Search Results (2,213)

Excavation adjacent to operating urban rail transit faces formidable deformation control challenges. To address this, a parametric collaborative optimization framework integrating micro steel pipe pile isolation and temporary intermediate partition wall reinforcement is proposed. Taking a foundation pit project at Shangdi Station of Beijing Metro Line 13 as a case study, a three-dimensional finite element model was established using the Hardening Soil constitutive model and calibrated with field monitoring data. Optimization analysis reveals that micro-pile spacing is the dominant factor controlling local rail settlement, while intermediate partition wall thickness primarily dictates global surface settlement. By balancing stringent safety limits with construction economy through a multi-objective evaluation, the preferred support configuration was calculated to be 273 mm diameter micro-piles at 500 mm spacing, combined with a 300 mm-thick partition wall. This collaborative configuration successfully truncates lateral soil displacement, reducing maximum rail settlement by over 55% and surface settlement by 53.6% compared to the baseline. Field monitoring results show high consistency with the numerical predictions (RMSE = 0.1438 mm), confirming the reliability of the proposed parametric collaborative optimization framework. Ultimately, this framework provides a validated, quantitative design methodology and a practical reference for support design in constrained excavations adjacent to existing sensitive infrastructure. Full article

Large-scale aerospace components (e.g., wings, fuselage sections, wing boxes, and rocket segments) feature large dimensions, low stiffness, complex interfaces, and strict assembly tolerances. Traditional rigid tooling and manual alignment struggle to meet the demands of high precision, efficiency, and flexibility in modern aerospace manufacturing. This paper presents a structured literature review on the automated assembly of large-scale aerospace components, summarizing advances in three core domains: pose adjustment and positioning mechanisms, digital measurement technologies, and trajectory planning and control. Particular emphasis is placed on two cross-cutting themes: measurement uncertainty analysis and flexible assembly, which are critical for high-quality docking. The review classifies pose adjustment mechanisms into four categories (NC positioners, parallel kinematic machines, industrial robots, and novel mechanisms) and digital measurement into five branches (vision metrology, large-scale metrology, measurement field construction, uncertainty analysis, and auxiliary techniques). It also outlines five trajectory planning and control routes, covering traditional methods, multi-sensor fusion, digital twins, flexible assembly, and emerging intelligent approaches. The analysis reveals that current research suffers from fragmentation among mechanism design, metrology, and control, with insufficient integration of uncertainty propagation and flexible deformation modeling. Future systems will rely on heterogeneous equipment collaboration, uncertainty-aware closed-loop control, high-fidelity flexible modeling, and digital twin-driven decision-making. This review provides a unified framework and a technical reference for developing reliable, flexible, and scalable automated assembly systems for next-generation aerospace structures. Full article

To address the challenges associated with laser powder bed fusion (LPBF) of overhanging structures—namely warping deformation, powder adhesion, and inadequate forming accuracy—this study investigates the optimization of the support–part contact interface using Inconel 625 alloy. The objective is to achieve high-quality part formation with minimal support structures. A Taguchi experimental design was employed to systematically evaluate the effects of key block support parameters—tooth height, tooth top length, tooth base length, and tooth base spacing—on the forming performance of overhanging structures, with forming accuracy and support removability as the optimization targets. The results reveal that tooth top length significantly influences both the forming accuracy of overhanging specimens and the ease of support removal. Specifically, an increase in tooth top length leads to a rapid reduction in specimen deformation, but simultaneously increases the difficulty of support removal. When the tooth top length was set to 0.1 mm, all overhanging specimens failed to form successfully. Tooth base length also plays a critical role in support removability, with removal difficulty initially decreasing and then stabilizing as the tooth base length increases. Based on the trade-off between forming quality and support removability, the optimal parameter combination was identified as: tooth height of 0.4 mm, tooth top length of 0.7 mm, tooth base length of 1.0 mm, and tooth base spacing of 0.3 mm. A validation experiment conducted using this optimized configuration demonstrated good forming accuracy in the support contact area, with a deformation value of −0.208 mm, confirming the effectiveness and reliability of the proposed parameters. This study not only provides a theoretical foundation for the optimal design of block supports in LPBF but also offers experimental data and practical guidance for selecting support parameters in the fabrication of overhanging structures. Full article

