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21.
In this study, fluid flow over an array of eight, 0.029 m × 0.029 m, square cross‐section cylinders in an octagonal configuration is studied numerically. The mean force coefficients (drag and lift) and the vortex formation characteristics of the array are calculated numerically by utilizing a three‐dimensional large eddy simulation mathematical model for turbulence. The numerical simulation is performed with commercial software ANSYS Fluent 19R1. To investigate the parametric influences, three spacings between the cylinders (0.07, 0.14, and 0.2 m), two array attack angles (0° and 15°), and two Reynolds numbers (4060 and 45 800) are considered. The results comprise flow patterns and force coefficients' variations with Reynolds numbers. The lift force of the downstream cylinder reaches its maximum at α = 15°, and the drag force of the upstream cylinders finds its peak at α = 0°. It is observed through velocity and viscosity contour plots that vortex formation length near the cylinder increases at higher Reynolds number. Velocity vector plots are also presented to show fluid flow behavior near the cylinder. Furthermore, the predicted mean forces on the cylinders are slightly different for different Reynolds numbers, spacings, and angles of attack. 相似文献
22.
优质电力园区以最低成本满足用户对电能质量的特殊需求,成为解决电压暂降问题的新途径,已在国内外开展了广泛的试点应用。针对中国优质电力园区规划缺少经济高效的优化配置方法的实际情况,提出了一种基于过程免疫力的动态电压恢复器优化配置方法。基于工业过程电压暂降免疫力,以满足用户用电需求为目标,以治理设备购置费用最低为约束,采用遗传算法对园区供电质量分级制定动态电压恢复器的优化配置方案,实现工业园区电压暂降治理的经济性。对大型精密温控系统的电压暂降治理装置的优化配置方法进行仿真计算,验证了所提方法的有效性与经济性。 相似文献
23.
刘景锦 《网络安全技术与应用》2014,(5):25-26
本文探讨利用RouterOS软路由来建设图书馆电子阅览室网络的低成本、高性能解决方案,介绍了ROS的特点及其安装和配置过程,尤其在电子阅览室网络安全方面进行了详细分析并给出有效的配置. 相似文献
24.
This paper proposes an address configuration scheme for a MANET. In this paper, the tree-based architecture and the algorithm of constructing a MANET are presented. In this architecture, a proxy node can assign a unique address for neighbor new nodes, so the address configuration task is distributed around all proxy nodes. The transmission of control packets is controlled within one-hop scope, so the cost is reduced and the delay is shortened. Through this architecture, the address resources released by failed nodes can be automatically reclaimed for reuse, so a proxy node has always the sufficient address space for assignment. In order to ensure the uniqueness of a node’s address, the paper also proposes the MANET merging and partitioning algorithms. Finally, this paper evaluates the performance metrics of both the proposed scheme and the existing schemes, and the results show that the proposed scheme reduces the address configuration cost and shortens the address configuration delay. 相似文献
25.
《Journal of the European Ceramic Society》2014,34(12):3119-3126
Different types of nano-CoAl2O4 pigments were prepared by controlling concentration of cetyltrimethylammonium bromide (CTAB) and polyvinyl pyrrolidone (PVP) as double capping agents in a co-precipitation process. The prepared nano-CoAl2O4 pigments were characterized by TGA, UV spectroscopy, and XRD. The optimum synthesized nano pigment was well dispersed into de-ionized water to form the ink. Rheology, surface tension and DLS of the prepared ink were examined. The prepared ink was printed onto a ceramic substrate. The printing process was repeated 1, 3 and 5 times in order to evaluate variations in the optical properties by changing thicknesses of the printed film. Appearance of the printed image and morphology of the prepared nano-pigments were observed by SEM. Moreover, shape and size of the nano-particles in the prepared ink were investigated by TEM. The obtained results revealed that the ink-jet printing method can be used to produce a nano-film of pigments on the ceramic. 相似文献
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将Z构型卢立康唑溶于适量N,N-二甲基甲酰胺中,以酸催化,在较温和的条件下将其转化为E构型,收率约34%,该构型转化提高了卢立康唑合成过程中的总收率,降低了生产成本。 相似文献
30.
Shuang Zheng Ming-Liang Chang Jing Zhou Jing-Wei Fu Qing-Wei Zhang Shao-Yong Li Wei Qiao Jun-Min Liu 《International journal of molecular sciences》2014,15(6):9844-9858
For all microhelices on aromatic rings of inherently chiral calix[4]arene, an expression was derived from one approximation and one hypothesis on the basis of the electron-on-a-helix model of Tinoco and Woody as follows: , where µ = 1 for the right-handed microhelix and µ = −1 for the left-handed microhelix; and H and K are constant and greater than zero. The expression correlates microhelical electronic energy (E) with the atom polarizability difference (Δα) on both microhelix ends, which intuitively and clearly shows the impact of helical substituent polarizability on helical electronic energy. The case analysis almost entirely proves that the qualitative analysis of the helical electronic energy of inherently chiral Calix[4]arenes with the expression is scientific and can be used to effectively assign their absolute configuration. 相似文献