Search Results (387)

A piezoelectric cantilever with a longitudinal slit splits one bending resonance into two closely spaced peaks. This is attractive for two-frequency sources. However, existing models fit, rather than predict, the resonances. We develop a predictive branched-beam model where the harvester consists of a full-width root splitting into two prongs with independent tip masses. The two resonances are the roots of a closed-form characteristic equation without fitted parameters, the anti-resonance is the transmission zero of the same branched model, and the formulation reduces to the classical cantilever in the no-slit limit. The second (anti-symmetric) mode is weakly tunable and is located near 45 Hz; the inversion leaves the first resonance free and pins the second effectively. It is predictive and inverted to size the tip masses. Three-dimensional finite-element analysis, which tracks 27.2 → 22.3 Hz (against a finite-element 28.9 → 23.5 Hz as the mass doubles) within about 6%, and the prong kinematics, confirm the tip-mass trend. The anti-resonance is called the charge cancellation effect and can be controlled by wiring the electrodes. For a two-line source (25/45 Hz), the design, tuned to the two lines, yields up to about 1.9× the power of a size-matched single-peak beam with two matched lines (1.6× when the second dominates, ≈1× for broadband), with the second peak being intrinsically smaller. A Monte-Carlo study shows a power coefficient of variation of about 72% with manufacturing and damping scatter, the two layer thicknesses accounting for about 83% of the variance, motivating post-fabrication tip-mass trimming. The model is rigorously validated against three-dimensional electromechanical finite-element analysis; experimental validation on a physical prototype is identified as the essential next step. This work transforms the slitted harvester into a designable monolithic dual-frequency device. Full article

The longitudinal seismic response of a high-pier long-span stiff-skeleton arch bridge is spatially asymmetric because unequal pier heights, the fixed–movable bearing arrangement, and arch–pier interaction create nonuniform force transfer paths, even when the installed fluid viscous dampers (FVDs) obey a symmetric velocity-dependent law. This study evaluates that response redistribution and the mitigation achieved by longitudinal FVDs under near-fault motions. A three-dimensional SAP2000 model was established using elastic beam elements for the girder, arch ribs, cap beams, and piers, Plastic (Wen) links for spherical steel damping bearings, foundation springs for pile–soil interaction, and Maxwell-type FVD links. Thirty combinations of damping coefficient and velocity exponent were first screened under an El Centro record scaled to 0.64 g. The selected case (α = 0.3 and C = 2000 kN·${\left(s/m\right)}^{\alpha }$) was then evaluated by paired analyses of models with and without FVDs under 15 records grouped descriptively as short-, medium-, and long-period pulse-like motions and non-pulse motions. Across the paired record set, the mean record-wise reductions were 21.34% for bridge-wide maximum bearing displacement, 27.56% for P2 pier-top displacement, 9.73% for bridge-wide maximum pier-base shear force, and 12.62% for bridge-wide maximum pier-base bending moment. Mean arch rib reductions ranged from 10.00% for axial force to 25.00% for bending moment. Seven of the eight monitored response metrics decreased under all 15 records; arch rib axial force decreased under 14 records and was unchanged under 1. Local force increases nevertheless occurred at several arch-supported piers in the spatial El Centro comparison, demonstrating that global mitigation does not imply spatially symmetric or uniformly beneficial component response. Within the selected record set, the medium-period group produced the largest average demands for several response measures, but this is a sample-specific observation rather than a resonance inference. Removing the extracted velocity pulse component reduced most responses, although the nonlinear original-versus-residual comparison cannot be interpreted as an additive pulse contribution. The paired record set check supports the robustness of the selected FVD case for the investigated sample, but does not establish record-independent optimality. Full article

