Search Results (630)

Ice hockey puck impacts combine high velocity, oblique loading, and spatially variable contact, yet conventional helmet assessments rely primarily on global head kinematics. This study quantified how puck impact velocity, angle, and location affect skull stress and brain tissue strain. A commercially available ice hockey helmet was reconstructed from three-dimensional scans and coupled with the Total Human Model for Safety (THUMS) Version 7.1 head model. Helmet response was benchmarked against standardized drop-test data at top, lateral, and rear locations. Eighteen nominal puck-impact conditions combined two velocities (30 and 40 m/s), three angles (0°, 45°, and 60°), and three locations; additional ±10% velocity runs assessed sensitivity. Peak skull von Mises stress (skull stress) and brain maximum principal strain (MPS) were compared descriptively. Benchmark peak linear acceleration differed from reference data by 0.5–5.8%. The greatest skull stress occurred at 40 m/s, 0°, lateral impact (0.556 MPa), whereas the greatest MPS occurred at 40 m/s, 0°, top impact (0.175). These different worst-case locations show that local skull loading and brain tissue deformation are not captured by a single metric. Multi-metric, location-specific evaluation may improve ice hockey helmet assessment and regional optimization. Full article

When large liquefied natural gas (LNG) storage tanks are constructed on deep non-rock sites, soil–foundation–structure interaction (SFSI) alters the dynamic characteristics of the system and affects the actual control effectiveness of the isolation layer. However, the current understanding of the coupling mechanism between the two remains insufficient. This paper takes a 220,000 m³ full-containment LNG storage tank as the study object and establishes a three-dimensional finite element model of the tank-pile group-site system in ABAQUS. Through comparative analyses of three model configurations, namely a rigid foundation model, a non-isolated model considering SFSI, and a lead-rubber bearing (LRB) isolated model considering SFSI, the SFSI effects and LRB isolation effectiveness are systematically separated. For the SFSI effects, the deep site attenuates medium- and high-frequency content while amplifying the response around approximately 1.6 Hz through site–foundation flexibility, transforming the heightwise acceleration amplification profile from an approximately linear pattern to a curvilinear one that bulges at mid-height, with peak pile-cap accelerations increasing by 25.1–76.9% relative to the rigid-base values. For the LRB isolation performance, the introduction of LRBs shifts the dominant system frequency below 1.0 Hz and reduces the maximum tank-wall acceleration amplification factor from 2.64 to 0.81. The resulting attenuation of superstructural inertial forces leads to reductions of 49.6–82.0% in pile-head shear and 57.4–78.0% in near-head bending moment, while the outer-to-inner pile-head moment ratio decreases from 2.94 to 1.13, indicating substantially improved pile-group force uniformity. Nevertheless, the beneficial effect of isolation diminishes with depth, and internal forces at abrupt soil-stiffness interfaces remain governed by kinematic interaction that the isolation layer cannot mitigate. The findings of this study can provide references for the seismic isolation design and pile foundation seismic optimization of super-large LNG storage tanks on deep overburden sites. Full article

Leg-spring hysteresis, the mechanical energy dissipated within the force–length loop during ground contact, is a whole-limb, indirect indicator of stretch-shortening cycle (SSC) function. Whether international-level track-and-field and club-level multi-sport athletes differ in hysteresis responses to drop height, and whether hysteresis is associated with jump height, remains unclear. Here, 40 athletes (15 international-level, 25 club-level) performed bilateral (BLJ), dominant-leg (DOM), and non-dominant-leg (NDOM) drop jumps from 0.26 to 0.42 m. Hysteresis and jump height were computed from three-dimensional kinematics (500 Hz) and ground reaction forces. Group × drop-height interactions were significant for hysteresis in all conditions (partial eta-squared, η²p = 0.647, 0.507, 0.466; p < 0.001): international-level athletes became increasingly negative (net active energy contribution) at 0.42 m, whereas club-level athletes became positive (net dissipation). Between-group differences at 0.42 m were large (Cohen’s d = −1.73, DOM; −1.95, NDOM); jump height was also higher in international-level athletes (d = 1.14–1.77). Pooled, hysteresis was associated with jump height (coefficient of determination, R² = 0.44–0.60), although caliber differences inflate this estimate, and within-group associations were weaker. Hysteresis discriminated reactive-jumping capacity beyond jump height alone; because competitive level was confounded with sport discipline and sex, these differences should not be attributed to caliber per se. Full article

