The aim of this study is to investigate the dynamic response of axially moving two-layer laminated plates on the Winkler and Pasternak foundations. The upper and lower layers are formed from a bidirectional functional...The aim of this study is to investigate the dynamic response of axially moving two-layer laminated plates on the Winkler and Pasternak foundations. The upper and lower layers are formed from a bidirectional functionally graded(FG) layer and a graphene platelet(GPL) reinforced porous layer, respectively. Henceforth, the combined layers will be referred to as a two-dimensional(2D) FG/GPL plate. Two types of porosity and three graphene dispersion patterns, each of which is distributed through the plate thickness,are investigated. The mechanical properties of the closed-cell layers are used to define the variation of Poisson’s ratio and the relationship between the porosity coefficients and the mass density. For the GPL reinforced layer, the effective Young’s modulus is derived with the Halpin-Tsai micro-system model, and the rule of mixtures is used to calculate the effective mass density and Poisson’s ratio. The material of the upper 2D-FG layer is graded in two directions, and its effective mechanical properties are also derived with the rule of mixtures. The dynamic governing equations are derived with a first-order shear deformation theory(FSDT) and the von Kármán nonlinear theory. A combination of the dynamic relaxation(DR) and Newmark’s direct integration methods is used to solve the governing equations in both time and space. A parametric study is carried out to explore the effects of the porosity coefficients, porosity and GPL distributions, material gradients, damping ratios, boundary conditions, and elastic foundation stiffnesses on the plate response. It is shown that both the distributions of the porosity and graphene nanofillers significantly affect the dynamic behaviors of the plates. It is also shown that the reduction in the dynamic deflection of the bilayer composite plates is maximized when the porosity and GPL distributions are symmetric.展开更多
为了解决传统双向DC/DC变换器的损耗较大和效率较低等实际问题,提出了一种将交错并联磁集成技术与软开关技术相结合的控制方法。首先,以三相交错并联磁集成双向DC/DC变换器为研究实例,分析了当变换器分别运行在一、二、三相电感时的3种...为了解决传统双向DC/DC变换器的损耗较大和效率较低等实际问题,提出了一种将交错并联磁集成技术与软开关技术相结合的控制方法。首先,以三相交错并联磁集成双向DC/DC变换器为研究实例,分析了当变换器分别运行在一、二、三相电感时的3种工作状态。在每种状态下,分别讨论了电感反向电流的持续时间和死区时间,从而总结出了变换器运行在每种状态下可以实现零电压开关(zero voltage switch,ZVS)的条件。最后,通过实验进一步验证了理论分析的正确性,证实了该设计方案的实用性。展开更多
文摘The aim of this study is to investigate the dynamic response of axially moving two-layer laminated plates on the Winkler and Pasternak foundations. The upper and lower layers are formed from a bidirectional functionally graded(FG) layer and a graphene platelet(GPL) reinforced porous layer, respectively. Henceforth, the combined layers will be referred to as a two-dimensional(2D) FG/GPL plate. Two types of porosity and three graphene dispersion patterns, each of which is distributed through the plate thickness,are investigated. The mechanical properties of the closed-cell layers are used to define the variation of Poisson’s ratio and the relationship between the porosity coefficients and the mass density. For the GPL reinforced layer, the effective Young’s modulus is derived with the Halpin-Tsai micro-system model, and the rule of mixtures is used to calculate the effective mass density and Poisson’s ratio. The material of the upper 2D-FG layer is graded in two directions, and its effective mechanical properties are also derived with the rule of mixtures. The dynamic governing equations are derived with a first-order shear deformation theory(FSDT) and the von Kármán nonlinear theory. A combination of the dynamic relaxation(DR) and Newmark’s direct integration methods is used to solve the governing equations in both time and space. A parametric study is carried out to explore the effects of the porosity coefficients, porosity and GPL distributions, material gradients, damping ratios, boundary conditions, and elastic foundation stiffnesses on the plate response. It is shown that both the distributions of the porosity and graphene nanofillers significantly affect the dynamic behaviors of the plates. It is also shown that the reduction in the dynamic deflection of the bilayer composite plates is maximized when the porosity and GPL distributions are symmetric.
文摘为了解决传统双向DC/DC变换器的损耗较大和效率较低等实际问题,提出了一种将交错并联磁集成技术与软开关技术相结合的控制方法。首先,以三相交错并联磁集成双向DC/DC变换器为研究实例,分析了当变换器分别运行在一、二、三相电感时的3种工作状态。在每种状态下,分别讨论了电感反向电流的持续时间和死区时间,从而总结出了变换器运行在每种状态下可以实现零电压开关(zero voltage switch,ZVS)的条件。最后,通过实验进一步验证了理论分析的正确性,证实了该设计方案的实用性。
