• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.110-116
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• 2013

A concrete structure has become bigger and higher because of development of construction technology and a change in construction environment. Also it tends to focus on repairing, reinforcement and exterior in harmony with environment for structure maintenance and performance improvement. The research is about eco friendly durable painting applicable to concrete structure using civil and architecture. it purpose to improve external beauties and durable problems due to flexibility by variation of temperature, adhesion of exterior wall, crack and delamination in existing organic and mineral painting. For those problems, we made a eco friendly pre-paint that is made with preliminary treatment mixture as a highly enriched waterproof agent and adhesive increasing agent in preprocessing mixture. Then we performed an experiment on durability of prevention neutralization of concrete, durability abrasion, hiding power, adhesion, temperature resistance and resistance to chemical attack. The result of an experiment shows that hiding power is over 0.96 in standard test, durability abrasion test got higher value 1mg than water paint 75mg and tensile strength is 6 times higher than standard waterproof specification.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.91-99
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• 2008

The method to prepare the large cemented sand specimen for calibration chamber test by air-pluviation is investigated in this study. The uniformity of cemented specimen is evaluated by performing the CPTs, DMTs, and bender element tests in the calibration chamber. The sand particles, pre-wetted with 0.5% water content, are mixed with gypsum to provide the homogeneous coating of gypsum particles on the grain surface. It was shown that the pre-wetting of particle surface is effective to minimize the potential for segregation between sands and gypsum during air-pluviation. It was observed that the extreme void ratios ($e_{max}\;and\;e_{mix}$) of the mixture of pre-wetted sand and gypsum powder increase at lower gypsum content while those of the mixture of dry sand and gypsum decrease with increasing gypsum content. It was also shown from the test results that large cemented specimens reconstituted in calibration chamber by rainer system are quite uniform in vertical and horizontal directions.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.114-119
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• 2016

In this study, we tried to add the conductivity to natural polymer like bacterial cellulose (BC) coated with the conductive polymer PEDOT:PEG, graphene and silver nano-wire (AgNW). Sulfuric acid of 10 to 20% was previously mixed with PEDOT:PEG and then the solution was electron spin-coated on the BC membrane. And then, additive coating with graphene and AgNW were done to improve conductivity, which was examined by hall effect. As the result, we confirmed a considerable improvement of conductivity compared to BC-coated film without sulfuric acid treatment as $2.487{\times}10^{10}$ vs $8.093{\times}10^{15}$ ($1/cm^3$), showing higher electron density with $3.25{\times}10^5$ times. Also, we identified that changed particle type to the polymer type by sulfuric acid using SEM analysis. For FT-IR analysis, it was confirmed that S-O radical ($1200cm^{-1}$) increased in the sulfuric acid treatment than non-treated sulfuric acid. As the method used very small amount of PEDOT:PEG, its transparency could be kept, and pre-treatment process of sulfuric acid will be able to simplify the production process.

• Journal of fish pathology
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• v.10 no.2
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• pp.75-86
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• 1997

Solid phase enzyme linked immunosorbent assay (ELISA) was developed to detect the whole cells of Edwardsiella tarda from infected tissues of flounder. Cross-reaction test was performed by ELISA against fish pathogens such as A. hydrophila ATCC7966. V. anguillarum HYUFP5001, Y, ruckeri 11-4, E. ictaluri and Streptococcus sp. NG8206. Rabbit anti-E, tarda Edk-2 sera highly cross-reacted with A. hydrophila ATCC7966 and V. anguillarum HUFP5001. However, the cross-reaction was removed by using the anti-serum pre-adsorbed with A, hydrophila ATCC7966 FKC. The intra-species cross-reaction among E. tarda isolates was very high. ELISA with the whole cell antigens present in tissue homogenate appeared with highly decreased sensitivity, presumably by the co-coating of lipid or proteins in tissues. Thus, it would be necessary to use the infected tissue homogenates diluted more than 100 times with PBS for diagnosis. Interestingly, compared with the using of FKC antigen, the direct detection of viable cells in tissue homogenate showed more sensitive results with detection limit of $1{\times}10^3$ cells/ml in buffer or diluted tissue homogenate. Consequently, the ELISA method developed in this study was specific, rapid and sensitive for diagnosing edwardsiellosis.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.728-734
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• 2004

