• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.2
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• pp.54-61
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• 1994

본 논문에서는 종래의 전파모드 영전압 스위칭 다중공진형 콘버터의 문제점을 극복하기 위하여 전파모드 영전압 다중공진형 콘버터의 스위칭 조건 개선방법을 제안한다. 기존의 전파모드 영전압 다중공진형 콘버터는 능동스위치의 기생커패시턴스에 저장된 에너지로 인한 턴-온 손실이 있다. 그러므로 종래의 손실을 제거시키기 위하여 역전류 저지 다이오드와 병렬로 작은 커패시터를 첨가한 개선된 전파모드 영전압 스위칭 다중공진형 콘버터를 제안하였다. 개선된 스위칭 조건은 Buck형 영전압 스위칭 다중공진형 콘버터에 적용하였으며 실험 결과 이 개선된 콘버터는 능동 스위치의 실질적인 영전압 스위칭이 이루어졌으며 능동 스위치의 턴-온 손실을 제거할 수 있었다.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.1160-1181
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• 2014

Springing and whipping are becoming increasingly important considerations in ship design as container ships increase in size. In this study, the springing and whipping characteristics of a large container ship were investigated through a series of systematic model tests in waves. A multi-segmented hull model with a backbone was adopted for measurement of springing and whipping signals. A conversion method for extracting torsion springing and whipping is described in this paper for the case of an open-section backbone. Higher-order springing, higher-mode torsion responses, and the effects of linear and nonlinear springing in irregular waves are highlighted in the discussion.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.673-678
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• 2015

Terahertz dual-band frequency selective surface filters made by perforating two different rectangular holes in molybdenum have been designed, fabricated and measured. Physical mechanisms of the dual-band resonant responses are clarified by three differently configured filters and the electric field distribution diagrams. The design process is straightforward and simple according to the physical concept and some formulas. Due to the weak coupling between the two neighboring rectangle holes with different sizes in the unit cell, good dual-band frequency selectivity performance can be easily achieved both in the lower and higher bands by tuning dimensions of the two rectangular holes. Three samples are fabricated, and their dual-band characteristics have been demonstrated by a THz time-domain spectroscopy system. Different from most commonly used metal-dielectric structure or metal-dielectric-metal sandwiched filters, the designed dual-band filters have advantages of easy fabrication and low cost, the encouraging results afforded by these filters could find their applications in dual-band sensors, THz communication systems and other emerging THz technologies.

• Journal of Advanced Marine Engineering and Technology
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• v.14 no.2
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• pp.35-47
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• 1990

The natural frequency of lateral vibration for ship's propulsion shafting tends to become lower as the relative stiffness of supproted system of the propulsion shafting decreases and the weight of shafting increases. Especially, the propulsion shafting of high-power ships such as car ferries, roll-on/roll-off, and container ships are susceptible to lateral vibration for their resonant speeds are happened to be in ordinary operating speed ranges. So far, many papers on the lateral vibration of ship's propulsion shaftings are published but they treated mainly special cases and not explained explicitly the calculation process. In this paper, the calculation processes of undamped and also forced damped lateral vibration by the transfer matrix method are presented and the calculation programs are developed. With the developed computer programs, a ship's propulsion shafting which was introduced on the published paper is analyzed for its lateral vibration and also the lateral vibration of the main drive shaft for a lathe is calculated to show the availiability of developed computer programs.

• Journal of Mechanical Science and Technology
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• v.20 no.10
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• pp.1702-1715
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• 2006

The increasing use of nano-positioners in a wide variety of laboratory and industrial applications has created a need for nano-mechatronics education in all engineering disciplines. The subject of nano-mechatronics is broad and interdisciplinary. This article focuses on the way nano-mechatronics is taught in department of mechanical engineering at Korea Advanced Institute of Science and Technology (KAIST). As one model of nano-positioning systems, design and experimental methodology is presented in this article. For design phase, the stiffness and resonant frequencies are found analytically and verified by using a commercial finite element analysis program. Next, for experimental phase, various tests are performed to access the performances of the designed nano-positioner, for example, sine-tracking, multi-step response and travel-range check etc. Finally, the definition of 'separation frequency' is described and some comments are discussed.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.413-414
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• 2015

본 논문에서는 트랜스포머를 공유하는 다입력 LLC 공진형 컨버터를 설계하기 위한 과정을 제시한다. 전원 종류에 따라 다입력 전원을 배터리 충전기에 사용되는 LLC 공진형 컨버터의 공진 네트워크를 설계한다. 시스템 효율을 증가시키기 위해 비대칭 듀티 제어법을 적용하였으며, 2.2kW/600W급 배터리 충전기를 제작 구현함으로써 설계과정의 타당성을 검증한다.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.191-194
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• 1995

소프트 스위칭 능동 클램프 회로와 위상 변위 제어회로를 이용하여 위상 변위 제어 클램프 모드 포워드 다중진공형 컨버터를 제안하였다. 제안된 컨버터는 일정한 스위칭 주파수에서 동작하므로 설계가 용이하고 주 스위치의 전압 스트레스를 입력 전압의 2-3배로 줄일 수 있다. 컴퓨터 시뮬레이션을 통해 제안된 회로의 이론적인 동작 파형을 확인하였으며 타당성을 입증하기 위하여 1MHz, 5V, 50W 위상 변위 제어 클램프 모드 포워드 다중공진형 컨버터를 제작하여 실험한 결과 주스위치의 최대 전압 스트레스는 입력전압의 3배로 저감하였고, 부하 전류가 증가함에 따라 주스위치에 걸리는 전압 스트레스와 전류 스트레스가 감소하며, 최고 84.2%의 효율을 얻었다.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.81-87
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• 2000

A new resonator that is fabricated by single polysilicon layer process is presented. The resonator can move in two orthogonal direction on the plane parallel to the substrate. And the resonant frequencies of the two modes are intrinsically designed to be identical since the overall structure of the resonator is symmetric about the two directions of motion. Since the resonator ideally has two identical vibration mode, it can be applied to various micro-devices that requires multi DOF motion, especially to microgyroscopes. To investigate the feasibility of application of the resonator, dynamic model of the resonator including the nonlinear behavior of driving electrodes is derived and evaluated with the fabricated one, and the self-tuning characteristics are proved though experiments.

• Journal of Institute of Convergence Technology
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• v.1 no.1
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• pp.18-23
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• 2011

Shaping an input command through considering the resonant modes of multi degrees of freedom system, it is possible to realize the wanted motion, without exciting the uncontrollable modes of the flexible system. But, an increase of modes to be considered brings inevitably about the time delay due to an excessive rising time. On the purpose of reducing the rising time, only the interesting and dominant modes can be considered to determine the timing pulses of input shaper. In this paper, an effect of shaper by the partial modes is analysed for a specific system and the input shapers by the partial modes are analysed for three d.o.f damped system, using Matlab simulation.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.244-245
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• 2010

본 논문은 1kW급 가정용 연료전지의 계통연계 및 고효율 전력변환 시스템 개발에 관한 것이다. 본 시스템에서 구현된 전력변환장치는 일반적인 연료전지용 PCS와 마찬가지로 DC/DC 컨버터부와 DC/AC 인버터부로 구성되며, 전체 시스템의 동작은, DC/DC 컨버터부에서는 고효율화를 위하여 공진형으로 동작되며, DC/AC 인버터부에서는 출력전력 제어와 계통연계를 수행한다.