• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.104-111
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• 2005

Dmitri Donskoi, the Russian cruiser launched in 1883, is known to have sunk near Ulleung Island (East Sea, Korea) on May 29, 1905, while it was participating in the Russo-Japanese War. In order to find this ship, information about its possible location was obtained from Russian and Japanese maritime historical records. The supposed location of the ship was identified, and we conducted a five-year geophysical survey from 1999 to 2003. A reconnaissance three-dimensional topographic survey of the sea floor was carried out using multi-beam echo sounder, marine magnetometer, and side-scan sonar. An anomalous body identified through the initial reconnaissance survey was identified by a detailed survey using a remotely operated vehicle, deep-sea camera, and the mini-submarine Pathfinder. Interpretation of the acquired data showed that the ship is hanging on the side of a channel, at the bottom of the sea 400 m below sea level. The location is about 2 km from Port Jeodong, Uleung Island. We discovered 152 mm naval guns and other war materiel still attached to the hull of the ship. In addition, the remnants of the steering gear and other machinery that were burnt during the final action were found near the hull. Strong magnetic fields, resulting from the presence of volcanic rocks in the survey area, affected the resolution of the magnetic data gathered; as a result, we could not locate the ship reliably using the magnetic method. Severe sea floor topography in the gully around the hull gave rise to diffuse reflections in the side-scan sonar data, and this prevented us from identifying the anomalous body with the side-scan sonar technique. However, the sea-floor image obtained from the multi-bean echo sounder was very useful in verifying the location of the ship.

• Journal of the Korean School Mathematics Society
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• v.24 no.1
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• pp.107-126
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• 2021

Lexicon is closely related to human thinking. In particular, a classroom lexicon results from objectifying the teaching-learning activity in classrooms, allowing humans to recognize and explore the activities and phenomena in classrooms explicitly. Therefore, using the lexicon and clarifying what the words mean is to enhance the understanding of teaching activities. The International Classroom Lexicon Project investigates and identifies each country's mathematics classroom lexicon, where ten countries participated. The purpose of this current study is to compare the differences in perceptions between teachers and pre-service teachers about the Korean classroom lexicon previously investigated as a part of the international collaborative project. By comparing the responses of 147 teachers and 127 pre-service teachers, the degree of familiarity with pedagogical terms and the frequency of occurrence or usage in classrooms were compared and analyzed to understand the recognition of pre-service teachers' pedagogical terms. Finally, we also discuss reflections on Korean mathematics teaching practices in Korea.

• Korean Journal of Remote Sensing
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• v.37 no.6_1
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• pp.1709-1718
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• 2021

The waveform data of the Airborne Bathymetric LiDAR (ABL; LiDAR: Light Detection And Ranging) system provides data with improved accuracy, resolution, and reliability compared to the discrete-return data, and increases the user's control over data processing. Furthermore, we are able to extract additional information about the return signal. Waveform decomposition is a technique that separates each echo from the received waveform with a mixture of water surface and seabed reflections, waterbody backscattering, and various noises. In this study, a new waveform decomposition technique based on a Gaussian model was developed to improve the point extraction performance from the ABL waveform data. In the existing waveform decomposition techniques, the number of decomposed echoes and decomposition performance depend on the peak detection results because they use waveform peaks as initial values. However, in the study, we improved the approximation accuracy of the decomposition model by adding the estimated potential peak candidates to the initial peaks. As a result of an experiment using waveform data obtained from the East Coast from the Seahawk system, the precision of the decomposition model was improved by about 37% based on evaluating RMSE compared to the Gaussian decomposition method.

