Search Results (5,435)

This study presents an analysis of the electromagnetic noise and vibration in a surface-mounted permanent magnet synchronous machine (SPMSM), focusing on their excitation sources. To investigate this, the excitation sources were identified through an analytical approach, and their effects on electromagnetic noise and vibration were evaluated using a finite element method (FEM)-based analysis approach. Additionally, an equivalent curved-beam model based on three-dimensional shell theory was applied to determine the deflection forces on the stator yoke, accounting for the tooth-modulation effect. The stator’s natural frequencies were derived through the characteristic equation in free vibration analysis. Modal analysis was performed to validate the analytically derived natural frequencies and to investigate stator deformation under the tooth-modulation effect across various vibration modes. Furthermore, noise, vibration, and harshness (NVH) analysis via FEM reveals that major harmonic components align closely with the natural frequencies, identifying them as primary sources of elevated vibrations. A comparative study between 8-pole–9-slot and 8-pole–12-slot SPMSMs highlights the impact of force variations on the stator teeth in relation to vibration and noise characteristics, with FEM verification. The proposed method provides a valuable tool for early-stage motor design, enabling the rapid identification of resonance operating points that may induce severe vibrations. This facilitates proactive mitigation strategies to enhance motor performance and reliability. Full article

(1) Background: This study aimed to evaluate the marginal and internal fit of ceramic crowns produced by various digital methods using microcomputed tomography (MCT) imaging. (2) Methods: The ceramic crown preparation was performed on typodont maxillary first premolar. The crown preparation was scanned with an intraoral scanner and a model scanner, and cone-beam computed tomography (CBCT) scans were performed with three different voxel sizes (0.075 mm, 0.1 mm, and 0.15 mm). The space between the crown and prepared teeth was measured at nine different points in both coronal and sagittal sections. Three different digital model acquisition techniques, namely, intraoral scanning, model scanning, and CBCT-based standard tessellation language (STL) reconstruction, were compared in terms of marginal and internal fit. (3) Results: Quantitative analyses revealed that model scanners exhibited the lowest marginal and internal gap values, indicating superior fit compared to intraoral scanners and CBCT-based models. The highest gap values were observed in the CBCT group with a voxel size of 0.15 mm. Overall, crowns obtained from model scanners demonstrated the highest success rates in both marginal and internal fit. (4) Conclusions: In conclusion, this study highlights the critical role of digital scanning accuracy in achieving clinically acceptable prosthetic fits and emphasizes the need for continued technological advancement. Full article

In this work, a novel analytical equation is developed to accurately predict the mechanical behavior of thin-walled beams. The FEM was used for building the model and obtaining the results. The new equation developed is useful for the calculation of the displacement of a beam simply supported at its ends subjected to torsion loads, applied in opposite side areas of the Finite Element Method (FEM) model. The software Eureqa 1.24.0 was used to find hidden analytical models that were validated thereafter. The aim is to provide a formula that makes possible the comparison of analytic calculations with numerical calculations on bending and torsion combined load. A FEM model of a hollow-box beam with rectangular cross-section loaded with torsion was built and analytical calculations were performed. The analytic calculations were compared with the numeric results in order to know if the results are approximated. The results show good agreement. In the future, other models, such as internally reinforced beams, could also be tested with this methodology. Also, different conditions could be applied to the model studied in this work in order to evaluate the limitations and validity of the developed analytical model. Full article

