Search Results (6,650)

Response spectra (RS) provide an efficient link between earthquake ground motions and structural demand. Still, rare event screening for long-period, resonance-sensitive systems is often approximated by applying uniform multipliers to a design-basis earthquake (DBE) spectrum to represent beyond-design-basis earthquake (BDBE) levels. This paper develops critical excitation (CE) based response spectra (CE-RS) as a spectrum-format, low-overhead screening tool that makes period-local resonance sensitivity explicit while remaining anchored to code-defined hazard levels. This paper develops CE-RS as a response-spectrum-based screening tool for identifying period-local resonance sensitivity at code-defined hazard levels by using the CE framework to search, within an admissible set defined by bounded power spectral density (PSD) content and intensity constraints, for the input that maximizes structural response. Code-based target spectra are adopted as hazard anchors, consistent with the intent of probabilistic seismic hazard analysis (PSHA), at representative sites in Australia (Canberra; AS 1170.4:2024, Site Class Be) and the United States (San Francisco; ASCE/SEI 7-22, Site Class BC). For each site, a spectrum-compatible seed accelerogram is generated to reproduce the 5% damped target spectrum and to calibrate admissible-set bounds using peak ground acceleration (PGA), peak ground velocity (PGV), and Arias intensity. CE is then performed period-by-period over the long-period range to obtain CE-RS ordinates, which are compared with the DBE target and conventional BDBE-type references formed by uniform spectrum scaling. The resulting framework provides a code-comparable, site-anchored interpretation of long-period demand influenced by resonance effects, supporting rapid prioritization in preliminary design and in the screening of existing long-period-sensitive infrastructure for strengthening/rehabilitation. Full article

 Rapid search for evasive targets using multiple Unmanned Aerial Vehicles (UAVs) presents significant challenges, as it requires real-time target-motion prediction, multi-agent coordination, and adherence to kinematic constraints. Existing cooperative search methods often assume non-adversarial target behavior or model target motion independently of UAV actions, which reduces their effectiveness against targets that actively evade based on UAV positions. To address these limitations, this study introduces the Cooperative Rapid Search Algorithm for Evasive Targets (CRS-AET). The proposed framework utilizes graph-theoretic modeling to represent spatial-temporal relationships among UAVs, targets, and environmental grids. A directional gradient-based motion prediction (DG-Prediction) method first estimates probable movement areas of dynamic targets within the graph-structured environment. An improved multi-round auction algorithm with graph-based utility propagation (IMRAA) then optimizes UAV resource allocation. Finally, Dubins-Constrained Trajectory Optimization (DC-RTO) is integrated within a distributed model predictive control (DMPC) scheme to ensure kinematic feasibility. Simulation results across three representative scenarios indicate that CRS-AET enables faster target detection, enhanced area coverage, and more efficient coordination than baseline methods. Hardware-in-the-loop (HIL) experiments further confirm the robustness and practical applicability of the framework in realistic operational environments.  Full article

To effectively enhance the seismic performance of traditional Chinese timber structures, this study proposes a reinforcement method utilizing friction dampers. Based on the working mechanism of friction dampers and the extended discrete element theory, an analytical model for timber structures equipped with these dampers was developed and validated through shake table tests. Subsequently, dynamic analyses were conducted to systematically evaluate the enhanced seismic energy dissipation capacity of the ancient timber structures by the reinforcement of friction dampers. The friction coefficient (μ), bolt pre-tension strain (ε), and action distance (l) were selected as key parameters. A multi-objective optimization function was constructed using the weighted sum method, enabling a multi-objective parameter optimization analysis for the friction dampers to identify the optimal parameter combination under specific conditions. The results indicate that the established extended discrete element model effectively simulates the dynamic characteristics of the structure. The installation of friction dampers significantly enhanced the structure’s energy dissipation capacity and substantially reduced the peak displacement. However, due to the initial stiffness introduced by the dampers, the lateral stiffness of the column frame increased markedly, leading to a significant amplification of the acceleration response, with a maximum increase in peak acceleration reaching 77%. The multi-objective optimization analysis revealed that with weighting coefficients λ_a = λ_b = 0.5, the optimal damper parameter combination is μ = 0.36, ε = 102 με, and l = 268 mm. Under these conditions, the structural displacement response decreased by 38.5%, while the acceleration response increased by 93.7%. It is noted that the derived optimal design solutions are pertinent to the specific structural typology and ground motions considered. Full article

