• Geomechanics and Engineering
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• v.31 no.3
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• pp.237-248
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• 2022

Nowadays, more and more subway tunnels were planed and constructed underneath the ground of urban cities to relieve the congested traffic. Potential damage may occur in existing tunnel if the new tunnel is constructed too close. So far, previous studies mainly focused on the tunnel-tunnel interactions with circular shape. The difference between circular and horseshoe shaped tunnel in terms of deformation mechanism is not fully investigated. In this study, three-dimensional numerical parametric studies were carried out to explore the effect of different tunnel shapes on the complicated tunnel-tunnel interaction problem. Parameters considered include volume loss, tunnel stiffness and relative density. It is found that the value of volume loss play the most important role in the multi-tunnel interactions. For a typical condition in this study, the maximum invert settlement and gradient along longitudinal direction of horseshoe shaped tunnel was 50% and 96% larger than those in circular case, respectively. This is because of the larger vertical soil displacement underneath existing tunnel. Due to the discontinuous hoop axial stress in horseshoe shaped tunnel, significant shear stress was mobilized around the axillary angles. This resulted in substantial bending moment at the bottom plate and side walls of horseshoe shaped tunnel. Consequently, vertical elongation and horizontal compression in circular existing tunnel were 45% and 33% smaller than those in horseshoe case (at monitored section X/D = 0), which in latter case was mainly attributed to the bending induced deflection. The radial deformation stiffness of circular tunnel is more sensitive to the Young's modulus compared with horseshoe shaped tunnel. This is because of that circular tunnel resisted the radial deformation mainly by its hoop axial stress while horseshoe shaped tunnel do so mainly by its flexural rigidity. In addition, the reduction of soil stiffness beneath the circular tunnel was larger than that in horseshoe shaped tunnel at each level of relative density, indicating that large portion of tunneling effect were undertaken by the ground itself in circular tunnel case.

• Economic Analysis
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• v.17 no.1
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• pp.131-168
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• 2011

We estimate consumer price indexes of eight major cities from 1907 to 1939, and then integrate them into a national level one. The data mainly came from the Statistical Yearbooks of the Government-General of Colonial Korea, and if necessary, we supplement them using wages and unit prices of public utility charges which are used as the price of housing and various services. We apply Laspeyres index method, and the composition ratios of consumption expenditure estimated by the commodity flow method are used as weights. The price indexes of 12 item groups as well as aggregate one are also calculated. In case of Seoul, it is possible to calculate the consumer price index from 1907 to 2009, showing a century-long pattern. This consumer price index is critical for measuring the real income and expenditure before the liberation.

• Journal of The Geomorphological Association of Korea
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• v.26 no.3
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• pp.69-85
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• 2019

Humans have been important driver to reconfigure the terrestrial surface of the Earth by altering its morphology and processes. The effect of human activities on the physical landscape, however, shows substantially uneven geographical patterns. Most of anthrogemorphoogical studies regarding human-induced denudation have focused on areas with a long history of human modifications such as humid landscapes, so the hypothesis is naturally a great human impact on landscapes. The effect of human activities on dryland Earth surfaces are far less commonly studied, although erosion is one of major concerns in arid and semi-arid region regarding land and water quality degradation. The urban metropolis of Phoenix, Arizona, USA provides an opportunity to explore the impact of the Anthropocene. The Phoenix metropolitan area rests on classic desert landforms, such as extensive pediments, alluvial fans and sand sheets. Human activities including cattle crazing, wildfire resulting from introduced grass species by human, and recent urbanization processes have impacted these classic desert landforms and altered geomorphic processes. The purpose of this paper, therefore, rests in examining Anthropocene in the geomorphology of the north-central Sonoran Desert. The objectives of this paper are: i) to understand the impact of the Anthropocene on the geomorphological processes and forms through field observations; ii) to quantify the magnitude of human impacts on landscape using a published two-decade long record of erosion dataset and natural background erosion dataset in submitted manuscript at the sprawling edge of the Phoenix metropolitan region; iii) to examine how geomorphic outcome can affect the sustainability of cities through the estimation of sediment yield under the condition of urban sprawl.

