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N/O/N 박막 다이아프레임을 이용한 광섬유 압력센서의 제작 및 그 압력특성
유양욱,김명규,박동수,김창원,김진섭,이정희,손병기 경북대학교 센서기술연구소 1995 센서技術學術大會論文集 Vol.6 No.1
The 0.6 μm N/O/N triple layer, Si_(3)N_(4)(150 nm)/SiO_(2)(300 nm)/Si_(3)N_(4)(150 nm), was deposited on silicon substrate and the N/O/N thin film diaphragm was formed using anisotropic etching technique. The stress of the formed diaphragm was very small with temperature variations. Combining this diaphragm and the optical fiber, intensity-type pressure sensor was fabricated and its pressure characteristics were investigated. The relation between the optical output power, inversely proportional to the deflection of the diaphragm, and the applied pressure was almost linear in 0~77 torr range.
주기적 기둥 패턴의 나노 구조물 위에서 힘을 받는 수액적의 거동 특성
정욱진(Woog-Jin Jeong),하만영(Man-Young Ha),윤현식(Hyun-Sik Yoon) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Using molecular dynamics simulations of an atomistic water model, we study the behavior characteristics of the water droplet under a constant horizontal force on graphite surfaces with periodic nano-sized pillars. We first select two heights of pillars that Cassie-Baxter state and Wenzel state are been in static equilibrium state when a water droplet is put on the pillar surfaces. Then, we apply a constant horizontal force to the water droplet that is in static equilibrium state and observe the behavior characteristics of it. The simulation results show that there is a interesting moving mechanism. In both cases, moving velocity of water droplet is similar or slightly low compared with a case of the flat surface in spite of the high static contact angle: this shows an enhancement of static hydrophobicity by existence of pillars does not leads to the increase of mobility of water droplet.
이진욱(Jin Woog Lee),이대성(Dae Sung Lee),하만영(Man Yeong Ha),윤현식(Hyun Sik Yoon) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.11
The incompressible viscous flow past a sphere under forced oscillation is numerically investigated at a Reynolds number of 300. The immersed boundary method is used to handle the sphere oscillating vertically to the streamwise direction. There are two important variables to characterize the oscillating state of a sphere. One is an oscillating amplitude normalized by the sphere diameter is set as a fixed number of 0.2. Another is the frequency ratio which is defined by fe/fo, where fe and fo are the excited frequency and the natural frequency of vortex shedding for the stationary sphere. In this study, three different frequency ratios of 0.8, 1.0 and 1.2 are considered. The results show a periodic flow with hairpin vortices shedding from upper and lower positions as well as vortical legs obliquely extended by oscillating motion of sphere. The enveloping vortical structure experience rupture twice in one period of oscillation. As the frequency of oscillation is increased, the vortical legs are getting shorter and eventually the hairpin vortices are much closer to the adjacent one.
고열유속에 놓인 수냉식 냉각장치 표면의 냉각 성능 개선
정욱진(Woog Jin Jeong),이근식(Geun Sik Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
In order to reduce the thermal stress of the water-cooling wall in high heat flux, it is necessary to reduce the wall temperature and its gradient. In this study, characteristics of inner flow and temperature field and the wall temperature distribution were numerically examined with variations of the water channel geometries (such as the length of inner wall separating between in and out water-flow, the rounding size of the comer, and swirl angle) and the external heat flux. As a result, the wall temperature was mainly reduced by extending the inner wall length compared with other channel geometries. However, in a point of view of the wall temperature gradient, only variations of the water channel geometries had difficulty in the reduction but decrease in external heat flux could be a desirable solution of the temperature gradient reduction.
이진욱(Jin Woog Lee),윤현식(Hyun Sik Yoon),하만영(Man Yeong Ha) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The objectives of this paper are to investigate the heat transfer characteristics of a cylinder concerning the primary instability with development of the unsteady von Karman vortex street. The flow around an infinitely long circular cylinder is a classical problem in fluid dynamics. Despite the simple geometry, it shows many physical phenomena that is often important for engineering problem to expect the drag and lift force as well as vortex shedding frequency. The fractional step method has been employed with generalized coordinates system to numerically solve the incompressible Navier-Stokes equations.
Dynamic Behavior of WaterDroplets on Solid Surfaceswith Pillar-Type Nanostructures
Jeong, Woog-Jin,Ha, Man Yeong,Yoon, Hyun Sik,Ambrosia, Matthew American ChemicalSociety 2012 Langmuir Vol.28 No.12
<P>In the present study, we investigated the static and dynamic behavior of water droplets on solid surfaces featuring pillar-type nano-structures by using molecular dynamics simulations. We carried out the computation in two stages. As a result of the first computational stage, an initial water cube reached an equilibrium state at which the water droplet showed different shapes depending on the height and the lateral and gap dimensions of the pillars. In the second computational stage, we applied a constant body force to the static water droplet obtained from the first computational stage and evaluated the dynamic behavior of the water droplet as it slid along the pillar-type surface. The dynamic behavior of the water droplet, which could be classified into three different groups, depended on the static state of the water droplet, the pillar characteristics (e.g., height and the lateral and gap dimensions of the pillars), and the magnitude of the applied body force. We obtained the advancing and receding contact angles and the corresponding contact angle hysteresis of the water droplets, which helped classify the water droplets into the three different groups.</P>
커먼레일을 장착한 대형 디젤엔진에서 디젤과 JP-8의 분무 및 연소특성 평가
전진욱(Jin-woog Jeon),이진우(Jin-woo Lee),박정서(Jung-seo Park),배충식(Choong-sik Bae) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
An experimental study was performed to assess the effect of diesel and JP-8 aviation fuel on the spray characteristics, performance and emissions in a single cylinder optical diesel engine. Both fuels were injected via an 8-hole solenoid-driven injector in a common-rail injection system. For better understanding of spray development, the macroscopic images were captured with high speed camera, offered evidences for the results of performance and emissions. From macroscopic spray images, the spray tip penetration of JP-8 shorter than that of diesel while spray angle of JP-8 was wider than that of diesel. It indicates that the vaporization of JP-8 is superior to that of diesel. The lower cetane number of JP-8 resulted in increased portion of premixed combustion. The IMEP with JP-8 is lower than that of diesel-fueled engine. Especially, using JP-8 has a potential for reducing soot.
Mobile Jaw crusher system의 Jaw crusher 밸런싱 해석
권진욱(Jin-Woog Kwon),김낙인(Nag-In Kim),기형호(Jason Ki) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4
The unbalanced masses of moving parts of Jaw crusher mechanism generate unbalanced forces. The unbalanced forces generate excessive vibration on the crusher structures so the forces transmitted main frame by crusher mounts generates the vibration of structures of the main frame. Therefore the simulation study is required to minimize the vibration using counter balance weight of the crusher flywheel. This paper shows that three forces(vertical force, horizontal force, and couple force) are generated on the crusher mounts. Also the couple force generated by vertical force on the first and the third mount of the jaw crusher was regarded as the key factor which generates the vibration of the main frame so the study that selects optimal weight and position of the counter-balance has been made to minimize the couple force.