• Korean Journal of Materials Research
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• v.21 no.1
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• pp.8-14
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• 2011

To improve the chemical stability of metal, the ceramic coatings on metallic materials have attracted interest from many researchers due to the chemical inertness of ceramic materials. To endure strong acids, SiOC coating on metal substrate was carried out by dip coating method using 20wt% polyphenylcarbosilane solution; SiC powder was added to the solution at 10wt% and 15wt% to improve the mechanical properties and to prevent cracks of the film. Thermal oxidation as a curing step was carried out at $200^{\circ}C$ for crosslinking of the polyphenylcarbosilane, and the coating samples were pyrolysized at $800^{\circ}C$ under argon to convert the polyphenylcarbosilane to SiOC film. The thicknesses of the SiOC coating films were $2.36{\mu}m$ and $3.16{\mu}m$. The quantities of each element were measured as $SiO_{1.07}C_{6.33}$ by EPMA, and it can be confirmed that the SiOC film from polyphenylcarbosilane was formed in a manner that was carbon rich. The hardness of the SiOC film was found to be 3.2Gpa through nanoindentor measurement. No defect including cracks appeared in the SiOC film. The weight loss of the SiOC coated stainless steel was within 2% after soaking in 10% HCl solution at $80^{\circ}C$ for one week. From these results, SiOC coating shows good potential for application to protect against severe chemical corrosion of stainless steel.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.1-9
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• 2004

This paper represents the permeability of chloride ions and the corrosion performance in the concrete blended with granulate blast furnace slag exposed to chloride environment. An ordinary cement (type I ) and sulfate resisting cement(type V) were used for the experiment. The two cements were combined with $0\%$, $25 \%$, $40\%$, and $55\%$ of the granulated blast furnace slag. The accelerated permeability tests of chloride ions were performed in accordance with ASTM C1202, and the accelerated corrosion tests of steel were carried out by using the method of immersion/drying cycles. After water curing 28 days, 56 days and 91 days, these tests were conducted until 30 cycles. In every cycle, test specimens were wetted in $3\%$ NaCl solution for three days and dried again in $60^{\circ}C$ air for four days. As an experimental results, the diffusion coefficient of chloride ions of the ordinary cement Concrete Combined granulated blast furnace slag was much lower than that of non granulated blast furnace slag concrete. Moreover, the diffusion coefficient of chloride ions of sulfate resisting cement concrete was higher than that of ordinary cement concrete. On the basis of the results of accelerated corrosion tests, corrosion resistance of the concrete mixed with granulated blast furnace slag shows good to corrosion resistance, however, the concrete with sulfate resisting cement shows bad to corrosion resistance.

• Composites Research
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• v.30 no.1
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• pp.71-76
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• 2017

The purpose of this study was to predict the long-term performance using the interlaminar shear strength of carbon fiber/epoxy composites exposed to environmental factors. Interlaminar shear specimens, manufactured by the filament winding method, were exposed to the conditions of drying at $50^{\circ}C$, $70^{\circ}C$, and $100^{\circ}C$ and of immersion at $25^{\circ}C$, $50^{\circ}C$, and $70^{\circ}C$ for up to 3000 hours, respectively. According to the results, the interlaminar shear strength did not vary significantly with the exposure time for the drying at $50^{\circ}C$ and $70^{\circ}C$, but it increased somewhat for the drying at $100^{\circ}C$ due to the post curing as the exposure time increased. The interlaminar shear strength of the specimens exposed to the immersion at $25^{\circ}C$ did not change significantly at the beginning of exposure, but it decreased with the exposure time and the degree of decrease increased as the environmental temperature increased. The linear regression equations for the environmental temperatures were obtained from the interlaminar shear strength of the specimens exposed to the immersion for up to 3000 hours. Using these linear regression equations, the interlaminar shear strength was estimated to be within 5.5% of the measured value at $25^{\circ}C$ and $50^{\circ}C$, and 2.3% of the measured value at $70^{\circ}C$. Therefore, the proposed performance prediction procedures can predict well the long-term interlaminar shear strength of carbon fiber/epoxy composites exposed to environmental factors.

