Search Results (5,659)

Alpine permafrost and seasonally frozen ground threaten the long-term safe operation of highway infrastructures. Aiming at the structural performance optimization of prefabricated corrugated steel plate retaining walls in alpine permafrost regions, this study adopted finite element numerical simulation combined with field test validation to systematically explore the influences of wall height, plate thickness, corrugation geometry, and tie reinforcement layout on structural deformation and internal force, and carried out targeted parameter optimization. The core innovations include the following: (1) Structural lateral displacement and internal force rise nonlinearly with the increase in wall height, and high retaining walls exhibit an accelerated growth trend of deformation and stress. (2) Increasing plate thickness can effectively reduce structural displacement and stress, while the improvement effect gradually weakens after exceeding a critical thickness. Specifically, when the thickness increases from 4 mm to 5 mm, the displacement decreases by 33.13%. (3) Appropriately increasing corrugation pitch and height improves structural equivalent stiffness and optimizes stress distribution. Increasing the corrugation pitch from 75 mm to 400 mm and corrugation height from 25 mm to 150 mm reduces the maximum horizontal displacement by 52.6%. This demonstrates that larger corrugation profiles significantly improve structural stiffness. For walls higher than 6 m, the spacing should be reduced to 0.8 m × 1.0 m to provide additional lateral restraint. (4) Furthermore, seasonal freeze–thaw cycles and a non-uniform temperature field significantly amplify structural displacement and stress. After 12 months of freeze–thaw cycles, the maximum horizontal displacement increases by 49.7% and the maximum equivalent stress increases by 56.9% compared to the initial state. This study clarifies the parameter control mechanism and temperature coupling effect and provides a reliable theoretical basis and design reference for the engineering application of prefabricated corrugated steel plate retaining walls in alpine permafrost areas. Full article

This study investigates residual stress development in double-lap T-joints fabricated from medium- and heavy-gauge steel plates. A three-dimensional thermo-mechanically coupled finite element model was developed in Abaqus and validated against blind-hole drilling measurements. Four distinct welding sequence schemes were systematically implemented to quantify their influence on the spatial distribution, peak magnitudes, and evolution trajectories of individual residual stress components (σ_x, σ_γ, σ_z). Results demonstrate that the inherent structural rigidity of medium-to-thick plate assemblies strongly constrains global distortion but does not eliminate sensitivity to sequencing at the local stress level. Although equivalent residual stress peaks remain largely insensitive to welding sequence, the distributions of principal stress components exhibit pronounced sequence-dependent heterogeneity. Specifically, single-side continuous unidirectional welding leverages interpass residual heat accumulation to suppress longitudinal tensile stress, achieving a peak value of 449.9 MPa, the lowest among all configurations. In contrast, double-sided alternating reverse welding promotes thermal dispersion across the joint, thereby reducing both transverse tensile stress magnitude and stress concentration in the distal heat-affected zone. Collectively, these findings establish that optimizing welding sequences for double-lap T-joints in medium-to-heavy plates centers not on minimizing global equivalent stress, but on deliberately tailoring the spatial partitioning and balance of individual stress components, a principle that directly informs robust, performance-driven weld path selection in structural fabrication. Full article

The Changbai Mountain area, the largest Cenozoic intraplate volcanic field in eastern China, features abundant high-temperature hot springs and high geothermal potential. However, the genesis and aggregation patterns of its geothermal systems remain poorly understood. This study recalculates crustal and residual deep/mantle heat- flow components along a representative profile and synthesizes published geological, geophysical, geochemical, and geothermal evidence to characterize the main geothermal system elements, including caprock, reservoirs, water source, and migration pathways. Controlling factors are examined from three dimensions: deep dynamics, magmatic heat source, and fault characteristics. Results reveal a “Cold crust–Hot mantle” thermal structure. The heat-flow calculation indicates that crustal radiogenic heat contributes approximately 40% of the surface heat flow, implying a dominant deep heat contribution. The available evidence suggests the presence of potential hydrothermal reservoirs in carbonate and clastic rocks, possible HDR targets in deeper metamorphic rocks, and locally effective basaltic sealing units. Fault systems and meteoric recharge likely control fluid circulation. Geothermal systems are controlled by mantle upwelling and lithospheric thinning due to western Pacific Plate subduction, multi-source heat coupling, effective caprock sealing, and fault-controlled water–heat conduction. These results provide a conceptual framework for future geothermal exploration and testing. This study elucidates the aggregation patterns and genetic mechanisms, providing a theoretical basis for exploration and development. Full article

