• Communications of Mathematical Education
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• v.22 no.1
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• pp.41-52
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• 2008

In this paper, some factors such as the perspective of children, instructional materials(especially activities in textbooks for elementary school mathematics), and teacher's questioning styles are discussed as ones influenced on students' immersion in leaner-centered instruction. This discussion is based on the author's two implementations of the kind of two instructions. About the first theme, constructivists assert that even children who are in elementary school can have reflective abstracting ability. Teachers' asking questions with the belief differ from ones with traditional perspective of children, which is relevant the third factor. They value and respect learners' thinking outcomes, even though they are not sometimes wrong and have errors. Also, they have them opportunities to think different from others and to ask how they get their answers. To do these, they frequently ask open-ended questions, not closed. All of them is possible through the activities provided in textbooks. Some characteristics which can prompt such teacher's questions using activities in elementary mathematics textbooks are discussed.

• Fire Science and Engineering
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• v.32 no.4
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• pp.42-49
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• 2018

In this study, in order to investigate whether or not the emergency broadcasting sound generated from an emergency broadcasting speaker is clearly transmitted to the occupant through architectural sound simulation, when the loudspeaker for emergency broadcasting is installed at intervals of 25 m according to NFSC 202 for a rectangular hallway. The sound pressure level and speech intelligibility index were analyzed according to changes in building finishing materials. With a reflective material finishing, sound pressure level satisfied the standard while speech intelligibility index was low. As a result of applying the sound absorbing material finishing, clarity and speech transmission index was improved to a level that could be understood by the occupant, whereas the sound pressure level delivered to the occupant decreased in the same space.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.3
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• pp.410-419
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• 2009

The purpose of this study was to develop the functionally improved winter work clothing for the Korean railroad workers. Based on the questionnaires, sample clothing for the Korean railroad workers was produced. The design, materials, and patterns were modified to increase mobility and comfort for workers. Water-repellent treatment was added to the material in order to decrease the dirt and stains while working. Also, reflective strips were added to side seams and hems of the trousers in order to increase the visibility and safety of the workers. In terms of the design and pattern, a circumference of 4.5cm was added to the crotch area in order to minimize tightness on the hip and crotch areas, but no additional circumference was added to the hip area. And a 1cm width dart was inserted between the side seams and yoke in order to add activity. Also three 1.4cm width tucks were used at 2.5cm space on the knees to alleviate tightness at the knees. The prototype was evaluated objectively and subjectively to compare with the existing working uniform. The assessment group consisted of 5 subject groups and 11 expert groups to evaluate external appearance and adaptability of the movements. Subject and panels were asked to evaluate the prototype that followed an ergonomic design and pattern. According to the results, the prototype was evaluated better than the existing working uniform in appearance and adaptability. A field test was conducted to compare the prototype and the existing working uniform. The field tests were performed by 6 workers in the Korean railroad. According to the results, the prototype advanced in terms of adaptability and comfort.

• Journal of the Korean Society of Earth Science Education
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• v.5 no.1
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• pp.95-104
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• 2012

The purpose of this study is to examine what effects the experiment class to stress discussion of small groups in scientific experiment class of the elementary school has on scientific achievement and attitude on the science of the students comparing to the usual scientific experiment class. For that purpose, this study has divided 49 students at the 6th grade of the M elementary school in P City into test groups of 24 students and control groups of 25 students. Classes have been progressed by giving sufficient time to the test groups for discussion by each small groups after experiment while by allowing the control groups to finish the experiment with arrangement of the experiment results. Conclusions of this study include: First, the more familiar the experiment materials are and the easier the experiment procedures are to be operated by the students, the more actively the small group discussion activities have been deployed. It shows that the students need a certain level of background knowledge before experiment for vital discussing activities. Second, it is appeared that the test groups given the scientific experiment class stressing small group discussing activity have significantly high scores comparing to the control groups given the existing scientific experiment class. It shows that the small group discussing activities have effects on promoting understanding of the students on the scientific achievement for the scientific experiment class. Third, it is appeared that the test groups given the scientific experiment class stressing small group discussing activity significantly high scores on attitude about the science comparing to the control groups given the existing scientific experiment class. It is considered that the students could have opportunities to compare their own thoughts with others and to have reflective thought to change their thoughts through the small group discussing activity. As shown above, it shows that the experiment class to stress discussing activities is more effective to increase scientific achievement and attitude about the science than the scientific experiment class to get and arrange the experiment results from the existing experiment classes.