The effect of microstructure of WC-Co substrates which have different WC grain sizes from submicron to 5 $\mu$m on the diamond-substrate adhesion strength was investigated. The substrates were pre-treated by two methods : chemical etching with Murakami's solution and subsequently with $H_2SO_4$, and thermal heat-treatment. The adhesion strength was estimated by degree of peeling after Rockwell indentation. Diamond films of 20 $\mu$m thickness deposited on the heat-treated substrates showed an excellent adhesion strength at the load of 100 kg, which ascribed to the large and elongated WC grains. However, the cutting edge of insert was deformed after heat treatment and the surface morphology of heat treated substrate strongly affected on the surface roughness of the deposited diamond films. On the contrary, the diamond film of 10 $\mu$m in thickness on the chemically etched substrates of average WC grain size over 2 $\mu$m showed good adhesion strength enough not to peel-off under a load of 60 kg. Especially, the substrate of average WC grain size over 5 $\mu$m exhibited much improved reliability of adhesion comparing with the substrate of average grain size under 2 $\mu$m. No substrate deformation was observed in this case after the chemical etching, which is more advantageous and more practical in terms of precious machining than the heat treatment case.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.77-77
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• 2017

Titanium and its alloys offer attractive properties in a variety of applications. These are widely used for the field of biomedical implants because of its good biocompatibility and high corrosion resistance. Titanium anodizing is often used in the metal finishing of products, especially those can be used in the medical devices with dense oxide surface. Based on SAE/AMS (Society of Automotive Engineers/Aerospace Material Specification) 2488D, it has the specification for industrial titanium anodizing that have three different types of titanium anodization as following: Type I is used as a coating for elevated temperature forming; Type II is used as an anti-galling coating without additional lubrication or as a pre-treatment for improving adherence of film lubricants; Type III is used as a treatment to produce a spectrum of surface colours on titanium. In this study, we have focused on Type II anodization for the medical (dental and orthopedic) application, the anodized surface was modified with gray color under alkaline electrolyte. The surface characteristics were analyzed with Focused Ion Beam (FIB), Scanning Electron Microscopy (SEM), surface roughness, Vickers hardness, three point bending test, biocompatibility, and corrosion (potentiodynamic) test. The Ti-6Al-4V alloy was used for specimen, the anodizing procedure was conducted in alkaline solution (NaOH based, pH>13). Applied voltage was range between 20 V to 40 V until the ampere to be zero. As results, the surface characteristics of anodic oxide layer were analyzed with SEM, the dissecting layer was fabricated with FIB method prior to analyze surface. The surface roughness was measured by arithmetic mean deviation of the roughness profile (Ra). The Vickers hardness was obtained with Vickers hardness tester, indentation was repeated for 5 times on each sample, and the three point bending property was verified by yield load values. In order to determine the corrosion resistance for the corrosion rate, the potentiodynamic test was performed for each specimen. The biological safety assessment was analyzed by cytotoxic and pyrogen test. Through FIB feature of anodic surfaces, the thickness of oxide layer was 1.1 um. The surface roughness, Vickers hardness, bending yield, and corrosion resistance of the anodized specimen were shown higher value than those of non-treated specimen. Also we could verify that there was no significant issues from cytotoxicity and pyrogen test.

