• The Journal of the Acoustical Society of Korea
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• 제19권1E호
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• pp.43-47
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• 2000

The paper describes a theoretical study on the speed of torsional elastic waves propagating in a circular rod whose material properties vary periodically as harmonic functions of the axial coordinate. An approximate solution for the phase speed has been obtained by using the perturbation technique for sinusoidal modulation of small amplitude. This solution shows that the wave speed in the nonuniform rod is dependent on the wave frequency as well as the periodic variation of the material properties. It implies that the torsional waves considered in this paper are dispersive even in the fundamental mode.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.44-45
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• 2000

GHz 급의 아주 높은 반복율을 가지면서, 피코초 단위의 펄스 열을 발진시키는 레이저를 만들기 위해 능동형 모드록킹 방법을 이용하였다. 이 방법은 공진기안에 광 변조기를 삽입하고, RF 신호를 가하여 시간적으로 공진기내에서의 손실을 변화시키는 방법이다.$^{(1)}$ 공진기 길이를 충분히 길게 하면서도 고 반복율을 가지는 레이저를 만들기 위해 조화 모드록킹 방법을 사용했는데, 이는 레이저 펄스의 반복율을 공진기 길이에 의한 기본 반복율의 정수배가 되도록 하는 방법이다.$^{(2),(3)}$ 3차 조화 모드록킹 방법을 이용한 Nd:YLF 레이저 시스템을 그림 1에서 나타내었다. (중략)

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1999년도 학술대회논문집-국제 전기방전 및 플라즈마 심포지엄 Proceedings of 1999 KIIEE Annual Conference-International Symposium of Electrical Discharge and Plasma
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• pp.162-167
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• 1999

In Auxiliary block of High speed train Power factor correction and Harmonics reduction is very important issue for efficient energy transport. The GTO-equipped PWM converter is used for traction untill resently. but the rising power capability of IGBTs resently allows to build IGBT-equipped PWM converter with a considerably increases switching frequency. In this paper presents switching pattern, control method, operation mode and tuned filter to reduce dc link voltage ripple for paralleled converter.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2010년도 춘계학술발표논문집 2부
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• pp.755-758
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• 2010

본 논문에서는 현재 Jazz에서 사용되어지는 화성기법을 Pat Metheny의 작품인 “Question & Answer”를 통해서 알아보았다. D Minor Pentatonic Scale이 선율에 주로 사용된 본 작품은 Intro부분에서는 Quater Voicing이 사용되었다. A 부분에서는 Line Cliche와 D Minor Scale과 D Harmonic Minor Scale의 Diatonic Chord를 사용하였지만 A Aeolian Mode적인 기법이 A부분 셋 번째 단에서 사용되어 Modal적인 분위기도 연출 하였으며 B부분에서는 John Coltrane이 자주 사용하였던 3 Tonic 기법이 사용되면서 동질의 화성이 일정간격으로 움직이는 Constant Structure기법도 사용되었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.186-187
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• 2013

역률 보상(Power Factor Correction) 회로의 입력 전압은 정현파이다. 부스트 역률 보상 회로의 경우, 정현파인 입력 전압의 크기가 충분히 작을 때 다이오드가 도통하지 않는 구간이 생긴다. 이 구간에서는 입력 전류 파형의 왜곡이 일어나고, 입력 전류의 전고조파왜율(Total Harmonic Distortion)이 증가하게 된다. 본 논문에서는 임계 도통 모드(Critical Conduction Mode) 역률 보상 부스트 컨버터에 한하여 두 가지 영전류 검출 방법을 사용하여 전고조파왜율을 개선하는 방법을 제안하고, 모의실험으로써 성능을 검증하였다.

• Structural Engineering and Mechanics
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• 제8권2호
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• pp.193-205
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• 1999

A formulation for the dynamic stability analysis of cylindrical shells resting on elastic foundations is presented. In this previously not studied problem, a normal-mode expansion of the partial differential equations of motion, which includes the effects of the foundation as well as a harmonic axial loading, yields a system of Mathieu-Hill equations the stability of which is analyzed using Bolotin's method. The present study examines the effects of the elastic foundation on the instability regions of the cylindrical shell for the transverse, longitudinal and circumferential modes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1120-1122
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• 2002

Switching power supply are widely used in many industrial field. Power factor improvement and harmonic reduction technique is very important in switching power supply. The power factor correction (PFC) circuit using boost converter used in input of power source is studied in this paper. It is analyzed distortional situations and harmonics of input currents that presented at continuous conduction mode(CCM) of boost PFC circuit. It is done simulations of harmonics distribution according to load variation by using PSPICE and MATLAB. From the actual experiment of boost PFC circuit the validity of the analysis is confirmed.

• Journal of Power Electronics
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• 제15권3호
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• pp.644-651
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• 2015

This paper introduces a novel digital one cycle control (DOCC) boost power factor correction (PFC) converter. The proposed PFC converter realizes the FPGA-based DOCC control approach for single-phase PFC rectifiers without input voltage sensing or a complicated two-loop compensation design. It can also achieve a high power factor and the operation of low harmonic input current ingredients over universal loads in continuous conduction mode. The trailing triangle modulation adopted in this approach makes the acquisition of the average input current an easy process. The controller implementation is based on a boost topology power circuit with low speed, low-resolution A/D converters, and economical FPGA development board. Experimental results demonstrate that the proposed PFC rectifier can obtain a PF value of up to 0.999 and a minimum THD of at least 1.9% using a 120W prototype.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.391-394
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• 2003

Laser direct writing process is developed 3rd harmonic Diode Pumped Solid State Laser with the near visible wavelength of 355 m sensitive polymer is irradiated by UV laser and developed using polymer solvent to obtain quasi-3D. It is important to reduce line width for image mode waveguides, so some investigations will be carried out in various conditions of process parameters such as laser power, writing speed, laser focus and optical properties of polymer. This process could be to fabricate a single mode waveguide without expensive mask projection method. Experimentally, the patterns of trapezoidal shape were manufactured into dimension of 8.4 mm width and 7.5 mm height. Propagation loss of straight waveguide measured 3 dB/cm at 1,550 nm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.187-189
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• 2003

Conventional Switched Mode Power Supplies(SMPS) with diode-capacitor rectifier have distorted input current waveform with high harmonic content. Typically, these SMPS have a power factor lower than 0,65. To improve with this problem the power factor correction(PFC) circuit of power supplies has to be introduced. Specially. to the reduce size and manufacture cost of power conversion device, the single-stage PFC converter is increased to demand as necessary of study. in this paper, The comparative analysis of power factor correction circuit using Feedforward control with average current mode flyback converter(single-stage) and boost converter(two-stage). Also, the validity of designed and manufactured high power factor flyback converter and boost converter is confirmed by simulation and experimental results.