Search Results (387)

This paper presents a detailed kinematic analysis of a double-toggle jaw crusher used for the primary crushing of hard and bulky materials. The study introduces an innovative mathematical modeling method for the motion of the mechanism’s components, eliminating the need for traditional decomposition into structural groups. General equations are developed to determine the positions, linear velocities, and angular displacements of the moving elements, providing a solid foundation for equipment design and study. The generated mathematical model was validated using real-world dimensions of an SMD-117-type jaw crusher and by comparison with simulation results obtained from Mathcad, Linkage, Roberts Animator, and GIM software. The results demonstrated a high degree of agreement between the calculated and simulated trajectories and linear velocities. The analysis of angular displacements and linear velocities confirmed the cyclic nature of the mechanism’s motion, characterized by sinusoidal variations and low oscillations, which are relevant for assessing variable loads. Through its rigorous approach and multi-source validation, the research makes a significant contribution to the development of more efficient, durable, and adaptable jaw crushers for modern industrial requirements. Full article

This study presents the design and fabrication of a glass fiber–poplar veneer composite plate, investigating how varying interlayer configurations of glass fiber (single- and double-layer) and the arrangement of poplar veneer layers (odd and even) impact the mechanical and thermal insulation characteristics of these composite plates. Compared to plywood made from natural wood, glass fiber significantly improved the properties of fast-growing poplar plywood. The highest impact strength increased by 3.62 times, while the flexural strength increased by 26.22% and the tensile strength by 29.66%. The thermal diffusion coefficient of the experimental group decreased by 40.74%, indicating better insulation. Interestingly, single-layer glass fiber is superior to a double-layer structure in terms of thermal insulation. An optimal interlayer structure was identified, comprising one veneer layer between two layers of glass fiber cloth, repeated three times. Abaqus 2019 was used for finite element analysis (FEA). The simulation results agree with the experimental data to within 5%. These findings confirm the importance of structural configuration in determining the properties of composite materials, providing a theoretical basis for the structural design of fiber–reinforced composite materials. Full article

In advanced structural applications—aerospace and automotive—fiber-laminated composite (FRP) materials are increasingly used for their superior strength-to-weight ratios, making the reliability of their mechanical joints a critical concern. Mechanically fastened joints play a major role in ensuring the structural stability of FRP Composite structures; however, accurately predicting their failure behavior remains a major challenge due to the anisotropic and heterogeneous nature of composite materials. This paper presents a progressive damage modeling approach to investigate the failure modes and joint strength of mechanically fastened carbon fiber-laminated (CFRP) composite joints. A 3D constitutive model based on continuum damage mechanics was developed and implemented within a three-dimensional finite element framework. The joint model comprises a composite plate, a steel plate, a steel washer, and steel bolts, capturing realistic assembly behavior. Both single- and double-lap joint configurations, featuring single and double bolts, were analyzed under tensile loading. The influence of clamping force on joint strength was also investigated. Model predictions were validated against existing experimental results, showing a good correlation. It was observed that double-lap joints exhibit nearly twice the strength of single-lap joints and can retain up to 85% of the strength of a plate with a hole. Furthermore, double-lap configurations support higher clamping forces, enhancing frictional resistance at the interface and load transfer efficiency. However, the clamping force must be optimized, as excessive values can induce premature damage in the composite before external loading. The stiffness of double-bolt double-lap (3DD) joints was found to be approximately three times that of single-bolt single-lap (3DS) joints, primarily due to reduced rotational flexibility. These findings provide useful insights into the design and optimization of composite bolted joints under tensile loading. Full article