• Asia Marketing Journal
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• v.11 no.3
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• pp.167-184
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• 2009

In the ever competitive world airline industry, Korean Air has been seeking on the one hand to streamline its operations through cost control and at the same time to boost customer loyalty and retention through a strong service differentiation strategy. As part of their service differentiation strategy, Korean Air has been actively engaging in culture marketing campaign. Their main activity involves entering into an alliance with the three leading museums of the world. Beginning with the Luvre of France, Korean Air supported the development of voice narration system that included the Korean language. This case describes the efforts of Korean Air to go beyond simply being a company that transports people and packages, to a global leading carrier that links the cities, cultures, and arts of the world. In the process, the case introduces the strategies and detailed actions behind Korean Air's culture marketing efforts.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.111-112
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• 2023

With the development of cities, the density of the population is continuously increasing as buildings become larger and more high-rise, but since the Haeundae residential complex fire in Busan in 2010, there has been a growing need to meet the fire protection performance of buildings as large-scale fires continue to occur every year. On the other hand, fire doors, which are one of the fire protection performance of buildings, have been judged unqualified in 82% of cases when fire doors constructed on the actual site were inspected after completion. The reason for this is that paper honeycomb and glasswool, which are used as core materials for fire doors, absorb moisture, reducing thermal insulation performance, and sagging due to increased weight, leading to performance degradation due to warping in empty spaces. To overcome these problems, research is underway to apply lightweight aerated concrete, an inorganic material, as a core material. Therefore, in order to select a blowing agent that produces stable bubbles prior to the production of lightweight bubble concrete for application as a fire door inner core, this study examined the physical performance according to the type of blowing agent and dilution concentration, and the following conclusions were drawn. Compared to vegetable bubbles and independent bubbles, synthetic bubbles have 3~8% higher thermal conductivity than independent bubbles, but 3~6% lower slurry density than vegetable bubbles, and 2~13% higher compressive strength, which is thought to be an improvement of synthetic bubbles.

• Journal of the Korean Society for Library and Information Science
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• v.57 no.4
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• pp.263-287
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• 2023

This study aims to find an efficient establishment and operation of a gallery in public libraries. A literature review, field case study, and interview method were used. 15 public library galleries in 5 regions in Korea and 11 public library galleries in 11 cities in 3 countries were examined. 22 people were interviewed and 21 (95.5%) of them claimed that a gallery needs to be operated in a public library. The result of the analysis proposes the followings for an efficient establishment and operation of a gallery in public libraries: firstly, employing an art gallery curator according to the library's situation. Secondly, establishing a gallery of at least 55m² in size. Thirdly, allocating an appropriate budget. Fourthly, if possible, gallery rental requests are reviewed by external experts and a gallery needs to be rented out to the public free of charge. Fifthly, having an operating manual or a regulation. Sixthly, a gallery should be operated directly by the library.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.3
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• pp.23-31
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• 2023

In this study, a smart bench was developed and researched smart benches that can contribute to user convenience and satisfaction by installing them in parks, bus stops, and tourist attractions in line with the rapidly changing construction of smart cities. The smart bench is automatically operated by the control system according to the external temperature and provides additional functions such as charging, lighting, and advertising to improve general bench functions as well as heating in winter and cooling in summer, making it suitable for smart urbanization. The developed smart bench is designed to be strong enough to withstand loads of about 2,500 N. It minimizes the visible parts such as assembled bolts and 220V power supply wires, It can also give aesthetic effects. The development was carried out with the aim of waterproofing and dustproofing of IP44 grade in accordance with the climate of Republic of Korea, which has four seasons, and it is advantageous for long-term use because the paint was selected for the weather ability (discoloration) grade 3 or higher. If smart bench is commercialized, it is believed that various options can be provided to the smart bench market, where buyers had few product options, as the parts were developed in an assembled type so that all functions can be responded in an optional form according to the installation environment and the buyer's budget.

