Search Results (2,359)

The fracture behavior of a locking pin used in the penultimate-stage blades of a 600 MW steam turbine in a thermal power plant was investigated through microstructural and microhardness characterization, fracture surface and energy-dispersive spectroscopy (EDS) analysis, as well as finite element load simulation. The microhardness values measured on the cross-section of the service pins ranged from 528 to 541 HV0.1, showing little difference from the unused pins. Scanning electron microscopy analysis revealed that approximately 70% of the fracture surfaces exhibited an intergranular “rock candy” morphology. The results indicate that pin failure was primarily caused by the combined effects of fretting wear and stress corrosion cracking (SCC). Specifically, vibration at the blade root, impeller, and pins due to start–stop cycles and load variations led to fretting wear, forming pits approximately 75 μm in size. Under the combined effects of weakly corrosive wet steam environments and shear stresses, SCC initiated at the high stress concentration points of these pits. Early crack propagation primarily followed original austenite grain boundaries, while later stages mainly extended along martensite plate boundaries. As cracks advanced, the cross-sectional area gradually decreased, causing the effective shear stress to increase until it exceeded the shear strength, ultimately leading to fracture. These findings not only provide a scientific basis for enhancing the reliability of steam turbine locking pins and extending their service life, but also contribute to a broader understanding of the failure mechanisms of key components operating under corrosive and fluctuating load environments. Full article

Background/Objectives: Long-distance running often requires athletes to carry their own hydration. Both the velocity of the runner and the load will affect the ground reaction forces (GRFs). Furthermore, carrying a liquid mass may have different outcomes on GRF compared to carrying a solid mass. This effect may in turn potentially result in a greater risk of injury. The goal of this study was to examine the GRF while jogging with different quantities of water in a hydration pack. It was expected that GRF measures would change with increased hydration pack weight. Methods: Twenty college-aged participants were asked to run over a force plate with an empty hydration pack and packs (0.71 kg) filled with 0.5 litres (1.21 kg), 1.5 litres (1.71 kg), and 2.5 litres (3.21 kg) of water. Results: No significant differences (p > 0.05) in the vertical, lateral, or forward–back measures were found between the different loads. These outcomes may be a result of the dampening effect the movement of the water may have on gait. Conclusions: It is believed that the benefit of having hydration readily available via a hydration pack will outweigh any potential for injury due to the added weight being carried. Full article

The interaction between equine hooves and various ground surfaces is a critical factor for injury prevention and performance in modern equestrian sports. Accurate measurement of surface grip is essential for evaluating the effectiveness of different hoof protection systems. This study introduces the Vienna Grip Tester (VGT), a novel sensor-based device developed to quantify rotational resistance—an important parameter for assessing hoof–surface interaction. The VGT utilizes a torque wrench and spring-loaded mechanism to simulate lateral hoof movements under a standardized vertical load (~700 N), enabling objective grip measurements across different conditions. Twenty combinations of hoof protection (barefoot, traditional iron shoe, and two glue-on models) and surfaces (sand, sand with fiber at 25 °C and −18 °C, frozen sand, and turf) were tested, yielding 305 torque measurements. Statistical analysis (repeated-measures ANOVA with Bonferroni correction) revealed significant differences in grip among surface types and hoof protection systems. Frozen surfaces (SDAF (31 ± 8.9 Nm and SDF 33 ± 8.7 Nm, p < 0.001) exhibited the highest grip, while dry sand (SDA (18.3 ± 3.3 Nm, p < 0.001) showed the lowest. Glue-on shoes (glue-on grip, 26 ± 10 Nm; glue-on, 25 ± 10 Nm) consistently provided superior grip compared to traditional or unshod hooves (bare hoof, 21 ± 7 Nm). These results validate the VGT as a reliable and practical tool for measuring hoof–surface grip, with potential applications in injury prevention, hoof protection development, and surface optimization in equestrian sports. Full article

