Search Results (64)

While size effects in composite structures have been widely studied under quasi-static uniaxial loading, their influence under fatigue conditions, particularly in the presence of multiaxial stress states and elevated temperatures, remains insufficiently understood. This study investigates the fatigue behaviour of thick-walled $\pm {45}^{\circ }$ braided glass fibre-reinforced polyurethane composite box structures under varying temperature and loading conditions. A combined experimental approach is adopted, coupling quasi-static and fatigue tests on large-scale structures with reference data from standardised coupon specimens. The influence of temperature (23–80 °C) and multiaxial shear–compression loading is systematically evaluated. The results demonstrate a significant temperature-dependent decrease in compressive strength and fatigue life, with a linear degradation trend that aligns closely between the box structure and coupon data. Under moderate multiaxial conditions, the fatigue life of box structures is not significantly impaired compared to uniaxial test coupon specimens. Complementary non-destructive testing using air-coupled ultrasound confirms these trends, demonstrating that guided-wave phase-velocity measurements capture the evolution of anisotropic damage and are therefore suitable for in situ structural health monitoring applications. Furthermore, these findings highlight that (i) the temperature-dependent fatigue behaviour of thick-walled composites can be predicted using small-scale coupon data and (ii) small shear components have a limited impact on fatigue life within the studied loading regime. Full article

The Nam Phong Formation, a key unit of the pre-Khorat Group in the western Khorat Plateau, provides critical insights into the Mesozoic geological evolution of northeastern Thailand. This study presents the first integrated petrographic and geochemical investigation of the formation within Khon Kaen Geopark to reconstruct its Late Triassic–Early Jurassic depositional settings, provenance, and paleoclimate. A detailed stratigraphic section and five supplementary sites reveal litharenite and lithic wacke sandstones, interbedded with red paleosols and polymictic conglomerates. Sedimentary structures—such as trough and planar cross-bedding, erosional surfaces, and mature paleosols—indicate deposition in a high-energy braided fluvial system under semi-arid to subhumid conditions with episodic subaerial exposure. Petrographic analysis identifies abundant quartz, feldspar, and volcanic lithic fragments. Geochemical data and REE patterns, including diagnostic negative Ce anomalies, provide compelling evidence for provenance from active continental margins and oxidizing weathering conditions. These findings point to a tectonically active syn-rift basin influenced by climatic variability. Strikingly, the Nam Phong Formation exhibits paleoenvironmental and sedimentological features comparable to the modern Ebro Basin in northeastern Spain, highlighting the relevance of uniformitarian principles in interpreting ancient continental depositional systems. Full article

Riverbed dynamics are natural processes that are strongly driven by human and climatic factors. In the last two centuries, the anthropogenic influence and impact of climate change on European rivers has resulted in significant degradation of riverbeds. This research paper aims to determine the historical evolution (1856–2021) and future trends of the Ialomița riverbed (Romania) under the influence of anthropogenic impact and climate change. The case study is a reach of 66 km between the confluences with the Ialomicioara and Pâscov rivers. The localisation in a contact zone between the Curvature Subcarpathians and the Târgoviște Plain, the active recent tectonic uplift of the area, and the intense anthropogenic intervention gives to this river reach favourable conditions for pronounced riverbed dynamics over time. To achieve the aim of the study, we developed a complex methodology which involves the use of Geographical Information System (GIS) techniques, hierarchical cluster analysis (HCA), the Mann–Kendall test (MK), and R programming. The results indicate that the evolution of the Ialomița River aligns with the general trends observed across Europe and within Romania, characterised by a reduction in riverbed geomorphological complexity and a general transition from a braided, multi-thread into a sinuous, single-thread fluvial style. The main processes consist of channel narrowing and incision alternating with intense meandering. However, specific temporal and spatial evolution patterns were identified, mainly influenced by the increasingly anthropogenic local influences and confirmed climate changes in the study area since the second half of the 20th century. Future evolutionary trends suggest that, in the absence of river restoration interventions, the Ialomița riverbed is expected to continue degrading on a short-term horizon, following both climatic and anthropogenic signals. The findings of this study may contribute to a better understanding of recent river behaviours and serve as a valuable tool for the management of the Ialomița River. Full article

