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김영민,김치경,김태진,Kim, Yeong-Min,Kim, Chee-Kyeong,Kim, Tae-Jin 한국전산구조공학회 2007 한국전산구조공학회논문집 Vol.20 No.6
본 연구에서는 새로운 비선형해석 알고리즘인 적응형 Newton-Raphson 반복기법을 제안한다. 제안된 기법은 기존 Newton-Raphson 기법을 근간으로 적응형 부구조물화 기법을 이용하여 강성등가하중을 구하고, 이미 역행렬이 계산되어 있는 초기강성행렬에 강성등가하중을 적용하여 보정변위를 구하는 것으로 요약된다. 제안된 알고리즘의 가장 큰 특징은 하중 구간의 수에 관계없이 구조물 강성행렬에 대한 역행렬 계산을 단 한번만 수행한다는 것이다. 제안된 기법의 효율성은 강성행렬 및 역행렬 계산 후 부재강성행렬이 변경된 부재들이 연결된 자유도 수와 전체 자유도 수의 비율에 직접 관계된다. 이 비율에 따라 제안된 기법을 기존 비선형해석 기법과 보완적으로 사용함으로써 전체 비선형해석 효율을 향상시킬 수 있다. This paper presents a new nonlinear analysis algorithm, that is, adaptive Newton-Raphson iteration method, The presented algorithm is based on the existing Newton-Raphson method, and the concept of it can be summarized as calculating the equivalent load for stiffness(ELS) and adapting this to the initial global stiffness matrix which has already been calculated and saved in initial analysis and finally calculating the correction displacements for the nonlinear analysis, The key characteristics of the proposed algorithm is that it calculates the inverse matrix of the global stiffness matrix only once irresponsive of the number of load steps. The efficiency of the proposed algorithm depends on the ratio of the active Dofs - the Dofs which are directly connected to the members of which the element stiffness are changed - to the total Dofs, and based on this ratio by using the proposed algorithm as a complementary method to the existing algorithm the efficiency of the nonlinear analysis can be improved dramatically.
김영민,이장희,주성호,Kim, Yeong-Min,Lee, Jang-Hui,Ju, Seong-Ho 한국기계연구원 2000 硏究論文集 Vol.30 No.-
We must stabilize quickly increasing waste matters in urban life and livestock industry. Biogas including landfill gas and digester gas is byproduct of anaerobic decomposition of organic waste matter and contains 40%-70% methane, which can be used for energy purposes. Utilization of biogas reduce the emission of methane into the atmosphere to minimize greenhouse effect and the carbon dioxide (CO2) emitted when biogas is converted to energy has been taken out of the atmosphere by growing plant. Recently, bioenergy is world-widely noticeable as all contributing to the greenhouse effect. This paper presents development process of a biogas engine for cogeneration system and results of application to digester gas and landfill gas in site. The biogas engine is a dual fuel engine operated on biogas with a diesel pilot. At present, the engine can substitute biogas for diesel fuel up to 85%. but it can be said that there is a possibility of improvement in performance.