• Structural Monitoring and Maintenance
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• 제2권1호
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• pp.1-18
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• 2015

Traditionally, it is not easy to carry out tests to identify modal parameters from existing railway bridges because of the testing conditions and complicated nature of civil structures. A six year (2007-2012) research program was conducted to monitor a group of 25 railway bridges. One of the tasks was to devise guidelines for identifying their modal parameters. This paper presents the experience acquired from such identification. The modal analysis of four representative bridges of this group is reported, which include B5, B15, B20 and B58A, crossing the Caraj$\acute{a}$s railway in northern Brazil using three different excitations sources: drop weight, free vibration after train passage, and ambient conditions. To extract the dynamic parameters from the recorded data, Stochastic Subspace Identification and Frequency Domain Decomposition methods were used. Finite-element models were constructed to facilitate the dynamic measurements. The results show good agreement between the measured and computed natural frequencies and mode shapes. The findings provide some guidelines on methods of excitation, record length of time, methods of modal analysis including the use of projected channel and harmonic detection, helping researchers and maintenance teams obtain good dynamic characteristics from measurement data.

• 자연, 터널 그리고 지하공간
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• 제3권2호
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• pp.32-44
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• 2001

Most of the major aspects of the high speed rail tunnels in Korea, including such items as the tunnel geometry, excavation methods, primary support, final lining, drainage and waterproofing, are similar to the practices followed in other countries. The tunnels in Korea provide the largest net internal area $(107\;m^2)$ as compared to the other counties addressed in this paper. The effective adaptation and modification of international practices and designs, combined with the integration of domestic practices, has resulted in the successful construction of these large tunnels. The experience gained from the completed work to date on the high speed line in Korea, combined with international technology input, will help to ensure future tunnels are constructed in an efficient manner with adequate design measures implemented for the long-term operational life of the tunnels. As has occurred in these other countries, further improvements and modifications to the Korea high-speed railway tunnels will occur as experience is gained and new technology develops.

• 한국안전학회지
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• 제38권5호
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• pp.43-50
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• 2023

With the advent of industrialization, consumers and end-users demand more reliable products. Meeting these demands requires a comprehensive approach, involving tasks such as market information collection, planning, reliable raw material procurement, accurate reliability design, and prediction, including various reliability tests. Moreover, this encompasses aspects like reliability management during manufacturing, operational maintenance, and systematic failure information collection, interpretation, and feedback. Improving product reliability requires prioritizing it from the initial development stage. Failure mode and effect analysis (FMEA) is a widely used method to increase product reliability. In this study, we reanalyzed using the FMEA method and proposed an improved method. Domestic railways lack an accurate measurement method or system for maintenance, so maintenance decisions rely on the opinions of experienced personnel, based on their experience with past faults. However, the current selection method is flawed as it relies on human experience and memory capacity, which are limited and ineffective. Therefore, in this study, we further specify qualitative contents to systematically accumulate failure modes based on the Failure Modes Table and create a standardized form based on the Master FMEA form to newly systematize it.

• 한국재난정보학회 논문집
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• 제18권4호
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• pp.713-728
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• 2022

연구목적: 본 연구의 목적은 소방안전체험관에서 안전교육을 담당한 전, 현직 직원을 대상으로 VR 안전체험 교육 콘텐츠 품질이 행동 의도에 미치는 영향을 파악하고 인터뷰를 통해 추가적인 운영 관련 의견을 수집하는 것이었다. 연구방법:소방안전체험관 전·현직 직원 93명을 대상으로 설문을 실시하고 체험관 15개소를 방문하여 인터뷰를 실시하였다. 연구결과: VR 안전체험교육 콘텐츠 품질 중 몰입감과 편리성이 이용 만족도, 추천 의도, 현업적용 의도에 유의미한 영향을 미쳤다. 그리고, 교육 효과에는 편리성, 심미적 체험이 유의미한 영향을 미쳤지만 몰입감, 다양성은 유의미한 영향을 미치지 않았다. 인터뷰에서는 VR 교육은 체험자 만족도가 높고 교육의 효과도 좋다는 의견을 제시하였다. 콘텐츠의 품질은 VR 교육의 중요한 요소로 특히 몰입감과 편리성이 중요하다고 하였다. 중장기적으로는 체험관의 인력, 전문성, 유지 보수 문제, 재난 분야별 표준 교수안 마련 등 필요하다고 하였다. 결론:본 연구 결과를 통해 VR 콘텐츠 품질이 행동 의도와 교육 효과에 영향을 미친다는 것과 VR 교육의 효과 증진을 위해 콘텐츠 품질 향상을 위한 노력과 투자가 필요하다는 것을 확인할 수 있었다. 그리고 인터뷰에서 도출된 내용은 효과적인 소방안전체험관 운영에 도움이 될 것이다.

