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The stiffened plate is one type of representative thin-walled structure consisting of plates reinforced by varying stiffeners to strengthen its resistance to buckling deformation. However, the mechanism by which stiffeners could efficiently improve the buckling resistance of such structures has not been well reported. Therefore, to investigate the mechanism and predict buckling behavior of the structures accurately, a refined Reddy-type global-local stiffened plate model (RGLS) is established firstly, which can fulfill continuous condition of in-plane displacement and transverse shear stress among the adjacent layers between the plate and stiffeners. In conjunction with the established model, a refined triangular element which can accommodate the continuous condition of transverse shear stresses at the interface between the plate and the stiffeners is constructed. Subsequently, on the basis of the unidirectional stiffened sandwich structures, the symmetric grid-stiffened sandwich structures are proposed. The buckling behavior of grid-stiffened structures is further explored by the present element. A full experimental study and a system of numerical examples have been performed to assess the reliability of the established elements. These examples demonstrate that the buckling loads could be captured by the developed element with high computational efficiency and accuracy. However, the models will significantly overrate buckling loads of the stiffened sandwich structures without considering the continuum condition of the transverse stresses at the plate-stiffener interface. [ABSTRACT FROM AUTHOR]

The atomically dispersed metal catalysts with full atomic utilization and well‐defined site structure hold great promise for various catalytic reactions. However, the single metallic site limits the comprehensive reaction performance in most reactions. Here, we demonstrated a photo‐induced neighbour‐deposition strategy for the precise synthesis of diatomic Ir1Pd1 on In2O3 applied for CO2 hydrogenation to methanol. The proximity synergism between diatomic sites enabled a striking promotion in both CO2 conversion (10.5 %) and methanol selectivity (97 %) with good stability of 100 h run. It resulted in record‐breaking space‐time yield to methanol (187.1 gMeOH gmetal−1 hour−1). The promotional effect mainly originated from stronger CO2 adsorption on Ir site with assistance of H‐spillover from Pd site, thus leading to a lower energy barrier for *HCOO pathway. It was confirmed that this synergistic effect strongly depended on the dual‐site distance in an angstrom scale, which was attributed to weaker *H spillover and less electron transfer from Pd to Ir site as the Pd‐to‐Ir distance increased. The average dual‐site distance was evaluated by our firstly proposed photoelectric model. Thus, this study introduced a pioneering strategy to precisely synthesize homonuclear/heteronuclear diatomic catalysts for facilitating the desired reaction route via diatomic synergistic catalysis. [ABSTRACT FROM AUTHOR]

Polypropylene-fiber-reinforced foamed concrete (PPFRFC) is often used to reduce building structure weight and develop engineering material arresting systems (EMASs). This paper investigates the dynamic mechanical properties of PPFRFC with densities of 0.27 g/cm3, 0.38 g/cm3, and 0.46 g/cm3 at high temperatures and proposes a prediction model to characterize its behavior. To conduct the tests on the specimens over a wide range of strain rates (500~1300 s−1) and temperatures (25~600 °C), the conventional split-Hopkinson pressure bar (SHPB) apparatus was modified. The test results show that the temperature has a substantial effect on the strain rate sensitivity and density dependency of the PPFRFC. Additionally, the analysis of failure models demonstrates that with the melting of polypropylene fibers, the level of damage in PPFRFC under dynamic loading increases, resulting in the generation of a greater number of fragments. [ABSTRACT FROM AUTHOR]

The precise detection of polyester filament yarn (PFY) tension in the spinning process is critical to ensure product quality. The laser Doppler vibrometer (LDV) method is proposed to achieve non-contact detection of PFY tension in this paper. By employing the Hamilton principle, the transverse dynamics differential equations of PFY are derived, which are discretized and solved by the Galerkin method and Runge–Kutta method, respectively. In the equations, the PFY between two adjacent rollers is simplified as an axially moving string to verify the generality of calculating natural frequencies. The calculated natural frequencies from the axially moving string model are compared with solved results from the transverse dynamics differential equations. It is shown that the approximation of natural frequencies can be obtained from the axially moving string model. This study attempts to establish an approximate generic model among the PFY tension, the spinning speed and the first natural frequency based on axially moving string model, from which the PFY tension can be calculated efficiently by employing the measured natural frequencies. The LDV method is used to measure the natural frequencies. A major advantage of the proposed method is to realize non-contact detection of PFY tension. The method is more useful under high-speed spinning conditions where contact tension detectors are not available. An experimental analysis is carried out to verify the effectiveness and accuracy of the proposed method. Therefore, it is believed that the non-contact detection of PFY tension in the spinning process by the LDV method is feasible. [ABSTRACT FROM AUTHOR]

In order to reduce the interference of noise in laser Doppler vibration signal, a laser Doppler vibration signal processing method based on improved wavelet de-noising was proposed. The scale was introduced into the threshold function' and a new evaluation index was established to select the optimal decomposition level. The improved algorithm was used to process the vibration signal. The improved algorithm and the original algorithm were adopted for processing the vibration signal. The simulation analysis and experimental verification were then carried out, and the vibration data before and after processing were obtained. The results indicate that the signal-to-noise ratio of simulated signals processed by the improved algorithm is 19.4% higher than that of the original soft and hard threshold algorithm. The measured tuning fork vibration frequency is 515Hz, which is consistent with the actual tuning fork frequency. This result is helpful to reduce the influence of noise in the laser Doppler vibration signal and obtain the vibration state. [ABSTRACT FROM AUTHOR]