• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.63-71
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• 2010

The artificial rains having different pH and weathering simulation test were performed for Gyeongju Namsan granite and dacitic tuff to predict the role of acid rain in the deterioration of stone monuments located in Gyeongju area. The pH 4.0 rain reacted with the fresh granite showed near neutral pH at the early stage due to the hydrolysis of minerals in the rock surface. But the pH changed back to the initial pH in the later stage. On the other hand, the pH 5.6 rain showed the neutral pH for a longer time than the experiment with pH 4.0 rain, reflecting slower reaction of minerals due to the weaker acidity. When the pH 5.6 rain reacted with the weathered granite, the water showed neutral pH longer than the case of the fresh granite. The similar tendencies were observed in the experiment of dacitic tuff, except that the pH 4.0 rain reacted with dacitic tuff took a longer time to go back to the initial pH as compared with the case of granite. These results may due to the differences in mineral composition and texture of two rocks. Dacitic tuff contains more fine-grained or glassy groundmass than granite and is more reactive with weaker acid rain. It was predicted that the weight loss and strength decrease rate of dacitic tuff would be approximatetly twice relative to those of granite in the same experimental environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.319-330
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• 2016

Recently, 3D printing technology has been applied to make a concept model and working mockup of an industrial application. On the other hand, this technology has limited applications in industrial products due to the materials and reliability of the 3D printed product. In this study, the components of a full cord switch module are proposed as a case of a 3D printed component that can be used as a substitute for a short period. These are hub-driven and lever lockup components that have the structural characteristics of breaking down frequently in the emergency operating status. To ensure the structural strength for a substitute period, research of structure optimization was performed because 3D printing technology has a limitation in the materials used. After optimizing the structure variables of the hub-driven component, reasonable results can be drawn in that the safety factors of the left and right switching mode are 1.243 (${\Delta}153.67%$) and 3.156 (${\Delta}404.96%$). The lever lockup component has a structural weak point that can break down easily on the lockup-part because of a cantilever shape and bending moment. The rib structure was applied to decrease the deflection. In addition, optimization of the structural variables was performed, showing a safety factor of 7.52(${\Delta}26%$).

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.4
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• pp.99-107
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• 2003

Normally coating is used a method for protecting reinforced concrete. For this purpose, organic as well as inorganic coatings are used. The advantages of inorganic coatings are lower absorption of UV, non-burning etc. On the other hand, organic coatings have the advantage of low permeability of $CO_2$, $SO_2$ and water. Organic coatings provide better protection for reinforced concrete. However, in organic coatings such as epoxy, urethane and acryl, long-term adhesive strength is reduced and the formed membrane of those is blistered by various causes. Also when organic coatings are applied to the wet surface of concrete, they have a problem with adhesion. So, we developed coating material, WGS-Eco which was hybridized with polymer and cement based material to protect concrete structures and solve problems of organic coatings. This study was conducted an comparative evaluation on physical and durable performance of developed coating material and previously used coating materials. As a result, the performance of developed coating material was not inferior to organic coating materials. So, the developed coating material was considered as a suitable coating material which had advantages of inorganic and organic coatings for protecting concrete.

• Journal of the Korean Society of Child Welfare
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• no.36
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• pp.261-288
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• 2011

This study focuses on adolescent prosocial behavior as one of the necessary elements for youth to grow as a healthy member of the society. The purpose of this study is to examine the effects of peer group on adolescent prosocial behavior by comparing the peer influence model and the individual characteristics model. For the study, we conducted hierarchical multiple regression analyses using the data from the Korean Youth General Survey 2008, administered by the Ministry of Health and Welfare. Results show that friends' prosocial behavior had a positive impact, but friends' antisocial behavior had a negative impact on adolescent prosocial behavior. When individual characteristics including self-esteem and empathy were analyzed simultaneously, empathy, self-esteem, friends' prosocial behavior, and friends' antisocial behavior were found to be statistically significant. The strength of association between individual characteristics and adolescent prosocial behavior was greater than that of friends' behaviors. Also, significant moderating effects of individual characteristics on the relationships between adolescent prosocial behavior and friends' behaviors were found. For example, the positive effect of friends' prosocial behavior on adolescent prosocial behavior increased as adolescent's level of self-esteem increased. On the other hand, the negative effect of friends' antisocial behavior on adolescent prosocial behavior decreased as adolescent's level of empathy increased. Based on the findings, both the peer influence model and the individual characteristics model were considered valid in explaining prosocial behavior of Korean adolescents. Finally, implications of this study for positive youth development were discussed.

