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Kim Y.W.,Pohang Institute of Metal Industry Advancement POMIA | Yoo J.Y.,Seoul National University
Optics and Lasers in Engineering

Transport of particles is commonly encountered in microfluidic channels that deal with solidliquid two-phase flows in conjunction with particles and cells to focus, separate, sort, extract, and filter them. In particular, there is a resemblance between microscale flows and macroscale flows in the sense that the inertial migration of particles cannot be neglected. Thus, the objective of the present article is to review how studies on the transport of solid particles have evolved from classical fluid dynamics to up-to-date microfluidics in view of measurement techniques, flow characteristics, and applications. © 2011 Elsevier Ltd. All Rights Reserved. Source

Jung W.,Seoul National University | Jung W.,Doosan Infracore | Kim Y.W.,Seoul National University | Kim Y.W.,Pohang Institute of Metal Industry Advancement POMIA | And 2 more authors.
Sensors and Actuators, A: Physical

In the present paper, we propose a microscale surface thermometry using SU8/Rhodamine-B thin layer (SRTL). The ultra-thin SRTL is coated on the microheater which serves as a heat source for microscale heating. Surface-temperature distribution of the SRTL is measured with high spatial and temperature resolutions in a temperature range between 30 and 80 °C. Propagation of isotherms on the SRTL is visualized with a temperature resolution on the order of 0.1 °C. Spatial error in the measurement was analyzed, which depends on the size of interrogation window. The present concept of SU8 thin film in combination with Rhodamine-B signifies a considerable improvement in the indirect measurement method of surface temperature inside polymer-based microfluidic channels. © 2011 Elsevier B.V. Source

Min J.,Pohang Institute of Metal Industry Advancement POMIA | Park J.H.,Pohang University of Science and Technology | Sohn H.-K.,Pohang Institute of Metal Industry Advancement POMIA | Park J.M.,Pohang University of Science and Technology
Journal of Industrial and Engineering Chemistry

Silicate conversion coating is considered as an alternative to hexavalent chromium conversion coating for corrosion protection of galvanized steels. However, the coating must be treated with hot air afterward in order to obtain a water resistant silicate layer and to increase corrosion resistance of the coating. Moreover, it is difficult to apply the uniform thermal treatments on the large irregular shaped metal parts. Furthermore, the heat treatment is an energy consuming process. In this work, the effects of adding potassium methyl siliconate (PMS) into the silicate conversion coating on the anti-corrosion properties were studied. The silicate coating layers were formed by the simple immersion into the silicate solutions and the subsequent ambient drying at room temperature. It was verified that the addition of PMS increased the temporary corrosion protection ability without the post-thermal treatments. Coating thickness was around 100. nm and K ion was distributed preferentially at zinc-silicate interface. It was proved that the more hydrophobic surface was formed mainly due to the substantial decrease of the concentration of K ion at the coating surface by the addition of PMS. It was a methyl group of PMS that changed the hydrophilic silicate layers into hydrophobic ones. Subsequently, the enhanced water barrier property of the hydrophobic silicate layers increased the corrosion resistance of the silicate-coated galvanized steel. © 2011. Source

Shon J.H.,Kumoh National Institute of Technology | Shon J.H.,Pohang Institute of Metal Industry Advancement POMIA | Song I.-B.,Kumoh National Institute of Technology | Cho K.-S.,Kumoh National Institute of Technology | And 4 more authors.
International Journal of Precision Engineering and Manufacturing

The aim of this study was to determine the effect of particle size distribution on the microstructure and mechanical properties of spark-plasma-sintered titanium made from commercial pure titanium (CP-Ti) powders. The spark plasma sintering (SPS) of 100-mesh, 200-mesh, 325-mesh CP-Ti powders and mixtures thereof (100-mesh and 325-mesh powders mixed in weight ratios of 3:7, 5:5, and 7:3) was carried out in a flowing atmosphere of Ar + H2 gas at 800∼850°C under a pressure of 30 MPa. Dense titanium with a relative density of up to 99% was found to form for SPS conditions of over 850°C and 30 MPa. The sintered body showed a difference in sintered properties depending on the particle size of the powder: the smaller the particle size, the more rapid the densification, and in terms of the grain size of the sintered body, equiaxed grain of about 20∼40 μm in diameter was formed regardless of the particle size distribution of the powder. Regarding the hardness and tensile properties in the fully densified sintered body, smaller average particle sizes gave rise to higher values because of the increase in the content of interstitial solid solution and the formation of a homogeneous and fine-grained structure through the rapid densification process. © 2014 Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg. Source

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