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Control of Line Width with Active Nano Fountain Pen(ANFP) for Nano manufacturing
Kyoil Hwang,Suk-Han Lee,Youn-Jea Kim,김훈모 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.7
In this paper, modeling of ANFP (active nano fountain pefuzzy algorithm is developed. It was found that line width is affected directly with initial mass of meniscus; velocity of patterning and concentration of ink directly affect line width. The control algorithm using the result of modeling successfully shows that the speed of patterning is increased and a variation of line width is possible compared with DPN (dip pen nano lithograph) and FPN (fountain pen nano lithograph). The control of line width system with ANFP is developed by using fuzzy algorithm. Finally, it is shown that it is possible to develop an effective control of variant line width with the same speed.
드래프트 관이 장착된 교반기 내의 유동 및 혼합특성 연구
황정훈,김윤제,Hwang, Jung-Hoon,Kim, Youn-Jea 한국유체기계학회 2007 한국유체기계학회 논문집 Vol.10 No.1
Because the mixing efficiency is influenced remarkably by varying the geometrical configurations, the study of flow characteristics inside the mechanical agitator is very important to improve the performances. The draught tube in the agitator makes intermixing between the screw and tube by interrupting radial flow, and it makes circulation region in a mixing chamber. In general, the helical screw agitator with a draught tube (HSA) is proved more efficient to mix than the others. Consequently, such as the shapes of helical screw, number of pitches and the variation of angular velocity are the main parameters for improving the capacity of HSA. And also the suspension of the solid particles in the agitator can be determined these parameters. The rate of solids suspension in the mixing chamber was quantified with a statistical average value, of. Numerical analyses were carried out, using a commercial CFD code, Fluent, to obtain the velocity, pressure and particle distributions under steady, laminar flow and no-slip conditions. Results are graphically depicted with various parameters.
Effect of nozzle tip configuration on the micro-droplet formation.
Kim, Byung-Jae,Hwang, In-Ju,Kim, Youn-Jea American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.12
<P>Micro-droplet formation is an emerging area of research due to its wide-ranging applications in micro-fluidic based devices. For high resolution patterning and coating processes in various industrial fields, the formation of micro-droplets should be controlled according to the rheological properties of the working fluids. However, the physical properties of the some of working fluids are limited to meet the industrial applications. In this paper, the effect of the nozzle tip configuration on the micro-droplet formation process was numerically observed. A two-phase level-set modeling method was employed for simulations, and the results for various nozzle shapes were compared. In order to validate the numerical results of ink-jet printing with various operating conditions, we introduced a dimensionless parameter Z which is the factor of correlation of dynamic viscosity with surface tension of a working fluid on the microfluidics of drop-on-demand (DOD) jets, and obtained reasonable values of Z. Also, the numerical results such as velocity and shear rate distributions, etc. were graphically depicted in two-dimensional coordinates.</P>
황정훈(Jung-Hoon Hwang),김준현(Joon Hyun Kim),김윤제(Youn-Jea Kim) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
Helical screw agitator (HSA) is widely used to stir the high viscous fluids in many industrial processes. In order to evaluate the capacity of a helical screw agitator, it is necessary to calculate the flow and mixing characteristics in the given configuration in the vessel with a draught tube. Numerical procedure for the determination of these characteristics is put forward, based on the prediction of transient phenomena such as flow fields and particle suspensions for an agitator in a draught tube. The effects of the rotational frequency and the shape of the screw were also considered. The rate of solid suspension in the agitator was qualitatively estimated with the variation (σ²) which is the representative statistical value. Using a commercial CFD code, Fluent, the velocity, pressure and particle distributions were obtained with unsteady, laminar flow and no-slip condition. Results are graphically depicted with various flow and geometrical parameters.
