• 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.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.175-178
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• 2010

동하중의 영향을 받는 구조물의 효율적인 구조 해석 및 최적화 수행을 위해 동하중을 등가정하중으로 변환하는 방법이 요구된다. 이 때 적절한 자유도를 선정하여 등가정하중을 부여하는 것이 중요하다. 기존방법에서는 시스템 축소기법을 통해 일정 개수 이상의 주자유도를 선택하여 등가정하중을 부여하고 그 결과 변위가 동하중 하에서의 변위와 같도록 하였다. 그러나 보수적인 결과를 얻기 위한 제한 조건의 지배적인 성격으로 인하여 등가정하중 하에서의 변위가 지나치게 크게 나타나 그 효율성이 떨어지게 되었다. 본 연구에서는 등가정하중의 변환에 있어서 효율성을 높이는 방안을 제안한다. 제안기법은 보수적 결과를 얻는 범위 내에서 과도응답해석 결과와의 오차를 크게 줄일 수 있다. 수치예제를 통해 제안기법의 결과를 기존 기법의 결과와 비교해본다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.2
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• pp.165-171
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• 2013

Due to the difficulty in considering dynamic load in the view point of a computer resource and computing time, it is common that external load is assumed as ideal static loads. However, structural analysis under static load cannot guarantee the safety of design of the structures under dynamic loadings. Recently, the systematic method to construct equivalent static load from the given dynamic load has been proposed. Previous study has calculated equivalent static load through the optimization procedure under displacement constraints. However, previously reported works to distribute equivalent static load were based on ad-hoc methods. Improper selection of equivalent static loading positions may results in unreliable prediction of structural design. The present study proposes the selection method of the proper locations of equivalent static loads to dynamically applied loads when we consider transient dynamic structural problems. Moreover, it is appropriate to take into account the stress constraint as well as displacement constraint condition for the safety design. But the previously reported studies of equivalent static load design methods considered only displacement constraint conditions but not stress constraint conditions. In the present study we consider not only displacement constraint but also stress constraint conditions. Through a few numerical examples, the efficiency and reliability of proposed scheme is verified by comparison of the equivalent stress between equivalent static loading and dynamic loading.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.421-427
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• 2014

Most of the structure of the real world is influenced under dynamic loads. However, when structure analysis and the structural optimization is performed, it is assumed that the static load acts on structure. When considering the actual load of dynamic loads in order to take into account a variety of loads, computational resources and time becomes a big burden in terms of cost. However, considering only the simple static load condition is not preferable for structural safety. For this reason, a lot of studies have been conducted trying to compensate this trouble by applying weight factor or replacing dynamic load with the equivalent static load. In this study, structural optimization techniques for structures under dynamic loads is proposed by applying the equivalent static load. From previous study, after determining the positions of equivalent static load based on primary degrees of freedom, the equivalent static load is calculated through the optimization process. In this process, the equivalent static load optimization of previous research is complemented by adding constraints to avoid excessively large load extraction. In numerical examples, dynamic load is applied to the truss structure and the plate. Then, the reliability of the proposed optimization technique is verified by carrying out size optimization with the equivalent static load.

• Defense and Technology
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• no.5 s.255
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• pp.18-25
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• 2000

T-50은 제 3세대 훈련기의 특징을 최대한 살려서 Total Traing System으로서의 가치를 높여야 한다. 즉, 항공기 뿐만 아니라 비행시뮬레이터를 비롯한 각종 지상비행훈련장비와 정비훈련장비 등으로 Total Traing System으로서의 시너지 효과를 높이는데 주력해야 할 것이다. 또한 KT-1과 조화롭게 연계된 비행훈련체계를 구축함으로써 세계 훈련기시장에서 제 3세대 훈련기의 선두주자로서의 인식과 함께 마케팅에도 상호보완효과를 유도해 낼 수 있을 것으로 예상된다. 이제 세계 훈련기 시장의 종주국으로 거듭나고 있는 한국의 항공산업은 때마침 구조조정에 의해 새로 탄생된 한국항공우주산업(주)의 출범과 맞물려 세계 항공업계의 주목을 받기 시작했다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.41-52
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• 2003

