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71.
Lyes Ait Ali Yahia Tobias Matthaeus Piepke Ross Barrett Ali Ozel Raffaella Ocone 《American Institute of Chemical Engineers》2020,66(6):e16945
A novel rheometer to study the behavior of granular materials in an aerated bed of particles has been developed. The device, called the aerated bed virtual Couette rheometer, is shown to be able to measure the shear stresses in the quasi-static and in the intermediate flow regimes. To validate the instrument, a Newtonian fluid of known viscosity was first sheared. The device was then used for measuring the shear stress of nonaerated glass beads with three -3D printed cells of different sizes to validate the optimal radial position, r*, where both shear rate and shear stress are independent of the cell radius. The results for the nonaerated glass beads displayed Coulomb behavior. The same behavior was observed when the bed was aerated. These experiments also showed that for a fixed shear rate the shear stress decreases as the aeration velocity, U. increases. 相似文献
72.
The traditional design procedure for the waveguide Fresnel lens was carried over from those of bulk optics and micro-optics. In this design it is assumed that the lens thickness is negligibly small with respect to the focal length. This criterion does not hold for many integrated optic devices, in particular those with small mode-index modulations and long wavelengths. Under these conditions, the focal properties of the lens become unpredictable and the lens efficiency is reduced, both of which severely limit the usefulness of the lens as a waveguide-to-fiber coupler. To correct for this shortcoming, the standard Fresnel lens design procedure was modified to acocunt for the thickness of the lens explicitly. Both the standard and the modified Fresnel lens designs are outlined. A comparison of the limitations of the two lenses predicts better performance for the modified Fresnel lens. This is supported through computersimulation results for a pair of test lenses. 相似文献
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为探究华北平原不同种植模式的作物耗水与生产能力以评价其缓解地下水超采的潜力,于2021—2022年在中国农业科学院北京市顺义试验站进行了冬小麦-夏玉米、冬小麦-夏大豆和冬小麦-夏休闲3种种植模式的对比试验。利用大型称重式蒸渗仪监测各种植模式的蒸散、土壤储水和渗漏,使用FAO-56推荐的双作物系数法估算不同种植模式的蒸散量,同时分析了估算效果和蒸散与环境的响应特征,并比较不同种植模式的水分利用效率和产量、效益的相对关系。结果表明:3种种植模式的实测蒸散量与净辐射呈指数函数关系、与气温呈二次函数关系、与水汽压差呈线性函数关系,可以使用双作物系数法或非线性拟合公式较好地估算不同种植模式的蒸散量;冬小麦-夏玉米种植模式的产量、水分利用效率和经济效益最高,耗水量也最高,地下水净消耗量为197.52 mm,而冬小麦-夏休闲模式净地下水消耗量最小,比冬小麦-夏玉米模式低72.28%。未来需要结合华北平原不同区域可利用和开采的地表水、地下水资源量和土壤储水能力以及作物耗水量优化作物种植模式,以达到地下水的采补平衡。 相似文献
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International Journal of Steel Structures - Having knowledge of dynamic properties named as natural frequency and mode shapes during the design process is important to determine proper design... 相似文献
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Efficient Charge Transfer and Fine‐Tuned Energy Level Alignment in a THF‐Processed Fullerene‐Free Organic Solar Cell with 11.3% Efficiency
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80.
Weiheng Xu Dharneedar Ravichandran Sayli Jambhulkar Yuxiang Zhu Kenan Song 《Advanced functional materials》2021,31(14):2009311
Carbon nanotube (CNT)-reinforced polymer fibers have broad applications in electrical, thermal, optical, and smart applications. The key for mechanically robust fibers is the precise microstructural control of these CNTs, including their location, dispersion, and orientation. A new methodology is presented here that combines dry-jet-wet spinning and forced assembly for scalable fabrication of fiber composites, consisting of alternating layers of polyacrylonitrile (PAN) and CNT/PAN. The thickness of each layer is controlled during the multiplication process, with resolutions down to the nanometer scale. The introduction of alternating layers facilitates the quality of CNT dispersion due to nanoscale confinement, and at the same time, enhances their orientation due to shear stress generated at each layer interface. In a demonstration example, with 0.5 wt% CNTs loading and the inclusion of 170 nm thick layers, a composite fiber shows a significant mechanical enhancement, namely, a 46.4% increase in modulus and a 39.5% increase in strength compared to a pure PAN fiber. Beyond mechanical reinforcement, the presented fabrication method is expected to have enormous potential for scalable fabrication of polymer nanocomposites with complex structural features for versatile applications. 相似文献