Search Results (1,316)

This study examines the potential of sustainable, biobased paper-based structures as panel/membrane sound absorbers. Although intact paper is naturally impermeable and a poor sound absorber, transforming it into complex three-dimensional origami geometries, specifically the Miura-ori pattern, could produce effective panel/membrane absorbers. Three distinct Miura-ori samples (A, B, and C) were fabricated with increasing geometric complexity, ranging from a simple triangular prism to a complex labyrinthine waveguide. The random incidence sound absorption coefficients of these samples were measured in a validated small-scale reverberation room. The underlying absorption mechanisms were further investigated through modal analysis and non-contact vibration velocity measurements. The results indicate that increased geometric complexity enhances acoustic performance. Sample C, the most complex structure, demonstrated the most consistent broadband absorption. The analysis confirmed a significant positive correlation between acoustic pressure modes, surface vibration velocity, and sound absorption peaks, indicating that acoustic energy dissipation is driven by the vibrational response of the paper membrane coupled with resonant modes in the air gap. This research demonstrates that tunable origami folding techniques using intact paper can be used to design lightweight acoustic treatments for diffuse sound fields in the mid-frequency range. Full article

This study experimentally investigates the aerodynamic mechanisms and dynamic responses of slender high-rise buildings subjected to oblique-downstream interference effects. Using a simulated open-terrain atmospheric boundary layer, a square prismatic principal building (aspect ratio 8.0) was evaluated alongside an identical interfering building. High-frequency force balance and aeroelastic vibration tests were conducted across four Scruton numbers ($S_{cr}$). Aerodynamic damping was quantified using the random decrement technique and a trial-and-error approximation. Results show pronounced resonant amplification under strict conditions. Specifically, at a low $S_{cr}$ (1.12), a reduced velocity ($U_r$) of 5.5, and an interference location of $\left(x/B,y/B\right)=\left(-1.5, 1.5\right)$, the principal building exhibits an inclined elliptical trajectory, driven by a negative aerodynamic damping effect of approximately −2%. Higher $S_{cr}$ values attenuate displacement, but rooftop acceleration amplifications persist, reaching an interference factor of 2.0. Ultimately, the synchronized rhythmic channeling required to excite the principal building necessitates a minimum wake width from the interfering structure (breadth-to-depth ratio > 0.5), highlighting critical aeroelastic instabilities in dense high-rise clusters. Full article

Infrared radiation spectra produced by vibration–rotation transitions in multicomponent gases within the vacuum plume of attitude and orbital control engines constitute crucial radiation sources for optical target identification and space maneuver recognition, and rapid prediction of these signatures is essential for real-time forecasting. This study introduces an axisymmetric vacuum plume flow field model based on a simplified point-source approach that accommodates multicomponent combustion gases. Using the Maxwellian velocity distribution and a velocity–position angle algorithm, normalized number density, velocity, and temperature distributions are derived. A plume–freestream interaction model founded on noncentral fully elastic collision theory is incorporated, and overall plume properties are obtained via density-weighted averaging. Neglecting non-equilibrium radiation effects, the high-temperature gas absorption coefficient is calculated using a statistical narrowband model and radiative transfer is solved via the line-of-sight method. The model is validated against direct simulation Monte Carlo results for single-gas and MBB bipropellant plumes and confirmed using infrared spectral data in the 2.0–4.5 μm band. The proposed framework achieves 10²–10³-fold higher computational efficiency than conventional DSMC approaches. Freestream effects on plume diffusion and momentum exchange diminish with increasing altitude, as does the freestream velocity’s enhancement of radiation intensity, whereas greater plume expansion at higher altitudes increases overall radiation intensity. Full article

Hydraulic oscillator tools (HOTs) are effective solutions for mitigating excessive drag encountered during sliding drilling in horizontal wells. However, their field performance remains unpredictable due to theoretical limitations in modeling nonlinear friction behavior under axial vibration. To address this gap, a series of friction tests was conducted on sandstone–steel pairs under water-based mud lubrication. Experimental results demonstrate that steady-state sliding friction follows the velocity-dependent Dieterich–Ruina model, while vibration–sliding coupled friction is accurately described by the Dahl model. Integrating these findings, a comprehensive drillstring dynamic model was developed. The model was solved using an explicit central difference method and validated against field hook load data from Well XX-1, with prediction errors below 9%. Parametric studies further quantified HOT performance, revealing that excitation force amplitude and HOT placement significantly impact drag reduction, whereas vibration frequency exerts a relatively modest influence. Meanwhile, the effective propagation distance induced by the hydraulic oscillator is relatively limited, resulting in a drag reduction rate of no more than 30% even under optimal parameter conditions. This work establishes a validated theoretical framework for optimizing hydraulic oscillator parameters in horizontal drilling. Full article