This study proposes a cooperative aerial transportation control method for cable-suspended payloads using multiple quadrotor unmanned aerial vehicles (UAVs), considering quadrotor viewpoint control during transportation. Conventional cooperative transportation methods typically fix the yaw angles of quadrotors to ensure stability and to avoid dynamic interference with suspended payloads. The novelty of this study lies in realizing a dynamically decoupled control framework for cable-suspended cooperative aerial transportation, in which quadrotor yaw motion is decoupled from the suspended-load dynamics. In the proposed framework, payload stabilization is maintained, while quadrotor yaw-direction control is integrated with mitigation of interference to the suspended-load dynamics, preserving the geometric structure of the system. The effectiveness of the proposed method is validated through numerical simulations of trajectory-tracking transportation with viewpoint control. Under the aggressive (fast) trajectory condition, the proposed method reduces the payload height RMS error by 68.4% and the maximum quadrotor yaw tracking error by 82.5% compared to conventional geometric control. Furthermore, stable payload transportation is achieved in both slow and fast scenarios while maintaining bounded yaw-direction tracking errors. These results suggest that the proposed framework reduces design interdependence between cooperative payload stabilization and yaw-direction control, thereby alleviating design complexity and expanding the structurally available yaw maneuvering freedom within the control framework. Full article

Historical masonry minarets are highly vulnerable to seismic actions due to their slender geometry, limited tensile capacity, and material heterogeneity. However, their response to near-fault ground motions characterized by velocity pulses remains insufficiently explored. This study investigates the seismic response of the historical Tavanlı Mosque Minaret (1894, Trabzon, Türkiye) subjected to pulse-like (PL) and non-pulse-like (NPL) near-fault ground motions. A three-dimensional finite element model (FEM) was developed in ANSYS Workbench and systematically calibrated using empirical formulations to represent the current dynamic condition of the structure. Seismic performance was evaluated through linear dynamic analyses in terms of displacement demands, principal stress distribution, and drift-ratio-based performance levels. The results indicate that model calibration significantly modifies the dynamic characteristics, increasing the fundamental frequency from 0.734 Hz to 1.126 Hz and reducing displacement demands by approximately 35–76% across the considered records. Despite this improvement, PL ground motions consistently generate more critical deformation demands than NPL motions, frequently exceeding Collapse Prevention (CP) limits even when Peak Ground Acceleration (PGA) values are relatively low. A key finding is that seismic demand cannot be reliably predicted by peak intensity measures or pulse-period ratios ($T_p/T_1$) alone; rather, velocity-related parameters and pulse coherence govern the structural response. These results demonstrate that integrating empirical model calibration with pulse-sensitive seismic analysis is essential for reliable seismic assessment and conservation planning of slender historical masonry structures located in near-fault regions. The study offers a systematic framework that integrates model calibration and pulse-sensitive seismic analysis for evaluating the drift-controlled response of slender historical masonry minarets in near-fault regions. Full article

