• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.957-964
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• 2010

The deactivated catalyzed diesel particulate filter-trap (DPF) was remanufactured by ultrasonic wave treatment with various prepared solutions, followed by active component re-impregnation, and the emission control performance and surface properties of remanufactured DPF were studied at various remanufacturing conditions. The proper ultrasonic wave cleaning time at various prepared solutions and optimal re-impregnation amounts of active component for the best emission control performance of DPF were investigated and its performance tests were also carried out with various temperatures for the conversions of CO, THC (total hydrocarbon) and PM (particulate matter) by catalytic reaction test unit using bypass gas from the diesel engine dynamo system. It was found that the emission control performance of DPF remanufactured with the high-temperature air washing, ultrasonic wave cleaning at acid/base solutions and active component re-impregnation method was recovered to 95% level of its activity compared to that of the fresh DPF, which was caused by removing the deactivating materials from the surface of the DPF, through the analyses of performance test and their surface characterization by Optical microscope, EDX, ICP, TGA, and porosimeter.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.97-104
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• 2023

In order to maximize the utilization of recycled fine aggregate, high strength mortar made of 100 % recycled fine aggregate was prepared, and its physical properties were evaluated to determine the possibility of using recycled fine aggregate as structural aggregate. The effect caused by the amount of nanosilica on the physical properties of w/b 0.2 recycled fine aggregate mortar consisting of cement, silica fume, and blast furnace slag. To improve the dispersion of nanosilica inside mortar, an aqueously dispersed nanosilica solution by ultrasonic tip sonication was prepared, and incorporated into the mortar to evaluate changes in mortar flow, porosity and compressive strength depending on nanosilica content. According to the experimental results, mortar flow decreased as the replacement ratio of nano-silica increased. As the replacement ratio of nanosilica increased up to 0.75 %, the porosity decreased and the compressive strength increased, but, at a replacement ratio of 1 %, the porosity increased and the compressive strength decreased. It was confirmed that the nano-silica replacement ratio of 0.75 % was optimum proportion to maximize the mechanical performance of high-strength recycled fine aggregate mortar.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.629-646
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• 2023

Host rock of Cheonjeon-ri petroglyph is shale belonging to the Daegu Formation of Cretaceous Gyeongsang Supergroup. The rocks were hornfelsified by thermal alteration, and shows high density and hardness. The petroglyph forms weathered zone with certain depth, and has difference in mineral and chemical composition from the unweathered zone. As the physical deterioration evaluations, most of cracks on the surface appear parallel to the bedding, and are concentrated in the upper part with relatively low density. Breakout parts are occurred in the upper and lower parts of the petroglyph, accounting for 6.0% of the total area and occurs to have been created by the wedging action of cracks crossing. The first exfoliation parts occupying the surface were 23.8% of the total area, the second exfoliations covered with 9.3%, and the exfoliation parts with three or more times were calculated as 3.4%. It is interpreted that this is not due to natural weathering, and the thermal shock caused by the cremation custom here in the past. As the ultrasonic properties, the petroglyph indicates highly strength in the horizontal direction parallel to bedding, and the area with little physical damage recorded mean of 4,684 m/s, but the area with severe cracks and exfoliations showed difference from 2,597 to 3,382 m/s on average. Physical deterioration to the Cheonjeon-ri petroglyph occurred to influence by repeated weathering, which caused the rock surface to become more severe than the inside and the binding force of minerals to weaken. Therefore, it can be understood that when greater stress occurs in the weathered zone than in the unweathered zone, the relatively weathered surface loses its support and exfoliation occurs.

• Composites Research
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• v.29 no.5
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• pp.306-314
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• 2016

In this study, to improve the thermal stabilities of the epoxy composite specimens in addition to the enhanced mechanical properties, those were reinforced with carbon nanotubes and micrometer-sized silica particles. To disperse the filler in matrix relatively simple physical process, specimens were fabricated using shear mixing and sonication. Tensile strength, coefficients of thermal expansion and thermal conductivity of the specimens were measured with varied contents of the two fillers. The mechanical and thermal properties were also discussed, and the experimental results of thermal expansion related to the thermal stability of the specimens were compared with those from several micromechanics models. The hybrid composites specimens incorporating 0.6 wt％ of carbon nanotubes and 50 wt％ of silica particles showed better mechanical properties than the others with increase in tensile strength up to 11％, with respect to those of the baseline specimens. As the silica contents were increased the thermal expansion was reduced down to 36%, and the thermal stability was improved with the decreased thermal deformation. Thermal conductivity of the epoxy composite specimens incorporating 50 wt％ of silica particles was enhanced, which demonstrate improvement of 72%. The mechanical and thermal properties of the hybrid composites specimens incorporating the two fillers were improved simultaneously.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4385-4391
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• 2012

