• The Journal of Engineering Geology
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• v.14 no.2
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• pp.223-233
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• 2004

When the groundwater outflow occurs due to tunnel excavation during the road and railroad construction, depletion of groundwater resources, deficiency in the living and agricultural waters, and changes in the surface water flux are expected. The MODFLOW is a most commonly used and three dimensional finite difference model to predict changes in the groundwater system due to the tunnel construction. A conceptual model is one of the most important elements for the proper modeling results. Essential information will not be extracted from an oversimplified conceptual model while excess time and resources with much field data are required for the very complicated one. This study presented a comparison of the modeling results depending on some conceptual models and discussed construction of the efficient conceptual model for reasonable and realistic results in the tunnel modeling.

• Journal of The Korean Association For Science Education
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• v.29 no.8
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• pp.886-897
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• 2009

One of useful strategies to change students' misconceptions into scientific conceptions in physics is the cognitive conflict strategy, the main point of which is to arouse cognitive conflicts by presenting anomalous phenomena to students. However, it has been reported that students experienced cognitive conflicts while expecting or reasoning results of an experiment before confronting an anomalous phenomenon. Therefore, we have examined how much students' cognitive conflicts were aroused before presenting an anomalous phenomenon. Then, we investigated the effects of the cognitive conflicts aroused prior to the students' confrontation with an anomalous phenomenon, both on the cognitive conflicts occurring after the students' confrontation with it, and on the students' conceptual changes. This study was performed during regular classes about light-source and weightlessness concepts. Subjects from two different middle schools in Pusan took part in the study. Preconceptions, degrees of cognitive conflicts before and after confronting anomalies, and postconceptions were checked during the classes. Then, delayed postconceptions were also checked in 3 weeks. As a result, the degree of cognitive conflicts before confronting an anomaly was as much as the degree of cognitive conflicts after it. There was significant correlation between both conflicts. Also the degree of cognitive conflicts before confronting an anomaly was a main factor in predicting the conceptual changes, while both conflicts had been related separately to the conceptual changes.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4125-4133
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• 2022

KAERI (Korea Atomic Energy Research Institute) developed the conceptual design of PGSFR (Prototype Gen-IV Sodium Cooled Fast Reactor) and Burner Reactor. Since the reactor characteristics of the PGSFR and Burner Reactor are different, the shape, size and the arrangement of the main components in the reactors must be different. Therefore, the conceptual design for the fuel handling and transfer systems needs to be performed coinciding with the structure of the reactor. Especially, because a redan structure dividing hot and cold pool is installed in the reactor vessel, the conceptual design of the fuel handling and transfer system largely changes depending on the location of the redan structure. Various elements of the conceptual design and an integral arrangement for the fuel handling and transfer system were arranged according to the characteristics, sizes and shapes of the reactors. In this paper, the conceptual designs of the fuel handling and transfer system for PGSFR and Burner Reactor are described. Especially, an A-frame method is selected as the fuel handling and transfer system for the Burner Reactor, considering the layout of the internal structure. The tilt angle, diameter and length of A-frame is determined and the strength evaluation of the A-frame is performed.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.1
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• pp.89-96
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• 2005

Ducted fans have advantages in noise as well as operational safety aspects compared to conventional tail rotors and are used as an anti-torque system for various classes of helicopters. The final goal of this study is to develop a ducted fan anti-torque system which can replace conventional tail rotors of existing helicopters to achieve safety enhancement and low noise level. In this paper, a conceptual design process and the results are described. Initially, the design requirement and the design parameter characteristics are analysed, and then initial sizing and configuration design are performed. There are several configuration changes due to specific technical reasons in each case. Finally, the required power and the pitch link load are predicted as an initial estimation. The conceptual design technique for the ducted fan in this study can be easily applied to the design of other ducted fans such as the lift fan for unmanned aerial vehicle.

• Journal of The Korean Association For Science Education
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• v.30 no.8
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• pp.1110-1122
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• 2010

The purpose of this study was to identify elementary school students' alternative conceptual types of the movement of the moon and to find out how these types change when confronted with cognitive conflict situations. To find out alternative conceptual types, 206 sixth graders were sampled, and to investigate how the alternative conceptual types were changed by cognitive conflict situations, and 30 students were systematically resampled by alternative conceptual types. Data were collected through the pre- and post-test instruments, including five items that were used for testing the students' alternative conceptual types and changes after conflict situations. After the pre-test, students were instructed to determine the change of the alternative preconceptions using conflict situations. We found that a majority of students had various kinds of alternative preconceptions formed from their early years of elementary school. The cognitive conflict situations were effective for the conceptual change of the movement of the moon. Specifically, in all groups, the subjects' understanding of "the movement of the early evening crescent moon" changed scientifically.