The damping capabilities of viscoelastic materials depend heavily on the operating temperature. Since these materials are used for passive vibration damping, it is necessary to determine the damping properties of selected materials across a range of temperatures. This paper presents the results of an experimental investigation into the effect of temperature on the damping performance of viscoelastic materials applied to aluminium cantilever beams using free-layer damping (FLD) and constrained-layer damping (CLD) techniques. Butyl rubber and bituminous materials were experimentally tested by modal analysis over a temperature range from 22 °C to −2 °C. Frequency response functions, resonance frequencies, resonance amplitudes, and modal loss factors were determined for selected bending modes. The results show that CLD provides better damping at room temperature, particularly for butyl rubber, due to enhanced shear deformation in the viscoelastic layer. However, as the temperature decreases, material stiffening alters the damping efficiency, and FLD becomes more competitive or superior in several modes. The findings confirm that passive damping effectiveness is strongly dependent on temperature, material type, and vibration mode. Full article

Background/Objectives: Intervertebral disc degeneration (IDD) is a multifactorial spinal degenerative condition influenced by inherited susceptibility and environmental exposures. Genetic evidence from Chinese Han populations remains limited. This study aimed to evaluate GWAS-informed and previously reported candidate single-nucleotide polymorphisms (SNPs) associated with IDD and to explore potential gene–gene and gene–environment interaction patterns. Methods: A hospital-based case–control study was conducted in 1951 unrelated Chinese Han participants, including 929 patients with magnetic resonance imaging-confirmed IDD and 1022 control subjects without evident IDD. Candidate SNPs were genotyped using the MassARRAY platform. Multivariable logistic regression was used to assess genetic associations under different genetic models, and linkage disequilibrium, haplotype associations, additive and multiplicative interactions, and generalized multifactor dimensionality reduction (GMDR) were further evaluated. Results: Of the 60 initially selected candidate SNPs, 49 passed quality control and were retained for association analyses. Several variants showed nominal associations with IDD susceptibility. Representative associations included MMP3 rs591058 under the recessive model (OR = 1.37, 95% CI: 1.06–1.79, p = 0.019) and VDR rs2228570 under the dominant model (OR = 1.52, 95% CI: 1.10–2.11, p = 0.012), whereas the CCDC26 rs6651255–rs7816342 AC haplotype showed a protective association (OR = 0.87, 95% CI: 0.76–0.99, p = 0.046). Exploratory interaction analyses suggested possible gene–gene interactions involving ACAN, IL1B, VDR, CASP3, and CEP162/RIPPLY2, as well as gene–environment interactions involving smoking, weight-bearing workload, and duration of bending work. Conclusions: This study provides preliminary genetic epidemiological evidence that GWAS-informed candidate variants and exploratory interaction patterns may be associated with IDD susceptibility in the Chinese Han population. These findings require further replication and functional validation. Full article

This paper systematically investigates the structural design and numerical characterization of ultra-compact low-loss waveguide bends on lithium niobate-on-insulator (LNOI) thin films via 3D-FDTD simulations. Six 90° bend architectures are analyzed to unravel transmission behaviors and intrinsic loss mechanisms, including three smooth bend optimizations: straight–bend lateral offset, local width tapering, and Euler–circular hybrid curvature modulation, alongside resonant-cavity and corner-mirror L-shaped bends. All structures achieve evident loss reduction within proper parameter windows. At R_eff = 5 μm, optimized smooth bends reach a minimum loss of 0.046 dB/90°, outperforming standard circular bends, while the double-corner-mirror bend exhibits the lowest loss of 0.467 dB/90° among right-angle configurations. Pairwise parametric scans disclose competitive effects among diverse loss-mitigation pathways, demonstrating that simultaneous use of two optimization strategies fails to cut extra loss at equal device dimensions. Broadband and fabrication tolerance simulations verify flat spectral response across the telecom C band; smooth curved bends possess strong robustness against inclined sidewalls, and etch depth acts as the dominant factor governing device loss. This work delivers systematic parametric guidelines for the design and optimization of miniaturized LNOI routing waveguides for photonic interconnects. Full article

