Search Results (3,893)

The growing demand for marine resource development and in-depth exploration of the marine environment has positioned soft biomimetic underwater vehicles (SBUVs) as a research hotspot in the fields of underwater equipment and soft robotics. SBUVs are characterized by bodies made of flexible and extensible materials, integrating the dual advantages of softness and biomimetics. They can achieve muscle-like continuous deformation to efficiently absorb collision energy, while mimicking the propulsion mechanisms of marine organisms—such as fish and jellyfish—through undulating body movements or cavity contraction and relaxation. Such biomimetic propulsion is highly compatible with the flexible actuation of soft materials, enabling excellent environmental adaptability while maintaining favorable propulsion efficiency. Compared with traditional rigid underwater vehicles, SBUVs offer higher degrees of freedom, superior environmental adaptability, enhanced impact resistance and greater motion flexibility. This review systematically summarizes typical actuation methods for SBUVs—including fluid-powered actuation, shape memory alloy actuation, and electroactive polymer actuation—elaborating on their working principles, key technological advances, and representative application cases on SBUVs. These actuation mechanisms each offer distinct advantages. Fluid-powered systems are valued for high power density and precise motion control through direct fluidic force transmission. Shape memory alloys provide high force output and accurate positional recovery via controlled thermal phase changes. Meanwhile, electroactive polymers stand out for their rapid (often millisecond-scale) dynamic response, low hysteresis, and fine, muscle-like deformation under electrical stimuli. Current challenges are also analyzed, such as limited actuation efficiency, material durability issues, and system integration difficulties. Despite these constraints, SBUVs show broad application prospects in marine resource exploration, ecological monitoring, and underwater engineering operations. Future research should prioritize the development of novel materials, coordinated optimization of actuation and control systems, and breakthroughs in core technologies to accelerate the practical implementation and industrialization of SBUVs. Full article

Weld cracking is a predominant damage mode in tubular connections. Such welds tend to crack prematurely before reaching their ultimate load-bearing capacity, and the damage mode of cracked joints differs significantly from that of seamless ones. This study focuses on the deformation behavior of K-joints with weld cracking at the root of the tension branch. The mechanical properties of the joints under various conditions were analyzed based on experimental observations, load–displacement curves, strain responses, and surface temperature distributions of specimens. Moreover, comparisons were made between the deformation behaviors of joints with and without cracks, and finite element analysis (FEA) was employed for corresponding validation. The main conclusions are as follows: Weld cracking significantly affects joint stiffness and remarkably alters the joint damage mode. Reinforcement plates can effectively strengthen members with cracked welds; however, this reinforcement enhances the stiffness of the tension branch region, thereby altering the force transmission mechanism of the joints. This research offers theoretical and experimental insights for the engineering application of K-joint structures. Full article

In response to the challenges of target recognition and misjudgment caused by varying target scales, diverse shapes, and interference such as lake surface reflections in river and lake scenarios, this paper proposes the YOLO v11n-DDH model for fast and detection of spatial targets in river and lake environments. The model builds upon YOLO v11n by introducing the Dynamic Snake Convolution (DySnakeConv) to enhance the ability to extract detailed features. It integrates the Deformable Attention Mechanism (DAttention) to strengthen key features and suppress noise, while combining the improved High-Level Screening Feature Pyramid Network (HSFPN) structure for multi-level feature fusion, thus improving the semantic representation of targets at different scales. Experiments on a self-constructed dataset show that the precision, recall, and mAP of the YOLO v11n-DDH model reached 88.4%, 78.9%, and 83.9%, respectively, with improvements of 3.4, 2.9, and 2.5 percentage points over the original model. Specifically, DySnakeConv increased mAP@50 by 0.6 percentage points, DAttention improved mAP@50 by 0.3 percentage points, and HSFPN contributed to a 0.9 percentage point rise in mAP@50. This patrol system can effectively identify and visualize various pollutants in river and lake areas, such as underwater waste, water quality pollution, illegal swimming and fishing, and the “Four Chaos” issues, providing technical support for intelligent river and lake management. Full article