• Korean Journal of Environmental Agriculture
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• v.22 no.2
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• pp.124-129
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• 2003

The objectives of this study are to manufacture an efficient $TiO_2$, photocatalyst and to delineate optimum operational parameters for TCE (trichloroethylene) degradation in a photocatalytic oxidative reactor. The $TiO_2$ photocatalyst irradiated by 365 nm UV light is expected to increase degradation of TCE in solution by a series of photocatalytic oxidations in the reactor. A new membrane $TiO_2$ photocatalyst wns eventually developed by coating a mixture of Davan-C(0.24 wt%) and PVA(0.16 wt%) on the surface of slips using the slip-casting method. Results show that increase in the number of coating of $TiO_2$ sol on surface of photocatalysts and in the surface thickness improved the endurance and photocatalysts, but these physical modifications caused significant decrease in the overall degradation efficiency of TCE. Pre-aeration or recirculation of the influents to the reactors containing TCE increased degradation efficiency of TCE. The optimum operational conditions far the surface area of photocatalysts and UV light intensity appeared to be $1.47\;mL/cm^2$ and $225\;W/cm^2{\times}100$, respectively, in the reactor. Based on the overall experimental results, the photocatalytic oxidation of TCE with the new membrane $TiO_2$ photocatalyst is found to be very effective under the operational conditions delineated in this study.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.67-75
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• 2005

For th aim of lightweight microwave absorbers, conductive and magnetic microspheres are fabricated by plating of Co films on hollow ceramic microspheres of low density. Metal plating was carried out in a two-step electroless plating process (pre-treatment of activation and plating). Uniform coating of the film with about $2{\~}3{\cal}um$ thickness was identified by SEM. High-frequency magnetic and microwave absorbing properties were determined in the rubber composites containing the Co-coated microspheres. Due to conductive and ferromagnetic behavior of the Co thin films, high dielectric constant and magnetic loss can be obtained in the microwave frequencies. Due to those electromagnetic properties, high absorption rate (25 dB) and thin matching thickness ($2.0{\~}2.5{\cal}mm$) are predicted in the composite layers containing the metal-coated microspheres of low density (about 0.84 g/cc) for the electromagnetic radiation in microwave frequencies.

• Food Science and Preservation
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• v.10 no.1
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• pp.1-5
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• 2003

This study was carried out to extend a marketing shelf-life of the Jeju greenhouse mandarin fruits. Total soluble solids were not showed any significant differences by the temperatures and pre-treatments during the marketing period. Acid content and firmness of the fruits were gradually decreased, which were better in cold than in room temperature treatment. The fruits washed in electrolyzed acid water(pH 2.4∼2.7) maintained freshness higher than those of control Internal CO$_2$concentration of those was 1.0 ％ more or less in the beginning marketing stage, but increased along the marketing period in mom temperature. Especially Internal CO$_2$concentration of wax-coated fruits rapidly increased more than any other, whereas it was a little decreased in cold treatment. After 10 days in room temperature, decay ratio of the fruits was below 4.0% in electrolyzed acid water washing, compared to 10.4% in control. After 30 days in cold temperature, decay ratio was only 3.7% in electrolyzed acid water washing compared to 4.4% of wax-coated treatment and 7.4% of control. The weight loss among the pre-treatments in room temperature had no significant differences and was higher than in cold one.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.1
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• pp.47-53
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• 2012

Bonding strength of Sn-3.0Ag-0.5Cu solder joint due to degradation characteristic of OSP surface finish was investigated, compared with SnPb finish. The thickness variation and degradation mechanism of organic solderability preservative(OSP) coating were also analyzed with the number of reflow process. To analyze the degradation degree of solder joint strength, FR-4 PCB coated with OSP and SnPb were experienced preheat treatment as a function of reflow number from 1st to 6th pass, respectively. After 2012 chip resistors were soldered with Sn-3.0Ag-0.5Cu on the pre-heated PCB, the shear strength of solder joints was measured. The thickness of OSP increased with increase of the number of reflow pass by thermal degradation during the reflow process. It was also observed that the preservation effect of OSP decreased due to OSP degradation which led Cu pad oxidation. The mean shear strength of solder joints formed on the Cu pads finished with OSP and SnPb were 58.1 N and 62.2 N, respectively, through the pre-heating of 6 times. Although OSP was degraded with reflow process, the feasibility of its application was proven.