Schatzker type V bicondylar tibial plateau fractures present a major challenge due to the difficulty of achieving stable fixation with minimally invasive strategies. This study introduces a dual-thread lag and locking plate (DLLP) design that integrates lag screw compression with unilateral locking plate fixation. A custom-built compression evaluation platform and standardized 3D-printed fracture models were employed to assess biomechanical performance. DLLP produced measurable interfragmentary compression during screw insertion, with a mean displacement of 1.22 ± 0.11 mm compared with 0.02 ± 0.04 mm for conventional single lateral locking plates (SLLPs) (p < 0.05). In static testing, DLLP demonstrated a significantly greater maximum failure force (7801.51 ± 358.95 N) than SLLP (6224.84 ± 411.20 N, p < 0.05) and improved resistance to lateral displacement at 2 mm (3394.85 ± 392.81 N vs. 2766.36 ± 64.51 N, p = 0.03). Under dynamic fatigue loading simulating one year of functional use, all DLLP constructs survived 1 million cycles with <2 mm displacement, while all SLLP constructs failed prematurely (mean fatigue life: 408,679 ± 128,286 cycles). These findings highlight the critical role of lag screw compression in maintaining fracture stability and demonstrate that DLLP provides superior biomechanical performance compared with SLLP, supporting its potential as a less invasive alternative to dual plating in the treatment of complex tibial plateau fractures. Full article

Articular cartilage (AC) is a specialised connective tissue covering joint surfaces. It enables smooth movement, distributes mechanical loads, and protects the underlying bone. In response to loading, AC adapts by modifying both its thickness and composition. AC is organised in different zones, with low cellularity and a high abundance of extracellular matrix (ECM). Mechanical overloading or immobilisation can lead to structural changes, potentially resulting in osteoarthritis (OA), for which no causal treatment currently exists. However, smaller defects can be treated using chondrocyte/cartilage transplantation or tissue engineering. A better understanding of the molecular composition of AC at different locations is essential to improve such therapeutic approaches. For this purpose, we performed a comprehensive analysis of porcine femoral knee cartilage at eight defined anatomical sites. Cartilage thickness and proteoglycan (PG) content were analysed histologically, while specific ECM proteins were assessed by proteomics and validated by immunohistochemistry and Western blot. Significant differences were identified, particularly between medial and lateral compartments, in terms of cartilage thickness, PG abundance, and ECM composition. Some proteins also showed zone-specific localisation patterns. These structural differences likely reflect adaptation to mechanical loading and should be considered to optimise future cartilage repair and tissue engineering strategies. Full article

Objectives: Ketamine has demonstrated rapid and sustained antidepressant effects; however, its clinical utility is limited by the risk of addiction and systemic side effects. This study aimed to develop ketamine-loaded nanodroplets (Ket-NDs) with high encapsulation efficiency (EE) and stability for targeted low-dose intravenous (IV) administration in a mice model of depression. Low-intensity focused ultrasound (LIFU) was employed to induce transcranial, region-specific drug release in the lateral habenula (LHb). Methods: Ket-NDs were synthesized using a thin-film hydration method with sonication and emulsification, incorporating perfluoropentane as the core material. Characterization was performed using light microscopy, cryogenic scanning electron microscopy (cryo-SEM), transmission electron microscopy, and dynamic light scattering (DLS). Drug EE and loading efficiency (LE) were quantified by reversed-phase high-performance liquid chromatography. A chronic restraint stress model was established, and Ket-NDs were administered intravenously followed by LIFU targeting the LHb. Antidepressant efficacy and biosafety were systematically evaluated. Results: (1) Ket-NDs exhibited uniform spherical morphology and a narrow size distribution, as confirmed by DLS (particle size: 139.75 ± 9.43 nm; Polydispersity index: 0.225 ± 0.025) and cryo-SEM analysis (number-average diameter: 109.5 ± 10.4 nm). The zeta potential was −15.93 ± 5.906 mV, and the formulation remained stable under 4 °C storage. (2) Ket-NDs demonstrated high EE (78.25 ± 16.13%) and LE (15.55 ± 4.49%). (3) In depressive mice, IV administration of Ket-NDs followed by LIFU targeting the LHb significantly improved behavioral outcomes: increased locomotor activity in the open field test, elevated sucrose preference index, and reduced immobility time in the tail suspension test. (4) Safety assessments revealed no significant organ toxicity or brain tissue damage in ultrasound-exposed regions. Conclusions: In summary, this study developed stable Ket-NDs. When combined with LIFU, they enable precise regional drug delivery to the brain, showcasing a promising treatment strategy for depression with reduced systemic side effects. Full article

