• Journal of the Korean Geographical Society
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• v.44 no.6
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• pp.833-851
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• 2009

Recently, there is a matter of common interests in 'classroom' because many pedagogues and teachers feel urgently the understanding of educational field. This study aims to investigates classroom researches for the last twenty years, asserts the theme 'the spatiality of classroom' which is important to understand diverse point of views in classroom theories and is overlooked at the same time, and considers it in terms of 'classroom space metaphors'. Specially, the author reviews the recent trend in classroom researches, and names it 'classroom theory' in that it deals with classroom not as a means but as an object and has undergone methodological transition. In the mean time, the author lays great emphasis on 'the spatiality of classroom' which is important to expand classroom theory and is overlooked at the same time. To approach this, the author categorizes the classroom space metaphors of existing classroom researches into 'classroom as a work space' and 'classroom as a learning space' by drawing the concept 'metaphor'. And then the author presents new metaphor 'classroom as a lived space' on the basis of the recent classroom theory, and tries to abstract its educational significance in classroom by way of Thirdspace.

• The Safety technology
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• no.17
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• pp.48-73
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• 1999

• The Safety technology
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• no.46
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• pp.80-91
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• 2001

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.1
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• pp.20-26
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• 2019

Purpose: Recently TF-adaptive movement is developed in order to increase the durability of TF files. The purpose of this study was to assess the effects of adaptive movement on durability and performance of twisted files. Materials and Methods: Resin blocks simulating artificial J-shape canals were used for this study. In TFC group, TF-adaptive ML-1 (25/.08 size) files were used to prepare the canals under continuous rotation 500 rpm/4.0 Ncm. In TFA group, TF-adaptive ML-1 (25/.08 size) files were used to prepare the canals under adaptive movement. After preparing each artificial canal, TF files were observed under dental microscope for assessing existence of unwinding, distortion, and fracture. If unwinding of flute was observed, the number of artificial canals until unwinding of flute occurs was recorded. Required time until instruments reach working length and distance of unwinded portion of files from D0 were measured. All test results were conducted by Mann-Whitney U test at a 0.05 level of significance. Results: No Ni-Ti instrument's separation was observed. Number of resin blocks until file unwinding happens and working time was significantly high in TFA group compared to TF group. Distance of distortion from D0 didn't show significant difference between TFA, TF groups. Conclusion: The number of resin blocks prepared until unwinding happens and working time were significantly high in TFA group. The location of unwinding showed no significant difference between 2 groups. Adaptive movement increased the number of canals prepared until unwinding occurs and working time of twisted files.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.3
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• pp.271-277
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• 2019

Objectives: A 46-year-old woman who had worked on cleaning stainless steel containers with Initially unknown powders died from acute silicosis. To determine whether the acute silicosis was related to his work environment, we conducted exposure assessment the level of exposure to respirable crystalline silica(RCS) during cleaning stainless steel containers with unknown powders. Methods: The exposure assessment of RCS were undertaken according to the National Institute for Occupational Safety and Health(NIOSH) method 7500. The components of the unknown powder were analyzed using X-ray Diffraction. Results: The unknown powder was found to be natural diatomaceous earth, which contained 12% and 9% quartz and cristobalite, respectively, crystalline silica. In the case of cleaning stainless steel containers with diatomaceous earth powder, the primary measurement resulted in 1.3 times higher occupational exposure limit of MOEL(in sum of quartz and cristobalite concentration) and 3.9 times higher in secondary measurement. The workbench was equipped with a local exhaust system, but because there was no hood at the end of the duct, the wind speed at the opening of the duct was 12 m/sec, whereas the controlled wind speed at the working position was only 0.3 m/sec below the legal standard. Conclusions: There is an urgent need to install the hood, conduct safety and health education for employers and workers, and periodically monitoring and manage the working environment.