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选取1、4和15年的脐橙种植林以及针阔混交林为研究对象,对不同林地枯落物持水性能、土壤蓄水能力、入渗性能、土壤有机碳等参数进行测定,并结合主成分分析法研究脐橙种植对水源涵养能力的影响。结果表明:1)针阔混交林枯落物有效拦蓄量分别为4年和15年脐橙林的166.87倍和61.50倍,脐橙种植对枯落物水文效应影响显著。2)不同林地土壤层总孔隙度变化范围为43.92%~60.13%,3种不同种植年限脐橙林土壤容重均值较针阔混交林分别提高了2.17%,11.76%和20.74%,随种植年限增加有明显增加趋势。3)1年脐橙林土壤初渗速率、稳渗速率较针阔混交林分别下降了20.70%和55.00%,脐橙林土壤下渗速率随种植年限增加而下降。土壤下渗速率、容重是影响当地水源涵养能力的主要因子。 相似文献
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TiO_2 composite electron transport layers for planar perovskite solar cells by mixed spray pyrolysis with precursor solution incorporating TiO_2 nanoparticles 下载免费PDF全文
Perovskite solar cells with planar structure are attractive for their simplified device structure and reduced hysteresis effect. Compared to conventional mesoporous devices, TiO_2 porous scaffold layers are removed in planar devices. Then,compact TiO_2 electron transport layers take the functions of extracting electrons, transporting electrons, and blocking holes.Therefore, the properties of these compact TiO_2 layers are important for the performance of solar cells. In this work, we develop a mixed spray pyrolysis method for producing compact TiO_2 layers by incorporating TiO_2 nanoparticles with different size into the precursor solutions. For the optimized nanoparticle size of 60 nm, a power conversion efficiency of 16.7% is achieved, which is obviously higher than that of devices without incorporated nanoparticles(9.9%). Further investigation reveals that the incorporation of nanoparticles can remarkably improve the charge extraction and recombination processes. 相似文献
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Based on the Dyson-Schwinger Equations (DSEs), the two-quark vacuum condensate, the four-quark vacuum condensate, and the quark gluon mixed vacuum condensate in the non-perturbative QCD vacuum state are investigated by solving the DSEs with rainbow truncation at zero- and finite-temperature, respectively. These condensates are important input parameters in QCD sum rule with zero and finite temperature, and in studying hadron physics, as well as predicting the quark mean squared momentum m02-also called quark virtuality in the QCD vacuum state. The present calculated results show that these physical quantities are almost independent of the temperature below the critical point temperature Tc=131 MeV, and above Tc the chiral symmetry is restored. For comparison we calculate the temperature dependence of the "in-hadron condensate" for pion. At the same time, we also calculate the ratio of the quark gluon mixed vacuum condensate to the two-quark vacuum condensate by using these condensates, and the unknown quark mean squared momentum in the QCD vacuum state has been obtained. The results show that the ratio m02(T) is almost flat in the temperature region from 0 to Tc, although there are drastic changes of the quark vacuum condensate and the quark gluon mixed vacuum condensate at the region. Our predicted ratio comes out to be m02(T)=2.41 GeV2 at the Chiral limit, which is consistent with other theory model predictions, and strongly indicates the significance that the quark gluon mixed vacuum condensate has played in the virtuality calculations. 相似文献
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在增材制造技术中,树枝晶的表征对于分析激光熔覆层的机械性能至关重要,但目前树枝晶的标记主要由人工完成,耗时长且容易引入人为误差,而深度学习可提高目标识别准确度。基于U-net网络提出了适于识别分割树枝晶的BNC-Unet网络,将串行注意力机制和Batch Normalization层有效地部署在上采样和下采样区域,调整图像特征的权重信息。选取交并比作为分割结果的评价指标,并对比了原Unet以及不同的改进方法在该指标下的结果。在测试集中,BNCUnet网络分割树枝晶准确率指标为84.2%,比原U-net网络结果提升了8.97%。该指标表明网络能准确地从激光熔覆层金相图中识别出树枝晶形貌,且识别树枝晶的准确率显著提高,便于在激光熔覆试验后评估熔覆层性能。 相似文献
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随着温度的降低,超导块材表现出的超导特性也随之变化.本文结合现有实际应用的车载超导块材冷却方法,通过改变气压的方式营造过冷液氮温度条件,探究块材组合与Halbach轨道之间的悬浮特性.由于实验测量存在一定局限性,只能完成部分工况条件下的研究.为了更加系统全面的研究,本文对过冷状态下超导块材的悬浮特性进行仿真计算,通过与实验结果对比来确定仿真参数.结果显示,仿真计算与实验数据吻合度较高,为后期的研究工作提供了仿真工具. 相似文献
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