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The flow of a micropolar fluid in a semi-porous channel with an expanding or contracting wall is investigated. The governing equations are reduced to ordinary ones by using similar transformations. To get the analytic solution to the problem, the homotopy analysis method (HAM) is employed to obtain the expressions for velocity fields. Graphs are sketched and discussed for various parameters, especially the effect of the expansion ratio on velocity and micro-rotation fields. 相似文献
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研究了运动的粘性导电流体中可渗透收缩壁面上非稳态磁流体边界层流动,利用解析和数值方法对问题进行了研究,并考虑了壁面速度滑移的影响.提出了一个新的解析方法(DTM-BF),并将其应用于求解带有无穷远边界条件的非线性控制方程的近似解析解.对所有的解析结果和数值结果进行了对比,结果显示两者非常吻合,从而证明了DTM-BF方法的有效性.另外,对不同的参数,得到了控制方程双解和单解的存在范围.最后,分别讨论了滑移参数、非稳态参数、磁场参数、抽吸/喷注参数和速度比例参数对壁面摩擦、唯一解速度分布和双解速度分布的影响. 相似文献
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细菌纤维素基柔性锌离子电池正极的构筑及性能研究 总被引:1,自引:0,他引:1
柔性锌离子电池(ZIBs)具有高安全性、低成本和高能量密度等优势, 但是现有的ZIBs柔性电极难以兼具高电化学性能和力学稳定性. 其中, 缺少适合的基底材料是限制柔性电极发展的关键. 本工作中, 以细菌纤维素(BC)为基底材料, 结合原位聚合及真空过滤方法, 制备了具有3D多孔结构的BC/聚苯胺/碳纳米管(BC/PANI/CNTs)柔性电极. BC固有的高抗拉伸强度和超细纳米纤维网络结构等特点, 在赋予柔性电极高弯曲特性的同时, 还有利于活性物质的负载及电解液离子的快速扩散. 结果表明, BC/PANI/CNTs具有高柔韧性、7.3 mg/cm2的负载量和157 mAh/g的比容量. 以BC/PANI/CNTs电极构建的准固态ZIBs展现了109 mAh/g的比容量, 且200次充放电循环后容量保持率大于90%. 相似文献
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本文通过改变肋柱宽度和间距, 构造了二级和多级梯度微结构表面, 采用格子-Boltzmann方法对液滴在两种梯度表面上的铺展过程进行了研究, 探析液滴运动的机理和调控方法. 结果表明, 在改变肋柱间距的二级梯度表面上, 当液滴处于Cassie态时, 接触角滞后大小与粗糙度梯度成正比关系; 当液滴从Cassie态转换为Wenzel态或介于两者之间的不稳定态时, 这一正比关系不再遵循. 在改变肋柱宽度的二级梯度表面上, 接触角滞后大小与粗糙度梯度始终成正比关系. 在多级梯度表面上, 随液滴初始半径增大, 接触角滞后减小, 但液滴平衡位置相较于初始位置偏离增大. 对梯度微结构表面上液滴运动和接触角滞后的定量分析, 可为实现梯度微结构表面液滴运动调控提供理论依据. 相似文献
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Mesoporous silica SBA-15 consists of uniform hexagonal, unconnected cylindrical channels with diameters that can be tuned within a range of 1.5 nm-30 nm, and is thought to have a special thermal conductivity. The theoretical investigation of the shell thermal conductivity of the mesoporous silica is performed in the relaxation time approximation in this paper and an available one-dimensional heat transfer model is used to predict the effective thermal conductivity (ETC) of the mesoporous silica. The experimental result of the ETC is also presented for comparison. The shell thermal conductivity of the mesoporous silica decreases with mesochannel radius increasing or wall thickness decreasing, but does not strictly decrease with porosity increasing. The thermal radiation possibly plays a primary role in heat transfer at the large porosity scale. The predicted ETC of SBA-15 with only conduction considered is quite low at the large porosity, even lower than the thermal conductivity of the silica aerogels. To realize it, doping carbon or other matters which can strongly absorb infrared light into SBA-15 is a possible way. 相似文献
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Anti-perovskite solid-state electrolyte Li2 OHCl usually exhibits orthorhombic phase and low ionic conductivity at room temperature. However, its ionic conductivity increases greatly when the temperature is up to 40℃, while it goes through an orthorhombic-to-cubic phase transition. The cubic Li2 OHCl with high ionic conductivity is stabilized at room temperature and even lower temperature about 10℃ by a simple synthesis method of wet mechanical milling. The cubic Li2 相似文献