• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.24 no.5
• /
• pp.44-54
• /
• 2010

Optimal efficiency control of synchronous reluctance motor(SynRM) is very important in the sense of energy saving and conservation of natural environment because the efficiency of the SynRM is generally lower than that of other types of AC motors. This paper is proposed a novel efficiency optimization control of SynRM considering iron loss using multi adaptive fuzzy learning controller(AFLC). The optimal current ratio between torque current and exciting current is analytically derived to drive SynRM at maximum efficiency. This paper is proposed an efficiency optimization control for the SynRM which minimizes the copper and iron losses. There exists a variety of combinations of d and q-axis current which provide a specific motor torque. The objective of the efficiency optimization control is to seek a combination of d and q-axis current components, which provides minimum losses at a certain operating point in steady state. The control performance of the proposed controller is evaluated by analysis for various operating conditions. Analysis results are presented to show the validity of the proposed algorithm.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.15 no.6
• /
• pp.451-459
• /
• 2010

This paper describes the performance comparison results for a hybrid back-to-back converter, which is composed of a 3-level 24-pulse converter and a 3-level PWM converter, in order to interconnect a large scale wind farm with the power grid. Also it describes the performance comparison results when the 24-pulse converter operates in only firing-angle control, and both firing-angle and the zero-voltage control. For the purpose of systematic performance comparison, computer simulations with PSCAD/EMTDC software were carried out, and based on simulation results a scaled hardware model with 2 kVA rating was built and tested.

• Journal of the Korean Electrochemical Society
• /
• v.8 no.2
• /
• pp.99-105
• /
• 2005

In this study, the $PPy/CLO_4$ and PPy/PVS composite electrodes were prepared at various polymerization potential by incorporating electrolyte anions of different anion size during constant potential polymerization. The reulting Polypyrrole surfaces were inspected by SEM, and their electrochemical Properties were investigated with CV and ac impedance method. The results of electrochemical analysis were suggested that anion for $PPy/CLO_4$ electrode and cation fir PPy/PVS electrode were transferred during redox reaction. As constant potential of polymerization was increased, the charge transfer resistance of $PPy/CLO_4$ and PPy/PVS was decreased and the electric double layer capacitances of $PPy/CLO_4$ was higher than that of PPy/PVS. The change of PPy/PVS surface was relatively smaller than that of $PPy/CLO_4$ according to electropolymerization potential.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.8 no.9
• /
• pp.1359-1364
• /
• 2013

After platform changed from PC-based internet to mobile, SNS became new interactive media which relaces face-to-face interaction. the SNS users have already begun to recognize SNS as daily necessity. SNS market has been subdivided. In other words, SNS has entered into a period of vertical SNS that focus on contents and specific target. Therefore, It is necessary to analyze users for SNS planners. For this reason, analyzing why office workers who have the most powerful purchasing power use SNS is meaningful for SNS planners. Therefore, in this study, we analyzed the reasons for using SNS of office workers by studying relationship among office workers' stress, social support, self-expression and the use of SNS. As a result, the use of SNS has a significantly positive correlation with social support and self-expression. The self-expression in the SNS is not associated with stress, but rather it is the characteristics of the office workers. However the social support in the SNS affects to stress.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.256-256
• /
• 2017