• Journal of dental hygiene science
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• v.23 no.3
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• pp.225-235
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• 2023

Background: This study aimed to analyze the effects of periodontal treatment and individual- and tooth-related factors on tooth extraction in people with disabilities. Methods: The Korea National Health Insurance claims data of individuals with disabilities aged 40~64 years with chronic periodontitis in 2008 were obtained. Of these, data on the disabled who underwent scaling/root plaining, subgingival curettage/periodontal surgery, or non-periodontal treatments, and data on their teeth were selected. The extraction of 716,688 teeth from 39,097 patients was tracked until 2018, and the patient- and tooth-level factors related to tooth loss were identified using a mixed-effect logistic regression analysis. Results: Data from approximately 17% of the teeth were extracted during a follow-up period of approximately 11 years. Among the tooth-level variables, scaling/root planing treatment at baseline and periodontal treatment during the follow-up period were associated with a lower risk of tooth loss (odds ratio=0.692 and 0.769, respectively, p<0.001). Non-vital teeth increased the risk of tooth loss by 3.159 times (p<0.001). Among the patient-level variables, females were less likely to have lost their teeth than males, and those with orthopedic impairment or brain lesions/mental disabilities, a higher age group, lower income level, or residents in medium/small cities or rural areas were more likely to have lost their teeth (p<0.001). Conclusion: Through approximately 11 years of follow-up, scaling or root planing, experience with periodontal treatment at least once, female sex, older age, lower income, smaller residential areas, type of disability, and pulp vitality were found to be associated with tooth loss in individuals with disabilities aged 40~64 years with chronic periodontitis. To prevent tooth loss in individuals with disabilities, it is necessary to establish a dental treatment plan that considers the timing of periodontal treatment and the characteristics of the patient and teeth.

• Journal of Practical Engineering Education
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• v.15 no.2
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• pp.459-466
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• 2023

This study was conducted to investigate the mediating effect of academic stress on the relationship between smartphone overdependence and the communication competence of nursing students. The research subjects were nursing students in cities A and Y. The research period was from March 2 to March 9, 2023, and the number of subjects analyzed was 139. Descriptive statistics, Pearson correlation were analyzed using SPSS/WIN 26.0, Process macro program the collected data. The results of the mediating effect of academic stress on the relationship between smartphone dependence and communication competence showed that academic stress (β=.226, p=.005) mediated the effect on the relationship between smartphone dependence and communication competence(Z=-3.131, p=.002). As a result, the combined explanatory power of the variables on nursing student's communication competence was 15.4%. In addition, in order to reduce nursing students' smartphone overdependence, it is necessary to educate them about smartphone use and develop self-control, provide interventions to cope with academic stress, and develop intervention programs to improve communication competence.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.568-575
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• 2023

This paper aims to evaluate the quality characteristics and healing performance of precast concrete incorporating self-healing technology as a key technique for the construction of smart cities. The study found that precast concrete mixed with hybrid capsules exhibited a tendency of reduced slump and air content, impacting the quality characteristics. Specifically, the slump decreased by up to 14 %, and the air content by up to 9 %. Moreover, the inclusion of hybrid capsules in the concrete resulted in a maximum decrease of 16 % in compressive strength and 18 % in flexural strength. However, the introduction of hybrid capsules significantly enhanced the crack healing performance. The assessment through water permeability tests showed that the healing rate of 0.3 mm crack width after a 28-day healing period improved as the mixing ratio increased, with the healing rates at 1 %, 3 %, and 5 % hybrid capsule mixtures observed to increase by approximately 16 %, 25 %, and 32 %, respectively.