Background/Objectives: Although proximal first metatarsal osteotomy is a common treatment for hallux valgus (HV), its effect on dynamic first tarsometatarsal (TMT) joint mobility remains unclear. Previous assessments have largely relied on static radiographic parameters, which may not capture functional joint kinematics. The aim of this study was to evaluate changes in first TMT joint mobility during the stance phase of gait using a synchronized ultrasound and three-dimensional motion capture system after combined hallux valgus surgery incorporating proximal first metatarsal osteotomy. Methods: We prospectively studied 23 feet of 21 female patients with symptomatic HV undergoing combined hallux valgus surgery incorporating proximal closing-wedge osteotomy. We also evaluated 11 feet of 11 healthy female volunteers as controls. Per clinical indications, additional concomitant procedures were performed for 21 of the 23 feet. Vertical displacement of the first metatarsal and medial cuneiform as well as the first TMT joint gap was measured throughout the stance phase of gait using a synchronized ultrasound and motion capture system. Pre- and postoperative kinematics (>1 year follow-up) were compared with those in the control group using one-dimensional statistical parametric mapping (SPM). Results: Radiographically, the HV and intermetatarsal angles significantly improved, while sagittal plane parameters showed no significant changes. SPM analysis revealed no significant differences in the first TMT joint gap or first metatarsal displacement among groups. Preoperatively, compared with the controls, HV feet exhibited significantly greater plantar displacement of the medial cuneiform during late terminal stance. Postoperatively, this abnormal displacement was significantly decreased, with no significant difference between groups. Conclusions: Combined hallux valgus surgery incorporating proximal first metatarsal osteotomy was associated with reduced dynamic medial column hypermobility, specifically shifting vertical displacement of the medial cuneiform towards patterns observed in healthy controls during the terminal stance phase. These functional improvements occurred despite minimal changes in static sagittal radiographic alignment. The findings highlight the importance of dynamic assessment for evaluation of postoperative medial column biomechanics. Full article

Coherent vortices alter flapping-foil energy harvesting, but wake-generated vortex properties and timing are coupled to upstream-body kinematics. We use two-dimensional immersed boundary–lattice Boltzmann simulations of a prescribed heaving–pitching NACA0015 foil at $Re=1100$. An independently prescribed Taylor vortex allows nominal encounter phase, body-fixed offset, diameter, and intensity to be varied at fixed kinematics. Production-grid ${\overline{C}}_P$ is within $0.10\%$ of the fine-grid result; the fine-grid diffusion test gives a maximum full-field velocity $L_2$ error of $0.0690\%$ against the analytical solution over $0\le t^{*}\le 4$. For the reference vortex with a pivot-centered nominal target ($D/c=v_{\theta m}/U_{\infty }=1$), nominal-encounter-aligned mean power coefficients of $0.747$, $0.862$, and $0.987$ occur at ${\psi }_e=0.10$, $0.40$, and $0.60$, respectively, compared with $0.832$ without gusts. These define the power-reducing (PR), near-baseline (NB), and power-enhancing (PE) cases. Within the sampled ranges, diameter is associated mainly with disturbance reach and duration, intensity with loading magnitude, and offset with spatial overlap and interaction timing. Power variations are consistent with the timing of vortex-modified loading relative to prescribed foil motion. In three same-sign, once-per-cycle sequences, the PR–NB–PE ordering persists despite residual-wake interactions, with sustained mean power coefficients of $0.763$, $0.916$, and $0.965$, respectively. Nominal encounter phase and foil placement should be considered jointly for repeatable or predictable vortex passages. Full article

