• Journal of the Society of Naval Architects of Korea
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• v.49 no.5
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• pp.410-415
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• 2012

An experimental study is carried out to investigate the near-wake characteristics of a NACA 0018 foil with a flat plate. Two-frame grey-level cross correlation PIV method is used to measure the local flow characteristic around a pitch damping foil to control the vertical motion of high speed crafts in a circulating water channel. The analysis also includes angles of attack 10 and 20 degrees respectively. Reynolds number $Re{\fallingdotseq}3.5{\times}10^4$ based on the chord length(C=100mm) of NACA0018 has been applied during the whole experiments. The distance between the foil and the flat plate is D/C=0.5, 1.0 and 1.5 respectively. The channel effect according as the distance between the foil and the flat plate has a close relation with the velocity distributions around the foil. In the wake of 20-degree of attack, the complex turbulent flow and a thick boundary layer are formed due to the processes of vortex generation and dissipation.

• Resources Recycling
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• v.9 no.4
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• pp.50-55
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• 2000

Recycling technology of aluminum foil scraps into aluminum flake powder by ball milling in dry or wet conditions was studied. Aluminum foil were laminated each other, elongated through microforging by the falling balls, fragmented into small foils and then changed into flake powder during ball milling. It is also possible to recycle foil scraps with thickness less than $60\mu\textrm{m}$ into aluminum paste by wet ball milling. As initial foil thickness decreases, foil is easily milled to flake powder by wet milling in mineral spirits. the appearance and the opaque character of glass painted with aluminum paste obtained by wet milling of foils are similar to those of aluminum paste made by ball milling of gas atomized powder.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.49-53
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• 2005

The objective of this research was to establish the size limitation of micro metal forming and analyze the formability of foil. Flat-rolled ultra thin metallic copper foil($3{\mu}m$ in thickness) was used as a forming material and foil was annealed to improve the formability at the temperature of $385^{\circ}C$. Forming die was fabricated by using etching technique of DRIE(deep reactive ion etching) and HNA isotropic etching. For the forming die and coupe. foil were vacuum packed and the forming was conducted as applying hydrostatic pressure of 250MPa to the vacuum packed unit. We successfully obtained the micro channels of $12\~14{\mu}m$ width and $9{\mu}m$ depth from micro forming process we designed. We also investigated the thickness strain distribution of foil from experiment and FE simulation result. Micro channels had a good formability of smooth surface and size accuracy. We expect that micro metal forming technology will be applied to production of micro parts.

• Journal of the Korean Society of Visualization
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• v.16 no.3
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• pp.52-58
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• 2018

In this study, an experimental facility has been built to measure the cooling performance of a piezoelectric fan. The facility is composed of a heat source made of $50{\mu}m$ Ni-Cr foil, a piezoelectric fan and a rotary fan for cooling the heat source. For two cases where the foil is vertical or horizontal, the surface temperature on the foil has been measured by an IR camera with and without cooling and the cooling performance of both fans has been analyzed. With cooling by both fans, the rotary fan lowers the surface temperature of the foil as a whole, while the piezoelectric fan lowers the surface temperature at the center of the foil locally. It is also found that the cooling effectiveness of the piezoelectric fan is higher on the horizontal foil than on the vertical foil because the natural convection interferes with the jet from the piezoelectric fan.

• Journal of the Korean institute of surface engineering
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• v.22 no.2
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• pp.62-68
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• 1989

Pb2+ ino, added in ctching sohing, is electrodeposited on a alumiunm foil for electrolycic condenser to promote its capacitance. In addition, several factoral factors in etching process are varied to examine how they change the capacitance of the condenser. The capacitance of the condenser made of 0.1 ppm pb electrodeposited aluminum foil is enhanced about 20% than of conventional ane. It is thought out that the enhanement is the result of the act of PbO2, which existed for the conveting of electrodeposited Pb, as a promoter tunnel etching of aluminum foil.

