• Journal of Coastal Disaster Prevention
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• v.5 no.4
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• pp.163-172
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• 2018

To propose the design technique and the execution manual of the LWFS(Lightweight Foamed Soil) method using dredged soil, the operation system for the test-bed integrated management, and to establish an amendment for the domestic quantity per unit and specifications, and a strategy for its internationalization. In order to utilize the dredged soil from the coastal area as a construction material, we constructed the embankment with LWFS on soft ground and monitored its behavior. As a result, it can be expected that the use of LWFS as an embankment material on the soft ground can improve the economic efficiency by reducing the depth and period of soil improvement as well as the uses of nearby dredged soil. To verify the utilization of the dredged soil as a material for light-weighted roadbed, soft ground and foundation ground, and surface processing, perform an experimental construction for practical structures and analyze the behavior. It is expected to be able to improve the soft ground with dredged soil and develop technique codes and manuals of the dredged soil reclamation by constructing a test-bed in the same size of the fields, and establish the criteria and manual of effective dredged soil reclamation for practical use. The application technology of the dredged soil reclamation during harbor constructions and dredged soil reclamation constructions can be reflected during the working design stage. By using the materials immediately that occur from the reclamation during harbor and background land developments, the development time will decrease and an increase of economic feasibility will happen. It is expected to be able to apply the improved soil at dredged soil reclamation, harbor and shore protection construction, dredged soil purification projects etc. Future-work for develop the design criteria and guideline for the technology of field application of dredged soil reclamation is that review the proposed test-bed sites, consult with the institutions relevant with the test-bed, establish the space planning of the test-bed, licensing from the institutions relevant with the test-bed, select a test-bed for the dredged soil disposal area.

• Bulletin of the Korean Chemical Society
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• v.10 no.3
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• pp.243-247
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• 1989

Two crystal structures of dehydrated $Ag^+\;and\;Ca^{2+}$ exchanged zeolite A, $Ag_2Ca_$5-A, reacting with 0.01 Torr of Cs vapor at $200^{\circ}C$ for 2 hours and 0.1 Torr of Cs vapor at $250^{\circ}C$ for 48 hours, respectively, have been determined by single crystal X-ray diffraction techniques. Their structures were solved and refined in the cubic space group Pm3m at $21(1)^{\circ}C$. The stoichiometry of first crystal was $Ag_2Ca_5$-A (a = 12.294(1)${\AA}$), indicating that Cs vapor did not react with cations in zeolite A and that of second crystal was $Ag_2Cs_{10}$-A (a = 12.166(1)${\AA}$), indicating that all $Ca^{2+}$ ions were reduced by Cs vapor and replaced by $Cs^+$ ions. Full-matrix least-squares refinements of $Ag_2Ca_5-A\;and\;Ag_2Cs_{10}$-A has converged to the final error indices, $R_1\;=\;0.041\;and\;R_2$ = 0.048 with 227 reflections, and $R_1\;=\;0.117\;an\;n\;fdd\;R_2$ = 0.120 with 167 reflections, respectively, for which I > $3{\sigma}$(I). In the structure of $Ag_2Ca_5$-A, both $Ag^+$ ions and $Ca^{2+}$ ions lie on two crystal symmetrically independent threefold axis sites on the 6-rings; $2\;Ag^+$ ions are recessed 0.33 ${\;AA}$ from the (111) planes of three O(3) oxygens and 5 $Ca^{2+}$ ions lie on the nearly center of each 6-oxygen planes. In the structure of $Ag_2Cs_{10}-A,\;Cs^+$ ions lie on the 5 different crystallographic sites. 3 $Cs^+$ ions lie at the centers of the 8-rings at sites of D4h symmetry. 6 $Cs^+$ ions lie on the threefold axes of unit cell: $4\;Cs^+$ ions are found deep in the large cavity and 2 $Cs^+$ ions are found in the sodalite cavity. One $Cs^+$ ion is found in the large cavity near a 4-ring.