Modeling choice is key to modal analysis of rib-reinforced vibration test fixtures; however, systematic criteria for selecting shell or solid finite element (FE) models remain limited. This study proposes a decision framework that translates comparisons between shell and solid models into selection criteria. Five headlamp vibration test fixtures were modeled using shell and solid elements under identical material properties, boundary conditions, bonded contacts, and mounted point mass conditions. Natural frequency differences ranged from 1.81% to 11.21% for the first three modes, averaging 6.52%. The shell models reproduced the overall lower mode deformation trends of the solid models, particularly global bending and torsional modes. The dominant effective mass direction was consistent in most individual mode comparisons. Shell models required fewer nodes and elements, with analysis times of only 3.99% to 11.97% of those for solid models. Shell models are suitable for preliminary and iterative modal assessment, whereas solid models are recommended when the margin for resonance avoidance is small, dominant effective mass directions differ, or the representation of local three-dimensional stiffness is important. These results indicate that the proposed framework provides practical criteria for selecting shell or solid FE models for individual modes according to the analysis objective and design stage. Full article

Despite the aim of meeting the demand for long-term online monitoring of structural cracks in fields such as infrastructure, rail transit, aerospace and others, traditional detection methods fail to realize passive wireless, flexible conformal and non-contact measurement. This paper proposes a flexible wireless passive crack sensor based on resonant rings. Taking polyimide (PI) as the substrate, the sensor integrates a sensitive interdigital resonant ring structure. Variations in crack width disturb the electromagnetic field, which further leads to a resonant frequency shift to realize crack width detection. The sensing mechanism is elaborated based on microwave resonance and equivalent circuit theories. Structural optimization and crack width sensitivity analysis are carried out via electromagnetic simulation. Samples are fabricated by flexible printing technology, and a test platform is established. Experiments reveal that the sensor achieves excellent linearity within the crack width range of 0~2.5 mm, with the resonant frequency decreasing monotonically as crack width increases, and a sensitivity of 67.02 MHz/mm. It can operate stably under varying distances, installation angles and bending conditions, demonstrating outstanding flexible conformability. Featuring no power supply requirement, a chip-free design, a simple structure and strong anti-interference capability, the sensor is suitable for long-term crack monitoring of metal structures. Compared with existing studies, the proposed sensor exhibits prominent advantages in flexible adaptability, wireless passive performance and engineering practicability and can provide a novel wireless passive solution for structural health monitoring. Full article

Prestressed concrete hybrid-reinforced solid square (PCHSS) piles combine strands and rebars for improved ductility. This study presents large-scale shaking table tests (1:2 scale) on PCHSS pile–superstructure systems embedded in soft and stiff clay, subjected to four ground motions with distinct frequency contents. The experimental program systematically captured the evolution of natural frequencies, damping ratios, dynamic earth pressure distributions, bending moment profiles, curvature ductility demands, and post-test cracking patterns. Results reveal that ground stiffness governs the degradation pathway and energy dissipation mode: soft clay exhibited 37.3% frequency degradation (1.33× that in stiff clay), while stiff clay showed a 101% damping increase (>3× soft clay). Long-period ground motions generated maximum curvature ductility demands and peak bending moments 2–3 times those of short-period records under identical PGA, attributed to near-resonance coupling. Pile–soil interaction transitions from compatible deformation to progressive separation with increasing seismic intensity, with gap spacings of 40–53 mm observed in soft clay. Notably, the code-specified 4D reinforcement zone was found insufficient for soft clay foundations, where crack distributions extended to 4D–7D, warranting an extended zone up to 7D. The findings provide experimental benchmarks for numerical model calibration and offer practical guidance for extending hybrid-reinforced precast piles into moderate-to-high-seismicity regions. Full article

