• 한국압력기기공학회 논문집
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• 제17권2호
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• pp.137-144
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• 2021

The mode superposition time history analysis method is commonly used in a seismic analysis. The maximum response in the time history analysis can be derived by combining the responses of individual modes. The residual mode response is the response of the modes which are not considered in the time history analysis. In this paper, the residual vector method to consider the residual mode response in the time history analysis is introduced and evaluated. Seismic analyses for a sample structure model and a reactor vessel model are performed to evaluate the residual vector method. The analysis results show that residual mode response is well calculated when the residual vector method is used. It is confirmed that the residual vector method is useful and acceptable to consider the residual mode response in a seismic analysis of the nuclear power plant equipment.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권2호
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• pp.89-96
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• 1999

This paper proposes a common-mode voltage reduction method base on SVPWM(Space-Vector Pulsewidth Modulation) in three phase PWM converter/inverter system. By shifting the active voltage vector of inverter and aligning this to the active vector of converter, it is possible to eliminate a common-mode voltage pulse in one control period. Since the proposed PWM method maintains the active voltage vector, it does not affect the control performance of PWM converter/inverter system. Without any extra hardware, overall common mode voltage dv/dt and conrresponding leakage current can be reduced to two-third of the conventional three phase symmetric SVPWM scheme.

• 전기학회논문지
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• 제66권12호
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• pp.1732-1739
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• 2017

This paper presents a sensorless vector control algorithm of closed loop Gopinath flux observer to enhance the robustness at low speed by switching P/PI mode. Closed loop Gopinath flux observer has the problem in sensorless vector control of induction motor at low speed. This paper solves the problem using the characteristic function of closed loop Gopinath flux observer. P mode shows better performance than PI mode under the cut-off frequency of observer. But P mode always has a flux error due to DC offset, so this paper combines P mode and PI mode. This algorithm shows good performance over wide speed range. The performance has been confirmed through computer simulations using MATLAB SIMULINK and experiments.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.135-139
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• 2016

I propose a vector passive harmonic mode-locked fiber laser based on topological insulator Bi2Se3 interacting with a fiber taper with a diameter of 7 μm. The particles of topological insulator are deposited uniformly onto the fiber taper with light pressure effect. By incorporating the fabricated saturable absorber into an Er-doped fiber laser cavity, stable mode-locked fiber is obtained. Due to the intense evanescent field of the fiber taper, strong confinement of light enhances the nonlinearity of the laser cavity, and passive harmonic mode-locking is performed. I observe a maximum harmonic mode-locking of 356th, corresponding to a frequency of 3.57 GHz. The pulse duration is 824 fs, and the full width at half maximum of the spectrum is about 8.2 nm. The polarization dependent loss of the saturable absorber is ~ 2.5 dB in the wavelength range of the C band. As the cavity contains no other polarization dependent device, the mode-locked laser is functioning in the vector state. The harmonic order vs pump power is investigated. To the best of our knowledge, this report is the highest frequency mode-locked fiber laser based on Bi2Se3. Experimental results indicate that the topological insulator Bi2Se3 functioning with a thin fiber taper is effective for vector harmonic mode-locking.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.171-175
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• 1998

This paper proposes the advanced PWM method that can reduce common-mode voltage in three-phase PWM converter-inverter system. By the proper distribution of the zero-voltage vector of inverter, it is possible to cancel out a common-mode voltage pulse in a sampling period. Since the proposed PWM method maintains the effective-voltage vector, it does not affect the control performance of converter-inverter system. Without any extra hardware, overall common-mode voltage can be decreased by one-third compared with conventional PWM scheme.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권10호
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• pp.634-640
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• 2004

In this paper, the control strategy for high speed operation in light rail transit system is proposed. Recently, the vector control strategy is used to get high capacity control characteristic in low speed area. But Six step mode that is one pulse mode is used in high speed region to use DC link voltage to the maximum. Therefore, in high speed area, the vector control can not be used but scalar control method is used. To get a driving performance to be stabilized, the method of smooth mode change between the low speed and high speed area and PWM control is desired. So this paper proposes the control strategy using vector control include the one pulse mode. And also proposes overmodulation method that makes to change in one pulse mode softly. The performance of traction system will be verified by simulation results using MATLAB and experimental results.

