• Bulletin of the Korean Mathematical Society
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• v.36 no.2
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• pp.403-409
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• 1999

In this paper we introduce the notions of expansive homeomorphism and its properties, and study the relation between countable compacta and ordinal numbers. Our results extend and improve those of T.Kimura and others.

• Geomechanics and Engineering
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• v.15 no.6
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• pp.1219-1225
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• 2018

In this study, a comprehensive laboratory experimental programme was conducted on expansive soil with a high swelling potential to study the influence of different additive materials on swelling pressure and index properties. Lime, sand, multifilament fiber and fibrillated fiber were used for stabilization of expansive soil. Lime, sand and fibers were respectively added to the expansive soil at 0-7%, 0-80%, 0-0.5%. On each mixture that was prepared by the proportions mentioned above, Atterberg limits, compaction, and swelling pressure tests were conducted. From the result of these experiments, the swelling pressure-time relation could be replaced by a rectangular hyperbola established to facilitate the prediction of ultimate percent swelling with a few initial data points. The best type of additive and its optimum ratio for engineering purposes could be estimated rapidly by this approach.

• Journal of the Chungcheong Mathematical Society
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• v.28 no.2
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• pp.287-305
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• 2015

Hyperbolicity is a core of dynamics. Shadowness and expansiveness for homeomorphisms have been studied by J. Om-bach([3], [4], [5]). We study the hyperbolicity (i.e., expansivity and the shadowing property) and the Anosov relation for a closed relation.

• Geomechanics and Engineering
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• v.32 no.1
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• pp.85-96
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• 2023

Microbially induced carbonate precipitation (MICP) is extensively discussed as a promising topic for ground stabilization. The practical effect of stabilizing the expansive soil is presented in this paper with a logical process from the bacterial activity to the treatment technology. Temperature, pH, shaking frequency, and inoculation amount are discussed to evaluate the bacterial activity. The physic-mechanic properties are also evaluated to discuss the effect of the MICP process on expansive soil. Results indicate that the MICP method achieves the mitigation of expansion. The treated soil has a low proportion of fine particles (< 5 ㎛), the plasticity index significantly decreases, and strength values improve much. MICP process has a significant cementation effect on the soil matrix. Moreover, the infiltration model test presents the coating effect on the topsoil. According to the relation between the CaCO₃ content and the treatment effect, the topsoil has better treatment than the deeper soil.

• The Journal of Engineering Geology
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• v.8 no.3
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• pp.207-213
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• 1998

A study was conducted to determine the characteristics of acoustic emission(AE) events generated by the expansive cement induced rock fracturing. The dominant frequency and the maximum amplitude of the AE events are changed in relation to the rate of expansive pressure development in the hole. The dominant frequencies are in the range of 150∼230kHz for the small hole tests and 400∼500kHz for the large hole test. The maximum amplitudes are in the range of 0.015∼0.050cm/sec and 0.025∼0.064cm/sec, respectively. The fact that AE events of higher amplitude with higher frequency on the large hole test and lower amplitude with lower frequency on the small hole tests were detected, may strongly imply that the amount of energy consumed for a macro-crack in both tests may be similar. The expansive cement induced crack propagates stably without any distinguished event having higher amplitude and this implies that a macro-crack is a result of stable growth of micro cracks.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.193-200
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• 1999

An experimental study is described in which a 305-mm-diameter instrumented drilled shaft was installed in a moderately expansive clay soil during the dry season and monitored over a period of about 18 months. The purpose of the study was In investigate the effects of seasonal moisture changes in the soil on the shear stresses imposed on the sides of the drilled shaft and movements of the shaft head. The soil in the vicinity of the test shaft was instrumented to measure suction and ground surface movement and the relation between suction, total stress and shear strength of the soil at the test site was determined through laboratory triaxial compression testing. Daily rainfall and temperatures were also monitored at the test site, the National Geotechnical Experimentation Site at the University of Houston, where control on surface grading and vegetation existed. Over the course of the study induced unit side shear values of up to 54 kPa were measured in the test shaft. A simple computational model was developed that related observed suction changes to unit side shear induced by the expansion of the soil through the use of the laboratory suction-total stress-shear strength relation.