Aim: This retrospective observational clinical cohort study evaluated 84-month clinical and radiographic outcomes of a regenerative protocol combining autologous dentin grafts processed with the Tooth Transformer^® device and Concentrated Growth Factors (CGFs) in patients with severe maxillary atrophy undergoing sinus augmentation with simultaneous implant placement. Materials and Methods: Thirty-one patients (30–75 years) with residual crestal bone height ≥ 5 mm and requiring extraction of ≥2 molars were included. Extracted teeth were processed with the Tooth Transformer^® to obtain demineralized dentin granules (500–1000 µm), which were combined with CGFs prepared using the Medifuge MF200^® to form “sticky bone.” All patients underwent sinus lift via a lateral window approach (Hilt Tatum technique) with simultaneous placement of 98 implants (12–14 mm), which were loaded after six months. Results: At the 84-month follow-up, no implant failures or peri-implantitis were recorded. CBCT and clinical evaluations showed stable regenerated bone volume and absence of peri-implant bone resorption. All patients received fixed prostheses within six months without complications. Conclusions: The combined use of processed autologous dentin and CGFs proved to be a safe, predictable, and effective regenerative technique in cases of severe maxillary atrophy, with a 100% implant survival rate at five years. Full article

The main purposes of the present paper are to present the mathematical and algorithmic aspects of the ANM/FEM numerical model and to show how it is applied to analyze elastic and thermo-elastic nonlinear solid mechanical problems. ANM is a robust continuation method based on a perturbation technique for solving nonlinear problems dependent on a loading parameter. Historically, this technique has been successfully applied to problems in various fields of solid and fluid mechanics. This paper shows how ANM is used to solve nonlinear elastic and nonlinear thermo-elastic problems involving elastic behavior and geometrical nonlinearities. The implementation of ANM for FEM in the FreeFEM++ language is then presented. The FEM software development platform, called FreeFEM++, is structured to work with variational formulations and, therefore, is well adapted to implement ANM for instability problems in solid mechanics. In order to illustrate the great efficiency of FreeFEM++, scripts will be presented for computing the different steps of ANM continuation for solid elastic structures, considering simple geometries subjected to conservative loading. For the purpose of validation, the problem of a cantilever subjected to an applied force is presented. Next, the new numerical model is applied to study wrinkles appearing in a planar film/substrate system that is subjected to compressive surface forces at the lateral faces of the film. Finally, the model is applied to a spherical film/substrate system subjected to thermo-elastic shrinkage. In both cases, the ANM/FEM prediction method, together with a Newton–Riks correction (if needed), identifies the equilibrium paths efficiently, especially after the post-buckling regime. Full article

To analyze the dynamic response of tension leg platform (TLP) tendons under irregular ocean wave action, the governing equations of coupled vibration between the platform and tendon under irregular wave action are established based on Hamilton’s principle and the Kirchhoff hypothesis. Using the spectrum representation–random function method, the power spectral density function of the irregular wave load is derived, and the lateral wave forces at different tendon locations are calculated. The coupled lateral and axial responses of the tendon system are obtained through the fourth-order Runge–Kutta method. Considering the parametric vibrations of both the platform and tendon, the extreme lateral deflection of the tendon is employed as the control index to derive the probability density curves of the tendon deflection under irregular wave load. The results show that the amplitude of the wave load increases gradually along the height of the tendon, with a faster growth rate at locations closer to the water surface. The tendon’s lateral deflection response changes more drastically due to coupled parametric vibration of the platform. Based on 628 complete samples of irregular wave loads, the probability density curve and cumulative distribution curve of the extreme lateral deflection of the tendon under irregular wave loads are obtained. Under typical sea state conditions generated from the P-M wave spectrum, the reliability of the tendon under irregular wave load increases with the initial tension force. Full article

