• Steel and Composite Structures
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• 제28권2호
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• pp.123-138
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• 2018

Eccentrically braced frames (EBF) represent an optimal structural solution for seismic prone areas, being able to provide high dissipative capacity and good elastic stiffness, to withstand strong seismic events without significant loss of bearing capacity and to avoid damage to non-structural elements in case of low and moderate earthquakes. The accurate knowledge of the cyclic behaviour of the dissipative links, characterizing the whole performance of EBFs, is required to optimize the structural properties and to refine the design techniques adopted for multi-storey buildings' analysis. Reliable numerical models for the links, at the same time requiring a limited computational effort, are then needed. The present work shows the results of a wide experimental test campaign executed on real-scale one storey/one bay frames with horizontal and vertical links, together with the elaboration of a simple semi-analytical model for the quick representation of the cyclic behaviour of shear links.

• 대한수학회지
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• 제32권4호
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• pp.869-876
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• 1995

Piezo devices such as piezoceramic patches knwon as collocated rate sensor and actuators are commonly used in control of flexible structure (see, e.g., [1]) and noise reduction. Recently, Ito and Kang ([4]) developed a nonlinear feedback control synthesis for regulating fluid flow using these devices.

• Journal of applied mathematics & informatics
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• 제10권1_2호
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• pp.17-26
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• 2002

A stability analysis of a non-linear prey-predator system under the influence of one dimensional diffusion has been investigated to determine the nature of the bifurcation point of the system. The non-linear bifurcation analysis determining the steady state solution beyond the critical point enables us to determine characteristic features of the spatial inhomogeneous pattern arising out of the bifurcation of the state of the system.

• 폴리머
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• 제25권4호
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• pp.536-544
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• 2001

실험적 사실에 근거하여 고분자 유체의 점탄성 구성방정식에 빈번히 적용되어온 time-strain separability 가설의 타당성을 수학적 안정성 관점에서 분석한다. 안정성 조건으로는 방정식의 빠른 응답과 관련된 Hadamard 안정성과 소산 성질에 의하여 결정되는 소산 안정성이 있으며, asymptotic 분석을 이용한 결과 가설을 따르는 구성방정식은 Hadamard 또는 소산 불안정함이 증명되었다. 응력완화 실험에서 이미 관찰된 짧은 시간영역에서 time-strain separability의 가설이 적용되지 않는다는 사실은 본 결과와 일치한다. 따라서 separability를 구성방정식에 적용하는 것은 수학적 불안정뿐 아니라 열역학적 모순점을 나타내게 되며, 또한 실험에서도 그 타당성의 한계에 주의할 필요가 있다. 더욱이 damping 함수 역시 실제와는 무관한 가상적 값을 제공하므로 damping 함수의 사용은 긴 시간영역에서 응력완화 거동을 기술하기 위한 curve fitting 이상의 의미는 없다 하겠다.

• 한국지진공학회논문집
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• 제23권3호
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• pp.159-167
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• 2019

2016 Gyeongju and 2017 Pohang earthquakes led Koreans to acknowledge that the Korean peninsula is not an earthquake-free zone anymore. Among various buildings crucial to after-shock recovery, general hospital buildings, especially existing old ones, are very significant so seismic retrofitting of those must be an important issue. Self-centering energy dissipative(SCED) brace is one of retrofitting methods, which consists of tendon with restoring force and friction device capable of dissipating seismic energy. The strength of the SCED brace is that the tendon forces a structure to go back to the original position, which means residual drift can be negligible. The residual drift is a very important parameter to determine usableness of general hospitals after shock. To the contrary, buckling-restrained braces(BRB) are also a very effective way to retrofit because they can resist both compressive and tensile, but residual drift may exist when the steel core yields. On this background, the seismic retrofitting effect of general hospitals reinforced with SCED braces was investigated and compared to that of the BRD in this study. As a result, although the floor acceleration cannot be reduced, the story drift and residual drift, and the shear demand of walls significantly decreased. Consequently, seismic retrofitting by SCED braces are very effective for domestic low-rise general hospitals.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.56-62
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• 2003

The WENO filter is presented for unsteady flow analysis. The filter is low dissipative and dispersive. The results using the present WENO filter show more accurate resolution than those using other filters. The numerical analyses for several test cases are performed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.546-552
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• 2000

Dynamic behavior of laminated composite plates undergoing moderately large deflection is investigated taking into account the viscoelastic behavior of material properties. Based on von Karman's non-linear deformation theory and Boltzmann's superposition principle, non-linear and hereditary type governing equations are derived. Finite element analysis and the method of multiple scales is applied to examine the effect of large amplitude on the dissipative nature of viscoelastic laminated plates.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.551-555
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• 2004

The two-transformer full bridge (TTFB) PWM converter has two transformers which act as the output inductor as well as the main transformer, i.e. as the forward and the flyback transformer. Although the doubled leakage inductor of the TTFB makes it easier to achieve the zero-voltage switching (ZVS) of the lagging leg switch along the wide load range, it instigates a serious voltage ringing in the secondary rectifier diodes, which would require the dissipative snubber circuit, cause the serious power dissipation, and increase the voltage stress across those diodes. To overcome these problems, a, new lossless diode-clamp rectifier (LDCR) is employed as the output rectifier, which helps the voltage across rectifier diodes to be clamped on a half the output voltage $(V_o/2)$ or the output voltage $(V_o)$. Therefore, no dissipative snubber for rectifier diodes is needed and a high efficiency as well as low noise output voltage can be realized. The operations, analysis and design consideration of proposed converter are presented in this paper. To verify the validity of the proposed converter, experimental results from a 425W, 385-170Vdc prototype for the plasma display panel (PDP) sustaining power module (PSPM) are presented.

• 전력전자학회논문지
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• 제10권3호
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• pp.302-311
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• 2005

본 논문에서는 액티브 클램프 포워드컨버터 2차 측에 탭-인덕터와 스너버 커페시터, 두 개의 다이오드로 구성된 무손실 스너버를 적용한 개선된 액티브클램프 포워드컨버터를 제안하였고, 종래의 컨버터와 비교하여 제안된 컨버터가 보다 적은 자화전류조건에서도 영전압 스위칭(ZVS)이 가능함을 보였다. 제안된 컨버터의 동작원리 및 모드를 분석하였고, 300W출력용량의 컨버터 시제품을 제작 실험하여 제안된 컨버터의 효율특성이 개선됨을 보였다.

• 한국항공우주학회지
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• 제32권9호
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• pp.12-26
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• 2004

수치점성을 효과적으로 줄이기 위한 새로운 AUSM-type 수치기법을 개발하였다. TVD 제한자 분석을 통하여 제어면에서의 불성치를 보다 정확하게 예측할 수 있는 기준을 찾아내고 이를 이용하여 제어면의 물성치를 적절히 정의하는 M-AUSMPW+를 개발하였다. M-AUSMPW+의 장점은 다차원 유동을 해석하는데 있어 분명히 나타난다. M-AUSMPW+ 는 유동과 격자계가 일치하지 않는 격자계에서 수치점성을 효과적으로 제거할 수 있기 때문에 다차원 유동을 계산하는데 있어 기존의 어떠한 수치기법보다 정확하고 효과적인 계산이 가능하다. 접촉불연속면, 와류 유동, 충격파 경계층 상호작용, 정성 충격파관 문제를 통해 이를 확인하였다.