고온 벽면과 충돌하는 단일 액적의 거동에 관한 연구

강보선,이동환,Kang, Bo-Seon,Lee, Dong-Hwan 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.7

In this paper an experimental study is presented of the problem of dynamic behavior of a water droplet impinging upon a heated surface. The experiments are mainly focused on the effects of impinging angle of a droplet and surface temperature on the impact dynamics of the droplet. It Is clarified that the droplet exhibits much different behavior depending on the normal momentum of an impinging droplet before impact. At surface temperature In the nucleate boiling regime. the disintegration of a droplet doesn't occur, whereas the deforming droplet adheres to the surface. The spreading and contraction of the liquid film is repeated a couple of times for the horizontal surface but the expanded droplet just slips without noticeable contraction for the inclined surfaces. In the film boiling regime, the impinging droplet spreads over the surface as a liquid film which is separated from the surface by produced vapor. Depending on the magnitude of the normal momentum of the droplet the disintegration into the several irregular shapes of liquid elements occurs for the horizontal and 30o-inclined surfaces, whereas the impinging droplet for the 60o-inclined surface doesn't break up and tends to recover the original spherical shape.

스마트 그리드 내의 비인가 기기를 이용한 개인정보 위협에 관한 연구

강보선 ( Bo-seon Kang ),이근호 ( Keun-ho Lee ),윤성현 ( Sunghyun Yun ) 한국정보처리학회 2014 한국정보처리학회 학술대회논문집 Vol.21 No.2

M2M기술의 발전으로 새로운 기술들이 생겨나고 있다. 그중에서도 에너지를 능률적이고 보다 안전하게 운용할 수 있게끔 해주는 스마트 그리드에 대한 개념과 지금 현재 스마트 그리드 보안 위협에 대해 살펴보자. 보안 위협 시나리오를 수립한 다음 정보통신 사회에서 보다 안전하고 능률적인 보안 대 응 방안을 체계적으로 분석한다.

충돌 제트로 형성되는 분무의 속도 특성에 대한 연구

강보선 ( Bo Seon Kang ),추연준 ( Yeon Jun Choo ),오대진 ( Dai Jin Oh ) 한국분무공학회 2001 한국액체미립화학회지 Vol.6 No.2

In this study, the velocity characteristics of liquid elements formed by two impinging jets is analysed using double pulse image capturing technique. For the droplets formed by low speed impinging jets, the droplet velocities are higher with smaller azimuthal and impingement angle. The maximum droplet velocities are about 25 % lower than jet velocity. With an increase of azimuthal angle, the shedding angles increases but remains lower than azimuthal angle. The velocities of ligaments formed by high speed impinging jets gradually decreases with an increase of azimuthal angle. The maximum ligament velocities are about 40 % lower than jet velocity. Higher impingement angles produce lower ligament velocities. The shedding angles of ligament almost increases with the same value of azimuthal angle, which implies that the moving direction of ligaments is radial from the origin as the impingement point.

분무 액적을 위한 디지털 입자 홀로그래피의 파라미터 해석

강보선 ( Bo Seon Kang ),( Yan Yang ) 한국분무공학회 2007 한국액체미립화학회지 Vol.12 No.4

핵의학과에서 환경방사선량 측정에 대한 연구

강보선(Kang, Bo-Sun),임창선(Lim, Chang-Seon) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.6

국내의 경우 방사선작업종사자의 개인피폭관리는 선량한도를 초과한 피폭의 유무를 확인하여 사후 조치를 취하는 것에 초점이 맞추어져 있다. 그러나 의료기관 핵의학과의 경우 개봉선원을 사용하므로 작업환경이 방사선에 노출될 가능성이 많고, 방사성의약품 투여 후 수 시간 혹은 수 일 동안은 환자 자체가 방사선원이 되므로 방사선작업 종사자나 수시출입자, 환자보호자들의 방사선 피폭 가능성이 매우 높다. 따라서 환자보호자 등 일반출입자의 방사선 피폭을 방지하기 위해서는 환경방사선관리가 적절하게 실시되어야 한다. 일본에서는 「방사성동위원소등에 의한 방사 선장해의 방지에 관한 법률」등에 근거하여 방사선작업환경에 대한 환경방사선량을 정기적으로 측정, 보관하도록 하 고 있다. 이에 대전시 소재 대학병원 핵의학과에서 일본에서 시행하고 있는 것과 같은 방법으로 핵의학과 내 8개소에 유리선량계를 설치하여 환경방사선을 측정한 결과 8개소 모두 「진단용 방사선 발생장치의 안전관리에 관한 규칙」 에 규정된 방사선구역의 외부방사선량인 주당 0.3 mSv에는 훨씬 미치지 못하는 적은 선량이 측정되었다. 그러나 접 수대에서는 3개월 누계 선량률이 0.51 mSv로서 접수대 종사자는 일반인 연간 유효선량한도인 1 mSv를 초과할 가능 성이 높았으며, 환자 및 보호자 대기실에서도 0.23 mSv(3개월 누계치 0.69mSv)가 측정되어 유리선량계를 설치한 8개 소 가운데 가장 높은 선량률을 보였다. 이것은 일반인의 연간 유효선량한도인 1 mSv를 초과하는 값이며, 「방사선방 호 등에 관한 기준 고시」에 환경상 위해방지를 위해 규정된 연간 유효선량 0.25 mSv를 초과하는 값이다. 따라서 접 수대 근무자, 환자보호자 및 제3자 보호를 위해 핵의학과 내 환경방사선량 감소를 위한 적극적인 대책이 필요한 것으 로 나타났다. Korean individual occupational exposure control is focused on the retrospective service to the over-exposed person by the reading of personal dosimeter. Since the radiophamaceuticals using in the nuclear medicine department are uncontained radiation sources, the potential exposure at working environment is very high. Moreover, a patient remains radioactive for hours or even days after the administration of a radiopharmaceutical for diagnosis or treatment. Thus, the proper working environmental exposure control must be established and executed to protect not only the affiliated employees, but also guardians accompanying patients and temporarily visiting public from the exposure by the patients. Japanese radiation protection law regulates working environmental radiation exposure by regularly measuring and filing the environmental dose for years. This study was aimed at measuring working environmental radiation dose in the nuclear medicine department of an university hospital located in Daejeon, Korea. We measured the accumulation radiation dose in air at 8 locations in the nuclear medicine department by using the same method as in Japan with glass dosimeters. The highest dose rate, 0.23 mSv per month, was measured at the waiting room, and the second one is at reception desk. Even though the doses were lower than the Korean constraint dose rate (0.3 mSv/week) at the boundary of the radiation controlled area, it was over the dose limit of public (1 mSv/y) and environment (0.25 mSv/y). Conclusionally, it was found that the new or additional procedure was necessary to less the exposure dose to the receptionist and guardians by the environmental radiation dose in the nuclear medicine department.

