• Journal of Korean Society of Water and Wastewater
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• v.37 no.6
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• pp.347-361
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• 2023

Water utilities are making various efforts to reduce water losses from water networks, and an essential part of them is to recognize the moment when a pipe burst occurs during operation quickly. Several physics-based methods and data-driven analysis are applied using real-time flow and pressure data measured through a SCADA system or smart meters, and methodologies based on machining learning are currently widely studied. Water utilities should apply various approaches together to increase pipe burst detection. The most intuitive and explainable water balance method and its procedure were presented in this study, and the applicability and detection performance were evaluated by applying this approach to water supply pipelines. Based on these results, water utilities can establish a mass balance-based pipe burst detection system, give a guideline for installing new flow meters, and set the detection parameters with expected performance. The performance of the water balance analysis method is affected by the water network operation conditions, the characteristics of the installed flow meter, and event data, so there is a limit to the general use of the results in all sites. Therefore, water utilities should accumulate experience by applying the water balance method in more fields.

• Journal of The Korean Association For Science Education
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• v.17 no.3
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• pp.289-299
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• 1997

This study has been undertaken in the light of constructivist view of teacher education. Participant observation, unstructured interview and questionnaire were used to explore the process and the role of practicum in science teacher education. The subjects were 19 student teachers majoring in physics education; 8 had participated at boys junior high school, 11 at senior high school. The student teachers had very critical and negative perception on their school days' science lessons. They had expected to do 'better' in their practicum but there were only 3 to 5 opportunities of teaching under the umbrella of textbook. Explanation in the classroom and solving exercise problem were the main features of student teachers' lessons. Much of the lessons were similar when it is to same topic and the main reference for their lesson preparation was the textbook. The student teachers felt the design of teaching approach as the most difficult thing during their lesson preparation. They realized that teaching is harder than they thought and they should consider students' level and responses. Though they had become to have more positive perception on teaching job through their field experiences, their decision on job preference did not change. More than half did not want to be a teacher. The student teachers recognised the courses related with science education as the most useful to their teaching in practice among the program of college of education which they had taken. The experience of writing one lesson plan or teaching in front of their peers, designing a new demonstration equipment were recognised as valuable and helpful element of the courses. They proposed to reduce the amount of general education courses and to emphasize the courses relevant with science education and practicum. The limited opportunity of teaching in practicum was pointed out as problematic. Though the practicum was recognized as a 'good' experience to student teachers, it was confined by textbook and limited teaching opportunity. In conclusion, the practicum was not organized and implemented as a meaningful experience of science teaching and learning. There should be more structured studies on what kind of perceptions and experiences the student teachers had brought to the science teacher education program, how they interact with the elements of the program and how they affect to their science teaching. The structure and content of practicum also should be studied and developed so as to make practicum as a meaningful experience of science teaching and learning.

• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.293-304
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• 2024

In this paper, efficient and reliable methodologies for conducting sea trials to evaluate the performance of hull-mounted sonar systems is discussed. These systems undergo performance verification during ship construction via sea trials. However, the evaluation procedures often lack detailed consideration of variabilities in detection performance due to seabed topography, seasonal factors. To resolve this issue, temperature and salinity structure data were collected from 1967 to 2022 using ARGO floats and ocean observers data. The paper proposes an efficient and reliable sea trial method incorporating Bellhop modeling. Furthermore, a machine learning model applying a Physics-Informed Neural Networks was developed using the acquired data. This model predicts the sound speed profile at specific points within the sea trial area, reflecting seasonal elements of performance evaluation. In this study, we predicted the seasonal variations in sound speed structure during sea trial operations at a specific location within the trial area. We then proposed a strategy to account for the variability in detection performance caused by seasonal factors, using results from Bellhop modeling.

• Journal of The Korean Association For Science Education
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• v.31 no.2
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• pp.198-209
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• 2011

In this study, pre-service science teachers' reflective thinking in their journal writing was investigated. To do this, the authors used pre-service science teachers' journal writing abilities, wherein they not only reported data and result formally, but also wrote their feelings and reflections about an inquiry-based physics experiment they performed. Pre-service science teachers' writings were decomposed into sentences and each sentence was analyzed into a framework with 4 dimensions: knowledge, procedure, orientation and attitude. Reflective thinking in knowledge dimension included reflection on what they know before the experiment, what they still do not know and what they learned from the experiment. Reflective thinking in procedure dimension included recalls of experiences about general experimental procedures and specific experimental skill. Reflective thinking in orientation dimension included their views about the nature of science and science teaching and learning, and reflective thinking in attitude dimension consisted of interests, motives and values about the experiment they performed. While there were some variations in frequency distribution of reflective thinking by the topic of experiments, pre-service science teachers' reflective thinking in journal writings revealed their metacognition on their knowledge and learning, epistemological belief about science and science learning, and affective domain related to experiment. This study can infer that such kind of writing with 'their own language' in an informal way followed by formal 'scientific' reports in a scientific experiment has a significance not only as a mediator representing reflective thinking but also as an instructional activity to facilitate reflective thinking in science learning and teaching.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1207-1216
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• 2018