Although garnet-type Li₇La₃Zr₂O₁₂ (LLZO) solid electrolytes are promising candidates for high-energy-density all-solid-state batteries, their practical applications are limited by high-voltage oxidation instability and interfacial degradation. To address these limitations, Al-doped LLZO (Al-LLZO) solid electrolytes were synthesized via a conventional solid-state reaction method, and the effects of PE-ALD-derived Al₂O₃ nanocoatings on electrochemical properties and interfacial stability were investigated. Al₂O₃ nanocoatings with different structures (5 and 10 nm single-side, and 5 nm double-side) were deposited on Al-LLZO pellets using plasma-enhanced atomic layer deposition. The Al₂O₃ coating reduced electronic conductivity by approximately one order of magnitude while maintaining similar ionic conductivity. Linear sweep voltammetry revealed that initial oxidation onset voltage increased from ~4.2 V (bare Al-LLZO) to ~5.0 V (5 nm-coated samples), while the 10 nm-coated sample exhibited the most delayed anodic current response (~5.2 V). The 5 nm double-side coated sample showed the best Li plating/stripping stability with a critical current density of 1.10 mA/cm² and stable long-term galvanostatic cycling behavior over 200 h at 0.05 mA/cm². Thus, ALD-based Al₂O₃ interfacial engineering can simultaneously improve the high-voltage oxidation and Li metal interfacial stabilities of garnet-type Al-LLZO solid electrolytes for practical all-solid-state batteries. Full article

This review synthesizes findings from more than 100 journal articles, reports, and design standards on the design, simulation, and testing of steel beam-to-column connections, with emphasis on semi-rigid bolted extended end-plate (EEP) joints. The core objective of this study is to highlight the critical importance of accurately capturing this semi-rigid behavior, given the significant implications of improper modeling for the global response, safety, and design reliability of steel frames. While connections are often idealized as fully rigid or pinned, EEP connections typically exhibit a semi-rigid response governed by nonlinear moment–rotation (M–θ) behavior. The reviewed literature is organized around: (i) mechanical response and key failure mechanisms (end-plate yielding, bolt fracture, and prying action); (ii) analytical and numerical prediction methods, including component-based models and finite-element approaches capable of representing contact, bolt pretension, and cyclic degradation; and (iii) system-level implications for steel frames. Approaches used in major standards (AISC and Eurocode 3) for classifying connection stiffness and strength are compared, and experimental programs are summarized to identify the dominant parameters controlling resistance, ductility, and failure mode. Translating these component-level findings to the structural-system level, the review highlights how appropriately detailed semi-rigid EEP connections can enable moment redistribution, reduce member demands, and support stable inelastic deformation under seismic actions. Key research gaps include three-dimensional and multiaxial loading, impact and other high-rate actions, and the performance of alternative materials such as stainless steel. Full article

By itself or combining with other cooling technologies, the dew point indirect evaporative cooler (DIEC) will be the preferred solution for cooling buildings. However, there are still some gaps in the research on DIEC performance, one of which is that 3-D (3-dimensional) models and methods are not widely used to comprehensively indicate the cooling mechanism. Most of the available numerical methods adopted 1-D or 2-D models. Existing 3-D models and methods either ignore the water film and plate or are so complicated in the grid system and numerical calculation induced by huge size differences among calculation regions that their attractions are weak. A novel simplified numerical method for DIEC performance is first suggested in this paper, and then, its validity and more efficiency than an existing 3-D numerical method are verified with the help of experimental data and numerical results. Finally, the effects of structure and operating parameters on the performance of a plate DIEC are analyzed by this present method and COMSOL Multiphysics 6.3 software, especially η/η₀ (the reinforcement factor), which was innovatively introduced. Similar results to those of existing literature were obtained, which further indicated the practicability of this simplified method. In the conditions involved in this paper, a channel length of 1.5 m, a width of 4 mm, Re_in (the Reynolds number at the inlet) of 1483, and a (the air ratio) of 0.33 are recommended. In the condition suggested by this paper, η/η₀ is close to 1.2. In the same conditions, this proposed method reduces the number of mesh elements by approximately 58% and the wall-clock computational time by approximately 52% under the reported workstation conditions, and its value would be more obvious for more complicated problems. Full article