Embedded 3D printing of hydrophilic hydrogels in aqueous support baths often suffers from filament deformation, positional deviation, and diffusion before complete cross-linking, while practical parameter-selection guidelines for specific material systems remain limited. In this work, an integrated engineering evaluation method was developed to characterize filament formation and early-stage evolution during embedded printing of gelatin/sodium alginate inks in Carbomer support baths. Filament quality was assessed using cross-sectional geometry, contour irregularity, deposition position, and early-stage diffusion ratio. The effects of printing kinematics and material rheology are systematically examined to establish a practical process window for this hydrophilic ink–bath system. The results show that the speed ratio between substrate and ink is a primary factor controlling filament geometry and deposition position, and a ratio close to 1 yields the most balanced cross-sectional morphology without position shift from the printed nozzle. Ink with high viscosity maintains contour irregularity within a narrow range of 0.005–0.009 and suppresses early diffusion, whereas a support bath with high viscosity and ink with high viscosity combination further slows diffusional evolution by about 70%. Based on the identified process window, several three-dimensional hydrogel structures were fabricated successfully. The proposed workflow provides a practical route for process evaluation and parameter selection in hydrophilic embedded printing, especially for continuous filament and tubular structures, and offers engineering guidance for bio-soft material fabrication in applications. Full article

Unauthorized low-altitude UAVs can challenge conventional fixed-parameter interception algorithms through agile maneuvers. This study develops a three-dimensional one-on-one terminal-interception simulation environment that incorporates protected-zone penetration, a within-step geometric interception criterion, and kinematic constraints. The intruder, denoted as the red UAV, combines six physically interpretable maneuver templates to generate structured evasive penetration behavior. The defender, denoted as the blue UAV, augments blended generalized proportional navigation (B-GPN) with a bounded residual corrective acceleration produced by deep reinforcement learning, thereby forming a hybrid architecture that combines a geometry-based nominal guidance command with reward-driven bounded compensation. In standardized tests on 1000 unseen scenarios, the implemented residual PPO pipeline increased the interception rate from 63.8% for nominal guidance to 94.1% (95% Wilson interval: 92.46–95.40%) and maintained at least 88.0% interception under the tested control-delay, kinematic, and noise perturbations. It also achieved the highest interception rate among the evaluated residual-learning implementations under both the stable-configuration comparison and the auxiliary task-side-controlled check; this result is limited to the reported implementations and is not a general ranking of algorithm families. These findings indicate that bounded residual learning can compensate for structural limitations of conventional guidance under the evaluated conditions. Full article

Background: Impaired lumbopelvic control and inefficient bending mechanics are associated with low back pain and functional limitations. The Founder Exercise is a movement retraining strategy intended to promote hip-dominant movement, trunk control, and postural awareness during forward bending. However, empirical evidence examining movement performance following Founder Exercise instruction is limited. This study examined immediate pre-to-post differences in hip hinge kinematics and movement confidence surrounding a standardized Founder Exercise instructional session in healthy adults. Methods: A within-subject pretest-posttest design was used. Thirty-three healthy adults (72.7% female; mean age, 25.1 ± 2.9 years) completed assessments of foot orientation, sagittal-plane joint kinematics, and movement confidence before and after a single Founder Exercise instructional session. Joint kinematics were assessed using two-dimensional video analysis. Paired-samples t-tests or Wilcoxon signed-rank tests, as appropriate based on the distributions of the paired differences, were used to evaluate the kinematic outcomes. The exploratory summed confidence score and individual ordinal confidence items were evaluated using Wilcoxon signed-rank tests. Holm adjustments were applied separately to the 11 kinematic comparisons and the 10 individual-item comparisons. Results: Statistically significant immediate pre-to-post differences were observed in several kinematic variables. Hip flexion increased from 80.7° ± 18.1° at pretest to 104.6° ± 14.3° at posttest, shoulder flexion increased from 62.8° ± 23.9° to 145.3° ± 13.9°, and craniovertebral angle decreased from 25.7° ± 12.9° to 11.2° ± 10.0° (all p < 0.001). The summed score from the unvalidated, study-specific confidence scale was higher at posttest (median = 49.0, IQR = 40.0–50.0) than at pretest (median = 40.0, IQR = 36.0–50.0; p < 0.001). After Holm adjustment of the individual ordinal-item analyses, statistically significant differences remained for five of the 10 items; all confidence findings were considered exploratory. No statistically significant differences were observed in knee flexion or ankle motion after Holm adjustment. Conclusions: A brief Founder Exercise instructional session was followed by immediate differences in selected two-dimensional hip hinge angles and higher exploratory movement-confidence scores in healthy adults. These findings do not establish changes in lumbopelvic control, muscle activation, spinal loading, movement efficiency, or clinical outcomes. Controlled studies incorporating direct measures of lumbar and pelvic motion, muscle activity, external forces, and clinically relevant outcomes are needed before biomechanical or clinical conclusions can be drawn. Full article