• Human Ecology Research
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• 제60권2호
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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.

• 인간식물환경학회지
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• 제23권2호
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• pp.233-243
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• 2020

This study collects social big data used in various fields in the past 9 years and explains the patterns of major keywords of the arboretums and botanical gardens to use as the basic data to establish operational strategies for future arboretums and botanical gardens. A total of 6,245,278 cases of data were collected: 4,250,583 from blogs (68.1%), 1,843,677 from online cafes (29.5%), and 151,018 from knowledge search engine (2.4%). As a result of refining valid data, 1,223,162 cases were selected for analysis. We came up with keywords through big data, and used big data program Textom to derive keywords of arboretums and botanical gardens using text mining analysis. As a result, we identified keywords such as 'travel', 'picnic', 'children', 'festival', 'experience', 'Garden of Morning Calm', 'program', 'recreation forest', 'healing', and 'museum'. As a result of keyword analysis, we found that keywords such as 'healing', 'tree', 'experience', 'garden', and 'Garden of Morning Calm' received high public interest. We conducted word cloud analysis by extracting keywords with high frequency in total 6,245,278 titles on social media. The results showed that arboretums and botanical gardens were perceived as spaces for relaxation and leisure such as 'travel', 'picnic' and 'recreation', and that people had high interest in educational aspects with keywords such as 'experience' and 'field trip'. The demand for rest and leisure space, education, and things to see and enjoy in arboretums and botanical gardens increased than in the past. Therefore, there must be differentiation and specialization strategies such as plant collection strategies, exhibition planning and programs in establishing future operation strategies.

• 한국CDE학회논문집
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• 제12권1호
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• pp.1-7
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• 2007

In this paper, we present a machining time estimation algorithm for 5-axis high-speed machining. Estimation of machining time plays an important role in process planning and production scheduling of a shop. In contrast to the rapid evolution of machine tools and controllers, machining time calculation is still based on simple algorithms of tool path length divided by input feedrates of NC data, with some additional factors from experience. We propose an algorithm based on 5-axis machine behavior in order to predict machining time more exactly. For this purpose, we first investigated the operational characteristics of 5-axis machines. Then, we defined some dominant factors, including feed angle that is an independent variable for machining speed. With these factors, we have developed a machining time calculation algorithm that has a good accuracy not only in 3-axis machining, but also in 5-axis high-speed machining.

• 산업공학
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• 제20권3호
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• pp.418-426
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• 2007

This study is to suggest the government's support direction for the small and medium sized enterprises (SMEs) by examining the relations among technology level, innovation factors, entrepreneur's characteristics, and start-up reasons. The management bottlenecks and the necessary fields of government's support are also investigated across the company's growth stages. Empirical analysis was conducted based on the 318 Korean SMEs' data receiving the Venture and/or Inno-biz certification. Results show that managing difficulties of the company have typical pattern according to the stage of growth. The characteristics of an entrepreneur such as age, education background and past experience affect the early stage of starting business. We also found that the technology level is closely connected with operational innovation activities and circumstances, entrepreneur's characteristics, start-up motives, and technological innovation activities.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.886-890
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• 1992

Recent investigations have been made on polymer Insulators of various types. The findings are related to experience on operational lines in foreign countries, design concepts, materials and tests about outdoor properties. Over last decade improvements have been occured in the design and construction techniques of polymer insulators. For transmission and distribution lines, it may be advantageous or even necessary to replace, the conventional porcelain or tempered glass insulators by lighter polymer insulators which have better mechanical properties.

• 한국항공운항학회지
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• 제22권2호
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• pp.16-26
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• 2014

After the GBAS ground system installing at the airport, a GBAS ground and flight testing must be conducted to verify functionality and performance of the system. Since Korea has no experience of the GBAS ground system installation, GBAS test and evaluation methods have never been studied so far. Therefore this paper analyzes the test items and methods for the GBAS ground and flight testing based on ICAO documents, FAA flight inspection manual and testing reports of other countries. As a result of the analysis, this paper proposes the GBAS ground and flight testing items in korea, also describes the flight procedures for the GBAS flight testing.