A novel variable damper using an adjustable energy harvesting structure is proposed for semi-active vibration systems. The fluid flowing in a hydraulic cylinder is employed to drive an electromagnetic generator for ha...A novel variable damper using an adjustable energy harvesting structure is proposed for semi-active vibration systems. The fluid flowing in a hydraulic cylinder is employed to drive an electromagnetic generator for harvesting vibration energy, which on the other hand, leads to a damping effect of the hydraulic damper. To make the damping force variable, an adjustable resistor is adopted to tune the capability of energy harvesting. The present approach is validated by both theoretical analysis and experimental evaluation. When connected with different resistance loads, the prototype damper has different equivalent damping coefficients ranging from 3. 987 × 104 to 2. 488 × 105 N· s/m. The results show that the damping force of the damper is variable in response to the adjustable load for the vibration energy harvesting.展开更多
Aimed at the difficulty in revealing the vibration localization mechanism of mistuned bladed disks by using simple non-linear model,a mechanical model of the bladed disk with random mistuning of hysteretic dry frictio...Aimed at the difficulty in revealing the vibration localization mechanism of mistuned bladed disks by using simple non-linear model,a mechanical model of the bladed disk with random mistuning of hysteretic dry friction damping was established.Then,the incremental harmonic balance method was used to analyze the effects of the parameters of bladed disks,such as the mistuning strength of dry friction force,coupled strength,viscous damping ratio and friction strength,on the forced response of the bladed disks.The results show that the vibrational energy localization phenomenon turns up in the tuned bladed disks if the nonlinear friction damping exists,and the random mistuning of the dry friction force intensifies this kind of vibration localization.展开更多
The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In ord...The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In order to describe the energy dissipation by the motion of the structure under dynamic loading,a damping model which only includes stiffness damp stress was proposed and incorporated into the proposed rate dependent model to consider the energy dissipation at the material scale.The proposed model was developed in ABAQUS via UMAT and was verified by the simulations of concrete specimens under both tension and compression uniaxial loading at different strain rates.The nonlinear analysis of Koyna concrete dam under earthquake motions indicates that adding stiffness damp into the constitutive model can significantly enhance the calculation efficiency of the dynamic implicit analysis for greatly improving the numerical stability of the model.Considering strain rate effect in the model can affect the displacement reflection of this structure for slightly enhancing the displacement of the top,and can improve the calculation efficiency for greatly reducing the cost time.展开更多
The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast,as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature.Granato and Lucke dis...The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast,as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature.Granato and Lucke dislocation pinning model was employed to explain damping properties of the alloys.It is found that reducing impurity content can decrease the amount of second-phase particles,increase grain size and improve damping capacity of the as-cast alloy slightly.The as-extruded alloy with lower impurity content is found to possess obviously higher damping capacity in the relatively high strain region than that with higher impurity concentration,which appears to originate mainly from different dislocation characteristics.The variation tendency of damping property with change of impurity content after solution-treatment is also similar to that in the as-extruded and as-cast states. Meanwhile,the purification of the alloy results in an evident improvement in tensile yield strength in the as-extruded state.展开更多
An alternate non-Fourier heat conduction equation is derived from consideration of translation motion of spinless electron under a driving force due to an applied temperature gradient. This equation is a eapite ad cal...An alternate non-Fourier heat conduction equation is derived from consideration of translation motion of spinless electron under a driving force due to an applied temperature gradient. This equation is a eapite ad calcem,temperature. Elimination of the rate of change of velocity with respect to time leads to a non-Fourier heat conduction equation with a accumulation of temperature or ballistic term in it. The new constitutive heat conduction equation is combined with the energy balance equation in one dimension. The governing equation for transient temperature a partial differential equation （Eq. （23）） is solved for by the method of Laplace transforms. The problem considered is the semi-infinite medium with constant thermo physical properties with constant wall temperature boundary condition. A closed form analyticalexpression for the transient temperature was obtained （Eq. （36）） after truncation of higher order terms in the infinite binomial series and use of convolution and lag properties. This solution is compared with that obtained using the parabolic Fourier model and the damped wave model as presented in an earlier study. The predictions of Eq. （36） are closer to the Fourier model. The convex nature of the temperature curve is present.展开更多
