Search Results (44)

A critical research gap persists in modular steel construction regarding the seismic behavior of inter-module connections between square steel tubular columns and H-shaped steel beams. While numerous connection systems have been proposed, two fundamental challenges remain unresolved: the inherent conflict between construction efficiency and mechanical performance, and the insufficiency of restoring force models that systematically describe hysteretic characteristics and stiffness degradation under cyclic loading. To address these issues, a novel box-type modular connection between square steel tubular columns and H-shaped steel beams is proposed. A finite element model was established using ABAQUS, and the modeling methodology was validated against experimental results from the literature. The seismic behavior was systematically investigated, and a restoring force model with theoretical saturation and linear degradation was developed. Results show that the novel joint is a semi-rigid connection that satisfies the “strong column–weak beam” design principle. The outer ring plate shifts the plastic hinge away from the vulnerable beam end region, preventing failure at the beam–column connection. Among the detrimental factors identified, the insert-to-column gap has the most severe impact, causing up to a 49.5% reduction in energy dissipation and a 6.5% reduction in initial stiffness; the outer ring plate thickness below the beam flange thickness causes a 44.6% drop in energy dissipation. The proposed restoring force model, validated against nine calibration specimens and one independent specimen, predicts peak load with a deviation of only 1.14% and the equivalent viscous damping coefficient with a relative error of 14.7%, confirming its reliability in capturing the cyclic behavior of the joint. This study provides both design recommendations for engineering practice and a theoretical foundation for elasto-plastic analysis of modular frames with this connection type. Full article

In thermal power plants, accurate detection of torsion faults in tubular belt conveyors is crucial for operational safety. Traditional methods lack efficiency and accuracy, while existing deep learning models struggle with real-time processing demands. This paper introduces an enhanced Dynamic-UNet architecture, incorporating depthwise separable convolutions, a quality-aware gating module, and a simplified decoder structure. Evaluated on a dedicated industrial dataset, our model achieves a 97.89% mean Intersection over Union (mIoU) and a 32.28 Frames Per Second (FPS) inference speed on an NVIDIA RTX 3090, which is 2.72 percentage points higher in accuracy and 2.2× faster in inference than the original UNet, and outperforms mainstream semantic segmentation models. Real-world deployment on a Huawei Atlas DK A2 edge platform with a dynamic Region of Interest (ROI) mechanism further delivers an effective inference speed of 33.46 FPS, fulfilling industrial real-time requirements. Full article

In this paper, we deal with the canal hypersurfaces that are formed as the envelope of a family of pseudo-hyperspheres or pseudo-hyperbolic hyperspheres with centers lying on a pseudo-null curve with Bishop vector fields in four-dimensional Lorentz–Minkowski space. We give main theorems which contain the parametric expressions of these canal hypersurfaces along with their Gaussian, mean, and principal curvatures and important geometric characterizations. We also provide these characterizations for tubular hypersurfaces. Finally, we construct an example to allow for better understanding and comprehension of the results. Full article

With Aligned Formable Fibre Technology (AFFT^™), fibers are reformatted into highly oriented epoxy prepreg tapes, enabling the structural reuse of recycled composite waste. The present study investigates whether discontinuous fiber laminates produced with AFFT^™ can be characterized and optimized with the same finite-element workflows long established for continuous fiber composites and whether the resulting structures meet demanding stiffness targets. Initially, various manufacturing methods were adopted, including vacuum bagging, compression molding at 7 bar to simulate autoclave conditions, and compression molding at 90 bar, comprising the three most reasonable manufacturing processes for AFFT^™ laminates. Experimentally measured orthotropic properties were introduced into a finite-element model representing an idealized bicycle top tube, which was chosen as a case study. A genetic algorithm screened candidate stacking sequences, minimizing the combined bending-and-torsion deflection. The best lay-ups reduced deformation by more than 30% compared to a quasi-isotropic baseline, showing that well-oriented short fibers can significantly contribute to the stiffness of composites. Tubes produced with the optimized lay-up were tested in three-point bending tests, and the measured stiffness matched simulations within 5%. These results confirm a key point for sustainable engineering: despite the absence of continuous fibers, conventional simulation strategies accurately predict the performance of AFFT^™ laminates and can be used as the basis for effective genetic optimization. This validation is significant: it enables the design of stiff, high-performance structures from recycled materials using established, cost-effective methods. By proving that optimization strategies developed for traditional continuous fiber composites apply to AFFT^™, this study offers a trusted and accessible pathway to scale circular economy solutions in next-generation composite products. Full article