• Journal of Korean Elementary Science Education
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• v.40 no.4
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• pp.480-497
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• 2021

This study intends to explore the content and organization characteristics of elementary school science textbooks in the astronomical domain from the perspective of understanding the astronomical spatial concept. This study analyzed the relevant unit of the achievement criteria in the 2015 revised science curriculum for the 'space' domain in elementary school science textbooks in comparison with that in secondary school textbooks according to the spatial concept analysis criteria by texts, illustrations, and inquiry activities. As a result, elementary school science textbooks were found to be organized around phenomena rather than concepts, targeting observable celestial bodies linked to real life in order to optimize the amount of learning content. However, the learning contents of astronomical observation related to observation and phenomena-centered real life should stimulate the curiosity and imagination of elementary school students and encourage their intellectual participation. Students need to be supported for understanding of the spatial concept to find an answer to the question of 'why'. The content organization for core concepts should be organized around the transferable spatial concept rather than simply focusing on presenting results by accurately describing the phenomena observed by students through scientific practice in order for students to answer various questions that arise in the course of scientific practice.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.6
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• pp.571-585
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• 2021

Various studies have analyzed urban decline at a universal level using the general characteristics of declining cities. However, urban decline at the city level should be considered because this decay occurs based on the unique attributes of a particular city. In addition, since this phenomenon occurs and spreads in microspaces, studies should consider smaller spatial units continuously. This study aims to develop an urban decline measurement model that considers regional characteristics to analyze the urban decline of Ulsan Metropolitan City over time and space. The index value of Ulsan, compared to the national average, is calculated and reflected in the weight to reflect regional characteristics in the model. In addition, after analyzing urban decline by administrative dong units, we also performed analysis by counting district units using spatial hierarchical structure to demonstrate evaluation on smaller unit spaces. As a result of analyzing urban decline patterns by associating the index calculated using the model with the social phenomenon of Ulsan Metropolitan City, urban decline formed clusters and spread to adjacent regions over time. In addition, results confirmed that external factors such as new towns and urban regeneration projects affect urban decline. By illustrating the degree of urban decline proposed measurement model used in this study, it is possible to present the priority of areas required for urban regeneration projects. Results are also helpful to test the effectiveness of completed or presently-implemented urban regeneration projects.

• Journal of the Korean Society of Earth Science Education
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• v.14 no.3
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• pp.225-235
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• 2021

The purpose of this study is to obtain implications for the improvement direction of astronomical education methods and development of educational materials or software. In connection with the 5th grade 1st semester elementary science 'Solar System and Stars' unit, elementary pre-service teachers were given a reorganization task to compare the relative distances from the sun to the planets, and then this was analyzed. Pre-service teachers are 11 male and 19 female students in the second year of the music education department at the elementary school teacher training university in B city. The implications of the study results are as follows. First, the 'distance comparison activity using a roll of tissue paper' is suitable for simply comparing the distances from the sun to the planet, but it has limitations in allowing students to experience the vastness of the solar system or inducing student participation-centered classes. Second, it is necessary to develop software materials for elementary school students that can simultaneously reflect the size of the planet and the distance to the planet that can be applied indoors, and also experience the vastness of the solar system, as well as a wide learning space. Third, textbook materials for students have an important influence on the class design of pre-service teachers.

• Journal of the Korea Computer Graphics Society
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• v.27 no.5
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• pp.63-71
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• 2021

Among drone autonomous flight technologies, obstacle avoidance is a very important technology that can prevent damage to drones or surrounding environments and prevent danger. Although the LiDAR sensor-based obstacle avoidance method shows relatively high accuracy and is widely used in recent studies, it has disadvantages of high unit price and limited processing capacity for visual information. Therefore, this paper proposes an obstacle avoidance algorithm for drones using camera-based PPO(Proximal Policy Optimization) reinforcement learning, which is relatively inexpensive and highly scalable using visual information. Drone, obstacles, target points, etc. are randomly located in a learning environment in the three-dimensional space, stereo images are obtained using a Unity camera, and then YOLov4Tiny object detection is performed. Next, the distance between the drone and the detected object is measured through triangulation of the stereo camera. Based on this distance, the presence or absence of obstacles is determined. Penalties are set if they are obstacles and rewards are given if they are target points. The experimennt of this method shows that a camera-based obstacle avoidance algorithm can be a sufficiently similar level of accuracy and average target point arrival time compared to a LiDAR-based obstacle avoidance algorithm, so it is highly likely to be used.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.29-35
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• 2022