The Lower–Middle Jurassic of the Kuqa Depression consists of terrestrial clastic deposits containing coal seams and thick lacustrine mudstones, and is of great significance for oil and gas exploration. Based on the comprehensive analysis of core, well-logging, outcrop, and seismic data, the sequence stratigraphy, depositional systems, and the controlling factors of the basin filling in the depression are systematically documented. Four primary depositional systems, including braided river delta, meandering river delta, lacustrine, and swamp deposits, are identified within the Ahe, Yangxia, and Kezilenuer Formations of the Lower–Middle Jurassic. The basin fills can be classified into two second-order and nine third-order sequences (SQ1–SQ9) confined by regional or local unconformities and their correlative conformities. This study shows that the sedimentary evolution has undergone the following three stages: Stage I (SQ1–SQ2) primarily developed braided river, braided river delta, and shallow lacustrine deposits; Stage II (SQ3–SQ5) primarily developed meandering river, meandering river delta, and extensive deep and semi-deep lacustrine deposits; Stage III (SQ6–SQ9) primarily developed swamp (SQ6–SQ7), meandering river delta, and shore–shallow lacustrine deposits (SQ8–SQ9). The uplift of the Tianshan Orogenic Belt in the Early Jurassic (Stage I) may have facilitated the development of braided fluvial–deltaic deposits. The subsequential expansion of the sedimentary area and the weakened sediment supply can be attributed to the planation of the source area and widespread basin subsidence, with the transition of the depositional environments from braided river delta deposits to meandering river delta and swamp deposits. The regional expansion or rise of the lake during Stage II was likely triggered by the hot and humid climate conditions, possibly associated with the Early Jurassic Toarcian Oceanic Anoxic Event. The thick swamp deposits formed during Stage III may be controlled by the interplay of rational accommodation, warm and humid climatic conditions, and limited sediment supply. Milankovitch cycles identified in Stage III further reveal that coal accumulation was primarily modulated by long-period eccentricity forcing. Full article

Evaluating how dams modify hydrological regimes and their long-term impacts on riverine ecosystems is critical. This study evaluated trends and change points in Fractional Vegetation Cover (FVC) of braided riverbanks downstream of the Xiaolangdi Dam (1990–2020) using time-series decomposition and structural breakpoint analysis. Distinct temporal periods corresponding to different dam construction and operational phases were identified. Partial correlation analysis and linear mixed-effects modeling were employed to elucidate the spatiotemporal linkages between FVC and key driving factors. The results identified 1997 and 2004 as significant change points in FVC, corresponding to the dam’s construction and initial interception in 1997, and its subsequent comprehensive water and sediment regulation from 2004 onwards, respectively. Although dam construction may have initially posed short-term challenges to downstream vegetation, the post-operational phase witnessed a notable increase in significant vegetation growth compared to the pre-dam period, primarily attributed to the altered hydrological conditions. Notably, the dam operation’s contribution to the total FVC increase was 56% in the near-dam Xiaolangdi–Jiahetan reach. The analysis revealed distinct differences in vegetation responses to these hydrological alterations between the upstream Xiaolangdi–Jiahetan and downstream Jiahetan–Gaocun river sections, with the latter demonstrating greater ecological sensitivity to the dam-induced hydrological changes. Full article

