Search Results (623)

To improve the application of carbon-fiber-reinforced polymers (CFRPs) in civil engineering, the long-term durability of CFRP anchorage systems has become a critical issue. Temperature fluctuations can significantly impact the bond performance between CFRPs and the load transfer medium (LTM), making it essential to understand the effects of temperature on the durability of CFRP anchorages. Therefore, this study investigates the influence of temperature on the durability of CFRP anchorages through aging tests on 30 epoxy-filled CFRP-bonded anchorage specimens, followed by pull-out tests. The long-term degradation of CFRP cable anchorage performances in representative regions of the globe was predicted using Arrhenius theory. The experimental results show that after long-term temperature exposure, the maximum bond strength of the CFRP-LTM interface in the anchoring zone degrades after 30 days but continues to increase after 150 days. In contrast, the residual bond strength of the CFRP-LTM interface in the anchorage zone continuously decreases over time, with the degradation rates gradually decreasing over time. Higher temperatures lead to more severe degradation of anchoring performance. Based on the experimental results, it is predicted that the anchoring performance of a CFRP cable anchorage system will reach degradation rates of 63.72%, 83.36%, and 94.73% after 50 years in regions with average annual temperatures of 0 °C, 10 °C, and 20 °C, respectively. Therefore, the temperature has a significant long-term impact on the anchoring performance of CFRP cable bonding systems, necessitating a more conservative design in higher-temperature areas. Full article

In this research, the adhesive contact between a hard steel and a soft elastomer cylinder was experimentally studied. In the experiment, the hard cylinder was indented into the soft one, after which the two cylinders were separated. The contact area between the cylinders was elliptical in shape, and the eccentricity of this increased as the angle between the axes of the contacting cylinders decreased. Additionally, the adhesive pull-off force and the contact area increased with a decrease in the angle between the cylinders. The use of a transparent elastomer allowed for observation of the shape of the contact in real time, which facilitated the creation of videos demonstrating the complete process of contact failure and the evolution of the ellipse shape, depending on the distance between the cylinders and normal force. These findings contribute to a better understanding of adhesive interactions in elliptical contacts between cylinders and can be applied to fields such as soft robotics, material design, and bioengineering, where precise control over adhesion and contact mechanics is crucial. Full article

Existential threats, including threats to the self, society, and the planet, are present throughout the lifespan and form a core element of the human experience. To consolidate knowledge and constructs about how people can adequately respond to existential threats, we convened an interdisciplinary working group, which consisted of eight researchers from the fields of psychology, systemic theology, practical theology, religious studies, cognitive science, palliative care, and sustainability science. The group met one day per week for 9 months to engage in an interactive co-creative process of data collection and analyses, discussion, iterative presentations, and writing. The process resulted in the development of an interdisciplinary model that pulls together the key themes of how people, societies, and systems can foster existential resilience and transformation. The model consists of three axes across which we (individuals, groups, systems) have to strengthen or stretch our “inner muscles”: connectedness, agency, and time. All axes contribute to the development of our inner capacities and, ultimately, meaning and purpose, which are crucial to support resilience and transformation. Our interdisciplinary overarching model provides a common conceptualization for existential resilience and transformation that can bridge existing research to support individual, collective, and large-scale system-change work. Its relevance and potential implementation are illustrated and presented from different disciplinary angles. Full article

In this study, the mechanical performance and failure modes of cold-potted inserts within sandwich structures were examined, focusing on the influence of the potting radius, while maintaining constant insert radius and specimen characteristics. In this research, destructive testing was used to evaluate the pull out, load-carrying capacity, and failure mechanisms of the inserts. The methods of stiffness degradation and acoustic emissions (AE) were employed for structural health monitoring to capture real-time data on failure progression, including core buckling, core rupture, and skin delamination. The results indicated that increasing the potting radius significantly altered the failure modes and critical failure load of the insert system. A critical potting radius was identified where maximum stiffness was achieved. Beyond this point, insert fracture became the dominant failure mode, with minimal damage to the surrounding core and CFRP skins. Larger potting radii also led to reduced displacement at failure, increased ultimate loads, and elevated stiffness, which were maintained until sudden structural failure. Through detailed isolation and observation of each failure event and with the use of AE data, precise identification of system damage in real time was allowed, offering insights into the progression and causes of failure. Full article

