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This paper presents a method to predict the acoustic characteristics and steady-state responses of a flexible plate strongly coupled with rectangular cavity based on energy principle theory and Legendre polynomial series. First, the displacement of the plate and the sound pressure in the cavity are constructed in the form of two-dimensional and three-dimensional Legendre polynomial series, respectively. The unknown expansion coefficients are obtained using the Rayleigh–Ritz technique based on the energy expressions for the strongly coupled plate-cavity system. The accuracy, convergence, and efficiency of the present method are verified by comparing with the results available in the FEM and literature. Finally, the effects of the structural boundary conditions, cavity depth, and structural length-width ratio on the coupling natural frequency and the steady-state responses under three excitation conditions are analyzed. [ABSTRACT FROM AUTHOR]

This paper presents a method to predict the acoustic characteristics and steady-state responses of a flexible plate strongly coupled with rectangular cavity based on energy principle theory and Legendre polynomial series. First, the displacement of the plate and the sound pressure in the cavity are constructed in the form of two-dimensional and three-dimensional Legendre polynomial series, respectively. The unknown expansion coefficients are obtained using the Rayleigh–Ritz technique based on the energy expressions for the strongly coupled plate-cavity system. The accuracy, convergence, and efficiency of the present method are verified by comparing with the results available in the FEM and literature. Finally, the effects of the structural boundary conditions, cavity depth, and structural length-width ratio on the coupling natural frequency and the steady-state responses under three excitation conditions are analyzed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The elastic Ag@PPy sponge was synthesized via in situ polymerization technique. • The Ag@PPy sponge possess well mechanical property. • The bandwidth (RL < −10 dB) of the Ag@PPy sponge could cover the whole X-band. • The water ratios play a vital role in microwave absorption properties. Abstract Three-dimensional (3D) porous structure has attracted considerable interest owing to its flexibility, low density and potential applications. Here, Ag@PPy sponge was synthesized via solvothermal, in situ polymerization and freeze-drying techniques. The Ag@PPy sponge exhibits well elasticity and water absorption capacities due to the 3D network structure. The microwave absorption properties of the Ag@PPy sponge were measured by coaxial line and wave guide methods. The results show that the effective bandwidth (reflection loss values of less than −10 dB) of the Ag@PPy sponge without resin or paraffin matrix could cover the whole X-band (8.2–12.4 GHz) at the thickness of 5 mm. Besides, the complex permittivity of the Ag@PPy sponge can be modulated by adjusting the water ratios from 0 to 78.4 wt%. When the water ratio is 26.2 wt%, the Ag@PPy-26.2 sponge exhibits optimal microwave absorption properties, which the minimum reflection loss (RL) value reaches −33 dB at 8.8 GHz with the thickness of 3 mm. Our research provides a new strategy to design microwave absorbers by using water. [ABSTRACT FROM AUTHOR]

• A new type of highly flexible flame retardant gel polymer electrolyte. • The electrolyte combines high ionic conductivity with robust mechanical properties. • The PPC37 is suitable for high-temperature batteries. In recent years, rechargeable lithium-ion batteries (LIBs) have been extensively studied and applied in portable electronics, electric vehicles, and new energy storage devices. Gel polymer electrolytes (GPEs), currently a research hotspot, inherit the high ionic conductivity of liquid electrolytes and great mechanical properties and safety of solid electrolytes, exhibiting great application potential. Herein, we demonstrate a flexible flame retardant GPE (PPC37) that forms a polymer network through intermolecular hydrogen bonding. During the charge–discharge cycle, the formation of a LiF-rich solid electrolyte interface (SEI) facilitates the uniform electrochemical deposition of Li+ and achieves a long life cycle without dendrites. PPC37 possesses high ionic conductivity (1.06 mS cm−1 at 25 °C) and robust mechanical properties (198% fracture length and 2.43 MPa fracture strength). The Li|PPC37|LiFePO 4 batteries presented great cycling stability with an initial capacity of 151.9 mAh/g and a discharge capacity retention of 86.4% after 500 cycles at a high current density of 3C at 55 °C. The excellent thermal stability, interfacial stability, flame retardancy, flexibility and electrochemical stability demonstrated with PPC37 demonstrate the safety of high-temperature batteries, indicating their great application potential in flexible electronic devices and high-temperature environments. [ABSTRACT FROM AUTHOR]

