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개선된 입자와법을 이용한 급 출발하는 실린더 주위의 비정상 점성 유동 시뮬레이션
진동식,이상환,이주희,Jin, Dong-Sik,Lee, Sang-Hwan,Lee, Ju-Hee 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.5
We solve the integral representation of the Navier-Stokes equations in a lagrangian view by tracking the particles, which have vortex strengths. We simulate the unsteady viscous flow around an impulsively started cylinder using the vortex particle method. Particles are advanced via the Biot-Savart law for a lagrangian evolution of particles. The particle strength is modified based on the scheme of particle strength exchange. The solid boundary satisfies the no-slip boundary condition by the vorticity generation algorithm. We newly modify the diffusion scheme and the boundary condition for simulating an unsteady flow efficiently. To save the computation time, we propose the mixed scheme of particle strength exchange and core expansion. We also use a lot of panels to ignore the curvature of the cylinder, and not to solve the evaluation of the surface density. Results are compared to those from other theoretical and experimental works.
CZT 반도체 검출기를 활용한 중성자 및 감마선 측정과 분석 기술에 관한 연구
진동식(Dong-Sik Jin),홍용호(Yong-Ho Hong),김희경(Hui-Gyeong Kim),곽상수(Sang-Soo Kwak),이재근(Jae-Geun Lee) 대한방사선과학회(구 대한방사선기술학회) 2022 방사선기술과학 Vol.45 No.1
CZT detectors, which are compound semiconductors that have been widely used recently for gamma-ray detection purposes, are difficult to detect neutrons because direct interaction with them does not occur unlike gamma-rays. In this paper, a method of detecting and determining energy levels (fast neutrons and thermal neutrons) of neutrons, in addition of identifying energy and nuclide of gamma-rays, and evaluating gamma dose rates using a CZT semiconductor detector is described. Neutrons may be detected by a secondary photoelectric effect or compton scattering process with a characteristic gamma-ray of 558.6 keV generated by a capture reaction (113Cd + 1 n → 114Cd + γ) with cadmium (Cd) in the CZT detector. However, in the case of fast neutrons, the probability of capture reaction with cadmium (Cd) is very low, so it must be moderated to thermal neutrons using a moderator and the material and thickness of moderator should be determined in consideration of the portability and detection efficiency of the equipment. Conversely, in the case of thermal neutrons, the detection efficiency decreases due to shielding effect of moderator itself, so additional CZT detector that do not contain moderator must be configured. The CZT detector that does not contain moderator can be used to evaluate energy, nuclide, and gamma dose-rate for gamma-rays. The technology proposed in this paper provides a method for detecting both neutrons and gamma-rays using a CZT detector.
김형섭,진동식,조광수,서문호,Kim Hyungsup,Jin Dong Sik,Cho Kwang-Soo,Seo Moon Hwo 한국섬유공학회 2005 한국섬유공학회지 Vol.42 No.4
The filtration behaviors of glass filters were studied by measuring the air permeability, pressure drop and SEM images of five HEPA grade filter material. Based on the observations, the filtration mechanism was described in terms of fiber diameter, packing density and filter depth. The results indicate that the finer fibers and fibers on/near the filter media surface show better filtration performance. Also the captured particles on the fibers formed dendrites, which influenced further filtration.