Background: Venous sinus stenting is a promising treatment for intracranial venous disorders, such as idiopathic intracranial hypertension and pulsatile tinnitus, associated with transverse sinus stenosis. The VIVA Stent System (VSS) is a novel self-expanding braided venous stent designed to navigate tortuous cerebral venous anatomy. This preclinical study assessed the safety, thrombogenicity, and performance of the VSS in a swine model. Methods: Fifteen swine underwent bilateral internal mammary vein stenting with either the VSS (n = 9) or the PRECISE^® PRO RX stent (n = 6, reference). Fluoroscopy and thrombogenicity assessments were conducted on the day of stenting, clinical pathology analysis was carried out throughout the in-life phase, and CT Venography was performed before sacrifice. Animals were sacrificed at 30 ± 3 or 180 ± 11 days post-stenting for necropsy and histological evaluation. Results: Fluoroscopic angiography confirmed the successful VSS deployment with complete venous wall apposition and no vessel damage. The VSS achieved the highest scores on a four-point Likert scale for most performance parameters. No thrombus formation was observed on either delivery system. CT Venography confirmed vessel patency, no stent migration, and complete stent integrity. Histopathology showed a mild, expected foreign body reaction at 30 days, which resolved by 180 days, indicating normal healing progression. Both stents showed increased luminal diameter and decreased wall thickness at 180 days, suggesting vessel recovery. No adverse reactions were observed in non-target organs. Conclusions: The VSS exhibited favorable safety, procedural performance, and thromboresistance in a swine model, supporting its potential clinical use for treating transverse sinus stenosis and related conditions. Full article

Using low-cost transition-metal chlorides and furfuryl alcohol as raw materials, the (TiZrHfNbTa)C precursor was prepared, and a three-dimensional braided carbon fiber preform (C/C) coated with pyrolytic carbon (PyC) was used as the reinforcing material. A C/C-(TiZrHfNbTa)C composite was successfully fabricated through the precursor impregnation pyrolysis (PIP) process. Under extreme oxyacetylene ablation conditions (2311 °C/60 s), this composite material demonstrated outstanding ablation resistance, with a mass ablation rate as low as 0.67 mg/s and a linear ablation rate of only 20 μm/s. This excellent performance can be attributed to the dense (HfZr)₆(TaNb)₂O₁₇ oxide layer formed during ablation. This oxide layer not only has an excellent anti-erosion capability but also effectively acts as an oxygen diffusion barrier, thereby significantly suppressing further ablation and oxidation within the matrix. This study provides an innovative strategy for the development of low-cost ultra-high-temperature ceramic precursors and opens up a feasible path for the efficient preparation of C/C-(TiZrHfNbTa)C composites. Full article

Accurate remote sensing identification of river ice not only provides scientific evidence for climate change but also offers early warning information for disasters such as ice jams. Currently, many researchers have used remote sensing index-based methods to identify river ice in alpine regions. However, in high-altitude areas, these index-based methods face limitations in recognizing river ice and distinguishing ice-snow mixtures. With the rapid advancement of machine learning techniques, some scholars have begun to use machine learning methods to extract river ice in northern latitudes. However, there is still a lack of systematic studies on the ability of machine learning to enhance river ice identification in high-altitude, complex terrains. The study evaluates the performance of machine learning methods and the RDRI index method across six aspects: river type, altitude, river width, ice periods, satellite data, and snow cover interference. The results show that machine learning, particularly the RF method, demonstrates superior generalization ability and higher recognition accuracy for river ice in the complex high-altitude terrain of the Tibetan Plateau by leveraging a variety of input data, including spectral and topographical information. The RF model performs best under all types of test conditions, with an average Kappa coefficient of 0.9088, outperforming other machine learning methods and significantly outperforming the traditional exponential method, demonstrating stronger recognition capabilities. Machine learning methods are adaptable to different types of river ice, showing particularly improved recognition of river ice in braided river systems. RF and SVM exhibit more accurate river ice recognition across different altitudinal gradients, with RF and SVM significantly improving the identification accuracy of river ice (0–90 m) on the plateau. RF and SVM methods offer more precise boundary recognition when identifying river ice across different ice periods. Additionally, RF demonstrates better generalization in the transfer of multisource satellite data. RF’s performance is outstanding under different snow cover conditions, overcoming the limitations of traditional methods in identifying river ice under thick snow. Machine learning methods, which are well suited for large sample learning and have strong generalization capabilities, show significant potential for application in river ice identification within high-altitude, complex terrains. Full article

