• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.92-96
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• 2019

In the presence of ${\mu}-tip$ embedded in a slot-die head for stripe coatings, there arises the capillary flow that limits an increase of the stripe density, which is required for the potential applications in organic light-emitting diode displays. With an attempt to suppress it, we have employed a computational fluid dynamics software and performed simulations by varying the ${\mu}-tip$ length and the contact angles of the head lip and ${\mu}-tip$. We have first demonstrated that such a capillary flow phenomenon (a spread of solution along the head lip) observed experimentally can be reproduced by the computational fluid dynamics software. Through simulations, we have found that stronger capillary flow is observed in the hydrophilic head lip with a smaller contact angle and it is suppressed effectively as the contact angle increases. When the contact angle of the head lip increases from $16^{\circ}$ to $130^{\circ}$, the distance a solution can reach decreases sharply from $256{\mu}m$ to $44{\mu}m$. With increasing contact angle of the ${\mu}-tip$, however, the solution flow along the ${\mu}-tip$ is disturbed and thus the capillary flow phenomenon becomes more severe. If the ${\mu}-tip$ is long, the capillary flow also appears strong due to an increase of flow resistance (electronic-hydraulic analogy). It can be suppressed by reducing the ${\mu}-tip$ length, but not as effectively as reducing the contact angle of the head lip.

• Analytical Science and Technology
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• v.17 no.6
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• pp.470-475
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• 2004

The mercury film thin layer flow cell (MFTLFC) which yielded the highest sensitivity for the electrochemical reduction of doxorubicin was constructed by coating the glassy carbon working electrode (GCE; $A=0.208cm^2$) with $5{\mu}L$ of HgO coating solution (0.5% HgO + 0.25% polystyrene/cyclohexanone) and subsequently followed by applying a potential of -0.40 V for 300 sec in the flow stream of an acetate buffer of pH 4.5. The voltammogram of doxorubicin reached the diffusion current plateau at -0.53 V vs. a Ag/AgCl (3 M NaCl) in the MFTLFC. The diffusion current (Id) of doxorubicin at the MFTLFC was 1.7 times greater than the Id obtained at the TLFC employing a bare glassy carbon working electrode. When the peak areas (electric charge) were plotted vs. concentrations of standard anthracyclines, the calibration factors of doxorubicin and daunorubicin were $1.12{\times}10^8{\mu}C/M$ (coefficient of determination; $R^2$: 0.969) and $0.98{\times}10^8{\mu}C/M$> ($R^2$: 0.999), respectively in the concentration range between $1.0{\times}10^{-8}M$ and $1.0{\times}10^{-6}M$.

• Journal of the Korean Magnetics Society
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• v.25 no.3
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• pp.67-73
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• 2015

This is a basic research for improving soft magnetic property of Fe based nano crystalline alloy powder core. The main study is done around characteristics of permeability, core loss, and DC bias depending on amount of insulation coating agent and particle size. First, $Fe_{73.5}Si_{13.5}B_9Nb_3Cu_1$ amorphous alloy ribbon was fabricated by using the planar flow casting (PFC) device. Then, heat treatment and ball milling were done to obtain alloy powder. The amount of polyether imide (PEI) added to it was varied by 0.5, 1.0, 2.0, 2.5 wt% to have compression molding into $16ton/cm^2$. After going through crystalline heat treatment, the made toroidal nano crystalline powder core ($OD12.7mm^*ID7.62mm^*H4.75mm$) had smaller permeability as amount of insulation coating agent decreases. However, it was found out that core loss and DC bias characteristics have been improved. The reason for this results were expected to be because green density of power core decreases as amorphous alloy powder particles become smaller as amount of alloy powder insulation coating agent increases, it was determined that 1 wt% of insulation coating agent is appropriate. Also, for powder core made based on alloy powder size with amount of insulation coating agent fixed at 1 wt%, effective permeability and core loss were outstanding as particle size became bigger. However, characteristics of DC bias became worse as applied DC field increases. This is expected to be due to insulation effect, residual pores, or molding density of powder core resulting from thickness of coating on surface of alloy powder.

