• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.22-33
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• 2021

In the case of open phase faults caused by the disconnection of distribution feeders interconnected to a PV system, many problems can occur depending on the core type and wiring method of the grid-connected transformers. Moreover, open phase faults are difficult to detect because the open phase voltage of the existing protection relay (Open Phase Relay (47)) can be maintained, even though a disconnection fault occurred, depending on the wiring method and the iron core type of the grid-connected transformer for a PV system. Therefore, this paper proposes a novel algorithm to detect open phase faults by comparing the currents and phases between the primary and secondary sides of a grid-connected transformer. In addition, this paper presents the modeling of a distribution system and protection devices for detecting open phase faults using PSCAD/EMTDC S/W, and implements a test protection device for detecting open phase faults based on the above-mentioned modeling. The simulation and test results confirmed that the proposed algorithm is useful for detecting open phase faults according to the wiring method and iron core type of grid-connected transformer for a PV system because operation slope and unbalance rate of the primary current exceed the setting value (30[%]) of the protection device.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.493-503
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• 2021

In this study aviation authority officials were classified into four cultural groups according to culture theory, and then questioned to determine the effects of cultural bias on their social acceptance of a new air traffic flow management system. Based on previous studies, cultural biases were categorized as egalitarianistic, individualistic, fatalistic, and hierarchical, and social acceptances were considered to be influenced by four variables, that is, perceptions of usefulness, work attitude, intention to use, and behavior (job absorption). Empirical analysis showed that hierarchy had a significant positive effect on social acceptance, and egalitarianism was found to have a significant positive effect on social acceptance with 95% credibility. We propose the organizational culture of Korean government be changed to accept the diverse opinions of government officials during the implementation phase of the new system recommended by ICAO.

• Journal of vocational education research
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• v.36 no.4
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• pp.1-20
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• 2017

The purpose of this study is to identify the cognitive and psychological precedence factors of career preparation behaviors of university students and to clarify the structural relationships between the variables. First, the effects of reflective learning on university students' career preparation behaviors were examined and the mediating effect of grit between reflective learning and career preparation behavior was verified. The research analyzed 307 university students in the 3rd and 4th year. The results of the study have shown that the reflective learning had a significant positive relationship with all variables of grit and career preparation behavior, but non-reflective learning have an insignificance relationship with all the main variables. In addition, reflective learning has a direct positive effect on career preparation behavior, and grit has a mediating effect on the relationship between reflective learning and career preparation behavior. The results of this study indicate that the more original variables are further identified and extended to improve career preparation behaviors of university students. It is significant that they are provided with the basic data for the development of career and job preparation education programs that can be applied in the university education field. In addition, it has been confirmed that it is important for university students to improve their ability to critically reflect on themselves, their surroundings and circumstances in order to keep them engaged and to maintain their interests. Moreover, higher education institutions should provide fundamental and extensible method of practice and educational environment.

• Journal of Bio-Environment Control
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• v.28 no.1
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• pp.16-27
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• 2019

Using virtual reality technology, users can learn and experience many interactions in virtual space like the actual physical space. This study was conducted to develop air flow simulator that allows farmers and consultants to consult air flow through VR devices by creating a greenhouse or pigpen model. It can help educate farmers about the importance of ventilation effects for agricultural facilities. We proposed CFD visualization system by building a virtual reality environment and constructing database of CFD and structure of agricultural facilities. After consultants can set up situations according to environmental conditions, the users experience the visualized air flow of agricultural facility according to the ventilation effects. Also it can provide a quantified environmental distribution in the agricultural facility. Currently, the CFD data in agricultural facilities are established during winter and summer. In order to experience various environmental conditions in the developed system, The experts need to run CFD data under various environmental conditions and register them in the system requirements.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.346-357
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• 2019

The purpose of this study was to examine the effects of flipped learning and explore the learners' experiences. Data were collected from 64 students who participated in flipped learning for 7 weeks at N university. The results were as follows. First, after applying flipped learning, learners feel more comfortable learning together and prefer collaborative learning. Second, flipped learning had no significant effects on learner's overall metacognition, but it had positive effects on the awareness and cognitive strategies. Third, flipped learning had no significant effects on academic self-efficacy, but it positively affected the task difficulty preference and confidence of learners who had a lower level of collaborative tendencies. Fourth, flipped learning had no significant effects on SDL ability, but it positively affected the learning plan of learners who had a higher level of collaborative tendencies. Fifth, learners' class satisfaction of flipped learning was generally very high. We suggested a policy, instructional design and strategies for effective implementation of flipped learning.

