• 한국자기학회지
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• 제11권2호
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• pp.50-57
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• 2001

강자성 극박소재에 유기된 잔류응력을 검출하기 위하여 자기유도형 탐촉자(probe)를 설계·제작하였으며, 이를 장착한 잔류음력 평가시스템은 박판내에 유기된 잔류응력의 주응력 방향과 크기를 효과적으로 결정하여 준다. 이 시스템을 반도체 칩 팩키지(package)용으로 사용하는 Fe-42Ni계 lead frame 판재의 잔류응력 검출에 적용한 결과, 양호재 및 잔류응력과다 불량재에 대한 출력전압은 명확히 구별되었고, 잔류응력이 축적된 판재는 양호재와 비교하여 응력의 분포 및 크기에 있어 항상 차이를 나타내었다. 이러한 차이는 탐촉자에 투입하는 전류와 주파수의 함수로 잘 분해되어질 수 있음을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.922-923
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• 2008

This paper is proposed to a novel DC-DC buck-boost converter added electric isolation by using a soft switching method. To be achieved of high efficiency system, the proposed converter is constructed by using a partial resonant circuit. The control switches using in the converter are operated with soft switching for a partial resonant method. The controlling switches are operated without increasing their voltage and current stresses by the soft switching technology. The result is that the switching loss is very low and the converter efficiency is high. And the proposed converter is added in a electric isolation. When the power conversion system is required to electric isolation, the proposed converter is adopted with system development of high efficiency. The soft switching operation and the system efficiency of the proposed converter is verified by digital simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.142-144
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• 2008

This paper is studied on the characteristic analyses of a high performance buck-boost converter added electric isolation by using a soft switching method. To be achieved of a high performance system, the proposed buck-boost converter is constructed by using a partial resonant circuit. The control switches using in the converter are operated with soft switching for a Partial resonant method. The controlling switches are operated without increasing their voltage and current stresses by the soft switching technology. The result is that the switching loss is very low and the converter efficiency is high. And the proposed converter is added in a electric isolation. When the power conversion system is required to electric isolation, the proposed converter is adopted with the system development of high efficiency. The soft switching operation and system efficiency of the proposed converter is verified by digital simulation and experimental results.

• 한국표면공학회지
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• 제56권3호
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• pp.169-179
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• 2023

This work studies dielectric breakdown behavior of AAO (anodic aluminum oxide) films formed on pure aluminum at a constant current density in 5 ~ 20 vol.% sulfuric acid (SA) and 2 ~ 8 wt.% oxalic acid (OA) solutions. It was observed that dielectric breakdown voltage of AAO film with the same thickness increased with increasing concentration of both SA and OA solutions up to 15 vol.% and 6 wt.%, respectively, above which it decreased slightly. The dielectric breakdown resistance of the OA films appeared to be superior to that of SA films. After dielectric breakdown test, cracks and a hole were observed. The crack length increased with increasing SA film thickness but it did not increase with increasing OA film thickness. To explain the reason why shorter cracks formed on the OA films than the SA films after dielectric breakdown test, the generation of tensile stresses at the oxide/metal interface was discussed in relation to porosity of AAO films obtained from cross-sectional morphologies.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.15-16
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• 2010

This paper is study on a high efficiency DC-DC converter of discontinuous conduction mode (DCM) added electric isolation. The converters of high efficiency are generally made that the power losses of the used semiconductor switching devices is minimized. To achieve high efficiency system, the proposed converter is constructed by using a quasi resonant circuit. The control switches using in the converter are operated with soft switching by quasi resonant method. The control switches are operated without increasing their voltage and current stresses by the soft switching technology. The result is that the switching loss is very low and the efficiency of the system is high. The proposed converter is also added electric isolation which is used a pulse transformer. When the power conversion system is required electric isolation, the proposed converter is adopted with the converter system development of high efficiency. The soft switching operation and the system efficiency of the proposed converter are verified by digital simulation and experimental results.