Multibeam echosounder systems (MBESs) are widely used in unmanned surface vehicle swarms (USVs) to perform various marine bathymetry surveys because of their excellent performance. To address the challenges of systematic error superposition and edge beam error propagation in multibeam bathymetry surveying, this study proposes a novel error adjustment method integrating crossover error density clustering and beam incident angle (BIA) compensation. Firstly, a bathymetry error detection model was developed based on adaptive Density-Based Spatial Clustering of Applications with Noise (DBSCAN). By optimizing the neighborhood radius and minimum sample threshold through analyzing sliding-window curvature, the method achieved the automatic identification of outliers, reducing crossover discrepancies from ±150 m to ±50 m in the deep sea at a depth of approximately 5000 m. Secondly, an asymmetric quadratic surface correction model was established by incorporating the BIA as a key parameter. A dynamic weight matrix ω = 1/(1 + 0.5θ²) was introduced to suppress edge beam errors, combined with Tikhonov regularization to resolve ill-posed matrix issues. Experimental validation in the Western Pacific demonstrated that the RMSE of crossover points decreased by about 30.4% and the MAE was reduced by 57.3%. The proposed method effectively corrects residual systematic errors while maintaining topographic authenticity, providing a reference for improving the quality of multibeam bathymetric data obtained via USVs and enhancing measurement efficiency. Full article

With the advancement of modern engineering structures, traditional cement concrete is increasingly unable to meet the mechanical performance requirements under complex conditions. To overcome the performance limitations of materials, modified concrete has become a focal point of research. By incorporating modifying materials such as fibers, polymers, or mineral admixtures, the properties of concrete can be significantly enhanced. Among these, rubberized concrete has attracted considerable attention due to its unique performance advantages. This study conducted fracture tests on rubberized concrete using non-standard concrete three-point bending beam specimens of varying dimensions to evaluate its fracture performance. Employing conventional concrete fracture theoretical models, the fracture toughness parameters of rubberized concrete were calculated, and a comparative analysis was performed regarding the applicability of various theoretical calculation formulas to rubberized concrete. The results indicated that the fracture performance of rubberized concrete varied significantly with changes in specimen size. The initial toughness exhibited a consistent size-dependent variation across different theoretical models. The fracture toughness corresponding to crack height ratios between 0.05 and 0.25 showed contradictory trends; however, for crack height ratios between 0.3 and 0.5, the fracture toughness became consistent. This study integrated boundary effect theory and employed Guinea’s theory to propose an optimization coefficient γ for the double-K fracture toughness formula, yielding favorable optimization results. Full article

This study investigates two novel prefabricated frame joints: prestressed steel sleeve-connected prefabricated reinforced concrete joints (PSFRC) and non-prestressed steel sleeve-connected prefabricated reinforced concrete joints (SSFRC). A total of three PSFRC specimens, four SSFRC specimens, and one cast-in-place joint were designed and fabricated. Seismic performance tests were conducted using different end-plate thicknesses, grout strengths, stiffener configurations, and prestressing tendon configurations. The experimental results showed that all specimens experienced beam end failures, and three failure modes occurred: (1) failure of the end plate of the beam sleeve, (2) failure of the variable cross-section of the prefabricated beam, and (3) failure of prefabricated beams at the connection with the steel sleeves. The load-bearing capacity and initial stiffness of the structure are increased by 35.41% and 32.64%, respectively, by increasing the thickness of the end plate. Specimens utilizing C80 grout exhibited a 39.05% higher load capacity than those with lower-grade materials. Adding stiffening ribs improved the initial stiffness substantially. Specimen XF2 had 219.08% higher initial stiffness than XF1, confirming the efficacy of stiffeners in enhancing joint rigidity. The configuration of the prestressed tendons significantly influenced the load-bearing capacity. Specimen YL2 with symmetrical double tendon bundles demonstrated a 27.27% higher ultimate load capacity than specimen YL1 with single centrally placed tendon bundles. An analytical model to calculate the moment–rotation relationship was established following the evaluation criteria specified in Eurocode 3. The results demonstrated a good agreement, providing empirical references for practical engineering applications. Full article