In view of the application status and technical challenges of steel–wood composite joints in architecture, this paper proposes an innovative connection technology to solve issues such as susceptibility to pry-out at beam–column joints and low load-bearing capacity and to provide various reinforcement methods in order to meet the different structural requirements and economic benefits. By designing and manufacturing four groups of beam–column joint specimens with different reinforcement methods, including no reinforcement, structural adhesive and angle steel reinforcement, 4 mm thick steel sleeve reinforcement, and 6 mm thick steel sleeve reinforcement, monotonic loading tests and finite element simulations were carried out, respectively. This research found that unreinforced specimens and structural adhesive angle steel-reinforced joints exhibited obvious mortise and tenon compression deformation and, moreover, tenon pulling phenomena at load values of approximately 2 kN and 2.6 kN, respectively. However, the joint reinforced by a steel sleeve showed a significant improvement in the tenon pulling phenomenon and demonstrated excellent initial stiffness characteristics. The failure mode of the steel sleeve-reinforced joints is primarily characterized by the propagation of cracks at the edges of the steel plate and the tearing of the wood, but the overall structure remains intact. The initial rotational stiffness of the joints reinforced with angle steel and self-tapping screws, the joints reinforced with 4 mm thick steel sleeves, and the joints reinforced with 6 mm thick steel sleeves are 3.96, 6.99, and 13.62 times that of the pure wooden joints, while the ultimate bending moments are 1.97, 7.11, and 7.39 times, respectively. Using finite element software to simulate four groups of joints to observe their stress changes, the areas with high stress in the joints without sleeve reinforcement are mainly located at the upper and lower ends of the tenon, where the compressive stress at the upper edge of the tenon and the tensile stress at the lower flange are both distributed along the grain direction of the beam. The stress on the column sleeve of the joints reinforced with steel sleeves and bolts is relatively low, while the areas with high strain in the beam sleeve are mainly concentrated on the side with the welded stiffeners and its surroundings; the strain around the bolt holes is also quite noticeable. Full article

Open-source software (OSS) projects rely on collaborative contributions, yet sustaining long-term engagement remains a challenge. This study examines how contributor activity frequency and network centrality impact sustained contributions in 672 GitHub repositories. Using k-core decomposition and model checking, we find that contributors with higher k-core values manage more pull requests. Additionally, they show greater resilience in continuing to contribute after pull request rejections, a behavior rarely seen in non-core contributors. Moreover, the likelihood of long-term engagement increases significantly when contributors’ pull requests are processed swiftly, with delayed or rejected pull requests resulting in higher disengagement, particularly among peripheral contributors. We also observe that as project networks grow more complex over time, core contributors become essential in maintaining project sustainability. These findings offer new insights into fostering core contributor retention and underscore the need for efficient governance and PR management practices in OSS projects. Full article

This study aimed to examine the intra- and inter-session reliability of kinetic variables in the isometric mid-thigh pull (IMTP) and isometric belt squat test (IBSqT) in strength-trained individuals. Fifteen men (26.9 ± 8.9 years; 1.78 ± 0.05 m; 86.9 ± 10.5 kg) and six women (23.8 ± 4.6 years; 1.66 ± 0.06 m; 65.8 ± 10.3 kg), experienced in strength training, completed a familiarization session followed by two experimental sessions. The peak force (PF) and relative peak force to body weight (RPF), were collected for both isometric tests. Additionally, force (F), impulse (I), and rate of force development (RFD) were analyzed across different time windows (50, 100, 150, 200, and 250 ms). The intraclass correlation coefficient (ICC), coefficient of variation (CV), standard error of measurement (SEM), smallest worthwhile change (SWC) and Bland-Altman plots were calculated and displayed. Intra-session reliability was excellent for PF and RPF (ICC ≥ 0.98, CV ≤ 10%) in both IMTP and IBSqT. However, RFD and IMP displayed higher variability (CV > 10%), with low to good reliability depending on time frames. Inter-session reliability was excellent for PF and RPF (ICC ≥ 0.96, CV ≤ 5.3%) in both tests. Force at various time points exhibited moderate to excellent reliability (ICC = 0.70–0.90). PF and RPF demonstrated the highest sensitivity to performance changes, with SWC0.2 values exceeding SEM. In contrast, RFD and impulse showed larger variabilities. These findings indicate that PF and RPF are the most reliable and sensitive metrics for monitoring performance. Coaches and practitioners can use IMTP and IBSqT to detect meaningful changes in maximal isometric force production. Full article

