Shenzhen Metro (China)

The long-term durability of hydraulic concrete infrastructure is severely compromised by water penetration, carbonation, and chloride ion erosion, necessitating the development of high-performance protective coatings. This study designed two polyaspartic ester polyurea coatings, PAE-PTMEG and PAE-PPG, derived from isocyanate prepolymers with polytetramethylene ether glycol (PTMEG) and polypropylene glycol (PPG) soft segments, respectively. The results demonstrated that the PTMEG-based prepolymer exhibited higher reactivity, leading to shorter curing times. The resulting PAE-PTMEG coating showed outstanding mechanical properties (tensile strength: 43.8 Mpa; elongation: 646.1%) and excellent water resistance (<1% absorption), attributable to its well-defined microphase-separated structure. When formulated into a practical paint (PAE-C), it surpassed mechanical standards for waterproofing and demonstrated exceptional resistance to chloride ion penetration (1.3 × 10-4 mg·cm-2·d-1), complete carbonation resistance, and high frost resistance (200 cycles). This work confirms that tailoring the soft segment structure is a crucial strategy for developing durable polyurea coatings, with PAE-PTMEG showing significant potential for protecting critical water conservancy infrastructure.

Multimodal object detection utilizing RGB and infrared (IR) imagery has become a critical research area for unmanned aerial vehicle (UAV) surveillance applications, providing reliable perception under various lighting and environmental conditions. Nevertheless, current methods encounter three primary challenges: (1) insufficient utilization of frequency-domain properties in heterogeneous modalities, (2) restricted adaptability in crossmodal feature integration across different environmental scenarios, and (3) inadequate modeling of fine-grained spatial relationships for accurate object localization. To overcome these limitations, we introduce MFE-DETR, a novel Multimodal Feature-Enhanced Detection Transformer that achieves superior RGB-IR fusion through three complementary innovations. First, we present the Dual-Modality Enhancement Module (DMEM) with two specialized processing streams: the Haar wavelet decomposition stream (HWD-Stream) that conducts multi-resolution frequency-domain analysis to independently enhance low-frequency structural components and high-frequency textural information, and the Attention-guided Kolmogorov–Arnold Refinement Stream (AKR-Stream) that employs learnable spline-parameterized activation functions for adaptive nonlinear feature refinement. Second, we enhance the Cross-scale Channel Feature Fusion module by integrating an Adaptive Feature Fusion Module (AFAM) with complementary gating mechanisms that dynamically adjust modality contributions according to spatial informativeness. Third, we introduce the Bilinear Attention-Enhanced Detection Module (BADM) that models second-order feature interactions through factorized bilinear pooling, facilitating fine-grained crossmodal correlation analysis. Extensive experiments on the DroneVehicle benchmark show that MFE-DETR attains 78.6% mAP50 and 57.8% mAP50:95, outperforming state-of-the-art approaches by 5.3% and 3.7%, respectively. Additional evaluations on the VisDrone dataset further confirm the excellent generalization performance of our method, especially for small object detection with 18.6% APS, achieving a 1.5% improvement over existing techniques. Comprehensive ablation studies and visualizations offer detailed insights into the effectiveness of each proposed component.

ABSTRACT Existing fiber‐based fire detectors, while capable of rapid response, often suffer from limited flame retardancy and poor long‐term durability. To address these limitations, this work proposes a coaxial MXene fiber (CoaxMXeneFib) inspired by the sunflower stem. It features a polyvinyl alcohol (PVA)/Ti 3 C 2 T x MXene semiconductor core for temperature‐responsive detection, encapsulated by an outer flame‐retardant PVA sheath for protection. By strategically incorporating boric acid as a crosslinker during coaxial wet‐spinning, a gradient interface was formed, enhancing the tensile strength from 0.56 MPa (core only) to 19.9 MPa for CoaxMXeneFib while effectively delaying core oxidation (only 1.23% resistivity increase after 10 days at 80°C). Upon heating, PVA catalyzes MXene oxidation into a C/N‐TiO 2 network, enabling ultrafast fire warning (&lt;2 s), while the generated TiO 2 promotes sheath carbonization, achieving a high limiting oxygen index (LOI) of 44.6%. The fiber demonstrates excellent stability under harsh conditions (acid, alkali, solvent, and UV‐humidity) with only minor performance degradation in alkaline environments. It also maintains stable warning functionality after 15 000 friction cycles, 1000 bending cycles, and 30 washing cycles. Integrating rapid response, high flame retardancy, mechanical robustness, and environmental durability, the CoaxMXeneFib offers a promising solution for next‐generation flexible fire‐safety systems.

