Search Results (945)

Large stadiums commonly employ long-span spatial steel roof systems and require efficient non-contact monitoring. This study presents a millimeter-wave-radar-based detection and safety assessment method for a large in-service stadium roof. Ambient vibration tests were conducted on a representative steel truss using millimeter-wave radar and co-located accelerometers, and the modal frequencies and mode shapes were identified using peak picking and stochastic subspace identification. An undamaged finite-element model was established to interpret the measured modal information and simulate local stiffness-reduction scenarios. The first four vertical frequencies identified by radar were 3.32, 7.03, 10.35, and 13.18 Hz, compared with 3.32, 7.03, 10.35, and 13.48 Hz obtained from the accelerometers. The first three frequencies were identical at the reported precision, and the fourth-frequency difference was approximately 2.2%. Numerical results showed that the modal-curvature-based Safety Indicator was sensitive to local stiffness degradation and could indicate approximate abnormal regions. No pronounced localized modal anomaly was observed in the field-tested truss, consistent with the on-site inspection. The study demonstrates an integrated workflow combining non-contact radar measurement, operational modal identification, finite-element-supported interpretation, and preliminary condition assessment for large stadium roofs. Full article

Subsurface faults in sediment-covered basins often lack clear surface expressions, necessitating integrated geophysical reconnaissance to identify structural complexities. The eastern margin of the Sofia Basin contains normal faults, with the geometry and activity of unmapped structures near Lozen Mountain being poorly understood. This study examines a presumed subsurface discontinuity using a ~216.2 m passive seismic profile across the Lozen Fault zone. Ambient vibrations from twelve point stations and a fixed reference station were analyzed to map structural anisotropy and wavefield variations using relative vertical-component spectral amplitudes, polarization parameters, and horizontal-to-vertical (H/V) spectral ratios. The spectral amplitude profiling revealed a significant lateral contrast of 6.21 dB across a depth interval of 0–140 m (p = 0.0043), suggesting a potential fault boundary. A two-level step model identified a horizontal transition at 109.0 m, with analyses indicating a zonal wavefield response. Southern stations recorded a more stable polarization axis (mean direction 37.32°) compared to the dispersed northern records (mean direction 60.43°, p = 0.097), while directional shifts in H/V distributions were significant (p = 0.0022). While these observations provide a clear structural indicator rather than direct proof of faulting, they effectively demonstrate that non-tectonic lithological and hydrological variations generate these identical spectral signatures. The results establish a well-constrained spatial target for future multi-profile surveys, electrical resistivity tomography, active-source seismic imaging, and paleoseismological trenches required to conclusively verify the geometry, age, and present-day activity of the fault structure. Full article

Large integrated station–bridge buildings combine track-bearing members, station floors, transfer structures, columns, and urban-rail facilities within a single coupled structural system. For such buildings, refined train–track–station dynamic simulations can reproduce train-induced vibration, but repeated time-history analysis remains costly when many operating conditions must be screened. This study develops a simulation-based response-database framework for multi-horizon forecasting of front-end carbody vertical acceleration (FCVA), defined here as the vertical acceleration at the front-end floor evaluation point of the leading carbody, in the integrated station–bridge building of Yichang North Railway Station. The project-specific database contains 700 operating cases constructed from 100 Latin-hypercube-sampled combinations of a dimensionless track-spectrum amplitude multiplier (TSA), structural damping ratio (DR), and track-spectrum initial moving position (TSIP), each evaluated at seven train speeds. With a sampling interval of 0.002 s, supervised samples were constructed using a 200-point historical window, and prediction horizons from 20 to 300 steps (0.04–0.60 s) were evaluated under a case-level split. Classical regression, tree ensembles, a multilayer perceptron, recurrent networks, a temporal convolutional network, and a Transformer were compared after automated hyperparameter selection. For the 20-step task, Extra Trees achieved the best performance, with a root mean squared error (RMSE) of 0.00336 m/s² and $R^2$ = 0.9958. In the independently refitted reference-fixed horizon experiment, Extra Trees retained $R^2$ = 0.9526 at the 300-step horizon, while the temporal convolutional network (TCN) RMSE increased from 0.00394 to 0.01502 m/s². The results show that the response database preserves exploitable short- to medium-range dynamic continuity, although phase drift and peak-timing uncertainty increase as the forecast horizon becomes longer. Parameter analysis indicates that train speed dominates both response energy and forecast error, whereas TSA mainly affects amplitude-related response metrics. On a common central processing unit (CPU) platform, the saved Extra Trees model processed 10,000 held-out windows in $0.1404\pm 0.0008$ s. The proposed method provides a computationally efficient response-screening and post-processing layer for design-stage assessment and operating-scenario comparison within the modeled parameter domain, complementing rather than replacing refined dynamic simulation and field validation. Full article