In this article, the effects of shear mixing on the dispersion improvement of the carbon nanotube fillers in epoxy composites were studied. Through the scanning electron microscope images showing the quantitative results and the tensile tests giving the qualitative data, we can see the dispersion improvement of the fillers. The composite specimen containing 0.6 wt% fillers shows the biggest value of tensile strength. For the tensile stiffness, the specimens containing more filler have the larger values of tensile stiffness.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.362-367
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• 2005

Ultrasonic backward radiation profile is frequency-dependent when the incident region has deptional gradient of acoustical properties or multi-layers. Until now, we have measured the profiles of principal frequencies of an used transducers so that it was not easy to characterize the frequency dependence of the SAW(surface acoustic wave) from the backward radiation profile. We tried to measure the spectral backward radiation profiles using DFP(digital filer package) in a Lecroy DSO(digital storage oscilloscope). The measured spectral profiles showed that the steel specimen of #1200 surface treatment have 2% SAW velocity dispersion of the loaded case and the severly rusty steel specimen have the very big changes in the shape and pattern of the spectral profile. It is concluded that the spectral backward radiation profiles could be very effective tool to evaluate the frequency dependence of surface area.

• Journal of the Korean Society of Costume
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• v.54 no.1
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• pp.1-10
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• 2004

The purpose of this study was to compare the efficiency of four different cleaning method of silk and to fabrics, which were excavated from the sixteenth century tombs. The four cleaning methods were hand washing in water and hand washing in solvent, washing in ultrasonic cleaner, and using of ultrasonic gun after washing in ultrasonic cleaner. The following is the result of the experiment: ㆍBoth silk and jute fabrics shrank the most after hand-wash in water. This cleaning method decreased their thickness the most but changed their strength the least. However, the color of the fabric changed the most after had-wash in water. This washing method might discolor the dyed fabric, so one must check the condition of the fabric thoroughly before washing it. ㆍThe weight and the thickness of the fabric changed little after ultrasonic cleaning. This cleaning method, therefore. is less efficient than hand-water-wash. The use of ultrasonic gun after ultrasonic wash for partial cleansing enhanced the efficiency a little. Nevertheless, this method left stain around the area where the gun was used, and the injected water could damage the fabric. ㆍThe excavated fabric became softer in the cleaning process as the dirt was washed away. In both cases of silk and jute fabrics cleaning, solvent made the fabric softer than water. Washed in solvent, the fabric did not swell. But water penetrated to the fiber during the cleaning process and made the fabric swell. When the water evaporates, the swollen fiber structure collapses and the fabric become stiff. Ultrasonic wash did not cause much change in the flexibility of the fabric, for this method does not remove the dirt as effectively as the other method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.1-10
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• 2011

Recently harbor remodeling projects are seriously considered to enhance the loading and unloading capability of old container terminals and to make decrepit ports as eco-friendly harbor and waterfront spaces in many countries. In such a case, quantitative and qualitative evaluations on concrete harbor facilities are mandatory to determine the current structural integrity condition of aged materials. Once the remodeling project is determined to be carried out, the reusability of individual structural members and facilities including caissons, cell-blocks, and tetra-pods need to be decided based on the simple and economic visual inspection and/or nondestructive testing. In this study, the systematic quantitative evaluation procedure for determining the structural integrity condition and the reusability is studied based the nondestructive testing and evaluation methods. Conventional methods including Schmidt hammer test and ultrasonicpulse velocity methods and elastic wave based methods including impact echo test and surface wave test are applied to the old harbor facilities in five different sites. The compressive tests are also carried out to determine the elastic modulus and compressive strength of concrete materials.

• Journal of Conservation Science
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• v.30 no.4
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• pp.439-446
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• 2014

We carried out monitoring of deterioration condition for the Rock-carved Buddha Triad in Seosan after dismantlement of protective facilities and conservation treatment. As the results of ultrasonic velocity measurement, physical properties of rock were evaluated to maintain similar the past. Result of digital image analysis, white discoloration was reoccured after four years of conservation treatments. And biodeterioration of unknown in the past was generated left side on the Rock-carved Buddha. Phenomenon of biodeterioration on the surface rocks was estimated by variation of sunshine and water contents according to topography condition.

• Journal of Conservation Science
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• v.34 no.3
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• pp.167-177
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• 2018

The Bayon style Avalokitesvara statue from the $13^{th}$ century Angkor period is on display at the Cambodia Angkor Conservation Office. This statue is composed of dark green felthspathic greywacke, the surface of which has been shown light brown discoloration, detected calcite crystallization. As a result of condition assessment, the statue was damaged due to overlap scaling and cracking. Ultrasonic tests have investigated remarkable physical weathering area, flaking and fragmentation in lower velocity. The physical condition of the statue requires a conservation method that improves the binding power. To protect against salt weathering and to ensure physical stability, new conservation material composed of mixed ethyl silicate and sandstone powder similar to that composing the statue was created. The material affected by damage was removed and replaced with the new conservation material.