Search Results (1,560)

Torque-limiting mechanisms are safety-critical elements in mechanical, automotive, robotic, aerospace and medical systems, where controlled torque transmission is required to avoid overload failure. However, the influence of dent–slot geometry on torque stability, variability and tolerance sensitivity remains insufficiently quantified. This study examines the effects of dent height, dent angle and spring plate thickness on the torque response of a compact elastic, shape-dependent torque-limiting mechanism. An integrated methodology comprising conceptual design, mathematical modelling, theoretical analysis, finite element analysis, manufacturability assessment, material characterisation, dynamic testing and VIKOR-based decision-making was implemented. Five feasible spring-drive plate configurations were investigated using two dent heights, two dent angles and two spring plate thicknesses. Material and interface properties for the Ck67–SINT D39 tribological pair were determined through tensile, flexural and friction tests, while dynamic torque and output-force data were obtained using a dedicated test bench and statistically evaluated after Chauvenet-based removal of isolated peak values. The mathematical, theoretical, numerical and experimental results showed close agreement, with torque deviations below approximately 1.5% for the main comparison metrics. Increasing dent height from 1.40 to 1.80 mm reduced relative torque variability by 34.6%, whereas reducing the dent angle from 110° to 90° increased relative torque variability by 95.0%. Configuration A2 provided the best balance, confirming dent geometry as a controllable design variable. Full article

Triply Periodic Minimal Surfaces (TPMSs) represent a progressive class of cellular materials with high potential for high-tech applications. This review provides a comprehensive analysis of TPMS architectures, linking their mathematical underpinnings and advanced CAD modeling in PTC Creo Parametric 12 with technological aspects of additive manufacturing and macroscopic mechanical response. The work critically compares dominant topologies such as Schoen Gyroid, Schwarz Diamond, and Schwarz Primitive, focusing on the differences between uniform and functionally graded (FG-TPMS) structures. From a production perspective, this study identifies key process limitations of PBF-LB/M and SLA additive technologies, in particular the issues of unsintered powder accumulation, geometric deviations, and the negative impact of surface roughness (satellite particles) on fatigue life. Analysis of mechanical behavior confirms the superiority of sheet-based modifications in kinetic energy absorption, where specifically tailored FG-TPMS topologies exhibit stable deformation plateaus and controlled, progressive failure modes under compression. The conclusion of the work summarizes established applications in biomedical engineering for the elimination of stress shielding, as well as emerging trends in the field of 4D printing and acoustic metamaterials. This review serves as a comprehensive engineering guide for the optimization and implementation of next-generation porous structures. Full article

Parturient paresis remains a major economic challenge in global ruminant production, causing acute periparturient hypocalcemia and predisposing high-yielding animals to a cluster of secondary pathologies. Traditional narratives often treat regulatory pathways in isolation, whereas this review synthesizes multi-organ endocrine networks to address the kinetic dysynchrony between mammary calcium drain and homeostatic recruitment velocity. Beyond the classical parathyroid hormone–vitamin D axis, we integrate the mammary–gut–bone axis into a unified endocrine model, highlighting the critical role of the serotonin–parathyroid hormone-related protein rheostat for skeletal mineral mobilization and the fibroblast growth factor 23–Klotho axis in prepartum phosphorus-induced feedback suppression. We evaluate the molecular mechanisms underlying target-organ receptor resistance, driven by vitamin D receptor downregulation and epigenetic aging, which precipitate homeostatic feedback failure. Regarding clinical management, this synthesis contrasts reactive parenteral interventions with proactive nutritional priming strategies, such as negative dietary cation–anion difference acidification, zeolite-based gastrointestinal binders, and exogenous vitamin D or 5-hydroxytryptophan supplementation. Additionally, the role of microbiota-derived short-chain fatty acids in gut-bone communication and the potential of genomic selection to breed livestock with heritable metabolic resilience are explored. Ultimately, this comprehensive framework emphasizes a paradigm shift from emergency treatment to precision nutritional and genetic prophylaxis to mitigate PP across diverse ruminant species. Full article