Integrated optical waveguide amplifiers, with their compact footprint, low power consumption, and scalability, are the basis for optical communications. The realization of high gain in such integrated devices is made more challenging by the tight optical constraints. In this work, we present efficient amplification in an erbium–ytterbium-based hybrid slot waveguide consisting of a silicon nitride waveguide and a thin-film active layer/electron-beam resist. The electron-beam resist as the upper cladding layer not only possesses the role of protecting the waveguide but also has tighter optical confinement in the vertical cross-section direction. On this basis, an accurate and comprehensive dynamic model of an erbium–ytterbium co-doped amplifier is realized by introducing quenched ions. A modal gain of above 20 dB is achieved at the signal wavelength of 1530 nm in a 1.4 cm long hybrid slot waveguide, with fractions of quenched ions f_q = 30%. In addition, the proposed hybrid waveguide amplifiers exhibit higher modal gain than conventional air-clad amplifiers under the same conditions. Endowing silicon nitride photonic integrated circuits with efficient amplification enriches the integration of various active functionalities on silicon. Full article

This paper presents an integrated computational framework for predicting temperature fields in glulam beam–column connections under fire conditions, combining finite element modeling, automated parametric analysis, and deep learning techniques. A high-fidelity heat transfer finite element model was developed, incorporating the anisotropic thermal properties of wood and temperature-dependent material behavior, validated against experimental data with strong agreement. To enable large-scale parametric studies, an automated Abaqus model modification and data processing system was implemented, improving computational efficiency through the batch processing of geometric and material parameters. The extracted temperature field data was used to train a DeepONet neural network, which achieved accurate temperature predictions (with a L2 relative error of 1.5689% and an R² score of 0.9991) while operating faster than conventional finite element analysis. This research establishes a complete workflow from fundamental heat transfer analysis to efficient data generation and machine learning prediction, providing structural engineers with practical tools for the performance-based fire safety design of timber connections. The framework’s computational efficiency enables comprehensive parametric studies and design optimizations that were previously impractical, offering significant advancements for structural fire engineering applications. Full article

Based on the engineering background of a new type of segmental-assembled steel temporary beam buttress, the fatigue strength evaluation method of the steel box girders with open longitudinal ribs was taken as the research objective. The fatigue stress calculation analysis and the full-scale fatigue loading test for the steel box girder local component were carried out. The accuracy of the finite-element model was verified by comparing it with the test results, and the rationality of the fatigue strength evaluation methods for welded joints was deeply explored. The results indicate that the maximum nominal stress occurs at the weld toe between the transverse diaphragm and the top plate at the edge of the loading area, which is the fatigue-vulnerable location for the steel box girder local components. The initial static-load stresses at each measuring point were in good agreement with the finite-element calculation results. However, the static-load stress at the measuring point in the fatigue-vulnerable position shows a certain decrease with the increase in the number of cyclic loads, while the stress at other measuring points remains basically unchanged. According to the finite-element model, the fatigue strengths obtained by the nominal stress method and the hot-spot stress method are 72.1 MPa and 93.8 MPa, respectively. It is reasonable to use the nominal stress S-N curve with a fatigue life of 2 million cycles at 70 MPa and the hot-spot stress S-N curve with a fatigue life of 2 million cycles at 90 MPa (FAT90) to evaluate the fatigue of the welded joints in steel box girders with open longitudinal ribs. According to the equivalent structural stress method, the fatigue strength corresponding to 2 million cycles is 94.1 MPa, which is slightly lower than the result corresponding to the main S-N curve but within the range of the standard deviation curve. The research results of this article can provide important guidance for the anti-fatigue design of welded joints in steel box girders with open longitudinal ribs. Full article

To address the issue of deformation mismatch between the exterior wall panels and the resilient frame structure under large deformations, two novel flexible devices (FDs) with different working principles are proposed in this paper. These FDs enable the exterior wall panels to achieve cooperative deformation with frame columns or beams under horizontal loads, thus improving the seismic performance of the frame structure with additional exterior wall panels. This study begins by explaining the specific design thought of the FDs based on examining the deformation characteristics of frame structures. Then, a series of low-cycle loading tests are conducted on frame specimens to demonstrate the effectiveness of the FDs. The experimental results indicate that the FDs can improve the interaction between the exterior wall panels and the main frame, reduce plastic damage to the wall panels, and increase the peak load-bearing capacity of the overall structure by approximately 17–21%. In addition, a refined finite element modeling method for the proposed FDs is presented using the ABAQUS software, providing a basis for further research on frame structures with additional exterior wall panels. Full article