This paper presents a fully automated platform for real-time monitoring of fatigue-induced microstructural changes in metallic materials, using Rayleigh surface waves and Laser Doppler Vibrometry (LDV). The system integrates ultrasonic excitation, non-contact optical sensing, and high-speed signal processing in a unified LabVIEW environment. Rayleigh waves are generated via a contact transducer, while LDV captures surface vibrations with sub-nanometric velocity resolution, ensuring repeatability and eliminating coupling variability. The software automates synchronization, deterministic data acquisition, filtering, FFT analysis, and extraction of nonlinear coefficients (β₂, β₃) at high execution rates without the need for post-processing. Experimental validation under cyclic loading revealed a clear sensitivity hierarchy: the Rayleigh wave velocity remained invariant, the acoustic attenuation responded gradually, while the nonlinear parameters exhibited the earliest and steepest response to fatigue damage, confirming their superiority as early-stage indicators. The system offers low-latency timing, long-term stability, and modular design, establishing a robust data-streaming foundation that can support future integration with digital twin frameworks and machine learning models. Furthermore, the acoustic findings were successfully cross-validated using Infrared Thermography, which confirmed the critical damage transition phase. This work bridges nonlinear acoustics and software automation, providing a scalable diagnostic solution for predictive maintenance within structural health monitoring systems. Full article

The vibronic spectra of the first excited singlet state (S₁) and the cation spectra of the ground state of the cation (D₀) of jet-cooled cyclopropylbenzene (CPB) were investigated using resonance-enhanced multiphoton ionization (REMPI) and photoelectron velocity-map imaging techniques, respectively. The vibronic spectra indicated the existence of only the bisected conformer, a finding corroborated by quantum chemical calculations. The S₀ → S₁ electronic transition originated at 36,858.5 cm⁻¹, with an adiabatic ionization energy of 66,846 ± 15 cm⁻¹. Vibrational levels in both states were assigned with the assistance of theoretical geometry optimization and frequency calculations. These experimental spectra and theoretical calculations provided valuable insights into the structural and vibrational characteristics of CPB in its excited and cationic states. Full article

Vanadium borate (V₃BO₆) has recently been synthesized and identified as a promising material for use in energy storage applications, particularly as a potential anode for lithium-ion batteries. However, despite previous studies highlighting its electrochemical performance, a comprehensive understanding of its intrinsic mechanical, thermal, and vibrational properties remains limited. The compound crystallizes in an orthorhombic phase with the Pnma (No. 62) space group. To explore its intrinsic physical characteristics, full geometry optimization of the unit cell and atomic positions was performed using density functional theory (DFT) within the CASTEP framework. The Perdew–Burke–Ernzerhof (PBE) functional under the generalized gradient approximation (GGA) was used to model exchange–correlation effects. A plane-wave cut-off of 408 eV and a 6 × 6 × 13 Monkhorst–Pack grid were employed to ensure numerical convergence. The optimized lattice constants (a = 9.9025 Å, b = 8.4751 Å and c = 4.5354 Å) are highly consistent with experimental data, which confirms the reliability of the computational approach adopted. The elastic behaviour was further investigated using the first-principles strain-energy method, yielding nine independent elastic constants consistent with orthorhombic symmetry. The calculated bulk and shear moduli, along with the anisotropy parameters, suggest that V₃BO₆ has a favourable balance of mechanical robustness and moderate ductility. A Vickers hardness of 10.95 GPa and a B/G ratio of approximately 1.93 corroborate these findings. Additional parameters, such as Poisson’s ratio, Debye temperature and average sound velocities, were derived to gain deeper insight into the material’s thermomechanical performance. These results provide a solid theoretical foundation for understanding the mechanical stability and potential anode suitability of V₃BO₆ in lithium-ion battery systems. Full article

This paper presents the application of a structural finite element model (FEM) of a light patrol aircraft for numerical flutter analysis. The thin-walled structure was developed using 2D shells and additional 1D beam elements. The virtual structure was supplemented with additional point elements imitating lumped masses of non-structural on-board components. The model was subjected to validation for qualities such as the mass distribution, its CG location, the structural stiffness of its airframe units, and the similarity of natural modes. The comparative analyses showed satisfactory consistency of the mass and stiffness properties of the FEM with the actual aircraft. Numerical flutter analysis was then performed with the MD Nastran for an integrated aeroelastic model consisting of the FEM and the simplified aerodynamic model. The critical velocities of basic flutter modes were determined. Using simplified kinematic models of flight control systems built into the FEM, an analysis of the sensitivity of control surface flutter due to the pilot’s influence was carried out. The stick grip and the support of control pedals with the pilot’s legs cause specific conditions related to the imposition of additional stiffness and mass on the control manipulators. These conditions directly affect the natural frequencies of control surface modes, which translates into a change in the critical flutter speed of the tail. For the established range of changes in stiffness and mass added to the stick and pedals, a series of analyses of natural vibrations and flutter were carried out. The influence of the change in the support conditions of control manipulators was illustrated in graphs. Full article

