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Abstract [Objective] The Yarlung Zangbo River is the most important river in the Tibetan Plateau, and the study of aboveground biomass and species diversity of the Yarlung Zangbo River is of great significance for the understanding of grassland resources and ecological conservation in the region. [Methods] This study investigated the characteristics of vegetations along elevation gradients in the alpine meadows in the upper reaches of the Yarlung Zangbo River, the distributional differences of aboveground biomass and species diversity along the gradients, and the relationship between aboveground biomass and species diversity. We also studied the effects of environmental factors on aboveground biomass and species diversity. [Results] (1) There was no significant relationship between aboveground biomass and elevation, temperature and precipitation (P >0.05). (2) Species diversity indices showed a significant negative correlation with elevations, and the Shannon-Weiner index (H ) and Patrick index (R) showed a declining trend with elevation. Species diversity showed a significant positive correlation with temperature and precipitation (P

In order to explore the influence of magnetron sputtering process parameters on the corrosion resistance and high-temperature oxidation resistance of CoCrFeNiCu coatings, the coatings were prepared by DC magnetron sputtering with different sputtering powers (50, 100, 150, and 200 W). The phase compositions, microstructures, and corrosion resistance of the coatings were tested using X-ray diffraction, scanning electron microscopy, energy spectrum analysis, and electrochemical experiments. The high-temperature oxidation resistance of the coatings was measured using the cyclic oxidation method. The influence of sputtering power on the high-temperature oxidation resistance of the coating was explored by analyzing its oxidation kinetics curve and the surface morphology of the oxide layer. The results showed that the coating prepared with the sputtering power of 50 W had a quasi-amorphous structure and better corrosion resistance. However, with the increase in sputtering power, the coating grains became coarser gradually, and its corrosion resistance decreased. The oxidative kinetic curves of the coatings prepared at the lower power increased roughly linearly with oxidation time at 800 ℃ in the air, and an amount of pores appeared on the surface of the oxide layer, which weakened the oxidation resistance of the coating. The oxidation kinetic curves of coatings prepared at the higher power presented a parabolic change, and the formed oxide layers became relatively dense, which could effectively protect the coatings. Therefore, the larger thickness and the higher hardness of the CoCrFeNiCu coating with an FCC solid solution prepared at the higher sputtering power are beneficial for improving the oxidation resistance of the coatings at elevated temperature.

In order to obtain titanium alloys with better mechanical properties, Ti-Ta-Mo alloys with different element contents were obtained by spark plasma sintering with the addition of β -phase stable elements Ta and Mo to Ti. The effects of sintering temperature and the content of Ta and Mo elements on the microstructure and mechanical properties of the alloy were systematically studied. The results show that the microstructure of Ti-Ta-Mo alloy is mainly composed of α-Ti phase and β-Ti phase. With the increase of sintering temperature, the β phase in the alloy increases gradually. With the increase of Ta and Mo contents, the content of β phase in the alloy increases and the grain size decreases. When the sintering temperature is 1 250 ℃ and the Ta and Mo content (mass fraction) is 16%, the hardness and density of the alloy are higher. The compressive strength and yield strength of Ti-Ta-Mo alloy increase with the increase of sintering temperature and β -phase stable elements, while the elastic modulus shows an opposite trend.

In order to study the effects of different sintering temperatures and heat treatment on the microstructure and properties of copper alloys, TiH2/Ti-doped Cu-Y2O3 composite powders were prepared by high-energy ball milling in this paper. After pressing-sintering-heat treatment, copper matrix composites were obtained. The microstructure of the composite was characterized by optical microscope (OM) and scanning electron microscope (SEM), and Vickers hardness tester was used to test its hardness and eddy current conductivity tester. The results show that after high-energy ball milling and mixed powder, elements Y, Ti and O are evenly distributed on the surface of the composite powder. The sintering temperature and heat treatment has an important influence on the microstructure and properties of TiH2/Ti-doped Y2O3 reinforced copper-based composites. The TiH2/Ti-doped Y2O3 reinforced copper matrix composites achieved the excellent properties after sintering at 850 ℃ for 2 h and aging at 450 ℃ for 3 h. The electrical conductivity and hardness of TiH2-doped Y2O3 reinforced copper-based composites are 86.9% IACS and 70.1 HV respectively, and the electrical conductivity and hardness of Ti-doped Y2O3 reinforced copper-based composites are 76.8% IACS and 73.6 HV.