Search Results (157)

In injection molding, draft angle design plays a critical role in ensuring smooth de-molding and maintaining surface quality. With the growing emphasis on aesthetics and the increasing demand for the appearance of plastic products, the need for textured plastic components has continuously risen. The coupling between surface texture replication and dimensional accuracy has become an important indicator of product performance. However, systematic studies on the interaction between different polymer materials and draft angle design remain limited. This study aims to investigate the influence of draft angle variation on the surface texture quality and dimensional stability of injection-molded parts by comparing the differences between crystalline and amorphous thermoplastic materials, as well as between commodity and engineering plastics. Four representative polymers, namely polypropylene (PP), polyoxymethylene (POM), acrylonitrile-butadiene-styrene (ABS), and polycarbonate (PC), were selected to examine the impact of material characteristics on surface texture replication after molding. In addition, product geometries incorporating eight draft angles (0° to 3.5°) were designed. Surface texture replication was analyzed using scanning electron microscopy (SEM) and surface profilometry, while dimensional deformation was measured with a high-precision optical measuring instrument. The results show that draft angle variation has a limited influence on the overall trend of dimensional deformation, but it has a significant effect on the clarity of surface replication. Crystalline polymers exhibited generally higher surface roughness than amorphous polymers, and the distinction between commodity and engineering plastics, particularly those requiring higher processing temperatures, also led to higher roughness (PP > POM; ABS > PC). Dimensional deformation was more pronounced in crystalline polymers (POM > PP > ABS > PC). SEM observations further confirmed that higher roughness corresponded to clearer and more distinguishable texture patterns, whereas lower roughness resulted in blurred or indistinct textures. Full article

Objective: The purpose of this study is to present a kyphosis measurement method based on quadratic spline fitting through three key vertebral landmarks: T12, T8 and T4. This approach aims to capture thoracic spine curvature more continuously and accurately than traditional methods such as the Cobb angle and circle fitting. Methods: A dataset of 560 lateral thoracic spine radiographs was retrospectively analyzed, including cases of postural kyphosis, Scheuermann’s disease, osteoporosis-induced kyphosis and ankylosing spondylitis. Two trained raters independently performed three repeated landmark annotations per image. The kyphosis angle was computed using two methods: (1) a quadratic spline fitted through the three landmarks, with the angle derived from tangent vectors at T12 and T4; and (2) a least-squares circle fit with the angle subtended between T12 and T4. Agreement with reference Cobb angles was evaluated using Pearson correlation, MAE, RMSE, ROC analysis and Bland–Altman plots. Reliability was assessed using intraclass correlation coefficients (ICC). Results: Both methods showed excellent intra- and inter-rater reliability (ICC ≥ 0.967). The spline method achieved lower MAE (5.81°), lower RMSE (8.94°) and smaller bias compared to the circle method. Both methods showed strong correlation with Cobb angles (r ≥ 0.851) and excellent classification performance (AUC > 0.950). Conclusions: Spline-based kyphosis measurement is accurate, reliable and particularly robust in cases with severe spinal deformity. Significance: This method supports automated, reproducible kyphosis assessment and may enhance clinical evaluation of spinal curvature using artificial intelligence-driven image analysis. Full article