Cracks in concrete structures significantly affect structural safety, durability, and serviceability. To address key limitations of conventional concrete defect detection techniques, this study proposes a new crack localization method based on the AE signal attenuation characteristics. In a laboratory environment, multiple sets of concrete columns are prepared, and a controlled excitation method is used to generate vibration sources. A series of AE sensors are arranged to monitor and analyze the propagation and attenuation characteristics of vibration signals in the concrete medium in real time. The research results indicate that by analyzing the maximum amplitude attenuation characteristics of signals collected by four sensors, this method can effectively determine the approximate location of cracks on the concrete surface, providing a reliable basis for the preliminary identification of cracks. This method differs from the conventional detection concept centered on “wave velocity changes” and does not require large detection equipment. It is suitable for rapid non-destructive testing of concrete beams and columns on site. This technical approach has not yet been widely reported in existing research. This provides a new technical reference for the detection of cracks in concrete structures and adds promising solutions to the field of non-destructive test. Full article

This paper numerically investigates the flow past two circular cylinders of equal diameter arranged in tandem with respect to the incident flow. The upstream cylinder is fixed, and the downstream cylinder is located within the wake interference region for a streamwise center-to-center spacing of L = 5D (D is the cylinder diameter). The downstream cylinder is forced to vibrate transversely in the wake of the upstream cylinder to investigate a regime of wake-induced vibration ($WIV$) at a Reynolds number of $Re=65,000$. The non-dimensional vibration amplitude is fixed at $A/D=0.15$, and the reduced velocity is set to $V_R=5$. The literature has reported that $WIV$ is a phenomenon resulting from the interaction between the incoming wake and the downstream flexible structure, in which the downstream cylinder vibrates significantly over a wide velocity range, and the cross-flow fluid force is not in phase with the body’s motion. The phenomenon of $WIV$ appears combined with a resonant regime, in which the downstream cylinder vibrates at the resonant velocity similar to the vortex-induced vibration ($VIV$) of a single cylinder. The results show that the individual resonant regime is captured for both surfaces without roughness effects. The main contribution of this paper is to demonstrate that the roughness effect variation of the downstream cylinder surface desynchronizes the $WIV$ regime and simultaneously promotes synchronization through the emergence of harmonic frequencies, indicating competition between $VIV$ and $WIV$. Full article

Blasting-induced ground vibrations, typically quantified by peak particle velocity (PPV), pose one of the most critical environmental challenges in surface mining and can damage nearby structures and disrupt surrounding ecosystems. Consequently, the development of reliable and accurate predictive models is essential for designing safe, environmentally responsible, and sustainable blasting operations. This study develops a robust predictive framework using a harmonized database of 506 blasting events, from which 386 high-quality records were retained after preprocessing to model PPV as a function of charge per delay (Q), monitoring distance (R), and rock mass rating (RMR). Several machine learning (ML) algorithms, including artificial neural networks trained using the Levenberg–Marquardt algorithm (ANN-LM), adaptive neuro-fuzzy inference systems (ANFIS), Gaussian process regression (GPR), and decision trees (DT), were evaluated alongside conventional empirical models such as the USBM, Ambraseys–Hendron, Langefors–Kihlstrom, and BIS. To further enhance predictive capability, two optimization strategies, Bayesian optimization (BO) and differential evolution (DE), were applied to the GPR model, producing optimized BO-GPR and DE-GPR variants. Model performance was assessed using the correlation coefficient (r), variance accounted for (VAF), mean absolute error (MAE), and relative root mean square error (RRMSE). Results indicate that the BO-GPR model achieved the best predictive performance during testing for both the two-input (Q, R) and three-input (Q, R, RMR) configurations, with r values of 0.97426 and 0.98381, respectively, and VAF values exceeding 94%. SHAP analysis revealed monitoring distance as the dominant attenuating factor controlling PPV. The optimized framework provides an accurate, interpretable tool for vibration prediction and precision blast design, supporting environmentally responsible, sustainable mining operations. Full article

To address the complexities inherent in evaluating electric motorcycle ride comfort across diverse road profiles and operating speeds, this study establishes a systematic evaluation framework utilizing a multi-level fuzzy comprehensive assessment approach. Empirical investigations were conducted on asphalt, Belgian block, and speed-bump terrains at varying velocities. Triaxial acceleration data were acquired from the seat, footrest, and handlebar interfaces to compute weighted Root Mean Square (RMS) acceleration, Vibration Dose Value (VDV), and Power Spectral Density (PSD). By synthesizing subjective ratings, a correlation between tactile perception and objective metrics was derived to calibrate the two-level fuzzy model. Analysis reveals that vibration energy is predominantly concentrated in the vertical low-frequency domain (0–20 Hz) independent of test conditions. Notably, a 50% increase in velocity precipitated a 22.4% decrement in the comprehensive ride comfort index, degrading the classification from “Moderate” to “Fair.” The proposed framework provides a rigorous quantitative paradigm for vibration mitigation strategies and informed speed management in electric vehicle engineering. Full article