A theoretical and numerical study has been performed on an air film dumper attached to a plate structure. Combined with the analysis by Fox and Whittorg a damping model of the air fiim damper has been developed. A com...A theoretical and numerical study has been performed on an air film dumper attached to a plate structure. Combined with the analysis by Fox and Whittorg a damping model of the air fiim damper has been developed. A complex stiffness was introduced to represent the air pressure in the damper cavity. The stain energy and dissipated energy were integrated from the real part and imaginary part of the complex stiffness to determine the stiffness and damping. The response of the plate with the air film damper was considered by treating the air film as multiple discrete damping-stiffness elements using ANSYS.展开更多
This paper proposes a multi-layer multi-agent model for the performance evaluation of powersystems,which is different from the existing multi-agent ones.To describe the impact of the structureof the networked power sy...This paper proposes a multi-layer multi-agent model for the performance evaluation of powersystems,which is different from the existing multi-agent ones.To describe the impact of the structureof the networked power system,the proposed model consists of three kinds of agents that form threelayers:control agents such as the generators and associated controllers,information agents to exchangethe information based on the wide area measurement system (WAMS) or transmit control signals tothe power system stabilizers (PSSs),and network-node agents such as the generation nodes and loadnodes connected with transmission lines.An optimal index is presented to evaluate the performance ofdamping controllers to the system's inter-area oscillation with respect to the information-layer topology.Then,the authors show that the inter-area information exchange is more powerful than the exchangewithin a given area to control the inter-area low frequency oscillation based on simulation analysis.展开更多
This paper is concerned with the decay estimate of high-order energy for a class of special time-dependent structural damped systems represented by Fourier multipliers. This model is widely used in the fields of semic...This paper is concerned with the decay estimate of high-order energy for a class of special time-dependent structural damped systems represented by Fourier multipliers. This model is widely used in the fields of semiconductivity, superconductivity, electromagnetic waves, electrolyte and electrode materials, etc.展开更多
The initial boundary value problem for a Kirchhoff equation with Lipschitz type continuous coefficient is studied on bounded domain.Under some conditions,the energy decaying and blow-up of solution are discussed.By re...The initial boundary value problem for a Kirchhoff equation with Lipschitz type continuous coefficient is studied on bounded domain.Under some conditions,the energy decaying and blow-up of solution are discussed.By refining method,the exponent decay estimates of the energy function and the estimates of the life span of blow-up solutions are given.展开更多
基金The National Natural Science Foundation of China(No.51375517)the Natural Science Foundation of CQ CSTC(No.2012JJJQ70001)the Project of Chongqing Innovation Team in University(No.KJTD201313)
文摘A novel variable damper using an adjustable energy harvesting structure is proposed for semi-active vibration systems. The fluid flowing in a hydraulic cylinder is employed to drive an electromagnetic generator for harvesting vibration energy, which on the other hand, leads to a damping effect of the hydraulic damper. To make the damping force variable, an adjustable resistor is adopted to tune the capability of energy harvesting. The present approach is validated by both theoretical analysis and experimental evaluation. When connected with different resistance loads, the prototype damper has different equivalent damping coefficients ranging from 3. 987 × 104 to 2. 488 × 105 N· s/m. The results show that the damping force of the damper is variable in response to the adjustable load for the vibration energy harvesting.
基金Project(2007CB707706) supported by the National Basic Research Program of China
文摘Aimed at the difficulty in revealing the vibration localization mechanism of mistuned bladed disks by using simple non-linear model,a mechanical model of the bladed disk with random mistuning of hysteretic dry friction damping was established.Then,the incremental harmonic balance method was used to analyze the effects of the parameters of bladed disks,such as the mistuning strength of dry friction force,coupled strength,viscous damping ratio and friction strength,on the forced response of the bladed disks.The results show that the vibrational energy localization phenomenon turns up in the tuned bladed disks if the nonlinear friction damping exists,and the random mistuning of the dry friction force intensifies this kind of vibration localization.
基金Project(2006BAJ03A03)supported by the National Key Technology R&D Program during the 11th Five-Year Plan Period of China
文摘The elasto-plastic damage model for concrete under static loading,previously proposed,was extended to account for the concrete strain-rate through viscous regularization of the evolution of the damage variables.In order to describe the energy dissipation by the motion of the structure under dynamic loading,a damping model which only includes stiffness damp stress was proposed and incorporated into the proposed rate dependent model to consider the energy dissipation at the material scale.The proposed model was developed in ABAQUS via UMAT and was verified by the simulations of concrete specimens under both tension and compression uniaxial loading at different strain rates.The nonlinear analysis of Koyna concrete dam under earthquake motions indicates that adding stiffness damp into the constitutive model can significantly enhance the calculation efficiency of the dynamic implicit analysis for greatly improving the numerical stability of the model.Considering strain rate effect in the model can affect the displacement reflection of this structure for slightly enhancing the displacement of the top,and can improve the calculation efficiency for greatly reducing the cost time.
