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881.
《Journal of Manufacturing Processes》2014,16(2):335-343
Unsatisfactory corrosion resistance is one of the major disadvantages of magnesium alloys that impede their wide application. Microstructural changes, especially grain sizes, of Mg alloys have significant influence on their corrosion resistance. Cryogenic machining was reported to effectively induce grain refinement on Mg alloys and has a potential to improve their corrosion resistance. It is important to model these changes so that proper machining conditions can be found to enhance the corrosion rate of Mg alloys. In this paper, a preliminary study was conducted to model the microstructural changes of AZ31B Mg alloy during dry and cryogenic machining using the finite element (FE) method and a user subroutine based on the dynamic recrystallization (DRX) mechanism of Mg alloys. Good agreement in terms of grain size and affected layer thickness was found between experimental and predicted results. A numerical study was conducted using this model to investigate the influence of rake angle on microstructural changes after cryogenic machining. 相似文献
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883.
Particulate pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. Urban plants play an important role in reducing particulate pollution. Physicochemical characteristics of ambient particles settling upon leaf surfaces of eleven roadside plants at four sites of Beijing were studies. Results showed that density of particles on the leaf surfaces greatly varied with plant species and traffic condition. Fraxinus chiuensis, Sophora japonica Ailanthus altissima, Syringa oblata and Prunus persica, had larger densities of particles among the tall species. Due to resuspension of road dust, the densities of particles of Euonymus japonicns and Parthenocissus quinquefolia with low sampling height were 2-35 times to other taller tree species. For test plant species, micro-roughness of leaf surfaces and density of particles showed a close correlation. In general, the larger micro-roughness of leaf surfaces is, the larger density of particles is. Particles settling upon leaf surfaces were dominantly PM30 （particulate matter less than 10 μm in aerodynamic diameter; 98.4%） and PM2.5 （particulate matter less than 2.5 μm in aerodynamic diameter; 64.2%） which were closely relative to human health. Constant elements of particles were C, O, K, Ca, Si, Al, Mg, Na, Fe, S, Cl and minerals with higher content were SiO2, CaCO3, CaMg（CO3）2, NaCI and 2CASO4. H2O, SiO2. CaCO3 and CaMg（CO3）2 mainly came from resuspension of road dust. 2CaSO4. H2O was produced by the reaction between CaCO3 derived from earth dust or industrial emission and SO2, H2SO4 or sulfate. NaCl was derived from sea salt. 相似文献
884.
ＩｎｔｒｏｄｕｃｔｉｏｎＭａｎｄｉｒｔｉｅｓｔｈｅａｉｒｗｉｔｈｇａｓａｎｄｓｍｏｋｅ ,ｐｏｉｓｏｎｓｔｈｅｗａｔｅｒｗｉｔｈｃｈｅｍｉｃａｌｓａｎｄｏｔｈｅｒｓｕｂｓｔａｎｃｅｓ,ａｎｄｄａｍａｇｅｓｔｈｅｓｏｉｌｗｉｔｈｔｏｏｍａｎｙｆｅｒｔｉｌｉｚｅｒｓａｎｄｐｅｓｔｉｃｉｄｅｓ .Ｐｅｏｐｌｅｒｕｉｎｔｈｅｅａｒｔｈ’ｓｎａｔｕｒａｌｂｅａｕｔｙｂｙｓｃａｔｔｅｒｉｎｇｊｕｎｋａｎｄｌｉｔｔｅｒｏｎｔｈｅｌａｎｄａｎｄｉｎｔｈｅｗａｔｅｒ.Ｔｈｅｂａｄｌｙｐｏｌｌｕｔｅｄａｉｒｃａｎｃａｕｓ… 相似文献
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886.
887.
道路交通环境影响评价的物元模型 总被引：5，自引：0，他引：5
分析了城市道路交通环境影响因素,提出了一套道路交通环境影响评价指标体系,并应用物元分析理论建立了相应的评价物元模型 相似文献
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890.