• Journal of Information Display
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• v.2 no.2
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• pp.52-60
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• 2001

The electrical and mechanical properties in indium-tin-oxide films deposited on polymer substrate were examined. The materials of substrates were polyethersulfone (PES) which have gas barrier layer and anti-glare coating for plastic-based devices. The experiments were performed by rf-magnetron sputtering using a special instrument and buffer layers. Therefore, we obtained a very flat polymer substrate deposited ITO film and investigated the effects of buffer layers, and the instrument. Moreover, the influences of an oxygen partial pressure and post-deposition annealing in ITO films deposited on polymer substrates were clarified. X-ray diffraction observation, measurement of electrical property, and optical microscope observation were performed for the investigation of micro-structure and electro-mechanical properties, and they indicated that as-deposited ITO thin films are amorphous and become quasi-crystalline after adjusting oxygen partial pressure and thermal annealing above $180^{\circ}C$. As a result, we obtained 20-25 ${\Omega}/sq$ of ITO films with good transmittance (above 80 %) of oxygen contents with under 0.2 % and vacuum annealing. Furthermore, using organic buffer layer, we obtained ITO films which have a rather high electrical resistance (40-45 ${\Omega}/sq$) but have improved optical (more than 85 %) and mechanical characteristics compared to the counterparts. Consequently, a prototype reflective color plastic film LCD was fabricated using the PES polymer substrates to confirm whether the ITO films could be realized in accordance with our experimental results.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.3
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• pp.379-400
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• 1992

The purpose of this study was to analyze the magnitude and distribution of stress using a photoelastic model from the mandibular distal extension removable partial dentures with the mesial or distal placement of the occlusal rest and the mesial or distal connection in the back-action clasp with the five various designs of the back-action clasp, that is, the mesial connection and the distal rest, the distal connection and mesial rest, the mesial connection and mesial rest, the distal connection and the mesial and distal rest, and the mesial connection, and the mesial and distal rest. A photoelastic model was made of the epoxy resin(PC-1) and the hardner(PLH-1) with the acrylic resin teeth used and was coated with the plastic cement-1 at the lingual surface of the model and then five kinds of the removable partial dentures on the photoelastic model were set. A unilateral vertical load of 12.5 kg was applied on the central fossa of the first molar with the use of specially designed loading device and the pattern and distribution of the stress of the photoelastic model under each condition was analyzed by the reflective circular polariscope. The following results were obtained. 1. In the back-action clasp with the mesial connection and mesial rest of the case 3, the effect of the stress distribution was the most favorable. 2. In the back-action clasp with the mesial and distal rest, of the case 4 and 5, the stress distribution was more greatly showed in the terminal abutment. 3. Generally, the stress distribution was more favarable in the mesial connection than in the distal connection. 4. In the back-action clasp with the mesial connection of the case 1, 3 and 5, the stress distribution was the most favorable in the mesial rest.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.390-392
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• 2005

The digital radiation detectors are used clinically by diagnostic apparatus. However the digital radiation detector are some problem like high operating voltage, light blurring, low conversion efficiency, low fill factor, etc. Thus we propose a new radiation detector that the photoconductor layer and liquid crystal layer are coupled in sandwich structure. X-ray absorption in the photoconductor layer controls the state of the liquid crystal via creation of charge carrier and the light modulation of liquid crystal make image formation. The advantage of the new radiation detector is that high resolution image is acquired and the signal amplification is possible by external visible light source. In this study, we study the optical properties and electrical properties of the new radiation detector to irradiate X-ray. The Mercury Iodide($HgI_2$) was used by photoconductor material, and the aluminum is used by reflective layer. The thickness of Mercury Iodide is about $200{\mu}m$, the operating voltage of the liquid crystal is 1.5~5V. The electrical properties of Mercury Iodide was measured, and the transmission efficiency of liquid crystal was measured by modulation potential.

