Search Results (209)

The use of vibrational transport for granular materials has significantly increased in the technological industry due to its reliability, operational efficiency, cost-effectiveness, and relatively uncomplicated technological setup. These transportation methods typically utilize various forms of asymmetry, such as kinematic, temporal (time), wave, and power asymmetry, to induce controlled motion on oscillating surfaces. This study analyses the motion of the granular materials on an inclined plane, where the central innovation lies in the creation of an additional system asymmetry of frictional conditions that enables the granular materials to move upward. This asymmetry is created by introducing dry friction dynamic manipulations. A mathematical model has been developed to describe the motion of particles under these conditions. The modelling results proved that in an inclined transportation system, the asymmetry of frictional conditions during the oscillation cycle—created through dynamic dry friction manipulations—generates a net frictional force exceeding the gravitational force, thereby enabling the upward movement of granular particles. Additionally, the findings highlighted the key control parameters governing the motion of granular particles. λ, which represents the segment of the sinusoidal period over which the friction is dynamically louvered, serves as a parameter that controls the velocity of a moving particle on an inclined surface. The phase shift ϕ serves as a parameter that controls the direction of the particle’s motion at various inclination angles. Experimental investigations were conducted to assess the practicality of this method. The experimental results confirmed that the granular particles can be transported upward along the inclined surface with an inclination angle of up to 6 degrees, as well as provided both qualitative and quantitative validation of the model by illustrating that motion parameters exhibit comparable responses to the control parameters, and strongly agree with the theoretical findings. The primary advantage of the proposed vibrational transport method is the capacity for precise control of both the direction and velocity of granular particle transport using relatively simple mechanical setups. This method offers mechanical simplicity, low cost, and high reliability. It is well-suited to assembly line and manufacturing environments, as well as to industries involved in the processing and handling of granular materials, where controlled transport, repositioning, or recirculation of granular materials or small discrete components is required. Full article

Background/Objectives: Limited ankle dorsiflexion has been associated with compensatory movement patterns throughout the lower extremity kinematic chain. This study investigated relationships between weight-bearing dorsiflexion capacity and lower limb kinematics and plantar pressure patterns during gait. Methods: Twenty-seven healthy adults (age: 22.8 ± 3.4 years) performed a weight-bearing lunge test (WBLT) and walked at a standardized pace across a pressure-sensing walkway while wearing inertial measurement units. Statistical Parametric Mapping assessed correlations between WBLT dorsiflexion and kinematic variables throughout the stance phase. Partial correlations controlled for walking velocity and were used to examine relationships with discrete plantar pressure measurements. Results: Reduced dorsiflexion capacity during the WBLT showed bilateral moderate associations with less ankle dorsiflexion (LEFT: peak r = 0.53; RIGHT: peak r = 0.60) and knee flexion (LEFT: peak r = 0.56; RIGHT: peak r = 0.58) during terminal stance and push-off. Proximal compensations demonstrated limb-specific patterns. Hip abduction was strongly negatively correlated in the left leg only (peak r = −0.65), while pelvic tilt showed bilateral relationships with opposing temporal patterns (LEFT: peak r = −0.58 early stance; RIGHT: peak r = 0.62 terminal stance). Plantar pressure analysis revealed that reduced dorsiflexion was associated with decreased heel relative impulse bilaterally (r = 0.53–0.56) and altered temporal patterns of midfoot loading on the left leg (r = 0.56). Conclusions: Limited dorsiflexion under load is associated with compensatory movement patterns extending from the ankle to the pelvis bilaterally. The evaluation of loaded ankle mobility should be considered an essential component of lower extremity movement assessment. Full article

