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The basalt-fiber-reinforced copper-matrix composites were fabricated using spark plasma sintering. The effect of basalt fiber content on the mechanical and tribological properties of copper-matrix composites was investigated. The results show that the relative density decreased, the hardness increased and the tensile strength first increased and then decreased with the increase in fiber content. The optimal tensile strength of 276 MPa was obtained when the content of basalt fiber was 1.5 wt.%. The friction coefficient of the composites decreased, and the wear volume first decreased and then increased with the increase in the fiber content. The addition of basalt fibers reduced the plastic deformation of the copper matrix during the friction test due to its strengthening effect. Moreover, the detached basalt fibers from the Cu matrix were ground into fine particles and were helpful for forming a mechanical mixing layer, which can decrease the friction coefficient of composites. [ABSTRACT FROM AUTHOR]

Soil-dissolved organic matter (DOM) drives the carbon (C) and nitrogen (N) cycles in agroecosystems. Despite many studies on DOM dynamics, hardly any attention has been directed toward DOM quality, particularly DOM composition. The aim of this study was to elucidate how C and N management practices alter soil water-extractable organic matter (WEOM) in a loess soil agroecosystem. Field experiments were conducted with a winter wheat monoculture. Three N fertilization rates (0, 120, and 240 kg ha−1 year−1) were applied for 17 years (2002–2019), combined with five C practices (zero, low, and high rates of sheep manure or wheat straw) for three years (2016–2019). The results reveal that soil organic carbon (SOC) and water-extractable organic carbon (WEOC) concentrations in the topsoil (0–20 cm) were increased by organic amendments considerably but were not affected by N fertilization. The fluorescence excitation–emission matrix spectra (EEM) of WEOM were resolved to two humic-like components (C1 and C2) and two soluble microbial byproduct-like components (C3 and C4). The proportions of C1 and C2 were increased, while the proportion of C3 was decreased by both C and N management practices. In conclusion, organic amendments increased both WEOM quality and its proportion of humic-like components, whereas N fertilization increased the proportion of humic-like components without variations of WEOM quality in the topsoil of loess soil. [ABSTRACT FROM AUTHOR]