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This article establishes a nonlinear flutter system for a long-span suspension bridge, aiming to analyze its supercritical flutter response under the influence of nonlinear aerodynamic self-excited force. By fitting the experimental discrete values of flutter derivatives using the least squares method, a polynomial function of flutter derivatives with respect to reduced wind speed is obtained. Flutter critical value is determined by the linear matrix eigenvalues of a state-space equation. The occurrence of a supercritical Hopf bifurcation in the nonlinear system is determined by the Jacobian matrix eigenvalues of the state-space equation and the system's vibrational response at the critical state. The vibrational response of the supercritical state is obtained through Runge–Kutta integration, revealing the presence of stable limit cycle oscillation (LCO) and unstable limit cycle oscillation in the system, and through analyzing the relationship between the LCO amplitude and wind speed. Considering cubic nonlinear damping and stiffness, the effects of different factors on the nonlinear flutter system are analyzed. [ABSTRACT FROM AUTHOR]

This paper presents the problem of nonlinear aero-thermo-elastic response of cracked plate. Bending equations of two-dimensional simply supported cracked plate subjected to supersonic flow and thermal effect is derived based on classical plate theory (CPT) and Von Kármán nonlinear relations. Linear piston theory is utilized to evaluate the aerodynamic pressure with uniform temperature variations. By applying Galerkin's method and Runge-Kutta scheme, the equations are solved. The effects of parameters such as flow condition, crack dimension, temperature changes, plate aspect ratio, mass ratio, static pressure on the plate stability, flutter point and limit cycle oscillation (LCO) of the plate are examined. [ABSTRACT FROM AUTHOR]

This article establishes a nonlinear flutter system for a long-span suspension bridge, aiming to analyze its supercritical flutter response under the influence of nonlinear aerodynamic self-excited force. By fitting the experimental discrete values of flutter derivatives using the least squares method, a polynomial function of flutter derivatives with respect to reduced wind speed is obtained. Flutter critical value is determined by the linear matrix eigenvalues of a state-space equation. The occurrence of a supercritical Hopf bifurcation in the nonlinear system is determined by the Jacobian matrix eigenvalues of the state-space equation and the system’s vibrational response at the critical state. The vibrational response of the supercritical state is obtained through Runge–Kutta integration, revealing the presence of stable limit cycle oscillation (LCO) and unstable limit cycle oscillation in the system, and through analyzing the relationship between the LCO amplitude and wind speed. Considering cubic nonlinear damping and stiffness, the effects of different factors on the nonlinear flutter system are analyzed.

A digital low-dropout (DLDO) regulator is described which is controlled by voltage-controlled oscillator (VCO) based feedback loop. There are two VCOs in the control loop whose frequencies are controlled by the output voltage and reference level, respectively. By comparing the phase between the output clocks of the two VCOs and modulating the number of enabled power transistors and their on-times, the output voltage is regulated. The proposed VCO-based control is a hybrid of digital and analog control schemes because the number of enabled power transistors is controlled in discrete step while the on-time is modulated continuously. In order to improve the transient speed, transient detector is employed in the DLDO regulator. The DLDO regulator with the proposed VCO-based control has been implemented in a 65-nm CMOS process. The DLDO regulator can provide the output from 0.5 to 1.1 V from the input ranging from 0.9 to 1.2 V. The load transient time is smaller than 90 ns for both step-up and step-down changes of load current. The peak current efficiency is 99.3%. [ABSTRACT FROM AUTHOR]