Background: Virtual, augmented, and mixed reality (or collectively extended reality, XR) serious games, combined with motion-tracking technologies, are increasingly used for motor and cognitive rehabilitation and training. As XR and tracking technologies advance, a systematic mapping of the related research area could offer relevant insights. Objectives: This review aims to map interactive XR serious games, using motion-tracking technologies for physical or cognitive rehabilitation or training, and describe intervention characteristics and evaluation methods. Eligibility Criteria: Eligible studies were English, peer-reviewed journal articles published between 2015 and October 2025, with more than three participants, using custom XR serious games for rehabilitation or training. Studies were excluded if they focused on technical aspects, passive XR, diagnostic evaluation, psychological therapies, minor participants, procedural training, or education. Charting Methods: Data were charted using a structured form capturing XR characteristics, hardware configurations, study characteristics, and evaluation methods. Results: 61 studies were included. Most employed non-immersive or fully immersive VR interventions, targeting physical upper-body rehabilitation, especially post-stroke and Parkinson’s disease. Usability, acceptability and user experience, and training effectiveness were commonly evaluated with positive outcomes. Conclusions: The findings highlight opportunities for research into augmented and mixed reality approaches, particularly for cognitive function, and use of XR-based interventions across broader populations. Full article

To address the issue of normal displacement deviation induced by the geometric nonlinearity of cross-spring flexural pivots in pendulum-type interferometers, which leads to modulation attenuation, this study proposes a co-simulation method combining Finite Element Analysis (FEA) and Physical Optics. First, an optomechanical model was established based on the retroreflective property of cube-corner prisms and a double-pendulum differential scanning architecture (where the optical path difference is four times the mechanical displacement). Using the ANSYS Workbench 2022 R1 transient dynamics module with the “Large Deflection” algorithm enabled, the nonlinear motion trajectories of single-pivot and dual-pivot flexural hinges were quantitatively compared. Subsequently, a multi-physics data mapping interface was established to map mechanical motion errors into a physical optics simulation model, where the interference modulation was accurately calculated via electromagnetic field tracing. Results demonstrate that under ambient temperature (25 °C) and a spectral resolution of 1 cm⁻¹, the normal displacement deviation of the single-pivot hinge is only 0.00165 mm, representing a 95.6% reduction compared to the dual-pivot structure (0.03765 mm). Furthermore, the modulation of the single-pivot structure remains above 0.98 throughout the scanning range, significantly outperforming the nonlinear decay characteristic of the dual-pivot structure. These findings provide a theoretical basis for the structural optimization and selection of high-precision portable FTIR spectrometers. Full article

Shaking table testing has become a fundamental experimental approach in geotechnical earthquake engineering for investigating seismic soil–structure interaction. Although numerous studies have examined the dynamic behavior of reinforced retaining walls and soil slopes, the existing body of literature remains fragmented, with significant variations in scaling approaches, boundary conditions, input motions, and instrumentation methods. To date, no comprehensive review has critically synthesized these studies to identify consistent behavioral trends and methodological limitations. This paper presents a systematic and critical review of shaking table investigations of geosynthetic-reinforced retaining walls and clayey soil slopes. The review consolidates global experimental findings to evaluate how key parameters—including excitation characteristics, soil density, surcharge loading, reinforcement configuration, and boundary conditions—influence displacement patterns and acceleration amplification. Recurring response mechanisms are identified, such as elevation-dependent amplification, nonlinear frequency effects, and the confinement benefits of reinforcement and surcharge. The review further examines discrepancies among studies and between experimental and numerical results, highlighting challenges related to similitude requirements, boundary effects, and signal fidelity By synthesizing dispersed experimental evidence and critically evaluating methodological variations, this review provides a clearer understanding of seismic response mechanisms and offers guidance for improving experimental consistency and promoting future standardization in shaking table testing. Full article

The soil–pile–structure interaction (SPSI) has an important effect on the design of earthquake-resistant structures and becomes more complicated for irregular structures constructed on liquefiable soils. Using pile foundations is an efficient method for improving structure stability because they enhance bearing capacity and reduce structural settlement. To assess the effects of SPSI, a 10-story irregular reinforced concrete structure supported by a group of five piles was modeled in PLAXIS2D. To examine the effect of input shaking amplitude on system response, four sinusoidal ground motions with different amplitudes and a real earthquake record were used. The results were assessed, considering the superstructure’s inter-story drift, rotation, and basement settlement. Furthermore, the distributions of curvature and internal forces along the piles were compared in various scenarios. Several failure modes were investigated, including bending, buckling, bending–buckling interaction, shear, and slenderness instability. The results show that internal forces and curvature development in piles are strongly influenced by the shaking amplitude, pile diameter, superstructure load magnitude, and presence of a liquefied layer. These factors also determine the failure mode that is experienced. Full article