In this paper, a novel type of polarization-insensitive terahertz metal metasurface with cross-shaped holes is presented, which is designed based on the theory of bound states in continuous media. The fundamental unit of the metasurface comprises a metal tungsten sheet with a cross-shaped hole structure. A thorough analysis of the optical properties and the quasi-BIC response is conducted using the finite element method. Utilizing the symmetry-breaking theory, the symmetry of the metal metasurface is broken, allowing the excitation of double quasi-BIC resonance modes with a high quality factor and high sensitivity to be achieved. Analysis of the multipole power distribution diagram and the spatial distribution of the electric field at the two quasi-BIC resonances verifies that the two quasi-BIC resonances of the metasurface are excited by electric dipoles and electric quadrupoles, respectively. Further simulation analysis demonstrates that the refractive index sensitivities of the two quasi-BIC modes of the metasurface reach $404.5 \mathrm{G}\mathrm{H}\mathrm{z}/\mathrm{R}\mathrm{I}\mathrm{U}$ and $578.6 \mathrm{G}\mathrm{H}\mathrm{z}/\mathrm{R}\mathrm{I}\mathrm{U}$, respectively. Finally, the functional material PHMB is introduced into the metasurface to achieve highly sensitive sensing and detection of CO₂ gas concentrations. The proposed metallic metasurface structure exhibits significant advantages, including high sensitivity, ease of preparation, and a high Q-value, which renders it highly promising for a broad range of applications in the domains of terahertz biosensing and highly sensitive gas sensing. Full article

The deterioration of freshwater ecosystems in anthropogenic wetlands is intensified due to phosphorus inputs from fertilizers applied in agricultural areas. In addition, managing the excess green waste generated in these ecosystems increases the complexity of the problem. To move towards a sustainable society based on the circular economy, the use of controlled combustion of green waste to obtain bioenergy—followed by the application of the resulting ash for phosphorus removal from freshwater bodies via adsorption processes—should be considered. Furthermore, those ashes could be used as natural fertilizers and incorporated into the cultivated fields. This paper presents a deep study of the adsorption of phosphorus ions using ashes from the main green waste produced in wetlands. Various experiments were conducted to determine the effects of different variables in the removal process. A double kinetic model was necessary to explain the presence of two different removal processes. The Langmuir model described the equilibrium isotherm data of both adsorbents through an endothermic process. Acidic pH in the initial solutions was preferred because it promotes phosphorus removal by calcium dissolution. The alkalinity did not have a substantial effect on the adsorbent capacity. Calcium was the element that had a more significant influence on the overall process. Finally, a removal study using blended materials was performed. A combined model was proposed and validated based on the original isotherm models for the pure materials. Full article

Vehicle collisions with street lighting poles generate extremely high impact forces, often resulting in serious injuries or fatalities. Therefore, enhancing the structural resilience of pole bases is a critical engineering objective. This study investigates a comprehensive dynamic analysis conducted with respect to base material behavior and energy absorption of GFRP lighting pole structures under impact loads. A finite element (FE) model of a 5 m-tall tapered GFRP pole with a steel base sleeve, base plate, and anchor bolts was developed. A 500 kg drop-weight impact at 400 mm above the base simulated vehicle collision conditions. The model was validated against experimental data, accurately reproducing the observed failure mode and peak force within 6%. Parametric analyses explored variations in pole diameter, wall thickness, base plate size and thickness, sleeve height, and anchor configuration. Results revealed that geometric parameters—particularly wall thickness and base plate dimensions—had the most significant influence on energy absorption. Doubling the wall thickness reduced normalized energy absorption by approximately 76%, while increases in base plate size and thickness reduced it by 35% and 26%, respectively. Material strength and anchor bolt configuration showed minimal impact. These findings underscore the importance of optimizing pole geometry to enhance crashworthiness. Controlled structural deformation improves energy dissipation, making geometry-focused design strategies more effective than simply increasing material strength. This work provides a foundation for designing safer roadside poles and highlights areas for further exploration in base configurations and connection systems. Full article