This research investigated and compared the structural behavior of reinforced concrete straight beams and beams made with out-of-plane parts. This study focused on the influence of the location and number of out-of-plane parts, as well as encasing the beams with a steel section, on the ultimate strength, deflection, and rotation in addition to the ductility, energy absorption, and failure mode. A total of nine beams were modelized numerically, divided into three series. The first one included one straight beam, while the remaining two series included four beams each made with out-of-plane parts with and without steel sections. The beams with out-of-plane parts connected the two, three, four, and five concrete segments. The outcomes revealed that the beams made with out-of-plane parts showed less strength than straight beams, which increased the connected segments and reduced the ultimate strength capacity. The regular beam’s linearity was dissimilar to the zigzag beams, which showed a linearity of 32% and was reduced to 22%, 20%, 19.67%, and 16% for beam out-of-plane parts made with two, three, four, and five segments, respectively. Forming a zigzag in the plane of the beams reduced the cracking load, but the decrement depended on the number of parts, which led to more reduction in the yielding load. Concerning the deflection and deformations, the concrete straight beams failed in flexure, with maximum deflection occurring at the midspan of the beam, which was different for beams without plane parts, which showed a combined shear-torsional failure for which the maximum deformation occurred at the midspan with inclination of connected parts on the interior perpendicular axis. Encasing the beams’ out-of-plane parts with steel sections enhanced the structural behavior. The ductility and energy absorption of the out-of-plane parts beams were less than the straight ones, but encasing the beams with a steel section improved the ductility and energy absorption twice. Full article

The growing demand for reliable and secure vehicle-to-vehicle (V2V) communication in next-generation intelligent transportation systems has accelerated the adoption of reconfigurable intelligent surfaces (RIS) as a means of enhancing link quality, spectral efficiency, and physical layer security. In this paper, we investigate the problem of secrecy rate maximization in a cooperative dual-RIS-aided V2V communication network, where two cascaded RISs are deployed to collaboratively assist with secure data transmission between mobile vehicular nodes in the presence of eavesdroppers. To address the inherent complexity of time-varying wireless channels, we propose a novel evolutionary transformer-gated recurrent unit (Evo-Transformer-GRU) framework that jointly learns temporal channel patterns and optimizes the RIS reflection coefficients, beam-forming vectors, and cooperative communication strategies. Our model integrates the sequence modeling strength of GRUs with the global attention mechanism of transformer encoders, enabling the efficient representation of time-series channel behavior and long-range dependencies. To further enhance convergence and secrecy performance, we incorporate an improved gray wolf optimizer (IGWO) to adaptively regulate the model’s hyper-parameters and fine-tune the RIS phase shifts, resulting in a more stable and optimized learning process. Extensive simulations demonstrate the superiority of the proposed framework compared to existing baselines, such as transformer, bidirectional encoder representations from transformers (BERT), deep reinforcement learning (DRL), long short-term memory (LSTM), and GRU models. Specifically, our method achieves an up to 32.6% improvement in average secrecy rate and a 28.4% lower convergence time under varying channel conditions and eavesdropper locations. In addition to secrecy rate improvements, the proposed model achieved a root mean square error (RMSE) of 0.05, coefficient of determination ($R^2$) score of 0.96, and mean absolute percentage error (MAPE) of just 0.73%, outperforming all baseline methods in prediction accuracy and robustness. Furthermore, Evo-Transformer-GRU demonstrated rapid convergence within 100 epochs, the lowest variance across multiple runs. Full article