Small satellite constellations are becoming increasingly integrated with emerging services such as cloud computing and big data, which imposes strict requirements on compactness, light weight, low-power consumption, and high integration of space mechanisms. Herein, we report a millimeter-scale bar-type piezoelectric ultrasonic motor (USM) operating in the coupled resonant mode of two first-order bending (B₁) vibration modes whose stator has an outer diameter of only 2 mm. Compared with conventional bar-type USMs driven by four excitation sources, the proposed configuration requires only two excitation signals, and the inner electrode does not need to be led out, thereby reducing both power consumption and fabrication difficulty. The dependence of output performance on driving frequency, driving voltage, and mechanical load was then systematically investigated. Specifically, at a voltage of 200 V_pp, the proposed motor achieved an output torque density of 0.85 μNm/mm³, which is more than 30% higher than those of typical reported USMs. Then, eight bar-type motors were integrated into one compact arrayed module as an application demonstration. These results indicate that the proposed miniature USM has excellent comprehensive actuation performance and great potential for precision driving in small satellite systems. Full article

Wearable textile antennas are commonly used in various applications nowadays, such as watches and clothes; however, they are still subjected to degradation in the reflection coefficient and shift in the resonance frequency due to bending or twisting. This study presents a neutral axis-based encapsulation technique to improve the electromagnetic stability of flexible antennas. A 2.45 GHz CPW patch antenna is designed using a polyester substrate, silver conductive layer, and TPU as encapsulation for the encapsulated antenna. By aligning the conductive layer with the neutral axis, the proposed antenna achieved stable resonance characteristics under both convex and concave bending conditions. In contrast, the non-encapsulated antenna exhibited significant resonance degradation under deformation. Comparative analysis further showed that displacing the conductive layer away from the neutral axis increased the maximum resonance frequency shift to 8.38%, whereas the neutral axis aligned configuration maintained a substantially lower shift of only 3.55%. These results validate the effectiveness of neutral axis engineering for enhancing the deformation resilience of flexible wearable antennas. Full article

To address the severe threats posed by stay cable fractures, this study investigates a fatigue fracture of a fork-eye anchor head induced by excessive cable vibrations on a landscape cable-stayed bridge. A comprehensive methodology integrating field monitoring, theoretical analysis, and finite element simulation is employed to reveal the vibration characteristics, fatigue mechanism, and multi-factor coupled effects. Field tests identify wind-induced vibration and parametric resonance as the primary external triggers for fatigue damage. A simplified mechanical model of the fork-eye anchor head is established to evaluate the stress state under combined axial tension and bending moment. Fatigue analysis using the stress–life method elucidates how vibration-induced alternating stress significantly reduces the fatigue life of the connecting screw. The multi-factor coupled fracture mechanism is revealed, and practical mitigation measures including supplementary dampers and regular inspection are proposed. The findings provide a theoretical basis and engineering guidance for the design, maintenance, and safety assessment of similar landscape cable-stayed bridges. Full article

This study proposes a surrogate-assisted framework to characterize system-level equivalent stiffness parameters of composite resilient floor subsystems from global resonance features, calibrated and assessed for consistency using actual building acoustic tests. Since intrinsic material characterization alone may not fully capture the contribution of resilient layers under complex in situ boundary conditions, a parametric finite element model utilizing a transversely isotropic formulation with five independent stiffness-related parameters is coupled with Gaussian Process surrogates and a genetic algorithm. Repeated laboratory impact tests provide empirical bending and torsion resonance targets near 60 Hz and 155–160 Hz. The trained surrogates predict these targets with a root mean square error (RMSE) below 0.02, enabling the inverse estimation to identify representative parameter sets within a ±5% tolerance. The optimization yields a finite admissible parameter region, reflecting the inherent non-uniqueness of the inverse problem. To establish framework consistency, the identified equivalent parameters are integrated into a hybrid vibro-acoustic scheme and assessed for consistency against sound pressure level measurements from real-world building tests. Crucially, the sensitivity analysis indicates a mechanical divergence: in-plane stiffness primarily governs resonance-frequency reproduction, whereas out-of-plane stiffness is more influential in the noise-related structural wall-response-energy assessment within the admissible solution region. This behavioral mismatch demonstrates resonance matching alone is insufficient for design prioritization. The proposed framework establishes a configuration-level tool to systematically evaluate structural improvement directions without direct intrinsic material testing. Full article