This study investigates the joint mechanical power (JMP) distribution in the half squat (HS) exercise through the Power-Based Training (PBT) framework, with the primary aim of providing preliminary methodological validation of this analytical approach and illustrating its capacity to characterize joint contributions across movement phases and load levels. Five professional weightlifters performed HS under five progressive loads (20–80% 1RM), while kinematics and kinetics were recorded with a Vicon motion capture system and force platforms. JMP at the hip, knee, and ankle was analyzed in four distinct movement phases. Results indicated that joint contributions varied with load and phase. Under light loads the knee tended to produce most power. As load increased, contributions shifted proximally: the hip increased both absorption and production, and the ankle’s relative contribution grew in the final lifting phase. The main eccentric (lowering deceleration) and concentric (lifting acceleration) phases concentrated the highest JMP values, though differences between phases diminished at higher loads, suggesting a more homogeneous effort distribution. These findings support the feasibility of the PBT framework for methodological joint-level analysis. Given the pilot scope and purposive elite sample, results are not intended for population inference but inform about methodological applications in training, rehabilitation, and injury-risk assessment. Full article

Sperm cryo-tolerance resulted in significant variations in post-thaw semen quality among breeds and individual boars. In the present study, semen samples from thirty-seven large white boars were cryopreserved to select individuals with strong and weak freezing tolerance according to their post-thaw sperm quality. Comparative TMT-based quantitative proteomic analysis between the two groups identified 22 significantly differentially expressed proteins. NT5C1B and ADA, the significantly downregulated proteins in the semen of the low cryo-tolerance group, were supplemented in the semen samples with lower cryo-tolerance. Supplementation with 1 µg/mL of NT5C1B dramatically (p < 0.05) improved kinematic parameters and structural integrity. In comparison with the control group, mitochondrial activity and antioxidant capacity were significantly enhanced in post-thaw sperm. In vitro fertilization assays revealed that the NT5C1B-treated group also has notably (p < 0.05) high sperm penetration and embryonic cleavage rates. ADA supplementation did not exhibit obvious freezing tolerance effects. NT5C1B can be a potential key functional protein to enhance the quality and cryo-tolerance during cryopreservation. Specifically, supplementation with 1 µg/mL NT5C1B significantly improved post-thaw motility, structural integrity, mitochondrial activity, and antioxidant capacity and ultimately enhanced the sperm penetration rate and embryonic cleavage rate in cryo-sensitive sperm, confirming its role as a functional protector during cryopreservation. Full article

Suction embedded plate anchors (SEPLAs) are widely used in offshore engineering, but their keying process is often accompanied by embedment loss, which reduces the holding capacity. To minimize embedment loss, inwardly rotating keying flaps have been introduced, though their kinematics and effects on embedment loss remain insufficiently understood. In this study, transparent soil model tests, combined with particle image velocimetry (PIV), were conducted to directly visualize the keying behavior of SEPLAs with inwardly rotating keying flaps. Five anchor configurations were tested, including a reference model without flaps and four models with flap lengths ranging from 0.2 to 0.5 times the anchor breadth. The results show that inwardly rotating keying flaps significantly reduce embedment loss, with the configuration featuring a flap length of 0.4 times the anchor breadth exhibiting the optimal performance. The findings provide valuable insight into the influence of flap length on SEPLA keying behavior and embedment loss, offering practical guidance for optimizing flap design. Full article

The distributed actuation mechanism (DAM) is inspired by the motion of biological muscles and enables efficient modulation between speed and force through a variable gearing concept. This study proposes an advanced modeling-based multi-objective optimization framework that enhances the dynamic performance of a DAM-based manipulator by simultaneously improving its end-effector velocity and payload capacity. The kinematic and dynamic characteristics of the DAM are mathematically modeled to capture the interactions among design parameters, and a high-fidelity multibody dynamics model is developed using RecurDyn. Then, a sequential quadratic programming (SQP) algorithm implemented in MATLAB is employed to perform optimization under geometric and physical constraints. The results demonstrate that the proposed optimization method achieved increases of approximately 46.5% in maximum velocity and over 40% in maximum payload, confirming the effectiveness of the advanced modeling-based optimization strategy. It was also found that link-length ratios and hinge offsets play critical roles in determining the DAM’s dynamic behavior. The proposed framework provides a systematic and practical approach for integrating mathematical modeling with design optimization and offers valuable guidelines for improving the structural design and performance of distributed-actuation-based robotic manipulators. Full article