Background: Genioplasty is a well-established surgical technique for reshaping the chin and enhancing facial harmony. However, conventional fixation methods may present biomechanical and aesthetic limitations. Objective: This study introduces and evaluates a novel Anatomical Chin Plate (ACP), designed to enhance mechanical performance and facial aesthetics compared to the conventional chin plate (CP). Methods: A three-dimensional finite element analysis (FEA) was conducted to compare stress distribution in ACP and CP models under a standardized oblique load of 60 N, simulating muscle forces from the mentalis and digastric muscles. Plates were modeled using Blender and analyzed using ANSYS software 2025 r2. Mechanical behavior was assessed based on von Mises stress, concentration sites, and potential for plastic deformation or fatigue failure. Results: The ACP demonstrated a significantly lower maximum von Mises stress (77.19 MPa) compared to the CP (398.48 MPa). Stress distribution in the ACP was homogeneous, particularly around the lateral fixation holes, while the CP exhibited concentrated stress between central screw holes. These findings indicate that the anatomical geometry of the ACP enhances load dispersion, reduces critical stress concentrations, and minimizes fatigue risk. Conclusions: The ACP design offers superior biomechanical behavior and improved aesthetic potential for genioplasty procedures. Its optimized shape allows for better integration with facial anatomy while providing stable fixation. Further studies are recommended to validate in vitro performance and explore clinical applicability in advanced genioplasty and complex osteotomies. Full article

A physics-based vehicle–track coupled dynamic model embedding a hydraulic electromechanical regenerative damper (HERD) is developed to quantify electrical power recovery and wear depth in high-speed service. The HERD subsystem resolves compressible hydraulics, hydraulic rectification, line losses, a hydraulic motor with a permanent-magnet generator, an accumulator, and a controllable; co-simulation links SIMPACK with MATLAB/Simulink. Wheel–rail contact is computed with Hertz theory and FASTSIM, and wear depth is advanced with the Archard law using a pressure–velocity coefficient map. Both HERD power regeneration and wear depth predictions have been validated against independent measurements of regenerated power and wear degradation in previous studies. Parametric studies over speed, curve radius, mileage and braking show that increasing speed raises input and output power while recovery efficiency remains 49–50%, with instantaneous electrical peaks up to 425 W and weak sensitivity to curvature and mileage. Under braking from 350 to 150 km/h, force transients are bounded and do not change the lateral wear pattern. Installing HERD lowers peak wear in the wheel tread region; combining HERD with flexible wheelsets further reduces wear depth and slows down degradation relative to rigid wheelsets and matches measured wear more closely. The HERD electrical load provides a physically grounded tuning parameter that sets hydraulic back pressure and effective damping, which improves model accuracy and supports calibration and updating of digital twins for maintenance planning. Full article

Leishmaniasis is a zoonotic disease caused by protozoan parasites of the genus Leishmania, transmitted by phlebotomine sandflies. While domestic dogs are the main hosts in the Mediterranean basin, wild carnivores have also been proposed as potential reservoirs. This study assessed the presence of Leishmania spp. in 250 animals from the Valencian Community, eastern Spain—an endemic region—using TaqMan qPCR on spleen samples from 216 wild carnivores and sera from 34 feral cats, and ELISA serology on 174 wild carnivores. DNA of Leishmania spp. was detected in 14 out of 250 individuals (5.6%), with red foxes representing most positive cases (10/102; 9.8%). Seropositivity was observed only in red foxes, with 5 out of 174 individuals testing positive (2.9%). Most qPCR-positive animals had high Ct values, consistent with low parasite loads. One fox, positive by both methods, showed advanced skin lesions and was later diagnosed with sarcoptic mange, suggesting possible interaction with Leishmania infection. The overall low prevalence and parasite burden suggest limited circulation in the surveyed wildlife. These findings contribute to understanding the epidemiological role of wild mesocarnivores and highlight the relevance of wildlife monitoring within a One Health approach. Full article

