• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.259-266
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• 2009

The steel pipe of steel-concrete composite piles increases the pile strength and induces the ductile failure by constraining the deformation of the inner concrete. In this research, the numerical models and the related input parameters were analyzed to simulate the axial load-movement relations, which were obtained from the compression loading tests for the cylindrical specimens of the steel pipe, the concrete, and the steel-concrete composite. As the results, the behavior of the steel pipe was simulated by the von-Mises model and that of the concrete by the strain-softening model, which decreases cohesion and dilation angles as the function of plastic strains. In addition, the reinforcing bars in the concrete were simulated by applying the yielding moment and decreasing the sectional area of the bars. The applied numerical models properly simulated the yielding behavior and the reinforcement effect of the steel-concrete composite piles. The parametric study for the real-size piles showed that the material strength of the steel-concrete composite pile increased about 10% for the axial loading and about 20~45% for the horizontal loading due to the reinforcement effect by the surrounding steel pipe pile.

• Journal of Practical Agriculture & Fisheries Research
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• v.21 no.2
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• pp.5-13
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• 2019

Orostachys species grow from anywhere in Korea. This variety, which lives in the harsh areas of the beach and mountains, is known to have as much change as it was isolated. It has been used as a medicine for a long time, and now the flower is beautiful and has been developed for horticulture. As a result of morphological characteristics and component analysis of three Orostachys species, the following results were obtained. 1. Orostachys species showed two types of leaves according to the growing environment. O. japonica (Maxim.) A. Berger and O. minuta (Kom.) A. Berger were lanceolate, and O. chongsunensis Y. N. Lee was obovate. 2. The leaves were all green. However, some of the O. japonica (Maxim.) A. Berger had white powder. Some of the O. minuta (Kom.) A. Berger was green with red spots on the back. O. chongsunensis Y. N. Lee showed strong gray before flowering but weak green when flowering. 3. The thorns of the leaves were O. japonica (Maxim.) A. Berger and O. minuta (Kom.), but O. chongsunensis Y. N. Lee was not. 4. Whether it was a leaf dot or not, there were dots in O. japonica (Maxim.) A. Berger and there were dots on the O. minuta (Kom.) and the O. chongsunensis Y. N. Lee. 5. The flowers were all white, and the stamens were red in O. japonica (Maxim.) A. Berger and O. minuta (Kom.) A. Berger and white in O. chongsunensis Y. N. Lee. 6. It was confirmed that the ingredients in Orostachys species contained kaempferol, quercetin, flavonoid etc., which have high antioxidant activity.

• Journal of the Korean Institute of Landscape Architecture
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• v.51 no.6
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• pp.75-87
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• 2023

This study presents an experimental design for demonstrating the role of nature-based solutions to climate change in the landscape and garden sector. The study suggests spatial strategies for a carbon-neutral society and its role as a cultural industry. This paper describes the use of a low-maintenance garden as part of a strategy for carbon reduction with the goal of protecting the environment and forming a carbon-neutral society. To this end, this study involved the design and construction of a realistic model garden to provide scientific data on the functions, spatial elements, and carbon neutrality of carbon-reducing gardens. The target site is located in the Sejong National Arboretum. The test area in which the carbon-reducing function is measured is located in the centre of the site, and other spaces include dry gardens, community gardens, and flower gardens intended for exhibition and relaxation. The experimental area is divided into several smaller areas within which the carbon-reducing effect is analysed according to the amount of biochar installed, the planting density, and the plant species present. The application of facilities and construction methods to promote carbon reduction were based on the method known as '10 types of carbon gardening for the earth'. In the model garden, we employed rainwater utilization facilities and used low-carbon certified wood and local materials. The carbon reduction effect of each facility and construction method is compared and presented here. The results are expected to serve as an important basis for realizing a carbon-neutral society and can be used as a reference in various fields that require sustainable development, such as the garden industry.

• Geophysics and Geophysical Exploration
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• v.26 no.4
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• pp.171-184
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• 2023

Machine learning (ML)-based cavity detection using a large amount of survey data obtained from vehicle-mounted ground penetrating radar (GPR) has been actively studied to identify underground cavities. However, only simple image processing techniques have been used for preprocessing the ML input, and many conventional seismic and GPR data processing techniques, which have been used for decades, have not been fully exploited. In this study, based on the idea that a cavity can be identified using diffraction, we applied ML-based diffraction separation to GPR data to increase the accuracy of cavity detection using the YOLO v5 model. The original ML-based seismic diffraction separation technique was modified, and the separated diffraction image was used as the input to train the cavity detection model. The performance of the proposed method was verified using public GPR data released by the Seoul Metropolitan Government. Underground cavities and objects were more accurately detected using separated diffraction images. In the future, the proposed method can be useful in various fields in which GPR surveys are used.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.138-143
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• 2023

In this study, the crack healing performance of each crack healing agent manufacturing method was analyzed by adding crack healing agents in the form of alginate gel and spore suspension inoculated with endospores of calcium carbonate-forming bacteria to mortar. In addition, by applying it to an full-scale structure in the form of a box-type culvert, we attempted to create an environment in which the developed crack healing agent can be applied not only to a laboratory environment but also to an actual field. The crack healing agent using the dry heat drying method showed crack healing performance, but in the case of the freeze drying method, many spores were killed by freeze hardening and therefore the crack healing performance was lost. As a result of SEM and XRD pattern analysis of the presumed crack healing material extracted from the crack of a full-scale structure, it was found to be calcite, one of the calcium carbonate crystals produced by microorganisms applied to the crack healing agent. In conclusion, it was found that the crack healing by microorganisms can be implemented in a real structure.