Springs are widely used in industries such as aerospace and automotive. As the demand for emission reduction grows, the research on lightweight spring performance is becoming increasingly important. This study analyses the mechanical performance of triple-layer braided composite helical springs (TCHS) under various loads and compression angles. Firstly, the optimal high-temperature curing condition of the epoxy resin was determined through tensile and three-point bending analysis. Then, TCHS were fabricated based on optimal epoxy curing conditions, and multi-angle compression tests under different loads were carried out. Simultaneously, strain gauges were installed at various positions and orientations on the inner and outer sides of the spring wire to reveal strain patterns during the compression. The test results indicate that stiffness decreases with increasing compression angle. Additionally, the strain in the inner and outer positions in different directions of the same region increased with the rise in compression force and angle, and strains in the helical direction were the largest. Subsequently, strain in the helical direction across different regions further showed that maximum strain occurred in the centre coil (region 2), with inner and outer helical direction strains reaching −5116.89 με and 5700.15 με, respectively, which are 71.3% and 90.4% higher than those in region 1 and 73.2% and 92.9% higher than those in region 3. As the compression load increased, cracks appeared on the outer side of the centre coil. In addition, the crack was perpendicular to the helical direction, further confirming that the highest strain occurred in the helical direction. This study provides an in-depth analysis of the impact of angle-specific loads on TCHS, offering valuable insights for the design and optimisation of composite helical springs and laying a theoretical foundation for their future development. Full article

This study investigates the effect of hygrothermal environments on the compressive properties of three-dimensional four-directional braided composites through experiments and finite element simulations, revealing the degradation behavior under various hygrothermal conditions. The results indicate that the moisture absorption behavior of the material conforms to Fick’s law. The longer the hygrothermal aging duration and the higher the temperature, the more significant the reduction in compressive performance, as evidenced by the continuous decline in ultimate stress. The hygrothermal environment primarily affects material performance through moisture absorption and thermal expansion characteristics of the epoxy resin, while the carbon fibers exhibit high stability in such conditions, maintaining the integrity of the three-dimensional four-directional structure. Microscopic observations reveal that hygrothermal aging exacerbates damage at the resin–fiber interface, leading to more pronounced stress concentration. Finite element simulations further quantify the internal stress distribution under hygrothermal conditions, demonstrating that moisture-induced expansion stress is more significant than thermal expansion stress, providing theoretical support and design guidance for improving the performance of composites in extreme environments. Full article

Recent breakthrough exploration wells in the Huagang Formation in the Y-area of the central anticlinal zone of the Xihu Sag have confirmed the significant exploration potential of structure–lithology complex hydrocarbon reservoirs. However, limited understanding of the provenance system, sedimentary facies, and microfacies has hindered further progress in complex hydrocarbon exploration. Analysis of high-precision stratigraphic sequences and seismic facies data, mudstone core color, grain-size probability cumulative curves, core facies, well logging facies, lithic type, the heavy-mineral ZTR index, and conglomerate combinations in drilling sands reveals characteristics of the source sink system and provenance direction. The Huagang Formation in the Y-area represents an overall continental fluvial delta sedimentary system that evolved from a braided river delta front deposit into a meandering river channel large-scale river deposit. The results indicate that the primary provenance of the Huagang Formation in the Y-area of the Xihu Sag is the long-axis provenance of the Hupi Reef bulge in the northeast, with supplementary input from the short-axis provenance of the western reef bulge. Geochemical analysis of wells F1, F3, and G in the study area suggests that the prevailing sedimentary environment during the period under investigation was characterized by anoxic conditions in nearshore shallow waters. This confirms previous research indicating strong tectonic reversal in the northeast and a small thickness of the central sand body unrelated to the flank slope provenance system. The aforementioned findings deviate from conventional understanding and will serve as a valuable point of reference for future breakthroughs in exploration. Full article

