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신대식,김경천,Shin, Dae Sig,Kim, Kyung Chun 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.7
In the fully developed internal flow fields, there are complex transition flows caused by interaction of the cross flow and jet when jet is Injected Into the flow. These interactions are studied by means of the flow visualization methods. An instantaneous laser tomographic method is used to reveal the physical mechanism and the structure of vortices formation in the branch pipe flow. The velocity range of cross flow of the pipe is 0.7m/s and the corresponding Reynolds number $R_{cf}$, based on the duct height is $5.6{\times}10^3$, diameter/height ratios(d/H) 0.14 and velocity ratios 3.0. Oil mist with the size of $10{\mu}m$ diameter is used for the scattering particle. The instantaneous topological features of the vortex ring roll-up of the jet shear layer and characteristics of this flow are studied in detail by performing flow visualization in rectangular duct flow. It is found that the formation and roll-up of ring vortices is a periodic phenomenon. The detailed topology of the vortices in the near field of a cross -flow jet and the mechanism associated with them give enforced hints of vortex breakdown within the vortex system due to the interaction of the jet and the cross-flow.
고해상도 PIV 기법을 이용한 타원형 제트의 근접 유동장 해석
신대식,이상준,Shin, Dae-Sig,Lee, Sang-Joon 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.3
Flow characteristics of turbulent elliptic jets were experimentally investigated using a single-frame PIV system. A sharp-edged elliptic nozzle with aspect ratio(AR) of 2 was tested and the experimental results were compared with those of circular jet having the same equivalent diameter($D_e$). The Reynolds number based on the nozzle exit velocity and nozzle equivalent diameter was about $1{\times}10^4$. The spreading rate along the major and minor axis are different remarkably. The jet half width along the major axis decreases at first and then increases with going downstream. But along the minor axis the jet width increases steadily. The elliptic jet of AR=2 has one switching points at $X/D_e=2$ within the near field. Turbulence properties are also found to be significantly different along the major and minor axis planes.
용융아연 도금공정에서의 SNOUT 내부 유동장 해석 ( I )
신대식,최제호,이상준,Shin, Dae Sig,Choi, Jayho,Lee, Sang-Joon 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.10
PIV(Particle Image Velocimetry) velocity field measurements inside the snout of a1/10 scale model of the Zn plating process were carried out at the strip speed $V_s=1.5m/s$. Aluminum powder particles ($1{\mu}m$) and atomized olive oil ($3{\mu}m$) were used as seeding particles to simulate the molten Zinc flow and deoxidization gas flow, respectively. A pulsed Nd:Yag laser and a $2K{\times}2K$ high-resolution CCD camera were synchronized for the PIV velocity field measurement. From flow visualization study, it is found that the liquid flow in the Zn pot is dominantly governed by the uprising flow caused by the rotating sink roll, with its effect on the steel strip inside the snout largely diminished by installing of the snout. The deoxidization gas flow in front of the strip inside the snout can be characterized by a large-scale vortex rotating clockwise direction formed by the moving strip. In the rear side of the strip, a counter-clockwise vortex is formed and some of the flow entrained by the moving strip impinges on the free surface of molten zinc. The liquid flow in front of the strip is governed by the flow entering the snout, caused by the spinning sink roll. Just below the free surface a counter-clockwise vortex is formed near the snout wall. The moving strip affects dominantly the flow behind the strip inside the snout, and large amount of the liquid flow follows the moving strip toward the sink roll. The thickness of the flow following the strip is very thin in the front side due to the uprising flow, however thick boundary layer is formed in the rear side of the strip. Its thickness is increased as moving downstream toward the sink roll. Inside the snout, the deoxidization gas flow above the free surface is much faster than the liquid flow in the zinc pot. Due to the larger influx of the flow following the moving strip in the rear side of the strip, higher percentage of imperfection can be anticipated on the rear surface of the strip.
