• Journal of Welding and Joining
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• v.32 no.2
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• pp.37-42
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• 2014

In this study, non-load-carrying fillet welded joints fabricated using EH grade-steel are evaluated with the structural stress approach. The thickness effect was investigated by a study on welded steel joints with thickness ranging from 25 to 80mm. As-welded joint for main plate thickness of 25 to 80mm, the fatigue strength is reduced gradually. On the other hand, in case of main plate thickness of 25 to 80mm, the structural stress concentration factor increases gradually. As a result, for structural stress approach, thickness effect is not required for correction. Based on these results, a new evaluation fillet welded joint for fatigue design purposes has been proposed FAT 125.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.279-282
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• 2005

Recently, due to the launching of digital broadcasting service, a demand of PDP TV with large screen size is sharply rising. PDP power module is mainly divided into power factor correction (PFC) stage and sustaining power stage. Especially, sustaining power module has pulsating load characteristics. So, the hard switching at light load condition causes low efficiency and thermal problem. Therefore, a new power conversion circuit for sustaining power module of 60' PDP is proposed whose ZVS is obtained by additional ZVS tank. This paper presents properties of the proposed converter through mode analysis, numerical analysis. And a 900w prototype for sustaining power module of 60' PDP is produced to verify the analytic results. As an experimental results, ZVS is achieved from full load to 10% load variation and more than 92% of high efficiency is obtained at 10% load condition.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.141-143
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• 2007

기존 역률 개선용 부스트 컨버터는 주 스위치의 전도 및 차단 시 전압과 전류의 중첩에 따른 큰 스위칭 손실과 다이오드 역회복 특성에 의한 소자 발열 및 서지 전류 발생으로 인해 시스템 효율과 신뢰성 측면에서 심각한 문제점이 존재한다. 이러한 문제점을 개선하기 위하여 본 논문에서는 새로운 무손실 스너버를 제안하며, 제안된 회로의 분석을 수행하고, 600W급 시작품을 이용한 실험적 분석을 통해 그 우수성을 검증한다.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.353-355
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• 2007

A simple technique for PFC circuit is presented using UC3854. This technique is about current peak controlling by a reference current generator. Decreased peak currents of the boost pre-regulator reduce circuit current stress and so rated currents of circuit elements are minimized. Simulation and experimental results will verify the viability of the new scheme.

• Journal of Power Electronics
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• v.8 no.2
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• pp.141-147
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• 2008

This paper deals with a new and improved control technique for shunt active filters (AF) used for compensating unwanted harmonic currents injected in the mains due to nonlinear varying loads. This work is motivated by the need to find a permanent solution to the rigorous hit and trial method for evaluating system parameters in an indirect control of AF. A fuzzy pre-compensated PI (Proportional-Integral) controller is used to fuzzify the reference DC voltage of AF to the controller input so that the overshoots and undershoots in its DC link voltage are minimized and the settling time is improved. A three-phase diode rectifier with R-L (Resistive-Inductive) load is used as a non-linear load to study the effectiveness of the proposed controller of the AF. Robustness to filter parameter variations, insensitivity to controller parameter variations, and transient response has been taken as performance evaluation parameters. The results are shown through simulations in Matlab using power system block sets to demonstrate the capability of the proposed controller of the AF.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.199-200
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• 2014

본 논문에서는 저 용량에서 많이 사용되는 임계 도통 모드 부스트 역률 보상 회로의 새로운 제어 방법을 제안한다. 제안하는 제어 방법은 임계 도통 모드로 동작 시에 회로의 주요 파형들을 수식적으로 분석하여 입력 전류가 입력 전압을 추종할 수 있는 최적의 온-시간을 도출하는 방식이다. 100W 급 하드웨어를 통하여 제안하는 제어 방법의 실험 결과를 검증하였다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.370-376
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• 2008

Power capacitors is widely used for power factor correction and component of passive filter in the user power systems. Recently, application of non-linear load is gradually increased. Non-linear load produces harmonic components of current. There are series resonance and parallel resonance when capacitors are applied in the user electrical application. If this harmonic component matches resonance, voltage and current is magnified and has severely an influences on capacitor. This paper purposes a new method for the magnitude of voltage and current by the frequency scan analysis without equivalent circuit for the actual circuit at the resonance condition.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.109-111
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• 1998

A novel mode of parallel operation of 3-phase AC-DC flyback converter for power factor correction along with tight regulation was recently analyzed and presented. The advantage of the proposed converter does not require expensive high voltage and high current devices that are normally needed in popular boost type 3-phase AC-DC flyback converter is provided for control purposes and also experimental results are included to confirm the validity of the analysis.

• Advances in nano research
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• v.5 no.2
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• pp.113-126
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• 2017

This paper proposes a new nonlocal higher-order hyperbolic shear deformation beam theory (HSBT) for the static bending and vibration of nanoscale-beams. Eringen's nonlocal elasticity theory is incorporated, in order to capture small size effects. In the present model, the transverse shear stresses account for a hyperbolic distribution and satisfy the free-traction boundary conditions on the upper and bottom surfaces of the nanobeams without using shear correction factor. Employing Hamilton's principle, the nonlocal equations of motion are derived. The governing equations are solved analytically for the edges of the beam are simply supported, and the obtained results are compared, as possible, with the available solutions found in the literature. Furthermore, the influences of nonlocal coefficient, slenderness ratio on the static bending and dynamic responses of the nanobeam are examined.

• Journal of Multimedia Information System
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• v.8 no.2
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• pp.111-120
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• 2021

As recent virtual reality technologies provide a more natural three-dimensional interactive environment, users naturally learn to explore space and interact with synthetic objects. The virtual reality researcher develops a technique that realizes realistic sensory feedback to get appropriate feedback to sense input behavior. Although much recent virtual reality research works extensively consider the human factor, it is not easy to adapt to all new virtual environment contents. Among many human factors, distance perception has been treated as very important in virtual environment interaction accuracy. We study the experiential virtual environment with the feature of the virtual object connected with the real object. We divide the three-dimensional interaction, in which distance perception and behavior have a significant influence, into two types (whole-body movement and direct manipulation) and analyze the real and virtual visual distance perception heterogeneity phenomenon. Also, we propose a statistical correction method that can reduce a near-body movement and manipulation error when changing the interaction location and report the experiment results proving its effectiveness.