• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.304-311
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• 2006

Experiments on evaporative spray cooling on the square plate heaters with plain or micro-porous coated surfaces were performed in this study. Micro-porous coated surfaces were made by using DOM [Diamond particle, Omegabond 101, Methyl-Ethyl-Keton] method. In case of purely air-jet cooling, the micro-porous coating doesn't affect the cooling capacity. In spray cooling three different flow patterns (complete wetting, evaporative wetting, dryout) are observed on both plain and micro-porous coated surfaces. The effects of various operating conditions, such as water flow rate, particle size, and coating thickness were investigated on the micro-porous coated surfaces. It is found that the level of surface wetting is an important factor to determine the performance of spray cooling. It depends on the balance between absorbed liquid amount by capillary force over porosity and the evaporative amount. The micro-porous coated surface has largest cooling capacity, especially in the evaporative wetting zone. It is found that the effects of liquid flow rate and coating thickness are significant in evaporative wetting zone, but are not in complete wetting and dryout zones.

• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.9_10
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• pp.1153-1159
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• 2003

The effects of changing aqueous solution properties by nonionic surfactants on wetting behavior and water retention properies of hydrophobic PET (polyethylene terephthalate) fabric were reported. The aqueous solution properties were diversified by mixing and diluting two nonionic surfactants, i.e., sorbitan monolaurate (Span 20) and polyoxyethylene(20) sorbitan monolaurate (Tween 20). The surface wetting properties ($cos{\theta}$) of PET fabric were greatly improved by adding $10^{-1}g/dl$ Tween 20 and further improved by mixing Span 20 to the system. The water retention properties (W) of PET fabric were also greatly increased by addition of $10^{-1}g/dl$ Tween 20. In diluted surfactant systems, the $cos{\theta}'s$ were increased with decreasing surface tension of aqueous liquids. The ratios of aqueous liquid retained in the pore structure to liquid retention capacity (W/H) were also increased with decreasing surface tension, however, W/H values were dramatically increased right after critical micelle concentration (cmc). The existence of micelles was important for the retention of aqueous liquids in the fabric. The critical surface tension of PET fabric used was found to be 28.7dyne/cm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.249-254
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• 2020

An 80 nm thick zinc aluminate thin film was deposited on a glass substrate via radio-frequency (rf) magnetron sputtering and heat treated to analyze changes in the wetting angles due to a surface modification. The thin films were modified from hydrophilic to hydrophobic by a simple thermal treatment. The surface modification from a heat treatment increased the wetting angles up to 111°, which was explained by the relationship with the excess surface area. The wetting angles of the annealed thin films decreased with increasing exposure time under ambient conditions, which was attributed to the oxygen vacancies in the films that were introduced during deposition. The annealed thin films were treated by ionized oxygen via oxygen plasma. After the oxygen plasma treatment, the decreased wetting angles were maintained at ~95° for 11 days.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.2
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• pp.173-177
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• 2007

Electro-wetting display (EWD) that displays information by controling movement of fluid is one of the strong candidates for electronic paper display (EPD). In EWD cell. the movement of oil which locates between hydrophobic insulation layer and deionized water is rather random, which makes it difficult to realize gray scale, fast response time, and good color characteristics. In this paper, we investigated how to control the oil movement in specific one direction by surface treatment and pattered electrodes. From these experiments, we could control oil movement in a desired direction.

• Weed & Turfgrass Science
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• v.6 no.4
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• pp.313-321
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• 2017

Wetting agent is designed to reduce the surface tension of the liquid and spread more easily across or penetrate into the soil against water repellency. The effect of wetting agent to seed germination is not clear. Using germination enhancer is one of the methods to increase the germination speed of turfgrass seeds and to shorten establishment period. The objective of the study was to evaluate germination enhancer and wetting agent for quick establishment of various Kentucky bluegrass cultivars. The germination enhancer was used at two levels of 0.3 and $0.6ml\;kg^{-1}$ as low and high, respectively. Two levels of wetting agent were of 0.46, and $0.92ml\;m^{-2}$ as low and high, respectively. Germination enhancer has no synergistic effect with wetting agent. When quick establishment is required, selection of cultivar would be more effective instead of using germination enhancer and wetting agent. Among Kentucky bluegrass cultivars, 'Award' had the greatest turfgrass coverage for establishment and the greatest turfgrass color and quality based on the result of the study. When quick establishment is required, selection of cultivar would be more effective instead of using germination enhancer and wetting agent.

• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.497-502
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• 2005

This study investigated the effects of the substrate and powder content on the fabrication of SiO$_{2}$ photonic crystals by evaporation method. Photonic crystals were self-assembled on quartz, Corning 1737 glass, slide glass, and ITa glass to verify the effects of the wetting angle and surface morphology. The powder contents of the solution were varied from 0.2 to 2.0 wt$\%$. The number of photonic crystal layers increased according to the decrease of wetting angle and surface roughness. The resultant photonic crystals showed the best optical characteristics when the number of photonic crystal layers was within 40 and 50. In addition, the intensity peak of Fabry¡?Perot fringes increased when the wetting angle was large and the particle size was small. Photonic crystals coated on ITO glass showed the highest reflectance peak of 63$\%$ relative intensity.

• Structural Engineering and Mechanics
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• v.80 no.5
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• pp.523-538
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• 2021

The mechanical behaviour and stability of coal mining engineering underground is significantly affected by ground water. In this study, nuclear magnetic resonance imaging (NMRI) technique was employed to determine the water distribution characteristics in coal specimens during saturation process, based on which the functional rule for water distribution was proposed. Then, using discrete element method (DEM), an innovative numerical modelling method was developed to simulate water-weakening effect on coal behaviour considering moisture content and water distribution. Three water distribution numerical models, namely surface-wetting model, core-wetting model and uniform-wetting model, were established to explore the water distribution influences. The feasibility and validity of the surface-wetting model were further demonstrated by comparing the simulation results with laboratory results. The investigation reveals that coal mechanical properties are affected by both water saturation coefficient and water distribution condition. For all water distribution models, micro-cracks always initiate and nucleate in the water-rich area and thus lead to distinct macro fracture characteristics. With the increase of water saturation coefficient, the failure of coal tends to be less violent with less cracks and ejected fragments. In addition, the core-wetting specimen is more sensitive to water than specimens with other water distribution models.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.184-185
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• 2011

In this study, in order to obtain a high reflectivity for the LED lead frame, tin dip coating and tin plating were conducted respectively, and wettability of LED lead frame with tin solder also was tested by wetting balance tester. A Cu sheet was plated in Cu brighten electroplating bath and followed by immersion in a Sn electro-less plating bath [1]. On the other hand, in the dip coating process, a Cu sheet was dipped into molten tin. In the progress of wetting test, besides wetting balance curve, the maximum measured force($F_m$), the maximum withdrawal force($F_w$) and zero-cross time($t_0$) were obtained in various temperatures. With the maximum withdrawal force, the surface tension was calculated at different temperatures. The Cu sheet plated with bright Cu and Sn show a silver bright property while that of Cu dipped with Sn possessed a high reflectance density of 1.34GAM at $270^{\circ}C$.

• Korean Journal of Metals and Materials
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• v.50 no.8
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• pp.591-597
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• 2012

This paper presents regularly micro-textured glass surfaces ensuring the superhydrophobic properties in the Cassie-Baxter regime. The proposed surfaces were fabricated simply and efficiently by filling the glass material into a silicon micro-mold with periodic micro-cavities based on a thermal-reflow process, resulting in a successful demonstration of the textured glass surface with periodically-arrayed micro-pillar structures. The static and dynamic wetting properties of the micro-textured glass surfaces were characterized by measuring the static contact angle (SCA) and contact angle hysteresis (CAH), respectively. In addition, the surface wettability was estimated theoretically based on Wenzel and Cassie-Baxter wetting theories, and compared with the experimental ones. Through the experimental and theoretical observations, it was clearly confirmed that the proposed micro-textured glass surfaces showed the slippery superhydrophobic behaviors in the Cassie-Baxter wetting mode.

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.8
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• pp.1444-1452
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• 2001

Textile materials are frequently in contact with surfactant solutions during their manufacturing or finishing processes as well as cleaning processes in use. Liquid wetting, wicking and absorbency of textile materials, and the liquid properties, surface characteristics and pore geometry of textile materials, and the liquie-solid interactions, In this paper, 10 different nonionic surfactants, including Span 20, Twen 20, 40, 60, 80, 21, 61, 81, 65, 85, were used. The surfactants were characterized by their hydrophile-lipophile-balance (HLB) values, structures, and surface tensions. The 0.1g/dL and 1.0g/dL surfactant solutions, which were both above critical micelle concentration (CMC), were used to see the concentration effects on the wetting and absorbency of cotton fabrics. The wetting behavior and liquid retention properties of hydrophobic cotton fabrics with different nonionic surfactant solutions are reported. The contact angles are greatly decreased and the water retention values are greatly increased by adding most of the surfactants studied into the system. The extents of this effects are influenced by the characteristics of surfactants and its solutions. Hydrophilic surfactants which have low number of carbon atoms or unsaturated hydrophobe structures are more effective in improving the wetting and absorbancy of hydrophobic cotton fabrics. The water retention of hydrophobic cotton fabrics has positive relations with $cos{\theta}$, adhesion tension and work of adhesion. The 1.0g/dL surfactant solutions show similar, but slightly improved wetting and absorbency characteristics of hydrophobic cotton fabrics compared to the 0.1g/dL surfactant solutions.