• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2757-2772
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• 2023

The fluid retention effect of the Volume Control Tank (VCT) leads to a long time delay in Reactor Coolant System (RCS) concentration during the boration process. A coupled model combining a lumped-parameter sub-model and a computational fluid dynamics sub-model is currently used to investigate the concentration dynamic characteristic of RCS during the boration process. This model is validated by comparison with experimental data, and the predicted results show excellent agreement with experimental data. We provide detailed fields in VCT and concentration variations of RCS to study the interaction between mixing in VCT and the transient responses of RCS. Moreover, the impacts of the inlet flow rate, inlet nozzle diameter, original concentration, and replenishing temperature of VCT on the RCS concentration characteristic are studied. The inlet flow rate and nozzle diameter of VCT remarkably affect the RCS concentration characteristic. Too-large or too-small inlet flow rates and nozzle diameters will lead to unacceptable long delays. In this work, the optimal inlet flow rate and nozzle diameter of VCT are 5 m³/h and 58.8 mm, respectively. Besides, the impacts of the original concentration and replenishing temperature of VCT are negligible under normal operating conditions.

• 한국소음진동공학회논문집
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• 제14권3호
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• pp.224-229
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• 2004

In order to control the railway noise, the radiation characteristic of the noise when the train passes by should be analyzed. Generally, the major noise sources of the Korea Train Express are the rolling noise and power unit noise up to 300km/h. In this paper, a train model that is considered to be a row of point sourcesis introduced to analyze the radiation characteristic. The analysis results are compared with the measurement ones. It is shown that the propagation characteristic of the rolling noise is a dipole type and the noise generated by the power unit is radiated as a cosine type. With increasing of the train speed, the noise level at a receiving point is increased in the direction of motion and reduced in the direction opposite to the motion. The analysis results including the moving effect of the noise source at 300km/h show good agreement with the measurement results.

• 한국초전도ㆍ저온공학회논문지
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• 제15권3호
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• pp.9-12
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• 2013

Current-voltage characteristic models of superconducting material are suggested by many researchers. These current-voltage characteristic models are important because they can be used for design or simulation of superconductor devices. But widely used current-voltage models of superconductor wire still have some limitations. For example, a standard E-J power model has no parameters related with stabilizer's resistance in superconductor wire. In this paper, a current-voltage characteristic modeling method for high temperature superconductor (HTS) tape with considering the effect of stabilizer is introduced. And a current-voltage characteristic of a HTS tape is measured under different stabilizer conditions. Those measured current-voltage characteristics of the HTS tape modeled with proposed modeling method and the modeling results are compared.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.160-163
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• 2009

HPA(High Power Amplifier)는 무선통신 시스템에서 필수적으로 요구되는 요소 중의 하나다. 그러나 전력 증폭기는 비선형 특성을 가지고 있으며 신호의 비선형 왜곡을 유발 시키고 인접채널 간섭을 심화시켜 시스템의 효율을 떨어뜨린다. 이러한 문제점을 해결하기 위해 많은 선형화 기법들이 제시되어왔다. 다항식 사전왜곡 기법은 증폭기로 입력되는 신호가 미리 증폭기의 역 특성을 갖도록 하는 기법으로 다항식을 통하여 증폭기를 모델링하기 때문에 수렴 속도가 빠르고 다른 기법들에 비해 좋은 성능을 보인다. 하지만 다항식으로 역 비선형 특성을 구할 경우, 증폭기의 포화영역에서 역 비선형 특성이 거의 무한대가 되어야 하기 때문에 선형화기의 성능이 크게 떨어진다. 본 논문에서는 이러한 문제점을 해결하기 위하여 PAPR(Peak-to-Average Power Ratio) 기법을 적용하여 다항식 사전왜곡 기법의 성능을 향상 시켰다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.566-569
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• 2001

In this paper, we investigated the electrical characteristics through DC power at manufacturing the MIS capacitor insulator AIN thin film based on reactive sputtering method. In case of deposition temperature 250$^{\circ}C$, pressure 5mTorr, total flow rate 8sccm(Ar:4sccm N2:4sccm), AIN thin film was deposited with changing DC power. As DC power increses, resistivity is observed a little increase. When AIN thin film is deposited at 100W, the result shows leakage current 10$\^$-8/A/$\textrm{cm}^2$ at 0.1MV/cm. Otherwise, In case of depositing at 150W and 200W, the result shows that the characteristic of leakage current is under 10$\^$-9//$\textrm{cm}^2$ at 0.1MV/cm. In C-V characteristic with DC power, deep depletion phenomenon is observed at inversion region in 100W and 150W. In 200W, that phenomenon, however, was showed to decrease. It shows that the hysterisis increases with being increasing DC power.

