悬臂结构在航空航天领域应用广泛,由于结构受到激励作用而产生共振行为,因此结构的振动抑制问题显得尤为重要。非线性能量阱(Nonlinear Energy Sink,NES)以质轻、能量单向传递以及减振效率高等特点,为其引入到航空航天结构的减振设计中...悬臂结构在航空航天领域应用广泛,由于结构受到激励作用而产生共振行为,因此结构的振动抑制问题显得尤为重要。非线性能量阱(Nonlinear Energy Sink,NES)以质轻、能量单向传递以及减振效率高等特点,为其引入到航空航天结构的减振设计中提供了条件。利用NES对悬臂矩形板进行减振研究。考虑Kirchhoff经典薄板模型,建立了薄板与NES耦合的动力学方程,通过模态截断研究了薄板一阶横向弯曲时结构的响应问题,分析了不同参数下NES的减振效果,发现NES对结构响应位置较为敏感,并且在位移响应最大位置处减振效果最大。以期为悬臂结构在工程应用中提供一些理论上的支持。展开更多
为了解决OFDM(orthogonal frequency division multiplexing)传输系统中接收端对微弱OFDM信号的检测问题,本文将双稳阱内随机共振系统与OFDM信号增强和解调过程相结合,推导了多载波信号激励下双稳阱内随机共振系统从零状态变化到势阱状...为了解决OFDM(orthogonal frequency division multiplexing)传输系统中接收端对微弱OFDM信号的检测问题,本文将双稳阱内随机共振系统与OFDM信号增强和解调过程相结合,推导了多载波信号激励下双稳阱内随机共振系统从零状态变化到势阱状态所需时间的解析表达式,分析了暂态响应导致的多载波信号在一个符号内的能量损失问题;推导了系统稳态输出方程,分析了稳态过程对子载波已调信号叠加直流偏置分量的问题;探讨了在不同系统参数和噪声强度下阱内随机共振对OFDM信号解调性能的影响。仿真结果表明:该方法可有效实现信号与噪声阱内协同作用,提高OFDM信号的检测性能。展开更多
In this paper, the nonlinear transient dynamic response of functionally graded material （FGM） sandwich doubly curved shell with homogenous isotropic material core and functionally graded face sheet is analyzed using...In this paper, the nonlinear transient dynamic response of functionally graded material （FGM） sandwich doubly curved shell with homogenous isotropic material core and functionally graded face sheet is analyzed using a new displacement field on the basis of Reddy＇s third-order shear theory for the first time. The equivalent material properties for the FGM face sheet are assumed to obey the rule of simple power law function in the thickness direction. Based on Reddy＇s theory of higher shear deformation, a new displacement field is developed by introducing the secant function into transverse displacement. Four coupled nonlinear differential equations are obtained by applying Hamilton＇s principle and Galerkin method. It is assumed that the FGM sandwich doubly curved shell is subjected to step loading, air-blast loading, triangular loading, and sinusoidal loading, respectively. On the basis of double-precision variable- coefficient ordinary differential equation solver, a new program code in FORTRAN software is developed to solve the nonlinear transient dynamics of the system. The influences of core thickness, volume fraction, core-to-face sheet thickness ratio, width-to-thickness ratio and blast type on the transient response of the shell are discussed in detail through numerical simulation.展开更多
In this paper, a hybrid approach was developed to investigate the transient responses of a multi span non uniform flexible spinning shaft with nonlinear and asymmetric supports. The non uniform spinning shaft with ...In this paper, a hybrid approach was developed to investigate the transient responses of a multi span non uniform flexible spinning shaft with nonlinear and asymmetric supports. The non uniform spinning shaft with variable parameters was modeled as a Bernoulli Euler beam column with sectional constant cross section properties by the finite element method. The supporting stiffness behavior of the nonlinear supports was described as a piecewise linear and asymmetric model. The equations of motion in the matrix form of a multi span non uniform spinning shaft with nonlinear and asymmetric supports were formulated using Hamilton's principle and the assumed mode method. As an example, a spinning rocket with many variable stiffness supports was numerically simulated by the direct integration method. The transient response and dynamic behavior of this rotate dynamic system are analyzed.展开更多
文摘悬臂结构在航空航天领域应用广泛,由于结构受到激励作用而产生共振行为,因此结构的振动抑制问题显得尤为重要。非线性能量阱(Nonlinear Energy Sink,NES)以质轻、能量单向传递以及减振效率高等特点,为其引入到航空航天结构的减振设计中提供了条件。利用NES对悬臂矩形板进行减振研究。考虑Kirchhoff经典薄板模型,建立了薄板与NES耦合的动力学方程,通过模态截断研究了薄板一阶横向弯曲时结构的响应问题,分析了不同参数下NES的减振效果,发现NES对结构响应位置较为敏感,并且在位移响应最大位置处减振效果最大。以期为悬臂结构在工程应用中提供一些理论上的支持。
文摘为了解决OFDM(orthogonal frequency division multiplexing)传输系统中接收端对微弱OFDM信号的检测问题,本文将双稳阱内随机共振系统与OFDM信号增强和解调过程相结合,推导了多载波信号激励下双稳阱内随机共振系统从零状态变化到势阱状态所需时间的解析表达式,分析了暂态响应导致的多载波信号在一个符号内的能量损失问题;推导了系统稳态输出方程,分析了稳态过程对子载波已调信号叠加直流偏置分量的问题;探讨了在不同系统参数和噪声强度下阱内随机共振对OFDM信号解调性能的影响。仿真结果表明:该方法可有效实现信号与噪声阱内协同作用,提高OFDM信号的检测性能。
基金the support from the National Natural Science Foundation of China(NNSFC) through Grant No.11472056Beijing Key Laboratory Open Research Project KF20171123202
文摘In this paper, the nonlinear transient dynamic response of functionally graded material （FGM） sandwich doubly curved shell with homogenous isotropic material core and functionally graded face sheet is analyzed using a new displacement field on the basis of Reddy＇s third-order shear theory for the first time. The equivalent material properties for the FGM face sheet are assumed to obey the rule of simple power law function in the thickness direction. Based on Reddy＇s theory of higher shear deformation, a new displacement field is developed by introducing the secant function into transverse displacement. Four coupled nonlinear differential equations are obtained by applying Hamilton＇s principle and Galerkin method. It is assumed that the FGM sandwich doubly curved shell is subjected to step loading, air-blast loading, triangular loading, and sinusoidal loading, respectively. On the basis of double-precision variable- coefficient ordinary differential equation solver, a new program code in FORTRAN software is developed to solve the nonlinear transient dynamics of the system. The influences of core thickness, volume fraction, core-to-face sheet thickness ratio, width-to-thickness ratio and blast type on the transient response of the shell are discussed in detail through numerical simulation.
文摘In this paper, a hybrid approach was developed to investigate the transient responses of a multi span non uniform flexible spinning shaft with nonlinear and asymmetric supports. The non uniform spinning shaft with variable parameters was modeled as a Bernoulli Euler beam column with sectional constant cross section properties by the finite element method. The supporting stiffness behavior of the nonlinear supports was described as a piecewise linear and asymmetric model. The equations of motion in the matrix form of a multi span non uniform spinning shaft with nonlinear and asymmetric supports were formulated using Hamilton's principle and the assumed mode method. As an example, a spinning rocket with many variable stiffness supports was numerically simulated by the direct integration method. The transient response and dynamic behavior of this rotate dynamic system are analyzed.