Background: In comparative anatomy, muscles of the gluteal and hamstring groups are categorized and described inconsistently between, but also within, different species. Due to insufficient information on the exact topography of the individual muscles and a lack of illustrations, it is partly difficult to compare the data provided. Particularly for the albino rat, there is only limited information available for these muscles. The aim of this study was therefore to investigate the presence and morphology of the gluteal and hamstring muscles in the albino rat, and to compare them with other species, including humans. Methods: Both hind limbs of 30 formalin-embalmed male albino rats were carefully dissected. The individual muscles were identified based on their position in relation to nerves and to each other. Therefore, previous descriptions of other species were considered. Results: The gluteus superficialis and tensor fasciae latae muscles formed always a continuous musculoaponeurotic plate. The femorococcygeus and gluteus accessorius muscles were constant structures. The gluteus medius, piriformis and gluteus profundus muscles could always be identified. Within the hamstring group, the two-headed semitendinosus, the one-headed biceps femoris, the semimembranosus, and the caudofemoralis muscles were always present. Conclusions: In this study, a detailed description and dissection guide of the systematic anatomy and topography of the gluteal and hamstring muscles of the albino rat is provided for the first time. The outcomes are intended to help improve knowledge of the anatomy of these muscle groups and to serve as a basis for future studies using rats as an animal model. Full article

This study examines two articulated peripheral plates of a carettochelyid turtle from the Moghra Formation (Early Miocene, 19.6–18.2 Ma) in Egypt. This research represents the first record of shell pathologies in an African carettochelyid. The specimens were analyzed through detailed macroscopic observation and computed tomography (CT) imaging. To characterize the observed anomalies, a comparative analysis was conducted based on standardized clinical and veterinary osteopathological methodologies. The results revealed significant external and internal structural alterations, including irregular globular outgrowths and internal remodeling evidenced by high-density bone formation. These features enable the identification of pathological conditions that differ from the bioerosive traces and other surface modifications that have been documented previously in the turtle fauna of the Moghra Formation. Full article

6082 aluminum alloy is widely applied in marine engineering, rail transportation and other industries owing to its excellent comprehensive performance. Welding heat source characteristics exert a decisive influence on the microstructure and mechanical properties of welded joints and become a major constraint for the application of medium-thick aluminum alloy welded structures. In this work, comparative tests of TIG and MIG welding were carried out on 16 mm thick 6082 aluminum alloy plates. Combining thermal simulation, metallographic observation and mechanical property tests, the temperature field distribution, microstructure, microhardness, tensile properties and bending properties of the two kinds of joints were systematically studied. The results show that TIG welding possesses high heat input, forming a broad temperature field with steep thermal gradients. Its weld microstructure is coarse and accompanied by severe coarsening of Mg₂Si precipitates, and the joint presents a highly fluctuating M-shaped microhardness distribution. The average tensile strength of TIG welded joints is 194 MPa, and all specimens fracture in the heat-affected zone. By contrast, MIG welding with low heat input produces a uniform temperature field, as well as a fine and homogeneous weld microstructure with dispersed precipitates. Its microhardness distribution is stable, and the average tensile strength reaches 256 MPa, 32% higher than that of TIG joints. Both welding methods deliver favorable bending performance. The difference in heat input and cooling behavior changes the grain evolution and precipitate characteristics and further dominates the final mechanical performance of joints. MIG welding is more suitable for multi-layer, multi-pass welding of 16 mm thick 6082 aluminum alloy. This work clarifies the correlation between heat input, microstructure and mechanical properties, and the optimized process can effectively improve the microstructural uniformity of the weld joint and enhance its mechanical properties. Full article