• Journal of the Korean Geotechnical Society
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• v.39 no.11
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• pp.33-40
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• 2023

This study explores the performance of pile foundations in highly expansive soil, incorporating magnesium oxide-based refractory materials. A controlled model chamber, housing a fixed pile, was utilized to induce ground expansion through fused magnesia (FM). The investigation focused on measuring the vertical displacement of FM-sand mixtures and the axial load on the pile in relation to depth and time. The study varied the amount of FM content (FM_c) at 30%, 50%, and 70%. The upward movement exhibited an augmentation with increasing FM_c, tapering off with depth as accumulation progressed toward the mixture surface. Compression and tensile forces were both evident along the pile for FM_c at 30% and 50%, while only a tensile force was observed at an FM_c of 70%. These results offer valuable insights for the analysis of pile behavior within FM-sand mixtures.

• Journal of the Korean Home Economics Association
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• v.39 no.11
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• pp.193-208
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• 2001

The changes of neighbor relation by joining communal childcare cooperative are as follows. Neighbors who are cooperative members are consultant who advise on childcare and communal parents who nurture children in communal local society. They are also consultant on problems of couples because one can reveal difficulties and troubles in the relation with the spouse easily to the neighbors. They admit gradually that their daily life can also be shared with other families. Living with neighbors extend the boundary of family and form a sound family culture. On the other hand, because their relationship is satisfactory, they have no need to form relationship with neighbors who are not cooperative members. They regard neighbors who are not cooperative members as 'peoples with different color from us'. Also they recognize exclusive eyesight from neighbor who are not cooperative members. The changes of family relation by joining communal childcare cooperative are as follows. In the relationship between wife and husband, both husband and wife take equal responsibility of childcare and that husband gets to familiar with household matters. In the relationship between parents and children, equality comes true and parents get to blow wars to be good parents. And they neither attach to their children nor bear expansive delusions on their children.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.851-863
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• 2002

Corrosion products of reinforcement in concrete induce pressure to the adjacent concrete due to the expansion of steel. This expansion causes tensile stresses around the reinforcing bar and eventually induces cracking through the concrete cover The cracking of concrete cover will adversely affect the safety as well as the service life of concrete structures. The purpose of the this study is to examine the critical corrosion amount which causes the cracking of concrete cover. To this end, a comprehensive experimental and theoretical study has been conducted. Major test variables include concrete strength and cover thickness. The strains at the surface of concrete cover have been measured according to the amount of steel corrosion. The corrosion products which penetrate into the pores and cracks around the steel bar have been considered in the calculation of expansive pressure due to steel corrosion. The present study indicates that the critical amount of corrosion, which causes the initiation of cracking, increases with an increase of compressive strength. A realistic relation between the expansive pressure and average strain of corrosion product layer in the corrosion region has been derived and the representative stiffness of corrosion layer was determined. A concept of pressure-free strain of corrosion product layer was introduced to explain the relation between the expansive pressure and corrosion strain. The proposed theory agrees well with experimental data and may be a good base for the realistic durability design of concrete structures.

• Journal of Applied Tourism Food and Beverage Management and Research
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• v.17 no.1
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• pp.41-67
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• 2006

The study is aimed to analyze the influence of FTA(Free Trade Agreement) between Korea and Japan on tourism and to suggest ways to increase tourists exchange between them by considering countermeasures of Korea's tourism based on the analysis and deriving political significance. The results of the study showed that the expected effects of FTA between Korea and Japan on tourism would overall be positive. There would be increases in employment and a higher rate of foreign-exchange earning, which plays a critical role in the cash flow. Therefore the government is required to prepare for several political measures as follows. First, ways to promote investment in tourism have to be established in a systematic way for FTA. Second, restructuring of tourism has to be considered seriously for tourism to be a high value-added industry after FTA. Third, the tourism information industry needs to be included in the tourism promotion act to promote e-tourism using information technology. In addition to this, an expansive cluster strategy needs to be developed, which relates tourism to other industries like culture and movies and to find ways to re-locate and re-educate manpower currently engaged in the tourism industry. Though the study investigated the influence of FTA on tourism through a practical analysis, it was restricted only to Korea. So the influence of FTA between Korea and Japan on the tourism of Japan should be included in further study. Furthermore, in subsequent studies the CGE(Computable General Equilibrium) model will be applied for objective analysis of the effects. Or measuring the ripple effect with multinational inter-industry relation table will be made for the study to make practical contributions to the development of government policy.