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Traditional physics-based mathematical models of viscoelastic (VE) damper often exhibit different degrees of prediction errors under complex working conditions, whereas data-driven approaches have shown significant potential for overcoming such problems, and have not been introduced into any study to describe the dynamic mechanical properties of VE damper. In this paper, the architecture of microsphere model is adopted to represent the spatial distribution of molecular chain structure of VE damping material, which is categorized into free chains and elastic chains. Then, the physics-informed neural network surrogates are introduced to describe the statistical stress–strain behaviors of free chains and elastic chains. Finally, by constructing the physics-constrained loss function based on the combination of physics-based model and data-driven model, a physics-constrained data-driven model is proposed to characterize the dynamic mechanical behaviors of VE damper used for structure vibration control. Based on the existing experimental data, the prediction ability and robustness of the proposed model are comparatively verified, the results reveal that the proposed model can accurately reflect the stiffness and energy dissipation of VE damper under different ambient temperatures, excitation frequencies, and deformation conditions. This study proves the potential of physics-informed neural network theory in characterizing the complex mechanical behaviors of VE damper. [ABSTRACT FROM AUTHOR]

The mechanical properties of viscoelastic (VE) dampers directly affect the aseismic performance of viscoelastically damped structures; therefore, it is of great significance to accurately describe the nonlinear mechanical characteristics of VE dampers in the aseismic design and analysis of structures. However, most of the existing mathematical models for VE dampers have been established from a macroscopic perspective, and there is a general lack of a comprehensive connection to the microstructure characteristics of VE materials and external influence factors such as loading frequency, ambient temperature, and strain amplitude. In this paper, inspired by the molecular chain network models and fractional derivative theory, a microstructure-based equivalent visco-hyperelastic model is proposed for VE dampers with consideration of temperature dependence and the filler reinforcement effect. To verify the characterization capacity of the proposed model, laboratory experiments on the dynamic property of VE dampers were carried out with varying frequencies, temperatures, and strain amplitudes, and the proposed model was then employed to predict the experimental results. Finally, model parameter analysis was conducted to clarify the relationship between material microstructure and its macroscopic performance. The experiments indicate that the VE damper possesses an excellent energy-dissipation capability, and characteristic parameters of VE dampers tend to be more sensitive in the low ranges of frequency and temperature than in the high ranges. Comparisons between the experimental and numerical results suggest that the proposed model can describe the mechanical properties of VE dampers at different frequencies, temperatures, and strain amplitudes with good accuracy. Parameter analysis demonstrates that the proposed model can reflect the influence of material microstructure on the macroscopic mechanical properties of VE dampers. [ABSTRACT FROM AUTHOR]

The earthquake usually causes multi-dimensional vibration for the large span grid structure, how to effectively isolate and mitigate the vibration response of structure is an important problem in engineering. In this paper, a novel viscoelastic bio-inspired multi-dimensional vibration isolation (VBM-VI) device is proposed under the inspiration of bionic design of the bird legs, which possesses multi-dimensional vibration isolation performance by constituting of viscoelastic core pad and VE-LLS device together. The property experiment of the VBM-VI device is performed to explore the mechanical performance at vertical and horizonal directions, the hysteretic curves and characteristic parameters are discussed to reveal the influence of the excitation frequency and amplitude on the mechanical properties of the VBM-VI device, the experimental results show that the mechanical properties express significant frequency and amplitude dependence at vertical and horizontal directions. To further describe the mechanical proprieties of the VBM-VI device, the mathematical models are established at vertical and horizontal directions respectively, and the comparison analysis between experimental and theoretical results indicates that the established mathematical models can precisely describe mechanical performance of the VBM-VI device. [ABSTRACT FROM AUTHOR]

Viscoelastic (VE) damper exhibits significant mechanical nonlinearity under dynamic loads due to variations in the temperature, excitation frequency, and the occurrence of large strains. However, in the existing research literature, such nonlinearity is barely considered, and its effects on the aseismic behaviours of viscoelasticlly damped structure (referred to as VE structures) are also unclear. In this paper, a modified equivalent fractional Kelvin model is established to depict the mechanical nonlinearity of VE damper with the introduction of internal variable parameters. Through the comparison with the existing mathematical models for the performance of an individual VE damper, it is found that the proposed model has a high prediction accuracy, especially in the large-strain working condition. To incorporate the effects of real-time change of the mechanical properties of VE dampers on the seismic responses of structures equipped with such dampers, an approximate method is devised for the numerical calculations. Two representative VE structure with proportionally and non-proportionally damped system are analysed with consideration of the time-varying mechanical nonlinearity of VE dampers. The discrepancy between the seismic responses of the VE structure with and without considering the nonlinearity is discussed. The results indicate that the mechanical nonlinearity of VE dampers could introduce a negative effect on the actual seismic resistance capacity of a VE structure, leading potentially to the structure not meeting the design requirements of codes when the mechanical nonlinearity occurs. The study concludes that it is necessary to take the mechanical nonlinearity into account in the design and performance evaluation of VE structures. • A modified equivalent fractional Kelvin model with high prediction accuracy is established to depict the viscoelastic nonlinearity of VE damper. • An approximate method is devised to incorporate the effects of mechanical properties of VE dampers on the seismic response of VE structures. • The viscoelastic nonlinearity can introduce a negative effect on aseismic capacity of a VE structure, leading potentially risks to the structure. [ABSTRACT FROM AUTHOR]