Reinforced concrete (RC) columns play a vital role in structural integrity, and accurately predicting their failure modes is essential for enhancing seismic safety and performance. This study explores the use of a supervised machine learning approach—specifically, an artificial neural network (ANN) model—to classify failure modes of RC columns. The model is trained using data from the well-established Pacific Earthquake Engineering Research Center (PEER) structural performance database, which contains results from over 400 cyclic lateral-load tests on RC columns. These tests encompass a wide range of column types, including those with spiral or circular hoop confinement, rectangular ties, and varying configurations of longitudinal reinforcement with or without lap splices at critical sections. The ANNs were evaluated using a randomly selected subset from the PEER database, achieving classification accuracies of 94% for rectangular columns and 95% for circular columns. Notably, in certain cases, the model’s predictions aligned with or exceeded the accuracy of traditional building code-based methods. These findings underscore the strong potential of machine learning—particularly ANNs—for reliably postdicting failure modes (even the brittle ones) in RC columns, signaling a promising advancement in the field of earthquake engineering. Full article

Open Ground-Storey (OGS) buildings, widely adopted for functional openness, are highly vulnerable to seismic collapse due to stiffness irregularity at the ground storey (GS). The magnification factor (MF), defined as the amplification applied to GS column design forces, acts as a practical strengthening measure to enhance GS stiffness and thereby mitigate the soft storey failure mechanism. While earlier studies recommended fixed MF values, their lack of adaptability often left stiffness deficiencies unresolved. This study develops a rational framework to quantify and predict the required MF for OGS columns, enabling safe yet functionally efficient design. A comprehensive set of three-dimensional reinforced concrete OGS models was analyzed under seismic loads, covering variations in plan geometry, ground-to-upper-storey height ratio (Hr), and GS infill percentage. Iterative stiffness-based evaluations established the MF demand needed to overcome stiffness deficiencies. To streamline prediction, advanced machine learning (ML) models were applied. Among these, black-box models achieved high predictive accuracy, but Symbolic Regression (SR) offered an interpretable closed-form equation that balances accuracy with transparency, making it suitable for design practice. A sensitivity analysis confirmed the Hr as the most influential parameter, with additional contributions from other variables. Validation on additional OGS configurations confirmed the reliability of the SR model, while seismic response comparisons showed that Modified OGS (MOGS) frames with the proposed MF achieved improved stiffness, reduced lateral displacements, uniform drift distribution, and shorter fundamental periods. The study highlights the novelty of integrating interpretable ML into structural design, providing a codifiable and practical tool for resilient OGS construction. Full article

This study investigates the seismic performance of existing reinforced concrete (RC) buildings, focusing on the influence of near-fault ground motions caused by proximity to fault lines. Compared to ordinary or far-fault earthquakes, near-fault earthquakes may have diverse effects on the response of buildings resulting from directivity and intense velocity pulses, which significantly amplify seismic demands. For this purpose, nonlinear time history analyses were carried out on a seven-story RC residential building that was subjected to near-fault effects and sustained heavy damage during the Kahramanmaraş earthquakes on 6 February 2023. The analyses used both near-fault and far-fault ground motion records, and four structural models were developed by gradually reducing the number of shear wall elements to assess the impact of diminishing lateral-load-resisting capacity. The results revealed that near-fault ground motions led to significant increases in base shear, inter-story drift ratios, and structural damage levels. Furthermore, a reduction in shear wall content resulted in a noticeable decline in seismic performance. These findings underscore the necessity of accounting for near-fault effects in seismic design and the critical role of lateral stiffness. The study emphasizes that considering near-fault characteristics is essential for ensuring the seismic resilience of RC buildings located in active seismic zones. Full article