Search Results (559)

The expansion of urban rail transit has exacerbated environmental issues related to low-frequency noise (LFN), yet the impact of geometric symmetry breaking on structure-borne noise remains underexplored. This study aims to quantify the mechanism by which cross-sectional asymmetry influences the vibro-acoustic coupling of viaducts. A 2.5D Hybrid Finite Element-Boundary Element Method (FEM-BEM) was employed to model a parametric box girder under eccentric track loading, and the numerical framework was validated against analytical benchmarks. The “Modal Symmetry Index” (MSI) and “Acoustic Asymmetry Indicator” (AAI) were defined to evaluate the effects of the asymmetry parameter ($\alpha$) on sound field distribution. Numerical results reveal a nonlinear “V-shaped” relationship between geometric asymmetry and acoustic directivity. While severe asymmetry ($\alpha >0.15$) exacerbates noise deflection via flexural–torsional coupling, a critical “self-balance zone” exists. Specifically, moderate asymmetry ($\alpha \approx 0.07$) effectively neutralizes load eccentricity, reducing the AAI from 1.5 dB (in strictly symmetric designs) to nearly 0 dB. Robustness analysis under right-side loading conditions further confirms a “reverse deflection” phenomenon, verifying that the proposed self-balance design minimizes directional sensitivity. These findings challenge the traditional assumption that geometric symmetry is acoustically optimal. A “competition–compensation” mechanism is identified, suggesting that deliberate, slight geometric asymmetry can serve as an effective passive noise control strategy for viaducts. Full article

Background: Basketball performance depends strongly on physical preparation. A novel approach is accentuated eccentric loading within contrast training, though its acute effects using dumbbells remain underexplored. Methods: Twelve youth basketball players (age = 16.0 ± 0.3 years; body mass = 81.5 ± 7.6 kg) completed three sessions with dumbbell loads equivalent to 15%, 30% and 45% BW. CMJ performance was measured using dual wireless dual force plates. Assessments were conducted before the protocol and at 3, 9, and 15 min post intervention. Subjective responses were collected via wellness, RPE and readiness questionnaires. A two-way repeated measures ANOVA with Bonferroni corrections was applied, and the significance level was set to α = 0.05. Results: Significant decreases in jump height (p = 0.010) and average propulsive power (p = 0.005) were observed in the 45% BW condition at 3 and 9 min. Jump momentum decreased significantly at 30% and 45% BW at 3 and 9 min (p = 0.010; p = 0.033). No significant differences were detected in other CMJ force–time metrics (p > 0.05). Conclusions: Dumbbell-loaded CMJs as an accentuated eccentric loading contrast exercise did not produce generalized improvements but induced acute decreases at higher loads. However, they may still be useful in individual cases for athletes with favorable responses after monitoring. Full article

Background: Full versus partial range of motion (ROM) bench press (BP) training has only been investigated at submaximal loads with discrete joint angles during training. The aim of this study was to compare the effects of a 4-week supramaximal progressive partial ROM (pROM) BP program to a traditional submaximal full range of motion (fROM) program on 1-RM strength and bar kinematics. Methods: Sixteen resistance-trained males (22.2 ± 1.4 years, 180.1 ± 6.3 cm, 88.5 ± 8.6 kgs, 1RM ≥ 1.25× body mass, 6 years’ experience) were randomized into pROM (n = 7) or fROM (n = 9). The pROM group performed BP at 105% 1RM using Bench Blokz to decrease the distance from the bar to the sternum by 1″ increments each week (5″ to 2″). The fROM group followed a strength oriented linear periodization model (80–87.5% 1RM). Both 1RM strength and 3D kinematics were assessed pre- and post-intervention using a 2 × 2 (Group × Time) ANOVA with Bonferroni corrected pairwise comparisons. Results: Both groups significantly increased 1RM strength (F = 45.82, p < 0.001), with no significant differences between groups. Pairwise comparisons revealed that only the fROM group experienced significant increases in 1st peak velocity (p = 0.023), eccentric velocity (p = 0.009), mean concentric force (p = 0.04) and quartile 2 mean concentric force (p = 0.01). Conclusions: Supramaximal pROM training is an effective strategy for increasing 1RM strength in experienced lifters, yielding results comparable to traditional fROM training over the course of a 4-week strength block. However, there are notable changes in bar kinematics surrounding the eccentric-concentric phase change that were only observed after fROM training. Full article