To study the evolution of stress on the ring and segment interfaces during the construction process of the concrete encapsulation of the main arch ring in a rigid-frame arch bridge, alongside its impact on the ultimate load-bearing capacity of the main arch ring, a 1:10 scale model experiment was conducted by taking the 600 m Tian'e Longtan Bridge as the prototype. The key cross-section concrete strain data were collected during the entire construction process of the main arch ring via fiber-optic strain sensors, which were used to investigate the stress evolution at ring and segment interfaces. ANSYS APDL was employed to simulate the ultimate bearing capacity under various loading conditions of two different finite element models, which were, respectively, formed segmentally and by single pouring. The results revealed that (1) after the closure of the concrete encapsulation of the main arch ring, the concrete stress in the cross-section exhibits significant stress disparities. At the same cross-section, the level of the web concrete stress can reach 76% of the floor concrete stress, while the roof concrete stress level is less than 20% of the floor concrete stress. (2) At the junction of two adjacent work planes, there are considerable differences in the stress levels of the concrete on both sides. After the closure of the main arch ring, the intersegment stress ratios of the floor, web, and roof concrete are 60~70%, 40~60%, and 0~5%, respectively. (3) Loading conditions remarkably affected the ultimate bearing capacity of the main arch ring. Under mid-span loading and 1/4 span symmetrical loading conditions, compared to single-pour concrete encapsulation, the ultimate bearing capacity of the main arch ring with concrete encapsulated by segmented and ring-divided pouring decreased by 19.16% and 5.23%, respectively, compared to single-pour concrete encapsulation. This suggests that the non-uniformity of stress distribution in the concrete sheath can lead to reductions in the ultimate bearing capacity of the arch ring. [ABSTRACT FROM AUTHOR]

In this research, we analyze the acoustic–vibration coupling of liquid-filled cylindrical shells under complex excitations. A calculation model to determine the acoustic characteristics and steady-state response of a cylindrical shell coupled to an acoustic cavity is proposed. The displacement and sound pressure of the cylindrical shell are described by a Chebyshev–Fourier series in three dimensions. The uncertain expansion coefficient is determined with a Rayleigh–Ritz model. The accuracy and convergence of this method are compared with those of the finite element method. The spring constraint is applied to simulate arbitrary boundary parameters. The impact of these parameters on the coupled natural frequency is analyzed. Finally, the steady-state response of a coupled system for various excitation parameters is analyzed. [ABSTRACT FROM AUTHOR]

• Ceramic waste slag-based lightweight aggregate services well after 14 years' curing. • Chloride ion permeability level of 14-year-old LWAC is very low. • Enhanced interfacial transition zone is observed in LWAC with CLWA. • Consuming ceramic waste slag in LWAC is feasible and effective. Lightweight aggregate concrete (LWAC) characterized with low dead weight and high performance, has been applied widely in concrete structures in the past two decades. Mostly, LWAC components play a crucial role in reducing structural weight and keeping structures in good service condition. However, long-term properties of LWAC, especially those prepared with industrial waste-based aggregate, directly affect the durability of structure but have not been explored yet. In the present study, 14-year LWAC incorporating with ceramic waste-based lightweight aggregate (CLWA) were experimentally studied. Traditional LWAC with furnace slag lightweight aggregate (FLWA) was designed as a contrast. Properties of 14-year LWAC such as compressive strength, chloride ion permeability, X-ray diffraction and open porosity were evaluated. In addition, high magnification electron microscope, scanning electron microscope and energy dispersive spectroscopy (SEM-EDS) were adopted to characterize the interfacial transition zone (ITZ) and microstructure of LWAC. Results indicates that after 14 years' curing, no strength reduction is detected and the chloride ion permeability maintains in very low level for LWAC. Long-term performance of LWAC with CLWA is superior to that with FLWA, thanks to the disconnected uniform pores/rough particle surface distributed in CLWA and the compact ITZ between aggregates and mortar. [ABSTRACT FROM AUTHOR]

• The STL curve of the FMPPs has a distinct resonance peak. • Low bending stiffness results in poor sound insulation effects. • The STL curve remains unchanged when the arrangement order transposed symmetrically. • Decreasing the perforation rate decreased from the sound source side is beneficial to improve the absorption effect. It is unlikely to ignore the coupling effect between the structure of the micro-perforated panel (MPP) and the water medium during the application of MPP in the water medium. Theoretical and experimental studies on the sound transmission characteristics of multi-layer flexible micro-perforated panels (FMPPs) under normal incidence conditions were performed. The transfer impedance of finite-sized FMPPs was calculated with the modal superposition method, and the transmission and energy dissipation factor of the FMPPs was derived using the transfer matrix method. Besides, the studies on the effect of panel elastic properties and the arrangement order on the sound insulation performance were carried out. The sound transmission loss (STL) curve remains unchanged when the arrangement order was transposed symmetrically, and it was beneficial to improve the energy dissipation factor when the perforation rate decreased from the sound source side. Theoretical results were verified on a water-filled impedance tube using the two source-location methods. [ABSTRACT FROM AUTHOR]