• Composites Research
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• v.31 no.4
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• pp.139-144
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• 2018

Long Fiber-reinforced composites have advantages of excellent production efficiency and formability of complex shapes compared to conventional continuous fiber reinforced composite materials. However, if we need to make complicated composite shapes or to assemble parts made of different materials, a variety of joining methods are needed. In general, long fiber prepreg sheet (LFPS) contains mold release agent to facilitate demolding after thermoforming. Therefore, mechanical fastening is required in addition to the adhesive bonding to get proper joining strength. In this study, we proposed a stainless steel insert for co-cure bonding which cures LFPS and bonds the stainless steel insert through thermoforming process. The wing of the insert which is spread during the thermoforming process induces adhesion and mechanical wedging effect and serves as a hook to resist the pulling force. The burn-out method was used to confirm the unfolded state of the stainless steel insert wings inserted into the composite material. The static pull-out test was performed to quantitatively evaluate the joining strength. From these experimental results, the condition which guarantees the most appropriate joining strength was derived.

• Journal of Korean Medical classics
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• v.24 no.6
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• pp.101-110
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• 2011

There are not a few cases in Oriental medicine where a different prescription should be given to some of the patients whose symptoms are similar to each other. In other words, there might happen a misdiagnosis due to an extremely delicate difference in symptoms of the same diseases, causing a patient's condition to get worse or to be even on the brink of death. In such a context, the records in "WooJam JabJeo(愚岑雜著)" are worthwhile to do in-depth research on. Jang-Taegyung described his first-hand experience in major medical treatment very vivaciously during his ages between 25 and 42. Particularly, most of the prescriptions recorded in this book include not only his empirical prescriptions on the patients who life was almost on the brink of death but it also so plentifully contained the process of overcoming the side effect caused by other clinics' misdiagnosis; thus, that this book is drawing attention in that it could be indispensable materials not only in the research on medical history but also for clinical treatment. Particularly, as regards two cases of insanity, this book mentions the reason for using totally different prescription on one case from the other case even though the two cases had a similar symptom, through which we can acquire somewhat concrete experience in curing scenes though indirectly during the period of the Joseon Dynasty. We were able to get the result from the analysis of the two cases of insanity as follows: 1. WooJam, in treating the two cases of insanity due to the severe exacerbation of yang energy, managed to treat the one case by inducing a bowel movement and the other case by inducing urination. Such a different treatment seems to be greatly attributable to the constitutional factor of the two patients. Such an Oriental-medicine-based method of diagnosis and prescription as WooJam's is rarely found in Western medicine-i.e., that's why more thorough research on Oriental medicine is deeply required. 2. In case of the second patient, the patient arrived at insanity due to another clinic's treatment on perspiration on the patient with severe mouth thirst. This medical story once again highlights the importance of a diagnosis in today's Oriental medicine and at the same time it's a good example showing how big the side effect caused by the abuse of medicinal herbs is. The second patient's body fluids ran dry and finally his yang energy got exacerbated all the more due to the treatment by perspiration.

• Journal of Conservation Science
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• v.30 no.1
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• pp.103-109
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• 2014

This study aimed to develop materials to compensate for problems of restoration for lost parts and material problems in the conservation treatment. First, there are several problems with existing materials as follows: secondary damage due to the high shrinkage rate and low adhesive strength, sense of difference due to the severe yellowing, remelting due to irreversibility of materials, processability due to the high strength, sag due to the prolonged setting time in the work process and surface contamination of artifacts due to tools or gloves. In order to solve these problems, this study set developmental goals after understanding the types and physical properties based on epoxy resin among the currently used restoration materials of pottery and earthenware. The developed epoxy resin is epoxy putty, which is cured within 5 minutes, for earthenware restoration. In the earthenware restoration method, the epoxy putty enhanced the workability by quickly curing in paste form and compensated disadvantages such as surface contamination. In addition, the use of white micro-balloon for the epoxy stock solution made coloring easier and weight lighter, and a restoration material with low shrinkage and superior processability was developed.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.573-580
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• 2009

This paper presents the mix composition, production method, and curing condition applied to the extruded ECC(Engineered Cementitious Composite) panel which are able to exhibit multiple cracking and potential pseudo strain-hardening behavior. In addition to the production technique of extruded ECC panel, the effect of fiber distribution characteristics, which are uniquely created by applying extrusion process, on the flexural behavior of the panel is also focussed. In order to demonstrate fiber distribution, a series of experiments and analyses, including image processing/analysis and micro-mechanical analysis, was performed. The optimum mix composition of extruded ECC panel was determined in terms of water matrix ratio, the amount of cement, ECC powder, and silica powder. It was found that flexural behavior of extruded ECC panel was highly affected by the slight difference in mix composition of ECC panel. This is mainly because the difference in mix composition results in the change of micro-mechanical properties as well as fiber distribution characteristics, represented by fiber dispersion and orientation. In terms of the average fiber orientation, the fiber distribution was found to be similar to the assumption of two dimensional random distribution, irrespective of mix composition. In contrast, the probability density function for fiber orientation was measured to be quite different depending on the mix composition.