The mechanical response of cellular structures is governed not only by relative density and average cell geometry but also by the spatial arrangement of cells. However, the manner in which arrangement-dependent effects evolve with increasing cell number has not been systematically clarified. In this study, the compressive behavior of closed-cell structures with varying cell numbers was investigated using finite element analysis under dynamically equilibrated compression conditions while maintaining constant relative density and identical material parameters. Cellular models were generated using hierarchical Poisson disk sampling combined with Voronoi tessellation. The number of cells was increased through three distinct approaches: mirror replication of a reference structure, enlargement of the overall specimen size, and refinement of cell size under fixed external dimensions. To characterize arrangement-dependent effects, two distinct features of the compressive response were introduced: averaging, defined as a reduction in variability across responses from different initial cell arrangements, and smoothing, defined as the suppression of abrupt stress fluctuations within an individual response. Quantitative metrics were employed to evaluate both effects. Averaging was observed in plate-type models compressed in the z-direction and in fixed-size models, whereas mirror-connected models retained strong arrangement dependence despite large cell numbers. Smoothing occurred predominantly in plate-type models compressed in the z-direction and was strongly correlated with the number of cell layers aligned along the compression direction rather than with total cell number alone. The simulations were conducted in a dynamically equilibrated regime in which internal stress equilibrium was achieved during deformation. These results demonstrate that compressive behavior is governed not only by cell number but also by structural arrangement and directional cell-layer alignment, providing mechanistic insight into the transition from arrangement-dependent variability to stable macroscopic response under dynamic compression. Full article

To address the application bottlenecks of organic phase change materials characterized by low thermal conductivity and susceptibility to liquid leakage, this study utilized natural poplar wood as a raw material to construct a three-dimensional carbon/silver heterogeneous porous skeleton via delignification, gradient carbonization, and in situ electroless silver plating. Polyethylene glycol (PEG) was then vacuum-encapsulated within this structure to prepare form-stable composite phase change materials (CPCMs). The regulatory effects of carbonization temperature and metal interface modification on the microscopic morphology and thermophysical properties of the materials were systematically investigated. The results indicate that the skeleton carbonized at 800 °C achieves an optimal balance between pore distribution and skeleton rigidity, ensuring the uniform conformal growth of silver nanoparticles and endowing the material with excellent anti-leakage performance. The thermal conductivity of the optimal sample reaches as high as 0.683 W/(m·K), with the melting latent heat maintained at 133.9 J/g, while also demonstrating an agile and stable photothermal conversion response. Non-equilibrium molecular dynamics (NEMD) simulations further confirm that the silver nanoparticle modification layer smooths the phonon vibration frequency mismatch between the carbon substrate and organic segments, significantly reducing the interfacial thermal resistance. This research provides an important reference for the structural design and microscopic heat transfer mechanism analysis of high-performance phase change energy storage materials. Full article

Ultrasonic thickness resonance can be effectively used to detect and quantify the level of corrosion in steel nuclear storage containers as well as other corrosion-prone thin-walled structures, such as pipes and storage tanks. Electro-Magnetic Acoustic Transducers (EMATs) have several advantages over more traditional piezoelectric-based transducers; namely, they can be used in a non-contact fashion on robotic platforms, allowing for measurements regardless of surface conditions or temperature. The major challenge of EMAT application is the power required to counteract the low actuation efficiency, which is achieved with a high-power ultrasonic pulse generator and a transformer circuit. Resonance techniques, in which most of the energy is concentrated near structural resonance frequencies, are preferable to improve efficiency of electro-magnetic acoustic measurements. This methodology was applied to 316L stainless steel thin plates subjected to uniform corrosion as well as pitting corrosion imitating different damage scenarios in a nuclear waste container. The resonant peak frequency shift was found to be proportional to the severity of corrosion for minimally corroded samples. However, the complete disappearance of the resonance peak was observed in the samples with severe corrosion damage. The EMAT liftoff distance was studied to quantify its effect on the amplitude, spread, and frequency of resonant peaks. Recommendations for use of EMATs for assessing corrosion damage are presented. The study demonstrates the success of frequency-based detection of corrosion damage in 316L stainless steel used in fabrication of nuclear waste storage containers. Full article