Background: Although the difficulty level of figure skating programs has increased in the last two decades, particularly at the junior level, trends in performance have not been reported. This retrospective observational study investigated performance development trends among the top five junior figure skaters competing at international levels in both the ladies’ and men’s singles disciplines from 2005 to 2020. Data from 160 junior single ladies and 160 junior single men were analyzed. The focus was on the progression of technical elements—particularly jumps—and their potential correlation with injury risk. It was hypothesized that younger athletes are increasingly performing jumps with more revolutions, thereby enhancing overall competition standards. Materials and Methods: Using data from the Junior World Championships and Junior Grand Prix Finals, linear regression analysis and one-way ANOVA were conducted to track the frequency of double, triple, and quadruple jumps, as well as trends in age development among athletes in the singles categories from 2005 to 2020. Results: The results indicate a significant increase in the execution of higher-revolution jumps among junior athletes. Between 2005 and 2012, the frequency of double jumps declined across all events, with the most pronounced reductions observed in the Ladies’ Junior World Championships (Δ = 0.216, p = 0.004, d = 1.64) and the Men’s Junior World Championships (Δ = 0.500, p = 0.001, d = 1.82). From 2005 to 2011, the frequencies of triple and quadruple jumps increased, while double jumps remained stable or showed only slight increases. Triple jumps showed slight downward trends (e.g., R² = 0.0202 at the Men’s Junior World Championships). Although still rare, the frequency of quadruple jumps has shown a consistent upward trend across multiple competitions. Between 2000 and 2009, all four events exhibited declining age trends, with decreases ranging from −0.029 to −0.078 years of age per year. In the subsequent decade (2010–2020), when averaged across all events, the observed difference slope (Δ = 0.014) indicated a continued decline in athlete age. Conclusions: In summary, increases in more difficult jumps were found, with simultaneous decreases in less difficult jumps. As jump complexity rises, a parallel increase in sport-specific injury incidence can be anticipated, highlighting the need for proactive strategies for injury prevention and athlete well-being. Full article

Double-skin façades (DSFs) are promising sustainable design elements of buildings. However, they are prone to overheating problems in warm seasons due to high outdoor temperatures and intense solar radiation. Although phase-change material (PCM) blinds have proved to be effective at enhancing the thermal performance of DSFs, the impacts of the design parameters are crucial to the overall thermal performance of the system. This study focused on analyzing the impacts of design parameters on the thermal performance of a ventilated DSF system, which consisted of a macro-encapsulated phase-change material (PCM) blind with an aluminum shell. A simulation study was conducted using ANSYS Workbench FLUENT software, and the temperature distributions of the integrated system were compared with different blind tilt angles and ratios of cavity depth to blind width. The results show that both the blind tilt angle and ratio of cavity depth to blind width had a significant influence on the thermal performance of the DSF system. For instance, lower air-cavity temperatures within the range of 37~40 °C were achieved with the PCM blind at tilt angles of 30° and 60° compared with other selected tilt angles (0° and 90°). In terms of the cavity depth to blind width ratio, a ratio of 2.5 resulted in a lower air-cavity temperature and a better thermal performance by the DSF. With the optimal blind tilt angle and cavity depth to blind width ratio, the integrated DSF and macro-encapsulated PCM-blind system can reduce the cavity temperature by as much as 2.9 °C during the warm season. Full article

Oil shale, an unconventional oil and gas resource, can generate the required hydrocarbons through high-temperature pyrolysis. In situ conversion extraction technology utilizes downhole heaters to directly inject high-temperature heat into the oil shale layer to achieve the effect of oil and gas recovery. For the metal material components of the combustion heaters, the uneven temperature fields experienced during the start of operations, processing, and end of operations can lead to fatigue conditions, such as high-temperature creep, micro-damage, and micro-deformation due to thermal effects. To prevent the occurrence of the aforementioned issues, it is necessary to conduct fatigue life analysis of downhole combustion heaters. By combining actual combustion heater operation experiments with finite element simulation, this paper analyzes the impact of temperature, structure, and stress amplitude on the fatigue life of heaters. The results indicate that the fatigue life of the heaters is most significantly influenced by the metal gaskets, and the higher the exhaust gas temperature, the lower the fatigue life of the heater. Heating operations significantly reduce the fatigue life of the heater, while cooling operations have almost no effect on the fatigue life. Circular-pore metal gaskets have a higher fatigue life than those with a square hole shape. Considering only the thickness of the metal gaskets, the thicker the gasket, the higher the fatigue life. Stress amplitude has the most significant impact on the fatigue life of the heater; when the stress amplitude is doubled, the metal gaskets quickly undergo fatigue damage. Full article

This work investigates the applicability of Bayesian inverse analysis for identifying parameters from non-standard aluminum specimens with notches that induce stress concentrations. Unlike conventional standardized specimens, the notched samples used in this work are typically unsuitable for direct parameter extraction due to geometric irregularities and size effects. The experimental procedure involved tensile tests conducted using a universal testing machine, with deformation data collected via LVDT sensors and optical measurements with digital image correlation. The numerical simulations were performed using a quadrilateral finite element model with embedded strong discontinuities to capture the complete material response, including elastic, plastic, and fracture behavior. The proposed identification procedure successfully provided reliable posterior parameter estimates on aluminum rectangular and single-notch specimens. Furthermore, the identified parameters were validated on a double-notch specimen made of the same material. The results highlight the importance of parameter interpretation and show that the Bayesian framework can reliably identify key material and model-dependent parameters from non-standard specimens while accounting for uncertainty in both measurements and model formulation. Full article