전극형상 변화가 진공차단기내 축방향 자기장 특성에 미치는 영향
황정훈(Jung-Hoon Hwang),이종철(Jong-Chul Lee),김윤제(Youn-Jea Kim) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.1
The vacuum interrupter (VI) is used for medium-voltage switching circuits due to its abilities and advantages as a compacted environmental friendly circuit breaker. In general, the application of a sufficiently strong axial magnetic field (AMF) permits the arc to be maintained in a diffused mode to a high-current vacuum arc. A full understanding of the vacuum arc physics is very important since it can aid to improve the performance of vacuum interrupter. In order to closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and hydrodynamic fields, simultaneously. In this study, we have investigated the effect of changing geometrical parameters for electromagnetic behaviors of high-current vacuum arcs with two different types of AMF contacts, which are coil-type and cup-type, using a commercial finite element analysis (FEA) package, ANSYS. The present results are compared with those of MAXWELL 3D, a reliable electromagnetic analysis software, for verification.
황정훈(Jung-Hoon Hwang),김윤제(Youn-Jea Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Mechanical agitators are used throughout the industries in which are required to mix two or more reactants in a short time, or mix some of the high viscous fluids. In general, simple impeller type is applied to mix low viscous fluids, while a helical screw agitator (HSA) is applied to the high viscous fluids. The study of flow characteristics inside the agitator is important because the mixing efficiency is greatly affected by changing the geometrical configuration. The HSA with a draught tube is known more efficient than the others. The draught tube makes intermixing between the screw and tube by obstructing radial flow. Consequently, the shapes of helical screw and number of pitches are the main parameters for improving the performance of HSA. In the present study, numerical analyses were carried out, using a commercial CFD code, Fluent, to obtain the velocity and pressure distributions under steady, laminar flow and no-slip condition. Results are graphically depicted with various parameters.
드래프트 관 장착 교반기의 혼합 성능에 관한 수치적 연구
황정훈(Jung-Hoon Hwang),김윤제(Youn-Jea Kim) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
In this study, the performance of a helical screw agitator to mix high viscous fluids has been investigated. The suspension of the solid particles in the agitator can be determined by several parameters including particle diameter, shape of vessel, impeller size and its angular velocity, and rotating direction of stirrer. One of them, the number of pitches of the impeller was the primary factor affecting the mixing efficiency on inelastic fluids, and the influence of the rotational speed ratio on the flow pattern was evaluated. The rate of solids suspension in the mixing chamber was quantified with a statistical average value, σ². Numerical analyses were carried out, using a commercial CFD code, Fluent, to find the best mixing conditions based on the velocity, pressure and particle distributions. From these results, mixing characteristics and performance of an agitator have been analyzed, and results are graphically depicted.
CHARACTERISTICS OF SMOKE CONCENTRATION PROFILES WITH UNDERGROUND UTILITY TUNNEL FIRE
Kim Hong Sik,Hwang In Ju,Kim Youn-Jea Korea Society of Computational Fluids Engineering 2005 한국전산유체공학회지 Vol.10 No.1
Accurate prediction of the fire-induced air velocity, temperature and smoke flow in underground utility tunnel becomes more important for the optimization of design and placement of heat and smoke detectors. In order to improve the safety of underground utility tunnel systems, the behaviors of fire-induced smoke flow and temperature distributions are investigated. Especially, two different cross-sectional shapes of tunnel, such as rectangular and circular types are modeled. Also, fire source is modeled as a volumetric heat source. Three-dimensional thermal-flow characteristics in an underground tunnel are solved by means of FVM using SIMPLE algorithm. The effects of shape geometry on the fire-induced flow characteristics are graphically depicted. It is desirable that heat and smoke detectors are installed on the cables and the top of the wall.
Kim, Hak-Jun,Hwang, In-Ju,Kim, Youn-Jea American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.12
<P> The current transparent oxide semiconductors (TOSs) technology provides flexibility and high performance. In this study, multi-stack nano-layers of TOSs were designed for three-dimensional analysis of amorphous indium-gallium-zinc-oxide (a-IGZO) based thin film transistors (TFTs). In particular, the effects of torsional and compressive stresses on the nano-sized active layers such as the a-IGZO layer were investigated. Numerical simulations were carried out to investigate the structural integrity of a-IGZO based TFTs with three different thicknesses of the aluminum oxide (Al<SUB>2</SUB>O<SUB>3</SUB> insulator (<TEX>$\delta$</TEX>= 10, 20, and 30 nm), respectively, using a commercial code, COMSOL Multiphysics. The results are graphically depicted for operating conditions. </P>