• Journal of ILASS-Korea
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• v.16 no.1
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• pp.37-43
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• 2011

The present study conducted computational simulation for multiphase flow in the flame spray coating process with commercially available Ni-Cr powders. The flows in a flame spray gun is characterized by very complex phenomena including combustion, turbulent flows, and convective and radiative heat transfer. In this study, we used a commercial computational fluid dynamics (CFD) code of Fluent (ver. 6.3.26) to predict gas dynamics involving combustion, gas and particle temperature distributions, and multi-dimensional particle trajectories with the use of the discrete phase model (DPM). We also examined the effect of particle size on the flame spray process. It was found that particle velocity and gas temperature decreased rapidly in the radial direction, and they were substantially affected by the particle size.

• Journal of Power System Engineering
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• v.16 no.2
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• pp.49-53
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• 2012

Thermal spray coatings developed by deposition of splats, it formed by impacting molten droplets on substrates during thermal spray process. In this study, the Ni-based coatings were fabricated by thermal spray process with two different process parameters, oxygen gas flow and acetylene gas flow, with three different levels of each parameters. The morphology of splats and microstructure were observed by optical microscope. Hardness test were performed on the Ni-based coatings. It was confirmed that process parameters of thermal spray process have effect in morphology of splats. These effects also have important implications on the deposit microstructure and properties of Ni-based coatings.

• Journal of Power System Engineering
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• v.16 no.2
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• pp.54-59
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• 2012

In the present study, process optimization for thermal-sprayed Ni-based alloy coating has been performed using Taguchi method and analysis of variance(ANOVA). Ni-based alloy coatings were fabricated by flame spray process on steel substrate, and the hardness test and wear test were performed. Experiments were designed as per Taguchi's L9 orthogonal array and tests were conducted with different Oxygen gas flow, Acetylene gas flow, Powder feed rate and Spray distance. Multi response signal to noise ratio (MRSN) was calculated for the response variables and the optimum combination level of factors was obtained simultaneously using Taguchi's parametric design.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.417-419
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• 1995

Polymer-coated piezoelectric crystals were applied to analyze response characteristic of organic gases. AT-cut quartz crystal with 9 MHz resonant frequency can measure mass of 1 nanogram. Flow type gas-sensing system was used in this experiment. Flow type gas-sensing system has very simple apparatus and shows very fast frequency response for injection of organic gas. We have made parameter using relaxation ratio of frequency response for organic gas. Consequently, we found that the parameter had no relation with quantity of gas injection and dipping.

• Tribology and Lubricants
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• v.26 no.3
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• pp.157-161
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• 2010

This study investigated the effects of spray parameters on wear behavior of the Ni-based hard coatings fabricated by thermal spray process. The experiment was designed by an orthogonal array, the Ni-based hard coatings were fabricated according to this experimental design. The wear test was performed on these coatings using ball-on-disk wear tester. The ANOVA was used to analyze the effects of spray parameters on the wear rate of these coatings, as a result, oxygen gas flow and acetylene gas flow were determined as main factors effected on the wear rate. The effects of these two factors on wear behavior were observed by using SEM and EDX.

• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.2
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• pp.66-75
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• 2006

The effect of antifreeze solution liquid film on the frost prevention is experimentally investigated. It is desirable that the antifreeze solution spreads widely on the heat exchanger surface forming thin liquid film to prevent frost nucleation while having small thermal resistance across the film. A porous layer coating technique is adopted to improve the wettability of the antifreeze solution on a parallel plate heat exchanger. The antifreeze solution spreads widely on the heat exchanger surface with $100{\mu}m$ thickness by the capillary force resulted from the porous structure. It is observed that the antifreeze solution liquid film prevents a parallel plate heat exchanger from frosting. The reductions of heat and mass transfer rate caused by the thin liquid film are only $1{\sim}2%$ compared with those for non-liquid film surface.

• Advances in materials Research
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• v.6 no.4
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• pp.343-348
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• 2017

High-pressure gas atomization was employed to prepare the Fe-based $Fe_{50}Cr_{24}Mo_{21}Si_2B_3$ alloy powder. The effect of flow rate of atomizing gas on the median powder diameter was studied. The results show that the powder size decreased with increasing the flow rate of atomizing gas. Fe-based alloy coatings with amorphous phase fraction was then prepared by high velocity oxygen fuel spraying (HVOF) of gas atomized $Fe_{50}Cr_{24}Mo_{21}Si_2B_3$ powder. Microstructural studies show that the coatings present dense layered structure and low porosity of 0.17% in about $200{\mu}m$ thickness. The Fe-based alloy coating exhibits an average hardness of about 1230 HV. Our results show that the HVOF process results in dense and well-bonded coatings, making it attractive for protective coatings applications.