• Journal of Power Electronics
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• v.13 no.1
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• pp.1-8
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• 2013

This paper presents a resonant non-inverting buck-boost converter in which all switches operate under ZCS conditions. In a symmetric configuration, a CLL resonant tank along with an inverter arm and a rectifying diode are employed. The diode is turned off at ZCS and hence the problem of its reverse recovery is obviated also. As a result switching losses and EMI are reduced and switching frequency can be increased. The converter can work at DCM and CCM depend on the switching frequency and the load-current. Experimental results from a 200W/200KHz laboratory prototype verify operation of the proposed converter and the presented theoretical analysis.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.3
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• pp.409-419
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• 1994

This paper deals with the design criteria and conduction noise reduction of electronic ballast system which is based on half-bridge series inverters. The system is theoretically analyzed in six modes and operating frequency range is selected to obtain the high efficacy and no sound noise. It is proposed the criteria for determining the values of L and C which are the dey points in system design Because of high operating frequency, electromagnetic noise, especially conduction noise, is a serious problem in electronic ballasts. To reduce the conduction noise, the operation and attenuation characteristics of noise filter are analyzed and the method to determine the values of filter elements is proposed. Also, the parasitic components of the inductor and capacitor are taken into consideration in filter analysis. Digital simulations and experiments are carried out to prove the theoretical results. And perfor mances of the system are verified through tests.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.538-550
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• 1998

The variable frequency and variable voltage AC source made by a conventional inverter which is composed of power semi-conductors includes much noises in sine wave due to high frequency switching of DC source. In this paper the 3rd low pass LC filter for a variable speed 3 phase induction motor driven by a full bridge inverter is introduced to solve the EMI problem by serious noise current. The utility of a modified 3rd order Butterworth LC filter is confirmed through FFT analysis of sine waves and noiseless ACsource can be obtained by the proposed LC filter. The speed of a 3 phase induction motor driven by a full bridge inverter with a LC filter is satisfactorily controlled by a digital PID controller under the condition of stepwise load and setpoint changes.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.381-386
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• 2002

Recently, The machine tools have been needed for high speed and accuracy to increase productivity. The most important thing to get a more stabilized machine is to know the frequncy response which has an effect on manufacture a lot. This problem should be considered seriously by many researchers. There are many programs about FEM. but just using FEM program to get information of the object is not enough to put our confidence in the stability of the structure design. Therefore, the purpose of this research is to make a study for proving one of the ways to design to produce stabilized a machine more efficiently by comparing FRT with Simulation through FEM. At this two tests, we can learn about the frequency response area causing resonance and we can reconfirm the result to trust.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.4
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• pp.22-31
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• 2005

The purpose of this study is to design a flexural structure that has a function of pan and tilt for an artificial eyeball. The artificial eyeball system has a function of image stabilization, which compensate panning and tilting vibration of the body on which the artificial eyeball is attached. The target closed loop control bandwidth is 50Hz, so the mechanical resonance frequency is required to be more than the control bandwidth, which is a tough design problem because of a big mass of camera and actuator. In this study, the design process including the selection of the principal parameters by numerical analysis with ANSYS will be described, as well as the design results and frequency response.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.60-70
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• 2001

In multi-purpose lathe, the design of tilting turret slide system has an important and critical role to enhance accuracy of the machining process. Tilting turret unit is traveled by 3-axis slide systems. There is a need to design this part very carefully. In this research, 3-axis sliding system with tilting turret unit is modeled by considering the element dividing, material proprties, and boundary conditions with PATRAN. Normal mode and frequency analysis of each structures such as saddle, cared, and turret are simulated by NASTRAN, for the purpose of developing the effective design. The results of mode analysis and frequency analysis are visualized with PATRAN, and the design method which can solve the resornance problem by eigenvalues and eigenvectors of each axis is developed as well.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.6
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• pp.68-73
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• 2005

Tire manufactures have dealt with noise problem by varying the pitch of the tread. The various formulas for the variations are generally determined differently, however. Often these variations are based on a combination of trial and error, intuition, and economics. Some manufactures have models and analogs to test tread patterns and their variations. These efforts, however practical, do not determine the best variation beforehand or guarantee the best results. For this reason it was felt that a general mathematical approach fur determining the best variation was needed. Moreover, the method should be completely general, easy to use, and sufficiently accurate. This paper discusses a mathematical method called Mechanical Frequency Modulation(MFM) which meets the above requirements. Thus, MFM pertains to computing an irregular time sequence of events so that the resulting excitation spectrum is shaped to a preferred form. The first part of this paper treats the theoretical basis for computing an optimum variation ; the second part discusses experimental results and simulation program which corroborate the theory.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.5
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• pp.114-120
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• 2009

In outdoor visible light communication channels and LED road illumination communications for the intelligent transport systems (ITS), inter symbol interference (ISI) due to multipath propagation prevents high data rate transmission. Indoor wireless optical communication systems utilizing white LED lights and on the road illumination have been studying about it. Generally, plural lights are installed in room and considered to the traffic information system using existing LED traffic lights. Therefore, their optical path difference must be considered. In this paper, the influence of an optical path difference has been investigated and two approaches against this problem are introduced. One uses on-off keying, return-to-zero (OOK-RZ) coding and the other uses optical orthogonal frequency division multiplexing(OFDM).

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.171-174
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• 2010

적절한 근사화 과정을 통하여 구축된 축소 시스템은 전체 시스템의 거동을 적은 수의 정보를 통하여 효과적으로 표현할 수 있다. 효과적인 시스템 축소를 위하여 본 연구에서는 주파수 영역 Karhunen-Loeve (Frequency-domain Karhunen-Loeve, FDKL) 기법과 시스템 등가 확장 축소 과정(System equivalent expansion reduction process, SEREP)을 연동한 축소 기법을 제안한다. 적합직교분해(Proper orthogonal decomposition)의 한 방법인 FDKL기법을 통하여 최적모드(Optimal mode)를 구하고 이에 SEREP을 적용하여 자유도 변환 행렬을 구한다. 이때 주자유도 선정은 2단계 축소기법을 적용한다. 최종적으로 제안된 기법은 수치예제를 통하여 검증한다.

• Journal of Korean Association for Spatial Structures
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• v.17 no.1
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• pp.93-100
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• 2017

With increasing number construction of high-rise building which has about 40 to 60 floors there have been many kinds of problem which related with usage from vibration. To predict response acceleration, it is important to assess correct natural frequency. However, due to the noise of MEMS sensor, it is difficult to measure dynamic characteristic such as natural frequency when measuring ambient vibration using MEMS sensor within cell phone. Therefore, a comparative analysis on vibration measuring applications was performed after measuring ambient vibration of 2 skyscrappers which have height between 133.5~244.3m that are located in Seoul and Observation tower using I-jishin APP with noise reduction function of MEMS sensor in order to verify the effectiveness of low noise type vibration measurement APP.