• The Korean Journal of Archival Studies
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• no.68
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• pp.5-39
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• 2021

In this study, the origin of the record continuum theory was analyzed in conjunction with the record management situation in Australia after the mid-20th century and record lifecycle model. For an in-depth understanding of the record continuum theory, it is necessary to consider the background and process of its formation, and to analyze the lifecycle model itself in terms of a theoretical system built with reflections on the lifecycle model. To this end, first of all, with the aim of analyzing the historical background of the formation of the record continuum theory, the background and process that led to intensive illumination of the US lifecycle model in the process of seeking an independent public records management system in Australia in the 1950s were reviewed. Then, the meaning and limitations of the lifecycle model were considered along with the background of the formation. In order to examine the main contents, significance, and limitations of the lifecycle model, it is necessary to analyze the circumstances under which it was formed. Based on this analysis, finally, the problems associated with the application of the lifecycle model in Australia's new record creation environment, as well as the factors that were the origin of the newly born record continuum theory were examined.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.251-257
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• 2021

An underwater platform operating a passive sonar needs to acquire the target position to perform its mission. In an environment where sea-floor reflections exist, the position of a target can be estimated using the difference in the arrival time between the signals received through multipaths. In this paper, a method of localization for passive sonar is introduced, based on the EKF (Extended Kalman Filter) using the multipath time difference of arrival in underwater environments. TMA (Target Motion Analysis) requires accumulated measurements for long periods and has limitations on own-ship movement, allowing it to be used only in certain situations. The proposed method uses an EKF, which takes measurements of the time differences of the signal arrival in multipath environments. The method allows for target localization without restrictions on own-ship movement or the need for an observation time. To analyze the performance of the proposed method, simulation according to the distance and depth of the target was performed repeatedly, and the localization error according to the distance and water depth were analyzed. In addition, the correlation with the estimated position error was assessed by analyzing the arrival time difference according to the water depth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.76-84
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• 2021

The quality assurance activities can detect the factors that affect the quality based on risk identification in the course of mass production. Risk identification is conducted with risk analysis, and the risk analysis method for the rotorcraft landing system is selected by failure mode effects analysis (FMEA). FMEA is a method that detects the factors that can affect the product quality by combining severity, occurrence, and detectability. The results of FMEA were prioritized using the risk priority number. On the other hand, these methods have certain shortcomings because the severity, occurrence, detectability are weighted equally. Dempster-Shafer evidence theory can conduct uncertainty analysis for the opinions with personal reflections and subjectivity. Based on the theory, the belief function and the plausibility function can be formed. Moreover, the functions can be utilized to evaluate the belief rate and credibility. The system is exposed to impact during take-off and landing. Therefore, experts should manage failure modes in the course of mass production. In this paper, FMEA based on the Dempster-Shafer evidence theory is discussed to perform risk analysis regarding the failure mode of the rotorcraft landing system. The failure priority was evaluated depending on the factor values. The results were derived using belief and plausibility function graphs.

• Journal of the Korean School Mathematics Society
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• v.24 no.4
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• pp.369-390
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• 2021

It would be reasonable as a teacher to make efforts not only to reflect on the class on their own but also to improve the teacher' teaching e pertise by reflecting on the class with fellow teachers through lesson reflection sharing. This paper attempted to develop a lesson reflective framework that can provide standards and focus for lesson reflection and lesson sharing. First, based on the class evaluation criteria of previous studies, class reflection elements and a draft of lesson reflection were prepared. In a class conducted on 27 third graders at C High School where the co-researcher worked as a teacher, four peer teachers at the same high school were required to write personal opinions on the class based on the draft of lesson reflection. Based on this, lesson sharing was conducted, and modifications of the lesson reflection framework were developed by analyzing the case of class sharing. The implications of this paper indicate the need to clarify the perspective of viewing the lesson by sharing the intention of each question in advance. In addition to writing lesson reflections, it is necessary to share classes simultaneously.