최근 기후변화가 가속화되면서 집중호우가 급증하고 계획홍수량을 초과하는 홍수재해가 빈번하게 발생하고 있다. 이에 주요 선진국들은 홍수대응을 위한 새로운 패러다임을 도입하고 있다. 구조적 측면에서는 기존 제방 위주의 홍수방어에서 벗어나 유역에서 홍수 방어구획 설정, 대심도 터널 등 다원적 홍수방어체계로 전환하고 있다. 또한 ICT를 활용하여 다양한 수문정보를 실시간으로 관측하고 홍수상황을 신속하게 전파 대응할 수 있는 비구조적 대책도 적극적으로 개발하고 있다. 미국의 경우, 홍수량과 발생 확률을 예측한 정보를 시민들에게 조기에 제공함으로써 선제적으로 대응할 수 있도록 지원하고 있다. 그러나 우리나라의 홍수대응은 여전히 구조적 대책과 사후복구에 집중되어 있는 안타까운 상황이다. 세계 최고수준인 우리나라의 ICT 인프라를 이용하여 실시간 수문자료를 공유하고 이를 홍수대응에 활용하면 재난을 미연에 방지하는데 크게 기여할 수 있을 것으로 판단된다. 그러나 홍수관련 유관기관 자료를 연계한 실시간 수문상황 모니터링 시스템을 구축하는 것만으로는 지자체 홍수피해 저감에 한계가 있을 수 있다. 이를 보완하기 위해 수집된 실시간 수문정보를 활용한 홍수분석 및 하천수위별 대응기준 수립을 통한 예방적 재난대응 체계를 마련해야 한다. 이에 본 연구에서는 A지자체를 대상으로 홍수분석 모형을 구축하고, 구축된 모형의 계산결과를 활용하여 예상강우별 도달시간, 수위상승 등을 예측하고, 하천수위별 대응기준을 수립하는 연구를 진행하였다. 수위별 대응기준은 현장에서 계측되는 수위값을 기준으로 홍수예보기준, 하천기본계획의 제방고 및 주변 제약 사항을 고려하여 직접알람 기준으로 활용하였다. 또한 대상 수위국에 대하여는 2~3년간의 관측자료 확보 및 유량측정을 통해 대응기준의 보완을 진행할 예정이다. 재난관련 골든타임을 확보하고 홍수피해 최소화를 위한 홍수재해 통합관리 체계 구축은 이제 선택이 아닌 필수라 할 수 있다. 특히 본 연구로 산정된 홍수대응기준과 함께 물관리 유관기관의 실시간 수문자료 공유체계 구축, 홍수통제기관 또는 기술력을 보유한 재해대책 책임기관과의 유기적인 기술교류 등을 통해 지자체 홍수피해 저감을 위한 능동적인 홍수대응 체계 구축이 수행되어야 할 것이다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.452-452
• /
• 2018

최근에는 지구온난화의 영향으로 집중 호우, 가뭄 등 기상 이변이 빈번하게 발생하고 있어서 물 관리의 복잡성과 불확실성이 매우 높아지고 있다. 특히 중소하천은 하천의 경사가 급하고 하천길이가 짧아 홍수파의 이동시간이 짧기 때문에 홍수대비를 위한 시간이 매우 짧다. 국회예산정책처(2012)에 따르면 과거 5개년간(2007~11) 발생한 자연재해 피해 중 87%가 집중 호우 및 태풍에 의한 피해이며, 이 중 98.7%가 중 소규모 하천에서 발생하였다. 그러나, 중소하천 관리를 담당하는 지자체는 열악한 재정 여건으로 인해 예방보다 사후복구에 집중할 수밖에 없는 상황이다. 또한 최근 하천 고수부지에 주차장, 위락시설 등 공간적 활용이 증가함에 따라 홍수발생시 위험성도 증가하고 있어 예방 및 대응 중심의 홍수대응기준 수립이 시급하다. ICT 인프라를 이용하여 유관기관의 실시간 수문자료를 공유하고, 수집된 실시간 수문자료를 활용한 홍수분석 및 홍수대응 기준 대응기준 수립을 통한 예방적 재난대응 체계를 마련해야 한다. 이에 본 연구에서는 A지자체를 대상으로 홍수분석 모형을 구축하고, 구축된 모형의 계산결과를 활용하여 예상강우별 도달시간, 수위상승 등을 예측하고, 하천수위별 홍수대응기준을 수립하였다. 수위별 대응기준은 현장에서 계측되는 수위값을 기준으로 홍수예보기준, 하천기본계획의 제방고 및 주변 제약 사항을 고려하여 직접알람 기준으로 활용하였다. 특히 A지자체는 상류에 B댐이 위치하여 홍수시 B댐 수위 및 운영의 영향을 반영하는 홍수대응기준의 수립이 요구된다. 본 연구에서는 강우 시나리오별 모형분석을 통하여 예상되는 호우사항에 대한 홍수대응기준을 제시하였다. 향후 본 연구로 산정된 홍수대응기준의 지속적인 보완, 실시간 수문자료 공유체계 확대, 재해관련 책임기관과의 유기적인 기술교류 등을 통해 지자체 및 중소하천 홍수피해 저감을 위한 능동적인 홍수대응 체계 구축이 수행되어야 할 것이다.