The performance of ultra-high-performance fiber-reinforced concrete (UHPFRC) under repeated low-velocity impacts, particularly in the context of nominally fixed boundaries relevant to protective structures, remains underexplored. In practice, protective components made of UHPFRC, such as falling object barriers and vehicle parapet systems, are exposed to foreseeable repeated low-velocity impacts; however, no standardized design provisions or residual capacity assessment methods exist for such members, particularly under nominally fixed boundary conditions. This study presents an integrated experimental and numerical investigation into the progressive damage and failure mechanisms of a 50 mm thick UHPFRC plate with nominally fixed (bolted clamping) boundaries subjected to sequential low-velocity impacts. A custom drop-weight test setup was used for impact loading, while high-speed 3D digital image correlation (3D-DIC) captured the quarter-field transient kinematics, which were reconstructed back to the full field based on verified test symmetry and complemented by traditional accelerometer and strain gauge measurements. The results demonstrate a distinct progression of damage. Initial low-energy impacts (196 J/drop) caused negligible damage, highlighting the material’s tolerance. Subsequent higher-energy impacts induced a transition from flexural cracking to a combined flexural–punching shear failure mode. The model-assisted nominal secant stiffness indicator decreased by 5.3% over the repeated 0.5 m drops and fell by 50.8% after the 2.0 m drop, quantifying the transition in structural behavior. A finite element (FE) model, incorporating the concrete damaged plasticity (CDP) model with an energy-based degradation law, was developed and evaluated against the experimental data. This model replicated both the quantitative dynamic responses (with model-to-test ratios of peak acceleration, strain, and displacement between 0.86 and 1.30 across three energy levels) and the qualitative damage evolution. The model thus evaluated enabled a model-derived reconstruction of the critical impact force–time history, revealing the evolution of structural degradation toward the exhaustion of the plate’s global flexural resistance and the transition to a punching shear mechanism. Full article

To elucidate the mechanisms responsible for the low strength, pronounced variability, and long-term deformation of carnallitite, and to provide a basis for stope parameter design in deep potash mines, two carnallitite seams from a potash mine were investigated. Group C carnallitite and Group D halite-dominated rock salt were subjected to short-term compression tests and multiscale comparative analyses, while Groups A and B carnallitite specimens were tested under multistage creep loading. Particle Flow Code (PFC) simulations were conducted to evaluate the influence of particle size distribution. The results indicate the following: (1) The representative Group C specimens exhibited an average uniaxial compressive strength of 7.83 MPa, which was substantially lower than that of Group D. The acoustic emission (AE), scanning electron microscopy (SEM), and computed tomography (CT) analyses revealed greater heterogeneity in damage evolution and failure behavior, mainly associated with polymineralic composition, weak particle–matrix interfaces, local pores, and insufficient particle connectivity. (2) Particle-scale heterogeneity influenced the load-bearing capacity of carnallitite. In the PFC sensitivity analysis, narrowing the prescribed particle-size-distribution range from 0.4–8.0 mm to 4.0–4.0 mm at a mean particle size of 4.0 mm was associated with an increase in simulated strength from 7.82 to 10.40 MPa. Because quantitative contact-network descriptors were not extracted, the corresponding contact-network interpretation is treated as mechanistic rather than direct quantitative evidence. (3) The long-term uniaxial strengths of Groups A and B were estimated as 3.3 MPa and 4.8 MPa, respectively, using the adopted specific-failure-energy method. The modified Burgers model provided a good fit to the creep data within the tested stress levels, yielding coefficients of determination of 0.957 and 0.964 and root-mean-square error (RMSE) values of 0.0803 and 0.0552 percentage points. Based on the long-term strength constraints and the site-specific design assumptions adopted in this study, the calculated inter-room pillar widths were 6 m for Group A and 4 m for Group B. These findings provide insights into the multiscale damage mechanisms and long-term stability assessment of carnallitite stopes in deep potash mines. Full article