Background: Large language models (LLMs) such as DeepSeek-V3, Google Gemini 2.0 Pro, and ChatGPT-4o are increasingly used by patients seeking online medical information. However, their accuracy, reliability, and reproducibility in patient-facing content related to chest wall deformities (CWD) remain unclear. This study aimed to compare the performance of three contemporary LLMs in generating information on pectus excavatum, pectus carinatum, and related thoracic deformities. Methods: Eighty patient-facing questions were developed across eight thematic domains and independently submitted to each model using newly created accounts over two consecutive days. Accuracy was assessed using a validated four-point rubric by blinded physiatrists, and reproducibility was evaluated using agreement metrics and weighted Cohen’s kappa. Results: ChatGPT-4o achieved the highest overall accuracy (median score: 1.20), the greatest proportion of fully accurate responses, and the lowest hallucination rate (5.0%). Gemini showed intermediate accuracy, while DeepSeek-V3 demonstrated the lowest accuracy and highest hallucination rate (11.25%). Across all models, general-information and quality-of-life domains had the best performance, whereas treatment-related questions showed the most errors. Reproducibility was highest for ChatGPT-4o (weighted κ = almost perfect), followed by Gemini and DeepSeek-V3. Inter-rater reliability was substantial (Fleiss’ κ = 0.69). Conclusions: Contemporary LLMs can generate largely accurate and reproducible patient-facing information on CWD, with ChatGPT-4o showing the strongest overall performance. This study provides the first domain-specific comparative evaluation of LLMs in CWD and integrates reproducibility analysis alongside accuracy and reliability assessment. While these tools may support patient education, treatment-related responses require caution, and LLMs should be used as adjuncts rather than substitutes for clinical counseling. Full article

Focusing on the construction of a 58-m-diameter double-layer steel space frame dome at the Han Culture Museum Assembly Hall, this study addresses scheme selection and safety control challenges in staggered jacking of large-span spatial structures. A three-dimensional finite element model in MIDAS Gen simulated the three-stage jacking process to compare three temporary support layouts. Numerical evaluation metrics included maximum vertical displacements, peak internal forces, the proportion of members undergoing stress state transitions, and spatio-temporal evolution of stress concentrations. Scheme B demonstrated superior performance, reducing peak vertical displacement by 44% under critical conditions, lowering peak stresses, and enabling more uniform internal force redistribution—effectively mitigating tension–compression cycling and buckling risks. Crucially, only nodal displacements and support elevations were monitored in situ using a 3D system based on magnetic prisms and total stations; no strain or force measurements were conducted due to practical constraints during construction. Monitoring data show good agreement with simulated displacements and support elevations under Scheme B, validating the model’s deformation response. However, localized deviations—including a 29 mm deflection discrepancy and elevation errors up to 28 mm—reveal the influence of uneven boundary conditions, with potential implications for long-term structural behavior. The findings confirm that numerical predictions of deformation are reliable, while internal forces remain unvalidated by field data. The integrated approach of “scheme comparison–construction simulation–full-process displacement monitoring” proves effective for safety control and decision-making in complex jacking operations, offering a transferable framework for similar large-span double-layer space frame projects. Full article

Coal mining in plain regions and its related surface subsidence and geological hazards have been extensively studied, whereas research on mining-induced hazards in mountainous areas remains limited. This knowledge gap has contributed to the frequent occurrence of mining disasters, particularly under steep ridge-type mountain geometry, where deformation characteristics, large-scale slope failure risks, and mining-induced hazard mechanisms remain poorly understood. In this study, a mining area in Zhenxiong, Zhaotong, Yunnan Province, China, is investigated using SBAS-InSAR, GNSS observations, UAV surveys, optical satellite imagery, and detailed field investigations. Surface hazards triggered by coal extraction are identified, and the response relationship between surface subsidence and mining activities is analyzed to reveal the development mechanisms of surface deformation beneath steep ridge-type mountain geometry. The results show that: (1) deep coal mining can still induce significant surface deformation due to the combined amplification effects of steep slopes and lithological conditions; (2) mining-induced deformation does not necessarily evolve into large-scale slope collapse and may gradually stabilize through natural adjustment processes; (3) SBAS-InSAR, validated by GNSS and field observations, provides an effective approach for detecting mining-related subsidence; (4) surface deformation in the study area is jointly influenced by multiple working faces; and (5) strong coupling between the unique steep ridge-type mountain geometry and underlying coal extraction leads to a compound disaster chain under multi-source interactions. These findings offer a critical scientific understanding of mining-induced deformation beneath steep ridge-type mountain geometry and provide important guidance for geological hazard prevention and control in similar mountainous mining areas. Full article