Al–Zn–Mg–Cu alloys are well known for their outstanding strength, toughness, and corrosion resistance, arising from the balanced addition of Mg, Zn, and Cu. However, conventional casting methods often lead to grain boundary segregation and the formation of coarse Fe-rich phases, which severely limit subsequent heat treatment and plastic processing. To overcome these drawbacks, this study systematically investigates the effects of the Continuous Rheo-Extrusion (CRE) process on the microstructure and mechanical performance of Al–Zn–Mg–Cu alloys using XRD, EBSD, SEM, and TEM analyses. The CRE process refines the average grain size from 53.5 μm to 16.1 μm and raises the fraction of high-angle grain boundaries to 88.8%. Moreover, coarse Fe-rich phases are fragmented to below 5 μm, while the elemental distribution of Zn, Mg, and Cu becomes more homogeneous, effectively reducing grain boundary segregation. The Al₂Cu precipitates are refined from 106.3 nm to 11.7 nm, corresponding to an 88.9% size reduction. These microstructural optimizations yield a remarkable increase in tensile strength (from 204.7 ± 23.7 MPa to 338.0 ± 9.3 MPa) and elongation (from 11.4 ± 2.4% to 13.8 ± 1.3%). Quantitative analysis confirms that dislocation and precipitation strengthening are the dominant contributors to this improvement. Overall, the CRE process enhances microstructural uniformity through the synergistic effects of shear deformation, continuous dynamic recrystallization (CDRX), and dynamic precipitation, thereby providing a solid theoretical and practical foundation for short-process fabrication of high-strength, high-ductility Al–Zn–Mg–Cu alloys. Full article

Background/Objectives: Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine that can negatively impact on quality of life, pulmonary function, and body image. Its conservative management includes various interventions, among which the Schroth method stands out. This approach is based on three-dimensional corrective exercises and rotational breathing. This review aimed to analyze the effectiveness of the Schroth method, applied either alone or in combination with other conservative therapies, on variables such as Cobb angle, angle of trunk rotation (ATR), pulmonary function, and health-related quality of life in patients with AIS. Methods: A scientific literature search was conducted using the PubMed database. We searched for randomized controlling trials (RCTs), systematic reviews, and meta-analyses reported in English from 2020 to 2025. Different combinations of the terms and MeSH terms “adolescent”, “idiopathic”, “scoliosis”, and “Schroth” connected with various Boolean operators. Results: Overall, 82 articles were reviewed from the selected database. After removing duplicated papers and title/abstract screening, 13 studies were included in our review. The results showed that the Schroth method proved effective in reducing the Cobb angle and ATR, particularly in patients with mild curves and in early stages of skeletal growth. Improvements were also observed in health-related quality of life and aesthetic perception, and to a lesser extent, in pulmonary function. Moreover, therapeutic adherence and treatment continuity were important to maintaining long-term benefits. Conclusions: The Schroth method could be an effective treatment associated with orthopedic treatment, yielding satisfactory results. Its implementation requires structured programs, professional supervision, and strategies to enhance therapeutic adherence. Nevertheless, to validate its long-term effectiveness, we need more homogeneous studies with longer follow-up durations. Full article

Conventional projection systems typically require a fixed spatial configuration relative to the projection surface, with strict control over distance and angle. In contrast, UAV-mounted projectors overcome these constraints, enabling dynamic, large-scale projections onto non-planar and complex environments. However, such flexible scenarios introduce a key challenge: severe geometric distortions caused by intricate surface geometry and continuous camera–projector motion. To address this, we propose a novel image registration method based on global dense matching, which estimates the real-time optical flow field between the input projection image and the target surface. The estimated flow is used to pre-warp the image, ensuring that the projected content appears geometrically consistent across arbitrary, deformable surfaces. The core idea of our method lies in reformulating the geometric distortion correction task as a global feature matching problem, effectively reducing 3D spatial deformation into a 2D dense correspondence learning process. To support learning and evaluation, we construct a hybrid dataset that covers a wide range of projection scenarios, including diverse lighting conditions, object geometries, and projection contents. Extensive simulation and real-world experiments show that our method achieves superior accuracy and robustness in correcting geometric distortions in dynamic UAV projection, significantly enhancing visual fidelity in complex environments. This approach provides a practical solution for real-time, high-quality projection in UAV-based augmented reality, outdoor display, and aerial information delivery systems. Full article

