• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.137-143
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• 2017

There has been a number of research on concrete durability. specially, as a research on chemical ingression, the research on the degradation against acid, alkali, and sulfate has been conducted. On the other hand, for the research on oils, especially, the influence of various oils on cement mortar with Supplementary Cementitious Materials(SCMs) is not sufficiently studied. hence, in this research, the degradation of cement mortar incorporated fly ash and blast furnace slag is researched when the cement mortar is submerged in various oils. For the result of experiment, as the content of fatty acid in the oils, the degradation of cement mortar with SCMs was occurred more, and the cement mortar with SCMs suffered more degradation than the ordinary portland cement regarding the oil submerging.

• Journal of Energy Engineering
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• v.29 no.3
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• pp.74-85
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• 2020

This paper presents an algorithm that evaluated the overload influence by bus upon the distribution system by calculating the daily load curve of PEVs charging by bus based on the daily charging patterns of PEVs according to PEVs penetration scenarios. The proposed algorithm calculates the number of PEVs to estimate the number of households by bus; the probability density function of the charging start time of PEVs, considering driving characteristics of PEVs and the daily load curve of PEVs charging by bus considering battery characteristics according to PEVs penetration scenarios. To verify the evaluation of the overload influence by bus on the distribution system in terms of the proposed algorithm, the cases were reviewed on the target bus(apartment and detached houses) among the feeders of the distribution systems at Dongtan new-town in Korea.

• Land and Housing Review
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• v.6 no.4
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• pp.185-193
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• 2015

Since the introduction of New Towns in Seoul MSA, land price has steadilly been risen due to the financial burden of constructing metropolitan transportation facilities. Despite metropolitan transportation facilities are utilized by New Towns as well as its surrounding area, the current situation is that most of the burdens, which is supposed to be shared with local governments, fall to developers. This study, with the case of Dongtan New Town, is to deduce rational structure of cost-sharing by the analysis of travel demands of metropolitan transportation facilities. Also, for the financing of the cost, the application methods of TIF(Tax Incremental Financing) have been suggested. The results showed that the proportion of travel which origins from New Town was 35.1%, which results in 800 billion won for the share of local government. For financing this amount of the cost, at least 20 years of financial period and the rate of 2% increase of real estate are needed in operating the TIF.

• Tunnel and Underground Space
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• v.26 no.4
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• pp.293-303
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• 2016

Underground $CO_2$ storage technology is one of the most effective methods to reduce atmospheric $CO_2$. In this study, $CO_2$ storage condition was simulated in the laboratory. Sandstone and shale specimens were saturated in 1M NaCl and were reacted at $45^{\circ}C$, 10 atm for 4 weeks. The physical and microstructural properties of rock specimens were measured. Variations on physical properties of shale specimens were bigger than those of sandstone specimens, such as volume, density, elastic wave velocity, Poisson's ratio and Young's modulus. Microstructure were analyzed using X-ray computed tomography. Total number of pores were decreased, and average volume, average area and average equivalent diameter of each pore were changed after $CO_2$ reaction. Swelling and leakage of clay mineral caused by $CO_2$-mineral reaction were the reason of changes. The results of this study can be applied to predict the physical and microstructural changes in underground $CO_2$ storage condition.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.4
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• pp.304-312
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• 1998

In order to assure the reliability and integrity of structures such as bridges, Power and petrochemical plants, nondestructive evaluation techniques are recently playing more important roles. Among the various kinds of nondestructive evaluation techniques, ultrasonic technique is one of the most widely used methods for nondestructive inspection of internal defects in structures. For the reliable quantitative evaluation of internal defects from the experimental ultrasonic signals, a numerical analysis of ultrasonic scattering field due to a defect distribution is absolutely required. In this paper, the SH-wave scattering by multi-cavity defects using elastodynamic boundary element method is studied. The effects of shape of defects on transmitted and reflected fields are considered. The interaction of multi-cavity defects in 50-wave scattering is also investigated. Numerical calculation by the boundary element method has been carried out to predict near field solution of scattered fields of ultrasonic SH-wave. The presented results would be useful to improve the sensitivity of flaw defection for inverse analysis and pursue quantitative nondestructive evaluation for inverse problem.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.623-631
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• 2018

