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비선형 시스템의 invariance immersion 적용제어
이의권(Eui Kwon Lee),조성수(Sung Su Cho),이호진(Ho Jin Lee),이금원(Keum Won Lee),이준모(Jun Mo Lee) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.10
본 논문에서는 비행기 모델을 대상으로 invariance and immersion방법을 적용하여 비선형 제어기를 설계한다. 이 방법을 사용하면 추정오차에 대한 추정식 형태로 off-the-manifold 좌표축을 정의하고, dynamics를 구하고, 이로부터 파라미터 적응규칙을 유도한다. 제어기는 이와 관련된 파라미터로부터 선형화하지 않고 직접 설정하며, 마지막으로 리아프노프 함수를 통하여 알고리즘의 안정성을 증명한다.
김석원,이의권 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.9
This study aims to investigate the effects of vanadium(V) and titanium(Ti) alloying elements additions and cooling rate on the morphologies of eutectic carbide, secondary carbide, the austenite retention in the matrix, and heat treatment characteristics for hypoeutectic chromium cast iron with 2.5% C, 14% Cr, 0% to 2.2% V, or 0% to 0.6% Ti alloying elements. The specimens for unidirectional solidification were melted at 1500℃ and casted into an exothermic furan mold(30㎜×70㎜) placed on the water cooled copper chill, and were solidified unidirectionally. Also, the specimens for study of heat treatment characteristics were casted into the furan mold and were treated by different heat treatments (cyclic heat treatment, destabilization heat treatment). The eutectic and eutectoid transformation temperature rise both with the increase of Ti and V contents in the specimen. With the increase in Ti and V contents, the eutectic carbide is decreased, the second carbide is increased. The morpholigies shape of second carbide is changed from the bar to the finer granular type as increase in both(Ti,V) contents. For cyclic heat treatment, the hardness is improved with the increase of number of cycles, because hardness depend on the fine matrix as well as the amount of carbide and martensite.
Al-Si / SiCp 복합조직에 미치는 Rheo-compocasting 의 제조조건 및 Mg 첨가의 영향
김석원,이의권,전우용 ( Sug Won Kim,Eui Kweon Lee,Woo Yeoung Jeon ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.6
N/A Dispersion behaviors of SiC particles and microstructures in Al-2%Si/SiCp composite prepared by Rheo-compocasting were studied with change of fabrication conditions(slurry temperature, agitation time) and additions of Mg(0∼3wt.%). Also, the microhardness change of matrix, interface and total in composites were examined with additions of Mg (0∼3wt.%). The dispersion of particles in the composites became relatively homogeneous with increase of Mg additions, agitation time and decrease of slurry temperature. Rate of occupied area by particle in matrix was increased as increase of Mg additions due to improvement of wettability between SiC particle and matrix. A favorable composites were obtained by melting under Ar atmospheric SiCp injection and bottom pouring system. According to the analysis of X-ray diffraction, Mg₂Si, Al₄C₃, SiO₂and MgO, etc, intermetallic compounds were formed by chemical interreaction at interface of matrix and particles. The microhardness of interface is higher than that of matrix due to more strengthening of above intermetallic compounds. It was considered that the total hardness of the composites is improved by dispersing of SiCp and addition of Mg.
Al-SiCp 복합재료에서 SiCp 의 용해거동에 관한 연구
김석원,이의권,전우용 ( Sug Won Kim,Eui Kweon Lee,Woo Yeoung Jeon ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.4
N/A Aluminum base composites reinforced with various amount of SiC particles and Mg contents have been investigated by different fabrication method for twenty-years. In this paper, how the decomposition and dissolution behaviors of SiCp(20㎛) in the melt of Al composites arised was studied. As the results, the decomposition and dissolution of SiCp into the melt of Al composites increased with increase of the temperature above 720℃, and holding time at a given melting temperature. Because SiC is thermodynamically unstable in this Al-SiCp composite at temperature above the liquidus, SiCp dissolves and reacts with Al in matrix to form Al₄C₃according to following chemical equation 4Al+3SiC→Al₄C₃+3Si, Si decomposed and dissolved from SiCp increases Si content of matrix, while liquidus temperature of matrix decrease with increase of SiC content in matrix. The hardness of SiCp decreased with increase of the melting temperature, the hardness of the matrix /particle interface increased with increase of the melting temperature due to increase of the Mg₂Si and Al₄C₃intermetallic compounds, etc.