Argillaceous slate (AS) is a typical metamorphic rock with well-developed bedding, widely distributed globally. Its bedding structure significantly impacts slope stability assessment, and the challenges associated with slope anchoring and support arising from bedding characteristics have become a focal point in the engineering field. In this study, with bedding dip angle as the key variable, mechanical tests such as uniaxial compression, triaxial compression, direct shear, and Brazilian splitting tests were conducted on AS. Additionally, field anchoring grouting diffusion tests on AS slopes were carried out. The aim is to investigate the basic mechanical properties of AS and the grout diffusion law under different bedding dip angles. The research results indicate that the bedding dip angle has a remarkable influence on the failure mode, stress–strain curve, and mechanical indices such as compressive strength and elastic modulus of AS specimens. The stress–strain curves in uniaxial and triaxial tests, as well as the stress-displacement curve in the Brazilian splitting test, all undergo four stages: crack closure, elastic deformation, crack propagation, and post-peak failure. As the bedding dip angle increases, the uniaxial and triaxial compressive strengths and elastic modulus first decrease and then increase, while the splitting tensile strength continuously decreases. The consistency of the bedding in AS causes the grout to diffuse in a near-circular pattern on the bedding plane centered around the borehole. Among the factors affecting the diffusion range of the grout, the bedding dip angle and grouting angle have a relatively minor impact, while the grouting pressure has a significant impact. A correct understanding and grasp of the anisotropic characteristics of AS and the anchoring grouting diffusion law are of great significance for slope stability assessment and anchoring design in AS areas. Full article

Natural cracks are prone to form in toppling deformed rock masses during the toppling process, and these cracks are likely to undergo hydraulic fracturing failure under the action of high water head. This paper leverages the advantage of the extended finite element method (XFEM) in simulating crack propagation, considers the effect of water pressure on the crack surface, conducts numerical simulation and analysis on the hydraulic fracturing of cracks in toppling deformed rock masses, and studies the influences of different crack lengths, rock formation dip angles and crack surface water pressures on crack propagation. The main conclusions are as follows: (1) After hydraulic fracturing occurs in the rock mass, with the continuous rise in the water level, the crack propagation rate is slow first and then fast. When the water pressure is low, microcracks extend slowly; when the water pressure reaches a certain level, the rock formation cracks expand rapidly and eventually fracture. (2) Under the same water pressure, rock formations with longer initial crack lengths are more prone to hydraulic fracturing, and their cracks expand faster; rock formations with a dip angle of 45° are more likely to undergo hydraulic fracturing than those with other dip angles, while rock formations with a dip angle close to 90° are hardly susceptible to hydraulic fracturing. (3) The instability failure mechanism of hydraulic fracturing in toppling deformed rock masses is tension shear action. As the fissure water pressure rises, the tensile stress at the crack tip will increase sharply. Once new microcracks appear in the initial crack, it will be in an unstable expansion state. Full article

Fractured rock masses in cold regions are subject to long-term seasonal freeze–thaw cycles. To investigate the fatigue damage characteristics of sandstone with different fracture inclinations under freeze–thaw cycling conditions, samples containing fractures of varying inclinations were prepared using sandstone from Altay, Xinjiang. After vacuum saturation and freeze–thaw cycling treatment (−30 °C to 30 °C), uniaxial cyclic loading tests were conducted to analyze strain, elastic modulus, Poisson’s ratio, and damage variables. The results showed that under cyclic loading, the strain of the sandstone exhibited a “stepwise accumulation” characteristic, with peak and residual strain increasing with the progression of the cycle. Among them, the specimen with a fracture angle of 45° exhibited the fastest strain increase before failure. The peak elastic modulus showed a “continuous decrease within each stage and an initial increase followed by a decrease between stages,” while the residual elastic modulus continued to decrease, with both experiencing a sudden, sharp drop at the end of the cycle. The peak Poisson’s ratio decreases with the number of cycles in the early stage, then transitions to logarithmic growth in the later stage, rapidly increases near failure, and finally, the residual Poisson’s ratio in the final cycle exceeds the peak Poisson’s ratio; the evolution of damage variables exhibits an S-shaped three-stage characteristic, with the initial stage showing an irreversible deformation growth rate exceeding 10% due to compaction. In the middle stage, it grows steadily due to microcrack propagation, and in the final stage, it approaches 1. Samples with steep inclination angles exhibit earlier damage initiation and faster growth rates. The study reveals that crack inclination angle influences the evolution rhythm by regulating the proportion of compaction and shear damage, providing a theoretical basis for assessing the engineering stability of fractured rocks in cold regions. Full article

