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The thermal conductivity of glasses is well-known to be significantly harder to theoretically describe compared to crystalline materials. Because of this fact, the fundamental understanding of thermal conductivity in glasses remain extremely poor when moving beyond the case of simple glasses, e.g., glassy SiO2, and into so-called "modified" oxide glasses, that is, glasses where other oxides (e.g., alkali oxides) have been added to break up the network and alter, e.g., elastic and thermal properties. This lack of knowledge is apparent despite how modified glasses comprise the far majority of known glasses. In the present work, we study an archetypical series of sodium silicate [xNa2O–(100 − x)SiO2] glasses. Analyses of modal contributions reveal how increasing Na2O content induces increasing vibrational localization with a change of vibrations to be less ordered and a related general decrease in modal contributions to thermal conductivity. We find the vibrational phases (acoustic vs optical) of sodium vibrations to be relatively disordered compared to the network-forming silicon and oxygen species, explaining how increasing Na2O content decreases thermal conductivity. Our work sheds new light on the fundamentals of glassy heat transfer as well as the interplay between thermal conduction and modal characteristics in glasses. [ABSTRACT FROM AUTHOR]

In this work, we present a simple design of a compact and miniaturized wideband bandpass filter (BPF) based on substrate integrated waveguide (SIW) and microstrip line. Through the order extension, the filtering effect and the order of the Chebyshev response of the designed BPF can be indirectly controlled by preserving square notches (SNs) on the SIW. By introducing one or two SNs in the SIW structure, the resonance frequencies of different modes can be controlled, thus achieving dual- and tri-mode BPFs with wideband and low insert loss. The working principle of the designed BPFs was illustrated by modal analysis, field distribution, and equivalent circuit theory. Based on this, the dual- and tri-mode BPFs with center frequencies of 6.8 and 7 GHz were designed and demonstrated numerically. Further experimental results indicate that the proposed tri-mode BPF has low insertion loss (0.25 dB), compact size (0.27λg2), and wideband bandwidth (60%). In addition, the tri-mode BPF achieves a broadband out-of-band rejection of 1.5f0 (f0 is the center resonance frequency) below the −10 dB level, making it highly promising for various applications in related fields. [ABSTRACT FROM AUTHOR]

Abstract\nHIGHLIGHTSThis study investigates how resonator placement and boundary conditions influence bandgap formation in a locally resonant beam metastructure. The steady-state response of the structure, subjected to a concentrated harmonic load, is then computed using the modal analysis. Four different boundary conditions are considered. For each boundary condition, the resonator array is shifted, and the corresponding responses are calculated. The study reveals that, for a cantilever beam, the widest bandgap occurs when the last resonator in the periodic array is positioned at the free end. For the other cases, no significant change in bandgaps is observed.Resonator placement and boundary conditions effect on bandgap formation.Used modal analysis to study bandgap formation in a finite locally resonant beam metastructure.Resonators target specific vibration modes in the host structure.Frequency response analyzed for various resonator placements. [ABSTRACT FROM AUTHOR]

To investigate the vibration characteristics of long-span suspension bridges under the impact of high-speed trains, a method for conducting a time–frequency domain analysis of the dynamic response of a coupled system is presented in this study. First, the finite element model of a suspension bridge is established to conduct modal analysis, and simulation results are compared with measured data to validate the correctness of the bridge model. Subsequently, a multi-body dynamics model of a high-speed train is developed. Then, two approaches, the dummy method and flexible-track method, are employed to create the train–bridge coupled system. Finally, the flexible-track method is used to perform time–frequency domain analysis of the system under complex operational conditions. The research revealed that large-span suspension bridges exhibit lower natural frequencies. The vertical bending vibrations of the main beam have the potential to significantly impact train operations. Under the combined impact of cable tension and wheel–rail forces, the vibration patterns of large-span suspension bridges become notably intricate. The number of trains and their loading configurations both exert influence over the dominant frequencies and amplitudes in the PSD of bridges. In the complex traffic of large-span suspension bridges, the rational arrangement of travel lanes can reduce the possibility of resonance in the bridge–train system. [ABSTRACT FROM AUTHOR]

Most studies on human–structure interactions have focused on vertical coupling, which refers to the interaction between human bodies and structures in the vertical direction. This study, however, analyzes horizontal coupling. Several experiments on mass–structure and human–structure systems were conducted, and two horizontal-coupling human–structure models are proposed. The experimental results indicate that a stationary human body should not be regarded as a simple mass. As the number of individuals increases, the horizontal self-resonance frequency gradually decreases by approximately 0.2–0.3 Hz, whereas the damping ratio increases. Based on experimental data and horizontal human–structure models, the horizontal frequency ranges of the human body are found to be 0.236–3.748 Hz for front–back motion and 0.194–5.32 Hz for left–right motion. It is proposed that the single-human model and experimental results be extended to crowd–structure interactions. [ABSTRACT FROM AUTHOR]