This study develops a systematic kinematic upper-bound framework to evaluate the ultimate bearing capacity and failure mechanisms of prefabricated cast-in-place slab–wall joints in overlapped metro stations. Recognizing the complex shear–compression interaction in these critical structural nodes, a novel three-dimensional short-block shear failure model is established based on the principle of energy balance. The analysis employs a modified Mohr–Coulomb strength criterion incorporating a finite tensile strength cut-off, enabling more accurate representation of cracking and tensile resistance effects. Analytical solutions are derived to predict the ultimate capacity and critical failure angle, followed by a comprehensive parametric analysis. The results reveal that cross-sectional dimensions dominate the bearing capacity, while the internal friction angle and tensile-to-compressive strength ratio significantly influence both the magnitude and mode of failure. A narrower load distribution width enhances capacity and reduces the optimal failure angle. Overall, the proposed 3D model provides a rigorous and efficient theoretical tool for the design optimization and safety assessment of prefabricated underground structures. Full article

Designing a mechanical gripper, achieving the combined capabilities of high loading capacity, flexible environmental adaptability, and dexterous kinematic performance, is highly desired in human–machine interaction and industrial production efficiency improvement, yet this combination of grasping encounters irreconcilable challenges. Although rigid–flexible coupled mechanical grippers exhibit promising advantages compared with conventional rigid mechanical grippers and pure soft grippers, they still get stuck in problems of grasping stability owing to the mechanical mismatch between rigid and flexible materials. Inspired by the hybrid structure of the human finger, we designed an underactuated rigid–flexible coupled mechanical gripper (U-RFCG) to expand the grasping range of existing mechanical grippers. We utilized an embedded flexible microcolumn array to couple the rigid underactuated fingers with a flexible silicone rubber finger segment and integrated a flexible silicone rubber cavity into each rigid–flexible coupling finger segment, thereby addressing issues such as slippage and fracture at the coupling interface of the rigid–flexible structure. This design enables the mechanical gripper to possess the superior characteristics of both rigid and flexible grippers, along with simple execution control. We established mathematical models to analyze the static and kinematic properties of the fingers. Based on these models, we optimized the dimensional parameters of the underactuated links to ensure reasonable contact force distribution and stable motion. Repeated experiments demonstrated that the contact force exerted by each phalanx consistently stabilized at approximately 3.58 N during operation. Lastly, we integrated the U-RFCG into a 3D motion platform. Our mechanical gripper demonstrates significant adaptability and high load capacity for grasping various objects, including irregular cauliflowers, fragile fried instant noodles, and heavy cabbages. It successfully handled objects spanning a weight range of 30–1500 g without causing damage to them. These results confirm that our design balances load capacity and grasping safety through the synergy of rigid and flexible properties, providing a new solution for robotic grasping in complex scenarios. Full article

To enhance the precision, load capacity, disturbance rejection, and reliability of shipborne parallel stabilization platforms under complex sea conditions, this paper proposes a redundant, actuated, parasitic-motion-free 3-DOF 3RRS-RUS parallel stabilization platform. Based on the proposed 3RRS-RUS shipborne parallel stabilization platform, a Linear Active Disturbance Rejection Control (LADRC) approach, integrated with a Sliding Mode Disturbance Observer (SMDO), is developed. First, the mechanism is synthesized using screw theory, and its 2R1T 3-DOF characteristics are verified through parasitic motion analysis. Second, the inverse kinematics model is established. Third, the conventional LADRC is decoupled, and a new Linear Extended State Observer (LESO) together with its corresponding control law is designed. Moreover, an SMDO is incorporated into the motor’s three-loop control scheme to alleviate the estimation burden on the LESO and enhance the system’s disturbance rejection capability. Finally, experimental validations were carried out on both the CSPACE and SimMechanics platforms. The results demonstrate that the proposed SMDO–LADRC achieves superior tracking performance, high robustness, and strong disturbance rejection capability, The tracking errors along the RX, RY, and Z axes were reduced by 6.5%, 1.1%, and 16.6%, respectively, compared with the conventional LADRC, while also confirming the feasibility of the newly designed 3-DOF 3RRS-RUS shipborne parallel stabilization platform. Full article