The masticatory cycle is a coordinated sequence of mandibular movements closely associated with masticatory muscle activity. However, the chewing pattern may be altered in temporomandibular disorders (TMDs). The aim of this study was to evaluate the masticatory cycle in patients with TMD through an integrated electromyographic and kinematic analysis, comparing the results with the correlations previously reported in the literature for healthy subjects. In this cross-sectional study, twenty-four adults diagnosed with TMD (mean age: 26 ± 6.7 years; 16 females and 8 males) were recruited at the Department of Dentistry at San Raffaele Hospital, Milan. The jaw tracking system Modjaw^® (version 3.6.4; MODJAW SAS, Villeurbanne, France) made it possible to record three-dimensional mandibular movements, including opening and closing, protrusion, lateral movements and the masticatory cycle. As for surface electromyography, the Myowise^® device (software version 1.4; Cometa S.r.l., Bareggio, Italy) was used to assess the electrical activity of the masticatory muscles during chewing. Subsequently, descriptive statistics were performed, and possible correlations between selected kinematic and electromyographic parameters were investigated. No statistically significant correlations were identified, except for a moderate negative correlation between right masticatory cycle height and right masseter muscle impact. Mandibular kinematics showed limited associations with electromyographic parameters in patients with temporomandibular disorders, differing from the correlations previously reported in healthy subjects. Full article

Background/Objectives: Human gait analysis is essential for identifying biomechanical alterations associated with pathological conditions. However, conventional laboratory systems that combine optical motion capture and force plates remain costly, space-demanding, and difficult to implement in routine or accessible settings. This study proposes a dual-model artificial intelligence framework designed to bridge kinematics and dynamics and subsequently support gait health-status classification from motion data. Methods: The first model was developed to estimate ground reaction forces (GRF) and center of pressure (CoP) signals from kinematic inputs. Public datasets containing synchronized kinematics and dynamics were used to train and evaluate long short-term memory (LSTM) and one-dimensional convolutional neural network (CNN1D) architectures. A robustness stage further adapted the dynamic prediction model to markerless-like kinematic inputs through domain-adaptation training. The second model was implemented as a multichannel convolutional classifier using normalized GRF/CoP signals and metadata. Three variants were compared: signals only, signals with minimal metadata, and signals with rich metadata. Finally, a bridge block connected both models, and a proof-of-concept deployment was performed using markerless kinematics obtained with Move AI and Blender. Results: The final dynamic prediction model achieved an overall RMSE of 0.0676, with reconstructed-signal RMSE of 0.0500 and reconstructed contact accuracy of 0.9736. The best classification variant achieved a balanced accuracy of 0.9608, while the minimal-metadata variant was selected for pipeline integration due to its compatibility with accessible data acquisition. In the full pipeline evaluation, the predicted dynamics correctly classified the healthy-control samples. In the Move AI/Blender proof-of-concept, all five healthy participants were classified as healthy controls, with a mean non-pathological classification probability consistent with this outcome. Conclusions: The proposed dual-model framework demonstrates the operational feasibility of linking kinematic acquisition, dynamic prediction, and gait classification within a single artificial intelligence pipeline. The Move AI/Blender stage represents a preliminary proof of concept rather than clinical validation, and further evaluation with pathological participants and synchronized force-plate measurements is required. Full article

