• Analytical Science and Technology
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• v.19 no.1
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• pp.39-44
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• 2006

Puh-erh tea was extracted with water and then fractionated sequentially with n-hexane, ethyl acetate, n-butanol to find antioxidative compounds. The fractions were examined on the antioxidant activity using two different methods, free radical scavenging activity measurement and reductive potential. Those antioxidant activities were compared to standard antioxidants such as butylated hydroxyanisole(BHA), butylated hydroxytoluene (BHT), and ${\alpha}$-tocopherol. EA fraction of Pu-erh tea was showed excellent antioxidative activities over BHA and BHT.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.831-837
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• 2008

Korean construction industry faces diverse social and economical changes. Labor shortage, Free Trade Agreements (FTA), high oil prices alert industry practitioners to the new challenges and opportunities. It is time to make novel approaches for significant improvement of industry performance. Korean government and companies have plans for interdisciplinary research and development efforts. To this end, technology evaluation and market needs analysis should be extensively carried out prior to research initiation. Research programs developed in this way are presented in term of budget estimate, research scope and timeline. A framework for construction technology valuation methodology is also suggested to evaluate the holistic technology value and return on investment of research, development and commercialization.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.39-46
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• 2023

In this study, the dynamic behavior of friction bearings of PSC (Pre-Stressed Concrete) box train continuous bridge was numerically analyzed at 10 km/h intervals up to 600 km/h according to the increasing speed of the next-generation high-speed train. A frame model was generated targeting the 40-meter single-span and two-span continuous PSC box bridges in the Gyeongbu High-Speed Railway section. The interaction forces including the inertial mass vehicle model with 38 degrees of freedom and the irregularities of the bridge and track were considered. It was calculated the longitudinal displacement, cumulative sliding distance and displacement speed of the bridge bearings at each running speed so that compared with the dynamic behavior trend analysis of the bridge. In addition, long-term friction test standards were applied to evaluate the durability of friction plates.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.2
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• pp.214-221
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• 2024

The present study concerns the resistance of calcium aluminate cement (CAC) to steel corrosion. The corrosion behavior of steel, chloride binding/buffering and chloride transport were evaluated in order to predict the risk of steel corrosion. The CAC mortar exhibited no corrosion on steel, irrespective of the curing temperature and CAC types, whereas ordinary Portland cement (OPC) showed a severe corrosion on the steel surface. The chloride binding capacity of CAC found to be was lower than that of OPC, yet buffering capacity against pH decrease was found to be significantly higher in the CAC paste. Furthermore, chloride ingress at all depths was found to be reduced in CAC, thereby reducing the risk of corrosion.

• Journal of Life Science
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• v.25 no.9
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• pp.1014-1020
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• 2015

This study suggests that fermented rice bran extract contains natural antioxidants. The contents of bioactive materials (e.g., polyphenolic compounds and flavonoids), antioxidative properties (DPPH (α,α'- diphenyl-β-picrylhydrazyl) free radical scavenging activity, Fe reducing, Cu reducing power, peroxidation of linoleic acid and rat hepatocyte microsome) were tested by in vitro experimental models using fermented rice bran (FRB) extract. The concentrations of phenolic compound and flavonoid were 19.92 mg/g and 11.56 mg/g, respectively. In oxidation in vitro models using DPPH free radical scavenging activity, (free radical scavenging activity 69.8%) Fe reducing power and Cu reducing power (effect of dose-dependent manner), Fe²⁺/ascorbate induced linolenic acid peroxidation by ferric thiocyanate and thiobarbituric acid (TBA) methods (inhibition activity 81%), and autooxidation of rat hepatic microsomes membrane (lipid peroxidation inhibition activity 38%), antioxidative activities were stronger in FRB extract than FRS (Fermented Rice and Soybean, positive control) extract and, these effects were dose-dependent manner. From these results, FRB extract was shown to have the most potent antioxidative properties and contain the highest amounts of antioxidative compounds such as phenolic compounds and flavonoids. Overall, these results may provide the basic data to understand the antioxidative properties of fermented rice bran for development of functional foods.

• Education of Primary School Mathematics
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• v.17 no.2
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• pp.77-93
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• 2014

The purpose of this study was to investigate the relationships between thinking styles and the components of mathematical ability of elementary math gifted children. The results of this study were as follows: First, there were differences in thinking styles: The gifted students prefer legislative, judical, hierarchic, global, internal and liberal thinking styles. General students prefer oligarchic and conservative thinking styles. Second, there were differences in components of mathematical ability: The gifted students scored high in all sections. And if when they scored high in one section, then they most likely scored high in the other sections as well. But the spacial related lowly to the generalization and memorization. There is no significant relationship between memorization and calculation Third, there was a correlation between thinking styles and components of mathematical ability: Some thinking styles were related to components of mathematical ability. In functions of thinking styles, legislative style have higher effect on calculation. And executive, judical styles related negatively to the inference ability. In forms of thinking styles monarchic style had higher effect on space ability, hierarchic style had higher effect on calculation. Monarchic, hierarchic styles related negatively to inference ability. In level of thinking styles global, local styles have higher effect on calculation. Local styles related negatively to the inference ability. In the scope of thinking styles, internal style had a higher effect on generalization, and external style had a higher effect on calculation. And there is no significant relationship leaning of thinking styles.