In off-road scenes, segmentation targets exhibit significant scale progression due to perspective depth effects from oblique viewing angles, meaning that the size of the same target undergoes continuous, boundary-less progressive changes along a specific direction. This asymmetric variation disrupts the geometric symmetry of targets, causing traditional segmentation networks to face three key challenges: (1) inefficientcapture of continuous-scale features, where pyramid structures and multi-scale kernels struggle to balance computational efficiency with sufficient coverage of progressive scales; (2) degraded intra-class feature consistency, where local scale differences within targets induce semantic ambiguity; and (3) loss of high-frequency boundary information, where feature sampling operations exacerbate the blurring of progressive boundaries. To address these issues, this paper proposes the ProCo-NET framework for systematic optimization. Firstly, a Progressive Strip Convolution Group (PSCG) is designed to construct multi-level receptive field expansion through orthogonally oriented strip convolution cascading (employing symmetric processing in horizontal/vertical directions) integrated with self-attention mechanisms, enhancing perception capability for asymmetric continuous-scale variations. Secondly, an Offset-Frequency Cooperative Module (OFCM) is developed wherein a learnable offset generator dynamically adjusts sampling point distributions to enhance intra-class consistency, while a dual-channel frequency domain filter performs adaptive high-pass filtering to sharpen target boundaries. These components synergistically solve feature consistency degradation and boundary ambiguity under asymmetric changes. Experiments show that this framework significantly improves the segmentation accuracy and boundary clarity of multi-scale targets in off-road scene segmentation tasks: it achieves 71.22% MIoU on the standard RUGD dataset (0.84% higher than the existing optimal method) and 83.05% MIoU on the Freiburg_Forest dataset. Among them, the segmentation accuracy of key obstacle categories is significantly improved to 52.04% (2.7% higher than the sub-optimal model). This framework effectively compensates for the impact of asymmetric deformation through a symmetric computing mechanism. Full article

Satellite-based target positioning is vital for applications like disaster relief and precision mapping. Practically, satellite errors, e.g., thermal deformation and attitude errors, lead to a mix of fixed and random errors in the measured line-of-sight angles, resulting in a decline in target-positioning accuracy. Motivated by this concern, this study introduces a systematic error self-correction target-positioning method under continuous observations using a single video satellite. After analyzing error sources and establishing an error-inclusive positioning model, we formulate a dimension-extended equation estimating both target position and fixed biases. Based on the equation, a projection transformation method is proposed to obtain the linearized estimation of unknown parameters first, and an iterative optimization method is then utilized to further refine the estimate. Compared with state-of-the-art algorithms, the proposed method can improve positioning accuracy by 98.70% in simulation scenarios with large fixed errors. Thus, the simulation and actual data calculation results demonstrate that, compared with state-of-the-art algorithms, the proposed algorithm effectively improves the target-positioning accuracy under non-ideal error conditions. Full article

