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The real-time assessment of structural damage in concrete structures using the acoustic emission (AE) technique presents substantial challenges. Traditional AE parameters often fail to effectively quantify the extent of concrete damage in real time. To address this limitation, an Instantaneous Dominant Frequency (IDF) method is proposed for identifying critical damage in concrete. This method leverages empirical mode decomposition (EMD), a self-adaptive time-frequency analysis approach, to process AE signals. By identifying the primary intrinsic mode function (IMF) and extracting the instantaneous frequency with the largest amplitude—termed the IDF—this method captures the dominant frequency characteristics of complex damage sources. The variation in IDF values provides insights into the progression of structural damage. In this study, AE signals obtained from uniaxial compression and four-point bending tests were analyzed using the IDF method. The results show that when the IDF value exceeds 300 kHz, significant damage, such as critical damage, occurs. These findings suggest that the IDF method offers an effective and reliable approach for identifying critical damage and determining the structural damage state during the failure process. [ABSTRACT FROM AUTHOR]

AbstractFree vibration and bending behavior of laminated plates are investigated using a combination of Reissner’s mixed variational theorem and the meshless radial point interpolation method. By introducing Reissner’s mixed variational theorem, a refined transverse shear stress field is derived based on three-dimensional (3D) elasticity equations. The efficiency and accuracy of this model are demonstrated through numerical examples. It is found that accurate prediction of shear stresses significantly improves the prediction of natural frequency for composite laminated plates. The difference between shear stresses derived from 3D equilibrium equations and that from constitutive equations is significant. [ABSTRACT FROM AUTHOR]

The optimization design method of 3Z（ Ⅱ） planetary gear train is studied. The multiple object optimization model,whose objective functions are the minimum of volume of gear train and the maximum of transmission efficiency is built. The constrained optimization is transformed into unconstrained optimization by penalty function,and a solution algorithm is proposed based on parallelism selection genetic algorithm（ GA）.The case shows,the proposed method can apply to the optimization methods of 3Z（ Ⅱ） planetary gear train and the optimization effects are noticeable. There is much for reference of this method to other optimization of planetary gear train.

The key challenge in the practical application of electrochromic energy storage devices (EESDs) is the fabrication of high-performance electrode materials. Herein, we deposited K7[La(H2O)x(α2-P2W17O61)] (P2W17La) onto TiO2 nanowires (NW) to construct an NW–P2W17La nanocomposite using a layer-by-layer self-assembly method. In contrast to the pure P2W17La films, the nanocomposite exhibits enhanced electrochromic and electrochemical performance owing to the 3D sea-cucumber-like microstructure. An EESD using the NW–P2W17La film as the cathode exhibited outstanding electrochromic and energy storage properties, with high optical modulation (48.6% at 605 nm), high switching speeds (tcoloring = 15 s, tbleaching = 4 s), and high area capacitance (5.72 mF cm−2 at 0.15 mA cm−2). The device can reversibly switch between transparent and dark blue during the charge/discharge process, indicating that electrochromic contrast can be used as a quantitative indicator of the energy storage status. [ABSTRACT FROM AUTHOR]