The anisotropic properties of wood make timber beams prone to developing longitudinal cracks. Notably, cracks occurring at the mid-height position are both highly common and critically detrimental to structural load-bearing capacity. This study focuses on the influence mechanisms of such cracks through four-point bending tests on 860 specimens, finite element simulations, and fracture morphology analyses. By introducing a horizontal crack location parameter called crack eccentricity (e), the influence of cracks at different horizontal positions on timber beam load-bearing capacity was investigated. The experimental results show that the horizontal position of the crack has a “critical eccentricity effect”: when e is below the critical value, cracks will not propagate and will have a minor impact on the load-bearing performance of timber beams; when e exceeds the critical value, cracks will propagate and their harmfulness will increase dramatically. As a special case, specimens with side-opening cracks (e = 1) exhibit “damage saturation” characteristics. That is, when the crack length exceeds the threshold (half of the beam span), regardless of further lengthening, the bearing capacity is unchanged and the damage evolution reaches a saturation plateau. The above analysis results suggest that the influence of cracks on the bearing capacity of timber beams may be counterintuitive. The calculation method for the “crack hazard coefficient” proposed in this study can provide a reference for crack hazard assessments. Full article

Quantitative data on the bending capacity and rotational stiffness of corner joints made from acrylic solid-surface PMMA/ATH composites are limited, despite their widespread use in furniture and interior components. The study provides comparative bending moment and rotational-stiffness benchmarks for 18 PMMA/ATH corner-joint series, using a stiffness-evaluation procedure tailored to corner-joint testing. L-type joints produced from two commercial PMMA/ATH materials (Kerrock and Corian) at 6- and 12-mm thickness were manufactured in 18 configurations, including glued butt, 45° mitre, reinforced mitre, rebate, groove variants, and detachable Minifix eccentric and Lamello Clamex connectors. Specimens were tested under arm-compression bending and maximum bending moment (M_max), and joint rotational stiffness was derived. The best-glued solution was the 12 mm Kerrock 45° mitre with M_max 186.21 N·m, whereas the strongest 6 mm joint reached 40 N·m. Reinforcing the 12 mm Kerrock mitre joint increased stiffness to 9521 N·m/rad but did not increase bending capacity relative to the non-reinforced mitre. Detachable joints formed a clearly distinct low-rigidity class with bending moments of 2.22–3.89 N·m and stiffness below 194 N·m/rad. Overall, thickness and joint geometry dominate both strength and stiffness, and the tested detachable connectors should be reserved for applications requiring disassembly rather than for load-bearing corners. Full article

Background/Objectives: Noncontact knee ligament injuries, including anterior cruciate ligament (ACL) ruptures and medial collateral ligament (MCL) sprains, are prevalent in sports that involve frequent cutting and pivoting. Conventional rigid knee braces can offer stability but often compromise comfort and performance, whereas soft sleeve-type supports provide minimal mechanical protection. The purpose of this study was to evaluate the acute biomechanical effects of a tensioned cable knee bracing system on peak knee valgus angle and external knee abduction moment during a controlled lateral shuffle task. Methods: Ten physically active adults (mean age 21.7 ± 3.8 years) performed submaximal lateral shuffle movements under three conditions: unbraced, sleeve-only (zero-tension), and a novel tensioned cable brace. Three-dimensional knee kinematics and ground reaction forces were collected, and peak knee valgus angle and external abduction moment were calculated during the eccentric phase of each movement. Results: Wearing the knee brace under tension significantly reduced knee valgus angle (4.5° vs. 7.9°) and peak external knee abduction moment (1.6 vs. 2.0–2.1 Nm/kg) compared to the unbraced condition. Conclusions: These findings indicate that the tensioned cable brace effectively reduced frontal plane knee loading during a lateral shuffle task, indicating its potential as an effective bracing approach. Full article