Monitoring dam stability is critical to ensure structural safety and operational reliability. This study integrates Persistent Scatterer Interferometry (PSI) based on Sentinel-1 SAR imagery (2020–2023) with Finite Element Method (FEM) simulations to assess the behavior of the Koyna Dam in India. PSI detected crest displacements between −1.0 and −1.8 mm yr⁻¹, while FEM simulations predicted a maximum vertical displacement of approximately −3.2 mm at the crest. Although these results represent different quantities (time-averaged displacement rates versus peak static displacement), both approaches indicate millimeter-scale deformation and a consistent pattern of settlement at the dam crest, supporting the interpretation of hydrologically driven structural response. The observed differences are primarily attributed to differences in spatial resolution and methodology between point-based FEM outputs and pixel-averaged satellite observations. The study demonstrates that combining satellite-based monitoring with numerical simulations provides a robust and cost-effective framework for dam safety assessment. This integrated approach supports improved interpretation of deformation behavior and offers practical value in extreme conditions, such as during flood events or climate-driven hydrological changes. Furthermore, continued advances in remote sensing and numerical modeling are expected to enhance the reliability of such approaches, making this methodology a transferable and sustainable solution for dam management worldwide. Full article

Reliable and energy-efficient capacity control in high-pressure single-rotor screw compressors requires precise regulation of adjustable ring mechanisms operating under combined gas and thermal loading. Thermo-mechanical deformation, friction-induced torque demand, and stress concentration near discharge windows significantly influence structural integrity, clearance stability, and actuation performance. This study presents an integrated thermo-structural and analytical investigation of a regulating ring system with a hydraulic wedge-groove drive concept. Three groups of geometric variants (nine configurations total) were analyzed using coupled Steady-State Thermal and Static Structural finite element modeling in ANSYS 19.2. Thermal asymmetry between suction (22 °C) and discharge (120 °C) regions produced peak thermally induced deformation of 0.17–0.18 mm, consuming up to 60–70% of nominal operating clearance. Neglecting thermal effects underestimated peak thermally induced structural deformation of the regulating ring by 12–15%. Among the configurations, variant 2b provided the most balanced response, reducing peak equivalent stress by 12–15% and required actuation torque by 8–11%. An analytical model for friction torque and driving force was derived based on distributed contact pressure. The results reveal quadratic sensitivity of torque to contact radius and strong dependence on groove geometry. The proposed framework supports reliable clearance design and efficient actuation in heavy-duty rotating machinery. Full article

Ground-Based Interferometric Synthetic Aperture Radar (GB-InSAR) is widely used for geohazard and infrastructure health assessment because it enables high-precision deformation monitoring. However, long-term time series observations often contain phase discontinuities caused by localized deformation with large spatial gradients, which can severely compromise phase unwrapping reliability. To address this limitation, we propose an Adaptive Shortest-Path Network (ASPN) method for GB-InSAR phase unwrapping. A temporal sliding window strategy is used to partition the acquisition stream into processing units. Within each unit, arc quality is quantified by least squares inversion using the mean square error (MSE) and temporal coherence. The unreliable arcs are removed, and the network is then reconnected using Dijkstra’s shortest-path algorithm to improve unwrapping stability and accuracy. The method is evaluated on a corner reflector-controlled deformation dataset and a stope slope dataset. In the controlled experiment, ASPN reduces the root mean square error (RMSE) of cumulative deformation from 1.684 mm to 0.037 mm, representing a 97.8% reduction, while in the stope slope experiment, it reduces the mean phase residual by 30.3% relative to the Delaunay network and by 11.6% relative to APSP. Overall, ASPN provides an efficient dynamic update mechanism and a robust, high-accuracy solution for long-term GB-InSAR time series deformation monitoring. Full article

Egyptian papyri are commonly documented using high-resolution two-dimensional imaging, which enhances legibility but does not adequately capture the micrometric surface morphology required for material and conservation studies. To address this limitation, we developed and validated an integrated, fully non-contact imaging workflow combining Ultra-Close-Range Multiband Photogrammetry with Reflectance Transformation Imaging (RTI) and normal map integration. The protocol was tested on six papyrus fragments from the Museo Egizio di Torino (XXI Dynasty–Byzantine period) exhibiting different conservation conditions. Multiband photogrammetry in the visible and visible-induced infrared luminescence bands achieved a Ground Sample Distance of 17 µm/px and a point cloud density of approximately 170 points/mm², enabling detailed analysis of fiber morphology, surface deformation, and the spatial distribution of Egyptian blue. RTI-based normal map integration provided complementary high-frequency surface information with reduced acquisition and processing times. To overcome RTI low-frequency distortions, a revised normal integration strategy was implemented using surface planarization and frequency-domain fusion with photogrammetric data based on Power Spectral Density analysis. The resulting hybrid models combine metric reliability with enhanced surface detail, providing a scalable and non-invasive approach for papyrological documentation and conservation research. Full article

