• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6B
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• pp.635-642
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• 2008

The influence of unsubmerged resistance bodies in a channel turbulence flow on energy loss was investigated by hydraulic experiments. Square-shaped multi-piers were used for unsubmerged structure or rigid vegetation in an open channel. In experimental channel flows multi-piers were arranged in double or single row along the channel direction, and mean-concept uniform elevations were attained and measured with a set of discharges and channel slopes. Applying the experimental results to the Manning equation, the equivalent resistance coefficient n, which implicates flow resistance and energy loss due to bottom friction as well as drag, was evaluated with varying the interval of piers and the uniform water depth. And the experimentally evaluated n values were compared with the semi-theoretical formula of the equivalent resistance coefficient derived from momentum analysis including a drag interaction coefficient. From the comparisons it was found that the interaction effect of piers on flow resistance was significant for the overall energy losses in a channel flow. The n values decrease when the interval of piers in flow-direction is less than about 2.2 times of the pier width. And it was also found that the n values increase with the 2/3 power of water depth in the theoretical formula, since the drag interaction coefficient was found to be mostly dependent on the interval of piers.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.34 no.1
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• pp.18-25
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• 2024

Objectives: The primary aim of this study is to create an Occupational Safety and Health (OSH) guide for high-risk maintenance tasks, specifically one designed for maintenance work (MW) in the electronics industry. Methods: The methodology involved a literature review, field investigations, and discussions. An initial draft of the OSH guide was created and then refined through consultations with experts possessing extensive experience in MW for electronic processes. Results: Specific MW tasks within electronics processing facilities identified as high-risk by the research were selected. A comprehensive OSH guide for these tasks was developed consisting of approximately 11 to 12 components and encompassing about 20-25 pages. Implementing safety and health measures before, during, and after MW is crucial for the protection of maintenance personnel. The guide is enriched with real-case scenarios of industrial accidents and occupational diseases to enhance maintenance workers' comprehension of the OSH principles. For a clearer understanding of and adherence to the safety protocols, the guide incorporates visual aids, including cartoons and photographs. Conclusions: This OSH guide is designed to ensure the protection of workers involved in maintenance activities in the electronics industry. It aligns with global standards set by the International Organization for Standardization (ISO) and Semiconductor Equipment and Material International (SEMI) to ensure a high level of safety and compliance.

• The Korean Journal of Financial Management
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• v.26 no.3
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• pp.103-138
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• 2009

In this article we examine a unique data set of intraday fair disclosure(FD) releases to shed light on market efficiency within the trading day. Specifically, this paper analyze the response of stock prices on fair disclosure disseminated in real-time through KIND(Korea Investor's Network for Disclosure) on Korea stock exchange during the period from January 2003 to September 2004. We find that the prices of stock experiences a statistically and economically significant increase beginning seconds after the fair disclosure is initially announced and lasting approximately two minutes. The stock price responds more strongly to fair disclosure on smaller firm but the response to fair disclosure on the largest firm stock is more gradual, lasting five minutes. We also examine the profitability of a short-term trading strategy based on dissemination of fair disclosure. After controlling for trading costs we find that trader who execute a trade following initial disclosure generate negative profits, but trader buying stock before initial disclosure realize statistically significant positive profit after two minute of disclosure. Summarizing overall results, our evidence supports that security prices on Korea stock exchange reflects all available information within two minutes and the Korea stock market is semi-strongly efficient enough that a trader cannot generate profits based on widely disseminated news unless he acts almost immediately.

• Journal of the Korean Chemical Society
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• v.63 no.5
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• pp.360-375
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• 2019

The purpose of this study was to investigate beginning science teachers' perceptions of inquiry-based science instruction using open-ended questionnaire and semi-structured interview. Participants of this study voluntarily set up a goal of inquiry-based science instruction, planned inquiry-based science lessons, and shared and reflected their teaching experiences in their professional learning community for more than a year. Participant teachers recognized students' construction of core scientific concepts through performing scientific inquiry as a goal of science inquiry instruction. Participant teachers indicated that goals of science education such as 'learning scientific core concepts', 'improving students' interest of science', 'improving scientific thinking', and 'understanding the nature of science' can be achieved through students' active engagement in scientific inquiry. Participant teachers recognized not only the importance of teachers' role, but also what roles science teachers should play in order to enable students to perform scientific inquiry. Participant teachers emphasized teachers' roles such as 'identifying core concepts', 'reorganizing science curriculum', 'considering student ability', 'asking questions and providing feedbacks to students', 'explaining scientific concepts', and 'leading students' argumentation.'

• Journal of The Korean Association For Science Education
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• v.39 no.2
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• pp.221-232
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• 2019

Despite the continuing emphasis on the importance of scientific inquiry, research studies have commented that authentic scientific inquiry is not implemented in school science classroom due to a lack of understanding of scientific inquiry by the teacher. The purpose of this study is to investigate understanding of scientific inquiry developed by beginning teachers through open-ended questionnaire and semi-structured interview. They voluntarily set up the goal of inquiry-based classes, planned inquiry-based classes, shared and reflected their teaching experience in professional learning community for more than a year. It appeared that participant teachers understood scientific inquiry as 'what scientists do', 'process how students do science' and 'science teaching methods.' All teacher participants described scientific inquiry as 'what scientists do', and understood 'the process of doing scientific investigation to solve problems related to natural phenomenon' and 'the process of constructing scientific knowledge using scientific practice.' Two participant teachers seemed to understand scientific inquiry as a 'teaching method' based on the understanding of the process how scientists or students do science. Participant teachers had a limited understanding of scientific inquiry that it is the same as laboratory works or hands-on activities prior to engaging the professional learning community, but they developed an understanding of scientific inquiry that there are various ways to conduct scientific inquiry after engaging in professional learning community.