충돌 제트에 의해 형성되는 액막의 두께 특성에 관한 연구

추연준,강보선,Choo, Yeon-Jun,Kang, Bo-Seon 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.2

In this research, a study on the characteristics of the liquid sheet formed by two impinging jets is presented. Using the interference phenomena of light, the thickness of the liquid sheet, which seems to heavily affect the size of the droplets, is measured and compared with existing theoretical modelings. Thinner liquid sheet is produced with larger impinging angle, smaller orifice diameter, and higher azimuthal angle but the jet velocity doesn't affect the thickness. More viscous liquid produces thicker liquid sheet. The theoretical modelings predict the same trend as the experiments but the thickness values are overestimated at low azimuthal angles. This difference is gradually decreased as the azimuthal angle is increased: The breakup mechanism of the droplets from the liquid sheet is visualized by a high speed camera. The crest around the edge of the liquid sheet is protruded with the accumulation of liquid at the end of protuberance, which contracts into a spherical shape and then becomes detached when the stem breaks down, producing large droplets with a few small size of satellites.

Randomized Hough 변환을 이용한 타원형 액적의 형상 검출

추연준,강보선,Choo, Yeon-Jun,Kang, Bo-Seon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.10

In this study, the image processing program for deducing parameters of the elliptic shape of the partially overlapped liquid droplets was developed using the randomized Hough transform and the parameter decomposition. The procedure for the shape detection consists of three steps. For the first step, the candidate centers of ellipses are determined by the geometric property of the ellipse. Next, the rest parameters are estimated by the randomized Hough transform. In the final step for the post-processing, optimally approximated parameters of ellipses are determined. The developed program was applied to the simulated overlapped ellipses, real overlapped droplets, and real spray droplets. The shape detection was very excellent unless there existed inherent problems in original images. Moreover, this method can be used as an effective separating method for the overlapped small particles.

분무 액적 특성 계측을 위한 디지털 입자 홀로그래피 시스템의 개발

( Yang Yan ),강보선 ( Bo Seon Kang ) 한국분무공학회 2010 한국액체미립화학회지 Vol.15 No.2

포스터 전시회 : MR 유체 입자유동가시화를 위한 디지털 홀로그래피 현미경 시스템

진학붕 ( Hepeng Chen ),강보선 ( Bo-seon Kang ) 한국액체미립화학회 2015 한국액체미립화학회 학술강연회 논문집 Vol.2015 No.-

Nowadays, digital holography(DH) has become a useful approach to measure flow fields because it can instantaneously record three-dimensional information of flow fields. It has several advantages including high efficiency, simplicity and real-time analysis etc. However, due to the limited resolution of CCD sensor, digital holography sometimes cannot satisfy the needs of research with very small length scales. Therefore, a magnification lens is necessary to be added into digital holographic configuration. This new setup can be applied in a new application field, which is called digital holographic microscopy(DHM). It combines the benefits of DH and optical microscope imaging, which is quite suitable for particle imaging velocimetry. In this study, a digital holographic microscopic system for visualization of particle flow field in magnetorheological(MR) fluids is demonstrated. An in-line digital holographic microscopy configuration was adopted to measure particle movement in MR fluids, so that high resolution of particle velocity measurements can be obtained. In addition, development of image processing algorithms is another significant part of this research. The correlation coefficient method was utilized in order to locate the exact focal plane of particles. For the sake of improving the quality of holograms and reconstructed images, the Wiener filter was applied. To obtain good binary images of particles, the two-threshold and image segmentation methods were employed.

알루미늄 나선형 와이어로 직조된 다층 Kagome Truss PCM의 유동 및 열전달 특성에 관한 연구

주재황(Jai-Hwang Joo),강보선(Bo-Seon Kang),강기주(Ki-Ju Kang) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.1

Recently, ultra-lightweight materials with open, periodic cell structures take much attention owing to its potential for multi-functionality such as load bearing, thermal dissipation, and actuation. This paper presents experimental results on the fluid flow and heat transfer characteristics for the Wire-woven Bulk Kagome (WBK) composed of aluminum 1100 wires. The overall pressure drop and heat transfer of the WBK specimen was experimentally investigated under forced air convection condition. The pressure loss and heat transfer performance of the aluminum WBK were compared with other heat dissipation media. It was shown that heat transfer characteristics depended on relative density and surface area density. Comparison with metal foams and other heat dissipation media such as packed beds, lattice frame materials, louvered fins, and others suggests that the aluminum WBK competes favorably with the best available heat dissipation media in heat transfer performance.