The longitudinal equivalent bending stiffness is a critical parameter for assessing the longitudinal responses of Double-O-Tube (DOT) shield tunnels under adjacent construction activities. Based on a longitudinal equivalent continuous model and the characteristics of the DOT shield tunnel cross-section, an analytical solution for the longitudinal equivalent bending stiffness (LEBS) of the DOT shield tunnel has been derived. Given that the cross-section of the DOT shield tunnel is an irregular structure, two scenarios are considered: one in which the neutral axis is located at the waist of the tunnel and another where it is situated at the lower arch. Using the structural design of the DOT shield tunnel for Shanghai Metro Line M8 as a case study, the effects of bolt number, segment thickness, segment width, and pillar height on the longitudinal equivalent bending stiffness have been investigated. Additionally, formulas for calculating the deformation and stress indices of the DOT shield tunnel have been established. The results indicate that increasing the number of bolts and widening the segments can enhance the longitudinal equivalent bending stiffness efficiency (LEBSE), resulting in an upward shift of the neutral axis. Conversely, as the segment thickness increases, the LEBSE decreases linearly while the neutral axis moves downward; however, the value of LEBS itself increases. With an increase in the pillar height angle, the neutral axis shifts upward, leading to an increase in the LEBS. When the pillar height angle is increased from 10° to 45°, the LEBSE decreases rapidly, followed by a gradual increase with further elevation in the pillar height angle. When the tunnel curvature radius exceeds 15,000 m, the bolts, segments, and joint openings remain in a safe state. However, when the curvature radius decreases to 5233 m, the maximum tensile stress on the bolts reaches their yield limit, and the joint openings exceed the warning threshold. Full article

On 18 December 2023, a M_w 6.2 earthquake occurred in close proximity to Jishishan County, located on the northeastern edge of the Qinghai–Tibet Plateau. The event struck the structural intersection of the Haiyuan fault, Lajishan fault, and West Qinling fault, providing empirical evidence for investigating the crustal compression mechanisms associated with the northeastward expansion of the Qinghai–Tibet Plateau. In this study, we successfully acquired a high-resolution coseismic deformation field of the earthquake by employing interferometric synthetic aperture radar (InSAR) technology. This was accomplished through the analysis of image data obtained from both the ascending and descending orbits of the Sentinel-1A satellite, as well as from the ascending orbit of the ALOS-2 satellite. Our findings indicate that the coseismic deformation is predominantly localized around the Lajishan fault zone, without leading to the development of a surface rupture zone. The maximum deformations recorded from the Sentinel-1A ascending and descending datasets are 7.5 cm and 7.7 cm, respectively, while the maximum deformation observed from the ALOS-2 ascending data reaches 10 cm. Geodetic inversion confirms that the seismogenic structure is a northeast-dipping thrust fault. The geometric parameters indicate a strike of 313° and a dip angle of 50°. The slip distribution model reveals that the rupture depth predominantly ranges between 5.7 and 15 km, with a maximum displacement of 0.47 m occurring at a depth of 9.6 km. By integrating the coseismic slip distribution and aftershock relocation, this study comprehensively elucidates the stress coupling mechanism between the mainshock and its subsequent aftershock sequence. Quantitative analysis indicates that aftershocks are primarily located within the stress enhancement zone, with an increase in stress ranging from 0.12 to 0.30 bar. It is crucial to highlight that the structural units, including the western segment of the northern margin fault of West Qinling, the eastern segment of the Daotanghe fault, the eastern segment of the Linxia fault, and both the northern and southern segment of Lajishan fault, exhibit characteristics indicative of continuous stress loading. This observation suggests a potential risk for fractures in these areas. Full article