Pedestrian comfort is not only related to the health of the human body, but also directly impacts the efficiency and lifespan of building materials. Raised floors have more complex geometric characteristics and structural dynamic properties compared to traditional flooring, which necessitates an analysis of pedestrian comfort. This study explores four different configurations of raised floors in prefab bathroom units to evaluate their pedestrian comfort. Through theoretical and experimental modal analysis, the natural frequencies and potential deformation areas are identified, enabling the calculation of peak acceleration of the raised floors under walking excitation. The study then quantitatively assesses the pedestrian comfort of raised floors based on natural frequency and peak acceleration measurements, proposing an optimization design method using a multi-island genetic algorithm (MIGA). By adjusting parameters such as the support leg distance, beam shape, and support board surface layer thickness, an optimal balance between pedestrian comfort and heat transfer performance is achieved. Through the integration of simulation and experimental techniques, the study presents an efficient and cost-effective optimization design method for raised floors and explores the impact mechanism between design variables and pedestrian comfort performance. [ABSTRACT FROM AUTHOR]

With the promotion of carbon neutrality policies, hydrogen burners are widely used in the industrial field, and exploring the combustion characteristics and stable combustion technology of hydrogen industrial burners has important engineering application significance. This study investigates the flow characteristics and combustion oscillation mitigation of a specific hydrogen industrial burner for heating thermal oil through experiments and numerical simulations. The oscillating combustion with a frequency of 100 Hz is discovered during the field test. The dynamic characteristics are reproduced via large eddy simulation (LES), and the pressure amplitude is reduced by 22% via the active control strategy. LES results show that corner recirculation zone and main recirculation zone occur in the flame holding chamber, with maximum recirculation velocity and maximum temperature of −20 m/s and 2110 K, respectively. The unstable modes and key elementary reactions are revealed by modal analysis and eigen-analysis. The clustered neural network with horizons (CNNH) controller is constructed to suppress the combustion instability. The CNNH controller can effectively suppress the pressure oscillation by perturbing the inlet mass flow rate of main H 2 , reducing the peak amplitude in the frequency domain by 67%. By optimizing the controller parameters, the CNNH controller can be further applied to different scenarios of hydrogen industrial burners. • Flow characteristics of a hydrogen industrial burner are analysed with LES. • Oscillating combustion is analysed by modal analysis and eigen-analysis. • Dominant species and reactions are identified during oscillating combustion. • Active control strategy is constructed to suppress the oscillating pressure. • The influence of controller parameters on control performance is studied. [ABSTRACT FROM AUTHOR]

We propose a general method for analyzing a multilayer left-handed metamaterial (LHM) optical waveguide structure with a localized arbitrary Kerr-type nonlinear guiding film. To the best of our knowledge, the proposed method has not been reported before. The available electromagnetic simulation software like cannot be used to analyze the case of the proposed multilayer photonic metamaterial slab optical waveguide structures with a localized arbitrary Kerr-type nonlinear guiding film. It gives detailed modal analyses of TE-polarized waves in the proposed photonic metamaterial slab optical waveguide structures. The analytical results are accompanied by some numerical examples. The method can also be degenerated to analyze planar conventional optical waveguide structures with a localized arbitrary Kerr-type nonlinear guiding film. It can also help researchers to calculate the evolutions of TE waves propagating in the proposed waveguide structures. Based on this general method, the analysis and calculation of planar LHM multilayer slab optical waveguide structure with a localized arbitrary Kerr-type nonlinear guiding film and planar conventional multilayer slab optical waveguide structure with a localized arbitrary Kerr-type nonlinear guiding film can be achieved easily. [ABSTRACT FROM AUTHOR]

In response to the issue of providing a wireless power supply to the magnetic focusing rotor torque and torsion sensors on the rotating shaft systems, loose-coupled transformers (LCTs) are difficult to disassemble and install due to their large size. In addition, their large mass has a significant impact on the dynamic balance of the shaft system. Consequently, in this paper, a structural design of an flexible printed circuit (FPC)-stacked receiving coil is proposed, with its mathematical model, physical model, and simulation model established. The optimal structure is obtained by simulating the coil-induced voltage under different structural parameters through COMSOL electromagnetic simulation. Through modal simulation analysis of the rotor in ANSYS, it is found that the FPC-stacked receiving coil has less impact on the dynamic balance of the rotating shaft system. [ABSTRACT FROM AUTHOR]