Adhesion-based space climbing robots, with their flexibility and multi-functional capabilities, are seen as a promising candidate for in-orbit maintenance. However, challenges such as uncertain adhesion establishment, unexpected detachment, and body motion unsteadiness in microgravity environments persist. To address these issues, this paper proposes a coordinated force–position compliance control method that integrates novel adhesion establishment and rotational detachment strategies, integrated into the gait schedule for a space climbing robot. By monitoring the foot-end reaction forces in real time, the proposed method establishes adhesion without risking damaging the spacecraft exterior, and smooth detachment is achieved by rotating the foot joint instead of direct pulling. These strategies are dedicated to reducing unnecessary control actions and, accordingly, the required adhesion forces in all feet, reducing the possibility of unexpected detachment. Climbing experiments have been conducted in a suspension-based gravity compensation system to examine the merits of the proposed method. The experimental results demonstrate that the proposed rotational detaching method decreases the required pulling force by 65.5% compared to direct pulling, thus greatly reducing the disturbance introduced to the robot body and other supporting legs. When stepping on an obstacle, the compliant control method is shown to reduce unnecessarily aggressive control actions and result in a reduction in relevant normal and shear adhesion forces in the supporting legs by 44.8% and 35.1%, respectively, compared to a PID controller. Full article

Background: Radial forearm free flap (RFFF) is considered one of the workhorses in modern head and neck reconstruction surgery due to its technical simplicity, versatility and less time-consuming harvest. Methods: In this report, we present the case of a 56-year-old woman with sublingual squamous cell carcinoma (SCC) who underwent surgical resection and reconstruction of the defect with a RFFF. Results: The preoperative Allen test showed normal blood flow, and the ultrasound did not recognize any blood vessel abnormalities in the left arm. However, during the RFFF harvest, when the dissection of the pedicle came to the cubital fossa, there was no brachial artery bifurcation. While trying to find the bifurcation, the dissection almost came to the axillary region. Hence, the RFFF was converted to a pedicle flap and was pulled through to the intraoral defect where it was used for reconstruction. Conclusions: Hence, during the preoperative radiological ultrasound, besides the usual characteristics such as the radial artery diameter, flow and possible obstructions, it is also important to explore if there are any other anatomical abnormalities that could influence the operation. Full article

Background: Prostheses are becoming more advanced and biomimetic with time, providing additional capabilities to their users. However, prosthetic sensation lags far behind its natural limb counterpart, limiting the use of sensory feedback in prosthetic motion planning and execution. Without actionable sensation, prostheses may never meet the functional requirements to match biological performance. Methods: We propose an approach for upper limb prosthetic grasp security feedback, delivered to the wearer through direct nerve stimulation proportional to the likelihood of objects slipping from grasp. This proportional feedback is based on a linear regression of the sensors embedded in a prosthetic hand to predict slip before it occurs. Four participants with transhumeral amputation performed pulling tasks with their prosthetic hand grasping an object at predetermined grip forces, attempting to pull the object with as much force as possible without slip. These trials were performed with two different prediction notification paradigms. Results: At lower grasp forces, where slip was more likely, a strong, single impulse notification of impending slip reduced the incidence of object slip by a median of 32%, but the maximum achieved pull forces did not change. At higher grasp forces, where slip was less likely, the maximum achieved pull forces increased by a median of 19% across participants when provided with a stimulation strength inversely proportional to the grasp security, but slip incidence was unchanged. Conclusions: These results suggest that this approach may be effective in recreating a lost sense of grip stability in the missing limb that can be incorporated into motor planning and ultimately prevent unanticipated object slips. Full article

In this research, a feedback nonlinear control law was designed and tested to perform acquisition and station-keeping maneuvers for a lunar navigation constellation. Each satellite flies an Elliptical Lunar Frozen Orbit (ELFO) and is equipped with a steerable and throttleable low-thrust propulsion system. Lyapunov stability theory was employed to design a real-time feedback control law, capable of tracking all orbital elements (including the true anomaly), expressed in terms of modified equinoctial elements (MEEs). Unlike previous research, control synthesis was developed in the complete nonlinear dynamical model, and allows for driving the spacecraft toward a time-varying desired state, which includes correct phasing. Orbit propagation was performed in a high-fidelity framework, which incorporated several relevant harmonics of the selenopotential, as well as third-body effects due to the gravitational pull of the Earth and Sun. The control strategy at hand was successfully tested through two Monte Carlo campaigns in the presence of nonnominal flight conditions related to estimation errors of orbit perturbations, accompanied by the temporary unavailability and misalignment of the propulsive thrust. Full article