• Proceedings of the KAIS Fall Conference
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• 2001.11a
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• pp.91-94
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• 2001

리튬전지의 vent cap ass'y용의 AI foil에 LDPE(low density polyethylene)만을 coating하였으나 LDPE는 vent cover인 sus와의 열접착성이 우수하지 못하기 때문에 vent 조립시 상당한 주의가 필요했다. 그러나, LDPE보다 열접착성이 우수한 EVA(ethylene vinylacetate)와 EAA(ethylene acrylic acid)의 2중 coating된 AI foil을 이용함으로 열접착성을 향상시킬 수 있었다. 이에 따라, 전해액 누액 등의 전지 불량 원인을 제거함과 동시에 vent cap ass'y의 조립시 공정 불량까지 감소시킬 수 있었다.

• Journal of Radiation Protection and Research
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• v.36 no.1
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• pp.44-51
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• 2011

Activation foil-based Bonner sphere spheres are used to obtain neutron energy spectra of nuclear power plants or accelerator-produced neutrons. The position and the foil mass dependence of response functions should be studied carefully before measurement of Bonner spheres. This study showed that the normal incidence to the foil surface made a large shift of responses while parallel and isotropic incidence made no position dependence. The correlation between foil mass and response was not linear. Therefore, the response functions of activation-foil based Bonner spheres should be calculated for every different foil mass and the direction of Bonner spheres for parallel incidence will be preferred for radioactive neutron source or accelerator target produced neutrons.

• Tribology and Lubricants
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• v.37 no.4
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• pp.117-124
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• 2021

In this study, we perform a 3D CFD conjugate analysis according to the shape of the foil ramp of the air foil thrust bearing, analyze the flow characteristics inside the bearing, and compare the results corresponding to the two shapes. Air has a lower viscosity than lubricating oil. Therefore, the thrust runner of the bearing must rotate at high speed to support the load. The gap between thrust runner and foil is significantly smaller than that of the oil bearing. Hence, it is crucial to analyze the complex flow characteristics inside the bearing to predict the complex flow inside the bearing and performance of the bearing. In addition, flow characteristics may appear differently depending on the ramp shape of the bearing foil, which may affect bearing performance. In this study, we numerically analyze the main flow path of air flowing into the bearing and the secondary flow path used for cooling the bearing using the commercial CFD software ANSYS CFX and compare the flow characteristics for straight and curved foil ramp shapes. Notably, there is a difference in the speed of the flowing air according to the shape of the ramp, which affects the bearing performance.

• Tribology and Lubricants
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• v.40 no.1
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• pp.17-23
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• 2024

This study analyzes the thermal effects on the performance of an air foil thrust bearing (AFTB) using COMSOL Multiphysics to approximate actual bearing behavior under real conditions. An AFTB is a sliding-thrust bearing that uses air as a lubricant to support the axial load. The AFTB consists of top and bump foils and supports the rotating disk through the hydrodynamic pressure generated by the wedge effect from the inclined surface of the top foil and the elastic deformation of the bump foils, similar to a spring. The use of air as a lubricant has some advantages such as low friction loss and less heat generation, enabling air bearings to be widely used in high-speed rotating systems. However, even in AFTB, the effects of energy loss due to viscosity at high speeds, interface frictional heat, and thermal deformation of the foil caused by temperature increase cannot be ignored. Foil deformation derived from the thermal effect influences the minimum decay in film thickness and enhances the film pressure. For these reasons, performance analyses of isothermal AFTBs have shown few discrepancies with real bearing behavior. To account for this phenomenon, a thermal-fluid-structure analysis is conducted to describe the combined mechanics. Results show that the load capacity under the thermal effect is slightly higher than that obtained from isothermal analysis. In addition, the push and pull effects on the top foil and bump foil-free edges can be simulated. The differences between the isothermal and thermal behaviors are discussed.

• 프린팅코리아
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• v.14 no.8
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• pp.88-89
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• 2015

마이크로큐닉스(주)(대표이사 이병열)는 이스라엘 야브네(YAVNE)에 본사를 둔 Heret Printing이 MGI의 디지털 스팟 UV 코팅기 JETvarnish 3D와 핫포일 스댐핑 장비 iFOIL을 도입했다고 최근 밝혔다. 마이크로큐닉스(주)는 MGI의 JETvarnish 3D와 iFOIL 국내 총판을 맡고 있다.