Objectives: The aim of this study was to determine whether direct evidence shows that contemporary guideline-directed heart failure (HF) pharmacotherapies influence cardiac remodeling through hydrogen sulfide (H₂S) signaling, and to define the resulting evidence gap. Design: A systematic review was conducted according to PRISMA 2020. Registration: PROSPERO CRD420251238589. Data Sources: MEDLINE (PubMed), Web of Science, Scopus, and the Cochrane Library; searches were initiated in March 2025, covered publications from January 2007 onward, and were last updated in November 2025. Eligibility Criteria: Primary studies had to include (A) an HF or cardiac-remodeling model, (B) an HF-relevant pharmacological intervention, (C) direct assessment or manipulation of H₂S biology, and (D) at least one cardiac-remodeling endpoint. Results: Of the 40,796 unique records screened, 50 reports underwent full-text assessment and 14 unique studies were included. No study demonstrated that the remodeling benefits of ACE inhibitors, ARBs, ARNIs, beta-blockers, MRAs, hydralazine/isosorbide dinitrate, or SGLT2 inhibitors are mediated by endogenous H₂S signaling. Doiron et al. evaluated empagliflozin with or without the H₂S donor SG1002 in experimental HFpEF; the combination improved several outcomes beyond empagliflozin alone, but this adjunctive design does not establish H₂S mediation of empagliflozin action. Most eligible evidence concerned exogenous H₂S donors in animal models and reported improvements in fibrosis, hypertrophy, oxidative stress, mitochondrial injury, and cardiac function. The overall certainty was low because of preclinical predominance, heterogeneous models and H₂S assays, donor-specific pharmacology, and incompletely reported randomization and blinding. Conclusions: The principal finding is negative but clinically important: direct evidence that H₂S mediates established HF pharmacotherapy is currently absent. H₂S remains a promising experimental therapeutic candidate rather than an established shared mechanism or clinically validated treatment target. Full article

Gob-side entry retaining by roof cutting and pressure relief (CRRE) eliminates coal pillar waste and mitigates mining-induced stress concentration. Although widely applied in mines shallower than 1000 m, systematic research on asymmetric deformation mechanisms and matched control technologies under ultra-deep conditions (>1000 m, σH > 60 MPa) remains limited. This study investigates the 5307 working face of Anju Coal Mine (burial depth: 1127–1195 m) using theoretical analysis, FLAC3D numerical simulation, and 480 m of field monitoring. The stress evolution, deviatoric stress field response, and asymmetric deformation mechanisms of the surrounding rock under ultra-deep mining conditions are systematically analyzed, based on which a targeted collaborative control technology is proposed. The key findings indicate that (1) CRRE significantly attenuates advanced abutment pressure compared with conventional pillar retention, with an average stress reduction of 20.1 ± 1.2% (95% CI: 17.8–22.4%, p < 0.01). (2) During the advanced mining stage, the second invariant of deviatoric stress exhibits a saddle-shaped distribution with a pronounced concentration at the mid-rib, identifying this as the dominant zone for rib bulging failure. (3) In the post-mining entry-forming stage, the roof deviatoric stress field demonstrates marked asymmetric evolution, with the distortion energy on the solid-coal side substantially exceeding that on the gob side; moreover, the low-position roof strata exhibit high distortion and poor stability, rendering them prone to bending fractures. Grounded in these mechanisms, a full-cycle differentiated surrounding rock control technology is developed, integrating pre-mining directional roof pre-splitting, active tough support reinforcement, post-mining temporary roof control and pressure relief, and gangue retaining with rib collaborative protection. The key parameters include a roof cutting height of 7 m, a cutting angle of 15°, NPR constant-resistance anchor cables with W-steel belts, and temporary support extending 300 m behind the working face. Field monitoring reveals staged deformation evolution, with stabilization achieved 250 m behind the working face. Maximum roof subsidence, floor heave, and total roof-floor convergence were 180 mm, 329 mm, and 422 mm, respectively, below the 500 mm allowable threshold for ultra-deep retained entries. Full article

Determining the shear strength parameters of granular materials in high waste rock dump slopes is essential for reliable slope stability analysis. In this study, dump materials were sampled from six benches (elevations 2800–2950 m) of an open-pit mine dump slope, and in situ density tests, gradation analyses, and large-scale consolidated drained (CD) triaxial tests were performed. Two PFC2D slope models—one with uniform (spatially averaged) parameters and one with elevation-dependent (layered) parameters—were then established to quantify how spatial heterogeneity affects stability predictions. The results show pronounced vertical heterogeneity: density, porosity, gradation, and shear strength parameters vary systematically among benches, reflecting the combined effects of compaction history and particle segregation during dumping. All specimens exhibited strain hardening and continuous shear contraction, and specimens with a denser, better-graded structure showed higher strength and lower compressibility. The layered model yields a higher factor of safety and shallower, bench-scale slip surfaces, whereas the uniform model underestimates stability and misplaces the critical slip zones. These findings demonstrate that elevation-dependent parameter assignment better represents the heterogeneous failure mechanism of high dump slopes and should be preferred over uniform parameterization in stability analyses of similar waste rock dumps. Full article