Autonomous acoustic sensing systems are increasingly investigated for unmanned aerial vehicle (UAV)-based surveillance and environmental monitoring applications due to their passive operation and relatively low computational requirements. However, the integration of acoustic classification and direction-of-arrival estimation on UAV-mounted microphone arrays remains challenging, particularly because realistic flight conditions introduce propulsion noise, aerodynamic flow, vibration, and complex acoustic interference. This paper presents a static ground validation of an AI-assisted acoustic target detection and azimuth estimation framework integrated on a flying-wing vertical take-off and landing (VTOL) UAV equipped with a distributed microphone array. The proposed system combines MFCC-based chainsaw sound classification using a Random Forest model with amplitude-based and SRP-PHAT-based azimuth estimation. Four HiFiBerry measurement microphones were mounted on a 4 m wingspan flying-wing VTOL UAV and connected to a Raspberry Pi 5 processing unit. Experimental validation was conducted under controlled indoor laboratory conditions using loudspeaker playback, with the UAV propulsion system inactive and only the acoustic acquisition and processing subsystem powered. The tests included single-source angular measurements, simultaneous multi-source acoustic scenarios, and source height variation. The SRP-PHAT method achieved a mean angular error of 3.55° in the single-source tests and 4.81° in the multiple-source tests, outperforming the amplitude-based baseline. The results support the feasibility of the proposed acoustic-processing framework under static ground conditions. However, because propulsion noise and in-flight aerodynamic effects were not included in the present validation, future work must address simulated propulsion noise injection, propulsion-on static testing, outdoor validation with real chainsaw sources, and eventual in-flight experiments. Because propulsion noise, aerodynamic flow, and in-flight vibration were not included in the present experimental campaign, the results should be interpreted as baseline static ground validation results rather than evidence of in-flight robustness. Full article

For the problem that, under the soybean-maize strip intercropping pattern, the installation of anti-drift shields changes the mass and inertia characteristics of the boom of a shielded sprayer, making it prone to severe vibration under complex field excitations and thereby affecting application uniformity and operational safety, a semi-active boom vibration damping system based on a magnetorheological damper was designed and tested. First, an equivalent mechanical model of the boom considering added mass and stiffness variation was established, and the characteristics of excitation sources such as road spectra and start-stop impacts were clarified. Second, based on the Bouc–Wen model, the magnetorheological damper was selected and its output force boundaries were designed. The stroke was determined to be 80–110 mm, and the maximum damping forces in the compression and rebound strokes were 1.15 kN and 3.44 kN, respectively. Furthermore, a semi-active vibration damping system with an LK3U-14MT PLC as the core controller was developed. Finally, simulation analysis, free-vibration decay tests, obstacle-crossing tests, and field operation tests were conducted to verify the vibration damping performance of the developed semi-active system. The field test results showed that, at typical operating speeds of 3–5 km/h, the semi-active vibration damping system reduced the maximum vertical amplitude at the boom tip by 28.6–43.1% and the maximum inclination angle by 12.2–55.6%, effectively improving the attitude stability and roll resistance of the boom of the shielded sprayer. Full article

Roll motion induced by steering maneuvers and vertical vibration excited by road unevenness are strongly coupled in active suspension vehicles. Neglecting this coupling may deteriorate the performance of coordinated chassis control and compromise both roll stability and ride comfort. To improve roll stability and ride comfort under combined steering and road excitation conditions, this paper develops a roll–vertical coupled control framework. First, a nine-degree-of-freedom roll–vertical coupled vehicle model is established by integrating lateral–yaw dynamics, sprung mass heave motion, roll and pitch motion, and four unsprung mass vertical dynamics. Second, an adaptive square root cubature Kalman filter (ASRCKF) is designed to estimate key roll states, including the roll angle and roll rate. The square root structure improves numerical stability, while the Sage–Husa adaptive estimator updates the measurement noise covariance online using the innovation sequence. Third, a load transfer ratio-based rollover risk assessment method and a model predictive control (MPC)-based active suspension controller are introduced to realize coordinated roll–vertical control. Finally, the proposed framework is validated using a MATLAB/Simulink–CarSim co-simulation platform. The results demonstrate that the proposed method effectively improves vehicle roll stability and vertical ride performance under complex driving conditions. Full article