In this study, compared with traditional scaffolds, the arrangement and structural dimensions of steel tubular crossing frames used in transmission engineering are significantly different, making it difficult to efficiently and accurately evaluate their structural stability using existing specifications and conventional methods. Therefore, a finite element model of a steel tubular crossing frame considering the semi-rigid characteristics of joints was established, and the influence of frame parameters on structural stability and the effective length factor (μ) of the vertical members was analyzed. On this basis, the main factors affecting the effective length factor μ were identified using orthogonal testing and multiple linear regression, and a predictive formula was obtained through curve fitting. The results show that the step distance and number of steps of the horizontal members are the primary factors influencing the bearing capacity and μ value of the crossing frame, followed by the spacing of vertical members, the number of spans, and the number of rows. The height of the bottom sweeping member has a weak influence within the range of 0.1–0.6 m but becomes significantly more influential when it exceeds 0.7 m. The installation of peripheral cross bracing increases the bearing capacity of the crossing frame by at least 20%. The accuracy of the proposed formula was verified by comparing the stresses of the vertical members calculated using the formula, the specifications JGJ130-2019 and BS5975-2019, and the finite element analysis results. The findings provide a useful reference for the stability assessment and erection scheme design of steel tubular crossing frames in transmission engineering. Full article

This study presents an integrated, low-cost system for measuring extremely small displacements in Ionic Polymer–Metal Composite (IPMC) actuators operating in aqueous environments. A custom optical setup was developed, combining a glass tank, a tubular microscope with a 10× achromatic objective, a digital USB camera and uniform LED backlighting, enabling side-view imaging of the actuator with high contrast. The microscopy system achieves a spatial sampling of 0.536 μm/pixel on the horizontal axis and 0.518 μm/pixel on the vertical axis, while lens distortion is limited to a maximum edge deviation of +0.015 μm/pixel (≈+2.8%), ensuring consistent geometric magnification across the field of view. On the image-processing side, a predictive grid-based tracking algorithm is introduced to localize the free tip of the IPMC. The method combines edge detection, Harris corners and a constant-length geometric constraint with an adaptive search over selected grid cells. On 1920 × 1080-pixel frames, the proposed algorithm achieves a mean processing time of about 10 ms per frame and a frame-level detection accuracy of approximately 99% (98.3–99.4% depending on the allowed search radius) for actuation frequencies below 2 Hz, enabling real-time monitoring at 30 fps. In parallel, dedicated electronic circuitry for supply and load monitoring provides overvoltage, undervoltage, open-circuit and short-circuit detection in 100 injected fault events, all faults were detected and no spurious triggers over 3 h of nominal operation. The proposed microscopy and tracking framework offer a compact, reproducible and high-resolution alternative to laser-based or Digital Image Correlation techniques for IPMC displacement characterization and can be extended to other micro-displacement sensing applications in submerged or challenging environments. Full article

A trussed concrete-filled square steel tubular (CFSST) composite column frame is proposed for multi-story residential buildings. The frame provides high lateral resistance and can be integrated within wall systems. To evaluate its seismic performance, three full-scale specimens were subjected to quasi-static cyclic loading. The failure modes, load-carrying capacity, stiffness degradation, and energy dissipation characteristics were examined and compared. The results show that, compared to the H-shaped steel column frame (HK) with equivalent steel consumption, the trussed CFSST composite column frame exhibits an 88.3% increase in yield load and an 87.1% increase in peak load, together with significant improvements in stiffness and energy dissipation. Compared with an ordinary CFSST column frame (FK), the proposed system required 41% more steel but attained a 56% increase in load-carrying capacity, along with corresponding enhancements in stiffness and energy dissipation. Finite element (FE) models were developed based on the experimental results, and parametric analyses were performed to investigate the effects of corner-end column spacing, number of truss diagonal bars, truss joint type, axial compression ratio, and steel strength. Design recommendations are provided accordingly. Full article

In this study, We explore for Minkowski 3-space ${\mathbb{E}}_1^3$ harmonic surfaces’ geometric features by employing a common tangent vector field along a curve situated on the surface. Our analysis is grounded in the rotation minimizing (RM) Darboux frame, which offers a robust alternative to the classical Frenet frame particularly valuable in the Lorentzian setting, where singularities frequently arise. The RM Darboux frame, tailored to curves lying on surfaces, enables the expression of fundamental invariants such as geodesic curvature, normal curvature, and geodesic torsion. We derive specific conditions that characterize harmonic surfaces based on these invariants. We also clarify the connection between the components of the RM Darboux frame and thesurface’s mean curvature vector. This formulation provides fresh perspectives on the classification and intrinsic structure of harmonic surfaces within Minkowski geometry. To support our findings, we present several illustrative examples that demonstrate the applicability and strength of the RM Darboux approach in Lorentzian differential geometry. Full article