• Journal of Animal Science and Technology
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• v.54 no.1
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• pp.35-41
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• 2012

The aim of this study was to offer information about appropriate processing method for dry cured-ham with controlled ripening condition. In this study, three different treatments were performed: High salt group (HS), 18 hams were salted with 70 g $kg^{-1}$ salt (w/w) Middle salt group (MS), 18 hams were salted with 50 g $kg^{-1}$ salt Low salt group (LS), 18 hams were salted with 30 g $kg^{-1}$ salt. Also three drying periods were applied (180 days, 270 days and 360 days). The weight loss in HS was higher (5.62%) on curing step and in LS was higher (12.35%) on post-salting step compared to other groups. On fermentation stage, weight loss of HS was higher than that of LS (p<0.05). Weight loss on drying was increased as the drying period passes (p<0.05). Moisture contents were significantly (p<0.05) decreased and fat contents were significantly (p<0.05) increased in all treatment groups as drying period increased. The different drying periods affected fatty acid compositions on all salting levels; saturated fatty acid contents were increased (p<0.05) with more drying, whereas unsaturated fatty acid contents were decreased (p<0.05) as drying period increased.

• International Journal of Highway Engineering
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• v.15 no.2
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• pp.29-37
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• 2013

PURPOSES : This study aims to review the possibility of developing a road snow-melting system that can prevent slip accidents by maintaining a constant temperature of the winter roads and enhance performance of structures, including improvement of compressive strength by mixing carbon nanotube (hereafter referred to as CNT) with cement paste, the basic material. METHODS : To achieve the above purpose, an experiment was conducted by mixing power-type CNT and wrap-type CNT up to cement paste formulation by weight of 0.0wt%~4.1wt% in accordance with "KS L ISO 679(of cement strength test method)", and compressive strength was measured at 28 days of curing. In addition, the volume resistivity of the specimen was measured to test thermal and electrical characteristics, and the rate of temperature changes in specimen surface by power consumption was measured by passing electricity through the cross-sections of the specimen. Meanwhile, the criteria for checking the performance as a road snow-melting system was determined as volume resistivity of $100{\Omega}{\cdot}cm$ or less. RESULTS : A comparative analysis between specimen with 0wt% CNT content in plain status and specimen containing various types of CNTs was carried out. From its results, it was found that compressive strength increased approximately 19%, showing the highest rate when 0.2wt% of wrap-type CNT was contained, but volume resistivity of $100{\Omega}{\cdot}cm$ or less appeared only in specimens containing more than 0.2wt% CNT. In addition, it was observed that the surface temperature increased by $4.62^{\circ}C$ per minute on average in specimens containing 3.2wt% CNT. CONCLUSIONS : In this study, CNT was examined as an underlying material for a road snow-melting system, and the possibility of developing the road now-melting system was reviewed by conducting various experiments using CNT-Cement composites. From the experimental results, the specimens were found to have a superior performance when compared to the existing road snow-melting systems that place the heat transfer medium such as copper on the road. However, satisfactory strength performance were not obtained from the specimen containing CNT(2.0% or more) that functions as a heating element, which leads to the need for reviewing methods to increase the strength by using plasticizer or admixture.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.19-28
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• 2012

In this study, cause of longitudinal crack which is found on duct slab of road tunnel is studied. In-depth investigation, such as visual inspection, non-destructive testing and geometrical surveying of duct slab, is carried out. In order to perform cause analysis, the investigated results are compared to the results of numerical analysis. Many factors, which cause longitudinal crack, are classified as constrained condition of the duct slab, location of the rebar, temperature, shrinkage and so on. According to the classified causes of longitudinal crack, numerical analysis is performed considering construction stage of the tunnel lining. Especially, in order to predict shrinkage stain due to discrepancy of curing date, ACI-209 model, KCI structural design code and other researcher's shrinkage test results are compared. The results show that shrinkage strain is one of the main factors causing longitudinal crack. Other investigated tunnels are classified along with the construction method of duct slab and patterns of cracks. As a result, improving ways to construct duct slab are suggested.