• Title/Summary/Keyword: 메니스커스

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A Study on High Viscosity Phosphor Dispensing Process for Implementation of High-Efficiency White LED (고효율 백색 발광다이오드 구현을 위한 고점도 형광체 정량 토출 공정 연구)

  • Yang, Young-Jin;Kim, Hyung-Chan;Ko, Jeong-Beom;Yang, Bong-Su;Dang, Hyun-Woo;Doh, Yang-Hoi;Cho, Kyung-Ho;Choi, Kyung-Hyun
    • Clean Technology
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    • v.20 no.2
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    • pp.97-102
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    • 2014
  • Currently various studies are underway for dispensing high-viscosity phosphor. These studies have reported limitations and challenges in the dispensing process. The discharged amount of phosphor was approximately the same each time which is important for the implementation of high-efficiency white LED technology. This paper present high-viscosity phosphor dispensing process for white LED implementation by using electrostatic printing technology. The voltage controlled DOD (Drop-On-Demand) discharge experiment was studied to determine angle of drop meniscus at nozzle and dot diameter. With increase in Discharge voltage, the discharge angle of meniscus increased while dot diameter decreased. Therefore it can be concluded that we can control the discharge rate by controling the discharge angle of meniscus.

Study on a Shape Deformation of Water Meniscus for the Rectangular and Circular Tips Moving Horizontally (사각 및 원형 팁의 횡운동에 의한 물 메니스커스 형상변화에 관한 연구)

  • Kim, Sang-Sun;Son, Sung-Wan;Ha, Man-Yeong;Yoon, Hyun-Sik;Kim, Hyung-Rak
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.12
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    • pp.843-851
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    • 2011
  • A two-dimensional immiscible water meniscus deformation phenomena on a moving tip in a channel has been investigated by using lattice Boltzmann method involving two-phase model. We studied the behavior of a water meniscus between the tip and a solid surface. The contact angles of the tip and a solid surface considered are in the range from $10^{\circ}$ to $170^{\circ}$. The velocity of the tip used in the study are 0.01, 0.001, and 0.0001. The shapes of tip considered are rectangular and circular. The behavior of water confined between the tip and a solid surface depends on the contact angles of the tip and a solid surface, and the tip velocity. When the tip is moving, we can observe the various behaviors of shear deformation of a water meniscus. As time goes on, the behavior of a water meniscus can be classified into three different patterns which are separated from the tip or adhered to the tip or sticked to a solid surface according to the contact angles and the tip velocity.

Slot-die Coating Method for Manufacturing Large-area Perovskite Solar Cell (대면적 페로브스카이트 태양전지 제작을 위한 슬롯-다이코팅 방법)

  • Oh, Ju-young;Ha, Jae-jun;Lee, Dong-geun
    • The Journal of the Korea Contents Association
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    • v.21 no.12
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    • pp.918-925
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    • 2021
  • The perovskite solar cell is a next-generation solar cell that replaces the existing silicon solar cell. It is a solar cell device using an organic-inorganic hybrid material having a perovskite structure as a photoactive layer. It has advantages for the process and has shown rapid efficiency improvement over the past decade. In the process of commercialization of such perovskite solar cells, research and development for a large-area coating method should be carried out. As one of the large-area perovskite solar cell large-area coating methods, the slot-die coating method was studied. By using a meniscus to pass over the substrate and coating the solution, the 3D printer was equipped with a meniscus so that it could be coated. Variables that act during coating include bed temperature, coating speed, N2 blowing interval, N2 blowing height, N2 blowing intensity, etc. By controlling these, the perovskite absorption layer was manufactured and the coating conditions for manufacturing large-area devices were optimized.

Phase Matching of Pressure Wave in a Drop-On-Demand Inkjet Print Head (요구 적출형 잉크젯 프린트 헤드에서의 압력파 위상 정합)

  • Kim, Myong-Ki;Hwang, Jun-Young;Lee, Sang-Ho;Kang, Kyung-Tae;Kang, Heui-Seok
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.9
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    • pp.116-125
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    • 2008
  • Inkjet printing technology with a drop-on-demand (DOD) inkget head technology has been recognized as one of versatile and low cost manufacturing tools in the electronics industry. Concerned with control of driving signal, however, general strategy to optimize jetting stability has not been understood well, because of the inherent complex multi-physics nature in inkjet phenomena. Motivated by this, present study investigates the effect of driving waveforms of piezoelectric head on jetting characteristics of DOD inkjet system focused on jetting stability with phase matching of pressure waves in the print head. The results show that velocities and volumes of the ink jetted droplets were linear relations with the driving signal's maximum voltage, while periodic behaviors are observed with the driving signal's pulse widths.

Micro droplet driven by thermocapillary and capillary valve (열모세관에 의한 미소액적 구동과 모세관 밸브)

  • Lim, Nam-Hyuk;Kim, Sung-Wook;Yoo, Jung-Yul
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1777-1782
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    • 2003
  • This paper presents the design, fabrication, and testing of the capillary-induced pressure drop valve, thermocapillary pumping of liquid droplet in hydrophilic channels and the splitting of droplet. The capillaryinduced pressure drop is derived with thermodynamic approach considering three-dimensional meniscus shape which is essential for calculating pressure drop in the diverging shape channel when the aspect ratio is close to one. The micro channel is fabricated via MEMS processes, which consists of the liquid stop valve to retard the liquid droplet, thermocapillary pumping region and the bifurcation region. Also the micro heaters are fabricated to drive the droplet by thermocapillary. The theoretical approaches agree well with the experimental data. The functionality of capillary valve is confirmed to be valid when the aspect ratio is smaller than one. To overcome the difficulty in splitting of the droplet due to the pressure drop in the general Y-shape channel, the protrusion shape is employed for easy splitting in the bifurcation channel.