To address the challenges in understanding the raceway failure mechanisms of bearings under dynamic radial excitations, this study proposes a vibration evolution analysis method based on multi-source data fusion and a Granger causality test. Firstly, a vertical bearing vibration test bench that can simulate the dynamic excitation in engineering practice is built, and the bearing acceleration, inner ring displacement and cage data are collected at the same time. Subsequently, the evolution law and correlation relationship of bearing vibration signals during the expansion process of bearing raceway damage were studied. Based on this, a multi-source vibration data fusion method was proposed, and the effectiveness of different data fusion schemes in characterizing raceway damage expansion was compared. Finally, the Granger causality test was applied to analyze the causal relationship between the evolution of various vibration behaviors during the damage propagation process. Research results demonstrate that under complex loading conditions during sustained operation, the “False Brinelling” indentation gradually develops into raceway surface damage. The vibration behavior of bearings exhibits distinct stage-specific characteristics under dynamic radial excitations. Notably, variations in vibration behavior amplitude and transition timing between different operational phases demonstrate significant discrepancies. Significant alterations in causal relationships between vibration behaviors were observed throughout different degradation phases. The combined approach proposed in this paper, encompassing complex load simulation, multi-source data fusion, and causal analysis, offers a new understanding of the raceway failure mechanism of bearings under real-world operating conditions. Full article

Long-span cable-stayed bridges undergo substantial changes in mass distribution, boundary conditions, cable forces, and load paths during erection, yet their stage-dependent free-vibration characteristics are less documented than those of completed bridges. This study establishes a refined finite element (FE) model of the Liulu Yongjiang Extra-large Bridge and evaluates the frequency evolution over 26 construction stages. Detailed modal interpretations are provided for the maximum double-cantilever, maximum single-cantilever, and completed-bridge configurations. The subspace iteration eigensolver is used for modal extraction, and ambient-vibration measurements at the three representative stages provide an independent frequency check. The calculated fundamental frequencies are 0.399, 0.417, and 0.436 Hz for the three configurations, respectively. The governing mode changes from antisymmetric vertical girder bending at the maximum double-cantilever stage to lateral girder bending at the maximum single-cantilever and completed-bridge stages. Across CS1-CS26, cantilever extension generally reduces the governing frequency, cable installation produces a diminishing vertical-stiffening effect, and the modeled 390 t form-traveler mass lowers both lateral and vertical frequencies. Field tests indicate that the measured frequencies at three stages deviate less than 9.6% from the FE values, confirming the reliability of the model. The revealed evolution laws and influencing mechanisms of dynamic characteristics during construction provide theoretical support for vibration control and safety assurance of similar bridges. Full article

Vertical Roller Mills (VRMs) are extensively used in the cement industry for their high energy efficiency. Nonetheless, the start-up phase remains a critical operational challenge due to its pronounced sensitivity to changing process conditions. Such variations frequently induce excessive vibrations, which can trigger unplanned shutdowns, mechanical damage, and diminished throughput. The underlying cause lies in the intrinsic variability of raw materials, particularly in parameters such as moisture, particle size distribution, and hardness, which exert a direct influence on the mill’s dynamic response during the transition to steady-state operation. This study presents the real-world implementation of an Expert System designed to automate the start-up sequence. By applying logical reasoning to key process setpoints, the system enables a controlled and gradual ramp-up, minimizing transient instabilities. Seamlessly integrated into the plant’s control infrastructure, it facilitates remote unattended operation, enhancing process reliability and operational efficiency. The proposed architecture addresses a key challenge in cement production and enables advanced control and intelligent optimization. Full article