During jacking construction of prefabricated utility tunnels, asynchronous jack output and interface friction may induce internal force redistribution and deformation amplification at the leading end. Taking a triple-cell prefabricated utility tunnel in Xiong’an New Area as a case study, a three-dimensional finite element model was established considering inter-segment contact, equivalent bolted connections, and bottom-slab-bedding friction. Jack asynchrony was idealized as a quasi-static thrust imbalance, and a synchronous case, asynchronous cases with thrust differences of 5–30%, and varying friction coefficients were analyzed. For the 30% thrust-difference condition, structural responses were examined at both the gasket-compression stage and the maximum jacking-force stage. The results show that jacking loads attenuate along the tunnel length in a staged manner, with the leading end acting as the primary load-transfer zone. Increasing thrust imbalance drives the response from axial compression toward eccentric compression-bending, accompanied by monotonic increases in principal stresses and vertical displacement. Higher friction further amplifies the leading-end response; nevertheless, for the investigated configuration, stresses and deformations under a 30% thrust imbalance remain within engineeringly acceptable limits. The findings provide a basis for identifying critical leading-end locations, arranging monitoring schemes, and supporting construction control under asynchronous jacking. Full article

Objective: This study compared the effects of submaximal and supramaximal accentuated eccentric loading (AEL) on lean mass and function in the trained (TL) and contralateral non-trained (NTL) legs of women. Methods: Twenty recreationally trained women were randomly assigned to submaximal (90% 1-RM) or supramaximal (120% 1-RM) AEL leg press training (2/week, 10 weeks, 4 sets of 8 repetitions) with 30% 1-RM concentric loading. Total thigh lean mass (TTLM), unilateral leg press 1-RM, mechanical power at 40% (P40), 60% (P60), and 80% (P80) of 1-RM, unilateral countermovement (CMJ) and drop jump (DJ) height, and muscle endurance (XRM) were assessed for each leg before and after intervention. Results: Regarding the TL, the submaximal group showed significant (p < 0.05) increases in 1-RM, P40, CMJ, and DJ, while the supramaximal group showed increased TTLM, 1-RM, P40, P60, and XRM. No significant differences were observed between groups. In the NTL, both groups showed significant increases in 1-RM and P40. Additionally, the submaximal group demonstrated improvements in P60, while the supramaximal group showed significant increases in both P60 and P80, and in TTLM. TL and NTL changes correlated significantly for 1-RM, CMJ, and TTLM. However, TL and NTL changes differed significantly for 1-RM and P40 in the submaximal group and for TTLM in the supramaximal group. Conclusions: Submaximal and supramaximal AEL resulted in similar neuromuscular improvements in both TL and NTL in women. Supramaximal loading provided additional benefits in mechanical power lean mass, while submaximal loading improved explosive performance. Supramaximal loading may not be necessary for active women. Full article

Background: Patellofemoral pain (PFP) is a prevalent overuse injury among recreational cyclists worldwide. Despite its ubiquity, little is known about the lived experiences of people with PFP, especially in Saudi Arabia, where healthcare and cultural factors may have a specific impact on how the condition is managed. The aim of this study was to explore the lived experiences of recreational cyclists with patellofemoral pain in Al Madinah, Saudi Arabia. Method: A qualitative, descriptive design using reflexive thematic analysis was employed. Eleven male recreational cyclists aged 28–44 years diagnosed with PFP were purposely recruited from Al Madinah Physical Therapy Centre. Female participants were excluded due to cultural constraints regarding sports participation. The participants consented to participate in the study and to be audio recorded. Data were collected through semi-structured interviews using an interview guide. The interview data were transcribed verbatim and thematically analysed using Atlas.ti, version 24. Results: The thematic analysis revealed six themes highlighting the multidimensional impact of PFP. The participants described localised mechanical impairment with rapid onset during activity and persistent symptoms lasting up to two weeks. Pain was exacerbated by eccentric loading and cycling-specific stressors, such as uphill riding, leading to significant anxiety and avoidance behaviours. To maintain activity, these cyclists employed adaptive strategies, including bike modifications and self-management. Notably, PFP imposed substantial cultural and social burdens, hindering spiritual practices, specifically Salah (prayer) postures, professional duties, and family caregiving. While the participants demonstrated resourcefulness through a hybrid of physiotherapy and independent research, pharmacological relief was viewed as a transient solution. Conclusions: Patellofemoral pain imposes significant multidimensional burdens on recreational cyclists in Al Madinah, which are exacerbated by cultural practices. Physiotherapy offers targeted interventions for pain relief, functional restoration, and participation enhancement, necessitating the need for culturally sensitive management programmes. Full article