• Journal of the Korean earth science society
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• v.25 no.7
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• pp.545-557
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• 2004

The purpose of this study is to classify types of preconception on the seasonal change to middle school students and to find out how the developed multimedia material changes their conception in the seasonal change. The questionnaire about the variation of season consisted of 10 items. Questions are given to 80 ninth graders. Control and experimental group was 23 and 57 students, respectively and they were instructed for two class periods. A learning method using multimedia was applied to the experimental group. On the other hand, traditional teaching-learning method was used for the control group. A learning method using multimedia in this study had an effect on the conceptual changes (p$<$0.01). Data in this study was divided into six levels to classify the changes of concepts in detail. As a result, it showed that a learning method using multimedia was effective for students to make progress from unscientific to scientific concepts, to build up scientific concepts, to build up scientific concepts, and to elaborate scientific concepts as compared with traditional method.

• Journal of The Korean Association For Science Education
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• v.24 no.2
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• pp.216-225
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• 2004

Cognitive conflict plays a very important role towards conceptual change in science education. Many research were conducted on the topic, but they were limited and failed to determine the effectiveness of cognitive conflict strategies for conceptual change on science instruction. It is worth noting that the levels of cognitive conflict varied the same given situation. Besides, the conceptual change resulted in different forms, despite the same level of cognitive conflict. Assuming that one explanation could be found in the learners' characteristics, this study investigated the cognitive conflict and scientific conceptual change by learners' characteristics of middle school students. A proper understanding of the cognitive conflict will help science teachers to apply effectively the strategies towards science conceptual instruction. In this study, learners' characteristics are 'intelligence', 'cognitive level', 'general grade of science subject', 'cognitive style', 'personality', and 'attitudes related to science'. The results says; the intensity of cognitive conflict correlated with students' personality (reflectiveness) and attitudes related to science, and conceptual change correlated with intelligence and cognitive level.

• Environmental Engineering Research
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• v.25 no.3
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• pp.366-373
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• 2020

The autonomous vehicles (AVs) could make a positive or negative impact on reducing mobile emissions. This study investigated the changes of mobile emissions that could be caused by large-scale adoption of AVs. The factors of road capacity increase and speed limit increase impacts were simulated using a conceptual modeling approach that combines a hypothetical speed-emission function and a traffic demand model using a virtual transportation network. The simulation results show that road capacity increase impact is significant in decreasing mobile emissions until the market share of AVs is less than 80%. If the road capacity increases by 100%, the mobile emissions will decrease by about 30%. On the other hand, driving speed limit increase impact is significant in increasing mobile emissions, and the environmentally desirable speed limit was found at around 95 km/h. If the speed limit increases to 140 km/h, the mobile emissions will increase by about 25%. This is because some vehicles begin to bypass the congested routes at high speeds as speed limit increases. Based on the simulation results, it is clear that the vehicle platooning technology implemented at reasonable speed limit is one of the AV technologies that are encouraging from the environmental point of view.

• Journal of Science Education
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• v.34 no.1
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• pp.47-57
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• 2010

The purpose of this study was to investigate how the lesson using the newly developed Phase Change Model of Venus can change ninth graders' geocentrical concept related to the progression of the phase of Venus. In order to know students' concept change of the progression of the phases of Venus, test sheets and a questionnaire regarding solar systems were developed and used pre and post test. The results showed that many students have an astronomical preconception of geocentricism, and some students have an especially poor scientific understanding of the solar system. However, there were significant changes in students' conceptual levels (p<.05) after teaching with the Venus's Phase Change Model. Therefore, teaching with the Phase Change Model of Venus was effective on students' scientific conceptual change from geocentricism to heliocentricism.

• Journal of Korea Multimedia Society
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• v.19 no.9
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• pp.1738-1746
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• 2016

This study is on moving images among the various media created by the screen-based image media in the multimedia age. Moving images shown in the image media are reinterpreted in various forms and are necessary to have a conceptual definition as expression media to meet the changes. Therefore, the study identified the conceptual definition of moving images from the perspective of objects, and subdivided them into the visual cognitive area to satisfy the recent characteristics of visual media. It also suggested the guidelines required for analyzing the image media based on the results of the case analysis of 8 different works.