End-effector obstacle-avoidance trajectory planning is essential for improving the autonomy, safety, and executability of industrial robotic manipulators in constrained workspaces. Conventional Rapidly Exploring Random Tree (RRT) planners provide effective exploration capability but often suffer from stochastic tree expansion, redundant trajectories, and insufficient directional guidance near obstacle regions, which limits planning efficiency and trajectory quality. This study proposes a clearance-field-guided RRT framework with behavior-cloning-assisted refinement for end-effector obstacle-avoidance trajectory planning of industrial robotic manipulators. The proposed method formulates the planning problem in Cartesian space based on an end-effector kinematic model and introduces local clearance-field guidance into the RRT sampling process. Candidate samples are evaluated by considering obstacle clearance, reference-line deviation, and goal distance, enabling the search tree to preferentially expand toward effective traversable regions while maintaining the exploration capability of conventional RRT. Behavior cloning is further introduced as an offline auxiliary strategy to investigate the influence of expert trajectories on local motion-direction learning and trajectory continuity. A Python–Unity joint simulation–verification framework and a physical manipulator experimental platform are established to evaluate the feasibility and practical executability of the generated trajectories. Python is used for offline trajectory generation, expert dataset construction, behavior-cloning training, and performance evaluation, while Unity is employed for three-dimensional manipulator modeling and trajectory reproduction. The experimental results demonstrate that the proposed Field-guided RRT achieves a better balance among path efficiency, planning time, obstacle-clearance maintenance, and trajectory execution capability compared with conventional RRT-based methods. The proposed framework provides an effective solution for collision-free end-effector trajectory planning in industrial applications such as assembly, welding, component placement, and robotic inspection. Full article

Three-dimensional motion capture provides high-fidelity kinematic trajectories, but the extent to which different marker configurations retain discriminative information for tennis stroke recognition remains unclear. This study combined 3D motion capture with MiniRocket to compare seven upper-limb and racket marker configurations using data from 40 tennis-trained participants, 13 stroke types, and 10,133 valid movement samples. The configurations were the full-information group (ALL), full-arm group (AB), forearm group (FA), forearm + racket group (FR), upper-arm group (UA), racket group (RK), and watch group (WT). Model performance was evaluated using leave-one-subject-out cross-validation. All configurations achieved high performance in the three-class task. In the 13-class task, Macro-F1 was highest for ALL (78.76%), followed closely by FR (78.71%) and RK (78.28%). Holm-adjusted pairwise comparisons showed no significant differences among ALL, FR, and RK. FR significantly outperformed AB, FA, UA, and WT, whereas RK significantly outperformed FA, UA, and WT. Serve and overhead strokes were easiest to recognize, while several fine-grained baseline and net-play strokes showed lower F1-scores. These findings indicate that discriminative information is more strongly represented in the forearm-wrist-racket chain rather than simply increasing with marker count. Full article

To address the problems of the Electromagnetic Wave Propagation Algorithm (EMWPA)—insufficient initial-population coverage, an imbalance between exploration and exploitation, and a tendency to fall into local optima—in high-dimensional complex optimization problems, this paper proposes a boosted electromagnetic wave propagation optimization algorithm, BEMWPA. First, a cubic chaotic map is introduced in the population-initialization stage to enhance the uniformity of the initial-solution distribution and the search-space coverage. Second, nonlinear phase modulation is applied to the electric- and magnetic-field driving terms, and a differentiated probabilistic switching mechanism is constructed to improve the dynamic coordination between global exploration and local exploitation. Furthermore, a Beta-distribution opposition-based learning strategy is introduced to enhance the algorithm’s ability to escape local optima by generating high-quality opposite candidate solutions. To verify the effectiveness of the proposed algorithm, systematic comparative experiments are conducted on the CEC2017 benchmark function set, and BEMWPA is combined with rapidly-exploring random tree (RRT) and applied to path planning of a welding manipulator in complex multi-workpiece scenarios. For a three-dimensional welding scenario containing 12 workpieces, 12 closed weld seams, and multiple obstacle constraints, BEMWPA-RRT reduces the initial inter-seam transfer path length of RRT from 586.00 mm to 479.11 mm, representing a relative reduction of 18.24%, and the complete end-effector path length is reduced from 2974.00 mm to 2867.11 mm, representing a relative reduction of 3.59%. Meanwhile, the optimized transfer path length is only 1.59 mm longer than the obstacle-free ideal transfer length of 477.52 mm, indicating that the proposed method can approach the geometric lower bound of this scenario while satisfying the obstacle-avoidance constraints. Kinematic verification on a seven-degrees-of-freedom welding manipulator further shows that the optimized Cartesian-space path can be converted into a continuously executable joint-space trajectory, providing an effective method for offline welding path planning of complex multi-workpiece tasks. Full article