This study devised a blasting experiment to establish a dynamic quantified relationship between blasting and movement, failure, and ejection of rock masses. The experiment was conducted using the 3D digital image correlation method (3D-DIC), which provided high-speed images capturing the process of shallow-buried tunnel blasting. The study analyzed the mechanical behavior of full-section rock mass under blasting action through cross-scale image processing. Yield and elastic points were distinguished based on the time–displacement curve. Then, the spatial vector method was employed to deduce flying rock trajectory and throwing distance, enabling the subdivision of underground space based on risk assessment. The results show that the rock in the cut zone starts moving within 3 ms after initiation, ultimately exhibiting a maximum visible off-plane displacement of 215 mm. Displacements are related to delay time and distance. Different zones show distinct dominant directions of rock mass displacement. The rock mass becomes flying rocks separated from the cross-section. The initial velocity of the flying rocks ranges from 11.8 m·s⁻¹ to 29.9 m·s⁻¹. Around 85% of the flying rocks fall within the range of 0 to 40.8 m. Only 5% of the flying rocks fall outside 64.3 m. Appropriate protective measures should be taken for equipment during experiments. Full article

This study investigates the structural behavior of steel I-beams containing corrosion-induced section loss and web openings, along with the effectiveness of fiber-reinforced polymer (FRP) strengthening as a retrofit strategy. Although previous studies have investigated the effects of corrosion, web openings, and FRP strengthening in steel beams, limited attention has been given to comparing the structural response of slender and deep steel beams under these deterioration scenarios and assessing strengthening strategies according to their distinct failure mechanisms. The analysis considers two structural response regimes: slender beams governed predominantly by flexural behavior and deep beams where shear deformation plays a significant role. Three-dimensional (3D) nonlinear solid finite element (FE) models are developed to evaluate the influence of corrosion location, web opening position, and FRP-strengthening schemes on load-carrying capacity and failure behavior. The results indicate that corrosion-induced flange thinning significantly reduces flexural capacity in slender beams, while web degradation has a comparatively smaller effect. FRP strengthening of the tension flange is found to be the most effective strategy for restoring flexural performance in slender beam configurations. In contrast, deep beams exhibit higher sensitivity to shear-related damage, where web openings located in shear transfer regions lead to substantial reductions in load capacity. Strengthening of the web region using FRP significantly improves shear resistance and overall structural performance. Overall, the study highlights distinct differences in damage sensitivity and strengthening effectiveness between slender and deep beam responses under corrosion and web opening effects, providing practical guidance for condition assessment and retrofit design of deteriorated steel I-beams. Full article

To examine the deformation behavior and failure mechanisms of large-scale mine chutes under complex service conditions, we performed multiple C-ALS three-dimensional laser scanning surveys on the 1#, 2# and 3# chutes at an iron mine in Anhui Province. The results showed that all three chutes had severe non-uniform expansion, with maximum diameters of 12.2 m, 14.8 m and 16.9 m, respectively. The maximum annual wear rates during the detection period were 2.4 m, 6.0 m and 2.5 m, respectively. The failure of the chutes was mainly caused by local block collapse drops, influenced by the joints and fissures of the surrounding rock, and the wear showed significant discontinuous and non-uniform characteristics. Based on the detection data, a three-peak Gaussian model is established to describe the nonlinear distribution of the expansion along depth, with peak centers located at −462 m, −497 m and −520 m. By comparing linear and exponential models, it is determined that the expansion exhibits a linear evolution trend with time. Based on the maximum diameter and annual wear rate, we estimate the remaining safe service life of each chute, and provide the confidence interval for the expansion value at a 90% confidence level (such as [1.31 m, 4.83 m] at −520 m). Research shows that high-precision 3D laser scanning can effectively reveal the deformation and evolution laws inside the chute. It is recommended to immediately take reinforcement measures for chute 2 and establish a dynamic monitoring system for the common weak zone between −480 m and −520 m. Research on the evolution of surrounding rock fractures should be carried out to provide a scientific basis for chute life assessment and risk control. Full article