This paper proposes an approach for finite element (FE) model updating and response prediction of frame structures based on optimal sensor placement (OSP), which integrates sensor placement optimization, mode expansion, and model updating techniques. Firstly, sensor optimization layout and modal testing analysis are conducted on a bolted laboratory frame structure. The covariance-driven stochastic subspace identification (SSI-COV) method identifies the real-world structure's natural frequencies, modal damping, and mode shapes. Secondly, the complete mode shapes are expanded using the measured incomplete modal data from the limited number of sensors. Thirdly, a multi-objective function based on frequency and mode shapes is established to adjust the parameters of the FE model. This ensures that the updated model accurately represents the dynamic properties of the actual structure within a specific frequency range. Finally, the Rayleigh damping of the frame structure is estimated, and the damping matrix is assembled to enhance the accuracy of dynamic response prediction in the updated model. By comparing the response prediction results of the updated FE model with and without considering the updated damping effects to the measurement data of the real-world structure, it is demonstrated that the proposed method considering updated damping effects can more effectively predict the structural response. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the vibration and response performance of the core component support bracket in the DXZ32/900 oceanic bridge fabrication machine (movable formwork) to provide a foundation for its structural optimization. A finite element model of the support bracket is established, and three analyses are conducted: modal analysis to determine inherent frequencies and vibration modes, harmonic response analysis to evaluate steady-state behavior under sinusoidal loads, and transient dynamic analysis to assess displacement responses to dynamic loads. The frequency distribution indicates that the natural frequencies are densely packed without abrupt jumps, reflecting the complexity of the dynamic performance of the support bracket. Moreover, frequencies below the fourth order exhibit minimal deformation and limited impact on the overall dynamics. Sensitivity analysis is conducted to evaluate the impact of sectional parameter optimization on material efficiency and dynamic performance, ensuring robust design improvements. In summary, the findings reveal key vibration characteristics and response patterns, providing theoretical insights to guide the improvement of the support bracket and ensure the safety and efficiency of the bridge fabrication machine. [ABSTRACT FROM AUTHOR]

The vibration suppression of flexible robotic arms is challenging due to their nonlinear spatiotemporal dynamics. This paper presents a novel physics-informed neural network (PINN)-based input-shaping method for the vibration suppression problem. Through a two-phase training process of a neural network based on a loss function that follows both the physical model constraints and the vibration modal conditions, we identify optimal input-shaping parameters to minimize residual vibration. With the use of powerful computational resources to handle multimode information about the vibration, the PINN-based approach outperforms traditional input-shaping methods in terms of computational efficiency and performance. Extensive simulations are carried out to validate the effectiveness of the method and highlight its potential for complex control tasks in flexible robotic systems. [ABSTRACT FROM AUTHOR]

The simple spring structure, with detachable electrical contacts, is a very suitable solution for many applications, such as electromechanical relays and connectors. However, they are prone to exhibit instantaneous interruption faults under mechanical vibration environments. In this paper, the governing equations of the modal analysis of a beam with cantilever-Hertzian contact boundary conditions are presented. Then, the time domain analysis method and frequency domain analysis method for solving the forced vibration response are described explicitly. Next, the effect of the axial force on the modal frequency of a detailed model sourced from the practical relay is investigated by using commercial ANSYS Workbench 2021R1 software. Afterward, the harmonic response of the beam is numerically solved individually by using the transient analysis model and the harmonic analysis model in ANSYS Workbench 2021R1 software. Then, the influences of the damping coefficient and excited frequency on the contact force response are investigated. The experimental results of transient displacement and contact resistance of the beam structure agree well with the simulation outcomes. It is proven that there is a linear relationship between the stiffness coefficient and the mass coefficient, which are used for characterizing the damping of the structures in the time domain method and frequency domain methods. [ABSTRACT FROM AUTHOR]

This article presents a non-destructive method, based on the response to free vibrations, which can be used with efficiency and reliability to determine the Young's modulus of polymer composite materials reinforced with natural or synthetic fibers. The non-destructive tests are carried out by measuring the frequencies of bending free vibrations of cantilever beams with additional masses. By using inverse methods, the experimental values of elasticity modulus E are assessed and validated by numerical simulation, using the finite element method (FEM). For FEM modeling, the materials are considered linear, homogeneous, isotropic, and viscoelastic. [ABSTRACT FROM AUTHOR]