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광학식 입자 계수기 내 샘플 노즐 직경이 측정 효율 및 특성에 미치는 영향에 대한 실험적 연구
송현우,김태욱,송순호,Song, Hyunwoo,Kim, Taewook,Song, Soonho 한국입자에어로졸학회 2017 Particle and Aerosol Research Vol.13 No.4
The detection efficiency and characteristics of an optical particle counter (OPC), with various sample nozzle outlet diameters, were experimentally investigated. The OPC system, which was built with original design, was made up of a diode laser, two photodetectors, and a variety of optics such as a beam splitter and a concave mirror. The cone-shaped sampling nozzle was designed to be changeable to alter the outlet diameter, within the range of 1 to 3 mm. For samples, sets of polystyrene latex (PSL) standard particle with various sizes of 1 to $3{\mu}m$, were used. As a result, detection efficiency of the OPC greatly decreased with larger nozzle outlet diameter. Moreover, increased nozzle outlet diameter means broader sample flow, thus caused light interference and multiple scattering which results in abnormal high peaks in scattered light signal. The ratio of abnormal peaks to regular signal of single particle increased with larger nozzle outlet diameter.
송현우,최철,최경식,오제명,Song Hyunwoo,Choi Cheol,Choi Kyungshik,Oh Jemyung 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.3
Two different nanofluids were prepared by dispersing $Al_{2}O_3$ nanoparticles in transformer oil after hydrophobic surface modification. The agglomerated alumina nanoparticles with diameters from ${\mu}m$ to mm were ball-milled and then treated with surfactants such as lauric acid, stearic acid and oleic acid. The surface characteristics of modified nanoparticles were examined by FTIR spectroscopy. It showed that the hydrophobicity of nanoparticles was caused by esterification between hydroxyl groups on the particle surface and functional groups of surfactant. The shape and size distribution of ball-milled particles were analyzed by TEM and PSA. The results compared with the primary particles indicated that the size distributions of nanoparticles were dependant on milling times. The dispersion stability of modified nanoparticles dispersed in oil was highly dependent on the composition and amounts of surfactants.
무인선박의 자율운항을 위한 저가형 LiDAR센서 기반의 장애물 회피 시스템 구현
송현우(HyunWoo Song),이광국(Kwangkook Lee),김동헌(Dong Hun Kim) 대한전기학회 2019 전기학회논문지 Vol.68 No.3
In this paper, we propose an obstacle avoidance system for an unmanned ship to navigate safely in dynamic environments. Also, in this paper, one-dimensional low-cost lidar sensor is used, and a servo motor is used to implement the lidar sensor in a two-dimensional space. The distance and direction of an obstacle are measured through the two-dimensional lidar sensor. The unmanned ship is controlled by the application at a Tablet PC. The user inputs the coordinates of the destination in Google maps. Then the position of the unmanned ship is compared with the position of the destination through GPS and a geomagnetic sensor. If the unmanned ship finds obstacles while moving to its destination, it avoids obstacles through a fuzzy control-based algorithm. The paper shows that the experimental results can effectively construct an obstacle avoidance system for an unmanned ship with a low-cost LiDAR sensor using fuzzy control.
DMA 내 막대형 시스 유동 층류화 장치에 의한 샘플 유동 정렬 및 입자 분류 효율 향상
송현우(Hyunwoo Song),이상면(Sang-Myun Lee),김용준(Yong-Jun Kim),송준호(Soonho Song) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.4
경제성을 고려한 독자적인 설계로 제작된 DMA의 시스 흐름 층류화 장치 장착에 따른 입자 분류 효율 개선에 대하여 연구하였다. DMA는 평행판형 구조를 채택하여 제작되었고, 넓은 목표 입경 범위를 충족하기 위해 높은 에어로졸/시스 유량비를 사용하였다. 시스 흐름 층류화 장치는 유로 내 중심선 상에 수직으로 위치한 원기둥형 막대 모양이며, 간단한 CFD를 통해 에어로졸 흐름 정렬도 향상을 목표로 최적화하였다. 연구 결과, 층류화 장치가 장착되었을 때 유로 상단 벽 방향으로의 에어로졸 흐름 정렬도가 크게 개선된 것을 확인하였다. 시스 층류화 장치로 인한 에어로졸 흐름 정렬 개선이 실제로 입자 분류 효율에 미치는 영향을 검증하기 위해 실험을 수행하였고, 200nm 단분산 입자 샘플과 1:5의 에어로졸/시스 유량비 조건에서 91.1%의 분류 효율 향상이 관찰되었다. The improvement in particle classification performance of a differential mobility analyzer (DMA), based on an original cost-effective design, was investigated using a simple sheath flow laminarizing structure. The DMA was designed as a parallel-type, and was used with high aerosol/sheath flow ratios to achieve a wide particle diameter range. The sheath flow of the laminarizing structure consisted of a vertical rod located at the center of the flow channel. A computational fluid dynamics (CFD) optimization was performed for enhancing aerosol flow alignment. With the flow laminarizer, the aerosol flow alignment toward the channel upper wall significantly improved. Subsequently, experiments were performed to examine the effects of the sheath flow laminarization and aerosol flow alignment on the particle classification performance of the DMA. As a result, the classification efficiency increased by 91.1, with a 200 nm particle sample and aerosol/sheath flow ratio of 1:5.