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주파수 선택적 투과막이 결합된 복합재료의 잔류응력평가 및 선택적 투과막 설계
김가연 ( Ka Yeon Kim ),전흥재 ( Heoung Jae Chun ),강경탁 ( Kyung Tak Kang ),이경원 ( Kyung Won Lee ),홍익표 ( Ic Pyo Hong ),이명건 ( Myoung Keon Lee ) 한국복합재료학회 2011 Composites research Vol.24 No.1
본 연구에서는 최적화 알고리즘 중 하나인 PSO기법을 이용하여 주파수 선택적 표면을 설계하였으며, 설계된 주파수 선택구조를 적용한 하이브리드 레이돔의 잔류응력을 예측하였다. 주파수 선택 구조로서 Square Loop의 등가회로모델에 PSO를 적용하여, K-band(23GHz)에서 차단특성을 갖는 최적의 설계값을 구하였다. 또한 FSS와 복합재료의 하이브리드 레이돔을 제작할 때 발생하는 잔류응력의 효과가 클 경우 구조적 안정성이 떨어질 뿐만 아니라 층간분리가 발생하여 FSS의 전파투과특성에 영향을 미칠 수 있으므로, 하이브리드 레이돔의 제작 시에 동시경화 후 상온으로 냉각되는 과정에서 발생하는 잔류 열응력에 대하여 예측하였으며, FSS패턴과 복합재료의 적층각 변화에 따른 영향을 비교하였다. In this paper, Particle Swarm Optimization(PSO) is applied to the design of the Frequency Selective Surface(FSS) and residual stresses of hybrid radome is predicted. An equivalent circuit model with Square Loops arrays was derived and then PSO was applied for acquiring the optimized geometrical parameters with proper resonant frequency. Residual stresses occur in the FSS embedded composite structures after cocuring and have a great influence on the strength of the FSS embedded composite structures. They also effect transmission quality because of delamination. Therefore, the thermal residual stresses of FSS embedded composite structures were analyzed using finite element analysis with considering the effects of FSS pattern, and composite stacking sequence.
주파수 선택적 투과막이 결합된 복합재료의 잔류응력에 따른 주파수 변화 예측
강경탁(Kyoung-Tak Kang),전흥재(Heoung-Jae Chun),황인한(In-Han Hwang),김가연(Ka-Yeon Kim),이명건(Myoung-Gun Lee),홍익표(Ic-Pyo Hong) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
In this study, the thermal residual stresses of FSS embedded composite structures were analyzed using finite element analysis, with considering the effect of FSS pattern, FSS size and stacking sequence and fiber orientation of composite laminates. In the analysis, various FSS patterns, such as Square Loop (SL), Gridded Square Loop (GSL), and Double Square Loop (DSL), were considered and effects of dimensional change of design parameters of FSS pattern on the residual stresses in the hybrid composites were investigated for the fixed resonance frequency and pitch cases. Not only for the pattern and stacking angle, the effect of the design variables on each FSS pattern and relationships between these design variables were evaluated through analysis of variance. Then the effect of variable changes on transmission characteristics of FSS were analyzed using FSS Simulator.
금속 패턴이 들어간 복합재료 라미네이트의 잔류응력 예측 및 검증
황인한(In-Han Hwang),전흥재(Heoung-Jae Chun),강경탁(Kyoung-Tak Kang),김가연(Ka-Yeon Kim),이명건(Myoung-Gun Lee),홍익표(Ic-Pyo Hong) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Fiber-reinforced composite materials have been advanced in various applications for their excellent mechanical and electromagnetic properties. However, The residual stresses occur in the frequency selective surface (FSS) embedded composite structures after co-curing due to mismatch between the coefficient of thermal expansions between the FSS and composite materials. It is well known that residual stress has a great influence on the strength and fatigue life of the FSS embedded composite structures. In this paper, the thermal residual stresses of hybrid structures in the bonding layer of the co-cure bonded FSS embedded composite structures were analyzed using finite element analysis, with composite laminates. In oder to validate the predicted residual stress using FEM, tensile test were carried out by fabricating hybrid structure specimens.
강경탁(Kyoung-Tak Kang),전흥재(Heoung-Jae Chun),손주현(Ju-Hyun Son),김호중(Ho-Joong Kim),문성환(Seong-Hwan Moon),이환모(Hwan-Mo Lee),김가연(Ka-Yeon Kim) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.7
Previous studies have introduced the technique of spinous process osteotomy to decompress spinal stenosis, a procedure which aims to afford excellent visualization while minimizing destruction of tissues not directly involved in the pathologic process. However, biomechanically it has not been investigated whether the sacrifice of posterior spinous process might have potential risk of spinal instability or not, even though supra-spinous and inter-spinous ligaments are preserved. Therefore the aim of this study is to evaluate the biomechanical properties after spinous process osteotomy, using finite element analysis. The model of spinous process osteotomy exhibited no significant increase in disc stress or change in segmental range of motion. It is due to the fact that the instability of lumbar spine has been maintained by the two-types of ligaments compared with the prior surgical technique. Therefore, according to the finite element result on this study, this osotetomy was considered to be a clinically safe surgical procedure and could not cause the instability of the lumbar spine.
김가연,김연술 全南大學校 藝術硏究所 1997 藝術論集 Vol.2 No.-
Arnold Schoenberg invented the tone technique as the new composition technique to express the sound which does not exist in the accepted tonal structure and to devleop the newer musical principles than the old tonal structure. The 12 tone series is the creative one invented by him, and the key and the melody are not dulpicated because each sound in it is equally treated as an important one. In this thesis, I analize the tone series in "Suit for Piano, Op.25" composed with the 12 tone technique for the first time. This work is consisted of 6 movements arragned with the movements of the Baroque suits. The striking characteristics of this work are to unify the whole work as making the 12 tone series the Akkord with three groups of each 4 tone series to select the tone series, and to emphasize the tritone intentionally in the harmony. I conclude Schoenberg unified the piece more effectually with the 12 tone technique than the old one, and attempts the new tonal structure to pursuit the harmnony and the beauty in this piece.