• 한국노년학
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• v.37 no.1
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• pp.103-123
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• 2017

The purpose of this study is to explore the phenomenon in-depth with its context that what are changes of life in the older patients with social admission by applying the phenomenological research method, and to understand the essential meanings and structure of change experiences of life in elderly patients with social admission. The participants were 15 patients with chronic disease over 65 ages who were selected by convenience sampling. Data were collected through individual in-depth interviews from April to July 2016, and were analyzed using Colaizzi (1978)'s phenomenological analysis method. The essential meanings and structure of change experiences of life in the older patients with social admission were derived into six clusters of themes as follows: 'A lot of concerns are solved', 'New relationship', 'Life as a ordinary person that it looks nothing like a patient', 'The body and mind are comfortable', 'Fear of discharge','Social isolation'. The results of this study contributed to promoting a deeper understanding of change of life in older patients with social admission, and provided for the basic data of strategic approach in solving the social admission problem in long-term hospital.

• Journal of Platform Technology
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• v.6 no.4
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• pp.59-68
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• 2018

The objective of this study is to develop an embedded antenna structure with NFC and WPC composite functions. By selecting stable materials, the optimal component ratio of the polymer sheet was determined. The low cost embedded winding method compared to the existing FPCB was devised. During the winding process, characterization and process technology were developed. We also fabricated a ferrite mold to process the WPC grooves and developed the process technology for optimizing the WPC antenna. The following conclusions were obtained. (1) Optimum composition ratio was derived as Fe 87.5%, Si 7%, Al 5.5% and selected as the final material. (2) Optimal sheet conditions were derived from the experimental evaluation method and the experimental design method through the combination test of the optimized sheet and the conventional mass production FPCB. (3) According to coil diameter and inner diameter, Q value fluctuation, resistance value and efficiency fluctuation are obtained. Therefore, the most suitable coil condition is selected and Rx matching is performed. (4) The EMV load modulation test and the cognitive distance test of the polymer sheet and the ferrite sheet showed that the recognition distance of the polymer sheet at 1k and 4K was 32-33 mm and the recognition distance of the ferrite sheet at the same condition was 30-31 mm.

• Journal of Korean Academy of Oral Health
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• v.42 no.4
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• pp.159-166
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• 2018

Objectives: The aim of this study was to investigate the association between masticatory ability, oral health-related quality of life, and cognitive function in an elderly population using structural equation modeling. Methods: A total of 308 subjects, aged 65 years and over, were recruited from the senior citizen center in Daegu, South Korea and provided consent for inclusion in the study. The Korean version of the Mini-Mental State Examination (K-MMSE) was used to assess the level of cognitive function. Masticatory ability was evaluated through chewing tests, patient-perceived masticatory function and, measurement of relative occlusal forces on molar teeth using the T-Scan $III^{(R)}$ system. All data were analyzed using ${\chi}^2$ tests, t-tests, and one-way ANOVA in SPSS version 23.0 for windows. Structural equation modeling was performed using SPSS AMOS version 22.0. Results: There was a significant association between cognitive function and molar teeth occlusal force. Ability of food chewing score and patient-perceived masticatory function could affect oral health-related quality of life (P>0.05). Higher occlusal forces on molar teeth, compared to anterior teeth, positively correlated with higher cognitive function. Conclusions: These results suggest that an individual's oral health condition could affect molar teeth occlusal forces and may be related to a risk of developing dementia. Therefore, there is a need for implementing nation-wide policies to improve oral health, such as masticatory function, in the elderly population.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.595-598
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• 2014

In order to provide the Mobile Stations operating in IEEE 802.11 Wireless LAN network with seamless handover, a comprehensive study on the functions of handover considering various networking environments and characteristics of Mobile Stations is required. Note that the channel scan process finding a new AP takes the major portion of handover time, and this is the most significant issue with seamless handover for real-time multimedia service in WLAN environment. In this paper the functions required to provide seamless handover in IEEE 802.11 WLAN network are identified, and a new scanning technique is proposed with which the Mobile Stations can selectively scan the channels to reduce the channel scan time in various network environments. Here each Mobile Station awares of the channels the neighbor APs are using by scanning them in advance according to the proposed technique. Afterwards, when handover is actually required, the optimal AP is decided quickly by scanning only the predetemined group of channels and order of scan without unnecessary scan of all the channels. In addition, proposes to enter the Scan Trigger Value and Handover Threshold Value in mobile phones in order to prevent the phenomenon can not handover.