• Journal of the International Relations & Interdisciplinary Education
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• v.2 no.2
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• pp.81-95
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• 2022

The core of this study is to develop an edutech utilization program to be applied to 5th grade students by utilizing school curriculum time, and the conclusions based on the results of the study are as follows. First, for the development of future educational programs using edutech, a content preference survey was conducted and significant responses were confirmed from 27 teachers and 216 students, excluding missing values. In the future education implementation, UCC (video shooting, editing, etc.) and work activities (3D pen, 3D printer, etc.) were selected based on the need for separate edtech devices. Second, in order to develop a future education program using edutech, the future education class module was set in 4 stages based on previous research. First of all, in Make a foundation, theories by subject are developed, and in Open an activity, future education experience activities using key edutech are developed. In Organize evaluation, individual self-evaluation was conducted, and based on this, customized in-depth supplementary activities were conducted in Act individually. Third, in order for future education programs using edutech to be organized in the regular curriculum, sufficient connectivity with the curriculum must be secured. The basis for systematic and stable research was prepared by analyzing the curriculum of the 5th grade subject of the study and securing hours in connection with creative experiential activities. The data developed through this process were modified and supplemented based on the content validity test. The fact that the program application and verification steps were not performed is a limitation of this study, but it is expected that this program will expand the possibility of future education practice in the school field.

• Tunnel and Underground Space
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• v.33 no.5
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• pp.399-413
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• 2023

The present study conducted a numerical modeling of CO₂ injection at the Janggi Basin using the TOUGH-FLAC simulator, and examined the hydro-mechanical stability of the aquifer and the fault. Based on the site investigations and a 3D geological model of the target area, we simulated the injection of 32,850 tons of CO₂ over a 3-year period. The analysis of CO₂ plume with different values of the aquifer permeability revealed that assuming a permeability of 10^-14 m² the CO₂ plume exhibited a radial flow and reached the fault after 2 years and 9 months. Conversely, a higher permeability of 10^-13 m² resulted in predominant westward flow along the reservoir, with negligible impact on the fault. The pressure changes around the injection well remained below 0.6 MPa over the period, and the influence on the hydro-mechanical stability of the reservoir and fault was found to be insignificant.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.2
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• pp.1-13
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• 2022

This study derived the success factors of youth enterprises by applying the Delphi Method to start-up experts. Through this, it aims to improve understanding of youth enterprises in entrepreneurship education and start-up support projects and contribute to the development of education and support programs suitable for youth enterprises. Also The purpose of this study is to help youth entrepreneurs solve their curiosity about the success factors of youth enterprises, identify the factors that youth entrepreneurs should first secure or perform among the factors they need to consider during start-ups, and use limited resources efficiently and effectively to succeed. In this study, the Delphi Survey was conducted twice in total. The first Delphi Survey utilized the Modified Delphi Method using structured closed-ended questions, and a pilot test was conducted on youth entrepreneurs and start-up experts to compensate for the problem of the Modified Delphi Method. In the first Delphi Survey, IBM SPSS Statistics 22 and Microsoft Office Excel 2016 were used to calculate the mean, standard deviation, median, interquartile range, and content validity ratio. In the Delphi 2nd survey, the same statistical values in the 1st survey and additionally cronbach's alpha were calculated. As a result of the Delphi Survey, four factors, such as the entrepreneurial characteristics, entrepreneurial preparation, entrepreneurial strategy, and entrepreneurial environment, and 22 sub-factors were derived as success factors for youth enterprises.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.17 no.1
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• pp.76-81
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• 2024

Recently, agricultural methods are changing from experience-based agriculture to data-based agriculture. Changes in agricultural production due to the 4th Industrial Revolution are largely occurring in three areas: smart sensing and monitoring, smart analysis and planning, and smart control. In order to realize open-field smart agriculture, information on the physical and chemical properties of soil is essential. Conventional physicochemical measurements are conducted in a laboratory after collecting samples, which consumes a lot of cost, labor, and time, so they are quickly measured in the field. Measurement technology that can do this is urgently needed. In addition, a soil analysis system that can be carried and moved by the measurer and used in Korea's rice fields, fields, and facility houses is needed. To solve this problem, our goal is to develop and commercialize software that can collect soil samples and analyze the information. In this study, basic soil composition measurement was conducted using soil composition measurement sensors consisting of hardness measurement and electrode sensors. Through future research, we plan to develop a system that applies soil sampling using a CCD camera, ultrasonic sensor, and sampler. Therefore, we implemented a sensor and soil analysis UI that can measure and analyze the soil condition in real time, such as hardness measurement display using a load cell and moisture, PH, and EC measurement display using conductivity.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.9-18
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• 2023

Climate change affects the safety of river revetments, especially those associated with external flooding. Research on slope reinforcement has been actively conducted to enhance revetment safety. Recently, technologies for producing embankment blocks using recycled materials have been developed. However, it is essential to analyze the impact of block shapes on the flow characteristics of exclusion zones for revetment safety. Therefore, this study investigates the influence of revetment block shapes on the hydraulic characteristics of revetment surfaces through 3D numerical simulations. Three block shapes were proposed, and numerical analyses were performed by installing the blocks in an idealized river channel. FLOW-3D was used for the 3D numerical simulations, and the variations in maximum flow velocity, bed velocity beneath the revetment, and maximum shear stress were analyzed based on the shapes of the revetment blocks. The results indicate that for irregularly sized and spaced revetment blocks, such as the natural stone-type vegetation block (Block A), when connected to the revetment in an irregular manner, the changes in flow velocity in the revetment installation zone are more significant than those for Blocks B and C. It is anticipated that considering the topographical characteristics of rivers in the future will enable the design of revetment blocks with practical applicability in the field.