• Communications of Mathematical Education
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• v.24 no.1
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• pp.259-282
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• 2010

In this paper, we introduce a modified Moore Method designed for the multivariable calculus course, and discuss about the effective teaching and learning method by observing the changes in the understanding of students' learning and the effects on students' learning in the class implemented by this modified Moore Method. This teaching experiment research was conducted with the 15 students who took the multivariable calculus course offered as a 3 week summer session in 2008 at H University. To guide the students' active preparation, stepwise course materials structured in the form of questions on the important mathematical notions were provided to the students in advance. We observed the process of the students' small-group collaborative learning activities and their presentations in the class, and analysed the students' class journals collected at the end of every lecture and the survey carried out at the end of the course. The analysis of these results show that the students have come to recognize that a deeper understanding of the subjects are possible through their active process of search and discovery, and the discussion among the peers and teaching each other allowed a variety of learning experiences and reflective thinking.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.10-14
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• 2019

In this study, we synthesized two $Y_3Al_5O_{12}:Ce^{3+}$ phosphors ($7{\mu}m$-sized and $2{\mu}m$-sized YAG) with different sizes by controlling particles sizes of starting materials of the phosphors for white LED. In the smaller one ($2{\mu}m$-sized YAG), its photoluminescence intensity in the reflective mode was 63 % that of the bigger one ($7{\mu}m$-sized YAG); the quantum efficiencies were 93 % and 70 % for the smaller and the bigger ones. Two kinds of white LED packages with the same color coordinates were fabricated with a blue package (chip size $53{\times}30$) and two phosphors. The luminous flux of the white LED package with the smaller YAG phosphor was 92 % of that with the bigger one, indicating that the quantum efficiency of phosphor dispersed inside LED package was higher than that of the pure powder. It was consistently confirmed by the optical simulation (LightTools 6.3). It is notable according to the optical simulation that the white LED with the smaller phosphor showed 24 % higher luminous efficiency. If the smaller one had the same quantum efficiency as the bigger one (~93 %). Therefore, it can be suggested that the higher luminous efficiency of white LED can be possible by reducing the particle size of the phosphor along with maintaining its similar quantum efficiency.

• Human Ecology Research
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• v.60 no.2
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• pp.187-209
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• 2022

The objective of this study was to conduct a 'Theory of Home Economics Education' class using online problem-based learning(PBL) for prospective home economics(HE) teachers. The aim was to enable teachers to analyze the learning experience in the classroom, and to prepare operational strategies for online PBL on this basis. In order to achieve this, online PBL was applied to 31 students participating in the 'Theory of Home Economics Education' at the Department of HE in a university in Seoul, and the results were collected from the learning process. This also involved a reflective journal, a survey on the learning experience and the impacts was conducted. Moreover, analysis was undertaken on the learning activities, learning difficulties, and improvements. The main research results are as follows. Firstly, students accessed Webex, an online video conferencing program, and performed two PBL tasks: 'Making Home Economics Promotion Materials' and 'Presenting Teaching Strategies to Improve Learner's Immersion in Online Classes'. Secondly, learners established their own identity of HE learned about the HE class plans themselves. They also encountered realistic experience as HE teachers and learned communication and collaboration skills. Furthermore, they acquired creative problem-solving and self-directed learning ability, community consciousness, as well as the attitude of consideration and respect. Thirdly, students lacked knowledge of learning content and encountered difficulty in solving data research, analysis processes, and unstructured problems. They were affected by a lack of time and encountered problem in communicating with other team members in an online environment. As an improvement in online class operation, it was considrered necessary to reduce the learning burden by securing time and reducing the number of assignments, as well as to explain active interaction with instructors and PBL.