Discharge or water level predictions at tidally affected river reaches are currently still a great challenge in hydrological practices. This research aims to predict water level of the tide dominated site, Jamsu bridge in the Han River downstream. Physics-based hydrodynamic approaches are sometimes not applicable for water level prediction in such a tidal river due to uncertainty sources like rainfall forecasting data. In this study, TensorFlow deep learning framework was used to build a deep neural network based LSTM model and its applications. The LSTM model was trained based on 3 data sets having 10-min temporal resolution: Paldang dam release, Jamsu bridge water level, predicted tidal level for 6 years (2011~2016) and then predict the water level time series given the six lead times: 1, 3, 6, 9, 12, 24 hours. The optimal hyper-parameters of LSTM model were set up as follows: 6 hidden layers number, 0.01 learning rate, 3000 iterations. In addition, we changed the key parameter of LSTM model, sequence length, ranging from 1 to 6 hours to test its affect to prediction results. The LSTM model with the 1 hr sequence length led to the best performing prediction results for the all cases. In particular, it resulted in very accurate prediction: RMSE (0.065 cm) and NSE (0.99) for the 1 hr lead time prediction case. However, as the lead time became longer, the RMSE increased from 0.08 m (1 hr lead time) to 0.28 m (24 hrs lead time) and the NSE decreased from 0.99 (1 hr lead time) to 0.74 (24 hrs lead time), respectively.

• Journal of The Korean Association For Science Education
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• v.27 no.4
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• pp.346-353
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• 2007

In order to be efficient in teaching, a teacher should understand the current learner's level through diagnostic evaluation. This study has examined the major issues arising from the noble diagnostic assessment tool based on the theory of knowledge space. The knowledge state analysis method is actualizing the theory of knowledge space for practical use. The knowledge state analysis method is very advantageous when a certain group or individual student's knowledge structure is analyzed especially for strong hierarchical subjects such as mathematics, physics, chemistry, etc. Students' knowledge state helps design an efficient teaching plan by referring their hierarchical knowledge structure. The knowledge state analysis method can be enhanced by computer due to fast data processing. In addition, each student's knowledge can be improved effectively through individualistic feedback depending on individualized knowledge structure. In this study, we have developed a diagnostic assessment test for measuring student's learning outcome which is unattainable from the conventional examination. The diagnostic assessment test was administered to middle school students and analyzed by the knowledge state analysis method. The analyzed results show that students' knowledge structure after learning found to be more structured and well-defined than the knowledge structure before the learning.

• Journal of The Korean Association For Science Education
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• v.25 no.5
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• pp.603-609
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• 2005

Students obtain most concepts through textbooks, and teaching-learning activities between teachers and students. Accordingly, if science teachers already have misconceptions they will inevitably affect students' scientific concept. This study found many problems in teachers' cognition on the concepts of nuclear radiation. Because 12th grade physics II is classified as an optional subject in the 7th curriculum, teachers have few chances to teach it and, more importantly, have difficulty in teaching it because of the need to prepare students for the university entrance examination. The concept of radiation must be taught correctly because of its emergence in the 'environment' unit of 10th grade Science. Finally, results from this study can help science teachers teach these difficult concepts more correctly. In addition, results can also be useful in in-service retraining programs.

• Journal of The Korean Association For Science Education
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• v.24 no.5
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• pp.1008-1017
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• 2004

In physics education, language is an fundamental learning tool as in other subjects. In writing activity, students can get fair opportunities to express their own ideas during the class. Even though there are various styles of writing, students are usually supposed to make a report in their science classes. But there have been few studies in science education on the tasks and features of student's science writing. In this research, different styles of writing tasks were designed for science classes, and students' writing was analysed in terms of conceptual and emotional aspects. Also the usefulness of each task type was discussed relating to school physics education. Four types of writing, i.e. , , , and writing were developed, and 'The reflection of light' was selected as the theme and given to students. Four types of writing were analysed in this paper. In each type of writing, students showed different features in their conception. They also showed emotional expressions in imaginative writing types, that is, and types. Based on these results, it is recommended that in physics teaching various types of writing need to be designed, developed and applied according to the aim of a particular lesson.

• Journal of Science Education
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• v.44 no.2
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• pp.225-239
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• 2020

This study aims to analyze the characteristics of reflective thoughts of students during experiments in general physics experiments. The participants were 32 college students, they submitted 10 experiment reports including answers to questions for reflective thinking. The results were as follows: First, students show reflective thinking broadly in the experiment, levels were followed by practical reflection, technical reflection, and critical reflection. Also, they actively accepted the knowledge related to experiments, but were passive in connecting new knowledge and experiences obtained through the experiments or forming new questions. Second, the reflective thinking of students show high correlation with experiments related to prior knowledge or the easy-to-understand process. Third, through the qualitative analysis of open-ended questions, it was confirmed that technical reflection occurs in individual evaluation, practical reflection in group evaluation, and practical reflection and critical reflection in improvement proposal. While the students' reflective thinking were superficial or mainly functional, however, they recursively examined the learning contents and the experimental process concurrently.

• Journal of The Korean Association For Science Education
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• v.30 no.4
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• pp.519-531
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• 2010

In this study, we investigated the elementary school students' images of science class and the factors influencing their formations. 280 sixth graders were selected from nine elementary schools in Gyeonggi province and Gangwon province and the DASCT-C (Draw-A-Science-Class-Test Checklist) was administered. In addition, four students were individually interviewed in order to investigate their responses deeply. Analyses of the results revealed that the students' images of science class for four science subjects (physics, chemistry, biology, and earth science) were more 'student-centered' than 'teacher-centered' or 'neutral'. The students of the teacher with student-centered image of science class had also more student-centered images than those with teacher-centered images. Many students answered that the main factors affecting their images of science class were the experiences of impressed or funny science classes, the perceptions of wanted science classes, the active science learning experiences, the educational experiences outside the school curriculum, and the negative science learning experiences. Educational implications of these findings are discussed.