The rising prevalence of physical comorbidities among patients with mental illness has increased the relevance of physical rehabilitation within psychiatric care. However, specific physical rehabilitation practices in specialized psychiatric hospitals in Japan remain insufficiently documented. This exploratory and descriptive study aimed to characterize the rehabilitation content provided and to categorize patient characteristics and comorbidities in a single specialized psychiatric hospital using an expert-led consensus approach. Clinical data from 150 patients (median age 71.0 years) who received physical rehabilitation were retrospectively analyzed. Patient categorization was conducted through a multidisciplinary consensus-building process involving an expert panel of physical therapists, occupational therapists, psychiatrists, and nurses, each with over 10 years of clinical experience. Using a hierarchical rule set based on International Classification of Diseases, 10th Revision (ICD-10) codes and clinical referral data, five distinct categories were identified: Disuse Syndrome (41%), Neurologic Disorders (20%), Lower Limb Lesions (18%), Parkinson’s Syndrome (15%), and Upper Limb Lesions (6%). Across all categories, rehabilitation interventions focused on foundational motor therapies, such as range of motion (27%) and strength training (23%). Mobility-oriented interventions were selectively provided to patients with high bedridden status based on clinical potential. Overall, practices in this setting primarily targeted disuse syndrome and maintenance of basic motor function and were delivered with input from multiple professional disciplines; such practices may inform future research on structured multidisciplinary rehabilitative approaches, especially for aging psychiatric populations. Full article

3D electrodeposition printing is an emerging process for fabricating metallic parts with controllable geometry, yet the coupled influences of electrochemical kinetics, ion transport, and tool motion on layer height remain difficult to interpret. This work presents a physics-based process model that links key process inputs, current density, electrolyte concentration, the inter-electrode gap, and tool scanning speed, to the resulting layer height in 3D electrodeposition printing of nickel-based structures. The model combines species transport in the inter-electrode gap with Butler–Volmer kinetics, under carefully stated assumptions regarding current efficiency, overpotential, and lateral spreading. Model predictions are validated against experimentally reported layer heights over a range of process conditions, yielding average errors (9–15%) and root-mean-square errors (0.13–0.28 µm) that demonstrate good agreement and highlight the impact of simplifying assumptions. Systematic parametric studies reveal how each process input monotonically influences layer height in ways consistent with Faraday’s law and diffusion-controlled growth, while also quantifying the relative sensitivity to different parameters. Building on these results, we introduce a dimensionless 3D Electrodeposition Printing Index that consolidates the key process and material parameters into a single scalar describing the geometric growth regime. The index enables construction of process maps that capture how combinations of current density, scan speed, concentration, and gap affect achievable layer height within the validated operating window. The scope and limitations of the proposed modeling framework and the index, particularly regarding other materials, more complex geometries, and pulsed or strongly convective regimes, are explicitly discussed, providing a basis for future model extensions and experimental validation. Full article

This paper investigates the finite-horizon survival probability for a system of correlated arithmetic Brownian motions with heterogeneous drifts and volatilities, focusing on the event in which one component remains strictly below all others. Using a whitening transformation of the covariance structure, we reduce the problem to the survival of a standard Brownian motion in a simplicial cone, characterized by its spherical cross-section. While explicit solutions are available in low dimensions, we address the computationally challenging tetrahedral angular case. We derive a semi-analytic formula for the survival probability via an eigenfunction expansion of the Dirichlet Laplace–Beltrami operator on this curved domain. For efficient implementation, we construct a diffeomorphism from the spherical tetrahedron to a fixed Euclidean tetrahedron, enabling the computation of angular eigenpairs through a stable finite-element scheme. For higher-dimensional regimes, we also introduce a covariance-based difficulty index and geometric bounds based on an inscribed spherical cap to assess spectral convergence and estimate long-time decay rates. Numerical experiments show that this offline–online approach achieves high accuracy and substantial speedups relative to Monte Carlo benchmarks. Full article