Background: Trail running (TR) is an endurance discipline characterized by prolonged exercise, irregular terrain, and marked elevation changes, which increase eccentric muscular load and may induce muscular, neuromuscular, and cardiac damage. Objective: This study aimed to systematically review the evidence on muscular, neuromuscular, and cardiac damage associated with TR participation. Methods: This systematic review followed PRISMA 2020 guidelines and was registered in PROSPERO (CRD420251135043). Five databases (PubMed, Web of Science, Scopus, SportDiscus, and ScienceDirect) were searched up to 31 August 2025. Observational, longitudinal, prospective, and case studies involving healthy adolescent or adult trail runners were included. Outcomes comprised muscle damage biomarkers (e.g., creatine kinase, alanine aminotransferase), neuromuscular function (e.g., squat jump performance, maximal voluntary isometric contraction), and cardiac biomarkers (e.g., CK-MB, cardiac troponins, NT-proBNP). Methodological quality was assessed using the National Heart, Lung, and Blood Institute Study Quality Assessment Tool. Results were synthesized qualitatively. Results: Fifteen studies met the inclusion criteria, including a total of 247 participants. Post-race analyses consistently showed marked increases in muscle damage biomarkers and significant reductions in neuromuscular performance. Transient elevations in cardiac biomarkers were also observed, suggesting acute but reversible cardiac stress following TR events. Limitations: Evidence was limited by methodological heterogeneity, small sample sizes, and underrepresentation of female athletes. Conclusions: It was found that trail running induces substantial acute muscular, neuromuscular, and cardiac stress, particularly in events with high eccentric loading. Monitoring biochemical and neuromuscular markers may support training load optimization, recovery strategies, and injury prevention. Full article

Background: Orientation discrimination tasks provide a core measure of visual sensitivity and are widely used to study how perceptual performance varies with stimulus uncertainty and visual field location. Here, we examined how external noise, retinal eccentricity, and individual perceptual efficiency shape orientation discrimination thresholds. Methods: Forty-two adults (mean age = 32.35 years, SD = 7.23) completed a two-alternative forced-choice task judging the orientation (clockwise vs. counterclockwise) of briefly presented Gabor patches under varying levels of external noise (low, medium, high) and eccentricity (0°, 5°, 10°). Orientation offsets ranged from −8° to +8°. Thresholds were estimated using psychometric functions and analyzed via rm ANOVA, linear mixed-effects models, and supervised machine learning. Results: Accuracy declined with increasing noise (ω² = 0.48, p < 0.001) and improved with larger orientation offsets (ω² = 0.62, p < 0.001). Thresholds increased with both noise (ω² = 0.31, p = 0.002) and eccentricity (ω² = 0.27, p = 0.003). Signal-to-noise efficiency was the strongest predictor (β = −0.72, p < 0.001); age alone was nonsignificant, but its interaction with eccentricity showed selective peripheral declines. Mixed-effects models confirmed spatial effects (β = 0.058, p < 0.001) and residual between-subject variability (σ² = 0.14). Predictive models generalized well (R² = 0.54). Conclusions: Orientation discrimination is shaped by both stimulus-level difficulty and individual differences in perceptual efficiency, which account for variability in sensitivity across visual conditions. Age-related differences emerge primarily under spatial load and depend on interactions between observer traits and task demands. Full article

This paper proposes a novel mortise-and-tenon grouted masonry (MTGM) structure to enhance the mechanical performance and engineering applicability of masonry. The axial and eccentric compressive behavior of the system was systematically investigated through experimental testing and numerical simulation. A refined three-dimensional finite element model, developed in DIANA, effectively accounted for material nonlinearity and interfacial contact, with its high accuracy confirmed by experimental results. The parametric analysis of 52 numerical models elucidated the influence of block strength, core material type, wall thickness, steel fiber content, and geometric ratios on the compressive strength, deformation capacity, and failure modes. The results demonstrate that using steel fiber-reinforced concrete (SFRC) as the core filling material significantly enhances ductility and toughness; an SFRC content of 1.6% increased the ultimate strain by approximately 37%. Furthermore, increasing the eccentricity from 0.1 to 0.3 led to an average 40% reduction in load-bearing capacity. Theoretical analysis led to the derivation of calculation formulae relating to key axial compression parameters. Furthermore, a stress–strain constitutive relationship suitable for MTGM was established, featuring a parabolic ascending branch and a linear descending branch (R² = 0.992). For eccentric compression, a practical design method was developed based on the plane section assumption, which demonstrated superior predictive accuracy compared to existing code provisions. This study provides a reliable theoretical foundation and practical computational tools for the structural design and application of MTGM. Full article

