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A quasi-three dimensional model is proposed for the vibration analysis of functionally graded (FG) micro-beams with general boundary conditions based on the modified strain gradient theory. To consider the effects of transverse shear and normal deformations, a general displacement field is achieved by relaxing the assumption of the constant transverse displacement through the thickness. The conventional beam theories including the classical beam theory, the first-order beam theory, and the higherorder beam theory are regarded as the special cases of this model. The material properties changing gradually along the thickness direction are calculated by the Mori-Tanaka scheme. The energy-based formulation is derived by a variational method integrated with the penalty function method, where the Chebyshev orthogonal polynomials are used as the basis function of the displacement variables. The formulation is validated by some comparative examples, and then the parametric studies are conducted to investigate the effects of transverse shear and normal deformations on vibration behaviors.

A unified approach is developed for vibration and flutter analysis of elastically restrained stiffened functionally graded plates. A nonlinear temperature distribution throughout the thickness is considered in this study. The temperature dependent material properties assumed to change continuously along thickness is estimated by the Voigt model combined with a simple power- law distribution. The formulation is based on generalized variational principle and the first-order shear deformation theory, in which displacement variables of the plate is adopted to express the displacement field of stiffeners by imposing displacement continuous conditions at the interface. According to the linear piston theory the aerodynamic force is obtained. The penalty function method is used for simulation of the general boundary conditions. By selecting a modified Fourier series as the basis for the displacement variables, the solution can be obtained. The present approach is verified by comparisons between calculated results and those from the existing literature. The influence of the stiffener, gradient index, temperature change and elastic restraints on the dynamic behavior of stiffened FGM plates is discussed.

This paper presents a size-dependent variable-kinematic beam model for free vibration of functionally graded micro-beams. In the formulation, the variable-kinematic description is obtained by expanding the displacement fields in terms of thickness coordinate by any desired order Taylor expansion. The size effect is taken into account by the modified couple stress theory. The effective material properties are calculated by the Mori-Tanaka model. The solution is obtained by using Chebyshev-Ritz method where boundary function is introduced to deal with various boundary conditions. The numerical comparisons are provided to prove the validity of the formulation. The influence of key parameters on the vibration characteristics is further studied.

The objective of this study is to develop a strategy to identify the temperature-dependent properties of a thermo-elastic structure in an unsteady temperature environment, where time-varying material properties and thermal stresses are taken into account. The identification problem is formulated as an updating procedure of the finite element model. Due to the unsteady temperature environment, this procedure is based on a time-variant finite element model because the system matrices change over time. The temperature-dependent properties are expressed as low-order polynomials first. Then, an integrated objective function is established by using errors of the instantaneous frequencies and the sum of the highest order of the polynomials for all the parameters. Subsequently, the particle swarm optimisation is performed to minimise the above objective function to simultaneously determine the coefficient and the order of the polynomials. To demonstrate the effectiveness of the proposed procedure, the identification of a simply supported beam with an axially movable boundary subjected to an unsteady, uniformly distributed temperature field is presented. The numerical verification shows that the identified temperature-dependent properties well track the trends of the true values with high accuracy.

ICESat-2 data was considered as a new land cover classification data source, and a method was proposed to classify land cover using ICESat-2 data with random forest, to explore the application potential of the space-borne photon counting lidar in the land cover classification. The method used the photon number, the proportion of horizontal and vertical distribution of different types of photons, signal-to-noise ratio, solar conditions and atmospheric conditions as the input of classification, and was verified by the experiment of multi-category land cover in China's Yangtze River Delta. For four categories of water, forest, low vegetation and urban/barren, the classification results show that the overall accuracy of strong beam and weak beam is better than 85%. For three categories of water, forest, and low vegetation/urban/barren, the classification results show that the overall accuracy of strong beam and weak beam is better than 90%.

An experimental study was made for the identification procedure of time-varying modal parameters and the finite element model updating technique of a beam-like thermal structure in both steady and unsteady high temperature environments. An improved time-varying autoregressive method was proposed first to extract the instantaneous natural frequencies of the structure in the unsteady high temperature environment. Based on the identified modal parameters, then, a finite element model for the structure was updated by using Kriging meta-model and optimization-based finite-element model updating method. The temperature-dependent parameters to be updated were expressed as low-order polynomials of temperature increase, and the finite element model updating problem was solved by updating several coefficients of the polynomials. The experimental results demonstrated the effectiveness of the time-varying modal parameter identification method and showed that the instantaneous natural frequencies of the updated model well tracked the trends of the measured values with high accuracy.