• Journal of Power Electronics
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• 제15권3호
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• pp.712-720
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• 2015

A model predictive current control (MPCC) method that does not employ a cost function is proposed. The MPCC method can decrease common-mode voltages in loads fed by three-phase voltage-source inverters. Only non-zero-voltage vectors are considered as finite control elements to regulate load currents and decrease common-mode voltages. Furthermore, the three-phase future reference voltage vector is calculated on the basis of an inverse dynamics model, and the location of the one-step future voltage vector is determined at every sampling period. Given this location, a non-zero optimal future voltage vector is directly determined without repeatedly calculating the cost values obtained by each voltage vector through a cost function. Without utilizing the zero-voltage vectors, the proposed MPCC method can restrict the common-mode voltage within ± V_dc/6, whereas the common-mode voltages of the conventional MPCC method vary within ± V_dc/2. The performance of the proposed method with the reduced common-mode voltage and no cost function is evaluated in terms of the total harmonic distortions and current errors of the load currents. Simulation and experimental results are presented to verify the effectiveness of the proposed method operated without a cost function, which can reduce the common-mode voltage.

• 전산구조공학
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• 제9권2호
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• pp.115-120
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• 1996

구조물의 동적해석의 주된 관점은 적은 갯수의 모우드형상과 계산과정으로 적정정도의 해를 구하는 것이다. Component mode method는 부분구조물 기법을 이용하여 자유도를 줄이는 방법을 이용하였으나 동하중의 특성이 고려되지 않는 단점이 있으며 이를 보완하기 위한 Ritz Vector법은 많은 반복연산이 필요하며 오차가 가중되는 단점이 있다. 본 연구에서는 Component mode method의 효율성을 개선시키고자 기존의 장점을 유지하면서 직접적분과정에서의 계산량을 현저히 줄일 수 있는 Lanczos 알고리즘을 도입하였다. 이 방법의 효율성을 검증하기 위하여 예제구조물을 해석하여 SAP90의 결과와 비교하였다.

• 반도체디스플레이기술학회지
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• 제13권1호
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• pp.109-112
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• 2014

H.264/AVC is an international video coding standard that is established in cooperation with ITU-T VCEG and ISO/IEC MPEG, which shows improved code and efficiency than the previous video standards. Motion estimation using various macroblock from 44 to 1616 among the compression techniques of H.264/AVC contributes much to high compression efficiency. Generally, in the case of small motion vector or low complexity about P slice is decided $P16{\times}16$ mode encoding method. But according to circumstances, macroblock is decided $P16{\times}16$ mode despite large motion vector. If the motion vector variance is more than threshold and final select mode is $P16{\times}16$ mode, it is switched to $P8{\times}8$ mode, so this paper shows that the storage capacity is reduced. The results of experiment show that the proposed algorithm increases the compression efficiency of the H.264/AVC algorithm to 0.4%, even reducing the time and without increasing complexity.

• 한국컴퓨터산업학회논문지
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• 제2권8호
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• pp.1075-1088
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• 2001

본 논문에서는, H.263 부호화기에 있어, 비제한 움직임 벡터(Unrestricted Motion Vector, UMV)모드와 기본 예측 모드(Default Prediction Mode)의 동적 선택을 위한 방법을 제안한다. 여기서, 움직임 보상된 영상과의 오차와 움직임 벡터의 크기를 이용하였다. 제안된 전략에서, UMV 모드는 모션 벡터의 크기와 움직임 보상된 영상의 오차에 따라 동적으로 적용된다. 이러한 전략은 UMV나 DPM을 고정적으로 전체 영상에 적용한 결과에 비해 화질 면에서 개선할 점을 제공한다. UMV 모드가 고정적으로 적용된 경우에 비해 움직임 추정 시 탐색 점의 수를 크게 줄일 수 있다. 제안된 방법은 카메라의 이동을 갖는 보다 긴 영상 신호에 대해 보다 효과적으로 적용될 수 있다.