This study presents the experimental and model-based characterization of polydimethylsiloxane (PDMS) as a damping medium in a torsional vibration viscous damper. Particular emphasis is placed on the influence of the PDMS viscosity on the dynamic response of the damper under variable hydrodynamic loading generated by torsional vibrations of the system and the mass of the inertia ring. Investigations were conducted over a wide range of kinematic viscosities, enabling the identification of damper operating regimes and the assessment of lubricating film stability. The developed mathematical model, based on hydrodynamic lubrication theory, describes the relationships between the PDMS viscosity, the relative angular velocity, and the eccentricity of the inertia ring. Experimental results confirm the model’s ability to predict transitions between stable, unstable, and boundary operating modes of the damper. The proposed approach enables the functional, system-level characterization of PDMS under hydrodynamic loading conditions within a torsional vibration damper. In this framework, the rheological properties of PDMS are directly linked to the dynamic response and operational stability of the mechanical system. Full article

Modern power transmission systems are required to meet increasingly stringent demands, including a wide range of transmission ratios, compact dimensions, high precision, energy efficiency, reliability, and thermal stability under dynamic operating conditions. Among the solutions that satisfy these requirements, cycloidal reducers are particularly prominent, with their application continuously expanding in industrial robotics, computer numerical control (CNC) machines, and military and transportation systems, as well as in the satellite industry. However, as with all mechanical power transmissions, friction in the contact zones of load-carrying elements in cycloidal reducers leads to power losses and an increase in operating temperature, which in turn results in a range of adverse effects. These undesirable phenomena strongly depend on lubrication conditions, namely on the type and properties of the applied lubricant. Although manufacturers’ catalogs provide general recommendations for lubricant selection, they do not address the fundamental tribological mechanisms in the most heavily loaded contact pairs. At the same time, the available scientific literature reveals a significant lack of systematic and experimentally validated studies examining the influence of lubricant type on the energetic and thermal performance of cycloidal reducers. To address this identified research gap, this study presents an analytical and experimental investigation of the effects of different lubricant types—primarily greases and mineral oils—on the thermal stability and efficiency of cycloidal reducers. The results demonstrate that grease lubrication provides lower total power losses and a more stable thermal operating regime compared to oil lubrication, while oil film thickness analyses indicate that the most unfavorable lubrication conditions occur in the contact between the eccentric bearing rollers and the outer raceway. These findings provide valuable guidelines for engineers involved in cycloidal reducer design and lubricant selection under specific operating conditions, as well as deeper insight into the lubricant behavior mechanisms within critical contact zones. Full article

Slender, lightweight and modern footbridges are particularly susceptible to vibrations induced by pedestrian activity. While extensive research has focused on vertical and lateral forces produced by walking, torsional moments generated by eccentrically walking pedestrians remain largely overlooked. Traditional assessments typically neglect these torsional effects, which can be critical when eccentric pedestrian loading excites torsional modes, especially in footbridges with asymmetric geometries. To address this, the paper considers the coupling between bending and torsional effects in both the pedestrian action and structure reaction, including pedestrian forces and moments, as well as bending-induced deflections and torsion-induced rotations of the cross-sections. A simplified method is also presented, allowing standard bending-only analyses to be easily adapted to include torsional effects using analytically derived correction factors. For validation, several experimental tests are conducted on an asymmetric curved footbridge located in Modena, Italy, characterised by coupled bending-torsional vertical modes and hosting different pedestrian densities, pacing frequencies, and crowd distributions (both uniform and eccentric). Experimental and numerical analyses demonstrate that neglecting torsional effects oversimplifies the assessment, highlighting the importance of accounting for bending-torsion coupling for the serviceability of asymmetric footbridges under eccentric near-resonance loading. Full article