Objective: Although prior research developed an artificial intelligence (AI)-based classification system predicting colorectal lesion histology, the heavy computational demands limited its practical application. Recent advancements in medical AI emphasize decentralized architectures using edge computing devices, enhancing accessibility and real-time performance. This study aims to construct and evaluate a deep learning-based colonoscopy image classification model for automatic histologic categorization for real-time use on edge computing hardware. Design: We retrospectively collected 2418 colonoscopic images, subsequently dividing them into training, validation, and internal test datasets at a ratio of 8:1:1. Primary evaluation metrics included (1) classification accuracy across four histologic categories (advanced colorectal cancer, early cancer/high-grade dysplasia, tubular adenoma, and nonneoplasm) and (2) binary classification accuracy differentiating neoplastic from nonneoplastic lesions. Additionally, an external test was conducted using an independent dataset of 269 colonoscopic images. Results: For the internal-test dataset, the model achieved an accuracy of 83.5% (95% confidence interval: 78.8–88.2%) for the four-category classification. In binary classification (neoplasm vs. nonneoplasm), accuracy improved significantly to 94.6% (91.8–97.4%). The external test demonstrated an accuracy of 82.9% (78.4–87.4%) in the four-category task and a notably higher accuracy of 95.5% (93.0–98.0%) for binary classification. The inference speed of lesion classification was notably rapid, ranging from 2–3 ms/frame in GPU mode to 5–6 ms/frame in CPU mode. During real-time colonoscopy examinations, expert endoscopists reported no noticeable latency or interference from AI model integration. Conclusions: This study successfully demonstrates the feasibility of a deep learning-powered colonoscopy image classification system designed for the rapid, real-time histologic categorization of colorectal lesions on edge computing platforms. This study highlights how nature-inspired frameworks can improve the diagnostic capacities of medical AI systems by aligning technological improvements with biomimetic concepts. Full article

The eccentrically braced frame (EBF) is a typical structural system used in high-rise buildings. Current related design methods focus on the concrete and steel structures rather than on the complex composite structure. In addition, they tend to overlook the contribution of the energy-dissipation unit and its corresponding additional influence on the structure. In this study, a precast composite EBF structure is selected as a case study, including the partially steel-reinforced concrete (PSRC) beam and the concrete-filled steel tubular (CFST) column. A modified energy-based design method is proposed to leverage the excellent seismic performance of the precast composite EBF structure. The multi-stage energy-dissipation mechanism and the additional influence of the eccentric braces are systematically considered through the energy distribution coefficient and the layout of dampers. A case study of a 12-floor, three-bay precast composite EBF structure is conducted using a series of nonlinear time-history analyses. Critical seismic responses, including the maximum inter-story drift ratio, residual inter-story drift ratio, and peak acceleration, are systematically analyzed to evaluate the effectiveness of the proposed design theory. The distribution coefficient is recommended to range from 0.70 to 0.80 to balance the energy-dissipation contribution between the frame and the eccentric braces. In terms of the damper layout, the energy-dissipation contribution of the eccentric brace should differ among the lower, middle, and upper floors. Full article

This paper aims to examine the seismic response of prestressed self-centering moment-resisting frames (PSC-MRFs) based on concrete-filled double steel tubular (CFDST) columns and RC beams. The beam of this novel connection is divided into two parts, connected by bolts and tendons, and the beam includes a gap opening feature, which could be regarded as a normal single beam in the field. Cyclic loading analysis was performed on one-story frames with different initial parameters arranged in adjacent bays. Nonlinear dynamic analysis was conducted on a six-story frame under two seismic hazard levels. The cyclic loading analysis showed favorable self-centering performance of the frame even when the hysteretic energy dissipation ratio reached 0.808. Seismic analysis results showed that compared with the in situ reinforced concrete frame, PSC-MRFs generally had similar maximum inter-story drifts under fortification earthquakes, but the residual inter-story drifts were reduced by 33%; under rare earthquakes, the maximum inter-story drifts and residual inter-story drifts of PSC-MRFs were reduced by 22% and more than 90%, respectively. In the adjacent bays on the same story of PSC-MRFs, connections with smaller imminent moments of gap opening opened earlier under earthquake, and the maximum opening angle was larger. The general seismic performance and self-centering of PSC-MRFs was significantly more advantageous than that of in situ reinforced concrete frames. Full article

