• Journal of Power Electronics
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• v.16 no.5
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• pp.1743-1751
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• 2016

The increasing demand for high voltage DC grids resulting from the continuous installation of offshore wind farms in the North Sea has led to the concept of multi-terminal direct current (MTDC) grids, which face some challenges. Power (current) flow control is a challenge that must be addressed to realize a reliable operation of MTDC grids. This paper presents a reduced switch count topology of a current flow controller (CFC) for power flow and current limiting applications in MTDC grids. A simple control system based on hysteresis band current control is proposed for the CFC. The theory of operation and control of the CFC are demonstrated. The key features of the proposed controller, including cable current balancing, cable current limiting, and current nulling, are illustrated. An MTDC grid is simulated using MATLAB/SIMULINK software to evaluate the steady state and dynamic performance of the proposed CFC topology. Furthermore, a low power prototype is built for a CFC to experimentally validate its performance using rapid control prototyping. Simulation and experimental studies indicate the fast dynamic response and precise results of the proposed topology. Furthermore, the proposed controller offers a real solution for power flow challenges in MTDC grids.

• KIPS Transactions on Software and Data Engineering
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• v.8 no.4
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• pp.153-162
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• 2019

Recently, it is necessary to develop a technology for quantitatively evaluating railway vibration to prevent civil complaints about orbital structures caused by railway noise and normal operation of ultra-precise equipment of orbital industrial complexes. The existing analytical method requires a very complicated dynamic response model, and it is difficult to secure the reliability of the result due to the inaccuracy of the demand model. Therefore, in this paper, we propose a railway vibration evaluation algorithm and system that deduce the vibration value generated from railway operation by using Linear Regression and Gradient Descent technique based on actual measurement railway vibration database that classifies factors affecting railway vibration. The prediction results obtained by the proposed algorithm show higher efficiency and accuracy than the existing analytical methods.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.32 no.1
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• pp.61-70
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• 2024

In response to the continuously increasing demand for air travel, various studies are being conducted. This research focuses on the design of a simulation model for improving airport slot allocation in the strategic phase. It addresses three aspects of model design, introducing considerations such as the objective function. Additionally, it explains the conceptual procedures for the overall simulation operation and detailed processes within the model including input and output data. Emphasizing the SAL, this study excludes policy and qualitative judgments from its scope. The target airport for application will be confirmed in future research. This study marks a crucial first step toward optimizing air traffic flow, with expectations of contributing to the enhancement of operational efficiency at airports.

• Environmental Engineering Research
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• v.20 no.1
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• pp.65-72
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• 2015

A comparative study on response of a toxic compound thiocyanate ($SCN^-$) was carried out in continuous and fed batch moving bed reactor systems. Both systems had three sequential anaerobic, anoxic and aerobic reactors and operated at same hydraulic retention time. Feed $SCN^-$ was first increased from 600 mg/L to 1,000 mg/L for 3 days (shock 1) and then from 600 to 1,200 mg/L for 3 days (shock 2). In anaerobic continuous reactor, increase of effluent COD (chemical oxygen demand) due to shock load was only 2%, whereas in fed batch reactor it was 14%. In anoxic fed batch reactor recovery was partial in terms of $SCN^-$, phenol, COD and $NO{_3}{^-}$-N and $NO{_2}{^-}$-N removals and in continuous reactor complete recovery was possible. In both systems, inhibition was more significant on aerobic reactors than anaerobic and anoxic reactors. In aerobic reactors ammonia removal efficiency deteriorated and damage was irreversible. Present study showed that fed batch reactors showed higher substrate removal efficiency than continuous reactors during regular operation, but are more susceptible to toxic feed shock load and in nitrifying reactor damage was irreversible.