The use of adhesive joints in naval applications requires a thorough understanding of their fatigue performance. This paper reports on the fatigue experiments performed on double cantilever beam specimens with thick adhesive bondline manufactured under shipyard conditions. The specimens have an initial crack at the steel–adhesive interface and are tested in unaged, salt-spray-aged and immersion-aged conditions to determine the interface mode I fatigue properties. The strain energy release rate is calculated using the Kanninen–Penado model, and the fatigue crack growth curve is determined using a power law model. The crack growth rate slope for salt-spray-aged specimens is 16.5% lower than for unaged specimens, while that for immersion-aged specimens is 66.1% lower and is shown to be significantly different. The fracture surfaces are analyzed to identify the failure mechanisms and the influence of the aging process on the interface properties. Since the specimens are manufactured under shipyard conditions, the presence of voids and discontinuities in the adhesive bondline is observed and as a result leads to scatter. Hence, Bayesian linear regression is performed in addition to the ordinary least squares regression to account for the scatter and provide a distribution of plausible values for the power law coefficients. The results highlight the impact of aging on the fatigue property, underscoring the importance of considering environmental effects in the qualification of such joints for marine applications. Full article

Background and Objectives: Evaluating jaw augmentation procedures usually necessitates pre- and postoperative tomographic imaging. Ethical considerations emphasize minimizing radiation exposure. Given that panoramic radiographs (PR, 2D) offer a lower radiation dose compared to cone-beam CT (CBCT, 3D), this study explores the feasibility of estimating tooth root volume from PR, potentially allowing safer clinical assessments with reduced radiation exposure. Materials and Methods: To develop a mathematical approximation method, the 2D tooth root surface in PR was defined as an elliptical model and a cuboid (3D). The true root volume (mm³) was gathered from CBCTs. The missing link for tooth root volume assessment in 2D radiographs is the depth of the root (vestibulo-oral dimension). It was hypothesized that the tooth root surface and its volume are related. A correlation factor “r” corresponding to the tooth roots’ depths was then calculated. Descriptive and inferential statistics were computed (p < 0.05). Results: The mathematical model was performed on 27 molars with an average volume of 472.83 mm³ (±130.25–CBCT). The factor “r” (obtained by dividing the true root volume from CBCT by the total root surface from PR) was computed as 8.04 (±1.90). Using “r” for the volume calculation in the cuboid model, an average volume of 472.37 (±152.92) for the 27 molars was computed. These volumes did not differ significantly. Conclusions: This study demonstrates that a mathematical model using elliptical projections from panoramic radiographs reliably estimates molar root volume, yielding comparable results to CBCT while reducing radiation exposure. Full article

Reinforced concrete deep beams (RCDBs) provide significant strength and serviceability for building structures. However, a simple, general, and universally accepted procedure for predicting their shear strength (SS) has yet to be established. This study proposes a novel data-driven approach to predicting the SS of RCDBs using an enhanced CatBoost (CB) model. For this purpose, a newly comprehensive database of RCDBs with shear failure, including 950 experimental specimens, was established and adopted. The model was developed through a customized procedure including feature selection, data preprocessing, hyperparameter tuning, and model evaluation. The CB model was further evaluated against three data-driven models (e.g., Random Forest, Extra Trees, and AdaBoost) as well as three prominent mechanics-driven models (e.g., ACI 318, CSA A23.3, and EU2). Finally, the SHAP algorithm was employed for interpretation to increase the model’s reliability. The results revealed that the CB model yielded a superior accuracy and outperformed all other models. In addition, the interpretation results showed similar trends between the CB model and mechanics-driven models. The geometric dimensions and concrete properties are the most influential input features on the SS, followed by reinforcement properties. In which the SS can be significantly improved by increasing beam width and concert strength, and by reducing shear span-to-depth ratio. Thus, the proposed interpretable data-driven model has a high potential to be an alternative approach for design practice in structural engineering. Full article