To resolve the fatigue fracture occurring at the tip trailing edge of thin-walled single-crystal turbine rotor blades for a specific aero-engine, this paper derives the relationship between the single-crystal constitutive stiffness matrix and crystal orientation, and clarifies the influence mechanism of crystal orientation on blade-vibration characteristics. The influence rules and degrees of uncertain parameters on the vibration characteristics of thin-walled and thickened-profile blades are comparatively investigated. The results reveal that blade dynamic frequency is strongly affected by both blade profile thickness and crystal orientation, and blade profile optimization can effectively weaken the effects of crystal orientation and blade thickness on the dynamic frequency of critical modes. Based on the above results, the hazardous resonance overlooked in conventional engineering approaches is detected using uncertainty-based vibration analysis. The corresponding failure mechanism is illustrated, the resonant speed range is determined, and the risk of bending–torsion coupled flutter is detected. The outcomes provide valuable guidance for the frequency tuning design of turbine blades. Full article

Piezoelectric cantilever beams are among the most popular vibration energy harvesting devices. Maximization of the spatial distribution of axial strain along this beam (objective function) increases harvesting efficiency. In vibro-impact systems, mechanical contact can excite higher-order vibration modes, making the second eigenfrequency particularly relevant for energy harvesting under such nonlinear operating conditions. Therefore, the harvester geometry should be designed to maximize the harvested energy associated with this mode. In many practical applications, cantilever-based harvesters are subjected to complex and broadband excitation conditions, where multiple vibration modes, including the second eigenfrequency, contribute to the overall response. Therefore, optimization at the second eigenfrequency is essential for improving energy harvesting performance under realistic operating conditions. In this study, to maximize axial strain, a thickness shape optimal design is proposed, and a finite element-based optimization scheme is constructed to maximize harvesting efficiency. Optimization is performed subject to a fixed second eigenfrequency of the cantilever beam, using the eigenmode equation as the state equation in the optimization procedure. The optimized shape for maximal strain integral at the second bending resonance is determined. Experimental results validate the findings of the optimization, showing an increase in strain for the optimized-shaped beam compared to a uniform-thickness beam with the same eigenfrequency. It should be noted that experimental validation is subject to certain limitations, including manufacturing precision and environmental influences. The manufacturing of specimens can only be achieved within a limited precision, resulting in deviations from the ideal optimized geometry. Additionally, the experimental environment may influence the measured response, and simplified boundary conditions can introduce discrepancies between numerical and experimental results. Full article

The first approximation ($N=1$) of a three-dimensional micropolar elastic prismatic body in moments of displacement and rotation, obtained via Legendre polynomial expansion, is applied to two related problems: field reconstruction and damage identification. In the first problem, two- and three-dimensional field distributions are reconstructed for a simply supported square prismatic body under three loading configurations, with first-order moment loading as the primary case. Two distinct resonances are identified within the $N=1$ framework. At the material cutoff ${\omega }_c=\sqrt{4\alpha /J}$, micro-rotation amplitudes are amplified while translational amplitudes are suppressed (displacement locking). At the geometric cutoff ${\omega }_{\mathrm{geo}}\propto h^{-1}$, the bending mode is resonantly excited while micro-rotation remains near its quasi-static level. In the second problem, a scalar damage model ${\alpha }_{\mathrm{eff}}=\alpha (1-D)$ is introduced. The material cutoff follows ${\omega }_c\left(D\right)={\stackrel{o}{\omega }}_c\sqrt{1-D}$, confirmed numerically for all four decoupled subsystems and different prismatic body thicknesses. Geometric branches remain insensitive to damage, producing a spectral separation that may serve as a damage indicator. A critical thickness $h^{*}$ is identified where ${\omega }_{\mathrm{geo}}={\stackrel{o}{\omega }}_c$, leading to role reversal between material and geometric branches. Numerical results are presented for the polyurethane foam of Lakes. Full article