The search for stable, lead-free perovskite materials is critical for developing efficient and environmentally friendly energy solutions. In this study, machine learning methods were applied to predict the bandgap and formation energy of double perovskites, aiming to identify promising photovoltaic candidates. A dataset of 1053 double perovskites was extracted from the Materials Project database, with 50 feature descriptors generated. Feature selection was carried out using Pearson correlation and mRMR methods, and 23 key features for bandgap prediction and 18 key features for formation energy prediction were determined. Four algorithms, including gradient-boosting regression (GBR), random forest regression (RFR), LightGBM, and XGBoost, were evaluated, with XGBoost demonstrating the best performance (R² = 0.934 for bandgap, R² = 0.959 for formation energy; MAE = 0.211 eV and 0.013 eV/atom). The SHAP (Shapley Additive Explanations) analysis revealed that the X-site electron affinity positively influences the bandgap, while the B″-site first and third ionization energies exhibit strong negative effects. Formation energy is primarily governed by the X-site first ionization energy and the electronegativities of the B′ and B″ sites. To identify optimal photovoltaic materials, 4573 charge-neutral double perovskites were generated via elemental substitution, with 2054 structurally stable candidates selected using tolerance and octahedral factors. The XGBoost model predicted bandgaps, yielding 99 lead-free double perovskites with ideal bandgaps (1.3~1.4 eV). Among them, four candidates are known compounds according to the Materials Project database, namely Ca₂NbFeO₆, Ca₂FeTaO₆, La₂CrFeO₆, and Cs₂YAgBr₆, while the remaining 95 candidate perovskites are unknown compounds. Notably, X-site elements (Se, S, O, C) and B″-site elements (Pd, Ir, Fe, Ta, Pt, Cu) favor narrow bandgap formation. These findings provide valuable guidance for designing high-performance, non-toxic photovoltaic materials. Full article

The human coagulation pathway orchestrates a complex series of events vital for maintaining vascular integrity, in which the intrinsic pathway plays a pivotal role in amplifying and propagating the coagulation response. Dysregulation of this pathway can lead to various bleeding disorders and thrombotic complications, posing significant health risks. In this pathway, the activation of Factor (F) X zymogen is catalyzed by the FVIIIa-FIXa binary complex, but knowledge about this is still incomplete. Understanding the structural and functional intricacies of the FVIIIa-FIXa-FX (zymogen) complex is imperative for unraveling the molecular mechanisms underlying coagulation regulation and guiding the development of targeted therapeutic interventions. In this study, utilizing Alphafold-Multimer and molecular dynamics (MD) simulations, we provide insights into factor interactions within the ternary complex and propose novel functional mechanisms contributing to the functional defects inflicted by their cross-reactive material (CRM) positive mutations. The amino acid residue replacement impairs the coagulation function by interfering with structure elements, including the following: (1) a knot-like structure between Arg-562 of FVIIIa’s 558-Loop (residue 555–571) and the 333-Loop of FIXa (residue 333–346) contributes to FVIIIa-FIXa binding; (2) the a2 region of FVIIIa (residue 716–740) opens the lid of active site (FIXa’s 266-Loop, residue 256–270) and facilitates substrate binding; (3) the activation peptide (AP) of FX zymogen (residue 143–194) not only assists in the activation of itself but also adheres the interface of the three factors like a double-sided tape. Our work provides novel insights for the pathogenesis of a number of reported clinical CRM-positive mutations and may lay the groundwork for the structure-based development of therapeutic interventions. Full article

