• Title/Summary/Keyword: flow focusing

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Nanoparticle patterning using nanoparticle focusing mask (나노입자 집속 마스크를 이용한 나노입자 패턴 형성)

  • You, Suk-Beom;Lee, Hee-Chul;Kim, Hyoung-Chul;Choi, Man-Soo
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.1713-1717
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    • 2008
  • We have developed a nanoparticle focusing mask which can generate particle arrays directly on the large area with high resolution. Using this mask, nanomaterials are precisely deposited onto desired positions on a substrate surface. We obtained various sizes of arrays ranging from 80 nm to 6 ${\mu}m$ with silver and copper nanoparticles that are generated by a spark discharge and an evaporation-condensation method. The feather size is much smaller than that of mask openings due to the focusing effects, like electrostatic lens, caused by charge or electric potential on insulator mask surface, which also prevent a mask clogging. The particle array size depends on the size of mask open patterns and focusing effects near the mask relate to ion flow rate and electric potential. We have demonstrated that diverse size of arrays with high resolution could be obtained repeatedly using the same sized mask in atmosphere.

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A Study on the Flow State Scale of English Speaking and Listening in the e-Learning Environment (e-Learning 환경에서 영어 말하기와 듣기 학습자의 몰입경험(flow) 척도개발에 관한 탐색적 연구)

  • Kang, Jung-Hwa;Han, Kum-Ok;Shin, Dong-Ro
    • Journal of Digital Convergence
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    • v.6 no.3
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    • pp.13-22
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    • 2008
  • The purpose of this study is to explore 'Flow Experience' of those studying English speaking and listening in the e-Learning environment. The exploration of flow experience in this study is based on the literature research of Csikszentmihalyi's flow models and other studies. There have been many studies on flow experience focusing on arts, leisure and sports in accordance with Csikszentmihalyi's original theory, however, his flow theory has recently been adapted to the educational field. Nonetheless, it is in the e-learning environment, rather than the face-to-face traditional teaming environment, that there is not enough flow state measurement scale. Therefore, it is important to develop as a stepping stone a flow state scale for those who study English speaking and listening by the cyber-native-speaker on e-Learning environment to improve their satisfaction and achievement.

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An Experimental Study of The Effects of The Mixing Vane on Air-water Mixed Flow

  • Kim, Soo-Hyung;Baek, Won-Pil;Chang, Soon-Heung
    • Proceedings of the Korean Nuclear Society Conference
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    • 1996.05b
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    • pp.331-336
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    • 1996
  • The effects of a mixing vane on air-water mixed flow have been experimentally studied in this work, to investigate the basic mechanisms that the mixing vane affects critical heat flux (CHF). Experiment was performed for various flow rates focusing on bubbly flow and annular flow patterns. Acrylic tube (1.7m long, 11 mm I.D.) and the split vane type mixing vane were used, and ring-type conductance probes were used to measure the liquid film thickness in annular flow. Experimental results show that, (a) bubbly-to slug flow transition and churn-to-annular flow transition occur respectively near the mixing vane compared to the tests without mixing vane, (b) in bubbly flow region, the mixing vane breaks the bubbles into smaller ones and forwards bubbles to the center region of the tube by the centrifugal force, (c) the liquid film thickness in annular flow is decreased near the mixing vane for mass fluxes.

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Effect of taper on fundamental aeroelastic behaviors of super-tall buildings

  • Kim, Yong Chul;Tamura, Yukio;Yoon, Sung-Won
    • Wind and Structures
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    • v.20 no.4
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    • pp.527-548
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    • 2015
  • Aeroelastic wind tunnel experiments were conducted for conventional and tapered super-tall building models to investigate the effect of taper on fundamental aeroelastic behaviors in various incident flows. Three incident flows were simulated: a turbulent boundary-layer flow representing urban area; a low-turbulent flow; and a grid-generated flow. Results were summarized focusing on the effect of taper and the effect of incident flows. The suppression of responses by introducing taper was profound in the low-turbulence flow and boundary-layer flow, but in the grid-generated flow, the response becomes larger than that of the square model when the wind is applied normal to the surface. The effects of taper and incident flows were clearly shown on the normalized responses, power spectra, stability diagrams and probability functions.

Electroosmotic Flows in Microfluidic Chips

  • Yang R.-J.;Fu L.-M.;Lee G.-B.
    • 한국전산유체공학회:학술대회논문집
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    • 2003.10a
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    • pp.123-125
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    • 2003
  • Understanding the physics of electroosmotic flow is important to the optimum design and operation of microfluidic systems. Recent development on the topic in our group is summarized in this presentation. Applications to the variable-volume-Injection, micro flow switch, electrokinetic focusing, and flow cytometer will be presented with our novel design and control.