Background/Objectives: Orthotopic heart transplantation results in complete surgical denervation of the donor heart. Although partial functional reinnervation has been reported in some recipients, the histopathological features of intracardiac innervation in long-term failing cardiac allografts remain poorly characterized. We present a unique case of a cardiac allograft explanted 11 years after transplantation that enabled detailed histological and digital assessment of neural remodeling. Case Description: An explanted cardiac allograft obtained after retransplantation for chronic graft dysfunction was examined using whole-heart histopathological reconstruction and immunohistochemistry (CD3, CD68, C3, C4d, HLA-DR, NLRP3, VEGF, and UCHL-1). Digital quantitative analysis of UCHL-1-positive nerve fibers, including spatial density mapping and comparison with a reference non-diseased myocardium, demonstrated profound and heterogeneous loss of intracardiac innervation. Marked denervation was observed not only within fibrotic and infarcted regions but also in the morphologically preserved myocardium. Neural injury was associated with perineural and endoneurial inflammatory infiltrates, complement deposition, HLA-DR expression within nerve fibers and reduced perivascular and epicardial adipose tissue innervation. Distinct regional patterns of denervation and neural remodeling were also identified in the aortic segments of the transplantation complex. Conclusions: This case demonstrates that chronic cardiac allograft dysfunction may involve extensive injury of the intracardiac nervous system extending beyond areas of ischemic myocardial damage. The findings suggest that immune-mediated inflammation, complement activation, and chronic ischemia contribute to progressive neural remodeling in the transplanted heart. Histopathological evaluation of intracardiac innervation may provide additional insight into mechanisms of long-term graft failure and represents an underrecognized component of cardiac allograft pathology. Full article

When flexible job shop scheduling faces concurrent disturbances such as machine failures and rush orders, worker-centric constraints emphasized under Industry 5.0 must also be satisfied. Existing deep reinforcement learning methods for the Dynamic Flexible Job Shop Scheduling Problem (DFJSP) seldom treat worker workload balance as an explicit constraint, and most depend on static penalty coefficients that are difficult to tune across different scenarios. In this paper, we suggest ALP-PPO, an adaptive Lagrangian penalty-enhanced proximal policy optimization algorithm, for real-time rescheduling under concurrent machine breakdowns and rush orders. We formulate the scheduling environment as a constrained Markov decision process. Worker skill heterogeneity, fatigue accumulation and workload equity are modeled as coupled constraints alongside classical scheduling objectives. By decoupling operation sequencing, machine allocation and worker assignment into coordinated sub-decisions, a hierarchical action space is constructed. Dual Lagrangian multipliers for workload balance and fatigue are updated adaptively during training, so that manual penalty tuning is no longer required. An event-triggered mechanism selects between right-shift and full rescheduling on the basis of a disruption severity index. We employ weighted-sum scalarization of makespan, energy consumption and workload variance during training, and Pareto solution sets are obtained by systematically varying the weight vectors across independent training runs. On extended Brandimarte benchmarks augmented with worker and dynamic event parameters, ALP-PPO delivers superior scheduling performance across makespan, energy consumption and workload variance when compared with Double DQN, Dueling DQN, standard PPO, NSGA-II and MOEA/D, as measured by Hypervolume (HV) and Inverted Generational Distance (IGD) indicators. Ablation studies indicate that the adaptive Lagrangian mechanism reduces constraint violations by more than 40% relative to fixed-penalty alternatives while keeping the primary objectives competitive. An analysis of computational efficiency shows that ALP-PPO completes online inference in under 20 ms per decision step, making real-time rescheduling practically feasible. Generalization experiments on previously unseen instances further validate the transferability of the learned policy. These findings support human-centric intelligent scheduling in Industry 5.0 manufacturing. Full article

