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TAEJOO KIM,김종록,CHEULMUU SIM,SUNGHO LEE,YOUNGJIN SON,MOOHWAN KIM 한국원자력학회 2009 Nuclear Engineering and Technology Vol.41 No.1
In this investigation, we prepared a 1 and 3-parallel serpentine single PEMFC, which has an active area of 100 cm2 and a flow channel cross section of 1x1mm. Distribution and transport of water in a non-operating PEMFC were observed by varying flow types and the flow rates (250, 400, and 850 cc/min). This investigation was performed at the neutron imaging facility at the COld Neutron RAdiography facility (CONRAD), HMI, Germany of which the collimation ratio and neutron fluence rate are 250, 1 106 n/s/cm2, respectively. The neutron image was continuously recorded by a scintillator and lens- CCD coupled detector system every 10 seconds. It has been observed that although the distilled water was supplied into the cathode channel only, the neutron image showed a water movement from the cathode to the anode channel. The water at the cathode channel was completely discharged as soon as the pressurized air was supplied. But the water at the anode channel was not easily removed by the pressurized air except for the 3-parallel serpentine type with 850 cc/min of air flow rate. Moreover, the water at the MEA wasn’t removed for any of the cases.
Taejoo Roh(노태주),Sangwon Seo(서상원) 한국산업경영시스템학회 2017 한국산업경영시스템학회지 Vol.40 No.3
Defense industries which require high reliability need an optimized quality management system with well-planned implementation. And the government should examine the overall status of defense industries, then establish practical policies with a proper support plan in required areas to upgrade the quality management level of manufacturers. Thus, DTaQ developed the model for 2 years from 2014, which specialized in quality management level analysis for defense industries. And a survey has been undertaken with that model by DTaQ and Korea Research Center in 2016. The surveyed companies randomly sampled among those which have more than 30 employees and delivery history over past 3 years, and finally 106 defense industries were selected. This paper present survey method and indexes for survey of defense industry quality management level. The survey was conducted in the order of planning, data collection and data processing, and the validity and reliability of the data were verified to increase objectivity of survey results. The survey contents mainly consist of system quality and management quality. System quality includes Product Development Management, Production Operation Management, supply chain quality management, Safety & Environment Management and Reliability Management, on the other hand, management quality includes Strategic Leadership, Human Resource Management, Customer Market Management and Information & Knowledge Management. Thus this proposes the current overall quality management status of the 106 defense industries and shows level differences by company sizes and manufacturing sectors based on the result of survey. Specifically, this paper enables to track the areas which need prompt government support with the policy directions to make quality management level higher. Therefore, it is expected that this can be used as reference data in establishing quality policies for military supplies in the future.
유동환경용 FSS 전극 유전체 장벽 방전 구조 플라즈마 발생기의 X-Band 내 RCS 감소 효과
오태주(Taejoo Oh),조창석(Changseok Cho),안욱현(Wookhyun Ahn),육종관(Jong-Gwan Yook),이장재(Jangjae Lee),유신재(Shinjae You),임진우(Jinwoo Yim),하정제(Jungje Ha),배지훈(Gihun Bae),유흥철(Heung Cheol You),이용식(Yongshik Lee) 한국전자파학회 2021 한국전자파학회논문지 Vol.32 No.11
본 논문에서는 주파수 선택 표면(FSS: frequency selective surface)을 전극으로 활용한 유전체 장벽 방전 (DBD: dielectric barrier discharge) 플라즈마 발생기를 제안하고, 이를 기반으로 2차원 평면형 타겟의 레이다 단면적(RCS: radar cross section)을 감소시키는 것을 실험적으로 검증한다. 주파수 선택 표면의 통과대역이 레이다 신호의 대역과 일치하도록 설계함으로써 기존 평행판 커패시터형 DBD 발생기와 달리 발생기를 타겟에 부착하는 과정에서 발생하는 타겟의 RCS 왜곡과 레이다 신호의 편파에 따라 응답이 달라지는 현상을 최소화할 수 있다. 나아가서 유전체 테두리를 활용함으로써 전극과 4.572 mm의 간격을 두고 존재하는 접지면 사이의 공간을 완전 격리시켜 유동환경에서도 안정적인 플라즈마 방전이 가능하다는 것을 확인하였다. 제안된 플라즈마 발생기를 제작하여 플라즈마 최적 방전 및 RCS 측정 실험을 통해 X-band 에서 최대 2.9 dB의 RCS 감소 효과를 얻을 수 있음을 실험적으로 검증하였다. In this study, an frequency selective surface (FSS) electrode of a dielectric barrier discharge (DBD) plasma generator, with a two-dimensional planar target, for radar cross section (RCS) reduction is proposed and measured. The electrode of the proposed plasma generator is based on a cross FSS array conductor. Therefore, it is possible to minimize the amount of RCS change according to the efficient plasma discharge and polarization of the signal from the radar. In addition, a frame of FR-4 dielectric material is placed between the 4.572 mm gap of the ground surface and the electrode to reduce RCS owing to stable plasma discharge in a fluid environment in which the aircraft operates. The proposed plasma generator is fabricated to determine the optimal plasma discharge and RCS measurement. The measurement results showed a 2.9 dB RCS reduction in the X-band.