Mulangil point of the mainstream of Gapcheon, the ratio of BOD load and TOC load were as high as 58% and 47%, respectively. At the basin of Bonggok 2 Bridge and Mulangil, the loads downstream of Dugyecheon including the Gyeryong public sewage treatment plant were as high as 43% for TN and 56% for TP, respectively, indicating that Dugyecheon had a major impact on the water quality at the mainstream of Gapcheon.

• 한국분말재료학회지
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• 제30권6호
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• pp.509-515
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• 2023

Lead-free perovskite ceramics, which have excellent energy storage capabilities, are attracting attention owing to their high power density and rapid charge-discharge speed. Given that the energy-storage properties of perovskite ceramic capacitors are significantly improved by doping with various elements, modifying their chemical compositions is a fundamental strategy. This study investigated the effect of Zn doping on the microstructure and energy storage performance of potassium sodium niobate (KNN)-based ceramics. Two types of powders and their corresponding ceramics with compositions of (1-x)(K,Na)NbO₃-xBi(Ni_2/3Ta_1/3)O₃ (KNN-BNT) and (1-x)(K,Na)NbO₃-xBi(Ni_1/3Zn_1/3Ta_1/3)O₃ (KNN-BNZT) were prepared via solid-state reactions. The results indicate that Zn doping retards grain growth, resulting in smaller grain sizes in Zn-doped KNN-BNZT than in KNN-BNT ceramics. Moreover, the Zn-doped KNN-BNZT ceramics exhibited superior energy storage density and efficiency across all x values. Notably, 0.9KNN-0.1BNZT ceramics demonstrate an energy storage density and efficiency of 0.24 J/cm³ and 96%, respectively. These ceramics also exhibited excellent temperature and frequency stability. This study provides valuable insights into the design of KNN-based ceramic capacitors with enhanced energy storage capabilities through doping strategies.

• 한국재난정보학회 논문집
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• 제20권1호
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• pp.60-68
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• 2024

연구목적: 화학물질 취급, 사용 등의 플랜트 및 사업장 설계 시 국내 안전관리 관련 법령을 준수하여 설계가 이루어졌는지 자동으로 판단할 수 있는 체계를 마련하여 검토 시간의 단축과 정확성을 높이고자 한다. 연구방법: 화학물질 취급, 사용 사업장에 대한 안전 설계 기준을 조사하고, 조문을 의미단위로 구분하여 자동으로 설계오류를 판단할 수 있는 유형과 체계를 도출하였다. 연구결과: 건물 설계 시 수행하던 자동 설계 검토 방법을 화학물질 취급 사업장을 설계 시 요구되는 안전설계 사항을 Rule Checker 개발을 통해 검토할 수 있는 체계를 제안하였다. 법 적용 대상 여부의 확인 후 전처리를 통해 의미단위로 안전설계 Rule을 구분한다. 구분된 결과는 4가지 유형으로 분류할 수 있고, 특정 장치 및 설비에 대한 사양, 공간, 조건, 상황에 대한 부분과 안전성을 강화하기위한 특정 장치 및 설비에 대한 사항이 대표적인 유형으로 분석되었다. 각각의 안전설계 Rule에 대한 Diagram을 작성하고, 이를 Rule checker 프로그램을 통해 검토할 수 있도록 하는 체계를 제안한다.

• 한국전자통신학회논문지
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• 제17권6호
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• pp.1249-1258
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• 2022

해양쓰레기란 고의 또는 부주의로 해안에 방치되거나 해양으로 유입·배출되어 해양환경에 해로운 결과를 미치거나 미칠 우려가 있는 물질로 정의된다. 본 연구에서는 효율적인 해양쓰레기 수량 파악 방법 및 변화량 분석을 위하여 객체 탐지 기법을 이용한 해양쓰레기 탐지 및 해양쓰레기의 변화량 분석을 수행하였다. 연구지역은 거제도 북동부 유호 몽돌 해수욕장이며 2022년 9월 12일부터 10월 14일까지 32일 동안 15분 간격으로 수집한 이미지를 통해 변화량을 분석하였다. One-Stage 방식의 객체 탐지 모델인 YOLOv5x를 이용한 해양쓰레기 탐지는 페트병 mAP 0.869, 스티로폼 부표 mAP 0.862의 성능을 도출하였다. 결과적으로 해양쓰레기는 8일 간격으로 큰 감소 폭을 보였으며, 성상별로는 스티로폼 부표의 수량이 3배 정도 많고 변화폭 역시 더 크게 나타남을 파악하였다.

• 대한조선학회논문집
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• 제60권5호
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• pp.375-387
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• 2023

The subsea power cables are increasingly important for harvesting renewable energies as we develop offshore wind farms located at a long distance from shore. Particularly, the continuous flexural motion of inter-array dynamic power cable of floating offshore wind turbine causes tremendous fatigue damages on the cable. As the subsea power cable consists of the helical structures with various components unlike a mooring line and a steel pipe riser, the fatigue analysis of the cables should be performed using special procedures that consider stick/slip phenomenon. This phenomenon occurs between inner helically wound components when they are tensioned or compressed by environmental loads and the floater motions. In particular, Vortex-induced vibration (VIV) can be generated by currents and have significant impacts on the fatigue life of the cable. In this study, the procedure for VIV fatigue analysis of the dynamic power cable has been established. Additionally, the respective roles of programs employed and required inputs and outputs are explained in detail. Demonstrations of case studies are provided under severely sheared currents to investigate the influences on amplitude variations of dynamic power cables caused by the excitation of high mode numbers. Finally, sensitivity studies have been performed to compare dynamic cable design parameters, specifically, structural damping ratio, higher order harmonics, and lift coefficients tables. In the future, one of the fundamental assumptions to assess the VIV response will be examined in detail, namely a narrow-banded Gaussian process derived from the VIV amplitudes. Although this approach is consistent with current industry standards, the level of consistency and the potential errors between the Gaussian process and the fatigue damage generated from deterministic time-domain results are to be confirmed to verify VIV fatigue analysis procedure for slender marine structures.