Background/Objectives: Three-dimensionally (3D) printed resins are increasingly used for removable orthodontic appliances, but how their mechanical reliability changes in the oral environment is unclear. This study evaluated the effect of bio-ageing environment and material type on the biaxial flexural strength and Weibull reliability of one conventional acrylic resin (Orthocryl, OC) and two 3D-printed photopolymer resins (BioMed Clear, BMC; and KeySplint Hard, KH). The Weibull modulus (m) reflects how consistent, or predictable, the strength is among specimens, independent of its average value. Methods: Disc specimens (n = 32) were aged for 24 h at 37 °C in pooled human saliva, a Streptococcus mutans biofilm, or water, and the biaxial flexural strength was measured by the piston-on-three-balls method (1 mm/min). Data were analysed with two- and three-parameter Weibull statistics to estimate the Weibull modulus (m), characteristic strength (σ₀), strength at 5% failure probability (σ₅%), and threshold strength (σ_μ), with model selection guided by the Akaike Information Criterion. Results: Biofilm exposure lowered m while σ₀ was preserved: m fell from 9.96 (saliva) and 7.98 (water) to 1.95 for OC, and from 17.61 and 13.01 to 2.62 for BMC, whereas σ₀ stayed near 55 MPa (OC) and 64 MPa (BMC). Under biofilm the modulus of all three converged to low values (1.4–2.6), abolishing the differences among materials; OC and BMC required a three-parameter model only after biofilm (σ_u ≈ 41 MPa), whereas KH required it in every environment (σ_u = 28.9–38.7 MPa). Conclusions: Biofilm ageing mainly reduced strength predictability, while characteristic strength was largely preserved. This indicates that flexural strength alone may be insufficient to qualify resins for removable appliances, and that printed resins studied here are not inherently superior or inferior to conventional acrylic. Full article

Background: Occlusal splints are exposed to prolonged intraoral conditions, including saliva, temperature fluctuations, and mechanical loading, which may alter their mechanical performance over time. The increasing use of SLA 3D-printed photopolymer resins for splint fabrication has introduced new materials whose aging-related mechanical stability remains insufficiently characterized. Objectives: This in vitro study evaluated the effects of accelerated aging in artificial saliva on the Shore D hardness and flexural properties, including flexural modulus, flexural strength, and strain at failure, of four polymeric materials used for occlusal splint fabrication: a thermoformed PETG material (Duran, C), a milled PMMA (Bilkim Polywax, F), and two SLA-printed photopolymer resins (HARZ Labs Dental Clear, H; NextDent Ortho Rigid, N). Materials and Methods: Eighty rectangular specimens (n = 20/material) were fabricated following ASTM D790 and subjected to accelerated aging in Fusayama artificial saliva at 60 °C for 24, 48, and 72 h. Shore D hardness was assessed first as a non-destructive measurement, followed by three-point bending tests yielding flexural modulus, flexural strength, and strain at failure. Data were analyzed using one-way ANOVA and post hoc multiple comparisons at a significance level of α = 0.05. Results: Aging effects were material-dependent. Duran (C) showed no statistically significant changes in Shore D hardness (p = 0.651) and only non-progressive variations in flexural behavior. Bilkim Polywax (F) exhibited a significant hardness reduction at 48 h (p = 0.004) and selective changes in flexural strength at 72 h. HARZ Labs Dental Clear (H) showed the most severe and progressive deterioration, with significant reductions in all evaluated parameters, including hardness decreases of up to 5.8% and flexural modulus reductions exceeding 49%. NextDent Ortho Rigid (N) demonstrated an initial hardness decrease followed by stabilization, with a significant reduction in flexural modulus at 72 h. Conclusions: Under the accelerated hydrothermal aging conditions employed in this study, the two investigated SLA-printed photopolymer resins (HARZ Labs Dental Clear and NextDent Ortho Rigid) exhibited greater mechanical deterioration than the tested thermoformed PETG and milled PMMA materials. These findings are limited to the investigated materials, standardized rectangular specimens, and the specific accelerated aging protocol used in this study. Among the tested materials, thermoformed PETG demonstrated the greatest mechanical stability. Material-specific evaluation of aging resistance remains advisable before routine clinical application, particularly for digitally fabricated occlusal splints intended for prolonged intraoral service. Full article