BACKGROUND: Overhead athletes are at increased risk of shoulder dysfunction due to repetitive, high-velocity movements that can disrupt scapular muscle activation patterns. Whole-body vibration (WBV) has been proposed as a training modality to enhance neuromuscular activation, but its effects on scapular muscle activity and activation timing remain unclear. METHODS: This randomized controlled trial investigated the effects of WBV-assisted push-up training on scapular muscle activation and onset latency in university-level overhead athletes. Forty participants were randomly assigned to a WBV group or a control group performing identical push-up exercises without vibration for four weeks. Surface electromyography was used to assess normalized muscle activation (%MVIC) and activation latency of the upper trapezius (UT), serratus anterior (SA), and lower trapezius (LT) before and after the intervention. A 2 × 2 mixed-model ANOVA was applied for statistical analysis. RESULTS: Significant time × group interactions were found for muscle activation in LT and SA (p < 0.01). The WBV group demonstrated substantially greater increases in activations in these muscles compared with the control group, with the largest improvements observed in the serratus anterior. No statistically significant between-group differences were identified for muscle onset latency (p > 0.05). CONCLUSIONS: Adding WBV to push-up training significantly enhances key scapular muscle activation in overhead athletes but does not significantly affect muscle onset latency. WBV-assisted push-ups may act as a practical, low-load strategy to improve scapular muscle recruitment and potentially reduce the risk of sports-related shoulder injuries and pain in overhead athletes. Full article

Therapeutic interventions within the urinary system are often limited by the complex and tortuous anatomy of the renal pelvis and ureters, restricting access to deep regions and increasing the risk of mucosal trauma. In this study, we present a multifunctional, magnetically controlled ferrofluid droplet robotic platform engineered for high deformability and precision navigation. A custom electromagnetic actuation system was developed and optimized via COMSOL Multiphysics (version 6.3, COMSOL Inc., Stockholm, Sweden) simulations to generate programmable magnetic fields. Experimental validation in both simplified environments and anatomically realistic 3D-printed urinary tract models demonstrated the droplets’ capacity for controlled locomotion, reversible deformation, and traversing constrictions significantly smaller than their resting diameter. The droplets’ locomotion and extreme deformability are governed by the dynamic balance between the applied magnetic gradient forces, the restoring interfacial tension of the ferrofluid, and the fluidic viscous drag. Quantitatively, the droplets achieved robust translational velocities up to 260 mm/s under single-coil actuation (51 mT, 20 Hz) and 108 mm/s under a more stable dual-coil configuration (51 mT, 8.3 Hz). Furthermore, two clinically relevant functionalities were successfully executed: rapid vibration-induced release of encapsulated dye for targeted drug delivery, and the precise mechanical capture and transport of artificial kidney stones. These results establish a highly versatile platform for minimally invasive urological procedures, highlighting the immense potential of soft magnetic microrobotics for integrated therapeutic applications. Full article

To monitor online the operational condition and quality of a desktop fused deposition modeling (FDM) printer, the dynamics of vibro-acoustics must be accurately understood. In this paper, an electromechanical coupling (EMT) framework is established to relate the dynamics of stepper actuation, the transmission chain, and machine motion, deriving a steady-state frequency–velocity mapping for steady or near steady printing segments. The mapping is evaluated by numerical calculation to obtain a theoretical drive frequency for different toolpath directions and commanded printing velocities. Validation is performed on the experiment platform I. Drive-side vibration is measured by an accelerometer mounted on the x-axis beam near the motor end. An acoustic channel is recorded as an auxiliary qualitative cross-check rather than for quantitative error evaluation. For steady printing segments, the dominant frequency in drive-side vibration is compared with the theoretical drive frequency. In the tested steady segments and toolpath directions, the relative error remained below 3%. In a further case study, the G-code is modified to introduce two constant printing velocity segments (40 mm/s and 80 mm/s) within the same continuous record, enabling a direct comparison of dominant frequencies between two steady segments. The results show that, under open-loop stepper drive and within the steady/near steady scope adopted here, a drive-related dominant frequency can be observed stably in the x-axis beam vibration response and matches the theoretical drive frequency. When the commanded constant printing velocity is doubled, the dominant frequency in drive-side vibration in the corresponding steady segment changes by approximately a proportional factor. This study provides a verifiable drive referenced frequency–velocity mapping for steady segments under the tested configuration and a traceable frequency reference for steady segment comparisons within the same print record in subsequent case studies. Full article