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The issues about the characterization of rough surfaces are always of concern to tribologist. Because the statistical parameters used conventionally are not ideal to characterize rough surfaces, it is very necessary to investigate the new characterization methods and characterization parameters. In this paper, the fractal geometry is applied, and a roughness parameter called the characteristic fractal parameter τ* is put forth by combining fractal dimension D and scale coefficient C. Its definition, geometric meaning and mathematical express are given. Four surfaces with different roughness formed by turning, milling, grinding and sandpaper polishing machining are characterized with the characteristic fractal parameter τ*. And the results of characterizing these surfaces are compared with that of Ra. It is proved that the characteristic fractal parameter is not only more objective but also more sensitive to characterize rough surfaces than the conventional characterization parameter Ra.

Inappropriate grazing management is one of the most common causes of grassland degradation, and thus, an assessment of soil properties under different grazing intensities is critical for understanding its effects on ecosystem nutrient cycling and for formulating appropriate management strategies. However, the responses of certain main elements, including soil carbon, nitrogen, and phosphorus, to grazing in alpine meadow ecosystems remain insufficiently clarified. Here, we measured carbon, nitrogen, and phosphorus contents in the topmost 30 cm of soil in an alpine meadow under three grazing intensities (light, moderate, and heavy) and found clear differences in soil physical and chemical properties among different grazing intensities and soil layers. As grazing intensity increased, soil water content, carbon and nitrogen contents and stocks, and carbon to phosphorus and nitrogen to phosphorus ratios decreased, whereas soil bulk density increased. However, soil phosphorus and carbon to nitrogen ratio remained stable. Our findings highlight the negative impacts of heavy grazing intensity, in terms of soil carbon and nitrogen loss and phosphorus mineralization. Moreover, we emphasize that further related studies are necessary to gain a more comprehensive understanding of the effects of grazing on grassland ecosystems, and thereby provide information for sustainable management practices and eco-compensation policies.

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