The transition from electrical to optical interconnects, enabled by the adoption of co-packaged optics (CPO) in advanced processors, is accelerating the scale-up to high volumes and redefining wafer-level test requirements. As optical interfaces migrate closer to the compute die, an increasing share of functional characterization must occur at the probe, where stringent sub-micron alignment, the mechanical stability necessary to preserve optical coupling against dynamic disturbances, and opto-electrical co-validation introduce new technical challenges. Ensuring repeatable and precise fiber-array-unit (FAU) engagement at the wafer level is therefore essential to enable scalable manufacturing of photonic-enabled processors. This paper introduces the EclipsePhotonic probe card, which embeds the Eclipse Dynamic piezoelectric positioning mechanism into a standard vertical-needle probe head as a route toward six-degree-of-freedom FAU manipulation with nanometric positioning accuracy. This architecture is designed to support repeatable coupling to on-wafer photonic structures without requiring specialized probe-head designs, thereby reducing integration complexity and addressing alignment-related yield risks. The platform is also intended to support multi-site electrical and optical probing, providing a path toward parallel test execution once the corresponding layout, optical-routing, and validation constraints are satisfied. A core innovation of the platform is its embedded sensor network, which integrates low- and higher-frequency displacement sensors, relative displacement sensors, and temperature sensors around a microcontroller-based supervisor. The vibration sensor fulfills a dual operational role: it detects environmental and test-cell disturbances that may have influenced optical coupling, providing essential context for binning decisions or targeted retest, and it contributes to probe card lifecycle monitoring by ensuring that the mechanical signature of the probe card remains within a validated operational “swim lane” throughout its service life. Recently published characterization of the underlying Eclipse Dynamic alignment engine shows that, in the production-optimized high-speed regime with effective hysteresis compensation, the Fixed Gradient routine provides the best normalized trade-off among the evaluated routines, with a normalized alignment cost of 1.44 a.u., 95.8% convergence reliability, and 99.4% of the global maximum optical coupling. These values should be interpreted as inherited algorithmic benchmarking results rather than as absolute wall-clock performance of the fully integrated sensor-augmented platform. Full article

Rack railway systems operating on steep-gradient routes rely on rack-and-pinion propulsion mechanisms that generate substantial vibrational excitation through cyclic gear mesh contact, adversely affecting passenger comfort and long-term mechanical reliability. Conventional integrated steel gears transmit propulsive forces without inherent vibration attenuation, and a systematic design methodology for optimising the internal rubber spring configuration of elastic gears for such applications has not been established. This study develops a kinematic spring-mass model for both conventional steel and elastic rubber gear configurations in a Korean rack railway propulsion system and validates it through controlled experimental testing. A high-speed rail–wheel contact simulator was employed to measure vertical vibrational accelerations under rigid–rigid (steel–steel) and rigid–resilient (steel–rubber elastic gear) contact conditions, with a load simulating steep-gradient operational forces applied to the gear assembly. The elastic gear achieved a 25.1-fold reduction in vertical vibrational acceleration relative to the steel gear baseline (6.4 m/s² vs. 160.7 m/s²). Time-domain statistics (mean, RMS, standard deviation and peak envelope) are reported for both configurations from repeated runs. Analysis of the normalised effective stiffness as a function of the number of rubber springs predicts that four springs represent a practical optimum, beyond which the incremental stiffness change falls below 0.5%; experimental validation of intermediate spring counts is identified as future work. A spring-number optimisation framework is proposed that returns both a spring count and a rubber compound specification, balancing vibration attenuation against load distribution, torque-transmission capacity and component fatigue life. Full article

The development of suspension systems for urban micro-mobility vehicles, such as bicycles and e-bikes, requires balancing effective road filtering with structural simplicity. Traditional solutions, such as telescopic forks and rear shock absorbers, face significant challenges related to weight, bulk, and mechanical complexity, which increase production and maintenance costs. The integration of in-wheel motors into wheel hubs further complicates the design by increasing unsprung mass and vertical vibrations, negatively affecting ride comfort. The In-Wheel Suspension (IWS) system offers an innovative solution by incorporating elastic and damping elements directly into the wheel rim, eliminating the need for frame modifications and reducing overall weight. This study proposes an integrated approach to optimising the internal geometries of IWS elastic elements, using structural analyses with LS-Dyna and dynamic simulations in the Simulink environment for comfort assessment. Results demonstrate that optimising the geometry of spokes and rims significantly reduces stiffness variations and self-induced vibrations, with enhancements in ride comfort and resistance to fatigue. The optimized IWS design minimises discomfort peaks at critical speeds and improves vibration attenuation. However, the high average stiffness limits filtering performance at speeds above 10 km/h. While IWS systems represent a promising alternative to traditional suspensions due to their advantages in weight reduction, compactness, and construction simplicity, further improvements—such as the use of composite materials and alternative geometries—are necessary to further increase comfort and to ensure structural resistance to variable loads. Full article

