• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.81-88
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• 1998

During an earthquake, there are three main components of excitation : horizontal excitation of the ground, vertical excitation of the pile due to superstructure feedback produced by vertical excitation of the ground, and the seawater excitation induced by the vertical ground shaking, that is, "the seaquake." These excitations could have effects on the soil plugs in open-ended pipe piles installed at offshore sites. In this study, seaquake excitation induced by the vertical ground shaking was simulated by pulsing the water pressure at the seabed. During a seaquake, due to induced excess porewater pressure and pressure gradients in the soil, the capacity of open-ended pipe piles installed in a simulated sea depth of greater than 220 m was reduced serevely and the soil plugging resistance was degraded by more than 80%. The soil plug was failed because of the upward seepage forces that developed in the soil plug due to excess pore water pressure produced in the bottom of the soil plug during the seaquake. The compressive capacity of an open-ended pile in a simulated sea depth of less than 220m was reduced only by about 10%, and the soil plug resistance was degraded by less than 5%.s than 5%.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.7
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• pp.987-994
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• 2013

In this paper, a dual-band open-ended circular ring moNopole antenna for WLAN(Wireless Local Area Networks) applications. The proposed antenna is based on a planar moNopole design, and composed of open-ended one circular ring of radiating patches for dual-band operation. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and found the parameters that effect antenna characteristics. Using the obtained parameters, the proposed antenna is fabricated. The fabricated antenna is measured at the operating frequencies(2.4-2.484 GHz, 5.15-5.825 GHz), and the return loss coefficient, gain, and radiation patterns are determined.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.23-30
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• 1998

During an earthquake, there are three components of excitation : horizontal excitation of the ground, vertical excitation of the pile due to superstructure feedback produced by vertical excitation of the ground, and the seawater excitation by the vertical ground shaking, that is, "the seaquake." These excitations could have effects on the pore pressure buildup mode induced in the near-field of open-ended pile and the soil plugs in open-ended pipe piles installed at offshore sites. While the ground and pile excitation could be modeled by exciting the soil and pile with simulated motions, seaquake excitation induced by the vertical ground shaking can be modeled by pulsing the water pressure at the seabed. The objectives of this study were to observe buildup trend for the porewater pressures developed in near-field of open-ended pipe pile installed in the calibration chamber during the simulated earthquake and seaquake and, also to confirm the cause for reduction of soil plugging according to pore pressure buildup. During the simulated horizontal seismic motion, there was no upward flow through soil plug because the similar magnitude of excess porewater pressure were occurred at the top and under the toe of soil plug. During the horizontal seismic motion, relatively higher hydraulic gradients caused upward flow in the soil plug and then the degradation of plugging resistance was about 20%. During seaquake, in the case of the open-ended pile installed in a deep sea with more than 220m of water depth, soil plug failed completely because of high upward hydraulic gradients through soil plug.soil plug.

• The Mathematical Education
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• v.62 no.1
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• pp.57-78
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• 2023

Students' engagement in lessons not only determines the direction and result of the lessons, but also affects academic achievement and continuity of follow-up learning. In order to provide implications related to teaching strategies for encouraging students' engagement in elementary mathematics lessons, this study implemented lessons for middle-low achieving fifth graders using open-ended tasks and analyzed characteristics of students' engagement in the light of the framework descripors developed based on previous research. As a result of the analysis, the students showed behavioral engagement in voluntarily answering teacher's questions or enduring difficulties and performing tasks until the end, emotional engagement in actively expressing their pleasure by clapping, standing up and the feelings with regard to the topics of lessons and the tasks, cognitive engagement in using real-life examples or their prior knowledge to solve the tasks, and social engagement in helping friends, telling their ideas to others and asking for friends' opinions to create collaborative ideas. This result suggested that lessons using open-ended tasks could encourage elementary students' engagement. In addition, this research presented the potential significance of teacher's support and positive feedback to students' responses, teaching methods of group activities and discussions, strategies of presenting tasks such as the board game while implementing the lessons using open-ended tasks.