Permanent deformation, manifested as rutting, remains one of the most critical threats to the structural integrity and functional performance of flexible pavements. The Mechanistic–Empirical Pavement Design Guide (MEPDG) includes rutting models that are highly sensitive to the dynamic modulus (E*) of asphalt mixtures—a parameter that can be determined experimentally or predicted by analytical models. In this study, the influence of E* prediction error on rutting estimation is systematically evaluated by comparing laboratory-measured E* values with those predicted by two models: NCHRP 1-37A and a locally calibrated model. The dynamic pavement behavior and rut depth predictions were determined using the finite layer program 3D-Move under standard traffic loads. Comparative analysis revealed that the NCHRP 1-37A model tends to underestimate E*, leading to significant overestimation of vertical strains and accumulated permanent deformation. In contrast, the locally calibrated model provided predictions that closely matched the laboratory measurements, resulting in minimal deviation in rut depth estimates. The results highlight the importance of local calibration and model selection to improve the reliability of mechanistic–empirical pavement predictions, enabling smarter pavement performance evaluation and supporting more sustainable pavement management practices, especially when laboratory testing is not feasible. Full article

Background: Gait analysis offers a comprehensive assessment of locomotion and postural control, which are often altered in individuals with spinal deformities. After validating a stereophotogrammetric protocol for whole-body kinematics, including spinal motion in healthy subjects, its application to clinical populations is needed to assess its clinical relevance. Patients treated with spinal arthrodesis for scoliosis may show reduced trunk mobility and compensatory gait strategies. Methods: The validated spinal protocol was applied to 10 patients with scoliosis who underwent arthrodesis and 5 healthy controls. For each participant, the range of motion (ROM) of the upper thoracic, lower thoracic, and lumbar districts was computed. Group differences were assessed with the Mann–Whitney U test, and time-normalized angular curves were compared using Statistical Parametric Mapping (SPM1d). Results: In the pathological group, the protocol showed moderate-to-excellent intra- and inter-operator reliability (ICC > 0.594). Compared with controls, patients exhibited a significant reduction in ROM in fused or adjacent districts. SPM analysis identified altered upper thoracic flexion–extension patterns, particularly relative to the lower thoracic segment, throughout the gait cycle. Conclusions: The protocol demonstrated preliminary feasibility and sensitivity in identifying segmental and phase-dependent changes in spinal motion after arthrodesis, indicating that it may serve as a useful tool for exploratory postoperative gait evaluation. Full article

Background: Sciatic scoliosis is a nonstructural, compensatory spinal deformity secondary to lumbar disc herniation. In adolescents and young adults, sciatic scoliosis is frequently misdiagnosed as adolescent idiopathic scoliosis due to the low prevalence of lumbar disc herniation in this demographic. Early clinical suspicion is essential, as radiographic features, particularly minimal or absent vertebral rotation on standing radiographs, help distinguish sciatic scoliosis from structural curves such as adolescent idiopathic scoliosis. Key differentiating features include painful scoliosis, a highly positive straight leg raise test, and minimal or absent vertebral rotation on standing radiographs. Delayed diagnosis or inappropriate management may result in residual deformity, highlighting the importance of early surgical decompression. Despite recognition for decades, the literature is fragmented, largely composed of case reports, small series, and retrospective studies, with heterogeneous definitions, radiological assessments, and outcome measures. Objective: Provide a comprehensive, up-to-date systematic synthesis of the clinical presentation, radiological characteristics, management strategies, and outcomes of lumbar disc herniation-associated sciatic scoliosis. Methods: Thirteen studies evaluating conventional open discectomy and minimally invasive endoscopic procedures (FEID/PELD) were included. Data on demographics, surgical approach, clinical improvement (VAS, ODI, Macnab), and radiographic correction (Cobb angle, trunk list, sagittal alignment) were extracted and synthesized. Results: Surgical decompression consistently leads to clinical improvement. Trunk list and coronal deformity were rapidly corrected, with resolution rates ≥ 85% within 6 months across most series. Both open and endoscopic approaches were effective, with minimally invasive techniques offering advantages in tissue preservation and recovery. Conclusions: Sciatic Scoliosis is a reversible, nonstructural deformity that responds reliably to surgical decompression. Accurate recognition, particularly in adolescents and young adults, and timely intervention targeting the underlying nerve root compression are critical for optimal outcomes. This review consolidates fragmented evidence, providing a comprehensive synthesis of current knowledge. Full article