Hydraulic synchronous jacking technology is extensively employed in bridge reconstruction and new construction, with jacking supports serving as core components whose blast resistance is critical to the structural safety of the bridge jacking system. This study numerically investigates the dynamic response and damage behavior of bridge jacking supports subjected to under-deck gas explosion loading through the finite-element software LS-DYNA. The TNT equivalent method is adopted to convert gas explosion load into equivalent TNT detonation load for simulation, and the effects of TNT detonation location on the blast-resistance performance of the jacking support are analyzed. The results indicate that the bridge segment temporarily loses contact with the jacking support under the action of gas explosion loading. The bridge segment around the web plate undergoes shear damage because of the deformation constraint effect of the web plate. The shear damage level of the bridge segment increases with the increase in TNT mass. The displacement of the jacking support increases with the increase in the mass of the explosive. The enhanced rod around the edge steel pipe support is more prone to damage due to its low local stiffness. The damage level of the bridge segment increases with the decrease in the distance between the TNT detonation and the bridge segment, and then the blast-resistance performance of the jacking support is almost unrelated to the vertical distance. The transverse distance between the TNT detonation and the jacking support has a significant effect on the response of jacking support. Full article

This paper presents and validates a unified spreadsheet-based framework for engineering mechanics education and preliminary design. Three modules are integrated within a single openly available workbook: multi-point resultant force and moment computation; axial normal stress with stress concentration effects for three geometric configurations (plate with hole, shoulder plate, stepped shaft); and beam deflection for simply supported and cantilever configurations under point loads. All governing equations are implemented as explicit closed-form expressions validated against analytical reference solutions for six independent cases; relative errors fall below ${10}^{-10}$ in all cases. Three worked exercises demonstrate the practical scope of the framework. A biomechanical multi-point force system yields joint moments of $-6880$, −33,421, and −58,241 N·mm at the wrist, elbow, and shoulder, respectively. A tensile shoulder plate with $K_t\approx 1.85$ produces ${\sigma }_{max}=232$ MPa against ${\sigma }_y=200$ MPa, identifying a design failure; a parametric redesign with fillet radius $r=10$ mm reduces $K_t$ to approximately 1.59 and ${\sigma }_{max}$ to approximately 198.7 MPa, restoring structural safety. A cantilever beam subjected to a 20,000 N tip load yields a maximum deflection of 13,133 μm. The framework constitutes a validated intermediate layer between manual analytical derivations and high-fidelity numerical simulations, applicable to preliminary design, parametric sensitivity studies, and engineering education at the linear elastic level. Full article

Instance segmentation of surface defects is one of the research hotspots in the field of image segmentation. Due to limitations such as restricted receptive fields or the loss of fine-grained details, traditional neural network models still struggle to achieve sufficiently high-segmentation accuracy for surface defects. To meet the demand for high precision segmentation of surface defects on copper strips and plates in industrial quality inspection, this paper proposes a feature fusion segmentation network, termed DSFFNet. First, a dual-branch structure is designed in DSFFNet to fuse spatial-domain features with discrete cosine transform (DCT)-domain features, thereby obtaining richer feature information. Second, a 2D-DCT frequency feature extraction module is developed to more effectively capture the edge information of targets. Third, a triplet attention mechanism is introduced into the backbone network to form an attention-centric network. Finally, a bidirectional fusion module and a multi-scale fusion network are designed to capture finer-grained feature information. Comparative experiments conducted on the KUST-SEG-Dataset demonstrate that DSFFNet achieves 94.66% ± 1.07% (mask)mAP₅₀ and 95.38% ± 0.06% (box)mAP₅₀, outperforming several classic image segmentation methods. Furthermore, generalization experiments on the public NEU-Seg dataset yield a (mask)mAP₅₀ of 86.27% ± 0.01%. The generalization results indicate that DSFFNet is robust to datasets with similar defect types. Full article