Steep rock slopes are widely distributed in the karst mountainous regions of southwestern China, where structurally controlled rockfalls frequently threaten transportation infrastructure and human safety. Accurate identification of unstable rock blocks (URs) and quantitative assessment of their post-failure hazards remain major challenges because of complex discontinuity networks and fragmentation during rockfall motion. Taking the Zuojiaying steep rock slope in Guizhou Province as a representative case, this study integrates high-resolution UAV photogrammetry, automatic discontinuity identification, unstable rock block detection, and three-dimensional rockfall simulation to investigate the formation mechanisms and hazard characteristics of discontinuity-controlled rockfalls. A high-resolution three-dimensional terrain model was reconstructed from UAV imagery, and six dominant discontinuity sets were automatically identified using the I-MinPts-constrained DBSCAN algorithm. Combined with the Rock Occurrence Kinematic Analysis (ROKA) algorithm and Block Theory, 54 unstable rock blocks were identified, with wedge failure and toppling failure representing the dominant instability modes. The results indicate that discontinuity combinations govern both rock mass segmentation and unstable rock block geometry. Specifically, discontinuity sets J1, J3, and J5 mainly control wedge-shaped blocks, and J2 and J4 dominate columnar toppling blocks, whereas J6 further promotes the formation of isolated unstable rock blocks. Three-dimensional RockGIS simulations considering fragmentation reproduced the complete rockfall process from detachment to final deposition. The maximum travel distance, kinetic energy, and bounce height reached 395 m, 748.5 kJ, and 40.1 m, respectively. Fragmentation increased the number of rock blocks from 54 to 1013, substantially enlarging the potential impact area. A raster-based Rockfall Hazard Index (RHI) further revealed that the middle–lower slope and slope toe constitute the principal high-hazard zones, and under extreme scenarios, high-energy fragments may reach the G246 National Highway and adjacent infrastructure. This study revealed the formation mechanisms and hazard characteristics of unstable rock blocks controlled by discontinuity combinations in the study area, providing a case reference for rockfall hazard identification and mitigation on similar high-steep rock slopes in karst mountainous regions. Full article

Carbon fiber reinforced plastic (CFRP) composites have been widely adopted in the aerospace industry due to their excellent mechanical and physical properties. However, their anisotropy and weak interlaminar bonding make them prone to defects such as delamination and fiber pull-out during conventional drilling (CD). Longitudinal-torsional coupled ultrasonic vibration-assisted drilling (LTC-UAD) integrates axial and circumferential vibrations to suppress hole defects and is considered a promising machining method for improving the quality of holes drilled in CFRP. Based on kinematic analysis, a model for the working rake angle of the main cutting edge is established to obtain the variation law of the maximum working rake angle along the cutting edge. Compared with CD and longitudinal ultrasonic vibration-assisted drilling (L-UAD), LTC-UAD significantly increases and homogenizes the maximum working rake angle of the main cutting edge, which helps optimize its cutting performance. A three-dimensional finite element model of CFRP is constructed to analyze the dynamic fiber removal process under typical fiber orientations. Finally, drilling experiments are performed to observe the hole wall micro-morphology at various fiber angles. The simulation results indicate that ultrasonic vibration causes periodic changes in the fiber cutting angle, subjecting the fibers to a directional shear state and making them more prone to shear fracture. Two-dimensional ultrasonic vibration cutting enhances the directional shear effect, promotes fiber fracture, accelerates chip removal, and improves the quality of the machined surface. Experimental observations confirm LTC-UAD alleviates fiber crushing, bare fibers, and surface cavities with uniform resin coverage. Furthermore, ultrasonic vibration suppresses thrust force. L-UAD and LTC-UAD yield 10.6% and 17.1% reductions via periodic cutting depth variation and facilitated carbon fiber shear fracture. Full article