To investigate the effects of high humidity on the instantaneous and creep mechanical properties of deep mine pillars, in this study, presandstone samples are subjected to a controlled high-humidity environment in a custom-built simulation apparatus for 180 days. Humidity levels are meticulously set at 70%, 80%, 90%, and 100% relative humidity (RH) to delineate their effects on the specimens. The specimens are exposed to four predetermined humidity levels (70%, 80%, 90%, and 100% RH) and subsequently undergo uniaxial compression strength and creep testing. A constitutive model to assess rock creep damage, incorporating the interactive effects of humidity and stress, is developed based on the established Burgers model. Utilizing scanning electron microscopy and X-ray diffraction analysis, the study examines the impact of high humidity on the damage mechanisms of mechanical properties through microstructural and mineralogical alterations. The findings reveal that (1) under varying humidity conditions, relative to a 70% RH baseline, specimens in a 100% RH environment exhibited a 27.59% reduction in peak strength, a 43.53% decrease in elastic modulus, and an 11.43% increase in Poisson's ratio. (2) The humidity environment significantly influences the creep properties of sandstone, with increasing humidity levels linearly enhancing the initial instantaneous elastic strain of the material. (3) The integration of a viscoelastic component into the creep constitutive equation for rock masses in high-humidity environments compensates for the traditional Burgers model's lack of detail in describing the accelerated creep stage. The theoretical results of the model have a high degree of agreement with the test results and can more accurately reflect the entire process of rock mass creep. (4) Under high-humidity conditions, sandstone undergoes chemical reactions, including dissolution and hydrolysis, which diminish interparticle friction and consequently lead to irreversible damage to the mechanical properties of the rock.

ABSTRACT Current studies predominantly focus on macroscopic tectonic evolution, addressing the scientific challenges of insufficient understanding of the distribution and evolution of bedrock in source areas and unclear mechanisms of proximal sediment supply within regional provenance system research. However, research on the fine classification of bedrock types within source areas and their dynamic linkages with the ‘source‐ to‐sink’ system remains notably inadequate. Based on high‐resolution 3D seismic data, drilling and logging information, this study provides a new case for understanding the distribution patterns and evolution of bedrock in the source area of the ‘source‐sink’ system, as well as a reference for studying depressions that supply sediments in close proximity. Our study demonstrates the following: (1) The Enping‐Yangjiang low uplift area encompasses three bedrock types—granite, volcanic and sedimentary rocks—each corresponding to distinct seismic facies (SF1–SF3). Granite basement is directly intersected by multiple wells; sedimentary rocks exhibit stratified reflection characteristics; whereas volcanic rocks are characterised by a strong reflection envelope with weak, chaotic internal reflections. (2) The distribution of bedrock shows significant zoning. Jurassic granite dominates the main body, sedimentary rocks are concentrated in the northern arcuate fault zone, volcanic rocks are distributed in the southwest and there is a mixed zone of sedimentary and volcanic rocks in the southeast. (3) Governed by diverse tectonic systems, the evolution of bedrock has undergone three stages: compressional uplift during the Late Jurassic–Early Cretaceous, extensional processes in the Late Cretaceous and re‐compressional uplift during the Late Cretaceous–Paleogene. This study clarifies the geological attributes of the Enping‐Yangjiang low uplift area as a hub for proximal sediment supply, with its bedrock distribution pattern and evolutionary stage directly regulating the composition and structure of sediments in surrounding depressions. It provides a replicable research paradigm of ‘source area characterisation‐sink area response’ for provenance analysis in rift basins and has significant guiding implications for predicting hydrocarbon accumulation patterns under similar tectonic settings.

This study presents an eccentric pipe separator (EPS) designed according to the shallow pool principle and Stokes’ law as a compact alternative to conventional gravitational tank separators for offshore platforms. To investigate the internal oil-water flow characteristics and separation performance of the EPS, both field experiments with crude oil on an offshore platform and computational fluid dynamics (CFD) simulations were conducted, guided by dimensional analysis. Crude oil volume fractions were measured using a Coriolis mass flow meter and the fluorescence method. The CFD analysis employed an Eulerian multiphase model coupled with the renormalization group (RNG) k-ε turbulence model, validated against experimental data. Under the operating conditions examined, the separated water contained less than 50 mg/L of oil, while the separated crude oil achieved a purity of 98%, corresponding to a separation efficiency of 97%. The split ratios between the oil and upper outlets were found to strongly influence the phase distribution, velocity field, and pressure distribution within the EPS. Higher split ratios caused crude oil to accumulate in the upper core region and annulus. Maximum separation efficiency occurred when the combined split ratio of the upper and oil outlets matched the inlet oil volume fraction. Excessively high split ratios led to excessive water entrainment in the separated oil, whereas excessively low ratios resulted in excessive oil entrainment in the separated water. Crude oil density and inlet velocity exhibited an inverse relationship with separation efficiency; as these parameters increased, reduced droplet settling diminished optimal efficiency. In contrast, crude oil viscosity showed a positive correlation with the pressure drop between the inlet and oil outlet. Overall, the EPS demonstrates a viable, space-efficient alternative for oil-water separation in offshore oil production.