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梅逊增益公式参数在方块图中的定义和说明 被引量:1
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作者 李平 钱琳琳 +1 位作者 牛瑞燕 李秀丽 《北京联合大学学报》 CAS 2009年第2期34-36,共3页
在自动控制理论中,梅逊增益公式用于求解复杂的信号流图传递函数是很有效的。但求解复杂方块图的传递函数须将方块图转化为信号流图才可应用梅逊增益公式。分析了信号流图与方块图之间的内在关系,对梅逊增益公式中的参数在方块图中进行... 在自动控制理论中,梅逊增益公式用于求解复杂的信号流图传递函数是很有效的。但求解复杂方块图的传递函数须将方块图转化为信号流图才可应用梅逊增益公式。分析了信号流图与方块图之间的内在关系,对梅逊增益公式中的参数在方块图中进行了定义和说明,定义了方块图中互不接触的概念。提出了直接将梅逊增益公式用于求解复杂方块图传递函数的表述。 展开更多
关键词 梅逊增益公式 方块图 互不接触
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A two-scale contact model for collisions between blocks in CDEM 被引量:5
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作者 LI ShiHai TANG DeHong WANG Jie 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2015年第9期1596-1603,共8页
Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of mu... Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of multiple blocks. Currently, the penalty method, in which mathematical springs with high stiffness values are employed, is always used to calculate the contact forces. High stiffness values may cause numerical oscillations and limit the time step. Furthermore, their values are difficult to identify. The intention of this study is to present a two-scale contact model for the calculation of forces between colliding blocks. In this new model, a calculation step taken from the moment of contact will be divided into two time stages: the free motion time stage and the contact time stage. Actually, these two time stages correspond to two real physical processes. Based on this, we present a new numerical model that is intended to be more precise and useful in calculating the contact forces without mathematical springs. The propagation of the elastic wave during collision is of a characteristic length, which determines the volume of material involved in the contact force calculation. In conventional contact models, this range is always regarded as the length of one element, which may lead to an inaccurate calculation of contact forces. In fact, the real scale of this range is smaller than the length of a single element, and subdivided elements, which are refined according to the characteristic length and are presented in the new contact model. 展开更多
关键词 TWO-SCALE contact model COLLISION elastic wave element subdivision
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