This paper proposes a fuel cell education framework installed on a Metaverse environment, which is to reduce the burden of education costs and improve the effect of education or learning. This Meta-Fuel cell platform utilizes the Unity 3D Web and enables not only theoretical education but also hands-on training. The platform was designed and developed to accommodate a variety of unit education contents, such as ppt documents, videos, etc. The platform, therdore, integrates ppt and video demonstrations for theoretical education, as well as software content "STACK-Up" for hands-on training. Theoretical education section provides specialized liberal arts knowledge on hydrogen, including renewable energy, hydrogen economy, and fuel cells. The software "STACK-Up" provides a hands-on practice on assembling the stack parts. Stack is the very core component of fuel cells. The Meta-Fuelcell platform improves the limitations of face-to-face education. It provides educators with the opportunities of non-face-to-face education without restrictions such as educational place, time, and occupancy. On the other hand, learners can choose educational themes, order, etc. It provides educators and learners with interesting experiences to be active in the metaverse space. This platform is being applied experimentally to a education project which is to develop advanced manpower in the fuel cell industry. Its improvement is in progress.

• Communications of Mathematical Education
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• v.35 no.4
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• pp.547-573
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• 2021

Capacity is a concept that has been covered in elementary mathematics textbooks but its meaning has not been accurately defined in the textbooks. Two units, liter (L) and milliliter (mL), are introduced as the units of capacity in the textbooks, but they are the units of volume according to the International System of Unit. These stimulated us to analyze what capacity is, and how the capacity is related to the concept of volume. This study scrutinized how the different elementary mathematics textbooks that were developed from the first national curriculum to the most recently revised curriculum introduced the capacity and explained the relationship between capacity and volume. This study also examined the understanding of capacity by elementary school teachers using a questionnaire. The results of this study showed that the concept of capacity has been mostly introduced in the third grade in common but that there were differences among textbooks in terms of how they presented and used the concept of capacity as well as whether they described its definition or relationship with the concept of volume. Regarding the results of teachers' understanding, most teachers could explain the capacity as either "the size of the inner space of the container" or "the amount that can be contained" but some of them provided only superficial or inappropriate feedback for the students with the common misunderstandings of capacity. Based on these results, this paper presents implications for textbook developers and teachers to better address the concept of capacity.

• Journal of the Korean Association of Geographic Information Studies
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• v.25 no.2
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• pp.18-29
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• 2022

The purpose of this study is to examine the spatial characteristics and factors in the occurrence of COVID-19 from January 20 to August 30 of 2020. The exploratory spatial data analysis and spatial econometrics model are used. The spatial unit of analysis is 255 si-gun-gu in Korea. As a result of the analysis, COVID-19 infection did not appear to be a significant factors(host and environment) influencing the emergence of existing new infectious diseases, but there was a relationship between spatially adjacent areas and their occurrence. It also showed a close relationship with the outbreak pattern of group 4 infectious diseases, another type of new infectious disease in Korea. The result of this study shows that COVID-19 is not a new pattern of emerging infectious diseases. It means that the properties of the space where new infectious diseases appear must be continuously managed in order to effectively control new infectious diseases.

• Korean Journal of Construction Engineering and Management
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• v.24 no.2
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• pp.13-23
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• 2023

Unlike building construction projects, where the activity is repeatedly carried out in a limited area, civil engineering projects such as roads and railroads are carried out in a linear type in a horizontal working space over several tens of kilometers. Each activity is managed with a station number that has a unit of distance from the starting point to the end point. For this reason, since the work location information of the activity is a major management factor, the Gantt chart system that expresses only schedule information may have limitations. In this study, authors propose a method for constructing a linear schedule chart that can simultaneously express schedule information indicating the start and finish dates and location information indicating the start and end positions of each activity, and develop a system for generating a linear schedule chart. In the study, the coordinate axes of the linear schedule chart consisted of distance and date values on the X and Y axes, respectively, and each activity was expressed as a symbol that can infer the type of work to increase the visibility of the linear schedule chart compared to the simple bar chart method. The linear schedule chart generation system was reviewed for practical applicability by utilizing the actual schedule data of bridge structures in a railroad project.