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3차원 유동 시뮬레이션을 위한 Supercompact 다중 웨이블릿
양승철(Seungcheol Yang),이도형(Dohyung Lee) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.12
본 논문에서는 supercompact 다중 웨이블릿 기법과 이 기법의 유동 시뮬레이션 데이터에의 적용을 발표한다. Supercompact 웨이블릿 방법은 간결한 지원(support)을 제공할 수 있고 또 속성이 다른 떨어져 있는 데이터와(예: 충격파의 불연속구간 또는 와동을 가로지르는 부분) 불필요한 상호작용을 피할 수 있는 점에서 유동 시뮬레이션 데이터를 위한 적합한 웨이블릿 방법이라 할 수 있다. 데이터 압축을 위한 임계처리법(thresholding)은 다중 웨이블릿의 공분산 벡터 구조 기반 하에 적용된다. 본 논문은 3차원으로의 기법 확장이 설명 분석되었다. 수치실험은 본 방법이 여러 이론적인 이점을 제공할 수 있고 실제 결과에 있어서 큰 데이터 압축 비율을 산출 할 수 있음을 보여준다. This paper presents a supercompact multi-wavelet scheme and its application to fluid simulation data. The supercompact wavelet method is an appropriate wavelet for fluid simulation data in the sense that it can provide compact support and avoid unnecessary interaction with remotely located data (e.g. across a shock discontinuity or vortices). thresholding for data compression is applied based on a covariance vector structure of multi-wavelets. The extension of this scheme to three dimensions is analyzed. The numerical tests demonstrate that it can allow various analytic advantages as well as large data compression ratios in actual practice.
양승철(SeungCheol Yang),김하은(Haeun Kim),김동현(Donghyun Kim),정연길(Yeon-Gil Jung),권화빈(Hwabhin Kwon),박희성(Heesung Park),이동수(Dongsoo Lee),황인성(Insung Hwang),송태섭(Taeseup Song) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.5
염분차발전은 해수와 담수 사이의 염분농도차를 이용해 전기를 생산하는 해양 신재생 에너지원이다. 최근 새로운 염분차발전 기술로 무한한 이온흡착용량을 지니는 흐름전극의 이온 흡착/탈착을 활용하는 흐름전극-축전식혼합 (F-Capmix, flow-electrode capacitive mixing)이 제안되었다. 하지만, F-Capmix는 타 염분차발전 기술 대비 낮은 출력밀도를 지니고 있어 향후 상용화를 위해 이를 개선해야 할 필요가 있다. 본 연구에서는 F-Capmix 염분차발전 기술의 낮은 출력밀도의 개선을 위해, (1) 흐름전극 내 다공성 탄소 입자 사이의 효율적인 charge percolation을 위한 개선된 조성을 지니는 흐름전극, (2) 그래파이트가 코팅된 금속 집전체를 활용해 전기저항이 낮아진 집전체, (3) 집전체와 흐름전극 내 다공성 탄소 입자 사이의 효율적인 charge percolation을 위한 유로 디자인에 대한 연구를 수행하였다. 이를 통해, F-Capmix 염분차발전의 낮은 출력밀도가 개선되었음을 확인했다. Salinity differential power generation (SGP) is a marine renewable energy that generates electricity by salt concentration difference between seawater and freshwater. As a new SGP technology, flow-electrode capacitive mixing (F-Capmix) has been proposed that utilizes ion adsorption/desorption of a flow-electrode with infinite ion adsorption capacity. However, F-Capmix has a lower power density compared to other SGP technologies, so it needs to be improved for commercialization. In this study, in order to improve the low power density of the F-Capmix, we conducted various studies on (1) a flow-electrode with an improved composition for efficient charge percolation between porous carbon particles in the flow-electrode, (2) a current collector with low electrical resistance by using a graphite-coated metal current collector, and (3) flow path design for efficient charge percolation between the current collector and the porous carbon particles in the flow electrode. Through this, it was confirmed that the low power density of the F-Capmix was improved.
감액 특성 향상을 위한 하이브리드(Sb/Ca) 액식 연축전지 개발
송승윤,임태섭,김성준,정연길,양승철,Song, Seung Yun,Lim, Tae Seop,Kim, Sung Jun,Jung, Yeon-Gil,Yang, SeungCheol 한국재료학회 2022 한국재료학회지 Vol.32 No.3
One disadvantage of deep cycle flooded lead-acid batteries is increasing water loss caused by use of (+) Pb-Sb / (-) Pb-Sb alloy grid. Water loss is generated by the emission of hydrogen gas from the (-) electrode during battery charging. In this paper, we maintain cycle life aspect through the development of hybrid flooded lead-acid batteries to which a (+) Pb-Sb / (-) Pb-Ca grid is applied and deal with the improvement of water loss. The amount of water loss compared to that of the (-) Pb-Sb grid decreased when Ca was added to the (-) Pb grid. For the (-) Pb-Ca grid, it was confirmed that the time to reach 0.0 V, at which water decomposition occurs, was increased compared to that of the (-) Pb-Sb grid at the NPV (Negative Potential Voltage). In the cycle life test conducted with the BCI (Battery Council International) standard, compared to the (+) Pb-Ca grid, the (+) Pb-Sb grid increased the life cycle of the batteries and the (+) Pb-Ca grid showed an early end of life due to PbO corrosion layer generation, as determined through SEM / EDS and Tear Down analysis. In conclusion, by addition of Sb to (+) Pb grid and Ca to (-) Pb grid, we developed a hybrid flooded lead-acid battery that meets user requirements to improve water loss characteristics and preserve cycle life characteristics.
과붕산나트륨 양극 활물질 첨가에 따른 차량용 납산배터리 성능 특성
임태섭,김성준,김상동,양승철,정연길,Lim, Tae Seop,Kim, Sung Jun,Kim, Sang Dong,Yang, SeungCheol,Jung, Yeon-Gil 한국재료학회 2020 한국재료학회지 Vol.30 No.8
The performance characteristics of a lead acid battery are investigated with the content of Sodium Perborate Tetrahydrate (SPT, NaBO<sub>3</sub>·4H<sub>2</sub>O) in a positive plate active material. SPT, which reacts with water to form hydrogen peroxide, is applied as an additive in the positive plate active material to increase adhesion between the substrate (positive plate) and the active material; this phenomenon is caused by a chemical reaction on the surface of substrate. A positive plate with the increasing content of SPT is prepared to compare its properties. It is confirmed that the oxide layer increases at the interface between the substrate and the active material with increasing content of SPT; this is proven to be an oxide layer through EDS analysis. Battery performance is confirmed: when SPT content is 2.0 wt%, the charging acceptance and high rate discharge properties are improved. In addition, the lifetime performance according to the Standard of Battery Association of Japan (SBA) S0101 test is improved with increasing content of SPT.