Viscoelastic (VE) dampers are widely used for structural response control, but broader engineering adoption is often constrained by temperature- and amplitude-dependent properties and limited full-scale evidence on reliable performance when deformation demands exceed the conventional 300% shear-strain design domain. This study experimentally characterizes a full-scale TRCS-type VE damper (TRCS500T-10) employing a styrene–olefin thermoplastic elastomer, with an emphasis on large-deformation and beyond-design behavior. Four nominally identical specimens were tested in a temperature-controlled chamber using sinusoidal, displacement-controlled loading at target shear strains of 300% (≈30 mm) and 450% (≈45 mm). Effective engineering parameters were obtained from stable hysteresis loops using a Kelvin–Voigt-based reduction, including effective stiffness K_eff, effective damping coefficient C_eff, effective damping ratio ξ_eff, and dissipated energy per cycle W_d. At 300% shear strain, the dampers exhibited stable hysteresis with acceptable specimen-to-specimen variability and only modest changes in K_eff, C_eff, and W_d over an ambient-temperature interval of approximately 20–33 °C, while ξ_eff remained around 0.40–0.42. Beyond-design tests at 450% shear strain maintained stable force–displacement loops with substantial load capacity (peak forces ≈ 435–492 kN) and increased per-cycle energy dissipation (approximately 4.0 × 10⁴ kN·mm). Manufacturer-provided polynomial relations were used to standardize the measured properties to a reference condition and to compile a parameter-estimation table for preliminary engineering application. A monotonic ultimate test on specimen TRC500T-05 indicated an ultimate shear deformation capacity of approximately 850% without interface debonding. Collectively, the results provide full-scale evidence of a widened usable deformation range and a practical, design-oriented parameterization for thermoplastic VE dampers under large deformation demands. Full article

This paper develops a nonlinear strain wedge (SW) model for analyzing laterally loaded piles installed in the proximity of sandy slopes, with consideration of slope surface deformation. This model is first developed for piles at the slope crest, characterizing the slope surface deformation to calculate soil strain and incorporating the reduction in effective vertical stress. Furthermore, this model provides a smooth transition between piles located at varying distances from the slope and those at the crest, accounting for varying near-slope distances. Thus, a comprehensive model is established that considers the influence of slope effects on pile–soil interactions. Predictions from the proposed model show good agreement with a series of centrifuge tests and three model tests. Finally, the effects of applied load, slope angle, near-slope distance, Poisson’s ratio, and friction angle on the pile response, slope surface deformation, and soil deformation are discussed. Full article

Under dynamic loading (e.g., earthquakes, extreme rainfall), multi-stage slope slumps occur as downstream slopes lose anti-sliding stability, triggering intensive lateral sediment supply that governs mountainous channel evolution. This study uses a coupled CFD-DEM model to simulate how water–sediment conditions regulate sediment transport and riverbed deformation. Results show that during the first sediment supply event, particle motion is initially slower under wet than dry conditions but accelerates due to buoyancy, with the peak average particle velocity along the gully axis decreasing by 11.5% and exhibiting negligible flow rate dependence. In the channel, higher flow rates raise particle velocity and downstream sediment flux, while a prolonged supply interval elevates peak velocity and delays its occurrence. For subsequent events, peak gully axis and vertical velocities increase with sediment supply mass, with weak dependence on flow rate or interval. Post-peak particle motion accelerates with these three factors, enhancing sediment entrainment effects. Increasing flow rate from 1.7 to 2.2 L/s, supply mass from 0.75 to 1.50 kg, and interval from 4 to 6 s significantly strengthens substrate dynamic response, with the peak average velocity rising by 78.3%, 33.3%, 67.0% and maximum displacement by 80.7%, 51.2%, 67.6%, respectively. Channel particle velocity is more sensitive to flow rate but suppressed by greater sediment mass and shorter intervals. The deposited riverbed has three zones: first-supply-dominated, mixed, and subsequent-supply-dominated. Higher flow rates restrict depositional area expansion but increase thickness, whereas greater subsequent sediment expands its dominant zone while reducing thickness, with minimal influence from supply intervals. This study offers theoretical insights for preventing water–sediment disasters in mountainous areas. Full article