Background: Firefighters are at elevated risk of low back pain (LBP), yet predictors, mechanisms, and interventions for LBP in this occupation remain poorly defined. The purpose of this study was to systematically review the literature and synthesize the evidence on functional biomarkers associated with the risk of LBP in firefighters. Methods: PubMed, EMBASE, CINAHL, and PEDro were searched for studies evaluating functional biomarkers in firefighters with or without LBP, including aerobic capacity, anthropometric measures, disability/kinesiophobia, functional work tasks/capacity, imaging/structural/morphological characteristics, kinematics, movement quality/range of motion, muscular fitness, overall physical fitness, physical activity. Empirical evidence statements were generated for each biomarker domain, under Protocol Registration PROSPERO (CRD420251010061). Results: Eighteen studies (n = 32,977) met inclusion criteria and were predominantly cross-sectional (14/18) with fair quality (13/18), which suggests a substantial risk of bias. Higher disability/kinesiophobia and poorer functional work task performance were linked to increased risk of LBP, although causal relationships cannot be determined. Associations for the eight other biomarkers were inconsistent. Two interventional studies demonstrated benefits from trunk-focused exercise. Conclusions: The literature examining functional biomarkers and LBP in firefighters is fragmented, which precludes making robust and broad clinical recommendations for evidence-based implementation. Findings of future research may ultimately lead to approaches to improve the safety and health of firefighters with LBP through patient-centered and tailored programs addressing integrated functional biomarkers across the continuum of prevention, clinical care, and resilience development. Full article

The conventional deadlift is frequently performed in multiple-repetition sets at loads exceeding 80% of one-repetition maximum (RM) to increase maximal strength in the posterior chain. Fatigue-induced intra-set movement alterations have been observed in various exercises and loading ranges, but whether they occur under strength-specific deadlift conditions remains poorly understood. This study compared the intra-set development of spinal and lower extremity kinematics, net joint moments (NJMs) of the lower extremities, and surface electromyography (sEMG) amplitudes during a 3RM deadlift using statistical parametric mapping. Ten strength-trained women (body mass: 69.2 ± 8.1 kg, height: 166.3 ± 3.1 cm, age: 23.2 ± 3.7 years) lifted 100.6 ± 18.1 kg for a set of 3RM deadlifts. Across repetitions, spinal flexion and hip extension angles increased, while barbell velocity and peak angular hip extension velocity decreased. In contrast, hip NJMs and sEMG amplitudes showed minimal or no significant differences between repetitions. These findings suggest that as fatigue accumulates during a 3RM set, lifting capacity is maintained primarily through kinematic adjustments rather than increased hip extensor contribution. Full article

Conventional balance assessments often miss subtle deficits in sarcopenia patients due to compensatory strategies. This study develops a computational framework using multidimensional temporal analysis of center-of-pressure (COP) signals to quantify variations in compensatory reserve—the capacity to mask balance impairments—within these patients. COP data were collected from 82 older adults (sarcopenia vs. controls) during static standing on a standard clinical force platform (routine for geriatric balance testing). The framework integrates Dynamic Time Warping distances from a healthy template, fixed-weight LSTM embeddings, and statistical metrics, with feature selection and 5-fold cross-validation (SMOTE) to mitigate overfitting. Semi-tandem stance was most discriminative, achieving 0.84 ± 0.04 accuracy and 0.86 ± 0.05 ROC-AUC—outperforming conventional kinematic features. SHAP analysis identified DTW-based features as primary drivers, correlating with clinical severity indicators, while intra-group variability in prediction probabilities indicated a compensatory reserve gradient. This study introduces a feasible bioengineering methodology based on clinical COP platform analysis, laying the groundwork for future validation and translation into routine clinical assessment tools. Full article