Taking into account the requirements to reduce the release of harmful emissions into the environment, the EU’s environmental standards when transitioning to the Euro 7 standard in 2025 will actually lead vehicles having to operate without producing emissions in all driving situations. Carmakers believe that the new, much stricter regulations will mark the end of the internal combustion engine era. For example, in 2030, the manufacturer SEAT will cease its activities, leaving behind the Cupra brand, which will be exclusively electric in the future. This trend will apply not only to private vehicles (passenger cars), but also to utility vehicles, which is the subject of our research, namely the spatial tubular frame in the Bogdan ERCV27 garbage truck, presented in the form of a solid model. The peculiarity of the studied model is the installation of a battery block behind the driver’s cabin, causing an additional load to be placed on the spatial frame of the garbage truck, which in terms of its architecture is more like the body of a bus. During the conditions involving various modes of operation of a full-scale Bogdan ERCV27 garbage truck sample, questions about the strength and uniformity of its load-bearing spatial frame inevitably arise, which are decisive, even at the stage of designing and preparing the technical documentation. The main static load mode, which, despite its name, also covers dynamic conditions, was modeled using the appropriate coefficient k_d = 2.0. The maximum stresses on the model during the “bending” mode were 381.13 MPa before structure optimization and 270.5 MPa as a result of the improvement measures. The spatial frame mass was reduced by 4.13%. During the “torsion” mode, the maximum deformation values were 12.1–14.5 mm, which guarantees the normal operation of the aggregates and units of the truck. Full article

Based on the incremental dynamic analysis (IDA) method, this paper conducts seismic fragility analysis of a CFST plane frame, a CFST spatial frame under 1D (one-dimensional) ground motions, and a CFST spatial frame under 2D (two-dimensional) ground motions, with different attacking angles. Firstly, nine-story, three-span CFST frame structures (including the plane frame and spatial frame) were modeled in OpenSees, based on the accurate simulation of the hysteresis performance of the test CFST frames. Then, twenty-five groups of ground motions were employed to analyze the seismic response. Lastly, the IDA curve clusters, probabilistic demand models, and seismic fragility curves of frame structures were researched, respectively. The analytical results showed that the exceeding probability of the spatial frame under 2D ground motions was successively greater than that under 1D ground motions, and greater than the plane frame, and the maximum difference at each performance level was up to 6% and 16%, respectively. The fragility analysis result of the spatial frame was sensitive to the attacking angle of ground motion, and the exceeding probability of the 135°, 150°, and 165° fragility curves was larger than that of the 0° (original attacking angle) fragility curve at each performance level. The research results provide a reference for seismic fragility analysis of CFST frame structures employing the IDA method. Full article

The present study analyzes the behavior of connections with flange-web welded plates using the finite element method in tubular columns filled with concrete, and beam, type I. An analytical study of the structural dynamic behavior of a Special Moment Frame (SMF) was carried out, in 5 levels, with HEB structural profiles, for IPE-type columns and beams, according to the requirements established by the AISC-360-16, ANSI-341 standards, and the Ecuadorian standard NEC-2015. The design process of the special frame structure was validated with the help of specialized software. Subsequently, the structural profiles were replaced following the actual construction situation in Ecuador. 3D models of the structural system and the elements of metallic connections were obtained for evaluation through the analysis of finite elements. These models were subjected to virtual tests according to the AISC 341-16 protocols and FEMA 350 standards. The evaluation of the connections showed that they did not meet the flexural strength criterion at 0.04 rad, but they exceeded $80\%$ of the plastic moment at $0.02$ rad. Thus, flange-web welded plate connections can be valid for intermediate moment frames (IMF) in areas with moderate seismicity. In addition, it was observed that the columns filled with concrete optimize the structural elements in terms of dimensions; but do not contribute significantly to soldered connections due to the later development of plastic ball joints. Full article

Significant inelastic deformations induced in structural systems lead to structures possibly possessing some degree of permanent lateral deformation following major seismic events. These permanent deformations have led to considerable research being conducted over the past 20 years into developing structural systems that exhibit self-centring behaviour. For a structural system such as the concentrically braced frame (CBF), for which the dissipating mechanism is the tensile yielding and compressive buckling of the diagonal steel tubular members, these residual deformations present a problem when considering the structure’s overall resilience to the seismic loading both during and after an event. This paper describes the numerical modelling of a novel self-centring, concentrically braced frame (SC-CBF) system that combines a conventional CBF with a self-centring arrangement to produce a structure that possesses the desirable lateral load-resisting capacity of the CBF but which also re-centres when subjected to many cycles of large inelastic brace deformation. First, an experimental test programme for the SC-CBF is briefly described, followed by a numerical model to capture the SC-CBF’s characteristics during cyclic loading. This numerical model is validated using the experimental test data, showing that the experimental and numerical simulation data match rather well. This development presents a platform upon which further research through experimental testing and numerical simulation can be conducted. The proposed SC-CBF system can then be developed into a viable lateral load-resisting system that will provide a more resilient system than the current conventional CBF. Full article