• Journal of Life Science
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• v.17 no.9 s.89
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• pp.1237-1243
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• 2007

This study was investigated on the antioxidant capacity of 80% ethanol extract of lotus root in vitro. The ex-traction yields of 80 % ethanol extract was 9.14%. Lotus root ethanol extract was fractionated by the following: n-hexane, chloroform, ethylacetate and n-butanol. n-Butanol fraction showed the highest ex-traction yield of all fractions. Antioxidative activities of different fractions were examined by l.l-diphenyl-2-picrylhydrazyl(DPPH) radical generation, the Rancimat test, the nitrite scavenging ac-tivity and the thiobarbituric acid(TBA) method, and compared with the properties of the commercial antioxidant butylated hydroxytoluene(BHT). The antioxidative capacity of the ethylacetate fraction was the highest among fractions and its fraction showed higher contents of total polyphenol. Furthermore, the antioxidative capacity of the ethylacetate fraction was similar to that of BHT. In conclusion, these results suggest that lotus root may be a good candidate as a natural antioxidant source.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.914-921
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• 2017

The experimental research on a high-altitude environment simulation of space launch vehicle is important for securing independent technologies with launching space vehicles and completing missions. This study selected an altitude of 65 km for the experiment environment where it exceeded Mach number of 6 after the launch of Korean Space Launch Vehicle(KSLV-II). Shock tunnel was used to replicate the flight condition. After flow establishment, in order to confirm aerodynamic characteristics and normal and oblique shockwaves, the flow verification was carried out by measuring stagnation pressure and heat flux of a forebody model, and shockwave stand-off distance of a hemispherical model. In addition, a shock-free technique to recover free-stream condition has been developed and verified. From the results of the three verification tests, it was confirmed that the flow was replicated with the error of about ${\pm}3%$. The error between the slope angle of inclined shockwave of the scaled down transition section model using the shock-free shape and the slope angle of the horizontal plate model, and between the theoretical and the experimental value of the static pressure of the model were confirmed to be 2% and 1%, respectively. As a result, the efficiency of the shockwave cancellation technique has been verified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.480-488
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• 2018

The development of information and communication technology has been carried out actively in the field of agriculture to generate valuable information from large amounts of data and apply big data technology to utilize it. Crops and their varieties are determined by the influence of the natural environment such as temperature, precipitation, and sunshine hours. This paper derives the climatic factors affecting the production of crops using the garlic growth process and daily meteorological variables. A prediction model was also developed for the production of garlic per unit area. A big data analysis technique considering the growth stage of garlic was used. In the exploratory data analysis process, various agricultural production data, such as the production volume, wholesale market load, and growth data were provided from the National Statistical Office, the Rural Development Administration, and Korea Rural Economic Institute. Various meteorological data, such as AWS, ASOS, and special status data, were collected and utilized from the Korea Meteorological Agency. The correlation analysis process was designed by comparing the prediction power of the models and fitness of models derived from the variable selection, candidate model derivation, model diagnosis, and scenario prediction. Numerous weather factor variables were selected as descriptive variables by factor analysis to reduce the dimensions. Using this method, it was possible to effectively control the multicollinearity and low degree of freedom that can occur in regression analysis and improve the fitness and predictive power of regression analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.3
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• pp.195-205
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• 2020

This study addresses analysis on reactions which are induced in restraint system for airframe full-scale static structural test. This system restraints 6 degrees of freedom of a test article. It is valuable to study evaluating test error through analysis on the reactions which include all errors in a test. It is required to calculate fistly right reactions for the evaluation. This study focuses on calculation of the right reactions. The reaction is represented by sum of nominal reaction(Rn) and testing error reactions(Rce, Rerr) and is analyzed by two steps (inital vs relative reaction) in this study. It would evaluate intrinsic error at 0%DLL and error induced from applying test load, separately. Based on analysis using test data of a full-scale static test(canard type aircraft), resultant force of Rces and Rce_rs are distributed within 82.8N while resultant force of Rerr_rs shows to increase upto max. 808N as load level increment. Such well distribution of the Rce within the small range is caused from TMF values characteristics which are well distributed within -30N~40N. Additionally, it is shown through qualitative analysis on three components(X0, Y0, Z0) of the relative reaction(Rerr_r) that the reactions must be calculated with considering deformation of test article to calculate correctly reactions. This study shows also that equations characterizing deformation of components of test article are required to calculate the correct reactions, the equations must include information which will be used to calculate movement of all loading points.