• The Journal of the Korea Contents Association
• /
• v.19 no.7
• /
• pp.323-334
• /
• 2019

The purpose of this study is to propose agenda concerning the direction of agricultural science convergence research and development (R&D) under the fourth industrial revolution. For this study, we apply the Analytic Hierarchy Process (AHP) targeted at experts in the fields of agricultural academia and research operating R&D currently. Results suggest the following agendas; first, human resource training toward future is more emphasized rather than fragmentary technology innovation. Second, a flexible road map for agricultural science R&D need to be made for responding to short and long term issues relevant to the innovation. Third, mutual exchange and cooperative system need to be constructed between academia and research in order to create synergy effects. Finally, both institutional improvement and humanistic literacy should be emphasized for rapidly changing conditions and better human life under the fourth industrial revolution.

• The Journal of the Korea Contents Association
• /
• v.19 no.3
• /
• pp.1-9
• /
• 2019

The purposes of the study are to investigate Koreans' perception about Vietnam by analyzing social big data and to seek changing direction in perception. For the purposes, the texts about Vietnam in Naver Blog and Twitter and the number of search and click for Vietnam in Naver were analyzed by Social Metrics of Daum Soft and Datalab of Naver. The study also analyzed the annual change of their interest in Vietnam based on social media. The results showed that Koreans still remember the Vietnam war, have a positive emotion toward Vietnam, and view Vietnam as a country where we can gain mutual benefit by exchange. The findings also indicated that Koreans perceive Vietnam as a favorite tourist spot regardless of age. Meanwhile, children under 12 showed a different pattern of an annual change in perception. It might be a positive sign that Koreans' interest region toward Vietnam would be diversified because children under 12 would be the central axis of cultural contents.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.24 no.5
• /
• pp.567-575
• /
• 2020

As online social networks are used as a critical medium for modern people's information sharing and relationship, their users are increasing rapidly every year. This not only increases usage but also surpasses the existing media in terms of information credibility. Therefore, emerging marketing strategies are deliberately attacking social networks. As a result, public opinion, which should be formed naturally, is artificially formed by online attacks, and many people trust it. Therefore, many studies have been conducted to detect agents attacking online social networks. In this paper, we analyze the trends of researches attempting to detect such online social network attackers, focusing on researches using social network graph characteristics. While the existing content-based techniques may represent classification errors due to privacy infringement and changes in attack strategies, the graph-based method proposes a more robust detection method using attacker patterns.

• Knowledge Management Research
• /
• v.21 no.4
• /
• pp.157-173
• /
• 2020

In accommodation sharing economy, customers take a risk of uncertainty about product quality, which is an important factor affecting users' satisfaction. This risk can be lowered by the information disclosed by the facility provider. Self-presentation of the hosts can make a positive effect on listing performance by eliminating psychological distance through emotional interaction with users. This paper analyzed the self-presentation text provided by Airbnb hosts and found key aspects in the text. In order to extract the aspects from the text, host descriptions were separated into sentences and applied the Attention-Based Aspect Extraction method, an unsupervised neural attention model. Then, we investigated the relationship between aspects in the host description and the listing performance via linear regression models. In order to compare their impact between the three facility types(Entire home/apt, Private rooms, and Shared rooms), the interaction effects between the facility types and the aspect summaries were included in the model. We found that specific aspects had positive effects on the performance for each facility type, and provided implication on the marketing strategy to maximize the performance of the shared economy.