• Korean Security Journal
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• no.56
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• pp.83-105
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• 2018

Special security guards play the role to safely operate and manage nuclear power plants from unintended internal and external threats. Physical fitness management of special security guards is one of the most important factors for improving and maintaining the level of physical protection. Thus, the purpose of this study is to analyze the physical fitness factor and physical fitness level required for mission accomplishment through job analysis of special security guards. The special security guards of Nuclear Power Plant in Korea were performing 7 jobs, 26 duties, 159 tasks. In order to accomplish theses tasks, the following physical fitness were required: muscle strength and muscle endurance of the hand, upper limb, lower limb and core, quickness, agility and Cardio function. The duties that require a lot of physical fitness were in the order of conducting arrest and self-defense, conducting unarmed defensive tactics, demonstrating proficiency with semiautomatic rifle, using protective equipment, performing emergency plan and defensive strategy, etc. The results of this study are expected to provide basic data necessary for establishing guidelines for fitness qualification and training of special security guards in the future and contribute to enhancement of physical protection of nuclear power plants.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.2
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• pp.129-140
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• 2018

A residual stress generated in the steel structure is broadly categorized into initial residual stress during manufacturing steel material, welding residual stress caused by welding, and heat treatment residual stress by heat treatment. Initial residual stresses induced during the manufacturing process is combined with welding residual stress or heat treatment residual stress, and remained as a final residual stress. Because such final residual stress affects the safety and strength of the structure, it is of utmost importance to measure or predict the magnitude of residual stress, and to apply this point on the design of the structure. In this study, the initial residual stress of steel structures having thicknesses of 25 mm and 70 mm during manufacturing was measured in order to investigate initial residual stress (hereinafter, referred to as initial stress). In addition, thermal elastic plastic FEM analysis was performed with this initial condition, and the effect of initial stress on the welding residual stress was investigated. Further, the reliability of the FE analysis result, considering the initial stress and welding residual stress for the steel structures having two thicknesses, was validated by comparing it with the measured results. In the vicinity of the weld joint, the initial stress is released and finally controlled by the weld residual stress. On the other hand, the farther away from the weld joint, the greater the influence of the initial stress. The range in which the initial stress affects the weld residual stress was not changed by the initial stress. However, in the region where the initial stress occurs in the compressive stress, the magnitude of the weld residual compressive stress varies with the compression or tension of the initial stress. The effect of initial stress on the maximum compression residual stress was far larger when initial stress was considered in case of a thickness of 25 mm with a value of 180 MPa, while in case of thickness at 70 mm, it was 200 MPa. The increase in compressive residual stress is almost the same as the initial stress. However, if initial stress was tensile, there was no significant change in the maximum compression residual stress.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1205-1214
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• 2021

Precipitation is one of a major causes of landslides by rising of pore water pressure, which leads to fluctuations of soil strength and stress. For this reason, precipitation is the most frequently used to determine the landslide thresholds. However, using only precipitation has limitations in predicting and estimating slope stability quantitatively for reducing false alarm events. On the other hand, Soil Moisture (SM) has been used for calculating slope stability in many studies since it is directly related to pore water pressure than precipitation. Therefore, this study attempted to evaluate the appropriateness of applying soil moisture in determining the landslide threshold. First, the reactivity of soil saturation level to precipitation was identified through time-series analysis. The precipitation threshold was calculated using daily precipitation (P_daily) and the Antecedent Precipitation Index (API), and the hydrological threshold was calculated using daily precipitation and soil saturation level. Using a contingency table, these two thresholds were assessed qualitatively. In results, compared to P_daily only threshold, Goesan showed an improvement of 75% (P_daily + API) and 42% (P_daily + SM) and Changsu showed an improvement of 33% (P_daily + API) and 44% (P_daily + SM), respectively. Both API and SM effectively enhanced the Critical Success Index (CSI) and reduced the False Alarm Rate (FAR). In the future, studies such as calculating rainfall intensity required to cause/trigger landslides through soil saturation level or estimating rainfall resistance according to the soil saturation level are expected to contribute to improving landslide prediction accuracy.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.331-335
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• 2018