• Smart Structures and Systems
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• 제26권3호
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• pp.391-401
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• 2020

The present article reports the feasibility of the electrical energy generation from ambient low-frequency vibration using a piezoelectric material mounted on a bimorph cantilever beam actuator. A corresponding higher-order analytical model is developed using MATLAB in conjunction with finite element method under low-frequency with both damped and undamped conditions. An alternate model is also developed to check the material and dimensional viability of both piezoelectric materials (mainly focussed to PVDF and PZT) and the base material. Also, Genetic Algorithm is implemented to find the optimum dimensions which can produce the higher values of voltage at low-frequency frequencies (≤ 100 Hz). The delamination constraints are employed to avoid inter-laminar stresses and to increase the fracture toughness. The delamination has been done using a Teflon sheet sandwiched in between base plates and the piezo material is stuck to the base plate using adhesives. The analytical model is tested for both homogenous and isotropic material characteristics of the base material and extended to investigate the effect of the different geometrical parameters (base plate dimensions, piezo layer dimensions and placement, delamination thickness and placement, excitation frequency) on the model responses of the bimorph cantilever beam. It has been observed that when the base material characteristics are homogenous, the efficiency of the model remains higher when compared to the condition when it is of isotropic material. The necessary convergence behaviour of the current numerical model has been established and checked for the accuracy by comparing with available published results. Finally, using the results obtained from the model, a prototype is fabricated for the experimental validation via a suitable circuit considering Glass fibre and Aluminium as the bimorph material.

• Structural Engineering and Mechanics
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• 제76권1호
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• pp.141-151
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• 2020

This manuscript tends to investigate influences of nanoscale and surface energy on a static bending and free vibration of piezoelectric perforated nanobeam structural element, for the first time. Nonlocal differential elasticity theory of Eringen is manipulated to depict the long-range atoms interactions, by imposing length scale parameter. Surface energy dominated in nanoscale structure, is included in the proposed model by using Gurtin-Murdoch model. The coupling effect between nonlocal elasticity and surface energy is included in the proposed model. Constitutive and governing equations of nonlocal-surface perforated Euler-Bernoulli nanobeam are derived by Hamilton's principle. The distribution of electric potential for the piezoelectric nanobeam model is assumed to vary as a combination of a cosine and linear variation, which satisfies the Maxwell's equation. The proposed model is solved numerically by using the finite-element method (FEM). The present model is validated by comparing the obtained results with previously published works. The detailed parametric study is presented to examine effects of the number of holes, perforation size, nonlocal parameter, surface energy, boundary conditions, and external electric voltage on the electro-mechanical behaviors of piezoelectric perforated nanobeams. It is found that the effect of surface stresses becomes more significant as the thickness decreases in the range of nanometers. The effect of number of holes becomes significant in the region 0.2 ≤ α ≤ 0.8. The current model can be used in design of perforated nano-electro-mechanical systems (PNEMS).

• 전기전자학회논문지
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• 제13권4호
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• pp.82-88
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• 2009

본 논문에서는 새로운 고효율의 절연형 스텝 업-다운 DC/DC 초퍼에 대해 해석하였다. 일반적으로 고효율의 초퍼를 만들기 위해서는 전력변환기내에 사용된 반도체 스위칭 소자의 손실이 최소화 되어야 한다. 본 논문에서는 부분공진 회로를 초퍼에 추가하여 고효율을 실현시킨다. 제안한 초퍼에 사용된 제어용 스위칭 소자들은 부분공진기법에 의해 소프트 스위칭으로 동작하고, 이에 따른 제어용 스위칭 소자들은 전압과 전류의 스트레스 없이 동작한다. 그 결과 제안한 초퍼는 스위칭 손실의 저감에 의해 고효율로 구동한다. 그리고 제안한 초퍼는 펄스 변압기를 이용하여 입력단과 출력단을 절연시켜, 전기적 절연이 요구되는 전력변환기들에 적용되어 고효율의 전력변환시스템을 개발할 수 있는 장점이 부여된다. 제안한 절연형 스텝 업-다운 초퍼의 소프트 스위칭 동작과 시스템 효율은 다양한 시뮬레이션과 실험결과를 통해 그 타당성이 입증된다.