Glass fiber reinforced polypropylene composite plates have gradually attracted more attention because of their repeated molding, higher toughness, higher durability, and fatigue resistance compared to glass fiber reinforced thermosetting composites. In practical engineering applications, composite plates have to undergo bending effect at different angles in corrosive environment of concrete, including bending bars from 0~90°, and stirrups of 90°, which may lead to long-term performance degradation. Therefore, it is important to evaluate the long-term performance of glass fiber reinforced polypropylene composite bending plates in an alkali environment. In the current paper, a new bending device is developed to prepare glass fiber reinforced polypropylene bending plates with the bending angles of 60° and 90°. It should be pointed out that the above two bending angles are simulated typical bending bars and stirrups, respectively. The plate is immersed in the alkali solution environment for up to 90 days for long-term exposure. Mechanical properties (tensile properties and shear properties), thermal properties (dynamic mechanical properties and thermogravimetric analysis) and micro-morphology analysis (surface morphology analysis) were systematically designed to evaluate the influence mechanism of bending angle and alkali solution immersion on the long-term mechanical properties. The results show the bending effect leads to the continuous failure of fibers, and the outer fibers break under tension, and the inner fibers buckle under compression, resulting in debonding of the fiber–matrix interface. Alkali solution (OH⁻ ions) corrode the surface of glass fiber to form soluble silicate, which is proved by the mass fraction of glass fiber decreased obviously from 79.9% to 73.65% from thermogravimetric analysis. This contributes to the highest degradation ratio of tensile strength was 71.6% (60° bending) and 65.6% (90° bending), respectively, compared to the plate with bending angles of 0°. A high curvature bending angle (such as 90°) leads to local buckling of fibers and plastic deformation of the matrix, forming microcracks and fiber–resin interface bonding at the bending area, which accelerates the chemical erosion and debonding process in the interface area, bringing about an additional maximum 10.56% degradation rate of the shear strength. In addition, the alkali immersion leads to the obvious degradation of storage modulus and thermal decomposition temperature of composite plate. Compared with the other works on the long-term mechanical properties of glass fiber reinforced polypropylene, it can be found that the long-term performance of glass fiber reinforced polypropylene composites is controlled by the corrosive media type, bending angle and immersion time. The research results will provide durability data for glass fiber reinforced polypropylene composites used in concrete as stirrups. Full article

Three-roll planetary rolling technology has emerged as a primary method for manufacturing seamless tubes due to its advantages, including significant single-pass deformation, low energy consumption, and the ability to continuously roll long workpieces. Based on the forming characteristics of three-roll planetary rolling, this study established a simulation model of the rolling process, which includes key parameters such as the friction coefficient, roll speed, and roll deflection angle. Using finite element software, the effects of these parameters on the rolling process are simulated and analyzed. By comparing critical indicators such as the equivalent stress, rolling temperature, and roundness of the workpiece, the influence of the process parameters on the forming quality of three-roll planetary rolling is revealed. The optimal parameter combination is determined as follows: a friction coefficient of 0.3, roll speed of 120 rpm, and roll deflection angle of 9°. This research provides a reliable theoretical foundation for subsequent roll profile design and process parameter optimization in three-roll planetary rolling. Full article

In this study, we investigated the two-phase hardening behavior and microstructural evolution of S32750 duplex stainless steel during the tensile deformation process. The analysis was conducted using in situ electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and microhardness testing. It was observed that strain transfer occurred between the two phases in the position away from the fracture. The ferrite phase exhibited softening, while the austenite phase underwent hardening. In the region less than 1 mm from the fracture site, both phases experienced a rapid hardening, with the maximum hardness difference between the two phases near the fracture reaching approximately 45 HV. In situ EBSD results indicate that the kernel average misorientation (KAM) value for the ferrite phase consistently exceeds that of the austenite phase during the initial stages of deformation. Conversely, in the final stages of deformation, the KAM value for austenite surpasses that of ferrite. In the initial stage of deformation, the type of grain boundaries in both phases remains largely unaltered. However, in the later stages of deformation, there is a marked increase in the number of small-angle grain boundaries within ferrite, which become approximately three times that of the large-angle grain boundaries. As deformation progresses, the maximum orientation distribution density of the ferrite phase is reduced by approximately 50%, with the preferred orientation shifting from the {100} plane to the {111} plane. In contrast, the orientation distribution of the austenite remains relatively uniform, with no significant change in the maximum orientation distribution density observed. This indicates that after substantial deformation, the rotation of ferrite grains significantly increases the deformation resistance, whereas the austenite phase continues to harden. This differential behavior leads to the continuous accumulation of strain at the phase boundaries, ultimately causing cracks to form at these boundaries and resulting in the sample’s fracture. Full article