Changjiang Water Resources Commission

ABSTRACT Quantifying flow resistance in open channels with mixed‐height vegetation is essential for predicting stage–discharge relationships and assessing conveyance and habitat conditions in vegetated floodplains. In staggered tall–short vegetation, strong lateral velocity contrasts and inter‐patch momentum transfer alter the flow structure and hinder the direct use of conventional roughness formulations. Based on flume experiments with rigid cylindrical surrogates arranged as laterally adjacent tall and short patches in a staggered layout, this study develops a physics‐based procedure to estimate the drag coefficient and the equivalent Manning coefficient across emergent to submerged conditions. A two‐patch momentum‐balance model is formulated by explicitly accounting for the measured water‐surface slope, vegetation drag within each patch and an apparent shear stress representing interfacial momentum exchange between the tall and short patches. Closed‐form expressions are then derived to invert patch‐averaged drag coefficients from readily measurable hydraulic variables and flow‐facing area metrics, providing a tractable alternative to purely empirical calibration. The analytically inverted drag coefficients are further consolidated with literature data recast under consistent definitions of Reynolds number and a density descriptor, yielding an empirical predictor C d ( R e, λ ) for rigid vegetation in staggered canopies. Finally, a practical linkage between the mean vegetation drag coefficient and Manning coefficient is established by incorporating vegetation area density and hydraulic‐radius scaling, enabling computation of an equivalent Manning coefficient for mixed‐height, staggered vegetation within the tested parameter range. The proposed framework offers a parameter‐consistent basis for resistance estimation in laterally heterogeneous vegetated channels and supports hydraulic assessment and management of vegetated floodplains.

Evaluating the quality of synthesized maps remains a critical challenge in generative cartography. Prevailing methods rely on pixel-wise computer vision metrics (e.g., PSNR, SSIM). However, these metrics prioritize low-level signal fidelity over high-level geographical logic features and treat pixels as independent units, which prevents them from capturing the complex topological interdependencies and global semantics inherent in maps. Consequently, they inadequately assess essential cartographic features and spatial relationships, often producing outputs with semantic and structural artifacts. To address this limitation, we introduce the map feature perception (MFP) metric, a novel approach that quantifies disparities in high-level cartographic structures and spatial configurations. Unlike pixel-based comparisons, MFP extracts deep elemental-level features to encode cartographic structural integrity and topological relationships comprehensively. Experimental validation demonstrates MFP’s superior capability in evaluating cartographic semantics. Furthermore, when implemented as a loss function, our MFP-based objective consistently outperforms conventional loss functions across diverse generative frameworks and benchmarks. Our findings establish that explicitly optimizing for cartographic features and spatial coherence is crucial for enhancing the geographical plausibility of synthesized maps.

Research on the dynamics and driving mechanisms of submerged macrophytes communities during the natural restoration period of lakes with different trophic level remains relatively scarce. This study aims to investigate the structural characteristics of submerged macrophytes communities and their coupling relationships with environmental factors in urban lakes of varying trophic states in Wuhan during a natural restoration phase. Six lakes in Wuhan (comprising two mesotrophic, two light-eutrophic, and two medium-eutrophic lakes) were selected as study areas. Simultaneous monitoring of submerged macrophytes and aquatic environmental factors was conducted from August 2023 to April 2024. The results showed that a total of eight submerged macrophytes species were recorded, with Vallisneria natans, Myriophyllum spicatum, and Hydrilla verticillata identified as dominant species. As trophic levels decreased, the species richness, biomass, and diversity indices of submerged macrophytes significantly increased, whereas community structure became more stable. PCoA analysis revealed distinct community differentiation among lakes with different trophic states. The trophic levels of the lakes determined the key environmental factors influencing submerged macrophytes: biomass in mesotrophic lakes was primarily associated with water temperature (WT) and turbidity (Turb); in light-eutrophic lakes, the dominant factors shifted to chemical oxygen demand and nitrate; in medium-eutrophic lakes, Turb and dissolved oxygen exerted strong constraints. Plant co-occurrence network analysis indicated that interspecific interactions within the community appeared to be dominated by competition, which may result in a relatively loose network structure. Random forest models identified nitrogen as the core driver. Structural equation modeling further confirms that nutrients exert a direct negative effect on submerged macrophytes biomass by increasing Turb and chlorophyll a (path coefficient = -0.629), while WT exhibits a positive effect (0.454). This study enhances our understanding of the response patterns of submerged macrophyte communities in urban lakes during natural recovery to trophic levels and environmental factors, highlighting the key roles of nitrogen control and improved physico-hydrological conditions in promoting the recovery of submerged macrophytes. These findings provide theoretical support for adaptive management strategies in the ecological restoration of eutrophic lakes.

This study investigates the performance and microstructure evolution of high-ferrite Portland cement (HFC) concrete under the coupled action of abrasion and freeze-thaw cycles (CAA-FTC). The 3D surface morphology of deteriorated concrete was studied; abrasion depth and volume loss evolution data were collected, while analyzing the abrasion depth fractal dimension. The characteristics of hydration products were determined using mercury intrusion porosimetry and 29Si nuclear magnetic resonance method. The ITZ's micromechanical properties and thickness were investigated via nanoindentation and SEM-EDS. The results show that under the CAA-FTC conditions, concrete deterioration is significantly exacerbated, leading to increased abrasion depth and volume loss compared to single-factor abrasion. A significant inverse relationship between the abrasion depth fractal dimension and abrasion resistance was revealed. Under CAA-FTC conditions, CG1 and CD1 exhibit increased total porosity with enlarged large pore proportions and reduced medium pores, whereas HFC1 outperforms HFC2-based concrete, showing 8.2-26.4% higher abrasion resistance and 6.5-12.0% greater nanoindentation elastic modulus in the ITZ. Regarding the deterioration factors' influence weight, abrasion time exhibits a deterioration weight 4.8 times to 10.0 times greater than freeze-thaw cycling, making the former a dominant factor and the latter a secondary contributor. Mechanistically, freeze-thaw cycles reduce the average molecular chain length of C-S-H gel, increase harmful pores and total porosity, and degrade the ITZ's microstructure, while abrasion causes surface-to-core physical damage and freeze-thaw cycling induces core-to-surface expansive damage. This interaction results in surface scaling, mortar spalling, and structural loosening, significantly reducing physical and mechanical properties of the concrete under study.