신대식(Dae-Sik Shin),김훈(Hoon Kim) 한국조명·전기설비학회 2013 조명·전기설비학회논문지 Vol.27 No.6
In this paper, we proposed a smart lighting management system controls the lighting efficiently to reduce energy consumption while satisfying user’s lighting requirements. The proposed system considers the available daylight intensity and indoor light source to satisfy the lighting requirements of each user according to the work environment. In addition, for user convenience, we have developed different user interfaces for lighting control including local interface, and remote interface through internet or Bluetooth for personal computer as well as smart phones. The proposed system satisfies the lighting requirements of each user according to the corresponding work environment. The proposed smart lighting management system utilizes the lighting energy efficiently, and can be considered a significant contribution towards future green buildings.
다중 상관기를 이용한 고속 항체용 GPS 수신기의 TTFF 성능 향상
신대식(Dae Sik Shin),김정원(Jeong Won Kim),황동환(Dong-Hwan Hwang),이상정(Sang Jeong Lee) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
GPS 수신기에서 항법을 수행하기 위해서 신호탐색, 신호추적, 데이터 동기, 데이터 복조, 측정치 생성 및 위치 계산의 과정을 거쳐야 한다. TTFF(Time To First Fix)는 이러한 시간의 합으로 수신기의 성능을 나타내는 중요 평가지수 중의 하나이다. 일반적인 수신기의 TTFF는 80~90초인 것으로 알려져 있으며, 고속으로 운동하는 항체의 경우, 빠른 TTFF를 필요로 하므로 가장 긴 시간이 소비하는 신호탐색 과정의 시간을 줄여야 한다. 본 논문에서는 고속으로 운동하는 항체에서 GPS 신호의 코드 탐색 시간을 줄이기 위하여 다중 상관기 구조를 가지는 수신기를 설계 하고자한다. 설계한 수신기는 수신된 신호의 코드위상을 여러 개의 상관기에서 동시에 탐색하도록 다중 상관기를 구성하여 코드위상 검색에 소요되는 시간을 단축시킨다. 이를 검증하기 위하여 GPS 모의 신호 발생기를 이용하여 실험을 수행하였다. GPS 신호는 IF 데이터 수집 장치로부터 수집된 신호를 이용하며, 실험 수행 결과 다중 상관기를 이용하였을 때 TTFF가 단축되는 것을 확인하였다.
신대식(Dae Sik Shin),조종철(Jong Chul Cho),김용현(Yong Hyun Kim),신미영(Mi Young Shin),한상설(Sang Sul Han),박찬식(Chansik Park),전향식(Hyang-Sig Jun),남기욱(Gi-Wook Nam),이상정(Sang Jeong Lee) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.12
본 논문에서는 GPS, GPS 현대화, Galileo, SBAS 및 GBAS등의 항법 시스템을 모두 고려하여 한국 지역에서의 GNSS 무결성 감시의 가용성을 분석하였다. 현대화된 GPS, Galileo 및 SBAS를 사용하면 Cat. Ⅰ에 근접한 성능을 얻을 수 있음을 시뮬레이션을 통해 확인 하였다. 그러나 여전히 수직오차의 영향으로 Cat. Ⅱ 및 Ⅲ를 만족시키지 못하므로 GBAS와 같은 보다 개선효과가 큰 보강 항법 시스템이 필요함을 확인하였다. 본 논문의 연구 결과는 보강 시스템의 구축뿐 아니라 지역 위성항법시스템 구축을 위한 기초 자료로 활용될 수 있다. In this paper, integrity analysis in Korean region using GPS, modernized GPS, Galileo, SBAS and GBAS is given. The simulation results show that Cat. Ⅰ requirement can be met using modernized GPS and Galileo alone, however, Cat. Ⅱ and Ⅲ are not met even augmenting SBAS because of VPL. A more efficient augmentation such as GBAS reduces VPL to meet Cat. Ⅱ and Ⅲ requirements in Korean region. This result will be used to design and implement not only an augmentation system but also regional satellite navigation system.