Liquefied natural gas (LNG) sloshing occurs during marine transportation and storage due to vessel motion or external disturbances, leading to complex fluid–structure interactions within the containment system. This study employs OpenFOAM to develop a numerical model of LNG sloshing. The model solves the incompressible multiphase Navier–Stokes equations and utilizes the Volume of Fluid (VOF) method to capture the dynamic behavior of gas–liquid interface. The numerical model was validated against experimental data. Based on this model, the key hydrodynamic characteristics are investigated for LNG sloshing, including nonlinear free surface, transient pressure distribution on the tank walls due to liquid impact, and energy dissipation mechanisms. By varying excitation frequencies, amplitudes, and the configuration of internal components such as baffles or anti-sloshing devices, the study explores the sloshing response and effective control strategies. The results indicate that appropriately designed baffles can significantly mitigate sloshing-induced impact pressures on tank walls and enhance system stability. In the future, this study could extend to multi-layer fluids, multi-degree-of-freedom motions, and simulations under more complex real-world conditions. Full article

This study addresses key challenges in high-precision industrial motion control, including dynamic load disturbances, nonlinear parameter coupling, and degradation in synchronization accuracy. A dual-motor cross-coupled synchronous control strategy is proposed, integrating Hertzian contact theory with an adaptive fuzzy PI control algorithm. First, a precise pressure measurement model for the printing contact zone is established based on Hertzian contact theory. The model quantitatively characterizes the relationship between structural parameters and pressure distribution. Key parameters include cylinder radius and plate thickness. This provides a theoretical foundation for precise regulation. Subsequently, a fuzzy PI controller with parameter self-tuning capability is incorporated into the motor speed loop, enabling real-time adjustment of control parameters to effectively compensate for system nonlinearities and time-varying disturbances. Furthermore, a cross-coupled synchronization architecture is designed to enable bidirectional compensation between the two motors, significantly improving synchronization accuracy under complex operating conditions. Simulations were performed in MATLAB/Simulink. The tests covered typical operational scenarios, including load start-up, single-motor disturbance, and multi-disturbance conditions. The results demonstrate that the proposed system achieves high performance: dual-motor speed synchronization accuracy reaches 99.5%; the response time for disturbance compensation is within 0.3 s; and printing-pressure fluctuation is confined to ±0.8%. This performance represents a 62.5% improvement in stability over conventional single-motor control systems. This research not only resolves the long-standing issue of pressure non-uniformity in flexographic printing but also provides a generalizable framework for multi-motor synchronous control in precision manufacturing. The findings offer substantial academic insight and practical value for advancing intelligent industrial measurement and control technologies. Full article

Port areas are core hubs for national logistics and high-risk security zones that require constant vehicle access control. However, ensuring the reliability of automatic license plate recognition (ALPR) systems in port environments is severely challenged by complex image degradations, such as dense haze, low light, and motion blur. In this study, we propose a stage-wise degradation-aware restoration network (SDR-Net), which effectively addresses harsh port conditions by sequentially restoring photometric and structural degradations. Particularly, SDR-Net first secures visual cues lost to haze and low light through a photometric restoration module involving a dark-channel-prior-based dehazing and adaptive brightness adjustment. Next, a structural restoration module based on a generative adversarial network featuring edge-guided structural feature blocks and edge-aware refinement blocks is employed to precisely reconstruct character strokes and outlines damaged by motion blur, stably restoring license plate legibility even under complex degradation conditions. Experiments across various intensities of complex degradation demonstrate that SDR-Net maintains high character recognition accuracies of over 97.35% under mild motion blur and low-concentration haze conditions, indicating its superiority over state-of-the-art models. Notably, the performance gap between SDR-Net and comparison models widened as the degradation intensity increased, and SDR-Net achieved the highest multiscale structural similarity index scores across all intervals. Full article