In order to understand the plasma jet-liquid media interaction characteristics, a high speed digital camera system was used to record the propagation process of plasma jet in liquid media in cylindrical chamber. The properties of the axial and radial displacements of plasma jet in liquid media and the change in its spread speed with time were obtained. Based on experiment, a two-dimensional-axisymmetrie, unsteady mathematical model was developed. Numerical simulation of this process was carried out. The temporal and spatial distributions of volume fractions of plasma and liquid were obtained. The axial displacement calculated from the numerical simulation matches well with that from experiment. The distributions of pressure, velocity and temperature of the flow filed were obtained, and the discontinuous mechanism of Taylor cavity was analyzed. [ABSTRACT FROM AUTHOR]

Abstract: Within a competitive electric power market, electricity price is one of the core elements, which is crucial to all the market participants. Accurately forecasting of electricity price becomes highly desirable. This paper propose a forecasting model of electricity price using chaotic sequences for forecasting of short term electricity price in the Australian power market. One modified model is applies seasonal adjustment and another modified model is employed seasonal adjustment and adaptive particle swarm optimization (APSO) that determines the parameters for the chaotic system. The experimental results show that the proposed methods performs noticeably better than the traditional chaotic algorithm. [Copyright &y& Elsevier]

The application of shape memory alloy (SMA) in seismic-resistant devices has received extensive attention due to its unique superelastic and shape memory effect. The poor energy dissipative capacity, insufficient reliability, and small bearing capacity are the main challenges that hinder the application of the developed SMA braces and dampers. The new system of self-centering energy dissipative (SCED) brace was proposed, fabricated, and tested, and the numerical model was defined and verified. The dates manifest that the load-displacement curve of the new dual-system SCED brace displays a typical flag shape. The new dual-system SCED brace exhibits the desirable energy dissipative ability and self-centering capacity and the theoretical and FE model established in this research can preferably express the hysteretic performance. The FE parametric analysis shows that the SMA screw preload has a small effect on the hysteretic curve of the new system brace, but it plays a decisive role in the shape of the hysteretic curve under small deformation. Furthermore, the bearing capacity and stiffness of the dual-system SCED brace can be adjusted by designing key parameters. The research shows that the new dual-system SCED device compensates for the shortcomings of the existing SMA braces and dampers, and it is a very promising and recommended self-centering energy dissipative device to use the wedge block system as the main energy dissipative system and SMA system as the main self-centering system. • The dual-system SCED brace equipped with SMA screws and a variable friction device is developed and introduced. • The force mechanism of the new system is described and the specimens are fabricated, tested, and analyzed. • The theoretical equation of the dual-system SCED brace is defined, numerical, and verified compared with the test results. • The simulation model of the dual-system SCED brace is identified and the parametric analysis is further disclosed. [ABSTRACT FROM AUTHOR]

The drying curves, moisture effective diffusivity and drying activation energy of winter jujube slices were here investigated at different drying temperatures (55, 60, 65, 70, 75, and 80°C), wind speeds (6, 7, 8, 9, and 10 m/s) and pulsation rates (rotatational speed of material disk: 4, 5.5, and 7 rpm) in a single-factor experiment design. A mathematical model of pulsed air-jet impingement drying for winter jujube slices was fitted and verified. The results showed that the entire drying process could be described as falling rate drying; the moisture effective diffusivity was in the range 1.52-4.93 × 10-9 m²/s and increased with increasing drying temperature, wind speed and pulsation rate. The drying activation energy was 43.9 kJ/mol as determined using the Arrhenius equation. According to the statistical parameters of the correlation coefficient (R²), root mean square error (RMSE) and the sum of squared errors (SSE), the modified Page model was selected as best for representing the correlation between moisture ratio and drying time. [ABSTRACT FROM AUTHOR]