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Modeling grassland net primary productivity and water-use efficiency along an elevational gradient of the Northern Tianshan Mountains 被引量:5
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作者 qifei han GePing LUO +2 位作者 ChaoFan LI Hui YE YaoLiang CHEN 《Journal of Arid Land》 SCIE CSCD 2013年第3期354-365,共12页
Mountainous ecosystems are considered highly sensitive and vulnerable to natural disasters and cli- rnatic changes. Therefore, quantifying the effects of elevation on grassland productivity to understand ecosys- tem-c... Mountainous ecosystems are considered highly sensitive and vulnerable to natural disasters and cli- rnatic changes. Therefore, quantifying the effects of elevation on grassland productivity to understand ecosys- tem-climate interactions is vital for mountainous ecosystems. Water-use efficiency (WUE) provides a useful index for understanding the metabolism of terrestrial ecosystems as well as for evaluating the degradation of grasslands. This paper explored net primary productivity (NPP) and WUE in grasslands along an elevational gradient ranging from 400 to 3,400 m asl in the northern Tianshan Mountains-southern Junggar Basin (TMJB), Xinjiang of China, using the Biome-BGC model. The results showed that: 1 ) the NPP increased by 0.05 g C/(m2-a) with every increase of 1-m elevation, reached the maximum at the mid-high elevation (1,600 m asl), and then decreased by 0.06 g C/(m2.a) per 1-m increase in elevation; 2) the grassland NPP was positively correlated with temperature in alpine meadow (AM, 2,700-3,500 m asl), mid-mountain forest meadow (MMFM, 1,650-2,700 m asl) and low-mountain dry grassland (LMDG, 650-1,650 m asl), while positive correlations were found between NPP and annual precipitation in plain desert grassland (PDG, lower than 650 m asl); 3) an increase (from 0.08 to 1.09 g C/(m2.a)) in mean NPP for the grassland in TMJB under a real climate change scenario was observed from 1959 to 2009; and 4) remarkable differences in WUE were found among different elevations, in general, WUE increased with decreasing elevation, because water availability is lower at lower elevations; however, at elevations lower than 540 m asl, we did observe a decreasing trend of WUE with decreasing elevation, which may be due to the sharp changes in canopy cover over this gradient. Our research suggests that the NPP simulated by Biome-BGC is consistent with field data, and the modeling provides an opportunity to further evaluate interactions between environmental factors and ecosystem productivity. 展开更多
关键词 elevational gradient net primary production water-use efficiency CLIMATE
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2050铝锂合金板材拉伸力学性能三维各向异性
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作者 胡锦龙 邱义 +4 位作者 钱锋 韩启飞 闫杨予 王俊升 郭跃岭 《材料工程》 EI CAS CSCD 北大核心 2023年第9期97-106,共10页
随着铝锂(Al-Li)合金在航空航天领域的应用愈发广泛,对其各向异性研究有助于Al-Li合金的进一步开发利用。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、电子背散射衍射(EBSD)等对T3态2050 Al-Li合金板材进行显微观察... 随着铝锂(Al-Li)合金在航空航天领域的应用愈发广泛,对其各向异性研究有助于Al-Li合金的进一步开发利用。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、电子背散射衍射(EBSD)等对T3态2050 Al-Li合金板材进行显微观察,通过拉伸实验对合金板材轧制方向、垂直轧制方向、厚度方向的拉伸力学性能三维各向异性进行研究。结果表明:T3态2050 Al-Li合金轧制板材轧向中间层强度最高,屈服强度为370 MPa,抗拉强度为465 MPa,而伸长率最小,为9.6%;合金板材横向表面层强度最低,屈服强度为325 MPa,抗拉强度为431 MPa,伸长率最高为19.2%。合金板材不同厚度层断口形貌、晶粒大小不同;2050 Al-Li合金板材不同厚度层各向异性程度不同:0T(表面层)、0.25T(中间层)屈服强度和抗拉强度各向异性强,伸长率各向异性弱;而0.5T(中心层)屈服强度和抗拉强度各向异性弱,伸长率各向异性强。2050 Al-Li合金板材不同厚度层各向异性主要由晶粒取向、织构引起,0T和0.5T厚度层最强织构类型均为{011}〈211〉黄铜织构。 展开更多
关键词 2050Al-Li合金 轧制 力学性能 各向异性 织构
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Comparative Study on Wire-Arc Additive Manufacturing and Conventional Casting of Al–Si Alloys:Porosity,Microstructure and Mechanical Property 被引量:1
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作者 Yueling Guo qifei han +7 位作者 Jinlong Hu Xinghai Yang Pengcheng Mao Junsheng Wang Shaobo Sun Zhi He Jiping Lu Changmeng Liu 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2022年第3期475-485,共11页
Here,we compare the porosity,microstructure and mechanical property of 4047 Al–Si alloys prepared by wire-arc additive manufacturing(WAAM)and conventional casting.X-ray microscopy reveals that WAAM causes a higher vo... Here,we compare the porosity,microstructure and mechanical property of 4047 Al–Si alloys prepared by wire-arc additive manufacturing(WAAM)and conventional casting.X-ray microscopy reveals that WAAM causes a higher volume fraction of gas pores in comparison with conventional casting.Effective refi nements ofα-Al dendrites,eutectic Si particles and Ferich intermetallic compounds are achieved by WAAM,resulting from its rapid solidifi cation process.Both ultimate tensile strength(UTS,up to 205.6 MPa)and yield stress(YS,up to 98.0 MPa)are improved by WAAM at the expense of elongation after fracture.The mechanical property anisotropy between scanning direction and build direction is minimal for alloys via WAAM.Additional microstructure refi nement and strength enhancement are enabled by increasing the travel speed of welding torch from 300 to 420 mm/min. 展开更多
关键词 Wire-arc additive manufacturing Al–Si alloy POROSITY Microstructure STRENGTH
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