Variations in liner vibration among cylinders can lead to non-uniform lubrication, accelerated wear, and cavitation in multi-cylinder diesel engines. This study investigated the origin of these variations in a heavy-duty straight-six diesel engine using a transient dynamic model of the cylinder assembly, modal analysis, and VMD. An elastic transient model of the block, liner, and piston system was developed with measured cylinder pressure, cylinder head bolt preload, and piston thermal deformation applied as boundary conditions. The model was validated against modal testing and bench measurements of liner acceleration. Under nominally identical piston excitation across all six cylinders, the computed liner responses were decomposed using VMD to extract intrinsic mode components and dominant frequency bands. The results show that the primary vibration response is concentrated in the upper-middle region of the liner, while the end cylinders exhibit higher vibration levels than the central cylinders. A dominant component centred at approximately 1800 Hz is identified and linked to an engine block mode whose spatial deformation pattern matches the cylinder-to-cylinder distribution of liner vibration and cavitation risk. These findings indicate that the inter-cylinder discrepancy is linked to engine block modal and non-uniformity constraints. The proposed model provides a basis for reliability-oriented mitigation of vibration and cavitation in multi-cylinder diesel engines. Full article

A novel auxetic honeycomb (RSSHR) is developed by introducing the arc-shaped structure into the re-entrant star-shaped honeycomb (RSSH). Based on theoretical models and finite element methods, the dynamic crushing responses of RSSH and RSSHR plate (RSSH_P and RSSHR_P) structures are investigated to elucidate the dependence of plateau stress, negative Poisson’s ratio (NPR), deformed shape and specific energy absorption (SEA) on crushing velocity. The stress–strain curves of two types of structures are calculated to analyze configuration–mechanical property relationships. The results exhibit that the plateau stress and SEA of the RSSH_P and RSSHR_P structures increase as the crushing velocity increases. Owing to the stress-mitigating effect of the arc-shaped structure, the RSSHR_P structure exhibits a stronger NPR effect. And the SEA of the RSSHR_P structure is higher than that of the RSSH_P structure. In addition, it is also found that at low crushing velocity, the stress–strain curves of the two structures exhibit three distinct stages: the elastic stage (I), the stress plateau stage (II) and the densification stage (III). During the crushing process, there are three deformed shapes. They are the global deformed shape, the local deformed shape and the layer-by-layer deformed shape. Full article

To tackle the safety performance concerns of Squat shear walls in nuclear island structures (which serve as shields for powerhouses) under seismic action, this research endeavors to explore the seismic performance of such shear walls with different reinforcement ratios. Pseudo-static loading tests were carried out on 6 shear wall specimens, which were divided into 3 groups (with different reinforcement ratios). The focus was on analyzing the specimens’ failure process, load-deformation hysteretic curves, shear strength, ductility, strain, and other crucial parameters. The experimental findings demonstrate that all specimens underwent shear failure, which was characterized by the compression of web concrete. A higher reinforcement ratio can alleviate the buckling extent of structural steel. Specifically, an elevated horizontally distributed steel ratio notably enhances the ductility and energy dissipation capacity of the specimens, thereby effectively improving the yield load, stiffness, and ductility of squat shear walls. Nevertheless, its influence on cumulative energy dissipation and crack development is limited. Based on the analysis of the specimens’ failure modes, hysteretic curves, skeleton curves, energy dissipation, and stiffness degradation laws, finite-element numerical analysis was carried out on selected specimens. Comparison with the experimental results showed a good consistency between the two. Ultimately, the influence of the reinforcement ratio on the seismic performance of the shear walls was ascertained, and the research on the variation rules of the seismic performance parameters of squat shear walls was completed after verification through finite-element modeling. Based on this, a nonlinear fitting approach was employed to construct a regression prediction model for the seismic performance of shear walls in the Hainan Changjiang Multipurpose Modular Small Reactor Technology Demonstration Project. Typical squat shear walls were chosen for seismic response analysis, and the corresponding outcomes were acquired. Finally, a series of seismic vulnerability curves for nuclear island shear walls with varying guarantee rates were formulated for verification. Full article