In marine renewable energy applications, offshore steel pipelines are subjected to complex combined loads during installation and operation, leading to significant plastic deformation and potential catastrophic fracture. To accurately characterize pipeline fracture failure, this study develops an enhanced failure assessment framework based on the Modified Mohr–Coulomb (MMC) criterion, integrating experimental parameter evaluation with numerical simulation for in-service offshore pipelines. The key parameters of the MMC model were determined directly from in-service pipeline samples to account for operational degradation. First, the plastic parameters were obtained by fitting the Swift hardening law to uniaxial tensile tests. Fracture parameters were then calibrated using a suite of five notched tensile specimens. Mesh sensitivity was analyzed using CT experiments to establish a suitable mesh size for the MMC-based damage model, enabling precise characterization of crack evolution from initiation to final tearing. Unlike prior applications, this framework is employed to investigate the response of X80 pipelines under combined tension, bending, and external pressure loading. Three-dimensional finite element models were developed to systematically analyze the stress–strain response, moment–curvature behavior, and evolution of hoop stress distribution. Results show that while the failure stress remains relatively stable under varying external pressure, both the critical strain and critical curvature increase markedly with pressure, by up to 20.9%. They also reveal a pronounced hierarchy in the influence of crack geometry on the failure behavior. Crack depth dominates failure sensitivity, affecting critical strain and pressure response far more than crack width or length. The reduction in failure stress for deep cracks under 12 MPa external pressure is over three times greater than for shallow cracks. In contrast, variations in crack length exert the most negligible influence on failure characteristics, with observed discrepancies of less than 6%. Overall, this research provides a high-precision failure prediction framework for in-service pipelines by quantitatively analyzing failure behavior under combined loads. It effectively characterizes failure evolution paths that differ from design conditions and dynamically tracks the residual fracture resistance after time-dependent degradation, offering a fundamental reference for the reliability assessment of pipelines in complex marine environments. Full article

Dam deformation monitoring is essential for ensuring the safe operation of hydraulic structures, yet practical data are often compromised by missing values and noise, while spatial coupling among monitoring points further complicates prediction. To address these challenges, this study proposes a Spatio-Temporal Multi-Graph Attention Fusion Network (STMGAFN) for dam deformation prediction and risk early warning under incomplete data conditions. Data quality is enhanced through a data-quality-aware hierarchical adaptive imputation mechanism combined with a VMD–wavelet joint denoising strategy. A multi-graph spatial modeling framework integrating temporal similarity, spatial proximity, structural zoning, and measuring-line connectivity is constructed, and fuses multi-source spatial features through a lightweight adaptive attention mechanism. A parameter-sharing recursive probabilistic temporal modeling approach is adopted to jointly predict deformation values and their associated uncertainties. Based on the predicted confidence intervals, a four-level risk classification and early-warning scheme is established. Experimental results on real GNSS monitoring data from dam sites demonstrate that the proposed method achieves an RMSE of 0.3588 mm, an MAE of 0.1738 mm, and an R² of 0.9865, outperforming baseline models including LSTM, TCN, CNN-LSTM, and STGCN. Moreover, the correlation between predictive uncertainty and actual error reaches 0.892, verifying the effectiveness and reliability of the proposed method for dam safety monitoring under complex conditions. Full article

The mechanical characterization of elastomers requires particular attention to multiaxial deformation states, as their service behavior is rarely governed by simple loads. Instead, performance and failure mechanisms are strongly influenced by complex, combined stress states. The present work introduces a compact electromechanical tension–torsion testing machine capable of applying axial and torsional loads both independently and synchronized for multiaxial testing. The system also enables torsional cyclic tests over a wide range of frequencies with efficient stress reversal through a “zero-backlash” actuation solution, while allowing free axial expansion and contraction of the specimen to achieve pure torsion across the full deformation range. The device integrates industrial-grade components within a modular architecture, ensuring reliability, maintainability, and scalability. FE analyses were carried out to optimize the frame design and verify its stiffness under critical load cases. The resulting system provides a versatile and cost-effective solution for complete multiaxial testing and mechanical characterization of elastomers, as well as other materials, expanding current experimental capabilities for academic and industrial research needs. Full article

Accurate modeling of smart composite dampers is crucial for simulation and model-based control. This study focuses on the constitutive modeling of a novel damper that synergistically combines an Entangled Metallic Wire Mesh (EMWM) with a magnetorheological (MR) fluid. Unlike traditional MR dampers, the interaction between the field-responsive MR fluid and the rate-sensitive, deformable EMWM matrix introduces strong coupled current–frequency dependence. To capture this essential characteristic, a control-oriented, bivariate (current–frequency) hysteresis model is formulated, wherein all parameters are explicit, continuous functions of both the control current (I) and excitation frequency (f). A systematic two-step identification method is employed to derive these functions from dynamic tests. A key finding is that the identified damping exponent (α) consistently exceeds unity across the tested operational range. This quantitatively indicates a transition from viscous-dominated to inertial-flow-dominated dissipation within the EMWM matrix, a distinctive mechanism attributed to non-Darcian flow in its porous structure. The fully parameterized model demonstrates high fidelity (R² > 0.99) within the characterized low-frequency, small-amplitude regime and shows reliable predictive capability for interpolated conditions. The presented model serves as a ready-to-use constitutive tool for the simulation and design of low-frequency vibration isolation systems utilizing EMWM-MR composites, and the revealed inertial flow mechanism provides fundamental insight for the development of next-generation adaptive dampers. Full article