• East Asian mathematical journal
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• v.32 no.4
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• pp.545-563
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• 2016

The aim of this study was to observe processes and implication to a given program for the 20 gifted children grade 5 by making the number from 1 to 100 with natural numbers 4,4,9 and 9. Revelation of creativity, mathematical tendency of students and meaningful responses were observed by the qualitative records of this game activity and the analysis of result. The major result of a study is as follows: The mathematical creativities of students were revealed and developed by this activity. And the mathematical attitude were changed and developed, so student could actively participate. And students could experience collaborative and social composition learning by presentations and discussion, competition with a permissive atmosphere and open-game rule. It was meaningful that mathematical ideas (negative number, square root, factorial, [x]: the largest integer not greater than x, absolute value, percent, exponent, logarithm etc.) were suggested and motivated by students themselves.

• Korean Journal of Child Studies
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• v.21 no.3
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• pp.53-68
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• 2000

This study investigated differences between the ability of children and young adults to describe their experience. Forty 5-year-olds and 40 16-year-olds viewed 12 pictures(Azmitia, 1987) and responded to open-ended, closed and misleading questions. Responses were categorized by the SPSS WIN program into rate of correctness, incorrectness, unresponsiveness and "don't know". Data were analyzed by t-test. On open-ended questions, the rate of incorrectness by young adults was higher than that of children. On closed questions, children had a higher rate of incorrectness than young adults. On misleading questions, children showed a lower performance in the rate of correctness and "don't know" and the rate of incorrectness by children was higher than that of young adults.

• Journal of the Korea Convergence Society
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• v.9 no.8
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• pp.247-264
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• 2018

The purpose of this study was to establish the concept of self - management in university athletes through two integrated research methods as an open-ended questionnaire and focus group interview. Data collection was conducted with open questionnaire for 157 athletes attending in Seoul Gyeonggi-do university and the 14 university athletes were collected data by focus group interview. Results from a series of research procedures are as follow. First, the result of open-ended questionnaire's inductive content analysis, university athletes' self management included 8 general sectors such as life management, training management, competitive management, emotion management, study management, interpersonal management, goal(motivation) management, equipment management. Second, in the focus group interview results, inductive content analysis was more properly supported, and interviews focused on sports field were deeply derived. The results of this study will be used as a basic data to establish strategies for successful athletes' life and develop to university athletes' self management.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.118-124
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• 2017

An air cooling, open cathode type polymer electrolyte membrane fuel cell (PEMFC) has the advantages of system simplification and cost effectiveness. Open cathode PEMFC could suffer from reduced performance due to the membrane dehydration in low humidity of air. Effects of the cathode air flow rate, anode purge interval and long term storage on PEMFC performance were investigated in this work. Fan voltage is an important factor on air cooling PEMFC performance because the cathode air flow rate and stack temperature were controlled by fan voltage. The dead ended anode (DEA) method was applied to increase hydrogen usage. Periodical purge was used to discharge accumulated water and gas. The influence of long term non-operating condition on PEMFC performance degradation due to the membrane dehydration was also studied and the quick recovery method was developed.

• Journal of Gifted/Talented Education
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• v.19 no.3
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• pp.647-667
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• 2009

This study intends to analyze open-ended inquiry activities of elementary science-gifted students in terms of how similar they are to authentic science inquiry and suggest desirable ways to make more effective programs for the gifted. For this study, we selected a small group with five elementary science-gifted students who had participated in the open inquiry program of summer camp held in the Institute for Science Gifted Education and collected data through recording and video-taping their discussion and performance from planning to coordinating inquiry results. The data was analyzed in terms of epistemological features and cognitive process in authentic science inquiry. The results is as follows. In terms of epistemology, students' inquiry methods were theory laden and they constructed knowledge in collaborative groups. For example, the students often discussed about performing the thought experiment and scientific concept related to inquiry task or their opinion. And in terms of cognitive process, their designing inquiry was similar to authentic science inquiry especially selecting variables, planning procedures, controlling variables, planning measures.

• Journal of the Korean School Mathematics Society
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• v.10 no.2
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• pp.221-235
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• 2007

Open problems can provide experiences for students to yield originative and various products in their level, because it is open with respect to its departure situation, goal situation, or solving method. Teachers need to pose and utilize open problems in forms of solution-finding or proving problems. For this we first have to specify which resource and method to use by concrete examples. In this article, we exemplify a method and procedure of posing an open problem by the two cases in which we pose open problems by reorganizing given closed problems. And we analyze students' responses for the two posed open problems. On the basis of these, we reflect implications for mathematical education of open problems.