• Journal of Radiation Protection and Research
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• v.41 no.3
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• pp.301-309
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• 2016

Background: A contamination screening process for the local population in radiation emergencies is discussed. Materials and Methods: We present an overview of the relevant Korean governmental regulations that underpin the development of an effective response system. Moreover, case studies of foreign countries responding to mass casualties are presented, and indicate that responses should be able to handle a large demand for contamination screening of the local public as well as screening of the immediate victims of the incident. Results and Discussion: We propose operating procedures for an off-site contamination screening post operated by the local government for members of the public who have not been directly harmed in the accident. In order to devise screening categories, sorting strategies assessing contamination and exposure are discussed, as well as a psychological response system. Conclusion: This study will lead to the effective operation of contamination screening clinics if an accident occurs. Furthermore, the role of contamination screening clinics in the overall context of the radiation emergency treatment system should be clearly established.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.4
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• pp.1-17
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• 2022

As pedestrian deaths account for a high proportion of traffic accident deaths in Korea, interest in pedestrian safety is growing. In particular, it is necessary to develop various pedestrian-centered traffic signal operation techniques to improve the pedestrian environment at signal intersections. Therefore, in this study, a method for time-of-day operating a pedestrian signal based on residual pedestrians was studied. To this end, the pedestrian signal operation technique in response to the pedestrian demand, which is operated by extending the pedestrian signal time only during the time when the pedestrian demand and the number of remaining pedestrians increase, was applied to the field. The difference in safety according to the application of the new pedestrian signal operation technique was statistically analyzed. As a result of the analysis, the residual pedestrian rate decreased by 20% (3.3 people) before application and 8% (1.4 people) after application, and the residual pedestrian rate in the crosswalk at the time of red signal decreased by 12% (1.9 people), And it was analyzed that the position of the residual pedestrian decreased by 3.3m from 5.2m before application to 1.9m after application.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2795-2803
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• 2011

Due to speed acceleration, higher requirements have been put forward to high speed railway communication and signaling system. The railway applications, including intra-train, train to ground and trackside networks, demand larger bandwidth, higher reliability and shorter response time from railway communication networks to ensure security operation and passenger communication. However, the current railway communication and signaling system has lagged behind the railway development, so advanced communication technologies are needed to improve the current situation. This paper presents high speed railway communication and signaling system based on 4G LTE technology, introduces its network architecture, key technology and analyzes its technical advantages compared with GSM-R system. According to analysis, LTE based high-speed railway communication network is more effective and reliable.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.410-411
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• 2011

본 논문에서는 태양광 전원, 배터리, 마이크로터빈, 스마트 홈 등 다양한 목적과 특성을 가진 요소로 구성된 마이크로그리드를 효율적으로 제어, 관리하기 위한 분산 지능형 제어원리를 제안한다. 기존의 중앙집중식 제어원리는 중앙에서 전체 시스템에 대한 정보를 취득하여 운영에 대한 의사결정을 독점하는 구조였다면 제안하는 원리는 마이크로그리드의 구성요소가 각각 지능형 에이전트를 기반으로 스스로 데이터를 취득하고 이웃 에이전트와의 대화와 협조를 통해 분산제어를 수행하는 방식이다. 각 에이전트 사이는 근거리 무선통신 방식인 Zigbee를 이용하였고 마이크로그리드를 실시간으로 해석하기 위하여 MATLAB 기반의 실시간 시뮬레이터를 이용하였다. 실시간 마이크로그리드 시뮬레이션 모델과 에이전트 역할을 하는 마이크로 컨트롤러를 연계하여 Hardware-in-the-loop 기반의 데모시스템을 구축하였고 제안하는 원리에 대해 검증하였다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.652-653
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• 2011

수요반응(DR : Demand Response)은 스마트 그리드(Smart Grid)를 구성하는 핵심 요소 중 하나이다. 본 논문에서는 스마트 그리드 환경 하에서 ISO(Independent System Operator)의 수요자원시장에 참여함과 동시에 말단 수용가들을 대상으로 다수의 DR 프로그램을 운영하는 LA(Load Aggregator)사업자의 DR자원 운영 시스템에 대한 전반적인 개념 및 흐름에 대하여 기술하였다. 또한, 스마트 그리드 하에서 LA사업자의 DR자원 운영 시스템 설계 중 LA사업자의 DR자원 최적배분 전략에 대한 개념 및 예시를 제시하였다.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.565_566
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• 2009

전력거래소는 시장원리를 적용한 지원금 입찰제에 의한 수요시장을 설계하고 시장운영에 필요한 시스템을 구축하여 수요반응을 측정하기 위한 수요자원시장을 2008년도에 시범적으로 운영하였다. 본 논문에서는 작년도 수요자원시장 운영결과를 분석하여 개선점을 도출하고 수요반응에 입각한 전력수요 자원을 효율적으로 활용하기 위한 방안에 대하여 소개한다.