• The Journal of the Acoustical Society of Korea
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• v.41 no.5
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• pp.557-563
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• 2022

The cortical bone thickness of the tibia is related to fracture risk and overall bone status. The present study aims to investigate the feasibility of two different ultrasonic methods for measuring the cortical bone thickness in bovine tibia in vitro. In the reflection technique, the tibial cortical thickness was determined from ultrasonic reflections from the periosteum and the endosteum producing specific peaks in the signal envelope. In the axial transmission technique, the tibial cortical thickness was determined from ultrasonic guided wave velocities measured along the axial direction of the tibia. The cortical bone thickness determined by using the reflection technique correlated significantly with that measured by using a caliper, with a Pearson's correlation coefficient of r = 0.97 (p < 0.0001). In contrast, the correlation coefficients for the axial transmission technique were r = 0.92 (p < 0.0001) for the first arriving signal method and r = 0.89 (p < 0.0001) for the slow guided wave method. Clinical feasibility should be demonstrated with an in vivo application to address the question whether the ultrasonic methods presented here could be useful as a screening tool for osteoporosis and potentially could be applied to other skeletal sites such as the femur and the radius.

• Journal of Korean Home Economics Education Association
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• v.33 no.2
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• pp.27-44
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• 2021

This study is to identify the concept of action from the critical science perspective and to explore the agency of home economics teachers for the purpose of teacher education. The context and various characteristics of home economics teacher' agency were identified in terms of philosophy and teacher education. The results of the study indicates, first, the concept of action refers to an activity of individuals involving one's own intentions, and include the ability to reveal a unique identity that aims to reach a set purpose and decision, and this can be identified by mutual meaning in the public sphere. Second, teacher agency is influenced by a teacher's professional experiences and cultural and structural aspects, and it can create an environment which can promote self-directed and cooperative relationships among individuals and communities. Therefore, home economics teachers should be able to reasonably judge, contemplate, and act through reflections on the circumstances and consequences in which their agency is exercised. Third, home economics teachers can reflect and think critically about the values, roles, and sense of purpose of home economics education based on agency. Teachers should focus on the process of achieving their agency rather than on completing it, and they can continuously develop it through a perceived shared understanding among teachers. Therefore, the conceptualization of the agency of home economics teachers is to understand the practice revealed in a teacher's actions. This requires environmental support in school settings because it acts as a mechanism for strengthening the thinking and reflection of teachers through the creation of interactive environments in which professional knowledge and experiences can be shared.

• Journal of Korean Elementary Science Education
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• v.41 no.4
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• pp.754-770
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• 2022

For teachers, noticing refers to paying attention to something, indicating they interpret it and how they are willing to react to it in the context of their own instruction. Analysis of noticing features enables us to understand the overall characteristics of the teacher's lesson design, practice, and reflection, which are core agents in the educational design and implementation. This can also be taken to be the basis of education design for competency reinforcement for teachers. Therefore, in this study, the characteristics of noticing shown in teachers' reflections after class design and demonstration were identified. For this purpose, the self-reflection journals of 106 elementary pre-service teachers enrolled in the College of Education in Gangwon-do were analyzed. In particular, the journals were gathered that were written after the demonstration dealing with the change of gas volume by temperature in science class. After designing a noticing analysis frame consisting of the five dimensions 'agent', 'stage', 'topic', 'focus', and 'stance', the frequency and ratio of noticing by each dimension's components were derived. The frequency and ratio of noticing for the dimension of 'focus' were analyzed for the dimensions of 'stage' and 'topic'. The results of the study were as follows. For the dimension of 'agent', the frequency of teacher and student was the highest, and for the dimension of 'stage', inquiry activity was the highest. For the 'topic' dimension, class design according to the teaching strategy appeared most frequently, and in the 'focus' dimension, the cases that did not specify the goal of the class and the competencies to be achieved by the students appeared most frequently. In the 'stance' dimension, description showed the highest frequency. From the analysis of how the 'focus' changes according to the 'stage' and 'topic', it was found that a characteristic focus appeared for each component of the dimension. From these results, the implications of the noticing characteristics of pre-service teachers for the design and implementation of teacher education were discussed.