The Asymmetric Double Cantilever Beam (ADCB) is a common test configuration used to produce mixed mode I/II in composite materials. It consists of two sublaminates with different thicknesses or elastic properties, a situation that usually occurs in bimaterial adhesive joints. During this test, the sample undergoes rotation. In this work, the influence of this rotation on the calculation of the energy release rate (ERR) in modes I and II was studied using the Finite Element Method (FEM). Several models with different degrees of asymmetry (different thickness ratio and/or elastic modulus ratio) and different applied displacements were prepared to obtain different levels of rotation during the test. As is known, the concept of modes I and II refers to the components of the energy release rate calculated in the direction perpendicular and tangential to the delamination plane, respectively. If the model experiences significant rotation during the application of the load, this non-linearity must be considered in the calculation of the mode partition I/II. In this work, appreciable differences were observed in the values of modes I and II, depending on their calculation in a global system or a local system that rotates with the sample. When performing crack growth calculations, the difference between critical loads can be in the order of 4%, while the difference between mode I and mode II results can reach 4% and 14%, respectively, for an applied displacement of only 5 mm. Currently, this correction is not usually implemented in Finite Element calculation codes or in analytical developments. The purpose of this article is to draw attention to this aspect when the rotation of the specimen is not negligible. Full article

A diverse range of granitoids in the North Qilian Orogenic Belt (NQOB) offers valuable insights into the region’s tectonomagmatic evolution. In this study, we undertook a geochronological, mineralogical, geochemical, and zircon Hf isotopic analysis of granodiorites from the Yaogou area of the NQOB. Zircon U-Pb dating reveals that the Yaogou granodiorites formed during the Early–Middle Ordovician (473–460 Ma). The Yaogou granodiorites have high SiO₂ (63.3–71.1 wt.%), high Al₂O₃ (13.9–15.8 wt.%) contents, and low Zr (96–244 ppm), Nb (2.9–18 ppm), as well as low Ga/Al ratios (10,000 × Ga/Al ratios of 1.7–2.9) and FeO^T/MgO ratios (1.9–3.2), and are characterized by elevated concentrations of light rare earth elements and large-ion lithophile elements such as Rb, Th, and U, coupled with significant depletion in heavy rare earth elements and high-field-strength elements including Nb, Ta, and Ti. Additionally, the presence of negative europium anomalies further reflects geochemical signatures typical of I-type granitic rocks. The zircon grains from these rocks display negative ε_Hf(t) values (−14.6 to −10.7), with two-stage Hf model ages (T_DM2) from 2129 to 1907 Ma. These characteristics suggest that the magmatic source of the Yaogou granodiorites likely originated from the partial melting of Paleoproterozoic basement-derived crustal materials within a tectonic environment associated with subduction in the North Qilian Ocean. Integrating regional geological data, we suggest that during the Early Paleozoic, the North Qilian Oceanic slab underwent double subduction: initially southward, followed by a northward shift. Due to the deep northward subduction of the Qaidam continental crust and oceanic crust along the southern margin of the Qilian Orogenic Belt, the southward subduction of the North Qilian ocean was obstructed, triggering a reversal in subduction polarity. This reversal likely decelerated the southward subduction and initiated northward subduction, ultimately leading to the formation of the Yaogou granodiorites. These findings enhance our understanding of the complex tectonic processes that shaped the North Qilian Orogenic Belt during the Early Paleozoic, emphasizing the role of subduction dynamics and continental interactions in the region’s geological evolution. Full article

This study addresses the challenge of optimizing seal structure design through a novel two-stage interpretable optimization framework. Focusing on O-ring waterproof performance under hyperelastic material behavior, this study proposes a double-layer optimization method integrating explainable machine learning with hierarchical clustering algorithms. The key innovation lies in employing modified hierarchical clustering to categorize design parameters into two interpretable groups: bolt preload and groove depth. This clustering enables dimensionality reduction while maintaining the physical interpretability of critical parameters. In the first layer, systematic parameter screening and optimization are applied to the preload variable to reduce the database, with six remaining data points that constitute one-seventh of the original data. The second layer subsequently refines configurations using E-TOPSIS (Entropy Weight—Technique for Order Preference by Similarity to Ideal Solution) optimization. All evaluations are performed through FEA (finite element analysis) considering nonlinear material responses. The optimal design is a groove depth of 0.8 mm and a preload of 80 N. The experimental validation demonstrates that this method efficiently identifies optimal designs meeting IPX8 waterproof requirements, with zero leakage observed in both O-ring surfaces and motor interiors. The proposed methodology provides physically meaningful design guidelines. Full article