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On-demand electrohydrodynamic printing with meniscus controls by a piezoelectric actuator (압전 액츄에이터의 메니스커스 제어를 통한 온 디멘드(On-demand) 전기 수력학 프린팅)

  • Kim, Y.J.;Kim, D.H.;Hwang, J.H.;Kim, Y.J.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2009.06a
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    • pp.351-352
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    • 2009
  • On-demand ejection of ultra-fine droplets that uses both electrohydrodynamic (EHD) force and mechanical actuation is presented. The liquid meniscus was controlled by a piezoelectric actuator and droplets were ejected by EHD force. Through these effects, it was possible to obtain a high operational jetting frequency of 5kHz with a short delay-time (about 50 us) when compared with existing on-demand EHD jetting methods, such as the pulsating jet mode (3-10 msec) and the pulsed-voltage cone-jet mode(3.6 msec). Also, we obtained ultra-fine droplets at a volume that was at the femto-liter level simultaneously. The jetting characteristics were examined for both hydrophobicity and hydrophilicity of the surface of a capillary.

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The Study of annealing condition and press method of glass for making glasses lens (안경렌즈 제작을 위한 유리의 열처리조건과 성형방법에 관한 연구)

  • Cha, Jung Won;Ha, Tae Wook
    • Journal of Korean Ophthalmic Optics Society
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    • v.6 no.1
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    • pp.133-137
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    • 2001
  • The method to make glass is tried first thing in domestic study for glasses lens. Tg of glass KzFSl was measured by DSC experiment and press method of glass of meniscus shape was studied for minimize the cost. Tg was increased $483^{\circ}C$ to $501^{\circ}C$ with increasing heating rate $2^{\circ}C/min$ to $20^{\circ}C/min$. It shows Arrhenius temperature dependence and the activation energy of Tg is ${\Delta}E$=409 kJ/mole(4.25eV) by using Ozawa method and Tg is near $480^{\circ}C$. The melt of KzFSl powder was poured to concave cast stainless and pressed convex cast stainless. The quenched glass was slow cooled with cooling rate $0.25^{\circ}C/min$ in temperature range $520{\sim}430^{\circ}C$. The glass was made without strain. It has meniscus shape and same size to commercial glasses lens.

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The Fluxless Wetting Properties of TSM-coated Glass Substrate to the Pb-free Solders (TSM(Top Surface Metallurgy)이 증착된 유리기판의 Pb-free 솔더에 대한 무플럭스 젖음 특성)

  • 홍순민;박재용;박창배;정재필;강춘식
    • Journal of the Microelectronics and Packaging Society
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    • v.7 no.2
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    • pp.47-53
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    • 2000
  • The fluxless wetting properties of TSM-coated glass substrate were evaluated by the wetting balance method. We could estimate the wettability of the TSM with new parameters obtained from the wetting balance test for one side-coated specimen. It was more effective in wetting to use Cu as a wetting layer and Au as a protection layer than to use Au itself as a wetting layer. The SnSb solder showed better wettability than SnAg, SnBi, and SnIn solders. The contact angle of the one side-coated glass substrate to the Pb-free solders could be calculated from the farce balance equation by measuring the static force and the tilt angle.

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Effects of the Mass of Working Fluid on the Thermal Performance of Heat Pipe with Axial Grooves (그루브형 히트파이프에서 작동유체량이 히트파이프 성능에 미치는 영향)

  • Suh, Jeong-Se;Park, Young-Jun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.1
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    • pp.1-8
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    • 2003
  • An analytical and experimental study of the thermal performance of axial heat pipe with axial groove is conducted to determine the optimal mass of working fluid for the maximum heat transport capacity of heat pipe with axial grooves. Generally, the mass of working fluid has been fully charged by considering only a geometrical shape of axial grooves embedded in a heat pipe. When the heat pipe is operated in a steady state, the meniscus re-cession phenomena of working fluid is occurred in the evaporator region. In this work, the optimal mass of working fluid was obtained from the axial variation of capillary pressure, the radius of curvature and wetting angle of meniscus of liquid-vapor interface. Experimental results were also obtained by varying the mass of working fluid within a heat pipe, and presented for the maximum heat transport capacity corresponding to the operating temperature and the elevation of heat pipe. Finally, the analytical results of the optimal mass of working fluid were compared with those of the experimental mass of working fluid.

Soil Properties in Relation to Elastic Wave (탄성파를 이용한 흙의 특성연구)

  • 조계춘;이인모
    • Journal of the Korean Geotechnical Society
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    • v.18 no.6
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    • pp.83-101
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    • 2002
  • Elastic waves provide an important information about the soil mass in the near-surface. Soil properties in relation to elastic wave parameters are clarified to facilitate the application of geophysical technique to soil characterization. As an example, experiments are performed to gain further insight into the behavior of unsaturated particulate materials using bender elements. The small strain stiffness is continuously measured on specimens subjected to drying, and changes in stiffness are related to changes in interparticle forces such as capillarity, bonding due to ion sharing, buttress effect due to fine migration, and cementation due to salt precipitation. The rate of menisci regeneration is studied after a perturbation as well. Finally, several phenomena associated with the evolution of capillary forces during drying are identified.