A novel hierarchical honeycomb structure is proposed as the core layer of sandwich panels, replacing the hexagonal vertices with other shapes. Its vibration and sound insulation performance are further discussed. Structural acoustic finite element analysis methods were used to simulate the natural frequency, sound transmission loss (STL), and sound pressure distribution within the acoustic domain of the sandwich panels. Within the given simulation parameter range, the sound insulation efficiency of the new hierarchical honeycomb sandwich panel was significantly improved, and the triangular vertex configuration exhibited the best noise reduction ability. By varying the vertex size and the dimensions of the units, the sandwich panels’ vibration reduction and noise insulation capabilities can be further optimized. The average sound transmission loss (STLo) for hierarchical parameter (the ratio of the vertex edge length to the wall length) $\lambda$ = 0.4 increases by 17.2% compared to $\lambda$ = 0.2, greatly improving sound reduction efficiency. When the size of the honeycomb unit is small, the sandwich panel exhibits enhanced acoustic transmission loss within the resonance frequency range. The hierarchical honeycombs after vertex triangle rotation show an STLo level of around 43.08–44.24 dB. The influence of vertex triangle rotation on the STLo of hierarchical honeycomb is closely related to the hierarchical parameters, with STLo increasing by 14.8% for λ = 0.2 and 4% for λ = 0.3, while the opposite phenomenon occurs when$\lambda$ is 0.4. The research results provide valuable insights into improving the vibration reduction and sound insulation performance of honeycomb sandwich panels within the target frequency range by introducing hierarchical features. However, related engineering applications need to rely on subsequent experimental verification. Full article

Recent advances in structural engineering have enabled lightweight and slender footbridges. However, these structures are often susceptible to excessive vibrations induced by pedestrian activities, primarily impacting urban footbridge serviceability. Most studies evaluate human–structure interaction (HSI) uniaxially based on peak dynamic sensitivity. Nevertheless, this approach may overlook multidirectional mechanisms in footbridges with similar vertical and lateral modal properties. This study presents an extensive experimental assessment of HSI effects on a functional urban pedestrian bridge, known as the Premier-Footbridge, which exhibits clear multiaxial dynamic sensitivity within the frequency range associated with human walking. The structure was characterized by using operational modal analysis (OMA) based on ambient vibration measurements. Subsequently, a comprehensive human gait campaign evaluated different pedestrian density loads (PDL) and gait conditions, including synchronized, non-synchronized, and random walking. The results show that the multiaxial interaction effects were predominantly concentrated around the first lateral vibration mode (1.07 Hz), despite concurrent dynamic sensitivity in both lateral (1.07 Hz) and vertical (1.98 Hz) directions. Increasing PDL levels led to higher vibration amplitudes and measurable changes in HSI-related structural dynamics, including apparent damping and pedestrian step frequency. The experimental results indicated an apparent increase in effective structural damping with increasing pedestrian density, as identified through nonlinear trend fitting of the measured modal response parameters. Despite the multiaxial dynamic sensitivity of the structure, lateral vibrations remained the dominant factor governing the serviceability response, even under moderate PDL conditions. Full article

Speed bumps are commonly used as traffic calming devices to reduce vehicle speeds on urban road sections. However, their geometric design and implementation quality are critical not only for traffic safety but also for vehicle occupants’ comfort. If speed bumps are not designed in accordance with relevant standards, they may generate excessive vibration and negatively affect driver and passenger comfort. This study investigates the compliance of 10 different speed bumps with design standards and evaluates their effects on driver and passenger comfort. Field experiments were conducted using triaxial accelerometers at different vehicle speeds under two- and four-passenger loading conditions. The measured vibration data were evaluated using vertical acceleration and Overall Vibration Total Value (OVTV)-based comfort criteria. The results showed that only one of the examined speed bumps fully complied with the relevant design standards. The statistical results indicated that vehicle speed, speed bump type, passenger loading condition, and passenger position significantly influenced OVTVs. Overall, the study demonstrates that improperly designed or constructed speed bumps can substantially reduce vehicle occupant comfort. The proposed field-based evaluation approach can be used to assess existing speed bumps and support the design of safer and more ergonomic traffic calming devices. Full article