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A Study on Numerical Analysis and Performance Improvement of Ventilation Systems in Coating Room (코팅 룸 배기시스템 수치해석 및 성능개선에 대한 연구)

  • Lee, Ki Yeon;Kim, Kug Weon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.5
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    • pp.2086-2091
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    • 2013
  • One of the most important objects for the industrial ventilation is to protect worker's health from the harmful substances. Mainly in industrial ventilation, the harmful substances broken out through manufacturing process are to be quickly emitted outside. Recently the importance of the industrial ventilation increases with the recognition change of industrial ventilation from manufacturing focusing to human focusing. In this paper, the air flow simulation inside the coating room is performed. All the coating room and the ventilation system are modeled by SolidWorks program and air flow distribution and ventilation performance are analyzed by Flow simulation program. And the air flow directions and the air flow velocities inside the coating room are enhanced with the use of local ventilation.

A Study on the Flow Characteristics of the Spiral Flow Nozzle with the Width Change of Annular Slit

  • Kim, T.H.;Setoguchi, T.;Lee, Y.W.
    • Journal of the Korean Society of Visualization
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    • v.7 no.1
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    • pp.14-20
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    • 2009
  • In comparison with previous researches fur swirling flow, the spiral flow self-generated in the spiral flow nozzle has some different characteristics. It is not needed a compulsive tangential momentum to get its velocity component and has long potential core, relatively low swirl ratio, and high focusing ability. In this study, the self-generated mechanism of the spiral flow was clarified and the effect on the width of annular slit on spiral flow characteristics was investigated experimentally and numerically. As a result, the existence of tangential velocity component regardless of a compulsive angular momentum is clarified and the results obtained by experiment have a satisfactory agreement with those by numerical method, quantitatively and qualitatively.

A Study on Parameter Estimation for SWAT Calibration Considering Streamflow of Long-term Drought Periods (장기 가뭄기간의 유출량을 고려한 SWAT 보정 매개변수 추정 연구)

  • Kim, Da Rae;Kim, Seong Joon
    • Journal of The Korean Society of Agricultural Engineers
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    • v.59 no.2
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    • pp.19-27
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    • 2017
  • Recently, the hydrological model Soil Water Assessment Tool (SWAT) has been applied in many watersheds in South Korea. This study estimated parameters in SWAT for calibrating streamflow in long-term drought periods. Therefore, we focused on the continuous severe drought periods 2014~2015, and understand the model calibrated parameters. The SWAT was applied to a $366.5km^2$ Gongdo watershed by using 14 years (2002~2015) daily observed streamflow (Q) including two years extreme drought period of 2014~2015. The 9 parameters of CN2, CANMX, ESCO, SOL_K, SLSOIL, LAT_TIME, GW_DELAY, GWQMN, ALPHA_BF were selected for model calibration. The SWAT result by focusing on 5 normal years (2002~2006) calibration showed the 14 years average Nash-Sutcliffe model efficiency (NSE) for Q and 1/Q with 0.78 and 0.58 respectively. On the other hand, the 14 years average NSEs of Q and 1/Q by focusing on 2 drought years (2014~2015) calibration were 0.86 and 0.76 respectively. Thus, we could infer that the SWAT calibration trial by focusing on drought periods data can be a good approach to calibrate both high flow and low flow by controlling the 9 drought affected parameters.

Numerical Simulations of an Unsteady Shock Wave Propagating into a Helmholtz Resonator (Helmholtz 공명기 내부를 전파하는 비정상 충격파의 수치해석)

  • Lee, Y.K.;Gweon, Y.H.;Shin, H.D.;Kim, H.D.;AOKI, T.
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1643-1648
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    • 2004
  • When a shock wave propagates into a Helmholtz resonator, very complicated wave phenomena are formed both inside and outside the resonator tube. Shock wave reflection, shock focusing phenomena and shock-vortex interactions cause strong pressure fluctuations inside the resonator, consequently leading to powerful sound emission. In the present study, the wave phenomena inside and outside the Helmholtz resonator are, in detail, investigated with a help of CFD. The Mach number of the incident shock wave is varied below 2.0 and several types of resonators are tested to investigate the influence of resonator geometry on the wave phenomena. A TVD scheme is employed to solve the axisymmetric, compressible, Euler equations. The results obtained show that the configuration of the Helmholtz resonator significantly affects the peak pressure of shock wave focusing, its location, the amplitude of the discharged wave and resonance frequency.

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Model for the Inertial Focusing of Particles Using an Atmospheric Aerodynamic Lens (상압 공기역학적 렌즈의 입자 관성집속 모델)

  • Lee, Jin-Won;Lee, Min-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.3
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    • pp.315-321
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    • 2001
  • Aerodynamic lenses are widely used in generating particle beams of high density and small diameter, but analytical or modeling studies are limited only in the free molecular regime. In this study, it is shown that generating particle beam is also possible in atmospheric pressure range, and the mechanism of generating particle beam using an orifice is analysed into three different parts : fluid dynamic contraction, diffusional defocusing, and inertial focusing. In laminar flow conditions, the diffusional defocusing effect can be neglected, and the effects of inertial focusing can be expressed in terms of the orifice size and Stokes number. Numerical experiments are done for two different orifices, d/D=1/5 and 1/10 and particle diameter d(sub)p=1-10 ㎛. The results for two different orifices can be made into a single curve when a modified Stokes number is used. The inertial focusing effect diminishes when the modified Stokes number becomes smaller than 10(sup)-2.