基金Project(50725413)supported by the National Natural Science Foundation of ChinaProject(2009BB4215)supported by the Natural Science Foundation of Chongqing Science and Technology Commission,ChinaProject(2008AB4114)supported by the Major Program of Chongqing Science and Technology Commission,China
文摘The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast,as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature.Granato and Lucke dislocation pinning model was employed to explain damping properties of the alloys.It is found that reducing impurity content can decrease the amount of second-phase particles,increase grain size and improve damping capacity of the as-cast alloy slightly.The as-extruded alloy with lower impurity content is found to possess obviously higher damping capacity in the relatively high strain region than that with higher impurity concentration,which appears to originate mainly from different dislocation characteristics.The variation tendency of damping property with change of impurity content after solution-treatment is also similar to that in the as-extruded and as-cast states. Meanwhile,the purification of the alloy results in an evident improvement in tensile yield strength in the as-extruded state.
文摘An alternate non-Fourier heat conduction equation is derived from consideration of translation motion of spinless electron under a driving force due to an applied temperature gradient. This equation is a eapite ad calcem,temperature. Elimination of the rate of change of velocity with respect to time leads to a non-Fourier heat conduction equation with a accumulation of temperature or ballistic term in it. The new constitutive heat conduction equation is combined with the energy balance equation in one dimension. The governing equation for transient temperature a partial differential equation （Eq. （23）） is solved for by the method of Laplace transforms. The problem considered is the semi-infinite medium with constant thermo physical properties with constant wall temperature boundary condition. A closed form analyticalexpression for the transient temperature was obtained （Eq. （36）） after truncation of higher order terms in the infinite binomial series and use of convolution and lag properties. This solution is compared with that obtained using the parabolic Fourier model and the damped wave model as presented in an earlier study. The predictions of Eq. （36） are closer to the Fourier model. The convex nature of the temperature curve is present.
文摘A theoretical and numerical study has been performed on an air film dumper attached to a plate structure. Combined with the analysis by Fox and Whittorg a damping model of the air fiim damper has been developed. A complex stiffness was introduced to represent the air pressure in the damper cavity. The stain energy and dissipated energy were integrated from the real part and imaginary part of the complex stiffness to determine the stiffness and damping. The response of the plate with the air film damper was considered by treating the air film as multiple discrete damping-stiffness elements using ANSYS.
基金supported in part by the National Natural Science Foundation of China under Grants Nos. 50707035, 50595411, 60425307, 60221301 and 50607005, in part by the 111 project (B08013)Program for Changjiang Scholars and Innovative Research Team in University (IRT0515)in part by the Program for New Century Excellent Talents in University (NCET-05-0216)
文摘This paper proposes a multi-layer multi-agent model for the performance evaluation of powersystems,which is different from the existing multi-agent ones.To describe the impact of the structureof the networked power system,the proposed model consists of three kinds of agents that form threelayers:control agents such as the generators and associated controllers,information agents to exchangethe information based on the wide area measurement system (WAMS) or transmit control signals tothe power system stabilizers (PSSs),and network-node agents such as the generation nodes and loadnodes connected with transmission lines.An optimal index is presented to evaluate the performance ofdamping controllers to the system's inter-area oscillation with respect to the information-layer topology.Then,the authors show that the inter-area information exchange is more powerful than the exchangewithin a given area to control the inter-area low frequency oscillation based on simulation analysis.
基金supported by the National Natural Science Foundation of China (No.10871175)
文摘This paper is concerned with the decay estimate of high-order energy for a class of special time-dependent structural damped systems represented by Fourier multipliers. This model is widely used in the fields of semiconductivity, superconductivity, electromagnetic waves, electrolyte and electrode materials, etc.
基金the Natural Science Foundation of Hunan Province (No.05jj40008)the Youth-items Research Fund of Hengyang Normal University (No.08A27)
文摘The initial boundary value problem for a Kirchhoff equation with Lipschitz type continuous coefficient is studied on bounded domain.Under some conditions,the energy decaying and blow-up of solution are discussed.By refining method,the exponent decay estimates of the energy function and the estimates of the life span of blow-up solutions are given.