The purpose of this study is to investigate the feasibility of CFBC artificial fine aggregate as a substitute for natural aggregate used in dry mortar. The basic performance of the flow, compressive strength and dry shrinkage of the dry mortar was evaluated. Four types of test dry mortar specimens using natural aggregate without expansion admixture, a specimen with modified CaO expansion admixture and natural aggregate, a specimen with modified CaO expansion admixture and CFBC artificial fine aggregate, and a specimen using CFBC artificial fine aggregate without modified CaO expansion admixture were evaluated respectively. As a result of evaluation of drying shrinkage performance at 20th day of age, the dry shrinkage performance of the specimen using modified CaO expansion admixture was found to be the highest at $250{\times}10^{-6}$. On the other hand, the specimen containing the modified CaO expansion admixture with CFBC artificial aggregate exhibited a shrinkage of $410{\times}10^{-6}$, and the drying shrinkage of specimen using natural fine aggregate without expansion admixture was $450{\times}10^{-6}$. When the modified CaO expansion material was used, and exhibited performance equal to or higher than that of the shrinkage-drying property.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.3
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• pp.379-385
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• 2019

Osteoporosis is a disease that increases the risk of fractures by inducing a decrease in bone strength by the changes in hormones and a decrease in minerals. Recent reports have indicated that the long-term administration of Adefovir dipivoxil (ADV), which is used as a treatment for the hepatitis virus and AIDS, may have osteoporotic side effects. On the other hand, there are few studies on the cytopathic correlation of these causes. In this study, the biological relevance of ADV was evaluated using osteoblast hFOB1.19 and vascular endothelial cell HUVEC. First, the cells were treated with ADV at different concentrations, and DAPI and crystal violet staining were performed for morphological analysis of each cell and nucleus. A CCK-8 assay, real-time PCR, alkaline phosphatase (ALP) staining, and activity was performed to evaluate the drug effects on cell proliferation, gene expression, and osteoblast differentiation. As a result, ADV induced cell hypertrophy in hFOB1.19 cells and HUVEC cells. Furthermore, ADV not only inhibited cell proliferation and TGF-${\beta}$ expression but was also involved in osteoblast differentiation. Overall, these results provide basic data to help better understand the mechanism of ADV-induced osteoporosis and its clinical implications.

• Korean Journal of Heritage: History & Science
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• v.49 no.4
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• pp.114-125
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• 2016

Lacquer is one of the most widely used natural resin in East Asia since Neolithic Age. As a major ingredient of lacquerware, lacquer is waterproof, insect-proof and rot-proof to be durable and anti-abrasion, generally utilized for mainly painting purpose. According to lacquerware excavated from several sites of Japan and China, lacquerware seems to appear in Neolithic Age. On the other hand in case of excavation research in Korea, lacquerwares are found after the Bronze Age. The initial purpose of lacquer is estimated to be adhesive, regarding the literatures mentioning bitumen(Yeoksceong ), animal glue(Kyeo) and egg alumen(Nanbaek). Especially piece of jar coffin unearthed in Pyeongtaek Daechu-ri site had trace of restoration by lacquer and hemp as an evidence of lacquer for adhesion in Pre-Three Kingdoms period. Since then a trend to restore the broken ceramics with lacquer and decorate with golden foil lasted especially in Joseon Dynasty. In the field of gold plated lacquer method, mother-of-pearl inlaying technique for lacquerware and restoration of buildings, lacquer is still used as adhesive. Due to matter of reversibility lacquer is being avoided for conservation and restoration of cultural heritage. Lacquer as a traditional material for adhesive since ancient times, however, has advantage in adhesion strength and durability. Because synthetic resin adhesive has problem of emission of volatile organic compounds and aging over time, lacquer receives attention recently. On the contrary, by combination adhesive from mixing lacquer and animal glue, already proved the possibility of applicability and chemical modification. A research to utilize lacquer as modern paint or functional material is also conducted continuously also in China and Japan. To put traditional material into practical use and modernize, chemical research from the molecular level of the lacquer is necessary in the near future.