• Proceedings of the Korean Society for Information Management Conference
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• 2017.08a
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• pp.103-103
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• 2017

생태학 분야에서는 생물의 분포, 변동, 서식환경요인의 변화, 등의 여러 종류의 데이터들이 수집되고 있는데 데이터의 형태가 다양하여 데이터의 관리와 활용형태도 다양하게 나타나고 있다. 근래에 들어 각 종 측정기기들이 개발되면서 생태조사 분야에서도 데이터의 양이 급증하는 시점에 있다. 수생태계 분야에서도 전통적인 생물상조사의 데이터는 크게 증가하지 않고 있지만 자동측정센서가 개발된 항목의 경우에는 데이터가 급증하는 단계에 있다. 수생태계에서 흔히 조사되는 플랑크톤의 군집구조 자료를 보면 하나의 조사대상 시료에서 출현하는 종의 수가 50 종정도에 이르며 각 개체의 종을 육안으로 확인하고 있으므로 종조성조사는 아직 자동화가 어렵다. 그러므로 플랑크톤 자료의 특성은 조사의 시료수(case)는 적고 측정항목(변수 variable)이 많은 특성을 가진다. 반면에 센서가 개발된 수질과 관련된 항목들은 자동측정설비가 확대되고 있어 변수는 적지만 장기간의 time series 들이 수집되고 있다. 녹조현상이 관심을 끌면서 여러 곳에 식물플랑크톤의 양을 측정하는 chlorophyll 센서가 설치되고 있는 것이 대표적인 사례이다. 그 외에 정량화되지 못하는 정성적 자료들도 수집되고 있으며 자료수집방법의 표준화도 미흡한 예가 많이 있고, 자료의 형태가 다양하여 데이터의 관리와 활용을 어렵게 한다. 환경부는 전국의 주요 하천 지점에서 정기적으로 수질을 측정하여 공개하고 있으며, 일부 지점에는 자동수질측정시설을 설치하여 측정의 빈도를 높이고 있다. 하천이나 호수에서 센서를 이용한 고빈도 모니터링은 그 동안 인지하지 못하였던 단기적 생태계 변화에 대해 새로운 정보를 제공하여 연구의 장르를 넓혀 가고 있다. 도시하천에서 산소를 측정한 사례를 보면 강우 시에 일시적으로 산소가 고갈되는 현상이 관찰되며, 부영양한 호수와 하천에서는 주야간 산소의 급격한 변동이 생태계 스트레스 요인으로 작용하고 있음을 알 수 있었다. 식물플랑크톤 센서의 연구에 의해 단기적인 변동이 크게 나타나고 있음이 새로이 밝혀지기도 하였다. 데이터의 수집과 활용도를 높이려는 노력도 이루어지고 있다. 과거에는 개인단위로 이루어지던 연구가 이제는 데이터를 수집하고 공유하는 플랫폼이 만들어 지면서 공동연구가 확대되고 있고, 국제적으로 지역을 초월하는 공동연구도 가능하게 되었다. 국제호수관측망학회(Global Lake Ecological Observatory Network, GLEON)이 그 사례이며 세계 여러 나라의 학자들이 참여하여 국제적으로 데이터를 공유하고 공동연구를 촉진하는 역할을 하고 있다. 생태계데이터의 증가는 생태학자들의 연구역량을 초과하는 데이터의 관리와 활용의 능력을 요구할 것이며 환경 생태 IT 분야의 융합연구의 필요성이 크게 대두되고 있다. 그간 데이터베이스의 구축에는 일부 성과가 있었으나 아직 수집된 데이터의 활용도를 높이고 타분야와의 협력연구 시너지를 확대하려는 노력은 부족하다. 이제는 데이터의 수집과 저장뿐 아니라 데이터의 활용도를 높일 수 있도록 학제적 협력연구를 촉진하는 off-line 모임도 확대할 때이다.