In this study, the degree of deterioration of concrete was investigated in the laboratory under conditions of carbonation and freeze-thaw cycling, which are the major causes of the deterioration of its performance. In this test, the carbonated concrete was subjected to combined freeze-thaw deterioration tests for up to 300 cycles, and its dynamic elastic modulus and compressive strength were measured. The evaluation of the effect of the water-binder ratio on normal concrete subjected to combined carbonization and freezing-thawing showed that its resistibility against such combined deterioration decreased more rapidly in the concrete with a water-binder ratio of 55 % compared with that having a water-binder ratio of 35 %. In the case where the concrete was blended with a mineral admixture consisting of fly ash and blast furnace slag at the same water-binder ratio, it showed an increase of its resistibility against combined deterioration.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.165-182
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• 2006

In this study, field test was performed to investigate the strength-improvement effect of shotcrete mixed Micro-silica fume and shotcrete quality was estimated by EFNARC standard. Deterioration test combined the Freezing-thawing and Carbonation was also performed in order to investigate a long-term durability of high-strength shotcrete. As a result of test, the compressive strength of shotcrete using Micro-silica fume was 45.2~55.8MPa and flexible strength was 5.01~6.66MPa, so a promotion ratio of strength was 37~79%, 17~61% respectively. And the strength-improvement effect of strength by silica fume addition ratio of 7.5~10% for cement mass was more superior to the others. Due to relative dynamic modulus, mass decrease rate and carbonation progress of shotcrete mixed Micro-silica fume, it was especially realized that Micro-silica fume reduced deterioration caused by steel fiber and improved a long-term durability of shotcrete.

• International Journal of Highway Engineering
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• v.16 no.3
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• pp.35-41
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• 2014

PURPOSES : The dynamic modulus for a specimen can be determined by using either the non-destructed or destructed testing method. The Impact Resonance Testing (IRT) is the one of the non-destructed testing methods. The MTS has proved the source credibility and has the disadvantages which indicate the expensive equipment to operate and need a lot of manpower to manufacture the specimens because of the low repeatability with an experiment. To overcome these shortcomings from MTS, the objective of this paper is to compare the dynamic modulus obtained from IRT with MTS result and prove the source credibility. METHODS : The dynamic modulus obtained from IRT could be determined by using the Resonance Frequency (RF) from the Frequency Response Function (FRF) that derived from the Fourier Transform based on the Frequency Analysis of the Digital Signal Processing (DSP)(S. O. Oyadigi; 1985). The RF values are verified from the Coherence Function (CF). To estimate the error, the Root Mean Squared Error (RMSE) method could be used. RESULTS : The dynamic modulus data obtained from IRT have the maximum error of 8%, and RMSE of 2,000MPa compared to the dynamic modulus measured by the Dynamic Modulus Testing (DMT) of MTS testing machine. CONCLUSIONS : The IRT testing method needs the prediction model of the dynamic modulus for a Linear Visco-Elastic (LVE) specimen to improve the suitability.

• Spatial Information Research
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• v.20 no.1
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• pp.19-26
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• 2012

Since $CO_2$ emissions are recognized as the biggest contribution to climate change, the needs and international efforts for $CO_2$ emissions reduction are increasing. The developed countries are driving strategies to boost green industry as a new growth engine. Following this global trend, based on the ongoing U-City project as a new city model, it is required to analyze the changes of $CO_2$ emissions in U-City to identify its potential for reducing carbon dioxide emissions. This study aims at identifying the potential and effects on $CO_2$ reduction by analyzing the level of $CO_2$ emissions before and after introducing U-City. Bundang-Gu, Seongnam-City & Ilsan-Gu, Goyang-City among Phase I new tow ns were selected as model cities before introducing U-City and Dongtan-Dong, Hwaseong-City as a model city after introducing U-City. The result showed 30% reduction of $CO_2$ emissions in the comparison of tw o models.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.4
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• pp.65-71
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• 2008

In this study, two residential complexes, both built in the New City area after 2006 and both composed of over 500 households, were selected to estimate an efficient accessibility and connectivity index using accessibility and connectivity theories and methods from previous studies. With architectural blueprints, the nodes and edges of both residential complexes were drawn out and the accessibility matrixes were derived using these nodes and edges. As a result, the connectivity indices of both residential complexes were lower than 1, the accessibility index of Dong-tan was 86.922 being smaller than the accessibility index of Ilsan, 96.199, and the efficiency index of both residential complexes were similar being 0.26. With these indices it is expected to geometrically estimate the residential complexes and predict the pedestrian passing conveniences.