Applied muscular strain and hamstring strain capacity have a joint interaction on hamstring strain injury (HSI) with modifiable risk factors frequently assessed. However, to date there is limited observations on the interaction between these factors. The purpose of the present study was to observe if spatiotemporal characteristics, running kinematics and muscle activation were related to modifiable risk factors of HSI. Twenty-two competitive team sport athletes (24.7 ± 4.3 years, 1.82 ± 0.07 m, 84.9 ± 8.5 kg) participated whereby the Bicep femoris long head (BF_LH) fascicle length assessed via ultrasound and isokinetic eccentric hamstring strength was assessed. With running assessment performed at 18 km/h, capturing running kinematics and muscle activation. Multiple linear regressions were used to examine the relationship of running kinematics and muscle activation on the modifiable risk factors of HSI on. The overall model (F_2,19) was statistically significant for both relative eccentric hamstring strength (F = 23.58, p < 0.001) and BF_LH fascicle length (F = 18.87, p < 0.001) highlighting spatiotemporal characteristics, running kinematics and hamstring activation were found to be significantly related to the modifiable risk factors. There is a complex interrelationship between running mechanics and hamstring muscle properties, with the potential of either cause or consequence association. Full article

This work introduces a novel variable camber mechanism that combines the high-load capacity, structural stability, and mechanical efficiency of rigid-body mechanisms with the adaptability, lightweight design, and continuous and smooth motion of compliant mechanisms. The proposed mechanism, featuring an articulated airfoil structure with revolute joints and a cantilever beam that models and controls airfoil camber morphing, employs both standard and higher kinematic pairs to constrain mobility and facilitate camber adjustments through beam deflection and coordinated kinematic interactions. Through multidisciplinary optimization, this study determined the optimal mechanism configuration and airfoil shapes for a small fixed-wing UAV (Unmanned Aerial Vehicle), meeting its morphing and mission requirements, showing the potential for drag reduction by up to 13% across various cruise conditions, thus lowering overall mission drag and energy usage. 2D (airfoil) and 3D (wing) prototypes were built to demonstrate the working principle of the proposed mechanism and to highlight its morphing capabilities. It can morph into multiple airfoil configurations, producing continuous, smooth and efficient airfoil shapes. Moreover, the mechanism is robust, simple, and easy to manufacture, effectively harnessing the strengths of both rigid-body and compliant mechanisms. Full article

This study examined the influence of physiological parameters on peak velocity (Vpeak) and of kinematic variables on running economy (RE) during an outdoor incremental VAM-EVAL test completed by eleven national-level triathletes. Maximal oxygen uptake (VO₂max), ventilatory thresholds, RE, and minimum muscle oxygen saturation (SmO₂min) were obtained with a portable gas analyzer and near-infrared spectroscopy (NIRS), while cadence, stride length, vertical oscillation, and contact time were recorded with a foot-mounted inertial sensor. Multiple linear regression showed that VO₂max and SmO₂min together accounted for 86% of the variance in Vpeak (VO₂max: r = 0.76; SmO₂min: r = −0.68), whereas RE at 16 km·h⁻¹ displayed only a moderate association (r = 0.54). Links between RE and kinematic metrics were negligible to weak (r ≤ 0.38). These findings confirm VO₂max as the primary determinant of Vpeak and suggest that SmO₂min can be used as a complementary, non-invasive marker of endurance capacity in triathletes, measurable in the field with portable NIRS. Additionally, inter-individual differences in cadence, stride length, vertical oscillation, and contact time suggest that kinematic adjustments are not universally effective but rather highly individualized, with their impact on RE likely depending on each athlete’s specific characteristics. Full article