• International Journal of Highway Engineering
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• v.10 no.4
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• pp.31-40
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• 2008

The dynamic moduli of asphalt concrete are very important for the analysis and the design of asphalt pavement systems. The dynamic modulus master curve is usually represented by a sigmoidal function. The Ramberg-Osgood model was widely used for fitting of normalized modulus reduction curves with strain of soils in soil dynamic fields. The master curves were obtained by both sigmoidal functions and modified Ramberg-Osgood model for the same dynamic modulus data set, the fitting abilities of both methods were excellent. The coefficients in sigmoidal function are coupled. Therefore, it is not possible to separate the characteristics of the master curve with absolute value and shape. However, the each fitting coefficient in the Ramberg-Osgood model has a unique effect on the master curve, and the coefficients are not coupled with each other.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.4
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• pp.53-60
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• 2009

Recently, the Korean government has amended the "National Territory Planning Act" by adding criteria to designate the Impact Fee Zone on the basis of the population increase rate. Taking the Dongtan Newtown in Hwasung City as the case, the study first tries to apply a grid analysis method to figure out the cells that exceed the legal population increase rate criteria. Then, the study, for rather a practical purpose, introduces a scenario analysis that tries to envelope the cells into a spatially contiguous groups based on their degrees of stepwise adjacency by cell buffer formation. By overlapping the selected cell groups chosen by such stepwise scenarios over the actual zoning map of land-uses for the vicinity, it seems clear that the chosen areas rationally coincide with those residential blocks and commercial areas with the high population density in the Newtown.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.23-30
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• 2011

In this study, deterioration degrees of concrete were investigated at laboratory under seawater attack and cycling freeze-thaw, which are major durability performance deterioration factors of concrete. Deteriorations of mixed concrete using Portland & blended cement were examined by instrumental analysis of changes in relative dynamic modulus of elasticity and compressive strength. After 520 cycles of freeze-thaw, relative dynamic modulus of elasticity and compressive strength of concrete mixed with normal Portland and LHC over 75% showed relatively low resistance of approximately 44% of those values of SRC. Concrete replaced with 50% fine powder of blast furnace slag showed the most excellent freeze-thaw resistance among the tested blended cement concrete.

• Fire Science and Engineering
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• v.29 no.1
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• pp.1-6
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• 2015

In this study, the damages of high strength concrete exposed to high temperature have been evaluated by the impact echo method. Elastic wave velocity and dynamic modulus of elasticity were measured by the impact echo method, and the compressive strength and the static modulus of elasticity were measured by the compression testing method after exposure to high temperature. The results showed that elastic wave velocity has a linear correlation with the compressive strength and dynamic modulus of elasticity has a linear correlation with static modulus of elasticity. Based on results, it is concluded that the impact echo method can be effectively applied to evaluate the mechanical properties of fire damaged high strength concrete.

• Journal of the Korean Association of Geographic Information Studies
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• v.12 no.4
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• pp.74-83
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• 2009

In September 2008, the Korean government has legally pronounced criteria to designate the Impact Fee Zone on the basis of the population increase rate. Taking the Dongtan Newtown in Hwasung City as the case, the study tries a grid analysis method to figure out the cells that exceed the legal population increase rate criteria. The study then performs scenario analyses that try to envelope the cells into spatially contiguous groups based on their degrees of stepwise adjacency either by the cell buffer or the cell distance standards. By overlapping the selected cell groups over the actual land-use map for the vicinity, it is found that the selected areas reasonably coincide with the blocks of the high population density in the Newtown.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.419-424
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• 2021

This study investigated the possibility of early determination of frost damage on the concrete surface by using the rebound hardness method, widely used for estimation the compressive strength of concrete on the site. For this purpose, the surface damage of concrete was compared by measuring the rebound hardness and the relative dynamic modulus of the concrete for the multi-sided and single sided concrete surface exposed to freeze and thaw condition. Compared to the resonance vibration method, the rebound hardness method was able to show the frost damage 150 cycles quicker for the single-sided exposed concrete specimen and 50 cycles quicker for the multi-sided exposed concrete specimen. Therefore, it is considered that the rebound hardness method can determine the concrete surface damage more quickly than that of the resonance vibration method.