• 전력전자학회논문지
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• 제20권4호
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• pp.337-343
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• 2015

The multi-level inverters are highly efficient for high-power and medium-voltage AC driving applications, such as high-speed railway systems and renewable energy resources, because such inverters generate lower total harmonic distortion (THD) and electromagnetic interface (EMI). Lower switching stress occurs on switching devices compared with conventional two-level inverters. Depending on the multi-level inverter topology, the required components and number of switching devices are different, influencing the overall efficiency. Comparative studies of multi-level inverters based on loss analysis and output characteristic are necessary to apply multi-level inverters in high-power AC conversion systems. This paper proposes a theoretical loss analysis method based on piecewise linearization of characteristic curves of power semiconductor devices as well as loss analysis and output performance comparison of five-level neutral-point clamped, flying capacitor inverters, and high-level cascaded H-bridge multi-level inverters.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.475-477
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• 2010

IEEE 802.11에 정의된 전력 절약 메카니즘에서 모든 노드들은 동일한 ATIM(Ad hoc Traffic Indication Map) 윈도우 크기와 동일한 비이콘(beacon) 간격을 사용한다. ATIM 윈도우 크기는 처리율과 에너지 소모에 크게 영행을 미치기 때문에 고정된 ATIM 윈도우 크기는 좋은 성능을 나타내지 못한다. 본 논문에서는 네트워크 상태에 따라 ATIM 윈도우 크기를 조절하는 기법을 제시한다. 제시된 기법은 네트워크 특성을 반영하기 위해 (m,k)-firm 스트림 기법을 적용하였다. 제시된 기법의 성능을 평가하기 위해 ns-2 시뮬레이터를 이용한 성능 평가를 수행했다. 수행된 결과를 보면 제시된 프로토콜은 기존의 프로토콜 보다 많은 양의 에너지 절약을 하고 있음을 볼 수 있다.

• Journal of Power Electronics
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• 제15권3호
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• pp.763-774
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• 2015

This study investigates the inherent influence of a DC-link voltage controller on both DC-link voltage control and the compensation performance of a three-phase, four-wire shunt active power filter (APF). A nonlinear variable-parameter DC-link voltage controller is proposed to satisfy both the dynamic characteristic of DC-link voltage control and steady-state compensation performance. Unlike in the conventional fixed-parameter controller, the parameters in the proposed controller vary according to the difference between the actual and the reference DC-link voltages. The design procedures for the nonlinear voltage controller with variable parameters are determined and analyzed so that the proposed voltage controller can be designed accordingly. Representative simulation and experimental results for the three-phase, four-wire, center-spilt shunt APF verify the analysis findings, as well as the feasibility and effectiveness of the proposed DC-link voltage controller.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1123-1128
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• 2008

Marine facilities like buoy, lighthouse are operated with stand alone power supply system. This power system can consist of a stand-alone type power system such as PV(Photovoltaic) system, wave system or hybrid system which is not cooperated with a commercial power system. Generally, PV power system for marine facilities can not supply a sufficient power to buoy, because it is so influenced from weather condition. For solving this problem the hybrid power system with PV and wave is studied on a various area, that is why a hybrid power system is requires to overcome these problems. This paper will describe a generation characteristic of WEC(Wave Energy Converter) for buoy, and an AFS(Anti-Fouling System) influence on WEC.

• 전기학회논문지P
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• 제60권2호
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• pp.99-104
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• 2011

In this paper, the intelligent landscape lighting power control and monitoring system with solar sell generator equipment is proposed. The first, the intelligent landscape lighting power controller is designed using the fuzzy logic control method. And the fuzzy logic controller is used to save power consumption for various reference intensity of the illumination. The second, the GUI monitoring system is presented. It has control and display faculty. And the practical experiment device is used to evaluate the performance criteria of the proposed intelligent landscape lighting power control system with the solar cell power generation equipment. From the experiment results, we present the property of proposed fuzzy controller such as steady state error, the tracking and power consumption characteristic for the reference intensity of illumination. And also we show the superiority of power control as well as the characteristic of GUI monitoring system in the proposed system.