Background: Consuming collagen hydrolysate (CH) may improve symptoms of exercise-induced muscle damage (EIMD); however, its acute effects have not been compared to dairy protein (DP), the most commonly consumed form of protein supplement. Therefore, this study compared the effects of CH and DP on recovery from EIMD. Methods: Thirty-three males consumed either CH (n = 11) or DP (n = 11), containing 25 g of protein, or an isoenergetic placebo (n = 11) immediately post-exercise and once daily for three days. Indices of EIMD were measured before and 30 min and 24, 48, and 72 h after 30 min of downhill running on a −15% slope at 80% of VO_2max speed. Results: Downhill running induced significant EIMD, with time effects (all p < 0.001) for the delayed onset of muscle soreness (visual analogue scale), countermovement jump height, isometric midthigh pull force, maximal voluntary isometric contraction force, running economy, and biomarkers of muscle damage (creatine kinase) and inflammation (interleukin-6, high-sensitivity C-reactive protein). However, no group or interaction effects (all p > 0.05) were observed for any of the outcome measures. Conclusions: These findings suggest that the post-exercise consumption of CH or DP does not improve indices of EIMD during the acute recovery period in recreationally active males. Full article

In this paper, the case of the power dependence between strain and stress is studied, along with the way in which this dependence modifies the calculation methodologies and the results that are obtained in classic cases of stress. The main cases studied are compression (squashing), tension (pulling), bending, shear (cutting), and torsion (twisting). Simple relationships are thus obtained for a wide class of materials that fall into this category. They can be useful to designers because they provide information on mechanical structures in a short time with good precision. Full article

Apples are widely cultivated primarily for fresh consumption. During mechanized harvesting, the extraction of fruit stalks can significantly impact the storage duration of fresh apples. The tensile force applied to the abscission layers is a critical factor in retaining the stalks; yet, few researchers have focused on preventing stalk pull-out during picking. In this research, we studied the phenomenon of missing stalks during mechanical picking by analyzing the tensile force exerted on the abscission layer during picking and optimizing the attitude of the end effector to achieve the highest stalk retention rate. Firstly, the tangential and normal energy release rates of the abscission layer were used as key parameters to model the cohesive zone of the abscission layer, a finite element model of the fruit–stalk–branch system was developed, based on which the actual fruit picking process using direct-pulling and twisting was simulated. Subsequently, the data obtained from the simulation were analyzed using response surface analysis, and the maximum tensile force at the time of fracture of the delamination and the time of its fracture were used as optimization parameters to find the optimal solution of the angle, direct-pulling speed, and twisting speed d to achieve the highest stalk retention rate. Finally, through field experiments, it was demonstrated that the optimal picking conditions could effectively improve the picking success rate and stalk retention rate. The results show that, when the end effector picks close to the fruit at about 58°, the stalk retention rate can reach 94.0%. Full article

Background: Deep brain stimulation (DBS) is an effective treatment for movement disorders, but its long-term efficacy may be undermined by hardware complications such as lead fractures. These complications increase healthcare costs and necessitate surgical revisions. The frequency, timing, and clinical factors associated with lead fractures remain poorly understood. Objective: This study aimed to determine the incidence, timing, and clinical factors associated with lead fractures in a large cohort of DBS patients over a 10-year period. Methods: This retrospective study analyzed data from 325 patients who underwent bilateral DBS implantation at the National Centre for Neurosurgery from 2013 to 2023. The analysis specifically focused on 17 patients who experienced lead fractures during the long-term follow-up period. Results: Among the 325 patients, lead fractures were identified in 17 patients (5.23%), affecting 18 electrodes. The majority of cases involved patients with Parkinson’s disease (76.5%) or dystonia (23.5%), with an average age of 59.17 ± 8.77 years. Nearly all patients with lead fractures had a history of trauma. Additionally, two cases were associated with active engagement in sports, particularly activities involving movements like pulling up on a horizontal bar, while Twiddler’s Syndrome was identified in two other cases. All electrode fractures required surgical revision. Conclusions: Lead fractures, while rare, remain a significant complication in DBS systems. Precise surgical techniques, early detection, and advancements in DBS hardware design may help to mitigate this risk. Future innovations, such as durable leads or wireless systems, may improve long-term outcomes in DBS therapy for movement disorders. Full article