Inflatable structures have attracted increasing attention in recent years due to their light weight, translucency, rapid assembly or disassembly, mobility, and self-cleaning performance. Meanwhile, their flexible characteristics and low-damping behavior render the structures prone to significant deformation and vibration under wind and snow loads and may even lead to structural failure. Therefore, numerous researchers have conducted in-depth investigations into the mechanical response of such structures under wind and snow loads. However, existing studies on inflatable structures subjected to wind and snow loads have mainly focused on an air-supported form, and the mechanical behavior of inflatable ribbed arch structures has not yet been sufficiently investigated. To investigate the mechanical behavior and deformation patterns of inflatable ribbed arch structures subjected to wind and snow loads, static tests were conducted on three specimens with varying spans, heights, and cable arrangements. Following inflation to an internal pressure of 250 kPa and preloading with the tarpaulin weight, the wind load and snow load were converted to the equivalent concentrated loads and applied in five incremental stages. Displacement monitoring points (DMPs) were tracked using a total station. Under the wind load, a consistent wind-induced deformation pattern was observed across specimens characterized by inward displacement in Region I, upward displacement in Region II, and negligible change in Region III. The maximum horizontal displacements of Specimens A, B, and C were 76 mm, 140 mm, and 249 mm, respectively. Under snow load, the upper sections of all three specimens experienced significant downward displacement, while both sides demonstrated a slight tendency for outward expansion and upward lift. The maximum vertical displacements of Specimens A, B, and C were −27 mm, −233 mm, and −255 mm, respectively. The findings of this study provide deeper insights into the mechanical behavior of inflatable arch structures under wind and snow loads and can serve as a valuable reference for their design and optimization. Full article

High-platform timber structures represent a typical structural form in ancient Chinese architecture, where the platform and the upper timber structure constitute a mechanically coupled system with interacting mechanical properties and response behaviors. However, a systematic understanding of their global coupling mechanism and its impact on structural response remains unclear. This study investigates a representative high-platform timber structure, i.e., Xi’an Bell Tower, to analyze the static and dynamic response characteristics of the platform–superstructure system using in situ dynamic testing and finite element simulation. The results indicate that the simulated first two natural frequencies align well with in situ measurements, validating the model’s rationality. The global coupling effect alters the system’s mass and stiffness distribution, leading to an overall lengthening of the structural natural periods. Structural self-weight is identified as the dominant factor inducing vertical deformation under serviceability conditions, with significant deformation observed at the platform’s edges and corners. Under lateral loads, deformations concentrate in the second story of the timber superstructure, with seismic actions exerting a more pronounced influence than wind loads. Under rare earthquake conditions, the maximum inter-story drift ratio reaches 1/70. Local tensile stresses at the joints, architrave ends, and the Dou-Gong layer exceed the timber’s tensile strength parallel to the grain, identifying these components as the weak links in the structure’s seismic performance. Full article

In indoor environments, the elderly, children, and people with disabilities are prone to abnormal behaviors like violent injuries and falls, threatening their health and safety and requiring real-time technical monitoring. However, existing technologies face issues including target occlusion, heavy background interference, feature ambiguity, posture deformation, and large-scale differences when detecting such behaviors in complex scenarios. To tackle these challenges, the present study puts forward the SCGS-YOLO real-time algorithm by improving YOLOv8s: replacing its backbone with ShuffleNet V2 to improve inference efficiency in resource-constrained environments; integrating CBAM into its backbone and SimAM into the feature fusion module, strengthening key features via dual-stream attention to suppress background interference and alleviate occlusion ambiguity; and using GIoU as the positioning loss function to facilitate model convergence and improve localization precision for complex human postures. Experiments on self-built VD-2025 and FD-2025 datasets show that SCGS-YOLO achieves 98.20% precision, 96.10% recall, and 98.70% mAP@0.5 for violence detection, and 97.10% precision, 93.80% recall, and 96.70% mAP@0.5 for fall detection. Compared to the original YOLOv8s and several representative models, it effectively balances detection precision and real-time response for the aforementioned groups’ indoor abnormal behaviors. Full article