As the threat of unstable braided river geomorphology to the resilience of local communities grows, a better understanding of the morphological changes in a river subject to climate is essential. However, little research has focused on the long-term planform change of the braided reaches and its response to hydrological changes. The reach around Majuli Island (Majuli Reach), the first and typical braided reach of the Brahmaputra River emerging from the gorge, experiences intense geomorphological change of the channels and loss of riparian area every year due to the seasonal hydrological variability. Therefore, focusing on the Majuli Reach, we quantitatively investigate changes in its planform morphology from 1990 to 2020 using remote sensing images from the Landsat dataset and analyze the influence of discharge in previous years on channel braiding. The study shows that the Majuli Reach is characterized by a high braiding degree with an average Modified Plan Form Index (MPFI) of 4.39, an average reach width of 5.58 km, and the development of densely migrating bars and active braided channels. Analysis shows a control point near Borboka Pathar with little morphological change, and the braided channel shows contrasting morphological changes in the braiding degree, bars, and main channel between the reach upstream and downstream of it. The area of the riparian zone of the Majuli Reach decreased by more than 50 km² during the study period due to migration of the main channel toward the island. The braiding degree of Majuli Reach is positively correlated with the discharge in previous years, with the delayed response time of the MPFI to discharge being just 3–4 years, indicating the unstable feature of the Majuli Reach with varied hydrology conditions. Full article

A critical challenge in wearable electrothermal textiles is achieving effective insulation while maintaining sheath flexibility, which is essential for enhancing the mechanical properties and durability of conductive materials under everyday conditions, such as washing, stretching, and twisting. In this work, we employ a coaxial tubular braiding technique to coat a high-conductivity carbon nanotube (CNT) yarn with a high-strength insulation layer made of ultra-high-molecular-weight polyethylene (UHMWPE) multifilaments, resulting in a core–sheath-structure CNT yarn with excellent electrothermal performance. By adjusting the number of UHMWPE multifilaments and the sheath braiding angle, we achieve high flexibility, high tensile strength, and abrasion and wash resistance, as well as improved electrical stability for the CNT yarns. Additionally, the CNT yarns with an insulation layer effectively prevent short-circuiting during use and achieve superior thermal management, with a significant increase in steady-state temperature under operational conditions, exhibiting significant potential for applications in wearable electronic devices. Full article

The River Ter is one of the axes which, in a west-east direction, has historically articulated the population of the extreme north-east of the Iberian Peninsula. Although its upper, middle and part of the lower courses do not present any problems in its course, its mouth in the Mediterrane-an Sea has raised many questions due to the existence of two potential branches, one to the north that would flow into the Gulf of Roses and another to the south that would flow into the Bay of Pals. In 2016, an exhaustive documentary study on the potential southern branch provided exhaustive information on the existence of lake areas and their relationship with the settlement between the 9th and 11th centuries, but raised doubts about the existence of the river in the bay from Pals. Subsequently, between 2020 and 2022, geological studies have been carried out in this area which demonstrate the existence of the river in this area but with a variable course, with changes in the river channel (meandering, diffuse and braided), and with notable changes that conditioned the settlement of this sector of the coast and as was recorded in written documentation between the 9th and 11th centuries. Full article

This manuscript presents set-theoretical solutions to the Yang–Baxter equation within the framework of GE-algebras by constructing mappings that satisfy the braid condition and exploring the algebraic properties of GE-algebras. Detailed proofs and the use of left and right translation operators are provided to analyze these algebraic interactions, while an algorithm is introduced to automate the verification process, facilitating broader applications in quantum mechanics and mathematical physics. Additionally, the Yang–Baxter equation is applied to spin transformations in quantum mechanical spin-${\displaystyle \frac{1}{2}}$ systems, with transformations like rotations and reflections modeled using GE-algebras. A Cayley table is used to represent the algebraic structure of these transformations, and the proposed algorithm ensures that these solutions are consistent with the Yang–Baxter equation, offering new insights into the role of GE-algebras in quantum spin systems. Full article