In this paper, three-dimensional thermo-mechanical properties of carbon-phenolic 8-hamess satin weave composites were predicted considering geometric parameters of microstructures. The effective properties were calculated by a series of numerical experiments based on unit cell analysis. The microstructural details were modeled through macro-elements, and the periodic boundary conditions were derived for corresponding un it cell types. The Monte Carlo method was employed to consider the random phase shift between the layers, and the results were investigated on the effect of the geometric parameters of shift, number of layers and waviness ratios. Experimental tests were also performed and the results were compared.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.2
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• pp.23-34
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• 1998

This research proposes on effective analytical methodology for vertical vibration of three dimensional frame structures including slabs. The consideration of slabs, although allows more precise results, requires large amount of computer time and memory space due to the use of plane stress elements. In consideration of these problems, a method to properly manage nodal points and degrees of freedom is proposed based on matrix condensation technique. Also studied is the use of super elements to obtain fast and reliable results with simple input data when they are applied to conventional building structures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.439-450
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• 2008

In this study, the reduced system for the dynamic analysis is proposed and the selection criterion of the primary degrees of freedom is presented considering the relation between natural frequency and external loading frequency. A well-constructed reduced system can assure the accurate representation of the dynamic behavior under arbitrary dynamic loads. For selecting the primary degrees of freedom of the reduced system, we employ the robust two-level condensation scheme of which the reliability has been proven through previous study. In the numerical examples, the reliability of the dynamic analysis based on the reduced system is demonstrated through comparing with those of global system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.236-240
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• 2013

Due to difficulty of considering dynamic load in side of a computer resource and computing time, it is common that external load is assumed as ideal static load. However, structural analysis under static load cannot guarantee the safety of structural design. Recently, the systematic method to construct equivalent static load from the given dynamic load has been proposed. Previous study has calculated equivalent static load through the optimization procedure under displacement constraints. And previously reported works to distribute equivalent static load were based on ad hoc methods. However, it is appropriate to take into account the stress constraint for the safety design. Moreover, the improper selection of loading position may results in unreliable structural design. The present study proposes the methodology to optimize an equivalent static which distributed on the primary DOFs, DOFs of the constraint elements, DOF of an external load as positions. In conclusion, the reliability of proposed method is demonstrated through a global optimization.

• Journal of Korean Philosophical Society
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• v.116
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• pp.437-464
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• 2010

The article, focusing on the theory of Zhong-He, sheds a new light on the philosophy of Daizhen. The theory of Zhong-He, according to the philosophical system of Zhuxi, serves as the theoretical foundation in erecting the apriori moral nature and guiding mental cultivation of subjects. Daizhen, on the contrary, criticizes the doctrine of Zhonghe in Zhuxi's philosophy as it produces negative side-effects of moral dogmatism. Zhuxi's doctrine, according to Daizhen, as it reduce the origin of morality to apriori condition of consciousness and delimit the range of cultivation to psychological realm of subjects, restricts moral subjects in the fortress of their own subjectivity. In this vein of his criticism, Daizhen attempts new interpretation on Zhonghe. The character Zhong (中), according to him, does not refer to apriori moral state or metaphysical moral substance as it does in the doctrine of Zhuxi. On the contrary, it denotes the state in which diverse existent beings are placed in their own position by their own dispositions. Similarly, the other character He (和) does not refer to the condition where an individual's consciousness is in equilibrium, but to the process of achieving the harmony of entire society in which diverse existent beings are communicating to each other. With his novel interpretation of the theory of Zhong-He, Daizhen could dissolve the tradition of Weifa (未發) and moral subjectivism in Zhuxi's philosophy and provide a way of establishing reciprocal communication and harmony between various individuals. It is in his ethics of rational mutual understanding where the significance of Daizhen's philosophy should be found.