• The Journal of the Korea Contents Association
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• v.18 no.11
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• pp.455-461
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• 2018

This paper presents experimental investigations about flexural strength and durability of reinforced concrete beams repaired using ductile fiber reinforced cementitious composite (DFRCC) and carbon fiber sheet through freezing and thawing test. Total 14 RC beams of $100{\times}100{\times}400mm$ size were tested by 3-point bending and freezing and thawing test by KS F 2456. The beams were reinforced using 3D10 steels on both the tensile and compressive sides, and repaired on 3 sides expect on top cycle. Test results showed that the beams repaired using fiber carbon sheet revealed about 15% higher values of flexural strength compared than the cases of DFRCC motar. On the other hand, the results did not showed meaningful differences in the aspect of durability. For further research, consideration of the steel interference effect and real old specimens such as taken from real deteriorated structures are needed to be tested after repairing with DFRCC and carbon fiber sheet.

• Journal of The Korean Society of Clinical Toxicology
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• v.16 no.2
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• pp.116-123
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• 2018

Purpose: The social environment of easy access to medicines and arbitrary personal decisions leading to overdose aggravate unintentional medicine poisoning. This study aimed to investigate the characteristics of patients who visited emergency departments with unintentional medicine poisoning and reasons for poisoning based on age group. Methods: We retrospectively collected patients who experienced unintentional medicine poisoning based on data from the national injury surveillance system between 2013 and 2016. Subjects were classified into three groups based on age (0-14 years, 15-64 years, and ${\geq}65\;years$). We identified sex, insurance, time of poisoning, place, alcohol co-ingestion, hospitalization, death, and reason for poisoning in each age group. Results: A total of 27,472 patients visited an emergency department with poisoning during the study period; 1,958 patients who experienced unintentional poisoning were enrolled in this study. Respiratory medicine was the most frequent medicine in those younger than 15 years of age, and sedatives and antipsychotic drugs were the most common in patients older than 15 years of age. In total, 35.1% of patients older than 65 years were hospitalized. The most common reasons for poisoning were careless storage of medicine in those younger than 15 years of age and overdose due to arbitrary decisions in those older than 15 years of age. Conclusion: Unintentional medicine poisoning has distinct characteristics based on age group, and strategies to prevent poisoning should be approached differently based on age.

• The Journal of the Korea Contents Association
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• v.20 no.12
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• pp.529-536
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• 2020

This paper presents experimental investigations about compressive strength and durability of reinforced concrete compressive members repaired using ductile fiber reinforced cementitious composite (DFRCC) and carbon fiber sheet through freezing and thawing test. Total 24 RC specimens of 100x100x400mm size were tested by compressive strength test and freezing and thawing test by KS F 2456. The specimens were reinforced using 4D10 steels and repaired on 4 sides expect on top cycle. Test results showed that the specimens repaired using fiber carbon sheet revealed about 5% higher values of the compressive strength compared than the cases of DFRCC motar. On the other hand, the resurts did not showed meaningful differences in the aspect of durability. For further research, considerations of the steel interference effect and real old specimens such as taken from real deteriorated structures are needed to be tested after repairing with DFRCC and carbon fiber sheet.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.144-151
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• 2023

In this study, a database was established by collecting experimental results on various concrete mixtures subjected to freeze-thaw cycles, based on which an artificial neural network-based prediction model was developed to estimate durability resistance of concrete. A regression analysis was also conducted to derive an equation for estimating relative dynamic modulus of elasticity subjected to freeze-thaw loads. The error rate and coefficient of determination of the proposed artificial neural network model were approximately 11% and 0.72, respectively, and the regression equation also provided very similar accuracy. Thus, it is considered that the proposed artificial neural network model and regression equation can be used for estimating relative dynamic modulus of elasticity for various concrete mixtures subjected to freeze-thaw loads.